KR102360274B1 - Method for manufacturing a cathode current collector in the form of a slurry - Google Patents

Abstract

The present invention relates to a method for manufacturing a positive electrode current collector in the form of a slurry. A method for manufacturing a positive electrode current collector in the form of a slurry according to an embodiment of the present invention comprises the steps of: (a) pulverizing a current collector material; (b) mixing the pulverized current collector material with a binder material to form a slurry; and (c) drying the formed slurry to form a positive electrode current collector.

Description

Method for manufacturing a cathode current collector in the form of a slurry

The present invention relates to a method for manufacturing a positive electrode current collector in a slurry form, and more particularly, to a method for manufacturing a positive electrode current collector in a slurry form using a current collector material pulverized in a powder form.

The secondary battery may be used as a charge/discharge battery based on OER and ORR reactions. In general, secondary batteries that perform OER and ORR reactions have problems in that a charging/discharging gap is large and power capacity is low.

This may be because the over-potential of the OER/ORR reaction, which is an anode reaction, is large, and thus the resistance increases, causing these problems.

For OER and ORR reactions, a carbon material with a high specific surface area (eg, carbon felt, carbon cloth, WIZMAC) is used, and among them, a carbon fiber called WIZMAC, which is a cloth type, is used as a current collector. material can be used.

In the conventional case, charging and discharging studies have been conducted using only WIZMAC in the form of cloth and a large specific surface area without a catalyst material, but there is a problem in that high charging and discharging characteristics are still displayed.

In addition, when charging and discharging for a long time, fine carbon fibers are separated by an electrochemical reaction to contaminate seawater, and there is a problem that such fine carbon materials may bring another environmental problem.

[Patent Document 1] Korean Patent Publication No. 10-2019-0120740

The present invention was created to solve the above problems, and an object of the present invention is to provide a method for manufacturing a positive electrode current collector in the form of a slurry.

Another object of the present invention is to provide a method for manufacturing a positive electrode current collector using a current collector material pulverized in a powder form.

Another object of the present invention is to provide a method for manufacturing a positive electrode current collector using a hydrophilic binder material.

Another object of the present invention is to provide a method for manufacturing a positive electrode current collector using ethanol as a solvent.

Objects of the present invention are not limited to the objects mentioned above, and other objects not mentioned will be clearly understood from the description below.

In order to achieve the above objects, a method for manufacturing a positive electrode current collector in the form of a slurry according to an embodiment of the present invention comprises the steps of: (a) pulverizing a current collector material; (b) mixing the pulverized current collector material with a binder material to form a slurry; and (c) drying the formed slurry to form a positive electrode current collector.

In an embodiment, the step (a) may include ball milling the current collector material to pulverize the current collector material in a powder form.

In an embodiment, the ball milling of the current collector material may be performed for 3 to 5 minutes.

In an embodiment, the binder material may include a hydrophilic binder material.

In an embodiment, the step (b) may include mixing the pulverized current collector material and the binder material with an ethanol solvent to form the slurry.

In an embodiment, the slurry may further include a catalyst material.

Specific details for achieving the above objects will become clear with reference to the embodiments to be described in detail below in conjunction with the accompanying drawings.

However, the present invention is not limited to the embodiments disclosed below, but may be configured in various different forms, and those of ordinary skill in the art to which the present invention pertains ( Hereinafter, "a person skilled in the art") is provided to fully inform the scope of the invention.

According to an embodiment of the present invention, by using a current collector material pulverized in a powder form and a hydrophilic binder material to prepare a positive electrode current collector in the form of a slurry, it is possible to prevent desorption from the solid electrolyte in water.

Effects of the present invention are not limited to the above-described effects, and potential effects expected by the technical features of the present invention will be clearly understood from the following description.

