Sodium-ion battery positive electrode slurry and preparation method thereof

Abstract

The invention discloses sodium ion battery positive electrode slurry and a preparation method thereof, and belongs to the technical field of batteries. The preparation method comprises the following steps: S1, mixing raw materials containing a first conductive agent and a positive electrode material, and stirring and dispersing to obtain solid powder; s2, mixing the solid powder in the step S1, a dispersing aid solution and a part of binder solution, and stirring and dispersing under a vacuum condition to obtain slurry I; s3, mixing the slurry I in the step S2 with the residual binder solution, and stirring and dispersing under a vacuum condition to obtain slurry II; s4, mixing the slurry II in the step S3 with a second conductive agent, and stirring and dispersing under a vacuum condition to obtain slurry III; s5, mixing the slurry III in the step S4 with a solvent, and stirring and dispersing under a vacuum condition to obtain slurry IV; and S6, carrying out defoaming treatment and sieving on the slurry IV in the step S5 to obtain the sodium ion battery positive electrode slurry.

Description

Technical Field

[0001] This application belongs to the technical field of batteries, and particularly relates to a positive electrode slurry for a sodium-ion battery and a preparation method thereof. Background Art

[0002] Currently, the slurry of sodium-ion batteries is usually prepared by a traditional wet pulping process. The main steps are to first dissolve the binder in a solvent to form a very low-concentration colloidal solution, and then add powder materials such as conductive agents and positive electrode materials to the colloidal solution and mix and stir to obtain the slurry.

[0003] However, in the existing wet pulping process, since the chain structure of the binder cannot be well opened, the viscosity of the slurry is relatively large, and the viscosity can reach 10000 - 2000 mPa·s. In order to be able to coat normally, a large amount of solvent for dispersion and homogenization needs to be added, resulting in a low solid content in the slurry. The solid content is not more than 45%. The friction between the powder bodies in the slurry is small, and it is difficult to achieve a good dispersion effect, and the fineness of the obtained slurry is poor. In addition, due to the low solid content of the slurry, a large amount of solvent needs to be evaporated during drying, resulting in low coating efficiency, high energy consumption, and increased production costs. Summary of the Invention

[0004] In view of this, this application provides a positive electrode slurry for a sodium-ion battery and a preparation method thereof, and the main purpose is to solve the technical problems of poor dispersion, poor fineness, low solid content, and high drying energy consumption of the positive electrode slurry.

[0005] On the one hand, this application provides a preparation method for a positive electrode slurry of a sodium-ion battery. The preparation method includes the following steps:

[0006] S1: Mix and stir-disperse the raw materials containing the first conductive agent and the positive electrode material to obtain solid powder materials;

[0007] S2: Mix the solid powder materials in step S1, the dispersion aid solution, and a partial amount of the binder solution, and stir-disperse under vacuum conditions to obtain slurry I;

[0008] S3: Mix the slurry I in step S2 and the remaining amount of the binder solution, and stir-disperse under vacuum conditions to obtain slurry II;

[0009] S4: Mix the slurry II in step S3 and the second conductive agent, and stir-disperse under vacuum conditions to obtain slurry III;

[0010] S5: Mix the slurry III in step S4 and the solvent, and stir-disperse under vacuum conditions to obtain slurry IV;

[0011] S6: Perform defoaming treatment and sieving on the slurry IV in step S5 to obtain the positive electrode slurry of the sodium-ion battery.

[0012] During the entire pulping process of the present invention, the environmental dew point range is required to be -20 to -40.

[0013] In the pulping process of the present invention, the powder materials are first mixed evenly; then a dispersion aid and a part of the binder solution are added and mixed. Under the condition of extremely high solid content, excellent mixing at the microscopic level is obtained through sufficient friction of the powder, so that the cathode material, the conductive agent and the binder particles are evenly dispersed, and a good conductive network structure and a bonding structure are constructed. In this application, the fineness is first reduced by sufficient friction between the powder particles, and the chain structure of the binder is opened by sufficient pulling between the powder and the binder to achieve sufficient dispersion. Then, a solvent is added to adjust to a solid content suitable for coating. Both the binder and the solid powder can be well dispersed, and a sodium-ion battery cathode slurry with moderate viscosity, good fineness and high solid content is obtained.

[0014] Optionally, in step S2, the solid powder materials, the dispersion aid solution and a part of the binder solution are mixed, and the solid content is controlled to be 60-65% (that is, the total mass of the solid powder materials, the dispersion aid and the binder accounts for 60-65% of the total mass of the solid-liquid mixture).

