The Research On The Performance Attenuation Mechanism Of The Air Electrode In The Zinc-air Fuel Cells

Because of the advantages of high energy density,good electrochemical stability,and environmental protection,zinc air fuel cells are increasingly attracting people’s attention.In the charge-discharge process of the zinc-air battery,the air electrode flooding,salt leakage,catalyst loss and other factors lead to deterioration of the performance of the zinc-air battery.Therefore,it is necessary to study the specific mechanism of air electrode performance degradation of zinc air battery.In this paper,the air electrode has been experimentally verified by studying the cycle life of the battery,and the parameters such as the arrangement sequence of the air electrode layers,process technology,the composition of the gus diffusion layer,the composition of the catalyst layer,the selection of the current collector,and the thickness of the air electrode have been optimized.The key factors affecting the attenuation of air electrode performance were also analyzed.The experimental methods of contact angle measurement,electron microscopy scanning,quasi-steady-state polarization curve measurement,electrochemical alternating current impedance test,and cycle life test were comprehensively used in the experiment.The results and conclusions obtained were summarized as follows:(1)Optimization of air electrode constituent materials.Through experiments,it was found that when the PTFE content in the gus diffusion layer was 30% and the mass ratio of the pore former to the activated carbon was 2:1,the number of air inlet holes in the gus diffusion layer was large,the pore size was reasonable,the distribution was uniform,and the hydrophobic performance was good.It has high mass transfer efficiency and optimum performance.When the catalyst layer contains 62% of active carbon,20% of manganese dioxide,10% of graphite,and 8% of PTFE,the catalytic activity is high and the catalytic performance is the best.When the thickness is 1mm,the overall performance of the air electrode can be optimized.(2)Study on the factors that cause flooding of air electrodes,loss of salt and loss of catalyst.Experiments have shown that with the increase of electrolyte concentration,temperature,internal pressure and discharge current of the battery,the time for flooding of the air electrode is continuously shortening;with the increase of the concentration of carbon dioxide in the air,the concentration and the temperatuer of the electrolyte,the time for the salt to appear on the electrode is getting shorter and shorter;the faster the flow rate of the electrolyte,the faster the loss of carbon,catalysts and other substances in the catalyst layer,especially in areas where the flow rate of the electrolyte changes greatly;The corrosive nature of the alkaline solution on the air electrode can lead to the loss of the catalyst,mainly because the adhesion of PTFE is reduced after the PTFE is corroded,resulting in a decrease in the physical structure and strength of the micelles composed of activated carbon,catalysts,graphite,etc.,which ultimately leads to Loss of catalyst.Through the research on the degradation mechanism of air electrode performance,I have further deepened the understanding of key factors that restrict the performance and service life of zinc air batteries.The research also lays a solid theoretical foundation for further research on zinc air batteries,and also indicates the direction for future research work to me.