Electrode having a dual layer structure, method for manufacturing thereof, and lithium secondary battery comprising the same

Patent metadata

Field	Value
Publication number	US-9742000-B2
Application number	US-201514834490-A
Country	US
Kind code	B2
Filing date	Aug 25, 2015
Priority date	Oct 2, 2014
Publication date	Aug 22, 2017
Grant date	Aug 22, 2017

Abstract

The present invention relates to an electrode having a dual layer structure, a method for manufacturing the same, and a lithium secondary battery comprising the same, the electrode comprising: an electrode current collector; a middle layer formed on at least one side of the electrode current collector; and an electrode active material layer formed on the middle layer, wherein the middle layer comprises a first binder, wherein the electrode active material layer comprises an electrode active material and a second binder, and wherein the first binder and the second binder are the same kind of material but have different crystalline phases.

First claim

The invention claimed is:

1. An electrode having a dual layer structure, comprising:
an electrode current collector;
a middle layer formed on at least one side of the electrode current collector; and
an electrode active material layer formed on the middle layer,
wherein the middle layer comprises a first binder,
wherein the electrode active material comprises an electrode active material and a second binder, and wherein the first binder and the second binder are the same kind of material but have different crystalline phases and different molecular weights.

2. The electrode having a dual layer structure according to claim 1 , wherein the first binder has an α/β ratio ranging from 0.3 to 0.8.

3. The electrode having a dual layer structure according to claim 1 , wherein the second binder has an α/β ratio ranging from 0.05 to 0.25.

4. The electrode having a dual layer structure according to claim 1 , wherein the first binder has a weight average molecular weight ranging from 60,000 to less than 270,000.

5. The electrode having a dual layer structure according to claim 1 , wherein the second binder has a weight average molecular weight ranging from 330,000 to 1,000,000.

6. The electrode having a dual layer structure according to claim 1 , wherein the first binder and the second binder are at least one selected from the group consisting of: poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), and fluororubber.

7. The electrode having a dual layer structure according to claim 1 , wherein the electrode is a positive electrode and the electrode active material is a positive electrode active material.

8. The electrode having a dual layer structure according to claim 7 , wherein the positive electrode active material is at least one selected from the group consisting of:
an oxide of the following formulae 1 to 3; V2O5, TiS, and MoS
Li1+x[NiaCobMnc]O2  [Formula 1]

(where −0.5≦x≦0.6; 0≦a, b, c≦1; x+a+b+c=1)
LiMn2−xMxO4  [Formula 2]

(where M is one or more elements selected from the group consisting of: Ni, Co, Fe, P, S, Zr, Ti, and Al; 0≦x≦2)
Li1+aFe1−xMx(PO4−b)Xb  [Formula 3]

(where M is one or more elements selected from the group consisting of: Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y; X is one or more elements selected from the group consisting of: F, S, and N; −0.5≦a≦+0.5; 0≦x≦0.5; 0≦b≦0.1).

9. The electrode having a dual layer structure according to claim 7 , wherein the positive electrode active material is at least one selected from the group consisting of: LiCoO 2 , LiNiO 2 , LiMnO 2 , LiMn 2 O 4 , Li[Ni a Co b Mn c ]O 2 (where 0<a, b, c≦1; a+b+c=1), and LiFePO 4 .

10. The electrode having a dual layer structure according to claim 1 , wherein the middle layer has a thickness ranging from 0.5 μm to 5 μm.

11. The electrode having a dual layer structure according to claim 1 , wherein the electrode active material layer has a thickness ranging from 40 μm to 120 μm.

12. A method for manufacturing an electrode having a dual layer structure according to claim 1 , comprising the steps of:
1) preparing a predispersed slurry comprising a third binder;
2) forming a middle layer by coating at least one side of an electrode current collector with the predispersed slurry; and
3) forming an electrode active material by coating the middle layer with an electrode active material slurry comprising a fourth binder,
wherein the third binder and the fourth binder are the same kind of material but have different molecular weights.

13. The method for manufacturing an electrode having a dual layer structure according to claim 12 , wherein the predispersed slurry of step 1) is prepared by addition of a conductive agent to the fourth binder and high-shear mixing of the same.

14. The method for manufacturing an electrode having a dual layer structure according to claim 13 , wherein the high-shear mixing is carried out under a pressure condition of 20,000 psi to 40,000 psi.

15. The method for manufacturing an electrode having a dual layer structure according to claim 12 , wherein the coating of step 2) comprises a painting step and a drying step, wherein the drying is carried out by conducting heat treatment for 10 to 24 hours at a temperature range of 140° C. to 160° C.

16. The method for manufacturing an electrode having a dual layer structure according to claim 12 , wherein the coating of step 3) comprises a painting step and a drying step, wherein the drying is carried out by conducting heat treatment for 10 to 24 hours at a temperature range of 120° C. to 140° C.

17. The method for manufacturing an electrode having a dual layer structure according to claim 12 , wherein the middle layer comprises a first binder, the electrode active material layer comprises a second binder, and the first binder and the second binder are the same kind of material but have different crystalline phases.

18. The method for manufacturing an electrode having a dual layer structure according to claim 17 , wherein the first binder is formed by heat treating the third binder, and the first binder has an α/β ratio ranging from 0.3 to 0.8.

19. The method for manufacturing an electrode having a dual layer structure according to claim 17 , wherein the second binder is formed by heat treating the fourth binder, and the second binder has an α/β ratio ranging from 0.05 to 0.25.

20. The method for manufacturing an electrode having a dual layer structure according to claim 12 , wherein the third binder has a weight average molecular weight ranging from 60,000 to less than 270,000.

21. The method for manufacturing an electrode having a dual layer structure according to claim 12 , wherein the fourth binder has a weight average molecular weight ranging from 330,000 to 1,000,000.

22. The method for manufacturing an electrode having a dual layer structure according to claim 12 , wherein the electrode is a positive electrode and the electrode active material is a positive electrode active material.

23. The method for manufacturing an electrode having a dual layer structure according to claim 12 , wherein the positive electrode active material is a mixture of: at least one selected from the group consisting of: an oxide of the following formulae 1 to 3; V2O5, TiS, and MoS
Li1+x[NiaCobMnc]O2  [Formula 1]

(where −0.5≦x≦0.6; 0≦a, b, c≦1; x+a+b+c=1)
LiMn2−xMxO4  [Formula 2]

(where M is one or more elements selected from the group consisting of: Ni, Co, Fe, P, S, Zr, Ti, and Al; 0≦x≦2)
Li1+aFe1−xMx(PO4−b)Xb  [Formula 3]

(where M is one or more elements selected from the group consisting of: Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y; X is one or more elements selected from the group consisting of: F, S, and N; −0.5≦a≦+0.5; 0≦x≦0.5; 0≦b≦0.1).

24. The method for manufacturing an electrode having a dual layer structure according to claim 22 , wherein the positive electrode active material is at least one selected from the group consisting of: LiCoO 2 , LiNiO 2 , LiMnO 2 , LiMn 2 O 4 , Li[Ni a Co b Mn c ]O 2 (where 0<a, b, c≦1; a+b+c=1), and LiFePO 4 .

Assignees

• Lg Chemical Ltd

Inventors

• Lee Sang Kyun
• Kim Je Young
• Lee Taek Soo

Classifications

• H01M4/131 Primary

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

• H01M4/0404

  by coating on electrode collectors · CPC title

• H01M4/623

  fluorinated polymers · CPC title

• H01M4/622

  being polymers · CPC title

• H01M10/052

  Li-accumulators · CPC title