ORGANIC/INORGANIC COMPOSITE MICROPOROUS MEMBRANE AND ELECTROCHEMICAL DEVICE PREPARED THEREBY

• US 20090111025A1
• Filed: 12/22/2005
• Published: 04/30/2009
• Est. Priority Date: 12/22/2004
• Status: Active Grant

• Current Assignee: Tulip Innovation KFT
• Original Assignee: LG Chem Limited (LG Corporation)
• Inventors: KIM, Seok Koo, AHN, Soon Ho, HONG, Jang Hyuk, LEE, Sang Young, YONG, Hyun Hang, SUK, Jung Don
• Granted Patent: US 7,662,517 B2
• Time in Patent Office: Days
• US Class Current: 429/251
• 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 50/403 Manufacturing processes of separators, membranes or diaphragms
• CPC Class Codes: H01M 50/446 Composite material consisting of a mixture of organic and inorganic materials
• CPC Class Codes: H01M 50/451 comprising layers of only organic material and layers containing inorganic material
• CPC Class Codes: H01M 50/46 Separators, membranes or diaphragms characterised by their combination with electrodes
• CPC Class Codes: H01M 50/489 Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
• CPC Class Codes: H01M 50/491 Porosity
• CPC Class Codes: H01M 50/497 Ionic conductivity
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y10T 29/49108 Electric battery cell making
• CPC Class Codes: Y10T 29/49115 including coating or impregnating

Abstract

Disclosed is an organic/inorganic composite porous separator comprising: (a) a polyolefin-based separator substrate; and (b) an active layer formed by coating at least one region selected from the group consisting of a surface of the substrate and a part of pores present in the substrate with a mixture of inorganic particles and a binder polymer, wherein the inorganic particles in the active layer are interconnected among themselves and are fixed by the binder polymer, and interstitial volumes among the inorganic particles form a pore structure. A method for manufacturing the same separator and an electrochemical device including the same separator are also disclosed. An electrochemical device comprising the organic/inorganic composite porous separator shows improved thermal and electrochemical safety and quality, simultaneously.

Claims

1. An organic/inorganic composite porous separator, which comprises:

(a) a polyolefin-based separator substrate; and

(b) an active layer formed by coating at least one region selected from the group consisting of a surface of the substrate and a part of pores present in the substrate with a mixture of inorganic particles and a binder polymer, wherein the inorganic particles in the active layer are interconnected among themselves and are fixed by the binder polymer, and interstitial volumes among the inorganic particles form a pore structure.

2. The separator according to claim 1, wherein the inorganic particles are at least one selected from the group consisting of:

(a) inorganic particles having a dielectric constant of 5 or more;

(b) inorganic particles having piezoelectricity; and

(c) inorganic particles having lithium ion conductivity.

3. The separator according to claim 2, wherein the inorganic particles (b) having piezoelectricity cause an electric potential difference due to positive charges and negative charges generated on both surfaces upon application of a certain pressure.

4. The separator according to claim 2, wherein the inorganic particles (c) having lithium ion conductivity are inorganic particles containing lithium elements and having a capability of conducting lithium ions without storing lithium.

5. The separator according to claim 2, wherein the inorganic particles (a) having a dielectric constant of 5 or more are SrTiO₃, SnO₂, CeO₂, MgO, NiO, CaO, ZnO, ZrO₂, Y₂O₃, Al₂O₃, TiO₂ or SiC;

the inorganic particles (b) having piezoelectricity are BaTiO₃, Pb(Zr,Ti)O₃ (PZT), Pb_1-xLa_xZr_1-yTi_yO₃ (PLZT), Pb(Mg₃Nb_2/3)O₃—

