Researchers have developed a new glass cage-like coating to improve the performance of lithium-sulphur batteries.
Lithium-sulphur batteries have the ability to produce up to 10 times more energy than conventional batteries, which means they hold great promise in energy-demanding electric vehicles, researchers said.
However, there have been fundamental road blocks to commercialising these sulphur batteries.
One of the main problems is the tendency for lithium and sulphur reaction products, called lithium polysulfides, to dissolve in the battery's electrolyte and travel to the opposite electrode permanently. This causes the battery's capacity to decrease over its lifetime.
Researchers in the Bourns College of Engineering at the University of California, Riverside have investigated a strategy to prevent this "polysulfide shuttling" phenomenon by creating nano-sized sulphur particles, and coating them in silica (SiO2), otherwise known as glass.
They have been working on designing a cathode material in which silica cages "trap" polysulfides having a very thin shell of silica, and the particles' polysulfide products now face a trapping barrier - a glass cage. The team used an organic precursor to construct the trapping barrier.
"Our biggest challenge was to optimise the process to deposit SiO2 - not too thick, not too thin, about the thickness of a virus," researchers Mihri Ozkan said.
Researchers also found that silica-caged sulphur particles provided a substantially higher battery performance, but felt further improvement was necessary because of the challenge with the breakage of the SiO2 shell.
"We have decided to incorporate mildly reduced graphene oxide (mrGO), a close relative of graphene, as a conductive additive in cathode material design, to provide mechanical stability to the glass caged structures," said researchers Cengiz Ozkan.
The new generation cathode provided an even more dramatic improvement than the first design, since the team engineered both a polysulfide-trapping barrier and a flexible graphene oxide blanket that harnesses the sulphur and silica together during cycling.
The research was published in the journal Nanoscale.
