A slurry, an electrode tab, a preparation method thereof, and a battery

Abstract

The application discloses a slurry, a pole piece, a preparation method of the slurry and a battery. The preparation method of the slurry comprises the following steps: adding a premix of an active material and a conductive agent into a rubber compound containing a binder, mixing, and grinding to obtain the slurry; wherein the particle size D50 of the premix of the active material and the conductive agent is 12-20 mu m; the fineness of the rubber compound containing the binder is <10 mu m; and the fineness of the slurry is <45 mu m. The viscosity and the fineness of the slurry prepared by the application are uniform. The battery assembled by the pole piece prepared by using the slurry has better consistency and stability of test results, can effectively avoid the problem that the test result consistency repeatability is poor due to the inconsistent density of the current collector (copper foil / aluminum foil), and provides data support for researchers to make objective and reasonable evaluation.

Description

Technical Field

[0001] This invention relates to lithium batteries, specifically to a slurry, an electrode, a method for preparing the same, and a battery. Background Technology

[0002] Lithium-ion batteries, as a major force in new energy applications, have made significant progress in the field of energy storage. Early methods typically used coin cells (usually consisting of a positive electrode and a lithium metal sheet, or a negative electrode and a lithium metal sheet) to conduct preliminary electrochemical performance tests and evaluations of the positive and negative electrode materials of lithium-ion batteries. Clearly, accurate measurement of electrode material performance is of great guiding significance for the subsequent development and preparation of these materials, as well as the design and application of full cells.

[0003] Currently, commonly used coin cell casings include CR2032, CR2025, and CR2016. A lithium-ion coin cell mainly consists of the following parts: positive electrode casing, negative electrode casing, (positive / negative) electrode sheets, lithium metal sheets, separator, gasket, spring sheet, and electrolyte. The conventional method for manufacturing a coin cell is as follows: First, prepare a slurry by weighing active material, conductive agent, and binder in a specific ratio. Mix the three materials, add a certain amount of solvent to dissolve the binder, and then use magnetic stirring to create the slurry. Second, select a suitable current collector for coating and vacuum bake to produce the electrode sheets. Third, roll the electrode sheets, cut them into appropriately sized circular sheets, and weigh and record the electrode sheet mass. Fourth, assemble the coin cell in a glove box, with the assembly order from bottom to top as follows: electrode casing, spring sheet, gasket, lithium metal sheet, separator, electrolyte, electrode sheet, gasket, spring sheet, and electrode casing. The fifth step involves sealing the cells using a sealing machine, completing the button cell fabrication. The sixth step is to allow them to stand and then test them. The slurry produced using the conventional methods described above has a high viscosity and fineness, leading to poor electrochemical performance of the button cells, particularly low initial efficiency, low charge capacity, and low discharge capacity. Furthermore, button cells involve many components and have a complex structure, requiring highly skilled personnel. The resulting button cells are prone to short circuits and micro-leakage, resulting in a low yield rate. Key reasons for these issues include: firstly, the existing slurry preparation methods result in high viscosity and fineness; secondly, differences in the density of the current collector (copper foil / aluminum foil) lead to variations in current collector quality, which is closely related to the quality of the active material in the slurry, and the quality of the active material in turn affects the electrochemical performance of the resulting button cells. These defects all contribute to poor electrochemical performance, inconsistent test results, and poor repeatability, making it difficult for researchers to make objective and reasonable evaluations of the materials. Summary of the Invention

[0004] The technical problem this invention aims to solve is to overcome the shortcomings of existing technologies, such as the high viscosity and fineness of the prepared slurry, inconsistent current collector density leading to deviations in the calculation of current collector mass and active material mass, poor test result consistency, and difficulty for researchers to make objective and reasonable evaluations. This invention provides a slurry, electrode, its preparation method, and a battery. The slurry prepared by this invention has uniform viscosity and fineness. Batteries assembled using electrodes prepared with this slurry exhibit better consistency and stability in test results, effectively avoiding the problem of poor repeatability of test results due to inconsistent current collector (copper foil or aluminum foil) density, and providing data support for researchers to make objective and reasonable evaluations.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] The present invention provides a method for preparing a slurry, which includes the following steps: adding a "premix of active substance and conductive agent" to a binder-containing adhesive, mixing, and grinding to obtain the slurry;

[0007] The particle size D50 of the premix of active material and conductive agent is 12-20 μm; the fineness of the adhesive containing binder is <10 μm; and the fineness of the slurry is <45 μm.

