Abstract LiTi2O4 is metallic, has the cubic spinel structure and is known to react with one further lithium atom to form Li2Ti2O4. We find that the related spinel Li 4 3 Ti 5 3 O4, which is electrically insulating, also reacts reversibly with one lithium atom. Both Li/LiTi2O4 and Li/Li 4 3 Ti 5 3 O4 cells cycle reversibly with little capacity loss for over 100 cycles, but have subtle differences in their voltage profiles. We interpret the differences in cell behaviour using arguments based on the band structure of Li1+xTi2−xO4