Research Progress and Perspectives on Pre-Sodiation Strategies for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) with abundant elements have garnered significant attention from researches as a promise compensation to lithium-ion batteries (LIBs). However, the large-scale commercial application of SIBs is partially hindered by the limited initial coulombic efficiency (ICE) due to the irreversible formation of solid electrolyte interphase (SEI) and intercalation into the defects in the anode. Similar to pre-lithiation techniques, pre-sodiation approaches are considered to be one of the most direct and effective way to compensate for the loss of active sodium at the anode side of SIBs during the initial cycle. In this context, additional sodium ions are pre-injected to the cathode/anode material by chemical/electrochemical methods, aiming to improve battery span life and energy density. This review delves into the necessity and impact of pre-sodiation techniques, compiling the latest research progress, for instance, self-sacrificing cathode additives, over-sodiated cathode materials, direct contact and solution chemical pre-sodiation. Notably, the research mechanisms underlying solution chemical pre-sodiation are highlighted. This comprehensive overview aims to foster a deeper understanding of the pre-sodiation techniques and expects to provide guidance for realizing the commercial application of high energy density sodium-ion batteries.