KR101856822B1 - Pouch type secondary battery comprising a current interrupt electrode lead - Google Patents

Abstract

A pouch-type secondary battery capable of securing safety by implementing a current interruption function according to an increase in internal pressure is provided. A pouch type secondary battery according to the present invention includes an electrode assembly having an electrode tab, an electrode lead connected to the electrode tab, a pouch outer case for receiving and sealing the electrode assembly to expose a part of the electrode lead, And a second sealant interposed between a lower surface of the electrode lead and an inner surface of the pouch outer cover material. The pouch type secondary battery of the present invention is characterized in that the electrode lead includes a first sealant interposed between an upper surface of the pouch case and an inner surface of the pouch skin material, And a fuse portion between the junction portion and the terminal portion, wherein the fuse portion has a horizontal slit parallel to the width direction of the electrode lead at a center thereof, and a fuse portion between the fuse portion and the terminal portion, And a rupture portion connected to the separation groove and separating the terminal portion from the joint portion, And the first sealant and the second sealant have different shapes so that when the internal pressure of the secondary battery rises, a deformation force of the pouch exterior member acts in an opposite direction to the upper and lower surfaces of the electrode lead, .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a pouch type secondary battery including a current limiting function electrode lead,

The present invention relates to a pouch type secondary battery, and more particularly, to a pouch type secondary battery having improved structure of an electrode lead joined to an electrode tab to improve overcharge safety.

Secondary batteries having high electrical properties such as high energy density and high ease of application according to the product group are widely used not only in portable devices but also in electric vehicles (EVs) or hybrid vehicles (HVs) driven by electric driving sources Has been applied. Such a secondary battery is not only a primary advantage that the use of fossil fuel can be drastically reduced, but also produces no by-products resulting from the use of energy, and thus is attracting attention as a new energy source for enhancing environmental friendliness and energy efficiency.

The secondary battery can be classified into various types including a can type battery in which internal elements are constituted by a metallic hard case or the like depending on the application form and structure. With the recent miniaturization of a mobile device, demand for a thin square prism, a pouch type Is increasing. Particularly, there is a high interest in a pouch type secondary battery which is easily deformed in shape, low in manufacturing cost, and small in weight. In addition, pouch-type secondary batteries are being developed and commercialized as power sources for electric vehicles or hybrid electric vehicles that require high output and large capacity.

The pouch type secondary battery includes an electrode assembly, an electrode tab extending from the electrode assembly, an electrode lead welded to the electrode tab, and a pouch outer case made of a laminate sheet of a polymer resin and aluminum, . In the pouch-type secondary battery, when the internal temperature of the battery increases due to overcharging or internal short-circuit which exceeds the allowable current or voltage, the internal pressure is increased due to vaporization of the electrolyte. As a result, the pouch- (swelling) phenomenon occurs. When the swelling phenomenon occurs, a short circuit may occur locally as the battery deforms, and the battery may ignite or explode in an extreme situation.

That is, one of the main research tasks of the pouch-type secondary battery is to improve the safety. In order to solve the swelling phenomenon due to the increase of the internal pressure, techniques for venting gas generated inside the pouch outer casing have been proposed . In Korean Patent Application Publication No. 2009-0060497, for example, Korean Patent Application Laid-Open No. 2009-0060497 discloses a method for manufacturing a battery, which comprises forming a minute hole in a metal plate used as an electrode tab to provide a safety vent, Discloses a technique for a pouch-type secondary battery that can be easily vented.

However, although the above-described gas venting is effective in reducing the internal pressure of the battery, there is a limit to the solution to the fundamental problem of increase in internal pressure such as overcharging. That is, even if the gas is vented, the electrode assembly and the electrode tab are continuously connected to each other, so that the overcharging from the outside is continued without interruption.

In the case of cylindrical and prismatic secondary batteries, a hard packing material is used, and an overcharge safety device of the concept of CID (Current Interrupt Device) can be applied. This is a principle in which, when the internal pressure of the battery rises due to the gas generated in the overcharging process, the electrode assembly and the electrode tab are separated at the same time as the CID operation and the current flow is limited originally. However, in the case of a pouch type secondary battery, it is difficult to apply the above CID concept because it uses a packaging material that is easy to deform. Accordingly, in the pouch-type secondary battery, when a swelling phenomenon occurs due to overcharging or the like, it is required to develop a technique capable of limiting the flow of current and fundamentally eliminating the risk of overcharging and greatly improving safety have.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems of the conventional art described above, and it is an object of the present invention to provide a pouch type secondary battery which can secure a current by implementing a current interruption function according to an increase in internal pressure.

