Electrode sheet and preparation method therefor, and battery, battery pack and electric device

Abstract

An electrode sheet and a preparation method therefor, and a battery, a battery pack and an electric device. The electrode sheet comprises an electrode current collector and an electrode coating located on at least one side surface of the electrode current collector, wherein the degree of order u of the electrode coating satisfies 1≤u≤1.85; and u=R1 / R2, where R1 represents the reflectivity of the electrode coating on the electrode sheet under incident light having a wavelength of λ, and R2 represents the reflectivity of powder formed from the electrode coating on the electrode sheet under the incident light having the wavelength of λ, with λ ranging from 750nm to 4μm.

Description

An electrode sheet and its preparation method, a battery, a battery pack, and an electrical device thereof.

[0001] This application claims priority to Chinese Patent Application No. 202411645278.4, filed on November 15, 2024, entitled "An electrode sheet and its preparation method, a battery, a battery pack and an electrical device thereof", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of batteries, and more specifically, to an electrode sheet and its preparation method, a battery, a battery pack, and an electrical device. Background Technology

[0003] Batteries are common electrochemical devices with wide applications. Electrode plates (positive and negative electrodes) are important components of batteries. During the charging and discharging process, active ions (such as lithium ions in lithium-ion batteries) are inserted and extracted between the positive and negative electrodes to achieve the charging and discharging process. 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

[0004] The purpose of this application is to provide an electrode sheet and its preparation method, a battery, a battery pack and an electrical device, so as to at least solve the defects of the prior art, such as high battery internal resistance, fast charging performance and rate performance.

[0005] In a first aspect, this application discloses an electrode sheet, including an electrode current collector and an electrode coating located on at least one side surface of the electrode current collector; the degree of order u of the electrode coating satisfies 1≤u≤1.85; R1 is the reflectance of the electrode coating on the electrode sheet under incident light with wavelength λ, and R2 is the reflectance of the powder formed by the electrode coating on the electrode sheet under incident light with wavelength λ; wherein, λ is 750nm~4μm.

[0006] According to one embodiment of this application, the λ is 1000-3500nm; preferably, the λ is 1465nm, 1700nm or 2000nm.

[0007] According to one embodiment of this application, 1 ≤ u ≤ 1.65.

[0008] According to one embodiment of this application, when λ = 1465nm, 1.1 ≤ u ≤ 1.6; and / or, when λ = 1700nm, 1.2 ≤ u ≤ 1.65; and / or, when λ = 2000nm, 1.3 ≤ u ≤ 1.65.

[0009] According to one embodiment of this application, R1 is 5% to 37%; preferably, when λ = 1465nm, R1 is 6% to 28%; preferably, when λ = 1700nm, R1 is 10% to 30%; preferably, when λ = 2000nm, R1 is 7% to 33%.

[0010] According to one embodiment of this application, the porosity of the electrode coating is 20% to 50%.

[0011] According to one embodiment of this application, the areal density of the electrode coating is 130 g / m³. 2 ~500g / m 2 ; and / or, the compaction density of the electrode coating is 1.2 g / cm³. 3 ~1.8g / cm 3 .

[0012] According to one embodiment of this application, the electrode sheet is a negative electrode sheet; preferably, the electrode coating includes an electrode active material, and the electrode active material includes graphite.

[0013] According to one embodiment of this application, the electrode sheet is a positive electrode sheet; preferably, the electrode coating includes an electrode active material, which includes one or more of the following: positive ternary material, lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, and lithium nickel manganese oxide.

[0014] Secondly, this application discloses a method for preparing the above-mentioned electrode sheet, comprising the following steps: coating an electrode paste for forming the electrode coating onto the surface of the electrode current collector to form an electrode coating with an order degree u satisfying 1≤u≤1.85, thereby obtaining the electrode sheet.

[0015] Thirdly, this application discloses a battery comprising the above-described electrode sheet or an electrode sheet prepared according to the above-described electrode sheet preparation method.

[0016] Fourthly, this application discloses a battery pack including the aforementioned battery.

[0017] Fifthly, this application discloses an electrical device, including the aforementioned battery or battery pack.

[0018] In combination with the above technical solutions, this application can effectively reduce the battery internal resistance, improve the battery rate performance, and enhance the battery fast charging performance by controlling the order degree u of the electrode coating on the electrode sheet to satisfy 1≤u≤1.85. Specifically, the battery has a lower DC internal resistance, a higher 4C / 0.2C discharge capacity ratio, and a shorter fast charging time in the range of 0 to 80% SOC. Attached Figure Description

[0019] Figure 1 is a cross-sectional SEM image of the negative electrode coating of Example 1;

[0020] Figure 2 is a cross-sectional SEM image of the negative electrode coating of Comparative Example 1. Detailed Implementation

[0021] To enable those skilled in the art to better understand the solutions of this application, a further detailed description of this application is provided below. The specific embodiments listed below are merely descriptions of the principles and features of this application; the examples are only for explaining this application and are not intended to limit its scope. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0022] This application provides an electrode sheet, including an electrode current collector and an electrode coating located on at least one side surface of the electrode current collector; the degree of order u of the electrode coating satisfies 1≤u≤1.85; R1 is the reflectance of the electrode coating on the electrode sheet under incident light with wavelength λ, and R2 is the reflectance of the powder formed by the electrode coating on the electrode sheet under incident light with wavelength λ; where λ is 750nm~4μm.

