WO2025009098A1 - Method for producing electrode for secondary battery - Google Patents

Abstract

In the present invention, in order to produce an electrode in a small number of steps, powder layers (102c, 104c) are formed by applying a powder of an active substance and a powder of a binder-containing binding agent to the surface of collectors (102a, 104a) and then the binder is melted to form active layers (102b, 104b).

Description

Method for manufacturing secondary battery electrodes

The present invention relates to a method for manufacturing electrodes for secondary batteries.

A method for manufacturing an electrode catalyst layer for a secondary battery is known in which a first ink containing an active material and a conductive agent but no binder is ejected by an inkjet method, and then a second ink containing a binder but no active material or conductive agent is ejected by an inkjet method (Patent Document 1).

Patent No. 4720176

However, if the first ink containing the active material and conductive agent and the second ink containing the binder are sprayed separately as in the above-mentioned conventional technology, two ink preparation steps are required, as well as two ink drying steps, resulting in a problem of a large number of steps.

The problem that this invention aims to solve is to provide a method for manufacturing electrodes for secondary batteries that can be produced with a small number of steps.

The present invention solves the above problem by scattering an active material powder and a binder powder containing a binder on the surface of a current collector to form a powder layer, and then melting the binder contained in the powder layer to form an active material layer.

According to the present invention, electrodes are manufactured through a process of forming a powder layer and a process of melting the binder, so electrodes can be manufactured with a small number of processes.

1 is a plan view showing an example of a secondary battery to which an embodiment of a method for manufacturing a secondary battery electrode according to the present invention can be applied; FIG. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 2 is an enlarged cross-sectional view showing a part of the power generating element of FIG. 1 . 1A to 1C are process diagrams showing an embodiment of a method for producing an electrode for a secondary battery according to the present invention. 5A to 5C are process diagrams showing another embodiment of the method for producing an electrode for a secondary battery according to the present invention. 5A to 5C are process diagrams showing still another embodiment of the method for producing an electrode for a secondary battery according to the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<Structure of secondary battery>
First, an example of the structure of a secondary battery 10 to which an embodiment of the manufacturing method of an electrode according to the present invention can be applied will be described. Fig. 1 is a plan view showing the secondary battery 10 of this example, and Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1. Note that the structure of the secondary battery 10 shown in the figure is not limited to the structures shown in Figs. 1 and 2, and may be applied to secondary batteries of other structures.

As shown in Figures 1 and 2, the secondary battery 10 of this example is composed of a power generating element 101 having three positive electrode layers 102, seven electrolyte layers 103, and three negative electrode layers 104, positive electrode tabs 105 connected to each of the three positive electrode layers 102, negative electrode tabs 106 connected to each of the three negative electrode layers 104, and an upper exterior member 107 and a lower exterior member 108 that house and seal the power generating element 101, positive electrode tabs 105, and negative electrode tabs 106.

The number of positive electrode layers 102, electrolyte layers 103, and negative electrode layers 104 is not particularly limited, and the power generating element 101 may be composed of one positive electrode layer 102, three electrolyte layers 103, and one negative electrode layer 104, or the number of positive electrode layers 102, electrolyte layers 103, and negative electrode layers 104 may be appropriately selected as necessary.

The positive electrode layer 102 has a positive electrode side collector 102a extending to the positive electrode tab 105, and a positive electrode active material layer 102b formed on each of the two main surfaces of the positive electrode side collector 102a. The positive electrode side collector 102a can be made of an electrochemically stable metal foil such as aluminum foil, aluminum alloy foil, copper titanium foil, stainless steel foil, etc. Metals that can be used to make the positive electrode side collector 102a include nickel, iron, copper, etc., as well as clad materials of nickel and aluminum, clad materials of copper and aluminum, etc. The positive electrode side collector 102a is not limited to metal materials, and can also be made of conductive resin, and the conductive resin can be a resin obtained by adding a conductive filler to a non-conductive polymer material as necessary.

