Electrode plate, battery and electric equipment

Abstract

The invention relates to an electrode plate, a battery and electric equipment. The electrode plate comprises a current collector layer and an active material layer, the active material layer is arranged on at least one side of the current collector layer, the active material layer comprises a plurality of active particles and a first adhesive, and the glass transition temperature Tg of the first adhesive ranges from-60 DEG C < = Tg < = 0 DEG C, the first adhesive comprises first particles and second particles, the first particles are distributed among gaps of the multiple active particles, the second particles are arranged on the surfaces of the active particles, the first long axis of each first particle is L1, the second long axis of each second particle is L2, the expansion coefficient alpha of the first adhesive is equal to L2 / L1, and the expansion coefficient alpha of the second adhesive is equal to L2 / L1. And the expansion coefficient alpha is greater than or equal to 1.2 and less than or equal to 3.3.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and particularly relates to an electrode sheet, a battery and an electrical device using the same. Background Art

[0002] With the development of lithium-ion batteries, dry electrodes have great development potential. In the manufacturing process of dry electrodes, solvents are not used, avoiding solvent recovery and reducing environmental pollution. The preparation of dry electrodes does not require a drying process, which can save a large amount of energy. At the same time, problems such as the floating of binders and cracks in the electrode sheet caused by coating and drying in the wet process are avoided. However, the preparation of dry electrodes also has certain shortcomings. Among them, the selection range of polymer binders used in the electrode sheet is small. Currently, the most commonly used one is polytetrafluoroethylene (PTFE). However, when using polytetrafluoroethylene alone, the cohesive force of the electrode sheet is relatively low, and the structural stability of the electrode sheet is poor. Summary of the Invention

[0003] In view of this, the present application provides an electrode sheet, a battery and an electrical device using the same, and the electrode sheet has a relatively high cohesive force.

[0004] The present application provides an electrode sheet, which includes a current collector layer and an active material layer. The active material layer is disposed on at least one side of the current collector layer. The active material layer includes a plurality of active particles and a first binder. The glass transition temperature Tg of the first binder ranges from -60°C to 0°C. The first binder includes a first particle and a second particle. The first particle is distributed among the gaps between the plurality of active particles, and the second particle is disposed on the surface of the active particle. The first major axis of the first particle is L1, and the second major axis of the second particle is L2. Then, the expansion coefficient α of the first binder is α = L2 / L1, and the range of the expansion coefficient α is 1.2 ≤ α ≤ 3.3.

[0005] Further, the first minor axis of the first particle is L3, and the first particle satisfies the relationship: 0.5 ≤ L3 / L1 ≤ 1; the second minor axis of the second particle is L4, and the second particle satisfies the relationship: 0.2 ≤ L4 / L2 ≤ 0.65.

[0006] Further, the area of the active particle is S1, the number of the second particles on the surface of a single active particle is N, and the average value of the areas of the plurality of second particles on the surface of the same active particle is S2. Then, the relationship 0.3 ≤ N×S2 / S1 ≤ 0.9 is satisfied.

[0007] Further, the material of the first adhesive is selected from at least one of isooctyl acrylate, butyl acrylate, methyl methacrylate, vinyl acetate, acrylic acid, 2-hydroxyethyl methacrylate, toluene diisocyanate, diphenylmethane diisocyanate, polyester polyol, polyether polyol, and N-methylol acrylamide.

[0008] Further, the range of the particle size D of the first adhesive is: 10 μm ≤ D ≤ 100 μm.

[0009] Further, the active material layer further includes a second adhesive, the second adhesive is a second adhesive, and in the active material layer, the second adhesive has a fibrous structure.

[0010] Further, at least a part of the first adhesive and the second adhesive overlap, and in the active material layer, the mass fraction m1 of the first adhesive and the mass fraction m2 of the second adhesive satisfy the relationship: 0.66 ≤ m1 / m2 ≤ 5.

[0011] Further, in the active material layer, the range of the mass fraction m1 of the first adhesive is: 1.5% ≤ m1 ≤ 2.5%, and the range of the mass fraction m2 of the second adhesive is: 0.5% ≤ m2 ≤ 3%.

[0012] The present application provides a battery, which includes the electrode pole piece provided by the present application and the electrolyte provided by the present application, and the electrolyte is used to infiltrate the electrode pole piece.

[0013] The present application provides an electrical device, which includes a device body and the battery provided by the present application, and the battery powers the device body.

[0014] In the present application, the active material layer includes a plurality of active particles and a first binder. The first binder is used to bond the plurality of active particles so that the active material layer has good structural stability, facilitating the insertion and extraction of active ions such as lithium ions when the electrode sheet is applied to a battery. The glass transition temperature Tg of the first binder satisfies the range: -60°C ≤ Tg ≤ 0°C. Since the first binder has a low glass transition temperature, the first binder exhibits a highly elastic state at a relatively low temperature, showing higher flexibility and elasticity, which is conducive to maintaining good bonding performance to better bond the plurality of active particles. When the first binder is applied to the active material layer, the first particles are distributed among the gaps between the plurality of active particles, and the second particles are disposed on the surfaces of the active particles. Compared with the first particles, the second particles undergo a compaction process during the compaction of the electrode sheet, so that the second major axis is greater than the first major axis of the first particles, enabling the second particles to bond two relatively large surfaces of the oppositely disposed active particles to enhance the bonding performance between the two oppositely disposed active particles. The first particles are distributed among the gaps between the plurality of active particles to bond two adjacent active particles. The use of the first binder can reduce the amount of the second binder in the active material layer to make up for the defects in the bonding performance of the second binder and improve the cohesion of the electrode sheet. When the expansion coefficient α of the first binder satisfies the range 1.2 ≤ α ≤ 3.3, the expansion coefficient of the first binder is within a reasonable range. In other words, the ratio of the second major axis of the second particles to the first major axis of the first particles is within a reasonable range. In other words, during the compaction of the electrode sheet, the second particles are compacted and the degree of compaction is within a reasonable range, enabling the second particles to effectively bond two relatively large surfaces of the oppositely disposed active particles. The second particles cooperate with the first particles to enhance the bonding performance between the active particles, so that the electrode sheet has high cohesion and good structural stability, reducing the occurrence of powder shedding during the preparation of the electrode sheet, which may affect the preparation process. When the electrode sheet is applied to a battery and during charge and discharge, the electrode sheet has good structural stability to prevent the active material layer from peeling off during the insertion and extraction of lithium ions, so that the battery has a high capacity and good cycle performance. When the expansion coefficient α of the first binder is too large, correspondingly, the second major axis of the second particles is too large, and the degree of compaction of the second particles is too large, which will increase the compaction degree of the electrode sheet, thus increasing the processing difficulty of the electrode sheet.When the expansion coefficient α of the first adhesive is too small, the degree of deformation of the second particles is too small compared to the first particles. On the surface of the active particles per unit area, the contact area between the second particles and the active particles is too small, weakening the bonding performance of the second particles to the active particles, thereby making the cohesive force of the electrode sheet relatively small. Description of the Drawings

[0015] To more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the implementation will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0016] Figure 1 Partial cross-sectional structure schematic diagram of an electrode sheet according to an embodiment of the present application;

[0017] Figure 2 Simple structure schematic diagram of active particles applied to an electrode sheet according to an embodiment of the present application;

[0018] Figure 3 Scanning electron microscope image of the active material layer of an electrode sheet according to an embodiment of the present application;

[0019] Figure 4 Structure schematic diagram of a battery according to an embodiment of the present application;

[0020] Figure 5 Structure schematic diagram of an electrical device according to an embodiment of the present application;

[0021] Figure 6 Circuit block diagram of an electrical device according to an embodiment of the present application.

[0022] Explanation of the reference numerals in the drawings:

[0023] 100 - Electrode sheet, 110 - Current collector layer, 120 - Active material layer, 200 - Battery, 210 - Electrolyte, 300 - Electrical device, 310 - Device body. Detailed Embodiments

[0024] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0025] In the description, claims and the above-mentioned drawings of this application, terms such as "first", "second", etc. are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "comprise" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products or devices.

