KR20190079080A - Packaging material for battery and battery cell comprising the same - Google Patents

Abstract

The present invention relates to a packaging material for batteries having excellent thermal conductivity and flexibility and a battery cell comprising the same. The packaging material for batteries comprises a first resin layer, a graphite sheet and a second resin layer. The packaging material for batteries is light and has excellent heat radiation effects so a battery cell comprising the packaging material for batteries has improved battery efficiency and can manage the temperature consistently.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a packaging material for a battery,

The present invention relates to a packaging material for a battery having excellent thermal conductivity and flexibility and a battery cell comprising the same. The battery packaging material is light and has excellent heat radiation effect. Accordingly, the battery cell including the battery cell has improved battery efficiency, It is possible.

The electric vehicle battery generates a local temperature difference or a high temperature due to heat generated due to high output, high speed and repeated charging, thereby causing a thermal runaway phenomenon which hinders the efficiency and stability of the battery. This problem is caused by insufficient heat dissipation and diffusion ability to the outside than heat generated inside the battery.

In order to solve the above problem, a component such as a heat sink that emits heat to an electric vehicle battery is mounted. Aluminum has been widely used as a material for such a heat dissipation part, but attempts have been made to replace aluminum by using graphite having excellent thermal diffusion characteristics. However, graphite has a disadvantage in that it is not easy to shape due to its material properties.

On the other hand, the lithium ion battery is used as a power source of a portable electronic device with a cell operating voltage of 3.6 V or higher, or a plurality of cells connected in series to be connected to a high output such as a hybrid electric vehicle (HEV) or a pure electric vehicle It is attracting attention as a power source of environment-friendly vehicles. Such a lithium ion battery can be manufactured in various forms, and in the case of a pouched type battery cell which is widely used recently, the shape of the packaging material itself is relatively freely flexible.

The packaging material of the pouch type battery cell needs excellent flexibility and thermal conductivity in order to prevent the electrolyte from leaking from the lithium ion battery and to reduce the risk of explosion due to the volume expansion of the battery and the temperature rise inside the battery.

Conventional pouch-type packaging materials for battery cells have excellent thermal conductivity including metals such as aluminum or aluminum alloys (see Korean Patent No. 10-1308592).

Korean Patent No. 10-1308592

However, the above Korean registered patent includes aluminum or an aluminum alloy, which makes the weight of the battery heavy, and there is a limitation in effectively releasing heat generated from the battery of the pouch type due to heat anisotropy.

Accordingly, an embodiment of the present invention is to provide a packaging material for a battery, which includes a graphite sheet and is lightweight, excellent in thermal conductivity and flexibility compared to a metal material, and a battery cell containing the same.

In order to achieve the above object,

A first resin layer, a graphite sheet and a second resin layer,

Wherein the surface of the graphite sheet is in the form of a fabric woven with a weft and a warp.

In another embodiment,

A first cell packing material, a battery cell, and a second cell packing material,

Wherein the first battery packing material, the second battery packing material, or all of them comprise the battery packing material.

The cell packing material according to the embodiment is lighter than the metal material including the graphite sheet and the polymer resin layer, and has excellent thermal conductivity and flexibility. In addition, the pouch-type battery including the battery packing material has excellent heat dissipation efficiency and is capable of continuous temperature management, thus providing excellent battery efficiency.

1 is a schematic view of the surface of a graphite sheet of one embodiment.
2 is a photograph of the surface of the graphite sheet of one embodiment.
3 is a photograph of the surface of the graphite sheet of one embodiment observed with an atomic force microscope (AFM).
4 to 7 are cross-sectional views of a packaging material for a battery in one embodiment.
8 and 9 are cross-sectional views of a pouch type battery of one embodiment.

The cell packing material of the embodiment

A first resin layer, a graphite sheet and a second resin layer,

The surface of the graphite sheet is in the form of a fabric in which weft and warp are woven.

The graphite sheet has a fabric-like structure in which the surface of the graphite sheet is woven with weft and warp, so that the characteristic of conducting heat along the weft and warp can be ensured. As a result, heat conduction occurs along a continuous medium Excellent heat-generating characteristics can be secured. Furthermore, the graphite sheet can secure excellent interfacial adhesion between the first resin layer and the second resin layer on both surfaces thereof, as compared with the case where the surface structure is not present through the surface structure, Durability can be improved.

