Synthesis and electrochemical performances of LiNi0.6Co0.2Mn0.2O2 cathode materials

LiNi_0.6Co_0.2Mn_0.2O₂ was prepared from LiOH·H₂O and MCO₃ (M=Ni, Co, Mn) by co-precipitation and subsequent heating. XRD, SEM and electrochemical measurements were used to examine the structure, morphology and electrochemical characteristics, respectively. LiNi_0.6Co_0.2Mn_0.2O₂ samples show excellent electrochemical performances. The optimum sintering temperature and sintering time are 850 °C and 20 h, respectively. The LiNi_0.6Co_0.2Mn_0.2O₂ shows the discharge capacity of 148 mA·h/g in the range of 3.0?4.3 V at the first cycle, and the discharge capacity remains 136 mA·h/g after 30 cycles. The carbonate co-precipitation method is suitable for the preparation of LiNi_0.6Co_0.2Mn_0.2O₂ cathode materials with good electrochemical performance for lithium ion batteries.     

锂离子电池正极材料LiNi0.5Mn0.5O2的循环性能

采用共沉淀法可以制备出首次放电容量高达210 mA.h/g的LiNi0.5Mn0.5O2材料(2.8~4.5 V,电流密度30 mA/g),但材料循环性能受制备过程中的处理工艺影响很大,处理不严格将导致材料循环性能严重下降。围绕材料的循环性问题,对其机理进行了分析并在此基础上对制备工艺进行了进一步改善:分别从配锂方式,烧结过程中的升降温速率以及烧结的保温制度进行了系统研究。结果表明:采用改进配锂方式,缓慢升温速率(2℃/min),高低温结合的烧结制度和快速风冷工艺所制备的材料首次放电容量达到188 mA.h/g,30个循环后仍保持在174 mA.h/g,循环效率有了明显的提高。     

正极材料LiNi0.8Co0.1Mn0.1O2的合成及电化学性能

将液相共沉淀法制备的Ni0.8Co0.iMn0.1(OH)2与LiOH·H2O混合,固相烧结合成微米级的LiNi0.8Co0.1Mn0.1O2正极材料.XRD谱表明,合成的LiNi0.8Co0.1Mn0.1O2正极材料为典型的α-NaFeO2层状结构,无杂质峰;从SEM像可以看出,产物颗粒为类球形,分散性好,由一次粒子紧密堆积而成,平均粒径为3 μm;电化学测试结果表明,在2.8～4.3 V电压范围内,750℃焙烧15h合成的LiNi0.8Co0.1Mn0.1O2材料的电化学性能最优,0.1C时,其首次放电容量为186.748mA·h/g,分别高于700和800℃时的首次放电容量172.947和180.235mA·h/g.材料在0.5和2C时循环40次后,容量保持率分别为98.32％和88.72％,循环性能良好.     

LiNi0.7Co0.15Mn0.15O2 microspheres as high-performance cathode materials for lithium-ion batteries

Advanced uniform LiNi0.7Co0.15Mn0.15O2 microspheres were successfully synthesized and examined as cathode materials for lithium-ion batteries. The structure,morphology, and electrochemical performance of LiNi0.7-Co0.15Mn0.15O2 calcined at different temperatures ranging from 650 to 900 °C were systematically investigated. The XRD results show that the material has a well-ordered layered structure with small amount of cation mixing. A distinct spherical morphology of the obtained powders prepared at different temperatures can be seen from the SEM images. The as-synthesized LiNi0.7Co0.15Mn0.15O2 powders have a very high-tap density of about 2.37 g·cm^-3. Among all the samples,the sample calcined at 750 °C exhibits the best electrochemical performance with an initial discharge capacity of185.2 mAh·g^-1（3.0–4.3 V, 0.2C rate） and capacity retention〉94.77 %after50cycles.Moreover,thismaterialshowshighspecific capacity and good cycling stability. The LiNi0.7-Co0.15Mn0.15O2 microspheres with high-specific capacity and high-tap density are promising to use as cathode materials for next-generation high-energy-density lithium-ion batteries.     

