Patent Description:
The present invention relates to a venting device, and more particularly, to at least one venting device, which is inserted into a sealing part of a pouch of a secondary battery to discharge a gas within the pouch to the outside and minimize bending of a plate spring in a closed state.

In general, secondary batteries include nickelcadmium 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.

The secondary battery may be deteriorated in safety due to various problems such as internal short circuit due to an external impact, heat generation due to overcharging and overdischarging, electrolyte decomposition due to the generated heat, and a thermal runaway phenomenon. Particularly, when a gas is generated due to decomposition of an electrolyte to increase in pressure within the secondary battery, a problem occurs that the secondary battery is exploded.

Particularly, when the secondary battery is repeatedly charged and discharged, a gas is generated by electrochemical reaction between the electrolyte and an electrode active material. 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. Thus, in the case of the can type secondary battery, a protection member such as a CID filter and a safety vent is provided to physically interrupt an electrical connection when an internal pressure of a case increases. However, in the case of the pouch type secondary battery according to the related art, the protection member is not sufficiently provided. Such known secondary batteries with safety vents are described in <CIT> and <CIT>.

An object of 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 a gas within the pouch to the outside and minimize bending of a plate spring in a closed state.

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.

A venting device, which is inserted into a sealing part of a pouch of a secondary battery, according to an embodiment of the present invention for solving the above problem includes: a housing inserted between both surfaces of the sealing part so as to be sealed together with the sealing part; a sheet which is formed in the housing and through which a passage, through which the inside and outside of the pouch communicate with each other, passes; a plate spring which opens and closes the passage according to an internal pressure of the pouch and is made of made of a metal having elasticity; and a ball disposed between the sheet and the plate spring so as to contact or be spaced apart from the sheet at an outlet-side of the passage, thereby closing or opening the passage, wherein the ball has a hemispherical shape to be attached to an inner surface of the plate spring.

Also, the plate spring may include: a central portion formed at a center thereof; and a peripheral portion extending outward from the central portion, wherein the ball may be attached to the central portion, and a gas exhaust hole may be punched in the peripheral portion.

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

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

Also, the plate spring may have a flat plate shape and contact the sheet.

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

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

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.

Also, the present invention provides a pouch type secondary battery in which the venting device is inserted into a sealing part of a pouch, a battery module including the pouch type secondary battery as a unit cell, and a device including the battery module.

The device may include a computer, a notebook, a smart phone, a mobile phone, a tablet PC, a wearable electronic device, a power tool, an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or a power storage device, but is not limited thereto.

The structures of the battery module and the device and the method for manufacturing them are well known in the art, and thus their detailed descriptions will be omitted herein.

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.

The bending of the plate spring may be minimized in the state in which the venting devices are closed to reduce the deviation in opening pressure between the venting devices.

Also, the deviation between the numerical value of the opening pressure, which is designed before manufacturing the venting device, and the actual opening pressure may be reduced.

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 invention, and implementation methods thereof will be clarified through following embodiments described with reference to the accompanying drawings. The present invention may, however be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. 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 a process of manufacturing a pouch type secondary battery <NUM>, first, slurry in which an electrode active material, a binder, and a plasticizer are mixed with each other is applied to a positive electrode collector and a negative electrode collector to manufacture electrodes such as a positive electrode and a negative electrode. Thereafter, the negative electrode and the positive electrode are respectively stacked on both sides of a separator to form an electrode assembly <NUM> having a predetermined shape, and then, the electrode assembly <NUM> is inserted into a battery case <NUM>, an electrolyte is injected, and sealing is performed.

Specifically, the electrode assembly <NUM> includes two types of electrodes, such as the positive electrode and the negative electrode, and the separator interposed between the electrodes to insulate the electrodes from each other. The electrode assembly <NUM> may be a stack type, a jelly roll type, a stacked and folding type, or the like. Each of the two types of electrodes, i.e., the positive electrode and the negative electrode has a structure in which active material slurry is applied to the electrode collector having a metal foil or metal mesh shape. The slurry may be usually formed by agitating a granular active material, an auxiliary conductor, a binder, and a plasticizer with a solvent added. The solvent may be removed in the subsequent process.

