CN109616655B - Double-layer coated lithium iron borate/nickel pyrophosphate lithium battery positive electrode material and preparation method thereof - Google Patents
Double-layer coated lithium iron borate/nickel pyrophosphate lithium battery positive electrode material and preparation method thereof Download PDFInfo
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Abstract
The invention relates to the technical field of lithium battery anode materials, and provides a double-layer coated lithium iron borate/nickel pyrophosphate lithium battery anode material and a preparation method thereof. According to the method, lithium titanate is generated in situ through a hydrothermal reaction to coat lithium iron borate particles, then a nickel pyrophosphate layer is formed on the surface of the lithium titanate coated lithium iron borate particles through spray deposition, and an organic silicon polymer protective film is further coated to prepare the double-layer coated lithium iron borate/nickel pyrophosphate composite particles. Compared with the traditional method, the lithium titanate and the organic silicon polymer are used for double-layer coating of the lithium iron borate/nickel pyrophosphate composite anode material, so that the defects of poor conductivity of the lithium iron borate material and rapid reduction of electrochemical performance caused by contact with air are overcome, and the defects of large volume change and poor cycle stability of the nickel pyrophosphate material are overcome.
Description
Technical Field
The invention belongs to the technical field of lithium battery anode materials, and provides a double-layer coated lithium iron borate/nickel pyrophosphate lithium battery anode material and a preparation method thereof.
Background
Lithium batteries operate primarily by movement of lithium ions between a positive electrode and a negative electrode. During charging and discharging, Li+Intercalation and deintercalation to and from two electrodes: upon charging, Li+The lithium ion battery is extracted from the positive electrode and is inserted into the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state; the opposite is true during discharge. The lithium battery has the following characteristics: high voltage, high capacity, low consumption, no memory effect, no public hazard, small volume, small internal resistance, less self-discharge and more cycle times. Because of the above characteristics, lithium batteries have been widely used in various civil and military fields such as mobile phones, notebook computers, video cameras, digital cameras, electric vehicles, and the like.
The anode material of the lithium battery is generally selected from lithium intercalation transition metal oxides, borides, silicides, phosphides and the like which have higher potential and are relatively stable in the air. Research and application of novel positive electrode materials have become an important issue in the development of lithium batteries.
The lithium iron borate is a novel lithium ion battery anode material with practical prospect, the structure of the lithium iron borate belongs to a monoclinic system C2/C space group, people attract attention due to the advantages of environmental friendliness, low cost, high specific capacity, high energy density and the like, and the development of the lithium iron borate is limited due to the defects of air sensitivity, low conductivity and the like of the surface of the lithium iron borate. In addition, the pyrophosphate compound is used as a novel polyanion type cathode material, has a three-dimensional network structure and shows better structural stability, and compared with the traditional phosphate type cathode material, the pyrophosphate can provide a two-dimensional tunnel structure capable of freely moving for lithium ions, so that the pyrophosphate compound has good electrochemical performance, but the nickel pyrophosphate material has large volume change and influences the cycling stability of the material.
Therefore, the existing lithium iron borate material for the lithium battery cathode material has the defects of poor conductivity and rapid reduction of electrochemical performance caused by contact with air, and the nickel pyrophosphate material has the defects of large volume change and poor cycle stability.
Therefore, the lithium iron borate/nickel pyrophosphate composite material is used as the lithium battery anode material, and the defects of the lithium iron borate/nickel pyrophosphate composite material and the lithium battery anode material are overcome by adopting a certain technical means, so that the lithium iron borate/nickel pyrophosphate composite material has important significance.
Disclosure of Invention
The invention provides a double-layer coated lithium iron borate/nickel pyrophosphate lithium battery positive electrode material and a preparation method thereof, which overcome the defects of poor conductivity of a lithium iron borate material and rapid reduction of electrochemical performance caused by contact with air, and overcome the defects of large volume change and poor cycle stability of a nickel pyrophosphate material.
