Sodium Compensation of Cathodes and Anodes in Sodium-Ion Batteries: A Comprehensive Review

Abstract

The large-scale application of sodium-ion batteries (SIBs) faces low initial Coulombic efficiency (ICE), which leads to substantial reduction in energy density. The state-of-the-art advancements involve the pre-doping of sodium into cathode or anode materials. This approach not only enhances ICE to 100% but also improves the overall cycle life of the battery. This review emphasizes the critical role of sodium compensation in SIBs and provides a concise overview of the most prominent presodiation techniques. While existing review articles primarily focus on presodiation methods, this work offers an in-depth analysis of electrodes pretreated via Na+ pre-insertion. Furthermore, the strategies employed to mitigate irreversible sodium loss during the initial charge/discharge cycle of the cell are provided, and we discuss the current challenges in sodium compensation and propose potential future research directions for developing high-energy-density SIBs.