Electrode plate and battery

Abstract

The invention provides an electrode plate and a battery. The electrode plate comprises an electrode current collector and an electrode coating positioned on at least one side surface of the electrode current collector, the electrode coating comprises an electrode active material layer and a bottom coating positioned between the electrode active material layer and the electrode current collector; the bottom coating comprises a first conductive agent, and an included angle alpha between the length direction of the first conductive agent and the surface of the electrode current collector is more than or equal to 60 degrees and less than or equal to 90 degrees. The impedance of the electrode plate and the internal resistance of the battery can be reduced.

Description

Technical Field

[0001] The present invention relates to the field of batteries, and in particular to an electrode sheet and a battery. Background Art

[0002] Electrode sheets are a crucial component of batteries. In related technologies, due to factors such as the electrode sheet's structure, the sheet's impedance is high, resulting in high internal resistance and impacting the battery's electrochemical performance. This is especially true for thick electrodes, where the thickness of the electrode sheet increases its resistivity and the diffusion impedance of active ions (such as lithium ions in lithium-ion batteries) within the electrode sheet. This, in turn, results in a higher internal resistance and impacts the battery's electrochemical performance. Summary of the Invention

[0003] The present invention provides an electrode sheet and a battery, which can reduce the impedance of the electrode sheet, especially the impedance of thick electrodes, thereby reducing the internal resistance of the battery, and effectively overcoming the defects of the prior art.

[0004] In one aspect of the present invention, an electrode sheet is provided, comprising an electrode current collector and an electrode coating located on at least one side of the electrode current collector; the electrode coating comprises an electrode active material layer and an undercoat layer located between the electrode active material layer and the electrode current collector; the undercoat layer comprises a first conductive agent, and an angle α between a length direction of the first conductive agent and a surface of the electrode current collector satisfies 60°≤α≤90°.

[0005] According to one embodiment of the present invention, 60°≤α≤88°.

[0006] According to one embodiment of the present invention, the first conductive agent includes one or more of carbon black, carbon nanotubes, and graphene.

[0007] According to one embodiment of the present invention, the particle size D50 of the carbon black is 25 to 85 nm.

[0008] According to one embodiment of the present invention, the aspect ratio of the carbon nanotubes is 500-800.

[0009] According to one embodiment of the present invention, the average sheet diameter of the graphene is 0.5 to 5 μm.

[0010] According to one embodiment of the present invention, the mass percentage of the first conductive agent in the primer layer is 75% to 98%.

[0011] According to one embodiment of the present invention, the primer layer further includes a first binder.

[0012] According to one embodiment of the present invention, the primer layer further includes an electrode active material.

[0013] According to one embodiment of the present invention, the thickness of the primer layer is 2 to 6 μm.

[0014] According to one embodiment of the present invention, the thickness of the electrode active material layer is 90 to 110 μm.

[0015] According to one embodiment of the present invention, the electrode sheet is a positive electrode sheet.

[0016] According to one embodiment of the present invention, the electrode active material layer includes an electrode active material, and the electrode active material includes one or more of lithium iron phosphate, lithium cobalt oxide, and a positive electrode ternary material.

[0017] According to one embodiment of the present invention, the electrode sheet is a negative electrode sheet.

[0018] Another aspect of the present invention provides a battery comprising the above-mentioned electrode sheet.

[0019] The implementation of the present invention has at least the following beneficial effects: by introducing an undercoat layer containing a first conductive agent between the electrode active material layer and the electrode current collector, and ensuring that the angle α between the length direction of the first conductive agent in the undercoat layer and the surface of the electrode current collector satisfies 60°≤α≤90°, the vertical orientation of the first conductive agent in the undercoat layer can reduce the contact impedance between the electrode active material layer and the electrode current collector. Furthermore, the vertical orientation of the first conductive agent in the undercoat layer can also reduce the obstruction of active ion diffusion and reduce the liquid-phase diffusion impedance of the electrode sheet. As a result, the present invention can reduce the resistivity of the electrode sheet, the liquid-phase diffusion impedance, and the internal resistance of the battery, thereby improving the electrochemical performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic structural diagram of an electrode sheet according to an embodiment of the present invention;

[0021] Figure 2 This is a schematic structural diagram of a magnetic component in a process of preparing an electrode sheet according to an embodiment of the present invention;

[0022] Figure 3 Schematic diagram of the arrangement structure of N-pole magnetic blocks and S-pole magnetic blocks in a magnetic assembly according to an embodiment of the present invention.

[0023] Explanation of reference numerals: 1: electrode current collector; 2: electrode coating; 21: undercoat layer; 22: electrode active material layer; 3: magnetic component; 31: S-pole magnetic block; 32: N-pole magnetic block; H 21 : Thickness of the primer layer; H 22: thickness of the electrode active material layer; A: length direction of the first conductive agent; T: thickness direction of the electrode sheet; B: moving direction of the electrode current collector 1 coated with the primer slurry; C: first arrangement direction of the S-pole magnetic block and the N-pole magnetic block; D: magnetic field direction; E: thickness direction of the magnetic component; F: second arrangement direction of the S-pole magnetic block and the N-pole magnetic block; α: angle between the length direction of the first conductive agent and the surface of the electrode current collector; β: angle between the moving direction of the electrode current collector 1 coated with the primer slurry and the first arrangement direction of the S-pole magnetic block and the N-pole magnetic block. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below. The specific embodiments listed below are only for describing the principles and features of the present invention. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts are within the scope of protection of the present invention.