The positive electrode active material constituting the positive electrode active material layer 102b is not particularly limited, but examples thereof include layered rock salt type active materials such as LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiVO ₂ , and Li(Ni-Mn-Co)O ₂ , spinel type active materials such as LiMn ₂ O ₄ and LiNi _0.5 Mn _1.5 O _{4 ,} olivine type active materials such as LiFePO ₄ and LiMnPO ₄ , and Si-containing active materials such as Li ₂ FeSiO ₄ and Li ₂ MnSiO ₄ . In addition, examples of oxide active materials other than those mentioned above include Li ₄ Ti ₅ O ₁₂ . A composite oxide containing lithium and nickel is preferably used, and more preferably Li(Ni-Mn-Co) _O2 and those in which a part of these transition metals is replaced by other elements (hereinafter, also simply referred to as "NMC composite oxide"). NMC composite oxides also include composite oxides in which a part of the transition metal element is replaced by other metal elements. In this case, examples of the other elements include Ti, Zr, Nb, W, and P. In addition, a positive electrode active material other than the above may be used.

The shape of the positive electrode active material may be, for example, particulate (spherical, fibrous), thin film, etc. The amount of the positive electrode active material in the positive electrode active material layer 102b is not particularly limited. The positive electrode active material layer 102b may further contain a conductive additive as necessary. The conductive additive forms an electron conduction path and reduces the electron transfer resistance of the positive electrode active material layer 102b and the negative electrode active material layer 104b, which can contribute to improving the output characteristics of the battery at high rates.

The conductive assistant includes, but is not limited to, metals such as aluminum, stainless steel, silver, gold, copper, and titanium, alloys or metal oxides containing these metals, carbon fibers (specifically, vapor-grown carbon fibers (VGCF), etc.), carbon nanotubes (CNT), carbon nanofibers, and carbon black (specifically, acetylene black, Ketjen Black (registered trademark), furnace black, channel black, thermal lamp black, etc.), but is not limited to these. In addition, particulate ceramic materials and resin materials coated with the above-mentioned metal materials by plating or the like can also be used as conductive assistants. Among these conductive assistants, from the viewpoint of electrical stability, it is preferable to include at least one selected from the group consisting of aluminum, stainless steel, silver, gold, copper, titanium, and carbon, more preferably to include at least one selected from the group consisting of aluminum, stainless steel, silver, gold, and carbon, and even more preferably to include at least one selected from the group consisting of carbon. These conductive assistants may be used alone or in combination of two or more.

The conductive assistant is preferably particulate or fibrous in shape. When the conductive assistant is particulate, the shape of the particles is not particularly limited, and may be any shape, such as powder, sphere, rod, needle, plate, column, irregular shape, scale, spindle shape, etc.

In the secondary battery 10 of this example, each of the three positive electrode collectors 102a constituting the three positive electrode layers 102 is joined to one positive electrode tab 105. The positive electrode tab 105 can be made of aluminum foil, aluminum alloy foil, copper foil, nickel foil, or the like.

The negative electrode layer 104 has a negative electrode side current collector 104a that extends to the negative electrode tab 106, and a negative electrode active material layer 104b formed on each of the two main surfaces of the negative electrode side current collector 104a. The negative electrode side current collector 104a can be made of an electrochemically stable metal foil such as nickel foil, copper foil, stainless steel foil, or iron foil.

The negative electrode active material constituting the negative electrode active material layer 104b is not particularly limited, but may include carbon materials, metal oxides, and metal active materials. Examples of carbon materials include natural graphite, artificial graphite, mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon. Examples of metal oxides include Nb ₂ O ₅ , Li ₄ Ti ₅ O ₁₂ , and SiO. Examples of metal active materials include metal elements such as In, Al, Si, and Sn, and alloys such as TiSi and La ₃ Ni ₂ Sn ₇ .

The negative electrode active material may be a metal containing Li, and such a negative electrode active material is not particularly limited as long as it is an active material containing Li, and may be Li metal or a lithium alloy containing Li. Examples of lithium alloys include alloys of lithium and at least one metal selected from gold (Au), magnesium (Mg), aluminum (Al), calcium (Ca), zinc (Zn), tin (Sn), and bismuth (Bi). Examples of lithium alloys include alloys of lithium and two or more of the above-mentioned metals. Specific examples of lithium alloys include lithium-gold alloy (Li-Au), lithium-magnesium alloy (Li-Mg), lithium-aluminum alloy (Li-Al), lithium-calcium alloy (Li-Ca), lithium-zinc alloy (Li-Zn), lithium-tin alloy (Li-Sn), and lithium-bismuth alloy (Li-Bi).

