KR20230173318A - Cap assembly and secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a cap assembly that is coupled to the top of the opening of a secondary battery case and includes a top cap, a safety vent, a current blocking element, and a CID gasket, wherein the CID gasket includes two or more parts with different properties. It's about assembly.

Description

Cap assembly and secondary battery including the same {CAP ASSEMBLY AND SECONDARY BATTERY COMPRISING THE SAME}

The present invention relates to a cap assembly and a secondary battery including the same. Specifically, the present invention relates to a cap assembly in which the shape of a CID gasket is maintained even when the internal temperature of the secondary battery increases, and a secondary battery including the same.

Recently, the price of energy sources has risen due to the depletion of fossil fuels, and interest in environmental pollution has increased, and the demand for eco-friendly alternative energy sources has become an essential factor for future life. Accordingly, research continues on various power production technologies such as nuclear power, solar power, wind power, and tidal power, and there is also great interest in power storage devices to use the energy produced in this way more efficiently.

In particular, as technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing, and accordingly, much research is being conducted on batteries that can meet various needs.

In general, secondary batteries refer to batteries that can be charged and discharged, unlike primary batteries, which cannot be recharged. They are widely used in electronic devices such as mobile phones, camcorders, laptops, and electric vehicles. In particular, lithium secondary batteries are used as a power source for electronic equipment. It has a capacity more than three times that of the widely used nickel cadmium batteries or nickel hydrogen batteries, and its use is rapidly increasing because it has excellent energy density per unit weight.

Depending on the shape of the battery case, secondary batteries are classified into cylindrical batteries and square batteries in which the electrode assembly is housed in a cylindrical or square metal can, and pouch-type batteries in which the electrode assembly is housed in a pouch-shaped case of aluminum laminate sheet. .

A cylindrical secondary battery generally includes a cylindrical can, an electrode assembly stored inside the cylindrical can, and a cap assembly coupled to the top of the cylindrical can. The cap assembly is located in the upper opening of the cylindrical can and includes a top cap, safety vent, etc.

In a conventional cylindrical secondary battery, when gas is generated from the inside of the battery can due to causes such as overcharging and the internal pressure increases, the safety vent deforms its shape and protrudes upward. At this time, the safety vent is separated from the current blocking member to block the current. is blocked.

Accordingly, the safety of the secondary battery is ensured because charging and discharging no longer proceeds. Furthermore, when the pressure inside the battery increases above a certain value, the safety vent ruptures, and the pressurized gas flows through the rupture area into the tower. Explosion of the battery is prevented by exhaustion through the gas hole in the cap.

However, under the above structure, when an external short circuit occurs in the cylindrical secondary battery, the CID gasket surrounding the current blocking member is easily melted and deformed by high temperature. Accordingly, there is a high risk that the current blocking member and the safety vent come into contact and become stuck together, and when the current blocking member and the safety vent come into contact, there is a risk of the battery exploding because the current blocking member and the safety vent cannot block the current. there was.

Accordingly, there is a very high need for technology that can improve the safety of secondary batteries by preventing shape deformation of the CID gasket.

Korean Patent Publication No. 10-2016-0039803

Focusing on the problems of the prior art described above, the present invention seeks to provide a cap assembly that prevents the CID gasket from being deformed by heat generated from the secondary battery during a short circuit, and a secondary battery including the same.

One embodiment of the present invention is a cap assembly that is coupled to the top of the opening of a secondary battery case and includes a top cap, a safety vent, a current interruptive device (CID), and a CID gasket, wherein the CID gasket has properties of each other. A cap assembly comprising two or more different parts is provided.

In one embodiment of the present invention, the CID gasket includes a first area surrounding at least a portion of an end of the current blocking element, a second area located on one surface of the current blocking element facing the safety vent, and the first area. and a third region connecting the second region.

In one embodiment of the present invention, the first to third regions of the CID gasket include a thermoplastic resin, and the surface of the third region is coated with a thermosetting resin.

