Electrode sheet and battery

Abstract

The present disclosure relates to the field of batteries, and in particular to an electrode sheet and a battery. The electrode sheet comprises a current collector, an adhesive layer arranged on at least one side surface of the current collector, and an active material layer arranged on the outer surface of the adhesive layer; the active material layer comprises an active material and fiber particles; and the glass transition temperature of the adhesive layer is 70°C-190°C. The electrode sheet of the present disclosure comprises the adhesive layer arranged between the current collector and the active material layer, and the adhesive layer has a specific glass transition temperature, so that the adhesive layer has excellent bonding strength, sealing performance and thermal stability, and can improve the bonding strength between the active material layer and the current collector, preventing the active material layer from cracking or falling off. In addition, the electronic conductivity, flexibility and mechanical strength of the electrode sheet are further improved, facilitating the improvement of the cycle stability of batteries.

Description

Electrode and battery Technical Field

[0001] The present disclosure relates to the field of batteries, and in particular to a pole piece and a battery comprising the pole piece. Background Art

[0002] Electrodes for non-aqueous electrolyte secondary batteries such as lithium-ion batteries are generally produced by a wet process in which an electrode composite material slurry containing an active material, a binder, etc. is applied to the surface of a metal foil core material, and the coated film is dried and compressed.

[0003] In this case, there is a technical problem of migration of the binder material during the coating drying process. When the binder material migrates, the amount of binder material increases on the side of the active material layer away from the current collector, resulting in a deviation in the binder material distribution along the thickness of the active material layer. This can easily cause the active material layer to crack or even fall off, seriously affecting battery performance. Summary of the Invention

[0004] The present invention aims to overcome the problem in the prior art that the active material layer is prone to cracking or even shedding, which seriously affects the performance of the battery. The invention provides a pole piece and a battery including the pole piece. The pole piece of the present invention includes a glue layer disposed between the current collector and the active material layer. The glue layer has a specific glass transition temperature, which enables the glue layer to have excellent bonding strength, sealing performance, and thermal stability. It can improve the bonding strength between the active material layer and the current collector, prevent the active material layer from cracking or shedding, and at the same time, improve the electronic conductivity, flexibility, and mechanical strength of the pole piece, which is conducive to improving the cycle stability of the battery.

[0005] In a first aspect of the present disclosure, a pole piece is provided, which includes a current collector, a glue layer arranged on at least one side of the current collector, and an active material layer arranged on the outer surface of the glue layer; the active material layer includes active material and fiber particles; the glass transition temperature of the glue layer is 70°C-190°C.

[0006] A second aspect of the present disclosure provides a battery, comprising the pole piece described in the first aspect of the present disclosure.

[0007] Through the above technical solution, the present disclosure has at least the following advantages compared with the prior art:

[0008] (1) The electrode disclosed in the present invention has excellent electronic conductivity, which improves the cycle performance of the battery;

[0009] (2) The electrode sheet disclosed herein has excellent flexibility and mechanical strength, which can effectively inhibit the shedding of active materials during battery preparation and use, and significantly improve the cycle stability of the battery;

[0010] (3) The electrode disclosed in the present invention can significantly reduce the temperature and rolling pressure during its preparation process, effectively reduce energy consumption and save costs.

[0011] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG1 is a schematic cross-sectional view of a pole piece in an example of the present disclosure.

[0013] FIG2 is a schematic diagram of a pole piece in an example of the present disclosure.

[0014] FIG3 is a schematic diagram showing the difference between the length of the glue layer and the length of the active material layer in an example of the present disclosure.

[0015] FIG4 shows the thermogravimetric analysis curves of the subbing layer and the active material layer in Example 3. DETAILED DESCRIPTION

[0016] The present disclosure will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanations of the present disclosure and should not be construed as limiting the scope of protection of the present disclosure. All technologies implemented based on the above content of the present disclosure are included within the scope of protection intended by the present disclosure.

[0017] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the reagents, materials, etc. used in the following examples are all commercially available unless otherwise specified.

[0018] In the description of the present disclosure, it should be noted that the terms "first", "second", etc. are only used for descriptive purposes to distinguish different substances or usage methods, and do not indicate or imply relative importance.

[0019] The first aspect of the present disclosure provides a pole piece, which may include a current collector, a glue layer provided on at least one side of the current collector, and an active material layer provided on the outer surface of the glue layer. As shown in Figure 1, a cross-sectional schematic diagram of a pole piece in an example of the present disclosure is shown, wherein Figure 1(a) shows the case where the glue layer is provided on one side, and Figures 1(b) and 1(c) show the cases where the glue layer is provided on both sides; in Figure 1(a), the pole piece includes a current collector 1, a glue layer 2 provided on one side of the current collector 1, and an active material layer 3 provided on the outer surface of the glue layer 2; in Figures 1(b) and 1(c), the pole piece includes a current collector 1, a glue layer 2 provided on both sides of the current collector 1, and an active material layer 3 provided on the outer surface of the glue layer 2.

[0020] In the present disclosure, the active material layer may include an active material and fiber particles. The fiber particles may include a first binder.

[0021] In the present disclosure, the first binder may include at least one of polyvinylidene fluoride, styrene-butadiene rubber, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyacrylic acid, and polytetrafluoroethylene. The first binder may be fiberized, for example, the first binder includes polytetrafluoroethylene, and the polytetrafluoroethylene is fiberized.

[0022] In the present disclosure, the active material layer may further include a first conductive agent. The first conductive agent may include at least one of conductive carbon black, carbon nanotubes, and graphene.

[0023] The glass transition temperature of the adhesive layer is 70°C-190°C, for example, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, 185°C or 190°C.

[0024] In the present disclosure, “the outer surface of the glue layer” refers to the surface of the glue layer away from the current collector.

[0025] In one embodiment, the fiber particles in the active material layer are formed by applying a fibrillated first binder to the fiber particles by heating and rolling. The first binder is subjected to a force to form fibrillated particles.

[0026] In one example, the fiber particles in the active material layer are fiberized particles formed by a dispersion treatment (eg, a rotation speed of 3000 rpm-6000 rpm) of the first binder.

[0027] In one embodiment, the active material layer can be produced by a dry process, i.e., the active material, the fiber particles, and the first conductive agent are dry-mixed without using a solvent to produce a composite material having a solid content concentration of substantially 100%. Dry mixing refers to a method in which the active material and the fiber particles are mixed without using a solvent at a solid content concentration of substantially 100%. During dry mixing, the first conductive agent, etc., may be added in addition to the active material and the fiber particles. Even when materials other than the active material and the fiber particles are added, the solid content concentration in the dry mixing is substantially 100%.

[0028] The adhesive layer slurry is then applied to the current collector and dried to form a hot-melt current collector. The composite material is then rolled into a sheet to form the active material layer. The hot-melt current collector and active material are then stacked and hot-pressed to form the electrode sheet.

