KR102188446B1 - Pouch for secondary battery and secondary battery using the same - Google Patents

Abstract

The present invention relates to a pouch for a secondary battery and a secondary battery using the same, and more particularly, including a case body and a cover to which respective outer portions are bonded to each other, and in at least one of the outer portions to be bonded, a flat portion is provided with the outer portion. A core plate disposed in the negative plane direction and a safety vent portion surrounding the core plate and including a thermoplastic resin matrix having a different coefficient of thermal expansion than the core plate are further included, thereby providing a pouch for a secondary battery capable of preventing explosion and ignition. .

Description

Pouch for secondary battery and secondary battery using same {POUCH FOR SECONDARY BATTERY AND SECONDARY BATTERY USING THE SAME}

The present invention relates to a pouch for a secondary battery and a secondary battery using the same.

Typically, a secondary battery is a battery capable of charging and discharging, and is widely used in the field of advanced electronic devices such as mobile phones, notebook computers, and camcorders. In particular, lithium secondary batteries have three times higher operating voltage than nickel-cadnium (Ni-Cd) batteries or nickel-hydrogen (Ni-MH) batteries, which are widely used as power sources for electronic equipment, and have excellent energy density per unit weight. There is a lot of research and development going on.

These lithium secondary batteries can be classified into liquid electrolyte batteries and polymer electrolyte batteries according to the type of electrolyte. In general, batteries using a liquid electrolyte are referred to as lithium ion batteries, and batteries using a polymer electrolyte are referred to as lithium polymer batteries. It is called G.

A typical lithium ion battery includes a porous positive electrode current collector, an electrode assembly in which a negative electrode current collector and a separator are alternately overlapped with each other, and a cell exterior material for accommodating the electrode assembly and an electrolyte. These battery cells are also classified into can-type battery cells or pouch-type battery cells depending on the shape of the cell exterior material.

In general, unlike primary batteries, rechargeable secondary batteries capable of charging and discharging are actively researching advanced fields such as digital cameras, cellular phones, notebook computers, and hybrid vehicles. Examples of the secondary battery include a nickel-cadmium battery, a nickel-metal hydride battery, a nickel-hydrogen battery, and a lithium secondary battery. Among them, lithium secondary batteries have an operating voltage of 3.6V or higher and are used as power sources for portable electronic devices, or are used in high-power hybrid vehicles by connecting several in series, and are used for nickel-cadmium batteries or nickel-metal hydride batteries. Compared to this, the operating voltage is three times higher and the energy density per unit weight is excellent, so the use is rapidly increasing.

The lithium secondary battery can be manufactured in various forms, and representative shapes include a cylinder type and a prismatic type mainly used for lithium ion batteries. Lithium polymer batteries, which are recently in the spotlight, are manufactured in a pouched type with flexibility, and thus their shape is relatively free. In addition, the lithium polymer battery is excellent in safety and light in weight, so it will be said that it is advantageous for slimming and lightening portable electronic devices.

Among them, the pouch-type secondary battery includes an electrode assembly 20 that generates a predetermined current and a pouch 10 that surrounds and seals the electrode assembly 20 as shown in FIG. 1. In the electrode assembly 20, a lead 17 serving as an electrical path to the outside is connected to an electrode tab 14 extending from one side thereof, and the lead 17 is an electrode tape 16 on its surface. Is adhered and installed to partially protrude to the outside of the pouch 10.

The pouch 10 includes a case body 12 provided with an internal space to accommodate the electrode assembly 20 and a cover 11 covering the case body 12. The case body 12 and the outer portion 15 of the cover 11 are bonded to each other to seal the pouch 10.

On the other hand, when the internal voltage of the secondary battery increases due to overcharging, gas is generated and there is a risk of expansion or explosion. In particular, the lithium ion battery has a problem in that the liquid electrolyte is decomposed due to overcharging, releasing gases such as carbon dioxide or carbon monoxide, thereby increasing the internal pressure of the battery. In addition, when an overcurrent flows due to overdischarge or short circuit, the temperature inside the battery rises and the liquid electrolyte turns into gas, which increases the pressure and temperature inside the battery. In particular, there is a risk of ignition, so there is a big problem in safety. come.

