WO2023145581A1 - 二次電池用正極及び二次電池 - Google Patents

二次電池用正極及び二次電池 Download PDF

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Publication number
WO2023145581A1
WO2023145581A1 PCT/JP2023/001407 JP2023001407W WO2023145581A1 WO 2023145581 A1 WO2023145581 A1 WO 2023145581A1 JP 2023001407 W JP2023001407 W JP 2023001407W WO 2023145581 A1 WO2023145581 A1 WO 2023145581A1
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Prior art keywords
positive electrode
region
electrode mixture
band
conductive material
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English (en)
French (fr)
Japanese (ja)
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朋宏 原田
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Panasonic Energy Co Ltd
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Panasonic Energy Co Ltd
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Priority to US18/832,221 priority Critical patent/US20250105276A1/en
Priority to JP2023576834A priority patent/JPWO2023145581A1/ja
Priority to CN202380018420.XA priority patent/CN118591901A/zh
Publication of WO2023145581A1 publication Critical patent/WO2023145581A1/ja
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present disclosure relates to positive electrodes for secondary batteries and secondary batteries.
  • Patent Documents 1 and 2 disclose a positive electrode current collector and a positive electrode mixture layer formed on the positive electrode current collector.
  • the layer includes a positive electrode active material and a first conductive material, and the first conductive material has a ratio of D band/G band of Raman spectroscopy obtained from the positive electrode mixture layer by Raman spectroscopy to 0.6. is greater than 10, and in the constituent material mapping image of the positive electrode mixture layer obtained using the Raman spectroscopy, the ratio of the area occupied by the first conductive material to the area occupied by the positive electrode active material is 1 0.5 or more and 5 or less is disclosed.
  • An object of the present disclosure is to provide a positive electrode for a secondary battery and a secondary battery that can suppress an increase in direct current resistance (DCR) when the battery is repeatedly charged and discharged.
  • DCR direct current resistance
  • a positive electrode for a secondary battery which is one aspect of the present disclosure, includes a positive electrode current collector and a positive electrode mixture layer provided on the positive electrode current collector and containing a positive electrode active material, wherein the positive electrode mixture layer is When the layer is divided into two equal parts in the thickness direction, the lower half on the positive electrode current collector side is the first region, and the upper half on the surface side of the positive electrode mixture layer is the second region, the first region and the second region are formed.
  • the regions include the same type of conductive material, and the D band/G band ratio (X) of the Raman spectroscopy spectrum obtained from the conductive material in the first region is It is characterized by being larger than the D band/G band ratio (Y) of the obtained Raman spectroscopic spectrum.
  • a secondary battery according to one aspect of the present disclosure includes the positive electrode for a secondary battery.
  • a positive electrode for a secondary battery and a secondary battery that can suppress an increase in direct current resistance (DCR) when the battery is repeatedly charged and discharged.
  • DCR direct current resistance
  • FIG. 1 is a schematic cross-sectional view of a secondary battery that is an example of an embodiment
  • FIG. 1 is a schematic cross-sectional view of a positive electrode that is an example of an embodiment
  • FIG. 1 is a schematic cross-sectional view of a secondary battery that is an example of an embodiment
  • FIG. 1 is a schematic cross-sectional view of a secondary battery that is an example of an embodiment.
  • the battery case 15 is composed of a bottomed cylindrical case body 16 and a sealing member 17 that closes the opening of the case body 16 .
  • the wound electrode body 14 another form of electrode body such as a stacked electrode body in which positive and negative electrodes are alternately stacked via a separator may be applied.
  • Examples of the battery case 15 include cylindrical, rectangular, coin-shaped, button-shaped, and other metal cases, and resin cases formed by laminating resin sheets (so-called laminate type).
  • the electrolyte may be an aqueous electrolyte, but is preferably a non-aqueous electrolyte containing a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.
  • non-aqueous solvents include esters, ethers, nitriles, amides, and mixed solvents of two or more thereof.
