KR20140070160A - Separator for secondary battery - Google Patents

Abstract

The present invention relates to a separator for a secondary battery which comprises a porous coating layer which includes pillar-shaped particles made of an inorganic compound in at least one surface of the porous substrate. Because the separator comprises the porous coating layer, heat resistance is improved and the moving path of lithium ions is minimized, thereby having excellent battery performance.

Description

SEPARATOR FOR SECONDARY BATTERY Technical Field [1] The present invention relates to a separator for a secondary battery,

The present invention relates to a separator for a secondary battery, and relates to a separator having high heat resistance and excellent ion conductivity.

Recently, interest in energy storage technology is increasing. As the application fields of cell phones, camcorders, notebook PCs and even electric vehicles are expanding, efforts for research and development of electrochemical devices are becoming more and more specified. Electrochemical devices have attracted the greatest attention in this respect. Among them, the development of rechargeable secondary batteries has become a focus of attention. In recent years, in order to improve capacity density and specific energy, And research and development on the design of the battery.

Among the currently applied secondary batteries, the lithium secondary battery developed in the early 1990s has advantages such as higher operating voltage and higher energy density than conventional batteries such as Ni-MH, Ni-Cd and sulfuric acid-lead batteries using an aqueous electrolyte solution . However, such a lithium ion battery has safety problems such as ignition and explosion when using an organic electrolytic solution, and it is disadvantageous in that it is difficult to manufacture. Recently, the lithium ion polymer battery is considered to be one of the next generation batteries by improving the weak point of the lithium ion battery. However, since the capacity of the battery is still relatively low as compared with the lithium ion battery, Is urgently required.

Such electrochemical devices are produced in many companies, but their safety characteristics are different. It is very important to evaluate the safety and safety of such an electrochemical device. The most important consideration is that the electrochemical device should not injure the user in case of malfunction. For this purpose, the safety standard strictly regulates the ignition and fuming in the electrochemical device. In the safety characteristics of the electrochemical device, there is a high possibility that the electrochemical device will be overheated to cause thermal runaway or explosion if the separator is penetrated. Particularly, the polyolefin-based porous substrate commonly used as a separator of an electrochemical device exhibits extreme heat shrinkage behavior at a temperature of 100 DEG C or higher owing to the characteristics of the manufacturing process including material properties and elongation, . ≪ / RTI >

To overcome this problem, a method of introducing a porous coating layer of inorganic particles and an organic binder mixture into a separation membrane has been proposed. However, since the migration path of lithium ions in the porous coating layer uses an interstitial space generated in contact with the inorganic particles, since the inorganic particles are disorderly present, the movement path of lithium ions becomes long, do.

Accordingly, an object of the present invention is to provide a separator excellent in heat resistance and also excellent in ion conductivity.

In order to solve the above problems, the present invention provides a separator for a secondary battery, comprising a porous coating layer comprising columnar particles comprising an inorganic compound on at least one surface of a porous substrate.

It is preferable that an angle formed between the columnar vertical axis of the columnar particles and the horizontal axis of the porous substrate is 60 to 90 degrees. The columnar particles may be stacked in two or more layers.

The thickness of the porous coating layer may be 1 to 60 탆, and the porosity of the porous coating layer may be 10 to 60%.

The inorganic compound is preferably an inorganic compound having a dielectric constant of 5 or more, a piezoelectric inorganic compound, and an inorganic compound having a lithium ion transporting ability.

The inorganic compound having a dielectric constant of 5 or more is BaTiO ₃ , Pb (Zr, Ti) O ₃ , (PZT), Pb _{1 -x} La _x Zr _{1 -y} Ti _y O ₃ (PLZT, 0 <x < y <1), Pb (Mg 1/3 Nb 2/3) O 3 -PbTiO 3 (PMN-PT), hafnia _{(HfO 2), SrTiO 3,} SnO 2, CeO 2, MgO, NiO, CaO, ZnO , ZrO ₂ , SiO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC, and TiO ₂ .

To the piezoelectric inorganic compound is _{a-AlPO 4, a-SiO} 2, LiTaO 3, BaTiO 3, LiNbO 3, Sr x Ba y Nb 2 O 8, Pb 5 Ge 3 O 11, Tb 2 (MoO 4) 3, Li _{2 B 4 O 7, CdS,} ZnO, Bi 12 SiO 20, Bi 12 GeO single crystal or Pb (ZrTi) O, such as ₃₃ (typically, _{PZT), Pb (Fe 1/} 2 T 1/2) O 3, Pb ( a polycrystalline material such as _{Mg 1/3 Nb 2/3} ) O 3 can be used.

