KR20230065468A - Case for battery comprising colored layer and secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a battery case including: a sealant layer; a barrier layer disposed on the sealant layer; a base layer disposed on the barrier layer; and a dye layer disposed between the sealant layer and the barrier layer. The present invention allows an observer to easily detect defects in the battery case or a secondary battery.

Description

A battery case including a dye layer and a secondary battery including the same {CASE FOR BATTERY COMPRISING COLORED LAYER AND SECONDARY BATTERY COMPRISING THE SAME}

The present invention relates to a battery case including a dye layer and a secondary battery including the same, and more particularly, to a battery case and a secondary battery including a dye layer and capable of visually detecting defects such as cracks in the battery case. .

Demand for lithium secondary batteries as an energy source is rapidly increasing with the development of technologies such as electric vehicles and portable electronic devices.

Lithium secondary batteries may be classified into cylindrical, prismatic, and pouch-type secondary batteries according to the shape of the battery case. Among them, the pouch-type secondary battery manufactures a pouch by molding a battery case composed of a sealant layer of polymer material, a barrier layer of metal material, and a substrate layer protecting the barrier layer, and the electrode assembly and electrolyte are stored in the cup portion of the pouch. and then sealed.

For the manufactured pouch-type secondary battery, normal products and defective products are classified, and normal products are shipped, and defective products are discarded or re-produced.

There are various types of defective products, but among them, mechanical defects, such as cracks, occur in a battery case and the pouch-type secondary battery does not operate normally. As a specific example, when a crack occurs in the battery case and the barrier layer is damaged, foreign matter, air, or moisture from outside the battery flows into the battery and oxidizes contents such as the electrode assembly or electrolyte so that it cannot function properly. damage

In order to detect defective products damaged as described above, an observer goes through a process of determining defects in appearance of the battery case. Since mechanical defects such as cracks are very small in size, it is not easy to detect defective products in appearance.

In addition, when a battery module or battery pack including a plurality of pouch-type secondary batteries is manufactured and used in practice, since the battery module or battery pack is in an environment with little light such as inside a container, each pouch-type secondary battery There is a problem in that it is not easy to detect whether there is a defect or not.

In order to solve the above problems, it is intended to provide a battery case and a secondary battery capable of visually detecting defects such as cracks in a battery case including a dye layer.

In one embodiment of the present invention, the sealant layer; a barrier layer disposed on the sealant layer; a substrate layer disposed on the barrier layer; and a dye layer disposed between the sealant layer and the barrier layer.

In addition, in another embodiment of the present invention, the electrode assembly; electrolytes; and a battery case accommodating the electrode assembly and the electrolyte.

The battery case according to the present invention includes a dye layer disposed between the sealant layer and the barrier layer, so that an observer can easily detect defects in the battery case or the secondary battery visually.

More specifically, the battery case according to the present invention includes a dye layer disposed between the sealant layer and the barrier layer, so that the observer may be aware that a part of the barrier layer is lost and foreign substances, air, moisture, etc. are introduced into the secondary battery. It is possible to more easily detect battery cases or secondary batteries having potential serious defects.

In addition, since the dye layer of the battery case according to the present invention contains a fluorescent dye, even when the battery case or secondary battery is in a lightless environment such as a container, an observer can easily determine whether the battery case or secondary battery is defective. it is possible to detect

In addition, since the dye layer of the battery case according to the present invention includes silica gel, when a mechanical defect such as a crack occurs in the battery case, the silica gel of the dye layer absorbs moisture to form a barrier layer, a sealant layer, an electrode assembly or It is possible to effectively prevent contents such as an electrolyte from being oxidized.

The following drawings attached to the specification illustrate preferred embodiments of the present invention, and serve to further understand the technical idea of the present invention together with the contents of the above-described invention, so the present invention is limited only to those described in the drawings. and should not be interpreted.
1 is a view schematically showing a cross section of a battery case according to an embodiment of the present invention.
FIG. 2 is a diagram schematically illustrating a case in which a crack occurs in the battery case of FIG. 1 .
3 is a diagram schematically illustrating a secondary battery according to an embodiment of the present invention.

