JP2012009276A - Lithium ion secondary battery and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery which includes an electrode plate where conductive material distribution inside a cathode composite layer is made uniform and binding material does not cover the active substance.SOLUTION: A cathode coating liquid kneading-and-mixing process includes a binding material solution preparation step, a conductive material dispersion step, and a cathode active material mixing step. In the binding material solution preparation step, a binding material is mixed in a solvent and also dispersed in the solvent to produce a binding material solution. In the conductive material dispersion step, a conductive material and the binding material solution are mixed in a solvent and also the conductive material is dispersed in the solvent to produce a conductive material-and-binding material-dispersed solution. In the cathode active material mixing step, a cathode active material is mixed in and also kneaded and mixed in the conductive material-and-binding material dispersed solution to produce a cathode coating liquid.

Description

  The present invention relates to a lithium ion secondary battery and a method for manufacturing the same. More specifically, the present invention relates to a lithium ion secondary battery in which the distribution of a conductive material is made uniform inside a positive electrode mixture layer and a method for manufacturing the same.

  Secondary batteries are used in various fields such as electronic devices such as mobile phones and personal computers, vehicles such as hybrid vehicles and electric vehicles. Such a secondary battery includes a positive electrode plate, a negative electrode plate, and an electrolyte. Moreover, it is common to use the laminated electrode body which laminated | stacked the positive electrode plate, the negative electrode plate, and the separator which insulates them.

  The positive electrode plate used for the laminated electrode body is obtained by forming a positive electrode mixture layer on a metal foil serving as a positive electrode core material. The positive electrode mixture layer is formed by applying a coating liquid containing a positive electrode active material to a metal foil and then drying it. In this coating solution, a positive electrode active material, a binder, a thickener, and the like are mixed in a solvent.

In lithium ion secondary batteries, lithium composite oxides such as lithium nickelate (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), and lithium cobaltate (LiCoO ₂ ) are used as the positive electrode active material. The electric resistance of these lithium composite oxides is somewhat large for use in electrodes. Therefore, by mixing the conductive material into the coating solution, the electron conductivity of the positive electrode mixture layer is increased.

  The electron conductivity in the positive electrode mixture layer is higher when the conductive material is uniformly distributed in the positive electrode mixture layer. If the conductive material is unevenly distributed, the electron conductivity at the point where the conductive material is concentrated is sufficient, but instead, the electron conductivity at the point where the conductive material is sparse is insufficient. . Accordingly, considering the positive electrode mixture layer as a whole, the positive electrode mixture layer in which the conductive material is uniformly distributed is superior in electron conductivity to the positive electrode mixture layer in which the conductive material is unevenly distributed.

  When the positive electrode mixture layer has high electron conductivity, the battery performance such as cycle characteristics and rate characteristics of the lithium ion secondary battery is generally high. Thus, in order to suppress uneven distribution of the conductive material, it is preferable that the conductive material is well dispersed in the solvent in the kneading step for preparing the coating liquid. Therefore, in the kneading process, a technique for well dispersing the conductive material in the solvent has been developed.

  For example, Patent Document 1 discloses an electrode using a coating liquid in which a carbon-based conductive material and a dispersion solvent are kneaded to disperse the carbon-based conductive material, and then an active material and a binder are kneaded in the dispersion solvent. A method for producing an electrode for a lithium ion battery for producing a plate is disclosed. As a result, the carbon-based conductive material is well dispersed in the dispersion solvent, and the battery performance is improved.

JP-A-10-144302

  However, as in Patent Document 1, when the carbon-based conductive material and the dispersion solvent are kneaded to disperse the carbon-based conductive material, the active material and the binder are kneaded into the dispersion solvent. There is a possibility that the active material may be covered with the binder. This is because the carbon-based conductive material is already dispersed in the dispersion solvent, but the positive electrode active material is charged in a state where the binder is not dispersed in the dispersion solvent. Therefore, when the positive electrode active material and the binder are put into the kneader at the same time, the positive electrode active material may be covered with the binder. In the positive electrode active material covered with the binder, the electrode reaction hardly occurs.

  The present invention has been made to solve the above-described problems of the prior art. That is, the problem is that the distribution of the conductive material within the positive electrode mixture layer is made uniform, and the lithium ion secondary battery having an electrode plate in which the binder does not cover the active material, and The manufacturing method is provided.

  The manufacturing method of the lithium ion secondary battery of the present invention made for the purpose of solving this problem is to mix at least a positive electrode active material, a conductive material, and a binder into a solvent and knead to prepare a positive electrode coating solution The positive electrode coating liquid kneading step, the positive electrode plate coating and drying step in which the positive electrode coating liquid is applied to the positive electrode core material and then dried to form the positive electrode plate, and the positive electrode plate and the negative electrode plate are interposed between them. It is a manufacturing method of a lithium ion secondary battery which has an electrode body preparation process which piles up in the state which pinched | interposed the separator, and makes it an electrode body. The positive electrode coating liquid kneading step includes a binder material preparation step in which a binder is mixed in a solvent to form a binder solution, and a conductive material and the binder solution are mixed in the solvent. Conductive material dispersion step in which conductive material is dispersed to form conductive material binder dispersion solution, and positive electrode active material in which positive electrode active material is mixed and kneaded into the conductive material binder dispersion solution to form positive electrode coating liquid A mixing step. In such a method for producing a lithium ion secondary battery, a lithium ion secondary battery can be produced using a positive electrode coating liquid in which a conductive material and a binder are well dispersed. Therefore, in the lithium ion secondary battery manufactured using this manufacturing method, the conductive material within the positive electrode mixture layer is almost uniformly distributed.

  In the method of manufacturing a lithium ion secondary battery described above, the conductive material dispersing step includes mixing the conductive material into the solvent and mixing the conductive material into the solvent before mixing the conductive material and the binder solution into the solvent. It is preferable to have a primary dispersion step of dispersing the conductive material solution and a secondary dispersion step of mixing the conductive material solution and the binder solution into the conductive material binder dispersion solution. This is because a lithium ion secondary battery can be manufactured using a positive electrode coating liquid in which the conductive material and the binder are more dispersed.