In one embodiment of the present invention, the first to third regions of the CID gasket include a thermoplastic resin, and the entire surface of the CID gasket is coated with a thermosetting resin.

In one embodiment of the present invention, the first and second regions of the CID gasket include a thermoplastic resin, and the third region includes a thermosetting resin.

In one embodiment of the present invention, the first region and the second region include a thermoplastic resin and a thermosetting resin, and the third region includes a thermosetting resin.

In one embodiment of the present invention, the CID gasket includes a main body and a coating layer located on the surface of the main body and having different properties from the main body, and the coating layer is applied to the surface of 30% to 100% of the total surface area of the main body. Provided is a cap assembly that is positioned.

In one embodiment of the present invention, the CID gasket includes a thermoplastic resin and a thermosetting resin, and the volume ratio of the thermoplastic resin and the thermosetting resin is 10:90 to 70:30 with respect to the total volume of the CID gasket. Provides an in-cap assembly.

Another embodiment of the present invention includes a secondary battery case including an opening on one side; A secondary battery including the cap assembly and a battery assembly accommodated within the secondary battery case is provided.

The cap assembly and the secondary battery including the same according to an embodiment of the present invention can maintain the shape of the CID gasket even in a high temperature and high pressure environment.

1 is a cross-sectional view showing a secondary battery including a cap assembly according to an exemplary embodiment of the present invention.
Figure 2 is a cross-sectional view showing a CID gasket according to an exemplary embodiment of the present invention.
Figure 3 is a cross-sectional view showing a CID gasket according to another embodiment of the present invention.

The detailed description of the present invention is intended to completely explain the present invention to those skilled in the art. Throughout the specification, when a part is said to “include” a certain component or is “characterized” by a certain structure and shape, this means excluding other components or excluding other structures and shapes unless specifically stated to the contrary. It does not mean that it does, but that it can include other components, structures, and shapes.

Since the present invention can be modified in various ways and can have various embodiments, specific embodiments will be presented and explained in detail in the detailed description. However, this is not intended to limit the content of the invention by examples, and should be understood to include all transformations, equivalents, and substitutes included in the spirit and technical scope of the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings. However, the drawings are for illustrating the present invention, and the scope of the present invention is not limited by the drawings.

Figure 1 is a cross-sectional view showing a secondary battery 100 including a cap assembly 10 according to an exemplary embodiment of the present invention.

The secondary battery 100 according to the present invention may include an electrode assembly 20, a case 30, and a cap assembly 10.

The electrode assembly 20 is a power generation element capable of charging and discharging consisting of a stacked structure of an anode/separator/cathode, and may include a jelly-roll type structure wound with a separator interposed between a long sheet-like anode coated with an active material and a cathode. there is.

In the secondary battery 100 according to the present invention, a first insulating plate (not shown) and a second insulating plate (not shown) may be positioned on the upper and lower portions of the electrode assembly 20, respectively. The first insulating plate may insulate between the electrode assembly 20 and the cap assembly 10, and the second insulating plate may insulate between the electrode assembly 20 and the lower portion of the case 30.

The electrode assembly 20 may be provided with electrode tabs (not shown) on a surface facing the bottom surface of the case 30 and on a surface opposite to the bottom surface of the case 30 . For example, if the electrode tab protruding on the side facing the bottom of the case is a negative electrode tab, the electrode tab protruding on the opposite side, that is, the side in the direction in which the cap assembly 10 is located, is a positive electrode tab. It can be. Additionally, the positive electrode tab may be in electrical contact with the cap assembly 10.

Additionally, the electrode assembly 20 may further include a center pin (not shown) at the center. The center pin prevents the electrode assembly 20 wound in a jelly-roll shape from being unwound and can serve as a passage for gas to move inside the secondary battery 100.

