In‐Situ Coupled Macromolecular Bridge Enables All‐Solid‐State Lithium Metal Batteries Capable of Extremely High Temperature Operation

ABSTRACT High‐performance and temperature‐resistant lithium metal batteries (LMBs) can operate at extremely high temperatures (i.e., > 150°C), and there is a high demand for them in high‐temperature scenarios or in special fields such as military application. However, due to the unstable organic solvents, traditional liquid electrolytes usually undergo severe degradation and pose serious safety risks at elevated temperatures (i.e., > 60°C). Herein, functional Li 7 La 3 Zr 2 Ta 0.5 O 12 @methoxy polyethylene glycol (LLZT@mPEG) is synthesized via a novel and effective method known as in situ coupled macromolecular bridge, and corresponding all‐solid‐state composite polymer electrolyte (LLZT@mPEG‐CPE) is further prepared. Rigid LLZT cores and flexible ionic conductive polymer side‐chains are closely combined by electrostatic interaction, thus resolving the challenge of interface compatibility between different phases. The introduction of mPEG‐COOH can further improve the dispersibility of LLZT@mPEG, enhance the stability of electrolyte/electrode interface, effectively inhibit the continuous decomposition of the polymer, enabling LMBs with high thermal tolerance and fast‐cycling ability. As a consequence, our LLZT@mPEG‐CPE shows great thermal stability and outstanding electrochemical performance. Remarkably, Li|LLZT@mPEG‐CPE|LFP cell delivers superior temperature‐resistance with a capacity retention of 94% after 500 cycles at high rate of 5 C and extreme temperature as high as 160°C. This study provides an innovative design principle for advanced all‐solid‐state CPEs of LMBs capable of extremely high temperature operation.