HNBA-PAA composite positive electrode binder for secondary battery and preparation method and application of HNBA-PAA composite positive electrode binder

Abstract

The invention discloses a hydrogenated butadiene-acrylonitrile rubber (HNBA)-polyacrylic acid (PAA) composite positive electrode binder for a secondary battery as well as a preparation method and application of the hydrogenated butadiene-acrylonitrile rubber-polyacrylic acid composite positive electrode binder. The composite positive electrode binder comprises the following raw materials: HNBA and PAA in a mass ratio of (1-10): (1-10); the content of residual hydrogen bonds in the HNBR is 1-10%, and the content of ACN is 10-40%; the molecular weight of the PAA is 3 * 10 < 5 >-1 * 10 < 6 >. The adhesive is compounded through a solution blending method, and based on the synergistic effect between HNBR and PAA, the viscosity of the material is greatly improved on the premise that it is guaranteed that the adhesive has excellent corrosion resistance. When the binder is used for preparing the positive pole piece of the secondary battery, not only can the bonding strength and the mechanical property among the components of the positive pole be effectively improved, but also the interfacial compatibility of the material can be effectively improved, the ion transmission efficiency can be improved, and the comprehensive performance of the battery can be effectively improved.

Description

Technical Field

[0001] The present invention relates to a cathode binder for batteries, and specifically to a secondary battery HNBA-PAA composite cathode binder, its preparation method and application, belonging to the technical field of battery materials. Background Art

[0002] Lithium-ion batteries have become the main power devices in fields such as portable electronic devices, electric vehicles, and energy storage systems due to their advantages such as high energy density, long cycle life, and no memory effect. However, with the continuous improvement of application requirements, higher demands are put forward for the energy density, power density, and cycle stability of lithium-ion batteries. Although the binder accounts for a small proportion in lithium-ion batteries, it mainly disperses the electrode active material and the conductive agent evenly and connects them with the current collector, preventing the battery short circuit caused by the agglomeration of the active material, improving the safety of the battery, and forming a stable electrode structure. Therefore, it will have a huge impact on the battery performance. The traditional cathode binder, polyvinylidene fluoride (PVDF), although has good chemical stability and bonding performance, its electronic conductivity is poor, and its compatibility with the electrolyte is not good, which limits the further improvement of battery performance.

[0003] In recent years, researchers have been committed to developing new cathode binders to overcome the limitations of traditional binders. Hydrogenated nitrile rubber (HNBR), as a high-performance elastomer, has good mechanical properties, chemical corrosion resistance, and thermal stability. However, there are still many problems in using HNBR as a cathode material binder, mainly including: 1. The production process of HNBR is relatively complex, and precious metal catalysts such as palladium and platinum are required in the production process, resulting in high costs; 2. At present, the mechanical processing performance of HNBR is not good, and it takes a long time to dissolve in the coating process during the preparation of the slurry, making it difficult to achieve continuous production; 3. The adhesiveness of HNBR is poor, and this characteristic makes it extremely easy to generate cracks during long-term cycling, thus seriously reducing the service life of the battery. Therefore, there is an urgent need in the existing market for an HNBR modified composite material to solve the above technical problems while retaining its thermal stability and corrosion resistance, so as to expand the application scenarios of HNBR in the battery field. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the first object of the present invention is to provide a secondary battery HNBA-PAA composite cathode binder. Based on the synergistic effect between HNBR and PAA, this composite cathode binder greatly improves the material elasticity and adhesiveness on the premise of ensuring its excellent corrosion resistance, and uses the carboxyl groups on the surface of PAA to strengthen the ionic conductivity of the material, thereby greatly improving the long-cycle performance of this cathode binder.

[0005] The second object of the present invention is to provide a method for preparing a secondary battery HNBA-PAA composite cathode binder. In this method, HNBR and PAA are subjected to a composite reaction by a one-step solution blending method. The solvent used in this process is the same as the solvent in the cathode slurry. On the one hand, the composite process is greatly simplified, and the determination standard of the composite process is simple and clear. On the other hand, no additional chemical reagents need to be added, effectively avoiding the introduction of other impurities.

