Inorganic electrolyte additives to suppress the degradation of graphite anodes by dissolved Mn(II) for lithium-ion batteries

It is well known that when the carbon/LiMn2O4-based cathode battery was operated at elevated temperatures, the severe capacity loss occurred in following cycles. As we recently described, the capacity loss is mainly due to the degradation on the carbon anode side caused by the deposition of manganese at the carbon followed by the irreversible decomposition at the graphite/deposited Mn/electrolyte interface. It was found that inorganic additives in electrolyte, such as LiI, LiBr, and NH4I effectively suppressed the degradation of graphite anode to improve the battery performance. In case of LiI and LiBr, the irreversible reaction at the Mn/electrolyte interface was suppressed by specific adsorption of iodide or bromide anions on the metallic Mn surface. Further, the reduction of Mn(II) would be suppressed by adding NH4I into electrolyte which could be due to the formation of a stable amine complex of Mn(II). (C) 2003 Elsevier Science B.V All rights reserved.