Nonflammable Polyfluorides‐Anchored Quasi‐Solid Electrolytes for Ultra‐Safe Anode‐Free Lithium Pouch Cells without Thermal Runaway

The safe operation of rechargeable batteries is crucial because of numerous instances of fire and explosion mishaps. However, battery chemistry involving metallic lithium (Li) as the anode is prone to thermal runaway in flammable organic electrolytes under abusive conditions. Herein, an in situ encapsulation strategy is proposed to construct nonflammable quasi‐solid electrolytes through the radical polymerization of a hexafluorobutyl acrylate (HFBA) monomer and a pentaerythritol tetraacrylate (PETEA) crosslinker. The quasi‐solid system eliminates the inherent flammability of ether electrolytes with zero self‐extinguishing time owing to the gas‐phase radical capturing ability of HFBA. Additionally, the graphitized carbon layer generated during the decomposition of PETEA at high temperatures obstructs the heat and oxygen required for combustion. When coupled with Au‐modified reduced graphene oxide anodic current collectors and lithium sulfide cathodes, the assembled anode‐free Li‐metal cell based on the quasi‐solid electrolyte exhibits no signs of cell expansion or gas generation during cycling, and thermal runaway is eliminated under multiple mechanical, electrical, and thermal abuse scenarios and even rigorous strikes. This nonflammable quasi‐solid configuration with gas‐ and condensed‐phase flame‐retardant mechanisms can drive a technological leap in anode‐free Li‐metal pouch cells and secure the practical applications necessary to power this society in a safe manner. The present work proposes a flame‐retardant polyfluorinated hexafluorobutyl acrylate (HFBA) as the monomer for implementing an in situ radical polymerization with pentaerythritol tetraacrylate (PETEA) crosslinker to convert the liquid electrolyte into a quasi‐solid system. The as‐constructed quasi‐solid electrolyte eliminates the intrinsic flammability due to the synergistic gas‐phase radical scavenging effect of HFBA and the condensed‐phase flame‐retardant effect of PETEA.