JP2015138658A - Method for producing electrode for lithium secondary battery and granulated product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an electrode for a lithium secondary battery capable of manufacturing an electrode with a small number of solvents used and a small weight, and a granulated material.SOLUTION: A method for manufacturing an electrode for a lithium secondary battery comprises: a first step S110 of acquiring a first granulated material by mixing an electrode active material, a first thickening material, a solvent, and a binder; a second step S120 of acquiring a second granulated material by cracking the first granulated material while mixing it with a powdery second thickening material; a third step S130 of molding the second granulated material into a sheet-like compact; and a fourth step S140 of arranging the compact on a collector.

Description

  The present invention relates to a method for producing an electrode for a lithium secondary battery and a granulated product.

  In JP2013-77560A (Patent Document 1), a compacted layer forming step of compressing a composite particle powder obtained by a fluidized bed granulation method or a spray drying granulation method to form a compacted layer, and A method for producing an electrode for an electrochemical element having a transfer step of transferring a green compact layer to a sheet-like current collector is disclosed.

JP2013-77560A

  Conventionally, the most common method for producing an electrode for a lithium secondary battery is to paint an electrode material and apply the paint onto a current collector using a die coater or a comma coater (registered trademark) and then dry. Is the method. However, this manufacturing method requires a large amount of solvent for electrode coating, and requires a corresponding amount of heat and time for drying the solvent. At present, the consumption of a large amount of solvent accompanying this electrode production is one of the reasons for the decline in price competitiveness, and it is strongly desired to reduce the amount of solvent used.

  As a production method using a small amount of solvent, a method of producing an electrode by pressing a granulated product (composite particle powder) into a sheet is known. However, in this production method, it is difficult to obtain a sheet-like molded body having a small basis weight (mass per unit area), and cannot cope with various battery specifications. That is, since the granulated product has a large particle size, when a thin molded body (sheet) is obtained by pressure molding, a problem that through holes are formed in the finished molded body frequently occurs. When the molded body is pressure-bonded to the current collector, the current collector can be seen through the through-hole (this state is also referred to as “through” in this specification). When the transparent electrode is used in a lithium secondary battery, a problem such as lithium being deposited on the current collector along with charge / discharge is assumed.

  Therefore, in Patent Document 1, by using a fluidized bed granulation method or a spray-drying granulation method, the diameter of the granulated material is reduced, and the formability into a sheet with a small basis weight (hereinafter referred to as “thin weight”). ) Has been improved. However, the spray-drying granulation method or the like is not preferable from the viewpoint of price competitiveness because it forms a paint using a solvent and dries in the production process of the granulated product.

  The present invention has been made in view of the problems as described above, and the object thereof is to produce an electrode for a lithium secondary battery capable of producing an electrode with a small amount of solvent and a small basis weight. It is to provide a method and granulation.

  The present inventor obtained the idea that if a coarse granulated product obtained with a small amount of solvent is pulverized into a small-diameter granulated product, an electrode with a small basis weight may be produced. I tried to realize the idea. However, even if the coarse granulated material is crushed, it is re-agglomerated in the process up to molding, and as a result, it is difficult to produce an electrode with a small basis weight. However, the present inventor does not stop there, and continues to research, and by adding a powdery thickening material at the time of crushing, the powdery thickening material (dry powder) acts as a kind of dusting powder and is crushed. The present inventors have found that reaggregation of the granulated products can be prevented, and have completed the present invention. That is, the manufacturing method of the electrode for lithium secondary batteries of this invention is equipped with the following structures.

  (1) A method for producing an electrode for a lithium secondary battery includes: a first step of obtaining a first granulated product by mixing an electrode active material, a first thickener, a solvent, and a binder; A second step of obtaining the second granulated product by crushing the first granulated product while mixing the second thickener which is in the form of a sheet, and the second granulated product as a sheet A third step of forming a green molded body and a fourth step of arranging the molded body on a current collector.

  By employing a process for obtaining an electrode from a granulated product without using a paint as described above, the amount of solvent used can be greatly reduced as compared with the conventional case. And in the 2nd process, reaggregation after crushing is prevented by crushing the 1st granulated material (coarse granulated material), mixing the 2nd thickener which is powdery. A second granulated product having a reduced diameter can be obtained. Thereby, in the third step, a sheet-like molded body with a small basis weight can be obtained without causing problems such as see-through, and the molded body can be arranged on the current collector without difficulty in the fourth step. it can.

  In the third step, the second granulated product is compressed between the first roll (molding roll) and the second roll (transfer roll), thereby forming a sheet-like molding on the second roll. A step of obtaining a body is preferred.

  Moreover, it is preferable that a 4th process is a process of transcribe | transferring a molded object from a 2nd roll on a collector, and a molded object between a 2nd roll and a 3rd roll (crimp roll). More preferably, it is a step of pressure-bonding to a current collector.

  Thus, productivity can be improved by performing shaping | molding, transcription | transfer, and pressure bonding continuously.

  (2) The first step is a step of mixing the electrode active material, the first thickener and the solvent to obtain a primary aggregate, and mixing the primary aggregate and the binder to obtain the first A step of obtaining a granulated product.

Thus, in obtaining the first granulated product, preliminary granulation is performed to form a primary aggregate including the electrode active material and the first thickener, and then the binder is mixed. By making it into a container, it is possible to prevent the surface of the electrode active material from being covered with a binder which is a resistance component. Thereby, the movement of lithium ions (Li ⁺ ) is not hindered by the binder, and the IV resistance of the battery can be reduced.

  (3) When the viscosity of the 1% by weight solution of the first thickener is η1 and the viscosity of the 1% by weight solution of the second thickener is η2, it is preferable that η1 ≧ η2 is satisfied.

  Here, the viscosity of the 1% by mass solution of the thickener can be considered as an index of the solubility of the thickener in a solvent (typically water) and the solvent retention of the thickener. That is, it can be said that the lower the viscosity of a 1% by mass solution, the higher the solubility in the solvent, and the higher the viscosity, the higher the solvent retention.

  Therefore, satisfying η1 ≧ η2 indicates that the first thickener has a high solvent retention and the second thickener has high solubility. Thereby, when the 2nd granulated material is compressed in the 3rd process and the 4th process, and the solvent currently held by the 1st thickener exudes on the surface of the 2nd granulated material. The second thickener can be easily dissolved in the oozed solvent. Therefore, the second thickener acts as a kind of lubricant, and the fluidity of the second granulated product during molding is improved.

  The 1% by mass solution can also include a solution using a solvent other than water. On the other hand, 1 mass% aqueous solution mentioned later shall show the solution which dissolved the thickener in the water solvent.

