CN108832183B - Preparation method of lithium ion battery - Google Patents
Preparation method of lithium ion battery Download PDFInfo
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- CN108832183B CN108832183B CN201810601003.9A CN201810601003A CN108832183B CN 108832183 B CN108832183 B CN 108832183B CN 201810601003 A CN201810601003 A CN 201810601003A CN 108832183 B CN108832183 B CN 108832183B
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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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
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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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
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- 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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- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The invention relates to the technical field of lithium ion battery electrode materials, in particular to a preparation method of a lithium ion battery, which comprises the following steps: preparing a positive plate: preparing an active substance of the positive plate, and mixing the active substance of the positive plate, acetylene black, a polyvinylidene fluoride adhesive and absolute ethyl alcohol according to the weight percentage of 80: 1: 2: 60's proportion drops into the stirring at the uniform velocity in the reation kettle, obtain anodal thick liquids, and with anodal thick liquids coating on the aluminium foil mass flow body, cut and obtain the positive plate, so, in this application, when preparing positive plate active material, be through using carbon nanotube and graphite alkene as the modified additive, including forming a lithium iron phosphate positive electrode material, the structure of amorphous carbon cladding outside, have fine ionic conductivity, these lithium-rich compounds can decorate the surface structure of lithium phosphate simultaneously, thereby make the electron conductivity on lithium phosphate surface improve.
Description
Technical Field
The invention relates to the technical field of lithium ion battery electrode materials, in particular to a preparation method of a lithium ion battery.
Background
The lithium battery is a primary battery using lithium metal or lithium alloy as a negative electrode material and using a non-aqueous electrolyte solution, unlike a lithium ion battery, which is a rechargeable battery, and a lithium ion polymer battery. The inventor of lithium batteries was edison. Because the chemical characteristics of lithium metal are very active, the requirements on the environment for processing, storing and using the lithium metal are very high. Therefore, lithium batteries have not been used for a long time. With the development of microelectronic technology at the end of the twentieth century, miniaturized devices are increasing, and high requirements are made on power supplies. The lithium battery has then entered a large-scale practical stage. Lithium iron phosphate system anode reaction: lithium ions are intercalated and deintercalated during discharge and charge. During charging: LiFePO4 → Li1-xFePO4 + xLi + + xe-when discharging: li1-xFePO4 + xLi + + xe- → LiFePO4 negative electrode, negative electrode material: graphite is mostly used. New studies found that titanate may be a better material. And (3) cathode reaction: lithium ions are deintercalated during discharge and are intercalated during charge. During charging: when xLi + + xe- + 6C → LixC6 discharges: LixC6 → xLi + + xe- + 6C. The lithium iron phosphate battery has the characteristics of good safety, high energy density and the like, and is a mainstream battery in a power battery. However, in a low-temperature environment, resistance to lithium ion coming out of the positive electrode material and migrating in the electrolyte is increased, and the charge and discharge performance and the cycle performance of the lithium iron phosphate battery are sharply reduced, so that the improvement of the charge and discharge performance and the cycle performance of the lithium iron phosphate battery in the low-temperature environment is of great significance.
