JP2017204334A - Method for manufacturing electrode, nonaqueous electrolyte secondary battery, and power storage unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a method for manufacturing an electrode, which is low in electrode plate resistance and which enables the decrease in gas generation in a battery; a nonaqueous electrolyte secondary battery including the electrode; and a storage battery including the nonaqueous electrolyte secondary battery.SOLUTION: A method for manufacturing a positive electrode 1 positive electrode including an active material and a negative electrode 2 including a negative electrode active material comprises: a step a for mixing a binder, and the positive or negative electrode active material or a conductive assistant material in a dry manner to prepare an electrode mixture; a step b for dispersing the electrode mixture in a nonaqueous solvent to prepare an electrode mixture solution; a step c for adding, of the positive or negative electrode active material, and the conductive assistant material, the one which is not included in the electrode mixture to the electrode mixture solution to prepare a slurry, provided that the steps a, b and c are performed in turn. In the method for manufacturing the electrodes 1, 2, the slurry is less than 75 wt% in solid content concentration (SC).SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrode manufacturing method, a non-aqueous electrolyte secondary battery, and a power storage unit.

  Non-aqueous electrolyte secondary batteries used for applications such as portable devices, hybrid cars, electric cars, and household power storage systems have been studied for their production methods for the purpose of improving capacity and stability.

  For example, as an electrode manufacturing method, a method is used in which an electrode active material, a conductive additive, and a slurry in which a binder for binding them is dispersed in a solvent are applied onto a current collector to form an electrode. However, in this method, it is important to prepare an electrode with low electrode plate resistance by preparing a highly dispersed slurry in which materials are uniformly dispersed.

  Patent Document 1 discloses an electrode manufacturing method in which an electrode with reduced electrode plate resistance is obtained by adjusting a slurry containing an electrode active material, an ionic surfactant, and a conductive material.

JP 2006-302617 A

  However, in the technique of Patent Document 1, the inventors have found that the addition of a surfactant causes gas generation in the battery.

  The present invention has been made to solve the problem. An object of the present invention is to provide an electrode manufacturing method with low electrode plate resistance while reducing gas generation in the battery, a nonaqueous electrolyte secondary battery including the electrode, and a storage battery including the nonaqueous electrolyte secondary battery. It is in.

  The method for producing an electrode according to the present invention comprises a step a in which a binder, a positive electrode active material or a negative electrode active material, or a conductive additive is dry-mixed to prepare an electrode mixture, and the electrode mixture is used as a nonaqueous solvent. The step b of preparing the electrode mixture solution by dispersing, the step of adjusting the slurry by adding one of the positive electrode active material or the negative electrode active material, and the conductive additive not included in the electrode mixture to the electrode mixture solution c) are sequentially performed so that the solid content concentration (SC) of the slurry is less than 75 wt%.

  According to the electrode manufacturing method of the present invention, an electrode having a low electrode plate resistance, a nonaqueous electrolyte secondary battery including the electrode, and a storage battery including the nonaqueous electrolyte secondary battery are obtained.

It is sectional drawing of the nonaqueous electrolyte secondary battery concerning this invention.

  The nonaqueous electrolyte secondary battery according to the present invention will be described with reference to FIG. 1 which is an embodiment for easy understanding.

  FIG. 1 is a cross-sectional view of a non-aqueous electrolyte secondary battery. The nonaqueous electrolyte secondary battery 10 includes a laminate 5 composed of a positive electrode 1, a negative electrode 2, and a separator 3, a nonaqueous electrolyte solution 6, a terminal 7, and an enclosure 8.

<Positive electrode and negative electrode>
The electrodes (positive electrode 1 and negative electrode 2) have a function of inserting and removing metal ions, that is, an electrode reaction, and the nonaqueous electrolyte secondary battery is charged and discharged by the electrode reaction.

  The electrode includes an active material layer containing an active material and a current collector. In the positive electrode 1, the positive electrode active material layer 23 is formed on one surface or both surfaces of the positive electrode current collector 22, and in the negative electrode 2, the negative electrode active material layer 33 is formed on one surface or both surfaces of the current collector 32.

  The electrode may be in a form in which the positive electrode active material layer 23 is formed on one side of the current collector and the negative electrode active material layer 33 is formed on the other side, that is, a bipolar type (bipolar).

  The active material is a substance that contributes to the electrode reaction.

  As the positive electrode active material, lithium transition metal composite oxides such as lithium cobaltate, lithium nickelate, lithium manganate, or lithium iron olivine are preferably used, and lithium manganate is more preferable from the viewpoint of excellent stability. .

Lithium manganate includes Li _{1 + x} MyMn _2−xy O ₄ (0 ≦ x ≦ 0.2, 0 <y ≦ 0.6, M is an element belonging to Group 2-13 and belonging to the 3rd to 4th periods. Any spinel type lithium manganate represented by at least one selected from the group consisting of:

  The spinel type lithium manganate is preferably M, Al, Mg, Zn, Ni, Co, Fe, Ti, Cu, Zr, or Cr from the viewpoint of excellent stability, Al, Mg, Zn, Ni, Ti, Cr is more preferable, and Al, Mg, Zn, Ti, or Ni is more preferable from the viewpoint of more excellent stability.

