Cylindrical secondary battery and method of manufacturing the same

Abstract

Disclosed are a cylindrical secondary battery and a method for manufacturing the cylindrical secondary battery. The cylindrical secondary battery is configured such that a hole is provided on a bottom portion of the cylindrical secondary battery, the cylindrical secondary battery is prepared using a metal can, and the hole is sealed using a flexible material such as rubber.

Description

Technical Field

[0001] This application claims the benefit of priority from Korean Patent Application No. 2019-0169530, filed on December 18, 2019, the disclosure of which is incorporated herein by reference in its entirety.

[0002] The present invention relates to a cylindrical secondary battery provided with a flexible input portion. More specifically, the present invention relates to a cylindrical secondary battery configured such that a hole is provided at the bottom portion of the cylindrical secondary battery manufactured using a metal can, and the hole is hermetically sealed using a flexible material such as a thermoplastic polymer resin or rubber. Background Art

[0003] Secondary batteries are classified based on the shape of their battery cases. They can be primarily categorized into: cylindrical batteries, which have an electrode assembly housed in a cylindrical metal can; prismatic batteries, which have an electrode assembly housed in a prismatic metal can; and pouch batteries, which have an electrode assembly housed in a pouch-shaped case made of an aluminum laminate sheet.

[0004] The electrode assembly installed in the battery case is a power generation element that has a structure including a positive electrode, a negative electrode, and a separator inserted between the positive and negative electrodes, and can be charged and discharged. Electrode assemblies are classified as either jelly-roll-type electrode assemblies, in which a long sheet of a positive electrode coated with an active material and a long sheet of a negative electrode coated with an active material are wound with a separator inserted between the positive and negative electrodes, or as stacked-type electrode assemblies, in which a plurality of positive electrodes of a predetermined size and a plurality of negative electrodes of a predetermined size are stacked in sequence with separators inserted between the positive and negative electrodes, respectively. Among these electrode assemblies, the jelly-roll-type electrode assembly has the advantage of being easy to manufacture and having a high energy density per unit weight.

[0005] The jelly-roll type electrode assembly may be mounted in a cylindrical metal can to constitute a cylindrical secondary battery. Cylindrical secondary batteries are widely used in fields requiring high-capacity secondary batteries, such as electric vehicles.

[0006] Unlike pouch-shaped batteries, cylindrical secondary batteries are activated after they are assembled. When assembling cylindrical secondary batteries, the canister that forms the outer casing is hermetically sealed. During the activation process, gases are inevitably generated. Pouch-shaped batteries are hermetically sealed only after the gases generated within the battery are exhausted to the outside. Secondary batteries do not have a separate exhaust port to facilitate the discharge of gases generated within the battery.

[0007] Cylindrical secondary batteries begin to be used with the pressure already built up inside them. This increases the pressure within the battery, causing the electrolyte in the battery to evaporate to a greater extent than other types of batteries, shortening the battery life and deteriorating its performance.

[0008] Patent document 1 relates to a cylindrical battery including an electrolytic solution injection port, which is a secondary battery having the following structure: in this structure, an electrode assembly having a positive electrode / separator / negative electrode structure is installed in a cylindrical can, wherein a cover assembly is installed at the open upper end portion of the can, at least one opening is formed in the outer surface of the can by perforation, the at least one opening is configured to allow a user to inject an electrolytic solution through the opening, and a sealing member is forcibly inserted into the opening so as to hermetically seal the opening with the outside, and an electrolytic solution injection needle can extend through the sealing member.

[0009] In patent document 1, 1) since the side surface of the cylinder is perforated, it is not easy to perforate the side surface at a consistent position on the side surface of the cylinder, 2) perforating the side surface of the cylinder requires technical attention, and 3) it is necessary to manufacture a separate supporting portion with a corresponding shape in order to seal the hole set in the side surface of the cylinder. In the case of stretching the iron sheet to manufacture the can in a state where the iron sheet is perforated in advance, the iron sheet cannot be stretched uniformly due to the perforated area of ​​the iron sheet. For this reason, the can must be perforated after the can is manufactured. In addition, 4) when several can-type secondary batteries are combined to manufacture a battery module, each secondary battery may be stuck by the protrusion of the supporting portion, or due to the supporting portion set at the side surface of the cylinder, it is difficult to package the secondary batteries in the same shape. 5) Although supported by a separate supporting portion, the load applied to the sealing member may not be uniform or symmetrical because the sealing member is connected to the side surface of the cylinder. In addition, 6) patent document 1 does not specifically disclose the sealing material.

