Thin film electrodes and electrolytes, especially grown epitaxially and approximating a single crystal, can be utilized as model systems to correlate electrochemical processes with structural changes on an atomic scale. In addition, studying the thin film components can be of importance for understanding and improving technology of the all-solid-state batteries. In our research program the focus is on making epitaxial intercalation cathodes by pulse laser deposition (PLD) on single-crystal SrTiO₃ (STO) substrates of different orientations. Placing an epitaxial conductive SrRuO₃ (SRO) layer on STO, that is acting as a current collector, allows performing electrochemical testing with either liquid or solid electrolytes. By inducing different charge/discharge states, the pseudo-single-crystal cathodes can be studied by high-resolution transmission electron microscopy (HRTEM) in great details. In this presentation we will discuss successes and difficulties related to the thin-film synthesis, in particular of such cathode materials as LiCoO₂, Li₂MnO₃, commercial Li-rich HE5050 (Li_1.2Mn_0.55Ni_0.15Co_0.1O₂) and Na(Fe,Mn)O_2. We will also present HRTEM results on the structural changes occurring at different stages (voltage and number of cycles) of electrochemical testing; some of the results, e.g. formation of Co3O4 spinel on the {104} facets, could be obtained only with the thin-film approach.