Method for preparing ferric sodium pyrophosphate by taking ferrous phosphate as precursor

Abstract

The invention specifically discloses a method for preparing ferric sodium pyrophosphate by taking ferrous phosphate as a precursor. The method comprises the following steps: S100, preparing a ferrous phosphate powder precursor through a reverse titration coprecipitation method; s200, the ferrous phosphate powder precursor, sodium pyrophosphate and a carbon source are placed in a ball milling container for a ball milling reaction, and a ferric sodium pyrophosphate precursor is prepared; and S300, calcining the obtained ferric sodium pyrophosphate precursor under a second preset temperature condition, and cooling after the calcination is finished, so as to obtain the ferric sodium pyrophosphate powder. The method for preparing the ferric sodium pyrophosphate with the ferrous phosphate as the precursor is easy to operate, low in cost and beneficial to industrial production, in addition, the ferric sodium pyrophosphate prepared through the method has the advantages of being uniform in particle size, uniform in morphology and high in purity, and the method is suitable for industrial production. And when being applied to the sodium-ion battery, the sodium-ion battery shows relatively high capacity, good rate capability and excellent cycle performance.

Description

Technical Field

[0001] The present application belongs to the technical field of preparation of positive electrode materials for sodium ion batteries, and in particular, relates to a method for preparing sodium ferric pyrophosphate in one step using ferrous phosphate as a precursor. Background Art

[0002] With the growing demand for efficient use of renewable energy, large-scale energy storage technology has made significant progress. Compared with lithium-ion batteries, sodium resources are abundant and low-cost. Therefore, the development of sodium-ion batteries (SIBs) technology is of strategic significance for promoting large-scale energy storage technology. In order to meet the requirements of high energy density and cycle stability, it is necessary to develop more suitable positive electrode materials for sodium-ion batteries. At present, the positive electrode materials of sodium-ion batteries mainly include polyanionic compounds, transition metal oxides and Prussian blue. Among them, polyanionic iron-based phosphates (sodium iron pyrophosphate, Na4Fe3(PO4)2P2O7) have a three-dimensional framework structure, excellent structural stability and suitable theoretical capacity (129mAh / g), environmental friendliness and small volume change during charging and discharging, which has attracted widespread attention in practical applications.

[0003] At present, there are two methods for preparing Na4Fe3(PO4)2P2O7: a liquid phase method and a solid phase method. In the liquid phase method, a mixed solution formed by soluble raw materials is usually subjected to a sol-gel process or spray drying and then sintered to obtain Na4Fe3(PO4)2P2O7. For example, the invention patent with application publication number CN 118183670A heats, stirs, dries, and sinters an iron source, a phosphorus source, a sodium source, citric acid, deionized water, and a titanium source to obtain doped sodium ferric pyrophosphate. However, the products prepared by the pure liquid phase method can only select raw materials without impurities, which has higher requirements on cost. In addition, due to the volatilization of the solvent or the decomposition of the components, more pores will be generated, and the compacted density of the product is low, which is not conducive to industrial production. The solid phase method is to prepare sodium ferric pyrophosphate by grinding, drying and calcining non-soluble raw materials. For example, the invention patent with application publication number CN 117438560 A discloses a method for preparing carbon-coated sodium ferric pyrophosphate. The raw materials such as sodium source, iron source, phosphorus source, carbon source, etc. are ball-milled in ethanol. After drying and calcination, sodium ferric pyrophosphate can be obtained. However, many raw materials cannot be completely refined in ball milling, and each component cannot be evenly distributed. Therefore, the characteristic peak of the X-ray diffraction of the sodium ferric pyrophosphate formed is not obvious. Another example: the invention patent with authorization publication number CN114538403 B selects sodium pyrophosphate, metal iron powder, iron phosphate, doped element phosphate and conductive agent for ball milling and sintering to prepare sodium ferric pyrophosphate. Among them, the introduction of iron phosphate not only cannot solve the problem that many ball milling raw materials are difficult to refine and elements are difficult to be uniform, but has higher requirements for iron phosphate raw materials, and is not suitable for large-scale preparation. For another example, the invention patent with application publication number CN 118387852 A prepares multi-element doped ferrous phosphate octahydrate by co-precipitation, which is then mixed with a sodium source, a phosphorus source and an organic solvent, ground, and freeze-dried, and finally mixed with a carbon source and pure water, spray-dried and sintered to obtain carbon-coated multi-element doped sodium ferric pyrophosphate; the preparation process of this method requires the use of concentrated sulfuric acid and an organic solvent, and requires multiple steps such as ball milling, freeze-drying, and spray-drying, and the preparation process is cumbersome and costly. Summary of the invention