At present, the synthesis method of lithium iron phosphate materials is mainly divided into a solid phase method and a liquid phase method. The solid phase method mainly utilizes iron salt, lithium salt and phosphate to realize the synthesis of the lithium iron phosphate by high-temperature sintering. The liquid phase method is to dissolve soluble iron salt, lithium salt and phosphate in a solvent, prepare lithium iron phosphate or a precursor thereof by utilizing an ion reaction, and then prepare a finished product by high-temperature sintering. The solid phase method has simple reaction, easy processing of raw materials and high yield, but the morphology of the raw materials is not easy to control, and the tap density and the compacted density of the product are low. For example, the invention patents CN101200289, CN1762798, CN101140985 and the like all adopt a solid phase synthesis process route. Some new synthetic methods, such as microwave synthesis (CN 101172597, CN 101807692A) and ultrasonic coprecipitation (CN 101800311A), can be classified into solid phase synthesis. The liquid phase method requires pretreatment by using a reaction kettle, and also requires processes such as drying and filtering, and the process is complex. But the product has generally better sphericity, higher tap density and excellent capacity and high rate performance. The invention patents CN101172599, CN101047242 and CN101121509 all adopt the process routes. The successful application of iron phosphate materials is that the surface is coated with a conductive carbon layer. Is actually a lithium iron phosphate/carbon composite material. Only the lithium iron phosphate material coated with carbon can normally exert the electrochemical performance. However, carbon added in the general process is loose in texture and is loosely distributed among lithium iron phosphate particles, so that the bulk density of the lithium iron phosphate material is seriously reduced. The cathode material is one of the key materials of the lithium ion battery, and the lithium ion battery cathode material which is commercially used at present is mainly a carbon cathode material. The lithium ion battery has the advantages of high specific capacity (200-400 mAh/g), low electrode potential (less than 1.0V vs Li +/Li), high cycle efficiency (more than 95%), long cycle life and the like. The carbon negative electrode material comprises mesocarbon microbeads (MCMB), graphite and amorphous carbon, wherein the graphite has good conductivity and high crystallinity and has a good layered structure, the reversible specific capacity can reach more than 300mah/g, Chen and other people have invented a superfine graphite negative electrode material, auxiliary materials after high-end graphite production are adopted as main raw materials of the product, the granularity is reduced to 5um by fine crushing, the reference is the standard, surface treatment is carried out, 3000-degree graphitization sintering is carried out after 1200-degree carbonization, corresponding products are obtained by coarse crushing and sieving, and the product has good conductive effect, low resistance, good processing performance in the production process of lithium ion batteries, stable performance and high cost performance, and is the optimal negative electrode material of a multiplying power lithium battery. But the disadvantages are that the graphite material has poor structural stability and poor compatibility with electrolyte, and the diffusion speed of Li ions in the ordered layered structure is slow, so that the material cannot be charged and discharged at a large multiplying power. The soft carbon has low crystallinity, small crystal grain size, large crystal face spacing and good compatibility with electrolyte, but has good charge-discharge irreversible capacity for the first time and small application range, and the artificial graphite has certain structural defects of the lithium ion battery cathode material itself, and needs to be subjected to further surface modification and modification in order to obtain the cathode material with high electrochemical performance.
Disclosure of Invention
The invention overcomes the defects of the prior art and provides a preparation method of a lithium ion battery.
The technical problem to be solved by the invention is realized by adopting the following technical scheme: a preparation method of a lithium ion battery comprises the following steps:
(1) preparing a positive plate: preparing an active substance of the positive plate, and mixing the active substance of the positive plate, acetylene black, a polyvinylidene fluoride adhesive and absolute ethyl alcohol according to the weight percentage of 80: 1: 2: 60, putting the mixture into a reaction kettle, stirring at a constant speed to obtain anode slurry, coating the anode slurry on an aluminum foil current collector, and cutting to obtain an anode plate;
(2) preparing a negative plate: preparing a negative plate active substance, and mixing the negative plate active substance, an acrylic acid aqueous solution with a solid content of 30%, acetylene black and absolute ethyl alcohol according to a weight percentage of 82: 1: 1: 55, putting the mixture into a reaction kettle, stirring at a constant speed to obtain negative electrode slurry, coating the negative electrode slurry on a copper foil current collector, and cutting to obtain a negative electrode sheet;
(3) and (3) Z-shaped lamination of the positive plate, the negative plate and the diaphragm, tab welding, packaging, battery core baking, liquid injection, pre-charging and liquid pumping molding are carried out to prepare the lithium ion battery, wherein the electrolyte adopts a film forming additive electrolyte added with vinylene sulfate and fluoroethylene carbonate.
