Secondary battery

Abstract

This secondary battery includes an electrode assembly, a can, a cap plate, and a heat dissipation unit. The electrode assembly includes a first electrode, a separator, and a second electrode. The can accommodates the electrode assembly in the inner space thereof. The cap plate is coupled to an opening-side end of the can to seal the can. The cap plate includes a notch groove and at least one opening spaced apart from the notch groove. The heat dissipation unit is filled in the opening to seal the opening, and discharges internal heat and gas during melting.

Description

secondary battery

[0001] The present disclosure relates to a secondary battery, and more particularly, to a structure of a secondary battery for improving high-temperature safety.

[0002] Secondary batteries are used in a variety of applications, including powering small electronic devices like mobile phones and laptops, and powering motors in transportation vehicles like electric and hybrid vehicles. In the latter case, battery modules composed of multiple cylindrical secondary batteries are used. The trend in cylindrical secondary batteries is to increase the diameter of the electrode assembly to secure larger capacities.

[0003] The hotbox test, a safety assessment method for secondary batteries, involves placing a secondary battery in a chamber, raising the chamber temperature to 130°C, and maintaining it for 30 minutes. Previously, to meet the hotbox requirements, the anode and cathode materials were improved to control heat generation in the electrode assembly. However, high-capacity materials initiate heat generation at relatively lower temperatures, which tends to degrade hotbox performance as secondary batteries become larger.

[0004] The present disclosure seeks to provide a secondary battery capable of improving high-temperature safety by allowing internal heat to be discharged when the internal temperature of the secondary battery exceeds a set temperature.

[0005] According to one embodiment, a secondary battery includes an electrode assembly, a can, a cap plate, and a heat dissipation unit. The electrode assembly includes a first electrode, a separator, and a second electrode. The can accommodates the electrode assembly in an internal space. The cap plate is coupled to an open end of the can to seal the can, and the cap plate is provided with a notch groove and at least one opening positioned at a distance from the notch groove. The heat dissipation unit fills the opening to seal the opening, and when melted, discharges internal heat and gas.

[0006] The cap plate may include a first part and a second part divided by a first opening. The heat dissipation unit may seal the first opening and integrally connect the first part and the second part. The first part may be located at the center of the cap plate, the heat dissipation unit may be formed in a ring shape surrounding the first part, and the second part may surround the heat dissipation unit. The notch groove may be located in the second part.

[0007] On the other hand, a plurality of second openings having an arc shape may be positioned in the cap plate, and a plurality of heat dissipating portions may be provided to seal each of the plurality of second openings. The plurality of heat dissipating portions may be arranged along a circle of any radius based on the center point of the cap plate, and the notch groove may be positioned to surround the plurality of heat dissipating portions.

[0008] Alternatively, a third cross-shaped opening may be positioned in the cap plate, and the heat dissipation member may seal the third opening. The center of the heat dissipation member may be aligned with the center of the cap plate, and the notch groove may be positioned to surround the heat dissipation member.

[0009] Alternatively, a fourth circular opening may be positioned in the cap plate, and the heat dissipation member may seal the fourth opening. The center of the heat dissipation member may coincide with the center of the cap plate, and the notch groove may be positioned to surround the heat dissipation member.

[0010] The heat dissipation member may include a polymer material that melts at 80° C. to 130° C. The heat dissipation member may include one or more of polystyrene (PS), low density polyethylene (LDPE), high density polyethylene (HDPE), and acrylonitrile butadiene styrene (ABS).

[0011] According to another embodiment, a secondary battery includes an electrode assembly, a can, a cap plate, and a heat-dissipating film. The electrode assembly includes a first electrode, a separator, and a second electrode. The can includes a bottom portion and a side portion, and accommodates the electrode assembly in an internal space surrounded by the bottom portion and the side portion. The cap plate is coupled to an end of the side portion to seal the can. The cap plate has at least one opening filled with a polymer material that releases internal heat and gas when melted, and a notched groove surrounding the opening. The heat-dissipating film is attached to an outer surface of the side portion.

[0012] The polymer material can melt at 80°C to 130°C. The polymer material can include one or more of polystyrene (PS), low density polyethylene (LDPE), high density polyethylene (HDPE), and acrylonitrile butadiene styrene (ABS).

[0013] The opening may be provided in the center of the cap plate in the form of a circular ring, a cross, or a circle. Alternatively, the openings may be provided in multiple numbers spaced apart from each other along a circle of any radius.

