Prussian blue analogue material, preparation method thereof and aqueous zinc ion battery

Abstract

The invention relates to a Prussian blue analogue material, a preparation method thereof and an aqueous zinc ion battery, and the preparation method comprises the following steps: mixing a transition metal mixed solution and an alkali metal hexacyanoferrate salt solution for reaction, and aging to obtain the Prussian blue analogue material, wherein the transition metal mixed solution comprises transition metal salt, a chelating agent and a solvent; the chelating agent comprises nitrogen-based functional groups with the number of M being more than 0 and less than or equal to 2 and carboxyl with the number of N being more than or equal to 3 and less than or equal to 6. The chelating agent can form a stable chelate with transition metal ions, the chelated transition metal ions are slowly released from the chelate along with the addition of a ferricyanide alkali metal salt solution, and the crystallization rate of the Prussian blue analogue is reduced, so that the defect rate of a crystal structure in the material is reduced, the crystal form is complete, and the stability of the material is improved. The capacity and the cycle performance of the material are improved; in addition, the corresponding chelation effect can be achieved by adopting a small amount, the effect is more remarkable, and the production cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of zinc ion batteries, and in particular to a Prussian blue analog material and a preparation method thereof, and an aqueous zinc ion battery. Background Art

[0002] Battery energy storage technology is of great significance for promoting the transformation of the country's traditional energy and achieving the "dual carbon" strategic goal. The current mainstream lithium-ion batteries are limited in their application in the field of large-scale energy storage due to safety issues such as low natural abundance of lithium resources, high prices and flammability. In contrast, aqueous zinc-ion batteries have the advantages of high safety, low cost and environmental protection. They are a large-scale energy storage battery technology with broad application prospects. However, aqueous zinc-ion batteries currently still have bottleneck problems such as low energy density and poor cycle stability. This is mainly because zinc ions themselves have a high charge density, and during the charging and discharging process, they will have a strong electrostatic repulsion with the positive electrode material, resulting in the destruction of the positive electrode material structure.

[0003] Using Prussian blue analogues as positive electrode materials for aqueous zinc-ion batteries can provide a larger storage space for zinc ions with higher charge density, effectively alleviating the electrostatic repulsion of zinc ions during the charge and discharge process, thanks to the unique three-dimensional framework structure and good electrochemical properties of Prussian blue analogues. This makes Prussian blue analogues, as positive electrode materials, show great potential in improving the energy density and cycle stability of batteries.

[0004] However, in the existing co-precipitation synthesis scheme, the rapid reaction kinetics of Prussian blue analogs results in the presence of a large amount of [Fe(CN) 6 ] vacancies, resulting in capacity loss and weakened structural stability. At present, the use of chelating agents can slow down the nucleation rate of Prussian blue analogs, improve the crystallinity of the material, and thus improve the specific capacity and cycle performance of the material. However, the chelating force of the commonly used citric acid / citrate chelating agents is weak, the effect is not obvious, and a large amount of citric acid / citrate needs to be used, which increases the preparation cost and waste of resources.

[0005] CN118439630A discloses a method for preparing a Prussian blue cathode material, using sodium citrate and sodium carboxymethyl cellulose as chelating agents, freezing and crushing a first mixed solution containing a chelating agent and ferric chloride to obtain a first powder, freezing and crushing a second mixed solution containing sodium ferrocyanide decahydrate and a saturated sodium chloride solution to obtain a second powder, mixing the first powder and the second powder in a low temperature environment, stirring and reacting under inert gas protection and centrifuging, washing and freeze-drying the obtained precipitate to obtain a Prussian blue cathode material, so that the chelating agent is slowly released by freezing and crushing, which can effectively alleviate the problem of Prussian blue vacancies. However, in this preparation process, although the vacancy problem can be improved by freezing and crushing, the first discharge specific capacity of Prussian blue is still low, far lower than the theoretical specific capacity, and the preparation process is cumbersome.

