KR101405621B1 - Pouch for secondary battery and Secondary battery using the same - Google Patents

Abstract

The present invention provides a pouch packing material for a secondary battery having at least one heat resistant reinforcing layer in a metal thin layer and a pouch type secondary battery using the same.

The present invention further includes a heat resistant reinforcing layer on at least one side of the inner layer in a pouch package having an inner layer, a metal foil layer, and an outer layer sequentially laminated, thereby suppressing the collapse of the inner layer and inhibiting the metal foil from being exposed to the electrolyte Thereby providing a pouch packaging material excellent in insulation characteristics.

Heat-resistant reinforcing layer * Secondary battery * Pouch * Insulation

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pouch type secondary battery,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pouch packing material used as a container of a secondary battery electrode assembly having improved insulation characteristics including a heat resistant reinforcing layer and a pouch type secondary battery using the same.

As the use of portable electric appliances such as video cameras, portable phones, and portable PCs is being activated, the importance of secondary batteries, which are mainly used as driving power sources, is increasing. In particular, the lithium secondary battery has a higher energy density per unit weight and can be rapidly charged as compared with conventional lead-acid batteries and other secondary batteries such as nickel-cadmium batteries, nickel-hydrogen batteries and nickel-zinc batteries. It is actively proceeding.

Unlike conventional primary batteries, which can not be charged, secondary batteries capable of charging and discharging are under active research in the development of 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, the lithium secondary battery is used as a power source of a portable electronic device at an operating voltage of 3.6 V or more, or several series are connected in series to be used in a high-output hybrid vehicle. Compared with a nickel-cadmium battery or a nickel-metal hydride battery The operating voltage is three times higher and the energy density per unit weight is also excellent.

The lithium secondary battery can be classified into a lithium ion battery using a liquid electrolyte and a lithium ion polymer battery using a polymer solid electrolyte depending on the type of electrolyte. The lithium ion polymer battery can be divided into a fully solid lithium ion polymer battery containing no electrolytic solution and a lithium ion polymer battery using a gel polymer electrolyte containing an electrolyte depending on the kind of polymer solid electrolyte.

In the case of a lithium ion battery using a liquid electrolyte, it is usually used in a form in which a cylinder or a rectangular metal can is used as a container and welded and sealed. Since the can type secondary battery using such a metal can as a container is fixed in shape, there is a disadvantage that it restricts the design of an electrical product using the metal can as a power source, and it is difficult to reduce the volume. Therefore, a pouch-type secondary battery in which two electrodes, a separator, and an electrolyte are put in a film-made pouch and sealed is developed and used.

The pouch of a commonly used lithium ion polymer battery includes an inner layer of a polyolefin resin layer, which is a thermal bonding layer having a thermal adhesion property in order to serve as a sealing material, a base material that maintains mechanical strength, An aluminum layer (AL / Aluminum Layer) serving as a metal foil serving as a protective layer, and a nylon layer serving as a protective layer. Commonly used as a polyolefin-based resin layer is CPP (Casted Polypropylene).

The pouch type secondary battery has flexibility in shape and has the advantage that a secondary battery of the same capacity can be realized with a smaller volume and mass. However, unlike the can type, the pouch type uses a soft pouch as the container, so the mechanical strength is weak and the reliability of the seal may be lowered. Therefore, it is mainly used in a gel type or fully solid lithium ion polymer battery, rather than a lithium ion secondary battery using a large amount of electrolyte.

When the CPP layer, which is an inner layer, is broken even if it is finely broken, the metal foil layer is exposed to the inside of the battery. In this case, when the electrolyte layer is sealed with the electrode body and the electrolyte, A side reaction occurs due to the reactivity with the compound.

When the side reaction is generated, the active layer of the electrode is mechanically collapsed and moisture penetration is facilitated, so that the lifetime of the battery drastically decreases. Due to such a problem, when the thermal fusion is weakened, the moisture penetration characteristic through the sealing part is increased, and the life of the battery is seriously adversely affected.

