2162-8769/2015/4(2)/M1/5/$31.00 © The Electrochemical Society Atomic Layer Deposition of Titanium Oxide for Pseudocapacitive Functionalization of Vertically-Aligned Carbon Nanotube Supercapacitor Electrodes

Using atomic layer deposition, vertically-aligned multi-walled carbon nanotube (MWCNT) supercapacitors were coated with conformal and uniform layers of titanium oxide to introduce pseudocapacitive charge storage properties to the electrodes. The results suggest that the addition of a controlled thickness of titania to the MWCNT structure improves the performance of the capacitors, with an increase in specific capacitance (more than 300%) as compared to the control supercapacitors, with values up to 73 F/g normalized to electrode mass (MWCNT and titania) and 1,364 F/g normalized to titania mass. Furthermore, the series resistance of the control supercapacitors (1.21 ) did not significantly increase with the addition of titania, until 300 atomic layer deposition cycles were performed. Improvements of the specific power and energy were also observed, with the maximum specific power and energy seen being 24.8 ± 4.8 W/g and 14.0 ± 4.1 Ws/g respectively. © 2014 The Electrochemical Society. [DOI: 10.1149/2.0141502jss] All rights reserved. Manuscript submitted June 2, 2014; revised manuscript received November 24, 2014. Published December 4, 2014. The 21st century has seen a rise in the development of environ-mentally preferable alternative energy sources such as wind, solar, and geothermal power. Despite this trend, the storage of the produced en-ergy still relies largely on batteries, which incorporate relatively harm-ful materials (lead-acid, lithium and others) with low power densit