CN107845791B - Preparation method of double-layer asphalt carbon-coated lithium iron phosphate cathode material - Google Patents
Preparation method of double-layer asphalt carbon-coated lithium iron phosphate cathode material Download PDFInfo
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- 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 discloses a preparation method of a double-layer asphalt carbon-coated lithium iron phosphate positive electrode material, and belongs to the technical field of new energy material preparation. The method comprises the steps of firstly, taking low-softening-point asphalt as a carbon source, carrying out ball milling on the low-softening-point asphalt and a lithium iron phosphate precursor material, roasting at a low temperature to obtain a carbon-coated lithium iron phosphate pre-sintered substance, then mixing the carbon-coated lithium iron phosphate pre-sintered substance with high-softening-point asphalt at a high speed, and finally obtaining the double-layer asphalt carbon-coated lithium iron phosphate anode material through two steps of low-temperature softening and high-temperature. The low-softening-point asphalt used in the method can effectively prevent the growth of lithium iron phosphate grains, preliminarily realizes carbon coating, and can optimize the surface potential energy distribution state of the lithium iron phosphate after being mixed with the high-softening-point asphalt and sintered, thereby improving the high-speed transmission of lithium ions in the material. The lithium iron phosphate anode material prepared by the invention has the advantages of high electronic and ionic conductivity, high specific capacity and the like, and is very suitable for being used as an anode material of a lithium ion power battery.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a preparation method of a double-layer asphalt carbon-coated lithium iron phosphate cathode material.
Background
Lithium ion batteries have high specific energy, long cycle life, and the like, and are widely used in the fields of portable electronic devices, computers, and the like. The lithium ion battery mainly comprises four major parts, namely a positive electrode material, a negative electrode material, a diaphragm and electrolyte, wherein the positive electrode material is one of the most key technologies which restrict the performance and the price of the battery, so that the research on the positive electrode material becomes the focus of attention, and the more researched positive electrode materials mainly comprise lithium iron phosphate, lithium cobaltate, lithium manganate, a lithium-rich manganese base and the like. Goodenough in 1997 firstly proposes that lithium iron phosphate can be used as a positive electrode material of a lithium ion battery, and the lithium iron phosphate positive electrode material has the advantages of rich raw materials, low price, no pollution, good safety, obvious charge and discharge platform, good rate charge and discharge characteristics and cycle stability and the like, and is very suitable for the positive electrode material of a power type lithium ion battery. The preparation method of the lithium iron phosphate material comprises a high-temperature solid phase method, a carbothermic reduction method, a hydrothermal method, a coprecipitation method and the like.
However, the electronic conductivity and the ionic conductivity of lithium iron phosphate are low, and the exertion of electrochemical properties is greatly influenced. Carbon coating is also called carbon doping, and is an effective method for improving the conductivity of lithium iron phosphate, the commonly used carbon precursors at present comprise sucrose, glucose, polyvinyl alcohol, citric acid, polyacrylic acid, starch and the like, and the commonly used carbon precursors are usually mixed with the lithium iron phosphate or the precursors thereof, pyrolyzed at a certain temperature to generate conductive carbon, and coated on LiFePO4LiFePO is formed on the surface of the particles4a/C composite material. The method is an in-situ coating method, and the carbon precursor can play a role in reduction and prevent LiFePO in the roasting process4The growth and agglomeration of the particles are greatly improved, so that the performance of the particles is improved to a certain extent, and the particles are concerned. But the electrochemical performance of the materials prepared by the precursor carbon is improved to a limited extent. The selection of an appropriate carbon precursor is a matter that needs to be addressed urgently.
In view of the current situation of the prior art, the invention provides a preparation method of a double-layer asphalt carbon-coated lithium iron phosphate anode material, which has the advantages of low cost and simple operation and is very suitable for large-scale production.
Disclosure of Invention
Based on the technical problems in the background art, the invention provides a preparation method of a double-layer asphalt carbon-coated lithium iron phosphate anode material, which adopts low-softening-point asphalt to effectively prevent the growth of lithium iron phosphate crystal grains, preliminarily realizes carbon coating, is mixed with high-softening-point asphalt and sintered to optimize the surface potential energy distribution state of lithium iron phosphate and improve the high-speed transmission of lithium ions in the material, and the obtained lithium iron phosphate anode material has the advantages of high electronic and ionic conductivity, high specific capacity and the like, and is very suitable for being used as an anode material of a lithium ion power battery.