In order to solve the above problems, the inventors of the present application have conducted intensive research and various experiments, and have developed a pouch type secondary battery by modifying the shape of an electrode lead and a sealant. In this case, It was confirmed that the electrode lead was broken due to the deformation force of the pouch exterior material due to the increase of internal pressure when the ring phenomenon occurred, and the electrical flow path was cut off, thereby greatly improving the overcharge safety.

A pouch type secondary battery according to the present invention includes an electrode assembly having an electrode tab, an electrode lead connected to the electrode tab, a pouch case for receiving and sealing the electrode assembly to expose a part of the electrode lead, And a second sealant interposed between a lower surface of the electrode lead and an inner surface of the pouch outer cover material. The pouch type secondary battery of the present invention is characterized in that the electrode lead includes a first sealant interposed between an upper surface of the pouch case and an inner surface of the pouch skin material, And a fuse portion between the junction portion and the terminal portion, wherein the fuse portion has a horizontal slit parallel to the width direction of the electrode lead at a center thereof, and a fuse portion between the fuse portion and the terminal portion, And a rupture portion connected to the separation groove and separating the terminal portion from the joint portion, And the first sealant and the second sealant have different shapes so that when the internal pressure of the secondary battery rises, a deformation force of the pouch exterior member acts in an opposite direction to the upper and lower surfaces of the electrode lead, .

 In the present invention, the connection groove may be further included in the separation groove. The connecting portion may be formed at the center of the horizontal slit. At this time, a notch may be formed in the connection portion, and the notch may be formed on at least one of the upper surface and the lower surface of the electrode lead. The notch may have any one of a wedge shape, a rounded shape, and a rectangular shape. Instead of the notches, at least one through-hole may be formed in the connection portion.

According to a preferred embodiment, the terminal portion of the electrode lead is completely separated from the remaining portion of the electrode lead while being separated from each other in the opposite direction.

In the present invention, the pouch exterior member has a sealing region at its rim, the horizontal slit is spaced from the sealing region toward the junction, and the rupture portion is formed within the sealing region. The first sealant may be formed on the upper electrode lead portion of the horizontal slit, and the second sealant may be formed on the horizontal slit side electrode lead portion.

For example, the first sealant may have a strip shape that crosses the upper surface of the electrode lead to be adhered to the pouch exterior member, and has a portion protruding toward the horizontal slit so as to cover the upper surface of the horizontal slit upper electrode lead, The second sealant may be formed in a strip shape across the bottom surface of the electrode lead to be adhered to the pouch exterior member and may include protruded portions formed on the bottom surface of the electrode lead to the outside of the vertical slit.

In one embodiment, the junction may be wider than the terminal portion. In this case, the horizontal slit may have a length equal to the width of the terminal portion. In this case, the separating groove may further include a vertical slit which is perpendicular to the width direction of the electrode lead at both ends of the horizontal slit and which faces the terminal portion, and the breaking portion is located toward the terminal portion on an extension of the vertical slit have.

In another embodiment, the horizontal slit is shorter than the width of the terminal portion, and the separation groove further includes a slanted slit that is directed to the terminal portion at both ends of the horizontal slit, and the rupture portion is formed on an extension of the slanted slit, As shown in Fig.

In the present invention, a notch may be formed in the rupture part. The notch may be formed on at least one of an upper surface and a lower surface of the electrode lead. The notch may have any one of a wedge shape, a rounded shape, and a rectangular shape. The rupture part may have at least one through hole, that is, a hole.

In the present invention, the electrode lead may be at least one of a positive electrode lead and a negative electrode lead.

The present invention proposes an electrode lead structure capable of blocking current in an overcharge state in a pouch type secondary battery such as a CID of a cylindrical or prismatic battery. According to the present invention, the safety of the cell can be ensured by adding a current interruption function in accordance with an increase in internal pressure in the pouch type secondary battery. Accordingly, when the pouch-type secondary battery used in automobiles and small-sized electronic products is over -charged or has a problem in safety due to abnormal use, the problem can be solved by effectively blocking the problem.

Particularly, in the present invention, since the front end of the breaking portion is partially cut, the breaking distance is shortened, and the current blocking can be cut more quickly in order to restrict the current path after the breaking. Including a connection in the separation groove can provide additional current paths.

