Design of Gel Polymer Electrolytes With High Ionic Conductivity via Anion–Cation Synergy for Stable‐Interface Lithium Metal Batteries

ABSTRACT Gel polymer electrolytes (GPEs) are considered as a highly promising strategy for achieving long‐term stable and high‐safety lithium metal batteries. However, conventional GPEs struggle to simultaneously achieve efficient ion transport and stable electrode/electrolyte interfaces. This work proposes an anion–cation synergy to obtain a GPE (PHN5) that simultaneously exhibits high ionic conductivity and a stable electrode/electrolyte interface. In the PHN5, 4‐aminobenzonitrile (ABN) contains both anion‐affine amino group and strongly polar cyano group, enabling it to bind with both anions and cations simultaneously and form a novel solvation structure. This structure not only enhances the concentration of free Li + in the electrolyte, but also promotes anion migration to the electrode/electrolyte interface, participating in the formation of an inorganic‐rich solid electrolyte interphase (SEI) layer, thereby improving both ionic conductivity and long‐term cycling stability. As a result, PHN5 exhibits a high ionic conductivity of 1 × 10 −3 S cm −1 at 25°C, along with stable Li plating/stripping cycling over 1600 h at a current density of 0.5 mA cm −2 . More importantly, the Li|PHN5|LiFePO 4 full cell delivers an initial discharge specific capacity of 159.3 mAh g −1 at 0.5 C, with a capacity retention rate of 92.7% after 600 cycles.