In the last section of the manuscript, the electrochemical properties of TiO2 without conductive agents were investigated. The TiO2 polymorph used in the work was anatase, not rutile, as stated in the paper. All discussion of the results applies to both polytypes indistinctively. Nonetheless, a more suitable citation for ref. [48] would be M. Wagemaker, W. J. H. Borghols and F. M. Mulder, J. Am. Chem. Soc. 2007, 129, 4323, which describes the lithiation of anatase, instead of rutile.