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1.
Layered LiNi0.2Mn0.2Co0.6O2 phase, belonging to a solid solution between LiNi1/2Mn1/2O2 and LiCoO2 most commercialized cathodes, was prepared via the combustion method at 900 °C for a short time (1 h). Structural, electrochemical and magnetic properties of this material were investigated. Rietveld analysis of the XRD pattern shows this compound as having the α-NaFeO2 type structure (S.G. R-3m; a = 2.8399(2) ?; c = 14.165(1) ?) with almost none of the well-known Li/Ni cation disorder. SQUID measurements clearly indicate that the studied compound consists of Ni2+, Co3+ and Mn4+ ions in the crystal structure. X-ray analysis of the chemically delithiated LixNi0.2Mn0.2Co0.6O2 phases reveals that the rhombohedral symmetry was maintained during Li-extraction, confirmed by the monotonous variation of the potential-composition curve of the Li//LixNi0.2Mn0.2Co0.6O2 cell. LiNi0.2Mn0.2Co0.6O2 cathode has a discharge capacity of ∼160 mAh g−1 in the voltage range 2.7-4.3 V corresponding to the extraction/insertion of 0.6 lithium ion with very low polarization. It exhibits a stable capacity on cycling and good rate capability in the rate range 0.2-2 C. The almost 2D structure of this cathode material, its good electrochemical performances and its relatively low cost comparing to LiCoO2, make this material very promising for applications. 相似文献
2.
Xiao-Jian Guo Yi-Xiao LiMin Zheng Jian-Ming ZhengJie Li Zheng-Liang GongYong Yang 《Journal of power sources》2008
A series of cathode materials with molecular notation of xLi[Li1/3Mn2/3]O2·(1 − x)Li[Ni1/3Mn1/3Co1/3]O2 (0 ≤ x ≤ 0.9) were synthesized by combination of co-precipitation and solid state calcination method. The prepared materials were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques, and their electrochemical performances were investigated. The results showed that sample 0.6Li[Li1/3Mn2/3]O2·0.4Li[Ni1/3Mn1/3Co1/3]O2 (x = 0.6) delivers the highest capacity and shows good capacity-retention, which delivers a capacity ∼250 mAh g−1 between 2.0 and 4.8 V at 18 mA g−1. 相似文献
3.
A new type of Li1−xFe0.8Ni0.2O2–LixMnO2 (Mn/(Fe + Ni + Mn) = 0.8) material was synthesized at 350 °C in air atmosphere using a solid-state reaction. The material had an XRD pattern that closely resembled that of the original Li1−xFeO2–LixMnO2 (Mn/(Fe + Mn) = 0.8) with much reduced impurity peaks. The Li/Li1−xFe0.8Ni0.2O2–LixMnO2 cell showed a high initial discharge capacity above 192 mAh g−1, which was higher than that of the parent Li/Li1−xFeO2–LixMnO2 (186 mAh g−1). We expected that the increase of initial discharge capacity and the change of shape of discharge curve for the Li/Li1−xFe0.8Ni0.2O2–LixMnO2 cell is the result from the redox reaction from Ni2+ to Ni3+ during charge/discharge process. This cell exhibited not only a typical voltage plateau in the 2.8 V region, but also an excellent cycle retention rate (96%) up to 45 cycles. 相似文献
4.
The pure-phase Li1.2V3O8 was synthesized by ultrasonically dispersing Li2CO3 and NH4VO3 reactants. Its structure and morphology compared with the pristine Li1+xV3O8 obtained from the solid-state reaction were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that the compound synthesized at 570 °C from the precursor obtained by ultrasonic treatment in anhydrous ethanol has low crystallinity and homogeneous morphology with bar-like shape. Charge–discharge cycling, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) experiments indicate that this sample has relatively high initial discharge capacity and good cycle ability, and it is beneficial to the reversible insertion/extraction of Li+ ions because of the low kinetic resistance. Its discharge capacity reaches 270 mAh g−1 in the 2nd cycle at 0.2 C discharge rate and still retains 210 mAh g−1 in the 100th cycle in the range of 2.0–4.0 V. 相似文献
5.
