CN108063248B - Lithium iron phosphate anode material, preparation method thereof and lithium ion battery - Google Patents
Lithium iron phosphate anode material, preparation method thereof and lithium ion battery 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 provides a lithium iron phosphate anode material, which comprises a lithium iron phosphate array and granular lithium iron phosphate, wherein the lithium iron phosphate array is formed by a plurality of columnar lithium iron phosphates arranged in an array; in the lithium iron phosphate array, a gap is formed between every two adjacent columnar lithium iron phosphates, and granular lithium iron phosphate is filled between the gaps. Therefore, the lithium iron phosphate anode material with the specific morphology can have higher compacted density and lithium ion conductivity. The invention also provides a preparation method of the lithium iron phosphate anode material and a lithium ion battery.
Description
Technical Field
The invention relates to the field of lithium ion batteries, in particular to a lithium iron phosphate anode material, a preparation method thereof and a lithium ion battery.
Background
Lithium ion batteries are a new generation of green high-energy batteries, and increasingly play an important role in various fields. As an important group of lithium ion batteriesIn part, the positive electrode material of lithium ion batteries determines the performance, price and development of lithium batteries. Currently, the most studied positive electrode material is LiCoO2、LiNiO2、LiMn2O4、LiFePO4(lithium iron phosphate). Wherein LiCoO is concentrated in the lithium iron phosphate anode material2、LiNiO2、LiMn2O4The battery has the advantages of high structural stability, good safety performance, moderate working voltage, good platform characteristics, large theoretical capacity and the like, and gradually becomes a hot spot of competitive research of battery workers.
However, lithium iron phosphate has a significant disadvantage of low compacted density, which results in low volumetric specific capacity of the lithium iron phosphate, and thus practical application of the lithium iron phosphate is hindered. Therefore, it is necessary to provide a lithium ion battery positive electrode material with high compaction density.
Disclosure of Invention
In view of this, the invention provides a lithium iron phosphate positive electrode material with high compaction density, which is used for solving the problem of low compaction density of a lithium iron cobalt phosphate material in the prior art.
Specifically, the invention provides a lithium iron phosphate positive electrode material, which comprises a lithium iron phosphate array formed by a plurality of columnar lithium iron phosphates arranged in an array, and granular lithium iron phosphate distributed in the lithium iron phosphate array; in the lithium iron phosphate array, a gap is formed between every two adjacent columnar lithium iron phosphates, and granular lithium iron phosphate is filled between the gaps.
In the lithium iron phosphate array, columnar lithium iron phosphate is arranged in parallel along the length direction of the lithium iron phosphate array.
The lithium iron phosphate anode material is columnar, spherical or spheroidal. Examples of the spheroidal shape include an ellipsoidal shape, a button shape, and a heart shape.
Preferably, the lithium iron phosphate positive electrode material is columnar; the thickness is 150-500 nm.
The size of the columnar lithium iron phosphate along the direction vertical to the arrangement direction of the columnar lithium iron phosphate is nano-scale. That is, the radial dimension of the columnar lithium iron phosphate is on the order of nanometers, and preferably 50 to 100 nm.
Wherein the length range of the columnar lithium iron phosphate is 0.5-5 microns. In the lithium iron phosphate array, the lengths of the columnar lithium iron phosphate may be the same or different.
Wherein the gap between two adjacent columnar lithium iron phosphates is 10-60 nm.
Wherein the diameter of the granular lithium iron phosphate is 10-80 nm. Preferably 20-60 nm.
Wherein the gaps of the lithium iron phosphate array are not completely filled with the granular lithium iron phosphate. Preferably, the filling rate of the granular lithium iron phosphate in the gap is 20-80%. The gaps which are not completely filled by the granular lithium iron phosphate can increase Li+Diffusion channel of (2), shortening of Li+The diffusion distance of the lithium iron phosphate anode material is increased, and the lithium ion conductivity of the lithium iron phosphate anode material is also improved.
