Zinc-lignin batteries : A storage solution for low-income countries?

Researchers at Linköping University in Sweden have developed an inexpensive, rechargeable battery which they believe could be a game-changer in poorer countries, where access to electricity is limited.

In areas where there is a reliance on renewables for energy supply, storage is crucial, for those times when the sun doesn’t shine and the wind doesn’t blow. 

The availability of a storage system to provide this energy buffer has been identified as the bottleneck to further implementation of renewable energy sources.

Rechargeable batteries are ideal to provide stored energy on demand, for a short time-scale but the research team set out to develop an alternative to lithium-ion batteries for a number of reasons. Not least because they are too expensive for the applications discussed here, not to mention comparatively unsafe and compromised in terms of their own carbon footprint.

Batteries manufactured using zinc are considered an ideal alternative for energy storage because zinc is widely available and is good at it. The trouble has always been making zinc-based batteries rechargeable.

When the zinc reacts with the water in the battery’s electrolyte solution it generates hydrogen gas, which causes dendritic growth of the zinc, which shorts the battery, rendering it useless.

To stabilise the zinc, the team used a substance called potassium polyacrylate based water-in-polymer salt electrolyte (WiPSE) which, when used in a battery containing zinc and lignin, made it very stable.

Zinc and lignin are two cost-effective and environmentally friendly materials and in terms of energy density (how much energy a battery contains in proportion to its weight), the battery is comparable to lead-acid batteries, without the toxicity of the lead.

The battery is sufficiently stable that it can be recharged over 8,000 cycles, while maintaining about 80% of its performance. Additionally, it can retain its charge for around a week, significantly longer than other zinc-based batteries that discharge in just a few hours.

Of course, the batteries which the team have developed in the lab are small, but they believe that they can scale them to the size of a car battery, thanks to the abundance of both lignin and zinc at low cost. Mass production would require the involvement of a commercial entity.

Reverant Crispin, professor of organic electronics at Linköping, said: ‘Solar panels have become relatively inexpensive, and many people in low-income countries have adopted them. However, near the equator, the sun sets at around 6 PM, leaving households and businesses without electricity. The hope is that this battery technology, even with lower performance than the expensive Li-ion batteries, will eventually offer a solution for these situations.

‘We can view it as our duty to help low-income countries avoid making the same mistakes we did. When they build their infrastructure, they need to start with green technology right away. If unsustainable technology is introduced, it will be used by billions of people, leading to a climate catastrophe.’

 Ziyauddin Khan, a researcher at the Laboratory of Organic Electronics at LiU. said: ‘While lithium-ion batteries are useful when handled correctly, they can be explosive, challenging to recycle, and problematic in terms of environmental and human rights issues when specific elements like cobalt are extracted. Therefore, our sustainable battery offers a promising alternative where energy density is not critical.

‘Both zinc and lignin are super cheap, and the battery is easily recyclable. And if you calculate the cost per usage cycle, it becomes an extremely cheap battery compared to lithium-ion batteries.’

The full research can be read here.

Photo: Thor Balkhed