In this application, it is preferable that the positive electrode sheet active material in the step (1) is prepared by:
(4.1) mixing the components in a mass ratio of 2: 1, putting graphene and carbon nanotubes into ethanol, carrying out ultrasonic primary crushing treatment, mixing and stirring for 4-6 minutes at normal temperature, heating to 40-60 ℃ at a speed of 2-4 ℃/min in an inert gas protection environment, preserving heat for 4-6 hours, and naturally cooling to room temperature to obtain a mixed solution;
the graphene is multilayer graphene, the interior of the multilayer graphene is of a three-dimensional conductive network structure, the carbon nano tubes are inserted in the three-dimensional conductive network, and the particle size of particles formed after the multilayer graphene and the carbon nano tubes are reacted is 700 nm-22 um;
(4.2) crushing the lithium iron phosphate to a particle size of 3-6 um, and putting the lithium iron phosphate into a stirring kettle, wherein the mass ratio of the lithium iron phosphate to the distilled water is = 1: 2-7, slowly adding distilled water, adding a coupling agent and acetylene black, quickly stirring for 10-16 min, adding the mixed solution obtained in the step (4.1) into a stirring kettle, and uniformly stirring to obtain a modified intermediate;
(4.3) adding the modified intermediate prepared in the step (4.2) into an atomizer for spray drying treatment, wherein in the process, a gaseous carbon source is blown in under the action of protective gas, so that the gaseous carbon source is cracked on the surface of the modified intermediate to form amorphous carbon, and the amorphous carbon is coated on the surface of the modified intermediate to form a uniform coating layer;
and (4.4) drying the powder particles obtained in the step (4.3) in vacuum, and calcining for 3-4 hours at the temperature of 250-350 ℃ under the action of protective gas to obtain the active substance of the positive plate.
In the present application, preferably, the coupling agent is gamma-mercaptopropyltrimethoxysilane, methyl isobutyl ketoximosilane or vinyltriethoxysilane: acetylene black: the mass ratio of the mixed solution is as follows: (0.1-2: 1-1.6: 100);
and (4.3) putting the modified intermediate into an atomizer, heating to 500-700 ℃ under the protection of nitrogen for annealing, loading 24-26% of gaseous carbon source into protective gas at the gas flow rate of 50-1000 ml/min, starting the atomizer, bringing the atomized fine components in the atomizer into a high-temperature furnace by the protective gas, preserving the temperature for 1-12 hours, cracking the gaseous carbon source on the surface of the modified intermediate to form amorphous carbon, and coating the amorphous carbon on the surface of the modified intermediate to form a uniform coating layer with the thickness of 0.3-30 nm.
In this application, preferably, the negative electrode sheet active material is prepared by:
(5) mixing the following components in a mass ratio of 2: 1, putting graphene and carbon nanotubes into absolute ethyl alcohol, carrying out ultrasonic primary crushing treatment, mixing and stirring for 4-6 minutes at normal temperature, heating to 40-60 ℃ at a speed of 2-4 ℃/min in an inert gas protection environment, preserving heat for 4-6 hours, and naturally cooling to room temperature to obtain a mixed solution;
the graphene is multilayer graphene, the interior of the multilayer graphene is of a three-dimensional conductive network structure, the carbon nano tubes are inserted in the three-dimensional conductive network, and the particle size of particles formed after the multilayer graphene and the carbon nano tubes are reacted is 600 nm-20 um;
(6) the method comprises the following steps of (1) adopting petroleum asphalt as a base material, crushing and ball-milling the base material until the particle size is 120-140 um, and then putting the treated particles into a reaction kettle for modification treatment, wherein the method comprises the following steps:
(6.1) introducing nitrogen at the air speed of 80-120 per hour, heating to 300-420 ℃, keeping the temperature at 40-60 ℃/h, and keeping the temperature for 2-6 h;
(6.2) taking part of the asphalt in the step (6.1) to be crushed until the particle size is below 20 mu m, measuring the softening point, and preserving the heat for 4-6 h at the temperature until the measured softening point is 180-380 ℃ of the asphalt base material;
(6.3) naturally cooling the asphalt base material in the step (6.2) to room temperature, and then crushing the asphalt base material to obtain the modified asphalt base material with the particle size of 18-20 um;
(7) dissolving the asphalt screen base material obtained in the step (6) in tetrahydrofuran to obtain a tetrahydrofuran solution of asphalt, pouring the prepared tetrahydrofuran solution of asphalt into the mixed solution, stirring for 20-40 min to obtain mixed slurry, and then adding a solvent to adjust the solid mass percentage content of the mixed slurry to 10-20%;
(8) and (3) drying the mixed slurry obtained in the step (7) through a closed circulation spray dryer, wherein the inlet temperature and the outlet temperature of the closed circulation spray dryer are respectively 120-140 ℃ and 70-60 ℃, and the rotating speed of an atomizer of the closed circulation spray dryer is 24000-26000 r/min, so as to obtain the cathode plate active material.