According to the present invention, even if an abnormal phenomenon such as an overcurrent flows in the pouch-type secondary battery due to the normal operation of the protection circuit, the electrode lead is quickly broken, thereby securing safety in use of the secondary battery.

The present invention particularly relates to a pouch type secondary battery in which the shape of the electrode lead and the sealant are modified differently from the conventional ones so that the electrode lead is broken by a smaller force than when the overcharge or swelling phenomenon occurs, So that further current flow can be prevented and the risk of overcharging can be reduced.

In addition, unlike the conventional method of forming a complicated safety vent, the secondary battery can be manufactured by changing the shape of the electrode lead and the sealant, which is advantageous in that the manufacturing process is very simple and simple.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments of the invention and, together with the description of the invention, It should not be construed as limited.
FIG. 1 is a top view of an electrode lead according to an embodiment of the present invention, FIG. 2 is a bottom view, and FIG. 3 is a sectional view taken along line III-III 'of FIG.
FIGS. 4 and 5 are views for explaining various shapes of a notch that may be formed at the rupture portion of the electrode lead according to the embodiment of the present invention.
FIG. 6 is a top view of a secondary battery according to an embodiment of the present invention, and FIG. 7 is a bottom view of the secondary battery.
8 corresponds to V III -V III 'section of FIG. 6 and shows a steady state.
Fig. 9 shows a state in which the secondary battery internal pressure of Fig. 8 rises and swells.
Fig. 10 shows a state before and after the electrode lead is broken.
11-13 are top views of various electrode leads according to other embodiments of the present invention.
14 is a top view of an electrode lead according to another embodiment of the present invention in which a current path is additionally secured.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. It is provided to let you know. The shape of the elements and the like in the drawings are exaggerated in order to emphasize a clearer description, and the same reference numerals denote the same elements.

Different secondary battery types have different physical characteristics in overcharging, so the technology that reflects them in safety improvement also differs. According to the present invention, the electrode leads of the pouch type secondary battery are improved to break the electrode leads when the internal pressure rises, and the broken portions are separated from each other by deforming the sealant shape, thereby facilitating complete separation.

The present invention proposes an electrode lead structure capable of blocking current in an overcharge state in a pouch type secondary battery such as a CID of a cylindrical or prismatic battery. The present invention can secure the safety of the cell by adding a current interruption function according to an increase in internal pressure in the pouch type secondary battery.

When the secondary battery is exposed to an abnormal use environment, the following chemical / physical phenomenon occurs. Safety devices applied to ensure safety are operated by such physics / chemical triggers.

- Temperature rise and gas generation due to reaction between positive and negative electrode and electrolyte

- Voltage rise above the allowable value

- Deformation of cell due to difference of inner and outer pressure

Similar to the operation mechanism of the existing CID, the present invention proposes to limit the current through the deformation force due to the pressure rise inside the secondary battery.

When the pouch type casing is inflated by overcharge of the pouch type secondary battery, the electrode tab protruded from the electrode assembly and the electrode lead connected thereto are separated or the electrode lead itself is broken to block the path for receiving the current from the outside The risk of overcharging can be greatly reduced. Particularly, according to the present invention, it is not a local rupture in which a part of an electrical connection part is ruptured, but an electric current interruption due to complete separation is attempted, so that continuation of overcharging can not be completely blocked.

FIG. 1 is a top view of an electrode lead according to an embodiment of the present invention, FIG. 2 is a bottom view, and FIG. 3 is a sectional view taken along line III-III 'of FIG. A sealant used together with the electrode lead when assembled with the secondary battery is also shown.

As shown in FIGS. 1 to 3, the electrode lead according to the present invention has a shape different from that of a conventional rectangular electrode lead, for example, an inverted T-shape, and changes the shape of the electrode lead as well as the shape of the sealant So that the electrode lead can be easily broken at the time of deformation of the pouch outer casing due to the increase of the inner pressure.

The electrode lead (40) of the present invention is made of a metal material serving as a current path. The material can be any metal with conductivity. The electrode lead 40 has a joint portion 10 to be joined to an electrode tab (not shown), a terminal portion 20 to be exposed to the outside of the pouch exterior member (not shown), and a fuse (30).

