Ethylene Carbonate/2‐Methyltetrahydrofuran Electrolyte for Li/Amorphous  V 2 O 5 ‐  P 2 O  Secondary Batteries

The electrolyte characteristics of ethylene carbonate/2MeTHF/LiAsF6 and the cell properties of Li//ethylene carbonate/2MeTHF//1.5M LiAsF6//a-V2O5-P2O5 relevant to lithium secondary batteries are reported. The electrolyte conductivity showed a maximum value when the ethylene carbonate/2MeTHF mixing volume ratio is around 1/1 at 25 C. The maximum conductivity shifted to a higher 2MeTHF mixing ratio with decreasing temperature. The ethylene carbonate/2MeTHF electrolyte, because of its higher conductivity, showed better utilization than the 2MeTHF electrolyte. Figures of merit of ethylene carbonate/2MeTHF electrolytes showed strong dependence on the amount of impurity. Typical cycling results at 25 C show a linear charge-discharge profile. It is concluded that the ethylene carbonate/2MeTHF//LiAsF6 electrolyte is excellent for achieving a high charge-discharge rate and a long cycle life in Li batteries and can work even at low temperatures. 6 references.