KR20170021487A - Positive Electrode Coated with Conductive Adhesion Layer for Secondary Battery and Lithium Secondary Battery Comprising the Same - Google Patents

Abstract

The present invention relates to a positive electrode for a secondary battery in which a positive electrode active material, a binder, and a positive electrode material mixture containing a conductive material are applied to a current collector,
A conductive adhesive layer on which a mixture of a conductive material and a polymer material is pattern-coated is applied on one side or both sides of the current collector;
The positive electrode mixture is coated on the conductive adhesive layer at the portion where the conductive adhesive layer has been applied by the pattern coating and is directly applied to the current collector at the portion where the conductive adhesive layer is not applied .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive electrode for a secondary battery coated with a conductive adhesive layer and a lithium secondary battery comprising the positive electrode,

The present invention relates to a positive electrode for a secondary battery coated with a conductive adhesive layer and a lithium secondary battery comprising the same.

In recent years, the demand for environmentally friendly alternative energy sources has become an indispensable factor for the future, as the increase in the price of energy sources due to depletion of fossil fuels and the interest in environmental pollution are amplified. Various researches on power generation technologies such as nuclear power, solar power, wind power, and tidal power have been continuing, and electric power storage devices for more efficient use of such generated energy have also been attracting much attention.

Particularly, as technology development and demand for mobile devices increase, the demand for batteries as energy sources is rapidly increasing. Recently, the use of secondary batteries as a power source for electric vehicles (EV) and hybrid electric vehicles (HEV) In addition, the use area has been expanded for use as a power auxiliary power source through a grid, and accordingly, a lot of researches on a battery that can meet various demands have been conducted.

In recent years, there has been a growing interest in environmental issues, and as a result, electric vehicles (EVs) and hybrid electric vehicles (HEVs), which can replace fossil-fueled vehicles such as gasoline vehicles and diesel vehicles, And the like. Although a nickel metal hydride (Ni-MH) secondary battery is mainly used as a power source for such an electric vehicle (EV) and a hybrid electric vehicle (HEV), a lithium secondary battery having a high energy density, a high discharge voltage, Research is being actively carried out, and some are commercialized.

Generally, a lithium secondary battery has a structure in which a lithium electrolyte is impregnated into an electrode assembly composed of a cathode including a lithium transition metal oxide as an electrode active material, a cathode including a carbonaceous active material, and a separator. The lithium secondary battery has a non-aqueous composition, and the electrode is generally manufactured by coating an electrode slurry on a current collector. The electrode slurry includes an electrode active material for storing energy, a conductive material for imparting electrical conductivity, And an electrode mixture composed of a binder for adhering it to the current collector and for providing a bonding force to each other is mixed with a solvent such as N-methyl pyrrolidone (NMP). As the current collector of the secondary battery, copper foil, aluminum foil and the like are generally used.

Also, the secondary battery is classified according to how the electrode assembly having the anode / separator / cathode structure is formed. Typically, the long battery-shaped anodes and cathodes are jelly- A stacked (stacked) electrode assembly in which a plurality of positive electrodes and negative electrodes cut in units of a predetermined size are sequentially stacked with a separator interposed therebetween, a stacked (stacked) electrode assembly in which a predetermined unit of positive and negative electrodes are stacked, A stack / folding type electrode assembly having a structure in which a bi-cell or a full cell stacked in a single state is wound is exemplified.

FIG. 1 schematically shows an exploded perspective view showing a general structure of a typical conventional pouch type secondary battery.

1, a pouch type secondary battery 10 includes a stacked electrode assembly 20 having a plurality of electrode tabs 21 and 22 protruding therefrom, two stacked electrode assemblies 20 and 22 connected to the electrode tabs 21 and 22, And a battery case 40 having a structure in which the stacked electrode assembly 20 is received and sealed such that a part of the electrode leads 30 and 31 and a part of the electrode leads 30 and 31 are exposed to the outside.

The battery case 40 includes a lower case 42 including a concave shaped storage portion 41 on which the stacked electrode assembly 20 can be placed and a stacked electrode assembly 20 And an upper case 43 for sealing the upper case 43. The upper case 43 and the lower case 42 are thermally fused with the stacked electrode assembly 20 built therein to form a sealing part (not shown) along the outer surface of the battery case.

