Sometimes a charge can last roughly a day. Cho, along with research associate Jeongwoon Hwang, worked with other regional scientists to improve lithium-sulphur batteries, long considered by many to be an evolution from lithium-ion batteries. Lithium-sulphur batteries have important advantages over lithium-ion batteries. According to Cho, they are less expensive to make, weigh less, store almost twice the energy of lithium-ion batteries and are better for the environment.
"A lithium-sulphur battery is what most of the research community thinks is the next generation of battery," Cho said. "It has a capacity of about three to five times higher than lithium-ion batteries, meaning if you are used to a phone lasting for three hours, you can use it for nine to 15 hours with a lithium-sulphur battery," he said. However, lithium-sulphur batteries are not without problems. Sulphur is a poor electrical conductor and can become unstable over just several charge-and-recharge cycles.
Electrodes breaking down is another reason lithium-sulphur batteries are not mainstream. Scientists have tried to improve lithium-sulphur batteries by putting lithium metal on one electrode and sulphur on the other. However, lithium metal often is too unstable, and sulphur too insulating. The scientists discovered a technology that produced a sulphur-carbon nanotube substance that created more conductivity on one electrode, and a nanomaterial coating to create stability for the other.
The researchers discovered that molybdenum, a metallic element often used to strengthen and harden steel, creates a material that adjusts the thickness of the coating when combined with two atoms of sulphur, a coating thinner than the silk of a spider-web. They found it improved stability and compensated for poor conductivity of sulphur, thus allowing for greater power density and making lithium-sulphur batteries more commercially viable.
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