Therefore, it is recognized that it is important to fuse the internal CPP layer without destroying it, and research for solving the above problems is needed.

Therefore, in the present invention, as described above, the problem of moisture infiltration or the like generated due to heat fusion in the pouch packaging material of the secondary battery is solved and the performance of the battery is improved.

Accordingly, the present invention provides a pouch packaging material in which an inner layer, a metal foil layer, and an outer layer are sequentially stacked, wherein a heat resistant reinforcing layer is further provided on at least one surface of the inner layer to suppress collapse of the inner layer, It is possible to provide a pouch packing material excellent in insulation characteristics.

Accordingly, an object of the present invention is to provide a pouch for a secondary battery that can lower moisture permeation from the outside without breaking the inner layer, and thus has excellent insulation characteristics.

Another object of the present invention is to provide a pouch-type secondary battery having improved battery performance by using a pouch capable of preventing moisture penetration from the outside as described above.

In the pouch packaging material in which the inner layer, the metal foil layer and the outer layer are sequentially stacked as in the present invention, the heat resistant reinforcing layer is further provided on at least one surface of the inner layer to suppress the collapse of the inner layer to suppress the metal foil from being exposed to the electrolyte Thereby providing a pouch packaging material having excellent insulation characteristics.

In order to accomplish the above object, the pouch outer cover of the battery of the present invention includes at least one heat resistant reinforcing layer in the metal foil layer.

In addition, the secondary battery of the present invention is characterized by including the pouch exterior material.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

The pouch outer casing used in a conventional secondary battery is composed of the inner layer 30 / the metal foil layer 20 / the outer layer 10 as shown in FIG. However, the pouch exterior material according to the present invention has at least one heat-resistant reinforcing layer 40 in the metal foil layer 20, and then has a structure as shown in FIG.

By providing at least one heat resistant reinforcing layer 40 in the metal foil layer 20 as in the present invention, it is possible to suppress the collapse of the internal polymer layer at the time of sealing, thereby suppressing the metal foil layer from being exposed to the electrolyte,

The metal foil layer of the pouch exterior material has a proper thickness and prevents penetration of water vapor and gas from the outside to the inside, and prevents leakage of the electrolytic solution. As the metal foil layer, an alloy of iron (Fe), carbon (C), chromium (Cr) and manganese (Mn), an alloy of iron (Fe), carbon (C), chromium (Cr) Aluminum (Al), copper (Cu), or an equivalent thereof may be used, but the present invention is not limited thereto. However, when the metal foil layer is made of iron-containing material, the mechanical strength is strengthened, and when the metal foil layer is made of aluminum-containing material, flexibility is improved. Normally, an aluminum metal foil is preferably used.

The at least one heat-resistant reinforcing layer formed on the metal foil layer is preferably formed of a heat-resistant polymer having a melting point of 180 ° C or higher. Such a heat-resistant polymer may be selected from the group consisting of polyethylene terephthalate, an acrylic polymer, a polyacrylonitrile, a polyimide, a polyamide, a cellulose, an aramid, a nylon, a polyester, a polyparaphenylenebenzobisoxazole, a polyarylate, , But is not limited thereto.

The heat resistant reinforcing layer may be coated or laminated on one side of the metal foil layer to have a small thickness. The heat-resistant reinforcing layer may be formed by laminating the heat-resistant polymer resin on one surface of the metal foil layer, or by laminating the heat-resistant polymer in advance in the form of a film by various laminating methods. In addition, the heat-resistant reinforcing layer included in the present invention may be either a single layer or a multiple layer, and may be selected as required.

When the thickness of the heat resistant reinforcing layer is out of the above range, the sealing performance of the battery is lowered, so that external moisture can penetrate into the battery. Further, due to an unnecessary increase in thickness, There is a problem that the energy density is lowered, which is undesirable.