[0006] The third object of the present invention is to provide an application of the secondary battery HNBA-PAA composite cathode binder for preparing a secondary battery cathode plate. Based on the excellent properties of the above materials, when used to prepare the secondary battery cathode, it can not only effectively improve the bonding strength and mechanical properties between the components of the cathode, but also effectively improve the interfacial compatibility of the materials, improve the ion transport efficiency, and effectively improve the comprehensive performance of the battery.

[0007] To achieve the above technical objectives, the present invention provides a secondary battery HNBA-PAA composite cathode binder, which is characterized in that: the binder raw materials include HNBA and PAA with a mass ratio of 1~10:1~10; the content of residual hydrogen bonds in the HNBR is 1~10%, and the ACN content is 10~40%; the molecular weight of the PAA is 3×10 5 ~1×10 6 .

[0008] Based on the synergistic effect between HNBR and PAA, the present invention further realizes the synchronous improvement of the adhesiveness and ion transport efficiency of the binder. Among them, HNBR has good chemical stability and mechanical stability, but its solubility is poor. The combination of the two can not only improve the solubility of the binder, but also utilize the abundant carboxyl functional groups on the surface of PAA to form a strong interaction with the cathode material; further, the carboxyl group in PAA is also helpful for the transport of lithium ions, can increase the ionic conductivity, reduce the electrode polarization, and promote the active ions to transfer more smoothly between the electrode and the electrolyte during the charge and discharge process of the battery, improving the charge and discharge efficiency and power performance of the battery.

[0009] As a preferred solution, the binder raw materials include HNBA and PAA with a mass ratio of 1~5:1~5.

[0010] The present invention controls the viscosity and ion transport efficiency of the binder by strictly controlling the mass ratio between HNBA and PAA. It should be noted that the mass ratio of the two needs to be strictly implemented in accordance with the above requirements. When PAA is too low, it cannot improve the viscosity of HNBR, and a large number of cracks will still occur during long cycling. When the content of PAA is too high, although theoretically it can improve the viscosity of the material and provide a large number of carboxyl groups to enhance the ion transport efficiency, in fact, too high PAA will cause the viscosity of the slurry to be too large, making it difficult for the binder to be uniformly mixed with other components, and the carboxyl functional groups in PAA cannot be uniformly covered on the surface of the positive active material, resulting in a decline in the comprehensive performance of the battery.

[0011] The present invention also provides a preparation method of a secondary battery HNBA-PAA composite positive electrode binder. The process is as follows: HNBR is fully dissolved in N-methylpyrrolidone, and then PAA is added under slow stirring for a composite reaction until no solid residue remains, thus obtaining the product.

[0012] The present invention also provides an application of a secondary battery HNBA-PAA composite positive electrode binder for preparing a positive electrode plate of a secondary battery; the secondary battery is at least one of a liquid battery, a semi-solid battery, and a solid battery.

[0013] Based on the excellent viscosity and ion transport efficiency of the above binder, the present invention greatly improves the cycle stability of the secondary battery while effectively improving its rate performance. After testing, for the secondary battery prepared with this composite positive electrode binder, after 500 cycles at a 1C rate, the surface of the electrode is flat and has no cracks. Further, at a 5C rate, the capacity retention rate of the battery is 69%, and at a 10C rate, the capacity retention rate of the battery is 57%.

[0014] As a preferred solution, the raw materials of the secondary battery positive electrode include the following components in parts by mass: 60-80 parts of positive active material, 1-5 parts of HNBA-PAA composite positive electrode binder solution, and 10-20 parts of conductive agent.

[0015] Compared with the traditional PVDF binder, the addition amount of the composite positive electrode binder provided by the present invention is only half of the latter, effectively increasing the addition ratio of the positive active material, and thus effectively improving the energy density of the battery while ensuring the stable combination of each component of the positive electrode.

[0016] As a preferred solution, the solute concentration in the HNBA-PAA composite positive electrode binder solution is 0.5-1%. Further preferably, the solute concentration in the HNBA-PAA composite positive electrode binder solution is 0.75%.

[0017] As a preferred solution, the positive active material is one of lithium salts, sodium salts, and potassium salts.

[0018] As a preferred embodiment, the solvent of the HNBA-PAA composite cathode binder solution is N-methyl-2-pyrrolidone.

[0019] As a preferred embodiment, the conductive agent is acetylene black and / or carbon nanotubes.