Graphite  Sheet

When the battery packaging material comprises a graphite sheet, it is lighter than the battery packaging material containing a metal material, has excellent heat radiation effect, and is excellent in flexibility and processability.

The graphite sheet may comprise an inner layer comprising graphitized fibers and an outer graphite layer. Specifically, the graphite sheet may comprise an inner layer comprising graphitized fibers and a graphite outer layer covering either or both surfaces of the inner layer.

The inner layer may comprise a fiber bundle comprising a plurality of graphite fibers. Specifically, the inner layer may be composed of a fiber bundle containing a plurality of graphite fibers. In addition, the fiber bundle may include voids formed between a plurality of graphite fibers. Further, the inner layer may comprise a weft and warp-woven fabric form consisting of graphite fibers or graphite fiber bundles.

The inner layer may comprise natural fibers or graphitized fibers. Specifically, the inner layer may be made of fibers in which natural fibers or synthetic fibers are carbonized and graphitized.

The natural fibers may be at least one selected from the group consisting of cellulose fibers, protein fibers and mineral fibers. The cellulose fibers may be, for example, (i) seed fibers such as cotton or kerosene, (ii) stem fibers such as flax, jute, hemp or jute, (iii) Leaf fibers such as Manila hemp, Abaca or Sisalma. The protein fiber may be, for example, (i) wool fiber, (ii) silk fiber and (iii) hair fiber. The mineral fibers include, for example, artificial mineral fibers such as (i) glass wool and minerals, and (ii) fiberized liquefied glass, rock and other minerals at high temperatures. Specifically, the natural fiber may include at least one member selected from the group consisting of cotton, hemp, wool, and silk.

The man-made fibers may be at least one selected from the group consisting of organic fibers and inorganic fibers. The organic fibers may be, for example, (i) cellulose-based fibers such as rayon, tencel (lyocell), modal and the like, or regenerated fibers containing protein-based fibers, (ii) cellulose fibers such as acetate, triacetate, (Iii) a semisynthetic fiber including a polyamide fiber, a polyolefin fiber, a polyurethane fiber, a polyethylene fiber, a polyvinyl chloride fiber, a polyfluoroethylene fiber, a polyvinyl alcohol fiber, an acrylic fiber or a polypropylene fiber And synthetic fibers such as fibers. Specifically, the synthetic fiber may be at least one synthetic fiber selected from the group consisting of nylon, polyester, polyurethane, polyethylene, polyvinyl chloride, polyfluoroethylene, polyvinyl alcohol, acrylic and polypropylene; Or at least one cellulosic fiber selected from the group consisting of rayon, acetate, and triacetate.

The graphite sheet can increase the efficiency of the process of carbonizing and graphitizing the natural fiber or the synthetic fiber of the above-mentioned kind as a raw material of the inner layer, and it is possible to improve the heat generation performance including the inner layer of the graphitized fiber It can be excellent.

The graphite outer layer may cover both the end face and the both faces of the inner layer. Specifically, the graphite outer layer is composed of a first graphite outer layer coated on one surface of the graphite inner layer and a second graphite outer layer coated on the other surface of the graphite inner layer, and a part of the first graphite outer layer and the second graphite outer layer Can be connected.

The graphite outer layer may be one in which the polymer resin is graphitized. In addition, the graphite outer layer may comprise natural graphite or expanded graphite.

The polymer resin may include at least one member selected from the group consisting of polyimide, polyamic acid, polyvinyl chloride, polyester, polyurethane, polyethylene, polyfluoroethylene, polyvinyl alcohol, acrylic and polypropylene. Specifically, the polymer resin may include at least one member selected from the group consisting of polyimide, polyamic acid and polyvinyl chloride having a weight average molecular weight of 200,000 to 300,000 g / mol.

Specifically, the graphite sheet may be produced by producing a laminate including a fibrous base material and a polymer coating layer on one side or both sides of the fibrous base material, and then carbonizing and graphitizing the laminate. By carrying out the process of carbonization and graphitization at a predetermined temperature, the fiber base material and the polymer coating layer constituting the laminate are both graphitized, whereby a graphite sheet can be produced.

