CN114725310A - Positive electrode slurry and preparation method thereof, positive plate and secondary battery - Google Patents

Positive electrode slurry and preparation method thereof, positive plate and secondary battery Download PDF

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Publication number
CN114725310A
CN114725310A CN202210375325.2A CN202210375325A CN114725310A CN 114725310 A CN114725310 A CN 114725310A CN 202210375325 A CN202210375325 A CN 202210375325A CN 114725310 A CN114725310 A CN 114725310A
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positive electrode
stirring
slurry
positive
solvent
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陈黄
钟欣
曾敏
李雄成
王林桥
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Hunan Nafang New Energy Technology Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention belongs to the technical field of secondary batteries, and particularly relates to a positive electrode slurry and a preparation method thereof, a positive plate and a secondary battery, which comprise the following steps: step S1, mixing the positive electrode active substance, the conductive agent and the polyimide adhesive to obtain a premix; step S2, adding part of the solvent into the premix, and mixing and stirring to obtain first mixed slurry; and step S3, adding the first mixed slurry into the residual solvent, mixing and stirring to obtain the anode slurry. According to the preparation method of the anode slurry, the polyimide binder replaces the traditional PVDF binder and does not contain a fluorine group binder, so that the gel with an alkaline active substance can be effectively avoided, the dispersion effect and the fluidity of the anode slurry are good, and no agglomeration exists.

Description

Positive electrode slurry, preparation method thereof, positive plate and secondary battery
Technical Field
The invention belongs to the technical field of secondary batteries, and particularly relates to a positive electrode slurry, a preparation method of the positive electrode slurry, a positive plate and a secondary battery.
Background
The existing positive electrode slurry is usually a nickel cobalt lithium manganate material, a lithium iron phosphate material and the like, and along with the rapid development and development requirements of battery technology, the sodium ion battery also becomes a research hotspot in succession, and compared with a lithium battery, the cost of the sodium ion battery can be reduced by more than 30%.
The main materials of the positive electrode of the sodium-ion battery are generally divided into four types, namely layered transition metal oxide, polyanion material, Prussian blue analogue and organic positive electrode material, wherein the layered transition metal oxide is one of the earliest and higher energy density materials in the current research and is one of the most popular materials in the research field of the sodium-ion battery. The layered transition metal oxide is NaxMO2(M is at least one of Ni, Co, Mn, Fe, Cu, Ti and V, and x is more than 0 and less than or equal to 1), but the electron conductivity of the material per se is poor, and conductive materials with excellent electrical property, such as carbon nano tubes, graphene and the like, need to be added to meet the requirement of the gram capacity of the material to meet the design requirement of the product. Meanwhile, the layered transition metal oxide is a nano-grade material generally, and has high residual alkali content, which puts higher requirements on the processing of the anode slurry. Therefore, it is necessary to develop a preparation method.
Disclosure of Invention
One of the objects of the present invention is: aiming at the defects of the prior art, the polyimide binder is used for replacing the traditional PVDF binder, the phenomenon that the polyimide binder gels with alkaline active substances can be effectively avoided, the solvent is added in two times, the positive active substances are crushed and mixed in a high-viscosity state, and the positive slurry which is good in dispersion effect and fluidity and free of agglomeration is obtained.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of positive electrode slurry comprises the following steps:
step S1, mixing the positive electrode active substance, the conductive agent and the polyimide adhesive to obtain a premix;
step S2, adding part of the solvent into the premix, and mixing and stirring to obtain first mixed slurry;
and step S3, adding the first mixed slurry into the residual solvent, mixing and stirring to obtain the anode slurry.
Preferably, the weight part ratio of the positive electrode active material to the conductive agent to the polyimide binder is 90-98: 1-5: 1-4.
Preferably, the weight part ratio of the positive electrode active material to the conductive agent to the polyimide binder to the solvent is 90-98: 1-5: 1-4: 30-50.
Preferably, the amount of the solvent added in the step S2 is 10% to 25% of all the solvents, and the amount of the solvent added in the step S3 is 75% to 90% of all the solvents.
