Solid State Chemistry
Diffusion and Transport in Battery Electrolytes via Pulsed-Field Gradient Nuclear Magnetic Resonance (PFG-NMR)
The Tang Group, together with Prof. Jeffrey A. Reimer at UC Berkeley, have designed and developed pulsed-field gradient diffusion and multidimensional relaxometry methods to assess the transport of small molecules and ions in complex porous media. The dynamics of these species are of fundamental importance to the development of theories for transport, as well as the crafting of new electrochemical systems for energy storage and conversion.
We have implemented electrophoretic NMR, wherein we discern ionic and molecular transport under an applied electrochemical potential to further our fundamental understanding and design of battery electrolytes.
Nuclear Magnetic Resonance (NMR) in Battery and Catalysis
Nuclear Magnetic Resonance (NMR) and Electron Paramagnetic Resonance (EPR) spectroscopies offer invaluable data about real-time changes in the local and electronic structures of electrochemical devices. NMR, which investigates the local structure surrounding selected atoms within a material, is becoming a favored method for studying processes within electrode and electrolyte materials in devices like batteries and fuel cells. The use of EPR spectroscopy, which analyzes environments with unpaired electrons, is advantageous especially since numerous electrode materials are paramagnetic, meaning they possess unpaired electrons, often originating from transition metal species.
Our group is actively working to advance high-resolution NMR and EPR techniques for exploring paramagnetic electrode materials, such as those containing unpaired transition metal electrons. In addition, we are creating theoretical tools to forecast paramagnetic NMR and EPR parameters. While most NMR and EPR analyses on battery materials are done ex situ, meaning studying samples at different stages of charging or discharging, we are progressing towards creating operando electrochemical cells. These cells would enable us to track redox and structural changes continuously while the battery is charging or discharging within the NMR and EPR magnet.
