Discovery of hexagonal ternary phase Ti₂InB₂ and its evolution to layered boride TiB

M_n+1AX_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, Ti₂InB₂, a stable boron-based ternary phase in the Ti-In-B system, using a computational structure search strategy. This predicted Ti₂InB₂ 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 P6₃/mmc (No. 194), the symmetry group of conventional M_n+1AX_n phases. Moreover, a strategy for the synthesis of MXenes from M_n+1AX_n phases is applied, and a layered boride, TiB, is obtained by the removal of the indium layer through dealloying of the parent Ti₂InB₂ 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 Ti₃C₂.