In the secondary battery 10 of this embodiment, the three negative electrode layers 104 are configured such that each negative electrode side current collector 104 a constituting the negative electrode layer 104 is joined to a single negative electrode tab 106 .
In the secondary battery 10 of this example, each of the three negative electrode collectors 104a constituting the three negative electrode layers 104 is joined to one negative electrode tab 106. As the negative electrode tab 106, a copper foil, a copper alloy foil, a copper and nickel clad material foil, or the like can be used.

The electrolyte layer 103 is a layer in which an electrolyte is held in the separator 103a, and is located between the positive electrode active material layer 102b and the negative electrode active material layer 104b to prevent direct contact between the two. The separator 103a in this example has the function of holding the electrolyte to ensure lithium ion conductivity between the positive electrode layer 102 and the negative electrode layer 104, and the function of acting as a partition between the positive electrode layer 102 and the negative electrode layer 104. Examples of the separator 103a in this example include a porous sheet separator made of a polymer or fiber that absorbs and holds the electrolyte, and a nonwoven fabric separator.

The electrolyte used in the electrolyte layer 103 in this example is not particularly limited, and examples include an electrolyte solution or a gel polymer electrolyte. By using these electrolytes, high lithium ion conductivity can be ensured.

The positive electrode layer 102 and the negative electrode layer 104 are alternately stacked with the electrolyte layer 103 interposed therebetween, and the electrolyte layer 103 is further stacked on the top and bottom layers, respectively, thereby forming the power generating element 101.

The power generating element 101 configured as described above is housed and sealed in an upper exterior member 107 and a lower exterior member 108. The upper exterior member 107 and the lower exterior member 108 for sealing the power generating element 101 are formed of a flexible material, for example, a resin film such as polyethylene or polypropylene, or a resin-metal thin film laminate material in which both sides of a metal foil such as aluminum are laminated with a resin such as polyethylene or polypropylene, and by heat-sealing the upper exterior member 107 and the lower exterior member 108, the power generating element 101 is sealed with the positive electrode tab 105 and the negative electrode tab 106 protruding to the outside.

Note that the positive electrode tab 105 and the negative electrode tab 106 are provided with a sealing film 109 at the portions in contact with the upper exterior member 107 and the lower exterior member 108 in order to ensure adhesion with the upper exterior member 107 and the lower exterior member 108. The sealing film 109 is not particularly limited, but can be made of a synthetic resin material with excellent electrolyte resistance and heat fusion properties, such as polyethylene, modified polyethylene, polypropylene, modified polypropylene, or ionomer.

<Electrode manufacturing method>
Next, an embodiment of a method for manufacturing an electrode for a secondary battery according to the present invention will be described. Fig. 3 is an enlarged cross-sectional view showing a part of the power generating element 101 in Fig. 1, showing a basic unit structure in which one positive electrode layer 102 and one negative electrode layer 104 are laminated with one electrolyte layer 103 interposed therebetween. As described above, the positive electrode layer 102 has a positive electrode active material layer 102b formed on both sides of a positive electrode side current collector 102a, and the negative electrode layer 104 has a negative electrode active material layer 104b formed on both sides of a negative electrode side current collector 104a. The electrolyte layer 103 is made of a separator 103a that holds an electrolyte.

In the manufacturing method of the secondary battery electrode of this embodiment (hereinafter also simply referred to as the manufacturing method), when forming the positive electrode active material layer 102b on the surface of the positive electrode collector 102a and/or when forming the negative electrode active material layer 104b on the surface of the negative electrode collector 104a, a powder of the active material and a powder of a binder containing a binder are spread (laid) on the surface of the collector to form a powder layer (first step), and then the powder layer is pressed to melt the binder and form an active material layer (second step).

