Slurry for positive electrode material as well as preparation method and application of slurry

Abstract

The invention discloses slurry for a positive electrode material as well as a preparation method and application of the slurry, and belongs to the technical field of batteries. The preparation method of the slurry for the positive electrode material comprises the following steps: stirring and mixing an N-methyl pyrrolidone solvent and polyvinylidene fluoride, then adding a conductive agent and modified carbon quantum dots, and stirring to obtain the slurry, the modified carbon quantum dots are prepared by the following steps: dissolving carbon quantum dots in absolute ethyl alcohol, then adding oleic acid or fatty amine, reacting at 55-65 DEG C under a stirring condition, and then adding a coupling agent to obtain the modified carbon quantum dots. In addition, the invention also provides the slurry for the positive electrode material prepared by the preparation method, or application of the slurry for the positive electrode material or the slurry for the positive electrode material in preparation of a soft package battery. After the slurry is mixed with a positive electrode material, the slurry is not in a jelly shape under the humidity of 20%, and the viscosity is normal.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a slurry for positive electrode materials, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium-ion batteries, the current mainstream energy storage technology, are widely used in portable electronic devices and electric vehicles. However, with lithium resources becoming increasingly scarce, the development of alternative energy storage technologies has become increasingly important. In this context, sodium-ion batteries (Na-ion batteries) have gained increasing attention due to their reliance on the Earth's abundant and widespread sodium resources. Sodium is present in much higher concentrations in the Earth's crust than lithium and is relatively cheap to extract, offering significant resource and cost advantages. This makes Na-ion batteries promising for large-scale energy storage applications. Therefore, accurately testing their performance in the laboratory can significantly reduce R&D costs. However, the commonly used coin cell testing method in the laboratory has limitations. Due to the relatively simple packaging structure of coin cells, it is difficult to accurately simulate the actual operating environment of the battery during testing, resulting in test results that often fail to fully reflect the electrochemical performance of the material. In contrast, pouch cells better simulate the operating conditions found in real-world applications, particularly under high current and long-term cycling conditions. The assembly and testing of pouch cells allows for a more comprehensive assessment of the material's actual performance, including energy density, power output, and cycle life. Therefore, assembling pouch cells for testing is a critical step in accurately evaluating the actual performance of Na-ion battery materials.

[0003] After sintering, general sodium-ion battery positive electrode materials usually have residual alkali on the surface (sodium oxide and sodium carbonate, etc.), which is very easy to deliquesce with moisture in the air to produce more alkaline sodium hydroxide. This strong alkaline substance will further react chemically with the binder, changing the molecular structure of the binder, resulting in an abnormal increase in the viscosity of the slurry, which appears to be "jelly-like". At the same time, it reduces the adhesion of the binder, causing the powder material to be at risk of falling off the current collector. Therefore, the preparation of soft packs usually needs to be carried out in a dry room. This requirement significantly increases the operating costs of the laboratory, thereby increasing research and development expenses. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above technical deficiencies, provide a slurry for positive electrode material and its preparation method and application, and solve the technical problem in the prior art that the slurry easily becomes jelly-like after being mixed with the positive electrode material when preparing soft-pack batteries.

[0005] In order to achieve the above technical objectives, the technical solution of the present invention provides a method for preparing a slurry for a positive electrode material, comprising the following steps: stirring and mixing N-methylpyrrolidone solvent and polyvinylidene fluoride, and then adding a conductive agent and modified carbon quantum dots and stirring; the modified carbon quantum dots are prepared by the following steps: dissolving the carbon quantum dots in anhydrous ethanol, and then adding oleic acid or fatty amine, and reacting at 55-65°C under stirring conditions, and then adding a coupling agent to obtain the modified carbon quantum dots.

[0006] In any embodiment, the coupling agent is one or both of EDC and DCC; and / or the fatty amine is octylamine.

[0007] In any embodiment, the reaction time at 55-65° C. is 2-4 hours.

[0008] In any embodiment, the conductive agent is Super-p; and / or the positive electrode material is sodium iron pyrophosphate positive electrode material.

[0009] In any embodiment, citric acid is further added. Specifically, N-methylpyrrolidone solvent, citric acid and polyvinylidene fluoride are stirred and mixed.

