2024 AIChE Annual Meeting
Zinc- and Copper-Ion Intercalation and Plating on Chevrel-Phase Mo6Se8 Cathodes in Aqueous Electrolytes
One possible failure mechanism for ion intercalation-based energy storage systems (e.g.,
lithium (Li)-ion) is uncontrolled metal electrodeposition (plating), where metal ions from the
electrolyte reduce on the electrode surface to deposit metal instead of intercalating. This work
investigates zinc (Zn) and copper (Cu)-ion intercalation and metal plating on chevrel-phase
Mo6Se8 cathodes in aqueous electrolytes. The objective is to develop a better understanding of
the competition between electrochemical intercalation and plating of these metal cations into a
model battery electrode; the results will be analyzed with respect to lithium cation intercalation
versus lithium metal plating on graphite anodes to yield a general understanding of how ion
charge density and size affect these competing electrochemical processes.
We studied Zn and Cu-ion intercalation and metal plating in two-electrode coin cells
comprised of either Zn and Cu metal anodes and Mo6Se8 cathodes in 1 M ZnSO4 and 1 M CuSO4,
respectively. We demonstrate for the first time that Zn and Cu metal electrochemically plate on
Mo6Se8 cathodes. The presence of both metallic Zn and Cu metal deposits was determined using
scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, and X-ray diffraction
on galvanostatically discharged Mo6Se8 electrodes. Zn- and Cu-ion intercalation and metal plating
on Mo6Se8 was investigated further through variable-temperature (+50 °C down -10 °C), constant current (10 mA/g) discharge of Zn/Cu-Mo6Se8 coin cells. Specifically, the results show that the discharge of Zn-Mo6Se8 cells reveal a temperature-dependent interplay between Zn2+
intercalation, hydrogen evolution reaction (HER), and Zn plating on the Mo6Se8 electrode surface.
However, the discharge of Cu-Mo6Se8 suggests that an interplay between Cu-ion intercalation and
Cu metal plating occurs in the absence of HER even at +20 °C. Arrhenius analysis on an empirically defined rate constant (𝑘𝑝𝑙) for Zn metal plating shows that the Zn plating process possesses a negative apparent activation energy, indicative of a multi-step plating process that includes Zn2+
adsorption on the Mo6Se8 electrode surface.
This work enables the study of Zn and Cu metal plating as an analog to Li plating and
establishes a connection among the three metal plating processes. Building a mechanistic
understanding of Zn, Cu, and Li plating as failure modes could improve each metal’s respective
battery chemistries in more demanding cycling conditions including fast- and low-temperature
charge/discharge.
lithium (Li)-ion) is uncontrolled metal electrodeposition (plating), where metal ions from the
electrolyte reduce on the electrode surface to deposit metal instead of intercalating. This work
investigates zinc (Zn) and copper (Cu)-ion intercalation and metal plating on chevrel-phase
Mo6Se8 cathodes in aqueous electrolytes. The objective is to develop a better understanding of
the competition between electrochemical intercalation and plating of these metal cations into a
model battery electrode; the results will be analyzed with respect to lithium cation intercalation
versus lithium metal plating on graphite anodes to yield a general understanding of how ion
charge density and size affect these competing electrochemical processes.
We studied Zn and Cu-ion intercalation and metal plating in two-electrode coin cells
comprised of either Zn and Cu metal anodes and Mo6Se8 cathodes in 1 M ZnSO4 and 1 M CuSO4,
respectively. We demonstrate for the first time that Zn and Cu metal electrochemically plate on
Mo6Se8 cathodes. The presence of both metallic Zn and Cu metal deposits was determined using
scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, and X-ray diffraction
on galvanostatically discharged Mo6Se8 electrodes. Zn- and Cu-ion intercalation and metal plating
on Mo6Se8 was investigated further through variable-temperature (+50 °C down -10 °C), constant current (10 mA/g) discharge of Zn/Cu-Mo6Se8 coin cells. Specifically, the results show that the discharge of Zn-Mo6Se8 cells reveal a temperature-dependent interplay between Zn2+
intercalation, hydrogen evolution reaction (HER), and Zn plating on the Mo6Se8 electrode surface.
However, the discharge of Cu-Mo6Se8 suggests that an interplay between Cu-ion intercalation and
Cu metal plating occurs in the absence of HER even at +20 °C. Arrhenius analysis on an empirically defined rate constant (𝑘𝑝𝑙) for Zn metal plating shows that the Zn plating process possesses a negative apparent activation energy, indicative of a multi-step plating process that includes Zn2+
adsorption on the Mo6Se8 electrode surface.
This work enables the study of Zn and Cu metal plating as an analog to Li plating and
establishes a connection among the three metal plating processes. Building a mechanistic
understanding of Zn, Cu, and Li plating as failure modes could improve each metal’s respective
battery chemistries in more demanding cycling conditions including fast- and low-temperature
charge/discharge.