KR101147605B1 - Method of Preparing Secondary Battery - Google Patents

Abstract

The present invention is a method for manufacturing a secondary battery that mounts an electrode assembly in a case of a laminate sheet including a metal layer and a resin layer, and heat-bonds the case along the outer circumferential surface of the electrode assembly accommodating part, using one sealing block. By providing a secondary battery, characterized in that at the same time forming a sealing portion in which the electrode terminal of the electrode assembly is located and the side sealing portion adjacent thereto, the secondary battery is to prevent damage to the battery case at the intersection of the sealing portion It is possible to reduce the manufacturing cost by improving the safety of the battery and reducing the number of battery manufacturing processes.

Description

Manufacturing method of secondary battery {Method of Preparing Secondary Battery}

1 is a perspective view of a typical representative pouch type battery;

Figure 2 is a schematic diagram of the sealing step of the conventional pouch-type battery manufacturing process;

Figure 3 is a schematic diagram of the sealing step of the manufacturing process of the pouch-type secondary battery according to an embodiment of the present invention;

4 is a vertical cross-sectional schematic diagram of the sealing block A-A 'of FIG.

The present invention relates to a method for manufacturing a secondary battery, and more particularly, to a secondary battery in which an electrode assembly is mounted on a case of a laminate sheet including a metal layer and a resin layer, and the case is heat-sealed along the outer circumferential surface of the electrode assembly accommodating part. A manufacturing method of the present invention relates to a secondary battery characterized by simultaneously forming a sealing portion in which an electrode terminal of an electrode assembly is located and a side sealing portion adjacent thereto by using one integrated sealing block.

As technology development and demand for mobile devices are increasing, the demand for batteries as energy sources is rapidly increasing, and accordingly, a lot of researches on batteries capable of meeting various demands have been conducted.

Typically, in terms of the shape of a battery, there is a high demand for a prismatic secondary battery and a pouch-type secondary battery which can be applied to products such as mobile phones with a small thickness, and has advantages such as high energy density, discharge voltage, There is a high demand for lithium secondary batteries such as lithium ion batteries and lithium ion polymer batteries.

In addition, secondary batteries are classified according to the structure of the electrode assembly having a cathode / separation membrane / cathode structure. Representatively, a jelly having a structure in which long sheet-shaped anodes and cathodes are wound with a separator interposed therebetween -Roll (electrode) electrode assembly, a stack (stacked type) electrode assembly in which a plurality of positive and negative electrodes cut in units of a predetermined size are sequentially stacked with a separator, and the positive and negative electrodes of a predetermined unit are interposed through a separator And a stacked / folding electrode assembly having a structure in which a bi-cell or full cells stacked in a state are wound.

Recently, a pouch-type battery having a structure in which a stack type or a stack / fold type electrode assembly is incorporated into a pouch type battery case of an aluminum laminate sheet has attracted much attention due to its low manufacturing cost, small weight, and easy shape deformation. Its usage is also gradually increasing.

1 is a perspective view schematically showing a typical representative pouch-type battery, and FIG. 2 is a schematic diagram of a sealing step of the pouch-type battery manufacturing process.

First, referring to FIG. 1, the pouch-type battery 10 has a structure in which two electrode leads 11 and 12 protrude from each other to protrude from an upper end and a lower end of the electrode assembly 13. The battery case 14 is composed of two unit members of an upper case and a lower case, and both side surfaces 14a which are mutually contacting portions with an electrode assembly (not shown) mounted on an accommodating portion formed on an inner surface thereof. The battery 10 is made by attaching the upper and lower ends 14b and 14c. The battery case 14 has a laminate structure of a resin layer / metal foil layer / resin layer, and can be attached by mutually fusion bonding the resin layer by applying heat and pressure to both side surfaces 14a and upper and lower ends 14b and 14c which are in contact with each other. In some cases, the adhesive may be attached using an adhesive. Since both side surfaces 14a are in direct contact with the same resin layer of the upper and lower battery cases 14, uniform sealing is possible by melting. On the other hand, since the electrode leads 11 and 12 protrude from the upper end 14b and the lower end 14c, the sealing properties are improved in consideration of the thickness of the electrode leads 11 and 12 and the heterogeneity with the material of the exterior member 14. Heat-sealing is carried out in the state which interposed the film-like sealing member 16 between the electrode leads 11 and 12 so that it may be made.

