Unveiling the Role of Interfacial Electrostatic Homogeneity in Shielding Dendrite Growth for Gel Polymer Electrolyte Lithium Batteries

Abstract

Polymer-ceramic composite electrolytes are commonly engineered with highpermittivity fillers to enhance ion transport; however, the bulk dielectric constant alone is insufficient to explain interfacial ion-transport behavior and dendrite growth. Here, we identify interfacial electrostatic homogeneity as a physically meaningful descriptor governing Li + transport and deposition stability in composite electrolytes. Using a fixed polymer-salt-scaffold framework with ceramic fillers of different dielectric responses, we show that filler-induced polarization reconstructs the spatial electrostatic potential landscape at the electrolyte interface, a feature not captured by volume-averaged permittivity. Combined density functional theory calculations, Kelvin probe force microscopy, and phase-field simulations reveal that the electrochemical performance is not dictated simply by maximizing filler permittivity, but by achieving an appropriate dielectric match between the filler and polymer matrix, which leads to a more continuous interfacial electrostatic landscape and more uniform Li + flux, thereby suppressing dendrite nucleation. Quantitative statistical analysis of surface potential distributions further shows that reduced potential fluctuation is closely associated with enhanced critical current density and improved interfacial stability. Guided by this principle, the optimized composite electrolyte delivers high ionic conductivity, a widened electrochemical stability window, and stable, dendrite-free cycling for over 2500 h in symmetric cells, as well as durable operation in Li||LiFePO 4 and Li||LiNi 0.8 Co 0.1 Mn 0.1 O 2 full cells. This work shifts the design strategy for dielectric composite electrolytes from maximizing bulk permittivity to regulating interfacial electrostatic landscapes, offering a useful framework for developing quasi-solid-state batteries.