Fluoroether Design Enables High‐Voltage All‐Solid‐State Lithium Metal Batteries

Abstract Developing high‐voltage all‐solid‐state lithium metal batteries (ASSLMBs) holds transformative potential for next‐generation energy storage technologies but remains a formidable challenge. Herein, a new prototype design is presented that integrates fluorinated ether segments into the traditional oxide nanocomposite phase, enabling poly(ethylene oxide)‐based composite electrolytes with exceptional anti‐oxidation durability and enhance overall electrochemical performance. Through a combination of experimental and computational analyses, it is demonstrated that the superior performance is attributed to the formation of reconstructed Li⁺ solvation with weakly coordinating environments. The proposed formulation exhibits excellent Li‐metal compatibility, enabling stable cycling in symmetric Li||Li cells for over 9500 h. The solid‐state electrolyte also exhibits outstanding high‐voltage stability with LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathodes, extending the operational voltage from 4.0 to 4.5 V. Moreover, the LiMn 1‐x Fe x PO 4 ||Li cells have delivered remarkable cycling performance, achieving over 1200 cycles with 99% capacity retention after 500 cycles. This work establishes an innovative platform for designing electrolytes with superior antioxidation properties and enhance structural durability, paving the way for the advancement of high‐voltage all‐solid‐state lithium metal batteries.