KR20240123007A - Pouch forming device, pouch type battery case and lithium secondary battery - Google Patents

Abstract

The forming device of a pouch film according to the present invention includes a step portion in a die and a punch, so that a pouch-shaped battery case formed by drawing using the forming device of the present invention has an extra space portion having a step portion on the outside of a receiving portion in which an electrode assembly is received.
The surplus space portion having a storage portion and a step has the effect of improving insulation performance by suppressing the creation of poly-balls during sealing by a sealing member, thereby reducing the risk of cracks occurring in the adhesive portion around the sealing portion.

Description

Pouch forming device, pouch type battery case and lithium secondary battery

The present invention relates to a molding device for a pouch for a secondary battery having improved appearance wrinkles, improved insulation performance destruction prevention, and improved functions of preventing gas traps in electrodes, a pouch-shaped battery case, and a lithium secondary battery.

In general, types of secondary batteries include nickel cadmium batteries, nickel hydrogen batteries, lithium ion batteries, and lithium ion polymer batteries. These secondary batteries are used in not only small products such as digital cameras, P-DVDs, MP3Ps, mobile phones, PDAs, portable game devices, power tools, and e-bikes, but also large products requiring high output such as electric vehicles or hybrid vehicles, as well as power storage devices that store surplus generated power or renewable energy and backup power storage devices.

To manufacture such a secondary battery, first, an electrode active material slurry is applied to a positive electrode current collector and a negative electrode current collector to manufacture a positive electrode and a negative electrode, and these are laminated on both sides of a separator to form an electrode assembly of a predetermined shape. Then, the electrode assembly is housed in a battery case, an electrolyte is injected, and then sealed.

Secondary batteries are classified into pouch type and can type depending on the material of the case that accommodates the electrode assembly. The pouch type accommodates the electrode assembly in a pouch made of a flexible polymer material. The can type accommodates the electrode assembly in a case made of a material such as metal or plastic.

The pouch, which is a case of a pouch-type secondary battery, is manufactured by performing press processing on a flexible pouch film to form an electrode assembly receiving portion. Then, when the receiving portion is formed, the electrode assembly is received in the receiving space of the receiving portion and the side is sealed to manufacture a secondary battery.

Among these press processes, drawing forming is performed by inserting a pouch film into a forming device such as a press machine and applying pressure to the pouch film with a punch to stretch the pouch film.

Fig. 1 is a schematic diagram of a conventional pouch forming device, Fig. 2 is a cross-sectional view of a conventional pouch-shaped battery case formed by a conventional pouch forming device, and Fig. 3 is a conceptual diagram for explaining problems of a conventional pouch-shaped battery case.

Referring to these drawings, a conventional pouch forming device (20) includes a die (22) in which a forming space (21) is formed in a portion where a pouch film (1) is placed, a partition (23) that divides the forming space into two, a punch (26) that presses the pouch film (1) placed in the die (22) to form an electrode assembly receiving portion, and a stripper (27) that presses and fixes the pouch film from above.

When drawing and forming a pouch film using a conventional forming device, there is a problem in that wrinkles occur at the corners of the storage section because the amount and direction of inflow of the pouch film are different depending on the location due to the surface pressure action for fixing the pouch film.

And, the conventional pouch-shaped battery case (30) formed by drawing using such a conventional forming device, when the electrode assembly is placed in the receiving portion (31) and the battery case is sealed using the sealing member (3), some of the molten polymer invades the unsealed portion to form a bonding portion including a bead-shaped poly-ball. However, when the portion is folded in a subsequent process, cracks may occur in the bonding portion around the poly-ball, as shown in FIG. 3, and when cracks occur, there is a problem that the insulation performance of the pouch-shaped battery case deteriorates.

In addition, in the case of a conventional pouch-type battery case, if the area of the gas pocket is small compared to the amount of gas generated during the jig formation process, there is a concern that excess gas that is not accommodated in the gas pocket may flow back into the electrode assembly storage portion and become trapped within the electrode assembly, which may result in a decrease in battery performance.

Accordingly, there is a need for technological development for a pouch film forming device and a pouch-type battery case that can improve the above-mentioned problems.

Republic of Korea Patent Publication No. 10-2021-0150864

The purpose of the present invention is to provide a pouch film forming device, a pouch-type battery case, and a lithium secondary battery including the same to solve the above-mentioned problems.

According to the present invention, a pouch film forming device is provided, comprising: a die having a molding space formed by recessing inwardly from the upper surface on which a pouch film is settled; and a punch disposed above the molding space and lowering to insert the pouch film into the molding space and form it, wherein the die has a first step formed at a connection portion between a bottom surface and a side wall of the molding space, and the punch has a second step formed in a shape that interlocks with the first step corresponding to the first step.

In a pouch film forming device according to one embodiment of the present invention, the die has first and second forming spaces that form a pair, and a partition wall may be formed between the first and second forming spaces.

In a pouch film forming device according to one embodiment of the present invention, the first step portion may have a protrusion formed therein that protrudes from an upper surface of the first step portion toward the punch.

