Visualizing Reaction Distributions for Materials Validation and Failure Analysis in Li-Ion Batteries

The market for lithium-ion batteries (LIBs) is projected to grow from 36.7 billion to 128.3 billion in less than a decade 1. Large-scale demands for more robust LIBs are limited by battery cycle life and cost. In order to expedite the development of battery technology, current analytical techniques used to validate electrode morphology must be improved. Even excellent battery materials may result in poor electrode performance due to poor processing, such as suboptimal mixing, coating, or drying. Flawed processing leads to heterogeneities at either the particle or electrode length scale, resulting in inhomogeneous transport of lithium ions and eventually degradation and failure in LIBs 2. Limited techniques can deconvolute materials from processing effects through visualization. Methods visualizing reaction distribution in LIBs include thermal imaging, which is suitable technique for macroscale pack-level analysis, and state-of-charge electronic structure maps, which are suited for molecular analysis. These techniques are unable to characterize electrode performance at the mesoscale level and thus are inappropriate for characterizing local reactivity of electrode. Optical microscopy provides a compromise between spatial resolution and experimental accessibility. However, it is constrained to graphite and a few other battery materials that change color. In this work, we explore fluorescent microscopy as a technique to visualize battery reaction distributions. A redox-active fluorescent probe molecule illuminates electrode heterogeneities, such as hot-spots or dead-zones 3. Developing facile techniques by which researchers can evaluate electrode materials beyond cell cycling will be critical for meeting future battery technology demands. Choudhary, A. & Prasad, E. Lithium-ion Battery Market Size and Share | Industry Analysis by 2027. Allied Market Research https://www.alliedmarketresearch.com/lithium-ion-battery-market. Chung, D.-W., Shearing, P. R., Brandon, N. P., Harris, S. J. & García, R. E. Particle Size Polydispersity in Li-Ion Batteries. J. Electrochem. Soc. 161, A422–A430 (2014). Harris, S. J. & Lu, P. Effects of Inhomogeneities—Nanoscale to Mesoscale—on the Durability of Li-Ion Batteries. J. Phys. Chem. C 117, 6481–6492 (2013).