The inner layer constituting the pouch outer cover material may be a thermoplastic adhesive layer such as modified polypropylene such as casted polypropylene (CPP), polypropylene, butylene, and ethylene terpolymer. The heat-adhesive layer is coated or laminated on the other surface of the metal foil layer to a thickness of about 30 to 80 mu m.

The outer layer constituting the pouch exterior member acts as a substrate and a protective layer, and is usually composed of nylon or polyethylene terephthalate.

In the case of the pouch case having the structure as shown in FIG. 1, as shown in FIG. 3, when the external heat or pressure is applied, the inner layer (CPP layer) collapses and electrolyte penetrates, There was a problem.

However, in the case of using the pouch outer cover material having the heat resistant reinforcing layer as in the present invention, since the heat resistant reinforcing layer suppresses the breakdown of the insulation resistance even when heat or pressure is externally applied as shown in FIG. 4, .

Meanwhile, the pouch type secondary battery of the present invention includes an electrode assembly including a first electrode, a second electrode, and a separator interposed therebetween; And a pouch cover having a pouch cover at least one side of which is in contact with the pouch main body, wherein the outer casing comprises at least an outer layer / a metal foil layer / an inner layer And at least one heat-resistant reinforcing layer is included in the metal foil layer.

The electrode assembly may include a first electrode, a second electrode, and a jelly-roll structure wound therebetween with a separator interposed therebetween, or may be provided with a stacked electrode assembly in which the electrode assembly is stacked.

The first electrode and the second electrode have different polarities from each other and may be used as an anode or a cathode. The first electrode and the second electrode include a current collector and an electrode active material coated on at least one surface of the current collector, that is, a cathode active material or a negative electrode active material.

When the first electrode or the second electrode is used as an anode, the electrode collector may be formed by surface-treating carbon, nickel, titanium or silver on the surface of stainless steel, nickel, aluminum, titanium or an alloy thereof, aluminum or stainless steel Or the like may be used, and among them, aluminum or an aluminum alloy is preferable.

When the first electrode or the second electrode is used as a cathode, the electrode current collector may be formed by surface-treating carbon, nickel, titanium or silver on the surface of stainless steel, nickel, copper, titanium or an alloy thereof, copper or stainless steel Or the like can be used, and among them, copper or a copper alloy is preferable.

As the cathode active material, a lithium-containing transition metal oxide or a lithium chalcogenide compound can be generally used. Typical examples thereof include LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , or LiNi _{1 -xy} Co _x M _y O ₂ (0? x? 1, 0? y? 1, 0? x + y? 1, and M is a metal such as Al, Sr, Mg, or La). As the negative electrode active material, a carbon material such as crystalline carbon, amorphous carbon, carbon composite, or carbon fiber, lithium metal, lithium alloy, or the like can be used.

The separation membrane prevents a short circuit between the first electrode and the second electrode and provides a passage for lithium ion. The separation membrane may be formed of a polyolefin-based polymer membrane such as polypropylene or polyethylene or a multiple membrane thereof, a microporous film, a woven fabric, The same known ones can be used.

The first electrode tab and the second electrode tab of the electrode assembly are attached to the first electrode tab and the second electrode tab, respectively, so as to be energizable by welding or conductive adhesive agent such as laser welding, ultrasonic welding, or resistance welding.

These electrode tabs are formed to protrude from the electrode assembly in a direction perpendicular to the direction in which the electrode assembly is wound. The first electrode tab and the second electrode tab of the electrode assembly are drawn out through a sealing portion of the sealing portion which is located opposite to the side where the case body and the case cover are connected. A protective tape made of an insulating material is attached to the electrode tab to prevent a short circuit between the electrodes.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited thereto.