1 is a view showing a method for manufacturing a positive electrode current collector in the form of a slurry according to an embodiment of the present invention.
2A is a diagram illustrating a manufacturing process of a positive electrode current collector in the form of a slurry according to an embodiment of the present invention.
2B is a diagram illustrating a current collector material in a powder form according to an embodiment of the present invention.
3 is a view showing a coin-type secondary electrode using a positive electrode current collector according to an embodiment of the present invention.
4A to 4D are views illustrating a change in length of a current collector material in powder form with respect to various ball milling times according to an embodiment of the present invention.
5 is a view illustrating a graph showing a change in length of a current collector material in powder form with respect to various ball milling times according to an embodiment of the present invention.
6A and 6B are diagrams illustrating changes in slurry stability with respect to various ball milling times according to an embodiment of the present invention.
7A and 7B are diagrams illustrating changes in slurry stability for various binder materials according to an embodiment of the present invention.
8 is a diagram illustrating a power capacity graph according to an embodiment of the present invention.
9 is a diagram illustrating a manufacturing process of a pouch-type secondary battery according to an embodiment of the present invention.
10A is a diagram illustrating a power capacity graph of a pouch-type secondary battery using a slurry according to an embodiment of the present invention.
10B is a diagram showing a power capacity graph of a pouch-type secondary battery using a conventional cloth-type WIZMAC.
Figure 10c is a view showing the stability of the slurry in the pouch-type secondary anterior teeth according to an embodiment of the present invention.
11A and 11B are diagrams illustrating charge/discharge stability graphs of a pouch-type secondary battery according to an embodiment of the present invention.
12 is a view showing a surface of an anode according to an embodiment of the present invention.
13A is a diagram illustrating a WIZMAC-based BET surface area graph according to an embodiment of the present invention.
13B is a diagram illustrating a BET surface area graph based on ball milling according to an embodiment of the present invention.
14A and 14B are diagrams illustrating a CV graph according to an embodiment of the present invention.
15A and 15B are diagrams illustrating voltage change graphs for charging and discharging according to an embodiment of the present invention.

Since the present invention can have various changes and can have various embodiments, specific embodiments are illustrated in the drawings and described in detail.

Various features of the invention disclosed in the claims may be better understood upon consideration of the drawings and detailed description. The apparatus, methods, preparations, and various embodiments disclosed herein are provided for purposes of illustration. The disclosed structural and functional features are intended to enable those skilled in the art to specifically practice the various embodiments, and are not intended to limit the scope of the invention. The disclosed terms and sentences are for the purpose of easy-to-understand descriptions of various features of the disclosed invention, and are not intended to limit the scope of the invention.

In describing the present invention, if it is determined that a detailed description of a related known technology may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

Hereinafter, a method for manufacturing a positive electrode current collector in the form of a slurry according to an embodiment of the present invention will be described.

1 is a view showing a method for manufacturing a positive electrode current collector in the form of a slurry according to an embodiment of the present invention.

Referring to FIG. 1 , step S101 is a step of pulverizing the current collector material.

In an embodiment, the current collector material may be ball milled to pulverize the current collector material into a powder form. In this case, ball milling of the current collector material may be performed for 3 to 5 minutes.

In one embodiment, the binder material may include a hydrophilic binder material.

Step S103 is a step of mixing the pulverized current collector material with a binder material to form a slurry.

In an embodiment, the pulverized current collector material and the binder material may be mixed with an ethanol solvent to form the slurry. In one embodiment, the slurry may further include a catalyst material.

Step S105 is a step of drying the slurry to form a positive electrode current collector. That is, in the case of the method for manufacturing a positive electrode current collector in the form of a slurry according to the present invention, a hydrophilic-adhesive binder material is used for stable driving while simultaneously fixing the current collector material and the catalyst material, and the binder material and the catalyst material are used to the maximum. For this, it may be formed in the form of a slurry.

2A is a diagram illustrating a process 200 for manufacturing a positive electrode current collector in the form of a slurry according to an embodiment of the present invention. 2B is a diagram illustrating a current collector material in a powder form according to an embodiment of the present invention.

For example, referring to FIG. 2A , the process 200 for preparing the positive electrode current collector in the form of a slurry may include a grinding process 210 , a mixing process 220 , and a drying process 230 .

In the pulverization process 210 , the current collector material may be sonication. For example, the current collector material may include carbon fiber.

In one embodiment, referring to FIG. 2B , the current collector material may be pulverized in a powder form through ball milling for 3 minutes.

