Electron Paramagnetic Resonance in Rechargeable Battery Science: A Review

As the demand for higher energy density and improved safety in battery energy systems continues to grow, gaining a more detailed understanding of the underlying microscopic mechanisms has become critical. However, conventional characterization techniques often fall short of fully elucidating complex battery processes. Electron paramagnetic resonance (EPR), by detecting unpaired electrons during battery charge–discharge processes, offers a powerful tool for probing these microscopic reactions. In this Review, we first provide a brief background on the importance of EPR in battery research, followed by the fundamental principles of this technique, and then discuss its recent applications in battery systems from three perspectives: the cathode, the electrolyte, and the anode. Furthermore, we explore how EPR, in combination with advanced complementary characterization methods, can be employed to investigate battery reaction mechanisms in greater depth. Finally, we summarize the current challenges facing EPR in the context of rechargeable battery science and outline potential directions for future advancements.