Nonaqueous Liquid Electrolytes for Sodium‐Ion Batteries: Fundamentals, Progress and Perspectives

Abstract

Sodium‐ion batteries (SIBs), driven by sustainability and cost advantage, have been recognized as one of the most promising electrochemical energy storage devices. Electrolytes, as the most unique component that not only ionically connect while insulating electronically electrodes but also determine the eventual improvements in performance mainly regarding cycle life, Coulombic efficiency, energy density, and safety, hold the key to the practical implementation of SIBs. In this review, the fundamental design principles of Na+‐ion electrolytes and the chemical properties of the Na+ cation over the Li+ cation in terms of ion transport, salt dissolution, and solvation structure are first discussed. Then, a sequence of crucial experimental discoveries and strategical achievements in the field of electrolytes for SIBs are presented, with focuses on the ether‐based electrolytes for co‐intercalation into graphite, diluted and highly concentrated electrolytes, wide temperature range electrolytes, nonflammable electrolytes, indispensable electrolyte components (functional additives and new sodium salts). Finally, a detailed analysis of research trends of practically feasible Na+‐ion electrolytes is presented to aid in the ongoing quest for better SIBs of the future.

Eutectic Electrolytes Convoying Low-Temperature Metal-Ion Batteries

“…In an electrolyte, the thermodynamics of salt dissolution described by the Born–Haber cycle indicate that the solubility of a salt is mainly determined by the lattice and solvation energy of its cations and anions . Reversing back to the thermodynamic instability of the metal anode caused by aqueous electrolytes, eutectic electrolytes concededly offer admirable properties. − Particularly, water–joint eutectic construction is extremely important, owing to its high safety and cost-efficiency. Besides, water–eutectic complexes deliver excellent inhibition of ice nucleation because of the successful reconstruction of the H-bond network.…”

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

“…Sodium-ion batteries (SIBs) are considered as promising energy storage technologies as a result of abundant sodium resources and low cost. , Electrolytes are essential in ion transport between two electrodes, in which organic electrolytes exhibit high ionic conductivity and excellent interface wettability compared to ionic liquids, aqueous electrolytes, and solid electrolytes. − Organic electrolytes composed of sodium salts, organic solvents, and functional additives have been employed in SIBs at present. Ester- and ether-based electrolytes are widely used because of their unique advantages in physicochemical properties.…”

Heterostructured Mn–Sn Bimetallic Sulfide Nanocubes Confined in N, S-co-Doped Carbon Framework as High-Performance Anodes for Sodium-Ion Batteries

“…Moreover, metal Na possesses similar physicochemical properties to metal Li. , Especially, the cheap price, abundant reserves, and homogeneous distribution of raw materials endow SIBs with abundant interest and attention. , Importantly, the mature manufacturing crafts of commercial LIBs can directly serve as a guide for the manufacturers of SIBs. Unfortunately, compared to Li + ions, Na + ions possess a bigger ionic radius, which endows the commercial graphite anodes in LIBs no longer suitable for SIBs, leading to a low capacity (35 mAh g –1 ) and sluggish insertion/extraction reaction kinetics. , Hence, exploring suitable sodium-storage anode materials has been the priority for the development of high-performance SIBs. Recently, numerous sodium-host materials have been developed as anodes for SIBs such as carbon-based materials , and metallic compounds (alloys, oxides, , chalcogenides, , and phosphides).…”