A modified Prussian derivative and its preparation method and application

Abstract

The present invention discloses a modified Prussian derivative, its preparation method, and application. The modified Prussian derivative comprises a vanadium compound and a Prussian derivative; the Prussian derivative contains the vanadium compound on its surface and / or within its interior. The modified Prussian derivative of the present invention exhibits good thermal stability, regular morphology, and excellent electrochemical performance. By coating and doping the Prussian derivative with a vanadium compound, the present invention improves the surface morphology, making the material's morphology more regular. The metal cations in the vanadium compound can quickly enter the crystal lattice of the Prussian derivative, occupying the positions of the original lattice water, reducing structural defects in the material, increasing the integrity of the material's crystal structure, and removing lattice water from internal defects. Furthermore, the vanadium compound coating and doping protects the Prussian derivative, preventing it from hygroscopicity and oxidation, thereby increasing the rate performance of the battery.

Description

Technical Field

[0001] The present invention belongs to the field of battery materials, and in particular relates to a modified Prussian derivative and a preparation method and application thereof. Background Art

[0002] In recent years, lithium-ion batteries have seen rapid growth in the new energy industry, with widespread application in electric vehicles, portable electronic devices, and smart home appliances. This has led to an even greater shortage of already scarce lithium resources. Furthermore, these shortages and rising lithium prices have severely hampered the development of lithium-ion batteries. However, sodium, a member of the same main group, is relatively abundant and widespread in the Earth's crust, and its physical and chemical properties are similar. Therefore, sodium-ion batteries (Na-ion batteries) hold promise as a new energy storage alternative to Li-ion batteries.

[0003] Prussian-type materials are currently one of the most promising cathode materials for sodium-ion batteries. Their open nanoframework structure, large interstitial spaces and ion channels, high specific surface area, and controllable functionalization facilitate rapid sodium ion insertion and extraction. Consequently, Prussian-type materials have attracted considerable attention and have been extensively studied. However, due to their inherent structural properties, Prussian-type materials suffer from two significant drawbacks. The first is the presence of significant amounts of lattice water and coordinated water within their structure, resulting in a high water content that significantly impacts both the rate and cycling performance of the battery. The second is the water absorption and susceptibility of Prussian-type materials to oxidation in air, which severely impacts the specific capacity of batteries containing these materials. This presents a significant technical challenge that must be addressed in the application of Prussian-type materials in cathode materials. Summary of the Invention

[0004] In order to overcome the problems existing in the prior art, one of the objectives of the present invention is to provide a modified Prussian derivative.

[0005] The second object of the present invention is to provide a method for preparing modified Prussian derivatives.

[0006] A third object of the present invention is to provide a positive electrode material.

[0007] A fourth object of the present invention is to provide a modified Prussian derivative for use in sodium ion batteries or potassium ion batteries.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] The first aspect of the present invention provides a modified Prussian derivative, comprising a vanadium compound and a Prussian derivative; the Prussian derivative contains the vanadium compound on its surface and / or inside.

[0010] When the surface of a Prussian-type derivative contains a vanadium compound, the modified Prussian-type derivative in the present invention is a Prussian-type derivative modified by coating with a vanadium compound. When the interior of a Prussian-type derivative contains a vanadium compound, the modified Prussian-type derivative in the present invention is a Prussian-type derivative modified by doping with a vanadium compound. When the surface and interior of a Prussian-type derivative contain a vanadium compound, the modified Prussian-type derivative in the present invention is a Prussian-type derivative modified by coating with a vanadium compound.

[0011] Prussian white or Prussian blue materials have excellent sodium storage electrochemical properties, but in practical applications, they generally suffer from low utilization, low efficiency, poor rate performance, and unstable cycles. The present invention solves the problem of severe water absorption and oxidation of Prussian sodium cathode materials when exposed to air by coating and / or doping with vanadium compounds; at the same time, some cations in the vanadium compound enter the Prussian crystals and occupy the position of the material lattice water, thereby reducing the structural defects of the Prussian material. This is because the large-radius metal cations occupy part of the Na in the lattice of the Prussian material. + or K + In the ion position, cations with large ionic radius occupy more space, forcing lattice water molecules to be excluded, and the removal of lattice water reduces the defects of the material; at the same time, the coating and doping of vanadium compounds on the surface and / or inside of Prussian materials can effectively inhibit the adsorption of water adsorbed on its surface. At the same time, vanadium in vanadium compounds has multiple valence states, which provides more redox potentials for battery charging and discharging, thereby increasing the specific capacity of the battery; secondly, cations with large ionic radius enter the lattice, increase the gap of ion transport channels, and improve the transport performance of sodium ions and electrons; this not only reduces the defects of Prussian derivatives, but also further improves the electrochemical properties of the material. This method solves the problems of low rate performance, poor cycle performance and severe water absorption existing in Prussian materials.

