CN115995539A - Quick ion conductor coated lithium iron phosphate positive electrode material, and preparation method and application thereof - Google Patents
Quick ion conductor coated lithium iron phosphate positive electrode material, and preparation method and application thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of lithium ion battery anode materials, and particularly relates to a fast ion conductor coated lithium iron phosphate anode material, and a preparation method and application thereof. The positive electrode material comprises a lithium iron phosphate matrix and a coating layer coated on the outer surface of the matrix, wherein the molecular formula of the lithium iron phosphate matrix is LiFe 1‑x M x PO 4 Wherein x is more than or equal to 0 and less than or equal to 0.02, M is at least one of manganese, titanium, magnesium, aluminum, zirconium and rare earth elements; from the matrix outwards, the coating layer sequentially comprises a lithium selenate inner layer and a carbon outer layer. The invention firstly forms a layer of selenium carbonate coating inner layer on the surface of the ferric phosphate precursor through in-situ reaction, and then coats a layer of selenium carbonate coating outer layerAnd the carbon source layer is subjected to high-temperature calcination to obtain the lithium selenate cladding inner layer and the carbon outer layer, and the material agglomeration phenomenon is obviously reduced due to the cladding of the lithium selenate, so that the primary particles of the material are more uniform, the primary particles and the secondary particles are smaller, and the ultra-long cycle performance of the lithium iron phosphate is ensured.
Description
Technical Field
The invention belongs to the technical field of lithium ion battery anode materials, and particularly relates to a fast ion conductor coated lithium iron phosphate anode material, and a preparation method and application thereof.
Background
The lithium iron phosphate battery has the characteristics of low price, long cycle life and the like, and becomes a research hot spot in the field of new energy. In recent years, as battery technologies such as blade batteries, CTCs and CTPs have been developed, lithium iron phosphate batteries have also been developed rapidly. At present, lithium iron phosphate is divided into power and energy storage according to different application fields, wherein the power has high requirements on energy density, and the energy storage field has more severe requirements on circulation. Conventional energy storage can be circulated for 4000 weeks generally, and high-end energy storage generally requires 8000 or even 10000 weeks. Aiming at the requirement of the battery on long circulation, the lithium iron phosphate has good electric conductivity and faster ion conduction capacity, and ensures lower impedance and polarization of the lithium iron phosphate material in the circulation process. The lithium iron phosphate anode material is required to be coated uniformly and compactly, and has concentrated particle size distribution and smaller particles. The uniform and compact coating layer ensures good electronic conductivity and structural integrity of the material in the cyclic process; the particle size distribution is concentrated and the particle size is smaller, so that high ion conduction and consistent conduction rate are ensured, and the polarization of the material is reduced.
At present, the industry and academia mainly improve the conductivity of materials through carbon coating, wherein the materials comprise organic carbon and inorganic carbon, and the coating effect is improved through optimizing the types, the addition amount and the coating mode of coating raw materials; for example, chinese patent CN103441269B discloses a machine preparation method of lithium pyrophosphate/carbon coated lithium iron phosphate composite, wherein mixing and grinding a lithium source, an iron source and a phosphorus source, drying, sintering, mixing with a phosphorus source and an organic carbon source in an organic solvent system, sintering and sieving are disclosed. In the prior art, the particle size of primary particles is controlled by controlling the calcination temperature and the calcination time, and the particle size of secondary particles is controlled by jet milling, so that the purposes of concentrated size distribution and small particle size of the primary particles and the secondary particles are finally realized. The carbon coating is generally formed by carbonizing at a high temperature after the presence of an organic coating. However, due to the fact that the carbonization rate is low and the carbon coating is brittle, the carbon coating layer is broken in the crushing process, coating is uneven, the material is high in internal resistance finally, a serious polarization phenomenon exists in the charging and discharging process, and the circulation performance is seriously affected.
However, by reducing the calcination temperature or reducing the calcination time to reduce the particle primary size, there may be a decrease in the crystallinity of the material, thereby affecting the recycling properties of the material. If the secondary particle size is controlled by jet milling, the coating layer is broken, and furthermore, the jet milling cannot control the primary particle size.
