Monolayer MBenes: prediction of anode materials for high-performance lithium/sodium ion batteries

The design and fabrication of new high-performance electrode materials are critical for driving the development of next-generation energy conversion and energy storage devices. Here, we report a series of orthogonal two-dimensional transition metal borides (MBenes) based on first-principles density functional theory, which can be obtained by mechanically stripping an MBene from a large MAB phase, including V₂B₂, Cr₂B₂, Mn₂B₂, Ti₂B₂, Zr₂B₂, and Nb₂B₂. The thermodynamic and kinetic stability of monolayer MBenes at room temperature was confirmed by AIMD simulations and phonon spectra. We investigated the potential of two-dimensional MBenes (V, Cr, Mn) as lithium/sodium ion anode electrode materials. Research shows that MBenes have inherent metallic properties, and their mechanical properties indicate that MBenes have high Young's modulus and anisotropy, low diffusion potential and low open-circuit voltage, with outstanding rate performance and good chemical stability in practical applications. In addition, functionalization tends to strongly reduce electrochemical performance and should be avoided as much as possible in experiments. These interesting findings fully demonstrate that the predicted monolayer MBenes are attractive anode materials for lithium/sodium ion batteries.