Comparative studies of hexagonal boron phosphide/V2CS2 heterostructure and homogeneous bilayers as metal-ion battery anodes

Heterostructures can not only maintain/avoid the desired characteristics/defects of their monolayers, but also have synergistic effects due to the contribution of an internal electric field from the heterostructure interlayer. Hexagonal boron phosphide (h-BP) and V2CS2 were constructed into heterostructure (h-BP/V2CS2) and homogeneous bilayers (Dh-BP and DV2CS2), which were studied comparatively for their storage performances as anodes for metal (Li/Na/Mg/Ca)-ion batteries (LIBs/NIBs/MIBs/CIBs) using first-principles. The h-BP/V2CS2 can adsorb five layers of Mg atoms while Dh-BP cannot adsorb any Mg atoms; heterostructures with a maximum adsorption concentration are stable at room temperature, while Dh-BP structures are unstable in the same cases, which make Dh-BP unsuitable as LIB/NIB/MIB/CIB anodes. h-BP/V2CS2 completely exceeds DV2CS2 in capacity, average OCV or interlayer barrier for LIBs/NIBs/MIBs/CIBs owing to its stronger internal electric field. In particular, for MIBs/NIBs, the capacity of heterostructure is 1219/732 mA h g-1, which is much higher than the 753/226 mA h g-1 of DV2CS2; the average OCV of heterostructure is 0.07/0.35 V, as low as half of that of DV2CS2. The excellent storage performance of the heterostructure in NIBs/MIBs makes it very worthy of attention due to the urgent need for NIBs/MIBs with high energy density.