Solid polymer electrolyte chemistries tailored by solvation structures

Solid polymer electrolytes (SPEs) endow lithium (Li) metal batteries with superior safety and energy density. However, sluggish Li ion (Li + ) transport within the SPE inhibits its practical application. Understanding the nature of solvation in SPEs is critical for manipulating ion transport and electrode interfaces, but insights remain limited. In this review, we first discuss the definition and characteristics of the solvation cage/structure. Next, we analyze the correlation between the participating degree/chemistry of polymers and solvation structure. Strategies for regulating solvation cages by directly or indirectly tuning interactions between Li + and other compositions are then evaluated, followed by a discussion of characterization techniques for revealing solvation features (e.g., kinetics, ionic coordination states). Finally, we speculate on the future development of solvation in SPEs. This review provides new insights for understanding the bulk and interface behaviors of SPEs from their solvation chemistry, opening a new avenue for designing SPEs to achieve energy-dense solid-state Li metal batteries.