KR101502966B1 - Endothermic separator for electrochemical elements and electrochemical elements comprising the same - Google Patents

Abstract

The present invention is characterized in that when a heat is generated due to an internal short circuit due to an external impact or the like, the capsule contains a phase change material (PCM) on the outer periphery of the separation membrane. The PCM capsule dissolves while absorbing heat to block the lithium ion path, The present invention relates to an endothermic separation membrane for an electrochemical device capable of preventing physical and chemical deformation of the separation membrane due to high temperature or accumulated heat and ultimately suppressing a change in electrochemical device resistance, In addition to the above-described effects, the present invention has an effect that productivity is improved and the volume of the electrode assembly is reduced as compared with the conventional heat absorbing sheet.

Description

TECHNICAL FIELD The present invention relates to an endothermic separator for electrochemical devices and an electrochemical device containing the same,

The present invention relates to an endothermic separation membrane for an electrochemical device and an electrochemical device containing the same. More specifically, the present invention relates to an endothermic separation membrane for an electrochemical device, which comprises a phase change material (PCM) The present invention relates to an endothermic separator for an electrochemical device that improves the safety of a battery by blocking the lithium ion path when the PCM capsule absorbs heat while generating heat due to an internal short circuit due to an external shock or the like by including a capsule ('PCM capsule' To an electrochemical device containing the same.

As technology development and demand for mobile devices have increased, the demand for electrochemical devices, especially secondary batteries, as an energy source has been increasing rapidly. Many researches have been made on lithium secondary batteries having high energy density and high discharge voltage among such secondary batteries Has been commercialized and widely used.

Conventional lithium secondary batteries have a risk of ignition and explosion when exposed to high temperatures. Also, even if large current flows in a short time due to overcharge, external short circuit, nail penetration, local crush, etc., there is a risk of ignition / explosion as the battery is heated by IR heat. That is, when the temperature of the battery rises, the reaction between the electrolyte and the electrode is promoted. As a result, the reaction heat is generated and the temperature of the battery further rises, so that the reaction between the electrolyte and the electrode is further accelerated. By this circulation, a thermal runaway phenomenon occurs in which the temperature of the battery rises sharply, and when the temperature rises to a certain level or higher, the battery may ignite. Further, as a result of the reaction between the electrolyte and the electrode, gas is generated and the internal pressure of the battery is increased, and the lithium secondary battery explodes at a certain pressure or higher. The risk of such ignition and explosion is the most fatal disadvantage of lithium secondary batteries.

Therefore, it is necessary to secure safety for the development of lithium secondary batteries. As an effort to secure such safety, there is a method of attaching an element to the outside of the cell and a method of using a substance inside the cell. Electronic devices include PTC devices that use temperature changes, CID devices, protection circuits that use changes in voltage, and safety vents that use changes in the internal pressure of batteries. The latter is the addition of substances that can change chemically or electrochemically.

Devices mounted on the outside of the cell use a temperature, a voltage and a withstand voltage, so they can be surely interrupted. However, it is known that it does not play a protective role when a fast response time is required such as an internal short circuit, acupuncture penetration, and local damage.

As a method of using a substance inside a cell, there is a method of adding an additive for improving safety to an electrolyte or an electrode. The chemical safety device has the advantage that it can be applied to all kinds of batteries, but it has a problem that the performance of the battery deteriorates due to the addition of the material. These materials include a material forming a floating film on the electrode and a material increasing the resistance of the electrode due to the volume expansion during temperature rise. However, each of these has a problem in that byproducts are generated during the formation of the floating film, thereby deteriorating the performance of the battery, or the volume of the battery is large, thereby reducing the capacity of the battery.

Therefore, there is a high demand for development of new safety means for preventing ignition and explosion more rapidly due to external impact, etc., without deteriorating the overall performance of the battery.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and the technical problems required from the past.

More specifically, the present invention aims at solving the problem of the present invention, in which, when an internal short circuit occurs due to an external impact or the like, the PCM capsule absorbs heat and melts to lower the temperature of the battery, And to provide an electrochemical device having the separator and the separator, wherein the risk of explosion can be significantly reduced by blocking the flow. Another technical problem to be solved by the present invention is to provide a method for easily manufacturing a separator having the above-mentioned object.

According to one aspect of the present invention, there is provided a porous substrate having pores; And a porous organic-inorganic coating layer formed on at least one surface of the porous substrate, the porous organic-inorganic coating layer including a mixture of inorganic particles and a binder polymer, wherein at least a portion of the end of the porous organic- Thereby forming a phase change material layer region.

The phase-change material may be a mixture of one or more selected from the group consisting of alkanes having from 11 to 50 carbon atoms, polyethylene glycol, inorganic hydrates, organic acids, and sugar alcohols.

The phase change material may be supported on the capsule.

The capsule may be made of an inert material.

Wherein the inert material is one or two kinds selected from the group consisting of polyolefin, polystyrene, polyacrylate, polyamide, polyester, polycaprolactone, polyurethane, gelatin, chitosan, cellulose, melamine resin, urea resin and derivatives thereof Or mixtures or copolymers of the above.

The phase change material layer region may further include a thermally conductive material.

The phase change material layer region may form an outermost portion when the separator is wound.

The porous substrate may be a polyolefin-based porous membrane or a nonwoven fabric.

The porous substrate may be selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polypropylene polyethylene terephthalate, polybutyleneterephthalate, polyester, polyacetal, polyamide, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylenesulfroid and polyethylene naphthalene (polyethylenenaphthalene), or a mixture of two or more thereof.

The inorganic particles may be selected from the group consisting of inorganic particles having a dielectric constant of 5 or more, inorganic particles having lithium ion transporting ability, and mixtures thereof.

