Vacancy and architecture engineering of porous FeP nanorods for achieving superior Li+ storage

Abstract

With high theoretical capacity (926 mAh g−1) and safer voltage platform, Iron phosphide (FeP) as an anode material for lithium ion batteries has attracted a lot of attention. However, FeP also suffers serious capacity fading and unsatisfied rate capability, which are triggered by inferior intrinsic conductivity and large volume expansion. Herein, oriented by density functional theory (DFT) calculations, MOF-derived porous FeP nanorods modified by abundant P vacancies (denoted as V-FeP) were ingeniously designed via a simplified approach to alleviate the above obstacles. As a result, the V-FeP nanorods electrode delivered extraordinary specific capacity (1228.3 mAh g−1 at 0.1 A g−1 after 120 cycles) and long-cyclic performance (590.7 mAh g−1 at 2.0 A g−1 after 1000 cycles). Transmission electron microscopy, X-ray absorption fine structure, electron paramagnetic resonance and so on were used to character the V-FeP nanorods. The results indicated the supernormal electrochemical performances of V-FeP nanorods were originated from abundant P vacancies and good distribution of FeP nanoparticles in conductive carbon network, which enhanced electrical conductivity, provided more active sites, shortened the diffusion distances of Li ions and relieved the volume variations. The strategy demonstrates a further direction to effectively improve the lithium storage performance of transition metal phosphides.