[0023] According to the applicant's research, by controlling the degree of 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 at least that the degree of order u of the electrode coating to satisfy 1≤u≤1.85 can make the particles of the main electrode material (electrode active material) in the electrode coating on the electrode sheet oriented and orderly, making the arrangement of the main electrode material particles in the electrode coating more neat, improving the degree of order of the arrangement of the main electrode material particles in the electrode coating, reducing the tortuosity, forming an ordered ion transport channel, thereby reducing the internal resistance of the battery and improving the rate performance and fast charging performance of the battery.

[0024] Specifically, according to the applicant's research and analysis, the electrode material particles in the electrode coating on the electrode sheet form a grating-like device. The slit spacing between the gratings in the electrode coating with different orientations is not equal (i.e., the slit spacing of the gratings formed by different orientations of the electrode material in the electrode coating on the electrode sheet is different). At the same time, due to factors such as the fact that the electrode material particles (effective particles) are generally non-standard spherical, the slit depth caused by the orientation will also be different. The width and depth of the microscopic slits will be reflected in the reflectivity of the electrode coating on the electrode sheet (i.e., the reflectivity is also different depending on the slit width and depth). Therefore, the embodiments of this application are 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 has completed its directional alignment, R2 is the reflectivity of the powder formed by the electrode coating on the electrode sheet, and after the electrode coating forms powder, the directional alignment of the electrode main material therein disappears, that is, R2 is the reflectivity after the directional alignment of the electrode main material in the electrode coating disappears), combined with the powder formed by the electrode coating. The reflectance R2 under incident light of wavelength λ and the reflectance R1 of the electrode coating on the electrode sheet under incident light of wavelength λ are measured. Starting from the degree of order of the electrode coating on the electrode sheet, by controlling the degree of order u of the electrode coating to satisfy 1≤u≤1.85, the orientation degree and other properties of the electrode main material particles in the electrode coating on the electrode sheet can be regulated. Specifically, the electrode main material in the electrode coating on the electrode sheet can be oriented and arranged in an orderly manner, thereby improving the degree of order of the electrode main material particles in the electrode coating, forming an ordered ion transport channel, thereby reducing the internal resistance of the battery and improving the battery's rate capability and fast charging performance.

[0025] According to the applicant's further research, by further controlling 1≤u≤1.65, it is more conducive to regulating the degree of orderly arrangement of the main electrode material in the electrode coating on the electrode sheet, thereby further reducing the battery's internal resistance and improving the battery's rate performance and fast charging performance.

[0026] It should be noted that during the test u, R1 and R2 are test results at the same wavelength λ. That is, using emitted light of the same wavelength λ, the reflectivity R1 of the electrode coating on the electrode sheet under this emitted light and the reflectivity R2 of the powder formed by the electrode coating on the electrode sheet under this emitted light are tested, and then based on... Calculate the degree of order u of the electrode sheet under the emitted light.

[0027] For example, the above λ can be a range of 750nm, 800nm, 900nm, 1000nm, 1200nm, 1450nm, 1465nm, 1500nm, 2000nm, 2500nm, 3000nm, 3500nm or any two of them.

[0028] In some embodiments, λ can be 1000–3500 nm. The degree of order u of the electrode sheet is measured within this wavelength range, and 1 ≤ u ≤ 3 is controlled. This helps 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 degree of order u of the electrode sheet within this wavelength range to satisfy 1 ≤ u ≤ 3, it helps to further improve the directional arrangement order of the electrode material particles in the electrode coating on the electrode sheet, forming ordered ion transport channels, thereby reducing the internal resistance of the battery and improving the battery's rate and fast charging performance.

[0029] In some optional embodiments, λ can be 1465nm, 1700nm, or 2000nm, which helps to further reduce the battery's internal resistance and improve its rate and fast charging performance. The reason for this is that by controlling the degree of order u of the electrode sheet at wavelengths of 1465nm, 1700nm, or 2000nm to satisfy 1≤u≤1.85, it is beneficial to further improve the directional arrangement order of the electrode material particles in the electrode coating on the electrode sheet, forming an ordered ion transport channel, thereby reducing the battery's internal resistance and improving its rate and fast charging performance.

[0030] Specifically, when λ = 1465 nm, the degree of order u of the electrode coating (hereinafter referred to as u) 1465 The value 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. In one optional implementation, u 1465 The range is 1.1 to 1.6 (i.e., 1.1 ≤ u). 1465 ≤1.6), which helps to further reduce the internal resistance of the battery and improve the battery's rate capability and fast charging performance.

