KR20080042966A - Process for preparation of prismatic secondary battery - Google Patents

Abstract

A method for preparing a prismatic secondary battery is provided to prevent the battery cell from thickening by effectively discharging gases generated during pre-formation and formation steps. A method for preparing a prismatic secondary battery includes the steps of: (a) putting an electrode assembly into a prismatic can, and combining a top cap to an opened top end of the prismatic can, wherein the top cap comprises a dented part(200) having a micro hole(220), and an electrolyte injection hole(130); (b) putting a metal plate(210) on the dented part to seal the micro hole; (c) injecting an electrolyte through the electrolyte injection hole, and performing charging for pre-formation; (d) discharging gas generated during the pre-formation, sealing the electrolyte injection hole, and performing full charging/full discharging and high-temperature aging for formation; and (e) punching the metal plate to discharge gas generated during the formation step, and welding a metal plate onto the micro hole.

Description

Process for Preparation of Square Secondary Battery {Process for Preparation of Prismatic Secondary Battery}

1 is a plan view of a bottom surface of a top cap used in a square battery according to the prior art;

2 is a plan view and a partial cross-sectional view of a bottom surface of a top cap used in a square battery according to one embodiment of the present invention;

3A to 3C are schematic cross-sectional views of manufacturing steps according to the method of manufacturing a rectangular secondary battery of the present invention;

4 is a schematic diagram of an assembly process of a square battery according to an embodiment of the present invention.

The present invention relates to a method of manufacturing a secondary battery in which an electrode assembly is embedded in a rectangular can. More specifically, the electrode assembly is inserted into a rectangular can, and a metal plate is placed on an indentation where the fine through hole of the top cap is perforated. After coupling and injecting the electrolyte through the electrolyte inlet, the filling is performed for the first activation, the gas generated is discharged and the electrolyte inlet is sealed, and the full charge / full discharge and high temperature aging are performed for the second activation. The present invention relates to a method for manufacturing a rectangular secondary battery comprising a process of welding a metal plate to a fine through hole after discharging the gas generated by punching the metal plate.

As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing, and accordingly, a lot of researches on batteries that can meet various demands have been conducted.

Typically, there is a high demand for lithium secondary batteries such as high energy density, discharge voltage, and output stability lithium ion polymer battery in terms of battery material. There is a high demand for square batteries and pouch-type batteries that can also be used as batteries of stacked battery modules.

An electrode assembly in which a battery reaction occurs in a secondary battery generally has a structure in which an electrolyte solution is impregnated into a cathode plate coated with a cathode active material, an anode plate coated with an anode active material, and a separator. The electrode assembly of the secondary battery is classified into a jelly-roll type (wound) electrode assembly and a stacked type (laminated) electrode assembly according to its structure. Thus, a rectangular battery is produced by storing a jelly-roll type electrode assembly or a stacked type electrode assembly in a rectangular metal case.

In general, a rectangular battery is assembled with an electrode assembly inside a rectangular metal can, an upper insulator mounted on an open top thereof, and then welded with a top cap on it, and then injected with an electrolyte to seal it. At this time, a predetermined amount of electrolyte is injected and the primary filling (pre-formation) is performed to activate the battery without sealing the electrolyte inlet, and the gas generated in the first activation process is discharged through the electrolyte inlet. After the electrolyte is injected again, the electrolyte inlet is sealed. Then, secondary charging (secondary activation) by full charge / full discharge and high temperature aging is performed.

Gas generated in a large amount during the first activation process in the manufacturing process is discharged through the electrolyte inlet. However, the additional gas generated through the charging and discharging of the battery cell and the exposure to the high temperature during the secondary activation process is sealed in the electrolyte injection hole of the top cap, and thus is not discharged to the outside and is in a pressurized state. The internal pressure of the battery cell causes a problem of pushing the battery can outward to increase the thickness of the battery cell.

In order to solve this problem, Korean Patent Registration No. 0615155 has a gas discharge port other than the electrolyte injection hole formed on one side of the rectangular can body, and after performing the charge / discharge test of the battery cell in a state where the gas discharge port is closed with a metal sheet. In addition, the structure of sealing the metal thin plate of the gas outlet by discharging the internal gas and inserting and welding the plug into the broken hole is sealed.

However, since the body thickness of the rectangular can is generally significantly thinner than the top cap area, when the metal sheet is welded to the gas outlet of the body of the can, or when the plug is welded to the hole which is broken after the charge / discharge test, the rectangular can is wrinkled. There is a high possibility of deformation such as losing phenomenon, and the assembly process is complicated.

