CN114050259A - Preparation of single crystal high compaction lithium iron phosphate by primary reduction shaping secondary liquid phase coating method - Google Patents

Preparation of single crystal high compaction lithium iron phosphate by primary reduction shaping secondary liquid phase coating method Download PDF

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CN114050259A
CN114050259A CN202111490724.5A CN202111490724A CN114050259A CN 114050259 A CN114050259 A CN 114050259A CN 202111490724 A CN202111490724 A CN 202111490724A CN 114050259 A CN114050259 A CN 114050259A
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iron phosphate
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程冲
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • HELECTRICITY
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    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/36Selection of substances as active materials, active masses, active liquids
    • H01M4/58Selection 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 method for preparing single-crystal high-compaction lithium iron phosphate by a primary reduction reshaping secondary liquid phase coating method, which comprises the steps of carrying out primary coarse grinding, primary fine grinding, primary spraying and primary sintering on a lithium source, an iron source, a phosphorus source and a small amount of carbon source in a liquid phase system to obtain a lithium iron phosphate precursor, and then carrying out secondary coarse grinding, secondary fine grinding, secondary spraying and secondary sintering on the obtained lithium iron phosphate precursor and the carbon source in the liquid phase system again to obtain the final lithium iron phosphate/carbon composite material. The raw materials and the precursor are shaped to a certain extent through two times of coarse grinding and two times of fine grinding, so that the prepared lithium iron phosphate/carbon composite material has high carbon coating quality, uniform primary particle size and smooth surface, and simultaneously shows good processing performance, electrochemical performance and higher compaction density.

Description

Preparation of single crystal high compaction lithium iron phosphate by primary reduction shaping secondary liquid phase coating method
Technical Field
The invention relates to a preparation method of a lithium battery anode material, in particular to a method for preparing single crystal high-compaction lithium iron phosphate by a primary reduction shaping secondary liquid phase coating method.
Background
At present, the prior art puts higher requirements on the electrical property and the compaction density of the lithium battery anode material. LiFePO4The theoretical capacity of the catalyst is 170mAh/g, and the electrochemical reaction is performed on LiFePO4And FePO4The two phases are conducted alternately. Currently, LiFePO is prepared4The main synthesis method of the powder is a one-step sintering method, and in addition, water is addedThermal methods, sol-gel methods, microwave synthesis methods, and the like. Among them, the one-time synthesis method of iron phosphate precursor is the most mature method, and the method is simple, convenient and easy to operate, for example, in chinese patent (CN108011102B), LiFePO is prepared by using solid anhydrous iron phosphate and lithium carbonate as raw materials and using a solid phase method4The raw materials are usually mixed unevenly, the product particles are large, and the production cost is high; meanwhile, due to the action of high-temperature melting, the lithium iron phosphate prepared by one-time sintering is polycrystalline in crystalline phase, more in edges and corners and irregular in shape, so that the improvement of the compacted density of the powder is not facilitated, and the shape of a finished product is limited by the shape of the anhydrous iron phosphate as a raw material. The Chinese patent (CN107834069B) adopts a primary reaction carbon source without considering the influence of residual carbon on the secondary grinding effect, and the primary sintering temperature is 350-550 ℃, so that a pure-phase lithium iron phosphate material is not formed to almost achieve the primary shaping effect, and the secondary sintering process still has a process of melting to form a new lithium iron phosphate crystal phase, so that the carbon coating is not comprehensive enough, the product compaction and the electrical property are not improved qualitatively, and the energy density is not improved greatly.
Chinese patent (CN102244241B) A preparation method of lithium pyrophosphate modified lithium iron phosphate composite material, the method uniformly mixes lithium source, iron source and phosphorus source in a liquid system according to a certain proportion, the obtained slurry is dried and then presintered under the protection of inert gas atmosphere, thus obtaining the lithium iron phosphate to be modified; and uniformly mixing the pre-sintered product with a lithium source and a phosphorus source in a liquid system according to a certain proportion, drying the obtained slurry, and sintering under the protection of an inert gas atmosphere. When the obtained composite material is used as a lithium ion battery anode material, the rate, low temperature and cycle performance of the battery can be greatly improved, and meanwhile, the composite material has excellent processing performance and good flexibility and winding performance of a pole piece. However, the invention has not been investigated in relation to compaction, while the 0.2C discharge gram capacity is relatively low.
