5D Analysis of Capacity Degradation in Battery Electrodes Enabled by Operando CT‐XANES

Abstract

For devices encountering long‐term stability challenges, a precise evaluation of degradation is of paramount importance. However, methods for comprehensively elucidating the degradation mechanisms in devices, particularly those undergoing dynamic chemical and mechanical changes during operation, such as batteries, are limited. Here, a method is presented using operando computed tomography combined with X‐ray absorption near‐edge structure spectroscopy (CT‐XANES) that can directly track the evolution of the 3D distribution of the local capacity loss in battery electrodes during (dis)charge cycles, thereby enabling a five‐dimensional (the 3D spatial coordinates, time, and chemical state) analysis of the degradation. This paper demonstrates that the method can quantify the spatiotemporal dynamics of the local capacity degradation within an electrode during cycling, which has been truncated by existing bulk techniques, and correlate it with the overall electrode performance degradation. Furthermore, the method demonstrates its capability to uncover the correlation among observed local capacity degradation within electrodes, reaction history during past (dis)charge cycles, and electrode microstructure. The method thus provides critical insights into the identification of degradation factors that are not available through existing methods, and therefore, will contribute to the development of batteries with long‐term stability.

Development of Measurement/Analysis Techniques to Bridge Microscopic and Macroscopic Electrochemical Phenomena in Energy Storage Devices

“…Against this background, the author and his colleagues have been developing techniques based on spectroscopic chemical imaging techniques using synchrotron radiation, that enables operando 3D visualization of the heterogeneous electrochemical reactions within the composite electrode of LIBs and solid-state LIBs (SSLIBs). [30][31][32] This section introduces our work on operando 3D observations of the heterogeneous reactions in composite SSLIB electrodes.…”

“…Using this technique, we analyzed the capacity degradation mechanism of a model composite SSLIB electrode, employing LiNi 0.33 Mn 0.33 Co 0.33 O 2 (NMC) as the cathode active material and a LISICON-type oxide electrolyte as the solid electrolyte, during (dis)charge cycles. 32 Figure 4 shows an example of the 3D differential image analysis of the capacity degradation in the model composite SSLIB electrode. The upper part of Fig.…”

“…Furthermore, by analyzing the correlation with the electrode microstructure, the harsh degradation during discharge was found to be more pronounced near the electrode/solid electrolyte interface. 32 As described above, while the charge-discharge curves can only provide information on the average capacity degradation of the entire electrode, the 3D capacity loss maps can offer more detailed and quantitative insights into the local capacity degradation within electrodes, providing crucial insights into the design guidelines of the electrodes with better performance and longer lifespan that were previously inaccessible through conventional approaches.…”