二氟草酸硼酸钠作为电解液添加剂对石墨负极性能的影响

Sodium Difluoro(oxalato) borate as An Electrolyte Additive to Improve the Electrochemical Performance of Graphite Anode

锂离子电池日益广泛的应用对其性能提出越来越高的要求,而在电解液中加入适当的添加剂能够显著提升电极材料的电化学性能.本文首次在1 mol·L-1Li PF6/EC+DMC+EMC(体积比1:1:1)的电解液中添加一定量的二氟草酸硼酸钠(NaDFOB),并通过循环伏安(CV)、电化学阻抗图谱(EIS)和扫描电子显微镜(SEM)等分析考察了其对石墨负极材料性能的具体影响.结果显示,添加NaDFOB的电解液显著提高了石墨材料在常温下的可逆充放电容量和循环性能,同时明显改善了石墨材料的高温循环性能.其机理在于NaDFOB的阴阳离子同时参与了石墨表面固体电解质界面膜(SEI)的形成,形成高稳定性的电解液/电极界面.

The fast development in applications in Li-ion batteries （LiBs） in daily life urges for better electrochemical performance of LiBs, which can be promoted by adding appropriate electrolyte additives. This work studied the effect of NaDFOB as the addi- tive on a common electrolyte formula （1 mol· L-1 LiPF6 in EC＋DMC＋EMC, 1：1：1 by volume）. Analysis methods such as electro- chemical test such as CV, EIS and SEM were adopted to study electrochemical performance of experimental battery and interface profiles. It was revealed that the reversible charge-discharge capacity and cycling performance of graphite anode had been dramati- cally improved. In addition, the cycling performance of graphite anode at moderate temperature was obviously improved by the adoption of NaDFOB. Both anion and cation in NaDFOB participated the formation of SEI film on the graphite anode surface and thus generated a highly stable electrolyte/electrode interface.