In Situ Grown Multi‐Functional Siloxane‐Based Organic–Inorganic Hybrid Matrix toward Robust Sulfide‐Lithium Metal Interface for All‐Solid‐State Batteries

ABSTRACT All‐solid‐state lithium metal batteries (ASSLMBs) employing sulfide electrolytes promise superior energy density and safety but are hindered by interfacial chemical incompatibility and mechanical failure between sulfide electrolytes and lithium metal. Herein we construct a multi‐functional siloxane‐based organic–inorganic hybrid interphase (PD3F‐Li) through in situ reduced inorganic nanodomains (LiIn/In, LiF and LiSi x O y ) within a flexible siloxane network directly on the lithium surface via ring‐opening polymerization of 1,3,5‐trimethyl‐1,3,5‐tris(3,3,3‐trifluoropropyl) cyclotrisiloxane (D3F). The one‐pot solution process forms a 10 µm‐thick interlayer chemically immune to Li 5.5 PS 4.5 Cl 1.5 (LPSC) and mechanically stable toward lithium dendrites. Moreover, the hybrid matrix blocks interfacial side reactions, suppresses dendrite propagation and sustains intimate contact and fast ion transport kinetics during lithium plating/stripping. Resultantly, the symmetric cell PD3F‐Li||PD3F‐Li delivers an ultrahigh critical current density of 3.8 mA cm −2 . Full cell PD3F‐Li|LPSC|LiNi 0.7 Co 0.1 Mn 0.2 O 2 delivers an initial capacity of 136.0 mA h g −1 , a high‐capacity retention of 84.6 after 250 cycles, which is more than 2 times higher than those of the bare Li cell (36.7%). The full cell also achieves a long cycle life of 1100 cycles with capacity retention of 79.5% at 2C. This siloxane‐In‐coupled chemistry offers a scalable, low‐cost route to construct durable sulfide–lithium interfaces for next‐generation high‐energy‐density and long‐cycle life ASSLMBs.