Method for preparing solid electrolyte for solid oxide fuel cell, and method for preparing unit cell

A method of preparing a unit cell of a solid oxide fuel cell (SOFC), the method comprising:

• preparing a YbScSZ solid electrolyte material using coprecipitation;
• forming an electrolyte slurry by mixing a solvent, a dispersant, and a binder with the YbScSZ solid electrolyte material;
• forming an electrolyte film by applying the electrolyte slurry using tape casting;
• forming an anode slurry by mixing NiO and YSZ at a ratio of 60:40;
• forming an anode sheet by applying the anode slurry using tape casting;
• stacking multiple sheets of the anode sheet and stacking multiple sheets of the electrolyte films on the stacked anode sheets;
• forming an anode supporter type electrolyte assembly by performing lamination, calcination, and cofiring in the state of being stacked;
• applying a cathode formed by mixing LSM and YSZ at a ratio of 60:40 to an electrolyte of the assembly using screen printing;
• and
• calcining and cofiring the cathode-applied assembly,
• wherein the preparing comprises:
• providing a starting material comprising ytterbium nitrate [Yb(NO3)3.H2O], scandium nitrate [Sc(NO3)3.H2O], and zirconium oxychloride [ZrOCl2.H2O] at a ratio of 6:4:90 by mol;
• forming a mixture metal salt aqueous solution by dissolving the starting material;
• forming a precursor by mixing the mixture metal salt aqueous solution and a chelating agent and coprecipitating the obtained mixture;
• washing the precursor with ultrapure water multiple times;
• filtering the washed precursor using a vacuum filtration apparatus;
• and
• forming a solid electrolyte powder by heat treating the filtered precursor.