JP6211429B2 - Method for producing electrode for lithium ion battery - Google Patents

Description

  The present invention relates to a method for producing an electrode for a lithium ion battery, in which a powder containing an electrode active material or the like is compression molded to produce an electrode for a lithium ion battery.

  The demand for lithium-ion batteries that are compact and lightweight, have high energy density, and can be repeatedly charged and discharged is expected to increase in the future from the environmental viewpoint. Lithium-ion batteries are used in the fields of mobile phones and notebook PCs because of their high energy density, but with the expansion and development of applications, further improvements in performance such as lower resistance and larger capacity Is required.

  The electrode for a lithium ion battery can be obtained as an electrode sheet. For example, Patent Document 1 discloses powder rolling in which an electrode sheet is obtained by continuously compressing powder supplied between a pair of press rolls onto a current collector using a pair of press rolls. An apparatus is disclosed.

JP 2009-212113 A

  However, when manufacturing an electrode sheet using the above-described powder rolling apparatus, air accompanying the moving base material or air accompanying the moving press roll enters the press portion of the press roll. The air that has entered the press section is pushed out from between the press rolls to form a flow of air when the powder is pressed onto the substrate by the press roll. Therefore, when compression molding is performed on the substrate by this air flow, the powder is blown and the portion where the thickness of the powder layer is insufficient or the flowing powder is moved and overlapped by the air flow, so that the powder layer Dendrite short (due to lithium metal deposits in the uneven thickness part when the lithium ion battery is repeatedly charged and discharged repeatedly. Due to the development of dendritic lithium metal, a short circuit between the positive electrode and the negative electrode) occurred, and as a result, performance such as safety, discharge efficiency, and cycle life of the lithium ion battery was reduced.

  An object of the present invention is to produce a thin-film lithium ion battery electrode having a smooth surface and improved reliability, safety, discharge efficiency, and cycle life.

  As a result of intensive studies, the inventors have provided an entrained flow suppression unit at the front part of the press part of the press roll, and by suppressing the entrainment of air when pressing the powder with the press roll, the above object is achieved. The inventors have found that this can be achieved and have completed the present invention.

That is, according to the present invention,
(1) In a method for producing an electrode for a lithium ion battery, a powder containing an electrode active material is compacted on a base material using a pair of press rolls to produce an electrode for a lithium ion battery. The powder layer while suppressing entrainment of air by the step of forming a leveled powder layer on the roll or the base material and the entrainment flow suppression part provided in the front part of the press part of the pair of press rolls A method of manufacturing a lithium ion battery electrode, comprising: a step of transporting the powder layer to the press portion; and a step of compacting the powder layer onto the surface of the substrate by the pair of press rolls,
(2) The lithium ion according to (1), wherein the entrained flow suppression unit includes an airflow control member that suppresses entrainment of air when the powder layer is consolidated by the pair of press rolls. Battery electrode manufacturing method,
(3) The method for producing an electrode for a lithium ion battery according to (2), wherein the airflow control member includes an airflow control plate having a plate shape,
(4) The lithium ion battery according to (1), wherein the entrained flow suppression unit includes a vacuum chamber that suppresses entrainment of air when the powder layer is consolidated by the pair of press rolls. Electrode manufacturing method,
Is provided.

  ADVANTAGE OF THE INVENTION According to this invention, it is an electrode for thin film lithium ion batteries with the smooth surface, and the electrode for lithium ion batteries which improved the performance can be manufactured.

It is a figure which shows the outline of the powder molding apparatus which concerns on 1st Embodiment. It is a figure which shows the outline of the powder molding apparatus which concerns on 2nd Embodiment. It is a figure which shows the outline of the powder molding apparatus which concerns on 3rd Embodiment. It is a figure which shows the outline of the powder molding apparatus which concerns on 4th Embodiment.

  Hereinafter, a method for manufacturing an electrode for a lithium ion battery according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an outline of a powder molding apparatus 2 used for manufacturing a lithium ion battery electrode according to the first embodiment. As shown in FIG. 1, the powder molding apparatus 2 includes a hopper 6 that accommodates the powder 4 and a squeegee that averages the powder 4 supplied from the hopper 6 to the base material 8 and forms a powder layer 10. A pressing plate 14 for compacting the plate 12 and the powder layer 10 is provided. Here, the press roll 14 has a pair of press rolls 14A and 14B, and each of the press rolls 14A and 14B has a horizontal tangent line at the press portion, and is pressed above the press roll 14B. It arrange | positions so that the use roll 14A may be located.