The inorganic particles having lithium ion transferring ability include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y < (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 <x <2, 0 <y <1, 0 <z <3), (LiAlTiP) _x O _y series glass (0 <x <4, 0 <y <13), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0 <x <2, 0 <y <3), lithium germanium thiophosphate (Li _x Ge _y P _z S _w , 0 <x <4, 0 <y <1, 0 <z <1, 0 <w <5), lithium nitride (Li _x N _y , 0 <y <2), SiS ₂ (Li _x Si _y S _z , 0 <x <3, 0 <y <2, 0 <z <4) series glass and P ₂ S ₅ (Li _x P _y S _z , 0 <x <3, 0 <y <3, 0 <z <7) series glass, or a mixture of two or more thereof.

The porous substrate may be a polyolefin-based porous substrate. Such a polyolefin-based porous substrate is preferably made of polyethylene, polypropylene, polybutylene, polypentene or the like.

The present invention relates to a positive electrode; cathode; And a separator interposed between the positive electrode and the negative electrode, wherein the separator is interposed between the positive electrode and the negative electrode.

The present invention, which is a separator having a porous coating layer containing columnar particles, improves heat resistance through a porous coating layer, and minimizes the movement path of lithium ions, thereby improving battery performance.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments of the invention and, together with the description of the invention, It should not be construed as limited.
BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing a separator in which columnar particles are coated on the surface of a porous substrate according to an embodiment. Fig.
Fig. 2 is a view showing the inclination between a columnar particle and a porous substrate in a separator in which columnar particles are coated on the surface of the porous substrate according to the embodiment. Fig.
3 is a three-dimensional view showing a separator coated with columnar particles in a multilayered structure on the surface of a porous substrate according to an embodiment.
4 is a view showing the concept of lithium ion migration of a separator coated with inorganic compound particles on the surface of a porous substrate.
5 is a view showing the concept of lithium ion migration of a separator in which columnar particles are coated on the surface of a porous substrate.
6 is a view showing a concept of lithium ion migration of a separator coated with a columnar particle in a multilayer stacked on the surface of a porous substrate.

Hereinafter, the present invention will be described in detail with reference to the drawings. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

1 shows a separator according to an embodiment of the present invention. It should be noted, however, that the embodiments shown in the following description and the configurations shown in the drawings are only the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It should be understood that various equivalents and modifications may be present.

Referring to FIG. 1, the separator for a secondary battery of the present invention includes a porous coating layer including columnar particles 40 including inorganic compounds on at least one side of a porous substrate 10. The shape of the columnar particles 40 formed on the surface of the porous substrate is not particularly limited, but a columnar particle having a regular polygonal cross-section may be used, but it is more preferable to use a columnar particle Do. In order to ensure the porosity of the porous coating layer, it is necessary to provide a gap even when the columnar particles adhere to each other. Therefore, it is more preferable to use a circular plate rather than a polygonal plate.

2, the vertical axis (y) of the pillar-shaped particles 40 in the column direction and the vertical axis (y) of the pillar-shaped particles 40 are perpendicular to the pore- It is preferable that the angle &amp;thetas; formed by the horizontal axis (x) of the base 10 is 60 DEG to 90 DEG.

Referring to FIG. 3, the columnar particles 50 may be stacked on at least one surface of the porous substrate 10 in two or more layers. FIG. 3 illustrates a separator according to an embodiment of the present invention. When the columnar particles 50 are laminated in a plurality of layers, the flexibility of the separator can be improved as compared with the case in which the columnar particles 40 have one columnar shape.

In a lithium secondary battery, a polyolefin-based porous substrate commonly used as a separator exhibits extreme heat shrinkage behavior at a temperature higher than a certain temperature owing to characteristics of the manufacturing process including material properties and elongation, In order to overcome this problem, a porous coating layer of a mixture of inorganic particles and an organic binder is used for the separator. However, such a porous coating layer hinders the mobility of lithium ions. 4 is a cross-sectional view of a separator in which a spherical inorganic particle 30 is coated on one surface of a porous substrate 10, wherein the movement of the lithium ions 20 is irregularly arranged Due to the inorganic particles 30, the movement path of the lithium ions 20 becomes longer, and the mobility of the lithium ions is lowered.

5 shows a cross section of a separator in which columnar particles 40 are coated on the surface of a porous substrate 10. Lithium ions 20 are injected into columnar particles 40 arranged in regular alignment The movement path of the shortest distance is provided, so that the deterioration of the mobility of lithium ions is small. 6 is a cross-sectional view of a separator coated with columnar particles 50 laminated on the surface of the porous substrate 10 in the same manner as in Fig. 5, 50, the lithium ions 20 have a movement path of the shortest distance, so that the deterioration of the mobility of the lithium ions is small. Therefore, the separator of the present invention has excellent heat resistance and minimizes the movement distance of lithium ions, and thus has excellent battery performance.