The "filling ratio" herein refers to a ratio of a total volume of the granular lithium iron phosphate to a volume of the gaps in all the gaps of the lithium iron phosphate array.
Preferably, the compacted density of the lithium iron phosphate cathode material is 2.5-2.8g/cm3。
Wherein the tap density of the lithium iron phosphate anode material is 1.2-1.6g/cm3。
Wherein the D50 of the lithium iron phosphate positive electrode material is 0.20-1.50 μm.
Wherein the first discharge specific capacity of the lithium iron phosphate anode material at room temperature can reach 155-165 mAh/g; the 2C discharge specific capacity of the lithium iron phosphate anode material can reach 120-140 mAh/g.
The lithium iron phosphate positive electrode material provided by the first aspect of the invention comprises cylindrical lithium iron phosphate and granular lithium iron phosphate, wherein the cylindrical lithium iron phosphate is orderly arranged along a certain direction, a gap is formed between adjacent cylindrical lithium iron phosphate, and granular lithium iron phosphate is filled between the gaps. The regularly arranged cylindrical lithium iron phosphate provides more gaps for the filling of the granular lithium iron phosphate, and the granular lithium iron phosphate is convenient to enter. WhileThe granular lithium iron phosphate filled in the gap improves the compaction density of the lithium iron phosphate anode material, thereby improving the energy density when the lithium iron phosphate anode material is used as a lithium ion battery. The gaps which are not completely filled by the granular lithium iron phosphate can increase Li+Diffusion channel of (2), shortening of Li+The diffusion distance of (a) and the lithium ion conductivity of the positive electrode material are also improved.
The second aspect of the invention provides a preparation method of a lithium iron phosphate anode material, which comprises the following steps:
(1) mixing a lithium source, an iron source and a phosphorus source in a molar ratio of Li: fe: p is 1: 1:1 to obtain a mixed material;
(2) ceramic grinding is carried out on the mixed material by adopting a nano ceramic grinding machine to obtain a powdery precursor; wherein, the ceramic grinding is carried out in a plane-to-plane grinding mode;
(3) sintering the powdery precursor under protective gas, and cooling to obtain a lithium iron phosphate anode material; the sintering comprises a first sintering stage, a second sintering stage and a third sintering stage, wherein the first sintering stage is that the temperature is increased from room temperature to a first sintering temperature at a first heating rate, and the first sintering time is kept; the second sintering stage is that the temperature is increased from the first sintering temperature to a second sintering temperature at a second temperature-increasing rate, and the second sintering time is kept; the third sintering stage is that the temperature is increased from the second sintering temperature to a third sintering temperature by adopting a third temperature-increasing rate, and the third sintering time is kept; wherein the second temperature rise rate is (1.5-4) times the first temperature rise rate, and the third temperature rise rate is equal to the first temperature rise rate.
Wherein, in the step (1), the lithium source is at least one selected from the group consisting of lithium oxide, lithium hydroxide, lithium chloride, lithium nitrite, lithium nitrate, lithium oxalate, lithium acetate, lithium carbonate, lithium phosphate, lithium dihydrogen phosphate and lithium dihydrogen phosphate.
The iron source is at least one selected from ferrous nitrate, ferrous oxalate, ferrous chloride, ferrous phosphate, ferrous acetate, ferrous pyrophosphate, ferrous carbonate, ferrous hydroxide, ferric chloride, ferric phosphate, ferric nitrate, ferric acetate and ferric citrate.
The phosphorus source is at least one selected from phosphoric acid, ammonium dihydrogen phosphate, ammonium monohydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate, iron phosphate and lithium dihydrogen phosphate.
The lithium source, the iron source and the phosphorus source are not added with elements except Li, Fe, P and C, O, N as much as possible. Wherein, when lithium phosphate, lithium dihydrogen phosphate or lithium dihydrogen phosphate is selected, the materials can be used as a lithium source and a phosphorus source at the same time. When iron phosphate, ferrous pyrophosphate or the like is selected, these materials can be used as a lithium source and an iron source at the same time.