[0029] Compared with the existing wet method for preparing pole pieces, in its production process, it is necessary to mix the solvent, active material and binder to form a slurry, and then apply the slurry to the surface of the current collector, and then dry the slurry coating on the surface of the current collector to volatilize the solvent. It can be seen that the drying process of the wet method makes the production process of the battery more complicated and reduces the production efficiency. In the embodiment of the present disclosure, by adopting a dry method to prepare the pole piece, there is no need to use a solvent, the active material and fiber particles are mixed to form a composite material, the composite material is rolled into a sheet, and then the sheet active material layer is hot-pressed with the hot-melt current collector. There is no need to dry the slurry coating on the surface of the current collector to volatilize the solvent, thereby simplifying the production process of the pole piece and improving the production efficiency of the battery.

[0030] Furthermore, research has found that when a glue layer is provided between the current collector and the active material layer, the electronic conductivity of the electrode can be significantly improved, thereby improving the cycle performance of the battery. The reason may be that in the relevant dry electrode technology, the adhesion between the current collector and the active material layer is mainly achieved by the high temperature and high pressure generated by the roller pressing equipment in the hot pressing process. However, after the hot pressing process, the bonding force between the current collector and the active material layer is still not ideal; if a glue layer is provided between the current collector and the active material layer, the glass transition of the glue layer is used to generate viscosity, which can not only ensure a strong bonding force between the current collector and the active material layer, but also significantly reduce the temperature and pressure of the hot pressing process. Further research has found that in the dry process, since no solvent is required, the fiber particles are fully distributed in the thickness direction of the active material layer during the preparation process, that is, the stress on the electrode in the thickness direction is evenly distributed, and when the glass transition temperature of the adhesive layer is within a specific range, the adhesive layer has excellent bonding strength, sealing performance and thermal stability. The bonding force generated and the uniformly distributed stress in the electrode can effectively bond the current collector and the active material layer, thereby avoiding the problem of peeling, deformation or failure of the electrode coating, thereby ensuring the normal use of the battery; and when the glass transition temperature of the adhesive layer is within a specific range, the battery can also exhibit excellent cycle stability under extreme conditions (such as high temperature 45°C-60°C).

[0031] In one embodiment, the glass transition temperature of the adhesive layer is 100° C.-130° C.

[0032] In the present disclosure, the ratio of the glass transition temperature of the adhesive layer (in ° C.) to the thickness of the adhesive layer (in μm) can be (20-600):1, for example, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, 100:1, 110:1, 120:1, 130:1, 140:1, 150:1, 160:1, 170:1, 180:1, 190:1, 200:1, 250:1, 300:1, 350:1, 400:1, 450:1, 500:1, 550:1 or 600:1.

[0033] In one example, the ratio of the glass transition temperature (in degrees Celsius) of the adhesive layer to the thickness (in micrometers) of the adhesive layer is (95-200):1.

[0034] Research has found that when the ratio of the glass transition temperature of the glue layer (in ° C) to the thickness of the glue layer (in μm) is within a specific range, the glue layer and the active material layer can form a stable composite structure; when the ratio is too large, the viscosity provided by the glue layer is insufficient to meet the peeling strength between the current collector and the active material layer, which will affect the cycle performance of the battery; and when the ratio is too small, the mass proportion of the active material may be reduced, thereby reducing the energy density of the battery, and may also expand the ion transmission path between the current collector and the active material layer, which is not conducive to the fast charging performance of the battery.

[0035] In the present disclosure, the thickness of the adhesive layer may be 0.1 μm-3 μm, for example, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm or 3 μm.

[0036] In one embodiment, the thickness of the adhesive layer is 0.5 μm-1.5 μm.

[0037] In one embodiment, the thickness of the adhesive layer is 0.6 μm-1.3 μm.

[0038] In the present disclosure, the thermogravimetric analysis curve of the adhesive layer at 650° C. may show a weight change rate of 5%-45%, for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% or 45%.

[0039] In one embodiment, a thermogravimetric analysis curve of the adhesive layer shows a weight change rate of 7%-30% at 650°C.

[0040] In the present disclosure, the thermogravimetric analysis curve of the active material layer may have a weight change rate at 650°C of 0.1%-10%, for example, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%.

[0041] In one embodiment, a thermogravimetric analysis curve of the active material layer shows a weight change rate of 1%-3% at 650° C.

[0042] In the present disclosure, in the thermogravimetric analysis curve of the glue layer and the thermogravimetric analysis curve of the active material layer, the ratio of the weight change rate of the glue layer at 650°C to the weight change rate of the active material layer at 650°C can be (3-100):1, for example, 3:1, 4:1, 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, 55:1, 60:1, 65:1, 70:1, 75:1, 80:1, 85:1, 90:1, 95:1 or 100:1.

[0043] In one example, in the thermogravimetric analysis curve of the adhesive layer and the thermogravimetric analysis curve of the active material layer, the ratio of the weight change rate of the adhesive layer at 650°C to the weight change rate of the active material layer at 650°C is (4.5-16):1.

[0044] Research has found that at 650°C, when the ratio of the weight change rate of the glue layer to the weight change rate of the active material layer is within a specific range, the energy density and rate performance of the battery can be improved. The reason may be that when the ratio of the two is within a specific range, the mass proportion of the active material can be increased while ensuring the bonding force; and reducing the content of the binder in the active material layer is conducive to optimizing the ion channels inside and between the active materials.

[0045] In the present disclosure, the ratio of the porosity of the active material layer to the porosity of the glue layer may be (2-4):1, for example, 2:1, 2.5:1, 3:1, 3.5:1 or 4:1.

[0046] In one example, the ratio of the porosity of the active material layer to the porosity of the adhesive layer is (2.5-3.5):1.

[0047] Research has found that when the ratio of the porosity of the active material layer to the porosity of the glue layer is within a specific range, it is beneficial to the migration speed of lithium ions, thereby improving the rate performance of the battery.

[0048] In the present disclosure, the porosity of the active material layer is 35%-45%, for example, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44% or 45%.

[0049] In the present disclosure, the porosity of the glue layer is 10%-20%, for example, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%.

[0050] In the present disclosure, in the first direction, the length of the glue layer is greater than or equal to the length of the active material layer.

[0051] In the present disclosure, the first direction refers to the length direction of the electrode sheet. As shown in FIG. 2, which is a schematic diagram of an electrode sheet in an example of the present disclosure, where FIGS. 2(a) and 2(b) are cross-sectional views along the length direction of the electrode sheet, and FIGS. 2(c) and 2(d) are top views; in FIGS. 2(a) and 2(c), in the length direction of the electrode sheet, the length of the adhesive layer 2 is equal to the length of the active material layer 3; in FIGS. 2(b) and 2(d), in the length direction of the electrode sheet, the length of the adhesive layer 2 is greater than the length of the active material layer 3.

[0052] In one example, in the first direction, the length of the adhesive layer is greater than the length of the active material layer.

[0053] In the present disclosure, in the first direction, the difference between the length of the adhesive layer and the length of the active material layer is a, where 1 mm ≤ a ≤ 10 mm. For example, a = 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm or 10 mm.

[0054] In one example, 4 mm ≤ a ≤ 6 mm.