[0010] In any embodiment, the mass ratio of the citric acid to the conductive agent is 1:(5-6).

[0011] In any embodiment, the mass ratio of the N-methylpyrrolidone solvent to the polyvinylidene fluoride is (25-30):1; and / or the mass ratio of the conductive agent to the N-methylpyrrolidone solvent is (0.025-0.035):1.

[0012] In addition, the present invention also provides a slurry for positive electrode materials, which is prepared by the above preparation method.

[0013] In addition, the present invention also provides a positive electrode material slurry, comprising the above-mentioned slurry for positive electrode material and positive electrode material, which is obtained by mixing the positive electrode material and the slurry for positive electrode material.

[0014] In addition, the present invention also proposes the use of the slurry for positive electrode material prepared by the above preparation method or the above slurry for positive electrode material or the above positive electrode material slurry in the preparation of soft-pack batteries.

[0015] Compared with the prior art, the beneficial effects of the present invention include: stirring and mixing N-methylpyrrolidone solvent and polyvinylidene fluoride, then adding a conductive agent and modified carbon quantum dots and stirring to obtain a slurry for the positive electrode material. After the slurry is mixed with the positive electrode material, it does not appear jelly-like at 20% humidity and has normal viscosity, which is suitable for preparing soft-pack batteries under room temperature conditions. The prepared soft-pack batteries have excellent charge and discharge capacity and cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the preparation process of the sodium iron pyrophosphate soft-pack battery of the present invention.

[0017] Figure 2 The charge and discharge curves of the sodium iron pyrophosphate soft-pack battery prepared with the sodium iron pyrophosphate positive electrode material slurry corresponding to Examples 1-2 and Comparative Example 6.

[0018] Figure 3 This is a cycle performance diagram of sodium iron pyrophosphate soft-pack batteries prepared with the sodium iron pyrophosphate positive electrode material slurry corresponding to Examples 1-2 and Comparative Example 6.

[0019] Figure 4 This is a photo of the sodium iron pyrophosphate positive electrode material slurry of Example 1.

[0020] Figure 5 This is a photo of the sodium iron pyrophosphate positive electrode material slurry of Comparative Example 1. DETAILED DESCRIPTION

[0021] The "ranges" disclosed herein are defined in terms of lower and upper limits, where a given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive of the end values ​​and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise indicated, the numerical range "a to b" is a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0022] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0023] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0024] This specific embodiment provides a method for preparing a slurry for a positive electrode material, comprising the following steps: stirring and mixing an N-methylpyrrolidone solvent and polyvinylidene fluoride, and then adding a conductive agent and modified carbon quantum dots and stirring to obtain a slurry; the conductive agent is Super-p; the positive electrode material is a sodium ferric pyrophosphate positive electrode material; the mass ratio of the N-methylpyrrolidone solvent to the polyvinylidene fluoride is (25-30):1; the mass ratio of the conductive agent to the N-methylpyrrolidone solvent is (0.025-0.035):1;

[0025] The modified carbon quantum dots are prepared by the following steps: dissolving the carbon quantum dots in anhydrous ethanol, then adding excess oleic acid or fatty amine, and reacting at 55-65°C for 2-4 hours under stirring conditions, and then adding a coupling agent to obtain the modified carbon quantum dots; the coupling agent is one or both of EDC and DCC; and the fatty amine is octylamine.

[0026] In some embodiments, citric acid is further added. Specifically, N-methylpyrrolidone solvent, citric acid and polyvinylidene fluoride are stirred and mixed; the mass ratio of the citric acid to the conductive agent is 1:(5-6).

[0027] This specific embodiment also provides a slurry for positive electrode materials, which is prepared by the above preparation method.

[0028] This specific embodiment further provides a positive electrode material slurry, which includes the above-mentioned slurry for positive electrode material and positive electrode material, and is obtained by mixing the positive electrode material and the slurry for positive electrode material.

[0029] This specific embodiment also proposes the use of the slurry for positive electrode material prepared by the above preparation method or the above slurry for positive electrode material or positive electrode material slurry in the preparation of soft-pack batteries; the amount of the positive electrode material added is 1%-1.1% of the mass of the N-methylpyrrolidone solvent.

