Electrode plate and preparation method thereof, battery, battery pack and electric equipment

Abstract

The invention provides an electrode plate and a preparation method thereof, a battery, a battery pack and electric equipment. 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 degree of order u of the electrode coating is more than or equal to 1 and less than or equal to 1.85; # imgabs0 # R1 is the reflectivity of the electrode coating on the electrode plate under the incident light with the wavelength of lambda, and R2 is the reflectivity of powder formed by the electrode coating on the electrode plate under the incident light with the wavelength of lambda; wherein lambda is in a range of 750 nm to 4 [mu] m. The internal resistance of the battery can be reduced, and the rate capability and the fast charging performance of the battery are improved.

Description

Technical Field

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

[0002] Batteries are common electrochemical devices with a wide range of applications. Electrodes (positive and negative) are essential components of batteries. During the battery's charge and discharge process, active ions (such as lithium ions in lithium-ion batteries) are intercalated and deintercalated between the positive and negative electrodes, enabling the battery's charge and discharge. However, existing batteries generally suffer from defects such as high internal resistance, poor fast-charging performance, and poor rate performance, which urgently need to be addressed. Summary of the Invention

[0003] The present invention provides an electrode sheet and a preparation method thereof, a battery, a battery pack and an electrical device, so as to at least solve the defects of the prior art such as large internal resistance, fast charging performance and rate performance of the battery.

[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 order degree u of the electrode coating satisfies 1≤u≤1.85; R1 is the reflectivity of the electrode coating on the electrode sheet under incident light of wavelength λ, and R2 is the reflectivity of the powder formed by the electrode coating on the electrode sheet under incident light of wavelength λ; wherein λ is 750nm~4μm.

[0005] According to one embodiment of the present invention, the λ is 1000-3500 nm; preferably, the λ is 1465 nm, 1700 nm or 2000 nm.

[0006] According to one embodiment of the present invention, 1≤u≤1.65.

[0007] According to one embodiment of the present invention, when λ=1465 nm, 1.1≤u≤1.6; and / or, when λ=1700 nm, 1.2≤u≤1.65; and / or, when λ=2000 nm, 1.3≤u≤1.65.

[0008] According to one embodiment of the present invention, the R1 is 5% to 37%; preferably, when the λ=1465nm, the R1 is 6% to 28%; preferably, when the λ=1700nm, the R1 is 10% to 30%; preferably, when the λ=2000nm, the R1 is 7% to 33%.

[0009] According to one embodiment of the present invention, the porosity of the electrode coating is 20% to 50%.

[0010] According to one embodiment of the present invention, the surface density of the electrode coating is 130 g / m 2 ~500g / m 2 ; and / or, the compacted density of the electrode coating is 1.2 g / cm 3 ~1.8g / cm 3 .

[0011] According to one embodiment of the present invention, the electrode sheet is a negative electrode sheet; preferably, the electrode coating comprises an electrode active material, and the electrode active material comprises graphite.

[0012] According to one embodiment of the present invention, the electrode sheet is a positive electrode sheet; preferably, the electrode coating includes an electrode active material, and the electrode active material includes one or more of a positive electrode ternary material, lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, and lithium nickel manganese oxide.

[0013] Another aspect of the present invention provides a method for preparing the above-mentioned electrode sheet, comprising the following steps: applying an electrode slurry for forming the electrode coating on the surface of the electrode current collector to form an electrode coating with an order u satisfying 1≤u≤1.85, thereby preparing the electrode sheet.

[0014] Another aspect of the present invention provides a battery, comprising the electrode sheet or the electrode sheet prepared according to the method for preparing the electrode sheet.

[0015] Another aspect of the present invention provides a battery pack comprising the above-mentioned battery.

[0016] Another aspect of the present invention provides an electrical device comprising the above-mentioned battery or the above-mentioned battery pack.

[0017] The implementation of the present invention has at least the following beneficial effects: by controlling the order degree u of the electrode coating on the electrode sheet to satisfy 1≤u≤1.85, the internal resistance of the battery can be effectively reduced, the rate performance of the battery can be improved, and the fast charging performance of the battery can be improved. Specifically, the battery has a lower DC internal resistance, a higher 4C / 0.2C discharge capacity ratio, and a shorter strategic fast charging time in the range of 0-80% SOC. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a cross-sectional SEM image of the negative electrode coating of Example 1;

[0019] Figure 2 This is a cross-sectional SEM image of the negative electrode coating of Comparative Example 1. DETAILED DESCRIPTION

[0020] 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.

[0021] An embodiment of the present invention provides an electrode sheet, comprising an electrode current collector and an electrode coating located on at least one side of the electrode current collector; the order degree u of the electrode coating satisfies 1≤u≤1.85; R1 is the reflectivity of the electrode coating on the electrode sheet under incident light of wavelength λ, and R2 is the reflectivity of the powder formed by the electrode coating on the electrode sheet under incident light of wavelength λ; wherein λ is 750nm to 4μm.

[0022] According to the inventor's research, by controlling the order u of the electrode coating to satisfy 1≤u≤1.85, the internal resistance of the battery can be effectively reduced and the rate performance and fast charging performance of the battery can be improved. The reason for this is that at least when the order u of the electrode coating satisfies 1≤u≤1.85, the electrode main material (electrode active material) particles in the electrode coating on the electrode sheet can be oriented and arranged in an orderly manner, so that the electrode main material particles in the electrode coating are arranged more neatly, the order of the arrangement of the electrode main material particles in the electrode coating is improved, and the tortuosity is reduced to form an ordered ion transmission channel, thereby reducing the internal resistance of the battery and improving the rate and fast charging performance of the battery.