In order to achieve the purpose, the invention relates to the following specific technical scheme:
the preparation method of the double-layer coated lithium iron borate/nickel pyrophosphate lithium battery anode material comprises the following specific steps of:
(1) adding nano titanium dioxide and nano lithium iron borate into a deionized water solution of lithium hydroxide, performing ultrasonic dispersion for 10-20 min, transferring the solution to a hydrothermal reaction kettle, heating for reaction, cooling, performing suction filtration, washing with absolute ethyl alcohol for 2-3 times, then washing with deionized water for 2-3 times, then performing vacuum drying at 70-80 ℃ for 15-20 h, and then grinding to obtain lithium titanate-coated lithium iron borate particles;
(2) adding nano nickel pyrophosphate into deionized water, performing ultrasonic dispersion for 20-30 min, spraying a dispersion liquid, and depositing a layer of nickel pyrophosphate on the surface of the lithium titanate coated lithium iron borate particle prepared in the step (1) to prepare a single-layer coated lithium iron borate/nickel pyrophosphate composite particle;
(3) and (3) adding the organic silicon polymer into n-hexane, stirring until the organic silicon polymer is completely dissolved, then adding the composite particles prepared in the step (2), stirring and mixing uniformly, heating at 80 ℃ to remove the solvent n-hexane, and coating the organic silicon polymer on the surfaces of the composite particles to prepare the double-layer coated lithium iron borate/nickel pyrophosphate composite particles.
Preferably, the raw materials in the step (1) comprise, by weight, 3-4 parts of nano titanium dioxide, 30-40 parts of nano lithium iron borate, 2.5-3 parts of lithium hydroxide and 53-64.5 parts of deionized water.
Preferably, the temperature of the hydrothermal reaction in the step (1) is 160-170 ℃ and the time is 9-11 h.
Preferably, the raw materials in the step (2) comprise, by weight, 15-20 parts of nano nickel pyrophosphate, 50-65 parts of deionized water and 20-30 parts of lithium titanate-coated lithium iron borate particles.
Preferably, the silicone polymer in step (3) is at least one of methyl silicone rubber, methyl vinyl silicone rubber and fluorosilicone rubber. The silicone rubber is raw rubber.
Preferably, the raw materials in the step (3) comprise, by weight, 1.5-2 parts of an organosilicon polymer, 58-68.5 parts of n-hexane and 30-40 parts of composite particles.
Preferably, the stirring speed in the step (3) is 300-500 r/min, and the time is 2-3 h.
Preferably, the average particle size of the nano titanium dioxide is 10-20 nm; the average particle size of the nano lithium iron borate is 100-150 nm; the average particle size of the nano nickel pyrophosphate is 50-100 nm.
When the lithium iron borate is used as a positive electrode material of the lithium ion battery, the lithium iron borate has the defect of poor conductivity, and not only is the electronic conductivity low, but also the lithium ion diffusion rate is low. Moreover, lithium iron borate is sensitive to moisture and oxygen, and the specific capacity is rapidly reduced when the lithium iron borate is contacted with a small amount of air at room temperature. When the nickel pyrophosphate is used as a positive electrode material of a lithium ion battery, the volume change of the material is obvious in the process of lithium ion intercalation and deintercalation, so that the cycle stability of the positive electrode material is reduced.
In order to overcome the defects of lithium iron borate and nickel pyrophosphate materials and improve the conductivity and stability of the composite cathode material, the invention prepares the double-layer coated lithium iron borate/nickel pyrophosphate composite particle, and the structural schematic diagram of the double-layer coated lithium iron borate/nickel pyrophosphate composite particle is shown in the attached figure 1 of the specification. The function of the organic silicon polymer coating layer is mainly as follows: firstly, a protective film is formed on the surface of the particles to resist the invasion of moisture and oxygen in the air, and the reduction of the electrochemical performance of the anode material after being exposed in the air is reduced; and secondly, the good elasticity of the organic silicon crude rubber is utilized to balance the volume change of the nickel pyrophosphate material, and the change of the crystal structure of the material is prevented, so that the stability is improved. The lithium titanate coating layer mainly has the following functions: firstly, the good electronic conductivity of lithium titanate is utilized, and the 3D structure of lithium titanate can provide a channel for lithium ion diffusion, so that the electronic conduction and the lithium ion diffusion between lithium iron borate and nickel pyrophosphate are promoted, and the conductivity of the material is improved; and secondly, the stability of the lithium titanate under high voltage is utilized to play a role in stabilizing the structure of the composite cathode material.
