Investigating lithium intercalation and diffusion in Nb-doped TiO2 by first principles calculations

•Lithium intercalation and diffusion in Nb-doped TiO2 were investigated using density functional theory.•Three common polymorphs were considered: anatase, rutile, and TiO2(B).•Nb-doping enhances lithium intercalation in TiO2, but slightly increases the energy barrier for lithium diffusion.•The band gap narrows due to Nb-induced dopant states and the fermi level shifts towards the conduction band, improving material conductivity.•Nb-doped rutile shows significantly improved electronic properties compared to other studied polymorphs.