[0006] CN115650254A discloses a raw material pre-placed iron-based Prussian blue analog and a preparation method thereof, wherein sodium cyanide is used as a complexing cyanide source, reduced iron powder is used as an iron source, sodium citrate is used as a complexing agent and a supplementary sodium source, and the coprecipitation method is used for direct synthesis; the complexing agent sodium citrate is a mixture of disodium citrate and trisodium citrate. The synthesis process pre-places the synthetic raw materials of the iron-based Prussian blue analog, simplifies the types of salts in the system, and has the characteristics of short process flow, low production cost, and obvious advantages in technical and economic indicators. However, the iron-based Prussian blue analog obtained by the preparation method still has the problem of low first discharge specific capacity.

[0007] The citric acid / citrate chelating agents used in the above-mentioned prior arts still have the problem of low discharge specific capacity even if different preparation processes are used to prepare the Prussian blue / Prussian blue analog materials.

[0008] Therefore, how to select a class of chelating agents with moderate chelating ability and more stable chelation, thereby reducing the defects in the internal crystal structure of Prussian blue analogs and improving the capacity and cycle performance of Prussian blue analog materials, has become a problem that needs to be solved urgently. Summary of the invention

[0009] In order to solve the above technical problems, the present invention provides a Prussian blue analog material and a preparation method thereof and an aqueous zinc ion battery. The chelating agent used in the present invention includes a nitrogen-based functional group and a carboxyl group, the number of the nitrogen-based functional groups is 0<M≤2, and the number of the carboxyl groups is 3≤N≤6. This type of chelating agent can form a stable chelate with transition metal ions. With the addition of an alkali metal ferrocyanide salt solution, the chelated transition metal ions are slowly released from the chelate, the crystallization rate of the Prussian blue analog is reduced, and the defect rate of the internal crystal structure of the Prussian blue analog material is reduced, the crystal form is complete, and the capacity and cycle performance of the material are improved; in addition, a small amount can achieve the corresponding chelation effect, and the effect is more significant, thereby reducing the production cost.

[0010] To achieve this object, the present invention adopts the following technical solutions:

[0011] In a first aspect, the present invention provides a method for preparing a Prussian blue analog material, the preparation method comprising the following steps:

[0012] The transition metal mixed solution is mixed with the alkali metal ferrocyanide salt solution for reaction, and then aged to obtain a Prussian blue analog material;

[0013] Wherein, the transition metal mixed solution comprises a transition metal salt, a chelating agent and a solvent;

[0014] The chelating agent includes nitrogen-based functional groups and carboxyl groups, the number of the nitrogen-based functional groups is 0<M≤2, for example, M can be 1 or 2, etc.; the number of the carboxyl groups is 3≤N≤6, for example, N can be 3, 4, 5 or 6, etc.

[0015] The chelating agent structure used in the present invention is rich in nitrogen-based functional groups and carboxyl functional groups, which can form multiple coordination bonds. The electronegativity of N in the nitrogen-based functional group (about 3.04) is stronger than the electronegativity of C (about 2.55), and the electron-withdrawing ability is stronger. The surrounding electrons tend to gather toward the nitrogen-based functional group, and the chelating performance is improved. In the chelating agent, the number of nitrogen-based functional groups is 0<M≤2, and the number of carboxyl groups is 3≤N≤6. This type of chelating agent has good chelation performance with transition metal ions (such as Mn 2+ , Fe 2+ 、Co 2+ 、Ni 2+ , Cu 2+ In the process of binding, the stability constant K is relatively large. In the absence of external factors (pH or temperature, etc.), 3.67<lgK<13.87, a stable chelate can be formed. With the addition of ferrocyanide alkali metal salt solution, the chelate is stable and the chelated transition metal ions will not be quickly released to react with ferrocyanide ions, thereby controlling the crystallization rate of Prussian blue analogs and reducing [Fe(CN) 6] The generation of vacancies reduces the defect rate of the crystal structure, completes the crystal form, and improves the structural stability of the Prussian blue analog material, thereby improving the capacity and cycle performance of the Prussian blue analog material; in addition, the chelating ability of this type of chelating agent is moderate, which can ensure the formation of a stable chelate without causing the chelate to be too stable due to excessive chelating ability, making the release of transition metal ions difficult, and affecting the generation of Prussian blue analogs.