Aiming at the problems in the prior art, the invention provides a method for synthesizing lithium iron phosphate without new phase formation by primary shaping and secondary uniform coating, which effectively improves the carbon coating quality, compaction density and electrochemical performance of a lithium iron phosphate/carbon composite material by using a secondary mixing (two-time coarse grinding and two-time fine grinding to achieve the shaping purpose of the material) and secondary sintering (two-time sintering) process.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a method for preparing single-crystal high-compaction lithium iron phosphate by a primary reduction shaping secondary liquid phase coating method.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the invention provides a method for preparing a lithium iron phosphate material, which comprises the following steps:
(1) mixing precursors: coarse grinding and uniformly mixing a lithium source compound, an iron source compound, a phosphorus source compound, a carbon source and water to obtain coarse powder slurry;
(2) finely grinding, drying and sintering the coarse powder slurry obtained in the step (1) to obtain a lithium iron phosphate precursor;
(3) secondary shaping: and (3) coarsely grinding and uniformly mixing the lithium iron phosphate precursor, the carbon source and water, finely grinding again, unloading, drying and sintering again to obtain the lithium iron phosphate material.
Further, the molar ratio of lithium in the lithium source compound, iron in the iron source compound and phosphorus in the phosphorus source compound is 1-1.1: 0.9-1: 1.0-1.05.
Further, the content of carbon in the carbon source accounts for 0.1-1% of the weight of the target synthetic product lithium iron phosphate material.
Further, the molar ratio of the carbon source in the step (3) to the carbon source in the step (1) is 1-30: 1.
Further, the lithium source compound comprises one or more of lithium carbonate, lithium hydroxide and lithium acetate.
Further, the iron source compound comprises one or more of ferric oxide, ferric nitrate, ferroferric oxide and hydroxyl ferric oxide.
Further, the phosphorus source compound comprises one or more of phosphoric acid, ammonium dihydrogen phosphate and diammonium hydrogen phosphate.
Further, the carbon source comprises one or more of sucrose, glucose, lactose and citric acid.
Further, the final carbon content of the lithium iron phosphate material is 1.2% -5%.
Further, the drying in step (2) and step (3) is spray drying.
Further, the sintering temperature in the step (2) and the sintering temperature in the step (3) are both 600-.
Further, the sintering in the step (2) and the step (3) is performed under an inert gas or a reducing gas.
The invention also provides the single-crystal high-compaction lithium iron phosphate prepared by the method.
The technical effects obtained by the invention are as follows:
(1) the lithium iron phosphate precursor formed after the primary sintering is subjected to spherical grinding to effectively shape the material, so that the final synthesized lithium iron phosphate has ultrahigh powder compaction and battery pole piece compaction, and the powder compaction is as high as 2.7g/cm3
(2) The invention uses secondary sintering to evenly coat carbon, the carbon coating is more compact, so that the final synthesized lithium iron phosphate has excellent electrical property, and the 0.1C discharge gram capacity can reach 158.5 mAh/g.
(3) Because a small amount of carbon source is added in the primary mixing process to reduce the ferric iron, the incomplete reaction of the ferric iron in the secondary carbon coating process in the later period is avoided, and the purity and the stability of the product are improved again.
(4) The lithium iron phosphate anode material prepared by the method has the advantages of good crystallization and small particle size, and a single crystal product, and after a lithium battery is manufactured in the later stage, the lithium iron phosphate synthesized by the method can support higher-voltage charging and discharging, and the structure is not easy to collapse.
Drawings
FIG. 1 is an SEM morphology of shaped lithium iron phosphate in example 1;
fig. 2 is an SEM morphology of lithium iron phosphate before shaping in comparative example 1.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
Before the present embodiments are further described, it is to be understood that the scope of the invention is not limited to the particular embodiments described below; it is also to be understood that the terminology used in the examples is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention.
When numerical ranges are given in the examples, it is understood that both endpoints of each of the numerical ranges and any value therebetween can be selected unless the invention otherwise indicated. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It should be noted that the raw materials used in the present invention are all common commercial products, and thus the sources thereof are not particularly limited.
Example 1:
according to mol ratio of Li: fe: p ═ 1.05: 1: and 1.03 feeding. The feeding process comprises the following steps: 234g of lithium carbonate Li were weighed in turn2CO3(99.5%), 490g Fe iron trioxide2O3(98%), 713g of phosphoric acid H3PO4(85%) 30g of sucrose is put into a stirring mill containing 5L of deionized water, after coarse grinding for 40min, and then sand grinding for 120min, spray drying is carried out, after spraying is finished, the obtained spray powder is placed into a chamber sintering furnace under the nitrogen atmosphere, the temperature rise speed is 5 ℃/min, the temperature is heated to 600 ℃, and the temperature is kept constant for 4 hours, so that 960g of the lithium iron phosphate precursor with the carbon content of 0.2% is obtained.
