KR101704759B1 - Stack/folding-typed electrode assembly and electrochemical device including the same - Google Patents

Abstract

The present invention relates to a stack / folding type electrode assembly and an electrochemical device including the stacked / folded type electrode assembly, and more particularly, to a stacked / folded type electrode assembly comprising unit cells including a cathode, an anode, and a separator interposed between the cathode and the anode, Wherein the separator sheet comprises a first porous substrate having a gurley air permeability value of 700 sec / 100cc or less, wherein the separator sheet has a heating dimensional change rate (heating at 150 DEG C for 30 minutes) Of the second porous substrate is less than < RTI ID = 0.0 > -10%. ≪ / RTI >
According to the present invention, the use of a painful separator as a separator for a unit cell interposed in a unit cell improves the performance of the electrochemical device without sacrificing safety, and at the same time, By using a separator sheet having high heat resistance as a separator sheet for use, it is possible to prevent a short circuit due to heat shrinkage phenomenon, thereby improving the safety of an electrochemical device.

Description

[0001] Stack / folding type electrode assembly and electrochemical device including same [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stack / folding type electrode assembly and an electrochemical device including the stack / folding type electrode assembly, and more particularly, to a stack / folding type electrode assembly which simultaneously improves the performance and safety of an electrochemical device and an electrochemical device will be.

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 has received the most attention in this respect. Of these, the development of a rechargeable secondary battery has become a focus of attention. Recently, in developing such a battery, Research and development on the design of electrodes and batteries are underway.

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 .

The electrochemical device may be classified according to the structure of the electrode assembly having the cathode / separator / anode structure. Typically, the electrochemical device is a structure in which the cathode and the anode are rolled up with the separator interposed therebetween. (Stacked) electrode assembly in which a plurality of cathodes and anodes cut in units of a predetermined size are sequentially stacked with a separator interposed therebetween.

However, such conventional electrode assemblies have some problems.

First, the jelly-roll electrode assembly is manufactured by winding a long sheet-like cathode and an anode in a densely packed state to have a cylindrical or elliptical structure. Therefore, stress caused by the expansion and contraction of the electrode during charging and discharging is accumulated in the electrode assembly And when the accumulated stress exceeds a certain limit, deformation of the electrode assembly occurs. As a result of the deformation of the electrode assembly, the spacing between the electrodes becomes non-uniform, the performance of the battery is rapidly deteriorated and the safety of the battery is threatened due to an internal short circuit. In addition, since the long cathode-like anode and the anode are required to be wound up, it is difficult to rapidly wind the anode and the cathode while keeping the distance between the cathode and the anode constant.

Since the stacked electrode assembly requires a plurality of cathode and anode units to be sequentially stacked, a process of transferring an electrode plate for manufacturing a unit body is separately required, and a time and effort are required for a sequential stacking process, resulting in low productivity Has a problem.

In order to solve such a problem, an electrode assembly having a progressive structure of a jelly-roll type and a stack type mixed type is used. The electrode assembly includes a bi-cell or a full- A stack / folding type electrode assembly having a structure in which a unit cell having a full cell is wound by using a continuous separator sheet having a long length has been developed.

Although the stack / folding electrode assembly significantly complements the disadvantages of the jelly-roll and stacked electrode assemblies, more research and development is still required to improve performance and safety at the same time.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a separator for a unit cell which is interposed in a unit cell and which uses a painful separator as a separator for folding and which is interposed between a plurality of unit cells, A stack / folding type electrode assembly capable of simultaneously improving the performance and safety of an electrochemical device, and an electrochemical device including the same.

According to an aspect of the present invention, there is provided a stack / folding type electrode assembly in which unit cells including a cathode, an anode, and a separator interposed between the cathode and the anode are folded by a separator sheet Wherein the separator comprises a first porous substrate having a gurley air permeability value of not more than 700 sec / 100cc, wherein the separator sheet has a second porosity of not more than -10% in a heating dimensional change rate (heating at 150 DEG C for 30 minutes) A stacked / folded electrode assembly is provided that includes a substrate.

The unit cell includes a cathode, a separator, and an anode sequentially stacked; A cathode bi-cell in which a cathode, a separator, an anode, a separator, and a cathode are sequentially stacked; Or an anode bi-cell in which an anode, a separator, a cathode, a separator, and an anode are sequentially stacked.