[0004] In view of the technical defects existing in the existing sodium ferric pyrophosphate preparation method, the present application provides a method for preparing sodium ferric pyrophosphate using ferrous phosphate as a precursor. The method is simple to operate, low in cost, and conducive to industrial production. Moreover, the sodium ferric pyrophosphate prepared by the method has the characteristics of uniform particle size, uniform morphology and high purity, and comprises the following steps:

[0005] S100, uniformly dispersing an iron source and a phosphorus source in water respectively, and adding the prepared phosphorus source solution into a reaction vessel at a first preset temperature, and then continuously dropping the prepared iron source solution and a precipitant into the reaction vessel respectively and continuously stirring, introducing an inert gas during the reaction and controlling the pH value of the reaction solution, and aging and drying the reaction solution in the reaction vessel after the reaction is completed, so as to obtain a ferrous phosphate powder precursor;

[0006] S200, placing the obtained ferrous phosphate powder precursor, sodium pyrophosphate and a carbon source in a ball milling container, and then adding a dispersant to perform a ball milling reaction to obtain a carbon-coated sodium ferrous pyrophosphate precursor;

[0007] S300, calcining the obtained sodium iron pyrophosphate precursor under a second preset temperature condition, and cooling after the calcination to obtain sodium iron pyrophosphate powder.

[0008] In some embodiments, in step S100, the iron source is at least one of ferrous sulfate, ferrous chloride, ferrous oxalate dihydrate, and ferrous citrate, the phosphorus source is at least one of phosphoric acid, sodium dihydrogen phosphate, trisodium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium pyrophosphate, trisodium monohydrogen pyrophosphate, disodium dihydrogen pyrophosphate, and monosodium trihydrogen pyrophosphate, and the precipitant is at least one of ammonia water, sodium hydroxide, and potassium hydroxide.

[0009] In some embodiments, the concentration of the ferrous salt solution is 0.2-2 mol / L, and the concentration of the phosphoric acid or hydrogen phosphate solution is 0.2-2 mol / L.

[0010] In some embodiments, the step S100 is specifically as follows: the iron source and the phosphorus source are dispersed evenly in deionized water, and the prepared phosphorus source solution is added to a reactor at a first preset temperature, and then the prepared iron source solution and the precipitant are continuously dripped into the reactor by a peristaltic pump and stirred continuously, argon is introduced during the reaction process and the pH value of the reaction solution is controlled, and after the reaction is completed, the reaction solution in the reactor is aged and dried to obtain a ferrous phosphate powder precursor. Among them, the first preset temperature is 0-30°C, the pH value of the reaction solution is controlled between 4-8, the stirring rate in the reactor is 100-1500r / min, the reaction time is 60-240min, and the aging time is 2-12h.

[0011] In some embodiments, in step S200, the molar ratio of the ferrous phosphate powder precursor to the sodium pyrophosphate is 1:0.6-1.4.

[0012] In some embodiments, in step S200, the carbon source includes one or more of glucose, sucrose, starch and polyols.

[0013] In some embodiments, the amount of the carbon source added is 5-30 wt % of the mass of the ferrous phosphate powder precursor.

