KR20130123748A - A separator, the manufacturing method thereof, and electrochemical device containing the same - Google Patents

Abstract

A separator of the present invention comprisies a porous substrate having pores; and a porous organic-inorganic coating layer formed on at least one surface of the porous substrate, comprising a binder polymer having a cation exchange resin and a mixture of inorganic particles. The separator of the present invention is a porous organic-inorganic coating layer formed on the porous substrate, and improves the safety of the separator. Addtionally, the binder polymer included in the porous organic-inorganic coating layer contatins the cation exchange resin so as to capture a metal ion caused by a lithium metal oxide, and thereby can increase the life property of a electrochemical element including the separator according to the present invention.

Description

A separator, a manufacturing method thereof, and an electrochemical device having the same {A SEPARATOR, THE MANUFACTURING METHOD THEREOF, AND ELECTROCHEMICAL DEVICE CONTAINING THE SAME}

The present invention relates to a separator of an electrochemical device such as a lithium secondary battery, a method of manufacturing the same, and an electrochemical device having the same, and more particularly, a porous organic-inorganic coating layer formed of a mixture of inorganic particles and a binder polymer on a porous substrate surface. It relates to a separator having an electrochemical device having the same.

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. The electrochemical device is the most attracting field in this respect, and among them, the development of a secondary battery capable of charging and discharging has become a focus of attention. Recently, in developing such a battery, research and development on the design of a new electrode and a battery have been conducted in order to improve capacity density and specific energy.

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 has been considered as one of the next generation batteries by improving the weakness of the lithium ion battery, but the capacity of the battery is still relatively lower than that of the lithium ion battery, and the discharge capacity is improved due to insufficient discharge capacity at low temperatures. This is urgently needed.

In order to solve the safety problem of such an electrochemical device, Korean Patent Laid-Open Publication No. 10-2007-231 discloses a method of coating a porous organic-inorganic hybrid material by coating a mixture of inorganic particles and a binder polymer on at least one surface of a porous substrate having a plurality of pores, A separator in which an inorganic coating layer is formed has been proposed. In the separator, the inorganic particles in the porous organic-inorganic coating layer coated on the porous substrate serve as a kind of spacer capable of maintaining the physical form of the porous organic-inorganic coating layer, so that the porous substrate is thermally shrunk . In addition, an interstitial volume exists between the inorganic particles to form fine pores.

Meanwhile, a lithium secondary battery has a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and components of an electrolyte injected therein. The metal ion is derived from a positive electrode material including lithium metal oxide during the operation of the lithium secondary battery. There is a possibility of negative reaction with the electrolyte and negative electrode, which may adversely affect the life characteristics of the battery. Recently, as products using secondary batteries become higher performance, it is time to increase the performance of batteries such as battery life characteristics.

Therefore, the technical problem to be solved by the present invention is to solve the above-described problems, to provide a separator and an electrochemical device having the same that can improve not only the safety of the electrochemical device but also the life characteristics.

The technical problem to be solved by the present invention is to provide a method that can easily manufacture a separator for the above-mentioned object.

In order to solve the above problems, the separator of the present invention comprises

A porous substrate having pores; And

It is formed on at least one surface of the porous substrate, and comprises a porous organic-inorganic coating layer comprising a mixture of a binder polymer containing a cation exchange resin and inorganic particles.

The cation exchange resin includes at least one cation selected from the group consisting of lithium, sodium, and ammonium.

Preferably, the cation exchange resin may use at least one alumino-slicate, alumino-phosphate, etc. containing at least one cation selected from the group consisting of lithium, sodium, and ammonium. Can be.

In addition, the content of the binder polymer containing the cation exchange resin is preferably 2 to 30 parts by weight based on 100 parts by weight of inorganic particles.

The manufacturing method of the separator of this invention,

(S1) preparing a porous substrate having pores;

(S2) inorganic particles are dispersed, and a slurry in which a binder polymer containing a cation exchange resin is dissolved in a solvent is coated on at least one surface of the porous substrate and dried to form a porous organic-inorganic coating layer.

The separator of the present invention is interposed between the positive electrode and the negative electrode and can be used in an electrochemical device such as a lithium secondary battery or a supercapacitor device.

The separator of the present invention improves the safety of the separator with a porous organic-inorganic coating layer formed on the porous substrate. In addition, the binder polymer included in the organic-inorganic coating layer may contain a cation exchange resin to capture metal ions resulting from lithium metal oxide. Therefore, life characteristics of the electrochemical device including the separator of the present invention can be improved.

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.
1 is a cross-sectional view schematically showing a separator of the present invention.