The separator may be formed by laminating two or more first porous substrates.

The separator sheet may be formed by stacking two or more second porous substrates.

The first porous substrate may be at least one selected from the group consisting of polyethylene, polypropylene, polybutylene, polypentene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone , Polyethersulfone, polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalene, or a mixture of two or more thereof.

The second porous substrate may be at least one selected from the group consisting of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyimide, polyamide, polyamideimide, polycarbonate, polyetheretherketone, polyaryletherketone , Polyvinylidene fluoride, and copolymers comprising at least two repeating units thereof; Polyester-based elastomer; And a polyamide-based elastomer; or a mixture of two or more thereof.

The separator may further include a porous coating layer on at least one surface of the first porous substrate or the separator sheet may further include a porous coating layer on at least one surface of the second porous substrate, Binder.

At this time, the inorganic particles may be inorganic particles having a dielectric constant of 5 or more, inorganic particles having a lithium ion transporting ability, or a mixture thereof.

Then, the inorganic particles is greater than or equal to the dielectric constant of _{5, BaTiO 3, Pb (Zr x} , Ti 1 -x) O 3 (PZT, where, 0 <x <1 _{Im), Pb 1 - x La x} Zr 1 -y Ti _y O ₃ (PLZT, where, 0 <x <1, 0 <y <1 Im), (1-x) Pb (Mg 1/3 Nb 2/3) O 3 -xPbTiO 3 (PMN-PT, where , 0 <x <1), hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC, TiO ₂ , SiO ₂ , AlOOH and Al (OH) ₃ , or a mixture of two or more thereof.

The inorganic particles having the 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- 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 average particle diameter of the inorganic particles may be 0.001 to 100 mu m.

The polymer binder may be selected from the group consisting of polyvinylidene fluoride (PVDF), hexafluoro propylene (HFP), polyvinylidene fluoride-co- hexafluoro propylene, polyvinylidene fluoride-co-trichlorethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, But are not limited to, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate (cellulose acetate propionate), cyanoethylpullulan n), cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile styrene butadiene Acrylonitrile-styrene-butadiene copolymer and polyimide, or a mixture of two or more thereof.

The cathode may include a cathode active material containing a lithium-containing oxide.

The lithium-containing transition metal oxide may be at least one selected from the group consisting of Li _x CoO ₂ (0.5 <x <1.3), Li _x NiO ₂ (0.5 <x <1.3), Li _{x MnO 2 (0.5 <x <} 1.3), Li x Mn 2 O 4 (0.5 <x <1.3), Li x (Ni a Co b Mn c) O 2 (0.5 <x <1.3, 0 <a <1, 0 <b <1, 0 < c <1, a + b + c = 1), Li x Ni 1 -y Co y O 2 (0.5 <x <1.3, 0 <y <1), Li x Co 1 - _{y Mn y O 2 (0.5 <} x <1.3, 0≤y <1), Li x Ni 1 -y Mn y O 2 (0.5 <x <1.3, O≤y <1), Li x (Ni a Co b Mn _c ) O ₄ (0.5 <x <1.3, 0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), Li _x Mn _{2 -z} Ni _z O ₄ 0.5 <x <1.3, 0 < z <2), Li x Mn 2 -z Co z O 4 (0.5 <x <1.3, 0 <z <2), Li x CoPO 4 (0.5 <x <1.3) , and Li _x FePO ₄ may be (0.5 <x <1.3) or any mixture of two or more of those selected from the group consisting of.

The anode may include an anode active material including lithium metal, a carbon material, a metal compound, or a mixture thereof.

The metal compound may be at least one selected from the group consisting of Si, Ge, Sn, Pb, P, Sb, Bi, Al, Ga, In, Ti, Mn, Fe, Co, Ni, Cu, Zn, Ag, Or a mixture of two or more thereof.

According to another aspect of the present invention, there is provided an electrode assembly comprising: an electrode assembly; A nonaqueous electrolytic solution for impregnating the electrode assembly; And a battery case housing the electrode assembly and the non-aqueous electrolyte, wherein the electrode assembly is an electrochemical device that is a stack / folding type electrode assembly of the present invention.

Here, the electrochemical device may be a lithium secondary battery.

