Flower-shaped iron phosphate, preparation method thereof, preparation method of lithium iron phosphate and lithium battery

Abstract

This invention relates to the field of lithium battery technology, specifically to a flower-shaped iron phosphate and its preparation method, a method for preparing lithium iron phosphate, and a lithium battery. The preparation method of the flower-shaped iron phosphate includes the following steps: S1. A titanium-containing iron source and a phosphorus source are subjected to a precipitation reaction to form a grayish-blue slurry, followed by solid-liquid separation and washing to obtain a washed filter cake; S2. The washed filter cake is prepared into a slurry, hydrogen peroxide is added, and Fe... 2+ Oxidized to Fe 3+ Phosphoric acid is added to the slurry, and the mixture is heated for aging. After solid-liquid separation and drying, flower-shaped iron phosphate dihydrate is obtained. The iron phosphate dihydrate prepared by the method of this invention has a flower-shaped structure with rod-plate stacking. The preparation process is simple and energy-efficient, and it can be used to prepare high-rate lithium iron phosphate electrode materials. Lithium batteries assembled from the high-rate lithium iron phosphate electrode materials have the advantages of large capacity, high initial efficiency, and good rate performance.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and more specifically, to a flower-shaped iron phosphate and its preparation method, a method for preparing lithium iron phosphate, and a lithium battery. Background Technology

[0002] Lithium iron phosphate (LFP) is considered one of the most competitive electrode materials for lithium-ion batteries due to its excellent electrochemical performance, good safety, and low cost. As a crucial raw material for the synthesis of LFP, the morphology of iron phosphate plays a key role in its performance; therefore, preparing iron phosphate with different morphologies is of great significance to the development of LFP.

[0003] Chinese patent application CN116143097A discloses a composite lithium iron phosphate cathode material, its preparation method, and its application. The method involves synthesizing polycrystalline flower-shaped iron phosphate using a microwave hydrothermal method, and then mixing it with a lithium source to prepare the composite lithium iron phosphate cathode material. This polycrystalline flower-shaped morphology can significantly improve the cycle performance and rate performance of the lithium iron phosphate cathode material.

[0004] Chinese patent application CN108448105A discloses a method for preparing lithium iron phosphate / reduced graphene oxide cathode material for lithium-ion batteries. The method uses a hydrothermal method to synthesize a flower-like structure FePO4 / GO, which is then mixed with a lithium source and sintered to prepare LiFePO4 / RGO. This flower-like structure can increase the specific surface area of ​​the material, allowing more lithium ion insertion / extraction channels to contact the electrolyte, thereby improving the capacity of the material and its charge / discharge performance at high rates.

[0005] The above-mentioned methods mostly use hydrothermal synthesis of flower-shaped iron phosphate to prepare high-rate lithium iron phosphate, but they have problems such as being unable to be prepared on a large scale, requiring high-temperature and high-pressure equipment, and high energy consumption.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The primary objective of this invention is to provide a method for preparing flower-shaped iron phosphate, thereby addressing the problems of existing technologies that require high-temperature and high-pressure equipment, have high energy consumption, and cannot be mass-produced. The method of this invention features a simple preparation process, mild and controllable conditions, eliminates the need for high-temperature and high-pressure equipment, has low energy consumption, and produces iron phosphate with a flower-like structure of rod-plate stacking, which can be used to prepare high-rate lithium iron phosphate.

[0008] The second objective of this invention is to provide a flower-shaped ferric phosphate, which is prepared by the method described above.

[0009] The third objective of this invention is to provide a method for preparing lithium iron phosphate, which uses the flower-shaped iron phosphate as described above as an iron source and a phosphorus source.

[0010] A fourth objective of this invention is to provide a lithium battery comprising lithium iron phosphate material prepared by the method described above.

[0011] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0012] A method for preparing flower-shaped ferric phosphate includes the following steps:

[0013] S1. The titanium-containing iron source and phosphorus source are subjected to precipitation reaction to become a gray-blue slurry. After solid-liquid separation and washing, a first-wash filter cake is obtained.

