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Graphene sponge paves the way for future batteries
https://www.chalmers.se/en/departments/physics/news/Pages/Graphene_sponge_paves_the_way_for_future_batteries.aspx
The Chalmers design for a lithium sulphur battery. The highly porous quality of the graphene aerogel allows for high enough soaking of sulphur to make the catholyte concept worthwhile.
Illustration: Yen Strandqvist
Graphene sponge paves the way for future batteries
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 roughly 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.
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The problem with lithium sulphur batteries so far has been their instability, and consequent low cycle life. Current versions degenerate fast and have a limited life span with an impractically low number of cycles. But in testing of their new prototype, the Chalmers researchers demonstrated an 85% capacity retention after 350 cycles.
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