In addition, in Korean Patent No. 0319111, in order to prevent the volume expansion of the battery due to the gas generated during the initial charging of the assembled secondary battery, a gas outlet is formed on the cap plate and an inlet tube extending upward from the insulator is connected to the gas outlet. It suggests a technology configured to communicate.

However, the patent requires a manufacturing of an insulator including a suction pipe, and a process of manufacturing a battery is very complicated and requires a high level of difficulty, such that a small suction pipe must be precisely matched to a gas outlet during the assembly of the battery. Have

In addition, the patents refer only to the primary battery activation process, which is the initial charging stage after battery manufacture, and to remove the internal gas during the secondary battery activation process for activating the battery, which is the final stage of the battery manufacturing process, and screening out defective products. The method is silent. That is, the patents do not provide a technology that can discharge the gas generated in the second activation process.

As the use of high-capacity electrodes has increased recently, the amount of internal gas generated is higher than before, and the gas inside the cell is removed during the high temperature ripening step as well as the first activation process, which is the initial charging process for battery activation. Therefore, there is a high need for a technology capable of reducing cell thickness.

Accordingly, an object of the present invention is to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

After extensive research and various experiments, the inventors of the present application forge in a state in which a fine through hole for exhausting gas is formed on one side of the top cap to form an indentation having a small step, and until the second activation process. After the metal plate is sealed in the indentation part, the metal plate part is punched out after the second activation process, the gas is discharged, and then welded to seal the fine through hole, so that not only the primary activation process but also the gas generated during the secondary activation process can be effectively It was confirmed that the discharge can be significantly prevented from increasing the thickness of the battery cell, and came to complete the present invention.

The method for manufacturing a rectangular secondary battery according to the present invention is a method for manufacturing a secondary battery in which an electrode assembly is incorporated in a rectangular can,

(a) inserting an electrode assembly into the rectangular can, and coupling a top cap having an indentation in which a fine through hole is formed and an electrolyte injection hole to an open upper end of the rectangular can;

(b) temporarily attaching a metal plate on the indentation to seal the fine through hole;

(c) injecting electrolyte through the electrolyte injection hole and performing charging for pre-formation;

(d) sealing the electrolyte inlet after discharging the gas generated in the first activation process, and performing full charge / full discharge and high temperature aging for the second activation;

(e) punching the metal plate to discharge the gas generated during the second activation process and welding the metal plate to the fine through hole;

It is configured to include.

Therefore, according to the manufacturing method of the present invention, the gas generated during the first activation process, which is the initial charging step in manufacturing the battery, is discharged to the outside through the electrolyte injection hole, and the gas generated during the secondary activation process is located above the indentation of the top cap. By punching out the metal plate is bonded to the outside through the fine through-hole formed in the indentation, it is possible to completely prevent the increase in the thickness of the battery cell due to gas, thereby reducing the initial thickness of the battery cell Can be greatly reduced.

The 'activation' process is charging performed in the process of manufacturing a battery, and means a process of supplying electrical energy to the rectangular secondary battery to change the electrochemical energy, and the 'first activation' process is a process of manufacturing the battery. In the first charging step, the 'secondary activation' process is a charge and discharge process performed in the last step in the battery manufacturing process, and proceeds by the method of full charge, full discharge and high temperature aging (aging: Aging).

In addition, charging and discharging of the secondary activation step is carried out for the purpose of checking the capacity of the battery and sorting out defective products together with activation of the battery cell, and high temperature aging is carried out for the purpose of substantially selecting the defective products.

For example, the high temperature aging process maintains a battery cell at a temperature of 50 to 60 ° C. for 24 hours, and then checks the voltage of the battery cell. Check for defects. That is, when a minute short is present in the manufacturing process of the battery, the battery cell is brought to a high temperature state and the defect can be confirmed within a short time by promoting the progress of the minute short.

In the step (a), if the metal plate is preliminarily bonded to the indentation of the top cap before the top cap is coupled to the open top of the rectangular can, the step (b) is omitted and the step (c) is performed. It can be prepared by reducing the two steps (a) and (b) into one step. That is, by coupling the top cap to which the metal plate is preliminarily coupled to the open upper end of the rectangular can, the number of manufacturing processes can be reduced from the above five steps to four steps.