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0031] In the present invention, references to “some embodiments”, “this embodiment”, examples, etc. describe a subset of all possible embodiments, but it can be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments, and may be combined with each other without conflict.

[0032] If similar descriptions of "first / second" appear in the application documents, the following explanation is added. In the following description, the terms "first\second\third" are merely used to distinguish similar objects and do not represent a specific order of the objects. It can be understood that "first\second\third" can be interchanged with the specific order or sequence where permitted, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein.

[0033] In this embodiment, the term "and / or" is merely a description of the association relationship between associated objects, indicating that three relationships may exist. For example, object A and / or object B may represent three situations: object A exists alone, object A and object B exist at the same time, and object B exists alone.

[0034] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0035] Example 1

[0036] This embodiment provides a slurry for positive electrode materials, which is prepared by the following steps:

[0037] Weigh 900g of N-methylpyrrolidone solvent (NMP) and 30g of polyvinylidene fluoride (PVDF) in a stirred reactor and stir at high speed. Set the stirrer revolution speed to 60r / min and the rotation speed to 3000r / min. Stir for 1 hour until the PVDF is evenly dispersed and free of particles. Evacuate to <-0.085MPa, set the stirrer revolution speed to 50r / min and the rotation speed to 1000r / min. Stir at low speed for 30 minutes until the glue is light brown, transparent, free of impurities and obvious bubbles. Then add 25g of conductive agent Super-p and 5g of modified carbon quantum dots. Stir at low speed for 10 minutes until the material is soaked, then stir at high speed for 1 hour until the slurry is uniform and free of particles. Stirring is complete.

[0038] The modified carbon quantum dots of this embodiment are prepared by the following steps:

[0039] First, carbon quantum dots (CQDs) were dissolved in anhydrous ethanol, and excess oleic acid was added. The mixture was stirred at 60°C for 3 hours. An appropriate amount of coupling agent, EDC, was added to promote esterification / amidation between carboxyl groups and amines or hydroxyl groups. After the reaction, unreacted materials were removed by centrifugation and multiple ethanol or acetone washes. Finally, the CQDs were vacuum-dried or redispersed in a nonpolar solvent to obtain surface-hydrophobic modified CQDs.

[0040] The carbon quantum dots of this embodiment were prepared by the following steps: 1g of citric acid and 1g of urea were dissolved in 20mL of deionized water, stirred evenly, and transferred to a 100mL hydrothermal reactor lined with polytetrafluoroethylene, and reacted at 180°C for 4 hours. After the reaction, it was cooled naturally to obtain a yellow or brown transparent CQDs solution. Subsequently, a 500Da dialysis bag was used to remove small molecule impurities, or centrifugation + filtration was used for purification, and finally the hydrophilic CQDs dry powder was obtained by concentration or freeze drying.

[0041] 940 g of sodium ferric pyrophosphate (NFPP) cathode material was mixed with the above-prepared slurry and stirred for 3 h to obtain sodium ferric pyrophosphate cathode material slurry.

[0042] Example 2

[0043] The difference between the slurry for positive electrode material of the present embodiment and Example 1 is that 5g of citric acid is further added. Specifically, 900g of N-methylpyrrolidone solvent (NMP), 5g of citric acid and 30g of polyvinylidene fluoride (PVDF) are weighed and stirred at high speed in a stirred reactor. The speed of the stirrer revolution is set to 60r / min, and the speed of rotation is 3000r / min. Stirring for 1h is uniform and non-granular to PVDF. Evacuate to <-0.085MPa, set the speed of the stirrer revolution to 50r / min, and the speed of rotation is 1000r / min. Stirring at low speed for 30min is completed until the glue is light brown, transparent, free of impurities and has no obvious bubbles. Then add 25g of conductive agent Super-p and the modified carbon quantum dots obtained in Example 1 of 5g, first stir at low speed for 10min to infiltrate the material, then stir at high speed for 1h to achieve uniform and non-granular slurry, and stirring is completed.

[0044] 940 g of sodium ferric pyrophosphate (NFPP) cathode material was mixed with the above-prepared slurry and stirred for 3 h to obtain sodium ferric pyrophosphate cathode material slurry.