[0023] Specifically, according to the inventor's research and analysis, the electrode main material particles in the electrode coating on the electrode sheet form a device similar to a grating, and the slit spacing between the gratings in the electrode sheet coatings with different orientation degrees is not equal (that is, the orientation degree of the electrode main material in the electrode coating on the electrode sheet is different, and the slit spacing of the grating formed is different). At the same time, due to factors such as the fact that the electrode main material particles (effective particles) are generally non-standard spherical, the slit depth caused by the orientation degree will also be different, and the microscopic slit width and depth will be reflected in the reflectivity of the electrode coating on the electrode sheet to light (that is, the slit width and depth are different, and the reflectivity is also different). Therefore, the embodiment of the present invention is based on the properties of the powder formed by the electrode coating (also the powder forming the electrode coating) and the electrode coating on the electrode sheet (R1 is the reflectivity of the electrode coating on the electrode sheet, that is, R1 is the reflectivity of the electrode coating after the electrode active material (electrode main material) in the electrode coating completes the directional arrangement, R2 is the reflectivity of the powder formed by the electrode coating on the electrode sheet, after the electrode coating forms the powder, the directional arrangement of the electrode main material therein disappears, that is, R2 is the reflectivity after the directional arrangement of the electrode main material in the electrode coating disappears), combined with the powder formed by the electrode coating The reflectivity R2 of the electrode under incident light of wavelength λ, and the reflectivity R1 of the electrode coating on the electrode sheet under incident light of wavelength λ, starting from the order of the electrode coating on the electrode sheet, controlling the order u of the electrode coating to satisfy 1≤u≤1.85, can regulate the orientation degree and other properties of the electrode main material particles in the electrode coating on the electrode sheet, specifically, the electrode main material in the electrode coating on the electrode sheet can be oriented and arranged in an orderly manner, and the order of the arrangement of the electrode main material particles in the electrode coating can be improved to form an ordered ion transmission channel, thereby reducing the internal resistance of the battery and improving the battery's rate and fast charging performance.

[0024] According to further research by the inventors, by further controlling 1≤u≤1.65, it is more conducive to regulating the properties such as the degree of orderly arrangement of the electrode main material in the electrode coating on the electrode sheet, further reducing the internal resistance of the battery, and improving the battery's rate performance and fast charging performance.

[0025] It should be noted that when testing u, R1 and R2 are the test results under the same wavelength λ, that is, using the same wavelength λ of the emitted light, the reflectivity R1 of the electrode coating on the electrode sheet under the emitted light, and the reflectivity R2 of the powder formed by the electrode coating on the electrode sheet under the emitted light are tested, and then according to Calculate the order degree u of the electrode sheet under the emitted light.

[0026] Illustratively, the λ may be 750 nm, 800 nm, 900 nm, 1000 nm, 1200 nm, 1450 nm, 1465 nm, 1500 nm, 2000 nm, 2500 nm, 3000 nm, 3500 nm, or a range consisting of any two thereof.

[0027] In some embodiments, λ can be 1000~3500nm. The order u of the electrode sheet is measured in this wavelength range and controlled to be 1≤u≤3, which is beneficial to further reduce the internal resistance of the battery and improve the battery's rate and fast charging performance. The reason for analysis is that by controlling the order u of the electrode sheet in this wavelength range to satisfy 1≤u≤3, it is beneficial to further improve the directional arrangement order of the electrode main material particles in the electrode coating on the electrode sheet, forming an ordered ion transmission channel, thereby reducing the internal resistance of the battery and improving the battery's rate and fast charging performance.

[0028] In some preferred embodiments, λ can be 1465nm, 1700nm or 2000nm, which is beneficial to further reduce the internal resistance of the battery and improve the battery's rate and fast charging performance. The reason for this is that by controlling the order u of the electrode sheet at a wavelength of 1465nm, 1700nm or 2000nm to satisfy 1≤u≤1.85, it is beneficial to further improve the directional arrangement order of the electrode main material particles in the electrode coating on the electrode sheet, forming an ordered ion transmission channel, thereby reducing the internal resistance of the battery and improving the battery's rate and fast charging performance.

[0029] Specifically, when λ = 1465 nm, the order degree u (hereinafter referred to as u 1465 ) can be 1 to 1.82 (i.e. 1≤u 1465 ≤1.82), u 1465 For example, 1, 1.2, 1.25, 1.28, 1.3, 1.4, 1.45, 1.47, 1.5, 1.54, 1.59, 1.62, 1.65, 1.7, 1.75, 1.78, 1.8 or 1.82, etc., preferably 1.1 to 1.6 (i.e. 1.1≤u 1465 ≤1.6), which is beneficial to further reduce the internal resistance of the battery and improve the battery's rate and fast charging performance.

[0030] Specifically, R1 and R2 are measured under the incident light with a wavelength of 1465nm, that is, infrared light with a wavelength of 1465nm is used as the detection wavelength, and R1 (hereinafter referred to as R1 1465 ) and R2 (hereinafter referred to as R2 1465 ), and then according to The calculated u is u 1465 .