Specifically, as spinel type lithium manganate,
_{Li 1 + x Al y Mn 2} -x-y O 4 (0 ≦ x ≦ 0.1,0 <y ≦ 0.1),
Li _{1 + x} Mg _y Mn _2-xy O ₄ (0 ≦ x ≦ 0.1, 0 <y ≦ 0.1),
Li _{1 + x} Zn _y Mn _2-xy O ₄ (0 ≦ x ≦ 0.1, 0 <y ≦ 0.1),
_{Li 1 + x Cr y Mn 2} -x-y O 4 (0 ≦ x ≦ 0.1,0 <y ≦ 0.1),
Li _{1 + x} Ni _y Mn _2-xy O ₄ (0 ≦ x ≦ 0.05, 0.45 ≦ y ≦ 0.5),
Li _{1 + x} Ni _yz Al _z Mn _2−xy O ₄ (0 ≦ x ≦ 0.05, 0.45 ≦ y ≦ 0.5, 0.005 ≦ z ≦ 0.03),
And it is preferably at least one selected from Li1 + xNiy-zTizMn2-x- yO 4 (0 ≦ x ≦ 0.05,0.45 ≦ y ≦ 0.5,0.005 ≦ z ≦ 0.03),
_{Li 1 + x Al y Mn 2} -x-y O 4 (0 ≦ x ≦ 0.1,0 <y ≦ 0.1),
Li _{1 + x} Mg _y Mn _2-xy O ₄ (0 ≦ x ≦ 0.1, 0 <y ≦ 0.1),
Li _{1 + x} Ni _y Mn _2-xy O ₄ (0 ≦ x ≦ 0.05, 0.45 ≦ y ≦ 0.5),
Or _{Li 1 + x Ni y-z} Ti z Mn 2-x-y O 4 (0 ≦ x ≦ 0.05,0.45 ≦ y ≦ 0.5,0.005 ≦ z ≦ 0.03) is more preferable.

  The positive electrode active material may further contain a layered rock salt type compound.

  Examples of the layered rock salt type compound include a cobalt compound not containing Li, a lithium transition metal composite oxide having a layered rock salt type structure, and the like.

As a cobalt compound not containing Li, cobalt oxide such as Co ₃ O ₄ or Co ₂ O ₃ , cobalt hydroxide such as CoO (OH), cobalt carbonate such as CoCO ₃ , cobalt chloride, cobalt sulfate, cobalt-containing An organic compound or cobalt fluoride is preferably used, and cobalt oxide, cobalt hydroxide, or cobalt carbonate is more preferable from the viewpoints of suppressing gas generation and increasing the effect of increasing the charge end voltage.

As the lithium transition metal composite oxide having a layered rock salt type structure, Li _a Ni _b Co _c Mn _d X _e O ₂ (where X is B, Mg, Al, Si, Ti, V, Cr, Fe, Cu) , Zn, Ga, Ge, Sr, Zr, Nb, Mo, In, Sn, at least one selected from the group consisting of 0 <a ≦ 1.2, 0 ≦ b, c, d, e ≦ 1, and b + c + d + e = 1) is preferable, and since the effect of reducing gas generation and increasing the charge end voltage is large, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , LiNi _0.5 Mn _0.5 O ₂ , LiMn _0.4 Ni _0.4 Co _0.2 O ₂ , LiMn _0.1 Ni _0.1 Co _0.8 O _{2, LiNi} 0.8 _{Co 0.16} Al _{0 04 O 2, LiNi 0.8 Co 0.15} Al 0.05 O 2, LiNiO 2, LiMnO 2, and one is more preferably selected from LiCoO _2, LiCoO ₂ is more preferred.

In addition, Li _a Ni _b Co _c Mn _d X _e O ₂ may be a so-called lithium rich system in which a is greater than 1.

  The ratio of the layered rock salt type compound in the positive electrode active material is preferably 1 wt% or more and 10 wt% or less.

  In particular, when the weight of the spinel type lithium manganate in the positive electrode active material is A and the weight of the layered rock salt type compound is B, it is preferable to include a range of 0.01 ≦ B / (A + B) ≦ 0.1. Within such a range, the effect of reducing the amount of gas generated is great, and the effect of increasing the charge end voltage is also great.

  The surface of the positive electrode active material may be covered with a carbon material, a metal oxide, a polymer, or the like in order to improve conductivity and stability.

As the negative electrode active material, a carbon material, silica (Si), SiO ₂ , tin (Sn), or a titanium-containing oxide is preferably used, and a titanium-containing oxide is more preferable because the material itself has high stability.