[0015] Optionally, in step S2, the solid content is selected from any value of 60%, 61%, 62%, 63%, 64%, 65% or the range value between any two of them.

[0016] Optionally, in step S5, the slurry III and the solvent are mixed, and the solid content is controlled to be 50-55%.

[0017] Optionally, in step S5, the solid content is selected from any value of 50%, 51%, 52%, 53%, 54%, 55% or the range value between any two of them.

[0018] Optionally, in step S5, the viscosity of the slurry IV is controlled to be 4000-7000 mPa·s.

[0019] Optionally, when the slurry I and the remaining binder solution are mixed in step S3, the stirring speed is 20-60 rpm.

[0020] Optionally, when the slurry II and the second conductive agent are mixed in step S4, the stirring speed is 20-60 rpm.

[0021] Optionally, the stirring speeds in step S3 and step S4 are independently selected from any value of 20, 30, 40, 50, 60 rpm or the range value between any two of them.

[0022] Optionally, in steps S2, S3 and S5, the dispersion linear velocity under vacuum conditions is independently 10-15 m s -1, the degree of vacuum is independently -80 to -100 kPa for each.

[0023] Optionally, in steps S2, S3 and S5, the dispersion linear velocity under vacuum conditions is independently 10, 11, 12, 13, 14, 15 m s -1 any value among them or a range value between any two of them.

[0024] Optionally, in step S6, the stirring speed for the defoaming treatment of the slurry IV is 10 to 30 rpm, and the defoaming time is 0.5 h to 2 h.

[0025] In the present invention, to completely remove bubbles, a reverse stirring method can be adopted.

[0026] Optionally, the stirring and dispersion time in step S1 is 30 to 90 min.

[0027] Optionally, the stirring and dispersion time in step S1 is any value among 30, 40, 50, 60, 70, 80, 90 min or a range value between any two of them.

[0028] Optionally, the stirring and dispersion time in step S2 is 60 to 90 min.

[0029] Optionally, the stirring and dispersion time in step S2 is any value among 60, 70, 80, 90 min or a range value between any two of them.

[0030] Optionally, the stirring and dispersion time in step S3 is 30 to 60 min.

[0031] Optionally, the stirring and dispersion time in step S3 is any value among 30, 40, 50, 60 min or a range value between any two of them.

[0032] Optionally, the stirring and dispersion time in step S4 is 20 to 40 min.

[0033] Optionally, the stirring and dispersion time in step S4 is any value among 20, 30, 40 min or a range value between any two of them.

[0034] Optionally, the stirring and dispersion time in step S5 is 30 to 40 min.

[0035] Optionally, the positive electrode material is selected from layered oxide materials and / or polyanion compounds.

[0036] Optionally, the first conductive agent is selected from highly conductive graphite and / or conductive carbon black.

[0037] Optionally, the second conductive agent is selected from carbon nanotube dispersion liquid and / or graphene dispersion liquid.

[0038] Optionally, the solute in the binder solution is polyvinylidene fluoride and / or polytetrafluoroethylene.

[0039] Optionally, the solute in the dispersion aid solution is selected from polyvinylpyrrolidone or a copolymer modified material of acrylic acid and acrylate derivatives.

[0040] Optionally, the solvents in the dispersion aid solution and the binder solution are both N-methylpyrrolidone.

[0041] The present invention provides a specific preparation method for a positive electrode material of a sodium-ion battery, which specifically includes the following steps:

[0042] Step 1: Add a conductive agent and a positive electrode material into a stirring device. After stirring and mixing evenly, start dispersion until the two materials are completely dispersed.

[0043] Step 2: Add a dispersion aid solution and a part of the binder solution into the stirring device. Stir until all solid powders are fully wetted by the binder solution and the dispersion aid solution, and then start high dispersion and vacuum until all materials are mixed and dispersed evenly.

[0044] Step 3: Add the remaining binder solution into the stirring device. Stir until the solution and the slurry are mixed evenly, and then start high dispersion and vacuum; stir and disperse until all materials are mixed evenly.

[0045] Step 4: Add a second conductive agent dispersion liquid into the stirring device. Stir until the solution and the slurry are mixed evenly, and then start dispersion, start vacuum stirring, and disperse and mix evenly.

[0046] Step 5: Add a solvent into the stirring device and adjust the solid content to 50-55%. Start high dispersion, start vacuum, and control the viscosity of the slurry to be 4000-7000 mPa·s.

[0047] Step 6: Carry out a low-speed stirring and defoaming treatment on the slurry in the stirring device under vacuum, and then screen it to obtain a positive electrode slurry for a sodium-ion battery.