[0055] Through research, it is found that when the adhesive layer is disposed between the current collector and the active material layer, and in the first direction, the length of the adhesive layer exceeds the length of the active material layer within a specific range, the flexibility of the electrode sheet can be ensured, preventing it from breaking during the preparation process, thereby reducing the defect rate in the manufacturing process and being beneficial to improving the battery stability; and it can relieve the fracture of the current collector caused by different stresses between the current collector and the electrode sheet; in addition, when the length of the adhesive layer exceeds the length of the active material layer within a specific range, the adhesion force with the separator can be improved without affecting the battery performance, thereby improving the safety of the battery during dropping.

[0056] As shown in FIG. 3, which is a schematic diagram of the difference between the length of the adhesive layer and the length of the active material layer in an example of the present disclosure. In FIG. 3, a1 is the difference between the length of the adhesive layer and the length of the active material layer on one side along the length direction of the electrode sheet; a2 is the difference between the length of the adhesive layer and the length of the active material layer on the other side along the length direction of the electrode sheet, where a1 + a2 = a.

[0057] In one example, 0 mm < a1 < 10 mm (such as 0.1 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm or 9.9 mm); 0 mm < a2 < 10 mm (such as 0.1 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm or 9.9 mm).

[0058] In one example, 2 mm ≤ a1 ≤ 3 mm.

[0059] In one example, 2 mm ≤ a2 ≤ 3 mm.

[0060] In the present disclosure, the adhesive layer may include a second adhesive and a second conductive agent. The second adhesive may include at least one of a polyolefin, a polyester, a polyamide, and a polyurethane. The second conductive agent may include at least one of conductive carbon black, carbon nanotubes, and graphene.

[0061] In the present disclosure, the polyolefin-based materials include, for example, polyethylene, polypropylene, and poly-1-butene. The polyester-based materials include, for example, polyacrylate, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyarylate (PAR). The polyamide-based materials include, for example, polyamide-6, polyamide-66, and polyamide-610. The polyurethane-based materials include, for example, polyisocyanate-based polyurethane, prepolymer-based polyurethane, and end-capped polyurethane.

[0062] In the present disclosure, the second binder may include at least one of poly(p-methylstyrene), poly(o-methylstyrene), poly(p-chlorostyrene), polyvinyl chloride, and polycarbonate.

[0063] Research has found that a specific second binder has strong adhesion, good high-temperature resistance, chemical corrosion resistance, and minimal impact from ambient humidity, further improving the battery's cycling stability. Further research has found that a specific second conductive agent can increase the roughness of the adhesive layer, thereby improving the adhesion between the current collector and the active material layer, further enhancing the battery's cycling stability.

[0064] In one example, the second conductive agent includes conductive carbon black.

[0065] In one example, the first binder and the second binder are different.

[0066] In the present disclosure, the weight average molecular weight of the second binder may be 5×10 4 g / mol-7×10 5 g / mol, for example 5×10 4 g / mol, 6×10 4 g / mol, 7×10 4 g / mol, 8×10 4 g / mol, 9×10 4 g / mol, 10×10 4 g / mol, 1.5×10 5 g / mol, 2×10 5 g / mol, 2.5×10 5 g / mol, 3×10 5g / mol, 3.5×10 5 g / mol, 4×10 5 g / mol, 4.5×10 5 g / mol, 5×10 5 g / mol, 5.5×10 5 g / mol, 6×10 5 g / mol, 6.5×10 5 g / mol or 7×10 5 The weight average molecular weight of the first binder can be 1×10 5 g / mol-9×10 7 g / mol, for example 1×10 5 g / mol, 2×10 5 g / mol, 3×10 5 g / mol, 4×10 5 g / mol, 5×10 5 g / mol, 6×10 5 g / mol, 7×10 5 g / mol, 8×10 5 g / mol, 9×10 5 g / mol, 1×10 6 g / mol, 2×10 6 g / mol, 3×10 6 g / mol, 4×10 6 g / mol, 5×10 6 g / mol, 6×10 6 g / mol, 7×10 6 g / mol, 8×10 6 g / mol, 9×10 6 g / mol, 1×10 7 g / mol, 2×10 7 g / mol, 3×10 7 g / mol, 4×10 7 g / mol, 5×10 7 g / mol, 6×10 7 g / mol, 7×10 7 g / mol, 8×10 7 g / mol or 9×10 7 g / mol.

[0067] Research has found that when the weight-average molecular weight of the first binder and the second binder is within a specific range, the bonding force between the glue layer and the current collector and the bonding force between the glue layer and the active material layer can be improved; at the same time, the content of the second binder in the glue layer and the content of the first binder in the active material layer can be effectively reduced, thereby increasing the energy density of the battery and further improving the electronic conductivity of the electrode.

[0068] In the present disclosure, the ratio of the weight average molecular weight of the second binder to the weight average molecular weight of the first binder can be 1:(1.5-20), for example, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19 or 1:20.

[0069] Research has found that when the ratio of the weight-average molecular weight of the second binder to the weight-average molecular weight of the first binder is within a specific range, the bonding force between the active material layer and the current collector can be ensured, reducing the risk of the second binder and the first binder dissolving in the electrolyte, improving the battery's kinetic performance, improving lithium plating, and improving the cycle capacity retention rate.

[0070] In one example, a ratio of the weight average molecular weight of the second binder to the weight average molecular weight of the first binder is 1:(2.6-5).

[0071] In the present disclosure, the adhesive layer may further include a dispersant, wherein the dispersant includes at least one of carboxymethyl cellulose, sodium carboxymethyl cellulose, and lithium carboxymethyl cellulose.

[0072] In the present disclosure, based on the total weight of the adhesive layer, the content of the second binder can be 5-30 weight % (for example, 5, 10, 15, 20, 25 or 30 weight %), the content of the second conductive agent can be 35-65 weight % (for example, 35, 40, 45, 50, 55, 60 or 65 weight %), and the content of the dispersant can be 15-55 weight % (for example, 15, 20, 25, 30, 35, 40, 45, 50 or 55 weight %).

[0073] In one example, based on the total weight of the adhesive layer, the content of the second binder is 8-25 weight %, the content of the second conductive agent is 40-60 weight %, and the content of the dispersant is 20-50 weight %.

[0074] In the present disclosure, based on the total weight of the active material layer, the content of the first binder can be 0.5-5 weight % (for example, 0.5, 1, 2, 3, 4 or 5 weight %), and the content of the first conductive agent can be 1-5 weight % (for example, 1, 2, 3, 4 or 5 weight %).

[0075] In one example, based on the total weight of the active material layer, the content of the first binder is 1-3 weight %, and the content of the first conductive agent is 1-3 weight %.

[0076] The present disclosure also provides a method for preparing the pole piece, the method comprising at least the following steps:

[0077] (1) mixing a second binder, a second conductive agent, and a dispersant, adding a solvent to obtain a second mixed material slurry, coating the second mixed material slurry on a current collector, and drying to obtain a hot-melt current collector;

[0078] (2) uniformly mixing the active material and the first conductive agent, adding the first binder, mixing uniformly, and performing a dispersion treatment to obtain a first mixed material;

[0079] (3) Extruding the first mixed material and rolling it, and hot pressing it onto the hot melt current collector.

[0080] The specific selection of materials and their dosage are as described above and will not be repeated here.

