KR20220026789A - Method for manufacturing electrode - Google Patents

Abstract

A method for manufacturing an electrode according to an embodiment of the present invention includes the steps of: forming an active material layer by applying slurry containing electrode active materials on a current collector; and adding a conductive material to the active material layer. The step of adding a conductive material includes a step of distributing the conductive material between the electrode active materials by spraying a dispersion containing the conductive material on the active material layer.

Description

Electrode manufacturing method {METHOD FOR MANUFACTURING ELECTRODE}

The present invention relates to a method for manufacturing an electrode, and more particularly, to a method for manufacturing an electrode for a secondary battery.

Recently, interest in energy storage technology is increasing. Efforts for research and development of electrochemical devices are becoming more concrete as the field of application expands to cell phones, camcorders, notebook PCs, and even the energy of electric vehicles.

Electrochemical devices are receiving the most attention in this aspect, and among them, the development of rechargeable batteries capable of charging and discharging is the focus of interest. In recent years, in the development of secondary batteries, research and development on the design of new electrodes and batteries in order to improve capacity density and specific energy have been actively carried out.

Among the currently applied secondary batteries, lithium secondary batteries developed in the early 1990s have a higher operating voltage and significantly higher energy density than conventional batteries such as Ni-MH, Ni-Cd, and lead sulfate batteries that use aqueous electrolyte solutions. is in the spotlight as

While expectations for these electrochemical devices are increasing, further improvements such as low resistance, high capacity, and improvement of mechanical properties and productivity are required for these electrochemical devices along with the expansion and development of uses. In such a situation, the manufacturing method with higher productivity is calculated|required also about the electrode for electrochemical elements.

The electrode for electrochemical elements is a thing formed by laminating|stacking the electrode active material layer formed by binding an electrode active material and the electrically conductive material used as needed normally with a binder on an electrical power collector normally. In other words, the electrode may be manufactured by applying a slurry for a coating electrode including an electrode active material, a binder, a conductive material, etc. on a current collector and removing the solvent by heat or the like.

Specifically, for the production of the positive electrode and the negative electrode, a mixing process of mixing raw materials, as well as coating, drying, roll pressing, taping, slitting, etc. go through the processes. In this case, the mixing process is a process of mixing raw materials such as an electrode active material, a conductive material, and a binder to make a slurry in a uniform state. However, in such a mixing process, process problems such as aggregation may occur when the conductive material is input. That is, there is a great difficulty in dispersing the conductive material. Conductive materials having a large surface area and high surface tension, especially dispersing force, have a very strong tendency to agglomerate, so it is very difficult to uniformly disperse the conductive material in the mixture. In order to maintain the cell performance, attempts have been made, such as adding an excessive amount of a conductive material with large particles, but there is still a limit to the dispersion of the conductive material. The conductive material is added to improve the conductivity between the electrode active materials, and when a phenomenon such as agglomeration occurs, there is a problem in that the desired conductivity is not secured even after the coating process or the roll pressing process.

There is a high need for development of a method for manufacturing an electrode capable of improving dispersibility of a conductive material and thus suppressing an increase in electrode resistance.

An object of the present invention is to provide a method of manufacturing an electrode capable of improving the dispersibility of a conductive material.

However, the problems to be solved by the embodiments of the present invention are not limited to the above problems and may be variously expanded within the scope of the technical idea included in the present invention.

A method of manufacturing an electrode according to an embodiment of the present invention includes forming an active material layer by applying a slurry containing an electrode active material on a current collector; and adding a conductive material to the active material layer. The adding of the conductive material may include distributing the conductive material between the electrode active materials by spraying a dispersion containing the conductive material on the active material layer.

The adding of the conductive material may include a high-pressure spraying step of spraying the dispersion at a high pressure and a low-pressure spraying step of spraying the dispersion at a low pressure.

In the step of adding the conductive material, the dispersion may be sprayed at a pressure of 1 kgf/cm ² or more and 50 kgf/cm ² or less.

The adding of the conductive material may include a high-pressure spraying step of spraying the dispersion at a pressure of 10 kgf/cm ² or more and 50 kgf/cm ² or less.

The adding of the conductive material may include a low-pressure spraying step of spraying the dispersion at a pressure of 1 kgf/cm ² or more and less than 10 kgf/cm ² .

The method of manufacturing the electrode may further include a low pressure maintaining step of maintaining the current collector and the active material layer in a low pressure state, and the low pressure state may be an atmospheric pressure of 100 nPa or more and 100 kPa or less.

The method of manufacturing the electrode may further include a heating step of heating the current collector and the active material layer, and the heating temperature in the heating step may be 30 degrees Celsius or more and 150 degrees Celsius or less.

