Sodium ferric phosphate pyrophosphate derivative, preparation method thereof and sodium ion battery

Abstract

The invention relates to the technical field of battery positive electrode materials, in particular to a ferric sodium pyrophosphate derivative, a preparation method thereof and a sodium ion battery. The preparation method comprises the following steps: weighing a sodium source, a second metal source, a phosphorus source and a carbon source in proportion, and adding a modifier and a dispersant to form a mixed raw material; the second metal source contains an iron element. The molecular structure of the modifier comprises carboxyl, and further comprises at least one of amino and substituted amino, and the molar ratio of the modifier to metal elements in the second metal source is any one of 1: (10-100). And mechanically activating, pre-sintering and sintering the mixed raw material to obtain the ferric sodium phosphate pyrophosphate derivative, and assembling by taking the ferric sodium phosphate pyrophosphate derivative as a positive active material to obtain the sodium ion battery. The carboxyl group of the modifier acts with the second metal source to form a stable carboxylation connection structure, and the amino group or substituted amino group adsorbs phosphate radicals through the heterogeneous charge phase adsorption effect, so that the second metal source and the phosphorus element are uniformly distributed, and the electrochemical performance of the material is improved.

Description

Technical Field

[0001] This invention relates to the field of battery cathode material technology, and in particular to a sodium iron pyrophosphate derivative, its preparation method, and a sodium-ion battery. Background Technology

[0002] Sodium iron pyrophosphate (Na4Fe3(PO4)2P2O7, NFPP) and its derivatives possess a three-dimensional framework structure, providing a rapid transport channel for sodium ions, thus exhibiting superior electrochemical performance. When NFPP and its derivatives are used as cathode materials in sodium-ion batteries, the batteries exhibit high reversible specific capacity and capacity retention, as well as long cycle life, excellent thermal stability, and low-temperature resistance. They can effectively suppress structural distortion during sodium ion insertion / extraction, significantly improving battery safety and reliability. Furthermore, they can maintain efficient charge / discharge at lower temperatures, adapting to cold environments. In addition, the raw material and preparation costs of NFPP materials are relatively low, making them highly practical.

[0003] The preparation of NFPP and its derivatives typically requires the homogeneous mixing of iron, sodium, and phosphorus sources followed by activation and sintering. In a laboratory setting, solution mixing is often used to improve the uniformity of the raw material mixture. However, solution mixing is inefficient and limited in scale. To achieve large-scale production, multiple solid raw materials need to be mechanically mixed and activated, currently often using sand milling. Due to the low uniformity of mechanical mixing, and the fact that materials such as ferric phosphate, commonly used as iron sources, often carry a negative charge on their surface during sand milling, this causes them to repel the phosphate ions used to provide phosphorus. This leads to segregation during mixing, with the molar ratio of iron to phosphorus deviating from 3:4 in some areas. When the molar ratio of iron to phosphorus in some areas is greater than or equal to 1:1, it results in the formation of an inert NaFePO4 impurity phase, which is detrimental to the performance of NFPP materials. Summary of the Invention

[0004] The purpose of this invention is to provide a sodium iron pyrophosphate derivative capable of suppressing the formation of NaFePO4 impurity phase, its preparation method, and a sodium-ion battery.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a sodium iron pyrophosphate derivative, comprising: A sodium source, a second metal source, a phosphorus source, a carbon source, a dispersant, and a modifier are weighed and mixed to obtain a mixed raw material. The second metal source contains iron, and the phosphorus source is soluble in the dispersant. The molar ratio of sodium, metal from the second metal source, and phosphorus in the mixed raw material is any value in the range of (3.9~4.1):3:(4.0~4.2). The modifier has a molecular structure that includes a carboxyl group and at least one of amino and substituted amino groups. The molar ratio of the modifier to the metal from the second metal source is any value in the range of 1:(10~100). The mixed raw materials were mechanically activated and dried to obtain the precursor; The precursor is pre-calcined at a first temperature for a first time in an inert atmosphere, and then heated to a second temperature for a second time to obtain the sodium iron pyrophosphate derivative.

[0006] Optionally, the modifier has a molecular structure that includes a carboxyl group, and the chain length of the molecular chain that includes at least one of amino and substituted amino groups is less than or equal to 50.

[0007] Optionally, the modifier is one or more of trimethylglycine hydrochloride, ampicillin, arginine, lysine, creatine, carnitine, and chemoresine.

[0008] Optionally, the second metal source contains one or more of the following elements: manganese, chromium, zirconium, aluminum, zinc, copper, and molybdenum.

