Influence of heterovalent substitution in the titanium sublattice on the electrochemical intercalation of lithium in M$_y$Ti$_{1-y}$Se$_2$ (M = Cr, V)

The influence of heterovalent substitutions Ti–V and Ti–Cr on the electrochemical intercalation of lithium into titanium diselenide has been investigated. It has been found that both types of doping insignificantly decrease the electromotive force (emf) with respect to metallic lithium. The substitution of vanadium for titanium provides a significant increase in the intercalation capacity of the material. The effect has been explained by the decrease in the solubility of lithium, which prevents the formation of a blocking phase with an extremely high lithium concentration (three atoms per formula unit). The substitution of chromium does not lead to a similar effect, because the decrease in the solubility of lithium is accompanied by an increase in the concentration of superstoichiometric titanium that occupies the lattice sites accessible to the diffusion of lithium in TiSe$_2$.