Practical challenges and future perspectives of solid polymer electrolytes: microscopic structure and interface design

Lithium metal is widely regarded as the most promising anode material for lithium batteries. However, its practical application has been hindered by the issue of dendrite formation. Solid electrolytes have emerged as a potential solution to mitigate dendrite growth, overcoming the limitations of liquid electrolytes. Among these, solid polymer electrolytes (SPEs) have garnered considerable attention due to their exceptional safety features and excellent processability. Nonetheless, certain intrinsic properties of SPEs, including ion conductivity, mechanical strength, and electrochemical stability, still fall short of the requirements for practical application, posing significant challenges to their progress. This review focuses on strategies aimed at enhancing these intrinsic properties, shedding light on the underlying mechanisms from a microscopic perspective. Key aspects have been discussed including ion-pair and/or chemical interactions, formation of ion channels, influence of physicochemical properties of fillers, micro-phase separation of SPEs, and achieving favorable electrode/SPE interfaces. By providing a comprehensive overview of these strategies, we aim to explore and understand in depth the critical intrinsic properties of SPEs from a microscopic standpoint. Ultimately, this work aims to pave new pathways for improving the overall performance of SPEs.