[0026] Reference herein to "embodiment" or "embodiment manner" means that a particular feature, structure or characteristic described in connection with the embodiment or embodiment manner can be included in at least one embodiment of this application. The phrase appears at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0027] With the development of lithium-ion batteries, dry electrodes have great development space. Dry electrodes do not use solvents during the manufacturing process, avoiding solvent recovery and reducing environmental pollution. The preparation of dry electrodes does not require a drying process, which can save a large amount of energy and avoid problems such as the floating of adhesives and cracks in the electrode sheets caused by the coating drying in the wet process. However, the preparation of dry electrodes also has certain drawbacks. Among them, the choice of polymer adhesives used in the electrode sheets is limited. Currently, the most commonly used is polytetrafluoroethylene (PTFE). However, when using polytetrafluoroethylene alone, the internal cohesion of the electrode sheets is relatively low, making the electrode sheets prone to surface powdering, which affects the preparation of the electrode sheets. In addition, the lower the internal cohesion of the electrode sheets, the worse the structural stability of the electrode sheets. During the process of lithium ion insertion and extraction, the coating of the electrode sheets with low internal cohesion is prone to peeling, which will lead to the attenuation of the battery capacity and the shortening of the cycle life.

[0028] Please refer to Figure 1 and Figure 2, this application provides an electrode tab 100, the electrode tab 100 includes a current collector layer 110 and an active material layer 120, the active material layer 120 is disposed on at least one side of the current collector layer 110, the active material layer 120 includes a plurality of active particles and a first binder, the glass transition temperature Tg of the first binder ranges from -60°C ≤ Tg ≤ 0°C, the first binder includes a first particle and a second particle, the first particle is distributed among the gaps of the plurality of active particles, the second particle is disposed on the surface of the active particle, the first major axis of the first particle is L1, the second major axis of the second particle is L2, then the expansion coefficient α of the first binder is α = L2 / L1, and the range of the expansion coefficient α is: 1.2 ≤ α ≤ 3.3.

[0029] Optionally, in some embodiments, the active material layer 120 is disposed on one side of the current collector layer 110; in other embodiments, the number of layers of the active material layer 120 is two, and the two active material layers 120 are respectively disposed on opposite sides of the current collector layer 110.

[0030] Specifically, the value of the glass transition temperature Tg of the first binder may be, but is not limited to, -60°C, -55°C, -50°C, -48°C, -44°C, -40°C, -35°C, -30°C, -25°C, -20°C, -15°C, -10°C, -5°C, and 0°C, etc.

[0031] Specifically, the value of the expansion coefficient α may be, but is not limited to, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, and 3.3, etc.

[0032] It can be understood that the second major axis of the second particle is longer than the first major axis of the first particle.

[0033] It can be understood that in the terms of this application, "a plurality" means greater than or equal to two, and may be, but is not limited to, two, ten, fifty, one hundred, etc.

[0034] It can be understood that the number of the first particles is a plurality, and the number of the second particles is a plurality.

[0035] It can be understood that the first major axis of the first particle is the maximum radial dimension of the first particle, and the second major axis of the second particle is the maximum radial dimension of the second particle.

[0036] Understandably, the distribution positions of the first particles and the second particles in the active material layer 120 are different. Compared with the first particles, the second particles undergo a compaction process. In other words, the structure of the second particles before compaction is similar to the structure of the first particles.

[0037] Understandably, the expansion coefficient can characterize the change in the structure of the second particles before and after compaction. The larger the expansion coefficient, the greater the change in the structure of the second particles before and after compaction; the smaller the expansion coefficient, the smaller the change in the structure of the second particles before and after compaction.

[0038] Understandably, Figure 2 The embodiment shows a simple schematic structural diagram of the application of active particles to the electrode plate 100. Figure 2 In which A indicates the first particles, Figure 2 In which B indicates the second particles. When the first particles and the second particles are applied to the electrode plate 100, they are compacted. Figure 2 It shows a schematic cross-sectional view of the first particles and the second particles after being compacted.

[0039] In this embodiment, the active material layer 120 includes a plurality of active particles and a first binder. The first binder is used to bond the plurality of active particles so that the active material layer 120 has better structural stability. When the electrode plate 100 is applied to the battery 200, it is convenient for active ions such as lithium ions to be embedded and extracted. The glass transition temperature Tg of the first binder satisfies the range: -60°C ≤ Tg ≤ 0°C. Since the first binder has a low glass transition temperature, the first binder exhibits a highly elastic state at a low temperature, showing higher flexibility and elasticity, which is convenient for maintaining good bonding performance to better bond a plurality of active particles. When the first binder is applied to the active material layer 120, the first particles are distributed among the gaps between the plurality of active particles, and the second particles are disposed on the surfaces of the active particles. Compared with the first particles, the second particles undergo a compaction process during the compaction of the electrode plate 100, so that the second major axis is greater than the first major axis of the first particles, so that the second particles can be used to bond two relatively large surfaces of the relatively arranged active particles to improve the bonding performance between the two relatively arranged active particles. The first particles are distributed among the gaps between the plurality of active particles to bond two adjacent active particles. The use of the first binder can reduce the amount of the second binder in the active material layer 120 to make up for the defects of the second binder in bonding performance and improve the cohesion of the electrode plate 100. When the expansion coefficient α of the first binder satisfies the range: 1.2 ≤ α ≤ 3.3, the expansion coefficient of the first binder is within a reasonable range. In other words, the ratio of the second major axis of the second particles to the first major axis of the first particles is within a reasonable range. In other words, during the compaction of the electrode plate 100, the second particles are compacted and the degree of compaction is within a reasonable range, so that the second particles can effectively bond two relatively large surfaces of the relatively arranged active particles. The second particles cooperate with the first particles to improve the bonding performance between the active particles, so that the electrode plate 100 has high cohesion and good structural stability, and to slow down the situation that the electrode plate 100 drops powder during the preparation process and affects the preparation. When the electrode plate 100 is applied to the battery 200 and during charge and discharge, the electrode plate 100 has good structural stability to prevent the active material layer 120 from falling off during the embedding and extraction of lithium ions, so that the battery 200 has a high capacity and good cycle performance. When the expansion coefficient α of the first binder is too large, correspondingly, the second major axis of the second particles is too large, and the degree of compaction of the second particles is too large, which will increase the compaction degree of the electrode plate 100, thereby increasing the processing difficulty of the electrode plate 100.When the expansion coefficient α of the first adhesive is too small, the degree of deformation of the second particles is too small compared to the first particles. On the surface of the active particles per unit area, the contact area between the second particles and the active particles is too small, weakening the bonding performance of the second particles to the active particles, thereby making the cohesive force of the electrode sheet 100 relatively small.

[0040] Optionally, the electrode sheet 100 may be a positive electrode sheet, and the electrode sheet 100 may also be a negative electrode sheet.

[0041] It can be understood that the expansion coefficient of the first adhesive is related to the hot pressing pressure when hot pressing the electrode sheet 100. Correspondingly, under the same other conditions, the greater the hot pressing pressure for hot pressing the electrode sheet 100, the greater the degree of compaction of the electrode sheet 100 and the second particles, and the greater the expansion coefficient of the first adhesive.

[0042] It can be understood that in the terms of this application, the surface of the active particles can represent the main material large surface of the active particles. By way of example, when the electrode sheet 100 is a negative electrode sheet and the active material is graphite, graphite has a layered structure, and the main material large surface of the active particles is the basal plane of the graphite, that is, the plane parallel to the layered structure in the graphite crystal.

[0043] In some embodiments, the first short axis of the first particles is L3, and the first particles satisfy the relational expression: 0.5 ≤ L3 / L1 ≤ 1; the second short axis of the second particles is L4, and the second particles satisfy the relational expression: 0.2 ≤ L4 / L2 ≤ 0.65.

[0044] It can be understood that the first particles are spherical or quasi-spherical, and the second particles are flat circular or elliptical.

[0045] It can be understood that when the value of L3 / L1 is equal to 1, the first particles are spherical.

[0046] Specifically, the value of L3 / L1 can be, but is not limited to, 0.5, 0.52, 0.54, 0.55, 0.58, 0.59, 0.6, 0.62, 0.65, 0.68, 0.7, 0.72, 0.75, 0.78, 0.8, 0.82, 0.85, 0.88, 0.9, 0.92, 0.95, 0.98, and 1, etc.