[0014] S2. Prepare the washed filter cake into a slurry, add hydrogen peroxide, and let Fe... 2+ Oxidized to Fe 3+ Phosphoric acid is added to the slurry, and the mixture is heated for aging. After solid-liquid separation, the mixture is dried to obtain flower-shaped ferric phosphate dihydrate with a rod-plate structure.

[0015] Preferably, in the titanium-containing iron source, the Ti content is 0.5wt%-1.4wt% of Fe.

[0016] Preferably, the titanium source in the titanium-containing iron source includes titanium dioxide and / or titanium oxysulfate.

[0017] Preferably, the iron source in the titanium-containing iron source includes at least one of ferrous sulfate, ferrous oxalate, and ferrous chloride; and / or, the molar ratio of Fe in the titanium-containing iron source to P in the phosphorus source is 2.5-3.5:2.

[0018] Preferably, the phosphorus source includes at least one of phosphoric acid, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

[0019] Preferably, the precipitation reaction is carried out at a temperature of 50-90°C for 0.5-4 hours.

[0020] Preferably, the endpoint pH of the precipitation reaction is 2.5-5.5.

[0021] Preferably, the amount of hydrogen peroxide added is 0.1-0.5 times the molar amount of Fe in the titanium-containing iron source.

[0022] Preferably, after adding the phosphoric acid, the pH of the slurry is 1.5-2.1.

[0023] Preferably, the aging temperature is 75-95℃ and the aging time is 0.5-4h.

[0024] A flower-shaped ferric phosphate is prepared by the method described in any one of the preceding embodiments.

[0025] A method for preparing lithium iron phosphate includes the following steps:

[0026] The flower-shaped iron phosphate as described above is mixed with a lithium source and a carbon source, and then subjected to sand milling, spray drying and sintering to obtain the final product.

[0027] Preferably, the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium dihydrogen phosphate, and lithium acetate.

[0028] Preferably, the amounts of the flower-shaped iron phosphate and the lithium source are measured according to a molar ratio of Li to P of 1.05-1:1.

[0029] Preferably, the carbon source includes at least one of glucose, sucrose, PEG6000, and PEG2000.

[0030] Preferably, the mass of the carbon source is 10%-20% of the flower-shaped iron phosphate.

[0031] Preferably, the particle size D50 of the sand mill is 0.32-0.39 μm.

[0032] Preferably, the sintering temperature is 650-750℃, and the sintering time is 6-24h.

[0033] A lithium battery comprising lithium iron phosphate material prepared by the method described above.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] (1) In the precipitation reaction section, this invention obtains flake-shaped Fe3(PO4)2 and granular Fe. 3+ The compound, through the addition of titanium, induces particulate Fe 3+ The compound particles are smaller in the first stage and are induced to transform from particulate FePO4 to rod-shaped particles in the aging process. The rod-shaped structure and the plate-shaped Fe3(PO4)2 self-assemble into a flower-shaped structure in the aging process. The amorphous Fe3(PO4)2 stacked on the plate transforms into the petals of the flower-shaped ferric phosphate, while the rod-shaped structure becomes the folded part of the flower-shaped ferric phosphate.

[0036] (2) Compared with the traditional hydrothermal method for preparing flower-shaped iron phosphate, the method of the present invention does not require high temperature and high pressure equipment, has low energy consumption, and the preparation process is simple, the conditions are mild and controllable, and it is easy to achieve mass production.

[0037] (3) In the preparation of lithium iron phosphate, the folded parts of the flower-shaped lithium iron phosphate have more exposed active sites, which is conducive to lithium ion extraction and insertion, while the rod-shaped morphology shortens the distance in the b-axis direction and reduces the Li-ion extraction and insertion. + The diffusion distance is beneficial for lithium-ion transport, improves electrochemical performance, and enables the production of high-rate lithium iron phosphate. Attached Figure Description

[0038] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0039] Figure 1 These are scanning electron microscope (SEM) images of the ferrous phosphate precipitate filter cake in Example 1 and the ferric phosphate precipitate filter cake in Comparative Example 1 of the present invention.

