Tailoring Stable PEO‐Based Electrolyte/Electrodes Interfaces via Molecular Coordination Regulating Enables 4.5 V Solid‐State Lithium Metal Batteries

Abstract Solid‐state lithium metal batteries (SSLMBs) with poly (ethylene oxide) (PEO)‐based electrolytes have increasingly become one of the most promising battery technologies due to high energy density and safety. However, adverse electrode/electrolyte interface compatibility issues hinder further application. Herein, a PEO‐based composite solid electrolyte with excellent anode and cathode interfacial compatibility is designed via the coordination modulation strategy induced by lithium difluorobis(oxalato)phosphate (DFBOP). By utilizing this electrolyte, the robust inorganic‐rich interphase involving LiF, Li x PO y F z , and P─O components is in situ generated on lithium (Li) anode and LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathode surfaces via forceful coordination among PEO, lithium bis(trifluoromethanesulphonyl)imide, and DFBOP and subsequent adjustment of front orbital energy levels. It contributes to homogeneous lithium deposition and an effective impediment of PEO oxidation decomposition at high voltage, promoting superior interfacial stability. Consequently, Li‐symmetric cells with modified electrolyte can achieve a stable cycle over 7000 h at 0.2 mA cm −2 . Specially, the cathode electrolyte interphase with a unique organic–inorganic interpenetration network structure enables the 4.5 V Li/NCM811 cells to cycle steadily over 100 cycles, with a high discharge capacity of 215.4 mAh g −1 and initial coulombic efficiency of 91.23%. This research has shed light on the interfacial design of PEO‐based electrolytes from the perspective of electrolyte coordination regulation to construct high‐performance SSLMBs.