Develop a disposable battery made of paper that is activated by water

in StemSocial3 months ago
Hello dear friends of Hive.

We know that nowadays we are very dependent on various types of electronic devices, and every year with the development of technology, the consumption of these is increasing, often because they become obsolete before fulfilling their useful life, however there are many types of devices that are specifically designed to be discarded after a single use, for example pregnancy tests, diagnostic devices for some diseases and smart tags. The fact is that these devices usually use button batteries, and given the rise of printed electronics, these types of disposable devices will surely continue to appear for various applications, so they begin to represent an important source of discarded batteries that need to be considered to minimize the environmental impact associated with this type of element. This is why a team of researchers from Empa's Cellulose and Wood Materials Laboratory focused on developing a disposable paper battery.

portada bat papel 2.png
A disposable battery made of paper would be suitable for many uses. Source: @emiliomoron, contains a public domain image.

Undoubtedly, to face the boom of these devices, it is necessary to advance in the use of more environmentally friendly materials and minimize the generation of electronic waste, especially batteries, since they contain different polluting substances and metals. And although great advances have been made in the field of batteries, the truth is that these advances have focused on increasing their performance, using new materials or increasing the charging speed, but the development of primary batteries that are biodegradable and provide the necessary energy requirements has been very limited.

And with the increased development and use of single-use electronic devices for applications such as tracking objects with smart tags, sensors for environmental measurements, and rapid tests for pregnancy and some diseases, there is growing concern about the increase in e-waste and the need for low environmental impact batteries.


Source: pexels.

In this sense, the EMPA research team has developed a disposable water-activated printed paper battery that could be used to power this type of single-use disposable electronic devices. Basically, the battery is based on a metal-air electrochemical cell in which zinc is used as the anode, graphite as the cathode, paper as the separator and water as the electrolyte. Recall that a metal-air cell is a type of cell in which the charge transport is caused by oxidation-reduction reactions between the pure metal at the negative electrode and the oxygen contained in the positive electrode of a porous material that allows air to enter the system.

esquema celda bat paepl 2.png
General scheme of operation. Source: image elaborated in Powerpoint.

According to research recently published in the journal Scientific Reports, the single-cell paper cell that has been developed is composed of a paper substrate sandwiched between the air cathode and a current collector on one side, and the zinc anode and current collector on the opposite side, and sodium chloride dispersed in the paper; and when water is added, it dissolves the salt and activates the circuit.

Essentially, on one side of a strip of paper an ink containing graphite is printed, acting as the cathode of the cell, while on the other side of the paper another ink containing zinc powder is printed, acting as the anode, then salt is dispersed on the paper and one end of the paper strip is dipped in wax, subsequently another graphite ink is printed on both sides of the paper acting as the current collector linking the positive and negative poles. When a small amount of water is added to the system, it is absorbed and diffuses through the paper, dissolving the salt and creating an ionic electrolyte that acts as a charge carrier and activates the system.
The simplest expression of the reactions involved in a zinc-air cell are as follows:

reaxxciones bat papel 2.png

Design tests of this type of battery showed that by adding a couple of drops of water, and with no power consuming elements connected, the battery activated within 20 seconds and managed to develop a stable voltage of 1.2V, and as a proof of concept they used the battery to power an alarm clock. But after an hour the voltage dropped to 0.5 V, a drop in performance that was attributed to the drying of the paper.

This is why the researchers are proposing its use in single-use electronic devices, since the biodegradability of the components could make it possible to minimize the environmental impact of disposable electronic devices.

Apart from the fact of using a paper substrate for the manufacture of the battery, the feature of its activation with water is very appropriate as it would allow the supply of energy when the user needs it or passively activated when the environment requires it.

Hopefully, this paper-based biodegradable battery technology will be available soon, since, despite its low performance compared to standard batteries, it is very important for a wide range of devices that are part of the disposable electronics that are becoming very common.


Well friends, I hope you liked the information. See you next time!


References

Poulin, A., Aeby, X. & Nyström, G. (2022). Water activated disposable paper battery. Sci Rep 12, 11919

Wikipedia.org. Celda electroquímica metal-aire

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This battery will be useful for so many devices, thereby leading to mass adoption, but the possibility of having a biodegradable rechargeable battery would be better. Humans can actually make anything become environmentally hazardous, especially in their disposing technique. Till date, it is still very difficult to dispose recyclable products in Third World countries.

You are right, it is still very difficult to find ways to recycle electronic waste, especially batteries, so we should support the development of biodegradable batteries.

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