CN108682833B - Preparation method of lithium iron phosphate-based modified cathode material - Google Patents
Preparation method of lithium iron phosphate-based modified cathode material Download PDFInfo
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- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
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- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
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Abstract
The invention relates to the technical field of lithium ion battery electrode materials, in particular to a preparation method of a lithium iron phosphate-based modified cathode material, which comprises the following steps: the method comprises the steps of putting a zirconium source compound into distilled water, crushing the mixture by a ball mill until the particle size is 2-12 um, modifying graphene and a carbon nano tube, bonding zirconium and carbon with the zirconium source compound, introducing zirconium to the surface of the graphene after heat treatment to obtain a zirconium-doped carbon material, modifying lithium iron phosphate by using the zirconium-doped carbon material, doping part of zirconium into lithium iron phosphate, increasing the conductivity between lithium iron phosphate particles, improving the compatibility between the surface of the material and electrolyte, reducing the resistance of lithium ion migration, and further improving the electrochemical performance of the battery in a low-temperature environment.
Description
The technical field is as follows:
the invention relates to the technical field of lithium ion battery electrode materials, in particular to a preparation method of a lithium iron phosphate-based modified positive electrode material.
Background art:
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 (CN101172597, CN101807692A) and ultrasonic coprecipitation (CN101800311A), 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 invention content is as follows:
the invention overcomes the defects of the prior art, and provides the uniform and compact cathode material which can reduce the polarization resistance of lithium ions in the processes of releasing and embedding on the surface of the cathode material and improve the rate capability of the material.
The technical problem to be solved by the invention is realized by adopting the following technical scheme: a preparation method of a lithium iron phosphate-based modified cathode material comprises the following steps:
(1) putting a zirconium source compound into distilled water, grinding the zirconium source compound by a ball mill until the particle size is 2-12 um, and mixing and stirring the zirconium source compound and the distilled water at normal temperature for 4-6 minutes to obtain a mixed solution A;
(2) mixing the following components in a mass ratio of 2: 1, putting graphene and a carbon nano tube into distilled water, carrying out ultrasonic primary crushing treatment, mixing and stirring for 4-6 minutes at normal temperature, heating to 40-60 ℃ at the 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 B;
(3) mixing the mixed solution A and the mixed solution B in a volume ratio (1-2): 1 to obtain a zirconium-doped carbon material precursor, and drying the zirconium-doped carbon material precursor by a closed-cycle spray dryer, wherein the inlet temperature and the outlet temperature of the closed-cycle spray dryer are respectively 800-960 ℃ and 70-60 ℃, and the rotating speed of an atomizer of the closed-cycle spray dryer is 24000-26000 r/min to form the zirconium-doped carbon material;
(3) crushing 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 distilled water is 1: (2-7) slowly adding distilled water, adding a coupling agent and a conductive agent, quickly stirring for 10-16 min, adding the zirconium-doped carbon material obtained in the step (3) into a stirring kettle, and uniformly stirring to obtain a modified intermediate;
(4) and (3) adding the modified intermediate prepared in the step (3) 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, the amorphous carbon is coated on the surface of the modified intermediate to form an even coating layer, and the thickness of the coating layer is 2-6 nm, so that the lithium iron phosphate-based modified cathode material is obtained.
Preferably, in the step (4), the modified intermediate in the step (3) is put into an atomizer, the temperature is raised to 500-700 ℃ under the protection of protective gas for annealing treatment, then 24-26% of gaseous carbon source is loaded by the protective gas, the gas flow rate is 50-1000 ml/min, the atomizer is started simultaneously, the protective gas brings the atomized fine components in the atomizer into a high-temperature furnace, the temperature is maintained for 1-12 hours, the gaseous carbon source is cracked on the surface of the precursor to form amorphous carbon, and the amorphous carbon is coated on the surface of the modified intermediate to form a coating layer with the uniform thickness of 2-6 nm, namely the lithium iron phosphate-based modified cathode material.
Preferably, in the present application, the mass ratio of the zirconium source compound to the distilled water in the step (1) is (2-6): 50; the mass ratio of the total mass of the graphene and the carbon nano tubes to the mass of the distilled water in the step (2) is (4-4.8): 50.
preferably, in step (3), the coupling agent is γ -mercaptopropyl-trimethoxysilane, methyl isobutyl ketoxime silane or vinyl triethoxysilane, the conductive agent is sucrose or glucose, and the coupling agent: conductive agent: the mass ratio of the zirconium-doped carbon material is as follows: (0.1-2: 1-1.6: 100).
