High‐performance rechargeable all‐solid‐state lithium metal batteries with high energy density and enhanced safety are attractive for applications like portable electronic devices and electric vehicles. Among the various solid electrolytes, argyrodite Li6PS5Cl with high ionic conductivity and easy processability is of great interest. However, the low interface compatibility between sulfide solid electrolytes and high capacity cathodes like nickel‐rich layered oxides requires many thorny issues to be resolved, such as the space charge layer (SCL) and interfacial reactions. In this work, in situ electrochemical impedance spectroscopy and in situ Raman spectroscopy measurements are performed to monitor the detailed interface evolutions in a LiNi0.8Co0.1Mn0.1O2 (NCM)/Li6PS5Cl/Li cell. Combining with ex situ characterizations including scanning electron microscopy and X‐ray photoelectron spectroscopy, the evolution of the SCL and the chemical bond vibration at NCM/Li6PS5Cl interface during the early cycles is elaborated. It is found that the Li+ ion migration, which varies with the potential change, is a very significant cause of these interface behaviors. For the long‐term cycling, the SCL, interfacial reactions, lithium dendrites, and chemo‐mechanical failure have an integrated effect on interfaces, further deteriorating the interfacial structure and electrochemical performance. This research provides a new insight on intra and intercycle interfacial evolution of solid‐state batteries.

Replacing organic liquid electrolytes (LEs) in lithium‐ion batteries (LIBs) with solid‐state electrolytes (SSEs) to achieve all‐solid‐state lithium batteries (ASSLBs) with improved safety and potential higher energy density has been attracting growing attention for their wide application in various electronic devices, electric vehicles and renewable energy integration. To achieve high‐performance ASSLBs, the design of SSEs with high ionic conductivity, easy processability, and compatible and stable interfaces with the cathode and anode has become a research priority in recent years. Among all the challenges and issues concerning interfaces, the mechanisms and suppression methods of interfacial reactions are particularly important in the rational design of efficient electrolyte/electrode interfaces. This review mainly focuses on interfacial reactions in various types of inorganic ASSLBs and significant negative effects on battery performance. We also highlight advanced characterization methods and summarize some notable approaches to stabilize interfaces. Finally, we believe the scientific prospect of ASSLBs interface research will be helpful to keep pace with future research trends.

Argyrodite-type sulfide solid electrolytes (SEs) Li6PS5X (X = Cl, Br, I) have attracted considerable interest lately by providing a promising lithium-ion transport capability for its application in all-solid-state lithium batteries (ASSLBs). However, other than Li6PS5Cl and Li6PS5Br, Li6PS5I shows poor ionic conductivity of 10–7 S cm–1, which is originated from the I–/S2– site ordered arrangement in its structure. Herein, we report a silicon-doped solid electrolyte Li6+x P1–x Si x S5I in this sulfide class, which can remarkably increase the conductivity to 1.1 × 10–3 S cm–1 and lower the activation energy to 0.19 eV as a consequence of changing the structural unit in the argyrodite network. The Li6+x P1–x Si x S5I solid electrolytes are employed in ASSLBs with Li­(Ni0.8Mn0.1Co0.1)­O2 (NCM-811) as cathode and Li metal as an anode to evaluate the electrochemical performance. With x = 0.55, the battery displays an initial discharge capacity of 105 mA h g–1 at a rate of 0.05C and achieves high Coulombic efficiency. Moreover, chemical reactions occurring on the interfaces of the NCM/SE and Li/SE in regard to the degradation of cell performance are also investigated.

In article number 1903311, Wenkui Zhang and co‐workers perform in situ and ex situ measurements to monitor the interfacial evolutions in an all‐solid‐state LiNi0.8Co0.1Mn0.1O2/Li6PS5Cl/Li battery. The interfacial evolutions (changes of space charge layer and chemical bond vibration) are very different inter‐ and intracycle. Li+ ion migration has a significant influence on these interfacial behaviors.

No abstract