A positive electrode sheet, a method for manufacturing the same, and a battery

Abstract

The application relates to the field of new energy batteries, in particular to a positive pole piece, a preparation method thereof and a battery; the positive pole piece comprises a current collector, a positive pole active material layer arranged on at least one side of the current collector in the thickness direction and a glue layer arranged on the surface of the positive pole active material layer away from the current collector; the glue layer comprises a binder; the thickness ratio of the glue layer to the positive pole active material layer is 1: (10-100). The setting of the protective layer in the positive pole piece facilitates long-term storage and classification and temperature and humidity control of the positive pole piece; in the battery assembly process, the protective layer is peeled off, and the remaining current collector and coating structure are assembled with a diaphragm, a negative pole piece and other battery components, the operation is simple and easy to operate. Meanwhile, the setting of the glue layer can avoid energy loss caused by dropping of the positive pole active material.

Description

Technical Field

[0001] This invention relates to the field of new energy batteries, specifically to a positive electrode sheet, its preparation method, and a battery. Background Technology

[0002] The current mainstream method for preparing solid-state battery cathodes involves coating an active slurry uniformly onto the surface of an aluminum foil current collector. This step directly determines the microstructure and macroscopic properties of the cathode and is a core process in the battery production chain. The smooth progress of the coating process depends primarily on accurately controlling the coating window of the slurry—this requires preliminary experiments to determine the suitable parameters of the slurry under specific temperature and humidity conditions, while ensuring the long-term stability of the slurry's properties. Specifically, the slurry needs to maintain a uniform dispersion to avoid problems such as active material sedimentation and stratification during storage and coating; its viscosity needs to be controlled within a reasonable range, ensuring both fluidity to meet the transport requirements of the coating equipment and sufficient viscosity to prevent the coating from easily peeling off; and the solid content needs to be precisely matched to the coating thickness requirements—too high a content can lead to coating blockage, while too low a content will affect the energy density and structural strength of the cathode.

[0003] During the coating process, even slight vibrations in the coating machine or minor deviations in the transmission system can directly cause uneven slurry coating, leading to localized thickness variations, edge lifting, and other defects, which in turn affect subsequent rolling and slitting processes. Furthermore, common appearance defects during production are equally significant: orange peel-like textures can cause excessive surface roughness of the positive electrode, increasing contact resistance with the electrolyte; linear scratches or stripes can disrupt the continuity of the active material, resulting in uneven current distribution. These defects not only cause significant fluctuations in key performance characteristics such as capacity and cycle life of the positive electrode, but also, because their formation is related to multiple factors including slurry characteristics, equipment precision, and environmental parameters, are difficult to precisely control in large-scale mass production, posing a significant challenge to the consistency of battery products. Summary of the Invention

[0004] In view of this, the present invention aims to provide a positive electrode sheet, its preparation method and battery, to solve the problems of uneven slurry coating, orange peel, linear defects and other defects that are prone to occur in the coating and production processes of positive electrode cells in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention is implemented as follows: A first aspect of the present invention provides a positive electrode sheet, the positive electrode sheet comprising a current collector, a positive electrode active material layer disposed on at least one side of the current collector along the thickness direction, and an adhesive layer disposed on the surface of the positive electrode active material layer away from the current collector; The adhesive layer includes an adhesive; the thickness ratio of the adhesive layer to the positive electrode active material layer is 1:(10~100).

[0006] A second aspect of the present invention provides a method for preparing a positive electrode sheet, the method comprising: A first composite layer is obtained by depositing an adhesive layer on the surface of a protective layer, and a second composite layer is obtained by depositing a positive electrode active material layer on the surface of the first composite layer, wherein the positive electrode active material layer is disposed on the side of the adhesive layer away from the protective layer; the second composite layer is wound up to prepare a positive electrode transfer adhesive paper. The positive electrode transfer adhesive paper is thermally transferred to the surface of the current collector, and during the transfer process, the positive electrode active material layer is close to the surface of the current collector; The protective layer is peelable.

[0007] A third aspect of the present invention provides a battery comprising a positive electrode; the positive electrode comprising the above-described positive electrode and / or a positive electrode prepared according to the above-described preparation method.

[0008] The beneficial technical effects of the present invention through the above technical solution are as follows: (1) The positive electrode sheet of the present invention has an adhesive layer on the surface of the positive electrode active material layer, and the thickness ratio of the adhesive layer to the positive electrode active material layer is controlled to be 1:(10~100). By setting the adhesive layer and limiting the thickness ratio of the adhesive layer, the present invention effectively controls the adhesion and peeling force between the adhesive layer and the positive electrode active material layer. When the positive electrode sheet of the present invention is assembled with the separator, the adhesion between the adhesive layer and the separator is strong, which can avoid energy loss caused by the shedding of the positive electrode active material.