  In addition, the lithium ion battery according to the present invention includes at least a positive electrode active material, a conductive material, and a binder mixed in a solvent and kneaded to prepare a positive electrode coating solution. After coating, the electrode body is dried to form a positive electrode plate, and the positive electrode plate and the negative electrode plate are stacked with a separator interposed therebetween. The positive electrode coating solution is obtained by mixing a binder into a solvent to form a binder solution, mixing the conductive material and the binder solution into the solvent, and dispersing at least the conductive material to bind the conductive material. A material dispersion solution was prepared by mixing and kneading the positive electrode active material in the conductive material binder dispersion solution. In such a lithium ion secondary battery, the conductive material within the positive electrode mixture layer is distributed almost uniformly. Therefore, its rate characteristics and cycle characteristics are excellent.

  According to the present invention, the distribution of the conductive material within the positive electrode mixture layer is made uniform, and the lithium ion secondary battery having an electrode plate whose binding material does not cover the active material, and its manufacture A method is provided.

It is sectional drawing for demonstrating the structure of the lithium ion secondary battery which concerns on embodiment. It is a perspective view for demonstrating the winding electrode body of the lithium ion secondary battery which concerns on embodiment. It is an expanded view for demonstrating the winding structure of the winding electrode body of the lithium ion secondary battery which concerns on embodiment. It is a perspective sectional view for explaining the structure of the positive electrode plate of the lithium ion secondary battery according to the embodiment. It is a perspective sectional view for explaining the structure of the negative electrode plate of the lithium ion secondary battery according to the embodiment. It is a figure for demonstrating the coating liquid kneading | mixing process for positive electrodes in the lithium ion secondary battery which concerns on 1st Embodiment. It is a schematic block diagram for demonstrating the coating dryer for creating the positive electrode plate and negative electrode plate of the lithium ion secondary battery which concerns on embodiment. It is a schematic block diagram for demonstrating the winding apparatus of the winding electrode body of the lithium ion secondary battery which concerns on embodiment. It is a figure for demonstrating the coating liquid kneading | mixing process for positive electrodes in the lithium ion secondary battery which concerns on 2nd Embodiment. It is a schematic cross section which shows the structure of the positive electrode plate of the lithium ion secondary battery which concerns on 3rd Embodiment. It is a graph which shows the relationship between the endothermic temperature of the carbon coat foil of the lithium ion secondary battery which concerns on 3rd Embodiment, and DSC calorie | heat amount. It is a graph which shows the relationship between the heat processing temperature of the carbon coat foil of the lithium ion secondary battery which concerns on 3rd Embodiment, and endothermic start temperature. It is a graph which shows the relationship between the heat processing temperature and film resistance of the carbon coat foil of the lithium ion secondary battery which concerns on 3rd Embodiment.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below in detail with reference to the accompanying drawings. In the present embodiment, the present invention is embodied with respect to a lithium ion secondary battery and a manufacturing method thereof.

(First embodiment)
1. Lithium ion secondary battery The battery according to the present embodiment is a cylindrical lithium ion secondary battery. FIG. 1 shows a cross-sectional view of the battery 100 of this embodiment. As shown in FIG. 1, the battery 100 is sealed by a battery case including a battery container 101 and a lid 102. The battery 100 includes a wound electrode body 200, a positive current collector 110, and a negative current collector 120. In addition, an electrolytic solution is injected into the battery container 101.

  The wound electrode body 200 repeatedly charges and discharges in the electrolytic solution and directly contributes to power generation. The positive electrode current collector plate 110 is a positive electrode current collector connected to a positive electrode core material of a wound electrode body 200 described later. The material is aluminum. The negative electrode current collector plate 120 is a negative electrode current collector connected to a negative electrode core material of a wound electrode body 200 described later. Its material is copper. FIG. 2 shows a perspective view of the wound electrode body 200 extracted from FIG. 1 connected to the positive electrode current collector plate 110 and the negative electrode current collector plate 120.

  The electrolyte injected into the battery container 101 is obtained by dissolving an electrolyte in an organic solvent. Examples of organic solvents include propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), 1,2-dimethoxyethane, 1,2-diethoxyethane. , Tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, 1,3-dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, acetonitrile, propionitrile, nitromethane, N, N-dimethylformamide, dimethyl sulfoxide, sulfolane, γ-butyrolactone, etc. A solvent or a combination of these can be used.

Further, as a salt that is an electrolyte, lithium perchlorate (LiClO ₄ ), lithium borofluoride (LiBF ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium hexafluoroarsenate (LiAsF ₆ ), LiCF ₃ SO _{3 , LiC 4 F 9 SO 3,} LiN (CF 3 SO 2) 2, LiC (CF 3 SO 2) 3, can be used a lithium salt such as LiI.

  FIG. 3 is a development view showing a wound structure of the wound electrode body 200. As shown in FIG. 3, the wound electrode body 200 is wound in a state in which a positive electrode plate P, a separator S, a negative electrode plate N, and a separator T are stacked in this order from the inside. Here, the separator S and the separator T are insulating members made of the same material. For the understanding of the above winding order, only the codes are distinguished as S and T.

  As shown in FIG. 3, the positive electrode plate P has a positive electrode coating portion P1 and a positive electrode non-coating portion P2. The positive electrode coating part P1 is a place where a positive electrode active material or the like is applied to the positive electrode core material. The positive electrode non-coating portion P2 is a portion where a positive electrode active material or the like is not applied to the positive electrode core material. Therefore, the thickness of the positive electrode coating part P1 is thicker than the thickness of the positive electrode non-coating part P2.

  The negative electrode plate N includes a negative electrode coating portion N1 and a negative electrode non-coating portion N2. The negative electrode coating portion N1 is a portion where a negative electrode active material or the like is applied to the negative electrode core material. The negative electrode non-coating portion N2 is a portion where a negative electrode active material or the like is not applied to the negative electrode core material. Therefore, the thickness of the negative electrode coating part N1 is thicker than the thickness of the negative electrode non-coating part N2.

  An arrow A in FIG. 3 indicates the width direction (vertical direction in FIG. 1) of the positive electrode plate P, the negative electrode plate N, and the separators S and T. An arrow B in FIG. 3 indicates the longitudinal direction of the positive electrode plate P, the negative electrode plate N, and the separators S and T (the circumferential direction of the wound electrode body 200 in FIG. 1).

