A new type of battery made from common materials that is safe, efficient and economical

nouvelle batterie aluminium soufre

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Lithium-ion batteries quickly conquered the market thanks to their high energy density. But due to the explosion in demand for the manufacture of automotive batteries, the price of lithium is today very high: around €45,000 per tonne (or around 360% more expensive than a year ago). In this context, a team from MIT has developed a battery made of abundant and cheap materials: aluminium, sulfur and salt. This new battery is not only cheaper to produce, but also very durable.

The other big drawback of lithium-ion batteries is that they contain a flammable electrolyte, so they can catch fire or explode if damaged or misused. However, the demand is not going to decrease in the short term: the massive deployment of solar panels and wind turbines must necessarily be accompanied by backup systems to cover the needs when the weather conditions are not favorable. As the world seeks to reduce its CO2 emissions by increasing the use of renewable energy and electric vehicles, finding safer and less expensive storage alternatives is essential.

The battery designed by Professor Donald Sadoway and his colleagues perfectly meets this need. It uses aluminum and sulfur as electrode materials, separated by a molten salt electrolyte. Aluminum quickly emerged as a material of choice: it is the most abundant metal on Earth and also the second metal on the market (after iron). Sulfur is the cheapest of all the nonmetals; it is found in large quantities in nature, in the form of sulfides and sulfates, and is also a by-product of petroleum refining.

Particularly high charging rates

For the electrolyte, the use of volatile and flammable organic liquids was excluded. Therefore, the researchers tested different molten salts with relatively low melting points, with the aim of overcoming insulation and anti-corrosion measures, Sadoway explains in a press release. His choice fell on a molten salt composed of NaCl-KCl-AlCl3. The team explains that molten chloroaluminates contain Al speciesNocl3(n+1) in the form of chains, whose Al-Cl-Al bonds confer easy desolvation kinetics of the Al ion3+resulting in high faradaic exchange currents to form the basis of high-speed battery charging.

We show that the multi-step conversion path between aluminum and chalcogen allows fast charging up to 200 °C, and that the battery withstands hundreds of cycles at very high charge rates. researchers report in Nature. From their experiments, they found that the charging rate strongly depended on the working temperature: at 110 °C, the rate turned out to be 25 times higher than at 25 °C. But the team clarifies that the battery does not need an external heat source to reach this temperature: the heat produced naturally by the charge and discharge cycle is enough.

In addition, the chloroaluminate salt chosen as the electrolyte had an unexpected benefit: It prevented the formation of aluminum dendrites—narrow spikes of metal that build up over time on one electrode and then grow until they come into contact with the other electrode, causing causes short circuits. circuits. The phenomenon has a great impact on the efficiency of lithium-ion batteries. Even at very high charging rates (charging less than a minute), the team did not observe any short circuits. A new example of serendipity in short. ” If we had started out trying to prevent dendritic shorting, I’m not sure we would have known how to do it. Sadoway said.

A solution to the massive deployment of electric vehicles

Another (and no less important) advantage is that the cost of an aluminum-sulfur cell should be less than a sixth of the cost of similarly sized lithium-ion cells. ” Composed of elements from the earth that can be ethically sourced and used at moderately high temperatures, just above the boiling point of water, this chemistry exhibits all the hallmarks of a cheap, rechargeable, durable, flame-retardant and recyclable battery. » concludes the team.

The researchers think that their battery would be ideal for installations of the order of a few tens of kilowatt hours (to store the energy of a house or a small business powered by renewable energies, for example).

Due to their fast charging, they would also be very practical for charging stations for electric vehicles. If the latter become the majority on the roads, we will need more and faster charging points. However, the amperage of the lines that supply the stations today is not sufficient for this use. Having such batteries to store energy and quickly release it when needed would prevent the installation of expensive new power lines.

The aluminum-sulfur battery patents were licensed to a spin-off company, called Avanti, co-founded by Sadoway and Luis Ortiz. The company’s first goal is to demonstrate that the system works at scale and then put it through a series of stress tests.

For larger grid-scale needs (that is, up to several hundred megawatt-hours), other technologies could be more efficient, including the liquid metal batteries that Sadoway and his students developed several years ago and will soon commercialize by Ambri (a company co-founded in 2010 by Sadoway and Ortiz too).

Source: Q. Pang et al., Nature

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