Scientists demonstrate a shape-shifting fluid battery
Researchers at Linköping University have developed a soft and flexible battery based on fluid electrodes. This allows the battery to take any shape and be integrated into future technology in a completely new way.
Fluid battery technology is well-suited for miniature medical devices such as insulin pumps, pacemakers, hearing aids, and various health monitoring sensors. It is also appropriate for soft robotics, e-textiles, and connected nerve implants.
“The texture is a bit like toothpaste. The material can, for instance, be used in a 3D printer to shape the battery as you please. This opens up a new type of technology,” says Aiman Rahmanudin, assistant professor at Linköping University.
“Batteries are the largest component of all electronics. Today, they are solid and quite bulky. But with a soft and conformable battery, there are no design limitations. It can be integrated into electronics completely differently and adapted to the user,” says Aiman Rahmanudin.
Alongside colleagues at the Laboratory of Organic Electronics (LOE), Aiman has developed a battery that is soft and malleable by transforming the electrodes from a solid to a liquid state.
Previous attempts to manufacture soft and stretchable batteries have been based on different mechanical functions, such as rubbery composite materials that can be stretched out or connections that slide on each other. However, this does not deal with the core of the problem — a large battery has higher capacity, but having more active materials means thicker electrodes and, thus, higher rigidity.
“Here, we’ve solved that problem, and we’re the first to show that capacity is independent of rigidity,” says Aiman Rahmanudin.
Fluid electrodes have been tested in the past but with limited success. At that time, liquid metals such as gallium were used. However, these materials can only function as an anode and risk solidifying during charging and discharging, thereby losing their fluid nature. Additionally, many of the stretchable batteries previously developed have utilised rare materials that significantly impact the environment when mined and processed.
Instead, the researchers developed their soft battery using conductive plastics (conjugated polymers) and lignin, a byproduct of paper production. This battery can be recharged and discharged over 500 times while maintaining its performance. It can also be stretched to twice its original length and still function effectively.
“Since the materials in the battery are conjugated polymers and lignin, the raw materials are abundant. 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,” says Mohsen Mohammadi, a postdoctoral fellow at LOE and one of the lead authors behind the article published in Science Advances.
The next step is to try to increase the electrical voltage in the battery. According to Aiman Rahmanudin, they need to overcome some limitations currently.
“The battery isn’t perfect. We have shown that the concept works, but the performance needs to be improved. The voltage is currently 0.9 V. So now we’ll look at using other chemical compounds to increase the voltage. One option we are exploring is using zinc or manganese, two metals common in the Earth’s crust,“ says Aiman Rahmanudin.
Image: Researchers at Linköping University have developed a battery that can take any shape. Credit Thor Balkhed.
https://doi.org/10.1126/sciadv.adr9010
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