As illustrated in <FIG>, the electrode assembly <NUM> includes an electrode tab <NUM>. The electrode tab <NUM> protrudes from each of the positive electrode and the negative electrode of the electrode assembly <NUM> to provide a path, through which electrons move, between the inside and outside of the electrode assembly <NUM>. A collector of the electrode assembly <NUM> is constituted by a portion coated with an electrode active material and a distal end, on which the electrode active material 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>. An insulation part <NUM> may be disposed to be limited within a sealing part <NUM>, at which an upper case <NUM> and a lower case <NUM> of the battery case <NUM> are thermally fused, so as to be 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> includes a positive electrode lead <NUM> having one end connected to a positive electrode tab <NUM> to extend in a direction in which the positive electrode tab <NUM> protrudes and a negative electrode lead <NUM> having one end connected to a negative electrode tab <NUM> to extend in a direction in which the negative electrode tab <NUM> protrudes. On the other hand, as illustrated in <FIG>, all of the other ends of the positive electrode lead <NUM> and the negative electrode lead <NUM> protrude to the outside of the battery case <NUM>. As a result, electricity generated in the electrode assembly <NUM> may be supplied to the outside. Also, since each of the positive electrode tab <NUM> and the negative electrode tab <NUM> is formed to protrude in various directions, each of the positive electrode lead <NUM> and the negative electrode lead <NUM> may extend in various directions.

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.

The battery case <NUM> is a pouch made of a flexible material. Hereinafter, the case in which the battery case <NUM> is the pouch will be described. 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 case <NUM> and the lower case <NUM>. A cup part <NUM> having an accommodation space <NUM> accommodating the electrode assembly <NUM> is formed in the lower case <NUM>, and upper case <NUM> may cover an upper side of the accommodation space <NUM> so that the electrode assembly <NUM> is not 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 case <NUM> to accommodate the electrode assembly <NUM> in the upper portion. As illustrated in <FIG>, one side of the upper case <NUM> and one side of the lower case <NUM> may be connected to each other. However, the present invention is not limited thereto. For example, the upper case <NUM> and the lower case <NUM> may be separately manufactured to be separated from each other.

After the upper case <NUM> and the lower case <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 an 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 cup part <NUM> of the lower case <NUM>, and the upper case <NUM> may cover an upper portion of the accommodation space <NUM>. Also, the electrolyte is injected, and the sealing part provided on an edge of each of the upper case <NUM> and the lower case <NUM> is sealed. The electrolyte may move lithium ions generated by electrochemical reaction of the electrode during charging and discharging of the secondary battery <NUM>. The electrolyte may include a non-aqueous organic electrolyte that is a mixture of a lithium salt and a high-purity organic solvent or a polymer using a polymer electrolyte. As illustrated in <FIG>, the pouch type secondary battery <NUM> may be manufactured through the above-described method.

<FIG> is a cross-sectional view of a pouch film <NUM> forming 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 elongated to form the cup part <NUM> having the accommodation space <NUM> having a bag shape when the pouch film <NUM> having the stacked 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 case <NUM> and the lower case <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.

The secondary battery <NUM> according to an embodiment of the present invention further includes at least one venting device <NUM>. According to an embodiment of the present invention, the bending of the plate spring <NUM> in the closed state of the venting device <NUM> may be minimized to reduce a deviation in opening pressure between the venting devices <NUM>. Also, the deviation between a numerical value of the opening pressure, which is designed before manufacturing the venting device <NUM>, and an actual opening pressure may be reduced. Here, the opening pressure means a specific pressure within the battery case <NUM> when the venting device <NUM> is opened.

