Dynamic Imine Bonds-Based Vitrimer Electrolytes for Stable Interfaces in Lithium Metal Electrodes

Abstract

Vitrimer solid polymer electrolytes (V-SPEs) incorporating dynamic imine bonds are developed as solid-state electrolytes for the use in lithium metal batteries (LMBs). By systematically tuning the ratio of ethylene oxide (EO) units to Li+ and the EO chain length, the ionic transport properties of the polymer matrix are optimized. The formulation containing extended EO segments achieves a considerable ionic conductivity of 2.88 x 10-4 S cm-1 at 60 degrees C. The V-SPE exhibits pronounced stress relaxation, where viscosity decreased linearly with temperature in accordance with the Arrhenius relationship, showing an activation energy of 48 kJ mol-1 derived from imine bond exchange dynamics. Owing to these reversible imine exchanges, the V-SPEs are capable of self-healing at room temperature. These dynamic exchanges result in a 75% decrease in interfacial resistance over 120 charge-discharge cycles, confirming the adaptive nature of the polymer network at the electrode-electrolyte interface. Furthermore, a full Li metal cell employing the optimized V-SPE delivers stable cycling performance with good C-rate capability up to 100 cycles at the conditions of 60 degrees C and 0.1 C. Overall, the results demonstrate the promise of V-SPEs as solid-state electrolytes for LMBs.