A Secondary Battery Based on the Copper(II)-(I) and (I)-(0) Couples in Acetonitrile

Abstract

A secondary cell based on the copper(II)‐(I) and (I)‐(0) couples in acetonitrile has been constructed and studied at room and low temperatures. The over‐all cell reaction is Cu+++normalCufalse(normalsfalse)⇄2Cu+ . A positive compartment consisting of a graphite sheet in contact with an acetonitrile solution of copper (II) perchlorate was separated by an anionic ion‐exchange membrane from a negative electrode of copper metal in acetonitrile. Lithium or sodium perchlorate was added to the negative compartment to decrease internal resistance. The cell develops an open‐circuit potential of 1.35V and is reversible at coulombic efficiencies of close to 100%. A test unit was carried through more than 45 charge and discharge cycles at room temperature. Discharge characteristics are poorer at −14°C than at room temperature. The anionic ion‐exchange membrane used as a separator was stable to the solvent, chemicals, and potentials used, and effectively blocked transport of copper (II) species. About 90% of full charge was retained after a wet stand of 2 months.

A Combined SNIFTIRS and XANES Study of Electrically Polarized Copper Electrodes in DMSO and DMF Solutions of Cyanate (NCO−), Thiocyanate (NCS−) and Selenocyanate (NCSe−) Ions

“…The observed ν(CN) stretching frequencies for both Se 2 (CN) 2 and Se(SeCN) 2 were reported as being at 2144 cm −1 . We therefore speculate from this previous literature evidence that the peak could be due to an (NCSe) 3 − species, because this species is thermodynamically favored when in equilibrium with its progenitor species (SeCN) 2 and NCSe − , according to Solangi et al 51 In the presence of K + ion (from the use of KSeCN), the (SeCN) 3 − ion may precipitate and become "trapped" in this form as a K(SeCN) 3 film on the electrode. This compound is known from earlier studies 9 involving the oxidation of selenocyanate on platinum electrodes in aqueous electrolytes containing 0.5 mol L −1 KSeCN and 0.1 mol L −1 NH 4 O 2 CMe at pH 7 and was attributed to an intense band at 2143 cm −1 that was observed when applied potentials >0.8 V (NHE) were used.…”

“…This compound is known from earlier studies 9 involving the oxidation of selenocyanate on platinum electrodes in aqueous electrolytes containing 0.5 mol L −1 KSeCN and 0.1 mol L −1 NH 4 O 2 CMe at pH 7 and was attributed to an intense band at 2143 cm −1 that was observed when applied potentials >0.8 V (NHE) were used. We therefore propose that the peak at 2138-2140 cm −1 is due to a film of K(SeCN) 3 on the Cu electrode.…”

“…In the Cu/NCS − and Cu/NCSe − electrochemical systems studied, Cu n+ /pseudohalide ion complexes were observed at less cathodic potentials relative to the Cu/NCO − electrochemical systems, with IR and XANES evidence collectively indicating that the Cu n+ /thiocyanate or selenocyanate complex ions generated in SNIFTIRS experiments were actually a mixture of oxidation states of Cu(I) and Cu(II). The Cu/NCS − and Cu/NCSe − electrochemical systems were also shown to form solid films of CuSCN and K(SeCN) 3 respectively when polarized at anodic potentials. IR transmission spectral data collected from model solutions prepared for all Cu/NCX − systems studied provided convincing evidence to support the assignments of the electrogenerated complex ion species of Cu detected in SNIFTIRS experiments.…”

Thermally regenerative copper nanoslurry flow batteries for heat-to-power conversion with low-grade thermal energy

“…Upon discharge, metallic copper is oxidized to Cu(I) on the negative electrode and Cu(II) is reduced to Cu(I) on the positive electrode. 31,[41][42][43][44] Copper complexing agents such as acetonitrile, ammonia, or chloride are required to stabilize the Cu(I) oxidation state. [45][46][47][48][49] With acetonitrile or ammonia this property can be used for advantage to realize a thermally regenerative battery, as destabilization of the Cu(I) can be achieved in a thermal reaction simply by removing the acetonitrile into the gas phase upon distillation.…”

“…5 One approach to increase the cell voltage is to remove water. Indeed, an all-copper battery in water-free acetonitrile has a cell voltage of 1.3 V 31 in comparison to an aqueous system cell voltage of 0.62 V. 24 It is important to note that the all-copper battery in non-aqueous acetonitrile reported by Kratochvil & Betty 31 cannot be charged with heat, as removal of all the solvent would result in a mixture of solid copper powder and Cu(II) salt precipitate. Therefore, a higher boiling point co-solvent such as water 24 or propylene carbonate utilized in this work is required to realize thermal charging.…”