Portland State University. Department of Physics
Term of Graduation
Date of Publication
Doctor of Philosophy (Ph.D.) in Applied Physics
1 online resource (xvi, 181 pages)
Since the beginning of the indusial revolution, the average global temperature has risen about 1 °C due increases in anthropogenic greenhouse gases emitted into the atmosphere. Of all human produced greenhouse gases, carbon dioxide is the most prevalent, with the production of electricity from fossil fuels being the major contributor.
Solar and wind power are promising net zero emission energy sources but only accounted for ~5% of global electricity generation in 2016. The most significant hurdle hindering their widespread adoption is the intermittent nature of the electricity generation. To overcome this limitation, significant resources need to be put into the development and implementation of energy storage systems (ESS). Rechargeable batteries are one possible solution to the demand for storage, with the lithium ion battery (LIB) being the current standard. However, due to the cost, safety concerns, and toxicity of LIBs, new battery technologies are needed to fully utilize renewable energy sources, such as wind and solar.
Metal hexacyanoferrates, or Prussian blue (PB) and Prussian blue analogues (PBAs), are one family of materials whose electrochemical and physical properties make them intriguing candidates for electrode materials for non lithium ion-based technologies. In particular, their open framework structure, high specific capacity, good ionic conductivity, facile synthesis, and tunability. The work in this dissertation examines four different PBAs as cathode materials in both aqueous and nonaqueous electrolytes with the aim of achieving the following objectives:
1. Develop cathode materials for non-lithium ion based batteries, with a particular focus on divalent ion systems. 2. Determine if the physical and electrochemical storage properties of a PBA could be improved if two binary metal hexacyanoferrates are incorporated into a hybrid metal hexacyanoferrate composite.
These objectives were achieved via performing the following investigations.
In the first study, Prussian blue (KFe3+[Fe2+(CN)6]) is adopted as a cathode material for a nonaqueous calcium ion battery. The work demonstrated for the first time the use of PB in a Ca based system. The cathode delivered a specific capacity of 150 mAhg-1 at a current density of 23 mAg-1.
The second study examined manganese-cobalt hexacyanoferrate in an aqueous Zn2+ electrolyte. The inclusion of Mn and Co in the same compound prevent the dissolution of Mn in the aqueous electrolyte. Additionally, the addition of Mn provided a 21% increase (29 mAhg-1) in storage capacity compared to CoHCF. However, the mixed metal system suffered from increased capacity loss compared to CoHCF.
The effects of coordinated and zeolitic H2O on a Cu[Fe(CN)6] cathode in a nonaqueous Mg2+ electrolyte are examined in the third study. Water was shown to play an important role in maximizing the specific capacity of copper hexacyanoferrate. Maintaining water within the CuHCF lattice resulted in a 25% increase in specific capacity compared to the dehydrated sample. However, both samples displayed strong rate capability and exhibited comparable Mg2+ diffusion coefficients. The last experimental study presents MnxNi1-x[Fe(CN)6] as a cathode material in a nonaqueous K+ electrolyte. Mn0.50Ni0.50[Fe(CN)6] displayed superior performance compared to all other materials investigated in this work. By combing Mn and Ni, the mixed metal system was able to overcome the poor K+ diffusion kinetics of Mn[Fe(CN)6] while delivering specific capacity 25% greater than Ni[Fe(CN)6]. Analysis of the FTIR and electrochemical data of MnxNi1-x[Fe(CN)6] suggested substitution of Mn for Ni in the PBA lattice caused a shift in electron density away from the nitrogen coordinated transition metal (either Mn or Ni) towards the Fe-C end of the cyanide. Density functional theory (DFT) calculations were performed to further study the effect of incorporation of Mn on the electronic properties of the mixed manganese-nickel hexacyanoferrate system. Initial computational results appeared to confirm the experimental hypothesis about the shifts in electron density with respect to manganese.
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Kuperman, Neal Walters, "Investigation of Prussian Blue Analogues as Cathode Materials for Next Generation Batteries" (2020). Dissertations and Theses. Paper 5614.
Available for download on Thursday, November 11, 2021