KR101882920B1 - Capsule type foaming agents, coating composition for separator comprising the same, the separator, and secondary cell comprising the same - Google Patents

Abstract

The present invention provides a capsule comprising a first shell, a first core comprised of the first shell, and a core-shell structure encapsulated in the first core, the capsule comprising a second shell and a second shell, Wherein the first shell is a thermoplastic resin and the first core agent comprises a volatile swelling agent, and a separator coating composition comprising the same, a separator thereof, and a secondary battery comprising the same According to the present invention, in the event of an accident of a secondary battery, due to the volume expansion of the separator during heating, current is prevented from flowing to the electrode by distancing the electrodes, thereby causing an overcurrent and an explosion of the battery due to short- .

Description

TECHNICAL FIELD [0001] The present invention relates to a capsule type foaming agent, a separator coating composition containing the same, a separator coating composition containing the same, a secondary battery including the separator, and a secondary battery comprising the same. BACKGROUND ART [0002]

The present invention relates to a capsule type foaming agent, a separator coating composition containing the same, a separator thereof, and a secondary battery comprising the same.

Video cameras, portable telephones, and portable PCs, the demand for secondary batteries as energy sources is rapidly increasing, and accordingly, many studies have been made on batteries that can meet various demands. Typically, a lithium cobalt polymer battery, which has high thickness and which has high demand for a prismatic battery and a pouch-type battery that can be applied to products such as mobile phones and the like, and has excellent energy density, discharge voltage, There is a high demand for the same lithium secondary battery.

However, when the secondary battery is overheated, there is a risk of explosion, so securing safety is one of the important tasks. Overheating of a secondary battery occurs for a variety of reasons, one of which is a case where an overcurrent exceeds a limit through a secondary battery. When the overcurrent flows, the temperature of the secondary battery rises and the internal temperature of the secondary battery rises rapidly. In addition, the rapid rise of the temperature causes a decomposition reaction of the electrolyte, thereby causing a thermal runaway, which eventually leads to the explosion of the battery.

The overcurrent is caused by the breakdown of the insulation between the anode and the cathode due to the shrinkage of the separator (separator) interposed between the positive electrode and the cathode, or the charging circuit or load connected to the outside, current is applied to the battery. Therefore, in order to prevent the deterioration of the secondary battery due to the overcurrent, there is a high need for a secondary battery having excellent safety that can quickly prevent the overcurrent.

The present invention provides a capsule-type foaming agent which is thermally expanded at a high temperature or is discharged from a flame retardant to prevent ignition.

In addition, the present invention provides a separator coating composition and a separator thereof which are excellent in safety by preventing a phenomenon such as an overcurrent and a battery explosion, which are generated from elements that threaten safety such as high temperature or short circuit, So as to provide a secondary battery excellent in safety.

According to one embodiment of the present invention, there is provided a method of manufacturing a capsule comprising a first shell, a first core comprised of the first shell, and a core-shell structure encapsulated in the first core, And a second core agent contained in the second shell, wherein the first shell is a thermoplastic resin, and the first core agent comprises a volatile swelling agent.

The thermoplastic resin may be at least one selected from the group consisting of an acrylonitrile copolymer and a vinylidene chloride copolymer.

The volatile swelling agent may be a hydrocarbon.

The first core agent may comprise a capsule of a plurality of core-shell structures.

The second shell may be at least one selected from the group consisting of a polyethylene-based resin, a polypropylene-based resin, and a polystyrene resin.

The second core agent may comprise a flame retardant material.

The flame retardant may be a fluoride-based compound.

The capsular foaming agent may have a thermal expansion operating temperature of 110 to 260 ° C.

According to one embodiment of the present invention, there is provided a separator coating composition comprising the encapsulated foaming agent and ceramic particles.

The capsule type foaming agent may be contained in an amount of 5 to 10% by weight based on the total weight of the separator coating layer composition.

The ceramic particles may be selected from the group consisting of Al ₂ O ₃ , BaTiO ₃ , CaO, CeO ₂ , NiO, MgO, SiO ₂ , SnO ₂ , SrTiO ₃ , TiO ₂ , Y ₂ O ₃ , ZnO, ZrO ₂ , Pb (Zr, ₃ (PZT), Pb _{1 -} from the group consisting of _{y TiyO 3 (PLZT), PB} (Mg 3 Nb 2/3) O 3 -PbTiO 3 (PMN-PT) and _{hafnia (HfO 2) - x La} x Zr 1 It may be more than one selected.

