Advanced Anode Materials for Rechargeable Sodium-Ion Batteries

Rechargeable sodium-ion batteries (SIBs) have been consideredaspromising energy storage devices owing to the similar "rockingchair" working mechanism as lithium-ion batteries and abundantand low-cost sodium resource. However, the large ionic radius of theNa-ion (1.07 angstrom) brings a key scientific challenge, restrictingthe development of electrode materials for SIBs, and the infeasibilityof graphite and silicon in reversible Na-ion storage further promotesthe investigation of advanced anode materials. Currently, the keyissues facing anode materials include sluggish electrochemical kineticsand a large volume expansion. Despite these challenges, substantialconceptual and experimental progress has been made in the past. Herein,we present a brief review of the recent development of intercalation,conversion, alloying, conversion-alloying, and organic anode materialsfor SIBs. Starting from the historical research progress of anodeelectrodes, the detailed Na-ion storage mechanism is analyzed. Variousoptimization strategies to improve the electrochemical propertiesof anodes are summarized, including phase state adjustment, defectintroduction, molecular engineering, nanostructure design, compositeconstruction, heterostructure synthesis, and heteroatom doping. Furthermore,the associated merits and drawbacks of each class of material areoutlined, and the challenges and possible future directions for high-performanceanode materials are discussed.