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Thermodynamic description of the LiNiO2–NiO2 pseudo-binary system and extrapolation to the Li(Co,Ni)O2–(Co,Ni)O2 system
Abstract
The LiNiO2–NiO2 pseudo-binary system has been studied using the CALPHAD approach coupled with ab initio calculations. The O1 phase, the H1-3 phase and the ordered and disordered O3 phases, are thermodynamically described using sublattice models. The phase equilibria and thermodynamic data are well reproduced by the present thermodynamic modeling. Based on the experimental information and present ab initio results, we consider the LiCoO2–CoO2 and LiNiO2–NiO2 systems to be ideally mixing. Using the extrapolated thermodynamic description of the Li(Co,Ni)O2–(Co,Ni)O2 system, the cell voltages of Li/O3- Li(Co,Ni)O2 cells are calculated and compared with experimental data. The good agreement shows the viability of the present approach.
... Meanwhile, the results from the ab initio calculations can be used as the input for the CALPHAD (CALculation of PHAse Diagrams) approach [14][15][16]. The CALPHAD approach can be used to develop phase diagrams and continuous property diagrams of LIBs [17][18][19][20][21][22][23][24][25][26] by predicating the phase equilibria and intrinsic properties (thermodynamic, electrochemical and physical), which are essential to understanding the composition−structure−property relationships and battery process during the charge and discharge. ...
... Phase diagrams are powerful tools to understand the working process of LIBs [19,27] because different phase regions correspond to different activities of the components. For example, in a binary system at a constant temperature, the chemical potential of an element is constant inside a two-phase region. ...
... Four phases are detected during cycling of the Li/LiNiO 2 cell, i.e., O1, H1-3, O3 and O3' (ordered O3) [28,[36][37][38][39][40][41][42][43][44]. Chang et al. [19] successfully modeled all the phases using the CALPHAD approach. The experimental heat capacity data of LiNiO 2 below room temperature and ab initio obtained formation enthalpy data of Li x NiO 2 (0 < x < 1) are well described [19], as shown in Fig. 5. Fig. 6 represents the calculated LiNiO 2 -NiO 2 phase diagram. ...
Phase diagrams provide fundamental knowledge about design map of new electrode materials for Li-ion batteries. The CALPHAD (CALculation of PHAse Diagrams) approach is widely applied to the development of phase diagrams and property diagrams in a thermodynamic language. Within the CALPHAD framework, the theoretical modeling can be performed to predict phase equilibria, thermodynamics, electrochemical and physical properties of electrodes. This review provides the successful application of high quality calculated phase diagrams and thermodynamic property diagrams in CALPHAD investigation to both cathodes and anodes of Li-ion batteries, including Li–Co–O, Li–Ni–O, Li–Co–Ni–O, Li–Mn–O, Li–Cu–O, Li–Si, Li–Sb and Li–Sn systems with. The intensive CALPHAD-type research may also predict electrochemical properties, cell performance of the Li-ion batteries to achieve more efficient development of electrode materials. Keywords: Li-Ion battery, Phase diagram, CALPHAD, Thermodynamic property, Electrochemical behavior
... Currently commercial lithium ion batteries based on conventional transition metal oxide cathode materials, such as LiCoO2 and spinel LiMn2O4, have been seriously prevented from extensive practical applications due to the underlying structural drawbacks [2]. Lithium transition metal oxides are amongst the most studied materials for, possessing high operating voltage, good reversibility and high capacity cathode in lithium ion batteries as secondary batteries [3,4]. Intercalation and deintercalation are the processes that occur in the rechargeable electrode in a lithium battery where the insertion and de-insertion of Li-ions into the electrode is topotactic and therefore, the structure of the host material was conserved during reaction. ...
... LiNiO2 has been considered as a promising positive electrode material for high energy rechargeable batteries [5][6][7][8][9]. LiNiO2 has layered structure similar to LiCoO2 and is cheaper than LiCoO2 [4,10,11]. ...
... However, LiNiO2 has high theoretical capacity, it is difficult to synthesis in its tendency of non-stoichiometric phase, is not easy to prepare on large scale, [11,12] due to its lower thermodynamic stability compare LiCoO2 and the presence of excess nickel on Li sites. These anti sites in LiNiO2 strongly affect the electrochemical properties of batteries [4]. In the case of doped LiNiO2, there are still some possible improvement. ...
Lithium cobalt nickel oxide cathodes had been doped with various metals in recent years to obtain a competitive high performance cathode material for lithium-ion batteries. Cathodes doped with Al and Mg were synthesized by solid-state reaction method. Structural investigation of this material was done using XRD. Galvanostatic charge/discharge and cyclic voltammetry were studied in order to outline the electrical performance of LiCo0.7Ni0.2Al0.09Mg0.01O2, LiCo0.7Ni0.2Al0.06Mg0.04O2 and LiCo0.7Ni0.2Al0.03Mg0.07O2 materials in lithium-ion batteries. Electrical impedance was done on all the materials and it gave decreasing conductivities with increasing temperature. The activation energies had negative values with increased magnesium content of the material. Larger conductivity variation with temperature was seen in the material with the higher magnesium content. Voltammographs of these materials showed good oxidation and reduction loops. Charge/discharge curve for LiCo0.7Ni0.2Al0.09Mg0.01O2 material showed about 96 mAh/g of discharge capacity for the first cycle.
... The cyclic voltammograms of the bare and LTO@NCM-1 samples for the first three cycles were shown in Fig. 5c and d. NCM sample showed two distinct redox peaks with a sharp oxidation peak at 3.969 V and a small oxidation peak at 4.245 V which appeared during charging because of multiphase transitions [8,25]. The corresponding reduction peaks were present at 3.664 V and 4.138 V. ...
... In other words, the redox peak at 4.18 V was well maintained during the lithium ion intercalation/deintercalation in LTO@NCM-1. It has been reported that the rapid volume contraction during the structural transformation from H2 to H3 mostly affects the capacity fading of NCM [8,25]. The lack of H2-H3 phase transition of LTO@NCM-1 indicated good reversibility of the electrode. ...
The cycling performance of LiNi0.8Co0.1Mn0.1O2 has been effectively enhanced by Li2TiO3 thin film coating. The Li2TiO3 coating layer with an average thickness of 1 nm has been proved by XRD, HRTEM, FFT and XPS. Compared with the 80.5% capacity retention of bare materials, the modified LiNi0.8Co0.1Mn0.1O2 materials Exhibit 98% capacity retention after 170 cycles at 1C rate. The reason for the improved cycling performance of LiNi0.8Co0.1Mn0.1O2 is due to the surface layer of Li2TiO3, which suppresses the direct contact between the active materials and the electrolytes, enhances the lithium ion diffusion between the electrode/electrolyte interface, and prevents the pulverization of the active materials during repeated charging/discharging.
... A CALPHAD model is usually refined as new data pertaining to the system are published, which may take place over periods of several years. The CALPHAD approach to the NMC system may be expected to provide a continuous description of properties related to the material according to composition and during battery cycle, as demonstrated in the studies of Chang et al. in their CALPHAD descriptions of the pseudo-binary equilibria LiCoO 2 -CoO 2 5 and LiNiO 2 -NiO 2 6 . The NMC crystals have a rhombohedral structure that belongs to the space group 7 . ...
The formation energies of LiCoO2, LiNiO2 and LiMnO2 were calculated using a combination of adequately selected Hess cycles and DFT computations. Several exchange-correlation functionals were tested and PBE for solids (PBEsol) turned out to be the most accurate. The enthalpies of formation at 0 K are -168.0 kJ mol at-1 for LiCoO2, -173.2 kJ mol at-1 for LiNiO2, -209.9 kJ mol at-1 for o-LiMnO2 and -208.8 kJ mol at-1 for r-LiMnO2. In comparison to experimental formation energy data, a difference of 1.6 and 0.01 kJ mol at-1 was obtained for LiCoO2 and LiMnO2, respectively. By contrast, a much larger discrepancy, around 24 kJ mol at-1, was obtained for LiNiO2 and confirmed by using an additional and independent Hess cycle. The influence of slight crystallographic distortions associated with magnetism and/or the Jahn-Teller effect on energy was carefully searched for and taken into account, as well as corrections arising from vibrational contributions. Hence, these results should motivate future measurements of the thermodynamic properties of LiNiO2, which are currently scarce. Vibrational contributions to the structural and energetic properties were computed within the harmonic and the quasi-harmonic approximations. The LiCoO2 heat capacity at constant pressure is in excellent agreement with experimental data, with a difference of only 3.3% at 300 K. In the case of LiNiO2 the difference reaches 17% at 300 K, which could also motivate further investigation. The Cp(T) value for the orthorhombic phase o-LiMnO2, for which no previous data were available, was computed. Structural properties such as specific mass, bulk modulus and coefficient of thermal expansion are presented.
... 40 Figure 3D. 44,46 At harsh conditions (high temperature and voltage), the consumption of surface active nickel will expedite the structural degradation for Ni-based materials. Surface degradation reaction will lead to some structure change from R-3 m to Fd-3 m and Fm-3 m structure. ...
High‐capacity layered oxide Ni‐rich cathodes are attractive to enhance the driving‐range of electric vehicles because of its preferential costs. Nevertheless, in Ni‐rich cathodes, there are still many issues such as microcracks generation along grain boundaries and interface side reaction between active substance and electrolyte, resulting in the rapidly deterioration of electrochemical property. Herein, improving the performance of Ni‐based cathodes by structural regulation is summarized. The remaining challenges and outlook are discussed as well.