2. FIG. 4 is a perspective sectional view of the positive electrode plate P. FIG. The direction indicated by arrow A in FIG. 4 is the same as the direction indicated by arrow A in FIG. That is, it is the width direction of the positive electrode plate P. The direction indicated by arrow B in FIG. 4 is the same as the direction indicated by arrow B in FIG. That is, it is the longitudinal direction of the positive electrode plate P.

  As shown in FIG. 4, the positive electrode plate P is obtained by forming a positive electrode mixture layer PA on a part of both surfaces of a strip-like positive electrode core material PB. On the left side in FIG. 4, a positive electrode non-coated portion P2 of the positive electrode plate P protrudes in the width direction. The positive electrode non-coated portion P2 is formed in a strip shape. The positive electrode uncoated portion P2 is a region where the positive electrode mixture is not applied to both surfaces of the positive electrode core material PB. Therefore, in the positive electrode non-coating portion P2, the positive electrode core material PB is still exposed. On the other hand, on the right side in FIG. 4, there is no protrusion corresponding to the positive electrode non-coated portion P2. In the positive electrode coating part P1, the positive electrode mixture layer PA is formed with a uniform thickness on both surfaces of the positive electrode core material PB.

The positive electrode mixture layer PA is formed by applying a composite material including a conductive material, a binder, and a thickener in addition to the positive electrode active material capable of occluding and releasing lithium ions to the aluminum foil as the positive electrode core material PB. Layer. As the positive electrode active material, lithium composite oxides such as lithium nickelate (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), and lithium cobaltate (LiCoO ₂ ) are used.

  Carbon materials such as carbon powder and carbon fiber can be used as the conductive material for the positive electrode. For example, carbon powder such as acetylene black, furnace black, ketjen black, etc., graphite powder, etc.

  The binder for the positive electrode is preferably a polymer that is insoluble (or hardly soluble) in the electrolyte and is dispersed in the solvent used for the positive electrode paste. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoro Fluorine resin such as ethylene copolymer (ETFE), vinyl acetate copolymer, styrene butadiene rubber (SBR), acrylic acid-modified SBR resin (SBR latex), rubber such as gum arabic can be used. Alternatively, a combination of these may be used. The binder is not necessarily limited to the above polymer.

  As the thickener for the positive electrode, cellulose such as carboxymethylcellulose (CMC), methylcellulose (MC), cellulose acetate phthalate (CAP), hydroxypropylmethylcellulose (HPMC), hydroxypropylmethylcellulose phthalate (HPMCP) or the like is used. However, it is not necessarily limited to cellulose as described above, and can be used.

  An example of the solvent is water. In addition, N-methyl-2-pyrrolidone (NMP, hereinafter referred to as NMP) may be used. Other lower alcohols and lower ketones can also be used.

  FIG. 5 is a perspective sectional view of the negative electrode plate N. FIG. The direction indicated by arrow A in FIG. 5 is the same as the direction indicated by arrow A in FIG. That is, it is the width direction of the negative electrode plate N. The direction indicated by the arrow B in FIG. 5 is the same as the direction indicated by the arrow B in FIG. That is, it is the longitudinal direction of the negative electrode plate N.

  As shown in FIG. 5, the negative electrode plate N is obtained by forming a negative electrode mixture layer NA on a part of both surfaces of a strip-shaped negative electrode core material NB. The negative electrode mixture layer NA is formed on both sides of the negative electrode core material NB that is a base material. Therefore, in the negative electrode plate N, the negative electrode mixture layer NA, the negative electrode core material NB, and the negative electrode mixture layer NA are arranged in this order from the upper side in the drawing.

  On the right side in FIG. 5, the negative electrode non-coated portion N2 of the negative electrode plate N protrudes in the width direction. The negative electrode non-coated portion N2 is formed in a strip shape. The negative electrode non-coated portion N2 is a region where the negative electrode mixture is not applied to both surfaces of the negative electrode core material NB. Therefore, in the negative electrode non-coating portion N2, the negative electrode core material NB is still exposed. On the other hand, there is no protrusion corresponding to the negative electrode non-coated portion N2 on the left side in FIG. In the negative electrode coating portion N1, the negative electrode mixture layer NA is formed with a uniform thickness on both surfaces of the negative electrode core material NB.

  The negative electrode mixture layer NA is a layer obtained by applying a mixture containing a negative electrode active material, a binder, and a thickener to a copper foil as the negative electrode core material NB and drying it. The negative electrode active material is a material that can occlude and release lithium ions. As the negative electrode active material, a carbon-based material containing a graphite structure at least partially is used. For example, amorphous carbon, non-graphitizable carbon (hard carbon), graphitizable carbon (soft carbon), graphite (graphite), or a carbon material having a combination thereof can be used.

  The binder for the negative electrode may be a polymer that is insoluble (or hardly soluble) in the electrolyte and is dispersed in the solvent used for the negative electrode paste. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoro Fluorine resin such as ethylene copolymer (ETFE), vinyl acetate copolymer, styrene butadiene rubber (SBR), acrylic acid-modified SBR resin (SBR latex), rubber such as gum arabic can be used. Alternatively, a combination of these may be used. The binder is not necessarily limited to the above polymer.

  As the thickener for the negative electrode, cellulose such as carboxymethylcellulose (CMC), methylcellulose (MC), cellulose acetate phthalate (CAP), hydroxypropylmethylcellulose (HPMC), and hydroxypropylmethylcellulose phthalate (HPMCP) is used. However, it is not necessarily limited to cellulose as described above, and can be used.

  An example of the solvent is water. In addition, NMP may be used. Other lower alcohols and lower ketones can also be used.

3. Method for Producing Lithium Ion Secondary Battery A method for producing a lithium ion secondary battery according to the present embodiment is obtained by kneading a positive electrode active material, a conductive material, a binder, and a thickener, and applying a coating liquid (paste) for the positive electrode , Hereinafter referred to as “paste”). Therefore, it demonstrates centering on the coating liquid kneading | mixing process for the positive electrode.

