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TEM images of LiFePO4/AB (a, b) and LiFePO4/SUC (c, d). e HRTEM image of LiFePO4/SUC. The inset is the corresponding FFT pattern. f Atomic resolution lattice image of LiFePO4/SUC
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Carbon-coated olivine-structured LiFePO4/C composites are synthesized via an efficient and low-cost carbothermal reduction method using Fe2O3 as iron source at a relative low temperature (600 °C). The effects of two kinds of carbon sources, inorganic (acetylene black) and organic (sucrose), on the structures, morphologies, and lithium storage prope...
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The high energy storage devices such as lithium-ion batteries (LIBs) have recently attracted extensive attention, and massive efforts have been made to synthesize the high-performance electrodes for Li-ion storage. Here, a facile in situ synthesis method was proposed to prepare the NiO/Ni nanocomposites embedded in three-dimensional (3D) porous car...
Citations
... In theory, all valence iron elements and their corresponding compounds can be used iron sources to prepare LiFePO 4 cathode material. According to the literature, the reported iron sources can be divided into four categories: trivalent iron sources (ferric oxide [8,9], iron phosphate [10,11], ferric citrate [12]), divalent iron sources, zero-valent iron sources, and various iron-containing wastes [10]. Thanks to its chemical stability in the air, ferrous oxalate is a frequently used divalent iron source material [13]. ...
A series of FePO4·2H2O particles were prepared via rapid precipitation method for process parameters optimizing. The influences of surfactant type, its amount, aging time, and ultrasound time were systematically investigated. The obtained FePO4·2H2O particles were characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM), thermogravimetric-differential scanning calorimetry (TG-DSC), Fourier transform infrared spectroscopy (FTIR), and iron–phosphorus ratio (n(Fe):n(P)). Results show that surfactant, aging time, and ultrasound time have significant effects on the agglomeration and morphology of FePO4·2H2O particles. The best conditions for preparing FePO4·2H2O particles with good dispersity are surfactant CTAB with adding 1.5% of the iron powder mass, 4 h aging, and 60 min of ultrasonic treatment, respectively. This work suggests that the optimized rapid precipitation method is a promising method to synthesize FePO4·2H2O used in industrialization.
... However, the energy densities of current power batteries such as lithium-ion batteries (LIBs) cannot satisfy the increasing demands of EVs, which inhibit the mileages of EVs. This problem mainly results from the low specific capacities of cathode materials in LIBs, such as layered LiCoO 2 (∼ 140 mAh g −1 , upper cutoff voltage of 4.2 V) [2], spinel LiMn 2 O 4 (∼ 120 mAh g −1 ) [3], and olivine LiFePO 4 (∼ 170 mAh g −1 ) [4]. Therefore, it is necessary to develop new cathode materials with higher capacity and specific energy density for LIBs [5,6]. ...
A Li1.2Ni0.13Co0.13Mn0.54O2 cathode material is prepared by a kilogram-scale carbonate co-precipitation method assisted with nano-grinding. Uniform hierarchical structure with nano-scale building blocks and low mixing degree of lithium and nickel are achieved. The obtained Li1.2Ni0.13Co0.13Mn0.54O2 cathode material shows high initial Coulombic efficiency and capacity delivery, attractive cycling stability, and high rate performance. At 1 C and 25 °C, it presents a higher discharge capacity of 266.3 mAh g⁻¹, and the capacity retention rates are 97.7% after 300 cycles and 92.8% after 500 cycles, respectively. Excellent high rate discharge capacities of 252.0 and 113.3 mAh g⁻¹ are obtained at 1 and 30 C, respectively. In addition, outstanding temperature dependency discharge capacities are gained. The pouch-type full cell fabricated by this cathode and graphite anode exhibits good cycling performance with 85.5% capacity retention after 350 cycles at 5 mA.
... Numerous methods were used to synthesize LiFePO 4 such as solid-state route [11] co-precipitation technique [12], solgel [13], hydrothermal [14], and carbothermal-reduction method [15]. High-temperature ball-milling method was employed to prepare LiFePO 4 /C in our earlier researches [16,17]. ...
