KR20230048765A - Secondary Battery and battery module including same - Google Patents

Abstract

The present invention relates to a secondary battery which can emit flame through a safety vent in the event of an internal short circuit due to penetration, so as to prevent a cap plate from being fired or a case from rupturing, and can minimize the spread of the flames discharged through the safety vent to adjacent secondary batteries by means of an insulating member, and a battery module including the same. According to an embodiment of the present invention, a secondary battery comprises an electrode assembly including a first electrode plate, a second electrode plate, and a separator, a case for accommodating the electrode assembly, and a cap plate for sealing the upper opening of the case. The cap plate includes a safety vent which opens at a predetermined pressure. The size (S) of the safety vent satisfies the C/S/E < R and 0.01 < R < 0.1 between the size (C) of the cap plate and the energy density (E) of the secondary battery.

Description

Secondary battery and battery module including the same {Secondary Battery and battery module including same}

Various embodiments of the present invention relate to a secondary battery and a battery module including the secondary battery.

A secondary battery is a battery that can be charged and discharged, unlike a primary battery that cannot be recharged. In the case of a low-capacity battery in which one battery cell is packaged in a pack form, it is used in small portable electronic devices such as mobile phones and camcorders. In the case of a large-capacity battery module in units of battery packs in which dozens of battery packs are connected, it is widely used as a power source for driving motors such as hybrid vehicles and electric vehicles.

A secondary battery may be configured by embedding an electrode assembly and an electrolyte formed by interposing a separator between a positive electrode plate and a negative electrode plate in a case, and installing a cap plate in the case. Here, a typical example of the electrode assembly may be a winding type or a stack type. In such an electrode assembly, the uncoated portion tab protrudes upward or sideways, and a current collecting member may be connected to the uncoated portion tab.

The above-described information disclosed in the background technology of the present invention is only for improving the understanding of the background of the embodiment of the present invention, and therefore may include information that does not constitute prior art.

According to the present invention, since flames are emitted through the safety vent in the event of an internal short circuit due to penetration, firing of the cap plate or rupture of the case can be prevented, and the flame discharged through the safety vent by the insulating member is propagated to the adjacent secondary battery. A secondary battery capable of minimizing and a battery module including the same is provided.

를 만족시킬 수 있다. A secondary battery and a battery module including the same according to various embodiments of the present invention include an electrode assembly including a first electrode plate, a second electrode plate, and a separator, a case accommodating the electrode assembly, and an upper opening of the case. A secondary battery including a cap plate for sealing, wherein the cap plate includes a safety vent that is opened at a certain pressure, and the size (S) of the safety vent is determined by the size (C) of the cap plate and the energy of the secondary battery. between the density (E)

can satisfy

The safety vent may include a circumferential portion contacting and coupled to the cap plate, and a central portion extending inwardly from the circumferential portion, facing the upper surface of the electrode assembly, and provided with a notch that is easily broken by internal pressure. can

The notches include a first notch in the form of a line located at the center of the safety vent and extending along one direction, and a second notch in the form of a line extending in the circumferential direction having an intersection from one end of the first notch. and a third notch symmetrical to the second notch, having a cross point from the other end opposite to one end of the first notch and extending in the direction of the circumference.

The second notch and the third notch may be two notches in a line shape extending in a circumferential direction to have a predetermined angle about an intersection point.

The size of the safety vent may be the width of the central portion.

를 만족시킬 수 있다. The size (S) of the safety vent is between the size (C) of the cap plate and the energy density (E) of the secondary battery.

can satisfy

An insulating member corresponding to the shape of the cap plate and interposed between the cap plate and the electrode assembly may be further included.

The insulating member has a vent hole penetrating between an upper surface and a lower surface thereof, and the lower surface of the center of the safety vent may face the electrode assembly through the vent hole.

The insulating member may be made of polypropylene (PP) or polyphenylene sulfide (PPS).

In the battery module including a plurality of secondary batteries according to an embodiment of the present invention, among the plurality of secondary batteries, an insulating insulating sheet interposed between long side surfaces of two adjacent secondary batteries may be included.

The insulating member of the secondary battery may be made of polyphenylene sulfide (PPS).

The secondary battery and the battery module including the secondary battery according to various embodiments of the present invention can prevent firing of the cap plate or rupture of the case because flames are emitted through the safety vent when an internal short circuit occurs due to penetration.

In addition, the secondary battery and the battery module including the secondary battery according to various embodiments of the present invention can minimize propagation of the flame discharged through the safety vent to the adjacent secondary battery by the insulating member.