  (4) η1 and η2 are viscosities of a 1% by mass aqueous solution, η1 is preferably 4.96 Pa · s or more, and η2 is preferably 4.96 Pa · s or less. Thereby, the fluidity | liquidity of a granulated material can be improved further.

  (5) It is preferable that the 1st thickener occupies 40 mass% or more and 90 mass% or less among the total amount of a 1st thickener and a 2nd thickener. This further improves the lightness.

  (6) The solid content concentration of the first granulated product is preferably 70% by mass or more. As a result, the amount of solvent used can be reduced.

  (7) A granulated product according to another aspect of the present invention is a granulated product used for an electrode for a lithium secondary battery, and is an agglomeration in which electrode active materials are bonded to each other by a first thickener. A nucleus is provided, and a second thickener in powder form is included on the surface of the agglomerated nucleus.

  A granulated product having such a structure is hardly re-aggregated and has excellent particle size stability. Accordingly, the diameter can be reduced and the sheet can be easily formed into a sheet with a small basis weight.

  (8) It is preferable that said granulated material further contains a binder on the surface of the aggregation nucleus. By adopting a configuration in which the binder is unevenly distributed on the surface of the granulated material in this way, the conductive path between the electrode active materials is not hindered by the binder when a sheet-like molded body is formed. Thus, the IV resistance of the battery can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method and granulated material of an electrode with few solvent usage-amounts and excellent in the thinness are provided.

It is a flowchart which shows the outline of the manufacturing method which concerns on one Embodiment of this invention. It is a flowchart which shows the outline of a 1st process. It is a mimetic diagram illustrating the primary aggregate concerning one embodiment of the present invention. It is a mimetic diagram illustrating the 1st granulation thing concerning one embodiment of the present invention. It is a schematic diagram illustrating the 2nd granulated material concerning one Embodiment of this invention. It is a schematic conceptual diagram which shows an example of a structure of the granulation apparatus used for a 1st process and a 2nd process. It is a schematic conceptual diagram which shows an example of a structure of the shaping | molding transfer apparatus used for a 3rd process and a 4th process. It is a schematic conceptual diagram illustrating a 3rd process and a 4th process. It is a typical section perspective view showing an example of the composition of the lithium secondary battery concerning one embodiment of the present invention. It is a flowchart which shows the outline of the manufacturing method of the lithium secondary battery concerning one Embodiment of this invention.

  Hereinafter, an embodiment of the present invention (hereinafter also referred to as “this embodiment”) will be described in detail, but the present embodiment is not limited thereto.

[First Embodiment: Method for Manufacturing Electrode for Lithium Secondary Battery]
FIG. 1 is a flowchart showing an outline of the manufacturing method of this embodiment. As shown in FIG. 1, the manufacturing method includes a first step S110, a second step S120, a third step S130, and a fourth step S140.

  Here, the first step can be restated as a granulation step, the second step as a crushing step, the third step as a forming (film forming) step, and the fourth step as a pressure bonding (transfer) step. Moreover, although this embodiment is applicable to any electrode of a positive electrode and a negative electrode, Preferably it is applied to manufacture of a negative electrode. Hereinafter, each step will be described.

First, materials and apparatuses used in the first step and the second step will be described.
(Electrode active material)
The electrode active material 4 only needs to function as an active material of a lithium secondary battery, and may be either a negative electrode active material or a positive electrode active material. As the negative electrode active material, for example, a carbon-based negative electrode active material such as natural graphite or artificial graphite, or an alloy-based negative electrode active material such as silicon or tin can be used. Examples of the positive electrode active material include LiCoO ₂ , LiNiO ₂ , LiNi _a Co _b O ₂ (a + b = 1, 0 <a <1, 0 <b <1), LiMnO ₂ , LiMn ₂ O ₄ , LiNi _a Co _b. Mn _c O ₂ (a + b + c = 1, 0 <a <1, 0 <b <1, 0 <c <1), LiFePO ₄ or the like can be used.

(Thickener)
As the first thickener 2 and the second thickener 8, a conventionally known thickener can be used. For example, sodium carboxymethylcellulose (CMC), methylcellulose (MC), sodium alginate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polyvinylpyrrolidone (PVD) and the like can be used. Among these, CMC is particularly preferable because of easy handling.

  In the present embodiment, CMC is classified into the following three types from the viewpoint of molecular weight and viscosity of a 1% by mass aqueous solution. That is, H-CMC (thickness of 1% by weight aqueous solution is 6.28 to 7.60 Pa · s), M-CMC (thickness of 1% by weight aqueous solution is 3.52 to 6.28 Pa · s), L -CMC (1 mass% aqueous solution viscosity is 2.07 to 3.52 Pa · s) is classified into three types. Since the solution viscosity of CMC depends on the average degree of polymerization of cellulose chains constituting the skeleton of the polymer structure, the viscosity of a 1% by mass aqueous solution can be used as an index of molecular weight. Further, it can be considered that the higher the viscosity of the 1% by mass aqueous solution is, the higher the water retention is, and the lower the viscosity of the 1% by mass aqueous solution is the higher the solubility in water (the faster the dissolution rate).

  The viscosity of a 1% by weight aqueous solution of CMC is measured by preparing a 1% by weight aqueous solution and using a commercially available B-type viscometer at 25 ° C. At this time, the rotor rotational speed of the viscometer is about 30 to 60 rpm.

(Binder)
Examples of the binder 6 include styrene butadiene rubber (SBR), nitrile butadiene rubber (NBR), acrylic rubber (ACR), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and tetrafluoroethylene-perfluoroalkyl. A vinyl ether copolymer (PFA) or the like can be used. For example, when water is used as the solvent, SBR and PTFE are preferable from the viewpoint of dispersibility.

(solvent)
The solvent of the present embodiment is not limited to water, and any solvent that can dissolve or disperse the thickener or the like can be used. Solvents other than water can also be used. For example, N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), acetone, diethyl ether, benzene, hexane, toluene and the like can be used.

(Granulating device)
A conventionally known powder mixing device can be used as the granulating device. For example, like the granulation apparatus 50 shown in FIG. 6, what is equipped with the container 52, the main stirring blade | wing 54 (agitator), and the crushing blade | wing 56 (chopper) is suitable. In the granulator 50, the particle diameter or structure of the granulated product can be controlled by adjusting the number of rotations of the main stirring blade 54 and the crushing blade 56, the stirring time, the material charging timing, and the like. An example of such an apparatus is “High Speed Mixer” manufactured by Earth Technica Co., Ltd.

<First step: Granulation step>
In 1st process S110, the electrode active material 4, the 1st thickener 2, the solvent (not shown), and the binder 6 are mixed, and the 1st granulated material 10 is obtained. Specifically, the first granulated product 10 can be obtained by weighing these materials, putting them into the containers 52 of the granulating apparatus 50, and stirring and mixing them under predetermined conditions.

