Electrode plate for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery

Abstract

This electrode plate for a non-aqueous electrolyte secondary battery has: an electrode core having an undercoat layer formed on the surface thereof; an electrode mixture layer formed on the undercoat layer of the electrode core. The undercoat layer is obtained by applying an undercoat dispersion on the surface of the electrode core and drying the same. A conductive auxiliary agent used for the undercoat layer is formed of carbon nanotubes. The average diameter of the conductive auxiliary agent is 12 nm or less. The aspect ratio (average length / average diameter) of the conductive auxiliary agent is 4000 or greater. The thickness of the undercoat layer is 0.10 μm or less.

Description

[Technical Field]

[0001] The present disclosure relates to an electrode plate for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery. [Background technology]

[0002] Patent Document 1 describes a lithium-ion secondary battery (nonaqueous electrolyte secondary battery) in which a slurry of carbon nanofibers mixed in a solvent is applied to the surface of an aluminum foil (electrode core) constituting a positive electrode plate, which is an electrode plate, and the slurry is dried and then heated to adhere the carbon nanofibers to the surface of the aluminum foil. Furthermore, the carbon nanofibers have an average fiber diameter of 5 to 80 nm and an average fiber length of 50 to 5,000 nm. Patent Document 1 also describes that this sufficiently reduces the surface resistance of the aluminum foil.

[0003] Patent Document 2 describes an electrode plate for a non-aqueous electrolyte secondary battery in which a base layer is formed from a conductive composition containing carbon nanotubes. The carbon nanotubes have a diameter, as a number average of the minor axis length, of 5 nm to 1000 nm, and an aspect ratio, (number average of the major axis length) / (number average of the minor axis length), of 1 to 2000. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5637114 [Patent Document 2] Patent No. 6476882 Summary of the Invention

[0005] In order to increase the output power and improve the durability of non-aqueous electrolyte secondary batteries, it is desirable to reduce the surface resistance of the electrode core of an electrode plate for a non-aqueous electrolyte secondary battery, more specifically, the interfacial resistance, which is the resistance between the electrode core and the electrode mixture layer. The carbon nanotube or carbon nanofiber configurations contained in the positive electrode plates described in Patent Documents 1 and 2 are not effective in reducing the interfacial resistance. In particular, when the secondary battery is in use, the electrode plate is in a swollen state with the non-aqueous solvent of the non-aqueous electrolyte, which is the electrolyte solvent. The electrode plates described in Patent Documents 1 and 2 did not have sufficiently low interfacial resistance in the swollen state. Reducing the interfacial resistance of the swollen electrode plate is desirable in order to increase the output power and improve the durability in actual use.

[0006] An electrode plate for a non-aqueous electrolyte secondary battery according to one embodiment of the present disclosure comprises an electrode core having an undercoat layer formed on its surface and an electrode composite layer formed on the undercoat layer of the electrode core, wherein the conductive additive used in the undercoat layer is carbon nanotubes, the conductive additive has an average diameter of 12 nm or less, and the aspect ratio (average length / average diameter) of the conductive additive is 4000 or more, and the undercoat layer has a thickness of 0.10 μm or less.

[0007] A nonaqueous electrolyte secondary battery according to one embodiment of the present disclosure includes a positive electrode plate, a negative electrode plate, and a nonaqueous electrolyte, and at least one of the positive electrode plate and the negative electrode plate is the electrode plate for a nonaqueous electrolyte secondary battery according to the present disclosure.

[0008] According to the electrode plate for a nonaqueous electrolyte secondary battery and the nonaqueous electrolyte secondary battery according to the present disclosure, the interface resistance of the electrode plate swollen by the nonaqueous electrolyte containing a nonaqueous solvent can be sufficiently reduced. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of a nonaqueous electrolyte secondary battery according to an example of an embodiment, showing the internal structure of a battery case with the front side of an exterior body removed. [Figure 2]FIG. 2 is a diagram schematically illustrating a cross section of a positive electrode plate, which is an electrode plate for a non-aqueous electrolyte secondary battery according to one example of the embodiment. [Figure 3] FIG. 3 is a diagram conceptually showing the distribution of the conductive additive when the undercoat layer shown in FIG. 2 is viewed from a direction perpendicular to the surface direction. DETAILED DESCRIPTION OF THE INVENTION

