Prussian blue-based positive electrode material and preparation method and application thereof

Abstract

The application provides a Prussian blue type positive electrode material and a preparation method and application thereof, and belongs to the technical field of sodium ion batteries. The disclosure removes crystal water of the Prussian blue material by vacuum freeze drying to form cavities and defects; meanwhile, the cavities and defects are filled and repaired by cations of a repairing agent, such as sodium ions, potassium ions and transition metal ions, so that the risk of rewater absorption of the Prussian blue type positive electrode material in the process of transportation and preparation of a positive electrode sheet is reduced, and the specific capacity and cycle stability of the Prussian blue type positive electrode material are improved.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of sodium ion batteries, in particular to a Prussian blue type positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] Sodium ion batteries are ideal large-scale energy storage technologies due to the wide availability and low cost of raw materials. Sodium ion secondary batteries have similar working principles to lithium ion secondary batteries, and based on existing lithium ion battery technology, sodium ion secondary batteries can be quickly developed.

[0003] Prussian blue analog materials have excellent theoretical specific capacity, high voltage platform, and open framework structure, which can provide a fast diffusion channel for sodium ions. In addition, such materials have the advantages of simple synthesis process, easy scaling up, low cost of raw materials and preparation, etc., and are ideal positive electrode materials for sodium ion batteries. The synthesis process of Prussian blue usually uses the coprecipitation method, which inevitably introduces crystallization water during the synthesis process. Although various means have been reported to reduce the crystallization water content of the material, such as using complexing agents, controlling the reaction environment, etc., the effect is not ideal, and the specific capacity is still far from the theoretical maximum capacity of 170 mAh / g. In addition, due to the water absorption of Prussian blue materials, water is still introduced during use. The presence of crystallization water will occupy active sites on the one hand, reducing the capacity of the electrode material. On the other hand, it will be decomposed and released during the battery cycle, causing the cycle performance of the battery to decrease and produce gas.

[0004] The patent CN2022109277207 provides a hydroxyethylidene diphosphonate salt with high complexing constant as a chelating agent, which slowly releases transition metal through complexation, controls the crystal growth rate, and reduces the crystallization water content in the material. However, there is still crystallization water in the material, and the specific capacity is 130 mAh / g. The effect is not ideal. SUMMARY

[0005] The present disclosure aims to overcome the shortcomings of the prior art and provide a Prussian blue type positive electrode material and a preparation method and application thereof. The Prussian blue type positive electrode material has a low crystallization water content, and the prepared sodium ion battery has excellent specific capacity and cycle stability.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present disclosure is as follows: In a first aspect, the present disclosure provides a preparation method of a Prussian blue type positive electrode material, comprising the following steps:

[0007] adding a repairing agent to a first solvent and stirring uniformly to obtain a first solution;

[0008] adding a Prussian blue material to the first solution and stirring uniformly, and vacuum freeze-drying and washing the obtained second solution to obtain a Prussian blue type positive electrode material;

[0009] The repairing agent is at least one of a sodium salt, a potassium salt, and a transition metal salt.

[0010] The first solvent is a mixture of water and an organic solvent, and the volume of the organic solvent is 20-99% of the volume of the first solvent. The organic solvent is at least one of ethylene glycol, glycerol, and dimethyl sulfoxide.

[0011] In the present application, the volume of the organic solvent can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 99% of the volume of the first solvent. The present application is not limited thereto, and preferably, the volume of the organic solvent is 52-84% of the volume of the first solvent.

[0012] The present disclosure removes the crystal water at the A and P sites of the Prussian blue material by vacuum freeze-drying to form cavities and defects; at the same time, the cavities and defects are filled and repaired by the cations (such as sodium ions, potassium ions, and transition metal ions) of the repairing agent, thereby reducing the risk of rehydration of the Prussian blue-based positive electrode material during transportation and preparation of the positive electrode sheet, and improving the specific capacity and cycle stability of the Prussian blue-based positive electrode material. The type of the organic solvent and the volume content of the organic solvent in the first solvent are the main key factors affecting the filling and repairing of the repairing agent. When the volume content of the organic solvent in the first solvent is too low, the cations (such as sodium ions, potassium ions, and transition metal ions) in the repairing agent cannot effectively move to fill and repair the cavities and defects, resulting in a decrease in the specific capacity and cycle stability of the Prussian blue-based positive electrode material. If the volume content of the organic solvent in the first solvent is too high, the repairing agent cannot be dissolved, and the repairing effect cannot be achieved. Preferably, the volume of the organic solvent is 52-84% of the volume of the first solvent, so as to obtain a Prussian blue-based positive electrode material with a low water content and improve the specific capacity and cycle stability of the Prussian blue-based positive electrode material.

