KR20130133444A - Endothermic separator for electrochemical elements and electrochemical elements comprising the same - Google Patents

Abstract

The present invention relates to an endothermic separating film for electrochemical elements for enhancing the safety of a battery by blocking a lithium ion path through having a PCM capsule to be melted while simultaneously absorbing heat when the heat is generated due to an internal short circuit by outer impact through including a capsule comprising the PCM at the outer part of winding part of the separating film. The present invention increases productivity and reducing the volume of an electrode assembly by easily manufacturing and maintaining optimal operating state by preventing the physical and chemical deformation of the separating film due to high temperature or accumulated heat and eventually suppressing the variation of the resistance of the electrochemical elements.

Description

Endothermic separator for electrochemical device and electrochemical device containing the same {Endothermic separator for electrochemical elements and electrochemical elements comprising the same}

The present invention relates to an endothermic separator for an electrochemical device and an electrochemical device containing the same. More specifically, a phase change material (PCM) is supported on an end region of the separator for an electrochemical device. An endothermic separator for an electrochemical device that includes a capsule ('PCM capsule') and heats due to an internal short circuit caused by an external shock, so that the PCM capsule absorbs heat and melts to block lithium ion paths to improve battery safety. It relates to an electrochemical device containing.

As technology development and demand for mobile devices increase, the demand for electrochemical devices as energy sources, especially secondary batteries, is increasing rapidly. Among them, many studies have been conducted on lithium secondary batteries with high energy density and high discharge voltage. It is also used commercially and widely.

Conventional lithium secondary batteries have a risk of ignition and explosion when exposed to high temperatures. In addition, even when a large current flows within a short time due to overcharging, an external short circuit, nail penetration, local crush, or the like, there is a risk of fire / explosion while the battery is heated by IR heating. In other words, when the temperature of the battery rises, the reaction between the electrolyte and the electrode is accelerated. As a result, heat of reaction is generated, and the temperature of the battery is further increased, thereby further accelerating the reaction between the electrolyte and the electrode. By this circulation, a thermal runaway phenomenon in which the temperature of the battery rises rapidly occurs, and when the temperature rises to a certain level or more, the battery may ignite. In addition, as a result of the reaction between the electrolyte and the electrode, gas is generated to increase the battery internal pressure, and the lithium secondary battery explodes above a certain pressure. The risk of ignition and explosion can be said to be the most fatal disadvantage of lithium secondary batteries.

Therefore, the essential considerations for the development of the lithium secondary battery is securing safety. In an effort to secure such safety, there are a method of mounting an element outside the cell and using a material inside the cell. PTC devices, CID devices, temperature protection circuits, and safety vents using changes in the breakdown voltage of the battery are examples of the former. The latter is the addition of substances that can be changed chemically and electrochemically.

Devices mounted outside the cell use temperature, voltage, and breakdown voltages, which can lead to reliable isolation. However, it is not known to play a protective role in the case of fast response time such as internal short circuit, bed penetration, local damage, etc.

One method of using a substance inside a cell is to add an additive that improves safety to an electrolyte or an electrode. Chemical safety devices have the advantage of being applicable to all kinds of batteries, but has the problem that the performance of the battery is degraded due to the addition of the material. As such a material, a material that forms a passivation layer on the electrode, a material that increases the resistance of the electrode while volume expansion occurs when the temperature rises, and the like have been reported. However, each of them has a problem in that by-products are generated during the formation of the passivation layer, thereby degrading the performance of the battery or increasing the volume of the battery.

Therefore, there is a high demand for the development of new safety means for preventing fire and explosion more quickly due to external impact or the like without degrading the overall performance of the battery.

The present invention aims to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

Specifically, the problem to be solved by the present invention is that when an internal short circuit occurs due to an external impact, the PCM capsule absorbs heat and melts, thereby lowering the temperature of the battery, as well as the molten liquid penetrates into the short circuit site. It is to provide a separator and an electrochemical device having the separator that can reduce the risk of explosion by blocking the flow. In addition, another technical problem to be solved by the present invention is to provide a method capable of easily manufacturing a separator having the above-mentioned object.

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

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

The phase change material may be supported in a capsule.

The capsule may be made of an inert material.

The inert material is one or two selected from the group consisting of polyolefin, polystyrene, polyacrylate, polyamide, polyester, polycaprolactone, polyurethane, gelatin, chitosan, cellulose, melamine resin, urea resin and derivatives thereof It may be a mixture or copolymer of the above.

The thermally conductive material may be further included in the phase change material layer region.

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 nonwoven fabric.