[0031] Specifically, R1 and R2 are measured under incident light with a wavelength of 1465nm, that is, infrared light with a wavelength of 1465nm is used as the detection wavelength to measure R1 (hereinafter referred to as R1). 1465 R1 and R2 (hereinafter referred to as R2) 1465 ), and then according to The calculated u is u 1465 .

[0032] Furthermore, when λ = 1700 nm, the degree of order u of the electrode coating (hereinafter referred to as u) 1700 The value is 1 to 1.85 (i.e., 1 ≤ u). 1700 ≤1.85), u 1700For example, it can be 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. In an optional implementation, u 1700 The range is 1.2 to 1.65 (i.e., 1.2 ≤ u). 1700 ≤1.65), which helps to further reduce the internal resistance of the battery and improve the battery's rate capability and fast charging performance.

[0033] Specifically, R1 and R2 are measured under incident light with a wavelength of 1700nm, that is, infrared light with a wavelength of 1700nm is used as the detection wavelength to measure R1 (hereinafter referred to as R1). 1700 R1 and R2 (hereinafter referred to as R2) 1700 ), and then according to The calculated u is u 1700 .

[0034] Furthermore, when λ = 2000 nm, the degree of order u of the electrode coating (hereinafter referred to as u) 2000 The value is 1 to 1.85 (i.e., 1 ≤ u). 2000 ≤1.85), u 2000 For example, it can be 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. In an optional implementation, u 2000 The range is 1.3 to 1.65 (i.e., 1.3 ≤ u). 2000 ≤1.65), which helps to further reduce the internal resistance of the battery and improve the battery's rate capability and fast charging performance.

[0035] Specifically, R1 and R2 are measured under incident light with a wavelength of 2000nm, that is, infrared light with a wavelength of 2000nm is used as the detection wavelength to measure R1 (hereinafter referred to as R1). 2000 R1 and R2 (hereinafter referred to as R2) 2000 ), and then according to The calculated u is u 2000 .

[0036] In the embodiments of this application, within the wavelength λ range (750nm~4μm) described above, R1 can be 5%~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 any combination thereof.

[0037] In some embodiments, when λ = 1465 nm, R1 (i.e., R1) 1465 The percentage 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 any combination thereof, which helps to further reduce the battery's internal resistance and improve the battery's rate capability and fast charging performance.

[0038] In some embodiments, when λ = 1465 nm, R2 (i.e., R2) 1465 The percentage 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 any combination thereof, which helps to further reduce the battery's internal resistance and improve the battery's rate capability and fast charging performance.

[0039] In some embodiments, when λ = 1700 nm, R1 (i.e., R1) 1700 The percentage 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 any combination of two of these.

[0040] In some embodiments, when λ = 1700 nm, R2 (i.e., R2) 1700 The percentage 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 any combination thereof.

[0041] In some embodiments, when λ = 2000 nm, R1 (i.e., R1) 2000 The percentage 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 any combination of two of these ranges. This helps to further reduce the battery's internal resistance and improve its rate capability and fast charging performance.

[0042] In some embodiments, when λ = 2000 nm, R2 (i.e., R2) 2000 The percentage 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 any combination of two of these.

[0043] In this embodiment of the application, a near-infrared spectrophotometer can be used to test reflectance R1 and R2. When testing reflectance R1 and R2, spectrally pure BaSO4 can be used as the reflectance background. Specifically, when testing the reflectance R1 of the electrode coating on the electrode sheet under incident light at wavelength λ, a 1.5cm diameter cutter can be used to sample the electrode sheet (i.e., cut out an electrode sheet sample). The obtained electrode sheet sample is then placed in the sample chamber, and its total reflectance (absorbance = 1 - reflectance) is measured in the integrating sphere of the near-infrared spectrophotometer under incident light at wavelength λ to obtain R1. When testing the reflectance R2 of the powder formed by the electrode coating on the electrode sheet under incident light at wavelength λ, a scraper can be used to scrape off the electrode coating from the electrode current collector surface of the electrode sheet. The scraped coating material is then crushed or ground into powder using a mortar and pestle to obtain the powder formed by the electrode coating on the electrode sheet. This powder is then used to measure its total reflectance in the integrating sphere of the near-infrared spectrophotometer under incident light at wavelength λ to obtain R2. The average particle size of the powder formed by the electrode coating on the electrode sheet is basically the same as the particle size of the electrode active material in the electrode coating. For example, the average particle size of the powder formed by the electrode coating on the electrode sheet is 0.5 μm to 50 μm.

[0044] In some embodiments, the porosity of the electrode coating can be 20% to 50%, for example, a range of 20%, 25%, 30%, 30.4%, 30.8%, 31%, 31.5%, 31.7%, 32%, 32.5%, 33%, 35%, 40%, 45%, 50%, or any combination thereof, which helps to further reduce the impedance of the electrode sheet while maintaining the high energy density of the electrode sheet, thereby further optimizing the battery performance.