The invention provides a preparation method of a double-layer asphalt carbon-coated lithium iron phosphate anode material, which comprises the following steps:
s1, mixing the low-softening-point asphalt with the mixed solvent, sequentially adding a lithium source, an iron source and a phosphorus source, then ball-milling, drying, and sintering under the protection of inert gas to obtain a carbon-coated lithium iron phosphate presintered substance;
and S2, mixing the carbon-coated lithium iron phosphate pre-sintered substance with high-softening-point asphalt, heating in an inert atmosphere, preserving heat, heating again, preserving heat, carbonizing, and cooling to obtain the double-layer asphalt carbon-coated lithium iron phosphate anode material.
Preferably, in S1, the low-softening-point asphalt has a softening point of 60-120 ℃.
Preferably, in S1, the mixed solvent is prepared by mixing water and alcohol compound in a volume ratio of 1: 1 are mixed to obtain the product.
Preferably, the alcohol compound is at least one of methanol, ethanol, ethylene glycol, n-propanol, propylene glycol, glycerol, n-butanol, and neopentyl alcohol.
Preferably, in S1, the lithium source is at least one of lithium carbonate, lithium oxide, lithium dihydrogen phosphate, lithium hydroxide, and lithium acetate.
Preferably, in S1, the iron source is at least one of ferric oxalate, ferric phosphate, ferrous ammonium phosphate, and ferric oxide.
Preferably, in S1, the phosphorus source is at least one of ammonium dihydrogen phosphate, ammonium hydrogen phosphate, lithium dihydrogen phosphate, iron phosphate, and phosphoric acid.
Preferably, in S1, the molar ratio of the lithium element, the iron element and the phosphorus element is 1: 1: 1.
preferably, in S1, the mass ratio of the theoretical synthesis amount of lithium iron phosphate to the low softening point asphalt is 1: 0.002 to 0.1.
Preferably, in S1, the ball milling time is 8-36 h.
Preferably, in S1, the drying temperature is 95-105 ℃, and preferably 100 ℃.
Preferably, in S1, the sintering temperature is 300-400 ℃ and the sintering time is 4-10 h.
Preferably, in S2, the mass ratio of the carbon-coated lithium iron phosphate pre-sintered material to the high softening point asphalt is 1: 0.05 to 0.2.
Preferably, in S2, the high-softening-point asphalt has a softening point of 270-350 ℃.
Preferably, in S2, mixing the carbon-coated lithium iron phosphate pre-sintered substance and the high-softening-point asphalt for 5-25 min, placing the mixture in a rotary furnace at the rotation speed of 1-15 revolutions per minute, heating to 250-350 ℃ in an inert atmosphere, preserving heat for 1-3 h, heating to 600-800 ℃, preserving heat for carbonization for 4-12 h, and naturally cooling to room temperature to obtain the double-layer asphalt carbon-coated lithium iron phosphate cathode material.
Preferably, in S2, the temperature rise rate is 5-15 ℃/min.
Preferably, the inert atmosphere is at least one of nitrogen, helium, neon, argon and xenon.
The invention also provides a double-layer asphalt carbon-coated lithium iron phosphate cathode material which is prepared by adopting the preparation method of the double-layer asphalt carbon-coated lithium iron phosphate cathode material.
Because the ball milling of the low-softening-point asphalt is relatively easy, the low-softening-point asphalt is used as a carbon source in the S1 process, so that the uniform dispersion of the asphalt in the ball milling process is facilitated, meanwhile, in the subsequent low-temperature sintering process, the low-softening-point asphalt can be fully infiltrated into the interior of the particles to form a conductive network, the growth of lithium iron phosphate grains is prevented, and meanwhile, a carbon layer with a certain thickness is preliminarily formed on the surfaces of the particles; s1, a mixed solution of water and alcohol is adopted, wherein the water can dissolve the lithium iron manganese phosphate precursor (namely a lithium source, an iron source and a phosphorus source), and the alcohol can dissolve asphalt and is beneficial to subsequent drying; s2, high-softening-point asphalt is used as a carbon source, on one hand, the high-softening-point asphalt is easy to generate heat due to high-speed blending, does not melt, can still keep a particle state, and is beneficial to uniform mixing of materials, and on the other hand, the high-softening-point asphalt has a higher carbonization rate and is beneficial to formation of a carbon layer; s2, when the high softening point asphalt is softened near the softening point by using a rotary furnace, the asphalt is fully soaked on the surface of the lithium iron phosphate pre-sintered object, and the surface of the lithium iron phosphate can be uniformly coated after the temperature is raised.
