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a) Simulated XRD patterns of NbO2 and lithiated NbO2. Crystal structure model of b) optimized pristine NbO2 and Li position at Li–NbO2 involving c) Li‐center and d) Li‐off‐center positions. All structures are shown from ab planes and bc planes (lithium: green balls, niobium: blue balls, and oxygen: red balls).
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Niobium dioxide (NbO2) features a high theoretical capacity and an outstanding electron conductivity, which makes it a promising alternative to the commercial graphite negative electrode. However, studies on NbO2 based lithium‐ion battery negative electrodes have been rarely reported. In the present work, NbO2 nanoparticles homogeneously embedded i...
Citations
... For instance, Ji et al. studied NbO 2 nanoparticles embedded in a carbon matrix for LIB applications. 21 Cho et al. demonstrated that chemically etched NbO 2 exhibited superior Li charge storage properties. 22 Park et al. showed that NbO 2 in Nb 2 O 5 /NbO 2 composites enhances rate performance. ...
... In the first cathodic scan, two peaks are observed around 0.86 and 0.65 V, possibly due to the formation of SEI and Li intercalation. In the anodic scan, two broad peaks around 0.99 and 2.06 V are observed, which could be attributed to the delithiation of Li. 21 In the subsequent cycles, one new cathodic peak emerges around 1.62 V, corresponding to the lithiation process, and the SEI peak at 0.86 V disappeared, indicating irreversible SEI formation. In the anodic scan, the broad peak around 2.06 V shifted to a lower potential of 1.83 V, possibly due to the activation of the electrode. ...
... In the anodic scan, the broad peak around 2.06 V shifted to a lower potential of 1.83 V, possibly due to the activation of the electrode. 21 It is to be noted that the CV peaks are almost overlapping from the third cycle onward, indicating a highly stable and reversible Li intercalation and deintercalation process. A similar lithiation/delithiation process has been observed in the GCD profiles measured at 100 mA g −1 and is shown in Figure 2b. ...
... The predominant Li + -uptake and Li + -release peaks presented in Figure 4a are reported also for the cycling of Nb-based oxides [87] such as LiNbO 2 [88], porous crystalline LiNbO 3 [53], K x Li y NbO 3 [77], and niobium-oxide polymorphs [16,55,58,63,75,87,[116][117][118][119]. They were observed also for metal oxides such as iron oxide [120,121], cobalt oxide [121,122], titanium oxide [123], molybdenum oxide [124,125], and copper oxide [122]. ...
... The Li + uptake II was allocated to the conversion reaction of the metal oxide [119] and may be tentatively attributed to the Nb 4+ /Nb 3+ redox couple [16]. Furthermore, peak II is observed in the first CV cycle from electrodes consisting of NbO 2 grains embedded inside a carbon matrix [118], and for mesoporous Nb 2 O 5 particles/grains embedded in carbon additives [116]. They were attributed to the lithiation of the resin-derived hard carbon [118] and the formation of a solid-state interphase layer [116]. ...
... Furthermore, peak II is observed in the first CV cycle from electrodes consisting of NbO 2 grains embedded inside a carbon matrix [118], and for mesoporous Nb 2 O 5 particles/grains embedded in carbon additives [116]. They were attributed to the lithiation of the resin-derived hard carbon [118] and the formation of a solid-state interphase layer [116]. The predominant Li + uptake III is attributed to SEI film formation by Refs. ...
Li-Nb-O-based insertion layers between electrodes and electrolytes of Li-ion batteries (LIBs) are known to protect the electrodes and electrolytes from unwanted reactions and to enhance Li transport across interfaces. An improved operation of LIBs, including all-solid-state LIBs, is reached with Li-Nb-O-based insertion layers. This work reviews the suitability of polymorphic Li-Nb-O-based compounds (e.g., crystalline, amorphous, and mesoporous bulk materials and films produced by various methodologies) for LIB operation. The literature survey on the benefits of niobium-oxide-based materials for LIBs, and additional experimental results obtained from neutron scattering and electrochemical experiments on amorphous LiNbO3 films are the focus of the present work. Neutron reflectometry reveals a higher porosity in ion-beam sputtered amorphous LiNbO3 films (22% free volume) than in other metal oxide films such as amorphous LiAlO2 (8% free volume). The higher porosity explains the higher Li diffusivity reported in the literature for amorphous LiNbO3 films compared to other similar Li-metal oxides. The higher porosity is interpreted to be the reason for the better suitability of LiNbO3 compared to other metal oxides for improved LIB operation. New results are presented on gravimetric and volumetric capacity, potential-resolved Li+ uptake and release, pseudo-capacitive fractions, and Li diffusivities determined electrochemically during long-term cycling of LiNbO3 film electrodes with thicknesses between 14 and 150 nm. The films allow long-term cycling even for fast cycling with rates of 240C possessing reversible capacities as high as 600 mAhg−1. Electrochemical impedance spectroscopy (EIS) shows that the film atomic network is stable during cycling. The Li diffusivity estimated from the rate capability experiments is considerably lower than that obtained by EIS but coincides with that from secondary ion mass spectrometry. The mostly pseudo-capacitive behavior of the LiNbO3 films explains their ability of fast cycling. The results anticipate that amorphous LiNbO3 layers also contribute to the capacity of positive (LiNixMnyCozO2, NMC) and negative LIB electrode materials such as carbon and silicon. As an outlook, in addition to surface-engineering, the bulk-engineering of LIB electrodes may be possible with amorphous and porous LiNbO3 for fast cycling with high reversible capacity.