[0010] The inventors of the present disclosure have found that when an electrode plate for a non-aqueous electrolyte secondary battery has an electrode core with an undercoat layer formed on its surface and an electrode mixture layer formed on the undercoat layer of the electrode core, the conductive additive used in the undercoat layer is carbon nanotubes, the conductive additive has an average diameter of 12 nm or less, the aspect ratio (average length / average diameter) of the conductive additive is 4000 or more, and the undercoat layer has a thickness of 0.10 μm or less, the interfacial resistance of the electrode plate can be sufficiently reduced when the electrode plate is swollen with a non-aqueous solvent and then dried. As a result, the inventors of the present disclosure have found that the above electrode plate for a non-aqueous electrolyte secondary battery can sufficiently reduce the interfacial resistance of an electrode plate swollen with a non-aqueous electrolyte containing a non-aqueous solvent.

[0011] An example of an embodiment of the present disclosure will be described in detail below. In the following, a case where the electrode plate on which the undercoat layer of the present disclosure is formed is a positive electrode plate will be described, but the electrode plate on which the undercoat layer is formed may be a negative electrode plate, or both a positive electrode plate and a negative electrode plate.

[0012] FIG. 1 is a perspective view of a nonaqueous electrolyte secondary battery 100 according to an embodiment, showing the internal structure of the battery case with the front side of the outer casing 1 removed. In this embodiment, the nonaqueous electrolyte secondary battery 100 includes a rectangular metal outer casing 1. However, the outer casing is not limited to a rectangular shape and may be, for example, cylindrical. While a wound electrode assembly 3 in which a positive electrode plate and a negative electrode plate are wound with a separator interposed therebetween is shown, a laminated electrode assembly in which multiple positive electrode plates and multiple negative electrode plates are alternately stacked one by one with separators interposed therebetween may also be used. While the positive electrode plate and the negative electrode plate are shown with composite layers formed on both sides of each core, the composite layers are not limited to being formed on both sides of each core, as long as they are formed on at least one surface. Hereinafter, the nonaqueous electrolyte secondary battery 100 will be referred to as a secondary battery 100.

[0013] 1, the secondary battery 100 includes a wound electrode assembly 3 formed in a flat shape having a flat portion and a pair of curved portions, in which a positive electrode plate 4 and a negative electrode plate 8 are wound with a separator interposed therebetween, a non-aqueous electrolyte, and an exterior body 1 that houses the electrode assembly 3 and the non-aqueous electrolyte. The open end of the exterior body 1 is closed by a sealing plate 2. Both the exterior body 1 and the sealing plate 2 are made of metal, preferably aluminum or an aluminum alloy.

[0014] The exterior body 1 has a bottom portion that is generally rectangular in bottom view, and sidewall portions that stand upright on the periphery of the bottom portion. The sidewall portions are formed generally perpendicular to the bottom portion.

[0015] FIG. 2 is a schematic diagram showing a cross section of a positive electrode plate 4 according to an example of the embodiment. The positive electrode plate 4 is an elongated body having a metallic positive electrode core 5 and positive electrode composite layers 7 formed on both sides of the positive electrode core 5 with undercoat layers 6 interposed therebetween. The positive electrode core 5 corresponds to the electrode core, and the positive electrode composite layers 7 correspond to the electrode composite layers. In FIG. 2, only the undercoat layer 6 and the positive electrode composite layer 7 on one side (the upper side in FIG. 2) of the positive electrode plate 4 are shown, and the undercoat layer and the positive electrode composite layer on the other side (the lower side in FIG. 2) are not shown. As shown in FIG. 1, the positive electrode plate 4 has a strip-shaped positive electrode core exposed portion 4a formed by exposing the positive electrode core 5 along the longitudinal direction at one end (the right end in FIG. 1) in the short direction when unfolded. Similarly, the negative electrode plate 8 is a long body having a metallic negative electrode core and negative electrode composite layers formed on both sides of the negative electrode core, and has a strip-shaped negative electrode core exposed portion 8a where the negative electrode core is exposed along the longitudinal direction at one end in the short direction when unfolded (the left end in FIG. 1). The electrode body 3 is wound with the positive electrode plate 4 and the negative electrode plate 8 interposed between them, with the positive electrode core exposed portion 4a of the positive electrode plate 4 disposed at one axial end side (the right side in FIG. 1) and the negative electrode core exposed portion 8a of the negative electrode plate 8 disposed at the other axial end side (the left side in FIG. 1).