The adding of the conductive material may include spraying the dispersion in a liquid plasma method.

The dispersion may be prepared by adding the conductive material to a solvent, and the solvent may include N-Methyl-2-pyrrolidone (NMP) or Deionized (DI) Water.

The dispersion may include CMC (Carboxymethyl Cellulose).

The dispersion may be sprayed into particles of 1 nm or more and 50 μm or less.

According to embodiments of the present invention, the conductive material may be evenly distributed between the electrode active materials by adding the conductive material by a spraying method instead of a mixing and applying method.

Effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

1 is a schematic view showing a method of manufacturing an electrode according to an embodiment of the present invention.
2 is an enlarged view of the active material layer in order to explain the effect of the high-pressure spraying step according to an embodiment of the present invention.
3 is an enlarged view showing the active material layer in order to explain the effect of the low-pressure spraying step according to an embodiment of the present invention.
4 is a schematic view for explaining a low pressure maintaining step according to an embodiment of the present invention.
5 is a view for explaining a heating step of performing heating according to an embodiment of the present invention.
6 is a view for explaining that the low pressure maintaining step and the heating step are sequentially performed according to an embodiment of the present invention.
7 is a cross-sectional perspective view for explaining a liquid plasma method according to another embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings, various embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. The present invention may be embodied in several different forms and is not limited to the embodiments described herein.

In order to clearly explain the present invention, parts irrelevant to the description are omitted, and the same reference numerals are assigned to the same or similar components throughout the specification.

In addition, since the size and thickness of each component shown in the drawings are arbitrarily indicated for convenience of description, the present invention is not necessarily limited to the illustrated bar. In order to clearly express various layers and regions in the drawings, the thicknesses are enlarged. And in the drawings, for convenience of description, the thickness of some layers and regions are exaggerated.

Also, when a part of a layer, film, region, plate, etc. is said to be “on” or “on” another part, it includes not only cases where it is “directly on” another part, but also cases where there is another part in between. . Conversely, when we say that a part is "just above" another part, we mean that there is no other part in the middle. In addition, to be "on" or "on" the reference part means to be located above or below the reference part, and to necessarily mean to be located "on" or "on" in the direction opposite to gravity not.

In addition, throughout the specification, when a part "includes" a certain component, this means that other components may be further included, rather than excluding other components, unless otherwise stated.

In addition, throughout the specification, when referring to "planar", it means when the target part is viewed from above, and "cross-sectional" means when viewed from the side when a cross-section of the target part is vertically cut.

1 is a schematic view showing a method of manufacturing an electrode according to an embodiment of the present invention.

Referring to FIG. 1 , in the method of manufacturing an electrode according to an embodiment of the present invention, a slurry 100 including an electrode active material is applied on a current collector 200 to form an active material layer 100L, and an active material and adding a conductive material to the layer 100L. In this case, the step of adding the conductive material includes distributing the conductive material between the electrode active materials by spraying the dispersion 300 including the conductive material on the active material layer 100L.

The current collector 200 is a rectangular metal sheet, and may be continuously moved in one direction by a device such as a roller 20 .

There is no particular limitation on the application method of the slurry 100 including the electrode active material, but the slurry 100 may be applied on the current collector 200 continuously moving in one direction using the die coater 10 .

The electrode according to the present invention may be a positive electrode or a negative electrode, and when the electrode is a positive electrode, the electrode active material may be a positive electrode active material, and when the electrode is a negative electrode, the electrode active material may be a negative electrode active material. That is, the method for manufacturing the electrode according to the present invention is not particularly limited to the positive electrode and the negative electrode and can be easily applied to any electrode manufacturing, depending on the material (eg, positive electrode active material or negative electrode active material) used for manufacturing each electrode. Different electrodes can be made.

The positive electrode active material may include a layered compound such as lithium cobalt oxide (LiCoO ₂ ) and lithium nickel oxide (LiNiO ₂ ) or a compound substituted with one or more transition metals; Lithium manganese oxides such as Formula Li _1+x Mn _2-x O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , and LiMnO ₂ ; lithium copper oxide (Li ₂ CuO ₂ ); vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , and Cu ₂ V ₂ O ₇ ; Ni site-type lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ (wherein M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3); Formula LiMn _2-x M _x O ₂ (where M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li ₂ Mn ₃ MO ₈ (where M = Fe, Co, lithium manganese composite oxide represented by Ni, Cu or Zn; LiMn ₂ O ₄ in which a part of Li in the formula is substituted with an alkaline earth metal ion; disulfide compounds; Although Fe2 _{(MoO4)3 etc. are} mentioned, It is not limited only to these.

