Researchers at the University of Bristol have created high-performance sodium and potassium ion batteries using sustainably sourced cellulose. Scientists at the Bristol Composites Institute use what they call a novel controllable unidirectional ice-templating strategy capable of tailoring the electrochemical performances of next-generation post-lithium-ion batteries.
The results open up the market for low-cost, sustainable and vastly available alternatives that could one day be used to power electric vehicles.
The team’s groundbreaking achievements, developed in collaboration with Imperial College, are set out in the scientific journal Advanced Functional Materials.
The performance of the new ion batteries has been proven to outperform many other comparable systems and makes use of cellulose, which is a sustainably sourced material.
Corresponding author, Steve Eichhorn, Professor of Materials Science and Engineering at the University of Bristol, said: “We were astounded with the performance of these new batteries.
“There is great potential to develop these further and to produce larger-scaled devices with the technology.”
He added: “In light of these findings, we now hope to collaborate with industries to develop this strategy on an industrial scale and to explore whether this unique technology can be easily extended to a variety of other energy storage systems such as zinc, calcium, aluminium and magnesium-ion batteries, thus demonstrating its universal potential in next-generation energy storage systems.”
The study has been published at a time when the world is witnessing a rapidly increasing demand for sustainable, ethical and low-cost energy storage.
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“The main route is through electrolysis of sodium chloride solution (salt solution or seawater).
“There are various ways to extract potassium too, some recent ones are ‘green’ processes from feldspar – a common mineral.”
Mr Eichorn added: “It’s true that the UK has lithium, but its mining is not without environmental cost wherever the extraction takes place.”
Batteries have two electrodes and a separator, plus an electrolyte between them that carries the charge.
Use of lithium results in a number of problems, including the build-up of the metal inside the devices, which can lead to short circuits and overheating.
Alternatives to lithium, such as sodium and potassium batteries have not historically performed as well in terms of their rate performance and the ability to use them lots of times.
The inferior performance is due to the larger sizes of sodium and potassium ions, and their ability to move through the porous carbon electrodes in the batteries.
However, Jing Wang, lead author and a PhD student in the Bristol Composites Institute, believes he and his colleagues may have hit upon a solution.
He explained: “We proposed a novel controllable ice-templating strategy to fabricate low-cost cellulose nanocrystals/polyethylene oxide-derived carbon aerogels with hierarchically tailored and vertically-aligned channels as electrode materials, which can be utilised to well-tuning the rate capability and cycling stability of sodium- and potassium-ion batteries.
“Benefiting from the renewability of the precursor and scalability at relatively low cost in the environmentally benign synthesis process, this work could offer an appealing route to promote large-scale applications of sustainable electric vehicles and large-scale energy storage grids in the near future.”