Optimal and systematic design of large-scale electrodes for practical Li–air batteries

Abstract

The battery market to enable the broad uses of electric vehicles and renewable energy sources is undergoing a rapid expansion given the requirements of light, safe, and low-cost materials. Li–air batteries are considered suitable candidates that can overcome the existing challenges in this field. Continuous progress in performance improvements triggered by the structure and design evolution of battery electrodes is essential to utilize Li–air batteries in future applications. In this study, an optimal design process is devised for the practical application of Li–air batteries with large-scale area and capacity levels. The primary difficulty in the large-scale design for practical use originates from the design complexity caused by the one-side (air cathode) open-cell structure for the proper air flow. To examine problems related to practical cell manufacturing, we attempted to explore the large-scale electrode on the charge/discharge performance with two current collectors, specifically Ni foam and a gas diffusion layer (GDL), in single and stacked Li–air cells. A large-scale stacked 1.07 Ah cell was manufactured using commercial carbon mixtures with tabless current collector of Ni foam. The single-cell capacity of tabless Ni foam presented approximately 440 mAh at full-depth scan, showing that the cell-specific gravimetric and volumetric energy densities were 385 Wh/kg and 428 Wh/L, respectively. In the case of tabless GDL, the cell capacity was 630 mAh at full-depth scan. The cell-specific gravimetric and volumetric energy densities of tabless GDL were 680 Wh/kg and 756 Wh/L, respectively. However, the use of a GDL current collector resulted in structural deformation during the charge/discharge reaction due to a self-reaction in spite of the 1.56 times higher energy density than that of Ni foam. Although the GDL helps to enhance the reactivity and performance by increasing the capacity when used with an active material, the extended cycle stability of the Li–air cell is hindered due to the self-reaction of the current collector. These results present case‐based evidence that extends our knowledge about the trade‐offs between capacity enhancements and long-cycle stability regarding the choices of materials for the manufacturing of Li-air cells, thus proving practical insights with regard to the fabrication of large-scale Li–air cells for commercialization.