[0016] As a preferred technical solution of the present invention, the chelating agent includes any one of methylglycine diacetic acid, trisodium methylglycine diacetate, ethylenediamine disuccinic acid, trisodium ethylenediamine disuccinate, tetrasodium glutamate diacetate, iminodisuccinic acid, tetrasodium iminodisuccinate or 3,3,3-nitrilotripropionic acid, or a combination of at least two thereof.

[0017] As a preferred technical solution of the present invention, the transition metal in the transition metal salt includes any one of V, Fe, Mn, Co, Ni, Cu or Zn, or a combination of at least two of them.

[0018] Preferably, the transition metal salt includes any one of acetate, fluoride, chloride, iodide, nitrate, sulfate or carbonate, or a combination of at least two thereof.

[0019] Preferably, the solvent comprises deionized water.

[0020] As a preferred technical solution of the present invention, the alkali metal ferrocyanide solution includes an alkali metal ferrocyanide salt and deionized water.

[0021] Preferably, the alkali metal ferrocyanide salt comprises potassium ferrocyanide or sodium ferrocyanide.

[0022] Preferably, the molar ratio of the transition metal salt, the chelating agent and the alkali metal ferrocyanide is (1-2):(0.25-5):(1-2), for example, 1:0.25:1, 1:0.5:1, 1:0.5:2, 1:1:1.5, 1:0.5:1.25, 1.5:1:2, 1:2.5:1, 1:2.5:0.5 or 1:5:1, etc.

[0023] In the present invention, a small amount of chelating agent can achieve the corresponding chelating effect, and the effect is more significant, while also reducing the production cost and avoiding the waste of resources.

[0024] Preferably, the concentration of the transition metal mixed solution is 0.01 mol / L-10 mol / L, for example, 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 3 mol / L, 5 mol / L, 8 mol / L or 10 mol / L.

[0025] Preferably, the concentration of the alkali metal ferrocyanide solution is 0.01 mol / L-10 mol / L, for example, 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 3 mol / L, 5 mol / L, 8 mol / L or 10 mol / L.

[0026] As a preferred technical solution of the present invention, the mixed reaction comprises: under stirring conditions, adding the transition metal mixed solution dropwise to the alkali metal ferrocyanide salt solution for reaction.

[0027] Preferably, the stirring rate is 400 rpm-1500 rpm, for example, 400 rpm, 600 rpm, 800 rpm, 1000 rpm, 1200 rpm, 1400 rpm or 1500 rpm, etc.

[0028] Preferably, the dripping flow rate is 0.1 mL / min-1000 mL / min, for example 0.1 mL / min, 1 mL / min, 10 mL / min, 50 mL / min, 100 mL / min, 300 mL / min, 500 mL / min, 800 mL / min or 1000 mL / min, etc.

[0029] Preferably, the reaction temperature is 20°C-90°C, for example, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C or 90°C.

[0030] Preferably, the reaction time is 0.5 h-12 h, for example 0.5 h, 1 h, 2 h, 4 h, 6 h, 8 h, 10 h or 12 h.

[0031] Preferably, the aging time is 12h-48h, for example 12h, 18h, 24h, 30h, 36h, 42h or 48h.

[0032] As a preferred technical solution of the present invention, after the aging, the method further includes sequentially subjecting the aged suspension to solid-liquid separation, washing and drying.

[0033] Preferably, the solid-liquid separation comprises centrifugation.

[0034] Preferably, the rotation speed of the centrifugal treatment is 8000 rpm-15000 rpm, for example, 8000 rpm, 10000 rpm, 12000 rpm, 14000 rpm or 15000 rpm.

[0035] Preferably, the centrifugal treatment time is 5 min-10 min, for example, 5 min, 6 min, 7 min, 8 min, 9 min or 10 min.

[0036] Preferably, the washing comprises washing with anhydrous ethanol and deionized water in sequence.

[0037] Preferably, the drying comprises vacuum drying.

[0038] Preferably, the vacuum drying temperature is 60°C-150°C, for example 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, etc.

[0039] Preferably, the vacuum degree of the vacuum drying is 80Pa-120Pa, for example, 80Pa, 90Pa, 100Pa, 110Pa or 120Pa.

[0040] Preferably, the vacuum drying time is 6 h to 24 h, for example, 6 h, 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h or 24 h.