The manufacturing method of the lithium ion secondary battery of this form has the manufacturing process shown next.
a. Positive electrode coating liquid kneading step a-1. Binder solution preparation step a-2. Conductive material dispersion step a-3. Positive electrode active material mixing step b. Negative electrode coating liquid kneading step c. Positive electrode plate coating and drying step d. Negative electrode plate coating drying step e. Electrode body preparation process f. Battery assembly process

a. Positive electrode coating liquid kneading step A positive electrode coating liquid kneading step for preparing a positive electrode paste for forming the positive electrode mixture layer PA will be described with reference to FIG. As shown in FIG. 6, the positive electrode coating liquid kneading step includes a binder solution preparation step (upper right of FIG. 6), a conductive material dispersion step (center of FIG. 6), and a positive electrode active material mixing step (lower portion of FIG. 6). It is a process including these. The positive electrode material described above may be used as the positive electrode active material, conductive material, thickener, binder, and solvent used here.

a-1. Binder Material Preparation Process In this embodiment, first, a binder solution is prepared. Here, the binder solution is a solution obtained by mixing a binder and a solvent as shown in FIG. In the binder solution, the binder is dispersed in the solvent. At this time, the positive electrode active material, the conductive material, and the solvent are not yet mixed with the binder solution.

a-2. Conductive Material Dispersing Step Subsequently, as shown in FIG. 6, the conductive material is mixed in the solvent. The solvent mixed with the conductive material is referred to as a dispersion solvent. The dispersion solvent is the same type of solvent as that used in the binder solution. Then, as shown in FIG. 6, a binder solution is also mixed into the dispersion solvent. As will be described later in the examples, the amount of the binder solution is sufficiently smaller than the amount of the dispersion solvent. In addition, a thickener may be mixed. Subsequently, the dispersion solvent in which the conductive material, the thickener, and the binder solution are mixed is stirred. As a result, the conductive material is dispersed in the dispersion solvent. In addition, the binder and the thickener are also dispersed in the dispersion solvent. The solution in which the conductive material or the like is dispersed is referred to as a conductive material binder dispersion solution. At this time, the positive electrode active material is not yet mixed with the conductive material binder dispersion solution.

a-3. Next, as shown in FIG. 6, the positive electrode active material is mixed into the conductive material binder dispersion solution that has undergone the conductive material dispersion step. Then, stir as appropriate. Of course, even after mixing the positive electrode active material, the conductive material remains well dispersed in the conductive material binder solution. Since the binder remains sufficiently dispersed in the conductive material binder dispersion solution, there is little possibility that the binder will cover the positive electrode active material. In this way, a positive electrode paste is prepared.

b. Negative electrode coating liquid kneading step The negative electrode may be kneaded in the conventional manner. That is, the negative electrode active material, the thickening material, and the binder are mixed together in the solvent. This is because the negative electrode active material is a conductive carbon-based material and it is not necessary to mix a conductive material separately. After mixing said negative electrode active material etc. in a solvent, it stirs suitably. Thereby, the paste for negative electrodes is created.

c. Positive electrode plate coating and drying step A positive electrode plate P is prepared using a coating and drying apparatus 1000 shown in FIG. First, the coating process will be described. The positive electrode core material PB is sent out from the unwinding shaft 1101. Next, the positive electrode coating liquid is applied to the positive electrode core PB with a predetermined width and thickness by the coating liquid supply unit 1210. Thereby, the paste layer of the positive electrode is applied on the positive electrode core material PB. Here, the coating liquid supplied from the coating liquid supply unit 1210 is for the positive electrode.

  Next, the drying process will be described. In the drying process, the coated positive electrode core material PB is conveyed into the drying furnace 1300. Inside the drying furnace 1300, the positive electrode core material PB is conveyed by a roller 1302. The paste layer on the positive electrode core material PB is dried by hot air H blown from the hot air nozzle 1301. Thereafter, the positive electrode core material PB having the dried paste layer is wound around the winding shaft 1401.

  The coating / drying apparatus 1000 shown in FIG. 7 is an apparatus that coats and dries only one side of the electrode core material. Therefore, in order to apply both surfaces, after forming the positive electrode mixture layer PA on one surface, the positive electrode mixture layer PA may be formed on the opposite surface. Therefore, the positive electrode core material PB is passed through the coating / drying apparatus 1000 twice. However, if a coating / drying apparatus that coats and dries both sides is used instead of the coating / drying apparatus 1000 of FIG. The double-sided coating / drying apparatus includes a coating liquid supply apparatus that coats the surface opposite to the coating surface downstream of the drying furnace 1300 in FIG. 7 and a drying furnace downstream thereof. Similarly, the negative electrode plate N can be coated on both sides.

d. Negative electrode plate coating and drying step Similarly to the positive electrode plate P, the negative electrode plate N is also prepared using the coating and drying apparatus 1000. That is, the negative electrode core material NB is unwound, the paste is applied by the coating liquid supply unit 1210, and the paste layer is dried inside the drying furnace 1300. However, the coating liquid supplied from the coating liquid supply unit 1210 is for the negative electrode. Further, the drying conditions such as the temperature of the drying furnace 1300 are different from those of the positive electrode. It should be noted that the order in which the positive electrode plate P and the negative electrode plate N are created may be first.

e. Next, the separators S and T are wound on the positive electrode plate P and the negative electrode plate N, which have already been dried, using the winding device 2000 shown in FIG. The winding device 2000 includes a positive electrode plate supply unit 2001, a negative electrode plate supply unit 2002, separator supply units 2003 and 2004, and a winding shaft 2005. Here, as shown in FIG. 3, the positive electrode plate P, the separator S, the negative electrode plate N, and the separator T are stacked and wound in order from the inside. The wound electrode body 200 is created by rotating the wound shaft 2005 in the direction of arrow F in FIG.

f. Battery Assembly Step Subsequently, the wound electrode body 200 is inserted into the battery container 101. Then, an electrolytic solution is injected into the battery container 101 and sealed. Thereby, the battery 100 is assembled. After this, it is advisable to perform processing such as conditioning and aging and various inspection processes.

4). Summary As described in detail above, the battery 100 manufacturing method according to the present embodiment is a method in which the conductive material is dispersed in a dispersion solvent before the positive electrode active material is charged in the positive electrode coating liquid kneading step. is there. Therefore, the conductive material can be well dispersed in the coating liquid. Further, the binder hardly covers the positive electrode active material.

