CN112271285A - Preparation process of lithium ion battery anode slurry - Google Patents
Preparation process of lithium ion battery anode slurry Download PDFInfo
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
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- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
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- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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- H—ELECTRICITY
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- H01M4/00—Electrodes
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- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
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Abstract
The invention belongs to the field of lithium ion battery manufacturing, and particularly relates to a preparation process of lithium ion battery anode slurry, which comprises the following steps: preparing anode powder; preparing polyvinylidene fluoride (PVDF) glue solution; uniformly adding a novel carbon black conductive agent ECP-600JD into a polyvinylidene fluoride glue solution, and fully stirring to obtain a carbon black conductive glue solution; uniformly adding the oil single-walled carbon nanotubes into the carbon black conductive glue solution, and stirring and dispersing to obtain composite conductive slurry; adding the anode powder into the composite conductive slurry for preliminary kneading; kneading and stirring for the second time; adding the rest PVDF glue solution and appropriate NMP, and crushing and dispersing at high speed. The invention effectively solves the technical problems of large specific surface area, small particle size and the like of the conductive agent and the single-walled carbon tube which are difficult to disperse, constructs an effective 0D and 1D composite conductive network, plays a role in length and length, improves the stability, rheological and dispersing effects of the system slurry, and simultaneously improves the production efficiency.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a preparation process of lithium ion battery anode slurry.
Background
The lithium ion battery has the advantages of high energy density, long cycle life, high reliability, good processability, environmental friendliness and the like, and is widely applied to various electronic devices and new energy automobiles at present.
A lithium ion battery generally includes a positive plate, a negative plate, a separator spaced between the positive and negative plates, an electrolyte, and a casing. The positive pole piece comprises a positive pole current collector and a positive pole dressing coating coated on the positive pole current collector, and the negative pole piece comprises a negative pole current collector and a negative pole dressing coating coated on the negative pole current collector. When the electrode plate is prepared, firstly, an active substance (such as lithium iron phosphate, ternary, graphite and the like), a conductive agent (such as acetylene black, a carbon nano tube, carbon fiber, graphene and the like), an adhesive (such as polyvinylidene fluoride, sodium carboxymethylcellulose, styrene butadiene rubber emulsion and the like) and a solvent (such as N-methyl pyrrolidone, water and the like) are prepared into electrode slurry, then the electrode slurry is coated on the surface of a current collector according to the process requirements, and then drying treatment is carried out to obtain the coating electrode plate required by the battery.
Among them, the stability and dispersion performance of the electrode slurry have a crucial influence on the performance of the lithium ion battery. The more evenly the components in the electrode slurry are dispersed, the higher the stability is, and the better the processing performance of the pole piece is, such as stable coating surface density, good flexibility of the pole piece after rolling and the like. Meanwhile, the electrode prepared from the uniform, stable and efficiently dispersed slurry has the advantages of uniform impedance distribution at all positions, lower resistivity, high peel strength and good electrolyte infiltration effect, the polarization effect is greatly eliminated during charging and discharging, the larger the active substance can be exerted, the larger the average gram capacity and the first effect of the active substance can be improved, and therefore the comprehensive performance of the whole battery is improved.
Among various conductive agents, carbon black conductive agent ECP-600JD and single-walled carbon nanotube belong to the new conductive agents with the performance attention of the industry. Because the single-walled carbon nanotube is in a linear tubular shape and has an ultra-large length-diameter ratio, the ECP-600JD has a rich spherical branched chain structure and a large specific surface area, and the primary particle of the ECP-600JD is in a nano-spherical structure. When the two novel conductive agents are uniformly dispersed, the tubes and the points can be in multi-point winding contact through bridging, a four-way eight-reach conductive network is formed, the electrochemical reaction active sites are enriched, and the conductive effect of the pole piece is improved. The introduction of the conductive agent is particularly suitable for a high-load and high-compaction thick electrode technology, the dosage of the conductive agent can be reduced, the proportion of active substances is improved, a high-energy density battery core is developed, the conductive agent has the characteristics of pore-forming, gap filling and fluid infusion, the heating temperature rise of the thick electrode can be reduced, the long-life cycle capacity of the battery is improved, and the comprehensive electrochemical performance of the battery is improved.
