KR100551395B1 - Method of fabricating pouch type lithium secondary battery - Google Patents

Abstract

Disclosed is a method for manufacturing a lithium secondary battery.

The present invention provides a method of forming a pouch-type bare cell battery in which grooves are formed, and bending edge regions of both sides of the electrode tab and subsequent side edges of the bare cell battery in a direction opposite to the direction in which the grooves are formed. Attaching a protective circuit structure to the core pack battery, and mounting the core pack battery in a hard case to form a hard pack battery.

Therefore, in the pouch type lithium secondary battery, the end of the pouch exposed metal foil is shorted with the negative electrode tab through the protective circuit structure forming the core pack, the conductor in the center of the accessory circuit mounted inside the hard case, and the metal foil of the pouch is corroded. The phenomenon can be prevented.

Description

Manufacturing method of pouch type lithium secondary battery {Method of fabricating pouch type lithium secondary battery}

1 is a perspective view showing a state before a pouch is sealed in an example of a conventional pouch type lithium secondary battery;

FIG. 2 is a perspective view showing a folded state of two opposite sides where electrode tabs are not drawn out in a conventional bare cell state; FIG.

3 is a perspective view schematically showing a state in which a protective circuit board is coupled to a bare cell during a process of forming a lithium secondary battery according to an embodiment of the present invention;

4 is a schematic cross-sectional view of a battery in a hard pack state formed according to the present invention cut perpendicularly to the direction in which the electrode leads of the electrode assembly are drawn out.

* Explanation of symbols for the main parts of the drawings

10: upper pouch 11: pouch membrane

13: metal foil 20: lower pouch

21: groove 23,43: edge portion

30 electrode assembly 100 pouch

31: anode 33: separator

35: negative electrode 37: negative electrode tab

38: positive electrode tab 39: tate

51: protection circuit board 60: hard case

63: accessory circuit 65: double-sided tape

The present invention relates to a method of manufacturing a lithium secondary battery using lithium ions, and more particularly, a method of manufacturing a pouch type lithium secondary battery having a form in which an electrode structure including a positive electrode, a negative electrode, and a separator is accommodated in a pouch. It is about.

Lithium secondary batteries use nonaqueous electrolytes because of their reactivity with lithium. This electrolyte may be a solid polymer containing lithium salts, or may be a liquid phase in which lithium salts dissociate in an organic solvent. When the lithium secondary battery is classified according to the type of electrolyte, the lithium secondary battery may be classified into a lithium metal battery using a liquid electrolyte, a lithium ion battery, and a lithium ion polymer battery using a polymer solid electrolyte.

In the case of a fully solid lithium ion polymer battery, there is no problem of leakage of the organic electrolyte, and in the case of a gel type lithium ion polymer battery containing the organic electrolyte, a problem of leakage of the organic electrolyte may occur. However, in the case of a lithium ion polymer battery, the leakage problem of the electrolyte can be prevented in a simpler form as compared with a lithium ion battery using a liquid electrolyte. For example, a lithium ion polymer battery may use a multilayer film pouch consisting of a metal foil and one or more polymer films covering the foil in place of a metal can of a lithium ion battery.

When using a multilayer film pouch, the weight of the battery can be significantly reduced than when using a metal can. Aluminum is usually used as a metal forming a foil in a multilayer film pouch. The polymer film forming the inner layer of the pouch film protects the metal foil from the electrolyte and prevents short circuit between the positive electrode, the negative electrode, and the electrode tabs.

1 is a perspective view showing a state before a pouch is sealed in an example of a pouch-type lithium secondary battery.

Referring to FIG. 1, a general forming method of a pouch-type lithium secondary battery is first formed by folding a rectangular pouch film in the middle to form an upper portion 10 and a lower portion 20 of the pouch. The lower part 20 is provided with a groove 21 in which the electrode assembly can be accommodated by pressing.

