KR101693359B1 - Aluminum current collector, electrode comprising the Aluminum current collector, and electrochemical device comprising the electrode - Google Patents

Abstract

An aluminum current collector comprising an aluminum base material and a carbon conductive layer formed on at least one surface of the aluminum base material and formed of a mixture of conductive carbon powder and a binder, wherein the surface of the aluminum current collector is covered with an energy dispersive spectroscope (EDS) As a result of elemental analysis of the surface, the aluminum (Al) content was 60 to 70 wt%, the oxygen (O) content was 1 to 3 wt%, and the content ratio of aluminum (Al) Al / C) of 1.5 to 2.5, an electrode employing the same, and an electrochemical device.

Description

TECHNICAL FIELD [0001] The present invention relates to an aluminum current collector, an electrode including the aluminum current collector, and an electrochemical device including the aluminum current collector,

More particularly, the present invention relates to an aluminum current collector for an electrode of an electrochemical device such as a lithium secondary battery or an ultra-high capacity capacitor, an electrode including the same, To an electrochemical device.

Electrochemical devices such as lithium secondary batteries have been developed and produced mainly for small batteries for use in small electronic devices and portable IT devices. In the future, there is a demand for a large-capacity battery for constituting a power supply for an electric vehicle and an energy storage system Is increasing. Large-capacity batteries require thousands of cycles of life unlike small batteries, requiring rapid charge-discharge and high output. In addition, securing the safety of the battery is important as the battery becomes larger. In order to satisfy the requirement of the battery, the active material which determines the capacity and the characteristics of the battery also has a high level of technical requirements.

Lithium cobalt oxide (LiCoO ₂ ) has been mainly used as a cathode active material for lithium secondary batteries, but due to the instability of the raw material Co, attention has focused on eliminating the use of rare metals such as Co. As a result, Spinel, and olivine structures have been developed and used. Also, the size of the powder particles is becoming smaller due to the demand for high output characteristics. Lithium iron phosphate (LiFePO ₄ ) has a stable crystal structure of olivine structure, theoretically has excellent battery life, and has an advantage of low price in mass production. Graphite powder is mainly used as an anode active material, but lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) is excellent in lifetime and output characteristics and can be rapidly charged.

The electrode of the lithium secondary battery is formed by applying a slurry containing active material powder, a conductive agent, a binder, a solvent and the like on a current collector made of thin aluminum or copper foil having a thickness of 5 to 30 microns, drying the solvent, . Aluminum is used as the current collector of the anode, and copper is used as the current collector of the anode. However, in the case of lithium titanium oxide, aluminum can be used because the reaction potential is higher than graphite and an alloy with lithium is not produced. Depending on the type of active material, the electrical conductivity of the powders is different and the characteristics of binding to the current collector are different. In particular, lithium iron phosphate (LiFePO ₄ ), which is a cathode active material, has a lower binding force to aluminum and lower conductivity than other active materials, and thus it is difficult to produce electrodes. In the case of other cathode active materials, when the powder particle size is less than 10 microns, It is difficult to coat and adhere to the whole.

In addition, supercapacitors or super capacitors are often referred to as supercapacitors or ultra capacitors, which have much higher capacities than conventional electrolytic capacitors. The ultra-high capacity capacitors are used for uninterruptible power supplies for instantaneous power failure compensation, wind power, electric vehicles and smart power grid. The electrode is composed of an active material having a large effective specific surface area such as activated carbon powder or activated carbon fiber, a conductive material for imparting conductivity, a binder for binding force between the respective components, and a current collector for electron transfer. In the current collector, aluminum whose surface area is widened by etching the surface of aluminum with a chemical material such as acid or alkali is used.

In such an electrode, the fact that the electrode material in the powder state is removed from the current collector made of metal foil or the like, or the electric resistance at the electrode layer and the current collector interface increases is an important factor in lowering the lifetime and output characteristics of the electrochemical device .

Therefore, in an electrochemical device such as a lithium secondary battery or a super capacitor, it is still required to develop an electrochemical device for improving the characteristics of the electrochemical device while suppressing an increase in the internal resistance of the electrode while improving the binding property of the electrode layer on the current collector.

A problem to be solved by the present invention is to provide a method of forming an electrode by coating an electrode layer composition such as an electrode material, a binder and a conductive agent on an aluminum current collector in an electrochemical device, The present invention provides an aluminum current collector capable of improving the lifetime and output characteristics without increasing the internal resistance of the device.

Another object of the present invention is to provide an electrode comprising the aluminum current collector.

Another object of the present invention is to provide an electrochemical device having the electrode.

To solve these problems, according to one aspect of the present invention,

Aluminum substrates; And

An aluminum current collector formed on at least one surface of the aluminum substrate and having a carbon conductive layer formed of a mixture of a conductive carbon powder and a binder,

The surface of the aluminum current collector was subjected to surface element analysis using an energy dispersive spectroscope (EDS). As a result, the content of aluminum (Al) was 60 to 70% by weight and the content of oxygen (O) %, And a content ratio of aluminum (Al) to carbon (C) (Al / C) is 1.5 to 2.5.

The thickness of the carbon conductive layer may be 0.1 to 2 탆.

The conductive carbon powder may be at least one selected from the group consisting of carbon black, graphite, carbon nanotube, and graphene.

