JP2011258333A - Method of manufacturing electrode composite for secondary battery, electrode for secondary battery and secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing an electrode composite for a nonaqueous electrolyte secondary battery with excellent battery characteristics from a gelatinized dispersed element used for manufacturing an electrode composite which can not be obtained from a conventional coating method.SOLUTION: The method of manufacturing an electrode composite for a secondary battery includes: (1) a gelatinization step of obtaining a gelatinized composition by gelatinizing a dispersed element by bringing at least a part of a binder into fibril-like form, where the dispersed element contains an electrode active material, the binder containing a polymer which can be brought into the fibril-like form, and a dispersant; and (2) a sheet forming step of forming the gelatinized composition into a sheet shape, removing the dispersant, and obtaining the sheet-like electrode composite for a secondary battery.

Description

  The present invention relates to a method for producing a secondary battery electrode composite, a secondary battery electrode, and a secondary battery.

  Conventionally, an electrode plate for a storage element is manufactured by forming a dispersion in which the material composing the electrode composite is uniformly dispersed in a dispersion medium, and then applying the paint-like dispersion to a current collector such as an aluminum foil or a copper foil. It is done by coating, drying and rolling. Especially for non-aqueous electrolyte secondary batteries such as lithium ion batteries, which are characterized by high energy density, it is important to form a homogeneous electrode composite in order to develop stable characteristics over a long period of time. is there. A homogeneous electrode composite was realized by forming a uniform coating film, and a uniform coating film was realized by applying and forming a dispersion having good coating properties.

One of basic dispersions for producing a positive electrode for a lithium ion battery is a positive electrode active material such as LiCoO ₂ , a conductive additive such as acetylene black, a binder such as polyvinylidene fluoride (hereinafter referred to as PVdF), and the like. It is a structure comprising a dispersion medium such as n-methylpyrrolidone (hereinafter referred to as NMP) (see Patent Document 1). The dispersion is applied to the current collector using an applicator, or is applied using a spray to form a coating film, which is dried and rolled to form an electrode.

  However, due to the decomposition of the dispersion medium due to the strong basicity of the lithium composite oxide, which is the positive electrode active material, and the strong stirring for dispersing the conductive agent with high hydrophobicity, the dispersion is high exceeding 10,000 mPa · S. In some cases, the viscosity increases and the gelation occurs. Usually, the viscosity of the dispersion preferable for coating film formation is supposed to be about 4000 mPa · S or less, although it depends on the coating method. The dispersion gelled as described above was difficult to apply to the current collector, and even if it could be applied, a uniform coating film could not be formed.

When the viscosity of the dispersion is high, it is possible to increase the amount of the dispersion medium and reduce the viscosity by dilution, but it is difficult to produce a thick film because the concentration of components effective for coating film formation is reduced. In addition, there is a problem that much energy is required for removing the dispersion medium. Furthermore, once the viscosity rises or gels, it is very difficult to form a homogeneous coating because it is microscopically non-uniform even when the viscosity is apparently reduced (see Patent Document 2). .)
Moreover, when a larger shear stress is applied by strong stirring to improve dispersibility, the electrode active material and the conductive aid particles may be crushed.

  On the other hand, non-aqueous electrolyte secondary batteries have begun to spread from various energy sources such as energy sources for mobile devices to in-vehicle storage and discharge systems, energy sources, and power storage systems, with higher power, higher energy density, and lower temperature. There are strong demands for characteristics such as reliability that can be used with confidence even in various environments such as under and high temperatures, and extremely safe characteristics even in unexpected situations. In order to improve these characteristics, various improvements have been made in the electrode active material in order to improve the characteristics such as having a Li-rich composition depending on the material and reducing the particle diameter depending on the material and application.

However, along with these improvements, for example, by making the electrode active material Li-rich, the basicity of the active material becomes stronger and the dispersion is more easily gelled, or the particle size is reduced and dispersed in the dispersion medium. It has become more difficult to form a coating film of a homogeneous dispersion due to a decrease in properties.
When the particle diameter of the electrode active material is reduced and the number of particles and the specific surface area are increased, a measure for increasing the binder binding force by increasing the binder amount is also conceivable. However, simply increasing the amount of binder results in a significant reduction in discharge capacity and output.

Japanese Patent No. 4177612 Japanese Patent Application Laid-Open No. 08-106897

  The present invention provides a method for producing a sheet-shaped electrode composite for a secondary battery having good battery characteristics from a gelled dispersion, which cannot form a uniform coating film by the above-described conventional coating method, and the production method. It aims at providing the secondary battery obtained using the electrode for secondary batteries formed from the electrode composite for secondary batteries obtained, and this electrode for secondary batteries.

In the present invention, the following configuration is adopted in order to solve the above problems.
[1] (1) A gelation step of obtaining a gelled composition by gelling a dispersion containing an electrode active material, a binder containing a polymer that can be made into a fibrillar form, and a dispersion medium, and (2) A method for producing a secondary battery electrode composite, comprising: forming the gelled composition into a sheet, and removing the dispersion medium to obtain a sheet-like secondary battery electrode composite. .

[2] The method for producing an electrode composite for a secondary battery according to [1], wherein the gelled composition has a viscosity at 25 ° C. of 5000 to 64000000 mPa · S.
[3] The method for producing an electrode composite for a secondary battery according to [1] or [2], wherein the binder is polytetrafluoroethylene and the dispersion medium is water.
[4] The method for producing an electrode composite for a secondary battery according to any one of [1] to [3], wherein the electrode active material has a particle size of 10 nm to 500 μm.
[5] The method for producing an electrode composite for a secondary battery according to any one of [1] to [4], wherein the dispersion further contains a conductive additive.

[6] The method for producing an electrode composite for a secondary battery according to any one of [1] to [5], wherein the binder includes at least one of an amorphous fluorine-containing polymer and an amorphous non-fluorine polymer. .
[7] An electrode composite for a secondary battery manufactured by the manufacturing method according to any one of [1] to [6].
[8] The electrode composite for a secondary battery according to [7], wherein the binder content is 0.01 to 15% by mass.
[9] An electrode for a secondary battery in which the secondary battery electrode composite according to [7] or [8] and a current collector are laminated.
[10] A secondary battery using the secondary battery electrode according to [9].

According to the production method of the present invention, a secondary battery electrode composite having an excellent effect of good homogeneity and battery characteristics is produced from a gelled dispersion which cannot form a homogeneous electrode composite depending on the coating method. Can do.
Furthermore, according to the present invention, it is possible to bind a fine electrode active material having an average particle size of 1 μm or less, which has been difficult to bind by a conventional method, with a small amount of binder.

FIG. 1 is a schematic cross-sectional view showing an outline of processing a gelled composition with a calendar processing machine. FIG. 2 is a schematic cross-sectional view showing the outline of rolling the gelled composition dispersion liquid with a calendering machine and then rolling with a rolling machine.

The method for producing an electrode composite for a secondary battery of the present invention (hereinafter simply referred to as “electrode composite”) includes an electrode active material, a binder containing a polymer that can be made into a fibril-like form, and a dispersion medium. The dispersion to be gelled to obtain a gelled composition.
The dispersion used in the present invention contains an electrode active material, a binder containing a polymer that can be made into a fibril-like form, a dispersion medium, and also contains a conductive additive and an additive as necessary.