At this time, the thickness of one polymer coating layer may be 30 탆 to 50 탆. For example, when the polymer coating layer is formed on both surfaces of the fiber substrate, the total thickness of the polymer coating layer may be 60 to 100 탆. When the thickness of the polymer coating layer is formed within the above-mentioned thickness range, the laminate may be exposed on the surface of the graphite sheet after carbonization and graphitization, and a weaving structure derived from the fiber base material.

The fibrous base material may be at least one selected from the group consisting of natural fibers and man-made fibers. The natural fibers and the synthetic fibers are as described for the inner layer.

The polymer coating layer is as described for the polymer resin of the graphite outer layer.

Fig. 1 schematically shows the surface structure of the graphite sheet according to one embodiment, and Fig. 2 is a photograph of the surface of the graphite sheet.

Referring to Fig. 1, the surface structure of the graphite sheet may be in the form of a woven fabric in which the weft A and the warp B are woven.

The warp yarns A and the warp yarns B may have widths d1 and d2 of 20 mu m to 200 mu m, 30 mu m to 170 mu m, or 50 mu m to 170 mu m, respectively. In addition, the weft (A) and the warp (B) may have pitches (P1 and P2) of 20 탆 to 200 탆, 30 탆 to 170 탆, or 50 탆 to 170 탆, respectively.

Also, the surface structure of the graphite sheet may satisfy a warp (A) × warp (B) of 80 to 130 × 100 to 150 count / inch. For example, the surface structure of the graphite sheet can satisfy 130 × 150 counts / inch, 100 × 120 counts / inch, or 80 × 100 counts / inch of warp (A) × warp (B).

The graphite sheet may have a predetermined surface roughness by having the surface structure described above. Specifically, referring to FIG. 1, the surface of the graphite sheet has a step between a portion (C) where the weft (A) and the warp (B) overlap and a portion (D) that is not overlapped.

Specifically, the graphite sheet may have a surface roughness Ra of 0.5 탆 to 10 탆 (see Fig. 3). More specifically, the graphite sheet may have a surface roughness (Ra) of 1 탆 to 8 탆, or 2 탆 to 6 탆.

The surface structure of the graphite sheet may be specifically derived from a fiber substrate which is a raw material of the inner layer. The fibrous base material may be a woven base material, and the surface structure of the graphite sheet produced using the fibrous base material may be a woven structure having the above-mentioned structure.

The average thickness of the graphite sheet may be from 10 탆 to 500 탆. Specifically, the average thickness of the graphite sheet may be from 50 탆 to 500 탆, from 70 탆 to 500 탆, from 70 탆 to 300 탆, from 10 탆 to 300 탆, from 10 탆 to 250 탆, or from 70 to 250 탆. When the thickness of the graphite is within the above range, it may be advantageous in terms of heat capacity.

The graphite sheet may have a vertical thermal conductivity of 1 to 20 W / m · K and a horizontal thermal conductivity of 800 to 2,000 W / m · K. Specifically, the graphite sheet has a vertical thermal conductivity of 1 to 15 W / mK, 1 to 10 W / mK, or 5 to 10 W / mK, a horizontal thermal conductivity of 900 to 2,000 W / m · K, 1,000 to 1,800 W / m · K, or 1,200 to 1,800 W / m · K.

As a result of the MIT bending test conducted under conditions of a curvature radius (R) of 5 mm, a bending angle of 180 degrees, a load of 0.98 N, and a bending speed of 90 revolutions per minute, the graphite sheet had a number of bending cycles . Specifically, the graphite sheet may have 10,000 to 20,000 cycles, 10,000 to 18,000 cycles, or 10,000 to 15,000 cycles as a result of the MIT flexural test.

The graphite sheet may have a specific heat of 0.5 to 1.0 J / g · K, 0.5 to 0.9 J / g · K, 0.6 to 0.9 J / g · K, or 0.7 to 0.9 J / g · K at 50 ° C. The graphite sheet may have a density of 0.5 to 2.5 g / cm 3, 0.5 to 2.0 g / cm 3, or 0.8 to 2.0 g / cm 3.

Resin layer

The first resin layer and the second resin layer may each include at least one selected from the group consisting of a polyolefin resin and a polyamide resin.