According to one embodiment of the present invention, by using a painful separator as a separator for a unit cell interposed in a unit cell, the performance of the electrochemical device can be improved without sacrificing safety, and at the same time, It is possible to prevent a short circuit due to heat shrinkage phenomenon and to improve the safety of the electrochemical device by using a separator sheet having high heat resistance.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description of the invention given above, serve to further the understanding of the technical idea of the invention, It should not be construed as limited.
1 is a cross-sectional view schematically showing a cross section of a stack / folding type electrode assembly according to an embodiment of the present invention.
2 is a diagram schematically illustrating a manufacturing process of a stack / folding type electrode assembly according to an embodiment of the present invention.
3 is a photograph showing an electrochemical device including a stack / folding type electrode assembly manufactured according to an embodiment of the present invention.
4 is a graph comparing cell voltages according to operation time of an electrochemical device manufactured according to Examples and Comparative Examples of the present invention.
FIG. 5 is a graph showing the temperature of the electrochemical device manufactured according to the embodiment of the present invention and the comparative example according to the operation time.

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.

Therefore, the embodiments described in the present specification and the constitutions described in the drawings are merely the most preferred embodiments of the present invention, and are not intended to represent all of the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

A stack / folding type electrode assembly according to one aspect of the present invention is a stack / folding type electrode assembly in which unit cells including a cathode, an anode, and a separator interposed between the cathode and the anode are folded by a separator sheet Wherein the separator comprises a first porous substrate having a gurley air permeability value of not more than 700 sec / 100cc, wherein the separator sheet has a second porosity of not more than -10% in a heating dimensional change rate (heating at 150 DEG C for 30 minutes) .

The unit cell includes a cathode, a separator, and an anode sequentially stacked; A cathode bi-cell in which a cathode, a separator, an anode, a separator, and a cathode are sequentially stacked; Or an anode bi-cell in which an anode, a separator, a cathode, a separator, and an anode are sequentially stacked.

The separator may be formed by laminating two or more first porous substrates, and the separator sheet may be formed by stacking two or more second porous substrates.

By using a plurality of porous substrates laminated and used as the separator or the separator sheet, it is possible to manufacture an electrode assembly that meets the desired properties of the user.

FIG. 1 is a cross-sectional view schematically showing a cross-section of a stack / folding type electrode assembly according to an embodiment of the present invention. FIG. 2 is a schematic view of a stack / folding type electrode assembly according to an embodiment of the present invention. Fig. Referring to these drawings, a plurality of pull cells 10, 11, 12, 13, and 14 in which a cathode / separator 15 / an anode are sequentially stacked as a unit cell are superimposed, (20) is interposed. The separator sheet 20 has a unit length that can wrap around the pull cells and is bent inward for each unit length and starts from the center pull cell 10 and continuously extends from the outermost pull cell 14 to each of the pull cells, Respectively. The distal end of the separator sheet 20 is heat-sealed or attached with an adhesive tape 25 or the like.

This stacked / folded electrode assembly can be used, for example, by arranging the pull cells 10, 11, 12, 13, 14 on a long length of separator sheet 20 and separating them from one end 21 of the separator sheet 20 And then winding them sequentially. The first pull cell 10 and the second pull cell 11 are spaced apart from each other by a width corresponding to at least one pull cell, The lower surface electrode of the first pull cell 10 is brought into contact with the upper surface electrode of the second pull cell 11 after the outer surface of the first pull cell 10 is completely coated with the separator sheet 20. Since the application length of the separator sheet 20 is increased in the sequential lamination process by winding, the pull cells 11, 12, 13, and 14 after the second pull cell increase the intervals between them in the winding direction sequentially Respectively.

The first pull cell 10 and the second pull cell 11 are configured such that the upper surface electrode is a pull cell that is a cathode and the third pull cell 12 and the third pull cell 12 are connected to each other at the interface between the cathode and the anode. Is a pull cell in which the upper surface electrode is an anode, the fourth pull cell 13 is a pull cell in which the upper surface electrode is a cathode, and the fifth pull cell 14 is made of a pull cell in which the upper surface electrode is an anode. That is, except for the first pull cell 10, the pull cell in which the top surface electrode is the cathode is alternately arranged in the order of the pull cell in which the top surface electrode is the anode.

