Stabilization strategies for bismuth-based anodes in sodium-ion batteries: From nanoscale engineering to carbon hybridization

Bismuth (Bi)-based anode materials hold significant potential for sodium-ion batteries (SIBs) because of their high theoretical capacity, cost-effectiveness, and environmental compatibility. However, severe volume expansion and structural instability during cycling critically impede their practical application. This review comprehensively examines recent progress in stabilizing Bi-based anode materials, emphasizing innovative strategies to mitigate mechanical degradation and enhance electrochemical durability. The pure Bi anodes are first analyzed, emphasizing electrolyte engineering and nanoscale designs that alleviate strain and promote the stable solid-electrolyte interphase formation. Bi-based alloys, including binary and ternary systems, are discussed for their synergistic effects in buffering volume changes while improving conductivity and cyclic reversibility. Next, Bi-based compounds (e.g., chalcogenides) and their heterostructures are explored for their ability to generate internal electric fields and stabilize ion transport pathways. Special attention is given to Bi-carbon composites, where 1D carbon frameworks, graphene encapsulation, and 3D core-shell architectures synergistically suppress pulverization and enhance interfacial stability. Advanced structural designs such as self-adaptive stress-relief configurations and binder-free flexible electrodes, are also evaluated for their role in achieving long-term cycling stability. Finally, we outline future directions, including multi-scale interface engineering, in-situ characterization of structural evolution and scalable fabrication of multifunctional composites. This review provides critical insights into stabilizing Bi-based anodes, paving the way for their deployment in high-performance SIBs.