[0009] (2) The positive electrode sheet of the present invention has a protective layer on the surface of the adhesive layer away from the positive electrode active material layer. The protective layer facilitates the long-term storage of the positive electrode sheet and the classification and control of temperature and humidity. By setting a peelable protective layer, the present invention allows the remaining current collector and coating structure to be peeled off during battery assembly, and then assembled with the separator, negative electrode sheet and other battery components. The operation is simple and easy to operate.

[0010] (2) The positive electrode preparation method of the present invention uses a transfer printing method to prepare the positive electrode, which can improve the coating process defects, effectively avoid the generation of poor cell coating, and can replace the coating process to a certain extent. It only requires attention to the temperature and position of the bare cell during the winding and heat transfer process, and no more production space is needed. Since the transfer printing technology has a certain plasticity, the method of the present invention can prepare irregularly shaped cells with different morphologies.

[0011] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0012] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0013] Figure 1 The diagram shown is a preferred embodiment of the positive electrode sheet of the present invention.

[0014] Explanation of reference numerals in the attached figures 1. Protective layer 2. Adhesive layer 3. Positive electrode active material layer 4. Primer layer 5. Current collector Detailed Implementation This invention discloses a positive electrode sheet, its preparation method, and a battery. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments. Those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0015] In the description of this invention, the list of items connected by the term "at least one of" or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0016] The endpoints and any values ​​of the ranges 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 endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0017] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0018] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0019] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0020] To address the problems of uneven slurry coating, orange peel, and linear defects that easily occur in the coating and production processes of positive electrode cells in existing technologies, the present invention adopts the following technical solution: A first aspect of the present invention provides a positive electrode sheet, the positive electrode sheet comprising a current collector, a positive electrode active material layer disposed on at least one side of the current collector along the thickness direction, and an adhesive layer disposed on the surface of the positive electrode active material layer away from the current collector; The adhesive layer includes an adhesive; the thickness ratio of the adhesive layer to the positive electrode active material layer is 1:(10~100).

[0021] The positive electrode sheet of the present invention has an adhesive layer disposed on the surface of the positive electrode active material layer, and the thickness ratio of the adhesive layer to the positive electrode active material layer is controlled to be 1:(10~100). By setting the adhesive layer and limiting the thickness ratio of the adhesive layer, the present invention effectively controls the adhesion and peeling force between the adhesive layer and the positive electrode active material layer. When the positive electrode sheet of the present invention is assembled with the separator after the protective layer is peeled off, the adhesion between the adhesive layer and the separator is strong, which can avoid energy loss caused by the shedding of positive electrode active material.

[0022] In some embodiments of the present invention, the roughness of the side of the adhesive layer away from the positive electrode active material layer is 0.6 μm to 3 μm. Exemplarily, the roughness of the side of the adhesive layer away from the positive electrode active material layer can be any value selected from 0.6 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, and 3 μm, or any value within the range formed by any pair of the above values. By ensuring that the roughness of the side of the adhesive layer away from the positive electrode active material layer is within the above range, capacity loss caused by material shedding during adhesive layer bonding can be avoided, and it can be ensured that the solid electrolyte can be bonded while the protective film is being peeled off from the adhesive layer.

[0023] In some embodiments of the present invention, the binder is selected from water-based acrylic and / or polyurethane. In a preferred embodiment of the present invention, the binder is selected from water-based acrylic. Water-based acrylic, as a base adhesive, has good high-temperature performance, which can enable the integrated coating to maintain the structure of the positive electrode material during transfer. At the same time, the water-based material has low adhesion in the battery, and the distance between the anode and cathode of the battery is large, which can improve the lithium plating situation at the battery corner.

[0024] In some embodiments of the present invention, in order to ensure the adhesion of the adhesive layer, the content of the adhesive, based on the total weight of the adhesive layer, can range from 50wt% to 75wt%. For example, based on the total weight of the adhesive layer, the content of the adhesive can be any value from 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, and 75wt%, or any value within the range formed by any pair of the above values.

[0025] In this invention, the thickness of the adhesive layer can be 1mm to 5mm; an adhesive layer within the above thickness range can ensure the adhesion between the positive electrode active material and the adhesive layer. For example, the thickness of the adhesive layer can be any value from 1mm, 2mm, 3mm, 4mm, and 5mm, or any value within the range formed by any two of the above values.

[0026] In a preferred embodiment of the present invention, the adhesive layer also contains a lithium replenishing agent. The addition of the lithium replenishing agent to the adhesive layer can effectively replenish lithium ions, improve the initial efficiency of the positive electrode, and at the same time, it does not hinder the specific capacity of the positive electrode active material and the formation of the CEI film.