[0008] In this invention, the active material can be a conventional active material used in lithium-ion batteries, such as lithium iron phosphate, lithium manganese oxide, or graphite. Typically, lithium iron phosphate and lithium manganese oxide can be used as active materials for positive electrode materials. Graphite can be used as an active material for negative electrode materials.

[0009] In this invention, the particle size D50 of the active substance can be 0.5-25 μm.

[0010] When the active material is lithium iron phosphate or lithium manganese oxide, the particle size D50 of the active material is preferably 0.5-20 μm.

[0011] When the active material is graphite, the particle size D50 of the active material is preferably 15-24 μm.

[0012] In this invention, the conductive agent can be a conventional active material used in lithium-ion batteries, such as conductive carbon black (SUPER-P), conductive graphite, or graphene.

[0013] In this invention, the particle size of the conductive agent can be 35±3nm.

[0014] In this invention, the resistance of the conductive agent can be ≤0.01Ω·m.

[0015] In this invention, the specific surface area (BET) of the conductive agent can be 62±3 g / m².2 .

[0016] In this invention, the preparation method of the premix of the active substance and the conductive agent preferably includes the following steps: first drying and grinding the active substance, then mixing it with the conductive agent and then grinding and drying it a second time.

[0017] The operation and conditions for the first drying step can be conventional in the art. The temperature for the first drying step is preferably 50-80°C, for example, 60°C. The drying time for the first drying step is preferably 1-5 hours, for example, 4 hours.

[0018] The time for the first grinding can be 10 min to 30 min, for example, 10 min.

[0019] The second grinding time can be 10 min to 30 min, for example, 10 min.

[0020] The operation and conditions for the second drying can be conventional in the art. The temperature for the second drying is preferably 50-80°C, for example, 60°C. The time for the second drying is preferably 10-30 minutes, for example, 20 minutes.

[0021] In this invention, the binder may be a conventional binder for lithium-ion batteries, such as polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), or styrene-butadiene rubber (SBR).

[0022] The PVDF can be used in positive electrode materials and / or negative electrode materials. The CMC and SBR can be used in negative electrode materials.

[0023] The molecular weight of the PVDF can be 1 million to 1.2 million g / mol.

[0024] The density of the PVDF can be 1.75-1.78 g / cm³. 3 .

[0025] The intrinsic viscosity of the PVDF can be 0.27-0.37 L / g.

[0026] When the adhesive is CMC and SBR, the mass ratio of CMC to SBR can be 1:1.

[0027] In this invention, the method for preparing the adhesive containing the binder preferably includes the following steps: mixing the binder and solvent, followed by a first grinding, drying, and a second grinding to obtain the final product.

[0028] The solvent may be a conventional solvent used in the art to dissolve binders in lithium-ion batteries, such as N-methylpyrrolidone (NMP).

[0029] The mass-to-volume ratio of the adhesive to the solvent can be (0.2-0.3g):(3-6ml), for example, 0.25g:5ml.

[0030] Before mixing the adhesive and solvent, the adhesive is generally dried. The drying operation and conditions can be conventional in the art. The drying temperature is preferably 50-80°C, for example, 60°C. The drying time is preferably 10-30 minutes, for example, 20 minutes.

[0031] The time for the first grinding can be 10 min to 30 min, for example, 20 min.

[0032] The drying operation and conditions can be conventional in the art. The drying temperature is preferably 50-80°C, for example, 60°C. The drying time is preferably 10-30 minutes, for example, 20 minutes.

[0033] The second grinding time can be 1 min to 5 min, for example 5 min.

[0034] In this invention, a solvent is generally added during the grinding process.

[0035] The solvent is typically N-methylpyrrolidone (NMP).

[0036] The volume-to-weight ratio of the solvent to the adhesive can be (1-3 ml):(250 mg), for example, 2 ml:0.25 g.

[0037] In this invention, the grinding time can be 10 min to 30 min, for example 20 min.

[0038] In this invention, the mass ratio of the active material, the conductive agent and the binder can be (80-98):(1-15):(1-15), preferably 80:10:10, 80:15:5, 90:5:5, 96:1:3 or 95:1:4.

[0039] In this invention, the fineness of the adhesive containing the binder is preferably <8μm.

[0040] In this invention, the particle size D50 of the "premix of active material and conductive agent" is preferably 12.5-19 μm, for example 12.6 μm, 13.7 μm or 18.7 μm.

[0041] In this invention, the fineness of the slurry is preferably <40μm, more preferably 30-40μm, for example 35μm.