  As the titanium-containing oxide, lithium titanate or titanium dioxide is preferable because of its small irreversible capacity during the charge / discharge reaction.

Lithium titanate is preferably a spinel structure or a ramsdellite type, and the molecular formula is expressed as Li ₄ Ti ₅ O ₁₂ from the viewpoint that the expansion and contraction of the active material during the electrode reaction is small and the cycle characteristics of the battery are good. The spinel structure is more preferable.

  Examples of titanium dioxide include bronze (B) type titanium dioxide, anatase type titanium dioxide, or ramsdellite type titanium dioxide, etc., but since irreversible capacity is small and cycle stability of the battery is excellent, B type titanium dioxide is preferable.

  The titanium-containing oxide may further contain a trace amount of elements other than titanium such as niobium (Nb).

  One type of these negative electrode active materials may be used, or two or more types may be used in combination.

  Further, the surface of the negative electrode active material may be covered with a carbon material, a metal oxide, a polymer, or the like for the purpose of improving conductivity and stability.

  The current collectors 22 and 32 are members that collect current from the active material layers 23 and 33.

  The positive electrode current collector 22 is preferably aluminum or an alloy thereof. The aluminum is not particularly limited since it is stable in the positive electrode reaction atmosphere, but is preferably high-purity aluminum represented by JIS standards 1030, 1050, 1085, 1N90, 1N99 and the like.

  As the negative electrode current collector 32, copper, SUS, nickel, titanium, aluminum, and alloys thereof are preferably used.

  The thickness of the current collectors 22 and 32 is not particularly limited, but is preferably 10 μm or more and 100 μm or less.

  The ratio between the electric capacity of the positive electrode and the electric capacity of the negative electrode satisfies 1 ≦ D / C ≦ 1.2 (C indicates the electric capacity per 1 cm 2 of the positive electrode and D indicates the electric capacity per 1 cm 2 of the negative electrode). Is preferred. If D / C is 1 or more, the potential of the negative electrode does not become the lithium deposition potential during overcharging. On the other hand, if D / C is 1.2 or less, side reactions due to the negative electrode active material are reduced, and gas generation is suppressed.

  The area ratio between the positive electrode and the negative electrode is not particularly limited, but preferably satisfies 1 ≦ F / E ≦ 1.2 (E represents the area of the positive electrode and F represents the area of the negative electrode). If F / E is 1 or more, the area of the negative electrode is larger than that of the positive electrode, and lithium deposition at the negative electrode is suppressed. On the other hand, if F / E is 1.2 or less, since the ratio of the negative electrode area in contact with the positive electrode is increased, side reactions due to the negative electrode active material not involved in the battery reaction are less likely to occur, and as a result, gas generation is suppressed.

   The positive electrode and the negative electrode may further contain a conductive additive. The conductive aid is a conductive substance having a function of assisting the conductivity of the electrode.

  The conductive additive for the positive electrode is suitably used as long as it is a carbon material, and is at least selected from the group consisting of natural graphite, artificial graphite, vapor-grown carbon fiber, carbon nanotube, acetylene black, ketjen black, and furnace black. One is preferred, and acetylene black and / or ketjen black is more preferred.

  Although it does not specifically limit as a conductive support material of a negative electrode, A metal material or a carbon material is preferable.

As the metal material, copper or nickel is preferably used. Examples of the carbon material include natural graphite, artificial graphite, vapor grown carbon fiber, carbon nanotube, acetylene black, ketjen black, and furnace black.

Conductive additive included in the positive electrode or the negative electrode has a specific surface area of preferably 400 meters ² / g or less, 100 m ² / g or less is more preferable.

  One kind of these conductive aids may be used, or two or more kinds may be used.

  The amount of the conductive additive contained in the positive electrode or the negative electrode is preferably 1 part by weight or more and 30 parts by weight or less, more preferably 2 parts by weight or more and 15 parts by weight or less with respect to 100 parts by weight of the positive electrode active material. If it is such a range, the electroconductivity of a positive electrode will be ensured and the adhesiveness of a collector and an active material layer will become suitable.

  The positive electrode and the negative electrode may further contain a binder. The binder is a material that enhances the binding property between the materials in the active material layers 23 and 33 and the binding property between the active material layers 23 and 33 and the current collectors 22 and 32.

  The binder is not particularly limited, but for example, at least one selected from the group consisting of polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber, polyimide, and derivatives thereof may be used. it can.

  The amount of the binder contained in the positive electrode or the negative electrode is preferably 1 part by weight or more and 30 parts by weight or less, more preferably 2 parts by weight or more and 15 parts by weight or less with respect to 100 parts by weight of the positive electrode active material. If it is such a range, the adhesiveness of an active material layer and a collector will become suitable.

<Method for producing electrode>
As an electrode manufacturing method, an electrode slurry containing a positive electrode active material or a negative electrode active material, a conductive additive, a binder, and a non-aqueous solvent is prepared, and then the electrode slurry is supported on a current collector, A method of removing the aqueous solvent and forming an active material layer on the current collector is preferably used.

