Chalmers University of Technology, in Phys.org

To meet the demands of an electric future, new battery technologies will be essential. One option is lithium sulphur batteries, which offer a theoretical energy density more than five times that of lithium ion batteries. Researchers at Chalmers University of Technology, Sweden, recently unveiled a promising breakthrough for this type of battery, using a catholyte with the help of a graphene sponge.

The researchers' novel idea is a porous, sponge-like aerogel made of reduced graphene oxide that acts as a free-standing electrode in the battery cell and allows for better and higher utilisation of sulphur.

A traditional battery consists of four parts. First, there are two supporting electrodes coated with an active substance, which are known as an anode and a cathode. In between them is an electrolyte, generally a liquid, allowing ions to be transferred back and forth. The fourth component is a separator, which acts as a physical barrier, preventing contact between the two electrodes whilst still allowing the transfer of ions.

The researchers previously experimented with combining the cathode and electrolyte into one liquid, a so-called 'catholyte.' The concept can help save weight in the battery, as well as offer faster charging and better power capabilities. Now, with the development of the graphene aerogel, the concept has proved viable, offering some very promising results.

Taking a standard coin cell battery case, the researchers first inserted a thin layer of the porous graphene aerogel. "You take the aerogel, which is a long thin cylinder, and then you slice it—almost like a salami. You take that slice, and compress it to fit into the battery," says Carmen Cavallo of the Department of Physics at Chalmers, and lead researcher on the study. Then, a sulphur-rich solution, the catholyte, is added to the battery. The highly porous aerogel acts as the support, soaking up the solution like a sponge.