Electrode plate for nonaqueous electrolyte secondary battery and nonaqueous electrolyte secondary battery

Abstract

An electrode plate for a non-aqueous electrolyte secondary battery comprises: an electrode core having a primer layer formed on its surface; and an electrode composite material layer formed on the primer layer of the electrode core. The primer layer is formed by applying a primer dispersion liquid to the surface of the electrode core and drying it. The average diameter of the conductive additive used in the primer layer is 12 nm or less, the molecular weight of the binder used in the primer layer is 900,000 or greater, the thickness of the primer layer is 0.20 μm or less, and the molecular weight of the binder used in the electrode composite material layer is 900,000 or greater.

Description

Technical Field

[0001] The present disclosure relates to an electrode plate for a nonaqueous electrolyte secondary battery and a nonaqueous electrolyte secondary battery. Background Art

[0002] Patent Document 1 describes the following configuration: To improve the performance of a lithium-ion secondary battery (non-aqueous electrolyte secondary battery), a slurry of carbon nanofibers mixed in a solvent is applied to the surface of an aluminum foil (electrode core) that forms the positive electrode plate, followed by drying and heating to adhere the carbon nanofibers to the surface of the aluminum foil. Patent Document 1 describes this as significantly reducing the surface resistance of the aluminum foil.

[0003] Patent Document 2 describes a structure in which an intermediate layer containing a conductive agent and a binder is provided between the positive electrode core (electrode core) and the positive electrode composite material layer (electrode composite material layer) in a positive electrode plate for a non-aqueous electrolyte secondary battery. Patent Document 1 describes a method of using a carbon material such as Ketjen black, carbon black, or carbon fiber as the conductive agent in the intermediate layer.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2013-77476

[0007] Patent Document 2: International Publication No. 2016 / 024394 Summary of the Invention

[0008] In order to achieve high power and improved durability of non-aqueous electrolyte secondary batteries, it is expected to reduce the surface resistance of the electrode core of the electrode plate for non-aqueous electrolyte secondary batteries, and more specifically, it is expected to reduce the resistance between the electrode core and the electrode composite material layer, that is, the interface resistance. In the composition of the carbon nanofibers contained in the positive plate described in Patent Document 1, the effect of reducing the above-mentioned interface resistance is not sufficient. In particular, the electrode plate is in a state of swelling due to the non-aqueous solvent of the non-aqueous electrolyte as the electrolyte solvent when the secondary battery is in use. The interface resistance of the electrode plate described in Patent Document 1 in this swollen state is not low enough. For the positive plate including the intermediate layer described in Patent Document 2, the effect of reducing the interface resistance of the electrode plate swollen with the non-aqueous solvent is also insufficient. From the perspective of achieving high power and improved durability in actual battery use, it is expected to reduce the above-mentioned interface resistance of the electrode plate in the swollen state.

[0009] As one embodiment of the present invention, an electrode plate for a non-aqueous electrolyte secondary battery comprises: an electrode core having a primer layer formed on the surface; and an electrode composite material layer formed on the primer layer of the electrode core, wherein the average diameter of the conductive additive used in the primer layer is less than 12 nm, the molecular weight of the binder used in the primer layer is greater than 900,000, the thickness of the primer layer is less than 0.20 μm, and the molecular weight of the binder used in the electrode composite material layer is greater than 900,000.

[0010] A nonaqueous electrolyte secondary battery as one embodiment of the present disclosure includes a positive electrode plate, a negative electrode plate, and a nonaqueous electrolyte, wherein at least one of the positive electrode plate and the negative electrode plate is an electrode plate for a nonaqueous electrolyte secondary battery of the present disclosure.

[0011] According to the electrode plate for a nonaqueous electrolyte secondary battery and the nonaqueous electrolyte secondary battery disclosed herein, the interface resistance of the electrode plate swollen by a nonaqueous electrolyte containing a nonaqueous solvent can be sufficiently reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a perspective view of a nonaqueous electrolyte secondary battery according to an example of an embodiment, showing the internal structure of the battery case with the front side of the outer case removed.

[0013] Figure 2 This is a diagram schematically showing a cross section of a positive electrode plate of an electrode plate for a non-aqueous electrolyte secondary battery as an example of an embodiment.

