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.     

Effect of ball milling and electrolyte on properties of high-voltage LiNi_(0.5)Mn_(1.5)O_4 spinel

1 INTRODUCTIONRecently ,several research groups have repor-ted transition-metal-substituted spinel materials(Li MxMn2 -xO4, M: Cr , Co , Fe , Ni , Cu) withhigh-voltage plateaus above 4 .5 V[1 5]. Amongthese materials ,Li Ni0 .5Mn1 .5O4is the most prom-ising and attractive one because of its good cyclicproperty and relatively high capacity with a plateauat around 4 .7 V[3 ,6].Now, a variety of methods were used forpreparation of Li Ni0 .5Mn1 .5O4,such as solid-statereaction[4 ,7 ,8]…     

LiNi_(0.5)Mn_(1.5)O_4/Ag复合材料的制备及其电化学性能

采用流变相法合成LiNi0.5Mn1.5O4粉末。以甲醛为还原剂,采用化学镀法制备LiNi0.5Mn1.5O4/Ag复合材料。通过X射线衍射分析、扫描电镜分析以及电化学测试等手段对LiNi0.5Mn1.5O4/Ag的微观结构、表面形貌和电化学性能进行研究。结果表明:在LiNi0.5Mn1.5O4/Ag中,LiNi0.5Mn1.5O4表面被包覆一层分散均匀且颗粒大小均匀的Ag,Ag颗粒的大小为200～300nm。Ag颗粒的存在增加LiNi0.5Mn1.5O4颗粒之间的电子导电性,降低电池的极化作用,减少锰的溶解,使得LiNi0.5Mn1.5O4/Ag具有比LiNi0.5Mn1.5O4更高的可逆容量、更稳定的循环性能和更好的倍率性能。以0.2C放电时,LiNi0.5Mn1.5O4/Ag的首次放电容量达到143.8mA·h/g;而经100次循环后,以0.2C和2.0C放电时,LiNi0.5Mn1.5O4/Ag的容量保持率分别达到99.2%和86.8%。     

5 V正极材料LiNi0.5Mn1.5O4的草酸共沉淀法合成及性能

通过草酸共沉淀法成功合成了5 V正极材料LiNi0.5Mn1.5O4,采用XRD、SEM、充放电试验和循环伏安法对合成产物进行表征。XRD和SEM分析结果表明,所合成的正极材料LiNi0.5Mn1.5O4具有立方尖晶石结构（空间群为Fdˉ3 m）,结晶度高,粒度适中且比较均匀。电化学测试结果表明,合成产物具有优良的电化学性能,它仅在4.7 V附近有一个放电平台,0.1 C的放电容量高达133 mAh/g,50次循环后放电容量仍保持在128 mAh/g以上,1和3 C的放电容量在30次循环后也分别保持在122和101 mAh/g以上     

Effect of ball milling and electrolyte on properties of high-voltage LiNi0.5 Mnl.5O4 spinel

Effect of ball milling and electrolyte on the properties of high-voltage LiNi0.5 Mn1.5 O4 was investigated. Ball milling has significant effect on the synthesis and property of LiNi0.5 Mn1.5O4. The X-ray diffraction（XRD） patterns indicate that LiNio.s Mn1.5O4 can＇t be synthesized without ball milling even calcined at 900 ℃. When synthesized with bail milling, LiNi0.5 Mn1.5O4 almost exhibits only one plateau at around 4.7 V. With the increase of ball milling time, the capacity of LiNi0.5Mn1.5O4 increases, but the cycling performance is not highly affected. The electrochemical property of LiNi0.5 Mn1.5O4 highly depends on the electrolyte. The stable and high-voltage-resistant electrolyte is much beneficial to enhancement of electrochemical property of LiNi0.5 Mn1.5O4, such as coulombic efficiency and cycling performance.     

