Pore Scale Study On The Electrochemical Reaction Mechanism Of Single-Flow Zinc-Nickel Battery Anode

Under the condition of increasing energy demand pressure and increasing environmental requirement,new energy technology has been developed gradually.In order to make rational and effective use of new energy,energy storage technology is a key part.Redox batteries have been developed by virtue of their flexible design and application.In this paper,the concentration polarization of Zinc-nickel single liquid flow battery and the phenomenon that the side reaction produces oxygen to hinder the further reaction were studied by using lattice Boltzmann method from the pore scale.The main research results are as follows:1.The mass transfer and reaction models of the porous positive electrode of two Zinc-nickel single liquid flow batteries in the charging process were established.The actual electric field was characterized by constant and solid-liquid electric potential respectively,and the coupling calculation was carried out with the flow field and concentration field inside the electrode,so as to explore the reaction mechanism of Zinc-nickel single liquid flow battery in the charging process.Charging current density,porosity and electrode thickness were selected as reference variables to study the internal transmission and reaction mechanism of the electrode under different conditions.It is proved that the model considering solid-liquid potential can better reflect the difference of reaction rate inside the electrode,so as to reflect the transmission and reaction mechanism inside the electrode more accurately.The actual law of the change of potential inside the electrode with the thickness of the electrode.The influence of electrode morphology on the reaction process was studied.The results show that the thickness of the electrode has the greatest influence on the polarization inside the electrode.Increasing the charge current density can improve the reaction current density and the concentration polarization is more obvious.When the porosity is reduced,the reaction area decreases,the reaction rate decreases and the concentration polarization increases.2.In this paper,based on Shan-Chen model,a numerical model describing the mass transfer and the primary and secondary reactions in the sintered nickel electrode of a Zinc-nickel single flow battery under transient conditions is established.Then the transient changes during the battery charging process is simulated,and the regularity of side reactions under different current densities was investigated,the effects of different contact angles and porosity on the growth and shedding of bubbles and the interaction with the skeleton were studied.The mechanism of bubble influence on electrode reaction was studied by using interface contact length parameter.It is found that the higher the current density is,the earlier the adverse reaction will start.With the increase of the contact Angle,it is more convenient for the oxygen ions inside the electrode to leave the skeleton.The greater the porosity,the smaller the oxygen production rate,and the greater the difficulty of exfoliation,and the impact of porosity is greater than the contact angle.Based on the above work,the mechanism of mass transfer and electrochemical reaction in porous anode of Zinc-nickel single liquid flow cell was obtained.