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

Abstract

The invention relates to the technical field of lithium batteries, in particular to flower-shaped iron phosphate and a preparation method thereof, a preparation method of lithium iron phosphate and a lithium battery. The preparation method of the flower-like iron phosphate comprises the following steps: S1, carrying out precipitation reaction on a titanium-containing iron source and a phosphorus source to obtain grey blue slurry, and carrying out solid-liquid separation and washing to obtain a primary washing filter cake; and S2, preparing the primary washing filter cake into slurry, adding hydrogen peroxide to oxidize Fe < 2 + > into Fe < 3 + >, adding phosphoric acid into the slurry, heating, aging, performing solid-liquid separation, and drying to obtain the flower-shaped iron phosphate dihydrate. The iron phosphate dehydrate prepared by the method disclosed by the invention has a flower-shaped structure formed by stacking rod-sheet structures, the preparation process is simple, the energy consumption is low, the iron phosphate dehydrate can be used for preparing a high-rate lithium iron phosphate electrode material, and a lithium battery assembled by the prepared high-rate lithium iron phosphate electrode material has the advantages of large capacity, high first efficiency and good rate capability.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a flower-shaped iron phosphate and a preparation method thereof, a preparation method of lithium iron phosphate and a lithium battery. Background Art

[0002] Lithium iron phosphate is considered to be one of the competitive lithium-ion battery electrode materials due to its excellent electrochemical properties, good safety and low price. As an important raw material for synthesizing lithium iron phosphate, the morphology of iron phosphate plays a key role in the performance of lithium iron phosphate. Therefore, the preparation of iron phosphate with different morphologies is of great significance to the development of lithium iron phosphate.

[0003] A Chinese patent application with publication number CN116143097A discloses a composite lithium iron phosphate positive electrode material, a preparation method and an application thereof. Polycrystalline flower-shaped iron phosphate is synthesized by microwave hydrothermal method, and then mixed with a lithium source to prepare a composite lithium iron phosphate positive electrode material. This polycrystalline flower-shaped morphology can significantly improve the cycle performance and rate performance of the lithium iron phosphate positive electrode material.

[0004] A Chinese patent application with announcement number CN108448105A discloses a method for preparing lithium iron phosphate / reduced graphene oxide, a positive electrode material for lithium-ion batteries. The flower-like structure FePO4 / GO is synthesized by a hydrothermal method, and 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 and extraction channels to contact the electrolyte, thereby improving the material's capacity and charging and discharging performance at high rates.

[0005] The above schemes mostly use the hydrothermal method to synthesize flower-shaped iron phosphate to prepare high-rate lithium iron phosphate, but there are problems such as the inability to prepare on a large scale, the need for high-temperature and high-pressure equipment, and high energy consumption.

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

[0007] The first purpose of the present invention is to provide a method for preparing flower-like iron phosphate to solve the problems in the prior art that the preparation of flower-like iron phosphate requires high-temperature and high-pressure equipment, has high energy consumption, and cannot be prepared on a large scale; the method of the present invention has a simple preparation process, mild and controllable conditions, does not require the use of high-temperature and high-pressure equipment, has low energy consumption, and the prepared iron phosphate has a flower-like structure of stacked rod-sheet structures, which can be used to prepare high-rate lithium iron phosphate.

[0008] The second object of the present invention is to provide a flower-shaped iron phosphate, which is prepared by the preparation method of the flower-shaped iron phosphate as described above.

[0009] The third object of the present 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 object of the present invention is to provide a lithium battery, comprising the lithium iron phosphate material prepared by the lithium iron phosphate preparation method as described above.

[0011] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

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

[0013] S1. The titanium-containing iron source and the phosphorus source are subjected to a precipitation reaction to form a gray-blue slurry, followed by solid-liquid separation and washing to obtain a washed filter cake;

[0014] S2. The washed filter cake is prepared into a slurry, and hydrogen peroxide is added to make Fe 2+ Oxidized to Fe 3+ Phosphoric acid is added to the slurry, the temperature is increased for aging, the solid-liquid separation is followed by drying to obtain flower-like iron phosphate dihydrate with a rod-like and sheet-like structure stack.

[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 comprises titanium dioxide and / or titanyl sulfate.

[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 temperature of the precipitation reaction is 50-90° C., and the time of the precipitation reaction is 0.5-4 h.

[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° C., and the aging time is 0.5-4 h.

[0024] A flower-shaped iron phosphate is prepared by the method for preparing the flower-shaped iron phosphate described in any one of the aforementioned embodiments.

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

[0026] The flower-shaped iron phosphate as described above is mixed with a lithium source and a carbon source, and then sand-milled, spray-dried and sintered to obtain the product.