In practical application, the conventional preparation method of the anode slurry is to dry and uniformly mix the conductive agent and the main material, then add the mixture into the prepared adhesive glue solution to carry out high-rotation-speed double-planet type dispersion, and stir and disperse the mixture for a certain time to obtain the final anode slurry. The dry powder conductive agent, especially the novel conductive agent, generally has a very large specific surface area and a complex and rich structure, so that the dry powder conductive agent is easy to agglomerate between different tubes and points. The uniformly dispersed anode slurry is difficult to obtain by the traditional anode slurry stirring mode, even if the anode slurry is further dispersed by methods such as ball milling and the like, the efficiency is low, the process is complex, and the realization of industrial production is difficult.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a preparation process of lithium ion battery anode slurry, which has higher slurry mixing efficiency, stronger slurry stability and better dispersibility.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a preparation process of lithium ion battery anode slurry comprises the following steps:
(1) pretreatment of the anode powder: respectively weighing positive active substances, adhesives and conductive agents, baking in a vacuum environment, cooling the baked powder, and sealing and storing the cooled material for later use;
the mass ratio of the positive active material powder, the adhesive and the conductive agent is (95-98.5) to (1-3) to (0.1-2) in sequence. The adhesive is polyvinylidene fluoride, and the conductive agent comprises a carbon black conductive agent ECP-600JD and single-walled carbon nanotubes;
(2) preparing polyvinylidene fluoride glue solution: uniformly adding polyvinylidene fluoride into an N-methyl pyrrolidone solution, and stirring in vacuum to obtain a polyvinylidene fluoride glue solution;
wherein the volume of the N-methyl pyrrolidone solution is 10-14 times of that of the polyvinylidene fluoride;
(3) uniformly adding two carbon black conductive agents ECP-600JD into the prepared polyvinylidene fluoride glue solution with the proportion of 60-80%, and stirring until the carbon black conductive agents ECP-600JD are uniformly dispersed to obtain uniformly dispersed carbon black conductive glue solution;
(4) uniformly adding the single-walled carbon nanotubes into the prepared carbon black conductive glue solution, and stirring until the single-walled carbon nanotubes are uniformly dispersed to obtain uniformly mixed conductive slurry;
(5) uniformly adding the positive active substance into the conductive slurry in several times, adding a solvent during the process, setting a stirring speed of 10-40 RPM and a dispersion speed of 100-200 RPM, and carrying out preliminary kneading and stirring to obtain a primary kneading slurry; wherein the addition amount of the solvent is 74-76% of the solid content; (this step may be referred to simply as a "high solids kneading process" to ensure adequate wetting of the internal voids of the dry powder);
(6) adding a proper amount of solvent into the primary kneading slurry, setting the stirring speed to be 10-40 Hz and the dispersion speed to be 100-200 RPM, and carrying out secondary kneading and stirring to obtain secondary kneading slurry; after the solvent is added, the solid content of the primary kneading slurry is 74-76%;
(7) adding the rest PVDF glue solution and a proper solvent, setting the stirring speed to be 25-50 RPM and the dispersion speed to be 2500-4500 RPM, and crushing and dispersing to prepare slurry with the solid content of 67-69%;
(8) and (4) adding NMP to adjust viscosity, shearing and dispersing the slurry in the step (7) at the speed of 3500-4500 RPM, and uniformly dispersing to obtain the lithium ion battery anode slurry with the solid content of 60-62%.
Preferably, the positive active material is a spheroidal lithium iron phosphate material, and the particle size of the material is D500.5 to 2 μm, and a specific surface area of 10 to 15m2The tap density of the mixture is 0.7-0.9 g/cm3。
Preferably, the mass ratio of the carbon black conductive agent ECP-600JD to the single-walled carbon nanotube is (1-3) to 1.