1 is a perspective view showing an exemplary secondary battery of the present invention.
2 is a cross-sectional view showing an exemplary secondary battery of the present invention.
3 is a perspective view of a battery module to which the secondary battery of FIG. 1 is applied.
FIG. 4 is an enlarged perspective view of a safety vent of the secondary battery of FIG. 1 .
FIG. 5 is an enlarged and exploded perspective view of a part of the secondary battery shown in FIG. 1 .
6 is an experimental result of Evaluation Example 1 for Examples and Comparative Examples of the present invention.
6 is an experimental result of Evaluation Example 2 for Examples and Comparative Examples of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art, and the following examples may be modified in many different forms, and the scope of the present invention is as follows It is not limited to the examples. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the spirit of the invention to those skilled in the art.

In addition, in the following drawings, the thickness or size of each layer is exaggerated for convenience and clarity of explanation, and the same reference numerals refer to the same elements in the drawings. As used herein, the term "and/or" includes any one and all combinations of one or more of the listed items. In addition, the meaning of "connected" in the present specification means not only when member A and member B are directly connected, but also when member A and member B are indirectly connected by interposing member C between member A and member B. do.

Terms used in this specification are used to describe specific embodiments and are not intended to limit the present invention. As used herein, the singular form may include the plural form unless the context clearly indicates otherwise. Also, when used herein, "comprise" and/or "comprising" specifies the presence of the recited shapes, numbers, steps, operations, elements, elements, and/or groups thereof. and does not exclude the presence or addition of one or more other shapes, numbers, operations, elements, elements and/or groups.

In this specification, terms such as first and second are used to describe various members, components, regions, layers and/or portions, but these members, components, regions, layers and/or portions are limited by these terms. It is self-evident that These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first member, component, region, layer or section described in detail below may refer to a second member, component, region, layer or section without departing from the teachings of the present invention.

Space-related terms such as “beneath,” “below,” “lower,” “above,” and “upper” are associated with an element or feature shown in a drawing. Used for easy understanding of other elements or features. Terminology related to this space is for easy understanding of the present invention according to various process conditions or use conditions of the present invention, and is not intended to limit the present invention. For example, if an element or feature in a drawing is flipped over, an element described as "lower" or "below" becomes "above" or "above." Accordingly, "below" is a concept encompassing "upper" or "below".

Here, the same reference numerals are attached to parts having similar configurations and operations throughout the specification. In addition, when a part is said to be electrically coupled to another part, this includes not only a case where it is directly connected but also a case where it is connected with another element interposed therebetween.

1 and 2 are perspective and cross-sectional views of an exemplary secondary battery. 3 is a perspective view of the battery module 10 in which the secondary batteries 100 of FIG. 1 and the insulating sheets 200 are alternately disposed.

In the battery module 10 , a plurality of secondary batteries 100 and a plurality of insulating sheets 200 may be sequentially stacked alternately along one direction. The insulating sheet 200 may be interposed between long side surfaces of two adjacent secondary batteries 100 . The battery module 10 may further include end plates (not shown) for fixing the plurality of secondary batteries 100 and the plurality of insulating sheets 200 at both ends. Here, the insulating sheet 200 may be made of an insulating material such as mica capable of blocking heat propagation between two adjacent secondary batteries 100 .

In the example shown in FIGS. 1 and 2 , the secondary battery 100 may include an electrode assembly 110 , a first terminal 120 , a second terminal 130 , a case 140 and a cap assembly 150 . can

The electrode assembly 110 may be formed by winding or overlapping a stack of the first electrode plate 111, the separator 113, and the second electrode plate 112 formed in a thin plate shape or film shape. The electrode assembly 110 has a winding axis in a horizontal direction (ie, a direction substantially parallel to the lengthwise direction of the cap assembly 150) or a vertical direction (ie, substantially perpendicular to the lengthwise direction of the cap assembly 150). In addition, the electrode assembly 110 may be a stack type rather than a winding type, and the shape of the electrode assembly 110 is not limited in the present invention. In addition, the electrode assembly 110 includes two or more The electrode assemblies 110 may be stacked such that their long sides are adjacent to each other, and the number of electrode assemblies 110 is not limited in the present invention.

The first electrode plate 111 of the electrode assembly 110 may serve as a cathode, and the second electrode plate 112 may serve as an anode. Of course, the reverse is also possible.