[0042] In this invention, the viscosity of the slurry can be 3000-6500 mpa·s, for example 4000 mpa·s, 5000 mpa·s or 5500 mpa·s.

[0043] In this invention, the solid content of the slurry can be 45%-50%, for example 45%, 47% or 48%.

[0044] This invention provides a slurry prepared by the method described above.

[0045] The present invention provides a method for preparing an electrode, which includes the following steps: coating the slurry onto a current collector, drying, and rolling to obtain the electrode.

[0046] In this invention, the current collector can be conventional in the art, such as aluminum foil or copper foil. Those skilled in the art will understand that the current collector for the positive electrode is typically made of aluminum foil, and the current collector for the negative electrode is typically made of copper foil.

[0047] In this invention, the purity of the current collector can be ≥98.0%.

[0048] In this invention, the thickness of the current collector can be 12μm-15μm.

[0049] In this invention, the diameter of the current collector can be 12mm-15mm.

[0050] In this invention, the coating equipment is preferably an infrared drying flat plate coating machine, such as the Kejing MSK-AFS-ES200 infrared drying flat plate coating machine.

[0051] In this invention, the thickness of the slurry on the current collector after coating can be 12-18 μm, for example 15 μm.

[0052] In this invention, the drying operation and conditions can be conventional in the art. The drying temperature can be 120°C. The drying time can be 2 hours.

[0053] In this invention, the operation and conditions of the rolling process can be conventional in the art. The rolling equipment is preferably an electric double-roll mill. The roll gap of the electric double-roll mill can be 0.01-0.04 mm, for example, 0.02 mm. The number of rolling passes can be 1-5 times, for example, 3 times.

[0054] In this invention, the thickness of the electrode sheet can be 30μm-40μm.

[0055] In this invention, the areal capacity of the electrode can be 2-4 mA·h / cm². 2 .

[0056] In this invention, the mass of the active material in the electrode sheet can be calculated as follows: Mass of active material = (m1-m0) × (Percentage of active material in the total mass of active material, binder and conductive agent); where m1 is the mass of the electrode sheet and m0 is the mass of the current collector.

[0057] The present invention provides a battery comprising the electrodes as described above.

[0058] In this invention, the battery may be a coin cell.

[0059] In this invention, the preferred method for assembling the battery is as follows: the negative electrode shell, gasket, lithium sheet, separator, electrolyte, electrode, and positive electrode shell are assembled sequentially and then sealed to obtain the battery.

[0060] The negative electrode shell or positive electrode shell may be of model CR2032, CR2025 or CR2016, preferably CR2016.

[0061] The gasket is preferably 16mm×0.5mm, 16mm×0.8mm or 16mm×1.0mm, with 16mm×0.8mm being the most preferred.

[0062] The lithium sheet preferably has a size of 15mm × 0.5mm.

[0063] The specifications refer to diameter × thickness.

[0064] The membrane is preferably made of polypropylene (PP) or polyethylene (PE).

[0065] Preferably, the thickness of the diaphragm is 0.03-0.12 μm.

[0066] Preferably, the porosity of the diaphragm is 40-50%.

[0067] The electrolyte can be conventional in the art, such as lithium hexafluorophosphate (LiPF6) and a solvent. The solvent can be ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). The volume ratio of EC, DMC, and EMC is 1:1:1.

[0068] The sealing device is preferably a manual button sealing machine.

[0069] Preferably, the sealing pressure is 1000 kg / cm². 3 .

[0070] The assembly is preferably performed inside a glove box.

[0071] The moisture content of the glove box is preferably <0.01ppm.

[0072] The oxygen content of the glove box is preferably <0.01ppm.

[0073] The positive and progressive effects of this invention are as follows:

[0074] (1) By improving the preparation process of the slurry and controlling the particle size or fineness of each component, the present invention has produced a slurry with suitable viscosity and uniform fineness.

[0075] (2) The present invention also improves the electrode manufacturing process. By weighing first, coating and rolling, the problem of inaccurate calculation of active material mass due to uneven current collector density can be effectively avoided, thus affecting electrochemical performance and improving the consistency, stability and repeatability of test results. Attached Figure Description

[0076] Figure 1 This is an assembly diagram of the button half-cells obtained in Comparative Examples 1-4.

[0077] Figure 2 This is an assembly diagram of the button half-cells obtained in Examples 1-3.

