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Recycling is a potential solution to narrow the gap between the supply and demand of raw materials for lithium-ion batteries (LIBs). However, the efficient separation of the active components and their recovery from battery waste remains a challenge. This paper evaluates the influence of three potential routes for the liberation of LIB components (namely mechanical, thermomechanical, and electrohydraulic fragmentation) on the recovery of lithium metal oxides (LMOs) and spheroidized graphite particles using froth flotation. The products of the three liberation routes were characterized using SEM-based automated image analysis. It was found that the mechanical process enabled the delamination of active materials from the foils, which remained intact at coarser sizes along with the casing and separator. However, binder preservation hinders active material liberation, as indicated by their aggregation. The electrohydraulic fragmentation route resulted in liberated active materials with a minor impact on morphology. The coarse fractions thus produced consist of the electrode foils, casing, and separator. Notwithstanding, it has the disadvantage of forming heterogeneous agglomerates containing liberated active particles. This was attributed to the dissolution of the anode binder and its rehardening after drying, capturing previously liberated particles. Finally, the thermomechanical process showed a preferential liberation of individual anode active particles and thus was considered the preferred upstream route for flotation. However, the thermal treatment oxidized Al foils, rendering them brittle and resulting in their distribution in all size fractions. Among the three, the thermomechanical black mass showed the highest flotation selectivity due to the removal of the binder, resulting in a product recovery of 94.4% graphite in the overflow and 89.4% LMOs in the underflow product.
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Lithium-Ion Battery RecyclingInfluence of Recycling Processes on
Component Liberation and Flotation Separation Eciency
Anna Vanderbruggen,*Neil Hayagan, Kai Bachmann, Alexandra Ferreira, Denis Werner, Daniel Horn,
Urs Peuker, Rodrigo Serna-Guerrero, and Martin Rudolph
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Supporting Information
ABSTRACT: Recycling is a potential solution to narrow the gap between the supply and demand of raw materials for lithium-ion
batteries (LIBs). However, the ecient separation of the active components and their recovery from battery waste remains a
challenge. This paper evaluates the influence of three potential routes for the liberation of LIB components (namely mechanical,
thermomechanical, and electrohydraulic fragmentation) on the recovery of lithium metal oxides (LMOs) and spheroidized graphite
particles using froth flotation. The products of the three liberation routes were characterized using SEM-based automated image
analysis. It was found that the mechanical process enabled the delamination of active materials from the foils, which remained intact
at coarser sizes along with the casing and separator. However, binder preservation hinders active material liberation, as indicated by
their aggregation. The electrohydraulic fragmentation route resulted in liberated active materials with a minor impact on
morphology. The coarse fractions thus produced consist of the electrode foils, casing, and separator. Notwithstanding, it has the
disadvantage of forming heterogeneous agglomerates containing liberated active particles. This was attributed to the dissolution of
the anode binder and its rehardening after drying, capturing previously liberated particles. Finally, the thermomechanical process
showed a preferential liberation of individual anode active particles and thus was considered the preferred upstream route for
flotation. However, the thermal treatment oxidized Al foils, rendering them brittle and resulting in their distribution in all size
fractions. Among the three, the thermomechanical black mass showed the highest flotation selectivity due to the removal of the
binder, resulting in a product recovery of 94.4% graphite in the overflow and 89.4% LMOs in the underflow product.
KEYWORDS: lithium-ion battery, automated mineralogy, liberation, froth flotation, recycling
Lithium-ion batteries (LIBs) are widely used nowadays in
various devices, from portable electronics to electric vehicles.
Growing global demands for Co, Mn, Ni, Li, and graphite, which
are present in LIBs, have further stressed the already scarce
supply of such raw materials worldwide.
These surging
demands can lead to supply risks, price fluctuations, and market
monopoly. Eective recycling strategies are thus necessary to
reduce the need of virgin raw materials and to promote resource
preservation and environmental protection. Such eorts are
exemplified in the current stipulation by the European Union,
where a minimum recycling eciency of 50 wt % for LIB
(Directive 2006/66/EC) is required, with an ongoing proposal
to reach 70 wt % by 2030.
Furthermore, the European Union
categorized Li was as a critical raw material in 2020, while Co
and natural graphite have been considered as such since 2010,
highlighting their economic importance and supply risks.
The current and emerging recycling technologies for LIBs
typically focus on the recovery of components that have high
economic value, such as Co, Ni, and Cu. To reach a higher
recycling eciency, new products such as graphite should be
considered, as it represents 1520% of LIB’s total mass.
Furthermore, to meet the revised Battery Directive with possible
specific material recovery targets, for example., 95% Co, Cu, and
Ni by 2030,
more robust recycling strategies are sorely needed.
It is also noteworthy that despite the aforementioned
Received: May 16, 2022
Revised: September 15, 2022
Accepted: September 15, 2022
© XXXX The Authors. Published by
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regulations, the supply risk of graphite has only recently gained
attention. Indeed, graphite will remain an essential component
of LIBs in the foreseeable future.
According to a survey carried
out by Benchmark Mineral Intelligence,
anode materials are
forecasted to experience the highest increase in demand among
all the raw materials used in LIBs, that is, +700% between 2018
and 2028. Currently, China has a dominant position regarding
this critical material, accounting for 64% of the flake graphite
global production and almost 90% of anodic spherical graphite.
As a result, Western countries are actively searching for
strategies to develop their own graphite supply chain for battery
production, including plans to integrate recycled graphite.
During typical LIB recycling processes, a comminution stage
is used as a first stage to separate electrode particles from their
current collectors, producing foils in the coarse size fraction and
active particles in the fine fraction. This is possible since
electrode foils present a ductile behavior and, as reported by
ductile materials can be liberated through shear,
cutting, and tearing stresses. The resulting fine fraction is
typically referred to as “black mass” and contains mixed cathode
and anode active materials.
Most of the state-of-the-art recycling technologies use black
mass resulting from the pretreatment (e.g., mechanical or
thermomechanical pretreatment) as a starting point for chemical
processes for metal recovery. Indeed, in industry, this black mass
is usually not further sorted and is directly fed to either
established or newly developed pyro- and/or hydrometallurgical
processes to extract metals from the lithium metal oxides
(LMOs), although at the expense of graphite losses.
In the case
of hydrometallurgical processes, the removal of graphite from
the black mass beforehand would lead to a feed with high metal
content, reducing significantly the volume of material to leach
and decreasing the leaching reagent consumption caused by the
porosity of graphite. Therefore, the feed composition to
metallurgical purification stages needs to be controlled to
minimize losses and operating costs and preconcentration with
froth flotation is an option that has recently gained attention.
Previous studies have demonstrated the use of froth flotation on
black mass to separate the graphite particles from the
either resulting in two valuable products for direct
remanufacturing or as feed streams for metallurgical stages with
an increased overall eciency of LIB recycling.
Nevertheless, one major challenge in the separation of black
mass components is the presence of a polymeric binder, which
adheres the active particles together and onto the current foils.
In LIBs, the anode is made of graphite particles calendered on
Cu, and the cathode of LMOs adhered to Al. Recently, eorts
have been carried out to develop removal strategies for the
polyvinylidene difluoride (PVDF) binder, one of the most
commonly used due to its good electrochemical stability.
Some studies propose PVDF decomposition by thermal
treatment over 450 °C
or with the aid of solvents such as
N-methyl-2-pyrrolidone (NMP)
or dimethyl isosorbide
On the other hand, water-soluble binders are more
common for anode electrodes, such as styrenebutadiene
Rubber (SBR),
resulting in higher liberation eciencies of
the anode components.
