Cotton drum? Alternatives to lithium and other ores developed by scientists and companies – 11/25/2023 – Environment

Poof! Energy is off.

But on a street in India, a self-service bank machine continues to work happily, handing out money to people. In part, thanks to the burning cotton.

This machine has a backup battery inside, which contains carbon from carefully burned cotton.

“The specific process is a secret, to tell you the truth,” says Inketsu Okina, head of intelligence at Japanese company PJP Eye, the battery manufacturer.

And he’s not kidding. “Temperature is a secret and the atmosphere is a secret. Pressure is a secret,” he continues cautiously.

Okina says that it is necessary to reach a high temperature — more than 3,000°C. And that 1 kg of cotton generates 200 g of carbon. As each battery cell only needs 2 g, the batch of cotton purchased by the company in 2017 continues to be used today, according to him.

Batteries are made up of three basic components: two electrodes and an electrolyte between them.

One of the electrodes becomes positively charged and is known as the cathode, while the electrode with a negative charge is called the anode.

During use, charged particles called ions flow from the anode to the cathode through the electrolyte. This flow allows the movement of electrons along the wires of the electrical circuit connected to the battery.

In the batteries developed by PJP Eye, together with researchers from Kyushu University in Fukuoka, Japan, carbon is used to form the anode — one of the two electrodes between which the ions, which are the batteries’ charged particles, flow.

Ions move in one direction when a battery is being charged and in the opposite direction when powering a device.

Most batteries use graphite as the anode, but PJP Eye argues that its approach is more sustainable, as it can produce anodes using cotton waste from the textile industry.

With immense demand for batteries expected in the coming years, driven by the rise of electric vehicles and large energy storage systems, researchers and companies have been frantically developing possible alternatives to the graphite and lithium-ion batteries so common today. .

Like PJP Eye, they argue that we could use much more sustainable and readily available materials for battery production.

ENVIRONMENTAL DAMAGE

Lithium mining can cause considerable impacts on the environment. Extracting the metal requires large amounts of water and energy and the process can leave huge scars on the ground.

Recovered lithium is often transported from the mining site over long distances to be refined in countries such as China. And graphite is also extracted from nature or produced from fossil fuels, both of which have negative environmental impacts.

“It’s very easy to imagine what the size of the carbon footprint could be as battery material goes through extraction and transportation,” according to Sam Wilkinson, an analyst at market information and analysis firm S&P Global Commodity Insights.

Another example is cobalt, used in many lithium-ion batteries. The metal is predominantly mined in the Democratic Republic of Congo — and there are reports of dangerous working conditions in that country.

From sea water to bio-waste and natural pigments, there is a long list of possible natural alternatives, much more easily available. The difficult thing is to prove that any of them can realistically compete with the batteries on the market, apparently so indispensable in our world full of devices.

PJP Eye also proposes the possibility of improving battery performance and making them greener.

“The surface of our carbon is larger than that of graphite”, according to Okina. He describes how the anode chemistry of his Cambrian brand single-carbon battery allows it to charge up to 10 times faster than existing lithium-ion batteries.

The battery’s cathode is made of a “base metal” oxide. Okina doesn’t say exactly what this metal is, but they include copper, lead, nickel and zinc, which can be obtained more easily and are less reactive than alkaline metals like lithium.

The company says it is developing a dual-carbon electrode battery, with both electrodes made from plant-based carbon. The technology is based on research carried out by researchers at Kyushu University, but the battery is not expected to be available before 2025.

Being able to charge a battery quickly doesn’t make much difference for a bank self-service machine, but it is important for electric vehicles, when you want to refuel to continue your journey.

Okina mentions that the Chinese company Goccia, in partnership with the Japanese company Hitachi, has developed an electric bicycle powered by the PJP Eye battery, which will be offered for sale in Japan. Okina states that the maximum speed of the bicycle is 50 km/h and you can travel a distance of 70 km on a single charge.