The porous substrate is a high density polyethylene, low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polypropylene polyethylene terephthalate (polyethyleneterephthalate), polybutylene terephthalate (polybutyleneterephthalate), polyester (polyester), polyacetal (polyacetal), polyamide (polyamide), polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfidro and polyethylenenaphthalene It may be formed of any one selected from the group consisting of (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.

The inorganic particles having a dielectric constant of 5 or more include 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 or It may be a mixture of two or more of them.

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

The binder polymer may be polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, Polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene vinyl acetate copolymer (polyethylene-co-vinyl acetate), polyethylene oxide oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethyl Polyvinyl alcohol (cyanoethylpolyviny) lalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose, or any mixture of two or more thereof. 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 include 10 to 400 parts by weight of the phase change material based on 100 parts by weight of the total of the inorganic particles and the binder polymer.

The formation 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, in an electrochemical device comprising an anode, a cathode, and a separator interposed between the anode and the cathode, an electrochemical device is provided in which the separator is the aforementioned separator.

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 strip type second interposed between adjacent unit cells in a plurality of unit cells stacked such that a cathode of one unit cell and an anode of another unit cell correspond to each other. In an electrochemical device including a separator, the first separator and the second separator are the aforementioned separators, and the phase change material layer region of the second separator is adjacent to each other at the center of the plurality of stacked unit cells. There is provided an electrochemical device interposed therebetween.

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

According to another aspect of the invention, the method comprising the steps of preparing a porous substrate having pores; Forming a porous organic-inorganic coating layer by coating and drying a first coating solution in which inorganic particles are dispersed and a binder polymer dissolved in a solvent on at least one surface of the porous substrate; And coating and drying the second coating solution including the inorganic particles, the binder polymer, and the phase change material, followed by the organic-inorganic coating layer on the remaining portion of the porous substrate which is not coated with the organic-inorganic coating layer. There is provided a method of manufacturing a separator comprising forming a.

The phase change material may be supported in a capsule.

As described above, the electrochemical device according to the present invention includes a PCM capsule in the end region of the separator, thereby preventing physical and chemical deformation of the separator due to high or accumulated heat, thereby ultimately changing the electrochemical device resistance. Inhibition has the effect of maintaining the optimum operating state.

In particular, 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, and when applied to a stacked electrochemical device, between a first separator and a unit cell in a unit cell. Since the second separator has a heat absorbing function dually, the stability is further improved.

In addition, compared to the conventional heat absorbing sheet is easy to manufacture productivity has the effect of reducing the volume of the electrode assembly.

1A is a view 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 a separator according to one embodiment of the present invention is wound for use in a cylindrical electrochemical device.
4 is a schematic perspective view of an embodiment of the present invention in which each unit cell includes a first separator and a plurality of such unit cells are arranged 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 or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

According to the present invention, the electrochemical device includes an electrochemical device including a plurality of unit cells as well as an electrochemical device including only one unit cell.

In the present invention, 'separator' and 'separator' are the same terms that may be used interchangeably.

In the present invention, 'first separator' and 'second separator' are terms used in a stacked electrochemical device including a plurality of unit cells, and 'first separator' is used in a unit cell to be interposed between an anode and a cathode. The term "separator" refers to a separator, and the term "second separator" is understood as a term referring 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 the electrochemical device including the positive electrode, the separator, the negative electrode, and the electrolyte, at least a part of the end of the porous organic-inorganic coating layer of the separator is formed of a phase conversion material layer region including a phase change material (PCM) In addition, the separator itself is endothermic, and the heat generated during the internal short circuit of the battery melts the phase change material to lower the temperature of the battery, and the molten liquid penetrates into the short circuit site to block the flow of electricity. The electrochemical device according to the present invention is to secure the safety of the electrochemical device in a manner different from the conventional method, unlike the case where a conventional device or a protective circuit is mounted on the outside of the cell is interposed between the electrode or wrap the cell The phase change material may act more sensitively to heat generation, thereby rapidly lowering the temperature, and furthermore, the melted phase change material may be introduced into the short-circuit to block electrical conduction. In addition, unlike the conventional method of using a chemical inside the cell has the advantage that no side effects such as performance degradation and capacity reduction of the battery at all.

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

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

The phase change material may undergo a phase change at the predetermined temperature, for example, a phase change from a solid phase to a liquid phase or a liquid phase to a solid phase, and exhibit latent heat at least greater than the heat capacity per unit temperature of the electrochemical element components. Branch means a substance. The phase change material may be a single compound, a mixture or a complex. The phase change of these materials includes not only the case of physical phase change at the predetermined temperature, but also the case where a mixture of two or more materials phase change by reversible physical or chemical reaction at the predetermined temperature.

