Cap assembly and secondary battery comprising same

Abstract

A cap assembly of the present invention comprises: a top cap; and a CID module provided under the top cap and blocking current when the inside of a secondary battery reaches a deformation temperature or higher, wherein the CID module includes: an upper plate provided under the top cap and having a protrusion; a lower plate which is arranged under the upper plate and is in contact with only the protrusion; an insulating plate provided between the edge of the upper plate and the edge of the lower plate; and a deformable body which is provided between the upper plate and the lower plate, and when the secondary battery reaches the deformation temperature or higher, lifts the upper plate to separate the protrusion and the lower plate from each other so that no current flows therethrough.

Description

Cap assembly and secondary battery including the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0100712, filed August 1, 2023, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a cap assembly having improved safety by applying a bimetal and a secondary battery including the same.

[0005] In general, secondary batteries are classified into cylindrical secondary batteries in which the electrode assembly is built into a cylindrical metal can, square secondary batteries in which the electrode assembly is built into a square metal can, and pouch-type secondary batteries in which the electrode assembly is built into a pouch-type case.

[0006] In addition, the electrode assembly is formed by a stacked structure of anode / separator / cathode, and such electrode assembly is classified into a jelly-roll type structure in which a separator is interposed between long sheet-shaped anodes and cathodes coated with active materials and wound, and a stack type structure in which a plurality of anodes and cathodes of a predetermined size are sequentially stacked with a separator interposed between them.

[0007] Among them, the jelly-roll type electrode assembly is the most widely manufactured because it has the advantages of being easy to manufacture and having a high energy density per weight, and the jelly-roll type electrode assembly is usually manufactured into a cylindrical secondary battery.

[0008] That is, the cylindrical secondary battery includes an electrode assembly, a can that accommodates the electrode assembly, and a cap assembly mounted in an opening of the can.

[0009] These cylindrical secondary batteries can undergo deformation as the jelly-roll electrode assembly undergoes repeated expansion and contraction during charging and discharging, potentially leading to internal short circuits. This can lead to heat generation from the internal short circuit, which can decompose the organic solvent, generating gas. This, in turn, can lead to an increase in gas pressure within the battery, potentially causing the battery to explode or rupture.

[0010] To solve the above problem, the cap assembly of the cylindrical secondary battery includes a safety vent for discharging high-pressure gas and a current interrupt device (CID) for interrupting current when the internal pressure of the secondary battery increases.

[0011] However, conventional cylindrical secondary batteries have limitations in increasing safety as their capacity increases, and therefore, structural improvements are needed to increase the safety of secondary batteries.

[0012] [Prior Art Literature]

[0013] [Patent Document]

[0014] (Patent Document 1) Patent Publication No. 10-2018-0000115.

[0015]

[0016] The present invention aims to provide a cap assembly and a secondary battery including the same, which can rapidly cut off current when a high temperature occurs by including a CID module using a bimetal, thereby significantly improving safety.

[0017] The cap assembly of the present invention includes a top cap; and a CID module provided at a lower portion of the top cap and cutting off current when the interior of a secondary battery rises above a deformation temperature, wherein the CID module may include an upper plate provided at a lower portion of the top cap and having a protrusion; a lower plate provided at a lower portion of the upper plate and in contact only with the protrusion; an insulating plate provided between a rim of the upper plate and a rim of the lower plate; and a deformation member provided between the upper plate and the lower plate and separating the protrusion and the lower plate so that current does not flow when the secondary battery rises above a deformation temperature by raising the upper plate.

[0018] The above-mentioned deformation body has a structure in which a first deformation layer and a second deformation layer are arranged in multiple stages, and the first deformation layer can be provided with a larger thermal expansion coefficient than the second deformation layer at the same temperature.

[0019] The above-mentioned deformation body can be made of a bimetal that undergoes deformation at a deformation temperature.

[0020] An insulator may be further provided on the outer surface of the first deformation layer or the outer surface of the second deformation layer.

[0021] The above insulator may have a thickness smaller than the first strain layer or the second strain layer.

[0022] The above-mentioned deformation body may have a through hole formed so that the protrusion penetrates.

[0023] An insulating layer may be coated on the inner surface of the through hole of the above-mentioned deformation body.

[0024] The first deformation layer may be formed thicker than the second deformation layer.

[0025] An insertion groove into which the deformation body is inserted can be formed in the lower plate.

[0026] The above transformation temperature may be 70°C or higher.

[0027] The secondary battery of the present invention may include a cap assembly.

