Laser structuring of graphite anodes and NMC cathodes – Proportionate influence on electrode characteristics and cell performance
By Hille, Lucas; Xu, Lingji; Keilhofer, Josef; Stock, Sandro; Kriegler, Johannes; Zaeh, Michael F.
Published in Electrochimica Acta
2021
Abstract
For this study, microscopic diffusion channels were introduced into graphite anodes and NMC622 cathodes through short-pulsed laser radiation. The impact on the performance of coin cells comprising anodes and cathodes in pristine and structured conditions, respectively, was investigated in a discharge rate test. At high rates (1 C – 3 C), particularly cells with laser-structured anodes showed a significant increase in capacity retention of up to 10 % in comparison to cells with pristine anodes. Characteristic features in the incremental capacities indicated cell polarization and diffusion inhibition as the rate-limiting mechanisms at high discharge rates and revealed differences in the dominating deintercalation stages between the cell configurations. Fitting an equivalent circuit model to the impedance spectra of symmetric cells showed a reduction of the ionic resistances by approx. 45 % for the anodes and approx. 21 % for the cathodes through laser structuring. A similar behavior was observed for the MacMullin numbers and effective tortuosities of the electrodes. In conclusion, laser structuring offers a particular potential to overcome the diffusion-limiting characteristics of the graphite anodes. The insights into the proportionate impact of anode or cathode structuring are of high value for the design and manufacturing of future lithium-ion batteries.