[0012] Preferably, the chemical formula of the Prussian derivative is: A x B y M z N a [(CN)6] b ;

[0013] Wherein, A is K or Na;

[0014] B is K or Na;

[0015] M is at least one of Co, Cu, Cr, Fe, Mn, Ni, Cr, and Zn;

[0016] N is Fe or Zn;

[0017] 0.5≤x+y≤2, z is 1, 2 or 3; 0.5≤a≤3, 0.5≤b≤2.

[0018] Preferably, the chemical formula of the Prussian derivative is: A x B y M z N a [(CN)6] b ;

[0019] Wherein, A is Na;

[0020] B is K;

[0021] M is at least one of Co, Cu, Cr, Fe, Mn, Ni, Cr, and Zn;

[0022] N is Fe or Zn;

[0023] 0.5≤x+y≤2, x>y, z is 1, 2 or 3; 0.5≤a≤3, 0.5≤b≤2.

[0024] In some preferred embodiments of the present invention, the Na content in the Prussian derivatives is greater than the K content; in other embodiments of the present invention, the K content in the Prussian derivatives may also be greater than the Na content, or the Prussian derivatives contain only K.

[0025] Preferably, in the chemical formula of the Prussian derivative, 0.8≤x+y≤2; further preferably, in the chemical formula of the Prussian derivative, 1≤x+y≤2; even further preferably, in the chemical formula of the Prussian derivative, x+y≤2; more preferably, in the chemical formula of the Prussian derivative, x+y=2.

[0026] Preferably, in the chemical formula of the Prussian derivative, z is 1 or 3; further preferably, in the chemical formula of the Prussian derivative, z is 1.

[0027] Preferably, in the chemical formula of the Prussian derivative, 0.7≤a≤3; further preferably, in the chemical formula of the Prussian derivative, 1≤a≤3; even further preferably, in the chemical formula of the Prussian derivative, a is 1, 2 or 3; more preferably, in the chemical formula of the Prussian derivative, a is 1 or 3.

[0028] Preferably, in the chemical formula of the Prussian derivative, 0.7≤b≤2; further preferably, in the chemical formula of the Prussian derivative, 1≤b≤2; even further preferably, in the chemical formula of the Prussian derivative, b is 1 or 2.

[0029] Preferably, the chemical formula of the Prussian derivative is: Ax B y M z N a [(CN)6] b ;

[0030] Wherein, A is K or Na;

[0031] B is K or Na;

[0032] M is at least one of Co, Cu, Cr, Fe, Mn, Ni, Cr, and Zn;

[0033] N is Fe or Zn;

[0034] x+y=2, z is 1, a is 1 or 3, and b is 1 or 2.

[0035] Preferably, the vanadium compound is at least one of alkali metal vanadate, alkaline earth metal vanadate, and transition metal vanadate.

[0036] Preferably, the alkali metal vanadate includes at least one of lithium vanadate, sodium vanadate and potassium vanadate.

[0037] Preferably, the alkaline earth metal vanadate includes at least one of calcium vanadate, magnesium vanadate and strontium vanadate.

[0038] Preferably, the transition metal vanadate includes at least one of manganese vanadate, iron vanadate, cobalt vanadate, nickel vanadate, copper vanadate, zinc vanadate, and silver vanadate.

[0039] Preferably, the molar ratio of the vanadium compound to the Prussian derivative is (0.1-20):100; further preferably, the molar ratio of the vanadium compound to the Prussian derivative is (0.1-10):100.

[0040] The second aspect of the present invention provides a method for preparing the modified Prussian derivative provided in the first aspect of the present invention, comprising the following steps:

[0041] The modified Prussian derivative is prepared by mixing a Prussian material with a vanadium compound for reaction.

