Electrochemical behavior of Fe xNb 1−xSe 3 (x=0 ≈ 0.25) with one-dimensional structure as new positive electrodes for secondary lithium batteries

Abstract

Electrochemical behavior of Fe xNb 1−xSe 3 (x=0 ≈ 0.25) as positive electrodes for lithium batteries were investigated in various lM LiClO 4 electrolytic solutions of propylene carbonate, butyrolactone, dimethyl sulfoxide and sulfolane. Fe 0.25Nb 0.75Se 3 electrode shows good reversibility and the practical energy density is about 300 Wh/Kg-selenide. The discharge potentials of NbSe 3 and Fe 0.25Nb 0.75Se 3, both having one-dimensional structure, strongly depend on the kind of solvent in the electrolyte, due to the insertion of a solvated Li +ion into the inner layer of the selenide. In addition, on the discharge of a series of NbSe x (x=1.7, 2, 3, 4 and 4.5), the number of electron transferred during discharge is found to correspond to the value of x but 1.7.