POSITIVE ELECTRODE ACTIVE MATERIAL FOR SECONDARY BATTERY, POSITIVE ELECTRODE FOR SECONDARY BATTERY, AND SECONDARY BATTERY

A secondary battery includes a positive electrode for a secondary battery, a negative electrode, and an electrolytic solution. The positive electrode for a secondary battery includes a positive electrode active material for a secondary battery. The positive electrode active material for a secondary battery includes first particles and second particles. The first particles have a median diameter D50 of greater than or equal to 15 micrometers and less than or equal to 30 micrometers and each include a lithium-containing compound. The second particles have a median diameter D50 of greater than or equal to 1 micrometer and less than or equal to 10 micrometers and each include a center part that includes a lithium-containing compound and a covering part provided on a surface of the center part. The covering part includes, in order from a side closer to the center part, an underlayer and a surface layer. The underlayer includes a reaction product of a first metal alkoxide in which no alkyl group is bonded to a metal atom. The surface layer includes a reaction product of a second metal alkoxide in which the alkyl group is bonded to the metal atom. The reaction product of the second metal alkoxide is bonded to the reaction product of the first metal alkoxide.