[0009] Optionally, the second metal source contains manganese.

[0010] Optionally, the second metal source includes one or more of iron phosphate, manganese phosphate, ferromanganese hydrogen phosphate, and ferromanganese ammonium phosphate.

[0011] Optionally, the sodium source includes one or more of sodium carbonate, sodium bicarbonate, sodium acetate, sodium dihydrogen citrate, sodium oxalate, sodium alginate, and sodium dodecylbenzene sulfonate; The phosphorus source includes one or more of the following: ammonium dihydrogen phosphate, sodium dihydrogen phosphate, diammonium hydrogen phosphate, disodium hydrogen phosphate, sodium phosphate, and ammonium phosphate. The carbon source includes one or more of citric acid, oxalic acid, ascorbic acid, tartaric acid, glucose, sucrose, starch, ethylenediaminetetraacetic acid, aminotriacetic acid, and polyacrylic acid. The dispersant includes water and / or ethanol.

[0012] Optionally, the first temperature is any value between 300℃ and 350℃, the first time is any value between 1h and 5h, the second temperature is any value between 400℃ and 600℃, the second time is any value between 1h and 24h, and the mechanical activation time is any value between 1h and 18h.

[0013] The present invention also provides a sodium iron pyrophosphate derivative, which is prepared by the above-described preparation method.

[0014] The present invention also provides a sodium-ion battery, using the above-mentioned sodium iron pyrophosphate derivative as the positive electrode active material.

[0015] The beneficial effects of this invention are as follows: The modifier contains both carboxyl and amino or substituted amino groups. Under weakly acidic or neutral conditions, the carboxyl group interacts with the second metal source through hydrogen bonding or coordination reactions to form a stable carboxylated linkage structure. The amino or substituted amino groups adsorb free phosphate ions through opposite charge phase adsorption, enabling precise molecular-scale assembly of phosphate ions dissolved in the dispersant with the insoluble second metal source. This prevents local enrichment of the second metal source in the precursor, which could lead to the formation of a NaFePO4 impurity phase, thus improving the electrochemical performance of the sodium iron pyrophosphate derivative and consequently enhancing the structural stability and capacity retention during cycling. This invention solves the problem of poor material performance caused by uneven mechanical synthesis in traditional methods, providing a new technical route for the industrial production of sodium iron pyrophosphate derivatives.

[0016] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0017] Figure 1 This is a flowchart of the preparation method of sodium iron pyrophosphate derivative shown in Embodiment 1 of the present invention; Figure 2 The X-ray diffraction pattern of the sodium iron pyrophosphate derivative shown in Embodiment 1 of the present invention is shown. Figure 3 The image shows a scanning electron microscope-energy dispersive X-ray spectrum of the sodium iron pyrophosphate derivative shown in Embodiment 1 of the present invention. Figure 4 The X-ray diffraction pattern of the sodium iron pyrophosphate derivative shown in Example 4 of this invention; Figure 5 The X-ray diffraction pattern of the sodium iron pyrophosphate derivative shown in Comparative Example 1 of this invention is shown. Figure 6The scanning electron microscope-energy dispersive X-ray spectrum of the sodium iron pyrophosphate derivative shown in Comparative Example 1 of the present invention is shown. Figure 7 The image shows the X-ray diffraction pattern of the sodium iron pyrophosphate derivative shown in Comparative Example 2 of this invention. Detailed Implementation

[0018] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments 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.

[0019] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0020] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0021] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0022] A method for preparing a sodium iron pyrophosphate derivative, comprising: S1. Weigh out sodium source, second metal source, phosphorus source, carbon source, dispersant and modifier and mix them to obtain mixed raw material. The second metal source contains iron element. The phosphorus source is soluble in dispersant. The molar ratio of sodium element in mixed raw material, metal element in second metal source and phosphorus element in mixed raw material is any value in (3.9~4.1):3:(4.0~4.2). The molecular structure of modifier includes carboxyl group and at least one of amino and substituted amino groups. The molar ratio of modifier to metal element in second metal source is any value in 1:(10~100).

[0023] S2. Mechanically activate the mixed raw materials and dry them to obtain the precursor.

[0024] S3. The precursor is pre-calcined at a first temperature for a first time in an inert atmosphere, and then heated to a second temperature for a second time to obtain sodium iron pyrophosphate derivative.