Then 960g of lithium iron phosphate precursor and 40g of sucrose are put into a reactor containing 5L of deionized waterIn the stirring mill of water, after coarse grinding for 40min, then sand grinding for 180min, spray drying is carried out, after spraying, the obtained spray powder is placed in a chamber sintering furnace under nitrogen atmosphere, the temperature rise speed is 5 ℃/min, the temperature is heated to 780 ℃, and the temperature is kept for 8 hours, so that the carbon content is 1.4 percent, and the powder compaction is 2.65g/cm3A lithium iron phosphate/carbon composite material. The SEM image is shown in FIG. 1.
Mixing a lithium iron phosphate/carbon composite material body, SP and PVDF according to the mass percentage of 90: 5: 5, uniformly mixing, then coating the mixture on an aluminum foil with the thickness of 0.02mm, fully drying to obtain a positive pole piece, and then packaging the positive pole piece in a glove box filled with argon to obtain an experimental battery; and finally, performing charge-discharge cycle performance test on a DC-5 type battery tester: the charging and discharging voltage is 2.0V-3.75V, the charging and discharging test is carried out at the constant current multiplying power of 0.1C, the first reversible specific capacity measured at room temperature is 158.5mAh/g, the charging and discharging test is carried out at the constant current multiplying power of 0.2C, and the first reversible specific capacity measured at room temperature is 156.5 mAh/g.
Example 2:
according to mol ratio of Li: fe: p ═ 1.04: 1: 1.04 feeding. The feeding process comprises the following steps: 232g of lithium carbonate Li are weighed in turn2CO3(99.5%), 490g Fe iron trioxide2O3(98%), 720g of phosphoric acid H3PO4(85%) 35g of glucose is put into a stirring mill containing 5L of deionized water, after coarse grinding for 40min, and then after sand grinding for 120min, spray drying is carried out, after spraying is finished, the obtained spray powder is placed into a chamber sintering furnace under the nitrogen atmosphere, and is heated to 700 ℃ at the temperature rising speed of 8 ℃/min, and the temperature is kept for 4 hours, so 965g of lithium iron phosphate precursor with the carbon content of 0.12% is prepared.
Putting 965g of lithium iron phosphate precursor and 50g of glucose into a stirring mill containing 5L of deionized water, coarsely grinding for 40min, then sanding for 120min, then carrying out spray drying, after spraying is finished, putting the obtained spray powder into a chamber sintering furnace in a nitrogen atmosphere, heating to 780 ℃ at a temperature rise speed of 5 ℃/min, and keeping the temperature for 8 hours to obtain the powder with the carbon content of 1.5 percent and the compacted powder of 2.7g/cm3A lithium iron phosphate/carbon composite material.
Mixing a lithium iron phosphate/carbon composite material body, SP and PVDF according to the mass percentage of 90: 5: 5, uniformly mixing, then coating the mixture on an aluminum foil with the thickness of 0.02mm, fully drying to obtain a positive pole piece, and then packaging the positive pole piece in a glove box filled with argon to obtain an experimental battery; and finally, performing charge-discharge cycle performance test on a DC-5 type battery tester: the charging and discharging voltage is 2.0V-3.75V, the charging and discharging test is carried out at the constant current multiplying power of 0.1C, the first reversible specific capacity measured at room temperature is 155.5mAh/g, the charging and discharging test is carried out at the constant current multiplying power of 0.2C, and the first reversible specific capacity measured at room temperature is 152.5 mAh/g.
Example 3:
according to mol ratio of Li: fe: p ═ 1.04: 1: and 1.03 feeding. The feeding process comprises the following steps: 232g of lithium carbonate Li are weighed in turn2CO3(99.5%), 534g of FeOOH (98%), 718g of ammonium dihydrogen phosphate (99%), 30g of glucose are put into a stirring mill containing 5L of deionized water, coarse grinding is carried out for 40min, then spraying and drying are carried out after 120min of sand grinding, after spraying is finished, the obtained spray powder is placed into a chamber sintering furnace under the nitrogen atmosphere, the temperature rise speed is 10 ℃/min, the temperature is raised to 650 ℃, and the temperature is kept for 3 hours, so that 955g of the lithium iron phosphate precursor with the carbon content of 0.12% is prepared.