[0041] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0042] Under the condition of a stirring rate of 400rpm-1500rpm, a transition metal mixed solution with a concentration of 0.01mol / L-10mol / L, including a transition metal salt, a chelating agent and deionized water, is added dropwise at a rate of 0.1mL / min-1000mL / min to a ferrocyanide alkali metal salt solution with a concentration of 0.01-10mol / L, and the reaction is carried out at 20°C-90°C for 0.5h-12h. After aging for 12h-48h, the resulting suspension is centrifuged at 8000rpm-15000rpm for 5min-10min, washed with anhydrous ethanol and deionized water in turn, and vacuum dried at a vacuum degree of 80Pa-120Pa and 60°C-150°C for 6h-24h to obtain a Prussian blue analog material;

[0043] The chelating agent comprises a nitrogen functional group and a carboxyl group, the number of the nitrogen functional groups is 0<M≤2, and the number of the carboxyl groups is 3≤N≤6; the chelating agent comprises any one of methylglycine diacetic acid, trisodium methylglycine diacetate, ethylenediamine disuccinic acid, trisodium ethylenediamine disuccinate, tetrasodium glutamate diacetate, iminodisuccinic acid, tetrasodium iminodisuccinate or 3,3,3-nitrilotripropionic acid, or a combination of at least two thereof; the alkali metal ferrocyanide solution comprises an alkali metal ferrocyanide and deionized water; the molar ratio of the transition metal salt, the chelating agent and the alkali metal ferrocyanide is (1-2):(0.25-5):(1-2).

[0044] In a second aspect, the present invention further provides a Prussian blue analog material, which is prepared according to the preparation method described in the first aspect.

[0045] As a preferred technical solution of the present invention, the chemical formula of the Prussian blue analog material is M[Fe(CN) 6 ].

[0046] Preferably, the M includes any one of V, Fe, Mn, Co, Ni, Cu or Zn, or a combination of at least two thereof.

[0047] In a third aspect, the present invention further provides an aqueous zinc ion battery, comprising a Prussian blue analogue material prepared by the preparation method described in the first aspect, or a Prussian blue analogue material described in the second aspect.

[0048] Compared with the prior art, the present invention has at least the following beneficial effects:

[0049] 1) The chelating agent used in the present invention can form a stable chelate with the transition metal ion. With the addition of the alkali metal ferrocyanide salt solution, the chelated transition metal ion is slowly released from the chelate, the crystallization rate of the Prussian blue analogue is reduced, and the defect rate of the internal crystal structure of the material is reduced, the crystal form is complete, and the capacity and cycle performance of the material are improved.

[0050] 2) The chelating agent used in the present invention only needs a small amount to achieve the corresponding chelating effect, and the effect is more significant, while also reducing the production cost and avoiding the waste of resources.

[0051] 3) The preparation process of the present invention is simple and easy to control, and the prepared Prussian blue analog material is used to assemble an aqueous zinc ion battery with high capacity and good cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 1 is the XRD pattern of the Prussian blue analogue material prepared in Example 1 of the present invention.

[0053] Figure 2 This is a SEM image of the Prussian blue analog material prepared in Example 1 of the present invention.

[0054] Figure 3 This is a first cycle charge and discharge capacity-voltage curve of an aqueous zinc ion battery at 0.5C current in Application Example 1 of the present invention.

[0055] Figure 4 This is a rate performance diagram of an aqueous zinc ion battery in Application Example 1 of the present invention at different current densities. DETAILED DESCRIPTION

[0056] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0057] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0058] Example 1

[0059] This embodiment provides a method for preparing a Prussian blue analog material, the preparation method comprising the following steps:

[0060] Dissolve manganese sulfate monohydrate and methylglycine diacetic acid in deionized water to obtain a transition metal mixed solution with a concentration of 0.05 mol / L, and dissolve potassium ferrocyanide in deionized water, and continuously stir to form a potassium ferrocyanide solution with a concentration of 0.05 mol / L after complete dissolution, wherein the molar ratio of manganese sulfate monohydrate, methylglycine diacetic acid and potassium ferrocyanide is 1:0.5:1;

[0061] Using a titration tool, under magnetic stirring at a speed of 800 rpm, the transition metal mixed solution was added dropwise to the potassium ferrocyanide solution at a rate of 1 mL / min, and the reaction was carried out at 25°C for 4 hours. After being aged for 24 hours, the resulting suspension with precipitate was centrifuged at a speed of 10,000 rpm for 10 minutes using a centrifuge. The precipitate was washed three times with deionized water and anhydrous ethanol respectively, and vacuum dried at 100 Pa and 80°C for 12 hours to obtain a Prussian blue analog material.