  • the non-aqueous solvent may contain a halogen-substituted product obtained by substituting at least part of the hydrogen atoms of these solvents with halogen atoms such as fluorine.
  • a lithium salt such as LiPF 6 is used as the electrolyte salt.
  • the electrolyte is not limited to a liquid electrolyte, and may be a solid electrolyte using a gel polymer or the like.
  • the case body 16 is, for example, a bottomed cylindrical metal container.
  • a gasket 28 is provided between the case body 16 and the sealing member 17 to ensure hermeticity inside the battery.
  • the case main body 16 has an overhanging portion 22 that supports the sealing member 17, for example, a portion of the side surface overhanging inward.
  • the protruding portion 22 is preferably annularly formed along the circumferential direction of the case body 16 and supports the sealing member 17 on the upper surface thereof.
  • the sealing body 17 has a structure in which a filter 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are layered in order from the electrode body 14 side.
  • Each member constituting the sealing member 17 has, for example, a disk shape or a ring shape, and each member except for the insulating member 25 is electrically connected to each other.
  • the lower valve body 24 and the upper valve body 26 are connected to each other at their central portions, and an insulating member 25 is interposed between their peripheral edge portions.
  • the lower valve body 24 deforms and breaks so as to push the upper valve body 26 upward toward the cap 27 side, breaking the lower valve body 24 and the upper valve body 26 .
  • the current path between is interrupted.
  • the upper valve body 26 is broken and the gas is discharged from the opening of the cap 27 .
  • the positive electrode lead 20 attached to the positive electrode 11 extends through the through hole of the insulating plate 18 toward the sealing member 17
  • the negative electrode lead 21 attached to the negative electrode 12 extends through the insulating plate 19 . It extends to the bottom side of the case body 16 through the outside.
  • the positive electrode lead 20 is connected to the lower surface of the filter 23, which is the bottom plate of the sealing member 17, by welding or the like, and the cap 27, which is the top plate of the sealing member 17 electrically connected to the filter 23, serves as a positive electrode terminal.
  • the negative lead 21 is connected to the inner surface of the bottom of the case body 16 by welding or the like, and the case body 16 serves as a negative terminal.
  • the positive electrode 11, the negative electrode 12, and the separator 13 are described in detail below.
  • FIG. 2 is a schematic cross-sectional view of a positive electrode that is an example of an embodiment.
  • the positive electrode 11 includes a positive electrode current collector 40 and a positive electrode mixture layer 42 provided on the positive electrode current collector.
  • a foil of a metal such as aluminum that is stable in the potential range of the positive electrode 11, a film in which the metal is arranged on the surface layer, or the like can be used.
  • the positive electrode mixture layer 42 contains a positive electrode active material and a conductive material.
  • the positive electrode mixture layer 42 preferably further contains a binder and the like.
  • a positive electrode mixture slurry containing a positive electrode active material, a binder, a conductive material, and the like is applied on the positive electrode current collector 40, dried to form a positive electrode mixture layer 42, and then rolled by a rolling roller or the like. , is produced by rolling the positive electrode mixture layer 42 .
  • the details of the method for producing the positive electrode mixture layer 42 will be described later.
  • the positive electrode mixture layer 42 shown in FIG. 2 is divided into two equal parts in the thickness direction, the lower half on the positive electrode current collector 40 side is defined as a first region 42a, and the upper half on the surface side of the positive electrode mixture layer 42 is defined as a second region. 42b.
  • the conductive material contained in the first region 42a and the second region 42b are of the same type.
  • the conductive material of the present embodiment is a carbon-based conductive material such as amorphous carbon (for example, carbon black, acetylene black, ketjen black, etc.), graphite, carbon nanotubes, and the like.
  • the D band/G band ratio (X) of the Raman spectrum obtained by Raman spectroscopy from the conductive material in the first region 42a is obtained by Raman spectroscopy from the conductive material in the second region 42b. Greater than the D-band/G-band ratio (Y) of the Raman spectroscopy spectrum.