Hereinafter, the present invention will be described in detail. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

The separator of the present invention includes a porous substrate having pores; And a porous organic-inorganic coating layer formed on at least one surface of the porous substrate and including a mixture of a binder polymer containing a cation exchange resin and inorganic particles.

The binder polymer included in the porous organic-inorganic coating layer contains a cation exchange resin, and the cation exchange resin captures metal ions derived from the lithium metal oxide included in the positive electrode so as not to cause side reactions with the electrolyte and the negative electrode.

In electrochemical devices such as lithium secondary batteries, metal ions derived from lithium transition metal oxides, more specifically, may adversely affect the life characteristics of the electrochemical devices. In order to solve this problem, the separator of the present invention has a binder polymer containing a cation exchange resin. Therefore, the electrochemical device including the separator according to the present invention improves the life characteristics of the electrochemical device through the capture of metal ions and the like.

In the present invention, since a lithium composite oxide such as lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or the like is used as the positive electrode active material used for the positive electrode, the metal ion derived from the lithium metal oxide is For example, it may be Mn ions, Co ions, Ni ions, Fe ions and the like present in these cathode active materials.

The cation exchange resin includes at least one cation selected from the group consisting of lithium, sodium, and ammonium, which are cations that can be substituted with metal ions derived from lithium metal oxides without adversely affecting battery performance.

More specifically, the cation exchange resin may use at least one of alumino-slicate, alumino-phosphate, and the like containing at least one cation selected from the group consisting of lithium, sodium, and ammonium. Can be.

In addition, the cation exchange resin may be included in an amount sufficient to capture metal ions resulting from the lithium metal oxide.

It will be apparent to those skilled in the art that the binder polymer according to the present invention may be used in combination with other binder polymers in addition to the above-described cation exchange resin within the scope of not impairing the object of the present invention.

The content of the binder polymer containing the cation exchange resin according to the present invention is preferably 2 to 30 parts by weight, more preferably 5 to 15 parts by weight based on 100 parts by weight of the inorganic particles. When the content of the binder polymer is less than 2 parts by weight, problems such as desorption of inorganic materials may occur. When the content of the binder polymer is more than 30 parts by weight, the binder polymer may block pores of the porous substrate to increase resistance and the porosity of the porous organic-inorganic coating layer. Can be degraded.

The binder polymer containing the cation exchange resin according to the present invention is preferably positioned as a coating layer on the surface or the whole of the inorganic particles so as to bind the inorganic particles and maximize the cation exchange function without adversely affecting the performance of the battery. Do.

That is, the binder polymer containing the cation exchange resin according to the present invention constitutes a separator by forming an organic-inorganic coating layer together with the inorganic particles. By introducing a cation exchange resin into the binder included in the organic-inorganic coating layer, not only the safety of the electrochemical device obtained as the organic-inorganic coating layer, but also the electrolyte and the negative electrode of the metal ion derived from the lithium metal oxide by the cation exchange resin By suppressing side reactions, a remarkable effect of improving life characteristics can be obtained.

In the separator of the present invention, the inorganic particles used for forming the porous organic-inorganic coating layer are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles usable in the present invention are not particularly limited as long as oxidation and / or reduction reaction does not occur in the operating voltage range of the applied electrochemical device (for example, 0 to 5 V based on Li / Li ⁺ ). Particularly, when inorganic particles having ion transfer ability are used, the ion conductivity in the electrochemical device can be increased to improve the performance.

When inorganic particles having a high dielectric constant are used as the inorganic particles, dissociation of an electrolyte salt, for example, a lithium salt, in the liquid electrolyte is also increased, and ion conductivity of the electrolyte can be improved.

Particularly, the above-mentioned BaTiO ₃ , Pb (Zr, Ti) O ₃ (PZT), Pb _{1 - x} La _x Zr _{1 - y} Ti _y O ₃ (PLZT, where 0 <x <1, 0 < ), inorganic particles, such as _{Pb (Mg 1/3 Nb 2} /3) O 3 -PbTiO 3 (PMN-PT), hafnia (HfO _2), not only exhibit a dielectric constant of 100 or more high dielectric constant characteristics, the predetermined pressure And a piezoelectricity is generated so that a potential difference is generated between both sides by generating a charge when being stretched or compressed so as to prevent the occurrence of an internal short circuit between the two electrodes due to an external impact so as to improve the safety of the electrochemical device can do. Further, when the above-mentioned high-permittivity inorganic particles and inorganic particles having lithium ion transferring ability are mixed, their synergistic effect can be doubled.

