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XPS study of duplex stainless steel as a possible current collector in a Li-ion battery
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
2012 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 0019-4686, Vol. 79, 82-94 p.Article in journal (Refereed) Published
Abstract [en]

The surface chemistry and corrosion property of a duplex LDX 2101 steel that had been cycled in a Li-ion battery with a 1 M LiPF6 in EC/DMC 1:1 electrolyte was studied. The results are compared to those of steel stored for the same length of time. Cyclic voltammetry was used to sweep the steel between 0 V and 5 V and the different reduction products were identified with SEM, XRD and XPS. A conversion reaction occurred during the cathodic sweep between 2.0 and 1.5 V where chromium and iron oxides were reduced forming Li2O and metal. At 0.5 V vs. Li+/Li a Solid Electrolyte Interface (SEI) was irreversibly formed predominantly during the first cycle. During the oxidation sweep the typical stainless steel passive layer of chromium and iron oxides/hydroxides formed at 2.5 V vs. Li/Li+. Li2O also decomposed at this potential. Simultaneously metal fluorides are formed. The XPS revealed a thicker SEI containing organic and inorganic species on the cycled electrode than on the stored. The stored sample showed chemical formation of CrF3 on the surface. Depth profiling of the cycled electrode by Ar+ etching showed a thick layer of CrF3 and a thin layer of FeF3. We conclude that the level of corrosion of this duplex steel is acceptable in the 3–4.5 V vs. Li+/Li region. However, in a Li-ion battery it is too reactive at low potentials to be considered as a replacement for copper as an anode current collector. We also observe that the PF6 anion from the electrolyte salt plays an important role in the formation of metal fluorides which is a fact generally neglected in the discussion of conversion reactions of metal-oxide anodes for Li-ion batteries. For stainless steel to be considered as current collectors for Li-ion batteries optimisation of alloy compositions need to be made to reduce corrosion occurring during cycling in organic solvents.

Place, publisher, year, edition, pages
Elsevier, 2012. Vol. 79, 82-94 p.
Keyword [en]
Passive layer; XPS; Li-ion battery; Duplex stainless steel; Voltammetry
National Category
Inorganic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
URN: urn:nbn:se:uu:diva-179310DOI: 10.1016/j.electacta.2012.06.057ISI: 000307920300011OAI: oai:DiVA.org:uu-179310DiVA: diva2:544163
Available from: 2012-08-13 Created: 2012-08-13 Last updated: 2012-11-23Bibliographically approved
In thesis
1. Depth Profiling of the Passive Layer on Stainless Steel using Photoelectron Spectroscopy
Open this publication in new window or tab >>Depth Profiling of the Passive Layer on Stainless Steel using Photoelectron Spectroscopy
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The physical properties of the protective passive films formed on the surface of stainless steels under electrochemical polarization in different electrolytes were studied. The structure of these films was analyzed as a function of depth using photoelectron spectroscopy (PES).

Depth profiling (using PES) of the surface layer was achieved by either changing the angle of incidence to achieve different analysis depths (ARXPS), by argon ion etching, or by varying the energy of the incoming x-rays by the use of synchrotron radiation. The use of hard x-rays with high resolution (HAXPES) provided novel quantified information about the nickel content underneath the passive films.

A complex environment was found in these surface layers composed of an outermost monolayer of iron on top of a layer of chromium hydroxides covering an underlayer of chromium oxides. Molybdenum was enriched in the interface between the metal and oxide. Nickel is enriched underneath the passive film and therefore nickeloxides are only present in the surface layer in low concentrations.

A comparison was performed on austenitic and duplex stainless prepared by hot isostatically pressed (HIP) or cast and forged processes. HIP stainless steel was produced using the burgeoning technique of pressing gas atomized powders together. The structure of these steels is far more homogenous with a lower porosity than that of the conventionally prepared equivalents. It was shown that hot HIP austenitic steel had better pitting corrosion resistance than its conventional counterpart.

Finally, the duplex steel was cycled in a Li-ion battery to explore its potential application as a current collector. It was shown that the passive film formed in the organic solvents is similar in composition and thickness to the films formed in aqueous solutions. However, it is doubtful if steel could be used as current collector in batteries due to its high reactivity with lithium.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 69 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 955
depth profile, stainless steel, passive film, XPS, HAXPES, corrosion, powder metallurgical
National Category
Materials Chemistry
Research subject
Chemistry with specialization in Materials Chemistry
urn:nbn:se:uu:diva-179399 (URN)978-91-554-8430-9 (ISBN)
Public defence
2012-09-28, Å2005, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Available from: 2012-09-05 Created: 2012-08-14 Last updated: 2013-01-22

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