富锂层状正极材料Li_(1.2)Mn_(0.54)Ni_(0.13)Co_(0.13)O_2的二次颗粒粒径对其倍率性能的影响

Effect of Different Second Particle Size on Rate Capability of Li-Rich Layered Cathode Materials Li_(1.2)Mn_(0.54)Ni_(0.13)Co_(0.13)O_2

采用碳酸盐共沉淀的方法成功制备了不同二次颗粒粒径的富锂层状正极材料Li1.2Mn0.54Ni0.13Co0.13O2。并运用X射线衍射(XRD)、场发射扫描电镜(FESEM)、激光粒度测试和电化学测试等手段对所得材料的结构、形貌、粒度分布及电化学性能进行表征。结果显示,不同二次颗粒粒径的Li1.2Mn0.54Ni0.13Co0.13O2在材料结构上没有明显的差别,且首次放电比容量接近,均达到了281m Ah·g-1。但是,二次颗粒粒径越小,富锂层状材料的表现出的倍率性能越优异,当二次颗粒的D50为4.59μm,其在3C倍率下的放电容量达到了199 m Ah·g-1。这是因为二次颗粒粒径越小,富锂层状材料可更好的与导电剂和电解液接触,且锂离子的扩散路径更短,从而表现出更好的倍率特性。

Li-rich layered cathode materials Li_（1.2）Mn_（0.54）Ni_（0.13）Co_（0.13）O_2with different second particle size distributionwere prepared by carbonate based co-precipitation. The samples were characterized by X-ray diffraction （XRD）,field emission scanning electron microscope （FESEM）, laser particle size analyze and electrochemicalperformance tests. The results showed that there were noLi_（1.2）Mn_（0.54）Ni_（0.13）Co_（0.13）O_2materials with different second particlecapacities （281 mAh· g-l） for the first cycle. However, the significant differences in structures between thesize, and the three samples had similar dischargesample with smaller second particle size showed amuch superior rate capability to the sample with bigger particle size. When the Dso of second particle sizereduced to 4.59 μm, the sample delivered a discharge capacity of 199 mAh .g-i at 3C-rate. The improvement inrate capability could be attributed to the smaller particle size, which gives a better contact between the activematerial and the electrolyte/conductive agent, at the same time a shorter diffusion path.