In a pouch film forming device according to one embodiment of the present invention, a length L1 by which the protrusion protrudes from the upper surface of the first step portion and a depth L2 by which the first step portion is sunken from the upper surface of the die can satisfy the following condition 1.

[Condition 1]

0.1L2 ≤ L1 ≤ 0.9L2

In a pouch film forming device according to one embodiment of the present invention, when a position connected to a first step portion from a bottom surface of a forming space is 0 and a position connected to an upper surface of the first step portion and a side wall of the forming space is 1, the protrusion may be located at a point of 0.5 or less.

In a pouch film forming device according to one embodiment of the present invention, the punch may have a protrusion receiving groove into which the protrusion can be inserted.

In a forming device for a pouch film according to one embodiment of the present invention, the end of the protrusion may have a round shape.

In a pouch film forming device according to one embodiment of the present invention, a first edge portion connected from an upper surface of the punch to a second step portion may have a chamfered shape, and a second edge portion connected to a bottom surface of the forming space and the first step portion may have a right-angled shape.

In a pouch film forming device according to one embodiment of the present invention, a third edge portion connected from the upper surface of the second step portion to the side surface of the punch may have a chamfered shape, and a fourth edge portion connected from the upper surface of the first step portion to the side wall of the forming space may have a right-angled shape.

In a pouch film forming device according to one embodiment of the present invention, the height of the first step is smaller than the sunken depth of the forming space.

In a pouch film forming device according to one embodiment of the present invention, the first step portion may be formed at each of the connection portions of the bottom surface of the forming space and the remaining three side walls excluding the side walls of the forming space connected to the bulkhead.

According to another embodiment of the present invention, a pouch-type battery case is provided, including a receiving portion in which an electrode assembly can be built by being sunken from a plane of a pouch film to a depth of D1; and a surplus space portion connected to a receiving space located at an upper portion of a bottom surface of the receiving portion and sunken from the plane of the pouch film to a depth of D2; wherein D2 is smaller than D1.

In a pouch-type battery case according to one embodiment of the present invention, the storage portion includes a first storage portion and a second storage portion formed to accommodate the electrode assembly by folding, and a bridge connecting the first storage portion and the second storage portion may be formed between the first storage portion and the second storage portion.

In a pouch-type battery case according to one embodiment of the present invention, a protrusion protruding upward may be formed on the bottom surface of the excess space portion.

In a pouch-type battery case according to one embodiment of the present invention, the length of the protrusion protruding from the bottom surface of the excess space may be 0.1 to 0.9 times the depth of the excess space.

In a pouch-type battery case according to one embodiment of the present invention, when the boundary between the receiving space and the excess space is 0 and the point where the bottom surface and the side wall of the excess space meet is 1, the protrusion can be located at a point of 0.5 or less.

According to another embodiment of the present invention, a lithium secondary battery is provided, which includes a pouch-shaped battery case and an electrode assembly built into a storage portion of the pouch-shaped battery case.

A pouch-shaped battery case formed by drawing using a forming device for a pouch film of the present invention includes a surplus space portion having a step and a storage portion outside a storage portion in which an electrode assembly is built, thereby suppressing the formation of poly-balls when the battery case is sealed by a sealing member, thereby improving insulation performance.

In addition, since the pouch-shaped battery case formed by drawing using the forming device of the pouch film of the present invention includes a projection protruding upward from the bottom surface of the surplus space portion, the phenomenon of gas in the gas pocket portion flowing back into the storage portion can be prevented, thereby improving the performance degradation of the secondary battery due to the gas trap.

Figure 1 is a schematic diagram of a conventional pouch forming device.
Fig. 2 is a cross-sectional view of a conventional pouch-shaped battery case formed by a conventional pouch forming device.
Figure 3 is a conceptual diagram for explaining the problems of a conventional pouch-type battery case.
Figure 4 is a schematic diagram of a pouch film forming device according to the first embodiment of the present invention.
FIG. 5 is a perspective view of a pouch film forming device according to the first embodiment of the present invention.
Figure 6 is an enlarged view of a portion of Figure 4.
Figure 7 is a cross-sectional view of a pouch-type battery case according to the first embodiment of the present invention.
Figure 8 is a conceptual diagram to explain the effect of the present invention.
Figure 9 is a schematic diagram of a pouch film forming device according to a second embodiment of the present invention.
Figure 10 is an enlarged view of a portion of Figure 9.
Fig. 11 is a cross-sectional view of a pouch-type battery case according to the second embodiment of the present invention.
Figure 12 is a cross-sectional view of the pouch film of the present invention.
Figure 13 is an assembly diagram of a secondary battery according to one embodiment of the present invention.

The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and the present embodiments are provided only to make the disclosure of the present invention complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used with a meaning that can be commonly understood by a person of ordinary skill in the art to which the present invention belongs. In addition, terms defined in commonly used dictionaries shall not be ideally or excessively interpreted unless explicitly and specifically defined.

The terminology used herein is for the purpose of describing embodiments only and is not intended to limit the invention. In this specification, the singular also includes the plural unless specifically stated otherwise. The terms "comprises" and/or "comprising" as used herein do not exclude the presence or addition of one or more other components in addition to the components mentioned.

