A Comparative Evaluation of Carbonaceous and Alloy Type Anodes for Sodium-Ion Batteries: Capacity, Scalability, and Sustainability Perspectives.

The demand for high-performance energy storage systems has intensified the search for alternative battery technologies beyond lithium-ion batteries (LIBs). Interestingly, sodium-ion batteries (SIBs) have emerged as promising candidates due to the natural abundance and cost-effectiveness of sodium (Na) resources. However, achieving competitive energy density remains a significant challenge, particularly at the anode counterpart. Traditional carbonaceous anodes, specifically graphite, which have demonstrated remarkable success in LIBs, tend to exhibit suboptimal electrochemical performance when applied to SIBs. This limitation primarily arises from the fundamental thermodynamic and kinetic differences between lithium (Li) and Na ions. In particular, Na possesses a significantly larger ionic radius than Li, which hinders its ability to intercalate efficiently into the graphite layers typically used in LIBs. Moreover, the weaker binding affinity of Na to the carbonaceous host leads to less favorable thermodynamics, further contributing to its sluggish intercalation kinetics. These issues result in poor Na-ion storage capacity, low initial Coulombic efficiency (ICE), and rapid capacity fading. To overcome these limitations, alloy-type anode materials are gaining attention for their high theoretical capacities and enhanced energy densities. Thus, this review intends to provide a comprehensive overview of recent advances in alloy-type anodes for SIBs, focusing on elucidating and unraveling the underlying mechanisms of Na storage. Key insights into the electrochemical behavior, phase transformations, and failure mechanisms of these materials are discussed, highlighting the critical factors that influence their performance. Additionally, the review examines the fundamental science behind the performance degradation of carbonaceous anodes, providing a comparative analysis to better understand the challenges and opportunities for next-generation SIB anodes. Overall, this work aims to bridge the knowledge gap in the design of high-energy-density anodes for SIBs, guiding future developments in the quest for efficient and sustainable energy storage solutions.