  The non-aqueous solvent has a function of dispersing a material such as an active material in the slurry.

  As the non-aqueous solvent, N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, methyl acetate, ethyl acetate, or tetrahydrofuran is preferably used.

<Method for producing slurry>
The manufacturing method of the slurry includes a step a in which a binder, a positive electrode active material or a negative electrode active material, or a conductive additive is dry-mixed to prepare an electrode mixture, and an electrode in which the electrode mixture is dispersed in a non-aqueous solvent Step b for preparing a mixture solution and Step c for adjusting the slurry by adding one of the positive electrode active material or the negative electrode active material and the conductive additive not included in the electrode mixture to the electrode mixture solution. Must be done sequentially.

  Dry mixing here refers to mixing of a solid material that does not contain a liquid. As the shape of the solid material, powder, granules, and the like are preferably used.

  As specific means of each step a to c, a revolving and revolving mixer, a ball mill, a planetary mixer, a jet mill, an ultrasonic disperser, or a thin film swirl mixer is preferably used, and a revolving and revolving mixer, A planetary mixer or a thin film swirl type mixer is more preferable, and a planetary mixer is more preferable from the viewpoint of excellent mass productivity.

  In the step a, the electrode active material and the binder may be dry mixed, or the conductive additive and the binder may be dry mixed.

  The solid content concentration of the slurry in step c is required to be less than 75 wt%, and is preferably 66 wt% or less, more preferably 30 wt% or more and 66 wt% or less, from the viewpoint of good electrode formation.

  The viscosity of the slurry in step c is preferably 500 cP or more and 8000 cP or less, more preferably 500 cP or more and 5000 cP or less from the viewpoint of good dispersibility of the active material, and 600 cP or more and 4000 cP or less from the point that the workability of the slurry is improved. More preferred is 1000 cP or more and 4000 cP or less.

  Further, after step c, the slurry may be diluted or concentrated for the purpose of adjusting the viscosity of the slurry. For the dilution, the same nonaqueous solvent as in step b may be used, or a solvent other than that may be used.

  From the point that excess air and moisture escape from the material and the dispersibility of the slurry becomes good, in steps a to c, at least step c is preferably performed under reduced pressure, and steps a to c are performed under reduced pressure. It is more preferable.

  The mixing conditions in the steps a to c are not particularly limited, but it is preferable if the temperature in the mixer is 0 to 40 ° C., the moisture concentration in the outside air is 2% or less, and the atmospheric pressure is indicated by gauge pressure −0.1 MPa or more and 0.0 MPa or less. It is.

<Separator>
The separator 3 is installed between the positive electrode 1 and the negative electrode 2 and has a function as a medium that mediates conduction of metal ions such as lithium ions therebetween.

  The separator is not particularly limited as long as it has an electrical insulation property and is impregnated with a non-aqueous electrolyte. Nylon, cellulose, polysulfone, polyethylene, polypropylene, polybutene, polyacrylonitrile, polyimide, polyamide, polyethylene terephthalate And a woven fabric, a nonwoven fabric or a microporous membrane in which two or more of them are combined are preferably used. Nylon, cellulose, polysulfone, polyethylene, polypropylene, polybutene, polyacrylonitrile, polyimide, polyamide, polyethylene terephthalate, and a nonwoven fabric obtained by combining two or more of them are preferable because of excellent stability of cycle characteristics.

  The separator may contain various plasticizers, antioxidants or flame retardants, and may be coated with a metal oxide or the like.

  The thickness of the separator is preferably 10 μm or more and 100 μm or less.

The area ratio between the separator and the negative electrode is not particularly limited, but 1 ≦ H / G ≦ 1.5 (
G represents the area of the negative electrode, and H represents the area of the separator. ) Is preferably satisfied.

  If H / G is 1 or more, contact between the positive electrode and the negative electrode is difficult to occur, and if it is 1.5 or less, the volume of the battery can be small. As a result, the output density of the battery increases.

<Laminated body>
The laminate is formed by winding or laminating a separator 3 disposed between the positive electrode 1 and the negative electrode 2.

<Non-aqueous electrolyte>
The nonaqueous electrolytic solution 6 has a function of mediating ion transfer between the positive electrode 1 and the negative electrode 2 and is an electrolytic solution in which a solute is dissolved in a nonaqueous solvent or an electrolytic solution in which a solute is dissolved in a nonaqueous solvent. A gel electrolyte in which a polymer is impregnated can be used.

  As the solute, lithium salts such as LiClO 4, LiBF 4, LiPF 6, LiAsF 6, LiCF 3 SO 3, LiBOB (Lithium Bis (Oxalato) Borate), and LiN (SO 2 CF 3) 2 are preferably used.