The first electrode plate 111 is formed by applying a first electrode active material such as graphite or carbon to a first electrode current collector formed of a metal foil such as copper, copper alloy, nickel, or a nickel alloy, and the first electrode active material is applied. It may include the first electrode tab 111a (or the first non-coated portion), which is an area that is not used. The first electrode tab 111a may serve as a passage for current flow between the first electrode plate 111 and the first terminal 120 .

In some examples, the first electrode tab 111a may be formed by cutting the first electrode tab 111 so as to protrude to one side when manufacturing the first electrode plate 111 , and may be integrally formed with the first electrode plate 111 . In some examples, the plurality of first electrode tabs 111a are gathered and tack-welded, and the first collector plate 121 of the first terminal 120 is welded and coupled to the tack-welded first electrode tabs 111a. can

The second electrode plate 112 is formed by applying a second electrode active material such as a transition metal oxide to a second electrode current collector formed of a metal foil such as aluminum or aluminum alloy, and is a region where the second electrode active material is not applied. The second electrode tab 112a (or the second uncoated portion) may be included. The second electrode tab 112a may serve as a passage for current flow between the second electrode plate 112 and the second terminal 130 .

In some examples, the second electrode tab 112a may be formed by cutting in advance to protrude to one side when the second electrode plate 112 is manufactured, and may be integrally formed with the second electrode plate 112 . In some examples, the plurality of second electrode tabs 112a are gathered and tack-welded, and the second collector plate 131 of the second terminal 130 is welded and coupled to the tack-welded second electrode tabs 112a. can

In some examples, the first electrode tab 111a may be positioned on one short side surface of the electrode assembly 110, and the second electrode tab 112a may be positioned on the other short side surface of the electrode assembly 110.

In some examples, the separator 113 is positioned between the first electrode plate 111 and the second electrode plate 112 to prevent a short circuit and enable the movement of lithium ions, and is made of polyethylene, polypropylene or poly It may include a composite film of ethylene and polypropylene. In addition, the separator 113 may be replaced with an inorganic solid electrolyte such as a sulfide, oxide, or phosphate compound that does not require a liquid or gel electrolyte.

Both ends of the electrode assembly 110 as described above are electrically connected to the first electrode uncoated portion 111a of the first electrode plate 111 and the second electrode uncoated portion 112a of the second electrode plate 112, respectively. The first terminal 120 and the second terminal 130 are connected thereto. In some examples, the electrode assembly 110 may be accommodated in the case 140 together with the electrolyte solution.

In some examples, the electrolyte may include a lithium salt such as LiPF6 or LiBF4 in an organic solvent such as EC, PC, DEC, EMC, or DMC. Also, the electrolyte solution may be in a liquid or gel state. In some examples, when an inorganic-based solid electrolyte is used, the electrolyte solution may be omitted.

The first terminal 120 is made of metal and may be electrically connected to the first electrode plate 111 . In some examples, the first terminal 120 may include a first collector plate 121 , a first terminal pillar 122 , and a first terminal plate 124 . In some examples, the first collector plate 121 may come into contact with the first electrode uncoated portion 111a protruding from one end of the electrode assembly 110 . Substantially, the first collector plate 121 may be welded to the first electrode uncoated portion 111a. In some examples, the first collector plate 121 is formed in a substantially '┎' shape, and a terminal hole 121a may be formed on the upper portion. In some examples, the first terminal pillar 122 may be inserted into the terminal hole 121a and then riveted and/or welded. In some examples, the first collector plate 121 may be made of copper or a copper alloy.

In some examples, the first terminal pillar 122 penetrates the cap plate 151 of the cap assembly 150 and protrudes and extends upward by a predetermined length, and the first collector plate 121 extends from the lower part of the cap plate 151. can be electrically connected to In addition, in some examples, the first terminal pillar 122 protrudes and extends a predetermined length above the cap plate 151, and at the same time, the first terminal pillar 122 is located under the cap plate 151. ) The flange 122a may be formed so as not to fall out. A region of the first terminal pillar 122 positioned below the flange 122a may be riveted and/or welded after being inserted into the first terminal hole 121a of the first collector plate 121 . In some examples, the first terminal post 122 may be made of copper, copper alloy, aluminum or aluminum alloy.

The first terminal plate 124 has a hole 124a, and the first terminal pillar 122 is coupled to the hole 124a and may be riveted and/or welded. In some examples, an interface between the upper exposed first terminal pillar 122 and the first terminal plate 124 may be welded to each other. For example, by providing a laser beam to a boundary region between the upwardly exposed first terminal pillar 122 and the first terminal plate 124, the boundary region may be melted, cooled, and welded. In some examples, the first terminal pillar 122 and the first terminal plate 124 may be electrically insulated from the cap plate 151 .

