Binder, positive electrode slurry, positive plate and battery

Abstract

The invention relates to a binder, positive electrode slurry, a positive plate and a battery. The adhesive comprises a first acrylic copolymer and a second acrylic copolymer, the structural formulas of the first acrylic copolymer and the second acrylic copolymer are respectively shown in a formula (1) and a formula (2), a and b are the polymerization degree of the first acrylic copolymer, c and d are the polymerization degree of the second acrylic copolymer, R1 is selected from C1-C10 alkyl, R2 is selected from-Li,-Na or-K, and R3 is selected from amido, cyano or alkyl. The binder provided by the invention has excellent processability and electrochemical performance, can effectively solve the process problems of difficult dispersion of lithium iron phosphate particles in the current aqueous positive electrode slurry, easy jelly of the positive electrode slurry, dry crack of coating and the like, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, and in particular to an adhesive, a positive electrode slurry, a positive electrode sheet, and a battery. Background Technology

[0002] Rechargeable batteries have excellent properties such as long life, high energy density and low self-discharge, and have gained great commercial application value in recent years, especially in the field of energy storage. Combined with functions such as photovoltaic power generation and grid regulation, rechargeable batteries will continue to be vigorously promoted and used in the future.

[0003] As one of the electrode materials in secondary batteries, binders have a significant impact on electrode processing performance, battery cycle life, rate capability, and capacity. Currently, acrylic binders are the most common type. Summary of the Invention

[0004] However, existing acrylic adhesives, due to the presence of numerous carboxyl functional groups in their molecular chains, are prone to water absorption, and excessive hydrogen bonds between carboxyl groups affect the material's flexibility, making processing difficult. Furthermore, existing lithium iron phosphate particles have a relatively small particle size (D...). 10 Because lithium iron phosphate particles are <0.8μm and have a carbon coating technology on their surface, they have poor affinity and dispersibility with water. As a result, when using existing (water-based) acrylic binders, the cathode slurry is prone to viscous (jelly-like) phenomena, layering, sedimentation, and coating cracking, which are process problems.

[0005] Therefore, there is an urgent need for a binder with excellent processing and electrochemical properties, which can help solve the process problems such as the difficulty in dispersing lithium iron phosphate particles in aqueous cathode slurries, the easy thickening (jelly-like) of cathode slurries, and coating cracking.

[0006] Therefore, it is necessary to address the aforementioned problems by providing a binder, a positive electrode slurry, a positive electrode sheet, and a battery. The binder provided by this invention has excellent processing and electrochemical properties, and can effectively solve the current process problems of difficult dispersion of lithium iron phosphate in aqueous positive electrode slurries, viscous (jelly-like) positive electrode slurries, and coating cracking, and has broad application prospects.

[0007] An adhesive comprising a first acrylic copolymer and a second acrylic copolymer, with structural formulas as shown in formulas (1) and (2), respectively, wherein a and b are the degrees of polymerization of the first acrylic copolymer, c and d are the degrees of polymerization of the second acrylic copolymer, and R1 is selected from C1 to C2. 10 The alkyl group, R2 is selected from -Li, -Na or -K, and R3 is selected from amide, cyano or alkyl.

[0008]

[0009] In one embodiment, the ratio of a to b is (2-3):(1-1.5);

[0010] And / or, the ratio of c to d is (0.5~1):(3~4).

[0011] In one embodiment, the mass ratio of the first acrylic copolymer to the second acrylic copolymer is (1.0-2.0):(1.5-2.5).

[0012] In one embodiment, R1 is selected from C1 to C3 alkyl groups.

[0013] In one embodiment, R3 is selected from -CONH2, -CONHCH3, -CN, -CH2CN, or C5~C. 11 Alkyl groups.

[0014] In one embodiment, the glass transition temperature Tg of the first acrylic copolymer is 70°C to 95°C;

[0015] And / or, the glass transition temperature (Tg) of the second acrylic copolymer is 65°C to 80°C.

[0016] A positive electrode slurry includes a positive electrode active material, a solvent, and a binder as described above.

[0017] In one embodiment, the mass ratio of the positive electrode active material to the binder is (92-95):(2.5-4.5).

[0018] In one embodiment, the positive electrode slurry further includes a conductive agent, and the mass ratio of the positive electrode active material to the conductive agent is (92-95):(0.7-3).