[0045] In this embodiment, the areal density of the electrode coating can be 130 g / m³. 2 ~500g / m 2 For example, 130g / m 2 160g / m 2 180g / m 2 200g / m 2 210g / m 2 220g / m2 230g / m 2 240g / m 2 250g / m 2 280g / m 2 300g / m 2 400g / m 2 500g / m 2 The range of either or both of these is advantageous in balancing the properties of low impedance and high energy density of the electrode sheets, thereby further improving the battery's rate capability and fast charging performance.

[0046] In this embodiment, the compaction density of the electrode coating is 1.2 g / m³. 3 ~1.8g / m 3 For example, 1.2g / m 3 1.3g / m 3 1.4g / m 3 1.5g / m 3 1.6g / m 3 1.7g / m 3 1.8g / m 3 The range of either or both of these is beneficial for balancing the properties of the electrode sheet, such as low impedance and high energy density, thereby further improving the battery's rate capability and fast charging performance.

[0047] In this embodiment, the electrode coating includes an electrode active material, which exists in the form of particles, i.e., the electrode coating includes electrode active material particles, the shape of which can be spherical or other regular or irregular shapes.

[0048] 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, a range of 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm, 20 μm, 23 μm, 25 μm, 28 μm, 30 μm or any two of these.

[0049] In some embodiments, the electrode sheet can be a negative electrode sheet, and correspondingly, the electrode current collector is a negative electrode current collector, the electrode coating is a negative electrode coating (negative electrode active material layer), and the electrode active material is a negative electrode active material, which may include carbon active material. The carbon active material may include graphite, such as artificial graphite and / or natural graphite. The electrode coating 1 may specifically include primary graphite particles and / or secondary graphite particles.

[0050] In some specific embodiments, the particle size Dv50 of the graphite in the negative electrode coating can be 5μm to 30μm, for example, 5μm, 8μm, 10μm, 13μm, 15μm, 18μm, 20μm, 23μm, 25μm, 28μm, 30μm or any combination thereof.

[0051] In this embodiment of the application, the particle size Dv50 of the electrode active material (such as graphite) can be measured by a laser particle size analyzer.

[0052] The embodiments of this application may employ conventional negative electrode current collectors in the art, for example, negative electrode current collectors may include copper foil.

[0053] In other embodiments, the electrode sheet is a positive electrode sheet, and correspondingly, the 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 includes, for example, nickel cobalt manganese ternary material (NCM) and / or nickel cobalt aluminum ternary material (NCA).

[0054] The embodiments of this application may employ conventional positive current collectors in the art, for example, positive current collectors may include aluminum foil.

[0055] In this embodiment, an electrode coating can be provided on one side of the electrode current collector, or an electrode coating can be provided on both sides of the electrode current collector. When an electrode coating is provided on both sides of the electrode current collector, the electrode coating on one side of the electrode current collector can satisfy the above-mentioned degree of order u (i.e., 1≤u≤1.85), or the electrode coatings on both sides of the electrode current collector can satisfy the above-mentioned degree of order u (i.e., 1≤u≤1.85).

[0056] Generally, the aforementioned electrode coating also includes 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) can be 70% to 99%, for example, 70%, 75%, 80%, 85%, 90%, 93%, 95%, 97%, 99%, or any combination thereof. The mass fraction of the 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 any combination thereof. The mass fraction of the 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 any combination thereof.

[0057] In the embodiments of this application, the conductive agent in the electrode coating can be a conventional conductive material in the art, such as one or more of carbon black, carbon nanotubes (CNT), acetylene black, graphene, Ketjen black, and carbon fiber.

[0058] In this embodiment, the binder in the electrode coating can be a conventional adhesive material in the art. For example, when the electrode sheet is a negative electrode sheet, the binder may include one or more of the following: carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, 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 the following: polyvinylidene fluoride (PVDF), polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, ethylene oxide-containing polymers, polyvinylpyrrolidone, and polyurethane.

[0059] This application embodiment also provides a method for preparing the above-mentioned electrode sheet, including the following steps: coating an electrode slurry for forming the electrode coating onto the surface of the electrode current collector to form an electrode coating with an order degree u satisfying 1≤u≤1.85, thereby obtaining the electrode sheet.

[0060] In practice, after coating the electrode paste onto the surface of the electrode current collector, an electrode coating with a preset degree of order u can be formed by applying a magnetic field or electric field to the wet film formed on the surface of the electrode current collector, thereby obtaining an electrode sheet.

[0061] In some embodiments, the preparation process of the electrode sheet may include: applying an electrode slurry for forming an electrode coating to the surface of an electrode current collector to form a wet film on the surface of the electrode current collector; then applying a magnetic field or electric field to the wet film to make the wet film reach a preset degree of order; and then drying and rolling to obtain the electrode sheet.

