Fabrication of FeP-based composite via N-doping into amorphous carbon and graphene-protecting strategy for lithium-ion batteries

Abstract

Conversion-type transition metal phosphating anode materials are favored by researchers because they have a very high theoretical capacity. It is still a great challenge to solve the two problems of large volume change and poor electronic conductivity during long-cycle cycling. In this work, we successfully explored an easy hydrothermal and carbonization method to wrap the capsule shaped FeP nanoparticles in a N-doping carbon layer (FeP@NC). At the same time, FeP@NC is anchored on the flake shaped rGO surface to form an interesting three dimensional (3D) structure FeP@NC@rGO (denoted as FPCG). The introduction of N-carbon and rGO improves the materials conductivity and high speed performance, and also overcomes the bulk collapse of the materials. As an anode for LIBs, the FPCG electrode materials displays a high reversible capacities of 927 ​mA ​h ​g−1 at 0.2C after 170 cycles, an excellent rate capacity of 486 ​mA ​h ​g−1 at 5 ​C, as well as an extraordinary durability (500 cycles, 863 mAh g−1 at 0.5C, 97.7% capacity retention). Pseudocapacitive behavior has a significant contribution to the performance of the above electrochemical performance. Using in-situ X-ray diffractometry (in-situ XRD), we revealed that the FPCG anode originated from its outstanding structure and composition advantages, and proved its iron phosphide conversion reaction mechanism further. In this work proposes a simple synthesis approach which can be used for construction and optimization of other electrodes and catalytic energy materials.