鋰電池(LIBs)被廣泛地運用在電子設備以及電動車中，因為鋰電池具有高能量儲存密度、高性能、重量輕，對環境的危害也很小。鋰電池的陽極粉末中有價金屬鈷與鋰，以經濟及環境的角度而言，都應該回收，確保資源永續利用與降低環境風險，所以他們的回收技術受到很大關注。現有回收技術包括高溫冶金、溼式冶金、以及生物治金，但是這些技術的缺點是排放有毒氣體、高耗能、反應耗時。考慮次臨界流體萃取對環境的危害度相對低，不須有機溶劑，萃取效率佳，此研究利用次臨界水回收廢鋰電池中鈷與鋰。本研究採用鹽酸及抗壞血酸，研究這兩種酸溶液在不同濃度、不同溫度下的傳統萃取反應以及次臨界萃取反應，以回收其中的鋰、鈷、錳。實驗結果發現抗壞血酸萃取效率比較好，原因是其不只是萃取劑，同時也是還原劑，可以促進萃取反應的進行。我們也發現萃取效率隨酸濃度上升而增加，同時也隨溫度上升而增加。透過適當的選擇反應條件，次臨界水可以達成完全的鋰、鈷、錳金屬萃取。此外，我們也初步嘗試利用置換反應分離萃取液中的鋰及鈷，實驗結果顯示效果有限，在65℃加入10 g/L的鋁，攪拌10分鐘後，約26.39%的鈷沉澱出來。

Lithium-ion batteries (LIBs) are widely used as the power source in electronic devices and electric vehicles due to their high energy density, high capability, lightweight, and less harm to the environment. Cathode powder of spent LIBs contains valuable metals such as lithium (Li) and cobalt (Co) that need to be recovered from economic and environmental perspectives. Various recovery techniques, including pyro-metallurgical, hydro-metallurgical, and bio-metallurgical have been examined. However, some disadvantages of the methods, including emission of toxic gas, high energy consumption, and time-consuming are recognized. Subcritical water extraction (SWE) is utilized in this study considering its environmental friendliness, low reagent consumption, short reaction time and high extraction yield.
Two leaching agent, hydrochloric acid (HCl) and ascorbic acid, were used to leach Li, Co, and Mn from cathode powder of spent LIBs at different concentrations under different temperatures. Experimental results indicated that ascorbic acid performed better to extract Li, Co, and Mn. It was probably because ascorbic acid not only acted as a leaching reagent but also as a reducing reagent that enhanced leaching reactions. In the SWE, effects of acid concentration and temperature were examined. Compared with conventional extraction methods, SWE performed better and could get the highest leaching efficiency of Li, Co, and Mn (100%) when using 0.5 M of HCl and ascorbic acid as the leaching agent.
In addition, cementation method was used to separate Co and Li from leachate solution. In the preliminary study, around 26.39% of Co (453.65 mg/L of Co) was cemented at 65oC, 300 rpm stirring rate for 10 min cementing time with 10 g/L aluminum dose.

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