[0031] In addition, when λ = 1700 nm, the order degree u (hereinafter referred to as u 1700 ) is 1~1.85 (i.e. 1≤u 1700 ≤1.85), u 1700For example, 1, 1.2, 1.3, 1.4, 1.43, 1.46, 1.5, 1.55, 1.58, 1.6, 1.61, 1.62, 1.65, 1.68, 1.7, 1.75, 1.8 or 1.85, preferably 1.2 to 1.65 (i.e., 1.2≤u 2000 ≤1.65), which is beneficial to further reduce the internal resistance of the battery and improve the battery's rate and fast charging performance.

[0032] Specifically, R1 and R2 are measured under the incident light with a wavelength of 1700 nm, that is, infrared light with a wavelength of 1700 nm is used as the detection wavelength, and R1 (hereinafter referred to as R1 1700 ) and R2 (hereinafter referred to as R2 1700 ), and then according to The calculated u is u 1700 .

[0033] In addition, when λ = 2000 nm, the order degree u (hereinafter referred to as u 2000 ) is 1~1.85 (i.e. 1≤u 2000 ≤1.85), u 2000 For example, 1, 1.3, 1.35, 1.4, 1.44, 1.47, 1.5, 1.55, 1.58, 1.6, 1.62, 1.64, 1.67, 1.7, 1.72, 1.75, 1.8 or 1.85, preferably 1.3 to 1.65 (i.e., 1.3≤u 2000 ≤1.65), which is beneficial to further reduce the internal resistance of the battery and improve the battery's rate and fast charging performance.

[0034] Specifically, R1 and R2 are measured under the incident light with a wavelength of 2000nm, that is, infrared light with a wavelength of 2000nm is used as the detection wavelength, and R1 (hereinafter referred to as R1 2000 ) and R2 (hereinafter referred to as R2 2000 ), and then according to The calculated u is u 2000 .

[0035] In an embodiment of the present invention, in the above-mentioned wavelength λ range (750 nm to 4 μm), R1 can be 5% to 37%, for example, 5%, 10%, 12%, 14%, 14.5%, 15%, 18%, 18.5%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 35%, 37% or a range consisting of any two of them.

[0036] In some embodiments, when λ=1465 nm, R1 (ie, R1 1465) can be 6% to 28%, for example, 6%, 10%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 22.6%, 24%, 24.5%, 25%, 25.5%, 25.52%, 26%, 26.3%, 26.5%, 27%, 27.5%, 28% or a range consisting of any two of them, which is beneficial to further reduce the internal resistance of the battery and improve the battery's rate performance, fast charging performance, etc.

[0037] In some embodiments, when λ=1465 nm, R2 (ie, R2 1465 ) can be 6% to 20%, for example, 6%, 9%, 12%, 14%, 14.2%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 18%, 19%, 20% or a range consisting of any two of them, which is beneficial to further reduce the internal resistance of the battery and improve the battery's rate and fast charging performance.

[0038] In some embodiments, when λ=1700 nm, R1 (ie, R1 1700 ) can be 10% to 30%, for example, 10%, 14%, 17%, 20%, 21%, 21.5%, 21.7%, 22%, 23%, 24%, 24.5%, 25%, 25.5%, 26%, 26.2%, 26.5%, 26.8%, 27%, 27.2%, 27.5%, 28%, 28.5%, 29%, 29.6%, 30% or a range consisting of any two of them.

[0039] In some embodiments, when λ=1700 nm, R2 (ie, R2 1700 ) can be 10% to 20%, for example, 10%, 15%, 15.2%, 15.5%, 15.8%, 16%, 16.2%, 16.5%, 16.8%, 17%, 17.3%, 17.5%, 18%, 19%, 20% or a range consisting of any two of them.

[0040] In some embodiments, when λ=2000 nm, R1 (ie R1 2000 ) can be 7% to 33%, for example, 7%, 10%, 14%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 28.2%, 28.5%, 29%, 29.5%, 30%, 30.2%, 30.5%, 31%, 32%, 32.5%, 33% or a range consisting of any two of them, which is beneficial to further reduce the internal resistance of the battery and improve the battery's performance such as rate and fast charging.

[0041] In some embodiments, when λ=2000 nm, R2 (ie R22000 ) can be 7% to 20%, for example, 7%, 9%, 13%, 15%, 15.5%, 16%, 16.2%, 16.5%, 16.7%, 17%, 17.3%, 17.5%, 17.7%, 18%, 18.5%, 19%, 19.5%, 20% or a range consisting of any two of them.

[0042] In the embodiment of the present invention, a near-infrared spectrophotometer may be used to test the reflectivities R1 and R2. When testing the reflectivities R1 and R2, spectrally pure BaSO4 may be used as a reflective background. Specifically, when testing the reflectivity R1 of the electrode coating on the electrode sheet under incident light with a wavelength of λ, a cutter with a diameter of 1.5 cm can be used to take a sample from the electrode sheet (i.e., cut out the electrode sheet sample), and then the obtained electrode sheet sample is placed in the sample chamber, and its total reflectivity is tested in the incident light with a wavelength of λ in the integrating sphere of the near-infrared spectrophotometer (absorbance = 1-reflectivity) to obtain R1; when testing the reflectivity R2 of the powder formed by the electrode coating on the electrode sheet under incident light with a wavelength of λ, a scraper can be used to scrape off the electrode coating on the surface of the electrode collector of the electrode sheet, and then the scraped coating material is crushed or ground into powder in a mortar, that is, a powder formed by the electrode coating on the electrode sheet is obtained, and then the powder is used to test its total reflectivity in the incident light with a wavelength of λ in the integrating sphere of the near-infrared spectrophotometer to obtain R2. The average particle size of the powder formed by the electrode coating on the electrode sheet is substantially the same as the particle size of the electrode active material in the electrode coating. The average particle size of the powder formed by the electrode coating on the electrode sheet is, for example, 0.5 μm to 50 μm.

