KR20170060990A

KR20170060990A - Lithium ion secondary battery jelly-roll tape

Info

Publication number: KR20170060990A
Application number: KR1020150165844A
Authority: KR
Inventors: 김재영; 김상은; 김남곤; 조아라; 문승현
Original assignee: 주식회사 테이팩스
Priority date: 2015-11-25
Filing date: 2015-11-25
Publication date: 2017-06-02
Also published as: KR101834561B1

Abstract

The present invention relates to a lithium ion secondary battery jelly roll finishing tape, and more particularly, to a lithium ion secondary battery jelly roll finishing tape which is capable of absorbing the volume expansion inside a battery due to charging and discharging of jelly roll, Ion secondary battery jelly roll finishing tape.

Description

LITHIUM ION SECONDARY BATTERY JELLY-ROLL TAPE [0002]

The present invention relates to a lithium ion secondary battery jelly roll finishing tape, and more particularly, to a lithium ion secondary battery jelly roll finishing tape which has adequate shrinking force and adhesive strength, and which can absorb a volume expansion inside a battery due to expansion of jelly roll To a secondary battery jelly roll finishing tape.

As technology development and demand for mobile devices are increasing, the demand for batteries as energy sources is rapidly increasing, and accordingly, a lot of researches on batteries capable of meeting various demands have been conducted.

In view of the shape of the battery, there is a high demand for a prismatic secondary battery and a pouch type secondary battery which can be applied to products such as mobile phones with a thin thickness. In terms of materials, lithium ion batteries with high energy density, discharge voltage, There is a high demand for lithium secondary batteries such as polymer batteries.

The secondary battery may be classified according to how the electrode assembly having the anode / separator / cathode structure is formed. Typically, the jelly-roll having the structure in which the anode and the cathode are wrapped with the separator interposed therebetween, (Stacked type) electrode assembly in which a plurality of positive electrodes and negative electrodes cut in units of a predetermined size are sequentially stacked with a separator interposed therebetween, a stacked (stacked) electrode assembly in which a predetermined unit of positive and negative electrodes are stacked A stack / folding type electrode assembly having a structure in which a bi-cell or a full cell stacked in a state of being wound is wound. Among these, the jelly-roll type electrode assembly has advantages of easy manufacture and high energy density per weight. In the case of a circular battery, for example, the electrode assembly may be housed in a cylindrical can and an electrolyte may be injected.

However, when a battery is manufactured by housing the electrode assembly in a circular can, since the electrode assembly is usually smaller than the circular can, a gap is formed between the electrode assembly and the inner wall of the can.

The electrode assembly housed in the can can flow inside the can due to external vibration or impact and rotate to a certain degree. In this case, for example, a phenomenon that the welding portion of the tab is broken and the internal circuit is broken Which may cause an increase in the internal resistance of the battery or damage of the electrode tab, thereby greatly reducing the performance of the battery. Therefore, a gap existing between the separated jelly roll and the cylindrical can is filled, and the jelly roll needs to be fixed.

Accordingly, a method of applying a swelling tape between a conventional electrode assembly and a circular can was developed. 1 and 2, the swelling tapes 100 and 200 including the adhesive layers 110 and 210 and the swelling layers 120 and 220 are formed into a jelly-roll type film including a negative electrode, A method of attaching the electrode assembly 201 to the outer periphery of the electrode assembly 201 has been developed.

However, when the high-cost swelling layers 120 and 220 are attached to the front surface of the electrode assembly 201 as described above, there is a disadvantage that the unit cost is higher than that of a conventional polypropylene (PP) tape.

In order to solve the problems of the related art as described above, the present invention has been made to solve the problems of the prior art as described above. After the battery is manufactured in the form of an article after the finish tape is attached to the jelly roll, the jelly roll is separated from the jelly roll and contracted. And to provide a lithium ion secondary cell jelly roll finishing tape of new material capable of reducing the pressure.

