Soft breakdown hidden in ASSLBs has been overlooked in most previous research. Here we propose a simple but effective strategy—cyclic voltammetry— to diagnose soft breakdown in all-solid-state batteries. Moreover, low-frequency electrochemical impedance spectroscopy is employed to quantify the soft breakdown. With this understanding, we establish a standard testing protocol, which could be used to unify future research endeavors if adopted. This work provides new insights into ASSLBs and establishes assessment metrics for this community.

All-solid-state lithium batteries using solid-state electrolytes offer unprecedented safety and high energy density but are plagued by complicated interfacial issues. Understanding the kinetics of interfacial ion and electron transport is of foremost importance for addressing the interfacial challenges, as discussed in this paper.

Polytetrafluoroethylene (PTFE) fibrilization was utilized to interweave inorganic solid electrolytes (SEs) into freestanding membranes. Representative SE membranes, including Li6PS5Cl, Li3InCl6, and Li6.5La3Zr1.5Ta0.5O12, demonstrate not only a thickness of 15–20 μm but also high room-temperature ionic conductivity (>1 mS cm–1).

Ammonium-assisted wet chemistry is reported to synthesize various solid-state halide electrolytes with an exceptional ionic conductivity (>1 microsiemens per centimeter). Microstrain-induced localized microstructure change is found to be beneficial to lithium ion transport in halide electrolytes.

This review aims to combine fundamental and engineering perspectives to rationally design practical SE-based ASSLBs with high energy density, covering SEs, interface, and practical all-solid-state pouch cells.