KR102032265B1 - Method for producing porous copper for a negative electrode current collector of a lithium secondary battery, and porous copper produced therefrom, and a negative electrode current collector of a lithium secondary battery - Google Patents

Abstract

The present invention relates to a method for manufacturing porous copper used for an electronic part, an electronic device heat radiating element, and a negative current collector of a lithium secondary battery, capable of providing an increased tensile strength without using toxic gas in a manufacturing process, and porous copper and a negative current collector of a lithium secondary battery manufactured thereby. More specifically, according to the present invention, the method comprises the steps of: (B) performing copper electroless plating for a prepared porous organic body; (C) performing copper electrolyte plating for the acquired product to manufacture a half-finished product; (D), which is a heat treatment step of the half-finished product, incompletely burning the half-finished product to remove the porous organic body, performing oxidation in an oxidation atmosphere to remove carbon, and performing sintering in an inert atmosphere; (E) performing partial copper plating, partial overlapping rolling, or partial plating/partial overlapping rolling for the acquired product; and (F) performing final rolling.

Description

METHOD FOR PRODUCING POROUS COPPER FOR A NEGATIVE ELECTRODE CURRENT COLLECTOR OF A LITHIUM SECONDARY BATTERY, AND POROUS COPPER PRODUCED THEREFROM, AND A NEGATIVE ELECTRODE CURRENT COLLECTOR OF A LITHIUM SECONDARY BATTERY}

The present invention relates to a method for producing porous copper for a lithium secondary battery negative electrode current collector and a porous copper and a lithium secondary battery negative electrode current collector prepared therefrom.

Porous copper is a form having numerous bubbles inside a metal material, also commonly referred to as Cu foam. Porous copper with an open pore structure is stable in structure, and has a very large and light weight ratio of surface area per unit volume. Therefore, lithium secondary battery battery electrodes, fuel cell components, filters for soot filtration devices, pollution control devices, In various industries such as catalyst supports, audio components, heat sinks Can be applied.

As a method for producing porous copper, copper powder is used as a raw material to obtain pores inside the mold, and a method of forming a foam in the molten copper while solidifying while foaming and plating porous copper on a porous base material such as polyurethane foam After that, thermal decomposition to remove the base metal is used industrially.

The method of producing porous copper using copper powder as a raw material has the advantage of having a relatively simple process of mechanically extruding or injecting and heating the copper powder, but in practice, since the empty spaces generated when the powders are bonded to each other are not so large. The method has a disadvantage in that it is impossible to produce a porous metal material having a porosity of 50% or more.

In addition, the foamed metal manufacturing method that generates bubbles in the molten copper is capable of producing a porous metal having a relatively large porosity, but it is expensive in energy because it must maintain a high temperature enough to melt the copper, in particular the bubble size due to the nature of the foaming process Since it is virtually impossible to control constantly, there are disadvantages in that the homogeneity of the product is greatly reduced and it is difficult to manufacture thin materials (5T (= mm) or less).

In addition, the method of removing the base material by thermal decomposition after plating copper on the porous base material, the main process is a step of imparting conductivity to the porous base material such as polyurethane (PU) foam and the like. The method of manufacturing the porous copper is relatively simple, the thickness can be adjusted, there is an advantage that can produce a product having a high specific surface area and porosity. However, when removing the polyurethane foam used as a support and sintering heat treatment of the plated particles, a high temperature and long heat treatment are required, and in order to completely remove the polyurethane foam, harmful gases such as H ₂ , CO, and CH ₄ must be used. Due to this, there is a great difficulty in commercialization.

Recently, various methods such as de-alloying and freezing-casting that reduce CuO after freezing using element solubility difference have been studied. However, in consideration of price and productivity, porous copper is required for commercialization. More research is still needed in terms of manufacturing method.

On the other hand, in order to secure the high capacity and high output performance of the lithium secondary battery (lithium secondary battery), a study to manufacture a current collector made of porous copper has been in progress.

In particular, in the lithium secondary battery, the current collector collects electrons generated from the active material (cathode and cathode material) of the lithium secondary battery, transfers them to an external circuit, and acts as an electrode matrix of the electrode active material. It is a key component that can drastically improve the fast charging performance of lithium secondary batteries used in medium and large electronic devices such as energy saving systems (ESS).

However, porous copper has a significantly lower tensile strength than bulk-type copper due to the bottleneck of the load due to the load being concentrated in the thickness or thinner width when the tensile force is applied. It is not applicable to the actual battery manufacturing process using the roll-to-roll method. In addition, an additional electrode tab must be attached to one side of the porous copper to move electrons (current) generated from the electrodes (active material and current collector) to the external conductor, which requires an additional process for this. It acts as a major factor. Therefore, in order to commercialize the porous copper manufacturing method, and to manufacture porous copper having excellent characteristics suitable for the current collector of a lithium secondary battery, improvement of tensile strength of the porous copper and porous copper having an integrated structure of the electrode body and the electrode tab Development of manufacturing technology is urgently needed.

Until now, the following patents have been applied for a method for manufacturing a porous metal and for applying the porous metal to a lithium secondary battery negative electrode current collector.

Korean Patent Laid-Open Publication No. 10-2010-0097575 discloses a method for producing iron foam using plasma vapor deposition (PVD) and electroplating. However, due to the increase in manufacturing cost by PVD, the process of temperature rising and cooling in four stages, and the high temperature and long heat treatment using hydrogen, the risk of explosion increases and productivity is sharply reduced.

Korean Patent Registration No. 10-1520345 includes an active material layer laminated on one or both surfaces of a three-dimensional porous body for application of a lithium secondary battery negative electrode current collector, and is collected at the periphery of the three-dimensional porous body including the stacked active material layer. The structure in which the whole is formed was disclosed. However, the method requires both a three-dimensional porous body and a thin metal film, and an assembly manufacturing process including attachment thereof is added, and an additional tab must be attached to the manufactured assembly, thereby increasing manufacturing cost and decreasing productivity. have.

The present invention is a method for producing a porous copper for environmentally friendly high-strength lithium secondary battery negative electrode collector with improved tensile strength without using harmful gas in the manufacturing process and the porous copper and lithium secondary battery negative electrode current collector prepared by the above method To provide.

