Swelling tape for filling gap

Abstract

A swelling tape for filling a gap, a method of manufacturing the swelling tape for filling a gap, a method of filling a gap, an electrode assembly and a secondary battery are provided. For example, the swelling tape can be applied inside a gap in which a fluid exists so as to fill the gap by becoming a 3D form, and can be useful at anchoring a subject in which the gap is formed, as necessary.

Claims

1. A secondary battery comprising: an electrode assembly comprising a swelling tape attached thereto; a can configured to accommodate the electrode assembly; and an electrolyte coming in contact with the swelling tape of the electrode assembly inside the can, wherein the swelling tape comprises: a substrate layer having a property of deforming in a longitudinal direction when coming in contact with a fluid, wherein the substrate layer contains a urethane bond, an ester bond or an ether bond, or includes a cellulose ester compound; and a pressure-sensitive adhesive layer that is formed on one surface of the substrate layer in a direction parallel to the longitudinal direction of the substrate layer, wherein the pressure-sensitive adhesive layer includes at least two pressure-sensitive adhesive regions and at least one non-pressure-sensitive adhesive region disposed between the at least two pressure-sensitive adhesive regions, wherein the pressure-sensitive adhesive region and the non-pressure-sensitive adhesive region are formed on a surface of the pressure-sensitive adhesive layer opposite to the substrate layer, and the non-pressure-sensitive adhesive region is embedded in the pressure-sensitive adhesive layer.

2. The secondary battery of claim 1, wherein the swelling tape has a three-dimensional (3D) structure having a height of 0.001 mm to 2.0 mm in a direction perpendicular to the longitudinal direction when coming in contact with the fluid.

3. The secondary battery of claim 1, wherein the substrate layer has a modification rate of 10% or more in the longitudinal direction according to the following Equation 1:
Modification rate in longitudinal direction=(L.sub.2L.sub.1)/L.sub.1100Equation 1 wherein L.sub.1 represents an initial length of the substrate layer before the substrate layer comes in contact with a fluid, and L.sub.2 represents a length of the substrate layer measured after the substrate layer comes in contact with the fluid at room temperature or 60 C. for 24 hours.

4. The secondary battery of claim 1, wherein a ratio of an area of the pressure-sensitive adhesive region to the entire area of a surface of the pressure-sensitive adhesive layer is in a range of 5% to 95%.

5. The secondary battery of claim 1, wherein the pressure-sensitive adhesive layer is a single-layered pressure-sensitive adhesive layer.

6. The secondary battery of claim 5, wherein a distance between the pressure-sensitive adhesive regions is in a range of 0.1 mm to 10 mm.

7. The secondary battery of claim 1, wherein the pressure-sensitive adhesive region or the non-pressure-sensitive adhesive region is disposed to form a striped pattern; or the pressure-sensitive adhesive region and the non-pressure-sensitive adhesive region are formed in a sea island pattern.

8. The secondary battery of claim 1, the pressure-sensitive adhesive layer comprises a non-pressure-sensitive adhesive material that forms the non-pressure-sensitive adhesive region by partly masking the pressure-sensitive adhesive layer.

9. The secondary battery of claim 1, wherein the pressure-sensitive adhesive layer has a peel strength at room temperature of 100 gf/25 mm or more, as measured at a peel angle of 180 and a peel rate of 5 mm/sec with respect to either an electrode assembly or glass plate having the gap formed therein.

10. The secondary battery of claim 1, wherein the pressure-sensitive adhesive layer includes an acrylic pressure-sensitive adhesive, a urethane pressure-sensitive adhesive, an epoxy pressure-sensitive adhesive, a silicon pressure-sensitive adhesive or a rubber pressure-sensitive adhesive.

11. The secondary battery of claim 1, wherein the swelling tape has a 3D structure formed by means of the electrolyte, and functions to anchor the electrode assembly in the can.

12. The secondary battery of claim 1, wherein the at least one non-pressure-sensitive adhesive region forms a striped pattern.

13. The secondary battery of claim 1, wherein the at least two pressure-sensitive adhesive regions and the at least one non-pressure-sensitive adhesive region form a sea island pattern.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic diagram showing a process of forming a swelling tape into a 3D form.

(2) FIGS. 2 and 3 are cross-sectional views of a swelling tape according to exemplary embodiments.

(3) FIGS. 4 to 6 are schematic diagrams showing a surface of a pressure-sensitive adhesive layer.