Preferably, in the present application, the protective gas in step (5) is nitrogen or argon.
Preferably, in the present application, the zirconium source is ZrO (NO)3)2Or ZrOCl2。
Compared with the prior art, the invention has the beneficial effects that:
(1) according to the method, firstly, a compound of a zirconium source is subjected to modification treatment of graphene and a carbon nano tube, zirconium and carbon form a bond, the zirconium is introduced to the surface of the graphene after heat treatment, a zirconium-doped carbon material is obtained, lithium iron phosphate is modified by the zirconium-doped carbon material, part of the zirconium is doped into the lithium iron phosphate, the intrinsic conductivity of lithium iron phosphate particles can be improved, meanwhile, the zirconium dispersed on the surface of the carbon material contains more electron holes and has a larger interaction force with the lithium iron phosphate, the carbon material can be kept stable in the charging and discharging process and is not easy to fall off from the surface of the lithium iron phosphate, the conductivity between the lithium iron phosphate particles is increased, the compatibility between the surface of the material and electrolyte is improved, the resistance suffered by lithium ion migration is reduced, and the electrochemical performance of a battery in a low-temperature environment is improved;
(2) according to the application, high conductivity of graphene and carbon nanotubes is utilized, the graphene is multilayer graphene, the interior of the multilayer graphene is of a three-dimensional conductive network structure, so that the migration speed of lithium electrons in a coating layer is improved, the carbon nanotubes are inserted into the three-dimensional conductive network, the particle size of particles formed after the multilayer graphene and the carbon nanotubes are acted is 700 nm-22 um, the process is that the particles are mixed and stirred for 4-6 minutes at normal temperature, then the temperature is raised to 40-60 ℃ at the speed of 2-4 ℃/min in an inert gas protection environment, the temperature is kept for 4-6 hours, and then the particles are naturally cooled to room temperature to obtain a mixed solution B, so that micro bubbles between the multilayer graphene and the carbon nanotubes can be further removed, a stable binding layer is formed, and the conductive characteristics of the graphene and the carbon nanotubes can be better exerted;
(3) in the application, the temperature is raised to 500-700 ℃ under the protection of protective gas for annealing treatment, the annealing treatment can further improve the stability of a modified intermediate, the acting force between graphene and a carbon nanotube in the modified intermediate is weakened, so that the prepared anode material has strong stability, then 24-26% of gaseous carbon source is loaded by the protective gas, the gas flow rate is 50-1000 ml/min, an atomizer is started, the protective gas brings atomized fine components in the atomizer into a high-temperature furnace, the temperature is kept for 1-12 hours, the gaseous carbon source is cracked on the surface of the modified intermediate to form amorphous carbon, the amorphous carbon is coated on the surface of the modified intermediate to form an even coating layer, and the lithium battery anode material is obtained, the thickness of the coating layer is 0.3-30 nm, and the main function of the coating layer is to protect the stability of the lithium battery anode in the formation process, because the coating clearance is great and thickness is less, the coating is netted structure, can not block lithium ion's migration, and this coating can wrap up anodal active material simultaneously, that is to say this parcel is on modified midbody to extension lithium cell life.
The specific implementation mode is as follows:
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 iron phosphate-based modified cathode material comprises the following steps:
(1) putting a zirconium source compound into distilled water, grinding the zirconium source compound by a ball mill until the particle size is 2-12 um, and mixing and stirring the zirconium source compound and the distilled water at normal temperature for 4-6 minutes to obtain a mixed solution A;
(2) mixing the following components in a mass ratio of 2: 1, putting graphene and a carbon nano tube into distilled water, carrying out ultrasonic primary crushing treatment, mixing and stirring for 4-6 minutes at normal temperature, heating to 40-60 ℃ at the 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 B;
(3) mixing the mixed solution A and the mixed solution B in a volume ratio of 1: 1 to obtain a zirconium-doped carbon material precursor, and drying the zirconium-doped carbon material precursor by a closed-cycle spray dryer, wherein the inlet temperature and the outlet temperature of the closed-cycle spray dryer are respectively 800-960 ℃ and 70-60 ℃, and the rotating speed of an atomizer of the closed-cycle spray dryer is 24000-26000 r/min to form the zirconium-doped carbon material;
(3) crushing 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 distilled water is 1: (2-7) slowly adding distilled water, adding a coupling agent and a conductive agent, quickly stirring for 10-16 min, adding the zirconium-doped carbon material obtained in the step (3) into a stirring kettle, and uniformly stirring to obtain a modified intermediate;
(4) and (3) adding the modified intermediate prepared in the step (3) 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, the amorphous carbon is coated on the surface of the modified intermediate to form an even coating layer, and the thickness of the coating layer is 2-6 nm, so that the lithium iron phosphate-based modified cathode material is obtained.
