Patent Description:
In general, secondary batteries include nickel-cadmium batteries, nickel-hydrogen batteries, lithium ion batteries, and lithium ion polymer batteries. Such a secondary battery is being applied to and used in small-sized products such as digital cameras, P-DVDs, MP3Ps, mobile phones, PDAs, portable game devices, power tools, E-bikes, and the like as well as large-sized products requiring high power such as electric vehicles and hybrid vehicles, power storage devices for storing surplus power or renewable energy, and backup power storage devices.

Such a secondary battery is classified into a pouch type secondary battery and a can type secondary battery according to a material of a case accommodating the electrode assembly. In the pouch type secondary battery, an electrode assembly is accommodated in a pouch made of a flexible polymer material. Also, in the can type secondary battery, an electrode assembly is accommodated in a case made of a metal or plastic material.

In the secondary battery, a gas may be generated by internal short-circuit, overcharging, overdischarging, or the like due to an external impact. In addition, when the secondary battery is stored at a high temperature, an electrochemical reaction between an electrolyte and an electrode active material is quickly accelerated by the high temperature to generate a gas.

Here, the generated gas may allow the secondary battery to increase in internal pressure to cause problems such as weakening of bonding force between components, damage of a case of the secondary battery, an early operation of a protection circuit, deformation of an electrode, internal short-circuit, explosion, and the like. To prevent these phenomena, in the case of the can type secondary battery, a protection member such as a CID filter and a safety vent is provided. Thus, when the pressure within the case increases, electrical connection may be physically interrupted. However, in the case of the pouch type secondary battery according to the related art, the protection member is not sufficiently provided.

Document <CIT> discloses a valve for a fuel injector. Document <CIT> relates to the sealing a pouch-type battery cell.

An object to be solved by the present invention is to provide at least one venting device, which is inserted into a sealing part of a pouch of a secondary battery to discharge an internal gas when an internal pressure of the pouch increases so as to adjust the internal pressure, and a method for manufacturing the same.

The objects of the present invention are not limited to the aforementioned object, but other objects not described herein will be clearly understood by those skilled in the art from descriptions below.

To solve the above problem, a venting device according to claim <NUM> is proposed.

Also, in the sheet, an edge of an outer circumference of the surface of the outlet-side of the passage may be chamfered or filleted.

Also, the plate spring may have one side having a cap shape that is convex outward and form an insertion space into which the sheet is inserted therein.

Also, the one side of the plate spring may include a central portion formed at a center thereof and a peripheral portion extending outward from the central portion, and a gas exhaust hole may be punched in the peripheral portion of the plate spring.

Also, an end of the other side of the plate spring may be bent toward the sheet inserted into the insertion space.

Also, the polymer includes an acid-treated polyolefin-based polymer.

Also, the metal may include aluminum or stainless steel.

Also, the surface treatment layer may include at least one of chromium, zirconium, and titanium.

Also, the housing may include an upper housing and a lower housing, which have shapes or sizes different from each other.

Also, the lower housing may have a width less than that of the upper housing.

Also, the upper housing may have a circular cylinder shape, and the lower housing may have an oval cylinder shape.

To solve the above problem, a method for manufacturing a venting device according to claim <NUM> is proposed.

Also, the step of forming the surface treatment layer may include: a step of debinding the metal plate; a primarily washing step; an etching step; a secondarily washing step; a surface treatment step; a tertiarily washing step; and a drying step.

Also, the surface treatment step may include a step of performing one of chromate treatment, zirconia treatment, and titanium treatment.

Also, after the step of seating the ball, the method may further include: a step of allowing a plate spring having a cap shape to surround the sheet and the ball; and a step of inserting the sheet into a housing inserted between both surfaces of the sealing part so as to be sealed together with the sealing part.

Particularities of other embodiments are included in the detailed description and drawings.

The embodiments of the present invention may have at least the following effects.

Even though all the ball and the sheet are made of the metal, the adhesion between the ball and the sheet may be improved to improve the sealability when the passage is closed.

The effects of the prevent invention are not limited by the aforementioned description, and thus, more varied effects are involved in this specification.

Advantages and features of the present disclosure, and implementation methods thereof will be clarified through following embodiments described with reference to the accompanying drawings. Further, the present invention is only defined by scopes of claims.

Unless terms used in the present invention are defined differently, all terms (including technical and scientific terms) used herein have the same meaning as generally understood by those skilled in the art. Also, unless defined clearly and apparently in the description, the terms as defined in a commonly used dictionary are not ideally or excessively construed as having formal meaning.

In the following description, the technical terms are used only for explaining a specific exemplary embodiment while not limiting the present invention. In this specification, the terms of a singular form may comprise plural forms unless specifically mentioned. The meaning of "comprises" and/or "comprising" does not exclude other components besides a mentioned component.

<FIG> is an assembled view of a secondary battery <NUM> including a venting device <NUM> according to an embodiment of the present invention, and <FIG> is a perspective view of the secondary battery <NUM> of <FIG>, which is completely manufactured.

In order to manufacture the secondary battery <NUM> according to an embodiment of the present invention, first, electrode active material slurry is applied to a positive electrode collector and a negative electrode collector to manufacture a positive electrode and a negative electrode. Then, the electrodes are laminated on both sides of a separator to form an electrode assembly <NUM> having a predetermined shape. Then, the electrode assembly <NUM> is accommodated in a battery case <NUM>, and also, an electrolyte is injected into the battery case <NUM> to perform sealing on the battery case <NUM>.