[0081] In step (1), the solvent may include deionized water.

[0082] In step (1), the coating can be performed by a coating machine commonly used in the art, such as a laminating machine.

[0083] In step (1), the drying may include a drying method conventionally used in the art, such as hot air drying.

[0084] In step (2), the dispersion process can be carried out by the conventional dispersion equipment used in this area, such as air flow mill. The dispersion process at least includes the first dispersion process and the second dispersion process. The rotating speed of the first dispersion process is less than or equal to 100rpm (such as 100rpm, 90rpm, 80rpm, 70rpm, 60rpm, 50rpm, 40rpm, 30rpm, 20rpm or 10rpm), and the time of the first dispersion process is 10 minutes to 30 minutes (such as 10 minutes, 20 minutes or 30 minutes). The rotating speed of the second dispersion process is 3000rpm to 6000rpm (such as 3000rpm, 4000rpm, 5000rpm or 6000rpm), and the time of the second dispersion process is 30 minutes to 100 minutes (such as 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes, 90 minutes or 100 minutes).

[0085] In the present disclosure, in step (2), the purpose of the second dispersion treatment is to fiberize the first binder.

[0086] In step (2), the first mixed material is in a dough-like state.

[0087] In step (3), the extrusion rolling can be performed by a screw pump. After the extrusion rolling, an active material layer is obtained.

[0088] In step (3), the hot pressing includes at least a first hot pressing and a second hot pressing. The temperature of the first hot pressing is 50°C-100°C (e.g., 50°C, 60°C, 70°C, 80°C, 90°C, or 100°C); the pressure of the first hot pressing is 0.5 tons-1 ton (e.g., 0.5 tons, 0.6 tons, 0.7 tons, 0.8 tons, 0.9 tons, or 1 ton). The temperature of the second hot pressing is 50°C-100°C (e.g., 50°C, 60°C, 70°C, 80°C, 90°C, or 100°C); the pressure of the second hot pressing is 0.5 tons-1 ton (e.g., 0.5 tons, 0.6 tons, 0.7 tons, 0.8 tons, 0.9 tons, or 1 ton). During the hot pressing, the conveying speed of the roller conveyor belt is 5 m / min-20 m / min (e.g., 5 m / min, 10 m / min, 15 m / min, or 20 m / min).

[0089] A second aspect of the present disclosure provides a battery, which may include the pole piece described in the first aspect of the present disclosure.

[0090] In the present disclosure, the battery may further include a separator. The bonding force between the glue layer and the active material layer may be 30 N / m-40 N / m (e.g., 30 N / m, 31 N / m, 32 N / m, 33 N / m, 34 N / m, 35 N / m, 36 N / m, 37 N / m, 38 N / m, 39 N / m, or 40 N / m). The bonding force between the active material layer and the separator may be 10 N / m-25 N / m (e.g., 10 N / m, 11 N / m, 12 N / m, 13 N / m, 14 N / m, 15 N / m, 16 N / m, 17 N / m, 18 N / m, 19 N / m, 20 N / m, 21 N / m, 22 N / m, 23 N / m, 24 N / m, or 25 N / m).

[0091] In the present disclosure, the ratio of the bonding force between the glue layer and the active material layer and the bonding force between the active material layer and the diaphragm can be (1.2-4):1, for example, 1.2:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1 or 4:1.

[0092] Research has found that when the ratio of the bonding force between the glue layer and the active material layer to the bonding force between the active material layer and the diaphragm is within a specific range, it can ensure that the bonding force provided by the glue layer can firmly bond the active material layer to the current collector and ensure close contact between the active material layer and the diaphragm; at the same time, it can inhibit the active material from falling off the current collector due to volume expansion during the charging and discharging process.

[0093] In the present disclosure, the battery may further include a positive electrode sheet and a negative electrode sheet. The positive electrode sheet may be the electrode sheet. The negative electrode sheet may be the electrode sheet.

[0094] <Positive electrode>

[0095] In the present disclosure, the current collector may include aluminum foil.

[0096] In the present disclosure, the active material layer may further include a positive electrode active material, and the positive electrode active material may be selected from the positive electrode active materials conventionally used in the art, for example, including at least one of lithium cobaltate, lithium nickel cobalt manganeseate, lithium nickel cobalt aluminumate, lithium nickel cobalt manganese aluminumate, lithium manganate, lithium nickel manganeseate, lithium nickelate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate and lithium-rich manganese.

[0097] <Negative electrode>

[0098] In the present disclosure, the current collector may include a copper foil.

[0099] In the present disclosure, the active material layer may further include a negative electrode active material, and the negative electrode active material may be selected from the negative electrode active materials conventionally used in the art, for example, at least one of artificial graphite, natural graphite, mesophase carbon microbeads, hard carbon, soft carbon, silicon, silicon oxide and silicon carbon.

[0100] In the present disclosure, the battery may further include a separator and an electrolyte.

[0101] The separator may include separators commonly used in the art, such as at least one of a polyethylene film and a polypropylene film.

[0102] In the present disclosure, the electrolyte can be selected from the electrolytes conventionally used in the art, for example, the electrolyte includes an organic solvent, an electrolyte salt and an additive. The organic solvent may include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl fluorocarbonate, ethyl methyl fluorocarbonate, ethylpropyl carbonate (EPC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methylpropyl carbonate (MPC), methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate (EA), propyl acetate, butyl acetate, methyl propionate, propionic acid At least one of ethyl ester, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, methyl difluoroacetate, ethyl difluoroacetate, γ-butyrolactone (GBL), γ-valerolactone, δ-valerolactone, ethylene glycol dimethyl ether (DME), 1,3-dioxolane (DOL), 1,4-dioxane (DOX), sulfolane, dimethyl sulfoxide (DMSO), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), diethyl sulfone (ESE), dichloromethane and dichloroethane. The electrolyte salt may include at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium hexafluoroantimonate (LiSbF6), lithium difluorophosphate (LiPF2O2), 4,5-dicyano-2-trifluoromethylimidazolium lithium (LiDTI), lithium bis(oxalato)borate (LiBOB), lithium bis(malonate)borate (LiBMB), lithium difluorooxalatoborate (LiDFOB), lithium bis(difluoromalonate)borate (LiBDFMB), lithium (malonate oxalato)borate (LiMOB), lithium bis(fluorosulfonyl imide) (LiFSI), and lithium bis(trifluoromethanesulfonyl imide) (LiTFSI). The additive may include at least one of fluoroethylene carbonate and vinylene carbonate.

[0103] The battery can be assembled in accordance with conventional methods in the art.

[0104] The present disclosure will be described in detail below through examples. The examples described in this disclosure are only a portion of the examples of the present disclosure, not all of the examples. Based on the examples in this disclosure, all other examples obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this disclosure.

[0105] In the following examples, unless otherwise specified, all materials used were commercially available analytical grade.

[0106] The following examples are provided to illustrate the batteries of the present disclosure.

