Nanostructures bimetallic transition metal-based oxides as an anode material for sodium-ion batteries: A review

Sodium-ion batteries (Na-ion batteries) have emerged as a viable alternative to lithium-ion battery systems for large-scale energy storage due to the natural abundance of sodium and the comparatively lower associated costs. However, large ionic radius of Na-ion and high molar mass contribute to lower electrochemical kinetics and poor cycling stability of the electrode. In recent years, conversion-type materials based on the transition bimetallic oxides (BMOs) have shown great promise since these materials demonstrate a high theoretical capacity due to the synergistic effect of two metal ions and thus boost the electronic conductivity when compared to single-metal oxides. Herein, the recent progress of transition BMOs as anodes for Na-ion batteries is reviewed, including the transition-metals with cobalt-based, ferrite-based, manganese-based, molybdenum-based, vanadium-based and nickel-based oxides. The review emphasizes the importance of structure and morphology, which influence overall cell performance. Various classes of nanostructured materials are explored, ranging from zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D), three-dimensional (3D) and heterostructures, with a focus on their ionic transport mechanisms and mechanical properties that facilitate stable cycling. Additionally, challenges and perspectives for future development of these materials are also discussed for better understanding and comprehensive outlook on potential directions as an anode material in Na-ion batteries.