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... A Li-ion battery (LIB), typically with an anode of graphite and a cathode of Lithium transition oxide, is widely used for portable electronic devices [1][2][3][4][5]. Because the ...
Inspired by the wisdom of metallurgists in designing new alloys, the Integrated Computational Materials Engineering (ICME) based design strategy is proposed for development of Si based anodes for Li-ion batteries (LIBs). The strategy starts with a rational component design of Si-X, where X is the additive component(s) helping to overcome the problems of the pure Si anodes. An optimization of the composition, structure, property and performance of the Si-X anode is followed to fulfill the requirements for its commercialization. In addition to the widely applied designing scheme for the nanostructured Si anodes, the presently proposed one from the ICME based rational component design is expected to accelerate the discovery of the promising Si based anodes for commercial LIBs.
... 9,[11][12][13] However, no model that can cover the complete composition range of doped HV spinel has been reported in literature up to now. CALculation of PHAase Diagram (CALPHAD) approach is already proven to be suitable for describing the continuous property changes in lithium ion batteries, [14][15][16][17][18] including LMO spinel cathodes. 19 Therefore, combination of ab initio calculations and CALPHAD approach can be a good tool for establishing a thermodynamic model for the co-doping behaviour of HV spinels. ...
High-voltage (HV) spinels obtained by partially substituting Mn with other elements in LiMn 2 O 4 are promising cathode materials for lithium-ion batteries (LIBs) due to their superior energy capacities and recyclability. The improved performance of HV spinels comes from the appearance of multi voltage plateaus without phase transformation during lithiation/delithiation process. To optimize the doping elements is one significant routine to develop new cathode materials. However, it is difficult to investigate HV spinels with multi doping elements due to increased variables. For the first time, we investigate the typical HV spinel, Li Ni , Mn 2 O 4 using one single thermodynamic model with Compound Energy Formalism (CEF), i.e., Va , Li + 1 Li + , Ni 2 + , Ni 4 + , Mn 3 + , Mn 4 + 2 O 2 − 4 and described Ni substitution of Mn as well as lithiation/delithiation behaviours. Both the high voltage (around 4.7 V) and low voltage (around 4.1 V) plateaus of the Li-Ni-Mn-O spinel cathodes are predicted by correctly describing competition between Mn 3 + / Mn 4 + and Ni 2 + / Ni 4 + redox pairs. Meanwhile, we have successfully modelled the key property parameters including the voltage profile, energy density, stability, and cyclability. The presented design scheme is based on the superior cell performance compared to the widely studied LiNi 0.5 Mn 1.5 O 4 , which results in the slightly Li-rich HV spinel Li 1 + x Ni 0.5 Mn 1.5 − x O 4 because of higher energy density and improved cyclability. The here adopted research strategy enables efficient design of the new-generation multi-doped HV spinel Li M , Mn 2 O 4 (M = Li, Al, Co, Cr, Cu, Mg, Fe, Ni, Zn, etc.).
... This is evident that the peaks are more crystalline at higher temperature. It means that a diminished crystallite size combined with tiny strain in the precious stone cross section [34]. This could be because of a specific level of confound in Ni 3+ (0·62 Å) ionic sizes. ...
LiNiO2 samples have been prepared by solid state reaction method at different annealing temperatures. Structure of the samples clearly shows that the sharp peak is observed at (0 0 3), which indicates the fcc lattice. The morphological surface of the samples and the grain size of the integrated oxides have been analyzed by SEM. The chemical complexation of the molecules is confirmed by FTIR studies. From the optical absorption results the bandgap of LiNiO2 has been observed at 1.20 and 1.40 eV, respectively. Raman band observed at 590 cm−1 is due to the symmetric O–Ni–O stretching vibration of NiO2 units. The sample which is prepared in the form of cell is measured galvanostatically in the potential territory 2.75–5.1 V. The cyclability of the prepared sample is displayed over 30 cycles. The thickness of the cell is found to be 198 𝜇A cm−2. The discharge capacity for both the samples have been calculated, and it is found out that for the annealed sample at 1450 °C shows more cyclic performance up to 325 mAh g−1, whereas the annealed sample at 1100 °C shows up to 270 mAh g−1. The obtained results have revealed that the LiNiO2 cathode material annealed at 1450 °C may be utilized in the preparation of microbatteries and also in other power supply source applications.
... Experimental and predicted enthalpies versus degree of lithiation for layered metal oxides.47,62,66,80,84,85,[74][75][76]61,63,64,67,[68][69][70]86 ...
Accurate models of thermal runaway in lithium-ion batteries require quantitative knowledge of heat release during thermochemical processes. A capability to predict at least some aspects of heat release for a wide variety of candidate materials a priori is desirable. This work establishes a framework for predicting staged heat release from basic thermodynamic properties for layered metal-oxide cathodes. Available enthalpies relevant to thermal decomposition of layered metal-oxide cathodes are reviewed and assembled in this work to predict potential heat release in the presence of alkyl-carbonate electrolytes with varying state of charge. Cathode delithiation leads to a less stable metal oxide subject to phase transformations including oxygen release when heated. We recommend reaction enthalpies and show the thermal consequences of metal-oxide phase changes and solvent oxidation within the battery are of comparable magnitudes. Heats of reaction are related in this work to typical observations reported in the literature for species characterization and calorimetry. The methods and assembled databases of formation and reaction enthalpies in this work lay groundwork a new generation of thermal runaway models based on fundamental material thermodynamics, capable of predicting accurate maximum cell temperatures and hence cascading cell-to-cell propagation rates.
... All the samples show the similar oxidation of Ni 3+ to Ni 4+ at around 3.8 V but with slight difference in the oxidation peaks which may be caused by the larger polarization for NCA-720 and NCA-765. It should also be noted that NCA-780 has another 4 Research oxidation peak at around 4.5 V which mainly is attributed to the phase transition from H1 to O1 [43]. As mentioned before, the LiNiO 2 -based materials decompose at high temperatures and form the nonstoichiometric Li 1-x NiO 2 phase. ...
Li ⁺ /Ni ²⁺ antisite defects mainly resulting from their similar ionic radii in the layered nickel-rich cathode materials belong to one of cation disordering scenarios. They are commonly considered harmful to the electrochemical properties, so a minimum degree of cation disordering is usually desired. However, this study indicates that LiNi 0.8 Co 0.15 Al 0.05 O 2 as the key material for Tesla batteries possesses the highest rate capability when there is a minor degree (2.3%) of Li ⁺ /Ni ²⁺ antisite defects existing in its layered structure. By combining a theoretical calculation, the improvement mechanism is attributed to two effects to decrease the activation barrier for lithium migration: (1) the anchoring of a low fraction of high-valence Ni ²⁺ ions in the Li slab pushes uphill the nearest Li ⁺ ions and (2) the same fraction of low-valence Li ⁺ ions in the Ni slab weakens the repulsive interaction to the Li ⁺ ions at the saddle point.
... 99 The R-3m spacegroup was assumed based on prior work. 78,100 Only 86 of the generated structures were optimized as above. The highly degenerate structures were discarded as the Li are far less homogenously distributed. ...
The electrochemical performance and mechanistic effects of incorporating two salts in an ether electrolyte in Li-metal cells were investigated experimentally and via molecular scale modeling. Improvements in efficiency and cycling...
... [56] A Gibbs energy change for formation from elements of DG f 0 = À514.96 kJ mol À1 [57] or À600 kJ mol À1 [58] at 300 K was also calculated. The heat capacity of LNO as a function of temperature was measured and found to be significantly higher than for LiCoO 2 . ...
LiNiO₂ (LNO) has been introduced as cathode active material (CAM) for Li‐ion batteries in 1990. After years of intensive research, it emerged that several instability issues plague the material, so that it was abandoned in favor of isostructural metal‐substituted compounds called NCA (for lithium nickel cobalt aluminum oxide) and NCM (lithium nickel cobalt manganese oxide). These sacrifice a certain amount of specific energy in exchange for stability, durability and safety. With few exceptions, NCA and NCM are nowadays the industrial standard when it comes to automotive applications; however, the continuous push towards electric cars with longer driving range is synonym, for these compounds, with increasing the nickel content (which is already beyond 80%), eventually leading back again to LiNiO₂. For this reason we provide here a comprehensive review of the material, almost 30 years after its introduction as CAM. We aim at highlighting its physicochemical peculiarities, which make LNO complex in every aspect. We specifically stress the effect of the Li off‐stoichiometry (Li1‐zNi1+zO2) on every property of LNO, especially the electrochemical ones. We then focus on the key instability issues that plague the compound and on the strategies implemented so far to overcome them. Finally, in the course of the review we point to open questions that still remain to be addressed by the scientific community, and to which research directions seem more promising to lead LNO to its full exploitation.
... A delithiated, disordered structure as in Figure 3C is thermodynamically more stable; thus, such a migration is energetically favorable. 33 Moreover, such a During data collection (indicated by the arrows), both cells were held at open circuit voltage (OCV), one in the charged and one in the discharged state, alternating upon cycling. This results in SXPD data collection for the same cell occurring after 14.5 cycles. ...
HE-NCM (High-Energy-NCM, Li1.17Ni0.19Co0.10Mn0.54O2) is a lithium-rich layered oxide with alternating Li- and transition metal- (TM-) layers in which excess lithium-ions replace transition metals in the host structure. HE-NCM offers roughly a 50 mAh g⁻¹ higher capacity compared to conventional layered oxides, but it suffers from capacity loss and voltage fade upon cycling. Differential capacity plots (taken over 100 cycles) show that the origin of the fading phenomenon is a bulk issue rather than a surface degradation. Although previous studies indicate only minor changes in the bulk material, long duration in situ synchrotron X-ray powder diffraction measurements, in combination with difference Fourier analysis of the data, revealed an irreversible transition metal motion within the host structure. The extensive work provides new insights into the fading mechanism of the material.