Forming device for pouch film according to first embodiment

FIG. 4 is a schematic diagram of a pouch film forming device according to the first embodiment of the present invention, FIG. 5 is a perspective view of a pouch film forming device according to the first embodiment of the present invention, FIG. 6 is an enlarged view of a part of FIG. 4, and FIG. 7 is a cross-sectional view of a pouch-type battery case according to the first embodiment of the present invention.

Referring to these drawings, a pouch film forming device (100, hereinafter referred to as a “forming device”) according to a first embodiment of the present invention includes a die (111) having a forming space (112) formed inwardly from the upper surface on which a pouch film (1) is settled; and a punch (121) disposed above the forming space (112) and lowered to insert and form the pouch film (1) into the forming space (112), wherein the die (111) has a first step (113) formed at a connecting portion between a bottom surface (114) and a side wall (115) of the forming space (112), and the punch (121) has a second step (123) formed in a shape that interlocks with the first step (113).

The first step (113) is a structure that forms a step between the upper surface of the die (111) and the bottom surface (114) of the molding space based on the vertical direction (z-axis direction) on the plane of the die (111).

The height of the first step (113) is smaller than the sinking depth of the molding space (112). Here, the height of the first step (113) can be defined as the minimum value of the distance from the bottom surface (114) of the molding space (112) to the upper surface of the first step (113), and the sinking depth of the molding space can be defined as the minimum value of the distance from the bottom surface (114) of the molding space (112) to the upper surface of the die (111).

When the pouch film (1) is drawn and formed by a forming device (100) like this, it is manufactured into a pouch-shaped battery case (1000) as shown in the upper part of Fig. 7, and when the pouch-shaped battery case (1000) in the upper part of Fig. 7 is folded, it becomes as shown below in Fig. 7.

Referring to FIG. 7, a pouch-shaped battery case (1000) formed by drawing using a forming device (100) of the present invention includes a receiving portion (1100) in which an electrode assembly can be built and which is sunken from a plane of a pouch film (1) by a depth of D1; and a surplus space portion (1200) which is connected to a receiving space (1120) located at an upper portion of a bottom surface (1110) of the receiving portion and is sunken from a plane of the pouch film by a depth of D2.

The above-mentioned surplus space portion (1200) is formed corresponding to the first step portion (113) and the second step portion (123). The pouch-type battery case (1000) formed by drawing using the forming apparatus (100) of the present invention includes a surplus space portion (1200) connected to at least one side of the receiving space (1120), and the battery cases (1000) surrounding the surplus space portion (1200) are spaced apart from each other as shown below in FIG. 7. Therefore, when the battery case is sealed by the sealing member, the generation of poly-balls can be suppressed as some of the molten polymer invades the unsealed portion. Therefore, the forming apparatus (100) of the present invention has the effect of enabling the manufacture of a pouch-type battery case with a reduced risk of cracks occurring due to poly-balls.

When forming a pouch film (1) using the pouch film forming device (100) of the present invention, only one electrode assembly receiving portion may be formed, but is not limited thereto and two receiving portions may be drawn and formed adjacent to each other.

To this end, as shown in FIGS. 4 and 5, two pairs of first and second molding spaces (112a, 112b) are formed adjacent to each other in the die (111), and a partition wall (116) can be formed between the two molding spaces (112a, 112b).

And, the punch (121) can be configured to correspond to a pair of molding spaces (112a, 112b) so that the punch (121a, 121b) can be inserted into the molding spaces (112a, 112b).

The bulkhead (116) may exist separately from the die (111), and the lower part of the bulkhead (116) may be joined/fixed to the die (111), or the bulkhead (116) and the die (111) may be integral.

When the pouch film (1) is drawn and formed while the punches (121a, 121b) are inserted into both of the forming spaces (112a, 112b), two receiving portions (1100) are formed in the pouch-shaped battery case (1000) corresponding to the two forming spaces (112a, 112b), and a bridge (1300) can also be formed between the two receiving portions (1100) corresponding to the partition wall (116).

A pressurizing unit (120) may be provided on the upper portion of the die unit (110) to pressurize the pouch film (1) positioned in the forming space (112a, 112b) to form an electrode assembly receiving portion (1100a, 1100b).

In one embodiment, the pressurizing unit (120) may include a moving part (122) that is provided to be lowerable toward the die (111), a stripper (124) provided at the lower portion of the moving part, and a punch (121) provided at the lower portion of the stripper (124).

When the pouch film (1) is placed on the upper surface of the die (111), the stripper (124) according to the present embodiment is lowered, and when the lower surface of the stripper (124) comes into contact with the upper surface of the pouch film (1), the stripper (124) and the die (111) can come into contact with each other with the pouch film (1) therebetween. At this time, the stripper (124) can press and fix the pouch film (1) from above, and when the electrode assembly receiving portion is formed by uniformly pressing the pouch film (1), the elongation force applied to the pouch film (1) can be uniformly distributed.