For this, the venting device <NUM>, which is inserted into a sealing part <NUM> of a pouch of the secondary battery <NUM>, according to an embodiment of the present invention 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 formed in the housing <NUM> and through which a passage <NUM>, through which the inside and outside of the pouch communicate with each other, passes; a plate spring <NUM> which opens and closes the passage <NUM> according to an internal pressure of the pouch and is made of made of a metal having elasticity; and a ball <NUM> disposed between the sheet <NUM> and the plate spring <NUM> so as to contact or be spaced apart from the sheet <NUM> at an outlet-side of the passage <NUM>, thereby closing or opening the passage <NUM>. The ball <NUM> may have a hemispherical shape to be attached to an inner surface of the plate spring <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, a sealant layer <NUM> of the sealing part <NUM> is fused to be sealed together with the housing <NUM>. 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, as described above, the lower housing <NUM> may have an oval cylinder shape having an oval transverse cross-section. Thus, the lower housing <NUM> may be easily sealed to the sealing part <NUM>, and the sealing may be maintained for a long time without being broken.

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>. 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> closes an 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 opened and 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> may be used to simplify the structure of the venting device <NUM> and miniaturize the venting device <NUM> so as to be inserted into the sealing part <NUM> of the secondary battery <NUM>.

<FIG> is a schematic view of the venting device <NUM> which is not part of the invention and in which the ball <NUM> has a spherical shape.

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>. However, when the ball <NUM> has the spherical shape as illustrated in <FIG>, the plate spring <NUM> may be largely bent even though a state in which the ball <NUM> contacts the sheet <NUM> to close the passage <NUM> is a state in which external force relatively minimally acts to the plate spring <NUM>. Therefore, when the plurality of venting devices <NUM> are manufactured, there is a problem that a deviation occurs in opening pressure between the plurality of venting devices <NUM> according to a degree of bending of the plate spring <NUM>. Also, there is a problem that a deviation occurs between a numerical value of the opening pressure, which is designed before manufacturing the venting device <NUM>, and a numerical value of an actual opening pressure after manufacturing the venting device <NUM>.

Furthermore, since the bent state of the plate spring <NUM> is maintained for a long time, a creep phenomenon occurs in the plate spring <NUM> to reduce the lifespan of the plate spring <NUM> and also reduce the lifespan of the whole venting devices <NUM>.

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

The sheet <NUM> is formed in the housing <NUM>, and the passage <NUM> passes through the sheet <NUM>. The sheet <NUM> may be made of a metal to improve durability, but may also be made of polymer to prevent a gap between components. In particular, the polymer may include a polyolefin-based polymer such as polypropylene (PP). As illustrated in <FIG>, in the sheet <NUM>, an edge of an inner circumference of a surface of the outlet-side of the passage <NUM> is chamfered or filleted.

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

According to an embodiment of the present invention, the ball <NUM> may have a hemispherical shape and be disposed at the outlet-side of the passage <NUM> formed in the sheet <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>. The ball <NUM> may be made of the polymer to more improve adhesion with respect to the sheet <NUM>. However, the ball <NUM> may be made of a metal to improve durability.

The ball <NUM> has a hemispherical shape and is attached to an inner surface of the plate spring <NUM>. Here, in order to be more easily attached to the plate spring <NUM>, a plane rather than the hemispherical surface of the ball <NUM> is attached to the inner surface of the plate spring <NUM>. The chamfered or filleted surface <NUM> of the sheet <NUM> has a predetermined inclination. As illustrated in <FIG>, the hemispherical surface of the ball <NUM> may face one surface <NUM> of the sheet <NUM> and may be easily seated.

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>. Then, when the ball <NUM> is seated, the plane of the ball <NUM> is formed at a height that is approximately similar to the highest point of the sheet <NUM>. As a result, since the plate spring <NUM> is not largely bent even in a state in which the ball <NUM> closes the passage <NUM>, the deviation in opening pressure between the venting devices <NUM> may be reduced, and also, the deviation between the numerical value of the opening pressure, which is designed before manufacturing the venting device <NUM>, and the actual opening pressure may be reduced. More preferably, the plane of the ball <NUM> may be slightly higher than the highest point of the sheet <NUM>. As a result, elastic force of the plate spring <NUM> may be efficiently applied to the ball <NUM> to improve the adhesion of the sheet <NUM> of the ball <NUM>.