The case 30 may have a pillar structure with a space formed therein. The case 30 may accommodate an electrode assembly 20 including an electrode and a separator and an electrolyte solution (not shown) in its internal space. The case 30 may have a structure in which one side is open (hereinafter referred to as an opening) and the other side can be sealed. Here, one side and the other side of the case 30 refer to ends located at the top and bottom along the direction of gravity or the central axis of the case 30.

The upper side of the opened case 30 may be provided with a beading portion 31 folded toward the center of the secondary battery 100. In addition, the case 30 may be provided with a crimping portion 32 on the upper side of the beading portion 31. That is, the crimping portion 32 may be located on the uppermost side of the case 30. Here, the upper part refers to the area from the center of the case 30 toward the opening.

Case 30 may be made of a lightweight conductive metal such as aluminum or aluminum alloy.

The cap assembly 10 is coupled to the top of the opening of the case 30 and includes a top cap 11, a safety vent 12, a current blocking element 13, a CID gasket 14, and a sealing gasket 15. You can.

The top cap 11 is located at the very top of the cap assembly 10 and may protrude in a direction opposite to the center of the case 30. The top cap 11 may serve as an electrode terminal so that the protruding portion is electrically connected to the outside. For example, the top cap 11 may serve as an anode terminal.

The top cap 11 may be coupled to an edge of the top cap 11 with a sealing gasket 15, and the sealing gasket 15 may be located inside the crimping portion 32 of the case 30. The sealing gasket 15 can increase the sealing force between the top cap 11 and the case 30.

The top cap 11 may include a protrusion protruding upward, an edge portion that contacts and is coupled to the sealing gasket 15, and a first connection portion connecting the protrusion and the edge portion.

The safety vent 12 is located below the top cap 11 and may be electrically connected to the top cap 11. At least a portion of the surface of the safety vent 12 facing the top cap 11 may be in contact with the top cap 11 . The safety vent 12 is in contact with the top cap 11 for a certain length from its end, and the portion excluding the contact length may be positioned at a certain distance away from the top cap 11. Additionally, the portion of the safety vent 12 that is in contact with the top cap 11 may be combined with the sealing gasket 15.

The separation distance between the safety vent 12 and the top cap 11 may increase as it moves from the area in contact with the top cap 11 to the center of the safety vent 12.

The safety vent 12 may include a contact part in contact with the top cap 11, a central part located in the center of the safety vent 12 and in contact with the current blocking element, and a second connection part connecting the contact part and the central part. In addition, the safety vent 12 may be provided with a bent portion (or notch) at a portion where the contact portion and the second connection portion, and the second connection portion and the central portion, are in contact.

In the secondary battery 100 according to the present invention, as the electrode assembly 20 accommodated inside the case 30 reacts with the electrolyte, gas is generated or heat is generated, thereby increasing the internal pressure.

When the pressure inside the secondary battery 100 increases, the safety vent 12 receives force in the direction of the top cap 11, and the bent portion ruptures, causing gas inside the secondary battery 100 to be discharged.

The current interruptive device (CID) 13 is located below the safety vent 12, and at least a portion of it may be connected to the safety vent 12.

When the safety vent 12 ruptures as the internal pressure of the secondary battery 100 increases, the current blocking element 13 is separated from the safety vent 12 and blocks the current.

More specifically, the current blocking element 13 has a central portion connected to the safety vent 12, a connecting portion protruding in the direction in which the safety vent 12 is located, an edge portion excluding the connecting portion, and a connecting portion connecting the connecting portion and the edge portion. It may include a coupling part. A plurality of coupling parts may be provided, and the plurality of coupling parts may be positioned to be spaced apart from each other.

When the safety vent 12 is deformed in the direction in which the top cap 11 is positioned, the joint may break and the joint may be separated from the edge portion. That is, the connection part is separated in the direction of the top cap 11 while being connected to the safety vent 12.

The CID gasket 14 surrounds the edge of the current blocking element 13 and can electrically separate the safety vent 12 from the edges and coupling parts other than the connection part of the current blocking element 13.