Hereinafter, the terms or words used in this specification and claims should not be construed as being limited to ordinary or dictionary meanings, and the inventor appropriately defines the concept of terms in order to explain his/her invention in the best way. It should be interpreted as meaning and concept consistent with the technical idea of the present invention based on the principle that it can be done.

<Battery case>

The battery case according to the present invention may be used for a secondary battery, and more specifically, may be a pouch-type secondary battery case.

A battery case according to the present invention includes a sealant layer; a barrier layer disposed on the sealant layer; a substrate layer disposed on the barrier layer; and a dye layer disposed between the sealant layer and the barrier layer.

Since the battery case includes a dye layer disposed between the sealant layer and the barrier layer, an observer can easily detect the dye layer with the naked eye when defects such as cracks occur in the exterior of the battery case.

Specifically, it is known that the role of the barrier layer is important in order to protect the electrode assembly accommodated inside the battery case from the external environment. The barrier layer generally includes a metal and serves to block foreign substances or moisture that may enter the battery case from the outside to the inside. When the barrier layer is damaged, the foreign matter or moisture is introduced into the battery case and adversely affects characteristics of the electrode assembly or the electrolyte. Therefore, before providing a pouch-type secondary battery as a final product, it is important to detect whether or not the barrier layer of the battery case is damaged in advance to determine whether or not it is defective.

Since the battery case according to the present invention includes a dye layer disposed between the sealant layer and the barrier layer, the barrier layer and the base material relatively disposed outside the battery case among the sealant layer, the dye layer, the barrier layer, and the substrate layer. When cracks occur in the layer, since the dye layer disposed immediately below the barrier layer is exposed to the outside, it is possible for an observer to easily detect with the naked eye that serious damage has occurred in the barrier layer.

Hereinafter, the present invention will be described in detail with reference to the drawings. In adding reference numerals to components of each drawing, the same numerals may have the same numerals as much as possible even though they are displayed on different drawings for the same components. In addition, in describing the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description may be omitted.

1 is a cross-sectional view of a battery case according to an embodiment of the present invention.

Referring to FIG. 1 , a battery case 100 according to the present invention includes a sealant layer 110, a barrier layer 120 disposed on the sealant layer 110, and a substrate disposed on the barrier layer 120. A layer 130 and a dye layer 140 disposed between the sealant layer 110 and the barrier layer 120 are included.

The sealant layer 110 may be an inner layer disposed on the innermost side of the battery case 100 . The sealant layer 110 may include a polyolefin-based resin, and for example, the sealant layer may include polyethylene; polypropylene; ethylene propylene copolymer; polypropylene-butyrene-ethylene terpolymer; copolymers of polyethylene and acrylic acid; And a copolymer of polypropylene and acrylic acid; may include at least one selected from the group consisting of. Preferably, the sealant layer may include polypropylene (PP). Insulation characteristics of the battery case 100 may be improved by including the polyolefin-based resin in the sealant layer.

The barrier layer 120 may be disposed on the sealant layer 110 . The barrier layer 120 may form an external structure of the battery case 100 while maintaining mechanical strength. In addition to improving the strength of the battery case 100, the barrier layer 120 may serve to protect contents such as an electrode assembly (not shown) or an electrolyte (not shown) by blocking the entry of moisture, oxygen, and light.

The barrier layer 120 may include metal. The barrier layer 120 may include, for example, aluminum (Al); iron (Fe); an alloy of chromium (Cr) and manganese (Mn); And an alloy of iron (Fe), carbon (C), chromium (Cr), and nickel (Ni); may include at least one selected from the group consisting of. Since the mechanical strength of the barrier layer 120 is improved by including the metal, the content contained in the battery case 100 can be more effectively protected.

