Amphiphilic Polymer Electrolyte Blocking Lattice Oxygen Evolution from High‐Voltage Nickel‐rich Cathodes for Ultra‐Thermal Stabile Batteries

Abstract

AbstractNi‐rich cathodes have been intensively adopted in Li‐ion batteries to pursuit high energy density, which still suffering irreversible degradation at high voltage. Some unstable lattice O2− species in Ni‐rich cathodes would be oxidized to singlet oxygen 1O2 and released at high volt, which lead to irreversible phase transfer from the layered rhombohedral (R) phase to a spinel‐like (S) phase. To overcome the issue, the amphiphilic copolymers (UMA‐Fx) electrolyte were prepared by linking hydrophobic C−F side chains with hydrophilic subunits, which could self‐assemble on Ni‐rich cathode surface and convert to stable cathode–electrolyte interphase layer. Thereafter, the oxygen releasing of polymer coated cathode was obviously depressed and substituted by the Co oxidation (Co3+→Co4+) at high volt (>4.2 V), which could suppressed irreversible phase transfer and improve cycling stability. Moreover, the amphiphilic polymer electrolyte was also stable with Li anode and had high ion conductivity. Therefore, the NCM811//UMA‐F6//Li pouch cell exhibited outstanding energy density (362.97 Wh/kg) and durability (cycled 200 times at 4.7 V), which could be stalely cycled even at 120°C without short circuits or explosions.