Negative electrode active material, mixed negative electrode active material, aqueous negative electrode slurry composition, and method for producing negative electrode active material

A negative electrode active material for a non-aqueous electrolyte secondary battery, containing negative electrode active material particles, wherein

• the negative electrode active material particles comprise silicon compound particles each containing a silicon compound represented by SiOx where 0.5≤x≤1.6,
• the silicon compound particle also contains at least one or more of Li2SiO3 and Li2Si2O5,
• the negative electrode active material comprises a phosphate,
• the negative electrode active material particles each have a surface containing lithium element,
• a ratio mp/ml satisfies 0.07≤mp/ml≤0.8, where ml represents a molar quantity of the lithium element present on the surfaces of the negative electrode active material particles per unit mass of the negative electrode active material particles, and mp represents a molar quantity of phosphorus element contained per unit mass of the negative electrode active material particles, and
• the negative electrode active material particles cause a dispersion containing 10 mass % of the negative electrode active material particles dispersed in pure water to have a pH value of 10 or more and 12.5 or less.