[0014] The heat dissipating film may include at least one heat dissipating layer and a plurality of polymer layers protecting the heat dissipating layer. The heat dissipating layer may include any one of aluminum, copper, and carbon nanotubes, and each of the plurality of polymer layers may include one or more of polyimide, polyethylene terephthalate, oriented polystyrene, oriented polypropylene, and polyethylene naphthalate.

[0015] The secondary batteries of the embodiments can gradually release internal heat by melting the heat dissipation part when exposed to high temperatures exceeding the normal range, and can simultaneously release a large amount of heat by breaking the cap plate based on the notch groove when a rapid increase in temperature and pressure occurs. The secondary batteries of the embodiments can enhance high-temperature safety by improving heat dissipation characteristics.

[0016] Figure 1 is a perspective view of a secondary battery according to the first embodiment.

[0017] Figure 2 is a cross-sectional view of the secondary battery illustrated in Figure 1.

[0018] Figure 3 is a partially enlarged cross-sectional view of an electrode assembly of the secondary battery illustrated in Figure 2.

[0019] Figure 4 is an exploded perspective view of the cap plate and heat dissipation portion of the secondary battery illustrated in Figure 1.

[0020] Figure 5 is an exploded perspective view of a cap plate and a heat dissipation portion of a secondary battery according to the second embodiment.

[0021] Figure 6 is an exploded perspective view of a cap plate and a heat dissipation portion of a secondary battery according to the third embodiment.

[0022] Fig. 7 is an exploded perspective view of a cap plate and a heat dissipation portion of a secondary battery according to the fourth embodiment.

[0023] Figure 8 is a perspective view of a secondary battery according to the fifth embodiment.

[0024] Hereinafter, with reference to the attached drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0025] Fig. 1 is a perspective view of a secondary battery according to the first embodiment, and Fig. 2 is a cross-sectional view of the secondary battery illustrated in Fig. 1. Fig. 3 is a partially enlarged cross-sectional view of an electrode assembly of the secondary battery illustrated in Fig. 2, and Fig. 4 is an exploded perspective view of a cap plate and a heat dissipation portion of the secondary battery illustrated in Fig. 1.

[0026] Referring to FIGS. 1 to 4, the secondary battery (100) of the present embodiment includes an electrode assembly (110), a can (120) that accommodates the electrode assembly (110) in an internal space, a cap plate (130) that is coupled to an open end of the can (120) to seal the can (120), and a heat dissipation unit (140) installed on the cap plate (130). The secondary battery (100) may further include first and second current collector plates (150, 160) and a rivet terminal (170).

[0027] An electrode assembly (110) includes a first electrode (10), a second electrode (20), and a separator (30). The electrode assembly (110) may be configured as a wound type in which a strip-shaped laminate is wound in the form of a jelly roll. The laminate may be configured in which a first electrode (10), a separator (30), a second electrode (20), and a separator (30) are sequentially laminated, and may be wound multiple times around a core (115). In the laminate, the positions of the first electrode (10) and the second electrode (20) may be exchanged.

[0028] The first electrode (10) includes a first substrate (11) and a first composite material (12) positioned on the first substrate (11). The first composite material (12) may be positioned on any portion of the first substrate (11) except for one side (lower side) edge. A portion of the first substrate (11) that is not covered by the first composite material (12) and has an exposed surface may be referred to as a first uncoated portion (13).

[0029] The second electrode (20) includes a second substrate (21) and a second composite material (22) positioned on the second substrate (21). The second composite material (22) may be positioned on any portion of the second substrate (21) except for the other (upper) edge. A portion of the second substrate (21) that is not covered by the second composite material (22) and has an exposed surface may be referred to as a second non-coated portion (23).

[0030] In a lithium ion secondary battery, the first substrate (11) may be composed of aluminum foil, and the first composite (12) may include a transition metal oxide such as LiCoO2, LiNiO2, LiMn2O4, Li(NiCoAl)O2, LiFePO4, Li(NiCoMn)O2, and a conductive material, a binder, etc. The second substrate (21) may be composed of copper foil or nickel foil, and the second composite (22) may include graphite, a conductive material, a binder, etc. The first electrode (10) may be referred to as a positive electrode, and the second electrode (20) may be referred to as a negative electrode.

