KR20070091877A - Secondary battery of improved sealability - Google Patents

Abstract

A secondary battery is provided to exhibit a high sealing property in sealing parts, and thus be suitable for use as a unit battery of a medium and large-sized battery pack having high output and large capacity. A secondary battery(100a) is manufactured by performing thermal fusion with an electrode assembly being provided in a battery case formed of a laminate sheet including a resin layer and a metal layer. Among sealing parts of the battery case formed by thermal fusion, sealing parts(241,261) with electrode terminals comprise crossed furrow-ridge grooves(600) which have a tilt angle to the periphery of the battery case and are formed on sealing interfaces of upper and lower cases except the electrode terminals, and the remaining sealing parts(251,271) without electrode terminals comprise furrow-ridge grooves(700) which are parallel to the periphery of the battery case and are formed on the sealing interfaces of the upper and lower cases.

Description

Secondary Battery of Improved Sealability

1 is an exploded perspective view of a conventional pouch type secondary battery using a laminate sheet as a battery case;

FIG. 2 is a partially enlarged view of an electrode lead coupling portion of the pouch-type battery of FIG. 1; FIG.

3 is a schematic diagram of a pouch-type battery in which electrode leads protrude from upper and lower portions of the battery case as another example of the prior art;

4 is a schematic diagram of a pouch-type battery in which grooves are formed in a sealing portion according to one embodiment of the present invention.

5 is an enlarged view of a portion A in FIG. 4;

FIG. 6 is an enlarged view of region B in FIG. 4; FIG.

FIG. 7 is a vertical cross-sectional view of the line C-C in FIG. 6.

The present invention relates to a secondary battery with improved sealability, and more particularly, a battery manufactured by thermally fusion in a state in which an electrode assembly is embedded in a battery case of a laminate sheet including a resin layer and a metal layer. Among the sealing portions of the battery case formed by the sealing portion, the electrode terminal is located at the sealing interface of the upper and lower case except the electrode terminal by crossing the valley and grooves of the floor inclined at a predetermined angle with respect to the outer peripheral surface of the battery case, The remaining sealing part in which the electrode terminal is not located relates to a secondary battery having a structure in which grooves and valleys parallel to the outer circumferential surface of the battery case are formed at the sealing interface of the upper and lower cases.

Recently, secondary batteries capable of charging and discharging have been widely used as energy sources of wireless mobile devices. Secondary batteries are also attracting attention as a power source for electric vehicles (EVs) and hybrid electric vehicles (HEVs), which are proposed as a way to solve air pollution in conventional gasoline and diesel vehicles that use fossil fuels. .

The secondary battery has a structure in which an electrode assembly having a cathode / separator / cathode structure capable of charging / discharging is embedded in a case of a laminate sheet including a cylindrical or rectangular metal can or a resin layer and a metal layer in an electrolyte-impregnated state. The former battery has an excellent structural stability, the latter battery has the advantages of low weight and easy manufacturing. Among them, the amount of batteries using the laminate sheet has been increasing in recent years in consideration of the tendency of small and light thinning of electronic devices and the weight reduction of medium and large battery packs.

Due to the shape of the case, a battery using such a laminate sheet is often referred to as a pouch type battery, and an electrode assembly embedded therein is often used as an electrode assembly impregnated with lithium electrolyte in a state in which a cathode and an anode are thermally fused to a separator. It may also be referred to as a lithium ion polymer battery.

1 is an exploded perspective view of the manufacture of one secondary battery (hereinafter sometimes abbreviated as "pouch-type battery") using a laminate sheet as a battery case.

Referring to FIG. 1, the pouch-type battery 100 includes an electrode lead 300 having an anode / separator / cathode mounted on a pouch-type battery case 200 formed of a polymer sheet and a laminate sheet of aluminum. 410 and 420 are manufactured by combining the battery case 200 in an exposed state.

The battery case 200 includes a lower case 220 and an upper cover 230 in which the accommodating part 210 is formed, and has a folding structure in which the lower end is integrated. In the state in which the electrode assembly 300 is seated on the accommodating part 210, the upper and both outer circumferential surfaces 222 of the lower case 220 and the contact surfaces of the upper cover 230 are adhered and sealed. Therefore, after assembly of the battery, the upper end and both outer peripheral surfaces 222 of the battery case 200 form a sealing part (sealing part).

Electrode tabs 310 and 320 protruding from the electrode assembly 300 are connected to the electrode leads 410 and 420. In order to prevent the leakage of the electrolyte solution and to prevent moisture in the air from penetrating into the battery, and to secure the electrical insulation of the electrode leads (410, 420) at the portion where the battery case 200 and the electrode leads (410, 420) are coupled. , The sealing film 500 is coupled.

FIG. 2 is a partially enlarged view of the electrode lead coupling portion of the pouch-type battery of FIG. 1.