The invention also provides the double-layer coated lithium iron borate/nickel pyrophosphate lithium battery positive electrode material prepared by the preparation method. The lithium battery positive electrode material is prepared by firstly coating lithium titanate generated in situ through a hydrothermal reaction on lithium iron borate particles, then forming a nickel pyrophosphate layer on the surfaces of the lithium titanate coated lithium iron borate particles through spray deposition, and further coating an organic silicon polymer protective film.
The invention provides a double-layer coated lithium iron borate/nickel pyrophosphate lithium battery positive electrode material and a preparation method thereof, compared with the prior art, the invention has the outstanding characteristics and excellent effects that:
1. the preparation method provided by the invention overcomes the defects that the lithium iron borate material is poor in conductivity and is in contact with air to cause rapid reduction of electrochemical performance.
2. The preparation method of the invention overcomes the defects of large volume change and poor cycle stability of the nickel pyrophosphate material.
Drawings
Fig. 1 is a schematic structural diagram of a double-layer coated lithium iron borate/nickel pyrophosphate positive electrode material.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments, but it should not be construed that the scope of the present invention is limited to the following examples. Various substitutions and alterations can be made by those skilled in the art and by conventional means without departing from the spirit of the method of the invention described above.
Example 1
(1) Adding nano titanium dioxide and nano lithium iron borate into a deionized water solution of lithium hydroxide, performing ultrasonic dispersion for 14min, transferring the solution to a hydrothermal reaction kettle, heating the solution for reaction, cooling the solution, performing suction filtration, washing the solution for 2 times by using absolute ethyl alcohol, then washing the solution for 3 times by using deionized water, then performing vacuum drying for 17 hours at 76 ℃, and then grinding the solution to prepare lithium titanate-coated lithium iron borate particles; the weight parts of the raw materials are 3 parts of nano titanium dioxide, 34 parts of nano lithium iron borate, 2.5 parts of lithium hydroxide and 60.5 parts of deionized water; the temperature of the hydrothermal reaction is 166 ℃, and the time is 10 h; the average grain diameter of the nano titanium dioxide is 16 nm; the average grain diameter of the nano lithium iron borate is 130 nm;
(2) adding nano nickel pyrophosphate into deionized water, performing ultrasonic dispersion for 26min, spraying a dispersion liquid, depositing a layer of nickel pyrophosphate on the surface of the lithium titanate coated lithium iron borate particle prepared in the step (1), and preparing a single-layer coated lithium iron borate/nickel pyrophosphate composite particle; the weight parts of the raw materials are 17 parts of nano nickel pyrophosphate, 59 parts of deionized water and 24 parts of lithium titanate coated lithium iron borate particles; the average particle size of the nano nickel pyrophosphate is 70 nm;
(3) adding an organic silicon polymer into n-hexane, stirring until the organic silicon polymer is completely dissolved, then adding the composite particles prepared in the step (2), stirring and mixing uniformly, heating at 80 ℃ to remove the solvent n-hexane, and coating the organic silicon polymer on the surfaces of the composite particles to prepare double-layer coated lithium iron borate/nickel pyrophosphate composite particles; the organic silicon polymer is methyl silicone rubber; the silicon rubber is raw rubber; the weight parts of the raw materials are 1.7 parts of organic silicon polymer, 64.3 parts of normal hexane and 34 parts of composite particles; the stirring speed is 380r/min, and the time is 2.5 h.