[0025] An embodiment of the present invention provides an electrode sheet, such as Figure 1 As shown, the electrode sheet includes an electrode current collector 1 and an electrode coating 2 located on at least one side surface of the electrode current collector 1; the electrode coating 2 includes an electrode active material layer 22 and an undercoat layer 21 located between the electrode active material layer 22 and the electrode current collector 1; the undercoat layer 21 includes a first conductive agent 20, and the angle α between the length direction A of the first conductive agent 20 and the surface of the current collector (the verticality of the first conductive agent) satisfies 60°≤α≤90°.

[0026] According to the inventor's research, a conductive coating (or primer 21) is provided between the electrode active material layer 22 of the electrode sheet and the electrode current collector 1, and the angle α between the length direction A of the first conductive agent 20 in the primer 21 and the surface of the electrode current collector 1 satisfies 60°≤α≤90°, so that the first conductive agent 20 in the primer 21 has good verticality in the thickness direction of the primer 21 (that is, the angle between the length direction A of the first conductive agent 20 and the thickness direction T of the electrode coating 2 (also the thickness direction of the electrode sheet) is closer to 0°). The first conductive agent 20 is basically arranged vertically in the primer 21, which is conducive to connecting the electrode active material layer 22 and the electrode current collector 1 and providing a channel for conducting electrons, that is, providing long-range conductivity, reducing the contact impedance between the electrode active material layer 22 (or dressing layer) and the electrode current collector 1. At the same time, the vertically oriented first conductive agent 20 in the primer 21 is more consistent with the movement direction of active ions (such as lithium ions) during the charging and discharging process of the battery, which can reduce the obstruction to the transmission of active ions and reduce the ion diffusion impedance. Therefore, the embodiments of the present invention can reduce the resistivity of the electrode sheet, the ion diffusion impedance (liquid phase diffusion impedance) and the internal resistance of the battery, and improve the electrochemical properties such as the rate performance of the electrode sheet and the battery.

[0027] Illustratively, the angle α between the length direction A of the first conductive agent 20 in the primer layer 21 and the surface of the electrode current collector 1 can be 60°, 63°, 65°, 68°, 70°, 73°, 75°, 78°, 80°, 83°, 85°, 88°, 90° or a range consisting of any two of them.

[0028] Generally, during the preparation of the electrode sheet, a magnetic induction technique can be used to induce the vertical orientation of the first conductive agent 20 in the primer layer 21, so that the included angle α between its length direction and the surface of the electrode current collector 1 satisfies 60°≤α≤90°. For example, the primer layer 21 can be formed by a coating method. After the primer slurry for forming the primer layer 21 is applied to the electrode current collector 1, a magnetic field can be applied thereto to induce the orientation of the first conductive agent 20 therein by the magnetic field. After subsequent treatment such as drying, the primer layer 21 is formed.

[0029] In some preferred embodiments, 60°≤α≤80°. This can effectively reduce the resistivity of the electrode sheet, the liquid phase diffusion impedance and the internal resistance of the battery, while facilitating the formation of the bottom coating 21 by magnetic induction and other means, thereby improving the production efficiency and yield of the electrode sheet.

[0030] In the above-mentioned primer layer 21, the first conductive agent 20 may include one or more of carbon black, carbon nanotubes (CNTs), and graphene, which is beneficial to reducing the resistivity of the electrode sheet, liquid phase diffusion impedance, and battery internal resistance.

[0031] In specific implementation, a primer slurry containing one or more of carbon black, carbon nanotubes (CNTs), and graphene can be applied to the surface of the electrode current collector 1, and then a magnetic field is applied to induce the first conductive agents 20 to be vertically oriented, achieving good verticality and reducing the electrode sheet impedance.

[0032] like Figure 1 As shown, the first conductive agent 20 exists in the base coating layer 21 in the form of particles, and the particles can be first conductive agent 20 particles (which can be spherical, quasi-spherical, elongated (such as carbon nanotubes), or flakes (such as graphene), or agglomerates formed by agglomeration of the aforementioned first conductive agent 20 particles. The length direction A of the aforementioned first conductive agent 20 can refer to the direction of the first conductive agent 20 particles or the length direction of the agglomerates formed by agglomeration of the first conductive agent 20 particles.

[0033] Specifically, when the first conductive agent 20 includes carbon black, it mainly exists in the base coating 21 in the form of aggregates (i.e., agglomerates, or polymers), that is, the carbon black particles in the base coating 21 agglomerate to form aggregate particles (carbon black agglomerates), and the aggregate particles are distributed in the base coating 21. The aggregate particles are generally formed by carbon black particles connected to each other in the vertical direction (the thickness direction of the base coating 21) to form a spindle-shaped structure with thinner upper and lower ends and thicker middle parts. Its arrangement in the vertical direction can connect the electrode active material layer 22 and the electrode current collector 1, provide a smooth electron channel, reduce the contact impedance between the electrode active material layer 22 and the electrode current collector 1, and reduce the transmission obstruction of active ions.

[0034] Among them, when the first conductive agent 20 is carbon black, the length direction of the first conductive agent 20 (i.e., the length direction of carbon black) A refers to the length direction of the agglomerate formed by the agglomeration of carbon black (i.e., the length direction of the agglomerate particles formed by the agglomeration of carbon black particles), that is, the angle between the length direction of the agglomerate formed by the agglomeration of carbon black and the surface of the electrode current collector 1 is the above-mentioned angle α (60°≤α≤90°).

[0035] Furthermore, when the first conductive agent 20 is a carbon nanotube, the length direction A of the first conductive agent 20 refers to the length direction of the carbon nanotube. The carbon nanotubes are less likely to aggregate in the primer layer 21, and are generally arranged vertically within the primer layer 21 (i.e., satisfying 60°≤α≤90°). In practice, the carbon nanotubes in the primer slurry can be evenly dispersed by stirring, further reducing aggregation. When a magnetic field is applied to the primer slurry, the carbon nanotubes interact more effectively with the magnetic field, further facilitating a vertical alignment of the carbon nanotubes and reducing the impedance of the electrode sheet.