[0040] Figure 2 This is a scanning electron microscope image of the ferric phosphate dihydrate prepared in Example 1 of the present invention;

[0041] Figure 3 This is a scanning electron microscope image of the iron phosphate dihydrate prepared in Comparative Example 1 of the present invention.

[0042] Figure 4 This is a scanning electron microscope image of the ferric phosphate dihydrate prepared in Comparative Example 2 of the present invention;

[0043] Figure 5 This is a scanning electron microscope image of the iron phosphate dihydrate prepared in Comparative Example 3 of the present invention. Detailed Implementation

[0044] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0045] A first aspect of the present invention provides a method for preparing flower-like ferric phosphate, comprising the following steps:

[0046] S1. The titanium-containing iron source and phosphorus source are subjected to precipitation reaction to become a gray-blue slurry. After solid-liquid separation and washing, a first-wash filter cake is obtained.

[0047] S2. Add water to the washed filter cake obtained in step S1 to make a slurry, then add hydrogen peroxide to make Fe 2+ Oxidized to Fe 3+The mixture turns into a yellow slurry. After the pH stabilizes, phosphoric acid is added to the slurry to adjust the pH. The mixture is then heated for aging. After solid-liquid separation, the mixture is dried to obtain flower-like ferric phosphate dihydrate with a rod-plate structure.

[0048] The method of this invention does not add an oxidizing agent during the precipitation reaction, and obtains flaky Fe3(PO4)2 through the precipitation reaction. Ferrous salts usually contain a certain amount of Fe. 3+ During the precipitation reaction, it forms particulate Fe. 3+ The compound (mainly composed of iron phosphate) was used to induce particulate Fe by adding a titanium source. 3+ The compound particles are smaller in the initial stage; during the aging process, due to crystal transformation and structural rearrangement, these two parts self-assemble to form a flower-like structure. Specifically, the plate-like amorphous ferrous phosphate transforms into the petals of the flower-like ferric phosphate, while the particulate FePO4, under the induction of the titanium source, transforms into rod-like structures, becoming the folded parts of the flower-like ferric phosphate. In the synthesis of lithium iron phosphate, the folded parts expose more active sites, which is beneficial for lithium ion extraction and insertion, while the rod-like morphology shortens the distance along the b-axis, reducing the Li-ion depletion. + The diffusion distance is advantageous for lithium-ion transport, improves electrochemical performance, and can be used to prepare high-rate lithium iron phosphate.

[0049] The method of this invention can produce a flower-like structure with rod-plate stacking. Compared with the traditional hydrothermal method for preparing flower-like ferric phosphate, it does not require high-temperature and high-pressure equipment and has low cost. Moreover, the synthesis process is simple, the conditions are mild and controllable, and it is easy to mass-produce.

[0050] In some specific embodiments of the present invention, in step S1, the Ti content in the titanium-containing iron source is 0.5wt%-1.4wt% of Fe. For example, it can be any single value or a range of any two values ​​from 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, and 1.4wt%. When the amount of titanium added is too small, Fe... 3+ The primary particles of the compound are relatively large, and the added titanium is insufficient to induce the formation of a rod-like structure, resulting in poor performance of the synthesized lithium iron phosphate battery. When too much titanium is added, Fe... 3+ The compounds are smaller in size and more prone to agglomeration, making it impossible to form flower-like structures. This results in poor performance and compaction density of the synthesized lithium iron phosphate batteries. Therefore, in order to obtain better flower-like morphology and performance, it is necessary to reasonably control the amount of titanium source added.

[0051] In some specific embodiments of the present invention, the preparation method of the titanium-containing iron source includes: adding a titanium source to an iron source solution and mixing them evenly; the added titanium source includes titanium dioxide and / or titanium oxysulfate.

