Sulfide solid electrolyte (S-SE) based all-solid-state batteries (ASSBs) have received particular attention due to their outstanding ionic conductivity and higher energy density over conventional lithium-ion batteries.

Due to its good mechanical properties and high ionic conductivity, the sulfide-type solid electrolyte (SE) can potentially realize all-solid-state batteries (ASSBs). Nevertheless, challenges, including limited electrochemical stability, insufficient solid-solid contact with the electrode, and reactivity with lithium, must be addressed. These challenges contribute to dendrite growth and electrolyte reduction. Herein, a straightforward and solvent-free method was devised to generate a robust artificial interphase between lithium metal and a SE. It is achieved through the incorporation of a composite electrolyte composed of Li₆PS₅Cl (LPSC), polyethylene glycol (PEG), and lithium bis(fluorosulfonyl)imide (LiFSI), resulting in the in situ creation of a LiF-rich interfacial layer. This interphase effectively mitigates electrolyte reduction and promotes lithium-ion diffusion. Interestingly, including PEG as an additive increases mechanical strength by enhancing adhesion between sulfide particles and improves the physical contact between the LPSC SE and the lithium anode by enhancing the ductility of the LPSC SE. Moreover, it acts as a protective barrier, preventing direct contact between the SE and the Li anode, thereby inhibiting electrolyte decomposition and reducing the electronic conductivity of the composite SE, thus mitigating the dendrite growth. The Li|Li symmetric cells demonstrated remarkable cycling stability, maintaining consistent performance for over 3000 h at a current density of 0.1 mA cm^-2, and the critical current density of the composite solid electrolyte (CSE) reaches 4.75 mA cm^-2. Moreover, the all-solid-state lithium metal battery (ASSLMB) cell with the CSEs exhibits remarkable cycling stability and rate performance. This study highlights the synergistic combination of the in-situ-generated artificial SE interphase layer and CSEs, enabling high-performance ASSLMBs.

Sulfide solid-state electrolytes (SSSEs) are considered an auspicious alternative for all-solid-state batteries, because of their ductility and high ionic conductivity. One obstacle that thwarts SSSEs in large-scale applications is their lack of stability upon exposure to humid air. We used Lewis acid additives to treat the argyrodite Li₆PS₅Cl SSSE particles at the nanoscale level by dispersing them in solution mixtures, a method that had minimal impact on ionic conductivity. A series of investigations were conducted, involving the utilization of X-ray diffraction, in situ Raman spectroscopy, solid-state nuclear magnetic resonance, and X-ray absorption near-edge structure for characterizations. The SSSE demonstrated notable atmospheric stability by establishing a Lewis acid–base interaction with the additives. This interaction effectively shields the SSSE from moisture in humid air, ensuring that the bulk region remains structurally intact and undeteriorated. Therefore, treating SSSEs using Lewis acid additives is an auspicious approach to improving their moisture stability.