KR100614340B1 - Current collector of secondary battery having ptc-characteristics and fabricating method thereof - Google Patents

Abstract

The present invention relates to a current collector provided on a positive electrode active material layer or a negative electrode active material layer of a secondary battery, comprising: a first current collector layer formed of metal foil and in contact with the active material layer; A PTC material layer provided on the first current collecting layer; And a second current collector layer formed of metal foil and symmetrically formed with the first current collector layer with the PTC material layer therebetween.

In addition, according to an embodiment of the present invention, a method for manufacturing a current collector provided on a positive electrode active material layer or a negative electrode active material layer of a secondary battery, the method comprising the steps of flowing a pair of metal foil between two rollers to rotate; Disclosed is a method for manufacturing a current collector for a secondary battery, comprising the steps of: putting a PTC material in a molten state between the metal foils immediately before the roller passing to form a compression laminate.

According to another embodiment of the present invention, a method for manufacturing a current collector provided on a positive electrode active material layer or a negative electrode active material layer of a secondary battery, comprising the steps of: mixing a PTC powder and a binder to form a slurry; Applying the slurry to the surface of the metal foil; A method for manufacturing a current collector for a secondary battery comprising a; pressing another metal foil on the slurry.

According to the present invention, since the action of the PTC material in the current collector, the current can be cut off more quickly when an abnormal state such as overcurrent occurs, and the battery performance can be prevented since it does not occupy the space of the active material layer.

Active material layer, current collector, PTC, lamination

Description

Current collector for secondary battery having PTC characteristics and its manufacturing method {CURRENT COLLECTOR OF SECONDARY BATTERY HAVING PTC-CHARACTERISTICS AND FABRICATING METHOD THEREOF}

The following drawings attached to this specification are illustrative of preferred embodiments of the present invention, and together with the detailed description of the invention to serve to further understand the technical spirit of the present invention, the present invention is a matter described in such drawings It should not be construed as limited to

1 is a cross-sectional view showing the internal configuration of a secondary battery according to the prior art.

2 is a cross-sectional view showing the configuration of a current collector for a secondary battery according to an embodiment of the present invention.

3 is a cross-sectional view showing the configuration of a current collector for a secondary battery according to another embodiment of the present invention.

Figure 4 is a schematic diagram showing a manufacturing process of a current collector for a secondary battery according to an embodiment of the present invention.

5 is a configuration diagram schematically showing a manufacturing process of a current collector for a secondary battery according to another embodiment of the present invention.

<Description of main reference numerals in the drawings>

10 positive electrode active material layer 20 negative electrode active material layer

B ... electrolyte layer 100a ... first collector layer

100b ... PTC material layer 100c ... second collector layer

200a, 200b ... roller

The present invention relates to a current collector for a secondary battery and a method for manufacturing the same, and more particularly, a PTC action is performed more quickly by including a material having a PTC characteristic at a portion other than the portion in contact with the active material layer or inside the active material layer. The present invention relates to a current collector for secondary batteries and a method of manufacturing the same, which can prevent performance degradation of a battery.

A material having a positive temperature coefficient (PTC) characteristic rapidly increases its resistance to hundreds of times or more when the ambient temperature rises or a current exceeding the allowable value induces heat generation. Since it serves to cut off the electrical connection between the circuits, it is particularly useful in the protection circuit of lithium-ion (Lithium-ion) secondary battery which has a risk of explosion when the temperature rises.

In order to protect the lithium ion secondary battery using a PTC element, for example, in the case of a square battery, a PTC element is connected between the outer wall of the battery can and an external terminal to cut off the current. It protects the battery from over current. However, these technologies have a disadvantage in that the volume of the secondary battery pack becomes large because the technique of attaching a PTC device separately to the secondary battery pack and then connecting the circuits may be large, and the connection part of the PTC device may be disconnected.

Alternative secondary battery technologies include, for example, directly injecting a PTC material into an electrode structure as disclosed in US Pat. Nos. 6,337,525, 6,651,616, 6,640,605, 63,99,252, 6114433, and the like. The technique to say is. Among these, US Patent No. 6346345, filed by Mitsubishi Corporation, proposes a secondary battery technology having a structure as shown in FIG. 1.

Referring to FIG. 1, the secondary battery is provided at each of the positive electrode (A) and the negative electrode (C) formed with the electrolyte layer (B) interposed therebetween, and the positive electrode (A) and the negative electrode (C) to perform a current collecting function. Including the current collector (12, 13), the positive electrode (A) and the negative electrode (B) is provided with a positive electrode active material layer 10 and a negative electrode active material layer 20, in particular inside the positive electrode active material layer 10 and the The PTC material 11 is provided between the positive electrode active material layer 10 and the current collector 12. Here, the PTC material 11 provided in the cathode active material layer 10 is bound to the cathode active material 10a.