[0047] Specifically, the value of L4 / L2 can be, but is not limited to, 0.2, 0.22, 0.25, 0.28, 0.3, 0.32, 0.35, 0.38, 0.4, 0.42, 0.45, 0.5, 0.52, 0.55, 0.58, 0.6, 0.62, 0.63, and 0.65, etc.

[0048] In this embodiment, the first particle has a first major axis L1 and a first minor axis L3, and the first particle satisfies the relationship 0.5 ≤ L3 / L1 ≤ 1. Then, the shape of the first particle is spherical or quasi-spherical, so as to be distributed among the gaps between multiple active particles and bond adjacent multiple active particles, so as to fill the gaps between multiple active particles and improve the bonding performance between adjacent multiple active particles. The second particle has a second major axis L2 and a second minor axis L4, and the second particle satisfies the relationship 0.2 ≤ L4 / L2 ≤ 0.65. Then, the shape of the second particle is flat circular or ellipsoidal. The second particle is disposed on the surface of the active particle. During the compaction process of the electrode plate 100, the second particle is compacted and finally presents a flat circular shape, so that on the surface of a single active particle, a single second particle is compacted and has a larger contact area with the active particle, thereby more effectively bonding two larger surfaces of two relatively arranged active particles, so as to improve the bonding performance between two relatively arranged active particles. The first particle and the second particle cooperate with each other, and the glass transition temperatures of the first particle and the second particle both satisfy the range: -60°C ≤ Tg ≤ 0°C. The first particle and the second particle can exhibit bonding performance at a lower temperature, and effectively bond adjacent active particles at different positions, effectively improving the cohesive force and structural stability of the electrode plate 100, so as to slow down the powder falling situation during the preparation process of the electrode plate 100 and improve the preparation performance of the electrode plate 100. When the electrode plate 100 is applied to the battery 200 and during the charge and discharge process, the active material layer 120 can be prevented from falling off during the process of lithium ion insertion and extraction, so that the battery 200 has a higher capacity and better cycle performance.

[0049] Optionally, in some embodiments, the first particle and the second particle further satisfy the relationship: L3 / L1 > L4 / L2.

[0050] In this embodiment, the first particles are distributed among the gaps between the plurality of active particles, and the second particles are disposed on the surfaces of the active particles. Compared with the first particles, the second particles undergo a compaction process during the compaction of the electrode sheet 100, such that the second major axis of the second particles is greater than the first major axis of the first particles, and the value of L3 / L1 is greater than the value of L4 / L2. The degree of compaction of the second particles is within a reasonable range, so that each second particle has a larger contact area with the active particles, which is beneficial for the second particles to effectively bond two relatively large surfaces of two opposite active particles, thereby facilitating the improvement of the cohesive force of the electrode sheet 100 and reducing the powder shedding during the preparation of the electrode sheet 100, and enhancing the preparation performance of the electrode sheet 100. In addition, the shedding of the active material layer 120 during the insertion and extraction of lithium ions can be avoided, so that the battery 200 has a high capacity and good cycling performance.

[0051] In some embodiments, the area of the active particles is S1, the number of the second particles on the surface of a single active particle is N, and the average area of the plurality of second particles on the surface of the same active particle is S2, then the relational expression is satisfied: 0.3 ≤ N×S2 / S1 ≤ 0.9.

[0052] Specifically, the value of N×S2 / S1 can be, but is not limited to, 0.3, 0.32, 0.34, 0.36, 0.38, 0.4, 0.42, 0.45, 0.5, 0.52, 0.55, 0.58, 0.6, 0.62, 0.64, 0.66, 0.68, 0.7, 0.72, 0.75, 0.78, 0.8, 0.82, 0.85, 0.88, and 0.9, etc.

[0053] Specifically, the value of N can be, but is not limited to, 6, 8, 10, 12, 15, 18, etc.

[0054] It can be understood that after the electrode sheet 100 is compacted, on the surface of the same active particle, each second particle is in a flat circular shape, and at least a part of the plurality of second particles overlap and form a sheet-like adhesive film.

[0055] It can be understood that on the surface of the same active particle, the area of the sheet-like adhesive film formed by the plurality of flat circular second particles is S3, then the relational expression is satisfied: S3 ≤ N×S2.

[0056] Understandably, on the surface of the same active particle, the film occupation coefficient β of the plurality of second particles satisfies the relationship: β = S3 / S1. If the plurality of second particles just touch without overlapping, then S3 = N×S2, that is, it satisfies the relationship β = N×S2 / S1, and the range of β is 0.3 ≤ β ≤ 0.9.

[0057] In this embodiment, the value of N×S2 can roughly represent the area of the plurality of second particles on the surface of the same active particle, that is, it represents the area of the sheet adhesive film formed by the plurality of flat circular second particles on the surface of one active particle. Here, the overlapping area of the plurality of second particles is ignored. When the second particles satisfy the relationship 0.3 ≤ N×S2 / S1 ≤ 0.9, then on the surface of the same active particle, the area of the sheet adhesive film formed by the plurality of second particles is within a reasonable range, so that the plurality of second particles have a large contact area with the surface of the active particle, and the plurality of second particles can effectively bond the surfaces of the two relatively arranged active particles to improve the bonding performance between the active particles, thereby improving the cohesion of the electrode sheet 100. When the value of N×S2 / S1 is too large, then when the area on the surface of the active particle is certain, the area of the sheet adhesive film formed by the plurality of second particles is too large, which causes waste of the first adhesive on the one hand and occupies the space of the active particle on the other hand, thus reducing the amount of active material in the active material layer 120 and lowering the capacity of the electrode sheet 100. When the value of N×S2 / S1 is too small, then when the area on the surface of the active particle is certain, the area of the sheet adhesive film formed by the plurality of second particles is too small, and the second particles are difficult to effectively bond the active particles, resulting in a lower cohesion of the electrode sheet 100 and a poor structural stability. When the electrode sheet 100 is applied to the battery 200, it may cause the active material layer 120 to fall off during the insertion and extraction of lithium ions, resulting in a lower capacity and a poor cycle performance of the battery 200.

[0058] Optionally, in some embodiments, the material of the first adhesive is selected from at least one of ester monomers, alcohol monomers or polyamide monomers, so as to facilitate the regulation of the glass transition temperature of the first adhesive, so that the glass transition temperature Tg of the first adhesive satisfies the range -60°C ≤ Tg ≤ 0°C.

[0059] In some embodiments, the material of the first adhesive is selected from at least one of isooctyl acrylate, butyl acrylate, methyl methacrylate, vinyl acetate, acrylic acid, 2-hydroxyethyl methacrylate, toluene diisocyanate, diphenylmethane diisocyanate, polyester polyol, polyether polyol and N-methylolacrylamide.

[0060] In the terms of this application, "at least one kind" means one kind or more kinds, and "a plurality of kinds" means two or more kinds, which can be but not limited to two kinds, three kinds, four kinds, etc.

[0061] In this embodiment, isooctyl acrylate, butyl acrylate, methyl methacrylate, vinyl acetate, acrylic acid, 2-hydroxyethyl methacrylate, toluene diisocyanate and diphenylmethane diisocyanate are ester monomers, all having a polar group ester group, and polyester polyol and polyether polyol are alcohol monomers, all having a polar group hydroxyl group, while N-methylolacrylamide is a polyamide monomer having an amide group. The above monomers are relatively active, facilitating the control of the degree of polymerization and molecular structure of the polymer formed by at least one of isooctyl acrylate, butyl acrylate, methyl methacrylate, vinyl acetate, acrylic acid, 2-hydroxyethyl methacrylate, toluene diisocyanate, diphenylmethane diisocyanate, polyester polyol, polyether polyol and N-methylolacrylamide, thereby regulating the glass transition temperature of the first adhesive so that the glass transition temperature of the first adhesive satisfies the range of -60°C ≤ Tg ≤ 0°C. The first adhesive exhibits a highly elastic state at a relatively low temperature, showing higher flexibility and elasticity, facilitating the maintenance of good adhesive properties to effectively adhere the plurality of active particles.

[0062] In some embodiments, the range of the particle size D of the first adhesive is: 10μm ≤ D ≤ 100μm.