The conductive carbon powder may have an average particle diameter of 10 to 500 nm.

The binder may be at least one selected from the group consisting of polysaccharides, fluorine-containing polymers, polyolefin oxides, elastomers, and polyacrylates.

The content of the binder may be 50 to 200 parts by weight based on 100 parts by weight of the conductive carbon powder.

The loading amount of the carbon conductive layer may be 0.1 to 2.0 g / m < ² > relative to the unit surface area of one surface or both surfaces of the aluminum substrate.

The carbon conductive layer may be formed so as to cover a part or all of at least one surface of the aluminum base material.

According to another aspect of the present invention,

There is provided an electrode comprising the aluminum current collector described above and an electrode layer formed on one surface of the aluminum current collector.

The electrode layer may be formed to have the same coated surface as the carbon conductive layer, or may have a coated surface that is as small as the width of 1 to 3 mm from both ends of the carbon conductive layer.

According to another aspect of the present invention, there is provided an electrochemical device including the electrode.

The electrochemical device may be a lithium secondary battery or a capacitor.

According to the present invention, in forming an electrode by coating an electrode layer composition such as an electrode material, a binder, and a conductive agent on an aluminum current collector, the electrode layer has a high peeling force with respect to the aluminum current collector, It is possible to provide an aluminum current collector capable of improving the life and output characteristics of an electrochemical device employing such an electrode without increasing the internal resistance.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description of the invention given below, serve to further the understanding of the technical idea of the invention, And should not be construed as limiting.
1 to 4 are SEM micrographs of a surface of an aluminum current collector according to an embodiment of the present invention.
5A and 5B are graphs and tables showing the analysis of the surface of the aluminum current collector of Example 3 and the measurement results, respectively.
6 is a photograph showing a measuring instrument for measuring a penetration resistance of an aluminum current collector according to an embodiment of the present invention.
Figs. 7 and 8 are photographs respectively showing the results of evaluating the wet adhesion of the positive electrode prepared in each of Example 4 and Comparative Example 4. Fig.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined.

Therefore, the embodiments described in the present specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

An aluminum current collector according to an aspect of the present invention includes an aluminum substrate; And a carbon conductive layer formed on at least one surface of the aluminum base material and formed of a mixture of a conductive carbon powder and a binder, wherein the surface of the aluminum current collector is covered with an energy dispersive spectroscope (EDS) As a result of the elemental analysis, the aluminum (Al) content was 60 to 70 wt%, the oxygen (O) content was 1 to 3 wt%, the aluminum (Al) C) is 1.5 to 2.5.

The aluminum substrate has high electrical conductivity and high electrochemical corrosion resistance, and is useful for the electrode of a lithium secondary battery or a capacitor, and may be in the form of a foil of aluminum or an aluminum alloy. At this time, the purity of aluminum may be 99.3% or more.

Examples of the aluminum foil include pure aluminum foil such as A1085 material, A1235 material, and A3003 material.

Such an aluminum base material may be a foil not having a hole, but also a punched metal foil, a foil having a hole such as a mesh, or a porous foil. In addition, the aluminum substrate may have a smooth surface, or may be a roughened foil by performing an electrical or chemical etching treatment or the like.

The thickness and the width of the aluminum substrate may be variously adjusted depending on the electrode form of the electrochemical device to be applied. For example, the thickness may be 5 to 50 μm and the width may be 20 to 1,200 mm.

When the thickness of the aluminum base material satisfies this range, the ratio of the current collector occupied in a predetermined volume of the electrochemical device or the like can be suppressed to a certain level or less and sufficient strength is given to the current collector and the electrode, can do.

The conductive carbon powder is not particularly limited as long as it is an electron conductive carbon particle that can smoothly move the charge between the current collector and the electrode active material layer. For example, the conductive carbon powder may be at least one selected from the group consisting of carbon black, graphite, carbon nanotubes, and graphene.

Examples of the carbon black include acetylene black, ketjen black, channel black, furnace black, thermal black and the like.

The average particle diameter of the conductive carbon powder is 10 to 500 nm, more preferably 25 to 100 nm, and the BET specific surface area is preferably 50 m ² / g or more, more preferably 50 to 200 m ² / g. By using such a conductive carbon powder, excellent electron conductivity can be imparted to the carbon conductive layer, and the internal resistance can be reduced.

The binder used for the carbon conductive layer is required to be capable of binding an aluminum substrate and a conductive carbon powder, and is excellent in ion permeability. In addition, the binder may be added to an organic solvent such as water or NMP (N-methylpyrrolidone) used in an electrode manufacturing process of an electrochemical device such as a battery or a supercapacitor and an organic solvent such as acetonitrile or carbonate It should not be dissolved and should be a stable material that is not electrochemically redox-stable in the range of 0.1 to 4.5V relative to the lithium standard electrode

Examples of the binder satisfying these properties include polysaccharides, fluorine-containing polymers, polyolefin oxides, elastomers, and polyacrylates, which may be used alone or as a mixture of two or more thereof.

First, polysaccharide is a polymer compound in which a monosaccharide (monosaccharide) or a derivative thereof is polymerized to a large extent by glycosidic bonds, and generally means that 10 or more monosaccharides or derivatives thereof are polymerized, but 10 or less monosaccharides Polymerized saccharides may also be used.

