Method for manufacturing electrode active material layer and method for manufacturing electrode laminate

Abstract

To provide a method for manufacturing an electrode active material layer, with which an electrode active material layer with no cracking even when subjected to high-speed drying can be formed.SOLUTION: A method for manufacturing an electrode active material layer according to the present disclosure includes: a step (S11) of applying a masking tape (MT) on a surface (11S) of a current collector so as to surround the formation area of an electrode active material layer along the outer periphery of the formation area of the electrode active material layer; a step (S12) of applying, on the formation area of the electrode active material layer on the surface (11S) of the current collector and at least a partial area on the masking tape (MT), an electrode mixture containing an electrode active material and a dispersion medium to form a coating film (CF); a step (S13) of drying the coating film (CF) to form an electrode active material layer (EL); and a step (S14) of peeling, from the current collector (11), the masking tape (MT) and the periphery of the electrode active material layer (EL) existing on the masking tape (MT).SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing an electrode active material layer and a method for manufacturing an electrode laminate. [Background technology]

[0002] A non-aqueous electrolyte secondary battery such as a lithium ion secondary battery may include an electrode sheet in which a negative electrode active material layer and / or a positive electrode active material layer is formed on at least one surface of a current collector, or an electrode laminate in which a plurality of such electrode sheets are stacked. In this specification, the negative electrode active material layer and / or the positive electrode active material layer are collectively referred to as the electrode active material layer. The electrode active material layer (negative electrode active material layer or positive electrode active material layer) can be formed by applying an electrode mixture containing an electrode active material (negative electrode active material or positive electrode active material) and a dispersion medium onto the surface of a current collector to form a coating film, and then heating and drying the coating film using hot air. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-63495 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional heat drying methods for coating films require energy and time, so methods of drying by irradiation with light such as infrared and laser light have been investigated as a drying method that requires less energy and allows for faster drying (hereinafter simply referred to as a fast drying method) instead of or in addition to hot air drying. For example, Patent Document 1 discloses a method of drying a coating film in which the coating film is irradiated with far-infrared light having a wavelength that is highly absorbent for organic solvents (Claim 1). In one example of Patent Document 1, the film dried by the above method is further irradiated with laser light to bake the film (paragraph 0009).

[0005] In the method for forming an electrode active material layer, an uncoated portion exists outside the coating film made of an electrode mixture, where the surface of the current collector is exposed without being coated with the electrode mixture. In the above-mentioned high-speed drying method, the uncoated portion of the current collector made of a metal foil or the like has a high thermal conductivity and is therefore more likely to increase in temperature than the coating film. Furthermore, since electrode mixtures are generally in a slurry or paste form and have fluidity, the peripheral portion of the coating film tends to become thinner due to the outward flow of the electrode mixture. When the above-mentioned high-speed drying method is used, the temperature rise in the uncoated portion of the current collector and the thinning of the peripheral portion of the coating film can cause the peripheral portion of the coating film to become overheated, potentially resulting in cracks.

[0006] The present disclosure has been made in view of the above circumstances, and aims to provide a method for manufacturing an electrode active material layer that can form an electrode active material layer that is free from cracks even when high-speed drying is performed. [Means for solving the problem]

[0007] The present disclosure provides the following methods for producing an electrode active material layer and methods for producing an electrode laminate. The method for producing an electrode active material layer according to the present disclosure includes: A method for manufacturing an electrode active material layer formed in a predetermined region on a surface of a current collector, comprising: a step (S11) of attaching a masking tape to the surface of the current collector along the periphery of the region where the electrode active material layer is formed so as to surround the region where the electrode active material layer is formed; a step (S12) of applying an electrode mixture containing an electrode active material and a dispersion medium to an area on the surface of the current collector where the electrode active material layer is to be formed and at least a portion of an area on the masking tape to form a coating film; a step (S13) of drying the coating film to form the electrode active material layer; and a step (S14) of peeling off the masking tape and the peripheral edge of the electrode active material layer present on the masking tape from the current collector.

[0008] In the method for producing an electrode active material layer of the present disclosure, the peripheral portion of the electrode active material layer that is located on the masking tape and that is thin and may have cracks is peeled off and removed together with the masking tape. In the method for producing an electrode active material layer of the present disclosure, the peripheral portion of the electrode active material layer that is thin and may have cracks can be cleanly peeled off by the simple operation of simply peeling off the masking tape, and a crack-free electrode active material layer of the desired thickness and with the desired planar shape can be neatly formed. According to the method for producing an electrode active material layer of the present disclosure, a crack-free electrode active material layer can be formed even when high-speed drying is performed.