In the mixing process 220 , the pulverized current collector material, the binder material, and the catalyst material may be mixed with an ethanol solvent to form a slurry.

For example, the binder material may include a polymer binder material. Also, for example, the catalyst material may include a platinum/carbon (Pt/C) catalyst.

In this case, when forming the slurry, in the conventional case, NMP (N-methyl-2-pyrrolidone) or DMF is used as a solvent, whereas in the present invention, since ethanol is used as a solvent, toxicity is low and eco-friendly, and at room temperature Since the slurry can be dried in the , it is possible to reduce the time and energy consumed in manufacturing the positive electrode current collector.

In the drying process 230 , the slurry may be dried to form a positive electrode current collector.

In an embodiment, in the mesh bonding process 240 , the formed positive electrode current collector may be combined with the mesh material. Here, the mesh material may include a Ti mesh. In this case, the reason for loading the mesh material on the positive electrode current collector is that the current collector material is broken due to ball milling, and there is a binder that acts as an insulator. Also, by bonding the mesh material, the slurry can be made conductive.

In one embodiment, in the assembly process 250 , the positive electrode current collector to which the mesh material is coupled may be coupled to the coin-type secondary battery. In this case, the structure of the coin-type secondary battery and the combined structure of the positive electrode current collector will be described in detail with reference to FIG. 3 below.

In an embodiment, at least one of the respective steps shown in FIG. 2A may be omitted. For example, the mesh bonding process 240 and the assembling process 250 may be omitted depending on the embodiment.

3 is a view showing a coin-type secondary preposition 300 using a positive electrode current collector according to an embodiment of the present invention.

Referring to FIG. 3 , the coin-type secondary battery 300 may include a cell upper end 310 , a positive electrode current collector 320 , a negative electrode unit 330 , and a cell lower end 340 .

One surface of the positive electrode current collector 320 may be coupled to the cell upper end 310 , and the other surface of the positive electrode current collector 320 may be coupled to one surface of the negative electrode unit 330 .

Also, the positive electrode current collector 320 may be manufactured using a slurry formed using a current collector material pulverized in a powder form.

The negative electrode unit 330 may include at least one of a top cover (cap), a solid electrolyte, an organic electrolyte, sodium metal, a spring, and a bottom cover. The cell lower end 340 may be coupled to the other surface of the negative electrode unit 330 .

Referring to FIG. 3 , the coin-type secondary battery 300 may include a cell upper end 310 , a positive electrode current collector 320 , a negative electrode unit 330 , and a cell lower end 340 . In various embodiments of the present invention, the coin-type secondary battery 300 is not essential to the configurations described in FIG. 3, so it has more configurations than the configurations described in FIG. 3, or to be implemented as having fewer configurations. can

In addition, in the case of FIG. 3 , although the positive electrode current collector 320 according to the present invention is applied to the coin-type secondary battery 300 , the shape of the secondary battery to which the positive electrode current collector 320 is applied is not limited and may be implemented in various forms. can be

4A to 4D are views illustrating a change in the length of a current collector material in powder form with respect to various ball milling times according to an embodiment of the present invention. 5 is a view illustrating a graph showing a change in length of a current collector material in powder form with respect to various ball milling times according to an embodiment of the present invention.

4A to 4D , the current collector material may be pulverized into a powder form by ball milling the current collector material for 3 minutes, 5 minutes, 10 minutes, and 15 minutes, respectively.

In this case, it can be seen that the length of the current collector material pulverized in powder form is changed according to the ball milling time, and as the ball milling time increases, the length of the current collector material becomes shorter, and thus the stability of the slurry in water increases. can confirm.

, 39.38

, 33.10

로 시간이 증가할수록 길이는 짧아짐을 확인할 수 있다. For example, referring to FIG. 5 , when the ball milling times are 5 minutes, 10 minutes, and 15 minutes, the length of each pulverized current collector material is 42.68

, 39.38

, 33.10

It can be seen that the length decreases as time increases.

6A and 6B are diagrams illustrating changes in slurry stability with respect to various ball milling times according to an embodiment of the present invention.