[0062] In the above preparation process, by applying a magnetic field or electric field of preset intensity to the wet film, the arrangement state of the electrode active materials in the wet film can be induced under the action of the magnetic field or electric field. Specifically, the magnetic field or electric field acts on the electrode active materials in the wet film, which can make them oriented and orderly arranged to form ordered ion transport channels. After subsequent drying and rolling processes, the wet film forms an electrode coating with a preset degree of order u (1≤u≤1.85), and an electrode sheet with an ordered stacked crystal structure of the electrode active materials in the electrode coating is obtained.

[0063] In this embodiment, a magnetic field can be applied to the wet film using a conventional magnetic field application method, and an electric field can be applied to the wet film using a conventional electric field application method.

[0064] In practice, the orientation of the electrode active material can be induced by adjusting the intensity of the magnetic or electric field, thereby forming an electrode coating with a predetermined degree of order u, and thus producing an electrode sheet. For example, a gaussmeter can be used to probe the surface of the wet film, and the measured value is the magnetic field strength H experienced by the wet film.

[0065] 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. The time for applying the magnetic field to the wet film (i.e., the magnetic field action time) can be 10s to 2min. In 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 degree of order u.

[0066] In the embodiments of this application, drying and rolling are conventional operations in the art and are not particularly limited thereto.

[0067] In this embodiment of the application, when electrode coatings are formed on both the front and back surfaces of the electrode current collector, electrode slurry can be applied to one side surface of the electrode current collector first, and then induced and dried by a magnetic field or electric field. Then, electrode slurry can be applied to the other side surface of the electrode current collector, and then induced and dried by a magnetic field or electric field. Finally, the electrode sheet is rolled to obtain an electrode sheet.

[0068] In this embodiment, the electrode slurry can be prepared using conventional methods in the art. For example, when the electrode sheet is a negative electrode sheet, the components used to form the negative electrode coating, such as the negative electrode active material, conductive agent, and binder, can be dispersed in a first solvent, such as deionized water and / or N-methylpyrrolidone (NMP), to prepare a negative electrode slurry (i.e., the electrode slurry mentioned above). This slurry is then coated onto the surface of the negative electrode current collector, and after processes such as magnetic field or electric field induction, drying, and rolling, a negative electrode sheet is obtained. When the electrode sheet is a positive electrode sheet, the components used to form the positive electrode coating, such as the positive electrode active material, conductive agent, and binder, can be dispersed in a second solvent, such as N-methylpyrrolidone (NMP), to prepare a positive electrode slurry (i.e., the electrode slurry mentioned above). This slurry is then coated onto the surface of the positive electrode current collector, and after processes such as magnetic field or electric field induction, drying, and rolling, a positive electrode sheet is obtained.

[0069] In practice, the above-mentioned electrode slurry can be prepared at a temperature of 20 to 45°C; the electrode slurry can be coated onto the surface of the electrode current collector using conventional coating equipment in the field, such as continuous coating equipment.

[0070] This application also provides a battery, including the above-described electrode sheet or an electrode sheet prepared according to the above-described electrode sheet preparation method. This battery has advantages corresponding to the above-described electrode sheet, which will not be described in detail here.

[0071] As mentioned above, using the aforementioned electrode sheet can reduce the battery's internal resistance and improve its rate performance and fast charging performance. Specifically, the battery's DC internal resistance can be as low as 93mΩ or less, the battery's 4C / 0.2C discharge capacity ratio can be as high as 56% or more, and the battery's fast charging time in the 0-80% SOC range can be as low as 40 minutes or less.

[0072] The battery in this application embodiment can be a lithium-ion battery (such as a lithium-ion power battery), a solar cell, or other novel energy storage battery.

[0073] Generally, a battery may include an electrolyte, a battery cell, and a package containing the battery cell. The electrolyte is injected into the battery cell within the package. The battery cell includes a positive electrode, a negative electrode, and a separator located between the positive and negative electrode. The battery cell may be a stacked battery cell, meaning it is composed of a positive electrode, a separator, and a negative electrode stacked together.

[0074] In this embodiment, the positive electrode can be an electrode sheet that satisfies the above-mentioned degree of order u (i.e., the degree of order of the positive electrode coating satisfies 1≤u≤1.85), or the negative electrode can be an electrode sheet that satisfies the above-mentioned degree of order u (i.e., the degree of order of the negative electrode coating satisfies 1≤u≤1.85), or both the positive electrode and the negative electrode can be electrode sheets that satisfy the above-mentioned degree of order u (i.e., the degree of order of the positive electrode coating of the positive electrode sheet satisfies 1≤u≤1.85, and the degree of order of the negative electrode coating of the negative electrode sheet satisfies 1≤u≤1.85).

