CN117501510A - Method for manufacturing gel polymer electrolyte secondary battery and gel polymer electrolyte secondary battery obtained thereby - Google Patents

Method for manufacturing gel polymer electrolyte secondary battery and gel polymer electrolyte secondary battery obtained thereby Download PDF

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CN117501510A
CN117501510A CN202380012215.2A CN202380012215A CN117501510A CN 117501510 A CN117501510 A CN 117501510A CN 202380012215 A CN202380012215 A CN 202380012215A CN 117501510 A CN117501510 A CN 117501510A
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secondary battery
polymer electrolyte
gel polymer
electrolyte secondary
manufacturing
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柳志勋
林太燮
金东规
尹汝敏
李廷弼
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LG Energy Solution Ltd
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LG Energy Solution Ltd
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Priority claimed from PCT/KR2023/000599 external-priority patent/WO2023136637A1/en
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Abstract

The present invention relates to a method for manufacturing a gel polymer electrolyte secondary battery and a gel polymer secondary battery obtained by the method. According to the method, it is possible to easily remove gas generated in the secondary battery, significantly improve resistance and life characteristics, and improve mechanical properties, thereby improving rigidity and safety of the battery.

Description

Method for manufacturing gel polymer electrolyte secondary battery and gel polymer electrolyte secondary battery obtained thereby
Technical Field
The present invention relates to a method for manufacturing a lithium secondary battery comprising a gel polymer electrolyte and a gel polymer electrolyte secondary battery obtained thereby. The present application claims priority from korean patent application No. 10-2022-0006079, korean patent application No. 10-2022-0006080, korean patent application No. 10-2022-0006081, and korean patent application No. 10-2022-0006082, filed on 1 month 14 of 2022 in republic of korea, the disclosures of which are incorporated herein by reference.
Background
Recently, energy storage technology has received increasing attention. As the application of energy storage technology has been extended to energy sources for cellular phones, camcorders and notebook computers, even to energy sources for electric automobiles, research and development work of electrochemical devices has been increasingly put into practice. In this case, the electrochemical device receives the most widespread attention. In such electrochemical devices, development of rechargeable secondary batteries has been attracting attention.
Among the secondary batteries that are commercially available, lithium secondary batteries developed in the early 1990 s are attracting attention because they have higher operating voltages and significantly higher energy densities than conventional batteries such as Ni-MH, ni-Cd, and lead sulfate batteries using aqueous electrolytes.
Such lithium secondary batteries can be classified into lithium ion batteries using a liquid electrolyte and lithium polymer batteries using a polymer electrolyte according to the electrolyte used exclusively.
Lithium ion batteries have the advantage of high capacity, but there is a risk of electrolyte leakage and explosion due to the use of liquid electrolytes containing lithium salts. Therefore, lithium ion batteries have a disadvantage in that they require a complicated battery design to overcome such disadvantages.
On the other hand, lithium polymer batteries use a solid polymer electrolyte or a gel polymer electrolyte containing an electrolyte, and thus exhibit improved safety and may have flexibility. Accordingly, the lithium polymer battery may be developed into various types, such as a compact battery or a thin film battery. According to the method of preparing the gel polymer electrolyte, the gel polymer electrolyte may be classified into a coated gel polymer electrolyte and an injected gel polymer electrolyte. The injectable gel polymer electrolyte may be prepared by injecting a liquid electrolyte including a crosslinkable monomer into a battery, uniformly wetting an electrode assembly with the liquid electrolyte, and performing a crosslinking process. During the crosslinking process, the electrolyte forms a matrix and converts into a gel-like electrolyte that does not have fluidity. Such a gel electrolyte has advantages in that it does not exhibit fluidity to eliminate leakage problems, and in that it increases the strength of the battery to strongly resist external impact, thereby providing high physical safety.
Meanwhile, a lithium secondary battery is generally obtained through an assembly step and a formation step. The assembling step includes a lamination step of bonding the separator with the electrode, a step of injecting an electrolyte, and the like. The formation step includes the step of charging and/or discharging under conditions required for formation. However, in the formation step, a large amount of gas is generated inside the secondary battery. If the generated gas is not removed, it may be trapped in the secondary battery and occupy a certain space, thereby causing deformation of the battery and adversely affecting the performance (such as capacity and power) and life.
In the case of a secondary battery using a liquid electrolyte, gas generated in the battery may be removed by applying pressure during or after the formation step.
However, the secondary battery using the gel polymer electrolyte has a problem in that gas cannot be removed even when pressure is applied during or after the formation step because the electrolyte is already in a gel state. In particular, in the case of laminating the gel polymer electrolyte secondary battery to bond the separator to the electrode, the separator is firmly adhered to the electrode. Therefore, the gas generated in the secondary battery cannot be discharged to the outside, but is trapped at the separator-electrode interface to form bubbles or interfere with lithium migration, resulting in problems of increased lithium ion concentration and lithium deposition in the vicinity of such bubbles.
Under these circumstances, there is a need to develop a method of manufacturing a gel polymer electrolyte secondary battery capable of removing gas generated during the formation step.
Disclosure of Invention
Technical problem
The present invention has been made to solve the problems of the prior art, and therefore it is an object of the present invention to provide a method for manufacturing a gel polymer electrolyte secondary battery, which can easily remove gas generated in the secondary battery and can provide significantly improved resistance and life characteristics.
The present invention is also directed to a method of manufacturing a gel polymer electrolyte secondary battery, which provides the secondary battery with improved mechanical properties and thus improved rigidity and safety, and a gel polymer electrolyte secondary battery obtained thereby.
It will be readily understood that the objects and advantages of the present invention may be realized by means of the instrumentalities and combinations particularly pointed out in the appended claims.
Technical proposal
The inventors of the present invention have found that the above technical problems can be solved by a method for manufacturing a gel polymer electrolyte secondary battery as described below and the gel polymer electrolyte secondary battery thus obtained.
According to a first embodiment, there is provided a method of manufacturing a gel polymer electrolyte secondary battery, including the steps of:
(S1) preparing a ceramic coated separator and an electrode, wherein the ceramic coated separator comprises a porous matrix and a ceramic coating comprising a first binder polymer and ceramic particles;
(S2) performing lamination of the separator and the electrode to provide an electrode assembly, wherein a composition comprising a second binder polymer is applied in a patterned shape onto at least one surface of the separator or electrode, and the separator is folded in a zigzag manner so that the electrode can be inserted into a region where the separator overlaps;
(S3) injecting a composition for a gel polymer electrolyte into the electrode assembly to obtain a battery; and
(S4) by heating at a temperature of 50 ℃ or higher and 0.1kgf/cm 2 To 5kgf/cm 2 The battery is charged at least twice under the pressure of (a) to perform formation.
According to a second embodiment, there is provided the method of manufacturing a gel polymer electrolyte secondary battery as defined in the first embodiment, wherein the lamination in step (S2) is performed at a temperature of 30 ℃ or less.
According to a third embodiment, there is provided a method of manufacturing a gel polymer electrolyte secondary battery as defined in the first or second embodiment, wherein the lamination in step (S2) is under ambient pressure conditions or at 3kgf/cm applied to the electrode assembly 2 The following pressure conditions were used.
According to a fourth embodiment, there is provided the method for manufacturing a gel polymer electrolyte secondary battery as defined in any one of the first to third embodiments, wherein in step (S2), the lamination step is not performed with the application of pressure.
According to a fifth embodiment, there is provided a method for manufacturing a gel polymer electrolyte secondary battery as defined in any one of the first to fourth embodiments, wherein the content of the first binder polymer is 0.1 to 10 wt% based on the total weight of the ceramic coating layer.
According to a sixth embodiment, there is provided a method for manufacturing a gel polymer electrolyte secondary battery as defined in any one of the first to fifth embodiments, wherein the first binder polymer is an acrylate-based binder polymer.
According to a seventh embodiment, there is provided the method of manufacturing a gel polymer electrolyte secondary battery as defined in any one of the first to sixth embodiments, wherein the patterned shape includes at least one of a dot pattern, a stripe pattern, and a grid pattern.
According to an eighth embodiment, there is provided the method for manufacturing a gel polymer electrolyte secondary battery according to any one of the first to seventh embodiments, wherein the composition for a gel polymer electrolyte comprises a polymerization initiator having a 10-hour half-life temperature of 60 ℃ or less, a polymerizable compound, a lithium salt, and a nonaqueous organic solvent.
According to a ninth embodiment, there is provided the method for producing a gel polymer electrolyte secondary battery as defined in any one of the first to eighth embodiments, wherein the 10-hour half-life temperature of the polymerization initiator is 55 ℃ or less.
According to a tenth embodiment, there is provided the method for manufacturing a gel polymer electrolyte secondary battery according to any one of the first to ninth embodiments, wherein the polymerization initiator is contained in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the composition for a gel polymer electrolyte.
According to an eleventh embodiment, there is provided the method of manufacturing a gel polymer electrolyte secondary battery as defined in any one of the first to tenth embodiments, wherein the pressure application in step (S4) includes applying pressure at least once by using a pressurizing device.
According to a twelfth embodiment, there is provided a method for manufacturing a gel polymer electrolyte secondary battery as defined in any one of the first to eleventh embodiments, wherein the step (S4) includes the steps of:
(S4 a) at 50℃to 60 DEG CTemperature, 0.1kgf/cm 2 To 1kgf/cm 2 Is initially charged to 20% or less of the capacity (state of charge, SOC) of the secondary battery; and
(S4 b) at a temperature of 50℃to 60℃and 3kgf/cm 2 To 5kgf/cm 2 Secondary charging is performed to 15% to 60% of the capacity (state of charge, SOC) of the secondary battery under the pressure of (a) the battery.