The punch (121) according to the present embodiment can form an electrode assembly receiving portion in the pouch film (1) by being inserted into the forming space (112a, 112b) while pressurizing the pouch film (1) located in the forming space (112a, 112b).

The punch (121) can be provided on each side of the lower portion of the moving part (122) with respect to the partition wall (116), and accordingly, an electrode assembly receiving portion can be formed on both sides of the pouch film (1) with respect to the partition wall (116).

The first step portion (113a, 113b) may be formed on a side wall portion facing the direction in which the partition wall (116) is located among the four side walls of the molding space (112a, 112b), as shown in FIGS. 4 and 5, but is not limited thereto.

Referring to FIG. 5, a first step portion (113a, 113b) may be formed at each of the three side walls (115a-1 to 115a-3, 115b-1 to 115b-3) excluding the side wall of the molding space connected to the bulkhead (116) and the connection portion of the bottom surface (114) of the molding space.

Referring to FIG. 6, in a preferred embodiment of the present invention, the first edge portion (126) connected to the second step portion (123a) from the upper surface (125) of the punch may have a chamfered shape, and the second edge portion (117) connected to the bottom surface (114a) of the molding space (112a) and the first step portion (113a) may have a right-angled shape.

Since the first edge portion (126) is chamfered and the second edge portion (117) that engages with the first edge portion (126) is of a right angle shape, when the punch (121) is inserted into the forming space (112a) while pressing the pouch film (1), a tolerance is formed at the relevant portion, thereby preventing the pouch film (1) from being damaged.

In addition, the third edge portion (128) connected to the side surface (127) of the punch from the upper surface of the second step portion (123a) may have a chamfered shape, and the fourth edge portion (119) connected to the side wall (115a) of the die (111) from the upper surface of the first step portion (113a) may have a right-angled shape. Even in this case, a tolerance is formed at the relevant portion to prevent damage to the pouch film (1).

Pouch-type battery case according to the first embodiment

First, the pouch film that is the material of the pouch-shaped battery case of the present invention will be described. The pouch film is drawn and formed by a forming device according to the present invention to form a pouch-shaped battery case.

Fig. 12 is a cross-sectional view of a pouch film according to one embodiment of the present invention. Referring to Fig. 12, the pouch film (1) may include a sealant layer (1a), a moisture barrier layer (1b), and a surface protection layer (1c), and may optionally further include a stretching auxiliary layer (1d).

The sealant layer (1a) is made of a first polymer and is formed as the innermost layer so as to be in direct contact with the electrode assembly. Here, the innermost layer refers to the layer located last when facing in the direction in which the electrode assembly is positioned based on the moisture barrier layer.

The sealant layer (1a) must have insulating properties because it comes into direct contact with the electrode assembly, and must have corrosion resistance because it also comes into contact with the electrolyte. In addition, it must have high sealing properties because it must completely seal the inside to block material movement between the inside and the outside. In other words, the sealing portion where the sealant layers (1a) are bonded together must have excellent thermal bonding strength.

In general, the first polymer for manufacturing such a sealant layer (1a) may be composed of one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon, and glass fiber. In particular, a polyolefin resin such as polypropylene (PP) or polyethylene (PE) is mainly used. Polypropylene (PP) has excellent mechanical properties such as tensile strength, rigidity, surface hardness, wear resistance, and heat resistance, and chemical properties such as corrosion resistance, and is therefore mainly used for manufacturing the sealant layer (1a) (1351). In addition, it may be composed of cationic polypropylene, acid-modified polypropylene, or polypropylene-butylene-ethylene terpolymer. Here, the acid-modified polypropylene may be MAH PP (maleic anhydride polypropylene). In addition, the sealant layer (1a) may have a single film structure composed of a single material, or a composite film structure in which two or more materials are each formed to form layers.

According to one embodiment, the thickness of the sealant layer (1a) may be 30 µm to 100 µm, preferably 40 µm to 90 µm, and particularly 50 µm to 85 µm.

A moisture barrier layer (1b) is laminated between the surface protection layer (1c) and the sealant layer (1a) to secure the mechanical strength of the pouch, block the ingress of gas or moisture from outside the secondary battery, and prevent leakage of electrolyte.

The moisture barrier layer (1b) may include a metal selected from the group consisting of copper (Cu), aluminum (Al), nickel (Ni), iron (Fe), carbon (C), chromium (Cr), manganese (Mn), and an alloy including two or more of these, but is not particularly limited thereto, and preferably, may include a metal selected from an aluminum alloy and stainless steel (SUS).

Aluminum alloys and stainless steels can secure mechanical strength above a certain level, while being light in weight and securing electrochemical properties complementary to the electrode assembly and electrolyte, as well as heat dissipation properties.

The above aluminum alloy may include various materials. For example, it may include one or more selected from the group consisting of iron (Fe), copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), and zinc (Zn).

The moisture barrier layer (1b) may have a single-layer structure or a multi-layer structure. For example, a multi-layer moisture barrier layer (1b) may be composed of an aluminum alloy layer and a stainless steel layer.

According to one embodiment, the thickness of the moisture barrier layer (1b) may be 20 µm to 100 µm, preferably 40 µm to 80 µm, and particularly 50 µm to 70 µm.

