KR20060000101A - Pouch type lithium secondary battery - Google Patents

Abstract

The present invention relates to a pouch-type lithium secondary battery that can reduce the possibility of ignition by preventing the rapid flow of current in the electrode assembly when the pouch-type secondary battery is penetrated by a conductive material from the outside.

Pouch type secondary battery, electrode assembly, conductive plate, fire prevention

Description

Pouch type lithium secondary battery

1 is a perspective view showing a state before a pouch is sealed in a conventional pouch type lithium secondary battery.

Figure 2 is a perspective view of a pouch-type lithium secondary battery is attached to the upper and lower conductive plates according to an embodiment of the present invention.

Figure 3 is a cross-sectional view A-A of FIG.

4 is a cross-sectional view of a pouch-type lithium secondary battery according to another embodiment of the present invention.

5 is a cross-sectional view of a pouch-type lithium secondary battery according to another embodiment of the present invention.

6 is a cross-sectional view showing the operation of the pouch-type lithium secondary battery according to the present invention.

* Explanation of symbols for the main parts of the drawings

100-Pouch 110-Upper Pouch

120-Lower Pouch Membrane 200-Electrode Assembly

400, 400a, 400b-conductive plate

410, 410a, 410b-upper conductive plate

420, 420a, 420b-bottom conductive plate

430-Connections tab

The present invention relates to a pouch type lithium secondary battery using lithium ions, and more particularly, to a pouch type lithium secondary battery having an electrode assembly including a positive electrode, a negative electrode, and a separator housed in a pouch.

Lithium secondary batteries that can be charged and discharged have higher energy density per unit weight and can be charged faster than conventional lead-acid batteries, nickel-cadmium batteries, nickel-hydrogen batteries, and nickel-zinc batteries due to the light atomic characteristics of lithium. Because of this, research and development on this is actively progressing.

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. A lithium ion polymer battery is a lithium ion polymer battery using a fully solid lithium ion polymer battery containing no organic electrolyte at all according to the type of polymer solid electrolyte and a gel polymer electrolyte containing an organic electrolyte solution. Can be divided.

In the case of a fully solid lithium ion polymer battery, there is no problem of leakage of the organic electrolyte. In the case of a gel-type lithium ion polymer battery containing an organic electrolyte, leakage of the organic electrolyte may occur. However, the leakage of the electrolyte may be prevented in a simpler form compared to a lithium ion battery using a liquid electrolyte. . For example, a lithium ion polymer battery may use a multilayer membrane pouch in place of a metal can of a lithium ion battery.

The use of a multilayer film pouch has the advantage of significantly reducing the weight of the battery than using a metal can. The polymer film forming the inner layer of the pouch film protects the metal foil of the intermediate layer from the electrolyte and prevents a 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 a conventional pouch type lithium secondary battery.

Referring to FIG. 1, a general method of forming a pouch-type lithium secondary battery will be described. First, the pouch is formed by folding the middle of the rectangular pouch film to form an upper portion 10 and a lower portion 20 of the pouch. The lower portion 20 of the pouch is formed with a groove 21 in which the electrode assembly 30 can be accommodated through a press process or the like.

The conventional electrode assembly 30 is formed by winding a separator 33 in which an organic electrolyte is impregnated between the positive electrode plate 31 and the negative electrode plate 35 and wound in the form of a jelly roll 30. . In order to prevent the short circuit between the positive electrode plate 31 and the negative electrode plate 35 when the electrode assembly 30 is formed, the separator 33 is formed to protrude from the upper and lower portions of the electrode assembly 30 to a predetermined height. The formed electrode assembly 30 is placed in the lower groove 21 of the pouch 20 and has three edges except for one side formed by a folded portion of the pouches 10 and 20 among four sides around the lower groove 21. The part is sealed by heating and pressing the upper and lower parts of the pouches 10 and 20 in close contact.

In order to electrically connect the positive electrode plate 31 and the negative electrode plate 35 of the electrode assembly 30 to the outside of the pouches 10 and 20, the electrode tabs 37 and 38 may be formed on one side of the positive electrode plate 31 and the negative electrode plate 35. Electrode leads are formed. These electrode tabs 37 and 38 are formed to protrude from the electrode assembly 30 in a direction perpendicular to the direction in which the jelly roll 30 is wound, and are sealed through one side 23 of the pouches 10 and 20. It is withdrawn through the pouch. The electrode tabs 37 and 38 may be attached with a sealing tape 39 to help seal the pouch.

