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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 10: Battery Materials (joint session KFM/CPP)

KFM 10.6: Vortrag

Donnerstag, 30. März 2023, 10:40–11:00, POT 51

The dielectric behaviour of lithium intercalated graphite anodes - as a function of the state of charge — •Simon Annies, Chiara Panosetti, and Christoph Scheurer — Fritz Haber Institut Berlin

The dielectric behaviour of battery materials is a crucial piece of information for understanding atomistic mechanics and modelling diffusion- and charging processes. However, for the most common anode material in today’s lithium ion batteries (lithium intercalated graphite), literature results regarding this property are sparse, conflicting and only available for graphite, i.e. the empty state of charge (SOC).

Utilizing our recently developed DFTB parametrization [1] which is based on a machine-learned repulsive potential, we are – for the first time – able to compute the dielectric behaviour of lithium intercalated graphite for the entire range of charge from 0% to 100% - finding a linear dependency from around є_r=7 at 0% SOC to around 25 at 100% SOC. We achieve this by sampling the Coulomb interactions between pairs of Li-ions and vacancies in large cells with varying intercalant concentrations in the adjacent layers.

Our results agree with experiments in the limit of "empty" graphite, as well as for (bilayer-) graphene, which we consider a validation of our approach. With this, we lay an important piece of foundation for the understanding and multi-scale modelling of entire charging and discharging cycles of graphite anodes in Li-ion batteries.
[1] Anniés, Simon, et al., Materials 14.21 (2021): 6633.