Method for producing a porous copper for lithium secondary battery negative electrode collector according to the present invention comprises the steps of (A) preparing an organic porous body; (B) pre-treating the prepared organic porous body, followed by copper electroless plating, wherein copper electroless plating is performed by immersing the organic porous body in a copper sulfate electroless plating solution at 20 ° C. to 30 ° C. for 30 seconds to 10 minutes. step; (C) copper electroplating the obtained product to produce a semi-electrolytic copper plated product, copper electroplating is immersed in a copper sulfate electrolytic plating solution, the product is 10 minutes to 10 minutes at a current density of 0.1 to 100 A / dm ² Performing by electroplating copper for time; (D) heat treatment of the semifinished product, incomplete combustion of the semifinished product to remove the organic porous body, oxidation in an oxidizing atmosphere to remove carbon, and then sintering in an inert atmosphere, wherein the incomplete combustion is carried out in an N ₂ inert atmosphere. Heat treatment at a temperature increase rate of 5 ℃ / min from 300 ℃ to 600 ℃ to decompose the organic porous body, leaving only carbon in the surface layer, oxidation stops the injection of N ₂ gas after incomplete combustion, and maintained for 1 to 20 minutes, sintering Heating at 850 ° C. to 950 ° C. at an elevated temperature rate of 3 ° C./min in an N ₂ inert atmosphere and then holding for 1 to 20 minutes; (E) partly plating, partly rolling, or partly plating and partly rolling the copper on the obtained product; And (F) final rolling.

The organic porous body may be in the form of open pores. The thickness of the copper plating layer formed by the (B) electroless plating step may be 0.5 μm to 5.0 μm. In the electroless plating step (B), the pretreatment may include an induction treatment and an activation treatment. After the heat treatment step (D) the semi-finished product, the surface of the product may be at least 99.6% by weight of Cu. Step (E) may be carried out from 1% to 49% of the total area of the product obtained in the previous step by partial plating or partial overlap rolling or both. The step (E) may be in the form of a band-shaped partial plating or partial overlap rolling or both in the rolling direction or the vertical direction of the width. The partial plating may be performed for 10 minutes to 10 hours at a current density of 0.1 to 100 A / dm ^{2 in} the vertical direction of the width of the sintered porous copper sheet. Step (E) may be rolled at a reduction ratio of 80% to 99% with respect to the total thickness of the overlapped porous copper. The partial overlap rolling may roll additionally overlapping additional porous copper having a pore size of 1 mm or less and a porosity of 98% or less in the vertical direction of the width of the sintered porous copper sheet.

The present invention is prepared by the above-described method for manufacturing a porous copper for a lithium secondary battery negative electrode current collector, a specimen having a width of 100mm or more, and a thickness of 0.01mm or more and a width of 30mm with a tensile strength of 50N or more when measuring the tensile force, the field emission In the crystal grain diameter measured by the crystal grain size analysis method with a type | mold scanning electron microscope (FE-SEM), porous copper whose average grain size is 0.1 micrometer-100 micrometers is contained. The overlapping rolled portion or the unplated portion of the porous copper may have a weight of 0.0448g or less when measured by a horizontal and vertical 1cm standard. The overlap rolling section cut surface may have a structure of close contact.

The present invention includes a lithium secondary battery negative electrode current collector which is integrally manufactured by using the above-described unrolled rolled portion or unplated portion of porous copper as an electrode portion by filling an active material slurry, and the overlapped portion or plated portion as an electrode tab.

The present invention does not use harmful gases such as CH ₄ , CO, H ₂ in the manufacturing process of porous copper for a lithium secondary battery negative electrode current collector. The method of manufacturing porous copper for a lithium secondary battery negative electrode current collector according to the present invention can reduce manufacturing time and manufacturing cost.

1 is an exemplary flow chart of a method for producing porous copper according to the present invention.
FIG. 2 is a heat treatment process graph illustrating the process conditions of the heat treatment step (ie, incomplete combustion, oxidation and sintering) of (D) semifinished product, for example in Example 1, according to the method for producing porous copper according to the present invention.
Figure 3 is a schematic diagram of the stack rolling process according to an embodiment of the present invention.
4 is a photograph of the surface (upper surface) of the porous copper produced by the partial overlap rolling process under an optical microscope.
5 is a structure photograph of the overlap rolling part (a) and the overlap rolling part (b) of the Cu foam prepared according to Example 3 of the present invention under an optical microscope.
Fig. 6 shows the difference between the strength increasing portion (= partial plating portion or overlap rolling portion) and the strength non-increasing portion (= portion not plating or overlap rolling) of the porous Cu foam obtained by the method for producing porous copper according to the present invention. It is a schematic diagram explaining.
7 is a photograph of a porous copper prepared according to Example 1 of the present invention.
8 is a graph comparing the tensile strength of porous copper with or without partial overlap rolling.
9 is a surface FE-SEM photograph of the porous copper prepared according to the manufacturing method of Example 1 of the present invention.
10 is a graph of EDS measurement results of analyzing surface components of porous copper prepared according to Example 2 of the present invention.
11 is a photograph taken by FE-SEM of the surface shape of the porous copper prepared by the method of Example 1 (a), Comparative Example 3 (b) and Comparative Example 4 (c), respectively.
12 is a photograph of observing the surface shape after electrolytic plating (C) in the method for producing porous copper according to the present invention with FE-SEM and measuring the thickness thereof. The smaller image at each top is x500 magnification, and the larger image at the bottom is x35 magnification.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily understand and implement the present invention. However, one of ordinary skill in the art to which the present invention pertains may implement in various modified forms within the scope of the present invention from the following description, and thus are not intended to be limited to the embodiments described herein.

