KR20090076279A - Pouch for secondary battery and secondary battery using the same - Google Patents

Abstract

A pouch for a secondary battery is provided to suppress the collapse of an inner layer by comprising a metal oxide layer in a metal thin layer contacting with the inner layer, and to prevent metal foil from being exposed to electrolyte. A pouch packing material(200) for a battery has at least one metal oxide layer on a thin metal layer(20) contacting with an inner layer(10). The metal oxide layer is formed by heat-treating the surface of the thin metal layer or treating it with oxidizing agent. The thickness of the metal oxide layer is 0.1-10 micron. The thin metal layer is selected from group consisting of an alloy consisting of iron(Fe), carbon(C), chrome(Cr), and manganese(Mn); an alloy consisting of iron(Fe), carbon(C), chrome(Cr), and nickel(Ni); and copper(Cu), aluminum(Al) or equivalent material.

Description

Pouch for secondary battery and pouch type secondary battery {Pouch for secondary battery and Secondary battery using the same}

The present invention relates to a pouch packaging material used as a container of a secondary battery electrode assembly including a metal oxide film with improved insulation characteristics, and a pouch type secondary battery using the same.

As the use of portable electric products such as video cameras, portable telephones and portable PCs is activated, the importance of secondary batteries mainly used as driving power thereof is increasing. In particular, lithium secondary batteries have higher energy density per unit weight and can be rapidly charged compared to other lead-acid batteries and other secondary batteries such as nickel-cadmium batteries, nickel-hydrogen batteries, and nickel-zinc batteries. It is actively underway.

Unlike primary batteries that are not normally rechargeable, rechargeable batteries that are capable of charging and discharging are being actively researched due to the development of advanced fields such as digital cameras, cellular phones, notebook computers, and hybrid cars. Examples of secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-hydrogen batteries, and lithium secondary batteries. Among these, lithium secondary battery is used as a power source for portable electronic devices with operating voltage of 3.6V or more, or used in high-power hybrid vehicles by connecting several in series. It is used in nickel-cadmium battery or nickel-metal hydride battery. Compared with the three times higher operating voltage and excellent energy density per unit weight, it is being used rapidly.

The lithium secondary battery may be classified into a lithium ion battery using a liquid electrolyte and a lithium ion polymer battery using a polymer solid electrolyte according to the type of electrolyte. Lithium ion polymer batteries can be classified into fully solid lithium ion polymer batteries containing no electrolyte solution and lithium ion polymer batteries using gel polymer electrolyte containing electrolyte solution, depending on the type of polymer solid electrolyte.

In the case of a lithium ion battery using a liquid electrolyte, a cylindrical or rectangular metal can is used as a container by welding sealing. Since the can-type secondary battery using the metal can as a container has a fixed shape, there is a disadvantage in restricting the design of an electrical product using the same as a power source, and it is difficult to reduce the volume. Accordingly, a pouch type secondary battery using two electrodes, a separator, and an electrolyte in a pouch made of a film and being sealed is developed and used.

The pouch of a lithium ion polymer battery that is commonly used serves as a polyolefin-based inner layer (Polyolefin layer), a thermal adhesive layer that serves as a sealing material in order to have a thermal adhesiveness sequentially, a substrate that maintains mechanical strength and a barrier layer of moisture and oxygen It consists of a multilayer film structure in which an aluminum layer (AL / Aluminum Layer), a base material, and an outer layer, a nylon layer serving as a protective layer, are laminated. Commonly used as the polyolefin-based resin layer is CPP (Casted Polypropylene).

Pouch type secondary battery has the advantage that can be flexible in form and to implement a secondary battery of the same capacity with a smaller volume and mass. However, unlike the can type, the pouch type uses a soft pouch as a container, so that the mechanical strength may be weak and the reliability of the sealing may be low. Therefore, it is mainly used in a gel-type or all-solid-state lithium ion polymer battery rather than in a lithium ion secondary battery using an electrolyte solution having a large leakage problem.

The pouch packaging material having the structure as described above is sealed through thermal fusion into an electrode body and an electrolyte solution. If the CPP layer, which is an inner layer, is broken even finely, the metal foil layer is exposed to the inside of the battery. Reactivity with causes side reactions.

When a side reaction occurs, the active layer of the electrode is mechanically collapsed and moisture permeation is facilitated, and the life of the battery is drastically reduced. Because of this problem, weakening the thermal fusion increases the water permeation characteristics through the sealing portion can also have a serious adverse effect on the life of the battery.

Therefore, it is recognized as an important technique to fuse without destroying the inner CPP layer, and research to solve the above problems is required.

Therefore, the present invention is to improve the performance of the battery by solving the problems such as moisture infiltration caused by thermal fusion in the pouch packaging material of the secondary battery having the structure as described above.

Accordingly, the present invention further includes a metal oxide film in the metal foil layer in contact with the inner layer in the pouch packaging material in which the inner layer, the metal foil layer, and the outer layer are sequentially stacked, thereby suppressing the metal foil from being exposed to the electrolyte, thereby improving insulation properties. It is now possible to provide excellent pouch packaging.