  3 and 4, the first granulated product 10 is a secondary aggregate, and includes a plurality of primary aggregates 10a in which the electrode active materials 4 are bonded to each other by the first thickener 2. It is out. Further, the first granulated product 10 includes a binder 6. Here, the binder 6 is preferably present on the surface of the primary aggregate 10a. This is because a conductive path between the electrode active materials 4 is secured, and an electrode having a low electrical resistance is obtained.

  As described above, the first granulated material 10 in which the binder 6 is present on the surface of the primary aggregate 10a is first subjected to preliminary granulation to obtain the primary aggregate 10a, and then the primary aggregate 10a and the binder. 6 and mixed.

  That is, in the first step S110, referring to FIG. 2, the electrode active material 4, the first thickener 2 and the solvent are mixed to obtain the primary aggregate 10a, and the primary aggregate 10a is combined. It is preferable to include step S112 of mixing the dressing 6 to obtain the first granulated product 10.

  In Step S111, from the viewpoint of enhancing the dispersibility of the electrode active material 4 and the first thickener 2, the electrode active material 4 and the first thickener 2 are mixed and then the solvent is gradually added. Is preferred. In step S112, the binder 6 may be in the form of powder, but is preferably dispersed in a solvent in advance, and is preferably dropped into the apparatus together with the solvent.

(First thickener)
The first thickener 2 may be in the form of a powder, or may be in a state dissolved or dispersed in a solvent. When the solvent is water, the viscosity η1 of the 1% by mass aqueous solution of the first thickener 2 is preferably 4.96 Pa · s or more. This is because the first thickener 2 having such an aqueous solution viscosity can retain a large amount of water and improve the fluidity of the granulated product. The viscosity η1 is more preferably 6.28 Pa · s or more, and particularly preferably 7.60 Pa · s or more. The upper limit of the viscosity η1 is not particularly limited, but is preferably 10.00 Pa · s or less from the viewpoint of dispersibility.

<Second step: crushing step>
In 2nd process S120, the 1st granulated material 10 is crushed and the 2nd granulated material 20 is obtained, mixing the 2nd thickener 8 which is a powder form. Specifically, the second thickening material 8 is charged into the container 52 of the granulating apparatus 50, and the rotational speed of the crushing blade 56 is made higher than the rotational speed in the first step S110. The 1st granulated material 10 can be crushed and the 2nd granulated material 20 can be obtained.

(Second thickener)
The second thickener 8 needs to be in powder form. When the second thickener 8 is in the form of powder (dry powder), the second thickener 8 adheres to the surface of the second granulated product 20 after pulverization, and the second thickener 8 Since this acts as a kind of dusting powder, reagglomeration of the second granulated product 20 can be prevented, and the second granulated product 20 can be reduced in diameter.

  It is preferable that the 2nd thickener 8 is a thing with high solubility to a solvent. Since the second thickener 8 attached to the surface of the second granulated product 20 has high solubility, the second thickener 8 is added to the solvent oozed from the second granulated product 20 during molding. This is because it dissolves and acts as a kind of lubricant to improve fluidity. According to the inventor's research, this action is obtained when the viscosity of the 1% by weight solution of the first thickener 2 is η1 and the viscosity of the 1% by weight solution of the second thickener 8 is η2. , Η1 ≧ η2 is easily achieved when the relationship is satisfied.

  Further, when the solvent is water, from the viewpoint of solubility in water, the viscosity η2 of the 1% by mass aqueous solution of the second thickener 8 is preferably 4.96 Pa · s or less, more preferably It is 3.52 Pa · s or less, and particularly preferably 2.07 Pa · s or less. The lower limit of the viscosity η2 is not particularly limited, but is preferably 1.00 Pa · s or more from the viewpoint of adhesiveness in the molded body 102.

(Molding transfer device)
Next, the molding / transfer apparatus 60 used in the third step S130 and the fourth step S140 will be described. A molding transfer device 60 shown in FIG. 7 includes a first roll Ra (molding roll), a second roll Rb (transfer roll), and a third roll Rc (crimping roll). The arrow in FIG. 7 has shown the rotation direction of the roll, and the conveyance direction of a member.

<Third step: molding step>
The second granulated product 20 obtained in the second step S120 is supplied between the first roll Ra and the second roll Rb. A load is applied to the first roll Ra in a direction from the first roll Ra to the second roll Rb. The magnitude of the load is, for example, about 0.5 to 2.0 tnf. The second granulated product 20 is compressed between the rolls between the first roll Ra and the second roll Rb to form a formed body 102. The basis weight of the molded body 102 is adjusted by a gap (gap) between the first roll Ra and the second roll Rb. The width of the gap can be adjusted by a spacer or shim.

<Fourth step: Crimping step>
The formed body 102 is conveyed on the second roll Rb in the direction of the arrow. The third roll Rc conveys the current collector 101 in the direction of the arrow. And the molded object 102 is crimped | bonded to the electrical power collector 101 between 2nd roll Rb and 3rd roll Rc. Thus, an electrode in which the molded body 102 is disposed on the current collector 101 is manufactured. Note that the molded body 102 may be dried at the time of pressure bonding or after pressure bonding.

  The current collector 101 is not particularly limited, and may be any material as long as it has conductivity. When the electrode active material 4 is a negative electrode active material, for example, a copper (Cu) foil can be used as the current collector 101. When the electrode active material 4 is a positive electrode active material, for example, an aluminum (Al) foil is used. The current collector 101 can be used.

(Mass ratio of the first thickener and the second thickener)
Here, considering the fluidity in the third step S130 and the fourth step S140, the first thickener 2 is based on the total amount of the first thickener 2 and the second thickener 8. It is preferable that it is 40 to 90 mass%.

  When the proportion of the first thickener 2 with respect to the total amount of the thickener is less than 40% by mass, the amount of the solvent retained in the first thickener decreases and the second thickener 8 In some cases, the amount of (dry powder) becomes excessive, the frictional resistance during compression between rolls increases, and the moldability decreases. On the other hand, when the ratio of the first thickener 2 to the total amount of the thickener exceeds 90% by mass, the granulated product is re-agglomerated due to the shortage of the second thickener 8 and the particle size is reduced. May increase and thinness may decrease. In addition, the ratio for which the 1st thickener 2 accounts with respect to the total amount of a thickener becomes like this. More preferably, it is 50 mass% or more, Most preferably, it is 60 mass% or more.

  As described above, by performing the first step S110 to the fourth step S140, it is possible to manufacture a lithium secondary battery electrode with a small basis weight while reducing the amount of solvent used for the coating process. it can.

