3186 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
analyzer (TGA 701 LECO). The temperature within the
TGA chamber rose from room temperature to 800°C with a
ramp rate of 1°C/min. The chamber was flushed with com-
pressed air at a flow rate of 7L/min. Both the morphology
and elemental composition of the particles in the sample
was determined using a FEI Philips XL 40 Environmental
Scanning Microscope (SEM).
RESULT AND DISCUSSION
Baseline: Gravity Separation of Recycled Electrode
Active Materials
In this section, separation of recycled electrode active mate-
rials from Li-ion batteries were performed with both new
and spent Li-ion battery pouch cells. Upon a mechanical
delamination process, a mixture of anode and cathode com-
posite materials were fed to the centrifugal gravity separa-
tion process. The top size of the feed materials was 104 µm.
Table 1 shows the composition of the concentrate product
after the gravity separation processes. Result showed that
for the recycled black mass from new Li-ion batteries, the
grade of cathode active materials in the concentrate product
reached 78.8 wt.% when using a low cut-off-point (COP)
in the rougher operation. The percentage of the cathode
active materials reached 95.09 %and 95.69 %after one
and two consecutive cleaner cycles, respectively.
Also shown in Table 1 are the results obtained with
spent Li-ion batteries. Two types of the feed materials were
prepared. One was the black mass obtained from spent
Li-ion batteries without sieving, and the top size of the
black mass sample was 104 µm. The other feed material
was the black mass sample sieving through a 45 µm sieve
screen. Results showed that the grade of CAM in the con-
centrate product reached 93.23% after one rougher stage.
The percentage of CAM in the concentrate product fur-
ther reached 97.76% and 98.35% after one cleaner and
two consecutive cleaner stages, respectively. Comparing
with the results obtained with the black mass recycled from
new cells, an improvement in the percentage of cathode
active materials in the concentrate product was found with
spent Li-ion batteries. This result indicated that the binding
energy between PVDF and cathode active materials was
weakened after long charging-discharging cycles, enabling a
better liberation between PVDF binders and cathode active
materials. Furthermore, the fine fraction (with a top size of
45 µm) of the black mass was used as the black mass mate-
rial feed. After one-stage gravity separation, the percent-
age of cathode active materials (CAM) in the concentrate
product reached 96.63%, which was higher than 93.23%
obtained with the entire fraction of the black mass. It is
possible that these large cathode composite materials were
rejected into the overflow product stream due to its lower
density (~2.0 g/cm3) due to the presence of PVDF binders
compared to individual cathode active materials (~5.0 g/
cm3).
To better understand the impact of feed materials dur-
ing the centrifugal gravity separation, both the concentrate
and tailing products were imaged under the scanning elec-
tron microscopy (SEM). Figure 2 shows the SEM image
of both concentrate and tailing products after the gravity
separation process. Results showed that individual cath-
ode active material was found in the rougher concentrate
product. Large-sized cathode agglomerate products were
reported to the tailing product. For –45 mm feed materials,
individual cathode active material was found in the con-
centrate product, while small cathode agglomerates were
reported to the tailing product. The present result confirms
that the loss of cathode active materials in the tailing prod-
uct was likely attributed to the low density of cathode com-
posite materials due to the presence of PVDF binder in
these composite materials.
Thermal Pyrolysis coupled with Gravity Separation
The presence of PVDF binder within cathode composite
materials effectively lowers its density and deteriorates the
separation performance. In this work, thermal pyrolysis
process was employed to process raw black mass. Figure 3
shows SEM and EDX mapping images of black mass after
a pyrolysis treatment in a box furnace at different tempera-
tures for 1 hour. Table 2 shows the composition of black mass
samples without and with thermal pyrolysis treatments. At
a temperature of 400 °C or above, composition of cathode
Table 1. Concentrate product analysis for rougher and cleaner stages after gravity separation of black mass from new and spent
Li-ion batteries
Samples New Cell, –104 µm Spent Cell, –104 µm Spent Cell, –45 µm
Composition of
concentrate Rougher 1st Cleaner 2nd Cleaner Rougher 1st Cleaner
2nd
Cleaner Rougher
%CAM 78.82% 95.09% 95.69% 93.23% 97.76% 98.35% 96.63%
%PVDF 2.48% 1.90% 1.88% 1.35% 1.21% 1.08% 1.25%
%Graphite 18.70% 3.01% 2.43% 5.42% 1.03% 0.57% 2.12%
analyzer (TGA 701 LECO). The temperature within the
TGA chamber rose from room temperature to 800°C with a
ramp rate of 1°C/min. The chamber was flushed with com-
pressed air at a flow rate of 7L/min. Both the morphology
and elemental composition of the particles in the sample
was determined using a FEI Philips XL 40 Environmental
Scanning Microscope (SEM).