The fuse portion 30 includes a separation groove 36 including a central horizontal slit 32 parallel to the width direction of the electrode lead 40. A breaking portion 38 connected to the separation groove 36 and separating the terminal portion 20 from the bonding portion 10 is formed. The front end of the rupturing portion 38 is partially cut.

The slit basically has an elongated shape. In the present invention, the term " horizontal " means parallel to the width direction of the electrode lead 40 (horizontal direction in the drawing). The electrical connection between the terminal portion 20 and the joint portion 10 is maintained so that the joint portion 10 and the terminal portion 20 can be completely separated from each other when the break portion 38 is broken, It is a role to play.

In the present embodiment, the junction 10 is wider than the terminal portion 20. At this time, the horizontal slit 32 may have the same length as the width of the terminal portion 20. The separation groove 36 further includes vertical slits 34 which are perpendicular to the width direction of the electrode lead 40 and face the terminal portion 20 at both ends of the horizontal slit 32. [ The rupture portion 38 is positioned toward the terminal portion 20 on the extension of the vertical slit 34. The vertical slit 34 plays a role of imparting the left and right fluidity of the lower end of the terminal portion 20 together with the horizontal slit 32 and serves to facilitate the breaking by shortening the length of the breaking portion 38. Particularly, the end of the vertical slit 34 can serve to cause a break through the rupture part 38 connected to the end of the vertical slit 34 while the external force is concentrated when an external force such as deformation of the pouch exterior material is applied. In this case, the terminal portion 20 is separated from the remaining portion of the electrode lead 40 in a rectangular shape.

Here, the lengths of the vertical slit 34 and the rupture portion 38 can be variously changed. If the vertical slit 34 is relatively long and the break portion 38 is relatively short, breakage can easily occur even with a small force, but if the current flow path is small and current is concentrated in the break portion 38, There is a possibility that the breakage portion 38 is broken in the situation. Conversely, when the vertical slit 34 is relatively short and the breakage portion 38 is relatively long, a large current is required to break the breakage portion 38 although the current flow path can be ensured. Therefore, the vertical slit 34 and the length of the rupture portion 38 are determined in consideration of various situations.

These lengths are also related to the position of the horizontal slit 32. If the horizontal slit 32 is formed near the lower end of the electrode lead 40 close to the joint 10 side, It is difficult to ensure the area of the joint 10, so this should be taken into consideration. If the lengths of the horizontal slit 32 and the vertical slit 34 are too short, it is difficult to expect the effect of the slit formation. Conversely, if the length is excessively long, the stress in the slits 32, The electrode lead 40 is cut off at that portion due to induction of concentration, which is not preferable.

The electrode lead 40 according to the present invention has a separation groove 36 formed between the bonding portion 10 and the terminal portion 20 and the bonding portion 36 extending laterally from the separation groove 36, And the terminal portion 20 are physically and electrically separated from each other. For faster operation in restricting the current path after rupture, the front end of the rupture portion 38 is partially cut to shorten the rupture distance as in the present embodiment. The separation groove 36 is formed by forming a hollow space and including a horizontal slit 32 and a vertical slit 34 or a horizontal slit 32 alone or a combination of horizontal slit 32 and another hollow space Lt; / RTI > The separation groove 36 may have a shape suitable for separating the joint portion 10 and the terminal portion 20 from each other so that the electrical cutoff can be reliably performed by the fuse portion 30. As shown in this embodiment, (32), and vertical slit (34). As a method for forming the separation groove 36, for example, a method of using a roll having a cutter on the surface thereof or using a frame provided with a cutter, is not limited to such a method. It may be formed so as to be included from the beginning when the electrode lead 40 is formed by a mold manufacturing method.

In order to easily break the desired portion, the notch V may be formed in the rupture portion 38, as can be seen in detail in the section of Fig. The notch V can concentrate the stress and propagate and adjust the position where the notch V is broken. Therefore, in the case of forming the notch V, the terminal portion 20 can be controlled while being controlled to a desired shape.

The notch V may be formed on both the upper surface and the lower surface of the electrode lead 40 as shown in FIG. 3, or may be formed on either the upper surface or the lower surface. The notch V shown in Fig. 3 is wedge-shaped, but a notch V 'or a rectangular notch V' may be formed in a rounded shape, as shown in Figs. 4 and 5, respectively. (V ', V' ') are formed on the upper surface of the electrode lead 40, but notches V' and V '' may be formed on both the upper surface and the lower surface, These notches V, V ', V "can be formed by a method of manufacturing a mold.