In this application, preferably, the ratio of the parts by weight of the graphene and the carbon nanotubes to the parts by weight of the absolute ethyl alcohol in the step (5) is 1: 1-1: 5.
in the application, preferably, the positive electrode slurry is coated on a 12-micron thick aluminum foil current collector, and the coating double-sided surface density is 500g/m2Cutting the roll with the thickness of 160 mu m to obtain a positive plate; the negative electrode slurry is coated on a copper foil current collector with the thickness of 6 mu m, the density of the coated double-sided surface is 230g/m2, and the thickness of the roll is 150 mu m;
the diaphragm is a ceramic diaphragm with the thickness of 12 microns, and the ceramic diaphragm is a polypropylene diaphragm with the thickness of 9 microns and is coated with Al with the thickness of 3 microns on one side2O3And (3) coating the ceramic.
Compared with the prior art, the invention has the beneficial effects that:
1. in the application, when the active material of the positive plate is prepared, the carbon nano tube and the graphene are used as the modified additive, so that a structure that the lithium iron phosphate positive material is coated with amorphous carbon is formed. On one hand, the addition of the graphene and the carbon nano tube is beneficial to the activation of transition lithium iron phosphate, and the lithium iron phosphate can prevent the graphene and the carbon nano tube from agglomerating, so that uniform and stable modified lithium iron phosphate can be obtained more easily;
2. in this application, when preparing positive plate active material, the coating is even fine and close amorphous carbon, and this amorphous carbon cladding is on the surface of modified midbody and forms even coating, and its thickness is 0.3nm ~30nm, and this makes it except possessing the advantage of traditional coating, and the ultra-thin coating of nanometer level thickness still is favorable to reducing the migration route of lithium ion in the coating, further improves the multiplying power performance of material, makes it have good lithium ion conduction characteristic.
3. In the application, when the active material of the positive electrode/negative electrode plate is prepared, the high conductivity of the graphene and the carbon nano tube is utilized, the graphene is multilayer graphene, the interior of the multilayer graphene is of a three-dimensional conductive network structure, further improving the migration speed of lithium electrons in the coating layer, inserting the carbon nano-tubes into the three-dimensional conductive network, wherein the particle diameter of particles formed by the action of the multilayer graphene and the carbon nano-tubes is 700 nm-22 um, the process comprises the steps of mixing and stirring for 4-6 minutes at normal temperature, then heating to 40-60 ℃ at the speed of 2-4 ℃/min in the environment protected by inert gas, then preserving heat for 4-6 hours, then naturally cooling to room temperature to obtain a mixed solution, so that micro bubbles between the multilayer graphene and the carbon nano-tube can be further removed to form a stable bonding layer, and the conductive characteristics of the graphene and the carbon nano-tube can be better exerted;
4. according to the process provided by the application, the graphene and the carbon nano tubes are completely distributed on the surface of the lithium iron phosphate material, so that a surface carbon layer with extremely high conductivity is formed, a loose and large carbon layer cannot be generated, the stacking density and the compaction density of the lithium iron phosphate anode material are effectively increased, and the reduction of the polarization resistance of lithium ions in the processes of releasing and embedding lithium ions on the surface of the anode material is facilitated;
5. when the cathode plate active material is prepared, firstly, a carbon nano-tube and graphene are modified, the high conductivity of the graphene and the carbon nano-tube is utilized, the graphene is multilayer graphene, the interior of the multilayer graphene is of a three-dimensional conductive network structure, the migration speed of lithium electrons in a coating layer is further improved, the carbon nano-tube is inserted into the three-dimensional conductive network, the particle size of particles formed after the multilayer graphene and the carbon nano-tube are acted is 700 nm-22 mu m, the process is that the particles are mixed and stirred for 4-6 minutes at normal temperature, then the temperature is increased to 40-60 ℃ at the speed of 2-4 ℃/min under the environment of inert gas protection, then the temperature is kept for 4-6 hours, then the mixed solution is naturally cooled to room temperature, and thus micro bubbles between the multilayer graphene and the carbon nano-tube can be further removed to form a stable bonding layer, the preparation method is favorable for better exerting the conductive characteristics of graphene and carbon nano tubes, then a precursor is prepared in a closed cycle spray drying mode, modified asphalt is uniformly dispersed on the surface of the graphene, after high-temperature heat treatment, the asphalt is carbonized to form a layer of amorphous carbon which tightly wraps the surface of the graphene to form a composite material with a core-shell structure, the existence of a coating layer not only reduces the specific surface area of the material and prevents an organic solvent from entering, and the purpose of obtaining an even and compact SEI film is achieved, but also the surface carbon material can fix a graphite flake and prevent the falling of the graphite surface layer, so that the primary efficiency, specific capacity and cycle stability of the material are improved to a certain extent.