  The battery 100 according to the present embodiment has a positive electrode plate in which the conductive material is distributed substantially uniformly in the positive electrode mixture layer. Therefore, the electron conductivity is high in the positive electrode mixture layer of the positive electrode plate of the battery 100 of this embodiment. Therefore, the battery 100 having excellent rate characteristics and cycle characteristics is realized. Further, since the binder hardly covers the positive electrode active material, there is almost no positive electrode active material that is not used for power generation. That is, the battery performance is high.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, an electrode body used for a battery is not limited to a wound electrode body. Therefore, the present invention can be applied even to a battery having flat electrode bodies. Any secondary battery using stacked electrode bodies stacked and stacked can be applied. The present invention can be applied not only to a cylindrical battery but also to a square battery.

  In addition, the positive electrode mixture layer PA and the negative electrode mixture layer NA are formed on both sides of the positive electrode core material PB and the negative electrode core material NB, respectively. However, the composite material layer may be formed on only one side. The present invention can also be applied to a case where two or more composite layers are formed on at least one of the positive electrode plate and the negative electrode plate.

(Second Embodiment)
A second embodiment will be described. The battery according to this embodiment is the same as that of the first embodiment. This embodiment is different from the first embodiment in its manufacturing method. In particular, the method for kneading the positive electrode paste is different. Therefore, the method for kneading the positive electrode paste will be mainly described.

The manufacturing method of the lithium ion secondary battery of this form has the manufacturing process shown next.
a. Positive electrode coating liquid kneading step a-1. Binder material preparation step a-4. Primary dispersion step a-5.2 Secondary dispersion step a-6. Positive electrode active material mixing step b. Negative electrode coating liquid kneading step c. Positive electrode plate coating and drying step d. Negative electrode plate coating drying step e. Electrode body preparation process f. Battery assembly process

  Each process other than the positive electrode coating liquid kneading process is the same as in the first embodiment. Therefore, it demonstrates centering on the coating liquid kneading | mixing process for positive electrodes.

a. Here, the positive electrode coating liquid kneading step in this embodiment is shown in FIG. As shown in FIG. 9, the positive electrode coating liquid kneading step of the present embodiment is a step including a binder solution preparation step, a primary dispersion step, a secondary dispersion step, and a positive electrode active material mixing step. .

a-1. Binder Material Creation Step First, a binder solution is created as in the first embodiment. At this point, the positive electrode active material, the conductive material, and the dispersion solvent are not yet mixed with each other.

a-4. Primary Dispersion Step Subsequently, the dispersion solvent and the conductive material are mixed into the kneader. Then, the dispersion solvent mixed with the conductive material is stirred in the kneader. Thereby, the conductive material is sufficiently dispersed in the solvent. In this way, a conductive material solution is created. At this time, the conductive material solution and the binder solution are not mixed. Moreover, the positive electrode active material is not mixed with these solutions.

a-5. Secondary Dispersion Step Subsequently, the binder solution is mixed into the conductive material solution that has undergone the primary dispersion step. Similar to the first embodiment, the amount of the binder solution is sufficiently smaller than the amount of the conductive material solution. A thickener is also mixed into the solution thus obtained. Then, the dispersion solution mixed with the conductive material, the binder, and the thickener is stirred. Thereby, the conductive material binder dispersion solution in which the conductive material, the binder, and the thickener are sufficiently dispersed is created. At this time, the positive electrode active material is not yet mixed with the conductive material binder dispersion solution.

a-6. Positive electrode active material mixing step Subsequently, the positive electrode active material is mixed into the conductive material binder dispersion solution that has undergone the secondary dispersion step. Then, the dispersion solution is stirred. Thereby, the paste for positive electrodes is completed. In the positive electrode paste of this embodiment, the conductive material is well dispersed in the dispersion solution. And it is disperse | distributing better than the paste for positive electrodes of 1st Embodiment. Further, since the binder is well dispersed in the dispersion solution, there is almost no possibility that the binder will cover the positive electrode active material.

  Other processes are the same as those in the first embodiment. That is, a positive electrode plate is prepared by applying a positive electrode paste to the positive electrode core PB and drying it. The same applies to the negative electrode plate. Next, the electrode body is formed by laminating them by winding or the like. Then, the battery 100 is manufactured by inserting the electrode body into the battery container and injecting the electrolytic solution.

  As described above in detail, the battery manufacturing method according to the present embodiment is a method in which only the conductive material is dispersed in the dispersion solvent before the positive electrode active material is charged. Therefore, the conductive material can be well dispersed in the coating liquid. In addition, since only the conductive material is dispersed in the dispersion solvent, the conductive material is better dispersed than in the first embodiment.

  The battery according to the present embodiment has a positive electrode plate in which the conductive material is distributed substantially uniformly in the positive electrode mixture layer. Therefore, electronic conductivity is high in the positive electrode mixture layer of the positive electrode plate of the battery of this embodiment. Therefore, a battery having excellent rate characteristics and cycle characteristics has been realized. Further, since the binder hardly covers the positive electrode active material, there is almost no positive electrode active material that is not used for power generation. That is, the battery performance is high.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, an electrode body used for a battery is not limited to a wound electrode body. Therefore, the present invention can be applied even to a battery having flat electrode bodies. Any secondary battery using stacked electrode bodies stacked and stacked can be applied. The present invention can be applied not only to a cylindrical battery but also to a square battery.

  In addition, the positive electrode mixture layer PA and the negative electrode mixture layer NA are formed on both sides of the positive electrode core material PB and the negative electrode core material NB, respectively. However, the composite material layer may be formed on only one side. The present invention can also be applied to a case where two or more composite layers are formed on at least one of the positive electrode plate and the negative electrode plate.

(Third embodiment)
A third embodiment will be described. FIG. 10 is a cross-sectional view showing the structure of the positive electrode plate of the battery according to this embodiment. In this embodiment, a carbon coated foil obtained by coating an aluminum foil with a carbon layer is used as the positive electrode core material. This is to prevent the positive electrode paste from corroding the aluminum foil.

