Black mass from lithium-ion batteries – close-up – processing in battery recycling

Battery recycling – View of the black mass after shredding – Material processing of lithium-ion batteries

Processing black mass: selectively separating and recovering valuable materials from lithium-ion batteries

Flotation and magnetic flotation for the separation of graphite and cathode-active materials for recycling, analytics and process development

Black mass, also known as slag, is a complex material stream from the recycling of lithium-ion batteries and consists primarily of graphite, cathode active materials, and residual materials such as binders, trace electrolytes, and fine metal particles. Targeted processing is crucial for the recovery of critical raw materials such as nickel, manganese, cobalt, and graphite. The goal is not only separation by particle size but, above all, the selective separation of the individual material phases based on their physical and chemical properties. Depending on the starting material, flotation processes, magnetic-assisted flotation (MAGFLO), suspension techniques, and sample division are employed. This results in reproducible fractions for recycling, laboratory analysis, process development, and quality assurance.

Test my material

LITech AI

The goal of black mass processing

The processing of black mass serves the purpose of selectively separating graphite and cathode active materials so that both fractions can be further processed, analyzed, or transferred to downstream recycling processes. Crucial factors include reproducible sample preparation, stable suspension conditions, and a separation method that can handle ultrafine particles, binder residues, and particle adhesion. Magnetic flotation extends conventional flotation by adding an additional physical selection mechanism, thereby improving CAM recovery.

Material data of black mass

Black mass is a fine recycled mixture of mechanically pretreated lithium-ion batteries. For flotation, the following are particularly important: the proportion of graphite and cathode active materials, residual binders such as PVDF, fine metal adhering, particle size, surface properties, and the extent of particle adhesion between graphite and CAM. These properties determine how selectively the fractions can be separated in the flotation cell.

Property	Value
Material name	Black Mass
Origin	mechanically pretreated lithium-ion batteries
Main factions	Graphite from the anode and cathode active materials (CAM)
Typical CAM in focus	NMC-based cathode materials
Other components	Binder residues such as PVDF, electrolyte residues, fine Al and Cu particles
Particle character	fine, heterogeneous, partly ultrafine
Separation-relevant property graphite	hydrophobic and non-magnetic
Separation-relevant property CAM	comparatively hydrophilic and magnetically susceptible
Typical challenge	Adhesion of fine CAM particles to graphite
Process-relevant disturbance variable	PVDF coating and other organic residues
Benefits of the processing	Separation into graphite- and CAM-rich fractions for recycling and analysis

Process description of black mass preparation

For processing, black mass is first provided as a defined sample and transferred into an aqueous suspension. In conventional flotation, hydrophobic graphite particles preferentially rise into the foam, while more hydrophilic CAM particles tend to remain in the suspension. Magnetic-assisted flotation complements this process with a magnetic field that utilizes the magnetic susceptibility of the cathode active materials. This improves the separation of CAM from graphite. It is important to note that binder residues and ultrafine CAM particles can lead to adhesion and entrainment. Pulsed magnetic operation can reduce this undesirable graphite entrapment.

Process step	Objective	Typical machine / method	Typical result
Sample division	Obtain a representative laboratory sample	Rotary sample divider	homogeneous subsample
Prepare suspension	Create defined flotation conditions	Mix with water	stable pulp
Conventional flotation	Separating graphite via surface properties	Flotation cell	graphite-rich foam trail fraction
Magnetic-assisted flotation	Improve CAM separation through magnetic field	Flotation cell with electromagnet	CAM-rich sink fraction
Optimize operating mode	Reduce takeaway and entanglement	continuous or pulsed magnetic operation	higher selectivity
Product separation	Process fractions separately	Deduction of Froth and residual pulp	separate product streams
Analytical control	Evaluate separation efficiency	SEM, recovery calculation, material characterization	Assessable product quality

Typical parameters for flotation and MAGFLO

The crucial parameters are not only cell geometry and magnetic field, but also cell material, magnetic mode, particle adhesion, surface chemistry, and the quality of pretreatment. The cited study investigated electromagnetic settings of 10, 20, and 30 volts, steel and stainless steel cells, and continuous and pulsed magnetic operation. For reproducible results, particle size distribution, solids content, water chemistry, and the homogeneity of the initial sample should also be documented.

