CN113381011A - Lithium iron phosphate anode material and preparation method and application thereof - Google Patents
Lithium iron phosphate anode material and preparation method and application thereof Download PDFInfo
- Publication number
- CN113381011A CN113381011A CN202110641040.4A CN202110641040A CN113381011A CN 113381011 A CN113381011 A CN 113381011A CN 202110641040 A CN202110641040 A CN 202110641040A CN 113381011 A CN113381011 A CN 113381011A
- Authority
- CN
- China
- Prior art keywords
- iron phosphate
- lithium iron
- carbon source
- positive electrode
- temperature
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Classifications
-
- 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
- H01M4/36—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
- H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Crystallography & Structural Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention provides a lithium iron phosphate anode material and a preparation method and application thereof. The preparation method comprises the following steps: (1) placing the lithium iron phosphate matrix in a sintering furnace, and carrying out primary heating in a protective atmosphere; (2) and introducing a gas carbon source, then carrying out secondary heating in a protective atmosphere, and sintering to obtain the lithium iron phosphate anode material. According to the invention, by using the gas carbon source as the carbon coating agent and adopting gradient temperature sintering, the uniformity of the coated carbon is improved, the thickness of the carbon coating layer is reduced, the crystallinity of the anode material is also improved, and the purposes of improving the conductivity of the lithium iron phosphate anode material, reducing the ion transmission impedance of the lithium iron phosphate anode material and further improving the rate capability of the material are finally realized.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and relates to a lithium iron phosphate anode material, and a preparation method and application thereof.
Background
The lithium iron phosphate material is considered to be one of the most promising positive electrode materials of the lithium ion battery due to low price, easy availability, environmental protection and excellent electrochemical performance. However, the further development of the lithium ion battery is restricted all the time due to the problems of low conductivity, slow lithium ion diffusion rate and the like. The carbon coating is one of the simple and effective methods for improving the electronic conductivity of the lithium iron phosphate material, but the carbon coating is adopted, namely the lithium iron phosphate phase occupation ratio is correspondingly reduced, the carbon coating is increased, the capacity is relatively reduced, and the carbon coating is loose and porous and has large specific surface area, and the surplus carbon influences the processing performance of the lithium iron phosphate when in application. Therefore, an appropriate carbon source needs to be selected for coating, so that the coating uniformity is improved, the carbon coating amount is reduced, the rate performance of the lithium iron phosphate is improved, and the processing performance and gram volume of the lithium iron phosphate can be improved or not influenced.
Currently, solid carbon sources (acetylene black, carbon black, graphene, carbon nanotubes, etc.) and soluble carbon sources (glucose, sucrose, polyethylene glycol) are generally adopted as coating agents for coating. The two types of carbon sources can improve the electron conduction performance to a certain degree, but the electron conduction performance of the lithium iron phosphate cannot be obviously improved due to the defects of high price and high cost of the solid carbon source, large particle size of the carbon source, large coating dosage, unobvious coating effect and the like; although the cost, the coating uniformity and the electronic conductivity of the lithium iron phosphate of the soluble carbon source coating are improved compared with the solid carbon source coating, the soluble carbon source coating process follows the following steps in the synthesis process: the method comprises the steps of mixing (a carbon source and uncoated lithium iron phosphate), drying (the carbon source is precipitated and crystallized into solid), and carbonizing (pyrolysis), wherein the method comprises the steps of dissolving the carbon source in water, mixing with the lithium iron phosphate to be coated, and drying to precipitate the carbon source, so that the energy consumption is increased, the productivity utilization rate is influenced, and crystal segregation (partial areas are too thick and partial areas are uncoated) exists in the drying process, so that certain defects exist in the coating uniformity. In addition, impurities are inevitably introduced into the solid carbon source or the liquid carbon source, which affects the purity of the lithium iron phosphate, and the most direct disadvantage is the reduction of gram capacity.
CN104743537A discloses a preparation method of a high-rate lithium iron phosphate/carbon composite anode material, which comprises the steps of (1) stirring and mixing a phosphorus source and an iron source solution, adding a dispersing agent, and controlling the pH value of the reaction to generate ferrous phosphate precipitation; (2) supplementing a phosphorus source to the obtained ferrous phosphate according to the phosphorus-iron ratio of 1: 1-7: 1, adding an oxidant, and adjusting the pH value to synthesize iron phosphate; (3) mixing iron phosphate with a lithium source and a carbon source in a stoichiometric ratio, and performing ball milling, drying and calcining to obtain the high-rate lamellar lithium iron phosphate/carbon composite cathode material. However, these introduced materials are difficult to achieve good dispersion among the nanoparticles on one hand, and on the other hand, they are expensive, so that the original cost performance advantage of the lithium iron phosphate is lost, and the lithium iron phosphate is in a market competition disadvantage.