PbTiO₃ (PMN-PT) or hafnia (HfO₂); and

the inorganic particles (c) having lithium ion conductivity are at least one selected from the group consisting of;

lithium phosphate (Li₃PO₄), lithium titanium phosphate (Li_xTi_y(PO₄)₃, 0<

x<

2, 0<

y<

3), lithium aluminum titanium phosphate (Li_xAl_yTi_z(PO₄)₃, 0<

x<

2, 0<

y<

1, 0<

z<

3), (LiAlTiP)_xO_y type glass (0<

x<

4, 0<

y<

13), lithium lanthanum titanate (Li_xLa_yTiO₃, 0<

x<

2, 0<

y<

3), lithium germanium thiophosphate (Li_xGe_yP_zS_w, 0<

x<

4, 0<

y<

1, 0<

z<

1, 0<

w<

5), lithium nitrides(Li_xN_y, 0<

x<

4, 0<

y<

2), SiS₂ type glass (Li_xSi_yS_z, 0<

x<

3, 0<

y<

2, 0<

z<

4) and P₂S₅ type glass (Li_xP_yS_z, 0<

x<

3, 0<

y<

3, 0<

z<

7).

6. The separator according to claim 1, wherein the inorganic particles have a size between 0.001 μ

m and 10 μ

m.

7. The separator according to claim 1, wherein the inorganic particles are present in the mixture of inorganic particles with the binder polymer in an amount of 50˜

99 wt % based on 100 wt % of the mixture.

8. The separator according to claim 1, wherein the binder polymer has a solubility parameter between 15 and 45 MPa^1/2.

9. The separator according to claim 1, wherein the binder polymer has a dielectric constant between 1.0 and 100 (as measured at a frequency of 1 kHz).

10. The separator according to claim 1, wherein the binder polymer is at least one selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethyl polyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxymethyl cellulose, and polyvinyl alcohol.

11. The separator according to claim 1, wherein the polyolefin-based separator substrate comprises at least one component selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, ultrahigh molecular weight polyethylene and polypropylene.

12. The separator according to claim 1, which has a thickness between 1 and 100 μ

m.

13. The separator according to claim 1, which has a pore size between 0.001 and 10 μ

m, and a porosity between 5% and 95%.

14. An electrochemical device comprising a cathode, an anode, a separator, and an electrolyte, wherein the separator is an organic/inorganic composite porous separator as defined in claim 1, the organic/inorganic composite porous separator comprising:

(a) a polyolefin-based separator substrate; and

(b) an active layer formed by coating at least one region selected from the group consisting of a surface of the substrate and a part of pores present in the substrate with a mixture of inorganic particles and a binder polymer, wherein the inorganic particles in the active layer are interconnected among themselves and are fixed by the binder polymer, and interstitial volumes among the inorganic particles form a pore structure.

15. The electrochemical device according to claim 14, which is a lithium secondary battery.

16. A method for manufacturing an organic/inorganic composite porous separator as defined in claim 1, which comprises the steps of:

(a) dissolving a binder polymer into a solvent to form a polymer solution;

(b) adding inorganic particles to the polymer solution obtained from step (a) and mixing them; and

(c) coating the mixture obtained from step (b) on at least one region selected from the group consisting of a surface of a polyolefin-based separator substrate and a part of pores present in the substrate, followed by drying.

17. The electrochemical device according to claim 14, wherein the inorganic particles are at least one selected from the group consisting of:

(a) inorganic particles having a dielectric constant of 5 or more;

(b) inorganic particles having piezoelectricity; and

(c) inorganic particles having lithium ion conductivity.

18. The electrochemical device according to claim 17, wherein the inorganic particles (b) having piezoelectricity cause an electric potential difference due to positive charges and negative charges generated on both surfaces upon application of a certain pressure.

19. The electrochemical device according to claim 17, wherein the inorganic particles (c) having lithium ion conductivity are inorganic particles containing lithium elements and having a capability of conducting lithium ions without storing lithium.

20. The electrochemical device according to claim 14, wherein the binder polymer has a solubility parameter between 15 and 45 MPa^1/2.