LiCl-LiF熔盐中Li_2CO_3在钨电极上的电化学行为

Electrochemical Behavior of Li_2CO_3 on Tungsten Electrode in LiCl-LiF Molten Salt

680℃、LiCl-LiF纯锂盐体系,以Li_2CO_3为原料熔盐电解法制备金属锂。采用电化学方法(循环伏安、计时电位法)分析了Li_2CO_3在钨丝工作电极上的电化学行为。金属锂在钨丝电极上的还原为一步得电子可逆反应过程,在氯气析出峰前的氧化峰为加入Li_2CO_3所致,Li_2CO_3在电场作用下分解成氧化锂和二氧化碳,氧离子在氯气析出峰前放电生成氧气。往LiCl-LiF熔盐体系加入1%Li_2CO_3使锂离子的扩散系数由1.98×10^(-8) cm^2/s减到0.82×10^(-8 )cm^2/s,最小还原电流密度由0.28A/cm^2增加到0.59A/cm^2,且锂离子在钨丝电极上的电化学还原过程由扩散环节控制。

LiB C03 was used as raw materials to prepare lithium metal in LiC1-LiF pure lithium salt system at 680 ℃ by molten salt electrolysis method. Electrochemical behavior of Li2CO3 on tungsten electrode was analyzed by electrochemical methods such as cyclic voltammetry and chronopotentiometry. The results show that lithium metal reduction on tungsten electrode is one step electron reversible reaction process. There is an oxidation peak before chlorine emission peak, which is caused by addition of Li2 CO3 under electric field. Li2 COa decomposes into lithium oxide and carbon dioxide. Oxygen ions are discharged to produce oxygen before chlorine emission peak. Diffusion coefficient of lithium ion drops from 1.98 ×10^-8cm^2/s to 0.82×10^-8cm^2/s after addition of 1%Li2CO3 to LiC1-LiF molten salt system, and the minimal reduction current density rises from 0.28 A/cm2 to 0.59 A/cm^2. The electrochemical reduction process of lithium on tungsten electrode is controlled by diffusion.