  • the “D band” indicates a Raman band around 1360 cm ⁇ 1 derived from defects and amorphous carbon components.
  • the D band/G band ratio of the Raman spectroscopic spectrum of the conductive material is thought to depend on the distribution state of the conductive material within the region. Specifically, the more agglomerated conductive material is present in the region, the more the intensity of the D band increases or the intensity of the G band decreases in the Raman spectrum obtained from the conductive material in the region. As a result, the D band/G band ratio increases. Therefore, the conductive material in the first region 42a exists in a more aggregated state than the conductive material in the second region 42b. , the conductive path of the first region 42a is difficult to cut. As a result, a conductive path between the positive electrode current collector 40 and the positive electrode mixture layer 42 is also less likely to be cut, so it is thought that an increase in DC resistance is suppressed.
  • the D band/G band ratio (Y) of the Raman spectroscopic spectrum obtained from the conductive material in the second region 42b with respect to the D band/G band ratio (X) of the Raman spectroscopic spectrum obtained from the conductive material in the first region 42a (Y/X) is preferably in the range of 0.85 to 0.98 from the viewpoint of further suppressing an increase in DC resistance due to repeated charging and discharging of the battery. Due to the Y/X ratio as described above, even if the positive electrode mixture layer expands and contracts, the conductive path in the first region 42a is more difficult to be cut, and the DC resistance increases due to repeated charging and discharging of the battery. can be further suppressed.
  • the electrolytic solution easily permeates from the surface of the positive electrode mixture layer 42, and the direct current resistance decreases due to repeated charging and discharging of the battery. It becomes possible to further suppress the increase.
  • the positive electrode 11 is embedded in a resin, and a cross section of the positive electrode mixture layer is produced by cross-section polisher (CP) processing or the like. Then, the cross section of the positive electrode mixture layer is subjected to Raman spectroscopy mapping in a field of view that covers the entire range in the electrode plate width of 100 ⁇ m ⁇ the thickness direction of the electrode plate to obtain mapping data of a Raman chart.
  • Raman spectroscopy mapping in a field of view that covers the entire range in the electrode plate width of 100 ⁇ m ⁇ the thickness direction of the electrode plate to obtain mapping data of a Raman chart.
  • measurements are taken at points divided by intervals of 1 ⁇ m in length and 1 ⁇ m in width in the field of view of the above range.
  • significant spectral components are separated from the Raman chart for each point.
  • the positive electrode active material, the conductive material, and the like are determined from the peak position, intensity, and intensity ratio of each component spectrum thus separated.
  • the conductive material has sharp peaks near 1360 cm ⁇ 1 (D band) and near 1580 cm ⁇ 1 (G band) in the Raman chart.
  • D band 1360 cm ⁇ 1
  • G band 1580 cm ⁇ 1
  • the spectral intensities of the D band and G band in the area were used.
  • Examples of positive electrode active materials contained in the positive electrode mixture layer 42 include lithium composite oxides containing transition metal elements such as Co, Mn, and Ni.
  • Lithium composite oxides include, for example, Ni, Co, Mn, Al, Zr, B, Mg, Sc, Y, Ti, Fe, Cu, Zn, Cr, Pb, Sn, Na, K, Ba, Sr, Ca, It may contain W, Mo, Nb, Si, or the like.
  • the lithium composite oxide may be used singly or in combination of multiple kinds.
  • the lithium composite oxide represented by the above general formula in general, the direct current resistance tends to increase due to repeated charging and discharging of the battery.
  • the present embodiment has the effect of suppressing an increase in DC resistance due to repeated charging and discharging of the battery. It is possible to suppress an increase in DC resistance due to repeated charging and discharging.
  • Binders contained in the positive electrode mixture layer 42 include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide, acrylic resins, styrene-butadiene rubber (SBR ), polyolefins, cellulose derivatives such as carboxymethyl cellulose (CMC) or salts thereof, and polyethylene oxide (PEO).
  • fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide, acrylic resins, styrene-butadiene rubber (SBR ), polyolefins, cellulose derivatives such as carboxymethyl cellulose (CMC) or salts thereof, and polyethylene oxide (PEO).
  • PTFE polytetrafluoroethylene
  • PVdF polyvinylidene fluoride
  • PAN poly
  • the positive electrode mixture layer 42 shown in FIG. 2 is divided into 10 equal parts in the thickness direction, and the 10 equal parts are divided into A region, B region, C region, D region, E region, and F in order from the positive electrode current collector 40 side. area, G area, H area, I area, and J area.
  • each region of D region, E region and F region with respect to the highest content (V) of the binder content contained in each region of A region, B region and C region The ratio (W/V) of the highest content (W) of the binder contained in is preferably less than 1.3.
  • W/V ratio is less than 1.3
  • the content of the binder in the regions A to C closer to the positive electrode current collector 40 is higher than when the W/V ratio is 1.3 or more. Since the amount is large, the adhesive strength between the positive electrode current collector 40 and the positive electrode mixture layer 42 is increased.
  • the content of binder contained in each region means the ratio of the amount of binder contained in each region to the total amount of binder contained in all regions (that is, regions A to J). do.
  • Such a content is analyzed with an electron probe microanalyzer (EPMA) along the surface side of the positive electrode mixture layer 42 from the positive electrode current collector 40 side with respect to the cross section of the positive electrode mixture layer 42, and in each region , to measure the content of the elements constituting the binder. Then, the content of the binder is converted from the measured content of the element.
  • EPMA electron probe microanalyzer
  • Model EMPA-1600 manufactured by Shimadzu Corporation is used as an electron probe microanalyzer
  • a positive electrode active material, a binder, a conductive material, and the like are mixed together with a solvent to prepare a first positive electrode mixture slurry.
  • a positive electrode active material, a binder, a conductive material, a dispersant, and the like are mixed together with a solvent to prepare a second positive electrode mixture slurry.
  • the second positive electrode mixture slurry is applied to a predetermined thickness on the first positive electrode mixture slurry, By drying, the positive electrode mixture layer 42 is formed.
  • the viscosity of the first positive electrode mixture slurry applied on the positive electrode current collector 40 higher than the viscosity of the second positive electrode mixture slurry applied on the first positive electrode mixture slurry,
  • the D band/G band ratio (X) of the Raman spectrum obtained from the conductive material in the second region 42b can be made larger than the D band/G band ratio (Y) of the Raman spectrum obtained from the conductive material in the second region 42b. It becomes possible.
  • the viscosity of the slurry may be adjusted, for example, by adjusting the amount of solids and the amount of solvent in the slurry.
  • the second positive electrode mixture slurry is applied to the dried coating film. It may be applied in a predetermined thickness and dried. However, by sequentially drying the slurry, after applying the first positive electrode mixture slurry to a predetermined thickness on the positive electrode current collector 40, the second positive electrode mixture slurry is applied on the first positive electrode mixture slurry. It is easier to adjust W/V to less than 1.3 by simultaneously drying the slurry by coating with a predetermined thickness and drying.
  • the content of the positive electrode active material contained in the positive electrode mixture layer 42 is preferably, for example, 90% by mass or more with respect to the total mass of the positive electrode mixture layer 42 .
  • the content of the conductive material contained in the positive electrode mixture layer 42 is preferably 0.3 mass % or more with respect to the total mass of the positive electrode mixture layer 42 .
  • the content of the binder contained in the positive electrode mixture layer 42 is preferably 0.3 mass % or more with respect to the total mass of the positive electrode mixture layer 42 .
  • the negative electrode 12 has a negative electrode current collector and a negative electrode mixture layer provided on the negative electrode current collector.
  • the negative electrode current collector for example, a foil of a metal such as copper that is stable in the potential range of the negative electrode, a film having the metal on the surface layer, or the like is used.
  • the negative electrode mixture layer preferably contains a negative electrode active material and further contains a binder, a conductive material, and the like.