Synthesis and electrochemical performance of the high voltage cathode material Li[Li0.2Mn0.56Ni0.16Co0.08]O2 with improved rate capability 总被引:1,自引:0,他引:1
J. LiR. Klöpsch M.C. StanS. Nowak M. KunzeM. Winter S. Passerini 《Journal of power sources》2011,196(10):4821-4825
The high voltage layered Li[Li0.2Mn0.56Ni0.16Co0.08]O2 cathode material, which is a solid solution between Li2MnO3 and LiMn0.4Ni0.4Co0.2O2, has been synthesized by co-precipitation method followed by high temperature annealing at 900 °C. XRD and SEM characterizations proved that the as prepared powder is constituted of small and homogenous particles (100-300 nm), which are seen to enhance the material rate capability. After the initial decay, no obvious capacity fading was observed when cycling the material at different rates. Steady-state reversible capacities of 220 mAh g−1 at 0.2C, 190 mAh g−1 at 1C, 155 mAh g−1 at 5C and 110 mAh g−1 at 20C were achieved in long-term cycle tests within the voltage cutoff limits of 2.5 and 4.8 V at 20 °C. 相似文献
6.
LiNi0.6CoxMn0.4−xO2 (x = 0.05, 0.10, 0.15, 0.2) cathode materials are prepared, and their structural and electrochemical properties are investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetric (DSC) and charge–discharge test. The results show that well-ordering layered LiNi0.6CoxMn0.4−xO2 (x = 0.05, 0.10, 0.15, 0.2) cathode materials are successfully prepared in air at 850 °C. The increase of the Co content in LiNi0.6Mn0.4−xCoxO2 leads to the acceleration of the grain growth, the increase of the initial discharge capacity and the deterioration of the cycling performance of LiNi0.6Mn0.4−xCoxO2. It also leads to the enhancement of the ratio Ni3+/Ni2+ in LiNi0.6CoxMn0.4−xO2, which is approved by the XPS analysis, resulting in the increase of the phase transition during cycling. This is speculated to be main reason for the deteriotion of the cycling performance. All synthesized LiNi0.6CoxMn0.4−xO2 samples charged at 4.3 V show exothermic peaks with an onset temperature of larger than 255 °C, and give out less than 400 J g−1 of total heat flow associated with the peaks in DSC analysis profile, exhibiting better thermal stability. LiNi0.6Co0.05Mn0.35O2 with low Co content and good thermal stability presents a capacity of 156.6 mAh g−1 and 98.5% of initial capacity retention after 50 cycles, showing to be a promising cathode materials for Li-ion batteries. 相似文献
7.
Mitsuharu Tabuchi Yoko NabeshimaKazuaki Ado Masahiro ShikanoHiroyuki Kageyama Kuniaki Tatsumi 《Journal of power sources》2007
Fe-substituted Li2MnO3 (Li1+x(FeyMn1−y)1−xO2, 0 ≤ x ≤ 1/3, 0.3 ≤ y ≤ 0.7) was synthesized using a combination of coprecipitation, hydrothermal, and heat-treatment methods. It exhibits high initial specific capacity greater than 200 mAh g−1 and small capacity, which fades up to the 50th cycle (>150 mAh g−1 at the 50th cycle) under electrochemical cycle testing at 60 °C. The attractive electrode properties appeared by controlling the chemical composition (x > 0.05, 0.3 ≤ y ≤ 0.5) and high specific surface area (>20 m2 g−1). The Fe-substituted Li2MnO3 is an attractive candidate as a novel 3 V-class positive electrode material. 相似文献
8.
Li-ming Li Hua-jun GuoXin-hai Li Zhi-xing WangWen-jie Peng Kai-xiong XiangXuan Cao 《Journal of power sources》2009
Li2FeSiO4/C cathodes were synthesized by combination of wet-process method and solid-state reaction at high temperature, and effects of roasting temperature and modification on properties of the Li2FeSiO4/C cathode were investigated. The XRD patterns of the Li2FeSiO4/C samples indicate that all the samples are of good crystallinity, and a little Fe3O4 impurity was observed in them. The primary particle size rises as the roasting temperature increases from 600 to 750 °C. The Li2FeSiO4/C sample synthesized at 650 °C has good electrochemical performances with an initial discharge capacity of 144.9 mAh g−1 and the discharge capacity remains 136.5 mAh g−1 after 10 cycles. The performance of Li2FeSiO4/C cathode is further improved by modification of Ni substitution. The Li2Fe0.9Ni0.1SiO4/C composite cathode has an initial discharge capacity of 160.1 mAh g−1, and the discharge capacity remains 153.9 mAh g−1 after 10 cycles. The diffusion coefficient of lithium in Li2FeSiO4/C is 1.38 × 10−12 cm2 s−1 while that in Li2Fe0.9Ni0.1SiO4/C reaches 3.34 × 10−12 cm2 s−1. 相似文献
9.
