The present invention provides: a battery wherein transparency of a particle-containing resin layer is improved, and the thickness of the particle-containing resin layer is highly accurately managed; a separator; electrodes; a paint; a battery pack using the battery, the separator, the electrodes and the paint; an electronic apparatus; an electric vehicle; an electricity storage device; and a power system. This battery is provided with a positive electrode, a negative electrode, an electrolytic solution, and a particle-containing resin layer that contains particles and a resin. A shape of each of the particles includes a planar surface, a planarity of the particles is more than 40% but equal to or less than 100%, and a refractive index of the particles is equal to or more than 1.3 but less than 2.4.