  The non-aqueous solvent preferably includes a cyclic aprotic solvent and / or a chain aprotic solvent. Examples of the cyclic aprotic solvent include cyclic carbonates, cyclic esters, cyclic sulfones and cyclic ethers. As the chain aprotic solvent, a solvent generally used as a solvent for nonaqueous electrolytes such as a chain carbonate, a chain carboxylic acid ester, a chain ether, and acetonitrile may be used. More specifically, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyl lactone, 1,2-dimethoxyethane, sulfolane, dioxolane, propion For example, methyl acid can be used. These solvents may be used alone or as a mixture of two or more. However, in view of the ease of dissolving the solute described below and the high conductivity of lithium ions, a mixture of two or more of these solvents. Is preferably used.

  When two or more types are mixed, the chain is exemplified by dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, and methyl propyl carbonate because of high stability at high temperatures and high lithium conductivity at low temperatures. Preferred is a mixture of one or more of the carbonates and one or more of the cyclic compounds exemplified by ethylene carbonate, propylene carbonate, butylene carbonate, and γ-butyllactone, dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate Particularly preferred is a mixture of one or more of the chain carbonates exemplified in 1) and one or more of the cyclic carbonates exemplified by ethylene carbonate, propylene carbonate, and butylene carbonate.

  The nonaqueous electrolytic solution 6 may further contain a film forming agent because it is suitable for imparting flame retardancy and suppressing side reactions between the nonaqueous electrolytic solution and the electrode.

  The solute concentration is suitably used as long as it is 0.5 mol / L or more and 2.0 mol / L or less.

  The amount of the nonaqueous electrolytic solution 6 is not particularly limited, but is preferably 0.1 mL or more per 1 Ah of battery capacity.

  The nonaqueous electrolytic solution 6 may be included in the positive electrode, the negative electrode, and the separator, or may be added to the laminate.

<Terminal>
The terminal 7 is a member that electrically connects the nonaqueous electrolyte secondary battery 10 and an external device.

  The terminal 7 is connected to the positive electrode forming member 15 and the positive electrode terminal 71, or the negative electrode forming member 16 and the negative electrode terminal 72.

  As the terminal 7, any conductor is preferably used, and aluminum is more preferable from the viewpoint of a good balance between performance and cost.

<Inclusion body>
The enclosure 8 has a function of protecting the laminate 5 and the non-aqueous electrolyte 6 from moisture and air outside the non-aqueous electrolyte secondary battery 10.

  As the enclosure 8, a composite film in which a thermoplastic resin layer for heat sealing is provided on a metal foil, a metal layer formed by vapor deposition or sputtering, or a square, oval, cylindrical, coin, button, or sheet shape. The metal can is suitably used, and a composite film is more preferable.

<Power storage device>
The nonaqueous electrolyte secondary battery of the present invention can be formed into an assembled battery by connecting a plurality of the nonaqueous electrolyte secondary batteries.

  The assembled battery of the present invention can be produced by appropriately connecting in series and / or in parallel depending on the desired size, capacity, and voltage.

  The assembled battery preferably has a control circuit for confirming the state of charge of the battery and improving safety.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited by these Examples, In the range which does not change the summary, it can change suitably.

<Example 1>
(Manufacture of spinel type lithium manganate)
A powder of Li _1.1 Al _0.1 Mn _1.8 O ₄ was produced by applying the method described in the literature (Electrochemical and Solid-State Letters, 9 (12), A557 (2006)).

(Manufacture of lithium cobaltate)
The cobalt hydroxide and lithium hydroxide monohydrate were weighed and mixed well so that the atomic ratio of cobalt atoms to lithium atoms was 1: 1.03. Then, lithium cobaltate was obtained by baking and grind | pulverizing the obtained powdery mixture for a predetermined time at the temperature of 850 degreeC in air | atmosphere atmosphere.

(Preparation of positive electrode)
First, 4 parts by weight of acetylene black (specific surface area 68 m ² / g) as a conductive additive and 4 parts by weight of PVdF as a binder were added to a planetary mixer, and the number of revolutions of a high-speed stirrer and a low-speed stirrer was set to 50 rpm. The mixture was mixed for a minute to obtain an electrode mixture.

  Next, 77 parts by weight of NMP was added, the rotation speed of the high-speed stirrer was set to 1000 rpm and the rotation speed of the low-speed stirrer was set to 90 rpm, and the mixture was mixed for 20 minutes to prepare an electrode mixture solution.

  Next, 92 parts by weight of a positive electrode active material obtained by mixing spinel type lithium manganate (LMO) and lithium cobaltate (LCO) at a weight ratio of 96: 4 was added, and the rotation speed of the high-speed stirrer was 400 rpm and the rotation speed of the low-speed stirrer Was set to 60 rpm and mixed for 10 minutes.

  Thereafter, the high speed stirrer was set to 2000 rpm and the low speed stirrer was set to 150 rpm, and mixed for 30 minutes to prepare a positive electrode slurry. At this time, the slurry was set to a solid content concentration (SC) of 56%.