  As shown in FIG. 10, there are carbon coat layers PC on both surfaces of a positive electrode core material PB that is an aluminum foil, and positive electrode mixture layers PA are formed on the outside of the carbon coat layer PC. Therefore, as shown in FIG. 10, layers are formed in the order of positive electrode mixture layer PA, carbon coat layer PC, positive electrode core material PB, carbon coat layer PC, and positive electrode mixture layer PA from the upper side in the thickness direction. For the negative electrode, the negative electrode plate N shown in FIG. 5 is used. That is, the negative electrode plate N is not coated with a carbon layer.

  The battery according to this embodiment is different from the battery 100 according to the first embodiment in that a carbon coat layer PC is formed on the positive electrode core material PB. Therefore, a method for forming the carbon coat layer PC will be described.

  First, a paste that is applied to the positive electrode core material PB and becomes the carbon coat layer PC is prepared. The paste is prepared by kneading only 95 parts by weight of carbon black in a solution obtained by dissolving 5 parts by weight of PVDF in NMP.

  Subsequently, a paste containing carbon black is applied to one surface of the positive electrode core material PB and then dried. As a result, the carbon coat layer PC is formed on the positive electrode core material PB. Thereafter, the paste is applied to the other surface of the positive electrode core material PB and then dried. Thereby, the carbon coat foil in which the carbon coat layer PC is formed on both surfaces of the positive electrode core material PB is created. Then, this carbon coat foil is put into a 150 degreeC high temperature tank, and heat processing is performed for 1 hour.

  Thereafter, the positive electrode mixture layer PA is formed on the carbon coat layer PC, whereby the positive electrode plate shown in FIG. 10 is produced. Using this positive electrode plate, a battery is manufactured through the same manufacturing process as in the first embodiment.

  The carbon coated foil produced in this way varies in contact resistance from lot to lot. In order to clarify the cause of the variation, the present inventors performed differential scanning calorimetry (DSC) on a carbon coated foil having a high contact resistance and a carbon coated foil having a low contact resistance. FIG. 11 is a graph comparing the differential scanning calorimetry (DSC) measurement values of the carbon coated foil with high and low contact resistance. The horizontal axis is temperature. The vertical axis represents the DSC heat quantity. A thick solid line L indicates the measured value of the carbon coated foil having a high contact resistance. A thin solid line M indicates a measured value of the carbon coated foil having a low contact resistance.

  From FIG. 11, in the carbon coat foil having the higher contact resistance, the melting start temperature of PVDF is 149 ° C. In the carbon coated foil having the lower contact resistance, the melting start temperature of PVDF is 144 ° C. In the carbon coated foil having the higher contact resistance, the first melting peak temperature is 156 ° C. In the carbon coated foil having the lower contact resistance, the first melting peak temperature is 152 ° C.

  FIG. 12 is a graph showing the relationship between the heat treatment temperature and the endothermic start temperature of the carbon coated foil. The horizontal axis is the heat treatment temperature. The vertical axis represents the endothermic start temperature. Here, the heat treatment temperature is the temperature inside the high-temperature bath. The endothermic start temperature is a temperature corresponding to the melting start temperature of PVDF in FIG. As is apparent from FIG. 12, as the heat treatment temperature rises, the endothermic start temperature rises accordingly.

  From these, the following can be considered as causes of variations in contact resistance. If the heat treatment temperature of the carbon coated foil is high, the crystal diameter of PVDF is considered to increase. Therefore, it is understood that the conductive path is cut by PVDF having a large crystal diameter, and as a result, the contact resistance is increased. In other words, it can be understood that the variation in the heat treatment temperature leads to the variation in the contact resistance of the carbon coated foil.

  FIG. 13 is a graph plotting values actually measured by the inventors about the heat treatment temperature of the heat treatment applied to the carbon coated foil and the film resistance of the carbon coated foil. The horizontal axis is the heat treatment temperature of the heat treatment applied to the carbon coated foil. The vertical axis represents the film resistance of the carbon coated foil. From FIG. 13, it can be seen that when the heat treatment temperature exceeds 150 ° C., the value of the film resistance increases rapidly. Therefore, the heat treatment temperature is preferably 150 ° C. or lower. This is for reducing the contact resistance of the carbon coated foil.

  However, the heat treatment applied to the carbon coated foil is a treatment for increasing the crystallinity of the binder and reducing the swelling property. Therefore, it is not preferable that the heat treatment temperature is too low. Therefore, the heat treatment temperature is preferably in the range of 138 to 150 ° C.

  As described above in detail, the battery manufacturing method according to the present embodiment is a method using a positive electrode plate obtained by applying a positive electrode active material to a carbon coated foil and drying it. And after carbon coating, it heat-processes at the temperature of 150 degrees C or less. Therefore, the contact resistance of carbon coated foil is low.

  In addition, the battery according to the present embodiment uses a carbon-coated foil coated with carbon black and dried and heat-treated at a temperature of 150 ° C. or lower as a positive electrode. The contact resistance of such a carbon coated foil is low. Therefore, the battery performance of the battery of this embodiment is high.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, an electrode body used for a battery is not limited to a wound electrode body. Therefore, the present invention can be applied even to a battery having flat electrode bodies. Any secondary battery using stacked electrode bodies stacked and stacked can be applied. The present invention can be applied not only to a cylindrical battery but also to a square battery.

  In addition, the positive electrode mixture layer PA and the negative electrode mixture layer NA are formed on both sides of the positive electrode core material PB and the negative electrode core material NB, respectively. However, the composite material layer may be formed on only one side. Further, the present invention can also be applied when three or more composite layers are formed on at least one of the positive electrode plate and the negative electrode plate.

  Next, an experiment performed on the lithium ion secondary battery according to the first embodiment and the second embodiment will be described. In this experiment, when preparing the positive electrode paste, a lithium ion secondary battery was prepared using the positive electrode paste kneaded under various conditions. The battery performance was examined using several methods.

1. Measurement method Evaluation items are A) rate characteristics and B) cycle characteristics. Here, the rate characteristic indicates the magnitude of a change in battery voltage that occurs when the battery is continuously discharged at a predetermined current. The cycle characteristic indicates the magnitude of the change in battery capacity that occurs when the battery is repeatedly charged and discharged with a predetermined current. Further, C) the BET specific surface area of the conductive material, and D) the gloss of the conductive material coating film were also measured. Therefore, these measurement methods will be described below.