[0028] The cap assembly of the present invention comprises a top cap; and a CID module provided on the lower portion of the top cap and configured to cut off current when the internal temperature of the secondary battery rises above the deformation temperature, thereby enabling the current to be quickly cut off when a high temperature occurs in the secondary battery, thereby significantly improving safety.

[0029] FIG. 1 is a perspective view illustrating a secondary battery according to a first embodiment of the present invention.

[0030] Figure 2 is a partial cross-sectional view of Figure 1.

[0031] Figure 3 is a perspective view showing a deformation body included in a secondary battery according to the first embodiment of the present invention.

[0032] Figure 4 is a cross-sectional view showing a deformation body included in a secondary battery according to the first embodiment of the present invention.

[0033] Fig. 5 is a cross-sectional view showing a deformed state of the deformed body shown in Fig. 4.

[0034] Figure 6 is a cross-sectional view showing another example of a deformation body included in a secondary battery according to the first embodiment of the present invention.

[0035] Fig. 7 is a cross-sectional view showing a deformed state of the deformed body shown in Fig. 6.

[0036] Figure 8 is a cross-sectional view showing a current blocking state of a secondary battery according to the first embodiment of the present invention.

[0037] FIG. 9 is a cross-sectional view illustrating a CID module included in a secondary battery according to a second embodiment of the present invention.

[0038] Fig. 10 is a partially enlarged view of Fig. 9.

[0039] Fig. 11 is a cross-sectional view showing a variant of a secondary battery according to a second embodiment of the present invention.

[0040] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. In addition, in the drawings, parts irrelevant to the description have been omitted to clearly explain the present invention, and similar parts have been designated with similar reference numerals throughout the specification.

[0041] [Secondary battery according to the first embodiment of the present invention]

[0042] FIG. 1 is a perspective view illustrating a secondary battery according to a first embodiment of the present invention, and FIG. 2 is a partial cross-sectional view of FIG. 1.

[0043] The secondary battery (1) of the present invention includes an electrode assembly (11), a can (12) that accommodates the electrode assembly (11), and a cap assembly (13) mounted in an opening of the can (12), as illustrated in FIGS. 1 and 2.

[0044] electrode assembly

[0045] The electrode assembly (11) includes two electrodes having different polarities and having a wide plate shape in the form of a roll, and a separator interposed between the electrodes or placed below or above one of the electrodes to mutually insulate the electrodes, and the two electrodes and the separator have a structure in which they are wound in the form of a 'jelly roll'.

[0046] And the two electrodes each have a structure in which an active material slurry is applied to a current collector in the form of a metal foil or metal mesh containing aluminum and copper, respectively.

[0047] Here, the two electrodes can be anode and cathode.

[0048] Meanwhile, the positive electrode is provided with a positive tab, and the positive tab is connected to the cap assembly (13). The negative electrode is provided with a negative tab, and the negative tab is connected to the bottom surface of the can (12).

[0049] can

[0050] As illustrated in Fig. 1, the can (12) is made of a lightweight conductive metal material such as aluminum or an aluminum alloy, and has a cylindrical structure with an open top and a sealed bottom opposite thereto. An electrode assembly (11) and an electrolyte (not illustrated) are accommodated inside the can (12).

[0051] Meanwhile, the electrolyte is intended to move lithium ions generated by electrochemical reactions at the positive and negative electrodes during charging and discharging of a secondary battery. For example, the electrolyte may be a non-aqueous organic electrolyte, which is a mixture of a lithium salt and a high-purity organic solvent, or a polymer using a polymer electrolyte.

[0052] FIG. 3 is a perspective view illustrating a deformable body included in a secondary battery according to a first embodiment of the present invention, FIG. 4 is a cross-sectional view illustrating a deformable body included in a secondary battery according to a first embodiment of the present invention, FIG. 5 is a cross-sectional view illustrating a deformed state of the deformable body illustrated in FIG. 4, FIG. 6 is a cross-sectional view illustrating another example of a deformable body included in a secondary battery according to the first embodiment of the present invention, and FIG. 7 is a cross-sectional view illustrating a deformed state of the deformable body illustrated in FIG. 6.

[0053] Cap assembly

[0054] The cap assembly (13) is mounted in the opening of the can (12), and includes a top cap (131) that supplies electricity to an external circuit, a CID (Current Interrupt Device) module that cuts off current when the inside of the secondary battery rises above the deformation temperature, and a gasket (133) that surrounds the edges of the top cap (131) and the CID module (132) and is coupled to the opening of the can.