Specific examples of such polysaccharides include polyglucosamine (chitosan), agarose, amylose, amylopectin, alginic acid, inulin, carrageenan, chitin, glycogen, glucan, quaternary sulfuric acid, colominic acid, chondroitin sulfate, cellulose, dextran, Starch, hyaluronic acid, pectin, pectinic acid, heparan sulfate, levan, lentinan, pullulan, curdlan and the like.

Derivatives of polysaccharides include hydroxyalkylated polysaccharides, carboxyalkylated polysaccharides, and sulfuric acid esterified polysaccharides. In particular, the hydroxyalkylated polysaccharide is preferable in that it can increase dispersibility into a solvent.

Examples of such polysaccharide derivatives include hydroxyethylchitosan, hydroxypropylchitosan, glycerylated chitosan, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylchitosan, carboxyethylchitosan, carboxymethylcellulose, carboxyethylcellulose and the like. .

Examples of the fluorine-containing polymer include polyvinylidene fluoride, polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-tetrafluoro Ethylene copolymers and the like.

Examples of the poly (olefin oxide) include polyethylene oxide, polypropylene oxide, and polyethylene oxide-propylene oxide copolymer. Examples of the elastomer include styrene butadiene block copolymer rubber (SBR), acrylic acid modified SBR resin and gum arabic. The ratio may be an ethylene-methacrylic acid copolymer or the like. In addition, a hydroxyl group-containing resin such as polyvinyl acetal, ethylene-vinyl alcohol copolymer, and polyvinyl alcohol may also be used.

The weight average molecular weight of such a binder is preferably 10,000 to 1,200,000, more preferably 50,000 to 1,000,000. When the weight average molecular weight of the binder satisfies the above range, the performance of dispersing the conductive carbon powder increases, the strength of the carbon conductive layer becomes high, and the thickness of the carbon conductive layer does not change with the temperature change.

The content of the binder may be preferably 50 to 200 parts by weight, more preferably 80 to 150 parts by weight, based on 100 parts by weight of the conductive carbon powder. When the range of the binder content is satisfied, the bonding strength between the conductive carbon powder and the aluminum base material increases, and the increase in the interface resistance between the current collector and the electrode active material can be suppressed, and the carbon conductive layer is not dissolved in the electrolyte solution.

The thickness of the carbon conductive layer is preferably 0.1 to 2 占 퐉, more preferably 0.3 to 1.0 占 퐉. When the thickness of the conductive layer satisfies this range, the conductive layer can be formed without surface defects, and when the electrode active material layer is formed on the carbon conductive layer, an increase in electrical resistance in the interface between them can be suppressed , The adhesive force between the electrode active material layer and the current collector is improved, and the cycle life characteristics of the battery are improved.

The amount of the carbon conductive layer to be loaded refers to the weight of the carbon conductive layer coated on one surface or both sides of the aluminum substrate relative to the unit surface area, preferably 0.1 to 2.0 g / m ² , more preferably 0.2 to 1.0 g / m 2 ² .

When the amount of loading of the carbon conductive layer is adjusted to such a range, an increase in electrical resistance in the interface between the electrode active material layer and the carbon conductive layer can be suppressed, The electrical resistance is lowered and the output characteristics and cycle life characteristics of the battery are improved.

Further, the carbon conductive layer may be formed so as to cover at least part of at least one surface of the aluminum substrate, or to cover the entire surface.

Since the carbon conductive layer is coated on the aluminum substrate in this manner, it is possible to prevent the electrode active material layer from being separated from the current collector during pressure molding (rolling) and cutting process, which is a manufacturing process of the electrode active material layer thereafter, , And the internal resistance and impedance of the electrochemical device obtained by using this current collector can be reduced. The rate at which this carbon conductive layer is coated can be controlled by the surface etching area of the gravure or microgravure metal roll of the coater.

The inventors of the present invention conducted close examination of various angles in order to solve the problem of the increase in resistance at the interface between the aluminum current collector and the electrode active material, which is a problem of the above-described conventional art, And the composition ratio of the three elements of oxygen plays an important role.

Therefore, the surface of the aluminum current collector of the present invention was subjected to elemental analysis on the surface thereof using an energy dispersive spectroscope (EDS). As a result, the content of aluminum (Al), the content of oxygen (O) By controlling the content ratio of carbon (C) (Al / C) to a predetermined range, it is possible to suppress the increase in resistance between the interfaces when the aluminum current collector is employed as the electrode, and to smoothly move electrons to the electrode active material.

The energy dispersive X-ray spectrometer (EDS) used in the present invention irradiates an electron beam to a sample and detects a characteristic X-ray generated from the electron beam to determine the type of the element, . The energy of the characteristic X-ray is converted into an electric signal and analyzed using a method of making a spectrum. do.

Specifically, the surface distribution of aluminum (Al) is preferably 60 to 70% by weight, and more preferably 63 to 70% by weight.

If the content of aluminum is less than 60% by weight, the carbon conductive layer may wrap the aluminum base material so that the contact between the electrode active material and the aluminum base material is minimized and the electrical resistance may be increased. If the aluminum content is more than 70% The active material is easily peeled off from the collector, which is not preferable.

