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1.
In order to get homogeneous layered oxide Li[Ni1/3Mn1/3Co1/3]O2 as a lithium insertion positive electrode material, we applied the metal acetates decomposition method. The oxide compounds were calcined at various temperatures, which results in greater difference in morphological (shape, particle size and specific surface area) and the electrochemical (first charge profile, reversible capacity and rate capability) differences. The Li[Ni1/3Mn1/3Co1/3]O2 powders were characterized by means of X-ray diffraction (XRD), charge/discharge cycling, cyclic voltammetry and SEM. XRD experiment revealed that the layered Li[Ni1/3Mn1/3Co1/3]O2 material can be best synthesized at temperature of 800 °C. In that synthesized temperature, the sample showed high discharge capacity of 190 mAh g−1 as well as stable cycling performance at a current density of 0.2 mA cm−2 in the voltage range 2.3-4.6 V. The reversible capacity after 100 cycles is more than 190 mAh g−1 at room temperature. 相似文献
2.
The layered Li[Ni1/3Co1/3Mn1/3]O2 powder with good crystalline and spherical shape was prepared by hydroxide co-precipitation method. The effects of pH value, NH4OH amount, calcination temperature and extra Li amount on the morphology, structure and electrochemical properties of the cathode material were investigated in detail. SEM results indicate that pH value affected both the morphology and the property of the cathode material, and the highest discharge capacity in the first cycle of 163 mAh g−1 (2.8-4.3 V) was obtained at pH value was 12. On the contrary, the NH4OH amount, which was used as a chelating agent, only affected the particle size distribution of the material. The calcination temperatures caused great difference in the structure and property of layered Li[Ni1/3Co1/3Mn1/3]O2, and the best electrochemical properties were obtained at the calcination temperature of 800 °C. Extra Li amount not only caused difference in the material structure, but also affected their electrochemical properties. With increasing Li amount, the lattice parameters (a and c) increased monotonously, and the highest first cycle coulombic efficiency (the ratio of discharge capacity to charge capacity in the first cycle) was obtained with the Li/M of 1.10. Therefore, the optimum synthetic conditions for the hydroxide co-precipitation reaction were: pH value was 12, NH4OH amount was 0.36 mol L−1, calcination temperature was 800 °C and the Li/M molar ratio was 1.10. 相似文献
3.
采用NH3-NaOH共沉淀法合成了L[Ni1/3Co1/3Mn1/3]O2正极材料,通过改变NH3·H2O浓度及加料方式研究材料的电化学性能.采用XRD、SEM对晶体的结构和形貌作表征.将正极材料Li[Ni1/3Co1/3Mn1/3]O2制成电极极片,组装成电池进行测试.分析测试结果表明,合成的极材料Li[Ni1/3Co1/3Mn1/3]O2具有典型的α-NaFeO2结构,粒径分布较好,呈类球形. 相似文献
4.
A carbonate co-precipitation method was employed to prepare spherical Li[Ni1/3Co1/3Mn1/3]O2 cathode material. The precursor, [Ni1/3Co1/3Mn1/3]CO3, was prepared using ammonia as chelating agent under CO2 atmosphere. The spherical Li[Ni1/3Co1/3Mn1/3]O2 was prepared by mixing the precalcined [Ni1/3Co1/3Mn1/3]CO3 with LiOH followed by high temperature calcination. The preparation conditions such as ammonia concentration, co-precipitation temperature, calcination temperature and Li/[Ni1/3Co1/3Mn1/3] ratio were varied to optimize the physical and electrochemical properties of the prepared Li[Ni1/3Co1/3Mn1/3]O2. The structural, morphological, and electrochemical properties of the prepared LiNi1/3Co1/3Mn1/3O2 were characterized by XRD, SEM, and galvanostatic charge-discharge cycling. The optimized material has a spherical particle shape and a well ordered layered structure, and it also has an initial discharge capacity of 162.7 mAh g− 1 in a voltage range of 2.8-4.3 V and a capacity retention of 94.8% after a hundred cycles. The optimized ammonia concentration, co-precipitation temperature, calcination temperature, and Li/[Ni1/3Co1/3Mn1/3] ratio are 0.3 mol L− 1, 60 °C, 850 °C, and 1.10, respectively. 相似文献
5.
The layered Li[Ni1/3Co1/3Mn1/3]O2 materials were synthesized by a spray pyrolysis method using citric acid as a polymeric agent. The Li[Ni1/3Co1/3Mn1/3]O2 powders were characterized by means of X-ray diffraction (XRD), charge/discharge cycling, cyclic voltammetry, and high-resolution transmission electron microscopy (TEM). The discharge capacity increases linearly with the increase of the upper cut-off voltage limit. TEM analysis showed that particles in the as-prepared powder possessed a polycrystalline structure. During cycling, the particle structure is mostly preserved although some surface grains on the polycrystalline particle became separated and transformed to the spinel phase. 相似文献
6.
