Modeling of Li-Ion Batteries with Highly-Ordered Hierarchical Electrode Design

The advent of battery-powered electric vehicles has generated a need for batteries that are both energy and power dense. Traditionally, thick electrodes with heavy active material loading are used for enhancing the energy density of a battery. However, thick electrodes (with a loading of > 2.5 mAh/cm2) limits the ionic transport inside the electrode, thereby limiting the power density of the battery1. Decreasing the thickness of the electrodes, as well as increasing the porosity, can enhance the power density of a battery, but this increases the fraction of electrochemically inactive materials, such as current collectors, separator, and packing material, leading to reduced energy density. Therefore, the conventional electrode design is constrained by the tradeoff between the energy density and power density. In this presentation, we examine the role of channels within a thick anode in reducing the ionic transport limitation2,3. We apply the porous electrode model4 to simulate the effect of the channels on the ionic concentration gradient and reaction rate, as well as the resultant rate capability of the cell. We will describe the parameterization of the model using three-electrode measurements. The model results show substantial improvement in the electrolyte salt concentration because of channels as compared to that in the conventional electrodes at high charge rates such as 4C and 6C. References: 1. Gallagher, K. G. et al. Optimizing areal capacities through understanding the limitations of lithium-ion electrodes. J. Electrochem. Soc. 163, A138–A149 (2016). 2. Kim, Y., Drews, A., Chandrasekaran, R., Miller, T. & Sakamoto, J. Improving Li-ion battery charge rate acceptance through highly ordered hierarchical electrode design. Ionics. 24, 2935–2943 (2018). 3. Nemani, V. P., Harris, S. J. & Smith, K. C. Design of bi-tortuous, anisotropic graphite anodes for fast ion-transport in Li-ion batteries. J. Electrochem. Soc. 162, A1415–A1423 (2015). 4. Newman, J. & Tiedemann, W. Porous-Electrode Theory with Battery Applications. AIChe J. 21, 25–41 (1975).