[0019] A positive electrode includes a current collector and a positive electrode material layer disposed on the surface of the current collector, the positive electrode material layer being made from a positive electrode slurry as described above.

[0020] A battery comprising a positive electrode as described above.

[0021] The aforementioned binders, including first acrylic copolymers and second acrylic copolymers with specific structures, achieve the following four performance advantages: First, the numerous carboxyl and hydroxyl groups can crosslink with active materials and foils, thereby achieving excellent bonding performance and effectively preventing material detachment; Second, they can effectively combine with the carbon coating layer of lithium iron phosphate particles, improving the dispersibility and stability of lithium iron phosphate particles in the cathode slurry and reducing problems such as viscosity (jelly-like), stratification, and sedimentation in the cathode slurry; Third, they can increase the flexibility of the binder and adjust its glass transition temperature, thereby reducing the coating cracking problem of the cathode slurry and better withstanding volume changes caused by lithium ion insertion and extraction during battery charge-discharge cycles, achieving excellent processing performance; Fourth, they can improve the bonding effect through electrostatic interaction, enhance the stability of the binder in the electrolyte, and reduce structural damage and poor electron conduction of electrode materials during high-rate charge-discharge processes, thereby improving the battery's rate performance and other properties.

[0022] Therefore, the binder provided by this invention has excellent processing and electrochemical properties, and can effectively solve the current process problems such as the difficulty in dispersing lithium iron phosphate particles in aqueous cathode slurries, the occurrence of viscous (jelly-like) cathode slurries, and coating cracking. It has broad application prospects. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a photograph of the positive electrode sheet obtained by coating the positive electrode slurry according to Example 1 of the present invention.

[0025] Figure 2 This is a graph showing the cycle performance of the battery obtained in Application Example 1 of the present invention at 25°C. Detailed Implementation

[0026] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. The optional scope of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0028] The adhesive provided by this invention comprises a first acrylic copolymer and a second acrylic copolymer, with structural formulas as shown in formulas (1) and (2), respectively, wherein a and b are the degrees of polymerization of the first acrylic copolymer, c and d are the degrees of polymerization of the second acrylic copolymer, and R1 is selected from C1 to C2. 10 The alkyl group, R2 is selected from -Li, -Na or -K, and R3 is selected from amide, cyano or alkyl.

[0029]

[0030] The aforementioned binder, through the synergistic effect of the first acrylic copolymer and the second acrylic copolymer with specific structures, effectively solves the current process problems in aqueous cathode slurry, such as the difficulty in dispersing lithium iron phosphate particles, the viscosity (jelly-like) of the cathode slurry, and the cracking of the coating, thereby improving the processing performance and electrochemical performance of the binder.

[0031] On the one hand, acrylic acid has a large number of carboxyl and hydroxyl groups, which can crosslink with active materials and foils to achieve excellent adhesion performance, effectively prevent material from falling off, and thus improve the processing performance of the adhesive.

[0032] On the other hand, by introducing specific functional groups, through the synergistic effect between the functional groups, firstly, it can effectively combine with the carbon coating layer of lithium iron phosphate particles, improving the dispersibility of lithium iron phosphate particles in the cathode slurry, thereby improving the dispersibility and stability of the cathode slurry and reducing problems such as viscosity (jelly-like), stratification, and sedimentation; secondly, it can increase the flexibility of the binder and adjust the glass transition temperature of the binder, thereby reducing the coating cracking problem of the cathode slurry, and better withstand the volume changes caused by lithium ion insertion and extraction during battery charge and discharge cycles, achieving excellent processing performance; furthermore, it can improve the bonding effect through electrostatic interaction, improve the stability of the binder in the electrolyte, and reduce structural damage and poor electron conduction of electrode materials during high-rate charge and discharge processes, thereby improving the battery's rate performance and other properties.

[0033] Furthermore, the cathode slurry prepared using the above-mentioned binder can improve the slurry's dispersibility and stability while using water as a solvent, effectively reducing battery costs and avoiding the pollution and health problems associated with using N-methylpyrrolidone (NMP) solvent.

[0034] In one embodiment, the ratio of a to b is (2-3):(1-1.5), which is beneficial to further improve the bonding performance and flexibility of the adhesive, thereby further improving the processing performance of the adhesive. The ratio of a to b includes, but is not limited to, any one of 4:3, 5:3, 2:1, 5:2, 8:3, 3:1 or any range between the two.

