Multi-component electrolytes for rechargeable lithium cells

Abstract

This paper reports the influence of various mixed solvent electrolytes on the discharge capacity and charge-discharge cycle life of coin-type lithium (Li) metal/amorphous (a-) V2O5-P2 O5 (95 : 5 in molar ratio) cells. The solvents used were ethylene carbonate (EC), propylene carbonate (PC), 2-mcthyltetrahydrofuran (2MeTHF), THR, 1,2-diethoxyethane and 4-methyl-l, 3dioxolane. LiAsF5 and LiCF3SO3 were used as the solute. The electrolyte solutions examined here contain binary, ternary and four solvent mixed systems. The purpose of this work is to obtain an electrolyte solution which realizes a higher rate capability than the previously studied EC/PC/2 MeTHF ternary mixed system while suppressing the reduction in the cycle life. Among the electolyte systems examined here, EC/PC/2 MeTHF/THF (15 : 70 : 7.5 : 7.5 in volume)-four solvent mixed system showed the best cell performance. Its rate capability at 5 m A cm-2 discharge was about twice that of EC/PC/2 Me THF ternary mixed solvent electrolyte with almost the same rechargeability.