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

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-1at100 mA g-1after 100 cycles,and ultra-long cycling stability with a capacity of 240 mAh g-1after 1000 cycles at 1 A g-1and 161 mAh g-1after 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.