CN103159201A discloses a high-pressure and low-temperature method for preparing a carbon-coated lithium iron phosphate lithium ion battery positive electrode composite material, which comprises the steps of mixing an iron source, a phosphorus source, a lithium source and a carbon source, and then carrying out ball milling and mixing by taking ethanol or water as a ball milling medium to obtain a mixed material; and then, carrying out vacuum drying on the mixed material, then placing the dried mixed material into a high-temperature-resistant and high-pressure-resistant sealed stainless steel reaction kettle, heating and calcining at the temperature of 400-650 ℃ for 4-8 h, and cooling to room temperature after calcining is finished to obtain the carbon-coated lithium iron phosphate lithium ion battery positive electrode composite material. In the document, glucose serving as a soluble carbon source is adopted for carbon coating, so that impurities are inevitably introduced to influence the purity of lithium iron phosphate, and the most direct defect is that the gram volume is reduced.
Therefore, how to improve the gram-capacity and rate capability of the lithium iron phosphate cathode material is a technical problem to be solved urgently.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a lithium iron phosphate positive electrode material and a preparation method and application thereof. According to the invention, by using the gas carbon source as the carbon coating agent and adopting gradient temperature sintering, the uniformity of the coated carbon is improved, the thickness of the carbon coating layer is reduced, the crystallinity of the anode material is also improved, and the purposes of improving the conductivity of the lithium iron phosphate anode material, reducing the ion transmission impedance of the lithium iron phosphate anode material and further improving the rate capability of the material are finally realized.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a preparation method of a lithium iron phosphate positive electrode material, which comprises the following steps:
(1) placing the lithium iron phosphate matrix in a sintering furnace, and carrying out primary heating in a protective atmosphere;
(2) and introducing a gas carbon source, then carrying out secondary heating in a protective atmosphere, and sintering to obtain the lithium iron phosphate anode material.
In the present invention, the sintering is carried out after the temperature is raised twice, and these two steps are continuously carried out.
In the present invention, the source of the lithium iron phosphate matrix is not limited, and may be pure-phase lithium iron phosphate prepared by a hydrothermal method, a coprecipitation method, a solvothermal method, or other methods.
According to the invention, by using the gas carbon source as the carbon coating agent and adopting gradient temperature sintering, the uniformity of the coated carbon is improved, the thickness of the carbon coating layer is reduced, the crystallinity of the anode material is also improved, and the purposes of improving the conductivity of the lithium iron phosphate anode material, reducing the ion transmission impedance of the lithium iron phosphate anode material and further improving the rate capability of the material are finally realized.
The gaseous carbon source is used as a coating agent, and compared with a solid or liquid phase coated carbon source, the gaseous carbon source has high dispersion-diffusion speed and uniformity, so that the coating uniformity is improved, and the purity of the gaseous carbon source is superior to that of the solid carbon source and that of the liquid phase coated carbon source; secondly, the impurities can be prevented from being introduced, meanwhile, the lithium iron phosphate can be cracked at low temperature, the energy consumption is reduced, and the agglomeration and growth of lithium iron phosphate particles at high temperature are avoided.
Gradient temperature sintering is adopted, after primary heating, a gas carbon source is introduced into a furnace body at a certain temperature, the gas carbon source can be cracked and adsorbed on the surface of the powder to form a fixed carbon source, and meanwhile, the dispersion-diffusion-cracking process can be balanced at the temperature, so that the phenomenon that gas is cracked to generate invalid carbon before reaching the surface of the powder due to too fast cracking is avoided, and the effect of uniform coating is achieved; meanwhile, sintering is carried out after temperature is continuously raised, on one hand, a cleavable carbon source is further cleaved, and on the other hand, the crystallinity of the sintered lithium iron phosphate is further improved, so that the electric conductivity of the sintered lithium iron phosphate is improved.