[0009] The method for producing an electrode stack according to the present disclosure includes: a step (S1) of producing a plurality of electrode sheets, each of which includes a step of producing the electrode active material layer on at least one surface of the current collector by the method for producing an electrode active material layer according to the present disclosure; and a step (S2) of attaching a resin frame containing a thermoplastic resin to the outer periphery of the current collector of each of the electrode sheets; A step (S3) of stacking a plurality of members including a plurality of the electrode sheets to which the resin frames are attached to obtain a temporary laminate; and a step (S4) of thermocompression bonding the plurality of resin frames included in the temporary laminate. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a method for producing an electrode active material layer that can form an electrode active material layer that is free from cracks even when high-speed drying is performed. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a flowchart of a method for producing an electrode active material layer according to the present disclosure. [Figure 2] 1A to 1C are schematic cross-sectional views of electrode sheets according to some embodiments. [Figure 3] 1A to 1C are schematic plan views showing several steps of a method for producing an electrode active material layer according to the present disclosure. [Figure 4]1A to 1C are schematic plan views showing several steps of a method for producing an electrode active material layer according to the present disclosure. [Figure 5] 1A to 1C are schematic diagrams illustrating several steps of a method for producing an electrode active material layer according to the present disclosure. [Figure 6] 1A to 1C are schematic cross-sectional views showing a method for producing an electrode stack according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Method of manufacturing electrode active material layer] The present disclosure relates to a method for manufacturing an electrode active material layer formed in a predetermined region on the surface of a current collector. As shown in the flowchart in Figure 1, The method for producing an electrode active material layer according to the present disclosure includes: a step (S11) of attaching masking tape to the surface of the current collector along the periphery of the region where the electrode active material layer is to be formed so as to surround the region where the electrode active material layer is to be formed; a step (S12) of applying an electrode mixture containing an electrode active material and a dispersion medium to an area on the surface of the current collector where an electrode active material layer is to be formed and at least a portion of an area on the masking tape to form a coating film; A step (S13) of drying the coating film to form an electrode active material layer; and a step (S14) of peeling off the masking tape and the peripheral edge of the electrode active material layer present on the masking tape from the current collector.

[0013] The electrode active material layer is a negative electrode active material layer or a positive electrode active material layer. The method for producing an electrode active material layer according to the present disclosure can be used to produce an electrode sheet including a current collector and an electrode active material layer formed on at least one surface of the current collector. 2, examples of the electrode sheet ES include an electrode sheet ES1 having a current collector 11 and a negative electrode active material layer 12 formed on at least one surface of the current collector 11, an electrode sheet ES2 having a current collector 11 and a positive electrode active material layer 13 formed on at least one surface of the current collector 11, and an electrode sheet ES3 having a current collector 11, a negative electrode active material layer 12 formed on one surface of the current collector 11, and a positive electrode active material layer 13 formed on the other surface of the current collector 11. Each diagram in FIG. 2 is a schematic cross-sectional view, and the same components are designated by the same reference numerals. The electrode sheets ES (ES1 to ES3) may contain one or more other components, such as a solid electrolyte membrane, in addition to the above, as needed.

[0014] Known materials can be used as the current collector 11, and metal foil is preferred. Examples of metals constituting the metal foil include aluminum, nickel, copper, alloys thereof, stainless steel, and combinations thereof. The metal foil may have a single-layer structure or a multilayer structure.

[0015] Each step of the method for producing an electrode active material layer according to the present disclosure will be described with reference to the drawings. Each of the drawings shown in Fig. 3 and Fig. 4 is a schematic plan view. First, as shown in the upper diagram of Fig. 3, a rectangular or strip-shaped (preferably strip-shaped) current collector 11 is prepared. An electrode active material layer formation area FA exists on a surface 11S of the current collector 11. The "electrode active material layer formation area FA" is the area where an electrode active material layer is to be formed. Next, as shown in the middle diagram of Figure 3, a masking tape MT is attached to the surface 11S of the current collector 11 along the periphery of the electrode active material layer formation area FA so as to surround the electrode active material layer formation area FA (step (S11)). The planar shape of the electrode active material layer formation area FA is not particularly limited and may be, for example, rectangular. In this case, masking tape MT is attached along each side of the rectangular electrode active material layer formation area FA.

