Abstract:

Sodium-ion batteries have attracted widespread attention due to their capacity and cost advantages. Carbon-based materials, represented by hard carbon, are currently the most used anode materials, but their limited theoretical capacity restrains the improvement in energy density for sodium-ion batteries. Antimony and bismuth are capable of reversibly alloying with Na⁺ and are highly promising anode materials owing to their high theoretical capacity, stability, and conductivity. However, due to the volume difference between different alloy phases, antimony and bismuth exhibit large volume expansion during sodiation/desodiation, which causes problems such as poor structural stability, destruction of the solid electrode interface (SEI), and continuous consumption of the electrolyte, limiting the industrial applications of these systems. This review summarizes the sodium storage mechanism, modification strategies, and methods for obtaining antimony- and bismuth-based metallic anode materials. At present, the modification strategies for antimony- and bismuth-based metallic anode materials mainly include fabricating nanostructures and composite materials. By building nanostructures, the particle size can be reduced, the particle morphology can be adjusted, and the strain can be reduced due to nano-effects. When using composite materials, alloy-based anodes can be can be combined with carbon-based and other materials to buffer volume changes using special structures such as core-shell systems. In addition, this review considers antimony bismuth alloy as an example to discuss binary alloy anodes. Finally, future research considerations such as the design of composite materials, development of large-scale manufacturing methods, and research on interfacial characteristics are proposed.

Key words: sodium-ion batteries, alloy, anode materials, antimony, bismuth