The polyolefin-based resin may include at least one selected from the group consisting of polyethylene-based, polypropylene-based and polybutylene-based resins. Specifically, the polyolefin-based resin may be a polypropylene resin or a copolymerized polypropylene resin.

The polyamide-based resin may include at least one selected from the group consisting of nylon 6, nylon 6.6, a copolymer of nylon 6 and nylon 6.6, nylon 6.10 and polymethoxy silylene diamide (MXD) have.

In one embodiment, the first resin layer comprises a polyamide-based resin, and the second resin layer may comprise a polyolefin-based resin.

The thickness of the first resin layer may be 10 to 30 탆. Specifically, the first resin layer is made of a polyamide-based resin and may have a thickness of 10 to 30 占 퐉. When the thickness of the first resin layer is within the above range, it is possible to prevent the problem that the function of protecting the cell due to the excessively thin thickness is difficult to perform and the problem that the battery is not thinned.

The thickness of the second resin layer may be 10 to 100 탆. Specifically, the second resin layer may be composed of a polyolefin-based resin and may have a thickness of 10 to 100 mu m. When the thickness of the second resin layer is within the above range, the buffering function is deteriorated due to the thinness of the thickness of the second resin layer, and the problem of not meeting the trend of thinning of the battery can be prevented.

Specifically, the first resin layer is a polyamide-based resin layer located outside the pouch-type battery, and the second resin layer is a polyolefin-based resin layer, and may be located inside the pouch-type battery adjacent to the battery cell .

Referring to FIG. 4, the cell packing material A may include a first resin layer 100, a graphite sheet 200, and a second resin layer 300 sequentially stacked.

Adhesive layer

The first resin layer and the graphite sheet, and the adhesive layer between the graphite sheet and the second resin layer, respectively.

The adhesive layer may include an adhesive having a melting point of 100 ° C or higher. Specifically, the adhesive layer may include an adhesive having a melting point of 100 to 200 占 폚, 100 to 150 占 폚, or 100 to 120 占 폚. When the melting point of the adhesive layer is within the above range, the durability of the battery packaging material at an elevated temperature is improved.

The adhesive layer may include at least one selected from the group consisting of a silicone-based adhesive, an epoxy-based adhesive, an acrylic-based adhesive, and a urethane-based adhesive.

The thickness of the adhesive layer may be from 1 to 10 mu m, or from 3 to 5 mu m. When the thickness of the adhesive layer is within the above range, it is possible to secure interfacial adhesion between the graphite sheet and the first resin layer or the second resin layer, and formation of an adhesive layer on the surface of the graphite sheet having the surface structure Can be advantageous.

5, the cell packaging material A includes a first resin layer 100, a first adhesive layer 410, a graphite sheet 200, a second adhesive layer 420, and a second resin layer 300, May be sequentially stacked.

Metal layer

And a metal layer between the first resin layer and the graphite sheet. The metal layer serves to impart excellent barrier performance and flexibility to the battery packaging material.

The metal layer may comprise aluminum or nickel. Specifically, the metal layer may include aluminum.

The thickness of the metal layer may be 30 to 100 탆. When the thickness of the metal layer has the thickness range, the metal layer protects the graphite sheet and improves the impact resistance of the cell packing material.

Referring to FIG. 6, the cell packing material may include a first resin layer 100, a metal layer 500, a graphite sheet 200, and a second resin layer 300 sequentially stacked.

7, the packaging material for a battery includes a first resin layer 100, a first adhesive layer 410, a metal layer 500, a second adhesive layer 420, a graphite sheet 200, a third adhesive layer 430 and the second resin layer 300 may be sequentially stacked.

Pouch type battery

The pouch type battery of another embodiment includes a first cell packing material, a battery cell, and a second cell packing material,

The first cell packing material, the second cell packing material, or both, as described above.

The first battery packaging material may include a first resin layer, a first graphite sheet, and a second resin layer, and the second battery packaging material may include a third resin layer, a second graphite sheet, and a fourth resin layer. Here, the third resin layer is as defined in the second resin layer, and the fourth resin layer is as defined in the first resin layer.

