A Multifunctional Phosphate-Containing Acrylic Monomer Enabling LiNO3 Solvation in a Flame-Retardant Gel Polymer Electrolyte for Lithium Metal Batteries

The wide application of lithium metal batteries is still hindered by several challenges, such as lithium dendrite growth, cathode degradation, and electrolyte flammability. Herein, a multifunctional phosphate-containing acrylic ester monomer (DMPMA) is designed to simultaneously address these issues by integrating LiNO3 solvation, in situ gelation, and intrinsic flame retardancy within a single carbonate-based electrolyte platform. DMPMA promotes LiNO3 dissolution through strong Li+-phosphate coordination, bringing NO3– into the innermost solvation sheath for inorganic-rich interphase formation. In situ polymerization yields a gel polymer electrolyte (GPE-N) that suppresses solvent evaporation, raises the Li+ transference number to 0.62, and widens the electrochemical stability window. The resulting electrolyte enables stable Li plating/stripping for over 1000 h, delivers 97.6% capacity retention in LiNi0.6Co0.2Mn0.2O2||Li full cells after 300 cycles, and exhibits immediate self-extinguishing behavior with enhanced pouch-cell safety. Spectroscopic and structural analyses reveal that the polymer framework redirects LiPF6 decomposition toward a protective LiF/LixPOyFz-rich cathode interphase, suppressing transition-metal dissolution and lattice distortion. This work establishes a molecular-to-interphase design paradigm in which solvation regulation, interfacial stabilization, and safety enhancement all originate from a single structural motif.