Negative Electrode, Secondary Battery Including the Negative Electrode, and Method of Preparing the Negative Electrode

Patent metadata

Field	Value
Publication number	US-2022238886-A1
Application number	US-202017616417-A
Country	US
Kind code	A1
Filing date	Jul 31, 2020
Priority date	Aug 1, 2019
Publication date	Jul 28, 2022
Grant date	—

Abstract

A negative electrode includes a negative electrode active material layer, wherein the negative electrode active material layer includes a negative electrode active material and a conductive agent, wherein the negative electrode active material includes a silicon-based active material, the silicon-based active material includes SiOx(0≤x<2), the conductive agent includes a carbon nanotube structure in which 2 to 5,000 single-walled carbon nanotube units are bonded side by side, and the carbon nanotube structure is included in an amount of 0.01 wt % to 1.0 wt % in the negative electrode active material layer. A secondary battery including the negative electrode, and a method of preparing same are also provided.

First claim

1 . A negative electrode comprising a negative electrode active material layer,
wherein the negative electrode active material layer comprises a negative electrode active material and a conductive agent, wherein the negative electrode active material comprises a silicon-based active material, the silicon-based active material comprises SiO x (0≤x<2), the conductive agent comprises a carbon nanotube structure in which 2 to 5,000 single-walled carbon nanotube units are bonded side by side, and the carbon nanotube structure is included in an amount of 0.01 wt % to 1.0 wt % in the negative electrode active material layer.

2 . The negative electrode of claim 1 , wherein, in the negative electrode, the carbon nanotube structures are connected to each other to represent a network structure.

3 . The negative electrode of claim 1 , wherein, in the carbon nanotube structure, the single-walled carbon nanotube units are arranged side by side and bonded.

4 . The negative electrode of claim 1 , wherein the single-walled carbon nanotube unit has an average diameter of 0.5 nm to 10 nm.

5 . The negative electrode of claim 1 , wherein the single-walled carbon nanotube unit has an average length of 1 μm to 100 μm.

6 . The negative electrode of claim 1 , wherein the carbon nanotube structure has an average diameter of 2 nm to 200 nm.

7 . The negative electrode of claim 1 , wherein the carbon nanotube structure has an average diameter of 5 nm to 50 nm.

8 . The negative electrode of claim 1 , wherein the single-walled carbon nanotube unit has a specific surface area of 500 m 2 /g to 1,000 m 2 /g.

9 . The negative electrode of claim 1 , wherein the carbon nanotube structure is included in an amount of 0.08 wt % to 0.3 wt % in the negative electrode active material layer.

10 . The negative electrode of claim 1 , wherein the silicon-based active material has an average particle diameter (D 50 ) of 0.1 μm to 20 μm.

11 . The negative electrode of claim 1 , wherein the silicon-based active material further comprises a carbon coating layer disposed on the SiO x (0≤x<2).

12 . The negative electrode of claim 1 , wherein the negative electrode active material layer further comprises a carbon-based active material, and
a weight ratio of the silicon-based active material to the carbon-based active material is in a range of 0.5:99.5 to 20:80.

13 . The negative electrode of claim 1 , wherein the negative electrode active material layer further comprises carboxymethyl cellulose.

14 . The negative electrode of claim 13 , wherein the carboxymethyl cellulose has a weight-average molecular weight of 50,000 g/mol to 150,000 g/mol.

15 . The negative electrode of claim 13 , wherein a degree of substitution of the carboxymethyl cellulose is in a range of 0.1 to 3.

16 . A method of preparing a negative electrode, the method comprising:
preparing a conductive agent dispersion (S 1 ) and forming a negative electrode slurry including the conductive agent dispersion and a negative electrode active material (S 2 ), wherein the preparing of the conductive agent dispersion (S 1 ) comprises: preparing a mixed solution containing a dispersion medium, a dispersant, and bundle-type single-walled carbon nanotubes (S 1 - 1 ); and dispersing the bundle-type single-walled carbon nanotubes by applying a shear force to the mixed solution by a homogenizer to form a carbon nanotube structure in which 2 to 5,000 single-walled carbon nanotube units are bonded side by side (S 1 - 2 ), wherein the negative electrode active material comprises a silicon-based active material, the silicon-based active material comprises SiO x (0≤x<2), and the carbon nanotube structure is included in an amount of 0.01 wt % to 1.0 wt % in the negative electrode active material layer.

17 . The method of claim 16 , wherein the dispersant comprises carboxymethyl cellulose, and
the carboxymethyl cellulose has a weight-average molecular weight of 50,000 g/mol to 150,000 g/mol.

18 . The method of claim 16 , wherein the bundle-type single-walled carbon nanotubes has a specific surface area of 500 m 2 /g to 1,000 m 2 /g.

19 . (canceled)

20 . The method of claim 16 , wherein a pressure applied to the mixed solution in the homogenizer is in a range of 500 bar to 1,800 bar.

21 . A secondary battery comprising:
the negative electrode of claim 1 ; a positive electrode; a separator disposed between the negative electrode and the positive electrode; and an electrolyte.

Assignees

• Lg Energy Solution Ltd

Inventors

• Kim Tae Gon
• Cho Hyung Man
• Moon Il Jae
• Park Sun Wook
• Kwak Min

Classifications

• H01M4/1391

  of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx · CPC title

• H01M4/131 Primary

  Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx · CPC title

• H01M4/625 Primary

  Carbon or graphite · CPC title

• H01M2004/022

  Electrodes made of one single microscopic fiber · CPC title

• H01M2004/027

  Negative electrodes · CPC title