Electrode body for secondary battery

Abstract

The invention relates to an electrode body for a secondary battery. An electrode body having a current collector layer and an active material layer laminated on the current collector layer, the active material layer having a first layer on the current collector layer and a second layer on the first layer, a first binder contained in the first layer being configured from surface-contact-shaped particles, and a second binder contained in the second layer being configured from point-contact-shaped particles.

Description

Technical Field

[0001] This disclosure relates to electrode bodies for secondary batteries. Background Technology

[0002] To improve the production efficiency of electrodes for secondary batteries, a method is used to shorten the drying time in the drying process after coating the current collector layer with the composite slurry. However, during high-temperature drying, the binder (adhesive) contained in the composite slurry undergoes so-called binder migration, which involves the movement of the binder from the bonding surface to the surface. If binder migration occurs, the current collector becomes easily peeled off from the active material layer, becoming a major cause of reduced battery performance.

[0003] Various methods have been disclosed to suppress binder migration. Japanese Patent Application Publication No. 2015-146272 discloses a method for manufacturing a negative electrode for a non-aqueous electrolyte secondary battery. In this method, a lower layer forming slurry and an upper layer forming slurry are prepared. The lower layer forming slurry has a specific surface area S1 of 3 to 20 m² based on the BET method. 2 The high BET negative electrode active material and binder are mixed in a solvent. The slurry for upper layer formation is prepared by having a specific surface area S2 of 2 to 6 m² based on the BET method. 2 The low BET negative electrode active material and binder are mixed in a solvent to produce a negative electrode. S1 and S2 are determined such that the ratio of S2 to S1 (S2 / S1) is between 0.1 and 0.9. A negative electrode active material layer consisting of a lower layer and an upper layer is formed by coating the lower layer forming slurry onto the negative electrode current collector, coating the upper layer forming slurry onto the lower layer forming slurry, and simultaneously drying the lower layer forming slurry and the upper layer forming slurry at 100 to 150°C. The coating of the lower layer forming slurry and the upper layer forming slurry is performed such that the ratio of the thickness T2 of the lower layer to the overall thickness TA of the negative electrode active material layer (T2 / TA) is between 0.02 and 0.3. According to this disclosure, it is believed that even when drying is performed at high temperatures above 100°C, a negative electrode that is difficult to peel off or collapse from the negative electrode active material layer can be provided.

[0004] Furthermore, Japanese Patent Application Publication No. 2015-015156 discloses a method for manufacturing an electrode having two active material layers formed using a binder with different compositions. Japanese Patent Application Publication No. 2015-015156 discloses a method for manufacturing a battery including a first layer formation step and a second layer formation step on the first layer. In the first layer formation step, a first layer is formed on the surface of the current collector using a first paste comprising a first positive electrode active material, a hydrophilic binder, and a first solvent. In the second layer formation step, a second layer is formed using a second paste comprising a second positive electrode active material, a hydrophobic binder, and a second solvent. The first solvent and the second solvent are selected such that the first solvent has a greater affinity for water than the second solvent. According to this disclosure, by ensuring the lower layer is sufficiently adhered to the surface of the current collector, durability is improved, and in the event of an overcharged state, current flow between the lower layer and the upper layer is suppressed, thus establishing a battery manufacturing technology with high safety. Summary of the Invention

[0005] The following active material layer is commonly known: a two-layer active material layer with an increased binder dosage in the lower layer to address the problem of easy peeling between the current collector and the active material layer due to binder migration, and a reduced binder dosage in the upper layer to suppress the increase in ionic resistance caused by the increased binder dosage. However, in this case, the low binder dosage in the upper layer results in low flexibility.

[0006] Therefore, the purpose of this disclosure is to provide a novel electrode for secondary batteries that can suppress the decrease in adhesion between the active material layer and the current collector, ensure flexibility, and suppress the increase in ionic resistance of the active material layer.

[0007] The above objectives are achieved by means of the following methods.