According to a thirteenth embodiment, there is provided a method for manufacturing a gel polymer electrolyte secondary battery as defined in any one of the first to twelfth embodiments, further comprising the steps of:
(S5) storing the battery subjected to the formation in the step (S4) at a temperature of 60 ℃ or higher and 3kgf/cm 2 Under the above pressure.
According to a fourteenth embodiment, there is provided the method for manufacturing a gel polymer electrolyte secondary battery as defined in any one of the first to thirteenth embodiments, wherein step (S5) is performed for 30 minutes to 5 hours.
According to a fifteenth embodiment, there is provided the method for manufacturing a gel polymer electrolyte secondary battery as defined in any one of the first to fourteenth embodiments, wherein the pressure application in step (S5) includes applying pressure at least once by using a pressurizing device.
According to a sixteenth embodiment, there is provided the method for manufacturing a gel polymer electrolyte secondary battery as defined in any one of the first to fifteenth embodiments, further comprising a step of vacuum sealing the battery at a pressure of less than-95 kPa after step (S3).
According to a seventeenth embodiment, there is provided the method for manufacturing a gel polymer electrolyte secondary battery as defined in any one of the first to sixteenth embodiments, wherein the vacuum sealing step is performed at a pressure of-100 kPa to-120 kPa.
According to an eighteenth embodiment, there is provided the method for manufacturing a gel polymer electrolyte secondary battery as defined in any one of the first to seventeenth embodiments, wherein the vacuum sealing step is performed for 5 seconds to 30 seconds.
According to a nineteenth embodiment, there is provided the method for manufacturing a gel polymer electrolyte secondary battery as defined in any one of the first to eighteenth embodiments, further comprising a step of degassing the battery at a pressure of less than-95 kPa after step (S4).
According to a twentieth embodiment, there is provided the method for manufacturing a gel polymer electrolyte secondary battery as defined in any one of the first to nineteenth embodiments, wherein the degassing is performed at a pressure of-100 kPa to-120 kPa.
According to a twenty-first embodiment, there is provided a gel polymer electrolyte secondary battery, which is obtained by the method defined in any one of the first to twentieth embodiments and has a rigidity of 4.0MPa or more.
Advantageous effects
The method for manufacturing a gel polymer electrolyte secondary battery according to one embodiment of the present invention is characterized by comprising the steps of: laminating a separator and an electrode by applying an adhesive polymer to one surface of the separator or the electrode in a patterned shape, folding the separator in a zigzag manner, inserting the electrode into a region where the separator overlaps to provide an electrode assembly; injecting a composition for a gel polymer electrolyte into an electrode assembly to obtain a battery; and performing formation of the battery under high temperature and high pressure conditions.
In this way, a sufficient level of adhesion between the separator and the electrode may be provided. Further, it is possible to easily discharge the gas generated in the secondary battery and further gel the gel polymer. Therefore, it is possible to improve the resistance and life characteristics of the gel polymer electrolyte secondary battery and to improve the mechanical properties of the battery.
Further, the method for manufacturing a gel polymer electrolyte secondary battery according to an embodiment of the present invention may use a composition for a gel polymer electrolyte including a specific polymerization initiator to reduce the time required for wetting with the electrolyte while being sufficiently wetted with the electrolyte to thereby inhibit pregelatinization.
In addition, the method of manufacturing a gel polymer electrolyte secondary battery according to an embodiment of the present invention may further include a step of storing the battery after formation under high temperature and high pressure conditions to further improve the above-described effects of the present invention.
In addition, the method of manufacturing a gel polymer electrolyte secondary battery according to an embodiment of the present invention may further include a step of sealing and degassing the battery under a pressure condition of less than-95 kPa to improve the above-described effects of the present invention. In particular, a higher level of vacuum may be applied during the sealing and degassing steps, so that the mechanical properties of the battery may be improved.
Drawings
The accompanying drawings illustrate preferred embodiments of the present invention and, together with the foregoing disclosure, serve to provide a further understanding of the technical features of the present invention, and therefore, the present invention should not be construed as being limited to the accompanying drawings. Meanwhile, the shape, size or proportion of some constituent elements in the drawings may be exaggerated for clarity of description.
Fig. 1 is a flowchart sequentially showing a method of manufacturing a secondary battery according to an embodiment of the present invention.
Fig. 2 is a schematic view illustrating steps of manufacturing an electrode assembly according to an embodiment of the present invention, wherein each step is sequentially illustrated in fig. 2a to 2 f.
Fig. 3 is an image showing traces of adhesive applied in a dot pattern determined by disassembling the battery obtained according to example a-1 of the present invention.
Fig. 4 is an exploded view of a battery obtained in comparative example a-3 according to the present invention.
Detailed Description
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Before the description, it should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present invention on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. Accordingly, the description herein is presented for purposes of illustration only of the preferred embodiments and is not intended to limit the scope of the invention, so it is to be understood that other equivalents and modifications may be made without departing from the scope of the invention.
Throughout the specification, unless stated otherwise, the expression "a component comprises or includes an element" does not exclude the presence of any additional elements, but means that the component may further comprise other elements.
As used herein, the terms "about" or "substantially" and the like are used as meanings adjacent to the stated values when addressing acceptable manufacturing and material defects that are characteristic of the meanings, and are used to prevent improper use by an uninduty infringer of the disclosure including precise or absolute values provided to aid in understanding the invention.
As used herein, the expression "a and/or B" refers to "A, B or both.
Generally, a manufacturing method of a secondary battery basically includes a formation step of performing charge/discharge. In this formation step, gas is generated in the secondary battery, and thus the performance of the secondary battery is affected. Therefore, it is an important technical problem to remove the gas in the secondary battery to improve the performance of the secondary battery.
Meanwhile, the secondary battery using the gel electrolyte exhibits improved safety and physical strength as compared to the secondary battery using the liquid electrolyte. However, since the inside of the secondary battery using the gel electrolyte is already present in a gel state in the formation step, there is a problem in that the gas inside cannot be easily discharged.
Under these circumstances, the inventors of the present invention have conducted intensive studies to provide a method of manufacturing a secondary battery using a gel polymer electrolyte, thereby improving the performance of the secondary battery by effectively removing gas generated in the secondary battery.
Method for manufacturing gel polymer electrolyte secondary battery
In one aspect of the present invention, there is provided a method of manufacturing a gel polymer electrolyte secondary battery, comprising the steps of:
(S1) preparing a ceramic coated separator and an electrode, wherein the ceramic coated separator comprises a porous matrix and a ceramic coating comprising a first binder polymer and ceramic particles;
(S2) performing lamination of the separator and the electrode to provide an electrode assembly, wherein a composition comprising a second adhesive polymer is applied in a patterned shape onto at least one surface of the separator or electrode, and the separator is folded in a zigzag manner so that the electrode can be inserted into a region where the separator overlaps;
(S3) injecting the composition for a gel polymer electrolyte into an electrode assembly to obtain a battery; and
(S4) by heating at a temperature of 50 ℃ or higher and 0.1 to 5kgf/cm 2 The battery is charged at least twice under the pressure of (a) to perform formation.
Hereinafter, each step will be explained in more detail.
First, a ceramic-coated separator and an electrode are prepared (S1). According to the invention, a ceramic coated separator has a porous matrix and a ceramic coating, wherein the ceramic coating comprises a first binder polymer and ceramic particles.
Ceramic coated separator
According to the invention, a ceramic coated separator has a porous substrate and a ceramic coating. A ceramic coated separator is interposed between the negative and positive electrodes to physically and electrically insulate the two electrodes from each other, thereby interrupting the internal short circuit, providing ion transport channels, and allowing wetting with electrolyte.
The porous substrate is not particularly limited as long as it has a structure including pores. For example, the porous matrix may comprise a porous polymer film made of a polyolefin-based polymer, such as an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer, or an ethylene/methacrylate copolymer, or a laminate structure comprising two or more thereof. The porous matrix may also include a porous nonwoven web, such as a nonwoven web made of high melting point glass fibers, polyethylene terephthalate fibers, and the like.
The ceramic coating may be disposed on at least one surface or both surfaces of the porous matrix and comprises a binder polymer and ceramic particles. The separator having the ceramic coating layer has excellent electrical insulation properties to suppress short circuits. In addition, even if a short circuit occurs, the expansion of the short circuit portion is suppressed, thereby contributing to the improvement of the safety of the battery.
The ceramic coating is an organic/inorganic composite layer comprising ceramic particles and a binder resin, wherein the organic/inorganic composite layer has porosity by virtue of pores formed by interstitial volumes between the ceramic particles. Here, the interstitial volume refers to a space defined by ceramic particles substantially contacting each other in the filled structure of the ceramic particles.
The ceramic particles can form voids between the ceramic particles, thereby functioning as micropores, and also functioning as spacers capable of maintaining a physical shape. In general, ceramic particles do not change in physical properties even at high temperatures of 200 ℃ or higher in nature, and thus have excellent heat resistance. The ceramic particles are not particularly limited as long as they are electrochemically stable. In other words, the ceramic particles are not particularly limited as long as they are in the range of the operating voltage of the available electrochemical device (e.g., 0 to 5V (based on Li/Li + ) Not causing oxidation and/or reduction. Specific examples of the ceramic particles may include Al 2 O 3 、AlOOH、Al(OH) 3 、AlN、BN、MgO、Mg(OH) 2 、SiO 2 、ZnO、TiO 2 、BaTiO 3 Or a mixture thereof.
