Vitrimer with dynamic imine bonds as a solid-state electrolyte for lithium metal batteries

In this study, vitrimer solid polymer electrolytes (V-SPEs) with dynamic imine bonds are synthesized for use in lithium metal batteries (LMBs). The optimal composition of V-SPEs is investigated by changing the ratio of ethylene oxide (EO) to lithium-ion and the length of the EO units. V-SPEs with longer EO segments exhibit high ionic conductivity of up to 3.25 × 10⁻⁴ S/cm at 60 °C. The stress relaxation behavior of the V-SPE demonstrates a gradual decrease in viscosity following the Arrhenius law and an activation energy of 52 kJ/mol, attributed to the dynamic exchange reaction. Furthermore, the imine exchange reaction endows self-healing capability to V-SPEs at ambient temperature. Note that the reduction in initial interfacial resistance over 40 charge-discharge cycles indicates enhanced compatibility between the electrode and electrolyte due to the dynamic exchange reaction. The LMB full cell having V-SPE shows a large initial discharge capacity of 154.7 mAh/g, good C-rate capability, and long cycle lives for at least 100 charge-discharge cycles at 60 °C and 0.1 C. This suggests that V-SPEs hold a great potential as solid electrolytes for LMBs.