According to the above configuration, when the current flowing through the current collectors 12 and 13 through the positive electrode active material layer 10 increases rapidly due to an abnormal state such as an internal short circuit, the PTC material 11 acts to cause a sudden increase in resistance. By suppressing the flow of current, the battery is protected.

However, such a structure increases the internal resistance of the battery because the PTC material 11 partially occupies a space in the positive electrode active material layer 10 which performs a substantial power generation function, and increases the amount of the positive electrode active material by the amount of the PTC material 11. There is a disadvantage that the activity of the battery may be reduced by decreasing the number 10a.

The present invention has been made to solve the above problems, provided with a material having a PTC characteristic in the electrode can be quickly cut off the circuit in the event of an abnormal state of the current, in the region other than the active material layer to prevent the active degradation An object of the present invention is to provide a secondary battery current collector and a method of manufacturing the same, including a PTC material to protect a battery.

Another object of the present invention is to provide a current collector manufacturing method for a secondary battery provided with a PTC material layer provided with flexibility to manufacture the battery sheet in a roll form.

In order to achieve the above object, a current collector for a secondary battery according to the present invention includes: a first current collector layer formed of metal foil and in contact with the active material layer; A PTC material layer provided on the first current collecting layer; And a second current collector layer formed of metal foil and symmetrically formed with the first current collector layer with the PTC material layer therebetween.

Preferably, the PTC material layer may contain a polymer resin and a conductive material in the range of 30 to 70wt%.

It is preferable that some or all of resins having crystallinity are used as the polymer resin, and the heat of fusion of the polymer resin is set to 30 J / g or more.

It is preferable that the PTC material layer has a specific resistance of 0.05 to 5Ω · cm at room temperature.

According to another aspect of the present invention, a method for manufacturing a current collector provided on a positive electrode active material layer or a negative electrode active material layer of a secondary battery, the method comprising the steps of flowing a pair of metal foil between two rollers to rotate; And inserting a PTC material in a molten state between the metal foils immediately before the roller passes to form a compression laminate.

Further, according to another embodiment of the present invention, in the method of manufacturing a current collector provided on the positive electrode active material layer or the negative electrode active material layer of the secondary battery, the step of mixing the PTC powder and the binder to make a slurry; Applying the slurry to the surface of the metal foil; And pressing the other metal foil on the slurry. There is provided a current collector manufacturing method including a secondary battery.

It is preferable that the average particle size of the said PTC powder has a range of 0.01-50 micrometers.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

2 is a cross-sectional view showing the configuration of a current collector for a secondary battery according to an embodiment of the present invention.

2, the current collector according to the present invention is provided on the positive electrode active material layer 10 and the negative electrode active material layer 20 of the secondary battery formed on both sides with the electrolyte layer B therebetween to perform a current collecting function. In this case, the positive electrode collector 100 or the negative electrode collector 101 plays a role of PTC together with the PTC action. In the drawings, an embodiment in which the present invention serves as the positive electrode current collector 100 is shown.

Referring to FIG. 2 again, the secondary battery current collector according to the preferred embodiment of the present invention is provided on the first current collector layer 10a and the first current collector layer 10a that are in contact with the positive electrode active material layer 10. A PTC material layer 10b and a second current collecting layer 10c symmetrically formed with the first current collecting layer 10a with the PTC material layer 10b interposed therebetween.

The first collector layer 10a and the second collector layer 10c may be formed of a thin film of metal such as aluminum or copper.

The PTC material layer 10b may be composed of a mixture of a polymer resin and a conductive material having some or all crystallinity. Herein, the content ratio of the polymer resin and the conductive material is determined based on the weight of the entire PTC material layer 10b in consideration of workability, optimum contact force and resistivity of the surfaces of the first and second current collector layers 10a and 10c. It is preferably 30 to 70wt% with respect to 0 to 10wt% of the other additives below.

In general, the PTC characteristic is that the melting point range of the polymer resin is important because the resistance is increased by expanding the volume of the crystalline polymer when the temperature of the crystalline polymer is increased and pushing the gap between the conductive materials. Considering the range and the internal electrolyte layer (B) and the explosion risk temperature of lithium, the melting point of the crystalline polymer is preferably in the range of 60 ~ 160 ℃, the heat of fusion of the crystalline polymer (Heat of fusion) value is It is preferable to correspond to the range of 30 J / g or more.