As illustrated in <FIG>, the electrode assembly <NUM> includes an electrode tab <NUM>. The electrode tab <NUM> is connected to each of a positive electrode and a negative electrode of the electrode assembly <NUM> to protrude to the outside of the electrode assembly <NUM>, thereby providing a path, through which electrons are moved, between the inside and outside of the electrode assembly <NUM>. The electrode collector of the electrode assembly <NUM> is constituted by a portion coated with the slurry and a distal end, on which the slurry is not applied, i.e., a non-coating portion. Also, the electrode tab <NUM> may be formed by cutting the non-coating portion or by connecting a separate conductive member to the non-coating portion through ultrasonic welding. As illustrated in <FIG>, the electrode tabs <NUM> may protrude from one side of the electrode assembly <NUM> in the same direction, but the present invention is not limited thereto. For example, the electrode tabs <NUM> may protrude in directions different from each other.

In the electrode assembly <NUM>, the electrode lead <NUM> is connected to the electrode tab <NUM> through spot welding. Also, a portion of the electrode lead <NUM> is surrounded by an insulation part <NUM>. The insulation part <NUM> may be disposed to be limited within a sealing part <NUM>, at which an upper pouch <NUM> and a lower pouch <NUM> of the battery case <NUM> are thermally fused, so that the electrode lead <NUM> is bonded to the battery case <NUM>. Also, electricity generated from the electrode assembly <NUM> may be prevented from flowing to the battery case <NUM> through the electrode lead <NUM>, and the sealing of the battery case <NUM> may be maintained. Thus, the insulation part <NUM> may be made of a nonconductor having non-conductivity, which is not electrically conductive. In general, although an insulation tape which is easily attached to the electrode lead <NUM> and has a relatively thin thickness is mainly used as the insulation part <NUM>, the present invention is not limited thereto. For example, various members may be used as the insulation part <NUM> as long as the members are capable of insulating the electrode lead <NUM>.

The electrode lead <NUM> may extend in the same direction or extend in directions different from each other according to the formation positions of the positive electrode tab <NUM> and the negative electrode tab <NUM>. The positive electrode lead <NUM> and the negative electrode lead <NUM> may be made of materials different from each other. That is, the positive electrode lead <NUM> may be made of the same material as the positive current collector, i.e., an aluminum (Al) material, and the negative electrode lead <NUM> may be made of the same material as the negative current collector, i.e., a copper (Cu) material or a copper material coated with nickel (Ni). Also, a portion of the electrode lead <NUM>, which protrudes to the outside of the battery case <NUM>, may be provided as a terminal part and electrically connected to an external terminal.

In the pouch type secondary battery <NUM> according to an embodiment of the present invention, the battery case <NUM> may be a pouch made of a flexible material. Hereinafter, the case in which the battery case <NUM> is the pouch will be described. Also, the battery case <NUM> accommodates the electrode assembly <NUM> so that a portion of the electrode lead <NUM>, i.e., the terminal part is exposed and then is sealed. As illustrated in <FIG>, the battery case <NUM> includes the upper pouch <NUM> and the lower pouch <NUM>. A cup part <NUM> having an accommodation space <NUM> accommodating the electrode assembly <NUM> is formed in the lower pouch <NUM>, and the upper pouch <NUM> covers an upper portion of the accommodation space <NUM> to prevent the electrode assembly <NUM> from being separated to the outside of the battery case <NUM>. Here, as illustrated in <FIG>, the cup part <NUM> having the accommodation space <NUM> may be formed in the upper pouch <NUM> to accommodate the electrode assembly <NUM> in the upper portion. As illustrated in <FIG>, one side of the upper pouch <NUM> and one side of the lower pouch <NUM> may be connected to each other. However, the present invention is not limited thereto. For example, the upper pouch <NUM> and the lower pouch may be separately manufactured to be separated from each other.

After the upper pouch <NUM> and the lower pouch <NUM> of the battery case <NUM> contact each other, the sealing part <NUM> formed on an edge may be sealed. Here, as illustrated in <FIG>, according to an embodiment of the present invention, the venting device <NUM> is inserted between both surfaces of the sealing part <NUM> so as to be sealed together with the sealing part <NUM> and thus be fixed within the sealing part <NUM>. Also, the venting device <NUM> includes a passage through which the inside and the outside of the battery case <NUM> communicate with each other. When an internal pressure of the battery case <NUM> increases, an internal gas is discharged to the outside to adjust the pressure. The venting device <NUM> will be described below in detail.

When the electrode lead <NUM> is connected to the electrode tab <NUM> of the electrode assembly <NUM>, and the insulation part <NUM> is provided on a portion of the electrode lead <NUM>, the electrode assembly <NUM> may be accommodated in the accommodation space <NUM> provided in the lower pouch <NUM>, and the upper pouch <NUM> may cover the upper side of the accommodation space <NUM>. Also, when the electrolyte is injected, and the sealing part <NUM> provided on the edge of each of the upper pouch <NUM> and the lower pouch <NUM> is sealed, the secondary battery <NUM> is manufactured as illustrated in <FIG>.

<FIG> is a cross-sectional view of the battery case <NUM> according to an embodiment of the present invention.

The battery case <NUM> is manufactured by performing drawing on the pouch film <NUM>. That is, the pouch film <NUM> is elongated to form the cup part <NUM>, thereby manufacturing the battery case <NUM>. As illustrated in <FIG>, the pouch film <NUM> includes a gas barrier layer <NUM>, a surface protection layer <NUM>, and a sealant layer <NUM>.

