Li+-migration influencing factors and non-destructive life extension of quasi-solid-state polymer electrolytes

Polymer-based quasi-solid-state electrolytes (QSSE) are believed to be the most feasible candidates for solid-state batteries, but they are hindered by relatively lower ionic conductivity and narrower electrochemical window. Here, we synthesize a series of ether-free acrylates containing Li+-ligands for high-voltage-stable QSSEs. Our findings demonstrate that the polymer-involved solvation structure is critical in determining the ionic conductivity, and low-temperature crystallization of the polymer can be used for non-destructive life extension of batteries. The prepared polymers do not contain ether unit and exhibit a polymerization degree of 99% in cells without residual double-bonded monomer, endowing them with high antioxidation capability and compatibility with high-voltage positive electrodes including LiNi0.85Co0.075Mn0.075O2, 4.6 V LiCoO2 and 4.8 V Li1.13Ni0.3Mn0.57O2. The confinement of liquid in QSSEs effectively suppresses the interfacial reactions, but the residual interface reactions still gradually consume liquid electrolytes and cause capacity fading, due to the limited diffusion of the confined solvent to wet the interface. Through crystallizing the polymer matrices at −50 °C, the confined liquid in QSSEs is released and re-wets the Li-metal/polymer interface, thereby recovering the capacity and extending the life of solid-state batteries in a non-destructive manner. Polymer electrolytes are promising but are limited by narrow electrochemical window. Here, authors develop a family of in situ polymerized gel electrolytes with long term stability up to 5.0 V and develop a non-destructive life extension strategy through freezing the cells.