In this embodiment, in the step (4), the modified intermediate in the step (3) is put into an atomizer, and heated to 500-700 ℃ under the protection of protective gas for annealing treatment, then 25% of gaseous carbon source is loaded into the protective gas, the gas flow rate is 50-1000 ml/min, the atomizer is started at the same time, the protective gas brings the fine atomized components in the atomizer into a high temperature furnace, the temperature is maintained for 1-12 hours, the gaseous carbon source is cracked on the surface of the precursor to form amorphous carbon, and the amorphous carbon is coated on the surface of the modified intermediate and forms a coating layer with a uniform thickness of 2-6 nm, so that the lithium iron phosphate-based modified positive electrode material is obtained.
In this embodiment, the mass ratio of the zirconium source compound to the distilled water in the step (1) is (2-6): 50; the mass ratio of the total mass of the graphene and the carbon nano tubes to the mass of the distilled water in the step (2) is (4-4.8): 50.
in this embodiment, in the step (3), the coupling agent is γ -mercaptopropyl trimethoxysilane, methyl isobutyl ketoxime silane, or vinyl triethoxysilane, the conductive agent is sucrose or glucose, and the coupling agent: conductive agent: the mass ratio of the zirconium-doped carbon material is as follows: (0.1-2: 1-1.6: 100).
In this embodiment, the protective gas in step (5) is nitrogen, and the zirconium source is ZrO (NO)3)2。
Example 2
The content of the present embodiment is substantially the same as that of embodiment 1, and the same points are not repeated, except that: and (3) mixing the mixed solution A and the mixed solution B according to a volume ratio of 2: 1 to obtain a zirconium-doped carbon material precursor, and drying the zirconium-doped carbon material precursor by a closed-cycle spray dryer, wherein the inlet temperature and the outlet temperature of the closed-cycle spray dryer are respectively 800-960 ℃ and 70-60 ℃, and the rotating speed of an atomizer of the closed-cycle spray dryer is 24000-26000 r/min to form the zirconium-doped carbon material.
Example 3
The content of the present embodiment is substantially the same as that of embodiment 1, and the same points are not repeated, except that: and (3) mixing the mixed solution A and the mixed solution B in a volume ratio of 1.5: 1 to obtain a zirconium-doped carbon material precursor, and drying the zirconium-doped carbon material precursor by a closed-cycle spray dryer, wherein the inlet temperature and the outlet temperature of the closed-cycle spray dryer are respectively 800-960 ℃ and 70-60 ℃, and the rotating speed of an atomizer of the closed-cycle spray dryer is 24000-26000 r/min to form the zirconium-doped carbon material.
Example 4
The content of the present embodiment is substantially the same as that of embodiment 3, and the same points are not repeated, except that: and (4) putting the modified intermediate in the step (3) into an atomizer, heating to 500-700 ℃ under the protection of protective gas for annealing, loading 24% of gaseous carbon source into the protective gas, starting the atomizer at the gas flow rate of 50-1000 ml/min, 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 precursor to form amorphous carbon, and coating the amorphous carbon on the surface of the modified intermediate to form a coating layer with the uniform thickness of 2-6 nm, thus obtaining the lithium iron phosphate-based modified positive electrode material.
Example 5
The content of the present embodiment is substantially the same as that of embodiment 3, and the same points are not repeated, except that: and (4) putting the modified intermediate in the step (3) into an atomizer, heating to 500-700 ℃ under the protection of protective gas for annealing, loading 26% of gaseous carbon source into the atomizer at a gas flow rate of 50-1000 ml/min, starting the atomizer, carrying 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 precursor to form amorphous carbon, and coating the amorphous carbon on the surface of the modified intermediate to form a coating layer with a uniform thickness of 2-6 nm, thus obtaining the lithium iron phosphate-based modified positive electrode material.
Comparative example 1
The content of the comparative example is basically the same as that of the example 1, and the same parts are not repeated, except that: and (3) mixing the mixed solution A and the mixed solution B in a volume ratio of 0.5: 1 to obtain a zirconium-doped carbon material precursor, and drying the zirconium-doped carbon material precursor by a closed-cycle spray dryer, wherein the inlet temperature and the outlet temperature of the closed-cycle spray dryer are respectively 800-960 ℃ and 70-60 ℃, and the rotating speed of an atomizer of the closed-cycle spray dryer is 24000-26000 r/min to form the zirconium-doped carbon material.
