Lithium secondary battery having anode containing aqueous binder

• US 9,711,794 B2
• Filed: 02/07/2013
• Issued: 07/18/2017
• Est. Priority Date: 02/16/2012
• Status: Active Grant

• Current Assignee: LG Energy Solution Limited (LG Corporation)
• Original Assignee: LG Chem Limited (LG Corporation)
• Inventors: Chung, Jae Bin, Bae, Joon Sung, Ahn, Byoung Hoon, Koo, Chang-Wan
• Primary Examiner(s): USYATINSKY, ALEXANDER
• Application Number:
  US14/374,051
• Publication Number:
  US 20150030923A1
• Time in Patent Office: 1,622 Days
• CPC Class Codes: C08L 9/06 Copolymers with styrene
• CPC Class Codes: C09J 101/286 substituted with acid radicals C09J101/282 takes precedence
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 10/0525 Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• CPC Class Codes: H01M 2220/20 Batteries in motive systems, e.g. vehicle, ship, plane
• CPC Class Codes: H01M 4/133 Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
• CPC Class Codes: H01M 4/505 of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
• CPC Class Codes: H01M 4/525 of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
• CPC Class Codes: H01M 4/583 Carbonaceous material, e.g. graphite-intercalation compounds or CFx
• CPC Class Codes: H01M 4/587 for inserting or intercalating light metals
• CPC Class Codes: H01M 4/621 Binders
• CPC Class Codes: H01M 4/622 being polymers
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

Disclosed is a lithium secondary battery that includes an anode coated with an anode mixture including an anode active material, a cathode coated with a cathode mixture including a cathode active material, and a non-aqueous electrolyte, wherein the anode mixture includes, as aqueous binders, carboxymethyl cellulose (CMC) having a degree of substitution of a hydroxyl group (—OH) with a carboxymethyl group (—CH₂CO₂H) of 0.7 to 1.2, a molecular weight (Mn) of 500,000 to 900,000, and a pH of 6.5 to 8.0 and styrene-butadiene rubber (SBR) having a particle diameter of 90 nm to 150 nm and a tensile strength of 90 kgf to 160 kgf, and the anode has an electrode coating amount of 10 to 20 mg/cm² and that enhances electrode processability and reduces a swelling phenomenon.

Claims

1. A lithium secondary battery comprising an anode coated with an anode mixture comprising an anode active material, a cathode coated with a cathode mixture comprising a cathode active material, and a non-aqueous electrolyte,

wherein the anode mixture comprises aqueous binders,

wherein the aqueous binders comprise a carboxymethyl cellulose (CMC) and a styrene-butadiene rubber (SBR),

wherein the CMC has a degree of substitution of a hydroxyl group (—

OH) with a carboxymethyl group (—

CH₂CO₂H) of 0.7 to 1.2, a molecular weight (Mn) of 500,000 to 900,000, and a pH of 6.5 to 8.0 in a 1% aqueous solution,

wherein the SBR has a particle diameter of 90 nm to 150 nm and a tensile strength of 90 kgf to 160 kgf, and

wherein the anode has an electrode coating amount of 10 to 20 mg/cm².

2. The lithium secondary battery according to claim 1, wherein the electrode coating amount of the anode is 13 to 18 mg/cm².

3. The lithium secondary battery according to claim 1, wherein the degree of substitution of the CMC is 0.9 to 1.1.

4. The lithium secondary battery according to claim 1, wherein the molecular weight of the CMC is 750,000 to 850,000.

5. The lithium secondary battery according to claim 1, wherein the pH of the CMC is 7.5 to 8.0.

6. The lithium secondary battery according to claim 1, wherein the particle diameter of the SBR is 110 nm to 130 nm.

7. The lithium secondary battery according to claim 1, wherein the tensile strength of the SBR is 100 kgf to 155 kgf.

8. The lithium secondary battery according to claim 1, wherein an amount ratio of the CMC to the SBR is 1:

0.1 to 1;

5 on a weight ratio basis.

9. The lithium secondary battery according to claim 1, wherein the anode active material is a carbon-based material.

10. The lithium secondary battery according to claim 9, wherein the carbon-based material is at least one selected from the group consisting of graphite-based carbon, coke-based carbon, and hard carbon.

11. The lithium secondary battery according to claim 10, wherein the graphite-based carbon comprises spherical particles and is natural graphite having a degree of crystallinity in which an R value [R=I₁₃₅₀/I₁₅₈₀] (I₁₃₅₀ is a Raman intensity around 1350 cm⁻

1 and I₁₅₈₀ is a Raman intensity around 1580 cm<sup>−

1</sup>) of a Raman spectrum is 0.30 to 1.0.

12. The lithium secondary battery according to claim 1, wherein the cathode active material comprises a lithium nickel-manganese cobalt oxide represented by Formula 1 below:

Li_aNi_xMn_yCo_zO₂ 

 

(1)

wherein 0.8≦

a<

1.2, 0.2≦

x<

1, 0<

y<

1, 0<

z<

1, and x+y+z=1.

13. A battery module comprising the lithium secondary battery according to claim 1 as a unit cell.

14. A battery pack comprising the battery module according to claim 13.