[0014] Figure 3 To schematically illustrate the direction of the plane when viewed from a direction perpendicular to the plane Figure 2 A diagram showing the distribution of the conductive additive in the primer layer. DETAILED DESCRIPTION

[0015] The inventors of the present disclosure have discovered that an electrode plate for a non-aqueous electrolyte secondary battery comprises: an electrode core having a primer layer formed on its surface; and an electrode composite material layer formed on the primer layer of the electrode core. The average diameter of the conductive additive used in the primer layer is 12 nm or less, the molecular weight of the binder used in the primer layer is 900,000 or greater, and the thickness of the primer layer is 0.20 μm or less. When the molecular weight of the binder used in the electrode composite material layer is 900,000 or greater, 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. The inventors of the present disclosure have thus discovered that the interfacial resistance of the electrode plate swollen by a non-aqueous electrolyte containing a non-aqueous solvent can be sufficiently reduced using the aforementioned electrode plate for a non-aqueous electrolyte secondary battery.

[0016] Hereinafter, an example of an embodiment of the present disclosure will be described in detail. Hereinafter, the electrode plate on which the undercoat layer is formed is a positive electrode plate. However, the electrode plate on which the undercoat layer is formed may also be a negative electrode plate, or both a positive electrode plate and a negative electrode plate.

[0017] Figure 1 The non-aqueous electrolyte secondary battery 100 is a three-dimensional view of an embodiment, which is a diagram showing the internal structure of the battery case in a state where the front side of the outer shell 1 is removed. In this embodiment, a non-aqueous electrolyte secondary battery 100 having a square metal outer shell 1 is shown, but the outer shell is not limited to a square shape, and may be, for example, cylindrical. In addition, a wound electrode body 3 is shown in which a positive electrode plate and a negative electrode plate are wound with a separator between them, but a stacked electrode body may also be formed in which a plurality of positive plates and a plurality of negative plates are alternately stacked one by one with a separator between them. In addition, a case is shown in which each composite material layer is formed on both sides of each core body on both the positive plate and the negative plate, but each composite material layer is not limited to being formed on both sides of each core body, and may be formed on the surface of at least one of them. Hereinafter, the non-aqueous electrolyte secondary battery 100 will be described as secondary battery 100.

[0018] like Figure 1 As shown, the secondary battery 100 includes: a wound electrode body 3 formed by winding a positive electrode plate 4 and a negative electrode plate 8 with a separator interposed therebetween, formed into a flat shape with a flat portion and a pair of curved portions; a non-aqueous electrolyte; and an outer case 1 that houses the electrode body 3 and the non-aqueous electrolyte. The open end of the outer case 1 is sealed by a sealing plate 2. Both the outer case 1 and the sealing plate 2 are made of metal, preferably aluminum or an aluminum alloy.

[0019] The outer shell 1 has a bottom portion that is substantially rectangular in bottom view, and a side wall portion that is erected on the periphery of the bottom portion. The side wall portion is formed substantially perpendicular to the bottom portion.

[0020] Figure 2 This figure schematically illustrates a cross-section of a positive electrode plate 4 according to an embodiment. The positive electrode plate 4 is a long strip having a metal positive electrode core 5 and positive electrode composite material layers 7 formed on both sides of the positive electrode core 5 with primer layers 6 interposed therebetween. The positive electrode core 5 corresponds to the electrode core, and the positive electrode composite material layers 7 correspond to the electrode composite material layers. Figure 2 In the figure, only one side of the positive electrode plate 4 is shown ( Figure 2 The undercoat layer 6 and the positive electrode composite material layer 7 are omitted on the other side ( Figure 2 Figure 2 shows the bottom coating layer and the positive electrode composite material layer on the lower side of the substrate. Figure 1 As shown, for the positive electrode plate 4, one end portion in the width direction in the unfolded state ( Figure 1The positive electrode core 5 is exposed along the length direction, thereby forming a strip-shaped positive electrode core exposed portion 4a. Similarly, the negative electrode plate 8 is a long strip having a metal negative electrode core and negative electrode composite material layers formed on both sides of the negative electrode core, and is formed with: one end in the width direction in the unfolded state ( Figure 1 The left end of the negative electrode core is exposed along the longitudinal direction of the negative electrode core. Figure 1 The positive electrode core exposed portion 4a of the positive electrode plate 4 is arranged on the right side of the positive electrode plate 4, and the positive electrode core exposed portion 4a of the positive electrode plate 4 is arranged on the right side of the positive electrode plate 4 Figure 1 The positive electrode plate 4 and the negative electrode plate 8 are wound with the separator interposed therebetween.