Detailed Description
In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further described with the specific embodiments.
Example 1:
a preparation method of a lithium ion battery comprises the following steps:
(1) preparing a positive plate: preparing an active substance of the positive plate, and mixing the active substance of the positive plate, acetylene black, a polyvinylidene fluoride adhesive and absolute ethyl alcohol according to the weight percentage of 80: 1: 2: 60, putting the mixture into a reaction kettle, stirring at a constant speed to obtain anode slurry, coating the anode slurry on an aluminum foil current collector, and cutting to obtain an anode plate;
(2) preparing a negative plate: preparing a negative plate active substance, and mixing the negative plate active substance, an acrylic acid aqueous solution with a solid content of 30%, acetylene black and absolute ethyl alcohol according to a weight percentage of 82: 1: 1: 55, putting the mixture into a reaction kettle, stirring at a constant speed to obtain negative electrode slurry, coating the negative electrode slurry on a copper foil current collector, and cutting to obtain a negative electrode sheet;
(3) and (3) Z-shaped lamination of the positive plate, the negative plate and the diaphragm, tab welding, packaging, battery core baking, liquid injection, pre-charging and liquid pumping molding are carried out to prepare the lithium ion battery, wherein the electrolyte adopts a film forming additive electrolyte added with vinylene sulfate and fluoroethylene carbonate.
In this example. The active material of the positive plate in the step (1) is prepared by the following steps:
(4.1) mixing the components in a mass ratio of 2: 1, putting graphene and carbon nanotubes into ethanol, carrying out ultrasonic primary crushing treatment, mixing and stirring for 4-6 minutes at normal temperature, heating to 40-60 ℃ at a speed of 2-4 ℃/min in an inert gas protection environment, preserving heat for 4-6 hours, and naturally cooling to room temperature to obtain a mixed solution;
the graphene is multilayer graphene, the interior of the multilayer graphene is of a three-dimensional conductive network structure, the carbon nano tubes are inserted in the three-dimensional conductive network, and the particle size of particles formed after the multilayer graphene and the carbon nano tubes are reacted is 700 nm-22 um;
(4.2) crushing the lithium iron phosphate to a particle size of 3-6 um, and putting the lithium iron phosphate into a stirring kettle, wherein the mass ratio of the lithium iron phosphate to the distilled water is = 1: 2-7, slowly adding distilled water, adding a coupling agent and acetylene black, quickly stirring for 10-16 min, adding the mixed solution obtained in the step (4.1) into a stirring kettle, and uniformly stirring to obtain a modified intermediate;
(4.3) adding the modified intermediate prepared in the step (4.2) into an atomizer for spray drying treatment, wherein in the process, a gaseous carbon source is blown in under the action of protective gas, so that the gaseous carbon source is cracked on the surface of the modified intermediate to form amorphous carbon, and the amorphous carbon is coated on the surface of the modified intermediate to form a uniform coating layer;
and (4.4) drying the powder particles obtained in the step (4.3) in vacuum, and calcining for 3-4 hours at the temperature of 250-350 ℃ under the action of protective gas to obtain the active substance of the positive plate.