A) Rate characteristics A method for measuring rate characteristics will be described. A lithium ion secondary battery using a positive electrode plate coated and dried with a positive electrode paste prepared under different conditions was charged in a constant current mode of 0.2 C (100 mA), and then a constant voltage of 4.2 V was applied. Charging was performed in voltage mode. Next, discharge was performed at current densities of 0.2 C (100 mA) and 2 C (1000 mA), and capacity was confirmed at a discharge voltage of 3 V. The rate characteristics used here are 2C discharge capacity with respect to 0.2C discharge capacity. Table 1 shows the value of the rate characteristic in each example and comparative example.

B) Cycle characteristics A method for measuring cycle characteristics will be described. The cycle characteristics used here are values obtained by dividing the discharge capacity measured at the 500th cycle of repeated charge / discharge by the discharge capacity measured at the first cycle. Table 1 shows the values of the cycle characteristics in each example and comparative example.

C) BET specific surface area of conductive material A method for measuring the BET specific surface area of a conductive material will be described. First, the amount of mixed conductive material (prepared weight) was measured. Then, the paste for positive electrodes was created using the electrically conductive material. Next, the positive electrode paste was applied to the positive electrode core material and dried with hot air at 120 ° C. The BET specific surface area of the positive electrode plate thus prepared was measured using a specific surface area measuring device (trade name: Macsorb (manufactured by Mountaintech)).

D) Conductive material coating film glossiness A method for measuring the conductive material coating film glossiness will be described. First, a conductive material paint was prepared in which a conductive material was mixed in a solvent and dispersed. The conductive material paint was applied onto the aluminum foil using an applicator having a gap of 150 μm. Next, a conductive material coating film was prepared by drying in an oven at 80 ° C. for 20 minutes. The coating film was measured with a portable gloss meter (trade name: PG-1M (manufactured by Nippon Denshoku Industries Co., Ltd.)) under conditions of incident light of 60 ° and reflected light of 60 °. Calibration was performed using a standard glossy plate.

2. Sample preparation method Next, a sample preparation method will be described. The samples were prepared in common in Examples 1-4, Example 5, and Comparative Examples 1-4.

2-1) Example 1-4
In Example 1, first, acetylene black (BET specific surface area 70 m ² / g) was used as a conductive material, NMP was used as a solvent, and polyvinylidene fluoride (PVDF) was used as a binder. The mixing ratio is 100 parts by weight of acetylene black, 400 parts by weight of NMP, and 25 parts by weight of PVDF. These were mixed and stirred and dispersed to obtain a conductive material paint.

  The conductive material paint thus obtained was applied onto an aluminum foil and dried to obtain a conductive material coating film. And the glossiness was measured.

  Further, after adding 42 parts by weight of this conductive material paint to 100 parts by weight of lithium nickelate and stirring and mixing, 100 parts by weight of lithium nickelate was further added. Thus, a positive electrode paste was prepared.

Thereafter, the positive electrode paste was applied to both sides of the aluminum foil using a die coater. The coating amount per side was 70.0 g / m ² . The thickness of the aluminum foil was 15 μm. Thereafter, the coated paste was dried. Then, a roll press was applied to the dried product. Then, it cut | judged to the predetermined dimension and created the positive electrode plate.

  A negative electrode plate was prepared as follows. 100 parts by weight of graphite material as the negative electrode active material, 0.8 parts by weight of styrene methacrylic acid butadiene (SMB) as the binder, 0.7 parts by weight of carboxymethyl cellulose-sodium salt (CMC-Na), solvent As a negative electrode paste, water was stirred and mixed.

Thereafter, the negative electrode paste was applied to both sides of the copper foil using a die coater. The coating amount per side was 40.0 g / m ² . The thickness of the copper foil was 10 μm. Thereafter, the coated paste was dried. Then, a roll press was applied to the dried product. Then, it cut | judged to the predetermined dimension and created the negative electrode plate.

And the positive electrode plate and the negative electrode plate were laminated | stacked through the film-form separator of polyethylene, and it was set as the electrode body. The electrode body was inserted into an aluminum outer case. Thereafter, ethylene carbonate containing LiPF ₆ at a rate of 1 mol / L was injected into the outer case as a nonaqueous electrolyte. Then, the electrolyte injection port of the outer case was sealed, and the battery was sealed by laser welding.

  For Example 2-4, a positive electrode paste was prepared in the same manner as in Example 1 using acetylene black having the BET specific surface area shown in Table 1. The negative electrode plate is the same as in Example 1.

2-2) Example 5
As a conductive material, acetylene black (BET specific surface area 70 m ² / g) was mixed with 100 parts by weight, and 400 parts by weight of NMP was mixed as a solvent. Then, the conductive material was dispersed by stirring the dispersion solvent. As a result, a conductive material paint was obtained. The glossiness of this conductive material paint was measured.

  Then, 40 parts by weight of this conductive material paint and 2 parts by weight of PVDF as a binder were added to 100 parts by weight of lithium nickelate. Then, a positive electrode paste was prepared by stirring and mixing.

Thereafter, the positive electrode paste was applied to both sides of the aluminum foil using a die coater. The coating amount per side was 70.0 g / m ² . The thickness of the aluminum foil was 15 μm. Thereafter, the coated paste was dried. Then, a roll press was applied to the dried product. Then, it cut | judged to the predetermined dimension and created the positive electrode plate.

  The negative electrode plate was prepared in the same manner as in Example 1.

2-3) Comparative Example 1-4
The positive electrode plate was prepared using a conductive material having a BET specific surface area shown in Table 1. And in kneading, each material was mixed at once. These parts by weight are the same as in Example 1. The negative electrode plate was prepared in the same manner as in Example 1.

3. Experimental results The experimental results are shown in Table 1.

3-1) Example 1
In Example 1, acetylene black having a BET specific surface area of 70 m ² / g was used as a conductive material. The gloss of the conductive material coating film was 60. The rate characteristic was 98%. The cycle characteristic was 80%. Thus, sufficient values were obtained in the rate characteristics and cycle characteristics.

