Air electrode/separator assembly and metal-air secondary battery

An air electrode/separator assembly, comprising:

• a hydroxide ion conductive separator comprising a hydroxide ion conductive solid electrolyte;
• an air electrode layer that is provided on one side of the hydroxide ion conductive separator and that comprises a hydroxide ion conductive material, an electron conductive material, and an air electrode catalyst, provided that the hydroxide ion conductive material may be the same material as the hydroxide ion conductive solid electrolyte or the air electrode catalyst, and provided that the electron conductive material may be the same material as the air electrode catalyst;
• and
• an interface layer between the hydroxide ion conductive separator and the air electrode layer, wherein the interface layer comprises:
• a plurality of platy particles composed of a hydroxide ion conductive solid electrolyte grown in a direction away from a surface of the hydroxide ion conductive separator, and
• an electron conductive material provided so as to fill a gap between the plurality of platy particles and/or unevenness formed by the plurality of platy particles;
• and
• wherein the interface layer has a thickness of 150 nm or smaller and wherein the air electrode layer has a thickness of 300 nm or smaller.