The barrier layer 120 may have a thickness of 30 μm to 70 μm, specifically 35 μm to 65 μm, and more specifically 40 μm to 60 μm. When the thickness of the barrier layer 120 satisfies the above numerical range, it is possible to properly protect the contents by preventing entry of moisture, oxygen, and light from the outside of the battery case 100, and a space for accommodating the contents. When the battery case 100 is molded to form, the formability of the battery case 100 is improved so that the appearance can be prevented from being distorted or damaged, and the overall thickness of the battery case 100 is reduced to an appropriate level. By adjusting the capacity per unit volume of the secondary battery can be secured to the maximum.

The base layer 130 is disposed on the outermost side of the battery case 100 to serve to protect the barrier layer 120, the dye layer 140, the sealant layer 140, and contents. .

The base layer 130 may include a single layer or a plurality of layers. When the base layer 130 includes a plurality of layers, the base layer 130 is used to protect the barrier layer 120, the dye layer 140, the sealant layer 140, and the contents from foreign substances, moisture, It can protect more effectively from oxygen, light, etc.

As a specific example, the base layer 130 may be, for example, polyethylene; polypropylene; polyethylene terephthalate; nylon; low density polyethylene (LDPE); high density polyethylene (HDPE); And linear low-density polyethylene (LLDPE); may include at least one member selected from the group consisting of. Since the base layer 130 includes the above materials, the insulating properties of the battery case 100 may be improved.

As another example, the base layer 130 includes a first layer 131 and a second layer 133, the first layer 131 includes nylon, and the second layer 133 includes polyethylene. terephthalate (PET). Since the first layer 131 includes nylon and the second layer 133 includes polyethylene terephthalate, the insulating properties of the battery case 100 can be further improved, and the first layer 131 The second layer 133 can prevent a phenomenon in which by-products are generated by reacting ) with the electrolyte.

The thickness of the first layer 131 may be 10 μm to 35 μm, preferably 12 μm to 25 μm. When the thickness of the first layer 131 satisfies the numerical range, the insulating properties of the battery case 100 may be secured.

The second layer 133 may have a thickness of 10 μm to 35 μm, preferably 12 μm to 30 μm. When the thickness of the second layer 133 satisfies the above numerical range, a side reaction between the first layer 131 and the electrolyte may be more effectively suppressed by the second layer 133 .

The dye layer 140 may be disposed between the sealant layer 110 and the barrier layer 120 . Since the dye layer 140 is disposed between the sealant layer 110 and the barrier layer 120, when a defect occurs in the barrier layer 120, the dye leaks from the dye layer so that an observer can see the barrier layer It is easy to detect that 120 is defective.

The role of the dye layer 140 will be described in more detail with reference to FIG. 2 .

Specifically, the role of the barrier layer 120 is important when the battery case 100 protects contents such as an electrode assembly or an electrolyte from external foreign substances, moisture, or air. Since the barrier layer 120 includes a material having high strength and high moisture and air barrier properties, the barrier layer 120 plays the greatest role in protecting contents such as an electrode assembly or an electrolyte compared to other layers.

Referring to FIG. 2 , a case in which a crack occurs in the battery case 100 may be assumed.

When a first crack C1 is generated in the battery case 100, a portion of the substrate layer 130 may be lost due to the first crack C1. Accordingly, the barrier layer 120 disposed directly below the base layer 130 may be exposed to the outside of the battery case 100 . However, even in this case, since the barrier layer 120 of the battery case 100 is not lost, it can be determined that the function of protecting contents such as the electrode assembly or the electrolyte is not significantly affected. In addition, since the appearance of the battery case 100 can be restored through a simple process when the base layer 130 is lost, the battery case 100 having damage by the first crack C1 is restored during the restoration process. can be reproduced through