In the present invention, the inorganic particles having a lithium ion transferring ability refer to inorganic particles containing a lithium element but not lithium and having a function of transferring lithium ions. The inorganic particles having lithium ion transferring ability are contained in the particle structure Since lithium ions can be transferred and transferred due to a kind of defect present, the lithium ion conductivity in the battery is improved, thereby improving battery performance. Examples of 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), 14Li ₂ O-9Al ₂ O ₃ -38TiO ₂ -39P ₂ O ₅ (0 <x <4, 0 <y <13), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0 <x <2, 0 <y <3), Li (LiAlTiP) _x O _y series glass _{3 .25} Ge _{0 .25} P _{0 .75} S ₄ Lithium, such as germanium Mani help thiophosphate lithium nitro, such as _{(Li x Ge y P z S} w, 0 <x <4, 0 <y <1, 0 <z <1, 0 <w <5), Li 3 N fluoride _{(Li x N y, 0 <} x <4, 0 <y <2), Li 3 PO 4 -Li 2 S-SiS 2 SiS 2 family, such as _{glass (Li x Si y S z} , 0 <x <3 , 0 <y <2, 0 <z <4), LiI-Li ₂ SP ₂ S ₅ There is P ₂ S ₅ based _{glass (Li x P y S z} , 0 <x <3, 0 <y <3, 0 <z <7) or a mixture thereof as such.

In the separator of the present invention, the inorganic particle size of the porous organic-inorganic coating layer is not limited. However, in order to form a coating layer having a uniform thickness and a proper porosity, it is preferable that the porous organic-inorganic coating layer is in the range of 0.001 to 10 μm. If it is less than 0.001㎛ dispersibility is not easy to control the physical properties of the separator, if it exceeds 10㎛ it may increase the thickness of the porous organic-inorganic coating layer may lower the mechanical properties, too large pore size This increases the probability of internal short circuits during battery charging and discharging.

In the porous organic-inorganic coating layer formed on the porous substrate, a binder polymer is located as a coating layer on part or all of the surface of the inorganic particles, the inorganic particles are connected and fixed to each other by the coating layer in close contact, the inorganic particles It is preferable that the pores are formed due to the empty space existing between them. In other words, the inorganic particles of the porous organic-inorganic coating layer are in close contact with each other, and the empty space generated when the inorganic particles are in close contact with the pores of the porous organic-inorganic coating layer.

Components of the porous organic-inorganic coating layer may further include other additives in addition to the binder polymer containing the above-described inorganic particles and cation exchange resin.

In addition, in the separator of the present invention, the porous substrate having pores is polyolefin, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenyl Any porous material such as a porous substrate formed of at least one of lenoxide, polyphenylene sulfide, and polyethylene naphthalene can be used as long as it can be used as a separator of an electrochemical device. As a porous substrate. Both membrane and nonwoven forms can be used. The thickness of the porous substrate is not particularly limited, but is preferably 5 to 50 μm, and the pore size and pore present in the porous substrate are also not particularly limited, but are preferably 0.01 to 50 μm and 10 to 95%, respectively.

1 is a cross-sectional view schematically showing a separator of the present invention having the above-described components. Referring to FIG. 1, the separator 10 of the present invention includes a porous organic-inorganic layer including a binder polymer 5 containing inorganic particles 3 and a cation exchange resin on a porous substrate 1 having pores. Formed.

Preferred manufacturing method of the separator according to the present invention is as follows.

First, a porous substrate having pores is prepared (step S1). The kind of porous substrate is as described above.

Subsequently, the binder polymer containing the above-mentioned cation exchange resin is dissolved in a solvent to prepare a binder solution, and the inorganic particles are added and dispersed. As the solvent, the solubility index is similar to that of the binder polymer containing the cation exchange resin to be used, and the boiling point is preferably low. This is to facilitate uniform mixing and subsequent solvent removal. Non-limiting examples of solvents that can be used include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone ( N-methyl-2-pyrrolidone, NMP), cyclohexane, water, or a mixture thereof. After adding the inorganic particles to the binder polymer solution, it is preferable to perform the crushing of the inorganic particles. In this case, the crushing time is suitably 1 to 20 hours, and the particle size of the crushed inorganic particles is preferably 0.001 to 10 탆 as mentioned above. As the crushing method, a conventional method can be used, and a ball mill method is particularly preferable.

The solution of the binder polymer in which the inorganic particles are dispersed is coated on a porous substrate and dried to form a porous organic-inorganic coating layer (step S2). Humidity condition during coating is preferably 10 to 80%, the drying process is possible any method such as hot air drying if the method can volatilize the solvent.