The second terminal 130 is also made of metal and can be electrically connected to the second electrode plate 112 . In some examples, the second terminal 130 may include a second collector plate 131 , a second terminal pillar 132 , and a second terminal plate 134 . The second collector plate 131 may be in contact with the second electrode uncoated portion 112a protruding from one end of the electrode assembly 110 . In some examples, the second collector plate 131 is formed in a substantially '┑' shape, and a terminal hole 131a may be formed at an upper portion. In some examples, the second terminal pillar 132 is inserted into and coupled to the terminal hole 131a. The second collector plate 131 may be made of, for example, but not limited to, aluminum or an aluminum alloy. The second terminal pillar 132 protrudes and extends upward by a predetermined length through the cap plate 151 described below, and may be electrically connected to the second collector plate 131 at the bottom of the cap plate 151. . A flange ( 132a) may be formed. A region of the second terminal pillar 132 positioned below the flange 132a may be riveted and/or welded after being inserted into the second terminal hole 131a of the second current collector 131 .

In some examples, the second terminal pillar 132 may be made of aluminum or aluminum alloy. The second terminal plate 134 has a hole 134a. In addition, the second terminal plate 134 is coupled to the second terminal pillar 132 . That is, the second terminal pillar 132 is coupled to the hole 134a of the second terminal plate 134 . Also, the second terminal pillar 132 and the second terminal plate 134 may be riveted and/or welded to each other. In some examples, a boundary region between the second terminal pillar 132 and the second terminal plate 134 exposed upward may be welded to each other. For example, by providing a laser beam to a boundary region between the upwardly exposed second terminal pillar 132 and the second terminal plate 134, the boundary region can be welded by melting and cooling each other.

In some examples, the second terminal pillar 132 and the second terminal plate 134 may be electrically insulated from the cap plate 151 . In some examples, the second terminal pillar 132 and the second terminal plate 134 may be electrically connected to the cap plate 151, and in this case, the cap plate 151 of the cap assembly 150 is connected to the second terminal 130. may have the same polarity (eg, anode).

The case 140 may have a substantially rectangular parallelepiped shape with an opening formed thereon. The electrode assembly 110 may be inserted into the case 140 through this opening. In addition, the first collector plate 121 of the first terminal 120 and the second collector plate 131 of the second terminal 130 may also be located inside the case 140 . The case 140 may include a rectangular bottom surface 141 and four side surfaces 142 extending substantially vertically from four sides of the bottom surface 141 .

The cap assembly 150 may be coupled to the case 140 . In some examples, the cap assembly 150 may include a cap plate 151, a seal gasket 152, a stopper 153, a safety vent 154, an upper coupling member 155, and an insulating member 156. .

The cap plate 151 seals the opening of the case 140 and may be formed of the same material as the case 140 . For example, but not limited to, the cap plate 151 may be coupled to the case 140 by laser welding. Here, since the cap plate 151 may have the same polarity as the second terminal 130 as described above, the cap plate 151 and the case 140 may have the same polarity. The cap plate 151 further includes an electrolyte injection hole 151a and a vent hole 151b penetrating between the upper and lower surfaces.

The seal gasket 152 is an insulating material and is between the cap plate 151 and the first terminal pillar 122 of the first terminal 120, and the second terminal pillar 132 of the cap plate 151 and the second terminal 130. ), sealing between the first terminal pillar 122 and the second terminal pillar 132 and the cap plate 151, respectively. The seal gasket 152 prevents external moisture from penetrating into the secondary battery 100 or prevents the electrolyte solution contained in the secondary battery 100 from leaking to the outside.

The stopper 153 may seal the electrolyte injection hole 151a after the electrolyte is injected into the case 140 through the electrolyte injection hole 151a of the cap plate 151 . The safety vent 154 is installed in the vent hole 151b of the cap plate 151, and a notch 154x is formed to be opened at a set pressure.

The configuration of the safety vent 154 will be described in detail below.