Specifically, the first resin layer and the fourth resin layer are polyamide-based resin layers having a thickness of 10 to 30 탆 and are located outside the pouch-type battery, and the second resin layer and the third resin layer have a thickness of 10 to 100 탆 Thick polyolefin resin layer, and may be located inside the pouch-type battery adjacent to the battery cell.

More specifically, the pouch type battery includes a stacked structure of a first resin layer, a first graphite sheet, a second resin layer, a battery cell, a third resin layer, a second graphite sheet and a fourth resin layer sequentially , The first resin layer and the fourth resin layer are polyamide-based resin layers, and the second resin layer and the third resin layer may be polyolefin-based resin layers.

8 and 9, the pouch type battery includes a first battery packing material 11, a battery cell 20, and a second battery packing material 12 stacked in this order, and the first battery packing material The packaging material for the second battery can be sealed with the engagement member (30). 8, the first cell packing material 11 and the second cell packing material 12 may each include a resin layer, a graphite sheet, and a resin layer sequentially stacked. Referring to FIG. 9, the first cell packing material 11 and the second cell packing material 12 may include a resin layer, an adhesive layer, a graphite sheet, an adhesive layer, and a resin layer, which are sequentially laminated.

The shape of the battery cell is not particularly limited as long as it includes an anode, a cathode, a separator, and an electrolyte. For example, the battery cell may have a configuration in which an anode, a cathode, a separator, and an electrolytic solution are contained in a rectangular aluminum case.

Hereinafter, the present invention will be described in detail with reference to examples. However, these examples are intended to further illustrate the present invention, and the scope of the present invention is not limited to these examples.

[ Example ]

Production Example 1: Production of graphite sheet

A fiber substrate (slope x weft = 98 x 100 count / inch) having a plain fiber structure and made of cellulosic fiber having a thickness of 180 탆 was prepared. A laminate was prepared by coating a liquid polyamic acid solution (manufactured by KOMEK, product name: KPI-900, weight average molecular weight: 250,000 g / mol) on both sides of the fiber substrate to a thickness of 30 탆.

Thereafter, the laminate was heated to 400 DEG C at a rate of 1 DEG C / minute in a nitrogen atmosphere, and heated at 400 DEG C for 10 hours to imidize the polyamic acid solution to form a polymer coating layer on each side of the substrate. Subsequently, the temperature was raised to 1,000 占 폚 at a rate of 1 占 폚 / min in a nitrogen atmosphere, and the mixture was carbonized by heating at 1,000 占 폚 for 3 hours. Thereafter, the temperature was raised at a rate of 5 ° C / minute, and the mixture was heated at 2,600 ° C for 1 hour to be graphitized. Thus, an inner layer including graphitized fibers and a graphite sheet having a thickness of 70 μm including graphite outer layers on both surfaces of the inner layer were manufactured Respectively. The surface of the graphite sheet was photographed and shown in Fig. Further, the surface structure of the graphite sheet was observed with an optical microscope (Nikon) at x 10 magnification, and the results are shown in Table 1.

Weft width Slope width Weft pitch Slope pitch Graphite sheet
Surface structure 109.46 탆 121.97 탆 89.38 탆 102 탆

Example  1. Manufacture of Cellular Packaging Materials

A urethane adhesive was applied to one surface of the graphite sheet of Production Example 1, and then a polypropylene film (thickness: 40 占 퐉) was laminated to form a second resin layer. Thereafter, a urethane-based adhesive was applied to the other surface of the graphite sheet, and then a nylon film (thickness: 15 탆) was laminated to prepare a cell packing material containing the first resin layer.

Comparative Example  One.

Except that a graphite sheet (thickness: 70 占 퐉) having a structure in which graphite particles (average particle diameter: 1 占 퐉) was dispersed in 100 parts by weight of a polyester-based binder resin instead of the graphite sheet of Production Example 1 was used. To prepare a cell packaging material.

Comparative Example  2.

A cell packaging material was prepared in the same manner as in Example 1, except that an aluminum sheet of the same thickness was used instead of the graphite sheet of Production Example 1. [

Experimental Example  1: Thermal conductivity

The graphite sheet of Production Example 1, the graphite sheet of Comparative Example 1 and the aluminum sheet of Comparative Example 2 were measured for thermal conductivity by a laser flash method. Specifically, the sheet was cut into a circle having a diameter of 25.4 mm, and the thermal conductivity in the plane parallel to the plane under the measuring conditions of In-plane, 304 V and medium mode was measured with a measuring device (Netzsch LFA447 Model) . The results are shown in Table 2.