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

Representative examples of the phase change material, n-Tetradedecane (n-Tetradecane), n-hexadecane (n-Hexadecane), n-Paraffin (n-Paraffin), n-Odecadecane (n-Octadecane), n- N-eicosane, n-heneicosane, n-docosane, trichoic acid (n-tricosane), tetracosane, hexacosane, hexacosane, nonacosane Alkanes 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 ) Inorganic hydrates such as ₂ 6H ₂ O and the like; Organic acids such as carboxylic acids such as acetic acid, butyric acid, palmitic acid, oxalic acid, tartaric acid, myristic acid, stearic acid, n-octanoic acid, ascorbic acid, uric acid, sulfonic acid, sulfinic acid, phenol and the like; Although sugar alcohols, such as xylitol, are mentioned, It is not limited only 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 about 75 ° C.), Na ₃ PO ₄ · 12H ₂ O (melting point about 75 ° C.) ), Mg (NO ₃ ) ₂ 6H ₂ O (melting point about 89 ° C.), xylitol (melting point about 93 to 95 ° C.) and the like can be used in particular.

In the present specification, the term "paraffin" refers to paraffin lead or liquid paraffin made of paraffinic hydrocarbons, and these materials are weak in reactivity 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, since the heat of fusion of a solid substance is used, paraffin lead, which is a solid paraffin, is used.

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

As used herein, the term "specific temperature" refers to a temperature that may impair the performance or lifespan of an electrochemical device or threaten safety. 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 ° C., or in a temperature range of 60 to 120 ° C.

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

The phase change material may be included in the separator in a state of being supported in a capsule, thereby providing endothermic function to the separator itself. The encapsulated phase change material may be more responsive to heat due to its high specific surface area.

The capsule carrying the phase change material must be at least inert to the components of the cell and the material that can remain sealed even after phase change.

Examples of such inert materials include polyolefins such as polyethylene, polypropylene, and the like; polystyrene; Polyacrylates such as polymethacrylate, polymethylmethacrylate, 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; It may be made of derivatives and the like, but is not limited thereto. In some cases, a combination of two or more of these materials may be used together to form a capsule. In addition, the capsule may be a blended polymer particle in which homopolymers such as polystyrene, polymethacrylate, polyethylene, and the like, and block copolymers such as polystyrene-polymethylmethacrylate and polyethylene oxide-polymethylmethacrylate are mixed with each other. . Such blend-type polymer particles may be formed of multilayer capsule particles having a core part and two or more shell parts by appropriately adjusting the type of polymer used.

Also, in some cases, the capsule may be made of a material that breaks down or breaks above a critical temperature. The threshold temperature may be, for example, a temperature at which a battery may ignite or explode in terms of safety of the battery.

The thickness of the capsule covering the phase change material is not particularly limited as long as it can exert the effect according to the present invention, and may be 0.01 to 5 μm, or 0.02 to 0.1 μm in consideration of thermal conductivity and form safety of the capsule. have.

If the thickness of the capsule is too thin, it is difficult to stably retain the phase change material. On the contrary, if the thickness is too thick, the thermal conductivity may decrease and the amount of phase change material may be relatively reduced.

In addition, the capsule may have a particle diameter of approximately 0.1 to 100 μm, or 0.5 to 10 μm. It may be a small particle size having a large surface area per unit weight in terms of exhibiting rapid reactivity with temperature changes, but too small a particle size may be difficult to manufacture the capsule itself carrying a phase change material, it is included in the battery Since there may be difficulties in the process to make, it can be determined appropriately in the above range.

In some cases, a thermally conductive material having a high thermal conductivity may be further added to the inert material in order 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.

As used herein, the term "phase conversion material layer region" refers to a region in which a phase change material is further included in at least a portion of an end portion of the porous organic-inorganic coating layer of the separator.

The phase change material layer region is formed at the end of the separator in contact with the porous organic-inorganic coating layer containing no phase change material in the separator.

In particular, in the electrochemical device including one unit cell, the phase change material layer region may form a winding outer portion when the separator is wound. In this case, the term 'winding outer part' is understood as a term meaning an end of the separator in which the separator starts to be wound together with the positive electrode and the negative electrode, that is, the end other than the winding core end. 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 the center of the stacked unit cells. can do.