[0027] According to a first aspect of the invention, the content of the lithium replenishing agent, based on the total weight of the adhesive layer, can range from 0.6 wt% to 3 wt%. Exemplarily, based on the total weight of the adhesive layer, the content of the lithium replenishing agent can range from any value among 0.6 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, and 3 wt%, or any value within a range formed by any pair of the above values. By keeping the content of the lithium replenishing agent within the above range, unavoidable lithium loss during manufacturing and use can be compensated, thereby significantly improving the energy density and cycle life of the battery.

[0028] In this invention, the Dv50 of the lithium replenishing agent particles can be 4.5μm to 12μm; for example, the Dv50 of the lithium replenishing agent particles can be any value among 4.5μm, 6μm, 8μm, 10μm and 12μm or any value within the range of any two of the above values.

[0029] The lithium replenishing agent in this invention can be a lithium-rich oxide, a lithium-rich nanocomposite material, a binary lithium compound, or an organic lithium replenishing agent. For example, the lithium replenishing agent is selected from at least one of Li₂NiO₂, Li₅FeO₄, Li₂O₂, and Li₂C₄O₄.

[0030] In some embodiments of the present invention, the thickness of the positive electrode active material layer can be 40mm to 80mm. Exemplarily, the thickness of the positive electrode active material layer can be any value selected from 40mm, 50mm, 60mm, 70mm, and 80mm, or any value within the range formed by any pair of the aforementioned values.

[0031] In some embodiments of the present invention, the positive electrode active material layer includes a positive electrode active material; the positive electrode active material is selected from at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium manganese iron phosphate, and lithium iron phosphate.

[0032] In some embodiments of the present invention, the positive electrode sheet further includes a protective layer disposed on the surface of the adhesive layer away from the positive electrode active material layer; wherein the protective layer is peelable. The positive electrode sheet of the present invention has a protective layer disposed on the surface of the adhesive layer away from the positive electrode active material layer, which facilitates long-term storage and classified control of temperature and humidity of the positive electrode sheet. By providing a peelable protective layer, the present invention allows for the removal of the protective layer during battery assembly, enabling the remaining current collector and coating structure to be assembled with the separator, negative electrode sheet, and other battery components, making the operation simple and easy to perform.

[0033] In some embodiments of the present invention, the peel force between the adhesive layer and the protective layer is 5 g / cm to 18 g / cm. Exemplarily, the peel force between the adhesive layer and the protective layer can be any value selected from 5 g / cm, 8 g / cm, 10 g / cm, 14 g / cm, and 18 g / cm, or any value within the range formed by any pair of the above values. By ensuring that the peel force between the adhesive layer and the protective layer is within the above range, effective composite strength between the adhesive layer and the protective layer can be guaranteed during the production process, and effective peeling can be achieved after heating under certain conditions.

[0034] In a specific embodiment of the present invention, the protective layer in the positive electrode sheet can be peeled off, and the positive electrode sheet after the protective layer has been removed can be assembled. That is, the outermost layer of the positive electrode sheet is an adhesive layer, and after assembly, the adhesive layer is close to the battery separator. In this embodiment, if the peeling force between the adhesive layer and the battery separator is too large, it may cause the microporous structure to be severely compressed or even closed, blocking the lithium-ion transport channels; if the peeling force between the adhesive layer and the battery separator is too small, it may increase the internal resistance and result in insufficient ion transport particle size, thereby affecting the rate performance and cycle performance of the battery. In some embodiments of the present invention, the peeling force between the adhesive layer and the battery separator is 10 g / cm to 20 g / cm. Exemplarily, the peeling force between the adhesive layer and the battery separator can be any value among 10 g / cm, 12 g / cm, 14 g / cm, 16 g / cm, 18 g / cm, and 20 g / cm, or any value within the range of any two of the above values.

[0035] In some embodiments of the present invention, the protective layer of the present invention employs a reusable release film, the material of which is selected from at least one of polyethylene, polyethylene terephthalate, and polypropylene.

[0036] like Figure 1 As shown, in some preferred embodiments of the present invention, a primer layer is further disposed between the current collector and the positive electrode active material layer. The combination of the primer layer and the primer layer ensures that the coating structure can be smoothly transferred to the aluminum foil surface at a certain temperature, and also increases the safety performance and improves the high-temperature performance of the battery cell. The coating structure of the present invention does not require separate coating on the aluminum foil surface, greatly reducing coating costs.

[0037] In some embodiments, the thickness of the primer coating ranges from 1 mm to 5 mm. Exemplarily, the thickness of the primer coating can be any value among 1 mm, 2 mm, 3 mm, 4 mm, and 5 mm, or any value within a range formed by any two of the above values. By ensuring the thickness of the primer coating is within the above range, it is possible to guarantee a continuous coating without delamination when the primer coating is combined with the current collector, thereby forming a complete conductive network and isolating the aluminum foil from the corrosion of the electrolyte.