[0107] Example 1

[0108] Prepare the battery as follows:

[0109] (1) Preparation of hot melt current collector

[0110] Poly(p-methylstyrene) (weight average molecular weight 2×10 5 g / mol-3×10 5 g / mol), conductive carbon black and sodium carboxymethyl cellulose are evenly mixed in a mass ratio of 8:42:50, deionized water is added to obtain a glue layer slurry, the glue layer slurry is coated on the current collector, and hot air is dried (aluminum foil with a thickness of 9 μm is used for the positive electrode sheet; copper foil with a thickness of 6 μm is used for the negative electrode sheet).

[0111] (2) Preparation of negative electrode sheet

[0112] Artificial graphite and conductive carbon black were mixed evenly, and polytetrafluoroethylene (weight average molecular weight of 8×10 5 g / mol-10×10 5 g / mol) were mixed evenly, wherein the mass ratio of artificial graphite, conductive carbon black and polytetrafluoroethylene was 95:3:2; the mixed material was placed in a jet mill for dispersion treatment (first at a speed of 50 rpm for 10 minutes; then at a speed of 5000 rpm for 50 minutes); the dispersed material was extruded and rolled by a screw pump to obtain a negative electrode active material layer; the negative electrode active material layer was hot pressed (the first hot pressing temperature was 50°C and the pressure was 1 ton; the second hot pressing temperature was 50°C and the pressure was 1 ton) ) to the surface of the hot-melt current collector to obtain a negative electrode sheet, wherein the weight-average molecular weight ratio of polyparamethylstyrene to polytetrafluoroethylene is 1:(2.6-5), a1 is the difference between the length of the glue layer and the length of the negative electrode active material layer on one side along the length direction of the negative electrode sheet; a2 is the difference between the length of the glue layer and the length of the negative electrode active material layer on the other side along the length direction of the negative electrode sheet, a1=a2=2mm, and in the first direction, the difference between the length of the glue layer and the length of the negative electrode active material layer is a=a1+a2=4mm.

[0113] (3) Preparation of positive electrode sheet

[0114] Lithium cobalt oxide and conductive carbon black were mixed evenly, and polytetrafluoroethylene (weight average molecular weight 8×10 5 g / mol-10×10 5 g / mol) were mixed evenly, wherein the mass ratio of lithium cobalt oxide, conductive carbon black and polytetrafluoroethylene was 95:3:2; the mixed material was placed in a jet mill for dispersion treatment (first at a speed of 50 rpm, for 10 minutes; then at a speed of 5000 rpm, for 50 minutes); the dispersed material was extruded and rolled by a screw pump to obtain a positive electrode active material layer; the positive electrode active material layer was hot pressed (the first hot pressing temperature was 50°C and the pressure was 1 ton; the second hot pressing temperature was 50°C and the pressure was 1 ton) to a hot melt A positive electrode sheet is obtained on the surface of the current collector, wherein the weight-average molecular weight ratio of polyparamethylstyrene to polytetrafluoroethylene is 1:(2.6-5), a1' is the difference between the length of the glue layer and the length of the positive electrode active material layer on one side along the length direction of the positive electrode sheet; a2' is the difference between the length of the glue layer and the length of the positive electrode active material layer on the other side along the length direction of the positive electrode sheet, a1'=a2'=2mm, and in the first direction, the difference between the length of the glue layer and the length of the positive electrode active material layer is a'=a1'+a2'=4mm.

[0115] (4) Preparation of batteries

[0116] The negative electrode sheet prepared in step (2), the separator (polypropylene film) and the positive electrode sheet prepared in step (3) are stacked and wound in sequence to obtain a core, which is then packaged and injected with an electrolyte (organic solvents EC, DEC and EMC are mixed in a mass ratio of 2:3:5, the concentration of the electrolyte salt LiPF6 is 1 mol / L, and the mass content of the additive fluoroethylene carbonate is 5%), and the battery is prepared by formation and sorting.

[0117] Example 2

[0118] (1) Preparation of hot melt current collector

[0119] Poly(o-methylstyrene) (weight average molecular weight 2×10 5 g / mol-3×10 5 g / mol), conductive carbon black and sodium carboxymethyl cellulose are evenly mixed in a mass ratio of 18:50:32, deionized water is added to obtain a glue layer slurry, the glue layer slurry is coated on the current collector, and hot air is dried (aluminum foil with a thickness of 9 μm is used for the positive electrode sheet; copper foil with a thickness of 6 μm is used for the negative electrode sheet).

[0120] (2) Preparation of negative electrode sheet

[0121] Artificial graphite and conductive carbon black were mixed evenly, and polytetrafluoroethylene (weight average molecular weight of 8×10 5g / mol-10×10 5 g / mol) were mixed evenly, wherein the mass ratio of artificial graphite, conductive carbon black and polytetrafluoroethylene was 95:3:2; the mixed material was placed in a jet mill for dispersion treatment (first at a speed of 80 rpm for 20 minutes; then at a speed of 4000 rpm for 80 minutes); the dispersed material was extruded and rolled by a screw pump to obtain a negative electrode active material layer; the negative electrode active material layer was hot pressed (the first hot pressing temperature was 70°C and the pressure was 0.8 tons; the second hot pressing temperature was 70°C and the pressure was 0.8 tons). tons) to the surface of the hot-melt current collector to obtain a negative electrode sheet, wherein the weight-average molecular weight ratio of poly-o-methylstyrene to polytetrafluoroethylene is 1:(2.6-5), a1 is the difference between the length of the glue layer and the length of the negative electrode active material layer on one side along the length direction of the negative electrode sheet; a2 is the difference between the length of the glue layer and the length of the negative electrode active material layer on the other side along the length direction of the negative electrode sheet, a1=a2=2.5mm, and in the first direction, the difference between the length of the glue layer and the length of the negative electrode active material layer is a=a1+a2=5mm.

[0122] (3) Preparation of positive electrode sheet

[0123] Lithium cobalt oxide and conductive carbon black were mixed evenly, and polytetrafluoroethylene (weight average molecular weight 8×10 5 g / mol-10×10 5 g / mol) were mixed evenly, wherein the mass ratio of lithium cobalt oxide, conductive carbon black and polytetrafluoroethylene was 95:3:2; the mixed material was placed in a jet mill for dispersion treatment (first at a speed of 80 rpm for 20 minutes; then at a speed of 4000 rpm for 80 minutes); the dispersed material was extruded and rolled by a screw pump to obtain a positive electrode active material layer; the positive electrode active material layer was hot pressed (the first hot pressing temperature was 70°C and the pressure was 0.8 tons; the second hot pressing temperature was 70°C and the pressure was 0.8 tons) to a hot press temperature of 70°C and a pressure of 0.8 tons. The surface of the melt fluid is obtained to obtain a positive electrode sheet, wherein the weight-average molecular weight ratio of poly-o-methylstyrene to polytetrafluoroethylene is 1:(2.6-5), a1' is the difference between the length of the glue layer and the length of the positive electrode active material layer on one side along the length direction of the positive electrode sheet; a2' is the difference between the length of the glue layer and the length of the positive electrode active material layer on the other side along the length direction of the positive electrode sheet, a1'=a2'=2.5mm, and in the first direction, the difference between the length of the glue layer and the length of the positive electrode active material layer is a'=a1'+a2'=5mm.

