Recent Advances in NASICON-Type Electrolytes for Solid-State Metal Batteries

Compared to traditional liquid electrolyte batteries, solid metal batteries offer advantages such as a wide operating temperature range, high energy density, and improved safety, making them a promising energy storage technology. Solid electrolytes, as the core components of solid-state batteries, are key factors in advancing solid-state battery technology. Among various solid electrolytes, Na super ionic conductor (NASICON)-type solid electrolytes exhibit high ionic conductivity (10⁻³ S·cm⁻¹), a wide electrochemical window, and good thermal stability, providing room for the development of high energy-density solid metal batteries. Since the discovery of NASICON-type solid electrolytes in 1976, interest in their use in all-solid-state battery development has grown significantly. In this review, we comprehensively analyze the common features of NASICON lithium-ion conductors and NASICON sodium-ion conductors, review the historical development of NASICON-type solid electrolytes, systematically summarize the transport mechanisms of metal cations in NASICON-type solid electrolytes, discuss the latest strategies for enhancing ionic conductivity, elaborate on the latest methods for improving mechanical stability and interface stability, and point out the requirements of high energy density devices for NASICON-type solid electrolytes as well as three types of in situ characterization techniques for interfaces. Finally, we highlight the challenges and potential solutions for the future development of NASICON-type solid electrolytes and solid-state metal batteries.