JP2016115567A - Method of manufacturing electrode for lithium ion battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing an electrode for a lithium ion battery capable of keeping peel strength between a powder layer and a base material high at both width-directional ends of the powder layer.SOLUTION: A method of manufacturing an electrode for a lithium ion battery in which an electrode sheet is manufactured by compacting powder 6 including an electrode active substance on a surface of a base material 14 with a pair of press rolls 4 includes: a powder supply process of supplying first powder 6a to a region including the width-directional center of the surface of the base material, and also supplying second powder 6b having a larger particle size than the first powder to both side parts of the first powder; a powder film formation process of leveling the first powder and the second powder, supplied to the surface of the base material, into a powder layer 10 using a squeegee member 12; and a compaction process of compacting the powder layer on the surface of the base material by passing the base material having the powder layer formed between the pair of press rolls.SELECTED DRAWING: 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, in Patent Document 1, 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 of manufacturing a lithium ion secondary battery that obtains an electrode sheet by continuously compression-molding a powder layer on the surface is disclosed.

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 supplied powder having a larger particle diameter to both ends in the width direction of the powder layer as compared to the central portion in the width direction, and the powder by flow in the width direction of the powder layer The inventors have found that the above object can be achieved by preventing the end of the layer from sagging, and have completed the present invention.

That is, according to the present invention,
(1) In the method for producing an electrode sheet for a lithium ion battery in which a powder containing an electrode active material is compacted on the surface of a base material by a pair of pressing rolls, A powder supply step of supplying a first powder to a region including the second powder and supplying a second powder having a particle diameter larger than that of the first powder to both sides of the first powder; A powder layer forming step of forming a powder layer by leveling the first powder and the second powder supplied to the surface of the substrate using a member, and the powder layer is formed A method for producing an electrode for a lithium ion battery, comprising: a compacting step of compacting the powder layer on a surface of the base material by passing the base material between the pair of press rolls;
(2) The second powder is characterized in that the volume average particle diameter D50 at which the cumulative detection frequency is 50% in the particle diameter distribution is 100% to 150% of the roll gap ( 1) The manufacturing method of the electrode for lithium ion batteries as described in
(3) The second powder has a value obtained by dividing the particle diameter D90 at which the cumulative detection frequency is 90% in the particle diameter distribution by the particle diameter D10 at which the cumulative detection frequency is 10% in the particle diameter distribution. The method for producing an electrode for a lithium ion battery according to (1) or (2), which is 1.7 or less,
(4) Any one of (1) to (3), wherein the second powder is supplied to an area having a width of 1 mm to 10 mm from the end of the powder layer to the center in the width direction. A method for producing an electrode for a lithium ion battery according to claim 1,
Is provided.

  According to the method for producing an electrode for a lithium ion battery of the present invention, the peel strength between the powder layer and the base material at both ends in the width direction of the powder layer can be maintained high.

It is the perspective view which looked at the powder molding device concerning an embodiment from the upper part. It is the figure which looked at the powder forming apparatus concerning an embodiment from the side. It is the figure which looked at the base material concerning an embodiment from the upper part. It is the figure which looked at a mode that a powder layer concerning an embodiment is compression-molded from a longitudinal direction of a substrate. It is the figure which looked at a mode that a powder layer is compression-molded in the conventional powder molding method from the longitudinal direction of a substrate.

  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 perspective view of a powder molding apparatus 2 used in a method for manufacturing an electrode for a lithium ion battery according to an embodiment of the present invention as viewed from above, and FIG. 2 is a diagram of this as viewed from the side. is there. As shown in FIGS. 1 and 2, the powder molding apparatus 2 includes a hopper 8, a squeegee roll 12, and a press roll 4.

  Here, the hopper 8 is a container for storing the powder 6 containing the electrode active material and the binder, and the first hopper 8A for storing the first powder 6a (see FIG. 4) and the first powder. A second hopper 8B that accommodates a second powder 6b (see FIG. 4) having a larger particle diameter than the body 6a is provided. The hopper 8 is located above the base material 14 which is a current collector conveyed in the horizontal direction, and the width of the base material 14 in the order of the second hopper 8B, the first hopper 8A, and the second hopper 8B from the front of FIG. Arranged in the direction.

  The first powder 6a has a volume average particle diameter D50 (volume average particle diameter at which the cumulative detection frequency is 50% in the particle diameter distribution) smaller than the size of the roll gap X described later. The second powder 6b has a volume average particle diameter D50 of about 100% to 150% of the roll gap X.