The porous coating layer may have a thickness of 1 to 60 탆, and the porosity of the porous coating layer is preferably 10 to 60%.

The inorganic compound of the present invention may be a compound selected from the group consisting of an inorganic compound having a dielectric constant of 5 or more, a piezoelectric inorganic compound, and an inorganic compound having lithium ion transporting ability, or a mixture of two or more thereof.

The inorganic particles having a dielectric constant of 5 or more include BaTiO ₃ , Pb (Zr, Ti) O ₃ (PZT), Pb _{1 -x} La _x Zr _{1 -y} Ti _y O ₃ (PLZT, 0 <x < y <1), Pb (Mg 1/3 Nb 2/3) O 3 -PbTiO 3 (PMN-PT), hafnia _{(HfO 2), SrTiO 3,} SnO 2, CeO 2, MgO, NiO, CaO, ZnO , ZrO ₂ , SiO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC, and TiO ₂ .

To the piezoelectric inorganic compound is _{a-AlPO 4, a-SiO} 2, LiTaO 3, BaTiO 3, LiNbO 3, Sr x Ba y Nb 2 O 8, Pb 5 Ge 3 O 11, Tb 2 (MoO 4) 3, Li _{2 B 4 O 7, CdS,} ZnO, Bi 12 SiO 20, Bi 12 GeO single crystal or Pb (ZrTi) O, such as ₃₃ (typically, _{PZT), Pb (Fe 1/} 2 T 1/2) O 3, Pb ( a polycrystalline material such as _{Mg 1/3 Nb 2/3} ) O 3 can be used.

The inorganic particles having lithium ion transferring ability include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y < (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 <x <2, 0 <y <1, 0 <z <3), (LiAlTiP) _x O _y series glass 0 <y <13), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0 <x <2, 0 <y <3), lithium germanium thiophosphate (Li _x Ge _y P _z S _w , x <4, 0 <y < 1, 0 <z <1, 0 <w <5), lithium nitrides _{(Li x N y, 0 <} x <4, 0 <y <2), SiS 2 (Li x _{Si y S z, 0 <x} <3, 0 <y <2, 0 <z <4) based glass, and _{P 2 S 5 (Li x P} y S z, 0 <x <3, 0 <y <3, 0 < z < 7) series glass, or a mixture of two or more thereof.

The porous coating layer of the present invention may include a binder polymer. Examples of such a binder polymer include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride (trichlorethylene), polyvinylidene fluoride -co-trichlorethylene, polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyvinyl alcohol polyvinyl alcohols, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, Cellulose acetate propionate (cel cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxymethylcellulose a carboxyl methyl cellulose and a low molecular weight compound having a molecular weight of 10,000 g / mol or less, or a mixture of two or more thereof.

As the porous substrate of the present invention, a polyolefin-based porous substrate can be used. As the polyolefin-based porous substrate, polyethylene, polypropylene, polybutylene and polypentene are preferably used.

The separator of the present invention can be produced by coating the separator after preparing the columnar particles according to the present invention or by depositing the precursor material of the columnar particles on the separator or by dispersing the columnar particles uniformly in the matrix, Inorganic composite membrane in the separator and then removing the matrix constituent material.

The present invention relates to a positive electrode; cathode; And a separator interposed between the positive electrode and the negative electrode, wherein the separator is interposed between the positive electrode and the negative electrode.

The positive electrode and the negative electrode of the present invention are not particularly limited, and the electrode active material may be bound to an electrode current collector according to a conventional method known in the art. Examples of the cathode active material include, but are not limited to, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a combination thereof It is preferable to use a lithium composite oxide. As a non-limiting example of the negative electrode active material, a conventional negative electrode active material that can be used for a negative electrode of an electrochemical device can be used. In particular, lithium metal or a lithium alloy, carbon, petroleum coke, activated carbon, Lithium-adsorbing materials such as graphite or other carbon-based materials and the like are preferable. Non-limiting examples of the positive current collector include aluminum, nickel, or a combination thereof. Examples of the negative current collector include copper, gold, nickel, or a copper alloy or a combination thereof Foil to be manufactured, and the like.

Electrolyte that may be used in the electrode assembly of the present invention is A ⁺ B ^- A salt of the structure, such as, A ⁺ comprises Li ^+, Na ^+, an alkali metal cation or an ion composed of a combination thereof, such as K ⁺ and B ^- is _{^{PF 6 -, BF 4 -,}} Cl -, Br -, I -, ClO 4 -, AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N (CF 3 SO 2) 2 -, C ( CF ₂ SO _{2) 3} ^- anion, or a salt containing an ion composed of a combination of propylene carbonate (PC like), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DMP), dimethylsulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC), gamma butyrolactone Butyrolactone), or a mixture thereof, but the present invention is not limited thereto. The electrolyte injection may be performed at an appropriate stage of the battery manufacturing process, depending on the manufacturing process and required properties of the final product. That is, it can be applied before assembling the cell or at the final stage of assembling the cell.