Example  1: Heat resistance The reinforcement layer  Manufacture of Exterior Pouch Exterior Material

An aluminum foil metal foil layer was formed on an inner layer made of a CPP film having a thickness of 40 mu m and a heat resistant reinforcing layer having a thickness of 20 mu m was formed on the aluminum foil layer using a polyethylene terephthalate polymer. Next, a nylon layer serving as an outer layer was laminated on the opposite surface of the aluminum foil layer on which the heat-resistant reinforcing layer was formed to manufacture a pouch exterior member.

Example  2: Heat resistance The reinforcement layer  Manufacture of Exterior Pouch Exterior Material

An aluminum foil metal foil layer was formed on an inner layer made of a CPP film having a thickness of 40 mu m and a heat resistant reinforcing layer having a thickness of 20 mu m was formed on the aluminum foil layer using polyimide. Next, a nylon layer serving as an outer layer was laminated on the opposite surface of the aluminum foil layer on which the heat-resistant reinforcing layer was formed to manufacture a pouch exterior member.

Comparative Example  One

In Example 1, a pouch outer sheath made of a conventional inner layer / metal layer / outer layer not including a metal oxide film was prepared.

Experimental Example

The secondary battery was manufactured by placing the conventional electrode assembly in the pouch outer case made in the above examples and comparative examples. Then, their insulating properties were evaluated as follows, and the results are shown in Table 1 below.

- Insulation characteristics: The resistance between the aluminum, which is the metal layer of the packaging material of the finished battery, and the negative electrode of the battery was measured using a mega- ohmmeter. The resistance was evaluated as poor when the resistance was below 10Mohm.

The total number of cells manufactured Insulated battery Good battery Example 1 100 3 97 Example 2 100 5 95 Comparative Example 1 100 25 75

As can be seen from the results of Table 1, it can be seen that the occurrence of insulation failure is improved in the case of a pouch having at least one heat-resistant reinforcing layer in the metal foil layer as in the present invention.

Fig. 1 shows the structure of a conventional battery pouch exterior member,

2 shows a structure of a pouch outer cover material for a battery including a heat resistant reinforcing layer according to the present invention,

3 is a view showing a state in which insulation resistance is destroyed by external heat or pressure when sealing a pouch exterior material for a conventional battery,

FIG. 4 is a view showing a state in which insulation resistance is destroyed by external heat or pressure when a battery pouch exterior member according to the present invention is sealed.

≪ Brief Description of Drawings &

100, 200: Pouch Exterior Material

30: inner layer

20: metal foil layer

10: outer layer

  40: heat-resistant reinforcing layer

Claims (10)

The outer layer / the metal foil layer / the heat-resistant reinforcing layer / the inner layer are successively laminated successively, Wherein the heat-resistant reinforcing layer is formed on at least one surface of one surface of the metal foil layer that faces the inner layer. The battery pouch exterior member according to claim 1, wherein the heat-resistant reinforcing layer is a heat-resistant polymer having a melting point of 180 ° C or higher. The heat-resistant polymer according to claim 2, wherein the heat-resistant polymer is at least one selected from the group consisting of polyethylene terephthalate, acrylic polymer, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylenebenzobisoxazole, polyarylate , Teflon, and glass fiber. ≪ IMAGE > [2] The battery pouch case according to claim 1, wherein the heat resistant reinforcing layer is formed by coating or laminating. The battery pouch exterior member according to claim 1, wherein the heat resistant reinforcing layer has a thickness of 5 to 40 탆. The metal foil of claim 1, wherein the metal foil layer is made of an alloy of Fe, C, Cr, and Mn, Fe, C, Cr, ), Aluminum (Al), and copper (Cu). 7. The battery pouch exterior member according to claim 6, wherein the metal foil layer is aluminum. delete The battery pouch case according to claim 1, wherein the inner layer is at least one selected from CPP, polyethylene, polyethylene-propylene copolymer and polypropylene-butylene-ethylene terpolymer. 10. A lithium secondary battery comprising the pouch exterior member according to any one of claims 1 to 7 and 9.

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