According to the invention, after the protective atmosphere and the gas carbon source are not introduced simultaneously, the primary heating and the secondary heating are carried out, because the protective gas is introduced firstly, the oxidizing atmosphere such as oxygen, water vapor and the like in the furnace body is discharged, the oxidizing atmosphere is prevented from oxidizing the material, and if the protective atmosphere and the gas carbon source are introduced simultaneously, the gas carbon source is discharged along with the gas carbon source, and the introduced gas carbon source is not cracked, so that the waste of raw materials is caused.
Preferably, the sintering furnace in the step (1) comprises any one of a rotary kiln, a shimmy rotary sintering furnace or a high-temperature rotary tube furnace.
According to the invention, the sintering furnace is selected, so that the lithium iron phosphate matrix to be coated is in a continuous rolling motion transition state in the sintering furnace, after a gas carbon source is introduced into the furnace body, the gas can be dispersed and diffused into the powder layer, the powder layer is fully mixed, the coating effect is more obvious and uniform, and the electronic conductivity of the material is improved.
Preferably, the gas of the protective atmosphere in step (1) and the gas of the protective atmosphere in step (2) are each independently any one or a combination of at least two of nitrogen, helium, neon, argon or hydrogen.
Preferably, the temperature after the primary temperature rise in the step (1) is 600 to 700 ℃, for example, 600 ℃, 610 ℃, 620 ℃, 630 ℃, 640 ℃, 650 ℃, 660 ℃, 670 ℃, 680 ℃, 690 ℃, 700 ℃ or the like.
In the invention, the temperature after the primary heating is in the range, so that the cracking reaction of the gas carbon source can be carried out, when the temperature is lower than the range, the gas carbon source cannot be cracked to achieve the coating effect, and when the temperature is higher than the range, the cracking reaction is too violent, the cracking reaction of the gas carbon source immediately occurs after the gas carbon source is introduced into a hearth, and the dispersion-diffusion-cracking cannot be carried out in time, so that the coating is not uniform, and the coating effect is poor.
Preferably, the gaseous carbon source of step (2) comprises any one of natural gas, methane, ethane or propane or a combination of at least two thereof.
In the invention, natural gas, methane, ethane and propane are used as gas carbon sources, and the carbon sources can be cracked at the temperature of below 700 ℃ without adding a catalyst or at a higher temperature, so that on one hand, the condition that the gram capacity and the rate capability of the lithium iron phosphate matrix are reduced due to the influence of the introduced catalyst (impurities) on the phase purity of the lithium iron phosphate matrix can be avoided, and on the other hand, the material carbon sources can be cracked at a low temperature, the energy consumption is reduced, and the condition that lithium iron phosphate particles are agglomerated and grown at a high temperature to form large-size lithium iron phosphate particles and the gram capacity and the rate capability of the anode material are influenced is avoided.
Preferably, the introduction pressure of the gaseous carbon source in the step (2) is 0.1 to 0.4MPa, such as 0.1MPa, 0.2MPa, 0.3MPa or 0.4 MPa.
Preferably, the introduction rate of the gaseous carbon source in the step (2) is 200-600 mL/min, such as 200mL/min, 300mL/min, 400mL/min, 500mL/min, or 600 mL/min.
Preferably, the temperature after the secondary heating in the step (2) is 700 to 800 ℃, for example 700 ℃, 710 ℃, 720 ℃, 730 ℃, 740 ℃, 750 ℃, 760 ℃, 770 ℃, 780 ℃, 790 ℃ or 800 ℃ and the like.
After the temperature is raised for the second time, when the sintering is carried out in the temperature range, the carbon cracked and coated on the surface of the lithium iron phosphate matrix can be further cracked and carbonized, meanwhile, the crystallinity of the lithium iron phosphate material is further improved after the sintering at the temperature, the crystal structure is more perfect, the rate capability of the material can be improved, and when the temperature is higher than the temperature range, the lithium iron phosphate can be agglomerated and grown to be large-size particles, so that the diffusion path of electrons and ions is increased, and the rate capability of the material is influenced.
Preferably, the sintering time in the step (2) is 1-10 h, such as 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10 h.
In the invention, the sintering time is too short to achieve the sintering effect, and the time is too long, so that the lithium iron phosphate particles are easy to agglomerate and grow into large-size particles at high temperature for a long time, thereby increasing the diffusion path of electrons and ions, influencing the rate capability of the material and simultaneously increasing the energy consumption.
Preferably, the mass of the gaseous carbon source in the step (2) is 40 to 80% of the mass of the lithium iron phosphate matrix in the step (1), for example, 40%, 50%, 60%, 70%, 80%, or the like.