Disclosure of Invention
In view of the above technical drawbacks, one of the purposes of the present invention is to provide a fast ion conductor coated lithium iron phosphate positive electrode material, and another purpose of the present invention is to provide a preparation method of the fast ion conductor coated lithium iron phosphate positive electrode material. The invention further provides application of the fast ion conductor coated lithium iron phosphate positive electrode material.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
in a first aspect, the present invention provides a fast ion conductor coated lithium iron phosphate positive electrode material, which comprises a lithium iron phosphate matrix and a coating layer coated on the outer surface of the matrix, wherein the molecular formula of the lithium iron phosphate matrix is LiFe 1-x M x PO 4 Wherein x is more than or equal to 0 and less than or equal to 0.02, M is at least one of manganese, titanium, magnesium, aluminum, zirconium and rare earth elements; from the matrix outwards, the coating layer sequentially comprises a lithium selenate inner layer and a carbon outer layer.
In the above fast ion conductor coated lithium iron phosphate positive electrode material, as a preferred embodiment, the surface phase in the outer surface layer of the lithium iron phosphate substrate is doped with a second additive, and the second additive is a nanomaterial for improving the ion conductivity of the positive electrode material; more preferably, the nanomaterial comprises at least one of nano alumina, nano zirconia, nano yttria, nano rare earth oxide, nano niobium oxide, and boric acid;
further, the mass of the second additive accounts for 0.01-1% (for example, 0.1%, 0.3%, 0.5%, 0.7%, 0.9%) of the mass of the fast ion conductor coated lithium iron phosphate positive electrode material.
In the above fast ion conductor coated lithium iron phosphate positive electrode material, as a preferred embodiment, the mass of the inner layer of the lithium selenate accounts for 0.01-2% (for example: 0.05%, 0.2%, 0.5%, 0.8%, 1.5%, 1.8%) of the mass of the fast ion conductor coated lithium iron phosphate positive electrode material;
and/or, the mass of the carbon outer layer accounts for 0.5-3% (for example, 0.5%, 2%, 2.5%) of the mass of the fast ion conductor coated lithium iron phosphate positive electrode material.
In the above-mentioned fast ion conductor coated lithium iron phosphate positive electrode material, as a preferred embodiment, the fast ion conductor coated lithium iron phosphate positive electrode material has a secondary particle diameter D50 of 0.5 to 2.5 μm (for example: 0.7 μm, 0.9 μm, 1.1 μm, 1.3 μm, 1.5 μm, 1.7 μm, 1.9 μm, 2.1 μm, 2.3 μm), a primary particle diameter of 200 to 450nm (for example: 210nm, 250nm, 300nm, 350nm, 400nm, 440 nm), and the primary particle diameter or primary particle size of the present invention is an average value.
In a second aspect, the invention provides a preparation method of the fast ion conductor coated lithium iron phosphate positive electrode material, which comprises the following steps:
preparing a precursor: dissolving soluble ferrous salt in water, adding or not adding a soluble salt additive containing M element, heating and stirring for the first time to obtain a first solution, adding a phosphorus source into the first solution, keeping the pH value between 1 and 4, heating and stirring for the second time after the phosphorus source is added, and filtering and washing to obtain an M element phase doped ferric phosphate precursor;
preparing a positive electrode material: and adding lithium carbonate, a carbon source and a selenium source into the precursor, performing ball milling, sanding and spraying, and then performing calcination and jet milling to obtain the fast ion conductor coated lithium iron phosphate anode material.
When the cathode material is prepared, a carbon source, lithium carbonate and a selenium source are added at one time, wherein the lithium carbonate and the selenium source react to generate precipitated selenium carbonate, the selenium carbonate is used as precipitate to be deposited and coated on the surface of a precursor material firstly, then a soluble carbon source is coated on the surface of the selenium carbonate, the selenium carbonate and the carbon source are coated on the surface of the material at one time, the process is simple, the coating effect is better, then the selenium carbonate is converted into a lithium selenate inner layer through calcination, and the carbon source layer is converted into a carbon outer layer. The pH is maintained between 1 and 4 during the addition of the phosphorus source during the precursor preparation step in order to complete the precipitation.
