KR101195081B1 - Carbon coated aluminum current collector with high conductivity and durability and fabrication method thereof - Google Patents

Abstract

PURPOSE: A carbon-coated aluminum current collector is provided to minimize surface resistance between a surface of aluminum and carbon active material, and to able to maximize adhesive strength. CONSTITUTION: A carbon-coated aluminum current collector comprises an oxidation layer comprising a nanostructure with many pores through anode oxidation on a surface of aluminum, a electroplating layer formed by plating after activating the oxidation layer, and a carbon layer formed by a thermal decomposition on the coated layer. The diameter of the pores is 100±50 nm, and the depth is 1-50 micron. The aluminum having the oxidation layer extend the diameter of the pores to 300-500 nm by dipping in a chromic acid solution for 40-50 minutes. [Reference numerals] (AA, CC,FF,GG) Aluminum; (BB) Oxidation of a Positive electrode; (DD) Nickel catalyst electroless plating; (EE) Highly conductive carbon layer CVD

Description

Carbon coated aluminum current collector with high conductivity and durability and fabrication method

The present invention relates to a carbon-coated aluminum current collector having a high electroconductivity, high durability, and a method of manufacturing the same, and more particularly, to overcome the problem of aluminum and carbon surfaces showing mutual exclusion. The present invention relates to a carbon coated aluminum current collector having high electroconductivity and high durability, and a method of manufacturing the same.

The current collector transfers electrons generated by the electrochemical reaction of the active material in a battery or an electrochemical capacitor to an external circuit. Since the current collector receives electrons generated in the active material through a contact interface with the active material, all parts of the current collector surface must be strongly adhered to the active material. On the other hand, in order to transfer the electrons received from the active material to the external circuit with minimal resistance, it is preferable that the current collector has high electrical conductivity. In addition, the current collector must be stable to the electrochemical reactions occurring in the capacitor.

Current collectors used in the positive electrode and electrochemical capacitor of lithium ion batteries are generally manufactured by applying a slurry made of a mixture of activated carbon powder, a binder, and a conductive material to aluminum foil, followed by drying or pressing at room temperature. However, current collectors manufactured by such a method have a problem in that adhesion between each other is not good due to the difference in surface energy of aluminum and carbon, so that the applied active material is peeled from the aluminum foil over time. In addition, since the binder used is generally nonconductive, there is a problem of lowering the conductivity of the current collector. In addition, a high oxidation voltage is applied to the aluminum during charging and discharging. In this process, an oxide film, which is a non-conductor, is formed on the surface of the aluminum, thereby reducing the electrical conductivity of the current collector.

In order to solve this conventional problem, the following inventions related to the current collector have been proposed.

Japanese Laid-Open Patent Publication No. 2006-100477 discloses a manufacturing method for improving the adhesion between the carbon active material layer and the aluminum foil by arranging aluminum coated with carbon in a hydrocarbon atmosphere and applying an aluminum melting temperature or less to form an aluminum carbide intervening layer. This is posted. According to the publication, the aluminum carbide cilia extending from the aluminum carbide deposition layer toward the aluminum layer and the carbon layer function to hold the carbon layer and the aluminum surface, improve the surface adhesion strength, and at the same time the electrical conduction path between the two layers Explain that it plays a role. However, this conventional technology has a problem that the binding process and the electrical conductivity are rather excellent but the process is complicated.

U.S. Patent No. 5,777,428 discloses a method of manufacturing a current collector by coating aluminum on a carbon fiber cloth by a plasma spray method and then thermally compressing the coated carbon fiber cloth on an aluminum foil at a temperature of about 300 degrees.

Japanese Laid-Open Patent Publication No. 2009-123664 discloses excellent bonding strength with an active material by removing an oxide on an aluminum surface and then spraying conductive titanium carbide with aluminium foil at high speed to form a bonding layer diffused in aluminum on a molecular scale. In addition, a method of manufacturing a current collector that suppresses the formation of surface oxides and improves durability is disclosed.

In addition, Korean Patent Publication No. 10-0511363 discloses a current collector manufactured by attaching a mixture of carbon nanotubes or carbon nanofibers and metal nanoparticles or metal oxides to aluminum and then thermocompressing them.

However, such a prior art also has a problem that the aluminum surface and the carbon surface are mutually exclusive.

