Unveiling the role of interfacial electrostatic homogeneity in shielding dendrite growth for gel polymer electrolyte lithium batteries

Polymer-ceramic composite electrolytes are commonly engineered with high-permittivity fillers to enhance ion transport; however, the bulk dielectric constant alone is insufficient to explain interfacial ion-transport behavior and dendrite growth. This work identifies interfacial electrostatic homogeneity as a key descriptor governing Li⁺ transport and deposition stability. By systematically comparing TiO₂, BaTiO₃, and Ba_0.7Sr_0.3TiO₃ fillers, we demonstrate that optimal dielectric matching between the filler and polymer matrix, rather than simply maximizing filler permittivity, is crucial for smoothing the interfacial electrostatic landscape and ensuring uniform Li⁺ flux. The optimized PLBST electrolyte achieves a high ionic conductivity of 6.15 × 10⁻⁴ S cm⁻¹ at 30 °C, a high Li⁺ transference number of 0.53, and a widened electrochemical stability window of 4.93 V. It enables stable, dendrite-free cycling for over 2500 h in symmetric cells at 0.3 mA cm⁻² and exhibits excellent compatibility in Li‖LiFePO₄ and Li‖LiNi_0.8Co_0.1Mn_0.1O₂ 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 gel polymer electrolyte batteries.