[0042] Preferably, the mixing reaction is specifically: allowing the Prussian material solution and the vanadium compound solution to react in a liquid phase.

[0043] Preferably, the liquid phase reaction temperature is 0-80°C; more preferably, the liquid phase reaction temperature is 5-80°C; even more preferably, the liquid phase reaction temperature is 5-40°C.

[0044] Preferably, the liquid phase reaction time is 5 to 80 minutes; more preferably, the liquid phase reaction time is 10 to 60 minutes.

[0045] Preferably, the stirring speed of the liquid phase reaction is 50-450 rpm; further preferably, the stirring speed of the liquid phase reaction is 100-400 rpm; even further preferably, the stirring speed of the liquid phase reaction is 200-400 rpm.

[0046] Preferably, the Prussian materials include Na2MnFe(CN)6, Na2CoFe(CN)6, Na2NiFe(CN)6, Na2CuFe(CN)6, Na2Zn3[Fe(CN)6]2, Na2FeFe(CN)6, Na 0.84 Ni[Fe(CN)6] 0.71 , Na2CrFe(CN)6, K2MnFe(CN)6, K2CoFe(CN)6, K2NiFe(CN)6, K2CuFe(CN)6, K2Zn3[Fe(CN)6]2, K2CrFe(CN)6, Na 1.63 At least one of FeFe(CN)6.

[0047] Preferably, the vanadium compound is prepared by reacting a vanadium-containing compound with a metal cation source. Further preferably, the vanadium compound is prepared by reacting a vanadium-containing compound solution with a metal cation source solution to obtain a vanadium compound solution.

[0048] Preferably, the vanadium-containing compound comprises orthovanadate, pyrovanadate, metavanadate or vanadium oxide.

[0049] Preferably, the orthovanadate comprises at least one of sodium vanadate, potassium vanadate, lithium vanadate, manganese vanadate, nickel vanadate, iron vanadate, copper vanadate, cobalt vanadate, silver vanadate, chromium vanadate, calcium vanadate, magnesium vanadate, tin vanadate, and ruthenium vanadate. The orthovanadate in the present invention is not limited to the types of orthovanadates listed above, and other metal vanadates may also be used.

[0050] Preferably, the metavanadate includes at least one of ammonium metavanadate, sodium metavanadate, potassium metavanadate, and silver metavanadate.

[0051] Preferably, the pyrovanadate includes at least one of sodium pyrovanadate, ammonium pyrovanadate, and potassium pyrovanadate.

[0052] Preferably, the vanadium oxide is vanadium oxide, vanadium trioxide, vanadium dioxide or vanadium pentoxide.

[0053] Preferably, the Prussian material needs to be prepared into a solution when used; further preferably, the preparation method of the Prussian material solution is: mixing the Prussian material with water under the protection of a protective gas.

[0054] Preferably, the protective gas is nitrogen or argon.

[0055] Preferably, the preparation method of the modified Prussian derivative further comprises the step of adding a surfactant and / or an additive.

[0056] Preferably, the surfactant and additive are both auxiliary agents commonly used in the battery field.

[0057] Preferably, the preparation method of the modified Prussian derivative specifically comprises the following steps:

[0058] (1) mixing a Prussian material with water, stirring, adding the mixture to a reactor, and introducing a protective gas to obtain a Prussian material solution;

[0059] (2) mixing a vanadium-containing compound and a metal ion source solution to react to obtain a vanadium compound solution;

[0060] (3) reacting the vanadium compound solution with the Prussian material solution at a temperature of 0 to 80° C. for 5 to 80 minutes, then filtering, washing, and drying to obtain the modified Prussian derivative.

[0061] The third aspect of the present invention provides a positive electrode material, comprising the modified Prussian derivative provided by the first aspect of the present invention.

[0062] The fourth aspect of the present invention provides the use of the modified Prussian derivative provided by the first aspect of the present invention in a sodium ion battery or a potassium ion battery.

[0063] The beneficial effects of the present invention are as follows: the modified Prussian derivatives of the present invention have the characteristics of good thermal stability, regular morphology and excellent electrochemical performance.

