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Development and characterization of composite nickel electrode for nickel-iron battery based energy storage
Author(s)
Zide, Dorcas
Date Issued
2021
Type
Thesis
Publisher
Cape Peninsula University of Technology
Abstract
In this study, a β-Ni(OH)2 material was synthesized using the co-precipitation method followed by
hydrothermal treatment. The effect of stirring, ageing and hydrothermal treatment step during the
synthesis of the Ni(OH)2 material were evaluated. Secondly, the impact of carbon black as a conductive
network for Ni(OH)2 active material was gauged. Thirdly, the effect of the partial substitution of Cu2+
for β-Ni(OH)2 material, Co2+ for β-Ni(OH)2 material, Al3+ for β-Ni(OH)2 material, Mg2+ for β-Ni(OH)2
material, Mn2+ for β-Ni(OH)2 material, was then optimised and evaluated for electrochemical
performance. Four weight percentages (5 wt.%, 10 wt.%, 25 wt.%, and 50 wt.%) of additives (Cu2+,
Co2+, Al3+, Mg2+, Mn2+) were partial substitutions for the β-Ni(OH)2 material. XRD, FTIR, TG-DTA,
and SEM were used to measure the morphologies of the material. SEM/EDS and ICP-OES were used
to confirm the composition of the material. Lastly, a novel bipolar battery cell prepared using
Ni0.75Cu0.25(OH)2 as the active cathode material was evaluated for Ni-Fe battery applications. The
physical characterization performed for β-Ni(OH)2 material concluded that the hydrothermal treatment
step was vital for this study to produce the expected Ni(OH)2-based materials. The addition of 5 wt.%,
carbon black powder improves the utilization of the active material; however, it leads to a decrease in
the stability of the electrode. For example, the specific discharge capacity (after 20 cycle activation)
was increased by 74% compared to 0 wt.% carbon black added to the positive nickel electrode.
However, a drastic decrease in specific discharge capacity was observed after an additional 60 cycles.
The specific discharge capacity of the synthesized Ni(OH)2 with 5 wt.% carbon black electrode
decreased by 66%, while the synthesized Ni(OH)2 with 0 wt.% carbon black decreased by only 18%
after the 80 cycles. In addition, the partial substitution of Cu2+ for β-Ni(OH)2 significantly improves the
coulombic efficiency of the β-Ni(OH)2 active material. It also increases the specific discharge capacity
and enhances the stability of the electrode. Lastly, a novel bipolar battery cell was prepared and
evaluated its discharge capacities for the Ni-Fe battery applications. The Ni0.75Cu0.25(OH)2 material was
first deposited onto both a graphite composite and Ni-mesh substrates to form the monopolar electrodes.
The bipolar-based Ni-Fe battery cell demonstrated a discharge capacity of 158 mAh/g after the 100th
cycle, corresponding to a coloumbic efficiency of 72%. A cost evaluation of the typical battery plant
for a bipolar based Ni-Fe was estimated, and it was found that the bipolar design reduces the production
cost by 33% from R12/Wh to R8/Wh.
hydrothermal treatment. The effect of stirring, ageing and hydrothermal treatment step during the
synthesis of the Ni(OH)2 material were evaluated. Secondly, the impact of carbon black as a conductive
network for Ni(OH)2 active material was gauged. Thirdly, the effect of the partial substitution of Cu2+
for β-Ni(OH)2 material, Co2+ for β-Ni(OH)2 material, Al3+ for β-Ni(OH)2 material, Mg2+ for β-Ni(OH)2
material, Mn2+ for β-Ni(OH)2 material, was then optimised and evaluated for electrochemical
performance. Four weight percentages (5 wt.%, 10 wt.%, 25 wt.%, and 50 wt.%) of additives (Cu2+,
Co2+, Al3+, Mg2+, Mn2+) were partial substitutions for the β-Ni(OH)2 material. XRD, FTIR, TG-DTA,
and SEM were used to measure the morphologies of the material. SEM/EDS and ICP-OES were used
to confirm the composition of the material. Lastly, a novel bipolar battery cell prepared using
Ni0.75Cu0.25(OH)2 as the active cathode material was evaluated for Ni-Fe battery applications. The
physical characterization performed for β-Ni(OH)2 material concluded that the hydrothermal treatment
step was vital for this study to produce the expected Ni(OH)2-based materials. The addition of 5 wt.%,
carbon black powder improves the utilization of the active material; however, it leads to a decrease in
the stability of the electrode. For example, the specific discharge capacity (after 20 cycle activation)
was increased by 74% compared to 0 wt.% carbon black added to the positive nickel electrode.
However, a drastic decrease in specific discharge capacity was observed after an additional 60 cycles.
The specific discharge capacity of the synthesized Ni(OH)2 with 5 wt.% carbon black electrode
decreased by 66%, while the synthesized Ni(OH)2 with 0 wt.% carbon black decreased by only 18%
after the 80 cycles. In addition, the partial substitution of Cu2+ for β-Ni(OH)2 significantly improves the
coulombic efficiency of the β-Ni(OH)2 active material. It also increases the specific discharge capacity
and enhances the stability of the electrode. Lastly, a novel bipolar battery cell was prepared and
evaluated its discharge capacities for the Ni-Fe battery applications. The Ni0.75Cu0.25(OH)2 material was
first deposited onto both a graphite composite and Ni-mesh substrates to form the monopolar electrodes.
The bipolar-based Ni-Fe battery cell demonstrated a discharge capacity of 158 mAh/g after the 100th
cycle, corresponding to a coloumbic efficiency of 72%. A cost evaluation of the typical battery plant
for a bipolar based Ni-Fe was estimated, and it was found that the bipolar design reduces the production
cost by 33% from R12/Wh to R8/Wh.
Additional information
Thesis (DPhil (Analytical Chemistry))--Cape Peninsula University of Technology, 2021
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