Inorganic particles is greater than or equal to the dielectric constant of 5, _{BaTiO 3, Pb (Zr x,} Ti 1 -x) O 3 (PZT, 0 <x <1), Pb 1 - x La x Zr 1 -y Ti y O 3 (PLZT , 0 <x <1, 0 <y <1), (1-x) Pb (Mg 1/3 Nb 2/3) O 3 - x PbTiO 3 (PMN-PT, 0 <x <1), 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 . And mixtures of two or more thereof.

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 <3), 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 (Li _x Ge _y P _z S _w , , 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 binder polymer may be at least one selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichlorethylene, polymethylmethacrylate, Polybutylene terephthalate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide (polyethylene) oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpyrrolidone, Polyvinyl alcohol (cyanoethylpolyviny or a mixture of two or more thereof selected from the group consisting of lanolin, lauroyl alcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose. have.

The content of the binder polymer may be 1 to 50 parts by weight based on 100 parts by weight of the inorganic particles.

The phase change material layer region may contain 10 to 400 parts by weight of phase change material based on 100 parts by weight of the total of the inorganic particles and the binder polymer.

The area of the phase change material layer region may be 1 to 20% of the total surface area of the porous substrate.

According to another aspect of the present invention, there is provided an electrochemical device comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, wherein the separator is the separator described above.

According to still another aspect of the present invention, there is provided a semiconductor device comprising: a plurality of unit cells each having a first separator and an anode and a cathode disposed on both sides of the first separator; And a plurality of unit cells arranged in a plurality of unit cells stacked so that the cathodes of one unit cell and the anodes of the other unit cell correspond to each other, Wherein the first separator and the second separator are the above-described separator, and the phase change material layer region of the second separator is formed of a plurality of unit cells adjacent to each other at a central portion of the plurality of stacked unit cells, An electrochemical device interposed therebetween is provided.

According to another aspect of the present invention, the electrochemical device is a lithium secondary battery.

According to another aspect of the present invention, there is provided a method of manufacturing a porous substrate, comprising: preparing a porous substrate having pores; Coating a first coating solution in which inorganic particles are dispersed and a binder polymer dissolved in a solvent on at least a part of at least one surface of the porous substrate to form a porous organic-inorganic coating layer; And a second coating solution containing inorganic particles, a binder polymer, and a phase change material are coated on the organic-inorganic coating layer, followed by drying to form a phase change material layer region Forming a separator on the surface of the separator.

The phase change material may be supported on the capsule.

As described above, the electrochemical device according to the present invention includes the PCM capsules in the end region of the separator to prevent physical and chemical deformation of the separator due to heat or accumulated heat, and ultimately to change the electrochemical device resistance So that an optimal operating state can be maintained.

Particularly, the separator of the present invention can be applied not only to an electrochemical device having one unit cell but also to a stacked electrochemical device including a plurality of unit cells. When the separator is applied to a stacked electrochemical device, Since the second separator has a dual heat absorbing function, the stability is further improved.

In addition, compared with the conventional heat absorbing sheet, the production is simple and productivity is improved and the volume of the electrode assembly is reduced.

1A is a diagram schematically showing a conventional heat absorbing sheet.
1B is a view schematically showing a separator according to an embodiment of the present invention.
2 is a view schematically showing a separator according to an embodiment of the present invention.
3 is a schematic top view of an embodiment in which the separator according to an embodiment of the present invention is wound to be used in a cylindrical electrochemical device.
4 is a schematic perspective view showing an embodiment of the present invention in which each unit cell includes a first separator and a plurality of such unit cells are aligned on the second separator.
5 is a schematic cross-sectional view of an electrode assembly according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It should be interpreted in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined.

According to the present invention, an electrochemical device includes not only an electrochemical device including only one unit cell but also an electrochemical device including a plurality of unit cells.

In the present invention, 'separator' and 'separator' are the same terms which can be used interchangeably.

In the present invention, 'first separator' and 'second separator' are used in a stacked electrochemical device including a plurality of unit cells. The 'first separator' is used in a unit cell and is interposed between an anode and a cathode Refers to a separator, and the term "second separator" refers to a separator interposed between adjacent unit cells.

The first separator and the second separator of the electrochemical device according to an aspect of the present invention may have the same or different structures.

In the present invention, in an electrochemical device including an anode, a separator, a cathode, and an electrolyte, at least a part of an end of the porous organic-inorganic coating layer of the separator is formed into a phase change material layer region including a phase change material (PCM) , The separator itself is provided with a heat absorbing function, and the phase change material is melted by the heat generated when the battery is short-circuited not only to lower the temperature of the battery but also to block the flow of electricity by penetrating the molten liquid into the short circuit portion. The electrochemical device according to the present invention secures the safety of an electrochemical device in a manner different from the conventional method. Unlike the case of mounting an element or a protective circuit on the outside of a cell, the electrochemical device is interposed between electrodes, The phase change material can act more sensitively to the heat generation, thereby rapidly lowering the temperature, and further, the melted silver phase conversion material can flow into the short circuit portion to block the electric conduction. In addition, unlike the conventional method of using a chemical substance inside a cell, there is an advantage that no side effects such as deterioration of a battery performance and capacity decrease occur at all.

First, according to one aspect of the present invention, there is provided a porous substrate having pores; And a porous organic-inorganic coating layer formed on at least one surface of the porous substrate, the porous organic-inorganic coating layer including a mixture of inorganic particles and a binder polymer, wherein at least a portion of the end of the porous organic- Thereby forming a phase change material layer region.

In the present invention, the phase change material is not particularly limited as long as it is a material capable of absorbing heat generated during charging and discharging of the electrochemical device, and may be a material having a large latent heat at the time of phase conversion at a predetermined temperature.