[0016] Next, as shown in the lower diagram of Figure 3, an electrode mixture containing an electrode active material and a dispersion medium is applied to the electrode active material layer formation area FA on the surface of the current collector 11 and at least a portion of the area on the masking tape MT to form a coating film CF (step (S12)). Since the electrode mixture is in a slurry or paste state and has fluidity, the electrode mixture tends to flow outward at the periphery of the coating film CF, resulting in a thinner thickness (see the schematic cross-sectional view in Figure 5).

[0017] As the negative electrode active material, known materials can be used, such as carbon, oxides, metals, and combinations thereof. The positive electrode active material may be any known material, and one or more Li-containing composite oxides are preferred, specifically LiCoO2, LiMnO2, LiNiO2, LiVO2, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc.; LiMn2O4 and Li(Ni 0.5 Mn 1.5 )O4 and other spinel-type oxides; and olivine-type oxides such as LiFePO4, LiMnPO4, LiNiPO4, and LiCuPO4. The dispersion medium is not particularly limited, and an organic dispersion medium such as N-methyl-2-pyrrolidone (NMP) is preferred. The electrode mixture may contain one or more additives, as needed, such as a binder such as polyvinylidene fluoride (PVDF); a conductive agent such as a carbon material such as acetylene black and graphite; or a thickener such as carboxymethyl cellulose (CMC).

[0018] Next, as shown in the upper diagram of FIG. 4, the coating film CF is dried to form an electrode active material layer EL (negative electrode active material layer 12 or positive electrode active material layer 13) (step (S13)). In the method for producing an electrode active material layer according to the present disclosure, in step (S13), the coating film CF can be irradiated with one or more types of light selected from the group consisting of infrared light and laser light to perform high-speed drying. In step (S13), other known drying techniques, such as hot air drying, may also be used in combination.

[0019] Next, as shown in the lower diagram of FIG. 4, the masking tape MT and the peripheral edge portion of the electrode active material layer EL present on the masking tape MT are peeled off from the current collector 11 (step (S14)). After step (S13) and / or step (S14), a step of pressing the electrode active material layer EL by a known method may be carried out, if necessary.

[0020] As shown in FIG. 5, a current collector 11 such as a strip of metal foil is unwound from a current collector roll such as a metal foil roll, and steps (S11) to (S14) are carried out in sequence to form a plurality of electrode active material layers EL spaced apart in the longitudinal direction on the current collector 11, and the current collector 11 may be cut between adjacent electrode active material layers EL. 5 is a schematic perspective view, and the same components as those in FIGS. 3 and 4 are given the same reference numerals and will not be described again. The direction of the thick arrow indicates the direction in which the current collector 11 is transported. The inside of the drying furnace 20 is shown in a perspective view. A schematic cross-sectional view of the workpiece W1 is shown in the upper left of FIG. 5. Work W1 is a work after the step (S12) of forming a coating film CF has been performed, work W2 is a work during the step (S13) of drying the coating film CF, and work W3 is a work after the step (S13) has been completed.

[0021] Step (S13) can be performed, for example, by passing current collector 11 having coating film CF formed on its surface through drying furnace 20 equipped with light irradiator 21 that irradiates current collector 11 with one or more types of light 22 selected from the group consisting of infrared light and laser light. Light 22 is preferably laser light, and light irradiator 21 is preferably a laser light irradiator (also simply referred to as laser). If necessary, a thermometer 23 for measuring the surface temperature inside the drying furnace 20 and / or the surface temperature of the coating film CF during the drying process can be placed inside the drying furnace 20. The thermometer 23 is preferably a radiation thermometer that detects infrared rays and measures the radiation temperature from the surface of the coating film CF during the drying process. The radiation thermometer used is one that does not detect the wavelength of the light 22. In this specification, unless otherwise specified, infrared light refers to light in the wavelength range of 780 nm or more and 2500 nm or less. The infrared light that can be used in step (S13) may be near infrared light, mid infrared light, far infrared light, or a combination thereof. The wavelength of the laser light can be appropriately selected depending on the type of dispersion medium, and is preferably, for example, near-infrared laser light of 900 nm or more and 1100 nm or less. As the laser, a semiconductor laser or the like is preferable.

[0022] As explained in the section "Problems to be Solved by the Invention," in the method for forming an electrode active material layer, an uncoated portion exists outside the coating film made of an electrode mixture, where the surface of the current collector is exposed without being coated with the electrode mixture. In the high-speed drying method, the uncoated portion of the current collector made of metal foil or the like has a high thermal conductivity and is therefore more susceptible to temperature rise than the coating film. Furthermore, because electrode mixtures are generally in a slurry or paste form and have fluidity, the peripheral portion of the coating film tends to become thinner due to the outward flow of the electrode mixture. When the high-speed drying method is used, the temperature rise in the uncoated portion of the current collector and the thinning of the peripheral portion of the coating film can cause the peripheral portion of the coating film to overheat, potentially resulting in cracks.