[Second Embodiment: Granulated Product]
2nd Embodiment is the granulated material used for the electrode for lithium secondary batteries, and the said granulated material is manufactured through the above-mentioned 1st process S110 and 2nd process S120.

  With reference to FIG. 5, the granulated product 20 of the present embodiment includes an agglomerated nucleus 20 a in which the electrode active materials 4 are bonded to each other by the first thickener 2, and a powder is formed on the surface of the agglomerated nucleus 20 a. The 2nd thickener 8 which is a shape is included. Since the granulated product 20 is covered with the dry powder (second thickener 8), it is difficult to re-aggregate and the particle size stability is high. Further, the second thickener 8 is excellent in fluidity at the time of molding and transfer because it dissolves in the solvent exuded from the inside when the granulated product 20 is compressed and reduces the frictional resistance at the time of molding. .

  Furthermore, the granulated product 20 preferably includes the binder 6 on the surface of the aggregation nucleus 20a. Thereby, when shape | molded in a sheet form, while the granulated material 20 adheres firmly, IV resistance can be reduced since the conductive path of electrode active material 4 is ensured.

  The granulated product 20 may contain a solvent. In that case, the mass ratio of the components excluding the solvent of the granulated product 20, that is, the solid content concentration (hereinafter also referred to as “NV: concentration of Non-Volatile contents”) is preferably 70% by mass or more. The upper limit of NV is not particularly limited, but is preferably 80% by mass or less, more preferably 75% by mass or less, and particularly preferably 73% by mass or less.

  The proportion of the electrode active material 4 in the solid content of the granulated product 20 is, for example, about 90 to 99% by mass, and the total amount of the thickeners (the first thickener 2 and the second thickener 8). ) Is, for example, about 0.5 to 5% by mass, and the binder 6 is, for example, about 0.5 to 5% by mass. The granulated product 20 may contain other components as long as it contains the above components. Examples of other components include a dispersant contained in a binder dispersion. Further, for example, when the electrode active material 4 is a positive electrode active material, a conductive aid such as acetylene black (AB) can be exemplified.

[Third Embodiment: Lithium Secondary Battery]
3rd Embodiment is a lithium secondary battery provided with the electrode for lithium secondary batteries manufactured by 1st Embodiment. Hereinafter, although a cylindrical battery will be described as an example, the present embodiment may be a prismatic battery or a pouch battery.

  Referring to FIG. 9, a lithium secondary battery 1000 includes an electrode body 400 and a non-aqueous electrolyte (not shown) inside a cylindrical exterior body 500. The electrode body 400 includes a positive electrode 200, a negative electrode 100, and a separator 300. The positive electrode 200 and the negative electrode 100 are long belt-like sheet members. The electrode body 400 is formed by winding the separator 300 so that the positive electrode 200 and the negative electrode 100 face each other. The separator 300 is a microporous film made of, for example, polyethylene (PE) or polypropylene (PP).

  Here, at least one of the positive electrode 200 and the negative electrode 100 is an electrode for a lithium secondary battery manufactured according to the first embodiment. Therefore, the lithium secondary battery 1000 has a low IV resistance, and is suitable for applications in which high-rate characteristics are important, such as in-vehicle applications. Moreover, since the amount of solvent used at the time of electrode preparation is small, it can be manufactured at low cost.

Further, when the negative electrode 100 is manufactured according to the first embodiment, the single-sided weight of the molded body 102 in the negative electrode 100 is preferably 40 g / m ² or less, more preferably 35 g / m ² or less. Particularly preferably, it is 30 g / m ² or less. This is because a further improvement in the high rate characteristics can be expected due to the small basis weight of the electrode.

[Fourth Embodiment: Method for Manufacturing Lithium Secondary Battery]
4th Embodiment is a manufacturing method of a lithium secondary battery including the manufacturing method of the electrode for lithium secondary batteries which is 1st Embodiment.

  FIG. 10 is a flowchart showing an outline of a manufacturing method of the lithium secondary battery of the present embodiment. As shown in FIG. 10, the manufacturing method includes steps S100a and S100b, step S300, step S400, step S500, and step S600.

  Here, for at least one of step S100a and step S100b, the method for manufacturing an electrode for a lithium secondary battery described as the first embodiment (that is, step S100) is used. Note that either the positive electrode 200 or the negative electrode 100 may be manufactured by a conventional coating process.

  In step S300, the electrode body 400 is produced. Referring to FIG. 9, electrode body 400 is obtained by winding so that positive electrode 200 and negative electrode 100 face each other with separator 300 interposed therebetween. And the electrode body 400 is inserted in the exterior body 500 (process S400).

Next, a non-aqueous electrolyte is injected into the outer package 500 (step S500). Non-aqueous electrolytes include, for example, cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), γ-butyrolactone (GBL) and vinylene carbonate (VC), and dimethyl carbonate (DMC). For example, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , Li (CF ₃ SO ₂ ) ₂ N, LiCF ₃ it can be used to dissolve the Li salt of SO ₃ and the like.

  Then, the lithium secondary battery 1000 can be manufactured by sealing the exterior body 500 (process S600).

  Hereinafter, although an example is given and this embodiment is described in detail, this embodiment is not limited to these.

[Experiment 1: Examination of granulation to electrode production process]
In Experiment 1, a granulated product was obtained by changing various conditions for the purpose of achieving the same or better thinness and low IV resistance as those of the coating process, and an electrode was produced from the granulated product. And about what was able to produce an electrode, the battery using this electrode was further manufactured, and IV resistance was evaluated.

<Common items>
First, common items in the following examples and comparative examples will be described. Unless otherwise specified in the following description, these materials, conditions, manufacturing methods, and the like are used in the examples and comparative examples.

(Materials used)
[1] Electrode active material Carbon powder (having a median diameter of 10 μm measured by laser diffraction scattering method) was used as the electrode active material.

[2] Thickening material Three types of CMC (H-CMC, M-CMC and L-CMC) having different molecular weights and viscosities of 1% by mass aqueous solutions were used as follows.

H-CMC (variety “BSH12”, manufactured by Daiichi Kogyo Seiyaku Co., Ltd .: 1% by weight aqueous solution having a viscosity of 7.60 Pa · s)
M-CMC (variety “MAC500LC”, manufactured by Nippon Paper Industries Co., Ltd .: 1% by weight aqueous solution having a viscosity of 4.96 Pa · s)
L-CMC (variety “MAC200HC”, manufactured by Nippon Paper Industries Co., Ltd .: 1% by weight aqueous solution having a viscosity of 2.07 Pa · s).

[3] Binder The SBR (variety “C23”, manufactured by JSR Corporation) dispersed in an aqueous solvent (hereinafter referred to as “SBR aqueous dispersion”) was used as the binder. The SBR concentration in the SBR aqueous dispersion is 44.2% by mass.

