CN111211321B - Oily graphene slurry and preparation method thereof, lithium iron phosphate anode slurry and preparation method thereof, and battery - Google Patents
Oily graphene slurry and preparation method thereof, lithium iron phosphate anode slurry and preparation method thereof, and battery Download PDFInfo
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Abstract
The invention discloses oily graphene slurry and a preparation method thereof, lithium iron phosphate anode slurry and a preparation method thereof, and a battery, and relates to the technical field of battery preparation. The oily graphene slurry comprises the following raw materials in percentage by weight: 0.2-10% of graphene, 0.3-3% of dispersant, 0.01-2% of stabilizer, 0.1-3% of first binder and the balance of first solvent. This oily graphene slurry can be used to prepare lithium iron phosphate positive electrode paste, this oily graphene slurry can show the electric conductivity that improves lithium iron phosphate positive electrode paste, effectively promote the transmission and the extraction of lithium ion, and compare in traditional conducting agent acetylene black, graphite alkene slurry addition quantity is still less, the electric conduction effect is better, the shared proportion is littleer in lithium iron phosphate positive electrode paste, can help improving the volume energy density of material, make this oily graphene slurry can improve defects such as lithium iron phosphate reversible capacity is low effectively, multiplying power performance is poor.
Description
Technical Field
The invention relates to the technical field of battery preparation, in particular to oily graphene slurry and a preparation method thereof, lithium iron phosphate anode slurry and a preparation method thereof, and a battery.
Background
Lithium ion batteries are widely used in the fields of electronic devices, new energy vehicles and the like due to the advantages of high energy density, no memory effect, long cycle life, small self-discharge effect and the like. With the rapid development of electric vehicles and hybrid electric vehicles and the continuous increase of market demand, lithium ion batteries are breaking through their bottlenecks and developing in the direction of high energy density, high rate performance and long cycle life.
Lithium iron phosphate is one of the lithium ion anode materials widely used at present, and has the advantages of low cost, high safety, environmental friendliness, stable working voltage, long charge-discharge cycle life and the like, but the crystal structure of the lithium iron phosphate also causes low electronic conductivity (10) -9 ～10 -10 S·cm -1 ) And lithium ion mobility (10) -13 ～10 -16 cm 2 ·S -1 ) The electrochemical performance of the lithium ion battery is severely limited, and the reversible capacity and rate capability of the lithium ion battery are further influenced.
In view of this, the invention is particularly proposed.
Disclosure of Invention
One of the purposes of the present invention is to provide an oily graphene slurry, which can be used for preparing a lithium iron phosphate positive electrode slurry, so as to improve the conductivity of a lithium iron phosphate positive electrode material, and promote the de-intercalation of lithium ions, thereby effectively improving the defects of low reversible capacity, poor rate capability, and the like of lithium iron phosphate.
The second purpose of the present invention is to provide a preparation method of an oily graphene slurry, which can simply and conveniently prepare the oily graphene slurry, has a simple and easily controllable process, and can effectively improve the preparation efficiency and quality of the oily graphene slurry.
The invention also aims to provide lithium iron phosphate anode slurry which is prepared from the oily graphene slurry. Therefore, the reversible capacity and the electrochemical performance of the lithium iron phosphate anode slurry can be effectively improved.
The fourth object of the present invention is to provide a method for preparing a lithium iron phosphate positive electrode slurry, which can simply and conveniently prepare the lithium iron phosphate positive electrode slurry, has a simple and easily controlled process, and can effectively improve the preparation efficiency and quality of the lithium iron phosphate positive electrode slurry.
The fifth object of the present invention is to provide a battery prepared from the lithium iron phosphate positive electrode slurry. Therefore, the electrochemical performance of the battery is excellent.
The embodiment of the invention is realized by the following steps:
in a first aspect, an embodiment provides an oily graphene slurry for preparing a lithium iron phosphate positive electrode slurry, where the oily graphene slurry includes the following raw materials in percentage by weight:
0.2-10% of graphene, 0.3-3% of dispersant, 0.01-2% of stabilizer, 0.1-3% of first binder and the balance of first solvent.
In an alternative embodiment, the dispersant comprises a non-ionic dispersant and/or a cationic dispersant.