[0025] The molar ratio of sodium in the mixed raw material, metal element in the second metal source, and phosphorus in the mixed raw material can be any value among (4:3:4), (3.9:3:4), (4.1:3:4), (4:3:4.1), and (4:3:4.2), for example. The molar ratio of modifier to metal element in the second metal source can be any value among (1:10), (1:20), (1:40), (1:60), (1:80), (1:90), and (1:100), for example.

[0026] The modifier contains both carboxyl and amino or substituted amino groups. Under weakly acidic or neutral conditions, the carboxyl groups interact with the second metal source through hydrogen bonding or coordination reactions to form a stable carboxylated linkage structure. The amino or substituted amino groups adsorb free phosphate ions through opposite charge phase adsorption, enabling precise molecular-scale assembly of phosphate ions dissolved in the dispersant with the insoluble second metal source. This prevents local enrichment of the second metal source in the precursor, which could lead to the formation of the NaFePO4 impurity phase, thus improving the electrochemical performance of the sodium iron pyrophosphate derivative. Simultaneously, the surface groups of the modifier also stabilize the carbon source, further enhancing the structural stability and capacity retention during cycling. This invention solves the problem of poor material performance caused by uneven mechanical synthesis in traditional methods, providing a new technical pathway for the industrial production of sodium iron pyrophosphate derivatives.

[0027] In some embodiments, the molecular structure of the modifier includes a carboxyl group, and the chain length of the molecular chain including at least one of amino and substituted amino groups is less than or equal to 50, for example, it can be any value among 5, 10, 20, 30, 40, and 45. The molecular chain of the modifier including a carboxyl group and at least one of amino and substituted amino groups is a structural chain. When the structural chain of the modifier is too long, the distance between the second metal source molecule and the phosphate group it constrains is large, and the molecular chain is more prone to entanglement, further obscuring the functional groups, which is not conducive to the bonding and assembly of the second metal source molecule and the phosphate group.

[0028] In some embodiments, the modifier is one or more of trimethylglycine hydrochloride, ampicillin, arginine, lysine, creatine, carnitine, and chemoresine.

[0029] In some embodiments, the second metal source contains one or more of manganese, chromium, zirconium, aluminum, zinc, copper, and molybdenum, which helps to optimize the electrochemical performance of the sodium iron pyrophosphate derivative.

[0030] In some embodiments, the second metal source contains manganese. Fe 2+ / Fe 3+ The electrode potential of the redox couple is 3.4 V, while Mn 2+ / Mn 3+ The redox couple exhibits a significant potential advantage of up to 4.1 V. Therefore, introducing Mn to substitute Fe in NFPP to form derivatives helps to improve the energy density of the material.

[0031] In some embodiments, the second metal source includes one or more of ferric phosphate, manganese phosphate, ferromanganese hydrogen phosphate, and ferromanganese ammonium phosphate. Ferric phosphate and manganese phosphate have the advantages of low cost and easy availability, and are common industrial iron and manganese sources. Because they contain phosphate ions, they do not introduce impurities into the NFPP material and can save phosphorus source. The uniform doping of manganese and iron elements in ferromanganese hydrogen phosphate and ferromanganese ammonium phosphate helps to improve the uniformity of manganese and iron element distribution in the NFPP material.

[0032] In some embodiments, the sodium source includes one or more of sodium carbonate, sodium bicarbonate, sodium acetate, sodium dihydrogen citrate, sodium oxalate, sodium alginate, and sodium dodecylbenzene sulfonate. Phosphorus sources include one or more of the following: ammonium dihydrogen phosphate, sodium dihydrogen phosphate, diammonium hydrogen phosphate, disodium hydrogen phosphate, sodium phosphate, and ammonium phosphate. Carbon sources include one or more of citric acid, oxalic acid, ascorbic acid, tartaric acid, glucose, sucrose, starch, ethylenediaminetetraacetic acid, aminotriacetic acid, and polyacrylic acid; Dispersants include water and / or ethanol.

[0033] In some embodiments, the first temperature is any value from 300°C to 350°C, for example, any value from 300°C, 310°C, 320°C, 330°C, 340°C, and 350°C; the first time is any value from 1h to 5h, for example, any value from 1h, 2h, 3h, 4h, and 5h; the second temperature is any value from 400°C to 600°C, for example, any value from 400°C, 450°C, 500°C, 550°C, and 600°C; and the second time is any value from 1h to 24h, for example, any value from 1h, 3h, 6h, 9h, 12h, 15h, 18h, 21h, and 24h.

