Study: New Lithium-Sulfur Battery Could Replace Lithium-Ion

A research team said it has found a way to lengthen the lifespan of lithium-sulfur batteries, creating a product that could potentially replace the lithium-ion batteries currently used in electrified vehicles.

The team from South Korea’s Hanyang University recently published its study on lithium-sulfur (li-S) batteries in the American Chemical Society’s Journal, Nano Letters.

“Lithium-sulfur batteries could become an excellent alternative to replace the currently used lithium-ion batteries due to their higher energy density and lower production cost,” said the researchers.

Finding a battery chemistry with a high energy density is essential for electrified vehicles, as explained by Sami Hakani in Yale Scientific Magazine.

“Energy density is a metric of how much energy a battery can store for every unit of its weight,” said Hakani.

“Because lithium-ion batteries use heavy transition metal components to operate, their energy density is low, and so is not optimized for bigger applications like electric vehicles.

“As a result, increasing the driving range for automotive applications by just adding more batteries would result in a significant weight gain and decreased overall performance.”

Reprinted with permission. Copyright 2015 American Chemical Society.

Reprinted with permission. Copyright 2015 American Chemical Society.

With more than twice the energy density of li-ion, the li-S batteries developed in this study could double the driving range of a battery electric vehicle without adding extra pounds or bulk.

Cost is also key, with rechargeable batteries constituting a significant portion of a vehicle’s price. Sulfur is readily available at a low cost, said the research team, making it an affordable alternative to li-ion.

But, up until this study, lithium-ion could outperform lithium-sulfur in one crucial category: lifespan.

SEE ALSO: Volkswagen Ponders Next Battery Type For EVs

“Lithium-ion batteries are known for their high cyclability, which is a measure of the number of times they can be recharged before they begin to break down,” Hakani said.

But problems with the materials in a traditional lithium-sulfur battery meant the battery also had a shorter lifespan.

“Commercialization of lithium–sulfur batteries has so far been limited due to the cyclability problems associated with both the sulfur cathode and the lithium–metal anode,” said the Hanyang University researchers.

To extend the battery’s lifespan, the team designed a battery cell that uses a lithiated silicon oxide (Si/SiOx) nanosphere anode in place of the lithium-metal anode. The sulfur cathode was also replaced with a highly reversible dual-type sulfur cathode (solid sulfur electrode and polysulfide catholyte).

SEE ALSO: Bosch: Battery Prices Will Drop, Electrified Powertrains Will Spread

According to the team’s tests, the newly-designed li-S battery had the same cycle life of a li-ion battery.

“We believe that these results might advance the development of practical lithium−sulfur batteries, particularly for use in emerging markets, including portable devices, electric vehicles, and large-scale power storage systems for renewable energies,” said the research team.

Carmakers are continually assessing the best chemistry for their rechargeable batteries. Most use li-ion battery packs, though a few brands still mount nickel metal hydride batteries in their electrified vehicles. If the Hanyang University team’s research leads to a commercially ready product that can outdrive and outlast li-ion, carmakers may soon have another option to consider.

 

Photo: An employee assembles lithium-ion battery modules at the Bayerische Motoren Werke AG (BMW) automobile manufacturing plant in Dingolfing, Germany. Photographer: Krisztian Bocsi/Bloomberg via Getty Images

 

Green Car Congress