  Thereafter, 15 parts by weight of NMP was added to the obtained positive electrode slurry, and a mixture obtained by dilution was used as slurry A for electrodes.

  Further, the electrode slurry B was prepared by mixing the electrode slurry A overnight with the rotation speed of the low-speed stirrer set to 10 rpm.

  Next, the electrode sheet in which the slurry A for electrodes was coated on both surfaces of an aluminum foil (15 μm) was vacuum-dried at 170 ° C. and punched into a size of 4 cm × 6 cm to obtain a positive electrode A 1.

  Moreover, after the electrode sheet which apply | coated the slurry B for electrodes on both surfaces of aluminum foil (15 micrometers) was vacuum-dried at 170 degreeC, the positive electrode B was obtained by punching out to a magnitude | size of 4 cm x 6 cm.

(Preparation of negative electrode)
First, Li ₄ Ti ₅ O ₁₂ powder was produced by the method described in the literature (Journal of Electrochemical Society, 142, 1431 (1995)).

Next, a negative electrode slurry containing 92 parts by weight of Li ₄ Ti ₅ O ₁₂ as a negative electrode active material, 3 parts by weight of acetylene black as a conductive additive, 5 parts by weight of PVdF as a binder, and 128 parts by weight of NMP as a solvent is prepared. Mixed.

  Next, the negative electrode slurry was applied to an aluminum foil (15 μm) and then vacuum-dried at 170 ° C., and the obtained electrode sheet was punched into a size of 4.3 cm × 6.3 cm to obtain a negative electrode.

(Preparation of non-aqueous electrolyte secondary battery)
13 positive electrodes A and 14 negative electrodes were superposed on each other so that the positive electrodes and the negative electrodes alternated with each other via polypropylene (22 μm), and these positive electrodes were combined into one positive electrode terminal. Were collectively welded to one negative electrode terminal to obtain an electrode group having terminals.

Next, the electrode group including this terminal is placed in a bag-like aluminum laminate sheet so that the terminal partially extends outward, and further, there is a non-aqueous electrolyte (ethylene carbonate as a non-aqueous solvent: 6 mL of dimethyl carbonate = 3: 7 (volume ratio), LiPF ₆ = 1 mol / L is used as a solute as a supporting salt), and the bag opening is sealed while reducing the pressure inside the bag, and further cured for 12 hours As a result, a non-aqueous electrolyte secondary battery was obtained.

<Example 2>
The process was the same as Example 1 except for the following steps. In preparation of the positive electrode, 92 parts by weight of the positive electrode active material of Example 1 and 4 parts by weight of PVdF were added to the planetary mixer, and the rotation speeds of the high-speed stirrer and the low-speed stirrer were set to 50 rpm and mixed for 10 minutes.

  Next, 53 parts by weight of NMP was added, the rotation speed of the high-speed stirrer was set to 1000 rpm, and the rotation speed of the low-speed stirrer was set to 60 rpm, and the mixture was mixed for 20 minutes to prepare an electrode mixture solution.

Next, 2 parts by weight of acetylene black and 2 parts by weight of ketjen black (specific surface area of 380 m ² / g) were added as conductive aids, and the speed of the high-speed stirrer was set to 400 rpm and the speed of the low-speed stirrer was set to 60 rpm. Mixed for minutes.

  Thereafter, 28 parts by weight of NMP was added, the rotation speed of the high-speed stirrer was set to 2000 rpm, and the rotation speed of the low-speed stirrer was set to 150 rpm, and mixed for 20 minutes to prepare a positive electrode slurry. At this time, SC of the slurry was 56%.

  Thereafter, 9 parts by weight of NMP was added to the obtained slurry, and a mixture obtained by dilution was designated as slurry A for electrodes. Further, the electrode slurry A was prepared by mixing the electrode slurry A overnight with the rotation speed of the low-speed stirrer set to 10 rpm.

  Next, the electrode sheet in which the slurry A for electrodes was coated on both sides of an aluminum foil (15 μm) was vacuum-dried at 170 ° C. and then punched out to a size of 4 cm × 6 cm to obtain a positive electrode A.

  Further, an electrode sheet obtained by coating the electrode slurry B on both surfaces of an aluminum foil (15 μm) was vacuum dried at 170 ° C. and then punched out to a size of 4 cm × 6 cm to obtain a positive electrode B.

<Comparative Example 1>
The process was the same as Example 1 except for the following steps. In producing the positive electrode, first, an electrode mixture containing 92 parts by weight of the positive electrode active material of Example 1 and 4 parts by weight of acetylene black was obtained.

  Furthermore, a solution was prepared by adding 46 parts by weight of NMP to 4 parts by weight of PVdF, dissolving 44 parts by weight of the solution and the electrode mixture, setting the rotation speed of the high-speed stirrer to 400 rpm and the rotation speed of the low-speed stirrer to 60 rpm, The electrode mixture solution was prepared by mixing for minutes.

