In‐Built Reactive Polymer as Versatile Electrolyte to Shield the Bi‐Electrode Surfaces for Practical Li‐Metal Batteries

ABSTRACT High‐voltage lithium metal batteries (LMBs) represent promising candidates for next‐generation energy storage systems, yet are fundamentally constrained by interfacial instability at both high‐voltage cathodes (≥4.3 V vs. Li/Li⁺) and lithium metal anodes. Herein, we in situ prepared a reactive polymer electrolyte (PTGI) with a narrow orbital energy gap and good electrode affinity, which is preferentially reacted prior to solvent to create thermo‐electrochemically robust cathode electrolyte interphase/solid electrolyte interphase, significantly suppressing the interfacial parasitic reactions and the structure degradation of single‐crystal LiNi 0.8 Co 0.1 Mn 0.1 O 2 (SC‐NCM) in a wide temperature range. Furthermore, the isocyanurate groups endow PTGI with enhanced capability to scavenge HF, while reducing the coordination power of the solvent molecules to promote a loose solvation shell for Li + migration. Consequently, the Li|PTGI|SC‐NCM cells deliver ultra‐long and stable cycle life over 1000 cycles at 1 C. LMBs with LiFePO 4 can also stably cycle for 1700 cycles with 76.1% capacity retention. The assembled 1.5 Ah pouch cells, featuring a high‐loading SC‐NCM cathode and lean PTGI electrolyte, also exhibit good cycling stability. The in‐built reactive strategy in this work provides new insights into developing advanced LMBs with high cycle stability and safety.