合成方法对LiNi0．4Co0．2Mn0．4O2电化学性能的影响

分别采用混合氢氧化物法和溶胶．凝胶法制备了三元的锂离子电池LiNi0．4Co0．2Mn0．4O2正极材料。采用XRD，SEM以及BET等方法对正极材料进行表征，并对其电化学性能进行测试。实验结果表明，不同的合成方法和工艺条件导致了材料的晶相结构、表观形貌、比表面积以及电化学性能上的差异。LiNi0．4Co0．2Mn0．4O2正极材料中出现的阳离子相互占位将导致其电化学性能变差。与溶胶．凝胶法制备的样品相比，混合氢氧化物法制备的样品具有较高的比表面积（3．2m2／g）和较高的放电比容量。在充放电电压范围为2．5～4．3V、充放电电流为20mA／g条件下，混合氢氧化物法所制备样品的首次放电比容量为180．1mAh·g^-1，20次循环后放电容量为160．2mAh·g^-1，并显示出较好的循环稳定性。     

Synthesis and electrochemical performance of 5V spinel LiNi0.5Mn1.5O4 prepared by solid-state reaction

Spinel compound LiNi0.5Mn1.5O4 with high capacity and high rate capability was synthesized by solid-state reaction. At first, MnCl2·4H2O and NiCl2·6H2O were reacted with (NH4)2C2O4·H2O to produce a precursor via a low-temperature solid-state route, then the precursor was reacted with Li2CO3 to synthesize LiNi0.5Mn1.5O4. The effects of calcination temperature and time on the physical properties and electrochemical performance of the products were investigated. Samples were characterized by thermal gravimetric analysis(TGA), scanning electron microscopy(SEM), X-ray diffractometry(XRD), charge-discharge tests and cyclic voltammetry measurements. Scanning electron microscopy(SEM) image shows that as calcination temperature and time increase, the crystallinity of the samples is improved, and their grain sizes are obviously increased. It is found that LiNi0.5Mn1.5O4 calcined at 800 ℃ for 6 h exhibits a typical cubic spinel structure with a space group of Fd3m. Electrochemical tests demonstrate that the sample obtained possesses high capacity and excellent rate capability. When being discharged at a rate as high as 5C after 30 cycles, the as-prepared LiNi0.5Mn1.5O4 powders can still deliver a capacity of 101 mA-h/g, which shows to be a potential cathode material for high power batteries.     

Effects of sodium substitution on properties of LiMn2O4 cathode for lithium ion batteries

Na-doped Li1.05Mn2O4 cathodes were synthesized using a sol-gel process.The samples were characterized by X-ray diffractometry(XRD),cyclic voltammetry(CV),electrochemical impedance spectroscopy(EIS)and charge-discharge measurements. The results show that all the samples exhibit the same cubic spinel phase structure without impurity.The lattice constant and unit cell volume decrease with increasing the sodium dopant amount.As the molar ratio of sodium to manganese(x=n(Na)/n(Mn))increases from 0 to 0.03,the initial discharge capacity of the Li1.05Mn2O4 cathodes decreases from 119.2 to 107.9 mA·h/g,and the discharge capability at large current rate and the storage performance decline dramatically,while cycling performance at room temperature and 55℃are improved.The CV and EIS studies indicate that reversibility of Li1.05Mn2O4 cathodes decreases and the electrochemical impedance increases with increasing the sodium dopant amount.     