[0020] As a preferred embodiment, the secondary battery is a liquid battery.

[0021] As a preferred embodiment, the positive electrode active material is lithium iron phosphate.

[0022] As a preferred embodiment, the conductive agent is acetylene black and carbon nanotubes, and the mass ratio of the two is 1-6:1.

[0023] As a preferred embodiment, the preparation process of the positive electrode of the secondary battery is as follows: after the positive electrode active material and the conductive agent are fully ground and mixed, a positive electrode precursor powder is obtained; the HNBA-PAA composite cathode binder is dissolved in the solvent under heating and stirring, and then the positive electrode precursor powder is added and mixed evenly to obtain a positive electrode paste; the positive electrode paste is evenly coated on an aluminum foil, and is successively dried, heat-treated and cut to obtain the positive electrode.

[0024] As a preferred embodiment, the conditions for heating and stirring are: the temperature is 30-70°C, and the stirring rate is 500-700 r / min.

[0025] As a preferred embodiment, the coating thickness of the positive electrode paste is 10-20 μm.

[0026] As a preferred embodiment, the drying method is vacuum drying, and the conditions are: the temperature is 80-120°C, and the time is 8-12 h.

[0027] As a preferred embodiment, the conditions for heat treatment are: heating in a forced-air drying oven, the temperature is 150-200°C, and the time is 60-120 min. It should be noted that during heat treatment, under the action of O2 in the air, the HNBR molecular chains are intertwined with each other, and further the PAA chelated with it is crosslinked in the intertwined HNBR molecular chains. On the one hand, the stability of the binder can be greatly improved, and its mechanical properties can be improved. On the other hand, the elasticity and adhesiveness of the binder can be improved through the crosslinked PAA, and the generation of gaps and cracks can be avoided.

[0028] Compared with the prior art, the beneficial technical effects of the technical solution of the present invention are:

[0029] 1) The composite cathode binder provided by the present invention is based on the synergistic effect between HNBR and PAA. On the premise of ensuring its excellent corrosion resistance, it greatly improves the elasticity and adhesiveness of the material, and uses the carboxyl groups on the surface of PAA to enhance the ionic conductivity of the material, thereby greatly improving the long-cycle performance of the cathode binder.

[0030] 2) The preparation method provided by the present invention conducts a composite reaction on HNBR and PAA by a one-step solution blending method. The solvent used in this process is the same as the solvent in the cathode slurry. On the one hand, it greatly simplifies the composite process, and the determination criteria for the composite process are simple and clear. On the other hand, there is no need to add other chemical reagents additionally, effectively avoiding the introduction of impurities.

[0031] 3) In the technical solution provided by the present invention, based on the excellent performance of the above composite cathode binder, it is used to prepare the cathode of a secondary battery, which can not only effectively improve the bonding strength and mechanical properties between the components of the cathode, but also effectively improve the interfacial compatibility of the material, improve the ion transport efficiency, and effectively improve the comprehensive performance of the battery. Compared with the PVDF binder, the prepared binder does not contain F elements and is environmentally friendly. Description of the Drawings

[0032] Figure 1 It is the 1C cycle performance graph of the lithium-ion batteries prepared with the binders provided in Comparative Examples 1-4 and Examples 1-5 of the present invention;

[0033] Figure 2 It is the rate performance graph of the lithium-ion batteries prepared with the binders provided in Comparative Examples 1-4 and Examples 1-5 of the present invention;

[0034] Figure 3 It is the pole piece peeling performance graph of the lithium-ion batteries prepared with the binders provided in Comparative Examples 1-4 and Examples 1-5 of the present invention;

[0035] Figure 4 It is the SEM graph of the pole piece of the lithium-ion battery prepared with the binder provided in Comparative Example 1 of the present invention after 500 long cycles at 1C rate;

[0036] Figure 5 It is the SEM graph of the pole piece of the lithium-ion battery prepared with the binder provided in Comparative Example 2 of the present invention after 500 long cycles at 1C rate;

[0037] Figure 6 It is the SEM graph of the pole piece of the lithium-ion battery prepared with the binder provided in Comparative Example 3 of the present invention after 500 long cycles at 1C rate;

[0038] Figure 7 It is the SEM graph of the pole piece of the lithium-ion battery prepared with the binder provided in Comparative Example 4 of the present invention after 500 long cycles at 1C rate;