Since the content of the phase change material may be determined by various factors such as the type of phase change material, the type and shape of the battery, the content of the phase change material is not particularly limited. As an example, the function of the porous organic-inorganic coating layer of the separator The phase change material layer may include 10 to 400 parts by weight, or 80 to 300 parts by weight of the phase change material based on 100 parts by weight of the total amount of the inorganic particles and the binder polymer so as to exert the desired effect in the present invention without inhibiting. can do.

The formation 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.

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

That is, the separator according to the embodiment of the present invention may extend to the phase change material layer region to further form an adhesive layer, and when the electrode assembly is wound with the separator, the adhesive layer of the end portion may be bonded to the opposing porous substrate. It is possible to serve to fix the electrode assembly.

In the present invention, not only an electrochemical device including one unit cell including a cathode and an electrode on both sides of the separator of the present invention is provided, but an electrochemical device including a plurality of such unit cells is also provided.

That is, a plurality of unit cells each having a first separator and a positive electrode and a negative electrode positioned on both sides of the first separator; And a strip type second interposed between adjacent unit cells in a plurality of unit cells stacked such that a cathode of one unit cell and an anode of another unit cell correspond to each other. In the electrochemical device comprising a separator, the first separator and the second separator is a separator including a phase change material layer region according to the present invention, wherein the phase change material layer region of the second separator is a plurality of stacked An electrochemical device is provided which is interposed between unit cells adjacent to each other at a central portion of the unit cells.

The phase change material layer region of the second separator is interposed between adjacent unit cells at the center of the stacked unit cells, and the center of the stacked unit cells corresponds to a section showing the highest temperature in the electrochemical device. This makes it possible to prevent the internal temperature from rising more efficiently. That is, in an electrochemical device composed of stacked unit cells, the temperature inside the cell increases as time passes during operation of the device. At this time, the cells adjacent to the upper and lower parts of the device are adjacent to a relatively low temperature atmosphere of the outside to radiate heat inside the cell, but the heat emitted from the unit cells located at the center of the stacked structure is not discharged to the outside. In addition, it accumulates in the center and provides a cause for raising the temperature inside the electrochemical device.

However, when an endothermic layer is introduced on the electrode surface or the separator surface of all the unit cells in order to absorb the heat dissipated early, a certain result may be achieved for the purpose of absorbing heat inside the device. A plurality of heat absorbing layers introduced into the unit cells may serve as a resistor of the electrochemical device, which may cause a decrease in the performance of the electrochemical device.

Therefore, the electrochemical device according to an aspect of the present invention introduces a phase conversion material layer region at a position corresponding to the central portion of the most heat generated in the stacked structure of the unit cells, thereby minimizing the impact on the performance of the electrochemical device abnormal In the operating state, it is possible to efficiently absorb the calorific value of the battery, and to improve temperature control and overcharge performance inside the cell.

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

1A and 1B are views illustrating a comparison between a conventional endothermic sheet and a separator including a phase change material region layer at an outer portion of a winding according to the present invention.

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

It is a schematic diagram of the cross-sectional structure which concerns on one aspect of the separator which concerns on this invention.

Referring to FIG. 2, a separator is provided with a porous organic-inorganic coating layer region 16 in which a phase change material is not dispersed, followed by a phase change material layer region 18 in which a phase change material is dispersed, and an adhesive layer 19. Is shown. In this case, the phase change material may be supported in a sealed form in a capsule made of an inert material as described above, and as a result, the phase change material has a large contact interface area per weight of the phase change material. Responsiveness can be further improved.

3 is a schematic top view of an embodiment in which the separator of the present invention is wound for use in a cylindrical electrochemical device.

Referring to FIG. 3, a separator interposed between the positive electrode and the negative electrode is wound together with the positive electrode and the negative electrode so that the phase change material layer region forms the winding outer portion 18, and the pore containing no phase change material therein. There will be an organic-inorganic coating layer region 16. In this case, the adhesive layer 19 may be further formed by selectively extending to the phase change material layer region.

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.

As such, when the second separator 26 having the plurality of unit cells 24 and the phase change material layer region 25 is wound to have the phase change material layer region 25 positioned at the center thereof, the electrode assembly illustrated in FIG. 5 is wound. Can be obtained.

Referring to FIG. 5, the electrode assembly 20 includes a plurality of unit cells 24 each having a first separator 22 and a cathode 21 and an anode 23 positioned at 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 the positive electrode current collector, and the negative electrode 21 has a structure in which a negative electrode active material layer is formed on both sides of the negative electrode current collector. As shown in FIG. 5, the unit cell has a full cell structure in which one anode 23 and one cathode 21 are positioned at both sides of the first separator 22, or a unit cell is formed on both sides of the anode 23 or the cathode 21. Each separator 22 may be disposed, and each of the first separators 22 may be formed of a unit cell having various structures such as a bi-cell structure in which a cathode 21 or an anode 23 is positioned.

