Design of Phosphide Anodes Harvesting Superior Sodium Storage: Progress, Challenges, and Perspectives

Sodium (Na) ion batteries (SIBs) are promising in stationary energy storage applications. Research is also afoot to seek suitable electroactive materials for use in SIBs. Recently, phosphides to be used in the anode for Na storage are particularly appealing due to their high specific capacities and low working potentials. The following matters are to deal with their inherent drawbacks of large volume variation and inferior interfacial stability upon Na insertion/extraction, which is believed to be largely responsible for capacity and cycling decay. Despite striking progress in addressing the above drawbacks, current studies on phosphides remain preliminary. In this review, an in-depth understanding of phosphides regarding Na storage mechanism, capacity assessment, phase change, and reaction types is provided. The effective strategies and the sound designs of phosphides for Na storage are also discussed. Their correlations between electrochemical behavior and chemical/structural characteristics are analyzed, in a bid to sort out the basic ideas for the design of high-performance phosphides that enable high-energy and durable SIBs. Doubtless, the experience and knowledge gained from the research on phosphides are shared, and the strategies are expected to extend the scope beyond phosphides.