The content of oxygen (O) is preferably 1 to 3% by weight, more preferably 1.5 to 2% by weight. At this time, the oxygen present on the surface of the collector serves as an element of the functional group in the binder of the carbon conductive layer and serves to increase the bonding force between the electrode active material or the aluminum substrate by van der Waals bonding. Therefore, when the oxygen content is less than 1 wt%, the bonding force between the electrode active material and the aluminum current collector is remarkably decreased. When the oxygen content is more than 3 wt%, the interface resistance between the electrode active material and the aluminum current collector is increased.

The content ratio of aluminum (Al) to carbon (C) (Al / C) is preferably 1.5 to 2.5, more preferably 1.6 to 2.3.

At this time, carbon is an element contained in the binder and the conductive carbon powder in the carbon conductive layer, and the content ratio (Al / C) of aluminum (Al) and carbon (C) shows the interface contact ratio between the current collector and the electrode material, When the content ratio (Al / C) is less than 1.5, the interfacial resistance increases. When the content ratio is more than 2.5, the adhesive strength between the current collector and the electrode material decreases.

The method for producing the aluminum current collector of the present invention can be exemplified as follows but is not limited thereto.

First, a binder is put into a dispersion medium and mixed to prepare a binder solution. Thereafter, a carbon conductive powder is added and dispersed to prepare a composition for forming a carbon conductive layer. At this time, as a mixing method, for example, a ball mill, a sand mill, an ultrasonic dispersing machine, a homogenizer, a planetary mixer, a Hobart mixer and the like can be used. Particularly, after the carbon conductive powder and the binder are added to the dispersion medium, the dispersion may be pulverized using a ball mill or the like to adjust the size of the inorganic particles. In this case, the crushing time is preferably 1 to 20 hours.

The dispersion medium is not particularly limited as long as it dissolves the binder, disperses the carbon conductive powder, is environmentally friendly, and does not easily change the viscosity of the composition. Examples thereof include organic solvents such as water, ethers, carbonates, amides, esters, and alcohols. Specific examples of such organic solvents include N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-pyrrolidone,? -Butylolactone, ethanol, isopropyl alcohol, .

The content of the dispersion medium may preferably be 70 to 98% by weight, more preferably 85 to 95% by weight in the composition for forming a carbon conductive layer.

When the content of the dispersion medium satisfies the above range, the viscosity of the composition for forming a carbon conductive layer is appropriately controlled, and the coating property is excellent, and the amount, thickness, and coverage of the carbon conductive layer can be easily controlled within a desired range Do.

Such a dispersion medium may be initially added in a desired amount, or a portion may be added first, and the remaining amount may be added after ball milling. In addition, the viscosity of the composition may be adjusted to, for example, 50 to 300 cps to facilitate application to an aluminum substrate.

According to an embodiment of the present invention, the composition for forming a carbon conductive layer may further include additives such as a dispersant, a thickener, a defoaming agent, and a leveling agent in addition to the carbon conductive powder, the binder, and the dispersion medium. The content of these additives may be 1 to 10 parts by weight based on 100 parts by weight of the total amount of the conductive carbon powder particles and the binder.

Thereafter, the prepared composition for forming a carbon conductive layer is applied to one side or both sides of the aluminum substrate, and heat treatment is performed to remove the dispersion medium.

The composition for forming the carbon conductive layer may be applied by a conventional method known in the art. For example, a bar coating, a gravure coating, a gravure reverse coating, a roll coating, a Meyer bar coating, a blade coating, Air knife coating, comma coating, slot die coating, slide die coating and dipping coating are preferable.

The composition for forming the carbon conductive layer may be applied to one surface or both surfaces of the aluminum base material. The application of the aluminum base material to both surfaces of the aluminum base material may be performed sequentially one by one and simultaneously.

The heat treatment of the aluminum substrate coated with the composition for forming a carbon conductive layer is carried out in order to remove the dispersion medium. The heat treatment method is not particularly limited, but a hot air method using an oven can be used. At this time, the heat treatment temperature is preferably 100 to 300 占 폚, more preferably 120 to 250 占 폚. The heat treatment time is preferably 10 seconds to 1 hour.

According to an aspect of the present invention, there is provided an electrode including an aluminum current collector and an electrode layer formed on one surface of the aluminum current collector.

The material used for the electrode layer and the method for forming the electrode layer are not particularly limited and known materials and methods used in the production of electrodes such as lithium ion secondary batteries, electric double layer capacitors, and hybrid capacitors can be employed.

When the electrode is used in a lithium secondary battery, the electrode layer includes an electrode active material, a conductive material, and a binder. In particular, a cathode active material may be used as the electrode active material.

As the cathode active material, a lithium-containing transition metal oxide may be preferably used. For example, Li _x CoO ₂ (0.5 <x <1.3), Li _x NiO ₂ (0.5 <x <1.3), Li _x MnO ₂ <x <1.3, 0 <a <1, 0 <b <1), Li _x Mn ₂ O ₄ (0.5 <x <1.3), Li _x (Ni _a Co _b Mn _c ) O ₂ , 0 <c <1, a + b + c = 1), Li x Ni 1-y Co y O 2 (0.5 <x <1.3, 0 <y <1), Li x Co 1-y Mn y O 2 (0.5 <x <1.3, 0≤y <1), Li x Ni 1-y Mn y O 2 (0.5 <x <1.3, O≤y <1), Li x (Ni a Co b Mn c) O 4 (0.5 <x <1.3, 0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), Li _x Mn _{2 -z} Ni _z O ₄ Li _x CoPO ₄ (0.5 <x <1.3) and Li _x FePO ₄ (0.5 <x <1.3, 0 <z <2), 0 <z <2, Li _x Mn _{2 -z} Co _z O ₄ <x <1.3), or a mixture of two or more thereof. The lithium-containing transition metal oxide may be coated with a metal such as aluminum (Al) or a metal oxide. In addition to the lithium-containing transition metal oxide, sulfide, selenide and halide may also be used.