Then 955g of lithium iron phosphate precursor and 50g of rock sugar are put into a stirring mill containing 5L of deionized water, after coarse grinding is carried out for 40min, then sand grinding is carried out for 180min, spray drying is carried out, after spraying is finished, the obtained spray powder is placed into a chamber sintering furnace under the nitrogen atmosphere, the temperature is increased by 5 ℃/min to 770 ℃, the temperature is kept for 7 hours, and the prepared powder is compacted to 2.41g/cm, wherein the carbon content is 1.5 percent3A lithium iron phosphate/carbon composite material.
Mixing a lithium iron phosphate/carbon composite material body, SP and PVDF according to the mass percentage of 90: 5: 5, uniformly mixing, then coating the mixture on an aluminum foil with the thickness of 0.02mm, fully drying to obtain a positive pole piece, and then packaging the positive pole piece in a glove box filled with argon to obtain an experimental battery; and finally, performing charge-discharge cycle performance test on a DC-5 type battery tester: the charging and discharging voltage is 2.0V-3.75V, the charging and discharging test is carried out at the constant current multiplying power of 0.1C, the first reversible specific capacity measured at room temperature is 156.0mAh/g, the charging and discharging test is carried out at the constant current multiplying power of 0.2C, and the first reversible specific capacity measured at room temperature is 153.5 mAh/g.
Example 4:
according to mol ratio of Li: fe: p ═ 1.06: 1: 1.04 feeding. The feeding process comprises the following steps: 236g of lithium carbonate Li are weighed in turn2CO3(99.5%), 464g of ferroferric oxide (98%), 832g of diammonium phosphate (99%) and 30g of glucose are put into a stirring mill containing 5L of deionized water, after coarse grinding for 40min, spraying and drying are carried out after sand grinding for 180min, after spraying is finished, the obtained spray powder is placed into a chamber sintering furnace under nitrogen atmosphere, the temperature is increased by 10 ℃/min to 650 ℃, and the temperature is kept for 3 hours, thus obtaining 960g of the lithium iron phosphate precursor with the carbon content of 0.15%.
Then 960g of lithium iron phosphate precursor and 50g of rock sugar are put into a stirring mill containing 5L of deionized water, after coarse grinding for 40min, then sanding for 120min and spray drying, after spraying, the obtained spray powder is put into a sintering furnace under nitrogen atmosphere, heated to 780 ℃ at a heating rate of 5 ℃/min, and kept at the constant temperature for 6 hours to obtain the powder with the carbon content of 1.6 percent and the compacted powder of 2.38g/cm3A lithium iron phosphate/carbon composite material.
Mixing a lithium iron phosphate/carbon composite material body, SP and PVDF according to the mass percentage of 90: 5: 5, uniformly mixing, then coating the mixture on an aluminum foil with the thickness of 0.02mm, fully drying to obtain a positive pole piece, and then packaging the positive pole piece in a glove box filled with argon to obtain an experimental battery; and finally, performing charge-discharge cycle performance test on a DC-5 type battery tester: the charging and discharging voltage is 2.0V-3.75V, the charging and discharging test is carried out at the constant current multiplying power of 0.1C, the first reversible specific capacity measured at room temperature is 155mAh/g, the charging and discharging test is carried out at the constant current multiplying power of 0.2C, and the first reversible specific capacity measured at room temperature is 152.8 mAh/g.
Comparative example 1:
according to mol ratio of Li: fe: p ═ 1.05: 1: and 1.03 feeding. The feeding process comprises the following steps: 234g of lithium carbonate Li were weighed in turn2CO3(99.5%), 490g Fe iron trioxide2O3(98%), 713g of phosphoric acid H3PO4(85%) 70g sucrose, in a stirred mill containing 5L deionized water, coarsely grinding for 40min, then sanding for 120min and spray drying, after spraying, the spray obtainedPlacing the fog powder in a sintering furnace in nitrogen atmosphere, heating to 780 ℃ at a heating rate of 5 ℃/min, and keeping the temperature for 8 hours to obtain the powder with the carbon content of 1.5 percent and the compacted powder of 2.35g/cm3A lithium iron phosphate/carbon composite material. The SEM image is shown in FIG. 2.
