Beyond A Simple Composite of Metal Oxide/Graphene/Carbon Nanotubes: Controlling Nanostructured Electrodes at Macroscopic Scale

Abstract

The development of electronic textiles, which have many potential healthcare and consumer applications, is currently limited by a lack of energy storage that can be effectively incorporated into such devices while having sufficient energy density, power density, and durability to perform well. The overall goal of this work was to improve the energy density and potential for use in electronic textile applications of a nanostructured composite of few-walled carbon nanotubes, manganese oxide, and reduced graphene oxide. Two approaches towards improving the desired properties by controlling the macroscopic structure of the composite were pursued: one, to make fiber or wire-shaped electrodes via wet-spinning in aqueous chitosan solutions (10% acetic acid), and the other, to make composite films with controlled porous structures using nitrocellulose as a sacrificial filler material. Both approaches yielded the desired macroscopic structures. The composite fibers were non-conductive due to the insulating nature of manganese oxide and its positioning on the surface of the fibers. Composite fibers of few-walled carbon nanotubes and reduced graphene oxide made by the same method were found to have good volumetric capacity, rate capability, stability and flexibility. Nonintuitively, electrochemical performance of composite films declined with increasing porosity due to a decrease in conductivity, highlighting the importance of balancing the interplay between properties important to device performance when designing controlled structures of complex materials.