The Interface Advancement In Porous Gas Diffusion Electrodes Of Zinc-air Battery

Battery plays an important role in modern society, among which the zinc-air battery has been widely concerned because of its large capacity, non-polluting and many other advantages. As the reaction place of oxygen, the gas diffusion electrode is the key technology of the zinc-air battery. The mainly used gas diffusion electrode is a porous media with pore size of about 1 micron. When gas diffusion electrodes work in high current density, the current density is mainly provided by the three phase boundary formed by air. electrolyte and electrode materials. We made the following four aspects of the innovation research work on the basis of previous research.1.The relationship between the weight of penetrated electrolyte and the volt ampere curve and peak power of the nickel foam skeleton electrode was experimented, result showed that the discharge performance could be divided into three stages:the discharge performance of the dry gas diffusion electrode slightly increased after the beginning, and achieved the best performance after 2 hours; during 2-24 hours, peak power gradually decayed to 75% of the beginning, and it was still in the working level; after 24 hours, the discharging performance declined rapidly with the increment of the penetrated electrolyte, and it was no longer decayed after 96 hours, at this point, the peak power was only 27% of the beginning. The result also showed that the penetrated rule was similar to a quadric curve whose symmetry axis was the time axis. And by deriving the advancing process of electrolyte driven by capillary force in a single cylindrical tube, the approximate rule of the process was got. The experiment result of the penetrated rule was similar to the theoretical derivation of the approximate rule in a single cylindrical tube.2.By transforming the microscope photo of gas electrode into a four channel two-dimensional topological grid, a numerical simulation of the advancing process of the electrolyte in porous electrode was made. The simulation showed that through the advancing process, the total length of the three phase boundary would also be gradually reduced after the increment in the beginning, which was similar to the experiment phenomena. So the change of electrode discharge performance could be explained, the discharge performance was directly related to the total length of the gas liquid solid three phase boundary.3.Through the experiment of changing the skeleton structure of the electrode, the electrolyte was found to advance rapidly along the skeleton. Therefore, two new-skeleton electrodes were preliminary designed, which effectively slowed down the advancing process of electrolyte interface. However due to the decline in conductivity and other reasons, the discharge performance declined a little. This research was in its initial stage, further research was expected to get gas diffusion electrode with better discharge performance and longer duration.4.By using a digital image method, the distribution and connectivity of the material in the electrode were visualized. The distributing of various components in the electrode materials with a certain proportion was understood. The rationality and feasibility of the method were verified by experiments.