Research Progress on Phosphorus-based Anode Materials for Sodium-Ion Batteries

The availability of renewable energy resources (e.g., solar, wind, and tides) is crucial for promoting sustainable development and alleviating environmental issues. However, the intermittent nature of renewable energy requires the application of grid-level electrical-energy storage (EES) technologies to achieve a continuous supply of electricity. As is well known, lithium-ion batteries (LIBs) with high energy density dominate the rechargeable battery market. When faced with the requirements of large-scale power stations, high cost, and limited availability of raw materials, these become serious issues in the application of LIBs. In contrast, sodium-ion batteries (SIBs), which share similar operation mechanisms with LIBs, are considered to be more suitable for grid-level storage due to easy accessibility and geographically available reserves of sodium raw material, with significant improvements in its processing technology made recently. Nevertheless, limited energy density and unsatisfactory cycling life hinder the commercialization of SIBs significantly, which necessitates the use of novel electrode materials with high specific capacities and extended durability. Compared with the accelerated development of cathodes, graphite, on the anode side, as a commercialized anode for LIBs fails to store Na-ions owing to unfavorable thermodynamics. Hence, discovering and designing novel anode materials for SIBs have become a significant challenge. Among different anode materials, phosphorus-based (including phosphides) anodes have been recognized as one of the most promising materials because of their high theoretical capacity (2596 mAh.g(-1) for phosphorus) and the abundance of phosphorus resources. Nonetheless, phosphorus-based anodes exhibit low conductivity and large volume expansion, resulting in inferior cycling performance and rating property. Therefore, various strategies, including nanosizing, morphology control, and carbon (non-carbon) modification, have been adopted to improve the performance of phosphorus-based anodes. In this review, the current progress on phosphorus-based anodes for SIBs are summarized. The Na-storage mechanisms of phosphorus-based materials are briefly discussed. Next, strategies for overcoming the disadvantages of phosphorus-based anodes are discussed extensively, including the size and morphology adjustment as well as the carbon (non-carbon) modification. Specifically, the carbon modification not only increases the conductivity but also decreases the volume expansion. Finally, the challenges and perspective of phosphorus-based anodes for SIBs are proposed. In this review paper, the development of suitable anode materials that can help to accelerate the commercialization of SIBs is highlighted.