[0008] Option 1

[0009] An electrode body has a current collector layer and an active material layer stacked on the current collector layer. The active material layer has a first layer on the current collector layer and a second layer on the first layer. The first layer contains a first binder composed of particles with a surface contact shape, and the second layer contains a second binder composed of particles with a point contact shape.

[0010] Option 2

[0011] According to the electrode body of Scheme 1, the peel strength between the current collector and the first layer is 0.06 N / cm or more.

[0012] Option 3

[0013] According to the electrode body of Scheme 1 or 2, the curvature of the second layer is less than 0.083.

[0014] Option 4

[0015] A secondary battery having an electrode body according to any one of embodiments 1 to 3.

[0016] Option 5

[0017] A method for manufacturing an electrode, the electrode having a current collector and an active material layer stacked on the current collector layer, the method comprising: stacking a first layer on the current collector; and stacking a second layer on the first layer, wherein a first binder contained in the first layer is composed of particles with a surface contact shape, and a second binder contained in the second layer is composed of particles with a point contact shape.

[0018] According to the electrode body disclosed herein, a novel electrode body for secondary batteries can be provided that can suppress the decrease in adhesion between the active material layer and the current collector, ensure flexibility, and suppress the increase in ionic resistance of the active material layer. Attached Figure Description

[0019] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and wherein:

[0020] Figure 1 This is a side cross-sectional view of one configuration of the electrode body of this disclosure;

[0021] Figure 2A A schematic diagram illustrating the bond between an active material layer and a current collector layer, where the adhesive consists of particles with surface contact shapes; and

[0022] Figure 2B This is a schematic diagram illustrating the bonding state between an active material layer and a current collector layer, where the adhesive consists of particles with point contact shapes. Detailed Implementation

[0023] Electrode

[0024] The electrode body disclosed herein has a current collector layer and an active material layer stacked on the current collector layer. The active material layer has a first layer on the current collector layer and a second layer on the first layer. A first binder contained in the first layer is composed of particles with a surface contact shape. A second binder contained in the second layer is composed of particles with a point contact shape.

[0025] The active material layer containing an adhesive (first adhesive) composed of particles with surface contact shapes exhibits excellent adhesion to the current collector layer. This is believed to be due to the fact that the first adhesive, composed of particles with surface contact shapes, provides a large contact area with the current collector layer. Furthermore, it is less prone to adhesive migration during high-temperature drying of the composite slurry.

[0026] An active material layer containing a binder (second binder) composed of point-contact shaped particles can maintain flexibility while exhibiting relatively low ionic resistance. This is believed to be because, without being bound by theory, the second binder, being composed of point-contact shaped particles, prevents the binder from hindering ion conduction pathways, even when a sufficient amount of binder is contained in the active material layer containing the second binder to maintain flexibility.

[0027] Specifically, for example, such as Figure 1 As shown, the electrode body 100 of this disclosure has a current collector layer 110 and an active material layer 120. The active material layer 120 is composed of a first layer 121 and a second layer 122.

[0028] In addition, Figure 2A In this case, the first layer 121, which contains the first adhesive 132 and the active substance 131, is bonded to the current collector layer 110. Because the first adhesive 132 is composed of particles with a surface contact shape, the contact area between the first adhesive 132 and the current collector layer 110 is large, making it less prone to adhesive migration during the high-temperature drying of the composite slurry. Therefore, the first layer 121 can have strong adhesion to the current collector layer 110.

[0029] On the other hand, Figure 2B In this case, the second layer 122 having the second adhesive 141 and the active substance 131 is bonded to the first layer 121. In the second layer 122 containing the second adhesive 141, in the case that a sufficient amount of adhesive is contained in order to maintain flexibility, and since the second adhesive 141 is composed of particles with a point contact shape, it is not easy for the adhesive to hinder the ion conduction pathway.