[0016] A positive electrode current collector 9 is connected to the laminated portion of the positive electrode substrate exposed portion 4a of the positive electrode plate 4, and a negative electrode current collector 10 is connected to the laminated portion of the negative electrode substrate exposed portion 8a of the negative electrode plate 8. The positive electrode terminal 11 has a positive electrode bolt portion 12 arranged on the battery exterior side of the sealing plate 2, and a positive electrode insertion portion 13 electrically connected to the positive electrode bolt portion 12 and inserted into a through hole provided in the sealing plate 2, and the positive electrode current collector 9 is electrically connected to the positive electrode terminal 11. The negative electrode terminal 14 has a negative electrode bolt portion 15 arranged on the battery exterior side of the sealing plate 2, and a negative electrode insertion portion 18 electrically connected to the negative electrode bolt portion 15 and inserted into a through hole provided in the sealing plate 2, and the negative electrode current collector 10 is electrically connected to the negative electrode terminal 14.

[0017] The positive electrode terminal 11 and the positive electrode current collector 9 are fixed to the sealing plate 2 via insulating members, respectively. The negative electrode terminal 14 and the negative electrode current collector 10 are fixed to the sealing plate 2 via insulating members, respectively.

[0018] The electrode assembly 3 is housed in the exterior housing 1. The sealing plate 2 is connected to the edge of the opening of the exterior housing 1 by laser welding or the like. The sealing plate 2 has an electrolyte injection hole 19, which is sealed with a sealing plug after a non-aqueous electrolyte is injected into the exterior housing 1.

[0019] The nonaqueous electrolyte contains a nonaqueous solvent and an electrolyte salt dissolved in the nonaqueous solvent. Examples of the nonaqueous solvent include carbonates, lactones, ethers, ketones, and esters, and two or more of these solvents can be mixed together. When two or more solvents are mixed together, a mixed solvent containing a cyclic carbonate and a chain carbonate is preferably used. For example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and the like can be used as the cyclic carbonate, and dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), and the like can be used as the chain carbonate. The nonaqueous solvent may contain a halogen-substituted compound in which at least a portion of the hydrogen atoms of the above solvents are substituted with halogen atoms such as fluorine. Examples of the electrolyte salt include LiPF6, LiBF4, LiCF3SO3, and mixtures thereof. The amount of electrolyte salt dissolved in the non-aqueous solvent can be, for example, 0.5 to 2.0 mol / L. Furthermore, an additive such as vinylene carbonate (VC) can also be added as needed.

[0020] The positive electrode plate 4, the negative electrode plate 8, and the separator that constitute the electrode assembly 3, with the positive electrode plate 4 in particular, will be described in detail below.

[0021] [Positive electrode] As shown in Fig. 2, the positive electrode plate 4 has a positive electrode core 5, an undercoat layer 6 formed on the surface of the positive electrode core 5, and a positive electrode composite layer 7 formed on the undercoat layer 6 of the positive electrode core 5. For the positive electrode core 5, for example, a foil of a metal such as aluminum that is stable in the potential range of the positive electrode, or a film with such a metal disposed on the surface layer, can be used. The positive electrode composite layer 7 includes, for example, a positive electrode active material, a binder as a binding material, a conductive additive, etc.

[0022] The undercoat layer 6 is obtained by applying an undercoat dispersion containing a conductive additive 6a (FIG. 3) to the surface of the positive electrode substrate 5 and drying it. The undercoat layer 6 contains the conductive additive 6a and a binder as a binding agent. The conductive additive 6a is carbon nanotubes (CNTs), which are carbon fibers. The average diameter of the conductive additive 6a is 12 nm or less, preferably 9 nm or less, and more preferably 6 nm or less.