In this study, a solution method was employed to synthesize LiFePO4-based powders with Li3PO4 and Fe2P additives. The composition, crystalline structure, and morphology of the synthesized powders were investigated by using ICP-OES, XRD, TEM, and SEM, respectively. The electrochemical properties of the powders were investigated with cyclic voltammetric and capacity retention studies. The capacity retention studies were carried out with LiFePO4/Li cells and LiFePO4/MCMB cells comprised LiFePO4-based materials prepared at various temperatures from a stoichiometric precursor. Among all of the synthesized powders, the samples synthesized at 750 and 775 °C demonstrate the most promising cycling performance with C/10, C/5, C/2, and 1C rates. The sample synthesized at 775 °C shows initial discharge capacity of 155 mAh g−1 at 30 °C with C/10 rate. From the results of the cycling performance of LiFePO4/MCMB cells, it is found that 800 °C sample exhibited higher polarization growth rate than 700 °C sample, though it shows lower capacity fading rate than 700 °C sample. For Fe2P containing samples, the diffusion coefficient of Li+ ion increases with increasing amount of Fe2P, however, the sample synthesized at 900 °C shows much lower Li+ ion diffusion coefficient due to the hindrance of Fe2P layer on the surface of LiFePO4 particles. 相似文献
10.
Mitsuharu Tabuchi Yoko Nabeshima Kuniaki Tatsumi Yoshiaki Nitta 《Journal of power sources》2010,195(3):834-844
Fe-substituted Li2MnO3 including a monoclinic layered rock-salt structure (C2/m), (Li1+x(FeyMn1−y)1−xO2, 0 < x < 1/3, 0.1 ≤ y ≤ 0.5) was prepared by coprecipitation-hydrothermal-calcination method. The sample was assigned as two-phase composite structure consisting of the cubic rock-salt () and monoclinic ones at high Fe content above 30% (y ≥ 0.3), while the sample was assigned as a monoclinic phase (C2/m) at low Fe content less than 20%. In the monoclinic Li2MnO3-type structure, the Fe ion tends to substitute a Li (2b) site, which corresponds to a center position of Mn4+ hexagonal network in Mn-Li layer. The electrochemical properties including discharge characteristics under high current density (<3600 mA g−1 at 30 °C) and low temperature (<−20 °C at 40 mA g−1) were severely affected by chemical composition (Fe content and Li/(Fe + Mn) ratio), crystal structure (monoclinic phase content) and powder property (specific surface area). Under the optimized Fe content (0.2 < y < 0.4), the Li/sample cells showed high initial discharge capacity (240-300 mAh g−1) and energy density (700-950 mWh g−1) between 1.5 and 4.8 V under moderate current density, 40 mA g−1 at 30 °C. Results suggest that Fe-substituted Li2MnO3 would be a non-excludable 3 V positive electrode material. 相似文献
11.
Hyun-Wook LeeP. Muralidharan Claudio M. MariRiccardo Ruffo Do Kyung Kim 《Journal of power sources》2011,196(24):10712-10716
One-dimensional ordered LiNi0.5Mn1.5O4 nanorods have been fabricated and investigated for use as a high power cathode in rechargeable Li-ion batteries. These highly crystalline nanorods, with an ordered spinel structure and diameters and lengths around 130 nm and 1.2 μm, respectively, were synthesized in two steps by using a hydrothermal reaction to produce β-MnO2 nanorods followed by solid-state lithiation. Electrochemical analysis showed the superior performance of nanorods as a cathode in Li-ion half cells. The specific charge and discharge capacities were found to be 120 and 116 mAh g−1 at a 0.5 C rate, and 114 and 111 mAh g−1 at a 1 C rate between 3.5 and 5.0 V vs. Li+/Li. Moreover, the nanorods exhibit high power capability, maintaining capacities of 103 and 95 mAh g−1 at specific currents of 732.5 and 1465 mA g−1 (5 and 10 C rates), respectively. 相似文献
12.
Gang Yang Haidong Liu Hongmei Ji Zhongzhong Chen Xuefan Jiang 《Journal of power sources》2010,195(16):5374-9112
Monoclinic Li3V2(PO4)3 can be rapidly synthesized at 750 °C for 5 min (MW5m) by using temperature-controlled microwave solid-state synthesis method (TCMS). The carbon-free sample MW5m presents well electrochemical properties. In the cut-off voltage 3.0-4.3, MW5m presents a charge capacity 132 mAh g−1, almost equivalent to the reversible cycling of two lithium ions per Li3V2(PO4)3 formula unit (133 mAh g−1), and discharge capacity 126.4 mAh g−1. In the cut-off voltage 3.0-4.8 V, MW5m shows an initial discharge capacity of 183.4 mAh g−1, near to the theoretical discharge capacity. In the cycle performance, the capacity fade of Li3V2(PO4)3 is dependent on the cut-off voltage and the preparation method. 相似文献
13.