The surface protection layer (1c) is made of a second polymer and is formed on the outermost layer to protect the secondary battery from friction and collision with the outside, while electrically insulating the electrode assembly from the outside. Here, the outermost layer refers to the layer located last when facing in the opposite direction to the direction in which the electrode assembly is located based on the moisture barrier layer (1b).

The second polymer for producing the surface protection layer (1c) may be one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon, and glass fiber. In particular, it is preferable to use a polymer such as polyethylene terephthalate (PET) which mainly has wear resistance and heat resistance. In addition, the surface protection layer (1c) may have a single film structure made of one material, or may have a composite film structure in which two or more materials are each formed to form layers.

According to one embodiment, the thickness of the surface protection layer (1c) may be 5 µm to 25 µm, preferably 6 µm to 20 µm, and particularly 7 µm to 15 µm.

According to one embodiment of the present invention, the pouch film may further include a stretching auxiliary layer (1d) made of a third polymer and laminated between the surface protection layer (1c) and the moisture barrier layer (1b). The stretching auxiliary layer (1d) is laminated between the surface protection layer (1c) and the moisture barrier layer (1b), and can prevent the surface protection layer (1c) and the moisture barrier layer (1b) from being peeled off when being stretched.

The third polymer for manufacturing the stretching auxiliary layer (1d) may be one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon, and glass fiber. In particular, since nylon resin easily adheres to polyethylene terephthalate (PET) of the surface protective layer (1c) and has similar behavior when stretched to the aluminum alloy of the moisture barrier layer (1b), nylon resin can be mainly used as the third polymer. In addition, the stretching auxiliary layer (1d) may have a single film structure made of one material, or may have a composite film structure in which two or more materials are each formed to form layers.

According to one embodiment, the thickness of the extension auxiliary layer (1d) may be 15 µm to 50 µm, preferably 25 µm to 45 µm, and particularly 25 µm to 40 µm.

According to one embodiment, the thickness of the pouch film can be selected within an appropriate range depending on the intended use of the battery, and specifically can be 70 ㎛ to 275 ㎛, 90 ㎛ to 250 ㎛, or 100 ㎛ to 220 ㎛.

FIG. 7 is a cross-sectional view of a pouch-type battery case according to the first embodiment of the present invention, and FIG. 8 is a conceptual diagram for explaining the effects of the present invention.

Referring to these drawings, a pouch-type battery case (1000) according to the present invention includes a receiving portion (1100) that is recessed from a plane of a pouch film (1) to a depth of D1 and into which an electrode assembly can be built; and a surplus space portion (1200) that is connected to a receiving space (1120) located at an upper portion of a bottom surface (1110) of the receiving portion and is recessed from the plane of the pouch film to a depth of D2; wherein D2 is smaller than D1.

Such a surplus space portion (1200) is located on the outside of the receiving space (1120) and can be formed at the connection portion between the corner portion of the storage portion (1100) and the upper surface of the battery case.

Since the sinking depth D2 of the surplus space portion (1200) is smaller than the sinking depth D1 of the storage portion (1100), a step is created between the bottom surface of the surplus space portion (1200) and the bottom surface (1110) of the storage portion.

In the pouch-type battery case (1000) according to the present invention, when forming the pouch film, only one electrode assembly receiving portion may be formed, but is not limited thereto, and as shown in FIG. 7, the pouch film may be drawn and formed so that two receiving spaces (1120) are adjacent to each other.

Specifically, the receiving portion (1100) includes a first receiving portion (1100a) and a second receiving portion (1100b) formed to receive the electrode assembly by folding, and a bridge (1300) connecting the first receiving portion (1100a) and the second receiving portion (1100b) may be formed between the first receiving portion (1100a) and the second receiving portion (1100b). In addition, a surplus space portion (1200a, 1200b) may be formed on one side of each of the first receiving portion (1100a) and the second receiving portion (1100b).

The bridge (1300) may be a reference part when folding the battery case (1000) later. When the manufacture of the secondary battery is completed, the bridge (1300) may form a folding part (not shown) on one side of the secondary battery.

The pouch-type battery case (1000) according to the present invention includes a surplus space portion (1200) on at least one side of the receiving space (1120), and the battery case surrounding the surplus space portion (1200) is spaced apart from each other, so that when the battery case is sealed by the sealing member (3), the creation of poly-balls that may be created when a portion of the molten polymer invades the unsealed portion can be suppressed.

Referring to (a) of Fig. 8, the battery cases surrounding the surplus space portion (1200) connected to the receiving space (1120) are spaced apart from each other. On the other hand, referring to (b) of Fig. 8, the conventional pouch-type battery case (30) does not include the surplus space portion (1200). Therefore, the pouch-type battery case (1000) of the present invention has a structure that is less advantageous in that a poly-ball is formed when a molten polymer invades the unsealed portion during the sealing process by the sealing member (3), compared to the conventional pouch-type battery case (30), and thus, the insulating performance can be improved.