Preferably, the solvent is N-methylpyrrolidone (NMP) with the concentration of 4-10%.
Preferably, in the step (5), the duration of the preliminary kneading and stirring is 20-40 min.
Preferably, in the step (6), the duration of the secondary kneading and stirring is 20-40 min.
Preferably, the viscosity value of the slurry prepared in the step (8) is 4000-8000 mPa.s, and the fineness of the slurry is less than or equal to 20 mu m.
Compared with the prior art, the invention has the following advantages and positive effects:
(1) the multi-type conductive agent is added respectively to form uniformly dispersed conductive slurry, so that the problems of large specific surface area of the dry powder conductive agent and difficult dispersion of a single-walled carbon tube are solved, effective 0D and 1D conductive networks are constructed, the advantages of long and short ranges of coordinated point-line action are exerted, the active sites of electrochemical reaction are effectively increased, and a short plate with poor conductivity of lithium iron phosphate powder is made up, so that the electronic conduction efficiency of the anode piece of the lithium ion battery is improved, and the comprehensive electrochemical performances such as heating temperature rise and long cycle characteristic of the battery electrode are improved;
(2) the addition of the main material anode active substance effectively combines the processes of gradient glue adding, two-step kneading and semi-dry mixing, ensures full wetting of particles and crushing and dispersing of aggregates, shortens the stirring time, and improves the slurry mixing efficiency, the stability and the dispersing performance of the slurry;
(3) the process is simple to operate, reduces energy consumption and is easy to realize industrial application.
Drawings
FIG. 1 evaluation results of stability of slurry (standing without stirring) under the process conditions of example 1, example 2, example 3, comparative example 1, comparative example 2 and comparative example 3.
Detailed Description
In order to make the objects, technical solutions and technical effects of the present invention more clearly apparent, the present invention will be described in further detail with reference to the accompanying drawings and detailed description. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
Example 1
A preparation process of lithium ion battery anode slurry comprises the following steps:
(1) pretreatment of the anode powder: respectively weighing positive active substances, adhesives and conductive agents, baking in a vacuum environment, cooling the baked powder, and sealing and storing the cooled material for later use;
the mass ratio of the positive active substance powder, the adhesive and the conductive agent is 97.7: 2: 0.3 in sequence;
the adhesive is polyvinylidene fluoride, and the conductive agent comprises a carbon black conductive agent ECP-600JD and single-walled carbon nanotubes;
(2) preparing a polyvinylidene fluoride glue solution: uniformly adding polyvinylidene fluoride into an N-methyl pyrrolidone solution, and stirring in vacuum to obtain a polyvinylidene fluoride gel solution;
wherein the volume of the N-methyl pyrrolidone solution is 14 times of that of the polyvinylidene fluoride;
(3) uniformly adding two carbon black conductive agents ECP-600JD into the prepared polyvinylidene fluoride glue solution with the proportion of 60-80%, and stirring until the carbon black conductive agents ECP-600JD are uniformly dispersed to obtain uniformly dispersed carbon black conductive glue solution;
(4) uniformly adding the single-walled carbon nanotubes into the prepared carbon black conductive glue solution, and stirring until the single-walled carbon nanotubes are uniformly dispersed to obtain uniformly mixed conductive slurry;
(5) uniformly adding the positive active substance into the conductive slurry in batches, adding the solvent during the process, setting the stirring speed to be 25RPM and the dispersion speed to be 135RPM, and carrying out preliminary kneading and stirring for 30min to obtain primary kneaded slurry; wherein the solid content of the primary kneaded slurry is 75%; (this step may be referred to simply as "high-solid content kneading process" to ensure sufficient wetting of the internal voids of the dry powder)
(6) Adding a solvent into the primary kneaded slurry, setting a stirring speed of 25RPM and a dispersion speed of 160RPM, and carrying out secondary kneading and stirring for 30min to obtain secondary kneaded slurry; wherein the addition of the solvent is 73% of the solid content;
(7) setting the stirring speed to be 35RPM and the dispersing speed to be 3500RPM, and crushing and dispersing to prepare slurry with the solid content of 67 percent; (this step may be simply referred to as "dilution stirring process");
(8) and (3) shearing and dispersing the slurry in the step (7) at the speed of 3500RPM, and uniformly dispersing to obtain the lithium ion battery anode slurry with the slurry viscosity value of 6500mPa & s, the slurry fineness of less than or equal to 20 mu m and the solid content of 63%.
