JP6628505B2 - Method and apparatus for manufacturing electrode for secondary battery and method for manufacturing secondary battery - Google Patents

Description

  The present invention relates to a method and an apparatus for manufacturing an electrode for a secondary battery and a method for manufacturing a secondary battery.

  Secondary batteries are widely used not only as power sources for portable devices such as mobile phones, digital cameras, and laptop computers, but also as power sources for vehicles and homes. Secondary batteries have become energy storage devices that are indispensable for daily life.

  Secondary batteries can be broadly classified into a wound type and a stacked type. A battery element of a wound type secondary battery has a structure in which a long positive electrode sheet and a long negative electrode sheet are wound a plurality of times in a state of being overlapped while being separated by a separator. The battery element of the stacked secondary battery has a structure in which a plurality of positive electrode sheets and a plurality of negative electrode sheets are alternately and repeatedly stacked while being separated by a separator. The positive electrode sheet and the negative electrode sheet are coated with an active material to connect an electrode part to an application part where an active material (including a mixture including a binder and a conductive material) is applied to a current collector. And an uncoated portion that has not been applied.

  In any of the wound secondary battery and the stacked secondary battery, one end of the positive electrode terminal is electrically connected to an uncoated portion of the positive electrode sheet, and the other end is drawn out of the outer container (outer case), The battery element is sealed in the outer container so that one end of the negative electrode terminal is electrically connected to an uncoated portion of the negative electrode sheet and the other end is drawn out of the outer container. An electrolytic solution is sealed in the outer container together with the battery element. Secondary batteries tend to have large capacities year by year, and accompanying this, if a short circuit occurs, the heat generation becomes greater and the danger increases, so that battery safety measures are becoming increasingly important.

  As an example of a safety measure, there is a configuration in which an insulating member is provided at a boundary portion between an applied portion and an uncoated portion in order to prevent a short circuit between a positive electrode and a negative electrode. However, when the battery element is partially thickened by providing a tape-shaped insulating member, for example, the energy density per volume is reduced, and the variation and cycle of the electrical characteristics due to the inability to uniformly hold the battery element are caused. There is a possibility that the quality of the battery is deteriorated, such as deterioration of the characteristics. Therefore, in Patent Document 1, the end of the active material layer is partially formed to be thin, and an insulating member is disposed between the thin portion and the uncoated portion. There is disclosed a configuration in which the battery is prevented from becoming thick and the quality of the battery is prevented from deteriorating. In Patent Literature 1, in order to form a thin portion of an active material layer, a shim is arranged in a discharge port of a die head that discharges an active material onto a current collector, and the shim discharges the active material from the discharge port. A configuration is employed in which a thin portion is formed so that a thick portion and a thin portion can be simultaneously formed. In order to form a large number of electrodes, while moving a long sheet-shaped current collector relative to the position facing the die head, a slurry containing an active material is discharged from the die head toward the relatively moving current collector. When performing so-called continuous coating, in which a thin portion, a thick portion, and an uncoated portion are simultaneously formed, a thick portion and a thin portion are formed by using a die head in which a shim is arranged in a discharge port as shown in Patent Document 1. Part can be formed.

  On the other hand, Patent Literatures 2 to 4 disclose a configuration for performing so-called intermittent coating in which an uncoated portion and a coated portion of the active material layer are repeatedly formed along the relative movement direction of the current collector. In the intermittent coating, the slurry is not discharged from the die head at the time of forming the uncoated portion, but the slurry is circulated in the circulation path formed in the area excluding the die head, instead of holding the slurry in the accommodation portion and not moving it. Is preferred. The reason is that if the slurry is not moved and remains stagnant, the viscosity changes due to the sedimentation of some components, etc., and the discharge performance changes when the formation of the coating section is resumed, resulting in the desired dimensions and characteristics. This is because there is a possibility that the active material layer cannot be formed. Even when the uncoated portion is formed, if the slurry is continuously moved (circulated) in a range excluding the die head, sedimentation of some components and a change in viscosity are unlikely to occur, and an active material layer having desired dimensions and characteristics can be formed. Easy to form. Whether the slurry is supplied to the die head to form the coating portion or the non-coated portion is formed by circulating a circulation path formed in a range excluding the die head is determined by a valve (coating) disposed between the die head and the storage portion. Valve and return valve).

International Publication WO2013 / 137385 pamphlet JP 2001-38276 A JP 2014-188426 A JP 2014-188449 A

  In the case of performing intermittent coating as described in Patent Documents 2 to 4, an application section including a thick portion and a thin portion using a die head in which a shim is arranged in a discharge port as shown in Patent Document 1 Cannot be formed. The formation of the thick portion and the thin portion in the intermittent coating is performed by controlling the discharge amount of the slurry from the die head, but this control is not easy, and it is difficult to form a thin portion having a desired thickness with high accuracy. It is.

  Therefore, an object of the present invention is to solve the above-described problems and to easily and accurately form a thin portion and a thick portion when sequentially forming a thin portion and a thick portion of an active material layer on a current collector. It is an object of the present invention to provide a method and apparatus for manufacturing a secondary battery electrode and a method for manufacturing a secondary battery.