[0013] In an embodiment, the sodium salt is at least one of sodium chloride, sodium sulfate, sodium nitrate, and sodium perchlorate.

[0014] In an embodiment, the potassium salt is at least one of potassium chloride and potassium sulfate.

[0015] In an embodiment, the transition metal salt is at least one of a transition metal nitrate, a transition metal acetate, and a transition metal sulfate; preferably, the metal ion in the transition metal salt is at least one of iron, manganese, nickel, copper, and zinc; and preferably, the transition metal salt is at least one of ferrous sulfate, nickel sulfate, copper chloride, zinc sulfate, and manganese sulfate.

[0016] The application avoids mixing of metal ions irrelevant to the Prussian blue type positive electrode material by selecting the types of sodium salt, potassium salt and transition metal salt, thereby improving the purity and integrity of the Prussian blue type positive electrode material and reducing the crystal water of the Prussian blue type positive electrode material.

[0017] In one embodiment, the molar concentration of the repairing agent in the first solution is 0.01-10 mol / L.

[0018] In the application, the molar concentration of the repairing agent in the first solution can be, but is not limited to, 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, 3.5 mol / L, 4.0 mol / L, 4.5 mol / L, 5.0 mol / L, 5.5 mol / L, 6.0 mol / L, 6.5 mol / L, 7.0 mol / L, 7.5 mol / L, 8.0 mol / L, 8.5 mol / L, 9.0 mol / L, 9.5 mol / L, 10.0 mol / L.

[0019] The application controls the molar concentration of the repairing agent, which is conducive to improving the migration of cations (such as sodium ions, potassium ions and transition metal ions) in the repairing agent, improving the filling and repairing effect of the repairing agent, further reducing the crystal water of the Prussian blue type positive electrode material and improving the specific capacity and cycle stability of the Prussian blue type positive electrode material.

[0020] Preferably, the molar concentration of the sodium salt in the first solution is 0.01-10 mol / L, preferably 0.1-1 mol / L.

[0021] Preferably, the molar concentration of the potassium salt in the first solution is 0.01-6 mol / L, preferably 0.1-1 mol / L.

[0022] Preferably, the molar concentration of the transition metal salt in the first solution is 0.01-5 mol / L, preferably 0.1-0.8 mol / L.

[0023] In one embodiment, the structural formula of the Prussian blue material is A x P y [R(CN)6] z ·nH2O, wherein 0≤x≤2, 0

[0024] In one embodiment, the vacuum freeze-drying is performed under the following conditions: temperature of 0-(-100)℃, pressure of 0-101kPa, and time of 0.5-168h.

[0025] Preferably, the vacuum freeze-drying is performed under the following conditions: temperature of (-30)-(-60)℃, pressure of 0-5Pa, and time of 4-48h.

[0026] The vacuum freeze-drying performed under the above conditions can effectively reduce the crystal water of the Prussian blue-based positive electrode material and improve the specific capacity and cycle stability of the Prussian blue-based positive electrode material.

[0027] In the present application, the stirring time for forming the first solution of the repairing agent is not particularly limited, as long as the repairing agent is completely dissolved.

[0028] In the present application, the stirring time for forming the second solution of the Prussian blue material is not particularly limited, as long as the Prussian blue material is uniformly dispersed, and the preferred stirring time is 0.5-48h, and further preferably 2-6h.

[0029] In a second aspect, a Prussian blue-based positive electrode material is provided, which is prepared by the above-mentioned method for preparing a Prussian blue-based positive electrode material.

[0030] In a third aspect, a sodium ion battery is provided, which comprises the Prussian blue-based positive electrode material.

[0031] Compared with the prior art, the present disclosure has the following beneficial effects: the present disclosure uses vacuum freeze-drying to remove the crystal water at the A and P sites of the Prussian blue material, forming vacancies and defects; at the same time, the vacancies and defects are filled and repaired by the cations (such as sodium ions, potassium ions, transition metal ions) of the repairing agent, reducing the risk of rewatering of the Prussian blue-based positive electrode material during transportation and preparation of the positive electrode sheet, and improving the specific capacity and cycle stability of the Prussian blue-based positive electrode material. DETAILED DESCRIPTION

[0032] In order to better illustrate the purpose, technical scheme and advantages of the present disclosure, the present disclosure will be further described below in combination with specific examples and comparative examples, the purpose of which is to understand the content of the present disclosure in detail, rather than to limit the present disclosure. All other examples obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present disclosure. The experimental reagents and instruments involved in the implementation of the present disclosure are all common ordinary reagents and instruments unless otherwise specified.

