Understanding kinetic and thermodynamic properties of blended cathode materials for lithium-ion batteries

Using electrodes with multiple types of active materials has been shown to be a promising approach to improve critical properties of Li-ion batteries, such as cost, lifetime, safety, and rate performance and is already applied in automotive applications. However, the impact of the type and content of components in the blend is still poorly understood, making it difficult to identify the most beneficial compositions and designs. The present work systematically investigates how specific electrochemical properties of the components affect the resulting electrochemical kinetics and thermodynamics of blended electrodes. The impact of component type and mass ratio on the voltage and entropy profiles, charge transfer kinetics, and lithium diffusivity is examined by thermodynamic analyses, galvanostatic titration, impedance spectroscopy, and chronoamperometry. Comparison of the results with models based on physical mixtures shows that the basic electrochemical properties of the blended electrodes correspond to expectations based on the components’ properties. Based on the present findings, direct mixing effects can be ruled out for future simulations and model-based design studies to effectively search for optimal compositions and electrode structures.