[0030] In this disclosure, "composite material" means a composition that directly constitutes the active material layer or is capable of constituting an active material layer by containing other components. Furthermore, regarding this disclosure, "composite material slurry" means a slurry that, in addition to the "composite material," also contains a dispersion medium, thereby enabling the formation of an active material layer through coating and drying.

[0031] The following describes the constituent elements of this disclosure.

[0032] The electrode body disclosed herein has a current collector layer and an active material layer stacked on the current collector layer.

[0033] <Active Material Layer>

[0034] The active material layer has a first layer on the current collector layer and a second layer on the first layer.

[0035] The peel strength between the current collector layer and the first layer can be above 0.06 N / cm, above 0.07 N / cm, or above 0.08 N / cm, or below 0.5 N / cm, below 0.4 N / cm, below 0.3 N / cm, or below 0.2 N / cm.

[0036] The peel strength between the current collector layer and the first layer is calculated according to JIS-K-6854-1. Specifically, the test material with the current collector layer laminated thereon is fixed to a rigid base member using double-sided tape or adhesive. Then, one end of the film is peeled off, and the end is fixed to a 90° peel tester. The film is peeled off while being stretched in a direction at 90° relative to the unpeeled portion of the test material. The tensile strength is measured using a load sensor or the like, and the peel strength is calculated accordingly.

[0037] The curvature of the second layer can be below 0.083, below 0.080, below 0.070, or below 0.050, or above 0, above 0.010, or below 0.020.

[0038] Bending degree is an indicator of the conductivity of ions in an active substance, calculated using the following formula. The smaller the bending degree value, the better the ionic conductivity and the lower the ionic resistance.

[0039] τ=Kε / K eff pos

[0040] τ: Curvature (-)

[0041] K: Electrolyte conductivity (S / cm)

[0042] ε: Porosity (-)

[0043] K eff pos Effective conductivity (S / cm)

[0044] The aforementioned effective conductivity can be calculated using the following formula.

[0045] K eff pos = L / (SRion)

[0046] K eff pos Effective conductivity (S / cm)

[0047] S: Electrode body area (cm²) 2 )

[0048] L: Electrode thickness (cm)

[0049] Rion: Electrode body resistance (Q)

[0050] The porosity (ε) mentioned above can be calculated using the following formula.

[0051] Porosity (ε) = 1 - [apparent density of the second layer (g / cm³)] 3 )] / [True density of the second layer (g / cm³) 3 )]

[0052] The apparent density of the second layer can be calculated using the volume obtained from the measured dimensions and the measured weight.

[0053] Regarding the resistance of the aforementioned electrode body, according to the AC impedance method, two electrode bodies with the same structure having only a second layer as an active material layer are prepared, and symmetrical battery cells are made with them facing each other. The impedance of the aforementioned electrode body individually is measured, thereby enabling the calculation of the electrode body resistance.

[0054] The flexibility of the second layer is preferably such that no cracks are visually observed in the active material layer when the electrode body is wound around a cylinder with a diameter of 25.0 mm. The diameter of the cylinder can be 24.5 mm, 24.0 mm, 23.5 mm, or less than 23.0 mm.

[0055] There is no particular limitation on the thickness of the active material layer; for example, it can be 100 μm or more, 200 μm or more, 300 μm or more, 350 μm or more, 370 μm or more, 390 μm or more, or 400 μm or more. The thickness of the active material layer can be, for example, less than 700 μm, less than 600 μm, less than 550 μm, less than 500 μm, less than 480 μm, less than 460 μm, or less than 450 μm.

[0056] From the viewpoint of adhesion to the current collector layer, it is preferable that the thickness of the first layer is 0.4 times, 0.5 times, 0.6 times, 0.8 times, or 1.0 times the thickness of the second layer. From the viewpoint of conductivity, it is preferable that the thickness of the first layer is 2.4 times or less, 2.3 times or less, 2.2 times or less, 2.0 times or less, or 1.8 times or less the thickness of the second layer.