The method of manufacturing an electrode for a secondary battery having a coating portion in which an active material layer is formed on a current collector according to the present invention includes a slurry containing an active material supplied from a housing portion to a die head via a valve mechanism. And forming a coating portion by discharging from the die head toward the current collector. The valve mechanism is located between the storage section and the die head, and is a return valve for opening and closing a return flow path for returning slurry to the storage section, and a coating for opening and closing a discharge side flow path for supplying slurry to the die head. A valve, and a connection passage connecting the return valve and the coating valve. The step of forming the application part includes a step of forming a thin part with a thin active material layer and a step of forming a thick part with a thick active material layer. In the step of forming the thin portion, a part of the slurry supplied from the storage unit is returned to the storage unit by opening the return valve while the coating valve is fully opened, and the remaining slurry is caused to flow toward the die head. In the step of forming the thick portion, while the coating valve is fully opened, by closing the return valve, the slurry supplied from the storage portion is allowed to flow only toward the die head and is not returned to the storage portion, or By opening the return valve at a smaller opening than when forming the thin portion, a smaller amount of slurry is returned to the storage portion than in the step of forming the thin portion, and the remaining slurry flows toward the die head.

According to the present invention, an apparatus for manufacturing an electrode for a secondary battery having an application portion in which an active material layer is formed on a current collector includes a die head that discharges a slurry containing an active material toward the current collector, An accommodating section for accommodating, a valve mechanism interposed between the die head and the accommodating section, a discharge-side flow path connecting the valve mechanism and the die head, and a supply flow path connecting the valve mechanism and the accommodating section. And a return passage, a valve mechanism for changing a flow rate of the slurry toward the discharge-side flow path and a flow rate of the slurry toward the return flow path, and a control device for adjusting an opening degree of the valve mechanism. The valve mechanism includes a return valve that opens and closes a return flow path, a coating valve that opens and closes a discharge-side flow path, and a connection flow path that connects the return valve and the coating valve. When forming a thin-walled portion having a thin active material layer on the current collector, the control device controls the return valve to be open while the coating valve is fully opened, so that the supply from the supply flow path is performed. The slurry to be flowed flows through both the discharge side flow path and the return flow path. When forming a thick portion where the thickness of the active material layer is thick on the current collector, it is supplied from the supply flow path by controlling the return valve to be closed while the coating valve is fully opened. By allowing the slurry to flow only to the discharge-side flow path, or by controlling the return valve to open with a smaller opening than when forming the thin-walled part, the slurry is flowed to the return flow path in the step of forming the thin-walled part The return valve and the coating valve are controlled so that a smaller amount of slurry than the amount of the slurry flows through the return flow path, and the remaining slurry flows toward the die head.

  According to the present invention, when sequentially forming a thin portion and a thick portion of an active material layer on a current collector, the thin portion and the thick portion can be easily and accurately formed.

(A) is a plan view showing a basic structure of a stacked secondary battery manufactured by the present invention, and (b) is a cross-sectional view taken along line AA. 2A is an enlarged plan view showing a main part of a positive electrode of the secondary battery shown in FIG. 1, and FIG. 2B is an enlarged sectional view thereof. FIG. 3 is a plan view illustrating a manufacturing process of the positive electrode of the secondary battery of the present invention. FIG. 4 is a plan view showing a step following the step shown in FIG. 3 in the manufacturing process of the positive electrode of the secondary battery of the present invention. FIG. 5A is a plan view showing a step following FIG. 4 in the process of manufacturing the positive electrode of the secondary battery of the present invention, and FIG. 5B is a plan view showing the positive electrode manufactured thereby. FIG. 4 is a plan view illustrating a manufacturing process of a negative electrode of the secondary battery of the present invention. FIG. 7A is a plan view showing a step subsequent to FIG. 6 in the manufacturing process of the negative electrode of the secondary battery of the present invention, and FIG. 7B is a plan view showing the negative electrode manufactured thereby. It is the schematic which shows typically an example of the manufacturing apparatus of the electrode for secondary batteries of this invention. FIG. 9 is a schematic diagram illustrating a valve mechanism and a control device of the manufacturing apparatus illustrated in FIG. 8. 4 is a graph showing a method for manufacturing an electrode for a secondary battery of the present invention. It is the schematic which shows typically the modification of the manufacturing apparatus of the electrode for secondary batteries of this invention. It is the schematic which shows typically the other modification of the manufacturing apparatus of the electrode for secondary batteries of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Configuration of secondary battery]
FIGS. 1A and 1B schematically show an example of the configuration of a stacked lithium ion secondary battery manufactured by the manufacturing method of the present invention. FIG. 1A is a plan view viewed from above perpendicularly to a main surface (flat surface) of the secondary battery, and FIG. 1B is a cross-sectional view taken along line AA of FIG. 1A. . FIG. 2 is an enlarged sectional view of a main part of the positive electrode.
The lithium ion secondary battery 1 of the present invention includes an electrode stack (battery element) 17 in which a positive electrode (positive electrode sheet) 2 and a negative electrode (negative electrode sheet) 3 are alternately stacked via a separator 4. I have. The electrode laminate 17 is housed together with the electrolytic solution 5 in an outer container made of the flexible film 6. One end of a positive electrode terminal 7 is connected to the positive electrode 2 of the electrode stack 17, and one end of a negative electrode terminal 8 is connected to the negative electrode 3. The other end of the positive electrode terminal 7 and the other end of the negative electrode terminal 8 are respectively drawn out of the flexible film 6. In FIG. 1B, a part of each of the layers constituting the electrode laminate 17 (a layer located at an intermediate portion in the thickness direction) is not shown, and the electrolyte 5 is shown. In FIG. 1B, the cathode 2, the anode 3, and the separator 4 are shown not to be in contact with each other for easy viewing, but actually, they are stacked closely.

