Development of innovative process for producing metalic lithium by converting raw material

本项目旨在建立以Li_2CO_3代替LiCl为原料，低成本生产高性能电池负极重要材料金属锂的工艺。与LiCl相比，Li_2CO_3具有价格低廉、无吸湿性、纯度高等优点。通过碳阳极反应，Li_2CO_3的分解电位比LiCl低1.5V左右。然而，由于溶解在电解质中的Li2CO3会与沉积在阴极上的金属锂发生反应，因此很难直接使用。因此，该项目是基于电解液被陶瓷隔膜分为阴极液和阳极液的想法进行的。锂沉积在阴极上，浸在由LiCl-KCl共晶熔体组成的阴极液中。另一方面，将Li_2CO_3注入阳极液中，与石墨阳极反应生成CO_2，与Cl_2相比，CO_2易于丢弃。首先，用LiCl-KCl共晶熔体在400C^0下进行电解，研究锂在阴极上沉积的电流效率！实验结果表明，该装置具有90%以上的高电流效率。然后，在500C^0的条件下，通过向LiCl-KCl阳极电解质中注入Li_2CO_3，研究CO_3^<2->的阳极电位。结果表明，虽然发现了电位变化，但反应速度很慢。基于以上结果，在800C^0的高温下进行了进一步的实验。发现阳极电位随着温度的升高而急剧下降。也就是说，消耗CO_3^<2->的反应具有很强的温度依赖性。在阳极上的反应机理很清楚：第一阶段是CI_2的演化，第二阶段是CO_3^<2->与石墨和Cl_2的反应。第一阶段的反应很容易发生。第二阶段反应具有较高的活化能。因此，第二阶段成为决定速率的步骤。结果表明，高于650C^0的温度有利于充分消耗CO_3^<2->。认为本课题所获得的知识对实现以Li_2CO_3为原料生产锂的工艺具有重要意义。少

The goal of present project is to establish the process for producing metallic lithium, which is important material as a negative electrode of high performance battery, with low cost by using Li_2CO_3 in stead of LiCl as a raw material. Li_2CO_3 has many advantages such as low price, no hygroscopicity and high purity compared with LiCl. Furthermore, the decomposition potential of Li_2CO_3 is about 1.5V lower than LiCl by reacting carbon anode. However, it was difficult to use Li2CO3 dissolved in the electrolyte directly because it reacts with metallic lithium deposited on the cathode.Therefore, the project was performed based on the idea that the electrolyte is divided with ceramic diaphragm into catholyte and anolyte. Lithium deposits on the cathode dipped in the catholyte which consists of just LiCl-KCl eutectic melt. On the other hand, Li_2CO_3 is fed into the anolyte and reacts with graphite anode to evolve CO_2 which is easy disposable compared with Cl_2.At first, the electrolysis … More was carried out at 400C^0 by using just LiCl-KCl eutectic melt to study the current efficiency of lithium deposition on the cathode! It was confirmed that high current efficiency higher than 90% was obtained. Next, anodic potential was studied to study the reaction of CO_3^<2-> by feeding Li_2CO_3 into the LiCl-KCl anolyte under 500C^0. As the result, reaction rate was very slow although the potential change was found.Based on above results, further experiments were performed at higher temperatures up to 800C^0. The anodic potential was found to decrease drastically by increasing temperature. Namely, the reaction to consume CO_3^<2-> has very strong temperature dependence. The mechanism of the reaction on the anode was clear as follows; first stage is CI_2 evolution and second stage is the reaction of CO_3^<2-> with graphite and Cl_2. First stage reaction occurs easily. However, second stage reaction has high activation energy. Therefore, second stage becomes the rate determining step. It was clear that the temperature higher than 650C^0 was effective to consume CO_3^<2-> sufficiently. It is considered that the knowledge obtained in this project is very useful to realize the process to use Li_2CO_3 as the raw material for producing lithium. Less