Batteries are a major focus for researchers trying to move away from polluting fossil fuels. From green transport to storing the energy produced by wind turbines, batteries are already revolutionising our consumption of fuel.
The current industry standard – lithium-ion batteries – are struggling to keep up with ever increasing demands. Material chemists are searching for the next generation of batteries that will be able to offer value, performance, and sustainability.
Lithium-sulphur batteries could be the answer. Sulphur is naturally abundant, and cheaper than the cobalt or iron compounds found in lithium-ion batteries. They also boast a huge potential energy capacity – up to 1675 mA h g−1 compared to only 300 mA h g−1 for their LIB counterparts.
But structural problems have hampered the commercialisation of Lithium-sulphur batteries. The so called polysulfide “shuttle” effect causes a progressive loss of material from the cathode, worsening the capacity and performance of the battery with each charge cycle.
In this study, published by RSC Advances, researchers targeted this problem by testing Sulphur/carbon composites for the cathode. Carbon can suppress the shuttle effect, but too much effects the energy density of the battery. So how much carbon is the perfect amount?
Another challenge is creating the sulphur/carbon composites via a safe method, which can be reproduced at mass scale in global manufacturing. The group selected dry melt-diffusion to load sulphur into the carbon, a method that will be sustainable in industry applications.
Group Leader Dr Chun Ann Huang says:
Although carbon black in the composite material increased electrical conductivity, we found that an increased amount of carbon black in melt-diffusion led to increased structural heterogeneity in the cathodes, more prominent cracks, and a lower mechanical strength. We reported a systematic study of the optimal proportion of carbon black in melt-diffusion to achieve the highest capacity at various C rates based on the total cathode mass and rationalised the performance through the number of C-S bonds in the composite material, surface area, pore size and pore volume, and homogeneity in the cathode microstructure.
This paper forms part of Tayeba Safdar’s doctoral research. Tayeba is funded by the Faraday Institution for her PhD at Imperial College London, and is a visitor in the physical sciences lab at Research Complex at Harwell. Read the full paper here.