[0048] In a second aspect, the present invention provides a positive electrode slurry for a sodium-ion battery, which is prepared by using the above preparation method.

[0049] Optionally, the viscosity of the positive electrode slurry for a sodium-ion battery is 4000-7000 mPa·s, and the fineness is 5-30 μm.

[0050] Optionally, the solid mass fraction of the positive electrode slurry for a sodium-ion battery is: 90-95% positive electrode material, 2-5% conductive agent, 3-5% binder, 0.1%-1% dispersion aid.

[0051] Optionally, the conductive agent includes a first conductive agent and a second conductive agent, and the mass ratio of the first conductive agent to the second conductive agent is 1.5 to 4:1.

[0052] Optionally, the mass ratio of the first conductive agent to the second conductive agent is any value among 1.5, 2, 2.5, 3, 3.5, 4 or a range value between any two of them.

[0053] In a third aspect, the present invention provides a sodium-ion battery, which includes a positive electrode slurry, and the positive electrode slurry is the above-mentioned sodium-ion positive electrode slurry.

[0054] Compared with the prior art, the present application has the following beneficial effects:

[0055] (1) The solid content of the positive electrode slurry of the sodium-ion battery prepared by the present invention is 50-55%, the viscosity of the slurry is moderate, the fluidity is good, the fineness of the slurry is small, and the processability is good.

[0056] (2) The addition of the dispersion aid in the present invention can quickly adsorb on the surface of the active particles, and the solvation chains stretch in the dispersion phase, so that the particulate matter has good fluidity. Through the charge effect and the steric hindrance effect, the aggregation of particles can be effectively avoided; the preparation time of the slurry can be greatly reduced, the use of the solvent can be significantly reduced, and the solid content and stability of the slurry can be improved.

[0057] (3) In the pulping process of the present invention, by adding part of the binder first, the powders are in close contact with each other and the collision probability is high, effectively destroying the aggregated structure formed between the powders, which helps the uniform dispersion of the conductive agent and the positive electrode material, and better improves the cycle performance and rate performance; in the high-viscosity slurry, the components pull and disperse each other, and it is not easy to form aggregates, and the dispersion effect is good, which helps to increase the solid content of the discharged material. Specific Embodiments

[0058] The following combines specific embodiments to further elaborate the present application. The following descriptions are only several embodiments of the present application and do not impose any form of limitation on the present application. Although the present application is disclosed in the following preferred embodiments, it is not intended to limit the present application. Any person skilled in the art, without departing from the scope of the technical solution of the present application, makes some changes or modifications using the technical content disclosed above, which are equivalent to equivalent embodiments and all fall within the scope of the technical solution.

[0059] Unless otherwise specified, the raw materials in the embodiments of the present application are purchased through commercial channels and used directly without any special treatment.

[0060] The chemical substances and technical terms in the following embodiments of the present invention are explained as follows:

[0061] NVP: Sodium vanadium phosphate;

[0062] SP: Nano-conductive carbon black;

[0063] CNT: Carbon nanotube;

[0064] PVDF: Polyvinylidene fluoride;

[0065] NFPP: Sodium iron pyrophosphate;

[0066] PTFE: Polytetrafluoroethylene;

[0067] NMP: N-Methylpyrrolidone;

[0068] NCFM: Sodium copper iron manganese;

[0069] KS-6: Artificial graphite;

[0070] NVPF: Sodium vanadium phosphate fluoride;

[0071] V50: Copolymer modified material of acrylic acid and acrylate derivatives;

[0072] PVP: Polyvinylpyrrolidone;

[0073] NMFPP: Sodium manganese iron phosphate;

[0074] Revolution: Corresponding to "stirring"; Rotation: Corresponding to "dispersion".

[0075] Viscosity: The test instrument is TMI SNB-2 digital viscometer;

[0076] Fineness: Measured by a scraping fineness gauge;

[0077] Solid content: Measured by the drying method;

[0078] Stirring device: It is a HY-DL.H7 4L type double planetary power mixer, with a revolution speed of 0 - 155 rpm and a rotation speed of 0 - 9000 rpm.

[0079] Example 1

[0080] In this example, the mass ratio of the effective solid components is:

[0081] NVP:SP:CNT:PVDF = 94:1.5:1:3.5.