According to the present invention, the first binder polymer is not particularly limited as long as it can provide a binding force between ceramic particles and a binding force between the porous coating layer and the electrode.
In particular, the first binder polymer may include a binder polymer that is insoluble in an organic solvent and capable of maintaining dispersibility. Further, the first binder polymer may include a particulate binder polymer that is insoluble in an organic solvent and maintains dispersibility while maintaining a particulate shape.
For example, the first binder polymer may include an acrylate-based binder polymer. The acrylic adhesive polymer may include polyacrylonitrile, acrylonitrile-styrene-butadiene copolymer, and polybutyl acrylate, homopolymers or copolymers of acrylate monomers, such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, butyl acrylate, isononyl acrylate, or 2-ethylhexyl acrylate, or mixtures thereof. According to the present invention, when an acrylic adhesive polymer is used as the first adhesive polymer, water may be used as a solvent to simplify the manufacturing process, and the thickness of the porous coating layer may be advantageously reduced.
The first binder polymer may be present in an amount of 0.1 to 10 wt% based on the total weight of the ceramic coating. In particular, the content of the first binder polymer may be 0.1 wt% or more, 1 wt% or more, 3 wt% or more, 10 wt% or less, or 8 wt% or less, based on the total weight of the ceramic coating.
In general, when the binder polymer is used within the above-defined range, a sufficient level of adhesion may not be ensured at the time of adhesion to the electrode, and problems including separation of the separator may occur during assembly of the electrode assembly. However, according to the method for manufacturing a gel polymer electrolyte secondary battery of the present invention, the content of the first binder polymer satisfies the above-defined range while solving the above-described problems. Therefore, the resistance of the separator can be reduced, and the energy density of the battery can be increased to save costs.
Electrode
According to the present invention, the electrode is a positive electrode and/or a negative electrode, and any electrode conventionally used for manufacturing lithium secondary batteries may be used. According to the present invention, an electrode may be obtained by combining an electrode active material with an electrode current collector according to a conventional method known to those skilled in the art.
Among the electrode active materials, non-limiting examples of the positive electrode active material may include a conventional positive electrode active material that may be conventionally used for a positive electrode of a lithium secondary battery, and specific examples thereof may include at least one selected from lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or lithium composite oxide prepared by a combination thereof.
Non-limiting examples of the anode active material may include a conventional anode active material that may be conventionally used for an anode of a lithium secondary battery. For example, the anode active material may include at least one selected from materials capable of intercalating/deintercalating lithium, such as lithium metal or lithium alloy, silicon and/or silicon-based compound, tin and/or tin-based compound, carbon, petroleum coke, activated carbon, graphite, or other carbonaceous material.
Non-limiting examples of the negative electrode current collector may include a foil made of copper, gold, nickel, or copper alloy, or a combination thereof, and non-limiting examples of the positive electrode current collector may include a foil made of aluminum, nickel, or a combination thereof.
Next, the separator and the electrode are laminated to form an electrode assembly (S2). In the step (S2) of forming the electrode assembly of the present invention, a composition including a second binder polymer is applied to at least one surface of the separator and/or the electrode in a patterned shape. Further, the separator is folded in a zigzag manner, and the electrode is inserted into the region where the separators overlap.
According to the present invention, by the step (S2) of forming the electrode assembly, it is possible to improve the problem that the separator and the electrode are separated from each other during the assembly and transfer of the electrode assembly, or during the folding of the separator.
Generally, when forming an electrode assembly, lamination is performed under high temperature and/or high pressure conditions in order to adhere the separator to the electrode. In particular, lamination is at a temperature of about 50℃to 150℃at about 5kgf/cm 2 Under the above pressure.
However, according to the present invention, a composition including a second adhesive polymer is applied in a patterned shape to one surface of the separator or the electrode, and the electrode is disposed between the zigzag folded separators to laminate the separator and the electrode. In this way, the problem of separation of the separator and the electrode from each other during the steps of assembling and transferring the electrode assembly or during the folding of the separator can be solved even if such conventional high temperature and/or high pressure conditions for lamination are not applied.
For example, the number of the cells to be processed,according to one embodiment of the present invention, the lamination in step (S2) may be performed at a temperature of 30 ℃ or less. In addition, the lamination in step (S2) may be under ambient pressure or at 3kgf/cm applied to the electrode assembly 2 The following pressure conditions were used. In a variation, in step (S2), the lamination step is not performed under pressurized conditions. In other words, according to one embodiment of the present invention, step (S2) may be performed without pressure.
By performing the lamination of step (S2) under the above conditions, the electrode assembly of the present invention exhibits a significantly low interfacial resistance between the separator and the electrode, thereby providing a reduced resistance to the battery.
The second binder polymer is not particularly limited as long as it can be dissolved in the composition for a gel polymer electrolyte. In particular, according to the present invention, the second binder polymer may be a polymer that can be dissolved in the electrolyte composition after injection into the electrolyte composition, and thus can reduce the interface resistance between the separator and the electrode. The second adhesive polymer is applied to at least one surface of the separator or the electrode and serves to bond the electrode and the separator to each other while improving the problem of separation of the separator and the electrode from each other or folding of the separator.
For example, the second binder polymer may include an acrylate-based binder polymer, or the like. When the acrylic polymer is used according to the present invention, it can be easily dissolved in the electrolyte composition after injection into the electrolyte composition.
In particular, the acrylic polymer may include a copolymer comprising: (A) 60.1 to 79.9% by weight of recurring units based on alkyl (meth) acrylate; and (B) 20.1 to 39.9% by weight of (meth) acrylate repeat units having terminal hydroxyl groups.
More specifically, in the acrylic polymer, the repeating unit (a) may be represented by the following chemical formula 1, and the repeating unit (B) may be represented by the following chemical formula 2.
[ chemical formula 1]
Wherein R is 1 Represents H or methyl; r is R 2 Represents a C1-C12 linear or branched alkyl group; n represents the number of repetitions of the repeating unit (a), and is an integer of 450 to 850.
[ chemical formula 2]
Wherein R is 3 Represents H or methyl; r is R 4 Represents a C1-C9 linear or branched alkyl group bonded to a hydroxyl group; m represents the number of repetitions of the repeating unit (B), and is an integer of 200 to 350.
More specifically, the acrylic polymer may include at least one selected from the group consisting of methyl acrylate (MMA), 2-ethylhexyl acrylate (2-EHA) and 2-hydroxyethyl acrylate (2-HEA), even more specifically, a combination of these three compounds.
By applying a composition including a second binder polymer in a patterned shape to one surface of the separator or the electrode, adhesiveness can be imparted to the patterned region.
The patterned shape may include a dot pattern, a stripe pattern, a grid pattern, and the like. In particular, the patterned shape has a dot pattern. Here, the diameter of the dots may be about 0.3 to 1.0mm. According to one embodiment of the present invention, about 30 spots having a diameter of about 0.5mm may be marked on an electrode having a size of 30cm x 10 cm. Three points may be marked at intervals of about 10cm in the longitudinal direction of 30cm in length, and ten points may be marked at intervals of about 0.35mm in the width direction of 10cm in length. Here, the interval and the number of the dots may be freely applied by those skilled in the art, and the pattern may be modified according to the size of the battery.
According to one embodiment of the present invention, the pattern may cover 0.0001 to 0.05% based on 100% area of the separator or the electrode. When the above-defined range is satisfied, the second binder may be dissolved in such a manner that the second binder does not adversely affect the performance of the battery after the composition for an electrolyte is subsequently injected, while imparting adhesiveness to the region where the pattern is formed.
In step (S2), the separator is folded in a zigzag manner, and the electrode is inserted into the region where the separator overlaps. In this way, the separator and the electrode are laminated.
Fig. 2 is a schematic view showing a lamination method of a separator and an electrode of the present invention.
For example, a lamination method of the separator and the electrode will be explained based on fig. 2a to 2f of fig. 2. First, the separator 21 is supplied onto the stacking table 1 by the separator supply unit 2 wound into a roll shape. The stacking table may be movable in the lateral direction, and the membrane may be folded in a zigzag manner. Further, the first electrode 31 and/or the second electrode 32 may be sequentially laminated in a region where the separator is folded in a zigzag manner. Further, the composition 41 including the adhesive polymer may be applied from the adhesive applying unit 4 to one surface of the separator or the electrode in a patterned shape.
For example, as shown in fig. 2a, the first electrode is laminated onto a stacking table supplied with a separator. As shown in fig. 2b and 2c, the stacking table moves so that the separator may be folded in a zigzag manner, and the composition including the adhesive polymer is applied to one surface of the separator in a patterned shape. Referring to fig. 2d and 2e, the second electrode is transferred and laminated onto the separator. Referring to fig. 2f, the electrode assembly including the laminate in which the first electrode and the second electrode are inserted into the region where the separator is overlapped by the zigzag folding is disposed on a stacking table, the stacking table is moved so that the separator can be folded in a zigzag manner, and the composition including the adhesive polymer is applied to one surface of the separator in a patterned shape.
In other words, the electrode assembly obtained according to the present invention comprises a first electrode and a second electrode, wherein the separator is interposed between the first electrode and the second electrode, wherein the first electrode is disposed on one surface of the separator and the second electrode is disposed on the other surface of the separator.
Then, the composition for a gel polymer electrolyte is injected into the electrode assembly to obtain a battery (S3).
In the method of manufacturing a lithium secondary battery according to an embodiment of the present invention, the composition for a gel polymer electrolyte may be a composition conventionally used for preparing a gel polymer electrolyte. In particular, the composition for a gel polymer electrolyte may include a polymerization initiator, a polymerizable compound, a lithium salt, and a nonaqueous organic solvent.