[0045] Comparative Example 1

[0046] The difference between the slurry for positive electrode material proposed in this comparative example and Example 1 is that modified carbon quantum dots are not added. Specifically, 900g N-methylpyrrolidone solvent (NMP) and 30g polyvinylidene fluoride (PVDF) are weighed and stirred at high speed in a stirred reactor. The speed of the stirrer revolution is set to 60r / min, the speed of rotation is 3000r / min, and stirring is continued for 1h until the PVDF is evenly dispersed and free of particles. Vacuum to <-0.085MPa, set the speed of the stirrer revolution to 50r / min, and the speed of rotation is 1000r / min. Stir at low speed for 30min until the glue is light brown, transparent, free of impurities, and free of obvious bubbles. Then add 30g conductive agent Super-p, first stir at low speed for 10min until the material is infiltrated, then stir at high speed for 1h until the slurry is uniform and free of particles, and stirring is completed.

[0047] 940 g of sodium ferric pyrophosphate (NFPP) positive electrode material was mixed with the slurry prepared in this comparative example and stirred for 3 h to obtain sodium ferric pyrophosphate positive electrode material slurry.

[0048] Comparative Example 2

[0049] The difference between the sodium iron pyrophosphate positive electrode material slurry proposed in this comparative example and that of comparative example 1 is that, before the homogenization process, the positive electrode material is subjected to a water washing process step, that is, the NFPP powder obtained by sintering is ultrasonically washed 3 times with deionized water (or ethanol / water mixture), centrifuged and dried at 80°C for 12 hours to remove residual alkali on the surface, and the washed NFPP powder is subjected to a homogenization process again. Specifically, 940 g of the washed sodium iron pyrophosphate (NFPP) positive electrode material is mixed with the slurry prepared in comparative example 1 and stirred for 3 hours to obtain the sodium iron pyrophosphate positive electrode material slurry.

[0050] Comparative Example 3

[0051] The difference between the slurry for positive electrode material proposed in this comparative example and that in comparative example 1 is that the added 30g conductive agent Super-p is replaced with 25g conductive agent and 5g multi-walled carbon nanotubes (MWCNT).

[0052] 940 g of sodium ferric pyrophosphate (NFPP) positive electrode material was mixed with the slurry prepared in this comparative example and stirred for 3 h to obtain sodium ferric pyrophosphate positive electrode material slurry.

[0053] Comparative Example 4

[0054] The difference between the slurry for positive electrode material proposed in this comparative example and that in comparative example 3 is that 5 g of multi-walled carbon nanotubes (MWCNTs) are replaced by 5 g of unmodified carbon quantum dots (CQDs) prepared in Example 1.

[0055] 940 g of sodium ferric pyrophosphate (NFPP) positive electrode material was mixed with the slurry prepared in this comparative example and stirred for 3 h to obtain sodium ferric pyrophosphate positive electrode material slurry.

[0056] Comparative Example 5

[0057] The difference between the slurry for positive electrode material proposed in this comparative example and that in comparative example 1 is that the mass of the added polyvinylidene fluoride (PVDF) is adjusted to 40 g, and the mass of the conductive agent Super-p is adjusted to 20 g.

[0058] 940 g of sodium ferric pyrophosphate (NFPP) positive electrode material was mixed with the slurry prepared in this comparative example and stirred for 3 h to obtain sodium ferric pyrophosphate positive electrode material slurry.

[0059] Comparative Example 6

[0060] The difference between the slurry for positive electrode material proposed in this comparative example and comparative example 1 is that 5g of citric acid is added and dissolved therein. Specifically, 900g of N-methylpyrrolidone solvent (NMP), 5g of citric acid and 30g of polyvinylidene fluoride (PVDF) are weighed and stirred at high speed in a stirred reactor. The speed of revolution of the stirrer is set to 60r / min, the speed of rotation is 3000r / min, and stirring is continued for 1h until the PVDF is evenly dispersed and free of particles. Vacuum to <-0.085MPa, set the speed of revolution of the stirrer to 50r / min, the speed of rotation is 1000r / min, and stir at low speed for 30min until the glue is light brown, transparent, free of impurities and no obvious bubbles. Then add 30g of conductive agent Super-p, first stir at low speed for 10min until the material is infiltrated, then stir at high speed for 1h until the slurry is uniform and free of particles, and stirring is completed.