[0043] In some embodiments, the porosity of the electrode coating can be 20% to 50%, for example, 20%, 25%, 30%, 30.4%, 30.8%, 31%, 31.5%, 31.7%, 32%, 32.5%, 33%, 35%, 40%, 45%, 50% or any two thereof, which is beneficial to further reduce the impedance of the electrode sheet while maintaining the electrode sheet's higher energy density and other properties, thereby further optimizing battery performance.

[0044] In the embodiment of the present invention, the surface density of the electrode coating can be 130g / m 2 ~500g / m 2 , for example 130g / m 2 , 160g / m 2 , 180g / m 2 , 200g / m 2 , 210g / m 2 , 220g / m 2 , 230g / m 2 , 240g / m2 , 250g / m 2 , 280g / m 2 , 300g / m 2 , 400g / m 2 , 500g / m 2 Or a range consisting of any two of them is conducive to maintaining the properties of the electrode sheet such as low impedance and high energy density, and further improving the battery's rate and fast charging performance.

[0045] In the embodiment of the present invention, the compaction density of the electrode coating is 1.2 g / cm 3 ~1.8g / cm 3 , for example 1.2 g / cm 3 , 1.3g / cm 3 , 1.4g / cm 3 , 1.5g / cm 3 , 1.6g / cm 3 , 1.7g / cm 3 , 1.8g / cm 3 Or a range consisting of any two of them is conducive to maintaining the properties of the electrode sheet such as low impedance and high energy density, and further improving the battery's rate and fast charging performance.

[0046] In the embodiment of the present invention, the electrode coating includes an electrode active material in the form of particles, that is, the electrode coating includes electrode active material particles, which may be spherical or have other regular or irregular shapes.

[0047] In some embodiments, the particle size Dv50 of the electrode active material (such as the negative electrode active material) can be 5 μm to 30 μm, for example, 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm, 20 μm, 23 μm, 25 μm, 28 μm, 30 μm or a range consisting of any two thereof.

[0048] In some embodiments, the above-mentioned electrode sheet can be a negative electrode sheet, and accordingly, the above-mentioned electrode current collector is a negative electrode current collector, the electrode coating is a negative electrode coating (negative electrode active material layer), and the above-mentioned electrode active material is a negative electrode active material, which may include a carbon active material, and the carbon active material may include graphite, for example, artificial graphite and / or natural graphite, and the electrode coating 1 may specifically include primary graphite particles and / or secondary graphite particles.

[0049] In some specific embodiments, the particle size Dv50 of the graphite in the negative electrode coating can be 5 μm to 30 μm, for example, 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm, 20 μm, 23 μm, 25 μm, 28 μm, 30 μm or a range consisting of any two thereof.

[0050] In the embodiment of the present invention, the particle size Dv50 of the electrode active material (such as graphite) can be measured by a laser particle size analyzer.

[0051] 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.

[0052] In other embodiments, the above-mentioned electrode sheet is a positive electrode sheet, and accordingly, the above-mentioned electrode current collector is a positive electrode current collector, the electrode coating is a positive electrode coating (positive electrode active material layer), and the electrode active material is a positive electrode active material, which may include a positive electrode ternary material and / or lithium iron phosphate, wherein the positive electrode ternary material, for example, includes a nickel-cobalt-manganese ternary material (NCM) and / or a nickel-cobalt-aluminum ternary material (NCA).

[0053] 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.

[0054] In an embodiment of the present invention, an electrode coating may be provided on one surface of the electrode collector, or an electrode coating may be provided on the surfaces of both opposite sides of the electrode collector. When electrode coatings are provided on the surfaces of both opposite sides of the electrode collector, the electrode coating on one surface may satisfy the above-mentioned order u (i.e., 1≤u≤1.85), or the electrode coatings on both opposite surfaces of the electrode collector may satisfy the above-mentioned order u (i.e., 1≤u≤1.85).

[0055] Generally, the electrode coating further comprises a conductive agent and a binder. Based on the total mass of the electrode coating, 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 coating) may 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 conductive agent may 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 binder may 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.

[0056] In an embodiment of the present invention, the conductive agent in the electrode coating may be a conventional conductive material in the art, for example, the conductive agent includes one or more of carbon black, carbon nanotubes (CNTs), acetylene black, graphene, Ketjen black, and carbon fiber.

[0057] In an embodiment of the present invention, the binder in the electrode coating may be a conventional binding material in the art. For example, when the electrode sheet is a negative electrode sheet, the binder may include one or more of carboxymethyl cellulose (CMC), 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 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.

[0058] An embodiment of the present invention also provides a method for preparing the above-mentioned electrode sheet, comprising the following steps: applying an electrode slurry for forming the electrode coating on the surface of the electrode current collector to form an electrode coating with an ordering degree u satisfying 1≤u≤1.85, thereby preparing the electrode sheet.

