Reconstructing Inorganic-Rich Interphases by Nonflammable Electrolytes for High-Voltage and Low-Temperature LiNi_0.5Mn_1.5O₄ Cathodes

Cobalt-free and spinel LiNi_0.5Mn_1.5O₄ (LNMO) cathodes commonly suffer from undesirable solvent decomposition, serious transition-metal dissolution, and unstable cathode electrolyte interphase (CEI) layers, incurring rapid capacity decay at high voltages and low temperatures. Herein, these issues are well addressed by utilizing fluorinated solvents with a low coordination number and ethyl propionate with a low melting point. A Li₂CO₃/LiF-rich heterostructured CEI layer, which possesses good electron blocking capability of LiF, fast Li⁺ transport kinetics of Li₂CO₃ and good mechanical stability, is generated by the synergistic decomposition of hybrid solvents. The robust, homogeneous, and well-balanced CEI layers subsequently prevent catalyzed parasitic side reactions, prohibit transition-metal dissolution, and ensure fast interfacial reaction kinetics crossover to the LNMO cathode, thus improving its cycling stability. Consequently, the LNMO cathode delivers a high-capacity retention of 95.8% over 500 cycles at 25 °C and 97.5% after 180 cycles at −20 °C. This work provides an encouraging alternative to design the high-voltage and low-temperature electrolyte for pushing the ongoing research to stabilize Co-free LNMO materials toward practical applications.