Heterogeneous-Structured Molybdenum Diboride as a Novel and Promising Anode for Lithium-Ion Batteries

With the development of electric vehicles, exploiting anode materials with high capacity and fast charging capability is an urgent requirement for lithium-ion batteries (LIBs). Borophene, with the merits of high capacity, high electronic conductivity and fast diffusion kinetics, holds great potential as anode for LIBs. However, it is difficult to fabricate for the intrinsic electron-deficiency of boron atom. Herein, heterogeneous-structured MoB₂ (h-MoB₂) with amorphous shell and crystalline core, is prepared by solid phase molten salt method. As demonstrated, crystalline core can encapsulate the honeycomb borophene within two adjacent Mo atoms, and amorphous shell can accommodate more lithium ions to strengthen the lithium storage capacity and diffusion kinetics. According to theoretical calculations, the lithium adsorption energy in MoB₂ is about -2.7 eV, and the lithium diffusion energy barrier in MoB₂ is calculated to be 0.199 eV, guaranteeing the enhanced adsorption capability and fast diffusion kinetic behavior of Li⁺ ions. As a result, h-MoB₂ anode presents high capacity of 798 mAh g^-1 at 0.1 A g^-1, excellent rate performance of 183 mAh g^-1 at 5 A g^-1 and long-term cyclic stability for 1200 cycles. This work may inspire ideas for the fabrication of borophene analogs and two-dimensional metal borides.