Negative electrode active material, mixed negative electrode active material, negative electrode for non-aqueous electrolyte secondary battery, lithium ion secondary battery, method for producing negative electrode active material, and method for producing lithium ion secondary battery

A negative electrode active material, wherein the negative electrode active material is a negative electrode active material comprising negative electrode active material particles;

• the negative electrode active material particles comprise silicon compound particles comprising a silicon compound (SiOx:
• 0.5≤x≤1.6);
• the silicon compound particles include at least any one kind or more kinds of Li2SiO3 and Li4SiO4;
• the negative electrode active material particles have a loose bulk density BD of 0.5 g/cm3 or more and 0.9 g/cm3 or less, a tapped bulk density TD of 0.7 g/cm3 or more and 1.2 g/cm3 or less, and a compression degree of 25% or less, the compression degree being defined by (TD−BD)/TD.

A method for producing a negative electrode active material, wherein the method is a method for producing a negative electrode active material comprising negative electrode active material particles which comprise silicon compound particles;

• the method comprising:
• a step of forming negative electrode active material particles comprising silicon compound particles which comprise a silicon compound (SiOx:
• 0.5≤x≤1.6);
• a step of inserting Li into the negative electrode active material particles so as to include at least any one kind or more kinds of Li2SiO3 and Li4SiO4 therein;
• a step of selecting, from the negative electrode active material particles, negative electrode active material particles having a loose bulk density BD of 0.5 g/cm3 or more and 0.9 g/cm3 or less, a tapped bulk density TD of 0.7 g/cm3 or more and 1.2 g/cm3 or less, and a compression degree of 25% or less, the compression degree being defined by (TD-BD)/TD, whereby producing the negative electrode active material by using the negative electrode active material particles thus selected.