Lignin-based cathodes could boost prospects for wind and solar power.
Design work is progressing on a revolutionary new battery cathode which could eventually lead to batteries produced from a sustainable by-product of growing plants. The devices are likely to be cheaper than existing batteries because they will no longer require the use of expensive and non-renewable precious metals such as cobalt, nickel, manganese and lithium.
The critical compound in the new battery cathodes is lignin, which is a natural substance found in plants. It is already stripped out of wood as a waste product during the process of making paper, where it is taken off in a by-product called brown liquor. This has long been used as a combustible fuel by paper mills, but now it might help make energy storage increasingly affordable – a vital step in boosting the potential of intermittent sources of power like wind or solar.
The development work on converting lignin into a cathode – the section of the battery where the current flows out – is being carried out by two European researchers. They are Olle Inganäs from Linköping University in Sweden and Grzegorz Milczarek from Poznan University of Technology in Poland.
So, how come a plant-based material can perform a function previously associated with a metal? Essentially, the lignin derivatives – which have insulating properties – can be combined with a conductive polymer called a polypyrole into a composite which can hold an electric charge.
Professor Inganäs said that design work was progressing, but he did not want to speculate at this stage on precise timescales and potential future usage of the technology. “It’s too early to talk about these things”, he said. “It has great potential but it needs further extensive work and study. With this kind of work, there is often a 15- to 20-year period between discovery and application, though it does not need to be that long. Much of it will be about marketing and beyond science.”
One of the main advantages of using lignin lies in its ready availability. The metal oxides which are used in traditional lithium-ion batteries can be harder to get hold of, and at least one, cobalt, is relatively rare. – Andrew Collier