... [42] In addition, other peaks at 1.3/ 1.6 V are observed, which should be ascribed to the lithiation/delithiation processes of NbO 2 . [44] Furthermore, in(ex) situ XRD measurements were used to verify the above electrochemical reaction process as analyzed above, and clarify the inherent lithium storage mechanism of O-CNO anode, as well as the phase conversion and structural changes during (dis)charging process. Figure 5a shows the in situ XRD patterns from 10 to 50°over the first original discharge/charge cycles at 0.1 A g −1 with the potential window from 0.01 to 3.0 V (vs Li/Li + ), and a sweep rate of 7°min −1 is set for this. ...
The orthorhombic CuNb2O6 (O‐CNO) is established as a competitive anode for lithium‐ion capacitors (LICs) owing to its attractive compositional/structural merits. However, the high‐temperature synthesis (>900 °C) and controversial charge‐storage mechanism always limit its applications. Herein, we develop a low‐temperature strategy to fabricate a nano‐blocks constructed hierarchical accordional O‐CNO framework by employing multi‐layered Nb2CTx as the niobium source. The intrinsic stress‐induced formation/transformation mechanism of the monoclinic CuNb2O6 to O‐CNO is tentatively put forward. Furthermore, the integrated phase conversion and solid solution lithium‐storage mechanism is reasonably unveiled with comprehensive in(ex)‐situ characterizations. Thanks to its unique structural merits and lithium‐storage process, the resulted O‐CNO anode is endowed with a large capacity of 150.3 mAh g−1 at 2.0 A g−1, along with long‐duration cycling behaviors. Furthermore, the constructed O‐CNO based LICs exhibit a high energy (138.9 Wh kg−1) and power (4.0 kW kg−1) densities with a modest cycling stability (15.8% capacity degradation after 3000 consecutive cycles). More meaningfully, the in‐depth insights into the formation and charge‐storage process here can promote the extensive development of binary metal Nb‐based oxides for advanced LICs.
... Carbon materials mainly include porous carbon [8], graphene oxide (GO) [9,10], carbon nanotubes (CNTs) [11], carbon nanofibers (CNFs) [12,13] and so on. Porous carbon material is a kind of carbon material with developed pore structure and large specific surface area [14], which is made of polymer resin [15,16] or biomass [17][18][19] through direct pyrolysis, template agent or chemical activator activation. It has a wide range of sources, low price and green environmental protection, and more importantly, its unique pore structure is liable to transport ions in electrolyte and shorten the diffusion distance of ions [20]. ...
In today’s era, there are numerous problems with energy depletion, therefore how to efficiently convert and store energy is a big challenge. Carbon is widely used in electrode materials because its good tailorability, inexpensiveness and versatility. Melamine formaldehyde resin (MF) containing large amounts of nitrogen (N) and amino groups, which can be used as carbon source and nitrogen source to the electrode material, and obtain superior electrochemical performance. However, the carbon residue rate of MF carbonization is low and the pore structure is underdeveloped. So, in-depth study is needed to improve this phenomenon. Starting from the preparation of MF, this paper introduces the carbonization methods, pore-forming methods, doping methods and composites with metal or other carbon materials to prepare electrode materials with better performance and longer life.
... Therefore, some researchers have begun exploring direct carbon coating. For example, Cui et al. [33] use CTAB to achieve carbon coating of porous silicon micron-sized particles for lithium battery anodes, Cheng et al. [34] use Bis-GMA to achieve carbon-coated NbO2 for lithium battery anodes and Guo et al. [35] use PAN to achieve carbon-coated SnO2 for lithium battery anodes. ...