Within the electrode assembly 20, each unit cell 24 is present in a stacked form. In this case, a strip-shaped second separator is disposed between the adjacent unit cells 24 so that the cathode of one unit cell and the anode of the other unit cell correspond to each other. Reference numeral 26 is provided in various forms as shown in FIG. 5 to perform a separator function between each unit cell 24.

In this case, 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 center of the stacked structure of the unit cells 24, and the second separator It is wrapped by 26 and introduced into the electrode assembly 20.

The inorganic particles used to form 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 inorganic particles are not oxidized and / or reduced in the operating voltage range (for example, 0 to 5 V on the basis of 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 aforementioned reasons, the inorganic particles may include high dielectric constant inorganic particles having a dielectric constant of 5 or more, or 10 or more, inorganic particles having a lithium ion transfer ability, or a mixture thereof. Non-limiting 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, where 0 <x <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 μm as much as possible in order to form a coating layer having a uniform thickness and an appropriate porosity. When the inorganic particle size satisfies this range, the dispersibility is maintained to easily control the physical properties of the separator, and the phenomenon of increasing the thickness of the porous organic-inorganic coating layer can be avoided, thereby improving mechanical properties. In addition, due to the excessively large pore size, the possibility of internal short circuit during battery charging and discharging may be reduced.

The binder polymer used to form 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. may be used, because it may improve mechanical properties such as flexibility and elasticity of the finally formed organic-inorganic coating layer. . Such a binder faithfully plays a role of a binder for stably connecting and stably separating inorganic particles, thereby contributing to preventing mechanical property degradation of the separator into which the porous coating layer is introduced.

In addition, the binder does not necessarily have an ion conducting ability, but when a polymer having an ion conducting ability is used, the performance of the electrochemical device may be further improved. Therefore, the binder may use one with the highest possible dielectric constant. In fact, since the degree of dissociation of the salt in the electrolyte depends on the permittivity constant of the electrolyte solvent, the higher the dielectric constant of the polymer, the higher the dissociation of salt in the electrolyte. The dielectric constant of such a binder can be in the range of 1.0 to 100 (measuring frequency = 1 kHz), in particular 10 or more.

In addition to the functions described above, the binder may have a feature that can exhibit a high degree of swelling of the electrolyte by gelling upon impregnation of the 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 ulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyimide or these And mixtures thereof. In addition, any material including the above-mentioned characteristics may be used alone or in combination.

The content of the binder polymer of 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 based on 100 parts by weight of inorganic particles. It may be 15 parts by weight. When the content of the binder polymer satisfies this range, problems such as desorption of the inorganic material, and a phenomenon in which the binder polymer blocks pores of the porous substrate may 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, a binder polymer is located as a coating layer on a part or all of the surface of the inorganic particles, the inorganic particles are connected and fixed to each other by the coating layer in close contact, Pores may be formed due to the empty space present between the inorganic particles. In other words, the inorganic particles of the porous organic-inorganic coating layer are in close contact with each other, and the empty space generated when the inorganic particles are in close contact with the pores of the porous organic-inorganic coating layer. The size of the void space present between the inorganic particles may be equal to or smaller than the average particle diameter of the inorganic particles. A binder polymer positioned as a coating layer on part or all of the surface of the inorganic particles connects and fixes the inorganic particles to each other, 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 inorganic particles and a binder polymer is not particularly limited, but may be in a range of 0.5 to 10 μm.

In the separator according to an 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 polyolefin, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenyl There are porous substrates formed of at least one of lensulfide and polyethylene naphthalene, and in general, any one that can be used as a separator of an electrochemical device can be used. As the porous substrate, both membrane and nonwoven fabrics may be used. The thickness of the porous substrate is not particularly limited, but may be 5 to 50 μm, and the pore size and pore present in the porous substrate are also not particularly limited, but may be 0.01 to 50 μm and 10 to 95%, respectively.

In addition, according to one aspect of the invention, preparing a porous substrate having pores; Forming a porous organic-inorganic coating layer by coating and drying a first coating solution in which inorganic particles are dispersed and a binder polymer dissolved in a solvent on at least one surface of the porous substrate; And coating and drying the second coating solution including the inorganic particles, the binder polymer, and the phase change material, followed by the organic-inorganic coating layer on the remaining portion of the porous substrate which is not coated with the organic-inorganic coating layer. There is provided a method of manufacturing a separator comprising forming a.