[0064] Specifically, the present invention improves the surface morphology of the Prussian-type derivative by coating and / or doping it with a vanadium compound, making the material more regular. The metal cations in the vanadium compound can quickly enter the Prussian-type derivative's crystal lattice, occupying the positions of the original lattice water, reducing the material's structural defects, increasing the integrity of the material's crystal structure, and removing lattice water from internal defects. Furthermore, the vanadium compound coating and / or doping protects the Prussian-type derivative from moisture absorption and oxidation, thereby increasing the battery's rate performance. Vanadium, as a multivalent metal element, can provide multiple redox sites when coated and doped in the Prussian-type positive electrode material, thereby increasing the relative theoretical capacity of the battery material.

[0065] The preparation method of the present invention has a few process flows, is simple to operate, uses cheap raw materials, uses an aqueous solution as the solvent, is environmentally friendly and pollution-free, and the obtained product is easy to purify and separate, thereby enabling industrial large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 This is an SEM image of the manganese-based Prussian white in Example 1.

[0067] Figure 2 This is the SEM image of the modified Prussian derivative in Example 1.

[0068] Figure 3 TEM image of the modified Prussian derivative in Example 1. DETAILED DESCRIPTION

[0069] The specific implementation of the present invention is further described in detail below with reference to the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that if there are processes that are not particularly described in detail below, they can be implemented or understood by those skilled in the art with reference to the prior art. If the manufacturer of the reagents or instruments used is not indicated, they are deemed to be conventional products that can be purchased commercially.

[0070] The manganese-based Prussian white, nickel-based Prussian blue, cobalt-based Prussian white, zinc-based Prussian white, and iron-based Prussian white in the embodiments of the present invention can all be prepared by referring to the preparation method of Prussian complexes in the prior art.

[0071] Example 1

[0072] The modified Prussian derivative in this example is prepared by using K2V6O 16 Coated doped Prussian white derivatives, the chemical formula of Prussian white derivatives is: Na 1.85 K 0.15 MnFe(CN)6.

[0073] The modified Prussian derivative in this example was prepared by the following preparation method, which specifically includes the following steps:

[0074] (1) Weigh 1 mol of manganese-based Prussian white (Na2MnFe(CN)6) and dissolve it in 500 mL of deionized water. Stir vigorously at a rate of 400 rpm to fully dissolve the manganese-based Prussian white in the water. Then place the solution in an ice bath at 5°C to obtain solution A.

[0075] (2) Weigh 3 mol of ammonium metavanadate and 1 mol of potassium chloride and dissolve them in 250 mL of deionized water. Stir vigorously to dissolve the ammonium metavanadate and potassium chloride in water and react fully to obtain Solution B.

[0076] (3) Solution B was slowly added dropwise to solution A containing manganese-based Prussian white, and the mixture was stirred slowly. The reaction temperature was controlled at 5°C and the reaction was aged for 10 minutes.

[0077] (4) The solution prepared in step (3) was filtered, washed, and dried in an oven at 80°C overnight to obtain the modified Prussian derivative in this example, denoted as: Na 1.85 K 0.15 MnFe(CN)6·@K2V6O 16 .

[0078] The SEM images of the manganese-based Prussian white and the modified Prussian derivatives in this example were tested using a scanning electron microscope. The SEM images of the manganese-based Prussian white are shown in FIG. Figure 1 As shown, the SEM images of the modified Prussian derivatives are as follows Figure 2 As shown, by comparison Figure 1 and Figure 2 It can be seen that the surface of the modified Prussian derivatives is more regular and has fewer structural defects.

[0079] The TEM images of the modified Prussian derivatives in this example were tested using a transmission electron microscope. The test results are shown in Figure 1. Figure 3 As shown by Figure 3 It can be seen that K2V6O 16 Successfully wrapped in Na 1.85 K 0.15 The surface of MnFe(CN)6, thus 1.85 K 0.15 A coating layer is formed on MnFe(CN)6, and the thickness of the coating layer is about 5 to 10 nm.

[0080] Example 2

[0081] The modified Prussian derivative in this example is a manganese-based Prussian white doped with Na3VO4, and the chemical formula of manganese-based Prussian white is: Na2MnFe(CN)6.

