10-time lithium rate improvement and 4-time photocatalytic performance enhancement have been achieved with TiO2 nanocrystals when coated with a thin layer of amorphous carbon. The enhanced performances can be attributed to lower lithium ion diffusion and electronic conduction resistance across the carbon layer into the TiO2 electrode material and better surface adsorption of the dye molecules and ions. Thus, the current study may provide us an alternative approach in improving the performances of TiO2 nanocrystals in both lithium ion battery and photocatalysis applications.