[Electrode active material]
The electrode active material is not limited at all for the positive electrode and the negative electrode, and can be freely selected from a wide range of electrode active materials.
As the positive electrode active material, metal oxides, metal sulfides, conductive organic compounds and the like are generally used. In particular, metal oxides such as lithium composite metal oxide and lithium metal phosphoolivine are preferable because stable battery characteristics can be expressed over a long period of time. These metal oxides are sometimes used as a composite oxide of Li and another metal, but are also used as a composite oxide composed of Li and other metals. For example, in the case of a lithium nickel composite oxide, LiNiO ₂ or the like is hardly used as a positive electrode of a lithium ion battery, and a part of Li or Ni is made of Co, Mn, Al, B, Cr, Cu, F, Fe, A material substituted with one or more elements selected from Ga, Mg, Mo, Nb, O, Sn, Ti, V, Zn, Zr, and the like is preferable. Further, for the purpose of increasing the electron conductivity, a material obtained by combining a conductive carbonaceous material on the surface of the electrode active material or inside the electrode active material is also preferably used in the present invention.

  As the negative electrode active material, graphite-based carbon, non-graphite-based carbon, or metal-based material can be preferably used. For example, carbon materials include natural graphite, artificial graphite, coal-based coke, petroleum-based coke, coal-based pitch carbide, petroleum-based pitch carbide, needle coke, pitch coke, carbides such as phenol resin and cellulose, and partially graphitized products of these carbides. Furnace black, acetylene black, carbon fiber and the like are preferably used. Metal systems such as tin, silicon, titanium, metal nitride, lithium, and lithium alloys are also preferably used. Furthermore, lithium titanium composite oxide and other oxide systems are also preferably used.

As an electrode active material, an average particle diameter of 10 nm-500 micrometers can be used. This range includes a particle size range smaller than the particle size range of the electrode active material conventionally used in secondary batteries. According to the present invention, an electrode composite can be produced even with an electrode active material having such a small particle diameter, and the produced electrode composite is an electrode when used as a battery production process or a secondary battery. Less loss of electrode active material from the composite.
The reason why an electrode composite can be produced even with an electrode active material having a smaller particle diameter is not clear, but the fibrils are highly developed in the gelation process and sheet forming process described later to form a denser network structure. This is considered to hold the substance stronger.

The content of the electrode active material in the dispersion used in the present invention is preferably 5 to 65% by mass and more preferably 10 to 60% by mass with respect to the total amount of the dispersion because of easy molding.
Since the main material responsible for the battery characteristics is the electrode active material, the electrode active material is preferably maximally formulated, and the material other than the electrode active material that does not contribute to the storage capacity is preferably the minimum compound capable of expressing the required function. .

[binder]
The binder in the present invention includes a polymer that can be in the form of a fibril. Specific examples of such a polymer include cellulose, polyolefin, polyacryl, polyester, polyamide, polyimide, a fluoropolymer, and a fibrous carbonaceous material. Of these, polyolefins and fluoropolymers are preferred because of their oxidation-reduction resistance when used as batteries. In addition, since the oxidation-reduction resistance is particularly excellent, ultrahigh molecular weight polyethylene is preferable among polyolefins, and polytetrafluoroethylene (hereinafter referred to as PTFE) is preferable among fluoropolymers. The molecular weight of the ultra high molecular weight polyethylene is preferably from 1,000,000 to 10,000,000. The molecular weight of polytetrafluoroethylene is preferably 500,000 to 50 million.

When the binder made of the polymer is used for the dispersion, it is preferably a powder or a dispersion, and more preferably a dispersion because it is easy to form a more homogeneous electrode composite. In the case of using the binder in the form of a dispersion, it is preferable that the polymer as the binder is dispersed in the dispersion medium. The dispersion medium in the dispersion is preferably the same as the dispersion medium contained in the dispersion in the present invention, and more preferably water.
The polymer which can be made into the fibril form used as a binder may be used individually by 1 type, and may be used in combination of 2 or more type.

  A preferred polymer in the binder used in the present invention is PTFE, and a preferred form of the binder is an aqueous dispersion. That is, it is preferable to use a PTFE aqueous dispersion as the binder polymer in the present invention. The average particle size of the PTFE particles dispersed in the PTFE aqueous dispersion is preferably 0.01 to 10 μm, more preferably 0.05 to 2 μm, and further preferably 0.1 to 1 μm. If the average particle diameter of the PTFE particles is within this range, the stability of the PTFE dispersion will be good, and fibril formation will be good when used as a binder.

As the binder in the present invention, another polymer that does not become a fibril-like form may be contained together with a polymer that can be made into a fibril-like form in order to enhance adhesion to the current collector.
The other polymer is preferably a fluorine-containing polymer because of its good oxidation-reduction resistance when used as a battery.

  Examples of the fluoropolymer include tetrafluoroethylene (hereinafter sometimes referred to as “TFE”), vinylidene fluoride (hereinafter sometimes referred to as “VdF”), hexafluoropropylene (hereinafter referred to as “HFP”). A first group of monomers such as perfluoro (alkyl vinyl ether), perfluoro (alkyloxyalkyl vinyl ether), chlorotrifluoroethylene (hereinafter sometimes referred to as “CTFE”), Fluorine-containing obtained by polymerizing at least two monomers selected from the monomers of the first group among the monomers of the second group such as alkyl vinyl ether, alkyloxyalkyl vinyl ether, alkyl vinyl ether, alkyl vinyl ester, ethylene, propylene Polymer, or first group of monomers Such as at least one and at least one copolymerizing fluorinated polymer obtained by selected from the monomers of the second group selected from can be suitably used. In addition to the first group of monomers and the second group of monomers, other copolymerizable monomers may be copolymerized as necessary. As these other polymers, amorphous fluorine-containing polymers are preferable among these fluorine-containing polymers.

Specifically, the fluorine-containing polymer includes a copolymer of TFE and HFP, a copolymer of TFE and perfluoroalkyl vinyl ether, a copolymer of TFE and alkyl vinyl ester, a copolymer of TFE and alkyl vinyl ether, and TFE. And copolymers of CTFE and alkyl vinyl ether are preferred. Among these, a copolymer of TFE and perfluoroalkyl vinyl ether, a copolymer of TFE and alkyl vinyl ester, a copolymer of TFE and propylene, A copolymer of CTFE and alkyl vinyl ether is more preferable.
Further, these fluorine-containing polymers may have polymerized units based on other monomers as required in addition to the polymerized monomers based on the monomers of the first group and the second group.

When non-fluorine polymers are used as other polymers, usable non-fluorine polymers include alkyl vinyl ethers, alkyloxyalkyl vinyl ethers, olefins such as ethylene and propylene, styrene, α-methylstyrene, and p-vinyl. Aromatic vinyl compounds such as toluene, aliphatic vinyl compounds such as vinyl acetate and vinyl crotonic acid, conjugated dienes such as 1,3-butadiene and isoprene, methacrylic acid, acrylic acid, maleic anhydride, itaconic anhydride, Examples thereof include non-fluorinated polymers obtained by polymerizing or copolymerizing one or more copolymerizable monomers such as maleic acid and itaconic acid.
As these other polymers, amorphous non-fluorine polymers are preferable among these non-fluorine polymers.