In the above preparation method, the selenium source may be an inorganic substance containing selenium element, such as selenium oxide, selenate or selenate, etc., and as a preferred embodiment, the selenium source includes one or more of selenium trioxide, selenate, ammonium selenate, lithium selenate. In the above preparation method, the carbon source includes an organic carbon source and an inorganic carbon source; as a preferred embodiment, the organic carbon source includes one or more of glucose, white sugar, polyethylene glycol; the inorganic carbon source comprises one or more of natural graphite, artificial graphite, acetylene black, carbon nanotubes, carbon fibers and graphene.
In the above preparation method, as a preferred embodiment, the soluble ferrous salt includes one or more of ferrous sulfate, ferrous nitrate, and ferrous chloride;
and/or the phosphorus source comprises one or more of phosphoric acid, monohydrogen phosphate, and dihydrogen phosphate.
Preferably, the monobasic phosphate comprises at least one of diammonium phosphate, disodium phosphate and dipotassium phosphate, and the monobasic phosphate comprises at least one of monoammonium phosphate, sodium dihydrogen phosphate and potassium dihydrogen phosphate.
In the above preparation method, as a preferred embodiment, the soluble salt additive includes one or more of soluble sulfates and nitrates of titanium, magnesium, aluminum, zirconium, and rare earth elements; the soluble salt additive realizes bulk doping in the precursor, and the effect of adding the soluble salt additive is to carry out bulk doping modification on the material so as to improve the ion conductivity of the material.
In the above preparation method, as a preferred embodiment, in the step of preparing the positive electrode material, the second additive is added while adding lithium carbonate, a carbon source, and a selenium source to the precursor, and the second additive is a nanomaterial for improving ion conductivity of the positive electrode material, more preferably, the nanomaterial includes at least one of nano alumina, nano zirconia, nano yttria, nano rare earth oxide, nano niobium oxide, and boric acid. The second additive is doped on the surface of the precursor, and the effect of adding the second additive is to carry out surface phase doping modification on the material so as to improve the ion conductivity of the material.
In the above preparation method, as a preferred embodiment, the concentration of the solution formed by dissolving the soluble ferrite in water is 1mol/L;
in the above preparation method, as a preferred embodiment, the addition amount of the soluble salt additive is 0.01% -1% (for example: 0.1%, 0.3%, 0.7%, 0.9%) of the mass of the fast ion conductor coated lithium iron phosphate positive electrode material;
in the above preparation method, as a preferred embodiment, the molar ratio of lithium carbonate, soluble ferrous salt, lithium, iron and phosphorus in the phosphorus source is (1-1.1): (0.9-1): 1, a step of;
in the above preparation method, as a preferred embodiment, the carbon source is added in an amount of 0.5-3% (e.g., 0.5%, 2%, 2.5%) by mass of carbon in the fast ion conductor coated lithium iron phosphate positive electrode material;
in the invention, when the carbon content of the final product is too high, free carbon is more, side reactions are more, the specific surface area is larger, the processing performance is influenced, the capacity is low, and when the carbon content is too low, the material coating effect is poor and the conductivity is poor.
In the preparation method, as a preferred embodiment, the addition amount of the selenium source is 0.01-2% (for example, 0.1%, 0.5%, 1%, 1.4%, 1.6%, 1.8%) of the mass of the fast ion conductor coated lithium iron phosphate positive electrode material;
in the invention, the addition amount of the selenium source is low, the ion conductivity is low, the addition amount of the selenium source is high, and the electron conductivity is low.
In the above preparation method, as a preferred embodiment, the second additive is added in an amount of 0.01-1% (e.g., 0.1%, 0.3%, 0.5%, 0.7%, 0.9%) of the mass of the fast ion conductor coated lithium iron phosphate positive electrode material.
In the above preparation method, as a preferable embodiment, the primary heating and stirring is performed at a temperature of 40-80deg.C (e.g. 50deg.C, 70deg.C) for a period of 2-8h (e.g. 3h, 5h, 6h, 7 h);
in the above preparation method, as a preferred embodiment, the temperature of heating in the secondary heating and stirring is 80-95 ℃ (e.g., 85 ℃); the heating and stirring time is 2-8h (for example, 3h, 4h, 5h and 7 h). The washing is conventional water washing.
