Optimization Design of Fluoro‐Cyanogen Copolymer Electrolyte to Achieve 4.7 V High‐Voltage Solid Lithium Metal Battery

Abstract Raising the charging voltage and employing high‐capacity cathodes like lithium cobalt oxide (LCO) are efficient strategies to expand battery capacity. High voltage, however, will reveal major issues such as the electrolyte's low interface stability and weak electrochemical stability. Designing high‐performance solid electrolytes from the standpoint of substance genetic engineering design is consequently vital. In this instance, stable SEI and CEI interface layers are constructed, and a 4.7 V high‐voltage solid copolymer electrolyte (PAFP) with a fluoro‐cyanogen group is generated by polymer molecular engineering. As a result, PAFP has an exceptionally broad electrochemical window (5.5 V), a high Li + transference number (0.71), and an ultrahigh ionic conductivity (1.2 mS cm −2 ) at 25 °C. Furthermore, the Li||Li symmetric cell possesses excellent interface stability and 2000 stable cycles at 1 mA cm −2 . The LCO|PAFP|Li batteries have a 73.7% retention capacity after 1200 cycles. Moreover, it still has excellent cycling stability at a high charging voltage of 4.7 V. These characteristics above also allow PAFP to run stably at high loading, showing excellent electrochemical stability. Furthermore, the proposed PAFP provides new insights into high‐voltage resistant solid polymer electrolytes.