Self-healing solid polymer electrolyte based on imine bonds for high safety and stable lithium metal batteries

Due to their low flammability, good dimensional stability and chemical stability, solid polymer electrolytes are currently attracting extensive interest for building lithium metal batteries. But severe safety issues such as cracks or breakage, resulting in short circuits will prevent their widespread application. Here, we report a new design of self-healing solid polymer electrolyte (ShSPE) based on imine bonds, fabricated from varying amounts of polyoxyethylenebis(amine) and terephthalaldehyde through a simple Schiff base reaction. Moreover, adding diglycidyl ether of bisphenol A improves the flexibility and high stretchability of the polymer electrolyte. The polymer networks exhibit good thermal stability and excellent self-healing characteristics. The ShSPE with the highest NH₂-PEG-NH₂ content (ShSPE-3) has an improved lithium ion transference number of 0.39, and exhibits an electrochemical stability up to 4.5 V vs. Li/Li⁺. ShSPE-3 shows the highest ionic conductivity of 1.67 × 10^-4 S cm^-1 at 60 °C. Besides, the interfacial stability of ShSPE-3 is promoted and the electrolyte membrane exhibits good cycling performance with LiFePO₄, and the LiFePO₄/Li cell exhibits an initial discharge capacity of 141.3 mA h g ^-1. These results suggest that self-healing solid polymer electrolytes are promising candidates for high safety and stable lithium metal batteries.