[0031] The separator (30) may be composed of a porous substrate or a porous substrate having a coating layer positioned on at least one surface. The porous substrate may include one or more of polyethylene, polypropylene, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyester, polycarbonate, and polyimide. The coating layer may include a binder, and the binder may include a polyvinylidene fluoride-based compound. The separator (30) insulates the first electrode (10) and the second electrode (20) while allowing the movement of lithium ions.

[0032] The first uncoated portion (13) can be folded toward the core (115) and overlapped with the first uncoated portion (13) located inside, and the first collector plate (150) can be fixed to the first uncoated portion (13) by welding or the like. The second uncoated portion (23) can also be folded toward the core (115) and overlapped with the second uncoated portion (23) located inside, and the second collector plate (160) can be fixed to the second uncoated portion (23) by welding or the like. At this time, a cut line is located in each of the first and second uncoated portions (13, 23) to facilitate folding of the first and second uncoated portions (13, 23). The electrode assembly (110) is accommodated in the internal space of the can (120) together with the electrolyte.

[0033] The can (120) is formed in a shape in which one side (top) is open so that the electrode assembly (110) and the first and second collector plates (150, 160) can be inserted. The can (120) may include a bottom portion (121) and a side portion (122) connected to the edge of the bottom portion (121). The bottom portion (121) may be referred to as a top portion when the top and bottom of the secondary battery (100) are reversed. The can (120) may be formed of steel, stainless steel, aluminum, or an aluminum alloy.

[0034] A terminal hole may be located in the center of the bottom portion (121), and a rivet terminal (170) may be installed in the terminal hole via a first insulator (181). The rivet terminal (170) may be coupled to the first collector plate (150), and may be charged with the same polarity as the first electrode (10) by the first collector plate (150) to function as a first terminal (positive terminal). The first insulator (181) insulates the rivet terminal (170) and the bottom portion (121), and seals the terminal hole to prevent leakage of the electrolyte. A second insulator (182) may be disposed on one side of the first collector plate (150) facing the bottom portion (121).

[0035] The cap plate (130) may be positioned on the outer side (upper side) of the second collector plate (160) and may be coupled to an end of the side portion (122) via a third insulator (183). A beading portion (123) and a crimping portion (124) may be positioned on the side portion (122). The beading portion (123) may be a portion in which a portion of the side portion (122) is concavely deformed toward the inside of the side portion (122), and the crimping portion (124) may be a portion in which an end of the side portion (122) is vertically bent toward the inside of the side portion (122).

[0036] The electrode assembly (110) can be prevented from moving inside the can (120) by the beading portion (123), and the edge of the third insulator (183) and the cap plate (130) can be compressed between the beading portion (123) and the crimping portion (124). The cap plate (130) can be firmly fixed to the can (120) by the crimping portion (124), and can be electrically non-polar by being insulated from the first electrode (10) and the second electrode (20).

[0037] The second collector plate (160) may include a connector (161) that contacts the inner surface of the side portion (122), for example, the inner surface of the bead portion (123). The can (120) may be charged with the same polarity as the second electrode (20) by the connector (161) and the second collector plate (160) and may function as a second terminal (negative terminal).

[0038] A notch groove (135) may be positioned on the inner surface (bottom surface) of the cap plate (130) to induce a fracture when the internal pressure increases and discharge internal gas. The notch groove (135) may have a V-shaped cross-section and may be an arc shape on the bottom surface (when the target object is viewed from below), but is not limited to this example. When the internal pressure of the secondary battery (100) rapidly increases, the cap plate (130) may fracture around the notch groove (135) to discharge internal gas.

[0039] The internal temperature of a secondary battery (100) may increase due to various reasons, such as rapid charging and discharging, external impact, and exposure to high-temperature environments, and the internal pressure may increase due to the vaporization of the electrolyte, etc. In addition, as the secondary battery (100) becomes larger and its capacity increases, the internal heat energy generated due to the temperature increase also increases significantly.

[0040] For example, 24cm 3 and a volume of 53cm 2 A first battery cell having a surface area of ​​133 cm 3 with a volume of 130cmn 2 Assuming a second battery cell having a surface area of ​​, the second battery cell shows a volume increase of approximately 5.5 times and a surface area increase of approximately 2.5 times compared to the first battery cell.

[0041] Due to their larger volume, the secondary battery cells initially generate heat more slowly. However, after a certain point, when internal self-heating begins, they generate approximately 5.5 times more heat energy than the primary battery cells. However, because the surface area available for dissipating this heat energy has increased only approximately 2.5 times, the temperature rises rapidly. In other words, the enlarged secondary battery cells are disadvantaged in heat dissipation (heat dissipation).

