A disposable paper battery that runs on water

A team of Swiss researchers have made a disposable battery out of paper.

The paper battery, described in the journal Scientific Reports, is printed with a couple of inks that perform the function of the battery. It’s inert until you add a few drops of water, which allows ions to move between the inks and electricity to flow.

It’s powerful enough to run a small LCD alarm clock, and can run for an hour – two hours if it’s dampened again. The researchers suggest that it could be used to drive single-use disposable devices – like components of the Internet of Things.

The battery is printed on a few square centimetres of paper. It uses two different inks as its anode and cathode: the anode ink is mostly zinc powder, while much of the cathode ink is graphite flakes. Both inks also have shellac, ethanol and polyethylene glycol in varying amounts to make them printable.

Photo of the paper battery. It is a piece of paper with 'empa' written on it in thick black and grey text. The e and the a are both connected to wires at either side of the paper. The paper between the m and the p is visibly damp.
The paper battery. The anode and cathode inks are printed in the name of the researchers’ institution, Swiss Federal Laboratories for Materials Science and Technology. Note the water between the m and the p. Credit: Alexandre Poulin

The anode and cathode inks are both connected to wires at the edges of the paper, and connected by a bridge of sodium chloride – table salt – in the middle. When dampened, the salt ions allow the anode and cathode inks to exchange positively and negatively charged particles, letting electrons flow through the wires and making the battery work.

The edges of the paper battery are protected by wax to stop them from getting wet. All components of the battery are harmless in the environment, and many are biodegradable.

More on sustainable batteries: Biodegradable batteries closer with polymer breakthrough

Paper battery connected to a small round clock via red and black alligator clips connected to the battery wires
The paper battery running an alarm clock. Credit: Alexandre Poulin.

The researchers found that their paper battery activated within 20 seconds of dampening and reached a stable voltage of 1.2 volts. For comparison, a standard AA alkaline battery is 1.5 volts. In their paper, they say that changing the amount of zinc powder in the ink could control the voltage even more precisely.

“We are very interested to see how this technology can be integrated in industrial applications and have already had a few first discussions with partners,” says senior author Dr Gustav Nyström, head of the Laboratory for Cellulose and Wood Materials at the Swiss Federal Laboratories for Materials Science and Technology, Switzerland.

“In the laboratory we are currently looking at how we can even further improve the performance of the battery as well as how we can enable other forms of processing techniques to make manufacturing more scalable.”

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