Although the battery case 13 in the drawing is composed of two units of independent members, in some cases, the structure of one unit of a member may be bent.

Heat sealing for sealing is, as shown in Figure 2, using a predetermined sealing block (not shown) is subjected to heat pressurization to the upper end portion 14b and the lower end portion 14c, and then heat pressurization to the side surface 14a This is done by going in the reverse order.

However, in the heat fusion process, the portion 140 where the sealing portions of the upper end portion 14b and the lower end portion 14c and the sealing portions of the side surface 14a cross each other is a process of sealing the side surface 14a and the upper end portion 14b. And since the heat fusion is performed in two steps in the process of sealing the lower end portion 14c, excessive melting phenomenon occurs and / or excessive pressure is applied to the innermost resin layer of the laminate sheet, the laminate of the battery case 14 The metal layers (for example, aluminum layers) of the sheet are in contact with each other and short-circuited, or the innermost sealant (non-stretched PP layer) projects out of the sealing portion.

In this regard, Japanese Patent Application Laid-Open No. 2003-036820 discloses a technique for accommodating an electrode assembly in a tube-shaped battery case and fusion sealing the opening part. However, since the production of the laminate sheet in the form of a tube is not easy in terms of actual mass production technology, the manufacturing process is complicated, the productivity is lowered, and precise battery case is required, so there is a problem in that the manufacturing cost increases.

Therefore, there is a high need for a technique capable of fundamentally solving such problems.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems of the prior art and the technical problems required from the past.

After extensive research and various experiments, the inventors of the present application mount an electrode assembly of a cathode / separation membrane / cathode structure in a sheet-shaped case in which an accommodating part is formed, and in a secondary battery having a structure sealed by heat fusion, When simultaneously forming the sealing part where the electrode terminal of the assembly is located and the side sealing part adjacent thereto using a single sealing block, the battery case can be prevented from being damaged at the intersection of the sealing parts, thereby greatly improving the safety of the battery. It was confirmed that the present invention was completed.

Accordingly, a method of manufacturing a secondary battery according to the present invention is a method of manufacturing a secondary battery in which an electrode assembly is mounted on a case of a laminate sheet including a metal layer and a resin layer, and the case is heat-sealed along the outer circumferential surface of the electrode assembly accommodating portion. By using one integrated sealing block, the sealing part (terminal sealing part) in which the electrode terminal of an electrode assembly is located, and the side sealing part (side sealing part) adjacent to it are formed simultaneously.

According to the manufacturing method of the present invention, when the battery case is sealed by heat welding in a state where the electrode assembly is incorporated in the pouch type case of the laminate sheet, the electrode terminal side sealing portion and the side sealing portion adjacent thereto are heat-sealed at the same time. Excessive thermal fusion at the parts where the parts cross each other damages the battery case and prevents the metal layers of the upper and lower laminate sheets from contacting each other, causing short circuiting or preventing the sealant layer at the innermost side of the laminate sheets from protruding to the outside. In addition, the sealability and safety of the battery can be greatly improved.

In addition, by forming the terminal sealing portion and the side sealing portion at the same time with one integrated sealing block, the process of manufacturing a battery is compared with the conventional method of sealing and sealing the terminal sealing portion and the side sealing portion in two steps sequentially. It is possible to simplify and thus reduce manufacturing costs.

In the present invention, the battery case is preferably a laminate sheet including a metal barrier layer and a resin layer, in particular, a pouch type case of an aluminum laminate sheet.

The laminate sheet may have a structure in which a resin outer layer having excellent durability is added to one surface (outer surface) of the metal barrier layer, and a heat-melt resin sealant layer is added to the other surface (inner surface).