Referring to FIG. 2, the anode lead 410 and the cathode lead 420 electrically connected to an electrode assembly (not shown) of the anode / separator / cathode are exposed from the top of the battery case 200 of the aluminum laminate sheet. It is sealed in the state. The sealing film 500 is interposed between the battery case 200 and the electrode leads 410 and 420. The adhesion of the upper cover 230 and the lower case 220 of the case 200 is mainly achieved by fusion (heat fusion) by applying heat and pressure, and in this bonding process, the sealing film 500 is also bonded.

As another example, FIG. 3 illustrates a perspective view of a pouch-type battery in which electrode leads protrude from upper and lower portions of the battery case, respectively.

Compared to the pouch-type battery 100 of FIG. 1, the pouch-type battery 101 of FIG. 3 has a lower case in which electrode leads 410 and 420 are disposed at an upper side and a lower side, respectively, and a battery case 201 is separated from each other. There is a difference in that it consists of 221 and the upper case (231). Therefore, the upper sealing part 241, the lower sealing part 261, and the both side sealing parts 251 and 271 are formed by the heat sealing of the battery case 201, respectively. The accommodating part 211 may be formed only in the upper case 231 or the lower case 221, or both cases 221 and 231 may be formed.

However, the pouch type battery as shown in FIGS. 1 and 3 has the disadvantage of low mechanical rigidity of the battery case, high risk of internal short circuit caused by external impact, and high risk of leaking flammable substances such as electrolyte due to separation of sealing parts. Have. Such leakage of internal short circuits and flammable materials may lead to ignition or explosion. In particular, in a medium-large battery pack in which a plurality of unit cells are electrically connected for the purpose of high output capacity, such ignition and explosion may cause a very serious situation. Can be.

The low strength of the battery case can be compensated to a certain extent by the high strength pack case, while the separation of the battery case sealing part requires a fundamental solution.

As one of ways to solve this problem, various attempts have been made to increase the bonding strength of the sealing portion, specifically, the thermal fusion bonding strength.

For example, Japanese Patent Application Laid-Open No. 2004-95401 discloses the unevenness of the laminate sheet on the outer surface of the laminate sheet at the electrode lead portion, which is particularly weak in sealing properties, thereby providing the adhesion of the laminate sheet to the electrode lead due to the unevenness during thermal welding. Partially different techniques are disclosed for improving the sealability. Although the bonding of the laminate sheet and the electrode lead may be improved due to the partial difference in the heat bonding force during thermal welding due to the unevenness formed on the outer surface of the laminate sheet, that is, both ends of the electrode lead The gap of is not compensated for, and in addition, the gap between the electrode lead front end portion and the laminate sheet (and / or the sealing film) may be further widened in the thermal fusion process, thereby accelerating the separation of the sealing portion. The application also discloses a technique of transforming the electrode lead and the laminate sheet into a bent form as an example of application, but the bending of the electrode lead causes a crack inside the metal material of the electrode lead, and such crack acts as a hot spot in an overcurrent. It may cause breakage.

Although not intended to improve the binding force of the sealing portion, examples of forming a bent portion in the sealing portion may include Korean Patent Registration No. 319108 and Japanese Patent Application Publication No. 2004-47185. The Korean Patent Registration No. 319108 discloses a technique for forming a notch uniformly along the sealing portion to facilitate vertical bending of the sealing portion after heat sealing, and Japanese Patent Application Laid-Open No. 2004-47185 discloses a sealing portion. Techniques for inserting the mold and bending the laminate sheet accordingly are presented. However, these techniques have a disadvantage in that the same curvature is formed in the laminate sheet throughout the sealing portion in the bending direction, and thus rather deteriorates the sealability at the electrode lead portion where bonding force is a problem.

Therefore, there is a high need for the development of a technology for improving the sealing property in a battery using a laminate sheet.

The present invention aims to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

After extensive research and various experiments, the inventors of the present application differ in the groove shape of a sealing part (sealing part) in which the electrode lead is located and the groove shape of a sealing part in which the electrode lead is not located, thereby corresponding to the laminate sheet for battery case. In the case of forming a curved structure forming a valley and a valley at the site, it can be confirmed that the sealing property of the sealing section formed by thermal fusion can be improved, and in particular, the sealing property of the electrode lead site, which is weak in bonding strength, can be greatly improved. It was completed.

That is, the secondary battery according to the present invention is a battery manufactured by thermally fusion in a state in which an electrode assembly is embedded in a battery case of a laminate sheet including a resin layer and a metal layer, and among the sealing parts of the battery case formed by the thermal fusion. The sealing part where the electrode terminal is located is formed at the sealing interface of the upper and lower case except the electrode terminal because the grooves and the grooves of the floor which are inclined at a predetermined angle with respect to the outer circumferential surface of the battery case cross each other and are formed at the sealing interface where the electrode terminal is not located. The part has a structure in which grooves of the valley and the floor parallel to the outer circumferential surface of the battery case are formed at the sealing interface of the upper and lower cases.