Specifically, the non-fluorine polymer is preferably a homopolymer or copolymer of acrylic acid, a copolymer of styrene and butadiene, a copolymer of acrylonitrile and butadiene, or a copolymer of ethylene and alkyl vinyl ether. Among these, a copolymer of styrene and butadiene, a copolymer of acrylonitrile and butadiene, and a copolymer of ethylene and alkyl vinyl ether, which are amorphous non-fluorine polymers, are more preferable.
Here, the term “amorphous” means that there is no endotherm due to crystal melting when differential scanning calorimetry is performed while raising the temperature at a rate of 10 ° C./min. Moreover, a non-fluorine-type polymer means the polymer which does not contain a fluorine atom.

The other polymer can be used in various forms, but is preferably a powder or a dispersion, and more preferably a dispersion because it is easy to form a more uniform electrode composite. In the dispersion when the binder is used in the form of a dispersion, other polymers are dispersed in the dispersion medium. The dispersion medium in the dispersion is preferably the same as the dispersion medium contained in the dispersion in the present invention, and more preferably water.
When another polymer is used as a binder together with a polymer that can be in the form of a fibril, the other polymer may be used alone or in combination of two or more. . 0.01-80 mass% is preferable and, as for content of the other polymer in all the binders, 0.01-60 mass% is more preferable.

Moreover, 0.0005-10 mass% is preferable with respect to the dispersion whole quantity, and, as for content of the binder in a dispersion, 0.001-6 mass% is more preferable.
Whether or not a polymer can be made into a fibril-like form depends on various factors such as the molecular weight of the polymer and the polarity of the units constituting the polymer, and even for the same polymer, it depends on the conditions such as the molecular weight. In some cases, a fibrillar shape may not be obtained.

[Conductive aid]
Examples of the conductive aid that can be used in the present invention include graphites such as natural graphite and artificial graphite, carbon blacks such as thermal black, furnace black, channel black, lamp black, and acetylene black, ketjen black, needle coke, and carbon fiber. Carbon nanotubes, carbon nanocoils, graphene, and the like are preferably used.

When water is used as the dispersion medium of the dispersion in the present invention, it is possible to use boronated acetylene black or other hydrophilic carbon black that has been subjected to hydrophilization because of its good dispersibility in water. I like it. The average particle size of these conductive aids is usually preferably from 3 to 1000 nm, more preferably from 5 to 200 nm. In the case of a fibrous carbon material, it is usually preferable that the fiber length is 100 μm or less because it is easy to handle. However, the fiber length is not limited as long as it is a flexible fibrous material such as a nanotube.
When using a conductive support agent, 1 type may be used individually as a conductive support agent, and 2 or more types may be used in combination. Moreover, 0.0005-10 mass% is preferable with respect to the dispersion whole quantity, and, as for content of the conductive support agent contained in a dispersion, 0.001-6 mass% is more preferable.

[Dispersion medium]
As a dispersion medium, aromatic compounds such as toluene and xylene, heterocyclic compounds such as N-methylpyrrolidone, aliphatic compounds such as hexane, isopropyl alcohol, ethyl acetate and methyl isobutyl ketone, water-soluble compounds such as water, water and alcohol Although various media such as an aqueous dispersion medium such as a mixture thereof can be selected, it is preferable to use an aqueous dispersion medium containing water that is easy to handle and has a small environmental load.
As the aqueous dispersion medium, only water such as distilled water and ion exchange water may be used, but an aqueous dispersion medium to which a water-soluble compound is added can also be used. When an aqueous dispersion medium to which a water-soluble compound is added is used, distortion of the composite is suppressed during the drying process, and a more homogeneous electrode composite having good adhesion to the current collector can be produced. The water-soluble compound preferably has a boiling point higher than that of water.

  Examples of the water-soluble compound include organic solvents such as dimethylformamide, dimethylacetamide, tetramethylene sulfone, N-methylpyrrolidone, ethylene glycols, propylene glycols and glycerin. Since the content rate of a water-soluble compound is easy to handle, 0-50 mass% is preferable with respect to the total amount of water and a water-soluble compound, and 0-20 mass% is more preferable.

A dispersion medium may be used individually by 1 type, and may be used in combination of 2 or more type. Further, the content of the dispersion medium in the dispersion is preferably 5 to 95% by mass, more preferably 10 to 80% by mass, and further preferably 15 to 65% by mass with respect to the total amount of the dispersion.
The dispersion medium is contained in the dispersion because it is easy to remove the dispersion medium because the electrode composite is produced at the same time as or after the formation of the gelled composition in the sheet forming step to remove the electrode composite. It is preferable that the amount of the dispersion medium to be obtained is the minimum amount within the range that can be formed.

[Additive]
Various additives can be added to the dispersion for the purpose of finely and evenly dispersing the electrode active material, the conductive additive, and the binder in the dispersion medium.
Additives include organic solvents such as butanol, ethylene glycol and glycerin, organic polymers such as carboxymethylcellulose and polyvinyl alcohol, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, polyoxyethylene lauryl ether, ammonium perfluorohexanoate Surfactants such as can be used. Among these, when water is used as a dispersion medium, it is preferable to use water-soluble organic solvents, surfactants, water-soluble polymers and the like. In particular, water-soluble polymers and surfactants are preferably used according to the present invention because they are effective in improving the dispersibility of the electrode active material and the conductive additive and also function in the stability of the dispersion. As the surfactants, polymer surfactants are more preferable.

Examples of water-soluble polymers include polyacrylic acids, methyl celluloses, carboxymethyl cellulose (hereinafter referred to as CMC), crown ethers, dextrins, and water-soluble dietary fibers. Examples of the polymer surfactant include fluorine-containing polymer surfactants containing a hydrophilic chain and a fluorine-containing olefin in one molecule.
Although some of the materials presented as the additives appear to function as binders, they are treated as dispersion stabilizers in the present invention.
The addition amount of the dispersion stabilizer is preferably 0.01 to 10% by weight with respect to the total amount of the dispersion.

  The dispersion in the present invention can be prepared using various methods, and is not limited at all. As the most general method, a method in which a predetermined amount of an electrode active material, a predetermined amount of a conductive additive, and a predetermined amount of a binder are added to a CMC aqueous solution and mixed can be exemplified. The electrode active material and the conductive additive are often handled in a powder state, but can be mixed after previously being dispersed in a dispersion medium such as water. The binder is often handled as a solution or a dispersion, but in the present invention, it is possible to perform a strong dispersion operation, and therefore it is possible to mix the powder as it is.

In the manufacturing method of the electrode composite for secondary batteries of this invention, the electrode composite for secondary batteries is obtained through the gelatinization process which gelatinizes the said dispersion, and the sheet forming process which shape | molds in a sheet form.
[Gelling process]
In the gelation step, the various substances contained in the dispersion are mainly homogenized and gelled. Since it is difficult to homogenize the gelled composition after gelation, it is preferable to perform the homogenization before gelation or simultaneously with gelation.

In the manufacturing method of the electrode composite for secondary batteries of this invention, the said dispersion is gelatinized and a gelled composition is obtained. Examples of the method for gelling the dispersion include the following two methods.
The first method is a method in which at least a part of a binder containing a polymer that can be made into a fibril-like form contained in the dispersion is made into a fibril-like form so as to be gelled. As a method for obtaining a specific gelling composition in this method, a method of gelling the dispersion by applying shear stress to the dispersion to make at least a part of the binder into a fibril-like form, a binder having a fibril form in advance is used. The method of mixing and gelatinizing a dispersion is mentioned. Examples of the latter method include a method of adding a PTFE aqueous emulsion to gel the dispersion.