This paper provides insights into the influence of three
liberation processes prior to froth flotation: mechanical (M),
thermomechanical (TM), and electrohydraulic fragmentation
(EHF). The impact of each strategy on the characteristics of
black mass particles was studied using automated mineralogy.
This novel approach for black mass characterization was recently
proposed by Vanderbruggen et al.
and Dadeet al.
provides information on the chemical composition, morphol-
ogy, and degree of liberation of LIB components. While most
research on LIB recycling has focused on the operating
conditions and design of separation processes, there is a need
to gain a fundamental understanding of particle behavior and
liberation as a result of treatment stages that systematically aect
their overall recycling eciency. Such knowledge could also
support the LIB design and production practices.
2.1. Material and Processing. The material for this study
consisted of 200 discharged identical LIBs (Samsung
INR18650-29E, batch n°BRGA29E82105). One battery was
manually opened and dismantled to estimate the mass of each
major component, as presented in Figure 1. In this particular
case, the active materials were scrapped o manually from the
foils. After dismantling, the recovered material was placed in an
oven at a maximum of 40 °C for safety reasons for 24 h and then
the weight of each fraction was measured with a scientific
balance (ENTRIS6202I1S, Sartorius Lab Instruments GmbH
& Co, Germany), and the dierence in weight corresponds to
the estimated electrolyte, which was evaporated (Figure 1). The
electrolyte value is quite low compared to the literature,
can testify that the electrolyte is not entirely evaporated at that
temperature and some electrolyte compounds such as the
conducting salts might have remained.
Complementary experiments have been carried out to identify
the nature of the binder, which is important information in order
to understand the electrode behavior during recycling. The
electrodes of a dismantled INR18650-29E were immersed in tap
water for 10 min. As observed in the Supporting Information
(Figure S1), all the graphite particles were thus detached from
the Cu foils, confirming the hypothesis of a water-soluble binder
for the anodic electrode. For the cathodic electrode, the LMOs
remained laminated on the Al foil, testifying to the presence of a
binder insoluble in water, likely PVDF.
For this study, the batteries underwent three recycling routes
(Figure 2), hereby referred to as M, TM, and EHF, to determine
the influence of each process on the liberation of battery
components and their eventual recovery. The pretreatment
processes are described next.
1. The M process used a single-shaft rotary impact shear
crusher UG300MS (MeWa universal granulator, Andritz,
Schwabisch, Germany) operated at a peripheral speed of
Figure 1. Estimation of INR18650-29E battery composition (wt %)
after manual dismantling.
ACS ES&T Engineering Article
6.4 m/s with a bottom grid of 10 mm. The feed consisted
of intact batteries producing shredded materials passing
through the discharge grate, while coarser particles
undertake further stress. The operating principle of this
crusher is the comminution of the feed material by
applying shearing stress between a block-shaped rotor and
stator tools, as detailed by Lyon et al.
2. In the TM route, vacuum pyrolysis was performed at
500650 °C. Subsequently, comminution of thermally
treated products was carried out using a Retsch SM 2000
cutting mill (Retsch, Inc., Newtown, USA) with a bottom
sieve of 10 mm mesh size.
3. The EHF route employed an EHF unit (EHF-400
ImpulsTec GmbH, Germany. The EHF uses three
cathodes at 40 kV to produce shock waves, discharging
at a rate of 1 to 4 Hz. The process produced two fractions:
float and sink, which were dried in an oven at 80100 °C.
Further information on this equipment is found in O
hl et
The resulting black mass products (<1000 μm) from M, TM,
and the sink fraction from the EHF process were classified with a
vibratory column sieve (Fritsch Analysette 3, Idar-Oberstein,
Germany) using four nominal sizes: 1000, 500, 125, and 63 μm.
For each fraction of the black mass, a representative subsample
of 1.5 g was taken using a rotary splitter (PT100, Retsch GmbH,
Haan, Germany) for analytical investigations. Each black mass
type had five samples, one per size fraction and two epoxy blocks
for the fraction 5001000 μm to minimize particle size eect on
samples representativeness.
In addition, the fine fraction (<63 μm) was further processed
by froth flotation to separate graphite particles from the LMOs.
The fraction below 63 μm was chosen in this study because it
was expected to contain the most liberated particles. The batch
flotation tests were conducted using a mechanically agitated
laboratory flotation machine (XFG, series Hang Slot). The black
mass sample was dispersed in water down to a solid
concentration of 50 g/L and with an impeller speed of 1200
rpm. The sample was dispersed for 2 min and then followed by
the conditioning stage, and the parameters were chosen based
on previous studies.
In all tests, 350 g/t EscaidTM 110
(ExxonMobil Hydrocarbon fluid, Product no. 20171206) was
used as a collector, conditioned for 3 min, followed by the
addition of 150 g/t methyl isobutyl carbinol (MIBC, 99% Alfa
Aesar Product no. A13435) as a frother, stirred for 1 min. During
flotation, the airflow rate was fixed to 20 mL/min, and the froth
was collected for 10 min. After each experiment, the flotation
products were dried in an oven under natural convection for 12 h
at 45 °C. Finally, a representative sample of the froth phase and
underflow products was collected with a rotary sample splitter
(Retsch PT100, Retsch GmbH, Haan, Germany) and was
submitted for automated mineralogy analysis.
2.2. Characterization. The chemical composition, degree
of liberation of LIB components, and their distribution were
evaluated using SEM-based automated image analysis, also
commonly called automated mineralogy. This analytical
technique combines high-resolution backscattered images
obtained by scanning electron microscopy (SEM) with energy
dispersive X-ray (EDX) measurements to determine the phase
composition (volume or mass fraction) and geometrical
parameters (e.g., size, shape, and association) of particles on a
polished surface.
The preparation of epoxy blocks followed the method as
originally suggested by Rahfeld and Gutzmer
to analyze
graphite particles and modified in Vanderbruggen et al.
particles were embedded in a homogeneous mixture of epoxy
resin and iodoform. To minimize errors and bias caused by
sedimentation and settling, vertical slices (B-sections) were
used, as suggested by Heinig et al..
These slices were rotated
90°and fixed in a new epoxy resin. The sample was then
polished and carbon-coated, thereby creating a conductive
surface and scanned by SEM.
The mineral liberation analysis (MLA) system hereby used
combines a SEM (FEI Quanta 650F) equipped with two EDX
spectrometers (Bruker Quantax X-Flash 5030). The image was
Figure 2. Studied recycling routes: M, TM, and (EHF). Followed by froth flotation of the fine black mass fraction.
ACS ES&T Engineering Article
processed with MLA Suite 3.1.4 software for automated data
acquisition. The working principle is summarized in Figure 3. In
the first place, a BSE image is obtained (Figure 3A), which is
used to determine the grain boundaries. Next, the sample is
scanned using the grain X-ray mapping (GXMAP); on each red
point in Figure 3B an X-ray spectrum was acquired. The same
operating conditions and measurement mode were applied to all
the samples, that is, 0.5 μm pixel size at 15 kV.
