C. Ziebert, Karlsruhe Institute of Technology (KIT), Institute
for Materials Research I (IMF I), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen,
Germany; A. Knorr, KIT, IMF
I, Hermann-von-Helmholtz-Platz
1, 76344 Eggenstein-Leopoldshafen, Germany; S.
Ulrich, KIT, IMF I,
Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany; D. Gerthsen,
KIT, Laboratory for Electron Microscopy, Kaiserstrasse
12, 76131 Karlsruhe, Germany
The basic demand on an electrolyte for a Li-ion
battery is the ability to conduct Li-ions. Because the ionic conductivity in
solid state electrolytes is smaller than in fluid systems, there is a strong
need for the development of thin film solid state electrolytes, which can
compensate this handicap by reducing the diffusion path of lithium ions due to
their small thickness. In this work amorphous thin films in the materials
system Li-V-Si-O (LVSO) were realized by applying a
combinatorial materials science approach. The films were deposited by non-reactive
r.f. magnetron sputtering from a segmented target
that consisted of two half-parts of circular LiVO3 and SiO2
ceramics. In each experiment, coatings of different
composition and/or microstructure were obtained simultaneously by placing
different substrates in individual positions relative to a segmented
target. The composition, crystal structure and topography were examined using
inductive coupled plasma optical emission spectroscopy, X-ray diffraction
(XRD), Raman spectroscopy, scanning electron and atomic force microscopy.
Moreover intrinsic stress, ionic and electrical conductivity and film density
were determined. The parameters working gas pressure (0.075 – 25 Pa) and bias
voltage (0 V – -60 V) were systematically varied to find parameters for thin
films that remain amorphous and Raman-inactive even after a heat treatment for
3 h at 600 °C (Ar:O2 = 4,5:5). XRD and Raman spectroscopy revealed
that films deposited at a pressure of 0.15 Pa and a substrate bias of -40 V
fulfilled these requirements. From electrical impedance measurements a ionic
conductivity at room temperature of 2.8·10-5 S cm-1 was
determined, that was significantly higher than all
values for the Li-V-Si-O system or any other thin
film electrolyte systems reported in literature up to now. This result clearly
confirms the potential of the combinatorial materials science approach with a
segmented target arrangement.