[0010] Patent document 2 relates to a secondary battery comprising: an electrode unit having a positive electrode and a negative electrode, the positive electrode and the negative electrode being installed with an insulating plate interposed between the positive electrode and the negative electrode; a cap assembly connected to the positive electrode of the electrode unit; a can connected to the negative electrode of the electrode unit, the electrode unit being inserted into the can; and an electrolytic solution injection device installed at the can.

[0011] The electrolytic solution injection device of Patent Document 2 includes: an injection hole formed in a tank; a body mounted on the tank, the body having a plurality of supply holes connected to the interior of the battery; a valve member inserted into the body to connect the injection hole and the supply hole to each other or disconnect the injection hole and the supply hole from each other; and a pressurizing member configured to apply a uniform force to the valve member. A spring is used as the pressurizing member.

[0012] In Patent Document 2, an opening and closing device using spring elasticity is added to the bottom portion of the tank. However, this has the following disadvantages: 1) the volume required to provide the physical elasticity, i.e., the spring, is large; 2) there is an inherent problem of electrolytic solution infiltration due to the physically movable structure; and 3) installation is complicated.

[0013] Under the situation that the technology of maximizing the battery capacity is urgently needed, the actual usable volume of the secondary battery is reduced due to the opening and closing device. Therefore, it can be easily recognized that Patent Document 2 is a technology that is used very restrictively or has many disadvantages.

[0014] Therefore, there is a need to develop technologies that can effectively and economically solve the problems associated with cylindrical secondary batteries, such as rapid evaporation of the original electrolytic solution due to initial sealing and commissioning of the battery, shortened battery life, and deteriorated battery performance. Furthermore, as the utilization of secondary batteries gradually increases, minimal deformation of battery modules or battery packs is a prerequisite for replacing conventional can-type batteries.

[0015] (Prior Art Document)

[0016] (Patent Document 1) Korean Patent Application Publication No. 2018-0010389 (January 31, 2018)

[0017] (Patent Document 2) Korean Utility Model Application Publication No. 1998-021641 (July 15, 1998) Summary of the Invention

[0018] Technical issues

[0019] The present invention is made in view of the above problems, and an object of the present invention is to provide a technology that can effectively and economically solve the problems associated with cylindrical secondary batteries, such as rapid evaporation of the original electrolytic solution due to the initial sealing and activation of the battery, shortened battery life, and deterioration of battery performance.

[0020] To this end, the present invention provides a cylindrical secondary battery that can be hermetically sealed after activation of the cylindrical secondary battery. Specifically, an object of the present invention is to provide a cylindrical secondary battery provided with a new flexible input portion, the input portion being configured so that: 1) additional electrolytic solution can be supplied even after hermetically sealing, 2) the performance of hermetically sealing is excellent, 3) even when the cylindrical secondary battery is used in a conventional battery module or a conventional battery pack, compatibility issues due to shell deformation are minimal, 4) the cylindrical secondary battery can be easily and economically manufactured, and 5) the capacity reduction of conventional secondary batteries due to the introduction of technology can be prevented.

[0021] Technical Solutions

[0022] In order to achieve the above-mentioned purpose, the cylindrical secondary battery according to the present invention includes: a cylindrical can, which is composed of a circular bottom part and a cylindrical outer wall connected to the outer periphery of the bottom part; a jelly-roll type electrode assembly, which is accommodated in the cylindrical can, and the jelly-roll type electrode assembly has a structure in which a positive electrode and a negative electrode are wound with a separator inserted between the positive electrode and the negative electrode; and a cover assembly, which is configured to hermetically seal the cylindrical can, wherein a through hole is formed in a part of the bottom part of the cylindrical can, and the through hole is hermetically sealed by the sealing part.

[0023] The bottom portion may be formed to have a curved surface concave toward the inside of the cylindrical secondary battery, and a central portion of the bottom portion may include a flat portion.

[0024] The bottom portion may be configured such that a radius of curvature of the concave curved surface increases from an outer peripheral edge of the bottom portion toward a central portion of the bottom portion.

[0025] The through hole may be provided at a central portion of the bottom portion of the cylindrical can. Specifically, the through hole may be provided at a central portion of the bottom portion of the cylindrical can except for an area of ​​the bottom portion welded to the negative electrode tab.

[0026] The specific shape of the through hole is not limited. For example, the shape of the through hole can be a restorative circular shape, and can be variously changed as needed.