The ordinary electrode assembly 30 is wound into a multi-layer film laminated in the order of the anode 31, the separator 33, and the cathode 35 in a spiral shape to form a jelly roll. When winding up the jelly roll, a separator is added to the electrode surface or the inner electrode surface that is exposed to the outside of the roll to prevent a short circuit between the positive electrode and the negative electrode. The formed jelly roll is placed in the lower groove 21 of the pouch film and heated and pressurized in a state in which the edge portion is in close contact with each other to perform pouch sealing.

In order to electrically connect the positive electrode 31 and the negative electrode 35 of the electrode assembly 30 to the outside of the pouch, electrode tabs 37 and 38 or electrode leads are formed at one side of the positive electrode 31 and the negative electrode 35. These electrode tabs 37 and 38 are formed to protrude from the jelly roll in the direction perpendicular to the direction in which the jelly roll is wound, and are drawn out through the sealed side of the pouch.

In the pouch sealing process, in order to enhance adhesion between the polymer film 11 on the inner surface of the pouch and the metal forming the electrode tabs 37 and 38, a specific component may be included on the surface of the polymer film or may have a good adhesive property before sealing. A separate tape 39 may be attached to the electrode tabs where the electrode tabs 37 and 38 adhere to the pouch.

A core pack is formed by attaching an accessory or structure, such as a protective circuit module (PCM) or a positive temperature coefficient (PTC), to a bare cell formed by pouch sealing.

Then, the core pack is built into the hard case and combined to form a completed hard pack battery. The hard case may be formed using a polypropylene resin or the like without a separate circuit or conductor part inside the hard case, but may have a separate accessory circuit or other conductor part inside the hard case depending on the characteristics of the device in which the battery is used. .

FIG. 2 is a perspective view showing a folded state of two opposite sides where electrode tabs are not drawn out in a conventional bare cell state. FIG.

Referring to FIG. 2, in the bare cell, if the hard pack is formed with the edge 23 formed like a flange at the periphery, in particular, the two edges facing each other outside the side through which the electrode leads pass, the hard pack is formed in the hard case. These parts take up unnecessary space. Therefore, while forming the core pack state in the bare cell, the process of folding the edge portion 23 toward the groove in which the electrode assembly is formed is performed.

However, if there is no additional taping at the end of the pouch 100, the aluminum foil forming the pouch film intermediate layer is exposed. In order to reduce the volume of the battery when forming the core pack, the protection circuit board 51 is installed in a space that is not occupied by a groove in which the electrode assembly is embedded in the space between the folded edges 23. As a result, the copper of the negative electrode tab 38 and the aluminum foil of the pouch film may be electrically connected through the conductive portion of the protective circuit board 51 in the step of forming the core pack.

In addition, even when the cathode tab 38 and the aluminum foil of the pouch layer are not directly connected in the core pack state, electrical connection may be made between a portion of the protective circuit board 51 and the aluminum foil. In this state, when the core pack is inserted into the hard case, the aluminum foil exposed at the end of the pouch may be electrically connected to the cathode through the circuit part or other conductive part in the hard case, the protective circuit board, or only through the conductive part in the hard case.

Once the cathode including the aluminum foil of the pouch film and the copper plate is connected directly or indirectly, the aluminum foil of the pouch film may be corroded by electrochemical action, and in particular, the corrosion may be accelerated when an electrolyte leaks from the pouch or the moisture becomes wet. .

If the aluminum foil, which acts as a barrier to moisture and oxygen, continues to corrode, the pouch membrane can no longer prevent water and oxygen from entering the pouch. This is because the diffusion of water molecules and oxygen molecules through the metal is extremely low, but the diffusion of water molecules and oxygen molecules through the polymer film increases with time. As the pouch's blocking ability drops, the battery can fail. That is, when the organic electrolyte of the separator evaporates or when external moisture or oxygen is introduced, abnormalities such as a swelling phenomenon in which pressure increases due to gas generation in a pouch may occur. Brings about.

The present invention is to eliminate the problems described above, in the pouch type lithium secondary battery, the end of the pouch exposed metal foil constituting a layer of the multi-layer pouch film, the protective circuit structure is installed in the pouch bare cell or the protective circuit When the core pack having the structure is mounted in the hard case, a lithium secondary battery manufacturing method capable of preventing corrosion by being electrically connected to other metals forming the electrode of the battery through a protective circuit structure or a conductor in the hard case. The purpose is to provide.