The temporary bonding of the metal plate on the indentation in which the fine through holes are drilled is to prevent the electrolyte from being ejected through the fine through holes in the first and second activation processes. For this purpose, the temporary coupling method of the metal plate may vary, for example, it may be formed by a bonding, welding or mechanical fastening method.

The square can and the metal plate are preferably aluminum or an aluminum alloy, in consideration of ease of processing and mechanical strength of a certain level, but are not limited thereto.

The diameter of the fine through hole formed in the indentation portion of the top cap is not particularly limited as long as it can discharge the gas inside the battery cell, but preferably has a size of 0.1 to 0.5 mm. If the diameter of the fine through hole is smaller than 0.1 mm, it may not be easy to discharge the gas within a short time. If the diameter of the fine through hole is larger than 0.5 mm, the welding area may become large and the sealability may be reduced.

The indentation formed on one side of the top cap is preferably formed in a small size so as not to substantially cause a decrease in strength of the top cap. In one preferred example, the diameter of the indentation may be in the range of 0.5 to 5 mm, which is larger than the diameter of the fine through hole, and the depth of the indentation may be formed to a depth of 0.2 to 0.6 mm based on the top surface of the top cap. . If the indentation is too small or the depth is too shallow, it may not be easy to break by punching the metal plate, and the gas may not be easily released during the breaking process. On the contrary, if the indentation is too large or too deep, the top cap It is not preferable because it may cause a decrease in strength.

Such indentation may be formed, for example, by a forging method by a portion corresponding to the lower portion of the top cap, where the 'forging method' is performed by using a mechanical method of pressing a solid metal material with a member such as a die. It means the operation method to make material into a certain shape.

The indentation part is sealed in its fine through hole during activation by the temporary coupling of the metal plate, and is utilized as a passage for discharging pressurized gas while punching after the secondary activation process, and then the fine sealing part is welded. Is sealed.

The metal plate is not particularly limited as long as it is a structure capable of performing such a role, and in one preferred embodiment, the outer diameter of the upper portion is larger than the inner diameter of the indentation portion, and the step is vertically crossed so that the lower portion can be inserted into the indentation portion. In the state where the metal plate is temporarily coupled on the indentation portion, the bottom surface is spaced apart from the top surface of the indentation portion to a height that allows punching, so that the center portion of the metal plate is broken during the punching operation to the upper surface of the indentation portion. It may be a structure in which gas is discharged to the outside of the top cap through a space formed while being in close contact.

As a result, in the above structure, the metal plate forms a tentatively coupled state in which the upper part of the large outer diameter is coupled on the outer circumferential surface of the indent and the lower end is spaced apart from the upper surface of the indent. Then, during the punching operation, the lower portion of the small outer diameter is cut off and falls onto the top surface of the indentation portion, and the pressurized gas may be discharged through the fine through hole through the separation space generated in this process. Therefore, it is preferable that the lower part of the metal plate is smaller than the inner diameter of the indentation portion so that a passage for discharging the pressurized gas can be secured.

The thickness of the metal plate is preferably formed to a thickness of 0.1 to 1 mm. If the thickness is too thin, it may not be easy to be temporarily bonded and it may be difficult to provide a desired sealability in the subsequent welding process, and if too thick, punching This may not be easy, so it is not preferred.

In one preferred embodiment, a predetermined notch is formed at a position corresponding to the outer diameter of the lower portion of the upper portion of the metal plate, so that it can be easily cut along the notch during the punching operation.

The welding of the metal plate to the fine through hole may be preferably performed by laser welding, and 'laser welding' refers to a welding method of heating and melting and attaching a metal of a desired part with a laser beam.

In the manufacturing method of the present invention, the activation process of the battery can be carried out by a known method, for example, in the first activation process, since the positive and negative active materials change from a low state to a high energy state, In order to supply a low current for a relatively long time so that the battery can be stably charged without difficulty, it may be performed by charging in a low C-rate and / or a multi-step process.

The 'C-rate' is a current flowing when the battery capacity is released in one hour, the 'low C-rate and multi-step process' is to charge while increasing the capacity sequentially in a slow charging method, not a fast charging method it means.

The present invention also provides a secondary battery produced by the above method.

Specifically, the secondary battery according to the present invention is a secondary battery in which the electrode assembly is embedded in a rectangular can, and an electrolyte injection hole is formed at one side of the top cap coupled to an open upper end of the rectangular can, and the other side is configured to discharge gas. An indentation through which the micro through hole is perforated is formed, and the micro through hole has a structure in which the micro through hole is sealed by a metal plate which is punched and welded after being bonded to the indentation in the battery manufacturing process.