尖晶石LiNi_(0.5)Mn_(1.5)O_4中掺杂Fe的作用机理

利用湿化学法结合固相反应法制备了尖晶石LiNi_(0.5)Mn_(1.5)O_4和掺杂Fe的LiNi_(0.45)Fe_(0.1)Mn_(1.45)O_4材料,从晶体结构、表面形貌、充放电曲线特点、倍率性能等方面比较了掺杂Fe以后对材料的影响,并结合热重实验,通过测试失重量,进而分析了材料中的氧缺陷含量,推导出掺杂Fe的作用机理:尖晶石LiNi_(0.5)Mn_(1.5)O_4材料中掺杂Fe元素,能够使材料晶体中保持一定的氧缺陷,从而使得材料含有一定量的Mn~(3+),提高了材料充放电倍率性能。     

初始Li/(Mn+Ni)摩尔比对LiNi0.5Mn0.5O2电化学性能的影响

以Li2CO3,MnCO3和Ni(OH)2为原料,采用一步固相反应制备锂离子电池层状结构正极材料LiNi0.5-Mn0.5O2,采用X射线衍射和扫描电镜对其结构和形貌进行表征,并研究配料时不同初始Li/(Mn Ni)摩尔比(1.0,1.05,1.1,1.2,1.5)对LiNi0.5Mn0.5O2电化学性能的影响。X射线衍射结果表明,在600℃预烧12 h而后800℃烧结24 h的条件下各样品结晶完整,初始Li/(Mn Ni)摩尔比为1.5时样品有未知相杂质生成。扫描电镜分析表明,随着初始Li/(Mn Ni)摩尔比的增大,颗粒团聚加剧。电化学测试结果表明,随着初始Li/(Mn Ni)摩尔比(≥1.05)的提高,初始容量有下降趋势。初始Li/(Mn Ni)摩尔比为1.05和1.1时样品首次放电容量分别为167.0 mA.h/g和147.2 mA.h/g,循环20次后容量保持率分别为88.2%和97.8%。     

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。     

5V锂离子电池尖晶石正极材料LiM0.5Mn1.5O4的研究评述

评述了锂离子电池锰酸锂正极材料的重要性，介绍了3d．过渡金属离子（Cr^3＋，Ni^2＋，Cu^2＋，Fe^3＋）掺杂在锰酸锂正极材料中的应用。研究了3d-过渡金属离子掺杂对锰酸锂正极材料结构和电化学性能的影响，并提出了其影响锂离子电池充放电和循环性能的机制。展望了3d-过渡金属离子掺杂在锂离子电池锰酸锂正极材料中的发展前景，并指出LiM0.5Mn1.5O4是非常有应用前景的5V锂离子电池正极材料。     

Effects of Na+ doping on crystalline structure and electrochemical performances of LiNi0.5Mn1.5O4 cathode material

Pristine LiNi_0.5Mn_1.5O₄ and Na-doped Li_0.95Na_0.05Ni_0.5Mn_1.5O₄ cathode materials were synthesized by a simple solid-state method. The effects of Na⁺ doping on the crystalline structure and electrochemical performance of LiNi_0.5Mn_1.5O₄ cathode material were systematically investigated. The samples were characterized by XRD, SEM, FT-IR, CV, EIS and galvanostatic charge/discharge tests. It is found that both pristine and Na-doped samples exhibit secondary agglomerates composed of well-defined octahedral primary particle, but Na⁺ doping decreases the primary particle size to certain extent. Na⁺ doping can effectively inhibit the formation of Li_xNi_1–xO impurity phase, enhance the Ni/Mn disordering degree, decrease the charge-transfer resistance and accelerate the lithium ion diffusion, which are conductive to the rate capability. However, the doped Na⁺ ions tend to occupy 8a Li sites, which forces equal amounts of Li⁺ ions to occupy 16d octahedral sites, making the spinel framework less stable, therefore the cycling stability is not improved obviously after Na⁺ doping.     

