Regensburg 2019 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 56: Focus: Computational Methods for the Energy Transition: Paving the Road to Future Materials and Storage Systems - organized by Stephan Kramer and Jochen Zausch

CPP 56.3: Hauptvortrag

Donnerstag, 4. April 2019, 15:45–16:15, H14

Increasing the rate capability of thick graphite electrodes: Insights from MRI, NMR and porous electrode theory modelling — •Jamie Foster — University of Portsmouth, Portsmouth, UK

Utilization of thicker electrodes is one route towards improving the energy density of Li-ion batteries because it decreases the number of electrodes per cell, thereby increasing the ratio of active material to current collectors. However, the increased thickness means that it is difficult to achieve sufficiently fast transport of the lithium to supply the deep regions of the electrode with reactant. At even moderate (dis)charge rates, thick electrodes exhibit significant polarization and undesirable under-utilization of capacity.

We report experimentally determined lithium concentration profiles in a 300 micron thick graphite electrode under operation. The observed behavior clearly shows the phase transforms that are known to occur within graphite during (de)lithiation; there are sharp boundaries between graphite areas lithiated to different stages. Comparison with porous electrode theory modelling reveals that a portion of the Li is temporarily stored in the electrode surface film prior to intercalation. Although it is often difficult to fully lithiate the thick electrode, we demonstrate that the inclusion of a short current reversal, facilitates more complete lithiation. We also demonstrate the value of this high-fidelity experimental data to the modelling community, by showing how it can be used for high-confidence parameter estimation when combined with inverse modelling techniques.