In addition, the secondary battery as described above can be safely used only when the temperature conditions during charging and the temperature conditions during use are observed.In the case of a harsh use environment, that is, when the temperature during charging and discharging is too high, If the operating temperature is too high, these external temperature conditions can increase the temperature of the battery and cause an explosion or ignition.

Accordingly, various types of safety devices that can prevent explosions have been proposed for secondary batteries.

For example, Korean Patent Application Publication No. 2004-0017094 discloses a configuration for a pouch-type secondary battery that has a safety valve and can prevent explosion and ignition of the battery.

However, in the case of a safety valve including an open piece provided with a polyethylene-based resin material disclosed in Korean Patent Laid-Open No. 2004-0017094, it is difficult to predict the point of breakage, and because the melting point of the open piece cannot be controlled, it is not broken at a desired temperature. There is a drawback, and there may be a case where the vent is not actually performed in the part where the open piece is located.

Korean Patent Publication No. 2004-0017094

An object of the present invention is to provide a pouch for a secondary battery capable of preventing unexpected explosion and ignition by opening a safety vent portion to discharge gas inside the battery when the internal temperature of the secondary battery rises above a reference value.

In addition, another object of the present invention is to provide a pouch for a secondary battery including a safety vent unit capable of consistent venting when the battery is overheated.

In addition, another object of the present invention is to provide a pouch for a secondary battery including a safety vent unit that can be installed without limitation of position.

1.A core plate including a case body and a cover to which each outer portion is bonded to each other, and in at least one of the bonded outer portions, a core plate having a flat portion disposed in a plane direction of the outer portion, and the core plate surrounding the core plate A pouch for a secondary battery further comprising a safety vent portion including a thermoplastic resin matrix having a different coefficient of thermal expansion and a different thermal expansion coefficient.

2. The pouch for a secondary battery according to the above 1, wherein the core plate has a higher melting point than the thermoplastic resin matrix.

3. The pouch for a secondary battery according to the above 1, wherein the core plate includes at least one material selected from the group consisting of metal, ceramic, polymer, and glass.

4. The pouch for a secondary battery according to the above 1, wherein the thickness of the core plate is equal to or smaller than the thickness of the thermoplastic resin matrix.

5. The pouch for a secondary battery according to the above 1, wherein the length in the direction from the inside to the outside of the pouch of the core plate is equal to or smaller than the length in the direction from inside the pouch of the outer portion

6. The pouch for a secondary battery according to the above 1, wherein the length of the pouch of the core plate is equal to or smaller than the length of the pouch from the inside to the outside of the pouch of the outer portion.

7. The pouch for a secondary battery according to the above 1, wherein the shape of the cross section cut from the inside to the outside of the pouch of the core plate has a rectangular shape.

8. The pouch for a secondary battery according to the above 1, wherein the shape of the cross section cut in the direction from the inside to the outside of the pouch of the core plate is a trapezoid or a triangle.

9. The pouch for a secondary battery according to the above 8, wherein the core plate having a trapezoidal cross section has a short side positioned on the inside of the pouch and a long side positioned on the outside of the pouch.

10. The pouch for a secondary battery according to the above 8, wherein the core plate having a trapezoidal cross section has a short side positioned on the outside of the pouch and a long side positioned on the inside of the pouch.

11. The pouch for a secondary battery according to the above 1, wherein a plurality of the core plates are included in the thermoplastic resin matrix.

12. The pouch for a secondary battery according to the above 1, wherein the thermoplastic resin matrix has a lower melting point than a material forming the case body and the cover.