The phase-change material is subjected to phase transformation at the predetermined temperature, for example, a phase change from a liquid phase or a liquid phase to a solid phase at a predetermined temperature, and at least a latent heat which is larger than a heat capacity per unit temperature of the electrochemical device constituent members A branch means a substance. The phase change material may be a single compound, a mixture or a complex, and the like. The phase transformation of these materials not only includes the case of a physical phase transformation at the predetermined temperature but also a case where a mixture of two or more materials undergoes a phase transformation by a reversible physical or chemical reaction at the predetermined temperature.

Since the phase change material has a critical temperature of phase transformation at the predetermined temperature, it is possible to prevent the temperature of the electrochemical device from rising sharply to a specific temperature or more.

Typical examples of the phase change material include n-tetradecane, n-hexadecane, n-Paraffin, n-Octadecane, n- N-eicosane, n-heneicosane, n-docosane, n-tricosane, tetracosane, hexacosane, nonacosane, Alkane having from 11 to 50 carbon atoms, such as polyethylene glycol; _{NaNH 4 SO 4 · 2H 2 O} , Na 2 SO 4 · 10H 2 O, Na 2 SiO 3 · 5H 2 O, NaHPO 4 · 12H 2 O, Na 2 HPO 4 · 12H 2 O, K 2 HPO 4 · 3H 2 _{O, K 3 PO 4 · 7H} 2 O, Fe (NO 3) 3 · 9H 2 O, FeCl 3 · 2H 2 O, Zn (NO 3) 2 · 6H 2 O, Na 2 S 3 O 3 · 5H 2 O _{, NaCH 3 COO 3 H 2 O} , Fe 2 O 3 4SO 3 · 9H 2 O, Ca (NO 3) 2 · 3H 2 O, CaCl 2 · 6H 2 O, Mg (NO 3) 2 6H 2 O, CH 3 _{COONa 3H 2 O, Na 2 S} 2 O 2 · H 2 O, NaOH · H 2 O, LiNO 3 and Mg (NO ₃₎ a mixture of _{2 6H 2 O, Na 3 PO} 4 · 12H 2 O, Mg (NO 3 ) ₂ 6H ₂ O and the like; Organic acids such as acetic acid, butyric acid, palmitic acid, oxalic acid, tartaric acid, myristic acid, stearic acid and n-octanoic acid, and carboxylic acids such as ascorbic acid, uric acid, sulfonic acid, sulfinic acid and phenol; And sugar alcohols such as xylitol. However, the present invention is not limited to these. Among them, paraffin having a relatively high latent heat or a mixture of LiNO ₃ and Mg (NO ₃ ) ₂ 6H ₂ O having a high melting temperature (melting point of about 75 ° C.), Na ₃ PO ₄ · 12H ₂ O (melting point of about 75 ° C. ), Mg (NO ₃ ) ₂ 6H ₂ O (melting point: about 89 ° C), xylitol (melting point: about 93 to 95 ° C)

In the present specification, 'paraffin' refers to paraffin lead or paraffin, which is a paraffinic hydrocarbon. These substances are weakly reactive and resistant to chemicals. The paraffin lead is a colorless translucent solid, also called solid paraffin, and the liquid paraffin is a colorless liquid. In the present invention, paraffin lead, which is a solid paraffin, is used because it is characterized by using the heat of fusion of a solid material.

The main component of paraffin lead is a straight chain paraffinic hydrocarbon, which can be represented by CH ₃ (CH ₂ ) _n CH ₃ . Here, the carbon number is in the range of 16 to 40, and the main component is 20 to 30 carbon atoms. The melting point of paraffin lead may vary within the range of 47 to 65 ° C, depending on the degree of refining and the components.

In the present specification, the term "specific temperature" refers to a temperature at which the performance, lifetime, or safety of the electrochemical device can be lowered. The predetermined temperature may be determined according to the structure, type, etc. of the electrochemical device, and may be determined, for example, in a temperature range of 50 to 150 占 폚, or a temperature range of 60 to 120 占 폚.

In particular, the predetermined temperature may be a temperature at which the physical and / or chemical deformation of the electrochemical device structural member is directly induced, or may be determined as a temperature at which aging of the material is caused by continuous heat accumulation.

The phase-change material may be included in the separator in a state of being supported on the capsule, and the separator itself may be provided with an endothermic function. The encapsulated phase change material may have a higher response to heat due to its high specific surface area.

The capsules carrying the phase change material should be inert at least to the components of the cell and the internal phase change material should be a material that can remain sealed after the phase change.

Examples of such inert materials include polyolefins such as polyethylene, polypropylene and the like; polystyrene; Polyacrylates such as polymethacrylate, polymethyl methacrylate and the like; Polyamides such as nylon; Polyesters such as polyethylene terephthalate, polybutylene terephthalate and the like; Polycaprolactone; Polyurethane; gelatin; Chitosan; cellulose; Melamine resin; Urea resin; Derivatives thereof, and the like, but the present invention is not limited thereto. In some cases, two or more of these materials may be used together to form a capsule. In addition, the capsule may be blended polymer particles in which a homopolymer such as polystyrene, polymethacrylate, polyethylene and the like and a block copolymer such as polystyrene-polymethyl methacrylate or polyethylene oxide-polymethyl methacrylate are mixed with each other . These blend-type polymer particles can be formed into multilayer capsule particles having a core portion and two or more shell portions by suitably controlling the kind of polymer used.

In some cases, the capsule may be made of a substance decomposed or destroyed at a temperature above the critical temperature. The critical temperature may be, for example, a temperature at which ignition or explosion of the battery can be induced in terms of safety of the battery.

The thickness of the capsules covering the phase change material is not particularly limited as long as it can exert the effects according to the present invention and may be 0.01 to 5 탆 or 0.02 to 0.1 탆 in consideration of heat conductivity and shape stability of the capsules. have.

