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Battery made of wood – Apparata

A battery made of wood is less of a strange idea than it seems. This has everything to do with the fine structure of wood.

Why lithium ion batteries have had their day

Lithium is the lightest metal and has an enormous energy density. Ideal for batteries. There’s only one problem. Lithium is very scarce and it takes a lot of energy to extract it. If we want the entire planet to switch to alternative energy sources, we need batteries that are at least as good as lithium batteries, but that do not use these kinds of scarce materials. Hence, sodium ion batteries are advancing rapidly. But other metals, such as zinc, and even organic batteries, are also being researched.

A replacement must also be found for graphite. Graphite is becoming increasingly scarce and graphite batteries cannot withstand heavy frost, as swearing and ranting Tesla drivers in the US have discovered. So here too we are looking for an alternative.

Source: Stora Enso, fair use

Once worthless lignin now very useful as a battery material

Wood consists almost entirely of two substances: cellulose and lignin. Cellulose provides the load-bearing capacity and lignin protects the wood against deterioration. Together they form very strong wood fibers, in which the cellulose is surrounded by lignin. Cellulose is processed en masse into paper pulp, but large amounts of lignin are left behind. 1/4-1/3 of all wood consists of lignin.

More and more chemical companies are now switching to lignin as a raw material, because there is a lot of it and it is cheap. However, large quantities still remain. At the moment about 17 billion kg per year. The Finnish company Stora Enso is responding to this and has now developed a new alternative to graphite. This is lignode, based on lignin. With their 50 million kg of lignin from their paper mill per year, they can continue for a while. Unlike graphite, their material contains many irregular pores. As a result, it is more accessible to lithium ions than graphite and charging is therefore faster.

Wood battery as a lithium-free battery

Ligna Energy from neighboring Sweden is one of the buyers of Stora Enso’s lignin. The Swedes go one step further and completely do away with lithium. With lignin, water and natural polymers as the main ingredients, their battery plus supercapacitor (0.6 farad) contains almost 80% organic matter.

In existing batteries, scarce metals such as cobalt are used for this purpose. The energy density is not very high, one sixth that of the lithium ion battery. But the batteries last more than 5000 charging cycles.

Biodegradable

At the moment you can already order a package of 5 (small) S-Power Ligna Energy batteries for 100 euros to experiment with. At the moment they mainly focus on supplying flat, light batteries for sensors. Very important, because soon there will be literally hundreds of billions of small sensors spread all over the world, related to the Internet of Things. They must be biodegradable. This is possible thanks to this invention. These sensors break down one hundred percent and leave no toxic substances behind.

Very elegant concept for wood battery

The company is somewhat secretive about the exact chemical reaction by which the battery stores energy. Here the lignin seems to play an active role. According to Ligna Energy, their battery can simply be put in the green bin, which seems to indicate a non-toxic metal. Or perhaps a metal-free redox reaction involving lignin.

For the nerds among you: it turned out to be a combination of the latter with zinc. The system is incredibly elegant and uses electricity-conducting molecules that transport electrons to and from the benzene rings of the lignin. This is really pure nanotechnology. Can’t get much smaller than this. It is explained exactly in this video below.

Nice solution for large-scale storage of peak power

Well, nice, you would say. What is the practical use of this battery? You will indeed not see this battery in a car or your mobile phone anytime soon. That is because the energy density is quite low. But of course there is no such problem if these batteries remain in the same place. The major disadvantage of alternative energy sources is that they do not provide energy when the sun is not shining or when the wind is at a standstill.

Do we really want to replace all fossil fuels with alternative energy sources? Then we need a good way to store energy. And in that respect, this battery can provide very good services. If you connect a considerably scaled-up version of the Ligna Energy batteries to solar panels, you have a battery that will last more than 15 years.

So who knows, maybe in a few years there will be a wooden battery in your backyard, on which you leave the lights on at night. And when the battery is exhausted, you can simply throw it on the compost heap. If the Swedes keep their promise, this could become very popular.

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