Studies of the Hydration of Transition Metal Cations Dissolved in Poly(ethylene oxide) by UV/Visible Spectroscopy

Abstract

Solid polymeric electrolytes formed by dissolving salts of Ni 2 § and Co 2 § in poly(ethylene oxide) (PEO) are strikingly different in their response to deliberate hydration/dehydration. Both PEOsNiBr2 and PEOI6CoBr2 readily absorb about 28-30 molecules of water per cation from humid nitrogen at room temperature. Surprisingly, an anhydrous sample of PEOsNiBr2 after having been hydrated and dehydrated has a much higher conductivity [10 -3 (f~-lcm-') at 150~ than in the initial as-cast anhydrous state [10 -8 (~-lcm -1) at 150~ This unexpected effect of hydration/dehydration is not observed with samples of PEO16CoBr2. UV-visible absorption spectroscopy shows that Ni 2 § in dry PEOsNiBr2 exists in a variety of square planar and tetrahedral complexes with PEO. The hydration of PEOsNiBr2 completely frees Ni 2 § ions from association with the PEO chains and results in the formation of [Ni(H20)6] 2+ species. In contrast, absorption of water does not appear to liberate Co 2 § ions from association with PEO and has no persistent effect on the properties of the electrolyte.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.122.253.212 Downloaded on 2015-05-28 to IP ABSTRACT A kinetic study on the chemical vapor deposition of titanium disulfide thin film using TIC14 and H~S as source gases is conducted. Titanium disulfide films having a crystallographic orientation in which the c-axis is parallel to the substrate plane are fabricated under conditions in which the surface reaction controls the reaction process. The rate determining step in the reaction is found to be the excitation process of H2S which is presented as a first-order reaction. The deposition rate increases in direct proportion to an increase in the partial pressure of H2S, and it reaches the maximum at a substrate temperature of 510~

Multivalent ion conduction in solid polymer systems

“…Though all the studies mentioned within include vacuum drying steps to remove excess solvent, the success of removal is not always quantified and can have significant implications for ion mobility and conductivity. [49][50] This points toward an underlying cause for the sometimes widely varying conductivity results reported for some multivalent conducting polymers and highlights the importance of a continued effort for precise control of preparation and measurement conditions. Multivalent salts mixed in PEO typically show reduced ionic conductivity compared to their monovalent counterparts ( Figure 3).…”

“…17 However, the mobility of multivalent ions depends dramatically on the presence of water or residual solvent as was shown for Ni 2+ -PEO electrolytes; thus care must be taken from the outset to mitigate water uptake and use low boiling point solvents. [49][50] A benefit of PEO which enhances ionic conductivity for Liion systems compared to other polyethers is the highly percolated network of nearby solvation sites for the ion to move into. 57 It is likely that solvation site connectivity also plays a large role for multivalent conduction and is an important but challenging factor to consider for new polymer electrolyte design.…”

Nano‐ or Microclustering as an Explanation for the Unusual Thermal Behavior of Nickel Polymer Electrolytes

“…The solubility of anhydrous NiBr2 in acetonitrile/methanol is quite low, and heating at about 60°C for 3 to 4 days is usually required to make a solution," although a more efficient approach using an ultrasonic bath has been reported. 16 Acetonitrile/methanol mixture is certainly a better solvent than PEO for anhydrous NiBr2. Because it is so difficult to dissolve NiBr, and because the films formed are so hygroscopic, there must be serious doubts concerning the formation of truly anhydrous electrolyte films of composition PEO,:NiBr2 (approximately 2.5 mol dm').…”