Nano-cages made of linalool and sulfur increase the service life and storage capacity of sodium-sulfur batteries
Lavender oil could help solve a problem in the energy transition. A team from the Max Planck Institute of Colloids and Interfaces has created a material from linalool, the main component of lavender oil, and sulfur that could make sodium-sulfur batteries more durable and powerful. Such batteries could store electricity from renewable sources.
In the future, linalool, a main component of lavender, could help to make sodium-sulphur batteries more durable and efficient.
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It is a crucial question in the energy transition: how can electricity from wind power and photovoltaics be stored when it is not needed? Large batteries are one option. And sulfur batteries, in particular sodium-sulfur batteries offer several advantages over lithium batteries as stationary storage units. The materials from which they are made are much more readily available than lithium and cobalt, two essential components of lithium-ion batteries. The mining of these two metals also often damages the environment and locally causes social and political upheaval. However, sodium-sulfur batteries can store less energy in relation to their weight than lithium batteries and are also not as durable. Lavender oil with its main component linalool could now help to extend the service life of sodium-sulfur-batteries, as a team from the Max Planck Institute of Colloids and Interfaces reports in the journal Small. "It's fascinating to design future batteries with something that grows in our gardens," says Paolo Giusto, group leader at the Max Planck Institute of Colloids and Interfaces.
80 percent of original charging capacity after 1500 charging cycles
The fact that usually the storage capacity of a sodium-sulfur battery drops significantly after a few charging cycles is mainly due to what is known as sulfur shuttling. Polysulfides, formed at the cathode, migrate to the anode, reacting with it and ultimately causing the battery to fail. Evgeny Senokos, who is developing alternatives to lithium batteries at the Max Planck Institute of Colloids and Interfaces, is now preventing this by locking the polysulfides in a carbon cage. "We create a stable and dense nanomaterial from linalool and sulfur and thus obtain batteries that are more durable and have a higher energy density than today's sodium-sulfur batteries", explains Evgeny Senokos. Linalool and sulfur form a nanostructured material whose nanopores are around 100,000 times narrower than a human hair and trap the bulky polysulfides. When charging and discharging the battery, however, the small sodium ions can still penetrate the pores or flow out of them. In consequence the battery cells tested by the Potsdam team achieved more than 80 percent of their original charging capacity after 1500 charging and discharging cycles.
The carbon-nanovessels enclosing the sulfur not only increase the service life of sodium-sulfur batteries, but also their storage capacity: as the sulfur is fixed in the cage, it is almost completely available for the reaction. The novel cathode material can therefore deliver more than 600. "By taking a creative look at nature, we are finding solutions to many of the challenges posed by the energy transition, " says Paolo Giusto. "I am confident that our development will attract increasing attention in the near future and enable us to make the leap of this technology from laboratory to practice."