[0014] In some embodiments, in step S200, the ball milling medium in the ball milling container is anhydrous ethanol, and the anhydrous ethanol accounts for 0.5-10 wt % of the total weight of the ferrous phosphate powder precursor, sodium pyrophosphate and carbon source.

[0015] In some embodiments, in step S200, the ball milling reaction time in the ball milling container is 4-16 hours, and the ball milling speed is 600-1000 r / min.

[0016] In some embodiments, in step S300, the second preset temperature is 450-650°C, the calcination time is 5-14h, and the calcination atmosphere is an inert atmosphere or an argon-hydrogen mixed atmosphere.

[0017] Compared with the prior art, the present application prepares ferrous phosphate by reverse titration coprecipitation method, which has the advantages of adjustable grain size, controllable performance and low raw material cost, and is easy to realize large-scale production, and finally obtains a ferrous phosphate precursor with uniform particle size and stable morphology structure; moreover, the present application adopts sodium pyrophosphate as the sodium source and pyrophosphate source, and the ferrous phosphate precursor as the phosphate and iron source, and sintered after being evenly mixed with the carbon source, and there are no by-products in the reaction process, which is a green and economical reaction. At the same time, the method for preparing sodium ferric pyrophosphate from ferrous phosphate provided by the present application has a controllable product formula, and the ferrous phosphate precursor and sodium pyrophosphate can obtain sodium ferric pyrophosphate with uniform element distribution and high purity in a wide ratio range, and its electrochemical performance is excellent, and the rate and cycle performance are good. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] 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.

[0019] Figure 1 It is a flow chart of a method for preparing sodium ferric pyrophosphate using ferrous phosphate as a precursor in the present application;

[0020] Figure 2 The X-ray diffraction pattern of the ferrous phosphate precursor prepared in Example 1 of the present application is given;

[0021] Figure 3 The X-ray diffraction pattern of the sodium iron pyrophosphate prepared in Example 1 of the present application is given;

[0022] Figure 4 The charge and discharge curve of the sodium iron pyrophosphate prepared in Example 1 of the present application at a rate of 0.1C is given;

[0023] Figure 5 The charge and discharge curve of the sodium iron pyrophosphate prepared in Example 1 of the present application at a 1C rate is given;

[0024] Figure 6 The rate performance diagram of the sodium iron pyrophosphate prepared in Example 1 of the present application is given;

[0025] Figure 7 The cycle performance diagram of the sodium iron pyrophosphate prepared in Example 1 of the present application at a 1C rate is given;

[0026] Figure 8 The X-ray diffraction pattern of the sodium ferric pyrophosphate prepared in Example 2 of the present application is given;

[0027] Fig. 9 The charge and discharge curve of the sodium iron pyrophosphate prepared in Example 2 of the present application at a rate of 0.1C is given;

[0028] Fig.10 The charge and discharge curve of the sodium iron pyrophosphate prepared in Example 2 of the present application at a 1C rate is given;

[0029] Fig.11 The rate performance diagram of the sodium iron pyrophosphate prepared in Example 2 of the present application is given;

[0030] Fig.12 The cycle performance diagram of the sodium iron pyrophosphate prepared in Example 2 of the present application at a 1C rate is given;

[0031] Fig.13 The X-ray diffraction pattern of the sodium iron pyrophosphate prepared in Example 3 of the present application is given;

[0032] Fig.14 The charge and discharge curve of the sodium iron pyrophosphate prepared in Example 3 of the present application at a rate of 0.1C is given;

[0033] Fig.15 The charge and discharge curve of the ferrous phosphate precursor prepared in Example 3 of the present application at a 1C rate is given;

[0034] Fig.16 The rate performance diagram of the sodium iron pyrophosphate prepared in Example 3 of the present application is given;

[0035] Fig.17 The cycle performance diagram of the sodium iron pyrophosphate prepared in Example 3 of the present application at a 1C rate is given;