The individual X-ray measurement (Figure 3B) was classified
using a generated reference phase list for this project (Figure
3C). For data processing, the spectra were grouped according to
battery components: anode active material, lithium metal oxides,
Cu foil, Al foil, and casing, as shown in Supporting Information
S2. The battery component can be estimated and highlighted on
the processed image (Figure 3D); the Al foil appears in green,
whereas the lithium metal oxides appear in blue. In addition, the
calculated assay obtained by MLA was cross-checked with bulk
analysis using X-ray fluorescence (XRF NitonTM XL3t 980
from Thermo Scientific), as explained in the paper Vander-
bruggen et al.
and can be found in Supporting Information S3.
In addition, SEM images with imposed colors were taken from
the polished grain mounts and also on loose powder. The loose
powder samples were fixed on a tab (PELCO Tabs TM, 6 mm
OD from TED PELLA, INC, Redding, CA, USA). For these
SEM images, the backscattered electron (BSE) image and
secondary electron (SE) image were superimposed, and false
colors were attributed for generating an image with composi-
tional, textural, and topographic information. The BSE signal
intensity is governed by the density [by means of the atomic
number (Z)] of the particles and shows a contrast in the
elemental composition between each particle. The blue color
was selected for high-density species, likely LMO particles made
of heavy metals, while the black color was used for low-density
material, highlighting the graphite and residual binder particles.
The SE signal is sensitive toward the topography of the substrate
surface and is highlighted through orange colors.
3.1. LIB Component Distribution. Each process was
compared according to their individual performances starting
from the mass distribution and losses, as presented in Figure 4.
The results indicated that losses of material occur for all the
processes from 5.8 to 24 wt %. The M process is the least at 5.8
wt %, likely including fine dust and electrolyte. The electrolyte in
LIBs consists of a mixture of organic solvents and conducting
salts, such as LiPF6. A significant amount of solvent may
evaporate when exposed to the atmosphere; however, some
electrolyte compounds, such as the conducting salts, might have
remained in the M-BM. Although new methods have been
explored to recover the electrolyte, they require controlled
atmospheres or the use of supercritical fluids, such as CO2.
On the other hand, the EHF process reported 11.1 wt % mass
losses corresponding to electrolyte removal, dispersion, or
dilution of fine particles such as conductive carbon and graphite
and partial binder dissolution.
Finally, the TM process presented the highest losses at 24.2 wt
%, which can be due to the decomposition and consumption of
organic materials during the vacuum pyrolysis stage. As reported
in the literature, the separator decomposes first, then
polypropylene (155 °C) and polyethylene (135 °C),
by binder decomposition, for example, PVDF (450 °C) and SBR
(248 °C).
In addition, possible graphite losses could occur
during pyrolysis, as shown by Lombardo.
In all processes, the particles associated with casing materials
are eciently recovered in the coarse fraction (<1000 μm). As
shown in Figure 5, almost no casing particles were identified in
the black mass (less than 0.4 wt %.) These heavy particles are
usually recovered by an established industrial process after
mechanical crushing using a densimetric table, such as those
practiced by Retriev Technologies, Recupyl Valibat, AkkuSer,
The main dierence between the processes results in the
distribution of the cell components. The comparatively low mass
of the black mass (36.2 wt %) obtained with mechanical
treatment shows that the majority of the components are not
comminuted and remained coarse, especially the Cu and Al foils.
Furthermore, due to its elasticity, the separator particles
remained in the coarse fraction, which can be easily recovered
using, for example, an air classifier.
Figure 3. Working principle of SEM-based automated image analysis. This example shows in blue LMOs (NCA spectra) and in green Al foils (Al
spectra). 3A: Backscattered image with SEM, 3B X-ray mapping with EDX, 3C phase composition, and 3D processed image by automated mineralogy.
Figure 4. Mass distribution and losses of LIB materials after three
dierent routes. (100% represents the initial battery feed, the standard
deviations for the weight fraction were obtained from the sieving
experiments, and the losses were calculated from the full process).
ACS ES&T Engineering Article
In the case of the EHF process, the separator particles may
also be recovered in a relatively simple manner. Indeed, during
experiments, these particles were reported to the surface of the
aqueous medium due to their low density.
In addition, the distribution of cathode and anode active
particles during each processing is distinct. These dierences
reflect the variable impact that each processing strategy has on
the properties of the LIB components. To understand this
influence and further evaluate these processes, it is necessary to
carry out an in-depth characterization of the resulting material
3.2. Black Mass Characterization. One of the most
relevant parameters for the evaluation of the eectiveness of a
recycling pretreatment operation is liberation, as it aects the
eciency of downstream separation processes. Therefore, the
three black masses (<1000 μm) were further evaluated by
automated mineralogy, as shown in Figure 6. The objective of
this characterization is to understand the behavior of each
species after processing, as will be discussed in subsequent
3.2.1. Mechanical Preprocessing. In the black mass treated
via mechanical preprocessing, the active particles, graphite, and
LMOs comprise over 95% of the mass in all size fractions
(Figure 6). These results are similar to the ones obtained by
Widikatmoko et al.,
where only a few particles of Al and Cu foils
were found below 850 μm after milling.
The M-BM contains the least Cu and Al foil residues
compared to the other processes, as foils are deformed rather
than comminuted in the rotary crusher (Figure 6A). The foils
are known to be ductile, non brittle, and have a good tensile
strength, requiring more energy and stress for their comminu-
The electrode foils were well delaminated from the
active particles.
Despite this eective delamination of the active particles from
the electrode foils, only 5.1 wt % of black mass was reported to
<63 μm (Figure 6B). This is due to the preservation of the
polymeric binder, as observed in Figure 7. During the battery
production, the active particles are coated with the binder,
forming aggregates that are laminated onto the foils using a
calendering process. Thus, mechanical comminution can
delaminate but not liberate individual active particles. The
aggregates shape resulting from lamination can be observed on
the Figure 6A.
3.2.2. Thermomechanical Preprocessing. The volume of
fine black mass obtained with the TM route is higher compared
to mechanical processing (i.e., 51 wt % than 36 wt %,
respectively). In this case, the anode active particles were not
evenly distributed within all size fractions, being preferentially
concentrated in sizes below 63 μm. Figure 6D shows
spheroidized graphite particles that are mostly well liberated,
highlighting the full decomposition of the anode binder. Indeed,
a binder such as SBR degrades above 248 °C.
Based on several studies, the PVDF cathode binder
decomposes above 450 °C
and optimal pyrolysis temper-
atures of 550 °C, according to Zhang et al.
Thus, the use of
vacuum pyrolysis above 500 °C should eliminate the binders.
However, despite the treatment of black mass at 550650 °C in
this work, the cathode electrodes preserved their lamination, as
observed in Figure 6C. This preservation could mean that only a
partial decomposition of PVDF was achieved. One of the
contributing factors for a partial decomposition of the cathode
binder might be that entire batteries were fed into the pyrolysis
chamber in this study. The compacted structure of the
electrodes in the battery may hinder the eciency of the
pyrolysis process because the electrode surfaces are not directly
exposed, reducing the decomposition of the binder.
Another explanation might be that Al melted, protecting the
laminated structure of the cathode. Also, despite the discharging
step for safety, a thermal runaway may have occurred, leading to
higher temperatures than expected in some areas of the
As seen in Figure 6C, there is a Cu particle containing
Al traces with patterns characteristic of melting, suggesting a
temperature above its melting point of Al at 660 °C was reached.
Al melting is an issue for LMO liberation, as mentioned by Li et
The TM-BM contains Al foils in its dierent size fractions
(Figure 6 in the modal composition). Unlike the M-BM, the Al
foils after thermal treatment appeared uneven and punctured
(Figure 8), probably caused by corrosion promoted by HF in the
electrolyte during pyrolysis. The thermal process caused fissures
and a subsequent increase in brittleness of the Al fraction.
