Eliminating Interfacial Stress Concentration Enables High-Energy and High-Safety Gel Polymer Lithium Metal Pouch Cells.

Interfacial stress concentration not only degrades electrochemical performance during cycling but also poses critical safety risks under extreme abuse conditions. Upon nail penetration, localized stress accumulation can trigger catastrophic mechanical failure and rapid thermal runaway. Herein, we report a gel polymer electrolyte (NFGPE) engineered to delocalize interfacial stress through a dual-anchoring polymer framework. The design integrates tri(2-acryloyloxyethyl) isocyanurate (TAIC) and N-[4-cyano-3-(trifluoromethyl)phenyl]methacrylamide (CTFMA) into a mechanically robust, highly cross-linked network. CTFMA can not only act as rigid molecular spacers to compensate for volumetric shrinkage of TAIC and relieve stress accumulation, but also anchor onto the cathode surface using its electron-deficient cyano groups to selectively attract anions and repel solvent molecules, thereby promoting the formation of a thin, inorganic-rich cathode-electrolyte interphase (CEI). Meanwhile, TAIC spontaneously adsorbs onto the lithium anode, facilitating the formation of a stable, inorganic-rich solid-electrolyte interphase (SEI). The bilateral anchoring structure of the crosslinking monomer, combined with the highly supportive structure, ensures void-free, intimate electrode||electrolyte contact across both interfaces, effectively delocalizing interfacial stress throughout the cell. The resulting NFGPE-based coin cell can stably operate from -20°C to 70°C, the lithium metal pouch cells ensure a high-energy density of 528.7 Wh kg-1, and pass nail penetration tests without thermal runaway.