Study on Ion Transport Mechanism of Zinc-Nickel Single-Flow Battery with Different Porous Electrode Structures based on Lattice Boltzmann Method

Abstract

Since the microstructure of porous electrode is very important to the performance of zinc-nickel single-flow battery, this paper reconstructed the microstructure of porous nickel oxide electrode by quartet structure generation set (QSGS) method. The flow mass transfer and electrochemical reaction in porous electrode were simulated by lattice Boltzmann method (LBM). The effects of different porous electrode structures (porosity, particle size and electrode thickness) on local ion concentration distribution and charging performance are studied from the perspective of seepage and mass transfer in pores. It is found that the ion concentration in the electrode presents an uneven distribution due to the randomness of the particle size and distribution of active substances. The uneven distribution of OH − concentration caused the difference of charging depth in the direction of electrode thickness, and the uneven distribution of H + concentration caused the difference of charging depth in the radial direction of particles. Under different pore structures, the decrease of porosity and particle size can increase the diffusion rates of OH − and H +, and then promote the electrochemical reaction rate, improve the charging speed of the battery, and improve the performance of the battery. The larger electrode thickness will increase the OH − diffusion resistance in the electrode, which is not conducive to the diffusion of OH − and reduce the electrochemical reaction rate, thus affecting the diffusion of H +, increasing the concentration polarization and affecting the charging efficiency of the battery. The uneven distribution of OH − concentration caused the difference of charging depth in the direction of electrode thickness, while the uneven distribution of H + concentration caused the difference of charging depth in the radial direction of particles. Under different pore structures, the decrease of porosity and particle size can increase the diffusion rate of OH − and solid phase H +, and then promote the electrochemical reaction rate and accelerate the charging speed. The larger electrode thickness increases the OH − diffusion resistance in the electrode, which is not conducive to OH − diffusion, and then affects H + diffusion and increases concentration polarization.