Återvinning av metaller från litiumjonbatterier

Abstract

As a result of the rapid transition to a more sustainable society, with lithium-ion batteries at its core, the development of efficient and sustainable recycling methods is of paramount importance. The lithium iron phosphate (LiFePO4, LFP) battery is one of many different battery chemistries in use today, and it has become increasingly important due to its long life cycle and its excellent thermal stability. As large quantities of these batteries are being produced, a growing volume of spent batteries are entering the waste stream, where their high metal concentration makes them both a valuable resource as well as an environmental hazard. This work investigates the leaching step of the hydrometallurgical method, which is one of many methods used for the recycling of critical metals from spent lithiumionbatteries. A comparison between an organic acid (acetic acid, CH3COOH) and an inorganic acid (nitric acid, HNO3) was made in order to compare the efficieny as well as the selectivity of each acid. Furthermore, the impact of temperature was also analyzed. The use of Inductively Coupled Plasma Optical Emission Specotrometry (ICP-OES) was implemented in order to analyze the leachates and the digested residues, while the precipitate that formed in the acetic acid solutions was analyzed using X-ray diffraction (XRD). The results showed that acetic acid achieved a lower leaching efficiency than that of nitric acid, but provided a higher selectivity, with the dissolution of iron and phosphorus remaining relatively low. Nitric acid achieved a high leaching efficiency for all metals, making it the stronger solvent at the cost of lithium-selectivity. Following each experiment with acetic acid at room temperature (25°C), a precipitate formed in the solution. Further analysis using XRD and ICP-OES indicated that the precipitate consisted mainly of iron-phosphate, suggesting the low dissolution of iron and phosphorus might be connected to precipitation reactions. This work demonstrates the differing behaviors of each acid and the fact that the choice of acid greatly impacts overall leaching efficiency and selectivity.