Preferably, the revolution rate of the stirring in the step S1 is 10rpm/min to 30rpm/min, the rotation rate is 250rpm/min to 350rpm/min, the stirring time is 80min to 100min, and the stirring temperature is 40 ℃ to 50 ℃.
Preferably, the revolution rate of the stirring in the step S2 is 20rpm/min to 30rpm/min, the rotation rate is 1500rpm/min to 1800rpm/min, the stirring time is 80min to 100min, and the stirring temperature is 40 ℃ to 50 ℃.
Preferably, the step S3 further includes, after mixing and stirring, removing bubbles by vacuum pumping, and filtering to obtain the positive electrode slurry, wherein the vacuum degree during the vacuum pumping is less than or equal to-85 KPa, and the pore size of the filter screen is 50 μm to 100 μm.
The second purpose of the invention is: aiming at the defects of the prior art, the positive electrode slurry is provided, the positive electrode active substance is fully crushed and mixed, the slurry has good dispersion effect and fluidity, and no agglomeration exists.
In order to achieve the purpose, the invention adopts the following technical scheme:
the positive electrode slurry is prepared by the preparation method of the positive electrode slurry.
The third purpose of the invention is that: aiming at the defects of the prior art, the positive plate has good electrochemical performance and stable performance.
In order to achieve the purpose, the invention adopts the following technical scheme:
the positive plate comprises a positive current collector and a positive active coating arranged on at least one surface of the positive current collector, wherein the positive slurry of the positive active coating is coated on the surface of the positive current collector and dried to form the positive active coating.
The fourth purpose of the invention is that: aiming at the defects of the prior art, the secondary battery is provided, and has good electrochemical performance and stable performance.
In order to achieve the purpose, the invention adopts the following technical scheme:
a secondary battery comprises the positive plate.
Compared with the prior art, the invention has the beneficial effects that: according to the preparation method of the anode slurry, the polyimide binder is used for replacing the traditional PVDF binder, the phenomenon that the polyimide binder is gelled with an alkaline active substance can be effectively avoided, the solvent is added twice, the anode active substance is crushed and mixed in a high-viscosity state, and the anode slurry with good dispersion effect and fluidity and no agglomeration is obtained.
Detailed Description
1. A preparation method of positive electrode slurry comprises the following steps:
step S1, mixing the positive electrode active substance, the conductive agent and the polyimide adhesive to obtain a premix;
step S2, adding part of the solvent into the premix, and mixing and stirring to obtain first mixed slurry;
and step S3, adding the first mixed slurry into the residual solvent, mixing and stirring to obtain the anode slurry.
According to the preparation method of the anode slurry, the polyimide binder is used for replacing the traditional PVDF binder, the phenomenon that the polyimide binder is gelled with an alkaline active substance can be effectively avoided, the solvent is added in two times, part of the solvent is added in the first time, the anode active substance is crushed and mixed in a high-viscosity state, and the rest of the solvent is added in the second time, so that the anode active substance is crushed and mixed in the second timeThe raw material components are fully mixed, so that the anode slurry with good dispersion effect and fluidity and no agglomeration is obtained. The positive active material comprises a layered transition metal oxide, a polyanion material, a Prussian blue analogue and an organic positive material, wherein the layered transition metal oxide is NaxMO2(M is at least one of Ni, Co, Mn, Fe, Cu, Ti and V, and x is more than 0 and less than or equal to 1). The conductive agent is one or more than two of Super-P, acetylene black, KS-6, VGCF, a carbon nano tube and graphene. The solvent is N-methyl pyrrolidone.
Preferably, the weight part ratio of the positive electrode active material to the conductive agent to the polyimide binder is 90-98: 1-5: 1-4. The weight part ratio of the positive electrode active material to the conductive agent to the polyimide binder is 95.3:2.2:2.5, 90:1.5:1.5, 92:2.5:3, 94:3.5:3.5, 95:1:4, 96:3.4:3.5 and 98:1: 2.5.
Preferably, the weight part ratio of the positive electrode active material to the conductive agent to the polyimide binder to the solvent is 90-98: 1-5: 1-4: 30-50. The weight ratio of the positive electrode active material to the conductive agent to the polyimide binder to the solvent is 95.3:2.2:2.5:30, 90:1.5:1.5:32, 92:2.5:3:40, 94:3.5:3.5:35, 95:1:4:38, 96:3.4:3.5:40, and 98:1:2.5: 50.