If the thickness of the capsule is too thin, it is difficult to stably retain the phase change material. Conversely, if it is too thick, the thermal conductivity may be lowered and the amount of the phase change material may be relatively decreased.

Further, the capsules may have a particle size of about 0.1 to 100 占 퐉, or 0.5 to 10 占 퐉. It may be a small particle size having a large surface area per unit weight in terms of rapid reactivity in accordance with the temperature change. However, a too small particle size may be difficult to manufacture the capsule itself carrying the phase change material, There is a possibility of difficulty in the process of making the film.

In some cases, a thermally conductive material having a high thermal conductivity may be further added to the inert material to increase the thermal conductivity of the capsule. Examples of such materials include ceramics, metal powders, graphite powders, and the like, but are not limited thereto.

Herein, the term 'phase change material layer region' refers to a region where at least a portion of the end portion of the porous organic-inorganic coating layer of the separator further contains a phase change material.

The phase change material layer region is formed at the end of the separator in contact with the porous organic-inorganic coating layer not containing the phase change material in the separator.

Particularly, in the electrochemical device including one unit cell, the phase change material layer region can form a wound outer frame portion when the separator is wound. Herein, the term "wound outer frame" refers to an end portion at which the separator starts to be wound together with the positive electrode and the negative electrode in the longitudinal direction of the separator, that is, an end other than the end of the winding core do.

Alternatively, in an electrochemical device including a plurality of unit cells, the first separator may include a phase change material layer region at one end thereof, and the second separator may include a phase change material layer region at a central portion of the stacked unit cells can do.

The content of the phase-change material may be determined by various factors such as the type of the phase-change material, the type and the shape of the battery, and thus is not particularly limited. For example, the function of the porous organic- The phase change material layer may contain 10 to 400 parts by weight or 80 to 300 parts by weight of a phase change material based on 100 parts by weight of the total amount of the inorganic particles and the binder polymer so as to exhibit the desired effect of the present invention, can do.

The area of the phase change material layer region may be 1 to 20%, or 5 to 10% of the total surface area of the porous substrate. When the formation area of the phase change material layer region satisfies the above range, the porous organic-inorganic coating layer of the separator functions, while at the same time, the heat is effectively absorbed when heat is generated due to an anomaly inside or outside the cell, It is possible to improve the stability of the secondary battery by blocking the path of the lithium ion and to act as a buffer to mitigate the volume expansion of the cathode due to the outer coating layer.

At least one surface of the phase change material layer region may be connected to an adhesive layer by a method such as adhesion.

That is, the separator according to an embodiment of the present invention may extend to the phase change material layer region to further form an adhesive layer. When the electrode assembly is wound with the separator, the adhesive layer at the distal end is adhered to the opposed porous substrate, Thereby making it possible to fix the electrode assembly.

The present invention provides not only an electrochemical device including one unit cell having cathodes and electrodes on both sides of the separator of the present invention but also an electrochemical device including a plurality of such unit cells.

A plurality of unit cells each including a first separator and an anode and a cathode disposed on both sides of the first separator; And a plurality of unit cells arranged in a plurality of unit cells stacked so that the cathodes of one unit cell and the anodes of the other unit cell correspond to each other, In an electrochemical device having a separator, the first separator and the second separator may be a separator including a phase change material layer region according to the present invention, and the phase change material layer region of the second separator may include a plurality of Wherein the electrochemical device is interposed between adjacent unit cells at a central portion of the unit cells.

The phase change material layer region of the second separator is sandwiched between unit cells adjacent to each other at a central portion of the stacked unit cells. The central portion of the stacked unit cells corresponds to a region showing the highest temperature in the electrochemical device So that it is possible to prevent an increase in the internal temperature more efficiently. That is, in an electrochemical device comprising stacked unit cells, the temperature of each unit cell increases with the lapse of time during operation of the device. At this time, in the case of the cells adjacent to the upper and lower parts of the device, the heat inside the cell can be dissipated because it is adjacent to the external relatively low temperature atmosphere, but the heat radiated from the unit cells located at the center of the stacked structure is not discharged to the outside And further accumulates in the center portion to provide a cause of raising the temperature inside the electrochemical device.

However, if an endothermic layer is introduced on the electrode surface or the surface of the separator of all the unit cells in order to absorb the heat radiated from the cells in an early stage, it may be possible to achieve a predetermined result for the purpose of absorbing heat inside the unit. The plurality of heat absorbing layers introduced into the unit cells may serve as resistors of the electrochemical device, which may cause deterioration of the performance of the electrochemical device.

Therefore, the electrochemical device according to one aspect of the present invention introduces a phase change material layer region at a position corresponding to the central portion where the heat is most generated in the stacked structure of unit cells, thereby minimizing the influence on the performance of the electrochemical device, It is possible to efficiently absorb the calorific power of the battery in the operating state, to control the temperature inside the cell, and to improve the overcharging performance.

Hereinafter, an electrochemical device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIGS. 1A and 1B are views showing a conventional heat absorbing sheet and a separator including a phase change material region layer in a wound outer frame according to the present invention.

1A and 1B, the conventional heat absorbing sheet is a dual sheet type in which a heat absorbing sheet including a heat absorbing material 11 is separately formed on a separator (not shown) The separator according to the embodiment includes a porous organic-inorganic coating layer region 16 on which a phase change material is not dispersed and a phase change material layer region in which a phase change material 17 is dispersed on a porous substrate, have. As a result, the separator according to the present invention has a heat absorbing function in at least a part of its end portion.

2 is a schematic view of a cross-sectional structure according to one embodiment of a separator according to the present invention.

Referring to FIG. 2, a phase change material layer region 18 in which a phase change material is dispersed followed by a porous organic-inorganic coating layer region 16 in which a phase change material is not dispersed, Are shown. At this time, the phase change material can be supported in a sealed form inside the capsule made of an inert material as described above. As a result, since the phase change material has a large contact area per weight of the phase change material, The reactivity can be further improved.

