JP6209457B2 - 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 laptop computers because of their high energy density. However, with the expansion and development of their applications, safety, low resistance, large capacity, etc. There is a need for improved performance. On the other hand, cost reduction is an important issue for the expansion of the market, and proposal of an inexpensive manufacturing method that realizes the production stability of electrodes for lithium ion batteries is also expected.

  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 an electrode sheet is manufactured using the above-described powder rolling apparatus, the press roll is adjusted until the powder adjusted by the powder supply apparatus and supplied between the rolls is compression-molded by the press roll. Dendritic short due to floating and missing from the top and depositing near the press point, resulting in uneven thickness and density of the electrode and repeated lithium-ion battery charge / discharge (A short circuit between the positive electrode and the negative electrode due to the development of dendritic lithium metal) occurred, and as a result, performance of the lithium ion battery such as safety, discharge efficiency, and cycle life was reduced.

  An object of the present invention is an electrode for a thin film lithium ion battery having no defects such as thickness unevenness and density unevenness of a powder layer including a compression-molded electrode active material, and is reliable, safe and discharge efficiency And manufacturing an electrode for a lithium ion battery with improved cycle life.

  As a result of intensive studies, the present inventors have found that the above object can be achieved by conveying the base material along the powder layer formed on the press roll to the press point, thereby completing the present invention. It came.

That is, according to the present invention,
(1) Lithium ion battery electrode for producing an electrode sheet by compacting a powder containing an electrode active material on the surface of a base material by a pair of press rolls provided below the other roll with respect to one roll In the manufacturing method, a first powder supply step of supplying the powder onto the one roll, and a first powder layer that forms the first powder layer by leveling the powder supplied onto the one roll. A powder layer forming step, a first powder layer conveying step of conveying the base material along the first powder layer formed on the one roll, and the powder on the other roll. Forming a second powder layer, forming a second powder layer by leveling the powder supplied on the other roll, and forming on the other roll A second powder layer transporting step for transporting the second powder layer formed, and the pair of press rolls The compression of compressing the second powder layer on the other surface of the substrate at the same time as the first powder layer is consolidated on one surface of the substrate by passing the substrate between A method for producing an electrode for a lithium ion battery, comprising a molding step,
(2) The pair of rolls are arranged such that an angle formed by a tangent to a point where the outer peripheral surfaces of the one roll and the other roll are closest to each other and a horizontal line is equal to or less than an angle of repose inherent to the powder. A method for producing an electrode for a lithium ion battery as described in (1),
(3) In the first powder supply step, the angle formed between the tangent to the outer peripheral surface of the one roll and a horizontal line is at a position on the one roll where the angle of repose is less than or equal to the repose angle specific to the powder. Powder is supplied, and in the second powder supply step, an angle formed between a tangent to the outer peripheral surface of the other roll and a horizontal line is not more than an angle of repose inherent to the powder on the other roll. The method for producing an electrode for a lithium ion battery according to (1) or (2), wherein the powder is supplied to a position,
Is provided.

  According to the present invention, there is provided an electrode for a thin film lithium ion battery having no defects such as uneven thickness and density of a layer made of a powder containing a compression-molded electrode active material, and the reliability, safety, and discharge efficiency. And the electrode for lithium ion batteries which improved the cycle life can be manufactured.

It is a figure which shows the outline of the powder molding apparatus which concerns 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.
A press roll 4 including a pair of rolls 4A and 4B is provided, and the other roll 4B is provided below one roll 4A. On one roll 4A, a hopper 8A that accommodates the powder 6, a squeegee member 12A that forms a powder layer 10A by leveling the thickness of the powder 6 supplied from the hopper 8A onto the one roll 4A, A guide roll 16 is provided to allow the base material 14 to follow the leveled powder layer 10A. Further, the guide roll 16 is arranged so that the angle formed by the tangent line at the point where the outer peripheral surface of the one roll 4A and the guide roll 16 are closest to each other and the horizontal line is equal to or less than the repose angle unique to the powder 6.
On the other roll 4B, there are a hopper 8B that accommodates the powder 6, and a squeegee member 12B that forms a powder layer 10B by equalizing the thickness of the powder 6 supplied from the hopper 8B onto the other roll 4B. I have. In addition, the pair of rolls 4 is arranged so that the angle formed by the tangent to the point where the outer peripheral surfaces of one roll 4A and the other roll 4B are closest to each other and the horizontal line is equal to or less than the repose angle unique to the powder 6. .

Further, the position at which the powder 6 is supplied from the hopper 8A onto the one roll 4A is one roll 4A in which the angle formed by the tangent to the outer peripheral surface of the one roll 4A and the horizontal line is equal to or less than the repose angle inherent to the powder 6. The position where the powder 6 is supplied from the hopper 8B onto the other roll 4B is preferably the upper position, and the angle formed by the tangent to the outer peripheral surface of the other roll 4B and the horizontal line is the angle of repose inherent to the powder 6 The position on the other roll 4B, which is the following, is preferred, but the position where the powder 6 is supplied from the hoppers 8A, 8B onto the rolls 4A, 4B is such that the tangent line and the horizontal line of the outer peripheral surface of the rolls 4A, 4B are When the angle formed is larger than the repose angle inherent to the powder 6, a member for preventing powder loss such as a slip-off prevention plate for preventing the powder 6 from sliding off the outer peripheral surface of the rolls 4A and 4B is provided. Of the outer peripheral surface of the rolls 4A and 4B Install on the side where the angle between the tangent line and the horizontal line becomes larger.
The squeegee member 12A is provided at a position where the angle formed by the tangent to the outer peripheral surface of one roll 4A and the horizontal line is equal to or less than the repose angle inherent to the powder 6, and the squeegee member 12B is the outer peripheral surface of the other roll 4B. The angle formed by the tangent line and the horizontal line is provided at a position where the angle of repose is less than or equal to the repose angle unique to the powder 6.