[0063] It can be understood that when the first adhesive is the first particle, the particle size of the first adhesive is the first major axis of the first particle; when the first adhesive is the second particle, the particle size of the first adhesive is the second major axis of the second particle.

[0064] Specifically, the value of the particle size D of the first adhesive can be but not limited to 10μm, 12μm, 15μm, 18μm, 20μm, 25μm, 28μm, 30μm, 32μm, 35μm, 40μm, 45μm, 50μm, 52μm, 55μm, 58μm, 60μm, 62μm, 65μm, 68μm, 70μm, 72μm, 75μm, 80μm, 82μm, 85μm, 90μm, 92μm, 95μm and 100μm, etc.

[0065] In this embodiment, when the value of the particle size D of the first adhesive satisfies the range of 10 μm ≤ D ≤ 100 μm, the particle size D of the first adhesive meets a reasonable range. The first adhesive not only has good adhesive properties but also can be uniformly dispersed in the active material layer 120, so that the first particles can be uniformly distributed among the gaps between the plurality of active particles, and the second particles can be disposed on the surfaces of the active particles. The first particles and the second particles cooperate to effectively bond the plurality of active particles, thereby enabling the active material layer 120 to have good adhesive properties inside. Further, there is also good adhesive performance between the active material layer 120 and the current collector layer 110, so that the electrode sheet 100 has good overall performance.

[0066] In some embodiments, the active material layer 120 further includes a second adhesive, and the second adhesive is a second adhesive. In the active material layer 120, the second adhesive has a fibrous structure.

[0067] In the electrode sheet 100 provided in this embodiment, the active material layer 120 includes the first adhesive and the second adhesive. The second adhesive has a fibrous structure, and a plurality of fibrous structures can preferentially form an adhesive film to be distributed among the plurality of active particles and finally form an adhesive network. The first particles of the first adhesive are distributed among the gaps between the plurality of active particles, and the second particles of the first adhesive are disposed on the surfaces of the active particles. The first particles and the second particles connect the plurality of active particles on the basis of the adhesive film. Moreover, the first adhesive exhibits high elasticity at a relatively low temperature, showing higher flexibility and elasticity, and can maintain good adhesive properties, so that there is good adhesive performance between the plurality of active particles inside the active material layer 120, thereby enabling the electrode sheet 100 to have high cohesive force and structural stability. Compared with the scheme of separately providing the first adhesive or the second adhesive in the active material layer 120 alone, in this embodiment, the first adhesive and the second adhesive cooperate with each other to form an adhesive network on the surfaces of the active particles, improving the adhesive performance between the plurality of active particles and also increasing the peel force between the active material layer 120 and the current collector layer 110, so that the electrode sheet 100 has greater cohesive force and better structural stability. Specifically, the second adhesive is compounded with the first adhesive to improve the cohesive force of the electrode sheet 100. In other words, the second adhesive and the first adhesive cooperate to have better adhesive properties. This is because polytetrafluoroethylene has a low surface energy and a small critical surface tension, while the first adhesive has a low glass transition temperature and has good flexibility and fluidity even at a relatively low temperature to contact and form an adhesive network with the second adhesive.

[0068] Specifically, in some embodiments, if the second adhesive is used alone, the cohesion of the electrode sheet 100 is about 10 N / m; if the first adhesive and the second adhesive are used simultaneously, the cohesion of the electrode sheet 100 is greater than 10 N / m. Preferably, if the first adhesive and the second adhesive are used simultaneously, the cohesion of the electrode sheet 100 is greater than or equal to 20 N / m.

[0069] Optionally, in some embodiments, part of the second adhesive is located between adjacent first particles and second particles, and part of the second adhesive penetrates through the first particles and the second particles. The first adhesive and the second adhesive cooperate with each other to form an adhesive network for effectively bonding the plurality of active particles.

[0070] In some embodiments, at least part of the first adhesive and the second adhesive overlap, and in the active material layer 120, the mass fraction m1 of the first adhesive and the mass fraction m2 of the second adhesive satisfy the relational expression: 0.66 ≤ m1 / m2 ≤ 5.

[0071] Specifically, the value of m1 / m2 can be, but is not limited to, 0.66, 0.67, 0.8, 0.9, 1, 1.2, 1.3, 1.5, 1.8, 2, 2.1, 2.3, 2.5, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.3, 4.5, 4.8, 4.9, and 5, etc.

[0072] In this embodiment, the first adhesive and the second adhesive at least partially overlap to form an adhesive network for effectively bonding the plurality of active particles and enhancing the cohesion of the electrode sheet 100. When the mass fraction of the first adhesive and the mass fraction of the second adhesive satisfy the relationship 0.66 ≤ m1 / m2 ≤ 5, the mass fractions of the first adhesive and the second adhesive are both within a reasonable range. On the one hand, the second adhesive can preferentially form an adhesive film to be distributed between the plurality of active particles and preliminarily connect the plurality of active particles. The first particles of the first adhesive are distributed in the gaps between the plurality of active particles, and the second particles of the first adhesive are disposed on the surfaces of the active particles. The first adhesive has a low glass transition temperature, so that the first particles and the second particles exhibit a highly elastic state at a lower temperature, showing higher flexibility and elasticity and maintaining good adhesive performance, thereby realizing effective bonding of the plurality of active particles. Further, compared with the scheme of using the second adhesive alone, the compounding of the second adhesive and the first adhesive can improve the adhesive performance between the plurality of active particles. This is because polytetrafluoroethylene has a low surface energy and a small critical surface tension, and the first adhesive has a low glass transition temperature and has good flexibility and fluidity even at a lower temperature to contact the second adhesive and form an adhesive network, thereby increasing the adhesive strength between the plurality of active particles and at the same time increasing the adhesive strength between the active material layer 120 and the current collector layer 110.

[0073] In some embodiments, in the active material layer 120, the range of the mass fraction m1 of the first adhesive is: 1.5% ≤ m1 ≤ 2.5%.

[0074] It can be understood that in the active material layer 120, the mass fraction of the first adhesive is the ratio of the mass of the first adhesive to the mass of the active material layer 120.

[0075] Specifically, the value of the mass fraction m1 of the first adhesive can be, but is not limited to, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, and 2.5%, etc.

[0076] In the active material layer 120 provided in this embodiment, when the mass fraction m1 of the first binder satisfies the range of 1.5% ≤ m1 ≤ 2.5%, the mass fraction of the first binder is within a reasonable range. The first binder has a relatively low glass transition temperature, so that the first binder can exhibit good bonding performance at a relatively low temperature. In addition, the first binder includes first particles and second particles. The first particles are distributed among the gaps of a plurality of active particles, and the second particles are disposed on the surfaces of the active particles. The first particles and the second particles cooperate to enable the electrode sheet 100 to have greater cohesive force. In other words, compared with the second binder, the first binder can enable the electrode sheet 100 to have greater cohesive force, thereby further improving the structural stability of the electrode sheet 100. When the mass fraction of the first binder is too large, it will affect the electrical performance of the battery 200 obtained from the electrode sheet 100. Under the same product design, the impedance of the battery 200 will increase and the capacity of the battery 200 will decrease. The reason is that when the mass fraction of the first binder is too large, it will affect the transport of active lithium ions in the active material layer 120, increase the charge transfer impedance, and thus reduce the transport efficiency of active ions in the battery 200. In addition, the first binder occupies too much space in the active material layer 120. Correspondingly, the proportion of active particles in the active material layer 120 is too small, which will reduce the capacity of the active material layer 120, and too much binder will occupy the active sites of the electrode sheet 100, reduce the contact area between the active particles and the electrolyte 210, and reduce the available power of the battery 200. When the mass fraction of the first binder is too small, correspondingly, in the active material layer 120, if the mass fraction of the second binder is still too large, the cohesive force of the electrode sheet 100 may still be weak, thereby reducing the structural stability of the electrode sheet 100.

[0077] In some embodiments, in the active material layer 120, the range of the mass fraction m2 of the second binder is: 0.5% ≤ m2 ≤ 3%.

[0078] It can be understood that in the active material layer 120, the mass fraction of the second binder is the ratio of the mass of the second binder to the mass of the active material layer 120.

