Two drops of water, a piece of paper, how to generate electricity for one hour?

Data from the United Nations University shows that in 2019, about 53.6 million tons of electronic products were discarded globally. It is expected that by 2030, this number will be as high as 74.7 million tons. If this trend cannot be reversed, by 2050, it will even reach 1.1 million tons. million tons.

Using more environmentally friendly materials and improving the recovery rate of resources is an important method to solve the problem of the flood of electronic waste, and biodegradable batteries are the hotspot of current battery research.

Now, a research team from the Swiss Federal Laboratory for Materials Science and Technology (Empa) has made a new breakthrough in biodegradable batteries - in a proof-of-concept study, they have proposed a water-activated disposable paper Battery.

According to reports, with just two drops of water, the new battery can continue to power an alarm clock with LEDs for an hour, and after an hour with two drops of water, it can continue to be used, and can be made into any shape and size. , the potential application scenarios are very broad.

The related research paper, titled "Water activated disposable paper battery", has been published in the scientific journal "Scientific Reports". Dr. Gustav Nyström from the Swiss Federal Laboratory for Materials Science and Technology is the corresponding author of the paper.

The research team said the paper battery could be used to power a variety of low-power, single-use, disposable electronics such as smart tags that track items, environmental sensors, and medical diagnostic equipment with minimal environmental impact.

How can paper batteries generate electricity?

In recent years, scientists have made important progress in green power technologies such as biodegradable optoelectronic devices, energy harvesters, and supercapacitors. However, the research of biodegradable disposable batteries as a highly complementary energy source that can provide higher energy density and more stable operation is still very limited.

Current research on batteries mainly focuses on the improvement of battery performance, that is, the continuous development of higher energy and power density, faster charging rate and better operating stability, mainly through the development of lithium-ion batteries that meet the current dominant market. required new materials to achieve.

However, as people become more aware of the hazards of e-waste and the emergence of disposable electronics for applications such as environmental sensing and food monitoring, there is a growing demand for environmentally friendly batteries.

So, how does this paper battery generate electricity?

According to the paper, just add a little water, and the salt on the paper will dissolve, releasing charged ions that disperse on the paper to activate the battery pack, allowing the zinc in the negative ink of the battery pack to release electrons, which are connected to electronic devices The wires on the top of the circuit can complete the circuit, allowing electrons to pass through the graphite and carbon black-containing inks, wires and equipment, from the negative electrode to the positive electrode (graphite-containing ink), where they are transferred to the oxygen in the surrounding air, and the current is positive. produced in these reactions.

To demonstrate the battery's ability to power low-power electronics, the research team combined two battery cells into a battery pack to drive an alarm clock with a liquid crystal display.

Performance analysis of a single-cell battery pack showed that with the addition of two drops of water, the pack would activate within 20 seconds, reaching a steady 1.2 volts when not connected to an energy-consuming device, while a standard AA alkaline battery (size 5) battery) is 1.5 volts.

After an hour, the performance of the single-cell battery pack quickly degrades as the paper dries. However, with two more drops of water, it was able to maintain a stable 0.5 volt operating voltage for over an hour.

The research team says the biodegradability of paper and zinc allows the battery to minimize the environmental impact of disposable, low-power electronics