[0023] The average length of the conductive assistant 6a used in the undercoat layer 6 is not particularly limited, but is preferably 10 μm or more, more preferably 40 μm or more, and even more preferably 100 μm or more.

[0024] Furthermore, the aspect ratio of the conductive additive, which is (average length / average diameter), is 4000 or more.

[0025] In this specification, the average diameter of the conductive additives 6a is a value obtained by observing 10 conductive additives 6a using a scanning electron microscope (SEM), measuring the diameters of the 10 conductive additives 6a, and calculating the number average value. Furthermore, the average length of the conductive additives 6a is a value obtained by observing 10 conductive additives 6a using a scanning electron microscope, measuring the lengths of the 10 conductive additives 6a, and calculating the number average value. More specifically, the conductive additives 6a were observed using a scanning electron microscope at an acceleration voltage of 5 kV, and images were taken at a magnification of 50,000 (1024 × 1280 pixels). In the captured images, the diameters and lengths of any 10 conductive additives 6a were measured, and the number average values ​​were calculated to obtain the average diameter and average length. The aspect ratio was then calculated from these values.

[0026] The BET specific surface area of ​​the conductive additive 6a of the undercoat layer 6 is not particularly limited, but is preferably 100 m 2 / g or more, and more preferably 200m 2 / g or more, more preferably 400m 2 / g or more. The content of the conductive additive 6a in the undercoat layer 6 is preferably 75 to 97.5%. The bulk density of the conductive additive 6a is not particularly limited, but is preferably 0.008 to 0.01 g / cm 3 It is preferable that:

[0027] Examples of binders used in the undercoat layer 6 include fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, and polyolefin resins. These may be used alone or in combination of two or more. Polyvinylidene fluoride (PVDF) is preferably used as the binder in the undercoat layer 6. The molecular weight of the binder in the undercoat layer 6 is not particularly limited, but is preferably 900,000 or more, and more preferably 1,400,000 or more. The binder content in the undercoat layer 6 is preferably 2.5 to 22.5%. A dispersant may also be added to the undercoat layer 6. The solid content (NV) of the undercoat layer 6 is preferably 0.5 to 2.5%.

[0028] When forming the undercoat layer 6 on the surface of the positive electrode core 5, a slurry for forming the undercoat layer is prepared by dispersing a conductive additive 6a in a solvent as an undercoat dispersion. Examples of the solvent for dispersing the conductive additive 6a include N-methyl-2-pyrrolidone (NMP). The prepared slurry is then applied to the surface of the positive electrode core 5 by a gravure coating method or the like, and dried to form the undercoat layer 6. For example, the drying can be performed by heat treatment in a hot air circulation path, but the drying method is not limited thereto.

[0029] Furthermore, the thickness of the undercoat layer 6 is 0.10 μm or less. In this specification, the thickness of the undercoat layer 6 is a value obtained by measuring the thickness of a cross section of the undercoat layer 6 processed with a cross section processing device (CP) using a scanning electron microscope and calculating the number average value of the thicknesses. More specifically, the thickness of the undercoat layer 6 was measured by observing the cross section using a scanning electron microscope at an acceleration voltage of 5 kV and taking a 50,000-magnification image (pixel count: 1024 × 1280). In the image, the length from the top of the positive electrode substrate 5 to the top of the undercoat layer 6 was measured at each of five arbitrary positions, and the number average value of these measurements was calculated to determine the thickness of the undercoat layer 6. Furthermore, the basis weight of the undercoat layer 6 is not particularly limited, but is preferably 110 mg / m 2 or less, more preferably 80 mg / m 2 or less, and more preferably 50 mg / m 2 The lower limit of the weight is 10 mg / m 2 It is preferable that the undercoat layer 6 is such that the interfacial resistance of the swollen positive electrode plate 4 can be reduced. The coverage of the undercoat layer 6 with respect to the surface of the positive electrode substrate 5 is preferably 20 to 100%.