Forming device for pouch film according to the second embodiment

FIG. 9 is a schematic diagram of a pouch film forming device according to a second embodiment of the present invention, and FIG. 10 is an enlarged view of a part of FIG. 9.

Referring to these drawings, the forming device (200) of the pouch film includes a die (211) having a forming space (212) formed inwardly from the upper surface on which a pouch film (1) is settled, and a punch (221) disposed above the forming space (212) and lowered to insert and form the pouch film (1) into the forming space (212), and the die (211) has a first step (213) formed at a connection portion between the bottom surface (214) and the side wall (215) of the forming space (212), and the punch (221) has a second step (223) formed in a shape that is engaged with the first step (213), and the first step (213) has a protrusion (217) that protrudes from the upper surface of the first step (213) toward the punch (221). In addition, the punch (221) may have a protrusion receiving groove (225) into which the protrusion (217) can be inserted.

When a pouch film (1) is drawn and formed by a forming device (200) like this, it is manufactured into a pouch-shaped battery case (2000) as shown in Fig. 11.

Referring to FIG. 11, the surplus space portion (2200) of the pouch-shaped battery case (2000) according to the second embodiment is provided with a protrusion (2400) formed corresponding to the protrusion (217) of the forming device (200). In addition, this protrusion (2400) functions to partition the electrode assembly receiving portion (2100) and the gas pocket portion (not shown) located on one side of the electrode assembly receiving portion (2100), so that it does not impede the internal gas generated during the formation process from moving to the gas pocket portion, but prevents the gas captured in the gas pocket portion from flowing back to the receiving portion (2100), and has the effect of facilitating the sealing of the battery case.

In one specific example, the length L1 by which the protrusion (217) protrudes from the upper surface of the first step (213a) and the depth L2 by which the first step (213a) is sunken from the upper surface of the die (211) can satisfy the following condition 1.

[Condition 1]

0.1L2 ≤ L1 ≤ 0.9L2

When the above L1 and L2 satisfy the above condition 1, the effect of preventing the gas captured in the gas pocket from flowing back to the storage unit (2100) can be further maximized as the protrusion (2400) of the battery case (2000) formed by the protrusion (217) has an appropriate length.

And, when the position connected to the first step (213a) from the bottom surface (214a) of the molding space is 0, and the position connected to the upper surface of the first step (213a) with the side wall (215a) of the molding space is 1, it is preferable that the protrusion is located at a point of 0.5 or less.

As the protrusion (217) approaches the inside of the molding space (212a) in the first step (213a), the protrusion (2400) formed corresponding to the protrusion (217) is also formed at a position closer to the inside of the receiving portion (2100), and as the protrusion (2400) approaches the receiving portion (2100), the risk of cracks occurring due to poly-balls formed during the sealing process by the sealing member can be reduced.

In addition, the end of the protrusion (217) may have a round shape. When the end of the protrusion has a round shape, the pouch film (1) can be prevented from being damaged during the process of pressure-forming the pouch film (1) by the die (211) and the punch (221).

Pouch-type battery case according to the second embodiment

FIG. 11 is a cross-sectional view of a pouch-type battery case according to a second embodiment of the present invention. Referring to FIG. 11, a pouch-type battery case (2000) according to the present invention includes a receiving portion (2100) that is recessed from a plane of a pouch film (1) to a depth of D1 and into which an electrode assembly can be built; and a surplus space portion (2200) that is connected to a receiving space (2120) located at an upper portion of a bottom surface (2110) of the receiving portion and is recessed from the plane of the pouch film to a depth of D2; and is characterized in that a protrusion (2400) that protrudes upward is formed on a bottom surface of the surplus space portion (2200).

Such a surplus space portion (2200) is located on the outside of the receiving space (2120) and can be formed at the connection portion between the corner portion of the storage portion (2100) and the upper surface of the battery case.

Since the sinking depth D2 of the surplus space portion (2200) is smaller than the sinking depth D1 of the storage portion (2100), a step is created between the bottom surface of the surplus space portion (2200) and the bottom surface (2110) of the storage portion.

The above protrusion (2400) is formed corresponding to the protrusion (217) of the forming device (200) of the present invention, and the protrusion (2400) has the function of dividing the receiving portion (2100) and the gas pocket portion (not shown), so that it does not impede the internal gas generated during the formation process from moving to the gas pocket portion, but prevents the gas captured in the gas pocket portion from flowing back to the receiving portion (2100), and has the effect of facilitating the sealing of the battery case.

The length of the projection (2400) protruding upward (in the z-axis direction) from the bottom surface of the surplus space portion (2200) may be 0.1 to 0.9 times, preferably 0.2 to 0.85 times, the depth (D2) of the surplus space portion. If the protrusion length of the projection (2400) is too long beyond the above range, it may impede the movement of gas to the gas pocket portion, which is undesirable, and if it is too short, the gas captured in the gas pocket portion may flow back to the storage portion (2100), which is undesirable.

In the pouch-type battery case (2000) according to the present invention, when forming the pouch film, only one electrode assembly receiving portion may be formed, but is not limited thereto, and as shown in FIG. 11, the pouch film may be drawn and formed so that two receiving spaces (2100) are adjacent to each other.

