We have studied the effects of Sn substitutional doping in anatase using a screened exchange density functional. We observe almost no change in the electronic structure of anatase and only small changes in morphology due to Sn doping. Upon Li insertion at different concentrations, the systems are found to be indirect bandgap semiconductors with a Ti dominated peak at the edge of the valence region. As Li is inserted in the structure, there is a change in the morphology from tetragonal to orthorhombic. However, the tetragonal structure is recovered for the maximum Li intake corresponding to stoichiometry of Li1Sn1/16Ti15/16O2. Importantly, in contrast to pristine anatase, we find that Sn doping stabilizes the voltage profile of Li insertion at high Li concentrations which allows Li intake beyond what is possible in pristine anatase.