In the step (2), the material obtained by mixing the lithium source, the iron source and the phosphorus source is subjected to ceramic grinding, the grinding is dry grinding, water is not required to be added to disperse the mixed material, other grinding media (such as zirconia balls) are not required to be added, the problem that the material is easy to stick to the wall caused by wet grinding or ball milling is solved, and the material can be more uniform through ceramic grinding. Moreover, the ceramic grinding process is carried out in a plane-to-plane grinding mode, namely, the material to be ground is positioned between the upper grinding surface and the lower grinding surface of the ceramic grinding machine. Under the grinding condition, the stress directions of the powdery precursor tend to be consistent, so that a more regular lithium iron phosphate precursor is conveniently obtained. In addition, the particle size of the powdery precursor can be controlled by controlling the gap between the upper and lower grinding surfaces of the ceramic grinding machine.
Preferably, in step (2), the particle size of the powdered precursor obtained after grinding the ceramic is less than 50nm, preferably 10-45 nm.
Further, the grinding time of the ceramic is 0.5-4 h.
Wherein in the step (3), the first heating rate is 2-15 ℃/min; the second heating rate is 5-30 ℃/min; the third heating rate is 2-15 ℃/min.
In the present invention, the third sintering temperature is higher than the second sintering temperature, and the second sintering temperature is higher than the first sintering temperature. Further, the first sintering temperature is 160-; the second sintering temperature is 350-450 ℃; the third sintering temperature is 500-650 ℃.
In the step (3), the powdery precursor obtained in the step (2) is subjected to three-stage sintering. The first sintering stage facilitates the formation of a crystalline lattice portion of the powdered precursor to form an initial structure. And the second sintering stage is raised to a second sintering temperature at a temperature rise rate significantly higher than that of the first sintering stage, and sintering is carried out for a second sintering duration. The faster rate of temperature rise may promote a faster growth of the initial structure into a columnar structure, and the second sintering time may be adjusted to cause the columnar structure to grow to a certain extent, and avoid the damage of the columnar structure caused by an excessively long sintering time. Moreover, the temperature of the second sintering stage does not need to be too high and the sintering time does not need to be too long to crystallize the initial structure formed with a part of the crystal lattice sufficiently further, based on having undergone the first sintering stage. The third sintering stage is raised to the third sintering temperature at a third temperature rise rate lower than the second temperature rise rate, and the columnar structure can be stabilized more slowly. In addition, in the ceramic grinding process based on the step (2), part of the powdery precursor with smaller particle size may be included among the powdery precursors with slightly larger particle size, and further grow up in the gaps in the segmented sintering process, and is filled in the gaps of the columnar lithium iron phosphate, so that the compaction density of the whole lithium iron phosphate anode material is improved. Therefore, by the synergistic effect of the ceramic grinding in the step (2) and the specific step sintering process in the step (3), the lithium iron phosphate positive electrode material specifically according to the first aspect of the present invention can be obtained.
Further, the first sintering time is 2-8 h. The second sintering time is 4-10 h. The third sintering time is 5-12 h.
Preferably, the second sintering time period is longer than the first sintering time period. For example, the first sintering time is 2-4 h; the second sintering time is 5-10 h.
Preferably, the third sintering time period is 3-6 h.
Wherein, in the sintering stage, the flow rate of the protective gas is 1100-1500 sccm.
Wherein the cooling is from the third sintering temperature to the normal temperature at a cooling rate of 1-5 ℃/min. The cooling rate in the cooling process is slower, which is beneficial to forming the lithium iron phosphate anode material crystal with good crystal form.
The whole sintering process of the invention is carried out in a constant temperature furnace, and any heat treatment equipment which can uniformly heat under the protection of atmosphere can be used in the sintering process, such as a vacuum furnace, a box furnace, a tunnel furnace, a rotary atmosphere furnace, a bell jar furnace, a tubular furnace, a shuttle furnace or a pushed slab kiln.