Disclosure of the Invention In order to solve the above-described problems, the present invention provides a substrate layer comprising at least one selected from the group consisting of polystyrene, polybutadiene, styrene-butadiene copolymer, and styrene-butadiene-styrene copolymer; And a pressure-sensitive adhesive layer formed on one side of the base layer, the pressure-sensitive adhesive layer being formed in a direction parallel to the base layer and comprising at least one selected from the group consisting of acrylic, rubber and urethane; The present invention provides a jelly roll finishing tape for a lithium ion secondary battery.

In the lithium ion secondary cell jelly roll finishing tape according to the present invention, the substrate layer is characterized by having a shrinkage ratio in the longitudinal direction of 5% or more at a temperature of 90 ° C or more and a shrinkage ratio of 5% or more in the direction perpendicular to the longitudinal direction .

In the jelly roll finishing tape of a lithium ion secondary battery according to the present invention, the substrate layer is formed by immersing the film in a carbonate-based single or mixed solution at room temperature for 15 minutes and having a longitudinal shrinkage of 5% or more, % Or more. That is, the lithium ion secondary battery jelly roll finishing tape according to the present invention is characterized by exhibiting a certain degree of shrinkage in a state of being immersed in an electrolyte by the production of a secondary battery.

In the lithium ion secondary battery jelly roll finishing tape according to the present invention, when the base material layer is a sheet or a film, the thickness is not particularly limited and may be, for example, And the like. In the lithium ion secondary battery jelly roll finishing tape according to the present invention, the base layer has a thickness of 10 mu m to 100 mu m.

In the jelly roll finishing tape for a lithium ion secondary battery according to the present invention, the adhesive layer has an adhesive strength of 100 gf / 25 mm or more and 500 gf / 25 mm or less as measured according to KS T 1028. In the lithium ion secondary battery jelly roll finishing tape according to the present invention, it is preferable that the adhesive layer is designed to have an appropriate peeling force. If the peeling force of the adhesive layer is 100 gf / 25 mm or less, the adhesive layer may not properly support the stress due to the expansion of the jellyroll roll, thereby failing to fill the gap. If the peeling force is 500 gf / 25 mm or more, It may be difficult to excessively deformation of the base layer and to separate the finishing tape from the jelly roll.

In the jelly roll finishing tape for a lithium ion secondary battery according to the present invention, the adhesive layer has an adhesive strength of 10 gf / 25 mm or more and 200 gf / 25 mm or less as measured according to KS T 1028 after immersing in a carbonate-based single or mixed solution for 15 minutes . Since the jelly roll finishing tape of the lithium ion secondary battery according to the present invention is used in the secondary battery, it is necessary that the adhesive force is maintained even after immersion in a carbonate-based single or mixed solution which is a main component of the secondary battery electrolyte. The ion secondary battery jelly roll finishing tape is characterized by having an adhesion of 10 gf / 25 mm or more and 200 gf / 25 mm or less as measured according to KS T 1028 after immersing in a carbonate-based single or mixed solution for 15 minutes.

In the lithium ion secondary battery jelly roll finishing tape according to the present invention, the thickness of the pressure-sensitive adhesive layer is 1 to 25 탆

In the case of the present invention, in place of the oriented polystyrene (OPS) film which is generally used as the base material of the conventional lithium ion secondary cell jelly roll finishing tape, polystyrene, polybutadiene, styrene-butadiene copolymer, And a styrene-butadiene-styrene copolymer.

Materials of base layer Oriented polystyrene (OPS) films that have been stretched have already been used. The heat shrinkable film is made of polyvinyl chloride (PVC), polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), linear low density polyethylene (LLDPE) It is known that any one of oriented polystyrene (OPS) and oriented polypropylene (OPP) can be used. The oriented polystyrene film is one of the heat shrinkable films and is known as a material which is easy to mold because of low melting temperature and melt viscosity at the time of molding. Since the orientated polystyrene film has adhesiveness upon heat pressing, when the orientated polystyrene film adheres to the outer surface of the electrode assembly, as the battery is charged and discharged, the electrode assembly, It is known that the jelly-roll type can be stably maintained.