The present invention was devised to overcome the conventional technology and basically introduced a method of depositing carbon on the surface of aluminum using a chemical vapor deposition (CVD) method. In order to overcome the problem of aluminum and carbon surfaces being mutually exclusive, CVD method using anodic aluminum oxide as a medium for carbon coating, which is friendly to both materials and can control the structure on a nanoscale through anodization, CVD In order to overcome the melting point problem of aluminum, which is the biggest limitation of the method, a nickel catalyst is attached to the surface of aluminum oxide so that carbon deposition can occur even at a relatively low temperature such as 600 ° C. Through this design, a carbon coated aluminum current collector having high conductivity and high durability, which can minimize the interface resistance between the surface of aluminum and the carbon active material and maximize the adhesive strength, and a method of manufacturing the same.

It is also an object of the present invention to provide a carbon-coated aluminum current collector having improved electrical conductivity and durability, and a method of manufacturing the same.

It is also an object of the present invention to attach a catalyst to the pores of nanostructures formed on the surface by anodic oxidation to form a carbon layer simply and conveniently. A carbon coated aluminum current collector having high electroconductivity and high durability, and a method of manufacturing the same. To provide.

An object of the present invention, the oxide layer comprising a nanostructure having a plurality of pores on the surface of aluminum by anodizing; A plating layer coated by plating after activating the oxide layer; It is achieved by a carbon-coated aluminum current collector comprising a; carbon layer formed on the surface of the plating layer by a pyrolysis method.

In addition, the diameter of the voids is in the range of 100 ± 50nm, the depth is preferably 1 ~ 5㎛.

Moreover, it is preferable to immerse the aluminum which has the said oxide layer in chromic acid solution for 40 to 50 minutes, and to expand the diameter of the said gap to 300-500 nm.

In addition, it is preferable to soak for 1 to 5 minutes in 0.1-10mM palladium chloride solution to activate the anode oxide of aluminum.

In addition, it is preferable to form the plating layer in the thickness of 0.05 ~ 0.1㎛ on the surface of the aluminum oxide by immersing in an electroless nickel plating solution.

In addition, it is preferable to form the carbon layer by maintaining the temperature for 4 hours ± 30 minutes after raising the temperature to 600 ~ 670 ℃ range at room temperature under a reducing gas atmosphere.

In addition, the metal forming the plating layer is preferably selected from the group of transition metals including nickel, iron, and cobalt.

In addition, in the case where the transition metal is not nickel, the metal is attached to the aluminum oxide layer by dipping and then reduced by heat treatment under an atmosphere containing hydrogen, or the metal is reduced by electroplating.

On the other hand, an object of the present invention, (1) forming an oxide layer comprising a nanostructure having a plurality of pores on the surface of the aluminum by anodizing; (2) coating the plating layer by plating after activating the oxide layer; (3) forming a carbon layer on the surface of the plating layer by a pyrolysis method; it is also achieved by the carbon coating aluminum current collector manufacturing method comprising a.

In addition, in the step (1), immersing a plurality of the pores formed by the anodizing method in a chromic acid solution to expand the diameter of the pores; preferably further includes.

In addition, it is preferable to further include; immersing in a palladium chloride solution in step (2) to activate the aluminum anodized layer.

In addition, it is preferable to form the plating layer in the thickness of 0.05 ~ 0.1㎛ on the surface of the aluminum oxide by immersing in an electroless nickel plating solution.

In addition, in the step (2), the metal constituting the plating layer is preferably selected from the group of transition metals including nickel, iron, cobalt.

In addition, when the transition metal is not nickel, attaching the metal to the aluminum oxide layer by using dipping, and then reducing the metal by heat treatment in an atmosphere containing hydrogen or reducing the metal by electroplating. It is desirable to.

According to the present invention, it is possible to provide a carbon-coated aluminum current collector having a high electroconductivity and high durability, which can minimize the interface resistance between the surface of aluminum and the carbon active material and maximize the adhesive strength, and a method of manufacturing the same.

In addition, it is possible to provide a carbon coated aluminum current collector having improved electrical conductivity and durability and a method of manufacturing the same.