The upper coupling member 155 may be formed between the cap plate 151 and each of the first terminal pillar 122 and the second terminal pillar 132 on the upper portion of the cap plate 151 . Also, the upper coupling member 155 is in close contact with the cap plate 151 . Moreover, the upper coupling member 155 may be in close contact with the seal gasket 152 as well. The upper coupling member 155 may insulate the first terminal pillar 122 and the second terminal pillar 132 from the cap plate 151 . In some examples, the upper coupling member 155 interposed between the second terminal plate 134 and the cap plate 151 may electrically connect the second terminal plate 134 and the cap plate 151, Accordingly, the cap plate 151 may have the same polarity as the second terminal 130 .

The insulating member 156 has a size substantially corresponding to that of the lower surface of the cap plate 151 and may adhere to the lower surface of the cap plate 151 . Of course, an electrolyte injection hole 156a and a vent hole 156b may be formed in the insulating member 156 at positions corresponding to the electrolyte injection hole 151a and the vent hole 151b formed in the cap plate 151 . The insulating member 156 may prevent unnecessary short circuits between the first current collector 121 and the cap plate 151 and between the second collector plate 131 and the cap plate 151 . In addition, the insulating member 156 is formed in a size corresponding to that of the cap plate 151, so that an unnecessary short circuit between the electrode assembly 110 and the cap plate 151 can be prevented. The insulating member 156 may be made of polyphenylene sulfide (PPS), which has a high melting point (285°C) and high tensile strength, and thereby prevents heat from an internal short circuit caused by penetration of the secondary battery 100 as a safety vent. Safety can be improved by preventing heat propagation to adjacent cells during emission through 154. Such an insulating member 156 may prevent heat due to an internal short circuit of the secondary battery 100 from being transferred to an adjacent secondary battery 100 through the cap assembly 150 . That is, when the secondary battery 100 is composed of one unit cell, it is not required to block heat propagation to the adjacent secondary battery 100, so polypropylene (PP) may also be applied as the insulating member 156.

FIG. 4 is an enlarged perspective view of a safety vent in the secondary battery 100 shown in FIG. It is an enlarged exploded perspective view showing an enlarged portion of the disassembled insulating member 156.

As shown in FIGS. 4 and 5 , the safety vent 154 is connected to the inner wall of the vent hole 151b of the cap plate 151 or the circumferential portion 154a coupled to the step, and is horizontal from the circumferential portion 154a. and a central portion 154b extending inwardly of the direction. That is, the peripheral portion 154a may be positioned at the outer edge of the central portion 154b. Here, the circumferential portion 154a may be welded to the inner wall or step of the vent hole 151b by, for example, but not limited to, a laser welding method. For this welding, the thickness of the circumferential portion 154a may be relatively thicker than that of the central portion 154b. Therefore, when the secondary battery 100 is in a normal state, the internal electrolyte solution is prevented from leaking to the outside along the interface between the safety vent 154 and the vent hole 151b. Also, the circumferential portion 154a may be interposed between the cap plate 151 and the insulating member 156 . A lower surface of the circumferential portion 154a may contact an upper surface of the insulating member 156 .

The central portion 154b may extend inwardly from the circumferential portion 154a. The center portion 154b may have a substantially elliptical flat plate shape, and may include a notch 154x having a thinner thickness than other areas.

The notch 154x intersects a line-shaped first notch 154xa provided at the center of the central portion 154b to extend along the longitudinal direction of the cap plate 151 and both ends of the first notch 154xa. Intersecting points C1 and C2 may be formed, and a second notch 154xb and a third notch 154xc extending from the crossing points C1 and C2 in the direction of the circumferential portion 154a, respectively, may be included. The second notch 154b may be two line-shaped notches extending in the direction of the circumferential portion 154a to have a predetermined angle with the intersection point C1 as the center. The third notch 154xc may be two line-shaped notches extending in the direction of the circumferential portion 154a to have a predetermined angle with the intersection point C2 as the center. In addition, the second notch 154xb, the third notch 154xc and the first notch 154xa may be symmetrical to each other.

For example, but not limited to, the central portion 154b may further include an embossed portion protruding upward or downward so that the notch 154x may be easily broken by internal pressure of the case 150 . Of course, the lower part of the center part 154b may face the upper surface of the electrode assembly 110 by the vent hole 156b of the insulating member 156.

The safety vent 154 may have a size that satisfies Equation 1 below so that internal heat can be easily discharged when a short circuit occurs inside the secondary battery 100 due to penetration.