[0036] In addition, when the first conductive agent 20 is graphene, the length direction A of the first conductive agent 20 refers to the length direction of the graphene. Graphene has a sheet structure, and the graphene sheets are vertically arranged in the base coating 21, which helps reduce the resistivity and ion diffusion resistance of the electrode sheet.

[0037] Specifically, the carbon black particle size D50 (i.e., the median particle size of the carbon black) can be 25 to 85 nm, for example, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, or any two thereof. The carbon black particle size D50 (25 to 85 nm) refers to the particle size before carbon black agglomeration. That is, in the undercoat layer, carbon black agglomerates are formed by agglomerating carbon black particles having a particle size D50 of 25 to 85 nm.

[0038] By controlling the particle size D50 of carbon black within the above range (25-85 nm), it is beneficial to reduce the resistivity of the electrode sheet, the liquid phase diffusion impedance and the internal resistance of the battery. The reason for this is that the particle size D50 of carbon black within the above range (25-85 nm) is beneficial to the carbon black having a more suitable degree of agglomeration under the induction of a magnetic field, improving the contact of carbon black, and reducing the resistivity of the electrode sheet, the liquid phase diffusion impedance and the internal resistance of the battery.

[0039] Specifically, the aspect ratio of the carbon nanotubes can be 500 to 800, for example, 500, 550, 600, 650, 700, 750, 800 or a range consisting of any two of them, which is beneficial to reducing the resistivity of the electrode sheet, the liquid phase diffusion impedance and the internal resistance of the battery. The reason for this is that by making the aspect ratio of the carbon nanotubes within the above range (500 to 800), it is beneficial to improve the contact between the carbon nanotubes, and at the same time improve the dispersion of the carbon nanotubes, inhibit the mutual entanglement between the carbon nanotubes, and make them easier to be separated during the magnetic field induction process, which is beneficial to improve the verticality α of the carbon nanotubes, thereby reducing the resistivity of the electrode sheet, the liquid phase diffusion impedance and the internal resistance of the battery.

[0040] Specifically, the average sheet diameter of graphene can be 0.5 to 5 μm, for example, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm or a range consisting of any two of them, which is beneficial to reducing the resistivity of the electrode sheet, the liquid phase diffusion impedance and the internal resistance of the battery. The reason for this is that by making the average sheet diameter of graphene within the above range (0.5 to 5 μm), the graphene has a more suitable size, and after being induced by the magnetic field, graphene particles with high verticality α are formed in the base coating 21. At the same time, graphene has lower steric hindrance, which is beneficial for the magnetic field to act on the graphene, that is, it is beneficial for the graphene particles to be induced by the magnetic field, thereby increasing the verticality α of the graphene, thereby reducing the resistivity of the electrode sheet, the liquid phase diffusion impedance and the internal resistance of the battery.

[0041] In an embodiment of the present invention, the first conductive agent 20 in the base coating 21 is vertically oriented, which is conducive to connecting the electrode active material layer 22 and the electrode current collector 1 through less first conductive agent 20 and providing a channel for conducting electrons, that is, providing long-range conductivity. Therefore, the present invention can reduce the resistivity of the electrode sheet, the liquid phase diffusion impedance and the internal resistance of the battery while also reducing the amount of the first conductive agent 20.

[0042] In some embodiments, the mass percentage of the first conductive agent 20 in the primer layer 21 (i.e., the ratio of the total mass of the first conductive agent 20 to the total mass of the primer layer 21) can be 75% to 98%, for example, 75%, 78%, 80%, 83%, 85%, 88%, 90%, 95%, 98%, or a range consisting of any two thereof, which is beneficial for reducing the resistivity of the electrode sheet, liquid phase diffusion impedance, and battery internal resistance. When the primer layer 21 contains multiple types of first conductive agents 20, the total mass of the first conductive agents 20 refers to the sum of the masses of these conductive agents.

[0043] In addition, the base coating 21 may also include a first binder. By introducing the first binder, it is beneficial to reduce the impedance of the electrode sheet while improving the adhesion between the electrode active material layer 22 and the base coating 21, and the adhesion between the base coating 21 and the electrode current collector 1, thereby improving the structural stability of the electrode sheet.

[0044] Specifically, the first binder may be a conventional binder material in the art. For example, the first binder includes polyvinylidene fluoride (PVDF).

[0045] Taking into further consideration factors such as the impedance and structural stability of the electrode sheet, in some embodiments, the mass percentage of the first binder in the base coating 21 can be 1.5% to 2.5%, for example, 1.5%, 1.8%, 2%, 2.3%, 2.5% or a range consisting of any two of them.

[0046] In addition, the base coating layer 21 may or may not include electrode active substances, and the mass percentage of the electrode active substances in the base coating layer 21 is 0 to 18%, for example, 0, 0.5%, 1%, 3%, 5%, 8%, 10%, 13%, 15%, 18% or a range consisting of any two of them.

[0047] Generally, the electrode active material layer 22 includes an electrode active material. When the undercoat layer 21 contains an electrode active material, the electrode active material in the undercoat layer 21 and the electrode active material in the electrode active material layer 22 may be the same or different.

[0048] In addition, the thickness H of the primer layer 21 is 21It can be 2 to 6 μm, for example, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm or any two of them. This helps the base coating 21 provide more sufficient space for the vertical arrangement of the first conductive agent 20, improves the verticality α of the first conductive agent 20, and at the same time maintains a relatively thin thickness of the base coating 21, thereby improving the energy density and other properties of the electrode sheet.

