NCM811/石墨全电池高温循环性能衰退机理研究

Investigation of high temperature cycling performance for NCM811/Graphite battery

将商业化生产的Ni_(0.8)Co_(0.1)Mn_(0.1)(OH)_2前驱体与LiOH充分混合后在氧气气氛下烧结制备了NCM811三元材料。以NCM811材料为正极,石墨为负极制备软包电池,1M LiPF_6的EC/EMC/DEC(3∶5∶2)为电解液。电池在45℃下以1C/1C进行恒电流充放电,电池循环500圈后,容量保持率为85%。将循环前后的电池拆解,用XRD,SEM和EIS等方法对循环前后的极片做对比分析,结果表明,循环后正极材料二次颗粒沿一次颗粒晶界发生破碎,导致电解液的消耗、正极材料失活和电池极化的迅速增加,最终引起电池循环性能的衰退。

Commercialized Ni_(0.8)Co_(0.1)Mn_(0.1)(OH)_2 precursor and LiOH were fully mixed and calcined at oxygen atmosphere to prepare the Ni-rich LiNi_(0.8)Co_(0.1)Mn_(0.1)O_2(NCM811 for short)cathode material.The as-prepared NCM811 cathode and graphite anode were used to prepare the pouchtype full cell,with 1M LiPF6 in EC/EMC/DEC(3∶5∶2)as electrolyte.The cells were cycled at1 Crate at 45℃,and 85% capacity was obtained after 500 cycles.The cells before and after cycling were disassembled and characterized via XRD,SEM and EIS method.The results demonstrate that the secondary particles formed cracks along the grain boundary of primary particles,leading to the electrolyte consuming,material deactivation,and polarization increasing,and the cycling performance was deteriorated as a result.