Self-regulating interfacial space charge through polyanion repulsion effect towards dendrite-free polymer lithium-metal batteries

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. (© 2024 Wiley‐VCH GmbH)