Isocyanurate‐Derivative Enables Highly Compatible Poly‐Dioxane Electrolyte for Dendrite‐Free Li Metal Batteries

Abstract The Li⁺ transport kinetics and electrochemical stability of advanced solid‐state Li metal batteries (SLMBs) are seriously limited by the actual electrolyte compositions. Here, a novel polyether‐based electrolyte (PTGDOX) is presented through in situ co‐polymerization by integrating 1,3‐dioxane with a multifunctional 1,3,5‐triglycidyl isocyanurate additive. The isocyanurate group in PTGDOX not only provides abundant coordinating sites for Li⁺ transfer and restricts the movement of anions, but also prompts a beneficial inorganic‐rich solid electrolyte interface on the Li electrode. As a result, PTGDOX exhibits a remarkably increased ionic conductivity of 0.48 mS cm⁻¹ at 30 °C and a reasonable Li‐ion transference number of 0.68, enabling the Li||Li symmetric cells to stably cycle for over 2000 h at 1 mAh cm⁻². Meanwhile, the assembled Li||LiFePO₄ exhibit a 97.4% capacity retention after 700 cycles at 3 C with excellent thermal stability. Moreover, PTGDOX also demonstrates excellent interfacial compatibility with high‐voltage LiNi_0.8Co_0.1Mn_0.1O₂ cathode. As such, this work provides a facile and accessible strategy for designing interface‐stable polymer electrolytes and achieving practical dendrite‐free SLMBs.