Examples of the negative electrode active material include carbon such as non-graphitizable carbon and graphitic carbon; Li _x Fe ₂ O ₃ (0≤x≤1), Li _x WO ₂ (0≤x≤1), Sn _x Me _1-x Me' _y O _z (Me: Mn, Fe, Pb, Ge; Me' : metal composite oxides such as Al, B, P, Si, elements of Groups 1, 2, and 3 of the periodic table, halogen; 0<x≤1;1≤y≤3;1≤z≤8); lithium metal; lithium alloy; silicon-based alloys; tin-based alloy; SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ , metal oxides such as Bi ₂ O ₅ ; conductive polymers such as polyacetylene; A Li-Co-Ni-based material or the like can be used.

The conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, graphite, such as natural graphite and artificial graphite; carbon black, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskeys such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

The dispersion 300 may be prepared by adding the conductive material to a solvent. The solvent may include N-Methyl-2-pyrrolidone (NMP) or Deionized (DI) Water. Specifically, when the prepared electrode is a positive electrode, the solvent may include N-Methyl-2-pyrrolidone (NMP). When the prepared electrode is a negative electrode, the solvent may include DI (deionized) water.

Meanwhile, Carboxymethyl Cellulose (CMC) may be further added to the dispersion 300 to improve the dispersibility of the conductive material.

Meanwhile, the step of adding the conductive material according to the present embodiment may include a high-pressure spraying step of spraying the dispersion 300 at a high pressure and a low-pressure spraying step of spraying the dispersion 300 at a low pressure.

Specifically, the dispersion 300 may be sprayed onto the active material layer 100L at a predetermined pressure by using the spraying device 30 spaced apart from the active material layer 100L by a predetermined interval. At this time, the injection device 30 may adjust the pressure of the dispersion liquid 300 to be sprayed, and the step of adding the conductive material according to the present embodiment includes the high-pressure spraying step and the low-pressure spraying step, the dispersion 300 can be sprayed at different pressures at each stage.

In the conventional case, a slurry was prepared by mixing an electrode active material and a conductive material through a mixing process, and then applied to a current collector to prepare an electrode. However, the conductive material having a large dispersing force has a very strong tendency to agglomerate, so it is very difficult to uniformly disperse the conductive material in the mixture. For this reason, there is a problem in that the conductive material is not evenly distributed in the manufactured electrode, and it is not possible to secure the desired conductivity.

In the electrode manufacturing method according to the present embodiment, the dispersion 300 containing the conductive material is sprayed at a predetermined pressure on the already applied active material layer 100L, rather than mixing the conductive material in advance with the electrode active material or the like. This may allow the conductive material to be evenly distributed in the active material layer 100L.

In addition, in forming the active material layer 100L by applying the slurry 100 , since the electrode active material and the like are distributed in three dimensions, a large number of pores exist in the gaps therebetween. The pores existing in the electrode may be filled with an electrolyte in the secondary battery to become a passage for ions and the like. At this time, when the dispersion 300 is sprayed according to the present embodiment, the sprayed dispersion 300 can be evenly distributed in the pores formed in the active material layer 100L, which can be more effective in improving conductivity.

In addition, since the manufacturing method of the electrode according to the present embodiment uses a spraying method, the size, number, or distribution of pores of the electrode are analyzed, and the size of the particles of the dispersion 300 or the sprayed pressure are adjusted accordingly. can In other words, by adjusting the size of the particles of the dispersion 300 or the sprayed pressure according to the pores of the prepared electrode, the dispersion 300 can be evenly distributed between the pores of the electrode. The size of the particles of the dispersion 300 may vary depending on the distribution or size of the pores of the electrode, but is preferably 1 nm or more and 50 μm or less. In addition, the pressure of the sprayed dispersion 300 may be 1kgf/cm ^{2 or more and 50 kgf/cm 2 or} less. If the pressure of the sprayed dispersion is less than 1 kgf/cm ² , it is difficult to distribute the dispersion to the inside of the active material layer 100L because the spraying pressure is weak. On the other hand, the pressure of the sprayed dispersion is 50 kgf/cm ² If it exceeds, the injection pressure may be too strong to damage the active material layer 100L. Meanwhile, in this embodiment, the distance d between the active material layer 100L and the injection device 30 may be 10 μm or more and 0.1 m or less. In consideration of the above-described pressure range for spraying the dispersion 300 , the dispersion 300 must be sprayed within the range of the distance d to be evenly distributed.