  In the case of manufacturing an electrode sheet as an electrode for a lithium ion battery using the powder forming apparatus 2, the powder 6 is supplied from the hopper 8A onto one roll 4A, and the supplied powder 6 is supplied to the squeegee. Leveling is performed by the member 12A, and the powder layer 10A is formed on one roll 4A. When the powder layer 10A formed on one roll 4A passes between the one roll 4A and the guide roll 16 according to the rotation of the roll 4A, the base material 14 arranged along the one roll 4A. After being covered, the substrate 14 is conveyed to the press point together with the base material 14. Further, the powder 6 is supplied from the hopper 8B onto the other roll 4B, the supplied powder 6 is leveled by the squeegee member 12B, and the powder layer 10B is formed on the other roll 4B. The powder layer 10B formed on the other roll 4B is conveyed to the press point as the roll 4B rotates. By passing the powder layer 10A, the base material 14 and the powder layer 10B through the press points of the pair of press rolls 4, the powder layer 10A is formed on the surface of the base material 14 facing the one roll 4A. The powder layer 10B is simultaneously consolidated on the surface of the material 14 facing the other roll 4B, and an electrode sheet is produced in which the powder layer 10A and the powder layer 10B are compression-molded on both surfaces of the base material 14.

  According to this powder molding apparatus 2, even if the centrifugal force accompanying the rotation of one roll 4A acts on the powder layer 10A formed on one roll 4A, the base material 14 remains in the powder layer 10A. , The powder layer 10A from the one roll 4A is prevented from being lifted. As a result, the powder layer 10A is transported to the press point in a state where there is no omission, and the missing powder is consolidated to the base material 14 by the pair of press rolls 4 without accumulating at the press point. Further, when the powder layer 10B formed on the other roll 4B is arranged so that the rotation shafts of the one roll 4A and the other roll 4B of the pair of press rolls 4 are at the same height. Since the angle formed by the tangent line of the outer peripheral surface of the roll 4B and the horizontal line at the press point is small compared to the press point, it is conveyed to the press point in a state where the loss of the powder 6 from the powder layer 10B is suppressed. The powder missing at the point is consolidated to the base material 14 by the pair of press rolls 4 without being deposited. Therefore, it is possible to produce an electrode sheet that is uniform in thickness and density.

  Further, in the above-described embodiment, the pair formed so that the angle formed by the tangent and the horizontal line at the closest point of the outer peripheral surface of one roll 4A and the other roll 4B is equal to or less than the repose angle unique to the powder 6. Since the roll 4 is disposed, the powder layer 10B can be conveyed to the press point in a state in which the loss of the powder 6 is suppressed from the powder layer 10B formed on the other roll 4B, which is preferable.

  In the above-described embodiment, the powder 6 is supplied to a position on the one roll 4A where the angle formed between the tangent to the outer peripheral surface of the one roll 4A and the horizontal line is equal to or less than the repose angle inherent to the powder 6. When the powder 6 is supplied to a position on the other roll 4B where the angle formed by the tangent to the outer peripheral surface of the other roll 4B and the horizontal line is equal to or less than the repose angle inherent to the powder 6, the powder 6 is supplied. Since the powder 6 is not missing from the powder layers 10A and 10B even in the step where the supplied powder 6 is averaged and the powder layers 10A and 10B are formed, There is no need to install this member, which is more preferable.

  Here, the angle of repose of the powder 6 is measured by a known method such as an injection method, a discharge method, a tilt method, etc. be able to.

  Here, 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. It is particularly preferable to apply an adhesive or the like to the surface of the base material 14 because the powder layers 10A and 10B formed on the base material 14 can be firmly held.

  Examples of the powder 6 accommodated in the hoppers 8A and 8B 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 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 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).

DESCRIPTION OF SYMBOLS 2 ... Powder molding apparatus, 4 ... Roll for press, 6 ... Powder, 8A, 8B ... Hopper, 10A, 10B ... Powder layer, 12 ... Squeegee member, 14 ... Base material, 16 ... Guide roll

Claims (1)

Tangent and the horizontal line and the angle formed by the outer peripheral surface closest point of one roll and the other roll, so that the following specific angle of repose in a powder containing an electrode active material, the relative said one of the rolls In the method for producing an electrode sheet for a lithium ion battery, the electrode sheet is produced by compacting the powder onto the surface of a base material by a pair of press rolls provided on the other side below,
A first powder supply step of supplying the powder to a position on the one roll where an angle formed by a tangent to the outer peripheral surface of the one roll and a horizontal line is equal to or less than an angle of repose inherent to the powder;
A first powder layer forming step of leveling the powder supplied on the one roll to form a first powder layer;
From the position on the one roll where the angle formed between the tangent to the outer peripheral surface of the one roll and the horizontal line is equal to or less than the repose angle specific to the powder, the outer peripheral surfaces of the one roll and the other roll are the most. A first powder layer transporting step of covering the first powder layer formed on the one roll with the base material and transporting the first powder layer while suppressing lifting up to a point approaching ;
A second powder supply step of supplying the powder to a position on the other roll at which an angle formed by a tangent to the outer peripheral surface of the other roll and a horizontal line is equal to or less than an angle of repose inherent to the powder;
A second powder layer forming step of leveling the powder supplied on the other roll to form a second powder layer;
A second powder layer transporting step of transporting the second powder layer formed on the other roll;
By passing the base material between the pair of press rolls, the first powder layer is consolidated against one surface of the base material, and at the same time, the second powder layer is formed on the other surface of the base material. Compression molding process to consolidate,
The manufacturing method of the electrode for lithium ion batteries characterized by including.

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