[0049] In the embodiment of the present invention, the primer layer 21 may be provided on one surface of the electrode current collector 1, or the primer layer 21 may be provided on both surfaces of the opposite sides in the thickness direction of the electrode current collector 1 (i.e., the front and back surfaces of the electrode current collector 1). When the primer layer 21 is provided on both the front and back surfaces of the electrode current collector 1, the thickness H of the primer layer 21 is 21 It refers to the thickness of the primer layer 21 on one surface of the electrode current collector 1 , not the sum of the thicknesses of the primer layers 21 on both surfaces.

[0050] Generally, thick electrode sheets have a thicker electrode active material layer 22, which maintains a higher energy density and facilitates longer battery life. However, the thicker the electrode active material layer 22, the higher the impedance. Embodiments of the present invention can effectively reduce the impedance of thick electrodes, specifically reducing the resistivity, ion diffusion impedance, and internal resistance of the thick electrode, thereby improving electrochemical properties such as the battery's rate capability.

[0051] In some embodiments, in the above-mentioned electrode sheet, the thickness H of the electrode active material layer 22 is 22 It can be 90 to 110 μm, for example, 90 μm, 93 μm, 95 μm, 98 μm, 100 μm, 103 μm, 105 μm, 108 μm, 110 μm or a range consisting of any two of them. By introducing the above-mentioned primer layer 21 between the electrode active material layer 22 and the electrode current collector 1, the angle α between the length direction A of the first conductive agent 20 in the primer layer 21 and the surface of the electrode current collector 1 is controlled to meet 60°≤α≤90°, which can effectively reduce the resistivity of the electrode sheet, the liquid phase diffusion impedance and the internal resistance of the battery, while maintaining the high energy density and other properties of the electrode sheet, thereby further improving the overall performance of the battery.

[0052] In the embodiment of the present invention, an electrode active material layer 22 may be provided on one side of the electrode current collector 1, or an electrode active material layer 22 may be provided on both the front and back surfaces of the electrode current collector 1. When an electrode active material layer 22 is provided on both the front and back surfaces of the electrode current collector 1, the thickness H of the electrode active material layer 22 may be 22 It refers to the thickness of the electrode active material layer 22 on one surface of the electrode current collector 1 , not the sum of the thicknesses of the electrode active material layers 22 on both surfaces.

[0053] In some embodiments, the above-mentioned electrode sheet is a positive electrode sheet, and accordingly, the above-mentioned electrode current collector 1 is a positive electrode current collector, the electrode active material layer 22 is a positive electrode active material layer, and the electrode active material is a positive electrode active material, which may include one or more of lithium iron phosphate, lithium cobalt oxide and positive electrode ternary materials, wherein the positive electrode ternary material includes, for example, nickel-cobalt-manganese ternary material and / or nickel-cobalt-aluminum ternary material.

[0054] The embodiment of the present invention may adopt a conventional positive electrode current collector in the art, for example, the positive electrode current collector includes aluminum foil.

[0055] In other embodiments, the electrode sheet may be a negative electrode sheet, and accordingly, the electrode current collector 1 is a negative electrode current collector, the electrode active material layer 22 is a negative electrode active material layer, and the electrode active material is a negative electrode active material, which may include graphite.

[0056] The embodiment of the present invention may adopt a conventional negative electrode current collector in the art, for example, the negative electrode current collector includes copper foil.

[0057] In general, the electrode active material layer 22 further includes materials such as a second binder and a second conductive agent. Based on the total mass of the electrode active material layer 22, the mass fraction of the electrode active material (i.e., the ratio of the mass of the electrode active material to the total mass of the electrode active material layer 22) can be 70% to 99%, for example, 70%, 75%, 80%, 85%, 90%, 93%, 95%, 97%, 99% or a range consisting of any two thereof. The mass fraction of the second conductive agent can be 0.5 % to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15% or a range consisting of any two thereof; the mass fraction of the second binder can be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15% or a range consisting of any two thereof.

[0058] In some embodiments, in the positive electrode active material layer, the mass ratio of the second conductive agent to the positive electrode active material may be 0.5% to 1.5%, and the mass ratio of the second binder to the positive electrode active material may be 1.5% to 2.5%.

[0059] In an embodiment of the present invention, the second conductive agent in the electrode active material layer 22 can be a conventional conductive material in the art, for example, the conductive agent includes one or more of conductive carbon black, carbon nanotubes (CNTs), acetylene black, graphene, Ketjen black, and carbon fiber.

[0060] In an embodiment of the present invention, the second binder in the electrode active material layer 22 can be a conventional binding material in the art. For example, when the electrode sheet is a negative electrode sheet, the second binder may include one or more of styrene-butadiene rubber (SBR), polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyvinyl alcohol, and sodium polyacrylate; when the electrode sheet is a positive electrode sheet, the second binder may include one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, etc.

[0061] In addition, when the electrode sheet is a negative electrode sheet, the electrode active material layer 22 (negative electrode active material layer) may further include a thickener. The thickener may include a carboxymethyl cellulose (CMC) thickener, specifically a carboxymethyl cellulose salt, such as sodium carboxymethyl cellulose (CMC-Na).

[0062] In an embodiment of the present invention, the primer layer 21 and the electrode active material layer 22 can be formed by a coating method. In a specific implementation, the primer slurry used to form the primer layer 21 can be coated on the surface of the electrode current collector 1, and the electrode current collector 1 coated with the primer slurry is passed through a magnetic field region with a magnetic field, thereby magnetically inducing the second conductive agent in the primer slurry coated on the electrode current collector 1 to make it vertically oriented; after the electrode current collector 1 coated with the primer slurry passes through the magnetic field region, it is dried, specifically, it can be placed in an oven for drying, so that the primer slurry on the surface of the electrode current collector 1 is dried to form the primer layer 21; then the slurry for forming the electrode active material layer 22 is coated on the surface of the primer layer 21. After drying, rolling and other processes, the electrode active material layer 22 is formed on the surface of the primer layer 21 to obtain an electrode sheet.

