高容量锂离子电池正极材料LiNi0.9Co0.05Mn0.025Mg0.025O2的合成及电化学性能

以β-Ni0.9Co0.05Mn0.025Mg0.025(OH)2和LiOH.H2O为原料通过高温固相法合成了球形LiNi0.9Co0.05Mn0.025Mg0.025O2。采用热重-差热分析了反应过程,采用X射线衍射和扫描电镜对粉末的结构和形貌进行了表征。采用充放电测试和循环伏安测试对材料电化学性能进行了研究。结果表明:750℃煅烧12 h合成的LiNi0.9Co0.05Mn0.025Mg0.025O2为Li原子混排较少的良好层状结构,二次颗粒尺寸在15μm左右,且具有最高的放电比容量和良好的循环性能,在0.2C,2.8~4.3 V的条件下,首次放电比容量达207 mAh.g-1,40次循环后容量保持率为92.5%。

Synthesis and Electrochemical Properties of High Capacity LiNi0.9Co0.05Mn0.025Mg0.025O2 Cathode for Lithium Ion Batteries

Layered structured LiNi0.9Co0.05Mn0.025Mg0.025O2 was successfully synthesized by heating a mixture of β-Ni0.9Co0.05Mn0.025Mg0.025(OH)2 and LiOH·H2O at elevated temperature.Differential scanning calorimetry(DSC) and thermogravimetry analysis(TGA) were employed to study the reaction process.The Ni0.9Co0.05Mn0.025Mg0.025(OH)2 and synthesized LiNi0.9Co0.05Mn0.025Mg0.025O2 were characterized by means of X-ray diffraction(XRD) and scanning electron microscope(SEM),while the electrochemical properties of LiNi0.9Co0.05Mn0.025Mg0.025O2 were investigated by charge-discharge test and cyclic voltammetry(CV).Structure analysis shows the LiNi0.9Co0.05Mn0.025Mg0.025O2 synthsized at 750 ℃ for 12 h possess a well-layered hexagonal structure and a low level of the cation-mixing of Li layer.Scaning electron micrographs reveal that the morphology of the samples is characterized by spherical second particles of ~15 μm.The analysis from electrochemical test suggests that heating the mixture at 750 ℃ for 12 h is the optimized synthesis condition for highest initial discharge capacity and best cycling performance.The first discharge specific capacity between 2.8 and 4.3 V at 0.2C is tested to be 207 mAh·g-1 and 92.5% of the discharge capacity remained after 40 cycles.The CV result shows that the multi-doping of Co,Mn and Mg has strengthened the cycling capability.