The change in mechanical properties of Al explains its presence
in all size fractions of the black mass after comminution. The
change in mechanical properties of Al explains its presence in all
size fractions of the black mass after comminution. Therefore, it
might be recommended to apply the mechanical-thermal (MT)
route: first a mechanical process to produce BM with a low
amount of fine Al impurity particles to avoid Al melting during
the subsequent pyrolysis. Another advantage of conducting the
pyrolysis on the BM and not on the input batteries is that it
would lead to more uniform binder decomposition due to
increase in exposed surfaces, which could facilitate liberation.
After pyrolysis, the produced MT-BM should then be milled to
liberate the active particles and concentrate them into the fine
Another aspect of the TM-BM is the dierence in metal oxide
species present. As observed in Figure 9, only the TM-BM
presented a NiCo phase. This suggests that during the thermal
process, there was a partial reduction of metal oxides. Yang et
concluded that Ni ions from NMC were reduced to metallic
Ni, while the Co3+ and Mn3+ ions appeared to maintain their
trivalent form. Various studies explained that thermal pretreat-
ment can promote the carbothermic reduction of the LMOs and
has the advantage of improving their leaching eciency and
decreasing the amount of reducing agents (e.g., H2O2) needed
during hydrometallurgical treatment.
3.2.3. Electrohydraulic Fragmentation Preprocessing.
Among the three routes, the EHF process leads to the highest
relative mass of LIB, reporting to the fraction below 1000 μm,
Figure 5. Composition of the black mass (<1000 μm) after the three
processes implemented derived from automated mineralogy data.
ACS ES&T Engineering Article
56.3 wt %. The EHF method uses only high voltage pulsations
and liberates battery components without comminution tools.
After thousands of pulsations, the batteries were completely
opened. Most of the active particles were well liberated from the
foils and concentrated in the fine fractions of the black mass. The
active particles, graphite, and LMOs conserved their spherical
shape during this process (Figure 6F). Ohl et al.
showed that
the LMOs after the EHF process can be reused in new battery
Figure 6. On the right: black mass modal composition, showing component percentage in each size fraction. (100% represents the initial battery feed).
On the left: processed images obtained from automated mineralogy: Pictures A, C, and E show the fraction of 5001000 μm (scale of 1000 μm), and
pictures B, D, and F show the fraction <63 μm (scale of 500 μm).
ACS ES&T Engineering Article
cell production but at a lower grade than the new material.
Alternatively, the EHF-BM can be further refined to pure
chemical elements via hydrometallurgy.
The presence of a water-soluble anode binder, such as CMC,
SBR, or PAA, helps graphite delamination from the Cu foil and
its deaggregation (as shown in the Supporting Information
Figure S1). The pH of water after the operation remained
neutral (ca. 7). Interestingly, while graphite particles appeared to
be well liberated, and its presence in the fraction <63 μm was
comparatively lower than for the TM route. A reaggregation
mechanism has occurred, leading to heterogeneous aggregates
containing liberated active particles, as observed in Figure 6E.
This can be due to the anode binder dissolution and its
rehardening during the drying stage. Indeed, in LIB production,
the water used as a solvent for the anode binder is removed by
evaporation before calendering onto the Cu foil.
On the SEM
image in Figure 10, the cathode particle is surrounded by a
matrix, which is not iodine epoxy resin and could be the
rehardened anode binder. Therefore, a continuously wet
recycling process might be the solution to maintain this
liberation eciency and avoid unselective agglomeration of
LIB components. A wet screening should be applied right after
the EHF process to further separate the foils from the liberated
active particles.
It is also observed in Figure 10 that most nonliberated cathode
active materials remain bound to the Al foil, proving that only
the anode binder is dissolving and revealing a dierent behavior
for the anode and cathode binders. Recently, Lyon et al.
showed that the combination of mechanical comminution to
open the batteries, followed by EHF for decoating of electrodes,
presented a higher liberation eciency for the cathode electrode
than the EHF alone.
3.3. Froth Flotation. Froth flotation was used to separate
graphite particles from the LMOs based on their dierence of
The results of the rougher flotation experiments
carried out in this study are summarized in Figure 11. Since the
feed of flotation have dierent grades of graphite and LMOs as a
result of the preparation process (Figure 6 modal composition),
the flotation eciencies cannot be directly compared.
The M-BM shows a moderate selectivity with a recovery of
63.2% graphite in the froth product and 66.6% LMOs in the
underflow product. This comparatively low selectivity is
attributed to the residual binder coating active particles,
resulting in a decrease in the wettability dierence between
the graphite and the LMO particles. Indeed, the commonly used
cathode binder, that is, PVDF, has a hydrophobic behavior
promoting the recovery of LMOs:
These results are
comparable to the study of Zhang et al.,
where they floated
crushed electrodes and 62.5% of the LMOs were recovered in
the underflow product. The low eciency of graphite recovery
may be the result of two conditions that require further study. In
the first place, it is dicult to disperse the oily kerosene used as a
collector, and thus, it may not be eciently adsorbed on the
graphite surface, even in cases where they are well liberated.
Furthermore, if both graphite particles and binder-coated LMOs
present similar hydrophobicity, this might result in a competitive
flotation eect.
The TM-BM presented the highest selectivity of the samples
hereby studied, with a graphite recovery of 94.4% in the froth
product and 89.4% LMOs particles in the underflow product.
With this treatment process, the active particles present a
stronger dierence in wettability due to a comparatively superior
binder removal. The anode binder is decomposed during the
pyrolysis stage, aiding kerosene adsorption on the graphite
surface. As mentioned above, the LMO phase has been modified
Figure 7. SEM image with imposed colors on loose powder of an LMO
aggregate from M-BM. The blue spheres are the LMOs, and in between,
there is the residual binder.
Figure 8. Left: SEM image with imposed colors on polished grain mount of a cathode particle. The dierence of grey colors shows the Al-oxidation on
the side of the foil. Some holes can be observed on the Al foils. The black particles, for instance, on the left of the foil, are the resin which went through
the porosity during sample preparation.
ACS ES&T Engineering Article
during this TM process (Figure 9), which might also aect their
wettability, an unexpected phenomenon that should be further
studied. With this TM process, the true flotation of the LMOs is
diminished due to binder removal. Furthermore, in a recent
publication by our research group, it was shown that the
flotation eciency of the TM black mass can be improved by
applying an attrition pretreatment.
Such pretreatment
refreshes the particle surface, removing the anode binder and
pyrolysis residues, resulting in an improved graphite flotation.
Attrition also removes a part of the cathode residual binder,
reducing the true flotation of LMOs. In addition, with this high-
shearing pretreatment, there is a disaggregation of graphite and
LMOs, decreasing the entrainment of the metals in the graphite
overflow product.
The EHF-BM shows graphite recovery in the overflow
product of 83.9%. As earlier discussed, it is possible that the
anode binder is better dissolved during the EHF process,
allowing a better adsorption of kerosene and thus leading to a
higher recovery. However, some graphite particles might be
trapped in heavy agglomerates and hence not recovered.
Nevertheless, the flotation selectivity was harmed by a
significant recovery of LMOs in the overflow product (
42.2%). Similar to the M-BM, the residual PVDF promoted
the recovery of LMO particles, in addition to some possible
Figure 9. Modal mineralogy of Ni phases in wt % occurring in the black mass samples, and three examples of processed images of particles.
