Sodium Ion Battery Development Since 2020 with Future Perspectives

Abstract

Sodium-ion batteries are gaining traction as low-cost, sustainable alternatives to lithium-ion systems, particularly for applications where energy density can be traded for safety, raw material abundance, and manufacturing simplicity. This review examines recent advances in electrode design, with emphasis on how structural modifications at the atomic and mesoscale influence electrochemical performance. In cathodes, developments in layered oxides such as P2, O3, and their biphasic hybrids have demonstrated how compositional tuning and interface engineering can suppress phase transitions and activate oxygen redox. Polyanionic compounds and Prussian Blue analogues provide distinct pathways for achieving structural stability and high-rate performance, supported by inductive effects and open-framework geometries. High entropy strategies have emerged as a unifying design principle that enables simultaneous optimisation of redox activity, sodium-ion diffusion, and phase robustness across multiple material classes. On the anode side, the performance of hard carbon has been advanced through control of pore architecture, heteroatom doping, and interfacial engineering to improve initial Coulombic efficiency. Finally, we highlight trends in industrial translation, including full-cell architectures, standardisation protocols, and scalable synthesis. Overall, these developments outline a maturing field defined by increasingly sophisticated materials chemistry and growing commercial viability.