In one preferred example, the metal blocking layer may be a material including aluminum having a barrier property to the gas and the like ductile to enable processing in the form of a thin film. Since the resin outer layer should have excellent resistance from the external environment, it may be made of polyethylene terephthalate (PET) and a stretched nylon film as a polymer resin having a predetermined tensile strength or weather resistance. In addition, the resin sealant layer has a heat sealability (heat adhesion), has a low hygroscopicity to suppress the invasion of the electrolyte, and is a non-stretched polypropylene film (CPP) -based resin, such as not expanded or eroded by the electrolyte This can be used.

The battery case of the laminate sheet may include a lower case that is concave to receive the electrode assembly and an upper case that is bent from one side of the lower case to cover the electrode assembly accommodating portion. In this structure, the upper case connected at one side of the lower case in which the electrode assembly is accommodated is folded to cover the lower case and then heated and pressurized the contact portions of the upper and lower cases using one integrated sealing block for sealing. The sealing part is formed.

In the pouch type secondary battery, the electrode assembly may be classified into an electrode assembly in which the positive electrode terminal and the negative electrode terminal are simultaneously formed on one side of the electrode assembly, and an electrode assembly in which the positive electrode terminal and the negative electrode terminal are formed to face each other. In the present invention, the electrode assembly may preferably have a structure in which the electrode assembly formed in the direction in which the positive electrode terminal and the negative electrode terminal face each other is accommodated in the battery case. Such a battery structure has advantages in that the electrode terminals can be easily electrically connected and the risk of short circuit can be reduced, particularly in a unit battery for a medium-large battery module in which a plurality of battery cells are stacked.

In addition, the electrode assembly is not particularly limited as long as it is a structure composed of a positive electrode and a negative electrode and a separator interposed therebetween, and examples thereof include a folding type, a stack type, or a stack / folding type structure. Details of the electrode assembly of the stack / foldable structure are disclosed in Korean Patent Application Publication Nos. 2001-0082058, 2001-0082059, and 2001-0082060, which are described in the context of the present invention. Incorporated by reference.

According to the manufacturing method of the present invention, after storing the electrode assembly in the battery case, using one integrated sealing block (sealing block), the upper and lower sealing parts and the side sealing adjacent to the electrode terminal of the electrode assembly is located. Form wealth at the same time.

Therefore, the sealing block is composed of one unit as an integral structure as a whole so that the upper and lower sealing parts and the side sealing part can be simultaneously formed.

In one preferred example, the sealing block has an edge (edge) in contact with the sealing portion of the battery case has a rounded structure, the contact end of the battery case is damaged by the angular edge when pressing the battery case for sealing Can be minimized.

In this case, the R value of both edges at which the sealing block is in contact with the battery case is preferably about 0.5 to 4, and when the R value is too small, it is difficult to expect the effect of reducing the damage of the battery case due to the edge. If large, the sealing area is reduced or it is not preferable because the sealing block must be made large for the same sealing site.

In particular, the secondary battery according to the present invention may be preferably applied to a pouch type lithium secondary battery in which an electrode assembly is incorporated in a pouch type case of a laminate sheet, specifically, an aluminum laminate sheet, including a metal layer and a resin layer.

The lithium secondary battery according to the present invention can be preferably used as a unit cell of a medium-large battery module having a high output large capacity due to its excellent life and safety.

Accordingly, the present invention also provides a medium-large battery module including a plurality of secondary batteries as a unit cell, and a high-output large-capacity battery pack including one or more such medium-large battery modules.

The sealing block used in the battery manufacturing method according to the present invention itself has a novel structure different from the conventional sealing block. Specifically, the sealing block has a high conductivity and is formed in a shape corresponding to the sealing portion, and has a rectangular sealing body in a vertical cross section, a heating rod inserted into a hole passing through the interior of the sealing body, and a surface in contact with the battery case. The temperature sensor is inserted into the lower side of the heating rod as a reference, and both edges of the sealing body in contact with the battery case have a rounded structure of R value of 0.5 to 4.