  An airflow control plate 16 that suppresses entrainment of air when the powder layer 10 is consolidated is disposed in front of the press portion of the pair of press rolls 14A and 14B, that is, upstream in the traveling direction of the powder layer 10. Has been. Here, the airflow control plate 16 is disposed at a predetermined angle with respect to the base material 8 and the powder layer 10, and the tip thereof is in contact with or close to the press roll 14 </ b> A. For example, in the case of a pair of press rolls 14 </ b> A and 14 </ b> B having a roll diameter of 350 mm, the airflow control plate 16 having a thickness of 5 mm is disposed at an angle of 0 to 30 ° with respect to the base material 8 and the powder layer 10. The closest distance between the tip of the airflow control plate 16 and the surface of the pressing roll 14A is set to 0 to 15 mm, and the closest distance between the tip of the airflow control plate 16 and the surface of the powder layer 10 is set to 1 to 20 mm. Yes. Note that a fluorine resin adhesive tape is attached to the tip of the airflow control plate 16 in order to reduce friction with the press roll 14A.

  When using this powder forming apparatus 2 to manufacture a rolled sheet 18 as an electrode for a lithium ion battery, the powder 4 is supplied from the hopper 6 to the base material 8 and the powder supplied to the base material 8 is supplied. 4 is leveled by a squeegee plate 12 to form a powder layer 10 on the substrate 8. The powder layer 10 formed on the substrate 8 is consolidated by a pair of press rolls 14A and 14B provided with an airflow control plate 16. Thereby, the rolled sheet 18 in which the sheet-like molded product 20 is formed on the base material 8 is manufactured.

  According to this powder forming apparatus 2, the airflow control plate 16 can prevent the air accompanying the press roll 14A and the air accompanying the base material 8 from entering the press portions of the pair of press rolls. it can. Therefore, when the powder layer 10 formed on the base material 8 is consolidated by the pair of press rolls 14A and 14B, the amount of air pushed out from the press portion of the pair of press rolls is reduced. As a result, the movement of the powder 4 forming the sheet-like molded product 20 due to the flow of air pushed out from the press portions of the pair of press rolls is suppressed, and the occurrence of see-through and wrinkles of the rolled sheet 18 is suppressed. Accordingly, it is possible to produce a lithium ion battery electrode having no uneven thickness.

  In the first embodiment described above, the plate-shaped airflow control plate 16 having a constant thickness is used. However, the thickness decreases as the press roll 14A is approached, and the cross section has a triangular or trapezoidal shape. An airflow control plate may be used. In this case, the air flow control plate 16 is arranged so that the surface on the base material 8 side is at an angle of 0 to 30 ° with respect to the base material 8, and the tip thereof is in contact with or close to the press roll. Deploy.

  Also in this case, when the front end of the airflow control plate 16 is brought into contact with the press roll 14A, in order to reduce friction with the press roll 14A, a fluororesin adhesive tape or the like is attached to the front end of the airflow control plate 16. It is preferable to apply a tape.

  Here, the substrate 8 may be a thin film substrate, and usually has a thickness of 1 μm to 1000 μm, preferably 5 μm to 800 μm. As the substrate 8, metal foil or carbon such as aluminum, platinum, nickel, tantalum, titanium, stainless steel, copper, and other alloys, conductive polymer, paper, natural fiber, polymer fiber, fabric, polymer resin A film etc. are mentioned, It can select suitably according to the objective. Examples of the polymer resin film include polyester resin films such as polyethylene terephthalate and polyethylene naphthalate, plastic films and sheets including polyimide, polypropylene, polyphenylene sulfide, polyvinyl chloride, aramid film, PEN, PEEK, and the like. It is done.

  Among these, when manufacturing the sheet | seat for lithium ion battery electrodes as the rolled sheet 18, metal foil, a carbon film, and a conductive polymer film can be used as the base material 8, and a metal is used suitably. It is done. Among these, it is preferable to use copper, aluminum, or an aluminum alloy in terms of conductivity and voltage resistance.

  Further, the surface of the base material 8 may be subjected to treatment such as coating treatment, drilling, buffing, sandblasting and / or etching. It is particularly preferable to apply an adhesive or the like to the surface of the substrate 8 because the sheet-like molded product 20 formed on the substrate 8 can be firmly held.

  Examples of the powder 4 accommodated in the hopper 6 include composite particles containing an electrode active material. The composite particles include an electrode active material and a binder, and may include other dispersants, conductive materials, and additives as necessary.