... While the analytic Gibbs free energy expression for LiCoO 2 from Abe and Koyama [14] estimates its heat capacity by assuming the Neumann-Kopp rule based on the assessed heat capacities of Li, Co, and O 2 , Chang et al. [15] developed a Gibbs energy expression for LiCoO 2 using experimental heat capacity data from Kawaji et al. [5], Emelina et al. [10], and Menetrier et al. [6]. Chang et al. [16] also modelled the Gibbs free energies of the phases in the LiNiO 2 -NiO 2 pseudobinary system. In that work, the analytic Gibbs free energy function of LiNiO 2 was developed using the assessed Gibbs energies of the pure elements Li, Ni, and O 2 . ...
An interlaboratory study was performed to determine the heat capacity of an active material for lithium-ion batteries with layered structure and nominal composition LiNi1/3 ·Mn1/3Co1/3O2 (NMC111). The commercial sample, which was characterized using powder X-ray diffraction and inductively coupled plasma-optical emission spectroscopy, is single phase (a-NaFeO2 crystal structure) with a composition of Li1.02Ni0.32Mn0.31Co0.30O2. Heat capacity measurements of the homogeneous sample were performed at five laboratories using different operators, methods, devices, temperature ranges, gas atmospheres and crucible materials. The experimental procedures from each laboratory are presented and the results of the individual laboratories are analyzed. Based on a comprehensive evaluation of the data from each laboratory, the heat capacity of the NMC111 sample from 315 K to 1 020 K is obtained with an expanded reproducibility uncertainty of less than 1.22%.
... While the analytic Gibbs free energy expression for LiCoO 2 from Abe and Koyama [14] estimates its heat capacity by assuming the Neumann-Kopp rule based on the assessed heat capacities of Li, Co, and O 2 , Chang et al. [15] developed a Gibbs energy expression for LiCoO 2 using experimental heat capacity data from Kawaji et al. [5], Emelina et al. [10], and Menetrier et al. [6]. Chang et al. [16] also modelled the Gibbs free energies of the phases in the LiNiO 2 -NiO 2 pseudobinary system. In that work, the analytic Gibbs free energy function of LiNiO 2 was developed using the assessed Gibbs energies of the pure elements Li, Ni, and O 2 . ...
... All structures were relaxed with respect to atomic positions and lattice parameters. A detailed description of this calculation technique can be found elsewhere [34,35]. The enthalpy of formation for the NMC at 0 K was calculated using Eq. ...
Layer-structured mixed transition metal oxides with the formula LiNixMnxCo1-2xO2 (0 ≤ x ≤ 0.5) are considered as important cathode materials for lithium-ion batteries. In an effort to evaluate the relative thermodynamic stabilities of individual compositions in this series, the enthalpies of formation of selected stoichiometries are determined by high temperature oxide melt drop solution calorimetry and verified by ab-initio calculations. The measured and calculated data are in good agreement with each other, and the results show that LiCoO2-LiNi0.5Mn0.5O2 solid solution approaches ideal behavior. By increasing x, i. e. by equimolar substitution of Mn⁴⁺ and Ni²⁺ for Co³⁺, the enthalpy of formation of LiNixMnxCo1-2xO2 from the elements becomes more exothermic, implying increased energetic stability. This conclusion is in agreement with the literature results showing improved structural stability and cycling performance of Ni/Mn-rich LiNixMnxCo1-2xO2 compounds cycled to higher cut-off voltages.
... 34,37 The material experiences structural transformation during Li deintercalation processes. 24,34,42,[46][47][48][49][50] The LiNiO 2 phase behavior is typically divided into four regions (Figure 3) during deintercalation: original hexagonal phase (H1), monoclinic (M), another hexagonal phase (H2), and, finally a third hexagonal phase (H3). 24,34 In particular, the anisotropic lattice changes along the a-and c-axes during the H2 and H3 phase transition, resulting in a large volume change (9%), can cause microcracks in LiNiO 2 particles in electrodes above 4.2 V vs. Li + /Li (> 0. 75 Li deintercalated). ...
The portable electronic market, vehicle electrification (electric vehicles or EVs) and grid electricity storage impose strict performance requirements on Li-ion batteries, the energy storage device of choice, for these demanding applications. Higher energy density than currently available is needed for these batteries, but a limited choice of materials for cathodes remains a bottleneck. Layered lithium metal oxides, particularly those with high Ni content, hold the greatest promise for high energy density Li-ion batteries because of their unique performance characteristics as well as for cost and availability considerations. In this article, we review Ni-based layered oxide materials as cathodes for high-energy Li-ion batteries. The scope of the review covers an extended chemical space, including traditional stoichiometric layered compounds and those containing two lithium ions per formula unit (with potentially even higher energy density), primarily from a materials design perspective. An in-depth understanding of the composition-structure-property map for each class of materials will be highlighted as well. The ultimate goal is to enable the discovery of new battery materials by integrating known wisdom with new principles of design, and unconventional experimental approaches (e.g., combinatorial chemistry).
... Two-dimensional triangular-lattice antiferromagnetic (AF) systems have attracted many researchers over the past two decades. Both theoretical [1][2][3][4][5][6] as well as experimental [7][8][9][10][11][12] studies are actively pursued in this regard. It exhibits fascinating physics since it uncovers many unconventional ground states (e.g. the resonating valence bond state [13] or the spin liquid state). ...
Two-dimensional triangular-lattice antiferromagnetic systems continue to be an interesting area in condensed matter physics and LiNiO2 is one such among them. Here we present a detailed experimental magnetic study of the quasi-stoichiometric LixNi2-xO2 system (0.67 < x < 0.98). It exhibits a variety of magnetic ground states-namely spin glass, cluster glass, re-entrant spin glass and ferromagnetic. This study deals with the magnetic properties of these four distinct ground states. The spin glass state is evidenced by the frequency-dependent peak shift as well as the time-dependent slow dynamics (magnetic relaxation, magnetic memory effect etc). By tuning the Li deficiency in a controlled manner, an increase in the ordering temperature is observed. Most strikingly, with the Li deficiency the nature of the magnetic ground state is changed from spin glass to ferromagnetic, with two intermediate states-namely cluster glass and re-entrant spin glass. The critical behaviour of the re-entrant spin glass is also studied here. The critical exponents (β, γ and δ) are extracted from the modified Arrot plot, Kouvel-Fisher method, and critical isotherm analysis. The critical exponents match with the long-range mean-field model. The values of the critical exponents are confirmed by the Widom scaling law: δ = 1 + γβ(-1). Furthermore, the universality class of the scaling relations is verified, where the scaled m and scaled h collapse into two branches. Finally, based on our observations, a phase diagram is constructed.
LiNi0.8Co0.1Mn0.1O2 has become a promising candidate as a cathode material of lithium ion batteries (LIBs) because of their high specific capacity, while the poor cycling and rate performances limit its commercial application. Herein, a thin layer of Li5AlO4 was in situ formed on the surface of LiNi0.8Co0.1Mn0.1O2 through a slow deposition process assisted by NaHCO3 and solid phase co-lithiation sintering. By employing the optimal amount (3 wt %) of Li5AlO4 coating on LiNi0.8Co0.1Mn0.1O2 cathode material (denoted as 3-NCM), the capacity retention rate of 3-NCM after 100 cycles increased from 75.06% to 89.15% at 2.8-4.3 V, and it also shows the most significantly enhanced rate performance. The outstanding electrochemical performance can be attributed to that the Li5AlO4 coating can impede the contact between the active materials and electrolyte, stabilize the material structure and inhibit the dissolution of transition metals during repeated charge–discharge cycles. And the superior conductivity of Li5AlO4 can improve the lithium ion diffusion rate. All these results connote that Li5AlO4-coated LiNi0.8Co0.1Mn0.1O2 cathode material might be employed in advanced lithium-ion batteries.
This Review provides a comprehensive overview of LiNiO2 (LNO), almost 30 years after its introduction as a cathode active material. We aim to highlight the physicochemical peculiarities that make LNO a complex material in every aspect. We specifically stress the effect of the Li off‐stoichiometry (Li1−zNi1+zO2) on every property of LNO, especially the electrochemical ones. The key instability issues that plague the compound and the strategies that have been implemented so far to overcome them are discussed in detail. Finally, the open questions that remain to be addressed by the scientific community are summarized, and the research directions that seem the most promising to enable LNO to be fully exploited are elucidated.
Nickel-rich LiNi0.8Co0.15Al0.05O2 (NCA) cathode possesses high specific capacity and high discharge voltage, as the most promising cathode for high energy density lithium ion batteries, but suffers from serious cycling degradation. The present study revealed that the NCA cathode is stable with excellent cycling stability at voltages below 4.2 V, but suffers from serious degradation at voltages above 4.35 V. The characterizations from SEM, TEM, XPS, FTIR, NMR, XRD and ICP as well as electrochemical measurements supported by theoretical calculations revealed that the trace of HF initially presented in battery grade electrolytes likely induces the cycling stability degradation of nickel-rich NCA cathode via accelerating the electrolyte decomposition. Our further research demonstrated that such cycling stability degradation can be eliminated through applying diethyl phenylphosphonite (DEPP) as an electrolyte additive, as DEPP is capable of shielding HF besides its ability to construct a protective cathode interphase, resulting in an excellent cycling stability of nickel-rich NCA cathode.