  Thereafter, the high speed stirrer was set to 2000 rpm and the low speed stirrer was set to 150 rpm, and mixed for 40 minutes to prepare a positive electrode slurry. At this time, the SC of the slurry was 71 wt%.

  Then, 6 parts by weight of the solution was added to the slurry, and diluted with 33 parts by weight of NMP was used as slurry A for electrodes.

<Comparative example 2>
The process was the same as Example 1 except for the following steps. In preparing the positive electrode, first, a dispersant liquid containing 4 parts by weight of acetylene black, 4 parts by weight of PVdF, 58 parts by weight of NMP, and a trace amount of a surfactant was prepared. Next, 92 parts by weight of the positive electrode active material obtained by mixing LMO and LCO at a weight ratio of 96: 4 and 34 parts by weight of the dispersant liquid were added to the planetary mixer, and the rotational speed of the high-speed stirrer was 400 rpm and the low-speed stirrer. Was set to 60 rpm and mixed for 20 minutes to prepare an electrode mixture solution.

  Next, the high speed stirrer was set to 2000 rpm and the low speed stirrer was set to 150 rpm, and mixed for 40 minutes to prepare a positive electrode slurry. At this time, SC of the slurry was 76%.

  Then, a slurry obtained by diluting and mixing the slurry with 32 parts by weight of the dispersant liquid of Example 2 was designated as an electrode slurry A.

<Comparative Example 3>
The process was the same as Example 1 except for the following steps. In preparing the positive electrode, first, an electrode mixture containing 92 parts by weight of the positive electrode active material of Example 1, 3 parts by weight of acetylene black, and 3 parts by weight of PVdF was used.

  Furthermore, the electrode mixture, 17 parts by weight of the dispersant solution of Comparative Example 2, and 20 parts by weight of NMP were mixed for 10 minutes while setting the rotation speed of the high-speed stirrer to 400 rpm and the rotation speed of the low-speed stirrer to 60 rpm. A solution was prepared. Thereafter, the number of rotations of the high-speed stirrer was set to 2000 rpm and the number of rotations of the low-speed stirrer was set to 150 rpm, and the mixture was mixed for 15 minutes to prepare a positive electrode slurry. At this time, the SC of the slurry was 74%.

  Then, a slurry obtained by diluting and mixing the slurry with 42 parts by weight of NMP was used as an electrode slurry A.

<Comparative Example 4>
The process was the same as Example 1 except for the following steps. In preparation of the positive electrode, first, an electrode mixture containing 3 parts by weight of acetylene black and 3 parts by weight of PVdF was obtained. Furthermore, it was set as the electrode mixture solution containing 17 weight part of dispersing agent liquid of the comparative example 2, 18 weight part of NMP, and an electrode mixture. And the positive electrode slurry containing 92 weight part of positive electrode active materials of Example 1 and an electrode mixture solution was prepared. At this time, the slurry was SC75%.

  Then, 44 parts by weight of NMP was added to the positive electrode slurry, and a mixture obtained by dilution was used as the slurry A for electrodes.

<Comparative Example 5>
The process was the same as Example 1 except for the following steps. In preparing the positive electrode, first, 92 parts by weight of the positive electrode active material of Example 1, 2 parts by weight of acetylene black, and 4 parts by weight of PVdF were added to the planetary mixer, and the rotation speeds of the high-speed stirrer and the low-speed stirrer were set to 50 rpm. Mixed. Thereafter, 37 parts by weight of NMP was added, the rotation speed of the high-speed stirrer was set to 400 rpm, and the rotation speed of the low-speed stirrer was set to 60 rpm, and mixing was performed for 10 minutes. Thereafter, 2 parts by weight of ketjen black and 4 parts by weight of NMP were added, the rotational speed of the high-speed stirrer was set to 400 rpm, and the rotational speed of the low-speed stirrer was set to 60 rpm, and mixed for 10 minutes to prepare an electrode mixture solution. Thereafter, the number of rotations of the high-speed stirrer was set to 2000 rpm and the number of rotations of the low-speed stirrer was set to 150 rpm, and the mixture was mixed for 15 minutes to prepare a positive electrode slurry. At this time, the slurry was SC 71 wt%.

  Further, 38 parts by weight of NMP was added to the positive electrode slurry and diluted and mixed to obtain an electrode slurry A.

(Evaluation of electrodes and batteries)
Electrode plate resistance values were measured for the positive electrode A and the positive electrode B of Examples and Comparative Examples. Furthermore, a storage test, a charge / discharge cycle test, and a gas generation amount measurement were performed on the nonaqueous electrolyte secondary batteries in Example 1 and Comparative Example 2.

(Plate resistance measurement)
The electrode resistance was measured by sandwiching one end of the electrode with a four-terminal probe connected to a circuit element measuring instrument and passing a current through the electrode at a measurement frequency of 1 kH.