The conductive material is not particularly limited as long as it is an electron conductive material that does not cause a chemical change in an electrochemical device. In general, carbon black, graphite, carbon fiber, carbon nanotube, metal powder, conductive metal oxide, organic conductive material and the like can be used. Commercially available products such as acetylene black series (denka black Denki kagaku kogyo (or Gulf Oil Company products, etc.), Ketjen Black EC series (Armak Company), Vulcan XC-72 (Cabot Company) and Super P (MM (MMM)). For example, acetylene black, carbon black and graphite.

The binder has the function of holding the electrode active material on the current collector and connecting the active materials, and a commonly used binder may be used without limitation.

For example, it is possible to use vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, styrene Various types of binder polymers such as styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), and the like can be used.

The electrode is kneaded using an electrode active material, a conductive agent, a binder, and a high boiling point solvent to prepare an electrode mixture, and then the mixture is coated on a copper foil or the like of a current collector, dried and pressed, At a temperature of from 1 to 5 hours under a vacuum.

At this time, the pressure molding is performed in order to further improve the homogeneity of the electrode layer, and it is preferable to use a metal roll, a heating roll, a sheet press machine or the like. The pressure forming conditions are preferably 500 to 7,500 kgf / cm ² , and when the pressure molding conditions are satisfied, the homogeneity of the electrode layer is improved and the electrode plate itself can be prevented from being damaged.

When the electrode is used for a capacitor, the electrode layer includes a conductive material and a binder. In particular, the conductive material may include conductive carbon such as acetylene black, ketjen black, carbon black, carbon nanofiber, desirable. By using such a conductive material, the electrical contact of the formed conductive coated film can be further improved, the internal resistance of the capacitor can be lowered, and the capacitance density can be increased

According to one embodiment of the present invention, the peeling force of the electrode layer on the aluminum current collector may be preferably 50 gf / cm or more, more preferably 50 gf / cm to 80 gf / cm.

When the peeling force of the electrode layer is adjusted to 50 gf / cm or more, the problem of the electrode layer being formed on the aluminum current collector is eliminated, and the electrical resistance can be reduced.

The reason why the peeling force of the electrode layer is controlled to be not less than 50 gf / cm is that the surface of the aluminum current collector is subjected to surface element analysis using an energy dispersive spectroscope (EDS). As a result, The carbon conductive layer is formed so that the content thereof is 60 to 70% by weight and the content of oxygen (O) is 1 to 3% by weight and the content ratio of aluminum (Al) and carbon (C) Due to the fact that it is equipped.

The electrode layer may be formed to cover a part or all of the carbon conductive layer of the aluminum current collector. Specifically, the electrode layer may be formed to have the same coated surface as the carbon conductive layer, or more preferably, may be formed to have a coated surface that is as small as the width of 1 to 3 mm from both ends of the carbon conductive layer. That is, in the latter case, the electrode layers are formed inwardly in the widths of 1 to 3 mm from both ends of the carbon conductive layer coated on the upper surface of the aluminum substrate, and the carbon conductive layers which are not covered with the electrode layers on both ends of the electrode layers are Exposed.

According to an embodiment of the present invention, the electrode layer and the coated surface of the carbon conductive layer may be coated to coincide with each other. In this case, however, coating of the electrode layer may be difficult to coat the electrode layer so as to coincide with the carbon conductive layer, since the electrode layer slurry is coated on the running aluminum current collector.

Therefore, the coating width tolerance of the electrode layer is determined by taking into consideration errors such as flow rate and pressure when the running error of the equipment (the aluminum current collector is shaken to the left or right during running of the electrode layer during the coating process of the electrode layer) And the carbon conductive layer may be formed to have a width that is 1 to 3 mm wider than the electrode layer, with respect to both ends.

As described above, in the case where the coated surface of the electrode layer is formed to be narrower than the carbon conductive layer according to the embodiment of the present invention, workability can be improved in forming the electrode layer on the aluminum current collector first. That is, the active material of the electrode layer is coated on the upper surface of the carbon conductive layer of the aluminum current collector. If the active material moves outside the carbon conductive layer, the active material directly faces the aluminum base material, and the effect of the carbon conductive layer may not be obtained.

The active material is coated during the production of the electrode layer and subjected to a rolling process to increase the bulk density of the active material. When the active material is pressed at a pressure of several tons, the active material may fall off from the surface of the carbon conductive layer. Therefore, according to the embodiment of the present invention, the coated surface of the electrode layer is formed to be narrower than the carbon conductive layer, thereby preventing the active material from falling off during the rolling process.

According to another aspect of the present invention, there is provided an electrochemical device including the electrode.