[0052] In some preferred embodiments of the present invention, the added titanium source is titanium liquid, the main component of which is titanium oxysulfate, and the TiO2 concentration is 180-200 g / L. After the titanium liquid is added as a solution, it is easier to mix evenly with the iron source solution, and titanium oxysulfate can decompose in situ to produce titanium dioxide, and the dispersibility of titanium dioxide is better.

[0053] In some preferred embodiments of the present invention, the iron source solution used contains Fe 2+ The content is 40-90g / L.

[0054] In some specific embodiments of the present invention, the iron source used includes at least one of ferrous sulfate, ferrous oxalate, and ferrous chloride; and / or, the molar ratio of Fe in the iron source to P in the phosphorus source is 2.5-3.5:2, for example, it can be any one value or a range of any two values ​​among 2.5:2, 2.8:2, 3:2, 3.2:2, and 3.5:2.

[0055] This invention uses ferrous salts as the iron source, does not add oxidants in the precipitation reaction stage, and rationally controls the molar ratio of Fe to P in the precipitation reaction. The aim is to ensure that the main component of the first-wash filter cake is flaky ferrous phosphate (e.g., ferrous phosphate flakes). Figure 1 As shown, during the aging process, it is used as petals to assemble flower-shaped ferric phosphate; a small amount of ferric iron forms granular ferric phosphate during precipitation, which is induced to form rods during aging, becoming the folded part of the flower-shaped ferric phosphate.

[0056] In some specific embodiments of the present invention, the phosphorus source includes at least one of phosphoric acid, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate. As an example, the phosphorus source is added in the form of a solution, wherein the mass percentage of phosphorus element is 2%-5%.

[0057] In some specific embodiments of the present invention, in step S1, the temperature of the precipitation reaction is 50-90°C, for example, it can be any one value or a range of any two values ​​among 50°C, 60°C, 70°C, 80°C, and 90°C; the time of the precipitation reaction is 0.5-4h, for example, it can be any one value or a range of any two values ​​among 0.5h, 1h, 2h, 3h, and 4h.

[0058] In some specific embodiments of the present invention, in step S1, the endpoint pH of the precipitation reaction is 2.5-5.5. For example, it can be any one value or a range of any two values ​​among 2.5, 3, 3.5, 4, 4.5, 5, and 5.5.

[0059] In some specific embodiments of the present invention, in step S2, the temperature of preparing the slurry is 25-75°C. For example, it can be any one value or a range of any two values ​​among 25°C, 30°C, 40°C, 50°C, 60°C, 70°C, and 75°C.

[0060] In some specific embodiments of the present invention, the mass concentration of the prepared slurry is 5%-25%, for example, it can be any one value or a range of any two values ​​among 5%, 10%, 15%, 20%, and 25%.

[0061] In some specific embodiments of the present invention, the amount of hydrogen peroxide added is 0.1-0.5 times the molar amount of Fe in the titanium-iron source. For example, it can be any one value or a range of any two values ​​from 0.1 times, 0.2 times, 0.3 times, 0.4 times, and 0.5 times.

[0062] In some specific embodiments of the present invention, the mass concentration of hydrogen peroxide used is 20%-50%, for example, it can be any one value or a range of any two values ​​among 20%, 30%, 40%, and 50%.

[0063] In some specific embodiments of the present invention, in step S2, after adding phosphoric acid to adjust the pH, the pH of the slurry is 1.5-2.1. For example, it can be any one value or a range of any two values ​​from 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1.

[0064] In some specific embodiments of the present invention, the aging temperature is 75-95°C, for example, it can be any one value or a range of any two values ​​among 75°C, 80°C, 85°C, 90°C, and 95°C; the aging time is 0.5-4h, for example, it can be any one value or a range of any two values ​​among 0.5h, 1h, 2h, 3h, and 4h.

[0065] A second aspect of the present invention provides a flower-shaped ferric phosphate, which is prepared by the method described in any of the foregoing embodiments.

