Researchers Invent First Soft, Bio-Based Energy Storage Solution

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Last Updated on: 12th April 2025, 09:14 pm

The bioeconomy of the future is beginning to branch off in all different directions, and energy storage is one of them. In a particularly interesting development, a research team at Linköping University has broken the longstanding connection between battery capacity and bulk, resulting in a first-of-its-kind soft, stretchy, 3D-printable, bio-based energy storage platform.

The Next Generation Of Energy Storage Is Inevitable

The world of the 21st century runs on portable gadgets thirsty for energy. “It is estimated that more than a trillion gadgets will be connected to the Internet in ten years’ time,” explains LiU.

“In addition to traditional technology such as mobile phones, smartwatches and computers this could involve wearable medical devices such as insulin pumps, pacemakers, hearing aids and various health monitoring sensors, and in the long term also soft robotics, e-textiles and connected nerve implants,” they add.

Not to pile on, but they left out the potential for futuristic energy storage applications in sports and entertainment among areas, the point being that the rigid batteries of today are not up to the tasks envisioned by the gadget-developing innovators of the future.

As noted by LiU researcher Aiman Rahmanudin, the rigid energy storage technology of today takes up quite a bit of space in electronic gear. “But with a soft and conformable battery, there are no design limitations. It can be integrated into electronics in a completely different way and adapted to the user,” Rahmanudin explains.

The Biobased Energy Storage Solution

The LiU team had its work cut out for it. The obstacles standing between soft, conformable batteries and commercial use are many, one being the traditional hookup between battery capacity and rigid materials. In conventional battery formulas, adding more active materials to the mix means that thicker, more rigid electrodes are needed.

Deferring solid electrodes in favor of a fluid is one way to break through the barrier, but that means finding the right fluid. The liquid metal gallium is an option, but it tends to solidify during charging cycles. Other fluid formulas rely on rare metals, opening up whole new cans of environmental worms.

The LiU solution involves a type of conductive plastics called conjugated polymers, along with lignin, which forms the tough cell walls in plants. Lignin is a byproduct of the papermaking industry, which offers the environmental twofer of using a biobased material while repurposing industrial waste.

“By repurposing a byproduct like lignin into a high value commodity such as a battery material we contribute to a more circular model. So, it’s a sustainable alternative,” emphasizes postdoctoral fellow Mohsen Mohammadi, who is also a lead author of the LiU study.

The Conjugated Polymer Connection

If you’re wondering what makes conjugated polymers so special, that’s a good question. “CPs exhibit a wide variety of fascinating electrical and optical properties which qualify them as active components of devices,” a research team based in Germany noted back in 2022.

“Nowadays, the need for innovative energy technologies and sustainable materials and processes as well as the emerging new opportunities of quantum technologies, are adding further momentum to CP research,” they added.

The LiU team, for one, did not let the conjugated polymer grass grow under their feet. “For the fluids, we used a model redox-active conjugated polymer system that was previously reported as solid-state electrodes,” they reported in their study, published in the journal Science Advances under the title, “Make it flow from solid to liquid: Redox-active electrofluids for intrinsically stretchable batteries.”

The cathode was fabricated from a modified form of lignin, and the anode deployed the conjugated polymer PACA [short for poly(1-amino-5-chloroanthraquinone)]. “Both active materials were twined with a conducting polymer poly(3,4-ethylenedioxythiophene (PEDOT) via in situ oxidative polymerization in the presence of the respective redox-active polymers to facilitate electrical transport within the particles,” the researchers elaborated.

They reported promising results for their energy storage application. Testing the concept on a battery of 0.9 volts, they cycled through more than 500 recharges and discharges without loss of performance. “It can also be stretched to double the length and still work just as well,” they noted.

Getting above 0.9 volts is the next-level challenge, especially considering the research team’s focus on sustainable materials. Part of the plan is to experiment with two abundant metals, zinc and manganese.

More & Better Biobased Energy Storage

If you’re waiting for the flexible battery of the future to power your next EV, you may have to wait a while. However, more conventional EV batteries that incorporate biobased materials are not too far off in the future. Aside from deploying various forms of agricultural waste such as apple peels and rice hulls, battery innovators have also been exploring chicken fat and other animal products.

Another variation on the plant-based energy storage theme is the field of phytomining, in which the commonly used battery material nickel can be harvested from plants. The trick is to develop a hyperaccumulator, meaning a plant capable of absorbing a significant amount of metal from the soil.

Scientists at the University of Massachusetts at Amherst are among those working out the kinks. UMass professor Om Parkash Dhankher notes that plant-based soil remediation is one way to make use of hyperaccumulators. The next step is to make use of the metals they take up.

The UMass team has settled on the weedy plant Camelina sativa, a fast-growing member of the mustard family. Camelina, which is also known as an oilseed crop, happens to be particularly good at taking up nickel from the soil while also contributing to improved soil fertility.

The plan is to re-boot Camelina with genes from the hyperaccumulator Odontarrhena (also Alyssum murale). Up to 3% of its biomass consists of nickel, but it is not a candidate for phytomining on its own. The slow-growing, finicky plant is classified as an invasive species in the US.

Aside from yielding nickel for energy storage applications and other purposes, fields of Camelina could be deployed to restore barren, nickel-rich soil to health while growing oilseeds for biofuel, too.

“We believe that there is currently enough nickel in the barren soil in the U.S. to supply us for 50 years of phytomining,” explains Dhankher, adding that could account for 20–30% of projected nickel demand over that period.

Photo (cropped): A first-of-its-kind stretchable battery is among the latest developments in the biobased energy storage field (by Thor Balkhed, courtesy of LiU via Eurekalert).