  • a negative electrode mixture slurry containing a negative electrode active material, a binder, etc. is prepared, this negative electrode mixture slurry is applied onto a negative electrode current collector, and dried to form a negative electrode mixture layer. It can be produced by rolling the negative electrode mixture layer.
  • the negative electrode active material is not particularly limited as long as it is a material capable of intercalating and deintercalating lithium ions.
  • Lithium alloys such as tin alloys, graphite, coke, carbon materials such as organic sintered bodies, metal oxides such as SnO 2 , SnO, TiO 2 and the like. These may be used singly or in combination of two or more.
  • the binding material and the conductive material include, for example, materials similar to those of the positive electrode 11 .
  • separator 13 for example, a porous sheet or the like having ion permeability and insulation is used. Specific examples of porous sheets include microporous thin films, woven fabrics, and non-woven fabrics. Suitable materials for the separator include olefin resins such as polyethylene and polypropylene, and cellulose.
  • the separator 13 may be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin resin.
  • a multilayer separator including a polyethylene layer and a polypropylene layer may be used, and a separator whose surface is coated with a material such as aramid resin or ceramic may be used.
  • Example 1 A lithium composite oxide represented by LiNi 0.80 Co 0.15 Al 0.05 O 2 , a conductive material paste, and polyvinylidene fluoride were mixed at a solid content mass ratio of 100:10:1 to form a mixture. Obtained.
  • the conductive material paste was prepared by mixing 10 parts by mass of Ketjenblack, 90 parts by mass of N-methyl-2-pyrrolidone, and 2 parts by mass of polyvinylpyrrolidone as a dispersing agent. Next, N-methyl-2-pyrrolidone was added so that the solid content was 74.2%, and then kneaded to obtain a positive electrode mixture with a solid content of 74.2% and a dispersant content of 0.2%.
  • a material slurry A was prepared.
  • a lithium composite oxide represented by LiNi 0.80 Co 0.15 Al 0.05 O 2 , a conductive material paste, and polyvinylidene fluoride were mixed at a solid content mass ratio of 100:10:1 to form a mixture. Obtained.
  • the conductive material paste was prepared by mixing 10 parts by mass of Ketjenblack, 90 parts by mass of N-methyl-2-pyrrolidone, and 2 parts by mass of polyvinylpyrrolidone as a dispersing agent. Next, N-methyl-2-pyrrolidone was added so that the solid content was 73.5%, and then kneaded to obtain a positive electrode mixture with a solid content of 73.5% and a dispersant content of 0.2%.
  • a material slurry B was prepared.
  • the positive electrode mixture slurry B was applied to both surfaces of a 15 ⁇ m thick aluminum foil, the positive electrode mixture slurry A was applied on the positive electrode mixture slurry B and then dried to form a coating film. After that, by rolling the coating film with a rolling roller, a positive electrode having positive electrode mixture layers formed on both sides of the positive electrode current collector was produced.
  • the coating thickness ratio of the positive electrode mixture slurry A and the positive electrode mixture slurry B was set to 50:50.
  • the lower half on the positive electrode current collector side is defined as the first region
  • the upper half on the surface side of the positive electrode mixture layer is defined as the second region.
  • the ratio (Y/X) of the D band/G band ratio (Y) of the Raman spectroscopic spectrum of the conductive material in the second region to the D band/G band ratio (X) of the Raman spectroscopic spectrum of the material is 0.96. there were.
  • the Raman spectroscopic measurement method is as described above.
  • the positive electrode mixture layer is divided into 10 equal parts in the thickness direction, and the 10 equal parts are divided into 10 equal parts in order from the positive electrode current collector side, A region, B region, C region, D region, E region, F region, G region, In the case of region H, region I, and region J, region D, region E, and region D, region E, and The ratio (W/V) of the highest content (W) of the binder contained in each region of the F region was 1.05.
  • the method for measuring the content of the binder in each region is as described above.
