Recovery of valuable metals from waste lithium-ion batteries by metallurgical routes

Abstract

This master's thesis aims primarily to develop a selective method for extracting vital metals from depleted lithium-ion batteries (LIBs). These include lithium, cobalt, nickel, copper, and manganese. Initially, the thesis explores the prevailing literature on the subject. Subsequently, two methods are selected for thorough investigation: hydrometallurgical leaching with hydrochloric acid and pyrometallurgical processing through induction and ash furnace smelting and roasting. The hydrometallurgical route employs segregated electrode materials derived from LIBs, which undergo leaching in a hydrochloric acid solution for a two-hour duration at an average temperature of 85.5 ºC. Post-leaching, the samples are analyzed using atomic absorption spectrometry, revealing the samples to contain fluctuating quantities of Mn, Cu, Ni, and Co, dependent on the dilution factor. The pyrometallurgical route subject's electrode samples to roasting at rising temperatures ranging from 700 ºC to 1500 ºC over spans of 1 to 3 hours. The findings from these experiments suggest that the primary elements extracted from the LIBs are Mn, Cu, Ni, and Co. It was established that by quickly elevating the temperature to a range between 1250 – 1350 ºC, direct metallic conversion of the valuable elements could be attained. Additionally, to mitigate any adhesive interaction between the sample and the ceramic crucible and to ensure a fully smelted sample, flux materials - silicon dioxide (silica) and sodium borate (borax) were utilized. The initiation of the experimental operation involved the sample undergoing smelting at a predetermined temperature spectrum of 1350 – 1400 °C, supplemented by a 15% carbon contribution. Sequential trials maintained the same temperature range while adjusting the carbon supplement's proportion and typology for optimizing the carbothermic reduction reaction. The resultant sample's elemental composition comprised a dominant 95% Mn, with 2% each of Cu and Co, and 1% Ni. The recovery rates, calculated from Table 5.6, for these metals in their metallic forms were: a substantial 65% for Mn, 52% for Co, and a notable 69% for Ni. A key observation was the 75% recovery rate of Mn in the metallic fraction, marking a significant advancement in the extraction process. In conclusion, the thesis finds the recovery of valuable metals from exhausted LIBs through metallurgical routes a promising technique. Both the investigated methods - hydrometallurgical leaching and pyrometallurgical processing, indicate the feasibility of significant metal recovery. Nevertheless, ongoing research is necessary to further refine the process and enhance its efficacy for large-scale applications. Overall, the thesis successfully illustrates the potential of recovering valuable metals from discarded lithium-ion batteries through metallurgical paths, contributing valuable insights for future research in this domain.