In addition, a carbon-coated aluminum current collector having high conductivity and high durability, which can easily and conveniently form a carbon layer by attaching a catalyst to pores of nanostructures formed on the surface by anodic oxidation, and a method of manufacturing the same can be provided. .

1 is a schematic view showing a manufacturing process of a carbon coated aluminum current collector according to an embodiment of the present invention,
2 (a) to 2 (h) is a photograph showing the SEM shape according to the manufacturing process of FIG.
3 is a graph showing contact resistance evaluation results according to various examples and comparative examples;
4 is a graph comparing the adhesion strength of Example 1 and Comparative Example 1.

The carbon-coated aluminum current collector having high electroconductivity and high durability according to the present invention and a manufacturing method thereof will be described in detail with reference to FIGS. 1 to 4.

1 is a schematic view showing a manufacturing process of a carbon-coated aluminum current collector according to an embodiment of the present invention, Figure 2 (a) to Figure 2 (h) is a photograph showing the SEM shape according to the manufacturing process of Figure 1, 3 is a graph showing contact resistance evaluation results according to various examples and comparative examples, and FIG. 4 is a graph comparing adhesion strengths of Example 1 and Comparative Example 1. FIG.

The carbon coated aluminum current collector having high conductivity and high durability according to the present invention and a method for manufacturing the same are CVD methods, which are three process elements: first, anodization, second, CVD catalyst deposition, and third And heat-treatment in gaseous hydrocarbons through CVD under a hydrocarbon atmosphere.

The overall manufacturing process, as schematically shown in FIG. 1, first uses surface anodic oxidation to produce surface nanostructures of aluminum or aluminum oxide having a concave structure with pores of 300-500 nm size and a depth within 1 μm. . The nickel catalyst is then attached to aluminum by filling the pores on the surface with a nickel precursor solution or by electroless plating the surface inside the pores. Then, carbon CVD is performed at a temperature of 600 to 670 ° C. in a methane or acetylene atmosphere to form a carbon layer using a nickel deposit as a catalyst on the surface of the aluminum structure.

Aluminum concave structures or oxide nanostructures serve to immerse aluminum foil in a nickel precursor solution or to uniformly apply the catalyst during nickel electroless plating, and aluminum oxide can be stably attached to various metal nanoparticles. It acts as a delay. In addition, aluminum oxide has excellent adhesion with aluminum, and since the carbon nanofiber layer grown with nickel seeds is well attached to aluminum oxide, aluminum oxide acts as a medium for bonding aluminum and carbon that do not adhere well to each other.

Although aluminum oxide has a problem that resistance due to oxide occurs when the oxide layer is used as a non-conductor, when the thickness of the aluminum oxide is thin, the interface resistance generated at the carbon layer and the aluminum surface is lower than that of aluminum oxide itself. Since it acts as a much larger resistance element, even if aluminum oxide is used, the above-mentioned advantages can be expected to improve the interface resistance.

Akinori et al. (See Korean Patent Publication No. 10-2005-118202, December 15, 2005) and Wu et al. (See Materials Chemistry and Physics, Vol. 117, (2009), p.294-300) When the aluminum foil was placed in 600 methane for 10 hours or more, a layer of about 100 nm of carbon and aluminum carbide was formed in the aluminum oxide layer. Aluminum carbide acts as a non-conductor as a resistor in itself, but acts as a medium for adhering aluminum and carbon to each other, and consequently, serves to reduce interfacial resistance. Here, aluminum carbide acts as a resistor in itself as a non-conductor, but acts as a medium for adhering aluminum and carbon to each other, and consequently, serves to reduce the interface resistance. In the present invention, aluminum oxide is intended to be used as an intermediate layer for reducing interfacial resistance and improving interfacial adhesion. When methane is used to CVD growth of the carbon layer on the aluminum surface and heat treatment is attempted for a long time, in addition to the growth of carbon nanotubes by the nickel catalyst, the aluminum oxide is carbonized and a mediator layer is formed between the CVD carbon layer and the aluminum foil. It is thought that

Through the configuration of the invention described as described above it is possible to manufacture a carbon-coated aluminum current collector maximized interfacial conductivity and adhesive strength.

Example 1

Anodizing a commercial aluminum foil having a purity of 99.9% by weight and a thickness of 100 µm with an electrolyte for about 3 hours with an electrolyte to form an aluminum oxide pore channel structure having a diameter of about 100 nm and a depth of about 5 µm on the surface.