Here, C is the size (width, ㎟) of the cap plate 151, S is the size (width, ㎟) of the central portion 154b of the safety vent 154, and E is the energy density (Wh) of the secondary battery 100 / kg). In addition, R is a constant and may have at least one value from 0.01 to 0.1. Here, when R is smaller than 0.01, it may not be easy to form the terminal plates 124 and 134 and the electrolyte injection port 151a on the cap plate 151 due to the increase in the size of the safety vent 154 . In addition, when R is greater than 0.1, it is not easy to release heat through the safety vent 154 when penetration occurs, and there is a risk of rupture, thermal runaway, or ignition/explosion. More preferably, when R is smaller than 0.073, heat can be easily discharged through the safety vent 154 when penetration occurs. In addition, although not limited, it is preferable that the breaking pressure of the notch 154x of the safety vent 154 is 10 kgf/cm ² .

In the present invention, the safety vent 154 is shown formed on the cap plate 151, but may be formed on the side or bottom of the case 150. Of course, the safety vent 154 may have a size that satisfies Equation 1, so that when a short circuit occurs inside the secondary battery 100, internal heat can be easily discharged. In addition, in the secondary battery 100, when the safety vent 154 is formed on the side surface of the case 140, the insulating member 156 also connects the side surface of the case 150 where the safety vent 154 is located and the electrode assembly 110. may be interposed between them. In addition, in the secondary battery 100, when the safety vent 154 is formed on the lower surface of the case 140, the insulating member 156 also connects the lower surface of the case 150 where the safety vent 154 is located to the electrode assembly 110. The bottom of the may be interposed between.

The present invention will be described in more detail with reference to Examples and Comparative Examples below. Embodiments in this specification are not intended to limit the scope of rights only for the detailed description of the invention.

Example 1: A secondary battery in which the size of the safety vent 154 is 300 mm2, the size of the cap plate 151 is 5760 mm2, the energy density is 264 Wh/kg, and the insulating member is PPS was manufactured. In this case, R may be 0.0726.

Example 2: A secondary battery in which the size of the safety vent 154 is 300 mm2, the size of the cap plate 151 is 5760 mm2, the energy density is 264 Wh/kg, and the insulation member is PP was manufactured. In this case, R may be 0.0726.

Comparative Example 1: A secondary battery having a safety vent 154 having a size of 200 mm 2 , a cap plate 151 having a size of 5760 mm 2 , an energy density of 264 Wh/kg, and an insulation member made of PP was fabricated. In this case, R may be 0.109.

Evaluation Example 1: Bottom Penetration Test of Secondary Battery

After fully charging the prepared secondary batteries of Examples and Comparative Examples under a voltage of 4.3 with a charging current of 20A, a nail having a diameter of 3 mm was used to penetrate the lower surface of the secondary battery by 20 mm, and then the ignition was observed for more than 2 minutes. did At this time, the penetration speed was set to 7 mm/sec. In addition, the evaluation test was conducted twice for each of the secondary batteries prepared in Examples 1, 2, and Comparative Example 1.

The experimental results may be shown in Table 1. Here, the unit is time for the numerical value of the experimental result, and the unit is seconds.

cell# Test
Result vent
spark vent flame
/smoke bottom flame Example 1 One L5 2 18 - 2 L5 2 24 - Example 2 One L5 2 13 - 2 L5 2 12 - Comparative Example 1 One L6 12 12 54 2 L6 15 15 51

Corresponds to Hazard level 5 of the battery shown in Example 1. That is, the secondary battery of Example 1 can prevent the secondary battery from bursting or exploding due to ignition or flame emission through the safety vent 18 seconds or 24 seconds after the nail penetrates the secondary battery. This corresponds to Hazard level 5 of the battery shown in Table 2.

In Example 2, as shown in the experimental results of FIG. 6, after the nail penetrates the secondary battery, ignition or flame is emitted through the safety vent 12 or 13 seconds later. In addition, separate ignition and explosion did not occur in the lower part of the secondary battery. This corresponds to Hazard level 5 of the battery shown in Table 2. That is, the secondary batteries of Examples 1 and 2 can be prevented from bursting or exploding due to ignition or emission of flame through the safety vent.

In Comparative Example 1, as shown in Table 1, after the nail penetrates the secondary battery, ignition or flame is emitted through the safety vent 12 or 15 seconds later. In addition, after the nail penetrated the secondary battery, after 54 seconds and 51 seconds after the cap plate was fired or/and the bottom surface was ruptured to dissipate internal heat of the secondary battery, a second flame was generated. This corresponds to Hazard level 6 of the battery shown in Table 1. That is, in the secondary battery of Comparative Example 1, it is not easy to ignite or emit flame through the safety vent, so that the lower or upper surface of the secondary battery is ruptured or the cap plate is fired.