(Storage test)
For the non-aqueous electrolyte secondary batteries of Example 1 and Comparative Example 2, first, the non-aqueous electrolyte secondary battery was fully charged to a voltage of 2.7 V, and then the fully charged non-aqueous electrolyte 2 The secondary battery was stored in an oven at 60 ° C. for 1 week.

(Charge / discharge cycle test)
About the nonaqueous electrolyte secondary battery of Example 1 and Comparative Example 2, 500 mA constant current charge and 1000 mA constant current discharge were repeated 800 times in a 60 ° C. environment. The charge end voltage and discharge end voltage at this time were 2.7 V and 2.0 V, respectively.

  The ratio (percentage value) calculated with the discharge capacity after one cycle in the charge / discharge cycle test as the denominator and the discharge capacity after 800 cycles as the numerator was defined as the capacity retention rate. And the relative value when the capacity maintenance rate of the comparative example 2 was set to 1 was made into the relative capacity maintenance rate.

(Gas generation measurement)
The volume difference of the battery before and after the storage test and before and after the charge / discharge cycle test was measured by the Archimedes method to obtain the generation amount of the storage gas and the generation amount of the cycle gas. The relative values when the storage gas generation amount and the cycle gas generation amount of Comparative Example 2 were set to 1 were defined as the storage gas generation amount ratio and the cycle gas generation amount ratio, respectively.

(Evaluation criteria for electrode slurry)
When the electrode plate resistance of the positive electrode A was 1Ω or more, it was determined that the dispersibility of the slurry was poor (x).

  Moreover, when the difference of the electrode plate resistance of the positive electrode A and the positive electrode B was ± 1Ω or more, it was determined that the storage stability of the slurry was poor (x).

(Evaluation criteria for electrodes)
When the electrode plate resistances of the positive electrode A and the positive electrode B were 1Ω or more, it was determined that the electrode plate resistance was poor (x).

(Battery evaluation criteria)
When the storage gas generation amount ratio and the cycle gas generation amount ratio were 1 or more, the storage gas generation amount and the cycle gas generation amount were determined to be bad (x).

(Review of Table 1)
In Examples 1-2, an electrode having an electrode plate resistance of less than 1Ω and a lower electrode plate resistance than Comparative Examples 1-5 was obtained. Further, in Example 1, both the storage gas generation rate ratio and the cycle gas generation rate ratio are less than 1, and the relative capacity retention ratio is 1.03, which is a gas generation amount in the battery as compared with Comparative Example 2. Less cycle characteristics were obtained.

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 5 Laminate body 6 Nonaqueous electrolyte 7 Terminal 8 Enclosure 9 Terminal extension part 10 Nonaqueous electrolyte secondary battery 15 Positive electrode formation member 16 Negative electrode formation member 22 Positive electrode collector 23 Positive electrode active material layer 32 Negative electrode current collector 33 Negative electrode active material layer 71 Positive electrode terminal 72 Negative electrode terminal

Claims (12)

A method for producing a positive electrode including a positive electrode active material and a negative electrode including a negative electrode active material,
A step of preparing an electrode mixture by dry-mixing a binder, a positive electrode or negative electrode active material, or a conductive additive; and
A step b of preparing an electrode mixture solution by dispersing the electrode mixture in a non-aqueous solvent;
The step of adjusting the slurry by adding one of the positive electrode active material or the negative electrode active material and the conductive additive not included in the electrode mixture to the electrode mixture solution and sequentially adjusting the slurry, A method for producing an electrode, wherein the solid content concentration (SC) is less than 75 wt%. The method for producing an electrode according to claim 1, wherein the binder is a water-insoluble polymer. A method for producing an electrode, wherein the steps a to c are performed with a planetary mixer. The method for producing an electrode according to any one of claims 1 to 3, wherein in the step a, the conductive additive and the binder are dry-mixed. 5. The method for manufacturing an electrode according to claim 1, wherein in steps a to c, at least step c is performed under reduced pressure. 6. The electrode manufacturing method according to claim 1, wherein the slurry has an SC of 30 wt% or more and 66 wt% or less. The method for producing an electrode according to claim 1, wherein the positive electrode active material contains lithium manganate. The conductive additive is at least one selected from the group consisting of natural graphite, artificial graphite, vapor-grown carbon fiber, carbon nanotube, acetylene black, ketjen black, and furnace black. 8. The method for producing an electrode according to any one of 7 above. The method for producing an electrode according to any one of claims 1 to 8, wherein a specific surface area of the conductive additive is 400 m / g or less. A nonaqueous electrolyte secondary battery comprising a laminate comprising a positive electrode, a negative electrode, and a separator obtained by the method according to claim 1, a nonaqueous electrolyte, a terminal, and an encapsulant. The nonaqueous electrolyte secondary battery according to claim 10, further comprising a negative electrode obtained by the method according to claim 1. The electrical storage apparatus containing the nonaqueous electrolyte secondary battery of Claim 10 or 11.

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