[0036] Fig.18 The X-ray diffraction pattern of the sodium iron pyrophosphate prepared in the comparative example of the present application is given;

[0037] Fig.19 The charge and discharge curve of the sodium iron pyrophosphate prepared in the comparative example of the present application at a rate of 0.1C is given;

[0038] Fig. 20 The charge and discharge curve of the sodium iron pyrophosphate prepared in the comparative example of the present application at a 1C rate is given;

[0039] Fig.21 The cycle performance diagram of the sodium iron pyrophosphate prepared in the comparative example of the present application at a 1C rate is given;

[0040] Fig. 22 A scanning electron microscope image of the sodium ferric pyrophosphate prepared in Example 1 of the present application is given;

[0041] Fig.23 A scanning electron microscope image of the sodium ferric pyrophosphate prepared in Example 2 of the present application is given;

[0042] Fig.24 A scanning electron microscope image of the sodium ferric pyrophosphate prepared in Example 3 of the present application is given;

[0043] Fig.25 A scanning electron microscope image of the sodium ferric pyrophosphate prepared in the comparative example of the present application is given. DETAILED DESCRIPTION

[0044] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0045] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0046] refer to Figure 1 As shown, the embodiment of the present application provides a method for preparing sodium ferric pyrophosphate using ferrous phosphate as a precursor, and the method comprises the following steps:

[0047] S100, uniformly dispersing an iron source and a phosphorus source in water respectively, and adding the prepared phosphorus source solution into a reaction vessel at a first preset temperature, and then continuously dropping the prepared iron source solution and a precipitant into the reaction vessel respectively and continuously stirring, introducing an inert gas during the reaction and controlling the pH value of the reaction solution, and aging and drying the reaction solution in the reaction vessel after the reaction is completed, so as to obtain a ferrous phosphate powder precursor;

[0048] In this step, the water used is deionized water, the reaction vessel is a reactor, the inert gas is argon, the first preset temperature is 0-30°C, the reaction time is 60-240min, and the aging time is 2-12h. The iron source is at least one of ferrous sulfate, ferrous chloride, ferrous oxalate dihydrate, and ferrous citrate, the concentration of the ferrous salt solution is 0.2-2mol / L, the phosphorus source is at least one of phosphoric acid, sodium dihydrogen phosphate, trisodium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium pyrophosphate, trisodium monohydrogen pyrophosphate, disodium dihydrogen pyrophosphate, and monosodium trihydrogen pyrophosphate, the concentration of the phosphoric acid or hydrogen phosphate solution is 0.2-2mol / L, the precipitant is at least one of ammonia water, sodium hydroxide, and potassium hydroxide, the stirring rate in the reactor is 100-1500r / min, and the pH value of the reaction solution is controlled between 4-8.

[0049] S200, placing the obtained ferrous phosphate powder precursor, sodium pyrophosphate and a carbon source in a ball milling container, and then adding a dispersant to carry out a ball milling reaction to obtain a carbon-coated sodium ferrous pyrophosphate precursor.

[0050] In this step, the carbon source includes one or more of glucose, sucrose, starch and polyols, the molar ratio of ferrous phosphate powder precursor to sodium pyrophosphate is 1:0.6-1.4, the added amount of the carbon source is 5-30wt% of the mass of the ferrous phosphate powder precursor, the ball milling medium in the ball milling container is anhydrous ethanol, and the anhydrous ethanol accounts for 0.5-10wt% of the total weight of the ferrous phosphate powder precursor, sodium pyrophosphate and the carbon source, the ball milling reaction time in the ball milling container is 4-16h, and the ball milling speed is 600-1000r / min.

[0051] S300, calcining the obtained sodium iron pyrophosphate precursor under a second preset temperature condition, and cooling after the calcination to obtain sodium iron pyrophosphate powder.

