Changes in structure and ionic resistance of lithium-ion battery graphite electrodes

The fast-charging performance of lithium-ion batteries is strongly influenced by the structure of porous electrodes and its evolution during battery operation. In such electrodes, ionic transport is governed by the electrolyte conductivity as well as by the porosity, tortuosity and thickness of the electrode. The latter parameters undergo both reversible and irreversible changes, induced by the lithiation and delithiation of graphite particles and by the formation of the solid–electrolyte interphase (SEI).

We will discuss how SEI formation alters electrode thickness, porosity and tortuosity. Particular emphasis will be placed on how these structural changes depend on the initial electrode porosity and how SEI formation can be quantitatively linked to the evolution of transport properties.

Second, we will address state-of-charge–dependent effects. Graphite particle expansion during lithiation changes the pore structure, influencing electrode porosity, thickness and pore volume. It will be shown how these changes affect ionic resistance and electrolyte transport, and how they connect to macroscopic effects such as the recently described electrolyte-motion–induced salt inhomogeneity (EMSI).

Together, these insights provide a coherent picture of how SEI formation and state-of-charge-dependent expansion alter ionic transport in porous graphite anodes, offering guidance for electrode design and improved methodologies for realistic parameter determination used in battery modelling and fast-charging optimisation.

Lennart Reuter received his PhD from the Technical University of Munich (TUM) in June 2025 under the supervision of Prof. Hubert Gasteiger and is now a postdoctoral researcher at Uppsala University. His research centres on identifying and quantifying material and electrolyte decomposition processes in lithium-ion batteries. He implemented OEMS for gas analysis in the presence of volatile commercial electrolytes and developed a novel three-electrode cell for the operando detection of parasitic side reactions. In addition, he investigated structural and transport changes in porous electrodes during operation, including the characterisation of porous transport properties by electrochemical impedance spectroscopy (EIS).

Jonas Dickmanns is a PhD candidate at the Chair of Technical Electrochemistry, supervised by Hubert Gasteiger at the Technical University of Munich (TUM), focusing on advanced lithium-ion battery cell chemistry and anode materials. He received his MSc.in chemistry from TUM, where he worked on the electrochemical characterisation of graphite. He later expanded his research to other anode materials, including microscale silicon and silicon/carbon composites. His work investigates key electrode processes such as solid–electrolyte interphase (SEI) formation, structural evolution of anodes, and electrolyte interactions. The goal of his research is to enhance the performance, stability and lifetime of next-generation lithium-ion batteries.