[0035] In one embodiment, the value of 'a' is selected from 2.5 to 3, which helps to ensure appropriate adhesion of the adhesive.

[0036] In one embodiment, b is selected from 1.3 to 1.5, which helps to ensure a certain degree of flexibility of the adhesive.

[0037] In one embodiment, the ratio of c to d is (0.5-1):(3-4), which is beneficial to further improve the flexibility of the binder, adjust the glass transition temperature of the binder, further improve the bonding effect, improve the stability of the binder in the electrolyte, reduce structural damage and poor electron conduction of the electrode material during high-rate charge and discharge, thereby improving the battery's rate performance, and further improve the bonding effect with the carbon coating layer of lithium iron phosphate particles, improve the dispersibility of lithium iron phosphate particles in the positive electrode slurry, thereby improving the dispersibility and stability of the positive electrode slurry. The ratio of c to d includes, but is not limited to, any one of 1:8, 1:7, 1:6, 1:5, 1:4, 1:3 or any range between two of them.

[0038] In one embodiment, c is selected from 0.5 to 0.8, which is beneficial to improving the rate performance of the battery.

[0039] In one embodiment, d is selected from 3 to 4, which is beneficial to improve the dispersibility of the positive electrode slurry.

[0040] To further improve the flexibility of the binder, adjust the glass transition temperature of the binder, further improve the bonding effect, enhance the processing performance of the binder, and further improve the binding effect between the binder and lithium iron phosphate particles, improve the dispersibility of lithium iron phosphate particles in the cathode slurry, and thus improve the process problems such as the difficulty in dispersing lithium iron phosphate particles in aqueous cathode slurry, the easy occurrence of viscosity (jelly-like) in cathode slurry, and coating cracking, the preferred mass ratio of the first acrylic copolymer to the second acrylic copolymer is (1.0~2.0):(1.5~2.5).

[0041] Understandably, the mass ratio of the first acrylic copolymer to the second acrylic copolymer includes, but is not limited to, any one of the following values: 2:5, 1:2, 2:3, 1:1, 7:6, 4:3, or any range between the two.

[0042] In one embodiment, R1 is preferably a C1 to C3 alkyl group, and the ester group of the first acrylic copolymer can further improve the flexibility of the binder, and better withstand the volume changes caused by lithium ion insertion and deintercalation during battery charge and discharge cycles, thereby further improving the processing performance of the binder.

[0043] It should be noted that, in order to further avoid corrosion of processing equipment, improve the service life of processing equipment, and reduce production costs, R2 is preferably -Li or -Na. Thus, the carboxyl groups in the second acrylic copolymer exist in the form of anions, which effectively improves the problems of strong water absorption and weak flexibility caused by the carboxyl groups in the form of organic matter in the first acrylic copolymer. The second acrylic copolymer can improve the bonding effect through electrostatic interaction, and at the same time help to improve the stability of the binder in the electrolyte. It can reduce the structural damage and poor electronic conduction of electrode materials during high-rate charging and discharging, which is beneficial to improving the battery's rate and other performance characteristics.

[0044] Currently, commercially available lithium iron phosphate (LFP) particles all employ carbon coating technology. However, due to the poor affinity of the carbon coating layer for water and the small particle size of LFP particles (D...),... 10 Because lithium iron phosphate particles are <0.8μm, their dispersion is poor in water-based cathode slurries, leading to viscous (jelly-like) consistency, stratification, and even sedimentation. To further address these issues, this invention employs a binder with a specific molecular structure, wherein R3 is preferably -CONH2, -CONHCH3, -CN, -CH2CN, or C5~C6. 11 The alkyl group can effectively combine with the carbon coating layer of lithium iron phosphate particles, promoting the full dispersion of lithium iron phosphate particles in water and maintaining high stability. This is beneficial to improving the dispersibility and stability of the cathode slurry. At the same time, it is beneficial to adjust the glass transition temperature (Tg) of the binder, thereby reducing the phenomenon of dry cracking of the electrode sheet during cathode slurry coating.