Figure 3 is a schematic top view of an embodiment in which the separator of the present invention is wound to be used in a cylindrical electrochemical device.

3, the separator interposed between the anode and the cathode is wound together with the anode and the cathode so that the phase-change material layer region forms the winding outer frame portion 18. Inside the phase change material layer region, a porous material An organic-inorganic coating layer region 16 is present. At this time, the adhesive layer 19 may be further formed to extend to the region of the phase change material layer.

4 is a schematic perspective view of a second separator in which a plurality of unit cells are aligned and a phase change material layer region is formed according to an embodiment of the present invention. 4, a plurality of unit cells 20 each having a cathode 21 and a cathode 23 disposed on both sides of the first separator 22 and the first separator 22 are disposed before the electrode assembly 20 is wound, A phase change material layer region 25 is formed on one end of the second separator 26 at this time.

When the second separator 26 in which the plurality of unit cells 24 and the phase change material layer region 25 are formed is wound such that the phase change material layer region 25 is positioned at the center, Can be obtained.

5, the electrode assembly 20 includes a first separator 22 and a plurality of unit cells 24 each having a cathode 21 and an anode 23 located on both sides of the first separator 22 do. The positive electrode 23 has a structure in which a positive electrode active material layer is formed on both surfaces of a positive electrode collector and the negative electrode 21 has a structure in which a negative electrode active material layer is formed on both surfaces of the negative electrode collector. 5, the unit cell may have a full cell structure in which one anode 23 and the cathode 21 are located on both sides of the first separator 22, And a bipolar structure in which a cathode 21 and an anode 23 are disposed on the first separator 22 and the first separator 22, respectively.

Within the electrode assembly 20, each unit cell 24 is in a stacked form. In this case, between the adjacent unit cells 24 so that the cathodes of one unit cell correspond to the anodes of the other unit cells, a second separator (not shown) (26) are interposed in various forms as shown in Fig. 5 to perform a separator function between each unit cell (24).

At this time, the phase change material layer region 25 including the phase change material 27 is interposed between the unit cells 24 adjacent to each other at the central portion of the lamination structure of the unit cells 24, (26) and introduced into the electrode assembly (20).

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 are not particularly limited as long as the 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.

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, inorganic particles having lithium ion transferring ability, or a mixture thereof. Nonlimiting examples of 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, <1, 0 <y <1 _{Im), 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, Y 2 O 3, Al 2 O 3, SiC, TiO 2 May be used alone or in combination of two or more.

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 as such (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 ), Li _{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 according to an embodiment of the present invention, the inorganic particle size of the porous organic-inorganic coating layer is not limited, but may be in the range of 0.001 to 10 탆, if possible, for forming a coating layer of uniform thickness and proper porosity. When the inorganic particle size satisfies this range, the dispersibility is maintained, the physical properties of the separator are easily controlled, the increase in the thickness of the porous organic-inorganic coating layer can be avoided, the mechanical properties can be improved, Also, an excessively large pore size can reduce the probability of an internal short circuit occurring during battery charge / discharge.

The binder polymer used for forming the porous organic-inorganic coating layer is not particularly limited as a binder polymer commonly used in the art.

In particular, a polymer having a glass transition temperature (T _g ) of -200 to 200 ° C can be used because it can improve the mechanical properties such as flexibility and elasticity of the finally formed organic-inorganic coating layer . Such a binder faithfully performs a binder function to connect and stably fix inorganic particles, thereby contributing to prevention of deterioration of mechanical properties of the separator into which the porous coating layer is introduced.

Further, the binder does not necessarily have the ion-conducting ability, but the performance of the electrochemical device can be further improved by using a polymer having ion-conducting ability. Therefore, a binder having a high permittivity constant can be used. Actually, the dissociation degree of the salt in the electrolytic solution depends on the permittivity constant of the solvent of the electrolyte. Therefore, the higher the permittivity constant of the polymer, the better the salt dissociation degree in the electrolyte. The permittivity constant of such a binder may be in the range of 1.0 to 100 (measurement frequency = 1 kHz), in particular, 10 or more.

In addition to the functions described above, the binder may be characterized by being capable of exhibiting a high degree of swelling of the electrolyte by gelation upon impregnation with a liquid electrolyte. Accordingly, the solubility parameter of the binder is from 15 to 45 MPa ^1/2 or 15 to 25 MPa ^1/2, and 30 to 45 MPa ^1/2 range. Therefore, hydrophilic polymers having many polar groups can be used more than hydrophobic polymers such as polyolefins. If the solubility is more than 15 MPa ^1/2 and less than 45 MPa ^1/2, because it can be difficult to swell (swelling) by conventional liquid electrolyte batteries.

Non-limiting examples of usable binder polymers include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-cotrichloroethylene, polymethylmethacrylate, But are not limited to, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide ), Cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylpolyvinylalcohol, Ethylcellulose (cyanoethylcell but are not limited to, polyvinyl alcohol, polyvinyl alcohol, polyvinylpyrrolidone, polyvinylpyrrolidone, polyvinylpyrrolidone, polyvinylpyrrolidone, polyvinylpyrrolidone, polyvinylpyrrolidone, polyvinylpyrrolidone, polyvinylpyrrolidone, polyvinylpyrrolidone, polyvinylpyrrolidone, And the like. In addition, any material including the above-mentioned characteristics may be used alone or in combination.

The content of the binder polymer in the porous organic-inorganic coating layer coated on the separator according to an embodiment of the present invention is, for example, 1 to 50 parts by weight, or 2 to 30 parts by weight, or 5 to 5 parts by weight, 15 parts by weight. When the content of the binder polymer satisfies the above range, it is possible to prevent problems such as the elimination of inorganic substances and the phenomenon that the binder polymer blocks the pores of the porous substrate to increase resistance and decrease the porosity of the porous organic-inorganic coating layer.