The electrochemical device includes all devices that perform an electrochemical reaction. Examples of the electrochemical device include capacitors such as all kinds of primary, secondary, fuel cell, solar cell, or super capacitor devices. In particular, a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery may be included in the secondary battery.

The electrochemical device further includes a separator and an electrolyte.

As the separator, a conventional porous polymer film conventionally used as a separator, for example, a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer The porous polymer film made of a polymer may be used alone or in a laminated form, or a nonwoven fabric made of a conventional porous nonwoven fabric such as a glass fiber having a high melting point, polyethylene terephthalate fiber or the like may be used. no.

The electrolyte may be a non-aqueous electrolyte, a solid electrolyte, or a gel electrolyte.

Double in the non-aqueous electrolyte is, A ⁺ B ^- A salt of the structure, such as, A ⁺ is Li ^+, Na ^+, include alkali metal cation or an ion composed of a combination thereof, such as K ^+, and B ^- is PF ₆ ^{-, _{BF 4 -, Cl -, Br}} -, I -, ClO 4 -, AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N (CF 3 SO 2) 2 -, C (CF 2 SO 2) ₃ ^- anion, or a salt containing an ion composed of a combination of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), such as, dimethyl (NMP), ethylmethyl carbonate (EMC), gamma-butyrolactone (g-butyrolactone), or a mixture of two or more of the above- Or an organic solvent composed of a mixture thereof, but the present invention is not limited thereto.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the following examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the following embodiments. Embodiments of the invention are provided to more fully describe the present invention to those skilled in the art.

Manufacture of aluminum collector

Example 1

12 parts by weight of ethylene and 20 parts by weight of methacrylic acid copolymer as a binder were mixed and dissolved in 160 parts by weight of water and then 10 parts by weight of acetylene black (Acetylene black, trade name, DENKA black, electrochemistry) was added as a conductive carbon powder Followed by ball milling for two hours, and then adding a further 80 parts by weight of water to adjust the viscosity to 50 to 70 cps to prepare a composition for forming a carbon conductive layer.

Thereafter, the composition for forming a carbon conductive layer was applied to both surfaces of an aluminum foil having a thickness of 20 탆, in which the surface oil had been removed, by gravure coating so as to have a thickness of 0.75 탆, followed by heat treatment in an oven at 150 캜 for 30 minutes An aluminum current collector was produced.

 The amount of aluminum (Al), the content of oxygen (O), the content of aluminum (Al), and the content of carbon (C) in the aluminum current collector produced, the amount of loading of the carbon conductive layer, The content ratios are shown in Table 1 below.

Example 2

Except that 10 parts by weight of carbon black was used as the conductive carbon powder and 4 parts by weight of carboxymethyl cellulose (CMC), 4 parts by weight of styrene-butadiene rubber (SBR) and 4 parts by weight of polytetrafluoroethylene (PTFE) An aluminum current collector was produced in the same manner as in Example 1.

The amount of aluminum (Al), the content of oxygen (O), the content of aluminum (Al), and the content of carbon (C) in the aluminum current collector produced, the amount of loading of the carbon conductive layer, The content ratios are shown in Table 1 below.

Example 3

12 parts by weight of polydiglucosamine (poly- (D) glucosamine) as a binder were mixed and dissolved in 160 parts by weight of water and 6 parts by weight of oxalic acid, and then acetylene black (trade name DENKA black, Ltd.) was added, ball milling was performed for 2 hours, and then 80 parts by weight of water was further added to prepare an aluminum current collector.

The amount of aluminum (Al), the content of oxygen (O), the amount of aluminum (Al), the amount of aluminum (Al) ) And carbon (C) are shown in Table 1 below.

SEM photographs of the surface of the produced aluminum current collector are shown in FIG. 1 (2,000 magnification), 2 (15,000 magnification), 3 (50,000 magnification) and 4 (100,000 magnification). 1 to 4, it was confirmed that the conductive carbon powder and the carbon conductive layer of the binder were uniformly distributed on the aluminum substrate.

Comparative Example 1

An aluminum current collector was prepared in the same manner as in Example 3 except that the composition for forming a carbon conductive layer was applied to both surfaces of an aluminum foil with a thickness of 0.5 탆.

The amount of aluminum (Al), the content of oxygen (O), the amount of aluminum (Al), the amount of aluminum (Al) ) And carbon (C) are shown in Table 1 below.

Comparative Example 2

An aluminum current collector was prepared in the same manner as in Example 3 except that the composition for forming a carbon conductive layer was applied to both surfaces of an aluminum foil with a thickness of 0.5 탆.

The amount of aluminum (Al), the content of oxygen (O), the amount of aluminum (Al), the amount of aluminum (Al) ) And carbon (C) are shown in Table 1 below.

aluminum Whole-house  Character rating

(1) Analysis of contents of aluminum, oxygen and carbon

(Al) content, oxygen (O) content, aluminum (Al) content and carbon (C) content were measured by performing elemental analysis of the surface of the aluminum current collector using a scanning electron microscope-energy dispersive spectroscopy Respectively. The graph of the surface of the aluminum current collector of Example 3 and the measurement results are shown in Figs. 5A and 5B, respectively.

(2) Peel force of the carbon conductive layer

And evaluated by the following two methods.

