Spinel LiMn2O4 Electrode in Room Temperature Molten Salt

Abstract

Room Temperature Molten Salt (RTMS) based on 1-methyl-3-ethylimidazolium chloride / AlCl3 /LiAlCl 4 is recently shown to provide a promising medium for lithium battery clue to its high current capability and inertness towards active material. In the present work, the electrochemical properties of a LixMn2O4 electrode in RTMS, the most commonly used positive electrode material, were investigated by cyclic voltammetry, coulometric titration and constant current cycling. From cyclic voltarnmetric studies, the Li xMn2O4 electrode in RTMS was found to exhibit the same electrochemical behavior as in other non-aqueous electrolytes. However, a new and very large irreversible anodic peak was found due to the insertion of AlCl4 - into the carbon current collector. During coulometric studies, coulombic efficiencies greater than 96 % were obtained at composition close to x=1 in LixMn2O4. However, for Range I (0 <x<1), a rapid decrease in coulombic efficiency was observed at x less than 0.6. For Range II (1<x<2), close to 86 % of the electrode material could be used. Thus, Range II was selected for battery application. For cycling at Range I, greater than 95% cycling efficiencies were obtained up to insertion / extraction capacities of 60 mAh/g, whereas at Range II, 98% cycling efficiencies at the first 20 cycles were obtained up to 120 mAh/g. The difference was attributed to the irreversible insertion of AlCl 4 - anions into the carbon current collector at high anodic potential and hence less lithium was extracted from the LixMn2O4, electrode in 0<x<1. The electrochemical performance of the LiMn2O4 electrode as positive electrode material for secondary lithium battery at different lithium insertion in RTMS was discussed in the light of the results obtained.