  The positive electrode 2 includes a positive electrode current collector (positive electrode current collector) 9 and a positive electrode active material layer (positive electrode active material layer) 10 applied to the positive electrode current collector 9. On the front surface and the back surface of the positive electrode current collector 9, a coated portion on which the positive electrode active material layer 10 is formed and an uncoated portion on which the positive electrode active material layer 10 is not formed are arranged along the longitudinal direction. Then, as shown in an enlarged manner in FIG. 2, the positive electrode active material layers 10 on both surfaces of the positive electrode current collector 9 of the present embodiment include a thick portion 10a and a thin portion 10b. The negative electrode 3 includes a negative electrode current collector (negative electrode current collector) 11 and a negative electrode active material layer (negative electrode active material layer) 12 applied to the negative electrode current collector 11. On the front surface and the back surface of the negative electrode current collector 11, an applied portion and an uncoated portion are located side by side along the longitudinal direction.

  Each uncoated portion of the positive electrode 2 and the negative electrode 3 is used as a tab for connecting to an electrode terminal (the positive electrode terminal 7 or the negative electrode terminal 8). The positive electrode tabs (positive electrode current collectors 9) of the positive electrode 2 are put together on the positive electrode terminal 7, and connected together with the positive electrode terminal 7 by ultrasonic welding or the like. The negative electrode tabs (negative electrode current collectors 11) of the negative electrode 3 are put together on the negative electrode terminal 8, and connected together with the negative electrode terminal 8 by ultrasonic welding or the like. Then, the other end of the positive electrode terminal 7 and the other end of the negative electrode terminal 8 are respectively drawn out of the outer container made of the flexible film 6.

  As shown in FIG. 2, a boundary portion 13 between the thin portion 10b of the coated portion where the positive electrode active material layer 10 is formed and the non-coated portion where the positive electrode active material layer 10 is not formed is formed. An insulating member 14 for preventing a short circuit with the negative electrode terminal 8 is disposed so as to cover (corresponds to the terminal position of the positive electrode active material layer 10). The sum of the thickness of the thin portion 10b and the thickness of the insulating member 14 in a portion where the insulating member 14 is located on the thin portion 10b is smaller than the average thickness of the thick portion 10a of the positive electrode active material layer 10. Therefore, since the positive electrode 2 is not partially thickened in the portion where the insulating member 14 is arranged, a decrease in energy density per volume can be suppressed, and the battery element can be uniformly pressed to fix the battery element. It is possible to suppress deterioration in battery quality such as variation in electric characteristics and deterioration in cycle characteristics.

The outer dimensions of the coated part of the negative electrode 3 (negative electrode active material layer 12) are larger than the outer dimensions of the coated part of the positive electrode 2 (positive electrode active material layer 10) and smaller than or equal to the outer dimensions of the separator 4.
The negative electrode 3 of the present embodiment is formed by forming a negative electrode active material layer 12 having a uniform thickness without a thin portion on both surfaces of a negative electrode current collector 11, and is not provided with an insulating member 14.

In the secondary battery of the present embodiment, as the active material forming the positive electrode active material layer 10, for example, LiCoO ₂ , LiNiO ₂ , LiNi _(1-x) CoO ₂ , LiNi _x (CoAl) _(1-x) O ₂ , Li ₂ MO ₃ -LiMO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ and other layered oxide materials, LiMn ₂ O ₄ , LiMn _1.5 Ni _0.5 O ₄ , LiMn _(2-x) Examples include spinel-based materials such as M _x O ₄ , olivine-based materials such as LiMPO ₄ , fluorinated olivine-based materials such as Li ₂ MPO ₄ F and Li ₂ MSiO ₄ F, and vanadium oxide-based materials such as V ₂ O _5. It is possible to use one or a mixture of two or more of these.

Examples of the active material constituting the negative electrode active material layer 12 include carbon materials such as graphite, amorphous carbon, diamond-like carbon, fullerene, carbon nanotube, and carbon nanohorn; lithium metal materials; alloy materials such as silicon and tin; An oxide-based material such as Nb ₂ O ₅ or TiO ₂ or a composite thereof can be used.

  The active material mixture forming the positive electrode active material layer 10 and the negative electrode active material layer 12 is obtained by appropriately adding a binder, a conductive assistant, and the like to each of the active materials described above. As the conductive aid, one or a combination of two or more of carbon black, carbon fiber, graphite, and the like can be used. Further, as the binder, polyvinylidene fluoride, polytetrafluoroethylene, carboxymethyl cellulose, modified acrylonitrile rubber particles and the like can be used.

  As the positive electrode current collector 9, aluminum, stainless steel, nickel, titanium, an alloy thereof, or the like can be used, and aluminum is particularly preferable. As the negative electrode current collector 11, copper, stainless steel, nickel, titanium, or an alloy thereof can be used.

  Examples of the electrolyte 5 include cyclic carbonates such as ethylene carbonate, propylene carbonate, vinylene carbonate, and butylene carbonate, ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and dipropyl carbonate (DPC). Chain carbonates, aliphatic carboxylic acid esters, γ-lactones such as γ-butyrolactone, chain ethers, cyclic ethers, and one or more of organic solvents such as Mixtures can be used. Further, a lithium salt can be dissolved in these organic solvents.

The separator 4 is mainly made of a porous film made of resin, a woven fabric, a nonwoven fabric, or the like. As the resin component, for example, a polyolefin resin such as polypropylene or polyethylene, a polyester resin, an acrylic resin, a styrene resin, or a nylon resin may be used. it can. In particular, a polyolefin-based microporous membrane is preferable because of its excellent ion permeability and performance of physically separating the positive electrode and the negative electrode. If necessary, a heat-resistant layer such as a layer containing inorganic particles and a layer mainly containing aromatic polyamide may be formed on the separator 4. Examples of the inorganic particles include insulating oxides, nitrides, and the like. Sulfides, carbides, and the like can be given. Among them, TiO ₂ and Al ₂ O ₃ are preferable.