[0082] The pulping process for the positive electrode of a sodium-ion battery includes the following steps:

[0083] (1) Add 1.5% of the conductive agent SP and 94% of the sodium vanadium phosphate (NVP) cathode material based on the total solid content into the stirring device, start the stirring device, with a revolution speed of 30 rpm and a rotation speed of 12 m s -1 , stir and disperse for 30 min;

[0084] (2) Add a V50 solution accounting for 0.3% of the total solids and a PVDF solution with a concentration of 4% (75% of the calculated dosage) into the stirring device. Among them, the concentration of the V50 solution is 10%. After revolving at 20 rpm for about 5 minutes, start the self-rotation at 13 m s -1 , turn on the vacuum, with a vacuum degree of -80 KPa, and stir and disperse for 55 minutes. At this time, the solid content is 63%;

[0085] (3) Add the remaining 25% of the PVDF glue solution into the stirring device. After revolving at 30 rpm for about 5 minutes, start the self-rotation at 10 m s -1 , turn on the vacuum, with a vacuum degree of -100 Kpa, and stir and disperse for 25 minutes; at this time, the solid content is 59%;

[0086] (4) Add a CNT dispersion solution accounting for 1% of the total solids into the stirring device. After revolving at 20 rpm for about 5 minutes, start the self-rotation at 10 m s -1 , turn on the vacuum, with a vacuum degree of -80 KPa, and stir and disperse for 25 minutes; at this time, the solid content is 58%;

[0087] (5) Add the diluting solvent NMP into the stirring device and adjust the solid content to 50%. After revolving at 20 rpm for about 5 minutes, start the self-rotation at 10 m s -1 , turn on the vacuum, with a vacuum degree of -80 Kpa, and stir and disperse for 35 minutes. Measure the viscosity of the slurry to be 4000 mPa·s;

[0088] (6) Vacuum the stirring device to -90 kPa, and carry out a low-speed stirring and defoaming treatment on the slurry at 20 rpm for 0.5 h, and then sieve it with a 425-mesh sieve to obtain the fineness of the positive electrode slurry for sodium-ion batteries to be 10 - 30 μm.

[0089] Example 2

[0090] In this example, the mass ratio of the effective solid components is:

[0091] NFPP:SP:graphene:PTFE = 93:2:0.5:4.5.

[0092] The pulping process for preparing the positive electrode of the sodium-ion battery includes the following steps:

[0093] (1) Add 2% of the conductive agent SP and 93% of the sodium iron pyrophosphate (NFPP) positive electrode material of the total solids into the stirring device, start the stirring device, revolve at 30 rpm, and self-rotate at 12 m s -1 , and stir for 70 minutes;

[0094] (2) Add a PVP solution accounting for 0.5% of the total solids and a 10% PTFE solution (75% of the calculated dosage) to the stirring device. Among them, the concentration of the PVP solution is 5%. After about 10 minutes of revolution at 60 rpm, start the rotation at 15 m s -1 , turn on the vacuum, with a vacuum degree of -100 KPa, and stir and disperse for 80 minutes. At this time, the solid content is 64%;

[0095] (3) Add the remaining 25% PTFE glue solution to the stirring device. After about 5 minutes of revolution at 60 rpm, start the rotation at 15 m s -1 , turn on the vacuum, with a vacuum degree of -80 Kpa, and stir and disperse for 55 minutes; at this time, the solid content is 60%;

[0096] (4) Add a graphene dispersion accounting for 0.5% of the total solids to the stirring device. After about 5 minutes of revolution at 60 rpm, start the rotation at 15 m s -1 , turn on the vacuum, with a vacuum degree of -90 KPa, and stir and disperse for 35 minutes; at this time, the solid content is 59%;

[0097] (5) Add the diluting solvent NMP to the stirring device and adjust the solid content to 55%. After about 5 minutes of revolution at 60 rpm, start the rotation at 15 m s -1 , turn on the vacuum, with a vacuum degree of -90 Kpa, and stir and disperse for 25 minutes. Measure the viscosity of the slurry to be 7000 mPa·s;

[0098] (6) Vacuum the stirring device to -90 kPa, and carry out low-speed stirring and defoaming treatment on the slurry at 30 rpm of revolution for 1 hour, and then sieve it with a 425-mesh sieve to obtain the fineness of the positive electrode slurry for sodium-ion batteries to be 5 - 30 μm.

[0099] Example 3

[0100] In this example, the mass ratio of the effective solid components is:

[0101] NCFM:KS-6:CNT:PVDF = 91:3:1:5.

