Cyclability and Dissolution of Manganese in Substituted Stoichiometric and Non-stoichiometric Lithium Manganese Oxides at High Temperature

Abstract

The cyc1ability of substituted stoichiometric spinels LiM_1/6Mn_11/6O₄ (M = AI, Co and Ni) has been investigated in the cell Li | 1 mol dm^-3 LiClO₄ + EC-DEC | LiM_1/6Mn_11/6O₄ at 50°C. The amount of manganese dissolved into the electrolyte from the spinel was measured at different cycle intervals by ICP technique. It was found that the capacity loss was considerably reduced in the case of substituted spinel compared to the parent one even at elevated temperature. Among these substituted compounds, the Ni-substituted spinel exhibited good capacity retention behavior with minimum loss of capacity followed by Co-substituted one. Non-stoichiometric spinels with metal excess structure which written as Li[M'_excess]_16c[M_1/6Mn_11/6]_16dO₄ (M' = Li, Mn, M ; M = Al, Ni) were synthesized under reduced partial pressure conditions. These compounds were observed to possess higher capacity and good cyclability in spite of their higher manganese dissolution over their corresponding stoichiometric counterparts.