  When the composite particles are used as a material for a lithium ion battery electrode, examples of the positive electrode active material include metal oxides capable of reversibly doping and dedoping lithium ions. Examples of the metal oxide include lithium cobaltate, lithium nickelate, lithium manganate, and lithium iron phosphate. In addition, the positive electrode active material illustrated above may be used independently according to a use, and may be used in mixture of multiple types.

  The active material of the negative electrode as the counter electrode of the positive electrode for lithium ion batteries includes graphitizable carbon, non-graphitizable carbon, low crystalline carbon such as pyrolytic carbon (amorphous carbon), graphite (natural graphite) , Artificial graphite), alloy materials such as tin and silicon, oxides such as silicon oxide, tin oxide, and lithium titanate. In addition, the electrode active material illustrated above may be used independently according to a use, and may be used in mixture of multiple types.

  The shape of the electrode active material for the lithium ion battery electrode is preferably a granulated particle. When the particle shape is spherical, a higher-density electrode for a lithium ion battery can be formed at the time of forming the electrode.

  The volume average particle diameter of the electrode active material for a lithium ion battery electrode is usually 0.1 to 100 μm, preferably 0.5 to 50 μm, more preferably 0.8 to 30 μm for both the positive electrode and the negative electrode.

  The binder used for the composite particles is not particularly limited as long as it is a compound capable of binding the electrode active materials to each other. A suitable binder is a dispersion type binder having a property of being dispersed in a solvent. Examples of the dispersion-type binder include high molecular compounds such as silicon polymers, fluorine-containing polymers, conjugated diene polymers, acrylate polymers, polyimides, polyamides, polyurethanes, and preferably fluorine-containing polymers. Polymers, conjugated diene polymers and acrylate polymers, more preferably conjugated diene polymers and acrylate polymers.

  The shape of the dispersion-type binder is not particularly limited, but is preferably particulate. By being particulate, the binding property is good, and it is possible to suppress deterioration of the capacity of the manufactured lithium ion battery electrode and deterioration due to repeated charge and discharge. Examples of the particulate binder include those in which the particles of the binder such as latex are dispersed in water, and particulates obtained by drying such a dispersion.

  The amount of the binder is such that the adhesion between the obtained electrode active material layer and the substrate can be sufficiently secured and the internal resistance can be lowered. The amount is usually 0.1 to 50 parts by weight, preferably 0.5 to 20 parts by weight, more preferably 1 to 15 parts by weight.

  As described above, a dispersant may be used for the composite particles as necessary. Specific examples of the dispersant include cellulose polymers such as carboxymethyl cellulose and methyl cellulose, and ammonium salts or alkali metal salts thereof. These dispersants can be used alone or in combination of two or more.

  As described above, a conductive material may be used for the composite particles as necessary. Specific examples of the conductive material include conductive carbon black such as furnace black, acetylene black, and ketjen black (registered trademark of Akzo Nobel Chemicals Bethloten Fennaut Shap). Among these, acetylene black and ketjen black are preferable. These conductive materials can be used alone or in combination of two or more.

  The composite particles are obtained by granulating using an electrode active material, a binder, and other components such as the conductive material added as necessary, and include at least an electrode active material and a binder, Each of the above does not exist as an independent particle, but forms one particle by two or more components including an electrode active material and a binder as constituent components. Specifically, a plurality of (more preferably several to several tens) electrode active materials are formed by combining a plurality of the individual particles of the two or more components to form secondary particles. It is preferable that the particles are bound to form particles.

  The production method of the composite particles is not particularly limited, and can be produced by a known granulation method such as a fluidized bed granulation method, a spray drying granulation method, or a rolling bed granulation method.

  The volume average particle diameter of the composite particles is usually in the range of 0.1 to 1000 μm, preferably 1 to 500 μm, more preferably 30 to 250 μm, from the viewpoint of easily obtaining an electrode active material layer having a desired thickness.

  The average particle size of the composite particles is a volume average particle size calculated by measuring with a laser diffraction particle size distribution measuring device (for example, SALD-3100; manufactured by Shimadzu Corporation).

  Next, with reference to FIG. 2, the manufacturing method of the electrode for lithium ion batteries which concerns on the 2nd Embodiment of this invention is demonstrated. FIG. 2 is a diagram showing an outline of a powder molding apparatus 22 used for manufacturing a lithium ion battery electrode according to the second embodiment. A powder molding apparatus 22 shown in FIG. 2 is provided with a vacuum chamber 24 in place of the airflow control plate 16 of the powder molding apparatus 2 shown in FIG. Therefore, a detailed description of the same configuration as that of the above-described powder molding apparatus 2 is omitted, and the same configuration as that of the above-described powder molding apparatus 2 is denoted by the same reference numeral.