[0075] The electrolyte in this application embodiment can be a conventional electrolyte in the art. For example, the electrolyte is a non-aqueous electrolyte, which may specifically include an organic solvent and an electrolyte salt. The organic solvent may include, for example, ethylene carbonate and / or diethyl carbonate. When the battery is a sodium-ion battery, the electrolyte salt may include a lithium salt, such as lithium hexafluorophosphate (LiPF6), but is not limited thereto.

[0076] In this embodiment, the separator is used to separate the positive electrode and the negative electrode to prevent the positive electrode and the negative electrode from short-circuiting due to contact. Conventional separators in the art can be used in this embodiment, and there are no special limitations.

[0077] In this embodiment, the battery cell can be packaged using conventional encapsulation (shell) materials in the art, and the battery can be a conventional battery type and structure in the art. For example, the battery can be a blade battery, but it is not limited to this.

[0078] The embodiments of this application can assemble components such as positive electrode, separator and negative electrode into a battery using conventional methods in the art, and there are no particular limitations thereto.

[0079] This application also provides a battery pack including the battery described above, which has advantages corresponding to the electrode plates described above, and will not be described in detail here.

[0080] Generally, a battery pack includes multiple batteries as individual cells, which are connected to form the battery pack. These batteries can be electrically connected using methods conventional in the art, such as series connection, parallel connection, or a combination of these connection methods, without any particular limitation.

[0081] This application also provides an electrical device, including the battery or battery pack described above. This electrical device has advantages corresponding to the electrode plates described above, which will not be elaborated further.

[0082] The electrical equipment in the embodiments of this application can be conventional electrical equipment in the art, such as power equipment (e.g., electric vehicles, electric cars), electronic devices (e.g., mobile phones, tablets, laptops, digital cameras, etc.), wearable devices (e.g., watches, bracelets, VR glasses, etc.), energy storage power stations, etc.

[0083] In this embodiment, the process of testing the areal density of the electrode coating may include: taking an electrode sample (specifically, a 1.5cm diameter cutter can be used for sampling), testing the total mass m1 of the electrode sample, and the surface area S of one side of the electrode sample in the thickness direction; then scraping off the electrode coating on the electrode sample, and testing the mass m2 of the obtained electrode current collector. The areal density of the electrode coating is then calculated as (m1-m2) / S. The total mass m1 of the electrode sample and the mass m2 of the electrode current collector can be weighed using an electronic scale.

[0084] In this embodiment, the compaction density of the electrode coating = the areal density of the electrode coating / the total thickness of the electrode coating. The testing process for the areal density of the electrode coating is as described above. The testing process for the total thickness of the electrode coating may include: taking an electrode sheet sample and testing the total thickness T1 of the electrode sheet sample (T1 = total thickness of the electrode coating + thickness of the electrode current collector; when both the front and back surfaces of the electrode current collector are respectively provided with electrode coatings, the total thickness of the electrode coating = the thickness of the electrode coating on one side of the electrode current collector + the thickness of the electrode coating on the other side of the electrode current collector); then scraping off the electrode coating on the electrode sheet sample and testing the thickness T2 of the obtained electrode current collector. Then the total thickness of the electrode coating = T1 - T2.

[0085] In practice, 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.

[0086] In practice, the battery can be disassembled to obtain the electrode sheets. The reflectivity (R1, R2), areal density, compaction density, and porosity of the electrode coating can then be tested. For example, when testing reflectivity R1 and R2, the battery can be disassembled, and the electrode sheets removed. Specifically, the electrode sheets can be washed in solvents such as DMC to remove electrolyte components such as lithium salts from their surface. After cleaning and drying, the reflectivity R1 is tested using incident light at wavelength λ. Then, the electrode coating on the electrode sheets is scraped off, and the scraped coating material is crushed into powder using a mortar and pestle. This powder is then used to test the reflectivity R2 under incident light at wavelength λ.

[0087] In practice, after obtaining the electrode sheet, the porosity of the electrode coating of the electrode sheet can be measured by mercury intrusion porosimetry.

[0088] The present application will be further described below through specific embodiments. In the following embodiments, the magnetic field strength, the areal density and compaction density of the electrode coating, and the reflectivity (R1) at each wavelength λ are used. 1465 R1 1700 R1 2000 R2 1465 R2 1700 R2 2000 ) and degree of order u(u 1465 u 1700 u 2000 The testing methods for parameters such as the porosity of the electrode coating on the electrode sheet are as described above and will not be repeated hereafter.

[0089] In the following examples and comparative examples, the ultraviolet-near-infrared spectrophotometer used for testing reflectance was a PERKIN EIMER LAMBDA1050, and the scanning electron microscope (SEM) used was a HITACHI FLEX SEM1000.

[0090] Example 1

[0091] 1. Preparation of negative electrode sheet

[0092] (1) Mix graphite (primary graphite particles with a particle size Dv50 = 10.5 μm), carbon black, CMC and SBR in a mass ratio of 100:1:1.6:3.3, add deionized water and NMP, stir evenly, and prepare a negative electrode slurry.