In step (S3), after injecting the composition for a gel polymer electrolyte, the composition for a gel polymer electrolyte may be polymerized to form a gel polymer electrolyte. For example, the polymerization may be performed at a temperature of 40 ℃ to 80 ℃ so that the polymerizable compound contained in the composition for a gel polymer electrolyte may be polymerized or crosslinked to form a gel polymer electrolyte.
Polymerization initiator
The composition for a gel polymer electrolyte of the present invention may contain a polymerization initiator in order to perform a reaction required for preparing the gel polymer electrolyte.
The polymerization initiator may include a conventional thermal polymerization initiator or photopolymerization initiator known to those skilled in the art. For example, the polymerization initiator may decompose by heating to form radicals and react with the crosslinking agent by radical polymerization to form a gel polymer electrolyte.
More specifically, non-limiting examples of the polymerization initiator may include, but are not limited to: organic peroxides such as benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-t-butyl peroxide, t-butyl peroxy-2-ethylhexanoate, cumene hydroperoxide and hydrogen peroxide; a hydroperoxide; or azo compounds such as 2,2' -azobis (2-cyanobutane), 2' -azobis (methylbutanenitrile), 2' -azobis (isobutyronitrile) (AIBN), 2' -azobis-dimethylvaleronitrile (AMVN), 2' -azobis-methoxy-dimethylvaleronitrile (AMVN), and the like.
Meanwhile, according to an embodiment of the present invention, the composition for a gel polymer electrolyte includes a polymerization initiator having a 10-hour half-life temperature of 60 ℃ or less, or a 10-hour half-life temperature of 55 ℃ or less.
When the composition of the gel polymer electrolyte contains a polymerization initiator having a 10-hour half-life temperature of 60 ℃ or less, the gel polymer electrolyte performance can be ensured by increasing the polymer conversion rate, and the wettability of the electrode with the electrolyte can be improved by preventing pregelatinization.
As used herein, "10 hour half life temperature" refers to the temperature at which the initial initiator decomposes half within 10 hours.
In particular, since the manufacturing method of the gel polymer electrolyte secondary battery of the present invention does not include a step of applying a pressure exceeding the ambient pressure during the manufacturing process of the electrode assembly, particularly before performing the formation step, the electrode and the separator do not adhere closely to each other. Thus, the electrolyte migration path is well formed after the composition for gel polymer electrolyte is injected, and thus wetting with electrolyte can be achieved more quickly.
Further, according to the present invention, since the content of the binder contained in the ceramic coated separator is reduced and the time required for the binder to swell is reduced, the total time of wetting with the electrolyte can be reduced.
In other words, since the method for manufacturing a gel polymer electrolyte secondary battery of the present invention can reduce the time required for wetting with an electrolyte, a polymerization initiator having a 10-hour half-life temperature of 60 ℃ or less is used as a highly reactive polymerization initiator (i.e., a polymerization initiator having excellent reaction initiation performance) to provide a secondary battery having excellent physical properties.
For example, according to the present invention, a polymerization initiator having a 10-hour half-life temperature of 60 ℃ or less in the azo compound exemplified above may be selected and used as the polymerization initiator. In particular, at least one selected from the group consisting of 2,2 '-azobis-2, 4-dimethylvaleronitrile (V65 available from Wako) and 2,2' -azobis-4-methoxy-2, 4-dimethylvaleronitrile (V70 available from Wako) may be used. In particular, the 10 hour half-life temperature of 2,2 '-azobis-2, 4-dimethylvaleronitrile is 51℃and the 10 hour half-life of 2,2' -azobis-4-methoxy-2, 4-dimethylvaleronitrile is 30 ℃.
The polymerization initiator may be decomposed by heating, for example, at 30 to 100 ℃, or may be decomposed at room temperature (5 to 30 ℃) to form radicals, and may react with the polymerizable compound by radical polymerization to form a gel polymer electrolyte.
The polymerization initiator may be used in an amount of 0.01 to 20 parts by weight, particularly 0.1 to 10 parts by weight, based on 100 parts by weight of the polymerizable compound.
When the polymerization initiator is used in the range of 0.01 to 20 parts by weight, the performance of the gel polymer electrolyte can be ensured by increasing the polymer conversion rate, and the wettability of the electrode with the electrolyte can be improved by preventing pregelatinization.
Polymerizable compound
The polymerizable compound is a compound having a polymerizable functional group selected from the group consisting of vinyl group, epoxy group, allyl group and (meth) acryl group and whose structure is capable of undergoing polymerization, and can be converted into a gel phase by polymerization or crosslinking. The polymerizable compound is not particularly limited as long as it is a polymerizable monomer, oligomer or copolymer conventionally used for preparing gel polymer electrolytes.
In particular, non-limiting examples of polymerizable monomers may include, but are not limited to: ethylene glycol diacrylate tetraethyl, polyethylene glycol diacrylate (molecular weight 50 to 20000), 1, 4-butanediol diacrylate, 1, 6-hexanediol diacrylate, trimethylolpropane triacrylate, trimethylolpropane ethoxylate triacrylate, trimethylolpropane propoxylate triacrylate, bis (trimethylolpropane) tetraacrylate, pentaerythritol ethoxylate tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, poly (ethylene glycol) diglycidyl ether, 1, 5-hexadiene diepoxide, glycerol propoxylate triglycidyl ether, vinylcyclohexene dioxide, 1,2,7, 8-diglycidyl octane, 4-vinylcyclohexene dioxide, butyl glycidyl ether, 1, 2-cyclohexanedicarboxylic acid diglycidyl ester, ethylene glycol diglycidyl ether, glycerol triglycidyl ether or glycidyl methacrylate, and the like. These compounds may be used alone or in combination.
Further, typical examples of the copolymer may include at least one selected from the group consisting of: allyl 1, 2-tetrafluoroethyl ether (TFE) - (2, 2-trifluoroethyl acrylate) copolymer, TFE-vinyl acetate copolymer, TFE- (2-vinyl-1, 3-dioxole) copolymer, TFE-vinyl methacrylate copolymer, TFE-acrylonitrile copolymer, TFE-vinyl acrylate copolymer, TFE-Methyl Methacrylate (MMA) copolymer, and TFE-2, 2-trifluoroethyl acrylate (FA) copolymer.
The polymerizable compound may be used in an amount of 0.01 to 10% by weight based on the total weight of the composition for a gel polymer electrolyte. When the content of the polymerizable compound is more than 10% by weight, gelation may occur in a premature time when the composition for a gel polymer electrolyte is injected into a battery, or the composition may become too concentrated to produce a gel having a high resistance. In contrast, when the content of the polymerizable compound is less than 0.01% by weight, gelation hardly occurs.
Lithium salt
Lithium salts are used as electrolyte salts and mediums for transporting ions in lithium secondary batteries. Typically, the lithium salt comprises Li + As the cation and at least one selected from the group consisting of: f (F) - 、Cl - 、Br - 、I - 、NO 3 - 、N(CN) 2 - 、BF 4 - 、ClO 4 - 、AlO 4 - 、AlCl 4 - 、PF 6 - 、SbF 6 - 、AsF 6 - 、B 10 Cl 10 - 、BF 2 C 2 O 4 - 、BC 4 O 8 - 、(CF 3 ) 2 PF 4 - 、(CF 3 ) 3 PF 3 - 、(CF 3 ) 4 PF 2 - 、(CF 3 ) 5 PF - 、(CF 3 ) 6 P - 、CF 3 SO 3 - 、C 4 F 9 SO 3 - 、CF 3 CF 2 SO 3 - 、(CF 3 SO 2 ) 2 N - 、(FSO 2 ) 2 N - 、CF 3 CF 2 (CF 3 ) 2 CO - 、(CF 3 SO 2 ) 2 CH - 、CF 3 (CF 2 ) 7 SO 3 - 、CF 3 CO 2 - 、CH 3 CO 2 - 、SCN - Sum (CF) 3 CF 2 SO 2 ) 2 N - 。
Such lithium salts may be used alone or in combination. The lithium salt may be used in an amount appropriately controlled within a generally applicable range. However, the lithium salt may be used in the electrolyte at a concentration of 0.5 to 2M, particularly 0.9 to 1.5M, in order to obtain an optimal effect of forming a coating film for preventing corrosion on the electrode surface.
Since the composition for a gel polymer electrolyte of the present invention contains 0.5M or more of electrolyte salt, it is possible to reduce resistance caused by lithium ion consumption during high-speed charge/discharge. Further, when the concentration of the electrolyte salt in the composition for a gel polymer electrolyte of the present invention satisfies the above-defined range, high lithium cations (Li + ) Ion mobility (i.e., cation transfer number) of lithium ions) and effects of reducing diffusion resistance of lithium ions, thereby achieving an effect of improving cycle capacity characteristics.
Nonaqueous organic solvents
The nonaqueous organic solvent is not particularly limited as long as it causes the decomposition caused by oxidation to be minimized during the charge/discharge cycle of the secondary battery, and may be combined with the additive to achieve desired properties. For example, the carbonate-based organic solvent, the ether-based organic solvent and the ester-based organic solvent may be used singly or in combination.
Among such organic solvents, the carbonate-based organic solvent may include at least one of a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent. Specific examples of the cyclic carbonate-based organic solvent may include at least one organic solvent selected from the group consisting of Ethylene Carbonate (EC), propylene Carbonate (PC), 1, 2-butylene carbonate, 2, 3-butylene carbonate, 1, 2-pentylene carbonate, 2, 3-pentylene carbonate, vinylene carbonate, vinyl ethylene carbonate, and fluoroethylene carbonate (FEC). In particular, the cyclic carbonate-based organic solvent may include a mixed solvent of ethylene carbonate having a high dielectric constant and propylene carbonate having a relatively low melting point compared to ethylene carbonate.