Pouch type lithium secondary battery manufacturing method of the present invention for achieving the above object,

Forming a pouch-type bare cell battery in which grooves are formed,

Bending the edge regions of both sides of the bare cell battery, the sides of which are formed with electrode tabs, and opposite sides of the bare cell battery in a direction opposite to that of the groove,

Attaching a protection circuit structure to the bare cell battery to form a core pack battery;

And mounting the core pack battery in a hard case to form a hard pack battery.
At this time, in the present invention, when installing the accessory circuit and the other conductor portion in the hard case is formed on the inner surface of the side facing the groove of the bare cell battery, so that the groove of the bare cell is adjacent to the conductor portion.

In the present invention, the forming of the pouch-type bare cell battery in which the groove is formed may include forming a groove in the center of a lower portion of a portion of the pouch film formed of two parts, placing an electrode assembly in the groove, and And overlapping the two portions with respect to the reference edge dividing the portions, and sealing the pouch film in the edge region excluding the groove.

delete

In the present invention, the protective circuit structure is preferably installed in a space formed by the outer side of the groove wall and the non-bent edge on the opposite side of the reference side.

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

3 is a perspective view schematically illustrating a state in which a protective circuit board is coupled to a bare cell during a process of forming a lithium secondary battery according to an embodiment of the present invention.

Looking at an example of a method of forming the state of Figure 3, first to form a rectangular pouch membrane formed in one piece, the upper and lower portions of the pouch by folding the middle in the longitudinal direction of one side. The lower portion is provided with a groove in which the electrode assembly can be accommodated by pressing. At this time, the pouch film usually has a multilayer structure formed by coating a polymer film such as polypropylene resin on and under an aluminum metal foil.

In a typical electrode assembly, a multilayer film including a cathode, a separator, and a cathode stacked in a spiral shape is formed in a jelly roll shape. When winding up the jelly roll, a separator is added to the outer or inner electrode surface of the roll to prevent a short circuit between the positive electrode and the negative electrode.

In this case, the positive electrode may be formed by coating a positive electrode active material layer containing lithium-based oxide as a main component on both surfaces of a positive electrode current collector made of a thin metal plate, such as aluminum foil, having excellent conductivity. The positive electrode tab is electrically connected to a region of the positive electrode current collector on which the positive electrode active material layer is not formed.

The negative electrode may be formed by coating a negative electrode active material layer containing a carbon material on both surfaces of a negative electrode current collector made of a conductive metal thin plate, such as a copper foil. The coating may be made by thinly coating the current collector with a paste active material mixed with a conductor, a binder, and other contents. The negative electrode tab is connected to the area | region of the negative electrode collector in which the negative electrode active material layer is not formed also in the negative electrode.

In the electrode assembly in the rolled jelly roll state, the positive electrode tab 38 and the negative electrode tab 37 are arranged side by side at regular intervals, protrude from the jelly roll in a direction perpendicular to the direction in which the jelly roll is wound, It is withdrawn through the pouch through one side of the sealed pouch 100.

The electrode tabs 37, 38 generally take the form of tabs of metal, usually aluminum, copper or nickel. They should have sufficient thickness and dimensions to be the passage of current without a noticeable voltage drop.

In general, a lithium ion polymer battery adopting a pouch type forms a separator and an electrolyte, and the polymer solid electrolyte may be formed in a completely solid type and a gel type containing no organic electrolyte.

In the pouch sealing process, certain components are included on the surface of the polymer film to enhance adhesion between the polymer film on the inner surface of the pouch and the metal forming the electrode tabs 37 and 38, or a separate tape having these components before sealing is used. (37,38) may be attached to the portion where the pouch is attached. In this case, the tape also serves to prevent a short circuit between the two electrodes and the electrode tabs.

Meanwhile, in another embodiment, the positive electrode and the negative electrode, and the positive electrode and the negative electrode tabs 37 and 38 may be disposed with different polarities.

When the edge portion around the lower groove where the electrode assembly is placed and the edge of the upper portion of the pouch layer are in close contact with each other are heated and pressurized, the pouch seal is formed while the inner polymer layer is fused to form a bare cell.

