“Probing bulk and interfacial properties of energy storage materials by high sensitivity solid state NMR spectroscopy”
The development of high-energy, long-lifetime energy storage systems based on rechargeable batteries relies on our ability to control charge storage and degradation processes in the bulk of the electrode materials and at the electrode-electrolyte interface. NMR spectroscopy is exceptionally suited to follow the electrochemical and chemical processes in the bulk of the electrodes and electrolyte, providing atomic scale structural insight into charge storage mechanisms and ion transport properties. However, processes at interfaces, which are governing charge transport between the electrode and the electrolyte, are much harder to study. These processes involve the formation of thin, heterogeneous, and disordered interphases. While NMR is in principle an excellent approach for probing disordered phases, its low sensitivity presents an enormous challenge in the detection of interfacial processes.
I will describe recent approaches to overcome this limitation by the use of Dynamic Nuclear Polarization (DNP). In DNP, the large electron spin polarization is used to boost the sensitivity of NMR spectroscopy by orders of magnitude. I will show how we can use this approach to detect the solid-electrolyte interphase (SEI), as well as the electrode’s bulk, with unprecedented sensitivity. Furthermore, I will discuss the feasibility of using magnetic resonance methods to correlate the SEI composition with its ion transport properties – the least understood aspect of the SEI, which is essential for developing long-lasting energy storage systems.