[0038] In some embodiments, the peel force between the primer adhesive layer and the current collector is 5 g / cm to 70 g / cm. Exemplarily, the peel force between the primer adhesive layer and the current collector can be any value selected from 5 g / cm, 15 g / cm, 30 g / cm, 50 g / cm, and 70 g / cm, or any value within a range formed by any two of these values. By ensuring that the peel force between the primer adhesive layer and the current collector is within the above range, it is possible to prevent the primer adhesive layer from detaching from the surface of the current collector while reducing the internal resistance of the electrode.

[0039] In some preferred embodiments, the primer layer includes a carbon material, such as carbon powder. The addition of carbon material to the primer layer in this invention ensures the peel strength between the primer layer and the current collector (e.g., aluminum foil) and the smoothness of the primer layer surface.

[0040] A second aspect of the present invention provides a method for preparing a positive electrode sheet, the method comprising: A first composite layer is obtained by depositing an adhesive layer on the surface of a protective layer, and a second composite layer is obtained by depositing a positive electrode active material layer on the surface of the first composite layer, wherein the positive electrode active material layer is disposed on the side of the adhesive layer away from the protective layer; the second composite layer is wound up to prepare a positive electrode transfer adhesive paper. The positive electrode transfer adhesive paper is thermally transferred to the surface of the current collector, and during the transfer process, the positive electrode active material layer is close to the surface of the current collector; The protective layer is peelable.

[0041] The positive electrode preparation method of this invention uses a transfer printing process to prepare the positive electrode, which can improve the coating process defects, effectively avoid the occurrence of poor cell coating, and can replace the coating process to a certain extent. It only requires attention to the temperature and position of the bare cell during the winding and heat transfer process, eliminating the need for additional production space. Because the transfer printing technology has a certain degree of plasticity, the method of this invention can prepare irregularly shaped cells with various morphologies.

[0042] In some embodiments, the present invention can improve the efficiency of bare cell preparation by modifying the winding machine to perform hot pressing transfer on the aluminum foil at the unwinding point.

[0043] In some embodiments of the present invention, the preparation method further includes: depositing a base coating layer on the surface of the second composite layer to obtain a third composite layer, and winding the third composite layer to prepare a positive electrode transfer paper; wherein the base coating layer is disposed on the side surface of the positive electrode active material layer away from the protective layer.

[0044] In some embodiments of the present invention, the method for preparing the positive electrode sheet may include the following specific steps: S1. Mix the adhesive, initiator, lithium supplementer and first conductive agent evenly to obtain an adhesive slurry; apply the adhesive slurry to the surface of the protective layer, and after standing, obtain a protective layer with an adhesive layer on the surface.

[0045] S2. Prepare a slurry containing positive electrode active material; spray the slurry containing positive electrode active material onto the surface of a protective layer with an adhesive layer by plasma spraying and then dry it to obtain a layer with an adhesive layer and a positive electrode active material layer on the surface.

[0046] S3. Prepare the base coating slurry; apply the base coating slurry to the surface on which the adhesive layer and the positive electrode active material layer are provided, and then wind it into the finished transfer positive electrode adhesive paper; S4. When winding the finished positive electrode transfer paper, heat it to a certain temperature and use a heat transfer method to transfer the coating on the finished positive electrode transfer paper onto the aluminum foil, and then wind it.

[0047] In step S1, as an example, the binder can be water-based acrylic acid, and the binder can be selected as a mixture obtained by mixing acrylic acid polymer monomers and acrylic acid, wherein the acrylic acid polymer monomers can be at least one of 2-ethylbutyl acrylate, butyl acrylate, and methyl methacrylate. As an example, the initiator can be azobisisobutyronitrile. As an example, the lithium supplement can be at least one of Li2NiO2, Li5FeO4, Li2O2, and Li2C4O4. As an example, the first conductive agent can be conductive carbon black. As an example, the protective layer is a release film. The mass ratio of the acrylic acid polymer monomers, initiator, lithium supplement, and first conductive agent can be (50~75):(0.2~0.7):(0.6~3):(0.2~1.5); the solid content of the adhesive slurry can be 30wt%~45wt%; the coating thickness of the adhesive slurry can be 0.8mm~4mm; and the standing time can be 1h~4h.

[0048] In step S2, as an example, the slurry containing the positive electrode active material may contain the positive electrode active material, the positive electrode conductive agent, the positive electrode binder, the positive electrode dispersant, and a solvent. The mass ratio of the positive electrode active material, the positive electrode conductive agent, the positive electrode binder, and the positive electrode dispersant can be (94~97):(1~2.5):(1~2.5):(1~2); the solid content of the slurry containing the positive electrode active material can be 40wt%~80wt%; the coating thickness can be 40mm~80mm; the drying process can be carried out in an oven at a temperature of 50℃~120℃ for 1min~10min. Preferably, the positive electrode active material layer is formed by plasma spraying. Plasma spraying can make the substrate surface wear-resistant, corrosion-resistant, and resistant to high-temperature oxidation. Using a plasma arc driven by DC electricity as a heat source, the material is heated to a molten or semi-molten state and sprayed at high speed onto the pre-treated workpiece surface to form a firmly adhered surface layer. This method can achieve a micron-level coating and improve the surface structure of the battery cell.