[0066] A third aspect of the present invention provides a method for preparing lithium iron phosphate, comprising the following steps:

[0067] The flower-shaped iron phosphate described in the foregoing embodiments is mixed with a lithium source and a carbon source, and then subjected to sand milling, spray drying and sintering to obtain the product.

[0068] In some specific embodiments of the present invention, the added lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium dihydrogen phosphate, and lithium acetate.

[0069] In some specific embodiments of the present invention, the amounts of flower-shaped iron phosphate and lithium source are measured according to a molar ratio of Li to P of 1.05-1:1.

[0070] In some specific embodiments of the present invention, the added carbon source includes at least one of glucose, sucrose, PEG6000, and PEG2000.

[0071] In some specific embodiments of the present invention, the mass of the added carbon source is 10%-20% of the flower-shaped iron phosphate, for example, it can be any one value or a range of any two values ​​among 10%, 12%, 15%, 18%, and 20%.

[0072] In some specific embodiments of the present invention, additives may be added during the preparation of lithium iron phosphate, including at least one of titanium dioxide, vanadium pentoxide, and magnesium oxide.

[0073] In some specific embodiments of the present invention, the mass of the added additive is 0.1%-0.5% of the flower-shaped ferric phosphate, for example, it can be any one value or a range of any two values ​​among 0.1%, 0.2%, 0.3%, 0.4%, and 0.5%.

[0074] In some specific embodiments of the present invention, when preparing lithium iron phosphate, the particle size D50 of the milling process is 0.32-0.39 μm. For example, it can be any single value or a range of any two values ​​among 0.32 μm, 0.33 μm, 0.34 μm, 0.35 μm, 0.36 μm, 0.37 μm, 0.38 μm, and 0.39 μm.

[0075] In some specific embodiments of the present invention, when preparing lithium iron phosphate, the sintering temperature is 650-750℃, for example, it can be any one value or a range of any two values ​​among 650℃, 670℃, 690℃, 700℃, 710℃, 730℃, and 750℃; the sintering time is 6-24h, for example, it can be any one value or a range of any two values ​​among 6h, 12h, 18h, and 24h.

[0076] A fourth aspect of the present invention provides a lithium battery comprising lithium iron phosphate material prepared by the method for preparing lithium iron phosphate as described in any of the foregoing embodiments.

[0077] The lithium battery provided by this invention has a large capacity, high initial efficiency, and excellent rate performance.

[0078] The following detailed description of some embodiments of the present invention is provided in conjunction with specific examples. Unless otherwise specified, all raw materials used in the embodiments can be obtained commercially available.

[0079] Example 1

[0080] The preparation of flower-shaped ferric phosphate includes the following steps:

[0081] S1. Add titanium solution to a 60 g / L ferrous sulfate solution, wherein the amount of Ti added is 0.7 wt% of the amount of Fe added, mix evenly to obtain a titanium-containing iron source; precipitate the titanium-containing iron source with ammonium dihydrogen phosphate with a phosphorus content of 2.5 wt% at 60 °C, the molar ratio of ferrous sulfate to ammonium dihydrogen phosphate is 3:2, keep warm for 2 h, the slurry color turns grayish blue, the pH of the precipitation endpoint is 4.0, and filter cake is obtained by pressure filtration and water washing;

[0082] S2. Prepare a slurry with a mass concentration of 15% by washing the filter cake at 60℃; add hydrogen peroxide with a mass concentration of 20% to the slurry to make Fe 2+ Oxidized to Fe 3+ The mixture turns into a yellow slurry. The amount of H2O2 added is 0.3 times the molar amount of the slurry (molar amount of ferrous sulfate) after washing and filtering. After the pH of the slurry stabilizes, 85% phosphoric acid is added to adjust the pH to 1.6. The temperature is raised to 90℃, and after the slurry turns pinkish-white, it is kept at this temperature for 1 hour. After pressure filtration, washing and drying, flower-shaped ferric phosphate dihydrate is obtained.