Mixing a lithium iron phosphate/carbon composite material body, SP and PVDF according to the mass percentage of 90: 5: 5, uniformly mixing, then coating the mixture on an aluminum foil with the thickness of 0.02mm, fully drying to obtain a positive pole piece, and then packaging the positive pole piece in a glove box filled with argon to obtain an experimental battery; and finally, performing charge-discharge cycle performance test on a DC-5 type battery tester: the charging and discharging voltage is 2.0V-3.75V, the charging and discharging test is carried out at the constant current multiplying power of 0.1C, the first reversible specific capacity measured at room temperature is 152.0mAh/g, the charging and discharging test is carried out at the constant current multiplying power of 0.2C, and the first reversible specific capacity measured at room temperature is 150.1 mAh/g.
Comparative example 2:
according to mol ratio of Li: fe: p ═ 1.04: 1: 1.04 feeding. The feeding process comprises the following steps: 232g of lithium carbonate Li are weighed in turn2CO3(99.5%), 490g Fe iron trioxide2O3(98%), 720g of phosphoric acid H3PO4(85%) 85g of glucose was put in a stirring mill containing 5L of deionized water, after coarse grinding for 40min, followed by sanding for 120min and spray drying, after spraying was completed, the obtained spray powder was placed in a chamber sintering furnace under nitrogen atmosphere and heated to 780 ℃ at a temperature rise rate of 5 ℃/min and held at constant temperature for 8 hours to obtain a powder compacted at 2.31g/cm with a carbon content of 1.7% and a carbon content of 1.313A lithium iron phosphate/carbon composite material.
Mixing a lithium iron phosphate/carbon composite material body, SP and PVDF according to the mass percentage of 90: 5: 5, uniformly mixing, then coating the mixture on an aluminum foil with the thickness of 0.02mm, fully drying to obtain a positive pole piece, and then packaging the positive pole piece in a glove box filled with argon to obtain an experimental battery; and finally, performing charge-discharge cycle performance test on a DC-5 type battery tester: the charging and discharging voltage is 2.0V-3.75V, the charging and discharging test is carried out at the constant current multiplying power of 0.1C, the first reversible specific capacity measured at room temperature is 151.1mAh/g, the charging and discharging test is carried out at the constant current multiplying power of 0.2C, and the first reversible specific capacity measured at room temperature is 149.5 mAh/g.
Comparative example 3:
according to mol ratio of Li: fe: p ═ 1.04: 1: and 1.03 feeding. The feeding process comprises the following steps: 232g of lithium carbonate Li are weighed in turn2CO3(99.5%), 534g of FeOOH (98%), 718g of ammonium dihydrogen phosphate (99%), 30g of glucose and 50g of rock candy are put into a stirring mill containing 5L of deionized water, coarse grinding is carried out for 40min, then spraying drying is carried out after 120min of sand grinding, after spraying is finished, the obtained spray powder is placed into a sintering furnace under the nitrogen atmosphere, the temperature rise speed is 5 ℃/min, the temperature is raised to 770 ℃, the constant temperature is kept for 7 hours, and the carbon content is 1.6%, and the powder is compacted to 2.3g/cm3A lithium iron phosphate/carbon composite material.
Mixing a lithium iron phosphate/carbon composite material body, SP and PVDF according to the mass percentage of 90: 5: 5, uniformly mixing, then coating the mixture on an aluminum foil with the thickness of 0.02mm, fully drying to obtain a positive pole piece, and then packaging the positive pole piece in a glove box filled with argon to obtain an experimental battery; and finally, performing charge-discharge cycle performance test on a DC-5 type battery tester: the charging and discharging voltage is 2.0V-3.75V, the charging and discharging test is carried out at the constant current multiplying power of 0.1C, the first reversible specific capacity measured at room temperature is 151.5mAh/g, the charging and discharging test is carried out at the constant current multiplying power of 0.2C, and the first reversible specific capacity measured at room temperature is 149.9 mAh/g.
Comparative example 4:
according to mol ratio of Li: fe: p ═ 1.06: 1: 1.04 feeding. The feeding process comprises the following steps: 236g of lithium carbonate Li are weighed in turn2CO3(99.5%), 464g of ferroferric oxide (98%), 832g of diammonium phosphate (99%), 30g of glucose and 50g of rock sugar are put into a stirring mill containing 5L of deionized water, coarse grinding is carried out for 40min, then spraying drying is carried out after sand grinding is carried out for 180min, after spraying is finished, the obtained spray powder is placed into a sintering furnace under the nitrogen atmosphere, the temperature rising speed of 5 ℃/min is carried out, the temperature is heated to 780 ℃, the temperature is kept for 6 hours, the carbon content is 1.6%, and the powder is compacted to 2.28g/cm3A lithium iron phosphate/carbon composite material.