Figure 10. SEM image with imposed colors on the polish grain mount of a cathode particle surrounded by a “matrix” and entrapped particles.
Figure 11. Grade and recovery of the graphite particles in the overflow
product (O/F). Grade and recovery of the LMO particles in the
underflow product (U/F).
ACS ES&T Engineering Article
Table 1. Summary Table of the Advantages and Drawbacks of the Three Studied Preprocessing Routes
Process type Advantages Drawbacks
Mechanical (M) (+) possibility of recovering the electrolyte and separator. () aggregates of active particles under the laminated shape due to the residual binder.
(+) low content of foils and casing particles in the BM. The BM contains mainly the active particles. () low volume of BM and especially in the fractions below 125 μm due to the
conservation of active particle lamination shape.
(+) good delamination of the foils present in the BM. () residual binder results in a lack of selectivity for flotation. True flotation of LMOs
due to coated organic binder.
() mix of active particles in the flotation; therefore, the products have to be sent to
hydrometallurgy to recover the metals. The graphite ends up in the leaching cake.
(TM)(+) anode binder well removed, resulting in a high liberation degree of the graphite and copper foils. () electrolyte and separator lost.
(+) low impurity content in the graphite flotation product, potential for graphite recycling. () Possibility of Al melting decreasing cathode liberation.
(+) ecient separation of LMOs and graphite with froth flotation due to binder removal. () after pyrolysis, Al foil has a brittle behavior. Al particles are spread in the whole BM.
These impurities are challenging for the following hydrometallurgy stage.
(+) LMO flotation product presents a high content of metals and a really low content of graphite particles compare
to the BM. The removal of the graphite particles, which are porous, reduces the acid reagent consumption during
hydrometallurgical treatment.
() partial reduction of metal oxides during pyrolysis so no possibility of direct
recycling of the LMOs. The LMO product needs to go through hydrometallurgical
treatment to recover the metals.
(+) partial reduction of the metal oxides has the advantage to improve their leaching eciency and decreasing the
amount of reducing agents needed during the hydrometallurgical treatment
(+) recovery of separator foil (skimming). () electrolyte lost.
(+) high liberation of the active particles from the foils. A wet screening can further separate the foils from the active
particles. () Al and especially Cu impurities, which are not found in the other BM.
(+) high volume of BM. () if followed by a drying stage, there is rehardening of the soluble binder, leading to
heterogeneous agglomerates. Therefore, it is recommended to remain in the wet
(+) liberation of active particles while conserving morphology, so there is possibility of direct recycling of LMOs
and graphite.
ACS ES&T Engineering Article
entrapment mechanisms. In addition, the fact that the EHF-BM
was dried after the EHF stage might influence the surface, and it
should be further studied. Nevertheless, to avoid binder
rehardening and, therefore, unselective agglomerates, it is
recommended that the BM remains under slurry between the
EHF product and the flotation process.
These results, compiled together, point out the need to
rethink binder chemistry. Indeed, the PVDF binder is one of the
biggest challenges during LIB recycling due to its toxicity and
the diculties to remove it, diminishing the cathode component
liberation during comminution and also flotation selectivity due
to its hydrophobic behavior. Therefore, finding alternatives for
the cathode binder chemistry, such as water-soluble binders,
which are already commercialized for the anode electrode,
would increase the LIB recycling eciency.
Currently, many dierent pretreatment methods are estab-
lished and produce a black mass of dierent quality. Based on the
obtained results, the advantages and drawbacks of each route is
summarized in Table 1.
The aim of increasing the recycling eciency of LIBs requires an
understanding of how the LIB components are liberated during
the recycling process. This paper characterized black mass
samples obtained from dierent preprocessing routes: M, TM,
and EHF. For the characterization, automated mineralogy
enabled qualitative and quantitative observations of the
properties of LIB components and their dependence on
comminution processes. As it is hereby shown, LIB liberation
is component-specific, a function of material properties, and
influenced by the methods employed, resulting in dierent black
masses. The presence of the binder and its preservation is found
to have a strong impact on the separation of active materials
using froth flotation.
With the M process, the active particles were well
delaminated from the electrode foils. The BM contained a
really low amount of foils and casing impurities. The
active particles remained under their lamination shape
due to the binder conservation, leading to only a fine
fraction of active particles being individually liberated. In
addition, the conservation of the cathode binder harmed
the flotation selectivity.
With the EHF route, most of the active particles were
individually liberated. Nevertheless, the following drying
step leads to anode binder rehardening, forming
unselective agglomerates. If a wet screening is performed
right after the EHF process, the foils and active particles
can be further separated, decreasing the content of foil
impurities in the BM. Therefore, this method showed
potential, provided that the recycling process is designed
to remain under wet conditions.
With the TM process, the Al foils were oxidized, corroded,
and sometimes melted, which increased their fragility.
These mechanisms scattered the Al foil and became a
contaminant in the separation process despite binder
decomposition. Therefore, it might be recommended to
first allow the mechanical process to produce a BM with a
low amount of Al foil, which is then pyrolyzed, reducing
the amount of fine Al impurities. In addition, the pyrolysis
stage decomposition of the binders leads to a dierence in
wettability between the active particles in the fine fraction
of the BM. Hence, this TM route is the preferred route for
a selective separation of the graphite and LMO particles.
By using automated mineralogy, this paper showed the unique
influences of three recycling operations, revealing their strengths
and weaknesses, which could be controlled, avoided, or
improved to increase the LIB recycling eciency. This work
also demonstrates that only by understanding the relationships
between the design of cell components and recycling it is
possible to identify the inherent challenges posed by the existing
battery designs, thus highlighting the design-for-recycling needs
for future battery technologies.
Supporting Information
The Supporting Information is available free of charge at
Dissolution of the binder; and major phases grouped
according to the LIB components (PDF)
Corresponding Author
Anna Vanderbruggen Helmholtz Zentrum Dresden
Rossendorf (HZDR), Helmholtz Institute Freiberg for
Resource Technology (HIF), Freiberg 09599, Germany;
Department of Chemical and Metallurgical Engineering,
School of Chemical Engineering, Aalto University, Aalto
00076, Finland;;
Neil Hayagan Helmholtz Zentrum Dresden Rossendorf
(HZDR), Helmholtz Institute Freiberg for Resource
Technology (HIF), Freiberg 09599, Germany;
Kai Bachmann Helmholtz Zentrum Dresden Rossendorf
(HZDR), Helmholtz Institute Freiberg for Resource
Technology (HIF), Freiberg 09599, Germany
Alexandra Ferreira Universitéde Lorraine, CNRS,
Laboratoire GeoRessources, Nancy F-54000, France;
Denis Werner Institute of Mechanical Process Engineering
and Mineral Processing, TU Bergakademie Freiberg, Freiberg
09599, Germany
Daniel Horn Fraunhofer Research Institution for Materials
Recycling and Resource Strategies IWKS, Hanau 63457,
Urs Peuker Institute of Mechanical Process Engineering and
Mineral Processing, TU Bergakademie Freiberg, Freiberg
09599, Germany
Rodrigo Serna-Guerrero Department of Chemical and
Metallurgical Engineering, School of Chemical Engineering,
Aalto University, Aalto 00076, Finland
Martin Rudolph Helmholtz Zentrum Dresden Rossendorf
(HZDR), Helmholtz Institute Freiberg for Resource
Technology (HIF), Freiberg 09599, Germany
Complete contact information is available at:
Author Contributions
Anna Vanderbruggen conceptualization, data curation, inves-
tigation, methodology, writing-original draft, writing-review &
editing; Neil Hayagan software, writing-review & editing; Kai
ACS ES&T Engineering Article
Bachmann software, writing-review & editing; Alexandra
Ferreira investigation, writing-review & editing; Denis Werner
investigation, resources, writing-review & editing; Daniel Horn
investigation, resources, writing-review & editing; Urs Peuker
supervision, writing-review & editing; Rodrigo Serna-Guerrero
supervision, writing-review & editing; Martin Rudolph super-
vision, writing-review & editing.