  The vacuum chamber 24 extends in the direction of the rotation axis of the press roll 14A and has an intake port 26 for sucking air accompanying the press roll 14A. The vacuum chamber 24 is disposed such that the air inlet 26 is in contact with or close to the press roll 14 </ b> A, and the surface on the substrate side is close to the powder layer 10. That is, the distance between the suction port 26 of the vacuum chamber 24 and the pressing roll 14A is 0 to 15 mm, and the distance between the surface of the vacuum chamber 24 on the substrate side and the surface of the powder layer 10 is 1 to 20 mm. Has been.

  Therefore, by providing the vacuum chamber 24, it is possible to suppress the air accompanying the press roll 14 </ b> A from being sucked from the air inlet 26 and entering the press portions of the pair of press rolls. Therefore, when the powder layer 10 formed on the base material 8 is consolidated by the pair of press rolls 14A and 14B, the amount of air pushed out from the press portion of the pair of press rolls is reduced. As a result, the movement of the powder forming the sheet-like molded product 20 due to the air flow pushed out between the pair of press rolls 14A and 14B is suppressed, and the occurrence of see-through and wrinkles of the rolled sheet 18 is suppressed. Accordingly, it is possible to produce a lithium ion battery electrode having no uneven thickness.

  Next, with reference to FIG. 3, the manufacturing method of the electrode for lithium ion batteries which concerns on the 3rd Embodiment of this invention is demonstrated. FIG. 3 is a diagram showing an outline of a powder molding apparatus 28 used for manufacturing a lithium ion battery electrode according to the third embodiment. 3 arranges a pair of press rolls 14A and 14B of the powder forming apparatus 2 shown in FIG. 1 so that the tangent line in each press portion is perpendicular to the horizontal direction. Instead of forming the powder layer 10 on the material 8, the powder layer 10 is formed on the press rolls 14 </ b> A and 14 </ b> B, and the powder layer 10 is consolidated on both surfaces of the base material 8 that proceeds downward. Is. Therefore, a detailed description of the same configuration as that of the above-described powder molding apparatus 2 is omitted, and the same configuration as that of the above-described powder molding apparatus 2 is denoted by the same reference numeral.

  In the powder forming apparatus 28, a hopper 6A and a squeegee plate 12A are provided for the press roll 14A, and an airflow control plate 16A is provided between the press roll 14A and the substrate 8. ing. The airflow control plate 16A has a predetermined angle with respect to the surface of the substrate 8 facing the pressing roll 14A, and the tip thereof is disposed close to the pressing roll 14A. That is, the airflow control plate 16 </ b> A is disposed at an angle of 0 to 30 ° with respect to the base material 8. The distance at the closest point between the tip of the airflow control plate 16A and the surface of the powder layer 10 formed on the pressing roll 14A is 1 to 30 mm, and the distance between the airflow control plate 16 and the substrate 8 is 0.1. It is set to ˜20 mm.

  Further, the powder molding apparatus 28 includes a hopper 6B and a squeegee plate 12B for the press roll 14B, and further, an airflow control plate 16B between the press roll 14B and the substrate 8. It has. The airflow control plate 16B has a predetermined angle with respect to the surface of the substrate 8 facing the press roll 14B, and the tip thereof is disposed close to the press roll 14B. That is, the airflow control plate 16 </ b> B is arranged at an angle of 0 to 30 ° with respect to the base material 8. The distance at the closest point between the tip of the airflow control plate 16B and the surface of the powder layer 10 formed on the press roll 14B is 1 to 30 mm, and the distance between the airflow control plate 16 and the substrate 8 is 0.1. It is set to ˜20 mm.

  In the case of producing a rolled sheet 30 as an electrode for a lithium ion battery using the powder forming apparatus 28, the powder 4 is supplied from the hoppers 6A and 6B onto the pair of press rolls 14A and 14B, respectively. The powder 4 supplied on the pair of press rolls 14A and 14B is averaged by the squeegee plates 12A and 12B, and the powder layer 10 is formed on the pair of press rolls 14A and 14B. The powder layer 10 formed on the pair of press rolls 14A and 14B is conveyed from above the pair of press rolls 14A and 14B by the pair of press rolls 14A and 14B provided with the airflow control plates 16A and 16B. The substrate 8 is compacted. Thereby, the rolling sheet 30 by which the sheet-like molded product 20 was formed in the surface facing the rolls 14A and 14B for press of the base material 8, respectively is manufactured.