Mixing a lithium iron phosphate/carbon composite material body, SP and PVDF according to the mass percentage of 90: 5: 5, uniformly mixing, then coating the mixture on an aluminum foil with the thickness of 0.02mm, fully drying to obtain a positive pole piece, and then packaging the positive pole piece in a glove box filled with argon to obtain an experimental battery; and finally, performing charge-discharge cycle performance test on a DC-5 type battery tester: the charging and discharging voltage is 2.0V-3.75V, the charging and discharging test is carried out at the constant current multiplying power of 0.1C, the first reversible specific capacity measured at room temperature is 152mAh/g, the charging and discharging test is carried out at the constant current multiplying power of 0.2C, and the first reversible specific capacity measured at room temperature is 150.1 mAh/g.
The specific statistics of the test results corresponding to the related products in each example are shown in the following table:
TABLE 1
Examples of the invention Compacting in g/cm3 0.1C discharge gram capacity mAh/g 0.2C discharge gram capacity mAh/g
Example 1 2.65 158.5 156.5
Example 2 2.70 155.5 152.5
Example 3 2.41 156.0 153.5
Example 4 2.38 155.1 152.8
Comparative example 1 2.31 151.1 150.1
Comparative example 2 2.31 151.1 149.5
Comparative example 3 2.30 151.5 149.9
Comparative example 4 2.28 152.0 150.1
Firstly, synthesizing a low-carbon pure-phase lithium iron phosphate material by reacting and sintering different raw materials; and secondly, improving the morphological characteristics of the lithium iron phosphate through secondary grinding and shaping. And thirdly, the secondary pure-phase carbon source coating maintains the shape of the shaped lithium iron phosphate, ensures that the carbon coating is more consistent and complete, greatly improves the compaction density and the capacitance of the lithium iron phosphate and ensures that the energy density of the lithium iron phosphate lithium battery is qualitatively improved.
Finally, it should be noted that the above-mentioned contents are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, and that the simple modifications or equivalent substitutions of the technical solutions of the present invention by those of ordinary skill in the art can be made without departing from the spirit and scope of the technical solutions of the present invention.

Claims (10)

1. A method for preparing a lithium iron phosphate material is characterized by comprising the following steps: the method comprises the following steps:
(1) mixing precursors: coarse grinding and uniformly mixing a lithium source compound, an iron source compound, a phosphorus source compound, a carbon source and water to obtain coarse powder slurry;
(2) finely grinding, drying and sintering the coarse powder slurry obtained in the step (1) to obtain a lithium iron phosphate precursor;
(3) secondary shaping: and (3) coarsely grinding and uniformly mixing the lithium iron phosphate precursor, the carbon source and water, finely grinding again, unloading, drying and sintering again to obtain the lithium iron phosphate material.
2. The method of claim 1, wherein: the molar ratio of lithium in the lithium source compound, iron in the iron source compound and phosphorus in the phosphorus source compound is 1-1.1: 0.9-1: 1.0-1.05.
3. The method of claim 1, wherein: the content of carbon in the carbon source accounts for 0.1-1% of the weight of the target synthetic product lithium iron phosphate material.
4. The method of claim 1, wherein: the molar ratio of the carbon source in the step (3) to the carbon source in the step (1) is 1-30: 1.
5. The method of claim 1, wherein: the lithium source compound comprises one or more of lithium carbonate, lithium hydroxide and lithium acetate.
6. The method of claim 1, wherein: the iron source compound comprises one or more of ferric oxide, ferric nitrate, ferroferric oxide and hydroxyl ferric oxide.
7. The method of claim 1, wherein: the phosphorus source compound comprises one or more of phosphoric acid, ammonium dihydrogen phosphate and diammonium hydrogen phosphate.
8. The method of claim 1, wherein: the carbon source comprises one or more of sucrose, glucose, lactose and citric acid.
9. The method of claim 1, wherein: the sintering temperature in the step (2) and the sintering temperature in the step (3) are both 600-.
10. Single crystal highly compacted lithium iron phosphate prepared by the method of any one of claims 1 to 9.
CN202111490724.5A 2021-12-08 2021-12-08 Preparation of single crystal high compaction lithium iron phosphate by primary reduction shaping secondary liquid phase coating method Pending CN114050259A (en)

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