The Graphene Carbon LatticeEnlarge Photo
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.