[4] Solvent Water was used as the solvent.

[5] Current collector A 10 μm thick Cu foil (manufactured by Furukawa Machine Metal Co., Ltd.) was used as the current collector.

(Granulation step: first step and second step)
[1] Granulator A high speed mixer (manufactured by Earth Technica Co., Ltd.) was used for the granulator.

[2] Granulation method The mass of the solid content was 0.6 kg, and the breakdown was electrode active material: CMC: SBR = 100: 1: 1 (mass ratio). The solid content concentration (NV) of the granulated product was 71% by mass. Other details will be described later for each example.

[3] Evaluation method of average particle diameter (d50) of granulated material 100 g of granulated material is spread in a stainless steel bat so that the granulated materials do not overlap each other, and dried in a hot air drying oven at 80 ° C. for 60 minutes. To do. Then, the mass of the granulated product after drying was measured, classified with a sieve, and the particle size at a cumulative mass of 50% (that is, d50 based on mass) was measured.

(Molding step and pressure bonding step: third step and fourth step)
With reference to FIG. 7, a molding transfer device 60 having three rolls was used.

The second roll Rb was fixed, and a load of 1 tnf was applied to the first roll Ra in the direction from the first roll Ra to the second roll Rb. The basis weight of the molded body 102 was adjusted by changing the gap (gap) between the first roll Ra and the second roll Rb using a spacer. For example, when the basis weight is 40 ± 2 g / m ² , the gap between the rolls is adjusted in the range of 65 ± 15 μm. For the 40 g / m ² less than the weight per unit area (25~40g / m ^2), corresponding by further narrowing the gap.

(Battery manufacturing process)
A cylindrical lithium secondary battery (18650 size, rated capacity 0.5 Ah) was produced as follows.

[1] Positive Electrode The positive electrode 200 is composed of a positive electrode active material (LiCoO ₂ ), a conductive additive (AB), a binder (PVdF), and a solvent (NMP), and LiCoO ₂ : AB: PVdF = 90: 8: 2 (mass). The positive electrode mixture slurry obtained by kneading to have a ratio) was prepared on a long strip of Al foil by coating, drying and rolling.

[2] Separator A PE microporous film (thickness: 16 μm) having a long belt shape was used as the separator 300.

[3] Electrolytic Solution The electrolytic solution used was a Li salt dissolved in a mixed solvent (LiPF ₆ = 1.0 mol / L, EC: DMC: EMC = 3: 4: 3 (volume ratio)).

[4] Assembly Referring to FIG. 9, an electrode body 400 is obtained by winding the separator 300 so that the positive electrode 200 and the negative electrode 100 face each other, and the electrode body 400 is inserted into the cylindrical exterior body 500. . Further, an electrolytic solution was injected into the outer package 500, and the opening of the outer package 500 was sealed to obtain a lithium secondary battery 1000.

(Measurement of IV resistance)
The state of charge (SOC) of the lithium secondary battery 1000 is adjusted to 60%, and 0.4C, 0.8C, 1.2C, 1.6C, 2.0C, 2.4C in a thermostatic chamber at -5 ° C. At 2.8C, 3.2C, 3.6C, 4.0C, 4.4C and 4.8C, the battery was discharged for 10 seconds, and the current value (I) and battery voltage (V) were measured. . And IV characteristic graph was created and IV resistance was computed from the inclination of the straight line. The unit of current value “C” indicates a current value for discharging the rated capacity of the battery in one hour.

Hereinafter, it demonstrates individually focusing on the difference of each Example and a comparative example.
<Example 1>
(First step S110)
[1] Carbon powder (electrode active material 4) and H-CMC (first thickener 2) were put into a high speed mixer. At this time, the amount of H-CMC charged was 90% by mass with respect to the total amount of CMC in the second granulated product 20. Next, in a high speed mixer, the rotational speed of the agitator was set to 200 rpm and the rotational speed of the chopper was set to 1000 rpm, and powder mixing was performed for 30 seconds.

  [2] While maintaining the rotational speeds of the agitator and chopper, water (solvent) was gradually added from the inlet of the apparatus over 30 seconds.

  [3] The chopper rotation speed was increased to 2000 rpm, and mixing and granulation were further performed for 3 minutes and 30 seconds. Thereby, the primary aggregate 10a was obtained (step S111).

  [4] The SBR aqueous dispersion was charged from the charging port of the apparatus, the rotational speed of the agitator was set to 200 rpm, and the rotational speed of the chopper was set to 2000 rpm, and mixing was performed for 30 seconds (step S112).

(Second step S120)
[5] Further, L-CMC powder (second thickener 8) was charged from the charging port of the apparatus, and pulverization and granulation were performed for 30 seconds while maintaining the rotational speed of the agitator and chopper. . Thereby, the 2nd granulated material 20 was obtained. At this time, the input amount of L-CMC was set to 10 mass% with respect to the total CMC amount in the second granulated product 20.

  When d50 of the 2nd granulated material 20 was measured according to the above-mentioned method, d50 was 0.8 mm.

(Third Step S130 and Fourth Step S140)
The powder of the second granulated product 20 is molded into a sheet-like molded body 102 having a basis weight of 40 g / m ² using the molding transfer device 60 shown in FIG. 7 (third step S130), and then Thus, the molded body 102 was pressure-bonded to the current collector 101, and the molded body 102 was placed on the current collector 101 (fourth step S140). Furthermore, an electrode (negative electrode 100) for a lithium secondary battery was obtained by slitting the obtained integrated body of the molded body 102 and the current collector 101 into a predetermined width.

(Manufacture of batteries and measurement of IV resistance)
A cylindrical lithium secondary battery 1000 was obtained according to the method described above, and the IV resistance of the battery was measured. The results are shown in Table 1.

<Example 2>
The second granulated product 20 (d50 = 0.8 mm) is the same as in Example 1 except that both the first thickener 2 and the second thickener 8 are M-CMC. A battery was fabricated and IV resistance was measured. The results are shown in Table 1.

<Example 3>
The second granulated product 20 (d50 = 0) is the same as in Example 1 except that the first thickener 2 is L-CMC and the second thickener 8 is H-CMC. 8 mm). Molding and pressure bonding were performed in the same manner as in Example 1. However, a sheet-like molded product cannot be obtained on the second roll Rb, and the plate-shaped molded product falls between the first roll Ra and the second roll Rb, making it difficult to produce an electrode. It was. However, if the arrangement method is different from the method of continuously transferring and pressing the second roll Rb to the current collector 101 (for example, a method of once forming a sheet and then pressing the current collector separately), It is estimated that electrode fabrication was possible.

<Comparative Example 1>
As described below, in Comparative Example 1, the binder was introduced at the initial stage of the granulation process, and granulation was performed without using the second thickening material in powder form.

