Quantification of preferred orientation in graphite electrodes for Li-ion batteries with a novel X-ray-diffraction-based method

Abstract

To answer the demand of increased autonomy in transportation applications, the energy density of battery electrode need to be enhanced. The porous electrode microstructure needs to be controlled to optimize battery performance and prevent electrode degradation (e.g., Li plating). Graphite negative electrodes generally consist of anisotropic particles that exhibit a preferred orientation. Graphite particles tend to stack perpendicular to ionic pathways which results in transport issues and reduces overall battery power capability. In this context, a method based on X-ray diffraction is described to quantify the preferred orientation of graphite particles in actual electrodes. A step orientation-distribution function is used to describe the pole-density profile of the diffracting graphite crystallites. A fraction of graphite particles oriented parallel to the electrode current collector within a tilt tolerance is derived from the step function. An application of this method is presented on a set of graphite electrodes that underwent different calendering conditions.