In the above preparation method, as a preferred embodiment, the ball milling is performed by wet ball milling;
the solid content is 30-50% during the wet ball milling; the liquid medium adopted by the wet ball milling is water or alcohol;
in the present invention, alcohols used in the wet ball milling liquid medium are commonly used in the art, and thus are not described herein. The organic carbon source can be coated on the surface of the material by adopting ball milling and spraying modes.
In the above preparation method, as a preferred embodiment, the particle size of the product after sand milling is 100 to 500nm (e.g., 300nm, 400 nm), more preferably 200 to 500nm. In the preparation method, the spray not only achieves the purpose of granulation, but also achieves the purpose of quick drying, so that the soluble carbon source is uniformly coated on the surface of the insoluble substance.
In the above preparation method, as a preferred embodiment, the temperature of the calcination is 650-750deg.C (e.g., 670 deg.C, 690 deg.C, 710 deg.C); and/or the calcination time is 4-16h (e.g., 6h, 8h, 12h, 14 h);
and/or the calcination is performed under a protective gas atmosphere, preferably, the protective gas includes one of nitrogen, helium, neon;
in a third aspect, the invention also provides application of the fast ion conductor coated lithium iron phosphate positive electrode material in a lithium ion battery.
Compared with the prior art, the invention has the following beneficial effects:
according to the invention, lithium carbonate is used as a lithium source, and precipitated selenium carbonate can be generated by utilizing the lithium carbonate and the selenium source, so that a layer of selenium carbonate coating inner layer is formed on the surface of an iron phosphate precursor through in-situ reaction, and then a layer of carbon source layer is coated outside the selenium carbonate, and the rapid ion conductor coated iron phosphate lithium anode material with a lithium selenate coating inner layer and a carbon outer layer is obtained through high-temperature calcination.
During the calcination, the growth of lithium iron phosphate crystals is inhibited due to the limitation of the inorganic coating layer (i.e., selenium-containing substance), so that a material having uniform particle size can be obtained. During the pulverization process, the pulverization of the lithium iron phosphate particles can also be reduced. In addition, through cladding selenium source, through high temperature calcination, it forms the lithium selenate, and the lithium selenate belongs to fast ion conductor, can effectively improve the lithium conductivity of material, reduces the ionic resistance. The cycling performance of the lithium iron phosphate is improved by limiting the growth of lithium iron phosphate crystals, stabilizing the crystal structure of the lithium iron phosphate and improving the conductivity of lithium iron phosphate ions.
Drawings
Fig. 1 is an SEM image of a fast ion conductor coated lithium iron phosphate positive electrode material according to example 1 of the present invention.
Detailed Description
The following is a further detailed description of a method for preparing a fast ion conductor coated lithium iron phosphate positive electrode material according to the present invention by way of examples, which are given only to illustrate the present invention and not to limit the scope of the present invention. All other embodiments, which are derived by a person skilled in the art based on the embodiments of the invention, fall within the scope of protection of the invention. The examples provided below may be used as a basis for further modifications and applications by those of ordinary skill in the art and are not intended to limit the scope of the invention in any way.
Example 1
The embodiment provides a preparation method of a fast ion conductor coated lithium iron phosphate positive electrode material, which comprises the following steps:
s1: ferrous sulfate is dissolved in water (the concentration of ferrous sulfate in the solution is 1 mol/L), 0.5wt% of titanium sulfate which is used for coating the mass of the lithium iron phosphate positive electrode material by a fast ion conductor is added, then the solution is heated to 60 ℃, the temperature is kept and stirred for 4 hours, ammonium dihydrogen phosphate and phosphoric acid are added after stirring, the pH value is kept at 2, after the materials are completely added, the solution is stirred for 6 hours at 90 ℃, and a precursor is obtained after filtering and washing, wherein the molar ratio of iron to phosphorus is 1:1.