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

The plate spring <NUM> may be manufactured by molding a metal plate. 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). Also, a drawing process of elongating the metal plate through 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, the one side <NUM> has a cap shape that is convex outward and provide an insertion space <NUM> into which the sheet <NUM> is inserted. 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> has elastic force to open and close the passage <NUM> formed in the sheet <NUM> together with the ball <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, since the ball <NUM> is attached to a bottom surface of a central portion <NUM> of the one side <NUM> to close the passage <NUM> formed in the sheet <NUM>, 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 of the <NUM> of the plate spring <NUM>.

An opening pressure of the venting device <NUM> may be changed according to the formed shape and area of the gas exhaust hole <NUM>. Thus, the gas exhaust hole <NUM> may be adjusted in shape and area to adjust the opening pressure of the venting device <NUM>. Here, the opening pressure means a specific pressure within the pouch when the venting device <NUM> is opened.

<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.

When the plate spring <NUM> is manufactured, as illustrated in <FIG>, the sheet <NUM> and the ball <NUM> are inserted into the insertion space <NUM>. 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 <NUM>, 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>.

The ball <NUM> is formed in a hemispherical shape, and the plane rather than the hemispherical surface of the ball <NUM> is attached to the inner surface of the plate spring <NUM>. Here, when the adhesive is applied to the plane of the ball <NUM>, and the sheet <NUM> and the ball <NUM> are inserted into the insertion space <NUM>, the plane of the ball <NUM> is attached to the inner surface of the central portion <NUM> of the plate spring <NUM>. Here, after the ball <NUM> is seated first on the sheet <NUM>, the ball <NUM> and the sheet <NUM> may be inserted into the insertion space <NUM> of the plate spring <NUM>, but is not limited thereto. For example, after the ball <NUM> is attached to the plate spring <NUM>, the sheet <NUM> may be inserted into the insertion space <NUM>.

As described above, the gas exhaust hole <NUM> may be formed in a 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 surface 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, the one side <NUM> of the plate spring <NUM> is pushed outward to provide a space to which the peripheral portion <NUM> of the one side <NUM> of the plate spring <NUM> moves inward.

<FIG> is a schematic view illustrating a state in which an end <NUM> of the other side 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 <NUM>, 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 a configuration of the venting device <NUM> manufactured by inserting the plate spring <NUM> and the sheet <NUM> into the housing <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. The venting device <NUM> manufactured as described above is inserted into the sealing part <NUM> of the pouch so as to be sealed together.

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>.

<FIG> is an operation diagram illustrating an operation of the venting device <NUM> according to an embodiment of the present invention.

In addition, when the secondary battery <NUM> is stored at a high temperature, an electrochemical reaction between the electrolyte and the electrode active material is quickly accelerated by the high temperature to generate a gas.

When the gas is generated in the pouch to gradually increase in internal pressure of the pouch and thus exceed a specific pressure, as illustrated in <FIG>, the gas pushes the ball <NUM> outward. As a result, since the ball <NUM> is pushed, the one side <NUM> of the plate spring <NUM> is pushed outward. Also, the plate spring <NUM> may be spaced apart from the sheet <NUM> so that the ball <NUM> is separated from the sheet <NUM> to open the outlet <NUM> of the passage <NUM>. Therefore, the gas within the pouch may be discharged to the outside through the passage <NUM> and the gas exhaust hole <NUM>. Here, as described above, it is preferable that the plate spring <NUM> is not slid with respect to the sheet <NUM>.

When the gas within the pouch is sufficiently discharged to the outside, the internal pressure of the pouch decreases again, and thus, the pressure of the gas pushing the plate spring <NUM> outward decreases. However, the plate spring <NUM> is made of the metal and thus has the elasticity. Thus, when the internal pressure of the pouch is less than a specific pressure, the plate spring <NUM> returns to its original position by the elasticity of the plate spring <NUM>. Also, the ball <NUM> is pushed inward from the outlet-side of the passage <NUM> formed in the sheet <NUM> by the elastic force of the plate spring <NUM>. As a result, the ball <NUM> is in close contact with the one surface <NUM> of the sheet <NUM> to close the outlet <NUM> of the passage <NUM>.