Referring to FIGS. 6A and 6B , it can be seen that the slurry stability changes with respect to various ball milling times when the hydrophilic-adhesive binder material is used.

That is, the slurry ball milled for 3 minutes as shown in FIG. 6a does not separate from the solid electrolyte (eg NASICON) when impregnated in water and the shape does not change even during the drying process, but as shown in FIG. 6b, the slurry ball milled for 20 minutes When immersed in water, it is separated from the solid electrolyte and it can be confirmed that the shape is deformed as it is dried and rolled up.

In other words, in a state in which the amount of the hydrophilic-adhesive binder used is fixed, as the length of the current collector material pulverized in powder form decreases, the amount of the current collector material capable of binding decreases, so that desorption may occur.

In one embodiment, it can be seen that the ball-milled slurry for 3 to 5 minutes has excellent stability in water that does not desorb. That is, a stable network may be formed by strongly forming a bond between the binder material, the pulverized current collector material, and the binder and the solid electrolyte.

When a current collector material with an increased ball milling time is used, desorption does not occur when the content of the binder material is increased, but it is determined that it can act as an insulator when the content of the binder material is increased Thus, it is possible to use a minimum amount of binder material and perform size optimization through ball milling.

7A and 7B are diagrams illustrating changes in slurry stability for various binder materials according to an embodiment of the present invention.

Referring to FIGS. 7A and 7B , when ball milling is performed for 3 minutes, slurry stability can be confirmed when a hydrophilic binder material is used and when a hydrophobic binder material is used.

Referring to FIG. 7b, when a slurry is prepared using a hydrophobic binder material, the hydrophobic binder material melts and separates upon contact with water. It can be confirmed that all are separated at the same time as the application is applied.

On the other hand, as shown in FIG. 7A , when the slurry is prepared using the hydrophilic binder material according to the present invention, it can be confirmed that the slurry is not separated even when it comes into contact with water.

In this case, even if the amount of the hydrophobic binder material is greater than the amount of the hydrophilic binder material, when the hydrophobic binder material is used, it can be confirmed that desorption from water occurs.

That is, in the case of a secondary battery used in water (eg, seawater), it can be confirmed that the stability of the slurry and the characteristics of the secondary battery are determined by the type of the binder material.

Therefore, it can be confirmed that the stability of the slurry according to the present invention is affected by both the type of the binder material and the length of the pulverized current collector material.

8 is a diagram illustrating a power capacity graph according to an embodiment of the present invention.

Referring to FIG. 8 , the power capacity of the coin-type secondary battery to which the slurry according to the present invention is applied can be confirmed.

In this case, when using the positive electrode current collector to which the slurry type is applied as in the present invention, the power capacity is higher than when using the cloth type WIZMAC (9 to 10 mW) for the positive electrode current collector as in the prior art. can be verified.

This may be due to the activation of charge/discharge due to the ORR catalyst, Pt/C. In addition, since the current collector material is in the form of powder rather than in the form of cloth, the specific surface area of the positive electrode current collector is widened, which may be because an area capable of reacting is increased. In addition, since it is possible to increase the amount of loading of the current collector material compared to the conventional WIZMAC in the form of cloth, it may be because the OER (oxygen evolution reaction)/ORR (oxygen reduction reaction) reaction rate increases.

As described above, it can be confirmed that the coin-type secondary battery to which the slurry according to the present invention is applied has a similar power capacity to that of the hydrophilic-adhesive binder material to which the non-slurry is applied.

9 is a view showing a pouch-type secondary battery manufacturing process 900 according to an embodiment of the present invention.

Referring to FIG. 9 , the pouch-type secondary battery manufacturing process 900 may include a pasting process 910 , a drying process 920 , and a bonding process 930 .

In the pasting process 910 , a slurry prepared in the form of a paste by mixing a pulverized current collector material, a binder material, a catalyst material, and ethanol may be coated on one surface of the solid electrolyte of the pouch-type secondary battery.

In this case, since the resistance of the electrode is reduced when the slurry is coated over a large area, the slurry must be coated as wide as possible.