13. The pouch for a secondary battery according to the above 1, wherein when the inner temperature of the pouch is greater than or equal to a preset vent operating temperature, the inner and outer sides of the pouch are communicated by being spaced apart between the core plate of the safety vent and the thermoplastic resin matrix.

14. In the above 1, when the inner temperature of the pouch is equal to or higher than the preset vent operating temperature and the pressure inside the pouch reaches the vent pressure, the thermoplastic resin matrix of the safety vent portion is melted and the core plate is discharged to the outside of the pouch. Battery pouch.

15. A pouch-type secondary battery comprising the pouch of any one of 1 to 14 above and an electrode assembly accommodated in the pouch.

In the pouch for a secondary battery according to the present invention, since the core plate and the thermoplastic resin matrix have different coefficients of thermal expansion, when the inside of the pouch becomes high temperature, the core plate and the thermoplastic resin surrounding it are spaced apart, so that the inside and the outside of the pouch are separated along the core plate. It communicates, and the gas inside the pouch is discharged therefrom to prevent explosion and ignition of the battery.

In addition, the pouch for a secondary battery according to the present invention has the advantage of being able to install a safety vent regardless of its location if it is an outer portion of the pouch.

In addition, in the pouch for a secondary battery according to the present invention, when the pressure inside the battery increases in a high temperature state, the core plate is discharged to the outside of the pouch by the internal pressure, thereby implementing a more reliable vent.

1 is a perspective view showing a schematic structure of a conventional pouch-type secondary battery.
2 is a perspective view schematically showing an embodiment of a pouch according to the present invention and a secondary battery including the pouch.
3 is a view schematically showing an embodiment of the operating mechanism of the safety vent according to the present invention.
4 is a perspective view schematically showing an embodiment of the safety vent part according to the present invention.
5 is a schematic side cross-sectional view of a core plate according to an embodiment of the present invention.
6 is a view schematically showing another embodiment of the operating mechanism of the safety vent according to the present invention.

The present invention includes a case body and a cover to which each outer portion is bonded to each other, and in at least one of the bonded outer portions, a core plate having a flat portion disposed in a plane direction of the outer portion, and a core plate surrounding the core plate. Since it further includes a safety vent portion including a thermoplastic resin matrix having a different coefficient of thermal expansion than the core plate, a pouch for a secondary battery capable of preventing explosion and ignition is provided.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings. However, the following drawings attached to the present specification illustrate preferred embodiments of the present invention, and serve to further understand the technical idea of the present invention together with the contents of the present invention, so the present invention is described in such drawings. It is limited to matters and should not be interpreted.

2 is a schematic view showing an embodiment of a pouch 100 and an electrode assembly 200 accommodated therein according to the present invention.

After the pouch 100 accommodates the electrode assembly 200 therein, the outer portion of the case body 110 and the cover 120 are bonded and sealed to form a pouch-type secondary battery. The pouch 100 includes a safety vent part 150 in at least one portion of the outer part to be bonded.

The safety vent part 150 includes a core plate 151 and a thermoplastic resin matrix 152 surrounding the core plate 151, and in a normal state, the thermoplastic resin matrix 152 seals the pouch together with the outer part. The core plate 151 is bound, and the core plate 151 contributes to maintaining the mechanical rigidity of the safety vent unit 150.

On the other hand, Figure 3 schematically shows an embodiment of the operating mechanism of the safety vent 150 according to the present invention. The core plate 151 and the thermoplastic resin matrix 152 have different coefficients of thermal expansion from each other. Referring to FIG. 3, the core plate 151 and the thermoplastic resin matrix 152 having different coefficients of thermal expansion may increase the temperature inside the pouch. Then, the degree of expansion (or contraction) is different from each other, so a gap is generated at the interface in contact with each other. In this case, the core plate 151 is disposed in the direction of the surface of the outer portion of the case body 110 and the cover 120, so that the gap is formed from the inside of the pouch to the outside. Accordingly, a vent through which gas and heat generated inside the pouch can be discharged to the outside may be provided to prevent explosion and ignition of the battery.

