The Anodic Behavior of Iron in Anhydrous Dimethoxyethane and Passivation by Solvent Electropolymerization

Abstract

The corrosion and passivity of high purity iron in anhydrous dimethoxyethane with 0.5M LiAsF6 have been studied by various electrochemical and surface analytical techniques. The motivations for this study were twofold; (i) to develop an understanding of the passivity of metals and alloys in anhydrous organic solutions at a fundamental level, and (it) to apply what is learned to improve the performance and useful life of high energy density lithium batteries which employ organic solvents. The data show that iron displays a stable passive region with low current densities over a large range of anodic potentials. Several different passivation mechanisms have been identified in this stable region. Among these mechanisms is passivation by solvent chemisorption. Our key finding is the observation of passivation by electropolymerization of the dimethoxyethane solvent. The polymerization reaction has not been observed when electrolytes other than LiAsF~ are used. Consequently, the potential at which breakdown of passivity occurs is lower in solutions containing alternative electrolytes. In addition, a bare oxide-free metal surface appears necessary for initiation of the electropolymerization reaction. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 129.173.72.87 Downloaded on 2015-06-22 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 129.173.72.87 Downloaded on 2015-06-22 to IP

Current Collectors for Positive Electrodes of Lithium-Based Batteries

“…With LiClO 4 the passivation broke down at 4.0 V vs Li/Li + . 84,85 In dry LiClO 4 /PC electrolyte Fe was passivated up to ca. 4.4 V vs Li/Li + , presumably through the formation of an insoluble Fe͑ClO 4 ͒ 2 layer.…”

Electrochemical behavior of current collectors for lithium batteries in non-aqueous alkyl carbonate solution and surface analysis by ToF-SIMS

“…Passive films are believed to be oxide/hydroxide containing water molecules, especially when formed in aqueous solution. Few examples show electrochemical behavior of those metals in anhydrous solutions [7][8][9][10][11][12][13][14][15][16][17][18]. Thus, little is known about the formed passive films and the formation processes.…”

Developing Concepts of Passivity and Passivity Breakdown to Improve Alloy Performance

“…In organic solutions, passivation is largely dependent on the functional group. Passivation by electropolymerization, was discovered to occur for iron [5] and carbon steel [6] in DME/0.5M LiAsF 6 solutions. At high temperatures (> 500˚C) various processes can produce complex gaseous environments that can have various effect on the passivation or corrosion of alloys and high temperature coatings applied on superalloys [7].…”