[0030] The positive electrode plate 4 can be produced, for example, by forming an undercoat layer 6 on the surface of a positive electrode core 5, applying a positive electrode composite slurry containing a positive electrode active material, a binder, a conductive additive, etc. onto the undercoat layer 6 of the positive electrode core 5, drying the slurry to form a positive electrode composite layer 7, and then rolling the positive electrode composite layer 7.

[0031] Examples of the positive electrode active material include lithium transition metal oxides containing transition metal elements such as Co, Mn, and Ni. x CoO2, Li x NiO2, Li x MnO2, Li x Co y Ni 1-y O2, Li x Co y M 1-y O z , Li x Ni 1-y My O z 、 Li x Mn2O4, Li x Mn 2-y M y O4, LiMPO4, Li2MPO4F (M; at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, B, 0 < x ≤ 1.2, 0 < y ≤ 0.9, 2.0 ≤ z ≤ 2.3). These may be used alone or in combination of multiple types. In terms of achieving a higher capacity of the secondary battery 100, the cathode active material is Li x NiO2, Li x Co y Ni 1-y O2, Li x Ni 1-y M y O z (M; at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, B, 0 < x ≤ 1.2, 0 < y ≤ 0.9, 2.0 ≤ z ≤ 2.3), etc., and preferably contains a lithium nickel composite oxide.

[0032] Examples of the conductive assistant used in the cathode composite material layer 7 include carbon-based particles such as carbon black (CB), acetylene black (AB), ketjen black, carbon nanotubes (CNT), and graphite. These may be used alone or in combination of two or more types. Preferably, carbon black is used as the conductive assistant in the cathode composite material layer.

[0033] Examples of the binder used in the cathode composite material layer 7 include fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide-based resins, acrylic resins, and polyolefin-based resins. These may be used alone or in combination of two or more types. Preferably, polyvinylidene fluoride is used as the conductive assistant in the cathode composite material layer 7. The molecular weight of the binder in the cathode composite material layer 7 is not particularly limited, but is preferably 900,000 or more, and more preferably 1,400,000 or more.

[0034] In the positive electrode plate 4 fabricated as described above, the undercoat layer 6 contains a conductive additive 6a, which is carbon nanotubes with an average diameter of 12 nm or less, and the conductive additive 6a has an aspect ratio of 4000 or more, and the undercoat layer 6 has a thickness of 0.10 μm or less. This sufficiently reduces the interfacial resistance of the positive electrode plate 4 swollen by the nonaqueous electrolyte containing the nonaqueous solvent. This will be explained using FIG. 3.

[0035] FIG. 3 is a conceptual diagram illustrating the distribution of the conductive additives 6a when viewed from a direction perpendicular to the surface of the undercoat layer 6. While FIG. 3 shows all of the conductive additives 6a as being spaced apart, it is estimated that in reality, several to about ten of them overlap. For example, when the average diameter of the conductive additives 6a is 12 nm or less, the gap between the surface of the swollen positive electrode core 5 and the positive electrode composite layer 7 tends to be small. This is estimated to facilitate the formation of an electrical path between the conductive additives 6a and the positive electrode core 5 and the positive electrode composite layer 7, thereby reducing interfacial resistance. Furthermore, when the aspect ratio is 4000 or greater, the conductive additives 6a tend to be thin and easily entangled. This is estimated to facilitate the formation of an electrical path between the conductive additives 6a and the positive electrode composite layer 7, thereby reducing interfacial resistance. For this reason, the aspect ratio is preferably 5000 or greater, and more preferably 7000 or greater. Considering the ease of forming the undercoat layer 6 on the positive electrode substrate 5 and the ease of dispersing the carbon nanotubes in the undercoat layer 6, the aspect ratio is preferably 35,000 or less, more preferably 18,000 or less, and even more preferably 15,000 or less.

[0036] Furthermore, when the thickness of the undercoat layer 6 is 0.10 μm or less, this also tends to reduce the gap between the surface of the positive electrode core 5 after swelling and the positive electrode composite layer 7, and it is presumed that this can reduce the interfacial resistance in the same way as above.

