Three-Dimensional Hierarchical Flowerlike FeP Wrapped with N-Doped Carbon Possessing Improved Li+ Diffusion Kinetics and Cyclability for Lithium-Ion Batteries

Transition-metal phosphides have a potential application in lithium-ion batteries (LIBs) because of their high theoretical capacities and low cost; nevertheless, they possess dramatic volumetric variation during cycling associated with poor conductivity, limiting their practical applications. Here, a three-dimensional (3D) hierarchical flowerlike FeP coated with nitrogen-doped carbon layer (FeP@N,C hybrid) was constructed through a solvothermal method, followed by a phosphating approach under low temperature. N-doped carbon not only suppresses the volume fluctuation of FeP, but also promotes electron transfer, accompanied by catalyzing the decomposition of Li3P to improve the reversibility of the FeP@N,C hybrid during cycling processes. In addition, a 3D flowerlike architecture assembled from porous nanosheets is also beneficial for shortening the migration path of ions as well as improving the contact area of electrode with electrolyte, which enhances the reaction kinetics and is proved by both experimental measurement of Li+ diffusion coefficient and resistivity, along with the calculation of density functional theory. Consequently, the 3D hierarchical flowerlike FeP@N,C hybrid performs excellent cyclic stability (569 mA h g–1 at a current density of 500 mA g–1 for the 300th cycle) and rate performance (331.94 mA h g–1 at a high current density of 5 A g–1) for LIBs. Based on above results, the fabrication strategy in this work could offer a thought to design other high-performance metal phosphide hybrids.