The gas barrier layer <NUM> may secure mechanical strength of the battery case <NUM>, block introduction and discharge of a gas or moisture outside the secondary battery <NUM>, and prevent the electrolyte from leaking. In general, the gas barrier layer <NUM> includes a metal. Particularly, aluminum (Al) foil is mainly used for the gas barrier layer <NUM>. Aluminum may secure the mechanical strength of a predetermined level or more, but be light in weight. Thus, aluminum may secure complement for electrochemical properties of the electrode assembly <NUM> and the electrolyte and heat dissipation. However, the present invention is not limited thereto. For example, the gas barrier layer <NUM> may be made of various materials. For example, the gas barrier layer <NUM> may be made of one material or a mixture of two or more materials selected from the group consisting of Fe, C, Cr, Mn, Ni and Al. Here, when the gas barrier layer <NUM> is made of a material containing iron, the mechanical strength may be improved. When the gas barrier layer <NUM> is made of a material containing aluminum, flexibility may be improved. Thus, the material forming the gas barrier layer <NUM> may be used in consideration of the characteristics of the gas barrier layer <NUM>.

The surface protection layer <NUM> is made of a polymer and disposed at the outermost layer to protect the secondary battery <NUM> against external friction and collision and also electrically insulates the electrode assembly <NUM> from the outside. Here, the outermost layer represents a direction opposite to a direction in which the electrode assembly <NUM> is disposed with respect to the gas barrier layer <NUM>, i.e., in an outward direction. The surface protection layer <NUM> may be made of at least one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymer, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, teflon, and glass fiber. Particularly, a polymer such as a nylon resin or polyethylene terephthalate (PET) having mainly abrasion resistance and heat resistance is used. Also, the surface protection layer <NUM> may have a single layer structure made of one material or a composite layer structure in which two or more materials are respectively formed as layers.

The sealant layer <NUM> is made of a polymer and disposed at the innermost layer to directly contact the electrode assembly <NUM>. The pouch type battery case <NUM> may be manufactured while a portion thereof is stretched to form the cup part <NUM> having the accommodation space <NUM> having a bag shape when the pouch film <NUM> having the lamination structure as described above is drawn by using a punch or the like. Also, when the electrode assembly <NUM> is accommodated in the accommodation space <NUM>, the electrolyte is injected. Thereafter, when the upper pouch <NUM> and the lower pouch <NUM> may contact each other, and thermal compression is applied to the sealing part <NUM>, the sealant layers <NUM> may be bonded to each other to seal the battery case <NUM>. Here, since the sealant layer <NUM> directly contacts the electrode assembly <NUM>, the sealant layer <NUM> may have to have insulating properties. Also, since the sealant layer <NUM> contacts the electrolyte, the sealant layer <NUM> may have to have corrosion resistance. Also, since the inside of the battery case <NUM> is completely sealed to prevent materials from moving between the inside and outside of the battery case <NUM>, high sealability has to be realized. That is, the sealing part <NUM> in which the sealant layers <NUM> are bonded to each other should have superior bonding strength. In general, the sealant layer <NUM> may be made of at least one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymer, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, teflon, and glass fiber. Particularly, a polyolefin-based resin such as polypropylene (PP) or polyethylene (PE) may be used for the sealant layer <NUM>. Polypropylene (PP) is excellent in mechanical properties such as tensile strength, rigidity, surface hardness, abrasion resistance, and heat resistance and chemical properties such as corrosion resistance and thus is mainly used for manufacturing the sealant layer <NUM>. Furthermore, the sealant layer <NUM> may be made of a cated polypropylene or a polypropylene-butylene-ethylene terpolymer. Also, the sealant layer <NUM> may have a single layer structure made of one material or a composite layer structure in which two or more materials are respectively formed as layers.

<FIG> is a perspective view of the venting device <NUM> according to an embodiment of the present invention.

As described above, the secondary battery <NUM> according to an embodiment of the present invention further includes at least one venting device <NUM>. At least one venting device <NUM> is inserted into the sealing part <NUM> of the pouch of the secondary battery <NUM> to discharge the internal gas when the internal pressure of the pouch increase, thereby adjusting the pressure. For this, the venting device <NUM> includes: a housing <NUM> inserted between both surfaces of the sealing part <NUM> so as to be sealed together with the sealing part <NUM>; a sheet <NUM> which is made of a metal and formed in the housing <NUM> and through which a passage <NUM> allowing the inside and the outside of the pouch to communicate with each other passes; and a ball <NUM> contacting or spaced apart from the sheet <NUM> at a side of an outlet <NUM> (hereinafter, referred to as an outlet-side) of the passage <NUM> to open and close the passage <NUM>. The venting device <NUM>, further comprises a plate spring formed to surround the ball and the sheet (<NUM>) and having elasticity to open and close the passage together with the ball according to an internal pressure of the pouch. The sheet <NUM> includes: a surface treatment layer formed on chamfered or filleted one surface <NUM> to face the ball <NUM> after an edge of an inner circumference of a surface of the outlet-side of the passage <NUM> is chamfered or filleted; and a polymer layer <NUM> made of a polymer and thermally fused to the surface treatment layer <NUM>.