The invention adopts the method of coating the low-softening-point asphalt and the high-softening-point asphalt one after another, can be more uniformly filled and dispersed among the particles of the lithium iron phosphate anode material than the common carbon source to form a conductive network structure, control the growth of lithium iron phosphate crystal grains, and simultaneously form double-layer carbon coating which is very uniformly coated on the surface of the lithium iron phosphate anode material, thereby optimizing the surface potential energy distribution state of the lithium iron phosphate and improving the high-speed transmission of lithium ions in the material.
The lithium iron phosphate anode material obtained by the invention has the advantages of high electronic and ionic conductivity, high specific capacity and the like, and is very suitable for being used as an anode material of a lithium ion power battery.
Drawings
Fig. 1 is an SEM picture of a double-layer pitch carbon-coated lithium iron phosphate positive electrode material obtained in example 3 of the present invention.
Fig. 2 is a schematic flow chart of a preparation method of a double-layer asphalt carbon-coated lithium iron phosphate positive electrode material provided by the invention.
Fig. 3 is a schematic diagram of a discharge curve of the double-layer pitch carbon-coated lithium iron phosphate positive electrode material according to embodiment 3 of the present invention at a magnification of 0.1C.
Detailed Description
As shown in fig. 1, 2, and 3, fig. 1 is SEM pictures of a double-layer pitch carbon-coated lithium iron phosphate positive electrode material obtained in embodiment 3 of the present invention, and fig. 2 is a schematic flow chart of a preparation method of the double-layer pitch carbon-coated lithium iron phosphate positive electrode material provided in the present invention. Fig. 3 is a schematic view of a discharge curve of the double-layer pitch carbon-coated lithium iron phosphate positive electrode material obtained in embodiment 3 of the present invention at a rate of 0.1C.
Example 1
Referring to fig. 2, a preparation method of a double-layer pitch carbon-coated lithium iron phosphate positive electrode material includes the following steps:
s1, mixing the low-softening-point asphalt with a mixed solvent, wherein the solvent is prepared by mixing water and ethanol according to a volume ratio of 1: 1, mixing to obtain; and sequentially adding lithium acetate, iron phosphate and lithium dihydrogen phosphate, wherein the molar ratio of the lithium element to the iron element to the phosphorus element is 1: 1: 1, the mass ratio of the theoretical synthesis amount of the lithium iron phosphate to the low-softening-point asphalt is 1: 0.002, ball-milling for 36h, drying at 95 ℃, and sintering for 4h at 400 ℃ under the protection of xenon gas to obtain a carbon-coated lithium iron phosphate presintering substance;
s2, mixing the carbon-coated lithium iron phosphate pre-sintered substance and the high-softening-point asphalt in a mass ratio of 1: and (3) mixing for 5min 0.2, placing in a rotary furnace at the rotating speed of 15 r/min, heating to 250 ℃ under the atmosphere of helium, preserving heat for 3h, heating to 600 ℃, preserving heat for carbonization for 12h, wherein the heating rate is 5 ℃/min, and naturally cooling to room temperature to obtain the double-layer pitch carbon-coated lithium iron phosphate cathode material. After the button cell is assembled by taking a metal lithium sheet as a negative electrode, the discharging specific capacity at 0.1C multiplying power is 161.5 mAh/g.
Example 2
A preparation method of a double-layer asphalt carbon-coated lithium iron phosphate anode material comprises the following steps:
s1, mixing the low-softening-point asphalt with a mixed solvent, wherein the solvent is prepared by mixing water and glycerol according to a volume ratio of 1: 1, mixing to obtain; and sequentially adding lithium oxide, ferric oxide and phosphoric acid, wherein the molar ratio of the lithium element to the iron element to the phosphorus element is 1: 1: 1, the mass ratio of the theoretical synthesis amount of the lithium iron phosphate to the low-softening-point asphalt is 1: 0.1, then ball-milling for 8h, drying at 105 ℃, and sintering for 10h at 300 ℃ under the protection of xenon gas to obtain a carbon-coated lithium iron phosphate presintering substance;
s2, mixing the carbon-coated lithium iron phosphate pre-sintered substance and the high-softening-point asphalt in a mass ratio of 1: 0.05, mixing for 25min, placing in a rotary furnace at the rotating speed of 1 r/min, heating to 350 ℃ under the atmosphere of neon, preserving heat for 1h, heating to 800 ℃, preserving heat for carbonization for 4h, wherein the heating rate is 15 ℃/min, and naturally cooling to room temperature to obtain the double-layer pitch carbon-coated lithium iron phosphate cathode material. After the button cell is assembled by taking a metal lithium sheet as a negative electrode, the discharging specific capacity at 0.1C multiplying power is 158.8 mAh/g.