In alternative embodiments, the dispersant comprises one or more of polyacrylic acid, KD1, polyphenylacetylene, surface active protein.
In an alternative embodiment, the stabilizer comprises polyvinyl alcohol.
In alternative embodiments, the first binder comprises one or more of polyethylene, polyacrylonitrile, polyurethane resin, epoxy resin.
In alternative embodiments, the first solvent comprises one or more of dimethylformamide, polyvinylpyrrolidone, isopropanol, ethanol, N-methylpyrrolidone, dimethyl ether, toluene, xylene, acetone.
In a second aspect, embodiments provide a method of preparing an oily graphene slurry according to any one of the preceding embodiments, including:
dispersing graphene in a first solvent added with a dispersing agent to obtain a graphene solution;
and sequentially carrying out vacuum stirring, planetary ball milling and sanding on the graphene solution, adding a first binder and a stabilizer, carrying out secondary vacuum stirring, and uniformly dispersing to obtain the oily graphene slurry.
In a third aspect, an embodiment provides a lithium iron phosphate positive electrode slurry, including:
the oily graphene slurry according to any one of the preceding embodiments or the oily graphene slurry obtained by the method for producing an oily graphene slurry according to the preceding embodiments, lithium iron phosphate, a second binder, and a second solvent.
In a fourth aspect, an embodiment provides a method for preparing lithium iron phosphate positive electrode slurry in the foregoing embodiment, including:
adding lithium iron phosphate into the oily graphene slurry, and uniformly mixing to obtain a mixed solution;
dissolving a second binder in a second solvent to obtain a binder solution;
and adding the binder solution into the mixed solution, and performing magnetic stirring to obtain the lithium iron phosphate anode slurry.
In a fifth aspect, an embodiment provides a battery, which includes a positive plate, and the positive plate is obtained by processing the lithium iron phosphate positive slurry obtained by the preparation method of the lithium iron phosphate positive slurry according to the foregoing embodiment or the lithium iron phosphate positive slurry according to the foregoing embodiment.
Embodiments of the invention have at least the following advantages or benefits:
the embodiment of the invention provides oily graphene slurry which comprises the following raw materials in percentage by weight: 0.2-10% of graphene, 0.3-3% of dispersant, 0.01-2% of stabilizer, 0.1-3% of first binder and the balance of first solvent. This oily graphene slurry can be used to prepare lithium iron phosphate positive electrode paste, this oily graphene slurry can show the electric conductivity that improves lithium iron phosphate positive electrode paste, effectively promote the transmission and the extraction of lithium ion, and compare in traditional conducting agent acetylene black, graphite alkene slurry addition quantity is still less, the electric conduction effect is better, the shared proportion is littleer in lithium iron phosphate positive electrode paste, can help improving the volume energy density of material, make this oily graphene slurry can improve defects such as lithium iron phosphate reversible capacity is low effectively, multiplying power performance is poor.
The embodiment of the invention also provides a preparation method of the oily graphene slurry, which comprises the steps of dispersing graphene in the first solvent added with the dispersing agent to obtain a graphene solution; and sequentially carrying out vacuum stirring, planetary ball milling and sanding on the graphene solution, adding a first binder and a stabilizer, carrying out secondary vacuum stirring, and uniformly dispersing to obtain the oily graphene slurry. According to the method, the oily graphene slurry can be simply and conveniently prepared by reasonably controlling the adding sequence of each component and the process flow of each step. Therefore, the preparation method is simple in process and easy to control, and can effectively improve the preparation efficiency and quality of the oily graphene slurry.
The embodiment of the invention also provides lithium iron phosphate anode slurry which is prepared from the oily graphene slurry. Therefore, the reversible capacity and the electrochemical performance of the lithium iron phosphate anode slurry can be effectively improved.
The embodiment of the invention also provides a preparation method of the lithium iron phosphate anode slurry, which can simply and conveniently prepare the lithium iron phosphate anode slurry, has a simple and easily controlled process, and can effectively improve the preparation efficiency and quality of the lithium iron phosphate anode slurry.
The embodiment of the invention also provides a battery which is prepared from the lithium iron phosphate anode slurry. Therefore, the electrochemical performance of the battery is excellent.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and those skilled in the art can also obtain other related drawings based on the drawings without inventive efforts.