[0049] In step S3, as an example, the primer slurry may contain toner, a first binder, a second conductive agent, and a solvent. The mass ratio of the toner, the first binder, and the second conductive agent is (80~90):(4~7):(3~16). As an example, the solid content of the primer slurry is 95.5wt%~98.2wt%; the thickness of the primer layer is 1mm~5mm.

[0050] In step S4, as an example, the temperature for heat transfer is 40℃~120℃.

[0051] A third aspect of the present invention provides a battery comprising a positive electrode; the positive electrode comprising the above-described positive electrode and / or a positive electrode prepared according to the above-described preparation method.

[0052] In this embodiment of the invention, the battery can be an all-solid-state battery or a semi-solid-state battery. Optionally, the solid-state battery or semi-solid-state battery of the present invention includes the provided positive electrode sheet as a cell. In addition, the solid-state battery or semi-solid-state battery may also include other structures known in the art, such as a casing, and there is no limitation thereto.

[0053] The following describes embodiments of the present invention. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the field or according to the product instructions. Reagents, materials, or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0054] The release film used in the examples and comparative examples is made of polyethylene (PE); the conductive agent is multi-walled carbon nanotubes; the positive electrode binder is polyvinylidene fluoride (PVDF); the positive electrode dispersant is polyvinylpyrrolidone (PVP); and the protective layer is a release film, specifically made of polyethylene.

[0055] Example 1-a (1) Preparation of adhesive layer The adhesive layer in this embodiment is a lithium-replenishing adhesive layer, and the adhesive of the lithium-replenishing adhesive layer is a water-based acrylate. The preparation method of the water-based acrylate used in this embodiment is as follows: 2-ethylbutyl acrylate, butyl acrylate, methyl methacrylate and acrylic acid are mixed in a mass ratio of 15:70:11:4.

[0056] The prepared binder, azobisisobutyronitrile, Li₂NiO₂, and conductive carbon black were mixed evenly at a mass ratio of 68:0.4:1.8:1 and dispersed using a pulping machine to prepare a slurry with a solid content of 40%. Then, a coating method was used to apply the slurry to the surface of the protective layer to a thickness of 1.2 mm. After standing at room temperature for 1.5 hours, a protective layer with an adhesive layer on its surface was obtained.

[0057] (2) Preparation of the positive electrode active material layer Lithium cobalt oxide, conductive agent, positive electrode binder, and positive electrode dispersant were added to a beaker at a mass ratio of 96:0.7:1.8:1.5 and stirred until homogeneous. NMP (N-methylpyrrolidone) solution was then added to prepare a slurry with a solid content of 60%. The slurry was stirred until it became translucent and then stored in a container for later use. The positive electrode active material slurry was then sprayed onto the surface of the protective layer with the adhesive layer prepared in step (1) using plasma spraying. The spraying thickness was 78 mm, and the layer was baked in an oven at 80°C for 6 minutes to obtain a protective layer with both an adhesive layer and a positive electrode active material layer. In this embodiment, the thickness ratio of the adhesive layer to the positive electrode active material layer was 1:65.

[0058] (3) Preparation of the primer adhesive layer slurry Carbon powder, PVDF resin and conductive agent were added to a beaker in a mass ratio of 86:5:3 and stirred. NMP (N-methylpyrrolidone) solution was added to obtain a slurry with a solid content of 68%. After it became viscous, it was prepared as a base coat adhesive slurry. The base coat adhesive slurry was then coated on the surface of step (2) with a coating thickness of 1.2 mm and wound into a finished transfer positive electrode adhesive paper.

[0059] (4) Transfer When the finished positive electrode transfer paper is wound, it is heated to 85°C and the coating on the finished positive electrode transfer paper is transferred to the aluminum foil using a heat transfer method, and then wound.

[0060] Example 1-b The preparation method of the adhesive layer in this embodiment is the same as that in Example 1-a, except that the adhesive slurry is coated with a thickness of 1 mm on the surface of the protective layer.

[0061] The preparation method of the positive electrode active material layer in this embodiment is the same as that in Example 1-a, except that the coating thickness is 80 mm.

[0062] The preparation method of the primer adhesive layer slurry and the transfer method in this embodiment are the same as in Embodiment 1.

[0063] Example 1-c In this embodiment, the preparation method of the adhesive layer is the same as in Example 1-a, except that the adhesive slurry is coated with a thickness of 1 mm on the surface of the protective layer.

[0064] The preparation method of the positive electrode active material layer in this embodiment is the same as that in Example 1-a, except that the coating thickness is 100 mm.

[0065] The preparation method of the primer adhesive layer slurry and the transfer method in this embodiment are the same as in Embodiment 1.

