Lithium Sulfur Batteries

I was introduced to Lithium Sulfur on joining OXIS Energy. I will not go into all the details, but in brief, lithium sulfur is quite unlike lithium ion chemistry. While lithium ion systems operate on intercalation, lithium sulfur is a solution chemistry based system. In the fully charged state, sulfur is present in the cathode, and the anode material comprises of metallic lithium. When the electrodes are connected through an external load, the sulfur reduces in a multi step reaction to form the final product of precipitated lithium sulfide. The reverse reaction takes place during charging.

Unlike lithium ion, the ions of the lithium sulfur system dissolve into solution and the redox reactions take place there as well. This makes it very difficult for scientists to understand the exact reaction mechanism, as there is no easy experimental method to gauge the exact reaction mechanism occurring at any given point in time. This is where modelling comes in. Using modelling, we can easily plot out a variety of different reaction mechanisms and start to assess if any particular path seems more in line with observed results.

However, my journey in lithium sulfur has been much more than just a study of its mechanism. I was initially a part of and then the technical lead of the Revolutionary Electric Vehicle Battery Project. This was a £3.5 million project sponsored by Innovate UK to develop a demonstrator battery module of Lithium Sulfur cells for an automotive application. Our consortium partners in this were Imperial College, Cranfield University and Ricardo Engineering. This fantastic collaboration was the start of a journey into all things battery, all the way from materials research into the actual assembly of the pack itself.

I started to look into the other engineering aspects of the problem as well. For a start, thermal management of these systems is critical in keeping the pack at operating temperature throughout its lifetime (thus extending the lifetime!). We need to understand how to choose cells that go into packs. Finally, standard battery management systems that apply to lithium ion systems cannot work with lithium sulfur, due to its two stage voltage profile. Thus we've even looked at innovative ways of developing battery management systems. In all of this work, I've been a part of numerous patents, papers and presentations, a few of which are listed below.

Papers associated with this work

  • 1. R. Purkayastha, 'Degradation in Lithium Sulfur batteries' Lithium Sulfur Batteries Eds. Mark Wild and Gregory Offer. London, Wiley 2018 Submitted
  • 2. I. Hunt, T. Zhang, M. Marinescu, R. Purkayastha, P. Kovacik, S. Walus, A. Swiatek, G.J. Offer, Journal of the Electrochemical Society, 165(1), A6073-6080, 2018
  • 3. V. Knap, D.I. Stroe, R. Purkayastha, S. Walus, D.J. Auger, A. Fotouhi, K. Propp, ECS Transactions, 77(11), 479-490, 2017
  • 4. V. Knap, T. Kalogiannis, R. Purkayastha, S. Beczkowski, D.I. Stroe, E. Schaltz, R. Teodorescu, ECS Transactions 77(11), 1919-1927 , 2017
  • 5. S. Walus, G.J. Offer, I. Hunt, Y. Patel, T. Stockley, J. Williams, R. Purkayastha, Energy Storage Materials, 2017
  • 6. A. Fotouhi, D.J. Suger, K. Propp, S. Longo, R. Purkayastha, L. O'Neill, S. Walus, IEEE Transactions on Vehicular Technology, 2017
  • 7. G. Minton, R. Purkayastha, L. Lue, Journal of the Electrochemical Society, 164(11), E3276-E3290, 2017
  • 8. V. Knap, D.I. Stroe, M. Swierczynski, R. Purkayastha, K, Propp, R. Teodorescu, E. Schaltz, Journal of Power Sources, 336, 325-331
  • 9. A. Fotouhi, N. Shateri, D.J. Auger, S. Longo, K. Propp, R. Purkayastha, M. Wild, Synthesis, modelling , Analysis and Simulation Methods and Applications to Circuit Design (SMACD), 2016, 13th International Conference, 2016
  • 10. M. Wild, L. O'Neill, T. Zhang, R. Purkayastha, G. Minton, M. Marinescu, G.J. Offer, Energy and Environmental Science, 8(12), 3477-3494, 2015

Conference presentations

  • 1. R. Purkayastha, S. Schleuter, S. Walus, G. Minton, COMSOL Conference, Munich 2016
  • 2. R. Purkayastha, G. Minton, S. Walus, T. Zhang, M. Marinescu, G. Offer, M. Wild, COMSOL Conference , Grenoble 2015
  • 3. R. Purkayastha ABACUS Seminar, Gaydon 2016