In the porous organic-inorganic coating layer formed on the porous substrate, the binder polymer is positioned as a coating layer on a part or the entire surface of the inorganic particles, and the inorganic particles are connected and fixed to each other by the coating layer in close contact, Pores may be formed due to the void space present between the inorganic particles. That is, the inorganic particles of the porous organic-inorganic coating layer exist in close contact with each other, and the void space formed when the inorganic particles are in close contact becomes the pores of the porous organic-inorganic coating layer. The size of the void space present between the inorganic particles may be equal to or less than the average particle size of the inorganic particles. The binder polymer located in a coating on a part or all of the surface of the inorganic particles connects and secures the inorganic particles together and fixes the inorganic particles in contact with the porous substrate to the porous substrate.

The thickness of the porous organic-inorganic coating layer composed of the inorganic particles and the binder polymer is not particularly limited, but may be in the range of 0.5 to 10 mu m.

In the separator according to one embodiment of the present invention, the substrate on which the organic-inorganic coating layer is formed is not particularly limited as a porous substrate having pores.

Examples of porous substrates having usable pores include polyolefins, polyethylene terephthalate, polybutylene terephthalate, polyacetals, polyamides, polycarbonates, polyimides, polyether ether ketones, polyethersulfones, A porous substrate formed of at least one of rhenium sulfide, rhenium sulfide, and polyethylene naphthalene, and the like can be used as long as it can be used as a separator of an electrochemical device. As the porous substrate, a membrane or a nonwoven fabric may be used. The thickness of the porous substrate is not particularly limited, but may be 5 to 50 탆, and the pore size and porosity present in the porous substrate are also not particularly limited, but may be 0.01 to 50 탆 and 10 to 95%, respectively.

According to an aspect of the present invention, there is also provided a method of manufacturing a porous substrate, comprising: preparing a porous substrate having pores; Coating a first coating solution in which inorganic particles are dispersed and a binder polymer dissolved in a solvent on at least a part of at least one surface of the porous substrate to form a porous organic-inorganic coating layer; And a second coating solution containing inorganic particles, a binder polymer, and a phase change material are coated on the organic-inorganic coating layer, followed by drying to form a phase change material layer region Forming a separator on the surface of the separator.

First, a porous substrate having pores is prepared. The specific contents such as the kind of the porous substrate are as described above.

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

A first coating solution in which inorganic particles are dispersed and a binder polymer is dissolved in a solvent is coated on a porous substrate and dried to form a porous organic-inorganic coating layer. The humidity condition may be 10 to 80% at the time of coating, and if the solvent can be volatilized, any method such as hot air drying may be used.

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

Next, a second coating solution containing inorganic particles, a binder polymer, and a phase change material is coated on the organic-inorganic coating layer and the second coating solution is coated on the remaining portion of the porous substrate on which the organic-inorganic coating layer is not coated, Regions. At this time, the coating and drying method for forming the phase change material layer region can be applied to the same method as described above.

In addition, the phase change material may be applied onto the capsule as described above. The method for producing capsules carrying such phase-change materials is not particularly limited as long as it is a technique for producing particles of a core / shell structure. For example, it can be prepared by dispersing a phase-change material through an emulsification process in an aqueous solution and polymerizing the polymer on the surface of the oil phase. As the polymerization method at this time, interfacial polymerization, in-situ polymerization, coacervation and the like can be used. Accordingly, encapsulation of the phase change material according to the present invention may be performed by any method for general microcapsulation.

In the present specification, a combination of the above-described components described in one embodiment is not separately described. However, all of the components may be combined in two or more of them and adopted in various configurations of the present invention.

According to another aspect of the present invention, there is provided an electrochemical device comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, wherein the separator is the separator described above.

According to another aspect of the present invention, there is provided a fuel cell comprising: a plurality of unit cells each having a first separator and an anode and a cathode disposed on both sides of the first separator; And a second separator in the form of a strip interposed between adjacent unit cells in a plurality of unit cells stacked so that the cathodes of one unit cell and the anodes of the other unit cell correspond to each other and surround each unit cell Wherein the first separator and the second separator are each a separator including a phase change material layer region according to the present invention, and the phase change material layer region of the second separator is formed by stacking a plurality of unit cells Are interposed between unit cells adjacent to each other at a central portion of the electrochemical device.

At this time, the electrochemical device includes all devices that perform an electrochemical reaction, and specific examples thereof include capacitors such as all kinds of primary, secondary cells, fuel cells, solar cells, or super capacitor devices. In particular, the present invention can be applied to 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. In addition, the electrochemical device according to an embodiment of the present invention can be a small electrochemical device including one or two or more battery cells and a middle or large electrochemical device including a plurality of battery cells as a unit cell.

The electrochemical device can be manufactured according to a conventional method known in the art. For example, the separator may be manufactured by winding a separator between the positive electrode and the negative electrode, winding the separator, and injecting an electrolytic solution. In this case, the electrode assembly may be a jelly-roll type electrode assembly in which a separator coated with an electrolyte is disposed between a positive electrode and a negative electrode coated with an active material on a current collector, have.

Alternatively, in the case of a stacked type electrochemical device, unit cells are manufactured by interposing a first separator between an anode and a cathode, then unit cells are arranged on a second separator manufactured by the above-described method, folding manner to produce an electrode assembly, and then injecting an electrolytic solution.

The electrode to be used together with the separator according to an embodiment of the present invention is not particularly limited, and electrode active materials 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 A lithium complex oxide may be used. 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. 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.