[0063] When a primer layer 21 is formed on both the front and back surfaces of the electrode collector 1, the primer slurry can be first coated on one surface of the electrode collector 1, and then enter the magnetic field area, and make the side of the electrode collector 1 coated with the primer slurry face away from the magnetic component 3 (that is, make the side of the electrode collector 1 not coated with the primer slurry face the magnetic component 3), after passing through the magnetic field area, it is dried to form a primer layer 21 on one surface of the electrode collector 1; then the primer slurry is coated on the other surface of the electrode collector 1, and then enter the magnetic field area, and make the side of the electrode collector 1 coated with the primer slurry face away from the magnetic component 3 (that is, make the side of the electrode collector 1 already formed with the primer 21 face the magnetic component 3), after passing through the magnetic field area, it is dried to form a primer layer 21 on the other surface of the electrode collector 1.

[0064] like Figure 2 As shown, the magnetic field in the magnetic field region is provided by the magnetic assembly 3, which includes staggered N-pole magnetic blocks 32 and S-pole magnetic blocks 31, wherein Figure 2 and Figure 3 As shown, the N-pole magnetic blocks 32 and the S-pole magnetic blocks 31 are arranged alternately in the first arrangement direction C and in the second arrangement direction F. The adjacent N-pole magnetic blocks 32 and S-pole magnetic blocks 31 can be in direct contact (close contact), and the magnetic field direction D of the generated magnetic field is basically perpendicular to the first arrangement direction C and the second arrangement direction F of the N-pole magnetic blocks 32 and S-pole magnetic blocks 31. The length of the magnetic field region in the first arrangement direction C of the N-pole magnetic blocks 32 and S-pole magnetic blocks 31 is basically equal to the length of the magnetic component 3, and the width of the magnetic field region in the second arrangement direction F of the N-pole magnetic blocks 32 and S-pole magnetic blocks 31 is basically equal to the width of the magnetic component 3.

[0065] The first arrangement direction C and the second arrangement direction F intersect, and may be substantially perpendicular to each other. Specifically, Figure 2 and Figure 3 As shown, the first arrangement direction C may be parallel to the length direction of the magnetic component 3 , and the second arrangement direction F may be parallel to the width direction of the magnetic component 3 .

[0066] Continue to refer Figure 2 and Figure 3 The thickness direction E of the magnetic component 3 is basically perpendicular to the first arrangement direction C and the second arrangement direction F of the N-pole magnetic block 32 and the S-pole magnetic block 31. In the process of the electrode collector 1 coated with the primer slurry passing through the magnetic field area, the electrode collector 1 coated with the primer slurry is located on one side of the thickness direction E of the magnetic component 3, and moves from one side of the magnetic component 3 in the first arrangement direction C to the other side of the magnetic component 3 in the first arrangement direction C. The width of the magnetic component 3 in the second arrangement direction F is greater than the width of the electrode collector 1 coated with the primer slurry in the second arrangement direction F, so that the magnetic field can cover the electrode collector 1 coated with the primer slurry.

[0067] When the electrode current collector 1 coated with the primer slurry passes through the magnetic field region, the moving direction B of the electrode current collector 1 coated with the primer slurry and the first arrangement direction C of the N-pole magnetic block 32 and the S-pole magnetic block 31 form an angle β.

[0068] In specific implementation, the length of the magnetic field area, the moving speed (travel speed) of the electrode collector 1 coated with the primer slurry when passing through the magnetic field area, the moving direction B of the electrode collector 1 coated with the primer slurry and the angle (deflection angle) β formed by the first arrangement direction C of the N-pole magnetic block 32 and the S-pole magnetic block 31, the distance between the electrode collector 1 coated with the primer slurry and the magnetic component 3, and other conditions can be adjusted to adjust the magnetic field strength and other conditions to induce the vertical arrangement of the first conductive agent 20 in the primer layer 21 and form a primer layer 21 that meets the preset α.

[0069] For example, the angle β formed by the moving direction B of the electrode current collector 1 coated with the primer slurry and the first arrangement direction C of the N-pole magnetic block 32 and the S-pole magnetic block 31 (the deflection angle of the electrode current collector 1 coated with the primer slurry) can satisfy 0°≤β≤10°; the length of the magnetic field region is, for example, 18 to 22 cm (such as 20 cm); the moving speed of the electrode current collector 1 coated with the primer slurry can be 1 to 5 m / min, for example, 1 m / min, 2 m / min, 3 m / min, 4 m / min, 5 m / min or a range consisting of any two of them; the distance between the electrode current collector 1 coated with the primer slurry and the magnetic component 3 can be 1 mm to 4 cm.

[0070] Among them, the distance between the electrode current collector 1 coated with the primer slurry and the magnetic component 3 refers to the vertical distance between the middle position of the magnetic component 3 in the first arrangement direction C of the N-pole magnetic block 32 and the S-pole magnetic block 31 and the electrode current collector 1 coated with the primer slurry.

[0071] In addition, the sizes of the N-pole magnetic block 32 and the S-pole magnetic block 31 can be the same. For example, the N-pole magnetic block 32 and the S-pole magnetic block 31 are both magnetic blocks with a length of 1 cm and a width of 1 cm (that is, their sizes are 1 cm*1 cm). That is, the length of the cross section of the N-pole magnetic block 32 perpendicular to the thickness direction E of the magnetic component 3 is 1 cm and the width is 1 cm, and the length of the cross section of the S-pole magnetic block 31 perpendicular to the thickness direction E of the magnetic component 3 is 1 cm and the width is 1 cm, but it is not limited to this.