Wherein the protective gas is at least one of nitrogen, argon and helium. The pre-firing is performed in a protective gas. The pre-sintering in the protective gas can prevent the ferrous ions in the lithium vanadium iron phosphate from being oxidized.
According to the preparation method of the lithium iron phosphate anode material provided by the second aspect of the invention, firstly, a mixed material formed by a lithium source, an iron source and a phosphorus source is subjected to plane-to-plane grinding type ceramic grinding treatment, then, a ground powdery precursor is subjected to specific three-stage sintering treatment, the overall sintering temperature is low, and the lithium iron phosphate anode material comprising columnar lithium iron phosphate arranged in an array and granular lithium iron phosphate filled between adjacent columnar lithium iron phosphate can be obtained through the synergistic effect among the steps. The preparation method is unique and effective, and the prepared lithium iron phosphate anode material is high in compacted density, large in volume specific capacity, good in conductivity and high in stability.
In a third aspect, the invention provides a lithium ion battery, which comprises the lithium iron phosphate positive electrode material provided by the first aspect of the invention.
The lithium ion battery comprises a positive pole piece, a negative pole piece, a diaphragm, electrolyte and a shell, wherein the positive pole piece consists of a current collector, the lithium iron phosphate positive pole material provided by the first aspect of the invention, a conductive agent and an adhesive.
Wherein, the current collector is an aluminum foil, a nickel net or an aluminum-plastic composite film.
Wherein the conductive agent is acetylene black.
Wherein, the binder is polyvinylidene fluoride (PVDF), styrene butadiene rubber latex (SBR), sodium carboxymethylcellulose (CMC) or the like, but is not limited thereto.
The selection of the negative electrode plate, the diaphragm, the electrolyte and the housing is the prior art in the industry, and is not limited herein.
The lithium ion battery provided by the third aspect of the invention has higher energy density, cycle performance and safety.
Advantages of embodiments of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of embodiments of the invention.
Drawings
Fig. 1 is a scanning electron microscope photograph of a lithium iron phosphate positive electrode material prepared in example 1 of the present invention;
fig. 2 is a graph showing the first 0.1C discharge curves of batteries fabricated with lithium iron phosphate positive electrode materials fabricated in examples 1 to 3 of the present invention and comparative examples 1 to 3;
fig. 3 is a graph showing the first 1C discharge curves of batteries fabricated with lithium iron phosphate positive electrode materials fabricated in examples 1 to 3 of the present invention and comparative examples 1 to 3;
fig. 4 is a graph showing the first 2C discharge curves of batteries fabricated with lithium iron phosphate positive electrode materials fabricated in examples 1 to 3 of the present invention and comparative examples 1 to 3;
fig. 5 is a graph showing cycle characteristics of batteries manufactured using the lithium iron phosphate positive electrode materials manufactured in examples 1 to 3 of the present invention and comparative examples 1 to 3.
Detailed Description
While the following is a description of the preferred embodiments of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.
Example 1:
a preparation method of a lithium iron phosphate positive electrode material comprises the following steps:
(1) taking 7.46g of lithium carbonate, 81.2g of ferric nitrate and 23.24g of ammonium dihydrogen phosphate, and uniformly mixing to obtain a mixed material;
(2) carrying out ceramic grinding on the mixed material by adopting a nano ceramic grinding machine, wherein the ceramic grinding is carried out for 4 hours in a plane-to-plane grinding manner to obtain a powdery precursor with the particle size of less than or equal to 40 nm;
(3) sintering the powdery precursor in a nitrogen atmosphere; wherein the sintering is divided into a first sintering stage, a second sintering stage and a third sintering stage; the first sintering stage is to heat the mixture from room temperature to 180 ℃ at the heating rate of 3 ℃/min, and sintering is carried out for 3 h; in the second sintering stage, the temperature is increased from 180 ℃ to 380 ℃ at the temperature increase rate of 10 ℃/min, and sintering is carried out for 6 hours; in the third sintering stage, the temperature is increased from 380 ℃ to 600 ℃ at the heating rate of 3 ℃/min, and sintering is carried out for 8 hours; and then reducing the temperature from 600 ℃ to normal temperature at the cooling rate of 2 ℃/min to obtain the lithium iron phosphate anode material.