The pouch film has a form in which the polymer film 11 is laminated on the inside and outside of the metal foil 13. The metal foil generally uses aluminum.

However, when the upper edge portion and the lower edge portion of the pouch are contacted and fused in the sealing process of the pouches 10 and 20, the temperature and pressure of the pouch 10, 20, etc. The polymer layer may be pushed out or damaged to cause a short circuit between the electrode tabs 37 and 38 and the metal foil of the pouch. When the electrode tabs 37 and 38 have a short circuit between the aluminum films 13, there is a high possibility that discharge occurs between the terminals through the aluminum film 13, resulting in overheating and swelling, resulting in poor product yield. Degrades.

In addition, when a short circuit occurs between the negative electrode tab and the aluminum film of the pouch, the aluminum film serving as a barrier continues to corrode, especially in an environment in which an electrolyte is present. Therefore, as the blocking ability of the pouch decreases, problems such as swelling, in which the organic electrolyte inside the jelly roll is evaporated or external moisture or oxygen flows in, may increase pressure due to gas generation in the pouch. Therefore, the aluminum film of the pouch should be careful not to cause a short circuit with the electrode tab, particularly the negative electrode tab.

As described above, a bare cell formed by pouch sealing is attached to a secondary protection device such as a protection circuit (PCM) and a positive temperature coefficient (PTC), which are not shown, to form a core pack. Then, the core pack is built into the hard case and combined to form a completed hard pack battery.

The hard case (not shown) used in the pouch type secondary battery is a simple box type, and is generally formed of a synthetic resin such as polypropylene resin, and thus has a low strength and may be deformed or penetrated according to external pressure.

Since the pouch-type lithium secondary battery is formed by a thin pouch film, unlike the can-type lithium secondary battery, it is easy to be damaged by external shocks. In particular, when the pouch membrane is penetrated by a sharp object such as a pin, the jelly roll inside the pouch is damaged, and the jelly roll may be penetrated by the pin. In this case, the positive electrode plate and the negative electrode plate of the jelly roll are shorted to each other by pins, so that a lot of current flows in an instant, and there is a problem that ignition occurs.

The present invention has been made to solve the problems of the conventional pouch-type lithium secondary battery as described above, when the pouch-type secondary battery is penetrated by a conductive material from the outside to prevent the rapid flow of current in the electrode assembly ignition possibility The purpose is to provide a pouch-type lithium secondary battery that can reduce the.

The present invention for solving the above problems is a pouch-type lithium secondary battery is wound in a jelly roll form is interposed between the positive electrode plate and the negative electrode plate and the separator isolating the positive electrode plate and the negative electrode plate, the positive electrode tab and the negative electrode plate respectively And a pouch type including an electrode assembly and an upper pouch layer and a lower pouch layer, and having an electrode assembly seated and sealed in a groove formed in the lower pouch layer, and having the positive and negative tabs pulled out. In the lithium secondary battery, the upper conductive plate of the electrode assembly which is formed to be at least the same size as the horizontal area of the electrode assembly, and seated on the upper pouch film at a position corresponding to the mounting position of the electrode assembly, and the electrode It is formed to be at least the same size as the horizontal area of the assembly, the upper conductive plate and the front And a conductive plate having a lower conductive plate which is connected to the lower pouch layer and is mounted on the lower portion of the lower pouch layer, and a connection tab which electrically connects the upper conductive plate or the lower conductive plate to the negative electrode tab.

In addition, the present invention, the upper conductive plate and the lower conductive plate may be formed of any one of copper, iron, nickel, aluminum.

In addition, in the present invention, the upper conductive plate and the lower conductive plate are preferably formed in a thickness of 10 to 100 μm.

In addition, the present invention can be electrically connected to the upper conductive plate and the lower conductive plate by a separate connection lead wire.

In addition, the present invention may be formed such that the upper conductive plate and the lower conductive plate are integrally formed to be entirely connected at one side.

