Improved ion adsorption capacities and diffusion dynamics in surface anchored MoS₂Mo_4/3B₂ and MoS₂Mo_4/3B₂O₂ heterostructures as anodes for alkaline metal-ion batteries

First-principles calculations were performed to analyze the atomic structures and electrochemical energy storage properties of novel MoS2 perpendicular to boridene heterostructures by anchoring MoS2 nanoflakes on Mo4/3B2 and Mo4/3B2O2 monolayers. Both thermodynamic and thermal stabilities of each heterostructure were thoroughly evaluated from the obtained binding energies and through first-principles molecular dynamics simulations at room temperature, confirming the high formability of the heterostructures. The electrochemical properties of MoS2 perpendicular to Mo4/3B2 and MoS2 perpendicular to Mo4/3B2O2 heterostructures were investigated for their potential use as anodes for alkaline metal ion batteries (Li+, Na+ and K+). It was revealed that Li+ and Na+ can form multiple stable full adsorption layers on both heterostructures, while K+ forms only a single full adsorption layer. The presence of a negative electron cloud (NEC) contributes to the stabilization of a multi-layer adsorption mechanism. For all investigated alkaline metal ions, the predicted ion diffusion dynamics are relatively sluggish for the adsorbates in the first full adsorption layer on MoS2 perpendicular to boridene heterostructures due the relatively large migration energies (>0.50 eV), compared to those of second or third full adsorption layers (<0.30 eV). MoS2 perpendicular to Mo4/3B2O2 exhibited higher onset and mean open circuit voltages as anodes for alkaline metal-ion batteries than MoS2 perpendicular to Mo4/3B2 hybrids because of enhanced interactions between the adsorbate and the Mo4/3B2O2 monolayer with the presence of O-terminations. Tailoring the size and horizontal spacing between two neighboring MoS2 nano-flakes in heterostructures led to high theoretical capacities for LIBs (531 mA h g(-1)), SIBs (300 mA h g(-1)) and PIBs (131 mA h g(-1)) in the current study.