Preferably, the amount of the solvent added in the step S2 is 10% to 25% of all the solvents, and the amount of the solvent added in the step S3 is 75% to 90% of all the solvents. The amount of the solvent added in step S2 is 10%, 13%, 15%, 17%, 19%, 20%, 22%, 24%, 25% of all the solvents, and the amount of the solvent added in step S3 is 75%, 76%, 78%, 79%, 80%, 82%, 84%, 86%, 88%, 90% of all the solvents.
Preferably, the revolution rate of the stirring in the step S1 is 10rpm/min to 30rpm/min, the rotation rate is 250rpm/min to 350rpm/min, the stirring time is 80min to 100min, and the stirring temperature is 40 ℃ to 50 ℃. The revolution rate of the stirring in step S1 was 10rpm/min, 12rpm/min, 14rpm/min, 16rpm/min, 18rpm/min, 20rpm/min, 24rpm/min, 26rpm/min, 28rpm/min, 30 rpm/min. The rotation speed is 250rpm/min, 270rpm/min, 280rpm/min, 300rpm/min, 320rpm/min, 340rpm/min and 350rpm/min, and the stirring time is 80min, 82min, 85min, 88min, 90min, 92min, 94min, 95min, 98min and 100 min. The stirring temperature is 40 deg.C, 42 deg.C, 43 deg.C, 45 deg.C, 46 deg.C, 47 deg.C, 49 deg.C, 50 deg.C.
Preferably, the revolution speed of the stirring in the step S2 is 20rpm/min to 30rpm/min, the rotation speed is 1500rpm/min to 1800rpm/min, the stirring time is 80min to 100min, and the stirring temperature is 40 ℃ to 50 ℃. The revolution rate of stirring in step S2 was 20rpm/min, 22rpm/min, 24rpm/min, 26rpm/min, 28rpm/min, and 30 rpm/min. The spin rate was 1500rpm/min, 1550rpm/min, 1600rpm/min, 1650rpm/min, 1700rpm/min, 1750rpm/min, 1800 rpm/min. Stirring for 80min, 82min, 85min, 90min, 93min, 96min, 98min, and 100min at 40 deg.C, 42 deg.C, 43 deg.C, 45 deg.C, 46 deg.C, 47 deg.C, 49 deg.C, and 50 deg.C.
Preferably, the step S3 further includes, after mixing and stirring, removing bubbles by vacuum pumping, and filtering to obtain the positive electrode slurry, wherein the vacuum degree during the vacuum pumping is less than or equal to-85 KPa, and the pore size of the filter screen is 50 μm to 100 μm. And vacuumizing is performed to facilitate gas discharge in the anode slurry, and the filter screen is used for filtering the anode slurry.
2. A positive electrode slurry is provided, in which positive electrode active materials are sufficiently crushed and mixed, and which has good dispersion effect and fluidity without aggregation. The positive electrode slurry is prepared by the preparation method of the positive electrode slurry. By using the preparation method of the anode slurry, the fluorine group in the existing PVDF binder is prevented from gelling with the alkaline active substance, the environmental pollution is avoided, and the material is environment-friendly. And the solvent is added in two times, the positive active material is crushed and mixed under the action of high viscosity for the first time, and the solvent is added for the second time, so that the raw material components are fully mixed to obtain stable positive slurry.
3. The positive plate has good electrochemical performance and stable performance. The positive plate comprises a positive current collector and a positive active coating arranged on at least one surface of the positive current collector, wherein the positive slurry of the positive active coating is coated on the surface of the positive current collector and dried to form the positive plate.
4. A secondary battery has good electrochemical performance and stable performance. A secondary battery comprises the positive plate. The secondary battery may be any one of a lithium ion battery, a sodium ion battery, a magnesium ion battery, a potassium ion battery, and a calcium ion battery, and preferably, the secondary battery is a sodium ion battery. The following is a sodium ion battery as an example.
Specifically, a sodium ion battery includes positive plate, negative plate, diaphragm, electrolyte and casing, positive plate and negative plate are separated to the diaphragm, and positive plate, negative plate, diaphragm and electrolyte are installed to the casing. The positive plate is prepared by the method.