The authors gratefully acknowledge the Helmholtz foundation
for base funding within the PoF III (project-oriented funding
part III) for the BooMeRanG project. A.V acknowledges her
recent funding through the BMBF Competence Cluster
Recycling and Green Battery (GreenBatt) within the project
“ecoLiga” (03XP0326B). R.S.G. acknowledges the BAT-
Circle2.0 project (Business Finland grant number 44886/31/
The authors declare no competing financial interest.
The authors would also like to thank Accurec GmbH for
pyrolyzing the batteries and UVR FIA GmbH for grinding the
pyrolyzed black mass and the XRF analysis. The authors thank
Roland Wuerkert, Michael Stoll, and Sebastian Thormeier from
Helmholtz Institute Freiberg for the epoxy block preparation,
Simon Obando Sierra and David Guzman Gallo for their help
with sample preparation, and Alejandro Abadías Llamas for his
help with the flowsheet design.
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ACS ES&T Engineering Article
... Most investigations were conducted with cells from other applications than EVs, such as mobile phones [22,23], or a black mass from an industrial recycling plant with undefined feed was used [17][18][19]. Not every study analysed all metals and they applied different methods for analysing the metal content, e.g., inductively coupled plasma-optical emission spectroscopy (ICP-OES) [17,18,20] or mass spectroscopy (ICP-MS) [22], X-ray fluorescence spectroscopy (XRF) [17,21,23], flame atomic adsorption spectroscopy (FAAS) [18] and automated mineralogy [14]. ...
... In most cases, the content of metals from the positive electrode coating is higher, which leads to a smaller size fraction [17,18,23]. Contrarily, Vanderbruggen et al. [14] measured the highest content of lithium metal oxides (around 60%) in the fraction of 500-1000 µm and the lowest content (around 40%) in the fine fraction of < 63 µm. For different studies, the accumulated content of Ni, Mn and Co ranged between 28 [19] and 45% [17] for different black mass sizes (from 0-200 to 0-2000 µm). ...
... [23]. Vanderbruggen et al. [14] reported an overall graphite content of around 50%, whereby the smaller the size fraction, the higher the graphite content [14]. [17], 2 [18], 3 [19], 4 [20], 5 [22], 6 [23], 7 [14]. ...
Full-text available
With the increasing number of electric vehicles (EVs) rises the need to recycle their used lithium-ion batteries (LIBs). During the mechanical process of the recycling of the LIB cells, a fine fraction, the so-called black mass, is created. This black mass consists mostly of the coatings originating from the cells’ electrodes and residues from the electrolyte, together with a low amount of Al and Cu from the crushed current collector foils. The amount of black mass as well as its composition is influenced by the chosen grid size at the crusher discharge. To reduce solvent emissions during the recycling process, a thermal pre-treatment can be added before crushing, which also influences the black mass and its properties due to changes in the adhesion between electrode foils and coating. This study investigates the influence of the crusher settings as well as the pre-treatment temperatures to find an optimum between the recovery of the coating and conductive salt, while limiting the amount of Al and Cu in the black mass.
... Mechanical crushing (M), thermomechanical (TM), and electrohydraulic fragmentation (EHF) are the primary methods developed for breaking down the robust battery cell casing, in which active materials can be liberated from current collectors (Figures 5A-5C). 51 In the M process, intact LIBs are fed into the system and crushed into small particle fragments under mechanical sheer force. 52 The high tensile strength of the metal current collector allows for effective delamination of the active particles during the deformation of the metal foils. ...
... The M process effectively liberates active particles with minimal material loss, accounting for only 5.8% of the total mass ( Figure 5D). 51 Moreover, the presence of metal impurities is low, comprising only 17.53% of the total mass ( Figure 5E). 51 However, the residual polyvinylidene fluoride (PVDF) binder in the M process leads to serious particle aggregation, resulting in particle sizes distributed above 1,000 mm. ...
... 51 Moreover, the presence of metal impurities is low, comprising only 17.53% of the total mass ( Figure 5E). 51 However, the residual polyvinylidene fluoride (PVDF) binder in the M process leads to serious particle aggregation, resulting in particle sizes distributed above 1,000 mm. The TM process exhibits relatively high materials loss (24%) attributed to the decomposition and consumption of organic materials during vacuum pyrolysis. ...
Full-text available
With the exponential expansion of electric vehicles (EVs), the disposal of Li-ion batteries (LIBs) is poised to increase significantly in the coming years. Effective recycling of these batteries is essential to address environmental concerns and tap into their economic value. Direct recycling has recently emerged as a promising solution at the laboratory level, offering significant environmental benefits and economic viability compared to pyrometallurgical and hydrometallurgical recycling methods. However, its commercialization has not been realized in the terms of financial feasibility. This perspective provides a comprehensive analysis of the obstacles that impede the practical implementation of direct recycling, ranging from disassembling, sorting, and separation to technological limitations. Furthermore, potential solutions are suggested to tackle these challenges in the short term. The need for long-term, collaborative endeavors among manufacturers, battery producers, and recycling companies is outlined to advance fully automated recycling of spent LIBs. Lastly, a smart direct recycling framework is proposed to achieve the full life cycle sustainability of LIBs.
... From industrial BM characterizations previously published by other authors, the total mass of active particles typically corresponds to 70%-90% of the total weight. 13,15,17,50 This is confirmed by the results of this work where the impurities are estimated to be ca. 10% of the total sample mass. ...
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A new method based on thermogravimetric analysis was developed to measure the graphite content in battery material mixture. This approach exploits the thermochemical reduction of cathodic Li-transition metal oxides with anodic graphite at elevated temperatures under an inert atmosphere. Using known composition artificial mixtures, a linear correlation between cathode mass loss and sample graphite content was observed. The method was validated using industrial black mass samples and characterized traditionally to estimate and rationalize potential error sources. Thermal degradation profiles of industrial battery waste reflected those in the artificial system, demonstrating its applicability. This work also demonstrates that thermogravimetric degradation profiles can distinguish between a cathode consisting of single or multiple Li-metal oxides. Although accuracy depends on active component mixture content and impurities, it is demonstrated that the method is useful for a fast graphite content estimation. Unlike other graphite characterization techniques, the method proposed is simple and inexpensive.
