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

本课题的目标是建立以Li2CO3代替LiCl3为原料，低成本生产高性能电池负极材料金属锂的工艺。与LiCl相比，Li2CO3具有价格低廉、无吸湿性、纯度高等优点。碳阳极反应后，Li2CO3的分解电位比LiCl低约1.5V。然而，由于Li2CO3溶解于电解液中与阴极上沉积的金属锂发生反应，直接利用Li2CO3是困难的，因此，该项目是基于电解液用陶瓷隔膜分为阴极液和阳极液的思想进行的。阴极上的锂沉积浸泡在阴极液中，阴极液只由LiCl-KCl共晶熔体组成。另一方面，Li_2CO_3被送入阳极液中，与石墨阳极反应生成比Cl2更容易处理的CO_2。首先，电解…在400℃下，仅用LiCl-KCl共晶熔体研究了锂在阴极上沉积的电流效率。结果表明，电流效率可达90%以上。其次，研究了在500℃下，将Li_2CO_3加入LiCl-KCl阳极溶液中，研究了CO_3~(2-)与Lt；2~-的反应。在此基础上，在800℃以下的高温下进行了进一步的实验。随着温度的升高，阳极电位急剧下降。也就是说，消耗CO_3^&t；2-&gt；的反应具有很强的温度依赖性。反应机理为：第一阶段为Cl2析出，第二阶段为CO_3与石墨、Cl2的反应，第一阶段反应容易发生。但第二阶段反应具有较高的活化能。因此，第二阶段成为决定利率的步骤。结果表明，650℃以上的温度有利于CO_3的充分消耗。认为本项目所取得的知识对实现以Li2CO3为原料生产锂的工艺是非常有用的。较少

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