Experimental Example 2: Heat radiation performance

The cell packaging materials of Examples 1 and 2 and Comparative Examples 1 and 2 were mounted on one surface of a heating element having a heating temperature of T1 and the surface temperature of the opposite surface of the cell packing facing the heating element was observed, The surface temperature (T2) of the starting point was measured. Then, the heat radiation performance was calculated by the following equation (1), and the results are shown in Table 2 below.

[Equation 1]

Heat radiation performance (%) = (T1-T2) / T1 X 100

Horizontal thermal conductivity
(mW / mK) Heat dissipation performance T1 (° C) T2 (占 폚) % Example 1 970 90 60 33 Comparative Example 1 350 90 75 17 Comparative Example 2 230 90 80 11

As shown in Table 2, the graphite sheet of Production Example 1 was superior to the graphite sheet of Comparative Example 1 and the aluminum sheet of Comparative Example 2 in the horizontal direction. In addition, it was found that the cell packing material of Example 1 was superior to the cell packing materials of Comparative Examples 1 and 2 in heat generation performance.

A: Cell packing material
100: first resin layer 200: graphite sheet
300: second resin layer 410: first adhesive layer
420: second adhesive layer 430: third adhesive layer
500: metal layer
11: first cell packing material 12: second cell packing material
20: battery cell 30: coupling member

Claims (15)

A first resin layer, a graphite sheet and a second resin layer,
Wherein the surface of said graphite sheet is in the form of a fabric woven with a weft and a warp.
The method according to claim 1,
Wherein the surface structure of the graphite sheet includes a structure of weft × slope of 80 to 130 × 100 to 150 count / inch,
Wherein the weft yarns and the warp yarns have a width and a pitch of 20 to 200 mu m, respectively.
The method according to claim 1,
Wherein the graphite sheet is produced by producing a laminate including a fibrous base material and a polymer coating layer on one or both sides of the fibrous base material and then carbonizing and graphitizing the laminate.
The method according to claim 1,
Wherein the graphite sheet comprises an inner layer comprising graphitized fibers and a graphite outer layer.
The method according to claim 1,
Wherein the graphite sheet has a surface roughness (Ra) of 0.5 to 10 占 퐉.
The method according to claim 1,
Wherein the first resin layer and the second resin layer each comprise at least one selected from the group consisting of a polyolefin resin and a polyamide resin.
The method according to claim 1,
Wherein the first resin layer and the graphite sheet, and the graphite sheet and the second resin layer each include an adhesive layer between the first resin layer and the graphite sheet.
8. The method of claim 7,
Wherein the adhesive layer comprises an adhesive having a melting point of 100 DEG C or higher.
The method according to claim 1,
Wherein the first resin layer has a thickness of 10 to 30 占 퐉,
Wherein the graphite sheet has a thickness of 10 to 500 탆,
And the thickness of the second resin layer is 10 to 100 占 퐉.
The method according to claim 1,
And a metal layer between the first resin layer and the graphite sheet.
11. The method of claim 10,
Wherein the metal layer comprises aluminum or nickel.
11. The method of claim 10,
Wherein the metal layer has a thickness of 30 to 100 占 퐉.
The method according to claim 1,
Wherein the cell packing material comprises a first resin layer, a graphite sheet and a second resin layer sequentially laminated.
A first cell packing material, a battery cell, and a second cell packing material,
Wherein the first cell packing material, the second cell packing material, or both all comprise the cell packing material of any one of claims 1 to 13.
15. The method of claim 14,
Wherein the first cell packaging material comprises a first resin layer, a first graphite sheet and a second resin layer,
Wherein the second battery packing material comprises a third resin layer, a second graphite sheet and a fourth resin layer,
Wherein the pouch type battery comprises a pouch type battery in which a first resin layer, a first graphite sheet, a second resin layer, a battery cell, a third resin layer, a second graphite sheet and a fourth resin layer are sequentially laminated, .

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