Investigation of the influence of 3D electrode architectures on lithium distribution in anode materials by laser-induced breakdown spectroscopy

For the development of thick film graphite and silicon/graphite electrodes a 3D battery concept is applied, which significantly improves lithium-ion diffusion kinetics, high rate capability, cell lifetime, and reduces mechanical stress. Our current research indicates that 3D architectures of anode materials can prevent cells from capacity fading at high C-rates, suppress the electrode degradation and reduce the overall cell impedance. Especially, the ultrafast laser-generated free spaces in silicon/graphite electrodes act as a buffer zone, which can remarkably reduce the internal mechanical stress during lithium-ion insertion and extraction. For further research and development of 3D battery concepts, it is important to understand scientifically the influence of laser-generated 3D anode architectures on lithium distribution during charging and discharging at elevated C-rates. Laser-induced breakdown spectroscopy (LIBS) is applied post-mortem for studying quantitatively the lithium concentration profiles within entire structured and unstructured graphite and silicon/graphite electrodes. Space-resolved LIBS measurements revealed that less lithium-ion content could be detected in structured electrodes at delithiated state in comparison to unstructured electrodes. This result indicates that 3D architectures established on anode electrodes can accelerate lithium-ion extraction process and reduce the formation of inactive materials during electrochemical cycling. Furthermore, LIBS measurements showed that at high C-rates lithium-ion concentration is increased along the contour of laser-generated structures indicating enhanced lithium-ion diffusion kinetics for 3D anode materials. This result is correlated with a significantly increased capacity retention. Moreover, the lithium-ion distribution profiles provide meaningful information about optimizing the electrode architecture with respect to film thickness, pitch distance, and battery usage scenario.