In the drying process 920 , the coated slurry may be dried to form a positive electrode current collector. In one embodiment, the drying process 920 may be performed at room temperature.

In the bonding process 930 , a pouch-type secondary battery may be manufactured by combining the titanium mesh and the frame member on the formed positive electrode current collector.

10A is a diagram illustrating a power capacity graph of a pouch-type secondary battery using a slurry according to an embodiment of the present invention. 10B is a diagram showing a power capacity graph of a pouch-type secondary battery using a conventional cloth-type WIZMAC. Figure 10c is a view showing the stability of the slurry in the pouch-type secondary anterior teeth according to an embodiment of the present invention.

Referring to FIGS. 10A and 10B , a comparison of the power of the pouch-type secondary battery using the slurry according to the present invention and the pouch-type secondary battery using the conventional cloth-type WIZMAC can be confirmed.

In this case, it can be confirmed that the pouch-type secondary battery using the slurry according to the present invention has a larger power capacity than the pouch-type secondary battery using the conventional cloth-type WIZMAC. For example, according to the present invention, it can be confirmed that ~40mW power capacity is improved compared to the conventional technique, which is due to the activation of the discharge due to the ORR catalyst Pt/C, and the current collector material is formed in a powder form. This may be because the charge/discharge site increased due to the increase of the specific surface area.

In addition, at this time, referring to FIG. 10C , it can be confirmed that the slurry is not separated in the pouch-type secondary battery using the slurry according to the present invention even before and after the power capacity test.

11A and 11B are diagrams illustrating charge/discharge stability graphs of a pouch-type secondary battery according to an embodiment of the present invention.

11A and 11B, it can be seen that the secondary battery using the slurry according to the present invention has a smaller overpotential than the secondary battery using the conventional cloth-type WIZMAC. Here, the overvoltage may mean a difference in voltage during charging and discharging of the secondary battery.

Here, as the overvoltage is smaller, it may mean that the polarization, which means the sum of resistances applied to the secondary preposition, is smaller. That is, it may mean that the resistance of the secondary battery is small.

At this time, the small difference in voltage, that is, the small charging/discharging gap, means that the energy efficiency that appears during charging and discharging is large, and the slurry type has a smaller energy loss during charging and discharging compared to the cloth type. When used as a battery, it may indicate excellent power capacity and stability.

In other words, as in the present invention, since the secondary battery using the slurry has a small overvoltage, it can be used as a secondary battery with higher efficiency.

12 is a view showing a surface of an anode according to an embodiment of the present invention.

Referring to FIG. 12 , when charging in a positive electrode having a high surface area, anions are agglomerated due to electrostatic interaction on the surface of the electrode, and cations solvated thereon This accumulation may occur. This accumulation allows it to perform the function of storing electric charge like a capacitor.

This charging layer has the effect of flowing charges as it falls during discharging, and it shows a phenomenon in which the charges flow in accordance with the change in voltage.

Since this phenomenon occurs in the current collector, the electrode having a larger surface area may form more charging layers. That is, if the specific surface area of the current collector is increased, a secondary battery showing good cycle performance can be manufactured. In one embodiment, this phenomenon may be referred to as an electric double layer capacitor (EDLC).

In one embodiment, the specific surface area is widely increased through ball milling, thereby resulting in better cycle performance than before ball milling.

In an embodiment, the BET surface area may be measured through physisorption analysis to determine whether the specific surface area is increased through ball milling.

13A is a diagram illustrating a WIZMAC-based BET surface area graph according to an embodiment of the present invention. 13B is a diagram illustrating a BET surface area graph based on ball milling according to an embodiment of the present invention.

Referring to Figure 13a, it can be confirmed the WIZMAC carbon cloth BET surface area measurement results. Referring to Figure 13b, it can be confirmed the ball milling carbon cloth BET surface area measurement results.

In one embodiment, it can be seen that the BET surface area is 1934.3 m ² /g after ball milling, which is significantly increased compared to 1787 m ² /g before ball milling. Through this, it can be confirmed that the performance of EDLC is further increased, and it exhibits more stable cycle performance compared to carbon cloth.