Example 2
(1) Adding nano titanium dioxide and nano lithium iron borate into a deionized water solution of lithium hydroxide, performing ultrasonic dispersion for 12min, transferring the solution to a hydrothermal reaction kettle, heating the solution for reaction, cooling the solution, performing suction filtration, washing the solution for 2 times by using absolute ethyl alcohol, then washing the solution for 2 times by using deionized water, then performing vacuum drying for 19 hours at 72 ℃, and then grinding the solution to prepare lithium titanate-coated lithium iron borate particles; the weight parts of the raw materials are 3 parts of nano titanium dioxide, 32 parts of nano lithium iron borate, 2.5 parts of lithium hydroxide and 62.5 parts of deionized water; the temperature of the hydrothermal reaction is 162 ℃ and the time is 10.5 h; the average grain diameter of the nano titanium dioxide is 12 nm; the average grain diameter of the nano lithium iron borate is 110 nm;
(2) adding nano nickel pyrophosphate into deionized water, performing ultrasonic dispersion for 23min, spraying a dispersion liquid, depositing a layer of nickel pyrophosphate on the surface of the lithium titanate coated lithium iron borate particle prepared in the step (1), and preparing a single-layer coated lithium iron borate/nickel pyrophosphate composite particle; the weight parts of the raw materials are 16 parts of nano nickel pyrophosphate, 62 parts of deionized water and 22 parts of lithium titanate coated lithium iron borate particles; the average particle size of the nano nickel pyrophosphate is 60 nm;
(3) adding an organic silicon polymer into n-hexane, stirring until the organic silicon polymer is completely dissolved, then adding the composite particles prepared in the step (2), stirring and mixing uniformly, heating at 80 ℃ to remove the solvent n-hexane, and coating the organic silicon polymer on the surfaces of the composite particles to prepare double-layer coated lithium iron borate/nickel pyrophosphate composite particles; the organic silicon polymer is methyl vinyl silicone rubber; the silicon rubber is raw rubber; the weight parts of the raw materials are 1.6 parts of organic silicon polymer, 66.4 parts of normal hexane and 32 parts of composite particles; the stirring speed is 350r/min, and the time is 3 h.
Example 3
(1) Adding nano titanium dioxide and nano lithium iron borate into a deionized water solution of lithium hydroxide, performing ultrasonic dispersion for 18min, transferring the solution to a hydrothermal reaction kettle, heating the solution for reaction, cooling the solution, performing suction filtration, washing the solution for 3 times by using absolute ethyl alcohol, then washing the solution for 3 times by using deionized water, then performing vacuum drying for 16 hours at 78 ℃, and then grinding the solution to prepare lithium titanate-coated lithium iron borate particles; the weight parts of the raw materials are 4 parts of nano titanium dioxide, 37 parts of nano lithium iron borate, 2.8 parts of lithium hydroxide and 56.2 parts of deionized water; the temperature of the hydrothermal reaction is 168 ℃, and the time is 9.5 h; the average grain diameter of the nano titanium dioxide is 18 nm; the average grain diameter of the nano lithium iron borate is 140 nm;
(2) adding nano nickel pyrophosphate into deionized water, performing ultrasonic dispersion for 28min, spraying a dispersion liquid, depositing a layer of nickel pyrophosphate on the surface of the lithium titanate coated lithium iron borate particle prepared in the step (1), and preparing a single-layer coated lithium iron borate/nickel pyrophosphate composite particle; the weight parts of the raw materials are 19 parts of nano nickel pyrophosphate, 54 parts of deionized water and 27 parts of lithium titanate coated lithium iron borate particles; the average particle size of the nano nickel pyrophosphate is 90 nm;
(3) adding an organic silicon polymer into n-hexane, stirring until the organic silicon polymer is completely dissolved, then adding the composite particles prepared in the step (2), stirring and mixing uniformly, heating at 80 ℃ to remove the solvent n-hexane, and coating the organic silicon polymer on the surfaces of the composite particles to prepare double-layer coated lithium iron borate/nickel pyrophosphate composite particles; the organic silicon polymer is fluorine silicon rubber; the silicon rubber is raw rubber; the weight parts of the raw materials are 1.9 parts of organic silicon polymer, 60.1 parts of normal hexane and 38 parts of composite particles; the stirring speed is 450r/min, and the time is 2 h.
