3D Architectures of a Thick Graphite Anode Enabled by Laser Patterning Process to Improve Capacity Density and Cycling Performance of LIBs

Abstract

Thick electrodes with condensed active materials have been employed to increase volumetric and gravimetric capacity/energy density of lithium ion batteries (LIBs) for electric vehicle (EV) applications. However, thick electrodes suffer from low ionic transportation at high current rates during charging process. Introduction of channels along the thickness of the electrode to make 3-dimensional (3D) architectures leads to better performance under fast charging conditions when compared to baseline electrodes without channels. This can be attributed to the fact that the main factor limiting capacity density at high rates of charging is the diffusion of lithium ions across the cell. 3D channel architectures facilitates a large pathway for ionic transportation that leads to an overall reduction in cell internal impedance, electrode tortuosity and increased active surface area, resulting in better electrochemical and cycling performance. In this paper, a laser patterning process was employed to create channels (in the z-direction) along the thickness of a 74 µm thick electrode made of Philips graphite with 26% porosity. The rate performance test results demonstrated an improvement of 47.6%/49.3% in gravimetric capacity density at extremely fast charging rates of 4C/6C when compared to the baseline electrode. The cycling performance test under 3C showed more than 3 times improvement in capacity retention after 200 cycles for the laser patterned electrode compared to the baseline electrode, indicating the superior performance of the laser-patterned electrodes.