ENGINEERING TECHNOLOGY

Add a little water and this disposable battery can be activated


A two-cell paper battery is driving an alarm clock with an LCD display. Image credit: Alexandre Poulin

One study proposed a disposable paper battery activated with water. The researchers believe it could be used to drive a variety of low-power, disposable electronics — such as smart tags that track items, environmental sensors and medical diagnostic devices — and minimize their environmental impact. The study was recently published in Scientific Reports.

The battery, designed by Gustav Nystrom and colleagues at the Swiss Federal Institute for Materials Testing and Development, consists of at least one cell measuring 1 square centimeter and containing 3 types of ink printed on a rectangular paper strip. The paper tape is distributed with sodium chloride salts, and the shorter end is soaked with wax. One type of ink contains graphite flakes printed on one side of the paper as the positive electrode (cathode) of the battery pack, and the reverse side of the paper is printed with an ink containing zinc powder as the negative electrode (anode). In addition, on both sides of the paper, on top of both inks, inks containing graphite flakes and carbon black are printed. This ink connects the positive and negative poles of the battery pack to two wires, which are located at the waxed end.

Add a little water, and the salts on the paper will dissolve, releasing charged ions. These ions disperse on paper to activate the battery pack, allowing zinc in the battery pack’s anode ink to release electrons. Wires attached to electronic devices can be connected to circuits that allow electrons to pass through graphite and carbon black inks, wires, and devices from the negative electrode to the positive electrode (graphite-containing ink), where they are transferred to oxygen in the surrounding air. The current generated by these reactions can be used to drive the equipment.

A template printed two-cell paper battery, EMPA is the name of the author’s research institution. The two cells are separated by a water compartment. Image credit: Alexandre Poulin

To demonstrate this ability of batteries to drive low-power electronics, the authors combined two battery cells into a battery pack that drives an alarm clock with a liquid crystal display. A performance analysis of the single-cell battery pack shows that with the addition of two drops of water, the battery pack activates within 20 seconds and reaches a stable 1.2 volts when not connected to the energy-consuming device. The voltage of a standard AA alkaline battery is 1.5 volts. After an hour, the performance of the single-cell battery pack degraded rapidly due to paper drying. But with two more drops of water, it can maintain a stable 0.5 volt operating voltage for more than an hour.

The authors argue that the biodegradability of paper and zinc allows such batteries to minimize the environmental impact of disposable, low-power electronics. They believe that by minimizing the amount of zinc used in the ink, the sustainability of such a battery can be further improved, which will also allow the current generated by the battery to be precisely controlled. (Source: China Science Daily Feng Weiwei)

Related paper information:https://doi.org/10.1038/s41598-022-15900-5



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