[0023] In the method for producing an electrode active material layer according to the present disclosure, in step (S12), an electrode mixture is applied to the electrode active material layer formation area FA on the surface of the current collector 11 and at least a portion of the area on the masking tape MT to form a coating film CF. The outer periphery of the coating film CF formed in this process is located on the masking tape MT and is located outside the outer periphery of the electrode active material layer formation area FA. The formation area of ​​the coating film CF formed in this process is wider than the electrode active material layer formation area FA. The peripheral edge of the coating film CF formed in this process is located on the masking tape MT.

[0024] The peripheral edge of the electrode active material layer EL, which will be formed by drying the coating film CF in the next step (S13), is present on the masking tape MT. In this step, cracks may occur in the peripheral edge of the electrode active material layer EL due to the rapid drying. The peripheral edge of the electrode active material layer EL, which is located on the masking tape MT and is thin and may have cracks, is peeled off and removed together with the masking tape MT in the next step (S14). In the manufacturing method of the electrode active material layer of the present disclosure, the peripheral edge of the electrode active material layer EL, which is thin and may have cracks, can be cleanly peeled off by simply peeling off the masking tape MT, and a crack-free electrode active material layer EL of the desired thickness and planar shape can be neatly formed. The electrode active material layer EL manufactured by the manufacturing method of the present disclosure has extremely high uniformity in thickness and planar shape. For example, in a cross-sectional view, the angle of the side surface of the electrode active material layer EL relative to the surface 11S of the current collector 11 can be approximately perpendicular, and in a plan view, the angle of each corner of the electrode active material layer EL can be approximately 90°.

[0025] The width EW of the peripheral portion of the coating film CF formed on the masking tape MT and peeled off together with the masking tape MT after drying is designed according to the thickness of the main portion CFm of the coating film CF (the desired thickness of the coating film CF) and the solids concentration of the electrode mixture, and can be determined so as to include a portion that will be thinner than the main portion CFm due to the flow of the electrode mixture when the coating film CF is applied to the current collector 11 without the masking tape MT attached. Here, the main portion CFm refers to the portion excluding the peripheral portion, including the center, which can be stably formed to the desired thickness. The width EW of the peripheral portion of the coating film CF can be, for example, 4 mm or more and 6 mm or less. The peripheral edge portion of the electrode active material layer EL that is peeled off is essentially an unnecessary portion, and therefore peeling off does not lead to a decrease in electrode performance.

[0026] As the masking tape MT, a known one can be used, and an adhesive tape having a base layer and an adhesive layer is preferred. When the coating film CF is irradiated with light such as infrared light or laser light in step (S13), the masking tape MT preferably contains a light-reflecting material. For example, a light-reflecting adhesive tape such as an aluminum tape having an aluminum substrate layer and an adhesive layer is preferred. This is preferable because it can suppress temperature rise in the masking tape MT and the coating film CF present thereon.

[0027] As described above, according to the present disclosure, it is possible to provide a method for manufacturing an electrode active material layer that can form an electrode active material layer that is free from cracks even when high-speed drying is performed. According to the manufacturing method of the present disclosure, the coating film can be dried at high speed, so the energy and time required for the drying process can be reduced compared to conventional methods.

[0028] [Method of manufacturing electrode laminate] The method for producing an electrode laminate of the present disclosure will be described with reference to the drawings, in which Fig. 6 is a schematic cross-sectional view. By the method for producing an electrode active material layer according to the present disclosure, an electrode active material layer EL (negative electrode active material layer 12 or positive electrode active material layer 13) is produced on at least one surface of a current collector 11, and a plurality of electrode sheets ES (ES1 to ES3) each including the current collector 11 and the electrode active material layer EL are produced (step (S1)), as shown in Fig. 2. In this step, one or more other constituent elements, such as a solid electrolyte membrane, other than those described above may be formed on at least one surface of the current collector 11, as necessary.

