LiPF6/LiBOB混合锂盐改善LiFePO4/石墨动力电池高温循环性能研究

摘要

分别以 LiPF6、LiBOB 和 LiPF6/LiBOB 混合盐为电解质,研究了不同电解液对 LiFePO4/石墨动力电池高温循环性能的影响。结果表明,LiBOB 盐抑制了正极溶铁行为,并提高了正极高温循环充放电效率；由于 LiBOB基电解液对正极的保护及在负极表面良好的成膜作用,使得LiFePO4/石墨电池高温循环性能得到明显改善,但是增大了电池阻抗。LiPF6/Li-BOB混合盐可以发挥 LiBOB盐的优点增加正极稳定性,在石墨表面形成致密的 SEI 膜并能够有效改善电池高温循环性能,同时避免了单纯使用 LiBOB盐时阻抗较高的缺点。使用 LiPF6/LiBOB 混合盐,利用LiPF6盐低阻抗特性及 LiBOB盐对正、负电极的保护作用,可以有效提高电池电化学性能。%LiPF6 ,LiBOB and LiPF6/LiBOB blend salt-based electrolytes were investigated for improving cycling performances of LiFePO4/graphite lithium-ion batteries at elevated temperature.It was demonstrated that dis-solution of Fe from LiFePO4 was depressed in LiBOB based electrolyte,and columbic efficiency of LiFePO4/Li cell at elevated temperature was increased;LiBOB was reduced earlier on anode surface,forming compact SEI layer;and the capacity retention of LiFePO4/graphite cells at 55℃ increases with LiBOB concentration due to protective depositions of LiBOB on cathode surface and the SEI layer on anode surface,while the impedance of the cell is increased.LiPF6/LiBOB blend salt-based electrolyte combines the advantages of the different salts and maximizes the performance of cells.When electrolytes with LiPF6/LiBOB blend salt was used,the LiFe-PO4/graphite cells have excellent capacity retention at 55℃,while the impedance was dramatically decreased.