The CID gasket 14 includes a first region 1 surrounding at least a portion of the end of the current blocking device 13, a second region 2 located on one side of the current blocking device facing the safety vent 12, and a first region 1. It may include a third region (3) connecting the region (1) and the second region (2).

Alternatively, the first region 1 may extend from a portion of the end of the current blocking element 13 to the other surface of the current blocking element 13. Here, the other side of the current blocking element 13 refers to the side opposite to the side where the second region 2 is located.

The third area 3 may be provided in a form that surrounds from the end of the current blocking element 13 to one surface of the current blocking element 13.

The CID gasket 14 may include two or more parts with different properties. The first to third regions 1, 2, and 3 of the CID gasket 14 may have different properties, or only one or two areas may have different properties. Alternatively, the surface and interior properties of the CID gasket 14 may be different.

The CID gasket 14 can be manufactured by injection molding using polymer resin. Polymer resin has moldability and ductility, making injection molding easy, and the CID gasket 14 containing polymer resin can increase contact with the current blocking element 13.

Different properties mean that their thermal behavior is different.

In one embodiment, the CID gasket 14 may include two or more polymer resins having different glass transition onset temperatures (Tg). In other words, the CID gasket 14 may include a portion where the glass transition onset temperature (Tg) is relatively high and a portion where the glass transition onset temperature (tg) is relatively low.

For example, if the electrode assembly 20 generates heat due to an external short circuit and the temperature within the secondary battery 100 increases, the CID gasket 14 may melt. When the internal temperature of the secondary battery 100 rises to 200°C to 250°C, the CID gasket 14 has a portion where the glass transition start temperature (Tg) is 200°C or less and a portion where the glass transition start temperature (Tg) exceeds 250°C. may include.

In addition, the glass transition onset temperature (Tg) may vary depending on differences in the degree of polymerization and molecular weight caused by the crosslinking agent, or may vary depending on the mixing ratio of materials with different degrees of polymerization, molecular weight, or glass transition onset temperature (Tg).

For example, the third region (3) has a mixed mass ratio of a material with a glass transition onset temperature (Tg) of 300°C and a material with a glass transition onset temperature (Tg) of 200°C of 9:1, and the first region (1) and the second region (2) ) may have a mixed mass ratio of a material with a glass transition onset temperature (Tg) of 300°C and a material with a glass transition onset temperature (Tg) of 200°C of 5:5. At this time, the third region 3 may have a higher glass transition onset temperature (Tg) than the first region 1 and the second region 2.

In another embodiment, the CID gasket 14 may include thermoplastic resin and thermoset resin with different properties.

The thermoplastic resin is not particularly limited as long as it is a polymer resin known in the art, but specifically includes polyethylene, polypropylene (PP), polypropylene-maleic anhydride (PP-MAH), thermoplastic polyester elastomer (TPEE), and tetrafluoroethylene. It may be one or more selected from the group consisting of ride-perfluoroalkyl vinyl ether copolymer (PFA) and polybutylene terephthalate (PBT), and more specifically, it may be polybutylene terephthalate (PBT).

The thermosetting resin may be one or more selected from polyimide, phenol resin, polyester resin, and polyurethane resin, but is not limited to these alone.

The CID gasket 14 may be composed of two or more parts with different properties bonded to each other with an adhesive or coated with materials with different properties.

Figure 2 is a cross-sectional view showing the CID gasket 14 according to an exemplary embodiment of the present invention. Figure 2(a) is a cross-sectional view showing the CID gasket 14 with the coating layer 5 coated only on a portion of the body 4 according to an exemplary embodiment, and Figure 2(b) is a cross-sectional view showing the coating layer 5 according to an exemplary embodiment. ) is a cross-sectional view showing the CID gasket 14 coated on the entire outer surface of the main body 4. Figure 3 is a cross-sectional view showing the CID gasket 14 according to another embodiment of the present invention. Figure 3 (a) is a cross-sectional view showing the CID gasket 14 showing the area where the coating layer is coated only on the outer surface of the third area (3), and Figure 3 (b) is a cross-sectional view showing the coating layer on the third area (3). This is a cross-sectional view of the CID gasket 14 showing the area where the coating layer is coated from 3) to the first area 1 and the second area 2.

