Lithium-Sulfur Battery Lab Tests Show High Energy Density

By  Antony Ingram – Nov 29, 2013
The Graphene Carbon LatticeThe Graphene Carbon Lattice

The month wouldn’t be complete without another battery technology breakthrough, and this time it’s the turn of lithium-sulfur technology.

Researchers at the US Department of Energy’s Lawrence Berkeley National Laboratory are experimenting with a lithium-sulfur battery design with twice the specific energy of lithium-ion batteries, and a usefully long life under repeated charging and discharging cycles.

According to Green Car Congress, such batteries would also be cheaper and safer than lithium-ion designs–without the overheating and fire issues that have made the news over the last few years.

In a paper in the ACS journal Nano Letters, the researchers explained how they’ve overcome one of the main limitations of existing lithium-sulfur designs–a poor life cycle.

Normally, lithium polysulfide particles dissolve in the electrolyte during discharging and react with the lithium anode, forming a barrier layer. The conversion reaction under charging and discharging can also cause the sulfur electrode to swell and contract, causing damage.

To prevent these issues, the team uses a sulfur-graphene oxide nanocomposite cathode.

Graphene–to recap–is considered one of the most important materials developed for many years. Nanoparticles of the material are built from single-atom-thick sheets of carbon–with incredibly strong bonds and a huge surface area that has seen them used widely in battery technology since its discovery.

Not only does the sulfur-graphene oxide cathode allow high charging and discharging rates, but its flexibility prevents electrode damage during the expansion and contraction process. This is further mitigated by an ‘elastromeric binder’.

A new ionic liquid electrolyte also improves the battery chemistry and prevents the dissolution of lithium polysulfide particles, helping the battery charge and discharge at a faster rate. After 1,500 cycles, the battery retains over 96 percent coulombic efficiency–the efficiency with which electrons are transferred during the battery’s cycles.

By now, you can probably guess the technology’s main benefits, as it’s common to other experimental battery technologies: High specific capacity means greater energy storage for electric cars with greater range–or smaller, lighter batteries for the same range. High reliability is also a benefit.

You can find out further developments in our electric car battery breakthrough guide.