1) The extent to which the carbon conductive layer was peeled off by rubbing the carbon conductive layer with a water-dipped cotton swab, and judged by the number of rubbing (swab method)

○: When peeled off when rubbed more than 10 times

X: peeled off when rubbing less than 10 times

2) The scotch tape was adhered to the top surface of the carbon conductive layer and peeled off. The degree of sticking to the scotch tape was visually judged (tape method)

A: When no carbon conductive layer was found on the adhesive surface of the scotch tape

DELTA: When the carbon conductive layer appears on less than 50% of the adhesive surface of the scotch tape

X: When the carbon conductive layer is over 50% or more of the bonding surface of the scotch tape, or carbon is entirely separated from the hard layer and the surface of the aluminum substrate is exposed

(3) Penetration resistance

A sample of the aluminum current collector was prepared by tapping with a diameter of 10 mm. The sample was then placed in the center of the jig and squeezed using a pneumatic cylinder at a pressure of 80 psi. Then, a constant current is passed through the resistor to measure the resistance. The apparatus used for evaluating such penetration resistance is shown in Fig.

(G / m &lt; 3 &gt;) of the carbon conductive layer aluminum
(Al) content The content of oxygen (O) Aluminum (Al) and carbon (C)
Content ratio Penetration resistance of the carbon conductive layer-coated current collector
(mΩ) The carbon conductive layer
Peel force
(Swab method / tape method) Example 1 0.66 66.99 1.85 2.15 21.2 ○ / ○ Example 2 0.64 60.70 1.32 1.60 20.6 ○ / ○ Example 3 0.70 62.60 1.75 1.76 17.3 ○ / ○ Comparative Example 1 0.34 85.46 1.58 6.57 22.0 X / X Comparative Example 2 0.88 55.30 2.02 1.30 35.6 ○ / ○

Manufacture of electrodes

Example 4

100 g of LiFePO ₄ as a powdery active material, ₅ g of carbon black as a conductive agent and 5 g of polyvinylidene fluoride as a binder were uniformly mixed and 100 ml of N-methylpyrrolidone (NMP) was added as a solvent to prepare a kneaded state , The anode electrode layer was uniformly coated on both sides of the aluminum current collector prepared in Example 1 by a width of 3 mm from both ends of the carbon conductive layer by a conventional method, followed by drying and compression to obtain a total thickness of 200 μm A positive electrode was prepared.

Example 5

A positive electrode was prepared in the same manner as in Example 4, except that the aluminum current collector produced in Example 2 was used.

Example 6

A positive electrode was prepared in the same manner as in Example 4, except that the aluminum current collector produced in Example 3 was used.

Comparative Example 3

A positive electrode was prepared in the same manner as in Example 4, except that the aluminum current collector produced in Comparative Example 1 was used.

Comparative Example 4

A positive electrode was prepared in the same manner as in Example 4 except that an aluminum base without a carbon conductive layer was used as a current collector.

Manufacture of electrochemical devices

Example 7 (Production of lithium secondary battery)

100 g of powdered graphite and 10 g of polyvinylidene fluoride as a binder were uniformly mixed and 100 ml of N-methylpyrrolidone (NMP) was added as a solvent to prepare a kneaded state. A copper foil The anode was uniformly coated on both sides by a conventional method, followed by drying and compression, thereby obtaining a cathode having a total thickness of 120 μm

The negative electrode prepared in Example 4 and the positive electrode prepared in Example 4 were cut into a predetermined size in the form of protruding current collectors where no electrode was applied and maintained in a vacuum oven at 140 ° C for 5 hours to obtain a water content of less than 1,000 ppm Lt; / RTI &gt;

The dried anode and cathode were successively laminated in this order in this order from the cathode / separator / anode / separator / cathode / separator in this order with a porous polyethylene separator (Wisconsin, thickness 20 μm) sandwiched therebetween and the protruded anode and cathode The terminals were fused with ultrasonic waves by adding aluminum and nickel lead wires, respectively, and connected in parallel.

Generally, a casing used for a battery is molded to form a groove, and the above-mentioned laminate is placed. An electrolytic solution in which LiPF ₆ has a concentration of 1.2 M and a solvent is composed of ethylene carbonate, diethyl carbonate and methyl ethyl carbonate in a volume ratio of 3: 3: 4 A lithium secondary battery having a capacity of 20 Ah was manufactured through a typical battery manufacturing process.

Example 8 (Production of lithium secondary battery)

A lithium secondary battery was produced in the same manner as in Example 7, except that the anode prepared in Example 5 was used.

Example 9 (Production of lithium secondary battery)

A lithium secondary battery was produced in the same manner as in Example 7, except that the anode prepared in Example 6 was used.

Example 10 (Production of supercapacitor)

The aluminum current collector produced in Example 3 was coated with an activated carbon slurry, dried and pressed to form an electrode. 4 parts by weight of carboxymethylcellulose (CMC), 4 parts by weight of styrene-butadiene (SBR) rubber and 4 parts by weight of polytetrafluoroethylene (PTFE), 10 parts by weight of activated carbon powder and 2 parts by weight of carbon black Respectively. As a separator, a porous polypropylene film was placed between the two electrodes, and the electrolyte was filled in a casing material and then an electrolytic solution in which 1 M Et ₄ NBF ₄ (tetraethylammonium tetrafluoroborate) was dissolved in a propylene carbonate solvent was filled into a 50 F-class electric double layer supercapacitor .