But it is still far from the only battery that uses carbon from biowaste. Stora Enso in Finland has developed a battery anode that uses carbon from lignin, a binding polymer found in trees.

Cotton can also be used in place of the electrolyte that allows ions to flow between the cathode and anode, potentially creating solid-state batteries that are more stable than those available today, according to some researchers.

But there are those who envision larger and potentially inexhaustible energy sources in nature.

The planet’s vast oceans represent a “practically limitless” storehouse of battery material, according to Stefano Passerini, deputy director of the Helmholtz Institute in Ulm, Germany.

He and his colleagues described the design of a battery that transfers sodium ions from seawater to build a deposit of the metal sodium in a paper published in May 2022. To do this, the team designed a special polymer electrolyte, using from which sodium ions can pass.

Here, seawater acts as the cathode, or the positively charged electrode. But there is no anode, as sodium does not receive a negative charge. It only accumulates in neutral form.

Passerini says that surplus solar or wind energy can be used to accumulate sodium, which can remain there until it is needed.

“When you need the energy, you can reverse the process and generate electricity,” he explains, describing how the metal would simply be returned to the ocean.

But there are difficulties in this process. Briefly, sodium, in a very similar way to lithium, reacts energetically when it comes into contact with water. In Passerini’s words, “you have a blast.”

Therefore, it is essential to ensure that there is no seawater leaking into the sodium deposit, to prevent disaster from occurring.

This possibility led other researchers to look for a material found naturally in our bones and teeth, among many other sources, as a safer alternative to cathodes: calcium.

It can, for example, be combined with silicon, which would help transport calcium ions to future batteries.

The list of materials that could power batteries in the future is getting stranger and weirder.

George John, from the City University of New York, in the United States, and his colleagues have long researched the potential of biological pigments called quinones, found in plants and other organisms, for use as battery electrodes.

They even achieved promising results with a molecule derived from henna — the dye used in tattoos, derived from the henna tree, Lawsonia inermis.

“This is our dream,” says John. “We want to make a sustainable battery.”

According to him, one of the obstacles is the strong solubility of the natural henna molecule. When used as a cathode, it gradually dissolves in a liquid electrolyte.

But, by combining four henna molecules and adding lithium, John explains that they are capable of producing a recyclable material with a much more resistant crystal structure.

“As crystallinity increases, solubility is reduced,” he explains.

John adds that the battery designs he and his colleagues have developed may not have enough capacity to power electric vehicles, but one day they could be used in small wearable devices — perhaps blood sugar meters for diabetics or other indicators. , for example.

Other researchers are studying the use of different materials, such as corn waste and melon seed shells, to generate new types of battery electrodes. But the challenge may be its production on scale, in order to meet the industry’s increasing demand.

In fact, the ongoing challenge for any alternative battery material is always to meet the expected extraordinary increase in demand.

If we continue using today’s lithium and graphite battery technology, the world will need around two million tons of graphite per year by 2030 to satisfy the growing battery industry, according to estimates by analyst Max Reid, from consultancy Wood Mackenzie.

Currently, annual consumption is 700 thousand tons.

“Demand will actually triple,” he says. This is, in part, why alternatives to graphite need to meet this high standard. “Achieving this scale will be incredibly difficult for any new material.”

Changing manufacturing processes, eliminating the use of graphite, would be very expensive and possibly a major commercial risk, according to battery engineer and scientist Jill Pestana, from California (USA), who currently works as an independent consultant.

She is skeptical about using biowaste for carbon anodes, as the sources of this waste may not always be very environmentally friendly. This is the case of a tree plantation with poor biodiversity management, for example.

On the other hand, in markets with consumers apparently concerned about the sustainability of the products they purchase, alternative battery materials, from suitable sources, may have a greater chance – whether the batteries are made from carbon derived from bio-waste or any other potentially more sustainable substance.

“The public can play an important role, really boosting these efforts”, indicates Pestana.

Read the original version of this report (in English) on the BBC Future website.