The article contains sections titled: 1 Introduction 2 Fields of Application 2.1 Primary Raw Materials (Minerals) 2.2 Secondary Raw Materials (Recycling Products) 2.3 Construction Materials 2.4 Agricultural, Biotechnological, and Food Raw Materials 2.5 Chemical Production 3 Schematic Description of Solid–Solid Separation 3.1 Preconditions 3.2 Liberation 4 Quantification of a Solid–Solid Separation Process Result 5 Presentation of the Result of a Solid–Solid Separation Process 5.1 Grade‐Recovery Curve to Quantify Solid–Solid Separation 5.2 Tromp Curve to Quantify Solid–Solid Separation 5.3 Multidimensional Quantification of Solid–Solid Separation 6 Separation Principles for Solid–Solid Separation 6.1 Manual and Automated Sorting 6.2 Density Separation 6.3 Magnetic Separation 6.4 Separation in Electric Fields 6.5 Flotation 7 Economic Aspects References
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Particle separation is an essential part of many processes. One mechanism to separate particles according to size, shape, or material properties is dielectrophoresis (DEP). DEP arises when a polarizable particle is immersed in an inhomogeneous electric field. DEP can attract microparticles toward the local field maxima or repulse them from these locations. In biotechnology and microfluidic devices, this is a well-described and established method to separate (bio-)particles. Increasing the throughput of DEP separators while maintaining their selectivity is a field of current research. In this study, we investigate two approaches to increase the overall throughput of an electrode-based DEP separator that uses selective trapping of particles. We studied how particle concentration affects the separation process by using two differently-sized graphite particles. We showed that concentrations up to 800 mg/L can be processed without decreasing the collection rate depending on the particle size. As a second approach to increase the throughput, parallelization in combination with two four-way valves, relays, and stepper motors was presented and successfully tested to continuously separate conducting from non-conducting particles. By demonstrating possible concentrations and enabling a semi-continuous process, this study brings the low-cost DEP setup based on printed circuit boards one step closer to real-world applications. The principle for semi-continuous processing is also applicable for other DEP devices that use trapping DEP.
Hydrothermal-based direct regeneration of spent Li-ion battery (LIB) cathodes has garnered tremendous attention for its simplicity and scalability. However, it is heavily reliant on manual disassembly to ensure the high purity of degraded cathode powders, and the quality of regenerated materials. In reality, degraded cathodes often contain residual components of the battery, such as binders, current collectors, and graphite particles. Thorough investigation is thus required to understand the effects of these impurities on hydrothermal-based direct regeneration. In this study, we focus on isolating the effects of aluminum (Al) scraps on the direct regeneration process. We found that Al metal can be dissolved during the hydrothermal relithiation process. Even when the cathode material contains up to 15 wt% Al scraps, no detrimental effects were observed on the recovered structure, chemical composition, and electrochemical performance of the regenerated cathode material. The regenerated NCM cathode can achieve a capacity of 163.68 mAh/g at 0.1C and exhibited a high-capacity retention of 85.58% after cycling for 200 cycles at 0.5C. Therefore, the hydrothermal-based regeneration method is effective in revitalizing degraded cathode materials, even in the presence of notable Al impurity content, showing great potential for industrial applications.
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Lithium-ion batteries (LIBs) are common in everyday life and the demand for their raw materials is increasing. Additionally, spent LIBs should be recycled to achieve a circular economy and supply resources for new LIBs or other products. Especially the recycling of the active material of the electrodes is the focus of current research. Existing approaches for recycling (e.g., pyro-, hydrometallurgy, or flotation) still have their drawbacks, such as the loss of materials, generation of waste, or lack of selectivity. In this study, we test the behavior of commercially available LiFePO4 and two types of graphite microparticles in a dielectrophoretic high-throughput filter. Dielectrophoresis is a volume-dependent electrokinetic force that is commonly used in microfluidics but recently also for applications that focus on enhanced throughput. In our study, graphite particles show significantly higher trapping than LiFePO4 particles. The results indicate that nearly pure fractions of LiFePO4 can be obtained with this technique from a mixture with graphite.
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The zigzag (ZZ) classifier is a sorting and classification device with a wide range of applications (e.g., recycling, food industry). Due to the possible variation of geometry and process settings, the apparatus is used for various windows of operation due to the specifications of the separation (e.g., cut sizes from 100 µm to several decimetres, compact and fluffy materials as well as foils). Since the ZZ classifier gains more and more interest in recycling applications, it is discussed in this paper, with regards to its design, mode of operation, influencing parameters and the research to date. Research on the ZZ-classifier has been ongoing on for more than 50 years and can be divided into mainly experimental studies and modelling approaches.
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Eramet uses a combination of physical and hydrometallurgical treatment to recycle lithium-ion batteries. Before hydrometallurgical processing, mechanical treatment is applied to recover the Black Mass which contains nickel, cobalt, manganese and lithium as valuable elements as well as graphite, solvent, plastics, aluminium and copper. To evaluate the suitability for hydrometallurgical recycling, it is essential to analyse the Black Mass chemically but also with respect to size, shape and composition of particles in the Black Mass. The Black Mass of various battery recyclers was investigated by using a combination of SEM/QEMSCAN® analyses. This specific QEMSCAN® database contains 260 subgroups, which comprise major and minor chemical variations of phases. The database was created using millions of point analyses. Major observations are: (1) particles can be micro-texturally characterised and classified with respect to chemical element contents; (2) important textural and chemical particle variations exist in the Black Mass from several origins leading to different levels of quality; (3) elements deleterious to hydrometallurgical processing (i.g. Si, Ca, Ti, Al, Cu and others) are present in well liberated particles; (4) components can be quantified and cathodes active material compositions (LCO, different NMC, NCA, LFP, etc.) that are specific for each battery type can be identified; (5) simulation of further physical mineral processing can optimise Black Mass purity in valuable elements.
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In order to ensure environmentally friendly mobility, electric drives are increasingly being used. As a result, the number of used lithium-ion batteries has been rising steadily for years. To ensure a closed recycling loop, these batteries must be recycled in an energy- and raw material-efficient manner. For this purpose, hydrometallurgical processes are combined with mechanical pre-treatment, including disintegration by mills, crushers and/or shears. Alternatively, electrohydraulic fragmentation (EHF) is also of great interest, as it is considered to have a selective fragmentation effect. For a better comparison, different application scenarios of EHF with other methods of mechanical process engineering for the treatment of lithium-ion batteries are investigated in the present study.
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The comminution of spent lithium-ion batteries (LIBs) produces a powder containing the active cell components, commonly referred to as “black mass.” Recently, froth flotation has been proposed to treat the fine fraction of black mass (<100 �m) as a method to separate anodic graphite particles from cathodic lithium metal oxides (LMOs). So far, pyrolysis has been considered as an effective treatment to remove organic binders in the black mass in preparation for flotation separation. In this work, the flotation performance of a pyrolyzed black mass obtained from an industrial recycling plant was improved by adding a pre-treatment step consisting of mechanical attrition with and without kerosene addition. The LMO recovery in the underflow product increased from 70% to 85% and the graphite recovery remained similar, around 86% recovery in the overflow product. To understand the flotation behavior, the spent black mass from pyrolyzed LIBs was compared to a model black mass, comprising fully liberated LMOs and graphite particles. In addition, ultrafine hydrophilic particles were added to the flotation feed as an entrainment tracer, showing that the LMO recovery in overflow products is a combination of entrainment and true flotation mechanisms. This study highlights that adding kerosene during attrition enhances the emulsification of kerosene, simultaneously increasing its (partial) spread on the LMOs, graphite, and residual binder, with a subsequent reduction in selectivity.