Jung-Min Kim 《Electrochimica acta》2004,49(21):3573-3580
With variations in compositions in layered Li[Ni,Co,Mn]O2, we could change the several factors that might be considered to influence the electrochemical properties. The crystallographic characteristics of the samples were studied by neutron diffraction Rietveld analysis. After electrochemical operation, we measured the macroscopic crystal structure changes, the valence state of transition metals and the variations of interatomic distance for M-O (M: transition metal) through XRD and XAS. The variation in macroscopic lattice parameters was well coincident with the variation in microscopic structure changes viz. the variation of interatomic distance. We discussed the characteristics of transition metals in the structure and their effects on the electrochemical properties of the samples under electrochemical operation. We found that Li[Li1/10Ni2/10Co3/10Mn4/10]O2 with the lowest Ni/(Mn + Co) ratio among the samples showed the best capacity retention up to the 30th cycle. 相似文献
7.
Jung-Min Kim 《Electrochimica acta》2004,49(6):937-944
In this research, we studied the first cycle characteristics of Li[Ni1/3Co1/3Mn1/3]O2 charged up to 4.7 V. Properties, such as valence state of the transition metals and crystallographic features, were analyzed by X-ray absorption spectroscopy and X-ray and neutron diffractions. Especially, two plateaus observed around 3.75 and 4.54 V were investigated by ex situ X-ray absorption spectroscopy. XANES studies showed that the oxidation states of transition metals in Li[Ni1/3Co1/3Mn1/3]O2 are mostly Ni2+, Co3+ and Mn4+. Based on neutron diffraction Rietveld analysis, there is about 6% of all nickel divalent (Ni2+) ions mixed with lithium ions (cation mixing). Meanwhile, it was found that the oxidation reaction of Ni2+/Ni4+ is related to the lower plateau around 3.75 V, but that of Co3+/Co4+ seems to occur entire range of x in Li1−x[Ni1/3Co1/3Mn1/3]O2. Small volume change during cycling was attributed to the opposite variation of lattice parameter “c” and “a” with charging-discharging. 相似文献
8.
Uniform and spherical Li(Ni1/3Co1/3Mn1/3)O(2−δ)Fδ powders were synthesized via NH3 and F− coordination hydroxide co-precipitation. The effect of F− coordination agent on the morphology, structure and electrochemical properties of the Li(Ni1/3Co1/3Mn1/3)O(2−δ)Fδ were studied. The morphology, size, and distribution of (Ni1/3Co1/3Mn1/3)(OH)(2−δ)Fδ particle diameter were improved in a shorter reaction time through the addition of F−. The study suggested that the added F improves the layered characteristics of the lattice and the cyclic performance of Li(Ni1/3Co1/3Mn1/3)O2 in the voltage range of 2.8-4.6 V. The initial capacity of the Li(Ni1/3Co1/3Mn1/3)O1.96F0.04 was 178 mAh g−1, the maximum capacity was 186 mAh g−1 and the capacity after 50 cycles was 179 mAh g−1 in the voltage range of 2.8-4.6 V. 相似文献
9.
10.
A Li[Ni0.4Co0.3Mn0.3]O2 cathode was modified by applying a La2/3−XLi3XTiO3 (LLT) coating. Transmission electron microscope (TEM) images reveal that the coating layer consists of nanoparticles. The coated cathode demonstrated an enhanced rate capability, discharge capacity, and cyclic performance than the uncoated cathode. However, the influence of the coating upon these electrochemical properties is highly dependent upon the composition of the LLT coating layer. Coating layers having high La and low Li contents, such as La0.67TiO3, effectively improved the rate capability of the cathode. However, coating layers with a low La and high Li content greatly enhanced the discharge capacity of the cathode under high cut-off voltage (4.8 V) conditions. Overall, the thermal stability of the Li[Ni0.4Co0.3Mn0.3]O2 electrode was improved by the LLT coating. Storage tests confirmed that the La2/3−XLi3XTiO3 coating dramatically suppressed the dissolution of transition metals into the electrolyte. 相似文献
11.
We present the mechanism for the synthesis of a layered Li(Ni1/3Co1/3Mn1/3)O2 compound by a modified radiated gel method. Pure-phase Li(Ni1/3Co1/3Mn1/3)O2 material was achieved when the polymer gel was calcined at 900 °C between 15 and 30 h. The unit cell parameter c decreased, and a varied slightly with increased sintering time. Electrochemical characterization revealed that the optimized sample (25 h) had a high initial discharge capacity of 188 mAh/g (2.8-4.5 V, 20 mA/g), an excellent capacity retention of 90.1% after 30 cycles and a good rate performance. 相似文献
12.