Method for producing a porous copper according to the present invention, (A) preparing an organic porous body; (B) electroless plating the organic porous body, wherein the copper electroless plating is performed by immersing the organic porous body in a copper sulfate electroless plating solution at 20 ° C. to 30 ° C. for 30 seconds to 10 minutes; (C) copper electroplating the obtained product to produce a semi-electrolytic copper plated product, copper electroplating is immersed in a copper sulfate electrolytic plating solution, the product is 10 minutes to 10 minutes at a current density of 0.1 to 100 A / dm ² Performing by electroplating copper for time; (D) heat treatment of the semifinished product, incomplete combustion of the semifinished product to remove the organic porous body, oxidation in an oxidizing atmosphere to remove carbon, and then sintering in an inert atmosphere, wherein the incomplete combustion is carried out in an N ₂ inert atmosphere. Heat treatment at a temperature increase rate of 5 ° C./min from 300 ° C. to 600 ° C. decomposes the organic porous body, leaving only carbon in the surface layer, and oxidation stops injection of N 2 gas after incomplete combustion and maintains for 1 to 20 minutes. ₂ is heated to 850 ℃ to 950 ℃ at an elevated temperature rate of 3 ℃ / min in an inert atmosphere and then maintained for 1 to 20 minutes; (E) partial plating, partial overlap rolling, or partial plating and partial overlap rolling of the obtained product, and (F) final rolling step.

The method for producing porous copper according to the present invention described above will be described in detail for each process with reference to FIG. 1.

(A) preparing an organic porous body

In order to produce porous copper (or copper foam (also referred to as Cu foam)), an organic porous body having an open cell form to be formed inside the Cu foam is prepared. The organic porous body is not limited as long as bubbles are connected therein and can be burned by heat treatment. Various polymer foams, nonwovens, porous plastics, organic fibers and the like can be used. Preferably, the organic porous body in the present invention is a polyurethane (PU) foam.

The organic porous body to be used as the substrate for the Cu foam is prepared in a size suitable for the purpose of the final product. The organic porous body may be prepared by cutting mainly into sheets.

In addition, the organic porous body may optionally be subjected to a pre-plating treatment, such as a washing treatment, an acid treatment, drying, etc., necessary for smoothly performing the plating. For example, a washing process is performed by immersing an organic porous body in ethanol solution. The cleaning process includes impurities and / or contaminants adhering to the surface of the organic porous body, including oily soil, etc. Implemented to a degree that can be easily removed. If necessary, an oil cleaner and a solid remaining on the surface of the organic porous body may be further removed by using an ultrasonic cleaner. Thereafter, the ethanol remaining on the surface is removed by immersion in distilled water for 10 to 15 seconds.

(B) Copper Electroless Plating Step

The organic porous body prepared in the previous step is copper electroless plated.

Before the electroless plating treatment, electroless plating pretreatment is first performed. Specifically, a sensitizing process is performed on the previously prepared organic porous body. The sensitization step is a step for facilitating adhesion of palladium (Pd) in an activation step described later. The sensitization step is performed by immersing the prepared organic porous body in the sensitization treatment liquid. For example, in the present invention, the organic porous body is added to the treatment liquid having a composition of 25-35 g / L tin chloride (SnCl ₂ · 2H ₂ O) and 20-25 mL / L of 35% HCl for 1 minute to 10 minutes. Immersed in the adsorbed Sn ^{+ 2} in an organic porous body surface. Subsequently, the organic porous body immersed in distilled water for 5 seconds to 15 seconds may be slightly shaken, and then the organic porous body immersed in water may be removed. At this time, if industrial water is used instead of distilled water, other ions present in the water are adsorbed, and since the adhesion of Pd ions is prevented in the activation process, distilled water should be used for washing. In addition, the organic porous body should be separated from water and dried sufficiently. Thus, it is intended to remove the impurities to a uniform deposition of Pd immersing in distilled water, after adsorption of Sn ^{+ 2.}

Subsequently, an activation process is carried out if necessary. This step is a step for preventing unnecessary chemical reactions in the electroless plating step described later. The activation process may be performed by immersing the organic porous body in which the sensitization process is completed in the activating liquid. For example, the product obtained in the previous step is sufficiently immersed in the activator for 1 to 10 minutes for a time to cause the reaction of Sn ^{2 +} + Pd ^{2 +} → Pd ⁰ + Sn ^{4 + on} the surface. . The activating solution consists, for example, of 0.5 to 1.5 g / L PdCl and 10 to 20 mL / L of 35% HCl. It is then removed to Sn ^{+ 4} through a water washing of the surface, and attaching haekman of palladium (Pd). As described above, palladium (Pd) attached in the activation process is utilized as the base plating for the electroless plating described later.

In the pretreatment process, if necessary, it can be properly cleaned. Cleaning is a process of removing excess reactants or products formed on the surface of the organic porous body through an sensitization process and / or an activation process. Cleaning can be conveniently selected and carried out by those skilled in the art based on the publicly known art of copper plating.

Next, copper electroless plating is performed on the organic porous body. Copper electroless plating in the present specification means copper sulfate electroless plating. Copper sulfate electroless plating is a plating in which metals are reduced-precipitated on a target object by a reducing agent in a solution containing copper ions, and the principle of depositing electrons emitted when the reducing agent is oxidized is deposited on the object to be plated while the metal ions are reduced. It is used. Copper sulfate electroless plating is carried out by immersing the prepared organic porous body in the electroless plating solution for 30 seconds to 10 minutes with the temperature of the copper sulfate electroless plating solution being 20 to 30 ° C. Electroless plating should be performed under the above temperature and time conditions to obtain a plating layer having fine grains and excellent surface roughness. If the temperature is less than the above conditions, the rate of precipitation of the copper particles is low, and the productivity is lowered. If the temperature is exceeded, rough plating becomes difficult to obtain a smooth surface. In addition, when less than the above time condition, a sufficient plating layer is not formed on the surface of the organic porous body, and when it is exceeded, rough plating is easily performed, and dropping may occur on the surface of the organic porous body due to the stress of copper particles.

The copper sulfate electroless plating solution contains copper sulfate (CuSO ₄ · 5H ₂ O) 3 to 10 g / L, lotel salt 20 to 30 g / L, 37 mass% formalin 5 to 15 mL / L, and the total pH of 12 to 12.5. It can be prepared by adding sodium hydroxide. At this time, when the pH of the plating solution is less than 12, the reaction does not occur or the reaction is too slow for Pd and Cu, and when the pH is higher than 12.5, the substitution reaction occurs in an instant, and is easy to be rough plated. The product obtained is then washed. Specifically, the cleaning is performed in water for a short time of about 5 to 15 seconds. Take out after dipping.