[0093] (2) A negative electrode slurry is coated on one side of the copper foil using a continuous coating equipment, and a magnetic field with a strength of H = 0.7T is applied to the wet film formed. The magnetic field is used to induce the orientation of graphite in each region. The magnetic field is applied for about 2 minutes, and the magnetic field is kept uniform and stable during this period. After the magnetic field is applied, the wet film is dried to form a coating layer.

[0094] (3) Then, the coating, magnetic field application and drying process of step (2) above is repeated on the other side of the copper foil to form coating layers on both the front and back surfaces of the copper foil. After rolling, a negative electrode sheet with negative electrode coatings formed on both the front and back surfaces of the copper foil is obtained.

[0095] Among them, the reflectivity R1 of the negative electrode coating on the electrode sheet at a wavelength of λ = 1465 nm was measured. 1465 The reflectivity R1 of the negative electrode coating on the electrode sheet at a wavelength λ = 1700 nm 1700 The reflectivity R1 of the negative electrode coating on the electrode sheet at a wavelength λ = 2000 nm 2000 The reflectance R2 of the powder formed by the negative electrode coating at a wavelength of λ = 1465 nm 1465 The reflectance R2 of the powder formed by the negative electrode coating at a wavelength of λ = 1700 nm 1700 The reflectivity R2 of the powder formed by the negative electrode coating at a wavelength λ = 2000 nm 2000 The degree of order u of the negative electrode coating at wavelength λ = 2000 nm 2000 The degree of order u of the negative electrode coating on the electrode sheet at a wavelength λ = 1700 nm 1700 The degree of order u of the negative electrode coating on the electrode sheet at a wavelength λ = 1465 nm 1465 The areal density, compacted density, and porosity of the negative electrode coating are shown in Table 1. Among these, the reflectance (R²) of the powder formed from the negative electrode coating was tested. 1465 R2 1700 R2 2000 When the powder formed by the negative electrode coating is applied, the average particle size Dv50 is approximately 10.5 μm.

[0096] 2. Preparation of the positive electrode sheet

[0097] 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. The mixture was stirred evenly to prepare a positive electrode slurry.

[0098] A positive electrode slurry is coated onto both sides of an aluminum foil. After drying and rolling, a positive electrode coating is formed on both sides of the aluminum foil, thus producing a positive electrode sheet. The areal density of the positive electrode coating is approximately 500 g / m³. 2 .

[0099] 3. Battery assembly

[0100] In a glove box under an argon atmosphere, positive electrode plates, separators, and negative electrode plates are alternately stacked and injected with electrolyte to assemble a soft-pack battery (with a designed capacity of 0.9 Ah). The composition of the electrolyte is as follows: the organic solvent is a mixture of ethylene carbonate and diethyl carbonate in a volume ratio of 1:1, and the concentration of LiPF6 in the electrolyte is 1 mol / L.

[0101] Example 2: The difference from Example 1 is that during the preparation of the negative electrode, the magnetic field strength H = 0.5T and the magnetic field time is about 1 minute. The remaining steps and conditions are the same as in Example 1.

[0102] Example 3: The difference from Example 1 is that during the preparation of the negative electrode, the magnetic field strength H = 0.41T and the magnetic field time is about 1 minute. The remaining steps and conditions are the same as in Example 1.

[0103] Example 4: The difference from Example 1 is that during the preparation of the negative electrode, the magnetic field strength H = 0.32T and the magnetic field time is about 1 minute. The remaining steps and conditions are the same as in Example 1.

[0104] Example 5: The difference from Example 1 is that the areal density of the negative electrode coating of the negative electrode sheet is 204.5 g / m². 2 The areal density of the positive electrode coating of the positive electrode sheet is approximately 456 g / m³. 2 In the preparation of the negative electrode, the magnetic field strength 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.

[0105] Example 6: The difference from Example 1 is that during the preparation of the negative electrode, the magnetic field strength H = 0.21T and the magnetic field time is about 10s. The remaining steps and conditions are the same as in Example 1.

[0106] 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, after the negative electrode slurry is coated on both the front and back surfaces of the copper foil, it is dried and rolled to form a negative electrode coating and obtain a negative electrode sheet). The remaining steps and conditions are the same as in Example 1.

[0107] Following the procedure below, the DC impedance (DCIR) and long-cycle performance (number of cycles when capacity decays to 80%) of the batteries in each embodiment and comparative example were tested respectively, and the results are shown in Table 1.

[0108] (1) DC internal resistance test: At 25℃, adjust the state of charge of the above soft pack battery to 50% SOC, and then discharge it at 1.5C rate for 30s. Record the voltage drop of the soft pack battery, and then calculate the DC impedance DCIR.

[0109] (2) Rate performance: At 25℃, the discharge capacity of the battery at 0.2C and 4C rates was tested as a function of the number of cycles, with a voltage range of 2.0-3.8V. The ratio of the first discharge capacity at 5C rate to the first discharge capacity at 0.2C rate was calculated, which is the rate performance test result (i.e., the 4C / 0.2C discharge capacity ratio in Table 1).