[0034] In some embodiments, the mechanical activation time is any value from 1h to 18h, for example, any value from 1h, 3h, 6h, 9h, 12h, 15h and 18h.

[0035] This invention also applies for protection of a sodium iron pyrophosphate derivative, which is prepared by the above-described preparation method and has a high degree of uniformity in the distribution of its internal elements.

[0036] In some embodiments, the carbon content in the sodium iron pyrophosphate derivative is any value from 0.5wt% to 10wt%, for example, any value from 0.5wt%, 2wt%, 4wt%, 6wt%, 8wt%, and 10wt%, preferably any value from 2wt% to 3wt%, for example, any value from 2wt%, 2.2wt%, 2.4wt%, 2.6wt%, 2.8wt%, and 3wt%.

[0037] This invention also applies for protection of a sodium-ion battery that uses the above-mentioned sodium iron pyrophosphate derivative as the positive electrode active material and has excellent electrochemical performance.

[0038] Please refer to the following examples for details.

[0039] Example 1: Please see Figure 1 A preferred embodiment of this application illustrates a method for preparing a sodium ferric pyrophosphate derivative, comprising: S1. Weigh out sodium source, second metal source, phosphorus source, carbon source, dispersant and modifier and mix them to obtain mixed raw material. The second metal source contains iron element. The phosphorus source is soluble in dispersant. The molar ratio of sodium element in mixed raw material, metal element in second metal source and phosphorus element in mixed raw material is any value in (3.9~4.1):3:(4.0~4.2). The molecular structure of modifier includes carboxyl group and at least one of amino and substituted amino groups. The molar ratio of modifier to metal element in second metal source is any value in 1:(10~100).

[0040] S2. Mechanically activate the mixed raw materials and dry them to obtain the precursor.

[0041] S3. The precursor is pre-calcined at a first temperature for a first time in an inert atmosphere, and then heated to a second temperature for a second time to obtain sodium iron pyrophosphate derivative.

[0042] In step S1, ferric ammonium manganese phosphate is used as the second metal source, sodium carbonate as the sodium source, diammonium hydrogen phosphate as the phosphorus source, citric acid as the carbon source, deionized water as the dispersant, and trimethylglycine hydrochloride as the modifier. The elemental ratio of Na:Fe:Mn:P in the mixed raw materials is 4:1.5:1.5:4, and the molar ratio of the modifier to the second metal source is 1:20. An appropriate amount of citric acid is added to ensure that the carbon content in the obtained sodium ferric pyrophosphate derivative is 2.5 wt%.

[0043] In step S2, the mixed raw materials are placed in a ball mill for mechanical activation for 15 hours.

[0044] In step S3, heat treatment is carried out in a nitrogen atmosphere. The first temperature is 300℃ and the first time is 3h. The second temperature is 500℃ and the second time is 15h. After the reaction is completed, sodium iron pyrophosphate derivative Na4Fe is obtained. 1.5 Mn 1.5 (PO4)2P2O7.

[0045] The sodium iron pyrophosphate derivative prepared in this example was detected using X-ray diffraction. Please refer to [link to relevant documentation]. Figure 2 It can be seen that the material is a pure phase and does not contain inert impurities such as sodium iron phosphate or sodium manganese phosphate.

[0046] The sodium iron pyrophosphate derivative prepared in this example was detected using scanning electron microscopy and energy-dispersive X-ray spectroscopy. Please refer to [link to relevant documentation]. Figure 3 As can be seen, the sodium iron pyrophosphate derivative particles prepared in this embodiment have a particle size between 0.5 μm and 1.5 μm, exhibiting strong particle size uniformity, which is beneficial to the electrochemical performance of the material. Furthermore, the four elements Na, Fe, Mn, and P are evenly distributed in the material, without local enrichment or segregation.

[0047] Using the prepared sodium iron pyrophosphate derivative as the positive electrode active material, it was weighed together with the conductive agent acetylene black and the binder polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1, and then thoroughly ground and mixed in a mortar. N-methylpyrrolidone (NMP) was added as a solvent, and grinding continued until a uniform black slurry was formed. The uniform slurry was placed on aluminum foil and evenly coated into a film of uniform thickness using a scraper. Using a sodium metal sheet as the counter electrode, a glass fiber membrane as the separator, and a 1 mol / L NaClO4 propylene carbonate (PC) solution as the electrolyte, a CR2032 coin cell was assembled in an anhydrous and oxygen-free argon atmosphere glove box.

