JP2016115432A - Method of manufacturing electrode for lithium ion battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an electrode for a lithium ion battery capable of maintaining high peel strength between a powder layer and a base material at both widthwise ends of the powder layer. SOLUTION: A coating step of coating a binder coating liquid on a surface of a base material 12 wider than a set width corresponding to a width of an electrode for a lithium ion battery, and the base material surface coated with the binder coating liquid. A supply step of supplying the powder 16 containing the electrode active material wider than the set width, a control step of controlling the basis weight of the powder on the surface of the base material, and a pair of pressing rolls 22A and 22B. A step of forming the powder layer 24 by pressing the powder on the surface of the base material, and a step of cutting the powder layer along the edges on both sides of the set width. A removing step of air-purging the powder layer formed outside the preset width from the surface of the base material. [Selection diagram] Figure 1

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 that after a binder is applied to a base material, powder is dispersed to form a powder layer on the surface of the base material, and the base material is passed between a pair of press rolls. A method for manufacturing a lithium ion secondary battery is disclosed in which an electrode sheet is obtained by continuously compression-molding a powder layer on the surface of the battery.

JP 2014-078497 A

  By the way, when manufacturing an electrode sheet using the above-described method for manufacturing a lithium ion secondary battery, when the base material is passed between a pair of press rolls, the powder flows to the outside in the width direction and the powder layer Sagging occurs at the end of the. For this reason, the width direction both ends of the powder layer are insufficiently pressed, and the adhesion force between the powder layer and the substrate is reduced. As a result, the powder layer and the substrate at both ends in the width direction of the powder layer There was a problem that the peel strength of the resin was lowered.

  The objective of this invention is providing the manufacturing method of the electrode for lithium ion batteries which can maintain the peeling strength of the powder layer and a base material in the width direction both ends of a powder layer high.

  As a result of intensive studies, the present inventors have found that the above object can be achieved by cutting the both ends in the width direction of the formed powder layer and removing the powder layer formed at both ends in the width direction. The headline and the present invention were completed.

That is, according to the present invention,
(1) An application step of applying a binder coating liquid wider than a set width corresponding to the width of the electrode for a lithium ion battery on the surface of the substrate; and the substrate surface on which the binder coating liquid is applied, A supply step of supplying a powder containing an electrode active material wider than the set width; a control step of controlling the basis weight of the powder on the surface of the substrate; and a pair of press rolls. A forming step of forming a powder layer by pressing the powder, a cutting step of cutting the powder layer along edges on both sides of the set width, and the set width from the substrate surface A step of air purging the powder layer formed outside, and a method for producing an electrode for a lithium ion battery,
(2) The method for producing an electrode for a lithium ion battery according to (1), wherein the cutting step is performed by cutting the powder layer using a rotary cutter.
Is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the electrode for lithium ion batteries which can maintain the peeling strength of the powder layer and base material in the width direction both ends of a powder layer high can be provided.

It is a figure which shows the outline of the powder molding apparatus which concerns on embodiment of this invention. It is a figure for demonstrating the structure and operation | movement of the rotary cutter and air purge apparatus which concern on embodiment of this invention.

  Hereinafter, a method for manufacturing an electrode for a lithium ion battery according to an 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 an embodiment of the present invention.

  As shown in FIG. 1, the powder molding apparatus 2 includes a hopper 18 that contains the powder 16, a squeegee member 20 that controls the basis weight of the powder 16 that is supplied from the hopper 18 to the surface of the base 12, and a base A pair of press rolls 22A and 22B for pressing the powder 16 supplied to the surface of the pair 12, and a pair of rotary cutters 4A and 4B for cutting at both ends in the width direction of the formed powder layer 24 (see FIG. 2) And a pair of air purge devices 6A and 6B (see FIG. 2) for jetting air toward the powder layer 24 formed at both ends in the width direction.

  The squeegee member 20 has a cylindrical shape and is disposed on the downstream side of the hopper 18 and on the upstream side of the pair of press rolls 22A and 22B. The rotation axis of the squeegee member 20 is parallel to the rotation axes of the pair of press rolls 22A and 22B.

  The pair of rotary cutters 4A and 4B has a disk shape, and a blade for cutting the powder layer 24 is formed at the edge of the disk so that the center of the disk can be rotated as a rotation axis. It is configured. FIG. 2 is a diagram for explaining the configuration and operation of the pair of rotary cutters 4A and 4B and the pair of air purge devices 6A and 6B. The pair of rotary cutters 4A and 4B are disposed on the downstream side of the pair of press rolls 22A and 22B, respectively, at both ends in the width direction of the powder layer 24 as shown in FIG. The rotary cutter 4A cuts 8A into the powder layer 24 along the edge on one end side (left end side in FIG. 2) of the set width D corresponding to the width of the lithium ion battery electrode. The rotary cutter 4B cuts 8B into the powder layer 24 along the edge on the other end side (the right end side in FIG. 2) of the set width D. Note that the pair of rotary cutters 4A and 4B do not cut the base material 12, but only cut the powder layer 24 with the cuts 8A and 8B.

  The pair of air purge devices 6A and 6B are disposed on the downstream side of the pair of rotary cutters 4A and 4B, respectively, at both ends in the width direction of the powder layer 24 as shown in FIG. The air purge device 6A sprays compressed air from the nozzle 6a onto the powder layer 24 formed on one outer side (left outer side in FIG. 2) from the set width D, that is, outside the cut 8A. The powder layer 24 formed outside the cut 8A is air purged from the substrate 12 by the air purge device 6A as shown in FIG. The air purge device 6B sprays compressed air from a nozzle (not shown) against the powder layer 24 formed on the other outer side (right outer side in FIG. 2) from the set width D, that is, outside the cut 8B. . As shown in FIG. 2, the powder layer 24 formed outside the cut 8B is air purged from the substrate 12 by the air purge device 6B.