  • Graphite, CMC, and SBR were mixed at a mass ratio of 98:1:1, and the mixture was kneaded with water to prepare a negative electrode mixture slurry.
  • This negative electrode mixture slurry was applied to both sides of a copper foil having a thickness of 8 ⁇ m, the coating film was dried, and then rolled with rolling rollers to form a negative electrode mixture layer on both sides of the negative electrode current collector. was made.
  • EC ethylene carbonate
  • MEC methyl ethyl carbonate
  • Example 2 A lithium composite oxide represented by LiNi 0.85 Al 0.15 O 2 , conductive material paste, and polyvinylidene fluoride were mixed at a solid content mass ratio of 100:10:1 to obtain a mixture.
  • the conductive material paste was prepared by mixing 10 parts by mass of Ketjenblack, 90 parts by mass of N-methyl-2-pyrrolidone, and 2 parts by mass of polyvinylpyrrolidone as a dispersing agent. Next, N-methyl-2-pyrrolidone was added so that the solid content was 74.2%, and then kneaded to obtain a positive electrode mixture with a solid content of 74.2% and a dispersant content of 0.2%.
  • a material slurry C was prepared.
  • a lithium composite oxide represented by LiNi 0.85 Al 0.15 O 2 , conductive material paste, and polyvinylidene fluoride were mixed at a solid content mass ratio of 100:10:1 to obtain a mixture.
  • the conductive material paste was prepared by mixing 10 parts by mass of Ketjenblack, 90 parts by mass of N-methyl-2-pyrrolidone, and 1 part by mass of polyvinylpyrrolidone as a dispersant. Next, N-methyl-2-pyrrolidone was added so that the solid content was 75.0%, and then kneaded to obtain a positive electrode mixture with a solid content of 75.0% and a dispersant content of 0.1%.
  • a material slurry D was prepared.
  • the positive electrode mixture slurry C was applied onto the positive electrode mixture slurry D and then dried to form a coating film. After that, by rolling the coating film with a rolling roller, a positive electrode having positive electrode mixture layers formed on both sides of the positive electrode current collector was produced.
  • the coating thickness ratio of the positive electrode mixture slurry C and the positive electrode mixture slurry D was set to 50:50.
  • the Y/X ratio in the produced positive electrode was 0.88, and the W/V ratio was 1.03.
  • a secondary battery was produced in the same manner as in Example 1, except that this positive electrode was used.
  • a lithium composite oxide represented by LiNi 0.85 Al 0.15 O 2 , conductive material paste, and polyvinylidene fluoride were mixed at a solid content mass ratio of 100:10:1 to obtain a mixture.
  • the conductive material paste was prepared by mixing 10 parts by mass of Ketjenblack, 90 parts by mass of N-methyl-2-pyrrolidone, and 1.5 parts by mass of polyvinylpyrrolidone as a dispersant. Next, N-methyl-2-pyrrolidone was added so that the solid content was 75.0%, and then kneaded to obtain a positive electrode mixture with a solid content of 75.0% and a dispersant content of 0.15%.
  • a material slurry E was prepared.
  • the positive electrode mixture slurry C was applied onto the positive electrode mixture slurry E and then dried to form a coating film. After that, by rolling the coating film with a rolling roller, a positive electrode having positive electrode mixture layers formed on both sides of the positive electrode current collector was produced.
  • the coating thickness ratio of the positive electrode mixture slurry C and the positive electrode mixture slurry E was set to 50:50.
  • the Y/X ratio in the produced positive electrode was 0.99, and the W/V ratio was 1.1.
  • a secondary battery was produced in the same manner as in Example 1, except that this positive electrode was used.
  • Example 4> After applying and drying the positive electrode mixture slurry E on both sides of an aluminum foil having a thickness of 15 ⁇ m, the positive electrode mixture slurry C is applied and dried on the coating film of the obtained positive electrode mixture slurry E, and the positive electrode mixture slurry C is applied and dried. A coating film of slurry C was formed. After that, by rolling the coating film with a rolling roller, a positive electrode having positive electrode mixture layers formed on both sides of the positive electrode current collector was produced. The coating thickness ratio of the positive electrode mixture slurry C and the positive electrode mixture slurry E was set to 50:50.