However, in the production of such an electrode, the adhesion force between the electrode mixture and the current collector is lowered in the pressing step or the subsequent manufacturing step, and dust or the like may be generated, and the electrode active material attached to the surface of the electrode tends to peel off It has problems. Such deterioration of adhesive strength and detachment of the active material due to the deterioration of the active material increases the internal resistance of the battery, thereby deteriorating output characteristics and decreasing the battery capacity.

Various methods for solving such problems have been proposed. For example, a method of increasing the bonding force with the current collector by etching the surface of the current collector to form fine irregularities has been proposed. This method has an advantage that a current collector having a high specific surface area can be obtained by a simple process, but has a problem that the lifetime of the current collector is lowered due to the etching treatment.

Further, in the prior art, a method of forming an adhesive layer having conductivity as a whole on one surface or both surfaces of the collector of the electrode has been proposed. However, since the conductive adhesive layer contains a conductive material, it has an electrical resistance higher than that of the conductive material because it contains an adhesive material and acts as a resistance between the current collector and the cathode active material, thereby increasing the internal resistance of the battery. Lt; / RTI >

Therefore, there is a high need for a technique capable of fundamentally solving such problems.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and the technical problems required from the past.

The inventors of the present application have conducted intensive research and various experiments and have found that a conductive adhesive layer in which a mixture containing a conductive material and a polymer material is pattern-coated on one surface or both surfaces of a collector of a cathode for a secondary battery The adhesive force between the positive electrode mixture and the current collector can be greatly improved by the structure of the positive electrode mixture applied on the conductive adhesive layer, and the peeling of the positive electrode active material due to the decrease in the adhesion force, the increase in the internal resistance of the battery, And the positive electrode mixture is directly applied on the current collector at the portion where the conductive adhesive layer is not applied. Therefore, the positive electrode mixture is directly bonded to the current collector in the portion where the conductive adhesive layer is not coated, Confirming that the deterioration of the electrical conductivity due to the addition of the adhesive layer can be minimized Thus, the present invention has been completed.

According to an aspect of the present invention, there is provided a positive electrode for a secondary battery,

A positive electrode for a secondary battery in which a positive electrode mixture containing a positive electrode active material, a binder and a conductive material is applied to a current collector,

A conductive adhesive layer on which a mixture of a conductive material and a polymer material is pattern-coated is applied on one side or both sides of the current collector;

By the pattern coating, the positive electrode material mixture is coated on the conductive adhesive layer at the portion where the conductive adhesive layer is applied, and is directly applied to the current collector portion at the portion where the conductive adhesive layer is not applied.

Here, the pattern means that a specific shape is repeatedly formed, and can be a simple pattern for mass production.

Therefore, in the case of forming the conductive adhesive layer in which the mixture containing the conductive material and the polymer substance is pattern-coated on one surface or both surfaces of the current collector of the anode for the secondary battery, the anode for a secondary battery according to the present invention, The structure of the positive electrode mixture can greatly improve the adhesive force between the positive electrode mixture and the current collector and can prevent the detachment of the positive electrode active material due to a decrease in the adhesion force, the increase in the internal resistance of the battery and the deterioration of the battery characteristics, The positive electrode material mixture is directly applied on the current collector in the portion where the conductive adhesive layer is not coated, so that the positive electrode material mixture is directly bonded to the current collector in a portion where the conductive adhesive layer is not coated, Can be minimized.

In one specific example, the current collector may be a metal foil. Specifically, for example, the metal foil may be made of at least one selected from the group consisting of stainless steel, aluminum, nickel, titanium, sintered carbon, . Further, the thickness of the metal foil may be from 5 탆 to 400 탆, more specifically from 100 탆 to 200 탆, and more specifically, to 150 탆.

In one specific example, the conductive material may be a carbon black based material, and in particular, the carbon black based material may be selected from acetylene black, ketjen black, furnace black, oil-furnace black, Channel black, lamp black, and summer black. In addition, the carbon black-based material may have an average particle diameter of 10 nanometers to 500 nanometers, more specifically, more than 80 nanometers and less than 200 nanometers, and more specifically, 100 nanometers.