  Note that the powder layer 24 formed within the set width D has a larger basis weight than the powder layer 24 formed outside the set width D, and the peel strength to the substrate 12 is also large. The outer powder layer 24 is not air purged. On the other hand, the powder layer 24 formed outside the set width D has a smaller basis weight than the powder layer 24 formed within the set width D and has a low peel strength to the base material 12, and thus is easily air purged. The

  When manufacturing an electrode sheet as an electrode for a lithium ion battery using the powder molding apparatus 2, first, a binder coating liquid is applied to the surface of the substrate 12 by a binder coating liquid coating apparatus (not shown). Apply wider than set width D. Specifically, it is applied from the edges on both sides of the set width D to the outside by about 0.1 mm to 5 mm. Next, the powder 16 is supplied from the hopper 18 to the surface of the base material 12 to which the binder coating liquid has been applied, wider than the set width D, that is, to the region where the binder coating liquid has been applied. Then, the basis weight of the powder 16 supplied to the surface of the base material 12 by the squeegee member 20 is controlled, and the powder 16 is pressed by passing between a pair of press rolls 22A and 22B, and the powder layer 24 is formed. Then, as shown in FIG. 2, the powder layer 24 is provided with cuts 8A and 8B along the edges on both sides of the set width D by a pair of rotary cutters 4A and 4B. The powder layer 24 formed outside the set width D, that is, outside the cuts 8A and 8B is air purged from the substrate 12 by the air purge devices 6A and 6B as shown in FIG. Thereby, an electrode sheet in which the powder layer 24 is compression-molded on the surface of the substrate 12 is manufactured.

  According to the method for manufacturing an electrode for a lithium ion battery according to this embodiment, first, the powder layer 24 wider than the set width D corresponding to the width of the electrode sheet to be manufactured is prepared, and both edges of the set width D are formed. A cut is made in the powder layer 24 along the portion, and the powder layer 24 on the outer side in the width direction is air purged from the cut. That is, the powder layer 24 formed at both ends in the width direction has a smaller basis weight of the powder 16 than the central portion in the width direction of the powder layer 24 and the peel strength of the powder 16 to the substrate 12 is reduced. Therefore, the peel strength between the powder layer 24 and the substrate 12 within the set width D can be kept high, and the powder layer 24 formed within the set width D is peeled from the surface of the substrate 12. Can be suppressed. In addition, since the powder layer 24 on the outer side in the width direction from the cuts 8A and 8B is air purged, the edges of both ends of the powder layer 24 within the set width D become smooth due to the cut, and the powder layer 24 is smooth. It is possible to improve the accuracy of the edge portion.

  In this embodiment, after the notches 8A and 8B are cut into the powder layer 24 by the pair of rotary cutters 4A and 4B, the powder layer 24 outside the set width D is air purged by the pair of air purge devices 6A and 6B. However, the powder layer 24 outside the set width D may be air purged by the pair of air purge devices 6A and 6B while the cuts 8A and 8B are inserted into the powder layer 24 by the pair of rotary cutters 4A and 4B. In this case, the rotary cutters 4A and 4B serve as barriers for preventing air from being sprayed onto the powder layer 24 within the set width D.

  In this embodiment, the substrate 12 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 base material 12, 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 an electrode sheet for a lithium ion battery electrode, a metal foil, a carbon film, or a conductive polymer film can be used as the substrate 12, and a metal is preferably used. 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 12 may be subjected to treatment such as coating treatment, drilling, buffing, sandblasting and / or etching.

  The binder coating liquid is an SBR aqueous dispersion, and the concentration of SBR is 10.0 to 40 wt%. The glass transition temperature of SBR is in the range of −50 ° C. to 30 ° C. The binder coating liquid may contain a thickener and a surfactant in order to adjust the viscosity and wettability of the coating liquid. Known thickeners and surfactants can be used. In addition to SBR, water-based polyacrylic acid (PAA), organic solvent-based polyvinylidene fluoride (PVDF), or the like may be used as the binder.

  Examples of the powder 16 accommodated in the hopper 18 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 an electrode material for a lithium ion battery, 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 shape of the particles is spherical, a higher density electrode can be formed during electrode molding.

  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 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).

  2 ... Powder forming device, 4A, 4B ... Rotary cutter, 6A, 6B ... Air purge device, 12 ... Base material, 16 ... Powder, 18 ... Hopper, 20 ... Squeegee member, 22A, 22B ... Press roll, 24 ... Powder layer.

Claims (2)

An application step of applying a binder coating liquid wider than a set width corresponding to the width of the lithium ion battery electrode on the substrate surface;
A supply step of supplying a powder containing an electrode active material wider than the set width to the surface of the base material to which the binder coating liquid has been applied;
A control step of controlling the basis weight of the powder on the substrate surface;
A forming step of forming a powder layer by pressing the powder on the surface of the substrate using a pair of press rolls;
A cutting process for cutting the powder layer along edges on both sides of the set width;
A removing step of air purging the powder layer formed outside the set width from the substrate surface;
The manufacturing method of the electrode for lithium ion batteries characterized by including.   The method for producing an electrode for a lithium ion battery according to claim 1, wherein the cutting step cuts the powder layer using a rotary cutter.

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