[0072] In an embodiment of the present invention, a primer slurry for forming the primer layer 21 and an electrode slurry for forming the electrode active material layer 22 can be prepared by conventional methods in the art. For example, the first conductive agent 20 and the first binder, etc., which are used to form the primer layer 21, are dispersed in a first solvent. The first solvent includes, for example, N-methylpyrrolidone (NMP) and / or water (specifically, deionized water can be used) to prepare the primer slurry; the electrode active material, the second conductive agent, the second binder, etc., which are used to form the electrode active material layer 22, are dispersed in a second solvent. The second solvent includes, for example, (NMP) and / or water (specifically, deionized water can be used) to prepare the electrode slurry, and then the coating process and the like are performed.

[0073] According to the inventors' research, the steric hindrance between the second conductive agent in the electrode active material layer 22 and the main material (electrode active material) particles is large. If a magnetic field is applied to the second conductive agent in the electrode active material layer 22 in order to induce a vertical arrangement orientation, the conditions such as the magnetic field strength are stringent. In the embodiment of the present invention, a primer layer 21 containing a first conductive agent 20 is introduced between the electrode active material layer 22 and the electrode current collector 1, and a magnetic field is applied to the primer layer 21 to induce a vertical arrangement orientation of the first conductive agent 20 therein. Since the particles of the first conductive agent 20 are small, they are significantly affected by the magnetic field, and the force between the particles of the first conductive agent 20 is small, and the steric hindrance between them is small. Therefore, a good magnetic field induction effect can be achieved, that is, the vertical arrangement state of the first conductive agent 20 in the primer layer 21 is achieved, so that it satisfies 60°≤α≤90°. Therefore, it can not only effectively reduce the impedance of the electrode sheet, but also facilitate the production of the electrode sheet. Without changing the electrode sheet coating process, the demand for an ultra-strong magnetic field is weakened. It has the advantages of simplicity and feasibility, which is conducive to actual industrial application.

[0074] An embodiment of the present invention further provides a battery, comprising the above-mentioned electrode sheet. The battery has corresponding advantages to the above-mentioned electrode sheet, which will not be described in detail.

[0075] The battery of the embodiment of the present invention may be a lithium-ion battery (such as a lithium-ion power battery), a solar cell, or other new energy storage batteries.

[0076] Generally, a battery consists of an electrolyte, a cell, and an enclosure that encapsulates the cell. The electrolyte is injected into the cell within the enclosure, and the cell includes a positive electrode sheet, a negative electrode sheet, and a separator located between the positive and negative electrode sheets. The cell can be a laminated cell, meaning that the cell is composed of a stacked positive electrode sheet, a separator, and a negative electrode sheet.

[0077] In the embodiment of the present invention, the positive electrode sheet may be an electrode sheet having the above-mentioned primer layer 21 , or the negative electrode sheet may be an electrode sheet having the above-mentioned primer layer 21 , or both the positive electrode sheet and the negative electrode sheet may be electrode sheets having the above-mentioned primer layer 21 .

[0078] The electrolyte of the embodiment of the present invention can be a conventional electrolyte in the field. For example, the electrolyte is a non-aqueous electrolyte, which can specifically include an organic solvent and an electrolyte salt. The organic solvent includes, for example, one or more of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC), and the lithium salt includes, for example, lithium hexafluorophosphate (LiPF6), etc., but is not limited thereto.

[0079] In the embodiment of the present invention, the separator is used to separate the positive electrode sheet and the negative electrode sheet to prevent the positive electrode sheet and the negative electrode sheet from short-circuiting. The embodiment of the present invention can adopt conventional separators in the art, for example, the separator includes a polypropylene film, but is not limited thereto.

[0080] In the embodiment of the present invention, conventional packaging (shell) materials in the art may be used to package the battery cell, and the battery may be of a conventional battery type and structure in the art. For example, the battery may be a soft-package lithium-ion battery, and the packaging may include an aluminum-plastic film.

[0081] In the embodiment of the present invention, components such as positive electrode sheets, separators and negative electrode sheets can be assembled into a battery by conventional methods in the art. For example, the positive electrode sheets, separators and negative electrode sheets can be stacked to produce a stacked battery cell; the battery cell is then placed in a shell (outer packaging), and after processes such as liquid injection (i.e., injecting electrolyte) and packaging, the battery is produced.

[0082] In the embodiment of the present invention, after obtaining the negative electrode sheet, the cross section of the electrode coating 2 (the cross section is substantially parallel to the thickness direction of the electrode sheet) can be observed by scanning electron microscopy (SEM), and the film layers such as the undercoat layer 21 and the electrode active material layer 22 can be determined based on the characteristics such as the particle size and morphology of different regions, and the thickness H of the undercoat layer 21 can be measured. 21 , the thickness H of the electrode active material layer 22 22 , and the verticality α of the first conductive agent; wherein, when performing SEM analysis, the verticality (i.e., the angle between the length direction of the first conductive agent and the surface of the electrode current collector) α of at least 20 first conductive agent 20 particles in the test field is tested, and the average value is taken as the final verticality α test result.

[0083] In embodiments of the present invention, after obtaining the electrode sheet, the primer layer 21 can be subjected to SEM analysis to measure the size and other characteristics of the first conductive agent 20. Specifically, during the SEM analysis, the sizes of at least 20 first conductive agent 20 particles within the field of view are measured, and the average value is taken as the final test result. When the first conductive agent 20 is carbon black, the measured size of the first conductive agent 20 is the median particle size D50 of the carbon black; when the first conductive agent 20 is carbon nanotubes, the measured size of the first conductive agent 20 is the aspect ratio of the carbon nanotubes; and when the first conductive agent 20 is graphene, the measured size of the first conductive agent 20 is the average flake diameter of the graphene.