[0042] Secondary batteries must dissipate the heat energy to the outside, as they begin to self-heat at a certain point when the surrounding temperature rises and the high temperature persists. The secondary battery (100) of the present embodiment dissipates the heat energy to the outside when the temperature rises by using the heat dissipation unit (140) described below, and then relieves the pressure by using the notch groove (135) described above when the pressure increases rapidly.

[0043] At least one opening is positioned in the cap plate (130), and a heat dissipation member (140) is filled in this opening to seal the opening. The heat dissipation member (140) is positioned at a predetermined distance from the notch groove (135), and is made of a polymer material that melts in a preset temperature range, and discharges heat and gas inside the secondary battery (100) under preset temperature conditions.

[0044] In the secondary battery (100) of the present embodiment, the cap plate (130) may be composed of two parts, i.e., a first part (131) and a second part (132), separated by a first opening (OP1). The heat dissipation portion (140) may be filled into the first opening (OP1) to seal the first opening (OP1) and simultaneously integrally connect the first part (131) and the second part (132). That is, the cap plate (130) may be composed of two parts (131, 132) positioned with the heat dissipation portion (140) interposed therebetween.

[0045] The first part (131) may be shaped like a disk and may be positioned at the center of the cap plate (130). The heat dissipation portion (140) may be shaped like a round ring surrounding the first part (131) and may have a constant width along the circumference. The thickness of the heat dissipation portion (140) may be equal to or smaller than the thickness of the cap plate (130). The thickness of the heat dissipation portion (140) may be appropriately determined in consideration of the sealing function of the heat dissipation portion (140) and the heat dissipation action by melting. The second part (132) may be shaped like a disk with a hollow center. The notch groove (135) may be arranged in an arc shape on the second part (132).

[0046] The heat dissipation member (140) may include a polymer material having a melting temperature of approximately 80° C. to 130° C. For example, the heat dissipation member (140) may include one or more of polystyrene (PS), low density polyethylene (LDPE), high density polyethylene (HDPE), and acrylonitrile butadiene styrene (ABS).

[0047] The heat dissipation unit (140) melts when the ambient temperature of the secondary battery (100) reaches its melting temperature, thereby slowly discharging the internal heat of the secondary battery (100). At this time, since the area occupied by the heat dissipation unit (140) on the cap plate (130) is not large, it does not discharge the internal heat of the secondary battery (100) all at once when melted, but rather gradually discharges the internal heat.

[0048] If the melting temperature of the heat dissipation unit (140) is lower than 80°C, the heat dissipation unit (140) may melt under normal use conditions, and in this case, the function of the secondary battery may be lost. If the temperature of the heat dissipation unit (140) exceeds 130°C, the hot-box characteristic, which is one of the safety evaluation items of the secondary battery, cannot be satisfied.

[0049] The hot-box test is an evaluation method in which a secondary battery is placed in a chamber, the temperature of the chamber is increased to 130°C, and then maintained for 30 minutes. The secondary battery (100) of the present embodiment, which is equipped with a heat dissipation unit (140), can prevent ignition and explosion of the secondary battery (100) by discharging internal heat energy through melting of the heat dissipation unit (140) within the chamber.

[0050] The secondary battery (100) of the present embodiment can slowly discharge internal heat by melting the heat dissipation part (140) when exposed to a high temperature exceeding the normal range, and can discharge a large amount of heat at once by breaking the cap plate (130) based on the notch groove (135) when a rapid increase in temperature and pressure occurs. The cap plate (130) can break after the heat dissipation part (140) melts, or can break when a rapid increase in temperature and pressure occurs before the heat dissipation part (140) melts.

[0051] The breaking pressure of the cap plate (130) by the notch groove (135) is approximately 10 kgf / cm 2 Up to 30 kgf / cm 2 It can be. The breaking pressure is 10 kgf / cm 2 If it is smaller, there is a risk that the cap plate (130) may break under the normal use environment of the secondary battery, and the breaking pressure is 30 kgf / cm 2 If the pressure exceeds , the rupture of the cap plate (130) is delayed, which may cause ignition and explosion of the secondary battery. According to the pressure range described above, it is possible to prevent the rupture of the cap plate (130) in a normal use environment of the secondary battery (100), while inducing early rupture of the cap plate (130) in the event of an abnormal pressure increase.

