用预循环方法控制富锂锰Li_(1.13)Mn_(0.54)Ni_(0.27)Al_(0.06)O_2的不可逆容量

研究了不同预循环电压对富锂锰正极材料Li_(1.13)Mn_(0.54)Ni_(0.27)Al_(0.06)O_2电化学性能的影响,重点考察了不可逆容量。电化学测试数据表明:采用上截止电压为4.4~4.6 V进行预循环可使初始不可逆容量降低一半;采用阶梯电压预循环制度可有效提高材料电化学性能,初始不可逆比容量从252 mAh/g降低至98 mAh/g,容量保持率达到94.4%,且在10 C倍率下放电比容量依然保持在81 mAh/g;富锂锰正极材料的初始不可逆容量主要来自三个方面:SEI膜的形成、Li_2MnO_3的活化和电解液分解。

Improvement of initial irreversible capacity by pre-cycling for lithium-rich cathode material Li1.13Mn0.54Ni0.27Al0.06O2

The lithium-rich cathode material Li1.13Mn0.54Ni0.27Al0.06O2 was synthesized by solid state reaction.The relationship between pre-cycling and the electrochemical performance was studied.Special attention was paid to the high initial irreversible capacity.The studies show that,as the cut-off voltage of pre-cycling has been set between 4.4 V to 4.6 V,the initial irreversible is only 52％ of the un-precycled one.Stepwise pre-cycling treatment can effectively reduce the initial irreversible capacity.It can also improve the capacity retention ability and rate properties.The irreversible specific capacity can be reduced from 252 mAh/g to 98 mAh/g after stepwise pra-cycling treatment.The capacity retention rate is 94.4％ and the specific capacity is 81 mAh/g at 10 C.The initial irreversible capacity of Li1.13Mn0.54Ni0.27Al0.06O2 is made up of three parts:formation of SEI film,activation of Li2MnO3 and the decomposition of electrolyte.