  The second method is a method in which the state of the dispersion such as pH, polarity and stabilizer is rapidly changed. As a specific method for obtaining a gelled composition in this method, a dispersion stabilizer or a solution having a different pH is mixed. An organic solvent or an organic solution is mixed with an acidic dispersion or an alkaline dispersion. For example, a method of mixing different dispersion liquids or a combination thereof. Although the mechanism of gelation in the second method is not clear, it is considered that the substances contained in the dispersion form relatively weak bonds such as hydrogen bonds and hydrophobic bonds.

  The resulting gelled composition preferably has a viscosity at 25 ° C. of 5000 to 64000000 mPa · S, more preferably 20000 to 10000000 mPa · S, and still more preferably 50000 to 5000000 mPa · S. When the viscosity is in the above range, the gelled composition can be easily handled and sheet molding can be easily performed.

[Sheet forming process]
The production method of the present invention includes a sheet forming step of forming the gelled composition into a sheet and removing the dispersion medium to obtain a sheet-like electrode composite for a secondary battery. The sheet forming step is considered to have the following two functions at the same time as forming the gelled composition into a sheet.
The first function is homogenization of the gelled composition. In many cases, the gelled composition obtained by the gelation step is not homogeneous because the degree of gelation is partially different. If an electrode composite for a secondary battery is produced from such a heterogeneous gelled composition without a homogenizing operation, the electrode composite also becomes non-homogeneous, causing various battery characteristics to be reduced when the battery is formed. Therefore, it is considered that the sheet forming process also has an effect of applying a shear stress to such a heterogeneous gelled composition to make it homogeneous.

  The second function is fibrillation of a binder containing a polymer that can be in a fibrillar form. The electrode active material contained in the electrode composite and the conductive assistant contained as necessary are considered to be firmly held by the fibrils in the electrode composite, and if the fibril development is insufficient, the electrode active material This may cause the material or conductive aid to fall off. In the sheet molding process, shear stress is applied to the gelled composition, and it is considered that the polymer that can be made into a fibrillar form is highly fibrillated by this shear stress. The fibrils in the secondary battery electrode composite preferably have a structure in which the fibrils are highly developed and entangled with each other to form a network (network-like shape).

  Any method may be used as a method for applying the shear stress as long as the method can apply the shear stress to the gelled composition, and the method is not limited at all. As a preferred method for adding shear stress, a method that can efficiently homogenize in a short time is preferable. For example, processing with a high-speed mixer, processing between two rotors with greatly different rotational speeds, between two disks, or between a rotor and a stator, or jetting at high pressure from a nozzle to collide with each other or shielding And a method of press forming into a plate shape after processing with a bead mill, a planetary ball mill, or a ball mill. It is also effective to form a rod or plate by injection or extrusion while mixing and kneading. These rods and plates are further rolled into a sheet having a predetermined thickness to form an electrode composite.

In addition, as a method for adding shear stress, a method that can efficiently homogenize the gelled composition and efficiently increase the fibrillar morphology is preferable.
The shear stress for making the fibrillar form or increasing the fibrillar form depends on the viscosity and temperature of the gelled composition. For example, when the polymer capable of making the fibrillar form is PTFE Is preferably 0.05 to 2000 Pa. If the shear stress is within this range, it is possible to achieve both uniformization of an efficient gelling composition and efficient formation of a fibril form.

From the viewpoint of homogenization of the gelled composition and development of the fibril form, it is preferable to apply the shear stress a plurality of times, a long time, or a plurality of times and a long time. Further, the direction in which the share stress is applied is not limited to one direction, and it is preferable to apply the stress in multiple directions. As a specific method of applying such shear stress, it is preferable to add so-called “kneading” by passing a plurality of times between a pair of rolls.
In the present invention, the sheet forming may be performed directly from the gelled composition, but for the purpose of further homogenization and fibrillation, before forming into a sheet shape, for example, so-called “kneading” A step of adding share stress may be included.

  The method for forming the gelled composition into a sheet can be performed by various methods as long as the method can form the sheet, and is not limited at all. As a suitable sheet molding method that can sufficiently fulfill the functions of the above-mentioned homogenization step and fibrillation step, for example, there is a calendar molding method in which the gelled composition is molded into a sheet shape through a gap between a pair of rolls. Can be mentioned. This method is particularly preferred because it makes it possible to produce a sheet-like molded body directly from the bulk gelled composition.

The process of calendering the gelled composition to form a sheet can be formed into a sheet having a predetermined thickness by a single calendering process. It is more preferable to form a predetermined network stepwise by combining rolling processes later in that a strong network of fibrils can be formed.
When calendar processing is performed twice or more times, the share stress applied to each time is usually not particularly limited as long as it is 0.05 to 2000 Pa. However, it is preferable to increase the stress every time it is repeated. Is preferably 2 to 10 times, more preferably 3 to 8 times, the share stress applied immediately before.

  FIG. 1 is a diagram schematically showing the most basic configuration and processing method of a calendar processing apparatus. The calendering process is performed once, which contains a polymer in the form of a fibril and is formed into a sheet by calendering through a gelled composition 1 gelled between two opposing rolls 2 and 3. A treated gelled composition 4 is obtained. When performing calendar processing a plurality of times, the same processing may be performed a plurality of times using the calendar processing apparatus of FIG. The number of treatments is preferably 2 times or more, and more preferably 3 times or more.

  FIG. 2 is a diagram schematically illustrating a processing method in which a rolling processing device is provided downstream of the calendar processing device in FIG. 1 and a sheet fed from the calendar processing device is rolled. A calendered gel that is formed into a sheet with a fibril-like binder by calendering through the gelled composition 1 gelled between two opposing rolls 2 and 3, and that is processed once. A calendered composition is obtained, and the sheet-like calendered gelled composition is passed between two opposing rolls 5 and 6, and further passed between two opposing rolls 7 and 8 The sheet is processed to obtain a sheet-like processed gelled composition 9 that has been subjected to a calendering process and a rolling process.

In the sheet forming step, the dispersion medium is also removed, but the removal of the dispersion medium may be performed at the same time as forming into the sheet shape, may be performed after forming into the sheet shape, or both. From the viewpoint of sufficiently removing the dispersion medium, it is preferable to perform a drying step after forming into a sheet shape. Although drying is dependent also on the material which comprises a dispersion medium and the electrode composite for secondary batteries, it is preferable to carry out for several minutes-one day at the temperature of 40-400 degreeC.
The gelled composition formed into a sheet is consolidated as necessary. The consolidation is usually performed at 50 to 1000 MPa, although it depends on the particle size of the electrode active material and the binder.

[Electrode composite]
The electrode composite in this invention contains the binder containing the polymer which can be made into an electrode active material and a fibril form, and also contains a conductive support agent and an additive as needed. Since the dispersion medium is removed from the gelled dispersion in the gelation step and the sheet forming step, the composition of the electrode composite is a composition obtained by removing the dispersion medium from the dispersion.
99.99-70 mass% is preferable with respect to the total mass of an electrode composite, and, as for content of the electrode active material contained in an electrode composite, 99.9-76 mass% is preferable.

The content of the binder contained in the electrode composite depends on the electrode active material and the conductive additive, but is preferably 0.01 to 15% by mass, and 0.1 to 12% by mass in the total mass of the electrode composite. Is more preferable, and 0.5-12 mass% is further more preferable. This range also includes a content range that is less than the content range of the binder in the electrode composites conventionally used in secondary batteries. When the particle size of the electrode active material is small, more binder is required for the production of the electrode composite. According to the present invention, even when the particle size of the electrode active material is small, the use of a small amount of binder is required. The electrode composite can be manufactured in quantity.
If the content of the binder in the electrode composite is within this range, the binder can sufficiently support the electrode active material and can stably ensure a sufficient energy density and durability when a secondary battery is obtained.