[0037] Furthermore, when the molecular weight of the binder used in each of the undercoat layer 6 and the positive electrode composite layer 7 is 900,000 or more, swelling of the binder is suppressed when the positive electrode plate 4 is immersed in a non-aqueous electrolyte. This also tends to reduce the gap between the surface of the positive electrode core 5 and the positive electrode composite layer 7 after swelling, which is presumably responsible for reducing the interfacial resistance in the same way as above.

[0038] [Negative electrode] The negative electrode plate 8 includes a negative electrode core and a negative electrode composite layer formed on the surface of the negative electrode core. For the negative electrode core, for example, a foil of a metal such as copper that is stable within the potential range of the negative electrode, or a film with such a metal disposed on the surface layer, can be used. The negative electrode composite layer includes a negative electrode active material. The negative electrode plate 8 can be produced by applying a negative electrode composite slurry containing the negative electrode active material onto the negative electrode core, drying it to form a negative electrode composite layer, and then rolling this negative electrode composite layer.

[0039] The negative electrode active material is not particularly limited as long as it can reversibly absorb and release lithium ions, and examples thereof include carbon materials such as natural graphite and artificial graphite, metals that alloy with lithium such as silicon (Si) and tin (Sn), or alloys and composite oxides containing metal elements such as Si and Sn. Carbon materials are preferred as the negative electrode active material, and natural graphite is more preferred. The negative electrode active materials may be used alone or in combination of two or more.

[0040] [Separator] The separator may be, for example, a porous sheet having ion permeability and insulating properties. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. Suitable materials for the separator include olefin-based resins such as polyethylene and polypropylene, and cellulose. The separator may be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin-based resin. Alternatively, the separator may be a multilayer separator including a polyethylene layer and a polypropylene layer, and a separator whose surface is coated with a material such as an aramid-based resin or ceramic may be used.

[0041] <Example> The positive electrode plate 4 as an electrode plate for a non-aqueous electrolyte secondary battery according to the present disclosure will be further described below with reference to examples, but the present disclosure is not limited to these examples.

[0042] Example 1 [Preparation of positive electrode plate] As the positive electrode active material, LiNi as lithium nickel cobalt manganese composite oxide 0.35 Co 0.35 Mn 0.30 A composite oxide represented by O2 was used. The positive electrode active material, PVDF as a binder, and carbon black were mixed in a mass ratio of 90.3:2.7:7.0, and kneaded while adding N-methyl-2-pyrrolidone to prepare a positive electrode composite slurry. The molecular weight of the PVDF in the composite layer was 1.1 million. An undercoat dispersion containing carbon nanotubes as the conductive additive 6a was applied to both sides of a long positive electrode substrate 5 made of aluminum foil with a thickness of 13 μm, and the coating was dried to obtain a positive electrode substrate 5 with an undercoat layer 6 formed on the surface. The average diameter of the conductive additive 6a was 7.5 nm, and the aspect ratio of the conductive additive 6a was 13333. PVDF with a molecular weight of 1.1 million was used as the binder for the undercoat layer 6. The basis weight of the undercoat layer 6 was 50 mg / m 2 The thickness was 0.07 μm. The weight of the composite layer was 109 mg / 10 cm on each side of the positive electrode substrate 5. 2 The thickness was 45 μm on each side of the positive electrode substrate 5. Table 1 shows the properties of the conductive additive 6a, PVDF, and undercoat layer 6 in the undercoat layer of Example 1. Table 1 also shows the properties of Examples 2 to 8 and Comparative Examples 1 to 7 described below. In Table 1, the average diameter of the conductive additive is shown as the diameter.

[0043] [Table 1]

[0044] Next, the positive electrode mixture slurry was applied onto the undercoat layer 6 of the positive electrode substrate 5, and the coating was dried. 3After compressing the positive electrode core 5 so as to have a shape similar to that shown in FIG.

[0045] <Example 2> The weight of the undercoat layer 6 is 13 mg / m 2 The positive electrode plate 4 was fabricated in the same manner as in Example 1, except that the thickness was set to 0.06 μm. The fabricated positive electrode plate 4 was designated as Example 2.

[0046] Example 3 A positive electrode plate 4 was produced in the same manner as in Example 1, except that the aspect ratio of the conductive additive 6a used in the undercoat layer 6 was set to 8000 and the thickness of the undercoat layer 6 was set to 0.08 μm. The produced positive electrode plate 4 was designated as Example 3.

