4.6 Article

Porous Electrode Model with Particle Stress Effects for Li(Ni1/3Co1/3Mn1/3)O2 Electrode

Journal

JOURNAL OF THE ELECTROCHEMICAL SOCIETY
Volume 166, Issue 13, Pages A2939-A2949

Publisher

ELECTROCHEMICAL SOC INC
DOI: 10.1149/2.0661913jes

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Funding

  1. Swedish Energy Agency

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A porous electrode model, incorporating particle stress effects, is developed for the electrode kinetic processes in the positive Li(Ni1/3Mn1/3Co1/3)O-2 or NMC111 electrode. The model is used to analyze experimental data from galvanostatic intermittent titration technique (GITT) during charging at the beginning of life. The equilibrium potential accounts for the influence of mechanical stress in the electrode particles. While the standard Newman-based model proves unable to capture the dynamic performance of NMC111, the extended model with stress allows good fits of the GITT responses for NMC half cells for a voltage range from 3.7-4.1 V vs Li/Li+ at 10 degrees C, 25 degrees C and 40 degrees C. Four physical parameters are extracted to analyze the underlying diffusive, kinetic, thermodynamic and stress phenomena from polarization to relaxation during a GITT transient. Strong dependencies of the kinetic rate constant k, slope of the open-circuit potential curve dE(conc)/dx(pos) and stress proportionality factor gamma(stress) with lithium concentration are found. The effective diffusion coefficients D-s,D-eff are similar to 10(-14) - 10(-13) cm(2)/s across voltages and temperatures. Diffusion limitation and particle surface stress are more profound at higher voltages and at higher temperatures. This leads to large lithium concentration gradient near particle surface, requiring longer relaxation time during GITT. (C) The Author(s) 2019. Published by ECS.

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