[0079] Specifically, the value of the mass fraction m2 of the second binder can be, but is not limited to, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.1%, 2.2%, 2.3%, 2.5%, 2.6%, 2.8%, 2.9%, and 3%, etc.

[0080] Understandably, if the active material layer 120 only includes the second binder and does not include the first binder, the mass fraction of the second binder should be higher than 3%. Correspondingly, the larger the mass fraction of the second binder, due to the defects in the bonding performance of the second binder, the cohesive force of the electrode sheet 100 may be smaller, resulting in poorer structural stability of the electrode sheet 100.

[0081] In the active material layer 120 provided in this embodiment, when the mass fraction m2 of the second binder satisfies the range 0.5% ≤ m2 ≤ 3%, the mass fraction of the second binder is within a reasonable range. Compared with the solution where the active material layer 120 only includes the second binder, in the solution of compounding the first binder and the second binder in this embodiment, the second binder preferentially forms a bonding film in the active material layer 120, and the first binder is distributed between the plurality of active particles and bonded to the second binder, so that the electrode sheet 100 has greater cohesive force and better structural stability. When the mass fraction of the second binder is too large, on the one hand, there are too many fluorine atoms in the second binder. Fluorine atoms have a strong electron affinity, so that the second binder is more likely to accept electrons and react with the lithium ions of the active material, thereby reducing the capacity retention rate of the electrode sheet 100. On the other hand, the larger the mass fraction of the second binder, the smaller the mass fraction of the first binder, and the synergistic effect between the first binder and the second binder is weakened. It is difficult for the first binder to make up for the difference in the bonding performance of the second binder, resulting in a relatively low cohesive force of the electrode sheet 100 and poor structural stability of the electrode sheet 100. When the mass fraction of the second binder is too small, it is difficult for the second binder to preferentially form a bonding network, so that it is difficult for the second binder to cooperate with the first binder, thereby weakening the bonding effect of the first binder and the second binder on the active particles.

[0082] Optionally, in some embodiments, the mass fraction of the second binder when the electrode sheet 100 is a positive electrode sheet is equal to the mass fraction of the second binder when the electrode sheet 100 is a negative electrode sheet; in other embodiments, the mass fraction of the second binder when the electrode sheet 100 is a positive electrode sheet is not equal to the mass fraction of the second binder when the electrode sheet 100 is a negative electrode sheet, and the mass fraction of the second binder when the electrode sheet 100 is a positive electrode sheet is greater than the mass fraction of the second binder when the electrode sheet 100 is a negative electrode sheet. This is because: the particles of the active material in the positive electrode sheet are smaller, and the larger the mass fraction of the second binder, the more conducive it is to form a bonding network on the surface of the active material, thereby improving the bonding performance when the second binder cooperates with the first binder.

[0083] Optionally, if the electrode sheet 100 is a positive electrode sheet, in the active material layer 120, the mass fraction m2 of the second binder ranges from 2% ≤ m2 ≤ 3%.

[0084] Optionally, if the electrode sheet 100 is a negative electrode sheet, in the active material layer 120, the mass fraction m2 of the second binder ranges from 0.5% ≤ m2 ≤ 3%.

[0085] Optionally, the present application also provides a preparation method of the first binder for preparing the first binder provided by the present application, and the preparation method includes:

[0086] S101, providing a polymerizable monomer and an aqueous solution containing an emulsifier, adding the polymerizable monomer to the aqueous solution containing the emulsifier to form a mixed solution, and adding an initiator or an azo compound to the mixed solution to perform emulsion polymerization to obtain an emulsion with a solid content of 15%.

[0087] It can be understood that the solid content of the emulsion affects the molecular weight of the formed first binder, thereby affecting the glass transition temperature of the first binder.

[0088] Optionally, the polymerizable monomer includes at least one of isooctyl acrylate, butyl acrylate, methyl methacrylate, vinyl acetate, acrylic acid, 2-hydroxyethyl methacrylate, toluene diisocyanate, diphenylmethane diisocyanate, polyester polyol, polyether polyol, and N-methylol acrylamide.

[0089] Optionally, the emulsifier includes at least one of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, or sodium dodecylsulfonate.

[0090] Optionally, the initiator includes but is not limited to peroxides, and the peroxides include but are not limited to benzoyl peroxide.

[0091] Optionally, the azo compound includes but is not limited to azobisisobutyronitrile.

[0092] Optionally, in step S101, based on the total mass of the emulsifier, the polymerizable monomer, and the initiator being 100%, the mass proportion of the emulsifier is 1% to 5%, the mass proportion of the polymerizable monomer is 70% to 99.8%, and the mass proportion of the initiator is 0.01% to 5%.

[0093] Optionally, in step S101, in the mixed solution, the total mass of the emulsifier, the polymerizable monomer, and the initiator accounts for 1% to 30% of the mixed solution.

[0094] Optionally, the reaction temperature of the emulsion polymerization is 60°C to 90°C, and the time of the emulsion polymerization is 4 h to 9 h.

[0095] S102, spray-dry the emulsion using a spray-drying device, spray it into the drying chamber through a nozzle, and at the same time supply hot air into the drying chamber to quickly evaporate the droplets in the chamber and form the first adhesive. The range of the glass transition temperature Tg of the first adhesive is: -60°C ≤ Tg ≤ 0°C.

[0096] Optionally, the material of the first adhesive is selected from at least one of isooctyl acrylate, butyl acrylate, methyl methacrylate, vinyl acetate, acrylic acid, 2-hydroxyethyl methacrylate, toluene diisocyanate, diphenylmethane diisocyanate, polyester polyol, polyether polyol, and N-methylolacrylamide.

[0097] In the preparation method provided in this embodiment, the glass transition temperature Tg of the first adhesive obtained by the preparation method satisfies the range of -60°C ≤ Tg ≤ 0°C, so that the first adhesive exhibits a high elastic state at a lower temperature, showing higher flexibility and elasticity, facilitating maintaining good adhesion performance. By compacting the first adhesive, the adhesion performance of the first adhesive can be fully exerted. When the first adhesive is applied to the active material layer 120, it can exert good adhesion performance and cooperate with the second adhesive to bond the plurality of active particles and bond the active material layer 120 to the current collector layer 110, thereby reducing the amount of the second adhesive used and compensating for the defect of the second adhesive in adhesion performance, so as to fully improve the cohesion and structural stability of the electrode sheet 100. On the one hand, when the first adhesive is applied to the electrode sheet 100, the first adhesive can effectively bond the plurality of active particles to slow down the powder falling phenomenon during the preparation of the electrode sheet 100 and improve the preparation performance of the electrode sheet 100. On the other hand, when the first adhesive is applied to the electrode sheet 100 and assembled in the battery 200, it can prevent the active material layer 120 from falling off during the insertion and extraction of active ions, so that the battery 200 has a higher capacity and better cycle performance.

[0098] Optionally, the hot pressing pressure P for hot pressing the electrode sheet 100 satisfies the range: 10 t ≤ P ≤ 20 t. Here, t represents ton.

[0099] Specifically, the value of the hot pressing pressure P for hot pressing the electrode sheet 100 can be, but is not limited to, 10t, 10.5t, 11t, 11.5t, 12t, 12.8t, 13t, 13.6t, 14t, 14.5t, 15t, 15.6t, 16t, 16.5t, 17t, 17.2t, 18t, 18.5t, 19t, 19.5t, 20t, etc.

[0100] In this embodiment, when the hot pressing pressure P for hot pressing the electrode sheet 100 satisfies a reasonable range, the compaction degree of the electrode sheet 100 and the second particles of the first adhesive is within a reasonable range, so that the expansion coefficient α of the first adhesive satisfies the range 1.2 ≤ α ≤ 3.3, thereby enabling the second particles of the first adhesive to have a large contact area with the active particles, improving the bonding performance between the active particles, and thus enabling the electrode sheet 100 to have greater cohesive force and structural stability.

[0101] It can be understood that when the hot pressing pressure P for hot pressing the electrode sheet 100 satisfies the range: 10t ≤ P ≤ 20t, the pressure for hot pressing the electrode sheet 100 is positively correlated with the expansion coefficient of the first adhesive. In other words, the greater the pressure for hot pressing the electrode sheet 100, the greater the expansion coefficient of the first adhesive, and the greater the second major axis of the second particles, so as to facilitate the regulation of the expansion coefficient of the first adhesive.