Specifically, the receiving portion (2100) includes a first receiving portion (2100a) and a second receiving portion (2100b) formed to receive the electrode assembly by folding, and a bridge (2300) connecting the first receiving portion (2100a) and the second receiving portion (2100b) may be formed between the first receiving portion (2100a) and the second receiving portion (2100b). In addition, a surplus space portion (2200a, 2200b) may be formed on at least one side of the first receiving portion (2100a) and the second receiving portion (3100b).

And, based on the extension direction (x-axis direction) of the pouch-shaped battery case, when the boundary between the receiving space (2100) and the surplus space portion (2200) is 0, and the point where the bottom surface of the surplus space portion (2200) meets the side wall (2230) is 1, it is preferable that the protrusion be located at a point of 0.5 or less.

Since the protrusion (2400) gets closer to the sealing portion as it gets farther away from the receiving space (2100), if the protrusion (2400) is located too far away from the receiving space (2100), the risk of cracks occurring due to poly-balls formed during the sealing process by the sealing member may increase, which is not desirable.

Lithium secondary battery

Figure 13 is an assembly diagram of a lithium secondary battery (1) according to one embodiment of the present invention.

A lithium secondary battery (B) according to one embodiment of the present invention is in a sealed form in which an electrode assembly (10) is built into a storage compartment of a pouch-type battery case (1000, 2000) of the present invention.

The lithium secondary battery (B) according to the present invention includes a surplus space (1200, 2200) between the storage portion (1100, 2100) of the pouch-type battery case (1000, 2000) and the gas pocket portion (not shown), so that the risk of cracks occurring due to poly-balls that may be formed during the sealing process by the sealing member can be reduced, thereby improving the insulating performance.

In addition, when a protrusion (2400) is formed on the bottom surface of the surplus space portion (2200), the protrusion (2400) prevents gas located in the gas pocket portion from flowing back to the storage portion (2100), thereby preventing a decrease in battery performance due to a gas trap.

The electrode assembly (10) is formed by alternately stacking electrodes and separators. First, an electrode slurry containing an electrode active material, a binder, a conductive agent, and a solvent is applied to a positive electrode current collector and a negative electrode current collector to manufacture electrodes such as a positive electrode and a negative electrode. Then, separators are stacked between the electrodes to manufacture an electrode assembly (10). A lithium secondary battery (B) can be manufactured by inserting the manufactured electrode assembly (10) into a pouch-type battery case (1000, 2000), injecting electrolyte, and then sealing.

Specifically, the electrode assembly (10) includes two types of electrodes, a positive electrode and a negative electrode, and a separator interposed between the electrodes to mutually insulate the electrodes. The electrode assembly (10) includes a stack type, a jelly roll type, a stack and folding type, etc. The two types of electrodes, i.e. the positive electrode and the negative electrode, each have a structure in which an active material slurry is applied to an electrode current collector in the form of a metal foil or metal mesh containing aluminum and copper, respectively. The electrode slurry can be formed by stirring a granular active material, a conductive material, a binder, a plasticizer, etc. while adding a solvent. The solvent is removed in a subsequent process.

The electrode assembly (10) includes an electrode tab (11), as illustrated in FIG. 13. The electrode tab (11) is connected to the positive and negative electrodes of the electrode assembly (10), respectively, and protrudes outward from the electrode assembly (10) to serve as a path through which electrons can move between the inside and the outside of the electrode assembly (10). The electrode current collector of the electrode assembly (10) is composed of a portion where an electrode active material is applied and a terminal portion where the electrode active material is not applied, i.e., a non-coated portion. In addition, the electrode tab (11) may be formed by cutting the non-coated portion or by connecting a separate conductive member to the non-coated portion by ultrasonic welding, etc. As illustrated in FIG. 13, the electrode tab (11) may protrude in different directions from each other in the electrode assembly (10), but is not limited thereto, and may be formed to protrude in various directions, such as protruding side by side in the same direction from one side.

An electrode lead (12) for supplying electricity to the outside of a secondary battery (1) may be connected to an electrode tab (11) of an electrode assembly (10) by spot welding or the like. In addition, a portion of the electrode lead (12) may be surrounded by an insulating portion (14). The insulating portion (14) is positioned limited to a side (S) where the upper case and the lower case of the battery case (1000, 2000) are thermally fused, thereby bonding the electrode lead (12) to the battery case (1000, 2000). In addition, it prevents electricity generated from the electrode assembly (10) from flowing to the battery case (1000, 2000) through the electrode lead (12), and maintains the sealing of the battery case (1000, 2000). Therefore, this insulating portion (14) is made of a non-conductive material that does not conduct electricity well. In general, as the insulating part (14), an insulating tape that is easy to attach to the electrode lead (12) and has a relatively thin thickness is often used, but it is not limited thereto and various materials can be used as long as they can insulate the electrode lead (12).