[0052] Fig. 5 is an exploded perspective view of a cap plate and a heat dissipation portion of a secondary battery according to a second embodiment. The secondary battery of the second embodiment has a configuration identical or similar to that of the first embodiment described above, except for the details described below.

[0053] Referring to FIG. 5, in the secondary battery of the present embodiment, at least two second openings (OP2) in an arc shape may be positioned in the cap plate (130A), and the heat dissipation portion (141) may be filled in the second opening (OP2) to seal the second opening (OP2). That is, at least two heat dissipation portions (141) in an arc shape may be positioned at a distance from each other in the cap plate (130A).

[0054] A plurality of heat dissipating portions (141) may be arranged along a circle of a specific radius centered on the center point of the cap plate (130A). The plurality of heat dissipating portions (141) may have the same length along the circumferential direction and may be positioned at the same distance from each other along the circumferential direction. In Fig. 5, two heat dissipating portions (141) are illustrated, but the number of heat dissipating portions (141) is not limited to the illustrated example. The notch groove (135) may be positioned on the outer side of the plurality of heat dissipating portions (141).

[0055] Fig. 6 is an exploded perspective view of a cap plate and a heat dissipation portion of a secondary battery according to a third embodiment. The secondary battery of the third embodiment has a configuration identical or similar to that of the first embodiment described above, except for the details described below.

[0056] Referring to FIG. 6, in the secondary battery of the present embodiment, a third opening (OP3) in a cross shape may be positioned in the cap plate (130B), and a heat dissipation portion (142) may be filled in the third opening (OP3) to seal the third opening (OP3). The heat dissipation portion (142) may be cross-shaped, and the center of the heat dissipation portion (142) may be positioned at the center point of the cap plate (130B). The notch groove (135) may be positioned on the outside of the heat dissipation portion (142).

[0057] Fig. 7 is an exploded perspective view of a cap plate and a heat dissipation portion of a secondary battery according to a fourth embodiment. The secondary battery of the fourth embodiment has a configuration identical or similar to that of the first embodiment described above, except for the details described below.

[0058] Referring to Fig. 7, in the secondary battery of the present embodiment, a fourth opening (OP4) having a circular shape may be positioned in the cap plate (130C), and a heat dissipation portion (143) may be filled in the fourth opening (OP4) to seal the fourth opening (OP4). The heat dissipation portion (143) may be circular, and the center of the heat dissipation portion (143) may be positioned at the center point of the cap plate (130C). The notch groove (135) may be positioned on the outside of the heat dissipation portion (143).

[0059] The cap plate (130) of the first embodiment described above is configured as two separate parts (131, 132), but the cap plates (130A, 130B, 130C) of the second to fourth embodiments form a single body. The planar shape of the heat dissipation portion (140, 141, 142, 143) is not limited to the above-described embodiments and may be modified in various ways. For example, the heat dissipation portion may be implemented in various shapes as long as it maintains a certain distance from the notch groove (135) and does not lower the strength of the cap plate (130) below an appropriate level.

[0060] In the above-described embodiments, at least one heat dissipation unit (140, 141, 142, 143) is located at the center of the cap plate (130). When the temperature of the electrode assembly (110) rises due to various causes, heat from the outer portion of the electrode assembly (110) may be released to the outside through the side portion (122) of the can (120), but heat from the center of the electrode assembly (110) may not be released and may accumulate. The heat dissipation unit (140, 141, 142, 143) located at the center of the cap plate (130) may release heat from the center of the electrode assembly (110) to the outside when melted.

[0061] Fig. 8 is a perspective view of a secondary battery according to a fifth embodiment. The secondary battery of the fifth embodiment has a configuration identical or similar to that of any one of the first to fourth embodiments described above, except for the details described below. Fig. 8 illustrates a case in which the heat dissipation unit (140) of the first embodiment is provided as an example.

[0062] Referring to Fig. 8, the secondary battery (100A) of the present embodiment may include a heat dissipation film (190). The heat dissipation film (190) may be attached to the outer surface of the side portion (122) excluding the beading portion (123) and the crimping portion (124). The side portion (122) to which the heat dissipation film (190) is attached may more quickly release the heat of the electrode assembly to the outside when the electrode assembly generates heat.

[0063] The heat dissipation film (190) may be composed of at least one heat dissipation layer and a plurality of polymer layers that protect the heat dissipation layer. For example, the heat dissipation film (190) may be composed of a laminated structure of a polymer layer, a heat dissipation layer, and a polymer layer, but is not limited to this example.

