Current Progress of Anode-Free Rechargeable Sodium Metal Batteries: Origin, Challenges, Strategies, and Perspectives

Anode-free sodium metal batteries (AFSMBs) as one new battery configuration, have attracted more attention in recent years and considered as the promising next-generation energy storage systems, owing to the advantages of high theoretical energy density, high safety, cost-saving, and simplified fabrication process. The practical application of AFSMBs, however, is impeded by their poor cycle life arising from the low coulombic efficiency (CE), the growth of metal dendrite, and unstable solid electrolyte interphase (SEI). Recently, some works are reported to dissolve the above-mentioned issues. In this review, it provides a comprehensive summary of AFSMBs including their origin, mechanism, advantages, challenges, strategies, and perspectives. First, the intrinsic issues of conventional sodium metal batteries are summarized as safety concerns and manufacturing difficulty, which is the background of promoting AFSMBs' birth. Subsequently, the mechanism, construction requirement, advantages, and challenges of AFSMBs are discussed. Furthermore, the strategies for improving AFSMBs performance in terms of the current collector, electrolyte, and protocols, are summarized based on an extensive literature survey. Finally, the summary and outlook on this emerging field are further discussed briefly. Anode-free sodium metal batteries (AFSMBs) with high safety and high energy density have attracted widespread attention from scientists. In this review, the background of AFSMBs is comprehensively retrospected, including their origin, configuration, working mechanism, benefits, challenges, and strategies. Profound suggestions and perspectives are made on the exploration of this potential energy storage system to higher professional levels at the end.image