Ultra-thick Li-ion battery electrodes using different cell size of metal foam current collectors

Abstract

In this study, ultra-thick Li-ion battery electrodes were prepared using 450, 800 and 1200 μm cell size of metal foam current collectors for large scale energy storage. The thickness and the mass loading of the electrodes were in the range of 300–600 μm and 30–60 mg cm⁻² respectively, which were much thicker and heavier comparing with the commercial electrodes. The cell using 1200 μm cell size of metal foam exhibited the highest capacity (8.8 mA h cm⁻²) at lower current density (1 mA cm⁻²) owing to the highest mass loading of the active material. However, the deterioration of capacity and the voltage drop in plateau region were relatively much more with the increase of current density so that the capacity of cell using 800 μm cell size of metal foam becomes the highest. AC impedance analysis showed that the charge transfer resistance difference between the cells using 450 and 800 μm cell size of metal foams was only 1.5 Ω cm² whereas it was 8 Ω cm² between the cells using 450 and 1200 μm cell size of metal foams. Furthermore, the slope of the straight line scanned at lower frequencies, which has relation with the diffusion limitation of Li was much lower for the cell using 1200 μm cell size of metal foam. Considering both of the cell capacity and rate performance, the cell size of metal foam between 450 and 800 μm is promising for commercial Li-ion batteries. Although the kinetic performance can be improved further by using the smaller cell size of metal foam, the cell capacity could be sacrificed due to the lower mass loading of the active material.