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。     

高容量正极材料Li[Li0.2Ni0.2Mn0.6]O2的合成及电化学性能

以LiOH.H2O、Ni(OH)2和Mn3O4为原料,采用固相法合成锂离子电池正极材料Li[Li0.2Ni0.2Mn0.6]O2。通过X射线衍射(XRD)、扫描电子显微镜(SEM)对所得样品的结构和形貌进行表征,并测试了该材料的倍率性能和高低温性能。结果表明:900℃下烧结10 h后可获得晶粒细小均匀的层状Li[Li0.2Ni0.2Mn0.6]O2材料,并具有良好的电化学性能,放电容量最高可达235.9 mA.h/g;在50℃下测试时该材料的放电容量高达284.4 mA.h/g,并表现出良好的循环性能,其倍率性能和低温性能还有待进一步改善。     

锂离子电池Li（Ni3／8Co3／8Mn2／8）O2层状正极材料的制备与电化学性能

采用液相共沉淀方法合成锂离子电池用Li(Ni3/8Co3/8Mn2/8)O2正极材料,以XRD、SEM、原子吸收光谱法和电池充放电循环测试方法表征Li(Ni3/8Co3/8Mn2/8)O2粉末的结构和性能.结果表明:900℃焙烧10 h合成的Li(Ni3/8Co3/8Mn2/8)O2粉末样品具有较好的综合电化学性能和良好的六角层状结构,阳离子混合度小,六角晶格有序性高,颗粒为由小晶粒结合而成的多晶体,平均粒径约为4.5 μm,I003/I104为1.25,R值为0.48,首次放电容量为172.9 mA·h/g(2.8～4.5 V,0.1C倍率),0.2C倍率循环20次后电容量为首次循环放电容量的96.1%.     

锂离子电池正极材料LiNi_(0.5)Co_(0.5)O_2制备与电化学性能

采用球磨湿混和旋转合成相结合的新工艺制备了锂离子电池正极材料LiNi0.5Co0.5O2,并对材料进行了粒度、化学成分以及电化学性能测试。球磨湿混工艺能将原料混合均匀,并能有效地使粒度细化。旋转合成工艺能使混合料在均匀的温度场中进行反应,并使反应产物粒度均匀和成分均匀。制备的LiNi0.5Co0.5O2为单一的α-NaFeO2层状结构,粉末粒度分布范围窄,平均粒径约为8μm-10μm。电化学性能测试结果表明,在0．2mA/cm^2充放电流密度和3．0V－4．2V电压范围内,首次充电容量为173mAh/g,放电容量为148mAh/g。循环次数达30次时, 放电容量还有129mAh/g,循环稳定性良好。球磨湿混和旋转合成相结合的固相合成新工艺能制备出电化学性能良好的LiNi0.5Co0.5O2正极材料。     

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     

锂离子电池正极材料LiNixCo1-2xMnxO2的制备及电化学性能

采用改进的高温固相法合成锂离子电池正极材料LiNixCo1-2xMnxO2.考察不同x值、不同Li/(Ni+Co+Mn)摩尔比、不同焙烧温度、不同煅烧时间对其电化学性能的影响并通过XRD对其结构进行表征.结果表明,提高Co含量可以改善材料的循环性能;当n(Li)/n(M)(M=Ni, Co, Mn)=1.10,在950~1000 ℃煅烧20 h时,可得到电化学性能优良的正极材料.     

层状Li(Ni0.5Mn0.5)1-xTixO2材料的合成及性能研究

以Li2CO3,Ni(OH)2,MnCO3,TiO2为原料,采用高温固相合成法制备了层状Li(Ni0.5Mn0.5)1-xTixO2。通过X射线衍射确定了不同钛掺杂量样品的相组成。用扫描电镜对组织形貌进行了观测。对用所制样品组装的电池的充放电和循环性能进行了测试。实验结果得出:所制备的Li(Ni0.5Mn0.5)1-xTixO2的结构为α-NaFeO2型层状结构,当x=0.02时,L(iNi0.5Mn0.5)1-xTixO2的首次放电容量为161mA·h/g,25次循环后容量仍保持在144mA·h/g,具有较高的比容量和良好的循环性。     

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.     

不同方法合成的LiVPO4F/C的电化学性能（英文）

通过一步固相反应和两步固相反应分别合成LiVPO4F/C,采用XRD、SEM和电化学性能测试对LiVPO4F/C进行性能表征。XRD研究表明一步固相反应合成的LiVPO4F/C与两步固相反应合成的样品一样,均属于三斜晶系结构。SEM研究表明:一步固相反应合成的LiVPO4F/C颗粒比两步固相反应合成的样品颗粒小,一步固相反应合成的 LiVPO4F/C 样品电化学性能得到提高是由于草酸作为还原剂和碳源合成的样品颗粒变小。交流阻抗研究表明步固相反应合成的LiVPO4F/C样品电化学阻抗减小。     

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。     

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%。     

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 …     

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 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]…     

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.     

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。