High-Temperature Behavior of Spent Li-Ion Battery Black Mass in Inert Atmosphere

Abstract

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

A simple methodology for the quantification of graphite in end-of-life lithium-ion batteries using thermogravimetric analysis

“…The new morphology appears to be formed by an inner layer of metallic Co surrounded by an intermediate phase where oxygen and carbon overlap, suggesting the presence of Li 2 CO 3 species. Indeed, Li 2 CO 3 has been identified by other authors 38 as an intermediate species during the reduction of cathode materials.

Figure 2 Detailed imaging and elemental mapping (EDS mode) of artificial BM (A) Bulk BM with 50 wt.

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“…Since the thermal decomposition occurred under an inert environment, the mass loss can only be explained as a result of the chemical reduction of the cathode materials by graphite. According to the work by Babanejad et al., 38 three types of reactions occur during this thermal reduction:

Figure 1 TGA-EGA of artificial black mass with 50 wt (A and B) % graphite and 50 wt. % NMC (A) and 50 wt.

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Synthesis of NMC111 Cathode from Spent Lithium-Ion Batteries (LIBs) using Acetic Acid as a Leaching Agent and Flame Assisted Spray Pyrolysis

“…The part II shows the binder (PVDF) begins to decompose at 300ºC and decomposition continues up to 627ºC, PVDF decomposition products include: CO 2 , H 2 O, and HF [29]. The gases formed (CxHy, CO 2 , and H 2 O) indicate the decomposition of organic compounds, which could be residual solvents or binders [31]. With the decomposition of PVDF, acetylene black (carbon) may be oxidized/decomposed with a decomposition peak around 500°C [30,32].…”

Modelling Binder Degradation in the Thermal Treatment of Spent Lithium-Ion Batteries by Coupling Discrete Element Method and Isoconversional Kinetics

“…The challenge is that, on the one hand, the binder should be degraded by thermal treatment in a certain amount of processing time and, on the other hand, other valuable components should not be decomposed [8]. Furthermore, the thermal treatment of the BM can release toxic gases such as hydrogen fluoride (HF), which can cause the corrosion of equipment and air pollution by decomposing the fluoride-containing components in spent LIBs, such as the binder PVDF, which must be considered in experimental security management [6]. Moreover, two common thermal processes are used to degrade the binder, calcination and pyrolysis, and an overview of industrial recycling routes can be found in [14].…”

“…Moreover, two common thermal processes are used to degrade the binder, calcination and pyrolysis, and an overview of industrial recycling routes can be found in [14]. Pyrolysis is more effective than calcination in preventing undesired graphite decomposition due to the absence of oxygen in the atmosphere [6,[15][16][17][18], which is one particular reason for our focus on pyrolysis conditions in this work. In order to tailor the binder degradation during the thermal treatment of black mass, efficient computational methods are necessary to optimize future thermal treatment processes and adapt flexibly to changing feeds in the recycling route.…”