[0124] (4) Preparation of batteries

[0125] The negative electrode sheet prepared in step (2), the separator (polypropylene film) and the positive electrode sheet prepared in step (3) are stacked and wound in sequence to obtain a core, which is then packaged and injected with an electrolyte (organic solvents EC, DEC and EMC are mixed in a mass ratio of 2:3:5, the concentration of the electrolyte salt LiPF6 is 1 mol / L, and the mass content of the additive fluoroethylene carbonate is 5%), and the battery is prepared by formation and sorting.

[0126] Example 3

[0127] (1) Preparation of hot melt current collector

[0128] Poly(p-chlorostyrene) (weight average molecular weight 2×10 5 g / mol-3×10 5 g / mol), conductive carbon black and sodium carboxymethyl cellulose are evenly mixed in a mass ratio of 28:52:20, deionized water is added to obtain a glue layer slurry, the glue layer slurry is coated on the current collector, and hot air is dried (aluminum foil with a thickness of 9 μm is used for the positive electrode sheet; copper foil with a thickness of 6 μm is used for the negative electrode sheet).

[0129] (2) Preparation of negative electrode sheet

[0130] Artificial graphite and conductive carbon black were mixed evenly, and polytetrafluoroethylene (weight average molecular weight of 8×10 5 g / mol-10×10 5 g / mol) were mixed evenly, wherein the mass ratio of artificial graphite, conductive carbon black and polytetrafluoroethylene was 95:3:2; the mixed material was placed in a jet mill for dispersion treatment (first at a speed of 90 rpm for 30 minutes; then at a speed of 3000 rpm for 100 minutes); the dispersed material was extruded and rolled by a screw pump to obtain a negative electrode active material layer; the negative electrode active material layer was hot pressed (the first hot pressing temperature was 90°C and the pressure was 0.5 tons; the second hot pressing temperature was 90°C and the pressure was 0 .5 tons) to the surface of the hot-melt current collector to obtain a negative electrode sheet, wherein the weight-average molecular weight ratio of polyparachlorostyrene to polytetrafluoroethylene is 1:(2.6-5), a1 is the difference between the length of the glue layer and the length of the negative electrode active material layer on one side along the length direction of the negative electrode sheet; a2 is the difference between the length of the glue layer and the length of the negative electrode active material layer on the other side along the length direction of the negative electrode sheet, a1=a2=3mm, and in the first direction, the difference between the length of the glue layer and the length of the negative electrode active material layer is a=a1+a2=6mm.

[0131] (3) Preparation of positive electrode sheet

[0132] Lithium cobalt oxide and conductive carbon black were mixed evenly, and polytetrafluoroethylene (weight average molecular weight 8×10 5 g / mol-10×10 5g / mol) were mixed uniformly, wherein the mass ratio of lithium cobalt oxide, conductive carbon black and polytetrafluoroethylene was 95:3:2; the mixed material was placed in a jet mill for dispersion treatment (first at a speed of 90 rpm for 30 minutes; then at a speed of 3000 rpm for 100 minutes); the dispersed material was extruded and rolled using a screw pump to obtain a positive electrode active material layer; the positive electrode active material layer was hot pressed (the first hot pressing temperature was 90° C. and the pressure was 0.5 tons; the second hot pressing temperature was 90° C. and the pressure was 0.5 tons). to the surface of the hot-melt current collector to obtain a positive electrode sheet, wherein the weight-average molecular weight ratio of polyparachlorostyrene to polytetrafluoroethylene is 1:(2.6-5), a1' is the difference between the length of the glue layer and the length of the positive electrode active material layer on one side along the length direction of the positive electrode sheet; a2' is the difference between the length of the glue layer and the length of the positive electrode active material layer on the other side along the length direction of the positive electrode sheet, a1'=a2'=3mm, and in the first direction, the difference between the length of the glue layer and the length of the positive electrode active material layer is a'=a1'+a2'=6mm.

[0133] (4) Preparation of batteries

[0134] The negative electrode sheet prepared in step (2), the separator (polypropylene film) and the positive electrode sheet prepared in step (3) are stacked and wound in sequence to obtain a core, which is then packaged and injected with an electrolyte (organic solvents EC, DEC and EMC are mixed in a mass ratio of 2:3:5, the concentration of the electrolyte salt LiPF6 is 1 mol / L, and the mass content of the additive fluoroethylene carbonate is 5%), and the battery is prepared by formation and sorting.

[0135] Example 4 Group

[0136] This group of examples is carried out with reference to Example 1, except that the glass transition temperature of the adhesive layer is changed by changing the second adhesive in the adhesive layer. Specifically:

[0137] In Example 4a, poly(p-methylstyrene) was replaced by polyvinyl chloride (weight average molecular weight of 2×10 5 g / mol-3×10 5 g / mol), and the glass transition temperature of the adhesive layer is 80°C;

[0138] In Example 4b, poly(p-methylstyrene) was replaced by polycarbonate (weight average molecular weight of 2×10 5 g / mol-3×10 5 g / mol), and the glass transition temperature of the adhesive layer is 180°C.

[0139] Example 5 Group

[0140] This group of examples is carried out with reference to Example 1, except that the thickness of the adhesive layer is changed. Specifically:

[0141] In Example 5a, the thickness of the adhesive layer is 0.2 μm;

[0142] In Example 5b, the thickness of the adhesive layer is 3 μm;

[0143] In Example 5c, the thickness of the adhesive layer is 1.3 μm.

[0144] Example 6

[0145] This group of examples is carried out with reference to Example 1, except that the length of the glue layer, the length of the positive electrode active material layer, and the length of the negative electrode active material layer are changed. Specifically:

[0146] In Example 6a, a1=a2=0.5 mm in the positive electrode sheet and a1=a2=0.5 mm in the negative electrode sheet;

[0147] In Example 6b, a1=a2=4 mm in the positive electrode sheet and a1=a2=4 mm in the negative electrode sheet;

[0148] In Example 6c, the length of the positive electrode active material layer is the same as the length of its corresponding glue layer; the length of the negative electrode active material layer is the same as the length of its corresponding glue layer.

[0149] Example 7 Group

[0150] This group of examples is carried out with reference to Example 1, except that the ratio of the weight average molecular weight of the second binder to the first binder is changed, specifically:

[0151] In Example 7a, the weight average molecular weight of poly(p-methylstyrene) is 4×10 5 g / mol-5×10 5 g / mol, that is, the ratio of the weight average molecular weight of the second binder in the glue layer to the weight average molecular weight of the first binder in the negative electrode active material layer is 1:(1.6-2.5), and the ratio of the weight average molecular weight of the second binder in the glue layer to the weight average molecular weight of the first binder in the positive electrode active material layer is 1:(1.6-2.5);

[0152] In Example 7b, the second binder was replaced with poly-o-methylstyrene (weight average molecular weight of 8×10 4 g / mol-10×10 4 g / mol), that is, the ratio of the weight average molecular weight of the second binder in the glue layer to the weight average molecular weight of the first binder in the negative electrode active material layer is 1:(8-12.5), and the ratio of the weight average molecular weight of the second binder in the glue layer to the weight average molecular weight of the first binder in the positive electrode active material layer is 1:(8-12.5).