[0029] Next, as shown in FIG. 6, a step ((S2)) is performed in which resin frames 15 containing one or more thermoplastic resins are attached to the outer peripheries of current collectors 11 of the individual electrode sheets ES (ES1 to ES3). The resin frame 15 is an annular member, and the outer periphery of the resin frame 15 can be similar in shape to the outer periphery of the electrode sheet ES in a plan view. For example, the electrode sheet ES can be rectangular, and the outer periphery of the resin frame 15 can also be rectangular. The thickness of the resin frame 15 is greater than the thickness of the electrode sheet ES, and the resin frame 15 can have a sheet insertion portion 15H, such as a recess or notch, on its inner periphery into which the outer periphery of the electrode sheet ES is inserted. As the thermoplastic resin, known ones can be used, and examples thereof include polyolefins such as polyethylene and polypropylene; methacrylic resins; and the like.

[0030] Next, as shown in FIG. 6, a plurality of electrode sheets ES (ES1 to ES3) with attached resin frames 15 are stacked to obtain a temporary laminate (step (S3)). In this step, separators 14 can be placed between adjacent electrode sheets ES as needed. In this case, resin frames 16 may be placed as spacers between adjacent resin frames 15 as needed. The resin frames 16 may be attached to the separators 14. The same resin frames as the resin frames 15 can be used as the resin frames 16.

[0031] Next, the plurality of resin frames 15 included in the temporary laminate and the resin frames 16 included as needed are thermocompression bonded (step (S4)) (not shown). The pressure is, for example, 1 kPa or more and 30 MPa or less, and preferably 0.1 MPa or more and 10 MPa or less. The heating temperature is appropriately selected depending on the material of the resin frame, and is, for example, 120°C or higher and 300°C or lower, preferably 150°C or higher and 250°C or lower. Heating can be performed using, for example, a radiant heater such as an infrared lamp heater. The output of each infrared lamp can be, for example, 100 W or more, 150 W or more, or 300 W or more. After the thermocompression bonding, the plurality of resin frames 15 and the plurality of resin frames 16 used as needed are integrated and can function as a sealing material S. In this manner, the electrode stack is manufactured.

[0032] [Electricity storage device] Using the electrode laminate, a power storage device such as a nonaqueous electrolyte secondary battery (e.g., a lithium ion secondary battery) or an electric double layer capacitor can be manufactured by a known method. The power storage device can include a solid electrolyte membrane or an electrolytic solution and an exterior body. The solid electrolyte membrane can be included in the electrode laminate.

[0033] [Application] Applications of the electrode sheets, electrode laminates, and electricity storage devices manufactured using the technology of the present disclosure include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric vehicles (BEVs), gasoline-powered vehicles, and diesel-powered vehicles, and are particularly suitable as power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and electric vehicles (BEVs). Other applications of the electrode sheets, electrode laminates, and power storage devices manufactured using the techniques of the present disclosure include power sources for moving bodies other than vehicles (e.g., railways, ships, and aircraft); power sources for electrical appliances such as information processing devices; and the like.

[0034] The present invention is not limited to the above-described embodiment, and appropriate design changes are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0035] 11 Current collector 12 Negative electrode active material layer 13 Cathode active material layer 14 Separator 15, 16 Resin frame CF coating film Periphery of the CFe coating film EL electrode active material layer ES, ES1 to ES3 electrode sheets FA Electrode active material layer formation area MT masking tape

Claims

1. A method for manufacturing an electrode active material layer formed in a predetermined region on a surface of a current collector, comprising: a step (S11) of attaching a masking tape to the surface of the current collector along the periphery of the region where the electrode active material layer is formed so as to surround the region where the electrode active material layer is formed; a step (S12) of applying an electrode mixture containing an electrode active material and a dispersion medium to a formation region of the electrode active material layer on the surface of the current collector and to a partial region on the masking tape to form a coating film; A step (S13) of drying the coating film to form the electrode active material layer; and a step (S14) of peeling off the masking tape and the peripheral edge portion of the electrode active material layer present on the masking tape from the current collector, the current collector includes a metal foil, The masking tape includes a light-reflecting material, In the step (S13), the coating film is irradiated with one or more types of light selected from the group consisting of infrared light and laser light.

2. The method for producing an electrode active material layer according to claim 1 , wherein the masking tape is an aluminum tape.

3. A process (S1) for producing a plurality of electrode sheets each including the current collector and the electrode active material layer, the process comprising the step of producing the electrode active material layer on at least one surface of the current collector by the method for producing an electrode active material layer according to claim 1 or 2; a step (S2) of attaching a resin frame containing a thermoplastic resin to an outer periphery of the current collector of each of the electrode sheets; A step (S3) of stacking a plurality of members including a plurality of the electrode sheets to which the resin frames are attached to obtain a temporary laminate; and (S4) thermocompression bonding the plurality of resin frames included in the temporary laminate.

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