In this embodiment, the coupling agent is γ -mercaptopropyl trimethoxysilane, methyl isobutyl ketoxime silane, or vinyl triethoxysilane, and the coupling agent: acetylene black: the mass ratio of the mixed solution is as follows: (0.1-2: 1-1.6: 100);
and (4.3) putting the modified intermediate into an atomizer, heating to 500-700 ℃ under the protection of nitrogen for annealing, loading 24-26% of gaseous carbon source into protective gas at the gas flow rate of 50-1000 ml/min, starting the atomizer, bringing the atomized fine components in the atomizer into a high-temperature furnace by the protective gas, preserving the temperature for 1-12 hours, cracking the gaseous carbon source on the surface of the modified intermediate to form amorphous carbon, and coating the amorphous carbon on the surface of the modified intermediate to form a uniform coating layer with the thickness of 0.3-30 nm.
In this embodiment, the negative electrode sheet active material is prepared through the following steps:
(5) mixing the following components in a mass ratio of 2: 1, putting graphene and carbon nanotubes into absolute ethyl alcohol, carrying out ultrasonic primary crushing treatment, mixing and stirring for 4-6 minutes at normal temperature, heating to 40-60 ℃ at a speed of 2-4 ℃/min in an inert gas protection environment, preserving heat for 4-6 hours, and naturally cooling to room temperature to obtain a mixed solution;
the graphene is multilayer graphene, the interior of the multilayer graphene is of a three-dimensional conductive network structure, the carbon nano tubes are inserted into the three-dimensional conductive network, and the particle size of particles formed after the multilayer graphene and the carbon nano tubes are acted is 600 nm-20 um.
(6) The method comprises the following steps of (1) adopting petroleum asphalt as a base material, crushing and ball-milling the base material until the particle size is 120-140 um, and then putting the treated particles into a reaction kettle for modification treatment, wherein the method comprises the following steps:
(6.1) introducing nitrogen at the air speed of 80-120 per hour, heating to 300-420 ℃, keeping the temperature at 40-60 ℃/h, and keeping the temperature for 2-6 h;
(6.2) taking part of the asphalt in the step (6.1) to be crushed until the particle size is below 20 mu m, measuring the softening point, and preserving the heat for 4-6 h at the temperature until the measured softening point is 180-380 ℃ of the asphalt base material;
(6.3) naturally cooling the asphalt base material in the step (6.2) to room temperature, and then crushing the asphalt base material to obtain the modified asphalt base material with the particle size of 18-20 um;
(7) dissolving the asphalt screen base material obtained in the step (6) in tetrahydrofuran to obtain a tetrahydrofuran solution of asphalt, pouring the prepared tetrahydrofuran solution of asphalt into the mixed solution, stirring for 20-40 min to obtain mixed slurry, and then adding a solvent to adjust the solid mass percentage content of the mixed slurry to 10-20%;
(8) and (3) drying the mixed slurry obtained in the step (7) through a closed circulation spray dryer, wherein the inlet temperature and the outlet temperature of the closed circulation spray dryer are respectively 120-140 ℃ and 70-60 ℃, and the rotating speed of an atomizer of the closed circulation spray dryer is 24000-26000 r/min, so as to obtain the cathode plate active material.
In this embodiment, the ratio of the parts by weight of the graphene and the carbon nanotube to the parts by weight of the absolute ethyl alcohol in the step (5) is 1: 1-1: 5.
in this embodiment, the positive electrode slurry is coated on a 12 μm thick aluminum foil current collector with a double-sided coated density of 500g/m2Cutting the roll with the thickness of 160 mu m to obtain a positive plate; the negative electrode slurry is coated on a copper foil current collector with the thickness of 6 mu m, the density of the coated double-sided surface is 230g/m2, and the thickness of the roll is 150 mu m;
the diaphragm is a ceramic diaphragm with the thickness of 12 microns, and the ceramic diaphragm is a polypropylene diaphragm with the thickness of 9 microns and is coated with Al with the thickness of 3 microns on one side2O3And (3) coating the ceramic.
