Theoretically-speaking, lithium-sulfur batteries [LiS] could be vastly superior to current lithium-ion [Li-Ion] battery technology, except for a couple of debilitating problems. Recent research done at Lawrence Berkeley National Laboratory [BNL] seems to indicate that graphene has come to the rescue, once again.
In comparison to Li-Ion batteries, LiS batteries have more capacity, up to four times more, according to some studies, up to ten times more in other studies. Lithium-sulfur batteries are also non-toxic and cheaper than Li-Ion. Unfortunately, there are a couple of problems. First, LiS batteries are brittle, which would make them fairly useless in an electric vehicle. Second, LiS batteries can only be cycled perhaps a dozen times before they can no longer accept a charge. The sulfur is the problem, which forms polysulfide ions that deposit on the lithium anode, eventually forming a barrier.
Researchers at BNL turned to graphene to solve their problem, a wonderful material that scientists and researchers are still trying to figure out uses for. In this case, BNL used nanoparticle graphene oxide coated with sulfur, or sulfur-graphene oxide [S-GO]. In a lithium-sulfur battery, S-GO is used as a cathode opposite a lithium metal anode. On discharge, the sulfur converts to lithium-sulfide, while the graphene-oxide keeps it from dispersing. On recharging, the lithium is released, while the graphene-oxide keeps the sulfur from bonding to the lithium anode.
Researchers at BNL are striving to double the energy density of current Li-Ion technology, around 400Wh/kg, while boosting the cycles up to 1,500 or so. Lithium-sulfur battery technology, boosted by sulfur-graphene oxide, could be the ticket to cheap and capable electric vehicles of the future.
Image © Lawrence Berkeley National Laboratory