4D operando X-ray nano-holo-tomography reveals multiscale chemomechanics in Silicon-Graphite anode

Abstract

Linking electrode microstructure to electrochemical performance is essential for optimizing Li-ion batteries. However, this requires mechanistic 4D observations at ultimate spatio-temporal scales, which remains elusive. Here we demonstrate the use of operando synchrotron X-ray nano-holo-tomography combined with Digital Volume Correlation to track chemomechanical dynamics at both particle (local) and electrode (averaged) scales. Quantitative scale-bridging image analysis is applied to a high-capacity silicon-graphite anode during its formation cycle. Our findings reveal that local diffusion properties, graphite particle morphology and position in the electrode, distance to silicon clusters, surface contact with electrolyte and mechanical deformations, all have a direct impact on the local electrochemical activity and irreversibility - but these parameters are not equally important. Particularly, we identify fast diffusion channels that play a key role and counterbalance intrinsic depth-dependent reaction heterogeneities due to ionic/electronic diffusion limitations. The various structural factors that determine Gr-Si battery performance beyond ensemble properties are classified using a scale of influence, providing a practical framework for the optimization of materials and electrode manufacturing.