A team of Engineers from Chalmers University of Technology, Sweden has revealed a breakthrough in battery tech.
The teams work focused on improving lithium-sulphur batteries and solving a number of issues with the existing technology.
Their breakthrough is based on using a sponge-like gel within the battery cell. Using this approach the team were able to create a battery which made better use of the sulphur in it.
How do tradtional batteries work?
To understand why this could be game-changing for our batteries we need to look at how batteries work.
A traditional battery is made from four elements.
Two supporting electrodes are coated with an active substance (these are known as an anode and a cathode).
In between is an electrolyte. Normally this is a liquid that allows ions to move freely between them.
Finally, there is a physical barrier which prevents the two electrodes from touching will still allowing the ions to move freely.
Introducing the “catholyte”
The dream in battery tech is to combine the electrolyte and cathode into a single liquid. A catholyte.
Doing this would be a big deal as it would allow batteries to weigh less and charge faster and hold more power.
The Chalmers team has done exactly that by developing a graphene aerogel.
Their proof of concept research proves the concept is viable and offers a promising glimpse at the future.
Carmen Cavallo of the Department of Physics at Chalmers, and lead researcher on the study explains that the team took the “aerogel, which is a long thin cylinder, and then you slice it—almost like a salami” then took “that slice, and compress[ed] it to fit into the battery”
Cavallo technique results is a rich sulphur solution – a catholyte – which can then be added to the battery. This gel is incredibly porous and acts as a support, soaking up the solution like a sponge.
Cavallo explains that “the porous structure of the graphene aerogel is key [as] it soaks up a high amount of the catholyte[.] 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.”
Has existing battery technology peaked?
The breakthrough is welcome. Currently, all commercially available batteries are lithium-ion based.
This type of battery is nearing its limits and new chemical approaches, like the teams’ research, are becoming critical for applications with higher power requirements.
A Lithium sulphur battery would offer several advantages over existing tech.
Importantly they have a much higher energy density than lithium-ion batteries. The very best lithium-ion batteries on the market operate at about 300 watt-hours per kg and in lab conditions, they offer a theoretical maximum of around 350.
Lithium sulphur batteries have a theoretical energy density of around 1000-1500 watt-hours per kg.
However, there are real-world changing implications if Lithium Sulphur hits the mainstream.
Sulhpur is cheap, abundant and environmentally friendly (compared to Lithium), and does not contain fluorine which is particularly environmentally harmful.
The new prototype still has some way to go before it becomes commercially viable.
The new design has improved on the common problems with existing lithium sulphur batteries – they can be unstable and have low-cycle life – but it still has a long way to go before we might see them on the shelves or in our phones.
Published: Carmen Cavallo et al, A free-standing reduced graphene oxide aerogel as supporting electrode in a fluorine-free Li2S8 catholyte Li-S battery, Journal of Power Sources (2019). DOI: 10.1016/j.jpowsour.2019.01.081