Comparative example 2
The content of the comparative example is basically the same as that of the example 1, and the same parts are not repeated, except that: and (3) mixing the mixed solution A and the mixed solution B in a volume ratio of 0.5: 1 to obtain a zirconium-doped carbon material precursor, and drying the zirconium-doped carbon material precursor by a closed-cycle spray dryer, wherein the inlet temperature and the outlet temperature of the closed-cycle spray dryer are respectively 800-960 ℃ and 70-60 ℃, and the rotating speed of an atomizer of the closed-cycle spray dryer is 24000-26000 r/min to form the zirconium-doped carbon material.
Comparative example 3
The content of the comparative example is basically the same as that of the example 1, and the same parts are not repeated, except that: and (3) mixing the mixed solution A and the mixed solution B in a volume ratio of 3: 1 to obtain a zirconium-doped carbon material precursor, and drying the zirconium-doped carbon material precursor by a closed-cycle spray dryer, wherein the inlet temperature and the outlet temperature of the closed-cycle spray dryer are respectively 800-960 ℃ and 70-60 ℃, and the rotating speed of an atomizer of the closed-cycle spray dryer is 24000-26000 r/min to form the zirconium-doped carbon material.
Comparative example 4
The content of the comparative example is basically the same as that of the example 3, and the same parts are not repeated, except that: and (4) putting the modified intermediate in the step (3) into an atomizer, heating to 500-700 ℃ under the protection of protective gas for annealing, loading 22% of gaseous carbon source into the atomizer at a gas flow rate of 50-1000 ml/min, starting the atomizer, carrying 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 precursor to form amorphous carbon, and coating the amorphous carbon on the surface of the modified intermediate to form a coating layer with a uniform thickness of 2-6 nm, thus obtaining the lithium iron phosphate-based modified positive electrode material.
Comparative example 5
The content of the comparative example is basically the same as that of the example 3, and the same parts are not repeated, except that: and (4) putting the modified intermediate in the step (3) into an atomizer, heating to 500-700 ℃ under the protection of protective gas for annealing, loading 28% of gaseous carbon source into the protective gas, starting the atomizer at the gas flow rate of 50-1000 ml/min, 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 precursor to form amorphous carbon, and coating the amorphous carbon on the surface of the modified intermediate to form a coating layer with the uniform thickness of 2-6 nm, thus obtaining the lithium iron phosphate-based modified positive electrode material.
Comparative example 6
The test results are recorded in table 1, using the positive electrode material in example 1 of chinese patent "a positive electrode material, a lithium ion battery containing the positive electrode material, and a method for manufacturing the same" disclosed in application No. CN 201710610430.9 "as a control group.
And (3) performance testing:
1. conductivity of material
The samples of examples and comparative examples were pressed into a sheet having a thickness of 1cm, square-shaped conductive silver paste was coated on both sides of the sheet and conductive silver wires were adhered, and the sheet was connected to an impedance analyzer (Solartron 1260 type impedance analyzer) to perform a test, and the test results were recorded in table 1.
2. Electrochemical performance test
The positive electrode materials obtained in the above examples and comparative examples were used to prepare electrode sheets: dissolving polyvinylidene fluoride into N-methyl pyrrolidone to prepare glue with the mass fraction of 7%, uniformly grinding a positive electrode material into paste, uniformly coating the paste on an aluminum foil, drying the aluminum foil under a baking lamp, finally baking the aluminum foil in a vacuum oven at 120 ℃ for 5 hours, cooling the aluminum foil to room temperature, and cutting the aluminum foil into electrode plates with the thickness of 8 x 8mm 2;
a lithium sheet is used as a negative electrode, a polypropylene film is used as a diaphragm, lithium hexafluorophosphate is used as a solute, a solution in which ethylene carbonate and ethylene carbonate are mixed and used as a solvent is used as an electrolyte, a button cell is assembled in a glove box under an argon protective atmosphere, a charge-discharge tester is used for carrying out constant-current charge-discharge test on the button cell under the room temperature condition, the test result is recorded in a table 1, and a low-temperature incubator (a GX-3000-80L high-low temperature incubator of Gaoxin detection equipment in Dongguan city) is used for setting and meeting the low-temperature condition required by the test.