[0027] The sealing portion may be made of a polymer resin. The polymer resin of the cylindrical secondary battery may be a thermoplastic polymer resin or a thermosetting polymer resin, particularly a thermoplastic polymer resin. Specifically, the polymer resin may be an elastomer.

[0028] As a non-limiting example of the sealing portion, the sealing portion may be configured as a plug having a central portion with a radius smaller than a radius of an outer peripheral edge of the plug.

[0029] The plug may be configured such that a protrusion whose radius gradually increases from an end portion toward a central portion of the plug and then abruptly decreases is formed at a portion of the plug configured to be inserted into the cylindrical secondary battery.

[0030] In another aspect, the present invention provides a method for manufacturing a cylindrical secondary battery. The method for manufacturing a cylindrical secondary battery comprises the following steps:

[0031] 1) forming a through hole in a bottom portion of a cylindrical can of a cylindrical secondary battery;

[0032] 2) accommodating the electrode assembly in the cylindrical can and assembling the cap assembly;

[0033] 3) placing the cylindrical secondary battery assembled in step 2) so that the bottom portion faces upward;

[0034] 4) injecting an electrolytic solution through the through-hole and starting or initially charging and discharging the cylindrical secondary battery; and

[0035] 5) Use the sealing portion to airtightly seal the through hole.

[0036] The method may further include injecting additional electrolytic solution between step 4) and step 5), and the hermetic sealing step of step 5) may include hermetically sealing the through hole using a plug having a central portion with a radius smaller than a radius of an outer periphery of the plug.

[0037] The hermetic sealing step of step 5) may include injecting a thermoplastic polymer resin into the through-hole to cover the negative electrode tab region welded to the cylindrical can, so as to hermetically seal the through-hole.

[0038] The present invention can be provided through various combinations of technical solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a vertical cross-sectional view of a conventional general cylindrical secondary battery.

[0040] Figure 2 is a cross-sectional view of a cylindrical secondary battery provided with a through hole according to an embodiment of the present invention and a cross-sectional view of the cylindrical secondary battery in a state where the through hole is hermetically sealed.

[0041] Figure 3 is a cross-sectional view showing lower portions of three cylindrical secondary batteries according to the present invention, each of which is provided with a through hole.

[0042] Figure 4 is a perspective view of a sealing portion according to the present invention.

[0043] Figure 5 is a diagram showing an example in which a through hole is hermetically sealed using a sealing portion according to the present invention.

[0044] Figure 6 is a schematic diagram illustrating an assembling process of a cylindrical secondary battery according to the present invention. DETAILED DESCRIPTION

[0045] Now, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that the preferred embodiments of the present invention can be easily implemented by those skilled in the art. However, when describing the operating principles of the preferred embodiments of the present invention in detail, when the detailed description of known functions and configurations contained herein may obscure the subject matter of the present invention, the detailed description of these functions and configurations will be omitted.

[0046] In addition, the same reference numerals will be used throughout the drawings to refer to parts that perform similar functions or operations. Where a part is referred to as being connected to another part in the specification, this part may not only be directly connected to the other part, but may also be indirectly connected to the other part via other parts. In addition, unless otherwise specified, the inclusion of a particular element does not mean the exclusion of other elements, but rather means that such elements may also be included.

[0047] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0048] Figure 1 is a vertical cross-sectional view showing a conventional generally cylindrical secondary battery. Figure 1 , the cylindrical secondary battery 100 is configured such that the electrode assembly 110 is accommodated in the cylindrical can 120 , the cap assembly 130 is located at an upper portion of the cylindrical can, and the cylindrical secondary battery 100 is hermetically sealed by a crimping gasket 133 .

[0049] The cover assembly 130 includes a vent member 132 located at the lower portion of the top cover 131 and wrapping around the outer periphery of the top cover, and a current interruption member 135 located at the lower portion of the vent member 132 and contacting the central portion of the vent member 132. A lower gasket 134 is located at the outer periphery of the current interruption member 135 and is configured to prevent the vent member 132 and the current interruption member 135 from contacting each other at portions of the vent member 132 other than the central portion of the vent member 132.

[0050] The positive electrode tab 111 of the electrode assembly 110 is attached to the lower surface of the current interruption member 135 so that the cap assembly 130 serves as a positive terminal, and the negative electrode tab 112 is coupled to the bottom portion of the cylindrical can 120 by welding.

[0051] Figure 2 2 is a cross-sectional view of a cylindrical secondary battery 200 provided with a through hole according to an embodiment of the present invention and a cross-sectional view of the cylindrical secondary battery 200 in a state where the through hole is hermetically sealed.

