Abstract: A low oxygen-type silicon nanoparticle-containing slurry that can inhibit a viscosity increase along with the nanosizing of silicon particles is provided. The low oxygen-type silicon nanoparticle-containing slurry can be used for the production of a lithium-ion secondary battery having excellent charge-discharge characteristics such as charge-discharge capacity, initial coulombic efficiency, and charge-discharge cycle characteristics. The low oxygen-type silicon nanoparticle-containing slurry contains low oxygen-type silicon nanoparticles, a nonaqueous solvent, and an additive. The low oxygen-type silicon nanoparticles have a ratio of a peak area (ii) in a range of ?100 to ?110 ppm to a peak area (i) in a range of ?75 to ?85 ppm [a (ii)/(i) ratio] of 1.0 or less in 29Si-NMR.

Abstract: Silicon nanoparticles for negative electrode active material in lithium ion secondary batteries are provided. The silicon nanoparticles have a 29Si-NMR peak which has a half width of 20 ppm to 50 ppm centered at ?80 ppm and is broad ranging from 50 ppm to ?150 ppm. The silicon nanoparticles have a length in the major axis direction of 70 to 300 nm and a thickness of 15 to 70 nm or less.