Deep-discharged LiCoMnO4 Lithium-Ion cathodes with high rate capability and long cycle life

Abstract

LiCoMnO4 (LCM) is a promising member of the 5V spinel cathode materials family, which is capable of providing high specific energy given its high working voltage vs. Li/Li+. Most of the prior studies reported in literature on LCM-based battery cells have focused on the operational regime above 3V. It is widely believed that for this class of Mn-bearing lithiated spinel cathode materials, the Jahn-Teller distortion that occurs when Mn4+ is reduced to Mn3+ upon deep discharge to the regime lower than 3V would introduce rapid capacity fade. In this work, we show that in solid-state thin film batteries using LCM cathodes, there is considerable available capacity under 3V associated with the cubic-tetragonal phase transitions without appreciable capacity fade with cycling. This finding is similar to our recent report for a material in the same class of lithiated spinel oxides, LiNi0.45Mn1.485Cr0.05O4 (LNM), which also showed stable cycling at deep discharge. However, we demonstrate here the LCM cathodes retain a greater fraction of the total capacity at high discharge rates in the lower voltage regime relative to LNM. At elevated temperature, the capacity in 3V region was increased without compromising cycle life. This work suggests that by using solid-state thin film techniques, we could utilize the capacity of LCM below 3V despite the Jahn-Teller distortion.