The housing <NUM> may be inserted between both the surfaces of the sealing part <NUM> so as to be sealed together with the sealing part <NUM>. When the housing <NUM> is inserted between both the surfaces of the sealing part <NUM>, a sealant layer <NUM> that is the innermost layer of the sealing part <NUM> contacts the housing <NUM>. Also, when heat and a pressure are applied, while the sealant layer <NUM> of the sealing part <NUM> is sealed, the housing <NUM> is fused to be sealed together. As illustrated in <FIG>, the housing <NUM> may include an upper housing <NUM> and a lower housing <NUM>, and a stepped portion may be formed between the upper housing <NUM> and the lower housing <NUM>. The stepped portion may be formed because the upper housing <NUM> and the lower housing <NUM> have shapes or sizes different from each other. For example, the upper housing <NUM> may have a transverse cross-section having a circular cylinder shape, and the lower housing <NUM> may have a transverse cross-section having an oval cylinder shape. Alternatively, the lower housing <NUM> may have a width less than that of the upper housing <NUM>. Thus, the lower housing <NUM> may be inserted between both the surfaces of the sealing part <NUM> so as to be sealed together with the sealing part <NUM>. Thus, the lower housing <NUM> may be fused to the inner surface of the sealing part <NUM>, and the upper housing <NUM> may protrude to the outside of the pouch. Here, if the lower housing <NUM> has an excessively large width, the sealing part <NUM> has to be deformed in size. Thus, the sealing of the sealing part <NUM> may be damaged. Thus, the lower housing <NUM> may have a width less than a thickness of the sealing part <NUM>. Particularly, it is preferable that a long axis of the transverse cross-section has a width that is <NUM> or more less. Also, if the upper housing <NUM> has an excessively large size, the upper housing <NUM> protruding to the outside of the pouch may interfere with other secondary batteries <NUM> that are disposed in the vicinity of the upper housing <NUM>. Thus, it may be difficult to assemble a package or module of the secondary battery <NUM>. Thus, the upper housing <NUM> may have a width less than a thickness of the sealing part <NUM>. Particularly, it is preferable that the transverse cross-section has a diameter <NUM> or more less. However, the present invention is not limited thereto. For example, the upper housing <NUM> and the lower housing <NUM> may have various shapes, for example, one cylinder shape without being distinguished from each other.

The sheet <NUM> may be formed in the housing <NUM> and made of a metal. Also, the passage <NUM> through which the inside and the outside of the pouch communicate with each other may be formed to pass through a center of the sheet <NUM>. The sheet <NUM> will be described below in detail.

The plate spring <NUM> may be made of a metal to open and close the passage <NUM> formed in the sheet <NUM> according to an internal pressure of the pouch. Particularly, when the internal pressure of the pouch is less than a specific pressure, the plate spring <NUM> may contact the sheet <NUM> to close the outlet <NUM> of the passage <NUM>. Also, when the internal pressure of the pouch gradually increase to exceed the specific pressure, the plate spring <NUM> may be spaced apart from the sheet <NUM> to open the outlet <NUM> of the passage <NUM>.

According to the related art, the passage <NUM> is closed by using a coil spring. However, the venting device has to be miniaturized so as to be inserted into the sealing part <NUM> of the secondary battery <NUM>. However, if the coil spring is used like the related art, the venting device may be complicated in structure and limited in miniaturization. Thus, according to an embodiment of the present invention, the plate spring <NUM> is used to simplify the structure of the venting device and miniaturize the venting device so as to be inserted into the sealing part <NUM> of the secondary battery <NUM>.

The ball <NUM> may have a spherical shape and be disposed at the outlet-side of the passage <NUM>. Also, the ball <NUM> may be disposed between the plate spring <NUM> and the sheet <NUM> so as to contact or be spaced apart from the sheet <NUM>, thereby closing or opening the passage <NUM>. Particularly, the ball <NUM> receives elastic force from a central portion <NUM> of one side <NUM> of the plate spring <NUM> toward the sheet <NUM> so as to be closely attached to the sheet <NUM>, thereby closing the passage <NUM>. Here, according to an embodiment of the present invention, surface treatment may be performed on one surface <NUM> of the sheet <NUM> to form a surface treatment layer <NUM>. Then, a polymer film may be fused, and a polymer layer <NUM> is laminated. Thus, the ball <NUM> may be closely attached to the polymer layer <NUM> to prevent a gap from occurring, thereby preventing sealability from being deteriorated. The ball <NUM> may be made of a polymer to more improve adhesion with respect to the sheet <NUM>, but may be deteriorated in durability. Thus, in order to improve the durability of the ball <NUM>, it may be preferable that the ball <NUM> is made of a metal.

<FIG> is a flowchart illustrating a method for manufacturing the venting device <NUM> according to an embodiment of the present invention.

According to an embodiment of the present invention, even though all the ball <NUM> and the sheet <NUM> are made of the metal, the adhesion between the ball <NUM> and the sheet <NUM> may be improved to improve the sealability when the passage <NUM> is closed. For this, a method for manufacturing the venting device <NUM> according to an embodiment of the present invention includes: a step (S501) of manufacturing a sheet <NUM> which is made of a metal, through which a passage <NUM> passes and in which an edge of an inner circumference of a surface of an outlet-side of the passage <NUM> is chamfered or filleted; a step (S502) of forming a surface treatment layer <NUM> on the chamfered or filleted one surface <NUM> of the sheet <NUM>; a step (S503) of fusing a film made of a polymer on the surface treatment layer <NUM>; and a step (S504) of seating a spherical ball <NUM> on the fused film. Thereafter, the method for manufacturing the venting device <NUM> may further include: a step (S505) of allowing a plate spring <NUM> to surround the sheet <NUM> and the ball <NUM>; and a step (S506) of inserting the sheet <NUM> and the plate spring <NUM> into a housing <NUM> that is inserted between both surfaces of a sealing part <NUM> so as to be sealed together with the sealing part <NUM>.

Hereinafter, each of the steps illustrated in the flowchart of <FIG> will be described with reference to <FIG>.

<FIG> is a schematic view of the sheet <NUM> according to an embodiment of the present invention.