The positive active material is a spheroidal lithium iron phosphate material, and the particle size of the material is D501.1 μm, specific surface area 12.5m2The tap density reaches 0.85g/cm3。
The mass ratio of the carbon black conductive agent ECP-600JD to the single-walled carbon nanotube is 2: 1.
The solvent was N-methylpyrrolidone (NMP) at a concentration of 7%.
Coating the slurry on a carbon-coated aluminum foil with the thickness of 13 mu m, baking and drying to obtain a battery pole piece, sampling and carrying out Scanning Electron Microscope (SEM) observation, wherein the result shows that no particle aggregates are found in the battery positive pole piece prepared by adopting a mode of adding multiple types of conductive agents step by step and adopting two-step kneading and semi-dry mixing processes in combination with the addition of a main material positive active substance, and the particle aggregates are proved to be well dispersed and uniformly coated on the surface of the positive active substance to form an effective 0D and 1D synergetic conductive network, so that the conductive efficiency of the lithium ion battery positive pole piece is improved, and the electrochemical performance of the battery is improved; meanwhile, the stirring time is shortened to about 5.5 hours from about 8.0 hours of the prior art (pure wet method), and the slurry mixing efficiency, the slurry stability and the dispersion performance are improved.
Example 2
A preparation process of lithium ion battery anode slurry comprises the following steps:
(1) pretreatment of the anode powder: respectively weighing positive active substances, adhesives and conductive agents, baking in a vacuum environment, cooling the baked powder, and sealing and storing the cooled material for later use;
the mass ratio of the positive active substance powder, the adhesive and the conductive agent is 98.3: 1.3: 0.4 in sequence;
the adhesive is polyvinylidene fluoride, and the conductive agent comprises a carbon black conductive agent ECP-600JD and single-walled carbon nanotubes;
(2) preparing a polyvinylidene fluoride glue solution: uniformly adding polyvinylidene fluoride into an N-methyl pyrrolidone solution, and stirring in vacuum to obtain a polyvinylidene fluoride gel solution;
wherein the volume of the N-methyl pyrrolidone solution is 13 times of that of the polyvinylidene fluoride;
(3) uniformly adding two carbon black conductive agents ECP-600JD into the prepared polyvinylidene fluoride glue solution with the proportion of 60-80%, and stirring until the carbon black conductive agents ECP-600JD are uniformly dispersed to obtain uniformly dispersed carbon black conductive glue solution;
(4) uniformly adding the single-walled carbon nanotubes into the prepared carbon black conductive glue solution, and stirring until the single-walled carbon nanotubes are uniformly dispersed to obtain uniformly mixed conductive slurry;
(5) uniformly adding the positive active substance into the conductive slurry in several times, adding a solvent during the process, setting a stirring speed of 30RPM and a dispersion speed of 185RPM, and carrying out primary kneading and stirring for 30min to obtain primary kneaded slurry; wherein the solid content of the primary kneaded slurry is 76%; (this step may be referred to simply as "high-solid content kneading process" to ensure sufficient wetting of the internal voids of the dry powder)
(6) Adding a solvent into the primary kneaded slurry, setting a stirring speed of 35RPM and a dispersion speed of 200RPM, and carrying out secondary kneading and stirring for 30min to obtain secondary kneaded slurry; wherein, the adding amount of the solvent is 74 percent of the solid content;
(7) setting a stirring speed of 45RPM and a dispersing speed of 4500RPM, and crushing and dispersing to obtain slurry with 68% of solid content (the step can be simply called as a dilution stirring process);
(8) and (4) shearing and dispersing the slurry in the step (7) at the speed of 4000RPM, and uniformly dispersing to obtain the lithium ion battery anode slurry with the slurry viscosity value of 8000mPa & s, the slurry fineness of less than or equal to 20 mu m and the solid content of 63%.