First, a porous substrate having pores is prepared. Specific contents such as the type of the porous substrate are as described above.

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

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

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

Subsequently, the organic-inorganic coating layer is coated with a second coating solution including the inorganic particles, the binder polymer, and the phase change material, followed by the organic-inorganic coating layer, and then dried on the remaining portion of the porous substrate which is not coated. Form an area. In this case, the coating and drying methods for forming the phase change material layer region may be equally applied.

In addition, the phase change material may be applied in a capsule as described above. The method for preparing a capsule supporting such a phase change material is not particularly limited as long as it is a technique for preparing particles having a core / cell structure. For example, the phase change material may be prepared by dispersing in an aqueous solution through an emulsification process and polymerizing a polymer on the surface of its oil phase. In this case, as the polymerization method, interfacial polymerization, in-situ polymerization, coacervation method, or the like may be used. Therefore, the encapsulation of the phase change material according to the present invention may be used as long as it is a method for general microcapsulation.

In the present specification, a combination example of the above-described components described as an embodiment is not separately indicated, but all the components may be combined with two or more of each other to be adopted in various configurations of the present invention.

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

In addition, according to another aspect of the invention, a plurality of unit cells each having a first separator and a positive electrode and a negative electrode located on both sides of the first separator; And a strip-shaped second separator interposed between adjacent unit cells in a plurality of unit cells stacked so that a cathode of one unit cell and an anode of another unit cell correspond to each other. In the electrochemical device, each of the first separator and the second separator is a separator including a phase change material layer region according to the present invention, wherein the phase change material layer region of the second separator is a plurality of unit cells stacked An electrochemical device is provided, which is interposed between unit cells adjacent to each other at a central portion of the same.

In this case, the electrochemical device includes all devices that undergo an electrochemical reaction, and specific examples thereof include capacitors such as all kinds of primary, secondary cells, fuel cells, solar cells, or supercapacitor devices. In particular, the secondary battery may 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 may be both a small electrochemical device including one or two or four battery cells and a medium to large electrochemical device including a plurality of battery cells as a unit cell.

Electrochemical devices can be prepared according to conventional methods known in the art. For example, the separator prepared by the above-described method may be manufactured by winding the separator between the positive electrode and the negative electrode and injecting the electrolyte solution. In this case, the electrode assembly may be a jelly-roll type electrode assembly in which a separator having an electrolyte is coated between a positive electrode and a negative electrode on which an active material is applied on a current collector is placed, wound, and made into a cylindrical structure and then compressed in a thickness direction. have.

Alternatively, in the case of a stacked electrochemical device, unit cells are manufactured by interposing a first separator between an anode and a cathode, and then unit cells are spaced apart from each other on a second separator manufactured by the above-described method, and then folded. The electrode assembly may be prepared by folding in a folding manner and then injected with an electrolyte solution.

The electrode to be applied together with the separator according to an embodiment of the present invention is not particularly limited, and according to a conventional method known in the art, the electrode active material may be prepared in a form bound to the electrode current collector. Non-limiting examples of the positive electrode active material of the electrode active material may be a conventional positive electrode active material that can be used for the positive electrode of the conventional electrochemical device, in particular lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide or combinations thereof One lithium composite oxide can be used. Non-limiting examples of the negative electrode active material may be a conventional negative electrode active material that can be used for the negative electrode of the conventional electrochemical device, in particular lithium metal or lithium alloys, carbon, petroleum coke, activated carbon, Lithium adsorbents such as graphite or other carbons. Non-limiting examples of the positive current collector include aluminum, nickel, or a combination thereof. Examples of the negative current collector include copper, gold, nickel, or a copper alloy or a combination thereof Foil to be manufactured, and the like.

Electrolyte that may be used in the present invention is A ⁺ B ^- A salt of the structure, such as, A ⁺ is Li ^+, Na ^+, K ^+, and contains the ion consisting of alkali metal cations or a combination of both B ^- is PF _{^{6 -, BF 4 -, Cl}} -, Br -, I -, ClO 4 -, AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N (CF 3 SO 2) 2 -, C (CF 2 Salts containing ions consisting of anions such as SO ₂ ) ₃ ^- or a combination thereof are propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC ), Dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethylcarbonate (EMC), gamma butyrolactone or mixtures thereof Some are dissolved or dissociated in the organic solvent, but are not limited thereto.