As described above, the sheet <NUM> is formed in the housing <NUM> and made of a metal. Also, as illustrated in <FIG>, in the sheet <NUM>, the edge of the inner circumference of the surface of the outlet-side of the passage <NUM> is chamfered or filleted. Thus, the ball <NUM> may be easily closely attached to the chamfered or filleted surface <NUM> of the sheet <NUM>. According to an embodiment of the present invention, the surface treatment layer <NUM> is formed on the chamfered or filleted surface <NUM> of the sheet <NUM>, and then, the polymer film is fused. Thus, the ball <NUM> closely attached to the sheet <NUM> may be improved in adhesion to improve sealability when the passage <NUM> is closed.

<FIG> is a flowchart illustrating a method for forming the surface treatment layer <NUM> on the one surface <NUM> of the sheet <NUM> according to an embodiment of the present invention.

As illustrated in <FIG>, the sheet <NUM> has a cylinder shape through which the passage <NUM> passes. Also, if the sheet <NUM> is made of a polymer, durability may be deteriorated to reduce a lifespan of the venting device <NUM>. Thus, the sheet <NUM> according to an embodiment of the present invention is made of a metal (S501). Particularly, the metal may include aluminum (Al) or stainless steel (STS). In the sheet <NUM>, the edge of the inner circumference of the surface of the outlet-side of the passage <NUM> may be chamfered or filleted. Here, although the passage <NUM> and the edge of the inner circumference are cut after the sheet <NUM> is manufactured first in the cylinder shape, the sheet <NUM> may be manufactured through various methods without being limited, for example, a melted metal may be injected into a casting mold in which the passage <NUM> and the edge of the inner circumference are filled to manufacture the sheet <NUM>.

The surface treatment layer <NUM> is formed on the chamfered or filleted one surface <NUM> of the sheet <NUM> (S502). According to an embodiment of the present invention, in order to form the surface treatment layer <NUM>, a step (S701) of debinding the one surface <NUM> of the sheet <NUM>; a primary washing step (S702); an etching step (S703); a secondary washing step (S704); a surface treatment step (S705); a tertiary washing step (S706); and a drying step (S707) are performed.

<FIG> is a schematic view illustrating a state in which the surface treatment layer <NUM> is formed on the one surface <NUM> of the sheet <NUM> according to an embodiment of the present invention.

In order to form the surface treatment layer <NUM>, the one surface <NUM> of the sheet <NUM> is debound (S701). Various metal processing processes may be performed to manufacture the sheet <NUM>. Here, in order to reduce friction between the sheet <NUM> and a metal processing device, a lubricant is applied to the one surface <NUM> of the sheet <NUM>. Thus, when the sheet <NUM> is completely manufactured, the lubricant, dusts, or other impurities may exist on the one surface <NUM> of the sheet <NUM>. The debinding process is performed to remove the lubricant, the dusts, or other impurities so that the sheet <NUM> is more efficiently surface-treated.

After, the debinding process, the primary washing step (S702) is performed to wash a solution used for the debinding. Here, the washing refers to a water cleaning or washing process. In order to prevent other impurities dissolved in water from being attached during the washing, it is preferable that distilled water in which the impurities are not dissolved is used as the water.

When the metal is left in air, the metal may be oxidized somewhat to produce an oxidizing material. Particularly, if the sheet <NUM> is made of aluminum, a film made of aluminum oxide may be formed on the one surface <NUM> of the sheet <NUM>. Thus, the etching (S703) is performed to remove the oxidized material produced on the one surface <NUM> of the sheet <NUM>.

After the etching process, the secondary washing (S704) is performed to wash the solution used for the etching. Also, the surface treatment (S705) is performed on the one surface <NUM> of the sheet <NUM>. The surface treatment is a process of chemically treating a surface of the metal such as aluminum to improve corrosion resistance or abrasion resistance of the metal, i.e., to change a physical property. The surface treatment includes anodizing, chemical film processing, electroplating, and the like.

Here, according to an embodiment of the present invention, the surface treatment may be chromate treatment using chromium. The chromate treatment is a kind of chemical film processing in which an insoluble chromate (chromates) film containing a chromium component is thinly formed on the surface of the metal. For this, the sheet <NUM> is immersed in an aqueous solution containing chromium ions. As a result, the chromium ions undergo oxidation reaction, and the insoluble chromium oxide is generated on the one surface <NUM> of the sheet <NUM> to form a chromate film. That is, the surface treatment layer <NUM> may be the chromate film containing chromium. Here, the chromium ions may be various types of ions without limitation such as hexavalent or trivalent ions. Also, the various non-limiting materials such as chromic anhydride, chromium nitrate, chromium sulfate, chromium acetate, and chromium chloride may be used as the aqueous solution containing chromium ions.

The surface treatment according to another embodiment of the present invention may be non-chromate treatment using a material other than chromium. Here, the material other than chromium may be, for example, zirconium. If zirconia treatment using zirconium is performed, the sheet <NUM> is immersed in an aqueous solution containing the zirconium ions. As a result, the zirconium ions undergo oxidation reaction, and zirconium oxide is generated on the one surface <NUM> of the sheet <NUM> to form a zirconia film. The non-chromate treatment is not limited thereto and may include titanium treatment using titanium. That is, according to another embodiment of the present invention, the surface treatment layer <NUM> may be the zirconia film containing zirconium or the titanium film containing titanium.