[0066] Example 1-d The preparation method of the adhesive layer in this embodiment is the same as that in Example 1-a, except that the adhesive slurry is coated on the surface of the protective layer with a thickness of 1.2 mm.

[0067] The preparation method of the positive electrode active material layer in this embodiment is the same as that in Example 1-a, except that the coating thickness is 12 mm.

[0068] The preparation method of the primer adhesive layer slurry and the transfer method in this embodiment are the same as in Embodiment 1.

[0069] Comparative Example 1 The preparation method of the adhesive layer in this comparative example is the same as that in Example 1-a, except that the adhesive slurry is coated on the surface of the protective layer with a thickness of 0.7 mm.

[0070] In this comparative example, the preparation method of the primer layer slurry and the transfer method are the same as in Example 1.

[0071] Comparative Example 2 The preparation method of the adhesive layer in this comparative example is the same as that in Example 1-a, except that the adhesive slurry is coated with an 8mm thickness on the surface of the protective layer.

[0072] In this comparative example, the preparation method of the primer layer slurry and the transfer method are the same as in Example 1.

[0073] The roughness (abbreviated as roughness) of the adhesive layer near the protective layer in Examples 1-a to 1-d and Comparative Examples 1 to 2; the peel force between the adhesive layer and the protective layer (abbreviated as peel force 1); the peel force between the adhesive layer and the battery separator after removing the protective layer (abbreviated as peel force 2); and the peel force between the base coating adhesive layer and the aluminum foil (abbreviated as peel force 3) were tested. The test results are shown in Table 1.

[0074] The roughness test method is optical sectioning, and the specific steps include: after the electrode is prepared, take the composite direction of the electrode and use a 45º beam to irradiate the surface of the electrode for testing.

[0075] The peel strength test method is the tape tensile test method. The specific steps include: taking a 10mm long and 25mm wide area of ​​the prepared electrode sheet, and testing the peel strength using Method 1 in GB / T2792-2014 "Test Method for Peel Strength of Adhesive Tapes".

[0076] Table 1 It should be noted that in the test, the adhesive layer of Examples 1-a to 1-d and Comparative Example 1 was easy to peel off from the protective layer, while the adhesive layer of Comparative Example 2 was relatively difficult to peel off from the surface of the protective layer; the base coating adhesive layer of Examples 1-a to 1-d adhered well to the aluminum foil, and there was no obvious material falling off the surface after peeling.

[0077] Example 2 (1) Preparation of adhesive layer The adhesive layer in this embodiment is a lithium-replenishing adhesive layer, and the adhesive of the lithium-replenishing adhesive layer is a water-based acrylate. The preparation method of the water-based acrylate used in this embodiment is as follows: 2-ethylbutyl acrylate, butyl acrylate, methyl methacrylate and acrylic acid are mixed in a mass ratio of 10:85:3:5.

[0078] The prepared binder, azobisisobutyronitrile, Li₂NiO₂, and conductive carbon black were mixed evenly at a mass ratio of 50:0.7:0.6:1.5 and dispersed using a pulping machine to prepare a slurry with a solid content of 30%. Then, a coating method was used to apply the slurry to the surface of the protective layer to a thickness of 4 mm. After standing at room temperature for 1.5 hours, a protective layer with an adhesive layer on its surface was obtained.

[0079] (2) Preparation of the positive electrode active material layer Lithium cobalt oxide, conductive agent, binder, and dispersant were added to a beaker at a mass ratio of 97:1:2.5:1 and stirred until homogeneous. NMP solution was then added to prepare a slurry with a solid content of 40%. The slurry was stirred until it became translucent and then stored in a container for later use. The positive electrode active material slurry was then sprayed onto the surface of the protective layer with the adhesive layer prepared in step (1) using plasma spraying. The spraying thickness was 40 mm, and the surface was baked in an oven at 120°C for 1 min to obtain a protective layer with an adhesive layer and a positive electrode active material layer. In this embodiment, the thickness ratio of the adhesive layer to the positive electrode active material layer was 1:10.

[0080] (3) Preparation of the primer adhesive layer slurry Carbon powder, PVDF resin and conductive agent are added to a beaker at a mass ratio of 90:4:4 and stirred. NMP solution is added to obtain a slurry with a solid content of 40%. After it becomes viscous, it is prepared as a base coat adhesive slurry. The base coat adhesive slurry is then coated on the surface of step (2) with a coating thickness of 5 mm and wound into a finished transfer positive electrode adhesive paper.

[0081] (4) Transfer When the finished positive electrode transfer paper is wound, it is heated to 40°C and the coating on the finished positive electrode transfer paper is transferred to the aluminum foil using a heat transfer method, and then wound.