[0082] The modified Prussian derivative in this example was prepared by the following preparation method, which specifically includes the following steps:

[0083] (1) Weigh 1 mol of manganese-based Prussian white (Na2MnFe(CN)6) and dissolve it in 500 mL of deionized water. Stir vigorously at a rate of 400 rpm to fully dissolve the manganese-based Prussian white in the water. Then place the solution in an ice bath at 5°C to obtain solution A.

[0084] (2) Weigh 1 mol of ammonium metavanadate and 3 mol of sodium chloride and dissolve them in 250 mL of deionized water to form solution B; stir vigorously to fully dissolve the ammonium metavanadate and sodium chloride in water.

[0085] (3) Slowly drop solution B into solution A containing manganese-based Prussian white, stirring continuously, maintaining the temperature at 5°C, and ageing for 1 hour.

[0086] (4) Finally, the solution obtained in step (3) was filtered, washed, and dried in an oven at 80°C overnight to obtain the modified Prussian derivative in this example, which was recorded as: Na2MnFe(CN)6·@Na3VO4.

[0087] Example 3

[0088] The modified Prussian derivative in this example is a Prussian blue derivative doped with KVO3. The chemical formula of the Prussian blue derivative is: Na 1.5 K 0.5 NiFe(CN)6.

[0089] The modified Prussian derivative in this example was prepared by the following preparation method, which specifically includes the following steps:

[0090] (1) Weigh 1 mol of nickel-based Prussian blue (Na2NiFe(CN)6) and dissolve it in 500 mL of deionized water. Stir vigorously at a stirring rate of 400 rpm to fully dissolve the nickel-based Prussian blue in the water. Then place the solution in an ice bath at 10°C to obtain solution A.

[0091] (2) Weigh 2 mol of ammonium metavanadate and 2 mol of potassium chloride and dissolve them in 250 mL of deionized water to form solution B; stir vigorously to fully dissolve the ammonium metavanadate and potassium chloride in water.

[0092] (3) Solution B was slowly added dropwise to solution A containing nickel-based Prussian blue, with continuous stirring. The temperature was controlled at 10°C and the reaction was allowed to age for 45 minutes.

[0093] (4) Finally, the solution obtained in step (3) was filtered, washed, and dried in an oven at 80°C overnight to obtain the modified Prussian derivative in this example, which was denoted as: Na 1.5 K 0.5 NiFe(CN)6·@KVO3.

[0094] Example 4

[0095] The modified Prussian derivative in this example is a Prussian white derivative doped with KVO3. The chemical formula of the Prussian white derivative is: Na 1.85 K 0.15 CoFe(CN)6.

[0096] The modified Prussian derivative in this example was prepared by the following preparation method, which specifically includes the following steps:

[0097] (1) Weigh 1 mol of cobalt-based Prussian white (Na2CoFe(CN)6) and dissolve it in 500 mL of deionized water. Stir vigorously at a rate of 400 rpm to fully dissolve the cobalt-based Prussian white in the water. Then, place the mixture in an ice bath at 3°C ​​to obtain solution A.

[0098] (2) Weigh 2 mol of ammonium metavanadate and 2 mol of potassium chloride and dissolve them in 250 mL of deionized water to form solution B; stir vigorously to fully dissolve the ammonium metavanadate and potassium chloride in water.

[0099] (3) Solution B was slowly added dropwise to solution A containing cobalt-based Prussian white, with continuous stirring, the temperature maintained at 3°C, and the reaction was allowed to age for 20 minutes.

[0100] (4) Finally, the solution obtained in step (3) was filtered, washed, and dried in an oven at 80°C overnight to obtain the modified Prussian derivative in this example, denoted as: Na 1.85 K 0.15 CoFe(CN)6·@KVO3.

[0101] Example 5

[0102] The modified Prussian derivative in this example is a Prussian white derivative doped with KVO3. The chemical formula of the Prussian white derivative is: Na 1.75 K 0.25 Zn3[Fe(CN)6]2.

[0103] The modified Prussian derivative in this example was prepared by the following preparation method, which specifically includes the following steps:

[0104] (1) Weigh 1 mol of zinc-based Prussian white Na2Zn3[Fe(CN)6]2·H2O and dissolve it in 500 mL of deionized water. Stir vigorously at a rate of 400 rpm to fully dissolve the zinc-based Prussian white in the water. Then place the mixture in an ice bath at 10°C to obtain solution A.