  As the outer container, a case or a can case made of the flexible film 6 can be used, and it is preferable to use a case made of the flexible film 6 from the viewpoint of reducing the weight of the battery. As the flexible film 6, a film in which a resin layer is provided on the front and back surfaces of a metal layer serving as a base material can be used. As the metal layer, a material having a barrier property such as preventing leakage of the electrolyte solution 5 or intrusion of moisture from the outside can be selected, and aluminum, stainless steel, or the like can be used. At least one surface of the metal layer is provided with a heat-fusible resin layer such as a modified polyolefin. The exterior container is formed by causing the heat-fusible resin layers of the flexible film 6 to face each other and heat-sealing the periphery of the portion where the electrode laminate 17 is housed. A resin layer such as a nylon film or a polyester film can be provided on the surface of the exterior body, which is the surface opposite to the surface on which the heat-fusible resin layer is formed.

  The positive electrode terminal 7 may be made of aluminum or an aluminum alloy, and the negative electrode terminal 8 may be made of copper, a copper alloy, nickel-plated copper or the like, or the like. The other ends of the terminals 7, 8 are drawn out of the outer container. In each of the terminals 7 and 8, a heat-fusible resin can be provided in advance at a portion corresponding to a portion to be thermally welded on the outer peripheral portion of the outer container.

  Polyimide, glass fiber, polyester, polypropylene, or a material containing these can be used for the insulating member 14 formed so as to cover the boundary portion 13 between the coated portion and the uncoated portion of the positive electrode active material layer 10. The insulating member 14 can be formed by applying heat to the tape-shaped resin member and welding it to the boundary portion 13, or by applying a gel-like resin to the boundary portion 13 and then drying it.

  A boundary portion or an end portion between the coated portion and the non-coated portion of the positive electrode 2 and the negative electrode 3 may be not a straight line perpendicular to the direction in which the current collectors 9 and 11 extend but a rounded curved line. In any of the positive electrode active material layer 10 and the negative electrode active material layer 12, for example, inevitable inclination, unevenness, roundness, and the like of each layer due to manufacturing variations and layer forming ability may occur.

[Method of Manufacturing Secondary Battery]
In manufacturing a secondary battery, first, an electrode for the secondary battery is manufactured. Specifically, as shown in FIG. 3, a positive electrode active material layer 10 is formed on a long strip-shaped positive electrode current collector 9 for manufacturing a plurality of positive electrodes (positive electrode sheets) 2. This positive electrode active material layer 10 is intermittently formed on both surfaces of the positive electrode current collector 9. Although difficult to understand in FIGS. 3 and 4, as described with reference to FIGS. 1 and 2, the positive electrode active material layer 10 is provided continuously with the thick portion 10 a as a main portion and one end of the thick portion 10 a. And a thin portion 10b. Details of the method for forming the positive electrode active material layer 10 will be described later. The end of the coated portion (positive electrode active material layer 10) at the boundary portion 13 with the uncoated portion is inclined as shown in FIG. You may. The boundary between the thin portion 10b and the thick portion 10a may also be substantially perpendicular to the positive electrode current collector 9 or may be inclined.

  Next, as shown in FIG. 4, a boundary portion 13 between the coated portion (the portion where the positive electrode active material layer 10 is formed) and the uncoated portion (the portion where the positive electrode active material layer 10 is not formed) is covered. The insulating member 14 is formed. As shown in FIG. 2, one end 14a of the insulating member 14 is located on the thin portion 10b of the positive electrode active material layer 10, and the other end 14b is located on the uncoated portion. If the thickness of the insulating member 14 is small, the insulating property may not be sufficiently ensured, so the thickness is preferably 10 μm or more. In order to securely fix the insulating member 14 to the thin portion 10b, the insulating member 14 is preferably formed so as to extend over 1.5 mm or more from the boundary portion 13 between the coated portion and the uncoated portion to the coated portion side. In addition, from the viewpoint of volume energy density, it is preferable that the length of the insulating member 14 extending from the boundary portion 13 toward the application portion is 20 mm or less. More preferably, the length of the insulating member 14 extending from the boundary portion 13 toward the application portion is 2 mm or more and 8 mm or less. In order to sufficiently obtain the effect of suppressing an increase in the thickness of the electrode laminate 17 according to the present invention, the thickness of the insulating member 14 must be equal to the thickness of the thick portion 10a and the thin portion 10b of the positive electrode active material layer 10. It is preferable that the difference be smaller than the difference in the height.

  Thereafter, in order to obtain the positive electrode 2 used for each of the stacked batteries, the positive electrode current collector 9 is cut and divided along a cutting line 15 indicated by a two-dot chain line in FIG. 2) to obtain a positive electrode 2 having a desired size. The cutting line 15 is a virtual line and is not actually formed.

  In addition, as shown in FIG. 6, a negative electrode active material layer 12 is intermittently applied to both surfaces of a large area negative electrode current collector 11 for manufacturing a plurality of negative electrodes (negative electrode sheets) 3. The negative electrode active material layer 12 has a constant thickness without a thin portion. The end of the negative electrode active material layer 12 (the end of the coated portion) may be slightly inclined or may be substantially perpendicular to the negative electrode current collector 11. Thereafter, in order to obtain the negative electrode 3 used for each of the stacked batteries, the negative electrode current collector 11 is cut and divided along a cutting line 16 shown by a two-dot chain line in FIG. The negative electrode 3 having a desired size shown in FIG. The cutting line 16 is a virtual line and is not actually formed.

  The positive electrode 2 shown in FIG. 5 (b) and the negative electrode 3 shown in FIG. 7 (b) thus formed are alternately stacked via the separator 4, and the positive terminal 7 and the negative terminal 8 are connected. Thereby, the electrode laminate 17 is formed. The secondary battery 1 shown in FIG. 1 is formed by housing the electrode laminate 17 together with the electrolytic solution 5 in an outer container made of the flexible film 6 and sealing it.