The coefficient of thermal expansion of each of the core plate 151 and the thermoplastic resin matrix 152 can be determined by selection of an appropriate material, and the thermoplastic resin matrix 152 expands thermally depending on molecular weight, etc. even if polymerized with the same monomer in addition to the type of thermoplastic resin used. Modulus or melting point may vary.

In this way, according to the adjustment of the thermal expansion coefficient and melting point of the core plate 151 and the thermoplastic resin matrix 152, the operating temperature of the vent at which the safety vent unit 150 according to the present invention operates may be set in advance. Accordingly, when the temperature inside the pouch is equal to or higher than the vent operating temperature, as described above, the core plate 151 and the thermoplastic resin matrix 152 may be spaced apart to form a gap communicating inside and outside the pouch. Gas and heat generated inside can be discharged to the outside.

In this respect, the core plate 151 may preferably have a higher melting point than the thermoplastic resin matrix 152. If such a material is not particularly limited, it may be used as a material of the core plate 151. For a more specific example, the core plate 151 includes at least one material selected from the group consisting of metal, ceramic, polymer, and glass. It may be made, but is not limited thereto.

4 is a perspective view schematically showing an embodiment of the safety vent part of the present invention.

It may be desirable that the thickness of the core plate 151 does not exceed the thickness of the thermoplastic resin matrix 152. Accordingly, the thickness of the thermoplastic resin matrix 152 may be equal to or smaller than the thickness of the thermoplastic resin matrix 152, and more preferably may be smaller than the thickness of the thermoplastic resin matrix 152. When the thickness of the core plate 151 is smaller than the thickness of the thermoplastic resin matrix 152, the contact area with the thermoplastic resin matrix 152 can be maximized, and accordingly, it can be more effective in forming a vent.

The length of the core plate 151 from the inside to the outside (x direction) of the pouch may be equal to or smaller than the length of the outer portion 121 from the inside of the pouch (x direction). Preferably, the same length of the outer portion 121 in the direction from the inside of the pouch to the outside may be more effective in forming the vent.

The length of the core plate 151 from the inside to the outside of the pouch (y direction) may be equal to or smaller than the length of the outer pouch from the inside to the outside (y direction). Preferably, the same length of the outer portion 121 from the pouch from the inside to the outside in the vertical direction may be more effective in forming the vent.

The core plate 151 may have various cross-sectional shapes as needed. Specifically, when the core plate is cut in a direction from the inside of the pouch to the outside, the shape of the cross section may be a rectangle, a trapezoid, or a triangle. In FIG. 5, some of the cases in which the cross section is a trapezoid (a) and a triangle (b) are illustrated by way of example.

In an embodiment of the present invention, when the cross-section is trapezoidal, the short side may be disposed inside the pouch and the long side may be disposed outside the pouch. In this case, it is easier for the core plate 151 to be released to the outside according to the safety vent operation mechanism described later.

In another embodiment of the present invention, when the cross section is trapezoidal, the short side may be disposed outside the pouch and the long side may be disposed inside the pouch. In this case, when the pressure inside the pouch increases, the area to which the core plate 151 receives the force increases, so that the separation between the core plate 151 and the thermoplastic resin matrix 152 can be made more smoothly. Communication may be easier.

If necessary, a plurality of core plates 151 may be included in the thermoplastic resin matrix 152. When a plurality of core plates 151 are included, it may be more desirable to strengthen the mechanical strength of the safety vent unit 150 in a normal state, and when the safety vent unit is operated, more vents may be formed. It may be more desirable.

The thermoplastic resin matrix 152 contributes to the sealing of the pouch together with the outer portion 121 in a normal state. Typically, the bonding of the outer portion 121 is achieved by heat-pressing the bonding surfaces of the case body 110 and the cover 120, so that the thermoplastic resin matrix 152 according to the present invention is Not only can the part 121 be used for bonding, but the outer part 121 may be disposed regardless of its position. Accordingly, the safety vent unit 150 according to the present invention may be disposed on the outer portion 121 regardless of its location, and may be disposed in two or more locations if necessary.