The amount of binder present in the electrode composite is preferably as small as possible in order to reduce the conductivity of the electrode. According to the present invention, since an electrode composite can be manufactured with a smaller amount of binder than in the prior art, a secondary battery manufactured using the electrode composite exhibits more excellent battery characteristics.
The reason why an electrode composite can be produced with a smaller amount of binder is not clear, but since the fibrillar form of the binder is highly developed in the gelation step and the sheet forming step, the binder composition for exhibiting the same binding ability is used. The amount is considered to be small.

0.01-15 mass% is preferable and, as for content of the conductive support agent contained in an electrode composite, 0.01-12 mass% is more preferable. If the content of the conductive assistant is within this range, it is preferable because a secondary battery with high power, high energy density and long life can be realized.
The thickness of the sheet-shaped electrode composite formed by the sheet forming step is preferably 0.5 to 2000 μm, more preferably 1 to 1000 μm, and particularly preferably 10 to 500 μm as the thickness after drying. If the thickness of the electrode composite is within this range, the energy density and output characteristics are good.

  It is also possible to add a new additional component for the purpose of improving the performance and extending the life after forming the secondary battery electrode composite. For example, if the additional component is a solid component, it can be added as a finely divided powder, a dispersion of the powder, or a highly processable precursor that can be converted into the target component by a simple treatment such as heating, and sprayed or immersed. . In addition, if the additional component is a liquid component, it can be added as it is by diluting and spraying as it is, or by adding and fixing the gas component as it is or by exposing it to a diluted atmosphere and heating it. it can.

Examples of the additional component include titanium oxide, aluminum oxide, zirconium oxide, niobium oxide, molybdenum oxide, lithium carbonate, and lithium phosphate.
The electrode composite obtained by the production method of the present invention has a high energy density when used as a battery by being able to utilize an electrode active material having a smaller particle diameter and reducing the amount of binder used than before. There is an advantage that high power characteristics can be expressed while maintaining.

The electrode composite obtained by the production method of the present invention is suitable as an electrode composite for secondary batteries such as lithium batteries such as lithium ion batteries, lithium polymer batteries, and lithium primary batteries, and nickel hydrogen batteries.
[Secondary battery electrodes]
The electrode composite obtained by the production method of the present invention can be laminated with a current collector to produce a secondary battery electrode.
The current collector is not particularly limited as long as it is made of a conductive material. In general, a metal foil made of a metal such as aluminum, nickel, stainless steel, or copper, a metal net, a metal porous body, etc. In the case of lithium ion batteries, an aluminum foil is preferably used as the positive electrode current collector, and a copper foil is preferably used as the negative electrode current collector. Nickel foil or nickel foam is used for the positive electrode current collector of the nickel metal hydride battery. The thickness of the current collector is preferably 1 to 100 μm. When the thickness of the current collector is in this range, the durability and reliability of the battery can be sufficiently secured, and the weight of the battery when it is used is reduced.

  The electrode composite and the current collector are preferably bonded together by pressure bonding with a roll or the like after lamination. From the viewpoint of enhancing the adhesiveness by pressure bonding, it is preferable to add the other polymer as a binder when preparing the dispersion. Other polymers that can further improve adhesion include tetrafluoroethylene and perfluoroalkyl vinyl ether copolymers, tetrafluoroethylene and propylene copolymers, chlorotrifluoroethylene and alkyl vinyl ether copolymers, Examples include acrylic acid, styrene butadiene rubber, and nitrile rubber.

  The electrode for a secondary battery manufactured using the electrode composite for a secondary battery manufactured by the manufacturing method of the present invention has an electrode active material, a conductive additive, a binder as described above for the electrode composite layer for the secondary battery. Since a structure in which the agent and other composite constituents are finely and uniformly arranged can be realized, a smooth charge transfer reaction can be realized. In addition, energy storage devices such as secondary batteries using such secondary battery electrodes have large charge / discharge capacity and high energy density, and have excellent cycle characteristics, high load characteristics, low temperature characteristics, high temperature characteristics, and safety. Can be realized. In particular, it is possible to achieve both high energy density and high load characteristics with high power and highly reliable safety. Therefore, high output, high energy density, high reliability and safety can be achieved even for medium and large-sized devices.

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples.
In the following (1) to (9), methods for preparing binders and electrode active materials used in Reference Examples, Examples and Comparative Examples of the present invention are shown.

(1) Preparation of PTFE aqueous dispersion (A) A 100-liter pressure-resistant polymerization tank was charged with 736 g of paraffin wax, 59 liters of ultrapure water, and 15 g of ammonium perfluorooctanoate (hereinafter referred to as APFO). After raising the temperature to 70 ° C., purging with nitrogen and then degassing, tetrafluoroethylene was introduced to an internal pressure of 1.9 MPa while stirring. 1 liter of a 0.5 mass% disuccinic acid peroxide aqueous solution was injected into this to initiate polymerization. The polymerization was carried out for 45 minutes while maintaining the polymerization pressure at 1.9 MPa while supplying tetrafluoroethylene, and then the temperature was raised to 90 ° C., and 1 liter of a 2.5 mass% APFO aqueous solution was added, and continued for 95 minutes. Aggregates and paraffin are removed from the obtained emulsion to obtain 25.1 kg of an aqueous PTFE dispersion having an average particle size of 0.21 μm and a PTFE content of 26.0% by mass and an APFO content of 0.05% by mass. It was.

  In this aqueous dispersion, 0.2 kg of a nonionic surfactant mainly composed of polyoxyethylene lauryl ether is added and dissolved, 0.3 kg of anion exchange resin is dispersed, stirred for 24 hours, and then filtered to perform anion exchange. The resin was removed. To the filtrate was added 0.04 kg of 28% by mass aqueous ammonia, concentrated by a phase separation method at 80 ° C. for 10 hours, and after removing the supernatant, 15 g of ammonium perfluorohexanoate (hereinafter referred to as APFH) was newly added. In addition, a PTFE aqueous dispersion (A) (hereinafter referred to as “binder”) having an average particle size of 0.21 μm and a PTFE content of 60.8% by mass, an APPFH content of 0.15% by mass, and an APFO content of 0.01% by mass. A) is sometimes referred to as 1). As a result of thermal analysis, the polymer taken out from a part of (A), purified and dried was a crystalline fluoropolymer having a melting point of 327 ° C. The obtained PTFE was a polymer that could be made into a fibrillar form.

(2) Preparation of PTFE aqueous dispersion (B) Concentration was performed in the same manner as aqueous dispersion (A) except that 15 g of sodium lauryl sulfate (hereinafter referred to as SLS) was used instead of APFH. PTFE aqueous dispersion (B) having a PTFE content of 59.8% by mass, a PFOA content of 0.01% by mass, and an SLS content of 1.1% by mass (hereinafter referred to as “binder (B)”) 10.5 kg was obtained. The obtained PTFE was a polymer that could be made into a fibrillar form.