On the other hand, as a comparative example of the present invention, a form of application such as simply flowing or applying the dispersion 300 to the active material layer 100L may be proposed. Since the active material layer 100L in which the pores are formed has a certain thickness, it is difficult to evenly distribute the conductive material between the electrode active materials as a whole only by applying the dispersion 300 on the surface thereof. Alternatively, the method for manufacturing the electrode according to the present embodiment may include the high-pressure injection step or the low-pressure injection step, so that the dispersion 300 may be sprayed at a different pressure for each step.

Hereinafter, effects of the high-pressure injection step or the low-pressure injection step will be described together with reference to FIGS. 2 and 3 . 2 is an enlarged view showing an active material layer to explain the effect of the high-pressure spraying step according to an embodiment of the present invention, and FIG. 3 is an active material to explain the effect of the low-pressure spraying step according to an embodiment of the present invention. This is an enlarged view of the layers.

First, as a high-pressure spraying step, the step of adding a conductive material according to an embodiment of the present invention may include a high-pressure spraying step of spraying the dispersion 300 at a pressure of 10 kgf/cm ² or more and 50 kgf/cm ² or less. there is. At this time, referring to FIG. 2, by allowing the dispersion 300 to permeate to the deep part of the active material layer 100L in which the pores 100P are distributed through the high-pressure spraying step, the active material layer close to the current collector 200 in cross section It is possible to evenly distribute the conductive material up to the inner side of (100L).

Next, as a low-pressure spraying step, the step of adding the conductive material according to an embodiment of the present invention may include a low-pressure spraying step of spraying the dispersion at a pressure of 1 kgf/cm ² or more and less than 10 kgf/cm ² . At this time, referring to FIG. 3, by allowing the dispersion 300 to evenly permeate the surface of the active material layer 100L in which the pores 100P are distributed through the low-pressure spraying step, the active material layer 100L in cross section conducts the outside of the conductive material Ash can be evenly distributed.

The electrode manufacturing method according to the present embodiment, by appropriately utilizing the high-pressure injection step and the low-pressure injection step, more evenly the dispersion 300 containing the conductive material in the pores 100P of the active material layer 100L of the electrode. can be distributed. If compared with the comparative example of the present invention, such as simply flowing or applying the dispersion 300 to the active material layer 100L, the effects of the high-pressure spraying step and the low-pressure spraying step according to this embodiment may be more clear.

4 is a schematic diagram for explaining a low pressure maintenance step according to an embodiment of the present invention. 5 is a view for explaining a heating step of performing heating according to an embodiment of the present invention. 6 is a view for explaining that the low pressure maintaining step and the heating step are sequentially performed according to an embodiment of the present invention.

First, referring to FIG. 4 , the method of manufacturing an electrode according to an embodiment of the present invention may include a low pressure maintaining step of maintaining the current collector 200 and the active material layer 100L in a low pressure state. Specifically, a predetermined section may be maintained in a low pressure state with respect to the active material layer 100L and the current collector 200 moving in one direction. Here, the low pressure may be a pressure of 100 nPa (nanopascal) or more and 100 kPa (kilopascal) or less. More preferably, the low pressure state may be a vacuum state, and specifically, a pressure of 100 nPa or more and 3 kPa or less.

In this case, the low pressure maintaining step may be continued from before the dispersion 300 is sprayed to after the dispersion 300 is sprayed. That is, it can be maintained in a low pressure state by the atmospheric pressure setting equipment in the low pressure maintaining area (A) shown in FIG. The barometric pressure setting device is not particularly limited as long as the barometric pressure can be adjusted.

According to this embodiment, the dispersion 300 may be sprayed onto the active material layer 100L while the low pressure state is maintained. After that, when the low pressure state, particularly the vacuum state, is released, the dispersion 300 injected due to the changed atmospheric pressure may be evenly distributed inside the pores 100P.

Meanwhile, referring to FIG. 5 , the method of manufacturing an electrode according to an embodiment of the present invention may include a heating step of heating the current collector 200 and the active material layer 100L. Specifically, heat may be applied to a predetermined section with respect to the active material layer 100L and the current collector 200 moving in one direction. In this case, the heating temperature may be 30 degrees Celsius or more and 150 degrees Celsius or less.

In this case, the heating step is performed simultaneously with the spraying of the dispersion 300 , and may continue until after the dispersion 300 is sprayed. That is, heat may be applied by heating equipment in the heating zone B shown in FIG. 5 . The heating equipment is not particularly limited as long as it can apply heat or increase the temperature. In the heating step according to the present embodiment, when heat is applied to the active material layer 100L onto which the dispersion 300 is sprayed, the dispersion 300 may be evenly spread inside the pores 100P by the thermal energy.

