This communication elucidates the charge storage mechanism of a TiO2 electrode in 1 mol dm− 3 AlCl3 for use in aqueous-ion batteries. Cyclic voltammetry studies suggest a surface contribution to charge storage and that cycle life can be improved by limiting the potential ≥ − 1.0 V vs SCE. In order to enhance this surface contribution, a simple vacuum impregnation technique was employed to improve electrode-electrolyte contact. This resulted in a significant improvement in the high rate performance of TiO2, where a capacity of 15 mA h g− 1 was maintained at the very high specific current of 40 A g− 1, a decrease of only 25% from when the electrode was cycled at 1 A g− 1. The vacuum impregnation process was also applied to copper-hexacyanoferrate, envisaged as a possible positive electrode, again resulting in significant improvements to high-rate performance. This demonstrates the potential for using this simple technique for improving electrode performance in other aqueous electrolyte battery systems.