Example 4
(1) Adding nano titanium dioxide and nano lithium iron borate into a deionized water solution of lithium hydroxide, performing ultrasonic dispersion for 10min, transferring the solution to a hydrothermal reaction kettle, heating the solution for reaction, cooling the solution, performing suction filtration, washing the solution for 2 times by using absolute ethyl alcohol, then washing the solution for 2 times by using deionized water, then performing vacuum drying for 20 hours at the temperature of 70 ℃, and then grinding the solution to prepare lithium titanate-coated lithium iron borate particles; the weight parts of the raw materials are 3 parts of nano titanium dioxide, 30 parts of nano lithium iron borate, 2.5 parts of lithium hydroxide and 64.5 parts of deionized water; the temperature of the hydrothermal reaction is 160 ℃, and the time is 11 h; the average grain diameter of the nano titanium dioxide is 10 nm; the average grain diameter of the nano lithium iron borate is 100 nm;
(2) adding nano nickel pyrophosphate into deionized water, performing ultrasonic dispersion for 20min, spraying a dispersion liquid, depositing a layer of nickel pyrophosphate on the surface of the lithium titanate coated lithium iron borate particle prepared in the step (1), and preparing a single-layer coated lithium iron borate/nickel pyrophosphate composite particle; the weight parts of the raw materials are 15 parts of nano nickel pyrophosphate, 65 parts of deionized water and 20 parts of lithium titanate coated lithium iron borate particles; the average particle size of the nano nickel pyrophosphate is 50 nm;
(3) adding an organic silicon polymer into n-hexane, stirring until the organic silicon polymer is completely dissolved, then adding the composite particles prepared in the step (2), stirring and mixing uniformly, heating at 80 ℃ to remove the solvent n-hexane, and coating the organic silicon polymer on the surfaces of the composite particles to prepare double-layer coated lithium iron borate/nickel pyrophosphate composite particles; the organic silicon polymer is methyl silicone rubber; the silicon rubber is raw rubber; the weight parts of the raw materials are 1.5 parts of organic silicon polymer, 68.5 parts of normal hexane and 30 parts of composite particles; the stirring speed is 300r/min, and the time is 3 h.
Example 5
(1) Adding nano titanium dioxide and nano lithium iron borate into a deionized water solution of lithium hydroxide, performing ultrasonic dispersion for 20min, transferring the solution to a hydrothermal reaction kettle, heating the solution for reaction, cooling the solution, performing suction filtration, washing the solution for 3 times by using absolute ethyl alcohol, then washing the solution for 3 times by using deionized water, then performing vacuum drying for 15 hours at the temperature of 80 ℃, and then grinding the solution to prepare lithium titanate-coated lithium iron borate particles; the weight parts of the raw materials are 4 parts of nano titanium dioxide, 40 parts of nano lithium iron borate, 3 parts of lithium hydroxide and 53 parts of deionized water; the temperature of the hydrothermal reaction is 170 ℃ and the time is 9 h; the average grain diameter of the nano titanium dioxide is 20 nm; the average grain diameter of the nano lithium iron borate is 150 nm;
(2) adding nano nickel pyrophosphate into deionized water, performing ultrasonic dispersion for 30min, spraying a dispersion liquid, depositing a layer of nickel pyrophosphate on the surface of the lithium titanate coated lithium iron borate particle prepared in the step (1), and preparing a single-layer coated lithium iron borate/nickel pyrophosphate composite particle; the weight parts of the raw materials are 20 parts of nano nickel pyrophosphate, 50 parts of deionized water and 30 parts of lithium titanate coated lithium iron borate particles; the average particle size of the nano nickel pyrophosphate is 100 nm;
(3) adding an organic silicon polymer into n-hexane, stirring until the organic silicon polymer is completely dissolved, then adding the composite particles prepared in the step (2), stirring and mixing uniformly, heating at 80 ℃ to remove the solvent n-hexane, and coating the organic silicon polymer on the surfaces of the composite particles to prepare double-layer coated lithium iron borate/nickel pyrophosphate composite particles; the organic silicon polymer is methyl vinyl silicone rubber; the silicon rubber is raw rubber; the weight parts of the raw materials are 2 parts of organic silicon polymer, 58 parts of normal hexane and 40 parts of composite particles; the stirring speed is 500r/min, and the time is 2 h.