[0047] Example 4 A positive electrode plate 4 was produced in the same manner as in Example 1, except that the aspect ratio of the conductive additive 6a used in the undercoat layer 6 was set to 5333 and the thickness of the undercoat layer 6 was set to 0.09 μm. The produced positive electrode plate 4 was designated as Example 4.

[0048] <Example 5> A positive electrode plate 4 was produced in the same manner as in Example 1, except that the average diameter of the conductive additive 6a used in the undercoat layer 6 was 12 nm and the aspect ratio was 6667. The produced positive electrode plate 4 was designated as Example 5.

[0049] Example 6 A positive electrode plate 4 was produced in the same manner as in Example 1, except that the average diameter of the conductive additive 6a used in the undercoat layer 6 was 12 nm and the aspect ratio was 5000. The produced positive electrode plate 4 was designated as Example 6.

[0050] Example 7 A positive electrode plate 4 was produced in the same manner as in Example 1, except that the aspect ratio of the conductive additive 6a used in the undercoat layer 6 was set to 4000. The produced positive electrode plate 4 was designated as Example 7.

[0051] Example 8 The weight of the undercoat layer 6 is 80 mg / m 2 A positive electrode plate 4 was produced in the same manner as in Example 1, except that PVDF having a molecular weight of 900,000 was used as a binder for the undercoat layer 6 and the composite layer, and the thickness was 0.09 μm. The produced positive electrode plate 4 was designated as Example 8.

[0052] <Comparative Example 1> Undercoat layer weight: 105mg / m 2 A positive electrode plate was fabricated in the same manner as in Example 1, except that the thickness was set to 0.15 μm. The fabricated positive electrode plate was designated Comparative Example 1.

[0053] <Comparative Example 2> The average diameter of the conductive additive used in the undercoat layer is 12 nm, the aspect ratio is 833, and the basis weight of the undercoat layer is 80 mg / m 2 A positive electrode plate was fabricated in the same manner as in Example 1, except that the thickness was set to 0.09 μm. The fabricated positive electrode plate was designated Comparative Example 2.

[0054] <Comparative Example 3> Undercoat layer weight: 130mg / m 2 A positive electrode plate was produced in the same manner as in Example 1, except that the thickness was set to 0.32 μm. The produced positive electrode plate was designated Comparative Example 3.

[0055] <Comparative Example 4> The average diameter of the conductive additive used in the undercoat layer is 50 nm, the aspect ratio is 200, and the weight of the undercoat layer is 80 mg / m 2 A positive electrode plate was produced in the same manner as in Example 1, except that the thickness was set to 1.34 μm. The produced positive electrode plate was designated Comparative Example 4.

[0056] <Comparative Example 5> The average diameter of the conductive additive used in the undercoat layer is 50 nm, the aspect ratio is 200, and the weight of the undercoat layer is 25 mg / m 2A positive electrode plate was produced in the same manner as in Example 1, except that the thickness was set to 0.18 μm. The produced positive electrode plate was designated Comparative Example 5.

[0057] <Comparative Example 6> A positive electrode plate was produced in the same manner as in Example 1, except that the aspect ratio of the conductive additive used in the undercoat layer was set to 2667. The produced positive electrode plate was designated Comparative Example 6.

[0058] <Comparative Example 7> A positive electrode plate was produced in the same manner as in Example 1, except that the average diameter of the conductive additive used in the undercoat layer was 12 nm, the aspect ratio was 1667, and the thickness of the undercoat layer was 0.06 μm. The produced positive electrode plate was designated Comparative Example 7.

[0059] In each of the above examples and comparative examples, the aspect ratio was adjusted by changing the stirring conditions of the Disper stirrer.

[0060] [Interface resistance measurement] In the positive electrode plate 4 of each example and each comparative example, the interface resistance (area resistivity Ωcm) between the positive electrode substrate 5 and the positive electrode composite layer 7 was 2 ) was measured. The interfacial resistance was measured after the positive electrode plate 4 was compressed as described above, and after the positive electrode plate 4 was compressed, swelled, and dried (after swelling and drying). An electrode resistance measuring device (device name: RM2610) manufactured by Hioki E.E. Corporation was used to measure the interfacial resistance.