[0039] Figure 8 The SEM image of the electrode of the lithium-ion battery prepared with the binder provided in Embodiment 1 of the present invention after 500 cycles at 1C rate;

[0040] Figure 9 The SEM image of the electrode of the lithium-ion battery prepared with the binder provided in Embodiment 2 of the present invention after 500 cycles at 1C rate;

[0041] Figure 10 The SEM image of the electrode of the lithium-ion battery prepared with the binder provided in Embodiment 3 of the present invention after 500 cycles at 1C rate;

[0042] Figure 11 The SEM image of the electrode of the lithium-ion battery prepared with the binder provided in Embodiment 4 of the present invention after 500 cycles at 1C rate;

[0043] Figure 12 The SEM image of the electrode of the lithium-ion battery prepared with the binder provided in Embodiment 5 of the present invention after 500 cycles at 1C rate.

[0044] Figure 13 The tensile property diagram of the rubber stick prepared from HNBR, PAA, and PVDF used in the present invention Detailed implementation manners

[0045] The technical solution of the present invention will be further described in detail below in conjunction with specific embodiments and the accompanying drawings. To facilitate the understanding of the present invention, the present invention will be described more comprehensively and in detail below in conjunction with the specification drawings and preferred embodiments. It should be noted that the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0046] In the embodiments of the present invention, those not specified in specific conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. For the reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained by conventional technical means or purchased through the market.

[0047] Embodiment 1

[0048] This embodiment provides a secondary battery HNBA-PAA composite cathode binder, which is composed of HNBA and PAA with a mass ratio of 5:1; the content of residual hydrogen bonds of the HNBR is 1-10%, and the ACN content is 10-40%; the PAA is a solid powder with a molecular weight of 3×10 5 ~1×10 6; The preparation process is as follows: 0.05 g of HNBR is fully dissolved in 5 ml of N-methylpyrrolidone, and then 0.01 g of PAA is added under slow stirring for a composite reaction until no solid residue remains, thus obtaining it;

[0049] The positive electrode sheet of the lithium-ion battery is prepared by using the above binder and consists of the following raw materials: 76.25% lithium iron phosphate, 3.75% HNBA-PAA composite positive electrode binder, and 20% conductive agent (acetylene black: CNT = 6:1).

[0050] The preparation process of the positive electrode sheet of the battery is as follows: After LFP and the conductive agent are fully ground and mixed, a positive electrode precursor powder is obtained; the HNBA-PAA composite positive electrode binder is dissolved in NMP under heating and stirring, and then the positive electrode precursor powder is added, and a variable-frequency stirrer and an ultrasonic oscillator are used for mixing to obtain a positive electrode slurry; the positive electrode slurry is uniformly coated on an aluminum foil with a coating thickness of 15 μm, vacuum dried at 100 °C for 10 h, then heat-treated at 180 °C for 90 min in a forced-air drying oven, and then cut into positive electrode sheets with a diameter of 12 mm.

[0051] Example 2

[0052] This example is exactly the same as Example 1, except that: the composite positive electrode binder consists of HNBA and PAA with a mass ratio of 2:1.

[0053] Example 3

[0054] This example is exactly the same as Example 1, except that: the composite positive electrode binder consists of HNBA and PAA with a mass ratio of 1:1.

[0055] Example 4

[0056] This example is exactly the same as Example 1, except that: the composite positive electrode binder consists of HNBA and PAA with a mass ratio of 1:2.

[0057] Example 5

[0058] This example is exactly the same as Example 1, except that: the composite positive electrode binder consists of HNBA and PAA with a mass ratio of 1:5.

[0059] Comparative Example 1

[0060] This comparative example is exactly the same as Example 1, except that: the binder is PVDF.

[0061] Comparative Example 2

[0062] This comparative example is exactly the same as Comparative Example 1, except that: the positive electrode of the lithium-ion battery is prepared from PVDF and consists of the following raw materials: 72.5% lithium iron phosphate, 7.5% HNBA-PAA composite positive electrode binder, and 20% conductive agent (acetylene black: CNT = 6:1).

[0063] Comparative Example 3

[0064] This comparative example is exactly the same as Example 1, except that: the binder is HNBR.

