Despite batteries powering almost every gadget we use, they are remarkably ineffective at holding their charge for long periods of time. The answer could come from an unlikely place: seaweed.
Common Lithium-sulphur batteries have twice the energy density of Lithium-ion packs, due to the cheap cost of sulphur. However, sulphur is cheap for a reason – it dissolves rapidly, particularly in battery casings. The sulphur holds the battery components together to ensure the electrical circuit doesn't break. When this dissolves, so does the battery's ability to hold a charge. Now, scientists at Berkeley Lab have devised a method of replacing this sulphur with seaweed, to give batteries longer-lasting life.
A derivative of red seaweed, known as carrageenan, can be used to stabilise a lithium-sulphur battery. When used as a binder, it can keep the battery's active materials together, reacting with sulphur to ensure it doesn't dissolve as quickly as it would on its own.
“There’s a lot of demand for energy storage, but there’s very little chemistry that can meet the cost target,” said author Gao Liu. “Sulfur is a very low-cost material — it’s practically free. And the energy capacity is much higher than that of Lithium-ion. So Lithium-sulfur is one chemistry that can potentially meet the target.”
Carrageenan is typically used as a food thickener and works as a synthetic polymer. Liu's team found that, when mixed with sulphur, it creates a remarkably stable electrode – using a material that is both naturally occurring and cost-effective.
Liu tested his carrageenan theory at Berkeley Lab’s Advanced Light Source, one of the world’s brightest sources of ultraviolet and soft X-ray beams.
“The light source provides unique X-ray based tools,” said Jinghua Guo at Berkeley's Advanced Light Source, “We want the tool to monitor the electrochemistry simultaneously while the battery is charging. In this case, we made a dedicated battery cell with the materials, then used X-rays to monitor the process under in situ conditions.”
The result was a new concept in battery chemistry – with this development in stabilising lithium-sulphur batteries, Liu is now seeking to improve the lifetime of batteries even further: “We want to get to thousands of cycles,” he explained.
This article was originally published by WIRED UK