In addition, a conductive material such as carbon may be used as the conductive material, and maleic anhydride for improving adhesion to the first and second collector layers 10a and 10c. However, a small amount of additives such as a crosslinking agent or an antioxidant for crosslinking between polymers may be contained. The conductive material has a specific resistance of 0.05 to 5Ω · cm at room temperature, while the temperature rises from hundreds to tens of thousands of times in the general temperature range of 60 to 160 ° C in an abnormal state such as overcurrent, and can effectively block the overcurrent flowing in the circuit. do.

In order to increase the energy density of the secondary battery, when the secondary battery is configured in a multilayered lamination (rolled) structure in the form of a roll, the current collector 100 of the present invention having a PTC characteristic is a roll-shaped sheet as shown in FIG. 3. It may be provided only at both ends.

The secondary battery current collector of the present invention having the configuration as described above is quickly converted to a high resistance value by performing a PTC operation in the current collector itself in which current is generated when an abnormal current such as a short circuit occurs to cut off the current.

Meanwhile, FIG. 4 schematically shows a manufacturing process of a current collector for a secondary battery according to an embodiment of the present invention.

Referring to FIG. 4, the present invention preferably introduces a metal foil of aluminum or copper between the two rollers 200a and 200b rotatably provided, and immediately before the metal foil passes through the roller. Lamination using the roller while injecting the molten state of the PTC material between the first collector layer (100a) and the second collector layer (100c) on both sides with the PTC material layer (100b) sandwiched in the form of a sheet Prepare a current collector.

5 schematically illustrates a manufacturing process of a current collector for a secondary battery according to another embodiment of the present invention.

Referring to FIG. 5, after the PTC powder and the binder are mixed to form a slurry, the slurry is applied to the surface of the metal foil, and then another metal foil is pressed onto the slurry using a predetermined pressing means (not shown) to press the PTC material. A current collector in the form of a sheet in which the first collector layer 100a and the second collector layer 100c are pressed and laminated on both sides with the layer 100b interposed therebetween is manufactured. According to such a configuration, since the PTC material layer 100b is formed of an aggregate of PTC powders 100b-1, flexibility may be provided according to the properties of the binder to manufacture a roll-type battery. To this end, the PTC powder (100b-1) is preferably a powder pulverized to an average particle size of 0.01 ~ 50㎛, polyvinylidene fluoride (polyvinylidene fluoride) may be used as the binder.

Although the present invention has been described above by means of limited embodiments and drawings, the present invention is not limited thereto and will be described below by the person skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of the claims.

According to the present invention, since a material having a PTC characteristic is provided in the current collector, a circuit can be quickly cut off when an abnormal state such as an overcurrent occurs, and unlike the related art, it is possible to prevent deactivation of the active material layer.

In addition, the present invention has the advantage that it can be applied to a roll-shaped secondary battery by providing flexibility by providing a powder-like PTC material to the current collector.

Claims (8)

In the current collector provided on the positive electrode active material layer or negative electrode active material layer of the secondary battery, A first collector layer formed of metal foil and in contact with the active material layer; A PTC material layer including a polymer resin and a conductive material on the first current collector layer and in contact with the active material layer; And And a second collector layer formed of a metal foil, the second collector layer being symmetrical with the first collector layer with the PTC material layer therebetween. The method of claim 1, The current collector for secondary batteries, characterized in that the polymer resin and the conductive material contained 30 to 70wt%, respectively. The method of claim 2, The secondary battery current collector, characterized in that the melting point of the polymer resin is 60 ~ 160 ℃. The method of claim 2 or 3, As the polymer resin, some or all resins having crystallinity may be employed. The secondary battery current collector, characterized in that the heat of fusion of the polymer resin is 30J / g or more. The method of claim 1, The specific resistance of the said PTC material layer at normal temperature is 0.05-5 ohm * cm, The collector for secondary batteries characterized by the above-mentioned. In the manufacturing method of the current collector provided on the positive electrode active material layer or the negative electrode active material layer of the secondary battery, Introducing a pair of metal foil between two rotating rollers; And And inserting a PTC material in a molten state between the metal foils immediately before the rollers so as to form a compression laminate. 2. In the manufacturing method of the current collector provided on the positive electrode active material layer or the negative electrode active material layer of the secondary battery, Mixing the PTC powder and the binder to make a slurry; Applying the slurry to the surface of the metal foil; And Comprising the step of pressing another metal foil on the slurry; current collector manufacturing method for a secondary battery comprising a. The method of claim 7, wherein The current collector manufacturing method for a secondary battery, characterized in that the average particle size of the PTC powder is in the range of 0.01 ~ 50㎛.

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