Fig. 1 is a TEM image of a uniformly dispersed graphene conductive paste prepared in example 1 of the present invention;
fig. 2 is a rate performance curve of a button cell prepared in example 2 of the present invention;
fig. 3 is a rate performance curve of a button cell prepared in example 4 of the present invention;
fig. 4 is a rate performance curve of a button cell prepared in example 6 of the present invention;
fig. 5 is a rate performance curve for a button cell prepared in example 8 of the present invention;
fig. 6 is a rate performance curve for the button cell prepared in comparative example 1;
fig. 7 is a rate performance curve for the button cell prepared in comparative example 2.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
The features and properties of the present invention are described in further detail below with reference to examples.
The embodiment of the invention provides oily graphene slurry which is mainly used for preparing lithium iron phosphate anode slurry, and the oily graphene slurry comprises the following raw materials in percentage by weight:
0.2-10% of graphene, 0.3-3% of dispersant, 0.01-2% of stabilizer, 0.1-3% of first binder and the balance of first solvent.
In detail, graphene has the advantages of excellent electronic conductivity, flexibility, mechanical properties, chemical and thermodynamic stability, high specific surface area and the like, and is widely applied to the field of energy conversion and storage. In the embodiment of the invention, the oily graphene slurry can obviously improve the conductivity of the lithium iron phosphate anode slurry and effectively promote the transmission and de-intercalation of lithium ions, and compared with the traditional conductive agent acetylene black, the oily graphene slurry has the advantages of less addition amount of the graphene slurry, better conductive effect, smaller proportion in the lithium iron phosphate anode slurry, contribution to improving the volume energy density of the material and capability of effectively improving the defects of low reversible capacity, poor rate capability and the like of lithium iron phosphate.
In detail, in this embodiment, the dispersant is used to effectively exfoliate the graphene after being dispersed by sanding or ball milling, so as to form few-layer or single-layer graphene, inhibit the aggregation of the graphene, and uniformly disperse the graphene in the solution, thereby ensuring the quality of the finished product.
Specifically, in this embodiment, the dispersant includes a nonionic dispersant and/or a cationic dispersant. The non-ionic dispersing agent contains an aromatic ring structure which can form pi-pi bond combination with the surface of graphene, so that the non-ionic dispersing agent can be effectively adsorbed on the surface of the graphene and form a steric hindrance effect to prevent the graphene from agglomerating again. And the positive ion dispersing agent generates electrostatic repulsive force after ionization and enables graphene to obtain good dispersing effect through steric hindrance effect formed by macromolecular chains of the positive ion dispersing agent.
In this embodiment, the selected dispersant preferably includes one or more of polyacrylic acid, KD1, polyphenylacetylene (PAA), and surface active protein. Of course, in other embodiments of the present invention, the kind of the dispersant may be adjusted and selected according to the requirement, and the embodiments of the present invention are not limited.
In detail, in this embodiment, the stabilizer prevents edges of graphene sheets from being oxidized, so that the graphene sheets have good stability at room temperature and high temperature, thereby further improving dispersion stability of graphene.
The stabilizer used in the examples of the present invention is polyvinyl alcohol. The addition of the polyvinyl alcohol can effectively prevent the edges of the graphene sheet layers from being oxidized, so that the preparation efficiency and quality of finished products are ensured.
In detail, in the embodiment of the present invention, the first binder is dissolved in the first solvent, and in such viscous liquid, the few-layer graphene obtained by sanding may stably exist, and the redispersion performance may be improved, and further, the graphene may be dispersed into the sheet-like graphene. And the graphene does not settle in the later stage, and the graphene slurry is not layered.
Specifically, in an embodiment of the present invention, the binder includes one or more of polyethylene, polyacrylonitrile, polyurethane resin, and epoxy resin. Of course, in other embodiments of the present invention, the type of the adhesive may also be selected according to requirements, and the embodiments of the present invention are not limited.
Specifically, in embodiments of the present invention, the first solvent comprises one or more of dimethylformamide, polyvinylpyrrolidone, isopropanol, ethanol, N-methylpyrrolidone, dimethyl ether, toluene, xylene, acetone.