[0048] Example 2: The only difference between this embodiment and Embodiment 1 is that in this embodiment, ferromanganese hydrogen phosphate is used as the second metal source, sodium bicarbonate as the sodium source, sodium dihydrogen phosphate is used as both the phosphorus and sodium source, oxalic acid as the carbon source, and ampicillin as the modifier, with a molar ratio of the modifier to the second metal source of 1:10. Mechanical activation is performed for 18 hours, at a first temperature of 350°C for 5 hours, at a second temperature of 600°C for 24 hours.

[0049] Example 3: The only difference between this embodiment and Embodiment 1 is that in this embodiment, ferromanganese hydrogen phosphate is used as the second metal source, sodium acetate as the sodium source, diammonium hydrogen phosphate as the phosphorus source, ascorbic acid as the carbon source, and arginine as the modifier. The molar ratio of the modifier to the second metal source is 1:100, and anhydrous ethanol is used as the dispersant. Mechanical activation is performed for 12 hours at a first temperature of 300°C for 3 hours, followed by a second temperature of 600°C for 20 hours.

[0050] Example 4: The only difference between this embodiment and Embodiment 1 is that, in this embodiment, ferric phosphate is used as the second metal source, sodium dihydrogen citrate is used as the sodium source, and disodium hydrogen phosphate is used as both the phosphorus and sodium source. The elemental ratio of Na:Fe:P in the mixed raw materials is 4:3:4. Glucose is used as the carbon source, lysine is used as the modifier, and the molar ratio of the modifier to the second metal source is 1:25. Anhydrous ethanol is used as the dispersant. Mechanical activation is performed for 13 hours at a first temperature of 330°C for 4 hours, followed by a second temperature of 520°C for 20 hours.

[0051] The sodium iron pyrophosphate derivative prepared in this example was detected using X-ray diffraction. Please refer to [link to relevant documentation]. Figure 4 It can be seen that the material is a pure phase and does not contain the electrochemically inert phase of sodium iron phosphate.

[0052] Example 5: The only difference between this embodiment and Embodiment 1 is that, in this embodiment, ferric phosphate is used as the second metal source, sodium oxalate as the sodium source, and sodium phosphate is used as both the phosphorus and sodium source. The elemental ratio of Na:Fe:P in the mixed raw materials is 4:3:4. Sucrose is used as the carbon source, creatine as the modifier, and the molar ratio of the modifier to the second metal source is 3:50. Anhydrous ethanol is used as the dispersant. Mechanical activation is performed for 13 hours at a first temperature of 300°C for 5 hours, followed by a second temperature of 580°C for 20 hours.

[0053] Example 6: The only difference between this embodiment and Embodiment 1 is that in this embodiment, an acrylic acid-acrylamide copolymer with a molecular chain length greater than 80 is used as the modifier.

[0054] Comparative Example 1: The only difference between this comparative example and Example 1 is that no modifier is added in this comparative example.

[0055] The sodium iron pyrophosphate derivative prepared in this comparative example was analyzed using X-ray diffraction. Please refer to [link to relevant documentation]. Figure 5 It can be seen that the material contains a large amount of electrochemically inert phases of sodium iron phosphate and sodium manganese phosphate. This is attributed to the presence of Mn during mechanical activation. 2 + Fe 3+ With PO4 3- Uneven local distribution leads to element segregation.

[0056] The sodium iron pyrophosphate derivative prepared in this comparative example was detected using scanning electron microscopy and energy-dispersive X-ray spectroscopy. Please refer to [link to relevant documentation]. Figure 3 It can be seen that the Fe, Mn, and P in the sodium iron pyrophosphate derivative prepared in this embodiment are unevenly distributed and the segregation is quite serious.

[0057] Comparative Example 2: The only difference between this comparative example and Example 4 is that no modifier is added in this comparative example.

[0058] The sodium iron pyrophosphate derivative prepared in this comparative example was analyzed using X-ray diffraction. Please refer to [link to relevant documentation]. Figure 7 It can be seen that the material contains a large amount of electrochemically inert phases of sodium iron phosphate and sodium manganese phosphate. This is attributed to the presence of Fe during mechanical activation. 3+ With PO4 3- The local precipitation kinetics imbalance led to severe elemental segregation. This impurity phase blocked sodium ion migration channels, severely impacting electrochemical performance.

[0059] The electrochemical performance of the sodium-ion batteries prepared in the various embodiments and comparative examples of the present invention was tested, and the test results are shown in Table 1 below.