Lithium-manganese oxide based-spinel is attractive as cathode materials in lithium ion batteries. A wide range of spinel solid solution can be directly sintered and result in different properties of the identical composition during the battery operation, making it extremely difficult to understand the intrinsic properties and evaluate the battery performance. In this work, a high-throughput computational framework combining ab initio calculations and CALPHAD (Calculation of Phase Diagrams) ap-proach is developed to systematically describe infinite composition–structure–property–performance relationships under sintered and battery states of spinel cathodes. Depending on composition and crystallography, various properties (physical, thermochemical and electrochemical) relating key factors (cyclability, safety and energy density) are quantitatively mapped. The overall performance is consequently evaluated and validated by key experiments. Finally, 4 V spinel cathodes with co-doping of reasonable Li and vacancies on the octahedral sites have been proposed. The presented strategy provides a general guide to evaluate the performance of cathodes with wide composition ranges.
Trace amount of Zirconium (Zr) has been adopted to modify the crystal structure and surface of the Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode material. During cycling at 1.0C, the Zr-modified NCM811 shows an improved capacity retention of 92% after 100 cycles, higher than 75% for pristine NMC811. In addition, the Zr-modified NCM811 is capable of delivering a discharge capacity of 107 mAh g-1 at 10.0C rate, much higher than 28 mAh g-1 delivered by pristine material. These improved electrochemical performances are ascribed to the dual functions of Zr modification. On one hand, part of the Zr enters the crystal lattice, which is beneficial for reducing the Li/Ni cation mixing and enhancing the crystal stability of the cathode. On the other hand, the rest of the Zr forms a 1~2 nm thick coating layer on the surface of the NCM811 cathode, which effectively prevents the direct contact between NCM and the electrolyte, thus suppressing the detrimental interfacial reactions. Therefore, the Zr-modified LiNi0.8Co0.1Mn0.1O2 exhibited significantly enhanced cycling stability and charging/discharging rate capability in comparison with the untreated counterpart.
Li(Ni1/3Mn1/3Co1/3)O2 as a cathode material for lithium ion batteries shows good thermal stability, high reversible capacity (290 mAh g⁻¹), good rate capability and better results in terms of environmental friendliness. In this paper thin film cathodes in the material system Li-Ni-Mn-Co-O were deposited onto silicon and stainless steel substrates, by non-reactive r.f. magnetron sputtering from a ceramic Li1.18(Ni0.39Mn0.19Co0.35)O1.97 target at various argon working gas pressures between 0.2 Pa and 20 Pa. A comprehensive study on the composition and microstructure was carried out. The results showed that the elemental composition varies depending on argon working gas pressure. The elemental composition was determined by inductively coupled plasma optical emission spectroscopy in combination with carrier gas hot extraction. The films showed different grain orientations depending argon working gas pressures. The degree of cation order in the lattice structure of the films deposited at 0.5 Pa and 7 Pa argon working gas pressure, was increased by annealing in an argon/oxygen atmosphere at different pressures for one hour. The microstructure of the films varies with annealing gas pressure and is characterized using X-ray diffraction and unpolarized micro-Raman spectroscopy at room temperature. Electrochemical characterization of as-deposited and annealed films was carried out by galvanostatic cycling in Li-Ni-Mn-Co-O half-cells against metallic lithium. Correlations between process parameters, constitution, microstructure and electrochemical behaviour are discussed in detail.
Thermal behaviour and thermophysical properties of two typical cathodes for lithium-ion batteries were studied in dependence of temperature. The cathode materials are composite thick films containing a mixture of 90 wt% LiMeO2 active material (with Me = Co or Me = Ni + Mn + Co, respectively) and additives (binder and carbon black), deposited on aluminium current collector foils. The thermal conductivity of each cathode type and their corresponding composite layers were determined up to 573 K from the measured thermal diffusivity, the specific heat capacity and the estimated density based on metallographic methods and structural investigations. In addition, the impact of lithiation degree x in LixMeO2 on the transport properties of cathode samples was also investigated. The quantitative determination and the homogeneity of Li content on the surface and within the bulk of the samples were validated by laser induced breakdown spectrometry. The results presented here explain at cell component level, i.e. cathode material, the thermal runaway behaviour of lithium-ion batteries in a combined approach of application oriented and fundamental research. Therefore, these data are significant for improving the simulation studies of their thermal management, in which the bulk properties are assumed, as a common approach, temperature and lithiation degree independent.
The cycling performance of LiNi0.8Co0.1Mn0.1O2 cathode material has been enhanced by improvement nickel-rich material on surface oxygen-keeping capability. LiNi0.8Co0.1Mn0.1O2 cathode material with lower surface oxygen defects is synthesized via covering Ni0.8Co0.1Mn0.1(OH)2 with manganese acetate and sintering with LiOH·H2O at high temperature. A good layered structure with lower surface oxygen defects in the outer layer has been identified by XRD, FFT, HADDF-STEM and XPS. Compared with the bare material maintaining 77.2% capacity retention, the modified LiNi0.8Co0.1Mn0.1O2 materials Exhibit 90.4% capacity retention and 166 mAh·g⁻¹ after 200 cycles at 1C rate. Electrochemical impedance spectroscopy, XRD and SEM of cycled electrodes tests results provide evidence that the improved cycling performance is mainly attributed to stable surface oxygen, the suppression of the interface reaction between the cathode and electrolyte and the improvement in the structural stability of material.
The phase transition, charge compensation and local chemical environment of Ni in LiNiO2 were investigated to understand the degradation mechanism. The electrode was subjected to a variety of bulk and surface sensitive characterization techniques under different charge-discharge cycling conditions. We observed the phase transition from original hexagonal H1 phase to another two hexagonal phases (H2, H3) upon Li deintercalation. Moreover, the gradual loss of H3 phase features was revealed during the repeated charges. The reduction in Ni redox activity occurred at both charge and discharge states, and it appeared both in the bulk and at the surface over the extended cycles. The degradation of crystal structure significantly contributes to the reduction of Ni redox activity, which in turn causes the cycling performance decay of LiNiO2.
Hardness, one key property of hard coatings, is proportional to shear modulus, which can be predicted using density functional theory (DFT). Besides considering hardness, a design methodology for hard coatings must include additional physical and chemical properties, such as thermal conductivity. Recently, also the hard coating–environment (or workpiece) and hard coating–substrate interfaces have been described, constituting new research directions. We have reviewed two commercially successful benchmark hard coatings from the DFT perspective: (i) amorphous diamond-like carbon (DLC) and (ii) metastable TiAlN. Major DFT contributions to the DLC research are the correlation between density and electronic structure as well as identification of reaction products formed during atmospheric exposure to be the main cause for low friction at elevated temperatures. In the case of TiAlN based hard coatings, DFT enabled atomic scale understanding of the phase stability, formation of defect structures and interfaces for the elastic properties, enhancement of toughness, initial stages of oxidation, and interaction with molten polymers and metals. Future DFT design challenges include broader high-throughput screening, additional properties, nucleation and growth phenomena, and multiple interfaces.
Supercritical fluid extraction is the most successful and well-organized way to extract precious component. Supercritical Fluid Extraction is a separation technique in which one component (the extractant) is separated from another component (the matrix) using supercritical fluids. In supercritical fluid extraction technique carbon dioxide is commonly used as supercritical fluid. Carbon dioxide is non toxic, eco friendly, inexpensive and its critical temperature is also low, all these things make it the best extracting solvent. Supercritical fluids are highly compressed gases, which have combined properties of gases and liquids in an intriguing manner. Supercritical fluids can show the way to reactions, which are not easy or even impractical to achieve in conventional solvents. Supercritical fluid extraction is a rapid process compared to conventional extraction methods. It can be completed in 10 to 60 minutes. After extraction supercritical fluid can be easily separated from analyte by simply releasing pressure, leaving almost no trace and provides a pure extract. Supercritical fluid extraction is one of the best analytical tools which have many biological applications. In this review paper information about Supercritical fluid and Supercritical fluid extraction with its biological applications is provided.
Für Lithiumionenakkumulatoren mit hohen Energiedichten gibt es eine überaus große Nachfrage im Bereich tragbarer elektronischer Geräte und Elektrofahrzeuge. Weil die Energiedichten der Lithiumionenakkumulatoren vor allem vom verwendeten Kathodenmaterial abhängen, wird nach alternativen Kathodenmaterialien mit besserer Lithiumnutzung und höherer spezifischer Energiedichte intensiv geforscht. Insbesondere Ni-reiche Lithium-Übergangsmetalloxid-Schichtverbindungen können höhere Kapazitäten als das klassische LiCoO2 bei geringeren Kosten bereitstellen. Sie gelten als besonders vielversprechend, aber sie bergen noch große Herausforderungen bezüglich Lebensdauer, Wärmestabilität und Sicherheit. Hier wird umfassend beschrieben, wie gezielte Veränderungen an der Struktur oder an den Grenzflächen in einer Leistungssteigerung von Ni-reichen Kathodenmaterialien resultieren. Die zugrundeliegenden Mechanismen und die noch zu bewältigenden Herausforderungen werden ebenfalls diskutiert.
High energy-density lithium-ion batteries are in demand for portable electronic devices and electrical vehicles. Since the energy density of the batteries relies heavily on the cathode material used, major research efforts have been made to develop alternative cathode materials with a higher degree of lithium utilization and specific energy density. In particular, layered, Ni-rich, lithium transition-metal oxides can deliver higher capacity at lower cost than the conventional LiCoO2 . However, for these Ni-rich compounds there are still several problems associated with their cycle life, thermal stability, and safety. Herein the performance enhancement of Ni-rich cathode materials through structure tuning or interface engineering is summarized. The underlying mechanisms and remaining challenges will also be discussed.
