Corrosion of Lithium‐Ion Battery Current Collectors

Abstract

The primary current‐collector materials being used in lithium‐ion cells are susceptible to environmental degradation: aluminum to pitting corrosion and copper to environmentally assisted cracking. Localized corrosion occurred on bare aluminum electrodes during simulated ambient‐temperature cycling in an excess of electrolyte. The highly oxidizing potential associated with the positive‐electrode charge condition was the primary factor. The corrosion mechanism differed from the pitting typically observed in aqueous electrolytes because each site was filled with a mixed metal/metal‐oxide product, forming surface mounds or nodules. Electrochemical impedance spectroscopy was shown to be an effective analytical tool for characterizing the corrosion behavior of aluminum under these conditions. Based on X‐ray photoelectron spectroscopy analyses, little difference existed in the composition of the surface film on aluminum and copper after immersion or cycling in LiPF6 electrolytes made with two different solvent formulations. Although Li and P were the predominant adsorbed surface species, the corrosion resistance of aluminum may simply be due to its native oxide. Finally, copper was shown to be susceptible to environmental cracking at or near the lithium potential when specific metallurgical conditions existed (work hardening and large grain size). © 1999 The Electrochemical Society. All rights reserved.

Factors That Influence Formation of AlF[sub 3] Passive Film on Aluminum in Li-Ion Battery Electrolytes with LiPF[sub 6]

“…The detection of phosphorus duplicates the finding of Braithwaithe et al 1 The presence of phosphorus is consistent with the suggestion of Zhang and Jow 7 that phosphorus, and not fluoride, is the key element in the protective film formed on aluminum. However, the mpe values measured in this study range from 18.0 g/F at low potentials to 9.8 g/F at high potentials and, in our view, are best explained by the formation of AlF 3 , accompanied at higher potentials by electrolyte oxidation (see below).…”

“…The new electrolyte was employed to match the electrolyte used in some batteries, 2 as well as in some earlier studies. 1,10 As shown below, the decrease in concentration of LiPF 6 from 1.2M to 1.0M and the change in solvent from EC+EMC to EC+DMC did not have an effect on the anodic polarization behavior of aluminum. anodic scans (not shown).…”

“…[1][2][3][4][5][6][7][8][9][10][11] At low potentials (below approximately 4V, according to results presented in the current paper) aluminum is protected against uniform and pitting corrosion by its air-formed oxide, 1,7,8 which is usually < 5 nm thick. 8 At high potentials…”

“…Inspections of aluminum current collectors indicate the incidence of corrosion is low but non-negligible, and that the corrosion is localized. 1,2 The localized nature of the corrosion is related to the cathode's through-the-thickness porosity, which exposes to the electrolyte a limited number of small regions of the current collector.…”

A SoH Diagnosis and Prognosis Method to Identify and Quantify Degradation Modes in Li-ion Batteries using the IC/DV technique

“…The growth of CL with respect to LAM and LLI is significantly lower (from 0% to 3%) showing that CL is less relevant in this experiment. This result is in agreement with [17], where is claimed that manufacturing processes in commercial Li-ion cells largely eliminate the degradation effects attributed to CL.…”