Discovery of hexagonal ternary phase Ti(2)InB(2) and its evolution to layered boride TiB

M(n+1)AX(n) phases are a large family of compounds that have been limited, so far, to carbides and nitrides. Here we report the prediction of a compound, Ti(2)InB(2), a stable boron-based ternary phase in the Ti-In-B system, using a computational structure search strategy. This predicted Ti(2)InB(2) compound is successfully synthesized using a solid-state reaction route and its space group is confirmed as P[Formula: see text] m2 (No. 187), which is in fact a hexagonal subgroup of P6(3)/mmc (No. 194), the symmetry group of conventional M(n+1)AX(n) phases. Moreover, a strategy for the synthesis of MXenes from M(n+1)AX(n) phases is applied, and a layered boride, TiB, is obtained by the removal of the indium layer through dealloying of the parent Ti(2)InB(2) at high temperature under a high vacuum. We theoretically demonstrate that the TiB single layer exhibits superior potential as an anode material for Li/Na ion batteries than conventional carbide MXenes such as Ti(3)C(2).