LiFePO4/C cathode material was prepared via high-temperature ball-milling route with ultrasonic dispersion as mixing process using eutectic molten salt (0.76 LiOH·H2O-0.24 Li2CO3) as lithium source. Box-Behnken design was used to study the combined effects of ultrasonic time, ball-milling temperature, and ball-milling time on the discharge capacity to obtain the optimum predicted conditions. The optimum conditions were as follows: ultrasonic time was 63 min, ball-milling temperature was 638 °C, and ball-milling time was 7 h. LiFePO4/C prepared from the optimized experimental conditions exhibited a well electrochemical performance; its discharge capacity was 161.3 mAh g⁻¹ at a 0.1 C-rate which was in consistence with the predicted discharge capacity of 160.2 mAh g⁻¹. Moreover, its capacity retention rate achieved 93.6% at a 10 C-rate over 100 cycles.
A novel state of charge (SOC) estimation method is proposed based on a gas-liquid dynamic model using a Cubature Kalman filter (CKF) with state constraints to improve the accuracy of estimations. The constraints derived from the principle of aerodynamic are introduced, which does not need the temperature correction coefficient and can achieve rapid SOC convergence due to its unique iterative form. Non-linear Kalman filter used to eliminate the violent jitter of the original algorithm when switching working conditions are also incorporated. Then, the proposed method is tested using a cylindrical-format ternary lithium-ion battery with a nominal capacity of 2.6 Ah and the estimated SOC were compared with the experimental results. As a result, comparative studies of two non-linear filters revealed that the CKF has the most outstanding performance based on concerning estimation accuracy, recovery time from an initial offset, and computational time. That is 36.4 % more accurate and the convergence time is 97.5 % shorter than the Extended Kalman filter (EKF) when the initial offset is 60 %, respectively.
In this study, carbon-coated lithium iron phosphate (LiFePO4/C, denoted as LFP/C) composite cathode materials were prepared through wet ball milling and spray drying. Ground and spherical α-Fe2O3 precursors were used to synthesize LFP samples. Wet ball milling and a solvothermal method were used to prepare α-Fe2O3 particles with a smaller size and spherical morphology, respectively. The as-prepared α-Fe2O3 was used to synthesize LFP/C composites in order to investigate the effects of α-Fe2O3 size and morphology on the electrochemical performance of LFP/C cathode materials. Charge-discharge measurements revealed that the LFP/C cathode materials prepared from the ground and spherical α-Fe2O3 precursors delivered a similar specific discharge capacity of approximately 150 mAh/g at 0.1 C and 96 mAh/g at 10 C, which was higher than that of the LFP/C cathode materials prepared using the irregular and unground α-Fe2O3 (the discharge capacity was 135 mAh/g at 0.1 C and 62 mAh/g at 10 C). The results reveal that the size and morphology of iron precursors have a profound influence on the electrochemical properties of LFP/C materials. The results obtained in this study can serve as a reference in the use of the solid-state method to produce low-cost LFP/C cathode materials with favorable consistent properties and high electrochemical performance.
The phase diagram of LiF-Li 3 PO 4 system is studied. The eutectic coordinates are 800±5°C, 8±1 mol% Li 3 PO 4 . A region of a solid solution based on lithium phosphate with a length of up to 11±2 mol% LiF was discovered. It is assumed that there is heterovalent isomorphism where anionic tetrahedron (PO 4 ) ³⁻ is replaced by tetrahedron (LiF 4 ) ³⁻ .
The phase diagrams of binary systems of gallium sulfate with lithium or sodium sulfate were studied for the first time. The Li2SO4–Ga2(SO4)3 system is of the eutectic type. The coordinates of the eutectic are (548°C, 30 mol % Ga2(SO4)3). The region of a solid solution based on the high-temperature modification α-Li2SO4 is small. In the Na2SO4–Ga2(SO4)3 system, compound Na3Ga(SO4)3 forms, which melts incongruently at 585°C. The coordinates of the eutectic are (538°C, 17 mol % Ga2(SO4)3). The region of a solid solution based on α-Na2SO4 reaches 8 ± 1 mol % Ga2(SO4)3. The X-ray powder diffraction pattern of Na3Ga(SO4)3 was indexed in a tetragonal unit cell with the parameters a = 9.451(3) Å and c = 7.097(3) Å; the unit cell parameters for an aluminum-containing analog, Na3Al(SO4)3, are a = 9.424(5) Å and c = 7.053(3) Å.
