Hyperpolarized ¹³C NMR by Dissolution DNP Enables Snapshot Detection of Degradation Products in Lithium-Ion Battery Electrolytes

Dissolution Dynamic Nuclear Polarization (dDNP) is a powerful hyperpolarization technique enabling sensitivity gains beyond 4 orders of magnitude in solution nuclear magnetic resonance (NMR). Over the last decades, researchers' efforts have led to an extension of dDNP applications in numerous research fields. Lithium-ion batteries are one of the most widespread types of rechargeable batteries, which calls for a deeper understanding of the various physicochemical mechanisms involved in making them more efficient, safe, and sustainable. One of the key challenges lies in better understanding the degradation of the battery electrolyte to mitigate it, as it can significantly impact the battery's performance. While NMR has been used in attempts to understand these mechanisms, notably by investigating the degradation products, the intrinsic lack of sensitivity of this technique, combined with the limited accessible volume of such compounds, makes its application often challenging. In this work, we combine several state-of-the-art dDNP methodologies, including the use of recently introduced hyperpolarizing polymers (HYPOPs), to acquire hyperpolarized ¹³C NMR spectra of battery electrolytes. We show that we can successfully detect ¹³C signals on formulated battery electrolyte solutions in different degradation stages on a 600 MHz spectrometer, with sensitivity gains of up to 3 orders of magnitude. This work paves the way for studying lithium-ion battery electrolyte degradation under real usage conditions (cycling, thermal aging, air exposure, etc.) with a ¹³C detection limit below the micromolar range. This methodology has the potential to provide new insights into degradation mechanisms and the role and effectiveness of additives to mitigate electrolyte degradation.