In one specific example, the polymeric material is selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene May be one or more selected from the group consisting of ethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, and fluorine rubber.

The weight ratio of the carbon black-based material to the polymeric material may be in the range of 1: 1 to 100: 1, more specifically, 1: 1 to 10: 1, : May be one. Specifically, if the proportion of the carbon black based material is less than 1: 1, the resistance of the conductive adhesive layer increases to deteriorate the performance of the battery. Conversely, if the carbon black based material exceeds 100: 1, It is difficult to prevent the phenomenon of separation into the collector of the positive electrode mixture.

In addition, the polymer material may further include a thickener, and the content ratio of the polymer material and the thickener may be in a range of 30:20 to 35:15 by weight.

In one specific example, the thickness of the coating of the conductive adhesive layer may be from 0.1 mu m to 20 mu m, more specifically from 1 mu m to 10 mu m, and more specifically from 2 mu m to 5 mu m. That is, when the coating thickness of the conductive adhesive layer is less than 0.1 탆, the adhesion strength can not be exerted to a predetermined level or higher and the improvement in the bonding strength due to the formation of the conductive adhesive layer can not be expected. On the other hand, The performance of the battery may be deteriorated.

In one specific example, the conductive adhesive layer may have an adhesive force of 3 gf / cm 2 to 200 gf / cm 2, more specifically 50 gf / cm 2 to 100 gf / cm 2, gf / cm to 80 gf / cm. Specifically, when the adhesive force is less than 3 gf / cm, for example, the shape of separating the positive electrode mixture from the current collector due to the change in the volume of the electrode assembly due to charge / discharge of the battery can not be prevented. Conversely, , The adhesive force is too large, and there may be difficulties in the operation of coating the conductive adhesive layer.

In one specific example, the conductive adhesive layer may have a sheet resistance of 1 mOhm / sq to 100 Ohm / sq, more specifically from 100 mOhm / sq to 50 Ohm / sq, and more specifically 1 Ohm / sq To 10 Ohm / sq.

In one specific example, the coating layer of the conductive adhesive layer may be applied with a coating area of 5% to 95% based on the total area of the current collector, specifically, 30% to 70% 35% to 60%. Specifically, when the coated area of the conductive adhesive layer is less than 5% based on the total area of the current collector, the area where the positive electrode mixture is adhered and fixed to the current collector is small and the shape in which the positive electrode mixture is separated from the current collector can not be prevented. If it is 95% or more, it is difficult to exert the effect of minimizing the deterioration of the electrical conductivity due to the addition of the conductive adhesive layer because the area where the positive electrode mixture is directly bonded to the current collector is small

In one specific example, the pattern may be a shape in which a plurality of strip shapes are repeatedly formed on a current collector on a flat surface within a plane range to which the positive electrode mixture is applied, It may be formed in a long form by being coated in the same direction as the direction in which the positive electrode mixture is applied to the whole phase. That is, in the case of a manufacturing process in which a positive electrode mixture is applied continuously on a sheet-like current collector formed in a long direction in one direction, the coating of the conductive adhesive layer is preferably performed in the same direction as the direction in which the positive electrode mixture is applied on the current collector It is preferable that the strip shape of the conductive adhesive layer is formed in a long form by being coated on the current collector in the same direction as the direction in which the positive electrode mixture is applied.

In another specific example, the pattern may be a shape in which a plurality of island shapes are formed at regular intervals on a plane. Specifically, such an island shape may be a square or a rectangle in plan view, and these island shapes are formed at regular intervals, so that the adhesive force of the conductive adhesive layer can be exerted evenly on the current collector as a whole.

In one specific example, the cathode active material may include a lithium metal oxide having a spinel structure represented by the following formula (1).

Li _x M _y Mn _{2 - y} O _{4 - z z} (1)

Wherein 0 < y < 2, 0 z < 0.2,

M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, ;

A is one or more of an anion of -1 or -2.

The present invention also provides a lithium secondary battery comprising the positive electrode for the secondary battery.

The present invention can also provide a battery pack characterized by including a lithium secondary battery as a unit cell.