The secondary battery according to the present invention may be variously applied regardless of the type and appearance of the battery cell, and may be preferably a lithium secondary battery.

Since other components, such as an electrode assembly constituting the secondary battery, are known in the art, a detailed description thereof will be omitted herein.

Hereinafter, the content of the present invention will be described with reference to the drawings, but the scope of the present invention is not limited thereto.

1 is a plan view of a bottom surface of a top cap according to the prior art used in a square battery, and FIG. 2 is a plan view and a portion of a bottom surface of a top cap according to an embodiment in the square battery of the present invention. A cross section is shown.

Referring to these drawings, the top cap 100 is made of a metal plate, such as aluminum or aluminum alloy, in the state that the connection member 110 for the protruding terminal in the center is electrically insulated by the gasket 120 of the insulating material Formed. Such a connection member 110 is welded to the cathode of the electrode assembly (not shown), the anode of the electrode assembly is welded to the top cap 100 itself.

One side of the top cap 100 is perforated electrolyte injection hole 130, the electrolyte injection hole 130 in the state that the top cap 100 is coupled to the open top of the rectangular can (not shown) containing the electrode assembly The electrolyte is injected through.

In the top cap 100 according to the present invention, as shown in FIG. 2, an indentation portion 200 is formed at a predetermined depth from an upper end surface thereof at an opposite portion of the electrolyte injection opening 130, and an indentation portion 200 is provided. ), The fine through hole 220 is formed to discharge the gas discharged in the secondary activation process for battery activation and defective product selection to the outside.

A metal plate 210 of a predetermined shape is temporarily coupled to the indentation 200, and the fine through hole 220 of the indentation 200 is substantially sealed by the metal plate 210 to which the indentation 200 is coupled.

3A to 3C are cross-sectional schematic diagrams according to the method of manufacturing a rectangular secondary battery of the present invention.

First, referring to FIG. 3A, an electrode assembly (not shown) is inserted into a rectangular can (not shown), and the indentation part 200 and the electrolyte injection hole (not shown) in which the fine through hole 220 is perforated are inserted. The top cap 100 is formed is coupled to the open upper end of the rectangular can, and then welded to the metal plate 210 on the indentation 200, by temporarily bonding, thereby sealing the fine through-hole 220. In some cases, the top cap 100 may be coupled to the rectangular can after the metal plate 210 is temporarily coupled onto the indentation 220.

The metal plate 210 has an outer diameter R ₁ of the upper portion 212 greater than an inner diameter r ₁ of the indentation portion 200, and an outer diameter R ₂ of the lower portion 214 has an inner diameter of the indentation portion 200. It is made of a step structure smaller than r ₁ ), the upper part 212 is coupled to the structure in which the lower part 214 is introduced into the indentation 200 while covering the top surface of the top cap 100. In such a temporary state, the micro through hole 220 is sealed by the metal plate 210.

In addition, the bottom surface 216 of the metal plate 210 is spaced apart from the top surface 202 of the indentation 200 by a predetermined height, and the upper portion 212 of the metal plate 210 has a lower portion 214. The notch 218 is formed in the position corresponding to an outer diameter. Thus, while applying a strong pressure to the upper portion of the metal plate 210, the lower portion 214 is cut along the notch 218 toward the top surface 202 of the indentation 200, that is, the fine through hole 220 May fall onto the bed.

This process can be easily understood with reference to FIG. 3B. After performing full charge, full discharge and high temperature aging in the secondary activation process, a predetermined die (not shown) is used to cover the center top of the metal plate. When pressurized and punched, the side portion 212a corresponding to the outer peripheral surface portion of the upper portion and the central portion 214a corresponding to the lower portion are broken and a passage for gas discharge is instantaneously secured. That is, a passage communicating with the outside is made for a short time while the central portion 214 falls and falls onto the fine through hole 220, and the pressurized gas can be easily discharged through the passage.

Then, as shown in FIG. 3C, when the laser is irradiated, some of the melt is injected into the fine through hole 220 while the side portion 212a and the center portion 214a of FIG. 3B are melted, and solidified to seal. Therefore, the fine through hole 220 is effectively sealed by the molten solidified metal plate 210a.

4 schematically shows an assembly process of a square battery according to an embodiment of the present invention.

