Manipulating Electrode/Electrolyte Interphases of Sodium-Ion Batteries: Strategies and Perspectives

After the past decade's rapid development, the commercial demands for sodium ion batteries (SIBs) have been put on the schedule for large-scale energy storage. Even though the electrode-electrolyte interphases play a very important role in determining the overall battery performance in terms of high energy density and long-cycling stability, studies regarding their fundamental understanding and regulation strategies are still in their infancy. Herein, we comprehensively review the current research status and the challenging issues of the as-generated SIB interphases from three main aspects. Firstly, a fundamental understanding of the main body interphase layers is introduced through the development of their formation mechanism, their composition/structure, and the dynamic evolution process involved, all of which are highly responsible for the Na+ ion transport behavior to determine the final kinetic diffusion. Then, interphase manipulation via the parental electrolyte is summarized in terms of electrolyte engineering strategies, such as the solvent/salt selection, the concentration effect, and the functional additive screening to build a more stable interphase layer for desirable electrochemical reversibility. Finally, potential effects from the chosen electrodes are discussed to provide necessary associations with the interphase formation and evolution. Critical challenges for building stable Na-based interphase are identified, and in particular, new ways of thinking about the interphase chemistry and the electrolyte chemistry based on SIBs, are strongly appealing. We believe that this work is likely to attract attention to the rational design of Na-based interphase layers towards high-energy and long-life-span batteries.