In addition, in the present invention, the upper conductive plate and the lower conductive plate may be formed in the form of a cap having an open front surface so that the pouch is inserted therein and is electrically connected to the negative electrode tab by the connection tab formed at a predetermined position. have.

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

2 is a perspective view of a pouch-type lithium secondary battery having conductive plates attached to upper and lower portions thereof according to an embodiment of the present invention.

3 is a cross-sectional view taken along the line A-A of FIG.

4 is a sectional view of a pouch-type lithium secondary battery according to another embodiment of the present invention.

5 is a sectional view of a pouch-type lithium secondary battery according to another embodiment of the present invention.

6 is a cross-sectional view showing the operation of the pouch-type lithium secondary battery according to the present invention.

2 and 3, the pouch-type lithium secondary battery according to the present invention includes a pouch 100, an electrode assembly 200, and a conductive plate 400.

The pouch 100 is generally folded in the middle of the rectangular pouch film formed integrally with respect to the length direction of one side to form the upper pouch film 110 and the lower pouch film 120 of the pouch. The lower portion 120 of the pouch is formed with a groove 130 in which the electrode assembly 200 is to be accommodated through pressing.

The pouch film is typically formed to have a laminated structure covered with a resin layer formed by laminating synthetic resins such as nylon, polypropylene or polyethylene on the upper and lower surfaces of an aluminum thin film, and the synthetic resin on the inner surface of the pouch for sealing is a heat-adhesive material. Is made of. That is, when the edges of the upper pouch layer 110 and the lower pouch layer 120 of the pouch are heated and pressurized, the heat adhesive materials are fused to each other to seal the pouch. After the electrode assembly 200 is accommodated in the groove 130 of the lower pouch layer 120, the pouch 100 is sealed to form a bare cell.

The electrode assembly 200 includes a positive electrode plate 210, a negative electrode plate 230, and a separator 220. The positive electrode plate 210 and the negative electrode plate 230 are formed by being stacked in a jelly-roll shape after being laminated with a separator 220 that insulates the positive electrode plate 210 and the negative electrode plate 230.

The positive electrode plate 210 may be formed by coating a positive electrode active material layer containing lithium-based oxide as a main component on a positive electrode collector made of a thin metal plate having excellent conductivity, such as an aluminum thin film. The negative electrode plate 230 may be formed by coating a negative electrode active material layer containing carbon as a main component on a negative electrode current collector made of a conductive metal plate, for example, copper foil.

The separator 220 is formed of a polymer layer and functions to accommodate an electrolyte together with a separator function between the positive electrode plate 210 and the negative electrode plate 230. At this time, the electrolyte is generally a gel (Gel) type containing the organic electrolyte in order to increase the ionic conductivity.

The positive electrode tab 242 is welded to the positive electrode plate 211, and an end portion of the positive electrode tab 242 protrudes above the electrode assembly 200. A negative electrode tab 244 is also welded to the negative electrode plate 230, and an end portion of the negative electrode tab 244 also protrudes above the electrode assembly 200. The positive electrode tab 242 and the negative electrode tab 244 are arranged side by side at regular intervals in a jelly roll state.

The electrode assembly 200 is placed in the lower groove 130 of the pouch 100 and the edges of the three sides except for one side formed by a portion where the pouch film is folded among four sides around the lower groove 130 are formed in the pouch 100. Seal by heating and pressing in a state where the upper and lower parts are in close contact. At this time, the positive electrode tab 242 and the negative electrode tab 244 are drawn out through one side of the pouch 100 when the pouch 100 is sealed.

The electrode tab 240 is formed of the positive electrode tab 242 and the negative electrode tab 244, and is generally formed of metal, usually aluminum, copper, or nickel. They must have sufficient thickness and dimensions to be the passage of current without significant resistance. In the sealing process of the pouch 100, in order to enhance adhesion between the polymer film on the inner surface of the pouch 100 and the metal forming the electrode tab 240, a specific component is included on the surface of the polymer film, or the adhesion before sealing the pouch 100 is performed. A separate sealing tape 246 having a well-formed component may be attached to a portion where the electrode tab 240 contacts the pouch 100.