According to an embodiment of the present invention, there is provided a separator for a secondary battery comprising a porous support and a coating layer formed on the at least one surface of the porous support with the sera paint coating composition.

The porous support may be a microporous membrane or a nonwoven fabric comprising at least one component selected from the group consisting of polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene terephthalate and polybutylene terephthalate.

The coating layer may have a thickness of 1.5 to 5.5 mu m.

According to an embodiment of the present invention, a secondary battery including the separator can be provided.

The capsular foaming agent according to an embodiment of the present invention has an effect of preventing thermal ignition due to thermal expansion or discharge of flammable material at a high temperature.

In addition, according to the present invention, by preventing the current from flowing to the electrode by distancing the gap between the electrodes due to the volume expansion of the separator during heat generation in the secondary battery, it is possible to prevent overcurrent and explosion of the battery due to short- . Further, since the volume expansion of the separator enables rapid venting, safety can be ensured.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 and FIG. 2 are diagrams schematically showing a cross section of a capsule-type foaming agent which is an embodiment of the present invention.
3 is a diagram schematically showing a cross section of a separator according to an embodiment of the present invention.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventive concept. Other embodiments falling within the scope of the inventive concept may readily be suggested, but are also considered to be within the scope of the present invention.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

The present invention relates to a capsule type foaming agent, a separator coating composition containing the same, a separator thereof, and a secondary battery comprising the same.

The capsule type foaming agent comprises: a first shell; a first core agent contained in the first shell; And a capsule of a core-shell structure contained in the first core agent, wherein the capsule is composed of a second core and a second core contained in the second shell, wherein the first shell is a thermoplastic resin, The first core agent is characterized by comprising a volatile swelling agent.

1 and 2 schematically show a cross section of a capsule type foaming agent 1 according to an embodiment of the present invention. According to Fig. 1, the capsule type foaming agent is contained in a first shell 2, The first core material may further include a core-shell structure. The capsule of the core-shell structure may consist of a second shell (4) and a second core article (5) contained in the second shell. 2, the capsule-type foaming agent of the present invention may include capsules of two or more core-shell structures in the foaming agent of the core-shell structure.

The first shell 2 is preferably made of a thermoplastic resin, and the thermoplastic resin can be used without limitation. For example, the first shell 2 may be at least one selected from the group consisting of an acrylonitrile copolymer and a vinylidene chloride copolymer . Particularly, it is preferable to use an acrylonitrile copolymer in terms of excellent heat resistance and chemical resistance.

The first core (3) contained in the first shell (2) preferably comprises a volatile swelling agent. The volatile swelling agent may be a hydrocarbon, and the hydrocarbon is preferably at least one selected from the group consisting of normal butane, normal pentane, and n-hexane.

The first core material 3 may include a core-shell structure, and the capsule may comprise a second core material 5 and a second core material 5 embedded in the second shell material. . The second shell may be at least one selected from the group consisting of a polyethylene resin, a polypropylene resin, and a polystyrene resin, and the second core agent may include a flame retardant material.

The flame retardant may be a fluoride-based compound, and it is preferable to use a fluoride-based compound. The fluoride compound is _{H (CF 2) 2 OCH 3} , C 4 F 9 OCH 3, H (CF 2) 2 OCH 2 CH 3, H (CF 2) 2 OCH 2 CF 3, H (CF 2) 2 CH ₂ O (CF ₂ ) ₂ H and CF ₃ CHFCF ₂ OCH ₃ , and CF ₃ CHFCF ₂ OCH ₂ CH ₃ .

The thermal expansion operating temperature of the capsular foaming agent (1) of the present invention is preferably 110 to 260 ° C. When heat of 110 to 260 ° C is applied to the encapsulated foaming agent, the softening of the first shell (2) starts and the volatile expanding agent of the first core (3) is vaporized to increase the internal pressure. As a result, Expansion can be achieved. The expansion state of the capsule type foaming agent can be maintained by balancing the internal pressure at the time of expansion and the tension (external pressure) of the first shell. On the other hand, if heating is continued in the above-mentioned temperature range, contraction may occur because the tension (external pressure) of the thinned first shell becomes larger than the internal pressure.

On the other hand, if heat of a high temperature exceeding 260 캜 is applied to the capsular foaming agent (1) of the present invention, rupture may occur in the first shell (2) and the second shell (4) 5 may be discharged to the outside of the capsular foaming agent. Therefore, when heat of more than 260 ° C is applied to the capsular foaming agent of the present invention, problems such as ignition that may occur at a high temperature can be prevented.