Example 6
(1) Adding nano titanium dioxide and nano lithium iron borate into a deionized water solution of lithium hydroxide, performing ultrasonic dispersion for 15min, transferring the solution to a hydrothermal reaction kettle, heating the solution for reaction, cooling the solution, performing suction filtration, washing the solution for 3 times by using absolute ethyl alcohol, then washing the solution for 2 times by using deionized water, then performing vacuum drying for 18 hours at the temperature of 75 ℃, and then grinding the solution to prepare lithium titanate-coated lithium iron borate particles; the weight parts of the raw materials are 3.5 parts of nano titanium dioxide, 35 parts of nano lithium iron borate, 2.8 parts of lithium hydroxide and 58.7 parts of deionized water; the temperature of the hydrothermal reaction is 165 ℃ and the time is 10 hours; the average grain diameter of the nano titanium dioxide is 15 nm; the average grain diameter of the nano lithium iron borate is 125 nm;
(2) adding nano nickel pyrophosphate into deionized water, performing ultrasonic dispersion for 25min, spraying a dispersion liquid, depositing a layer of nickel pyrophosphate on the surface of the lithium titanate coated lithium iron borate particle prepared in the step (1), and preparing a single-layer coated lithium iron borate/nickel pyrophosphate composite particle; the weight parts of the raw materials are 18 parts of nano nickel pyrophosphate, 57 parts of deionized water and 25 parts of lithium titanate coated lithium iron borate particles; the average particle size of the nano nickel pyrophosphate is 80 nm;
(3) adding an organic silicon polymer into n-hexane, stirring until the organic silicon polymer is completely dissolved, then adding the composite particles prepared in the step (2), stirring and mixing uniformly, heating at 80 ℃ to remove the solvent n-hexane, and coating the organic silicon polymer on the surfaces of the composite particles to prepare double-layer coated lithium iron borate/nickel pyrophosphate composite particles; the organic silicon polymer is fluorine silicon rubber; the silicon rubber is raw rubber; the weight parts of the raw materials are 1.8 parts of organic silicon polymer, 63.2 parts of normal hexane and 35 parts of composite particles; the stirring speed is 400r/min, and the time is 2.5 h.
Comparative example 1
Lithium iron borate/nickel pyrophosphate are coated with lithium titanate only in a single layer, and other preparation conditions are the same as those in example 6.
Comparative example 2
The lithium iron borate/nickel pyrophosphate is coated with a single layer only by using the organic silicon polymer, and other preparation conditions are consistent with those of example 6.
And (3) performance testing:
the anode material prepared by the invention is prepared into an anode plate, a Celgard2400 polypropylene microporous membrane is used as a diaphragm, and 1mol/L LiPF6The following tests were carried out with the mixed organic solvent (EC: DMC =1:1, volume ratio) as electrolyte and a metallic lithium sheet as counter-electrode sheet assembled in an argon-filled glove box to form a button cell of type CR 2025:
(1) electron conductivity, ion conductivity: after electrochemical circulation is carried out for 1 week by adopting a LandCT2001A battery test system, the electrochemical impedance of the material is measured by using a Zahner IM6ex type electrochemical workstation, the measurement frequency range is 10 kHz-10 mHz, the perturbation voltage is 5mV, and the electronic conductivity and the ionic conductivity of the anode material are tested and calculated;
(2) and (3) testing specific capacity through charge and discharge circulation: and (3) carrying out charge-discharge cycle test by adopting a battery performance test system, wherein the charge-discharge voltage range is 2-4V, exposing the test battery in the air for 0d, 1d and 5d respectively, and testing the charge-discharge specific capacity of the first time and 50 weeks of cycle under the multiplying power of 0.5C after the test battery is exposed in the air.
The data obtained are shown in Table 1.