The positive active material is a spheroidal lithium iron phosphate material, and the particle size of the material is D500.9 μm, specific surface area 13.5m2The tap density reaches 0.9g/cm3。
The mass ratio of the carbon black conductive agent ECP-600JD to the single-walled carbon nanotube is 3: 1.
The solvent was N-methylpyrrolidone (NMP) at a concentration of 8%.
Coating the slurry on a carbon-coated aluminum foil with the thickness of 13 mu m, drying to obtain a battery pole piece, sampling and carrying out Scanning Electron Microscope (SEM) observation, wherein the result shows that no particle aggregates are found in the battery positive pole piece prepared by adopting a mode of adding multiple types of conductive agents step by step and adopting steps of kneading two steps, semi-drying and mixing the main material positive active substance in combination with the addition of the main material positive active substance, and the particle aggregates are proved to be dispersed and uniformly coated on the surface of the positive active substance to form effective 0D and 1D conductive networks, so that the conductive efficiency of the positive pole piece of the lithium ion battery is improved, and the electrochemical performance of the battery is improved; meanwhile, the stirring time is shortened to about 5.5 hours from about 8 hours in the prior art (pure wet method), and the slurry mixing efficiency, the slurry stability and the dispersion performance are improved.
Example 3
A preparation process of lithium ion battery anode slurry comprises the following steps:
(1) pretreatment of the anode powder: respectively weighing positive active substances, adhesives and conductive agents, baking in a vacuum environment, cooling the baked powder, and sealing and storing the cooled material for later use;
the mass ratio of the positive active substance powder, the adhesive and the conductive agent is 97.5: 2: 0.5 in sequence;
the adhesive is polyvinylidene fluoride, and the conductive agent comprises a carbon black conductive agent ECP-600JD and single-walled carbon nanotubes;
(2) preparing a polyvinylidene fluoride glue solution: uniformly adding polyvinylidene fluoride into an N-methyl pyrrolidone solution, and stirring in vacuum to obtain a polyvinylidene fluoride gel solution;
wherein the volume of the N-methyl pyrrolidone solution is 12 times of that of the polyvinylidene fluoride;
(3) uniformly adding two carbon black conductive agents ECP-600JD into the prepared polyvinylidene fluoride glue solution with the proportion of 60-80%, and stirring until the carbon black conductive agents ECP-600JD are uniformly dispersed to obtain uniformly dispersed carbon black conductive glue solution;
(4) uniformly adding the single-walled carbon nanotubes into the prepared carbon black conductive glue solution, and stirring until the single-walled carbon nanotubes are uniformly dispersed to obtain uniformly mixed conductive slurry;
(5) uniformly adding the positive active substance into the conductive slurry in several times, adding the solvent during the process, setting the stirring speed at 20RPM and the dispersion speed at 100RPM, and carrying out primary kneading and stirring for 30min to obtain primary kneaded slurry; wherein the solid content of the primary kneaded slurry was 74%; (this step may be referred to simply as "high-solid content kneading process" to ensure sufficient wetting of the internal voids of the dry powder)
(6) Adding a solvent into the primary kneaded slurry, setting a stirring speed of 20RPM and a dispersion speed of 120RPM, and carrying out secondary kneading and stirring for 30min to obtain secondary kneaded slurry; wherein, the adding amount of the solvent is calculated by 72 percent of solid content;
(7) setting a stirring speed of 25RPM and a dispersion speed of 2500RPM, and crushing and dispersing to prepare slurry with 66% of solid content; (this step may be simply referred to as "dilution stirring process");
(8) and (3) shearing and dispersing the slurry obtained in the step (7) at the speed of 3000RPM, and uniformly dispersing to obtain the lithium ion battery anode slurry with the slurry viscosity value of 5000mPa & s, the slurry fineness of less than or equal to 20 mu m and the solid content of 61%.
