Li2ZrO3包覆锂离子电池正极材料Li[Li0.2Ni0.2Mn0.6]O2的制备及其电化学性能

富锂锰基材料因其具有较高的充放电比容量而备受关注。针对其首次库仑效率低、循环和倍率性能差的问题,将具有三维Li^+通道的锂离子导体Li2ZrO3引入至富锂锰基正极材料LiLi0.2Ni0.2Mn0.6]O2的表面对其进行包覆改性研究。通过XRD,TEM,SEM,EDS综合分析可知:Li2ZrO3成功包覆到样品表面。包覆层厚度为3 nm(包覆量1%,质量分数)时复合材料的电化学性能得到显著提升。0.1 C(1 C=200 mAh·g^-1)倍率下首次放电比容量可达271.5 mAh·g^-1,库仑效率为72.4%,降低了首次不可逆容量损失;0.5 C下循环100周次后放电比容量为191.5 mAh·g^-1,容量保持率为89.5%,5 C倍率放电比容量为75 mAh·g^-1,倍率性能提升。适当厚度的均匀Li2ZrO3包覆层可在样品表面形成核壳结构使样品更稳定,减少表面副反应,阻止生成较厚SEI膜,这得益于Li2ZrO3本身的高电导率、高电化学稳定性和较好的锂离子传导性。

Fabrication and electrochemical performance of Li[Li0.2Ni0.2Mn0.6]O2 coated with Li2ZrO3 as cathode material for lithium-ion batteries

Lithium-rich manganese-based materials have attracted much attention because of their high charge-discharge capacity. In order to solve the problems of low coulombic efficiency, poor cycling performance and poor rate capability, lithium-ion conductor Li2ZrO3 with three-dimensional Li^+ channel was employed to coat lithium-rich manganese-based cathode material LiLi0.2Ni0.2Mn0.6]O2. According to the structure and morphological analysis, different amounts of Li2ZrO3 were successfully coated on the surface of the sample. When the thickness of the coating layer is 3 nm(1% coating amount, mass fraction), the electrochemical performance of the composite material is significantly improved. The first discharge specific capacity is 271.5 mAh·g^-1 and the first coulombic efficiency is 72.4%. The first irreversible capacity loss is obviously reduced. The discharge specific capacity at 0.5 C is 191.5 mAh·g^-1 and the capacity retention is 89.5%. The specific capacity at 5 C is 75 mAh·g^-1 and the rate performance is improved. The results show that a uniform thickness of Li2ZrO3 coating layer can form a core-shell structure on the surface of the sample to make the sample more stable. It can reduce surface side reactions and prevent the formation of thicker SEI films. All of these results benefit from the high conductivity, high electrochemical stability and good lithium ion conductivity of Li2ZrO3 coating layer.