That is, since the temperature sensor is located below the heating rod, heat is applied to the sealing block only up to a temperature corresponding to a predetermined threshold value, and the edge of the sealing portion in contact with the battery case is formed in a rounded structure having a specific size, so that the sealing is performed. The battery case may be prevented from being damaged during the heating and pressing of the block, thereby increasing the life of the battery.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited by the scope of the present invention.

3 is a schematic diagram of the sealing step of the manufacturing process of the pouch-type secondary battery according to an embodiment of the present invention.

Referring to FIG. 3, the electrode assembly 13 has two electrode leads 11 and 12 protruding from each other at the upper end and the lower end thereof, and the battery case formed of the laminate sheet 14 is an electrode assembly 13. The lower case is formed to be concave so as to accommodate the upper case is formed to extend on one side of the lower case to cover the lower case.

The electrode assembly 13 is accommodated in the housing of the lower case, the corresponding portion of the upper case is folded to cover the lower case, and then protruded from the electrode assembly 13 using one integrated sealing block (not shown). The sealing portion in which the electrode leads 11 and 12 are located and the side sealing portion adjacent thereto are simultaneously formed as one continuous sealing portion 15. Therefore, since one continuous sealing portion 15 is formed by one heat pressing process, the intersection of the sealing portion where the electrode leads 11 and 12 are located and the side sealing portion adjacent thereto is as shown in FIG. There is no problem of excessive heat pressurization.

4 is a vertical cross-sectional schematic diagram for the sealing block (A-A ') portion.

Referring to FIG. 4, the sealing block 20 made of a material having high thermal conductivity has a shape corresponding to the sealing portion of the battery case 14 and a sealing body 22 having a substantially rectangular shape in a vertical cross section, such a sealing body. A heating rod 24 inserted into the hole penetrating the inside of the 22 and a temperature sensor 26 inserted below the heating rod 24 with respect to the surface in contact with the battery case 14. . Therefore, the high heat induced from the heating rod 24 is transferred to the battery case 14 through the sealing body 22 to perform a predetermined sealing, since the temperature sensor 26 is located below the heating rod 24. By accurately measuring the heat conducted from the heating rod 24 to the battery case 14, it is possible to control the excessive melting phenomenon in the battery case 14.

In addition, since the edges 22a and 22b of the sealing body 22, which are in contact with the battery case 14, have a rounded structure, the battery case 14 may be prevented from being damaged during the pressing process for sealing. have.

In the following Examples, Comparative Examples and Experimental Examples will be described in more detail, but the present invention is not limited thereto.

Example 1

95% by weight of LiCoO ₂ , 2.5% by weight of Super-P (conductor) and 2.5% by weight of PVdF (binder) were added to NMP (N-methyl-2-pyrrolidone) as a cathode active material to prepare a cathode mixture slurry. 95% by weight of artificial graphite, 1% by weight of Super-P (conductive agent), and 4% by weight of PVdF (binder) were added to NMP as a solvent to prepare a negative electrode mixture slurry, which was applied to aluminum foil and copper foil, respectively. After that, each was cut to prepare a positive plate and a negative plate. An electrode assembly was manufactured by sequentially stacking the positive electrode plate and the negative electrode plate prepared above with Celgard ^TM (TONEN) as a separator.

The electrode tab and the electrode lead of the electrode assembly were ultrasonically fused and stored in the lower case, and the corresponding portion of the upper case was folded to cover the lower case. 3 and 4, the integrated sealing block capable of simultaneously forming a sealing portion (terminal sealing portion) and a side sealing portion (side sealing portion) adjacent to the electrode terminal protruding from the electrode assembly. (Material: NaK, edge R value: 1) by applying heat and pressure at the same time, the upper case and the lower case was in close contact to complete the battery.

Comparative Example 1

As shown in FIG. 2, the battery was completed in the same manner as in Example 1 except that the edge sealing portion was formed by using separate sealing blocks having no rounding structure, and the terminal sealing portion and the side sealing portion were sequentially formed.

