We all depend on the performance of rechargeable batteries which are used in our mobile phones and laptops. With the increasing worldwide demand for energy and the efforts to move towards electric transportation and use of renewable energy sources (such as solar and wind) these batteries are bound to play an even more significant role in our lives. To do so, rechargeable batteries, which are currently based on lithium ion intercalation chemistry, need to provide more energy and last longer (while maintaining safety and low cost).
Thus there is great interest in developing high energy materials for lithium ion batteries as well as novel battery chemistries beyond lithium ion. The development of successful battery systems requires detailed mechanistic understanding of how the battery materials function at the molecular level. Furthermore, since battery cells are complex systems composed of electrodes, electrolyte salt and solvents, additives, polymer binders etc. their performance and cycle life depend strongly on the interactions between all these components.
Our research is focused on elucidating the electrochemical and chemical processes in Li-ion and novel battery chemistries. We use and develop advanced solid state NMR techniques to gain molecular level insight into how these systems function and why they fail – so that we can improve them. In addition to NMR we use more ‘traditional’ characterization tools such as X-ray diffraction and electron microscopy.
Some examples for the use of NMR in the study of battery cells and materials:
- Li-Oxygen (Air): Direct Detection of Discharge Products in Lithium-Oxygen Batteries by Solid State NMR. Angewandte Chemie (2012) 51:(34)8560-8563; Monitoring the Electrochemical Processes in the Lithium-Air Battery by Solid State NMR Spectroscopy. The Journal of Physical Chemistry C (2013) 117:(51)26929-26939; Cycling li-O2 Batteries Via Lioh Formation and Decomposition. Science (2015) 350:(6260)530-533.
- Li-Sulfur: Ab Initio Structure Search and in Situ 7li NMR Studies of Discharge Products in the li–s Battery System. Journal of the American Chemical Society (2014) 136:(46)16368-16377
- Li-ion: Multiple Redox Modes in the Reversible Lithiation of High-Capacity, Peierls-Distorted Vanadium Sulfide. Journal of the American Chemical Society (2015) 137:(26)8499-8508; Voltage Dependent Solid Electrolyte Interphase Formation in Silicon Electrodes: Monitoring the Formation of Organic Decomposition Products. Chemistry of Materials (2016) 28:(1)385-398.