A 30-year overview of sodium-ion batteries

Sodium-ion batteries (NIBs) have emerged as a promising alternative to commercial lithium-ion batteries (LIBs) due to the similar properties of the Li and Na elements as well as the abundance and accessibility of Na resources. Most of the current research has been focused on the half-cell system (using Na metal as the counter electrode) to evaluate the performance of the cathode/anode/electrolyte. The relationship between the performance achieved in half cells and that obtained in full cells, however, has been neglected in much of this research. Additionally, the trade-off in the relationship between electrochemical performance and cost needs to be given more consideration. Therefore, systematic and comprehensive insights into the research status and key issues for the full-cell system need to be gained to advance its commercialization. Consequently, this review evaluates the recent progress based on various cathodes and highlights the most significant challenges for full cells. Several strategies have also been proposed to enhance the electrochemical performance of NIBs, including designing electrode materials, optimizing electrolytes, sodium compensation, and so forth. Finally, perspectives and outlooks are provided to guide future research on sodium-ion full cells.