3
From Figure 4, a full discharge can be achieved at any
of the three pH values tested. However, it was interesting
to see the time difference for a complete discharge. For
instance, the pH 8 solution needed 3 hours to fully dis-
charge the battery, whereas at pH 12 the discharge time was
9 hours. Nonetheless, the discharge time met the minimum
industrial guideline requirements in the 3 cases.
Solution Characterization After Battery Discharge
ICP-MS was used to characterize the solutions after the
batteries were discharged. To have comparable data, all bat-
teries were left for 16 hours during the discharge process.
Table 1 shows the concentrations of various metals in solu-
tion at the three concentrations of NaCl tested in this study.
As seen in Table 1, the NaCl concentration of 0.12%
provided the best results because it leached almost a tenth
of Fe than concentrations 1.2% and 6%. It also leaches a
third of Al, a third of Co, half of Cu, and the fifth of Ni.
It would be good to let the battery discharge for a longer
period with this concentration to see if it reaches a com-
plete discharge without leaching valuable metals.
Table 2 shows the metal concentrations in 6% NaCl
solution after discharging at varying pH values.
At pH 8, the results resembled those obtained with
at neutral pH. The concentration ranges are as follows:
683.96–895.62 ppm Al, 1.23–1.71 ppm Co, 4.33–
4.45 ppm Cu, 2,020–2343.62 ppm Fe, 36.92–49.83 ppm
Li, and 55.98–56.93 ppm Ni.
The most favorable outcomes were achieved at pH 12.
Under these conditions, Fe and Ni concentrations were
the lowest among all the experiments, excluding the
0.12% NaCl test that did not produce satisfactory results.
Monitoring Fe and Ni is crucial, as a concentration of zero
indicates that the battery case is well-preserved, and metals
were not liberated.
For all metals, except Cu, the leaching trend increased
with increasing pH, reaching its peak at pH 10. However, it
is noteworthy that elevating the pH to 12 resulted in lower
metal concentrations.
CONCLUSIONS
The discharge of lithium-ion batteries usually required a
sodium chloride concentration greater than 12%. However,
findings from this research indicated that a complete dis-
charge can be achieved at 6% of NaCl in 3 hours. Using
a lower concentration of NaCl (6%) might not lead to
complete discharge within the set time limit of 16 hours.
For the 6% NaCl concentration, set as an optimal
concentration due to a slower corrosion rate, the discharge
time increased with an increase in pH. The concentration
of metals in this solution was consistently high regardless of
the pH. However, at pH 12, the concentrations of metals
were lower than those obtained with pH 8 and 10. This
could be attributed to specific chemical reactions or con-
ditions at pH 12 that result in a more controlled release
of metals, potentially mitigating their concentration com-
pared to other pH levels. For instance, at higher pH, some
metal hydroxides could form. Hydroxides are generally less
soluble and might form a protective layer on the battery
case surface, reducing further dissolution.
Figure 4. Battery discharge with 6% NaCl solution for
different pH’s
Table 1. Concentration of selected metals [ppm] in NaCl
solutions of various concentrations after complete discharge
Element
NaCl Concentration m/v
0.12% 1.2% 6%
Al 99.02 372.56 683.96
Co 1.71 12.94 10.89
Cu 4.45 19.32 6.55
Fe 398.47 2394.07 2020
Li 61.49 41.06 36.92
Ni 13.91 110.45 56.93
Table 2. Metal concentrations in 6% NaCl solution after
discharging at varying pH values.
pH 8 pH 10 pH 12
Al 895.62 1054.78 915.78
Co 1.09 1.9 1.23
Cu 3.38 3.69 4.33
Fe 2343.62 2271.39 1964.52
Li 49.83 57.49 47.28
Ni 55.98 48.82 41.56
From Figure 4, a full discharge can be achieved at any
of the three pH values tested. However, it was interesting
to see the time difference for a complete discharge. For
instance, the pH 8 solution needed 3 hours to fully dis-
charge the battery, whereas at pH 12 the discharge time was
9 hours. Nonetheless, the discharge time met the minimum
industrial guideline requirements in the 3 cases.
Solution Characterization After Battery Discharge
ICP-MS was used to characterize the solutions after the
batteries were discharged. To have comparable data, all bat-
teries were left for 16 hours during the discharge process.
Table 1 shows the concentrations of various metals in solu-
tion at the three concentrations of NaCl tested in this study.
As seen in Table 1, the NaCl concentration of 0.12%
provided the best results because it leached almost a tenth
of Fe than concentrations 1.2% and 6%. It also leaches a
third of Al, a third of Co, half of Cu, and the fifth of Ni.
It would be good to let the battery discharge for a longer
period with this concentration to see if it reaches a com-
plete discharge without leaching valuable metals.
Table 2 shows the metal concentrations in 6% NaCl
solution after discharging at varying pH values.
At pH 8, the results resembled those obtained with
at neutral pH. The concentration ranges are as follows:
683.96–895.62 ppm Al, 1.23–1.71 ppm Co, 4.33–
4.45 ppm Cu, 2,020–2343.62 ppm Fe, 36.92–49.83 ppm
Li, and 55.98–56.93 ppm Ni.
The most favorable outcomes were achieved at pH 12.
Under these conditions, Fe and Ni concentrations were
the lowest among all the experiments, excluding the
0.12% NaCl test that did not produce satisfactory results.
Monitoring Fe and Ni is crucial, as a concentration of zero
indicates that the battery case is well-preserved, and metals
were not liberated.
For all metals, except Cu, the leaching trend increased
with increasing pH, reaching its peak at pH 10. However, it
is noteworthy that elevating the pH to 12 resulted in lower
metal concentrations.
CONCLUSIONS
The discharge of lithium-ion batteries usually required a
sodium chloride concentration greater than 12%. However,
findings from this research indicated that a complete dis-
charge can be achieved at 6% of NaCl in 3 hours. Using
a lower concentration of NaCl (6%) might not lead to
complete discharge within the set time limit of 16 hours.
For the 6% NaCl concentration, set as an optimal
concentration due to a slower corrosion rate, the discharge
time increased with an increase in pH. The concentration
of metals in this solution was consistently high regardless of
the pH. However, at pH 12, the concentrations of metals
were lower than those obtained with pH 8 and 10. This
could be attributed to specific chemical reactions or con-
ditions at pH 12 that result in a more controlled release
of metals, potentially mitigating their concentration com-
pared to other pH levels. For instance, at higher pH, some
metal hydroxides could form. Hydroxides are generally less
soluble and might form a protective layer on the battery
case surface, reducing further dissolution.
Figure 4. Battery discharge with 6% NaCl solution for
different pH’s
Table 1. Concentration of selected metals [ppm] in NaCl
solutions of various concentrations after complete discharge
Element
NaCl Concentration m/v
0.12% 1.2% 6%
Al 99.02 372.56 683.96
Co 1.71 12.94 10.89
Cu 4.45 19.32 6.55
Fe 398.47 2394.07 2020
Li 61.49 41.06 36.92
Ni 13.91 110.45 56.93
Table 2. Metal concentrations in 6% NaCl solution after
discharging at varying pH values.
pH 8 pH 10 pH 12
Al 895.62 1054.78 915.78
Co 1.09 1.9 1.23
Cu 3.38 3.69 4.33
Fe 2343.62 2271.39 1964.52
Li 49.83 57.49 47.28
Ni 55.98 48.82 41.56