[0102] The pulping process for preparing the positive electrode of the sodium-ion battery includes the following steps:

[0103] (1) Add 3% of the conductive agent KS-6 and 91% of the sodium copper iron manganese oxide (NCFM) cathode material of the total solids to the stirring device, turn on the stirring device, revolve at 30 rpm, and rotate at 12 m s -1 , stir and disperse for 90 minutes;

[0104] (2) Add a V50 solution accounting for 0.1% of the total solids and a PVDF solution with a concentration of 10% (75% of the calculated dosage) into the stirring device. Among them, the concentration of the V50 solution is 20%. After about 5 minutes of revolution at 40 rpm, start the rotation at 10 m s -1 , turn on the vacuum, with a vacuum degree of -90 KPa, and stir and disperse for 70 minutes. At this time, the solid content is 60%;

[0105] (3) Add the remaining 25% of the PVDF glue solution into the stirring device. After about 5 minutes of revolution at 30 rpm, start the rotation at 10 m s -1 , turn on the vacuum, with a vacuum degree of -100 KPa, and stir and disperse for 45 minutes; at this time, the solid content is 57%;

[0106] (4) Add a CNT dispersion accounting for 1% of the total solids into the stirring device. After about 5 minutes of revolution at 40 rpm, start the rotation at 13 m s -1 , turn on the vacuum, with a vacuum degree of -90 KPa, and stir and disperse for 15 minutes; at this time, the solid content is 56%;

[0107] (5) Add the diluting solvent NMP into the stirring device and adjust the solid content to 53%. After about 5 minutes of revolution at 40 rpm, start the rotation at 13 m s -1 , turn on the vacuum, with a vacuum degree of -90 KPa, and stir and disperse for 15 minutes. Measure the viscosity of the slurry to be 6000 mPa·s;

[0108] (6) Vacuumize the stirring device to -90 kPa, and carry out low-speed stirring and defoaming treatment on the slurry at 10 rpm of revolution for 2 hours, and then sieve with a 425-mesh sieve to obtain the fineness of the positive electrode slurry for sodium-ion batteries to be 5 - 30 μm.

[0109] Example 4

[0110] In this example, the mass ratio of the effective solid components is as follows:

[0111] NVPF:SP:graphene:PVDF = 90:4:1:5.

[0112] The pulping process for preparing the positive electrode of the sodium-ion battery includes the following steps:

[0113] (1) Add a conductive agent SP accounting for 4% of the total solids and 90% of the self-made sodium vanadium fluorophosphate (NVPF) positive electrode material into the stirring device, turn on the stirring device, with a revolution of 30 rpm and a rotation of 12 m s -1 , and stir and disperse for 60 minutes;

[0114] (2) Add a PVP solution accounting for 0.3% of the total solid content and a PVDF solution with a concentration of 6% (75% of the calculated dosage) into the stirring device. Among them, the concentration of the PVP solution is 10%. After revolving at 30 rpm for about 5 min, start the self-rotation at 15 m s -1 , turn on the vacuum, with a vacuum degree of -100 KPa, and stir and disperse for 75 min. At this time, the solid content is 65%;

[0115] (3) Add the remaining 25% of the PVDF glue solution into the stirring device. After revolving at 40 rpm for about 5 min, start the self-rotation at 13 m s -1 , turn on the vacuum, with a vacuum degree of -80 KPa, and stir and disperse for 35 min; at this time, the solid content is 61%;

[0116] (4) Add a graphene dispersion accounting for 1% of the total solid content into the stirring device. After revolving at 50 rpm for about 5 min, start the self-rotation at 15 m s -1 , turn on the vacuum, with a vacuum degree of -80 KPa, and stir and disperse for 35 min; at this time, the solid content is 59%;

[0117] (5) Add the diluting solvent NMP into the stirring device and adjust the solid content to 55%. After revolving at 35 rpm for about 5 min, start the self-rotation at 13 m s -1 , turn on the vacuum, with a vacuum degree of -80 Kpa, and stir and disperse for 35 min. Measure the viscosity of the slurry to be 5800 mPa·s;

[0118] (6) Evacuate the stirring device to -90 kPa, and carry out low-speed stirring and defoaming treatment on the slurry at 20 rpm for 1 h, and then sieve it with a 425-mesh sieve to obtain the fineness of the positive electrode slurry for sodium-ion batteries to be 5 - 30 μm.

[0119] Example 5

[0120] In this example, the mass ratio of the effective solid components is:

[0121] NMFPP:SP:CNT:PTFE = 95:1.5:0.5:3.

