TiSe2 cathode for beyond Li-ion batteries

Multivalent-ion batteries (MVIBs) provide economical and energy-dense alternatives to Li-ion batteries. In the academic pursuit to finding high-performance beyond Li-ion batteries, identifying a suitable cathode is a primary issue. More specifically, a cathode that supports high energy density, competitive charge/discharge rates, diffusion kinetics, and cyclability is desireable. In this regard, we computationally investigate layered TiSe2 as a cathode for beyond Li-ion batteries. We find voltages as high as 2.0, 2.0, 1.1, and 1.8 V for Li, Na, Mg, and Ca respectively. We compute voltage profiles, diffusion energy barriers, and formation energies, as well as consider the impact of swelling and electronic properties. While we consider several intercalants, we are especially interested in Ca, which we find to experience an energy barrier of approximately 0.4 eV, similar to the energy barrier experienced by Li, and lower than that of Mg. While Mg is the popular choice for multivalent-ion battery materials, we find that TiSe2 is able to accept more Ca per formula unit than Mg, and exhibits higher voltages than Mg, while experiencing improved diffusion kinetics. We advocate for the exploitation of TiSe2 layered cathodes for beyond Li-ion batteries, and especially for Ca-ion batteries.