Carbon free composites Li1−xMgxFePO4 (x = 0.00, 0.02) were synthesized from LiOH, H3PO4, FeSO4 and MgSO4 through hydrothermal route at 180 °C for 6h followed by being fired at 750 °C for 6 h. The samples were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), flame atomic absorption spectroscopy and electronic conductivity measurement. To investigate their electrochemical properties, the samples were mixed with glucose as carbon precursors, and fired at 750 °C for 6 h. The charge–discharge curves and cycle life test were carried out at 23 ± 2 °C. The Rietveid refinement results of lattice parameters of the samples indicate that the magnesium ion has been successfully doped into the M1 (Li) site of the phospho-olivine structure. With the same order of magnitude, there is no material difference in terms of the electronic conductivities between the doped and undoped composites. Conductivities of the doped and undoped samples are 10−10 S cm−1 before being fired, 10−9 S cm−1 after being fired at 750 °C, and 10−1 S cm−1 after coated with carbon, respectively. Both the doped and undoped composites coated with carbon exhibit comparable specific capacities of 146 mAh g−1 vs. 144 mAh g−1 at 0.2 C, 140 mAh g−1 vs. 138 mAh g−1 at 1 C, and 124 mAh g−1 vs. 123 mAh g−1 at 5 C, respectively. The capacity retention rates of both doped and undoped samples over 50 cycles at 5 C are close to 100% (vs. the first-cycle corresponding C-rate capacity). Magnesium doping has little effects on electronic conductivity and electrochemical properties of LiFePO4 composites prepared via hydrothermal route. 相似文献
14.
The thermal properties of Li4/3Ti5/3O4 and Li1+xMn2O4 electrodes were investigated by isothermal micro-calorimetry (IMC). The 150-mAh g−1 capacity of a Li/Li4/3Ti5/3O4 half cell was obtained through the voltage plateau that occurs at 1.55 V during the phase transition from spinel to rock salt. Extra capacity below 1.0 V was attributed to the generation of a new phase. The small and constant entropy change of Li4/3Ti5/3O4 during the spinel/rock-salt phase transition indicated its good thermal stability. Accelerated rate calorimetry confirmed that Li4/3Ti5/3O4 has better thermal characteristics than graphite. The IMC results for a Li/Li1+xMn2O4 half cell indicated less heat variation due to the suppression of the order/disorder change by lithium doping. The heat profiles of the Li4/3Ti5/3O4/Li1+xMn2O4 full cell indicated less heat generation compared with a mesocarbon-microbead graphite/Li1+xMn2O4 cell. 相似文献
15.
Evolved gas analysis (EGA) by mass spectroscopy (MS) was carried out for the pyrolysis of Li1−xCo1/3Ni1/3Mn1/3O2 (185 mAh g−1 of charge capacity) and the results were compared with that of Li1−xCoO2 (140 mAh g−1). Electrochemically prepared Li1−xCo1/3Ni1/3Mn1/3O2 clearly shows that O2 evolution begins at much higher temperature than Li1−xCoO2, suggesting that Li1−xCo1/3Ni1/3Mn1/3O2 is superior to LiCoO2 with respect to thermal stability. High-temperature XRD measurements of charged LiCo1/3Ni1/3Mn1/3O2-electrodes at 4.45 V were also carried out and shown that the decomposition product by heating was identified as a cubic spinel consisting of cobalt, nickel, and manganese. This indicates that phase change from a layered to spinel-framework structure plays a crucial role in the suppression of oxygen evolution from the solid matrix. In order to show practicability of the new material, lithium-ion batteries with graphite-negative electrodes are fabricated and examined in the R18650-hardware. The new lithium-ion batteries show high rate discharge performances, excellent cycle life, and safety together with high-energy density. 相似文献
16.
Rate capability of LiNi0.8Co0.15Al0.05O2 in solid-state cells was investigated with 70Li2S-30P2S5 glass-ceramics as a sulfide solid electrolyte. It showed higher rate capability than LiCoO2; discharge capacity observed at a current density of 10 mA cm−2 was ca. 70 mAh g−1. Surface coating with Li4Ti5O12 onto the LiNi0.8Co0.15Al0.05O2 particles further improved the high-rate performance to give ca. 110 mAh g−1. The rate capability promises to realize all-solid-state lithium secondary batteries with very high performance. 相似文献
17.
