Smartphones with longer battery life in the offing

Scientists have developed a high-powered, environmentally-safe lithium-sulphur battery with a significantly longer life.

"Common lithium-ion batteries only have a certain capacity," said Kyeongjae Cho, a professor at The University of Texas at Dallas in the US.

"And most people want to use their phones for a longer time," said Cho.

Many smartphone users are familiar with the shelf life of lithium-ion batteries. 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.