MULTICOMPONENT NONAQUEOUS ELECTROLYTES FOR RECHARGEABLE LITHIUM CELLS

In this paper we examine the influence of various mixed-solvent electr olytes on the discharge capacity and charge-discharge cycle life of co in-type lithium (Li) metal/amorphous (a-) V2O5-P2O5 (95:5 in molar rat io) cells. The solvents used were ethylene carbonate (EC), propylene c arbonate (PC), 2-methyl-tetrahydrofuran (2MeTHF), THF, 1,2-diethoxyeth ane and 4-methyl-1,3-dioxolane, LiAsF6 and LiCF3SO3 were used as the s olute. The electrolyte solutions examined here contain binary, ternary and quaternary mixed solvent systems. The purpose of this work is to obtain an electrolyte solution which provides lithium cells with a hig her rate capability than the previously studied EC/PC/2MeTHF ternary m ixed system while suppressing the reduction in the cycle life. The sta ck pressure effect on the lithium cycling efficiency is minimized by t he spacious internal electrode structure of the coin cell used in this work in order to investigate the influence of the electrolyte materia ls on the cell properties. Among the electrolyte systems examined here , the EC/PC/2MeTHF/THF (15:70:7.5:7.5 in volume) four-solvent mixed sy stem provided the best cell performance. Its rate capability at 5 mA c m(-2) discharge was about twice that of EC/PC/2MeTHF ternary mixed sol vent electrolyte with almost the same rechargeability. (C) 1997 Elsevi er Science Ltd. All rights reserved.