LiNi sub(0.5)Mn sub(1.5)O sub(4) Thin-Film Cathodes on Gold-Coated Stainless Steel Substrates: Formation of Interlayers and Electrochemical Properties

Thin films of LiNi sub(0.5)Mn sub(1.5)O sub(4) (LNMO) were prepared on gold-coated stainless steel substrates via a poly(vinylpyrrolidone)-based sol-gel process. Films with a thickness in the range of 1 mu m were found to exhibit a capacity close to the theoretical one. The formation of interlayers...

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Bibliographic Details
Published in:Electrochimica acta 2014-07, Vol.133, p.146-152
Main Authors: Gellert, Michael, Gries, Katharina I, Zakel, Julia, Ott, Andrea, Spannenberger, Stefan, Yada, Chihiro, Rosciano, Fabio, Volz, Kerstin, Roling, Bernhard
Format: Article
Language:English
Subjects:
Carbonates
Electrochemical impedance spectroscopy
Gold
Impedance
Interlayers
Mixed oxides
Scanning transmission electron microscopy
Stainless steels
Thin films
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Summary:Thin films of LiNi sub(0.5)Mn sub(1.5)O sub(4) (LNMO) were prepared on gold-coated stainless steel substrates via a poly(vinylpyrrolidone)-based sol-gel process. Films with a thickness in the range of 1 mu m were found to exhibit a capacity close to the theoretical one. The formation of interlayers (i) between the LNMO films and the LP30 electrolyte (mixture of dimethyl carbonate (DMC) and ethylene carbonate (EC) (1:1 v/v) containing 1 mol.l super(-1)LiPF sub(6)) and (ii) between the LNMO films and the gold-coated substrate was studied by means of electrochemical impedance spectroscopy (EIS), time-of-flight secondary-ion mass-spectrometry (ToF-SIMS), and scanning transmission electron microscopy together with energy dispersive X-ray spectroscopy (STEM/EDX). The combination of these methods turns out to be very powerful for understanding the chemical composition and properties of interlayers and for identifying the origin of semicircles in Nyquist impedance plots. At the LNMO/LP30 interface, we observe an interlayer (solid electrolyte interface, SEI) with a thickness of about 50 nm, while at the LNMO/gold interface, a mixed oxide layer with a thickness in the range of 250 nm is found. The mixed oxide layer is caused by diffusion of Cr and Ni from the stainless steel through the gold layer. While the LNMO/LP30 interlayer contributes significantly to the interfacial impedance, the impedance of the LNMO/gold interlayer seems to be negligible, despite its larger thickness.
ISSN:0013-4686
DOI:10.1016/j.electacta.2014.03.184