Wide-temperature-range sodium-metal batteries: from fundamentals and obstacles to optimization

Sodium metal with a high theoretical specific capacity (similar to 1166 mA h g-1) and low redox potential (-2.71 V) shows tremendous application prospects in sodium-metal batteries (SMBs). However, studies of SMBs in extreme environments, especially at low temperature (LT) and high temperature (HT), have not received enough emphasis, and few reviews have summarize them. More seriously, some mechanistic issues, such as nucleation and deposition behavior, dendrite growth, interfacial chemistry and an unstable solid electrolyte interface (SEI), are perplexing. Herein, we start with the operation fundamentals of SMBs, simultaneously point out the obstacles faced by SMBs in different environments and propose various targeted optimization strategies, including construction of a three-dimensional (3D) framework, design of an artificial SEI and optimization of the liquid (solid-state) electrolyte/metal anode interface. Each strategy starts with carefully selected cases and then moves to illustrate the nucleation and deposition behavior of Na+ in the structure. Finally, we point out challenges, strategies and outlooks for the future practical applications of wide-temperature-range SMBs. Overall, this review provides a design guide for SMBs with high energy density, long lifespan, low-cost and high security, and could inspire more researchers to focus on the mechanism of batteries in extreme environments. This review comprehensively summarizes the operation fundamentals of SMBs in different environments and proposes various targeted optimization strategies.