Structural Strategies for Buffering Volume Expansion in Transition-Metal Oxides and Related Conversion/Alloying-Type Anodes for Sodium-Ion Batteries

The growing problem of energy shortage has undoubtedly promoted research and development in energy storage. Against this background, rechargeable sodium-ion batteries (SIBs) are considered one of the most promising candidates for replacing lithium-ion batteries (LIBs) due to their advantages of low cost, good thermal stability, and superior low-temperature performance. Therefore, the development of SIBs has received much attention and focus. Currently, research on SIBs faces the critical problem of large volume change of anode materials during charging and discharging. Despite the volume change problem, past research has been trying to buffer the volume changes, and there’s been a lot of progress. Transition metal oxides (TMOs) based on conversion reactions have become potential anode materials for SIBs due to their more stable crystal structures and good cycling stability. In this review, we first analyze the energy-storage principle of sodium-ion batteries (SIBs). Then, we outline a series of structural strategies for SIBs concerning the large volume change of the anode material during charging and discharging processes, and we classify and discuss the existing studies on nanostructures according to their morphological features. Finally, we summarize the challenges and future trends of TMOs for electrochemical energy storage in SIBs.