[0153] In the groups of Examples 1 to 7, the porosity of the glue layer is 10%-20%, the porosity of the positive active material layer is 35%-45%, the porosity of the negative active material layer is 35%-45%, and the ratio of the porosity of the positive active material layer / negative active material layer to the glue layer is in the range of (2.5-3.5):1.

[0154] The specific parameters of Example 1 to Example 7 are shown in Table 1.

[0155] Table 1

[0156] Comparative Example 1

[0157] Prepare the battery as follows:

[0158] (1) Preparation of positive electrode sheet

[0159] Lithium cobalt oxide, conductive carbon black and polytetrafluoroethylene are mixed evenly in a mass ratio of 95:3:2, dissolved in N-methylpyrrolidone, and stirred evenly to form a positive electrode slurry with a solid content of 70 weight%, which is evenly coated on aluminum foil and then dried, rolled and cut into positive electrode sheets.

[0160] (2) Preparation of negative electrode sheet

[0161] Lithium cobalt oxide, conductive carbon black and polytetrafluoroethylene are mixed evenly in a mass ratio of 95:3:2, added to deionized water, and stirred evenly to prepare a negative electrode slurry with a solid content of 50 weight%, uniformly coated on copper foil, and prepared into a negative electrode sheet after drying, rolling and slitting.

[0162] (3) Preparation of electrolyte

[0163] Lithium hexafluorophosphate with a concentration of 1 mol / L was used, the organic solvent was a mixture of EC, DEC, and EMC in a mass ratio of 2:3:5, and the additive was 5 wt% fluoroethylene carbonate.

[0164] (4) Preparation of batteries

[0165] The positive electrode sheet prepared in step (1), the polypropylene porous separator and the negative electrode sheet prepared in step (2) are stacked in sequence, wound to obtain a winding core, and then packaged, injected, formed and sorted to make a battery.

[0166] Comparative Example 2

[0167] (1) Preparation of negative electrode sheet

[0168] Artificial graphite, conductive carbon black and polytetrafluoroethylene were mixed uniformly in a mass ratio of 95:3:2, and the mixture was placed in a jet mill for dispersion treatment (first at a speed of 50 rpm for 10 minutes; then at a speed of 5000 rpm for 50 minutes); the dispersed material was extruded and rolled using a screw pump to obtain a negative electrode active material layer; the negative electrode active material layer was hot pressed (the first hot pressing temperature was 120°C and the pressure was 3 tons; the second hot pressing temperature was 120°C and the pressure was 3 tons) onto the surface of a copper foil to obtain a negative electrode sheet.

[0169] (2) Preparation of positive electrode sheet

[0170] Lithium cobalt oxide, conductive carbon black and polytetrafluoroethylene are mixed uniformly in a mass ratio of 95:3:2; the mixed material is placed in a jet mill for dispersion treatment (first at a speed of 50 rpm for 10 minutes; then at a speed of 5000 rpm for 50 minutes); the dispersed material is extruded and rolled by a screw pump to obtain a positive electrode active material layer; the positive electrode active material layer is hot pressed (the first hot pressing temperature is 120°C and the pressure is 3 tons; the second hot pressing temperature is 120°C and the pressure is 3 tons) onto the surface of an aluminum foil to obtain a positive electrode sheet.

[0171] (3) Preparation of batteries

[0172] The negative electrode sheet prepared in step (1), the separator (polypropylene film), and the positive electrode sheet prepared in step (2) are stacked and wound in sequence to obtain a core, which is then packaged and injected with an electrolyte (organic solvents EC, DEC, and EMC are mixed in a mass ratio of 2:3:5, the concentration of the electrolyte salt LiPF6 is 1 mol / L, and the mass content of the additive fluoroethylene carbonate is 5%), and then formed and sorted to obtain a battery.

[0173] Comparative Example 3

[0174] The same method as in Example 1 was used, except that the glass transition temperature of the adhesive layer was changed. Specifically, poly(p-methylstyrene) (weight average molecular weight of 2×10 5 g / mol-3×10 5 g / mol) was replaced with the same mass of poly-α-methylstyrene, and the test showed that the glass transition temperature of the adhesive layer was 192°C.

[0175] Comparative Example 4

[0176] The same method as in Example 1 was used, except that the glass transition temperature of the adhesive layer was changed. Specifically, poly(p-methylstyrene) (weight average molecular weight of 2×10 5 g / mol-3×10 5 g / mol) was replaced with the same mass of polyethyl methacrylate, and the test showed that the glass transition temperature of the adhesive layer was 65°C.

[0177] Test Case I

[0178] (1) Glass transition temperature test

[0179] The adhesive layers of the positive and negative electrodes prepared in the examples were tested for glass transition temperature. The specific method is as follows:

[0180] Using a differential scanning calorimeter (DSC), scrape the adhesive layer as the test sample, place 20 mg of the sample into the test equipment, and in a N2 atmosphere (50 ml / min), heat at a rate of 10 K / min, and set the cutoff temperature to 400 °C. The results are recorded in Table 1.

[0181] (2) Adhesion test

[0182] The positive electrode sheet and the negative electrode sheet prepared in the embodiment were subjected to an adhesion test, and the specific method is as follows:

[0183] A computerized tensile and compressive testing machine was used, and a stainless steel plate with a length of 25 cm and a width of 5 cm was taken as the base; an OPP film with a length of 25 cm and a width of 4 cm was pasted on the center of the steel plate (mainly to protect the steel plate); a double-sided tape with a length of 25 cm and a width of 24 mm (Nitto 500 double-sided tape) was pasted on the center of the OPP film (mainly to adhere the sample to the steel plate); a positive electrode sheet / negative electrode sheet with a length of 25 cm and a width of 24 mm was cut with a knife as the sample, and one side of the sample was pasted on the double-sided tape; a transparent tape with a length of 30 cm and a width of 24 mm was pasted on the other side of the sample; the steel plate was laid flat on the table, and a 2KG pressure roller was used to roll it horizontally three times. The steel plate was fixed in the fixture, and the test was started to obtain the adhesion test curve. The test result is the adhesion between the adhesive layer and the active material layer.

[0184] Similarly, the batteries prepared in Example 3 and Comparative Example 4 were disassembled, and the combination of the negative electrode sheet and the separator / the combination of the positive electrode sheet and the separator were used as samples for testing. The test results were the bonding strength between the active material layer and the separator, and the results are recorded in Table 2.

[0185] Table 2

[0186] (3) Thermogravimetric testing

[0187] The glue layer and active material layer of the positive electrode sheet and the negative electrode sheet prepared in the embodiment were subjected to thermogravimetric testing. The specific method is as follows:

[0188] Using a thermogravimetric analyzer, a 1 μm thick layer of glue powder was scraped off with a clean blade, and about 10 mg of powder was taken for testing at a temperature range of 20°C-1000°C. A 1 μm thick layer of active material powder was scraped off with a clean blade, and about 10 mg of powder was taken for testing at a temperature range of 20°C-1000°C. The results are recorded in Table 1, where the thermogravimetric analysis curves of the glue layer and active material layer of the negative electrode sheet of Example 3 are shown in Figure 4.