Further, the linear carbonate-based organic solvent is an organic solvent having a low viscosity and a low dielectric constant, and typical examples thereof may include at least one organic solvent selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl Methyl Carbonate (EMC), methyl propyl carbonate, and ethyl propyl carbonate. In particular, the linear carbonate-based organic solvent may include dimethyl carbonate.
The ether-type organic solvent may include any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methylethyl ether, methylpropyl ether and ethylpropyl ether, or a mixture of two or more thereof. However, the scope of the present invention is not limited thereto.
The ester organic solvent may include at least one selected from the group consisting of a linear ester organic solvent and a cyclic ester organic solvent.
Specific examples of the linear ester-type organic solvent may include any one organic solvent selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate, or a mixture of two or more thereof. However, the scope of the present invention is not limited thereto.
Specific examples of the cyclic ester organic solvent may include any one organic solvent selected from the group consisting of gamma-butyrolactone, gamma-valerolactone, gamma-caprolactone, sigma-valerolactone and epsilon-caprolactone, or a mixture of two or more thereof. However, the scope of the present invention is not limited thereto.
Among such organic solvents, the cyclic carbonate compound is a high-viscosity organic solvent, and can be preferably used because lithium salts are well dissociated in an electrolyte. When such a cyclic carbonate compound is used in a mixture form with a linear carbonate compound and a chain ester compound having low viscosity and low dielectric properties in a proper mixing ratio, a gel polymer electrolyte having high conductivity can be preferably prepared.
Additive agent
The composition for a gel polymer electrolyte of the present invention may further include a supplemental additive capable of forming a more stable ion-conductive coating film on the surface of an electrode, as needed, to prevent decomposition of a nonaqueous electrolyte and collapse of a negative electrode under a high power environment, or to improve low-temperature high-rate discharge characteristics, high-temperature stability, overcharge preventing effect, swelling suppressing effect of a battery at high temperature, and the like.
In particular, typical examples of such supplemental additives may include at least one first additive selected from the group consisting of: sultone compounds, sulfite compounds, sulfone compounds, sulfate compounds, halogen-substituted carbonate compounds, nitrile compounds, cyclic carbonate compounds, phosphate compounds, borate compounds and lithium salt compounds.
The sultone-based compound may include at least one compound selected from the group consisting of 1, 3-Propane Sultone (PS), 1, 4-butane sultone, ethylene sultone, 1, 3-propylene sultone (PRS), 1, 4-butene sultone, and 1-methyl-1, 3-propylene sultone, and may be used in an amount of 0.3 to 5 wt%, particularly 1 to 5 wt%, based on the total weight of the composition for a gel polymer electrolyte. When the content of the sultone-based compound in the composition for a gel polymer electrolyte is more than 5% by weight, an excessively thick coating film may be formed on the electrode surface, resulting in an increase in resistance and a decrease in output. Further, in this case, the electrical resistance may increase due to an excessive amount of additives in the composition for a gel polymer electrolyte, resulting in deterioration of power characteristics.
The sulfite-based compound may include at least one compound selected from the group consisting of ethylene sulfite, methyl ethylene sulfite, ethyl ethylene sulfite, 4, 5-dimethyl ethylene sulfite, 4, 5-diethyl ethylene sulfite, propylene sulfite, 4, 5-dimethyl propylene sulfite, 4, 5-diethyl propylene sulfite, 4, 6-dimethyl propylene sulfite, 4, 6-diethyl propylene sulfite and 1, 3-butylene glycol propylene sulfite, and may be used in an amount of 3 wt% or less based on the total weight of the composition for a gel polymer electrolyte.
The sulfone-based compound may include at least one compound selected from the group consisting of divinyl sulfone, dimethyl sulfone, diethyl sulfone, methyl ethyl sulfone and methyl vinyl sulfone, and may be used in an amount of 3% by weight or less based on the total weight of the composition for a gel polymer electrolyte.
The sulfate compound may include ethylene sulfate (Esa), trimethylene sulfate (TMS) or trimethylene methyl sulfate (MTMS), and may be used in an amount of 3 wt% or less based on the total weight of the composition for a gel polymer electrolyte.
In addition, the halogen-substituted carbonate compound may include fluoroethylene carbonate (FEC), and the amount thereof may be 5 wt% or less based on the total weight of the composition for a gel polymer electrolyte. When the content of the halogen-substituted carbonate compound is more than 5% by weight, the swelling quality of the battery may be reduced.
Further, the nitrile compound may include at least one compound selected from the group consisting of succinonitrile, adiponitrile (Adn), acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanonitrile, cyclohexanonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.
The cyclic carbonate compound may include Vinylene Carbonate (VC) or vinyl ethylene carbonate, and may be used in an amount of 3 wt% or less based on the total weight of the composition for a gel polymer electrolyte. When the content of the cyclic carbonate compound is more than 3% by weight, the battery swelling inhibition performance may be lowered.
The phosphate compound may include a compound selected from the group consisting of lithium difluorophosphate (bisoxalato) and lithium difluorophosphate (LiPO) 2 F 2 ) At least one compound of the group consisting of tetramethyltrimethylsilyl phosphate, trimethylsilyl phosphite, tris (2, 2-trifluoroethyl) phosphate and tris (trifluoroethyl) phosphite, and may be used in an amount of 3% by weight or less based on the total weight of the composition for a gel polymer electrolyte.
The borate/salt compound may include lithium oxalyl difluoroborate, and may be used in an amount of 3 wt% or less based on the total weight of the composition for a gel polymer electrolyte.
The lithium salt compound may include a compound different from the lithium salt contained in the nonaqueous electrolyte, in particular, a compound selected from the group consisting of LiPO 2 F 2 LiODFB, liBOB (lithium bisoxalato borate (LiB (C) 2 O 4 ) 2 ) And LiBF 4 At least one compound of the group consisting of, and the amount thereof may be 3% by weight or less based on the total weight of the composition for a gel polymer electrolyte.
Further, two or more supplemental additives may be used in combination, and the content of the supplemental additive may be 20% by weight or less, particularly 0.1 to 10% by weight, based on the total weight of the composition for a gel polymer electrolyte. When the content of the supplemental additive is less than 0.01% by weight, the effect of sufficiently improving the low-temperature output, high-temperature storage characteristics, and high-temperature life characteristics of the battery cannot be obtained. When the content of the supplemental additive is more than 20% by weight, excessive side reactions may occur in the composition for a gel polymer electrolyte during charge/discharge of the battery due to excessive amounts of the additive. In particular, when the additives are excessively added, they cannot be sufficiently decomposed at high temperature and may remain in the electrolyte in the form of unreacted materials or precipitates at room temperature. In this case, side reactions may occur, resulting in a decrease in the life span or resistance characteristics of the secondary battery.
According to one embodiment of the invention, the method may further comprise the step of vacuum sealing the battery at a pressure of less than-95 kPa after step (S3).
After the composition for a gel polymer electrolyte is injected in step (S3), a gel polymer electrolyte is formed, and then a vacuum sealing step may be performed under a high vacuum. In particular, the vacuum sealing step may be performed by applying a predetermined high vacuum degree to a battery having a battery case including the electrode assembly obtained from step (S2) and the composition for a gel polymer electrolyte injected therein.
In the case of a battery injected with a liquid electrolyte, the application of a high vacuum may cause evaporation of the electrolyte, resulting in problems of deterioration of long-term cycle characteristics and degradation of battery life. Therefore, when the liquid electrolyte is injected, a pressure of-95 kPa or more should be applied in the sealing step.
However, according to the present invention, the sealing step can be performed at a relatively high vacuum level as compared to the prior art, and the rigidity and life of the battery can be further improved since the gel polymer electrolyte has lower volatility as compared to the liquid electrolyte and the adhesion between the battery case and the electrode assembly is improved.
In particular, the cell obtained from step (S3) may be subjected to a vacuum sealing step at a pressure of less than-95 kPa or a pressure of-100 kPa to-120 kPa. When vacuum sealing is performed under the above-defined pressure conditions, it is possible to prevent water from penetrating into the composition for a gel polymer electrolyte injected into the battery and to prevent air from being introduced into the battery from the outside. It is also possible to increase the residual amount of electrolyte and the degree of gelation after the vacuum sealing step, and to improve the rigidity and life characteristics of the battery.
The vacuum sealing step may be performed for 5 seconds to 30 seconds.
In addition, the vacuum sealed battery may be gelled by polymerization or crosslinking under suitable temperature and time conditions to form a gel polymer electrolyte.
For example, the gelling may be performed at a temperature of about 50 ℃ to 100 ℃ or about 60 ℃ to 80 ℃. In addition, the gelation may be performed at the above-defined temperature range for 0.5 to 48 hours, or 0.5 to 24 hours. In this way, the polymerizable compound present in the composition for a gel polymer electrolyte is polymerized or crosslinked to form a gel polymer electrolyte.
Then, by a temperature of 50 ℃ or higher and 0.1kgf/cm 2 To 5kgf/cm 2 The battery is charged at least twice under the pressure of (a) to perform formation of the battery (S4).
The pressure application in step (S4) may include applying the pressure at least once by using a pressurizing means. The pressurizing means is not particularly limited as long as it can apply an appropriate level of pressure to the battery. For example, the pressurizing means may be a clamp. In particular, the pressure application may be performed by inserting the battery between a pair of jigs facing each other and pressurizing. For example, the pressurizing means may be at 0.1kgf/cm for applying pressure 2 To 5kgf/cm 2 Is pressurized to the cell. In addition, the pressurization may be performed for 1 minute to 10 hours, or 1 hour to 5 hours.