S2: adding lithium carbonate, glucose, selenium trioxide and nano niobium oxide into the precursor, ball milling, sanding and spraying to obtain a mixed material, wherein the molar ratio of lithium to phosphorus is 1.05:1, a step of; the glucose adding amount is added according to the carbon content of 1.0 weight percent in the final fast ion conductor coated lithium iron phosphate positive electrode material; the addition amount of the selenium trioxide is 1.2 weight percent of the mass of the fast ion conductor coated lithium iron phosphate anode material; the addition amount of the nano niobium oxide is 0.05wt% of the mass of the fast ion conductor coated lithium iron phosphate anode material; the particle size (D50) of the product after sanding was 200nm.
S3: and (3) loading the mixture into a pot, calcining the mixture in a nitrogen atmosphere of a roller kiln at the temperature of 730 ℃ for 10 hours, and finally carrying out jet milling to obtain the fast ion conductor coated lithium iron phosphate anode material with the particle size (D50) of the secondary particles of 1.2 mu m, wherein the primary particles are 321nm.
Fig. 1 is an SEM image of a fast ion conductor coated lithium iron phosphate positive electrode material in this embodiment, and as can be seen from fig. 1, the positive electrode material prepared by the method of the present invention has good particle size uniformity and good coating effect.
Example 2
The embodiment provides a preparation method of a fast ion conductor coated lithium iron phosphate positive electrode material, which comprises the following steps:
the difference between this example and example 1 is that the amount of diselenide added was 0.5wt%.
Example 3
The embodiment provides a preparation method of a fast ion conductor coated lithium iron phosphate positive electrode material, which comprises the following steps:
the difference between this example and example 1 is that the amount of diselenide added was 2wt%.
Example 4
The embodiment provides a preparation method of a fast ion conductor coated lithium iron phosphate positive electrode material, which comprises the following steps:
the difference between this example and example 1 is that the amount of glucose added was 0.5wt%.
Example 5
The embodiment provides a preparation method of a fast ion conductor coated lithium iron phosphate positive electrode material, which comprises the following steps:
the difference between this example and example 1 is that the amount of glucose added was 3wt%.
Example 6
The embodiment provides a preparation method of a fast ion conductor coated lithium iron phosphate positive electrode material, which comprises the following steps:
compared with example 1, the difference of this example is that the phosphorus-lithium ratio is 1:1.
example 7
The embodiment provides a preparation method of a fast ion conductor coated lithium iron phosphate positive electrode material, which comprises the following steps:
compared with example 1, the difference of this example is that the phosphorus-lithium ratio is 1:1.1.
example 8
The embodiment provides a preparation method of a fast ion conductor coated lithium iron phosphate positive electrode material, which comprises the following steps:
the difference between this example and example 1 is that the calcination temperature is 700 ℃.
Example 9
The embodiment provides a preparation method of a fast ion conductor coated lithium iron phosphate positive electrode material, which comprises the following steps:
the difference between this example and example 1 is that the calcination temperature is 750 ℃.
Example 10
The embodiment provides a preparation method of a fast ion conductor coated lithium iron phosphate positive electrode material, which comprises the following steps:
the difference between this example and example 1 is that the calcination time is 6h.
Example 11
The embodiment provides a preparation method of a fast ion conductor coated lithium iron phosphate positive electrode material, which comprises the following steps:
the difference between this example and example 1 is that the calcination time is 16h.
Comparative example 1
The embodiment provides a preparation method of a fast ion conductor coated lithium iron phosphate positive electrode material, which comprises the following steps:
the difference between this example and example 1 is that the amount of diselenide added was 0wt%.
Test case
Primary particle sizes of the positive electrode materials prepared in examples 1 to 11 and comparative example 1 were measured; the primary particle size test method comprises the following steps: the primary particle size was counted by SEM image.
