Lithium-sulphur battery given graphene boost
16 Dec 2014
Engineers have designed a cathode for lithium-sulphur batteries which features a thinly wrapped sheet of graphene to boost performance.
The UK-China team consisting of researchers from the University of Cambridge and the Beijing Institute of Technology employed metal organic frameworks (MOFs) as a means of producing a conductive porous carbon cage in which sulphur is designed to act as the host and each sulphur-carbon nanoparticle is designed to act as energy storage units where electrochemical reactions occur.
According to the researchers, MOFs are highly-prized thanks to their wide-ranging applications in hydrogen storage, carbon dioxide sequestration, catalysis and membranes - all of which could result in the commercialisation of performance-enhanced lithium-sulphur batteries.
“Modification of the unit or its framework by doping or polymer coating could take the performance to a whole new level
Lead researcher Kai Xi
Lithium-sulphur batteries are said to boast theoretical specific energy densities considerably greater than those of their cousin, lithium-ion batteries.
The UK-China team’s carbon scaffold design is engineered to act as a physical barrier to confine the active materials within its porous structure, the researchers said.
“This leads to improved cycling stability and high efficiency,” said University of Cambridge research scientist Kai Xi.
Xi and his research partners also found that by wrapping the sulphur-carbon energy storage unit within a thin sheet of flexible graphene, the speed at which electrons and ions could be transported was increased.
“This work provides a basic, but flexible, approach to both enhance the use of sulphur and improve the cycle stability of batteries,” Xi said.
“Modification of the unit or its framework by doping or polymer coating could take the performance to a whole new level.”
According to Xi, the research team will now focus on fabricating hybrid free-standing sulphur cathode systems to achieve high-energy density batteries.
“[That] will involve tailoring novel electrolyte components and building lithium ’protection layers’ to enhance the electrochemical performance of batteries,” he said.
However, using graphene to enhance the energy storage capabilities of lithium-sulphur batteries is by no means a new concept.
Researchers at Lawrence Berkeley Laboratories in California, for example, published a study earlier this year in which lithium-sulphur batteries were modified using graphene oxide.
In that instance, the lithium-sulphur batteries were reported to have the ability to store more than twice the watt-hour per kilogram that their lithium-ion counterparts.
An account of that research was covered in The Guardian newspaper in April.
