TECHNOLOGY/SCIENCE
Engineers at the University of California San Diego’s Sustainable Power and Energy Centre have developed a new cathode material for solid-state lithium-sulphur (SSLI) batteries that promises to dramatically boost the driving range of electric vehicles.
SSLI batteries are a type of rechargeable battery that offer a superior alternative to current lithium-ion batteries. They can store up to twice as much energy per kilogram as conventional lithium-ion batteries — in other words, they could double the range of electric vehicles without increasing the battery pack’s weight. And, using abundant, easily sourced materials makes them less expensive and more eco-friendly.
The SSLI battery has long been plagued by the sulphur itself. That’s because sulphur doesn’t conduct electricity very well and the cathodes themselves wear out in a short time. The cathode can’t transfer charge efficiently, compromising performance and longevity.
To overcome this, researchers at UC San Diego came up with a new cathode material: a crystal made of sulphur and iodine, which significantly boosts the cathode’s electrical conductivity, making it 100 billion times more conductive than crystals made of sulphur alone.
“We are very excited about the discovery of this new material,” says study co-senior author Ping Liu, a professor of nanoengineering and director of the Sustainable Power and Energy Centre. “The dramatic increase in electrical conductivity in sulphur is a surprise and scientifically very interesting.”
Moreover, the new material has a low melting point, meaning the cathode can be easily re-melted after the battery is charged to repair the damaged interfaces during repeated charging and discharging.
“The low melting point of our new cathode material makes repairing the interfaces possible, a long sought-after solution for these batteries,” says study co-first author Jianbin Zhou, a former nanoengineering postdoctoral researcher from Liu’s research group.
In tests, the battery remained stable for more than 400 recharges while retaining 87% of its capacity.
Study co-author Christopher Brooks, chief scientist at Honda Research Institute USA, notes, “The ability for a battery to self-heal simply by raising the temperature could significantly extend the total battery life cycle, creating a potential pathway toward real-world application of solid-state batteries.”
The research team is now working to improve cell engineering designs and scaling up the cell format.
“While much remains to be done to deliver a viable solid-state battery, our work is a significant step,” says Liu.