Electrochemical device with improved cycle characteristics

• US 9,368,777 B2
• Filed: 03/10/2014
• Issued: 06/14/2016
• Est. Priority Date: 10/05/2010
• Status: Active Grant

• Current Assignee: LG Energy Solution Limited (LG Corporation)
• Original Assignee: LG Chem Limited (LG Corporation), Toray Battery Separator Film Co., Ltd.
• Inventors: Lee, Joo-Sung, Hong, Jang-Hyuk, Kim, Jong-Hun, Ryu, Bo-Kyung
• Primary Examiner(s): Douyette, Kenneth
• Application Number:
  US14/202,294
• Publication Number:
  US 20140186681A1
• Time in Patent Office: 827 Days
• US Class Current: 1/1
• CPC Class Codes: C08J 5/2206 based on organic and/or inorganic macromolecular compounds
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 10/52 Removing gases inside the secondary cell, e.g. by absorption vent plugs or other mechanical arrangements for facilitating escape of gases H01M50/30
• CPC Class Codes: H01M 4/131 Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
• CPC Class Codes: H01M 4/133 Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
• CPC Class Codes: H01M 4/134 Electrodes based on metals, Si or alloys
• CPC Class Codes: H01M 50/403 Manufacturing processes of separators, membranes or diaphragms
• CPC Class Codes: H01M 50/417 Polyolefins
• CPC Class Codes: H01M 50/426 Fluorocarbon polymers
• 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 50/457 comprising three or more layers
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

Disclosed is an electrochemical device. The electrochemical device includes: (a) a composite separator including a porous substrate, a first porous coating layer coated on one surface of the porous substrate, and a second porous coating layer coated on the other surface of the porous substrate; (b) an anode disposed to face the first porous coating layer; and (c) a cathode disposed to face the second porous coating layer. The first and second porous coating layers are each independently composed of a mixture including inorganic particles and a binder polymer. The first porous coating layer is thicker than the second porous coating layer. The electrochemical device has good thermal stability and improved cycle characteristics.

Claims

1. An electrochemical device comprising:

(a) a composite separator comprising a porous substrate, a first porous coating layer coated on one surface of the porous substrate and composed of a mixture comprising inorganic particles and a binder polymer, and a second porous coating layer coated on the other surface of the porous substrate and composed of a mixture comprising inorganic particles and a binder polymer, wherein the first porous coating layer is thicker than the second porous coating layer, wherein interstitial volumes present between the inorganic particles of the first coating layer form a pore structure, and wherein interstitial volumes present between the inorganic particles of the second coating layer form a pore structure;

(b) an anode disposed to face the first porous coating layer; and

(c) a cathode disposed to face the second porous coating layer, wherein the thicknesses of the first and second porous coating layers satisfy the following relationship 1;

0.11≦

(T₁−

T₂)/T_tot≦

0.56

wherein T₁ and T₂ represent the thicknesses of the first and second porous coating layers, respectively, and T_tot represents the total thickness of the first and second porous coating layers, and

wherein the total thickness of the first and second porous coating layers is from 1.0 to 20.0 μ

m.

2. The electrochemical device according to claim 1, wherein the porous substrate is a porous polyolefin membrane.

3. The electrochemical device according to claim 1, wherein the porous substrate has a thickness of 1 to 100 μ

m.

4. The electrochemical device according to claim 1, wherein the binder polymers each independently have a solubility parameter of 15 to 45 Mpa^1/2.

5. The electrochemical device according to claim 1, wherein the inorganic particles present in each of the first and second porous coating layers have an average particle diameter of 0.001 to 10 μ

m.

6. The electrochemical device according to claim 1, wherein the weight ratio of the inorganic particles to the binder polymer in each of the first and second porous coating layers is from 50:

50 to 99;

1.

7. The electrochemical device according to claim 1, wherein the cathode comprises particles of at least one cathode active material selected from the group consisting of LiCoO₂, LiNiO₂, LiMn₂O₄, LiCoPO₄, LiFePO₄, LiNiMhCoO₂, and LiNi_1-x-y-zCo_xM1_yM2_zO_z (wherein M1 and M2 are each independently selected from the group consisting of Al, Ni, Co, Fe, Mn, V, Cr, Ti, W, Ta, Mg and Mo, and x, y and z represent the atomic fractions of the corresponding constituent elements of the oxide and satisfy the relations of 0≦

x<

0.5, 0≦

y<

0.5, 0≦

z<

0.5).

8. The electrochemical device according to claim 1, wherein the cathode comprises at least one cathode active material selected from the group consisting of LiCoO₂ and LiNiMnCoO₂.

9. The electrochemical device according to claim 1, wherein the anode comprises particles of at least one anode active material selected from the group consisting of natural graphite, artificial graphite, carbonaceous materials, LTO, silicon (Si), and tin (Sn).

10. The electrochemical device according to claim 1, wherein the electrochemical device is a lithium secondary battery.

11. The electrochemical device of claim 1, wherein the binder polymers are each independently selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethyl methacrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cyanoethylpullulan, cyanoethyl polyvinyl alcohol, cyanoethyl sucrose, pullulan, and mixtures of two or more kinds thereof.

12. The electrochemical device of claim 1, wherein the inorganic particles are each independently selected from the group consisting of BaTiO₃, Pb(Zr,Ti)O₃ (PZI), Pb_1-xLa_xZr_1-yTi_yO₃ (PLZT, 0<

x<

1, 0<

y<

1), Pb (Mg_1/3Nb_2/3)O₃—

PbTiO₃ (PMN-PT), hafnia (HfO₂), SrTiO₃, SnO₂, CeO₂, NiO, CaO, ZnO, Y₂O₃, Al₂O₃, TiO₂, SiC, Li₃PO₄, Li_xTi_y (PO₄)₃ (0<

x<

2, 0<

y<

3), Li_xAl_yTi_z (PO₄)₃ (0<

x<

2, 0<

y<

1, 0<

z<

3), (LiAllTiP)_xO_y (0<

x<

4, 0<

y<

13), (Li_xLa_yTiO₃, 0<

x<

2, 0<

y<

3), Li_xGe_yP_zS_w (0<

x<

4, 0<

y<

1, 0<

z<

1, 0<

w<

5), Li_xN_y (0<

x<

4, 0<

y<

2), Li_xSi_yS_z (0<

x<

3, 0<

y<

2, 0<

z<

4), Li_xP_yS_z (0<

x<

3, 0<

y<

3, 0<

z<

7), and mixtures of two or more kinds thereof.