| 摘要: | 本研究主要結合兩種深共熔溶劑 (Deep eutectic solvents, DESs)，氯化膽鹼:乳酸(ChCl:LA)及氯化膽鹼:草酸(ChCl:OA)對廢棄鋰電池粉末-黑粉(Black mass, BM)，進行石墨、鎳與鈷的分離回收，並對回收程序的溫度、組成進行討論。
分離程序總共分為三個步驟，在第一步驟我們利用ChCl:LA將大部分金屬離子溶解於浸出液，而黑粉中主要元素石墨則被保留於第一次沉澱物中;接著，在第二步驟中加入OA或ChCl:OA進行反應，我們發現加入ChCl:OA並在高溫120℃下反應能夠達到最好的Ni與Co分離率，這是因為高溫環境及ChCl:OA所提供之氯離子有助於穩定[CoCl4]2-結構，使Co溶解於第二次浸出液中，而Ni則與OA結合以NiC2O4·2H2O沉澱;在第三步驟中，加入H2O使[CoCl4]2-發生配位結構改變，由於CoC2O4·2H2O在水中的低溶解度，因此Co最終以CoC2O4·2H2O沉澱。
以雙深共熔溶劑回收所運用之材料相較於傳統溶劑回收法對於環境傷害更低，並且透過此程序，我們從黑粉中同時分離出可再利用的正極與負極材料。以回收石墨合成的再生負極展現出良好的電化學性能，在1C的電流密度下可以達到266 mAh/g的放電比電容值;而Co的回收率可以達到85%，經鍛燒後的回收物為Co3O4，能夠作為正極材料合成的前驅物，展現出優異的可再利用性，實現材料永續循環之目標。
;This study mainly combines two types of deep eutectic solvents (DESs), choline chloride:lactic acid (ChCl:LA) and choline chloride:oxalic acid (ChCl:OA), for the separation and recovery of graphite, nickel, and cobalt from waste lithium battery powder, also known as black mass (BM). The temperature and composition of the recovery process are discussed.
In this research, the separation process consists of three steps. In the first step, we dissolve the majority of metal ions in the leaching solution using ChCl:LA, while the main element graphite in the black powder is retained in the 1st precipitate. Then, in the second step, we add OA or ChCl:OA for the reaction. We found that adding ChCl:OA and reacting at a high temperature of 120℃ achieves the best separation efficiency for Ni and Co. This is because the high-temperature environment and the chloride ions provided by ChCl:OA help stabilize the [CoCl4]2- structure, allowing Co to dissolve in the 2nd leaching solution, while Ni combines with OA to form NiC2O4·2H2O. In the third step, we add H2O to induce a coordination structure change in [CoCl4]2-. Due to the low solubility of CoC2O4·2H2O in water, Co ultimately precipitates as CoC2O4·2H2O.
In conclusion, this study demonstrates a more environmentally friendly way to recycle the black mass compared to conventional methods. Through this procedure, we are able to separate both cathode and anode materials from the black mass. The regenerated anode, synthesized from the recovered graphite, exhibits good electrochemical performance, with a discharge specific capacitance of 227.5 mAh/g at a current density of 1C (1C=372mA/g) after 500 cycles. The recovery efficiency of cobalt can reach 85%, and the material obtained after calcination is Co3O4, which can be used as a precursor for synthesizing cathode materials. The materials recycled from this procedure demonstrate excellent reusability, thus contributing to the achievement of the goal of material sustainability. |