[0059] In specific implementation, after the electrode slurry is coated on the surface of the electrode current collector, a magnetic field or electric field can be applied to the wet film formed on the surface of the electrode current collector to form an electrode coating with a preset order u to obtain an electrode sheet.

[0060] In some embodiments, the preparation process of the above-mentioned electrode sheet may include: applying the electrode slurry for forming the electrode coating on the surface of the electrode current collector to form a wet film on the surface of the electrode current collector; then, applying a magnetic field or an electric field to the wet film so that the wet film reaches a preset degree of order; then, drying and rolling to obtain the electrode sheet.

[0061] In the above preparation process, a magnetic field or electric field of a preset intensity is applied to the wet film. Under the action of the magnetic field or electric field, the arrangement state of the electrode active material in the wet film can be induced. Specifically, the magnetic field or electric field acts on the electrode active material in the wet film, which can cause it to be arranged in a directional and orderly manner to form an ordered ion transmission channel. After subsequent drying and rolling processes, the wet film forms an electrode coating with a preset degree of order u (1≤u≤1.85), thereby obtaining an electrode sheet with an orderly stacked crystal structure of the electrode active material in the electrode coating.

[0062] In the embodiment of the present invention, a conventional magnetic field applying method may be used to apply a magnetic field to the wet film, and a conventional electric field applying method may be used to apply an electric field to the wet film.

[0063] In practice, the magnetic field or electric field strength can be manipulated to induce the alignment of the electrode active material, thereby forming an electrode coating with a predetermined degree of order u and producing an electrode sheet. For example, a gauss meter can be used to measure the surface of a wet film, and the measured value is the magnetic field strength H experienced by the wet film.

[0064] For example, the magnetic field strength of the applied magnetic field can be 0.2T to 0.7T, such as 0.2T, 0.25T, 0.3T, 0.35T, 0.4T, 0.45T, 0.5T, 0.6T or 0.7T, etc., and the time for applying the magnetic field to the wet film (i.e., the magnetic field action time) can be 10s to 2min. During specific implementation, the magnetic field strength H and the magnetic field action time can be adjusted as needed to form an electrode coating with a preset order u.

[0065] In the embodiment of the present invention, drying and rolling are conventional operations in the art and are not particularly limited thereto.

[0066] In an embodiment of the present invention, when electrode coatings are formed on both the front and back surfaces of the electrode collector, the electrode slurry can be first coated on one side of the electrode collector, and then induced and dried by a magnetic field or electric field, and then the electrode slurry is coated on the other side of the electrode collector, and then induced and dried by a magnetic field or electric field, and then rolled to obtain an electrode sheet.

[0067] In an embodiment of the present invention, the above-mentioned electrode slurry can be prepared by conventional methods in the art. For example, when the electrode sheet is a negative electrode sheet, the components for forming the negative electrode coating, such as the negative electrode active material, the conductive agent, and the binder, can be dispersed in a first solvent. The first solvent includes, for example, deionized water and / or N-methylpyrrolidone (NMP) to prepare a negative electrode slurry (i.e., the above-mentioned electrode slurry), which is then applied to the surface of the negative electrode collector. After magnetic field or electric field induction, drying, rolling and other processes, a negative electrode sheet is obtained. When the electrode sheet is a positive electrode sheet, the components for forming the positive electrode coating, such as the positive electrode active material, the conductive agent, and the binder, can be dispersed in a second solvent. The second solvent includes, for example, N-methylpyrrolidone (NMP), to prepare a positive electrode slurry (i.e., the above-mentioned electrode slurry), which is then applied to the surface of the positive electrode collector. After magnetic field or electric field induction, drying, rolling and other processes, a positive electrode sheet is obtained.

[0068] In specific implementation, the electrode slurry can be prepared at a temperature of 20-45° C.; the electrode slurry can be coated on the surface of the electrode current collector using conventional coating equipment in the art, such as a continuous coating equipment.

[0069] An embodiment of the present invention further provides a battery, comprising the above-mentioned electrode sheet or an electrode sheet manufactured according to the above-mentioned method for manufacturing the electrode sheet. The battery has corresponding advantages to the above-mentioned electrode sheet, which will not be described in detail.

[0070] As mentioned above, the use of the above-mentioned electrode sheet can reduce the internal resistance of the battery and improve the battery's rate performance and fast charging performance. Specifically, the battery's DC internal resistance can be reduced to below 93mΩ, the battery's 4C / 0.2C discharge capacity ratio can be as high as above 56%, and the battery's strategic fast charging time in the range of 0-80% SOC can be reduced to less than 40 minutes.

[0071] 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.

[0072] Generally, a battery includes 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.

[0073] In the embodiment of the present invention, the positive electrode sheet can be an electrode sheet that satisfies the above-mentioned order degree u (that is, the order degree of the positive electrode coating satisfies 1≤u≤1.85), or the negative electrode sheet can be an electrode sheet that satisfies the above-mentioned order degree u (that is, the order degree of the negative electrode coating satisfies 1≤u≤1.85), or both the positive electrode sheet and the negative electrode sheet are electrode sheets that satisfy the above-mentioned order degree u (that is, the order degree of the positive electrode coating of the positive electrode sheet satisfies 1≤u≤1.85, and the order degree of the negative electrode coating of the negative electrode sheet satisfies 1≤u≤1.85).

[0074] 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, ethylene carbonate and / or diethyl carbonate. When the battery is a sodium ion battery, the electrolyte salt can include a lithium salt. The lithium salt includes, for example, lithium hexafluorophosphate (LiPF6), etc., but is not limited thereto.