The thickness of the copper plating layer formed by the copper sulfate electroless plating step is 0.5 μm to 5.0 μm. If the thickness of the copper plating layer is less than 0.5㎛, the plating layer is not formed as a whole, the porosity is increased on the surface during the manufacture of semi-finished product using electrolytic plating, and when the thickness is greater than 5.0㎛, deformation of the organic porous body occurs when forming the electrolytic plating layer described below It is possible to form a rough plating having a high surface roughness. In this regard, reference may be made to the following embodiments and FIG. 12. The copper sulfate electroless plating process corresponds to a base plating process for achieving a smooth effect of the copper sulfate electrolytic plating process.

(C) copper electroplating

Copper electroplating in the present specification means copper sulfate electroplating. The copper sulfate electroplating process is the same as a general copper (copper) electrolytic plating process, and a person skilled in the art can easily carry out using known techniques known for the copper sulfate electroplating process in the art.

Specifically, the product obtained in the previous step is copper electroplated with a copper sulfate plating solution. The plating solution may be composed of copper sulfate (CuSO ₄ · 5H ₂ O) 140 to 180 g / L, sulfuric acid (H ₂ SO ₄ ) 40 to 70 mL / L, chlorine additive 25 to 45 mg / L. The chlorine additive may be selected from NaCl, HCl, CuCl and the like, for example. The electroplating may be performed for 10 minutes to 10 hours at a current density of 0.1 to 100 A / m ² to allow copper to be uniformly electrodeposited to a predetermined thickness on the surface of the organic porous body. The current density can be properly adjusted according to the size of the anode and the size of the specimen. The plating liquid may further include an additive selected from a leveler, a brightener, and the like as necessary.

The product in which copper is electroplated on the organic porous body through the above-described process is referred to herein as a semi-finished product or semi-finished Cu foam for convenience.

(D) heat treatment step of semifinished product

The semi-finished product obtained in the above step should remove the organic porous body therein and adhere the copper plated particles adsorbed on the surface through the sintering process.

Unlike the present invention, conventionally, complete combustion was performed to remove the organic porous body. That is, a high temperature long time heat treatment and a reducing gas were added to remove the organic porous body. However, since the reducing gas is an expensive harmful gas such as CH ₄ , CO, H _2, etc., it is disadvantageous in terms of cost and environmental protection.

According to the manufacturing method of the present invention, first, a semi-finished product obtained by electroplating is charged into a heat treatment furnace, and heat treated at an elevated temperature rate of 5 ° C./min at 300 to 600 ° C. under N ₂ inert atmosphere to incompletely burn the organic porous body. Let's do it. Incomplete combustion is less than 300 ℃ organic porous body decomposition reaction does not occur, if it exceeds 600 ℃ oxidation occurs rapidly during the oxidative heat treatment for the carbon to be described later, the copper oxide remains on the surface to obtain a final product of the desired purity. Preferably, incomplete combustion is 500 ° C. At this time, carbon residues remain inside and on the surface of the Cu foam due to incomplete combustion of the organic porous body under an oxygen-deficient N ₂ atmosphere.

Next, it oxidizes in an oxidizing atmosphere. Oxidation is achieved by stopping the N ₂ gas supply and holding for 1 to 20 minutes when the set incomplete combustion temperature is reached. At this time, since oxygen is introduced from the outside, the carbon remaining on the surface is oxidized to CO ₂ . In addition, if the oxidation time is too short (less than 1 minute) in the above process, a large amount of carbon remains after sintering, and if the oxidation time is too long (more than 20 minutes), it is impossible to obtain the physical properties and clean surface to be obtained by forming copper oxide as a whole. do.

Thereafter, sintering heat treatment is performed. Introduced N ₂ gas again 700 ℃ The sintering was completed by increasing the temperature to 3 to 950 ° C. at a rate of 3 ° C./min and maintaining it for 1 to 60 minutes. When the sintering temperature is less than 700 ° C, Cu particles are not sufficiently in contact with each other to obtain desired strength and electrical conductivity. If the sintering temperature is more than 950 ° C, it is disadvantageous to secure strength due to grain coarsening. There is a disadvantage that the contact force with the active material may be weakened in the whole application. Preferably, the sintering heat treatment is carried out at 900 ° C.

An exemplary graph of the process time and temperature of the heat treatment step of the semifinished product described above is shown in FIG. 2.

(E) copper partial plating, or partial overlap rolling, or partial plating and partial overlap rolling

Cu foam completed by the above-described heat treatment process is in the area of 1% to 49% of the total Cu foam area. Copper partial plating or partial overlap rolling or partial plating and partial overlap rolling processes are performed.

Partial plating may be carried out in the form of a strip in the vertical direction of the width of the sintered Cu foam sheet, that is, the side or center of the direction in which the force is applied to the Cu foam in the installation. Partial plating may be carried out by electrolytic plating, for example, within a range of about 10 minutes to 10 hours at a current density of 0.1 to 100 A / dm ² . In this case, the electrolytic plating solution may use the same electrolytic plating solution used in the copper sulfate electroplating process. Since the strength increases with the plating area, the plating time, and the amount of plating, partial plating can be performed considering the strength required in the final product.

Partial overlap rolling is used to solidify the overlapped Cu foams by passing additional rolls of Cu-shaped strips through a rolling roll in the vertical or vertical direction of the width of the sintered Cu foam sheet, i.e. in the direction of the force applied to the Cu foams in the installation. Roll bonding to bond is performed. The additional Cu foam attached at this time is pore size 1 mm or less, porosity 10 to 99% range. The additional Cu foam is passed through a rolling roll while increasing the number by the required strength. At this time, after fixing the gap of the rolling mill roll to a certain thickness, by changing the number of added Cu foam, both the thickness and the strength is easy to fit as desired.