[0078] Explanation of reference numerals in the attached figures:

[0079] 1 Positive electrode shell; 2 Spring sheet; 3 Gasket; 4 Lithium sheet; 5 Separator; 6 Electrolyte; 7 Electrode; 8 Gasket; 9 Spring sheet; 10 Negative electrode shell; 11 Positive electrode shell; 12 Electrode; 13 Electrolyte; 14 Separator; 15 Lithium sheet; 16 Gasket; 17 Negative electrode shell. Detailed Implementation

[0080] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0081] All raw materials used in the examples and comparative examples were commercially available. PVDF was purchased from Arkema (Changshu) Fluorochemicals Co., Ltd., specifically Kynar HSV 900, with a molecular weight of 1,000,000-1,200,000 g / mol and a density of 1.75-1.78 g / cm³. 3 The intrinsic viscosity is 0.27-0.37 L / g; the conductive agent (SUPER-P) was purchased from Imerys SUPER P-Li in France, with a particle size of 35±3 nm, a resistivity of ≤0.01 Ω·m, and a specific surface area (BET) of 62±3 g / m².2 The diaphragm was purchased from Celgard 2325 in the United States.

[0082] Examples 1-3 employ the following methods: Figure 2 The assembly diagram of the button cell shown is used to assemble the button cell.

[0083] Comparative Examples 1-4 were adopted as follows Figure 1 The assembly diagram of the button cell shown is used to assemble the button cell.

[0084] Example 1

[0085] The method for preparing the slurry includes the following steps:

[0086] (1) Place the active material (lithium iron phosphate, particle size D50 of 0.5-20μm) in a vacuum drying oven and dry at 60℃ for 4h. Grind 2.0000g of lithium iron phosphate for 10min.

[0087] (2) Mix 0.2500g of conductive agent (SUPER-P) with the dried lithium iron phosphate from step (1), grind for 10 min, place in a vacuum drying oven, and dry at 60℃ for 20 min to obtain a premix of active material and conductive agent. The particle size D50 of the premix of active material and conductive agent is 12.6 μm;

[0088] (3) Place 0.2500g of adhesive (PVDF) in a vacuum drying oven and dry at 60℃ for 20min.

[0089] (4) Mix the PVDF treated in step (3) with 5 ml of solvent (NMP), grind for 20 min, place in a vacuum drying oven, and dry at 60°C for 20 min to obtain a binder-containing adhesive. The mass-volume ratio of binder to solvent is 50 mg: 1 ml.

[0090] (5) Grind the adhesive containing the binder from step (4) for 5 minutes. The fineness of the adhesive containing the binder is <10μm.

[0091] (6) Mix the adhesive containing the binder from step (4) with the "premix of active material and conductive agent" from step (2), then add 2 ml of NMP and grind for 20 min to obtain a slurry. The slurry has a fineness of 30 μm, a viscosity of 5000 mPa·s, and a solid content of 45%.

[0092] The preparation method of the electrode includes the following steps:

[0093] (1) Weigh out the mass of 10 circular aluminum foils with a diameter of 12 mm, which is m0; wherein, the purity of the circular aluminum foils is 99.9% and the thickness is 12 μm;

[0094] (2) Adsorb the circular aluminum foil onto the flat plate, transfer the slurry to the infrared drying flat plate coating machine (model MSK-AFS-ES200), and adjust the doctor blade coating thickness to 15μm. Start the infrared drying flat plate coating machine to coat. After coating, start the drying function and dry at 120℃ for 2 hours;

[0095] (3) Adjust the roller gap of the electric roller press to 0.02mm, and roll the electrode sheet from step (2) three times. After completing the roller press, weigh the electrode sheet and record its mass as m1; wherein, the electrode sheet has a thickness of 35μm and an areal capacity of 3mA.h / cm³. 2 .

[0096] The battery includes a CR2016 positive and negative battery casing, gasket, electrolyte, lithium metal sheet, and separator.

[0097] Assemble the above materials inside a glove box, in the following order from bottom to top: negative electrode shell, gasket, lithium sheet, separator, electrolyte, electrode, and positive electrode shell. Use a vacuum pen to pick up the negative electrode shell, placing the gasket inside with its round side facing up. The lithium sheet should also be placed with its round side facing up and its shape regular. Next, place the separator, adding a drop of electrolyte to the center. Use a vacuum pen to pick up the electrode, placing it with the smooth side facing up and the active material side facing down, centered on the electrolyte to ensure it is fully wetted. Then, attach the positive electrode shell. Seal the glove box using a manual button sealer and wipe it with alcohol to obtain a button half-cell. The glove box contains 0.01 ppm water and 0.01 ppm oxygen. The electrolyte is LiPF6 and a solvent (EC, DMC, and EMC in a 1:1:1 volume ratio). The sealing pressure is 1000 kg / cm². 3 .