The state of each hazard level of the secondary battery may be as shown in Table 2 below.

Hazard level 0 No effect, no loss of functionality Hazard level 1 Passive protection activated (No defect, no leakage; no venting, fire or flame; no rupture; no explosion; no exothermic reaction or thermal runaway. Cell reversibly damaged →Repair of protection needed) Hazard level 2 Defect/damage (No leakage; no venting, fire or flame; no rupture; no explosion; no exothermic reaction or runaway. Cell irreversibly damaged →Repair needed Hazard level 3 Leak mass < 50% (No venting, fire or flame; no rupture; no explosion. Weight loss <50% of electrolyte(solvent+salt) weight) Hazard level 4 Venting mass ≥ 50% (No fire or flame; no rupture; no explosion. Weight loss ≥ 50% of electrolyte(solvent+salt) weight) Hazard level 5 No rupture; no explosion (i.e. no flying parts) Hazard level 6 rupture (No explosion, but flying parts of active mass) Hazard level 7 Explosion

Example 1-2: A battery module was fabricated by sequentially stacking the secondary batteries of Example 1 alternately with insulating sheets made of mica. Here, the battery module has 5 secondary batteries, and 4 insulating sheets are interposed between the adjacent secondary batteries.

Comparative Example 1-2: A battery module was fabricated by sequentially stacking the secondary batteries of Comparative Example 1 alternately with insulating sheets made of mica. Here, the battery module has 5 secondary batteries, and 4 insulating sheets are interposed between the adjacent secondary batteries.

Comparative Example 2: A secondary battery having a safety vent 154 of 200 mm2, a cap plate 151 of 5760 mm2, an energy density of 264 Wh/kg, and an insulation member of PPS was manufactured, and then an insulation sheet A battery module was fabricated by laminating with the cells. In this case, R may be 0.109. Here, the battery module has five secondary batteries, and four insulating sheets made of mica are interposed between the adjacent secondary batteries.

Comparative Example 3: After fabricating a secondary battery in which the size of the safety vent 154 is 300 mm2, the size of the cap plate 151 is 5760 mm2, the energy density is 264 Wh/kg, and the insulation member is PP, insulation sheets are prepared. and laminated to produce a battery module. In this case, R may be 0.0726. Here, the battery module has five secondary batteries, and four insulating sheets made of mica are interposed between the adjacent secondary batteries.

Evaluation Example 2: Thermal propagation confirmation experiment after penetrating the bottom of the battery module

After fully charging the secondary batteries included in the battery modules of the manufactured Examples and Comparative Examples under a voltage of 4.3 with a charging current of 20A, a nail having a diameter of 3 mm was used to locate the secondary batteries in the center (#3) of the battery module. After penetrating the bottom of the secondary battery by 20 mm, ignition and heat propagation were observed for more than 2 minutes. At this time, the penetration speed was set to 7 mm/sec.

The experimental results may be shown in Table 3. Here, Table 3 shows the result of measuring the heat propagation time to an adjacent cell after penetrating the secondary battery (unit: seconds).

Average #One #2 #3 #4 #5 Cap-plate Blast off Example 1-2 418 341 0 340 417 N Comparative Example 1-1 75 90 0 86 85 Y Comparative Example 2 260 176 0 181 270 N Comparative Example 3 205 116 0 136 233 Y

In Example 1-2, after the nail penetrates the secondary battery, it takes more than 300 seconds for heat to propagate to the adjacent secondary battery, and ignition or flame is emitted through the safety vent in the penetrated secondary battery, preventing the cap plate from being fired. (See Example 1) Also, in Example 1-2, since the safety vent of the penetrating secondary battery sufficiently emits ignition or flame, additional rupture or heat transfer due to firing of the cap plate can be minimized. there is. In addition, the transfer of the flame discharged through the safety vent of the penetrated secondary battery to the inside of the adjacent secondary battery is reduced in an insulating member having a high melting point and high tensile strength.

That is, since flames are emitted through the safety vent 154 of the penetrating secondary battery 100 in the battery module 10, it is possible to prevent the cap plate from being fired or the lower surface from being ruptured. Heat propagation to adjacent secondary batteries 100 can be minimized.

