Enhanced High-Temperature Stability of Li-Ion Battery with Li-Rich Oxide Cathode By Localized High-Concentration Electrolyte

摘要

Lithium (Li)-rich manganese (Mn)-rich oxides (LMR) have been considered as feasible cathode materials for high-energy lithium ion batteries because they possess high theoretical specific energy over 900 Wh kg~(-1). However, the undesirable cathode/electrolyte interfacial reaction due to the high working voltages, which results in electrolyte decomposition, transition-metal ion dissolution and surface corrosion, is considered one of the obstacles that significantly prevent their applications in electric vehicles for years. Although numerous efforts have been devoted to address the surface stability issues on LMR, most of them were limited to room temperature. The continuous upsurge in demand for electric vehicles requires lithium ion batteries to be operated under elevated temperatures. While, the state-of-the-art LiPF_6-organocarbonate electrolytes are not compatible with LMR cathode due to the high operating voltage, which also get worse at elevated temperatures. Here, an optimized localized high-concentration electrolyte (LHCEs) is studied in graphite (Gr)-based LMR full cells at 25, 45 and 60°C. The cycling stabilities and the interfacial properties on the surfaces of both cathode and anode under different temperatures are systemically investigated. It is revealed that the LHCE enables the formation of more protective electrode/electrolyte interphases on both anode and cathode, which, in turn, lead to significantly improved cycling stability and enhanced rate capability under the selected temperatures. The electrode/electrolyte interphases formed in LHCE are found to be less susceptible towards elevated temperatures than those in conventional LiPF_6-based electrolyte. The mechanistic understanding on the function of the LHCE in Gr||LMR cells under high temperatures provides valuable perspectives of electrolyte development for practical application of LMR cathodes in high energy density batteries over a wide temperature range.