Researchers have been using different techniques to create such structures, including microwaving recycled plastic.
“You take the aerogel, which is a long thin tube, and then you slice it – almost like a salami. You take that slice, and compress it, to fit into the battery,” said 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.
“The porous structure of the graphene aerogel is key. It soaks up a high amount of the catholyte, giving you high enough sulphur loading to make the catholyte concept worthwhile. This kind of semi-liquid catholyte is really essential here. It allows the sulphur to cycle back and forth without any losses. It is not lost through dissolution – because it is already dissolved into the catholyte solution,” she said.
Some of the catholyte solution is applied to the separator as well, in order for it to fulfil its electrolyte role. This also maximises the sulphur content of the battery. The new design avoids the two main problems with degradation of lithium sulphur batteries – one, that the sulphur dissolves into the electrolyte and is lost, and two, a ‘shuttling effect’, whereby sulphur molecules migrate from the cathode to the anode. In this design, these undesirable issues can be drastically reduced.
The researchers note, however, that there is still a long journey to go before lithium sulfur battery technology can achieve full market potential. "Since these batteries are produced in an alternative way from most normal batteries, new manufacturing processes will need to be developed to make them commercially viable," said Matic.