The negative plate comprises a negative current collector and a negative active material layer arranged on the surface of the negative current collector, wherein the negative active material layer comprises a negative active material, and the negative active material can be one or more of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based materials, tin-based materials, lithium titanate or other metals capable of forming an alloy with lithium. Wherein, the graphite can be selected from one or more of artificial graphite, natural graphite and modified graphite; the silicon-based material can be one or more selected from simple substance silicon, silicon-oxygen compound, silicon-carbon compound and silicon alloy; the tin-based material can be one or more selected from simple substance tin, tin oxide compound and tin alloy. The negative electrode current collector is generally a structure or a part for collecting current, and the negative electrode current collector may be any material suitable for use as a negative electrode current collector of a lithium ion battery in the art, for example, the negative electrode current collector may include, but is not limited to, a metal foil, and the like, and more specifically, may include, but is not limited to, a copper foil, and the like.
The lithium ion battery also comprises electrolyte, and the electrolyte comprises an organic solvent, electrolyte lithium salt and an additive. Wherein the electrolyte lithium salt may be LiPF used in a high-temperature electrolyte6And/or LiBOB; or LiBF used in low-temperature electrolyte4、LiBOB、LiPF6At least one of; or LiBF used in anti-overcharge electrolyte4、LiBOB、LiPF6At least one of, LiTFSI; may also be LiClO4、LiAsF6、LiCF3SO3、LiN(CF3SO2)2At least one of (a). And the organic solvent may be a cyclic carbonate including PC, EC; or chain carbonates including DFC, DMC, or EMC; and also carboxylic acid esters including MF, MA, EA, MP, etc. And additives include, but are not limited to, film forming additives, conductive additives, flame retardant additives, overcharge prevention additives, control of H in the electrolyte2At least one of additives of O and HF content, additives for improving low temperature performance, and multifunctional additives.
The separator may be any material suitable for a lithium ion battery separator in the art, and for example, may be a combination including, but not limited to, one or more of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, natural fiber, and the like.
Preferably, the material of the shell is one of stainless steel and an aluminum plastic film. More preferably, the housing is an aluminum plastic film.
The present invention will be described in further detail with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.
Example 1
Step S1, mixing 95.3 parts by mass of positive electrode active substance (layered oxide active substance), 2.2 parts by mass of polyimide binder (PI-2080) and 2.5 parts by mass of conductive carbon (carbon nano tube) in a double-planet mixer, firstly revolving at 20rpm/min by stirring, rotating at 300rpm/min by stirring, and stirring for 30min to obtain a premix;
step S2, adding 100 parts by mass of premix into 10 parts by mass of NMP solvent, wherein the amount of the NMP solvent accounts for 25% of the total solvent amount, mixing the premix and the solvent in a double-planet stirrer, and stirring the premix and the solvent at the speed of 15rpm/min for revolution and 300rpm/min for rotation, for 90min, and at the stirring temperature of 40 ℃;
step S3, adding 30 parts by mass of NMP solvent in the residual solvent into a double-planet stirrer for stirring, setting the revolution speed to be 25rpm/min, stirring and rotating at 1600rpm/min for 90min, and stirring at the temperature of 45 ℃ to obtain stable slurry with certain viscosity; and finally, opening vacuum, wherein the vacuum degree is less than or equal to-85 KPa, stirring and revolving at 15rpm/min, stirring and rotating at 600rpm/min for 45min, and sieving by using a filter screen with the specification of 75 micrometers/50 micrometers to obtain the slurry which is slowly stirred and stored for later use, wherein the viscosity of the slurry is 10560mPa.s, the solid content is 65%, and the fineness is 15 micrometers.
The results of the internal resistance test of the slurry sample feeding membrane and the viscosity stability test of the slurry show that the slurry has good dispersion effect, good slurry fluidity and no agglomeration.
Example 2
The difference from example 1 is that: the weight part ratio of the positive electrode active substance to the conductive agent to the polyimide binder to the solvent is 95:3:2: 40.
The rest is the same as embodiment 1, and the description is omitted here.
