Ambient-air-stable Li3InCl6 halide solid electrolyte, with high ionic conductivity of 1.49 × 10−3 S cm−1 at 25 °C, delivers essential advantages over commercial sulfide-based solid electrolyte.

Sulfide‐based solid‐state electrolytes (SSEs) for all‐solid‐state Li metal batteries (ASSLMBs) are attracting significant attention due to their high ionic conductivity, inherently soft properties, and decent mechanical strength. However, the poor incompatibility with Li metal and air sensitivity have hindered their application. Herein, the Sn (IV) substitution for P (V) in argyrodite sulfide Li6PS5I (LPSI) SSEs is reported, in the preparation of novel LPSI‐xSn SSEs (where x is the Sn substitution percentage). Appropriate aliovalent element substitutions with larger atomic radius (R > R

) provides the optimized LPSI‐20Sn electrolyte with a 125 times higher ionic conductivity compared to that of the LPSI electrolyte. The high ionic conductivity of LPSI‐20Sn enables the rich I‐containing electrolyte to serve as a stabilized interlayer against Li metal in sulfide‐based ASSLMBs with outstanding cycling stability and rate capability. Most importantly, benefiting from the strong Sn–S bonding in Sn‐substituted electrolytes, the LPSI‐20Sn electrolyte shows excellent structural stability and improved air stability after exposure to O2 and moisture. The versatile Sn substitution in argyrodite LPSI electrolytes is believed to provide a new and effective strategy to achieve Li metal‐compatible and air‐stable sulfide‐based SSEs for large‐scale applications.

All-solid-state lithium-ion batteries (SSLIBs) are promising candidates to meet the requirement of electric vehicles due to the intrinsic safety characteristics and high theoretical energy density. A stable cathodic interface is critical for maximizing the performance of SSLIBs. In this study, operando X-ray absorption near-edge spectroscopy (XANES) combined with transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) is employed to investigate the interfacial behavior between the Ni-rich layered cathodes and sulfide solid-state electrolyte. The study demonstrates a metastable intermediate state of sulfide electrolyte at high voltage and parasitic reactions with cathodes during the charge/discharge process, which leads to the surface structural reconstruction of Ni-rich cathodes. Constructing a uniform interlayer by atomic layer deposition (ALD) is also employed in this study to further investigate the cathodic interface stability. These results provide new insight into the cathodic interface reaction mechanism and highlight the importance of advanced operando characterizations for SSLIBs.

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Sulfide-based solid-state electrolytes (SSEs) are considered a key part in the realization of high-performance all solid-state lithium-ion batteries (ASSLIBs). However, the incompatibility between conductive additives and sulfide-based SSEs in the cathode composite challenges the stable delivery of high-rate capability. Herein, a poly­(3,4-ethylenedioxythiophene) (PEDOT) modification is designed as a semiconductive additive for cathode composites (cathode/SSE/carbon) to realize the high performance. The modified ASSLIB demonstrates a competitive rate capacity of over 100 mAh g–1 at 1C, which is 10 times greater than that of the bare cathode. Detailed surface chemical and structural evolutions at the cathodic interface indicate the PEDOT modification not only significantly suppresses the side reactions but also realizes effective electron transfer at the cathode/SSE/carbon three-phase interface. Introducing a controllable semiconductive additive for the cathode composites in this study offers a promising design to realize the high-rate performance and overcome long-term challenges in the application of conductive additives in sulfide-based ASSLIBs.