[0062] Figure 1 The XRD pattern of the Prussian blue analog material prepared in this example is shown. It can be seen from the figure that the purity and crystallinity of the Prussian blue analog material are both high, and there is no impurity peak.

[0063] Figure 2The SEM image of the Prussian blue analog material prepared in this example is shown. It can be seen from the image that the Prussian blue analog material is a cubic structure with clear edges and corners, a smooth surface, and no obvious defects.

[0064] Example 2

[0065] This embodiment provides a method for preparing a Prussian blue analog material, the preparation method comprising the following steps:

[0066] Dissolve manganese sulfate monohydrate and trisodium methylglycine diacetate in deionized water to obtain a transition metal mixed solution with a concentration of 10 mol / L, and dissolve potassium ferrocyanide in deionized water, and continuously stir to form a potassium ferrocyanide solution with a concentration of 10 mol / L after complete dissolution, wherein the molar ratio of manganese sulfate monohydrate, trisodium methylglycine diacetate and potassium ferrocyanide is 1:0.75:1;

[0067] Using a titration tool, under magnetic stirring at a speed of 400 rpm, the transition metal mixed solution was added dropwise to the potassium ferrocyanide solution at a rate of 5 mL / min, and the reaction was carried out at 20°C for 12 hours. After being aged for 48 hours, the resulting suspension with precipitate was centrifuged at a speed of 10,000 rpm for 10 minutes using a centrifuge. The precipitate was washed three times with deionized water and anhydrous ethanol respectively, and vacuum dried at 120 Pa and 60°C for 24 hours to obtain a Prussian blue analog material.

[0068] Example 3

[0069] This embodiment provides a method for preparing a Prussian blue analog material, the preparation method comprising the following steps:

[0070] Dissolving manganese sulfate monohydrate and ethylenediamine disuccinic acid in deionized water to obtain a transition metal mixed solution with a concentration of 5 mol / L, dissolving potassium ferrocyanide in deionized water, and continuously stirring to form a potassium ferrocyanide solution with a concentration of 5 mol / L after complete dissolution, wherein the molar ratio of manganese sulfate monohydrate, ethylenediamine disuccinic acid and potassium ferrocyanide is 1:0.9:2;

[0071] Using a titration tool, under magnetic stirring at a speed of 1500 rpm, the transition metal mixed solution was added dropwise to the potassium ferrocyanide solution at a rate of 100 mL / min, and the mixture was reacted at 90°C for 0.5 h. The mixture was allowed to stand for 12 h, and the resulting suspension with precipitate was centrifuged at a speed of 10000 rpm for 10 min. The precipitate was washed three times with deionized water and anhydrous ethanol respectively, and vacuum dried at 80 Pa and 150°C for 6 h to obtain a Prussian blue analog material.

[0072] Example 4

[0073] This example provides a method for preparing a Prussian blue analog material. The difference between the preparation method and Example 1 is that the chelating agent is trisodium ethylenediamine disuccinate in an equimolar amount, and the other preparation methods and parameters are consistent with those in Example 1.

[0074] Example 5

[0075] This example provides a method for preparing a Prussian blue analog material. The difference between the preparation method and Example 1 is that the chelating agent is an equimolar amount of tetrasodium glutamate diacetate, and the other preparation methods and parameters are consistent with Example 1.

[0076] Example 6

[0077] This example provides a method for preparing a Prussian blue analog material. The difference between the preparation method and Example 1 is that the chelating agent is an equimolar amount of iminodisuccinic acid, and the other preparation methods and parameters are consistent with Example 1.

[0078] Example 7

[0079] This example provides a method for preparing a Prussian blue analog material. The difference between the preparation method and Example 1 is that the chelating agent is an equimolar amount of tetrasodium iminodisuccinate, and the other preparation methods and parameters are consistent with Example 1.