(4) FIG. 7 is a schematic diagram showing a process of forming a swelling tape into a 3D form in manufacture of a battery.

EXPLANATION OF MARKS

(5) 103, 104: Subject in which the gap is formed 101: Swelling tape before forming 3D shape 102: Swelling tape formed 3D shape 11: Substrate later 12: Pressure-sensitive adhesive layer 12A: Pressure-sensitive adhesive region 12B: Non-pressure-sensitive adhesive region 51a, 51b: Swelling tape 52: Can 53: Electrode assembly

BEST MODES OF THE INVENTION

(6) Hereinafter, the tape, and the like will be described in further detail with reference to the following Examples and Comparative Examples, but the range of the tape is not limited to the following Examples.

(7) 1. Measurement of Modification Rate of Substrate Layers in Longitudinal Direction

(8) A substrate layer is cut into samples having a size of 10 cm50 cm (lengthwidth). The prepared samples are soaked in a carbonate-based electrolyte and kept at room temperature for a day in a sealed condition. Thereafter, the samples are pulled out of the electrolyte and lengths of the samples in a machine direction are measured. Then, a modification rate of the substrate layer in a longitudinal direction is calculated according to the following Equation A.
Modification rate in longitudinal direction=(L.sub.2L.sub.1)/L.sub.1100Equation A

(9) In Equation A, L.sub.1 represents an initial length (i.e., 50 mm) of a substrate layer in a machine direction before the substrate layer is soaked in an electrolyte, and L.sub.2 represents a length of the substrate layer in a machine direction measured after the substrate layer is soaked in the electrolyte.

(10) 2. Measurement of Peel Strength of Swelling Tape

(11) A swelling tape is cut into samples having a size of 25 cm200 cm (lengthwidth). The samples are attached to a glass plate via a pressure-sensitive adhesive layer using a 2 kg rubber roller, and stored at room temperature for 2 hours. Thereafter, peel strengths of the samples are measured using a tensile tester while peeling the swelling tape at a peel rate of 5 mm/sec and a peel angle of 180.

(12) 3. Evaluation of Probability of Realizing 3D Form of Swelling Tape

(13) The batteries prepared in Examples and Comparative Examples are kept at room temperature for a day, and dissembled to pull out electrode assemblies. The probability of becoming a 3D form is evaluated according to the following evaluation criteria by checking a state of the swelling tapes which were attached to the electrode assemblies.

(14) Criteria for Evaluating Probability of Becoming a 3D Form

(15) : A uniform 3D form of a swelling tape is observed.

(16) : A uniform 3D form of a swelling tape is not observed.

(17) x: A uniform 3D form of a swelling tape is not observed and the swelling tape is peeled off from an electrode assembly.

(18) 4. Evaluation of Gap-Filling Ability of Swelling Tape (Flow-Preventing Ability of Electrode Assembly)

(19) In this case, the gap-filling ability of the swelling tape may be evaluated using a method of evaluating a property of preventing movement of an electrode assembly. For example, the evaluation method includes a method of evaluating frequent vibration and a method of evaluating frequent impact. The method of evaluating frequent vibration is performed according to a vibration test method, UN38.3 standard. After the evaluation, when battery power cuts off, a terminal is proven to be disconnected due to movement. In the case of the method of evaluating frequent impact, a battery is put into an octagonal cylinder and rotated for a predetermined time. Then, when battery power cuts off, a terminal is proven to be disconnected due to movement. The gap-filling ability of the swelling tape evaluated according to the method is evaluated according to the following evaluation criteria.

(20) Criteria for Evaluating Gap-Filling Ability

(21) : Battery power is detected after evaluation of frequent vibration and frequent impact.

(22) : Battery power is detected after evaluation of frequent vibration and frequent impact but resistivity is increased by 10% or more.

(23) x: Battery power is not detected after evaluation of frequent vibration and frequent impact.

Preparative Example 1: Preparation of Urethane-Based Substrate Layer

(24) A composition including butanediol polyol and methylene diphenyl diisocyanate wherein a hydroxyl group of the polyol and an isocyanate group of the diisocyanate had an equivalent ratio of approximately 1:1 was formed into a film having a thickness of approximately 40 m using a T-die, and cured to prepare a substrate layer. The prepared substrate layer had a modification rate of about 100% in a longitudinal direction.