Fig. 1 is a Scanning Electron Microscope (SEM) photograph of the finished lithium iron phosphate cathode material prepared in example 1. As can be seen from fig. 1, the lithium iron phosphate positive electrode material is columnar and has a thickness of 200 nm. The lithium iron phosphate anode material comprises a plurality of cylindrical lithium iron phosphate arranged in parallel, gaps are formed between every two adjacent cylindrical lithium iron phosphate, and granular lithium iron phosphate is filled between the gaps. The radial size of the columnar lithium iron phosphate is 50nm, the length of the columnar lithium iron phosphate is 2-4 microns, the gap is 10-20nm, and the diameter of the granular lithium iron phosphate is 10-30 nm; the filling rate of the granular lithium iron phosphate in the gap is 40%.
Preparation method of lithium ion battery
Adding 800g of the lithium ion battery anode material prepared by the method, 100g of conductive agent acetylene black and 100g of binder polyvinylidene fluoride (PVDF) into 800g of N-methylpyrrolidone solution (NMP solution), and stirring for 2h in a vacuum stirrer to prepare anode slurry; the slurry was uniformly coated on an aluminum foil, then dried in a vacuum drying oven at 120 ℃ for 12 hours, and then punched into a disk having a diameter of 14mm as a positive electrode sheet. A positive plate, a negative plate (a metal lithium plate with the diameter of 14.5 mm), a diaphragm (Celgard 2400 microporous polypropylene film) and an electrolyte (1mo1/L LiPF)6the/EC + DMC (1: 1 by volume)) was assembled in a hydrogen-filled glove box into a CR2025 button lithium ion battery. And then the electrochemical performance of the prepared lithium ion battery can be tested.
Example 2:
a preparation method of a lithium iron phosphate positive electrode material comprises the following steps:
(1) lithium dihydrogen phosphate (i.e. a phosphorus source and a lithium source) and lithium acetate are mixed according to a molar ratio of Li: fe: p is 1: 1:1 to obtain a mixed material;
(2) carrying out ceramic grinding on the mixed material by adopting a nano ceramic grinding machine, wherein the ceramic grinding is carried out for 3 hours in a plane-to-plane grinding manner to obtain a powdery precursor with the particle size of less than 50 nm;
(3) sintering the powdery precursor in a nitrogen atmosphere; wherein the sintering is divided into a first sintering stage, a second sintering stage and a third sintering stage; the first sintering stage is to heat the mixture from room temperature to 200 ℃ at the heating rate of 5 ℃/min, and sintering is carried out for 5 hours; in the second sintering stage, the temperature is increased from 200 ℃ to 400 ℃ at the temperature increase rate of 20 ℃/min, and sintering is carried out for 8 hours; in the third sintering stage, the temperature is increased from 400 ℃ to 500 ℃ at the temperature increase rate of 5 ℃/min, and sintering is carried out for 10 hours; and then reducing the temperature from 500 ℃ to normal temperature at a cooling rate of 5 ℃/min to obtain the lithium iron phosphate anode material.
The method for preparing the lithium ion battery by using the prepared lithium iron phosphate cathode material is the same as that of the embodiment 1.
