Evaluation of Thick Electrode Architectures for High Energy Density Li-Ion Batteries

Abstract

Thick electrodes have attracted considerable interest due to their potential role in achieving high energy density Li-ion batteries for electric vehicle applications. Incorporating thick electrodes eliminates many of the inactive separator and current collector layers that add cost, weight, and volume to the battery. However, mass transport of Li ions becomes a limiting factor at these dimensions and leads to poor rate capability at high charge and discharge rates. Different electrode architectures have been proposed to facilitate Li ion transport throughout the entirety of the electrodes, but the connection between structure and performance remains unclear. We used two different active material particle sizes to create thick anodes and cathodes (~4 mAh/cm2) with different structures and pore size distributions to determine the effect of architecture on electrochemical performance. Seven graphite anodes and seven NMC 532 cathodes were coated in various single- and double-layer configurations and assembled into single-layer pouch cells in forty-nine different cathode/anode combinations. These cells were then subjected to charge and discharge rate performance testing. We found that both particle size and structural arrangement have significant impacts on the resulting rate performance. Mercury porosimetry was performed on all electrodes to help correlate pore size distribution with performance. In addition, the best- and worst-performing cells were selected for post-mortem analysis to further understand the nature of the observed electrochemical differences. Our results demonstrate that the rate performance of thick electrodes can be improved by altering the electrode architecture. More precise control over the structure could lead to further improvements and enable the implementation of thick electrode Li-ion battery designs for cheaper, long-range electric vehicles. Figure 1