LiFePO4 (LFPO)has great potential as the cathode material for lithium-ion batteries; it has a high theoretical capacity (170 m·A·h·g−1), high safety, low toxicity and good economic benefits. However, low conductivity and a low diffusion rate inhibit its future development. To overcome these weaknesses, three-dimensional carbon-coated LiFePO4 that incorporates a high capacity, superior conductivity and low volume expansion enables faster electron transport channels. The use of Cetyltrimethyl Ammonium Bromid (CTAB) modification only requires a simple water bath and sintering, without the need to add a carbon source in the LFPO synthesis process. In this way, the electrode shows excellent reversible capacity, as high as 159.8 m·A·h·g−1 at 2 C, superior rate capability with 97.3 m·A·h·g−1at 5 C and good cycling ability, preserving ~84.2% capacity after 500 cycles. By increasing the ion transport rate and enhancing the structural stability of LFPO nanoparticles, the LFPO-positive electrode achieves excellent initial capacity and cycle life through cost-effective and easy-to-implement carbon coating. This simple three-dimensional carbon-coated LiFePO4 provides a new and simple idea for obtaining comprehensive and high-performance electrode materials in the field of lithium cathode materials.
... The morphology of the raw cathode powder and leaching slag was investigated with field emission scanning electron microscopy (Hitachi S4800) at an accelerating voltage of 4 kV. (Ji et al., 2019;Zuo et al., 2017) ...
A new recovery method for fast and efficient selective leaching of lithium from lithium iron phosphate cathode powder is proposed. Lithium is expelled out of the Oliver crystal structure of lithium iron phosphate due to oxidation of Fe2+ into Fe3+ by ammonium persulfate. 99% of lithium is therefore leached at 40 °C with only 1.1 times the amount of ammonium persulfate without the help of acid treatment. The use of ammonium persulfate also avoids the necessity to remove other metal ions in the later purification process. Various characterization methods including SEM, XPS, XRD are used to explore the experimental leaching mechanism. Theoretical investigations are performed which reveals the E-pH diagram of Fe-P-Li-H2O thermodynamic equilibrium. It confirms the possibility and suggests appropriate pH range allowing direct conversion from lithium iron phosphate to iron phosphate with great energy saving and reduced use of acid and base. Based on the experimental and theoretical results, a green and efficient closed-loop recycling route for lithium iron phosphate is proposed.
... Even though Nb can readily form other binary oxides, such as NbO and Nb2O5 [1], NbO2 is an emerging compound prone to yield many exciting cutting-edge applications. NbO2 exhibits an amalgam of remarkable physical and chemical properties [4], including one of the highest Mott transition temperature (1081 K) [5][6][7], high specific capacity in Li ion batteries (up to 225 mAhg −1 ) [8,9], large relative dielectric constant (approx. 10) [10,11], large Seebeck coefficient (order of −200 μV K −1 ) [12][13][14][15], enhanced catalytic activity towards H2 [16] and N2 [17] as well as oxygen reduction reactions [18]. ...
... NbO2 is identified to form different types of nanostructures, including nanorods [11] and nanoslices [10,22]. Such attractive properties give rise to many high-tech applications of NbO2 (see Figure 1), including, but not limited to, memristors [23][24][25], x-point memory arrays [26], electro-optic switching [27][28][29], diodes and electron emitters [10,11], fuel cells [18], batteries [8,9], surface catalysis [16][17][18], and thermoelectric devices [14,15]. ...
... The activation energy for Li diffusion in NbO2 with W additions (NbO2:W) is 0.1-0.3 eV [88], allowing for a specific capacity up to 225 mAhg −1 in pristine NbO2 [8,9] as well as in NbO2:W [88]. The theoretical capacity of 429 mAhg −1 in NbO2 has not yet been reached [9]. ...
The present research front of NbO2 based memory, energy generation, and storage thin film devices is reviewed. Sputtering plasmas contain NbO, NbO2, and NbO3 clusters, affecting nucleation and growth of NbO2, often leading to a formation of nanorods and nanoslices. NbO2 (I41/a) undergoes the Mott topological transition at 1081 K to rutile (P42/mnm), yielding changes in the electronic structure, which is primarily utilized in memristors. The Seebeck coefficient is a key physical parameter governing the performance of thermoelectric devices, but its temperature behavior is still controversial. Nonetheless, they perform efficiently above 900 K. There is a great potential to improve NbO2 batteries since the theoretical capacity has not been reached, which may be addressed by future diffusion studies. Thermal management of functional materials, comprising thermal stress, thermal fatigue, and thermal shock, is often overlooked even though it can lead to failure. NbO2 exhibits relatively low thermal expansion and high elastic modulus. The future for NbO2 thin film devices looks promising, but there are issues that need to be tackled, such as dependence of properties on strain and grain size, multiple interfaces with point and extended defects, and interaction with various natural and artificial environments, enabling multifunctional applications and durable performance.