<FIG> is a schematic view illustrating a state in which a venting device 15a is completely manufactured according to another embodiment of the present invention.

According to an embodiment of the present invention, the plate spring <NUM> has the cap shape of which the one side <NUM> is convex outward, and the sheet <NUM> and the ball <NUM> are inserted into the insertion space <NUM> formed in the plate spring <NUM>. However, since the plate spring <NUM> has the cap shape, it may not be easy to attach the plane of the ball <NUM> to the correct position of the inner surface of the plate spring <NUM>.

Accordingly, in the venting device 15a according to another embodiment of the present invention, as illustrated in <FIG>, a plate spring 153a has a flat plate shape and contacts a sheet 152a. Also, a separate fixing ring (not shown) may be inserted into an upper housing <NUM> so as to be fixed to an upper portion of the plate spring 153a. The fixing ring has elasticity, and when being inserted into the upper housing <NUM>, external force may be applied to reduce a diameter, and then, after being inserted into the upper housing <NUM>, the external force may be removed to increase in diameter again. Thus, when the elastic force acts as normal force on an inner circumferential surface of the upper housing <NUM>, friction force between the fixing ring and the inner circumferential surface of the upper housing <NUM> may increase.

Therefore, according to another embodiment of the present invention, the ball <NUM> may be easily attached to an accurate position of the inner surface of the central portion 1531a of the plate spring 153a, and the plate spring 153a may be easily fixed to the inside of the housing <NUM> through the separate fixing ring.

<FIG> is an operation diagram illustrating an operation of the venting device 15a according to another embodiment of the present invention.

In the venting device 15a according to another embodiment of the present invention, when an internal pressure of a pouch exceeds a specific pressure, as illustrated in <FIG>, a gas pushes the ball <NUM> outward, and thus, as the ball is pushed, the plate spring 153a is also pushed outward. Also, the plate spring <NUM> may be spaced apart from a sheet 152a so that the ball <NUM> is separated from the sheet 152a to open an outlet <NUM> of a passage <NUM>. Thus, a gas within the pouch may be discharged to the outside through the passage <NUM> and a gas exhaust hole <NUM>.

When the gas within the pouch is sufficiently discharged to the outside, the internal pressure of the pouch decreases again, and thus, the pressure of the gas, which pushes the plate spring 153a outward, decreases. Thus, when the internal pressure of the pouch is less than the specific pressure, the plate spring 153a returns to its original position by the elastic force of the plate spring 153a. Also, the ball <NUM> is pushed inward from a side of an outlet <NUM> of the passage <NUM> formed in the sheet 152a by the elastic force of the plate spring 153a. As a result, the ball <NUM> is in close contact with one surface <NUM> of the sheet 152a to close the outlet <NUM> of the passage <NUM>.

Claim 1:
A venting device (<NUM>), which is configured to be inserted into a sealing part (<NUM>) of a pouch of a secondary battery, the venting device (<NUM>) comprising:
a housing (<NUM>) configured to be 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 formed in the housing (<NUM>) and through which a passage (<NUM>), through which the inside and outside of the pouch communicate with each other, passes;
a plate spring (<NUM>) which is configured to open and close the passage (<NUM>) according to an internal pressure of the pouch and is made of a metal having elasticity; and
a ball (<NUM>) disposed between the sheet (<NUM>) and the plate spring (<NUM>) so as to contact or be spaced apart from the sheet (<NUM>) at an outlet-side of the passage (<NUM>), thereby closing or opening the passage (<NUM>),
wherein the plate spring (<NUM>) has a flat plate shape and contacts the sheet (<NUM>) and characterized in that the ball (<NUM>) has a hemispherical shape to be attached to an inner surface of the plate spring (<NUM>), and
a plane rather than the hemispherical surface of the ball (<NUM>) is attached to the inner surface of the plate spring (<NUM>)