Catalyzing Li-Salt Dissociation and Decomposition for a Conformal Low-Impedance Solid Electrolyte Interphase in Solid-State Li Metal Batteries

Solid-state lithium metal batteries (SSLMBs) employing poly(vinylidene difluoride) (PVDF)-based polymer electrolytes face challenges of limited salt dissociation and unstable interfacial chemistry, while conventional filler strategies cannot uniformly resolve these issues due to restricted contact with Li salts. Here, we introduce a molecular catalysis approach using Hemin, a small molecule capable of directly interacting with Li salts within the PVDF matrix at the molecular level, to address these challenges. The pentacoordinated iron sites in Hemin adsorb with FSI^- anions, significantly enhancing salt dissociation and raising the free Li⁺ concentration from 22% to 44%. This improvement increases ionic conductivity from 2.26 × 10^-4 S cm^-1 to 1.13 × 10^-3 S cm^-1. Simultaneously, Hemin catalyzes uniform FSI^- decomposition at the Li anode surface, forming a conformal, LiF-rich solid electrolyte interphase (SEI) that stabilizes lithium deposition and suppresses dendrite growth. These combined effects enable Li||Li symmetric cells to operate stably for over 6000 h. Note that even under a high rate, the Li||LiFePO₄ full cells exhibit remarkable durability over 2000 cycles at 5 C, and Li||LiNi_0.8Co_0.1Mn_0.1O₂ cells maintain stable cycling over 1000 cycles at 2 C. This work highlights the molecular catalysis in bulk ion regulation and interfacial stabilization for high-performance SSLMBs.