Ethylene carbonate/ether solvents for electrolytes in lithium secondary batteries

An examination has been made of the effectiveness of ethylene carbonate(EC)/2-methyltetrahydrofuran(2-MeTHF) solvents incorporating LiAsF6 as the solute as electrolytes in secondary lithium batteries. From —10 to 30 °C, the conductivities of EC/2-MeTHF are higher than those of 2-MeTHF and EC/propylene carbonate (PC). For lithium-on-lithium cycling in a half cell, the FOM (figure of merit) of lithium in EC/2-MeTHF has a value 2.2 to 2.7 times higher than that in 2-MeTHF and EC/PC. A coin cell of Li/amorphous V2O 5-P2O5 with EC/2-MeTHF clearly exhibits higher capacity and longer cycle life than cells with 2-MeTHF or EC/PC. It is concluded that EC/2-MeTHF is a promising electrolyte system for secondary lithium battery applications.