The method for producing the base layer of the lithium ion secondary battery jelly roll finishing tape according to the present invention is not particularly limited. For example, a raw material containing the resin and, if necessary, known additives may be extruded or cast, But it is also possible to use a method of applying an appropriate treatment in the molding process so as to exhibit expansion characteristics.

Among them, the lithium ion secondary battery according to the present invention is more preferable than the lithium ion secondary battery jelly according to the present invention from the viewpoint that it is more difficult to elute as the electrolyte solution and the reactivity with the electrolyte in the electrolytic solution is low, The roll finishing tape is characterized in that the base layer contains 60 to 150 parts by weight of the styrene-butadiene-styrene copolymer per 100 parts by weight of the polystyrene. The copolymer comprising the polystyrene and the styrene-butadiene-styrene copolymer according to the present invention is composed of a copolymer of a hard polystyrene block and a flexible polybutadiene and polyisoprene. When heated, the copolymer shows fluidity, And the adhesive property is exhibited by the aggregation of the part and the ductility of the rubber part, and thus the adhesive effect is exhibited efficiently.

As the adhesive layer, various kinds of adhesive layers may be used as long as they can exhibit the peeling force. For example, the adhesive layer may include any one selected from the group consisting of an acrylic pressure-sensitive adhesive, a urethane pressure-sensitive adhesive, an epoxy pressure-sensitive adhesive, a silicone pressure-sensitive adhesive and a rubber pressure-sensitive adhesive, or a mixture of two or more thereof. The pressure-sensitive adhesive layer of the present invention is characterized by being made of an acrylic pressure-sensitive adhesive. The acrylic pressure-sensitive adhesive contains at least an acrylic polymer as a base polymer.

The above-mentioned pressure-sensitive adhesive layer can be obtained, for example, by preparing a coating liquid containing the acrylic polymer and the multi-functional crosslinking agent as described above, coating on one surface of the substrate layer, and performing crosslinking reaction of the polymer and the multi- .

The acrylic pressure sensitive adhesive in the present invention may contain other components (for example, a tackifier, a plasticizer, a filler, an antioxidant, etc.) in addition to the acrylic polymer and the crosslinking agent.

The pressure-sensitive adhesive layer of the present invention can be produced by preparing a coating liquid by diluting the acrylic pressure-sensitive adhesive with a solvent (for example, toluene, xylene, ethyl acetate, methyl ethyl ketone or the like) A release paper, etc.) and drying it. The pressure-sensitive adhesive layer of the present invention may be a single layer or a laminate of two or more layers. When the pressure-sensitive adhesive layer is a laminate of two or more layers, each layer may have the same composition or may be laminated by combining layers of different compositions. When the pressure-sensitive adhesive layer is provided on both sides of the substrate, the pressure-sensitive adhesive layer may have the same composition or different compositions.

If the thickness is 1 占 퐉 or less, it is difficult to obtain an adhesive force necessary for use for the purpose of preventing the short-circuit between electrodes due to penetration of the burr existing in the electrode plate into the battery case, There is a tendency to disappear. On the other hand, if the thickness of the pressure-sensitive adhesive layer is increased to increase the adhesive property of the pressure-sensitive adhesive tape and if the thickness exceeds 25 m, the pressure-sensitive adhesive is easily pushed out from the end face, It is difficult to perform the winding work such that the adhesive pushed out when the stacked body of the laminated body of the laminated body is attached to the opposing separator, the deformation of the adhesive tape and the pushing out of the paste from the substrate are liable to occur, There is a tendency to become easier. The thickness of the pressure-sensitive adhesive layer is not particularly limited as it can be suitably selected in accordance with the intended application, for example, the desired peel force or the size of the gap to be filled.

The jelly roll finishing tape of the lithium ion secondary battery according to the present invention is a tape for an electrode assembly and can be used for preventing the electrode assembly from being loosened during battery assembly and fixing the electrode assembly inside the battery can.

