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

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 S cm at 25°C, along with stable Li plating/stripping cycling over 1600 h at a current density of 0.5 mA cm. More importantly, the Li|PHN5|LiFePO full cell delivers an initial discharge specific capacity of 159.3 mAh g at 0.5 C, with a capacity retention rate of 92.7% after 600 cycles.