离子液体作为电解液添加剂对LiCoO_2电极电化学性能影响研究

Influence of ionic liquids as electrolyte additives on electrochemical properties of LiCoO_2 electrode

合成了三丁基(甲基醚)膦-双(三氟甲基磺酰)亚胺(P_(444(1O1))TFSI)和三丁基(乙基甲基醚)膦-双(三氟甲基磺酰)亚胺(P_(444(2O1))TFSI)两种离子液体,采用热分析(TG)和电化学技术研究了两种离子液体作为添加剂对有机电解液热稳定性和LiCoO_2电极电化学性能的影响。结果表明,两种离子液体均能提高有机电解液的热稳定性,且阳离子基团大小对LiCoO_2电极的电化学性能有较大的影响。当添加体积比15%的P_(444(2O1))TFSI时,在3.0~4.35 V、电流密度150 mA/g下,LiCoO_2电极的首次放电容量为164.6 mAh/g,100次循环后容量为144.7 mAh/g,容量保持率为89.9%,优于在传统有机电解液中的循环性能。

Tributyl（methoxymethyl）phosphonium bis（trifluoromethylsulfonyl）imide（P（444（1O1））TFSI） and tributyl（2-methoxyethyl）phosphonium bis（trifluoromethylsulfonyl）imide（P（444（2O1））TFSI） were synthesized,and their influences on the thermostability of organic electrolyte and electrochemical properties of LiCoO2 electrode were investigated by thermogravimetric analysis and electrochemical methods. The results showed that the phosphoniumionic liquids could improve the thermostability of organic electrolyte,and the size of the cationic group had a larger influence on the electrochemical properties of LiCoO2 electrode. The initial discharge capacity for the electrolyte with P（444（2O1））TFSI（volume ratio：15%） was 164. 6 mAh/g at the rate of 150 mA/g and 3. 0 ~4. 35 V. The discharge capacity upon 100 cycles was 144. 7 mAh/g,and the capacity retention was 89. 9%. The cycle performance was much better than that in conventional organic electrolytes.