Meanwhile, although not shown, when the unit cell is a bi-cell, the cathode bi-cell and the anode bi-cell are alternately arranged in a sequential arrangement.

As described above, the unit cell separator 15 interposed in the unit cell includes a porous porous substrate having a gurley air permeability value of 700 seconds or less. Here, the grit air permeability value is measured by the ASTM D726-94 method. The hook used here is the resistance to the flow of air and is measured by a densometer. The Gurley air permeability value described here is expressed in seconds (in seconds) for 100 cc of air to pass through a 1 in ² section under a pressure of 12.2 inH ₂ O.

In this case, the separator interposed in the unit cell has a relatively large resistance to heat shrinkage due to adhesion with the electrode, so that the performance of the electrochemical device can be improved without adversely affecting the safety of the electrochemical device even if a porous porous substrate is used .

A separator sheet for folding interposed between a plurality of unit cells has a heat-resistant separator sheet having a heat dimensional change ratio of -10% or less when heated at 150 占 폚 for 30 minutes. Here, the minus (-) sign indicates shrinkage.

When the heating dimensional change rate satisfies the above range, a short circuit or the like which may occur at the edge portion of the unit cell is prevented, and the safety of the electrochemical device is improved.

As a result, by using the first porous substrate as the separator as the separator and using the second porous substrate having the high heat resistance as the separator sheet, the performance of the electrochemical device can be improved and safety can be ensured.

The first porous substrate may be at least one selected from the group consisting of polyethylene, polypropylene, polybutylene, polypentene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone , Polyethersulfone, polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalene, or a mixture of two or more thereof. However, the present invention is not limited thereto. The nonwoven fabric may be a sponge-bonded nonwoven fabric or a meltblown nonwoven fabric composed of long fibers.

The second porous substrate may be at least one selected from the group consisting of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyimide, polyamide, polyamideimide, polycarbonate, polyetheretherketone, polyaryletherketone , Polyvinylidene fluoride, and copolymers comprising at least two repeating units thereof; Polyester-based elastomer; And a polyamide-based elastomer; or a mixture of two or more thereof.

At this time, the thicknesses of the first porous substrate and the second porous substrate are not particularly limited, but may be 1 탆 to 100 탆, or 5 탆 to 50 탆.

The separator may further include a porous coating layer on at least one surface of the first porous substrate, and the separator sheet may further include a porous coating layer on at least one surface of the second porous substrate. At this time, the porous coating layer comprises inorganic particles and a polymeric binder.

The inorganic particles in the porous coating layer serve as a kind of spacer capable of maintaining the physical form of the porous coating layer, thereby suppressing the heat shrinkage of the porous substrate when the electrochemical device is overheated. Even when the porous substrate is damaged, This prevents direct contact of the anode, thereby contributing to improvement of the safety of the electrochemical device.

At this time, the inorganic particles usable in the present invention 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 a high dielectric constant are used as the inorganic particles, the dissociation of the electrolyte salt, for example, the lithium salt in the liquid electrolyte, can be increased, and the ion conductivity of the electrolyte can be improved.

For the reasons stated above, the inorganic particles may include high-permittivity inorganic particles having a dielectric constant of 5 or more, or 10 or more. Nonlimiting examples of inorganic particles having a dielectric constant of 5 or more include BaTiO ₃ , Pb (Zr _x , Ti _{1 -x} ) O ₃ (PZT, where 0 <x <1), Pb _{1 -x} La _x Zr _{1- y} Ti _y O ₃ (PLZT, where, 0 <x <1, 0 <y <1 Im), (1-x) Pb (Mg 1/3 Nb 2/3) O 3 -xPbTiO 3 (PMN-PT, In this case, 0 <x <1), hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC, TiO ₂ , SiO ₂ , AlOOH and Al (OH) ₃ , or a mixture of two or more thereof.

As the inorganic particles, inorganic particles having a lithium ion transferring ability, that is, inorganic particles containing a lithium element but having a function of transferring lithium ions without storing lithium can be used. Non-limiting examples of 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 (Li _x N _y , 0 <x <4, 0 <y <2), Li ₃ PO ₄ -Li ₂ S-SiS ₂ SiS ₂ based glass, such as _{(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.