[0052] In this step, the second preset temperature is 450-650° C., the calcination time is 5-14 hours, and the calcination atmosphere is an inert atmosphere or an argon-hydrogen mixed atmosphere.

[0053] In order to further illustrate the technical principle and technical effect of the present application, the following describes the contents disclosed in the present application in more detail with several examples, which are only used for illustrative purposes, because it is obvious to those skilled in the art to make various modifications and changes within the scope of the present application. Unless otherwise stated, all reagents and raw materials used in the examples are commercially available or synthesized according to conventional methods, and the instruments and equipment used in the examples are commercially available.

[0054] Example 1

[0055] 1) 6.90 g of ammonium dihydrogen phosphate and 16.68 g of ferrous sulfate were dissolved in 150 ml of deionized water to obtain iron source and phosphorus source solutions, the prepared phosphorus source solution was added to a reactor and the temperature of the reactor was controlled to be 20° C. The ferrous salt solution was continuously dripped into the reactor under constant stirring using a peristaltic pump, and ammonia water was added to adjust the pH of the reaction solution to 6. The stirring rate in the reactor was 600 r / min until the dispersion was uniform. At the same time, argon was continuously introduced into the reactor during the reaction process. After the dispersion was uniform, the mixture was aged for 8 h, centrifuged, and vacuum dried to obtain a product ferrous phosphate powder precursor;

[0056] 2) 1.78 g of sodium pyrophosphate, 0.25 g of sucrose and 2.01 g of the obtained ferrous phosphate powder precursor were put into a ball mill, 10 ml of anhydrous ethanol was added, and the mixture was ball milled at a speed of 800 r / min for 8 hours and mixed evenly to obtain a sodium ferric pyrophosphate precursor;

[0057] 3) placing the sodium iron pyrophosphate precursor in a tubular furnace with a flowing argon atmosphere, heating it to 500° C. at 5° C. / min and sintering it for 10 h, and then naturally cooling it to room temperature to obtain the sodium iron pyrophosphate powder.

[0058] Example 2

[0059] 1) 6.90 g of ammonium dihydrogen phosphate and 16.68 g of ferrous sulfate were dissolved in 150 ml of deionized water to obtain iron source and phosphorus source solutions, the prepared phosphorus source solution was added to a reactor and the temperature of the reactor was controlled to be 30° C. The ferrous salt solution was continuously dripped into the reactor under constant stirring using a peristaltic pump, and ammonia water was added to adjust the pH of the reaction solution to 8, the stirring rate was 100 r / min, until the dispersion was uniform, and argon gas was continuously introduced into the reactor during the reaction process. After the dispersion was uniform, the mixture was aged for 12 h, centrifuged, and vacuum dried to obtain a product ferrous phosphate powder precursor;

[0060] 2) 1.61 g of sodium pyrophosphate, 0.37 g of glucose and the obtained 2.01 g of ferrous phosphate powder precursor were placed in a ball mill, 10 ml of anhydrous ethanol was added, and the mixture was uniformly mixed by high-energy ball milling, and ball milled at a speed of 1000 r / min for 4 h to obtain a sodium ferric pyrophosphate precursor;

[0061] 3) placing the sodium iron pyrophosphate precursor in a tubular furnace with a flowing argon atmosphere, heating to 550° C. at 4° C. / min, sintering for 5 h, and naturally cooling to room temperature to obtain sodium iron pyrophosphate powder.

