Discovery of hexagonal ternary phase Ti2InB2 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 6 6 ¯ 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 .