Ab Initio Study of Mg2+ and Ca2+ Intercalation in TiS3

In this study, the properties of TiS3 are investigated as a potential electrode material for electrochemical multivalent Ca- and Mg-ion batteries. Using density functional theory, we carry out calculations to thoroughly study this material. It is found that TiS3 is the most suitable material for cathodes of Ca-ion batteries. Intercalation of Ca2+ cations in TiS3-based cathode materials turned out to be energetically favorable, with an operating voltage of 1.98 V relative to Ca/Ca2+. This result is noteworthy because high-voltage electrodes for multivalent batteries are relatively rare. Diffusion coefficients of Mg2+ and Ca2+ amounted to 6.59 × 10–13 and 4.03 × 10–21 cm2 s–1, respectively. The diffusion coefficient can be further improved by lattice strain engineering and the use of two-dimensional materials. The maximum theoretical capacity values were 618 and 588 mAh/g for Mg0.5TiS3 and Ca0.5TiS3, respectively. The specific stored energy of Ca0.5TiS3 amounted to 1132 W h/kg, which exceeds that of LiCoO2 (1070 W h/kg), despite its lower electrochemical stability.