In the invention, the quality of the gas carbon source is too low, so that the amount of carbon coating layers obtained by cracking is small, the coating of the lithium iron phosphate matrix is incomplete, and the conductivity is not obviously improved; the mass is too large, so that the carbon coating layer accounts for too large, the lithium iron phosphate main phase accounts for less, and the gram capacity of the anode material is reduced finally.
Preferably, the sintered material of step (2) is cooled to room temperature and then crushed to obtain the cathode material.
As a preferable technical scheme, the preparation method of the lithium iron phosphate cathode material comprises the following steps:
(1) placing the lithium iron phosphate matrix in a sintering furnace, and heating to 600-700 ℃ for one time under a protective atmosphere;
(2) introducing a gas carbon source at an introduction rate of 200-600 mL/min under the pressure of 0.1-0.4 MPa, then heating to 700-800 ℃ for the second time under a protective atmosphere, sintering for 1-10 h, cooling to room temperature, and crushing to obtain the lithium iron phosphate cathode material;
wherein, the sintering furnace in the step (1) comprises any one of a rotary furnace, a shimmy rotary sintering furnace or a high-temperature rotary tube furnace; and (3) the mass of the gas carbon source in the step (2) is 40-80% of that of the lithium iron phosphate matrix in the step (1).
In a second aspect, the invention provides a lithium iron phosphate positive electrode material, which is prepared by the preparation method of the lithium iron phosphate positive electrode material in the first aspect, and comprises a lithium iron phosphate matrix and a carbon coating layer coated on the surface of the lithium iron phosphate matrix.
Preferably, the thickness of the carbon coating layer is 1 to 3nm, such as 1nm, 2nm or 3 nm.
In a third aspect, the present invention further provides a lithium ion battery, where the lithium ion battery includes the lithium iron phosphate positive electrode material according to the second aspect.
Compared with the prior art, the invention has the following beneficial effects:
according to the invention, by taking a gas carbon source as a carbon coating agent and adopting gradient temperature sintering, the uniformity of coated carbon is improved, the thickness of a carbon coating layer is reduced, the crystallinity of the anode material is also improved, and the purposes of improving the conductivity of the lithium iron phosphate anode material, reducing the ion transmission impedance of the lithium iron phosphate anode material and further improving the rate capability of the material are finally realized.
Detailed Description
The technical solution of the present invention is further illustrated by the following specific examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
The embodiment provides a preparation method of a lithium iron phosphate cathode material, which comprises the following steps:
(1) 200g of lithium iron phosphate matrix S1 is placed in a rotary tube furnace, then nitrogen is introduced into the furnace body, the temperature of the sintering furnace is raised to 700 ℃ once, and the temperature is kept constant;
(2) and introducing 160g of methane into the sintering furnace at the pressure of 0.4MPa and the speed of 600mL/min until all the required methane is introduced, switching to nitrogen and continuously introducing into the furnace body, continuously heating the furnace body to 800 ℃, preserving the temperature for 10 hours, cooling to room temperature, taking out the cooled lithium iron phosphate S2, and performing gas crushing to obtain the lithium iron phosphate anode material.
Example 2
The embodiment provides a preparation method of a lithium iron phosphate cathode material, which comprises the following steps:
(1) 200g of lithium iron phosphate matrix S1 is placed in a rotary tube furnace, then argon is introduced into the furnace body, the temperature of the sintering furnace is raised to 650 ℃ once, and the temperature is kept constant;
(2) and introducing 80g of ethane into the sintering furnace at the pressure of 0.1MPa and the speed of 200mL/min until all the required ethane is introduced, switching to argon gas and continuously introducing into the furnace body, continuously heating the furnace body to 700 ℃, preserving the temperature for 1h, cooling to room temperature, taking out the cooled lithium iron phosphate S2, and performing gas crushing to obtain the lithium iron phosphate anode material.
Example 3
The embodiment provides a preparation method of a lithium iron phosphate cathode material, which comprises the following steps:
(1) 200g of lithium iron phosphate matrix S1 is placed in a rotary tube furnace, then nitrogen is introduced into the furnace body, the temperature of the sintering furnace is raised to 600 ℃ once, and the temperature is kept constant;
(2) and (3) introducing 100g of natural gas into the sintering furnace at the pressure of 0.2MPa and the speed of 300mL/min until all the required natural gas is introduced, switching to nitrogen gas and continuously introducing into the furnace body, continuously heating the furnace body to 750 ℃, preserving the temperature for 5h, cooling to room temperature, taking out the cooled lithium iron phosphate S2, and performing gas crushing to obtain the lithium iron phosphate anode material.
