Enhanced Sodium Storage Kinetics by Rational Designed Volume Regulation and Surface Engineering in Hierarchical Porous FeP@C/rGO
Transition metal phosphides, such as iron phosphide (FeP), have been considered as promising anode candidates for high-performance sodium ion batteries (SIBs) owing to their high theoretical capacity. However, the development of FeP is limited by large volume change, low electrical conductivity and sluggish kinetics with sodium ions. Moreover, the sodium storage kinetics and dynamics behavior in FeP are still unclear. Herein, improved sodium storage ability of FeP is achieved by volume regulation and surface engineering via a rational designed hierarchical porous FeP@C/rGO nanocomposite. This FeP@C/rGO nanocomposite exhibits excellent rate capability and long cycle life as the anode of SIBs. In specific, FeP@C/rGO nanocomposite delivers high specific capacities of 635.7 and 343.1 mAh g-1 at 20 and 2000 mA g-1, respectively, and stable cycling with 88.2% capacity retention after 1000 cycles. The kinetics and dynamic studies demonstrate that the superior performance is attributed to the rational designed hierarchical porous FeP@C/rGO with a high capacitive contribution of 93.9% (at 2 mV s-1), and a small volume expansion of only 54.9% by in-situ Transmission electron microscopy (TEM) measurment. This work provides valuable insights of understanding the phase evolution of FeP during the sodiation/desodiation process for designing high-performance SIBs.