The partial overlap rolling step is preferably secured by rolling at a reduction ratio within the range of 80% to 99% relative to the total thickness of the partially plated or partially overlapped Cu foam. If it is less than 80%, the Cu foams may not be in close contact with each other, resulting in the Cu foam on the surface side, or the result that the desired strength cannot be obtained. The schematic diagram about the said partial overlap rolling is shown in FIG. Referring to FIG. 3, when the rolling process is performed by overlapping a band, a strong tension is secured enough to be applied to a rewinding facility during battery electrode operation. Furthermore, a structure in which the electrode tab and the electrode current collector are integrated can be formed. After the above process can be precisely adjusted to the desired thickness through the final rolling.

The surface (top) of the porous copper manufactured by the partial overlap rolling process may refer to FIG. 4. In this regard, Figure 4 is a photograph observed with an optical microscope so that both the overlap rolled portion and the overlap rolled portion of the porous copper specimen according to Example 2 to be described later.

The overlap rolling part cut surface has a structure of a close contact form. This structure can be confirmed through FIG. 5 is a structure photograph of the overlap rolling part (a) and the overlap rolling part (b) of the Cu foam prepared according to Example 3 of the present invention to be described later with an optical microscope. It can be seen that there is no empty space between the overlapping Cu foams, and it is in close contact. Since the overlap-rolled portion has a close-type structure, the porous copper prepared according to the present invention has excellent strength compared to general porous copper and has a low electric resistance value, thereby enabling the flow of a large current.

FIG. 6 shows a schematic view of a plated portion or an overlap rolled portion of a porous Cu foam obtained by the method for producing a porous copper according to the present invention and an unplated portion or an unrolled portion. The part where plating or overlap rolling has not occurred is called an unplated part or an overlap rolling part, or a general part.

(F) final rolling

Final rolling is carried out to make the thickness of the product which has been subjected to the above-described process precise and constant. Since the thicknesses of the partially plated or partially overlapped rolling portions and the general portion (unplated or overlapped rolling portions) may be slightly different, it is advantageous to precisely match the final thickness of the product through final rolling.

Porous copper produced by the production process according to the invention

Porous copper prepared according to the present invention has the characteristics of light weight due to high porosity, heat dissipation utilizing a large specific surface area, and increased interface area. For this reason, it is advantageous for the lithium secondary battery negative electrode collector.

Porous copper made of a thin plate according to the present invention, the electrode portion and the electrode tab portion of the negative electrode current collector of the lithium secondary battery through the partial plating or partial overlap rolling or partial plating and partial overlap rolling process as described above Because it can be produced in the process, the process is simple, the cost can be reduced and excellent strength can be ensured.

According to the production method disclosed in the present invention, porous copper of 100 mm or more in width and 0.01 mm or more in thickness can be produced. In order to improve productivity in a lithium secondary battery production process, a porous metal having a width of 100 mm or more is advantageous. Also If the thickness of the porous copper is less than 0.01mm, it is difficult to secure more than 50% porosity. Since the higher the porosity, the higher the integration rate of the porous copper internal active material, porous copper having a porosity of 50% or more is suitable for increasing the energy density of the lithium secondary battery.

The porous copper has a tensile strength of 50N or more when measured with a 30 mm wide specimen. In order to apply the roll-to-roll method to the battery manufacturing process, the porous copper must have a minimum tensile value of 50 N or more, which is drawn by the present invention. Satisfies The higher the tension value, the faster the speed can be and the productivity can be increased.

The prepared porous copper may have an average grain size of 0.1 μm to 100 μm in a crystal grain size measured by a grain size analysis method using a field emission scanning electron microscope (FE-SEM). If the average grain size is less than 0.1 µm, the Cu particles are not sufficiently in contact with each other to obtain desired strength and electrical conductivity. If the average grain size is more than 100 µm, the grains are coarse to obtain sufficient strength. In addition, there is a disadvantage in that the bonding strength with the active material can be reduced when the lithium secondary battery negative electrode current collector is applied.

The weight per unit volume of the porous copper (Cu foam) prepared by the above method may have a weight of 50 μm or less. The weight of 50μm copper foil per unit volume is 0.0448g when 50μm thick copper foil is cut to 1x1cm size and weighed. It means having a weight of. If the weight per unit volume is more than 0.0448g, the amount of plated Cu metal particles is exceeded, and it is difficult to obtain desired light weight and porosity as a lithium secondary battery component.

Porous copper prepared by the method for producing porous copper according to the present invention continuously removes the organic components and residual carbon of the organic porous body in a heat treatment process to provide porous copper having no impurities on the surface and having a purity of 99.6% by weight or more. If the purity is less than 99.6% by weight, the electrical resistance is increased to cause a loss of current and the heat of resistance is increased to increase the internal temperature of the battery, increasing the risk of fire.

Porous copper according to the present invention is used as an electronic component, an electronic device heat dissipation material, a catalyst, a filter material, a sensor, a lithium secondary battery negative electrode current collector. Particularly suitable for a lithium secondary battery negative electrode current collector, which will be described in more detail below.

Made of porous copper produced by the production process according to the invention Lithium secondary battery  Cathode current collector

Porous copper produced by the production method according to the invention is particularly suitable as a negative electrode current collector of a lithium secondary battery. In this case, the negative electrode current collector of the lithium secondary battery may have an integrated electrode part and an electrode tab part. Porous copper produced by the manufacturing method according to the present invention is used as an electrode current collector by filling the active material slurry into the pores after applying the active material in the unplated or unrolled rolled part during the lithium secondary battery electrode manufacturing process, and then compressed. Alternatively, the overlap rolling part may be used as an electrode tab.

Porous copper produced by the production method according to the present invention can increase the tensile strength through partial plating or partial overlap rolling, while maintaining the pores of the unplated or overlapped rolling section, high strength, light weight and large specific surface area Provide simultaneously.

As described above, the porous copper produced by the manufacturing method according to the present invention has a tensile strength of 50 N or more, so that a mass production facility such as an active material applicator, a linear shearer, a winder, and the like is used in an electrode manufacturing process of a lithium secondary battery. Application is possible.