Example 3
A preparation method of a lithium iron phosphate positive electrode material comprises the following steps:
(1) FePO of iron phosphate (i.e. iron source and phosphorus source)4.2H2O and lithium hydroxide in a molar ratio Li: fe: p is 1: 1:1 to obtain a mixed material;
(2) ceramic grinding is carried out on the mixed material for 4 hours by adopting a nano ceramic grinding machine, wherein the ceramic grinding is carried out for 4 hours in a plane-to-plane grinding mode, and a powdery precursor with the particle size of less than or equal to 35nm is obtained;
(3) sintering the powdery precursor in a nitrogen atmosphere; wherein the sintering is divided into a first sintering stage, a second sintering stage and a third sintering stage; the first sintering stage is to heat the mixture from room temperature to 220 ℃ at the heating rate of 10 ℃/min, and sintering is carried out for 6 h; in the second sintering stage, the temperature is increased from 220 ℃ to 420 ℃ at the temperature increase rate of 25 ℃/min, and sintering is carried out for 10 hours; in the third sintering stage, the temperature is increased from 420 ℃ to 640 ℃ at the temperature increase rate of 10 ℃/min, and the sintering is carried out for 12 hours; and then, reducing the temperature from 640 ℃ to the normal temperature at a cooling rate of 10 ℃/min to obtain the lithium iron phosphate anode material.
The method for preparing the lithium ion battery by using the prepared lithium iron phosphate cathode material is the same as that of the embodiment 1.
To highlight the beneficial effects of the present invention, the following comparative examples are now set up for example 1:
comparative example 1
Ball-milling the mixed material obtained in the step (1) in the embodiment 1, and then sintering the ball-milled material in a 3-stage manner which is the same as that of the embodiment 1 to obtain a lithium iron phosphate cathode material; wherein, the ball milling conditions are as follows: adding agate beads in a ball powder ratio of 10:1, and performing ball milling and refining on the mixed material by an agate grinding tank at 300rpm/2 h.
Comparative example 2
Ball-milling the mixed material obtained in the step (1) in the embodiment 1, and then sintering the ball-milled material in one step, wherein the sintering specifically comprises the following steps: heating to 550 ℃ at the speed of 5 ℃/min, and sintering at constant temperature for 8h to obtain the lithium iron phosphate anode material.
Comparative example 3
Performing one-step sintering on the powdery precursor obtained in the step (2) in the embodiment 1, wherein the sintering specifically comprises the following steps: heating to 600 ℃ at the speed of 5 ℃/min, and sintering at constant temperature for 8h to obtain the lithium iron phosphate anode material.
Comparative example 4
For the powdery precursor obtained in the step (2) of the embodiment 1, 2-stage continuous sintering is adopted, wherein the sintering specifically comprises the following steps: heating to 400 ℃ at the speed of 2 ℃/min, sintering at constant temperature for 6h, heating to 600 ℃ at the speed of 2 ℃/min, and sintering at constant temperature for 3h to obtain the lithium iron phosphate anode material.
The lithium iron phosphate positive electrode materials obtained in examples 1 to 3 and comparative examples 1 to 4 were measured for particle size, compacted density, tap density, and the like, and the results are shown in table 1 below. The electrical properties of the batteries manufactured using the lithium iron phosphate positive electrode materials manufactured in the above examples 1 to 3 and comparative examples 1 to 4 were measured, and the results are shown in fig. 2 to 5 and table 2 below.
TABLE 1
TABLE 2
As can be seen from table 1, the compacted density and tap density of the lithium iron phosphate positive electrode material prepared by the preparation method provided by the present invention are much higher than those of the lithium iron phosphate materials provided in comparative examples 1 to 4. As can be seen from table 2, the lithium ion battery made of the lithium iron phosphate positive electrode material provided by the present invention has a large first discharge specific capacity and a good battery cycle performance.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. The lithium iron phosphate anode material is characterized by comprising a lithium iron phosphate array and granular lithium iron phosphate, wherein the lithium iron phosphate array is composed of a plurality of columnar lithium iron phosphates arranged in an array, and the granular lithium iron phosphate is distributed in the lithium iron phosphate array; in the lithium iron phosphate array, a gap is formed between every two adjacent columnar lithium iron phosphates, granular lithium iron phosphate is filled between the gaps, and the gap of the lithium iron phosphate array is not completely filled with the granular lithium iron phosphate.
