Electrochemical Reaction Model Of Zinc-air Battery And Study On Dendrite Growth Inhibition

With the rapid development of modern technology in the new era,the demand for energy is increasing smoothly.However,the gradual depletion of traditional energy and the Greenhouse effects have forced the country to pursue a strategic transformation.New energy has received widespread attentions because of its clean,high-efficiency,and resource-rich characteristics.Zinc-air batteries show the advantages of environmental friendliness,high energy density,and low cost are expected to become an important part of new energy in the future.However,in the continuous charging and discharging process,dendrites are formed due to uneven deposition on the surface of the negative electrode,which causes irreversible damage to the separator,which means the growth of dendrites on the surface of zinc is a key scientific and technological problem to be solved urgently.Therefore,this article systematically studies the mechanism of dendrite growth in the process of charging and discharging,and documents the control conditions and influencing factors of inhibiting dendrite growth.Frist,the charge-discharge cycle test experiment was carried out on zinc-air batteries,and the morphology of the zinc anode after discharge and charge-discharge cycles at a current density of 25 m A·cm^-2 was studied and characterized.The results showed that the surface of the zinc anode changed after discharge.The unevenness provides conditions for the subsequent uneven deposition of electrolytic zinc on the electrode surface;dendrites with different morphologies grow on different positions on the surface after the charge and discharge cycle.Irregular and disordered dendrites grow in the middle area,and millimeter-level dendrites grow on the edges.The dendrites appear mossy and filamentous in the microscopic view.Secondly,the electrochemical reaction model of the zinc-air battery is established,and the current density,overpotential,and mass distribution of the electrodeposited zinc on the surface of the zinc anode after the charge-discharge cycle are studied,as well as the electrolyte and electrode under the conditions of the secondary current distribution and the tertiary current distribution,and the current density distribution and the law of the current density distribution of the flowing electrolyte are researched.After charging and discharging cycles at a current density of 25 m A·cm^-2,the current density,overpotential,and the distribution of the deposited zinc mass on the electrode surface all show a trend of increasing from the center to the edge,which is consistent with the experimental results.The results showed higher current density and overpotential would promote the electrodeposition of the crystals forms dendrites of the zinc.In the secondary current distribution,in the voltage range of 1.3V-1.65V,the current density is unevenly distributed and irregularly fluctuates,but in the tertiary current distribution,a flowing electrolyte with a flow rate of 5mm·s^-1 is added.The current density presents a relatively uniform distribution.The result is that the flowing electrolyte can drive the movement of ions in the electrolyte and affect the ion distribution.Therefore,during the charging process,the deposition of Zn²⁺after reduction to zinc will become uniform,achieving the purpose of reducing dendrite growth.Finally,based on the phase field equation to simulate the growth of the dendrites on the surface of the zinc anode,the interaction between the dendrites during the growth process of a single dendrite and the growth of multiple dendrites is studied.The results show that under the overpotential drive,the dendrite growth gradually increases with time,and the current density in the electrolyte and on the electrode presents an uneven distribution state;when multiple dendrites grow,there is competition among the dendrites Relationship;changing the influence of different control parameters in the phase field equation on the dendrite growth morphology,the results show that:the increase of anisotropy leads to the formation of more growth sites and main branches of the dendrites;the increase of the latent heat of phase change leads to the increase of the internal heat of the battery.As the temperature increases,zinc deposits more uniformly;reducing the appearance of pores can increase the compactness of zinc deposits and inhibit the growth of dendrites.