TiO₂ coated Si nanowire electrodes for electrochemical double layer capacitors in room temperature ionic liquid

Three TiO₂ deposition processes are used to coat the surface of Si nanowire array electrodes for electrochemical double layer capacitors in room temperature ionic liquid [Bmim][NTF₂]. The fabrication processes are based on wet chemistry only and temperature treatments are kept below 450 °C. Successful TiO₂ coatings are found to be those that are carried out at low pressure and with low TiO₂ coverage to avoid nanowires breakage. The best TiO₂ coated Si nanowire array electrode in [Bmim][NTF₂] showed energy densities of 0.9 Wh•kg⁻¹ and power densities of 2.2 kW•kg⁻¹ with a nanowire length of ~10 µm.