  According to the secondary battery 1, the increase in thickness due to the insulating member 14 formed so as to cover the boundary portion 13 between the coated portion and the uncoated portion of the positive electrode 2 is greater than the thick portion 10 a of the positive electrode active material layer 10. Since the thinned portion 10b is absorbed (canceled) by the thin portion 10b and the electrode laminate 17 is not partially thickened, the electrode laminate 17 can be pressed and held evenly, and variations in electrical characteristics and cycle characteristics can be reduced. Quality deterioration such as deterioration can be suppressed. If the difference in thickness between the thick portion 10a and the thin portion 10b is larger than the thickness of the insulating member 14, it is possible to prevent the insulating member 14 from partially increasing the thickness of the electrode laminate 17, so that the thickness is extremely small. It is effective. However, even if the difference between the thickness of the thick portion 10a and the thickness of the thin portion 10b is smaller than the thickness of the insulating member 14, the provision of the thin portion 10b suppresses a local increase in the thickness of the electrode stack 17 to a small value. And a certain effect can be obtained.

In the example shown in FIG. 7B, the uncoated portion of the negative electrode 3 does not exist at the position facing the uncoated portion (positive tab) of the positive electrode 2, and the coated portion is terminated. However, it is also possible to adopt a configuration in which an uncoated portion exists at a position of the negative electrode 3 facing the uncoated portion of the positive electrode 2. An uncoated portion serving as a negative electrode tab is provided at an end of the negative electrode 3 not facing the uncoated portion of the positive electrode 2. The end position of each of the active material layers 10 and 12 (the planar position of the end of the coating portion) may be different or the same on both surfaces of the current collectors 9 and 11.
In the present invention, the thickness and distance of each member mean an average value of measured values at arbitrary three or more points unless otherwise specified.

[Detailed production method of electrode]
Among the above-described methods for manufacturing a secondary battery of the present invention, a detailed method for manufacturing an electrode will be described. The following description relates to an example in which the positive electrode 2 is manufactured, but the negative electrode 3 can be manufactured by the following method.

  In the present invention, the method of forming the active material layer on the current collector is mainly performed by using a die coater including a die head, and applying and coating the active material mixture along the longitudinal direction of the long current collector. This is an intermittent coating method in which parts are alternately and repeatedly formed. FIG. 8 is a diagram showing an example of the configuration of a die coater (manufacturing apparatus) for performing intermittent coating in the present invention. As shown in FIG. 8, a die coater for performing intermittent coating contains a die head 20, a coating valve 21 connected to the die head 20, a return valve 29, a pump 22, and a slurry 23 of the active material mixture. A main tank 24 serving as a storage section is provided. A discharge side flow path 31 connecting the coating valve 21 and the die head 20 and a connection flow path 32 connecting the coating valve 21 and the return valve 29 are provided. Further, a supply flow path 33 that connects the main tank 24 and the connection flow path 32 is provided, and the pump 22 is disposed in the supply flow path 33. Further, a return flow path 35 connecting the return valve 29 and the main tank 24 is formed. With the above configuration, the slurry 23 in the main tank 24 is guided by the pump 22 to the connection flow path 32 through the supply flow path 33, and when the coating valve 21 is open, the discharge side flow It is supplied to the die head 20 through the path 31. When the return valve 29 is open, the slurry 23 in the connection flow path 32 returns to the main tank 24 through the return flow path 35. As described above, in the present embodiment, a valve mechanism including the coating valve 21, the return valve 29, and the connection flow path 32 is interposed between the housing section including the main tank 24 and the die head 20. At a position facing the die head 20, a relative moving means for moving the current collector 9 relative to the die head 20 is arranged. In the present embodiment, the current collector 9 on which the active material layer is to be formed is transported by the rotation of the roller 25, which is an example of a relative moving unit. Further, a control device (sequencer) 26 for mainly controlling the coating valve 21 and the return valve 29 is provided. The control device 26 may control the pump 22, the die head 20, and the roller 25 in addition to the coating valve 21 and the return valve 29.

  In the example shown in detail in FIG. 9, the coating valve 21 includes a valve box 21a communicating with the discharge side flow path 31 and the connection flow path 32, and a valve seat 21c provided inside the valve box 21a and having a through hole 21b. And a valve body 21d arranged on the valve seat 21c to open and close the through hole 21b, and a shaft 21e connected to the valve body 29d and protruding outside the valve box 21a. Similarly, the return valve 29 is disposed on the valve case 29a communicating with the return flow path 35 and the connection flow path 32, the valve seat 29c provided inside the valve case 29a and having the through hole 29b, and the valve seat 29c. A valve body 29d that opens and closes the through hole 29b and a shaft 29e that is connected to the valve body 29d and protrudes outside the valve box 29a. The control device 26 for controlling the valve mechanism includes a motor 26a connected to the shaft 21e of the coating valve 21 to move the shaft 21e and the valve body 21d, and a control device 26 connected to the shaft 29e of the return valve 29 and the shaft 29e and the valve body. It includes a motor 26b for moving 29d, and a control unit 26c for controlling the operation of the motors 26a and 26b.

  In the method of manufacturing an electrode according to the present invention using the die coater, as shown in FIG. 10, when forming the uncoated portion, the coating valve 21 is closed and the return valve 29 is opened while operating the pump 22. Accordingly, the slurry 23 in the main tank 24 is guided by the pump 22 to the connection flow path 32 through the supply flow path 33, and then returned to the main tank 24 through the return flow path 35 via the return valve 29. On the other hand, since the coating valve 21 is closed, the slurry 23 is not supplied to the die head 20, and the current collector 9 is conveyed by the rotation of the roller 25 without discharging the slurry 23 from the die head 20.