Parameter	Typical value / note
Procedural principle	Flotation or magnetic-assisted flotation (MAGFLO)
Examined material	NMC black mass
Voltage Electromagnet	10 V, 20 V or 30 V
Cell material	Steel cell or stainless steel cell
Magnetic mode	continuous or on/off interval
Separation target	Separating graphite from cathode active materials
Important influencing factor	Particle adhesion of CAM to graphite
Important influencing factor	PVDF binder on particle surfaces
Analytical support	SEM and recovery assessment
Observation of the study	The steel cell demonstrated higher separation efficiency.
Observation of the study	Over 90% CAM recovery in the steel cell
Important documentation	Particle size, homogeneity, water chemistry, operating mode

Variants, comparison and selection criteria

Conventional flotation vs. MAGFLO

Conventional flotation primarily separates particles based on hydrophobicity and hydrophilicity. MAGFLO complements this approach with a magnetic field, enabling more targeted manipulation of magnetically susceptible CAM particles.

Continuous vs. pulsed

A continuous magnetic field is simple from a process engineering perspective. However, a pulsed "on/off interval" operation can better remove particle adhesion and reduce the unwanted carryover of graphite.

Steel cell vs. stainless steel cell

The study showed that the steel cell had a higher overall separation efficiency. The choice of cell material therefore influences not only the cell's design but also its separation performance.

Machine recommendation for black mass

For black mass, a coordinated machine logic is recommended: a sample divider for the representative subsample, a laboratory flotation cell for the separation of graphite and CAM, and a magnetic module or electromagnet for MAGFLO tests. Depending on the sample characteristics, additional sieving, suspension techniques, or pretreatment steps may be useful. Decisive factors are particle size, binder content, material adhesion, and the desired separation between the foam path and the sink fraction.

Flotation machine

Separation through floating and sinking behavior

Machine:
More to Flotation machine

Cost:
Price of flotation machine

Machine:
More about rotary sample dividers

Cost:
Price of rotary sample divider

Machine:
on to cutting mills

Cost:
Price cutting mill

Rotor mill

Breaking up lumps in bulk materials

Machine:
More to Rotor mills

Cost:
Price rotor mill

Technical questions regarding black mass processing

Use LITech AI for questions about black mass, flotation, magnetic-assisted flotation, graphite CAM separation, binder influences, cell materials and suitable machines for laboratory and pilot plant.

Frequently asked questions about black mass

Black mass is the fine, valuable recycled mixture from pre-treated lithium-ion batteries. It primarily contains graphite and cathode active materials, as well as, depending on the pre-treatment, residual binders, traces of electrolyte, and fine metal particles.

Typical procedures include sample division, suspension in water, and subsequent flotation. MAGFLO additionally employs a magnetic field to improve the separation of CAM and graphite.

For laboratory applications, sample dividers, flotation cells, and – in the case of MAGFLO – a magnetic module or electromagnet are suitable. Depending on the feed, sieving and pretreatment steps are also advisable.

The goal is usually to separate the material into a graphite-rich fraction and a CAM-rich fraction, so that both streams can be further processed or analyzed in a targeted manner.

Black matter is very heterogeneous. Only a representative and homogenized sample provides reliable information about separation behavior, recovery, and product quality.

PVDF can alter the particle surface and impair the selectivity of flotation. This makes the separation of graphite and CAM more difficult.

The "on/off interval" operation can better remove particle adhesion and reduce the unwanted carryover of graphite. This improves the selectivity of the separation.

MAGFLO combines flotation with magnetic selection, thus opening up a sustainable, scalable way to recover graphite and cathode active materials from NMC black mass.

Ing. Klaus Ebenauer