(3) Preparation of fluorinated polymer aqueous dispersion (C) 1.0 liter of ion exchange water, 2.2 g of calcium carbonate, 0.7 g of ammonium persulfate, 31 g of polyoxyethylene alkyl ether, 31 g of lauryl sulfate in a 3 liter pressure-resistant polymerization tank Charge 1g of sodium, 161g of ethyl vinyl ether, 178g of cyclohexyl vinyl ether, 141g of 4-hydroxybutyl vinyl ether, degas by repeated cooling and nitrogen gas pressurization, then charge 482g of chlorotrifluoroethylene and polymerize at 30 ° C for 12 hours Reaction was performed. When aggregates are removed from the obtained emulsion, 1250 g of a fluoropolymer aqueous dispersion (C) having a polymer content of 50.1% by mass (hereinafter sometimes referred to as “binder (C)”) is obtained. It was. A polymer obtained by taking out a part of the aqueous dispersion (C), purifying and drying was an amorphous fluorine-based polymer having no crystalline melting point, and could not be made into a fibrillar form. This fluoropolymer corresponds to other polymers.

(4) Production of non-fluorinated polymer aqueous dispersion (D) In a 3 L pressure resistant reactor, ion-exchanged water 1000 g, sodium dodecylbenzenesulfonate 2.5 g, potassium persulfate 5 g, sodium bisulfite 2.5 g, styrene 235 g, 195 g of butadiene, 50 g of methyl methacrylate and 20 g of itaconic acid were charged, and after degassing by repeated cooling and nitrogen gas pressurization, a polymerization reaction was carried out at 45 ° C. for 6 hours. When aggregates are removed from the obtained emulsion, a non-fluorinated polymer aqueous dispersion (D) having a polymer (acryl-modified styrene butadiene rubber) content of 35.5% by mass (hereinafter referred to as a binder (D)). 1300 g was obtained. A polymer taken out from a part of the aqueous dispersion (D), purified and dried was an amorphous non-fluorine-based copolymer having no crystalline melting point, and could not be made into a fibrillar form. This non-fluorine polymer corresponds to other polymers.

(5) Synthesis of lithium iron phosphate (E) 616.2 g of 85% phosphoric acid was diluted with 2000 g of pure water. While stirring this phosphoric acid aqueous solution, 200.6 g of lithium carbonate was added and dissolved to obtain an aqueous solution of lithium phosphate. To this aqueous solution, 500.2 g of iron oxyhydroxide having a molecular weight of 92.4 per equivalent of iron was added, and 800 g of pure water was further added to obtain an aqueous paste as a raw material for lithium iron phosphate. This paste was subjected to bead milling for 2 hours using zirconia beads having a diameter of 0.1 mm, dissolved in 200 g of a caramel aqueous solution having a solid content concentration of 51.4% by mass, spray-dried, and D50 = 2.0 μm. A dry powder was obtained. The dried powder was heated to 600 ° C. at a temperature rising rate of 5 ° C./min while supplying 5% hydrogen containing nitrogen gas at a flow rate of 0.8 liter / min, and kept at 600 ° C. for 5 hours, and then −5 Cooling was performed at a temperature drop rate setting of ° C./min to obtain lithium iron phosphate (E) (hereinafter sometimes referred to as “electrode active material (E)”) with D50 = 2.1 μm.
Here, D50 represents the median value of the cumulative percentage of the particle diameter of all particles, and the measurement was performed by a laser diffraction scattering method.

(6) Synthesis of Lithium Iron Phosphate (F) If D50 of the spray-dried dry powder is 5.4 μm and the same as (5), then Lithium Iron Phosphate with D50 = 5.7 μm (F ) (Hereinafter sometimes referred to as “electrode active material (F)”).
(7) Synthesis of Lithium Manganese Composite Oxide (G) 7.6 mol of manganese carbonate and 2.2 mol of lithium carbonate were dispersed in 1000 g of pure water, subjected to bead mill treatment with zirconia beads having a diameter of 0.1 mm for 2 hours, and then spray dried. The obtained powder was granulated into pellets with a roller compactor. This granulated body was heated to 400 ° C. at a rate of 5 ° C./min while being supplied at a flow rate of 0.8 liter / min of synthetic air composed of 22% oxygen and 78% nitrogen and held for 15 hours. Then, after heating to 980 ° C. and holding for 15 hours in the same manner, the temperature was lowered to 400 ° C. at a rate of −2 ° C./min. After maintaining at 400 ° C. for 15 hours, it was similarly heated to 650 ° C. at a rate of 5 ° C./min. After 15 hours, the mixture was cooled and crushed at a temperature decrease rate of −2 ° C./min, and Li-excess lithium manganese composite oxide (G) with D50 = 1.3 μm (hereinafter referred to as “electrode active material (G)”) May be referred to as).

(8) Synthesis of lithium (nickel / manganese / cobalt) composite oxide (H) 3.3 mol of nickel oxide prepared by baking nickel carbonate for 15 hours at 700 ° C. in the atmosphere, and manganese carbonate at 700 ° C. in the atmosphere Then, 3.3 mol of manganese dioxide prepared by baking for 15 hours, 3.3 mol of cobalt oxyhydroxide having low crystallinity, and 5.05 mol of lithium carbonate were dispersed in pure water, and 1 with zirconia beads having a diameter of 0.5 mm. After a time bead mill treatment, the powder was spray-dried to obtain a dry powder. This is fired at 850 ° C. for 15 hours in the atmosphere, and lithium (nickel / manganese / cobalt) composite oxide (H) (hereinafter referred to as “electrode active material (H)”) having D50 = 4.1 μm. .)

(9) Synthesis of Lithium Titanium Composite Oxide (I) Titanium oxide and lithium carbonate were blended at a ratio of Li to Ti element ratio of 4.12 to 5 and mixed by ball milling, and temporarily preloaded at 500 ° C. for 8 hours. After firing, the mixture was crushed again with a ball mill and mixed, followed by main firing at 800 ° C. for 10 hours to obtain a lithium titanium composite oxide. This composite oxide was crushed in a ball mill in ethanol, then post-fired at 500 ° C. for 10 minutes, and D50 = 0.9 μm of lithium titanium composite oxide (I) (hereinafter referred to as “electrode active material (I)”) There is a thing.)

Next, reference examples, examples and comparative examples are shown.
(Example 1) (Reference example)
A dispersion in which an electrode active material (F) and a commercially available battery acetylene black (average particle size 50 nm, hereinafter referred to as AB) are dispersed in a 1.0% by mass aqueous solution of CMC and the weight of the dispersion is the same When glass beads were charged in a sealed container and vibrated for 2 hours and then removed, a dispersion composed of 89 g of electrode active material (F), 5 g of AB, and 100 g of CMC aqueous solution was obtained. A dispersion for electrode composite production that can be applied at a viscosity of 3500 mPa · s at 25 ° C. when 8.2 g of PTFE aqueous dispersion (A) is gradually added over 10 minutes while stirring this dispersion. Got. The electrode composite production dispersion capable of being coated can be produced only by adding the binder (A) little by little over a long period of time, and the efficiency is extremely poor.

This dispersion was coated on an aluminum foil using a doctor blade, dried, and rolled to obtain a positive electrode (1) in which an electrode composite layer having a thickness of about 100 μm was formed on the aluminum foil. When the positive electrode (1) was observed with a scanning electron microscope (SEM), fibrils having a diameter of 110 to 300 nm and aggregates not in a fibril-like form were observed. Although it can be interpreted that the aggregates that are not in the form of fibrils are bound as fibril knots, it is understood that PTFE is not effectively used as a binder.