Example 4
The present example is different from example 1 in that the temperature after the temperature rise once in step (1) of the present example is 550 ℃.
The remaining preparation methods and parameters were in accordance with example 1.
Example 5
The present example is different from example 1 in that the temperature after the temperature rise once in step (1) of the present example is 750 ℃.
The remaining preparation methods and parameters were in accordance with example 1.
Comparative example 1
The comparative example provides a preparation method of a lithium iron phosphate positive electrode material, which comprises the following steps:
and (2) fully and uniformly mixing 200g of lithium iron phosphate S1 and 2g of carbon black, placing the mixture in a sintering furnace, introducing nitrogen into the furnace body, heating the sintering furnace to 800 ℃, keeping the temperature for 10 hours, cooling to room temperature, taking out the cooled lithium iron phosphate S2, and performing gas crushing to obtain the lithium iron phosphate cathode material.
Comparative example 2
The comparative example provides a preparation method of a lithium iron phosphate positive electrode material, which comprises the following steps:
(1) dissolving 10g of glucose in 200g of deionized water, adding 200g of lithium iron phosphate S1 into the glucose solution, fully stirring to obtain a mixed suspension, and drying the mixed suspension by using a spray dryer to obtain lithium iron phosphate powder S2 with the surface coated with glucose;
(2) and (3) placing lithium iron phosphate S2 in a sintering furnace, introducing nitrogen into the furnace body, heating the sintering furnace to 750 ℃, preserving the heat for 10 hours, cooling to room temperature, taking out the cooled lithium iron phosphate S2, and performing gas crushing to obtain the lithium iron phosphate anode material.
Comparative example 3
The comparative example is different from example 1 in that the sintering was continued at 700 ℃ without performing the secondary temperature rise.
The remaining preparation methods and parameters were in accordance with example 1.
Comparative example 4
The difference between this comparative example and example 1 is that step (1) was not performed, and step (2) was adjusted to simultaneously introduce methane and nitrogen, and then the temperature was raised to 800 ℃ and maintained at 10 ℃.
The remaining preparation methods and parameters were in accordance with example 1.
The lithium iron phosphate positive electrode materials provided in examples 1 to 5 and comparative examples 1 to 4 were used as positive electrode active materials, and were mixed at room temperature and normal pressure to form a slurry according to a mass ratio of the lithium iron phosphate positive electrode material, conductive carbon black, carbon nanotubes, and PVDF binder, 95:2.0:0.5:2.5, and the slurry was uniformly coated on a current collector aluminum foil to produce a pole piece, thereby obtaining a positive electrode having a thickness of 60 μm. Taking metal lithium as a negative electrode, and the electrolyte solvent is as follows: ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC), dimethyl carbonate (DMC), LiPF6 with a solute of 1.0mol/L, and positive and negative electrode sheets, a separator, and an electrolyte were prepared into a C2032 type battery in a glove box protected by nitrogen.
The batteries prepared in examples 1 to 5 and comparative examples 1 to 4 were charged under the conditions of a constant current and a constant voltage of 0.1C and 2.5 to 3.8V, and the charging and discharging under the condition of a constant current discharging of 0.1C to 2.5V was regarded as the first charging; charging under the conditions of constant current and constant voltage of 1C and 2.5-3.8V, and recording the charging and discharging under the condition that the 1C constant current is discharged to 2.5V as 1C discharging; the electrochemical performance of the cell was obtained by charging at a constant current and a constant voltage of 1C and 2.5 to 3.8V, and charging and discharging at a constant current of 5C to 2.5V as 5C discharge, and the results are shown in table 1.
TABLE 1
From the data results of the embodiment 1 and the embodiments 4 and 5, it can be seen that the temperature after one-time temperature rise is too low, which is not favorable for cracking of the organic carbon source, the obtained carbon source is lower than the designed carbon source, which results in a decrease in carbon coating amount, a decrease in rate capability is obvious, and too high, which results in severe cracking of the organic carbon source, a gas carbon source is cracked without being uniformly dispersed among particles in the furnace body, which results in non-uniform coating, failure to achieve optimal coating, and a decrease in rate capability of the product is obvious.