  Next, in order to form the thin portion 10b of the active material layer 10, the coating valve 21 is opened and the return valve 29 is slightly closed to reduce the opening. A part of the slurry 23 guided from the main tank 24 to the connection flow path 32 through the supply flow path 33 is returned to the main tank 24 from the return flow path 35 through the return valve 29, and the remaining part is coated. It is sent from the discharge side flow path 31 to the die head 20 through the valve 21. Therefore, the amount of the slurry 23 discharged from the die head 20 toward the current collector 9 conveyed by the rotation of the roller 25 is small, and the thin portion 10b can be favorably formed.

  After the thin portion 10b having a desired size is formed, the return valve 29 is closed while the coating valve 21 is kept open, thereby shifting to the formation of the thick portion 10a. All of the slurry 23 guided from the main tank 24 to the connection flow path 32 through the supply flow path 33 does not flow to the return flow path 35 but passes from the discharge-side flow path 31 to the die head 20 through the coating valve 21. Sent. Then, the amount of the slurry 23 discharged from the die head 20 toward the current collector 9 conveyed by the rotation of the roller 25 is large, and the thin portion 10b can be favorably formed. When forming the thick portion 10a, the return valve 29 is slightly opened instead of completely closed, and the whole of the slurry 23 is not discharged, but is smaller than when the thin portion 10b is formed. The thick portion 10a may be controlled to a desired thickness by returning the amount of the slurry 23 to the return flow path 35 and discharging the remaining slurry 23.

  As described above, the control device 26 controls the opening and closing of the coating valve 21 and the return valve 29, so that the uncoated portion, the thin portion 10b of the coating portion, and the thick portion 10a can be improved. Specifically, during a period in which the coated portion is not formed (when the uncoated portion is formed and when the electrode is not formed), the main tank 24, the supply flow channel 33, the connection flow channel 32, The slurry 23 circulates through a circulation path formed by the return valve 29 and the return flow path 35. If the viscosity of the slurry 23 fluctuates due to the fact that the slurry 23 stagnates in each flow path or the main tank 24 and some components settle, for example, when the discharge of the slurry 23 from the die head 20 is resumed, There is a possibility that the ejection performance cannot be obtained and the coating unit 10 cannot be formed favorably. However, in the present invention, since the slurry continues to circulate in the circulation path described above, the possibility that some components settle is low, and the fluctuation of the viscosity can be suppressed. When restarted, the desired ejection performance can be realized, and the application section 10 can be formed satisfactorily.

  When forming the thin portion 10b, only a part of the slurry 23 supplied to the connection flow path 32 is supplied to the die head 20 to form the thin portion 10b. If the amount of the slurry 23 supplied to the die head 20 is adjusted by adjusting the opening of the coating valve 21, when the opening of the coating valve 21 changes, the opening 23 moves toward the discharge-side flow path 31. For example, the slurry 23 is pushed by the valve body 21d that adjusts the pressure, and the flow velocity of the slurry 23 in the discharge-side flow path 31 varies and the pressure fluctuates. The discharge performance of the slurry 23 from the die head 20 may be disturbed. As a result, unintended irregularities are generated in the active material layer 10 particularly at the end of the thin portion 10b and in the vicinity thereof, and when a secondary battery is manufactured using the electrode formed in such a manner, the battery characteristics vary. Can occur. On the other hand, in the present invention, the opening of the coating valve 21 is not adjusted and is fully opened, and the amount of the slurry 23 supplied to the die head 20 is adjusted by adjusting the opening of the return valve 29. Since the valve element 29d of the return valve 29 is not located in the discharge-side flow path 31 toward the die head 20, the slurry 23 in the discharge-side flow path 31 is directly moved by the movement of the valve element 29d when the opening of the return valve 29 is adjusted. It is not extruded, and changes in flow velocity and pressure can be made extremely small. Therefore, the thin portion 10a can be favorably formed without disturbing the discharge performance of the slurry 23 from the die head 20. When the thick portion 10a is formed, the return valve 29 is closed while the coating valve 21 is kept fully open. The fluctuation is not transmitted so much, and the thick portion 10a can be formed without disturbing the discharge performance of the slurry 23 from the die head 20.

  As described above, in the present embodiment, at the transition between the formation of the thin portion 10b and the formation of the thick portion 10a, the coating valve 21 adjacent to the discharge-side flow path 31 is not changed and is kept fully open. By adjusting the opening degree of the return valve 29 that does not directly affect the flow path 20 and the discharge-side flow path 31, the amount of the slurry 23 supplied to the die head 20 can be indirectly adjusted to change the supply amount. As a result, it is possible to form the thin portion 10b and the thick portion 10a satisfactorily with stable ejection performance while suppressing the occurrence of unintended irregularities particularly at the end portions.

[Modification]
As a modification of the present embodiment, in addition to the control of the coating valve and the return valve described above, the die head 20 is moved so as to move closer to or away from the current collector 9 and the roller 25 as shown in FIG. A configuration may be adopted in which a die head moving means (for example, a servomotor 37) is provided. In this case, the die head 20 is closer to the current collector 9 when the thin portion 10b is formed than when the thick portion 10a is formed, and when forming the thick portion 10a, the die head 20 is moved more than when the thin portion 10b is formed. Also, by moving away from the current collector 9, the transition from the thin portion 10b to the thick portion 10a can be performed at a short distance. Here, the die head 20 is moved by the servomotor 37 to change the discharge distance (the interval from the die head 20 to the current collector 9).