After the surface treatment (S705), the tertiary washing step (S706) is performed to wash the solution used for the surface treatment. Also, since the sheet <NUM> is dried (S707), the surface treatment layer <NUM> is formed on the one surface <NUM> of the sheet <NUM> as illustrated in <FIG>. As described above, the surface treatment layer <NUM> may be formed on the one surface <NUM> of the sheet <NUM> to secure the corrosion resistance and also secure fusibility that the polymer material is well fused to the surface.

<FIG> is a schematic view illustrating a state in which the polymer layer <NUM> is laminated on the surface treatment <NUM> layer according to an embodiment of the present invention.

As described above, if the ball <NUM> or the sheet <NUM> is made of the polymer, the durability may be deteriorated. If all the ball <NUM> and the sheet <NUM> are made of the metal, the gap may occur between the ball <NUM> and the sheet <NUM> to deteriorate the sealability. If the polymer film adheres by using an adhesive without performing the surface treatment on the one surface <NUM> of the sheet <NUM>, the one surface <NUM> of the sheet <NUM> may increase in thickness by the adhesive. In addition, if the adhesive performance of the adhesive is deteriorated as the venting device <NUM> is aged as time elapses, the polymer film may be delaminated. Thus, according to an embodiment of the present invention, the surface treatment is performed on the one surface <NUM> of the sheet <NUM> to form the surface treatment layer <NUM>, and the polymer film is fused to the surface treatment layer <NUM> to laminate the polymer layer <NUM> (S503).

Here, since the polymer film has a thin and wide film shape, and the edge of the inner circumference of the one surface <NUM> of the sheet <NUM> is chamfered or filleted, it is difficult to seat the polymer film on the one surface <NUM> of the sheet <NUM>. A sealing tool for fusing the polymer film has one end that protrudes in a shape corresponding to the one surface <NUM> of the sheet <NUM>. Thus, the polymer film is finely cut and seated on the one end of the sealing tool. Then, the one end of the sealing tool contacts the one surface <NUM> of the sheet <NUM>. As a result, the polymer film may be easily seated. Also, as illustrated in <FIG>, when heat and a pressure are applied through the sealing tool, the polymer film may be fused to laminate the polymer layer <NUM> on the surface treatment layer <NUM>.

According to an embodiment of the present invention, before the polymer film is fused, the polymer film temporarily adheres to the surface treatment layer <NUM> formed on the one surface <NUM> of the sheet <NUM>. That is, the polymer film is temporarily attached to the surface treatment layer <NUM>. Thus, even though the sheet <NUM> moves along a process line, the polymer film may not move from the sheet <NUM>. The temporarily adhering process of the polymer film is performed by applying a pressure of <NUM> MPa to <NUM> MPa for <NUM> seconds to <NUM> seconds under a temperature of <NUM> to <NUM>. Since the temporary adhesion is a process of temporarily attaching the polymer film, the polymer film has to be easily detached for performing the fusion process later. Thus, if the temporary adhesion is performed under a temperature of <NUM> or more, the polymer film may be more strongly attached. Also, if the temporary adhesion is performed under a temperature of <NUM> or less, the polymer film may not be properly attached.

Also, since the polymer film is fused by applying the heat and pressure for a predetermined time, the polymer layer <NUM> may be laminated on the surface treatment layer <NUM> of the sheet <NUM>. The fusion process may be performed under a temperature of <NUM> to <NUM>. In general, if the temperature is less than <NUM>, the polymer film, particularly, the film containing polypropylene may not be sufficiently melted to deteriorate fusibility. Also, if the temperature is greater than <NUM>, the polymer film may be excessively melted to be significantly deformed.

Also, the process of fusing the polymer film may be performed only once, but also may be repeated a plurality of times. If it is repeated three times, the one-time fusion is to remove air bubbles between the surface treatment layer <NUM> of the sheet <NUM> and the polymer film. Here, the process of fusing the polymer film may be performed by applying a pressure of <NUM> MPa to <NUM> MPa for <NUM> seconds to <NUM> seconds under a temperature of <NUM> to <NUM>, preferably, <NUM> to <NUM>. Since the one-time fusion is an initial fusion, it is preferably performed at a temperature of <NUM> or more at least higher than <NUM>, that is the lowest temperature, to improve the fusibility. Also, if the fusion temperature is excessively high in the state in which the polymer film temporarily adheres to the surface treatment layer <NUM> of the sheet <NUM>, it is difficult to correct the fused position of the polymer film when the polymer film is fused at a wrong position. Thus, it is preferable that the temperature is less than <NUM>. The two-time fusion is to secure the sealability between the one surface <NUM> of the sheet <NUM> and the polymer film. Here, the process of fusing the polymer film may be performed by applying a pressure of <NUM> MPa to <NUM> MPa for <NUM> seconds to <NUM> seconds under a temperature of <NUM> to <NUM>, preferably, <NUM> to <NUM>. Since the two-time fusion is merely to secure the sealability, the two-time fusion may be performed again at a temperature similar to that of the one-time fusion. Here, since the two-time fusion is not the initial fusion, the two-time fusion may be performed at a temperature of <NUM> that is the lowest temperature, or more. Also, the last three-time fusion is to enhance the fusibility of the polymer film. Here, the process of fusing the polymer film may be performed by applying a pressure of <NUM> MPa to <NUM> MPa for <NUM> seconds to <NUM> seconds under a temperature of <NUM> to <NUM>, preferably, <NUM> to <NUM>. That is, it is preferable that the last three-time fusion is performed at the highest temperature. However, as described above, if the temperature is higher than <NUM>, the polymer film may be excessively melted and thus significantly deformed. Also, if the temperature is less than <NUM>, the fusibility may not be more enhanced when compared to the fusibility after the two-time fusion is performed.

