LiFePO_(4)锂离子电池的低温性能改进

The improving of low temperature performance of LiFePO_(4) Li-ion battery

利用多巴胺自聚合原理,通过包覆一层氮掺杂的碳质材料(无定型碳)来降低磷酸铁锂(LiFePO_(4))材料的表面电阻,提高低温下Li+迁移速率。采用含氟有机溶剂氟代碳酸乙烯酯,以物质的量比为1∶1的双三氟甲磺酰亚胺锂(LiTFSI)和双(五氟乙基磺酰基)亚胺锂(LiBETI)为混合锂盐,制备1 mol/L混合锂盐电解液(MLiE),以解决电池在低温环境下性能下降的问题。与目前的商业LiFePO_(4)/石墨电池相比,组装使用MLiE的LiFePO_(4)锂离子电池在-20℃于3.65~2.50 V充放电,0.1 C、0.2 C、0.5 C和1.0 C放电容量分别增加了37.4%、44.6%、51.1%和65.3%。

A layer of nitrogen doped carbonaceous material(amorphous carbon)was coated to reduce the surface resistance of lithium iron phosphate(LiFePO_(4)) materials and improve the migration rate of Li^(+) at low temperature based on the principle of dopamine self-polymerization.A fluorine-containing organic solvent(fluorovinyl carbonate)was used to prepare mixed 1 mol/L lithium salt electrolyte(MLiE)by adding mixed lithium salt lithium trifluoromethylsulfonimide(LiTFSI)and lithium bis(pentafluoroethyl sulfonate)imine(LiBETI)with a molar ratio of 1∶1,so as to solve the problem of battery performance degradation in low temperature environment.Compared with the current commercial LiFePO_(4)/graphite battery,the discharge capacity of the assembled LiFePO_(4) Li-ion battery with MLiE at 0.1 C,0.2 C,0.5 C and 1.0 C(3.65-2.50 V)under-20℃increased by 37.4%,44.6%,51.1%and 65.3%,respectively.