[0105] (2) Weigh 2 mol of V2O3 and 2 mol of potassium chloride and dissolve them in 250 mL of deionized water to form solution B; stir vigorously to fully dissolve the V2O3 and potassium chloride in water.

[0106] (3) Slowly drop solution B into solution A containing zinc-based Prussian white, stir continuously, maintain the temperature at 10°C, and age the reaction for 30 minutes.

[0107] (4) Finally, the solution obtained in step (3) was filtered, washed, and dried in an oven at 80°C overnight to obtain the modified Prussian derivative in this example, which is denoted as: Na1.75 K 0.25 Zn3[Fe(CN)6]2·@KVO3.

[0108] Example 6

[0109] The modified Prussian derivative in this example is a Prussian white derivative doped with KVO3. The chemical formula of the Prussian white derivative is: Na 1.56 K 0.44 Fe Fe(CN)6.

[0110] The modified Prussian derivative in this example was prepared by the following preparation method, which specifically includes the following steps:

[0111] (1) Weigh 1 mol of iron-based Prussian white (Na2FeFe(CN)6·3.1H2O) and dissolve it in 500 mL of deionized water. Stir vigorously at a rate of 400 rpm to fully dissolve the iron-based Prussian white in the water. Then place the solution in an ice bath at 15°C to obtain solution A.

[0112] (2) Weigh 2 mol of ammonium metavanadate and 2 mol of potassium chloride and dissolve them in 250 mL of deionized water to form solution B; stir vigorously to fully dissolve the ammonium metavanadate and potassium chloride in water.

[0113] (3) Solution B was slowly dripped into solution A containing iron-based Prussian white, with continuous stirring, the temperature was controlled at 15°C, and the aging reaction was carried out for 40 minutes.

[0114] (4) Finally, the solution obtained in step (3) was filtered, washed, and dried in an oven at 80°C overnight to obtain the modified Prussian derivative in this example, which is denoted as: Na 1.56 K 0.44 Fe Fe(CN)6·@KVO3.

[0115] Example 7

[0116] The modified Prussian derivative in this example is a Prussian white derivative doped with Na3VO4. The chemical formula of the Prussian white derivative is: Na 0.84 Ni[Fe(CN)6] 0.71 .

[0117] The modified Prussian derivative in this example was prepared by the following preparation method, which specifically includes the following steps:

[0118] (1) Weigh 1 mol of nickel-based Prussian white Na 0.84 Ni[Fe(CN)6] 0.71Dissolve 6H2O in 500 mL of deionized water and stir vigorously at 400 rpm to fully dissolve the nickel-based Prussian white in the water. Then, place in an ice bath at 5°C to obtain solution A.

[0119] (2) Weigh 2 mol of ammonium metavanadate and 6 mol of sodium chloride and dissolve them in 250 mL of deionized water to form solution B; stir vigorously to fully dissolve the ammonium metavanadate and sodium chloride in water.

[0120] (3) Slowly drop solution B into solution A containing nickel-based Prussian white, stir continuously, slowly heat to 80°C, and age for 20 minutes.

[0121] (4) Finally, the solution obtained in step (3) was filtered, washed, and dried in an oven at 80°C overnight to obtain the modified Prussian derivative in this example, denoted as: Na 0.84 Ni[Fe(CN)6] 0.71 ·@Na3VO4.

[0122] The modified Prussian derivatives prepared in Examples 1 to 7 can all be used as positive electrode materials.

[0123] Comparative Example 1

[0124] In this example, the manganese-based Prussian white (Na2MnFe(CN)6) in Example 1 is used as the positive electrode material.