The sealing tape 246 attached to the electrode tab 240 not only increases the adhesiveness between the electrode tab 240 and the sealing surface of the pouch 100, but also improves the sealing reliability of the pouch at the portion where the electrode tab 240 passes. Height plays a role. In addition, the sealing tape 246 attached to the electrode tab 240 serves to buffer the difference in pressure between where the electrode tab 246 is and where it is not, thereby improving the sealing state. In addition, the sealing tape 246 also serves to prevent electrical connection between the aluminum thin film of the pouch film and the electrode tab 240.

The conductive plate 400 is formed to include an upper conductive plate 410, a lower conductive plate 420, and a connection tab 440.

The conductive plate 400 is formed of a thin conductive metal such as copper, iron, nickel, aluminum. The conductive plate 400 is preferably formed of a thin film having a thickness of 10 to 100 μm. That is, if the conductive plate 400 is too thin, there is a problem that is easily damaged, if too thick, there is a problem that the thickness of the pouch battery is increased. On the other hand, when the thickness 400 of the conductive plate is increased within the above range, there is a side effect of preventing the external impact, in particular, a sharp mechanism such as a pin from penetrating the conductive plate 400 to some extent.

The upper conductive plate 410 is formed to have an area equal to at least the area of the electrode assembly 200 seated inside the pouch 100, and adhered to an upper surface of the upper pouch layer 110 of the pouch 100. do.

Like the upper conductive plate 410, the lower conductive plate 420 is formed to have an area equal to the area of the electrode assembly 200 seated inside the pouch 100, and the lower conductive plate 420. Is bonded to the lower surface of the pouch lower pouch layer 120.

 The upper conductive plate 410 and the lower conductive plate 420 are integrally heat-sealed and bonded when the pouch is molded, or separately molded and adhered to the surfaces of the pouch layers 110 and 120 by an adhesive tape.

The upper conductive plate 410 and the lower conductive plate 420 may be electrically connected, and may be electrically connected by a separate connection lead line 430.

The connection tab 440 is formed by welding the upper conductive plate 410 to electrically connect the negative electrode tab 244 among the upper conductive plate 410 and the electrode tab. In this case, the connection tab 440 and the negative electrode tab 244 may be coupled by laser welding. The connection tab 440 is formed of a conductive metal such as copper, iron, nickel, aluminum, and the like as the conductive plate 400. In addition, the connection tab 440 may be formed by being connected to the lower conductive plate 420.

4 is a cross-sectional view of a pouch-type lithium secondary battery according to another embodiment of the present invention.

The conductive plate 400a is integrally formed with an upper conductive plate 410a installed at an upper portion and a lower conductive plate 420a provided at a lower portion thereof so as to be entirely connected at one side. Therefore, a separate connection lead wire is not used and a connection lead wire coupling process for electrically connecting the upper and lower portions of the conductive plate 400a is not required.

4 illustrates the conductive plate 400a formed by connecting the upper conductive plate 410a and the lower conductive plate 420a as a whole at the rear surface of the pouch. The conductive plate 400a is preferably formed by adhering the conductive plate film to the upper portion of the pouch film before molding and molding the conductive plate 400a integrally with the pouch film. Therefore, the conductive plate 400a is formed on both sides of the pouch 100 as well as the top and bottom thereof. The conductive plate 400a is electrically connected to the negative electrode tab 244 by the connection tab 440a formed at a predetermined position.

In addition, of course, the conductive plate may be formed by connecting the upper conductive plate and the lower conductive plate as a whole on one side of both sides of the pouch. In this case, after the formation of the pouch, the conductive plate is adhered to the pouch and the connection tab is coupled to the negative electrode tab.

5 is a cross-sectional view of a pouch-type lithium secondary battery according to another embodiment of the present invention.

The conductive plate 400b is formed as a cap-shaped cover to cover the pouch 100 not only at the top and bottom but also at both sides and the back. That is, the pouch 100 is inserted into the cap-shaped conductive plate 400b. Therefore, the conductive plate 400b is formed separately from the pouch, and after the formation of the pouch 100, the conductive plate 400b is assembled to the pouch 100 at the rear of the pouch. In this case, even if the pin is penetrated from both sides and the rear surface it is possible to perform the same action as the upper and lower cases.