[0057] In addition to active substances and binders, the active material layer may contain conductive additives, dispersants, and various other additives.

[0058] (Adhesive)

[0059] The first adhesive contained in the first layer consists of particles with a surface contact shape, and the second adhesive contained in the second layer consists of particles with a point contact shape.

[0060] Particles with surface contact shape are defined as particles in which, when viewed from above, the proportion (contact ratio) of the length of the particle relative to its outer periphery that is in contact with other particles such as active materials, current collectors, and binders is on average 50% or more.

[0061] As particles with surface contact shapes, styrene-butadiene copolymer (SBR), polyacrylic acid (PAA), etc., can be used.

[0062] Particles with point contact shape are defined as particles whose, when viewed from above, the proportion (contact ratio) of their outer periphery in contact with other particles such as active materials, current collectors, and binders is on average less than 50%.

[0063] As point-contact shaped particles, styrene-acrylate copolymer (SAR), polyvinylidene fluoride (PVDF), etc., can be used.

[0064] There is no particular limitation on the particle size of the point contact shape particles; for example, it can be 0.05 μm or more, 0.1 μm or more, 0.2 μm or more, 0.5 μm or more, or 1.0 μm or more. The particle size of the point contact shape particles can be 5.0 μm or less, 4.0 μm or less, 3.0 μm or less, or 2.0 μm or less.

[0065] In this disclosure, "particle size" refers to the average value of the equivalent diameter of the projected area circle obtained from scanning electron microscope (SEM) images or transmission electron microscope (TEM) images.

[0066] There are no particular limitations on the mass of the adhesive. For example, relative to 100 parts by mass of the first or second layer, it can be more than 0.1 parts by mass, more than 0.2 parts by mass, more than 0.5 parts by mass, more than 1.0 parts by mass, or more than 2.0 parts by mass. The mass of the adhesive can be less than 5.0 parts by mass, less than 4.5 parts by mass, less than 4.0 parts by mass, less than 3.5 parts by mass, or less than 3.0 parts by mass.

[0067] (Active substances)

[0068] The active material can be either a positive electrode active material or a negative electrode active material.

[0069] There is no particular limitation on the mass of the active substance. For example, relative to 100 parts by mass of the first or second layer, it can be 60 parts by mass or more, 70 parts by mass or more, 80 parts by mass or more, 90 parts by mass or more, 91 parts by mass or more, 92 parts by mass or more, 93 parts by mass or more, or 94 parts by mass or more. The mass of the active substance can be less than 100 parts by mass, less than 99 parts by mass, less than 98 parts by mass, less than 97 parts by mass, or less than 96 parts by mass.

[0070] There are no particular limitations on the material of the positive electrode active material, such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), and lithium nickel-cobalt-manganese oxide (NCM:LiCO3). 1 / 3 Ni 1 / 3 Mn 1 / 3 O2), Lithium nickel cobalt aluminum oxide (LiNi) 0.8 (CoAl) 0.2 O2), by Li 1+x Mn 2-x-y M y Li-Mn spinel and other types of stones with different elemental substitutions represented by O4 (where M is one or more metallic elements selected from Al, Mg, Co, Fe, Ni, and Zn).

[0071] There are no particular limitations on the positive electrode active material, and a coating layer may be present. The coating layer is a layer containing a substance that has conductive properties, low reactivity with the positive electrode active material and solid electrolyte, and maintains a non-flowing state even when in contact with the active material or solid electrolyte. Specific examples of materials constituting the coating layer, besides LiNbO3, include Li4Ti5O. 12 Examples include Li3PO4, but it is not limited to these.

[0072] The shape of the positive electrode active material is not particularly limited as long as it is the general shape of a positive electrode active material used in batteries. The positive electrode active material may be in particulate form, for example. There is no particular limitation on the particle size, which may be 5μm or more, 6μm or more, 8μm or more, 10μm or more, or 12μm or more, or less than 30μm, 25μm or less, 20μm or less, or less than 15μm.

