In order to interpret the experimental measurements and to identify factors governing phase transformation and the subsequent oxygen release, a multiphase-field model (PFM) is established to represent the coupled mechanical, chemical and transport behavior occurring in the LiCoO2 electrodes. The PFM was developed using the MOOSE framework.2,3 The model captures both the kinetics of the oxygen release by employing Fick’s diffusion law, as well as the stress build-up. This is achieved by coupling the evolution equation of the phase-field variables (i.e., oxygen concentration, existed phases) to the mechanical equations allowing to study diffusion induced phase transformation and stress generation. The model was validated against the above described experimental measurements by comparing the rate of phases growth and their thicknesses. This comparison allows the PFM to predict the oxygen composition depth and the stress profile in the layered, spinel and rock salt structures of the LiCoO2 during the heating. The simulation results indicate that the generated stress slows down the oxygen release, and changes the local oxygen concentration within the phases. In addition, the temperature ranges of the critical oxygen release were identified. Thus, this combined work provides suggestions for a safe operating window of the LiCoO2 electrodes.
1. S. R. Sharifi-Asl, F. Soto, A. Nie, Y. Yuan, H. Asayesh-Ardakani, T. Foroozan, V. Yurkiv, B. Song, F. Mashayek, R. Klie, K. Amine, J. Lu, P. Balbuena, R. Shahbazian-Yassar, Nano Lett., 17, 2165-2171 (2017).
2. M. R. Tonks, D. Gaston, P. C. Millett, D. Andrs, and P. Talbot, Comput. Mater. Sci., 51, 20–29 (2012).
3. D. Schwen, L. K. Aagesen, J. W. Peterson, and M. R. Tonks, Comput. Mater. Sci., 132, 36–45 (2017)