Regensburg 2013 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 31: Computational Materials Modelling - Diffusion & Kinetics II
MM 31.3: Vortrag
Mittwoch, 13. März 2013, 10:45–11:00, H24
Phase-field modeling of anisotropically diffusional growth during solid solid transformation: Li-insertion in LiFePO4-cathods for rechargeable Li-ion battery applications — •Holger Federmann, Michael Fleck, and Heike Emmerich — Material and Process Simulation, University of Bayreuth, Germany
The delithiation process in LiFePO4 is considered to be a first-order transformation process, where a Li-rich phase transforms into an Li-depleted one. In order to shed light on the delithiation process in LiFePO4-cathodes, a continuum phase field model was developed to describe the dynamics of Li-intercalation there. The cathode consists of nanoscale olivine particles and the model describes the phase transformation through Li-insertion. Within the phase-field method, moving phase boundaries between different phases are treated as diffuse interfaces of finite width. Then, the evolution of the diffuse phase boundary is driven by the mechanics and the thermodynamics of the adjacent bulk phases. In turn, the motion of the diffuse interface strongly influences the bulk properties such as mechanical or thermodynamical degrees of freedom. Generally, such a diffuse interface approach provides an elegant way to incorporate the complicated effects that occur in these materials, such as the highly anisotropic ionic mobility of the Li-ions in the olivine bulk crystal, the electrochemical reactions at the phase boundary, stress and strain effects due to density differences between the phases. Finally, this model at hand, it could be shown that the interpolation on level of eigenstrains should be preferred for the calculation of the elastic free energy densities of the system.