[0052] Reference Figure 2The cylindrical secondary battery 200 according to the present invention is a cylindrical secondary battery 200 including: a cylindrical can 220 composed of a circular bottom portion and a cylindrical outer wall connected to the outer circumference of the bottom portion; a jelly-roll-type electrode assembly 210 accommodated in the cylindrical can 220, the jelly-roll-type electrode assembly having a structure in which a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes are wound; and a cap assembly 230 configured to hermetically seal the cylindrical can 220. A through hole 250 is formed in a portion of the bottom portion of the cylindrical can 220, and the through hole 250 is hermetically sealed by a sealing portion 260.

[0053] Figure 3 is a cross-sectional view showing lower portions of three cylindrical secondary batteries each provided with a through hole according to the present invention.

[0054] Reference Figure 3 , the bottom portion of the secondary battery may be flat ( Figure 3 ), or may be formed to have an inwardly concave curved surface, wherein the curvature radius of the concave curved surface may increase from the outer periphery of the bottom portion toward the central portion ( Figure 3 Alternatively, the central portion of the bottom portion may comprise a flat portion ( Figure 3 (see the third figure of the figure).

[0055] from Figure 2 and Figure 3 It can be seen that the through hole 250 is provided at a central portion of the bottom portion of the cylindrical can 220 excluding an area of ​​the bottom portion welded to the negative electrode tab 212 .

[0056] Figure 4 is a perspective view of a sealing portion according to the present invention.

[0057] Reference Figure 4 Each of the sealing portion 260 and the sealing portion 264 may be made of a polymer resin. Each of the sealing portion 260 and the sealing portion 264 may be made of a thermoplastic polymer resin or a thermosetting polymer resin, particularly a thermoplastic polymer resin. In addition, the polymer resin may be an elastomer.

[0058] exist Figure 4 The sealing portion 260 shown at the upper portion of the may be configured as a plug having a central portion with a radius smaller than an outer peripheral edge of the plug, and Figure 4The sealing portion 264 shown at the lower portion may be configured such that a protrusion is formed at a portion of the sealing portion configured to be inserted into the cylindrical secondary battery 200 , the radius of which gradually increases from the end of the plug toward the central portion and then abruptly decreases.

[0059] Figure 5 : is a diagram showing an example in which a through hole is hermetically sealed using a sealing portion according to the present invention. Figure 5 , the sealing portion 260 can be inserted through the through hole to hermetically seal the through hole ( Figure 5 Alternatively, in the airtight sealing step, a thermoplastic polymer resin may be injected into the through hole 250 so as to cover the area where the negative electrode tab 212 is welded to the cylindrical can 220, thereby forming the sealing portion 262.

[0060] Figure 6 is a schematic diagram illustrating an assembling process of a cylindrical secondary battery according to the present invention.

[0061] In the present invention, a cylindrical secondary battery is assembled as follows.

[0062] The following steps are performed: a step of forming a through hole in the bottom portion of a cylindrical can of a cylindrical secondary battery; a step of accommodating an electrode assembly in the cylindrical can and assembling a cap assembly ( Figure 6 1); rotating the cylindrical secondary battery so that the bottom portion of the cylindrical secondary battery with the cap assembly mounted faces upward and the cap assembly faces downward, injecting an electrolytic solution through the through-hole and enabling the cylindrical secondary battery or performing an initial charge and discharge on the cylindrical secondary battery ( Figure 6 2); and a step of hermetically sealing the through hole using a sealing portion ( Figure 6 3), thereby completing the final cylindrical secondary battery ( Figure 6 4).

[0063] In addition, the present invention may provide a battery pack including the cylindrical secondary battery.

[0064] In particular, the battery pack can be used as a power source for devices that require high temperature resistance, long cycle characteristics, high rate characteristics, etc. Specific examples of the devices may include: mobile electronic devices; wearable electronic devices; power tools driven by battery-powered motors; electric vehicles such as electric vehicles (EVs), hybrid electric vehicles (HEVs), or plug-in hybrid electric vehicles (PHEVs); electric two-wheeled vehicles such as electric bicycles (E-bikes) or electric scooters (E-scooters); electric golf carts; and energy storage systems. However, the present invention is not limited thereto.

[0065] The structure and manufacturing method of the device are well known in the art to which the present invention pertains, and therefore a detailed description thereof will be omitted.

[0066] Those skilled in the art to which the present invention pertains will appreciate that various applications and modifications are possible within the scope of the present invention based on the above description.