That is, instead of applying a paste or slurry-like active material to which a binder has been added onto the surface of the current collector, a powdered active material without added binder and a powdered binder-containing binder are spread on the surface of the current collector to form a powdered powder layer, and then this powdered powder layer is pressed and the binder is melted to obtain an active material layer. More specifically, regarding the positive electrode layer 102, a powdered positive electrode active material without added binder and a powdered binder-containing binder are spread on the surface of the positive electrode side current collector 102a to form a powdered positive electrode powder layer, and then this powdered positive electrode powder layer is pressed while applying temperature to obtain the positive electrode active material layer 102b. Similarly, more specifically, the negative electrode layer 104 is formed by scattering a powdered negative electrode active material without the addition of a binder and a powdered binding agent containing a binder on the surface of the negative electrode side current collector 104a to form a powdered negative electrode powder layer, and then pressing this powdered negative electrode powder layer while applying heat to obtain the negative electrode active material layer 104b.

FIG. 4 is a process diagram showing one embodiment of a method for manufacturing electrodes for secondary batteries according to the present invention. In the manufacturing process of this embodiment, a conveyor device 21 is provided that transports the positive electrode side collector 102a or the negative electrode side collector 104a at a constant speed in the direction of the arrow. The sheet-shaped positive electrode side collector 102a or the negative electrode side collector 104a is transported at a constant speed from the left side to the right side of FIG. 4, and processing is carried out in the order of the first process and then the second process.

In the first step shown on the left side of FIG. 4, when the positive electrode layer 102 is manufactured, a mixed powder of a powdered positive electrode active material without the addition of a binder and a powdered binding agent containing a binder is spread on the surface of the positive electrode side current collector 102a to form a powdered positive electrode powder layer 102c. Similarly, when the negative electrode layer 104 is manufactured, a mixed powder of a powdered negative electrode active material without the addition of a binder and a powdered binding agent containing a binder is spread on the surface of the negative electrode side current collector 104a to form a powdered negative electrode powder layer 104c. The manufacturing methods for the positive electrode layer 102 and the negative electrode layer 104 are the same except for the materials used, so in the following explanation, the manufacturing method of this embodiment will be explained using the case of manufacturing the positive electrode layer 102 as an example.

In this specification, the term "powder" refers to an aggregate of particles (including granulated particles) in which the components present in the system are substantially solid, and the aggregate is defined as including at least one of particle units and aggregates in which a plurality of particles are aggregated. For example, if a relatively large amount of liquid components is present and the system is in a solution state, slurry state, or paste state, it is not a "powder". As long as it satisfies this definition, the powder may contain a liquid component such as an electrolyte. From the viewpoint of separating the aggregated particles and dispersing them uniformly on the surface of the current collector, it is preferable that the powder is a dry powder that does not contain a liquid component. From the viewpoint of easily adjusting the particle size, the powder made of solid particles may be a wet powder that contains a liquid component such as an electrolyte (preferably an electrolyte). The content of the liquid component in this case is not particularly limited as long as the "powder" state is maintained, but is preferably 0 to 10 mass%, more preferably 0.01 to 8 mass%, even more preferably 0.1 to 5 mass%, and particularly preferably 0.1 to 3 mass% relative to 100 mass% of the powder made of solid particles.

As described above, the positive electrode active material may be LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiVO ₂ , Li(Ni-Mn-Co)O ₂ or other layered rock salt type active material, LiMn ₂ O ₄ , LiNi _0.5 Mn _1.5 O ₄ or other spinel type active material, LiFePO ₄ , LiMnPO ₄ or other olivine type active material, Li ₂ FeSiO ₄ , Li ₂ MnSiO ₄ or other Si-containing active material, Li ₄ Ti ₅ O ₁₂ or other. As described above, the negative electrode active material may be carbon material, metal oxide, or metal active material. In addition, a conductive assistant is added to the positive electrode active material or the negative electrode active material as necessary, and as described above, the conductive assistant may be metal, metal oxide, carbon, or the like. The binder is not particularly limited, but examples thereof include polyvinylidene fluoride (PVdF) and a complex of polyvinylidene fluoride and hexafluoropropylene (HFP).

Furthermore, components contained in the binding agent include, in addition to the binders mentioned above, fibrous carbon materials such as carbon fibers such as vapor grown carbon fibers (VGCF), carbon nanotubes (CNTs), and carbon nanofibers. These fibrous carbon materials have the effect of increasing the entanglement between the powdered active material and powdered conductive additive and the powdered binder.