Formation of a battery is a step of initially charging the battery in order to activate an electrode active material and form a Solid Electrolyte Interface (SEI) layer on an electrode surface. In the case of the gel polymer electrolyte secondary battery of the present invention, such formation may be performed by applying a current to an electrode assembly wetted with the composition using the gel polymer electrolyte to a predetermined voltage level. In the battery formation step, gas is inevitably generated in the battery by decomposition of an electrolyte or the like. However, according to the present invention, the formation of the battery is performed under predetermined high temperature and high pressure conditions, and thus, the gas generated in the battery can be removed. In particular, in the case of a secondary battery using a gel polymer electrolyte, the electrolyte is already present in a gel state in the formation step, and thus gas cannot be removed by applying high pressure. However, since the manufacturing method of the secondary battery of the present invention does not include a step of applying a pressure exceeding the ambient pressure to the electrode assembly before the formation step is performed, the electrode does not adhere tightly to the separator, and the gas can be rapidly discharged by the high pressure applied in the formation step.
In particular, step (S4) may comprise the steps of: (S4 a) at a temperature of 50℃to 60℃and 0.1kgf/cm 2 To 1kgf/cm 2 Initial charging is performed to 20% or less of the capacity (state of charge, SOC) of the secondary battery; and (S4 b) 3kgf/cm at a temperature of 50℃to 60 ℃in the presence of a catalyst 2 To 5kgf/cm 2 Secondary charging is performed to 15% to 60% or less of the capacity (state of charge, SOC) of the secondary battery.
When the charging step in the formation step is divided into a plurality of steps having predetermined conditions, uniform charging may be performed by initial low-rate charging in step (S4 a) to form a uniform SEI layer, thereby causing the generation of a large amount of gas. Further, in step (S4 b), a higher magnification is applied to reduce the time, and the pressure is increased so as to remove the gas to the outside.
According to one embodiment of the present invention, the method may further comprise a step of measuring at 3kgf/cm 2 And a step (S5) of storing the battery formed in the step (S4) at a temperature of 60 ℃ or higher under the above pressure.
The step (S5) is a step of leaving the formed battery under high temperature and high pressure conditions for a predetermined time. The adhesive present in the separator may be softened by the step (S5) to improve the adhesion between the electrode and the separator, and the gas trapped in the electrode and/or at the interface of the electrode and the separator may be effectively discharged.
Step (S5) may also be referred to as a Clamping and Baking (CB) step. Hereinafter, the gripping and baking steps will be explained in more detail.
According to one embodiment of the present invention, the gas generated in the secondary battery may be removed by storing the formed battery under a predetermined high temperature and high pressure condition. In particular, in the case of a secondary battery using a gel polymer electrolyte, the electrolyte is already present in a gel state in the formation step, and thus gas cannot be removed by applying high pressure after the formation step. However, since the manufacturing method of the secondary battery of the present invention does not include a step of applying a pressure exceeding the ambient pressure to the electrode assembly before the formation step is performed, the electrode is not tightly adhered to the separator, and thus the high pressure applied in the clamping and baking steps after the formation step can accelerate the discharge of the gas.
In particular, the battery after formation may be stored at a temperature above 60 ℃, 60 ℃ to 100 ℃, or 70 ℃ to 90 ℃. The pressure application in step (S5) may include applying the pressure at least once by using a pressurizing means. The pressurizing means is not particularly limited as long as it can apply an appropriate level of pressure to the battery. For example, the pressurizing means may be a clamp. In particular, the pressure application may be performed by inserting the battery between a pair of jigs facing each other and pressurizing. For example, the pressurizing means may be at 3kgf/cm for applying pressure 2 Above, or 3kgf/cm 2 To 10kgf/cm 2 Is pressurized to the cell. In addition, the pressurization may be performed for 1 minute to 5 hours, or 30 minutes to 1 hour. When pressurization is performed under the above conditions, the activation gas trapped in the electrode and at the electrode/separator interface can be removed, thereby reducing the resistance, and lithium deposition caused by the trapped gas and a reduction in lifetime caused thereby can be suppressed.
Furthermore, according to an embodiment of the present invention, after step (S4), the battery may be degassed at a pressure of less than-95 kPa.
When the degassing step is performed, the gas generated in the formation step may be removed. In particular, in the degassing step, the formed battery may be degassed at a pressure of less than-95 kPa, or-100 kPa to-120 kPa.
In the case of a battery injected with a liquid electrolyte, the application of a high vacuum in the degassing step causes the electrolyte to evaporate, resulting in a decrease in the long-term cycle characteristics and the life of the battery. Therefore, in the case of a battery injected with a liquid electrolyte, a pressure of-95 kPa or more should be applied in the degassing step.
However, according to the present invention, the degassing step can be performed at a relatively high vacuum degree as compared with the prior art, and the rigidity and life of the battery can be further improved since the gel polymer electrolyte has lower volatility as compared with the liquid electrolyte and the adhesion between the battery case and the electrode assembly is improved.
The degassing step may be performed for 5 seconds to 30 seconds to remove the gas remaining in the battery case.
Meanwhile, according to an embodiment of the present invention, after the electrode assembly is formed, a step of wrapping the electrode assembly with a separation film is performed.
The separation membrane is a porous insulating membrane and may comprise a polymeric material. For example, with respect to the separation membrane, reference will be made to the description of the porous matrix of the membrane. When the electrode assembly is wrapped with the separation film, the separation film may not be applied to the lateral side portion of the lead tab. Meanwhile, the end of the separation membrane may be fixed by using a fixing tape or an adhesive material. When the electrode assembly is wrapped with the separation film as described above, the structure of the electrode assembly can be more stably maintained.
According to the present invention, the secondary battery is preferably a lithium secondary battery. Non-limiting examples of the lithium secondary battery may include lithium metal secondary batteries, lithium ion secondary batteries, lithium polymer secondary batteries, lithium ion polymer secondary batteries, and the like.
Meanwhile, in another aspect of the present invention, there is provided a gel polymer electrolyte secondary battery obtained by the manufacturing method of the gel polymer electrolyte secondary battery of the embodiment of the present invention. The secondary battery may have a rigidity of 4.0Mpa or more. In a modification, the secondary battery may have a rigidity of 4.5Mpa or more.
Here, the rigidity may be determined by using a UTM instrument. For example, a jig having a size of 3mm×3mm is applied to the top of the secondary battery to pressurize the center of the secondary battery at a rate of 10mm/min under a force of 30 gf. Here, the maximum force (bending stress, MPa) may be determined when the battery extends 2mm from the preload (the degree of pressurization of the battery from the reference value).
Examples
The embodiments will be described more fully hereinafter so that the invention may be readily understood. The following examples may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
Examples
Group A
Example A-1
(preparation of ceramic coated separator and electrode)
First, al as ceramic particles 2 O 3 And a first binder polymer (a mixture of TRD 202A available from JSR and AP-0821 available from APEC) at 96:4 to a solvent to prepare a slurry for ceramic coating.
The slurry for ceramic coating was applied to both surfaces of a polyethylene porous film (thickness 9 μm, porosity 45%) and then dried to provide a separator with ceramic coating. The thickness of the ceramic coating on one surface was about 1.5 microns.
Next, 97 wt% of LiNi as a positive electrode active material was prepared 0.8 Co 0.1 Mn 0.1 O 2 (NCM), 1 wt% of carbon black as a conductive material, and 2 wt% of polyvinylidene fluoride (PVDF) as a binder were added to N-methyl-2-pyrrolidone (NMP) as a solvent to obtain a positive electrode active material slurry. The positive electrode active material slurry was applied onto and dried on an aluminum (Al) foil having a thickness of about 20 μm as a positive electrode current collector, and then rolled to obtain a positive electrode.
Further, 96% by weight of carbon powder as a negative electrode active material, 3% by weight of PVDF as a binder, and 1% by weight of carbon black as a conductive material were added to NMP as a solvent to obtain a negative electrode active material slurry. The anode active material slurry was applied onto and dried on a copper (Cu) foil having a thickness of 10 μm as an anode current collector, and then rolled to obtain an anode.
(preparation of composition for gel Polymer electrolyte)
First, liPF is used 6 Dissolved in a composition of Ethylene Carbonate (EC): methyl ethyl carbonate (EMC) =30: 70 (volume ratio) of nonaqueous organic solventTo 1.0M. Next, 5 parts by weight of trimethylolpropane triacrylate as a polymerizable compound and 0.06 parts by weight of Azobisisobutyronitrile (AIBN) as a polymerization initiator were added to the nonaqueous electrolyte based on 100% by weight of the composition for a gel polymer electrolyte to prepare a composition for a gel polymer electrolyte.
(manufacture of electrode Assembly and Secondary Battery)
The negative electrode and the positive electrode are sequentially inserted into the portion where the ceramic coated separator is folded in a zigzag shape and overlapped. A composition comprising an acrylic polymer (a copolymer containing Methyl Methacrylate (MMA) -derived repeating units, 2-ethylhexyl acrylate (2-EHA) -derived repeating units, and 2-hydroxyethyl acrylate (2-HEA) -derived repeating units in a weight ratio of 40:30:30) was applied to one surface of the ceramic coated separator in a dot pattern having a diameter of 0.5 mm. Here, the size of the separator was 306.5mm (width) ×104.5mm (length), and the composition was applied to three points at intervals of 100mm in the transverse direction and 0.35mm in the longitudinal direction. The electrode assembly is manufactured under conditions of room temperature and ambient pressure.