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

[0028] Preferably, the flower-shaped iron phosphate and the lithium source are used in an amount such that the molar ratio of Li to P is 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° C., and the sintering time is 6-24 hours.

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

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The present invention obtains flaky Fe3(PO4)2 and granular Fe in the precipitation reaction stage. 3+ Compounds, by adding titanium, induce particulate Fe 3+ The compound has smaller primary particles and induces the transformation of granular FePO4 into rods in the aging stage; the rod-like structure and flaky Fe3(PO4)2 self-assemble into a flower-like structure in the aging stage, in which the flaky stacked amorphous Fe3(PO4)2 transforms into the petals of the flower-like iron phosphate, and the rod-like structure becomes the wrinkled part of the flower-like iron phosphate.

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

[0037] (3) In the process of preparing lithium iron phosphate, the active sites of the wrinkled part of the flower-like iron phosphate are more exposed, which is conducive to the release and embedding of lithium ions, while the rod-like morphology shortens the distance in the b-axis direction and reduces the Li + The diffusion distance is beneficial to the transmission of lithium ions, improving the electrochemical performance and producing high-rate lithium iron phosphate. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0039] Figure 1 The scanning electron microscope images of the ferrous phosphate precipitate filter cake in Example 1 of the present invention and the ferric phosphate precipitate filter cake in Comparative Example 1;

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

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

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

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

[0044] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

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

[0046] S1. The titanium-containing iron source and the phosphorus source are subjected to a precipitation reaction to form a gray-blue slurry, followed by solid-liquid separation and washing to obtain a washed filter cake;

[0047] S2. The washed filter cake obtained in step S1 is slurried with water to prepare a slurry, and hydrogen peroxide is added to make Fe 2+ Oxidized to Fe 3+, turning into a yellow slurry. After the pH is stabilized, phosphoric acid is added to the slurry to adjust the pH. The slurry is aged by heating, and dried after solid-liquid separation to obtain flower-like iron phosphate dihydrate with stacked rod-like and sheet-like structures.

[0048] The method of the present invention does not add an oxidant during the precipitation reaction process, and obtains flaky Fe3(PO4)2 through precipitation reaction. Ferrous salts usually contain a certain amount of Fe 3+ , which forms granular Fe during the precipitation reaction 3+ Compound (mainly iron phosphate), induced by adding titanium source particulate Fe 3+ The primary particles of the compound are smaller; in the aging stage, due to the crystal transformation, the structure is disrupted and reorganized, so that the two components self-assemble to form a flower-like structure; among them, the amorphous ferrous phosphate stacked in sheets is transformed into the petals of the flower-like iron phosphate, and the granular FePO4 is transformed into a rod-like shape under the induction of the titanium source, becoming the wrinkled part of the flower-like iron phosphate. In the process of iron lithium synthesis, the active sites of the wrinkled part of the iron phosphate are exposed more, which is conducive to the release and embedding of lithium ions, while the rod-like morphology shortens the distance in the b-axis direction and reduces the Li + The diffusion distance is beneficial to lithium ion transmission, improves electrochemical performance, and can be used to prepare high-rate lithium iron phosphate.

[0049] The method of the present invention is used to prepare ferric phosphate, and a flower-like structure of stacked rod-like and sheet-like structures can be obtained. Compared with the traditional hydrothermal method for preparing flower-like ferric phosphate, no high-temperature and high-pressure equipment is required, and the cost is low; and the synthesis process is simple, the conditions are mild and controllable, and it is convenient for mass production.

[0050] In some specific embodiments of the present invention, in step S1, the titanium-containing iron source has a Ti content of 0.5wt%-1.4wt% of Fe, for example, any point value among 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt% or a range value consisting of any two point values. When the amount of titanium added is too little, Fe 3+ The primary particles of the compound are large, and the added titanium is not enough to induce it to form a rod-like structure, resulting in poor electrical performance of the synthesized lithium iron phosphate; when too much titanium is added, Fe 3+ The primary particles of the compound are smaller and easier to agglomerate, and cannot form a flower-like structure, resulting in poor electrical performance and compaction density of the synthesized lithium iron phosphate; therefore, in order to obtain better flower-like morphology and performance, the amount of titanium source added needs to be reasonably controlled.

[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 titanyl sulfate.

[0052] In some preferred embodiments of the present invention, the added titanium source is titanium liquid, the main component of which is titanyl sulfate, 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 titanyl sulfate can decompose in situ to produce titanium dioxide, and the dispersion 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 point value among 2.5:2, 2.8:2, 3:2, 3.2:2, 3.5:2, or a range value consisting of any two point values.

