High-Conductivity and Moisture-Tolerant Sulfide Electrolyte Enabled by Bifunctional Coating for Practical All-Solid-State Lithium Batteries

Abstract

The pursuit of safer and higher-energy-density batteries has driven the advancement of all-solid-state lithium batteries (ASSLBs). Among various material systems, sulfide solid-state electrolytes (SEs) stand out as highly promising candidates owing to their exceptional ionic conductivity. Nevertheless, their extreme sensitivity to moisture results in the release of toxic H₂S and rapid structural degradation, which severely impedes their scalable manufacturing under ambient conditions. A bifunctional (3-mercaptopropyl)trimethoxysilane (MPTMS) coating strategy is herein presented to shield Li_5.5PS_4.5Cl_0.8Br_0.7 (LPSCBr) from moisture-induced degradation. The MPTMS layer forms a hydrophobic barrier of approximately 10 nm, which reduces H₂S emission by 93.0% after 35 min of exposure to 30% relative humidity, while maintaining 83.1% of the initial ionic conductivity (10.8 mS cm⁻¹). This approach tackles the core challenge associated with sulfide solid-state electrolytes: the realization of compatibility with controlled ambient air without sacrificing critical electrochemical properties. The modified electrolyte maintains a high ionic conductivity (> 5.7 mS cm⁻¹) even after 10 h of air exposure. When applied in all-solid-state cells paired with LiNi_0.83Co_0.11Mn_0.06O₂ cathodes, it exhibits remarkable electrochemical performance, delivering a capacity retention of 84.6% after 1000 cycles. By enabling moisture-tolerant processing, MPTMS-modified LPSCBr SEs lay a solid foundation for the scalable, high-performance, and cost-effective production of ASSLBs.