[0061] Here, the interfacial resistance of an electrode plate swollen in a nonaqueous solvent and then dried was evaluated. It is difficult to measure the interfacial resistance of an electrode plate that remains swollen in a nonaqueous solvent. Therefore, the electrode plate was measured for interfacial resistance after swelling and drying, when the electrode plate was close to a swollen state and interfacial resistance measurement was possible. To obtain the positive electrode plate 4 after swelling and drying, the positive electrode plate 4 was compressed as described above, then placed in a dimethyl carbonate solution and left overnight at a temperature of 85°C. The positive electrode plate 4 was then removed from the solution and dried in a dryer at a temperature of 130°C for 3 to 4 hours. After drying, the interfacial resistance was measured. Table 1 shows the results of measuring the interfacial resistance after compression and the interfacial resistance after swelling and drying for each example and comparative example.

[0062] From the results shown in Table 1, in Examples 1 to 8, the interface resistance of the positive electrode plate 4 after swelling and drying was significantly reduced compared to Comparative Examples 1 to 7. This is thought to be because the interface resistance value was significantly reduced even in an electrode plate in a state swollen with a nonaqueous solvent, confirming the effects of the present disclosure. For example, when comparing Examples 1 and 2 with Comparative Examples 1 and 3, the aspect ratio of the conductive additive 6a is the same, 4000 or more, in both cases, but the thickness of the undercoat layer 6 in Examples 1 and 2 is smaller, at 0.10 μm or less, compared to Comparative Examples 1 and 3, which is thought to have reduced the interface resistance of the positive electrode plate 4 after swelling and drying.

[0063] Comparing Examples 1 to 8 with Comparative Examples 2, 6, and 7, the thickness of the undercoat layer 6 is small, at 0.10 μm or less in all cases. However, in Examples 1 to 8, the aspect ratio of the conductive additive 6a is larger, at 4000 or more, than in Comparative Examples 2, 6, and 7, which is thought to have reduced the interfacial resistance of the positive electrode plate 4 after swelling and drying. [Explanation of symbols]

[0064] 1. Exterior body 2 Sealing plate 3 Electrode body 4 positive electrode plate 4a Exposed positive electrode core 5 Positive electrode core 6 Undercoat layer 6a Conductive additive 7 Positive electrode composite layer 8 negative electrode plate 8a Negative electrode core exposed part 9 Positive electrode current collector 10 Negative electrode current collector 11 Positive terminal 12 Positive bolt section 13 Positive electrode insertion part 14 Negative terminal 15 Negative electrode bolt section 18 Negative electrode insertion part 19 Electrolyte injection hole 100 Secondary battery.

Claims

1. an electrode core having an undercoat layer formed on its surface; and an electrode mixture layer formed on the undercoat layer of the electrode core; the electrode substrate is used to connect a current collector to the exposed portion, the conductive additive used in the undercoat layer is carbon nanotubes, The average diameter of the conductive additive is 6 nm or more and 12 nm or less, The aspect ratio of the conductive additive, which is (average length / average diameter), is 4,000 or more and 18,000 or less, The thickness of the undercoat layer is 0.06 μm or more and 0.10 μm or less. Electrode plate for non-aqueous electrolyte secondary batteries.

2. The electrode plate for a non-aqueous electrolyte secondary battery according to claim 1, The molecular weight of the binder used in the undercoat layer is 900,000 or more, The molecular weight of the binder used in the electrode mixture layer is 900,000 or more. Electrode plate for non-aqueous electrolyte secondary batteries.

3. The electrode plate for a non-aqueous electrolyte secondary battery according to claim 2, the binder used in the undercoat layer and the binder used in the electrode mixture layer both contain polyvinylidene fluoride; Electrode plate for non-aqueous electrolyte secondary batteries.

4. A positive electrode plate, a negative electrode plate, and a non-aqueous electrolyte, At least one of the positive electrode plate and the negative electrode plate is the electrode plate for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 3. Nonaqueous electrolyte secondary battery.

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