[0045] When the operating temperature is below Tg, the binder is in a glassy state, which is hard and brittle, with high mechanical strength but poor ductility. When the operating temperature is above Tg, the binder becomes soft and elastic, which is beneficial to improving its ability to adapt to the volume changes of the electrode material during charging and discharging.

[0046] Specifically, the glass transition temperature (Tg) of the first acrylic copolymer is 70°C to 95°C.

[0047] Specifically, the glass transition temperature (Tg) of the second acrylic copolymer is 65°C to 80°C.

[0048] Thus, through the synergistic effect of the first acrylic copolymer and the second acrylic copolymer, the binder has excellent flexibility, which can reduce the problem of dry cracking of the electrode sheet during the coating of the positive electrode slurry, and can better withstand the volume changes caused by lithium ion insertion and deintercalation during the battery charge and discharge cycle, thereby achieving excellent processing performance of the binder.

[0049] It should be noted that the present invention does not impose any particular limitations on the preparation methods of the first acrylic copolymer and the second acrylic copolymer, and they can be prepared using existing technologies in the industry, such as bulk polymerization, solution polymerization, suspension polymerization, or emulsion polymerization. Specifically, the monomers of each structural unit and the initiator can be added to a solvent and polymerized under certain temperature conditions. In addition, the first acrylic copolymer and the second acrylic copolymer of the present invention can also be purchased from relevant supplier companies.

[0050] This invention also provides a positive electrode slurry, comprising a positive electrode active material, a solvent, and a binder as described above. The positive electrode slurry exhibits excellent dispersibility and stability, effectively reducing phenomena such as viscosity (jelly-like consistency), layering, sedimentation, and coating cracking, thus improving processing performance and electrochemical performance. Furthermore, the use of water as a solvent reduces production costs, and it offers high safety and environmental friendliness, making it suitable for a wide range of applications.

[0051] Specifically, the positive electrode active material is selected from lithium iron phosphate.

[0052] Specifically, the solvent is selected from water.

[0053] In one embodiment, the mass ratio of the positive electrode active material to the binder is (92-95):(2.5-4.5), which is beneficial to further improve the process problems such as the difficulty in dispersing lithium iron phosphate particles, the easy occurrence of viscous (jelly-like) positive electrode slurry, and coating cracking.

[0054] In one embodiment, the positive electrode slurry further includes a conductive agent.

[0055] It should be noted that the present invention does not impose any special restrictions on the type and amount of the conductive agent, and those skilled in the art can select it according to their needs. For example, in order to improve the electrochemical performance of the battery, the mass ratio of the positive electrode active material to the conductive agent is (92-95):(0.7-3), and the conductive agent is conductive carbon black and multi-walled carbon nanotubes, with a mass ratio of (0.5-2):(0.2-1).

[0056] The present invention also provides a positive electrode sheet, comprising a current collector and a positive electrode material layer disposed on the surface of the current collector, the positive electrode material layer being made from the positive electrode slurry as described above.

[0057] The present invention also provides a battery comprising the positive electrode sheet as described above. The battery has excellent electrochemical performance and can be applied to electronic products, energy storage systems and other electrical devices, with broad application prospects.

[0058] The binder, positive electrode slurry, positive electrode sheet, and battery will be further described below through specific embodiments. However, those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0059] Example 1

[0060] The binder was obtained by mixing 0.15 kg of a first acrylic copolymer with R1 being ethyl (a = 2, b = 1.5, Tg = 85℃) and 0.2 kg of a second acrylic copolymer with R2 being -Li and R3 being -CN (c = 0.5, d = 4, Tg = 75℃). Both the first and second acrylic copolymers were purchased from Wanhua Chemical Group Co., Ltd.

[0061] 9.4 kg of lithium iron phosphate, 0.2 kg of conductive carbon black, 0.05 kg of multi-walled carbon nanotubes and the above binder were mixed and placed in 8 kg of deionized water solvent, and stirred thoroughly for 4 hours to obtain the positive electrode slurry.

[0062] Example 2

[0063] 0.2 kg of a first acrylic copolymer with R1 being propyl (a = 3, b = 1.5, Tg = 83℃) and 0.15 kg of a second acrylic copolymer with R2 being -Li and R3 being -CN (c = 1, d = 3, Tg = 75℃) were mixed to obtain an adhesive. Both the first and second acrylic copolymers were purchased from Wanhua Chemical Group Co., Ltd.