Preparative Example 2: Preparation of Urethane Acryl-Based Substrate Layer

(25) 30 parts by weight urethane acrylate and 70 parts by weight of a diluent, isobornyl acrylate (IBOA), were blended, and 0.5 parts by weight of a photoinitiator (Irgacure-184, 1-hydroxy cyclohexyl phenylketone) was further added, mixed and defoamed to prepare a composition. The prepared composition was coated on a polyester release film using a bar coater to a thickness of approximately 40 m. The resulting coating layer was covered with the polyester release film to prevent contact with oxygen, and the composition was then cured using a metal halide lamp by irradiating the composition with light of the UV-A region having a light intensity of 800 mJ/cm.sup.2, thereby preparing a substrate layer. The prepared substrate layer had a modification rate of about 12% in a longitudinal direction.

Preparative Example 3: Preparation of Cellulose-Based Substrate Layer

(26) A source material including a cellulose acetate propionate compound having a number average molecular weight (Mn) of 70,000 as measured using GPC was formed into a substrate layer having a thickness of about 40 m using a T-die. The formed substrate layer had a modification rate of about 20% in a longitudinal direction.

Example 1

(27) Preparation of Swelling Tape

(28) A pressure-sensitive adhesive layer having a peel strength of 1,900 gf/25 mm with respect to a glass plate and a thickness of 15 m was formed on one surface of the substrate layer (thickness: 40 m) prepared in Preparative Example 1 as an acrylic pressure-sensitive adhesive layer which included an acryl pressure-sensitive adhesive resin cross-linked by an isocyanate cross-linking agent, to thereby prepare a swelling tape. A tape was prepared by coating a non-pressure-sensitive adhesive material on the prepared pressure-sensitive adhesive layer using the printing method so that an adhesive area could amount to 22% level as shown in FIG. 4. Here, an acrylic compound having a glass transition temperature at which pressure-sensitive adhesive properties are not exhibited was used as the non-pressure-sensitive adhesive material.

(29) Preparation of Electrode Assemblies and Batteries

(30) The swelling tape was attached to a jelly-roll-shaped electrode assembly (sectional diameter: 17.2 mm) including a negative electrode, a positive electrode and a separator so that the swelling tape could cover approximately 50% of an area of an outer circumferential surface of the electrode assembly, and the electrode assembly was inserted into a cylindrical can (sectional diameter: 17.5 mm). Thereafter, a carbonate-based electrolyte was injected into the can and the can was sealed to manufacture a battery.

Examples 2 to 4 and Comparative Examples 1 and 2

(31) Swelling tapes and batteries were prepared in the same manner as in Example 1, except that substrate layers were exchanged as listed in the following Table 1 in preparation of the swelling tape, a pressure-sensitive adhesive layer having the same composition as in Example 1 was changed so that a peel strength of the pressure-sensitive adhesive layer with respect to glass could be exerted as listed in the following Table 1, and a shape of the coated non-pressure-sensitive adhesive material or an area of the pressure-sensitive adhesive area was changed as listed in the following Table 1.

(32) TABLE-US-00001 TABLE 1 Comparative Example Example 1 2 3 4 1 2 Substrate Kind Preparative Preparative Preparative Preparative PP PET layer Example 1 Example 1 Example 2 Example 3 Modification 100 100 12 20 0 0 rate Pressure- Composition Acrylic Acrylic Acrylic Acrylic Acrylic Acrylic sensitive Peel strength 1900 800 150 120 1500 60 adhesive layer Coated Shape FIG. 4 FIG. 5 FIG. 5 FIG. 6 FIG. 4 FIG. 6 non- Pressure- 22 22 50 35 22 35 pressure- sensitive sensitive adhesive adhesive area (%) layer Modification rate: Modification rate of substrate layer in longitudinal direction (unit: %) Peel strength: Peel strength with respect to glass plate (unit: gf/25 mm) PP: Polypropylene substrate layer having modification rate of 0% in longitudinal direction (thickness: 40 m) PET: Polyethyleneterephthalate substrate layer having modification rate of 0% in longitudinal direction (thickness: 25 m)

(33) The measured physical properties of the swelling tapes and the batteries prepared in the Examples and Comparative Examples are summarized in the following Table 2.

(34) TABLE-US-00002 TABLE 2 Comparative Example Example 1 2 3 4 1 2 Probability of realization of 3D form Gap-filling ability x x (Flow-preventing ability)

(35) The swelling tape can, for example, be applied inside a gap in which a fluid exists so as to fill the gap by becoming a 3D form, and can be useful in anchoring a subject in which the gap is formed, as necessary.

(36) While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention as defined by the appended claims.