  • the Y/X ratio in the produced positive electrode was 0.99, and the W/V ratio was 1.47.
  • a secondary battery was produced in the same manner as in Example 1, except that this positive electrode was used.
  • a lithium composite oxide represented by LiNi 0.80 Co 0.15 Al 0.05 O 2 , a conductive material paste, and polyvinylidene fluoride were mixed at a solid content mass ratio of 100:10:1 to form a mixture. Obtained.
  • the conductive material paste was prepared by mixing 10 parts by mass of Ketjenblack, 90 parts by mass of N-methyl-2-pyrrolidone, and 3 parts by mass of polyvinylpyrrolidone as a dispersing agent. Next, N-methyl-2-pyrrolidone was added so that the solid content was 75.0%, and then kneaded to obtain a positive electrode mixture with a solid content of 75.0% and a dispersant content of 0.3%.
  • a material slurry F was prepared.
  • the positive electrode mixture slurry F was applied to both sides of a 15 ⁇ m thick aluminum foil, the positive electrode mixture slurry A was applied on the positive electrode mixture slurry F and then dried to form a coating film. After that, by rolling the coating film with a rolling roller, a positive electrode having positive electrode mixture layers formed on both sides of the positive electrode current collector was produced.
  • the coating thickness ratio of the positive electrode mixture slurry A and the positive electrode mixture slurry F was set to 50:50.
  • the Y/X ratio in the produced positive electrode was 1.07, and the W/V ratio was 1.1.
  • a secondary battery was produced in the same manner as in Example 1, except that this positive electrode was used.
  • a lithium composite oxide represented by LiNi 0.85 Al 0.15 O 2 , conductive material paste, and polyvinylidene fluoride were mixed at a solid content mass ratio of 100:10:1 to obtain a mixture.
  • the conductive material paste was prepared by mixing 10 parts by mass of Ketjenblack, 90 parts by mass of N-methyl-2-pyrrolidone, and 1.8 parts by mass of polyvinylpyrrolidone as a dispersant. Next, N-methyl-2-pyrrolidone was added so that the solid content was 75.0%, and then kneaded to obtain a positive electrode mixture with a solid content of 75.0% and a dispersant content of 0.18%.
  • a material slurry G was prepared.
  • the positive electrode mixture slurry G was applied to both sides of an aluminum foil having a thickness of 15 ⁇ m
  • the positive electrode mixture slurry C was applied on the positive electrode mixture slurry G and then dried to form a coating film. After that, by rolling the coating film with a rolling roller, a positive electrode having positive electrode mixture layers formed on both sides of the positive electrode current collector was produced.
  • the coating thickness ratio of the positive electrode mixture slurry C and the positive electrode mixture slurry G was set to 50:50.
  • the Y/X ratio in the produced positive electrode was 1.04, and the W/V ratio was 1.11.
  • a secondary battery was produced in the same manner as in Example 1, except that this positive electrode was used.
  • a lithium composite oxide represented by LiNi 0.85 Al 0.15 O 2 , conductive material paste, and polyvinylidene fluoride were mixed at a solid content mass ratio of 100:10:1 to obtain a mixture.
  • the conductive material paste was prepared by mixing 10 parts by mass of Ketjenblack, 90 parts by mass of N-methyl-2-pyrrolidone, and 2 parts by mass of polyvinylpyrrolidone as a dispersing agent. Next, N-methyl-2-pyrrolidone was added so that the solid content was 73.5%, and then kneaded to obtain a positive electrode mixture with a solid content of 73.5% and a dispersant content of 0.2%.
  • a material slurry H was prepared.
  • the positive electrode mixture slurry H was applied to both sides of a 15 ⁇ m thick aluminum foil
  • the positive electrode mixture slurry C was applied on the positive electrode mixture slurry H and then dried to form a coating film. After that, by rolling the coating film with a rolling roller, a positive electrode having positive electrode mixture layers formed on both sides of the positive electrode current collector was produced.