[0073] There are no particular limitations on the material of the negative electrode active material; it can be metallic lithium or any material capable of adsorbing and releasing lithium ions or other metal ions. Examples of materials capable of adsorbing and releasing lithium ions or other metal ions include alloy-based negative electrode active materials, carbon materials, or lithium titanate (Li₄Ti₅O₂). 12 (etc.), but not limited to these.

[0074] There are no particular limitations on alloy-based anode active materials; examples include Si alloy-based anode active materials and Sn alloy-based anode active materials. Si alloy-based anode active materials include silicon, silicon oxides, silicon carbides, silicon nitrides, or their solid solutions. Furthermore, Si alloy-based anode active materials can contain metallic elements other than silicon, such as Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Sn, and Ti. Sn alloy-based anode active materials include tin, tin oxides, tin nitrides, or their solid solutions. Furthermore, Sn alloy-based anode active materials can contain metallic elements other than tin, such as Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Ti, and Si.

[0075] As a carbon material, there are no particular limitations; examples include hard carbon, soft carbon, and graphite.

[0076] There are no particular limitations on the shape of the negative electrode active material; any shape typical of negative electrode active materials used in batteries is acceptable. The negative electrode active material can be, for example, particulate. There are no particular limitations on the particle size; it can be 5μm or larger, 6μm or larger, 8μm or larger, 10μm or larger, or 12μm or larger, or less than 30μm, 25μm or smaller, 20μm or smaller, or less than 15μm.

[0077] (Dispersant)

[0078] There are no particular limitations on the dispersant, such as carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinylpyrrolidone (PVP), polyacrylate, polymethyl methacrylate, polyoxyethylene alkyl ether, polyalkylene polyamine, benzimidazole, etc.

[0079] There is no particular limitation on the mass of the dispersant. For example, relative to 100 parts by mass of the first or second layer, it can be 0.1 parts by mass or more, 0.3 parts by mass or more, 0.5 parts by mass or more, 1.0 parts by mass or more, or 2.0 parts by mass or more. The mass of the dispersant can be less than 5.0 parts by mass, less than 4.5 parts by mass, less than 4.0 parts by mass, less than 3.5 parts by mass, or less than 3.0 parts by mass.

[0080] (Conductive additive)

[0081] There are no particular limitations on the conductive additives. Examples of conductive additives include, but are not limited to, vapor-grown carbon fiber (VGCF), acetylene black (AB), Ketjen black (KB), carbon nanotubes (CNT), and carbon nanofibers (CNF). Conductive additives can be in particulate or fibrous form, and their size is not particularly limited. There are no particular limitations on the conductive additives; a single additive may be used, or two or more may be used in combination.

[0082] There is no particular limitation on the mass of the conductive additive. For example, relative to 100 parts by mass of the first or second layer, it can be 0.005 parts by mass or more, 0.01 parts by mass or more, 0.02 parts by mass or more, 0.03 parts by mass or more, or 0.05 parts by mass or more. The mass of the conductive additive can be less than 0.10 parts by mass, less than 0.09 parts by mass, less than 0.08 parts by mass, less than 0.07 parts by mass, or less than 0.06 parts by mass.

[0083] <Current Collector Layer>

[0084] There are no particular limitations on the material of the current collector layer that can be used in the positive electrode; materials commonly used as positive electrode current collectors in batteries can be appropriately used. Examples of materials for the positive electrode current collector layer include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel, but the application is not limited to these. Furthermore, the positive electrode current collector layer may have certain coatings on its surface for purposes such as adjusting resistance. Additionally, the positive electrode current collector layer may be a product of depositing or vapor-depositing the aforementioned metals onto a metal foil or substrate.

[0085] There are no particular limitations on the shape of the positive current collector layer; for example, it can be foil-shaped, plate-shaped, or sieve-shaped.

[0086] There is no particular limitation on the thickness of the positive electrode current collector layer; it can be 0.1 μm or more, or 1 μm or more, or less than 1 mm or less than 100 μm.