Sen Zhang 《Electrochimica acta》2007,52(25):7337-7342
Li[Ni1/3Co1/3Mn1/3]O2 cathode material for lithium ion batteries was prepared by mixing metal hydroxide, (Ni1/3Co1/3Mn1/3)(OH)2, with 6% excess LiOH followed by calcinations. The (Ni1/3Co1/3Mn1/3)(OH)2 with secondary particle of about 12 μm was prepared by hydroxide co-precipitation. The tap density of the obtained Li[Ni1/3Co1/3Mn1/3]O2 powder was 2.56 ± 0.21 g cm−3. The powder was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), particle size distribution (PSD) and galvanostatic charge-discharge cycling. The XRD pattern of Li[Ni1/3Co1/3Mn1/3]O2 revealed a well ordered hexagonal layered structure with low cation mixing. Secondary particles with size of 13-14 μm and primary particles with size of about 1 μm can be identified from the SEM observations. In the voltage range of 2.8-4.3 V, the initial discharge capacity of the Li[Ni1/3Co1/3Mn1/3]O2 electrode was 166.6 mAh g−1, and 96.5% of the initial capacity was retained after 50 charge-discharge cycling. 相似文献
13.
Li[Ni1/3Co1/3Mn1/3]O2 powders were synthesized from co-precipitated spherical metal hydroxide, (Ni1/3Co1/3Mn1/3)(OH)2. The preparation of metal hydroxide was significantly dependent on synthetic conditions, such as pH, amount of chelating agent, stirring speed, etc. The optimized condition resulted in (Ni1/3Co1/3Mn1/3)(OH)2, of which the particle size distribution was uniform and the particle shape was spherical, as observed by scanning electron microscopy. Calcination of the uniform metal hydroxide with LiOH at higher temperature led to a well-ordered layer-structured Li[Ni1/3Co1/3Mn1/3]O2, as confirmed by Rietveld refinement of X-ray diffraction pattern. Due to the homogeneity of the metal hydroxide, (Ni1/3Co1/3Mn1/3)(OH)2, the final product, Li[Ni1/3Co1/3Mn1/3]O2, was also significantly uniform, i.e., the average particle size was of about 10 μm in diameter and the distribution was relatively narrow. As a result, the corresponding tap-density was also high approximately 2.39 g cm−3, of which the value is comparable to that of commercialized LiCoO2. In the voltage range of 2.8-4.3, 2.8-4.4, and 2.8-4.5 V, the discharge capacities of Li[Ni1/3Co1/3Mn1/3]O2 electrode were 159, 168, and 177 mAh g−1, respectively. For elevated temperature operation (55 °C), the resulted capacity was of about 168 mAh g−1 with an excellent cyclability. 相似文献
14.
Ultrafine powders of Li(Ni1/3Co1/3Mn1/3)O2 cathode materials for lithium-ion secondary batteries were prepared under mild hydrothermal conditions. The influence of the molar ratio of Li/(Ni + Co + Mn) was studied. The products were investigated by XRD, TEM and EDS. The final products were found to be well crystallized Li(Ni1/3Co1/3Mn1/3)O2 with an average particle size of about 10 nm. 相似文献
15.
Zhaorong Chang Zhongjun Chen Feng Wu Xiao-Zi Yuan Haijiang Wang 《Electrochimica acta》2009,54(26):6529-6535
A lithium-ion battery cathode material, Li(Ni1/3Co1/3Mn1/3)O2, with excellent electrochemical properties was prepared via two-step isothermal sintering, using eutectic lithium salts (0.38LiOH·H2O–0.62LiNO3) mixed with Co, Ni, or Mn hydroxides. Based on analysis using X-ray diffraction (XRD), scanning electron microscopy (SEM), a thermogravimetric-differential scanning calorimetric (TG–DSC) analyzer, and Fourier-transform Infrared (FT-IR), this synthetic process consists of procedures including lithium salt melting, permeation, reaction, crystalline transformation, and crystallization. Due to the lower melting point of the eutectic molten salts compared with that of the single lithium salt, a relatively mild synthetic condition (low temperature) is needed, and the product can be highly crystallized with low cation mixing, which facilitates maintenance of the precursor morphology. The electrochemical properties of the product were investigated by constant current discharge–charge and cyclic voltammetry. The results show that the initial discharge capacity is 160 mhA g−1, with excellent cycling stability even after 50 cycles. We conclude that this novel eutectic molten salt method is a promising and practical approach for synthesizing cathode materials for lithium-ion batteries. 相似文献
16.