[0102] Optionally, the hot pressing temperature T for hot pressing the electrode sheet 100 satisfies the range: 60°C ≤ T ≤ 100°C.

[0103] Specifically, the value of the hot pressing temperature T for hot pressing the electrode sheet 100 can be, but is not limited to, 60°C, 65°C, 70°C, 76°C, 80°C, 82°C, 85°C, 90°C, 92°C, 95°C, 100°C, etc.

[0104] In this embodiment, when the hot pressing temperature T for hot pressing the electrode sheet 100 satisfies the range: 60°C ≤ T ≤ 100°C, within this range of hot pressing temperatures, the first adhesive can exhibit a highly elastic state, showing relatively high flexibility and elasticity, so as to exert its bonding performance under the action of hot pressing.

[0105] Optionally, the hot pressing time t for hot pressing the electrode sheet 100 satisfies the range: 3min ≤ t ≤ 10min.

[0106] Specifically, the value of the hot pressing time t for hot pressing the electrode sheet 100 can be, but is not limited to, 3 min, 3.2 min, 3.5 min, 3.8 min, 4 min, 4.2 min, 4.5 min, 4.8 min, 5 min, 5.2 min, 5.8 min, 6 min, 6.2 min, 6.5 min, 7 min, 7.2 min, 7.5 min, 7.8 min, 8 min, 8.2 min, 8.5 min, 9 min, 9.2 min, 9.5 min, 10 min, etc.

[0107] In this embodiment, when the hot pressing time t for hot pressing the electrode sheet 100 is within a reasonable range, the compaction degree of the electrode sheet 100 and the second particles of the first adhesive is within a reasonable range, so that the expansion coefficient α of the first adhesive satisfies the range 1.2 ≤ α ≤ 3.3, thereby enabling the second particles of the first adhesive to have a large contact area with the active particles, improving the bonding performance between the active particles, and thus enabling the electrode sheet 100 to have a large cohesive force and structural stability.

[0108] It can be understood that when the hot pressing time t for hot pressing the electrode sheet 100 satisfies the range: 3 min ≤ t ≤ 10 min, the hot pressing time for the electrode sheet 100 is positively correlated with the expansion coefficient of the first adhesive. In other words, the longer the hot pressing time for the electrode sheet 100, the larger the expansion coefficient of the first adhesive and the larger the second major axis of the second particles, so as to facilitate the regulation of the expansion coefficient of the first adhesive.

[0109] The technical solution of the present application will be further introduced in multiple embodiments as follows:

[0110] Examples 1 to 9, Comparative Examples 1 to 4:

[0111] 1. Preparation of the first adhesive:

[0112] A polymerization monomer and an initiator are added to an aqueous solution containing an emulsifier for emulsion polymerization. The polymerization monomer includes at least one of isooctyl acrylate, butyl acrylate, methyl methacrylate, vinyl acetate, acrylic acid, 2-hydroxyethyl methacrylate, toluene diisocyanate, diphenylmethane diisocyanate, polyester polyol, polyether polyol, N-methylol acrylamide, etc. The reaction temperature of the emulsion polymerization reaction is 60°C to 90°C, and the time is 4 h to 9 h. Finally, an emulsion with a solid content of 15% is obtained.

[0113] The emulsion is spray-dried using a spray-drying device. During the spray-drying process, an anti-sticking agent is added to prevent adhesion between the rubber particles. The anti-sticking agent is sprayed into the drying chamber through a nozzle, and at the same time, hot air is provided to the drying chamber to rapidly evaporate the droplets in the chamber, and the first adhesives of Examples 1 to 9 and Comparative Examples 1 to 4 are formed. The range of the glass transition temperature Tg of the first adhesive is: -60°C ≤ Tg ≤ 0°C.

[0114] 2. Preparation of the electrode sheet 100:

[0115] Taking the negative electrode sheet as an example. The active material (graphite), conductive agent (conductive carbon black), polytetrafluoroethylene adhesive, and first adhesive are mixed and pre-fibrillated under certain process conditions to form a mixture, which is pressed using a multi-stage roller. The roller temperature is maintained at 80°C. When the tensile strength of the formed film sheet > 0.088 Mpa, the active material layer 120 is formed, and it is respectively compounded with the base-coated current collector layer 110 (copper foil) and then rolled to obtain the electrode sheets 100 of Examples 1 to 9 and Comparative Examples 1 to 4. The compaction density of the electrode sheet 100 is 1.5 g / cm 3 . Among them, the values of the hot pressing pressure P, hot pressing temperature T, and hot pressing time t for hot pressing the electrode sheet 100 are shown in Table 1.

[0116] Among them, the first adhesive of Example 1 is applied to the electrode sheet 100 of Example 1, the first adhesive of Example 2 is applied to the electrode sheet 100 of Example 2, the first adhesive of Comparative Example 1 is applied to the electrode sheet 100 of Comparative Example 1, and so on. The first adhesive of Comparative Example 2 is applied to the electrode sheet 100 of Comparative Example 1, and so on. In the electrode sheets 100 of Examples 1 to 9 and Comparative Examples 1 to 4, after the first adhesive is compacted, the first adhesive includes first particles and second particles. The first particles are distributed among the gaps of a plurality of active particles, and the second particles are disposed on the surfaces of the active particles.

[0117] Among them, in the active material layer 120 of the electrode sheets 100 of Examples 1 to 9 and Comparative Examples 1 to 4, the mass fractions of the active material, conductive agent, first adhesive, second adhesive, the value of the expansion coefficient α of the first adhesive, and the value of the film occupation coefficient β = N × S2 / S1 are shown in Table 1.

[0118] Further, in the electrode plates 100 of Examples 1 to 9 and Comparative Examples 1 to 4, the measurement method for the value of the expansion coefficient α of the first binder is as follows: Take the scanning electron microscope spectrum of the active material layer 120, shoot it with a scale of 1 μm, and take the part where one active particle can be seen as the main perspective. Then, the first particles are distributed among the gaps between the active particles, and the second particles are distributed on the surfaces of the active particles. Specifically, please refer to Figure 3 , where the first particles located among the gaps between the active particles appear bright white, and the second particles located on the surfaces of the active particles appear dark. Use ImageJ software to measure the first major axis L1 of the first particles and the second major axis L2 of the second particles, and obtain the value of the expansion coefficient of the first binder through the formula α = L2 / L1.

[0119] Further, in the electrode plates 100 of Examples 1 to 9 and Comparative Examples 1 to 4, the measurement method for the value of the film occupation coefficient β of the first binder is as follows: Take the scanning electron microscope spectrum of the active material layer 120, shoot it with a scale of 1 μm, and take the part where one active particle can be seen as the main perspective. Then, the first particles are distributed among the gaps between the active particles, and the second particles are distributed on the surfaces of the active particles. Use ImageJ software to measure the area S1 of the active particles, the number N of the second particles on the surface of a single active particle, and the average value S2 of the areas of the multiple second particles on the surface of the same active particle, and obtain the value of the film occupation coefficient β through the formula β = N×S2 / S1.

[0120] It can be understood that the full name of ImageJ is "Image Processing and Analysis in Java", which is an open-source image processing and analysis tool based on the Java platform.

[0121] The following Table 1 shows the composition parameters of the active material layer 120, the hot pressing parameters, and the structural parameters of the electrode plates 100 of Examples 1 to 9 and Comparative Examples 1 to 4.

[0122] Table 1: Composition parameters of the active material layer 120, hot pressing parameters, and structural parameters of the electrode plates 100 of Examples 1 to 9 and Comparative Examples 1 to 4.

