Current oscillations during copper electrodissolution in lithium ion battery and acidic chloride electrolytes.

摘要

Electrochemical oscillations have become interests of numerous investigations because of their features of easy control, short time scale, straightforward monitoring, and practical importance of those reactions with oscillations. Although electrochemical oscillations are well-known phenomena, many of their formation mechanisms are not clearly understood. The present work introduced two types of potentiostatic oscillations, and their mechanisms were proposed.; The first type of oscillations was observed during copper electrodissolution in lithium ion battery electrolyte. They originated from a study of electrochemical stability of the copper. The oscillations were observed over certain ranges of solution stir rate and applied potential. The dynamic conditions of the electrolyte influenced the frequency and pattern of the oscillations. The amplitude of the oscillations increased with increasing potential. Also, cyclic voltammetry (CV) showed that the oscillatory current was correlated to the oxidation of the copper electrode. The magnetohydrodynamics (MHD) and solution dynamic effects were studied, and the oscillations were found to be consistent with a convection mechanism.; The second type of current oscillations was observed during copper electrodissolution in acidic NaCl conditions when the solution was sparged with nitrogen gas. The oscillations were present over the potential range of 0.3 to 0.7 V versus Ag/AgCl (3 M NaCl). The surface morphology of the copper was recorded by using a microscope, and the formation of a black film was correlated to the oscillations. The relationship between each oscillatory peak and a cycle of film formation and dissolution was established through the use of a combination of impedance spectroscopy and microscopy. Characterizations of the oscillations showed that they were related to pH, chloride concentration, and sparging rate conditions and were only present at proper combinations of those conditions. A mechanism consistent with mixing kinetics and diffusion control was proposed.