The sealants 50 and 55 are members to be adhered to the pouch exterior member, and may be called a sealing tape because they have a tape shape. The opposite pouch exterior member where the sealants 50 and 55 are located is bonded to the sealants 50 and 55 through thermal fusion. A first sealant 50 interposed between the upper surface of the electrode lead 40 and the inner surface of the pouch outer cover member and a second sealant 55 interposed between the lower surface of the electrode lead 40 and the inner surface of the pouch outer cover member, Are different from each other.

The first sealant 50 is formed in a strip shape across the upper surface of the electrode lead 40 so as to be adhered to the pouch exterior material. In particular, the first sealant 50 includes a horizontal slit 32 to cover the upper surface of the electrode lead 40 above the horizontal slit 32, As shown in Fig. The horizontal slit 32 is not formed in the lower electrode lead 40. If the vertical slit 34 reaches the sealing portion, a recessed portion is formed so as not to cover the vertical slit 34.

The second sealant 55 is also formed in a strip shape across the lower surface of the electrode lead 40 so as to be adhered to the pouch exterior member. In particular, the horizontal slit 32 is also formed on the lower surface of the electrode leads 40 on both sides. That is, the protruded portion is formed so as to be formed on the lower surface of the electrode lead 40 outside the vertical slit 34.

The first sealant 50 is adhered to the upper surface of the upper electrode lead 40 with respect to the horizontal slit 32 and the lower surface of the electrode lead 40 below the horizontal slit 32 is covered with only the second sealant 55 Adhesive.

Usually, the sealant is available in the form of a tape. The tape sealant is horizontally attached to the upper surface of the electrode lead 40 and attached to the upper surface of the electrode lead 40 above the horizontal slit 32, The first and second sealants 50 and 55 can be obtained as shown in the figure when the separation groove 36 is formed by punching the electrode lead 40 adhered vertically to the bottom surface of the electrode lead 40 outside the vertical slit 34 have. The separation grooves 36 may be formed first and then a tape sealant may be applied.

The sealants 50 and 55 are made of a film having insulation and heat-sealability. The sealants 50 and 55 may be formed of one or more material layers selected from polyimide (PI), polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET) (A single membrane or a multi-membrane). The sealants 50 and 55 prevent a short circuit between the electrode lead 40 and the metal layer of the pouch outer cover material, for example, between the aluminum sheets, and also improve the sealing force of the pouch outer cover material to prevent leakage of the electrolyte. do. Particularly, since the sealants 50 and 55 according to the present invention are formed in different positions on and below the electrode leads 40 as shown in FIGS. 1 and 2, the electrode leads 40 can be easily broken and separated.

6 and 7 show the assembling form in the secondary battery including such an electrode lead. 6 is a top view of the secondary battery, and Fig. 7 is a bottom view of the secondary battery.

The pouch type secondary battery 100 according to the present invention is composed of an electrode assembly 65 having a positive electrode / separator / negative electrode structure and a pouch outer cover material 70 of a laminate sheet for housing the electrode assembly 65. Here, the positive electrode or negative electrode is manufactured by applying and drying an electrode active material capable of intercalating / deintercalating lithium ions to a thin plate-shaped metal current collector such as aluminum or copper. The electrode assembly 65 can be a stacked, folded, stack-folded, jelly-roll type, or the like.

The electrode assembly (65) is provided with an electrode tab (60). The current collecting plate of the electrode assembly 65 is composed of a portion coated with the electrode active material and a terminal portion (hereinafter referred to as "plain portion") to which the electrode active material is not applied, and the electrode tab 60 is formed by cutting Or may be a separate conductive member connected to the non-conductive portion by ultrasonic welding or the like. The electrode tabs 60 may protrude in both directions of the electrode assembly 65 so as to face each other as shown in FIG.

The electrode tab 60 functions as an electron transfer path between the inside and the outside of the battery. The electrode lead 40 described with reference to FIGS. 1 to 3 is connected to the electrode tab 60 by spot welding or the like. The electrode leads 40 may extend in the same direction or in opposite directions depending on the formation positions of the positive electrode tab and the negative electrode tab. The positive electrode lead and the negative electrode lead may have different materials from each other. That is, the positive electrode lead may be made of the same aluminum (Al) material as the positive electrode plate, and the negative electrode lead may be made of the same copper material as the negative electrode plate or a copper material coated with nickel (Ni). Finally, the electrode lead 40 is electrically connected to the external terminal through the terminal portion 20.

