Negative electrode active material having double coating layer, method for preparing the same and lithium secondary battery including the same

Patent metadata

Field	Value
Publication number	US-10581069-B2
Application number	US-201515034666-A
Country	US
Kind code	B2
Filing date	Aug 26, 2015
Priority date	Aug 26, 2014
Publication date	Mar 3, 2020
Grant date	Mar 3, 2020

Abstract

The present invention relates to a negative electrode active material having a double coating layer of a first coating layer and a second coating layer, which has an excellent output property, effectively suppresses a side reaction with an electrolyte liquid, particularly a PC-containing electrolyte liquid, and has excellent electric conductivity, a method for manufacturing the same, a negative electrode including the same, and a lithium secondary battery including the negative electrode. The negative electrode active material according to the present invention is capable of effectively preventing a side reaction with an electrolyte liquid, particularly a PC-containing electrolyte liquid, and is capable of improving electric conductivity, and as a result, enhancing a rate determining property by reducing an OCV drop of a lithium secondary battery including the negative electrode active material, and enhancing a high rate property.

First claim

What is claimed is:

1. A negative electrode active material comprising:
a graphite core; and
a double coating layer including a first coating layer and a second coating layer,
wherein the first coating layer consists of an amorphous carbon material formed on the graphite core; and
the second coating layer includes carbon particles doped with nitrogen formed on the first coating layer,
wherein the first coating layer and the second coating layer are bound to each other by electrostatic attraction,
wherein the nitrogen is doped in 3 mol % to 7 mol % with respect to carbon atoms of the carbon particles for providing the carbon particles a positive charge to bind the first and second coating layers, and
wherein the amorphous carbon material has an average particle diameter (D50) of 4 μm to 9 μm.

2. The negative electrode active material of claim 1 , wherein the graphite core is artificial graphite, natural graphite or a combination thereof.

3. The negative electrode active material of claim 1 , wherein the graphite core has an average particle diameter (D 50 ) of 8 μm to 20 μm.

4. The negative electrode active material of claim 1 , wherein a coating amount of the first coating layer is greater than 1 wt % and less than or equal to 6 wt % based on a total weight of the negative electrode active material.

5. The negative electrode active material of claim 1 , wherein the amorphous carbon material is derived from a carbon precursor including one or more types selected from the group consisting of sucrose, a phenol resin, a naphthalene resin, polyvinyl alcohol, polyvinyl chloride, furfuryl alcohol, polyacrylonitrile, polyamide, a furan resin, cellulose, styrene, polyimide, an epoxy resin, coal-based pitch, petroleum-based pitch, mesophase pitch, tar and low molecular weight heavy oil.

6. The negative electrode active material of claim 1 , wherein the amorphous carbon material has a specific surface area of 7 m 2 /g to 15 m 2 /g and average lattice plane spacing d 002 of 0.3470 to 0.3520.

7. The negative electrode active material of claim 1 , wherein a coating amount of the second coating layer is greater than 1 wt % and less than or equal to 3 wt % based on a total weight of the negative electrode active material.

8. The negative electrode active material of claim 1 , wherein the carbon particles are graphene, carbon nanotubes or a combination thereof.

9. The negative electrode active material of claim 8 , wherein the graphene has a specific surface area of 80 m 2 /g to 120 m 2 /g and electron mobility of 1500 S/cm to 3000 S/cm.

10. The negative electrode active material of claim 8 , wherein the carbon nanotubes have a specific surface area of 35 m 2 /g to 50 m 2 /g, an average diameter of 50 nm to 200 nm, and an average major axis length of 500 nm to 3 μm.

11. A negative electrode comprising the negative electrode active material of claim 1 .

12. A lithium secondary battery comprising:
the negative electrode of claim 11 ;
a positive electrode; and
a separator provided between the negative electrode and the positive electrode.

13. A method for preparing the negative electrode active material of claim 1 , the method comprising:
1) preparing graphite with a first coating layer formed thereon by coating a graphite core with an amorphous carbon material precursor and heat treating the result;
2) preparing a graphite mixture with a second coating layer formed on the first coating layer by adding the first coating layer-formed graphite and nitrogen-doped carbon material particles to an aqueous alkaline solution and mixing the result; and
3) heat treating the graphite mixture.

14. The method for preparing the negative electrode active material of claim 13 , wherein the heat treatment of the step 1) is carried out in a temperature range of 700° C. to 1500° C.

15. The method for preparing the negative electrode active material of claim 13 , wherein the amorphous carbon material precursor is derived from a carbon precursor including one or more types selected from the group consisting of sucrose, a phenol resin, a naphthalene resin, polyvinyl alcohol, polyvinyl chloride, furfuryl alcohol, polyacrylonitrile, polyamide, a furan resin, cellulose, styrene, polyimide, an epoxy resin, coal-based pitch, petroleum-based pitch, mesophase pitch, tar and low molecular weight heavy oil.

16. The method for preparing the negative electrode active material of claim 13 , wherein the aqueous alkaline solution of the step 2) has a pH of 8 to 9.

17. The method for preparing the negative electrode active material of claim 13 , wherein the nitrogen doped carbon particles of the step 2) is prepared by injecting ammonia gas during carbon particle synthesis carried out through chemical vapor deposition.

18. The method for preparing the negative electrode active material of claim 13 , wherein the nitrogen doped carbon particles of the step 2) is prepared by adding carbon particles to a strong acidic solution to oxidize the particles, and then reducing the particles by adding a reducing agent.

19. The method for preparing the negative electrode active material of claim 18 , wherein the reducing agent is hydrazine, ammonia or a combination thereof.

20. The method for preparing the negative electrode active material of claim 13 , wherein the heat treatment of the step 3) is carried out in a temperature range of 800° C. to 1000° C.

Assignees

• Lg Chemical Ltd

Inventors

• Kim Hyun Wook
• Kim Eun Kyung
• Woo Sang Wook

Classifications

• H01M10/0525

  Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries · CPC title

• H01M4/587

  for inserting or intercalating light metals · CPC title

• H01M4/366 Primary

  as layered products · CPC title

• C01B32/05

  Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30 · CPC title

• H01M4/625

  Carbon or graphite · CPC title