[0065] Comparative Example 4

[0066] This comparative example is exactly the same as Example 1, except that: the binder is PAA.

[0067] It should be noted that although the positive electrode sheets of the batteries provided in the embodiments and comparative examples of the present invention were heat-treated in an air atmosphere, since the surface of the LFP powder was evenly covered with a carbon layer during the preparation process, no oxidation reaction occurred. Further, in order to verify this conclusion, taking the positive electrode sheet obtained in Example 1 of the present invention as an example, Fe 2+ titration tests were carried out, and the results are shown in Table 1.

[0068]

[0069] As can be seen from Table 1, the difference in the Fe 2+ content before and after heat treatment is only 0.95%, and hardly any change occurs, which effectively proves that the heat treatment process will not cause the active substances of the positive electrode sheet to be oxidized and inactivated.

[0070] Further, in order to verify the excellent technical effects of the composite positive electrode binder provided by the present invention, the positive electrodes obtained in the above embodiments and comparative examples were assembled into button batteries, and a series of performance tests were carried out. Among them, the process of assembling the battery is as follows: the positive electrode sheet prepared above is assembled into a liquid button battery in the order of negative electrode case, spring gasket, stainless steel gasket, metallic lithium, separator, electrolyte, positive electrode sheet, and positive electrode case in a glove box filled with argon (the oxygen and water contents are both <0.1 ppm).

[0071] The process of the performance test is as follows: the charge-discharge performance, Coulomb efficiency, cycle performance, and rate performance of the batteries were all tested using a Wuhan Blue Electric CT2001A battery test system. The cycle performance of all the batteries of the present invention was tested at 25°C and 1C rate, and the rate performance was tested in the order of 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, 10C, 0.1C at 25°C for 5 cycles.

[0072]

[0073]

[0074] Analyze Tables 2 and 3, Figure 1 From Comparative Examples 1, 3, and 4, it can be seen that when the binder is at the same mass ratio (when the proportion of the binder is relatively small), the performance of using HNBR or PAA alone is better than that of using PVDF alone. From Comparative Examples 1 and Examples 1-5, it can be seen that when the binder is at the same mass ratio, the HNBR-PAA composite binder has better cycling performance compared to PVDF. From Comparative Example 2 and Examples 1-4, it can be seen that when the dosage of the HNBR-PAA compound binder is half that of the PVDF binder, the performance is better. From Comparative Examples 3-4 and Examples 1-5, it can be seen that the battery performance of the HNBR-PAA composite binder is better than that of using HNBR or PAA alone as the binder. From Examples 1-5, it can be seen that the capacity retention rate of Example 3 is the best, so the proportion between HNBR and PAA in the HNBR-PAA compound binder has an obvious influence on the battery performance.

[0075] From the rate performance graph, it can be seen that when the HNBR-PAA composite binder is applied to the LFP half-cell, it has good rate performance. The capacity at the 5C rate in Examples 1-5 is about 110 mAh / g, and at the 10C rate it is 95 mAh / g.

[0076] Analyze the peel performance graph. At the same binder addition ratio, the bonding performance of the HNBR-PAA compound binder is significantly better than that of PVDF. From Comparative Example 3 and Examples 1-5, it can be seen that after mixing HNBR and PAA, the bonding performance of the HNBR-PAA compound binder is significantly improved compared to pure HNBR, and the bonding performance of Example 4 is the best. However, theoretically, as the amount of PAA increases, its bonding performance also increases. In fact, the bonding performance of Comparative Example 4 is not the best. It is speculated that during the slurry mixing process, as the amount of PAA increases, the slurry viscosity increases, and it is difficult for the binder to be evenly mixed with other components, and the carboxyl groups in PAA cannot evenly cover the surface of the active material, resulting in a decrease in the binder performance. Therefore, the proportion between HNBR and PAA in the HNBR-PAA compound binder has an obvious influence on the bonding performance of the electrode.