[0075] 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 without special limitation.

[0076] In the embodiment of the present invention, conventional packaging (shell) materials in the art may be used to encapsulate the battery cells, and the battery may be of a conventional battery type and structure in the art. For example, the battery may be a blade battery, but is not limited thereto.

[0077] In the embodiment of the present invention, the positive electrode sheet, the separator, the negative electrode sheet and other components can be assembled into a battery by conventional methods in the art, and there is no particular limitation on this.

[0078] An embodiment of the present invention further provides a battery pack including the above-mentioned battery. The battery has advantages corresponding to those of the above-mentioned electrode sheet, which will not be described in detail.

[0079] Generally, a battery pack includes multiple batteries as described above, which are connected as single cells to form a battery pack. These batteries can be electrically connected using conventional methods in the art, such as series connection, parallel connection, or a combination of these connection methods, without particular limitation.

[0080] An embodiment of the present invention further provides an electrical device, comprising the above-mentioned battery or the above-mentioned battery pack. The electrical device has advantages corresponding to those of the above-mentioned electrode sheet, which will not be described in detail.

[0081] The electrical equipment in the embodiments of the present invention can be conventional electrical equipment in this field, such as power equipment (such as electric vehicles, electric cars), electronic equipment (such as mobile phones, tablets, laptops, digital cameras, etc.), wearable devices (such as watches, bracelets, VR glasses, etc.), energy storage power stations, etc.

[0082] In an embodiment of the present invention, the test process for the surface density of the electrode coating may include: taking an electrode sheet sample (specifically, a 1.5 cm diameter cutter may be used to sample), measuring the total mass m1 of the electrode sheet sample, and the surface area S of a single side of the electrode sheet sample in the thickness direction; then scraping the electrode coating on the electrode sheet sample, and measuring the mass m2 of the electrode current collector obtained. The surface density of the electrode coating is then calculated as (m1-m2) / S. The total mass m1 of the electrode sheet sample and the mass m2 of the electrode current collector may be measured using an electronic scale.

[0083] In an embodiment of the present invention, the compacted density of the electrode coating = the surface density of the electrode coating / the total thickness of the electrode coating, wherein the testing process of the surface density of the electrode coating refers to the above, and the testing process of the total thickness of the electrode coating may include: taking an electrode sheet sample, testing the total thickness T1 of the electrode sheet sample (T1 = the total thickness of the electrode coating + the thickness of the electrode collector. When the front and back surfaces of the electrode collector are respectively provided with electrode coatings, the total thickness of the electrode coating = the thickness of the electrode coating located on one surface of the electrode collector + the thickness of the electrode coating located on the other surface of the electrode collector); then scraping off the electrode coating on the electrode sheet sample, testing the thickness T2 of the electrode collector, and the total thickness of the electrode coating = T1-T2.

[0084] In specific implementation, a micrometer can be used to measure the average thickness T1 of the electrode sheet and the average thickness T2 of the electrode current collector.

[0085] In a specific implementation, the battery can be disassembled to obtain the electrode sheet, and then the reflectivity (R1, R2) of the electrode coating of the electrode sheet, as well as the surface density and compacted density of the electrode coating, the porosity of the electrode coating and other characteristics are tested. For example, when testing the reflectivity R1 and R2, the battery can be disassembled and the electrode sheet can be taken out. Specifically, the electrode sheet can be washed in a solvent such as DMC to remove electrolyte components such as lithium salt on its surface. After the electrode sheet is washed clean, it is dried and the reflectivity R1 is tested using incident light with a wavelength of λ; then, the electrode coating on the electrode sheet is scraped off, and the scraped coating material is crushed into powder in a mortar to obtain a powder formed by the electrode coating on the electrode sheet. The powder is then used to test the reflectivity R2 under incident light with a wavelength of λ.

[0086] In a specific implementation, after the electrode sheet is obtained, the porosity of the electrode coating of the electrode sheet can be measured by mercury intrusion testing.

[0087] The present invention is further described below through specific examples. In the following examples, the magnetic field strength, the surface density and compaction density of the electrode coating, the reflectivity (R1 1465 、R1 1700 、R1 2000 、R2 1465 、R2 1700 、R2 2000 ) and order u(u 1465 、u 1700 、u 2000 ), the testing methods for parameters such as the porosity of the electrode coating of the electrode sheet are as mentioned above and will not be repeated below.

[0088] In the following examples and comparative examples, the ultraviolet-near infrared spectrophotometer used for measuring reflectivity was PERKINEIMER LAMBDA 1050, and the scanning electron microscope (SEM) used was HITACHI FLEX SEM 1000.

[0089] Example 1

[0090] 1. Preparation of negative electrode sheet

[0091] (1) Graphite (primary graphite particles with a particle size of Dv50 = 10.5 μm), carbon black, CMC, and SBR were mixed in a mass ratio of 100:1:1.6:3.3, and deionized water and NMP were added and stirred to prepare a negative electrode slurry;

[0092] (2) A continuous coating device is used to coat the negative electrode slurry on one side of the copper foil, and a magnetic field with a magnetic field strength of H = 0.7T is applied to the formed wet film. The orientation of the graphite in each area is induced by the applied magnetic field. The magnetic field is applied for about 2 minutes (magnetic field action time), during which the magnetic field is kept uniform and stable. After the application of the magnetic field is completed, the wet film is dried to form a coating layer.

