Lithium ion batteries recycling through high temperature processes

Abstract

Lithium-ion batteries are vital in today society, which is increasingly reliant on renewable energy production and storage. Depending on the principal purpose of rechargeable batteries, numerous types of cathode materials are used. Other frequent metals used in cathode materials include cobalt, nickel, manganese, and aluminum, in addition to lithium. The increasing number of new EVs increases the demand for raw materials during manufacture. Simultaneously, the number of used EVs and later retired lithium-ion batteries (LIBs) that must be disposed of is growing. As per current approaches, recycling looks to become one of the most promising options for End-of-Life (EOL) LIBs. Recycling and reusing waste materials would minimize raw material consumption as well as an environmental burden. This thesis focused on the literature review that was constructed based on 70 papers on "Recycling of Lithium-ion Batteries" with a specific focus on heat-treatment to improve subsequent metal recovery rates through hydrometallurgy. One of the emerging issues in hydrometallurgy recycling is to remove binder and organic. There is a different promising method to remove binder and organic by pretreatment. The objective of the literature review study was, therefore, to investigate if and how the thermal treatment removes binder, and organic and reduces the valance of metal to increase leaching efficiency. A review of the literature was carried out and the effects of heat treatment on the battery active materials as a function of treatment time, atmosphere, and temperature were investigated. Within the review, attention has been given to how several industrial lithium battery recycling processes are applied for thermal pre-treatment in an oxidative or inert atmosphere, or in a vacuum, to remove organic material and separate aluminum foil from cathode active material. In this work, the effects of thermal treatment under N2:CO2 atmosphere and N2:Ar on the composition of spent Lithium-ion batteries (LIBs) were investigated. LIBs with cathode active were sorted, discharged, crushed, and sieved of mixed cathode chemistries (LiCoO2, LiMnO2, LiNiO2, and Li(NixMnyCoz)O2) found by microscopical examinations were treated from 60 to 120 minutes at a temperature between 450-850°C. During the thermal treatment, reactions with C and CO(g) are responsible for a reduction of metal oxides, with Co, CoO, Ni, NiO, Mn, Mn3O4, Li2O, and Li2CO3 as the main products. The thermally treated products are analyzed by XRD and SEM-EDS, and the data shows that the cathode material after thermal treatment is primarily transformed into Co, CoO, Ni, NiO, Mn, Mn3O4, Li2O, and Li2CO3. Accordingly, the effect of several factors such as temperature, treatment time, and atmosphere are assessed on the leaching efficiency of valuable metals. Thermal analysis techniques are used to investigate the black mass thermal behavior. The results show that the two fractions have similar mineralogical and morphological features, while the proportions of carbon and organic components may differ. The binders dissolved when the BM was thermally treated until a temperature of 500 °C was reached, at which point hydrocarbon volatilization was seen, however, F largely remained in the black mass. At 600 °C, the Li-metal oxide was largely reduced to lower oxides and Li carbonate, with carbothermic reduction accounting for the majority of the mass loss. Metallic Co and Ni phases were produced as a result of this reaction, while a portion of the graphite remained unreacted. However, the solubility of Li2CO3 is relatively higher, so water leaching is used to treat at conditions of 2.5% pulp density, 25°C, 200 rpm, and 30 minutes to the thermally treated products. Then the filtrate residue is leached to recycle other metals with 2.0 M H2SO4,2.5% pulp density,60°C, 200 rpm, 240 minutes. The results indicate that, after thermal treatment at 550°C for 120 minutes in an N2:CO2 atmosphere,67% Li is preferentially recovered via water leaching, and more than 65% Co, Ni, and Mn are recycled via acid leaching without adding reductant. At higher temperature thermal treatment at 750°C for 120 minutes in both atmospheres, i.e. N2:CO2 and N2:Ar results indicate leaching efficiency of Co, Ni and Mn are more than 90% through sulfuric acid leaching without adding reductant but Li efficiency is less than 50%. Finally, the recovery of valuable (Co, Ni) metals is high at a higher temperature, which makes this process economically viable. The process has great potential for industrial-scale recycling from spent LIBs.