In Comparative Example 1-2, after the nail penetrates the secondary battery, heat propagation occurs to adjacent secondary batteries 100 seconds before. As shown in the experimental results of Comparative Example 1, heat propagation to adjacent secondary batteries can be generated more quickly by flames generated when the lower surface of the penetrating secondary battery is ruptured. Also, in Comparative Example 1-2, since it is not easy to ignite or emit flame through the safety vent in the pierced secondary battery, the cap plate is fired or the lower surface is ruptured (see Comparative Example 1). Heat propagates to adjacent secondary batteries, which are ruptured by flames or ignited.

In Comparative Example 2, after the nail penetrates the secondary battery, heat propagation occurs to adjacent secondary batteries 175 seconds later. In Comparative Example 2, since the safety vent of the penetrating secondary battery is not large enough to ignite or emit flame, the cap plate is fired or the lower surface is ruptured like Comparative Example 1-1. As a result, heat propagation to adjacent secondary batteries may be more rapidly generated by flames generated when the lower surface of the penetrating secondary battery is ruptured. Due to this, heat propagates from the penetrating secondary battery to an adjacent secondary battery that is ruptured by a flame or ignited. However, the transmission of the flame discharged through the safety vent of the penetrated secondary battery to the inside of the adjacent secondary battery can be partially reduced by an insulating member having a high melting point and high tensile strength.

In Comparative Example 3, after the nail penetrates the secondary battery, heat propagation is generated to adjacent secondary batteries 115 seconds later. In Comparative Example 3, since the safety vent of the penetrating secondary battery sufficiently emits ignition or flame, additional rupture or heat propagation to the secondary battery due to cap plate firing can be minimized (see Example 2) . However, when an event occurs in a secondary battery that ignites or emits flame through a safety vent, adjacent secondary batteries are ruptured by flames or ignited because the insulation member fails to block heat flowing into the interior through the upper part. That is, in the battery module including a plurality of secondary batteries, it is preferable that the insulating member is made of PPS to block heat propagation.

What has been described above is only one embodiment for implementing a secondary battery and a battery module including the same according to the present invention, and the present invention is not limited to the above-described embodiments, and as claimed in the following claims, the present invention Anyone with ordinary knowledge in the field to which the invention pertains without departing from the gist of the invention will say that the technical spirit of the present invention exists to the extent that various changes can be made.

100: secondary battery 110: electrode assembly
120: first terminal 130: second terminal
140: case 150: cap assembly
10: battery module 200: insulation sheet

Claims (11)

an electrode assembly including a first electrode plate, a second electrode plate, and a separator;
a case accommodating the electrode assembly; and
In the secondary battery including a cap plate sealing the top opening of the case,
The cap plate includes a safety vent that opens at a certain pressure,
The size (S) of the safety vent is between the size (C) of the cap plate and the energy density (E) of the secondary battery.

A secondary battery that satisfies According to claim 1,
The safety vent may include a circumferential portion contacting and coupled to the cap plate; and
A secondary battery comprising a central portion extending inwardly from the circumferential portion, facing an upper surface of the electrode assembly, and having a notch that is easily broken by internal pressure. According to claim 2,
The notch is
a first notch in the form of a line located at the center of the safety vent and extending along one direction;
a second notch in the form of a line extending in the direction of the circumference and having an intersection from one end of the first notch; and
A secondary battery comprising a third notch symmetrical to the second notch, having a cross point from the other end opposite to one end of the first notch and extending in the direction of the circumference. According to claim 3,
The second notch and the third notch are two notches in a line shape extending in a circumferential direction to have a predetermined angle with respect to an intersection point. According to claim 2,
The size of the safety vent is the size of the central portion of the secondary battery. According to claim 1,
The size (S) of the safety vent is between the size (C) of the cap plate and the energy density (E) of the secondary battery.

A secondary battery that satisfies According to claim 1,
The secondary battery further comprising an insulating member corresponding to the shape of the cap plate and interposed between the cap plate and the electrode assembly. According to claim 7,
The insulating member is provided with a vent hole penetrating between an upper surface and a lower surface,
A secondary battery in which a lower surface of the center of the safety vent faces the electrode assembly through the vent hole. According to claim 7,
The insulating member is
A secondary battery made of polypropylene (PP:Poly Propylene) or polyphenylene sulfide (PPS:Poly Phenylene Sulfide). In the battery module including a plurality of secondary batteries of any one of claims 1 to 9,
A battery module comprising a heat insulating insulating sheet interposed between long side surfaces of two adjacent secondary batteries, among the plurality of secondary batteries. According to claim 9,
The insulating member of the secondary battery is a battery module made of polyphenylene sulfide (PPS).

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