[0123]

[0124]

[0125] Performance test of the electrode plate 100:

[0126] The cohesive strength of the electrode sheets 100 of Examples 1 to 9 and Comparative Examples 1 to 4 was tested. The specific steps are as follows:

[0127] Step 1: Lay the electrode sheet 100 flat, and use a ruler and a craft knife to prepare the electrode sheet 100 into strips with a specification of 200 mm × 25 mm. Generally, 3 to 5 test strips need to be prepared for a group of samples;

[0128] Step 2: Stick one side of the double-sided tape to the middle of the steel plate, and roll it back and forth 3 times with a roller to firmly bond it to the test steel plate;

[0129] Step 3: Take out the green tape and the fixed electrode sheet 100. Align one end of the green tape with the top of the electrode sheet 100, and slowly stick it along the vertical direction of the electrode sheet 100 to the tail. Roll it 3 times in one direction with a roller to make the green tape and the electrode sheet 100 fit flat. Lift one end of the green tape to complete the pre-peeling action, and install the whole steel plate - electrode sheet 100 on the fixture. The bottom end of the steel plate needs to be aligned with the bottom end of the fixture, and tighten the four screws beside to fix the steel plate. Use a tensile machine to conduct the cohesive force test to obtain the cohesive force of the electrode sheet 100.

[0130] Step 4: Obtain the cohesive strength of the electrode sheet 100. The cohesive strength refers to the cohesive force of the electrode sheet 100 per unit width. In this application, the cohesive strength of the electrode sheet 100 is the ratio of the cohesive force of the electrode sheet 100 to the width (25 mm). Thus, the values of the cohesive strengths of the electrode sheets 100 of Examples 1 to 9 and Comparative Examples 1 to 4 are obtained.

[0131] Among them, the values of the cohesive strengths of the electrode sheets 100 of Examples 1 to 9 and Comparative Examples 1 to 4 are shown in Table 2.

[0132] The following Table 2 shows the performance parameters of the electrode sheets 100 of Examples 1 to 9 and Comparative Examples 1 to 4.

[0133] Table 2: Performance parameters of the electrode sheets 100 of Examples 1 to 9 and Comparative Examples 1 to 4.

[0134]

[0135]

[0136] Please refer to Table 1 and Table 2. From the data of Examples 1 to 9, Comparative Example 1 and Comparative Example 2, it can be seen that the active material layer 120 of the electrode plate 100 in Examples 1 to 9 includes both a first binder and a second binder, while the active material layer 120 of the electrode plate 100 in Comparative Example 1 and Comparative Example 2 only includes the second binder and does not include the first binder. This makes the cohesive strength of the electrode plate 100 in Examples 1 to 9 greater than that of the electrode plate 100 in Comparative Example 1 and Comparative Example 2. The reason is as follows: In the electrode plate 100 of Examples 1 to 9, the first binder and the second binder are compounded to improve the bonding performance between the active particles. Among them, the first binder includes a first particle and a second particle. The first particle is distributed between the gaps of the plurality of active particles, and the second particle is disposed on the surface of the active particle. The second particle can be used to bond two relatively large surfaces of the relatively arranged active particles to improve the bonding performance between the two relatively arranged active particles. The first particle is distributed between the gaps of the plurality of active particles to bond two adjacent active particles. The use of the first binder can reduce the amount of the second binder in the active material layer 120 to make up for the defect of the second binder in bonding performance and improve the cohesive strength of the electrode plate 100, so that the cohesive strength of the electrode plate 100 in Examples 1 to 9 is greater.

[0137] Further, please refer to Embodiment 1 to Embodiment 3, Embodiment 9 and Comparative Example 3. Under the same other conditions, the sum of the mass fraction of the first adhesive and the mass fraction of the second adhesive remains unchanged. As the mass fraction of the first adhesive gradually decreases, the mass fraction of the second adhesive gradually increases, and the film occupation coefficient of the first adhesive gradually decreases. Correspondingly, the cohesive strength of the corresponding electrode tab 100 gradually decreases. This shows that: under the same other conditions, the larger the film occupation coefficient of the first adhesive, the larger the area of the sheet adhesive film formed by multiple second particles on the surface of the same active particle, so that the multiple second particles have a larger contact area with the surface of the active particle, and the multiple second particles can effectively bond the surfaces of two relatively arranged active particles to improve the bonding performance between the active particles, thereby improving the cohesive strength of the electrode tab 100. In addition, in Embodiment 1 to Embodiment 3, the mass fraction m1 of the first adhesive and the mass fraction m2 of the second adhesive satisfy the range of 0.66 ≤ m1 / m2 ≤ 5. The value of m1 / m2 in Embodiment 9 and Comparative Example 3 is too small, making the cohesive strength of the electrode tab 100 in Embodiment 1 to Embodiment 3 significantly greater than that of the electrode tab 100 in Embodiment 9 and Comparative Example 3. This is because: the second adhesive is compounded with the first adhesive to improve the bonding performance between the multiple active particles. Polytetrafluoroethylene has a low surface energy and a small critical surface tension, while the first adhesive has a low glass transition temperature and has good flexibility and fluidity even at a low temperature to contact with the second adhesive and form a bonding network, thereby improving the bonding strength between the multiple active particles and at the same time improving the bonding strength between the active material layer 120 and the current collector layer 110, so that the electrode tab 100 of Embodiment 1 to Embodiment 3 has a large cohesive strength. In addition, the cohesive strength of the electrode tab 100 in Embodiment 9 is significantly greater than that of the electrode tab 100 in Comparative Example 3. This is because, although the value of m1 / m2 in Embodiment 9 is too small, its film occupation coefficient β still satisfies a reasonable range, while in Comparative Example 3, not only the value of m1 / m2 is too small, but also the value of the film occupation coefficient β is too small. Then, when the area on the surface of the active particle is certain, the area of the sheet adhesive film formed by the multiple second particles is too small, and the second particles are difficult to effectively bond the active particles, resulting in a low cohesive strength and poor structural stability of the electrode tab 100 in Comparative Example 3.

[0138] Further, please refer to Example 1, Example 4 and Comparative Example 4. Under the condition that other conditions are the same, the expansion coefficient of the first adhesive is related to the hot pressing pressure P for hot pressing the electrode plate 100. Specifically, as the hot pressing pressure for hot pressing the electrode plate 100 increases, the compaction degree of the electrode plate 100 and the second particles becomes greater, so that the expansion coefficient becomes greater. Correspondingly, the cohesive strength of the corresponding electrode plate 100 is greater. Among them, the pressure P for hot pressing the electrode plates 100 in Example 1 and Example 4 satisfies the range of 10t ≤ P ≤ 20t, and the expansion coefficient α of the first adhesive in Example 1 and Example 4 satisfies the range of 1.2 ≤ α ≤ 3.3. However, the pressure for hot pressing the electrode plate 100 in Comparative Example 4 is too small, and the expansion coefficient α of the first adhesive in Comparative Example 4 is too small, which makes the cohesive strength of the electrode plates 100 in Example 1 and Example 4 significantly higher than that of the electrode plates 100 in Comparative Example 4. The reason is that: in Example 1 and Example 4, the pressure P for hot pressing the electrode plates 100 in Example 1 and Example 4 is within a reasonable range, so the compaction degree of the electrode plate 100 and the first adhesive is within a reasonable range, so that the expansion coefficient α of the first adhesive satisfies the range of 1.2 ≤ α ≤ 3.3. The second particles can effectively bond two larger surfaces of the oppositely arranged active particles. The second particles cooperate with the first particles to improve the bonding performance between the active particles, so that the electrode plate 100 has a higher cohesive strength and better structural stability. In Comparative Example 4, the pressure for hot pressing the electrode plate 100 is too small, so the compaction degree of the electrode plate 100 and the first adhesive is too small, and the expansion coefficient α of the first adhesive in Comparative Example 4 is too small. It is difficult for a single second particle to expose a larger contact area on the surface of the active particle, so that the bonding performance of the second particle to the two oppositely arranged active particles is weakened, so that the cohesive strength of the electrode plate 100 in Comparative Example 4 is small.

[0139] Further, please refer to Example 1, Example 5 and Example 6. Under the condition that other conditions are the same, when the hot pressing temperature T for hot pressing the electrode plate 100 satisfies a reasonable range, the influence of the hot pressing temperature T for hot pressing the electrode plate 100 on the expansion coefficient of the first adhesive is not significant, so the influence on the compaction degree of the electrode plate 100 and the second particles is not significant, so that the expansion coefficients of the electrode plates 100 in Example 1, Example 5 and Example 6 are equal. Correspondingly, the cohesive strengths of the corresponding electrode plates 100 are basically equal. This shows that: when the hot pressing temperature T for hot pressing the electrode plate 100 satisfies the range of 60°C ≤ T ≤ 100°C, the first adhesive exhibits a high elastic state and cooperates with the second adhesive to fully exert the bonding performance.