In one embodiment, the CID gasket 14 may include a body 4 that determines the shape of the CID gasket 14 and a coating layer 5 coated on the surface of the body. At this time, the main body 4 may include a thermoplastic resin, and the coating layer 5 may include a thermosetting resin or a polymer resin having a glass transition onset temperature (Tg) of more than 250°C.

The coating layer 5 may be coated 50% to 100% of the total surface area of the main body 4.

And, when the CID gasket 14 includes the first to third regions (1, 2, and 3), the position of the coating layer 5 is located on the surface of the third region (3), or the third region ( 3) may extend in the direction of the first and second areas (1, 2). And, the coating layer 5 may be located on the entire surface of the first to third regions 1, 2, and 3.

If the coating layer 5 is coated within the above-mentioned numerical range out of the total surface area of the CID gasket 14, the overall shape of the CID gasket 14 will be maintained even if the main body of the CID gasket 14 melts as the internal temperature of the secondary battery rises. By maintaining this, it is possible to prevent a short circuit occurring when the current blocking element 13 comes into contact with the case 30 or the electrode assembly 20.

The CID gasket 14 may have a softening point of 200°C or higher and a melting point of 250°C or higher.

In another embodiment, the body 4 of the CID gasket 14 may be composed of an area containing a thermoplastic resin and an area containing a thermosetting resin. Alternatively, the main body 4 of the CID gasket 14 has a region containing a polymer resin with a glass transition onset temperature (Tg) of 200°C or less and a region containing a polymer resin with a glass transition onset temperature (Tg) exceeding 250°C. It can be included.

For example, the CID gasket 14 may be composed of thermoplastic resin and thermosetting resin in a volume ratio of 10:90 to 70:30 with respect to the total volume. Alternatively, the CID gasket 14 contains a polymer resin having a glass transition onset temperature (Tg) of 200°C or lower and a polymer resin having a glass transition onset temperature (Tg) exceeding 250°C in a volume ratio of 10:90 to 70:30 with respect to the entire volume. It can be included as .

Additionally, at least one of the first to third regions 1, 2, and 3 of the CID gasket 14 may include a thermosetting resin or a polymer resin having a glass transition onset temperature (Tg) of more than 250°C. In one embodiment, the third region 3 of the CID gasket 14 includes a thermosetting resin or a polymer resin having a glass transition onset temperature (Tg) exceeding 250° C., and the first region 1 and the second region (2) This may include a thermoplastic resin or a polymer resin having a glass transition onset temperature (Tg) of 200°C or lower.

Alternatively, the first region (1) and the second region (2) contain both a thermosetting resin and a thermoplastic resin, or a polymer resin with a glass transition onset temperature (Tg) exceeding 250°C and a glass transition onset temperature (Tg) of 200°C. It can include all polymer resins with a temperature of ℃ or lower.

For example, the first region (1) and the second region (2) are at a contact boundary with the third region (3) at a point of 1/2 to 2/3 of the first region (1) and the second region (2). A thermosetting resin may be placed up to, and a thermoplastic resin may be placed in the remainder.

If the volume occupied by the thermosetting resin or the polymer resin whose glass transition onset temperature (Tg) exceeds 250°C in the CID gasket (14) satisfies the above-mentioned numerical range, the thermoplastic resin or the glass transition onset temperature (Tg) of the CID gasket (14) satisfies the above-mentioned numerical range. ) Even if the area containing the polymer resin with a temperature of 200°C or lower melts, the CID gasket 14 is blocked by the current blocking element 13 due to the area containing the thermosetting resin or the polymer resin with a glass transition onset temperature (Tg) exceeding 250°C. It is possible to insulate between and the safety vent (12).