[0021] The stacked portion of the exposed positive electrode core portion 4a of the positive electrode plate 4 is connected to the positive electrode current collector 9, and the stacked portion of the exposed negative electrode core portion 8a of the negative electrode plate 8 is connected to the negative electrode current collector 10. The positive electrode terminal 11 includes a positive electrode bolt portion 12 disposed 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. The positive electrode terminal 11 is electrically connected to the positive electrode current collector 9. Furthermore, the negative electrode terminal 14 includes a negative electrode bolt portion 15 disposed 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. The negative electrode terminal 14 is electrically connected to the negative electrode current collector 10.

[0022] The positive electrode terminal 11 and the positive electrode current collector 9 are fixed to the sealing plate 2 via an insulating member. The negative electrode terminal 14 and the negative electrode current collector 10 are fixed to the sealing plate 2 via an insulating member.

[0023] The electrode assembly 3 is housed in the outer shell 1. The sealing plate 2 is connected to the opening edge of the outer shell 1 by laser welding or the like. The sealing plate 2 has an electrolyte injection hole 19, which is sealed by a sealing plug after the nonaqueous electrolyte is injected into the outer shell 1.

[0024] A non-aqueous electrolyte comprises: a non-aqueous solvent; and an electrolyte salt dissolved in the non-aqueous solvent. Examples of non-aqueous solvents include carbonates, lactones, ethers, ketones, and esters, and two or more of these solvents may be mixed. When two or more solvents are mixed, a mixed solvent containing cyclic carbonates and chain carbonates is preferably used. For example, cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), while chain carbonates include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC). The non-aqueous solvent may also contain a halogen-substituted product in which at least a portion of the hydrogen atoms in the above solvents are replaced with halogen atoms such as fluorine. Examples of electrolyte salts include LiPF6, LiBF4, LiCF3SO3, and mixtures thereof. The amount of electrolyte salt dissolved in the non-aqueous solvent may be, for example, 0.5 to 2.0 mol / L. Additives such as vinylene carbonate (VC) may also be added as appropriate.

[0025] Hereinafter, the positive electrode plate 4 , the negative electrode plate 8 , and the separator constituting the electrode assembly 3 , particularly the positive electrode plate 4 , will be described in detail.

[0026] [Positive plate]

[0027] like Figure 2 As shown, the positive electrode plate 4 comprises a positive electrode core 5; an undercoat layer 6 formed on the surface of the positive electrode core 5; and a positive electrode composite material layer 7 formed on the undercoat layer 6 of the positive electrode core 5. The positive electrode core 5 can be made of a foil of a metal that is stable in the positive electrode potential range, such as aluminum, or a thin film having such a metal disposed on the surface. The positive electrode composite material layer 7 includes, for example, a positive electrode active material, a binder as a binding material, and a conductive additive.

[0028] The undercoat layer 6 is formed by coating the surface of the positive electrode core 5 with a conductive auxiliary agent 6a ( Figure 3 ) and dried. The primer layer 6 comprises a conductive agent 6a and a binder as a binder. Carbon nanotubes (CNTs), which are carbon fibers, are preferably used as the conductive agent 6a. The average diameter of the conductive agent 6a is 12 nm or less, preferably 9 nm or less, and more preferably 6 nm or less.

[0029] The average length of the conductive auxiliary agent 6 a used in the primer 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.

[0030] In this specification, the average diameter of the conductive aid 6a is a value obtained by observing 10 conductive aids 6a using a scanning electron microscope (SEM), measuring the diameters of the 10 conductive aids 6a, and calculating the number average of the diameters. In addition, the average length of the conductive aid 6a is a value obtained by observing 10 conductive aids 6a using a scanning electron microscope, measuring the lengths of the 10 conductive aids 6a, and calculating the number average of the lengths. More specifically, the conductive aid 6a is observed using a scanning electron microscope at an accelerating voltage of 5 kV, and an image is taken at 50,000 times the magnification (pixel count 1024×1280). In the captured image, the diameter and length of any 10 conductive aids 6a are measured, and their number averages are calculated to obtain the average diameter and average length.

[0031] 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, more preferably 200m 2 / g or more, more preferably 400m 2 The content of the conductive agent 6a in the primer layer 6 is preferably 75 to 97.5%. The bulk density of the conductive agent 6a is not particularly limited, but is preferably 0.008 to 0.01 g / cm 3 .