In the first step of the manufacturing method of this embodiment, a powder of positive electrode active material, a powder of negative electrode active material, a powder of conductive additive, and a powder of binding agent containing a binder and a fibrous carbon material are prepared, and these powders are spread on the surface of the positive electrode side current collector 102a using the powder spreader 22 shown in Figure 4.

The volume average particle diameter D50 of the positive electrode active material powder and the negative electrode active material powder is not particularly limited, but if the particle diameter of the powder is too large, the gap between the particles will be large, which is thought to cause an increase in the resistance value, so it is preferably 310 μm or less, preferably 300 μm or less, more preferably 280 μm or less, even more preferably 240 μm or less, even more preferably 200 μm or less, and particularly preferably 180 μm or less. The lower limit of the volume average particle diameter D50 of the powder particles is not particularly limited, but if the particle diameter is too small, the fluidity will be poor and it will be difficult to form the electrode when making the electrode, so it is preferably 43 μm or more, more preferably 45 μm or more, even more preferably 50 μm or more, and particularly preferably 100 μm or more. The average particle diameter (primary particle diameter) of the conductive assistant is not particularly limited, but from the viewpoint of the electrical characteristics of the battery, it is preferably 0.01 to 10 μm. Furthermore, the average particle size (primary particle size) of the binder contained in the binding agent is not particularly limited, but from the viewpoint of producing a low-resistance positive electrode layer, it is more preferable that it is smaller than the average particle size of the conductive assistant.

The device for scattering the powder of the positive electrode active material, the powder of the negative electrode active material, the powder of the conductive additive, and the powder of the binder including the binder and fibrous carbon material on the surface of the current collector is not particularly limited, and any device capable of scattering the powder with a uniform film thickness will suffice. In the illustrated powder scattering device 22, a vibration of a predetermined frequency is applied to the stored powder, causing a fixed amount of powder to fall from the end per unit time.

In the first step shown in FIG. 4, a mixed powder of a positive electrode active material powder, a conductive additive powder, and a binder powder is stored in a powder spraying device 22, and vibration is applied to this mixed powder to simultaneously spray the positive electrode active material powder, the conductive additive powder, and the binder powder onto the surface of the positive electrode collector 102a. As a result, a positive electrode powder layer 102c is formed on the surface of the positive electrode collector 102a. This positive electrode powder layer 102c is a deposit of dry powder or wet powder with a very small amount of liquid component.

In the second step shown on the right side of FIG. 4, a press device 24 is used to melt (or soften) the binder contained in the binding agent. Examples of the press device 24 include a one-sided roll press as shown in the figure, a twin roll press in which the workpiece is passed between two rollers, and a flat plate press in which the workpiece is pressed by two flat plates. It is preferable that the press device 24 is equipped with a heating means. As a result, a positive electrode active material layer 102b is formed on the surface of the positive electrode side current collector 102a.

By carrying out the above-mentioned first and second steps, a positive electrode active material layer 102b is formed on one surface of the positive electrode collector 102a. The positive electrode collector 102a is then turned over, and the same first and second steps are carried out on the other surface of the positive electrode collector 102a to produce the positive electrode layer 102 shown in FIG. 3. The same applies to the negative electrode layer 104.

<<Another embodiment of the method for manufacturing an electrode>>
In the manufacturing method of the embodiment shown in Fig. 4, when forming the positive electrode powder layer 102c, a mixed powder of a positive electrode active material powder, a conductive assistant powder, and a binder powder is simultaneously spread on the surface of the positive electrode side current collector 102a using a powder spreader 22, but the manufacturing method of the present invention is not limited to this process, and the positive electrode active material powder, the conductive assistant powder, and the binder powder may be spread separately without being mixed. Fig. 5 is a process diagram showing another embodiment of the manufacturing method of a secondary battery electrode according to the present invention.