3-2) Example 2
In Example 2, acetylene black having a BET specific surface area of 1800 m ² / g was used as a conductive material. The gloss of the conductive material coating film was 60. The rate characteristic was 96%. The cycle characteristic was 89%. Thus, sufficient values were obtained in the rate characteristics and cycle characteristics.

3-3) Example 3
In Example 3, acetylene black having a BET specific surface area of 70 m ² / g was used as a conductive material. The glossiness of the conductive material coating film was 20. The rate characteristic was 97%. The cycle characteristic was 90%. Thus, sufficient values were obtained in the rate characteristics and cycle characteristics.

3-4) Example 4
In Example 4, acetylene black having a BET specific surface area of 70 m ² / g was used as a conductive material. The gloss of the conductive material coating film was 180. The rate characteristic was 98%. The cycle characteristic was 89%. Thus, sufficient values were obtained in the rate characteristics and cycle characteristics.

3-5) Example 5
In Example 5, acetylene black having a BET specific surface area of 70 m ² / g was used as a conductive material. The gloss of the conductive material coating film was 100. The rate characteristic was 99%. The cycle characteristic was 94%. Thus, sufficient values were obtained in the rate characteristics and cycle characteristics. Example 5 was the best value among all the examples in rate characteristics and cycle characteristics.

3-6) Comparative Example 1
In Comparative Example 1, acetylene black having a BET specific surface area of 5 m ² / g was used as a conductive material. Since a conductive material-only dispersion process was not performed, a conductive material coating film was not created. The rate characteristic was 70%. The cycle characteristic was 60%. Thus, sufficient values could not be obtained in rate characteristics and cycle characteristics. This is probably because the conductive material was not sufficiently dispersed in the solvent.

3-7) Comparative Example 2
In Comparative Example 2, acetylene black having a BET specific surface area of 220 m ² / g was used as a conductive material. Since a conductive material-only dispersion process was not performed, a conductive material coating film was not created. The rate characteristic was 71%. The cycle characteristic was 76%. Thus, sufficient values could not be obtained in rate characteristics and cycle characteristics. This is probably because the conductive material was not sufficiently dispersed in the solvent.

3-8) Comparative Example 3
In Comparative Example 3, acetylene black having a BET specific surface area of 70 m ² / g was used as a conductive material. Since a conductive material-only dispersion process was not performed, a conductive material coating film was not created. The rate characteristic was 69%. The cycle characteristic was 56%. Thus, sufficient values could not be obtained in rate characteristics and cycle characteristics. This is probably because the conductive material was not sufficiently dispersed in the solvent.

3-9) Comparative Example 4
In Comparative Example 4, acetylene black having a BET specific surface area of 70 m ² / g was used as a conductive material. Since a conductive material-only dispersion process was not performed, a conductive material coating film was not created. The rate characteristic was 68%. The cycle characteristic was 64%. Thus, sufficient values could not be obtained in rate characteristics and cycle characteristics. This is probably because the conductive material was not sufficiently dispersed in the solvent.

  As described above in detail, according to this experiment, the lithium ion secondary battery according to the first embodiment and the second embodiment was excellent in rate characteristics and cycle characteristics. This is considered to be because the conductive material is almost uniformly present in the positive electrode mixture layer because the positive electrode paste in which the conductive material is well dispersed is used.

DESCRIPTION OF SYMBOLS 100 ... Battery 101 ... Battery container 102 ... Cover 110 ... Positive electrode collector 120 ... Negative electrode collector 200 ... Winding electrode body 1000 ... Electrode manufacturing apparatus 1100 ... Unwinding part 1200 ... Coating part 1210 ... Coating liquid supply part 1220 ... Backup roller 1300 ... Drying furnace 1301 ... Hot air nozzle 1302 ... Roller 1400 ... Winding part 2000 ... Winding device 2001 ... Positive electrode plate supply part 2002 ... Negative electrode plate supply part 2003, 2004 ... Separator supply part 2005 ... Winding axis P ... Positive electrode plate PA ... Positive electrode mixture layer PB ... Positive electrode core material P1 ... Positive electrode coating portion P2 ... Positive electrode non-coating portion N ... Negative electrode plate NA ... Negative electrode mixture layer NB ... Negative electrode core material N1 ... Negative electrode coating portion N2 ... Negative electrode Non-coated part S, T ... Separator

Claims (3)

A positive electrode coating liquid kneading step of mixing at least a positive electrode active material, a conductive material, and a binder into a solvent and kneading to create a positive electrode coating liquid;
A positive electrode plate coating and drying step in which the positive electrode core material is coated with the positive electrode coating liquid and then dried to form a positive electrode plate;
In the method of manufacturing a lithium ion secondary battery, the electrode body creating step including stacking the positive electrode plate and the negative electrode plate with a separator interposed therebetween to form an electrode body,
The positive electrode coating liquid kneading step includes:
A binder solution preparation process in which a binder is mixed into a solvent to form a binder solution;
A conductive material dispersion step of mixing a conductive material and the binder solution in a solvent to disperse at least the conductive material into a conductive material binder dispersion solution;
A method for producing a lithium ion secondary battery, comprising: mixing a positive electrode active material into the conductive material binder dispersion solution and mixing the positive electrode active material into a positive electrode coating solution. In the manufacturing method of the lithium ion secondary battery of Claim 1,
The conductive material dispersing step includes
A primary dispersion step of mixing a conductive material in a solvent and dispersing the conductive material in the solvent to obtain a conductive material solution before mixing the conductive material and the binder solution in the solvent;
A method for producing a lithium ion secondary battery, comprising: a secondary dispersion step of mixing the conductive material solution and the binder material solution into a conductive material binder dispersion solution. At least a positive electrode active material, a conductive material, and a binder are mixed in a solvent and kneaded to create a positive electrode coating solution.
After coating the positive electrode coating liquid on the positive electrode core material, it is dried to obtain a positive electrode plate,
In a lithium ion secondary battery having an electrode body in which the positive electrode plate and the negative electrode plate are stacked with a separator interposed therebetween,
The positive electrode coating solution is:
Mix the binder with the solvent to make a binder solution,
Mix the conductive material and the binder solution in the solvent, and disperse at least the conductive material to obtain a conductive binder dispersion solution.
A lithium ion secondary battery produced by mixing and kneading a positive electrode active material in the conductive material binder dispersion solution.

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