[0087] There are no particular limitations on the material that can be used for the current collector layer of the negative electrode; materials commonly used as negative electrode current collectors in batteries can be appropriately used. Examples of materials that can be used for the negative electrode current collector layer include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, or carbon sheets, but these are not limited to. The negative electrode current collector layer may have certain coatings on its surface for purposes such as adjusting resistance.

[0088] There are no particular limitations on the shape of the negative electrode current collector layer; for example, foil, plate, or sieve-like shapes can be listed.

[0089] There is no particular limitation on the thickness of the negative electrode current collector layer; it can be 0.1 μm or more, or 1 μm or more, or less than 1 mm or less than 100 μm.

[0090] Secondary Batteries

[0091] The secondary battery disclosed herein has the aforementioned electrode body. The aforementioned electrode body can be either a positive electrode or a negative electrode.

[0092] Electrolytes

[0093] The electrolyte contained in the secondary battery disclosed herein can be a solid electrolyte or a liquid electrolyte held in a separator.

[0094] There are no particular limitations on the materials used for solid electrolytes; for example, they can be sulfide solid electrolytes, oxide solid electrolytes, or polymer electrolytes.

[0095] Examples of sulfide solid electrolytes include amorphous sulfide solid electrolytes, crystalline sulfide solid electrolytes, and sulfide-silver-germanium ore type solid electrolytes, but are not limited to these. Specific examples of sulfide solid electrolytes include the Li₂S-P₂S₅ system (Li₇P₃S₅). 11 , Li3PS4, Li8P2S9, etc.), Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-LiBr-Li2S-P2S5, Li2S-P2S5-GeS2 (Li 13 GeP3S 16 Li 10 GeP2S 12 etc.), LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li 7-x PS 6-x Cl x etc.; or combinations thereof, but not limited to these.

[0096] Examples of oxide solid electrolytes include Li7La3Zr2O 12 Li 7-x La3Zr 1-x Nb x O 12 Li 7-3x La3Zr2Al x O 12 Li 3x La 2 / 3-x TiO3, Li 1+x Al x Ti 2-x (PO4)3, Li 1+x Al x Ge 2-x (PO4)3, Li3PO4, or Li 3+ x PO 4-x N x (LiPON), etc.; or combinations thereof, but not limited to these.

[0097] Sulfide solid electrolytes and oxide solid electrolytes can be glass or crystallized glass (glass ceramics).

[0098] Examples of polymer electrolytes include polyethylene oxide (PEO), polypropylene oxide (PPO), and their copolymers, but are not limited to these.

[0099] There are no particular limitations on the liquid electrolyte, but it is preferred to contain a supporting salt and a solvent.

[0100] Lithium salts, which serve as supporting salts for liquid electrolytes with lithium-ion conductivity, are not particularly limited and can include inorganic lithium salts and organic lithium salts. Examples of inorganic lithium salts include LiPF6, LiBF4, LiClO4, and LiAsF6, but are not limited to these. Examples of organic lithium salts include LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(FSO2)2, and LiC(CF3SO2)3, but are not limited to these.

[0101] There are no particular limitations on the solvent used for liquid electrolytes, and cyclic carbonates and chain carbonates can be included. Examples of cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate (BC), but these are not limited to these. Examples of chain carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC), but these are not limited to these. There are no particular limitations on the liquid electrolyte; only one type can be used, or two or more can be used in combination.

[0102] There are no particular limitations on the separator (partition), and a separator generally used in batteries can be appropriately used. For example, nonwoven fabrics such as polyolefin-based, polyamide-based, and polyimide-based separators can be used as separators.

[0103] Manufacturing Method of Electrodes

[0104] The method for manufacturing an electrode body disclosed herein is a method for manufacturing an electrode body having a current collector and an active material layer stacked on the current collector layer.

[0105] The manufacturing method includes: stacking a first layer on a current collector; and stacking a second layer on the first layer.