Example 2:
the content of this example is substantially the same as that of example 1, and the same points are not repeated, except that in this example, the step (4.3) is not included when the positive electrode sheet active material is prepared, and the modified intermediate is directly subjected to the step (4.4) to obtain the positive electrode sheet active material, and the lithium ion battery is prepared and formed.
Example 3:
the content of this example is substantially the same as that of example 1, and the same points are not repeated, except that in this example, when the positive electrode sheet active material and the negative electrode sheet active material are prepared, only the graphene and the carbon nanotubes are mixed and crushed in step (4.1) and step (5) to obtain a mixed solution, so as to prepare the lithium ion battery.
Comparative example 1:
the lithium ion battery is prepared and formed by adopting the technical scheme in the application number of CN201710724700.9 in the comparative example.
Battery performance testing
Under the same conditions of compacted density, the porosity of the electrode was measured by using a mercury porosimeter, the electrolyte was dropped into a dry glove box to measure the liquid permeation time, and the lithium ion batteries prepared in examples 1 to 3 and comparative example 1 were subjected to battery cycle and self-discharge tests, and the results are shown in the following table 1:
TABLE 1 comparison of physical and electrochemical Properties of the electrodes
The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (4)
1. A preparation method of a lithium ion battery is characterized by comprising the following steps: the method comprises the following steps:
(1) preparing a positive plate: preparing an active substance of the positive plate, and mixing the active substance of the positive plate, acetylene black, a polyvinylidene fluoride adhesive and absolute ethyl alcohol according to the weight percentage of 80: 1: 2: 60, putting the mixture into a reaction kettle, stirring at a constant speed to obtain anode slurry, coating the anode slurry on an aluminum foil current collector, and cutting to obtain an anode plate;
(2) preparing a negative plate: preparing a negative plate active substance, and mixing the negative plate active substance, an acrylic acid aqueous solution with a solid content of 30%, acetylene black and absolute ethyl alcohol according to a weight percentage of 82: 1: 1: 55, putting the mixture into a reaction kettle, stirring at a constant speed to obtain negative electrode slurry, coating the negative electrode slurry on a copper foil current collector, and cutting to obtain a negative electrode sheet;
(3) z-shaped lamination of a positive plate, a negative plate and a diaphragm, tab welding, packaging, battery core baking, liquid injection, pre-charging and liquid pumping molding are carried out to prepare the lithium ion battery;
the active material of the positive plate in the step (1) is prepared by the following steps:
(4.1) mixing the components in a mass ratio of 2: 1, putting graphene and carbon nanotubes into ethanol, carrying out ultrasonic primary crushing treatment, mixing and stirring for 4-6 minutes at normal temperature, heating to 40-60 ℃ at a speed of 2-4 ℃/min in an inert gas protection environment, preserving heat for 4-6 hours, and naturally cooling to room temperature to obtain a mixed solution;
the graphene is multilayer graphene, the interior of the multilayer graphene is of a three-dimensional conductive network structure, the carbon nano tubes are inserted in the three-dimensional conductive network, and the particle size of particles formed after the multilayer graphene and the carbon nano tubes are reacted is 700 nm-22 um;
(4.2) crushing the lithium iron phosphate to a particle size of 3-6 um, and putting the lithium iron phosphate into a stirring kettle, wherein the mass ratio of the lithium iron phosphate to the distilled water is = 1: 2-7, slowly adding distilled water, adding a coupling agent and acetylene black, quickly stirring for 10-16 min, adding the mixed solution obtained in the step (4.1) into a stirring kettle, and uniformly stirring to obtain a modified intermediate;
(4.3) adding the modified intermediate prepared in the step (4.2) into an atomizer for spray drying treatment, wherein the step of adding the modified intermediate into the atomizer for spray drying treatment is to blow in a gaseous carbon source under the action of protective gas, so that the gaseous carbon source is cracked on the surface of the modified intermediate to form amorphous carbon, and the amorphous carbon is coated on the surface of the modified intermediate to form a uniform coating layer;