[0060] Table 1: Sample 0.1C initial discharge specific capacity (mAh / g) 1C first discharge Specific capacity (mAh / g) 5C first discharge Specific capacity (mAh / g) Capacity retention rate % (5C cycles, 5000 revolutions) Example 1: 124.2 102.4 84.2 89.0 Example 2: 125.5 102.7 82.1 89.8 Example 3: 123.8 100.2 80.3 88.3 Example 4: 128.5 108.6 92.6 94.2 Example 5: 128.1 108.2 94.6 94.9 Example 6: 112.8 92.5 73.6 57.4 Comparative Example 1: 102.0 83.1 60.5 50.6 Comparative Example 2: 108.8 90.7 71.6 54.2 As shown in Table 1, adding a modifier to the mixed raw materials prepared by the dry method to achieve the directional assembly of the second metal source and phosphate ions can significantly improve the electrochemical performance of the prepared sodium iron pyrophosphate derivative cathode material, including the 0.1 C initial discharge specific capacity, 1 C initial discharge specific capacity, 5 C initial discharge specific capacity, and 5 C 5000-cycle capacity retention rate. This indicates that the addition of the modifier effectively improves the electrochemical performance of the material by suppressing the co-occurrence of impurity phases.

[0061] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0062] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A process for the preparation of a sodium iron pyrophosphatederivative, characterized in that, Comprising: The sodium source, the second metal source, the phosphorus source, the carbon source, the dispersant and the modifier are mixed to obtain a mixed raw material, the second metal source contains iron element, the phosphorus source is soluble in the dispersant, the molar ratio of sodium element in the mixed raw material, metal element in the second metal source and phosphorus element in the mixed raw material is any value in (3.9~4.1):3:(4.0~4.2), the molecular structure of the modifier includes carboxyl, and at least one of amino and substituted amino, the molar ratio of the modifier and metal element in the second metal source is any value in 1:(10~100); The mixed raw material is mechanically activated, and the precursor is obtained after drying; The precursor is pre-fired at a first temperature for a first time under an inert atmosphere, and then heated to a second temperature for a second time to obtain the sodium iron pyrophosphate derivative.

2. The method for preparing sodium iron phosphate pyrophosphate derivatives according to claim 1, characterized in that, The molecular structure of the modifier includes carboxyl, and the chain length of the molecular chain including at least one of amino and substituted amino is less than or equal to 50.

3. The method for preparing sodium iron phosphate pyrophosphate derivatives according to claim 2, characterized in that, The modifier is one or more of trimethyl glycine hydrochloride, ampicillin, arginine, lysine, creatine, carnitine and goose sarcosine.

4. The process for the preparation of sodium iron pyrophosphates derivatives according to any one of claims 1 to 3, characterized in that, The second metal source contains one or more of manganese element, chromium element, zirconium element, aluminum element, zinc element, copper element and molybdenum element.

5. The method for preparing sodium iron phosphate pyrophosphate derivatives according to claim 4, characterized in that, The second metal source contains manganese element.

6. The method for preparing the sodium iron pyrophosphate derivative as described in claim 5, characterized in that, The second metal source includes one or more of iron phosphate, manganese phosphate, hydrogen manganese iron phosphate and manganese ammonium iron phosphate.

7. The preparation method of the sodium iron pyrophosphate derivative according to claim 1, wherein The sodium source includes one or more of sodium carbonate, sodium bicarbonate, sodium acetate, sodium dihydrogen citrate, sodium oxalate, sodium alginate and sodium dodecyl benzene sulfonate; The phosphorus source includes one or more of ammonium dihydrogen phosphate, sodium dihydrogen phosphate, diammonium hydrogen phosphate, disodium hydrogen phosphate, sodium phosphate and ammonium phosphate; The carbon source includes one or more of citric acid, oxalic acid, ascorbic acid, tartaric acid, glucose, sucrose, starch, ethylenediaminetetraacetic acid, aminotriacetic acid and polyacrylic acid; The dispersant includes water and / or ethanol.

8. The method for preparing a sodium ferric pyrophosphate derivative according to claim 1, wherein The first temperature is any value in 300℃~350℃, the first time is any value in 1h~5h, the second temperature is any value in 400℃~600℃, the second time is any value in 1h~24h, and the mechanical activation time is any value in 1h~18h.

9. A sodium iron phosphate pyrophosphate derivative, characterized in that, Prepared by the preparation method according to any one of claims 1 to 8.

10. A sodium-ion battery, characterized in that, The sodium iron pyrophosphate derivative prepared according to claim 9 is used as a positive active material.

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