The positive electrode materials prepared in examples 1 to 11 and comparative example 1 were used as active materials, respectively, mixed with polyvinylidene fluoride (PVDF) and superconducting carbon black (SuperP) in a mass ratio of 93.5:4.2:2.3, and ball-milled for 60min with NMP as a solvent; uniformly coating the slurry on a metal aluminum foil, vacuum drying at 80 ℃ for 2 hours, and finally cutting into a round pole piece with the diameter of 14mm by using a punch as a working electrode; in a purged glove box filled with Ar (O 2 Content of H less than 0.1ppm 2 O content less than 0.1 ppm), a metal lithium sheet is used as a counter electrode, a Celgard 2400 porous polypropylene film (PP) is used as a diaphragm, and an electrolyte is 1M L -1 Lithium hexafluorophosphate (LiPF) 6 ) Solution, solvent Ethylene Carbonate (EC): ethyl carbonate (DMC) =1: and (3) preparing the R2032 button cell by the mixed solution with the volume ratio of 1 according to a certain assembly process, and standing for 3h after the completion of the preparation to fully infiltrate the electrolyte and the electrode material. And (3) performing constant current charge and discharge experiments of the battery in a voltage range of 2.5-3.65V at room temperature (25 ℃ plus or minus 3), and testing the initial discharge specific capacity and the 200-week retention rate.
The calculation method of the 200-week retention rate comprises the following steps: the cycle 200 week capacity retention was calculated based on the first week discharge specific capacity.
The specific test results are shown in the following table:
| primary particle size (nm) | First-order specific capacity (mAh/g) | Maintenance rate of 200 weeks (%) | |
| Example 1 | 321 | 161 | 99.7 |
| Example 2 | 420 | 160 | 97.6 |
| Example 3 | 380 | 161 | 99.1 |
| Example 4 | 310 | 159 | 98.5 |
| Example 5 | 323 | 157 | 97.6 |
| Example 6 | 350 | 159 | 98.2 |
| Example 7 | 380 | 159 | 98.5 |
| Example 8 | 310 | 157 | 98.1 |
| Example 9 | 450 | 157 | 96.5 |
| Example 10 | 309 | 156 | 97.8 |
| Example 11 | 430 | 158 | 97.7 |
| Comparative example 1 | 490 | 155 | 94.6 |
As can be seen from the table above: the specific capacity and the cycle performance of the material can be effectively improved by controlling the granularity of primary particles through double coating of the carbon coating outer layer and the lithium selenate fast ion conductor material inner layer.
The foregoing description of the preferred embodiments of the invention is not intended to limit the invention to the particular embodiments disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A fast ion conductor coated lithium iron phosphate positive electrode material is characterized by comprising a lithium iron phosphate matrix and a coating layer coated on the outer surface of the matrixThe molecular formula of the lithium iron phosphate matrix is LiFe 1-x M x PO 4 Wherein x is more than or equal to 0 and less than or equal to 0.02, M is at least one of manganese, titanium, magnesium, aluminum, zirconium and rare earth elements; from the matrix outwards, the coating layer sequentially comprises a lithium selenate inner layer and a carbon outer layer.
2. The fast ion conductor coated lithium iron phosphate positive electrode material according to claim 1, wherein the surface phase in the outer surface layer of the lithium iron phosphate matrix is doped with a second additive, the second additive being a nanomaterial that improves the ionic conductivity properties of the positive electrode material.
3. The fast ion conductor coated lithium iron phosphate positive electrode material according to claim 2, wherein the nanomaterial comprises at least one of nano aluminum oxide, nano zirconium oxide, nano yttrium oxide, nano rare earth oxide, nano niobium oxide, boric acid;
and/or the mass of the second additive accounts for 0.01-1% of the mass of the fast ion conductor coated lithium iron phosphate positive electrode material;
and/or the mass of the lithium selenate inner layer accounts for 0.01-2% of the mass of the fast ion conductor coated lithium iron phosphate positive electrode material;
and/or the mass of the carbon outer layer accounts for 0.5-3% of the mass of the fast ion conductor coated lithium iron phosphate positive electrode material.
4. The fast ion conductor coated lithium iron phosphate positive electrode material according to any one of claims 1 to 3, wherein the fast ion conductor coated lithium iron phosphate positive electrode material has a secondary particle diameter D50 of 0.5 to 2.5 μm and a primary particle diameter of 200 to 450nm.
