|Abstract or Summary
- This research emphasized fundamental physical and electrochemical
studies of systems based on the room temperature fused salt, triethyl-ammonium
dichlorocuprate(I). Such systems, which must be maintained
under a protective atmosphere, were also used in some preliminary
Spectra of dark green solutions of copper (II) chloride in
triethylammonium dichlorocuprate(I) obey Beer's law, with an absorption
maximum at 402 nm, ε 2.02x10³ lit /mol cm. This behavior is typical of
chlorocuprate(II) complexes. No special behavior due to intervalence
transfer absorption is observed.
Densities of solutions of various salts in triethylammotium
dichlorocuprate(I) were determined dilatometrically in the range 25-50°C,
permitting concentrations to be expressed both on weight and molarity
bases. The endothermic formation of liquid triethylammonium dichlorocuprate(
I) involved a 10.9% increase in molar volume.
The specific conductance of triethylammonium dichlorocuprate(I)
increases from 4.3x10⁻³ to 1.2x10⁻² ohm⁻¹ cm⁻¹ in the range 25 to 50°C.
Solutions of copper(I), copper(II), lithium, and triethylammonium
chlorides in triethylammonium dichlorocuprate(I) all have lower conductances than the neat solvent. The viscosities of solutions of
copper(I) and copper(II) chlorides in triethylammonium dichlorocuprate(I)
were determined in the range 25-50°C and found to be greater than that
of the neat solvent. The temperature variations of the conductance and
of the viscosity were both found to show Arrhenius-type behavior. Activation
energies for viscous flow were in the typical range for fused
salts, but activation energies for conductance were about three times larger than usual. A relation proposed by Frenkel nk (En/EA) = constant, was closely followed by the mixtures. The Cu/Et₃NHCuC1₂ electrode was a satisfactory reference electrode
for potentiometric measurements in the fused salt systems. Its operational
potential was -.24 volt vs. SCE at 25°. In polarization studies
the time required to regain equilibrium following the passage of various
currents was measured.
Potentiometric measurements were made of the cells Cu/Et₃NHCuC1₂/Et₃NHCuC1₂, CuC1₂ (M)/Noble Metal. In addition to a platinum electrode,
a special Optically Transparent Thin Layer Electrode (OTTLE) was used,
made of gold minigrid having 82% optical transparency. Approximate
Nernstian behavior was observed only at low copper(II) concentrations.
Combined spectrophotometric and coulometric measurements of electrolysis
in the OTTLE cell Cu/Et₃NHCuC1₂/Au confirmed copper(II)
chloride and copper as the oxidation-reduction products. The relation
of faradays to moles of copper(II) was not accurate due to non-uniformity
of the latter on the minigrid.
Bipolar voltage sweep studies were carried out in triethylammonium
dichlorocuprate(I) cells with a platinum or glassy carbon working electrode, a platinum auxiliary electrode, and the copper reference
electrode. Shapes of the cyclic voltammograms showed great temperature
dependence in the range 13-51°C. Peak potentials and currents showed
linear dependence on the square root of the scan rate. Such behavior
indicates blockage of the electrode surface by a poorly conducting film
of electrolysis product. A viscous film of copper(II) chloride could
be observed visually.
The Butler-Volmer equation was applied to overpotential-current
relations in both high and low overpotential regions of the Cu/Et₃NHCuC1₂ and the Pt/Et₃NHCuC1₂, CuC1₂(M) half-cells. Linearity of current-overpotential
plots in the 5 mv > n > -5 mv region indicates that each
of these half-cells is reversible. Tafel slopes were constructed to
current-overpotential curves in the range 500 mv > n > -500 mv, from
which values of the transfer coefficient were calculated.
Preliminary design and testing of batteries was undertaken. These
batteries employed copper and flexible graphite or platinum foil electrodes,
with various separators. Some were prepared in a charged
condition with a solution of copper(II) chloride in triethylammonium
dichlorocuprate(I) in contact with the inert electrode. Some were prepared
using only triethylammonium dichlorocuprate(I) and were charged
by passage of current from an external source. Measurements of open
circuit voltages and of potential-current-time discharges were made.
The major practical problem with these cells was their high internal