[Other Modifications]
In still another modification, a sub tank 36 is provided in the return flow path 35 as shown in FIG. By providing the sub-tank 36, the transition of the sub-tank 36 between the formation of the uncoated portion in which the slurry 23 circulates through the circulation path including the return flow passage 35 and the formation of the coated portion in which the slurry 23 does not flow through the return flow passage 35 is performed. Due to the fluctuation of the liquid level, a large fluctuation of the liquid level of the main tank 24 can be suppressed. If the liquid level of the main tank 24 fluctuates greatly, the flow of the slurry 23 toward the die head 20 may become unstable. However, in the example shown in FIG. Fluid level fluctuations can be kept small. As described above, the discharge performance of the slurry 23 is improved by changing the opening of the return valve 29 instead of changing the opening of the coating valve 21 at the transition between the formation of the thin portion 10b and the formation of the thick portion 10a. In addition to stabilization, in the present modification, the discharge performance of the slurry 23 at the time of transition between the formation of the uncoated portion and the formation of the coated portion can be stabilized, so that the thick portion 10a and the thin portion 10b can be further reduced. It can be easily formed with high precision.

  The embodiment described above has a configuration in which the insulating member 14 is provided only on the positive electrode 2 and the insulating member is not provided on the negative electrode 3, and the positive electrode active material layer 10 includes a thick portion 10a and a thin portion 10b. And the negative electrode active material layer 12 is constituted only of a thick part (having no thin part). However, only the negative electrode 3 is provided with an insulating member, the positive electrode 2 is not provided with the insulating member 14, the positive electrode active material layer 10 is formed only of the thick portion 10a, and the negative electrode active material layer 12 is formed of the thick portion and the thin portion. And a configuration consisting of In addition, an insulating member may be provided on each of the positive electrode 2 and the negative electrode 3, and each of the positive electrode active material layer 10 and the negative electrode active material layer 12 may have a thick portion and a thin portion. In any configuration, in the active material layer having the thick portion and the thin portion, a part of the insulating member is disposed on the thin portion, and the insulating member is formed by a difference in thickness between the thick portion and the thin portion. By absorbing (cancelling) at least part of the increase in thickness caused by the above, an effect of suppressing an increase in the thickness of the battery element can be obtained.

  The present invention is useful for a method of manufacturing a lithium ion secondary battery and its electrode, but is also effective when applied to a secondary battery other than a lithium ion battery and a method of manufacturing its electrode.

1 Lithium ion secondary battery 2 Positive electrode (positive electrode sheet)
3 Negative electrode (negative electrode sheet)
Reference Signs List 4 separator 5 electrolytic solution 6 flexible film 7 positive electrode terminal 8 negative electrode terminal 9 current collector for positive electrode (positive electrode current collector)
10 Active material layer for positive electrode (positive electrode active material layer)
10a thick portion 10b thin portion 11 current collector for negative electrode (negative electrode current collector)
12 Active material layer for negative electrode (negative electrode active material layer)
13 Boundary part 14 Insulating member 17 Electrode laminate (battery element)
20 die head 21 coating valve (valve mechanism)
21a, 29a Valve box 21b, 29b Through hole 21c, 29c Valve seat 21d, 29d Valve element 21e, 29e Shaft 22 Pump 23 Active material mixture slurry 24 Main tank (housing section)
25 Relative moving means (roller)
26 Control devices 26a, 26b Motor 26c Control unit 29 Return valve (valve mechanism)
31 discharge side flow path 32 connecting flow path (valve mechanism)
33 supply flow path 35 return flow path 36 sub tank (housing section)
37 Die head moving means (servo motor)

Claims (15)

