Effects of Various Electrolytes on the Electrochemical Performance of Spinel LiMn2O4 in Aqueous Solutions

The effects of various electrolytes on the electrochemical performance of LiMn2O4 electrodes are investigated. It is shown that for an increased Li+-ion concentration, the potential of LiMn2O4 electrodes is shifted to a positive value, improving the kinetics. Anions in electrolytes exert a strong influence on the electrochemical performance of LiMn2O4 electrodes, which results from Mn dissolution and oxygen evolution. The electrode in a 5 M LiNO3 solution with minimal Mn dissolution and a high oxygen overpotential exhibited good rate capability and cyclability. Conversely, in a LiCl solution, the extent of Mn dissolution is large, and the electrode is affected simultaneously by O-2 and Cl-2 evolution. Although the addition of zinc salts inhibits certain side reactions, a sharp deterioration in the capacity results during charge/discharge cycling. The addition of zinc salts into the Li2SO4 solution also results in an increase in the amount of dissolved Mn. However, the oxygen evolution is markedly attenuated, and the capacity retention rate of the LiMn2O4 electrode in the sulfate solution is significantly improved, increasing from 35 to 58% after 1000 cycles at 2 C.