The thermoplastic resin forming the thermoplastic resin matrix 152 may be used without particular limitation as long as it is a thermoplastic resin known in the art. For example, polyethylene, polypropylene, or the like may be used, but is not limited thereto.

The melting point of the thermoplastic resin matrix 152 is preferably lower than that of the material forming the case body 110 and the cover 120. Typically, the case body 110 and the cover 120 are formed in a structure in which a metal layer and a polymer resin layer are stacked, and the melting point of the thermoplastic resin matrix 152 is the number of metal layers and polymers of the case body 110 and the cover 120 It is preferable that the melting point is lower than that of the stratum in terms of enabling the safety vent part 150 to operate before damage to the pouch 100.

6 schematically shows another embodiment of the operating mechanism of the safety vent 150 according to the present invention.

Typically, heat generation inside the pouch may be accompanied by an increase in internal pressure. The increase in the internal pressure inside the pouch is mostly caused by the generation of gas due to the decomposition of the electrolyte or electrolyte contained therein. In this way, when the temperature and pressure inside the pouch are increased at the same time, the safety vent unit 150 according to the present invention can implement an effective explosion and ignition prevention mechanism.

Referring to FIG. 6, when the inner temperature of the pouch 100 is equal to or higher than a preset vent operating temperature and the pressure inside the pouch reaches the vent pressure, the thermoplastic resin matrix 152 of the safety vent unit 150 is melted and the core The plate 151 may be discharged outside the pouch.

When the internal temperature of the pouch is higher than the vent operating temperature, the vent operating mechanism is as described above. That is, in this embodiment, the gap between the core plate 151 and the thermoplastic resin matrix 152 decreases the bonding force between the thermoplastic resin matrix 152 and the core plate 151, and accordingly, the inner pressure of the pouch increases. The core plate 151 can be discharged to the outside of the pouch by the internal pressure. The empty space of the safety vent unit 150 generated as the core plate 151 is discharged may more effectively respond to heat generation and relieving internal pressure inside the pouch. In addition, as described above, in order to facilitate the release of the core plate 151, it may be preferable that the cross-sectional shape of the core plate 151 is a trapezoid in which the short side is located inside the pouch as shown in Fig. 4(a). have.

The vent pressure of the safety vent unit 150 may be appropriately determined by selection of a specific material type of each of the core plate 151 and the thermoplastic resin matrix 152 and the thickness of the core plate 151. Therefore, it is possible to adjust the vent pressure according to the specific use of the battery to be used.

Other configurations other than the safety vent unit 150 of the pouch 100 according to the present invention may adopt a configuration known in the art without special limitation.

The case body 110 and the cover 120 may include a metal layer, a thermal bonding layer formed on one surface of the metal layer, and an insulating film layer formed on the other surface of the metal layer.

The metal layer blocks the inflow of moisture from outside into the battery and maintains the phenomenon after forming. The metal layer may be, for example, aluminum, stainless steel, iron, copper, nickel, or the like, and among them, aluminum has excellent function of blocking moisture at a light weight. In addition, the metal layer may be formed of one type of metal, or may be formed by integrating two or more types of metal layers.

The heat fusion layer may be formed of CPP (Cast Polypropylene) or PPA (Poly Phthal Amide). The case body 110 and the cover 120 are disposed so that the heat-sealing layers are in contact with each other, and the heat-sealing layers are bonded (heat-sealed) to each other to implement sealing of the pouch.

The insulating layer may be formed of either nylon or polyethylene terephthalate, but is not limited thereto. If necessary, the insulating layer may be formed of a plurality of layers, and in this case, a resin layer such as polyethylene, polypropylene, or polyethylene terephthalate may be further included on the outside of nylon or polyethylene terephthalate.