[0062] Example 3

[0063] 1) 6.90 g of sodium dihydrogen phosphate and 16.68 g of ferrous sulfate were dissolved in 150 ml of deionized water to obtain iron source and phosphorus source solutions, the prepared phosphorus source solution was added to a reactor and the temperature of the reactor was controlled to be 5° C. The ferrous salt solution was continuously dripped into the reactor under constant stirring using a peristaltic pump, and sodium hydroxide was added to adjust the pH value of the reaction solution to 4. The stirring rate was 1000 r / min until the dispersion was uniform. At the same time, argon was continuously introduced into the reactor during the reaction process. After the dispersion was uniform, the mixture was aged for 2 h, centrifuged, and vacuum dried to obtain a product ferrous phosphate powder precursor;

[0064] 2) 1.43 g of sodium pyrophosphate, 0.25 g of sucrose and the obtained 2.01 g of ferrous phosphate precursor were placed in a ball mill, 10 ml of anhydrous ethanol was added, and the mixture was ball milled at a speed of 600 r / min for 16 h to obtain a sodium ferric pyrophosphate precursor;

[0065] 3) placing the sodium iron pyrophosphate precursor in a tubular furnace with a flowing argon atmosphere, heating to 450° C. at 7° C. / min, sintering for 5 h, and naturally cooling to room temperature to obtain sodium iron pyrophosphate powder.

[0066] Comparative Example 1

[0067] Using the same phosphorus source and sodium source as in Example 1, without going through the ferrous phosphate precursor preparation step, weigh 4.46 g of sodium pyrophosphate, 2.30 g of ammonium dihydrogen phosphate, 10.05 g of ferric citrate, and 0.62 g of sucrose, add 20 ml of anhydrous ethanol as a dispersant, and directly ball-mill the raw materials to mix evenly. According to the same ball-milling and sintering conditions as in Example 1, heat treat the mixture at 500°C in a flowing argon atmosphere for 10 h.

[0068] The sodium iron pyrophosphate materials prepared in Examples 1-3 and Comparative Example 1 were assembled with sodium sheets into button cells, and their electrochemical properties and micromorphology were tested and characterized. The test results are shown in Tables 1 and Figure 2-Figure 25 shown.

[0069] Table 1 is the discharge capacity and cycle performance test data of sodium iron pyrophosphate obtained in the examples and comparative examples

[0070]

[0071] from Figure 1-2 It can be seen that the ferrous phosphate precursor has been successfully prepared using the given process.

[0072] From Table 1 and Figure 3-Figure 25 It can be seen that pure phase sodium iron pyrophosphate was successfully prepared in the products prepared in Examples 1-3, while the product prepared in Comparative Example 1 did not form Na4Fe3(PO4)2P2O7 crystalline compound, and its powder crystallization was extremely poor. The sodium iron pyrophosphate synthesized in Examples 1-3 had uniform particle size and good dispersibility, with an average particle size of about 500nm, while the sodium iron pyrophosphate prepared in Comparative Example 1 had different particle sizes and poor uniformity, with a maximum particle size of 10μm.

[0073] In addition, the sodium iron pyrophosphate materials prepared in Examples 1-3 have excellent rate cycle performance at 0.1C and 1C charge and discharge rates, and the charge and discharge efficiencies are all higher than 97%, especially the material prepared in Example 2 still maintains a discharge capacity of 104.2 mAh / g at a 1C charge and discharge rate; at the same time, Examples 1-3 have good cycle stability, and the capacity retention rate after 100 cycles at a 1C rate is greater than 95%, while the carbon-coated sodium iron pyrophosphate material prepared in Comparative Example 1 has a discharge capacity of only 73.4 mAh / g at a 0.1C charge and discharge rate, and a discharge capacity of only 49.9 mAh / g at a 1C charge and discharge rate, and the cycle stability is significantly lower than that of Examples 1-3.

[0074] It can be seen from this that the method for preparing sodium ferric pyrophosphate using ferrous phosphate as a precursor provided by the present application is not only simple to operate and low in cost, but also more conducive to industrial production. Moreover, the sodium ferric pyrophosphate prepared by the method has the characteristics of uniform particle size, uniform morphology and high purity. Furthermore, the material has a high capacity, good rate performance and excellent cycle performance. Therefore, the ferrous phosphate powder precursor prepared by the preparation method provided by the present application is of great significance to the synthesis route of high-performance sodium ferric pyrophosphate materials.

