Scientists at the Berkeley lab have discovered that a seaweed derivative could boost the stability of lithium-sulphur batteries, allowing for more cycling and an extended lifetime.
Lithium-sulphur batteries hold great promise as a low-cost, high-energy, energy source for vehicle and grid applications, according to the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab). But they have one major disadvantage: significant fading capacity. This is because the sulphur eventually starts to dissolve, creating what scientists call ‘the polysulphide shuttling effect’.
Researchers at Berkeley Lab have now made an unexpected discovery that could address this after they discovered that carrageenan, a seaweed derivative, binds or holds all the active materials in a battery cell together.
“A binder is like glue, and normally battery designers want a glue that is inert,” said Gao Liu, who led the research team. “We looked for something that was economical and readily available. It turns out carrageenan is used as a food thickener. And it actually worked just as well as the synthetic polymer – it worked as a glue and it immobilised the polysulfide, making a really stable electrode.”
By chemically reacting with the sulphur, the binder was able to stop it from dissolving, which in turn improves the batteries’ stability. With this breakthrough, Liu is now looking to improve the lifetime of lithium-sulphur batteries even further. “We want to get to thousands of cycles,” he said.
Lithium-sulphur batteries have more than twice the energy density of lithium-ion batteries, which currently dominate the market. According to Berkeley Lab, they are also much more lightweight, which means they have potential application in airplanes and drones.
“There’s a lot of demand for energy storage, but there’s very little chemistry that can meet the cost target,” Liu said. “Sulphur is a very low-cost material-it’s practically free. And the energy capacity is much higher than that of lithium-ion. So lithium-sulphur is one chemistry that can potentially meet the target.”