Therefore, the secondary battery according to the present invention has the upper and lower cases in close contact with each other in the shape of grooves different from each other in the sealing portion in which the electrode terminals are positioned in the battery case, and the remaining sealing portions, thereby providing a high sealing property.

First, the battery case has a sheet-like structure including a metal layer and a resin layer for the purpose of preventing moisture immersion, preventing leakage of an electrolyte solution, and providing airtightness during sealing. In one preferred example, the battery case is a laminate sheet of a metal layer and a resin layer, and is a unit member formed on one surface or one surface thereof integrally, and a structure in which the opening parts are bonded to each other and sealed in a state where the electrode assembly is incorporated. It may be a structure (see Fig. 3) to seal the contact portion of the outer circumferential surface in the state in which the electrode assembly is embedded therebetween (see Fig. 1) as a member of two units completely separated. Representative examples of such laminate sheets include aluminum laminate sheets having resin layers formed on both outer surfaces thereof.

The electrode assembly is not particularly limited as long as it is a structure in which a positive electrode and a negative electrode are configured to enable charge and discharge, and may be, for example, a jelly-roll type structure of a cathode / separation membrane / cathode or a stacked structure, and among them, a stack. More preferred is an electrode assembly. In one preferred example, the electrode assembly may be a lithium ion battery or a lithium ion polymer battery using a lithium transition metal oxide as a positive electrode active material and a carbon material as a negative electrode active material. Such a lithium secondary battery has a problem that the safety is low due to the detachability of the sealing unit despite the excellent performance and advantages as described above, it is possible to ensure more excellent safety by the configuration of the present invention.

The secondary battery of the present invention is manufactured by heat-sealing and sealing the contact surfaces of the battery case in a state in which the electrode assembly is embedded, and the electrode terminal protrudes outward from the sealing portion of the battery case and is formed on one surface of the battery case. The positive lead and the negative lead may be formed together (see FIG. 1), or may be formed on different surfaces, respectively (FIG. 3). The electrode terminal may be an electrode tab protruding from the current collector of the electrode assembly or an electrode lead to which the tabs are connected. The electrode terminal is made of a conductive material, for example, the positive electrode terminal is made of aluminum plate material and the negative electrode terminal is made of copper plate material.

The sealing part of the battery case formed by thermal fusion may be located on all four sides (see FIG. 3), or only on three sides (see FIG. 1) depending on the shape of the case. In the present invention, the shape of the groove in the sealing portion in which the electrode terminal is located and the remaining sealing portion among the sealing portions are different from each other as described above.

First, a groove means a curved structure formed on a sealing interface to which the upper case and the lower case of the battery case are bonded by heat fusion, and are closely adhered to each other so that the floor of the lower case matches the valley formed in the upper case. It is in a form that is. Such grooves may be formed by pressing the sealing part with a die or the like, and the grooves have a high bonding force at the sealing interface, and even when the fluid (external moisture, internal electrolyte, etc.) passes through the groove, Moisture penetration and electrolyte leakage can be suppressed.

In the sealing portion where the electrode terminals are located, a plurality of grooves formed of valleys and floors are formed to cross each other, and such grooves are not formed on the electrode terminals. When the grooves are formed on the electrode terminals, as described above, cracks are caused in the metal material forming the electrode terminals, which is not preferable.

The intersecting grooves are preferably inclined at an angle of at least 20 to 70 degrees, preferably 30 to 50 degrees with respect to the outer circumferential surface of the battery case, and preferably in a substantially regular checkered shape. These cross-sectional grooves, in the forming process by pressing (compressing) the sealing part, attract the laminate sheet on the electrode terminal to increase its adhesion to the electrode terminal, and the stepped portion of the laminate sheet made by both ends of the electrode terminal. Significantly reduces space to increase sealing power.

On the other hand, in the sealing portion where the electrode terminals are not located, grooves of the valley and the floor parallel to the outer circumferential surface of the battery case are formed, and the groove of the parallel structure is a sealing from the battery case accommodating portion in which the electrode assembly is built to the outer space. The sealing property is improved by making the length (distance) of an interface longer.

The number of the grooves is not particularly limited. Preferably, the number of grooves is 2 to 10 in the case of the horizontal structure groove, and 4 to 20 intersections are formed on the straight line on the width of the sealing part in the case of the cross structure groove.

The height of the groove may preferably be 20 to 150% based on the thickness of the sealing portion and the width of the groove may be 50 to 200% relative to its height.