Table 1:
Claims (9)
1. the preparation method of the double-layer coated lithium iron borate/nickel pyrophosphate lithium battery positive electrode material is characterized by comprising the following specific steps of:
(1) adding nano titanium dioxide and nano lithium iron borate into a deionized water solution of lithium hydroxide, performing ultrasonic dispersion for 10-20 min, transferring the solution to a hydrothermal reaction kettle, heating for reaction, cooling, performing suction filtration, washing with absolute ethyl alcohol for 2-3 times, then washing with deionized water for 2-3 times, then performing vacuum drying at 70-80 ℃ for 15-20 h, and then grinding to obtain lithium titanate-coated lithium iron borate particles;
(2) adding nano nickel pyrophosphate into deionized water, performing ultrasonic dispersion for 20-30 min, spraying a dispersion liquid, and depositing a layer of nickel pyrophosphate on the surface of the lithium titanate coated lithium iron borate particle prepared in the step (1) to prepare a single-layer coated lithium iron borate/nickel pyrophosphate composite particle;
(3) and (3) adding the organic silicon polymer into n-hexane, stirring until the organic silicon polymer is completely dissolved, then adding the composite particles prepared in the step (2), stirring and mixing uniformly, heating at 80 ℃ to remove the solvent n-hexane, and coating the organic silicon polymer on the surfaces of the composite particles to prepare the double-layer coated lithium iron borate/nickel pyrophosphate composite particles.
2. The preparation method of the double-layer coated lithium iron borate/nickel pyrophosphate lithium battery positive electrode material as claimed in claim 1, wherein the preparation method comprises the following steps: in the step (1), the raw materials comprise, by weight, 3-4 parts of nano titanium dioxide, 30-40 parts of nano lithium iron borate, 2.5-3 parts of lithium hydroxide and 53-64.5 parts of deionized water.
3. The preparation method of the double-layer coated lithium iron borate/nickel pyrophosphate lithium battery positive electrode material as claimed in claim 1, wherein the preparation method comprises the following steps: the temperature of the hydrothermal reaction in the step (1) is 160-170 ℃, and the time is 9-11 h.
4. The preparation method of the double-layer coated lithium iron borate/nickel pyrophosphate lithium battery positive electrode material as claimed in claim 1, wherein the preparation method comprises the following steps: in the step (2), the weight parts of the raw materials are 15-20 parts of nano nickel pyrophosphate, 50-65 parts of deionized water and 20-30 parts of lithium titanate coated lithium iron borate particles.
5. The preparation method of the double-layer coated lithium iron borate/nickel pyrophosphate lithium battery positive electrode material as claimed in claim 1, wherein the preparation method comprises the following steps: the organic silicon polymer in the step (3) is at least one of methyl silicone rubber, methyl vinyl silicone rubber and fluorosilicone rubber; the silicone rubber is raw rubber.
6. The preparation method of the double-layer coated lithium iron borate/nickel pyrophosphate lithium battery positive electrode material as claimed in claim 1, wherein the preparation method comprises the following steps: in the step (3), the raw materials comprise, by weight, 1.5-2 parts of an organic silicon polymer, 58-68.5 parts of n-hexane and 30-40 parts of composite particles.
7. The preparation method of the double-layer coated lithium iron borate/nickel pyrophosphate lithium battery positive electrode material as claimed in claim 1, wherein the preparation method comprises the following steps: and (3) stirring at the speed of 300-500 r/min for 2-3 h.
8. The preparation method of the double-layer coated lithium iron borate/nickel pyrophosphate lithium battery positive electrode material as claimed in claim 1, wherein the preparation method comprises the following steps:
the average particle size of the nano titanium dioxide is 10-20 nm;
the average particle size of the nano lithium iron borate is 100-150 nm;
the average particle size of the nano nickel pyrophosphate is 50-100 nm.
9. The double-layer coated lithium iron borate/nickel pyrophosphate lithium battery positive electrode material prepared by the preparation method of any one of claims 1 to 8.
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| WO2024065150A1 (en) * | 2022-09-27 | 2024-04-04 | 宁德时代新能源科技股份有限公司 | Positive electrode active material and preparation method therefor, and positive electrode sheet, secondary battery and electric device comprising same |
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