It is preferable that the polymer film has a thickness of <NUM> and includes a polyolefin-based polymer. Particularly, in order to improve the adhesion with respect to the sheet <NUM>, the polymer film may include the acid-treated polyolefin-based polymer. For example, the acid-treated polypropylene may be mixed with normal polypropylene, or acid-treated polyethylene may be mixed with the normal polypropylene. Alternatively, the polymer film may be simply made of only acid-treated polypropylene. Here, the acid-treated polypropylene may be maleic anhydride polypropylene (MAH PP).

<FIG> is a schematic view illustrating a state in which the ball <NUM> is seated on the polymer layer <NUM> according to an embodiment of the present invention.

The ball <NUM> made of a metal is seated on an upper portion of the polymer layer <NUM> laminated on the one surface <NUM> of the sheet <NUM> as illustrated in <FIG>. Since the edge of the inner circumference of the one surface <NUM> of the sheet <NUM> is chamfered or filleted, the sheet <NUM> has predetermined slope. Also, since the polymer layer <NUM> is laminated on the one surface <NUM> of the sheet <NUM>, when the ball <NUM> is seated, the adhesion between the ball <NUM> and the sheet <NUM> may be improved. The ball <NUM> has a diameter less than the widest width of the one surface <NUM> of the sheet <NUM> and larger than the narrowest width of the one surface <NUM> of the sheet <NUM> so that the ball <NUM> is easily seated on the sheet <NUM>. Also, when the ball <NUM> is seated, the highest point of the ball <NUM> is higher than the highest point of the sheet <NUM>. Thus, the ball <NUM> and the plate spring <NUM> may easily contact each other, and elastic force of the plate spring <NUM> may be efficiently applied to the ball <NUM> so that the ball <NUM> is closely attached to the sheet <NUM>.

As described above, in order to improve the durability, it is preferable that all the sheet <NUM> and the ball <NUM> are made of the metal. However, since the metal is not flexible, if the metals contact each other, a gap may occur between the ball <NUM> and the sheet <NUM> to deteriorate the sealability. However, according to an embodiment of the present invention, since the polymer layer <NUM> is laminated on the one surface <NUM> of the sheet <NUM>, the ball <NUM> is closely attached to the polymer layer <NUM> to prevent the gap from occurring, thereby preventing the sealability from being deteriorated.

<FIG> is a schematic view illustrating a state in which the plate spring <NUM> surrounds the sheet <NUM> and the ball <NUM> according to an embodiment of the present invention.

The plate spring <NUM> is formed to surround the ball <NUM> and the sheet <NUM> and has elasticity to open and close the passage <NUM> together with the ball <NUM> according to the internal pressure of the pouch. After the ball <NUM> is seated on the polymer layer <NUM> of the sheet <NUM>, a metal plate is formed to manufacture the plate spring <NUM>. The metal plate has a wide and thin plate shape and is made of a metal. Particularly, the metal plate may include aluminum (Al) or stainless steel (STS). A drawing process of elongating the metal plate by using a punch may be performed to manufacture the plate spring <NUM>. Particularly, the metal plate may be seated on a die, and a stripper may fix the metal plate. Then, the metal plate may be elongated through the punch to perform the drawing. As illustrated in <FIG>, in the plate spring <NUM> manufactured as described above, one side <NUM> that is the uppermost end has a cap shape that is convex outward, and an insertion space into which the sheet <NUM> is inserted is formed therein. The one side <NUM> of the plate spring <NUM> may mean a ceiling of the cap shape as illustrated in <FIG>. However, the present invention is not limited thereto. For example, the one side <NUM> of the plate spring <NUM> may include various portions.

The plate spring <NUM> opens and closes the passage <NUM> formed in the sheet <NUM> according to the internal pressure of the pouch. For this, it is preferable that a gas exhaust hole <NUM> is punched in the one side <NUM> of the plate spring <NUM>. Here, the one side <NUM> of the plate spring <NUM> includes a central portion <NUM> formed in a center thereof and a peripheral portion <NUM> extending outward from the central portion <NUM>. Also, a bottom surface of the central portion <NUM> of the one side <NUM> contacts the ball <NUM> to close the passage <NUM> formed in the sheet <NUM>, and thus, the gas exhaust hole <NUM> is not punched in the central portion <NUM>. Thus, it is preferable that the gas exhaust hole <NUM> is punched in the peripheral portion <NUM> of the one side <NUM> of the plate spring <NUM>.

When the plate spring <NUM> is manufactured, as illustrated in <FIG>, the sheet <NUM> and the ball <NUM> are inserted into the insertion space. As a result, the plate spring <NUM> surrounds the periphery of the sheet <NUM> and the ball <NUM>. When the sheet <NUM> and the ball <NUM> are inserted into the insertion space, it is preferable that the outlet-side of the passage <NUM> faces the one side <NUM> of the plate spring <NUM>. Thus, when the internal pressure of the pouch is less than a specific pressure, the one side <NUM> of the plate spring <NUM> pushes the ball <NUM> inward from the outlet-side of the passage <NUM> formed in the sheet <NUM> to close the passage <NUM>.

As described above, the gas exhaust hole <NUM> may be formed in the peripheral portion <NUM> of the one side <NUM> of the plate spring <NUM>. Thus, when the internal gas of the pouch pushes the one side <NUM> of the plate spring <NUM> outward, the passage <NUM> is opened so that the gas leaks to the outlet <NUM> of the passage <NUM>. Here, the leaking gas has to be discharged to the outside through the gas exhaust hole <NUM>. Thus, in the sheet <NUM>, the edge of the outer circumference of the outlet-side of the passage <NUM> may be chamfered or filleted. As a result, the gas may be guided to the gas exhaust hole <NUM>. Also, when the one side <NUM> of the plate spring <NUM> is pushed outward, a space to which the peripheral portion <NUM> of the one side <NUM> of the plate spring <NUM> moves inward, is provided.