  According to this powder forming apparatus 28, the air accompanying the pair of press rolls 14A and 14B and the air accompanying the base material 8 enter the press portions of the pair of press rolls by the air flow control plates 16A and 16B. This can be suppressed. Therefore, when the powder layer 10 formed on the press rolls 14A and 14B is compacted against the base material 8 by the pair of press rolls 14A and 14B, the air extruded from the press portions of the pair of press rolls The amount of decreases. As a result, the movement of the powder 4 forming the sheet-like molded product 20 due to the flow of air extruded from the press portions of the pair of press rolls is suppressed, and the occurrence of see-through and wrinkles in the rolled sheet 30 is suppressed. Accordingly, it is possible to produce a lithium ion battery electrode having no uneven thickness.

  Next, with reference to FIG. 4, the manufacturing method of the electrode for lithium ion batteries which concerns on the 4th Embodiment of this invention is demonstrated. FIG. 4 is a diagram showing an outline of a powder molding apparatus 32 used for manufacturing a lithium ion battery electrode according to the fourth embodiment. 4 is provided with air flow control plates 16C and 16D having different shapes in place of the air flow control plates 16A and 16B of the powder forming device 28 shown in FIG. Therefore, a detailed description of the same configuration as that of the above-described powder molding apparatus 28 is omitted, and the same configuration as that of the above-described powder molding apparatus 28 is denoted by the same reference numeral.

  The air flow control plates 16C and 16D have a triangular cross section where the thickness decreases as they approach the press portion that presses the powder layer 10 onto the substrate 8 by the press rolls 14A and 14B. The air flow control plates 16C and 16D have their tips close to the powder layer 10 formed on the press rolls 14A and 14B, and the surfaces of the air flow control plates 16C and 16D facing the base material 8 are close to the base material 8. Are arranged. That is, the airflow control plates 16C and 16D are arranged so that the closest distance between the tips of the airflow control plates 16C and 16D and the powder layer 10 is 1 to 30 mm, and the distance between the airflow control plate and the base material is 0.1 to 20 mm.

  According to the powder forming apparatus 32, the air accompanying the pair of press rolls 14A and 14B and the air accompanying the base material 8 enter between the pair of press rolls 14A and 14B by the air flow control plates 16C and 16D. Can be suppressed. Therefore, when the powder layer 10 formed on the press rolls 14A and 14B is compacted with respect to the base material 8 by the pair of press rolls 14A and 14B, the air extruded from the pair of press roll press portions The amount decreases. As a result, the movement of the powder forming the sheet-like molded product 20 due to the flow of air extruded from the pair of press roll press portions is suppressed, and the occurrence of see-through and wrinkles of the rolled sheet 30 is suppressed. Accordingly, it is possible to produce a lithium ion battery electrode having no uneven thickness.

2,22,28,32 ... powder molding apparatus, 4 ... powder, 6 ... hopper, 8 ... base material, 10 ... powder layer, 12 ... squeegee plate, 14 ... press roll, 16 ... airflow control plate , 18, 30 ... rolled sheet, 20 ... sheet-like molded product, 24 ... vacuum chamber, 26 ... air inlet

Claims (5)

In a method for producing an electrode for a lithium ion battery, a powder containing an electrode active material is compacted on a substrate using a pair of press rolls, and an electrode for a lithium ion battery is produced.
Leveling the powder on the press roll or the substrate to form a powder layer;
Conveying the powder layer to the press section while suppressing entrainment of air by an airflow control plate disposed in front of the press roll of the pair of press rolls and in contact with or close to the press roll And a process of
The step of compacting the powder layer onto the surface of the substrate by the pair of pressing rolls;
A method for producing a lithium ion battery electrode comprising: The air flow control plate, the manufacturing method of a lithium ion battery electrode according to claim 1, characterized in that it has a plate shape. The method for producing an electrode for a lithium ion battery according to claim 1 or 2, wherein the distance between the tip of the airflow control plate and the surface of the press roll is 0 to 15 mm. 4. The lithium ion battery according to claim 1, wherein the airflow control plate is disposed with a predetermined angle with respect to the base material and the powder layer. 5. For manufacturing an electrode. The said predetermined angle is 0-30 degrees, The manufacturing method of the electrode for lithium ion batteries of Claim 4 characterized by the above-mentioned.

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