The weight of the porous copper produced by the manufacturing method according to the present invention, as described above, the weight of the copper foil 50㎛ level or less, that is, the weight of less than 0.0448g when weighed by cutting the 50㎛ thick copper foil to 1x1cm standard and Since the porosity is 50% or more, the specific surface area of the lithium secondary battery negative electrode collector is similar to that of an electrolytic copper foil, and the specific surface area is much higher. Specifically, the porous copper of the three-dimensional solid structure is used as the current collector to increase the contact area and binding force between the current collector and the active material, thereby overcoming the electrode short circuit problem affecting the fast charging performance, long lithium ion diffusion distance, and low electron transfer problem. Can overcome. In addition, by providing a high porosity, it is possible to increase the integration rate of the porous copper internal active material, thereby increasing the capacity (energy density) of the battery.

Example

Example 1

As the organic porous body, a polyurethane foam (3 mm (T) x 380 mm (W) x 320 mm (L), pore size 600 µm, manufactured by Sponge Mart) was used. The polyurethane foam was prepared by immersing in ethanol for 5 minutes and then immersed in distilled water for 15 seconds (step (A)).

The prepared polyurethane foam was subjected to induction treatment (SnCl ₂ · 2H ₂ O 150g / L, HCl 115mL / L, soaked in distilled water after soaking for 3 minutes), followed by activation treatment (PdCl 1.5g / L, HCl 75mL / L, 3 Distilled water was washed after dipping for a minute) to complete the electroless plating pretreatment process. Electroless plating The pretreated polyurethane foam was immersed in an electroless copper plating solution (CuSO ₄ 50g / L, Rotsel salt 125g / L, NaOH 10g / L, HCHO 8ml / L) for 5 minutes to plate copper 3㎛ on the surface of polyurethane. To impart conductivity, and the resulting polyurethane foam was immersed in distilled water for 15 seconds to wash (step (B)).

Subsequently, the obtained foam was subjected to electroplating (CuSO ₄ 160g / L, H ₂ SO ₄ 40ml, SP-95 additive 1.5mL / L, current density 30A / dm ² ) to obtain a Cu foam semifinished product having a final plating thickness of 10 μm. Was prepared (step (C)).

Subsequently, a semi-finished electroformed Cu foam product was charged into an atmosphere heat treatment furnace (Lindberg, 380Wx380Hx380D), and the polyurethane foam was incompletely burned under N ₂ atmosphere at a rate of 5 ° C./min up to 500 ° C. When the internal temperature of the furnace reached 500 ° C, the N ₂ gas supply was stopped and maintained for 5 minutes to remove the carbon remaining on the surface. After the N ₂ gas was introduced again, the temperature was raised to 900 ° C. at 3 ° C./min, and then maintained for 5 minutes to complete sintering (step (D)).

Subsequently, partial overlap rolling was performed on the completed Cu foam. Partial overlap rolling was performed in three parts on both sides and the center at 10% of the total width in the vertical direction of the Cu foam sheet width, and the overlap condition was 97% by overlapping 8 layers of Cu foam having the same shape as that prepared. Rolling was carried out at a reduction ratio of to form a final product of Cu foam having a thickness of 0.5 tons in the form of a partial strip (step (E)). The thickness of the finished product was fixed at 0.5t, and the number of overlaps of the Cu foam was adjusted to the final thickness according to the reduction ratio. Final rolling precisely adjusted the thickness of the final product to 0.5t and smoothed the surface (step (F)). 7 is a photograph of the finished Cu foam prepared according to Example 1.

Example 2

Cu foam semi-finished products were prepared in the same manner as in Example 1.

After charging the Cu foam semi-finished product in the atmosphere heat treatment furnace, and incomplete combustion of polyurethane foam in N ₂ atmosphere at a rate of 5 ℃ / min to 500 ℃. When the internal temperature of the furnace reached 500 ℃ to block the inflow of N ₂ gas and oxidized for 10 minutes, the N ₂ gas was introduced again to increase the temperature to 3 ℃ / min at 900 ℃ and then maintained for 10 minutes to complete the sintering.

After partially sintering rolling the Cu foam after sintering at 95% reduction rate, the final product is precisely adjusted to 0.5t and the surface is flattened by final rolling. The finished product was prepared.

Example 3

Cu foam semifinished product was prepared in the same manner as in Example 1 until the incomplete combustion after oxidation and sintering heat treatment. After partial sintering to the Cu foam which completed sintering, partial overlap rolling was performed at 80% of the reduction ratio. After the final rolling, the finished product was manufactured by precisely adjusting the thickness of the final product to 0.5t and flattening the surface.

Example 4

Cu foam semi-finished products were prepared in the same manner as in Example 1.

Subsequently, Cu foam semi-finished products were charged into the atmosphere heat treatment furnace, and the polyurethane foam was incompletely burned in an N ₂ atmosphere at a rate of 5 ° C./min up to 350 ° C. When the internal temperature of the furnace reached 350 ℃ to block the inflow of N ₂ gas and oxidized for 10 minutes, the N ₂ gas was introduced again to increase the temperature to 3 ℃ / min at 800 ℃ and maintained for 15 minutes to complete the sintering.

After partial sintering and partial overlap rolling at 90% reduction rate, the final product is precisely adjusted to 0.5t thickness and flattened surface. The finished product was prepared.

Example 5

Cu foam semi-finished products were prepared in the same manner as in Example 1.

After charging the Cu foam semi-finished product in the atmosphere heat treatment furnace, and incomplete combustion of polyurethane foam in N ₂ atmosphere at a rate of 5 ℃ / min to 570 ℃. When the internal temperature of the furnace reached 570 ℃, the inflow of N ₂ gas was blocked and oxidized for 10 minutes, the N ₂ gas was introduced again to increase the temperature to 3 ℃ / min to 750 ℃ and maintained for 15 minutes to complete sintering.

After the sintering completed, the Cu foam was partially rolled and rolled at 93% reduction rate, and finally, the final product was precisely set to a thickness of 0.5t and the surface was flattened. The finished product was prepared.

Comparative Example 1

Cu foam was prepared in the same manner as in Example 2, except that the sintering temperature was 700 ° C. and the holding time was reduced to 5 minutes.

