A novel gel polymer electrolyte doped with MXene enables dendrite-free cycling for high-performance sodium metal batteries

Abstract

Sodium metal batteries (SMBs) are considered as one of the most promising devices for energy storage, but the short lifetime and safety issues caused by incompatibility between electrode and electrolyte remain a great challenge. Herein, we report the creation of a functional gel polymer electrolyte (GPE) based on poly(vinylidene fluoride-hexafluoro propylene) (PVDF-HFP) codoped with polyethylene glycol-4000 (PEG-4000) and conductive Ti₃C₂ (MXene) via weak hydrogen bond interactions. The 8 wt% MXene-50 wt% PEG-PVDF-HFP (PHPM) GPE shows a three-dimensional porous network structure with ionic conductivity up to 1.76 × 10⁻³ S cm⁻¹. Moreover, the introduction of MXene effectively inhibits the formation of metal dendrites by redistributing the concentration of Na⁺ in the interface. As a result, dendrite-free cycling for 1200 h at 5 mA cm⁻¹ was accomplished using PHPM as the electrolyte in a symmetric metal battery. The full battery NaTi₂(PO₄)₃/PHPM/Na exhibited excellent rate and cycling performance with capacity retention >93% after 8000 cycles at 20C. This work may be the inspiration for the modification of GPEs for use in practical SMBs.