Example 3
The difference from example 1 is that: the weight part ratio of the positive electrode active substance to the conductive agent to the polyimide binder to the solvent is 98:1:1: 40.
The rest is the same as embodiment 1, and the description is omitted here.
Example 4
The difference from example 1 is that: the weight part ratio of the positive electrode active material to the conductive agent to the polyimide binder to the solvent is 91:4.5:4.5: 40.
The rest is the same as embodiment 1, and the description is omitted here.
Example 5
The difference from example 1 is that: the weight ratio of the positive electrode active material to the conductive agent to the polyimide binder to the solvent is 93:3:4: 50.
The rest is the same as embodiment 1, and the description is omitted here.
Example 6
The difference from example 1 is that: the solvent amount used in step S2 was 15 parts, and the solvent amount used in step S3 was 25 parts.
The rest is the same as embodiment 1, and the description is omitted here.
Example 7
The difference from example 1 is that: the solvent amount used in step S2 is 20 parts, and the solvent amount used in step S3 is 20 parts.
The rest is the same as embodiment 1, and the description is omitted here.
Example 8
The difference from example 1 is that: the amount of the solvent used in step S2 was 30 parts, and the amount of the solvent used in step S3 was 10 parts.
The rest is the same as embodiment 1, and the description is omitted here.
Example 9
The difference from example 1 is that: the amount of the solvent used in step S2 was 8 parts, and the amount of the solvent used in step S3 was 32 parts.
The rest is the same as embodiment 1, and the description is omitted here.
Example 10
The difference from example 1 is that: the amount of the solvent used in step S2 is 5 parts, and the amount of the solvent used in step S3 is 35 parts.
The rest is the same as embodiment 1, and the description is omitted here.
Comparative example 1
Step one, mixing 2.2 parts by mass of PVDF binder and 2.5 parts by mass of conductive carbon in a double-planet stirrer, firstly revolving at 20rpm in a stirring manner, rotating at 1600rpm in a stirring manner, stirring for 180min at the stirring temperature of less than or equal to 45 ℃, remaining 30min in the stirring time, starting vacuum, and obtaining conductive adhesive slurry with the viscosity of 9800mPa.s, wherein the vacuum degree of the conductive adhesive slurry is less than or equal to-85 KPa;
step two, mixing the prepared conductive adhesive solution and the active substance of the layered oxide in a double-planet mixer, and mixing 100 percent of the conductive adhesive slurry and 95.3 parts by mass of Na in one stepxMO2Stirring and revolving the active substance at 20rpm for revolution, stirring and rotating at 1400rpm for 240min at the stirring temperature of less than or equal to 45 ℃, starting vacuum at the vacuum degree of less than or equal to-85 KPa, stirring and revolving at 15rpm for revolution, stirring and rotating at 600rpm for 45min, and slowly stirring and storing the slurry for later use, wherein the viscosity of the slurry is 12180mPa.s, solid content 65%, fineness 25 μm.
Comparative example 2
The difference from example 1 is that: polyvinylidene fluoride binders were used instead of polyimide-based binders.
The rest is the same as embodiment 1, and the description is omitted here.
Comparative example 3
The difference from example 1 is that: the preparation method comprises the following steps:
step S1, mixing the positive electrode active substance, the conductive agent and the polyimide adhesive to obtain a premix;
and step S2, adding all the solvents into the premix, and mixing and stirring to obtain the anode slurry.
The rest is the same as embodiment 1, and the description is omitted here.
And (3) performance testing: the positive electrode pastes prepared in the above examples 1 to 10 and comparative examples 1 to 3 were subjected to a 24-hour viscosity test and a 24-hour internal resistance test on a pole piece, and the test results are recorded in table 1, and the internal resistances of the membranes sampled at different time periods when the pastes of the example 1 and the comparative example 1 were left to stand were tested (four-probe method), and the test results are recorded in table 2. The slurries of example 1 and comparative example 1 were tested under slow agitation for various periods of time and the results are reported in table 3.