The positive active material is a spheroidal lithium iron phosphate material, and the particle size of the material is D501.2 μm, specific surface area 11m2The tap density reaches 0.82g/cm3。
The mass ratio of the carbon black conductive agent ECP-600JD to the single-walled carbon nanotube is 1: 1.
The solvent was N-methylpyrrolidone (NMP) at a concentration of 4%.
Coating the slurry on a carbon-coated aluminum foil with the thickness of 13 mu m, drying to obtain a battery pole piece, sampling and carrying out Scanning Electron Microscope (SEM) observation, wherein the result shows that no particle aggregates are found in the battery positive pole piece prepared by adopting a mode of adding multiple types of conductive agents step by step and adopting steps of kneading two steps, semi-drying and mixing the main material positive active substance in combination with the addition of the main material positive active substance, and the particle aggregates are proved to be dispersed and uniformly coated on the surface of the positive active substance to form effective 0D and 1D conductive networks, so that the conductive efficiency of the positive pole piece of the lithium ion battery is improved, and the electrochemical performance of the battery is improved; meanwhile, the stirring time is shortened to about 5.5 hours from about 8 hours of the prior art (pure wet method), and the slurry mixing efficiency, the slurry stability and the dispersion performance are improved.
Comparative example 1
The formula of the positive pole piece is set as lithium iron phosphate powder: carbon black conductive agent ECP-600 JD: PVDF accounts for 97.5 percent, 0.5 percent and 2 percent (mass ratio). Firstly, adding carbon black conductive agent ECP-600JD dry powder and lithium iron phosphate powder into a double planetary mixer, premixing for 30min at a low speed, then stirring for 90min at a revolution speed of 15RPM and a rotation speed of 1500RPM, then adding PVDF glue solution which is dissolved, stirred and dispersed by NMP in advance and a part of NMP pure solvent into the mixer, stirring for 240min at a revolution speed of 30RPM and a rotation speed of 2500RPM, and finally dispersing for 120min at a revolution speed of 40RPM and a rotation speed of 3500RPM to prepare finished anode slurry with the solid content of 62%.
The slurry is coated on a carbon-coated aluminum foil with the thickness of 13 mu m, the carbon-coated aluminum foil is dried to form a battery pole piece, a sample is taken for Scanning Electron Microscope (SEM) observation, and the obtained result shows that only a common anode pulping process is adopted, carbon black conductive agent ECP-600JD aggregates are not fully dispersed, and a good high-efficiency conductive effect cannot be achieved.
Comparative example 2
The formula of the positive pole piece is set as lithium iron phosphate powder: single-walled carbon nanotubes: PVDF accounts for 97.8 percent, 0.2 percent and 2 percent (mass ratio). Firstly, adding single-walled carbon nanotube TUBALL dry powder and lithium iron phosphate powder into a double planetary mixer, premixing at a low speed for 30min, then stirring at a revolution speed of 15RPM and a rotation speed of 1500RPM for 90min, then adding PVDF glue solution dissolved, stirred and dispersed by NMP in advance and a part of NMP pure solvent into the mixer, stirring at a revolution speed of 35RPM and a rotation speed of 2500RPM for 240min, and finally dispersing at a high speed of 40RPM and 3500RPM for 120min to prepare finished anode slurry with a solid content of 62%.
The slurry is coated on a carbon-coated aluminum foil with the thickness of 13 mu m, the carbon-coated aluminum foil is dried to form a battery pole piece, a sample is taken for Scanning Electron Microscope (SEM) observation, and the obtained result shows that the single-walled carbon nanotube aggregate is not dispersed basically and can not play a good conductive role only by adopting the common anode pulping process.