According to an embodiment of the present invention, a separator coating composition comprising the capsule-type foaming agent and the ceramic particles can be provided.

According to an embodiment of the present invention, there is provided a separator for a secondary battery, comprising a porous support and a coating layer formed by coating and curing the serpeter coating composition on at least one side of the microporous membrane. 2, the separator includes a porous support 7 and a coating layer 6. The coating layer comprises a capsule type foaming agent 1, .

The capsule-type foaming agent (1) according to the present invention includes the capsule-type foaming agent (1), which may cause expansion of the capsule-type foaming agent when the battery is heated in an accident situation caused by overcharging or the like. As a result, the coating layer 6 expands and the volume expansion of the separator occurs, so that the gap between the electrodes is kept away from flowing current to the electrodes. Therefore, there is an effect of preventing the overcurrent and the explosion of the battery from occurring due to the short circuit of the electrode when the temperature of the battery rises in an accident situation.

In addition, if the internal pressure of the battery increases when the temperature of the battery rises in an accident, so-called swelling of the pouch-shaped case may occur and the battery may be deformed to cause a short circuit or explosion. According to the present invention, rapid expansion of the separator occurs due to the expansion of the capsule-like foaming agent (1) contained in the separator before the swelling shape is generated, thereby enabling quick venting and securing safety.

The capsular foaming agent (1) contained in the separator coating composition of the present invention preferably has a thermal expansion operating temperature of 110 to 260 ° C. If the thermal expansion working temperature of the encapsulated foaming agent is less than 110 캜, the separator may expand at a low temperature at which no accident occurs, and the distance between the electrodes may be distanced. When the temperature exceeds 260 캜, The safety of the battery may be deteriorated.

If the average particle diameter of the capsular foaming agent (1) is 2 to 15 占 퐉 and the average particle diameter of the capsular foaming agent is less than 2 占 퐉, the capsule-type foaming agent particles themselves are small in size, If the thickness exceeds 15 탆, the performance of the cell may be deteriorated, and the thickness of the separator may become thicker, thereby increasing the distance between the cathode and the anode, thereby increasing the resistance.

The thermal expansion rate of the capsule type foaming agent (1) is preferably 5 times or more. If the thermal expansion rate is less than 5 times, overheating and explosion may occur due to continuous flow of electricity to the electrode in an accident situation even if expansion occurs in an accident situation. On the other hand, the upper limit of the thermal expansion coefficient of the capsule type foaming agent is not limited. However, if the thermal expansion rate is 20 times or more, the average diameter of the expanded capsule type foaming agent may exceed the thickness of the coating layer 6.

The capsule type foaming agent (1) is preferably contained in an amount of 5 to 10% by weight based on the total weight of the separator coating composition. If the content of the encapsulated foaming agent is less than 5% by weight, electricity may continuously flow to the electrode in the event of an accident, and overcurrent and explosion may occur. If the content is more than 10% by weight, the encapsulated foaming agent itself acts as a resistance, can do.

The ceramic particles contained in the coating layer 6 of the present invention are not particularly limited as long as they do not cause oxidation and / or reduction reaction, that is, electrochemical reaction with the positive electrode or the negative electrode current collector in the operating voltage range of the battery, TiO ₂ , Y ₂ O ₃ , ZnO, ZrO ₂ , and Pb (Zr, Ti), for example, Al ₂ O ₃ , BaTiO ₃ , CaO, CeO ₂ , NiO, MgO, SiO ₂ , SnO ₂ , SrTiO ₃ , _{O 3 (PZT), Pb 1} - the group consisting of _{y TiyO 3 (PLZT), PB} (Mg 3 Nb 2/3) O 3 -PbTiO 3 (PMN-PT) and _{hafnia (HfO 2) - x La} x Zr 1 . ≪ / RTI >

If the average diameter of the ceramic particles exceeds 600 nm, the performance of the cell may be deteriorated, the thickness of the separator may become thicker, and the distance between the cathode and the anode may be increased. There is an increasing problem.

According to one embodiment of the present invention, there can be provided a separator for a secondary battery comprising a porous support 7 and a coating layer 6 formed by coating and curing the serpentine coating composition on at least one surface of the porous support.