In an embodiment, the porous structure may be confirmed through the remodeling of the graphs shown in FIGS. 13A and 13B . In the porous structure, in the case of micropores, it may mean a pore having a diameter of 2 nm or less, and in the case of a mesopore, it may mean a pore structure having a diameter of 2 nm to 50 nm.

In one embodiment, when the relative pressure forms a plateau up to 1.0, it may mean that adsorption/desorption occurs in the micropore. Both graphs show the micropore structure, but in the case of ball milling powder, the micropore structure increases due to the increase in the cross-sectional area by ball milling, which may increase the BET surface area.

14A and 14B are diagrams illustrating a CV graph according to an embodiment of the present invention.

Referring to FIGS. 14A and 14B , cyclic voltammetry (CV) and chronoamperometry may be used to determine the charge amount (Q) and the unit coulomb (C). This value can be calculated by integrating the current with respect to time by the following <Equation 1>.

This information can be used to indicate the amount electrically plated or stripped, the adsorption range, the electrochemical surface area of the working electrode, and the concentration of the analyte. In addition, it can be an important factor in a wide range of applications such as electroplating, electroanalytical chemistry, electrochemical catalysts, and capacitors.

Also, referring to FIGS. 14A and 14B , it can be confirmed that the degree of EDLC is compared through CV. The voltage range may be 0 to 0.3V based on the Ag/AgCl reference electrode.

In this case, the area in the CV graph may mean the amount of charge, and it may be possible to calculate the amount of charge in the EDLC by calculating the area in an appropriate charge/discharge range. At this time, it can be seen that a larger value is shown compared to the bare WIZMAC fabric through area calculation.

15A and 15B are diagrams illustrating voltage change graphs for charging and discharging according to an embodiment of the present invention.

Referring to FIGS. 15A and 15B , charging and discharging are performed while changing the current in a galvanostatic charge/discharge experiment, and the resulting change in voltage can be confirmed. This may be in order to determine the formation information of the EDLC according to the current.

In this case, in the case of WIZMAC, it can be seen that the voltage gap widens as the current increases. However, in the case of the slurry, it can be seen that the voltage difference does not appear much.

This may be because the formation of EDLC in the micropore structure can occur easily because the effect of being pushed due to electrostatic interaction is less than that formed in the micropore structure, and thus stable formation is possible even at a fast reaction rate. Therefore, it is possible to stably form EDLC even at low and high currents, and it can be stably driven even at high currents compared to WIZMAC cloth.

The above description is merely illustrative of the technical spirit of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention.

Accordingly, the embodiments disclosed in the present specification are not intended to limit the technical spirit of the present invention, but to illustrate, and the scope of the present invention is not limited by these embodiments.

The protection scope of the present invention should be interpreted by the claims, and all technical ideas within the scope equivalent thereto should be understood to be included in the scope of the present invention.

200: positive electrode current collector manufacturing process
210: grinding process
220: mixing process
230: drying process
300: coin type secondary preposition
310: cell top
320: positive current collector
330: cathode
340: cell bottom
900: pouch-type secondary battery manufacturing process
910: Pasting process
920: drying process
930: bonding process

Claims (6)

(a) grinding the current collector material;
(b) mixing the pulverized current collector material with a binder material to form a slurry;
(c) drying the formed slurry to form a positive electrode current collector; and
(d) combining the positive electrode current collector with a titanium (Ti) mesh material
includes,
The step (a) is,
Pow the current collector material by ball milling the current collector material
It comprises the step of pulverizing in powder form,
Ball milling of the current collector material is performed for 3 to 5 minutes,
The current collector material is carbon fiber,
The binder material is a hydrophilic binder material,
A method for manufacturing a positive electrode current collector in the form of a slurry.
delete delete delete According to claim 1,
The step (b) is,
mixing the pulverized current collector material and the binder material with an ethanol solvent to form the slurry;
containing,
A method for manufacturing a positive electrode current collector in the form of a slurry.
According to claim 1,
The slurry further comprises a catalyst material,
A method for manufacturing a positive electrode current collector in the form of a slurry.

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