  In the following, the introduction of the binder at the initial stage of granulation or coating (in a state where NV is high with respect to the final product) as in Comparative Example 1 is referred to as “first-in”. The addition of the binder after adding the solvent to the mixture as described above is referred to as “post-insertion”.

  [1] Carbon powder, M-CMC, and SBR aqueous dispersion were charged into a high speed mixer. Next, in a high speed mixer, the rotational speed of the agitator was set to 200 rpm and the rotational speed of the chopper was set to 1000 rpm, and powder mixing was performed for 30 seconds.

  [2] While maintaining the rotational speeds of the agitator and chopper, water (solvent) was gradually added from the inlet of the apparatus over 30 seconds.

  [3] The chopper rotation speed was increased to 2000 rpm, and the mixture was further crushed and granulated for 4 minutes and 30 seconds to obtain a granulated product. It was 0.9 mm when d50 of this granulated material was measured according to the above-mentioned method.

  Thereafter, in the same manner as in Example 1, molding into a sheet and placement on a current collector were performed to obtain a negative electrode, a battery was produced, and IV resistance was measured. The results are shown in Table 1.

<Comparative Example 2>
As described below, in Comparative Example 2, a paint containing an electrode active material was prepared, and the paint was applied on a current collector to produce an electrode. In addition, when making the paint, the binder was added at the stage of kneading (first-in).

  [1] Carbon powder, M-CMC, and SBR aqueous dispersion were put into a commercially available planetary mixer, and water was added so that NV might be 75 mass%.

[2] The mixture was kneaded with a planetary mixer for 60 minutes.
[3] Viscosity was adjusted by repeating the addition of water and kneading for 10 minutes until NV was 50% by mass or less to obtain a paint.

[4] Using a comma coater, the paint was applied onto the current collector and dried so that the weight per unit area after drying was 40 g / m ² to obtain a negative electrode. And the battery was produced using this negative electrode and IV resistance was measured. The results are shown in Table 1.

<Comparative Example 3>
As described below, in Comparative Example 3, a coating material was prepared using the binder as a post-container when forming a coating material.

  [1] Carbon powder and M-CMC were put into a commercially available planetary mixer, and water was further added so that NV was 75% by mass.

[2] The mixture was kneaded with a planetary mixer for 60 minutes.
[3] Viscosity was adjusted by repeating the addition of water and kneading for 10 minutes until NV was 50% by mass or less. Then, at the time of the final addition of water, the SBR aqueous dispersion was added, and kneading was performed for 10 minutes to obtain a paint.

[4] Using a comma coater, the paint was applied onto the current collector and dried so that the weight per unit area after drying was 40 g / m ² to obtain a negative electrode. And the battery was produced using this negative electrode and IV resistance was measured. The results are shown in Table 1.

<Comparative Example 4>
As described below, in Comparative Example 4, granulation was performed by adding the entire amount of CMC in one time in the initial stage without adding CMC in two steps.

  [1] Carbon powder and H-CMC (total amount) were charged into a high speed mixer. Next, in a high speed mixer, the rotational speed of the agitator was set to 200 rpm and the rotational speed of the chopper was set to 1000 rpm, and powder mixing was performed for 30 seconds.

  [2] While maintaining the rotational speeds of the agitator and chopper, water (solvent) was gradually added from the inlet of the apparatus over 30 seconds.

  [3] The number of rotations of the chopper was increased to 2000 rpm, and crushing and granulation were further performed for 3 minutes and 30 seconds.

  [4] While maintaining the rotational speed of the agitator and chopper, the SBR aqueous dispersion was added and granulated for 1 minute to obtain a granulated product.

  It was 3.3 mm when d50 of this granulated material was measured according to the above-mentioned method. In the same manner as in Example 1, molding into a sheet and placement on a current collector were performed to obtain a negative electrode. When the obtained negative electrode was visually confirmed, a plurality of through-holes were generated in the molded body, and a large number of locations where the current collector could be seen through the molded body (see-through) were confirmed. Therefore, no battery evaluation was performed on this negative electrode.

<Comparative Example 5>
As described below, in Comparative Example 5, the coarse granulated product obtained in Comparative Example 4 was forcibly crushed to reduce the diameter, and an electrode was produced.

  The granulated product obtained in Comparative Example 4 was crushed and sized forcibly by sieving with a mesh opening of 2 mm using a quadrature mill (registered trademark) manufactured by POWREC Co., Ltd. A granulated product was obtained.

  It was 0.9 mm when d50 of this granulated material was measured by the above-mentioned method. However, when the shape of the granulated product was visually confirmed, it was not a spherical shape but a flat plate shape.

  Furthermore, when this granulated product was used to form a sheet and place it on a current collector in the same manner as in Example 1, initially, the fluidity was good, but the same operation was performed for about 10 minutes. When the continuation was continued, the granulated material formed the arch structure AS in the supply section, and a state in which the granulated product was not supplied between the rolls, a so-called bridge phenomenon occurred (see FIG. 8).

<Comparative Example 6>
As described below, in Comparative Example 6, granulation was performed with the amount of solvent decreased (that is, with higher NV) than in Comparative Example 4.

  [1] Carbon powder and H-CMC (total amount) were charged into a high speed mixer. Next, in a high speed mixer, the rotational speed of the agitator was set to 200 rpm and the rotational speed of the chopper was set to 1000 rpm, and powder mixing was performed for 30 seconds.

  [2] While maintaining the rotational speeds of the agitator and chopper, water was gradually added from the inlet of the apparatus over 30 seconds. At this time, the amount of water charged was reduced and the NV was adjusted to 73% by mass.

  [3] The number of rotations of the chopper was increased to 2000 rpm, and crushing and granulation were further performed for 3 minutes and 30 seconds.

  [4] While maintaining the rotational speed of the agitator and chopper, the SBR aqueous dispersion was added and granulated for 1 minute to obtain a granulated product.

  It was 2.7 mm when d50 of this granulated material was measured according to the above-mentioned method, and the result was not different from Comparative Example 4. Then, when the sheet was molded and placed on the current collector in the same manner as in Example 1, the molded body did not leave the second roll Rb and could not be transferred to the current collector ( Transfer failure).

<Comparative Example 7>
In Comparative Example 7, as described below, granulation was performed with the amount of thickener charged in half that of Comparative Example 4. That is, in Comparative Example 7, the breakdown of the solid content is electrode active material: CMC: SBR = 100: 0.5: 1 (mass ratio).

  [1] Carbon powder and H-CMC (total amount) were charged into a high speed mixer. Next, in a high speed mixer, the rotational speed of the agitator was set to 200 rpm and the rotational speed of the chopper was set to 1000 rpm, and powder mixing was performed for 30 seconds.