The high redox potential of LiMnPO4, ∼4.0 vs. (Li+/Li), and its high theoretical capacity of 170 mAh g−1 makes it a promising candidate to replace LiCoO2 as the cathode in Li-ion batteries. However, it has attracted little attention because of its severe kinetic problems during cycling. Introducing iron into crystalline LiMnPO4 generates a solid solution of LiFexMn1−xPO4 and increases kinetics; hence, there is much interest in determining the Fe-to-Mn ratio that will optimize electrochemical performance. To this end, we synthesized a series of nanoporous LiFexMn1−xPO4 compounds (with x = 0, 0.05, 0.1, 0.15, and 0.2), using an inexpensive solid-state reaction. The electrodes were characterized using X-ray diffraction and energy-dispersive spectroscopy to examine their crystal structure and elemental distribution. Scanning-, tunneling-, and transmission-electron microscopy (viz., SEM, STEM, and TEM) were employed to characterize the micromorphology of these materials; the carbon content was analyzed by thermogravimetric analyses (TGAs). We demonstrate that the electrochemical performance of LiFexMn1−xPO4 rises continuously with increasing iron content. In situ synchrotron studies during cycling revealed a reversible structural change when lithium is inserted and extracted from the crystal structure. Further, introducing 20% iron (e.g., LiFe0.2Mn0.8PO4) resulted in a promising capacity (138 mAh g−1 at C/10), comparable to that previously reported for nano-LiMnPO4. 相似文献
18.
Jiangfeng Ni Yoshiteru Kawabe Masaharu Watada Tetsuo Sakai 《Journal of power sources》2010,195(24):8322-8326
Lithium vanadium metasilicate (LiVSi2O6) with pyroxene structure has been exploited as an electrode material for Li-ion batteries. Galvanostatic charge and discharge tests show that LiVSi2O6 is able to deliver a capacity of 85 mAh g−1 at 30 °C, and a high capacity of 181 mAh g−1 at 60 °C. The high capacity is believed to be due to the reactions of V3+/V4+ and V2+/V3+redox couples, accompanied by the excess 0.42 Li+ insertion into the lattice forming a Li-rich phase Li1.42VSi2O6. High-energy synchrotron XRD combined with the Rietveld refinement analysis confirms that the electrochemical delithiation-lithiation reaction proceeds by a single phase redox mechanism with an overall volume variation of 1.9% between LiVSi2O6 and its delithiated state, indicating a very stable framework of LiVSi2O6 for Li+ ions extraction-insertion. 相似文献
19.
Small particle-sized orthorhombic LiMnO2 powders were prepared via Pechini's route with Li/Mn molar ratio ranging between 1.00 and 1.20, followed by calcinations at 300 °C in air and heat-treatment at temperatures between 700 and 900 °C for various durations under flowing nitrogen. The effects of heat-treatment conditions and starting Li/Mn molar ratio on the crystalline structure and the electrochemical properties were investigated with XRD, SEM, and capacity retention study. Orthorhombic phase were found exclusively in the samples prepared with starting Li/Mn molar ratios between 1.00 and 1.05 followed by heat-treatment at 800 °C for 15 h, whereas monoclinic Li2MnO3 and tetragonal Li2Mn2O4 were also observed in the samples prepared with Li/Mn ratios higher than 1.10. The charge/discharge curves of capacity retention studies and the cyclic voltammograms showed that the transformation of o-LiMnO2 into cycle-induced spinel phase proceeds more progressively and the capacity loss upon cycling are more significant for the samples containing the impurity phases than the well-ordered o-LiMnO2 sample. The sample synthesized with starting Li/Mn ratio of 1.05 followed by heat treatment at 800 °C for 15 h showed the most promising cycling performance among the prepared powders with the maximum discharge capacity of 158 mAh g−1 at 20th cycle and capacity loss of 3% between 20th and 80th cycles at 30 °C. 相似文献
20.
Layer-structured Zr doped Li[Ni1/3Co1/3Mn1−x/3Zrx/3]O2 (0 ≤ x ≤ 0.05) were synthesized via slurry spray drying method. The powders were characterized by XRD, SEM and galvanostatic charge/discharge tests. The products remained single-phase within the range of 0 ≤ x ≤ 0.03. The charge and discharge cycling of the cells showed that Zr doping enhanced cycle life compared to the bare one, while did not cause the reduction of the discharge capacity of Li[Ni1/3Co1/3Mn1/3]O2. The unchanged peak shape in the differential capacity versus voltage curve suggested that the Zr had the effect to stabilize the structure during cycling. More interestingly, the rate capability was greatly improved. The sample with x = 0.01 presented a capacity of 160.2 mAh g−1 at current density of 640 mA g−1(4 C), corresponding to 92.4% of its capacity at 32 mA g−1(0.2 C). The favorable performance of the doped sample could be attributed to its increased lattice parameter. 相似文献