Accordingly, it is an object of the present invention to provide a pouch of a secondary battery having excellent insulation characteristics because the internal layer can be destroyed and moisture permeation from the outside can be reduced.

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 metal foil layer is further included in the metal foil layer in contact with the inner layer to suppress the collapse of the inner layer so that the metal foil is exposed to the electrolyte. Suppression can provide a pouch packaging material with excellent insulation properties.

The pouch packaging material of the battery of the present invention for achieving the above object is characterized in that it comprises at least one metal oxide film in the metal foil layer in contact with the inner layer.

In addition, the pouch type secondary battery of the present invention is characterized in that it comprises the pouch packaging material.

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

Next, FIG. 1 illustrates a structure of a pouch case 100 formed of a conventional inner layer 10 / metal foil layer 20 / outer layer 30. The pouch packaging material 200 of the battery of the present invention has a structure as shown in FIG. 2 after the metal oxide film 40 is further provided on the metal foil layer 20 in contact with the inner layer 10.

By providing a metal oxide film 40 on at least one surface of the metal foil layer 20 in contact with the inner layer 10 as in the present invention, the metal foil layer 20 is suppressed by preventing the collapse of the inner layer 10 made of a polymer layer during sealing. The insulation characteristic can be improved by suppressing exposure to the electrolyte.

The metal oxide film may be formed by heat treating a metal constituting the metal foil layer or treating the surface with an oxidizing agent.

When heat-treating the metal constituting the metal foil layer, heat treatment conditions are possible by exposing at 200 to 600 ° C. for 5 seconds to 24 hours.

In addition, the oxidizing agent used when the metal surface constituting the metal foil layer is treated with an oxidizing agent is selected from the group consisting of iron (III) chloride, iron (III) sulfate, iron (III) parachromic acid, chromic acid, hydrogen peroxide and nitric acid, and the like. Preference is given to using the selected oxidant. When treating the metal surface using the oxidizing agent as described above, it is preferable to perform for 5 seconds to 24 hours.

In addition, the metal oxide film included in the present invention may be a single layer or a composite layer, and may be selected as necessary.

The thickness of the metal oxide film is 0.1 to 10 μm, and when the thickness of the metal oxide film is out of the above range, the metal oxide film may not exhibit insulation characteristics or may be easily cracked during pouch deformation.

The metal foil layer of the pouch packaging material maintains an appropriate thickness, prevents water vapor and gas from penetrating from the outside to the inside, and serves to prevent leakage of the electrolyte 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) and nickel (Ni), and copper One selected from (Cu), aluminum (Al), or equivalents thereof may be used, but is not limited thereto. However, when the metal foil layer is made of a material containing iron, the mechanical strength is strong, and when the material is made of aluminum, flexibility is improved. Usually, aluminum metal foils are preferably used.

In the case of the metal constituting the metal foil layer, for example, aluminum foil as in the present invention, when the surface thereof is treated with an oxidizing agent, the aluminum is changed to aluminum oxide, which is an insulator of aluminum oxide in the form of aluminum oxide. Will change. Therefore, even if the insulator is exposed to the electrolyte, it is not reactive with the electrolyte so that the insulation resistance is not destroyed.

The inner layer constituting the pouch packaging material may be a heat-adhesive layer, a modified polypropylene such as casted polypropylene (CPP), polypropylene and butylene, and an ethylene terpolymer. The inner layer is coated or laminated to the other side of the metal foil layer to a thickness of approximately 30 to 40 μm.

In addition, the outer layer constituting the pouch case serves as a substrate and a protective layer, and is usually composed of nylon or polyethylene terephthalate.

In general, in the case of the pouch packaging material having the structure as shown in FIG. 1, when an external heat or pressure is applied, the inner layer (CPP layer) collapses, the electrolyte penetrates, and the insulation resistance is broken.

However, when using a pouch case having a metal oxide film in the metal foil layer in contact with the inner layer as in the present invention, even if heat or pressure is applied from the outside, the metal oxide film is not reactive with the electrolyte, thereby preventing the insulation resistance from being destroyed. You can.

On the other hand, the pouch type secondary battery of the present invention comprises an electrode assembly including a first electrode, a second electrode and a separator interposed therebetween; And a case body including a case body in which a space portion for accommodating the electrode assembly is formed, and a case cover in contact with at least one side of the case body, wherein the battery case includes at least an inner layer 10. The metal foil layer 20 and the outer layer 30 are laminated, and the metal oxide layer 30 is included on at least one surface of the metal foil layer.

The electrode assembly may be provided in the form of a jelly-roll wound around a first electrode, a second electrode, and a separator therebetween, or may be provided as a stacked electrode assembly in which they are 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 applied to at least one surface of the current collector, that is, a positive electrode active material or a negative electrode active material.

In the case where the first electrode or the second electrode is used as an anode, the electrode current collector is a surface treatment of carbon, nickel, titanium, silver on the surface of stainless steel, nickel, aluminum, titanium or their alloys, aluminum or stainless steel The thing etc. can be used and aluminum or aluminum alloy is preferable among these.