Comparative example 3
The formula of the positive pole piece is set as lithium iron phosphate powder: single-walled carbon nanotubes: carbon Black ECP-600 JD: PVDF (97.7%: 0.2%: 0.1%: 2% (mass ratio). Firstly, sequentially adding a single-walled carbon nanotube TUBALL, carbon black ECP-600JD dry powder and lithium iron phosphate powder into a double planetary mixer, premixing for 30min at a low speed, then stirring for 90min at a revolution speed of 15RPM and a rotation speed of 1500RPM, then adding a PVDF glue solution dissolved and stirred and dispersed by NMP and a part of NMP pure solvent into the mixer, stirring for 240min at a revolution speed of 35RPM and a rotation speed of 2500RPM, and finally dispersing for 120min at a revolution speed of 40RPM and a rotation speed of 3500RPM to prepare a finished anode slurry with a solid content of 62%.
The slurry is coated on a carbon-coated aluminum foil with the thickness of 13 mu m, the carbon-coated aluminum foil is dried to form a battery pole piece, a sample is taken for Scanning Electron Microscope (SEM) observation, and the obtained result shows that the single-walled carbon nanotube and the ECP-600JD aggregate are not fully dispersed and can not play a good conductive role only by adopting the common anode pulping process.
Therefore, the process can solve the key problem that the novel dry powder conductive agent and the single-walled carbon tube are difficult to disperse due to large specific surface area, and an effective 0D and 1D conductive network is constructed, so that the conductive efficiency of the positive pole piece of the lithium ion battery is improved, and the conductive performance and the electrochemical performance of the battery are improved.
The following comparative tests were performed on the power lithium ion batteries manufactured in the above examples 1, 2, 3, 1, 2 and 3, respectively:
test 1: respectively representing the slurry stability under each process condition, and testing the resistivity of the prepared positive plate and the 100% SOC DCR of the battery after capacity grading under each process condition, wherein the results are respectively shown in the following figure 1 and table 1;
and (3) testing 2: the discharge performance of the batteries prepared under the process conditions is respectively compared by testing at different multiplying powers of 1C and 3C, and the results are shown in the following table 1;
and (3) testing: the cell prepared under each process condition was charged at 1C and discharged at 1C for a long-term cycle test at room temperature, and the results are shown in table 2 below.
Table 1 (design capacity 63Ah, single-side loading capacity of positive electrode 185-210 g/m)2)
TABLE 2
From the above analysis of the test data for example 1, example 2, example 3, comparative example 1, comparative example 2 and comparative example 3, we have found: 1. the slurry stability of the examples 1-3 is excellent by adopting a new positive electrode stirring process, while the viscosity of the comparative slurry is increased by more than 250% after 24 hours, and the performance is poor; 2. the resistivity of the pole pieces in the embodiments 1-3 is far lower than that of the comparative example, and the battery capacity exertion, first effect and rate discharge performance of the embodiments are obviously superior to those of the comparative example, and it is worth mentioning that the temperature rise of the embodiments is relatively small, so that the electrode heating can be effectively reduced, and the thick electrode cell is facilitated; 3. the long cycle level of the examples is obviously superior to that of the comparative examples, the cycle of the synergistic action of the single-wall carbon tube and the ECP-600JD of the comparative examples is superior to that of a single carbon tube or carbon black conductive agent, and the cycle under the stirring process of the anode is greatly superior to that of the comparative examples. The lithium iron phosphate battery positive electrode slurry prepared by the process method has the advantages of good processing performance, short processing period and the like; the lithium ion battery prepared by the slurry has the outstanding electrochemical performance advantages of low resistivity of a pole piece, small DCR, good multiplying power and power characteristics, excellent cycle performance and the like, and the battery prepared by the method can be widely applied to the fields of new energy electric automobiles, electric tools, 3C digital codes, 5G base stations, energy storage, UPS power supplies and the like.