Next, the operation of the pouch-type lithium secondary battery according to the present invention will be described.

Referring to FIG. 6, the pin 600 penetrating the upper conductive plate 110 and the upper pouch layer 110 on the upper portion of the pouch 100 passes through the electrode assembly 200 again. The pin 600 shorts the positive electrode plate 210 and the negative electrode plate 230 while penetrating through the positive electrode plate 210 and the negative electrode plate 230 of the electrode assembly in the jelly roll.

In addition, since the pin 600 penetrates the upper conductive plate 410, the pin 600 is electrically connected to the positive electrode plate 210 and the upper conductive plate 410 wound around the outer electrode assembly 200. The upper conductive plate 410 is connected to the negative electrode tab 244 by the connection tab 440 to act as a negative electrode plate. Therefore, the short circuit between the positive electrode plate 210 and the upper conductive plate 410 as well as the short circuit between the positive electrode plate 210 and the negative electrode plate 230 causes the flow of current. That is, when the pin 600 penetrates the pouch-type lithium secondary battery, a current caused by a short circuit between the positive electrode plate 210 and the negative electrode plate 230 is distributed to flow between the upper conductive plate 410 and the positive electrode plate 210. do. When the current flow between the positive electrode plate 210 and the negative electrode plate 230 is dispersed between the positive electrode plate 210 and the upper conductive plate 410 by the pin 600, the current flowing directly between the positive electrode plate 210 and the negative electrode plate 230 Since it is reduced to reduce the current flow in the electrode assembly 200 to reduce the ignition or explosion.

In the description of the above operation, the case in which the pin penetrates the upper conductive plate 410 of the pouch has been described, but the same operation is of course performed even when the pin 600 penetrates the lower conductive plate 420. That is, when the pin 600 is penetrated by the lower conductive plate 420, the lower conductive plate 420, the positive electrode plate 210, and the pin 600 form an electric circuit, and current flows in a dispersed manner.

As described above, the present invention is not limited to the specific preferred embodiments described above, and any person having ordinary skill in the art to which the present invention pertains without departing from the gist of the present invention claimed in the claims. Various modifications are possible, of course, and such changes are within the scope of the claims.

According to the present invention, even when a conductive pin penetrates through the pouch in a pouch-type lithium secondary battery, current flow in the jelly roll is dispersed to the outside to prevent current runaway in the jelly roll, thereby preventing the explosion or ignition of the battery. There is an effect that can be reduced.

Claims (6)

A positive electrode plate and a negative electrode plate and a separator that insulates the positive electrode plate and the negative electrode plate are interposed therebetween, and are wound in a jelly roll form. In the pouch-type lithium secondary battery comprising the pouch for mounting the electrode assembly is seated and sealed in the groove formed in the lower pouch film and the positive electrode tab and the negative electrode tab to the outside, An upper conductive plate formed on at least the same area as the horizontal area of the electrode assembly and seated on an upper portion of the upper pouch film at a position corresponding to a mounting position of the electrode assembly; A lower conductive plate formed at least equal to a horizontal area of the electrode assembly and electrically connected to the upper conductive plate and seated on a lower portion of the lower pouch layer; A pouch type lithium secondary battery, characterized in that it comprises a conductive plate having a connection tab for electrically connecting the upper conductive plate or the lower conductive plate and the negative electrode tab. The method of claim 1, The upper conductive plate and the lower conductive plate is a pouch type lithium secondary battery, characterized in that electrically connected by a separate connection lead wire. The method of claim 1, The upper conductive plate and the lower conductive plate is a pouch type lithium secondary battery, characterized in that formed integrally. The method of claim 2 or 3, The upper conductive plate and the lower conductive plate is a pouch type lithium secondary battery, characterized in that formed of any one of copper, iron, nickel, aluminum. The method of claim 2 or 3, The upper conductive plate and the lower conductive plate is a pouch type lithium secondary battery, characterized in that formed in a thickness of 10 to 100 μm. The method of claim 1, The upper conductive plate and the lower conductive plate are integrally formed in the form of a cap with an open front surface, and the pouch is inserted therein, and is electrically connected to the negative electrode tab by the connection tab formed at a predetermined position. Pouch type lithium secondary battery made with.

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