Scientists unveil extremely small battery for the world’s smallest computers

There was a time, not so long ago, when computers were so big they took up entire rooms. Today, some processing units can be as small as a few specks of dust.

Even next to a grain of rice, these stacks of micrometer-sized chips seem infinitesimal.

Shrinking computer batteries to fit this size, however, proved more difficult.

With little room for storage, smaller computers must rely on ultrasonic or photovoltaic cells to continually recharge microbatteries with energy from vibration or sunlight. This has its drawbacks, as the computer will not work without a constant power supply or in dark places like the human body.

Some scientists in Europe are therefore proposing an alternative structure: a microbattery based on the folding of thin micro layers like origami.

The battery is currently only a prototype, but the preliminary results are encouraging.

Battery prototype next to a grain of salt. (TU Chemnitz/Leibniz IFW Dresden)

“There is a desperate need to develop high-performance batteries for the millimeter and submillimeter-sized regime, as such energy storage systems would facilitate the development of truly autonomous microsystems,” the authors write.

Full-size computer batteries are generally based on “wet chemistry”, which means that electrically conductive metal foils are placed in contact with liquid electrolytes to create a flow of energy.

Chip-based batteries of a certain size, however, cannot support liquid electrolytes.

So the inventors of this new microbattery pressed a solid electrolyte between two microchips which are painted with a super thin film of electrodes, one positive, one negative.

This solid electrolyte, however, is not as efficient as using a liquid electrolyte, where folding comes into play.

By rolling a stack of flat batteries into a “Swiss roller cylinder”, scientists can squeeze a lot more surface area into a small space. That’s actually how the cylindrical cells in Tesla’s electric cars work.

At the cubic millimeter scale, it is extremely difficult to roll thin, brittle materials into this type of shape via external pressure.

Luckily, there is another way to bend material on your own, and it’s called “micro-origami.”

The technique works like a rolling blind. As the thin material is pulled down, you can let go of that mechanical tension and the whole thing will shoot up and roll into a cylinder.

ElectrodeCylinderIllustrations of layered thin films and a Swiss roll on a chip. (Zhu et al., Advanced Energetic Materials, 2022).

On a chip, the researchers were able to achieve this movement by attaching one side of the thin material to create, essentially, the bar of a blind.

Ultimately, the team was able to wrap a prototype microbattery in an area of ​​just 0.04 square millimeters, delivering eight times the capacity of what a similarly sized flat battery could achieve.

The authors say the cylinder resembles the standard Swiss roll structure used in larger batteries, comprising at least two collector layers, a cathode film, an anode film and an electrolyte film all rolled together.

Not only is the design rechargeable, but researchers say the battery as it is could power the smallest computers we have for around 10 hours. And there is still work to be done.

“There is still huge optimization potential for this technology, and we can expect much more powerful microbatteries in the future,” says physicist Oliver Schmidt from Chemnitz University of Technology in Germany.

The study was published in Advanced Energy Materials.