Battery from the tube: Soft material allows batteries to take on any shape

Scientists at Linköping University's Laboratory of Organic Electronics have developed a toothpaste-like material that can be used to produce batteries in any shape – also with a 3D printer. The technology could be used to produce batteries for devices that no longer have any design restrictions.

“Batteries are the biggest component of all electronics. Today they are massive and quite bulky. But with a soft and adaptable battery, there are no design constraints. It can be integrated into the electronics in a completely different way and adapted to the user,” says Aiman Rahmanudin, one of the scientists involved in the battery project at the Laboratory of Organic Electronics. He and his colleagues have succeeded in producing a battery that has the texture of toothpaste, as the researchers write in the study “Make it flow from solid to liquid: Redox-active electrofluids for intrinsically stretchable batteries”, which has been published in Science Advances. This means that the black material can also be processed using a 3D printer and molded into any shape.

Attempts to produce moldable batteries

Previous attempts to produce a soft, malleable battery were based on mechanically modifying existing battery technology so that it could be stretched. To this end, scientists have used malleable composite materials or connections that can slide over each other. Although there were promising approaches here, one problem was not yet sufficiently solved. This is because large batteries with a higher capacity contain more active materials, have thicker electrodes, and are correspondingly more rigid.

Attempts to use liquid electrodes, such as those made of gallium, failed. The material is only suitable as an anode, as it can change from a liquid to a solid state during charging and discharging. In addition, the materials required for the construction of such batteries are rare and their extraction and processing place a heavy burden on the environment.

“Waste products” for battery production

Instead, the researchers at Lingköping University use conductive plastics, so-called conjugated polymers, as well as lignin, a by-product from paper production. These materials are available “in abundance” and because they are produced anyway, are also sustainable.

The properties of the battery made from these materials are unusual: it can be extended to twice its length without losing any of its function. It can also be charged and discharged 500 times without any loss of performance, according to the researchers.

The battery still has limitations in terms of the level of electrical voltage output. This is currently only 0.9 volts. The researchers are now looking for ways to increase the voltage. To this end, they want to test other chemical compounds. One option is the use of zinc and manganese, both of which are also widely available.

(olb)