Facile fabrication of MoP nanodots embedded in porous carbon as excellent anode material for potassium-ion batteries

Abstract

Abstract Molybdenum phosphide (MoP), owing to its abundant reserve and high theoretical capacity, is regarded as a promising anode material for potassium-ion batteries. However, it still suffers from the problems of acute volume expansion and weak diffusion kinetics. This study reports a simple method to synthesize a composite of molybdenum phosphide and porous carbon (MoP@PC) through simple mixing and annealing treatment. In the MoP@PC, lots of MoP nanodots with an average diameter of about 4 nm uniformly embedded in the petal-like porous carbon. The MoP@PC shows reversible capacities of 330 mAh g−1 at 100 mA g−1 after 100 cycles, and ultra-long cycling stability with a capacity of 240 mAh g−1 after 1000 cycles at 1 A g−1 and 161 mAh g−1 after 1000 cycles at 5 A g−1. The structure of MoP@PC after charging-discharging cycles is also investigated by high resolution transmission electron microscope (HRTEM) and the result shows that MoP can still maintain the nanodot morphology without any agglomeration after 1000 cycles at 5 A g−1. The storage mechanism of potassium ions was studied as well, which reveals that MoP and potassium ion have a conversion reaction.