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%。     

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.     

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。     

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.     

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.     

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.     

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 …     

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.     

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…     

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.     

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。     

Mg、F复合掺杂尖晶石LiMg0.1Mn1.9O3.95F0.05的合成和电化学行为研究

以己二酸为配位体采用溶胶-凝胶法合成了LiMn2O4,Mg掺杂或Mg和F复合掺杂的尖晶石锂镁氧化物正极材料.对合成出的样品采用X-射线衍射仪、X-光电子能谱、扫描显微电子镜、循环伏安测试和充放电测试仪进行了详细的研究.X-射线衍射结果表明,所有的样品都具有相同的纯尖晶石相,LiMg0.1Mn1.9O4和LiMg0.1Mn1.9O3.95F0.05与LiMn2O4的样品相比,具有较小的晶格参数和晶胞体积.X-光电子能谱试验结果表明,在LiMn2O4中,Mn3 和Mn4 的相对量分别为50.2%和49.8%,而LiMg0.1Mn1.9O3.95F0.05中Mn3 和Mn4 的相对量分别为48.4%和51.6%.扫描电镜结果显示,LiMg0.1Mn1.9O3.95F0.05颗粒尺寸略小、尺寸分布窄,形态结构更为规整.循环伏安实验显示,Mg和F复合掺杂的尖晶石具有更好的可逆性.LiMn2O4,LiMg0.1Mn1.9O4,LiMg0.1Mn1.9O3.95F0.05样品的首次放电能量和能量保持率分别为123、111、114 mAh·g-1和86.5%、92.3%、90.9%,且LiMg0.1Mn1.9O4和LiMg0.1Mn1.9O3.95F0.05具有比LiMn2O4更高的库仑效率.     

以Mn3O4为前驱体制备尖晶石型LiMn2O4及其性能

采用改进的固相反应法合成了高性能的锂离子电池正极材料LiMn2O4。首先,以廉价的MnSO4为原料,通过水解氧化法制备纳米级Mn3O4前驱体;然后,将Mn3O4和Li2CO3混合均匀,在750℃固相反应20 h,得到尖晶石型LiMn2O4。用X射线衍射(XRD)和扫描电镜(SEM)对Mn3O4前驱体和LiMn2O4样品进行表征,用充放电测试和循环伏安技术对LiMn2O4样品进行电化学性能研究。结果表明:所制备的LiMn2O4具有完整的尖晶石型结构,且晶体粒子分布均匀。所制备的LiMn2O4材料在3.0~4.4 V之间,室温(25℃)下,在0.2C倍率下首次放电比容量为130.6 mA.h/g;在0.5C倍率下首次放电比容量为127.1 mA.h/g,30次循环后,容量仍有109.5 mA.h/g,且样品具有较好的高温性能。     

Structure and electrochemical performance of spinel LiMn2O4 synthesized by mechanochemical process

1　INTRODUCTIONLithium ion battery was used in many areasbecause of its high voltage, high energy densityand long cycle life and so on. Spinel lithium man ganese oxide was one of the most promising mate rials in term of its environmental benign, low cost,easy preparation and temperature safety. Mainproblem is the poor cycle life. As we all know thatboth the structure and electrochemical performanceof material strongly depended on the preparingmethod and starting…