Disulfide bond-embedded polyurethane solid polymer electrolytes with self-healing and shape-memory performance

Abstract

In order to prevent the deformation and fracture damage of polymer electrolytes, thus providing high safety for flexible batteries, solid-state polymer electrolytes with both self-healing and shape-memory properties (SSSPEs) are designed and fabricated based on disulfide bond-containing polyurethane and poly(ethylene oxide) (PEO) segments. The polymer electrolytes obtained through photo-initiated radical polymerization exhibit good flexibility and self-healing property because of a large fraction of hydrogen-bond interaction, as well as the dynamic exchange reaction of disulfide bonds. In addition, the polymer network acts as the permanent phase, while the polyurethane segment is engaged in the reversible transition between the permanent and temporary states under the stimulus of heating, leading to a shape-memory performance for SSSPEs. Variation of the network structure and disulfide bond position modulates the mechanical strength, self-healing efficiency and electrochemical properties of the electrolyte material. The assembled Li/LiFePO₄ (LFP) cells using the optimized electrolyte membrane show a favorable charge–discharge cycling stability with the capacity retention of 94.2% after 100 cycles (0.1 C, 60 °C) even after the cutting–repairing test.