[0055] The above top cap (131) includes a terminal portion (1311) that comes into contact with an electric circuit, a top cap peripheral portion (1312) formed along the edge of the terminal portion (1311), and a top cap connecting portion (1313) that connects the terminal portion (1311) and the top cap peripheral portion (1312) and forms a step between the top cap peripheral portion (1312) and the terminal portion (1311).

[0056] Meanwhile, when the secondary battery (1) is charged and discharged, the organic solvent is decomposed due to heat generation caused by an internal short circuit, generating high-temperature gas, and as a result, an explosion or rupture may occur due to an increase in gas pressure within the secondary battery (1).

[0057] To solve the above problem, it includes a CID module (132) that can quickly cut off the current when a high temperature higher than the deformation temperature occurs.

[0058] The CID module (132) is provided at the bottom of the top cap (131) and blocks current when the inside of the secondary battery (1) rises above the deformation temperature, and includes an upper plate (1321), a lower plate (1322), an insulating plate (1323), and a deformation body (1324).

[0059] The upper plate (1321) includes a contact portion (13211) provided at the lower portion of the top cap (131) and having a protrusion (132111) protruding downward, an upper plate peripheral portion formed along the edge of the contact portion (13211) and in contact with the top cap peripheral portion (1312), and an upper connecting portion (13213) connecting the contact portion (13211) and the upper plate peripheral portion and forming a step between the contact portion (13211) and the upper plate peripheral portion.

[0060] The lower plate (1322) is provided at the lower portion of the upper plate (1321) and includes a support portion (13221) that is supported so that only the protrusion portion (132111) of the upper plate comes into contact with it, a lower plate peripheral portion formed along the edge of the support portion (13221) and corresponding to the upper plate peripheral portion, and a lower connecting portion (13223) that connects the support portion (13221) and the lower plate peripheral portion and forms a step between the lower plate peripheral portion and the support portion (13221).

[0061] The above insulating plate (1323) is intended to insulate the remaining portions of the upper plate (1321) and the lower plate (1322) from contact except for the contact between the protrusion (132111) and the support (13221), and is provided between the upper peripheral portion (13212) and the lower peripheral portion (13222) to insulate between the upper peripheral portion (13212) and the lower peripheral portion (13222). Meanwhile, the insulating plate (1323) may be formed of a material such as epoxy, polyethylene, or polypropylene.

[0062] The deformation body (1324) is provided between the contact portion (13211) of the upper plate (1321) and the support portion (13221) of the lower plate (1322), and when the secondary battery (1) rises above the deformation temperature, the upper plate (1321) is raised to separate the protrusion (132111) and the lower plate (1322) so that no current flows through them, thereby quickly cutting off the current generated in the secondary battery (1).

[0063] That is, the above-mentioned deformation body (1324) has a structure in which the first deformation layer (13241) and the second deformation layer (13242) are arranged in multiple stages, and the first deformation layer (13241) is provided with a larger thermal expansion coefficient than the second deformation layer (13242) at the same temperature. In summary, the second deformation layer (13242) has a structure that does not expand as much as the first deformation layer (13241), and the first deformation layer (13241) has a structure that expands as much as the second deformation layer (13242).

[0064] And the deformable body (1324) can be provided in a donut shape with a through hole (13243) formed so that the protrusion (132111) can penetrate it. Accordingly, since the deformable body (1324) is supported by the protrusion (132111), the fixing force can be increased.

[0065] Accordingly, when the secondary battery (1) rises above the deformation temperature, the deformation body (1324) is deformed to a greater extent than the second deformation layer (13242) in which the first deformation layer (13241) having a large coefficient of thermal expansion is deformed as shown in FIG. 5, and accordingly, the height of the deformation body (1324) increases as it bends in the direction in which the second deformation layer (13242) is located, and at this time, the deformation body (1324) lifts the upper plate (1321) so that the protrusion (132111) and the support (13221) do not come into contact with each other.

[0066] Here, the deformable body (1324) may be formed as a bimetal that undergoes deformation at a deformation temperature. Meanwhile, a bimetal refers to two thin metal strips with different thermal expansion rates bonded together. That is, when the temperature of the bimetal increases, the lengths of the strips change due to the difference in expansion rates, and the strip bends toward the metal strip with the lower expansion rate. When the temperature decreases, the strip bends toward the opposite direction.

