Negative electrode active material, negative electrode, non-aqueous electrolyte secondary battery, and method for manufacturing negative electrode active material

Abstract

The present invention provides a negative electrode active material, a negative electrode, a non-aqueous electrolyte secondary battery, and a method for producing the negative electrode active material, which can improve the cycle characteristics of secondary batteries. [Solution] The method for producing the negative electrode active material according to the embodiment is silicon dioxide SiO a (0

Claims

1. It contains composite particles containing a Si phase and magnesium silicide oxide, The crystallite size of the Si phase and the crystallite size of at least one phase contained in the magnesium silicide oxide, as evaluated from the powder X-ray diffraction pattern, are 10 nm or less. Negative electrode active material.

2. The magnesium silicide oxide is Mg ２ SiO ４ and MgSiO ３ Including at least one of the following, The negative electrode active material according to claim 1.

3. At least one of the Si phase and the magnesium silicide oxide contained in the composite particle is amorphous. The negative electrode active material according to claim 1 or 2.

4. The amount of Si phase contained in the composite particles is 20% by mass or more and 70% by mass or less, based on the total mass of the composite particles. The negative electrode active material according to claim 1 or 2.

5. The composite particles substantially contain MgO. The negative electrode active material according to claim 1 or 2.

6. The composite particles are coated on the surface with a carbon-based material. The negative electrode active material according to claim 1 or 2.

7. The amount of the carbon-based material coating the composite particles is 5% by mass or more and 20% by mass or less, based on the amount of the composite particles (excluding the carbon-based material). The negative electrode active material according to claim 6.

8. Negative electrode current collector and A negative electrode active material layer formed on the negative electrode current collector, comprising the negative electrode active material according to claim 1 or 2, A negative electrode equipped with a

9. A non-aqueous electrolyte secondary battery comprising the negative electrode described in claim 8.

10. Silicon dioxide (SiO₂) ａ A reduction step in which (0 < a ≤ 2) reacts with metallic magnesium Mg, An acid treatment step in which the material after the reaction is treated with acid, The mechanical alloying step involves performing mechanical alloying on the material after the reaction until the crystallite size, as evaluated from the powder X-ray diffraction pattern, is 10 nm or less. A method for producing a negative electrode active material, including [the specified element].

11. The mechanical alloying is carried out by one or more means selected from the group consisting of planetary mills, rotary mills, vibrating mills, rolling mills, and stirring mills. A method for producing a negative electrode active material according to claim 10.

12. The aforementioned mechanical alloying is performed under an inert atmosphere. A method for producing a negative electrode active material according to claim 10 or 11.

13. In the aforementioned acid treatment step, MgO is removed by reacting with the acid. A method for producing a negative electrode active material according to claim 10 or 11.

14. In the reduction step, silicon dioxide SiO ａ A method for producing a negative electrode active material according to claim 10 or 11, wherein at least a portion of it is reduced to Si.

15. The process further includes a coating step of coating the material after the reaction with a carbon-based material. A method for producing a negative electrode active material according to claim 10 or 11.

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