Layer-stacking of chalcogenide-terminated MXenes Ti2CT2(T = O, S, Se, Te) and their applications in metal-ion batteries

Owning to limited supply of lithium for Li-ion batteries, the development of non-Li-ion batteries (such as Na+, K+ Mg2+, Ca2+, and Al3+ ion batteries) has attracted significant research interest. In this work, by means of the first-principles calculations, we systematically investigated the performance of chalcogenide-terminated MXenes Ti2CT2 (T = O, S, Se, and Te) as electrodes for Li-ion and non-Li-ion batteries, as well as the layer-stacking and electronic properties of Ti2CT2. We find that the stacking type of O and Te terminated Ti2C multilayers with AA stacking differs from that of S and Se terminated Ti2C multilayers with AB stacking. More importantly, Ti2CO2 monolayer can be potential anode material for Na- and K-ion batteries with high capacities and very low diffusion barriers (0.03-0.11 eV), while Ti2CS2 and Ti2CSe2 are promising anode materials with relatively low average open circuit voltages (OCVs) for Na-, K-, and Ca-ion batteries (0.4-0.87 V). Among these materials, Ti2CS2 exhibits the largest ion capacity of 616 mAh g(-1). These results of our work may inspire further studies of Ti2C-MXenes multilayers as electrodes for metal-ion batteries either experimentally or theoretically.