Porous silicon-based anode active material, method of preparing the same, and lithium secondary battery including the anode active material

Patent metadata

Field	Value
Publication number	US-9843034-B2
Application number	US-201414483283-A
Country	US
Kind code	B2
Filing date	Sep 11, 2014
Priority date	May 30, 2013
Publication date	Dec 12, 2017
Grant date	Dec 12, 2017

Abstract

Provided are a porous silicon-based anode active material including crystalline silicon (Si) particles, and a plurality of pores on surfaces, or the surfaces and inside of the crystalline silicon particles, wherein at least one plane of crystal planes of at least a portion of the plurality of pores includes a (100) plane, and a method of preparing the porous silicon-based anode active material. Since a porous silicon-based anode active material of the present invention may allow volume expansion, which is occurred during charge and discharge of a lithium secondary battery, to be concentrated on pores instead of the outside of the anode active material, the porous silicon-based anode active material may improve life characteristics of the lithium secondary battery by efficiently controlling the volume expansion.

First claim

The invention claimed is:

1. A porous silicon-based anode active material comprising:
crystalline silicon (Si) particles; and
a plurality of honeycomb-shaped pores on surfaces, or the surfaces and inside of the crystalline silicon particles,
wherein at least one plane of crystal planes of at least a portion of the plurality of honeycomb-shaped pores comprises a (110) plane and a length of the plurality of pores in the (110) plane direction of the pores is relatively smaller than a length of the pores in a plane direction other than the (110) plane direction.

2. The porous silicon-based anode active material of claim 1 , wherein 2 planes, 4 planes, or 6 planes of the crystal planes of the at least a portion of the plurality of pores comprise (110) planes.

3. The porous silicon-based anode active material of claim 1 , wherein the crystalline silicon particles comprise silicon particles having an axial direction of <110>, <100>, or <111>.

4. The porous silicon-based anode active material of claim 1 , wherein a diameter of the honeycomb-shaped pores is in a range of 10 nm to 2 μm.

5. The porous silicon-based anode active material of claim 1 , wherein an average particle diameter (D 50 ) of the porous silicon-based anode active material is in a range of 100 nm to 50 μm.

6. The porous silicon-based anode active material of claim 1 , wherein a specific surface area of the porous silicon-based anode active material is in a range of 0.5 m 2 /g to 100 m 2 /g.

7. The porous silicon-based anode active material of claim 1 , wherein an internal porosity of the porous silicon-based anode active material is in a range of 5% to 90%.

8. The porous silicon-based anode active material of claim 1 , wherein a volume of the porous silicon-based anode active material expands in a (110) plane direction of the honeycomb-shaped pores during intercalation of lithium ions.

9. The porous silicon-based anode active material of claim 1 , wherein the plurality of honeycomb-shaped pores further extend in a (110) plane direction of the honeycomb-shaped pores.

10. The porous silicon-based anode active material of claim 1 , further comprising a carbon coating layer on the crystalline silicon particles.

11. The porous silicon-based anode active material of claim 10 , wherein a thickness of the carbon coating layer is in a range of 5 nm to 100 nm.

12. A method of preparing a porous silicon-based anode active material according to claim 1 , the method comprising the steps of:
(i) depositing metal particles on a surface of a silicon wafer;
(ii) etching the silicon wafer by dipping the surface of the silicon wafer having the metal particles deposited thereon in an etching solution to form honeycomb-shaped pores on the surface, or the surface and inside of the silicon wafer; and
(iii) contacting the silicon wafer having the pores formed thereon with a metal removal solution to remove the metal particles and grinding the silicon wafer thus obtained to obtain crystalline silicon particles, and
the silicon wafer has an axial direction of <110>, <100>, or <111>.

13. The method of claim 12 , wherein the silicon wafer has an axial direction of <100>or <111>.

14. The method of claim 12 , wherein the depositing of the metal particles is performed by mixing a fluorinated solution and a metal precursor solution, and contacting the silicon wafer with the mixed solution.

15. The method of claim 14 , wherein the fluorinated solution comprises at least one selected from the group consisting of hydrogen fluoride (HF), hydrofluosilicic acid (H 2 SiF 6 ), and ammonium fluoride (NH 4 F).

16. The method of claim 14 , wherein the metal precursor solution comprises at least one metal particle selected from the group consisting of silver, gold, platinum, and copper.

17. The method of claim 14 , wherein the fluorinated solution and the metal precursor solution are mixed in a weight ratio of 10:90 to 90:10.

18. The method of claim 14 , wherein an amount of the contacted silicon wafer is in a range of 0.001 parts by weight to 50 parts by weight based on 100 parts by weight of the mixed solution of the fluorinated solution and the metal precursor solution.

19. The method of claim 12 , wherein the etching solution is a mixed solution of a HF solution and a hydrogen peroxide (H 2 O 2 ) solution.

20. The method of claim 19 , wherein the HF solution and the H 2 O 2 solution are mixed in a weight ratio of 10:90 to 90:10.

21. The method of claim 12 , wherein the etching is performed for 10 minutes to 5 hours.

22. The method of claim 12 , wherein the metal removal solution comprises at least one selected from the group consisting of nitric acid, sulfuric acid, and hydrochloric acid.

23. The method of claim 12 , further comprising coating surfaces of the crystalline silicon particles with carbon by mixing the crystalline silicon particles with a carbon precursor and performing a heat treatment, after step (iii).

24. The method of claim 23 , wherein the carbon precursor comprises pitch or a hydrocarbon-based material.

25. The method of claim 23 , wherein the heat treatment is performed in a temperature range of 300° C. to 1,400° C.

26. An anode comprising the porous silicon-based anode active material of claim 1 .

27. A lithium secondary battery comprising:
a cathode;
an anode;
a separator disposed between the cathode and the anode; and
an electrolyte in which a lithium salt is dissolved,
wherein the anode is the anode of claim 26 .

Assignees

• Lg Chemical Ltd

Inventors

• Lee Yong Ju
• Lee Mi Rim
• Yoo Jung Woo
• Kim Je Young

Classifications

• H01M4/386

  Silicon or alloys based on silicon · CPC title

• C01B33/02

  Silicon (forming single crystals or homogeneous polycrystalline material with defined structure C30B) · CPC title

• H01M4/366

  as layered products · CPC title

• Y10T428/2982

  Particulate matter [e.g., sphere, flake, etc.] · CPC title

• H01M4/134 Primary

  Electrodes based on metals, Si or alloys · CPC title