5. A method for preparing the fast ion conductor coated lithium iron phosphate positive electrode material according to any one of claims 1 to 4, comprising the following steps:
preparing a precursor: dissolving soluble ferrous salt in water, adding or not adding a soluble salt additive containing M element, heating and stirring for the first time to obtain a first solution, adding a phosphorus source into the first solution, keeping the pH value between 1 and 4, heating and stirring for the second time after the phosphorus source is added, and filtering and washing to obtain an M element phase doped ferric phosphate precursor;
preparing a positive electrode material: and adding lithium carbonate, a carbon source and a selenium source into the precursor, performing ball milling, sanding and spraying, and then performing calcination and jet milling to obtain the fast ion conductor coated lithium iron phosphate anode material.
6. The method for preparing the fast ion conductor coated lithium iron phosphate positive electrode material according to claim 5, wherein the fast ion conductor coated lithium iron phosphate positive electrode material is prepared by the following steps of,
the selenium source comprises one or more of selenium trioxide, selenic acid, ammonium selenate and lithium selenate
And/or, the carbon source comprises an organic carbon source and/or an inorganic carbon source;
and/or the phosphorus source comprises one or more of phosphoric acid, monohydrogen phosphate, and dihydrogen phosphate;
and/or the soluble salt additive comprises one or more of soluble sulfates and nitrates of titanium, magnesium, aluminum, zirconium and rare earth elements.
7. The method for preparing the fast ion conductor coated lithium iron phosphate positive electrode material according to claim 5, wherein the fast ion conductor coated lithium iron phosphate positive electrode material is prepared by the following steps of,
in the step of preparing the positive electrode material, the lithium carbonate, the carbon source and the selenium source are added to the precursor, and the second additive is added at the same time, wherein the second additive is a nano material for improving the ionic conductivity of the positive electrode material.
8. The method for preparing the fast ion conductor coated lithium iron phosphate positive electrode material according to claim 7, wherein the concentration of the solution formed by the soluble ferrous salt after being dissolved in water is 1mol/L;
and/or the addition amount of the soluble salt additive is 0.01% -1% of the mass of the fast ion conductor coated lithium iron phosphate anode material;
and/or the molar ratio of lithium carbonate, soluble ferrous salt and lithium, iron and phosphorus in the phosphorus source is (1-1.1): (0.9-1): 1, a step of;
and/or the addition amount of the carbon source is added according to the mass content of 0.5-3% of the carbon in the fast ion conductor coated lithium iron phosphate anode material;
and/or the addition amount of the selenium source is 0.01-2% of the mass of the fast ion conductor coated lithium iron phosphate anode material;
and/or the addition amount of the second additive is 0.01-1% of the mass of the fast ion conductor coated lithium iron phosphate positive electrode material.
9. The method for preparing the fast ion conductor coated lithium iron phosphate positive electrode material according to any one of claims 5 to 8, wherein in the primary heating and stirring, the heating temperature is 40 to 80 ℃, and the heating and stirring time is 2 to 8 hours;
and/or, in the secondary heating and stirring, the heating temperature is 80-95 ℃; heating and stirring for 2-8h;
and/or, the ball milling adopts wet ball milling; the solid content is 30-50% during the wet ball milling;
and/or, the product particle size after sanding is 100-500nm;
and/or the calcination temperature is 650-750 ℃, and the calcination time is 4-16h;
and/or the calcination is performed under a protective gas atmosphere.
10. Use of the fast ion conductor coated lithium iron phosphate positive electrode material according to any one of claims 1 to 4 or the fast ion conductor coated lithium iron phosphate positive electrode material obtained by the preparation method according to any one of claims 5 to 9 in a lithium ion battery.
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| CN117577832A (en) * | 2024-01-16 | 2024-02-20 | 中国第一汽车股份有限公司 | Lithium manganese iron phosphate positive electrode material and preparation method thereof, positive electrode plate and preparation method thereof, lithium ion battery and electric equipment |
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| CN117577832A (en) * | 2024-01-16 | 2024-02-20 | 中国第一汽车股份有限公司 | Lithium manganese iron phosphate positive electrode material and preparation method thereof, positive electrode plate and preparation method thereof, lithium ion battery and electric equipment |
| CN117577832B (en) * | 2024-01-16 | 2024-05-14 | 中国第一汽车股份有限公司 | Lithium manganese iron phosphate positive electrode material and preparation method thereof, positive electrode plate and preparation method thereof, lithium ion battery and electric equipment |
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