The jelly roll finishing tape of the lithium ion secondary battery according to the present invention can be obtained by mixing a polystyrene with a styrene-butadiene-styrene (SBS) copolymer so that the pressure-sensitive adhesive does not substantially dissolve or decompose in the battery electrolyte, The substrate is peeled and separated from the interface so that the shrinkage rate and the adhesive force are improved as compared with the existing finishing tape so that the jelly roll fixed by the tape can be relaxed and is effective for increasing the charge and discharge life when used in a cylindrical secondary battery.

Figures 1 and 2 illustrate a method of applying a swelling tape between a conventional electrode assembly and a circular can.

Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited by the following examples.

<Examples> Preparation of Base Layer

Polystyrene (PS) and styrene-butadiene-styrene (SBS) copolymers were mixed as shown in Table 1 below, and a base layer having a thickness of 25 μm was prepared by extrusion.

The polystyrene raw material used was GPPS grade sold by Kumho Petrochemical Co., and the styrene-butadiene-styrene copolymer used was KTR grade sold by Kumho Petrochemical.

polystyrene
GPPS
(g) Styrene-butadiene-styrene (SBS) block copolymer (g) Acryl PSA (g) Isocyanate (g) Melamine (g) Example 1 60 40 100 0.6 0 Example 2 60 40 100 0 One Example 3 60 40 100 0.6 One Example 4 50 50 100 0.6 0 Example 5 50 50 100 0 One Example 6 50 50 100 0.6 One Example 7 40 60 100 0.6 0 Example 8 40 60 100 0 One Example 9 40 60 100 0.6 One

In the above examples, the same procedure was followed except that an oriented polypropylene (OPP) film or a polyethylene terephthalate (PET) film was used instead of the polystyrene (PS) and styrene-butadiene-styrene (SBS) The base layer of the comparative example was prepared with the composition shown in Table 2 below.

OPP (%) PET (%) Acryl PSA (g) Isocyanate (g) Melamine (g) Comparative Example 1 100 0 100 0.6 0 Comparative Example 2 100 0 100 0 One Comparative Example 3 100 0 100 0.6 One Comparative Example 4 100 100 0.6 0 Comparative Example 5 100 100 0 One Comparative Example 6 100 100 0.6 One

&Lt; Experimental Example > Shrinkage test of substrate layer in a high temperature environment

The substrate layers prepared in the above Examples and Comparative Examples were exposed to the environment at 90 캜 for 1 minute, and the shrinkage ratio was measured. The results are shown in Table 3.

It can be seen that the shrinkage ratio of the substrate layer prepared according to the embodiment of the present invention is significantly increased as compared with the comparative example.

Shrinkage (%, @ 90 ° C) Shrinkage after electrolyte impregnation
(%, MD) Shrinkage after electrolyte impregnation
(%, TD) Example 1 0 31 25 Example 2 0 31 25 Example 3 0 31 25 Example 4 7.8 37 28 Example 5 7.5 37 28 Example 6 7.7 37 28 Example 7 17.5 41 30 Example 8 18.3 41 30 Example 9 20.3 41 30 Comparative Example 1 0 0 0 Comparative Example 2 0 0 0 Comparative Example 3 0 0 0 Comparative Example 4 0 0 0 Comparative Example 5 0 0 0 Comparative Example 6 0 0 0

&Lt; Experimental Example > Shrinkage test of substrate layer after electrolyte immersion

The substrate layers prepared in Examples and Comparative Examples were immersed in a solution prepared by mixing DMC, DEC, and EC used as an electrolyte of a lithium secondary battery at a room temperature at a ratio of 1: 1: 1 for 15 minutes and then dried at room temperature to obtain a shrinkage ratio And the results are shown in Table 3.