[0140] Further, please refer to Embodiment 1, Embodiment 7 and Embodiment 8. Under the condition that other conditions are the same, the expansion coefficient of the first adhesive is related to the hot-pressing time t for hot-pressing the electrode sheet 100. Specifically, as the hot-pressing time for hot-pressing the electrode sheet 100 increases, the compaction degree of the electrode sheet 100 and the second particles becomes greater, so that the expansion coefficient becomes greater. Correspondingly, the cohesive strength of the corresponding electrode sheet 100 is greater. Among them, the hot-pressing time t for hot-pressing the electrode sheets 100 in Embodiment 1, Embodiment 7 and Embodiment 8 satisfies the range of 3 min ≤ t ≤ 10 min, and the expansion coefficient α of the first adhesive in Embodiment 1, Embodiment 7 and Embodiment 8 satisfies the range of 1.2 ≤ α ≤ 3.3, which makes the electrode sheets 100 in Embodiment 1, Embodiment 7 and Embodiment 8 all have greater cohesive strength. In addition, as the expansion coefficient of the first adhesive increases, it indicates that the compaction degree of the second particles is greater, and on the surface of the active particles per unit area, the contact area between the second particles and the active particles is greater, which is beneficial to the second particles to fully exert the bonding performance, so that the electrode sheet 100 has higher cohesive force and better structural stability.

[0141] Please refer to Figure 4 , this application provides a battery 200, which includes the electrode sheet 100 provided by this application and the electrolyte 210 provided by this application, and the electrolyte 210 is used to infiltrate the electrode sheet 100.

[0142] In this embodiment, the electrolyte 210 is used to infiltrate the electrode plate 100. The active material layer 120 of the electrode plate 100 includes the first binder provided by the present application. The glass transition temperature Tg of the first binder satisfies the range of -60°C ≤ Tg ≤ 0°C. Since the first binder has a low glass transition temperature, the first binder exhibits a highly elastic state at a relatively low temperature, showing higher flexibility and elasticity, which is conducive to maintaining good bonding performance to better bond multiple active particles. Specifically, the first particles are distributed among the gaps between the multiple active particles, and the second particles are disposed on the surfaces of the active particles. Compared with the first particles, the second particles experience a compaction process during the compaction of the electrode plate 100, so that the second major axis is greater than the first major axis of the first particles. The expansion coefficient α of the first binder satisfies the range of 1.2 ≤ α ≤ 3.3, so that the second particles can be used to bond two relatively large surfaces of the oppositely arranged active particles to improve the bonding performance between the two oppositely arranged active particles. The first particles are distributed among the gaps between the multiple active particles to bond two adjacent active particles. The second particles cooperate with the first particles to improve the bonding performance between the active particles, so that the electrode plate 100 has high cohesive force and good structural stability. During the charge and discharge process of the battery 200, the electrode plate 100 has good structural stability to prevent the active material layer 120 from falling off during the insertion and extraction of lithium ions, so that the battery 200 has high capacity and good cycle performance.

[0143] Optionally, the battery 200 further includes a separator. The number of the electrode plates 100 is two, which are a positive electrode plate and a negative electrode plate respectively. The separator is disposed between the positive electrode plate and the negative electrode plate, and the electrolyte 210 is used to infiltrate the positive electrode plate, the separator and the negative electrode plate.

[0144] Please refer to Figure 5 and Figure 6 , the present application provides an electrical device 300, which includes a device body 310 and the battery 200 provided by the present application. The battery 200 powers the device body 310.

[0145] It can be understood that the battery 200 is electrically connected to the device body 310.

[0146] In this embodiment, the battery 200 includes the electrode tab 100, and the electrode tab 100 has high cohesive force and good structural stability. During the charge and discharge process of the battery 200, the active material layer 120 is prevented from falling off during the insertion and extraction of lithium ions, so that the battery 200 has high capacity and good cycle performance. When the battery 200 is applied to the electrical device 300, the battery 200 can provide stable electrical energy for the device body 310, which is beneficial to improving the user experience.

[0147] Optionally, the electrical device 300 in the embodiments of the present application may be, but is not limited to, portable electronic devices such as mobile phones, tablet computers, laptop computers, desktop computers, smart bracelets, smart watches, e-readers, game consoles, etc. It may also be means of transportation such as cars, trucks, sedans, freight trucks, bullet trains, high-speed rails, and electric scooters. In addition, it may also be various household appliances, etc. Figure 5 The electrical device 300 in the embodiments of the present application is an energy storage battery cabinet.

[0148] It can be understood that the electrical device 300 described in this embodiment is only one form of the electrical device 300 to which the battery 200 is applied, and should not be construed as a limitation on the electrical device 300 provided by the present application, nor should it be construed as a limitation on the electrical device 300 provided by each embodiment of the present application.

[0149] In the present application, the mention of "embodiment" and "embodiment" means that the specific features, structures or characteristics described in connection with the embodiment may be included in at least one embodiment of the present application. The appearance of the phrase at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described in the present application may be combined with other embodiments. In addition, it should also be understood that the features, structures or characteristics described in each embodiment of the present application may be combined arbitrarily without contradiction to form another embodiment that does not depart from the spirit and scope of the technical solution of the present application.

[0150] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and not to limit them. Although the present application has been described in detail with reference to the above preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. An electrode plate, characterized in that: The electrode plate comprises: a current collector layer; and An active material layer, wherein the active material layer is disposed on at least one side of the current collector layer, the active material layer includes a plurality of active particles and a first adhesive, the glass transition temperature Tg of the first adhesive is in the range of -60°C ≤ Tg ≤ 0°C, the first adhesive includes first particles and second particles, the first particles are distributed between the gaps of the plurality of active particles, the second particles are disposed on the surface of the active particles, the first major axis of the first particles is L1, and the second major axis of the second particles is L2, then the expansion coefficient α of the first adhesive is L2 / L1, and the range of the expansion coefficient α is 1.2≤α≤3.

3.

2. The electrode plate according to claim 1, characterized in that: The first minor axis of the first particle is L3, and the first particle satisfies the relationship: 0.5≤L3 / L1≤1; the second minor axis of the second particle is L4, and the second particle satisfies the relationship: 0.2≤L4 / L2≤0.

65.

3. The electrode plate according to claim 1, characterized in that: The area of ​​the active particle is S1, the number of the second particles on the surface of a single active particle is N, and the average area of ​​the multiple second particles on the surface of the same active particle is S2, then the relationship is satisfied: 0.3≤N×S2 / S1≤0.

9.

4. The electrode plate according to any one of claims 1 to 3, characterized in that: The material of the first adhesive is selected from at least one of isooctyl acrylate, butyl acrylate, methyl methacrylate, vinyl acetate, acrylic acid, hydroxyethyl methacrylate, toluene diisocyanate, diphenylmethane diisocyanate, polyester polyol, polyether polyol and N-hydroxymethyl acrylate.

5. The electrode plate according to any one of claims 1 to 3, characterized in that: The particle size D of the first adhesive is in the range of 10 μm ≤ D ≤ 100 μm.

6. The electrode plate according to any one of claims 1 to 3, characterized in that: The active material layer further includes a second binder, which is a second binder. In the active material layer, the second binder is in a fibrous structure.

7. The electrode plate according to any one of claims 1 to 3, characterized in that: The first binder at least partially overlaps with the second binder. In the active material layer, the mass fraction m1 of the first binder and the mass fraction m2 of the second binder satisfy the relationship: 0.66≤m1 / m2≤5.

8. The electrode plate according to claim 7, characterized in that: In the active material layer, the mass fraction m1 of the first binder is in the range of 0.5%≤m1≤2.5%, and the mass fraction m2 of the second binder is in the range of 0.5%≤m2≤3%.

9. A battery, characterized in that: The battery comprises: The electrode sheet according to any one of claims 1 to 8; and An electrolyte is used to soak the electrode plates.

10. An electrical device, characterized in that: The electrical equipment includes: The device itself; and The battery of claim 9, wherein the battery is used to power the device body.

Images