The above embodiments are merely preferred embodiments of the present invention, and any simple modification, modification and substitution changes made to the above embodiments according to the technical spirit of the present invention are within the scope of the technical solution of the present invention.
Claims (7)
1. A preparation process of lithium ion battery anode slurry is characterized by comprising the following steps:
(1) pretreatment of the anode powder: respectively weighing positive active substances, adhesives and conductive agents, baking in a vacuum environment, cooling the baked powder, and sealing and storing the cooled material for later use;
the mass ratio of the positive electrode active substance powder to the adhesive to the conductive agent is (95-98.5) to (1-3) to (0.1-2) in sequence;
the adhesive is polyvinylidene fluoride, and the conductive agent comprises a carbon black conductive agent ECP-600JD and single-walled carbon nanotubes;
(2) preparing polyvinylidene fluoride glue solution: uniformly adding polyvinylidene fluoride into an N-methyl pyrrolidone solution (NMP), and stirring in vacuum to obtain a uniform, clear and transparent polyvinylidene fluoride glue solution;
wherein the volume of the N-methyl pyrrolidone solution is 10-14 times of that of the polyvinylidene fluoride;
(3) uniformly adding a carbon black conductive agent ECP-600JD into a pre-prepared polyvinylidene fluoride glue solution with the proportion of 60-80%, and stirring until the carbon black conductive agent ECP-600JD is uniformly dispersed to obtain a uniformly dispersed carbon black conductive glue solution;
(4) uniformly adding the single-walled carbon nanotubes into the prepared carbon black conductive glue solution, and stirring until the single-walled carbon nanotubes are uniformly dispersed to obtain uniformly mixed conductive slurry;
(5) uniformly adding the positive powder into the conductive slurry in several times, adding a solvent during the process, setting a stirring speed of 10-40 RPM and a dispersion speed of 100-200 RPM, and carrying out primary kneading and stirring to obtain primary kneading slurry; after the solvent is added, the solid content of the primary kneading slurry is 74-76%;
(6) adding a proper amount of solvent into the primary kneading slurry, setting the stirring speed to be 10-40 RPM and the dispersion speed to be 100-200 RPM, and carrying out secondary kneading and stirring to obtain secondary kneading slurry; wherein the addition amount of the solvent is 72-74% of the solid content;
(7) adding the rest PVDF glue solution and the solvent, setting the stirring speed to be 25-50 RPM and the dispersion speed to be 2500-4500 RPM, and crushing and dispersing to obtain slurry with the solid content of 67-69%;
(8) and (3) adding NMP to adjust the viscosity, shearing and dispersing the slurry in the step (7) at the speed of 3500-4500 RPM, and uniformly dispersing to obtain the lithium ion battery anode slurry with the solid content of 60-62%.
2. The preparation process of the anode slurry of the lithium ion battery according to claim 1, wherein the anode active material is a spheroidal lithium iron phosphate material, and the particle size of the material is D500.5 to 2 μm, and a specific surface area of 10 to 15m2The tap density of the mixture is 0.7-0.9 g/cm3。
3. The preparation process of the lithium ion battery cathode slurry according to claim 1, wherein the mass ratio of the carbon black conductive agent ECP-600JD to the single-walled carbon nanotubes is (1-3) to 1.
4. The preparation process of the positive electrode slurry of the lithium ion battery according to claim 1, wherein the solvent is N-methylpyrrolidone (NMP) and the concentration is 4-10%.
5. The preparation process of the positive electrode slurry for the lithium ion battery according to claim 1, wherein in the step (5), the duration of the preliminary kneading and stirring is 20-40 min.
6. The preparation process of the positive electrode slurry for the lithium ion battery according to claim 1, wherein in the step (6), the duration of the secondary kneading and stirring is 20-40 min.
7. The preparation process of the lithium ion battery anode slurry according to claim 1, wherein in the step (8), the prepared slurry has a viscosity value of 4000-8000 mPa-s and a fineness of less than or equal to 20 μm.
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