As another example, when the second crack C2 occurs in the battery case 100, portions of the substrate layer 130 and the barrier layer 120 may be lost due to the second crack C2. Accordingly, not only the base layer 130 but also the barrier layer 120 disposed directly below the base layer 130 and the dye layer 140 disposed directly below the barrier layer 120 are exposed to the outside. may be exposed. In this case, due to the disappearance of the barrier layer 120, elements that adversely affect the function of the secondary battery, such as external foreign substances, air, or oxygen, may flow into the secondary battery. In addition, when the barrier layer 120 is lost, unlike the case where the base layer 130 is lost, restoration is impossible except by inserting a new undamaged barrier layer 120 . Therefore, when the second crack C2 occurs in the battery case 100, there is a need to determine the battery case 100 as an unrenewable case and discard it. According to the battery case 100 according to the present invention, the dye layer 140 is disposed directly below the barrier layer 120, so that an observer can determine that a serious defect in the battery case 100 has occurred and easily label it as a defect. can detect

The dye layer 140 may have a thickness of 1 μm to 20 μm, specifically 3 μm to 15 μm, and more specifically, 5 μm to 10 μm. When the thickness of the dye layer 140 satisfies the above numerical range, leaking of the dye from the dye layer 140 during molding of the battery case 100 can be prevented, and the dye layer 140 The function of the battery case 100 to block foreign substances, moisture, or air without changing the physical characteristics of the battery case 100 and the overall thickness of the battery case 100 is not excessively thick. may not have any effect.

Also, according to an embodiment of the present invention, the dye layer 140 may include a fluorescent dye.

A defect inspection of the battery case 100 and the secondary battery including the battery case 100 may be performed in a dark room. In particular, when the secondary battery is manufactured in the form of a secondary battery module or a secondary battery pack including a plurality of secondary batteries and is actually used, the defect inspection may be performed in an environment with little light such as inside a container. According to the present invention, since the dye layer 140 includes a fluorescent dye, serious defects such as loss of the barrier layer 120 of the battery case 100 can be easily detected by an observer even in the above environment. can

The fluorescent dye may include, for example, at least one selected from the group consisting of cobalt chloride and methyl violet. Since the fluorescent dye includes the above material, a serious defect such as loss of the barrier layer 120 of the battery case 100 can be easily detected by an observer even in an environment where there is little light as described above. .

In addition, the dye layer 140 may include a fluorescent dye and silica gel. Since the dye layer 140 includes the silica gel, when a crack occurs in the battery case 100 and the dye layer 140 is exposed to the outside, the silica gel absorbs moisture and the barrier layer 120 It can play a role in preventing oxidation. Accordingly, damage to contents inside the battery case 100 such as the barrier layer 120, the electrode assembly, and the electrolyte can be reduced.

In addition, in the embodiment in which the dye layer 140 includes a fluorescent dye and silica gel, when the barrier layer 120 is lost, the silica gel dyed with the fluorescent dye leaks out of the battery case 100. Therefore, a serious defect such as loss of the barrier layer 120 can be more easily detected by an observer even in an environment where there is little light.

Specifically, the fluorescent dye and the silica gel may be included in the dye layer 140 at a weight ratio of 1:0.5 to 2.5, and may be included in the dye layer 140 at a weight ratio of preferably 1:1 to 2. When the numerical range is satisfied, a serious defect such as disappearance of the barrier layer 120 by the fluorescent dye can be easily detected by an observer, and the barrier layer 120 and the sealant are formed by the silica gel. It is possible to effectively prevent oxidation of the layer 110, the electrode assembly, and the electrolyte by moisture.

The silica gel may have a particle diameter of 1 μm to 10 μm, specifically 2 μm to 8 μm, and more specifically 3 μm to 5 μm. When the particle diameter of the silica gel satisfies the above numerical range, the specific surface area of the silica gel is appropriately large, so that moisture is better adsorbed and the barrier layer 120, the sealant layer 110, the electrode assembly, and It is possible to more effectively prevent the electrolyte or the like from being oxidized by moisture.

Meanwhile, although not indicated by reference numerals, the battery case 100 according to the present invention may further include an adhesive layer between each layer. The adhesive layer may be bonded by adhering each layer, and may serve to prevent each layer from being physically separated from each other.

