Durable and Adjustable Interfacial Engineering of Polymeric Electrolytes for Both Stable Ni‐Rich Cathodes and High‐Energy Metal Anodes

(4.3 V)||Li batteries show excellent cycle life with high Coulombic efficiencies (>99%). This SIP strategy is also investigated and verified in sodium metal batteries. It opens a new frontier for solid electrolytes toward high-voltage and high-energy metal battery technologies.