Anode active material for lithium secondary battery and method of preparing the same
View Patent ↗Provided are an anode active material for a lithium secondary battery including a silicon-based composite formed of silicon (Si) and crystalline SiO 2 , wherein the Si and crystalline SiO 2 are in the form of grains, a method of preparing the same, and a lithium secondary battery including the anode active material. Since an anode active material according to an embodiment of the present invention includes a silicon-based composite including Si and SiO 2 in a grain state and the SiO 2 is crystalline SiO 2 , the reaction between amorphous SiO 2 and lithium in an electrolyte may be excluded. Thus, since the crystalline SiO 2 is included in the silicon-based composite, excellent capacity characteristics of a secondary battery may be maintained and initial efficiency and life characteristics may be improved when the silicon-based composite is used as an anode active material.
1. An anode active material, consisting of
a silicon-based composite particle consisting of crystalline silicon (Si) and crystalline SiO 2 ,
wherein the crystalline SiO 2 and Si are in a form of grains,
wherein the silicon-based composite is represented by SiO x (0<x<2), and
wherein the Si and crystalline SiO 2 grains are present in a ratio of 1−(x/2):(x/2), and
wherein an average diameter of the silicon-based composite particle is in a range of 0.5 to 20 μm.
2. The anode active material of claim 1 , wherein the crystalline SiO 2 is quartz, cristobalite, or tridymite.
3. The anode active material of claim 1 , wherein an average particle diameter of the crystalline Si is in a range of 0.05 nm to 100 nm.
4. A method of preparing an anode active material, comprising:
reducing crystalline SiO 2 to prepare the anode active material,
wherein the anode active material consists of a silicon-based composite particle consisting of crystalline silicon (Si) and crystalline SiO 2 ,
wherein the crystalline SiO 2 and Si are in a form of grains,
wherein the silicon-based composite is represented by SiO x (0<x<2), and
wherein the Si and crystalline SiO 2 grains are present in a ratio of 1−(x/2):(x/2), and
wherein an average diameter of the silicon-based composite particle is in a range of 0.5 to 20 μm.
5. The method of claim 4 , wherein the reducing of the crystalline SiO 2 is performed by thermally reducing the crystalline SiO 2 with metallic powder or metallic gas including a metal reducing agent in an inert atmosphere.
6. The method of claim 4 , wherein the reducing of the crystalline SiO 2 is performed by mixing the crystalline SiO 2 with metallic powder including a metal reducing agent and thermally reducing the mixture in a temperature range of 400° C. to 1,000° C. for 1 hour to 24 hours in an inert atmosphere.
7. The method of claim 5 , wherein the metal reducing agent comprises at least one selected from the group consisting of titanium (Ti), aluminum (Al), magnesium (Mg), and calcium (Ca).
8. The method of claim 5 , wherein an amount of the metal reducing agent included in the metallic powder is in a range of 100:0.1 to 100:100 as a molar ratio based on the crystalline SiO 2 .
9. The method of claim 4 , wherein the reducing of the crystalline SiO 2 is performed by thermally reducing in a rotary kiln.
10. The method of claim 4 , further comprising removing reduced impurities using an HCl aqueous solution after the preparation of the silicon-based composite.
11. The method of claim 10 , wherein the reduced impurities comprise MgO.
12. An anode comprising a current collector and the anode active material of claim 1 formed on at least one surface of the current collector.
13. A lithium secondary battery comprising the anode active material of claim 1 .
14. The anode active material of claim 1 , wherein the silicon-based composite is represented by SiO x (0<x<1).
15. The anode active material of claim 1 , wherein an average particle diameter of the crystalline Si is in a range of 100 nm to 500 nm.