In the bare cell, the edge 43 of both sides connected to the side from which the electrode tab is drawn out is bent in a direction opposite to the direction in which the groove is formed. Therefore, the folded edge 43 of the pouch 100 overlaps the upper surface of the pouch 100. The protective circuit board 51 is connected to the positive and negative electrode tabs 37 and 38 of the bare cell, and a structure such as a positive temperature coefficient (PTC) is attached to form a core pack.

At this time, the protective circuit board 51 is a space formed by the outer side of the wall and the edge of the bent edge formed on the opposite side of the side formed by the bent portion to form the upper and lower portions of the pouch, that is, the side where the electrode tabs 37 and 38 are formed. Is installed on. The electrode tab is bent twice and then connected to the cathode and anode terminals of the protection circuit board 51 by welding or the like. Therefore, the ends of the protective circuit board 951 and the pouch 100 are spaced apart so that a short circuit between the metal foil of the pouch film and the negative electrode tab exposed to the pouch end can be effectively prevented.

4 is a schematic cross-sectional view of a battery in a hard pack state formed according to the present invention cut perpendicularly to the direction in which the electrode leads of the electrode assembly are drawn out.

Referring to FIG. 4, an accessory circuit 63 is further provided on an inner surface of the hard case 60 facing the lower portion of the grooved pouch 100. The presence and configuration of such an accessory circuit 63 is determined in accordance with the characteristics of the electrical and electronic equipment in which the battery is used. The internal space of the hard case 60 is filled with the pouch 100 in which the electrode assembly is installed. A double-sided tape 65 is attached to the upper surface of the pouch 100 to stably mount the battery in the core pack state on the inner surface of the hard case 60. The hard case 60 is usually formed of a synthetic resin material such as polypropylene.

The ends of the edges on both sides of the pouch folded in a conventional manner, indicated by the dotted lines, that is, the portions where the metal foil is exposed, are likely to be in contact with the conductor portion in the accessory circuit 63 on the inner surface of the hard case 60. And, if the conductor portion is directly or indirectly connected to the negative electrode tab, which is not drawn out from the pouch 100, the metal foil is likely to corrode to cause abnormalities in the battery.

However, if both edge portions 43 of the pouch 100 are folded to overlap the upper surface of the pouch as in the method of the present invention, the ends of the pouch 100 are negative through the accessory circuit 63 and other conductive portions in the inner surface of the hard case 60. Is very unlikely to be connected. On the other hand, the upper surface of the pouch 100 and the inner surface of the hard case 60 is fixed with a double-sided tape 65, even if there is a folded edge portion of the pouch only occupies the space secured by the double-sided tape (65). Therefore, increasing the volume of the battery by taking up a separate space can also be prevented.

According to the present invention, a protective circuit structure in which a pouch end exposed a metal foil forms a core pack in a pouch-type lithium secondary battery through a simple process of folding both edges of the pouch in a reverse direction, and an accessory circuit mounted inside the hard case. It is possible to effectively prevent the metal foil from corroding by being shorted to the cathode of the pouch through a conductor in the middle.

Claims (4)

Forming a pouch-type bare cell battery in which grooves are formed; Bending edge regions of both sides of the bare cell battery, the sides of which are formed with electrode tabs, in the opposite direction to the direction in which the grooves are formed; Attaching a protection circuit structure to the bare cell battery to form a core pack battery; And attaching the core pack battery to a hard case having a conductive portion formed on an inner surface of the groove on which the groove is located to form a hard pack battery. The method of claim 1, Forming the pouch-type bare cell battery, Forming a groove in a center of a lower portion of a portion of the pouch film formed of two parts; Positioning an electrode assembly in the groove; And overlapping two portions of the pouch layer around a reference edge dividing the two portions, and heat-sealing the pouch layer in an edge region excluding the groove. 2. delete The method of claim 1, The protective circuit structure is a pouch type lithium secondary battery manufacturing method, characterized in that installed in the space formed by the outer wall of the groove and the edge of the side formed the electrode tab.

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