Powder electrochemical properties with different particle sizes of spinel LiAl0.05Mn1.95O4 synthesized by sol-gel method

An Al-doped spinel lithium manganese oxide was prepared by the adipic acid-assisted sol-gel method at 800℃, and the cathode materials （Liml0.05Mnl.9504） with different particle sizes were obtained through ball milling. The effects of particle size on the electrochemical performance of LiAl0.05Mnl.9504 samples were investigated by differential thermal analysis and thermogravimetry, X-ray diffraction, galvanostatic charge-discharge test, cyclic voltammetry, and electrochemical impedance spectroscopy. The results indicate that all samples with different particle sizes show the same pure spinel phase and good crystal structure; LiAlo.osMnl.9504 with Dso = 17.3 μm shows better capacity retention; LiAlo.osMnl.gsO4 cathode materials with small particle size have a bigger resistance of charge transfer than the large one, and the particle size has significant effects on the electrochemical performance of Al-doped spinel LiMn2O4 cathode materials.     

Effects of chromium doping on performance of LiNi0.5Mn1.5O4 cathode material

In order to improve the cycle and rate performance of LiNi_0.5Mn_1.5O₄, LiCr_2YNi_0.5–YMn_1.5–YO₄ (0≤Y≤0.15) particles were synthesized by the sucrose-aided combustion method. The effects of Cr doping in LiNi_0.5Mn_1.5O₄ on the structures and electrochemical properties were investigated. The samples were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), galvanostatic charge-discharge test and electrochemical impedance spectrum (EIS). The results indicate that the LiCr_2YNi_0.5–YMn_1.5–YO₄ possess a spinel structure and small particle size, and LiCr_0.2Ni_0.4Mn_1.4O₄ exhibits the best cyclic and rate performance. It can deliver discharge capacities of 143 and 104 mA·h/g at 1C and 10C, respectively, with good capacity retention of 96.5% at 1C after 50 cycles.     

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.     

Structure and electrochemical properties of Li(Ni_(0.5)Mn_(0.5))_(1-x)TixO_2 prepared by one-step solid state reaction

1Introduction Many efforts have been made to develop new materials as an alternative to LiCoO2due to the relatively high cost and toxicity of Co.Since OHZUKU and MAKIMURA[1]successfully synthesized LiNi0.5Mn0.5-O2with excellent performance by solid state …     

Heat treatment effect on electrochemical properties of spinel Li4Ti5O12

Anode material Li4Ti5O12 was prepared at 800℃ by a solid-state reaction, followed by heat-treatment at 600℃ for different times （0, 2, 8, and 12 h）. The effects of heat-treatment time on the particle morphology, rate-capability, and electrode kinetic process of the Li4Ti5O12 electrode, and on the lithium ion diffusion coefficient inside the Li4Ti5O12 electrode were investigated. Proper heat treatment could smoothen the particle surface of Li4Ti5O12 particles and increase the rate-capability of the electrode. Overlong heat treatment might cause particle aggregation and hence result in a poor electrode kinetic process. A sample with 8 h of heat treatment showed the best rate-capability and the lowest electrode reaction resistance. Heat treatment for 2-8 h does not significantly change the lithium ion diffusion coefficient inside the Li4Ti5O12 electrode, whereas, 12-h treatment results in a lower lithium ion diffusion coefficient.     

Synthesis and characterization of LiNi0.45Co0.10Mn0.45O2 cathode for lithium ion batteries

1INTRODUCTIONAdvanced rechargeable lithium ion batteriesare attractive for use in consumer electronic andelectric vehicle(EV)application because of a fa-vorable combination of voltage,energy density,cycling performance,and have been developed rap-idly worldwide during the past decade[1,2].LiCoO2has been widely used as a cathode material in com-mercial lithiumion battery because it is reasonableeasy to synthesize and shows a stable discharge ca-pacity[3].But due to its high cost and toxic…     

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.     

LiMgxNi0.5-xMn1.5O4的制备和电化学性能

为改善LiNi0.5Mn1.5O4的电化学性能,采用流变相法合成掺镁的锂离子电池正极材料LiMgxNi0.5-xMn1.5O4(x=0,0.05,0.1)。XRD测试结果表明所得材料仍为尖晶石结构。电化学性能测试结果显示:当x取值0.1,在3.5～4.9V电压范围内进行充放电循环时,材料LiMg0.1Ni0.4Mn1.5O4具有较好的循环性能,1C充放电时,初始放电比容量可达110.22mAh/g,30次循环后容量衰减率仅为7.7%。