Electrochemical performance of Li[Co0.1Ni0.15Li0.2Mn0.55]O2 modified by carbons as cathode materials
Jeong-Hun Ju Sung-Woo Cho Seung-Gi Hwang Su-Ryeon Yun Youngil Lee Han Mo Jeong Moon-Jin Hwang Kwang Man Kim Kwang-Sun Ryu 《Electrochimica acta》2011,56(24):8791
To enhance specific capacity, cycle performance and rate-capability of lithium-ion battery cathode materials, the Li[Co0.1Ni0.15Li0.2Mn0.55]O2 (LCMNO) is modified by coating them with amorphous carbons and by preparing nanocomposites with nanostructured carbons (carbon nanotube and graphene). The carbon-treated LCMNO powders and their cathodes are characterized by morphological observation, crystalline property analysis, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. The LCMNO nanocomposite shows a superior discharge capacity of ca. 290 mAh g−1 at low C-rates, due to a greater number of active sites embedded by nanostructured carbon species. In contrast, the carbon-coated LCMNO shows higher discharge capacity in high rate regions due to the carbon-coated layer in the carbon-coated LCMNO, suppressing the side reactions and enhancing the electrical conductivity. 相似文献
17.
综述了Al2O3包覆LiNi(1/3)Co(1/3)Mn(1/3)O2锂离子电池正极材料的研究现状与进展,并评述了其制备方法和包覆改性;讨论了包覆改善该正极材料性能的机理;提出了这种正极材料的研发过程中的一些问题并对其未来的发展前景作了展望。 相似文献
18.
K.M. Shaju 《Electrochimica acta》2003,48(11):1505-1514
Layered Li(Ni1/2Mn1/2)O2 was prepared by the solution and mixed hydroxide methods, characterised by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) and studied by cyclic voltammetry (CV) and charge discharge cycling in CC and CCCV modes at room temperature (r.t.) and at 50 °C. The XPS studies show about 8% of Ni3+ and Mn3+ ions are present in Li(Ni2+1/2Mn1/24+)O2 due to valency-degeneracy. The compound prepared at 950 °C, 12 h, solution method gives a second cycle discharge capacity of 150 mA h g−1 (2.5-4.4 V) at a specific current of 30 mA g−1 and retains 137 mA h g−1 at the end of 40 cycles. CV shows that the redox process at 3.7-4.0 V corresponds to Ni2+↔Ni4+ and clear indication of Mn3+/4+ couple was noted at 4.2-4.5 V. The observed capacity-fading (2.5-4.4 V) is shown to be contributed by the polarisation at the end of charging. The cathodic capacity is stable up to 40 cycles in the voltage window, 2.5-4.2 V both at room temperature and 50 °C. 相似文献
19.
Non-spherical Li(Ni1/3Co1/3Mn1/3)O2 powders have been synthesized using a two-step drying method with 5% excess LiOH at 800 °C for 20 h. The tap-density of the powder obtained is 2.95 g cm−3. This value is remarkably higher than that of the Li(Ni1/3Co1/3Mn1/3)O2 powders obtained by other methods, which range from 1.50 g cm−3 to 2.40 g cm−3. The precursor and Li(Ni1/3Co1/3Mn1/3)O2 are characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscope (SEM). XPS studies show that the predominant oxidation states of Ni, Co and Mn in the precursor are 2+, 3+ and 4+, respectively. XRD results show that the Li(Ni1/3Co1/3Mn1/3)O2 material obtained by the two-step drying method has a well-layered structure with a small amount of cation mixing. SEM confirms that the Li(Ni1/3Co1/3Mn1/3)O2 particles obtained by this method are uniform. The initial discharge capacity of 167 mAh g−1 is obtained between 3 V and 4.3 V at a current of 0.2 C rate. The capacity of 159 mAh g−1 is retained at the end of 30 charge-discharge cycle with a capacity retention of 95%. 相似文献
20.
A novel Li[Ni0.67Co0.15Mn0.18]O2 cathode material encapsulated completely within a concentration-gradient shell was successfully synthesized via co-precipitation. The Li[Ni0.67Co0.15Mn0.18]O2 has a core of Li[Ni0.8Co0.15Mn0.05]O2 that is rich in Ni, a concentration-gradient shell having decreasing Ni concentration and increasing Mn concentration toward the particle surface, and a stable outer-layer of Li[Ni0.57Co0.15Mn0.28]O2. The electrochemical and thermal properties of the material were investigated and compared to those of the core Li[Ni0.8Co0.15Mn0.05]O2 material alone. The discharge capacity of the concentration-gradient Li[Ni0.67Co0.15Mn0.18]O2 electrode increased with increasing upper cutoff voltage to 4.5 V, and cells with this cathode material delivered a very high capacity, 213 mAh/g, with excellent cycling stability even at 55 °C. The enhanced thermal and lithium intercalation stability of the Li[Ni0.67Co0.15Mn0.18]O2 was attributed to the gradual increase in tetravalent Mn concentration and decrease in Ni concentration in the concentration-gradient shell layer. 相似文献