Then, it was immersed in a sodium hydroxide or chromic acid solution for 50 minutes to expand the pores of aluminum oxide formed on the surface to about 300 ~ 400nm and the thickness of the channel of aluminum oxide was also reduced from 200nm to less than 100nm.

The aluminum oxide pore structure formed on the aluminum surface may be dissolved in the chromic acid solution to remove the bottom of the aluminum oxide pore structure and to remove a portion of the pore wall after a suitable time passes. Thus, the size of the pores can be adjusted to a size suitable for catalyst formation by making the size of the pore thin at about 300-400 nm and the thickness of 200 nm to 100 nm. In this case, if the dissolution time is too long, the oxide structure may disappear at all. Here, the size of the pores is preferably about 300 to 500nm. If the pore size is larger or smaller than this, it is not suitable for catalyst formation.

The anodized aluminum foil was immersed in a palladium chloride solution for 2 minutes to activate the surface of the anodic oxide, and then immediately immersed in a nickel electroless plating solution for 5 minutes to provide a nickel electroless plating layer having a thickness of 0.1 μm on the surface of the aluminum oxide channel structure. Formed.

Here, if the time for immersion in the solution is too short, a sufficient amount of catalyst for forming the carbon layer is not formed, and if too long, too much carbon layer may be formed. The thickness of the catalyst layer is also preferably in the range of 0.05 to 0.1 µm. This is because when the thickness of the catalyst layer is too thin, a sufficient amount of catalyst necessary for forming the carbon layer is not formed, and when the catalyst layer is too thick, too much carbon layer may be formed in the catalyst layer.

After anodizing and nickel electroless plating, aluminum foil was placed in a quartz glass tube, and the inside was filled so that the ratio of nitrogen: hydrogen: methane was 20: 10: 2. The pyrolysis carbon layer was formed on the surface of the anodized aluminum foil by heat treatment at a temperature of 4 hours. Here, it is preferable to keep in 600-670 degreeC range so that temperature may not be too high.

2 (a) to 2 (h) show SEM surface images and cross-sectional images of the manufacturing process according to Example 1;

Here, as for the depth of an aluminum oxide layer, 1-5 micrometers is preferable. If the depth is shallower than this range, no pores are formed in the oxide layer and do not exist in the form of an oxide film, making it difficult to make a structure in which the carbon layer is rooted based on the pores. In addition, when the depth is deeper than this range, the carbon layer becomes excessively thick, and the path through which electric current passes from the carbon layer to aluminum becomes long, thereby generating unnecessary resistance.

On the other hand, the smaller the pores, the longer the rooting point (rooting point) can be expected to form a more robust coating layer. However, there is a problem that it is difficult to form a catalyst layer for forming a carbon layer inside the pores having a diameter of modified nanometers. Therefore, the pore size is preferably in the range of 100 nm.

Example 2

Anodizing a commercial aluminum foil having a purity of 99.9 wt% and a thickness of 100 μm with an electrolyte of phosphoric acid for about 3 hours to form an aluminum oxide pore channel structure having a diameter of about 100 nm and a depth of about 5 μm on the surface, and then Soaking in a sodium or chromic acid solution for 50 minutes to expand the pores of aluminum oxide formed on the surface to about 300 ~ 400nm and the thickness of the channel of aluminum oxide was also reduced from 200nm to less than 100nm.

Anodized aluminum foil was placed in a quartz glass tube, and the inside thereof was filled with a nitrogen: hydrogen: methane ratio of 20: 10: 2, and then heat-treated at 600 ° C. for 4 hours.

As a result, the CVD carbon layer was not properly formed on the surface due to the absence of the nickel catalyst, and the oxide formed by the anodization acted as a resistor, resulting in greater interfacial contact resistance than when aluminum foil was used as it is.

Example 3

Anodizing a commercial aluminum foil having a purity of 99.9 wt% and a thickness of 100 μm with an electrolyte of phosphoric acid for about 3 hours to form an aluminum oxide pore channel structure having a diameter of about 100 nm and a depth of about 5 μm on the surface, and then Soaking in a sodium or chromic acid solution for 50 minutes to expand the pores of aluminum oxide formed on the surface to about 300 ~ 400nm and the thickness of the channel of aluminum oxide was also reduced from 200nm to less than 100nm.