The size of the inorganic particles is not limited, but may be in the range of 0.001 μm to 100 μm for an appropriate porosity of the separator and the separator sheet.

The polymer binder may be at least one selected from the group consisting of polyvinylidene fluoride (PVDF), hexafluoro propylene (HFP), polyvinylidene fluoride-co- hexafluoro propylene, polyvinylidene fluoride-co-trichlorethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, But are not limited to, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate (cellulose acetate propionate), cyanoethylpullulan n), cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile styrene butadiene Acrylonitrile-styrene-butadiene copolymer and polyimide, or a mixture of two or more thereof. However, the present invention is not limited thereto.

The thickness of the porous coating layer may be 1 탆 to 100 탆, but is not limited thereto.

The cathode has a structure in which the cathode layer including the cathode active material, the conductive material and the binder is supported on one or both surfaces of the current collector.

The cathode active material may include a lithium-containing oxide, and a lithium-containing transition metal oxide may be preferably used. For example, Li _x CoO ₂ (0.5 <x <1.3), Li _x NiO ₂ (0.5 <x <1.3), Li _x MnO ₂ (0.5 <x <1.3), Li _x Mn ₂ O _{4 1.3), Li x (Ni a} Co b Mn c) O 2 (0.5 <x <1.3, 0 <a <1, 0 <b <1, 0 <c <1, a + b + c = 1), Li _{x Ni 1 -y Co y O 2} (0.5 <x <1.3, 0 <y <1), Li x Co 1 -y Mn y O 2 (0.5 <x <1.3, 0≤y <1), Li x Ni _{1 -y} Mn _y O ₂ (0.5 <x <1.3, 0≤y <1), Li _x (Ni _a Co _b Mn _c ) O ₄ (0.5 <x <1.3, 0 <a < 2, 0 <c <2, a + b + c = 2), Li x Mn 2 -z Ni z O 4 (0.5 <x <1.3, 0 <z <2), Li x Mn 2 -z Co z O _{4 (0.5 <x <1.3,} 0 <z <2), Li x CoPO 4 (0.5 <x <1.3) and 2 out of any one or combinations selected from the group consisting of _{Li x FePO 4 (0.5 <x} <1.3) And the lithium-containing transition metal oxide may be coated with a metal such as aluminum (Al) or a metal oxide. In addition to the lithium-containing transition metal oxide, sulfide, selenide and halide may also be used.

The conductive material is not particularly limited as long as it is an electron conductive material that does not cause a chemical change in an electrochemical device. In general, carbon black, graphite, carbon fiber, carbon nanotube, metal powder, conductive metal oxide, organic conductive material and the like can be used. Commercially available products as the conductive material include acetylene black series (manufactured by Chevron Chemical Co., (Chevron Chemical Company or Gulf Oil Company products), Ketjen Black EC series (Armak Company), Vulcan XC-72 (Cabot Company) and Super P (MM (MMM)). For example, acetylene black, carbon black and graphite.

The anode has a structure in which the anode layer including the anode active material and the binder is supported on one or both surfaces of the current collector.

As the anode active material, a lithium metal, a carbonaceous material, a metal compound, or a mixture thereof may be used, in which lithium ions can be occluded and released.

Concretely, as the carbon material, both low-crystalline carbon and highly-crystalline carbon may be used. Examples of the low crystalline carbon include soft carbon and hard carbon. Examples of highly crystalline carbon include natural graphite, Kish graphite, pyrolytic carbon, liquid crystal pitch carbon fiber high temperature sintered carbon such as mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches and petroleum or coal tar pitch derived cokes.

Examples of the metal compound include metal elements such as Si, Ge, Sn, Pb, P, Sb, Bi, Al, Ga, In, Ti, Mn, Fe, Co, Ni, Cu, Zn, Ag, Mg, , And the like. These metal compounds may be a single substance, an alloy, an oxide (TiO ₂ , SnO ₂ Or the like), a nitride, a sulfide, a boride, an alloy with lithium, or the like, but an alloy with a single substance, an alloy, an oxide, and lithium can be increased in capacity. Among them, it may contain at least one element selected from Si, Ge and Sn, and it may further increase the capacity of the battery including at least one element selected from Si and Sn.

The binder used for the cathode and the anode has a function of holding the cathode active material and the anode active material in the current collector and also connecting the active materials, and a commonly used binder may be used without limitation.

