NEGATIVE ELECTRODE ACTIVE MATERIAL FOR LITHIUM ION SECONDARY BATTERIES, METHOD FOR MANUFACTURING NEGATIVE ELECTRODE ACTIVE MATERIAL FOR LITHIUM ION SECONDARY BATTERIES, LITHIUM ION SECONDARY BATTERY, AND METHOD FOR CHARGING LITHIUM ION SECONDARY BATTERY

摘要

PROBLEM TO BE SOLVED: To provide a novel and improved negative electrode active material for lithium ion secondary batteries which enables the improvement of a lithium ion secondary battery in cycle life while keeping a high discharge capacity of a silicon-based active material, and others.SOLUTION: To solve the problem, a negative electrode active material for lithium ion secondary batteries is provided according to an aspect of the present invention. The negative electrode active material for lithium ion secondary batteries comprises: surface-modified microparticles including silicon-based active material microparticles and a carbon material coating the surfaces of the silicon-based active material microparticles; and hard carbon composed with the surface-modified microparticles. The total mass of the carbon material is 0.35-3.5 mass% to the total mass of the silicon-based active material microparticles and the carbon material.