RESULT AND DISCUSSION
Baseline: Gravity Separation of Recycled Electrode
Active Materials
In this section, separation of recycled electrode active mate-
rials from Li-ion batteries were performed with both new
and spent Li-ion battery pouch cells. Upon a mechanical
delamination process, a mixture of anode and cathode com-
posite materials were fed to the centrifugal gravity separa-
tion process. The top size of the feed materials was 104 µm.
Table 1 shows the composition of the concentrate product
after the gravity separation processes. Result showed that
for the recycled black mass from new Li-ion batteries, the
grade of cathode active materials in the concentrate product
reached 78.8 wt.% when using a low cut-off-point (COP)
in the rougher operation. The percentage of the cathode
active materials reached 95.09 %and 95.69 %after one
and two consecutive cleaner cycles, respectively.
Also shown in Table 1 are the results obtained with
spent Li-ion batteries. Two types of the feed materials were
prepared. One was the black mass obtained from spent
Li-ion batteries without sieving, and the top size of the
black mass sample was 104 µm. The other feed material
was the black mass sample sieving through a 45 µm sieve
screen. Results showed that the grade of CAM in the con-
centrate product reached 93.23% after one rougher stage.
The percentage of CAM in the concentrate product fur-
ther reached 97.76% and 98.35% after one cleaner and
two consecutive cleaner stages, respectively. Comparing
with the results obtained with the black mass recycled from
new cells, an improvement in the percentage of cathode
active materials in the concentrate product was found with
spent Li-ion batteries. This result indicated that the binding
energy between PVDF and cathode active materials was
weakened after long charging-discharging cycles, enabling a
better liberation between PVDF binders and cathode active
materials. Furthermore, the fine fraction (with a top size of
45 µm) of the black mass was used as the black mass mate-
rial feed. After one-stage gravity separation, the percent-
age of cathode active materials (CAM) in the concentrate
product reached 96.63%, which was higher than 93.23%
obtained with the entire fraction of the black mass. It is
possible that these large cathode composite materials were
rejected into the overflow product stream due to its lower
density (~2.0 g/cm3) due to the presence of PVDF binders
compared to individual cathode active materials (~5.0 g/
cm3).
To better understand the impact of feed materials dur-
ing the centrifugal gravity separation, both the concentrate
and tailing products were imaged under the scanning elec-
tron microscopy (SEM). Figure 2 shows the SEM image
of both concentrate and tailing products after the gravity
separation process. Results showed that individual cath-
ode active material was found in the rougher concentrate
product. Large-sized cathode agglomerate products were
reported to the tailing product. For –45 mm feed materials,
individual cathode active material was found in the con-
centrate product, while small cathode agglomerates were
reported to the tailing product. The present result confirms
that the loss of cathode active materials in the tailing prod-
uct was likely attributed to the low density of cathode com-
posite materials due to the presence of PVDF binder in
these composite materials.
Thermal Pyrolysis coupled with Gravity Separation
The presence of PVDF binder within cathode composite
materials effectively lowers its density and deteriorates the
separation performance. In this work, thermal pyrolysis
process was employed to process raw black mass. Figure 3
shows SEM and EDX mapping images of black mass after
a pyrolysis treatment in a box furnace at different tempera-
tures for 1 hour. Table 2 shows the composition of black mass
samples without and with thermal pyrolysis treatments. At
a temperature of 400 °C or above, composition of cathode
Table 1. Concentrate product analysis for rougher and cleaner stages after gravity separation of black mass from new and spent
Li-ion batteries
Samples New Cell, –104 µm Spent Cell, –104 µm Spent Cell, –45 µm
Composition of
concentrate Rougher 1st Cleaner 2nd Cleaner Rougher 1st Cleaner
2nd
Cleaner Rougher
%CAM 78.82% 95.09% 95.69% 93.23% 97.76% 98.35% 96.63%
%PVDF 2.48% 1.90% 1.88% 1.35% 1.21% 1.08% 1.25%
%Graphite 18.70% 3.01% 2.43% 5.42% 1.03% 0.57% 2.12%