[0110] (3) Fast charging strategy: At 25℃, adjust the SOC of the above-mentioned soft-pack battery to 0% (i.e., fully discharge the battery), then charge at a rate of 0.33C to 3.8V, and then fully discharge the battery; then charge at a rate of 0.5C to 3.8V, and then fully discharge the battery; then charge at a rate of 1C to 3.8V, and then fully discharge the battery; then charge at a rate of 2C to 3.8V, and then fully discharge the battery; then charge at a rate of 3C to 3.8V, and then fully discharge the battery; then charge at a rate of 4C to... 3.8V, then fully discharge the battery; then charge at a 5C rate to 3.8V, then fully discharge the battery; then charge at a 6C rate to 3.8V. Calculate the SOC (State of Charge) of the battery at each charging rate (i.e., the proportion of the battery's discharged capacity to its full charge capacity). Subtract 20% from the SOC to calculate the charging time, which is the safe charging time at this rate. Add the safe charging times at different rates (gradually decreasing from 6C) to get the fast charging time for the 0-80% SOC strategy.

[0111] Table 1

[0112] As can be seen from Table 1, compared with 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 enables the battery to have a lower DC internal resistance (not higher than 98.2 mΩ), a larger 4C / 0.2C discharge capacity ratio (not lower than 53.32%), and exhibits good rate performance. At the same time, the battery has a shorter fast charging time (not higher than 40.15 min), exhibiting good fast charging performance.

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

[0114] Taking Example 1 and Comparative Example 1 as examples, the cross-sections of the negative electrode coating in Example 1 and Comparative Example 1 were observed using a scanning electron microscope (SEM) (the arrangement of graphite particles in the negative electrode coating was observed by SEM). The SEM image of the cross-section of the negative electrode coating in Example 1 is shown in Figure 1, and the SEM image of the cross-section of the negative electrode coating in Comparative Example 1 is shown in Figure 2. As can be seen from Figures 1 and 2, the deflection angles of the graphite particles in the negative electrode coatings 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, which reduces the impedance of the electrode sheet and 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 this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. An electrode sheet, characterized in that, Includes an electrode current collector and an electrode coating located on at least one side surface of the electrode current collector; The degree of order u of the electrode coating satisfies 1≤u≤1.85; R1 is the reflectance of the electrode coating on the electrode sheet under incident light with wavelength λ, and R2 is the reflectance of the powder formed from the electrode coating on the electrode sheet under incident light with wavelength λ; where λ is 750nm~4μm.

2. The electrode sheet according to claim 1, characterized in that, The value of λ is 1000–3500 nm.

3. The electrode sheet according to claim 2, characterized in that, The λ is 1465nm, 1700nm, or 2000nm.

4. The electrode sheet according to any one of claims 1-3, characterized in that, 1≤u≤1.65。 5. The electrode sheet according to any one of claims 1-4, 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.

6. The electrode sheet according to any one of claims 1-4, characterized in that, The R1 ranges from 5% to 37%.

7. The electrode sheet according to claim 6, characterized in that, When λ = 1465 nm, R1 is 6% to 28%.

8. The electrode sheet according to claim 6, characterized in that, When λ = 1700 nm, R1 is 10% to 30%.

9. The electrode sheet according to claim 6, characterized in that, When λ = 2000 nm, R1 is 7% to 33%.

10. The electrode sheet according to any one of claims 1-4, characterized in that, The porosity of the electrode coating is 20% to 50%.

11. The electrode sheet according to any one of claims 1-4, characterized in that, The areal density of the electrode coating is 130 g / m³. 2 ~500g / m 2 ; And / or, the compaction density of the electrode coating is 1.2 g / cm³. 3 ~1.8g / cm 3 .

12. The electrode sheet according to any one of claims 1-4, characterized in that, The electrode sheet is a negative electrode sheet.

13. The electrode sheet according to claim 12, characterized in that, The electrode coating includes an electrode active material, which includes graphite.

14. The electrode sheet according to any one of claims 1-4, characterized in that, The electrode sheet is a positive electrode sheet.

15. The electrode sheet according to claim 14, characterized in that, The electrode coating includes an electrode active material, which includes one or more of the following: ternary cathode material, lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, and lithium nickel manganese oxide.

16. A method for preparing an electrode sheet according to any one of claims 1-15, characterized in that, The process includes the following steps: applying an electrode paste for forming the electrode coating onto the surface of the electrode current collector to form an electrode coating with an order degree u satisfying 1≤u≤1.85, thereby obtaining the electrode sheet.

17. A battery, characterized in that, This includes the electrode sheet as described in any one of claims 1-15 or the electrode sheet prepared according to the method described in claim 16.

18. A battery pack, characterized in that, Includes the battery as described in claim 17.

19. An electrical appliance, characterized in that, Includes the battery of claim 17 or the battery pack of claim 18.

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