Swedish breakthrough: Pioneering liquid battery reshapes future

Scientists are somewhat in a "race" to develop new types of batteries. Recently, we reported on a discovery made by scientists at Ohio State University concerning a prototype battery that can be powered by nuclear waste. Meanwhile, Swedish scientists have revealed their work and are showcasing a liquid battery to the world.

In addition to working on batteries with greater capacity and better efficiency, scientists are simultaneously developing new ways to integrate them with other elements of devices. The goal is for the battery to perform different functions – for example, being part of the car's body or floor and the casing of a phone or laptop. Researchers from Linköping University have just created a liquid battery that could enable such combinations.

The material's texture is somewhat reminiscent of toothpaste. It can, for example, be used in a 3D printer to give the battery any shape. This opens the door to a new type of technology, says Prof. Aiman Rahmanudin, the author of the invention described in the journal Science Advances (DOI 10.1126/sciadv.adr9010).

Scientists point out that more than a trillion devices will be connected to the internet in the next ten years. In addition to already known technologies such as mobile phones, smartwatches, or computers, these will also include medical devices worn in or on the body – insulin pumps, pacemakers, hearing aids, or various sensors for health monitoring. Concurrently, technologies such as soft robotics, e-textiles, and even neural implants working in conjunction with networks are also being developed.

Batteries are the most significant component of all electronic devices. Currently, they are complex and quite bulky. However, thanks to a soft and flexible battery, today's design limitations will be overcome. The researcher explains that such a battery can be integrated with electronics in a completely different way and tailored to the user.

The key element of the new invention was transforming the electrodes from a solid state to a liquid. Previous attempts to create flexible and stretchable batteries relied mainly on mechanical solutions, such as stretchable composite materials or elements that could move relative to each other. However, such methods did not solve the fundamental problem: although a larger battery provides greater capacity, it also means using more active materials, and consequently, thicker electrodes, which are stiffer.

Prof. Rahmanudin says they solved this problem and were the first to demonstrate that capacity does not depend on stiffness.

Scientists recall that attempts to use liquid electrodes have been made before, but did not yield significant results. At that time, liquid metals, such as gallium, were used. As the researchers explain, this material can only function as an anode, and there is a risk that it will solidify during the charge and discharge cycle, causing a loss of liquid properties.

Moreover, many earlier stretchable batteries relied on rare raw materials, such as extraction and further processing, which severely burden the natural environment.

The Swedish team constructed their battery using conductive polymers and lignin, a substance that emerges as a byproduct during paper production. The developed cell can be charged and discharged over 500 times without noticeable performance loss. Moreover, the battery can be stretched to twice its size and work as effectively.

Since the battery uses conjugated polymers and lignin, the raw materials are easily accessible. Transforming a byproduct like lignin into a valuable material for battery production also contributes to a more circular economy model. Dr. Mohsen Mohammadi, one of the publication's authors, says we are thus talking about a sustainable alternative to current technologies.

However, Prof. Aiman Rahmanudin humbly emphasizes that the battery is imperfect. The working prototype is not a final product. The scientists' ambition is to increase the electrical voltage, which in the device's conceptual phase is 0.9 volts. The team is looking for chemical compounds that could improve the voltage.

Prof. Rahmanudin explains that one of the options we are exploring is using zinc or manganese, two metals commonly found in the Earth's crust.