Brush‐on‐Brush Topological Solid Polymer Electrolyte Enables Stable Lithium Metal Battery Cycling at 110°C

ABSTRACT High‐temperature batteries capable of operating above 100°C are crucial in various industry applications. However, conventional high‐temperature systems, such as lithium‐thionyl chloride batteries, are not rechargeable. Lithium metal batteries (LMBs) utilizing solid polymer electrolytes (SPEs) offer a promising pathway toward thermally stable, rechargeable energy storage. Here, we design and synthesize an SPE with unique brush‐on‐brush topology (BOB‐Li) to simultaneously enhance mechanical properties and electrochemical stability of electrolyte at elevated temperatures. The rigid poly(methyl methacrylate) (PMMA) backbone imparts sufficient mechanical strength, while the ether moieties on poly(ethylene glycol) acrylate (PEGA) brushes provide tight adhesion and ionic conductivity. Furthermore, BOB‐Li promotes anion‐rich solvation structure with LiTFSI, inducing stable solid‐electrolyte interphase (SEI). Consequently, Li||LiFePO 4 cell employing BOB‐Li retains 90% of its initial capacity after 1000 cycles at 1C and 110°C. Additionally, Li||LiNi 0.6 Co 0.2 Mn 0.2 O 2 cell can work steadily for 100 cycles at 85°C. This work validates a topological design strategy of thermally stable SPE as well as a viable route to fabricate LMBs for extreme high‐temperature applications.