The cheaper, more sustainable and energy-dense electrode material could pave the way for wider market penetration of this high-power, quick charging electric vehicle technology.
In the study, published in Advanced Science, teams at Imperial College London and used lignin - a bio-based by-product of the paper industry - to create free-standing electrodes with enhanced energy storage capacity.
UK supercapacitor results suggest challenge to battery technologies
The researchers believe this could be a game-changer for existing supercapacitor technology and emphasise the importance of reducing the production cost of carbon-based electrodes and the reliance on critical materials if free-standing supercapacitors are to play a major role in decarbonising transport alongside batteries and fuel cells.
With lignin in place of graphene-based carbon, the team produced a freestanding structure which is said to be lighter and smaller than current models without compromising energy storage capacity. This makes them ideal for use in short-distance electric vehicles like buses, taxis and trams where they have the capacity to charge in the time it takes for passengers to exit and enter a vehicle.
In a statement, co-corresponding author Dr Maria Crespo Ribadeneyra from the Department of Chemical Engineering at Imperial said: “Supercapacitors are an ideal candidate for electric transportation within urban centres, where pollution is an increasingly pressing concern. However, they are often overlooked because of the high cost of production.
“Our research is based on a low-cost and sustainable bio-based material that can store more energy per unit volume than many other expensive alternatives. This is particularly important in the automotive sector, where optimisation of the space and the costs of the components is crucial.”
Co-corresponding author Professor Magda Titirici from the Department of Chemical Engineering at Imperial added: “Creating sustainable multifunctional materials from waste biomass streams such as lignin…eliminate our dependence on critical materials like lithium.
“The idea of pressing several free-standing carbon papers together to store more charge in a small volume is innovative and holds potential for future structural development. Imagine that instead of the electrodes being supported in a phone case or on a car roof, they are the case or roof.”
The technique developed by the team used electrospun lignin nanofibre mats which they compressed together into a dense structure. This enabled them to tailor the internal microstructure of the electrodes by reducing the amount of micrometre-sized pores which do not contribute to energy storage, while retaining the porosity of the individual fibres that do store electric charge.
The research team are now working on ensuring this technology can be made commercially viable. To this end they are developing a new supercapacitor with a non-corrosive and more cost-effective electrolyte that could be implementable in commercial devices.
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