Building a bridge over the valley of death: a practical development of textile supercapacitors

Abstract

This thesis presents a practical development of textile supercapacitors for e-textile applications. Textile supercapacitors are seen as a crucial enabling technology for future e-textiles as a power management component. A wealth of research has gone into developing these devices over the previous decade, however, this research has broadly focused on electrochemical performance alone, and has led to the development of devices which are unlikely to transition from the laboratory to the real-world. Underpinned by a design philosophy of sustainability and scalability, this work has developed the performance of an all carbon single-layer textile supercapacitor without the need for exotic electrode materials or challenging production methodologies. The device is later integrated within a first of a kind textile power module capable of powering future e-textile applications.

A simple spray deposition technique is used to produce single-layer all textile
supercapacitors. Three commercial activated carbons are evaluated as potential
electrode materials and the electrode ink formulation is optimised with a 9:1 ratio of active material to conductive additive. A device with a capacitance of 23.6 mF.cm-2, energy density of 2.1 µWh.cm-2 and power density of 0.11 mW.cm-2 is achieved, demonstrating the capability of basic materials and industry friendly production methods.

The electrolyte plays a pivotal role in the performance of the textile supercapacitor, both in terms of energy density as well as operational voltage. A series of electrolytes are evaluated, including an aqueous PVA electrolyte, edible electrolyte and organic polymer electrolyte. The aqueous electrolyte is shown to have severe degradation over a few days, making it impractical for real-world use. The edible electrolyte is shown to outperforms the aqueous electrolyte but still suffers from low voltage limits.

The novel organic electrolyte is shown to be much more stable and increased the
energy device of the carbon textile supercapacitor by 9x, achieving an energy density of 18.9 µWh.cm-2, capable of power real-world applications.

A textile power module designed for built environment or low mobility applications is presented, produced from the developed textile supercapacitor from the previous chapters and a flexible rectenna. The prototype system presented a first of a kind design, and achieved a literature leading end-to-end efficiency of 38%. This was further developed and achieved an end-to-end efficiency of 46% and capable of power
a Bluetooth Low Energy transceiver system for >100 s from a single charge.

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Identifiers

ORCID for Nicholas David George Hillier: orcid.org/0000-0002-3544-8329

ORCID for Stephen Beeby: orcid.org/0000-0002-0800-1759

ORCID for Andrew Cruden: orcid.org/0000-0003-3236-2535

ORCID for Sheng Yong: orcid.org/0000-0002-8588-5981

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