[0067] (Explanation of Reference Numerals)

[0068] 100, 200: Cylindrical secondary batteries

[0069] 110, 210: electrode assembly

[0070] 111: Positive terminal lug

[0071] 112, 212: Negative terminal lug

[0072] 120, 220: cylindrical tank

[0073] 130, 230: Cover assembly

[0074] 131: Top cover

[0075] 132: Ventilation components

[0076] 133: Compression washer

[0077] 134: Lower washer

[0078] 135: Current interruption component

[0079] 250: Through hole

[0080] 260, 262, 264: Sealing part

[0081] Industrial Applicability

[0082] As apparent from the above description, in the present invention, the bottom portion of the cylindrical secondary battery is provided with a through hole, the through hole is hermetically sealed using a polymer resin or rubber, and even after the through hole is hermetically sealed, additional electrolytic solution can be supplied using a syringe.

[0083] Furthermore, the bottom of the secondary battery is concave. Therefore, even when the pressure inside the secondary battery is high, the bottom of the secondary battery is prevented from deforming. Since the center of the bottom is concave, the pressure inside the secondary battery is evenly distributed, resulting in excellent sealing of the secondary battery.

[0084] In addition, since a sealing portion is added to the central portion of the bottom portion of the cylindrical secondary battery, even in the case where the cylindrical secondary battery is used in a conventional battery module or a conventional battery pack, compatibility problems due to case deformation are rare.

[0085] In addition, the bottom portion of the cylindrical secondary battery is perforated and a sealing portion is added to the bottom portion. The perforation is performed easily and quickly, which is economical.

[0086] In addition, the sealing portion is added in a state in which the thickness of the sealing portion is minimized, whereby the capacity of the conventional secondary battery is not reduced.

[0087] Furthermore, the sealing portion is made of a thermoplastic polymer resin or rubber. Therefore, when a portion of the thermoplastic polymer resin or rubber is injected into the can to hermetically seal the can, the thermoplastic polymer resin or rubber surrounds the welded area of ​​the negative electrode tab to the inner bottom of the can. Consequently, even when the cylindrical secondary battery is used in a vehicle subject to strong external shock and vibration, damage to the welded area in the can can be prevented.

Claims

1. A cylindrical secondary battery comprising: a cylindrical tank, the cylindrical tank comprising a circular bottom portion and a cylindrical outer wall connected to the outer periphery of the bottom portion; a jelly-roll type electrode assembly housed in the cylindrical can, the jelly-roll type electrode assembly having a structure in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; and a cap assembly configured to hermetically seal the cylindrical can, wherein a through hole formed in a portion of the bottom portion of the cylindrical can, the through hole being hermetically sealed by a sealing portion; and The sealing portion made of a thermoplastic polymer resin covers a region where the negative electrode tab is welded to the bottom portion by injecting the thermoplastic polymer resin into the through hole.

2. The cylindrical secondary battery according to claim 1, wherein The bottom portion is formed to have a curved surface that is concave toward an inner side of the cylindrical secondary battery.

3. The cylindrical secondary battery according to claim 2, wherein A central portion of the bottom portion includes a flat portion.

4. The cylindrical secondary battery according to claim 2, wherein The bottom portion is configured such that a radius of curvature of the concave curved surface increases from an outer peripheral edge of the bottom portion toward a central portion of the bottom portion.

5. The cylindrical secondary battery according to claim 1, wherein The through hole is provided at a central portion of the bottom portion of the cylindrical can excluding a region of the bottom portion to which a negative electrode tab is welded.

6. The cylindrical secondary battery according to claim 5, wherein The through hole is circular.

7. A method for manufacturing the cylindrical secondary battery according to any one of claims 1 to 6, the method comprising the steps of: 1) forming a through hole in a bottom portion of a cylindrical can of a cylindrical secondary battery; 2) accommodating an electrode assembly in the cylindrical can and assembling a cap assembly; 3) placing the cylindrical secondary battery assembled in step 2) so that the bottom portion faces upward; 4) injecting an electrolytic solution through the through-hole and starting the cylindrical secondary battery or performing initial charging and discharging on the cylindrical secondary battery; as well as 5) The through hole is hermetically sealed using the sealing portion made of a thermoplastic polymer resin, and the region where the negative electrode tab is welded to the bottom portion is covered with the sealing portion.

8. The method according to claim 7, further comprising injecting additional electrolytic solution between step 4) and step 5).

9. The method according to claim 7, wherein: The hermetic sealing step of step 5) includes injecting a thermoplastic polymer resin into the through hole to cover the region of the negative electrode tab welded to the cylindrical can, so as to hermetically seal the through hole.

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