Abstract: A negative electrode active material including silicon monoxide particles, wherein the silicon monoxide particles satisfy that, in volumetric basis distribution measured with a laser-diffraction method particle size distribution measurement device, an accumulative 0.1%-particle-size D0.1 satisfies 1.2 ?m?D0.1?3.0 ?m, an accumulative 10%-particle-size D10 satisfies 3.5 ?m?D10?7.0 ?m, an accumulative 50%-particle-size D50 satisfies 6.0 ?m?D50?15.0 ?m, and an accumulative 99.9%-particle-size D99.9 satisfies 25.0 ?m?D99.9?50.0 ?m, and the silicon monoxide particles satisfy that a BET specific surface area Sm satisfies 1.0 m2/g?Sm?3.5 m2/g. The negative electrode active material can improve cycle characteristics when used as the negative electrode active material for a negative electrode of a secondary battery.

Abstract: A negative electrode active material including silicon monoxide particles coated with a carbon coating and doped with lithium, wherein the silicon monoxide particles satisfy that, in volumetric basis distribution measured with a laser-diffraction method particle size distribution measurement device, an integrated value of a relative amount of particles having a particle size of 1 ?m or less is 1% or less, an integrated value of a relative amount of particles having a particle size of 5 ?m or less is 20% or less, and an accumulative 50%-particle-size D50 satisfies 6.0 ?m?D50?15.0 ?m. This provides a negative electrode active material that can improve cycle characteristics while keeping high first efficiency when used as the negative electrode active material for a negative electrode of a secondary battery.