When the first electrode or the second electrode is used as a negative electrode, the electrode current collector is a surface treatment of carbon, nickel, titanium, silver on the surface of stainless steel, nickel, copper, titanium or their alloys, copper or stainless steel The thing etc. can be used and a copper or copper alloy is preferable among these.

As the cathode active material may be a conventional lithium-containing transition metal oxide or lithium kalko to use all of the cyanide compound, and representative examples include _{LiCoO 2, LiNiO 2, LiMnO 2} , LiMn 2 O 4, or LiNi _{1 -x- y} Co Metal oxides such as _x M _y O ₂ (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1, and M is a metal of Al, Sr, Mg, La, etc.) may be used. As the negative electrode active material, a carbon material such as crystalline carbon, amorphous carbon, carbon composite, carbon fiber, lithium metal, lithium alloy, or the like may be used.

The separator prevents a short circuit between the first electrode and the second electrode and provides a migration path for lithium ions, and includes a polyolefin-based polymer film such as polypropylene and polyethylene, or a multilayer film, a microporous film, a woven fabric and a nonwoven fabric thereof. The same well-known thing can be used.

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

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 the sealing part positioned opposite to the side of the sealing part to which 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 the following Examples, but the present invention is not limited thereto.

Example  1: by oxidizing agent Metal oxide film Formation example

The surface of the aluminum foil, which is a metal foil layer in contact with an inner layer made of a CPP film having a thickness of 40 μm, was treated with an aqueous solution of iron (III) chloride for 10 minutes to form a metal oxide film having a thickness of about 1 μm. Next, a pouch case having a nylon layer acting as a protective layer on the metal oxide layer was manufactured.

Example  2 to 3: by oxidizing agent Metal oxide film Formation example

A pouch case was manufactured in the same manner as in Example 1, except that the aluminum foil surface, which was a metal layer in contact with the inner layer, was treated with chromic acid and hydrogen peroxide, respectively, as an oxidant.

Example  4: by heat treatment Metal oxide film  formation

A pouch sheathing material was manufactured in the same manner as in Example 1, except that the aluminum foil surface, which is a metal foil layer in contact with the inner layer, was heat-treated at about 300 ° C. for 30 minutes to form a metal oxide film.

Comparative example  One

In Example 1, a pouch packaging material including a conventional inner layer / metal foil layer / outer layer without a metal oxide film was prepared.

Experimental Example

A secondary battery was manufactured by placing a conventional electrode assembly therein using the pouch packaging material prepared in Examples and Comparative Examples. Then, their insulating properties were evaluated as follows, and the results are shown in Table 1 below.

-Insulation property: The resistance between the aluminum of the packaging metal layer of the battery and the negative electrode of the battery was measured using a megaohmmeter, and the resistance value of less than 10Mohm was evaluated as defective.

Total number of manufactured cells Poor insulation battery A good battery Example 1 100 3 97 Example 2 100 2 98 Example 3 100 5 95 Example 4 100 7 93 Comparative Example 1 100 25 75

As can be seen from the results of Table 1, it can be seen that the occurrence of poor insulation in the case of the pouch manufactured using an aluminum foil having an oxide layer formed on the surface as in the present invention.

Figure 1 shows the structure of a conventional battery pouch packaging material,

Figure 2 shows the structure of the battery pouch packaging material including a metal oxide film according to the present invention,

<Short description of drawing symbols>

100, 200: Pouch exterior material

10: inner layer

20: metal foil layer

30: outer layer

40: metal oxide film

Claims (10)

A pouch packaging material for a battery, characterized in that it has at least one metal oxide film on the metal foil layer in contact with the inner layer. The pouch packaging material of claim 1, wherein the metal oxide film is formed by heat-treating the surface of the metal foil layer or by treating with an oxidizing agent. The pouch packaging material of claim 2, wherein the heat treatment is performed by exposing the metal foil layer for 5 seconds to 24 hours at a temperature of 200 to 600 ° C. The pouch packaging material according to claim 2, wherein the oxidizing agent is selected from the group consisting of iron (III) chloride, iron (III) sulfate, iron (III) paratoluene sulfonate, chromic acid, hydrogen peroxide and nitric acid. The pouch packaging material of claim 2, wherein the treatment of the oxidant is performed for about 5 seconds to 24 hours. The pouch packaging material of claim 1, wherein the metal oxide film has a thickness of 0.1 to 10 µm. The method of claim 1, wherein the metal foil layer is an alloy of iron (Fe), carbon (C), chromium (Cr) and manganese (Mn), iron (Fe), carbon (C), chromium (Cr) and nickel (Ni). The battery packaging material, characterized in that any one selected from the group consisting of alloys, copper (Cu), aluminum (Al) or equivalents thereof. The battery packaging material according to claim 7, wherein the metal foil layer is aluminum. The pouch packaging material of claim 1, wherein the inner layer is at least one selected from CPP, polyethylene, polyethylene-propylene copolymer, and polypropylene-butylene-ethylene terpolymer. A lithium secondary battery comprising the pouch packaging material according to any one of claims 1 to 9.

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