[0032] The adhesive used in the primer layer 6 can include fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, etc. These can be used alone or in combination. As the adhesive used in the primer layer 6, polyvinylidene fluoride (PVDF) is preferably used. The molecular weight of the adhesive of the primer layer 6 is more than 900,000, preferably more than 1.4 million. The content of the adhesive of the primer layer 6 is preferably 2.5 to 22.5%. A dispersant can also be added to the primer layer 6. The solid content ratio (NV) of the primer layer 6 is preferably 0.5 to 2.5%.

[0033] When the above-mentioned primer layer 6 is formed on the surface of the positive electrode core 5, a slurry for forming the primer layer is prepared as a primer dispersion liquid, in which the conductive auxiliary agent 6a is dispersed in a solvent. As a solvent for dispersing the conductive auxiliary agent 6a, N-methyl-2-pyrrolidone (NMP) can be mentioned. Then, the prepared slurry is applied to the surface of the positive electrode core 5 by a gravure coating method or the like, and dried to form the primer layer 6. For example, during drying, a heating treatment in a hot air circulation path can be used, but the drying method is not limited thereto.

[0034] Furthermore, the thickness of the primer layer 6 is less than 0.20 μm, preferably less than 0.15 μm, and more preferably less than 0.10 μm. In this specification, the thickness of the primer layer 6 is the thickness of the cross section of the primer layer 6 processed by the cross section processing device (CP) measured using a scanning electron microscope, and the value obtained by taking the number average. More specifically, for the thickness of the primer layer 6, a scanning electron microscope is used to observe the cross section at an accelerating voltage of 5 kV, and a 50,000-fold image (number of pixels 1024×1280) is taken. In the captured image, for the positions of any 5 points, the length from the upper part of the positive electrode core 5 to the upper part of the primer layer 6 is measured respectively, and their number average is calculated to obtain the thickness of the primer layer 6. By using such a primer layer 6, the interface resistance of the swollen positive electrode plate 4 can be reduced. The surface coverage of the primer layer 6 relative to the positive electrode core 5 is preferably 20 to 100%.

[0035] The positive electrode plate 4 can be produced, for example, as follows: a primer layer 6 is formed on the surface of the positive electrode core 5, a positive electrode composite material slurry containing a positive electrode active material, a binder, a conductive aid, etc. is applied to the primer layer 6 of the positive electrode core 5, and after drying to form a positive electrode composite material layer 7, the positive electrode composite material layer 7 is rolled to produce it.

[0036] Examples of positive electrode active materials include lithium transition metal oxides containing transition metal elements such as Co, Mn, and Ni. Examples of lithium transition metal oxides include Li 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 M y 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 can be used alone or in combination. From the perspective of achieving a high capacity of the secondary battery 100, the positive electrode active material preferably contains Li x NiO2、Li xCo y Ni 1-y O2、Li x Ni 1-y M y O z Lithium nickel composite oxides such as (M: at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and B, 0<x≤1.2, 0<y≤0.9, 2.0≤z≤2.3).

[0037] The conductive additive used in the positive electrode composite material layer 7 can include carbon black (CB), acetylene black (AB), Ketjen black, carbon nanotubes (CNT), graphite and other carbon particles. These can be used alone or in combination of two or more. As the conductive additive used in the positive electrode composite material layer, carbon black is preferably used.

[0038] The binder used in the positive electrode composite material layer 7 can include fluorine-based resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, etc. These can be used alone or in combination with two or more. As the conductive additive used in the positive electrode composite material layer 7, polyvinylidene fluoride is preferably used. The molecular weight of the binder of the positive electrode composite material layer 7 is more than 900,000, preferably more than 1.4 million.

[0039] In the positive electrode plate 4 prepared as described above, the primer layer 6 contains a conductive additive 6a having an average diameter of 12 nm or less, the molecular weight of the binder used in the primer layer 6 and the positive electrode composite material layer 7 is 900,000 or more, and the thickness of the primer layer 6 is 0.20 μm or less. As a result, the interface resistance of the positive electrode plate 4 swollen by the non-aqueous electrolyte containing a non-aqueous solvent can be sufficiently reduced. Figure 3 Explain this.

