Tree gum can sustainably supercharge supercapacitor lifespan

A waste gum produced by trees found in India could be the key to unlocking a new generation of better-performing, more eco-friendly supercapacitors, researchers say.

Scientists from universities in Scotland, South Korea and India are behind the development, which harnesses the unique properties of the otherwise useless tree gum to prevent supercapacitors from degrading over tens of thousands of charging cycles.

The team’s finding could help reduce the environmental impact of supercapacitors, an energy storage technology which carry less overall power than conventional batteries but charge and discharge much more quickly.

Supercapacitors are currently used in a wide range of electronic devices, in power grids, and electric vehicles. However, their long-term performance can be affected by their use of acidic electrolytes, which can cause unwanted side reactions with their metal electrodes, reducing their ability to hold their full charge over time.

Replacing and disposing of supercapacitors at the end of their lives contributes to the growing global problem of electronic waste, which can have harmful impacts on the environment.

In a paper published in the journal Energy Storage Materials, the researchers demonstrate how they combined gum kondagogu, a polysaccharide produced by the bark of the Cochlospermum Gossypium tree, to sodium alginate to manufacture a spongelike biopolymer they called “KS.”

They found that adding KS to the acidic electrolyte of a conventional supercapacitor helped to create a protective layer over its carbon electrodes. The KS layer helped prevent physical degradation of the electrodes while still allowing the ion transport process which enables the supercapacitor to charge and discharge.

In lab tests, they showed that their improved electrolyte boosted the supercapacitor’s performance significantly, helping it maintain 93% of its full energy capacity after 30,000 cycles. Over the same span, the capacity of an otherwise identical supercapacitor tested by the team dropped to just 58%.

Dr. Jun Young Cheong, of the University of Glasgow’s James Watt School of Engineering, is one of the paper’s corresponding authors. He said, “Tree gums have a wide range of uses in industry, in applications like pharmaceuticals, food, or cosmetics.

“However, the gums we’ve used in this study don’t have many practical uses, and are actually a bit of a headache for the Indian government to dispose of. With this research, we’ve found a way of making something genuinely impactful from this gum, creating a biodegradable, recyclable biopolymer which enables remarkable performance and could extend the useful life of supercapacitors dramatically.

“In the lab, we’ve shown excellent performance over 30,000 cycles. If we were to run one cycle per day, the supercapacitor could theoretically last more than 80 years without losing significant performance, which could mean that supercapacitors could be used in devices for much longer without being replaced.”

The research builds on Dr. Cheong’s ongoing research into using biowaste in batteries, which has also demonstrated the effectiveness of using water-soluble gum binders in graphite anodes in lithium-ion batteries.

Researchers from Ajou University (Prof. Tae Gwang Yun), Chung-Ang University (Prof. Byungil Hwang) and Myongji University in South Korea contributed to the research and co-authored the paper, along with colleagues from Amrita University (Prof. Vinod V. T. Padil) in India.