[Experimental Example 1]

In each of the 20 manufactured batteries in Example 1 and Comparative Example 1, it was confirmed whether the aluminum layer of the upper case and the aluminum layer of the lower case are in contact with each other at the intersection of the terminal sealing portion and the side sealing portion. The results are shown in Table 1 below.

TABLE 1

As shown in Table 1, the cells of Example 1 according to the present invention were not confirmed that the aluminum layers of the upper and lower casing contact each other in the batteries, but the batteries of Comparative Example 1 are in contact with each other in some cells The phenomenon was confirmed.

That is, in the batteries of Comparative Example 1 due to excessive heat and pressure applied to the intersection of the terminal sealing portion and the side sealing portion, the inner sealant layer was excessively melted and pushed toward the outer circumferential surface, resulting in the direct contact of the aluminum layers of the battery case. . In fact, as a result of visually examining the corresponding parts of the batteries in which the contact phenomenon was confirmed, it was confirmed that the inner sealant layer forming the inner surface of the battery case protruded to the outside. As such, the sealing portion of the portion directly contacted with the aluminum layer may be greatly deteriorated and leakage of the electrolyte may occur.

In addition, in some batteries of Comparative Example 1, it was confirmed that the aluminum layer was exposed to the upper surface at the inner portion of the battery case in contact with the edge of the sealing block. This is because the aluminum outer layer is exposed while the resin outer layer of the battery case is damaged by the edge of the angled sealing block during the pressing process, and the aluminum layer exposed to the outside may be quickly exposed by an external material such as, for example, brine. Corrosion may act as a cause of greatly reducing the battery life.

Although described above with reference to the drawings according to an embodiment of the present invention, those of ordinary skill in the art will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

As described above, the secondary battery according to the present invention forms the electrode terminal side sealing portion of the pouch type secondary battery and the side sealing portion adjacent thereto at the same time by using a single sealing block, whereby the battery case is damaged at the intersection of the sealing portions. It is possible to reduce the manufacturing cost by improving the safety of the battery and reducing the number of battery manufacturing processes.

Claims (11)

A method of manufacturing a secondary battery in which an electrode assembly is mounted on a case of a laminate sheet including a metal layer and a resin layer, and heat-sealed the case along the outer circumferential surface of the electrode assembly accommodating portion, using one integrated sealing block, A sealing part (terminal sealing part) in which the electrode terminal of the electrode assembly is located and a side sealing part (side sealing part) adjacent thereto are formed at the same time, and the sealing block has a high conductivity and has a shape corresponding to the sealing part, and has a vertical cross section. A rectangular sealing body, a heating rod inserted into a hole penetrating the inside of the sealing body, and a temperature sensor inserted into the lower side of the heating rod on the basis of a surface in contact with the battery case, wherein the battery case of the sealing body is included. Both edges in contact with the contact is characterized in that the rounded structure of the R value of 0.5 to 4. The method of claim 1 wherein the case is a pouch type case. 2. The laminate sheet according to claim 1, wherein the laminate sheet has a structure in which a durable resin outer layer is added to one surface (outer surface) of the aluminum barrier layer, and a heat-melt resin sealant layer is added to the other surface (inner surface). How to. The method of claim 3, wherein the case comprises a lower case in which an electrode assembly accommodating part is formed, and an upper case bent at one side of the lower case to cover the electrode assembly accommodating part. The method of claim 1, wherein the electrode assembly is formed in a direction in which the positive electrode terminal and the negative electrode terminal face each other. The method of claim 1, wherein the electrode assembly has a stacked structure or a stack / foldable structure. delete delete delete delete A sealing block for executing the method according to any one of claims 1 to 6, wherein the sealing block has a high conductivity and has a shape corresponding to the sealing portion, and has a rectangular shape in a vertical cross section, and a hole penetrating the inside of the sealing body. The heating rod is inserted, and the temperature sensor is inserted into the lower side of the heating rod on the basis of the surface in contact with the battery case, the edges of both sides of the sealing body in contact with the battery case has a rounding structure of R value of 0.5 to 4 Sealing block, characterized in that made.

Images