(4.4) drying the powder particles obtained in the step (4.3) in vacuum, and calcining for 3-4 hours at 250-350 ℃ under the action of protective gas to obtain an active substance of the positive plate;
the negative plate active material is prepared by the following steps:
(5) mixing the following components in a mass ratio of 2: 1, putting graphene and carbon nanotubes into absolute ethyl alcohol, carrying out ultrasonic primary crushing treatment, mixing and stirring for 4-6 minutes at normal temperature, heating to 40-60 ℃ at a speed of 2-4 ℃/min in an inert gas protection environment, preserving heat for 4-6 hours, and naturally cooling to room temperature to obtain a mixed solution;
the graphene is multilayer graphene, the interior of the multilayer graphene is of a three-dimensional conductive network structure, the carbon nano tubes are inserted in the three-dimensional conductive network, and the particle size of particles formed after the multilayer graphene and the carbon nano tubes are reacted is 600 nm-20 um;
(6) the method comprises the following steps of (1) adopting petroleum asphalt as a base material, crushing and ball-milling the base material until the particle size is 120-140 um, and then putting the treated particles into a reaction kettle for modification treatment, wherein the method comprises the following steps:
(6.1) introducing nitrogen at the air speed of 80-120 per hour, heating to 300-420 ℃, keeping the temperature at 40-60 ℃/h, and keeping the temperature for 2-6 h;
(6.2) taking part of the asphalt in the step (6.1) to be crushed until the particle size is below 20 mu m, measuring the softening point, and preserving the heat for 4-6 h at the temperature until the measured softening point is 180-380 ℃ of the asphalt base material;
(6.3) naturally cooling the asphalt base material in the step (6.2) to room temperature, and then crushing the asphalt base material to obtain the modified asphalt base material with the particle size of 18-20 um;
(7) dissolving the asphalt screen base material obtained in the step (6) in tetrahydrofuran to obtain a tetrahydrofuran solution of asphalt, pouring the prepared tetrahydrofuran solution of asphalt into the mixed solution, stirring for 20-40 min to obtain mixed slurry, and then adding a solvent to adjust the solid mass percentage content of the mixed slurry to 10-20%;
(8) and (3) drying the mixed slurry obtained in the step (7) through a closed circulation spray dryer, wherein the inlet temperature and the outlet temperature of the closed circulation spray dryer are respectively 120-140 ℃ and 70-60 ℃, and the rotating speed of an atomizer of the closed circulation spray dryer is 24000-26000 r/min, so as to obtain the cathode plate active material.
2. The method for preparing a lithium ion battery according to claim 1, wherein the coupling agent is gamma-mercaptopropyltrimethoxysilane, methyl isobutyl ketoximosilane or vinyltriethoxysilane, and the coupling agent: acetylene black: the mass ratio of the mixed solution is as follows: (0.1-2: 1-1.6: 100);
and (4.3) putting the modified intermediate into an atomizer, heating to 500-700 ℃ under the protection of nitrogen for annealing, loading 24-26% of gaseous carbon source into protective gas at the gas flow rate of 50-1000 ml/min, starting the atomizer, bringing the atomized fine components in the atomizer into a high-temperature furnace by the protective gas, preserving the temperature for 1-12 hours, cracking the gaseous carbon source on the surface of the modified intermediate to form amorphous carbon, and coating the amorphous carbon on the surface of the modified intermediate to form a uniform coating layer with the thickness of 0.3-30 nm.
3. The preparation method of the lithium ion battery according to claim 1, wherein the ratio of the total weight parts of the graphene and the carbon nanotubes to the weight parts of the absolute ethyl alcohol in the step (5) is 1: 1-1: 5.
4. the preparation method of the lithium ion battery according to any one of claims 1 to 3, wherein the positive electrode slurry is coated on a 12 μm thick aluminum foil current collector, the density of the coated double-sided surface is 500g/m2, the thickness of the coated roller is 160 μm, and a positive electrode sheet is obtained by slitting; the negative electrode slurry is coated on a copper foil current collector with the thickness of 6 mu m, the density of the coated double-sided surface is 230g/m2, and the thickness of the roll is 150 mu m;
the diaphragm is a ceramic diaphragm with the thickness of 12 microns, and the ceramic diaphragm is a polypropylene diaphragm with the thickness of 9 microns, and one side of the polypropylene diaphragm is coated with an Al2O3 ceramic coating with the thickness of 3 microns.
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