The battery according to the present invention can be preferably used as a unit cell, especially in the medium-large battery pack of high output large capacity. The unit cells used in the medium and large battery packs are generally much larger than the small battery packs, so that the volume expansion change during charging and discharging is large, and due to gas generated due to internal short circuit or deterioration of battery components. A large force tends to be applied to the sealing portion. Therefore, the high sealing property can be provided by the dual contact structure of sealing parts as mentioned above.

Accordingly, the present invention relates to a medium-large battery pack using the above secondary battery as a unit cell.

An example of constructing a medium-large battery pack using a plate-shaped secondary battery as a unit cell as in the present invention is well known in the art, and representatively, the Korean patent of the applicant for constituting a battery pack using a plurality of cartridges. The battery pack of the application 2004-111699 is mentioned. This application is incorporated by reference in the context of the present invention.

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

4 schematically illustrates a pouch-type battery in which grooves are formed in a sealing part according to one embodiment of the present invention.

Referring to FIG. 4, the pouch-type battery 100a has a structure in which electrode leads 410 and 420 are formed symmetrically with each other on the upper and lower portions of the battery case 201, as shown in FIG. 3. The upper case and the lower case, which are separated from each other, are manufactured by thermally fusion in a state in which an electrode assembly (not shown) is embedded. Grooves 600 and 700 are formed in the upper and lower sealing parts 241 and 261 and the two side sealing parts 251 and 271 formed by thermal fusion, respectively.

The grooves 600 formed on the upper and lower sealing parts 241 and 261 are formed only at portions except for the electrode leads 410 and 420, and as shown in FIG. 5, an enlarged view thereof, a plurality of grooves 601 and 602. ) Forms a predetermined angle with respect to the outer circumferential surface 201a of the battery case 201 and has a structure intersecting with each other. In the process of compressing the battery case 201 with a die or the like to form the cross-structure grooves 601 and 602, the laminate sheet on the electrode lead 410 is further pulled to closely contact the electrode lead 410, and the electrode lead is formed. The lateral end 412 of 410 reduces the space of the stepped portion 280 of the formed laminate sheet.

Referring to FIG. 4 again, the grooves 700 formed on both side sealing parts 251 and 271 have a plurality of grooves 701 and 702 as shown in FIG. 6, which is an enlarged view thereof. It is formed parallel to the outer peripheral surface 201a of the. As in the vertical cross-sectional structure of FIG. 7, the groove 700 has a high closeness because the groove and the valley formed on the upper case 231 correspond to the floor and the valley formed on the lower case. In addition, the sealing interface of the upper and lower cases 231 and 221 prevents leakage of external moisture or internal electrolyte due to a long path.

As described above, the secondary battery according to the present invention provides a high sealing property by forming a groove-shaped curved sealing interface which is dualized in the sealing portion where the electrode terminals are located and the remaining sealing portion. Such a secondary battery may be preferably used as a unit cell of a medium to large battery pack of high output large capacity.

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

Claims (9)

A battery manufactured by thermally fusion in a state in which an electrode assembly is embedded in a battery case of a laminate sheet including a resin layer and a metal layer. Among the sealing portions of the battery case formed by the thermal fusion, the sealing portion in which the electrode terminals are positioned is a battery case. The valleys and the grooves of the floor inclined at a predetermined angle with respect to the outer circumferential surface are formed at the sealing interface of the upper and lower cases except for the electrode terminals, and the remaining sealing portion where the electrode terminals are not located is parallel to the outer circumferential surface of the battery case. A secondary battery having a structure in which grooves of the floor are formed at a sealing interface of upper and lower cases. 2. The battery case of claim 1, wherein the battery case is a laminate sheet of a metal layer and a resin layer. The battery case is a unit member having one surface or a partial surface integrally formed thereon. Or a completely separated two-unit member, the secondary battery comprising a structure in which a contact portion on an outer circumferential surface is adhered and sealed in a state in which an electrode assembly is embedded therebetween. The secondary battery according to claim 1, wherein the battery is a lithium ion battery or a lithium polymer battery. The secondary battery of claim 1, wherein the grooves having the intersecting structure are formed at an angle of at least 20 to 70 degrees with respect to the outer circumferential surface of the battery case. The secondary battery of claim 4, wherein the cross-grooves have a regular checkered pattern. According to claim 1, wherein the grooves of the horizontal structure is formed 2 to 10, the grooves of the cross structure is formed by the number of 4 to 20 intersections are formed on a straight line on the width of the sealing portion. Secondary battery. The secondary battery of claim 1, wherein the height of the groove is 20 to 150% based on the thickness of the sealing part. The secondary battery of claim 1, wherein a width of the groove is 50 to 200% of its height. A high output large-capacity battery pack comprising the secondary battery according to any one of claims 1 to 8 as a unit cell.

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