[0082] Example 3 (1) Preparation of adhesive layer The preparation method of the adhesive layer in this embodiment is generally the same as in Example 1, except that the binder of the lithium-supplementing adhesive layer is a water-based acrylate. The preparation method of the water-based acrylate used in this embodiment is as follows: 2-ethylbutyl acrylate, butyl acrylate, methyl methacrylate, and acrylic acid are mixed in a mass ratio of 30:65:15:3 to obtain a mixture; the mixture, azobisisobutyronitrile, Li2NiO2, and conductive carbon black are mixed evenly in a mass ratio of 75:0.2:3:0.2, dispersed using a pulping machine, and prepared into an adhesive slurry with a solid content of 45%. Subsequently, a coating method is used to coat the adhesive slurry onto the release film surface with a thickness of 0.8 mm. After standing at room temperature for 4 hours, a protective layer with an adhesive layer on the surface is obtained.

[0083] (2) Preparation of the positive electrode active material layer Lithium cobalt oxide, conductive agent, positive electrode binder, and positive electrode dispersant were added to a beaker at a mass ratio of 94:2.5:1:2 and stirred until homogeneous. NMP solution was then added to prepare a slurry with a solid content of 50%. The slurry was stirred until it became translucent and then stored in a container for later use. The positive electrode active material slurry was then sprayed onto the surface of the protective layer with the adhesive layer prepared in step (1) using plasma spraying. The spraying thickness was 80 mm, and the layer was baked in an oven at 50°C for 10 minutes to obtain a protective layer with both an adhesive layer and a positive electrode active material layer. In this embodiment, the thickness ratio of the adhesive layer to the positive electrode active material layer was 1:100.

[0084] (3) Preparation of the primer adhesive layer slurry Carbon powder, PVDF resin and conductive agent are added to a beaker at a mass ratio of 80:7:1 and stirred. NMP solution is added to obtain a slurry with a solid content of 80%. After it becomes viscous, it is prepared as a base coat adhesive slurry. The base coat adhesive slurry is then coated on the surface of step (2) with a coating thickness of 1.2 mm and wound into a finished transfer positive electrode adhesive paper.

[0085] (4) Transfer When the finished positive electrode transfer paper is wound, it is heated to 120°C and the coating on the finished positive electrode transfer paper is transferred to the aluminum foil using a heat transfer method, and then wound.

[0086] Example 4 The preparation method of the adhesive layer in this embodiment is the same as that in Example 1, except that the adhesive for the lithium-supplemented adhesive layer is polyester ammonia. The preparation method of the polyester ammonia used in this embodiment is as follows: polyester polyurethane prepolymer (CAS: 103837-45-2), hydrogenated terpene phenolic resin (CAS: 1254557-84-0), polyisocyanate trimer (CAS: 28182-81-2), and silane coupling agent (CAS: 919-30-2) are mixed in a mass ratio of 15:70:11:4.

[0087] The preparation methods of the positive electrode active material layer, the preparation methods of the primer adhesive layer slurry, and the transfer method in this embodiment are the same as in Example 1.

[0088] Example 5 The preparation methods of the adhesive layer and the positive electrode active material layer in this embodiment are the same as in Example 1.

[0089] The preparation of the primer adhesive layer slurry in this embodiment includes: Alumina, PVDF resin and conductive agent were added to a beaker in a mass ratio of 86:5:3 and stirred. NMP solution was added to obtain a slurry with a solid content of 68%. After it became viscous, it was prepared as a base coat adhesive slurry. The base coat adhesive slurry was then coated on the surface of step (2) with a coating thickness of 1.2 mm and wound into a finished transfer positive electrode adhesive paper.

[0090] The transfer method in this embodiment is the same as in Embodiment 1.

[0091] Example 6 The preparation methods of the adhesive layer and the positive electrode active material layer in this embodiment are the same as in Example 1.

[0092] This embodiment does not involve the preparation of the base coating slurry. The protective layer with the adhesive layer and the positive electrode active material layer on the surface is wound into a finished positive electrode transfer paper. When the finished positive electrode transfer paper is wound, it is heated to 85°C and the coating on the finished positive electrode transfer paper is transferred to the aluminum foil by heat transfer method, and then wound.

[0093] The roughness (abbreviated as roughness) of the adhesive layer near the protective layer in Examples 2 to 6; the peel force between the adhesive layer and the protective layer (abbreviated as peel force 1); the peel force between the adhesive layer and the battery separator after removing the protective layer (abbreviated as peel force 2); and the peel force between the base coating adhesive layer and the aluminum foil (abbreviated as peel force 3) were tested. The test results are shown in Table 2.