[0080] Example 8

[0081] This embodiment provides a method for preparing a Prussian blue analog material. The difference between the preparation method and Example 1 is that the chelating agent is an equimolar amount of 3,3,3-nitrilotripropionic acid, and the rest of the preparation method and parameters are consistent with Example 1.

[0082] Example 9

[0083] This embodiment provides a method for preparing a Prussian blue analog material. The difference between the preparation method and Example 1 is that the molar ratio of manganese sulfate monohydrate, methylglycine diacetic acid and potassium ferrocyanide is 1:6:1; the other preparation methods and parameters are consistent with Example 1.

[0084] Example 10

[0085] This embodiment provides a method for preparing a Prussian blue analog material. The difference between the preparation method and Example 1 is that manganese sulfate monohydrate is replaced by an equimolar amount of vanadyl sulfate dihydrate, and the rest of the preparation method and parameters are consistent with Example 1.

[0086] Embodiment 11

[0087] This example provides a method for preparing a Prussian blue analog material. The difference between the preparation method and Example 1 is that manganese sulfate monohydrate is replaced by an equimolar amount of cobalt sulfate heptahydrate, and the rest of the preparation method and parameters are consistent with Example 1.

[0088] Comparative Example 1

[0089] This comparative example provides a method for preparing a Prussian blue analog material. The difference between the preparation method and Example 1 is that the chelating agent is citric acid, the molar ratio of manganese sulfate monohydrate, citric acid and potassium ferrocyanide is 1:10:1, and the other preparation methods and parameters are consistent with Example 1.

[0090] Comparative Example 2

[0091] This comparative example provides a method for preparing a Prussian blue analog material. The difference between the preparation method and Example 1 is that the chelating agent is glutamic acid in an equimolar amount, and the other preparation methods and parameters are consistent with those in Example 1.

[0092] Comparative Example 3

[0093] This comparative example provides a method for preparing a Prussian blue analog material. The difference between the preparation method and Example 1 is that the chelating agent is an equimolar amount of diethyltriaminepentaacetic acid, and the other preparation methods and parameters are consistent with Example 1.

[0094] Comparative Example 4

[0095] This comparative example provides a method for preparing a Prussian blue analog material. The difference between the preparation method and Example 1 is that the chelating agent is an equimolar amount of aminotrimethylenephosphonic acid, and the other preparation methods and parameters are consistent with Example 1.

[0096] Application Example 1

[0097] The Prussian blue analog material prepared in Example 1, the conductive agent Super P, and the binder sodium carboxymethyl cellulose were mixed and ground in a mass fraction of 7:2:1 for 30 minutes, an appropriate amount of deionized water was added, and the mixture was dispersed and stirred for 12 hours to prepare a uniformly dispersed electrode slurry, which was then coated on carbon paper, placed in a vacuum drying oven at 80° C. and vacuum dried for 12 hours, and then cut into discs with a diameter of 10 mm to obtain a positive electrode sheet; a zinc sheet with a diameter of 12 mm and a thickness of 50 μm was used as a negative electrode, GFA was used as a separator, and 70 μL of a 3 mol / L aqueous solution of zinc trifluoromethanesulfonate was used as an electrolyte to assemble a CR2032 button cell to obtain an aqueous zinc ion battery.

[0098] Application Example 2-11 and Comparative Application Example 1-4

[0099] The Prussian blue analogue materials prepared in Examples 2-11 and Comparative Examples 1-4 were assembled into CR2032 button batteries in the same manner as in Application Example 1 to obtain aqueous zinc ion batteries, corresponding to Application Examples 2-11 and Comparative Application Examples 1-4, respectively.

[0100] The aqueous zinc ion batteries of Application Examples 1-11 and Comparative Application Examples 1-4 were placed on the Blue Battery Test System and the electrochemical workstation for constant current charge and discharge performance tests and cyclic voltammetry curve tests. The voltage range was relative to Zn / Zn 2+ Set to 1.1-2.0V, the specific test data is shown in Table 1.

[0101] Figure 3 The first cycle charge and discharge capacity-voltage curve of the aqueous zinc ion battery of Application Example 1 of the present invention at 0.5C current is shown. It can be seen from the figure that the discharge specific capacity of the Prussian blue analog material is 138.0 mAh / g.