[0064] The heat dissipation layer may be composed of a thermally conductive material such as aluminum, copper, or carbon nanotubes, and dissipates heat transferred from the can (120) to the outside. The polymer layer may include one or more of, for example, polyimide, polyethylene terephthalate, oriented polystyrene, oriented polypropylene, and polyethylene naphthalate, and provides an insulating function to the heat dissipation film (190).

[0065] The secondary batteries of the aforementioned embodiments can be combined in multiple units to form a battery module. The multiple secondary batteries can be connected in series, parallel, or a combination of series and parallel via busbars, and can be used as a power source for vehicles such as electric and hybrid vehicles. The secondary batteries of the aforementioned embodiments can enhance the high-temperature safety of the battery module by improving heat dissipation characteristics.

[0066] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the patent claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

Claims

1. An electrode assembly including a first electrode, a separator, and a second electrode; A can accommodating the electrode assembly in an internal space; A cap plate coupled to the opening side end of the can to seal the can, the cap plate having a notch groove and at least one opening positioned at a distance from the notch groove; and A secondary battery including a heat dissipation part that is filled in the above opening, seals the above opening, and discharges internal heat and gas when melted.

2. In paragraph 1, The cap plate includes a first part and a second part divided by a first opening, A secondary battery in which the heat dissipation part seals the first opening and integrally connects the first part and the second part.

3. In paragraph 2, The above first part is located at the center of the cap plate, The above heat dissipation part is formed in a ring shape surrounding the first part, The above second part is a secondary battery surrounding the heat dissipation part.

4. In paragraph 3, The above notch home is a secondary battery located in the second part.

5. In paragraph 1, A plurality of second openings having an arc shape are positioned in the above cap plate, A secondary battery having a plurality of heat dissipating portions and sealing each of the plurality of second openings.

6. In paragraph 5, The above plurality of heat dissipating portions are arranged along a circle of arbitrary radius based on the center point of the cap plate, A secondary battery in which the above notch groove is positioned to surround the plurality of heat dissipating portions.

7. In paragraph 1, A third cross-shaped opening is located in the above cap plate, The above heat dissipation part is a secondary battery that seals the third opening.

8. In paragraph 7, The center of the above heat dissipation part coincides with the center of the above cap plate, A secondary battery in which the above notch groove is positioned to surround the heat dissipation portion.

9. In paragraph 1, A fourth circular opening is located in the above cap plate, The above heat dissipation part is a secondary battery that seals the fourth opening.

10. In paragraph 9, The center of the above heat dissipation part coincides with the center of the above cap plate, A secondary battery in which the above notch groove is positioned to surround the heat dissipation portion.

11. In any one of paragraphs 1 to 10, A secondary battery in which the heat dissipation part includes a polymer material that melts at 80°C to 130°C.

12. In paragraph 11, A secondary battery, wherein the heat dissipation member comprises at least one of polystyrene (PS), low density polyethylene (LDPE), high density polyethylene (HDPE), and acrylonitrile butadiene styrene (ABS).

13. An electrode assembly including a first electrode, a separator, and a second electrode; A can including a bottom portion and a side portion, and accommodating the electrode assembly in an inner space surrounded by the bottom portion and the side portion; A cap plate having at least one opening filled with a polymeric material that releases internal heat and gas when melted and is joined to an end of the side to seal the can, and a notched groove surrounding the opening; and A secondary battery comprising a heat dissipation film attached to the outer surface of the above side.

14. In paragraph 13, The above polymer material is a secondary battery that melts at 80°C to 130°C.

15. In paragraph 14, A secondary battery comprising the polymer material at least one of polystyrene (PS), low density polyethylene (LDPE), high density polyethylene (HDPE), and acrylonitrile butadiene styrene (ABS).

16. In paragraph 13, A secondary battery wherein the above opening is provided in one of a round ring shape, a cross shape, and a circle shape at the center of the cap plate.

17. In paragraph 13, The above apertures are provided in a plurality of secondary batteries spaced apart from each other along a circle of arbitrary radius.

18. In paragraph 13, The above heat dissipation film is a secondary battery comprising at least one heat dissipation layer and a plurality of polymer layers protecting the heat dissipation layer.

19. In paragraph 18, The heat dissipation layer comprises one of aluminum, copper, and carbon nanotubes, A secondary battery wherein each of the plurality of polymer layers comprises at least one of polyimide, polyethylene terephthalate, oriented polystyrene, oriented polypropylene, and polyethylene naphthalate.

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