Comparative Example 2

Cu foam was prepared in the same manner as in Example 1, but was prepared by reducing the incomplete combustion and oxidation heat treatment temperatures to 270 ° C.

Comparative Example 3

Cu foam was prepared in the same manner as in Example 1, but was prepared by increasing the incomplete combustion and oxidation heat treatment temperature to 650 ° C.

Comparative Example 4

Cu foam was prepared in the same manner as in Example 1, but only the sintering holding time was increased to 80 minutes.

Comparative example  5

Cu foam was prepared in the same manner as in Example 1, but no partial overlap rolling was performed.

Comparative Example 6

Cu foam was prepared in the same manner as in Example 1 except that the sintering temperature was increased to 970 ° C. and the holding time was increased to 15 minutes.

Comparative Example 7

Cu foam was prepared in the same manner as in Example 1, but was prepared by reducing the sintering temperature to 640 ℃.

Comparative Example 8

Cu foam was prepared in the same manner as in Example 1, but was prepared by reducing the overlap rolling reduction to 40%.

The process conditions of the said Examples 1-5 and Comparative Examples 1-8 are summarized in Table 1. 0.5T × 350W × 240L sized specimens were prepared for the test described below with Cu foam prepared according to each of Examples and Comparative Examples.

Test Example

Hereinafter, the method and results of the characterization of the porous copper specimens prepared according to the Examples and Comparative Examples will be described.

Tensile strength of each specimen was further processed to 30mm width and then measured by the ZWICK ROELL Z100 universal testing machine. The results are shown in Table 1 below.

The average grain size of the specimen microstructure was measured by using Quanta650FEG (FE-SEM) manufactured by FEI. In order to measure the average grain size, each specimen cut into a size of 10 mm x 10 mm was charged to the FE-SEM chamber, and the vacuum inside the chamber was maintained at 1x10 ^-5 or less, and the electron beam was irradiated to observe the crystal orientation analysis method.

When the weight per unit volume is measured by cutting the specimens according to the Examples and Comparative Examples to 1x1cm standard on the basis of 50μm thick copper foil, the results are all 0.0448g or less, which is 50μm thick copper foil mass, It described in 1.

The purity of Cu was measured using EDS (EDAX) installed in the Quanta650FEG (FE-SEM). As in the microstructure measurement, the specimen was charged into the chamber, and the component strength was obtained after maintaining the vacuum in the chamber at 1 × 10 ⁻⁵ or less. At this time, the measurement magnification was fixed at x 1000.

Table 1 shows the results of evaluation according to the above-described method for measuring Cu foam properties.

Heat treatment condition Increasing strength
Way Rolling condition evaluation Incomplete combustion / oxidation Sinter Heat Treatment Increasing strength
Way Rolling reduction
(%) Seal
burglar
(N) Average
decision
Particle diameter
(μm) Cu
water
(wt%) unit
Per volume
weight
(g) Temperature
( ^℃ ) maintain
time
(minute) Temperature
( ^℃ ) maintain
time
(minute) Example 1 500 5 900 5 Overlap rolling 97 125 6 99.7 0.00891 Example 2 500 10 900 10 Overlap rolling 95 114 15 99.8 0.00971 Example 3 500 10 900 10 Part plating 80 70 16 99.8 0.00890 EXAMPLE
4 350 10 800 15 Part plating
Rolled / overlap 90 123 22 99.8 0.00923 Example 5 570 10 750 15 Overlap rolling 93 93 18 99.7 0.00918 Comparative Example 1 500 10 700 5 Overlap rolling 95 37 - 99.6 0.01010 Comparative Example 2 270 5 900 5 Overlap rolling 97 - - 87.3 0.01214 Comparative Example 3 650 5 900 5 Overlap rolling 97 - - 72.1 - Comparative example
4 500 5 900 80 Overlap rolling 95 54 86 99.8 0.00955 Comparative Example 5 500 5 900 5 Not carried - 17 10 99.7 0.00913 Comparative Example 6 500 5 970 15 Overlap rolling 97 45 57 99.8 0.01108 Comparative Example 7 500 5 640 5 Overlap rolling 95 22 - 99.6 0.00924 Comparative Example 8 500 5 900 5 Overlap rolling 40 15 8 99.7 0.00948

In Table 1, in contrast to Example 1 and Comparative Example 4, Comparative Example 4 was subjected to sintering heat treatment for 80 minutes, the average grain size is increased by increasing the holding time of the sintering heat treatment compared to the specimen prepared according to Example 1 It can be seen that the tensile strength is lowered. In addition, when comparing Example 2 and Comparative Example 1 Comparative Example 1 in the manufacturing method of Example 2 reduced the sintering temperature to 700 ℃, the holding temperature to 5 minutes, due to the low sintering temperature crystal grains do not form properly It can be confirmed that there is difficulty in securing the tensile strength.

In addition, Comparative Example 2 is a condition in which the incomplete combustion and oxidation temperature was reduced to 270 ° C in Example 1, and due to the low temperature, the polyurethane foam could not be thermally decomposed to sufficiently oxidize carbon, and the remaining carbonization in the final product resulted in Cu. It can be seen that the purity of is slightly reduced.

On the other hand, Comparative Example 3 is a condition of increasing the incomplete combustion and oxidation temperature to 650 ℃ under the conditions of Example 1, the polyurethane foam was thermally decomposed after the thermal decomposition, a large amount of CuO and CuO ₂ remained on the surface even after sintering heat treatment . As a result, the brittleness was increased and the tensile strength could not be measured.

On the other hand, Comparative Example 5 was carried out in the same manner as in Example 1, but did not perform partial overlap rolling. As a result, it could be confirmed that the tensile strength was weak at 1/5 as compared to Example 1 at 17N.

On the other hand, Comparative Example 6 is a condition in which the sintering temperature was increased to 970 ° C. and the holding time was increased to 15 minutes under the conditions of Example 1, and at this time, the crystal grains coarsened due to the high sintering temperature, and thus the desired tensile strength could not be obtained.

