Aerosol-Jet-Printed CoFe2O4 Nanoparticle − Vertically Aligned Carbon Nanotube Composite for Microsupercapacitors

This work studied the design, fabrication, and characterization of a bimetallic CoFe2O4 nanoparticle (NP) − vertically aligned carbon nanotube (VACNT) composite for 3D microsupercapacitor (MSC) electrodes and devices. Aerosol jet printing (AJP) was used to deposit CoFe2O4 NPs onto planar interdigitated VACNT electrodes, and because of its high resolution (∼10 μm linewidth) and computer-aided design feature, it is capable of fabricating both symmetric and asymmetric CoFe2O4-VACNT 3D MSC devices. The study investigated varying the number of print passes (5, 10, and 15) and the device configuration (symmetric and asymmetric) to improve the electrochemical performance of printed CoFe2O4-VACNT 3D MSCs. Asymmetric CoFe2O4-VACNT MSCs with 10 print passes showed a high voltage window in an aqueous electrolyte (∼1.76 V) and increased area-specific capacitance by 13× at .23 mA cm–2 compared to the uncoated VACNT MSC device. It was the best performing device based on the parameters studied because of a combination of optimal composite morphology and device configuration resulting in an area-specific energy and power density increase of 43× and 15×, respectively (vs uncoated VACNT MSC). This study highlighted the benefits of AJP as a novel method for depositing a pseudocapacitive coating onto nanostructured 3D MSC electrodes.