The electrode lead (12) may have one end connected to the electrode tab (11) and the other end protruding outward from the battery case (1000, 2000). That is, the electrode lead (12) includes a positive lead (12-1) which has one end connected to the positive tab (11-1) and extending in the direction in which the positive tab (11-1) protrudes, and a negative lead (12-2) which has one end connected to the negative tab (11-2) and extending in the direction in which the negative tab (11-2) protrudes. Meanwhile, as illustrated in FIG. 13, the other ends of both the positive lead (12-1) and the negative lead (12-2) protrude outward from the battery case (1000, 2000). As such, electricity generated inside the electrode assembly (10) can be supplied to the outside. In addition, since the positive tab (11-1) and the negative tab (11-2) are formed to protrude in various directions, the positive lead (12-1) and the negative lead (12-2) can also extend in various directions, respectively.

The positive electrode lead (12-1) and the negative electrode lead (12-2) may be made of different materials. That is, the positive electrode lead (12-1) may be made of the same aluminum (Al) material as the positive electrode collector, and the negative electrode lead (12-2) may be made of the same copper (Cu) material as the negative electrode collector or a copper material coated with nickel (Ni). In addition, a portion of the electrode lead (12) protruding outside the battery case (1000, 2000) becomes a terminal portion and is electrically connected to an external terminal.

The scope of the present invention is indicated by the claims described below rather than the detailed description above, and various embodiments are possible derived from the meaning and scope of the claims and their equivalent concepts.

1: Pouch film
3: Absence of sealing
10: Electrode assembly
20, 100, 200: Pouch film forming device
111,211: Die
112,212: Plastic space
113,213: 1st step
115,215: Sidewall
116,216: Bulkhead
121,221: Punch
123,223: 2nd step
1000,2000: Pouch type battery case
1100,2100: Storage area
1200,2200: Surplus space
1300,2300: Bridge

Claims (17)

A die having a pouch film positioned on the upper surface and a molding space formed inwardly from the upper surface; and
A punch is disposed above the above molding space and is lowered to insert the pouch film into the molding space and form it.
The above die has a first step formed at the connection portion between the bottom surface and the side wall of the molding space,
A pouch film forming device, characterized in that the punch has a second step portion formed in a shape that interlocks with the first step portion.
In claim 1,
The above die,
It has paired 1st and 2nd molding spaces,
A pouch film forming device having a partition formed between the first and second forming spaces.
In claim 1,
A pouch film forming device, wherein a protrusion is formed on the first step portion and protrudes from the upper surface of the first step portion toward the punch.
In claim 3,
A pouch film forming device wherein a length L1 of the protrusion protruding from the upper surface of the first step portion and a depth L2 of the first step portion recessed from the upper surface of the die satisfy the following condition 1.
[Condition 1]
0.1L2 ≤ L1 ≤ 0.9L2
In claim 3,
A pouch film forming device, wherein the protrusion is located at a point of 0.5 or less, when the position connected to the first step from the bottom surface of the forming space is 0, and the position connected to the upper surface of the first step and the side wall of the forming space is 1.
In claim 3,
The above punch is a forming device for a pouch film having a projection receiving groove into which the projection can be inserted.
In claim 6,
The end of the above protrusion is a forming device for a pouch film having a round shape.
In claim 1,
The first edge portion connected to the second step portion on the upper surface of the above punch has a chamfered shape,
A pouch film forming device in which the bottom surface of the above-mentioned forming space and the second edge portion connecting the first step portion are in a right-angled shape.
In claim 8,
The third edge portion connected to the side of the punch from the upper surface of the second step portion is chamfered,
A pouch film forming device having a fourth edge portion connected to a side wall of the forming space on the upper surface of the first step portion and having a right-angled shape.
In claim 1,
A pouch film forming device, characterized in that the height of the first step is smaller than the sunken depth of the forming space.
In claim 2,
A pouch film forming device in which the first step portion is formed at each of the connection portions of the three side walls of the forming space, excluding the side walls of the forming space connected to the bulkhead, and the bottom surface of the forming space.
A storage portion in which an electrode assembly can be embedded by being sunken from the plane of the pouch film to a depth of D1; and
Including a surplus space portion connected to the receiving space located on the upper part of the bottom surface of the above storage portion and sunken from the plane of the pouch film by a depth of D2;
The above D2 is a pouch-type battery case smaller than D1.
In claim 12,
The above storage portion includes a first storage portion and a second storage portion formed to accommodate the electrode assembly by folding,
A pouch-type battery case having a bridge formed between the first storage section and the second storage section to connect the first storage section and the second storage section.
In claim 12,
A pouch-shaped battery case having an upwardly protruding projection formed on the bottom surface of the above-mentioned surplus space.
In claim 14,
A pouch-shaped battery case in which the length of the protrusion protruding from the bottom surface of the excess space is 0.1 to 0.9 times the depth of the excess space.
In claim 14,
A pouch-shaped battery case, wherein the protrusion is located at a point less than or equal to 0.5, when the boundary between the above-mentioned receiving space and the excess space is 0, and the point where the bottom surface and the side wall of the excess space meet is 1.
A pouch-type battery case according to claim 12;
A lithium secondary battery including an electrode assembly built into a storage compartment of the above pouch-type battery case.

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