In 1991, Sony launched the world’s first commercial lithium-ion battery... and since then the design hasn’t changed all that much.
Now, new research suggests that incorporating liquefied gas can allow lithium-ion batteries to work at much lower temperatures than previously possible.
Lithium-ion batteries are cheap, pretty reliable, and have a high energy density. They would be ideal for powering stuff out in space, but they don’t work too hot in the extreme cold. The carbonate liquid inside typical electrolytes freezes, reducing electric conductivity and turning, say, a Li-ion-powered planet rover into a brick.
Some researchers have explored solid-filled electrolytes or gas mixtures, but there hasn’t been exciting news on the weather front. Today, the lowest temperatures in which lithium ion batteries can work is about -20°C (-4°F).
When Shirley Meng, a nanoengineer at UC San Diego in California, was approached by a student with the idea of using liquefied gas for an electrolyte instead of liquid or solids, she was skeptical because it was just so different than existing research. “At first, I think it’s a quite out-of-the-box idea,” she says.
But in the new study, her team found that using liquefied gas in a redesigned lithium ion battery yields stability at -60°C (-76°F).
Most importantly, the new battery has an electrolyte with a tightly sealed container and a gas regulator. The gas of choice was fluoromethane, which takes a liquid form between about -60 to 60°C (-76° to 140°F).
The whole thing works a bit like a pressure cooker: if you take the seal off, the liquid escapes as a gas, but if you keep it tightly sealed then the gas molecules are under so much pressure that they remain a liquid that doesn’t freeze as easily as regular liquids. The team also created a super capacitor that functions at -80°C (-112°F) using difluoromethane.
The researchers ran the battery for 100 cycles and still had about 95 percent capacity – which doesn’t quite tell us much about its long-term potential, but is a fairly standard reporting time.
A paper describing the work appeared today in Science.
Donald Sadoway, a battery researcher at the Massachusetts Institute of Technology, told The Register: “I’m not sure of the practicality of resorting to liquefied gases that for operability require extra-ambient conditions (temperature or pressure or both).”
Kent Griffith, a materials chemistry PhD student at the University of Cambridge in the UK who studies new battery materials, says it opens a new avenue of research in trying to use different kinds of liquefied gas for batteries. However, in addition to safety, he was concerned about the greenhouse gas potential of liquefied gases, which are being phased out for refrigeration around the world due to regulation.
Meng says that the greenhouse gas emissions are lower than those in usual refrigeration systems. And she says that this type of battery could also be safer than others, since although at high temperatures the gas can escape the container, it’s not flammable. Liquid lithium ion batteries now are extremely flammable, she says.
The lead author, according to Meng, has started a company to sell batteries based on the liquefied gas project. Although the liquid gas tech probably won’t be needed for our mobile phones and laptops (which tend to function around room temperature), she’s hoping that someday low-temperature batteries could help make better cars or space rovers.