Next, a lead wire is attached to each of the positive electrode plate obtained by punching the positive electrode (1) to a predetermined size and the negative electrode plate obtained by cutting the lithium foil to a predetermined size, and is attached to a stainless steel cell case via a polyolefin-based separator. Then, an electrolyte solution in which 1 mol / liter of lithium hexafluorophosphate was dissolved in a mixed solution of ethylene carbonate and diethylene carbonate was injected to obtain a model cell of a lithium secondary battery. Attach the model cell charge and discharge tester, corresponding to the charging current 0.6 mA / cm ² was charged to a battery voltage 4.3V, the discharge current 2.0mA ^/ cm 2 (1.25C rate at 25 ° C. Table 1 shows the result of repeating 100 cycles of charge and discharge for discharging until 2.0 V was obtained. From Table 1, it was found that this model cell was a lithium secondary battery with good storage element characteristics.

(Example 2) (Example)
In the same manner as in Example 1, a dispersion composed of 89 g of the electrode active material (F), 5 g of AB, and 100 g of 1.0 mass% CMC aqueous solution was obtained. 8.4 g of binder (B) was added all at once while this dispersion was allowed to stand, and the mixture was allowed to stand for 10 minutes, and then gelled when stirred with a spoon. From this gelled composition (viscosity at 25 ° C., 1500,000 mPa · S), a coating film using the doctor blade of (Example 1) did not provide a good coating film, but by the following method using a roll molding machine A good electrode composite sheet could be produced.

  That is, the distance between two horizontally installed rolls as shown in FIG. 1 is 1.5 mm, the roll temperature is 65 ° C., the front roll is 3.0 rpm, and the rear roll is 2.6 rpm. Roll processing was performed to obtain a first belt-like sheet. The temperature of the gel during the roll treatment was 60 ° C. Subsequently, the first belt-like sheet was processed in the same manner as described above except that the roll interval was changed to 0.5 mm to obtain a second belt-like sheet. This second strip sheet was processed in the same manner as described above except that the roll interval was further changed to 0.2 mm, and a third strip sheet was obtained and received on the aluminum foil. The aluminum foil layered with the third belt-like sheet was laminated together by rolling at 105 ° C., dried at 120 ° C., and then rolled again to obtain the positive electrode (2). This positive electrode (2) was obtained by laminating an electrode composite layer having a thickness of 100 μm and an aluminum foil.

SEM observation of the electrode composite layer of the positive electrode (2) confirmed the structure in which fibrils having a diameter of 50 nm or less formed a network and was bound, and it was found that PTFE functions efficiently as a binder. Table 1 shows the characteristics of the model cell assembled in the same manner as in Example 1 using this positive electrode (2). From the table, it was found that this model cell was a lithium secondary battery with good power storage device characteristics.
The shear stress at the time of the roll treatment was calculated as 27 Pa when the roll interval was 1.5 mm, 128 Pa when 0.5 mm, and 425 Pa when 0.2 mm. Moreover, the pressure provided with the rolling roll was 350 Pa.

(Example 3) (Example)
In the same manner as in (Example 2), an attempt was made to prepare a dispersion composed of 89 g of the electrode active material (E), 5 g of AB, and 100 g of 1.0 mass% CMC aqueous solution. It was an overview. Therefore, it was possible to prepare a similar dispersion by using a composition in which 25 g of pure water was newly added (Example 2). This dispersion could be gelled in the same manner as in (Example 2), and the positive electrode (3) could be obtained in the same manner as in (Example 2). In addition, the 25 degreeC viscosity of the obtained gelled composition was 2500,000 mPa * S. SEM observation of the electrode composite layer of the positive electrode (3) confirmed the structure in which fibrils having a diameter of 50 nm or less formed a network and was bound, and it was found that PTFE functions efficiently as a binder. Table 1 shows the characteristics of the model cell assembled in the same manner as in Example 1 using the positive electrode (3). From the table, it was found that this model cell was a lithium secondary battery with good power storage device characteristics.

(Example 4) (Reference Example)
Commercially available PVdF and NMP for battery use were obtained, and a 12.0 mass% NMP solution of PVdF was prepared. Next, a dispersion liquid in which the electrode active material (F) and AB are dispersed in NMP and glass beads having a weight similar to the weight of this dispersion liquid are charged in a sealed container and shaken for 2 hours. A dispersion liquid comprising 90 g of the active material (E), 5 g of AB, and 153.3 g of NMP was obtained. While the dispersion was being stirred, 41.7 g of an NMP solution of PVdF was gradually added to obtain a dispersion for producing an electrode composite having good coatability. This dispersion was coated on an aluminum foil using a doctor blade, dried and rolled to obtain a positive electrode (4). The characteristics of the model cell assembled in the same manner as in Example 1 using the positive electrode (4) are shown in Table 1.

(Example 5) (Comparative example)
A positive electrode (5) was obtained in the same manner as in Example 4 except that the electrode active material (E) was used instead of the electrode active material (F). Using the positive electrode (5), an attempt was made to make a similar model cell (Example 1), but the lack of the electrode composite layer was large, and the model cell was abandoned. Since (D) is a fine particle type electrode active material, it was judged that an electrode composite with good adhesion could not be produced with a binder amount of 5% by mass in the electrode composite.

(Example 6) (Comparative example)
A positive electrode (6) was obtained in the same manner as in Example 4 except that 87.5 g was used in place of 41.7 g of the NMP solution of PVdF and the amount of the binder in the composite was 10% by mass. Like the positive electrode (5), the positive electrode (6) was largely missing the electrode composite layer, and the model cell was abandoned.
(Example 7) (Comparative example)
A positive electrode (7) was obtained in the same manner as in Example 4 except that 140 g was used instead of 41.7 g of the NMP solution of PVdF, and the amount of the binder in the composite was 15% by mass. From the positive electrode (7), a model cell can be produced in the same manner as in Example 1 without losing the electrode composite layer, and the characteristics are shown in Table 1. However, as is apparent from the table, the characteristics of the positive electrode (7) were not good. This was judged to be the effect of a large amount of binder. That is, it is interpreted that a large amount of binder has hindered smooth ion flow.

(Example 8) (Example)
Instead of 8.4 g of binder (B), 2.0 g of binder (C) and 6.6 g of binder (B) (the fluoropolymer solid content of binder (C) and the PTFE solid content of binder (B) are combined) 5 g, and the content ratio is 1 to 4 in terms of mass ratio.) The gelled composition (viscosity of 35,000 mPa · S at 25 ° C.) and the positive electrode (8) were obtained in the same manner as in Example 3. Got. SEM observation of the electrode composite layer of the positive electrode (8) confirmed the structure in which fibrils having a diameter of 50 nm or less formed a network and was bound, and it was found that PTFE functions efficiently as a binder. The characteristics of the model cell assembled in the same manner as in Example 1 using the positive electrode (8) are shown in Table 1. From the table, it was found that this model cell was a lithium secondary battery with good power storage device characteristics.

(Example 9) (Example)
Instead of 2.0 g of binder (C) and 6.6 g of binder (B), 11.8 g of binder (D) and 1.3 g of binder (B) (hydrocarbon polymer solids and binder of binder (D)) The gelled composition (viscosity at 25 ° C. of 2500000 mPa · S) was the same as in (Example 8) except that (B) the PTFE solid content was 5 g in total and the ratio was 84 to 16. And a positive electrode (9) was obtained. SEM observation of the electrode composite layer of the positive electrode (9) confirmed the structure in which fibrils with a diameter of 50 nm or less formed a network and was bound, and it was found that PTFE functions efficiently as a binder. The characteristics of the model cell assembled in the same manner as in Example 1 using the positive electrode (9) are shown in Table 1. From the table, it was found that this model cell was a lithium secondary battery with good power storage device characteristics.

