Revealing Lithiation Kinetics and Battery Degradation Pathway in LiMn₂O₄-Based Commercial Cathodes via Electrochemical Strain Microscopy

The capacity fade during the cycling of lithium batteries is a key factor limiting further progress in the improvement of electric vehicles, wearable electronic devices, alternative energy sources, etc. One of the main reasons for capacity loss is battery cathode degradation, which significantly influences the battery lifetime. Despite in-depth knowledge of battery degradation at the chemical level, the kinetics of the degradation at the resolution of the individual elements of the cathode are not fully understood. Here, we studied lithiation kinetics in commercial cathodes based on lithium manganese spinel using the electrochemical strain microscopy local method. Supported by the experimental finding, the “viscous fingers” model of lithium ions intercalation–deintercalation in individual particles of the cathode was proposed. The non-linear dynamics of the lithiation front were suggested to be stimulated by the non-uniform stress field and gradient of the chemical potential. Irregularity of the lithiation front causes the formation of the residual lithiated pocket in the delithiated particles, which effectively reduces the volume available for chemical reaction. The obtained results shed further light on the degradation of the lithium battery cathodes and can be applicable for other cathode materials.