The development of light, long-lasting rechargeable batteries (and the invention of the lithium-ion battery, now over 25 years ago) has been an integral part of the portable electronics revolution. This revolution has transformed the way in which we communicate and transfer and access data globally. Rechargeable batteries are now playing an increasingly important role in transport and grid applications, but the introduction of these devices comes with different sets of challenges. New technologies are being investigated, such as those using sodium and magnesium ions instead of lithium, and the flow of materials in an out of the electrochemical cell (in redox flow batteries).  Importantly, fundamental science is key to producing non-incremental advances and to develop new strategies for energy storage and conversion. 

The first part of this talk will focus on our work on the development of methods that allow devices to be probed while they are operating (i.e., in-situ). This allows, for example, the transformations of the various cell components to be followed under realistic conditions without having to disassemble and take apart the cell.  To this end, the application of new in and ex-situ Nuclear Magnetic Resonance (NMR), magnetic resonance imaging (MRI) and X-ray diffraction approaches to correlate structure and dynamics with function in lithium- and sodium-ion batteries and supercapacitors will be described. The in-situ approach allows processes to be captured, which are very difficult to detect directly by ex-situ methods.  For example, we can detect side reactions involving the electrolyte and the electrode materials, sorption processes at the electrolyte-electrode interface, and processes that occur during extremely fast charging and discharging. Complementary Ex-situ investigations allow more detailed structural studies to be performed, to correlate local and long-range structure with performance.  To illustrate, we have used NMR, theory and pair distribution function (PDF) analysis methods, to determine the local and longer range structures of a series of amorphous and disordered Li and Na anode structures, including C, Sn, Ge, Si and P.  Both thermodynamic and metastable phases are identified via theoretical (DFT) approaches and compared with NMR, PDF and (in situ) diffraction measurements, the materials often transforming via metastable structures.  Finally, many of the battery electrode materials are paramagnetic and their study has involved the development of new experimental (NMR) and theoretical approaches to acquire and interpret spectra. Recent studies to correlate lithium hyperfine shifts with local structure and to probe dynamics will be described.      

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