Electrode Mapping; Effects of Porosity and Thickness on NMC Full Cells

Abstract

While performance of a lithium ion battery is primarily determined by the materials used within, the cell design variables also play a significant role. Parameters such as electrode thickness and porosity can influence overall cell energy density, power/rate performance, and lifetime. Ideally, a cell design needs to include the effects from all relevant design variables and the interactions between these parameters. For example, increasing the electrode loading is a very effective method to improve overall cell energy density as decreasing the number of layers in the cell will improve the ratio of active/inactive components. However, the thicker electrodes can result in poorer rate or power performance. Porosity of the electrodes is also a key variable affecting both energy and power performance. Cell based models are effective tools to estimate overall cell energy density as the electrode loading and porosity varies. However, these models are less adequate to predict power or rate effects as the electrode parameters are changed. Capacity and power fade during cycling are not well described by current models or calculations. Therefore, experimental evaluation of a wide range of electrode designs is necessary to appreciate the complex variable space of electrode composition, loading, and porosity. In this poster, we will show the effects of cathode formulation, thickness, and porosity on key performance metrics for automotive applications. Results from these experiments were used to identify benefits and limits of high loading electrode designs in high energy and power automotive cells. The data were also inputted into automotive pack models to predict effects on system level performance. Furthermore the importance of a holistic approach to bridge the gap between lab scale experiments and a full scale application is discussed.