<FIG> is a schematic view illustrating a state in which an end of the other side <NUM> of the plate spring <NUM> is bent toward the sheet <NUM> according to an embodiment of the present invention.

It is preferable that the plate spring <NUM> is firmly fixed to the sheet <NUM>. Thus, when the internal gas of the pouch pushes the one side <NUM> of the plate spring <NUM> outward through the ball <NUM>, the one side <NUM> of the plate spring <NUM> moves outward. Here, the plate spring <NUM> is not entirely slid, but only one side <NUM> of the plate spring <NUM> is deformed to move. If the plate spring <NUM> is slid, the plate spring <NUM> may be separated from the venting device <NUM>. Particularly, only the central portion <NUM> of the one side <NUM> may be pushed outward, and the peripheral portion <NUM> of the one side <NUM> may move inward. Thus, the internal gas of the pouch may be discharged to the outside through the passage <NUM>.

According to an embodiment of the present invention, after the sheet <NUM> and the ball <NUM> are inserted into the insertion space, the end <NUM> of the other side of the plate spring <NUM> is bent toward the sheet <NUM> as illustrated in <FIG>. As a result, even though the internal gas of the pouch pushes the one side <NUM> of the plate spring <NUM> outward, the detachment (separation) of the plate spring <NUM> from the sheet <NUM> may be prevented to fix the plate spring <NUM> to the venting device <NUM> without separating the plate spring <NUM> from the venting device <NUM>.

<FIG> is a schematic view illustrating the venting device <NUM> manufactured by inserting the plate spring <NUM> and the sheet <NUM> in <FIG> into the housing <NUM> according to an embodiment of the present invention, and <FIG> is an operation diagram illustrating an operation of the venting device <NUM> according to an embodiment of the present invention.

The plate spring <NUM> into which the sheet <NUM> is inserted is inserted into the housing <NUM> as illustrated in <FIG>. As a result, the venting device <NUM> according to an embodiment of the present invention may be completely manufactured. Here, if the housing <NUM> includes the upper housing <NUM> and the lower housing <NUM>, it is preferable that the plate spring <NUM> and the sheet <NUM> are included in the upper housing <NUM>. Also, as illustrated in <FIG>, it is preferable that the one side <NUM> of the plate spring <NUM> faces an opening end of the upper housing <NUM>. Thus, the gas may be discharged to the outside through the gas exhaust hole <NUM> formed in the one side <NUM>. Also, as described above, the plate spring <NUM> is not slid as a whole, but only one side <NUM> is deformed in the fixed state. Thus, it is preferable that a gap between the plate spring <NUM> and the housing <NUM> is minimized when the plate spring <NUM> is inserted into the housing <NUM> so that frictional force acts largely between an outer circumferential surface of the plate spring <NUM> and an inner circumferential surface of the housing <NUM>. However, the present invention is not limited thereto. In order that the frictional force further increases, surface roughness of the outer circumferential surface of the plate spring <NUM> or the inner circumferential surface of the housing <NUM> may increase so that a frictional coefficient increases. Furthermore, the plate spring <NUM> may be fixed to the housing <NUM> through various methods, for example, a method in which a separate adhesive is applied between the plate spring <NUM> and the housing <NUM>, or a protrusion protrudes from one of the plate spring <NUM> and the housing <NUM>, and a groove is formed in the other of the plate spring <NUM> and the housing <NUM>.

The venting device <NUM> manufactured as described above is inserted into the sealing part <NUM> of the pouch so as to be sealed together. Also, when a gas is generated in the pouch so that an internal pressure of the pouch increases, the gas is discharged to the outside. That is, as described above, when the gas is generated in the pouch, and thus an internal pressure of the pouch gradually increases to exceed a specific pressure, the gas pushes the ball <NUM> outward as illustrated in <FIG>. Also, since the ball <NUM> is pushed, the one side <NUM> of the plate spring <NUM> is also pushed outward, and thus, the plate spring <NUM> opens the outlet <NUM> of the passage <NUM>. Here, as described above, it is preferable that the plate spring <NUM> is not slid with respect to the sheet <NUM>.

Claim 1:
A venting device (<NUM>) adapted to be inserted into a sealing part of a pouch of a secondary battery, the venting device comprising:
a housing (<NUM>) adapted to be inserted between both surfaces of the sealing part (<NUM>) and sealed together with the sealing part (<NUM>);
a sheet (<NUM>) which made of a metal and formed in the housing (<NUM>) and through which a passage (<NUM>) allowing the inside and outside of the pouch to communicate with each other passes; and
a ball (<NUM>) contacting or spaced apart from the sheet (<NUM>) at an outlet-side of the passage (<NUM>) to close or open the passage (<NUM>),
wherein, in the sheet (<NUM>), an edge of an inner circumference of a surface of the outlet-side of the passage is chamfered or filleted, and
the sheet (<NUM>) comprises:
a surface treatment layer formed on the chamfered or filleted one surface (<NUM>) to face the ball (<NUM>); and
characterized in that the venting device further comprises:
a polymer layer (<NUM>) made of a polymer and fused to the surface treatment layer, wherein the polymer comprises an acid-treated polyolefin-based polymer, and
a plate spring formed to surround the ball and the sheet (<NUM>) and having elasticity to open and close the passage together with the ball according to an internal pressure of the pouch.