The embodiment of the invention also provides a preparation method of the oily graphene slurry, which comprises the following steps:
dispersing graphene in a first solvent added with a dispersing agent to obtain a graphene solution; and sequentially carrying out vacuum stirring, planetary ball milling and sanding on the graphene solution, adding a first binder and a stabilizer, carrying out secondary vacuum stirring, and uniformly dispersing to obtain the oily graphene slurry.
In detail, the method can simply and conveniently prepare the oily graphene slurry by reasonably controlling the adding sequence of each component and the process flow of each step. Therefore, the preparation method is simple in process and easy to control, and can effectively improve the preparation efficiency and quality of the oily graphene slurry.
The embodiment of the invention also provides lithium iron phosphate anode slurry, which comprises the following components: the oily graphene slurry, the lithium iron phosphate, the second binder and the second solvent.
In detail, the mass ratio of the conductive agent in the conventional cathode slurry is about 10%, and the addition amount of the graphene slurry provided by the embodiment is less than 5% and about 0.5% -5%, so that the use amount of the conductive agent is reduced, the conductivity of the cathode material is improved, and the reversible capacity and the rate capability of the cathode material are improved. In addition, the oily graphene slurry prepared in the formula replaces the traditional conductive agent acetylene black, and due to the advantages of high conductivity, excellent mechanical property, high specific surface area and the like of graphene, the conductivity among lithium iron phosphate particles can be obviously improved, the transmission rate of lithium ions is enhanced, and the rate capability of the anode material is improved.
In the preparation method, the second binder may be polyvinylidene fluoride, and the second solvent may be N-methylpyrrolidone. In other embodiments, the types of the two may also be adjusted according to requirements, and the embodiments of the present invention are not limited.
The embodiment of the invention also provides a preparation method of the lithium iron phosphate anode slurry, which comprises the following steps: adding lithium iron phosphate into the oily graphene slurry, and uniformly mixing to obtain a mixed solution; dissolving a second binder in a second solvent to obtain a binder solution; and adding the binder solution into the mixed solution, and performing magnetic stirring to obtain the lithium iron phosphate anode slurry. The method can simply and conveniently prepare the lithium iron phosphate anode slurry, has simple and easily controlled process, and can effectively improve the preparation efficiency and quality of the lithium iron phosphate anode slurry.
The embodiment of the invention also provides a battery which is mainly prepared by the following method:
and coating the prepared lithium iron phosphate anode slurry on an aluminum foil to prepare a pole piece, carrying out vacuum drying on the pole piece, carrying out tabletting treatment under certain pressure, and then continuously carrying out vacuum drying under a high-temperature condition to obtain the anode piece. Meanwhile, in a glove box in an argon atmosphere, a lithium sheet is used as a counter electrode, a Celgard 2500 polyethylene porous membrane is used as a diaphragm, and a 1mol/L LiPF6/EC-EMC-DMC (volume ratio is 1.
The battery is prepared from the lithium iron phosphate positive electrode slurry. Therefore, the electrochemical performance of the battery is excellent.
The following is a detailed description of specific embodiments.
Example 1
The embodiment provides an oily graphene slurry, which is prepared by the following method:
s1: adding 0.4% wt KD1 into N-methylpyrrolidone (NMP), and magnetically stirring for 30min;
s2: adding 4 wt% of graphene powder into the solution, and performing ultrasonic dispersion for 0.5h to obtain a graphene solution;
s3: carrying out vacuum stirring and dispersion on the graphene solution; followed by ball mill dispersion in a planetary ball mill for 1.5h, followed by addition of 1.5% by weight of an epoxy resin and 0.2% by weight of polyvinyl alcohol to the solution, and ball mill dispersion for 45min with a sand mill to obtain a uniformly dispersed oily graphene slurry.
Fig. 1 is a TEM image of the uniformly dispersed graphene conductive paste prepared in example 1, and it can be seen that graphene has few sheets and little aggregation, which indicates that the dispersion is relatively uniform.