Preparation of LiNi1/3Co1/3Mn1/3O2 cathode materials from spent Li-ion batteries

A recycling process including separation of electrode materials by ultrasonic treatment, acid leaching, Fe-removing, precipitation of cobalt, nickel, manganese and lithium has been applied successfully to recycle spent lithium-ion batteries and to synthesize LiNi1/3Co1/3Mn1/3O2. When ultrasonic treatment with 2-nitroso-4-methylphenol（NMP） at 40 ℃ for 15 min, the electrode materials are separated completely. Above 99% of Co, Ni, Mn and Li, 95% of Fe in the separated electrodes are acid-leached in the optimized conditions of 2 mol/L H2SO4, 1：2 H2O2：H2SO4 （molar ratio）, 70 ℃, 1：10 initial S：L ratio, and l h. 99.5% of Fe and less than 1% of Co, Ni, Mn in the leaching solution can be removed in the conditions of initial pH value 2.0-2.5 adjusted by adding 18% Na2CO3, 90 ℃ and stirring time 3 h. After adjusted to be equal by adding NiSO4, COSO4 and MnSO4 solution, 97.1% of Ni, Co, Mn in the Fe-removing surplus leaching solution can be recovered as Ni1/3Co1/3Mn1/3（OH）2. 94.5% of Li in the surplus filtrate after the deposition of Co, Ni and Mn can be recovered as LiECO3. The LiNi1/3Co1/3Mnl/3O2, prepared from the recovered compounds, is found to have good characteristics of the layered structure and elecrtochemical performance.     

Effect of calcination temperature on characteristics of LiNi1/3Co1/3Mn1/3O2 cathode for lithium ion batteries

LiNi1/3Co1/3Mn1/3O2 was synthesized by sol-gel method and effect of calcination temperature on characteristics of LiNi1/3Co1/3Mn1/3O2 cathode was investigated. The structure and characteristics of LiNi1/3Co1/3Mn1/3O2 were determined by XRD, SEM and electrochemical measurements. The results show that the compound LiNi1/3Co1/3Mn1/3O2 has layered structure with hexagonal lattice. With the increase of calcination temperature, the basicity of the material decreases, and the size of primary particle rises. The LiNi1/3Co1/3Mn1/3O2 calcined at 900 ℃ for 12 h shows excellent electrochemical performances with large reversible specific capacity of 157.5 mA-h/g in the voltage range of 2.75-4.30 V and good capacity retention of 94.03% after 20 charge/discharge cycles. Capacity of LiNi1/3Co1/3Mn1/3O2 increases with enhancement of charge voltage limit, and specific discharge capacities of 179.4 mA.h/g, 203.1 mA.h/g are observed when the charge voltages limit are fixed at 4.50 V and 4.70 V, respectively.     

废旧LiCoO2材料再生LiNi0.8Co0.1Mn0.1O2正极材料及性能研究

针对废旧锂离子电池数量不断增加的现状,对废旧LiCoO2电池的回收和再生流程进行探究。以废旧LiCoO2电池为原料,通过预处理,酸浸,共沉淀步骤,实现了LiNi0.8Co0.1Mn.1O2正极材料的再生。ICP-OES分析浸出液中的元素含量,SEM和XRD表征材料形貌和结构,扣式电池的电化学测试定量分析材料的电化学性能。研究表明,利用浸出液可以再生形貌和层状结构良好的正极材料,在0.2C,2.8~4.3V电压范围内进行充放电循环测试,首周放电比容量可达到210.8 mAh/g,经过50周充放电循环后的容量保持率为87%,表现出良好的循环稳定性,为废旧锂离子电池的再生提供支撑和发展方向。     

烧结温度对LiNi（0.8）Co（0.1）Mn（0.1）O2材料倍率性能和循环性能的影响

以共沉淀法制备的球形Ni0.8Co0.1Mn0.1（OH）2和Li OH·H2O为原料,研究烧结温度对LiNi0.8Co0.1Mn0.1O2材料形貌、结构以及材料循环性能和倍率性能的影响。SEM和XRD结果表明：温度对材料形貌和结构有较大的影响,控制适当温度既能保证材料具有良好的形貌,也能抑制材料中锂镍的混排。电化学测试结果显示,当烧结温度从700℃升高至750℃时,材料性能逐渐提高,但是温度过高会恶化材料的性能。750℃和780℃烧结材料的循环性能几乎一致,200次循环后容量保持率为71.9%,但780℃烧结材料的倍率性能低于750℃材料的,其原因归结于温度过高,锂镍的混排加剧。在小电流充放电时,对材料性能影响有限,但是在大电流充放电时,3a位的Ni2＋将严重阻碍锂离子的扩散。     