Electrolyte that may be used in the electrode assembly of the present invention is A ⁺ B ^- A salt of the structure, such as, A ⁺ comprises Li ^+, Na ^+, an alkali metal cation or an ion composed of a combination thereof, such as K ⁺ and B ^- is _{^{PF 6 -, BF 4 -,}} Cl -, Br -, I -, ClO 4 -, AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N (CF 3 SO 2) 2 -, C ( CF ₂ SO _{2) 3} ^- anion, or a salt containing an ion composed of a combination of propylene carbonate (PC like), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DMP), dimethylsulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC), gamma butyrolactone Butyrolactone), or a mixture thereof, but the present invention is not limited thereto. The electrolyte injection may be performed at an appropriate stage of the battery manufacturing process, depending on the manufacturing process and required properties of the final product. That is, it can be applied before assembling the cell or at the final stage of assembling the cell.

10: Porous substrate 20: Lithium ion
30: spherical inorganic particles 40: columnar inorganic particles
50: stacked columnar inorganic particles

Claims (12)

1. A separator for a secondary battery, comprising: a porous coating layer comprising columnar particles comprising an inorganic compound on at least one surface of a porous substrate.
The method according to claim 1,
Wherein an angle &amp;thetas; formed by the columnar vertical axis of the columnar particles and the horizontal axis of the porous substrate is 60 DEG to 90 DEG.
The method according to claim 1,
Wherein the columnar particles are stacked in two or more layers.
The method according to claim 1,
Wherein the porous coating layer has a thickness of 1 to 60 占 퐉.
The method according to claim 1,
Wherein the porosity of the porous coating layer is 10 to 60%.
The method according to claim 1,
Wherein the inorganic compound is one kind of compound selected from the group consisting of an inorganic compound having a dielectric constant of 5 or more, a piezoelectric inorganic compound, and an inorganic compound having a lithium ion transferring ability, or a mixture of two or more kinds thereof.
The method according to claim 6,
The inorganic compound having a dielectric constant of 5 or more is BaTiO ₃ , Pb (Zr, Ti) O ₃ , (PZT), Pb _{1 -x} La _x Zr _{1 -y} Ti _y O ₃ (PLZT, 0 <x < y <1), Pb (Mg 1/3 Nb 2/3) O 3 -PbTiO 3 (PMN-PT), hafnia _{(HfO 2), SrTiO 3,} SnO 2, CeO 2, MgO, NiO, CaO, ZnO , ZrO ₂ , SiO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC, and TiO ₂ .
The method according to claim 6,
The piezoelectric inorganic compound may be at least one selected from the group consisting of a-AlPO ₄ , a-SiO ₂ , LiTaO ₃ , BaTiO ₃ , LiNbO ₃ , Sr _x Ba _y Nb ₂ O ₈ , Pb ₅ Ge ₃ O ₁₁ , Tb _{2 4} ) ₃ , Li ₂ B ₄ O ₇ , CdS, ZnO, Bi ₁₂ SiO ₂₀ and Bi ₁₂ GeO ₃ single crystals; _{Pb (ZrTi) O 3 (PZT} ), Pb (Fe 1/2 T 1/2) O 3 and _{Pb (Mg 1/3 Nb 2} /3) 1 kind or two kinds selected from the group consisting of O ₃ polycrystalline material Or more of the total weight of the separator.
The method according to claim 6,
As the inorganic particles having lithium ion transferring ability, lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y <3) phosphate _{(Li x Al y Ti z (} PO 4) 3, 0 <x <2, 0 <y <1, 0 <z <3), (LiAlTiP) _x O _y series glass (0 <x <4, 0 <y <13), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0 <x <2, 0 <y <3), lithium germanium thiophosphate (Li _x Ge _y P _z S _w , 0 <x <4, 0 <y <1, 0 <z <1, 0 <w <5), lithium nitride (Li _x N _y , 0 <y <2), SiS ₂ (Li _x Si _y S _z , 0 <x <3, 0 <y <2, 0 <z <4) series glass and P ₂ S ₅ (Li _x P _y S _z , And 0 <x <3, 0 <y <3, 0 <z <7) glass, or a mixture of two or more thereof.
The method according to claim 1,
Wherein the porous substrate is a polyolefin-based porous substrate.
11. The method of claim 10,
Wherein the polyolefin-based porous substrate is formed of any one selected from the group consisting of polyethylene, polypropylene, polybutylene, and polypentene.
anode; cathode; The secondary battery according to any one of claims 1 to 11, wherein the separator and the electrolyte are interposed between the positive electrode and the negative electrode.

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