[0098] Ten coin cells were prepared according to the above-described method for preparing slurry, electrodes, and batteries.

[0099] Example 2

[0100] The only difference from Example 1 is that in step (2) of the slurry preparation method, the active material is lithium manganese oxide (particle size D50 is 0.5-20 μm) (please confirm). Specifically, the binder-containing adhesive has a fineness of <10 μm, the premix of the active material and conductive agent has a particle size D50 of 13.7 μm, the slurry has a fineness of 35 μm, a viscosity of 5000 mPa·s, and a solid content of 48%.

[0101] Ten coin cells were prepared according to the above-described method for preparing slurry, electrodes, and batteries.

[0102] Example 3

[0103] The only difference from Example 1 is that in step (4) of the slurry preparation method, the active material is graphite (particle size D50 is 16-24 μm) (please confirm); and in step (1) of the electrode preparation method, it is circular copper foil. The binder-containing adhesive has a fineness of <10 μm, the premix of active material and conductive agent has a particle size D50 of 18.7 μm, the slurry has a fineness of 40 μm, a viscosity of 4000 mPa·s, and a solid content of 47%.

[0104] Ten coin cells were prepared according to the above-described method for preparing slurry, electrodes, and batteries.

[0105] Comparative Example 1

[0106] The difference from Example 1 is that a button cell half-cell is fabricated using a conventional method, as follows:

[0107] The method for preparing the slurry includes the following steps:

[0108] The active material (lithium iron phosphate), conductive agent (SUPER-P), and binder (PVDF) were mixed in a mass ratio of 80:10:10, and then mixed with 10 mL of solvent (NMP). The mixture was stirred magnetically to obtain a slurry with a viscosity of 10000 mPa·s, a fineness of 55 μm, and a solid content of 50%.

[0109] The preparation method of the electrode includes the following steps:

[0110] (1) Ten circular aluminum foils with a diameter of 12 mm were randomly cut and weighed. The average mass of the circular aluminum foils was 4.632 g.

[0111] (2) The slurry is manually coated on aluminum foil with a coating thickness of 15μm. After coating, it is placed in a vacuum drying oven and dried at 120℃ for 12h.

[0112] (3) Adjust the gap between the electric rollers to 0.02 mm and roll the electrode sheet from step (2) three times to cut it into 10 circular electrode sheets. Weigh and record the mass of each sheet as m1.

[0113] The battery includes a CR2016 positive and negative battery casing, spring sheet, gasket, electrolyte, lithium metal sheet, and separator.

[0114] Assemble the above materials inside a glove box, in the following order from bottom to top: negative electrode shell, spring sheet, gasket, lithium metal sheet, separator, electrolyte, electrode sheet, gasket, spring sheet, and positive electrode shell. Seal the box using a button sealing machine to complete the button cell assembly.

[0115] Ten coin cells were prepared according to the above-described method for preparing slurry, electrodes, and batteries.

[0116] Comparative Example 2

[0117] The difference from Example 2 is that a button cell half-cell is fabricated using a conventional method, the specific steps of which are as follows:

[0118] The method for preparing the slurry includes the following steps:

[0119] The active material (lithium iron phosphate), conductive agent (SUPER-P), and binder (PVDF) were mixed in a mass ratio of 80:10:10, and then mixed with 10 mL of solvent (NMP). The mixture was stirred magnetically to obtain a slurry with a viscosity of 7500 mPa·s, a fineness of 50 μm, and a solid content of 50%.

[0120] The preparation method of the electrode includes the following steps:

[0121] (1) Ten circular aluminum foils with a diameter of 12 mm were randomly cut and weighed. The average mass of the circular aluminum foils was 4.596 g.

[0122] (2) The slurry was manually coated on circular aluminum foil with a coating thickness of 15 μm. After coating, the foil was placed in a vacuum drying oven and dried at 120°C for 6 hours.

[0123] (3) Adjust the gap between the electric rollers to 0.02 mm and roll the electrode sheet from step (2) three times to cut it into 10 circular electrode sheets. Weigh and record the mass of each sheet as m1.

[0124] The battery includes a CR2016 positive and negative battery casing, spring sheet, gasket, electrolyte, lithium metal sheet, and separator.

