Materials' effects on the elevated and room temperature performance of [formula omitted] Li-ion batteries

Abstract

Li-ion rechargeable batteries based on LiMn 2O 4 suffer from relatively poor storage and cycling performance at elevated temperatures. In order to address this issue, a structural and electrochemical study of LiMn 2O 4-based systems at room and elevated temperatures were undertaken. Some of the spinel material characteristics such as morphology, defects, surface area, structural instability, single-versus two-phase lithium-insertion processes, cation and oxygen stoichiometry, and manganese solubility were investigated. We found that the sample surface area, which also influences the manganese dissolution and electrolyte oxidation, is one of the most critical parameters in controlling the rate of irreversible self-discharge, with the lowest irreversible self-discharge being observed for samples with the lowest surface area. These results are discussed in terms of active surface centers and the possibility of surface treatments to rectify this problem. The elevated temperature storage and room temperature cycling performance was found to be the best for those Li 4Mn 2O 4+δ samples having a low surface area (0.5–1 m 2/g), Li in excess ( x > 1.00), show no evidence of Jahn-Teller distortion down to −50 °C, and for which the Li-extraction mechanism occurs over a single-phase reaction at room temperature.