The electrolyte injection may be performed at an appropriate stage of the battery manufacturing process, depending on the manufacturing process and the required physical 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. Al ₂ O ₃ powder was added to the prepared binder polymer solution to a binder polymer / Al ₂ O ₃ = 10/90 weight ratio, and the Al ₂ O ₃ powder was crushed and dispersed using a ball mill for at least 12 hours. Slurry was prepared. The slurry thus prepared was coated by the method of dip coating except for a predetermined end of both sides of a polyethylene porous film (porosity 45%) having a thickness of 12 μm and dried at 40% relative humidity to obtain an organic-inorganic coating layer. Formed.

Phase transformation Material layer  Formation of zone

10 parts by weight of polystyrene (PS) was dissolved in 90 parts by weight of dichloromethane to prepare 20 parts by weight of the dispersion solution (a). In addition, 80 parts by weight of an aqueous solution (b) was prepared by combining 10 parts by weight of Mg (NO ₃ ) ₂ .6H ₂ O as a phase change material, 0.5 parts by weight of gelatin as a surfactant, and 89.5 parts by weight of distilled water. The dispersion (a) was added to the aqueous solution (b) to form an oil / water emulsion. Then, dichloromethane was removed by evaporation to obtain a polystyrene capsule carrying Mg (NO ₃ ) ₂ .6H ₂ O as a phase change material. This was washed several times in distilled water to prepare a capsule supporting the final phase change material. Since dichloromethane, surfactant, and distilled water used as raw materials were removed through washing and drying, only the phase change material and the polystyrene were included in the capsule carrying the final phase change material. At this time, the average diameter of the capsule produced was 1㎛.

By the same method as the method of forming the organic-inorganic porous coating layer except that 100 parts by weight of the capsule supporting the prepared phase change material, 90 parts by weight of Al ₂ O ₃ powder, 10 parts by weight of the prepared binder polymer solution. In the polyethylene porous film, the phase-conversion material layer region was formed at the end where the organic-inorganic porous coating layer was not formed, thereby finally preparing a separator.

Example  2: Manufacturing of Lithium Secondary Battery

Cathode manufacturing

N-methyl-2, a solvent, was prepared by using carbon powder as a negative electrode active material, polyvinylidene fluoride (PVdF) as a binder, and carbon black as a conductive material, respectively, at 96% by weight, 3% by weight, and 1% by weight. A negative electrode mixture slurry was prepared by adding to Rollidone (NMP). 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% by weight of a lithium cobalt composite oxide as a positive electrode active material, 4% by weight of carbon black as a conductive material, and 4% by weight of PVDF as a binder were added to N-methyl-2 pyrrolidone (NMP) as a solvent to slurry a positive electrode mixture. Was prepared. The positive electrode mixture slurry was applied to an aluminum (Al) thin film of a positive electrode current collector having a thickness of 20 μm, and a positive electrode was manufactured by drying, followed by roll press.

The lithium secondary battery  Produce

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

Example  3: Laminated type The lithium secondary battery  Produce

The separator prepared in Example 1 was used as the first separator and the second separator in this example.

The unit cells were assembled by stacking the first separator prepared in Example 1 and the anode and cathode manufactured in the manner described in Example 2.

Subsequently, the unit cells were spaced apart from each other in the longitudinal direction on the second separator manufactured in Example 1 and wound in a folding manner to prepare an electrode assembly. Then, a lithium secondary battery was prepared by injecting an ethylene carbonate / ethyl methyl carbonate (EC / EMC = 1: 2, volume ratio) -based electrolyte solution in which 1 M of lithium hexafluorophosphate (LiPF ₆ ) was dissolved.

Comparative Example  One

A lithium secondary battery was manufactured in the same manner as in Examples 1 and 2, except that a separator in which a phase conversion material layer region was not formed at the separator end (the wound outer portion) was used.

Comparative Example  2

This embodiment is to implement a lithium secondary battery embodiment produced using a conventional polyethylene porous film as a separator. That is, a lithium secondary battery was manufactured 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 polyethylene porous film.

Comparative Example  3

This comparative example implements a lithium secondary battery embodiment prepared by applying a capsule carrying a phase change material on one end of a polyethylene porous film in which the organic-inorganic porous coating layer is not formed.

That is, the same method as in Examples 2 and 3, except that Al ₂ O ₃ powder is not used, but 200 parts by weight of the capsule supporting the prepared phase change material and 10 parts by weight of the prepared binder polymer solution are used. A lithium secondary battery was prepared.