[0084] In a specific implementation, the battery can be disassembled to obtain the electrode sheet, and the negative electrode sheet is cleaned with an organic solvent (such as DMC) to wash away impurities such as electrolyte salt on the electrode sheet. After the electrode sheet is cleaned, it is dried to remove the organic solvent, and then the electrode sheet is subjected to the above-mentioned SEM and analysis processes to measure the thickness H of the primer layer 21. 21 , the thickness H of the electrode active material layer 22 22 , the size of the first conductive agent 20 in the primer layer 21 and other characteristics.

[0085] The present invention is further described below through specific examples.

[0086] 1. Preparation of positive electrode

[0087] (1) Mix the first conductive agent and PVDF (the type and amount of the first conductive agent are shown in Table 1), add NMP, stir evenly, and prepare a primer slurry;

[0088] (2) applying the primer slurry to one side of the aluminum foil, and allowing the aluminum foil coated with the primer slurry to enter the magnetic field region at a speed of 3 m / min (the length of the magnetic field region is 20 cm), and allowing the side of the aluminum foil coated with the primer slurry to face away from the magnetic component, so as to vertically orient the first conductive agent in the primer slurry through the magnetic field of the magnetic field region; after passing through the magnetic field region, entering the oven for drying to form a primer layer on one side of the aluminum foil; wherein the magnetic field in the magnetic field region is as follows: Figure 2 The magnetic assembly shown is applied, and the magnetic assembly is formed by alternatingly arranging 1 cm*1 cm N-pole magnetic blocks and 1 cm*1 cm S-pole magnetic blocks, with adjacent N-pole magnetic blocks and S-pole magnetic blocks in close contact, and there are 10 N-pole magnetic blocks and 10 S-pole magnetic blocks (the length of the magnetic assembly (also the length in the magnetic field direction) is 20 cm); the distance between the aluminum foil coated with the primer slurry and the magnetic assembly is about 1.5 mm, and in the process of the aluminum foil coated with the primer slurry passing through the magnetic field region, the moving direction B of the aluminum foil coated with the primer slurry and the first arrangement direction C of the N-pole magnetic blocks and the S-pole magnetic blocks form an angle (deflection angle of the aluminum foil coated with the primer slurry) β (see Table 1);

[0089] (3) continuously coating the primer slurry of step (1) on the other side of the aluminum foil, and following the process of step (2) (when passing through the magnetic field region, the side of the aluminum foil coated with the primer slurry faces away from the magnetic component), forming a primer layer on the other side of the aluminum foil to obtain a pole piece precursor with primer layers on both sides;

[0090] (4) Lithium iron phosphate, conductive carbon black, and PVDF were mixed in a mass ratio of 100:0.8:2.5, and NMP was added and stirred evenly to prepare a positive electrode slurry;

[0091] (5) The positive electrode slurry is coated on the front and back surfaces of the electrode precursor using a continuous coating device, and then placed in an oven for drying. After roller pressing, a positive electrode active material layer is formed to obtain a positive electrode sheet; wherein the thickness of the positive electrode active material layer is H 22 =96μm.

[0092] Examples 2 to 26: The differences from Example 1 are that the angle α between the length direction A of the first conductive agent in the primer layer and the surface of the electrode current collector (aluminum foil) (the verticality of the first conductive agent), the type of the first conductive agent, the size of the first conductive agent (carbon black particle size D50, aspect ratio of carbon nanotubes, average sheet diameter of graphene), the thickness H of the primer layer,21 , the mass percentage of the first conductive agent in the primer layer (the first conductive agent content in Table 1), the running speed of the aluminum foil coated with the primer slurry during the formation of the primer layer (the aluminum foil running speed in Table 1) and the deflection angle β are different. See Table 1 for details. Except for the differences shown in Table 1, the other conditions are the same as those in Example 1.

[0093] Comparative Example 1: The difference from Example 1 is that no primer layer is provided, that is, only the positive electrode active material layer is provided on both the front and back surfaces of the aluminum foil. For details, see Table 1. Except for the differences shown in Table 1, the other conditions are the same as those of Example 1.

[0094] Comparative Example 2: The difference from Example 1 is that, in the process of forming the primer layer, no magnetic field induction is performed, that is, the aluminum foil coated with the primer slurry does not enter the magnetic field area. Except for this process and the differences shown in Table 1, the other conditions are the same as those in Example 1.

[0095] The performance of the positive electrode sheets of each embodiment and comparative example was tested through the following process, and the results are shown in Table 2.

[0096] 3. 50% SOC DC internal resistance test

[0097] (1) Preparation of negative electrode sheet

[0098] Graphite, conductive carbon black, SBR, and CMC-Na were mixed in a mass ratio of 100:1:2.7:1.2, and deionized water was added and stirred to prepare a negative electrode slurry;

[0099] The negative electrode slurry is coated on the front and back surfaces of the copper foil. After drying and roller pressing, a negative electrode active material layer is formed on the front and back surfaces of the copper foil to produce a negative electrode sheet.

[0100] (2) Battery assembly

[0101] The positive electrode sheets, separators (polypropylene films with a thickness of 14 μm) and negative electrode sheets are alternately stacked to assemble into a laminated battery cell. The laminated battery cell is placed in an aluminum-plastic film and assembled into a soft-pack lithium-ion battery through processes such as liquid injection and packaging. The composition of the electrolyte used is as follows: the organic solvents are EC, EMC and DMC, the mass ratio of EC, EMC and DMC is 29:32:23, and the concentration of LiPF6 in the electrolyte is 1 mol / L.