[0055] The present invention adopts ferrous salt as the iron source, does not add an oxidant in the precipitation reaction section, and reasonably controls the molar ratio of Fe and P in the precipitation reaction, so as to make the main component of the first-wash filter cake be flaky ferrous phosphate (such as Figure 1 As shown), it is used as petals to assemble flower-shaped iron phosphate during the aging process; a small amount of trivalent iron forms granular iron phosphate during the precipitation process, and is induced to form rods during the aging process, becoming the wrinkled part of the flower-shaped iron 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 point value among 50°C, 60°C, 70°C, 80°C, 90°C, or a range value consisting of any two points; the time of the precipitation reaction is 0.5-4h, for example, it can be any point value among 0.5h, 1h, 2h, 3h, 4h, or a range value consisting of any two points.

[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 point value among 2.5, 3, 3.5, 4, 4.5, 5, 5.5 or a range value consisting of any two point values.

[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 point value among 25°C, 30°C, 40°C, 50°C, 60°C, 70°C, 75°C or a range value consisting of any two point values.

[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 point value among 5%, 10%, 15%, 20%, 25% or a range value consisting of any two point values.

[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-containing iron source, for example, it can be any point value among 0.1 times, 0.2 times, 0.3 times, 0.4 times, 0.5 times, or a range value consisting of any two point values.

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

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

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

[0065] A second aspect of the present invention provides a flower-shaped iron phosphate, which is prepared by the method for preparing the flower-shaped iron phosphate described in any one of the aforementioned 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 above embodiment is mixed with a lithium source and a carbon source, and then sand-milled, spray-dried and sintered to obtain the flower-shaped iron phosphate.

[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 point value among 10%, 12%, 15%, 18%, 20% or a range value consisting of any two point values.

[0072] In some specific embodiments of the present invention, additives may be added when preparing lithium iron phosphate, and the added additives include 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 iron phosphate, for example, it can be any point value among 0.1%, 0.2%, 0.3%, 0.4%, 0.5% or a range value consisting of any two point values.

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

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

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

[0077] The lithium battery provided by the present invention has large capacity, high initial efficiency and good rate performance.

[0078] The following is a detailed description of some embodiments of the present invention in conjunction with specific examples. The raw materials used in the examples can be purchased from the market unless otherwise specified.

[0079] Example 1

[0080] The preparation of flower-like ferric phosphate comprises the following steps:

[0081] S1. Add titanium liquid to 60g / L ferrous sulfate solution, wherein the amount of Ti added is 0.7wt% of the amount of Fe added, and mix well to obtain a titanium-containing iron source; carry out precipitation reaction of the titanium-containing iron source and ammonium dihydrogen phosphate with a phosphorus content of 2.5wt% at 60°C, the molar ratio of ferrous sulfate to ammonium dihydrogen phosphate is 3:2, keep warm for 2h, the slurry color turns gray-blue, the precipitation endpoint pH is 4.0, filter press and wash with water to obtain a washed filter cake;

[0082] S2. Prepare a slurry with a mass concentration of 15% at 60°C; add 20% hydrogen peroxide to the slurry to make Fe 2+ Oxidized to Fe 3+ , it turns into a yellow slurry. The added H2O2 is 0.3 times the molar amount of the filter biscuit material (molar amount of ferrous sulfate). After the pH of the slurry stabilizes, add 85% phosphoric acid to the slurry to adjust the pH to 1.6; heat it to 90°C, and keep it warm for 1 hour after the slurry turns pink. After filter pressing, washing and drying, flower-shaped ferric phosphate dihydrate is obtained.

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

[0084] The flower-shaped iron phosphate dihydrate prepared in this embodiment is sand-milled with lithium carbonate and glucose, spray-dried and sintered to prepare lithium iron phosphate, wherein the molar ratio Li:P is 1.01:1, the amount of glucose added is 10% of the mass of the flower-shaped iron phosphate dihydrate, the sand-milled particle size is 0.35 μm, the sintering temperature is 700°C, and the temperature is kept for 12 hours to obtain lithium iron phosphate material.

[0085] Example 2

[0086] Example 2 is similar to Example 1, except that when preparing flower-shaped ferric phosphate, in step S1, the 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] The iron phosphate prepared in this example is used to prepare lithium iron phosphate, and the preparation method is the same as that in Example 1.

[0088] Example 3

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

[0090] The iron phosphate prepared in this example is used to prepare lithium iron phosphate, and the preparation method is the same as that in Example 1.

[0091] Example 4

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

[0093] The iron phosphate prepared in this example is used to prepare lithium iron phosphate, and the preparation method is the same as that 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, no titanium liquid is added, hydrogen peroxide is added in the precipitation stage, 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, no hydrogen peroxide is added, and other conditions are the same as in Example 1.

[0096] The iron phosphate prepared in this comparative example is used to prepare lithium iron phosphate, and the preparation method is the same as that in Example 1.