[0040] Figure 3 This is a diagram schematically showing the distribution of the conductive additive 6 a when the undercoat layer 6 is viewed from a direction perpendicular to the planar direction. Figure 3In the figure, all the conductive aids 6a are shown as separated, but it is speculated that there are actually several to 10 overlapping ones. For example, the average diameter of the conductive aid 6a is 12nm or less, so the gap between the surface of the positive electrode core 5 and the positive electrode composite material layer 7 after swelling is easily reduced. Therefore, it is speculated that the conductive aid 6a easily forms an electrical path between the positive electrode core 5 and the positive electrode composite material layer 7, thereby reducing the interface resistance. In addition, the molecular weight of the binder used in the primer 6 and the positive electrode composite material layer 7 is 900,000 or more, thereby suppressing the bulging of the binder when the positive electrode plate 4 is immersed in the electrolyte. Therefore, the gap between the surface of the positive electrode core 5 and the positive electrode composite material layer 7 after swelling is also easily reduced, so it is speculated that the interface resistance can be reduced in the same way as above. Furthermore, by making the thickness of the primer 6 0.20μm or less, the gap between the surface of the positive electrode core 5 and the positive electrode composite material layer 7 after swelling is also easily reduced, so it is speculated that the interface resistance can be reduced in the same way as above.

[0041] [Negative plate]

[0042] The negative electrode plate 8 comprises a negative electrode core and a negative electrode composite material layer formed on the surface of the negative electrode core. The negative electrode core can be made of, for example, a foil of a metal stable within the negative electrode potential range, such as copper, or a thin film having such a metal disposed on the surface. The negative electrode composite material layer contains a negative electrode active material. The negative electrode plate 8 can be manufactured by applying a negative electrode composite material slurry containing the negative electrode active material onto the negative electrode core, drying the slurry to form the negative electrode composite material layer, and then rolling the negative electrode composite material layer.

[0043] As the negative electrode active material, there is no particular limitation as long as it can reversibly store and release lithium ions. For example, carbon materials such as natural graphite and artificial graphite, metals such as silicon (Si) and tin (Sn) alloyed with lithium, or alloys and composite oxides containing metal elements such as Si and Sn can be used. As the negative electrode active material, carbon materials are preferred, and natural graphite is more preferred. The negative electrode active material can be used alone or in combination of two or more.

[0044] [Separator]

[0045] The separator may be, for example, a porous sheet having ion permeability and insulating properties. Specific examples of the porous sheet include microporous films, woven fabrics, non-woven fabrics, and the like. As materials for the separator, olefin resins such as polyethylene and polypropylene, and cellulose are ideal. The separator may also be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin resin. Alternatively, a multilayer separator comprising a polyethylene layer and a polypropylene layer may be used, or a separator having a surface coated with a material such as an aramid resin or ceramic may be used.

[0046] <Example>

[0047] Hereinafter, the positive electrode plate 4 as the electrode plate for the non-aqueous electrolyte secondary battery of the present disclosure will be further described with reference to examples, but the present disclosure is not limited to these examples.

[0048] <Example 1>

[0049] [Production of positive electrode plate]

[0050] As the positive electrode active material, LiNi, a lithium nickel cobalt manganese composite oxide, was used. 0.35 Co 0.35 Mn 0.30 The composite oxide shown in O2. The positive electrode active material, PVDF as a binder, and carbon black are mixed in a mass ratio of 90.3:2.7:7.0, and kneading is performed while adding N-methyl-2-pyrrolidone to prepare a positive electrode composite material slurry. The molecular weight of the PVDF of the composite material layer is set to 1.1 million. In addition, a primer dispersion containing carbon nanotubes as a conductive aid 6a is applied to both sides of a long strip of positive electrode core 5 formed of aluminum foil with a thickness of 15 μm, and the coating is dried to obtain a positive electrode core 5 with a primer layer 6 formed on the surface. At this time, the average diameter of the conductive aid 6a is set to 7.5 nm, the average length of the conductive aid 6a is set to 100 μm, and the BET specific surface area is set to 550 m 2 / g. PVDF with a molecular weight of 1.1 million was used as a binder for the primer layer 6. The thickness of the primer layer 6 was set to 0.15 μm. Table 1 shows the conductive agent 6a, PVDF, and thickness of the primer layer 6 of the primer layer of Example 1. Table 1 shows Examples 2 to 8 and Comparative Examples 1 to 5 described later. In Table 1, the average diameter and average length of the conductive agent are shown as diameter and length, respectively.