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Lithium-ion battery which widely used as portable power sources with high energy density is greatly being increased due to the development and popularity of portable electronic device and vehicle. Lithium nickel oxide (LiNiO2) and their derivatives are promising positive cathode materials for next generation of lithium-ion batteries. LiNiO2 potentially offers a higher capacity at about 200 mAh/g. However it is more difficult to synthesized stoichiometric LiNiO2 because of the loss of lithium from host structure during high temperature calcination due the high vapor pressure of lithium and capacity fade when charging up to a high voltage (> 4.0V vs Li+Li) during deintercalation of lithium ion that affected cycling. The review is focused the electrochemical performance by substitution or effect doping of LiNiO2 and their derivative by other metals as a cathode materials for lithium ion batteries.
In the present work, we have studied the layered O3 and O2 structural LiCoO2–CoO2 pseudo-binary systems using the CALPHAD approach. In the O3 structural LiCoO2–CoO2 system, the O3-LiCoO2 phase is modeled based on the available thermodynamic information, especially the heat capacity data. The parameters of other phases, i.e. O3′ (ordered O3), H1-3 and O1, are accordingly adjusted based on the experimental and ab initio data. The whole system is then reassessed. In the O2 structural LiCoO2–CoO2 system, the O2-LiCoO2 phase is modeled based on the enthalpy difference from the O3-LiCoO2 phase. Other phases, i.e. O2′ (ordered O2), T#2, T#2′ (ordered T#2) and O6, are correspondingly described using appropriate sublattice models. The parameters for each phase are adjusted considering both the experimental and ab initio data. The thermodynamic calculations agree well with literature. Measured Li/LiCoO2 cell voltages were used to support the modeling and are well reproduced by the thermodynamic description.
In spite of numerous experimental and theoretical reports on LiNiO2, no consistent picture has emerged of the nature of its ground state. We have investigated the LixNiO2 system (0.1≤x≤1) by means of muon-spin spectroscopy and susceptibility to gain further insight from the effects of varying the magnetic ion concentration. Static magnetic order, most likely to be incommensurate to the spatial lattice period, was found for x≥0.6 at low temperatures (T), while disordered magnetism due to localized Ni moments appears for x=1/2–1/4 and, finally, Li0.1NiO2 exhibits almost fully nonmagnetic behavior down to the lowest T measured. The ground state of LiNiO2 is inferred to be a “static but short-range” A-type antiferromagnetic ordered system, in which the Ni3+ moments align ferromagnetically along the c axis in the NiO2 plane with an incommensurate modulation probably due to canting of the Ni3+ moments, but align antiferromagnetically between adjacent NiO2 planes.
The phase diagram of LixNiO2 (0<x<1) is calculated using a combination of first-principles energy methods and Monte Carlo simulations. The energy dependence of the Li-vacancy configurational disorder is parametrized with a cluster expansion. At room temperature ordered LixNiO2 phases appear in the phase diagram at x=1/4, 1/3, 2/5, 1/2, and 3/4. The predicted lithium-vacancy ordering at x=1/4 and 1/3 are in good agreement with experiments, while for the other phases no detailed experimental evidence has been reported. We predict a previously undetected phase at x=2/5 to dominate the phase diagram at low lithium content. The stability of ordered LixNiO2 structures is determined by short-ranged repulsive in-plane Li-Li interactions and long-range attractive interplane Li-Li interactions. These attractive interplane Li-Li interactions are due to the Jahn-Teller activity of Ni+3 ions. As a result, LixNiO2 behaves fundamentally different from LixCoO2 even though their host structures are identical and Co and Ni have similar ionic sizes.
The thermal degradation mechanism of LixNi1.02O2 and LixNi0.89Al0.16O2 (x = 0.50 and 0.30) was studied by in situ X-ray diffraction correlated with thermal gravimetric analysis coupled with mass spectrometry. The degradation mechanism appears to be the same for both types of samples. It consists of two steps: the first step, corresponding to the lamellar to pseudo-spinel transformation, is accompanied by an oxygen loss only for compounds with an initial (Li + M)/O ratio (M = Ni, Al) smaller than 3/4. The second step corresponds to the progressive transformation to a NiO-type structure, with an oxygen loss for both initial lithium compositions. The thermal stabilization obtained by partial aluminum substitution for nickel can be explained by the stability of the Al3+ ions in tetrahedral sites, which disrupts the cationic migrations necessary for the phase transformations observed upon increasing temperature to occur.
We present an efficient scheme for calculating the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set. In the first part the application of Pulay's DIIS method (direct inversion in the iterative subspace) to the iterative diagonalization of large matrices will be discussed. Our approach is stable, reliable, and minimizes the number of order N-atoms(3) operations. In the second part, we will discuss an efficient mixing scheme also based on Pulay's scheme. A special ''metric'' and a special ''preconditioning'' optimized for a plane-wave basis set will be introduced. Scaling of the method will be discussed in detail for non-self-consistent calculations. It will be shown that the number of iterations required to obtain a specific precision is almost independent of the system size. Altogether an order N-atoms(2) scaling is found for systems up to 100 electrons. If we take into account that the number of k points can be implemented these algorithms within a powerful package called VASP (Vienna ab initio simulation package). The program and the techniques have been used successfully for a large number of different systems (liquid and amorphous semiconductors, liquid simple and transition metals, metallic and semiconducting surfaces, phonons in simple metals, transition metals, and semiconductors) and turned out to be very reliable.
The structure of Li1−xNiO2 is studied as Li is electrochemically deintercalated from LiNiO2 with in situ X-ray diffraction methods. The electrochemical behavior of Li1−xNiO2 is investigated during the X-ray diffraction measurement and in other cells. We find three hexagonal phases and one monoclinic phase within the composition range 0.0 ⩽ x ⩽0.82. Three regions of x corresponding to two-phase coexistence are found by X-ray diffraction. The electrochemical measurements show strong peaks in in these coexisting phase regions in agreement with the X-ray data. A phase diagram for Li1−xNiO2 as a function of x is presented. A new in situ X-ray cell design, suitable for reliable operation with high voltage cathodes like Li1−xNiO2, is also described . Comparison to other recent work is made.
Thermodynamic data for the condensed phases of 78 elements as currently used by SGTE (Scientific Group Thermodata Europe) are tabulated. SGTE is a consortium of seven organisations in Western Europe engaged in the compilation of a comprehensive, self consistent and authoritative thermochemical database for inorganic and metallurgical systems. The data are being published here in the hope that they will become widely adopted within the international community as a sound basis for the critical assessment of thermodynamic data, thereby, perhaps, limiting unnecessary duplication of effort. The data for each phase of each element considered aie presented as expressions showing, as a function of temperature, the variation of (a) G-HSER, the Gibbs energy relative to the enthalpy of the “Standard Element Reference” ie the reference phase for the element at 298.15 K and (b) the difference in Gibbs energy between each phase and this reference phase (ie lattice stability). The variation of the heat capacity of the various phases and the Gibbs energy difference between phases are also shown graphically. For certain elements the thermodynamic data have been assessed as a function of pressure as well as temperature. Where appropriate a temperature— pressure phase diagram is also shown.Throughout this paper the thermodynamic data are expressed in terms of J mol−1. The temperatures of transition between phases have been assessed to be consistent with the 1990 International Temperature Scale (ITS90).
Lithium batteries are being intensively studied owing to the considerable challenge they represent for applications. From a fundamental point of view, the shape of the charge/discharge curves gives information on all the structural and physical properties modifications which occur during the intercalation/deintercalation process. Moreover, the electrochemical reaction is a way of synthesising metastable materials which cannot be obtained by classical methods. The ease of monitoring very accurately either the cell voltage (oxidation state of the material) or the number of electrons transferred (lithium content in the material) makes lithium batteries a new very convenient tool for the solid state chemist. Typical examples are presented.
The effective ionic radii of Shannon & Prewitt [Acta Cryst. (1969), B25, 925-945] are revised to include more unusual oxidation states and coordinations. Revisions are based on new structural data, empirical bond strength-bond length relationships, and plots of (1) radii vs volume, (2) radii vs coordination number, and (3) radii vs oxidation state. Factors which affect radii additivity are polyhedral distortion, partial occupancy of cation sites, covalence, and metallic character. Mean Nb5+-O and Mo6+-O octahedral distances are linearly dependent on distortion. A decrease in cation occupancy increases mean Li+-O, Na+-O, and Ag+-O distances in a predictable manner. Covalence strongly shortens Fe2+-X, Co2+-X, Ni2+-X, Mn2+-X, Cu+-X, Ag+-X, and M-H- bonds as the electronegativity of X or M decreases. Smaller effects are seen for Zn2+-X, Cd2+-X, In2+-X, pb2+-X, and TI+-X. Bonds with delocalized electrons and therefore metallic character, e.g. Sm-S, V-S, and Re-O, are significantly shorter than similar bonds with localized electrons.
The formal relationship between ultrasoft (US) Vanderbilt-type pseudopotentials and Blöchl's projector augmented wave (PAW) method is derived. It is shown that the total energy functional for US pseudopotentials can be obtained by linearization of two terms in a slightly modified PAW total energy functional. The Hamilton operator, the forces, and the stress tensor are derived for this modified PAW functional. A simple way to implement the PAW method in existing plane-wave codes supporting US pseudopotentials is pointed out. In addition, critical tests are presented to compare the accuracy and efficiency of the PAW and the US pseudopotential method with relaxed core all electron methods. These tests include small molecules (H2, H2O, Li2, N2, F2, BF3, SiF4) and several bulk systems (diamond, Si, V, Li, Ca, CaF2, Fe, Co, Ni). Particular attention is paid to the bulk properties and magnetic energies of Fe, Co, and Ni.
