Realization of high cycle life bismuth oxychloride Na-ion anode in glyme-based electrolyte

Two-dimensional bismuth oxychloride (BiOCl) is recently explored as an anode in rechargeable alkali-ion batteries because its layered structure facilitates ionic diffusion and higher specific capacities. However, its application is mainly challenged by rapid capacity decay originating from particle pulverization and unstable solid electrolyte interphase (SEI). Herein, we demonstrate the higher cycling stability of BiOCl anode in Na-ion batteries (NIBs) by simply coupling it with diglyme-based electrolyte. The BiOCl anode delivers reversible capacities greater than 295 mA h g(-1) for 650 cycles at 100 mA g(-1). It also displays excellent rate performances (similar to 278 and 267 mA h g(-1) at 200 and 500 mA g(-1), respectively) and higher durability under different current rates. Such stellar performance of BiOCl anode is attributed to the formation of stable SEI and maintenance of electrode integrity as revealed by the post-mortem studies. Besides, the electrochemical (de)sodiation mechanism of BiOCl anode is also clarified through in-operando X-ray diffraction (XRD) studies, which reveals the reversible formation of Bi <-> NaBi <-> cubic-Na3Bi phases. This report emphasizes the importance of electrolyte engineering as an excellent way to build stable SEI and achieve high-performance advanced alloy anodes for NIB application.