  [2] While maintaining the rotational speeds of the agitator and chopper, water was gradually added from the inlet of the apparatus over 30 seconds.

  [3] The number of rotations of the chopper was increased to 2000 rpm, and crushing and granulation were further performed for 3 minutes and 30 seconds.

  [4] While maintaining the rotational speed of the agitator and chopper, the SBR aqueous dispersion was added and granulated for 1 minute to obtain a granulated product.

  The d50 of this granulated product was measured according to the method described above and was 2.2 mm, and a granulated product having a small diameter was not obtained. Then, when the sheet was molded and placed on the current collector in the same manner as in Example 1, the molded body did not leave the second roll Rb and could not be transferred to the current collector ( Transfer failure).

<Comparative Example 8>
As described below, in Comparative Example 8, CMC having a molecular weight lower than that of Comparative Example 4 and a viscosity of a 1% by mass aqueous solution was used.

  [1] Carbon powder and L-CMC (total amount) were charged into a high speed mixer. Next, in a high speed mixer, the rotational speed of the agitator was set to 200 rpm and the rotational speed of the chopper was set to 1000 rpm, and powder mixing was performed for 30 seconds.

  [2] While maintaining the rotational speeds of the agitator and chopper, water was gradually added from the inlet of the apparatus over 30 seconds.

  [3] The number of rotations of the chopper was increased to 2000 rpm, and crushing and granulation were further performed for 3 minutes and 30 seconds.

  [4] While maintaining the rotational speed of the agitator and chopper, the SBR aqueous dispersion was added and granulated for 1 minute to obtain a granulated product.

  The d50 of this granulated product was measured according to the method described above, and it was 2.5 mm, and a small diameter granulated product was not obtained. Then, when the sheet was molded and placed on the current collector in the same manner as in Example 1, the molded body did not leave the second roll Rb and could not be transferred to the current collector ( Transfer failure).

<Comparative Example 9>
In Comparative Example 9, as described below, granulation was performed with the amount of the binder charged in half. That is, in Comparative Example 9, the breakdown of the solid content is electrode active material: CMC: SBR = 100: 1: 0.5 (mass ratio).

  [1] Carbon powder and H-CMC (total amount) were charged into a high speed mixer. Next, in a high speed mixer, the rotational speed of the agitator was set to 200 rpm and the rotational speed of the chopper was set to 1000 rpm, and powder mixing was performed for 30 seconds.

  [2] While maintaining the rotational speeds of the agitator and chopper, water was gradually added from the inlet of the apparatus over 30 seconds.

  [3] The number of rotations of the chopper was increased to 2000 rpm, and crushing and granulation were further performed for 3 minutes and 30 seconds.

  [4] While maintaining the rotational speed of the agitator and chopper, the SBR aqueous dispersion was added and granulated for 1 minute to obtain a granulated product.

  It was 1.5 mm when d50 of this granulated material was measured according to the above-mentioned method. Then, when the sheet was molded and placed on the current collector in the same manner as in Example 1, it was possible to place the sheet on the current collector. It was difficult to produce an electrode because it peeled off from the current collector.

<Results and discussion>
The above experimental results are summarized in Table 1.

(Binder input timing)
From the results of Comparative Examples 1 to 3 and Examples 1 and 2, it can be seen that when the SBR aqueous dispersion is added at the kneading stage, the IV resistance increases. This is presumably because the conductive path between the electrode active materials is obstructed by the binder when the binder is used first. On the other hand, when the binder is added later, after the primary aggregate (aggregated nucleus) in which the electrode active materials are bonded to each other is formed by the thickener, the binder is formed on the surface of the primary aggregate. Since it adheres, the conductive path between electrode active materials is not inhibited, and IV resistance can be reduced. Therefore, from the viewpoint of IV resistance, it is preferable to add the binder in the granulation process.

  That is, in the first step S110, the electrode active material, the first thickener, and the solvent are mixed to obtain a primary aggregate, the primary aggregate and the binder are mixed, and the first step S110 is performed. It is preferable to include step S112 for obtaining the granulated product.

(About d50 of granulated product)
In Comparative Example 5, the flowability of the granulated product was poor and continuous supply was difficult. However, the molded product after being pressure-bonded to the current collector had a part that was not transparent, and the film quality (quality of the molded product) was It was better than Comparative Example 4. Therefore, from the results of Comparative Example 4 and Comparative Example 5, it can be said that defects such as see-through can be improved by reducing the particle size (d50) of the granulated product.

  In Example 1, as compared with Comparative Example 4, d50 of the granulated product could be significantly reduced. When the granulated product obtained in Example 1 and Comparative Example 4 was observed, the granulated product that was secondary particles in Comparative Example 4 was primary particles in Example 1. From this, CMC is added in two portions, and the granulated product is crushed in a state where the powdered CMC is present on the surface of the granulated product. It is considered that pulverization and granulation can be performed while acting to prevent reaggregation of the granulated product.

(Mass ratio of solid content)
From the results of Comparative Examples 6 to 9, the granulated product can be slightly reduced in diameter by decreasing the solvent amount, the thickener amount, and the binder amount. Also, the diameter can be slightly reduced by reducing the molecular weight of CMC.

  However, when the amount of the solvent and the thickening material are reduced or the molecular weight of CMC is lowered, transfer defects occur. Further, when the amount of the binder is reduced, the flexibility of the molded body after drying is remarkably lowered, and the molded body cannot be accommodated in the bent portion of the conveyance path, and the molded body is peeled off and slipped.

(2-stage CMC introduction)
In Examples 1 to 3 in which CMC was added in two stages in the granulation step, d50 of the granulated product could be greatly reduced. As described above, this is considered to be due to the fact that the second CMC (second thickener) in powder form acts as a kind of dusting powder.

  In Example 3, the sheet after molding could not be stably supplied onto the roll. In Example 3, CMC (L-CMC) having a low molecular weight was used as the first thickener, and CMC (H-CMC) having a high molecular weight was used as the second thickener. Therefore, the water retention capacity of the first thickener is low, the amount of water that exudes from the granulated product during compression is reduced, and further, the dissolution rate of the second thickener is slow, so that undissolved residue is generated and flow It is thought that it is reducing the sex.

  Therefore, from these results, it can be said that the first thickener 2 is preferably H-CMC or M-CMC. That is, it can be said that the viscosity of the 1% by mass aqueous solution of the first thickener is preferably 4.96 Pa · s or more, more preferably 7.60 Pa · s or more.

  Since transfer was possible in Example 2, it can be said that the second thickener 8 is preferably M-CMC or L-CMC. That is, the viscosity of the 1% by mass aqueous solution of the second thickener is preferably 4.96 Pa · s or less, more preferably 2.07 Pa · s or less.

