Impact of Laser Structuring and Calendering on Electrode Characteristics and Cell Performance of Li-Ion Battery Graphite Anodes

Abstract

The strong compression of electrode coatings is a common approach to enhance the volumetric energy density of Li-ion batteries (LIBs). However, it results in a deterioration of the charge and discharge performance due to an increase in the ionic resistance of the electrodes. This conflict can be addressed by microscopic ion diffusion channels in the electrode coatings, which reduce the ionic resistance and thus enhance the performance of a LIB.In this study, the impact of laser micro structuring on different electrode properties was experimentally investigated for graphite anodes with varying initial porosities. All electrodes showed higher porosities after laser structuring, which can be attributed to an increase in the electrodes’ thicknesses and the removal of material. An equivalent circuit was fitted to the electrochemical impedance spectra of symmetric coin cells consisting of structured and pristine graphite anodes, respectively, to determine the ionic resistances, MacMullin numbers and tortuosities. The values were found to increase for decreasing initial porosities. Laser structuring significantly reduced the ionic resistances, MacMullin numbers and tortuosities of the electrodes in comparison to their pristine counterparts. Furthermore, the different graphite anode configurations were paired with NMC cathodes in coin cells and examined in a discharge rate test. At rates over 1 C, a significant increase in the discharge capacity through laser structuring was observed especially for cells with highly compressed anodes. Conclusively, this study empirically quantifies how laser structuring and calendaring influence different electrode characteristics of graphite anodes and the respective performance in LIBs.