[0102] Figure 4 The figure shows the rate performance diagram of the aqueous zinc ion battery of Application Example 1 of the present invention at different current densities. It can be seen from the figure that the Prussian blue analogue material obtains maximum discharge specific capacities of 138.0mAh / g, 125.7mAh / g, 115.3mAh / g, 109.8mAh / g, 105.4mAh / g, 101.2mAh / g, 98.6mAh / g and 136.5mAh / g at currents of 0.5C, 1C, 2C, 4C, 6C, 8C, 10C and 0.5C, respectively, and has good rate performance.

[0103] Table 1

[0104]

[0105] The test results show that:

[0106] (1) It can be seen from Application Examples 1 to 11 that the chelating agent used in the present invention, which includes nitrogen-based functional groups with a number of 0<M≤2 and carboxyl groups with a number of 3≤N≤6, can form a stable chelate with transition metal ions. With the addition of alkali metal ferrocyanide salt solution, the chelated transition metal ions are slowly released from the chelate, the crystallization rate of the Prussian blue analogue is reduced, and the defect rate of the internal crystal structure of the material is reduced, the crystal form is complete, and the capacity and cycle performance of the material are improved.

[0107] Furthermore, when the prepared manganese-based Prussian blue analogue is used as the positive electrode material, the 0.5C first-cycle discharge specific capacity of the aqueous zinc ion battery is above 130 mAh / g, and the capacity retention rate after 100 cycles at 0.5C is above 80%; when the prepared vanadium-based Prussian blue analogue is used as the positive electrode material, the 0.5C first-cycle discharge specific capacity of the aqueous zinc ion battery can also reach 168.5 mAh / g, and the capacity retention rate after 100 cycles at 0.5C can also reach 47.75%; when the prepared cobalt-based Prussian blue analogue is used as the positive electrode material, the 0.5C first-cycle discharge specific capacity of the aqueous zinc ion battery can also reach 79.1 mAh / g, and the capacity retention rate after 100 cycles at 0.5C can also reach 75.47%.

[0108] Furthermore, it can be seen from Application Examples 1 and 9 that only a small amount of the chelating agent used in the present invention is needed to achieve the corresponding chelating effect, and the effect is more significant. At the same time, the production cost is also reduced and the waste of resources is avoided. Even if too much chelating agent is added, the performance will not be further improved, but part of the capacity may be sacrificed.

[0109] (2) It can be seen from Application Example 1 and Comparative Application Example 1 that when citric acid is used as a chelating agent, its chelating ability is very weak because there are only three carboxyl groups in the structural formula of citric acid and it lacks a nitrogen-based functional group with stronger electronegativity. Even if an excess of citric acid is added, the capacity and cycle performance of the aqueous zinc ion battery assembled from the prepared Prussian blue analog material will be significantly reduced.

[0110] (3) It can be seen from Application Example 1 and Comparative Application Examples 2-4 that when the present invention does not use a chelating agent including nitrogen-based functional groups with a number of 0<M≤2 and a number of carboxyl groups with a number of 3≤N≤6 or uses a chelating agent that does not contain a carboxyl group, the chelating ability of the chelating agent is significantly reduced or the chelating ability is too strong, thereby affecting the structure of the Prussian blue analog material, and further affecting the capacity and cycle performance of the aqueous zinc ion battery.

[0111] In summary, the chelating agent used in the present invention includes a nitrogen-based functional group and a carboxyl group, the number of the nitrogen-based functional groups is 0<M≤2, and the number of the carboxyl groups is 3≤N≤6. This type of chelating agent can form a stable chelate with transition metal ions. With the addition of an alkali metal ferrocyanide salt solution, the chelated transition metal ions are slowly released from the chelate, the crystallization rate of the Prussian blue analogue is reduced, and the defect rate of the internal crystal structure of the Prussian blue analogue material is reduced, the crystal form is complete, and the capacity and cycle performance of the material are improved; in addition, a small amount can achieve the corresponding chelating effect, and the effect is more significant, thereby reducing the production cost.