The anodized aluminum foil was immersed in a palladium chloride solution for 2 minutes to activate the surface of the anodic oxide, and then immediately immersed in a nickel electroless plating solution for 5 minutes to provide a nickel electroless plating layer having a thickness of 0.1 μm on the surface of the aluminum oxide channel structure. Formed.

Nickel was more friendly to carbon than aluminum, so the interface contact resistance was somewhat lowered, but it was much less than carbon coating.

Example 4

A commercial aluminum foil with a purity of 99.9% by weight and a thickness of 100 μm is placed in a quartz glass tube as it is, and the inside thereof is filled with a ratio of nitrogen: hydrogen: methane to 20: 10: 2, and heat-treated at 600 ° C. for 4 hours for anodizing. A pyrolytic carbon layer was formed on the surface of the aluminum foil.

This result is that the CVD carbon layer is not properly formed on the surface because there is no nickel catalyst, the interface resistance between the carbon paper and the aluminum foil by the carbon coating layer was not reduced.

Example 5

A commercial aluminum foil having a purity of 99.9 wt% and a thickness of 100 µm was immersed in a palladium chloride solution for 2 minutes to activate the surface of the anodized oxide, and then immediately immersed in a nickel electroless plating solution for 5 minutes. However, the surface of aluminum was not evenly activated by palladium filadium, so a nickel electroless plating layer uniformly distributed on the surface of the aluminum foil could not be obtained.

Nickel electroless plating aluminum foil was placed in a quartz glass tube, and the inside thereof was filled so that the ratio of nitrogen: hydrogen: methane was 20: 10: 2, and then heat-treated at 600 ° C. for 4 hours. However, the CVD carbon layer was formed only where the nickel catalyst was distributed. As a result, only a slight reduction in interfacial resistance was obtained compared to Comparative Example 1, and the adhesion strength of the CVD carbon layer was also lower than that of Example 1 due to the structure in which the CVD carbon layer was simply placed on the surface.

Example 6

On the other hand, the carbon coated aluminum current collector having high conductivity and high durability according to the present invention may use a transition metal other than nickel.

Here, in the case of a transition metal other than nickel, it is preferable to attach the metal to the aluminum oxide layer by dipping and then reduce the metal by heat treatment in an atmosphere containing hydrogen or reduce the metal by electroplating. That is, it may be possible to use electroless plating or dipping irrespective of the type of transition metal only for the growth of the carbon layer. However, the reason for electroless plating is that the aluminum oxide layer is a ceramic structure, which includes the purpose of supplementing the vulnerable to mechanical stress such as impact.

Comparative Example 1

A commercial aluminum foil having a purity of 99.9% by weight and a thickness of 100 µm was used as a current collector.

(Interface resistance evaluation)

The prepared electrode was cut into 2cm × 2cm size, overlapped with TGPG-060 carbon paper, which is a virtual active material, sandwiched between copper plates, pressurized with a pressure of 10kgf / ㎠ using a pressurizer, and then a current-contacted pressure using a potentiostat. Got a straight line. In addition, the interfacial resistance to TGPH-060, a virtual active material of each sample, was evaluated by calculating the slope of the straight line and measuring the resistance between the copper plates. The evaluation results are shown in FIG. As can be seen in Figure 3 the results of Example 1 showed the lowest interfacial resistance.

(Adhesive evaluation)

The electrode prepared according to the above examples was cut out to a size of 1 cm × 2 cm, and then the Scotch Magic Tape was attached and detached to measure the mass of the detached coating to evaluate adhesion using the following equation.

Adhesion = (weight of stripped coating) / (weight of original coating)

The evaluation results are shown in FIG. As can be seen in Figure 4 Example 1 showed the best adhesion.