From the data results of example 1, comparative example 1 and comparative example 2, the carbon coating amount is 1%, and it is known that, under the condition of the same carbon coating amount, a gaseous carbon source is used as a carbon coating raw material, and under the charge and discharge of 0.1C, the technical effect comparable to that of a solid carbon source and a soluble carbon source can be achieved, or even better, and with the increase of the charge and discharge current, the rate capability of the battery provided by example 1 is obviously superior to that of the batteries provided by comparative examples 1 and 2, that is, the gram capacity and the discharge rate capability of the battery taking the lithium iron phosphate anode material as the anode can be simultaneously improved by using the gaseous carbon source and performing the carbon coating at the gradient temperature.
From the data results of the embodiment 1, the comparative example 3 and the comparative example 4, it can be seen that, without performing the secondary temperature-raising process, the carbon source is cracked and then is not continuously sintered, the powder particles are not continuously heat-treated, the crystal structure is not further sintered and perfect, the crystal grain defects are more, lithium ion transmission is not facilitated, the rate capability of the material is poor, and without performing the primary temperature-raising process, the carbon source is not conducive to cracking first and then heat treatment, so that it is difficult to coat the carbon source on the particle surface in the sintering process, inhibit the particle growth, cause the particle abnormal growth, the large-sized particles increase the diffusion path of lithium ions, and the rate capability of the material is poor.
The lithium iron phosphate positive electrode materials provided in examples 1 to 5 and comparative examples 1 to 4 were pressed into a green sheet having a diameter D of 20mm and a thickness H of 0.5mm under a pressure of 10Mpa, and then tested by a four-probe resistance meter, and the resistivity results are shown in table 2.
TABLE 2
From the data results of the embodiment 1, the embodiment 4 and the embodiment 5, it is known that the temperature is too low or too high after the temperature rise once, which is not beneficial to the cracking of the organic carbon source, and the obtained carbon source is lower than the designed carbon source, which results in the decrease of the carbon coating amount, the insufficient carbon coating amount and the higher resistivity; too high, the cracking of the organic carbon source is severe, and the gas carbon source is cracked before being uniformly dispersed among particles in the furnace body, so that the coating is not uniform, and the resistivity is higher.
From the data results of the embodiment 1, the comparative example 1 and the comparative example 2, it can be known that the resistance of the cathode material can be obviously reduced by coating with the gas carbon source, the electronic conductivity of the material is obviously improved, and the rate capability of the lithium iron phosphate cathode material is favorably improved.
From the data results of the embodiment 1, the comparative example 3 and the comparative example 4, it can be seen that the carbon coating at the gradient temperature does not cause the secondary heating process, the cracking of the carbon source and the subsequent sintering of the carbon source are not performed, the powder particles are not subjected to the subsequent heat treatment, the crystal structure is not further sintered and perfect, the crystal grain defects are more, the lithium ion transmission is not facilitated, and the material multiplying performance is poor; the carbon source is not subjected to cracking and heat treatment firstly without a primary heating process, so that the carbon source is difficult to coat the particle surface in the sintering process, the particle growth is inhibited, the abnormal growth of the particle is caused, the diffusion path of lithium ions is increased by large-size particles, and the multiplying power performance of the material is poor.
ICP tests were performed on the lithium iron phosphate positive electrode materials provided in examples 1 to 5 and comparative examples 1 to 4, and the results are shown in table 3.
TABLE 3
From the data results of examples 1-5 and comparative examples 1-2, it can be seen that the introduction of excessive impurities can be avoided by carbon coating at a gradient temperature using a gaseous carbon source as a carbon coating raw material, while the impurity species increase and the impurity content increases by coating with a solid carbon source or a soluble carbon source.
In conclusion, the invention adopts the gas carbon source as the carbon coating agent and adopts the gradient temperature sintering, thereby improving the uniformity of the coated carbon, reducing the thickness of the carbon coating layer, improving the crystallinity of the anode material, finally realizing the purposes of improving the conductivity of the lithium iron phosphate anode material, reducing the ion transmission impedance of the lithium iron phosphate anode material and further improving the rate capability of the material, and in addition, the gas carbon source can not introduce impurities, reduce the carbon coating amount, improve the gram capacity and the processing performance of the lithium iron phosphate anode material, and still have higher discharge efficiency of the battery under different charge and discharge currents, the discharge efficiency of 1C can reach more than 93.98 percent, the discharge efficiency of 5C is also more than 90.17 percent, and the resistivity is also reduced to some extent, and is more than 130.27 omega/cm.
