The increased demand for Li-ion batteries has prompted the scientific community to improve recycling routes in order to reuse the valuable materials in batteries. After their end-of-life, the batteries are collected, discharged, and mechanically disintegrated, generating plastic and metallic streams that are recycled directly; this leaves behind a small particle size fraction known as black mass (BM). BM is composed mainly of graphite and Li-metal complex oxides. Pyrometallurgy is a route known for recycling of BM, in which identifying the BM’s behavior at high temperatures is essential. In this study, two types of BM are characterized in two fractions of 150–700 µm and smaller than 150 µm. The thermal behavior of the BM is studied with thermal analysis techniques. The analyses demonstrate that the mineralogical and morphological properties of the two fractions do not significantly differ, while the amounts of C and organic materials might vary. When the BM was thermally treated, the binders decomposed until a temperature of 500 ℃ was reached, where the volatilization of hydrocarbons was observed, although F mostly persisted in the BM. The Li-metal oxide was partially reduced to lower oxides and Li carbonate at ⁓ 600 ℃, and the main mass loss was caused by carbothermic reduction immediately thereafter. As the products of this process, metallic Co and Ni phases were formed, and part of the graphite remained unreacted. Regarding the Li behavior, it was observed that in the presence of Al, AlLiO2 is the most likely composition to form, and it changes to LiF by increasing the F concentration in the composition. Graphical Abstract

Pyrometallurgy is a popular industrial method that is employed in the recovery of valuable elements from black mass (BM), which is produced by pretreatment of Li-ion batteries. This method struggles with some downsides, such as the incineration of graphite and high energy consumption. In this study, the goal is to utilize graphite in the BM to produce a master alloy in an attempt to decrease the energy input requirement. To achieve this, metal oxides (Fe2O3 and CuO) are added to the BM to produce an Fe/Cu-based alloy containing Co/Ni as alloying elements. Mechanical activation is also employed to decrease the energy requirement and to increase the amount of metal oxide that can be reduced by the graphite in the BM. The results revealed that it is possible to produce the aforementioned alloys, the efficiency of which can be improved by applying mechanical activation. After 1 h of milling, the required heat flow for producing Fe- and Cu-based alloys is lowered for ~10 and ~25 kWh, respectively. Plus, the direct CO2 emission decreases for 13–17% in the iron system and 43–46% in the copper system. Graphical Abstract