[0189] Test Case II

[0190] (1) Capacity retention test

[0191] The batteries prepared in the examples and comparative examples were tested for capacity retention, and the specific test method is as follows:

[0192] At 25°C, the battery was charged at a constant current of 1C to 4.45V, then charged at a constant voltage to a cutoff current of 0.05C. After 5 minutes of rest, it was discharged at a constant current of 1C to 3.0V. This constituted the first cycle, and this process was repeated 200 times. The capacity retention (%) of the battery after 200 cycles = discharge capacity after 200 cycles / discharge capacity after the first cycle × 100%. The results are recorded in Table 3.

[0193] (2) DC resistance (DCIR) test

[0194] The batteries prepared in the examples and comparative examples were subjected to a DC resistance test. The specific test method is as follows:

[0195] At 25°C, charge the battery at a constant current of 0.7C to full charge, then cut off at 0.05C, and let it rest for 30 minutes. Discharge at 0.1C for 10 seconds, recording the voltage as U1. Discharge at 1C for 10 seconds, recording the voltage as U2. Repeat the charge and discharge steps five times. DC resistance DCIR = (U2-U1) / (1C-0.1C), where "1C" is the current value required to completely discharge the lithium-ion battery in 1 hour. Record the results in Table 3.

[0196] Table 3

[0197] As can be seen from Table 3, the battery prepared using the electrode sheet disclosed in the present invention has a higher capacity retention rate and a lower DC resistance than that of the comparative example.

[0198] The preferred embodiments of the present disclosure are described in detail above, but the present disclosure is not limited thereto. Within the technical concept of the present disclosure, various simple variations of the technical solution of the present disclosure may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed by the present disclosure and fall within the scope of protection of the present disclosure.

Claims

1. A pole piece, characterized in that: The pole piece includes a current collector, a glue layer arranged on at least one side surface of the current collector, and an active material layer arranged on the outer surface of the glue layer; the active material layer includes active materials and fiber particles; the glass transition temperature of the glue layer is 70°C-190°C.

2. The pole piece according to claim 1, wherein: The glass transition temperature of the adhesive layer is 100°C-130°C; And / or, the ratio of the glass transition temperature of the adhesive layer to the thickness of the adhesive layer is (20-600):

1.

3. The pole piece according to claim 2, wherein: The ratio of the glass transition temperature of the adhesive layer to the thickness of the adhesive layer is (95-200):

1.

4. The pole piece according to any one of claims 1 to 3, wherein: The thickness of the adhesive layer is 0.1 μm-3 μm; Preferably, the thickness of the adhesive layer is 0.5 μm-1.5 μm, more preferably 0.6 μm-1.3 μm.

5. The pole piece according to any one of claims 1 to 4, wherein: In the thermogravimetric analysis curve of the glue layer and the thermogravimetric analysis curve of the active material layer, the ratio of the weight change rate of the glue layer at 650° C. to the weight change rate of the active material layer at 650° C. is (3-100):1, preferably (4.5-16):1; And / or, the thermogravimetric analysis curve of the adhesive layer has a weight change rate of 5%-45% at 650° C., preferably 7%-30%; And / or, a thermogravimetric analysis curve of the active material layer shows a weight change rate of 0.1%-10% at 650° C., preferably 1%-3%.

6. The pole piece according to any one of claims 1 to 5, wherein: The ratio of the porosity of the active material layer to the porosity of the adhesive layer is (2-4):1; Preferably, the ratio of the porosity of the active material layer to the porosity of the adhesive layer is (2.5-3.5):

1.

7. The pole piece according to any one of claims 1 to 6, wherein: The porosity of the active material layer is 35%-45%; And / or, the porosity of the adhesive layer is 10%-20%.

8. The pole piece according to any one of claims 1 to 7, wherein: In the first direction, the length of the glue layer is greater than or equal to the length of the active material layer; Preferably, in the first direction, the difference between the length of the glue layer and the length of the active material layer is a, 1mm≤a≤10mm, more preferably, 4mm≤a≤6mm.

9. The pole piece according to claim 8, wherein: a1 is the difference between the length of the glue layer and the length of the active material layer on one side of the electrode length; a2 is the difference between the length of the glue layer and the length of the active material layer on the other side of the electrode length, where a1+a2=a,0mm <a1<10mm,0mm<a2<10mm; Preferably, 2mm≤a1≤3mm; 2mm≤a2≤3mm.

10. The pole piece according to any one of claims 1 to 9, wherein: The adhesive layer includes a second adhesive and a second conductive agent; Preferably, the second binder includes at least one of polyolefins, polyesters, polyamides and polyurethanes; more preferably, the second binder includes at least one of poly(p-methylstyrene), poly(o-methylstyrene), poly(p-chlorostyrene), polyvinyl chloride and polycarbonate; Preferably, the second conductive agent includes at least one of conductive carbon black, carbon nanotubes and graphene; Preferably, the adhesive layer further comprises a dispersant, and the dispersant comprises at least one of carboxymethyl cellulose, sodium carboxymethyl cellulose and lithium carboxymethyl cellulose; More preferably, based on the total weight of the adhesive layer, the content of the second binder is 5-30% by weight, the content of the second conductive agent is 35-65% by weight, and the content of the dispersant is 15-55% by weight. Further preferably, based on the total weight of the adhesive layer, the content of the second binder is 8-25% by weight, the content of the second conductive agent is 40-60% by weight, and the content of the dispersant is 20-50% by weight.

11. The pole piece according to any one of claims 1 to 9, wherein: The active material layer further includes a first conductive agent, wherein the first conductive agent includes at least one of conductive carbon black, carbon nanotubes and graphene; and / or, the fiber particles include a first binder, wherein the first binder includes at least one of polyvinylidene fluoride, styrene-butadiene rubber, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyacrylic acid and polytetrafluoroethylene; Preferably, based on the total weight of the active material layer, the content of the first binder is 0.5-5% by weight, and the content of the first conductive agent is 1-5% by weight; More preferably, based on the total weight of the active material layer, the content of the first binder is 1-3% by weight, and the content of the first conductive agent is 1-3% by weight.

12. The pole piece according to claim 11, wherein: The adhesive layer includes a second adhesive, and the ratio of the weight average molecular weight of the second adhesive to the weight average molecular weight of the first adhesive is 1:(1.5-20), preferably 1:(2.6-5); And / or, the weight average molecular weight of the second binder is 5×10 4 g / mol-7×10 5 g / mol; And / or, the weight average molecular weight of the first binder is 1×10 5 g / mol-9×10 7 g / mol.

13. A battery, characterized in that: The battery comprises the pole piece according to any one of claims 1 to 12.

14. The battery according to claim 13, wherein The battery further includes a separator, and a ratio of the bonding force between the glue layer and the active material layer to the bonding force between the active material layer and the separator is (1.2-4):

1.

15. The battery according to claim 14, wherein The bonding force between the adhesive layer and the active material layer is 30N / m-40N / m; And / or, the bonding force between the active material layer and the separator is 10 N / m-25 N / m.

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