A method for manufacturing an electrode for a secondary battery having an application portion on which an active material layer is formed on a current collector,
A step of forming the coating section by discharging a slurry containing the active material supplied to the die head via the valve mechanism from the storage section toward the current collector from the die head,
The step of forming the application section includes a step of forming a thin portion in which the thickness of the active material layer is thin, and a step of forming a thick portion in which the thickness of the active material layer is thick,
The valve mechanism is located between the storage unit and the die head, a return valve for opening and closing a return flow path for returning the slurry to the storage unit, and a discharge side for supplying the slurry to the die head. A coating valve that opens and closes a flow path, including a connection flow path that connects the return valve and the coating valve,
In the step of forming the thin portion, by fully opening the coating valve and opening the return valve, a part of the slurry supplied from the storage unit is returned to the storage unit, the remaining slurry Let it flow towards the die head,
In the step of forming the thick portion,
By keeping the coating valve fully open and closing the return valve, the slurry supplied from the storage section is allowed to flow only toward the die head and is not returned to the storage section,
Alternatively, by opening the return valve at a smaller opening than when forming the thin portion, a smaller amount of the slurry is returned to the storage portion than in the step of forming the thin portion, and the remaining slurry is removed. Let it flow towards the die head,
A method for manufacturing an electrode for a secondary battery.   The method for manufacturing an electrode for a secondary battery according to claim 1, wherein in the step of forming the thin portion, the die head is closer to the current collector than in the step of forming the thick portion. Further comprising a step of forming an uncoated portion on which the active material layer is not formed on the current collector,
In the step of forming the uncoated portion, the coating valve is closed and the return valve is opened,
In the step of forming the thin portion, the coating valve, is opened to the equivalent time of forming the thick portion, the return valve opens less than when forming the uncoated portion, claim 1 3. The method for producing an electrode for a secondary battery according to item 2 . The storage section includes a main tank connected to the supply flow path and the return flow path connected to the valve mechanism, and a sub-tank is provided in the return flow path,
In the step of forming the uncoated portion, the slurry supplied from the main tank is returned to the sub tank,
In the step of forming the thin portion, the part of the slurry supplied from the main tank is returned to the sub tank, and the remaining slurry is supplied to the die head,
In the step of forming the thick portion, the slurry supplied from the main tank is allowed to flow only toward the die head, or a smaller amount of the slurry is supplied to the sub tank as compared to the step of forming the thin portion. The method for manufacturing an electrode for a secondary battery according to claim 3 , wherein the slurry is returned and the remaining slurry is supplied to the die head. In the step of forming the uncoated portion and the step of forming the thin portion, at least a part of the slurry is circulated through a circulation path including the storage section, the supply flow path, the return valve, and the return flow path. The method for producing an electrode for a secondary battery according to claim 4 . The method according to claim 3 , wherein the step of forming the uncoated portion, the step of forming the thin portion, and the step of forming the thick portion are repeatedly performed in order. A method for manufacturing an electrode for a secondary battery. The method for manufacturing an electrode for a secondary battery according to any one of claims 3 to 6 , further comprising: arranging an insulating member over the thin portion and the uncoated portion of the active material layer. Forming a positive electrode by forming an active material layer for the positive electrode on both surfaces of the current collector for the positive electrode, and forming an active material layer for the negative electrode on both surfaces of the current collector for the negative electrode to form the negative electrode And a step of laminating the positive electrode and the negative electrode with a separator interposed therebetween, comprising:
8. One or both of the step of forming the positive electrode and the step of forming the negative electrode include each step of the method for manufacturing an electrode for a secondary battery according to any one of claims 1 to 7. Manufacturing method of secondary battery. An apparatus for manufacturing an electrode for a secondary battery having a coating portion on which an active material layer is formed on a current collector,
A die head for discharging a slurry containing an active material toward the current collector,
A storage unit for storing the slurry,
A valve mechanism interposed between the die head and the housing,
A discharge-side flow path connecting the valve mechanism and the die head,
A supply flow path and a return flow path connecting the valve mechanism and the housing section,
A valve mechanism for changing the flow rate of the slurry toward the discharge-side flow path and the flow rate of the slurry toward the return flow path,
A control device for adjusting the opening of the valve mechanism;
Only including,
The valve mechanism includes:
A return valve for opening and closing the return flow path;
A coating valve for opening and closing the discharge side flow path,
Including a connection flow path connecting the return valve and the coating valve,
The control device includes:
When forming a thin portion where the thickness of the active material layer is thin on the current collector, while fully opening the coating valve, by controlling to open the return valve, from the supply flow path Causing the supplied slurry to flow through both the discharge-side flow path and the return flow path,
When forming a thick part where the thickness of the active material layer is thick on the current collector,
By controlling the return valve to be closed while the coating valve is fully opened, the slurry supplied from the supply channel is allowed to flow only to the discharge-side channel,
Alternatively, by controlling the return valve to open with a smaller opening than when forming the thin portion, a smaller amount than the amount of the slurry flowing through the return flow path in the step of forming the thin portion. Flow the slurry through the return flow path, control the return valve and the coating valve to flow the remaining slurry toward the die head ,
Equipment for manufacturing electrodes for secondary batteries. The control device is configured such that when forming an uncoated portion where the active material layer is not formed on the current collector, the coating valve is closed and the return valve is opened, and the thin portion is When forming, the coating valve and the return valve so that the coating valve is opened in the same manner as when forming the thick portion and the return valve is opened smaller than when forming the uncoated portion. The apparatus for manufacturing an electrode for a secondary battery according to claim 9 , wherein: The apparatus for manufacturing an electrode for a secondary battery according to claim 9 or 10 , wherein a circulation path including the storage section, the supply flow path, the return valve, and the return flow path is configured. The electrode for a secondary battery according to any one of claims 9 to 11 , wherein the housing part includes a main tank connected to the supply flow path, and a sub tank is provided in the return flow path. manufacturing device. The secondary according to any one of claims 9 to 12 , further comprising: a die head moving unit that moves the die head closer to the current collector when forming the thin portion than when forming the thick portion. Equipment for manufacturing electrodes for batteries. 14. The apparatus according to claim 9 , further comprising: a relative moving unit configured to relatively move the current collector at a position opposed to the die head; and a pump for supplying the slurry to the die head. 15. For manufacturing secondary battery electrodes. Manufacture of an electrode for a secondary battery in which a plurality of coated portions having an active material layer formed on a current collector and an uncoated portion having no active material layer formed on the current collector are formed intermittently. The method,
A step of forming the coating section by discharging a slurry containing the active material supplied to the die head via the valve mechanism from the storage section toward the current collector from the die head,
The valve mechanism is located between the storage unit and the die head, a return valve for opening and closing a return flow path for returning the slurry to the storage unit, and a discharge side for supplying the slurry to the die head. A coating valve that opens and closes a flow path, including a connection flow path that connects the return valve and the coating valve,
The step of forming the application section includes a step of forming a thin portion in which the thickness of the active material layer is thin, and a step of forming a thick portion in which the thickness of the active material layer is thick,
In the step of forming the uncoated portion, the coating valve is closed and the return valve is opened,
In the step of forming the thin portion, the slurry is discharged from the die head toward the current collector with the coating valve fully opened while the return valve is at least partially opened,
Wherein in the step of forming the thick portion, together with relatively moves the distance between the said to be longer than the distance in the step of forming the thin portion die head said collector of said collector and said die head, said the remains fully opened Nurikoben, close the return valve, or in a state of opening the return valve with a smaller opening than the opening in the step of forming the thin portion, the said slurry prior Symbol die head A method for producing an electrode for a secondary battery, which is discharged toward a current collector.

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