For example, polyvinylidene fluoride-hexafluoropropylene (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate various kinds of binders such as polymethyl methacrylate, styrene butadiene rubber (SBR), and carboxyl methyl cellulose (CMC) can be used.

The current collector used for the cathode and the anode may be any metal having a high conductivity and a metal which can easily adhere to the slurry of the active material and is not reactive in the voltage range of the battery. Specifically, examples of the current collector for a cathode include aluminum, nickel, or a combination thereof. Examples of the current collector for an anode include copper, gold, nickel, or a copper alloy or a combination thereof And the like. In addition, the current collector may be used by laminating the substrates made of the above materials.

The cathode and the anode are kneaded using an active material, a conductive material, a binder, and a high boiling point solvent to form an electrode mixture, and then the mixture is applied to a copper foil or the like of the current collector and dried and press- Respectively, for 2 hours under a vacuum.

The thickness of the electrode layer of the cathode may be 30 to 120 占 퐉 or 50 to 100 占 퐉, and the thickness of the electrode layer of the anode may be 1 to 100 占 퐉, or 3 to 70 占 퐉. When the cathode and the anode satisfy such a thickness range, the amount of the active material in the electrode material layer is sufficiently secured, the battery capacity can be prevented from being reduced, and the cycle characteristics and rate characteristics can be improved.

According to an aspect of the present invention, there is provided an electrochemical device comprising: an electrode assembly; A nonaqueous electrolytic solution for impregnating the electrode assembly; And a battery case housing the electrode assembly and the non-aqueous electrolyte. The electrode assembly is the stack / folding type electrode assembly of the present invention.

The electrochemical device according to an embodiment of the present invention includes all devices that perform an electrochemical reaction. Specific examples of the electrochemical device include a capacitor such as a primary cell, a secondary cell, a fuel cell, a solar cell, or a supercapacitor capacitor. 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 non-aqueous electrolyte may include an electrolyte salt and an organic solvent, and the electrolyte salt is a lithium salt. The lithium salt can be used without limitation as those conventionally used in an electrolyte for a lithium secondary battery. For example is the above lithium salt anion ^{F -, Cl -, Br -} , I -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF _{^{4 -, (CF 3) 3}} PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 - _{, (CF 3 SO 2) 2} N -, (FSO 2) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, ( CF ₃ SO ₂ ) ₃ C ^- , CF ₃ (CF ₂ ) ₇ SO ₃ ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- .

Examples of the organic solvent included in the above-mentioned non-aqueous electrolyte include those conventionally used for an electrolyte for a lithium secondary battery, such as an ether, an ester, an amide, a linear carbonate and a cyclic carbonate, Can be mixed and used.

Among them, a carbonate compound which is typically a cyclic carbonate, a linear carbonate, or a mixture thereof may be included.

Specific examples of the cyclic carbonate compound include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, Propylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, vinylethylene carbonate, and halides thereof, or a mixture of two or more thereof. Examples of such halides include, but are not limited to, fluoroethylene carbonate (FEC) and the like.

Specific examples of the linear carbonate compound include any one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate and ethyl propyl carbonate And mixtures of two or more of them may be used as typical examples, but the present invention is not limited thereto.

In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates in the carbonate-based organic solvent, are high-viscosity organic solvents having a high dielectric constant and can dissociate the lithium salt in the electrolyte more easily. In addition, such cyclic carbonates can be used as dimethyl carbonate and diethyl carbonate When a low viscosity, low dielectric constant linear carbonate is mixed in an appropriate ratio, an electrolyte having a higher electric conductivity can be produced.

As the ether in the organic solvent, any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether and ethyl propyl ether or a mixture of two or more thereof may be used , But is not limited thereto.

Examples of the ester in the organic solvent include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate,? -Butyrolactone,? -Valerolactone,? -Caprolactone,? -Valerolactone, ε-caprolactone, or a mixture of two or more thereof, but the present invention is not limited thereto.

The injection of the nonaqueous electrolyte solution can be performed at an appropriate stage of the manufacturing process of the electrochemical device according to the manufacturing process and required properties of the final product. That is, it can be applied before assembling the electrochemical device or in the final stage of assembling the electrochemical device.

