2
MATERIALS
Batteries
Batteries were obtained from Catalytic Innovations, a local
battery recycling company in Rolla, Missouri, USA. The
batteries utilized were of the 18650 types, featuring lith-
ium-ion chemistry.
Reagents
Sodium chloride solution was used as an electrolyte. To use
the same raw material intended for industrial use, plain salt
Great Value brand was purchased from a local supermar-
ket. Distilled water was used as a medium. Analytical grade
potassium hydroxide (KOH) was used to regulate solution’s
pH. It was purchased from Emplura, USA.
RESEARCH METHOLOGIES
Voltage Measurements
Voltage measurements were made with a Hyper Tough
Digital Multimeter TD35235J. The initial voltage of the
batteries was set at 4.2 Volts. Complete battery discharge
was reported to be at 3.5 Volts or less, as seen in Figure 2.
The maximum discharge time was set at 16 hours to ensure
the process practicability in industrial settings.
Discharge solution and characterization
The concentrations of the NaCl solutions used in the dis-
charging experiments were 0.12 %,1.2% and 6% m/v. The
optimal NaCl concentration, that was used in the conse-
quent experiments wherein pH was varied, was selected
based on the slowest complete discharge as it means less
corrosion. The optimal concentration was tested as three
pH values: pH 8, 10 and 12. The pH was regulated by add-
ing KOH. A pH meter (Fisher Scientific, USA) was used to
measure the pH. At the end of the discharge process, all the
6 solutions were collected and analyzed with an Inductively
coupled plasma – Mass spectrometry (ICP-MS).
RESULTS AND DISCUSSIONS
Battery Discharge at Different Concentrations and
Neutral pH
Figure 3 shows the discharge voltage versus time at three
different concentrations of NaCl.
As shown the 12% NaCl solution resulted in the fastest
discharge process in about 2 hours. The 6% NaCl solution
showed a complete discharge in less than 3 hours. The
0.12% and 1.2% did not provide satisfactory results
because the discharging process took more than 16 hours
(industry setting limit) Therefore, the 6% NaCl was selected
as an optimal concentration that was used in the conse-
quent discharging experiments at varying pH value.
Battery Discharge with a 6% NaCl at Different pH’s
The 6% NaCl solution was selected because it was the only
one of the 3 (0.12%, 1.2% and 6%) that complied with the
maximum discharge time of 16 hours. This solution was set
at pH 8, 10, and 12 because the Pourbaix diagram of iron
predicts that the steel battery case will not form soluble spe-
cies of iron at high pH’s. Complete discharge was obtained
with the three pH’s mentioned above. The results are shown
in Figure 4.
Figure 3. Discharging process at 0.12%, 1.2%, 6% and 12%
NaCl concentrations
Figure 1. Pourbaix Diagram for iron. At pH 7, a form
of Fe2+ is more prevalent. Fe2+ is highly soluble in water,
therefore, other forms of iron are likely to a lesser extent
(Earnshaw, 1997)
Figure 2. Discharge curve for an 18650 battery (Lozito et
al., 2020)
MATERIALS
Batteries
Batteries were obtained from Catalytic Innovations, a local
battery recycling company in Rolla, Missouri, USA. The
batteries utilized were of the 18650 types, featuring lith-
ium-ion chemistry.
Reagents
Sodium chloride solution was used as an electrolyte. To use
the same raw material intended for industrial use, plain salt
Great Value brand was purchased from a local supermar-
ket. Distilled water was used as a medium. Analytical grade
potassium hydroxide (KOH) was used to regulate solution’s
pH. It was purchased from Emplura, USA.
RESEARCH METHOLOGIES
Voltage Measurements
Voltage measurements were made with a Hyper Tough
Digital Multimeter TD35235J. The initial voltage of the
batteries was set at 4.2 Volts. Complete battery discharge
was reported to be at 3.5 Volts or less, as seen in Figure 2.
The maximum discharge time was set at 16 hours to ensure
the process practicability in industrial settings.
Discharge solution and characterization
The concentrations of the NaCl solutions used in the dis-
charging experiments were 0.12 %,1.2% and 6% m/v. The
optimal NaCl concentration, that was used in the conse-
quent experiments wherein pH was varied, was selected
based on the slowest complete discharge as it means less
corrosion. The optimal concentration was tested as three
pH values: pH 8, 10 and 12. The pH was regulated by add-
ing KOH. A pH meter (Fisher Scientific, USA) was used to
measure the pH. At the end of the discharge process, all the
6 solutions were collected and analyzed with an Inductively
coupled plasma – Mass spectrometry (ICP-MS).
RESULTS AND DISCUSSIONS
Battery Discharge at Different Concentrations and
Neutral pH
Figure 3 shows the discharge voltage versus time at three
different concentrations of NaCl.
As shown the 12% NaCl solution resulted in the fastest
discharge process in about 2 hours. The 6% NaCl solution
showed a complete discharge in less than 3 hours. The
0.12% and 1.2% did not provide satisfactory results
because the discharging process took more than 16 hours
(industry setting limit) Therefore, the 6% NaCl was selected
as an optimal concentration that was used in the conse-
quent discharging experiments at varying pH value.
Battery Discharge with a 6% NaCl at Different pH’s
The 6% NaCl solution was selected because it was the only
one of the 3 (0.12%, 1.2% and 6%) that complied with the
maximum discharge time of 16 hours. This solution was set
at pH 8, 10, and 12 because the Pourbaix diagram of iron
predicts that the steel battery case will not form soluble spe-
cies of iron at high pH’s. Complete discharge was obtained
with the three pH’s mentioned above. The results are shown
in Figure 4.
Figure 3. Discharging process at 0.12%, 1.2%, 6% and 12%
NaCl concentrations
Figure 1. Pourbaix Diagram for iron. At pH 7, a form
of Fe2+ is more prevalent. Fe2+ is highly soluble in water,
therefore, other forms of iron are likely to a lesser extent
(Earnshaw, 1997)
Figure 2. Discharge curve for an 18650 battery (Lozito et
al., 2020)