(上海海事大學(xué) 商船學(xué)院，上海 201306)
摘 要: 提出了具有漸變孔隙正極結(jié)構(gòu)的主動式鋰空氣液流電池，利用溶液泵驅(qū)動電解液循環(huán)，結(jié)合漸變孔隙正極結(jié)構(gòu)，強化電極內(nèi)部Li+和O2擴(kuò)散和結(jié)合能力，減弱電極鈍化。基于COMSOL Multiphysics 5.3，建立二維電化學(xué)模型，用Darcy定律、Butler-Volmer方程和組分輸運公式描述在漸變孔隙正極結(jié)構(gòu)(ε=0.55+αX等)下電極內(nèi)部電解液流動、正負(fù)極電化學(xué)反應(yīng)及電解液中Li+和O2濃度場分布。由于Li2O2積聚在正極孔隙內(nèi)，電極比表面積下降，采用Carman-Kozeny方程修正滲透率K。研究漸變孔隙率、壓強差、氧氣參數(shù)、正極厚度及動力學(xué)速率系數(shù)對該電池放電性能影響。結(jié)果表明：在放電電流密度0.1 mA/cm2，電池比電容量是被動式結(jié)構(gòu)的2.5倍；與ε=0.85-0.1X相比，采用ε=0.55+αX結(jié)構(gòu)的電化學(xué)性能較佳；在放電電流密度0.1 mA/cm2下，正極厚度為500~750 μm，電池放電性能較好。
關(guān)鍵字: 鋰空氣液流電池；主動式結(jié)構(gòu)；漸變孔隙率；數(shù)值仿真
（School of Merchant Marine, Shanghai Maritime University, Shanghai 201306, China）
Abstract:Lithium-air flow battery with active gradual-change porosity cathode was proposed in which more oxygen in the electrolyte and electrochemical reaction occured due to the utilization of solution pump to drive electrolyte recycled and gradual-change porosity to achieve better O2 migration in cathode. Based on COMSOL Multiphysics 5.3, a two-dimensional electrochemical model was established. The electrolyte flow, electrochemical reactions in the cathode and anode as well as the Li+ and O2 concentrations in the gradual-change porosity cathode of ε=0.55+αX etc, were described by Darcy’s law, Butler-Volmer equation and component transport formulae, respectively. The permeability K inside porous cathode changed with the electrochemical reaction as the occurrence of Li2O2 deposition in the pore, which was modified by Carman-Kozeny equation. The effects of discharge current density, porosity, pressure difference, oxygen parameters, cathode thickness and kinetic rate coefficient were investigated. The results show that the 2.5 times capacitance occurs in the active lithium-air battery at 0.1 mA/cm2 current density than that of a passive mode; more electrochemical reaction happens in the gradual-change porosity cathode of ε=0.55+αX in comparison with that of ε=0.85-0.1X; and better discharge performance can be obtained in the 500 μm to 750 μm thick cathode of active lithium-air battery at 0.1 mA/cm2 current density.
Key words: lithium-air flow battery; active cathode structure; gradual-change porosity; numerical simulation