Coating the solution of the binder polymer in which the inorganic particles are dispersed on the porous substrate may be a conventional coating method known in the art, for example, dip coating, die coating, roll Various methods such as coating, comma coating, or a mixture thereof can be used. In addition, the porous organic-inorganic coating layer may be selectively formed on both surfaces or only one surface of the porous substrate.

The separator of the present invention prepared as described above may be used as a separator of an electrochemical device. In other words, the separator of the present invention can be usefully used as a separator interposed between the positive electrode and the negative electrode and laminated with both electrodes. Electrochemical devices include all devices that undergo an electrochemical reaction, and specific examples include capacitors such as all kinds of primary, secondary cells, fuel cells, solar cells, or supercapacitor elements. Particularly, a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery is preferable.

The electrochemical device may be manufactured according to conventional methods known in the art, and for example, may be manufactured by injecting an electrolyte after assembling the separator described above between an anode and a cathode. .

As an electrode to be applied together with the separator of the present invention, an electrode active material may be manufactured in a form bound to an electrode current collector. Among the electrode active materials, the cathode active material may be a lithium composite oxide, such as lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a combination thereof. Non-limiting examples of the lithium negative electrode active material may be a conventional negative electrode active material that can be used in the negative electrode of the conventional electrochemical device, in particular lithium metal or lithium alloys, carbon, petroleum coke, activated carbon (activated carbon) Lithium adsorbents such as graphite or other carbons are preferred. 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 present invention is A ⁺ B ^- A salt of the structure, such as, A ⁺ is Li ^+, Na ^+, K ⁺ comprises an alkaline metal cation or an ion composed of a combination thereof, such as, 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 ) Salts containing ions consisting of anions such as ₃ ^- or combinations thereof include propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC) , Dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethylcarbonate (EMC), gamma butyrolactone or mixtures thereof Some are dissolved or dissociated in an organic solvent, but are 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.

Claims (14)

A porous substrate having pores;
A separator having a porous organic-inorganic coating layer formed on at least one surface of the porous substrate and comprising a mixture of a binder polymer containing a cation exchange resin and inorganic particles. The method of claim 1,
The cation exchange resin is a separator, characterized in that it comprises at least one cation selected from the group consisting of lithium, sodium, and ammonium. The method of claim 2,
The cation exchange resin is at least one member selected from the group consisting of aluminosilicate (alumino-slicate) and alumino phosphate containing at least one cation selected from the group consisting of lithium, sodium, and ammonium. Separator. The method of claim 1,
The content of the binder polymer containing the cation exchange resin is a separator, characterized in that 2 to 30 parts by weight based on 100 parts by weight of inorganic particles. The method of claim 1,
The average particle diameter of the inorganic particles is a separator, characterized in that 0.001 to 10 ㎛. The method of claim 1,
The inorganic particles are selected from the group consisting of inorganic particles having a dielectric constant of 5 or more, inorganic particles having a lithium ion transfer ability, and mixtures thereof. The method according to claim 6,
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, where 0 <x <1, 0 <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 And ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC and TiO ₂ . The method according to claim 6,
The inorganic particles having a lithium ion transfer ability include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y <3), and lithium aluminum titanium 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 (LixGeyPzSw, 0 <x <4, 0 <y <1, 0 <z <1, 0 <w <5), Lithium Nitride (LixNy, 0 <x <4, 0 <y <2), SiS ₂ (LixSiySz, 0 <x <3, 0 <y <2, 0 <z <4) A separator, characterized in that at least one selected from the group consisting of glass and P ₂ S ₅ (LixPySz, 0 <x <3, 0 <y <3, 0 <z <7) series glass. The method of claim 1,
The porous organic-inorganic coating layer has a thickness of 0.5 to 10 ㎛. The method of claim 1,
The porous substrate is polyolefin, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide and polyethylene naphthalene Separator formed in at least one selected from the group consisting of. (S1) preparing a porous substrate having pores;
(S2) the inorganic particles are dispersed, and the slurry comprising dissolving a binder polymer containing a cation exchange resin in a solvent coated on at least one surface of the porous substrate and dried to form a porous organic-inorganic coating layer of the separator Manufacturing method. In the electrochemical device comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode,
The anode comprises a lithium metal oxide, the separator is an electrochemical device, characterized in that the separator of any one of claims 1 to 10. 13. The method of claim 12,
The lithium metal oxide is an electrochemical device, characterized in that the lithium transition metal oxide. 13. The method of claim 12,
Wherein the electrochemical device is a lithium secondary battery.

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