[0093] (3) Then, the coating, magnetic field application and drying processes of the above step (2) are repeated on the other side of the copper foil to form a coating layer on both the front and back surfaces of the copper foil, and then the copper foil is rolled to obtain a negative electrode sheet with a negative electrode coating formed on both the front and back surfaces of the copper foil.

[0094] Among them, the reflectivity R1 of the negative electrode coating on the electrode sheet at wavelength λ = 1465nm is measured 1465 , the reflectivity R1 of the negative electrode coating on the electrode sheet at wavelength λ = 1700nm 1700 , the reflectivity R1 of the negative electrode coating on the electrode sheet at wavelength λ = 2000nm 2000 , the reflectivity R2 of the powder formed by the negative electrode coating at wavelength λ = 1465nm 1465 , the reflectivity R2 of the powder formed by the negative electrode coating at wavelength λ = 1700nm 1700 , the reflectivity R2 of the powder formed by the negative electrode coating at wavelength λ = 2000nm 2000 , the order degree u of the negative electrode coating at wavelength λ = 1200nm 2000 , the order degree u of the negative electrode coating on the electrode sheet at wavelength λ = 1700nm 1700 , the order degree u of the negative electrode coating on the electrode sheet at wavelength λ = 1465nm 1465 , the surface density of the negative electrode coating, the compacted density of the negative electrode coating, and the porosity of the negative electrode coating are shown in Table 1. Among them, when testing the reflectivity (R2 1465 、R2 1700 、R2 2000 ), the average particle size Dv50 of the powder formed by the negative electrode coating is about 10.5 μm.

[0095] 2. Preparation of positive electrode

[0096] Lithium iron phosphate, CNT, carbon black, and PVDF were mixed in a mass ratio of 100:0.3:0.5:2.5, and NMP was added and stirred evenly to prepare a positive electrode slurry;

[0097] The positive electrode slurry is coated on the front and back surfaces of the aluminum foil. After drying and rolling, a positive electrode coating is formed on the front and back surfaces of the aluminum foil to prepare a positive electrode sheet. The surface density of the positive electrode coating is about 500g / m 2 .

[0098] 3. Battery assembly

[0099] In a glove box, under an argon atmosphere, the positive electrode sheets, separators and negative electrode sheets were alternately stacked and injected with electrolyte to assemble into a soft-pack battery (the battery design capacity is 0.9Ah); the composition of the electrolyte used is as follows: the organic solvent is a mixture of ethylene carbonate and diethyl carbonate in a volume ratio of 1:1, and the LiPF6 concentration in the electrolyte is 1 mol / L.

[0100] Example 2: The difference from Example 1 is that during the preparation of the negative electrode sheet, the magnetic field strength is H=0.5T, the magnetic field is applied for about 1 minute, and the remaining steps and conditions are the same as in Example 1.

[0101] Example 3: The difference from Example 1 is that during the preparation of the negative electrode sheet, the magnetic field strength is H=0.41T, the magnetic field is applied for about 1 minute, and the remaining steps and conditions are the same as in Example 1.

[0102] Example 4: The difference from Example 1 is that during the preparation of the negative electrode sheet, the magnetic field strength is H=0.32T, the magnetic field is applied for about 1 minute, and the remaining steps and conditions are the same as in Example 1.

[0103] Example 5: The difference from Example 1 is that the surface density of the negative electrode coating of the negative electrode sheet is 204.5 g / m 2 The surface density of the positive electrode coating of the positive electrode sheet is about 456g / m 2 In the preparation process of the negative electrode sheet, the magnetic field strength is H=0.5T, the magnetic field is applied for about 1 minute, and the remaining steps and conditions are the same as those in Example 1.

[0104] Example 6: The difference from Example 1 is that during the preparation of the negative electrode sheet, the magnetic field strength is H=0.21T, the magnetic field is applied for about 10 seconds, and the remaining steps and conditions are the same as in Example 1.

[0105] Comparative Example 1: The difference from Example 1 is that no magnetic field is applied during the preparation of the negative electrode sheet (i.e., in Comparative Example 1, the negative electrode slurry is coated on both the front and back surfaces of the copper foil, and then dried and rolled to form a negative electrode coating to prepare the negative electrode sheet). The remaining steps and conditions are the same as in Example 1.

[0106] The DC impedance (DCIR) and long cycle performance (number of cycles when the capacity decays to 80%) of the batteries of each embodiment and comparative example were tested according to the following process. The results are shown in Table 1.

[0107] (1) DC internal resistance test: At 25°C, the state of charge of the soft-pack battery was adjusted to 50% SOC, and then discharged at a rate of 1.5C for 30s. The voltage drop of the soft-pack battery was recorded to calculate the DC resistance DCIR.

[0108] (2) Rate performance: At 25°C, the discharge capacity of the battery was tested at 0.2C and 4C rates as a function of the number of cycles, with a voltage range of 2.0-3.8V. The ratio of the first-cycle discharge capacity at 5C to the first-cycle discharge capacity at 0.2C was calculated as the rate performance test result (i.e., the 4C / 0.2C discharge capacity ratio in Table 1).

