Abstract: A secondary battery includes a positive electrode including a positive electrode active material, a negative electrode, and an electrolytic solution. The positive electrode active material includes a lithium composite oxide of a layered rock-salt type. The lithium composite oxide includes lithium, cobalt, aluminum, magnesium, an additional element, and oxygen as constituent elements. The additional element includes at least one of fluorine, phosphorus, or sulfur. According to an analysis of the positive electrode active material by inductively coupled plasma optical emission spectrometry, a content of aluminum is greater than a content of magnesium.

Abstract: A fuel cell stack includes: a substrate; a first fuel cell including a fuel side electrode, an electrolyte, and an oxygen side electrode on the substrate, the first fuel cell being a single fuel cell; a second fuel cell including a fuel side electrode, an electrolyte, and an oxygen side electrode on the substrate, the second fuel cell being a single fuel cell; an interconnector film electrically connecting the fuel side electrode of the first fuel cell and the oxygen side electrode of the second fuel cell; and a porous ceramic film covering at least the interconnector film in a region between the fuel side electrode of the first fuel cell and the fuel side electrode of the second fuel cell.

Abstract: A secondary battery includes a positive electrode including a positive electrode active material, a negative electrode, and an electrolytic solution. The positive electrode active material includes a lithium composite oxide of a layered rock-salt type. The lithium composite oxide includes lithium, cobalt, aluminum, magnesium, an additional element, and oxygen as constituent elements. The additional element includes at least one of fluorine, phosphorous, or sulfur. According to an analysis of the positive electrode active material by inductively coupled plasma optical emission spectrometry, a content of aluminum is greater than a content of magnesium.

Abstract: A fuel cell stack comprises: a substrate; a plurality of single fuel cells each of which includes a fuel side electrode, an electrolyte, and an oxygen side electrode deposited on the substrate; an interconnector film electrically connecting the fuel side electrode of one single fuel cell of adjacent single fuel cells of the plurality of single fuel cells and the oxygen side electrode of the other single fuel cell; and a porous ceramic film covering at least the interconnector film in a region between a first fuel side electrode of one single fuel cell of adjacent single fuel cells and a second fuel side electrode of the other single fuel cell.