[0051] [Table 1]

[0052]

[0053] Next, the positive electrode composite material slurry was applied to the undercoat layer 6 of the positive electrode core 5 and the coating was dried. The packing density was 2.5 g / cm 3 The dried coating film is compressed in a manner and then cut into a predetermined electrode size, thereby producing a positive electrode plate 4 having positive electrode composite material layers 7 formed on both sides of a positive electrode core 5 .

[0054] <Example 2>

[0055] A positive electrode plate 4 was produced in the same manner as in Example 1 except that the thickness of the undercoat layer 6 was set to 0.08 μm. The produced positive electrode plate 4 is designated as Example 2.

[0056] <Example 3>

[0057] A positive electrode plate 4 was produced in the same manner as in Example 1 except that the thickness of the undercoat layer 6 was set to 0.07 μm. The produced positive electrode plate 4 is designated as Example 3.

[0058] <Example 4>

[0059] A positive electrode plate 4 was produced in the same manner as in Example 1 except that the thickness of the undercoat layer 6 was set to 0.06 μm. The produced positive electrode plate 4 is referred to as Example 4.

[0060] <Example 5>

[0061] A positive electrode plate 4 was prepared in the same manner as in Example 1 except that the thickness of the undercoat layer 6 was set to 0.08 μm and the molecular weights of the PVDF used in the undercoat layer 6 and the PVDF used in the positive electrode composite material layer 7 were set to 1.4 million.

[0062] <Example 6>

[0063] A positive electrode plate 4 was prepared in the same manner as in Example 1 except that the thickness of the undercoat layer 6 was set to 0.07 μm and the molecular weight of the PVDF used in the positive electrode material layer 7 was set to 1.4 million.

[0064] <Example 7>

[0065] The average diameter of the conductive additive 6a was 12 nm, the average length was 20 μm, and the BET specific surface area was 270 m 2 / g and the thickness of the undercoat layer 6 was set to 0.09 μm, a positive electrode plate 4 was produced in the same manner as in Example 1. The produced positive electrode plate 4 is designated as Example 7.

[0066] <Example 8>

[0067] A positive electrode plate 4 was prepared in the same manner as in Example 1 except that the thickness of the undercoat layer 6 was set to 0.09 μm and the molecular weights of the PVDF used in the undercoat layer 6 and the PVDF used in the positive electrode composite material layer 7 were each set to 900,000.

[0068] <Comparative Example 1>

[0069] A positive electrode plate was produced in the same manner as in Example 1 except that the thickness of the undercoat layer was set to 0.32 μm.

[0070] The prepared positive electrode plate is used as Comparative Example 1.

[0071] <Comparative Example 2>

[0072] A positive electrode plate was prepared in the same manner as in Example 1 except that the thickness of the primer layer was changed to 0.08 μm and the molecular weights of the PVDF used in the primer layer and the PVDF used in the composite material layer were changed to 700,000.

[0073] <Comparative Example 3>

[0074] A positive electrode plate was prepared in the same manner as in Example 1 except that the thickness of the primer layer was changed to 0.07 μm and the molecular weight of the PVDF used in the composite material layer was changed to 700,000. The prepared positive electrode plate was designated as Comparative Example 3.

[0075] <Comparative Example 4>

[0076] The average diameter of the conductive additive was 50 nm, the average length was 10 μm, and the BET specific surface area was 110 m 2 / g and the thickness of the undercoat layer was 1.34 μm, a positive electrode plate was produced in the same manner as in Example 1. The produced positive electrode plate is designated as Comparative Example 4.

[0077] <Comparative Example 5>

[0078] The average diameter of the conductive additive was 50 nm, the average length was 10 μm, and the BET specific surface area was 110 m 2 / g and the thickness of the undercoat layer was 0.18 μm, a positive electrode plate was produced in the same manner as in Example 1. The produced positive electrode plate is designated as Comparative Example 5.

[0079] [Measurement of interface resistance]

[0080] In the positive electrode plates 4 of each embodiment and each comparative example, the resistance between the positive electrode core 5 and the positive electrode composite material layer 7, that is, the interface resistance (area resistivity Ωcm 2 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), the interface resistance was measured. The interface resistance was measured using an electrode resistance meter (RM2610) manufactured by Hioki Electric Co., Ltd.