[0061] 940 g of sodium ferric pyrophosphate (NFPP) positive electrode material was mixed with the slurry prepared in this comparative example and stirred for 3 h to obtain sodium ferric pyrophosphate positive electrode material slurry.

[0062] The environment in which the sodium iron pyrophosphate positive electrode material slurry of the above-mentioned embodiment or comparative example is prepared is: the constant temperature throughout the experimental process is 25°C, and no professional dry room is required. It is only necessary to use a conventional industrial dehumidifier to control the humidity at 20% (equivalent to a dew point of 2°C, which is much lower than the dew point of a general dry room of -30 to -40°C).

[0063] The viscosity of the sodium ferric pyrophosphate positive electrode material slurries obtained in Examples 1-2 and Comparative Examples 1-6 was tested in a viscometer, and the specific data are shown in Table 1. The positive electrode slurries with a viscosity below 9000 mPa*s and in normal condition were double-sided coated on a coating machine, and then the dried positive electrode sheets were roll-pressed and cut to obtain the desired sodium ferric pyrophosphate (NFPP) positive electrode sheets.

[0064] The positive electrode sheets obtained in Examples 1-2 and Comparative Example 6 were subjected to full electrical assembly tests. Figure 1 , as follows:

[0065] Preparation of hard carbon negative electrode sheet: Weigh 800g of deionized water and 15g of sodium carboxymethyl cellulose (CMC) in a stirred reactor and stir at high speed for 2h until the CMC is evenly dispersed and free of particles. Vacuum degassing and stir at low speed for 0.5h. Add 30g of conductive agent Super-p, stir at low speed for 2min and then at high speed for 2h. Then add 800g of hard carbon and follow the same steps, stir at low speed for 2min and then at high speed for 2h until the slurry is uniform and free of particles. Finally, add 80g of styrene-butadiene rubber (SBR) and stir at high speed for 0.5h; vacuum again to <-0.085MPa and stir at low speed for 0.5h to eliminate bubbles in the slurry to obtain hard carbon negative electrode material slurry; the obtained negative electrode slurry is double-sided coated on a coater, and then the dried positive electrode sheet is rolled and cut to obtain the required hard carbon negative electrode sheet.

[0066] Preparation of a full battery: The prepared positive and negative pole pieces are assembled on a stacking machine in the order of positive pole piece-diaphragm-negative pole piece and the set number of pieces. Then the aluminum tabs are welded to the tab positions of the positive and negative pole pieces. The aluminum-plastic film is cut into suitable sizes and the aluminum-plastic film is punched out on an aluminum-plastic film forming machine. The battery cell is placed in the pit of the aluminum-plastic film. After the aluminum-plastic film is folded in half, it is placed in a heat sealing machine with a heat sealing temperature of 180°C for side sealing. After sealing, it is placed in a vacuum drying oven at 100°C for 24 hours. Finally, the dried soft-pack battery is filled with 10g of electrolyte in an argon glove box according to the ratio of 1Ah to 10g. The filling port is heat-sealed in the glove box to complete the preparation of the full battery.

[0067] Full battery test: The sodium iron pyrophosphate soft-pack battery was subjected to a formation test in a horizontal hot press. The test temperature was set to 45°C. The formation program on the test cabinet was set to charge to 2.3V at 0.02C, hold for 10 minutes, charge to 3.6V at 0.05C, and then rest for 24 hours to complete the formation of the soft-pack battery. The battery was transferred to the secondary sealing machine, the head temperature was set to 170°C, and after sharp knife puncture and vacuuming, the formed battery was secondary sealed and the air bag above the battery was cut off. The cycle program on the Xinwei test cabinet was set to charge to 3.6V at 1C, charge to 0.05C at constant voltage, hold for 10 minutes, discharge to 1.7V at 1C, hold for 10 minutes, and cycle 2000 times before completion. The sodium iron pyrophosphate soft-pack battery was clamped on the test cabinet and the cycle test was completed according to this program.