  Furthermore, from these results, when the viscosity of the 1% by weight solution of the first thickener is η1, and the viscosity of the 1% by weight solution of the second thickener is η2, the flow satisfies η1 ≧ η2. It can be said that it is preferable from the viewpoint of sex.

[Experiment 2: Examination of first thickener and second thickener]
In Experiment 2, on the basis of Examples 1 and 2 in which a good quality electrode was obtained in Experiment 1, the mass ratio of the first thickener (first insertion) and the second thickener (rear insertion) therefrom Was changed, and the basis weight per unit area (limit amount per unit area) at which defects such as see-through occurred was evaluated.

<Examples 4 to 7>
As shown in Tables 2 and 3, the second granulated product was the same as in Examples 1 and 2 except that the mass ratio of the first thickener and the second thickener was changed. 20 was obtained, and an electrode was produced using the second granulated product 20. As for an electrode having a weight per unit area of 40 g / m ² , defects such as transfer failure and see-through occur while narrowing the gap (gap) between the first roll Ra and the second roll Rb. The limit basis weight was measured. The results are shown in Table 2 and Table 3.

  In Table 2 and Table 3, mass ratio makes the total amount of a 1st thickener and a 2nd thickener 100 mass%.

<Results and discussion>
From Table 2, it can be seen that by changing the mass ratio of the second thickener from 0% by mass to 10% by mass, the granulated product is rapidly reduced in diameter. However, even if the mass ratio of the second thickener is increased to 50% by mass or more, the change in d50 is small and the effect is saturated. Furthermore, when the mass ratio of the second thickener was 70% by mass, a defect that the molded body could not be conveyed onto the second roll Rb, that is, a transfer failure occurred (Example 6).

  From Table 3, when both the first thickener and the second thickener are M-CMC, when the mass ratio of the second thickener is 50% by mass, Example 6 The same transfer failure as in Example 7 occurred.

  From these results, when the mass ratio of the powdery second thickener (additional) increases, the second increase in the amount of water exuded from the granulated product when the granulated product is compressed. It is considered that the viscous material could not be completely dissolved and the second thickening material remained undissolved, thereby reducing the fluidity during molding and transfer. This tendency is more conspicuous when the second thickener is M-CMC than when the second thickener is L-CMC.

For Examples 6 and 7, according to a method in which the target value of the basis weight is set to a value larger than 40 g / m ² , or after the molded body is once formed, it is separately placed on the current collector. It may have been made.

  Also, from Table 2, when the first thickener is H-CMC and the second thickener is L-CMC, the result of the most excellent thinness when the mass ratio is 90:10. (Example 1).

  Accordingly, the first thickener preferably occupies 40% by mass or more and 90% by mass or less, and occupies 50% by mass or more and 90% by mass or less of the total amount of the first thickener and the second thickener. It is more preferable.

  Furthermore, Example 1 was more excellent in lightness than Example 2 in which both the first thickener and the second thickener were M-CMC.

  Therefore, it is preferable that the molecular weight of the first thickener is different from the molecular weight of the second thickener, from the viewpoint of lightness, and the molecular weight of the first thickener is the molecular weight of the second thickener. More preferably equal to or greater than.

  That is, when the viscosity of the 1% by weight solution of the first thickener is η1 and the viscosity of the 1% by weight solution of the second thickener is η2, it can be said that η1 ≧ η2 is preferably satisfied.

  From the above experimental results, the first step S110 for mixing the electrode active material 4, the first thickening material 2, the solvent, and the binder 6 to obtain the first granulated product 10 is in powder form. The second step S120 for obtaining the second granulated product 20 by crushing the first granulated product 10 while mixing the second thickener 8 and the second granulated product 20 as a sheet According to the method for manufacturing an electrode for a lithium secondary battery, comprising: a third step S130 for forming the green molded body 102; and a fourth step S140 for disposing the molded body 102 on the current collector 101. It was confirmed that the amount of use can be reduced and an electrode with a small basis weight can be provided.

  Further, granulation comprising an agglomerated nucleus 20a in which the electrode active materials 4 are bonded to each other by the first thickener 2, and the surface of the agglomerated nucleus 20a includes the second thickener 8 in powder form It can be said that the diameter of the object 20 can be reduced and it has been confirmed that it is excellent in moldability to a molded body with a small basis weight.

  Although the present embodiment and examples have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  2 First thickener, 4 Electrode active material, 6 Binder, 8 Second thickener, 10 First granulated product, 10a Primary aggregate, 20 Second granulated product, 20a Aggregated nucleus , 50 Granulator, 52 Container, 54 Main stirring blade, 56 Crushing blade, 60 Mold transfer device, Ra first roll (mold roll), Rb second roll (transfer roll), Rc third roll ( Pressure bonding roll), AS arch structure, 100 negative electrode, 101 current collector, 102 molded body, 200 positive electrode, 300 separator, 400 electrode body, 500 exterior body, 1000 lithium secondary battery.

Claims (8)

A first step of obtaining a first granulated product by mixing an electrode active material, a first thickener, a solvent, and a binder;
A second step of obtaining the second granulated product by crushing the first granulated product while mixing the second thickener in powder form;
A third step of forming the second granulated product into a sheet-like molded body;
And a fourth step of disposing the molded body on a current collector. A method for producing an electrode for a lithium secondary battery.   In the first step, the electrode active material, the first thickener, and the solvent are mixed to obtain a primary aggregate, and the primary aggregate and the binder are mixed. The manufacturing method of the electrode for lithium secondary batteries of Claim 1 including the process of obtaining a 1st granulated material.   The η1 ≧ η2 is satisfied, where η1 is a viscosity of a 1% by weight solution of the first thickener and η2 is a viscosity of a 1% by weight solution of the second thickener. 2. A method for producing an electrode for a lithium secondary battery according to 2. The η1 and the η2 are viscosities of a 1% by mass aqueous solution,
The method for producing an electrode for a lithium secondary battery according to claim 3, wherein the η1 is 4.96 Pa · s or more and the η2 is 4.96 Pa · s or less.   5. The lithium secondary battery according to claim 4, wherein the first thickener occupies 40% by mass or more and 90% by mass or less of the total amount of the first thickener and the second thickener. Electrode manufacturing method.   The method for producing an electrode for a lithium secondary battery according to any one of claims 1 to 5, wherein a solid content concentration of the second granulated product is 70% by mass or more. A granulated product used for an electrode for a lithium secondary battery,
Comprising an agglomerated nucleus in which electrode active materials are bonded to each other by a first thickener;
A granulated product comprising a second thickener in powder form on the surface of the agglomerated nuclei.   The granulated product according to claim 7, further comprising a binder on the surface of the agglomerated nuclei.

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