[0125] Assemble the above materials inside a glove box, in the following order from bottom to top: negative electrode shell, spring sheet, gasket, lithium metal sheet, separator, electrolyte, electrode sheet, gasket, spring sheet, and positive electrode shell. Seal the box using a button sealing machine to complete the button cell assembly.

[0126] Ten coin cells were prepared according to the above-described method for preparing slurry, electrodes, and batteries.

[0127] Comparative Example 3

[0128] The difference from Example 3 is that a button cell half-cell is fabricated using a conventional method, the specific steps of which are as follows:

[0129] The method for preparing the slurry includes the following steps:

[0130] The active material (graphite), conductive agent (SUPER-P), and binder (PVDF) were mixed in a mass ratio of 80:10:10, and then mixed with 12 mL of solvent (NMP). The mixture was stirred magnetically to obtain a slurry with a viscosity of 8000 mPa·s, a fineness of 55 μm, and a solid content of 60%.

[0131] The preparation method of the electrode includes the following steps:

[0132] (1) Ten circular copper foils with a diameter of 12 mm were randomly cut and weighed. The average mass of the circular copper foils was 9.913 g.

[0133] (2) The slurry was manually coated onto a circular copper foil with a coating thickness of 15 μm. After coating, it was placed in a vacuum drying oven and dried at 120°C for 6 hours.

[0134] (3) Adjust the gap between the electric rollers to 0.02 mm, and roll the electrode sheet from step (1) three times to cut it into 10 circular electrode sheets. Weigh and record the mass of each sheet as m1.

[0135] The battery includes a CR2016 positive and negative battery casing, spring sheet, gasket, electrolyte, lithium metal sheet, and separator.

[0136] Assemble the above materials inside a glove box, in the following order from bottom to top: negative electrode shell, spring sheet, gasket, lithium metal sheet, separator, electrolyte, electrode sheet, gasket, spring sheet, and positive electrode shell. Seal the box using a button sealing machine to complete the button cell assembly.

[0137] Ten coin cells were prepared according to the above-described method for preparing slurry, electrodes, and batteries.

[0138] Comparative Example 4

[0139] The difference from Example 1 lies in the different mixing order used to fabricate the button half-cell, as detailed below:

[0140] The method for preparing the slurry includes the following steps:

[0141] (1) Place 0.2500g of adhesive (PVDF) in a vacuum drying oven and dry at 60℃ for 20min.

[0142] (2) Mix the PVDF treated in step (1) with 5 ml of solvent (NMP), grind for 20 min, place in a vacuum drying oven, and dry at 60°C for 20 min to obtain a binder-containing adhesive. The mass-volume ratio of binder to solvent is 50 mg: 1 ml.

[0143] (3) Grind the adhesive containing the binder from step (2) for 5 minutes. The fineness of the adhesive containing the binder is <10μm.

[0144] (4) Place the active material (lithium iron phosphate) in a vacuum drying oven and dry it at 60°C for 4 hours. Grind 2.0000g of lithium iron phosphate for 10 minutes.

[0145] (5) Mix 0.2500g of conductive agent (SUPER-P) with the dried lithium iron phosphate from step (4), grind for 10 min, place in a vacuum drying oven, and dry at 60℃ for 20 min to obtain a premix of active material and conductive agent. The particle size D50 of the premix of active material and conductive agent is 13.6μm;

[0146] The mass ratio of the active substance in step (4), the conductive agent in step (5), and the binder in step (1) is 80:10:10.

[0147] (6) Mix the adhesive containing the binder from step (3) with the "premix of active material and conductive agent" from step (5), then add 2 ml of NMP and grind for 20 min to obtain a slurry. The slurry has a fineness of 55 μm, a viscosity of 9000 mPa·s, and a solid content of 48%.

[0148] Ten coin cells were prepared according to the above-described method for preparing slurry, electrodes, and batteries.

[0149] Example 1: Electrochemical performance test of the battery

[0150] The coin cells prepared in Examples 1-3 and Comparative Examples 1-4 were placed at room temperature (25±2℃) for 12 hours before electrochemical performance testing. The test conditions for the coin cells prepared in Examples 1-2 and Comparative Examples 1, 2, and 4 were: charge / discharge current 0.1C, voltage range 2.0-4.2V, and cutoff current 0.05C. The test conditions for the coin cells prepared in Example 3 and Comparative Example 3 were: charge / discharge current 0.1C, and test voltage 0.001-2.0V. The test results are shown in columns 6-8 of Tables 1-7 (0.1C charge specific capacity, 0.1C discharge specific capacity, and first-efficiency).