  • the coating thickness ratio of the positive electrode mixture slurry C and the positive electrode mixture slurry H was set to 50:50.
  • the Y/X ratio in the produced positive electrode was 1.08, and the W/V ratio was 1.03.
  • a secondary battery was produced in the same manner as in Example 1, except that this positive electrode was used.
  • a lithium composite oxide represented by LiNi 0.85 Al 0.15 O 2 , conductive material paste, and polyvinylidene fluoride were mixed at a solid content mass ratio of 100:10:1 to obtain a mixture.
  • the conductive material paste was prepared by mixing 10 parts by mass of Ketjenblack, 90 parts by mass of N-methyl-2-pyrrolidone, and 1 part by mass of polyvinylpyrrolidone as a dispersant. Next, N-methyl-2-pyrrolidone was added so that the solid content was 73.5%, and then kneaded to obtain a positive electrode mixture with a solid content of 73.5% and a dispersant content of 0.1%.
  • a material slurry I was prepared.
  • the positive electrode mixture slurry C was applied on the positive electrode mixture slurry I and then dried to form a coating film. After that, by rolling the coating film with a rolling roller, a positive electrode having positive electrode mixture layers formed on both sides of the positive electrode current collector was produced.
  • the coating thickness ratio of the positive electrode mixture slurry C and the positive electrode mixture slurry I was set to 50:50.
  • the Y/X ratio in the produced positive electrode was 1.22, and the W/V ratio was 1.05.
  • a secondary battery was produced in the same manner as in Example 1, except that this positive electrode was used.
  • the secondary batteries of each example and each comparative example were subjected to constant voltage charging at a constant current of 0.5C until the voltage reached 4.2V, and then constant voltage charging until the voltage reached 0.05C. After that, the battery was discharged at a constant current of 0.5C until the battery voltage reached 2.5V. This charging/discharging was regarded as one cycle, and 100 cycles were performed. Then, in an environment of 25 ° C., the secondary batteries of each example and each comparative example were discharged at a constant current of 0.5 C until the voltage reached 3.0 V, and then the DC resistance was measured by the same method as described above. asked for This is defined as the DC resistance after charge/discharge cycles.
  • the DC resistance increase rate was obtained by applying the initial DC resistance and the DC resistance after the charging/discharging cycle to the following formula.
  • DC resistance increase rate (DC resistance after charge/discharge cycle/initial DC resistance) x 100
  • Table 1 shows the DC resistance increase rates of other examples and comparative examples relative to the resistance increase rate of Comparative Example 1 (100%).
  • Example 3 showed a lower DC resistance increase rate than Example 4. Therefore, the positive electrode mixture layer is divided into 10 equal parts in the thickness direction, and the 10 equal parts are divided into A region, B region, C region, D region, E region, F region, G region, in order from the positive electrode current collector side.

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2015135770A (ja) * 2014-01-17 2015-07-27 株式会社東芝 負極及び非水電解質電池
JP2019003946A (ja) * 2013-09-18 2019-01-10 株式会社東芝 正極
WO2019167613A1 (ja) * 2018-02-28 2019-09-06 パナソニックＩｐマネジメント株式会社 非水電解質二次電池
JP2021057142A (ja) * 2019-09-27 2021-04-08 マクセルホールディングス株式会社 全固体電池用正極および全固体電池

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2019003946A (ja) * 2013-09-18 2019-01-10 株式会社東芝 正極
JP2015135770A (ja) * 2014-01-17 2015-07-27 株式会社東芝 負極及び非水電解質電池
WO2019167613A1 (ja) * 2018-02-28 2019-09-06 パナソニックＩｐマネジメント株式会社 非水電解質二次電池
JP2021057142A (ja) * 2019-09-27 2021-04-08 マクセルホールディングス株式会社 全固体電池用正極および全固体電池

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