Technological improvements in rechargeable solid-state batteries are being driven by an ever-increasing demand for portable electronic devices. Lithium-ion batteries are the systems of choice, offering high energy density, flexible and lightweight design, and longer lifespan than comparable battery technologies. We present a brief historical review of the development of lithium-based rechargeable batteries, highlight ongoing research strategies, and discuss the challenges that remain regarding the synthesis, characterization, electrochemical performance and safety of these systems.
A method is given for generating sets of special points in the Brillouin zone which provides an efficient means of integrating periodic functions of the wave vector. The integration can be over the entire Brillouin zone or over specified portions thereof. This method also has applications in spectral and density-of-state calculations. The relationships to the Chadi-Cohen and Gilat-Raubenheimer methods are indicated.
The Li–Co–O and Li–Ni–O systems, used as cathodes in lithium ion batteries, have been investigated by means of ab initio calculations and empirical methods. An approach based on ab initio calculations to obtain accurate enthalpies of formation for transition metal oxides is proposed. With the obtained enthalpies of formation and the empirical entropy data, the Gibbs energy functions of the binary and ternary oxides in the Li–Co–O and Li–Ni–O systems are determined. To prove the accuracy of this thermodynamic model, we calculate the cell voltages of lithium ion batteries. Compared to the previously calculated results, which underestimate the cell voltages of lithium ion batteries, our calculations are in good agreement with the experimental data. The present theoretical approaches are reliable to evaluate the thermodynamic and electrochemical properties of lithium-containing transition metal oxides.
In the present paper the effect of cobalt, as substituent, on the stabilization of layered lithium-nickel oxides has been shown. Using an original method of synthesis, the series LiCo1−xNixO2 (O<x<1), has been obtained and analysed by X-ray powder diffraction. The electrochemical characteristics has been obtained in a three-electrode glass cell using standard electrolyte of 1 M LiClO4 in propylene carbonate:dimethyoxyethene. It has been demonstrated by cyclic voltammetry that the reversibility in the ternary LiNiCoO system increases with the Co content due to the enhanced stability and structural order of materials.
The structural, magnetic, and electrochemical properties of the LiNi{sub 1-x}CoO samples with x= 0, 0.05, 0.1, and 0.25 have been investigated by powder X-ray diffraction analyses, magnetic susceptibility () measurements, and electrochemical charge and discharge test in non-aqueous lithium cell. According to the structural analyses using a Rietveld method, the occupancy of the Ni ions in the Li layer was estimated to be below 0.01 for all the samples and was eventually independent of x. The temperature (T) dependence of ¹ obtained with the magnetic field H=10 kOe indicated that all the samples are a Curie-Weiss paramagnet down to 100K. At low T, all the samples entered into a spin-glass-like phase below T{sub f}. The magnitude of T{sub f} was found to decrease almost linearly with x, as in the case for the x dependences of the lattice parameters of a{sub h}- and c{sub h}-axes, Weiss temperature, and effective magnetic moment. It is, therefore, found that the change of the magnetic properties with x is simply explained by a dilution effect due to the increase of the quantity of Co{sup 3+} ions. On the other hand, the electrochemical measurements demonstrated that the irreversible capacity at the initial cycle is drastically decreased by the small amount of Co ions. Furthermore, the discharge capacity (Q{sub dis}) for the x=0.05 and 0.1 samples are larger than that for the x=0 sample; namely, Q{sub dis}=180 mAh g¹ for x=0, Q{sub dis}=217 mAh g¹ for x=0.05, and Q{sub dis}=206 mAh g¹ for x=0.1. Comparing with the past results, the amount of Ni ions in the Li layer is found to play a significant role for determining the magnetic and electrochemical properties of LiNi{sub 1-x}CoO. - Graphical Abstract: The inter-relationship between structural, magnetic, and electrochemical properties of the lithium insertion materials LiNi{sub 1-x}CoO with 0{
The thermodynamic modeling of the LiCoO2–CoO2 pseudo-binary system, a positive electrode material of Li-ion batteries, was performed using the CALPHAD technique. The O3-LiCoO2 and the O1-CoO2 phases were described using the four-sublattice model with the formula (Li,V a)1/2(Li,V a)1/2(Co)1(O)2, and the three-sublattice model with the formula (Li,V a)1(Co)1(O)2. The H1_3 hybrid phase was treated as a non-stoichiometric compound. The thermodynamic quantities, such as the phase equilibria, formation enthalpies and cell voltage (vs. Li/Li+), were in agreement with data reported in the literature.
LiNi2O4 spinel-type phases were prepared by thermal treatment of electrochemically deintercalated layered Li0.5NiO2. The phase transformation was followed by 7Li NMR, showing a gradual change of the signal from the layered compound. The characteristic signal of the latter (related to local Li/vacancy and Ni3+/Ni4+ ordering) vanishes after heating to 150 °C and is replaced by a new signal showing faster exchange kinetics (originating from Ni3+/Ni4+ hopping around Li), which progressively transforms into a broad distribution of signals. Around 200 °C, a set of three positively shifted signals is observed, corresponding to the appearance of the spinel phase as seen from XRD; these signals disappear after heating to 240 °C, corresponding to the beginning of decomposition of the spinel into a disordered R3̄m type phase with oxygen evolution as previously shown by Guilmard et al. (Chem. Mater. 2003, 15, 4476 and 4484). In an ideal LiNi2O4 spinel, only one 7Li NMR signal is expected. DFT (GGA) calculations were carried out and show that the mechanism for the electron spin density transfer from NiO6 octahedra to corner-sharing LiO4 tetrahedra with close to 120° Ni−O−Li configuration is a delocalization one, although the p orbitals on oxygen do not present ideal orientation, leading to a much weaker transfer compared to cases where both Ni and Li are in octahedral coordination with 180° Ni−O−Li configuration. The complex but well-defined experimental NMR signals consistently observed show that the material is far from the ideal spinel structure. However, it could not be correlated to the actual stoichiometry of the compound. It was therefore tentatively assigned to structural defects resulting from incomplete migration of Ni ions from their site to the Li layer in the pristine compound, such as partial occupation of tetrahedral sites.
A study of the Li/LiâNi{sub 1.02}Oâ system at high potential has shown the successive formation of two phases with O3 (AB CA BC) and O1 (AB) oxygen packings, respectively, near the NiOâ composition. For the LiâNi{sub 1+z}Oâ phases with z ⥠0.07, only the O3 packing is observed at the end of lithium deintercalation: the extra nickel ions present in the interslab spaces destabilize the O1 type packing. The nonhomogeneous distribution of extra nickel ions from one interslab space to another leads to the presence of stacking faults in both phases. Lithium can be reversibly reintercalated into the NiOâ phase. Good stability is observed at low charge-discharge rates during long-term cycling of the Li/LiâNi{sub 1.02}Oâ system over a large potential range. This study also provided evidence for inhomogeneity in the starting material at the crystallite scale. The Li{sub 0.98}Ni{sub 1.02}Oâ material corresponds to a mixture of various phases with very similar stoichiometries. The crystallites which are closest to the ideal stoichiometry form an O1 type phase which is stable at high potential, whereas those which are farthest from stoichiometry lead to an O1 type phase which is slowly transformed into a new phase, characterized by an O3 type packing, through a Ni{sup 3+} migration from the slab to the interslab space.
We report the structural and thermal characteristics of highly delithiated (lithium extracted) compounds LixNiO2, which can be called “nickel dioxide.” We obtained Li0.10NiO2 and Li0.04NiO2 by treating LiNiO2 with sulfuric acid. Both products contained phases with NiO2 stacking similar to cadmium chloride (O3-type), but the latter also included a phase with NiO2 stacking similar to cadmium iodide (O1-type). We examined their thermal behavior using high temperature X-ray diffraction analysis together with thermogravimetric analysis and found that novel polymorphs, with similar chemical compositions but different structures, were obtained by heating them at appropriate temperatures. We discuss these results together with those for LixNiO2 obtained by electrochemical delithiation. We also report acid-treated products derived from Li0.93Ni1.07O2.
An Hand des Systems NiO-CoO wird ein Verfahren beschrieben und experimentell überprüft, das es gestattet, mittels EMK-Messungen die thermodynamischen Daten von solchen Mischoxid-systemen zu bestimmen, bei denen die beiden Oxide ähnliche Freie Bildungsenthalpien besitzen. Es fand dabei eine galvanische Kette des Typs Pt/Me, MeO/ZrO2 (+CaO)/Me, MeOss/Pt Verwendung. Für das System NiO-CoO ergab sich bei 1000 K eine geringe positive Abweichung vom Raoult'schen Gesetz, Während sich das System bei 1300 K bereits annähernd ideal verhält. A method is described to determine thermochemical data for systems of mixed oxides characterized by the fact that the Gibbs free energy of formation of the component oxides is similar in magnitude. The method is based upon the measurement of the electromotive force of an appropriate galvanic cell and has been successfully verified for the system NiO-CoO. In this study a cell of the type Pt/Me, MeO/ZrO2 (+CaO)/Me, MeOss/Pt has been employed. For the system investigated, i.e., NiO-CoO, a small positive deviation from Raoult's law was found at 1000 K, whereas at 1300 K an almost ideal behavior was met.