The outer shape of the electrochemical device is not particularly limited, but may be a cylindrical shape, a square shape, a pouch shape, a coin shape, or the like using a can.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention may be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Example

(1) Fabrication of electrode assembly

A cathode coated with a cathode active material based on lithium cobalt oxide as an anode, and an anode coated with a graphite anode active material as an anode, and a separator for a unit cell interposed between the cathode and the anode, wherein a gurley air permeability value A plurality of anode bi-cells and cathode bi-cells were fabricated using porous substrates made of polyethylene having 450 sec / 100 cc.

The stacked / folded type electrode assembly was fabricated using the above prepared anode bi-cells, cathode bi-cells, and a porous base material (separator sheet) made of polypropylene having a heating dimensional change rate of -8% Respectively.

(2) Preparation of non-aqueous electrolyte

An organic solvent mixed at a weight ratio of ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 1: 2 was prepared, and then LiPF ₆ as an electrolyte salt was added thereto so as to be 1 M to prepare a nonaqueous electrolytic solution.

(3) Manufacture of electrochemical devices

The prepared stack / folding type electrode assembly was inserted into a pouch-shaped battery case, and the non-aqueous electrolyte solution was injected and sealed to produce an electrochemical device. 3 is a photograph showing an electrochemical device including the stack / folding type electrode assembly manufactured as described above.

Comparative Example

An electrochemical device was produced in the same manner as in Example except that a porous substrate made of a polyethylene material having a gurley air permeability value of 450 sec / 100 cc was used as a separator and a separator sheet.

Character rating

The cell voltage and the temperature according to the operation time were measured for each of the electrochemical devices manufactured by the examples and the comparative examples, and they are shown in FIG. 4 and FIG.

FIG. 4 is a graph comparing cell voltages according to the operation time of the electrochemical device manufactured according to the above-described embodiment and comparative example, and FIG. 5 is a graph comparing the temperatures according to the operating time of the electrochemical device.

Referring to FIGS. 4 and 5, it can be seen that the electrochemical device manufactured according to the comparative example decreases to about 3.7 V when the operation time is over about 120 minutes. On the other hand, The cell voltage did not decrease significantly even when the operating time increased. In the case of the embodiment, it was confirmed that even if the operation time was about 120 minutes, the temperature was maintained at about 40 ° C, whereas in the comparative example, the sudden rise was observed at 100 ° C or more.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

10, 11, 12, 13, 14: Full cell
15: Separator
20: Separator sheet
21: one end of the separator sheet
25: Adhesive tape

Claims (19)