The pouch outer sheath 70 receives and seals the electrode assembly 65 such that a part of the electrode lead 40, that is, the terminal portion 20 is exposed. The first and second sealants 50 and 55 described above are interposed between the electrode lead 40 and the pouch outer casing 70.

The pouch sheathing 70 has a sealing region 75 at its rim and the horizontal slit 32 of the electrode lead 40 is spaced from the sealing region 75 toward the junction 10. That is, when the electrode lead 40 is inverted T-shaped, the leg portion of the T-shaped protrusion protrudes to the outside of the pouch exterior member 70, and a part of the T-shaped head is formed in the sealing region 75. The rupturing portion 38 is formed in the sealing region 75. The rear end of the rupture portion 38 is formed so as to protrude toward the electrode assembly 65 more toward the electrode assembly 65 than to the sealing region 75 as shown in FIG. There may be.

The first sealant 50 is formed on the sealing region 75 and the electrode lead 40 portion above the horizontal slit 32 and the second sealant 55 is formed on the sealing region 75 and the horizontal slit 32 on both electrode leads (40).

Since the first sealant 50 and the second sealant 55 have different shapes as described above, when the internal pressure of the secondary battery 100 rises, the deformation force of the pouch case 70 is applied to the upper surface and the lower surface of the electrode lead 40 in opposite directions So that the breakable portion 38 can be broken. Particularly, since the front end portion of the rupturing portion 38 is partially cut, the rupture portion 38 breaks very quickly at the time of rupture, and the current path can be quickly cut off. The degree of cutting can be varied. The cutting depth can be adjusted in consideration of the degree that the length of the rupture portion 38 is maintained to some extent to secure a current path and that rupture can occur quickly when the internal pressure of the secondary battery rises.

The breakable electrode leads 40 can be applied to both the positive electrode lead and the negative electrode lead, but may be applied to either of them. Usually, the anode lead plate is made of aluminum material and the anode current collector plate is made of copper material. When the swelling phenomenon occurs, the copper foil tends to rupture rather than the aluminum foil. Therefore, the cathode lead is more likely to break than the cathode lead. . In such a case, it may be desirable to form the negative electrode lead with such a breakable electrode lead 40.

6 and 7, the first and second sealants 50 and 55 interposed between the electrode lead 40 and the pouch outer sheath 70 are different in shape from the first and second sealants 50 and 55, The upper and lower surfaces of the secondary battery 100 are different from each other. The breakage of the electrode lead 40 proceeds through the deforming force of the pouch outer cover 70, so that the breaking point, that is, the sealing point with respect to the breakage portion 38, is changed.

8 corresponds to V III -V III 'section of FIG. 6 and shows a steady state. Fig. 9 shows a state in which the internal pressure of the pouch-type secondary battery of Fig. 8 rises and swells.

8, the electrode tabs 60 are welded together with the non-printed portions of the current collecting plate, and the bonding portions 10 of the electrode leads 40 are welded to the electrode tabs 60. [

When the pouch-type secondary battery 100 is overcharged due to an abnormal situation occurring in the pouch-type secondary battery 100, the internal pressure of the pouch-type secondary battery 100 is increased due to the generation of gas due to the high temperature state inside the pouch- A swelling phenomenon occurs in which the pouch-shaped secondary battery 100 swells up. The electrode leads 40 adhered to the pouch case 70 are deformed in the same direction as the pouch case 70 due to the deformation of the pouch case 70.

As shown in the figure, the electrode leads 40 bonded to the upper and lower pouch outer cover materials 70 through the first and second sealants 50 and 55 are deformed in opposite directions to each other, 38, and preferably, a fracture occurs at the interface where the notch V is formed.

That is, the electrode lead 40 is more easily ruptured and separated by the force applied while the pouch exterior member 70 is swollen, thereby preventing further current flow and preventing the electrode lead 40 from reaching an extreme situation. The terminal portion 20 of the electrode lead 40 is completely separated from the remaining portion of the electrode lead 40. This is because the electrode lead 40 Can perform a function similar to that of a CID in a cylindrical battery or the like.