The preparation and characterization of LiNi1−xCoxO2 compounds (0 ⩽ x ⩽ 1) having a space group Rm, for 4 volt secondary lithium cells were investigated. By developing processing methods, homogeneous LiNi1−xCoxO2 samples were obtained and characterized by XRD, ir and magnetic susceptibility measurements. When increasing x in LiNi1−xCoxO2, the unit cell dimensions a and c in hexagonal setting, decreased almost linearly as a function of x. Magnetic susceptibility measurements indicated that LiNi1−xCoxO2 consists of low-spin states of Co3+ (t62g e0g) and Ni3+ (t62ge1g). All samples may be used as positive electrodes in nonaqueous lithium cells. Of these, LiCoO2 showed the highest working voltage and about 120 mAh g−1 of rechargeable capacity, and LiNiCoO2 showed the lowest working voltage and about 130 mAh g−1 of rechargeable capacity in the voltage range 2.5–4.2 V in 1 M LiClO4 propylene carbonate solution. LiNiO2 has more than 150 mAh g−1 of rechargeable capacity with working voltages above 3.5 V. Secondary lithium ion cells which consisted of LiNi1−xCoxO2 cathodes and natural graphite anodes, were also examined and the specific problems of establishing an innovative secondary lithium cell were discussed.
Heat capacity of lithium nickel oxide of nearly stoichiometric composition (Li0.99Ni1.01O2) was measured using an adiabatic calorimeter between 13 and 300 K. Abnormally large heat capacity was observed below 20 K, and it seems be related to the spin glass transition observed in the magnetic susceptibility measurements of nearly stoichiometric samples of Li1−xNi1+xO2. The heat capacity value above 100 K was compared with LiCoO2, and it was found that the heat capacity of Li0.99Ni1.01O2 is much larger than that of LiCoO2 in spite of almost the same atomic weight of Ni and Co. The heat capacity difference was discussed in terms of the lattice vibrations and bond strength in the crystals.
Lithium de-intercalation from the nearly stoichiometric LiNiO2 phase (z = 0.02 in Li1-zNi1+zO2) entails a structural transition from the rhombohedral to the monoclinic symmetry. As this macroscopic lattice distortion appears in a wide composition range (0.50<x<0.75, x in 'LixNiO2'), a detailed electron diffraction study has been performed on the intermediate Li0.63Ni1.02O2 composition in order to find the driving force of this transition. A superstructure cell, four times bigger than the one deduced from the X-ray Rietveld refinement, has been derived from the electron diffraction data. The existence of such a superstructure is suggestive of a possible ordering of vacancies among the lithium layers. Indeed, the existence of three lithium crystallographic positions in this supercell allows us to understand, on the one hand, why a monoclinic distortion occurs, and, on the other hand, its composition limits (Li(0.50)square(0.25)square(0.25)'NiO2 and Li(0.50)Li(0.25)square(0.25)'NiO2). Moreover, the presence of twinned crystals has also been shown in this monoclinic phase and has been related to the structural change which occurs on lithium de-intercalation from the pristine rhombohedral Li0.98Ni1.02O2 phase.
LiNi1-yTiyO2 (y ≤ 0.15) layered oxides were synthesized at high temperature by solid-state reactions. Rietveld refinements of their X-ray and neutron diffraction patterns showed that these phases were characterized by an α-NaFeO2-type structure with the following cationic distribution: (Li1-zNi2+z)3b(Ti4+tNi2+t+zNi3+1-z-2t)3aO2 [t = y(1 + z)]. The amount of Ni2+ ions in the lithium site increases with y. A magnetic study confirmed the presence of paramagnetic ions in the interslab space and, therefore, the cationic distribution. These materials used as positive electrode in lithium batteries show reversible behavior. A large decrease of the capacity is observed with increasing y, because of the presence of extra nickel ions in the lithium sites. For the “LixNi0.95Ti0.05O2” composition, 144 mA h/g are obtained in discharge at the 14th cycle at the C/20 rate. The “LixNi1-yTiyO2” phases were characterized for y = 0.05 and 0.10: the simultaneous presence of titanium ions in the slab and of a significant amount of extra nickel ions in the lithium sites prevents phase transitions upon cycling.
Single phase LiCo1 − y
Niy
O2 (y = 0.4 and 0.5) with fine particles and high homogeneity was synthesized by “chimie douce” assisted by citric acid as the polymeric agent and investigated as positive electrodes in rechargeable lithium batteries. The long-range and short-range structural properties are investigated with experiments including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and superconducting quantum interference device magnetometry. The physicochemical properties of the powders (crystallinity, lattice constants, grain size) have been investigated in this composition. The powders adopted the α-NaFeO2 structure as it appeared from XRD and FTIR results. Magnetic measurements shows signal at low temperature attributed to the magnetic domains in the nanostructure sample from which we estimated that the cation mixing are 3.35 and 4.74% for y = 0.4 and 0.5 in LiCo1 − y
Niy
O2, respectively. LiCo0.5Ni0.5O2 cathode yields capacity (135 mAh g−1) compared to LiCo0.6Ni0.4O2 cathode (147 mAh g−1) when discharged to a cutoff voltage of 2.9 V vs. Li/Li+. Lower capacity loss and higher discharge efficiency percentage are observed for the cell of LiCo0.6Ni0.4O2 cathode.
The investigation of structural changes of intercalation materials during cycling is of primary importance to understand the factors that limit their cyclability. In particular in-situ measurements, allowing the simultaneous acquisition of structural and electrochemical data, consent to directly correlate the cycling performance of the material under test to its structure evolution and vice versa.The energy dispersive X-ray diffraction (EDXD) technique has been applied to the study of the structural evolution of LiNi0.8Co0.2O2 during several charge−discharge cycles performed with increasing anodic limits. This way of monitoring the effect of Li ions intercalation−deintercalation process on the host materials lattice parameters proved to be a valid alternative to the traditional angle dispersive X-ray diffraction (ADXD) method, solving some of its problems, first of all the question of the X-ray absorption.The results described in this paper confirm what reported in previous literature works based on in-situ ADXD and deepen the study of the LiNi0.8Co0.2O2 structural changes, with large oversampling and good statistical accuracy, extending the investigation to the first 7 cycles with increased anodic limits approaching full delithiation.
The synthesis and characterization of
for a 4 V secondary lithium cell was done. The
was prepared by ten different methods and characterized by x‐ray diffraction and electrochemical methods.
prepared from
and
[or
] exhibited more than 150 mAh · g−1 of rechargeable capacity in the voltage range between 2.5 and 4.2 V in 1M
propylene carbonate solution. The reaction mechanism was also examined and explained in terms of topotactic reaction. Lithium
nickelate(III) (R3̅m;
,
in hexagonal setting) was oxidized to nickel dioxide (R3̅m;
,
) via
having a monoclinic lattice (C2/m). The nickel dioxide could be reversibly reduced to lithium nickelate(III). Factors affecting
the electrochemical reactivity of
are given and the possibility of using
for 4 V secondary lithium cells is described.
The magnetic nature of lithium insertion materials of LiNi1−xCoxO2 (x = 0, 1/4, 1/2, 3/4, and 1) were investigated by means of positive muon-spin rotation/relaxation (μ+SR) spectroscopy combined with X-ray diffraction (XRD) analyses and susceptibility measurements. Zero field μ+SR spectra for all the samples below 300 K were well fitted by a dynamic Kubo–Toyabe function, indicating the existence of randomly oriented magnetic moments even at 2 K, i.e., disordered state. The field distribution width Δ due to magnetic Ni3+ ions decreases exponentially with increasing x, suggesting that the Co substitution is likely to simply dilute Ni moments. This also supports that cobalt and nickel ions are homogeneously distributed in a solid matrix even in a muon-scale (microscopically), which is consistent with the results of macroscopic measurements.
Samples of Li1 − zNi1 + xO2 with various x values were synthesized and their electrochemical properties, phase transitions, and ordering phenomena were investigated comparatively. In order to synthesize samples with a small x value, an excess lithium was used as a starting material to compensate for lithium loss during the calcination process. A stoichiometric sample with a large reversible capacity of more than 200 mAh g−1 is also described.
An approach for electronic structure calculations is described that generalizes both the pseudopotential method and the linear augmented-plane-wave (LAPW) method in a natural way. The method allows high-quality first-principles molecular-dynamics calculations to be performed using the original fictitious Lagrangian approach of Car and Parrinello. Like the LAPW method it can be used to treat first-row and transition-metal elements with affordable effort and provides access to the full wave function. The augmentation procedure is generalized in that partial-wave expansions are not determined by the value and the derivative of the envelope function at some muffin-tin radius, but rather by the overlap with localized projector functions. The pseudopotential approach based on generalized separable pseudopotentials can be regained by a simple approximation.
Lithiated metal oxides LiCo1−yNiyO2 were synthesized by a sol–gel method using succinic acid as chelating agent. Microcrystalline materials were formed by calcination in oxygen at 800°C. The physicochemical properties of the powders (crystallinity, lattice constants, size grain) has been investigated in the compositional range 0≤y≤1. Structural studies show that a layered single phase was obtained. The local cationic environment has been studied by Raman and FTIR spectroscopy. The changes in the vibrational spectra are well related to those observed by X-ray diffraction. It is shown that the lithium predominant layers are preserved in the entire range of substitution. Pelletized LiCo1−yNiyO2 powders (0.2≤y≤1.0) were tested in Li//LiCo1−yNiyO2 cells by galvanostatic titration. These cells have an initial capacity of 140 mAh/g in the voltage range 2.8–4.2 V and show attractive charge–discharge profiles upon cycling.
