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Within this paper we report on a lithium-ion battery with laser-structured graphite anodes, alleviating current drawbacks of lithiumion batteries such as the reduced discharge capacity at high Crates and the onset of lithium-plating during fast charging. These issues are intensified at low temperatures, as reaction and diffusion kinetics decelerate, which is why a focus of the presented work lies on low temperature performance. Electrochemical impedance spectroscopy was used to show a reduction in the impedances of cells with laser-structured anodes in comparison to their conventional counterparts. The discharge capacity retention at high Crates was enhanced by up to 27% compared to conventional cells, proving potential for high power applications. For the cells with laserstructured anodes, the onset of lithium-plating at 0°C was observed at higher charging Crates by analyzing the voltage relaxation after charging. At −15°C, a smaller amount of plated lithium was detected, even though lithium-plating could not be entirely avoided. Laser structuring also enabled shorter charging times, as the upper cutoff voltage was reached at a higher SOC. The results point out that laser structuring of the anode improves the fast charging capability of lithium-ion cells, especially under demanding operating conditions.

The influence of calendering and laser structuring on the pore structure and electrochemical performance of electrodes is reported. Graphite anodes of varying bulk porosity were micro structured with pulsed laser radiation. Using scanning electron microscopy and energy-dispersive X-ray spectroscopy, laser structuring was found to release superficial pore clogging caused by calendering and to result in binder agglomerates on the electrode surfaces. Structured electrodes showed higher porosities than their unstructured counterparts due to a thickness increase and material removal, but no significant change in the pore size distribution was detected using mercury intrusion porosimetry. Electrochemical impedance spectra of symmetric battery cells revealed increasing ionic resistances and tortuosities for decreasing electrode porosities. Laser structuring significantly reduced the underlying lithium-ion diffusion limitations at all porosity levels. In a discharge rate test, performance deteriorations at high currents were found to be amplified by calendering and could be diminished by electrode structuring. The performance improvements by laser structuring moved towards lower C-rates for stronger compressed anodes. Despite their growth in thickness and porosity, laser structured graphite anodes showed a higher volumetric energy density at high currents than unstructured electrodes, which demonstrates the potential of electrode structuring for highly compressed anodes.

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