[0064] 9.4 kg of lithium iron phosphate, 0.2 kg of conductive carbon black, 0.05 kg of multi-walled carbon nanotubes and the above binder were mixed and placed in 8 kg of deionized water solvent, and stirred thoroughly for 4 hours to obtain the positive electrode slurry.

[0065] Example 3

[0066] 0.15 kg of a first acrylic copolymer with R1 being ethyl (a = 3, b = 1.5, Tg = 85℃) and 0.2 kg of a second acrylic copolymer with R2 being -Na and R3 being ethyl (c = 0.5, d = 3, Tg = 76℃) were mixed to obtain an adhesive. Both the first and second acrylic copolymers were purchased from Wanhua Chemical Group Co., Ltd.

[0067] 9.4 kg of lithium iron phosphate, 0.2 kg of conductive carbon black, 0.05 kg of multi-walled carbon nanotubes and the above binder were mixed and placed in 8 kg of deionized water solvent, and stirred thoroughly for 4 hours to obtain the positive electrode slurry.

[0068] Example 4

[0069] 0.15 kg of a first acrylic copolymer with R1 being ethyl (a = 2.5, b = 1.5, Tg = 88℃) and 0.2 kg of a second acrylic copolymer with R2 being -Li and R3 being -CN (c = 0.5, d = 3, Tg = 75℃) were mixed to obtain an adhesive. Both the first and second acrylic copolymers were purchased from Wanhua Chemical Group Co., Ltd.

[0070] 9.4 kg of lithium iron phosphate, 0.2 kg of conductive carbon black, 0.05 kg of multi-walled carbon nanotubes and the above binder were mixed and placed in 8 kg of deionized water solvent, and stirred thoroughly for 4 hours to obtain the positive electrode slurry.

[0071] Example 5

[0072] 0.15 kg of R1 contains C 10 An alkyl-based first acrylic copolymer (a = 3, b = 4, Tg = 90℃) and 0.2 kg of a second acrylic copolymer (c = 0.5, d = 3, Tg = 68℃) with R2 = -Na and R3 = -CONH2 were mixed to obtain an adhesive. Both the first and second acrylic copolymers were purchased from Wanhua Chemical Group Co., Ltd.

[0073] 9.4 kg of lithium iron phosphate, 0.2 kg of conductive carbon black, 0.05 kg of multi-walled carbon nanotubes and the above binder were mixed and placed in 8 kg of deionized water solvent, and stirred thoroughly for 4 hours to obtain the positive electrode slurry.

[0074] Comparative Example 1

[0075] The difference between Comparative Example 1 and Example 1 is that 0.35 kg of a first acrylic copolymer with ethyl R1 (a = 3, b = 1.5, Tg = 85°C) was used as the binder.

[0076] Comparative Example 2

[0077] The difference between Comparative Example 2 and Example 1 is that 0.35 kg of a second acrylic copolymer with R2 as -Li and R3 as -CN (c = 0.5, d = 3, Tg = 78°C) was used as the binder.

[0078] Application examples

[0079] (1) Preparation of positive electrode sheet: After defoaming, the positive electrode slurry prepared in all examples and comparative examples is coated, rolled and cut, and then dried to obtain the corresponding positive electrode sheet;

[0080] (2) Preparation of negative electrode sheet: Weigh 9.5 kg of single-particle artificial graphite, 0.2 kg of conductive carbon black, 0.9 kg of styrene-butadiene rubber (SBR) binder and 0.15 kg of thickener sodium carboxymethyl cellulose (CMC-Na), mix them, coat them, roll them, cut them and dry them to obtain the negative electrode sheet.

[0081] (3) Stacking: The positive electrode, negative electrode, and separator are stacked sequentially, and the electrode tabs are welded, inserted into the shell, injected with electrolyte, and sealed. The separator is a porous polyethylene film prepared by wet process, the electrolyte is a lithium hexafluorophosphate solution containing 1 mol / L, the solvent is ethylene carbonate (EC) and ethyl carbonate (EMC) with a mass ratio of EC to EMC of 3:7, and the additives are 2% ethylene carbonate (VC) and 1% fluoroethylene carbonate (FEC).

[0082] (4) Formation and capacity testing: Charge at 0.1C for 5 hours, let stand for 24 hours, evacuate and seal, then charge at 0.2C to 3.65V, and discharge at 0.5C to 2.0V to complete the formation and capacity testing, and obtain the battery.