... Our group has developed a new concept to embed nanoscale ITMO (NbO 2 , Nb 2 O 5 , TiO 2 and Li 4 Ti 5 O 12 ) in carbon matrix using dimethacrylate-based dental resin monomer as the solvent and carbon source over the past few years [15][16][17][18][19]. Metal ions are incorporated into the polymer network during the curing process where the dental resin monomer reacts with the ITMO precursors. ...
... The pristine embedding type Nb 2 O 5 /C nanohybrids were prepared according to our previous work with the Bis-GMA/NbETO mass ratio of 1:1 [18]. The carbon-emcoating samples were prepared with further heat treatment at 900°C under CO 2 atmosphere with a flow rate of 0.5 L min −1 for 1 h. ...
... The phase transition from hexagonal phase to orthorhombic and further monoclinic phase is triggered with either extended time range or elevated temperature of the CO 2 activation treatment. It is noted that, according to our previous studies, Nb 2 O 5 would be reduced to NbO 2 through Equations (1) and (2), which is generated from the residual amount of CO 2 in the tube furnace [18]. While, in this study, under CO 2 atmosphere, the abundant CO 2 pushes the reaction of Equation (2) towards the left direction. ...
Intercalation transition metal oxides (ITMO) have attracted great attention as lithium-ion battery negative electrodes due to high operation safety, high capacity and rapid ion intercalation. However, the intrinsic low electron conductivity plagues the lifetime and cell performance of the ITMO negative electrode. Here we design a new carbon-em-coating architecture through single CO 2 activation treatment as demonstrated by the Nb 2 O 5 /C nanohybrid. Triple structure engineering of the carbon-emcoating Nb 2 O 5 /C nanohybrid is achieved in terms of porosity, composition, and crystallographic phase. The carbon-embedding Nb 2 O 5 /C nanohy-brids show superior cycling and rate performance compared with the conventional carbon coating, with reversible capacity of 387 mA h g −1 at 0.2 C and 92% of capacity retained after 500 cycles at 1 C. Differential electrochemical mass spectrometry (DEMS) indicates that the carbon emcoated Nb 2 O 5 nanohy-brids present less gas evolution than commercial lithium ti-tanate oxide during cycling. The unique carbon-emcoating technique can be universally applied to other ITMO negative electrodes to achieve high electrochemical performance.
... 202 Moreover, further based on the G 0 -Ellingham diagram of reduction reaction for different metals (Al, Li, Mg, La) and Nb 2 O 5 , Huang et al. developed connected La-reduced route to obtain black NbO 2 ( Fig. 4 H), 203 which has high conductivity and been considered as promising intercalation anodes. 206 Moreover, the Zheng et al. reported that after Zn addition, the light yellow TiCl 4 /EtOH changed into blue Zn 2 + /Ti 3 + /EtOH ( Fig. 4 I). After hydrothermal treatment, the blue TiO 2-x could be obtained. ...
Lithium ion batteries (LIBs) have become an indispensable part of human development and our lives, from spaceships to deep-sea submersibles as well as ordinary electronics. Since it was proposed in the 1970s and commercialized in 1991, LIBs have been pursuing higher energy, higher power, higher safety and higher durability. Therefore, there is an urgent need to develop more efficient anode materials to overcome the capacity and rate bottlenecks of commercial graphite. Oxide anodes stand out in terms of high capacity and working potential, e.g. , Li 4 Ti 5 O 12 has been a high-performance safe anode material. Yet developed early, most of oxide anodes suffer from low conductivity, low initial coulombic efficiency and large volume change during lithium/delithiation process. Recently, defect engineering has significantly improved the performance of oxide anodes and alleviated the above problems. In this review, we present the fundamentals, challenges and recent research progress on defective oxide anodes of LIBs. Firstly, the development history of LIBs and oxide anode is briefly introduced. Then, the definition, classification, preparation method, structure-function relationship between defect structure and electrochemical performance are introduced in detail, as well as the development perspective of defect oxide anode.
