Electrodeposition of Manganese Oxide for Zinc-ion Batteries

• Author / Creator

  Dhiman, Arjun

• With growing concerns regarding climate change, researchers are focusing on developing energy storage devices to store renewable energy for later use. Currently, lithium-ion batteries (LIBs) dominate the energy storage market, from portable electronics and emerging electric vehicles to grid storage applications. However, issues regarding the increasing cost of LIB materials, limited material supply, and safety concerns have pushed research towards developing safer and more environmentally friendly energy storage devices. Zinc-ion batteries (ZIBs) are the latest battery technology to be explored as an alternative to LIBs. This is largely due to Zn being environmentally benign, abundant, cheap, and possessing a high theoretical capacity. Additionally, ZIBs use aqueous electrolytes, which are safer and more environmentally friendly compared with the organic electrolytes used in LIBs. Still, there are many limitations preventing the wide adoption of ZIBs. In general, many cathode materials used for ZIBs have exhibited poor capacities, poor rate capabilities, poor cycling performance, or a combination of each. This is particularly true for Mn oxide cathode materials. Furthermore, the reaction mechanism for the charge and discharge of ZIBs is not completely understood.
  The purpose of this work is to use Mn oxide deposition techniques previously developed in the Ivey research group to develop high performing cathode materials for ZIBs. The first study employed two previously developed Mn oxide electrodeposition techniques to deposit Mn oxide onto stainless steel (SS) substrates to be used as a cathode for ZIBs. The first technique used was a direct anodic electrodeposition technique and the second technique was a pulsed anodic electrodeposition technique. This work was undertaken to determine if ZIBs could be fabricated in the laboratory and achieve comparable results to those observed in the literature. The first deposit was initially characterized using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The Mn oxide was deposited as rods with a flake-like morphology. Cyclic voltammetry (CV) testing and visual inspection showed that the first deposition method was not suitable for use as a cathode and was not pursued further. Samples from the second deposition method were initially characterized using SEM and EDS and showed a flake-like morphology that covered the entire SS surface. Through X-ray diffraction (XRD), the material was identified as a Mn3O4 spinel. When assembled into a ZIB, the cathode exhibited a good initial capacity of 287 mAh g-1. However, the capacity quickly faded upon cycling, resulting in a capacity retention of 35.5% after 35 cycles (capacity of 102 mAh g-1). The cathode was examined after the first charge and discharge and exhibited a plate-like morphology after discharge. The plate-like material is most likely zinc sulfate hydroxide (ZSH, Zn(OH)23ZnSO4*xH2O). On charge the ZSH dissolved, however, the morphology of the sample changed. Further materials characterization and electrochemical analysis were not completed due to the poor cycling performance of the material.
  The second study continued with the pulsed anodic electrodeposition technique that was explored in the first study. However, carbon paper (CP) was used as the substrate instead of SS. The deposited Mn oxide was initially characterized using SEM and transmission electron microscopy (TEM). The deposited material formed islands that had a flake-like morphology and were nano-crystalline in nature. Through a combination of XRD, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy (RS), the Mn oxide deposit was identified as Mn3O4. When assembled into a ZIB, the battery showed excellent cyclability with a capacity retention of 139% after 200 cycles at a specific current of 1 A g-1. The battery possessed a maximum capacity of 376 mAh g-1 using a specific current of 50 mA g-1. The Mn3O4 electrode also showed excellent rate capability performance with capacities of 201, 180, 164, 143, and 217 mAh g-1 at applied specific currents of 300, 600, 1200, 2400, and again at 300 mA g-1, respectively. Through a combination of electron microscopy, XPS, and electrochemical testing, the results point toward a two-step reaction mechanism for the Mn3O4 electrode.

• Subjects / Keywords

  • Electrodeposition
  • Manganese Oxide
  • Zinc-ion Battery

• Graduation date

  Spring 2020

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-fwtp-9j98

• License

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