[0122] The pulping process for preparing the positive electrode of the sodium-ion battery includes the following steps:

[0123] (1) Add 1.5% of the conductive agent SP and 95% of the self-made sodium iron manganese phosphate (NMFPP) positive electrode material of the total solid content into the stirring device, start the stirring device, revolve at 30 rpm, and self-rotate at 15 m s -1 , and stir for 50 min;

[0124] (2) Add a V50 dispersion aid solution accounting for 0.2% of the total solids and a PTFE solution with a mass concentration of 5% (75% of the calculated dosage) into the stirring device. Among them, the mass concentration of the V50 solution is 10%. After revolving at 50 rpm for about 10 min, start the self-rotation at 14 m s -1 , turn on the vacuum, with a vacuum degree of -90 KPa, and stir and disperse for 60 min. At this time, the solid content is 64%;

[0125] (3) Add the remaining 25% by mass of PTFE (concentration of 5%) colloidal solution into the stirring device. After revolving at 50 rpm for about 5 min, start the self-rotation at 13 m s -1 , turn on the vacuum, with a vacuum degree of -100 Kpa, and stir and disperse for 40 min; at this time, the solid content is 61%;

[0126] (4) Add a CNT dispersion liquid accounting for 0.5% of the total solids into the stirring device. After revolving at 45 rpm for about 5 min, start the self-rotation at 14 m s -1 , turn on the vacuum, with a vacuum degree of -100 KPa, and stir and disperse for 30 min; at this time, the solid content is 59%;

[0127] (5) Add the diluting solvent NMP into the stirring device and adjust the solid content to 54%. After revolving at 30 rpm for about 5 min, start the self-rotation at 14 m s -1 , turn on the vacuum, with a vacuum degree of -100 Kpa, and stir and disperse for 30 min. Measure the viscosity of the slurry to be 6300 mPa·s;

[0128] (6) Vacuum the stirring device to -90 kPa, and carry out a low-speed stirring and defoaming treatment on the slurry at 30 rpm for 40 min, and then sieve it with a 425-mesh sieve to obtain the fineness of the positive electrode slurry for sodium-ion batteries to be 5 - 30 μm.

[0129] Comparative Example 1

[0130] In this comparative example, the mass ratio of the effective solid components is:

[0131] NVP:SP:CNT:PVDF = 94:1.5:1:3.5 (the same as in Example 1).

[0132] The pulping process for the positive electrode of the sodium-ion battery includes the following steps:

[0133] (1) Add a PVDF colloidal solution accounting for 3.5% of the total solids, with a concentration of 4%, and the added amount is all the colloidal solution;

[0134] (2) Add the conductive agent Super P accounting for 1.5% of the total solids into the stirring device, revolve at 20 rpm for 5 min, start the self-rotation at 13 m s -1 , and stir for 40 min;

[0135] (3) Add sodium vanadium phosphate cathode material with a total solid content of 94% into the stirring device. After orbiting at 20 rpm for 5 min, start the rotation at 13 m s -1 , turn on the vacuum, with a vacuum degree of -80 KPa, and stir and disperse for 90 min. At this time, the solid content is 63%;

[0136] (4) Add CNT dispersion liquid with a total solid content of 1% into the stirring device. After orbiting at 20 rpm for about 5 min, start the rotation at 10 m s -1 , turn on the vacuum, with a vacuum degree of -80 KPa, and stir and disperse for 45 min; at this time, the solid content is 61%;

[0137] (5) Add 15% of NMP into the stirring device in three times. Each time 5% of NMP is added, and then stir and disperse at an orbiting speed of 25 rpm and a rotating speed of 10 m s -1 for 30 min to obtain a slurry with a solid content of 46% and a viscosity of 4500 mPa s;

[0138] (6) Vacuumize the stirring device to -90 kPa, and carry out low-speed stirring and defoaming treatment on the slurry at an orbiting speed of 20 rpm for 0.5 h. Then sieve with a 425-mesh sieve. It is found that part of the rubber material cannot pass through the sieve. The fineness of the cathode slurry is measured by a fineness meter to be 10 - 50 μm.

[0139] The difference between Example 1 and Comparative Example 1 is that in Example 1, the semi-dry pulping method adopted in the present invention is used, while in the comparative example, the wet pulping method is used. Through comparison, it can be found that the semi-dry pulping method can not only shorten the pulping time (250 min - 310 min), but also increase the solid content of the slurry, reduce the viscosity of the slurry, and optimize the fineness of the slurry.

