Effect of Operating Temperature and Additives to Chloroaluminate Ionic Liquid Electrolyte on Current Efficiency and Surface Morphology of Al Electrodeposit (Supporting Information)

To investigate the feasibility of the electrorefining process for aluminum (Al) upgrade recycling, Al electrodeposition employing an ionic liquid consisting of anhydrous aluminum chloride (AlCl3) and 1-ethyl-3-methylimidazolium chloride (EMIC) was conducted. The effects of the operating temperature on the current efficiency, specific energy consumption, deposit properties, and deposition rate were investigated using the AlCl3-EMIC bath containing 1,10-phenanthroline anhydride (OP) as an additive at the current density of 100 mA cm−2. A constant-current electrodeposition showed that the specific energy consumption decreased to 5605 kWh t−1 at 80 °C with increasing the operating temperature in the OP-added bath and the current efficiency was over 90 % at the operating temperatures of 60–80 °C, but decreased to below 90 % at 90–100 °C. The cross-sectional ultra-low accelerating voltage scanning electron microscope (ULV-SEM) images showed the smoothness of the deposit obtained from the OP-added bath at 70 °C, but not at 90 °C. The XRD patterns of the Al deposits obtained from the OP-added bath showed a preferential orientation to the {100} plane at 60–80 °C, but almost no preferential orientation at 90–100 °C. It has been revealed that the improvement in the specific energy consumption requires an increase in the operating temperature, and that the surface roughness of the Al deposit must be improved by preferentially orienting the {100} plane in the texture to prevent any Al deposit from dropping out in order to improve the current efficiency at the cathode, which implies Al recovery.

为探究电精炼工艺在铝（Al）升级回收中的可行性，本研究采用无水氯化铝（AlCl3）与1-乙基-3-甲基咪唑氯化物（EMIC）的离子液体进行铝电极沉积。通过在电流密度为100 mA cm−2的AlCl3-EMIC电解液中添加1,10-苯并芘二酮（OP）作为添加剂，研究了操作温度对电流效率、单位能耗、沉积物性质和沉积速率的影响。恒电流电极沉积结果表明，在添加OP的电解液中，随着操作温度的提高，单位能耗降至80°C时的5605 kWh t−1，且在60–80°C的操作温度下，电流效率超过90%，但在90–100°C时降至90%以下。横截面超低加速电压扫描电子显微镜（ULV-SEM）图像显示，在70°C时从添加OP的电解液中获得的沉积物表面光滑，而在90°C时则不然。来自添加OP的电解液的铝沉积物的XRD谱图表明，在60–80°C时对{100}晶面的优选取向，但在90–100°C时几乎无优选取向。研究揭示，单位能耗的改善需要提高操作温度，且通过在纹理中优先取向{100}晶面以改善铝沉积物的表面粗糙度，防止任何铝沉积物脱落，从而提高阴极的电流效率，这暗示了铝的回收。