Recent Advances and Practical Challenges in Organic Electrolytes of Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are expected to become attractive large-scale energy storage technologies owing to their abundant resources and low cost. However, sluggish reaction kinetics at the interface and poor thermodynamic stability of organic electrolytes lead to inferior cycle/rate performance and a low energy density of SIBs. The electrolyte engineering, including salt concentration adjustment, molecule design, and additive utilization, has been demonstrated to effectively optimize solvation structures and construct stable interfaces, resulting in accelerated Na+ transport and suppressed electrolyte decomposition. This review focuses on recent advances and fundamental design principles of organic electrolytes in terms of sodium salts, solvents, and functional additives. Furthermore, the crucial challenges for SIBs, including high operating voltage, wide working temperature range, and fast charge rate, are discussed. The corresponding solution strategies are introduced for the desired organic electrolytes in high-performance SIBs. Finally, several perspectives on the future development of organic electrolytes are presented for practical SIBs.