  The squeegee roll 12 is a cylindrical roll member extending in the width direction of the base material 14, and levels the powder 6 to form the powder layer 10 on the surface of the base material 14. A predetermined gap is formed between the squeegee roll 12 and the surface of the substrate 14, and the basis weight of the powder layer 10 is controlled when the powder layer 10 is formed.

  The press roll 4 includes a pair of first roll 4A and second roll 4B that press the base material 14 conveyed in the vertical direction. Here, the 1st roll 4A has a function which changes the advancing direction of the base material 14 conveyed in a horizontal direction to a perpendicular direction. Further, as shown in FIG. 4, a predetermined roll gap X is formed between the surface of the second roll 4 </ b> B and the surface of the base material 14.

  FIG. 3 is a view of the base material 14 as viewed from above. As shown in FIG. 3, the base material 14 is a belt-like sheet extending in one direction, and a binding material 18 for attaching the powder 6 to the base material 14 has a predetermined width on the surface of the base material 14. It has been applied.

  Next, the manufacturing method of the electrode sheet as an electrode for lithium ion batteries using this powder shaping | molding apparatus 2 is demonstrated. First, the powder 6 is supplied from the hopper 8 so as to adhere to the region where the binder 18 of the base material 14 conveyed in the horizontal direction is applied (powder supply step). Specifically, the first powder 6 a is supplied from the first hopper 8 </ b> A so as to adhere to a predetermined region including the central portion in the width direction of the binder 18. In addition, the second powder 6b is supplied from the second hopper 8B to both side portions of the first powder in the width direction so as to adhere to both ends of the binder 18.

  Next, the powder 6 supplied to the surface of the base material 14 is leveled by the squeegee roll 12, and the powder layer 10 is formed in a region where the binder 18 is applied on the surface of the base material 14 (powder). Body layer forming step).

  Next, the base material 14 on which the powder layer 10 is formed is conveyed from the horizontal direction to the vertical direction by the first roll 4A and conveyed to the press point, and a pair of first roll 4A and second roll It passes between 4B (consolidation process). Thereby, the electrode sheet by which the powder layer 10 was compression-molded on the surface of the base material 14 is manufactured.

  FIG. 4 is a view of the state in which the powder layer 10 is compression-molded in the consolidation step, as viewed from the longitudinal direction of the base material 14. As described above, since the second powder 6b has a volume average particle diameter D50 having a size of about 100% to 150% of the roll gap X, as shown in FIG. In the case of compression molding, the second powder 6b suppresses the flow in the width direction of the powder layer 10 and prevents the end of the powder layer 10 from sagging.

  When the volume average particle diameter D50 of the second powder 6b is smaller than 100% of the size of the roll gap X, that is, as in the conventional powder molding method shown in FIG. When the powder layer 10 using only the first powder 6a having the volume average particle diameter D50 smaller than the size is compression-molded, the flow of the powder layer 10 in the width direction cannot be suppressed. Sagging occurs at the end of the layer 10.

  In addition, when the volume average particle diameter D50 of the second powder 6b is larger than 150% of the size of the roll gap X, the second powder 6b is rolled into the roll gap X when the powder layer 10 is compression molded. And the basis weight of the both ends in the width direction of the powder layer 10 is insufficient. For this reason, the basis weight difference of the powder layer 10 formed on the electrode sheet is increased, and lithium is deposited at the time of charge and discharge, causing a short circuit between the electrodes. Therefore, there is a possibility that the safety as a battery, the discharge efficiency, the cycle life, and the like are reduced.

  Further, the second powder 6 b is supplied to an area having a width of 1 mm to 10 mm from the end of the powder layer 10 to the center in the width direction of the base material 14. Thereby, when the powder layer 10 is compression-molded, the powder layer 10 can be sufficiently suppressed from flowing in the width direction. Here, the width of the region to which the second powder 6 b is supplied is more preferably 1 mm to 5 mm from the end of the powder layer 10 to the center in the width direction of the base material 14.

  In addition, when the width | variety of the area | region where the 2nd powder 6b is supplied is made too narrow, when the powder layer 10 is compression-molded, it can fully suppress that the powder layer 10 flows into the width direction. This is not possible, and sagging occurs at the end of the powder layer 10. In addition, when the width of the region to which the second powder 6b is supplied is excessively widened, the basis weight of the both ends in the width direction of the powder layer 10 is extremely higher than the central portion in the width direction. Problems may arise.