In contrast, in the manufacturing method of the embodiment shown in FIG. 5, in the first step on the left side, a mixed powder of positive electrode active material powder and conductive additive powder is contained in powder sprayer 22, and binder powder is contained in powder sprayer 23. Like powder sprayer 22 shown in FIG. 4, the illustrated powder sprayer 22 applies vibrations of a predetermined frequency to the contained powder, causing a constant amount of powder to fall from an end per unit time. In contrast, the illustrated powder sprayer 23 applies a supply pressure to the contained powder to spray the powder under pressure. In other words, powder sprayer 23 can spray the powder under pressure at a higher pressure than powder sprayer 22, which sprays powder by natural fall.

Then, the powder is vibrated by the powder sprayer 22 to spray the mixed powder of the positive electrode active material powder and the conductive additive powder onto the surface of the positive electrode side current collector 102a. Next, the binder powder is sprayed under pressure by the powder sprayer 23 onto the surface of the positive electrode side current collector 102a onto which the mixed powder of the positive electrode active material powder and the conductive additive powder has been sprayed. This allows the binder powder to penetrate deep into the mixed powder of the positive electrode active material powder and the conductive additive powder sprayed onto the surface of the positive electrode side current collector 102a, improving the dispersibility of the binder.

In the manufacturing method of the embodiment shown in FIG. 5, when forming the positive electrode powder layer 102c, a mixed powder of a positive electrode active material powder and a conductive additive powder is simultaneously spread on the surface of the positive electrode side current collector 102a using a powder spreader 22, but the manufacturing method of the present invention is not limited to this process, and the positive electrode active material powder and the conductive additive powder may be spread separately without being mixed. FIG. 6 is a process diagram showing another embodiment of the manufacturing method of a secondary battery electrode according to the present invention.

In the manufacturing method of the embodiment shown in FIG. 6, in the first step on the left side, the powder of the positive electrode active material is accommodated in the powder spraying device 22, the powder of the conductive assistant is accommodated in the powder spraying device 25, and vibration is applied to each powder, so that the powder of the positive electrode active material and the powder of the conductive assistant are separately sprayed on the surface of the positive electrode side collector 102a. In this case, the powder of the positive electrode active material may be sprayed on the surface of the positive electrode side collector 102a, and then the powder of the conductive assistant may be sprayed on the surface of the positive electrode side collector 102a, or the powder of the conductive assistant may be sprayed on the surface of the positive electrode side collector 102a, and then the powder of the positive electrode active material may be sprayed on the surface of the positive electrode side collector 102a. However, the dispersion of the positive electrode active material and the conductive assistant in the positive electrode powder layer 102c formed after spraying is better when the powder with a larger particle size is sprayed first and then the powder with a smaller particle size is sprayed.

Then, in the first step, a powder spraying device 23 sprays binder powder under pressure onto the surface of the positive electrode collector 102a on which the mixed powder of the positive electrode active material powder and the conductive additive powder has been sprayed.

As described above, the manufacturing method of this embodiment includes a first step of dispersing a powder of a positive electrode active material and a powder of a binder containing a binder on the surface of the positive electrode collector 102a to form a positive electrode powder layer 102c, and a second step of melting the binder contained in the positive electrode powder layer 102c to form a positive electrode active material layer 102b, so that a positive electrode can be manufactured with fewer steps. Similarly, the manufacturing method of this embodiment includes a first step of dispersing a powder of a negative electrode active material and a powder of a binder containing a binder on the surface of the negative electrode collector 104a to form a negative electrode powder layer 104c, and a second step of melting the binder contained in the negative electrode powder layer 104c to form a negative electrode active material layer 104b, so that a negative electrode can be manufactured with fewer steps.

Furthermore, according to the manufacturing method of this embodiment, in the first step, the positive electrode powder layer 102c or the negative electrode powder layer 104c is formed by scattering a mixed powder of active material powder and binder powder on the surface of the current collector, which can improve the dispersibility of the binder.

Furthermore, according to the manufacturing method of this embodiment, in the first step, the positive electrode powder layer 102c or the negative electrode powder layer 104c is formed by first scattering an active material powder on the surface of the current collector, and then scattering a binder powder on the surface of the current collector, or by first scattering a binder powder on the surface of the current collector, and then scattering an active material powder on the surface of the current collector, so that the step of mixing the active material and the binder can be omitted.

Furthermore, according to the manufacturing method of this embodiment, the binder powder is pressurized and dispersed in the first step, which improves the mixing ability with the previously dispersed active material powder.

