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Thin Films / Battery Electrodes / Microscopical Analysis / Glass Membranes / Ionic ConductivityThin film ion-conductive materials may represent essential components of future all-solidstate batteries. Besides, they are also of interest from a fundamental point of view. In this article, the deposition of thin films of complex oxides and amorphous glasses is discussed. Methods of local chemical analysis by analytical electron microscopy and atom probe tomography are described and studies of atomic transport in sputtered network glasses are presented. As experimental examples, thin films of Li borate and silicate glasses, LiCoO 2 , V 2 O 5 , and Li 4 Ti 5 O 12 are addressed.

Thin film battery electrodes of the olivine structure LiFePO4 and the spinel phase LiMn2O4 are deposited through ion-beam sputtering. The intercalation kinetics is studied by cyclo-voltammetry using variation of the cycling rate over 4 to 5 orders of magnitude. The well-defined layer geometry allows a detailed quantitative analysis. It is shown that LiFePO4 clearly undergoes phase separation during intercalation, although the material is nano-confined and very high charging rates are applied. We present a modified Randles–Sevcik evaluation adapted to phase-separating systems. Both the charging current and the overpotential depend on the film thickness in a systematic way. The analysis yields evidence that the grain boundaries are important short circuit paths for fast transport. They increase the electrochemical active area with increasing layer thickness. Evidence is obtained that the grain boundaries in LiFePO4 have the character of an ion-conductor of vanishing electronic conductivity.