Preparation and characteristics of Li2FeSiO4/C composite for cathode of lithium ion batteries

A Li2FeSiO4/C composite cathode for lithium ion batteries was synthesized at 650 ℃ by solid-state reaction. The effects of carbon sources and carbon content on the properties of the Li2FeSiO4/C composites were investigated. The crystalline structure, morphology, carbon content and charge/discharge performance of Li2FeSiO4/C composites were determined by X-ray diffraction(XRD), scanning electron microscopy(SEM), carbon/sulfur analyzer and electrochemical measurements. As carbon content increases in the range of 5%-20%, the amount of Fe3O4 impurity phase decreases. The SEM micrographs show that the addition of the carbon is favorable for reducing the Li2FeSiO4 grain size. Using sucrose as carbon source, the Li2FeSiO4/C composite with 14.5% carbon synthesized at 650 ℃ shows good electrochemical performance with an initial discharge capacity of 144.8 mA-h/g and a capacity retention ratio of 94.27% after 13 cycles.     

球形LiNi1/3Co1/3Mn1/3O2的合成及其电化学性能

以化学共沉淀法制备的球形Ni1/3Co1/3Mn1/3CO3为前驱体合成了球形LiNi1/3Co1/3Mn1/3O2,研究LiNi1/3Co1/3Mn1/3O2合成工艺对产物形貌的影响.结果表明直接以前驱体Ni1/3Co1/3Mn1/3CO3与Li2CO3反应合成的LiNi1/3Co1/3Mn1/3O2的一次颗粒较大,以前驱体分解后的氧化物与Li2CO3反应合成的LiNi1/3Co1/3Mn1/3O2的一次颗粒相对细小;合成的LiNi1/3Co1/3Mn1/3O2均为具有层状结构的纯相物质;球形正极材料LiNi1/3Co1/3Mn1/3O2充放电过程中存在一个材料活化的过程,在前10周期充放电时,电池容量处于增加的状态;在2.7～4.3 V的电压范围内1 C倍率下电池的放电比容量达到149 mA·h/g,0.2 C倍率下为158 mA·h/g,经50次循环后容量无衰减.     

控制结晶法合成球形正极材料LiNi0.8Co0.2O2及其电化学性能

采用控制结晶法制备锂离子电池用高密度球形正极材料LiNi0.8Co0.2O2。对前驱体Ni0.8Co0.2(OH)2制备工艺进行优化,在金属盐溶液流速为8 mL/min,搅拌速率450 r/min,pH值为11.5,氨浓度20 g/L反应36 h的条件下,合成了振实密度为2.02 g/cm3的球形Ni0.8Co0.2(OH)2。并以Ni0.8Co0.2(OH)2为原料,与LiOH.H2O进行混合研磨进行高温烧结,考察烧结制度对合成材料LiNi0.8Co0.2O2电化学性能的影响。在Li/(Ni Co)配比为1.05、氧气流量为800 mL/min,750℃下烧结16 h所得材料LiNi0.8Co0.2O2电化学性能最优:在0.2 C,3.0~4.3 V的条件下,首次放电容量达到195.4 mA.h/g,循环50次后容量保持率达到89.2%。     

Effect of annealing treatment on electrochemical property of LiNi0.5Mn1.5O4 spinel

LiNi0.5Mn1.5O4 was prepared under different cooling conditions. The electrochemical properties of LiNi0.5Mn1.5O4 prepared under different cooling conditions were investigated. The results show that LiNi0.5Mn1.5O4 synthesized with or without annealing treatment has similar X-ray diffraction patterns that can be indexed to cubic spinel structure. The mass loss occurring above 650℃ during the heating process can be mostly gained during the cooling process. LiNi0.5Mn1.5O4 synthesized with an annealing treatment exhibits almost one voltage plateau at around 4.7 V and higher capacity with a quick fading upon cycling, whereas LiNi0.5Mn1.5O4 synthesized without annealing treatment shows two voltage plateaus at around 4.1 and 4.7 V and superior capacity retention upon cycling both at rates of 1/7C and 1 C, though the capacity is not high.     

