Patent ID: 10347908

Abstract:
A lithium ion secondary battery having a negative electrode includes a negative electrode active material containing at least one of two material of silicon and a silicon compound and carbon, a weight mixing ratio of at least one of two material of the silicon and the silicon compound and the carbon is 20:80 to 50:50, when D90 of particles of at least one of two material of the silicon and the silicon compound is x, D50 of particles of the carbon is y, and the weight mixing ratio of the carbon is z, y≤−1.17x+0.45z is satisfied, the x is between 2 μm and 10 μm, the y is between 10 μm and 23 μm, and the z is between 50% and 80% by weight, and a coefficient of expansion when the negative electrode is fully charged is 110% or more and 140% or less.