TABLE 1
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 (5)
1. The preparation method of the lithium iron phosphate-based modified cathode material is characterized by comprising the following steps of:
(1) putting a zirconium source compound into distilled water, grinding the zirconium source compound by a ball mill until the particle size is 2-12 um, and mixing and stirring the zirconium source compound and the distilled water at normal temperature for 4-6 minutes to obtain a mixed solution A;
(2) mixing the following components in a mass ratio of 2: 1, putting graphene and a carbon nano tube into distilled water, carrying out ultrasonic primary crushing treatment, mixing and stirring for 4-6 minutes at normal temperature, heating to 40-60 ℃ at the 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 B;
(3) mixing the mixed solution A and the mixed solution B in a volume ratio (1-2): 1 to obtain a zirconium-doped carbon material precursor, and drying the zirconium-doped carbon material precursor by a closed-cycle spray dryer, wherein the inlet temperature and the outlet temperature of the closed-cycle spray dryer are respectively 800-960 ℃ and 70-60 ℃, and the rotating speed of an atomizer of the closed-cycle spray dryer is 24000-26000 r/min to form the zirconium-doped carbon material;
(4) crushing 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 distilled water is 1: (2-7) slowly adding distilled water, adding a coupling agent and a conductive agent, quickly stirring for 10-16 min, adding the zirconium-doped carbon material obtained in the step (3) into a stirring kettle, and uniformly stirring to obtain a modified intermediate;
(5) adding the modified intermediate prepared in the step (4) 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, the amorphous carbon is coated on the surface of the modified intermediate to form a uniform coating, and the thickness of the coating is 2-6 nm, so that the lithium iron phosphate-based modified cathode material is obtained;
in the preparation method of the lithium iron phosphate-based modified cathode material, in the step (4), the coupling agent is gamma-mercaptopropyl trimethoxysilane, methyl isobutyl ketoxime silane or vinyl triethoxysilane, the conductive agent is sucrose or glucose, and the coupling agent: conductive agent: the mass ratio of the zirconium-doped carbon material is as follows: (0.1-2: 1-1.6: 100).
2. The method for preparing the lithium iron phosphate-based modified cathode material according to claim 1, wherein in the step (5), the modified intermediate in the step (4) is put into an atomizer, the temperature is raised to 500-700 ℃ under the protection of protective gas for annealing treatment, then 24-26% of gaseous carbon source is loaded by the protective gas, the gas flow rate is 50-1000 ml/min, the atomizer is started, the protective gas brings the atomized fine components in the atomizer into a high-temperature furnace, the temperature is maintained for 1-12 hours, the gaseous carbon source is cracked on the surface of the precursor to form amorphous carbon, and the amorphous carbon is coated on the surface of the modified intermediate to form a coating layer with a uniform thickness of 2-6 nm, so that the lithium iron phosphate-based modified cathode material is obtained.
3. The method for preparing the lithium iron phosphate-based modified cathode material according to claim 1, wherein the mass ratio of the zirconium source compound to the distilled water in the step (1) is (2-6): 50; the mass ratio of the total mass of the graphene and the carbon nano tubes to the mass of the distilled water in the step (2) is (4-4.8): 50.
4. the method for preparing a lithium iron phosphate-based modified cathode material according to claim 1, wherein the protective gas in step (5) is nitrogen or argon.
5. The method for preparing a lithium iron phosphate-based modified positive electrode material according to claim 1, wherein the zirconium source is ZrO (NO)3)2Or ZrOCl2。
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| CN109817902B (en) * | 2018-12-25 | 2021-09-28 | 江苏理工学院 | Method for improving battery cycle stability by using bimetallic coupling agent |
| CN112151781A (en) * | 2020-09-24 | 2020-12-29 | 贵州梅岭电源有限公司 | Rapid composite coating modification method for lithium battery positive electrode material |
| CN114314548B (en) * | 2021-12-29 | 2022-11-25 | 湖北万润新能源科技股份有限公司 | Titanium and zirconium co-doped carbon-coated lithium iron phosphate material and preparation method and application thereof |
| CN116544399B (en) * | 2023-07-06 | 2023-11-17 | 宜宾锂宝新材料有限公司 | Multi-stage coated positive electrode material, preparation method and lithium battery |
| CN117174831B (en) * | 2023-11-03 | 2024-03-26 | 杭州巴特瑞新能源科技有限公司 | Lithium ion battery applied to portable mobile power supply and preparation method |
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