Tunable Stabilization of Cuprous Ions via Kinetic and Thermodynamic Control of Cu Electrodeposition in Non-Aqueous Media

In this work, significant stabilization of Cu + ions is achieved in non-aqueous electrolytes containing TFSI – and Cl – anions with diglyme as solvent. When Cl – is absent, stabilization of Cu + occurs due to the very low stability constant of Cu 2+ in diglyme. However, in the presence of relatively low Cl – concentrations (i.e., equimolar relative to Cu 2+ ), both Cu + and Cu 2+ form extremely stable Cu 2+/+ [Cl – ] complexes resulting in a ∼1200 mV negative shift of the Cu +/0 redox couple relative to that of more easily reduced Cu + [TFSI – ][Cl – ] complexes. These results suggest that the lower solvation energies and wider electrochemical stability windows of non-aqueous solvents relative to water enable anions to play a much more significant role in guiding complexation behavior─providing new possibilities for (electro)chemical stabilization of reactive intermediates and highlighting the wealth of unexplored opportunities for electrolyte design in non-aqueous systems.