Every Thursday, Laboratory Equipment features a Scientist of the Week, chosen from the science industry’s latest headlines. This week’s scientist is Nikhil Koratkar from Rensselaer Polytechnic Institute. He and his team are working to create graphene batteries that could be used in electric cars.
Q: What made you interested in seeing how exposure to a laser would impact graphene paper?
A: We wanted to reduce graphene oxide to graphene in a simple and cost-effective manner, while at the same time opening up the tightly packed pores in graphene oxide. We felt that such an open structure might perform well in Li-ion batteries, especially for high rate (or high power) applications. One step photo-thermal reduction and exfoliation of graphene oxide seems to be a very elegant way to accomplish this.
Q: What are the future implications of your research and findings?
A: Graphite slurries are used in today's Li-ion cells. We make a strong case for replacing graphite with our graphene paper electrode. More work is needed in terms of scalability and going beyond coin cell testing, but the concept is very promising.
Q: What was the most surprising thing you found in your research?
A: We knew we had a open pore structure with a multitude of cracks, pores and inter-sheet voids, so we were confident that we would do well at high charge/discharge rates, since Li ions would be able to penetrate deep into the graphene structure via electrolyte transport and the distances over which the Li ions need to intercalate or diffuse would be drastically reduced.
However, we did not expect that the highly damaged graphene paper would give stable performance. We thought that it might disintegrate or deteriorate over time. We were pleasantly surprised to see that the electrodes have lasted for over 6,000 charge/discharge cycles in some cases without any loss in perforance.
We were also surprised at the low charge transfer and interfacial resistance of the graphene paper. This suggests that photo-thermal heating seems to have cross-linked the individual graphene sheets enabling efficient electron conductivity which is also an important attribute for high power electrodes.
Q: What is the take home message of your research and results?
A: We have an battery anode material that enables ultra-high power densities to be achieved in addition to high energy density. The electrode material is structurall robust and lasts for thousands of cycles of operation without any significant degradation in performance.
Q: What is next for you and your research?
A: We want to build a full cell by combining our electrode (anode) with a high rate capable cathode. We also want to study the mass scalability of the electrode by varying the graphene paper thickness.