A Novel Super‐Toughness and Self‐Healing Solid Polymer Electrolyte for Solid Sodium Metal Batteries

Solid sodium metal batteries (SSMBs) offer an alternative promising power source for electrochemical energy storage due to their high energy density and high safety. However, the inherent sodium dendrite growth and poor mechanical properties of electrolytes seriously limit their application. Herein, a network structure composed of polyethylene oxide‐based composite polymer electrolyte (CPE) is designed with liquid metal nanoparticles (LM) for SSMBs, in which LM can move in the solid electrolyte with the electric field driven. This effect can facilitate the inactivated sodium return to the metal sodium anode, and alloy with dendrites at the same time, which is beneficial for inhibiting the growth of dendrites. The symmetric cell with the CPE containing LM achieves good cyclic stability of more than 1800 and 800 h at 0.1 and 0.2 mA cm−2, respectively. The energy density of the pouch battery can reach 230 Wh kg−1. In sum, LM presents great potential to be employed as a performance reinforcement filler for CPEs, which paves the way for achieving high‐performance SSMBs. In this work, a polyethylene oxide‐based polymer electrolyte is prepared with liquid metal (GaInSn) nanoparticles (PEO@LM). The as‐prepared PEO@LM electrolyte exhibits high tensile elongation and Young's modulus. And the liquid metal nanoparticles can move back and forth in SPEs driven by the electric field, which endows the interface between the solid electrolyte and the anode with self‐healing properties and superior cycling stability.