Novel Flexible Materials for Sustainable Energy Storage

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The continued growth in world energy demand coupled with the increasingly pressing need to address climate change is rapidly driving a transition to renewable and sustainable energy sources. Renewable energy generation can often be intermittent and does not always align well with fluctuations in demand (for example, solar electricity generation can only occur during daylight, whereas peak energy demand may be in the evening) and there is a need for portable energy storage in applications as diverse as vehicles and personal electronics. Existing battery technologies have a limited lifetime, are difficult to recycle, and are produced from raw materials often mined unsustainably and with issues over the geopolitical location. Hence, there is a profound need for developing electrical energy storage with a long cycle life produced from sustainable materials by environmentally acceptable processes. The focus of this research project is to develop a highly performance-promising class of energy storage devices, known as supercapacitors for 'green' energy storage. Successful development of such devices can have a major impact on the rapid adoption of renewable energy and sustainable transport, ameliorating anthropogenic global climate change.Like batteries, supercapacitors are devices that store energy electrochemically. However, unlike the former, electrical charge is stored at the surface of the materials making up the electrodes within the device, rather than in the bulk. This has the twin advantages of allowing rapid charging/discharging and substantially reducing the rate at which their storage capacity degrades. However, they have a significant disadvantage in the amount of electrical energy which can be stored. Moreover, neither traditional battery nor supercapacitor materials have mechanical properties which enable them to be readily incorporated into durable wearable and flexible devices.To address these issues this project aims to develop novel materials and structures, particularly electrodes, which will enable the production of flexible supercapacitors with improved charge storage capacity produced from Earth-abundant and sustainably obtained materials through processes with limited environmental impact.Free-standing flexible composite electrodes will be created using a 'backbone' of carbon cloth onto which will be grown novel 'pseudocapacitive' materials. These materials will be chosen on the basis of an evaluation of their likelihood to combine high charge storage capacity (due to similarities with battery chemistry) with high cycle life and power output. Wet chemical techniques and hydrothermal growth will initially be to fabricate such electrodes and routes to sustainable production will be developed. Thorough characterization of their physical structure and chemical composition will be undertaken to understand appropriate structure-function relationships and optimize both materials and processing. The resulting electrodes will be assembled into flexible energy storage devices which will be evaluated for their electrochemical performance.