TABLE 1
Figure BDA0003590493970000091
Figure BDA0003590493970000101
TABLE 2
Figure BDA0003590493970000102
TABLE 3
Figure BDA0003590493970000103
As can be seen from tables 1 to 3, the positive electrode slurry obtained by the preparation method of the present invention has a more stable viscosity than the positive electrode slurry prepared by the prior art, and the membrane obtained by the preparation method of the present invention has a lower internal resistance than the membrane prepared by the prior art, because the positive electrode slurry prepared by the preparation method of the present invention has a good dispersion effect, better slurry fluidity, no agglomeration, and a small viscosity change, so that the prepared membrane has better and more stable performance. As can be seen from table 2, the films obtained by the preparation method of the present invention have the same or similar internal resistances of the films at different test points, which indicates that the anode slurry prepared by the present invention has good uniformity, the performance difference of the films at different places is not large, and the performance is stable. From 0h to 48h, the internal resistance of the diaphragm is increased from 6.27 to 6.77, only 7.97 percent is increased, the change rate of the internal resistance of the diaphragm is less, and compared with the internal resistance of the diaphragm of comparative example 1, which is increased from 9.93 to 14.03, 41.3 percent is increased, the change rate of the internal resistance of the diaphragm is large, which indicates that the performance of the slurry is unstable. From table 3, in the process of 0h to 48h, the viscosity of the positive electrode slurry is increased from 10560mpa.s to 11500mpa.s, the viscosity is increased by 8.9%, the viscosity change is less, and the influence on the performance of the electrode plate is less; the viscosity of the positive electrode slurry of the comparative document 1 is increased from 12180mpa.s to 41600mpa.s, the viscosity is increased by 241%, the viscosity is greatly changed, and the property of the slurry is changed, so that the performance of the electrode plate is affected.
Variations and modifications to the above-described embodiments may become apparent to those skilled in the art to which the invention pertains based upon the disclosure and teachings of the above specification. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims (10)

1. A preparation method of positive electrode slurry is characterized by comprising the following steps:
step S1, mixing the positive electrode active substance, the conductive agent and the polyimide adhesive to obtain a premix;
step S2, adding part of the solvent into the premix, mixing and stirring to obtain first mixed slurry;
and step S3, adding the first mixed slurry into the residual solvent, mixing and stirring to obtain the anode slurry.
2. The method for preparing the positive electrode slurry according to claim 1, wherein the weight part ratio of the positive electrode active material, the conductive agent and the polyimide binder is 90-98: 1-5: 1-4.
3. The method for preparing the positive electrode slurry according to claim 2, wherein the weight ratio of the positive electrode active material to the conductive agent to the polyimide binder to the solvent is 90-98: 1-5: 1-4: 30-50.
4. The method for preparing a positive electrode slurry according to claim 1, wherein the amount of the solvent added in the step S2 is 10% to 25% of the total amount of the solvent, and the amount of the solvent added in the step S3 is 75% to 90% of the total amount of the solvent.
5. The method for producing positive electrode slurry according to claim 1, wherein the revolution rate of stirring in step S1 is 10 to 30rpm/min, the rotation rate is 250 to 350rpm/min, the stirring time is 80 to 100min, and the stirring temperature is 40 to 50 ℃.
6. The method for producing positive electrode slurry according to claim 1, wherein the revolution rate of stirring in step S2 is 20 to 30rpm/min, the rotation rate is 1500 to 1800rpm/min, the stirring time is 80 to 100min, and the stirring temperature is 40 to 50 ℃.
7. The method for preparing the cathode slurry according to claim 1, wherein the step S3 further comprises, after mixing and stirring, removing bubbles by vacuum pumping, and filtering to obtain the cathode slurry, wherein the vacuum degree in the vacuum pumping is less than or equal to-85 KPa, and the pore size of the filter screen is 50 μm to 100 μm.
8. A positive electrode slurry produced by the method for producing a positive electrode slurry according to any one of claims 1 to 7.
9. A positive plate is characterized by comprising a positive current collector and a positive active coating arranged on at least one surface of the positive current collector, wherein the positive active coating is formed by coating the positive slurry of claim 8 on the surface of the positive current collector and drying the positive active coating.
10. A secondary battery comprising the positive electrode sheet according to claim 9.
CN202210375325.2A 2022-04-11 2022-04-11 Positive electrode slurry and preparation method thereof, positive plate and secondary battery Pending CN114725310A (en)

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