Effect of Meso- and Micro-Porosity in Carbon Electrodes on Atomic Layer Deposition of Pseudocapacitive V₂O₅ for High Performance Supercapacitors

Abstract

Atomic layer deposition (ALD) of vanadium oxide is a viable means to add pseudocapacitive layers to porous carbon electrodes. Two commercial activated carbon materials with different surface areas and pore structures were acid treated and coated by V2O5 ALD using vanadium triisopropoxide and water at 150 °C. The V2O5 ALD process was characterized at various temperatures to confirm saturated ALD growth conditions. Capacitance and electrochemical impedance analysis of subsequently constructed electrochemical capacitors (ECs) showed improved charge storage for the ALD coated electrodes, but the extent of improvement depended on initial pore structure. The ALD of V2O5 onto mesoporous carbon increased the capacitance by up to 46% after 75 ALD cycles and obtained a maximum pseudocapacitance of 540 F/g­(V2O5) after 25 ALD cycles, while maintaining low electrical resistance, high columbic efficiency, and a high cycle life. However, adding V2O5 ALD to microporous carbons with pore diameters of <11 Å showed far less improvement, likely due to “blocking off” of the micropores and reducing the accessible surface area. Results show that ALD is a viable means to construct high-performance supercapacitors from activated carbon which is the basis for commercial products, and a clear understanding of carbon electrode pore structure, layer conformality, and layer thickness are necessary to fully optimize performance.

Synthesis of hierarchically porous MnO2/rice husks derived carbon composite as high-performance electrode material for supercapacitors

“…An effective strategy to increase cell voltage over 1.0 V is to construct asymmetric supercapacitor, which generally utilizes pseudo-capacitive material as positive electrode [12]. As a consequence, electrochemical capacitive properties of various transition metal oxides, e.g., RuO 2 , Co 3 O 4 , NiO, V 2 O 5 and MnO 2 , have been widely studied in the last decades [13][14][15][16][17][18]. Except for poor electric conductivity (about 10 À5 S cm À1 ), manganese dioxide has attracted extensive attention due to high theoretical capacitance, low cost and environmental compatibility [19][20][21][22].…”

Enhanced Electrochemical Energy Storage by Nanoscopic Decoration of Endohedral and Exohedral Carbon with Vanadium Oxide via Atomic Layer Deposition

“…The authors explained this behavior with the limited access of the electrolyte ions to the bulk of the coating and the drop in electrical conductivity with increasing metal oxide content. 4 Our work has been sparked by the pioneering work, among others, from the Yushin Group 41 regarding the highly promising enhancement of electrochemical energy storage capacity by ALD decoration on carbon nanotubes, as well as by the most recent work of Daubert et al 47 , employing ALD on nanoporous carbons. Here, we present for the first time a comprehensive study on the impact of endohedral (AC) and exohedral (OLC) surface morphology on the ALD growth mechanism and the resulting electrochemical performance.…”

Recent Advances in Nanostructured Vanadium Oxides and Composites for Energy Conversion

“…[103,182] Additionally, the capacitance of electrodes is also related to the pore size of activated carbon support, whereas high-porosity with small pore size is optimized. [183] Composites of carbon nanotubes (CNTs) and V 2 O 5 were believed to produce interconnected networks with enhanced capacitive performance because of the shorten ion transfer distance and improved accessibility to electrolytes. CNTs/V 2 O 5 composites were studied to have two network structures, one is the stacked or intertwined fiber composites of V 2 O 5 nanowires and CNTs, and the other is the networks of CNTs@V 2 O 5 core-shell structures.…”