Abstract: A secondary battery includes a positive electrode, a negative electrode, and a separator. The separator is interposed between the positive electrode and the negative electrode. The separator includes a porous layer, a first adhesion layer, and a second adhesion layer. The first adhesion layer is provided between the porous layer and the positive electrode, and is adhered to the positive electrode. The second adhesion layer is provided between the porous layer and the negative electrode, and is adhered to the negative electrode. After the separator is heated at a heating temperature of 130° C.±5° C. for a heating time of one hour, an adhesion strength of the first adhesion layer with respect to the positive electrode is larger than an adhesion strength of the first adhesion layer with respect to the porous layer, and an adhesion strength of the second adhesion layer with respect to the negative electrode is larger than an adhesion strength of the second adhesion layer with respect to the porous layer.

Abstract: A secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode includes a lithium-nickel composite oxide. The negative electrode includes a lithium-titanium composite oxide. The electrolytic solution includes a carboxylic acid ester. The carboxylic acid ester includes at least one of ethyl acetate, propyl acetate, ethyl propionate, or propyl propionate. A first oxygen spectrum and a second oxygen spectrum are detectable by a surface analysis of the positive electrode by X-ray photoelectron spectroscopy. The first oxygen spectrum has a peak within a range of binding energy that is greater than or equal to 528 eV and less than or equal to 531 eV. The second oxygen spectrum has a peak within a range of binding energy that is greater than 531 eV and less than or equal to 535 eV. A ratio of an intensity of the first oxygen spectrum to an intensity of the second oxygen spectrum is greater than or equal to 0.30 and less than or equal to 0.80.

Abstract: A secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode includes a positive electrode active material layer. The positive electrode active material layer includes a lithium-nickel composite oxide of a layered rock-salt type.

Abstract: A secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode includes a positive electrode active material layer. The positive electrode active material layer includes a lithium-nickel composite oxide of a layered rock-salt type.

Abstract: A secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode includes a positive electrode active material layer. The positive electrode active material layer includes a lithium-nickel composite oxide of a layered rock-salt type.

Abstract: A positive electrode active material for a secondary battery includes a center part and a covering part. The center part includes a layered rock-salt lithium-nickel composite oxide. The covering part covers a surface of the center part and includes a boron compound. The positive electrode active material has a crystallite size of a (104) plane that is greater than or equal to 40.0 nm and less than or equal to 74.5 nm. The crystallite size is calculated by X-ray diffractometry and Scherrer equation. The positive electrode active material has a specific surface area that satisfies a condition represented by ?0.0160×Z+1.72?A??0.0324×Z+2.94 where Z is the crystallite size (nm), and A is the specific surface area (m2/g). The specific surface area is measured by BET specific surface area measurement method.

Abstract: A positive electrode includes first active material particles, second active material particles, and third active material particles, and the second active material particles include an aggregation of second primary particles. The average particle size D1 of the first active material particles, the average particle size D2 of the second active material particles, and the average particle size D3 of the third active material particles satisfy a relationship of D1>D2>D3. A first particle disintegration rate ?1 of the first active material particle and a third particle disintegration rate ?2 of the third active material particle are not more than 20%, and a second particle disintegration rate ? of the second active material particle is not less than 70%.

Abstract: A positive electrode includes first active material particles, second active material particles, and third active material particles, and the second active material particles include an aggregation of second primary particles. The average particle size D1 of the first active material particles, the average particle size D2 of the second active material particles, and the average particle size D3 of the third active material particles satisfy a relationship of D1>D2>D3. A first particle disintegration rate ?1 of the first active material particle and a third particle disintegration rate ?2 of the third active material particle are not more than 20%, and a second particle disintegration rate ? of the second active material particle is not less than 70%.