Example 2
This example provides a battery prepared by the following method:
s1: adding lithium iron phosphate (LFP) into the graphene slurry prepared in the embodiment 1, and magnetically stirring for 30min to uniformly mix the LFP and the oily graphene slurry;
s2: dissolving a binder polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP) to prepare a binder solution; after LFP and graphene slurry are uniformly mixed, adding a binder solution, and magnetically stirring for 1.5 hours to prepare lithium iron phosphate anode slurry; wherein, LFP in the lithium iron phosphate anode slurry: oily graphene slurry: the mass ratio of the binder is 86;
s3: coating the lithium iron phosphate anode slurry on an aluminum foil with the diameter of 10mm, carrying out vacuum drying on the pole piece at the temperature of 80 ℃ for 2h, carrying out tabletting treatment at the pressure of 15MPa, and then continuously carrying out vacuum drying at the temperature of 80 ℃ for 12h to obtain an anode piece;
s4: in a glove box under argon atmosphere, a lithium sheet is used as a counter electrode, a Celgard 2500 polyethylene porous membrane is used as a diaphragm, and 1mol/L LiPF6/EC-EMC-DMC (volume ratio of 1.
Constant current charge and discharge performance tests were performed on a battery test system (LAND CTR 2001A). Fig. 2 shows the charging and discharging test results of the button cell assembled in example 2 on a blue battery test system, and the rate performance is shown in the figure, and it can be seen from the results shown in the figure that the specific discharge capacity of the button cell assembled in example 2 is 157.9mAh/g, 156.4mAh/g, 149.6mAh/g, 144.6mAh/g and 133.1mAh/g after 5 cycles at the rates of 0.2C, 0.5C, 1C, 3C and 5C, respectively.
Example 3
The embodiment provides an oily graphene slurry, which is prepared by the following method:
s1: adding 0.5 wt% polyacrylic acid into N-methylpyrrolidone (NMP), and magnetically stirring for 30min;
s2: taking 5 wt% of graphene powder, adding the graphene powder into the solution, and performing ultrasonic dispersion for 1.0h to obtain a graphene solution;
s3: carrying out vacuum stirring and dispersion on the graphene solution; followed by ball milling dispersion in a planetary ball mill for 2.0h, followed by adding 1.0% by weight of polyacrylonitrile and 0.3% by weight of polyvinyl alcohol to the solution, and ball milling dispersion in a sand mill for 60min to obtain a uniformly dispersed oily graphene slurry.
Example 4
This example provides a battery prepared by the following method:
s1: adding lithium iron phosphate (LFP) into the oily graphene slurry prepared in the embodiment 3, and magnetically stirring for 30min to uniformly mix the LFP and the oily graphene slurry;
s2: dissolving a binder polyvinylidene fluoride (PVDF) in N-methyl pyrrolidone (NMP) to prepare a binder solution; after LFP and graphene slurry are uniformly mixed, adding a binder solution, and magnetically stirring for 1.5 hours to obtain iron phosphate positive electrode slurry; wherein, LFP: oily graphene slurry: the mass ratio of the binder is 88;
s3: coating the positive electrode slurry on an aluminum foil with the diameter of 10mm, carrying out vacuum drying on the pole piece at 80 ℃ for 2h, carrying out tabletting treatment at the pressure of 15MPa, and then continuously carrying out vacuum drying at 80 ℃ for 12h to obtain a positive electrode piece;
s4: in a glove box under argon atmosphere, a lithium sheet is used as a counter electrode, a Celgard 2500 polyethylene porous membrane is used as a diaphragm, and 1mol/L LiPF6/EC-EMC-DMC (volume ratio of 1.
Constant current charge and discharge performance tests were performed on a battery test system (LAND CTR 2001A). Fig. 3 shows the charging and discharging test results of the button cell assembled in example 4 on a blue battery test system, and the rate performance of the button cell assembled in example 4 is shown in the figure, and the specific discharge capacities of the button cell assembled in example 4 at 0.2C, 0.5C, 1C, 3C and 5C rates for 5 weeks are 156.1mAh/g, 153.9mAh/g, 147.3mAh/g, 147.6mAh/g and 140.5mAh/g, respectively.
Example 5
The embodiment provides an oily graphene slurry, which is prepared by the following method:
s1: adding 0.2 wt% of Polyphenylacetylene (PAA) into acetone, and magnetically stirring for 30min;
s2: taking 2 wt% of graphene powder, adding the graphene powder into the solution, and carrying out ultrasonic dispersion for 0.5h to obtain a graphene solution;
s3: carrying out vacuum stirring and dispersion on the graphene solution; followed by ball mill dispersion in a planetary ball mill for 1.5h, followed by addition of 1.2% by weight of a polyurethane resin and 0.2% by weight of polyvinyl alcohol to the solution, and ball mill dispersion for 30min in a sand mill to obtain a uniformly dispersed oily graphene slurry.