[0125] The materials prepared in Examples 1-7 and Comparative Example 1 were placed in a vacuum oven as positive electrode sheets and dried (80°C, 3h); they were then punched into discs with a diameter of 12mm. In the half-cell, a dried electrode sheet was used as the positive electrode, a sodium sheet was used as the negative electrode, and a glass fiber composite separator was used as the separator. The electrolyte consisted of a 1 mol / L mixed solution of NaPF6 + EC, DMC, and DEC (the volume ratio of EC, DMC, and DEC was 1:1:1, where EC refers to ethylene carbonate, DMC refers to dimethyl carbonate, and DEC refers to diethyl carbonate). The discharge performance of the prepared half-cells was tested using a CT2001A battery testing system. With a cutoff voltage of 2.0-4.0V, the cells were first charged at a constant current of 0.2C to 4.0V, then at a constant voltage of 4.0V to a current of ≤0.05C. Discharge performance tests were conducted at 0.1C, 1C, 3C, and 5C, respectively. The specific test results are shown in Table 1 below.

[0126] Table 1 Electrical properties of the materials obtained in Examples 1 to 7 and Comparative Example 1

[0127]

[0128] As can be seen from Table 1 above, compared with the manganese-based Prussian white positive electrode material in Comparative Example 1, the modified Prussian derivatives prepared in Examples 1 to 7 of the present invention are coated and doped with vanadate compounds for modification. Vanadium, as a multivalent metal element, is coated and doped on the Prussian derivative material, which can provide multiple redox sites, thereby increasing the relative theoretical capacity of the battery material, thereby significantly improving the electrical performance of the battery.

[0129] The water content of the modified Prussian derivatives prepared in Examples 1 to 7 before and after coating was tested respectively. The specific test results are recorded in Table 2 below.

[0130] Table 2 Water content test of modified Prussian derivatives in Examples 1 to 7

[0131]

[0132]

[0133] As can be seen from Table 2 above, the modified Prussian derivatives of the present invention can greatly reduce the water content in the Prussian derivative material after being coated with a vanadate compound. This further indicates that the metal cations in the vanadate compound can quickly enter the crystal lattice of the Prussian derivative, occupy the position of the original lattice water, remove the lattice water in the internal defects of the Prussian derivative, reduce the internal defects of the Prussian derivative material, and increase the integrity of the crystal structure of the Prussian derivative material.

[0134] While the embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A modified Prussian derivative, characterized in that: The invention comprises a vanadium compound and a Prussian derivative; the Prussian derivative contains a vanadium compound on its surface and / or inside; the vanadium compound is an alkali metal vanadate; the alkali metal vanadate comprises at least one of lithium vanadate, sodium vanadate and potassium vanadate; the chemical formula of the Prussian derivative is: A x B y M z N a [(CN)6] b ; Wherein, A is Na; B is K; M is at least one of Co, Cu, Cr, Fe, Mn, Ni, Cr, and Zn; N is Fe or Zn; 0.5≤x+y≤2, z is 1, 2 or 3; 0.5≤a≤3, 0.5≤b≤2.

2. The modified Prussian derivative according to claim 1, characterized in that: The molar ratio of the vanadium compound to the Prussian derivative is (0.1-20):

100.

3. The method for preparing the modified Prussian derivative according to any one of claims 1 to 2, characterized in that: The following steps are involved: The modified Prussian derivative is prepared by mixing a Prussian material with a vanadium compound for reaction.

4. The method for preparing the modified Prussian derivative according to claim 3, characterized in that: The mixing reaction specifically comprises: allowing the Prussian material solution and the vanadium compound solution to react in a liquid phase.

5. The method for preparing the modified Prussian derivative according to claim 4, characterized in that: The liquid phase reaction temperature is 0-80° C., and the liquid phase reaction time is 5-80 minutes.

6. The method for preparing the modified Prussian derivative according to claim 3, characterized in that: The Prussian materials include Na2MnFe(CN)6, Na2CoFe(CN)6, Na2NiFe(CN)6, Na2CuFe(CN)6, Na2Zn3[Fe(CN)6]2, Na2FeFe(CN)6, Na 0.84 Ni[Fe(CN)6] 0.71 , Na2CrFe(CN)6, K2MnFe (CN)6, K2CoFe(CN)6, K2NiFe(CN)6, K2CuFe(CN)6, K2Zn3[Fe(CN)6]2, K2CrFe(CN)6, Na 1.63 At least one of FeFe(CN)6.

7. A positive electrode material, characterized in that: The invention comprises the modified Prussian derivative according to any one of claims 1 to 2.

8. Use of the positive electrode material according to claim 7 in a sodium ion battery or a potassium ion battery.

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