[0097] Comparative Example 2

[0098] Comparative Example 2 is similar to Example 1, except that when preparing ferric phosphate, in step S1, no titanium liquid is added, and the other conditions are the same as in Example 1.

[0099] The iron phosphate prepared in this comparative example is used to prepare lithium iron phosphate, and the preparation method is the same as that in Example 1.

[0100] Comparative Example 3

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

[0102] The iron phosphate prepared in this comparative example is used to prepare lithium iron phosphate, and the preparation method is the same as that in Example 1.

[0103] Test example

[0104] The lithium iron phosphate prepared in each embodiment and each comparative example was used as the positive electrode material to prepare batteries, 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, the slurry was coated and dried, and then rolled and punched into 14 mm positive electrode discs. The lithium sheet was used as the negative electrode, and a 16 mm Celgard2400 was used as the separator. The electrolyte was a 1 mol / L mixture of LiPF6, dimethyl carbonate and ethyl methyl carbonate (volume ratio of 1:1:1). The cells were assembled into CR2025 button cells in a dry and argon-filled glove box. The test voltage was controlled in the range of 2.0-3.8 V. The test results are shown in Table 1.

[0106] Table 1

[0107]

[0108] From the data in Table 1, it can be seen that only by adding titanium source doping to induce the formation of a rod-like structure and using a step-by-step synthesis method to first synthesize a ferrous phosphate flake structure and then generate ferric phosphate, can a flower-like structure be formed, and the resulting lithium iron phosphate has 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 of stacked rod-plate structures; Figure 3 It can be seen that the iron phosphate prepared by the traditional method does not have a flower-like structure; Figure 4 It can be seen that without adding titanium source, the rod-like structure cannot be induced to form, and the flower-like structure cannot be formed; Figure 5 It can be seen that in the one-step synthesis process of iron phosphate, even if a titanium source is added, a flower-like structure cannot be formed; it also further explains that only when the titanium source induces the formation of a rod-like structure and first synthesizes a ferrous phosphate flake structure and then generates ferric phosphate, can flower-like iron phosphate be obtained.

[0110] Although the present invention has been illustrated and described with specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents without departing from the spirit and scope of the present invention. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing flower-shaped iron phosphate, characterized in that: The following steps are involved: S1. The titanium-containing iron source and the phosphorus source are subjected to a precipitation reaction to form a gray-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, and hydrogen peroxide is added to make Fe 2+ Oxidized to Fe 3+ , phosphoric acid is added to the slurry, the temperature is increased for aging, the solid-liquid separation is followed by drying to obtain flower-shaped iron phosphate dihydrate.

2. The method for preparing flower-shaped ferric phosphate according to claim 1, characterized in that: In the titanium-containing iron source, the Ti content is 0.5wt%-1.4wt% of Fe.

3. The method for preparing flower-shaped ferric phosphate according to claim 1, characterized in that: The titanium source in the titanium-containing iron source includes titanium dioxide and / or titanyl sulfate.

4. The method for preparing flower-shaped ferric phosphate according to claim 1, characterized in that: 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.

5. The method for preparing flower-shaped ferric phosphate according to claim 1, characterized in that: In step S1, at least one of the following features is included: (1) The phosphorus source includes at least one of phosphoric acid, diammonium phosphate, and diammonium hydrogen phosphate; (2) The temperature of the precipitation reaction is 50-90° C., and the time of the precipitation reaction is 0.5-4 h; (3) The endpoint pH of the precipitation reaction is 2.5-5.

5.

6. The method for preparing flower-shaped ferric phosphate according to claim 1, characterized in that: In step S2, at least one of the following features is included: (1) The amount of hydrogen peroxide added is 0.1-0.5 times the molar amount of Fe in the titanium-containing iron source; (2) after adding the phosphoric acid, the pH of the slurry is 1.5-2.1; (3) The aging temperature is 75-95°C, and the aging time is 0.5-4h.

7. A flower-shaped iron phosphate, characterized in that: The flower-shaped ferric phosphate is prepared by the preparation method of any one of claims 1 to 6.

8. A method for preparing lithium iron phosphate, characterized in that: The following steps are involved: The flower-shaped iron phosphate described in claim 7 is mixed with a lithium source and a carbon source, and then sand-milled, spray-dried and sintered to obtain the product.

9. The method for preparing lithium iron phosphate according to claim 8, characterized in that: Contains at least one of the following characteristics: (1) The lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium dihydrogen phosphate, and lithium acetate; (2) The flower-shaped iron phosphate and the lithium source are used in an amount such that the molar ratio of Li to P is 1.05-1:1; (3) The carbon source comprises 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°C, and the sintering time is 6-24h.

10. A lithium battery, characterized in that: Including the lithium iron phosphate material prepared by the lithium iron phosphate preparation method according to claim 8 or 9.

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