The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.
Claims (10)
1. The preparation method of the lithium iron phosphate cathode material is characterized by comprising the following steps of:
(1) placing the lithium iron phosphate matrix in a sintering furnace, and carrying out primary heating in a protective atmosphere;
(2) and introducing a gas carbon source, then carrying out secondary heating in a protective atmosphere, and sintering to obtain the lithium iron phosphate anode material.
2. The method for preparing a lithium iron phosphate positive electrode material according to claim 1, wherein the sintering furnace in step (1) comprises any one of a rotary furnace, a shimmy rotary sintering furnace or a high-temperature rotary tube furnace;
preferably, the gas of the protective atmosphere in step (1) and the gas of the protective atmosphere in step (2) are each independently any one or a combination of at least two of nitrogen, helium, neon, argon or hydrogen.
3. The method for preparing the lithium iron phosphate positive electrode material according to claim 1 or 2, wherein the temperature after the primary temperature rise in the step (1) is 600 to 700 ℃.
4. The method for preparing a lithium iron phosphate positive electrode material according to any one of claims 1 to 3, wherein the gaseous carbon source in the step (2) comprises any one of natural gas, methane, ethane or propane or a combination of at least two of the natural gas, the methane, the ethane or the propane;
preferably, the introducing pressure of the gaseous carbon source in the step (2) is 0.1-0.4 MPa;
preferably, the introducing rate of the gaseous carbon source in the step (2) is 200-600 mL/min.
5. The method for preparing the lithium iron phosphate positive electrode material according to any one of claims 1 to 4, wherein the temperature after the secondary temperature rise in the step (2) is 700 to 800 ℃;
preferably, the sintering time in the step (2) is 1-10 h.
6. The method for preparing the lithium iron phosphate positive electrode material according to any one of claims 1 to 5, wherein the mass of the gaseous carbon source in the step (2) is 40 to 80% of the mass of the lithium iron phosphate matrix in the step (1);
preferably, the sintered material of step (2) is cooled to room temperature and then crushed to obtain the cathode material.
7. The method for preparing a lithium iron phosphate positive electrode material according to any one of claims 1 to 6, comprising the steps of:
(1) placing the lithium iron phosphate matrix in a sintering furnace, and heating to 600-700 ℃ for one time under a protective atmosphere;
(2) introducing a gas carbon source at an introduction rate of 200-600 mL/min under the pressure of 0.1-0.4 MPa, then heating to 700-800 ℃ for the second time under a protective atmosphere, sintering for 1-10 h, cooling to room temperature, and crushing to obtain the lithium iron phosphate cathode material;
wherein, the sintering furnace in the step (1) comprises any one of a rotary furnace, a shimmy rotary sintering furnace or a high-temperature rotary tube furnace; and (3) the mass of the gas carbon source in the step (2) is 40-80% of that of the lithium iron phosphate matrix in the step (1).
8. The lithium iron phosphate positive electrode material is characterized by being prepared by the preparation method of the lithium iron phosphate positive electrode material according to any one of claims 1 to 7, and comprising a lithium iron phosphate matrix and a carbon coating layer coated on the surface of the lithium iron phosphate matrix.
9. The lithium iron phosphate positive electrode material according to claim 8, wherein the carbon coating layer has a thickness of 1 to 3 nm.
