In situ EPR imaging for lithium/sodium batteries

In situ electron paramagnetic resonance imaging (EPRI), particularly in situ top-view EPRI, is an indispensable analytical technique for revealing the electrochemical reaction mechanisms in battery research, holding broad promise for energy storage development. Benefiting from its inherently non-invasive visualization capability, the technique achieves real-time quantitative monitoring of internal phenomena through top-view observation, offering unprecedented two-dimensional and three-dimensional presentations of localized electrochemical processes. This review provides a comprehensive overview of in situ EPRI in lithium/sodium batteries. First, we briefly describe the basic theoretical background and hardware configuration of EPRI. Following that, we provide representative application cases for each specific battery system, illustrating in detail the usage of in situ top-view EPRI for characterizing lithium/sodium plating behavior, together with metal ions in the cathode and the electrolyte in liquid/solid batteries. Finally, we discuss the current challenges of the technique and proposed directions for development, aiming to foster deeper integration between EPR and battery research communities for mutual progress.