Recent advances in functional oxides for high energy density sodium-ion batteries

The rapid development of power generation from renewable energy, such as geothermal, wind, and tidal energy, arises the need for efficient and economic electrochemical energy storage systems for integrating electric power smoothly into power grids. The lithium-ion battery has been successfully utilized for a variety of portable electronic devices but its application in large-scale energy storage has raised concerns about safety, availability of lithium resources, and its increasing price. Alternatively, sodium-ion battery (SIB) has been in acquisition predominantly, because of the abundant sodium resources over the earth's crust at low cost. Developing high energy density electrode materials is one of the most intensive research topics. Oxides have been extensively investigated as the cathode and anode materials for high-performance and durable SIBs, owing to their various advantages including facile synthesis, versatile compositions, and easy structural tuning. In this review, we provide an in-time thorough summary of recent advances in oxide materials for cathodes and anodes for high energy density SIBs. The energy storage mechanism, challenges, categories, and optimizations of both electrodes are discussed. Existing research gaps and future perspectives are also outlined. This review is expected to accelerate the research for developing new pathways for tuning the properties of the oxide electrodes based on different sodium storage mechanisms.