(Example 10) (Comparative example)
Except that 2.0 g of the fluoropolymer aqueous dispersion (C) and 6.6 g of the PTFE dispersion (B) were replaced with 14 g of the hydrocarbon polymer aqueous dispersion (D) (Example 8); In the same manner, a gel was obtained and an attempt was made to produce a positive electrode (10). However, a continuous electrode composite layer could not be produced due to frequent cracks, and the model cell production was abandoned.

(Example 11) (Example)
Gelled composition (viscosity at 25 ° C. 20000 mPa · S) and positive electrode in the same manner as in Example 3 except that 89 g of lithium manganese composite oxide (G) was used instead of lithium iron phosphate (E) (11) was obtained. SEM observation of the electrode composite layer of the positive electrode (11) confirmed the structure in which fibrils having a diameter of 50 nm or less formed a network and was bound, and it was found that PTFE functions efficiently as a binder. The characteristics of the model cell assembled in the same manner as in Example 1 using the positive electrode (11) are shown in Table 1. From the table, it was found that this model cell was a lithium secondary battery with good power storage device characteristics.

(Example 12) (Example)
Gelled composition (viscosity of 3000000 mPa · S at 25 ° C.) and positive electrode (12) in the same manner as in Example 3 except that 89 g of electrode active material (H) was used instead of electrode active material (E) Got. The SEM observation of the electrode composite layer of the positive electrode (12) confirmed the structure in which fibrils having a diameter of 50 nm or less formed a network and was bound, and it was found that PTFE functions efficiently as a binder. The characteristics of the model cell assembled in the same manner as in Example 1 using the positive electrode (12) are shown in Table 1. From the table, it was found that this model cell was a lithium secondary battery with good power storage device characteristics.

(Example 13) (Example)
The gelled composition (viscosity at 25 ° C. of 850000 mPa · S) and the negative electrode (13) were the same as in Example 3 except that 89 g of the electrode active material (I) was used instead of the electrode active material (E). Got. When the electrode composite layer of the negative electrode (13) was observed with an SEM, a structure in which fibrils having a diameter of 50 nm or less were bound by forming a network could be confirmed. The battery evaluation of the negative electrode (13) was performed using a lithium foil as a counter electrode. Therefore, the negative electrode (13) is handled as the positive electrode in this evaluation. The model cell was produced in the same manner as (Example 1). Battery characteristics attach the model cell charge and discharge tester, it was charged to a battery voltage 2.0V at a charging current 0.6 mA / cm ² at 25 ° C., the discharge current 2.0mA ^/ cm 2 (1.25C The charge / discharge cycle of discharging to 1.3 V at a rate corresponding to the rate was determined by performing 100 cycles, and the results are shown in Table 1. From the table, it was found that this negative electrode (14) exhibited good electricity storage device characteristics.

(Example 14) (Example)
The dispersion prepared in the same manner as in Example 3 was subjected to a calendering process and a rolling process in succession using the equipment shown in FIG. 2 to obtain a positive electrode (14). The SEM observation of the electrode composite layer of the positive electrode (14) confirmed the structure in which fibrils having a diameter of 50 nm or less formed a network and was bound, and it was found that PTFE functions efficiently as a binder. The characteristics of the model cell assembled in the same manner as in Example 1 using the positive electrode (14) are shown in Table 1. From the table, it was found that this model cell was a lithium secondary battery with good power storage device characteristics.

(Example 15) (Example)
After adding 7 g of AB and 91 g of the electrode active material (E) to 100 g of 1.0 mass% CMC aqueous solution, add 1.7 g of binder (B) (PTFE solid content is 1 g) and rotate at a high speed of 12000 rpm. When a homogenizer treatment comprising a rotor and a stator was carried out for 20 minutes, a dispersion gel for producing an electrode composite having a viscosity at 25 ° C. of 900,000 mPa · s was obtained. This gel was roll-treated in the same manner as in (Example 2) to obtain a positive electrode (15). Table 1 shows the characteristics of the model cell assembled in the same manner as in Example 1 using the positive electrode (15). From the table, this model cell was a lithium secondary battery with good electrical storage element characteristics.

(Example 16) (Example)
Lithium iron phosphate having an average particle size of 0.35 μm was obtained. In Example 15, instead of the electrode active material (E), lithium iron phosphate (J) having an average particle size of 0.35 μm (hereinafter sometimes referred to as electrode active material (J)) was used. And a homogenizer treatment was carried out in the same manner as in Example 15 to obtain a dispersion gel for producing an electrode composite having a viscosity at 25 ° C. of 1300000 mPa · s. This gel was roll-treated as in (Example 2) to obtain a positive electrode (16). The characteristics of the model cell assembled in the same manner as in Example 1 using the positive electrode (16) are shown in Table 1. From the table, this model cell was a lithium secondary battery with good electrical storage element characteristics.

* Polymer I in the binder is a polymer that can be in the form of a fibril, and polymer II represents other polymers. The binder content represents the content of the binder in the electrode composite.

  According to the production method of the present invention, an electrode composite can be easily produced even from a dispersion that has been difficult to produce by gelation. In addition, since the electrode composite for secondary batteries produced by the production method of the present invention can also use an electrode active material having a smaller particle diameter, it is extremely effective as an electrode for a high-energy and high-power storage element. Used. In particular, it is effective for electrode composites for non-aqueous electrolyte secondary batteries such as lithium ion batteries, lithium ion polymers, and lithium polymer batteries.

DESCRIPTION OF SYMBOLS 1 Gelling composition 2 Calendering back roll 3 Roll before calendering 4 Calendering gelling composition 5 Rolling roll 1
6 Roll roll 2
7 Roll roll 3
8 Rolling roll 4
9 Calendered and rolled gelled composition

Claims (10)

  (1) a gelation step of obtaining a gelled composition by gelling a dispersion containing an electrode active material, a polymer-containing binder and a dispersion medium, and (2) the gelation A method for producing an electrode composite for a secondary battery, comprising: forming the composition into a sheet, and removing the dispersion medium to obtain a sheet-like secondary battery electrode composite.   The method for producing an electrode composite for a secondary battery according to claim 1, wherein the gelled composition has a viscosity at 25 ° C. of 5000 to 64000000 mPa · S.   The method for producing an electrode composite for a secondary battery according to claim 1, wherein the binder is polytetrafluoroethylene and the dispersion medium is water.   The particle diameter of the said electrode active material is 10 nm-500 micrometers, The manufacturing method of the electrode composite for secondary batteries as described in any one of Claims 1-3.   The manufacturing method of the electrode composite for secondary batteries as described in any one of Claims 1-4 in which the said dispersion | distribution contains a conductive support agent further.   The manufacturing method of the electrode composite for secondary batteries as described in any one of Claims 1-5 in which the said binder contains at least one of an amorphous fluorine-containing polymer and an amorphous non-fluorine-type polymer.   The electrode composite for secondary batteries manufactured by the manufacturing method as described in any one of Claims 1-6.   The electrode composite for a secondary battery according to claim 7, wherein the content of the binder is 0.01 to 15% by mass.   The electrode for secondary batteries formed by laminating | stacking the electrode composite for secondary batteries of Claim 7 or 8, and a collector.   A secondary battery using the secondary battery electrode according to claim 9.

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