2. The lithium iron phosphate positive electrode material according to claim 1, wherein in the lithium iron phosphate array, columnar lithium iron phosphate is arranged in parallel along a length direction thereof.
3. The lithium iron phosphate positive electrode material according to claim 1, wherein the lithium iron phosphate positive electrode material is columnar, spherical or spheroidal.
4. The lithium iron phosphate positive electrode material according to claim 2, wherein the columnar lithium iron phosphate has a nanoscale dimension in a direction perpendicular to the direction of arrangement thereof; the gap between two adjacent columnar lithium iron phosphates is 10-60 nm.
5. The lithium iron phosphate positive electrode material according to claim 1, wherein the diameter of the granular lithium iron phosphate is 10 to 80 nm.
6. The method for preparing the lithium iron phosphate positive electrode material according to any one of claims 1 to 5, comprising the steps of:
(1) mixing a lithium source, an iron source and a phosphorus source in a molar ratio of Li: fe: p is 1: 1:1 to obtain a mixed material;
(2) ceramic grinding is carried out on the mixed material by adopting a nano ceramic grinding machine to obtain a powdery precursor; wherein, the ceramic grinding is carried out in a plane-to-plane grinding mode;
(3) sintering the powdery precursor under protective gas, and cooling to obtain a lithium iron phosphate anode material; the sintering comprises a first sintering stage, a second sintering stage and a third sintering stage, wherein the first sintering stage is that the temperature is increased from room temperature to a first sintering temperature at a first heating rate, and the first sintering time is kept; the second sintering stage is that the temperature is increased from the first sintering temperature to a second sintering temperature at a second temperature-increasing rate, and the second sintering time is kept; the third sintering stage is that the temperature is increased from the second sintering temperature to a third sintering temperature by adopting a third temperature-increasing rate, and the third sintering time is kept; wherein the second temperature rise rate is (1.5-4) times the first temperature rise rate, and the third temperature rise rate is equal to the first temperature rise rate.
7. The method for preparing a lithium iron phosphate positive electrode material according to claim 6, wherein in the step (2), the particle size of the obtained powdery precursor is less than 50 nm.
8. The method for preparing a lithium iron phosphate positive electrode material according to claim 6, wherein the first temperature rise rate is 2 to 15 ℃/min; the second heating rate is 5-30 ℃/min.
9. The method for preparing the lithium iron phosphate cathode material as claimed in claim 6, wherein the first sintering temperature is 160-220 ℃; the second sintering temperature is 350-450 ℃; the third sintering temperature is 500-650 ℃.
10. A lithium ion battery comprising the lithium iron phosphate positive electrode material according to any one of claims 1 to 5.
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| CN109192948B (en) * | 2018-08-29 | 2021-05-07 | 深圳市德方纳米科技股份有限公司 | High-compaction-density lithium iron phosphate and preparation method thereof |
| CN109336077A (en) * | 2018-08-29 | 2019-02-15 | 深圳市德方纳米科技股份有限公司 | A kind of lithium iron phosphate positive material and preparation method thereof |
| CN109650366A (en) * | 2018-11-22 | 2019-04-19 | 湖北融通高科先进材料有限公司 | A kind of LiFePO4 and preparation method thereof |
| CN111755694B (en) * | 2020-06-15 | 2022-04-01 | 宁波锋成先进能源材料研究院 | Titanium phosphate composite material and preparation method and application thereof |
| CN112038629B (en) * | 2020-09-30 | 2022-07-05 | 合肥国轩高科动力能源有限公司 | Integrated high-rate lithium iron phosphate positive electrode material and preparation method and application thereof |
| CN115064668B (en) * | 2022-06-10 | 2024-04-26 | 江苏天合储能有限公司 | Lithium iron phosphate positive electrode material, preparation method thereof and lithium ion battery |
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