Fig. 10 shows the state before and after the electrode lead 40 is broken. It can be seen that the current path is limited along with the breakage. The terminal portion 20 of the electrode lead 40 is separated from the remaining portion of the electrode lead 40 in a direction opposite to that of the other portion of the electrode lead 40 while the breakage portion 38 is broken. The terminal portion 20 of the electrode lead 40 is subjected to the force pulled upward by the first sealant 50 and the remaining portion is subjected to the force pulled downward by the second sealant 55. That is, in the present invention, by deforming the shape of the electrode leads 40 and the sealants 50 and 55, when the swelling phenomenon occurs, the electrode lead 40 itself is broken even by a smaller force so that the terminal portion 20 and the remaining portion It can be easily separated completely, thereby preventing further current flow and securing overcharge safety.

As described above, according to the present invention, when the internal pressure rises, the electrode lead is cut through the deformation force of the pouch exterior member, and the current is cut off through the electrode lead.

Fig. 11 shows an embodiment in which the shape of the rupture portion 38 is different from that of Fig. A portion of the front end of the rupturing portion 38 may be cut and one or more through holes H may be formed in the rupturing portion 38. [ At this time, the electrode leads 40 are deformed in opposite directions when the electrode leads 40 are bonded to the upper and lower pouch outer sheaths with the first and second sealants having different shapes. Through this through-hole H, The rupture portion 38 is broken along the narrow gap between the end portions 38a and 38b.

12 shows another embodiment of the electrode lead.

The embodiment shown in Fig. 12 has no vertical slit 34 in comparison with the first embodiment. A portion of the front end of the rupture portion 38 is cut, and a notch may be formed or a through-hole may be formed as in the previous embodiments. In the case where the vertical slit 34 is not provided as in the present embodiment, the length of the front end of the rupture portion 38 cut can be made longer than the case where the vertical slit 34 is provided.

Figure 13 shows yet another embodiment.

In Fig. 13, the electrode lead 40 is shown in the inverted T shape, but it may have a rectangular shape. The horizontal slit 32 is shorter than the width of the terminal portion 20. The separation groove 36 further includes a slanted slit 35 which faces the terminal portion 20 at both ends of the horizontal slit 32. The break portion 38 is positioned toward the terminal portion 20 on the extension of the slit slit 35. [ At this time, the front end portion of the rupture portion 38 is cut, and a notch may be formed or a through-hole may be formed as in the previous embodiments. The oblique slit 35 may be a sloped slit inclined at a predetermined angle depending on the width of the terminal portion 20, the width of the horizontal slit 32, or the like. As a variant, a slit (curved slit) bent with a predetermined radius of curvature may be formed between the horizontal slit 32 and the rupture portion 38.

14 is a top view of an electrode lead according to another embodiment of the present invention in which a current path is additionally secured.

The electrode lead 40 shown in Fig. 14 has a part of the front end of the rupture part 38 cut, and the connection part 33 is included in the separation groove 36. The connection portion 33 may be included in any part of the separation groove 36 to ensure an additional current path. In this embodiment, the horizontal slit 32 is formed in particular. The connection portion 33 is formed at the center of the horizontal slit 32 to constitute a current path leading to the junction portion 10 and the terminal portion 20. A notch may be formed in the connection portion 33 so that the position of the breakage can be determined and the breakage can be made quickly when the breakage occurs. Such a notch may be formed in the same or similar shape and manner as the notches described above with reference to Figs. 3 to 5 above. The length of the connection 33 can be varied. The length of the connecting portion 33 can be adjusted by taking into consideration the degree of securing the current path by maintaining the length of the connecting portion 33 to some extent and breaking quickly when the internal pressure of the secondary battery rises.

An additional current path through the connecting portion 33 is ensured in the normal state through the present embodiment. In an emergency, breakage is made through the breaking portion 38 and the separation groove 36 to interrupt the current path, Can be achieved. If the flow of current is narrow, there is a fear of an increase in resistance of the electrode lead 40 and heat generation. However, if the connection portion 33 is included as in the present embodiment, an additional current path can be ensured, do.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not to be limited to the details thereof and that various changes and modifications will be apparent to those skilled in the art. And various modifications and variations are possible within the scope of the appended claims.