[0140] Comparative Example 2

[0141] In this Comparative Example 2, the mass ratio of the effective solid components is:

[0142] NFPP:SP:graphene:PTFE = 93:2:0.5:4.5 (the same as Example 2)

[0143] The pulping process for the positive electrode of the sodium-ion battery includes the following steps:

[0144] (1) Add PTFE glue solution with a total solid content of 4.5% into the stirring device, with a concentration of 10%, and the addition amount is the total glue solution;

[0145] (2) Add the conductive agent Super P with a total solid content of 2% into the stirring device, orbit at 20 rpm for 5 min, and start the rotation at 13 m s -1 , and stir for 40 min;

[0146] (3) Add sodium iron pyrophosphate phosphate cathode material with 93% of the total solid content into the stirring device. After orbiting at 20 rpm for 5 minutes, start the self-rotation at 13 m s -1 , start the vacuum, with the vacuum degree being -80 KPa, stir and disperse for 120 minutes. At this time, the solid content is 63%;

[0147] (4) Add graphene dispersion liquid with 0.5% of the total solid content into the stirring device. After orbiting at 20 rpm for about 5 minutes, start the self-rotation at 10 m s -1 , start the vacuum, with the vacuum degree being -80 KPa, stir and disperse for 60 minutes; At this time, the solid content is 61%;

[0148] (5) Add 15% of NMP into the stirring device in three times. After adding 5% of NMP each time, stir and disperse at the speed of orbiting at 25 rpm and self-rotation at 10 m s -1 for 30 minutes to obtain a slurry with a solid content of 48% and a viscosity of 8500 mPa s;

[0149] (6) Vacuumize the stirring device to -90 kPa, and carry out low-speed stirring and defoaming treatment on the slurry at 30 rpm for 1 hour. Then sieve with a 425-mesh sieve, and it is found that part of the rubber compound cannot pass through the sieve. The fineness of the positive electrode slurry is tested by a fineness meter to be 5 - 60 μm.

[0150] The difference between Example 2 and Comparative Example 2 is that in Example 2, the semi-dry pulping method adopted in the present invention is used, while in the comparative example, the wet pulping method is used. Through comparison, it can be found that the semi-dry pulping method can shorten the pulping time (355 min - 385 min), improve the solid content of the slurry, reduce the viscosity of the slurry, and optimize the fineness of the slurry.

[0151] Comparative Example 3

[0152] In this comparative example, the mass ratio of the effective solid components is:

[0153] NCFM:KS-6:CNT:PVDF = 91:3:1:5.

[0154] The pulping process for the positive electrode of the sodium-ion battery includes the following steps:

[0155] (1) Add PVDF glue solution with 5% of the total solid content into the stirring device, with a concentration of 10% and the added amount being all the glue solution;

[0156] (2) Add the conductive agent KS-6 with 3% of the total solid content into the stirring device, orbit at 20 rpm for 5 minutes, and start the self-rotation at 15 ms -1 , stir for 60 minutes;

[0157] (3) Add 91% of the total amount of sodium copper iron manganeseate (NCFM) cathode material into the stirring device. After orbiting at 20 rpm for 5 min, start the rotation at 13 m s -1 , turn on the vacuum, with the vacuum degree of -90 KPa, stir and disperse for 120 min. At this time, the solid content is 63%;

[0158] (4) Add 1% of the CNT dispersion liquid based on the total solid amount into the stirring device. After orbiting at 40 rpm for about 5 min, start the rotation at 14 m s -1 , turn on the vacuum, with the vacuum degree of -90 KPa, stir and disperse for 60 min; At this time, the solid content is 61%;

[0159] (5) Add 15% of NMP into the stirring device in three times. Each time after adding 5% of NMP, stir and disperse at the speed of orbiting at 25 rpm and rotating at 13 m s -1 for 30 min to obtain a slurry with a solid content of 50% and a viscosity of 7800 mPa s;

[0160] (6) Vacuum the stirring device to -90 kPa, and carry out low-speed stirring and defoaming treatment on the slurry at 10 rpm for 2 h. Then sieve with a 425-mesh sieve, and it is found that part of the glue cannot pass through the sieve. The fineness of the cathode slurry is measured by a fineness meter to be 10 - 55 μm.

[0161] The difference between Example 3 and Comparative Example 3 is that in Example 3, the semi-dry pulping method adopted in the present invention is used, while in Comparative Example 3, the wet pulping method is used. Through comparison, it can be found that the semi-dry pulping method can not only shorten the pulping time (295 min - 470 min), but also increase the solid content of the slurry, reduce the viscosity of the slurry, and optimize the fineness of the slurry.

[0162] Based on the above examples and comparative examples, it can be found that the semi-dry pulping method proposed in the present invention is applicable to phosphate-based cathode materials and layered oxide-based cathode materials. While shortening the pulping time and increasing the solid content of the slurry, it can also reduce the viscosity of the slurry to facilitate subsequent coating and leveling of the slurry, and at the same time optimize the fineness distribution of the slurry, and is particularly suitable for the preparation of cathode slurries for sodium-ion batteries.