Meanwhile, referring to FIG. 6 , in the method of manufacturing an electrode according to another embodiment of the present invention, the low pressure maintaining step and the heating step may be sequentially performed.

Specifically, the low pressure maintenance step of maintaining the active material layer 100L and the current collector 200 in a low pressure state may be continued from before the dispersion liquid 300 is sprayed to immediately after the dispersion liquid 300 is sprayed. That is, it can be maintained in a low pressure state by the atmospheric pressure setting equipment in the marked low pressure maintenance area (A'). Immediately after the dispersion 300 is sprayed, the low pressure maintenance is released, and a heating step of heating the active material layer 100L and the current collector 200 may be followed. That is, heat may be applied by the heating equipment in the indicated heating zone (B').

According to this embodiment, as the low pressure maintaining step and the heating step are sequentially performed, the dispersion 300 may be evenly distributed in the pores 100P.

7 is a cross-sectional perspective view for explaining a liquid plasma method according to another embodiment of the present invention.

Referring to FIG. 7 , the step of adding the conductive material according to another embodiment of the present invention may include spraying the dispersion 300 in a liquid plasma method.

Specifically, the dispersion liquid 300 may be designed to move the flow path P passing between the two electrodes 510 and 520 . The dielectric 530 is disposed between the first electrode 510 and the second electrode 520 , and the dispersion liquid passes through the first electrode 510 , the dielectric 530 , and the second electrode 520 sequentially and then to the outside. It may be designed to be discharged. The two electrodes 510 and 520 may be connected to a power supply unit 540 capable of applying a voltage, respectively. A DC, AC, bidirectional or unidirectional pulse voltage may be applied between the two electrodes 510 and 520 .

By applying a high voltage of 300V or more between the two electrodes 510 and 520 , a liquid plasma may be generated based on the dispersion 300 . In other words, when the dispersion liquid 300 moves through the flow path P, a high voltage is applied between the two electrodes 510 and 520 to generate plasma based on the dispersion liquid 300 . The plasma thus generated may be discharged toward the active material layer 100L (refer to FIG. 1 ) applied on the current collector 200 (refer to FIG. 1 ).

When the dispersion 300 is sprayed in this liquid plasma method, when the size of the pores on the surface of the active material layer 100L is small or the degree of distribution of the pores is low, the dispersion 300 containing the conductive material between the small pores can easily penetrate. Therefore, it can be effective for the distribution of the conductive material.

In this embodiment, terms indicating directions such as front, rear, left, right, up, and down are used, but these terms are for convenience of explanation only, and may vary depending on the location of the object or the position of the observer. .

Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also provided. is within the scope of the

100: slurry
100L: active material layer
200: current collector
300: dispersion

Claims (11)

forming an active material layer by applying a slurry containing an electrode active material on a current collector; and
adding a conductive material to the active material layer;
The adding of the conductive material comprises distributing the conductive material between the electrode active materials by spraying a dispersion containing the conductive material on the active material layer. In claim 1,
The step of adding the conductive material includes a high-pressure spraying step of spraying the dispersion at a high pressure and a low-pressure spraying step of spraying the dispersion at a low pressure. In claim 1,
In the step of adding the conductive material, the dispersion is 1kgf/cm ² or more and 50kgf/cm ² or less. A method of manufacturing an electrode in which the pressure is sprayed. In claim 1,
The step of adding the conductive material includes a high-pressure spraying step of spraying the dispersion at a pressure of 10 kgf/cm ² or more and 50 kgf/cm ² or less. In claim 1,
The adding of the conductive material includes a low-pressure spraying step of spraying the dispersion at a pressure of 1 kgf/cm ² or more and less than 10 kgf/cm ² . In claim 1,
Further comprising a low pressure maintaining step of maintaining the current collector and the active material layer in a low pressure state,
The method of manufacturing an electrode wherein the low pressure state is an atmospheric pressure of 100 nPa or more and 100 kPa or less. In claim 1,
Further comprising a heating step of heating the current collector and the active material layer,
In the heating step, the heating temperature is 30 degrees Celsius or more and 150 degrees Celsius or less. In claim 1,
The adding of the conductive material may include spraying the dispersion liquid in a liquid plasma method. In claim 1,
The dispersion is prepared by adding the conductive material to a solvent,
The solvent is a method of manufacturing an electrode comprising NMP (N-Methyl-2-pyrrolidone) or DI (Deionized) Water. In claim 9,
The dispersion is a method of manufacturing an electrode comprising CMC (Carboxymethyl Cellulose). In claim 1,
The method of manufacturing an electrode in which the dispersion is sprayed with particles of 1 nm or more and 50 μm or less.

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