Sodium plating on hard carbon anodes in sodium-ion batteries: mechanisms, detection, and mitigation strategies

Abstract

In light of sodium's abundance and cost advantages, sodium‐ion batteries (SIBs) represent a promising alternative to lithium‐ion batteries. The commercial adoption of hard carbon (HC) as an anode material—attributed to its low sodiation potential, high Na⁺ storage capacity, and extensive availability—further reinforces the potential of SIBs. Nevertheless, the inherent thermodynamic instability of HC anodes predisposes them to irreversible Na plating during operation. This phenomenon not only poses considerable safety hazards due to dendrite‐induced short circuits but also accelerates capacity degradation, thereby undermining the feasibility of large‐scale SIB deployment. This review comprehensively delineates the mechanisms underlying Na plating on HC anodes by examining internal factors—such as electrode structure, N/P ratio, and electrolyte composition—as well as external factors including state of charge, low temperature, and fast charging conditions. It further details various detection methods, encompassing both electrochemical techniques and physical characterization of surface morphologies, and outlines mitigation strategies such as electrode structure design, surface coating, and electrolyte regulation to suppress plating. By synthesizing current understanding, the review posits future directions for developing safer, high‐performance SIB anodes. Addressing Na plating is thus critical for advancing SIB technology toward large‐scale application.