10. A lithium ion battery, characterized in that the lithium ion battery comprises the lithium iron phosphate positive electrode material according to claim 8 or 9.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110641040.4A CN113381011A (en) | 2021-06-09 | 2021-06-09 | Lithium iron phosphate anode material and preparation method and application thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110641040.4A CN113381011A (en) | 2021-06-09 | 2021-06-09 | Lithium iron phosphate anode material and preparation method and application thereof |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN113381011A true CN113381011A (en) | 2021-09-10 |
Family
ID=77573000
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202110641040.4A Pending CN113381011A (en) | 2021-06-09 | 2021-06-09 | Lithium iron phosphate anode material and preparation method and application thereof |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN113381011A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114497538A (en) * | 2021-12-31 | 2022-05-13 | 乳源东阳光新能源材料有限公司 | Gradient-coated high-performance lithium iron phosphate composite material and preparation method thereof |
| CN117276520A (en) * | 2023-11-21 | 2023-12-22 | 天津容百斯科兰德科技有限公司 | Lithium iron manganese phosphate composite material and preparation method and application thereof |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101572301A (en) * | 2008-10-30 | 2009-11-04 | 喻维杰 | Method for preparing lithium iron phosphate material and cladding the material with carbon |
| CN107887583A (en) * | 2017-10-30 | 2018-04-06 | 贝特瑞（天津）纳米材料制造有限公司 | A kind of doped lithium iron phosphate anode material and preparation method thereof |
-
2021
- 2021-06-09 CN CN202110641040.4A patent/CN113381011A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101572301A (en) * | 2008-10-30 | 2009-11-04 | 喻维杰 | Method for preparing lithium iron phosphate material and cladding the material with carbon |
| CN107887583A (en) * | 2017-10-30 | 2018-04-06 | 贝特瑞（天津）纳米材料制造有限公司 | A kind of doped lithium iron phosphate anode material and preparation method thereof |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114497538A (en) * | 2021-12-31 | 2022-05-13 | 乳源东阳光新能源材料有限公司 | Gradient-coated high-performance lithium iron phosphate composite material and preparation method thereof |
| CN114497538B (en) * | 2021-12-31 | 2023-10-24 | 乳源东阳光新能源材料有限公司 | Gradient coated high-performance lithium iron phosphate composite material and preparation method thereof |
| CN117276520A (en) * | 2023-11-21 | 2023-12-22 | 天津容百斯科兰德科技有限公司 | Lithium iron manganese phosphate composite material and preparation method and application thereof |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN111082006B (en) | Silicon monoxide composite negative electrode material, preparation method thereof and lithium ion battery | |
| CN109817949B (en) | Silicon or oxide @ titanium dioxide @ carbon core-shell structure composite particle thereof and preparation | |
| JP2022518585A (en) | Silicon composite negative electrode material, its preparation method and lithium ion battery | |
| CN112366301A (en) | Silicon/silicon oxide/carbon composite negative electrode material for lithium ion battery and preparation method thereof | |
| CN112366299B (en) | Preparation method of graphite-silicon-based lithium ion battery negative electrode material and product thereof | |
| CN111952547A (en) | Surface-coated modified lithium ion battery positive electrode material and preparation method thereof | |
| WO2021136376A1 (en) | Silicon-based negative electrode material and preparation method therefor, battery, and terminal | |
| CN110783546A (en) | Lithium ion battery positive electrode material and preparation method thereof, lithium ion battery positive electrode slurry and positive electrode, lithium ion battery and equipment | |
| CN113381011A (en) | Lithium iron phosphate anode material and preparation method and application thereof | |
| CN114665058A (en) | Preparation method of lithium ion battery anode material lithium iron manganese phosphate | |
| CN113651304A (en) | Organic carbon-coated lithium iron phosphate cathode material and preparation method thereof | |
| CN114388738B (en) | Silicon-based anode material and preparation method and application thereof | |
| CN111740110A (en) | Composite negative electrode material, preparation method thereof and lithium ion battery | |
| CN109638231B (en) | Silicon monoxide composite negative electrode material, preparation method thereof and lithium ion battery | |
| WO2023165415A1 (en) | Negative electrode active material, preparation method therefor and application thereof | |
| CN115663153B (en) | Preparation method of metal doped silicon-based anode material, anode material and secondary battery | |
| CN113896193B (en) | Surface modified exfoliated graphite as well as preparation method and application thereof | |
| CN116190591A (en) | Preparation method of modified material modified lithium iron manganese phosphate material | |
| CN110600738B (en) | Method for preparing low-temperature lithium ion battery hard carbon negative electrode material | |
| CN113036091A (en) | Carbon-coated ternary positive pole piece and preparation method and application thereof | |
| CN113506867A (en) | MoS for lithium ion battery2N/N doped composite material and preparation method thereof | |
| CN112968155A (en) | Composite negative electrode material for lithium ion battery and preparation method thereof | |
| CN115849322B (en) | Porous iron-based phosphate lithium battery material and preparation method thereof | |
| CN112750993A (en) | Silicon-carbon composite material, preparation method thereof, negative electrode and battery | |
| CN110911643A (en) | Diatomite-based lithium ion battery negative electrode material and preparation method thereof |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| WD01 | Invention patent application deemed withdrawn after publication | ||
| WD01 | Invention patent application deemed withdrawn after publication |
Application publication date: 20210910 |