Abstract:

Zinc-air batteries have attracted widespread attention for their excellent safety, high capacity, low cost, and low self-discharge performance. A critical problem in commercializing rechargeable zinc-air batteries is finding a suitable bifunctional catalyst, in which the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) can work consistently over a long period. Therefore, a zinc-air battery with a tri-electrode configuration is a solution. Nevertheless, antileakage performance is critical for commercial batteries. We report a high-capacity prismatic zinc-air battery using a novel tri-electrode configuration. We introduce a design assuring a better connection between the cathode current collector and tab and a better sealing configuration for antileakage. Four highlights of this work are as follows: (1) excellent discharge performance, (2) antileakage, (3) high capacity, and (4) novel structure. When the cell was loaded with small amounts of zinc gel, it showed a low voltage of 1.10 V when discharging because the small amount of zinc gel might not cover the current collector and separator completely. However, leakage after discharge was observed when the cell was loaded with excess zinc gel. The amount of zinc gel, while being antileakage, was optimized by filling the anode case cavity with a proper amount of zinc gel, i.e., 87%. When the cell was discharged under a high current, it incurred a low voltage problem. However, discharging under a low current took long, and the surrounding carbon dioxide can seriously deteriorate the cathode catalyst's performance. Consequently, an optimal zinc loading as high as 97% in the zinc gel was used in an effective current discharge process. Moreover, the cell showed low voltage in a highly humid environment because of the high humidity affecting the active sites for the three-phase reaction. Notably, no leakage was detected even after the extreme conditioning test, i.e., the high-low temperature cycle test (70 ℃ to -20 ℃?) and high-temperature storage (45 ℃) for one month test. The tests demonstrated excellent antileakage performance of our cells compared to other commercial zinc-air batteries. An impressively high capacity of 356 A·h/kg was obtained for a single Cell-14 under a 600 mA discharge current, whereas batteries packed with the Cell-14 connected in series and parallel possessed a high energy density of 405 W·h/kg. Also, our optimized design strategies (the larger size anode cavity design, optimized zinc gel recipe, and improved catalyst performance) could theoretically be used to design a cell to obtain an energy density as high as 650 W·h/kg. The novel structure of a double-layered air cathode with tri-electrode configuration increases the effective air catalytic area, doubling the power density. Ultimately, our novel zinc-air battery with a unique tri-electrode structure, combined with gel polymer electrolytes, can be used to develop and commercialize a rechargeable zinc-air battery in the future.

Key words: zinc-air batteries, high capacity, tri-electrode, prismatic, commercial application