[0151] In Tables 1-7, the average 0.1C discharge values ​​represent the average 0.1C discharge specific capacity obtained by the above test methods.

[0152] Example 2

[0153] Calculate the mass of the active material in the button half-cells obtained in Examples 1-3 and Comparative Examples 1-4. The calculation method is as follows: Mass of active material = (m1-m0) × (Percentage of active material in the total mass of "active material, binder and conductive agent"), where m1 is the mass of the electrode in step (3) of the electrode preparation method in Examples 1-3 and Comparative Example 4, or the mass of the electrode in step (3) of the electrode preparation method in Comparative Examples 1-3; m0 is the mass of the circular aluminum foil or copper foil in step (1) of the electrode preparation method in Examples 1-3, or the average mass of the circular aluminum foil or copper foil in step (1) of the electrode preparation method in Comparative Examples 1-3. The calculation results are shown in column 5 (mass of active material) of Table 1-7.

[0154] Table 1. Effect data of Example 1

[0155]

[0156] Table 2. Effect data of Example 2

[0157]

[0158] Table 3. Effect data of Example 3

[0159]

[0160] Table 4 shows the effect data of Comparative Example 1.

[0161]

[0162] Table 5. Effect data of Comparative Example 2

[0163]

[0164] Table 6 shows the effect data for Comparative Example 3.

[0165]

[0166] Table 7 shows the effect data for Comparative Example 4.

[0167]

[0168] The data in the second column of Tables 4-6 (average mass of aluminum foil / copper foil) represent the average mass of aluminum foil / copper foil in step (1) of the preparation method of the electrodes of Comparative Examples 1-3.

[0169] The test method for the data in the third column of Tables 4-6 (actual mass of aluminum foil / copper foil) is as follows: After the above electrochemical performance test is completed on the button half-cells obtained in Comparative Examples 1-3, the button half-cells are disassembled, the electrodes are removed, the binder in the electrodes is dissolved, and the mass of the aluminum foil or copper foil is weighed.

[0170] Tables 1-7 show the performance data of electrodes prepared using the slurries obtained in Examples 1-3 and Comparative Examples 1-4 when applied to coin cells. Ten coin cells were prepared under the same conditions for each example or comparative example, and the stability of the initial efficiency data of the ten coin cells under the same conditions was analyzed.

[0171] Those skilled in the art will understand that the "percentage measure method" can be used to analyze data stability. The method involves determining stability by analyzing the percentage of the difference between the maximum and minimum values ​​of a parameter relative to the parameter's mean. The calculation formula is: 100 × (V max -V min ) / V avg ≤μ, where V max V is the maximum value of the parameter over a fixed period of time. min The minimum value of the parameter at a fixed time; V avg The parameters are the average values ​​over a fixed period of time, and the calculation results are shown in Table 8.

[0172] Table 8

[0173] Example 1 1.84％ Example 2 1.58％ Example 3 1.58％ Comparative Example 1 6.10％ Comparative Example 2 3.99％ Comparative Example 3 5.13％ Comparative Example 4 5.72％

[0174] As shown in Table 8, the percentage values ​​of Examples 1-3 are much smaller than those of Comparative Examples 1-4, which indicates that under the same conditions, the electrode sheets prepared from the slurry prepared in Examples 1-3 have higher stability, better consistency, and higher reliability in the electrochemical performance test results of coin cells when applied in coin cells.

Claims

1. A method for preparing a slurry, characterized in that, It includes the following steps: adding a "premix of active material and conductive agent" to a binder-containing adhesive, mixing, and grinding to obtain the slurry; wherein, a solvent is added during the grinding process, and the grinding time is 10 min-30 min; the volume weight ratio of the solvent added during the grinding process to the binder is (1-3 ml): (250 mg); The active material is lithium manganese oxide or graphite; the particle size D50 of the lithium manganese oxide is 0.5-20 μm; the particle size D50 of the graphite is 15-24 μm. The particle size D50 of the premix of active material and conductive agent is 13.7-18.7 μm; the fineness of the adhesive containing binder is <10 μm; the fineness of the slurry is 35-40 μm; the viscosity of the slurry is 4000-5000 mPa·s; and the solid content of the slurry is 47%-48%. The preparation method of the premix of the active substance and the conductive agent includes the following steps: first, the active substance is dried and ground for the first time; then, it is mixed with the conductive agent and ground and dried for the second time; the first grinding time is 10 min-30 min; the second grinding time is 10 min-30 min. The preparation method of the adhesive containing the binder includes the following steps: mixing the binder and solvent, followed by a first grinding, drying, and a second grinding to obtain the final product; the first grinding time is 10-30 minutes; the drying temperature is 50-80°C; the drying time is 10-30 minutes; and the second grinding time is 1-5 minutes.

