Electric-Field-Oriented Interfacial Solvent Engineering Enables High-Voltage Ether Electrolytes for Ni-Rich Lithium-Ion Batteries

High-voltage operation of nickel-rich cathodes (>4.5 V) significantly boosts the energy density of lithium-ion batteries but triggers catastrophic oxidative decomposition of conventional ether electrolytes. Under high-potential electric fields, ether molecules in the electric double layer orient their oxygen atoms toward the cathode surface. This intimate contact accelerates α-hydrogen dehydrogenation and subsequent degradation. Herein, we report an electric-field-oriented interfacial solvent engineering strategy that decouples the vulnerable ether linkage from the charging interface. By introducing a rigid, asymmetric solvent molecule, 4-cyano-tetrahydropyran (THP-CN), we exploit the preferential adsorption of the highly polar cyano group under the intense interfacial electric field, driving the formation of a self-assembled “cathode-cyano-ether-bulk” configuration that effectively shields the ether oxygen and adjacent α-hydrogen atoms from the reactive cathode surface, thereby suppressing oxidative decomposition. Meanwhile, cooperative FSI– and NO3– decomposition constructs a robust, inorganic-rich cathode electrolyte interphase, further stabilizing the cathode structure. Consequently, the low-concentration THP-CN-based ether electrolyte exhibits exceptional oxidative stability up to 4.8 V. Demonstrating practical viability, the assembled 1.5 Ah graphite||NCM811 pouch cell achieves an energy density of 331.2 Wh kg–1 and retains 83.5% capacity after 600 cycles within a 2.8–4.5 V window.