Green fields may one day grow key parts of "green" batteries.
Green fields may one day grow key parts of "green" batteries.

Imagine if farmers could grow batteries in their fields. Researchers are taking steps towards at least partially making that green dream a reality by using plant materials to make key components of energy storage devices. Pen-Chi Chiang and colleagues at the National Taiwan University review developments in this adventurous ambition in the journal Materials Today Energy.

“We consider the state-of-the-art challenges and issues for using plant-derived biomass materials for various energy storage applications, such as batteries and supercapacitors,” says Chiang.

Energy storage is an essential requirement for modern life. Without it, we couldn't have cellphones, laptops, or electric vehicles. From consumer electronics to transportation, electrical energy must be stored and be available at the flick of a switch. Current systems, such as the lithium-ion batteries common in many devices, are made from limited resources, and bring environmental problems associated with their disposal.

Chiang points out that a sustainable future will increasingly depend on replacing existing technologies with those using renewable materials that can readily be recycled without damaging the environment.

One of the most promising approaches towards sustainable energy storage devices is to convert plant biomass into a material called “porous carbon”. This is a form of carbon that can be fabricated into three-dimensional ordered “nanostructures” with a variety of useful electrochemical properties.

Small quantities of other atoms or chemical groups can be strategically incorporated into porous carbon nanostructures to create composites, which have the potential to become electrodes or conducting materials for rechargeable batteries or capacitors. Pore size and structure can be controlled in a variety of simple ways, such as varying the temperature at which the material is produced. Chiang and his co-authors review research that is developing these possibilities using plant materials, such as trees, cotton, bamboo, beans, seeds, tea leaves, fruit peel, and fungi, to name just a few.

This is early-stage research, which has a long way to go before significant amounts of plant-based materials will appear in commercialized devices. One key challenge is to convert the promise currently being shown in the laboratory into robust technologies. “Overcoming the challenges will require cross-disciplinary collaboration involving materials science, chemical engineering, mechanical engineering, and environmental management,” Chiang emphasizes.

Progress will likely be in little steps, with individual unsustainable parts of existing technologies being replaced, bit by bit, with viable and sustainable plant-based alternatives. “Here in National Taiwan University we have expert researchers working on the design and synthesis of many innovative materials that could be part of these green technologies leading us toward a sustainable future,” says Chiang.

Chiang, P-C. et al.: "A cross-disciplinary overview of naturally derived materials for electrochemical energy storage," Materials Today Energy (2018)