[0083] The dispersibility of the positive electrode slurry during coating was recorded for all examples and comparative examples. The batteries prepared for all application examples and comparative examples were subjected to cycle tests at 25°C. The test conditions were: 1.5C constant current charging to 3.65V, 3C constant current discharging to 2V, and resting time of 10 minutes. The capacity retention rate after 1200 cycles was recorded. The dispersibility results of the positive electrode slurry and the battery capacity retention rate are shown in Table 1.

[0084] Table 1

[0085] Positive electrode slurry dispersibility Battery capacity retention rate (%) Example 1 good 95.1 Example 2 good 94.9 Example 3 good 95.0 Example 4 good 94.9 Example 5 Dispersed 90.2 Comparative Example 1 Unable to disperse Unable to make batteries Comparative Example 2 Unable to disperse Unable to make batteries

[0086] like Figure 1 As shown, this is the positive electrode sheet obtained after coating the positive electrode slurry in Example 1 of the present invention. It can be seen that the positive electrode slurry after adding the binder of the present invention has good dispersibility, uniform coating, and good processing performance. Combined with the results in Table 1, it can be seen that the positive electrode slurry of all embodiments of the present invention has good dispersibility and relatively uniform coating, which is significantly better than the positive electrode slurry of all comparative examples; as Figure 2The figure shows the cycle performance of the battery in Application Example 1 of this invention at 25°C. It can be seen that the battery retains over 95% of its cycle capacity after 1200 cycles at 25°C, demonstrating excellent cycle performance. Furthermore, combined with the results in Table 1, it can be seen that under the same test conditions, the cycle capacity retention of the batteries in all application examples of this invention is significantly higher than that of the batteries in all application comparison examples. Therefore, the binder provided by this invention has excellent processing and electrochemical properties, effectively solving the current process problems of difficult dispersion of lithium iron phosphate particles in aqueous cathode slurries, easy thickening (jelly-like) of cathode slurries, and coating cracking, effectively improving the cycle performance of the manufactured batteries and showing broad application prospects.

[0087] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0088] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. An adhesive, characterized in that, The adhesive comprises a first acrylic copolymer and a second acrylic copolymer, with structural formulas as shown in formulas (1) and (2), respectively, wherein a and b are the degrees of polymerization of the first acrylic copolymer, c and d are the degrees of polymerization of the second acrylic copolymer, and R1 is selected from C1 to C2. 10 The alkyl group, R2 is selected from -Li, -Na or -K, and R3 is selected from amide, cyano or alkyl.

2. The adhesive according to claim 1, characterized in that, The ratio of a to b is (2-3):(1-1.5); And / or, the ratio of c to d is (0.5~1):(3~4).

3. The adhesive according to claim 1, characterized in that, The mass ratio of the first acrylic copolymer to the second acrylic copolymer is (1.0-2.0):(1.5-2.5).

4. The adhesive according to claim 1, characterized in that, R1 is selected from C1 to C3 alkyl groups.

5. The adhesive according to claim 1, characterized in that, The R3 is selected from -CONH2, -CONHCH3, -CN, -CH2CN, or C5~C 11 Alkyl groups.

6. The adhesive according to claim 1, characterized in that, The glass transition temperature (Tg) of the first acrylic copolymer is 70℃~95℃; And / or, the glass transition temperature (Tg) of the second acrylic copolymer is 65°C to 80°C.

7. A positive electrode slurry, characterized in that, The positive electrode slurry includes a positive electrode active material and a binder as described in any one of claims 1 to 6.

8. The positive electrode slurry according to claim 7, characterized in that, The mass ratio of the positive electrode active material to the binder is (92-95):(2.5-4.5).

9. The positive electrode slurry according to claim 7, characterized in that, The positive electrode slurry also includes a conductive agent, and the mass ratio of the positive electrode active material to the conductive agent is (92-95):(0.7-3).

10. A positive electrode plate, characterized in that, The positive electrode includes a current collector and a positive electrode material layer disposed on the surface of the current collector, the positive electrode material layer being made from the positive electrode slurry as described in any one of claims 7 to 9.

11. A battery, characterized in that, The battery includes the positive electrode as described in claim 10.

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