Modification And Electrochemical Properties Of Zinc Anode Of Secondary Zinc-Air Battery

Secondary zinc-air battery has the merits of high theoretical energy density,high safety and low cost.Zn anode,as the key part of rechargeable zinc-air battery,its hydrogen evolution corrosion,passivation and poor reversibility have seriously hindered the commercialization of secondary zinc-air battery.In this thesis,the zinc anode was modified by additive,surface coating,alloying and their mutual cooperation.The composition,structure and morphology of the modified zinc anode materials were analyzed and characterized by XRD,SEM,TEM and XPS.The electrochemical properties of zinc anodes and the performance of Zn/Ni OOH batteries were studied by cyclic voltammetry curve,Tafel curve and LAND system and so on.The main contents and results were as follows:（1）The effects of different zinc powder particle size and electrolyte solution on the electrochemical properties of zinc anode were analyzed.The results show that the corrosion current of zinc anode decreases first and then increases with the decrease of zinc powder particle size,and the corrosion current of zinc anode is the lowest when the zinc powder particle size is 800 mesh.Compared with 6mol/L KOH solution,although the Zn O saturated6mol/L KOH solution aggravates the hydrogen evolution corrosion of zinc anode,effectively inhibits the deformation of zinc anode and improves the cycle performance of zinc anode.（2）The zinc anode material was coated with ZrO₂ by sol-gel method,meanwhile,its electrochemical properties and cycle performance of Zn/Ni OOH batteries were studied.The results show that the ZrO₂ coating layer can prevent the direct contact between the active material zinc and electrolyte and inhibit the deformation of zinc anode,resulting in improving the corrosion resistance and active material utilization ratio of zinc anode.The optimum ZrO₂-coated amount is 2wt%,and the cycle numbers of Zn/Ni OOH battery are increased from 2 to 14.（3）The Bi-C and SnO₂/Sn-C composites were prepared by high temperature carbon reduction method.Meanwhile,the effects of Bi-C and SnO₂/Sn-C composites on the electrochemical properties of zinc anode and the cycle performance of Zn/Ni OOH batteries were studied.It was found that the Bi-C or SnO₂/Sn-C composite can improve the mass transfer conditions of zinc anode and increase the hydrogen evolution overpotential and conductivity of zinc anode,thus inhibiting its passivation and hydrogen evolution corrosion.The optimum addition amount of the Bi-C or SnO₂/Sn-C composite is 2wt%,which establishes a good balance between the substances needed to inhibit hydrogen evolution corrosion and delay passivation of zinc anode.When the amount of Bi-C or SnO₂/Sn-C composite is more than 2wt%,they will cover the reaction sites of zinc anode and aggravate the self-corrosion of zinc anode,thereby reducing the utilization rate of active materials of zinc anode.The cycle numbers of the Zn/Ni OOH battery containing 2wt%Bi-C or SnO₂/Sn-C composites are increased from 2 to 16 and 10 respectively.（4）The zinc anode was modified by synergistic method of alloying and surface coating.The electrochemical properties of Zn-Al alloy anodes with different mass ratios and the discharge performance of Zn/Ni OOH batteries were analyzed.It was found that the high activity of Al promotes the formation of porous zinc anode surface,aggravates the corrosion behavior of zinc anode and reduces the utilization ratio of active materials,resulting in the decline of batteries discharge performance.However,Al makes the open-circuit potential of zinc anode shift negatively and improves the reversibility of zinc anode,among all alloy anodes,the ZA73 alloy anode shows the best reversibility.The ZA73 alloy anode material was coated with ZrO₂ by sol-gel method,and its electrochemical properties and discharge performance of Zn/Ni OOH batteries were investigated.The results show that the ZrO₂ coating layer can inhibit the corrosion behavior of the ZA73 alloy anode and reduce the high activity of the ZA73 alloy anode to a certain extent,which effectively inhibits the capacity decay of the ZA73 alloy anode,resulting in enhancing the continuous discharge capacity of the batteries.When the ZrO₂-coated amount is 3wt%,the battery has the best discharge performance,the discharge time of the battery is increased from 15min to 118min.However,the ZrO₂ coating layer will hinder the diffusion of Zn²⁺and OH^-,resulting in reducing the reversibility of the ZA73 alloy anode.Considering the utilization ratio of active materials and reversibility of the ZA73 alloy anode,the optimum ZrO₂-coated amount is 3wt%.