Negative electrode active material, negative electrode for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery
Provided is a negative electrode active material containing SiO x and carbonaceous particles containing graphite and having both good discharge capacity and good electric conductivity. Also provided is a negative electrode using the negative electrode active material and a nonaqueous electrolyte secondary battery. When the carbonaceous particles have an average particle diameter D 50 of α (μm) and a BET specific surface area of β (m 2 /g), the α and the β satisfy the following Formulae (1) and (2). β≦−(12/18)α+12 (1) 5≦α≦15 (2).
1. A negative electrode, comprising:
a negative electrode active material containing a silicon oxide expressed by SiO x , where 0.3≦x<1, and carbonaceous particles containing graphite,
a conductive agent selected from acetylene black or ketjenblack, and
a binder,
wherein when the carbonaceous particles have an average particle diameter D 50 of α (μm) and a BET specific surface area of β (m 2 /g), the α and the β satisfying the following Formulae (3) and (2), wherein the α and β used in the following Formulae (3) and (2) are numerals:
β≦−(9/18)α+9 (3)
5≦α≦15 (2),
wherein a mass ratio of SiO x to graphite is 1:3 to 1:2,
wherein a content of the binder is 8-20% by mass in the case when a total mass of the negative electrode material is 100% by mass, and
wherein the carbonaceous particles comprise a graphite core and a carbon coating layer.
2. A nonaqueous electrolyte secondary battery having the negative electrode according to claim 1 .
3. The negative electrode according to claim 1 , wherein the coating of the carbonaceous particles is a material having electrical conductivity.
4. The negative electrode according to claim 1 , wherein the SiO x has a coating layer comprising a carbon material on a surface thereof.
5. The negative electrode according to claim 4 , wherein the carbon material of the coating layer of the SiO x is selected from the group consisting of graphite, synthetic graphite, coke, mesophase carbon, vapor-grown carbon fiber, pitch-based carbon fiber, and polyacrylonitrile-based carbon fiber.
6. The negative electrode according to claim 4 , wherein the coating layer of the SiO x is formed in a range of 5 to 30% by mass based on the total mass of the SiO x .
7. The negative electrode according to claim 1 , wherein the SiO x has a BET specific surface area of 2 to 3.5 m 2 /g.
8. The negative electrode according to claim 3 , wherein the SiO x has a coating layer comprising a carbon material on a surface thereof.
9. The negative electrode according to claim 8 , wherein the coating layer of the SiO x is formed in a range of 5 to 30% by mass based on the total mass of the SiO x .
10. The negative electrode according to claim 1 , further comprising a surfactant.
11. The negative electrode according to claim 1 , wherein the binder is selected from the group consisting of polyamideimide, polyvinylidene difluoride, and polytetrafluoroethylene.
12. The negative electrode according to claim 11 , wherein
the coating of the carbonaceous particles is a material having electrical conductivity,
the SiO x has a coating layer comprising a carbon material on a surface thereof,
the carbon material of the coating layer of the SiO x is selected from the group consisting of graphite, synthetic graphite, coke, mesophase carbon, vapor-grown carbon fiber, pitch-based carbon fiber, and polyacrylonitrile-based carbon fiber,
the coating layer of the SiO x is formed in a range of 5 to 30% by mass based on the total mass of the SiO x , and
the SiO x has a BET specific surface area of 2 to 3.5 m 2 /g.