Comparing the various examples and comparative examples described above is shown in Table 1.

division Example 1 Example 2 Example 3 Example 4 Example 5 Comparative example
air gap
channel Phosphoric Acid Solution
3 hours × × × 100 nm in diameter
Depth 5㎛ × × ×
air gap
expansion Sodium hydroxide or chromic acid solution
50 minutes soak × × × Void 300-400 nm Extended Channel / Reduced to 100 nm thick × × × surface
Activation Palladium chloride
2 minutes soak × Palladium chloride
2 minutes soak × Palladium chloride
2 minutes soak ×
Plated Nickel Electroless Plating Solution
5 minutes soak
0.1 μm × Nickel Electroless Plating Solution
5 minutes soak
0.1 μm × Nickel Electroless Plating Solution
5 minutes soak
0.1 μm ×
Heat treatment Quartz glass tube
Nitrogen: Hydrogen: Methane = 20: 10: 2
600 ℃
4 hours × Quartz glass tube
Nitrogen: Hydrogen: Methane = 20: 10: 2
600 ℃
4 hours × Used material Purity 99.9 wt%, Thickness 100㎛ Purity 99.9 wt%, Thickness 100㎛

Therefore, according to the present invention, it is possible to minimize the interface resistance between the surface of the aluminum and the carbon active material, to maximize the adhesive strength, and to attach the catalyst to the pores of the nanostructure formed on the surface by anodic oxidation to simplify the carbon layer. It can be conveniently formed, and can provide a carbon coated aluminum current collector having a high electroconductivity and high durability, and a method of manufacturing the same.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the invention. will be. The scope of the invention will be determined by the appended claims and their equivalents.

Claims (14)

An oxide layer comprising a nanostructure having a plurality of pores on the surface of aluminum by anodization;
A plating layer coated by plating after activating the oxide layer;
And a carbon layer formed on the surface of the plating layer by a pyrolysis method. The method of claim 1,
The diameter of the pores is in the range of 100 ± 50nm, the depth is 1 to 5㎛ carbon coated aluminum current collector. The method according to claim 1 or 2,
A carbon-coated aluminum current collector, wherein the aluminum having the oxide layer is immersed in a chromic acid solution for 40 to 50 minutes to extend the diameter of the pores to 300 to 500 nm. The method of claim 1,
A carbon-coated aluminum current collector, which is immersed in 0.1-10 mM palladium chloride solution for 1-5 minutes to activate the anode oxide of aluminum. About claim 1
A carbon coated aluminum current collector, immersed in an electroless nickel plating solution, to form the plating layer on the surface of the aluminum oxide with a thickness of 0.05 to 0.1 μm. 6. The method according to claim 1 or 5,
The carbon-coated aluminum current collector, characterized in that to form the carbon layer by maintaining the temperature for 4 hours ± 30 minutes after raising the temperature to 600 ~ 670 ℃ range in a reducing gas atmosphere. The method of claim 1,
The metal constituting the plating layer is a carbon-coated aluminum current collector, characterized in that selected from the group of transition metals including nickel, iron, cobalt. The method of claim 7, wherein
When the transition metal is not nickel, carbon is coated with aluminum by dipping to attach the metal to the aluminum oxide layer and then reducing the metal by heat treatment in an atmosphere containing hydrogen or by electroplating. Current collector. (1) forming an oxide layer comprising a nanostructure having a plurality of pores on an aluminum surface by anodizing;
(2) coating the plating layer by plating after activating the oxide layer;
(3) forming a carbon layer on the surface of the plating layer by a pyrolysis method; a carbon coated aluminum current collector manufacturing method comprising a. 10. The method of claim 9,
In the step (1), immersing a plurality of the pores formed by the anodizing method in a solution of chromic acid to expand the diameter of the pores; carbon coating aluminum current collector manufacturing method further comprising. 11. The method according to claim 9 or 10,
And immersing in a palladium chloride solution in step (2) to activate the aluminum anodized layer. 10. The method of claim 9,
A method of manufacturing a carbon-coated aluminum current collector, immersed in an electroless nickel plating solution, to form the plating layer on the surface of the aluminum oxide with a thickness of 0.05 to 0.1 μm. 10. The method of claim 9,
In the step (2), the metal forming the plating layer is a carbon-coated aluminum current collector manufacturing method, characterized in that selected from the group of transition metals including nickel, iron, cobalt. The method of claim 13,
If the transition metal is not nickel, attaching the metal to the aluminum oxide layer using dipping, and then reducing the metal by heat treatment in an atmosphere containing hydrogen or reducing the metal by electroplating. A carbon coated aluminum current collector manufacturing method.

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