Evaluations of Reaction Heterogeneities in Battery Electrodes upon Fast Charging using Operando Focused Beam X-Ray Diffraction

Recently, the use of thick electrodes in lithium-ion batteries has drawn extensive attention as it effectively promotes cell-level energy density by reducing the fraction of inactive components such as separators and current collectors. However, the spatially non-uniform reaction can easily arise within a thick electrode design due to the sluggish electrolyte transport. Understanding the heterogeneous reaction and preventing it is happening are therefore critical as it may result in inferior rate performance, fast capacity degradation, and even safety hazards. This study aims to experimentally evaluate the reaction heterogeneities in thick electrodes by employing operando focused beam X-ray diffraction (XRD). We will compare the traditional graphite anode with laser ablated sample in full cells upon 6C fast charging, therefore, quantitatively assessing the degree of reaction along the depth direction in electrodes under operational conditions. A detailed comparison between the experiments and simulations will help us better understand the origin of reaction heterogeneities in electrodes and guide the design of battery materials and structures in the future.