Example 6
The present example provides a battery, which is prepared by the following method:
s1: adding lithium iron phosphate (LFP) into the graphene slurry prepared in the embodiment 5, and magnetically stirring for 30min to uniformly mix the LFP and the oily graphene slurry;
s2: dissolving a binder polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP) to prepare a binder solution; after LFP and graphene slurry are uniformly mixed, adding a binder solution, and then magnetically stirring for 1.5 hours to obtain lithium iron phosphate anode slurry; wherein, LFP in the lithium iron phosphate anode slurry: oily graphene slurry: the mass ratio of the binder is 87;
s3: coating the positive electrode slurry on an aluminum foil with the diameter of 10mm, carrying out vacuum drying on the pole piece at 80 ℃ for 2h, carrying out tabletting treatment at the pressure of 15MPa, and then continuously carrying out vacuum drying at 80 ℃ for 12h to obtain a positive electrode piece;
s4: in a glove box in an argon atmosphere, a lithium sheet is used as a counter electrode, a Celgard 2500 polyethylene porous membrane is used as a diaphragm, and a 1mol/L LiPF6/EC-EMC-DMC (volume ratio is 1.
Constant current charge and discharge performance tests were performed on a battery test system (LAND CTR 2001A). Fig. 4 shows the results of the charge and discharge tests performed on the blue cell test system for the button cell assembled in example 6, showing the rate capability, and the specific discharge capacities of the button cell assembled in example 6 at 0.2C, 0.5C, 1C, 3C and 5C rates for 5 weeks were 165.1mAh/g, 170.0mAh/g, 160.8mAh/g, 147.6mAh/g and 144.6mAh/g, respectively.
Example 7
The embodiment provides an oily graphene slurry, which is prepared by the following method:
s1: adding 0.4 wt% of surface active protein to N-methylpyrrolidone (NMP), and magnetically stirring for 30min;
s2: taking 3 wt% of graphene powder, adding the graphene powder into the solution, and performing ultrasonic dispersion for 0.5h to obtain a graphene solution;
s3: carrying out vacuum stirring and dispersion on the graphene solution; followed by ball mill dispersion in a planetary ball mill for 1.0h, followed by addition of 1.5% by weight of an epoxy resin and 0.2% by weight of polyvinyl alcohol to the solution, and ball mill dispersion for 45min in a sand mill to obtain a uniformly dispersed oily graphene slurry.
Example 8
This example provides a battery prepared by the following method:
s1: adding lithium iron phosphate (LFP) into the graphene slurry prepared in the embodiment 7, and magnetically stirring for 30min to uniformly mix the LFP and the oily graphene slurry;
s2: dissolving a binder polyvinylidene fluoride (PVDF) in N-methyl pyrrolidone (NMP) to prepare a binder solution; after LFP and graphene slurry are uniformly mixed, adding a binder solution, and magnetically stirring for 1.5 hours to obtain lithium iron phosphate anode slurry; wherein, LFP in the lithium iron phosphate anode slurry: oily graphene slurry: the mass ratio of the binder is 86;
s3: coating the positive electrode slurry on an aluminum foil with the diameter of 10mm, carrying out vacuum drying on the pole piece at 80 ℃ for 2h, then carrying out tabletting treatment at the pressure of 15MPa, and then continuously carrying out vacuum drying at 80 ℃ for 12h to obtain a positive electrode plate;
s4: in a glove box under argon atmosphere, a lithium sheet is used as a counter electrode, a Celgard 2500 polyethylene porous membrane is used as a diaphragm, and 1mol/L LiPF6/EC-EMC-DMC (volume ratio of 1.
Constant current charge and discharge performance tests were performed on a battery test system (LAND CTR 2001A). Fig. 5 shows the charging and discharging test results of the button cell assembled in example 8 on a blue battery test system, and the rate performance of the button cell assembled in example 8 is shown in the figure, and the specific discharge capacities of the button cell assembled in example 8 at 0.2C, 0.5C, 1C, 3C and 5C rates after 5 weeks of cycling are 158.3mAh/g, 161.4mAh/g, 151.3mAh/g, 150.4mAh/g and 142.3mAh/g, respectively.