Furthermore, according to the manufacturing method of this embodiment, in the first step, the powder of the active material is pressurized and sprayed on the surface of the current collector at a first pressure, and then the powder of the binder is pressurized and sprayed on the surface of the current collector at a second pressure that is greater than the first pressure, thereby improving the mixing ability with the powder of the active material that was sprayed earlier.

Furthermore, according to the manufacturing method of this embodiment, in the first step, the powder of the active material is mixed with a powder of a conductive additive, so that an electron conduction path is formed, and the electron transfer resistance of the positive electrode active material layer 102b and the negative electrode active material layer 104b is reduced, thereby improving the output characteristics of the battery at high rates.

In addition, according to the manufacturing method of this embodiment, the average particle size of the binder powder is smaller than the average particle size of the conductive additive powder, so a positive electrode with lower resistance (higher performance) can be obtained.

In addition, according to the manufacturing method of this embodiment, the binder contains binder powder and fibrous carbon material, which can enhance the entanglement between the powdered active material and powdered conductive additive and the powdered binder.

Furthermore, according to the manufacturing method of this embodiment, in the second step, the powder layer is hot-pressed, so shape characteristics such as the thickness of the active material layer can be set at the same time as the binder is melted.

In addition, according to the manufacturing method of this embodiment, one electrode, either the positive electrode or the negative electrode, manufactured as described above, and the other electrode, either the positive electrode or the negative electrode, manufactured as described above, are stacked via a separator 103a, so that a secondary battery in which cracking of the electrodes is suppressed can be provided.

REFERENCE SIGNS LIST 10... Secondary battery 101... Power generating element 102... Positive electrode layer 102a... Positive electrode side collector 102b... Positive electrode active material layer 102c... Positive electrode powder layer 103... Electrolyte layer 103a... Separator 104... Negative electrode layer 104a... Negative electrode side collector 104b... Negative electrode active material layer 104c... Negative electrode powder layer 105... Positive electrode tab 106... Negative electrode tab 107... Upper exterior member 108... Lower exterior member 109... Sealing film 21... Conveyor device 22, 23, 25... Powder spraying device 24... Press device

Claims (11)

a first step of scattering an active material powder and a binder powder containing a binder on a surface of a current collector to form a powder layer;
a second step of melting the binder contained in the powder layer to form an active material layer. The method for manufacturing a secondary battery electrode according to claim 1, wherein in the first step, the powder layer is formed by scattering a mixed powder of the active material powder and the binder powder on the surface of the current collector. In the first step, the powder layer is
2. The method for manufacturing an electrode for a secondary battery according to claim 1, wherein the electrode is formed by spraying a powder of the active material onto the surface of the current collector, and then spraying a powder of the binder onto the surface of the current collector, or by spraying a powder of the binder onto the surface of the current collector, and then spraying a powder of the active material onto the surface of the current collector. The method for manufacturing an electrode for a secondary battery according to claim 3, wherein the binder powder is pressurized and dispersed in the first step. In the first step,
5. The method for manufacturing an electrode for a secondary battery according to claim 4, wherein the powder of the active material is sprayed on the surface of the current collector under pressure at a first pressure, and then the powder of the binder is sprayed on the surface of the current collector under pressure at a second pressure greater than the first pressure. The method for manufacturing an electrode for a secondary battery according to any one of claims 1 to 5, wherein in the first step, a powder of a conductive additive is mixed with the powder of the active material. The method for manufacturing a secondary battery electrode according to claim 6, wherein the average particle size of the binder powder is smaller than the average particle size of the conductive additive powder. The method for manufacturing a secondary battery electrode according to any one of claims 1 to 7, wherein the binder contains the binder powder and a fibrous carbon material. The method for manufacturing an electrode for a secondary battery according to any one of claims 1 to 8, wherein the powder layer is hot-pressed in the second step. One electrode produced by the method according to any one of claims 1 to 9;
A method for producing a secondary battery, comprising stacking the other electrode produced by the method according to any one of claims 1 to 9 with a separator interposed therebetween. A method for producing a secondary battery comprising the method according to any one of claims 1 to 9.

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