[0067] For example, the first strain layer (13241) may be nickel (Ni) and iron (Fe), and the second strain layer (13242) may be an alloy of nickel-manganese and iron, a nickel-molybdenum-iron alloy, or a nickel-manganese-copper alloy.

[0068] Meanwhile, the CID module (132) may be provided with an insulator (13244) for insulating between the deformable body (1324) and the upper plate (1321) or between the deformable body (1324) and the lower plate (1322). That is, the insulator (13244) may be further provided to prevent the upper plate (1321) and the lower plate (1322) from being electrically connected by the deformable body (1324).

[0069] Here, the insulator (13244) may be provided so as to cover the entire bottom surface of the second deformation layer (13242) when the first deformation layer (13241) and the second deformation layer (13242) are arranged vertically, as illustrated in FIGS. 3 and 4. Accordingly, when the deformation body is deformed, the outer edge of the deformation body (1324) is deformed downward, thereby increasing the height, and at this time, the upper plate (1321) is lifted.

[0070] Meanwhile, as illustrated in FIG. 6, the insulator (13244) may be provided so as to cover the entire upper surface of the first deformation layer (13241) when the second deformation layer (13242) and the first deformation layer (13241) are arranged vertically. Accordingly, when the deformation body (1324) is deformed, the outer edge of the deformation body (1324) is deformed upwards, thereby increasing the height, and at this time, the upper plate (1321) can be lifted.

[0071] Accordingly, the CID module (132) can insulate between the deformable body (1324) and the upper plate (1321) or the deformable body (1324) and the lower plate (1322) even if the deformable body (1324) is deformed by including the insulator (13244).

[0072] Meanwhile, the insulator (13244) may be made of a material having elasticity so that it can be deformed together with the deformable body (1324). For example, the insulator (13244) may be polyethylene (PE).

[0073] Meanwhile, the deformation temperature may be 70°C or higher, preferably 100°C or higher. Here, if the deformation temperature is 70°C or lower, there is a problem that the deformable body may be deformed even from a heat source generated during normal operation of the secondary battery (1).

[0074] Hereinafter, a modified example of the secondary battery (1) according to the first embodiment of the present invention will be described with reference to the attached drawings.

[0075] As illustrated in Fig. 8, when the secondary battery (1) is charged and discharged, the jelly-roll type electrode assembly undergoes repeated expansion and contraction, causing deformation. Accordingly, when the inside of the secondary battery (1) rises above the deformation temperature due to an internal short circuit, the deformable body (1324) of the CID module (132) is deformed, lifting the upper plate (1321). Accordingly, the protrusion (132111) of the upper plate (1321) and the support (13221) of the lower plate (1322) are separated, thereby cutting off the current.

[0076] To explain in more detail, when the inside of the secondary battery (1) rises above the deformation temperature, the first deformation layer (13241) and the second deformation layer (13242) of the deformation body (1324) expand. At this time, the first deformation layer (13241) expands more than the second deformation layer (13242) and bends in the direction of the second deformation layer (13242), thereby increasing the height of the deformation body (1324) and lifting the upper plate (1321). As a result, the protrusion (132111) of the upper plate (1321) is separated from the support (13221), so that the current can be quickly cut off.

[0077] At this time, the deformable body (1324) and the upper plate (1321) are insulated by the insulator (13244), thereby preventing current from flowing between the deformable body (1324) and the upper plate (1321).

[0078] Therefore, the secondary battery (1) according to the first embodiment of the present invention includes a cap assembly (13) equipped with a CID module (132), so that when the inside of the can rises above the deformation temperature, the deformation body (1324) of the CID module (132) is deformed, thereby blocking contact between the upper plate (1321) and the lower plate (1322), and as a result, the current can be quickly cut off, thereby enhancing safety.

[0079] Hereinafter, in describing other embodiments of the present invention, the same component symbols are used for components having the same functions as the above-described embodiments, and redundant descriptions are omitted.

[0080] [Secondary battery according to the second embodiment of the present invention]

[0081] FIG. 9 is a cross-sectional view illustrating a CID module included in a secondary battery according to a second embodiment of the present invention, FIG. 10 is a partial enlarged view of FIG. 9, and FIG. 11 is a cross-sectional view illustrating a variant (1324) of a secondary battery according to the second embodiment of the present invention.

[0082] A secondary battery (1) according to a second embodiment of the present invention includes an electrode assembly (11), a can (12), and a cap assembly (13), as illustrated in FIG. 9.

[0083] Here, the cap assembly (13) includes a top cap (131) and a CID module (132), and the CID module (132) includes an upper plate (1321), a lower plate (1322), an insulating plate (1323), and a deformation body (1324).