[0075] The above is a detailed introduction to a method for preparing sodium ferric pyrophosphate using ferrous phosphate as a precursor provided by the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application, and the description of the above embodiments is only used to help understand the core idea of ​​the present application. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A method for preparing sodium ferric pyrophosphate using ferrous phosphate as a precursor, characterized in that: The method comprises the following steps: S100, uniformly dispersing an iron source and a phosphorus source in water respectively, and adding the prepared phosphorus source solution into a reaction vessel at a first preset temperature, and then continuously dropping the prepared iron source solution and a precipitant into the reaction vessel respectively and continuously stirring, introducing an inert gas during the reaction and controlling the pH value of the reaction solution, and aging and drying the reaction solution in the reaction vessel after the reaction is completed, so as to obtain a ferrous phosphate powder precursor; S200, placing the obtained ferrous phosphate powder precursor, sodium pyrophosphate and a carbon source in a ball milling container, and then adding a dispersant to perform a ball milling reaction to obtain a carbon-coated sodium ferrous pyrophosphate precursor; S300, calcining the obtained sodium iron pyrophosphate precursor under a second preset temperature condition, and cooling after the calcination to obtain sodium iron pyrophosphate powder.

2. The method according to claim 1, characterized in that In the step S100, the iron source is at least one of ferrous sulfate, ferrous chloride, ferrous oxalate dihydrate, and ferrous citrate; the phosphorus source is at least one of phosphoric acid, sodium dihydrogen phosphate, trisodium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium pyrophosphate, trisodium monohydrogen pyrophosphate, disodium dihydrogen pyrophosphate, and monosodium trihydrogen pyrophosphate; and the precipitant is at least one of ammonia water, sodium hydroxide, and potassium hydroxide.

3. The method according to claim 1, characterized in that The concentration of the ferrous salt solution is 0.2-2 mol / L, and the concentration of the phosphoric acid or hydrogen phosphate solution is 0.2-2 mol / L.

4. The method according to claim 2 or 3, characterized in that: The step S100 is specifically as follows: the iron source and the phosphorus source are dispersed evenly in deionized water respectively, and the prepared phosphorus source solution is added to the reactor at the first preset temperature, and then the prepared iron source solution and the precipitant are continuously dripped into the reactor respectively by a peristaltic pump and stirred continuously, argon is introduced during the reaction process and the pH value of the reaction solution is controlled, and after the reaction is completed, the reaction solution in the reactor is aged and dried to obtain a ferrous phosphate powder precursor. Among them, the first preset temperature in the reactor is 0-30°C, the pH value of the reaction solution is controlled between 4-8, the stirring rate in the reactor is 100-1500r / min, the reaction time is 60-240min, and the aging time is 2-12h.

5. The method according to claim 4, characterized in that In the step S200, the molar ratio of the ferrous phosphate powder precursor to the sodium pyrophosphate is 1:0.6-1.

4.

6. The method according to claim 5, characterized in that In step S200, the carbon source includes one or more of glucose, sucrose, starch and polyols.

7. The method according to claim 6, characterized in that The amount of the carbon source added is 5-30wt% of the mass of the ferrous phosphate powder precursor.

8. The method according to claim 7, characterized in that In the step S200, the ball milling medium in the ball milling container is anhydrous ethanol, and the anhydrous ethanol accounts for 0.5-10wt% of the total weight of the ferrous phosphate powder precursor, sodium pyrophosphate and carbon source.

9. The method according to claim 8, characterized in that In the step S200, the ball milling reaction time in the ball milling container is 4-16 hours, and the ball milling speed is 600-1000 r / min.

10. The method according to claim 1, characterized in that In the step S300, the second preset temperature is 450-650°C, the calcination time is 5-14 hours, and the calcination atmosphere is an inert atmosphere or an argon-hydrogen mixed atmosphere.

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