[0068] Table 1 Corresponding viscosities of sodium iron pyrophosphate positive electrode material slurries prepared in Examples 1-2 and Comparative Examples 1-6

[0069]

[0070] Combined with Table 1, it can be seen that the sodium iron pyrophosphate cathode material slurries prepared in Examples 1-2 and Comparative Example 6 do not appear jelly-like. Figure 4 The state of the positive electrode material slurry in the normal state of Example 1 is: Figure 5 This is the state of the positive electrode material slurry of Comparative Example 1, which can be seen to be clearly "jelly-like".

[0071] Figure 2 The following are the electrochemical curves for soft-pack batteries prepared using the sodium iron pyrophosphate cathode material slurries of Example 1, Example 2, and Comparative Example 6. The designed cell is 4Ah. At a constant current charge and discharge rate of 2A, the actual charge and discharge capacity of Example 2 is 3.48Ah, accounting for 87% of the designed cell; the actual charge and discharge capacity of Example 1 is 3.32Ah, accounting for 83% of the designed cell. While the viscosity of the positive electrode slurry in Comparative Example 1 meets the coating requirements, the actual charge and discharge capacity after preparation into a soft pack is 3.08Ah, accounting for only 77% of the designed cell, significantly lower than the corresponding data of the soft pack in Example 2.

[0072] Figure 3 The long cycle test of the soft packs of Example 1, Example 2 and Comparative Example 6 at a constant current charge and discharge rate of 2A shows that after 2000 cycles, the cycle retention rate of the soft pack of Example 2 is 96.5%; the cycle retention rate of the soft pack of Example 1 is 74.3%; and the cycle retention rate of Comparative Example 6 is only 70.1%.

[0073] The present invention provides a slurry suitable for preparing soft-packs in the laboratory at room temperature and proposes a sodium-ion battery cell manufacturing process that can prevent the slurry from "jellying." This method greatly reduces adverse chemical reactions with the binder, maintains the molecular structure of the binder, and ensures that the slurry viscosity and the adhesiveness of the binder remain normal. The soft-pack batteries prepared by this method are low-cost and have good cycle performance, high safety, and strong universality, and can be used in the preparation of battery soft packs. It can be used in laboratories without dry room conditions, reducing R&D costs and laboratory maintenance costs.

[0074] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a slurry for a positive electrode material, characterized in that: The method comprises the following steps: stirring and mixing N-methylpyrrolidone solvent and polyvinylidene fluoride, and then adding a conductive agent and modified carbon quantum dots and stirring; the modified carbon quantum dots are prepared by the following steps: dissolving the carbon quantum dots in anhydrous ethanol, and then adding oleic acid or fatty amine, and reacting at 55-65°C under stirring conditions, and then adding a coupling agent to obtain the modified carbon quantum dots.

2. The method for preparing a slurry for a positive electrode material according to claim 1, wherein: The coupling agent is one or both of EDC and DCC; and / or the fatty amine is octylamine.

3. The method for preparing a slurry for a positive electrode material according to claim 1, characterized in that: The reaction time at 55-65°C is 2-4 hours.

4. The method for preparing a slurry for a positive electrode material according to claim 1, wherein: The conductive agent is Super-p; and / or the positive electrode material is sodium iron pyrophosphate positive electrode material.

5. The method for preparing a slurry for positive electrode materials according to claim 1, characterized in that: The method further comprises adding citric acid. Specifically, N-methylpyrrolidone solvent, citric acid and polyvinylidene fluoride are stirred and mixed.

6. The method for preparing a slurry for positive electrode materials according to claim 5, characterized in that: The mass ratio of the citric acid to the conductive agent is 1:(5-6).

7. The method for preparing a slurry for positive electrode materials according to claim 1, characterized in that: The mass ratio of the N-methylpyrrolidone solvent to the polyvinylidene fluoride is (25-30):1; and / or the mass ratio of the conductive agent to the N-methylpyrrolidone solvent is (0.025-0.035):

1.

8. A slurry for positive electrode material, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 7.

9. A positive electrode material slurry, characterized in that: The invention comprises the slurry for positive electrode material and the positive electrode material according to claim 8, which are obtained by mixing the positive electrode material and the slurry for positive electrode material.

10. Use of the slurry for positive electrode material prepared by the preparation method according to any one of claims 1 to 7, the slurry for positive electrode material according to claim 8, or the positive electrode material slurry according to claim 9 in preparing soft-pack batteries.

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