Synthesis and physicochemical properties of LiLa0.01Mn1.99O3.99F0.01 cathode materials for lithium ion batteries

Spinel lithium manganese oxide cathode materials were synthesized using the ultrasonic-assisted sol-gel method. The synthesized samples were investigated by differential thermal analysis （DTA） and thermogravimetry （TG）, powder X-ray diffraction （XRD）, scanning electron microscopy （SEM）, cyclic voltammetry （CV）, and the charge-discharge test. TG-DTA shows that significant mass loss occurs in two temperature regions during the synthesis of LiLa0.01Mn1.9903.99F0.01. XRD data indicate that all samples exhibit the same pure spinel phase, and LiLa0.01Mn1.9903.99F0.01 and LiLa0.01Mn1.9904 samples have a better crystallinity than LiMn2O4. SEM images indicate that LiLa0.01Mn1.9903.99F0.01 has a slightly smaller particle size and a more regular morphology structure with narrow size distribution. The charge-discharge test reveals that the initial capacities of LiMn2O4, LiLa0.01Mn1.99O4, and LiLa0.01Mn1.99O3.99F0.01 are 130, 123, and 126 mAh·g^-1, respectively, and the capacity retention rates of the initial value, after 50 cycles, are 84.8%, 92.3%, and 92.1%, respectively. The electrode coulomb efficiency and CV reveal that the electrode synthesized by the ultrasonic-assisted sol-gel （UASG） method has a better re- versibility than the electrode synthesized by the sol-gel method.     

Synthesis and characterization of LiNi0.95-xCoxAl0.05O2 for lithium-ion batteries

Samples of LiNi0.95-xCoxAl0.05O2 （x = 0.10 and 0.15） and LiNiO2, synthesized by the solid-state reaction at 725℃ for 24 h from LiOH-H2O, Ni2O3, Co2O3, and AI（OH）3 under an oxygen stream, were characterized by TG-DTA, XRD, SEM, and electrochemical tests. Simultaneous doping of cobalt and aluminum at the Ni-site in LiNiO2 was tried to improve the cathode performance for lithium-ion batteries. The results showed that co-doping （especially, 5 at.% A1 and 10 at.% Co） definitely had a large beneficial effect in increasing the capacity （186.2 mA.h/g of the first discharge capacity for LiNio.s.42OoaoAlo.0502） and cycling behavior （180.1 mA-h/g after 10 cycles for LiNio.85CooaoAlo.osO2） compared with 180.7 mA.h/g of the first discharge capacity and 157.7 mA.h/g of the tenth discharge capacity for LiNiO2, respectively. Differen- tial capacity versus voltage curves showed that the co-doped LiNio.95_xCoxmlo.osO2 had less intensity of the phase transitions than the pristine LiNiO2.     

Synthesis and electrochemical performance of Co3O4/C composite anode for lithium ion batteries

The Co3O4/acetylene black composite anodes were successfully prepared by combination of oxalate precipitation and pyrolysis of the precipitate. The composite and its precursor were characterized by thermo-gravimetric analysis(TGA), differential thermal analysis(DTA), X-ray diffractometry(XRD), scanning electronic microscopy(SEM) and electrochemical measurements. The effects of carbon content and calcination temperature on properties of the composite were investigated in detail. The cycling performance of the Co3O4 anode is improved remarkably by the addition of carbon. As the calcination temperature rises in the range of 300-450 ℃, the crystallinity of the composites increases, but their reversible capacity and cycling stability decrease. Being charged/discharged at a current density of 0.1C rate, the optimized Co3O4/C composite anode shows a large initial reversible capacity of 757 mA-h/g, and a capacity of 743 mA-h/g is observed after 10 cycles.