[0083] The preparation of lithium iron phosphate includes the following steps:

[0084] Lithium iron phosphate was prepared by milling, spray drying and sintering the flower-shaped iron phosphate dihydrate prepared in this embodiment with lithium carbonate and glucose. The molar ratio of Li:P was 1.01:1, the amount of glucose added was 10% of the mass of the flower-shaped iron phosphate dihydrate, the milling particle size was 0.35 μm, the sintering temperature was 700℃ and the holding time was 12h, thus obtaining the lithium iron phosphate material.

[0085] Example 2

[0086] Example 2 is similar to Example 1, except that in the preparation of flower-shaped iron phosphate, in step S1, titanium liquid is replaced with titanium dioxide, the amount of Ti added remains unchanged, and the other conditions are the same as in Example 1.

[0087] Lithium iron phosphate was prepared using the iron phosphate prepared in this embodiment, and the preparation method was the same as in Example 1.

[0088] Example 3

[0089] Example 3 is similar to Example 1, except that in the preparation of flower-shaped iron phosphate, the amount of Ti added in step S1 is 0.5 wt% of the amount of Fe added, and the other conditions are the same as in Example 1.

[0090] Lithium iron phosphate was prepared using the iron phosphate prepared in this embodiment, and the preparation method was the same as in Example 1.

[0091] Example 4

[0092] Example 4 is similar to Example 1, except that in the preparation of flower-shaped iron phosphate, the amount of Ti added in step S1 is 1.4 wt% of the amount of Fe added, and the other conditions are the same as in Example 1.

[0093] Lithium iron phosphate was prepared using the iron phosphate prepared in this embodiment, and the preparation method was the same as in Example 1.

[0094] Comparative Example 1

[0095] The difference between Comparative Example 1 and Example 1 is that the preparation method of ferric phosphate is different. Specifically, in step S1, titanium liquid is not added, hydrogen peroxide is added in the precipitation section, the molar ratio of ferrous sulfate to hydrogen peroxide is 1:0.75, and sodium hydroxide is added dropwise to adjust the pH to 2.0; in step S2, hydrogen peroxide is not added, and other conditions are the same as in Example 1.

[0096] Lithium iron phosphate was prepared using the iron phosphate prepared in this comparative example, and the preparation method was the same as in Example 1.

[0097] Comparative Example 2

[0098] Comparative Example 2 is similar to Example 1, except that titanium liquid was not added in step S1 when preparing iron phosphate, and the other conditions were the same as in Example 1.

[0099] Lithium iron phosphate was prepared using the iron phosphate prepared in this comparative example, and the preparation method was the same as in Example 1.

[0100] Comparative Example 3

[0101] Comparative Example 3 is similar to Example 1, except that hydrogen peroxide (the amount is the same as in Example 1) is added in step S1 when preparing ferric phosphate, but not in step S2. The other conditions are the same as in Example 1.

[0102] Lithium iron phosphate was prepared using the iron phosphate prepared in this comparative example, and the preparation method was the same as in Example 1.

[0103] Test case

[0104] Batteries were fabricated using lithium iron phosphate prepared in each of the embodiments and comparative examples as the cathode material, and the battery performance was tested. The battery assembly process and test conditions are as follows:

[0105] Lithium iron phosphate material, PVDF, and carbon black were mixed in a mass ratio of 94:3:3, coated and dried, and then rolled and stamped into 14mm positive electrode discs. Lithium sheet was used as the negative electrode, and a 16mm Celgard 2400 separator was used. The electrolyte was a 1mol / L mixture of LiPF6, dimethyl carbonate, and ethyl methyl carbonate (volume ratio 1:1:1). The CR2025 coin cell was assembled in a dry glove box filled with argon gas. The test voltage range was controlled between 2.0-3.8V. The test results are shown in Table 1.