[0102] (3) 50% SOC DC internal resistance test: At room temperature (25±5°C), the soft-pack lithium-ion battery was discharged at a constant current rate of 1 / 3C to 2.0V, charged at a constant current rate of 1 / 3C to 50% SOC, and left for 30 minutes; it was discharged at a constant current rate of 1.5C for 30 seconds, and the 50% SOC DC internal resistance was tested. The results are shown in Table 2.

[0103] 4. Liquid phase diffusion impedance test

[0104] Liquid-phase diffusion impedance is measured through electrochemical impedance spectroscopy (EIS). Based on the reference potential, a small-amplitude sinusoidal potential signal of a certain frequency is applied to the electrode. The impedance of the electrode system is measured as it changes with the sinusoidal frequency. The spectrum is then analyzed and fitted to obtain information on the electrode process kinetics and electrode interface structure, further characterizing the impedance value within the battery. The specific test process for liquid-phase diffusion impedance is as follows:

[0105] The two positive electrode sheets and the separator were assembled in sequence to form a core (with the separator between the two positive electrode sheets). The core was placed in an outer packaging shell (aluminum-plastic film), baked, and then injected with electrolyte. After packaging and impregnation, a liquid-phase diffusion impedance battery was obtained. The liquid-phase diffusion impedance battery was tested using an electrochemical workstation (Reference 3000) in the frequency range of 300,000 Hz to 0.05 Hz. The liquid-phase diffusion impedance was measured and the results are shown in Table 2. The electrolyte used was composed of the following organic solvents: EC, EMC, and DMC, with a mass ratio of EC, EMC, and DMC of 29:32:23, and a LiPF6 concentration of 1 mol / L.

[0106] 5. Electrode resistivity test: Place the positive electrode in a electrode resistivity meter (model BER2600) and test its resistivity at 25 MPa with a holding time of 25 seconds. The measured positive electrode resistivity is shown in Table 2.

[0107] Table 1

[0108]

[0109] Table 2

[0110]

[0111] It can be seen from Table 2 that, relative to Comparative Examples 1 to 3, in the positive electrode sheets of Examples 1 to 26, a primer layer is provided between the positive electrode active material layer and the positive electrode current collector (aluminum foil), and the verticality α of the first conductive agent in the primer layer is controlled within the range of 60°≤α≤90°, which can take into account the reduction of the positive electrode sheet resistivity, liquid phase diffusion impedance and battery internal resistance, and improve the electrochemical performance of the battery.

[0112] In addition, compared with Example 5 (carbon black particle size <25 nm) and Example 9 (carbon black particle size >85 nm), the carbon black particle size in Examples 6 to 8 is in the range of 25 to 85 nm, which is beneficial to further reduce the resistivity of the positive electrode sheet, liquid phase diffusion impedance and battery internal resistance.

[0113] In addition, compared with Example 13 (the aspect ratio of the carbon nanotubes is less than 500) and Example 17 (the aspect ratio of the carbon nanotubes is greater than 800), the aspect ratios of the carbon nanotubes in Examples 14 to 16 are in the range of 500 to 800, which is beneficial to further reduce the resistivity of the positive electrode sheet, the liquid phase diffusion impedance and the internal resistance of the battery.

[0114] In addition, compared with Example 22 (the average sheet diameter of graphene is less than 0.5 μm) and Example 26 (the average sheet diameter of graphene is greater than 5 μm), the average sheet diameter of graphene in Examples 23 to 25 is in the range of 0.5 to 5 μm, which is beneficial to further reduce the resistivity of the positive electrode sheet, the liquid phase diffusion impedance and the internal resistance of the battery.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrode sheet, characterized in that: It includes an electrode current collector and an electrode coating located on at least one side of the electrode current collector; the electrode coating includes an electrode active material layer and an undercoat layer located between the electrode active material layer and the electrode current collector; the undercoat layer includes a first conductive agent, and the angle α between the length direction of the first conductive agent and the surface of the electrode current collector satisfies 60°≤α≤90°.

2. The electrode sheet according to claim 1, characterized in that 60°≤α≤88°。 3. The electrode sheet according to claim 1, characterized in that The first conductive agent includes one or more of carbon black, carbon nanotubes, and graphene.

4. The electrode sheet according to claim 3, characterized in that The particle size D50 of the carbon black is 25 to 85 nm.

5. The electrode sheet according to claim 3, characterized in that The aspect ratio of the carbon nanotubes is 500-800.

6. The electrode sheet according to claim 3, characterized in that The average sheet diameter of the graphene is 0.5 to 5 μm.

7. The electrode sheet according to claim 1, characterized in that The mass percentage of the first conductive agent in the primer layer is 75% to 98%.

8. The electrode sheet according to any one of claims 1 to 7, characterized in that: The primer layer also includes a first binder.

9. The electrode sheet according to any one of claims 1 to 7, characterized in that: The primer layer also includes an electrode active material.

10. The electrode sheet according to any one of claims 1 to 7, characterized in that: The thickness of the primer layer is 2 to 6 μm.

11. The electrode sheet according to any one of claims 1 to 7, characterized in that: The thickness of the electrode active material layer is 90 to 110 μm.

12. The electrode sheet according to any one of claims 1 to 7, characterized in that: The electrode sheet is a positive electrode sheet.

13. The electrode sheet according to claim 12, characterized in that: The electrode active material layer includes an electrode active material, and the electrode active material includes one or more of lithium iron phosphate, lithium cobalt oxide, and a positive electrode ternary material.

14. The electrode sheet according to any one of claims 1 to 7, characterized in that: The electrode sheet is a negative electrode sheet.

15. A battery, characterized in that: The electrode sheet comprises the electrode sheet according to any one of claims 1 to 14.

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