The present invention provides a pouch-type secondary battery including the pouch described above and an electrode assembly accommodated therein.

The electrode assembly 200 is arranged in the order of a positive plate, a separator, and a negative plate and wound in one direction, or a plurality of positive plates, a separator, and a negative plate are stacked. Each electrode plate of the electrode assembly 200 is electrically connected to the positive electrode tabs and the negative electrode tabs 211 and 212.

One ends of the positive and negative electrode tabs 211 and 212 of the electrode plate protrude to the outside through the lead 230. One end of the protruding lead 230 is connected to an external terminal (not shown).

Each electrode tape 220 is provided on the outer surface of the lead 230 in order to prevent an electrical short between the case body 110 and the cover 120 and the lead 230 at a portion in contact with the outer portion 121. It is rolled up.

A plurality of pouch-type secondary batteries according to the present invention may be combined and used as a battery pack. The battery pack includes a power tool; Electric vehicles such as electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); Electric two-wheeled vehicles such as an E-bike or an E-scooter; Electric golf cart; Electric truck; And it can be used as a power supply for medium and large devices such as electric commercial vehicles.

100: pouch 110: case body
120: cover 150: safety vent part
151: core plate 152: thermoplastic resin matrix portion
210: electrode tab 220: electrode tape
230: lead

Claims (15)

It includes a case body and a cover to which each outer portion is bonded to each other,
In at least one of the outer portions to be joined, a safety vent portion including a core plate having a flat portion disposed in a plane direction of the outer portion, and a thermoplastic resin matrix having a different coefficient of thermal expansion from the core plate surrounding the core plate, and ,
When the inner temperature of the pouch is equal to or higher than a predetermined vent operating temperature, the core plate of the safety vent part and the thermoplastic resin matrix are separated from each other to communicate inside and outside the pouch.
The pouch for a secondary battery according to claim 1, wherein the core plate has a higher melting point than that of the thermoplastic resin matrix.
The pouch for a secondary battery according to claim 1, wherein the core plate comprises at least one material selected from the group consisting of metal, ceramic, polymer, and glass.
The pouch for a secondary battery according to claim 1, wherein the core plate has a thickness equal to or smaller than the thickness of the thermoplastic resin matrix.
The pouch for a secondary battery according to claim 1, wherein a length in a direction from an inside to an outside of the pouch of the core plate is equal to or smaller than a length in a direction from an inside to an outside of the pouch of the outer portion.
The pouch for a secondary battery according to claim 1, wherein a length of the pouch of the core plate is equal to or smaller than a length of the pouch of the outer portion in a direction from the inside to the outside and in a vertical direction.
The pouch for a secondary battery according to claim 1, wherein the shape of a cross section cut in a direction from the inside to the outside of the pouch of the core plate is a rectangle.
The pouch for a secondary battery according to claim 1, wherein the shape of the cross section cut in the direction from the inside to the outside of the pouch of the core plate is a trapezoid or a triangle.
The pouch for a secondary battery according to claim 8, wherein the core plate having a trapezoidal cross section has a short side positioned at an inner side of the pouch and a long side positioned at an outer side of the pouch.
The pouch for a secondary battery according to claim 8, wherein the core plate having a trapezoidal cross section has a short side disposed on an outer side of the pouch and a long side disposed on an inner side of the pouch.
The pouch for a secondary battery according to claim 1, wherein a plurality of the core plates are included in the thermoplastic resin matrix.
The pouch for a secondary battery according to claim 1, wherein the thermoplastic resin matrix has a lower melting point than a material forming the case body and the cover.
delete The pouch for a secondary battery according to claim 1, wherein when the inner temperature of the pouch is equal to or higher than a preset vent operating temperature and the pressure inside the pouch reaches the vent pressure, the thermoplastic resin matrix of the safety vent portion is melted and the core plate is discharged to the outside of the pouch. .
A pouch-type secondary battery comprising the pouch of claim 1 and an electrode assembly accommodated in the pouch.

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