Example 3
A preparation method of a double-layer asphalt carbon-coated lithium iron phosphate anode material comprises the following steps:
s1, adding 4g of low-softening-point (70-85 ℃) asphalt into a ceramic ball milling tank, taking water/methanol (volume ratio is 1: 1) as a solvent, and sequentially adding 9.37g of lithium carbonate, 45.6g of ferrous oxalate and 29.2g of ammonium dihydrogen phosphate, wherein the mass ratio of the theoretical synthesis amount of the lithium iron phosphate to the low-softening-point asphalt is 1: 0.1; putting the ball milling tank into a planetary ball mill for ball milling for 24 hours, taking out and putting into a drying oven at 100 ℃ for drying; then placing the mixture into a tubular furnace protected by nitrogen to sinter the mixture for 4 hours at the temperature of 400 ℃ to obtain a carbon-coated lithium iron phosphate presintering substance;
s2, mixing the carbon-coated lithium iron phosphate pre-sintered substance with high-softening-point (270-290 ℃) asphalt according to a mass ratio of 1: 0.2, mixing, high-speed mixing for 15min in a high-speed mixer, then placing into a rotary furnace, wherein the rotating speed of the furnace is 15 revolutions per minute, the heating rate is 5 ℃/min under the argon atmosphere, firstly heating to 290 ℃, keeping the temperature for 3h, then heating to 800 ℃, carbonizing for 4h at the constant temperature, naturally cooling to room temperature, and discharging to obtain the double-layer pitch carbon-coated lithium iron phosphate cathode material.
The double-layer pitch carbon-coated lithium iron phosphate cathode material obtained in this embodiment is subjected to electron microscope scanning, as shown in fig. 1. As shown in fig. 3, a schematic view of a discharge curve of the double-layer carbon-coated lithium iron phosphate cathode material according to this embodiment at a magnification of 0.1C is shown. After the button cell is assembled by taking the metal lithium sheet as the cathode, the discharging specific capacity at 0.1C multiplying power is 164.8 mAh/g.
Example 4
A preparation method of a double-layer asphalt carbon-coated lithium iron phosphate anode material comprises the following steps:
s1, adding 10g of low-softening-point (80-100 ℃) asphalt into a ceramic ball milling tank, taking water/propylene glycol (volume ratio is 1: 1) as a solvent, and sequentially adding 30.3g of lithium hydroxide, 228.0g of ferrous oxalate and 124.2g of phosphoric acid, wherein the mass ratio of the theoretical synthetic amount of the lithium iron phosphate to the low-softening-point asphalt is 1: 0.05; putting the ball milling tank into a planetary ball mill for ball milling for 8 hours, taking out and putting into a drying oven at 100 ℃ for drying; then placing the mixture into a helium-protected tube furnace to be sintered for 8 hours at 300 ℃ to obtain a carbon-coated lithium iron phosphate presintering substance;
s2, mixing the carbon-coated lithium iron phosphate pre-sintered substance with high-softening-point (290-300 ℃) asphalt according to a mass ratio of 1: 0.1, mixing at a high speed for 25min in a high-speed mixer, then placing into a rotary furnace at the rotating speed of 5 revolutions per minute, heating to 300 ℃ at the heating rate of 8 ℃/min under the nitrogen atmosphere, keeping the temperature for 2h, heating to 750 ℃, carbonizing for 12h at the constant temperature, naturally cooling to room temperature, and discharging to obtain the double-layer pitch carbon-coated lithium iron phosphate cathode material. After the button cell is assembled by taking a metal lithium sheet as a negative electrode, the discharging specific capacity at 0.1C multiplying power is 162.5 mAh/g.