The obtained electrode assembly was inserted into a battery case, and the composition for a gel polymer electrolyte prepared as described above was injected thereto to obtain a secondary battery. Then, the battery case was left at room temperature for 2 days so that it could be wetted by the electrolyte, and the composition of the gel polymer electrolyte was left in a chamber at 60 ℃ for 10 hours to perform polymerization.
(Battery formation step)
The formation of the secondary battery is performed in two steps.
Primary charging: by applying 0.1kgf/cm at 60 DEG C 2 Is charged to 20% of its capacity at a rate of 0.1C.
And (3) secondary charging: by applying 5kgf/cm at 60 DEG C 2 Is charged to 60% of its capacity at a rate of 0.2C.
Here, the pressure application during the initial charge and the secondary charge is performed by inserting the battery between a pair of jigs facing each other.
Example A-2
A battery was obtained in the same manner as in example A-1, except that, as a subsequent step, after the battery formation step was performed, a clamping and baking step was further performed, the secondary battery was interposed between a pair of jigs facing each other, and 5kgf/cm was applied thereto at a temperature of 80 ℃ 2 Is stored for 30 minutes under pressure.
Comparative example A-1
A battery was obtained in the same manner as in example a-1, and the secondary battery was charged once under the following conditions in the battery formation step.
Initial charging: the secondary battery was charged to 60% of its capacity at a rate of 0.2C at room temperature (25 ℃) without pressure.
Comparative example A-2
A battery was obtained in the same manner as in example a-1, except that the secondary battery was charged once under the following conditions in the battery formation step.
Initial charging: the secondary battery was charged to 60% of its capacity at a rate of 0.2C at a temperature of 60C without pressure.
Comparative example A-3
A battery was obtained in the same manner as in example A-1, except that the content of the binder polymer in the ceramic-coated separator was 30% by weight, and that when the electrode assembly was assembled, the separator was laminated at high temperature (80 ℃) and high pressure (3 kgf/cm 2 ) Conventional lamination is performed below.
Comparative examples A to 4
A battery was obtained in the same manner as in example a-1, except that the following battery formation step and clamping and baking steps were performed.
(Battery formation step)
Initial charging: the secondary battery was charged to 60% of its capacity at a rate of 0.2C at room temperature (25 ℃) without pressure.
(step of holding and baking)
The secondary battery was inserted between a pair of jigs facing each other at 80 deg.cTo which 5kgf/cm was applied at a temperature 2 Is stored for 30 minutes under pressure.
Test results
Physical properties of the gel polymer electrolyte secondary batteries in each of the examples and comparative examples of group a were evaluated as follows. The results are shown in Table 1 below.
TABLE 1
(1) Resistance measuring method
The resistance of each of the secondary batteries in the examples and comparative examples of group a was determined by using the voltage change (Δv) measured when discharging from SOC 50% at a rate of 2.5C for 10 seconds.
(2) Method for determining lifetime
The secondary batteries in each of the examples and comparative examples of group a were first charged/discharged (charged/discharged once) by using an electrochemical charger. Here, the secondary battery was charged to a voltage of 4.2V by applying a current having a current density of 0.33C magnification, and discharged to 2.5V at the same current density. The secondary battery was subjected to such charge/discharge cycles 100 times.
The voltage and the capacity in each of the positive electrode and the negative electrode included in each battery are determined in the above charge/discharge cycle.
Then, the capacity retention rate of each battery is calculated from the determined voltage and capacity according to the following formula.
Capacity retention (%) = (capacity of 100 th cycle/initial capacity) ×100
(3) Rigidity evaluation method
The rigidity of the secondary batteries in each of the examples and comparative examples of group a was measured by using a UTM instrument. The center of the secondary battery was pressurized under a force of 30gf and a rate of 10mm/min by applying a jig having dimensions of 3mm×3mm to the top of the secondary battery. Here, the maximum force (bending stress, MPa) may be determined when the battery extends 2mm from the preload (the degree of pressurization of the battery from the reference value).
(4) Safety evaluation based on nailing test
The secondary batteries of each of the examples and comparative examples of group A were fully charged to 4.4V at room temperature, and were subjected to the nail penetration test under the condition of GB/T (nail diameter 2.5mm, penetration speed 6 m/min). The test results are shown in table 1 above.
When secondary batteries using the compositions for gel polymer electrolytes of example a-1 and comparative examples a-1 to a-3 as electrolytes were compared with each other, it can be seen from table 1 that degassing was more easily achieved in the case of example a-1 in which high temperature and high pressure conditions were applied in the battery formation step, compared with comparative example a-1 in which formation was performed at room temperature and comparative example a-2 in which formation was performed at high temperature without applying pressure. This indicates that the secondary battery of example a-1 exhibited excellent resistance and life characteristics, rigidity, and safety.
Further, when comparing example a-1 with example a-2, in the case of example a-2, the clamping and baking step was further performed after the same battery formation step was performed, and the gas discharge was accelerated by the high pressure applied during the clamping and baking step, so that the secondary battery of example a-2 exhibited excellent battery performance.
In addition, in the case of comparative example A-3, the same battery formation step as in example A-1 was performed, but a larger amount of binder was contained in the ceramic coated separator than in example A-1, so that the secondary battery of comparative example A-3 exhibited inferior resistance characteristics. Further, unlike example A-1, comparative example A-3 includes lamination under high temperature and high pressure conditions. Therefore, even if the same battery formation step as in example a-1 was performed, the gas generated in the battery could not be easily removed, and thus the secondary battery of comparative example a-3 exhibited poor life characteristics.
Group B
Example B-1
A battery was obtained in the same manner as in example a-1. The 10-hour half-life temperature of the polymerization initiator AIBN (V59) used in example A-1 was 67 ℃.
Example B-2
A battery was obtained in the same manner as in example B-1, except that 2,2' -azobis-2, 4-dimethylvaleronitrile (V65) having a half-life temperature of 51℃for 10 hours was used as a polymerization initiator.
Example B-3
A battery was obtained in the same manner as in example B-1, except that, as a subsequent step, after the battery formation step was performed, a clamping and baking step was further performed, the secondary battery was interposed between a pair of jigs facing each other, and 5kgf/cm was applied thereto at a temperature of 80 ℃ 2 Is stored for 30 minutes under pressure.
Example B-4
A battery was obtained in the same manner as in embodiment B-2, except that, as a subsequent step, after the battery formation step was performed, a clamping and baking step was further performed, the secondary battery was interposed between a pair of jigs facing each other, and 5kgf/cm was applied thereto at a temperature of 80 ℃ 2 Is stored for 30 minutes under pressure.
Comparative example B-1
A battery was obtained in the same manner as in embodiment B-1, except that the content of the binder polymer in the ceramic-coated separator was 30 wt%, and that when the electrode assembly was assembled, the battery was manufactured at high temperature (80 ℃) and high pressure (3 kgf/cm 2 ) Conventional lamination is performed below.
Test results
Physical properties of the gel polymer electrolyte secondary batteries in each of the examples and comparative examples of group B were evaluated as follows.
In table 2, the results of the gelation ratio of the polymer are shown. In table 3, the performance results of the gel polymer secondary battery are shown. The method for determining physical properties in table 3 is the same as that described in group a.
TABLE 2
(1) Method for determining wetting completion time
The point in time of resistance convergence is determined by using Electrochemical Impedance Spectroscopy (EIS).
(2) Pre-gelation (%) at the completion of wetting and polymer conversion (%)
The pregelatinization (%) and the polymer conversion were calculated according to the following equation 1. In particular, the polymerizable compound present in the composition for a gel polymer electrolyte was quantitatively analyzed by NMR to determine the difference between the polymers before and after polymerization. In particular, NMR is used to quantitatively analyze the reactive sites of polymers and the remaining reactive sites of polymers. The results are shown in Table 2.
[ mathematics 1]
Polymer conversion (%) =100- (remaining reaction sites of post-polymerization polymer/reaction sites of pre-polymerization polymer) ×100
TABLE 3
Group B Example B-1 Example B-2 Example B-3 Example B-4 Comparative example B-1
Resistor (mOhm) 2.22 2.11 2.10 2.02 2.35
Life (%, 100 cycles) 98.9 99.2 98.5 99.0 92.7
Rigidity (MPa) 4.39 4.58 5.02 5.15 6.81
Nail thorn (pass/total) 3/3 3/3 3/3 3/3 3/3
As can be seen from Table 2, examples B-1 to B-4 completed wetting faster than comparative example B-1 and exhibited lower pre-gel ratios and higher post-gel polymer conversion than comparative example B-1. Further, in comparative example B-1, unlike examples B-1 to B-4, lamination was performed under high temperature and high pressure conditions. Thus, it can be seen that in comparative example B-1, the separator was in closer contact with the electrode, resulting in longer electrolyte wetting time.
Further, as can be seen from Table 3, in comparative example B-1, even if the same cell formation steps as in examples B-1 and B-2 were performed, the gas generated in the cells could not be easily removed. Therefore, the battery of comparative example B-1 exhibited poor life or resistance characteristics. It can also be seen that examples B-3 and B-4 provide improved cell stiffness by performing the clamping and baking steps.
Group C
Example C-1
A battery was obtained in the same manner as in example a-1.
Example C-2
A battery was obtained in the same manner as in example C-1, except that, as a subsequent step, after the battery formation step was performed, a clamping and baking step was further performed, the secondary battery was interposed between a pair of jigs facing each other, and 5kgf/cm was applied thereto at a temperature of 80 ℃ 2 Is stored for 30 minutes under pressure.