Comparative Example 5

A lithium secondary battery was prepared in the same manner as in Example 7 except that the positive electrode prepared in Comparative Example 3 was used.

The electrode resistance, the cell resistance and the cycle characteristics (cell capacity) of the electrodes and the batteries prepared in Examples 6 to 9 and Comparative Examples 4 and 5 were measured and are shown in Table 2 below.

Characterization of electrodes and batteries

(1) Evaluation of wet adhesion of electrodes

After the positive electrode prepared in Example 4 and Comparative Example 4 was immersed in a high temperature electrolytic solution (LiPF ₆ 1.2 mol, ethylene carbonate / diethyl carbonate / methyl ethyl carbonate) at 85 ° C for 12 hours, the adhesive force of the positive electrode active material layer The comparison results are shown in Figs. 7 and 8, respectively.

7, in the anode according to Example 4, the cathode active material layer was firmly adhered on the aluminum current collector manufactured in Example 1. On the other hand, referring to FIG. 8, in the anode of Comparative Example 4, The result of the peeling of the cathode active material layer formed on the pure aluminum substrate not having the anode active material layer was confirmed.

(2) Penetration resistance of anode

In the above-described evaluation method of the penetration resistance of the aluminum current collector, the same method was used except that the anode was used instead of the aluminum current collector.

(3) discharge resistance of the battery Discharge Resistance : DCR )

The battery was discharged to a SOC of 30% with a discharge current of 1 C (20 A), and then the rest time was maintained for 1 hour for voltage stabilization. One hour after the stoppage time, pulse discharge was performed for 10 seconds at a current of 5 C (100 A) to calculate the discharge resistance from the following pulse test data.

(4) Method of measuring battery life characteristics

The battery was charged and discharged by the constant current method until the voltage of the battery reaches 3.6 V at a current of 1.0 C (20 A) at room temperature. When the voltage reaches 3.6 V, the battery is switched to the constant voltage mode so that the current reaches 1 A The charging was stopped.

The discharge was performed at a constant current of 1.0 C (20 A) until the voltage of the battery reached 2.5 V. After that, charging and discharging were repeated. The number of cycles when the battery capacity reached 80% or less of the initial capacity was defined as the battery life

Anode penetration resistance (Ω) Battery discharge resistance (mΩ) Battery life (number of times) Example 6 0.69 (Not applicable) (Not applicable) Comparative Example 4 1.42 (Not applicable) (Not applicable) Example 7 0.74 2.33 2,850 Example 8 0.80 2.25 2,948 Example 9 0.69 2.12 2,880 Comparative Example 5 1.09 3.23 1,200

Referring to Table 2, the electrode (Example 6) according to an embodiment of the present invention has significantly reduced penetration resistance as compared with Comparative Example 4, and the secondary battery according to the embodiment of the present invention 9), compared with Comparative Example 5, the output characteristics in which the battery discharge resistance was greatly reduced was improved, and the battery life was remarkably improved.

Claims (12)

Aluminum substrates; And
An aluminum current collector formed on at least one surface of the aluminum substrate and having a carbon conductive layer formed of a mixture of a conductive carbon powder and a binder,
The carbon conductive layer is formed so as to cover a part of at least one surface of the aluminum substrate,
The surface of the aluminum current collector was subjected to elemental analysis using an energy dispersive spectroscope (EDS). As a result, the surface of the aluminum current collector on which the carbon conductive layer was formed had aluminum (Al) content of 60 to 70% The content ratio of aluminum (Al) to carbon (C) is 1.5 to 2.5,
The thickness of the carbon conductive layer formed on one surface of the aluminum substrate is more than 0.5 占 퐉 and less than 2 占 퐉,
Wherein the binder is selected from the group consisting of polysaccharides, derivatives of polysaccharides, poly (olefin oxides), acrylic acid modified styrene butadiene rubber, gum arabic, polyacrylates, polyvinyl acetals, ethylene-vinyl alcohol copolymers and polyvinyl alcohols Wherein the aluminum alloy is at least one selected from aluminum alloy.
delete The method according to claim 1,
Wherein the conductive carbon powder is at least one selected from the group consisting of carbon black, graphite, carbon nanotubes, and graphene. The method according to claim 1,
Wherein the conductive carbon powder has an average particle diameter of 10 to 500 nm. delete The method according to claim 1,
Wherein the content of the binder is 50 to 200 parts by weight based on 100 parts by weight of the conductive carbon powder. The method according to claim 1,
Wherein the amount of loading of the carbon conductive layer is 0.1 to 2.0 g / m &lt; ² &gt; relative to the unit surface area of one surface or both surfaces of the aluminum substrate. delete 7. An electrode comprising an aluminum current collector according to any one of claims 1, 3, 4, 6 and 7, and an electrode layer formed on an upper surface of the carbon conductive layer of the aluminum current collector. 10. The method of claim 9,
Wherein the electrode layer is formed so as to have the same coated surface as the carbon conductive layer or has a coated surface as small as a width of 1 to 3 mm from both ends of the carbon conductive layer. An electrochemical device comprising the electrode of claim 9. 12. The method of claim 11,
Wherein the electrochemical device is a lithium secondary battery or a capacitor.

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