Example 5
A preparation method of a double-layer asphalt carbon-coated lithium iron phosphate anode material comprises the following steps:
s1, adding 4g of low-softening-point (95-110 ℃) asphalt into a ceramic ball milling tank, taking water/n-butanol (the volume ratio is 1: 1) as a solvent, and sequentially adding 9.37g of lithium carbonate, 45.6g of ferrous oxalate and 29.2g of ammonium dihydrogen phosphate, wherein the mass ratio of the theoretical synthesis amount of the lithium iron phosphate to the low-softening-point asphalt is 1: 0.1; putting the ball milling tank into a planetary ball mill for ball milling for 12 hours, taking out and putting into a drying oven at 100 ℃ for drying; then placing the mixture into a tubular furnace protected by inert gas to be sintered for 8 hours at the temperature of 400 ℃ to obtain a carbon-coated lithium iron phosphate presintering substance;
s2, mixing the carbon-coated lithium iron phosphate pre-sintered substance with high-softening-point (330-350 ℃) asphalt according to a mass ratio of 1: 0.2, mixing at a high speed in a high-speed mixer for 15min, then placing into a rotary furnace at a rotating speed of 15 r/min, heating to 340 ℃ at a heating rate of 5 ℃/min under an inert atmosphere, keeping the temperature for 3h, heating to 700 ℃, carbonizing at the constant temperature for 8h, naturally cooling to room temperature, and discharging to obtain the double-layer pitch carbon-coated lithium iron phosphate cathode material. After the button cell is assembled by taking a metal lithium sheet as a negative electrode, the discharging specific capacity at 0.1C multiplying power is 165.0 mAh/g.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (21)
1. A preparation method of a double-layer asphalt carbon-coated lithium iron phosphate anode material is characterized by comprising the following steps:
s1, mixing the low-softening-point asphalt with the mixed solvent, sequentially adding a lithium source, an iron source and a phosphorus source, then ball-milling, drying, and sintering under the protection of inert gas to obtain a carbon-coated lithium iron phosphate presintered substance;
s2, mixing the carbon-coated lithium iron phosphate pre-sintered substance with high-softening-point asphalt, heating to 250-350 ℃ in an inert atmosphere, preserving heat for 1-3 hours, heating to 600-800 ℃, preserving heat for carbonization for 4-12 hours, and naturally cooling to room temperature to obtain a double-layer asphalt carbon-coated lithium iron phosphate cathode material;
in S1, the sintering temperature is 300-400 ℃, and the sintering time is 4-10 h.
2. The preparation method of the double-layer asphalt carbon-coated lithium iron phosphate positive electrode material as claimed in claim 1, wherein in S1, the softening point of the low-softening-point asphalt is 60-120 ℃.
3. The preparation method of the double-layer asphalt carbon-coated lithium iron phosphate positive electrode material according to claim 1 or 2, wherein in S1, the mixed solvent is prepared by mixing water and an alcohol compound according to a volume ratio of 1: 1, mixing to obtain; the alcohol compound is at least one of methanol, ethanol, ethylene glycol, n-propanol, propylene glycol, glycerol, n-butanol, and neopentyl alcohol.
4. The preparation method of the double-layer asphalt carbon-coated lithium iron phosphate positive electrode material according to claim 1 or 2, wherein in S1, the lithium source is at least one of lithium carbonate, lithium oxide, lithium dihydrogen phosphate, lithium hydroxide and lithium acetate; in S1, the iron source is at least one of ferric oxalate, ferric phosphate, ferrous ammonium phosphate and ferric oxide; in S1, the phosphorus source is at least one of ammonium dihydrogen phosphate, ammonium hydrogen phosphate, lithium dihydrogen phosphate, ferric phosphate and phosphoric acid; in S1, the molar ratio of the lithium element, the iron element, and the phosphorus element is 1: 1: 1.
5. the method for preparing the double-layer asphalt carbon-coated lithium iron phosphate positive electrode material according to claim 3, wherein in S1, the lithium source is at least one of lithium carbonate, lithium oxide, lithium dihydrogen phosphate, lithium hydroxide and lithium acetate; in S1, the iron source is at least one of ferric oxalate, ferric phosphate, ferrous ammonium phosphate and ferric oxide; in S1, the phosphorus source is at least one of ammonium dihydrogen phosphate, ammonium hydrogen phosphate, lithium dihydrogen phosphate, ferric phosphate and phosphoric acid; in S1, the molar ratio of the lithium element, the iron element, and the phosphorus element is 1: 1: 1.
