Designing weakly and strongly solvating polymer electrolytes: Systematically boosting high-voltage lithium metal batteries

Practical high-voltage lithium metal batteries hold promise for high energy density applications, but face stability challenges in electrolytes for both 4 V-class cathodes and lithium anode. To address this, we delve into the positive impacts of two crucial moieties in electrolyte chemistry: fluorine atom (-F) and cyano group (-CN) on the electrochemical performance of polyether electrolytes and lithium metal batteries. Cyano-bearing polyether electrolytes possess strong solvation, accelerating Li + desolvation with minimal SEI impact. Fluorinated polyether electrolytes possess weak solvation, and stabilize the lithium anode via preferential decomposition of F-segment, exhibiting nearly 6000-h stable cycling of lithium symmetric cell. Furthermore, the electron-withdrawing properties of -F and -CN groups significantly bolster the high-voltage tolerance of copolymer electrolyte, extending its operational range up to 5 V. This advancement enables the development of 4 V-class lithium metal batteries compatible with various cathodes, including 4.45 V LiCoO 2 , 4.5 V LiNi 0.8 Co 0.1 Mn 0.1 O 2 , and 4.2 V LiNi 0.5 Co 0.2 Mn 0.3 O 2 . These findings provide insights into design principles centered around polymer components for high-performance polymer electrolytes.