<Examples> Tape Manufacturing

The acrylic pressure-sensitive adhesive (PSA) in parts by weight shown in Tables 1 and 2 was diluted with a solvent, and isocyanate and melamine were mixed as additives. Then, one surface of the substrate layer prepared in Examples 1 to 9 and Comparative Examples 1 to 6 To prepare base material tapes of Examples 1-1 to 1-9 and Comparative Examples 1-1 to 1-6 having a total thickness of 30 mu m.

&Lt; Experimental Example >

The adhesive strengths of the base layer tapes of Examples 1-1 to 1-9 and Comparative Examples 1-1 to 1-6 were measured and are shown in Table 4 below.

Adhesion (gf / 25mm) Adhesion after electrolyte impregnation
(gf / 25 mm) Number of charge / discharge cycles
(80% of initial capacity) Example 1-1 722 436 231 Examples 1-2 530 357 230 Example 1-3 382 51 237 Examples 1-4 718 465 294 Examples 1-5 515 339 299 Examples 1-6 371 49 302 Examples 1-7 699 452 312 Examples 1-8 519 373 325 Examples 1-9 377 53 330 Comparative Example 1-1 738 455 194 Comparative Example 1-2 513 367 195 Comparative Example 1-3 382 51 210 Comparative Example 1-4 725 433 190 Comparative Example 1-5 551 361 192 Comparative Example 1-6 377 46 201

The tape produced in the above experiment was attached to a jelly roll (electrode assembly) of a lithium ion secondary battery, and the charge and discharge cycles were repeated until the capacity was maintained at 80%. The results are shown in Table 5.

In the following Table 5, it can be seen that the number of charge / discharge cycles for maintaining 80% of the initial capacity of the embodiment of the present invention is significantly increased as compared with the comparative example.

Number of charge / discharge cycles (80% of initial capacity) Example 1 231 Example 2 230 Example 3 237 Example 4 294 Example 5 299 Example 6 302 Example 7 312 Example 8 325 Example 9 330 Comparative Example 1 194 Comparative Example 2 195 Comparative Example 3 210 Comparative Example 4 190 Comparative Example 5 192 Comparative Example 6 201

Claims

A base layer comprising at least one selected from the group consisting of polystyrene, polybutadiene, styrene-butadiene copolymer, and styrene-butadiene-styrene copolymer; And
A pressure-sensitive adhesive layer formed on one surface of the base layer, the pressure-sensitive adhesive layer being formed in a horizontal direction with respect to the base layer, at least one selected from the group consisting of acrylic, rubber and urethane; A lithium ion secondary battery jelly roll finishing tape

The method according to claim 1,
Wherein the base layer has a shrinkage ratio of 5% or more in a longitudinal direction at 90 DEG C or more, and a shrinkage ratio of 5% or more in a direction perpendicular to the longitudinal direction
Finishing tape for lithium ion secondary battery

The method according to claim 1,
The substrate layer may have a longitudinal shrinkage of 5% or more and a shrinkage ratio of 5% or more in a longitudinal direction and a vertical direction after immersing the substrate layer in a carbonate-based single or mixed solution at room temperature for 15 minutes
Finishing tape for lithium ion secondary battery

The method according to claim 1,
The base layer has a thickness of 10 mu m to 100 mu m
Finishing tape for lithium ion secondary battery

The method according to claim 1,
The pressure-sensitive adhesive layer preferably has an adhesive strength of 100 gf / 25 mm or more and 500 gf / 25 mm or less as measured according to KS T 1028
Finishing tape for lithium ion secondary battery

The method according to claim 1,
The pressure-sensitive adhesive layer may have a pressure of 10 gf / 25 mm or more and 200 gf / 25 mm or less as measured according to KS T 1028 after immersing in a carbonate-based single or mixed solution for 15 minutes
Finishing tape for lithium ion secondary battery

The method according to claim 1,
The thickness of the pressure-sensitive adhesive layer is 1 to 25 占 퐉
Finishing tape for lithium ion secondary battery

The method according to claim 1,
Wherein the base layer comprises 60 to 150 parts by weight of the styrene-butadiene copolymer per 100 parts by weight of the polystyrene
Finishing tape for lithium ion secondary battery