[0106] The first adhesive contained in the first layer is composed of particles with a surface contact shape.

[0107] The second adhesive contained in the second layer consists of point-contact shaped particles.

[0108] According to the manufacturing method of the electrode body disclosed herein, a novel electrode body for secondary batteries can be provided that can suppress the decrease in adhesion between the active material layer and the current collector, ensure flexibility, and suppress the increase in ionic resistance of the active material layer even when the composite slurry is dried at high temperature.

[0109] The following describes the constituent elements of this disclosure.

[0110] <The first layer of layering>

[0111] The method for manufacturing the electrode body disclosed herein includes laminating a first layer onto a current collector. Furthermore, the first binder contained in the first layer is composed of particles with a surface-contact shape. For the current collector, the first layer, and the first binder, refer to the description of the electrode body above.

[0112] The first layer may include the application and drying of a first composite slurry. The first composite slurry refers to a slurry containing an active material and a first binder. For the active material, refer to the description of the electrode body above.

[0113] There is no particular limitation on the viscosity of the first composite slurry; for example, at a shear rate of 0.1 s... -1 The viscosity can be above 90 Pa·s, above 100 Pa·s, above 150 Pa·s, or above 200 Pa. The viscosity of the first composite slurry can be below 500 Pa·s, below 400 Pa·s, below 300 Pa·s, or below 250 Pa·s.

[0114] The coating process is the process of coating the first composite slurry onto the current collector layer.

[0115] There are no particular limitations on the coating method; for example, it can be blade coating, molding coating, gravure coating, spraying, electrostatic coating, bar coating, etc.

[0116] The drying process is the process of drying the first composite slurry that has been coated.

[0117] There are no particular limitations on the drying method; for example, it can be warm air drying, hot air drying, infrared drying, vacuum drying, induction heating drying, etc.

[0118] There are no particular restrictions on the drying temperature; it can be above 50℃, above 70℃, above 90℃, above 100℃, above 110℃, or above 120℃, or below 200℃, below 180℃, below 160℃, below 150℃, or below 140℃.

[0119] <The second layer of layering>

[0120] The method for manufacturing the electrode body disclosed herein includes laminating a second layer onto the first layer described above. Furthermore, the second binder contained in the second layer is composed of point-contact shaped particles. For details regarding the second layer and the second binder, please refer to the description of the electrode body described above.

[0121] The second layer may include the application and drying of a second composite slurry. The second composite slurry refers to a slurry containing an active material and a second binder. For the active material, refer to the description of the electrode body above.

[0122] There is no particular limitation on the viscosity of the second composite slurry; for example, at a shear rate of 0.1 s... -1 The viscosity can be above 90 Pa·s, above 100 Pa·s, above 150 Pa·s, or above 200 Pa. The viscosity of the second composite slurry can be below 500 Pa·s, below 400 Pa·s, below 300 Pa·s, or below 250 Pa·s.

[0123] The coating process involves applying the aforementioned second composite slurry onto the first layer. For the coating method, please refer to the description related to the lamination of the first layer.

[0124] The drying process is the process of drying the second composite slurry to form the second layer. It should be noted that the drying process can be performed on each layer after the first composite slurry is applied and after the second composite slurry is applied, or it can be performed on both layers simultaneously. For the coating method, please refer to the description related to the lamination of the first layer described above.

[0125] (Example 1)

[0126] This disclosure is illustrated by way of examples and comparative examples, but is not limited thereto.

[0127] Fabrication of Electrodes

[0128] <Example 1>

[0129] Lithium cobalt oxide (LiCoO2) as the active material, styrene-butadiene copolymer (SBR) as the binder for forming the surface contact shape of the particles, carbon nanotubes (CNTs) as the conductive agent, and carboxymethyl cellulose (CMC) as the dispersant were weighed at a mass ratio of 95:3.9:0.1:1. They were mixed with deionized water, and the mixture was adjusted to a viscosity of 120 Pa·s (shear rate 0.1 s⁻¹). -1 ), and produced the first composite slurry.

