First-principles study on screening doped TiO2(B) as an anode material with high conductivity and low lithium transport resistance for lithium-ion batteries

As a promising anode material, TiO2(B) has attracted much attention in recent years due to its high power and capacity performances. First-principles calculations are performed here to reveal the electronic properties and the transport of lithium (Li) in the bulk TiO2(B) with and without atomic doping. It is found that a 4-fold coordinated O atom has the lowest formation energy and the smallest bandgap and is the atom that most easily forms an O-vacancy (Ov). In this work, a series of p-type (N, P, As), n-type (F, Cl, Br), and isoelectronic (S, Se, Te) dopants in TiO2(B) are studied. For n-type dopants, the substitution of the F atom has no significant effect on the electronic structure, which results in the lowest formation energy. This result demonstrates that the F atom can provide high intrinsic stability. Analysis of the insertion process of Li in doped TiO2(B) shows that N-doping is the most competitive choice because it not only introduces a lower bandgap of TiO2(B) but it also has the highest binding energy with Li. The advantage of N-doping is derived from the self-compensation effect. Also, three possible transport paths of Li in TiO2(B) were studied via the CI-NEB method. The results show that the energy barrier of all diffusion paths of F doping is lower than that of pure TiO2(B), where path 2 along the b-axis channel has the lowest energy (0.32 eV). This study is expected to shed some light on the electronic structures of TiO2(B) and the transport properties of Li in it.