The present invention can also provide a device including the battery pack, wherein the device is an electric vehicle (EV), a hybrid electric vehicle (HEV), a hybrid electric vehicle An electric vehicle including a plug-in hybrid electric vehicle (PHEV) and the like; An electric motorcycle including an electric bike (E-bike) and an electric scooter (E-scooter); Power tools; And a power storage system, but the present invention is not limited thereto.

The structure and manufacturing method of such a device are well known in the art, so a detailed description thereof will be omitted herein.

As described above, the positive electrode for a secondary battery of the present invention is formed by forming a conductive adhesive layer in which a mixture containing a conductive material and a high molecular material is pattern-coated on one surface or both surfaces of a collector of a positive electrode for a secondary battery, It is possible to greatly improve the adhesive force between the positive electrode material mixture and the current collector by the structure of the positive electrode material mixture and to prevent the deterioration of the positive electrode material mixture due to the lowering of the adhesion force, The positive electrode material mixture is directly applied on the current collector in the portion where the conductive adhesive layer is not coated, so that the positive electrode material mixture is directly bonded to the current collector in a portion where the conductive adhesive layer is not coated, Can be minimized.

1 is an exploded perspective view of a general structure of a conventional pouch type secondary battery;
2 is a schematic plan view showing a cathode for a secondary battery according to an embodiment of the present invention;
Figure 3 is a schematic A-A 'cross-sectional view of the top view of Figure 2;
4 is a schematic plan view showing a cathode for a secondary battery according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited by the scope of the present invention.

FIG. 2 is a plan view schematically showing an anode 100 for a secondary battery according to an embodiment of the present invention, and FIG. 3 is a schematic view taken along line A-A 'of the plan view of FIG.

2, an anode 100 for a secondary battery according to the present invention includes a cathode 100 for a secondary battery 100, a cathode mixture 130 including a cathode active material, a binder, and a conductive material coated on one surface of a current collector 110 )to be.

A conductive adhesive layer 120 coated with a mixture of a conductive material and a polymer material is coated on one surface of the current collector 110 of the anode 100 for a secondary battery.

The positive electrode mixture 130 is coated on the conductive adhesive layer 120 at the portion where the conductive adhesive layer 120 is applied by the patterned conductive adhesive layer 120 and at the portion where the conductive adhesive layer 120 is not applied And is directly applied on the current collector 110.

The pattern of the conductive adhesive layer 120 is a shape in which a plurality of strip shapes are repeatedly formed on the current collector 110 in a plane on a plane within which the cathode mixture 130 is applied, Is formed on the current collector 110 in a direction S which is the same as the direction in which the positive electrode mixture 130 is applied.

Here, the current collector 110 is an aluminum alloy foil, and the thickness of the foil is 150 占 퐉.

Super-P, which is a carbon black-based material, was used as the conductive material, and the carbon black-based material had an average particle diameter of 10 nanometers to 500 nanometers.

Further, the polymer material is polyvinylidene fluoride, and the content ratio of the carbon black material and the polymer material is in the range of 1: 1 to 100: 1 by weight.

Further, the polymer material further contains a thickener, and the content ratio of the polymer material and the thickener is in the range of 30:20 to 35:15 by weight.

The coating thickness of the conductive adhesive layer 120 is 0.1 to 20 占 퐉.

The conductive adhesive layer 120 has an adhesive force of 3 gf / cm 2 to 200 gf / cm 2 to the cathode mix 130.

The conductive adhesive layer 120 has a sheet resistance of 1 mOhm / sq to 100 Ohm / sq.

The coating layer of the conductive adhesive layer 120 is coated with a coating area of 30% to 70% based on the total area of the current collector 110.

4 is a plan view schematically illustrating an anode 200 for a secondary battery according to another embodiment of the present invention.

4, a conductive adhesive layer 220 is formed on a current collector 210 in a pattern in which a plurality of island shapes are formed at regular intervals on a plane. The cathode mixture 230 is electrically connected to the conductive adhesive layer 220, And the current collector 210.

