Capping Black Phosphorene by h-BN Enhances Performances in Anodes for Li and Na Ion Batteries

Black phosphorus (BP), despite possessing a favorable direct band gap, suffers from structural instability at ambient conditions that limits its utility for lithium ion batteries (LIB). In this Letter, we have proposed h-BN as an effective capping agent for black-phosphorene (Pn) for application as an anode material in both LIBs and sodium ion batteries (SIBs). The binding energy of Li/Na in the h-BN/black-Pn heterostructure is greatly enhanced (2.81 eV/2.55 eV) vis-a-vis pristine Pn (1.80 eV/1.59 eV) along with reduction in the barrier for movement of Li/Na within the layers. Significantly, lithiation/sodiation of these heterostructures does not alter the packing patterns due to insignificant volume changes (similar to 1.5-2.0%). The theoretical specific capacities for h-BN/black-Pn is 607 and 445 mA h g(-1) for LIB and SIB, respectively, which are larger than those for existing commercial anode materials. Clearly, the high capacity, low open-circuit voltage, small volume change, and high mobility of Li/Na within the layers make h-BN-capped black-Pn an excellent anode material in LIBs/SIBs. The heterostructure exhibits metal electronic phase transition upon lithiation/sodiation. an interesting semiconductor -> metal electronic phase transition upon lithiation/sodiation.