[0130] Lithium cobalt oxide (LiCoO2) as the active material, styrene-acrylate copolymer (SAR) as the binder for forming point-contact particles, carbon nanotubes (CNTs) as the conductive agent, and carboxymethyl cellulose (CMC) as the dispersant were weighed at a mass ratio of 95:3.9:0.1:1. They were mixed with deionized water, and the mixture was adjusted to a viscosity of 120 Pa·s (shear rate 0.1 s⁻¹). -1 ), and produced the second composite slurry.

[0131] The first composite slurry was coated with a thickness of 210 μm onto the surface of the copper foil serving as the current collector layer, and then dried at 100°C for 3 minutes. Additionally, a second composite slurry was coated with a thickness of 210 μm onto the surface of the first composite slurry, and then dried at 100°C for 3 minutes, thus fabricating the electrode body of Example 1.

[0132] <Comparative Example 1>

[0133] Except that the second layer of Example 1 was not coated and the first layer was coated with a thickness of 420 μm, the electrode body as Comparative Example 1 was fabricated in the same manner as in Example 1.

[0134] <Comparative Example 2>

[0135] Except that the first layer of Example 1 was not coated and the second layer was coated with a thickness of 420 μm, the electrode body as Comparative Example 2 was fabricated in the same manner as in Example 1.

[0136] "evaluate"

[0137] <Evaluation of the adhesion between the active material layer and the current collector layer>

[0138] In Examples 1 and 2, the peel strength between the active material layer and the current collector layer was determined using a 90° peel tester, and the adhesion was evaluated. The evaluation criteria are as follows.

[0139] A: Peel strength is above 0.06 N / cm.

[0140] B: Peel strength is less than 0.06 N / cm.

[0141] <Evaluation of the flexibility of the electrode>

[0142] In Examples 1 and 2, the electrode body was wound around a cylinder with a diameter of 25 mm. The flexibility was then evaluated by visually inspecting for cracks in the active material layer. The evaluation criteria are as follows.

[0143] A: Cracks were confirmed in the active material layer.

[0144] B: No cracks were detected in the active material layer.

[0145] <Evaluation of the tortuosity of the active material layer>

[0146] In Examples 1 and 2, the tortuosity of the active material layer was measured to evaluate the ionic resistance of the active material layer. The evaluation criteria are as follows.

[0147] A: The curvature is below 0.083.

[0148] B: The curvature exceeds 0.083.

[0149] The evaluation results are shown in Table 1.

[0150] Table 1

[0151]

[0152] As can be understood from Example 1 and Comparative Example 2 in Table 1, a first layer of adhesive having a surface-contact current collector layer has high adhesion.

[0153] As can be understood from Example 1 and Comparative Example 1 in Table 1, flexibility is maintained while suppressing the increase of curvature by including a second layer containing an adhesive having particles with point contact shapes.

Claims

1. An electrode body having a current collector layer and an active material layer stacked on the current collector layer, the active material layer having a first layer on the current collector layer and a second layer on the first layer. The first adhesive contained in the first layer is composed of particles with a surface contact shape, and the second adhesive contained in the second layer is composed of particles with a point contact shape.

2. The electrode body according to claim 1, wherein, The peel strength between the current collector layer and the first layer is greater than 0.06 N / cm.

3. The electrode body according to claim 1 or 2, wherein, The curvature of the second layer is below 0.

083.

4. A secondary battery having the electrode body as described in claim 1 or 2.

5. A method for manufacturing an electrode, the electrode having a current collector and an active material layer stacked on the current collector layer, the method comprising: The first layer is stacked on top of the current collector; and A second layer is stacked on top of the first layer. The first adhesive contained in the first layer is composed of particles with a surface contact shape, and the second adhesive contained in the second layer is composed of particles with a point contact shape.

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