Referring to FIG. 4, the electrode assembly 410 is inserted into the rectangular metal can 400 in such a manner that the positive electrode 412 and the negative electrode 414 protrude upward. The electrode assembly 410 is made by winding the positive electrode sheet and the negative electrode sheet in a state in which a separator is interposed therebetween, and then compressing the electrode assembly 410 into a rectangular shape.

The upper insulating member 300 is mounted on the upper end of the electrode assembly 410 with both protruding supports 320 facing upwards. In this mounting process, the anode 412 and the cathode 414 of the electrode assembly 410 are inserted into the opening 330 to protrude from the insulating member 300.

The top cap 100 is coupled to the upper end of the metal can 400 by welding while the upper insulating member 300 is mounted. The metal plate 210 is temporarily coupled to the indentation 200 of the top cap 100, as shown in FIG. 3A, so that the fine through hole 220 remains sealed.

After the assembly process is completed, a predetermined amount of the electrolyte is injected through the electrolyte injection hole 130, and after the first activation, the internal gas is discharged through the electrolyte injection hole 130.

After replenishing the electrolyte and sealing the electrolyte injection port 130, the secondary activation is performed.

Then, as shown in FIG. 3b, the gas generated in a large amount inside the electrode assembly 410 by punching the metal plate 210 to the outside of the top cap 100 through the fine through hole 220 of the indentation 200. To be discharged.

Finally, as shown in FIG. 3C, the rectangular battery is completed by laser welding to seal the fine through hole 220.

Those skilled in the art to which the present invention pertains will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

As described above, the rectangular secondary battery according to the present invention is formed in the indentation having a small step by forging in the perforated state through the fine through-hole for gas discharge on the inner surface of the top cap, and until such a secondary activation process After the metal plate is sealed and punched out after the second activation process to discharge the gas, laser welding is applied to the upper part of the indentation to seal the fine through hole, thereby preventing the battery cell from increasing in thickness. There is.

Claims (15)

A method for manufacturing a secondary battery in which an electrode assembly is embedded in a rectangular can, (a) inserting an electrode assembly into the rectangular can, and coupling a top cap having an indentation in which a fine through hole is formed and an electrolyte injection hole to an open upper end of the rectangular can; (b) temporarily attaching a metal plate on the indentation to seal the fine through hole; (c) injecting electrolyte through the electrolyte injection hole and performing charging for pre-formation; (d) sealing the electrolyte inlet after discharging the gas generated in the first activation process, and performing full charge / full discharge and high temperature aging for the second activation; And (e) punching the metal plate to discharge the gas generated during the second activation process and welding the metal plate to the fine through hole; Manufacturing method comprising a. The method according to claim 1, wherein a metal plate is temporarily coupled to the indentation portion of the top cap in the step (a), and the step (c) is omitted and the step (c) is performed. The method according to claim 1, wherein the temporary bonding of the metal plate to the indentation is achieved by bonding, welding or mechanical fastening. The method of claim 1, wherein the rectangular can and the metal plate are made of aluminum or an aluminum alloy. The method of claim 1, wherein the fine through hole has a diameter of 0.1 to 0.5 mm. The method of claim 1, wherein the indentation has a diameter of 0.5 to 5 mm. The method of claim 1, wherein the indentation portion is formed to a depth of 0.2 to 0.6 mm. The method of claim 1, wherein the indentation portion is formed by a forging method. According to claim 1, wherein the outer diameter of the upper portion of the metal plate is larger than the inner diameter of the indentation, the step is formed in a vertical cross-section so that the lower portion can be inserted into the indentation, the metal plate is coupled to the indentation state And the bottom surface of the metal plate is spaced apart from the top surface of the indentation to a height capable of punching. 10. The manufacturing method according to claim 9, wherein a predetermined notch is formed at a position corresponding to an outer diameter of a lower portion of the metal plate. The method of claim 1, wherein the metal plate has a thickness of 0.1 to 1 mm. The method of claim 1, wherein the first activation process is performed by filling with a low C-rate and / or a multi-step process. The method of claim 1, wherein the welding of the metal plate to the fine through hole is performed by laser welding. A secondary battery in which an electrode assembly is embedded in a rectangular can, in which an electrolyte injection hole is formed at one side of a top cap coupled to an open upper end of the rectangular can, and an indentation in which a fine through hole for gas discharge is formed is formed at the other side. And the fine through hole is sealed by a metal plate which is punched and welded after being bonded onto the indentation in the manufacturing process of the battery. 15. The secondary battery of claim 14, wherein the battery is a lithium secondary battery.

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