Graphite – natural or synthetic – is the most dominant active material used for LIB anodes [1] . Natural graphite, however, is considered a critical material within the EU [2] , while synthetic graphite is obtained from coke [3] – a carbon precursor produced from coal or petroleum. Therefore, efficient recycling and reuse of graphite are essential towards sustainability and resource preservation [4] . Herein, we report a novel and highly efficient process to recover high-quality graphite from spent LIBs. Following a comprehensive physicochemical characterization of the materials obtained, we conducted an extensive electrochemical characterization in half-cells and graphite‖NMC 532 full-cells and compared the results with the data obtained for half-cells and full-cells using pristine commercial graphite. In half-cells, the recycled graphite shows remarkably high reversible specific capacities (e.g., 350 mAh g ⁻ ¹ at C/20) and very stable cycling for several hundred cycles at 1C. The graphite‖NMC 532 full-cells also show excellent cycling stability, with a capacity retention of 80% after about 1,000 cycles. Particularly, the comparison with the pristine graphite comprising full-cells reveals very comparable performance, highlighting the great promise of recycled and reused graphite as a pivotal step towards truly sustainable LIBs and the great goal of a circular economy. References [1] J. Asenbauer, T. Eisenmann, M. Kuenzel, A. Kazzazi, Z. Chen, and D. Bresser, “The success story of graphite as a lithium-ion anode material – fundamentals, remaining challenges, and recent developments including silicon (oxide) composites,” Sustain. Energy Fuels , 2020. [2] Comisión Europea, European Commission, Report on Critical Raw Materials and the Circular Economy, 2018 . 2018. [3] S. Richard, W. Ralf, H. Gerhard, P. Tobias, and W. Martin, “Performance and cost of materials for lithium-based rechargeable automotive batteries,” Nat. Energy , vol. 3, no. Li, pp. 267–278, 2018. [4] A. Vanderbruggen, E. Gugala, R. Blannin, K. Bachmann, R. Serna-Guerrero, and M. Rudolph, “Automated mineralogy as a novel approach for the compositional and textural characterization of spent lithium-ion batteries,” Miner. Eng. , vol. 169, p. 106924, 2021.
This paper investigates one aspect of surface air nucleation in froth flotation, namely the impact of frother-type surfactants like Methyl isobutyl carbinol (MIBC). During this study, tap water was pressurized in an autoclave to produce air-oversaturated water for air nucleation precondition in flotation. Various experiments were carried out with graphite particles to investigate the influences of gas nucleation and MIBC on flotation: micro-flotation, single bubble collision experiments in hydrodynamic conditions and pickup experiments in static conditions. In addition, microscopic observations were combined with agglomeration analysis to clarify the effects of the frother MIBC on the air nucleation and agglomerate formation. The experimental results show the combination of MIBC and air nucleation can significantly increase the graphite recovery compared to using air-oversaturated water or normal tap water with MIBC alone, respectively. The analysis indicates that MIBC can improve the air nucleation probability on graphite surfaces by enhancing the stability of the air nuclei to form more micro-bubbles on the surface. Meanwhile, the surface microbubbles can collide with other particles forming coarser aggregates, improving their collision probability and with this increasing the recovery of fine particles. Furthermore, the results show that MIBC can reduce the detachment of particles from the surface of nucleation bubbles, leading to an increase in particle load of the bubble-particle aggregates in hydrodynamic conditions, improving the graphite recovery significantly.
Spent lithium-ion batteries (LIBs) contain critical raw materials that need to be recovered and recirculated into the battery supply chain. This work proposes the joint recovery of graphite and lithium metal oxides (LMOs) from pyrolyzed black mass of spent LIBs using froth flotation. Since flotation is a water-intensive process, the quality of the aqueous phase directly impacts its performance. In pursuit of an improved water-management strategy, the effect of process water recirculation on black mass flotation is also investigated. The fine fraction (<90 µm) of the black mass from pyrolyzed and crushed spent LIBs was used. After flotation, 85% of the graphite in the overflow product and 80% of the LMOs in the underflow product were recovered. After flotation with 8 wt% solids, the process water contained about 1,000 mg/L Li and accumulated up to 2,600 mg/L Li after three cycles. The flotation with process water showed no significant impact on the recovery and grade of flotation products, suggesting the feasibility of water recirculation in black mass flotation.
Regenerating spent graphite from scrapped LIBs draws a significant role in utilizing spent graphite materials and protecting ecological environment. Heat treatment is an essential step in the regeneration process of spent anode. In this study, we focused on the effect of high-temperature treatment on graphite lattice structural reconstruction and electrochemical performance. Prior to heat treatment at different temperatures (e. g. 700, 900, 1100, 1300 and 1500 °C), spent graphite could be purified in sulfuric acid solution. Then, the structural analysis was performed by using XRD tests before and after regeneration, and the results show that when temperature reaches 900 °C, recovered graphite had already formed a good crystallinity. Additionally, the analysis of size distribution, surface area and pore diameter distribution were performed to characterize physical properties. The results showed that heat-treated graphite at 900 °C (HTT-900) displayed the optimal physical properties, which was close to that of commercial graphite. Furthermore, HTT-900 retained an outstanding initial specific capacity (358.1 mAh/g at 0.1 C) and a remarkable cycle stability (capacity retention of 98.8% after 100 cycles). Moreover, the reversible capacities of HTT-900 at 0.1–2.0 C and another 0.1 C reached up to 356.8, 340.1, 306.1, 242.6, 69.7 and 359.2 mAh/g, respectively.
In the upcoming years, todaýs e-mobility will challenge the capacity of sustainable recycling. Due to the presence of organic components (electrolyte, separator, casings, etc.), future recycling technologies will combine thermal pre-treatment followed by hydrometallurgical processing. Despite the ongoing application of such treatment, there is still a lack of information on how applied parameters affect subsequent metal recovery. In this study, both oxidative and reductive conditions in dependence on temperature and time were studied. Qualitative and quantitative characterizations of the samples after treatment were performed followed by leaching with 2 M sulphuric acid at ambient temperature to determine the leachability of valuable metals such as Co, Mn, Ni and Li. Moreover, the negative or positive effect of treatment on the leachability of the main impurities (Cu and Al) was determined. Since the presence of carbon affects the degree of active material reduction, it's content after each thermal treatment was determined as well. If all variables, temperature and time of thermal processing are taken into account, pyrolysis at 700 °C for 30 min is the optimal treatment. Under these conditions, full recovery is reached after 2 min for Li, 5 min for Mn and 10 min for both Co and Ni. In the case of the incineration, only processing at 400 and 500 °C promoted higher recovery of metals, while the treatment at 600 and 700 °C led to the formation of less leachable species.
In this study, the flotation technology is used for the separation and purification of cathode and anode material after removing organics by pyrolysis. Effects of surface microscopic properties on the flotation efficiency of spent electrode materials are investigated, and on this basis, surface analysis combined with flotation foundation tests are conducted to reveal pyrolysis-assisted surface modification mechanism. Residual electrolyte and organic binders decrease the difference in wettability of cathode and anode material, and hinder the interaction between electrode particles and collecting agent. Organics and their pyrolysis products can be adequately removed at the optimum pyrolysis temperature of 550 °C. After pyrolysis, the change of Zeta potential and surface free energy demonstrates that hydrophilic components of cathode material increase while the hydrophobic components of the anode material increase. The induction time of cathode material rises from 190 ms to 650 ms while the induction time of the anode material decrease from 145 ms to 37 ms. Collector adsorption capacity of anode material is obviously improved and anode material is easy to incorporate with bubbles and will be collected in the froth product. After one stage flotation, the recovery rate of cathode material is 83.75% with a high grade of 94.72%.