Construction Of Three-phase Reaction Interface Of Cathode Electrode In Zinc Air Flow Battery

Renewable energy power generation has the characteristics of discontinuous and unstable.In order to improve the utilization rate of renewable energy,it is urgent to develop the supporting technology of large-scale energy storage.Zinc-air flow battery has the advantages of low cost,high safety,high energy density,and good stability.It is one of the large-scale energy storage technologies with the good prospects.However,the positive electrode of the zinc-air flow battery still faces the problems of few three-phase reaction interfaces,the electrode oxidation and structural damage caused by high charging voltage,so then resulting in low energy efficiency and poor stability of the battery.In order to solve these problems,we designs and constructs the positive electrode three-phase reaction interface of the zinc-air flow battery,and evaluates its application performance in the battery.The specific research contents and results are as follows:1.Designed and constructed an oxygen electrode with a gradient hydrophilic/hydrophobic three-phase reaction interface.In view of the different requirements on the hydrophilic/hydrophobic of the three-phase reaction interface between the oxygen reduction reaction and the oxygen precipitation reaction,breaking the traditional oxygen electrode polytetrafluoroethylene hydrophobic agent and carbon powder to construct the gas diffusion layer as the support of the oxygen precipitation catalyst layer,using hydrophilic Polyvinyl alcohol modified the gas diffusion layer to construct a gradient hydrophilic/hydrophobic three-phase reaction interface.Studise have shown that the use of a gradient hydrophilic/hydrophobic gas diffusion layer can increase the utilization rate of the oxygen precipitation catalyst layer and enhance the transfer rate of oxygen and hydroxide ions at the three-phase reaction interface.Using the designed oxygen electrode,at an operating current density of 50 mA cm-2,the charging voltage of the zinc-air flow battery is reduced by 190 mV,the energy efficiency is increased by 6%,and it can operate stably for more than 100 hours without performance degradation.2.In order to further improve the efficiency and stability of the battery,we used nickel hydroxide to prepare a new " catalytic-diffusion"layer with both oxygen evolution catalysis and gas diffusion functions to replace the oxygen evolution catalytic layer and gas diffusion layer of traditional oxygen electrodes,increasing the three-phase reaction interface of the electrode.At a current density of 20 mA cm-2,the charging voltage of the zinc-air flow battery is reduced by 60 mV,and the energy conversion efficiency is increased to 75%.At the same time,thanks to the anti-oxidation corrosion and low charging voltage of the new "catalytic-diffusion" layer,the battery can work continuously and stably for more than 1100 hours,and the stability is far superior to the zinc-air flow battery(70h)which using traditional oxygen electrodes.The problem that the three-phase reaction interface of the oxygen electrode of the zinc-air flow battery is damaged by high-pressure oxidation is solved,and the efficiency and service life of the battery are greatly improved.