A stack / folding type electrode assembly in which unit cells including a cathode, an anode, and a separator interposed between the cathode and the anode are folded by a separator sheet,
Wherein the separator is composed of a first porous substrate having a gurley air permeability value of 700 sec / 100cc or less and a thickness of 1 mu m to 100 mu m,
The separator sheet is composed of a second porous substrate having a heat shrinkage change rate (heating at 150 캜 for 30 minutes) of 10% or less and a thickness of 1 탆 to 100 탆,
Wherein the first porous substrate and the second porous substrate are different from each other. The method according to claim 1,
The unit cell includes a pull cell in which a cathode, a separator, and an anode are sequentially stacked;
A cathode bi-cell in which a cathode, a separator, an anode, a separator, and a cathode are sequentially stacked; or,
Wherein the anode, the anode, the separator, the cathode, the separator, and the anode are sequentially stacked. The method according to claim 1,
Wherein the separator is formed by stacking two or more first porous substrates. The method according to claim 1,
Wherein the separator sheet is formed by stacking two or more second porous substrates. The method according to claim 1,
Wherein the first porous substrate is selected from the group consisting of polyethylene, polypropylene, polybutylene, polypentene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, poly Wherein the electrolyte membrane is made of any one selected from the group consisting of polyether sulfone, ether sulfone, polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalene, or a mixture of two or more thereof. The method according to claim 1,
Wherein the second porous substrate is selected from the group consisting of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyimide, polyamide, polyamideimide, polycarbonate, polyetheretherketone, polyaryletherketone, poly Vinylidene fluoride and copolymers comprising two or more of these repeating units; Polyester-based elastomer; And a polyamide-based elastomer, or a mixture of two or more thereof. The method according to claim 1,
Wherein the separator further comprises a porous coating layer on at least one side of the first porous substrate or the separator sheet further comprises a porous coating layer on at least one side of the second porous substrate,
Wherein the porous coating layer comprises inorganic particles and a polymeric binder. 8. The method of claim 7,
Wherein the inorganic particles are inorganic particles having a dielectric constant of 5 or more, inorganic particles having lithium ion transferring ability, or mixtures thereof. 9. The method of claim 8,
Inorganic particles is greater than or equal to the dielectric constant of _{5, BaTiO 3, Pb (Zr x} , Ti 1 -x) O 3 (PZT, where, 0 <x <1 _{Im), Pb 1 - x La x} Zr 1 -y Ti y O ₃ (PLZT, where, 0 <x <1, 0 <y <1 Im), (1-x) Pb (Mg 1/3 Nb 2/3) O 3 -xPbTiO 3 (PMN-PT, where 0 (x <1), hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC, TiO ₂ , SiO ₂ , AlOOH and Al (OH) ₃ , or a mixture of two or more thereof. 9. The method of claim 8,
Wherein the inorganic particles having lithium ion transferring ability are selected from the group consisting of lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y < 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 , 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. 8. The method of claim 7,
Wherein the inorganic particles have an average particle diameter of 0.001 to 100 m. 8. The method of claim 7,
The polymer binder may be selected from the group consisting of polyvinylidene fluoride (PVDF), hexafluoro propylene (HFP), polyvinylidene fluoride-co-hexafluoro propylene ), Polyvinylidene fluoride-co-trichlorethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylpyrrolidone, polyvinylpyrrolidone, But are not limited to, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate (cellulose acetate) acetate propionate, cyanoethylpullulan, But are not limited to, ethyl polyvinyl alcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-butadiene copolymer, styrene-butadiene copolymer, and polyimide, or a mixture of two or more thereof. The method according to claim 1,
Wherein the cathode comprises a cathode active material comprising a lithium-containing oxide. 14. The method of claim 13,
Wherein the lithium-containing oxide is a lithium-containing transition metal oxide. 15. The method of claim 14,
The lithium-containing transition metal _{oxides, Li x CoO 2 (0.5 <} x <1.3), Li x NiO 2 (0.5 <x <1.3), Li x MnO 2 (0.5 <x <1.3), Li x Mn 2 O 4 (0.5 <x <1.3), Li x (Ni a Co b Mn c) O 2 (0.5 <x <1.3, 0 <a <1, 0 <b <1, 0 <c <1, a + b + c 1), Li _x Ni _{1- y} Co _y O ₂ (0.5 <x <1.3, 0 <y <1), Li _x Co _{1 -y} Mn _y O _{2 ), Li x Ni 1 -y Mn} y O 2 (0.5 <x <1.3, O≤y <1), Li x (Ni a Co b Mn c) O 4 (0.5 <x <1.3, 0 <a <2 , 0 <b <2, 0 <c <2, a + b + c = 2), Li x Mn 2 -z Ni z O 4 (0.5 <x <1.3, 0 <z <2), Li x Mn 2 in _{-z Co z O 4 (0.5 <} x <1.3, 0 <z <2), Li x CoPO 4 (0.5 <x <1.3) and _{Li x FePO 4 (0.5 <x} <1.3) which is selected from the group consisting of One or a mixture of two or more thereof. &Lt; RTI ID = 0.0 &gt; 11. < / RTI &gt; The method according to claim 1,
Wherein the anode comprises an anode active material comprising a lithium metal, a carbonaceous material, a metal compound, or a mixture thereof. 17. The method of claim 16,
The metal compound may be at least one selected from the group consisting of Si, Ge, Sn, Pb, P, Sb, Bi, Al, Ga, In, Ti, Mn, Fe, Co, Ni, Cu, Zn, Ag, Or a mixture of two or more thereof. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt; An electrode assembly;
A nonaqueous electrolytic solution for impregnating the electrode assembly; And
And an electrode assembly and a battery case enclosing the non-aqueous electrolyte, the electrochemical device comprising:
The electrochemical device according to any one of claims 1 to 17, wherein the electrode assembly is a stack / folding type electrode assembly. 19. The method of claim 18,
Wherein the electrochemical device is a lithium secondary battery.

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