Self‐Regulating Interfacial Space Charge through Polyanion Repulsion Effect towards Dendrite‐Free Polymer Lithium‐Metal Batteries

Abstract Uncontrolled transport of anions leads to many issues, including concentration polarization, excessive interface side reactions, and space charge‐induced lithium dendrites at the anode/electrolyte interface, which severely deteriorates the cycling stability of lithium metal batteries. Herein, an asymmetrical polymer electrolyte modified by a boron‐containing single‐ion conductor (LiPVAOB), is designed to inhibit the nonuniform aggregation of free anions in the vicinity of the lithium anode through the repulsion effect improving the lithium‐ion transference number to 0.63. This LiPVAOB exerts a repulsion interaction with free anions even at a long distance and a selective effect for free anions transport, which diminishes uneven aggregation of free anions at the interface and suppresses space charges‐induced lithium dendrites growth. Consequently, the assembled Li||Li cell delivers an ultra‐long cycle for over 5400 h. The Li||LiFePO 4 cell exhibits outstanding cycle performance with a capacity retention of 93% over 4500 cycles. In particular, the assembled high‐voltage Li||Li 1.2 Ni 0.2 Mn 0.6 O 2 cell (charged to 4.8 V) exhibits good cycle stability with a high specific capacity of 245 mAh g −1 . This designed polymer electrolyte provides a promising strategy for regulating ion transport to inhibit space charge‐induced lithium dendrite growth for high‐performance lithium metal batteries.