6. the preparation method of the double-layer asphalt carbon-coated lithium iron phosphate positive electrode material as claimed in claim 1 or 2, wherein in S1, the mass ratio of the theoretical synthesis amount of lithium iron phosphate to the low-softening-point asphalt is 1: 0.002 to 0.1.
7. The preparation method of the double-layer asphalt carbon-coated lithium iron phosphate positive electrode material as claimed in claim 3, wherein in S1, the mass ratio of the theoretical synthesis amount of the lithium iron phosphate to the low-softening-point asphalt is 1: 0.002 to 0.1.
8. The preparation method of the double-layer asphalt carbon-coated lithium iron phosphate positive electrode material as claimed in claim 4, wherein in S1, the mass ratio of the theoretical synthesis amount of the lithium iron phosphate to the low-softening-point asphalt is 1: 0.002 to 0.1.
9. The preparation method of the double-layer asphalt carbon-coated lithium iron phosphate positive electrode material according to claim 1 or 2, wherein in S1, the ball milling time is 8-36 h.
10. The preparation method of the double-layer asphalt carbon-coated lithium iron phosphate positive electrode material as claimed in claim 3, wherein in S1, the ball milling time is 8-36 h.
11. The preparation method of the double-layer asphalt carbon-coated lithium iron phosphate positive electrode material as claimed in claim 4, wherein in S1, the ball milling time is 8-36 h.
12. The preparation method of the double-layer asphalt carbon-coated lithium iron phosphate positive electrode material as claimed in claim 5, wherein in S1, the ball milling time is 8-36 h.
13. The preparation method of the double-layer asphalt carbon-coated lithium iron phosphate positive electrode material according to claim 1 or 2, wherein in S2, the mass ratio of the carbon-coated lithium iron phosphate pre-sintered substance to the high-softening-point asphalt is 1: 0.05 to 0.2; in S2, the softening point of the high-softening-point asphalt is 270-350 ℃.
14. The method for preparing the double-layer asphalt carbon-coated lithium iron phosphate positive electrode material according to claim 3, wherein in S2, the mass ratio of the carbon-coated lithium iron phosphate pre-sintered substance to the high-softening-point asphalt is 1: 0.05 to 0.2; in S2, the softening point of the high-softening-point asphalt is 270-350 ℃.
15. The method for preparing the double-layer asphalt carbon-coated lithium iron phosphate positive electrode material according to claim 4, wherein in S2, the mass ratio of the carbon-coated lithium iron phosphate pre-sintered substance to the high-softening-point asphalt is 1: 0.05 to 0.2; in S2, the softening point of the high-softening-point asphalt is 270-350 ℃.
16. The method for preparing the double-layer asphalt carbon-coated lithium iron phosphate positive electrode material according to claim 5, wherein in S2, the mass ratio of the carbon-coated lithium iron phosphate pre-sintered substance to the high-softening-point asphalt is 1: 0.05 to 0.2; in S2, the softening point of the high-softening-point asphalt is 270-350 ℃.
17. The preparation method of the double-layer asphalt carbon-coated lithium iron phosphate positive electrode material according to claim 1 or 2, wherein in S2, the temperature rise rate is 5-15 ℃/min.
18. The preparation method of the double-layer asphalt carbon-coated lithium iron phosphate positive electrode material as claimed in claim 3, wherein in S2, the temperature rise rate is 5-15 ℃/min.
19. The preparation method of the double-layer asphalt carbon-coated lithium iron phosphate positive electrode material as claimed in claim 4, wherein in S2, the temperature rise rate is 5-15 ℃/min.
20. The preparation method of the double-layer asphalt carbon-coated lithium iron phosphate positive electrode material as claimed in claim 5, wherein in S2, the temperature rise rate is 5-15 ℃/min.
21. A double-layer asphalt carbon-coated lithium iron phosphate cathode material, which is characterized by being prepared by the preparation method of the double-layer asphalt carbon-coated lithium iron phosphate cathode material according to any one of claims 1 to 20.
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| CN110931756A (en) * | 2019-12-13 | 2020-03-27 | 成都爱敏特新能源技术有限公司 | High-performance silicon-carbon composite negative electrode material with adjustable particle size and preparation method thereof |
| CN111170294A (en) * | 2020-01-19 | 2020-05-19 | 江苏乐能电池股份有限公司 | Preparation method of low-cost lithium iron phosphate composite material |
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