<Secondary Battery>

A secondary battery according to the present invention includes an electrode assembly; electrolytes; and a battery case accommodating the electrode assembly and the electrolyte. Specifically, the secondary battery may be a pouch-type secondary battery.

The electrode assembly includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, and the electrode assembly may be, for example, a laminate in which the positive electrode, the separator, and the negative electrode are alternately stacked, and the positive electrode , It may be a jelly-roll type electrode assembly in which the separator and the negative electrode are alternately stacked and wound.

The electrolyte may serve to assist ion movement between the positive electrode and the negative electrode, and the electrolyte may include a material known in the art.

The battery case according to the present invention described above may be applied in the same manner.

Hereinafter, a secondary battery according to the present invention will be briefly described with reference to the drawings.

3 is a diagram showing a secondary battery according to an embodiment of the present invention.

Referring to FIG. 3 , the secondary battery 10 includes a battery case 20 and an electrode assembly (not shown) according to the present invention, and the electrode assembly is interposed between a positive electrode, a negative electrode, and the positive electrode and the negative electrode A separator electrically insulates between the positive electrode and the negative electrode, and the electrode assembly includes a positive electrode tab extending from the positive electrode and a negative electrode tab extending from the negative electrode.

After converging in a certain direction, the positive electrode tab and the negative electrode tab may be bonded to the respective electrode leads 31 and 32 by resistance welding, ultrasonic welding, or laser welding to form a single cell assembly. Each of the electrode leads 31 and 32 serves as an electrode of the secondary battery 10 and electrically connects the secondary battery 10 and an externally applied device to each other.

In addition, in the secondary battery 10, as shown in FIG. 3, the positive electrode lead and the negative electrode lead may be formed on the same side of the pouch case, and each electrode lead is formed on the other side of the pouch case according to an embodiment. It could be.

On the other hand, the battery case 20 may be joined by thermal fusion at the outer circumferential portion. Specifically, the lower surface of the upper battery case and the upper surface of the lower battery case may be bonded to each other, and the lower surface of the upper battery case and the lower battery case may be bonded to each other. The upper surface of the case may include, for example, casted polypropylene (CPP).

The lower surface of the upper battery case and the upper surface of the lower battery case may be heat-sealed by a heating jig (not shown), which is a medium providing heat and pressure. After the outer circumferential surface of the battery case is melted by the heat generated from the heating jig to increase the degree of freedom of flow, it can be heat-sealed and bonded by an appropriate cooling process.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein.

Example

<Manufacture of battery case>

(CPP layer) as a sealant layer, a mixture of cobalt chloride and silica gel in a weight ratio of 40:60 as a dye layer, an aluminum layer as a barrier layer, and biaxially stretched nylon (O-Ny) as the first layer of the base layer. A battery case according to the present invention was manufactured by laminating a PET layer as a layer and a second layer of the substrate layer. In addition, by forming an adhesive layer between each layer using an adhesive, separation of each layer from each other was prevented.

In the battery case of the embodiment, the sealant layer had a thickness of 80 μm, the dye layer had a thickness of 10 μm, the barrier layer had a thickness of 40 μm, the first layer had a thickness of 12 μm, and the second The thickness of the layer was 25 μm.

comparative example

<Manufacture of battery case>

A battery case was manufactured in the same manner as in the above example, except that the battery case of the above embodiment did not include a dye layer.

In the battery case of Comparative Example, the sealant layer had a thickness of 80 μm, the barrier layer had a thickness of 40 μm, the first layer had a thickness of 12 μm, and the second layer had a thickness of 25 μm.

Experimental example

(1) Detection of defective battery case appearance

An experiment was conducted to detect whether or not there was a defect in appearance with respect to the battery cases of Examples and Comparative Examples. A selected observer visually detected whether or not there was a defect in the appearance of the 24 battery cases having different cracks. An experiment to detect whether or not the appearance of the battery case is defective was conducted in a closed room environment of 10 pyeong in which 12 LED fluorescent lamps with 30W power were turned on. Whether or not the external appearance was defective was determined based on whether or not a crack was generated in the battery case and the damaged aluminum layer was visually confirmed.