  Further, the second powder 6b has a sharp particle diameter in which the value obtained by dividing the particle diameter D90 at which the cumulative detection frequency is 90% by the particle diameter D10 at which the cumulative detection frequency is 10% is 1.7 or less. It has a distribution and the variation in particle diameter is small. For this reason, among the particles contained in the second powder 6b, it has a particle diameter of 100% to 150% of the roll gap X, which is suitable for suppressing the sagging at the end of the powder layer 10. The proportion of particles increases. When the particle size distribution of the second powder 6b is broad, the ratio of particles having a small particle size is high, so that the flow in the width direction of the powder layer 10 cannot be sufficiently suppressed. However, since the ratio of large particles is high, there is a possibility that problems such as clogging of the second powder 6b in the roll gap X may occur.

  In the method for manufacturing an electrode for a lithium ion battery according to this embodiment, the powder layer 10 is fed by a pair of press rolls 4 by supplying powder having a large particle diameter to both ends in the width direction of the powder layer 10. It is possible to prevent the end of the powder layer 10 from sagging when compression molding is performed. Therefore, the adhesive force between the powder layer 10 and the base material 14 at both ends in the width direction of the powder layer 10 is improved, and the powder layer 10 and the base material 14 at both ends in the width direction of the powder layer 10 are improved. The peel strength can be kept high.

  The substrate 14 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 14, 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 electrode sheet used for the electrode for lithium ion batteries, metal foil, a carbon film, and a conductive polymer film can be used as the base material 14, and a metal is used suitably. Among these, it is preferable to use copper, aluminum, or an aluminum alloy in terms of conductivity and voltage resistance.

  In addition, the surface of the base material 14 may be subjected to processing such as coating treatment, drilling, buffing, sandblasting and / or etching. Examples of the binder 18 applied to the surface of the base material 14 include an SBR aqueous dispersion. 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 18 may contain a thickener or 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, the binder 18 may be water-based polyacrylic acid (PAA), organic solvent-based polyvinylidene fluoride (PVDF), or the like.

  Examples of the powder 6 supplied to the base material 14 include composite particles including an electrode active material and a binder. The composite particles may contain other dispersants, conductive materials, and additives as necessary.

  When the composite particles are used as an electrode 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. Due to the particulate form, the binding property is good, and it is possible to suppress the decrease in capacity of the manufactured battery and the deterioration of discharge efficiency and cycle life 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 10 to 350 μm, preferably 20 to 250 μm, more preferably 30 to 150 μm in the first powder 6a. Moreover, in the 2nd powder 6b, it is 50-750 micrometers normally, Preferably it is 60-450 micrometers, More preferably, it is the range of 70-300 micrometers.

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

  In the above-described embodiment, the particle size distribution of the first powder 6a and the second powder 6b is a dry laser diffraction / scattering particle size distribution measuring device (for example, Nikkiso Co., Ltd .: Microtrac MT- 3200 II) is a particle size distribution measured and calculated.

DESCRIPTION OF SYMBOLS 2 ... Powder molding apparatus, 4 ... Roll for press, 4A ... 1st roll, 4B ... 2nd roll, 6 ... Powder, 6a ... 1st powder, 6b ... 2nd powder, 8 ... Hopper, 8A ... 1st hopper, 8B ... 2nd hopper, 10 ... Powder layer, 12 ... Squeegee roll, 14 ... Base material

Claims (4)

In the method for producing an electrode for a lithium ion battery, wherein an electrode sheet is produced by compacting a powder containing an electrode active material on the surface of a substrate with a pair of press rolls,
The first powder is supplied to a region including the center in the width direction of the surface of the base material, and the second powder has a particle diameter larger than that of the first powder on both sides of the first powder. A powder supply process for supplying
A powder layer forming step of leveling the first powder and the second powder supplied to the surface of the substrate using a squeegee member to form a powder layer;
A lithium ion comprising: a compacting step of compacting the powder layer on a surface of the base material by passing the base material on which the powder layer is formed between the pair of press rolls. Manufacturing method of battery electrode.   The volume average particle diameter D50 at which the accumulation of detection frequency in the particle diameter distribution is 50% in the second powder has a size of 100% to 150% of the roll gap. Manufacturing method of electrode for lithium ion battery.   The second powder has a value obtained by dividing the particle diameter D90 at which the cumulative detection frequency is 90% in the particle size distribution by the particle diameter D10 at which the cumulative detection frequency is 10% in the particle size distribution. The manufacturing method of the electrode for lithium ion batteries of Claim 1 or 2 characterized by the following.   The said 2nd powder is supplied to the area | region of the width of 1 mm-10 mm in the width direction center side from the edge part of the said powder layer, The Claim 1 characterized by the above-mentioned. Manufacturing method of electrode for lithium ion battery.

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