Paper Batteries? Empa Says It’s Possible.

Researchers at Empa recently published a proof-of-concept study for a water-activated, disposable, paper battery. The new battery could be used to power a broad range of low-power, single-use disposable electronics, such as smart tracking labels, environmental sensors, and medical diagnostic devices. The team believes that the biodegradability of the components used could enable their battery to minimize the environmental impact of disposable, low-power electronics.

The battery consists of at least one cell that is one centimeter squared, which is then covered with sodium chloride salt, and one of its shorter ends dipped in wax. Three inks are printed on the paper:

  • on one side, an ink containing graphite flakes serves as the positive end of the battery (cathode);
  • on the other side, an ink containing zinc powder serves as the negative end of the battery (anode); and
  • on top of the other two inks, an ink containing graphite flakes and carbon black is printed on both sides of the paper. This links the battery’s positive and negative ends to two wires positioned at the wax-dipped end of the paper.

The salts in the paper dissolve when a small quantity of water is added, which releases charged ions. These ions spread across the paper to activate the battery.

To test the paper battery, the researchers combined two cells into one battery and used it to power an alarm clock with a liquid crystal display. Analysis of the performance showed that after two drops of water were added the battery activated within 20 seconds and – when not connected to an energy-consuming device – reached a stable voltage of 1.2 volts. (The voltage of a standard AA alkaline battery is 1.5 volts.) After one hour, the battery’s performance decreased significantly due to the paper drying, but after two more drops of water were added, it maintained a stable operating voltage of 0.5 volts for more than one additional hour.

Further tests will seek to increase the sustainability of the battery by minimizing the amount of zinc used within the ink, which could also allow for precise control of the amount of electricity the battery generates.