## 2 Materials and Methods  
### Synthesis and Characterization of the Electrolyte and Electrode Materials  
To obtain porous substrates and different functional layers, the electrolyte and electrode materials were synthesized using various techniques. Synthesis of the BCGCuO electrolyte material used for the suspension preparation and film formation was carried out using a nitrate combustion method. BaCO\({}_{3}\) (98.4% purity, Vekton, Russia), Gd(NO\({}_{3}\))\({}_{3}\)-6H\({}_{2}\)O (99%, Reaktiv, Russia), Ce(NO\({}_{3}\))\({}_{3}\) 6H\({}_{2}\)O (99%, Reaktiv, Russia), and CuO (99%, Reakhim, Russia) were used as raw materials; glycine and citric acid were used as a fuel and oxidizer, respectively. The details of the synthesis procedure are given elsewhere [16]. Following the final synthesis stage at 1050 \({}^{\circ}\)C (10 h), the BCGCuO powder was grinded for 2 h in a Pulverisette 6 planetary mill (Fritsch, Germany) in a Teflon drum with tetragonal ZrO\({}_{2}\)-Y\({}_{2}\)O\({}_{3}\) milling bodies in an isopropyl alcohol medium (weight ratio of 1:5:1). Synthesis of the LNFO electrode material for the cathode substrate was carried out using a modified Pechini method (designated as LNFO\({}_{\text{P}}\)). La(NO\({}_{3}\))\({}_{3}\)-6H\({}_{2}\)O (99%, Ural warehouse of chemicals, Russia), Fe(NO\({}_{3}\))\({}_{3}\).9H\({}_{2}\)O (99%, Reaktivtorg, Russia), and Ni(NO\({}_{3}\))\({}_{2}\).6H\({}_{2}\)O (99%, Reaktiv, Russia) were dissolved in distilled water, thoroughly mixed, and then, organic fuels such as citric acid and ethylene glycol were added. The obtained mixture was heated, evaporated, and decomposed at 450 \({}^{\circ}\)C. The obtained black ash was calcinated at 900 \({}^{\circ}\)C (8 h) and 1180 \({}^{\circ}\)C (8 h) with intermediate and final milling in the planetary mill in an agate drum with stainless-steel milling bodies in an isopropyl alcohol medium (weight ratio of 1:5:1). A nitrate combustion method was applied to prepare the LBNO powder (designated as LBNO\({}_{\text{nc}}\)) for the suspension preparation and EPD formation of the electrode functional sublayer on the top of porous LNFO substrates. The starting materials of La(NO\({}_{3}\))\({}_{3}\):6H\({}_{2}\)O (99%, Ural warehouse of chemicals, Russia), Ni(NO\({}_{3}\))\({}_{2}\):6H\({}_{2}\)O (99%, Reaktiv, Russia), and Ba(NO\({}_{3}\))\({}_{2}\) (99.9%, Vekton, Russia) were completely dissolved in distilled water and citric acid was added as a chelating agent (metal cations/citric acid mole ratio of 1:2). The pH value of the mixture equal to 8 was adjusted by addition of a 10% NH\({}_{4}\)OH solution. Then, the solution was heated up to 200 \({}^{\circ}\)C with consecutive evaporation, gelation, and combustion. The as-prepared powder was grinded and calcinated at 700 \({}^{\circ}\)C to remove residual organics. The obtained powder was ball-milled (1 h) with the following synthesis at 1100 \({}^{\circ}\)C (5 h). To obtain a fine powder for the suspension preparation, after the final step of the synthesis, the LBNO\({}_{\text{nc}}\) powder was milled for 1 h.  
The LBNO and LNFO materials for the cathode substrates were obtained via a two-stage solid state reaction method (designated as LBNO\({}_{\text{ss}}\) and LNFO\({}_{\text{ss}}\), respectively). The initial components La\({}_{2}\)O\({}_{3}\) (99.99%, Vekton, Russia), NiO (99%, Vekton, Russia), BaCO\({}_{3}\) (99%, Vekton, Russia), and Fe\({}_{2}\)O\({}_{3}\) (99%, Ormet, Russia) were taken in stoichiometric amounts, mixed and grinded in the planetary mill (1 h), and calcinated step-by-step at 1150 \({}^{\circ}\)C (2 h) and 1250 \({}^{\circ}\)C (5 h) with intermediate ball-milling (1 h). Following the final synthesis step, the powders were ball-milled for 1 h.  
The obtained powders were subjected to X-ray phase analysis via a D/MAX-2200 diffractometer (Rigaku, Japan) using CuK\(\alpha\) radiation in an angle range of 20\({}^{\circ}\)\(\leq\) 20 \(\leq\) 80\({}^{\circ}\).