[0109] (3) Strategic fast charging time: At 25°C, adjust the SOC of the above soft pack battery to 0% (i.e., discharge the battery completely), then charge it to 3.8V at a rate of 0.33C, and then discharge the battery completely; then charge it to 3.8V at a rate of 0.5C, and then discharge the battery completely; then charge it to 3.8V at a rate of 1C, and then discharge the battery completely; then charge it to 3.8V at a rate of 2C, and then discharge the battery completely; then charge it to 3.8V at a rate of 3C, and then discharge the battery completely; then charge it to 3.8V at a rate of 4C. 3.8V, then discharge the battery; then charge it at a 5C rate to 3.8V, then discharge the battery; then charge it at a 6C rate to 3.8V, calculate the SOC of the battery at different charging rates (that is, the proportion of the amount of electricity discharged by the battery to the amount of electricity when the battery is fully charged), subtract 20% from the SOC, calculate the charging time, which is the safe charging time at this rate, and add up the safe charging times at different rates (starting from 6C and gradually reducing the rate), which is the 0-80% SOC strategy fast charging time.

[0110] Table 1

[0111]

[0112] It can be seen from Table 1 that, relative to Comparative Example 1, in Examples 1 to 6, the u value of the negative electrode coating in the negative electrode sheet is in the range of 1 to 1.85, which can enable the battery to have a lower DC internal resistance (not higher than 98.2 mΩ), and the battery has a larger 4C / 0.2C discharge capacity ratio (not lower than 53.32%), showing good rate performance. At the same time, the battery has a shorter strategic fast charging time (not higher than 40.15 min), showing good fast charging performance.

[0113] In addition, relative to Example 6, Examples 1 to 5 can further reduce the DC internal resistance of the battery (not higher than 92.3 mΩ) by further controlling the u value of the negative electrode coating within the range of 1 to 1.65, increase the 4C / 0.2C discharge capacity ratio of the battery (not lower than 56.63%), and shorten the strategic fast charging time of the battery (not higher than 39.12 min).

[0114] Taking Example 1 and Comparative Example 1 as examples, a scanning electron microscope (SEM) was used to observe the cross-sections of the negative electrode coating in Example 1 and the negative electrode coating in Comparative Example 1 (the arrangement of graphite particles in the negative electrode coating was observed by SEM). The cross-sectional SEM image of the negative electrode coating in Example 1 was shown in FIG. Figure 1 The cross-sectional SEM image of the negative electrode coating of Comparative Example 1 is shown in FIG. Figure 2 ,from Figure 1 and Figure 2 It can be seen that the deflection angles of the graphite particles in the negative electrode coating of Example 1 and Comparative Example 1 are significantly different. The verticality of the graphite particles in the negative electrode coating of Example 1 is significantly improved, and the tortuosity is reduced, so that the impedance of the electrode sheet is reduced, which can improve the fast charging performance and rate performance 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: The invention comprises an electrode current collector and an electrode coating located on at least one side surface of the electrode current collector; The order degree u of the electrode coating satisfies 1≤u≤1.85; R1 is the reflectivity of the electrode coating on the electrode sheet under incident light of wavelength λ, and R2 is the reflectivity of the powder formed by the electrode coating on the electrode sheet under incident light of wavelength λ; wherein λ is 750nm~4μm.

2. The electrode sheet according to claim 1, characterized in that The λ is 1000-3500 nm; preferably, the λ is 1465 nm, 1700 nm or 2000 nm.

3. The electrode sheet according to claim 1, characterized in that 1≤u≤1.65。 4. The electrode sheet according to any one of claims 1 to 3, characterized in that: When λ=1465 nm, 1.1≤u≤1.6; and / or, when λ=1700 nm, 1.2≤u≤1.65; And / or, when λ=2000 nm, 1.3≤u≤1.

65.

5. The electrode sheet according to any one of claims 1 to 3, characterized in that: The R1 is 5% to 37%; Preferably, when λ=1465 nm, R1 is 6% to 28%; Preferably, when λ=1700 nm, R1 is 10% to 30%; Preferably, when λ=2000 nm, R1 is 7% to 33%.

6. The electrode sheet according to any one of claims 1 to 3, characterized in that: The porosity of the electrode coating is 20% to 50%.

7. The electrode sheet according to any one of claims 1 to 3, characterized in that: The surface density of the electrode coating is 130 g / m 2 ~500g / m 2 ; And / or, the compacted density of the electrode coating is 1.2 g / cm 3 ~1.8g / cm 3 .

8. The electrode sheet according to any one of claims 1 to 3, characterized in that: The electrode sheet is a negative electrode sheet; preferably, the electrode coating comprises an electrode active material, and the electrode active material comprises graphite.

9. The electrode sheet according to any one of claims 1 to 3, characterized in that: The electrode sheet is a positive electrode sheet; preferably, the electrode coating includes an electrode active material, and the electrode active material includes one or more of a positive electrode ternary material, lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, and lithium nickel manganese oxide.

10. A method for preparing an electrode sheet according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: applying an electrode slurry for forming the electrode coating on the surface of the electrode current collector to form an electrode coating whose ordering degree u satisfies 1≤u≤1.85, thereby preparing the electrode sheet.

11. A battery, characterized in that: The electrode sheet comprises the electrode sheet according to any one of claims 1 to 9 or the electrode sheet prepared according to the method for preparing the electrode sheet according to claim 10.

12. A battery pack, characterized in that: Including the battery according to claim 11.

13. An electrical device, characterized in that: The battery according to claim 11 or the battery pack according to claim 12 is included.

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