[0077] By comparing the SEM images of the electrodes after 500 long cycles at 1C rate for Comparative Examples 1-4 and Examples 1-5. From Comparative Examples 1 and 2, it can be seen that the reason why Comparative Example 1 could not achieve long cycling was that the amount of PVDF was too small and the adhesion performance was poor, resulting in a large number of microcracks on the electrode during long cycling. The poor cycling performance of Comparative Example 3 was due to the poor adhesion of HNBR, and cracks also appeared during cycling. In Comparative Example 4, PAA was very brittle, and during the charge and discharge process of the battery, the active material continuously underwent volume changes. Since PAA lacked elasticity, microcracks appeared during long cycling. In Examples 1-5, the addition of HNBR significantly improved the microcracks in Example 5 compared to Comparative Example 4. Even after long cycling in Examples 1-4, there were no obvious changes on the surface of the electrode.

[0078] Figure 13 It is the tensile property diagram of the dumbbell-shaped rubber rods prepared from HNBR, PAA, and PVDF used in the present invention. It can be seen from the figure that the tensile elongation rate of pure PAA is much lower than that of pure HNBR. However, the HNBR-PAA formed by the combination of HNBR and PAA has both excellent adhesion and elasticity, and also improves the tensile elongation rate of the material.

[0079] The above experiments show that the HNBR-PAA composite binder successfully combines the advantages of good adhesion of PAA and good elasticity of HNBR, and is expected to become a new binder for the positive electrode of lithium-ion batteries.

[0080] The specific implementation content described above is a specific description of the present invention in combination with preferred embodiments, but it cannot be determined that the specific implementation of the present invention is only limited to the described embodiments.

Claims

1. A secondary battery HNBA-PAA composite positive electrode binder, characterized in that: The binder raw material includes HNBA and PAA in a mass ratio of 1-10:1-10; the residual hydrogen bond content of the HNBR is 1-10%, and the ACN content is 10-40%; the molecular weight of the PAA is 3×10 5 ~1×10 6 .

2. The method for preparing a secondary battery HNBA-PAA composite positive electrode binder according to claim 1, characterized in that: Fully dissolve HNBR in N-methylpyrrolidone, then add PAA under slow stirring to carry out composite reaction until no solid remains to obtain the product.

3. The use of a secondary battery HNBA-PAA composite positive electrode binder according to claim 1, characterized in that: Used to prepare the positive electrode plate of a secondary battery; the secondary battery is at least one of a liquid battery, a semi-solid battery and a solid battery.

4. The use of a secondary battery HNBA-PAA composite positive electrode binder according to claim 1, characterized in that: The raw materials of the secondary battery positive electrode include the following components by weight: 60-80 parts of positive electrode active material, 1-5 parts of HNBA-PAA composite positive electrode binder solution and 10-20 parts of conductive agent; the solute concentration in the HNBA-PAA composite positive electrode binder solution is 0.5-1%.

5. The use of a secondary battery HNBA-PAA composite positive electrode binder according to claim 4, characterized in that: The positive electrode active material is one of lithium salt, sodium salt and potassium salt; the solvent of the HNBA-PAA composite positive electrode binder solution is N-methyl-2-pyrrolidone; and the conductive agent is acetylene black and / or carbon nanotubes.

6. The use of a secondary battery HNBA-PAA composite positive electrode binder according to claim 4, characterized in that: The secondary battery is a liquid battery; the positive electrode active material is lithium iron phosphate; the conductive agent is acetylene black and carbon nanotubes, and the mass ratio of the two is 1-6:

1.

7. The use of a secondary battery HNBA-PAA composite positive electrode binder according to claim 4, characterized in that: The preparation process of the secondary battery positive electrode is as follows: the positive electrode active material and the conductive agent are fully ground and mixed to obtain a positive electrode precursor powder; the HNBA-PAA composite positive electrode binder is dissolved in a solvent under heating and stirring, and then the positive electrode precursor powder is added and mixed evenly to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on an aluminum foil, and then dried, heat treated and cut in sequence to obtain the positive electrode slurry.

8. The use of a secondary battery HNBA-PAA composite positive electrode binder according to claim 7, characterized in that: The heating and stirring conditions are: a temperature of 30-70° C. and a stirring rate of 500-700 r / min; and a coating thickness of the positive electrode slurry of 10-20 μm.

9. The use of a secondary battery HNBA-PAA composite positive electrode binder according to claim 7, characterized in that: The drying method is vacuum drying, and the conditions are: temperature of 80-120°C and time of 8-12h; the heat treatment conditions are: drying in a blast drying oven, temperature of 150-200°C and time of 60-120min.

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