As a result of the experiment, the observer detected 24 battery cases out of 24 of the battery cases of Examples as having poor appearance. Accordingly, the observer was able to detect a battery case having a defect in appearance corresponding to 100%.

In addition, the observer detected 22 battery cases out of 24 battery cases of the comparative example as having poor appearance. Accordingly, the observer was able to detect 92% of the battery case having poor appearance.

According to the experimental results of the above Examples and Comparative Examples, in the case of the example including the dye layer, the case for the battery having poor appearance was detected 8% better by the observer than in the case of the comparative example not including the dye layer.

(2) Detecting defects in the appearance of the battery case under dark room conditions

Except for the experiment in a closed room environment of 10 pyeong in which one LED fluorescent lamp of 30W power was turned on, an experiment to detect a battery case with poor appearance was conducted in the same manner as in (1) above with respect to Examples and Comparative Examples.

As a result of the experiment, the observer detected 24 battery cases out of 24 of the battery cases of Examples as having poor appearance. Accordingly, the observer was able to detect a battery case having a defect in appearance corresponding to 100%.

In addition, the observer detected 13 battery cases out of 24 battery cases of the comparative example as having poor appearance. Accordingly, the observer was able to detect 54% of the battery case having poor appearance.

According to the experimental results of the above Examples and Comparative Examples, in the case of the example including the dye layer, the battery case having poor appearance was detected 46% better by the observer than in the case of the comparative example not including the dye layer.

10: secondary battery
20: battery case
31: positive lead
32: negative lead
100: battery case
110: sealant layer
120: barrier layer
130: base layer
131: first layer
133: second layer
140: dye layer
C1: first crack
C2: second crack

Claims (13)

sealant layer;
a barrier layer disposed on the sealant layer;
a substrate layer disposed on the barrier layer; and
A battery case comprising a; dye layer disposed between the sealant layer and the barrier layer.
According to claim 1,
The dye layer includes a fluorescent dye, a battery case.
According to claim 2,
The fluorescent dye includes at least one selected from the group consisting of cobalt chloride and methyl violet, battery case.
According to claim 1,
The dye layer includes a fluorescent dye and silica gel, a battery case.
According to claim 4,
The fluorescent dye and the silica gel are included in the dye layer in a weight ratio of 1: 0.5 to 2.5, battery case.
According to claim 1,
The thickness of the dye layer is 1 ㎛ to 20 ㎛, battery case.
According to claim 1,
The sealant layer may be polyethylene; polypropylene; ethylene propylene copolymer; polypropylene-butyrene-ethylene terpolymer; copolymers of polyethylene and acrylic acid; And a copolymer of polypropylene and acrylic acid; containing at least one member selected from the group consisting of, battery case.
According to claim 1,
The barrier layer may include aluminum (Al); iron (Fe); an alloy of chromium (Cr) and manganese (Mn); And alloys of iron (Fe), carbon (C), chromium (Cr) and nickel (Ni); containing at least one member selected from the group consisting of, battery case.
According to claim 1,
The thickness of the barrier layer is 30 ㎛ to 70 ㎛, battery case.
According to claim 1,
The base layer is polyethylene; polypropylene; polyethylene terephthalate; nylon; low density polyethylene (LDPE); high density polyethylene (HDPE); And linear low-density polyethylene (LLDPE); containing at least one member selected from the group consisting of, battery case.
According to claim 1,
The base layer includes a first layer and a second layer,
The first layer comprises nylon,
The second layer is a battery case comprising polyethylene terephthalate.
According to claim 1,
The battery case is a case for a pouch-type secondary battery, a battery case.
electrode assembly;
electrolytes; and
A secondary battery comprising a battery case according to claim 1 accommodating the electrode assembly and the electrolyte.

Images