掺Ga对锂离子电池正极材料LiCo0.3-xGaxNi0.7O2的影响

采用溶胶-凝胶法在0≤x≤0.5的范围内合成了LiCo0.3-xGaxNi0.7O2的单相.对样品进行了XRD、粒度、比表面积和充放电循环测试.随着掺Ga量的增加,LiCo0.3-xGaxNi0.7O2的放电容量增加.其中LiCo0.25Ga0.05Ni0.7O2在2.8～4.3V和0.2C时的首次放电容量为177.5mA·h/g,经25次充放电循环后无容量衰减.LiCo0.25Ga0.05Ni0.7O2的放电容量随着放电倍率的增大而减小,随着充放电域压上限的增加而增大.但是材料的放电容量在高放电倍率下放电后仍可以完全恢复,且其循环性能与放电域压上限无关.此外,LiCo0.25Ga0.05Ni0.7O2在充放电循环中结构稳定,无相变发生.

Effect of Gallium Doping on the Layered LiCo0.3-xGaxNi0.7O2 Cathode Materials for Lithium Secondary Batteries

Gallium-doped layered LiCo0.3-xGaxNi0.7O2 materials were synthesized by a sol-gel method. Single phase of LiCo0.3-xGaxNi0.7O2 could be prepared in 0≤x≤0.5 region. The samples were characterized by means of XRD, particle size, BET and charge/discharge test. The discharge capacity of {LiCo0.3-xGaxNi0.7O2} increased with the increase of gallium contents. The initial discharge capacity of {LiCo0.25Ga0.05Ni0.7O2} was 177.5 mA·h/g between 2.8 and 4.3 V at 0.2 C and had no capacity loss after 25 cycles. Furthermore, the discharge capacity of LiCo0.25Ga0.05Ni0.7O2 was completely recovered after cycling at high discharge-rates. The discharge capacity increased with the upper cut-off voltage limit with a good cycle-ability regardless of the upper cut-off voltage limit. Meanwhile, only one phase reaction took place during the electrochemical oxidation and reduction process, indicating no structure degradation.