It could almost be done at home, given the easy availability of the ingredients, the new battery developed by Massachusetts Institute of Technology (MIT) based on aluminum, sulfur and salt which surprised for performance and significant benefits compared to colleagues who use the increasingly expensive lithiumby the way susceptible to explosions and fires in case of damage or improper use.
The team of engineers at the American University looked for an inexpensive alternative, finding it in using aluminum and sulfur for the electrodes and a molten salt electrolyte in between; Interviewed by the journal Nature, Donald Sadoway of MIT, professor leading the team, said: “We wanted to invent something that was better, much better, than lithium-ion batteries for small-scale stationary storage and ultimately for [usi] automotive “.
The project has begun taking in hand the periodic table and going to look for the most common chemical element: after excluding iron Sadoway concentrated on aluminum, choosing it for the first electrode. At that point the most abundant of the non-metals was sulfur, so the second electrode was also arranged. And the electrolyte? “We would not have used volatile and flammable organic liquids” said the teacher, explaining that he had experimented, together with the rest of the team, different polymers and then moved towards some molten salts with relatively low melting points, close to boiling water, instead of the nearly 1,000 degrees Fahrenheit of many salts. “Once near body temperature is reached, it becomes practical to make batteries that do not require special insulation and anti-corrosion measures. “
At this point the team found itself on the hands a battery with a very low cost (1/6 of the lithium-ion equivalent) and with zero risk of fire, but which still had to prove its real value in practical use. In subsequent tests the cells were shown to withstand hundreds of cycles at exceptionally high charge rates; the charging speed strongly depended on the working temperature, the warmer the battery, the less time it took to recharge. In particular at 110 degrees Celsius the speed was 25 times higher than at 25 ° C.
The charging and discharging operations naturally take care of keeping the cells warm, so it is not necessary to supply it from the outside.
Icing on the cake, the chlorine-aluminate salt chosen by the team as an electrolyte stops the formation of dendrites in the budare thin metal tips that accumulate on one electrode and eventually expand to make contact with the other electrode, reducing the efficiency of the cell in the best cases, igniting a fire in the worst cases.
“We experimented at very high reload speeds, charging in less than a minute, and we never lost cells due to dendrite shorting.” Sadoway commented.
New technology is already the basis for one new company called Avantiwhich licensed the patents to the system “The first agenda for the company is to demonstrate that the battery works on a large scale”says Sadoway, “… And then subject it to a series of stress tests, including running hundreds of charge cycles.”
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