[0081] Here, the interface resistance of the electrode plate swollen with a non-aqueous solvent and dried is evaluated. It is difficult to directly measure the interface resistance of the electrode plate swollen with a non-aqueous solvent. Therefore, for the electrode plate, the interface resistance is measured and evaluated in a swollen and dried state close to the swollen state and capable of measuring the interface resistance. In order to prepare the positive electrode plate 4 after swelling and drying, the positive electrode plate 4 is compressed in the above-mentioned manner, placed in a dimethyl carbonate liquid, and left overnight at a temperature of 85°C. The positive electrode plate 4 is taken out of the liquid and dried in a dryer at a temperature of 130°C for 3 to 4 hours. After drying, the interface resistance is measured. Table 1 shows the results of the interface resistance after compression and the interface resistance after swelling and drying measured in each embodiment and each comparative example.

[0082] The results shown in Table 1 indicate that Examples 1-8 significantly reduced the interface resistance of the positive electrode plate 4 after swelling and drying, compared to Comparative Examples 1-5. This indicates that even when the electrode plate is swollen with the non-aqueous solvent, the interface resistance is significantly reduced, confirming the effectiveness of the present disclosure. For example, when comparing Examples 1-4 with Comparative Example 1, the thickness of the undercoat layer 6 in Examples 1-4 is reduced compared to Comparative Example 1, suggesting that the interface resistance of the positive electrode plate 4 after swelling and drying can be reduced.

[0083] Comparing Examples 2, 5, and 6 with Comparative Examples 2 and 3, although the thickness of the primer layer 6 is less than 0.20 μm, the molecular weight of PVDF in the primer layer 6 and the positive electrode composite material layer 7 is increased in Examples 2, 5, and 6 compared with Comparative Examples 2 and 3, which is believed to be able to reduce the interface resistance of the positive electrode plate 4 after swelling and drying.

[0084] Comparing Examples 2 and 7 with Comparative Example 4, although the molecular weight of PVDF in the primer layer 6 and the positive electrode composite material layer 7 is both above 900,000, compared with Comparative Example 4, in Examples 2 and 7, the thickness of the primer layer 6 becomes smaller and the diameter of the conductive additive 6a becomes smaller, which is believed to reduce the interface resistance of the positive electrode plate 4 after swelling and drying.

[0085] Comparing Example 4 and Comparative Example 5, although the thickness of the primer layer 6 is less than 0.20 μm and the molecular weight of the PVDF of the primer layer 6 and the positive electrode composite material layer 7 is more than 900,000, the diameter of the conductive additive 6a in Example 4 is smaller than that in Comparative Example 5, which is believed to reduce the interface resistance of the positive electrode plate 4 after swelling and drying.

[0086] Description of Reference Numerals

[0087] 1. Outer shell

[0088] 2 Sealing plate

[0089] 3 Electrode body

[0090] 4 positive plates

[0091] 4a Positive electrode core exposed part

[0092] 5. Positive electrode core

[0093] 6. Basecoat

[0094] 6a Conductive additive

[0095] 7. Positive electrode composite material layer

[0096] 8 Negative plate

[0097] 8a Negative electrode core exposed part

[0098] 9. Positive electrode collector

[0099] 10. Negative electrode current collector

[0100] 11 Positive terminal

[0101] 12 Positive electrode bolt

[0102] 13 Positive electrode insertion part

[0103] 14 Negative terminal

[0104] 15 Negative electrode bolt

[0105] 18 Negative electrode insertion part

[0106] 19 Electrolyte injection hole

[0107] 100 Secondary batteries.

Claims

1. An electrode plate for a non-aqueous electrolyte secondary battery, comprising: An electrode core having a primer layer formed on the surface thereof; and an electrode composite material layer formed on the primer layer of the electrode core, The average diameter of the conductive additive used in the primer layer is 7.5 nm or more and 12 nm or less. The molecular weight of the binder used in the primer layer is 900,000 or more and 1,400,000 or less. The thickness of the primer layer is 0.06 μm or more and 0.20 μm or less. The molecular weight of the binder used in the electrode composite material layer is 900,000 or more and 1,400,000 or less. The conductive additive is carbon nanotubes, The binder used in the primer layer and the binder used in the electrode composite material layer are both polyvinylidene fluoride.

2. The electrode plate for a non-aqueous electrolyte secondary battery according to claim 1, wherein The average length of the conductive additive is greater than 10 μm. The BET specific surface area of ​​the conductive additive is 100 m 2 / g or above.

3. A non-aqueous electrolyte secondary battery comprising 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 non-aqueous electrolyte secondary battery according to claim 1 or claim 2 .

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