[0106] Table 1

[0107]

[0108] As shown in Table 1, only by adding titanium source doping to induce the formation of rod-shaped structure, and by using a stepwise synthesis method to first synthesize ferrous phosphate sheet-like structure and then generate iron phosphate, can flower-like structure be formed, resulting in lithium iron phosphate with better electrochemical performance.

[0109] Depend on Figure 2 It can be seen that the iron phosphate prepared by the method of the present invention has a flower-like structure with rod-plate stacking; while the iron phosphate prepared by the present invention has a flower-like structure with rod-plate stacking; Figure 3 It is known that ferric phosphate prepared by traditional methods does not have a flower-like structure; Figure 4 It is known that without the addition of a titanium source, neither rod-like nor flower-like structures can be induced to form; Figure 5 It is evident that even with the addition of a titanium source, a flower-like structure cannot be formed in the one-step synthesis of iron phosphate. This further illustrates that only through the synergistic effect of two conditions—the formation of a rod-like structure induced by a titanium source and the prior synthesis of a ferrous phosphate sheet-like structure followed by the generation of iron phosphate—can flower-like iron phosphate be obtained.

[0110] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing flower-shaped ferric phosphate, characterized in that, Includes the following steps: S1. A titanium-containing iron source and a phosphorus source are subjected to a precipitation reaction to form a gray-blue slurry. The slurry is then separated into solid and liquid components and washed to obtain a washed filter cake. The titanium-containing iron source contains Ti at a content of 0.5 wt%-1.4 wt% of Fe. The titanium source in the titanium-containing iron source includes titanium dioxide and / or titanium oxysulfate. The iron source in the titanium-containing iron source includes at least one of ferrous sulfate, ferrous oxalate, and ferrous chloride. The precipitation reaction temperature is 50-90℃, and the precipitation reaction time is 0.5-4 h. The final pH of the precipitation reaction is 2.5-5.

5. S2. Prepare the washed filter cake into a slurry, add hydrogen peroxide, and let Fe... 2+ Oxidized to Fe 3+ Phosphoric acid is added to the slurry to adjust the pH of the slurry to 1.5-2.1, and the slurry is aged at 75-95℃ for 0.5-4 hours. After solid-liquid separation, the slurry is dried to obtain flower-like ferric phosphate dihydrate with a rod-plate structure.

2. The method for preparing flower-shaped ferric phosphate according to claim 1, characterized in that, The molar ratio of Fe in the titanium-containing iron source to P in the phosphorus source is 2.5-3.5:

2.

3. The method for preparing flower-shaped ferric phosphate according to claim 1, characterized in that, In step S1, the phosphorus source includes at least one of phosphoric acid, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

4. The method for preparing flower-shaped ferric phosphate according to claim 1, characterized in that, In step S2, the amount of hydrogen peroxide added is 0.1-0.5 times the molar amount of Fe in the titanium-containing iron source.

5. A flower-shaped ferric phosphate, characterized in that, It is prepared by the method of any one of claims 1-4.

6. A method for preparing lithium iron phosphate, characterized in that, Includes the following steps: The flower-shaped iron phosphate described in claim 5 is mixed with a lithium source and a carbon source, and then subjected to sand milling, spray drying, and sintering to obtain the final product.

7. The method for preparing lithium iron phosphate according to claim 6, characterized in that, It contains at least one of the following features: (1) The lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium dihydrogen phosphate, and lithium acetate; (2) The amounts of the flower-shaped iron phosphate and the lithium source are measured according to a molar ratio of Li to P of 1.05-1:1; (3) The carbon source includes at least one of glucose, sucrose, PEG6000, and PEG2000; (4) The mass of the carbon source is 10%-20% of the flower-shaped iron phosphate; (5) The particle size D50 of the sand mill is 0.32-0.39 μm; (6) The sintering temperature is 650-750℃ and the sintering time is 6-24h.

8. A lithium battery, characterized in that, This includes lithium iron phosphate materials prepared by the method for preparing lithium iron phosphate as described in claim 6 or 7.

Images