[0084] Here, the electrode assembly (11), can (12) and cap assembly (13) correspond to the electrode assembly (11), can (12) and cap assembly (13) described in the first embodiment, so overlapping descriptions are omitted.

[0085] Meanwhile, an insulating layer (13245) is coated on the inner surface of the through hole (13243) of the deformable body (1324). That is, an insulating layer (13245) is coated on the inner surface of the through hole (13243) of the deformable body (1324) to insulate between the inner surface of the deformable body (1324) and the protrusion (132111) of the upper plate (1321). Accordingly, current can be prevented from flowing between the deformable body (1324) and the protrusion (132111). Meanwhile, the insulating layer (13245) can be made of the same material as the insulator (13244).

[0086] In addition, the first deformation layer (13241) can be formed thicker than the second deformation layer (13242). Accordingly, the expansion force of the first deformation layer (13241) can be increased to be greater than that of the second deformation layer (13242), thereby increasing the strain of the deformation body (1324), thereby allowing the upper plate (1321) to be lifted more effectively.

[0087] Meanwhile, as shown in Fig. 10, an insertion groove (132211) into which the deformable body (1324) is inserted is formed in the lower plate (1322), and the fixing force of the deformable body (1324) can be increased.

[0088] Meanwhile, the insulator (13244) may have a thickness smaller than that of the first deformation layer (13241) or the second deformation layer (13242) to minimize the deformability degradation of the deformation body (1324), as illustrated in FIG. 11.

[0089] The scope of the present invention is indicated by the claims described below rather than the detailed description above, and various embodiments are possible derived from the meaning and scope of the claims and their equivalent concepts.

[0090]

[0091] [Explanation of symbols]

[0092] 1: Secondary battery

[0093] 11: Electrode assembly

[0094] 12: Can

[0095] 13: Cap assembly

[0096] 131: Top cap

[0097] 1311: Terminal section

[0098] 1312: Top cap circumference

[0099] 1313: Top cap connection

[0100] 132: CID module

[0101] 1321: Top plate

[0102] 13211: Contact

[0103] 132111: Protrusion

[0104] 13212: Upper circumference

[0105] 13213: Upper connection

[0106] 1322: Lower plate

[0107] 13221: Support

[0108] 132211: Insert Home

[0109] 13222: Lower circumference

[0110] 13223: Lower connection

[0111] 1323: Insulating plate

[0112] 1324: Variant

[0113] 13241: First deformation layer

[0114] 13242: Second deformation layer

[0115] 13243: Through hole

[0116] 13244: Insulator

[0117] 13245: Insulation layer

[0118] 133: Gasket

Claims

1. Top cap; and It includes a CID module installed at the bottom of the top cap and blocks current when the inside of the secondary battery rises above the deformation temperature. The above CID module, An upper plate provided at the lower portion of the top cap and having a protrusion; A lower plate provided at the lower portion of the upper plate and in contact only with the protrusion; An insulating plate provided between the edge of the upper plate and the edge of the lower plate; and A cap assembly including a deformation body provided between the upper plate and the lower plate, and which, when the secondary battery rises above a deformation temperature, raises the upper plate to separate the protrusion and the lower plate so that current does not flow.

2. In claim 1, The above variant is, It has a structure in which the first and second deformation layers are arranged in multiple stages. A cap assembly in which the first deformation layer has a larger coefficient of thermal expansion than the second deformation layer at the same temperature.

3. In claim 1, The above variant is, A cap assembly made of a bimetal that undergoes deformation at the deformation temperature.

4. In claim 2, A cap assembly further comprising an insulator on the outer surface of the first deformation layer or the outer surface of the second deformation layer.

5. In claim 4, The above insulator is a cap assembly having a thickness smaller than that of the first strain layer or the second strain layer.

6. In claim 1, The above-mentioned deformation body is a cap assembly in which a through hole is formed so that the protrusion penetrates.

7. In claim 6, A cap assembly in which an insulating layer is coated on the inner surface of the through hole of the above-mentioned deformation body.

8. In claim 2, A cap assembly in which the first deformation layer is formed thicker than the second deformation layer.

9. In claim 1, On the above lower plate, A cap assembly in which an insertion groove into which the above-mentioned deformation body is inserted is formed.

10. In claim 1, The above deformation temperature is 70℃ or higher for the cap assembly.

11. A secondary battery comprising a cap assembly provided according to claim 1.

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