(40k) Degradation Modeling of Nickel-Rich Nickel-Cobalt-Manganese Oxide Cathode
AIChE Annual Meeting
2017
2017 Annual Meeting
Transport and Energy Processes
Rechargeable / Secondary Battery Technologies for Energy Storage
Sunday, October 29, 2017 - 5:45pm to 6:00pm
Several degradation behaviors have been revealed such as transition metal dissolution, electrolyte oxidation, salt decomposition and gas generation.1,2 Especially for gas generation, the residual Li on the surface of the cathode such as LiOH and Li2CO3 is the main source of this phenomenon.3
In this study, we develop a electrochemical model coupled with the physics-based side-reaction for simulating the degradation of Ni-rich NCM cathode including gas generation. Most of known cathode degradation mechanisms are also considered in this study and implemented to the well-known Pseudo 2D electrochemical model.2,4 To model the gas generation, oxygen activation and related role of residual Li are included by assuming CO2 generation and oxygen activation reactions. Moreover, by constructing phase diagram, a critical level of delithiation of Ni-rich materials for oxygen generation is estimated. The corresponding equilibrium potential of oxygen activation reaction (UO2) is estimated from the open circuit potentials of Ni-rich NCM materials, which is obtained from DFT calculation. The suggested model successfully reproduces the experimental charge/discharge voltage profiles within errors less than 5% up to 50 cycles. Especially, the large discrepancy of capacity between 1st and 2nd cycle observed from experiments is also captured from the simulation by only changing the critical UO2. Based on the model, it will be discussed about the effect of residual Li and the positive correlation of metal dissolution and gas generation.
References
1 K. Min, S.-W. Seo, Y.Y. Song, H.S. Lee, and E. Cho, Phys. Chem. Chem. Phys. 19, 1762 (2017).
2X. Lin, J. Park, L. Liu, Y. Lee, A.M. Sastry, and W. Lu, J. Electro. Chem. Soc. 160, A1701(2013).
3S. Hy, F. Felix, J.Rick, W.-N. Su, and B.J. Hwang, J. Am. Chem. Soc. 136, 999(2014).
4M. Doyle, J. Newman, J. Electrochem. Soc. 143, 1890(1996).