Comparative example 1
And replacing the graphene slurry in the embodiment 2 with a conventional conductive agent acetylene black, and assembling the graphene slurry into a button cell to test the electrochemical performance of the button cell under the same other conditions.
Fig. 6 is a rate performance graph of the charge and discharge test of comparative example 1, and it can be seen that the specific discharge capacities of the lithium iron phosphate positive electrode material without the conductive agent at the rates of 0.2C, 0.5C, 1C, 3C and 5C after 5 cycles are 150.4mAh/g, 148.8mAh/g, 145.9mAh/g, 146.3 mAh/g and 133.1mAh/g, respectively.
Comparative example 2
The comparative example is different from the example 2 in that the button cell is assembled without adding the graphene conductive paste and under the same other conditions to test the electrochemical performance of the button cell.
Fig. 7 is a rate performance graph of the charge and discharge test of comparative example 2, and it can be seen that the specific discharge capacities of the lithium iron phosphate positive electrode material without the conductive agent at 0.2C, 0.5C, 1C, 3C, and 5C rates after 5 cycles are 139.9mAh/g, 138.4mAh/g, 131.6mAh/g, 126.6 mAh/g, and 115.1mAh/g, respectively.
According to the data, the conventional conductive agent acetylene black is replaced by the oily graphene slurry prepared in the embodiment in the process of preparing the battery, and meanwhile, due to the advantages of high conductivity, excellent mechanical property, high specific surface area and the like of graphene, the conductivity among lithium iron phosphate particles can be obviously improved, the transmission rate of lithium ions is enhanced, and the rate capability of the cathode material is improved.
In summary, the oily graphene slurry provided by the embodiment of the invention can be used for preparing a lithium iron phosphate positive electrode slurry, and the oily graphene slurry can significantly improve the conductivity of the lithium iron phosphate positive electrode slurry and effectively promote the transmission and deintercalation of lithium ions.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (7)
1. The oily graphene slurry is used for preparing a lithium iron phosphate positive electrode slurry, and is characterized by comprising the following raw materials in percentage by weight:
0.2-10% of graphene, 0.3-3% of dispersant, 0.01-2% of stabilizer, 0.1-3% of first binder and the balance of first solvent; the dispersing agent comprises one or more of polyacrylic acid, KD1, polyphenylacetylene and surface active protein; the first binder comprises one or more of polyethylene, polyacrylonitrile, polyurethane resin and epoxy resin; the stabilizer comprises polyvinyl alcohol.
2. The oily graphene slurry according to claim 1, wherein:
the dispersant comprises a non-ionic dispersant and/or a cationic dispersant.
3. The oily graphene slurry according to claim 1, wherein:
the first solvent comprises one or more of dimethylformamide, polyvinylpyrrolidone, isopropanol, ethanol, N-methyl pyrrolidone, dimethyl ether, toluene, xylene and acetone.
4. A method for preparing the oily graphene slurry according to any one of claims 1 to 3, comprising:
dispersing the graphene in the first solvent added with the dispersing agent to obtain a graphene solution;
and sequentially carrying out vacuum stirring, planetary ball milling and sanding on the graphene solution, adding the first binder and the stabilizer, carrying out secondary vacuum stirring, and uniformly dispersing to obtain the oily graphene slurry.
5. A lithium iron phosphate positive electrode slurry is characterized by comprising:
the oily graphene slurry according to any one of claims 1 to 3 or the oily graphene slurry prepared by the method for preparing the oily graphene slurry according to claim 4, lithium iron phosphate, a second binder, and a second solvent.
6. The method for preparing the lithium iron phosphate positive electrode slurry according to claim 5, comprising:
adding the lithium iron phosphate into the oily graphene slurry, and uniformly mixing to obtain a mixed solution;
dissolving the second binder in the second solvent to obtain a binder solution;
and adding the binder solution into the mixed solution, and performing magnetic stirring to obtain the lithium iron phosphate anode slurry.
7. A battery, which is characterized by comprising a positive plate, wherein the positive plate is prepared by processing the lithium iron phosphate positive slurry prepared by the preparation method of the lithium iron phosphate positive slurry according to claim 6 or the lithium iron phosphate positive slurry according to claim 5.
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