2. The method for preparing the slurry as described in claim 1, characterized in that, The fineness of the adhesive containing the binder is <8μm; And / or, the particle size D50 of the "premix of active material and conductive agent" is 13.7 μm or 18.7 μm; And / or, the fineness of the slurry is 35 μm; And / or, the viscosity of the slurry is 4000 mPa·s or 5000 mPa·s; And / or, the solid content of the slurry is 47% or 48%.

3. The method for preparing the slurry as described in claim 1, characterized in that, The conductive agent is conductive carbon black, conductive graphite, or graphene. And / or, the particle size of the conductive agent is 35±3nm; And / or, the adhesive is polyvinylidene fluoride, or sodium carboxymethyl cellulose and styrene-butadiene rubber.

4. The method for preparing the slurry as described in claim 1, characterized in that, In the preparation method of the premix of the active substance and the conductive agent, the temperature of the first drying is 50-80℃; And / or, in the method for preparing the premix of the active substance and the conductive agent, the first drying time is 1-5 hours; And / or, in the method for preparing the premix of the active substance and the conductive agent, the first grinding time is 10 min; And / or, in the method for preparing the premix of the active substance and the conductive agent, the second grinding time is 10 min; And / or, in the method for preparing the premix of the active substance and the conductive agent, the temperature of the second drying is 50-80°C; And / or, in the preparation method of the premix of the active substance and the conductive agent, the second drying time is 10 min to 30 min.

5. The method for preparing the slurry as described in claim 4, characterized in that, In the preparation method of the premix of the active substance and the conductive agent, the temperature of the first drying is 60°C; And / or, in the method for preparing the premix of the active substance and the conductive agent, the first drying time is 4 hours; And / or, in the method for preparing the premix of the active substance and the conductive agent, the temperature of the second drying is 60°C; And / or, in the method for preparing the premix of the active substance and the conductive agent, the second drying time is 20 min.

6. The method for preparing the slurry according to claim 1, characterized in that, In the method for preparing the adhesive containing the binder, the solvent is N-methylpyrrolidone; And / or, in the method for preparing the adhesive containing the binder, the mass-to-volume ratio of the binder to the solvent is (0.2-0.3g):(3-6ml); And / or, in the method for preparing the adhesive containing the binder, the binder is dried before mixing with the solvent; And / or, in the method for preparing the adhesive containing the binder, the first grinding time is 20 minutes; And / or, in the method for preparing the adhesive containing the binder, the drying temperature is 60°C; And / or, in the method for preparing the adhesive containing the binder, the drying time is 20 min; And / or, in the method for preparing the adhesive containing the binder, the second grinding time is 5 minutes.

7. The method for preparing the slurry as described in claim 6, characterized in that, In the method for preparing the adhesive containing the binder, the mass-to-volume ratio of the binder to the solvent is 0.25 g: 5 ml; And / or, the drying temperature of the adhesive is 60°C during drying; And / or, the drying time of the adhesive is 20 minutes.

8. The method for preparing the slurry as described in claim 1, characterized in that, The solvent added during the grinding process is N-methylpyrrolidone; And / or, the volume-to-weight ratio of the solvent added during the grinding process to the binder is 2 ml: 0.25 g; And / or, the grinding time is 20 minutes; And / or, the mass ratio of the active material, the conductive agent and the binder is (80-98):(1-15):(1-15).

9. The method for preparing the slurry as described in claim 8, characterized in that, The mass ratio of the active material, the conductive agent, and the binder is 80:10:10, 80:15:5, 90:5:5, 96:1:3, or 95:1:

4.

10. A slurry, characterized in that, It is prepared by any one of the preparation methods described in claims 1-9.

11. An electrode sheet, characterized in that, It includes the following steps: coating the current collector with the slurry as described in claim 10, drying, and rolling to obtain the electrode sheet.

12. The electrode sheet as described in claim 11, characterized in that, The thickness of the slurry on the current collector after coating is 12-18 μm; And / or, the thickness of the electrode is 30μm-40μm.

13. The electrode sheet as described in claim 12, characterized in that, The thickness of the slurry on the current collector after coating is 15 μm.

14. A battery comprising an electrode as claimed in any one of claims 11-13.

Images