檸檬酸與硫酸作為濕式冶金鋰電池回收浸出劑之比較及生命週期評估

Abstract

隨著電動車及消費性電子產品的普及，鋰離子電池的需求持續攀升，對鋰、鈷、鎳及錳等貴金屬的需求隨之增加。然而，鋰電池壽命有限，且含有多種重金屬及有毒電解液，使其廢棄後對環境的衝擊成為重要議題。本研究探討以硫酸與檸檬酸作為浸出劑，在濕式冶金回收18650 NCM型鋰電池中鎳、鈷及錳等金屬的回收效率，並進行生命週期評估（LCA），比較兩種浸出體系對環境的衝擊差異。 實驗首先以600°C熱裂解法去除陰極材料中的PVDF黏著劑及鋁箔，隨後進行酸浸條件的最佳化，變因包括酸液濃度、液固比、過氧化氫濃度及浸出時間。結果顯示，在硫酸濃度2M、過氧化氫10%、液固比30 ml/g及浸出120分鐘條件下，鋰、鈷、鎳、錳及鈀的萃取率分別達93.03%、97.06%、93.11%、91.86%及97.78%；而在檸檬酸濃度1.5M、過氧化氫10%、溫度60°C、液固比30 ml/g及浸出120分鐘下，鋰、鈷、鎳、錳及鈀的萃取率分別為100%、94.54%、96.12%、86.01%及97.67%。 生命週期評估結果指出，硫酸浸出法的整體環境負荷低於檸檬酸浸出法，儘管其酸性廢液對水體生態具潛在風險。檸檬酸浸出法則因供應鏈涉及糖類原料發酵、能源消耗及水資源使用，造成較高的碳足跡與潛在毒性排放，導致多數環境衝擊類別的結果高於硫酸浸出法。

With the widespread adoption of electric vehicles and consumer electronics, the demand for lithium-ion batteries has surged, driving up the global demand for precious metals such as lithium, cobalt, nickel, and manganese. However, the limited lifespan of these batteries, combined with their content of heavy metals and toxic electrolytes, has raised significant environmental concerns upon disposal. This study investigates the use of sulfuric acid and citric acid as leaching agents in hydrometallurgical recovery of cobalt, nickel, and manganese from 18650-type NCM lithium-ion batteries. Furthermore, a life cycle assessment (LCA) is conducted to compare the environmental impacts of the two leaching systems. The experiments began with the thermal decomposition of cathode materials at 600°C to remove the PVDF binder and aluminum foil. Subsequent optimization of leaching conditions focused on acid concentration, liquid-to-solid ratio, hydrogen peroxide concentration, and leaching time. Results indicate that under conditions of 2 M sulfuric acid, 10% hydrogen peroxide, a liquid-to-solid ratio of 30 ml/g, and a leaching time of 120 minutes, the extraction efficiencies for lithium, cobalt, nickel, manganese, and palladium reached 93.03%, 97.06%, 93.11%, 91.86%, and 97.78%, respectively. In contrast, using 1.5 M citric acid, 10% hydrogen peroxide, at 60°C, with a liquid-to-solid ratio of 30 ml/g and a leaching time of 120 minutes, extraction efficiencies were 100%, 94.54%, 96.12%, 86.01%, and 97.67%, respectively. The LCA results reveal that the overall environmental burden of the sulfuric acid leaching method is lower than that of the citric acid leaching method, despite the potential ecological risks associated with acidic effluent discharges. Citric acid leaching exhibited higher impacts across most environmental categories due to factors such as sugar fermentation in its supply chain, high energy consumption, and water use, resulting in a larger carbon footprint and higher potential toxic emissions compared to sulfuric acid leaching.