Aqueous Solution-Evaporation Route Synthesis and Phase Structural Research of the Li-Rich Cathode Li_(1.23)Ni_(0.09)Co_(0.12)Mn_(0.56)O_2 by In-Situ XRD

采用水溶-蒸发法成功合成了锂离子电池lI1.23nI0.09CO0.12Mn0.56O2正极材料.通过扫面电镜(SEM)、非原位X射线衍射(Xrd)、原位Xrd观察材料形貌、表征材料结构,并测试电极电化学性能.结果显示,材料为粒径330nM的多边形结构,是层状的固溶体—lI2MnO3结构,该正极0.1C首周期放电比容量250.8 MAH·g-1,40周期循环容量保持率86.5%.通过原位Xrd可确证电极在首周期放电过程产生少量lI0.9MnO2新相,在其后多周期循环过程电极层状结构趋于向尖晶石结构发生转变致使电极电化学性能恶化.此外,晶格参数C首周期充电过程先增后减在4.54 V左右保持稳定,放电与第2周期充电过程其值逐渐下降;晶格参数A则经历了下降平稳再升高的过程,该数值的变化均对应于相应电化学行为.The Li-rich Li 1.23 Ni0.09 Co0.12 Mn0.56 O2 material was synthesized via aqueous solution-evaporation route.The structure and morphology of the material were characterized by means of XRD and SEM.The results indicated that the single particle of the product was polygonal with the size of 330 nm and the structure was layered solid solution with a certain amount of Li2 MnO3.Electrochemical tests showed that the first discharge capacity of the Li-rich layered material was 250.8 mAh·g-1at 0.1C,the capacity retention was 86.5% after 40 cycles.Through in-situ XRD study a new phase Li0.9 MnO2 which would cause electrochemical properties deteriorated due to its structure transformation from layered to spinel came out with a small amout during the first discharge cycle.Moreover, the value of c-parameter increased first and decreased before 4.54 V, and remained stable till the end of the first charge, and then reduced from the first discharge to the second charge continually.However, the value of a-parameter underwent a falling-steady-rising course.The change in the values of the lattice parameters corresponded to the variation of electrochemical behaviors.国家自然科学基金项目(No.21273184); 科技部863项目(No.2011AA11A254); 973计划项目(No.2009CB220102)项目资