On the other hand, Comparative Example 7 is a condition in which the sintering heat treatment temperature was reduced to 650 ° C. under the conditions of Example 1, in which crystal grains were not formed due to low sintering temperature, and thus grain size could not be measured. It was confirmed to have.

In addition, Comparative Example 8 is a condition in which the overlap rolling reduction rate was reduced to 40% under the conditions of Example 1, and at this time, dropping occurred in the overlapping Cu foam portions due to the low reduction ratio, and thus an increase in strength was not obtained.

On the other hand, the tensile strength evaluation results of Example 1 and Comparative Example 5 are shown in FIG. The overlap rolled Cu foam prepared by the method of Comparative Example 5 had a tensile strength of 17 N, while the overlap rolled Cu foam prepared by the method of Example 1 had a tensile strength similar to that of 10 µm of electrolytic copper foil at 125 N. I could confirm that I had.

9 is a surface FE-SEM photograph of the porous copper prepared according to the production method of Example 1 of the present invention, the average grain size of 6μm as a result of measuring the grain size of the porous copper surface by the grain size measurement method.

FIG. 10 is a graph showing EDS measurement results of surface components of porous copper prepared according to Example 2 of the present invention. FIG.

11 is a photograph of the surface shape of the final Cu foam product prepared under the conditions of Example 1 (a) and Comparative Example 2 (b) to Comparative Example 3 (c) of the present invention by FE-SEM. When the incomplete combustion and oxidation temperatures were less than 300 ° C and more than 600 ° C, respectively, the carbonized part and the oxidized part remained, so that a Cu foam having a desired high purity component could not be obtained.

12 shows the surface shape after electrolytic plating according to copper sulfate electroless plating thickness. 12 is a semi-finished product prepared in the same manner as in Example 1 except that the copper sulfate electroless plating time was changed to 20 seconds (a) and 20 minutes (b), respectively, and the thickness measured immediately after copper sulfate electroless plating was 0.3. It was 탆 and 6.0 탆. In the case of (a), the copper sulfate electroless plating time was short, and copper plating was not formed to cover the entire surface of the polyurethane foam, and in (b), the copper sulfate electroless plating time was too long to form a rough plating surface. Through this, the difference in surface after electrolytic plating according to the copper sulfate electroless plating thickness can be confirmed.

Claims (16)

As a method of manufacturing porous copper for a lithium secondary battery negative electrode current collector,
(A) preparing an organic porous body;
(B) pretreatment of the prepared organic porous body, followed by copper electroless plating, wherein copper electroless plating is performed by immersing the organic porous body in a copper sulfate electroless plating solution at 20 ° C. to 30 ° C. for 30 seconds to 10 minutes. step;
(C) copper electroplating the obtained product to produce a semi-electrolytic copper plated product, copper electroplating is immersed in a copper sulfate electrolytic plating solution, the product is 10 minutes to 10 minutes at a current density of 0.1 to 100 A / dm ² Performing by electroplating copper for time;
(D) heat treatment of the semifinished product, incomplete combustion of the semifinished product to remove the organic porous body, oxidation in an oxidizing atmosphere to remove carbon, and then sintering in an inert atmosphere, wherein the incomplete combustion is carried out in an N ₂ inert atmosphere. Heat treatment at a temperature increase rate of 5 ℃ / min from 300 ℃ to 600 ℃ to decompose the organic porous body, leaving only carbon in the surface layer, oxidation stops the injection of N ₂ gas after incomplete combustion, and maintained for 1 to 20 minutes, sintering Heating at 850 ° C. to 950 ° C. at an elevated temperature rate of 3 ° C./min in an N ₂ inert atmosphere and then holding for 1 to 20 minutes;
(E) partial plating, partial overlap rolling, or partial plating and partial stack rolling of copper on the obtained product; And
(F) final rolling step
Method for producing a porous copper for a lithium secondary battery negative electrode current collector comprising a. The method of claim 1,
The organic porous body is a method for producing porous copper in the form of open pores (open cell). The method of claim 1,
The thickness of the copper plating layer formed by the (B) electroless plating step is 0.5㎛ to 5.0㎛ manufacturing method of porous copper. The method of claim 1,
In the (B) electroless plating step, the pretreatment is a method for producing porous copper comprising an sensitization treatment and an activation treatment. The method of claim 1,
After the heat treatment step of the (D) semi-finished product, the surface of the product is Cu 99.6% by weight or more method for producing porous copper. The method of claim 1,
The step (E) is a method for producing porous copper, wherein 1% to 49% of the total area of the product obtained in the previous step is subjected to partial plating or partial overlap rolling or both. The method of claim 6,
The step (E) is a method for producing porous copper in the form of performing a strip-shaped partial plating or partial overlap rolling or both in the rolling direction or the vertical direction of the width. The method of claim 6,
The partial plating is performed for 10 minutes to 10 hours at a current density of 0.1 to 100 A / dm ^{2 in} the vertical direction of the width of the porous copper sheet which has been sintered. The method of claim 7, wherein
The step (E) is a rolling method with a rolling reduction of 80% to 99% of the total thickness of the overlapped porous copper. The method of claim 6,
The partial overlap rolling is a method for producing porous copper, which partially rolls additional porous copper having a pore size of 1 mm or less and a porosity of 98% or less in the vertical direction of the width of the porous copper sheet that has been sintered. A specimen prepared by the manufacturing method according to any one of claims 1 to 10, having a width of 100 mm or more, a thickness of 0.01 mm or more, and a width of 30 mm, having a tensile strength of 50 N or more, and a field emission type scan. Porous copper whose average grain size is 0.1 micrometer-100 micrometers in the crystal grain size measured by the crystal grain size analysis method by the electron microscope (FE-SEM). The method of claim 11,
The overlapping rolled portion or the unplated portion of the porous copper has a weight of 0.0448g or less when measured in a horizontal and vertical 1cm standard. The method of claim 11,
The cut surface of the overlap rolling part or plating part has a porous structure Copper. The lithium secondary battery negative electrode current collector of the porous copper according to claim 11, wherein the unrolled rolled portion or unplated portion is filled with an active material slurry to form an electrode portion, and the overlapped portion or plated portion is formed as an electrode tab portion. delete delete

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