甲基三氟乙基碳酸酯对高电压三元材料的影响

Effects of methyl(2,2,2-trifluoroetyl)carbonate on high-voltage ternary material

以1 mol/L LiPF_(6)/EC+DEC+EMC(质量比3∶5∶2)为基础电解液,分别加入质量分数为3%、5%和7%的添加剂甲基三氟乙基碳酸酯(FEMC),研究FEMC对电极/电解液界面和电池性能的影响。添加FEMC,可以在三元正极材料LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)表面形成一层包覆均匀的电解质界面膜(CEI),电池的阻抗由160.3Ω降低至108.2Ω。在2.70~4.35 V充放电,添加5%FEMC的电池表现出良好的电化学性能,在0.5 C倍率下,循环100次的容量保持率仍高达94%;在5.0 C大倍率下,放电比容量由96.3 mAh/g提高至140.3 mAh/g。

1 mol/L LiPF_(6)/EC+DEC+EMC(mass ratio 3∶5∶2)was used as basic electrolyte,methyl(2,2,2-trifluoroetyl)carbonate(FEMC)with mass fraction of 3%,5% and 7% was used as additive.The effects of FEMC on electrode/electrolyte interface and the performance of Li-ion battery were researched.The FEMC additive could form a uniform cathode electrolyte interlayer(CEI)film on the surface of ternary cathode material LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2),thus reduced the impedance of the battery from 160.3Ωto 108.2Ω.When charged-discharged in 2.70-4.35 V,the cell with 5%FEMC exhibited fine cycle performance with high capacity retention of 94%after 100 cycles at a rate of 0.5 C.The specific discharge capacity increased from 96.3 mAh/g to 140.3 mAh/g at a high rate of 5.0 C.