We report the thermal behavior of Li1-yNiO2 up to 300°C which we investigated using thermogravimetry (TG) and differential scanning calorimetry (DSC). The decomposition mechanism was studied using the X-ray diffraction data obtained for the thermally decomposed products. At about 200°C Li1-yNiO2 turned into Li(1-y)/(2-y)Ni1/(2-y)O which has a rock-salt structure. This was accompanied by oxygen evolution. A significant exothermic process was observed for compounds with y ≥ 0.7 and this resulted in products with disordered rock-salt structures. Using these results, we propose a mechanism in which the exothermic behavior is caused by random cation mixing.
Software for calculation of phase diagrams and thermodynamic properties have been developed since the 1970's. Software and computers have now developed to a level where such calculations can be used as tools for material and process development. In the present paper some of the latest software developments at Thermo-Calc Software are presented together with application examples. It is shown how advanced thermodynamic calculations have become more accessible since: •—|A more user-friendly windows version of Thermo-Calc, TCW, has been developed.•—|There is an increasing amount of thermodynamic databases for different materials available.•—|Thermo-Calc can be accessed from user-written software through several different programming interfaces are available which enables access to the thermodynamic software from a user-written software. Accurate data for thermodynamic properties and phase equilibria can then easily be incorporated into software written in e.g. C++, Matlab and FORTRAN.Thermo-Calc Software also produces DICTRA, a software for simulation of diffusion controlled phase transformations. Using DICTRA it is possible to simulate processes such as homogenization, carburising, microsegregation and coarsening in multicomponent alloys. The different models in the DICTRA software are briefly presented in the present paper together with some application examples.
A crystal chemistry study of the LiNi1−yCoyO2 system has been realized. These materials exhibit a layered structure (R m-O3 type) for 0≤y≤1. They have been used as positive electrode in lithium batteries. Up to 0.6 lithium atom can be reversibly deintercalated for cell voltages lying in the 3.5–4 V range. For 0≤y≤0.5, the shape of all the charge curves is very similar with a small decrease in potential when y increases due to the influence of cobalt which, however, does not participate significantly in the redox process. For materials with a larger cobalt amount (y≥0.6) the nickel ions are first oxidized to the tetravalent state, before the cobalt ions. This behavior is confirmed by the evolution of the electronic properties versus the lithium amount.
The LiNiO2LiCoO2 system exhibits a complete solid solution. These materials crystallize in the rhombohedral system with a layered structure. They have been used as positive electrode in lithium batteries. Up to 0.5 lithium atom can be reversibly deintercalated in the 3.5 to 4.0 V potential range. The highest specific energy (close to 500 W h/kg) is obtained in the LixNi0.7Co0.3O2 system. Moreover, the very small volume change upon deintercalation increased their interest for application point of view.
Recent developments of materials for rechargeable lithium batteries are highlighted. The reactions using advanced batteries consist of lithium ion insertion into and extraction from a solid matrix without the destruction of core structures, (called topotactic reaction) enable us to study systematically battery materials. By applying a hard-sphere model the optimum chemical composition and element in terms of volumetric capacity in Ah·cm-3 are indicated to be □MeO2 or LiMeO2 (Me = transition metal elements). The calculated values, assuming one electron transfer per a transition metal ion, are in the range 1.15-1.5 Ah·cm−3 for both □MeO2 and LiMeO2 using available structural data, which is alone merely attainable using transition metal dioxides. The approximate operating voltages for the reaction Li + □MeO2 ⇆ LiMeO2 are pictured gainst the number of d-electrons. The order of operating voltages of transition metal (di) oxides is approximately; 3d>4d>5d and dn<dn+1 (n=0 to 6) distributed in the voltage between 0.5 and 4.5 V versus a lithium electrode. From these results, we discuss why transition metal (di) oxides are the most attractive materials for advanced lithium batteries. The specific problems in developing the insertion materials based on metal (di) oxides further are also discussed.
The thermodynamics and phase transitions in lithium intercalation oxides are discussed. Changes in the host structure can be driven by configurational Li-vacancy interactions, variations in electron count or by changes in the stability of the oxygen packing. The formalism to predict the lithium-vacancy ordered configurations and their free energy is presented and calculations of the phase diagram of LixCoO2 in the spinel and layered structure using this formalism are reviewed. Layered LixCoO2 has the richest phase diagram with ordering and staging transitions, and changes in host structure at low lithium contents. In general we find relatively low order–disorder transitions due to the strong screening of the lithium–lithium interaction by oxygen. From calculating the energy difference between the spinel and layered structure for several transition metal oxides it is found that a driving force for transition to spinel will always exist when a layered lithium transition metal oxide is delithiated. The limitations of current first principles methods in studying electronic transitions are discussed.
While has been widely studied in the past 15 years as a promising positive electrode material in lithium‐ion batteries, suprisingly, many questions are still unanswered concerning the electrochemical characteristics of the lithium intercalation material. Among these is the existence of an end member phase on complete lithium deintercalation. The use of dry plastic lithium‐ion battery technology has allowed the construction of an in situ x‐ray diffraction cell which allows structural characterization of at x values at and close to 0 for the first time. Instead of the expected destruction of the core structure of by a drastic increase in structural disorder, an increase in crystallographic quality occurred as x approached 0. For the first time, the end member phase was isolated. This phase is a hexagonal single‐layered phase (O1) believed to be isostructural with and has lattice parameters of a = 2.822 Å and c = 4.29 Å. The phase converted immediately back to a three‐layer (O3) delithiated type phase on lithium reinsertion. Electrochemical studies show that 95% of lithium can be reinserted back into the structure on complete delithiation and reversible cycling properties are maintained when cycled back to 4.2 V.
LiCoO2, LiNiO2 and their solid solution, LiNi1−xCoxO2, are important cathode materials for lithium ion batteries. Samples in this system were synthesized by solid state reaction of Co3O4, NiO and Li2CO3 or LiOH·H2O. Their lattice parameters were determined by Rietveld refinement. High temperature drop solution calorimetry in molten 3Na2O·4MoO3 and 2PbO·B2O3 solvents at 974 K was performed to determine the enthalpy of formation from the constituent oxides plus oxygen and the enthalpy of mixing in the solid solution series. There are approximately linear correlations between the lattice parameters, the enthalpy of formation from oxides (Li2O, NiO and CoO) plus O2 and the Co content in the compounds. The solid solution of LiCoO2 and LiNiO2 is almost ideal, showing a small positive enthalpy of mixing. The enthalpy of formation of LiCoO2 from oxides (Li2O, NiO and CoO) and oxygen at 298 K is −142.5±1.7 kJ/mol (from sodium molybdate calorimetry) or −140.2±2.3 kJ/mol (from lead borate calorimetry). That of LiNiO2 is −56.2±1.5 kJ/mol (from sodium molybdate calorimetry) or −53.4±1.7 kJ/mol (from lead borate calorimetry). The cobalt compound is thus significantly more stable than its nickel analogue. The phase assemblage LiCoO2, Li2O and CoO is seen at a lower oxygen pressure at constant temperature than the assemblage Co3O4/CoO, reflecting the stabilization of Co(III) in the ternary Li–Co–O system.
- T Ohzuku
- A Ueda
- M Nagayama
T. Ohzuku, A. Ueda, M. Nagayama, J. Electrochem. Soc. 140 (1993) 1862–1870.
- H J Monkhorst
- J D Pack
H.J. Monkhorst, J.D. Pack, Phys. Rev. B 13 (1976) 5188–5192.
- C Chazel
- M Ménétrier
- D Carlier
- L Croguennec
- C Delmas
C. Chazel, M. Ménétrier, D. Carlier, L. Croguennec, C. Delmas, Chem. Mater. 19
(2007) 4166–4173.
- J.-O Andersson
- T Helander
- L Höglund
- P Shi
- B Sundman
J.-O. Andersson, T. Helander, L. Höglund, P. Shi, B. Sundman, CALPHAD 26
(2002) 273–312.
- G Kresse
- J Furthmüller
G. Kresse, J. Furthmüller, Phys. Rev. B 54 (1996) 11169–11186.
- M Guilmard
- L Croguennec
- D Denux
- C Delmas
M. Guilmard, L. Croguennec, D. Denux, C. Delmas, Chem. Mater. 15 (2003)
4476–4483.
- C Nordling
- J Österman
C. Nordling, J. Österman, Physics Handbook for Science and Engineering, 8th
ed., Studentlitteratur AB, Lund, 2006.
- H Arai
- M Tsuda
- K Saito
- M Hayashi
- K Takei
- Y Sakurai
H. Arai, M. Tsuda, K. Saito, M. Hayashi, K. Takei, Y. Sakurai, J. Solid State Chem.
163 (2002) 340–349.
- A E Ghany
- A M A Hashem
- H A M Abuzeid
- A E Eid
- H A Bayoumi
- C M Julien
A.E. Abdel Ghany, A.M.A. Hashem, H.A.M. Abuzeid, A.E. Eid, H.A. Bayoumi,
C.M. Julien, Ionics 15 (2008) 49–59.
- W Masataka
W. Masataka, Mater. Sci. Eng. R 33 (2001) 109–134.
- L Croguennec
- E Suard
- P Willmann
- C Delmas
L. Croguennec, E. Suard, P. Willmann, C. Delmas, Chem. Mater. 14 (2002)
2149–2157.
- T Ohzuku
- A Ueda
- M Nagayama
- Y Iwakoshi
- H Komori
T. Ohzuku, A. Ueda, M. Nagayama, Y. Iwakoshi, H. Komori, Electrochim. Acta
38 (1993) 1159–1167.