In the separator of the present invention, the porous support (7) can be a known separator as it is. For example, the porous support (7) is made of a polyolefin resin, a fluorine resin, a polyester resin, a polyacrylonitrile resin and a cellulosic material And may be a microporous membrane or a nonwoven fabric composed of at least one component selected from the group consisting of More specifically, it may be a microporous film or nonwoven fabric comprising at least one component selected from the group consisting of polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene terephthalate and polybutylene terephthalate.

The porous support 7 is a fibrous porous support having fine pores having a size of 0.01 to 0.1 탆 at a distribution ratio of 90 to 97%. The porous support 7 can maintain excellent mechanical strength, and in particular, the ionic material can move more smoothly between the positive electrode and the negative electrode of the battery because the specific gravity of the open cell is very high.

If the thickness of the coating layer is less than 1.5 탆, the resistance of the cell may be reduced while the safety may be decreased. If the thickness of the coating layer exceeds 5.5 탆, the safety may be increased While the resistance of the cell can increase together.

The coating layer (6) of the present invention is formed by coating and curing the separator coating composition on at least one side of the porous support (7), and the coating method includes, but is not limited to, , A die coating method, a spray coating method, a paint coating method, or the like.

In still another embodiment of the present invention, there is provided a secondary battery including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a lithium salt-containing electrolyte, wherein the secondary battery includes the separator of the present invention have.

The secondary battery can be obtained by using the separator of the present invention and combining with conventionally known components such as electrolytic solution, negative electrode, and positive electrode. As a concrete manufacturing method, for example, a negative electrode and a positive electrode are stacked with a separator interposed therebetween, and the battery is wrapped in a battery container in such a manner that the battery is wound and bent, . If necessary, an overcurrent preventing element such as a fuse, a PTC element or the like, a lead plate or the like may be inserted to prevent an increase in pressure inside the battery and overcharge discharge. The shape of the battery can be coin, button, sheet, cylinder, square, flat, and the like.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be obvious to those of ordinary skill in the art.

1: Capsule type foaming agent
2: first shell
3: First core material
4: Second shell
5: Second core
6: Coating layer
7: Porous support

Claims (15)

A first shell;
A first core agent contained in said first shell; And
And a capsule of a core-shell structure contained in said first core agent,
Said capsule comprising a second shell and a second core comprised of said second shell,
The first shell is a thermoplastic resin,
Wherein the first core agent comprises a volatile swelling agent.
The method according to claim 1,
Wherein the thermoplastic resin is at least one selected from the group consisting of an acrylonitrile copolymer and a vinylidene chloride copolymer.
The method according to claim 1,
Wherein the volatile swelling agent is a hydrocarbon.
The method according to claim 1,
Wherein a plurality of capsules of a core-shell structure contained in said first core agent are present.
The method according to claim 1,
Wherein the second shell is at least one selected from the group consisting of a polyethylene-based resin, a polypropylene-based resin, and a polystyrene resin.
The method according to claim 1,
Wherein the second core agent comprises a flame retardant material.
The method according to claim 6,
Wherein the flame retardant is a fluoride-based compound.
The method according to claim 1,
Wherein the capsular foaming agent has a thermal expansion operating temperature of 110 to 260 ° C.
9. A capsule-type foaming agent according to any one of claims 1 to 8; And
A separator coating composition comprising ceramic particles.
10. The method of claim 9,
Wherein the capsule type foaming agent is contained in an amount of 5 to 10% by weight based on the total weight of the separator coating layer composition.
10. The method of claim 9,
The ceramic particles may be selected from the group consisting of Al ₂ O ₃ , BaTiO ₃ , CaO, CeO ₂ , NiO, MgO, SiO ₂ , SnO ₂ , SrTiO ₃ , TiO ₂ , Y ₂ O ₃ , ZnO, ZrO ₂ , Pb (Zr, ₃ (PZT), Pb _{1 -} from the group consisting of _{y TiyO 3 (PLZT), PB} (Mg 3 Nb 2/3) O 3 -PbTiO 3 (PMN-PT) and _{hafnia (HfO 2) - x La} x Zr 1 At least one selected.
A porous support; And
And a coating layer formed from the serpentine coating composition of claim 9 on at least one side of the porous support.
13. The method of claim 12,
Wherein the porous support is a microporous membrane or a nonwoven fabric comprising at least one component selected from the group consisting of polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene terephthalate and polybutylene terephthalate.
13. The method of claim 12,
Wherein the coating layer has a thickness of 1.5 to 5.5 占 퐉.
A secondary battery comprising the separator of claim 12.

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