Controlled design for integration of FeP into 3D carbon frameworks for superior Na storage

Abstract

Developing a facile but effective strategy to maintain structural stability and alleviate the intrinsic poor conductivity of transition metal phosphides is of great importance but challenging. Herein, the N, P-functionalized carbon frameworks are rationally integrated with FeP nanaoparticles through a recrystallization self-assembly process with green phytic acid (PA) as precursors. Such unique heterostructure can enhance the kinetics reaction and structural stability. In situ introduction of FeP nanoparticles into 3D carbon frameworks can dramatically reduce the risk of fracture and prevent the aggregation of nanoscale FeP particles during cycling, thus ensuing the integrity of electrode microstructure. Benefiting from the novel structure, serving as the anode for sodium storage, FeP@PNC electrode demonstrates a superior reversible capability (340.1 mA h g−1 at 0.1 A g−1), superb rate capability (84.1 mA h g−1 at 3 A g−1) and prolonged cycling life (a high capacity of 224.5 mA h g−1 over 4500 cycles at 0.5 A g−1). As evidenced by experiments and density functional theory calculations, the interface between FeP and carbon with vacancy can promote the charge transfer and enhance the interaction between active nanoparticles and Na atoms, contributing to the Na storage.