富锂正极材料的制备及电化学性能研究

用溶胶-凝胶法结合高温煅烧过程制备富锂正极材料Li_1.2Mn_0.54Ni_0.13Co_0.13O₂，对800℃和900℃煅烧后得到的2种材料（标记为S8和S9）进行物相和形貌表征以及电化学测试。电化学测试结果表明，样品S9具有较高的放电容量、较好的循环稳定性和较小的电荷转移电阻。样品S9在0.1 C（25 mA·g^-1）时的首次充电容量为345.0 mA·h·g^-1，首次放电容量为273.9 mA·h·g^-1，首次库伦效率为79.4%。1 C时，首次放电容量为188.1 mA·h·g^-1，循环30周后放电容量为173.3 mA·h·g^-1，容量保持率为92.1%。结果表明，尽管富锂正极材料R-3m层状结构在800℃煅烧后已经形成，但仍需要经过更高温度煅烧，以提高锂离子和过渡金属离子在各自层中的有序度，从而有效地提高材料的电化学性能。

Synthesis and electrochemical performance of lithium-rich cathode material

Lithium-rich cathode material Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ has been synthesized by sol-gel method followed by a high-temperature calcination process at 800℃ and 900℃ (signed as S8 and S9, respectively). The structure, morphology and electrochemical properties of as-synthesized materials are characterized in detail. Electrochemical test results show that sample S9 has higher discharge capacity, better cyclic stability and smaller charge transfer resistance. Sample S9 delivers the initial charge capacity of 345.0 mA·h·g^-1 and the initial discharge capacity of 273.9 mA·h·g^-1 at 0.1C (25 mA·g^-1) with a coulombic efficiency of 79.4%. The discharge capacity is 173.3 mA·h·g^-1 at 1 C after 30 cycles, remaining 92.1% of initial discharge capacity (188.1 mA·h·g^-1). The results indicate that the ordering between lithium and transition metal cations in their respective layers needs a higher calcination temperature in spite of the formation of the R-3m layered phase at 800℃. It is helpful to effectively improve the electrochemical properties.