In another embodiment, the CID gasket 14 may be configured by mixing the CID gasket 14 shapes of one embodiment and another embodiment.

For example, the CID gasket 14 may include a body 4 and a coating layer 5 according to one embodiment. The main body 4 may include first to third regions 1, 2, and 3, and the coating layer 5 may include a thermosetting resin or a polymer resin whose glass transition onset temperature (Tg) exceeds 250°C. You can. At this time, the third region (3) contains a thermosetting resin or a polymer resin whose glass transition onset temperature (Tg) exceeds 250°C, and the first region (1) and second region (2) contain a thermoplastic resin or a polymer resin whose glass transition onset temperature (Tg) exceeds 250°C. (Tg) may include a polymer resin of 200°C or lower. And, the coating layer 5 may be located only on the surfaces of the first region 1 and the second region 2, and the coating layer 5 may be located on at least the surfaces of the first region 1 and the second region 2. It can be located in some places.

Thermoplastic resins have excellent moldability and are easy to process, but are deformed by heat, and thermosetting resins are not deformed by heat, but are not easy to process.

Therefore, if the CID gasket 14 contains only thermoplastic resin, a problem occurs in which the shape of the CID gasket 14 is deformed by heat generated inside the secondary battery, and if the CID gasket 14 contains only thermosetting resin, a problem occurs. , problems that make molding difficult may occur.

The CID gasket 14 according to the present invention forms the main body 4 using a thermoplastic resin that has excellent moldability and is easy to process, and heat is generated inside the secondary battery to form the main body 4 containing the thermoplastic resin. To prevent deformation by heat, the coating layer 5 may include a thermosetting resin that is not deformable by heat.

Although the present invention has been described above with reference to preferred embodiments, those skilled in the art may make various modifications and changes to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. You will understand that you can do it.

100: secondary battery
10: Cap assembly
11: Top cap
12: Safety vent
13: Current blocking element
14: CID gasket
15: Sealing gasket
20: Electrode assembly
30: case
31: Beading part
32: Crimping part
1: First region
2: Second area
3: Third area
4: Body
5: Coating layer

Claims (10)

In the cap assembly coupled to the top of the opening of the secondary battery case and including a top cap, a safety vent, a current interruptive device (CID), and a CID gasket,
A cap assembly wherein the CID gasket includes two or more parts with different properties. The method according to claim 1, wherein the CID gasket includes a first area surrounding at least a portion of an end of the current blocking element, a second area located on one surface of the current blocking element facing the safety vent, and the first area and the second area. A cap assembly comprising a third region connecting the regions. The cap assembly according to claim 2, wherein the first to third regions of the CID gasket include a thermoplastic resin, and a surface of the third region is coated with a thermosetting resin. The cap assembly of claim 2, wherein the first to third regions of the CID gasket include a thermoplastic resin, and the entire surface of the CID gasket is coated with a thermosetting resin. The cap assembly of claim 2, wherein the first and second regions include a thermoplastic resin, and the third region includes a thermosetting resin. The cap assembly according to claim 2, wherein the first region and the second region include a thermoplastic resin and a thermosetting resin, and the third region includes a thermosetting resin. The method of claim 1, wherein the CID gasket includes a main body and a coating layer located on the surface of the main body and having different properties from the main body,
The cap assembly wherein the coating layer is located on a surface of 30% to 100% of the total surface area of the main body. The cap assembly according to claim 7, wherein the coating layer includes a thermosetting resin. The method according to claim 1, wherein the CID gasket includes a thermoplastic resin and a thermosetting resin,
The CID gasket is a cap assembly wherein a volume ratio of the thermoplastic resin and the thermosetting resin is 10:90 to 70:30 with respect to the total volume. A secondary battery case including an opening on one side;
A cap assembly according to any one of claims 1 to 9, and
Battery assembly accommodated inside the secondary battery case
A secondary battery containing a.