Impact of gradient porosity in ultrathick electrodes for lithium batteries

Technologies such as electric vehicles and portable electronic devices have an ever-present need for improved energy density and specific energy. To enhance these performance factors and reduce the cost of inactive components, ultrathick electrodes have become a large area of interest within the battery research field. However, ultrathick electrodes have not been incorporated into commercial batteries due to their sluggish kinetics, difficulty of fabrication, and poor high rate performances. To combat these challenges, this manuscript explores the utilization of gradient porosity in highly loaded LiCoO2 (LCO) electrodes of 54 mg/cm2 and an extreme ∼230 μm thickness. Novel gradient porosity electrodes were fabricated by a novel methodology to create monolithic electrodes of predesigned porosity. Homogeneous porosity electrodes of similar thicknesses were also fabricated and analyzed to compare to the gradient electrodes. Transport properties, such as tortuosity and high/low rate capabilities, were investigated for both the gradient and homogeneous porosity electrodes. For the first time, thick gradient porosity electrodes of predesigned porosity distribution have demonstrated much improved high rate capacity densities over benchmark homogeneous porosity electrodes of equivalent average porosity, while retaining low rate capabilities and very high capacity density.