A Dielectric-Gradient Composite Gel Polymer Electrolyte Synergistically Enhances Ion-Transport and Interfaces for High-Voltage Lithium-Metal Batteries

Abstract

High-voltage lithium-metal batteries offer exceptional energy density but suffer from poor stability due to challenges in ion transport and interfacial reactions. This work addresses these issues by designing a composite gel polymer electrolyte with a dielectric-gradient structure. This is achieved by incorporating nanofillers of contrasting dielectric constants into a polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) matrix: high-dielectric NaNbO3 (NNO) particles near the LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode to enhance bulk ion dissociation and concentration with a stable fluorinated Li/Na hybrid cathode-electrolyte interphase (CEI), low-dielectric Al2O3 particles near the metallic Li anode to increase Li + transference number and stabilize the interface, and a low concentration of NNO in the middle to facilitate smooth ion transfer. This spatially engineered configuration facilitates rapid ion conduction, suppresses lithium dendrite growth, and mitigates interfacial degradation. Consequently, the derived batteries exhibit outstanding cycling stability at a high cut-off voltage of 4.5 V (with a capacity retention rate as high as 66.22% after 1000 cycles at 5 C) and remarkable rate capability (still maintaining a discharge specific capacity of 219.1 mAh g -1 at 3 C), demonstrating a promising strategy for developing high-energy, durable lithium-metal batteries.