Mystical alkali metal flame: Sodiophilic insights into rapid preparation of the Na metal battery anode

Abstract

Extensive research has explored the utilization of tin oxide (SnO2) as a sodiophilic reagent in sodium metal batteries. However, achieving rapid encapsulation of sodium has remained elusive, despite efforts such as converting a side reaction yielding a sodiophobic Cu-Sn alloy into sodiophilic SnO2 on the Cu current collector's surface. Notably, the presence of preserved crystal water in SnO2 has proven pivotal, as it initiates the formation of a plasma-like alkali metal flame, facilitating swift encapsulation of metallic sodium at 400 °C. Analysis through XPS and TEM tests unveiled the interaction between crystal water and liquid sodium metal, leading to rapid heat release. This phenomenon results in the generation of sodium metal vapor (>882.9 °C) and the extraction of oxygen atoms from SnO2, forming Na2O within an argon environment. Consequently, Na2O, produced by the reaction of sodium and SnO2 with crystal water as the inducer, plays a critical role in the rapid encapsulation of sodium metal. Furthermore, the synthesized sodium metal electrode exhibited exceptional stability in cycles and resistance to dendrites. This discovery provides valuable insights into the reaction mechanisms of sodiophilic sites in sodium metals, serving as a crucial guide for further research in the field.