The electrolyte solution that can be used in the present invention is a salt having a structure such as A ⁺ B ^- , wherein A ⁺ includes ions consisting of alkali metal cations such as Li ⁺ , Na ⁺ , K ⁺ , or combinations thereof, and B ^{- _{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) such as, ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC ), Dimethylsulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC), gamma butyrolactone, But are not limited to, those dissolved or dissociated in an organic solvent.

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.

Hereinafter, embodiments of the present invention will be described in detail to facilitate understanding of the present invention. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the following embodiments. Embodiments of the invention are provided to more fully describe the present invention to those skilled in the art.

Example  One: Separator  Produce

Formation of organic-inorganic porous coating layer

5% by weight of a polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP) polymer was added to acetone and dissolved at 50 ° C for about 12 hours or more to prepare a binder polymer solution. The Al ₂ O ₃ powder was added to the binder polymer solution so that the binder polymer / Al ₂ O ₃ ratio was 10/90 by weight, and the Al ₂ O ₃ powder was pulverized and dispersed for 12 hours or more using a ball mill Slurry. The slurry thus prepared was coated on the both surfaces of a polyethylene porous film (porosity of 45%) having a thickness of 12 탆 by a dip coating method and dried at a relative humidity of 40% to remove the organic-inorganic coating layer / RTI &gt;

Phase transformation Material layer  Formation of regions

10 parts by weight of polystyrene (PS) was dissolved in 90 parts by weight of dichloromethane to prepare 20 parts by weight of dispersion solution (a). Further, 80 parts by weight of an aqueous solution (b) was prepared by adding 10 parts by weight of Mg (NO ₃ ) ₂ .6H ₂ O as a phase-change material, 0.5 part by weight of gelatin as a surfactant, and 89.5 parts by weight of distilled water. The dispersion solution (a) was added to the aqueous solution (b) to form an oil / water emulsion. Then, the dichloromethane was removed by evaporation to obtain a polystyrene capsule carrying Mg (NO ₃ ) ₂ .6H ₂ O, which is a phase-change material. This was washed several times with distilled water to prepare capsules carrying the final phase change material. Since the dichloromethane, surfactant and distilled water used as raw materials were removed through washing and drying processes, the capsules containing the final phase change material only contain phase change material and polystyrene. The average diameter of the prepared capsules was 1 占 퐉.

In the same manner as in the method for forming an organic-inorganic porous coating layer, except that 100 parts by weight of the capsules carrying the phase change material, 90 parts by weight of Al ₂ O ₃ powder and 10 parts by weight of the binder polymer solution were used , A phase change material layer region was formed on the end of the polyethylene porous film at which the organic-inorganic porous coating layer was not formed, and finally a separator was produced.

Example  2: Preparation of lithium secondary battery

Cathode manufacturing

(N-methyl-2-pyrrolidone) as a negative electrode active material, polyvinylidene fluoride (PVdF) as a binder and carbon black as a conductive material were respectively 96 wt%, 3 wt% and 1 wt% (NMP) to prepare a negative electrode mixture slurry. The negative electrode mixture slurry was applied to a copper (Cu) thin film as an anode current collector having a thickness of 10 탆 and dried to produce a negative electrode, followed by roll pressing.

Manufacture of anode

92 wt% of a lithium cobalt composite oxide as a positive electrode active material, 4 wt% of carbon black as a conductive material, and 4 wt% of PVDF as a binder were added to N-methyl-2-pyrrolidone (NMP) . The positive electrode mixture slurry was applied to an aluminum (Al) thin film of a positive electrode current collector having a thickness of 20 탆 and dried to produce a positive electrode, followed by roll pressing.

The lithium secondary battery  Produce

An electrode assembly having a negative electrode and a positive electrode on both sides of the separator manufactured in Example 1 was produced. Then, a cylindrical lithium secondary battery was prepared by injecting an electrolyte solution of ethylene carbonate / ethyl methyl carbonate (EC / EMC = 1: 2, volume ratio) in which 1 M of lithium hexafluorophosphate (LiPF ₆ ) was dissolved into the assembled electrode assembly.

Example  3: Laminated type The lithium secondary battery  Produce

The separator prepared in Example 1 was used as a first separator and a second separator in this embodiment.

The unit cells were assembled by stacking the positive and negative electrodes fabricated in the first separator manufactured in Example 1 and the method described in Example 2.

Then, the unit cells were arranged on the second separator prepared in Example 1 so as to be spaced apart from each other in the longitudinal direction, and wound in a folding manner to produce an electrode assembly. Then, an electrolyte solution of ethylene carbonate / ethylmethyl carbonate (EC / EMC = 1: 2, volume ratio) in which 1 M of lithium hexafluorophosphate (LiPF ₆ ) was dissolved was injected into the assembled electrode assembly to prepare a lithium secondary battery.

Comparative Example  One

A lithium secondary battery was produced in the same manner as in Examples 1 and 2 except that a separator in which no phase change material layer region was formed in the separator end (wound outer periphery) was used.

Comparative Example  2

The present embodiment is an embodiment of a lithium secondary battery in which a conventional polyethylene porous film is used as a separator. That is, a lithium secondary battery was produced in the same manner as in Example 2, except that neither the organic-inorganic porous coating layer nor the phase-change material was applied to the porous polyethylene film.

Comparative Example  3

In this comparative example, a lithium secondary battery was manufactured by applying a capsule containing a phase change material on one end of a polyethylene porous film having no organic-inorganic porous coating layer formed thereon.

That is, in the same manner as in Examples 2 and 3 except that Al ₂ O ₃ powder was not used, 200 parts by weight of capsules carrying the phase change material prepared above and 10 parts by weight of the prepared binder polymer solution were used To prepare a lithium secondary battery.

Test Example : Separator  Results of physical property evaluation

The results of measurement of the shutdown temperature of the lithium secondary battery manufactured in Examples 2 and 3 and Comparative Examples 1 and 2, the air permeability of the separator used in the lithium secondary battery, the melting point, and the heat amount are shown in Table 1 below.

Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Air permeability of the membrane used (sec / 100ml) 800 800 300 160 1000 Melting point of phase-change material (℃) 86 86 - - 89 The amount of heat of the phase change material (Kcal / g) 30 to 40 30 to 40 - - 90-100 Shutdown Temperature (℃) 90-100 90-100 120 ~ 130 120 ~ 130 90-100

From the above, it can be seen that the shutdown temperatures of the lithium secondary batteries produced in Examples 2 and 3 are much lower than those of the lithium secondary batteries of Comparative Examples 1 and 2, and the phase change materials of Examples 2 and 3 are the phase change materials of Comparative Example 3 It can be confirmed that the phase conversion is performed at a lower calorie value. Therefore, compared with the lithium secondary batteries of Comparative Examples 1 to 3, the lithium secondary batteries manufactured in Examples 2 and 3 can more reliably block the lithium ion path in the event of heat generation, which is superior in battery safety. In addition, when an internal event occurs in an internal short circuit, the phase change material causes a phase change when the temperature inside the cell rises, absorbing heat generated by the phase change material, thereby delaying the temperature rise for a predetermined time.

11: Endothermic material
16: Porous organic-inorganic coating layer region
17, 27: Phase change material
18: Phase change material layer region
19: Adhesive layer
20: electrode assembly
21: cathode
22: First separator
23: anode
24: Unit cell
25: phase-change material layer region of the second separator
26: Second separator

Claims (22)

A plurality of unit cells each having a first separator and an anode and a cathode disposed on both sides of the first separator; And a plurality of unit cells arranged in a plurality of unit cells stacked so that the cathodes of one unit cell and the anodes of the other unit cell correspond to each other, In an electrochemical device having a separator,
Wherein the first separator and the second separator each have pores; And a porous organic-inorganic coating layer formed on at least one surface of the porous substrate, the porous organic-inorganic coating layer including a mixture of inorganic particles and a binder polymer,
At least a part of an end of the porous organic-inorganic coating layer of the second separator is formed as a phase change material layer region further including a phase change material,
Wherein the phase change material layer region of the second separator is interposed between unit cells adjacent to each other at a central portion of the plurality of stacked unit cells.
A cylindrical electrochemical device comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode,
The separator comprising a porous substrate having pores; And a porous organic-inorganic coating layer formed on at least one surface of the porous substrate, the porous organic-inorganic coating layer including a mixture of inorganic particles and a binder polymer,
At least a portion of the end of the porous organic-inorganic coating layer is formed as a phase change material layer region further including a phase change material,
Wherein the phase change material layer region is formed at the outermost portion of the positive electrode, the negative electrode, and the separator interposed between the positive and negative electrodes.
3. The method according to claim 1 or 2,
Wherein the phase-change material is a mixture of one or more selected from the group consisting of alkanes having from 11 to 50 carbon atoms, polyethylene glycol, inorganic hydrates, organic acids, and sugar alcohols.
The method of claim 3,
Wherein the phase-change material is supported on a capsule made of an inert material.
5. The method of claim 4,
Wherein the inert material is one or two kinds selected from the group consisting of polyolefin, polystyrene, polyacrylate, polyamide, polyester, polycaprolactone, polyurethane, gelatin, chitosan, cellulose, melamine resin, urea resin and derivatives thereof Or a mixture or copolymer of the foregoing.
3. The method according to claim 1 or 2,
Wherein the phase change material layer region further comprises a thermally conductive material.
delete 3. The method according to claim 1 or 2,
Wherein the porous substrate is a polyolefin porous film or a nonwoven fabric.
3. The method according to claim 1 or 2,
Wherein the porous substrate is selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polypropylene polyethylene terephthalate, polybutyleneterephthalate, polyester, polyacetal, polyamide, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylenesulfroid and polyethylene naphthalene (polyethylenenaphthalene), or a mixture of two or more thereof.
3. The method according to claim 1 or 2,
Wherein 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 transporting ability, and mixtures thereof.
11. The method of claim 10,
Wherein the inorganic particles having a dielectric constant of 5 or more are BaTiO ₃ , Pb (Zr _x , Ti _{1 -x} ) O ₃ (PZT, 0 <x <1), Pb _{1 -x} La _x Zr _{1 -y} Ti _y O ₃ , 0 <x <1, 0 <y <1), (1-x) Pb (Mg _1/3 Nb _2/3 ) O _3-x PbTiO ₃ (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 . And a mixture of two or more thereof.
11. The method of claim 10,
Wherein the inorganic particles having lithium ion transferring ability are lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y <3), 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 (Li _x Ge _y P _z S _w , , 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 &Lt; 7) -glass, or a mixture of two or more thereof.
3. The method according to claim 1 or 2,
Wherein the binder polymer is selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichlorethylene, polymethylmethacrylate, Polybutylene terephthalate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide (polyethylene) oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpyrrolidone, Polyvinyl alcohol (cyanoethylpolyviny a mixture of two or more selected from the group consisting of lanolin, lanolin, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose. Characterized in that the electrochemical device.
3. The method according to claim 1 or 2,
Wherein the content of the binder polymer is 1 to 50 parts by weight based on 100 parts by weight of the inorganic particles. 3. The method according to claim 1 or 2,
Wherein the phase change material layer region comprises 10 to 400 parts by weight of a phase change material based on 100 parts by weight of the total of the inorganic particles and the binder polymer.
3. The method according to claim 1 or 2,
Wherein the area of the phase change material layer region is 1 to 20% of the total surface area of the porous substrate.
delete delete 3. The method according to claim 1 or 2,
Wherein the electrochemical device is a lithium secondary battery.
delete delete delete

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