Lithium-ion batteries (LIB) are the most used batteries nowadays and the most important energy storage devices regarding to electric vehicles. LIBs have a huge energy and power density compared to other battery chemistries, which is the reason for their widespread use. However, conventional particle and electrode structures do not yet fully exploit the potential of these materials.

It is already known that porous nanostructured particles show some benefits compared to bulk particles. The increased specific surface and shorter diffusion paths inside the active material enhance the rate capability and the small primary particle size prevents particle cracking and leads to an improved cycle stability. [1] However, the impact of these particle system on the electrode characteristics is not investigated up to now in every detail as ionic and electronic resistivity are determined by the structural parameters on multiple levels. Therefore, in addition to understanding and optimizing the chemistry of the active materials, it is also necessary to improve particle morphology and electrode structure.

A detailed look at the differences in tortuosity of electrodes with compact and porous particles provides a basic insight into transport properties. [2] This is applied and extended to multilayer electrodes with these particle morphologies. In the final step, porous particles with different particle sizes are used to separate the contributions of intergranular and intragranular pores and their influence on the overall transport resistance in the pore structure. Advanced electrodes like multi layered and blended electrodes have mainly been studied in terms of the electrochemical behaviour of various active materials, but the influence of particle morphologies on the electrode structure has not been considered. Therefore, the talk wants to close this gap and gives a debate contribution for such enhanced electrode structures.

The focus of this work is the measuring of tortuosity by impedance spectroscopy on electrodes with porous nanostructured and compact particles. The experimental set up is a symmetric cell with blocking conditions to fit the data with a transmission-line model approach. To get a deeper insight into porosity-tortuosity relation, multi layered electrodes, cathode coating with different layer thicknesses and porosities will be investigated and discussed.

[1] Müller, M., Schneider, L., Bohn, N., Binder, J. R. & Bauer, W. Effect of Nanostructured and Open-Porous Particle Morphology on Electrode Processing and Electrochemical Performance of Li-Ion Batteries. ACS Appl. Energy Mater (2021) doi:10.1021/acsaem.0c03187.

[2] Schneider, L., Klemens, J., Herbst, E.C., Müller, M., Scharfer, P., Schabel, W., Bauer, W. & Ehrenberg, H. Tortuosity of Electrodes with Compact vs Porous NCM Particles for Lithium-Ion Batteries (in progress)