10: connecting portion 20: terminal portion
30: fuse portion 32: horizontal slit
33: Connection
34: vertical slit 35: diagonal slit
36: separation groove 38:
40: electrode lead 50, 55: sealant
60: electrode tab 65: electrode assembly
70: Pouch Exterior Material 100: Pouch Type Secondary Battery
V, V ', V ": Notch H: Through hole

Claims (22)

An electrode assembly having an electrode tab;
An electrode lead connected to the electrode tab;
A pouch case for receiving and sealing the electrode assembly so that a part of the electrode lead is exposed; And
A first sealant interposed between an upper surface of the electrode lead and an inner surface of the pouch exterior material; and a second sealant interposed between a lower surface of the electrode lead and an inner surface of the pouch exterior material,
Wherein the electrode lead includes a joint portion to be joined to the electrode tab, a terminal portion exposed to the outside of the pouch exterior member, and a fuse portion between the joint portion and the terminal portion,
Wherein the fuse portion includes a separation groove including a central horizontal slit parallel to the width direction of the electrode lead and a break portion connected to the separation groove and separating the terminal portion from the bonding portion,
The front end of the breaking portion is partially cut,
The first sealant and the second sealant are different in shape so that when the internal pressure of the secondary battery rises, the deformation force of the pouch exterior member acts in an opposite direction to the upper and lower surfaces of the electrode lead,
Wherein the pouch exterior material has a sealing area at a rim, the horizontal slit is spaced from the sealing area to the junction, the rupture part is formed in the sealing area, and the first sealant is disposed on the upper electrode lead part of the horizontal slit And the second sealant is formed on the horizontal slit side electrode lead portions so that the upper surface of the electrode lead and the lower surface of the electrode lead are sealed with respect to the break portion,
And the terminal portion of the electrode lead is completely separated from the remaining portion of the electrode lead in a direction opposite to that of the other portion of the electrode lead. The pouch type secondary battery according to claim 1, further comprising a connection portion in the separation groove. The pouch type secondary battery according to claim 2, wherein the connection part is formed at the center of the horizontal slit. The pouch type secondary battery according to claim 2, wherein the connecting portion is formed with a notch. The pouch type secondary battery according to claim 4, wherein the notch is formed on at least one of an upper surface and a lower surface of the electrode lead. The pouch type secondary battery according to claim 4, wherein the notch has a shape selected from the group consisting of a wedge shape, a rounded shape, and a rectangular shape. The pouch type secondary battery according to claim 2, wherein at least one through hole is formed in the connection portion. delete delete delete The pouch type secondary battery according to claim 1, wherein the connection portion is wider than the terminal portion. 12. The pouch type secondary battery according to claim 11, wherein the horizontal slit has a length equal to a width of the terminal portion. 13. The semiconductor device according to claim 12, wherein the separation groove further comprises a vertical slit which is perpendicular to the width direction of the electrode lead at both ends of the horizontal slit and which faces the terminal portion, Wherein the pouch type secondary battery is a pouch type secondary battery. [14] The apparatus of claim 13, wherein the first sealant is formed in a strip shape crossing the upper surface of the electrode lead to be adhered to the pouch exterior member, and protrudes toward the horizontal slit so as to cover the upper surface of the upper electrode lead And the second sealant is formed in a strip shape across the bottom surface of the electrode lead so as to be adhered to the pouch exterior material and includes both protruding portions formed on the bottom surface of the electrode lead to the outside of the vertical slit Pouch type secondary battery. The slit-shaped slit of claim 1, wherein the horizontal slit is shorter than the width of the terminal portion, and the separation groove further includes a slanted slit that is disposed at both ends of the horizontal slit toward the terminal portion, Wherein the pouch type secondary battery is positioned toward the pouch type secondary battery. The pouch type secondary battery according to claim 1 or 2, wherein a notch is formed in the rupture portion. 17. The pouch type secondary battery according to claim 16, wherein the notch is formed on at least one of an upper surface and a lower surface of the electrode lead. The pouch type secondary battery according to claim 16, wherein the notch has a shape of a wedge shape, a rounded shape, and a rectangular shape. The pouch type secondary battery according to claim 1, wherein at least one of the through holes is formed in the rupture portion. The pouch type secondary battery according to claim 1, wherein the electrode lead is at least one of a positive electrode lead and a negative electrode lead. The pouch type secondary battery according to claim 1, wherein the electrode lead is inverted T-shaped, and a leg portion of the T-shaped protrusion protrudes outside the pouch exterior member, and a portion of the T-shaped head is formed in the sealing region. 2. The apparatus of claim 1, wherein the pouch exterior member has a sealing region at its rim, the horizontal slit is spaced from the sealing region toward the junction, the front end of the rupturing portion is cut into the sealing region, Wherein the pouch type secondary battery is formed to extend from the sealing region toward the electrode assembly.

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