[0094] Table 2 It should be noted that in the test, in Example 2, the bonding between the adhesive layer and the protective layer was difficult, the adhesion between the base adhesive layer and the aluminum foil was poor, and it was easy to peel off, but bonding the aluminum foil was difficult; in Example 3, the bonding between the adhesive layer and the protective layer was difficult, and the adhesion between the base adhesive layer and the aluminum foil was good; in Example 4, the adhesive layer was easy to peel off from the protective layer, the adhesion between the base adhesive layer and the aluminum foil was good, and there was no obvious material loss on the surface after peeling off; in Example 5, the adhesive layer was easy to peel off from the protective layer, and there was easy material loss between the base adhesive layer and the aluminum foil, resulting in an uneven surface; in Example 6, the adhesive layer was easy to peel off from the protective layer, but due to the lack of a base adhesive coating, the coating on the finished positive electrode transfer paper could not be transferred to the aluminum foil.

[0095] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0096] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0097] In the above description of the present invention, the reference to terms such as "one embodiment," "another embodiment," etc., indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate different embodiments or examples and features of different embodiments or examples described in the present invention without contradiction. Additionally, it should be noted that in the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A positive electrode plate, characterized in that, The positive electrode sheet includes a current collector, a positive active material layer disposed on at least one side of the current collector along the thickness direction, and an adhesive layer disposed on the surface of the positive active material layer away from the current collector. The adhesive layer includes an adhesive; the thickness ratio of the adhesive layer to the positive electrode active material layer is 1:(10~100).

2. The positive electrode sheet according to claim 1, characterized in that, The roughness of the adhesive layer on the side away from the positive electrode active material layer is 0.6 μm to 3 μm.

3. The positive electrode sheet according to claim 1, characterized in that, The peel force between the adhesive layer and the battery separator is 10 g / cm to 20 g / cm.

4. The positive electrode sheet according to claim 1, characterized in that, The adhesive is selected from water-based acrylic and / or polyurethane.

5. The positive electrode sheet according to claim 1, characterized in that, Based on the total weight of the adhesive layer, the content of the adhesive ranges from 50 wt% to 75 wt%.

6. The positive electrode sheet according to claim 1, characterized in that, The thickness of the adhesive layer is 1 mm to 5 mm.

7. The positive electrode sheet according to claim 1, characterized in that, The adhesive layer also contains a lithium supplement.

8. The positive electrode sheet according to claim 7, characterized in that, Based on the total weight of the adhesive layer, the content of the lithium supplement agent ranges from 0.6 wt% to 3 wt%; and / or, The lithium replenishing agent has a Dv50 of 4.5 μm to 12 μm.

9. The positive electrode sheet according to claim 7, characterized in that, The lithium supplement is selected from at least one of Li2NiO2, Li5FeO4, Li2O2 and Li2C4O4.

10. The positive electrode sheet according to claim 1, characterized in that, The thickness of the positive electrode active material layer is 40 mm to 80 mm.

11. The positive electrode sheet according to claim 1, characterized in that, The positive electrode active material layer includes a positive electrode active material; the positive electrode active material is selected from at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium manganese iron phosphate, and lithium iron phosphate.

12. The positive electrode sheet according to claim 1, characterized in that, The positive electrode sheet further includes a protective layer disposed on the surface of the adhesive layer away from the positive electrode active material layer; wherein the protective layer is peelable.

13. The positive electrode sheet according to claim 1, characterized in that, The peel force between the adhesive layer and the protective layer is 5 g / cm to 18 g / cm.

14. The positive electrode sheet according to claim 12, characterized in that, The material of the protective layer is selected from at least one of polyethylene, polyethylene terephthalate, and polypropylene.

15. The positive electrode sheet according to claim 1, characterized in that, An undercoat layer is also provided between the current collector and the positive electrode active material layer.

16. The positive electrode sheet according to claim 15, characterized in that, The thickness of the base coating is in the range of 1 mm to 5 mm; and / or, The peel force between the primer layer and the current collector is 5 g / cm to 70 g / cm.

17. The positive electrode sheet according to claim 15, characterized in that, The base coat contains carbon materials.

18. A method for preparing a positive electrode, characterized in that, The preparation method includes: A first composite layer is obtained by depositing an adhesive layer on the surface of a protective layer, and a second composite layer is obtained by depositing a positive electrode active material layer on the surface of the first composite layer, wherein the positive electrode active material layer is disposed on the side of the adhesive layer away from the protective layer; the second composite layer is wound up to prepare a positive electrode transfer adhesive paper. The positive electrode transfer adhesive paper is thermally transferred to the surface of the current collector, and during the transfer process, the positive electrode active material layer is close to the surface of the current collector; The protective layer is peelable.

19. The preparation method according to claim 18, characterized in that, The preparation method further includes: depositing a base coating layer on the surface of the second composite layer to obtain a third composite layer, and winding the third composite layer to prepare a positive electrode transfer paper; The base coating layer is disposed on the surface of the positive electrode active material layer away from the protective layer.

20. A battery, characterized in that, The battery includes a positive electrode sheet; the positive electrode sheet includes the positive electrode sheet according to any one of claims 1 to 17 and / or the positive electrode sheet prepared by the preparation method according to claim 18 or 19.

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