[0163] The above are only several embodiments of the present application, and do not impose any form of limitation on the present application. Although the present application is disclosed as above with preferred embodiments, it is not used to limit the present application. Any person skilled in the art, without departing from the scope of the technical solution of the present application, making some changes or modifications using the technical content disclosed above is equivalent to equivalent embodiments and all belong to the scope of the technical solution.

Claims

1. A method for preparing a positive electrode paste for a sodium-ion battery, characterized in that, The preparation method includes the following steps: S1: Mix and stir-disperse the raw materials containing the first conductive agent and the cathode material to obtain solid powder. S2: Mix the solid powder in step S1, the dispersion aid solution, and a partial amount of the binder solution, and stir-disperse under vacuum conditions to obtain slurry I. S3: Mix the slurry I in step S2 and the remaining amount of the binder solution, and stir-disperse under vacuum conditions to obtain slurry II. S4: Mix the slurry II in step S3 and the second conductive agent, and stir-disperse under vacuum conditions to obtain slurry III. S5: Mix the slurry III in step S4 and the solvent, and stir-disperse under vacuum conditions to obtain slurry IV. S6: Perform defoaming treatment and sieving on the slurry IV in step S5 to obtain the sodium-ion battery cathode slurry.

2. The method for preparing a positive electrode paste for a sodium-ion battery according to claim 1, characterized in that, In step S2, when the solid powder, the dispersion aid solution, and a partial amount of the binder solution are mixed, the solid content is controlled to be 60-65%. Preferably, in step S5, when the slurry III and the solvent are mixed, the solid content is controlled to be 50-55%.

3. The method for preparing a positive electrode paste for a sodium-ion battery according to claim 1, characterized in that, In step S5, the viscosity of the slurry IV is controlled to be 4000-7000 mPa·s. Preferably, in step S3, the stirring speed when the slurry I and the remaining amount of the binder solution are mixed is 20-60 rpm. In step S4, the stirring speed when the slurry II and the second conductive agent are mixed is 20-60 rpm.

4. The method for preparing a positive electrode paste for a sodium-ion battery according to claim 1, characterized in that, In steps S2, S3, and S5, the dispersion linear velocity under vacuum conditions is independently 10 to 15 m / s -1 , and the degree of vacuum is independently -80 to -100 kPa; Preferably, in step S6, the stirring speed for the defoaming treatment of the slurry IV is 10-30 rpm, and the defoaming time is 0.5 h-2 h.

5. The method for preparing a positive electrode paste for a sodium-ion battery according to claim 1, characterized in that, The stirring and dispersing time in step S1 is 30-90 min. Preferably, the stirring and dispersing time in step S2 is 60-90 min. Preferably, the stirring and dispersing time in step S3 is 30-60 min. Preferably, the stirring and dispersing time in step S4 is 20-40 min. Preferably, the stirring and dispersing time in step S5 is 30-40 min.

6. The method for preparing a positive electrode paste for a sodium-ion battery according to claim 1, characterized in that, The cathode material is selected from layered oxide materials and / or polyanion compound materials. Preferably, the first conductive agent is selected from highly conductive graphite and / or conductive carbon black. The second conductive agent is selected from carbon nanotube dispersion liquid and / or graphene dispersion liquid. Preferably, the solute in the binder solution is polyvinylidene fluoride and / or polytetrafluoroethylene. The solute in the dispersion aid solution is selected from polyvinylpyrrolidone or acrylic acid and acrylate derivative copolymer modified materials. The solvents in the dispersion aid solution and the binder solution are both N-methylpyrrolidone.

7. A positive electrode paste for a sodium-ion battery, characterized in that, It is prepared by the method described in any one of claims 1-6.

8. The positive electrode paste for a sodium-ion battery according to claim 7, characterized in that, The viscosity of the sodium-ion battery cathode slurry is 4000-7000 mPa·s, and the fineness is 5-30 μm.

9. The positive electrode paste for a sodium-ion battery according to claim 1, characterized in that, The solid mass fraction of the sodium-ion battery cathode slurry is: 90-95% of the cathode material, 2-5% of the conductive agent, 3-5% of the binder, and 0.1%-1% of the dispersion aid. Preferably, the conductive agent includes a first conductive agent and a second conductive agent, and the mass ratio of the first conductive agent to the second conductive agent is 1.5-4:

1.

10. A sodium-ion battery, comprising a positive electrode paste; characterized in that, The positive electrode paste is prepared by using the method described in any one of claims 1 to 6.