[0112] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a Prussian blue analog material, characterized in that: The preparation method comprises the following steps: The transition metal mixed solution is mixed with the alkali metal ferrocyanide salt solution for reaction, and then aged to obtain a Prussian blue analog material; Wherein, the transition metal mixed solution comprises a transition metal salt, a chelating agent and a solvent; The chelating agent comprises nitrogen-based functional groups and carboxyl groups, the number of the nitrogen-based functional groups is 0<M≤2, and the number of the carboxyl groups is 3≤N≤6.

2. The preparation method according to claim 1, characterized in that: The chelating agent includes any one of methylglycine diacetic acid, methylglycine diacetic acid trisodium, ethylenediamine disuccinic acid, ethylenediamine disuccinic acid trisodium, glutamate diacetic acid tetrasodium, iminodisuccinic acid, iminodisuccinic acid tetrasodium or 3,3,3-nitrilotripropionic acid or a combination of at least two thereof.

3. The preparation method according to claim 1 or 2, characterized in that: The transition metal in the transition metal salt includes any one of V, Fe, Mn, Co, Ni, Cu or Zn, or a combination of at least two thereof.

4. The preparation method according to any one of claims 1 to 3, characterized in that The alkali metal ferrocyanide solution comprises an alkali metal ferrocyanide salt and deionized water; Preferably, the alkali metal ferrocyanide salt comprises potassium ferrocyanide or sodium ferrocyanide; Preferably, the molar ratio of the transition metal salt, the chelating agent and the alkali metal ferrocyanide salt is (1-2):(0.25-5):(1-2); Preferably, the concentration of the transition metal mixed solution is 0.01 mol / L-10 mol / L; Preferably, the concentration of the alkali metal ferrocyanide solution is 0.01 mol / L-10 mol / L.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The mixed reaction comprises: under stirring conditions, dropping the transition metal mixed solution into the ferrocyanide alkali metal salt solution for reaction.

6. The preparation method according to any one of claims 1 to 5, characterized in that: After the aging, the method further includes sequentially performing solid-liquid separation, washing and drying on the aged suspension.

7. The preparation method according to claim 1, characterized in that: The preparation method comprises the following steps: Under the condition of a stirring rate of 400rpm-1500rpm, a transition metal mixed solution with a concentration of 0.01mol / L-10mol / L, including a transition metal salt, a chelating agent and deionized water, is added dropwise at a rate of 0.1mL / min-1000mL / min to a ferrocyanide alkali metal salt solution with a concentration of 0.01-10mol / L, and the mixture is reacted at 20°C-90°C for 0.5h-12h, aged for 12h-48h, and the resulting suspension is centrifuged at 8000rpm-15000rpm for 5min-10min, washed with anhydrous ethanol and deionized water in turn, and vacuum dried at a vacuum degree of 80Pa-120Pa and 60°C-150°C for 6h-24h to obtain a Prussian blue analog material; The chelating agent comprises a nitrogen functional group and a carboxyl group, the number of the nitrogen functional groups is 0<M≤2, and the number of the carboxyl groups is 3≤N≤6; the chelating agent comprises any one of methylglycine diacetic acid, trisodium methylglycine diacetate, ethylenediamine disuccinic acid, trisodium ethylenediamine disuccinate, tetrasodium glutamate diacetate, iminodisuccinic acid, tetrasodium iminodisuccinate or 3,3,3-nitrilotripropionic acid, or a combination of at least two thereof; the alkali metal ferrocyanide solution comprises an alkali metal ferrocyanide and deionized water; the molar ratio of the transition metal salt, the chelating agent and the alkali metal ferrocyanide is (1-2):(0.25-5):(1-2).

8. A Prussian blue analog material, characterized in that: The Prussian blue analog material is prepared according to the preparation method according to any one of claims 1-7.

9. The Prussian blue analog material according to claim 8, characterized in that The chemical formula of the Prussian blue analog material is M[Fe(CN)6]; Preferably, the M includes any one of V, Fe, Mn, Co, Ni, Cu or Zn, or a combination of at least two thereof.

10. An aqueous zinc ion battery, characterized in that: The aqueous zinc ion battery comprises a Prussian blue analog material prepared by the preparation method according to any one of claims 1 to 7, or a Prussian blue analog material according to claim 8 or 9.

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