Comparative example C-1
The same separator as the ceramic coated separator of example C-1 was used, except that the content of the binder polymer in the ceramic coated separator was 30 wt%.
An electrode assembly was obtained in the same manner as in example C-1, except that, when the electrode assembly was assembled, the electrode assembly was assembled at a high temperature (80 ℃) and a high pressure (3 kgf/cm 2 ) Conventional lamination is performed below.
A battery was obtained in the same manner as in example C-1, except that a nonaqueous electrolyte having the following composition was injected.
(preparation of nonaqueous electrolyte)
By passing LiPF 6 Dissolved in a composition of Ethylene Carbonate (EC): methyl ethyl carbonate (EMC) =30: 70 (volume ratio) in a nonaqueous organic solvent to 1.0M.
Comparative example C-2
The same separator as the ceramic coated separator of example C-1 was used, except that the content of the binder polymer in the ceramic coated separator was 30 wt%.
An electrode assembly was obtained in the same manner as in example C-1, except that, when the electrode assembly was assembled, the electrode assembly was assembled at a high temperature (80 ℃) and a high pressure (3 kgf/cm 2 ) Conventional lamination is performed below.
Comparative example C-3
A battery was obtained in the same manner as in example C-1, except that a nonaqueous electrolyte having the following composition was injected.
(preparation of nonaqueous electrolyte)
By passing LiPF 6 Dissolved in a composition of Ethylene Carbonate (EC): methyl ethyl carbonate (EMC) =30: 70 (volume ratio) in a nonaqueous organic solvent to 1.0M.
Test results
The gel polymer electrolyte secondary batteries of each of the examples and comparative examples of group C were subjected to a vacuum sealing step and a degassing step for 5 seconds to 30 seconds, respectively, under pressure conditions of-95 kPa and-105 kPa.
The evaluation results of the physical properties under each condition are shown in table 4 below.
TABLE 4
(1) Method for measuring residual quantity of electrolyte
The total volume of pores present in the positive electrode active material, the negative electrode active material, and the separator was taken to be 100%. The electrolyte injection amount (excess factor) was set to 125% in consideration of dead space existing inside the battery and the electrolytic quality required for cycle consumption, and the electrolyte residual amount after the degassing step was calculated.
(2) Method for measuring rigidity
The method for determining the rigidity of the secondary battery is the same as that described in group a.
The stiffness value determined in comparative example C-1 takes 100%, and the stiffness of each of examples C-1 and C-2 and comparative examples C-2 and C-3 is expressed in% units based thereon.
(3) Method for measuring resistance and lifetime
The method for determining the resistance and the lifetime of the secondary battery is the same as that described in group a.
(4) Determination of elevated firing temperature
When the battery was heated at a temperature rising rate of 0.5 deg.c/min, the temperature of the center portion of the battery was measured at the time of ignition.
As can be seen from Table 4, examples C-1, C-2 and comparative example C-2 using the composition for a gel polymer electrolyte showed better results in terms of electrolyte residual amount and battery rigidity than comparative examples C-1 and C-3 using a nonaqueous electrolyte.
In particular, when sealing and degassing performed at a pressure of-95 kPa are compared with sealing and degassing performed at a pressure of-105 kPa, examples C-1, C-2 and comparative example C-2 using the composition for a gel polymer provide further increased cell rigidity while maintaining the residual amount of electrolyte and resistance at the same level, in spite of an increase in vacuum degree. In contrast, comparative examples C-1 and C-3 using a nonaqueous electrolyte showed a decrease in the residual amount of electrolyte and an increase in the battery resistance.
Meanwhile, in the case of comparative example C-2, when the electrode assembly was formed, the content of the binder contained in the ceramic coated separator was greater than in examples C-1 and C-2, and the lamination step was performed under high temperature and high pressure conditions, unlike in examples C-1 and C-2. As a result, comparative example C-2 exhibited poor resistance characteristics and safety. In the case of examples C-1 and C-2, the separator maintained its physical shape even at high temperature and delayed thermal shrinkage to the maximum extent, thereby obtaining excellent safety. In particular, in the case of example C-2, the clamping and baking steps were further performed to improve the interfacial adhesion between the separator and the electrode, thereby reducing the resistance and further improving the rigidity of the battery.
Description of the reference numerals
1: stacking table
2: diaphragm supply unit
21: diaphragm
3: electrode supply unit
31: first electrode
32: second electrode
4: adhesive applying unit
41: composition comprising an adhesive polymer

Claims (21)

1. A method for manufacturing a gel polymer electrolyte secondary battery, comprising the steps of:
(S1) preparing a ceramic coated separator and an electrode, wherein the ceramic coated separator comprises a porous matrix and a ceramic coating comprising a first binder polymer and ceramic particles;
(S2) performing lamination of the separator and the electrode to provide an electrode assembly, wherein a composition comprising a second binder polymer is applied in a patterned shape onto at least one surface of the separator or electrode, and the separator is folded in a zigzag manner so that the electrode can be inserted into a region where the separator overlaps;
(S3) injecting a composition for a gel polymer electrolyte into the electrode assembly to obtain a battery; and
(S4) by heating at a temperature of 50 ℃ or higher and 0.1kgf/cm 2 To 5kgf/cm 2 The battery is charged at least twice under the pressure of (a) to perform formation.
2. The method for manufacturing a gel polymer electrolyte secondary battery according to claim 1, wherein the lamination in step (S2) is performed at a temperature of 30 ℃ or less.
3. The method for manufacturing a gel polymer electrolyte secondary battery according to claim 1, wherein the lamination in step (S2) is performed under an ambient pressure condition or at 3kgf/cm applied to the electrode assembly 2 The following pressure conditions were used.
4. The method for manufacturing a gel polymer electrolyte secondary battery according to claim 1, wherein in step (S2), the lamination step is not performed with the application of pressure.
5. The method of manufacturing a gel polymer electrolyte secondary battery according to claim 1, wherein the content of the first binder polymer is 0.1 to 10 wt% based on the total weight of the ceramic coating layer.
6. The method for manufacturing a gel polymer electrolyte secondary battery according to claim 1, wherein the first binder polymer is an acrylate-based binder polymer.
7. The method of manufacturing a gel polymer electrolyte secondary battery according to claim 1, wherein the patterned shape includes at least one of a dot pattern, a stripe pattern, and a grid pattern.
8. The method for producing a gel polymer electrolyte secondary battery according to claim 1, wherein the composition for a gel polymer electrolyte comprises a polymerization initiator having a 10-hour half-life temperature of 60 ℃ or less, a polymerizable compound, a lithium salt, and a nonaqueous organic solvent.
9. The method for producing a gel polymer electrolyte secondary battery according to claim 8, wherein the 10-hour half-life temperature of the polymerization initiator is 55 ℃ or lower.
10. The method for manufacturing a gel polymer electrolyte secondary battery according to claim 8, wherein the content of the polymerization initiator is 0.1 to 10 parts by weight based on 100 parts by weight of the composition for gel polymer electrolyte.
11. The method of manufacturing a gel polymer electrolyte secondary battery according to claim 1, wherein the pressure application in step (S4) includes applying pressure at least once by using a pressurizing device.
12. The method for manufacturing a gel polymer electrolyte secondary battery according to claim 1, wherein step (S4) comprises the steps of:
(S4 a) at a temperature of 50℃to 60℃and 0.1kgf/cm 2 To 1kgf/cm 2 To a capacity of the secondary battery, that is, to 20% or less of the state of charge SOC; and
(S4 b) at a temperature of 50℃to 60℃and 3kgf/cm 2 To 5kgf/cm 2 Secondary charging is performed to a capacity of the secondary battery, i.e., 15% to 60% of the state of charge SOC.
13. The method for manufacturing a gel polymer electrolyte secondary battery according to claim 1, further comprising the steps of:
(S5) storing the battery subjected to the formation in the step (S4) at a temperature of 60 ℃ or higher and 3kgf/cm 2 Under the above pressure.
14. The method for manufacturing a gel polymer electrolyte secondary battery according to claim 13, wherein step (S5) is performed for 30 minutes to 5 hours.
15. The manufacturing method of a gel polymer electrolyte secondary battery according to claim 13, wherein the pressure application in step (S5) includes applying pressure at least once by using a pressurizing device.
16. The method for manufacturing a gel polymer electrolyte secondary battery according to claim 1, further comprising a step of vacuum sealing the battery at a pressure of less than-95 kPa after step (S3).
17. The method for manufacturing a gel polymer electrolyte secondary battery according to claim 16, wherein the vacuum sealing step is performed at a pressure of-100 kPa to-120 kPa.
18. The method of manufacturing a gel polymer electrolyte secondary battery according to claim 16, wherein the vacuum sealing step is performed for 5 seconds to 30 seconds.
19. The method for manufacturing a gel polymer electrolyte secondary battery according to claim 1, further comprising a step of degassing the battery at a pressure of less than-95 kPa after step (S4).
20. The method for manufacturing a gel polymer electrolyte secondary battery according to claim 19, wherein the degassing is performed at a pressure of-100 kPa to-120 kPa.
21. A gel polymer electrolyte secondary battery obtained by the method of any one of claims 1 to 20 and having a rigidity of 4.0MPa or more.
CN202380012215.2A 2022-01-14 2023-01-12 Method for manufacturing gel polymer electrolyte secondary battery and gel polymer electrolyte secondary battery obtained thereby Pending CN117501510A (en)

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KR20220006082 2022-01-14
PCT/KR2023/000599 WO2023136637A1 (en) 2022-01-14 2023-01-12 Method of preparing gel polymer electrolyte secondary battery and gel polymer electrolyte secondary battery therefrom

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