As described above with reference to the drawings, the positive electrode for a secondary battery according to the present invention includes a conductive adhesive layer formed by pattern-coating a mixture containing a conductive material and a polymeric material on one surface or both surfaces of a current collector for a secondary battery, The adhesive force between the positive electrode mixture and the current collector can be greatly improved by the structure of the positive electrode mixture applied on the negative electrode active material layer, and the peeling of the positive electrode active material due to the decrease in the adhesion force, the increase in the internal resistance of the battery, And the positive electrode mixture is directly applied on the current collector at the portion where the conductive adhesive layer is not applied. Therefore, in the portion where the conductive adhesive layer is not coated, the positive electrode mixture is directly bonded to the current collector, The effect of minimizing the deterioration of the electrical conductivity due to the contact resistance can be obtained.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims (21)

A positive electrode for a secondary battery in which a positive electrode mixture containing a positive electrode active material, a binder and a conductive material is applied to a current collector,
A conductive adhesive layer on which a mixture of a conductive material and a polymer material is pattern-coated is applied on one side or both sides of the current collector;
Wherein the positive electrode mixture is coated on the conductive adhesive layer at the portion where the conductive adhesive layer is applied and directly on the current collector at the portion where the conductive adhesive layer is not applied by the pattern coating. The positive electrode for a secondary battery according to claim 1, wherein the current collector is a metal foil. The positive electrode for a secondary battery according to claim 2, wherein the metal foil is at least one selected from the group consisting of stainless steel, aluminum, nickel, titanium, sintered carbon, and aluminum alloy. The positive electrode for a secondary battery according to claim 2, wherein the thickness of the metal foil ranges from 5 占 퐉 to 400 占 퐉. The positive electrode for a secondary battery according to claim 1, wherein the conductive material is a carbon black-based material. The carbon black based material according to claim 5, wherein the carbon black based material is at least one selected from the group consisting of acetylene black, ketjen black, furnace black, oil-furnace black, Columbia carbon, channel black, lamp black, Anode for secondary battery. The positive electrode for a secondary battery according to claim 5, wherein the carbon black-based material has an average particle diameter of 10 nanometers to 500 nanometers. The method of claim 1, wherein the polymeric material is selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene Wherein the positive electrode is one or more selected from the group consisting of ethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, and fluorine rubber. The positive electrode for a secondary battery according to claim 5, wherein the content ratio of the carbon black material and the polymer material ranges from 1: 1 to 100: 1 by weight. The positive electrode for a secondary battery according to claim 1, wherein the polymer material may further include a thickener, and the weight ratio of the polymer material to the thickener is in the range of 30:20 to 35:15. The positive electrode for a secondary battery according to claim 1, wherein the coating thickness of the conductive adhesive layer is from 0.1 mu m to 20 mu m. The positive electrode for a secondary battery according to claim 1, wherein the conductive adhesive layer has an adhesive force of 3 gf / cm 2 to 200 gf / cm 2 to the positive electrode mixture. The positive electrode for a secondary battery according to claim 1, wherein the conductive adhesive layer has a sheet resistance of 1 mOhm / sq to 100 Ohm / sq. The positive electrode for a secondary battery according to claim 1, wherein the coating layer of the conductive adhesive layer is applied with a coating area of 5% to 95% based on the total area of the current collector. The positive electrode for a secondary battery according to claim 1, wherein the pattern is a shape in which a plurality of strip shapes are repeatedly formed on a current collector in a planar range over which the positive electrode mixture is applied, the positive electrode mixture being formed on the current collector. The positive electrode for a secondary battery according to claim 15, wherein the strip shape is formed to be long in the same direction as the direction in which the positive electrode mixture is applied on the current collector. 16. The anode for a secondary battery according to claim 15, wherein the pattern is a planar shape in which a plurality of island shapes are formed at regular intervals. The positive electrode for a secondary battery according to claim 1, wherein the positive electrode active material comprises a lithium metal oxide having a spinel structure represented by the following Formula 1:
Li _x M _y Mn _{2 - y} O _{4 - z z} (1)
Wherein 0 < y < 2, 0 z < 0.2,
M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, ;
A is one or more of an anion of -1 or -2. A lithium secondary battery comprising a positive electrode for a secondary battery according to any one of claims 1 to 18. A battery pack comprising the lithium secondary battery according to claim 19 as a unit cell. A device comprising a battery pack according to claim 20.

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