Test Example : Separator  Results of physical property evaluation

Shutdown temperature of the lithium secondary batteries prepared in Examples 2 and 3 and Comparative Examples 1 and 2, wherein the air permeability, melting point, and calorific value of the separator used in the lithium secondary battery are shown in Table 1 below:

Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Aeration of the separator used (sec / 100ml) 800 800 300 160 1000 Melting point of phase change material (℃) 86 86 - - 89 Calories of 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, the shutdown temperature of the lithium secondary batteries prepared in Examples 2 and 3 is much lower than that 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 seen that the phase change at lower calories. Therefore, the lithium secondary batteries prepared in Examples 2 and 3 can more reliably block the lithium ion path when heat is generated, compared to the lithium secondary batteries of Comparative Examples 1 to 3, which is excellent in terms of battery safety. In addition, when an event occurs due to an internal short circuit and the temperature inside the cell rises, the phase change material absorbs heat generated by causing a phase shift, 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 porous substrate having pores; And a porous organic-inorganic coating layer formed on at least one surface of the porous substrate and including a mixture of inorganic particles and a binder polymer.
At least a portion of an end of the porous organic-inorganic coating layer further includes a phase change material to form a phase change material layer region.
The method of claim 1,
The phase change material is a separator, characterized in that one or two or more selected from the group consisting of alkanes, polyethylene glycol, inorganic hydrates, organic acids and sugar alcohols having 11 to 50 carbon atoms.
The method of claim 1,
Separator characterized in that the phase change material is carried in a capsule.
The method of claim 3,
Separator, characterized in that the capsule is made of an inert material.
5. The method of claim 4,
One or two selected from the group consisting of polyolefin, polystyrene, polyacrylate, polyamide, polyester, polycaprolactone, polyurethane, gelatin, chitosan, cellulose, melamine resin, urea resin and derivatives thereof The separator characterized by the above-mentioned mixture or copolymer.
The method of claim 1,
And a thermally conductive material is further included in the phase change material layer region.
The method of claim 1,
And the phase change material layer region forms an outermost portion when the separator is wound.
The method of claim 1,
Wherein the porous substrate is a polyolefin porous film or a nonwoven fabric.
The method of claim 1,
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.
The method of claim 1,
Wherein the inorganic particles are 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.
The method of claim 10,
The inorganic particles having a dielectric constant of 5 or more include 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 or Separator which is a mixture of 2 or more types of these.
The method of claim 10,
The inorganic particles having the lithium ion transfer 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 <x <4 , 0 <y <1, 0 <z <1, 0 <w <5), lithium nitride (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) series glass and P ₂ S ₅ (Li _x P _y S _z , 0 <x <3, 0 <y <3, 0 <z <7) A separator, which is any one selected from the group consisting of series glass or a mixture of two or more thereof.
The method of claim 1,
The binder polymer is polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, Polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene vinyl acetate copolymer, polyethylene oxide oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethyl Polyvinyl alcohol (cyanoethylpolyviny) lalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose, or any mixture of two or more thereof. Separator characterized by the above.
The method of claim 1,
The separator is characterized in that the content of the binder polymer is 1 to 50 parts by weight based on 100 parts by weight of the inorganic particles. The method of claim 1,
And the phase change material layer region comprises 10 to 400 parts by weight of the phase change material based on 100 parts by weight of the total of the inorganic particles and the binder polymer.
The method of claim 1,
And the formation area of the phase change material layer region is 1 to 20% of the total surface area of the porous substrate.
In the electrochemical device comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode,
The separator is an electrochemical device according to any one of claims 1 to 16.
A plurality of unit cells each having a first separator and an anode and a cathode positioned 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,
Each of the first separator and the second separator is the separator according to any one of claims 1 to 16,
The phase change material layer region of the second separator is interposed between unit cells adjacent to each other at the central portion of the plurality of stacked unit cells.
18. The method of claim 17,
Wherein the electrochemical device is a lithium secondary battery.
19. The method of claim 18,
Wherein the electrochemical device is a lithium secondary battery.
Preparing a porous substrate having pores therein;
Forming a porous organic-inorganic coating layer by coating and drying a first coating solution in which inorganic particles are dispersed and a binder polymer dissolved in a solvent on at least one surface of the porous substrate; And
The organic-inorganic coating layer is coated with a second coating solution including the inorganic particles, the binder polymer and the phase change material followed by the organic-inorganic coating layer on the remaining portion of the porous substrate which is not coated. Method for producing a separator comprising the step of forming.
The method of claim 21,
The method of manufacturing a separator, wherein the phase change material is supported in a capsule.

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