Molybdenum Phosphide Nanostructures Connected to Ti3C2Tx via P−O Bond for Rapid Lithium-Ion Storage

Two-dimensional transition metal carbide/nitride MXenes have become a hot topic in the field of lithium-ion energy storage due to their unique surface chemistry and excellent electronic conductivity. However, electrodes made of multilayer MXenes suffer from low capacity, poor cycling performance, and slow lithiation kinetics. In this paper, the MoP2@Ti3C2Tx composite was prepared by adsorbing Mo cations on the surface of Ti3C2Tx followed by phosphatization. The uniformly distributed MoP2 nanostructure effectively increases the layer spacing, enlarges the specific surface area, and improves the structural stability of the material. At the same time, MoP2 and Ti3C2Tx are connected by a P−O bond, which accelerates the diffusion and migration of lithium ions and the charge transfer, and the strong covalent Ti−O−P bond can cause rapid charge transfer and stabilize the structure of the material. The electrochemical activity of MoP2 nanostructures also provides more active sites for lithium ions. The presence of the lamellar structure of Ti3C2Tx also inhibits to some extent the expansion of the transition metal phosphide volume with the cycling process, thus realizing more excellent lithium storage capacity. 1/2 MoP2@Ti3C2Tx material has a high reversible capacity of 165.7 mAh g−1 (172% improvement over the original material) at a current density of 3000 mA g−1. The assembled 1/2 MoP2@Ti3C2Tx//AC Li-ion hybrid capacitor LIC has 85.5% capacity retention after cycling at a current density of 1500 mA g−1. The ability of the assembled full battery to illuminate light-emitting diode (LED) light bulbs further confirms that the electrochemical reliability of the device meets the requirements of real-world applications. The results demonstrate that the strategy of constructing in situ-grown MoP2 nanostructures can effectively improve MXene high-energy-density applications in lithium-ion energy storage.