NEGATIVE ELECTRODE ACTIVE MATERIAL, NEGATIVE ELECTRODE SHEET USING SAME, AND ELECTRICITY STORAGE DEVICE

摘要

The present invention provides: an alloy-based negative electrode active material which is a silicon-copper alloy negative electrode active material represented by general formula (I) and containing a slight amount of oxygen, and which is capable of absorbing and desorbing lithium, while having high capacity, excellent cycle characteristics and excellent charged storage characteristics; a negative electrode sheet using this alloy-based negative electrode active material; and an electricity storage device. The negative electrode active material represented by general formula (I) is composed of a phase (A) which is mainly composed of SiOx that has the same crystal structure as elemental silicon and a phase (B) which is mainly composed of SiCu3Oy that has the same crystal structure as SiCu3. SipCuqMrOs (I) (In the formula, p + q + r + s = 100; s is 0.01-5; q is 5-50; r is 0-10; and M represents at least one element selected from among Be, B, Al, P, Zn, Ga, Ge, In, Sn, Sb, Y, Zr, Nb, Mo and W.)