[0033] Example 1

[0034] The present embodiment provides a method for preparing a Prussian blue-based positive electrode material, which comprises the following steps:

[0035] 0.02 mol of sodium chloride was added into 200 mL of a first solvent, stirred for 1 h to obtain a first solution; the first solvent was a mixture of deionized water and ethylene glycol, and the volume of ethylene glycol was 66% of the volume of the first solvent;

[0036] 5 g of Prussian blue material Na 1.6 FeFe[(CN)6]·4.2H2O was added into the first solution, stirred and dispersed for 1 h, and the obtained second solution was placed in a freeze dryer for vacuum freeze drying under the following conditions: a temperature of -40℃, a vacuum degree of 3 Pa, and a time of 24 h; the material obtained by vacuum freeze drying was sequentially washed with water and ethanol to obtain a Prussian blue type positive electrode material.

[0037] Example 2

[0038] The embodiment provides a preparation method of a Prussian blue type positive electrode material, and the method comprises the following steps:

[0039] 0.02 mol of potassium sulfate was added into 200 mL of a first solvent, stirred for 1 h to obtain a first solution; the first solvent was a mixture of deionized water and ethylene glycol, and the volume of ethylene glycol was 66% of the volume of the first solvent;

[0040] 5 g of Prussian blue material Na 1.4 FeFe[(CN)6]·3.8H2O was added into the first solution, stirred and dispersed for 1 h, and the obtained second solution was placed in a freeze dryer for vacuum freeze drying under the following conditions: a temperature of -40℃, a vacuum degree of 3 Pa, and a time of 48 h; the material obtained by vacuum freeze drying was sequentially washed with water and ethanol to obtain a Prussian blue type positive electrode material.

[0041] Example 3

[0042] The embodiment provides a preparation method of a Prussian blue type positive electrode material, and the method comprises the following steps:

[0043] 0.02 mol of sodium chloride was added into 200 mL of a first solvent, stirred for 1 h to obtain a first solution; the first solvent was a mixture of deionized water and ethylene glycol, and the volume of ethylene glycol was 61% of the volume of the first solvent;

[0044] 5 g of Prussian blue material Na 1.2 FeFe[(CN)6]·4.2H2O was added into the first solution, stirred and dispersed for 1 h, and the obtained second solution was placed in a freeze dryer for vacuum freeze drying under the following conditions: a temperature of -55℃, a vacuum degree of 1 Pa, and a time of 24 h; the material obtained by vacuum freeze drying was sequentially washed with water and ethanol to obtain a Prussian blue type positive electrode material.

[0045] Example 4

[0046] The embodiment provides a preparation method of a Prussian blue type positive electrode material, and the preparation method comprises the following steps:

[0047] 0.02 mol of sodium chloride and 0.01 mol of zinc chloride are added into 200 mL of a first solvent, and stirring is conducted for 1 h to obtain a first solution; the first solvent is a mixture of deionized water and ethylene glycol, and the volume of the ethylene glycol accounts for 66% of the volume of the first solvent;

[0048] 5 g of Prussian blue material Na 1.2 Fe 0.91 Fe[(CN)6]·4.2H2O is added into the first solution, stirring and dispersing are conducted for 1 h, the obtained second solution is placed in a freeze dryer for vacuum freeze drying, the vacuum freeze drying is conducted under the following conditions: the temperature is -40 DEG C, the vacuum degree is 1 Pa, and the time is 48 h; the material obtained through the vacuum freeze drying is sequentially washed by using water and ethanol to obtain the Prussian blue type positive electrode material.

[0049] Example 5

[0050] The embodiment provides a preparation method of a Prussian blue type positive electrode material, and the preparation method comprises the following steps:

[0051] 0.02 mol of sodium chloride and 0.01 mol of ferrous sulfate are added into 200 mL of a first solvent, and stirring is conducted for 1 h to obtain a first solution; the first solvent is a mixture of deionized water and ethylene glycol, and the volume of the ethylene glycol accounts for 66% of the volume of the first solvent;

[0052] 5 g of Prussian blue material Na 1.6 Mn 0.94 Fe[(CN)6]·4.2H2O is added into the first solution, stirring and dispersing are conducted for 1 h, the obtained second solution is placed in a freeze dryer for vacuum freeze drying, the vacuum freeze drying is conducted under the following conditions: the temperature is -40 DEG C, the vacuum degree is 1 Pa, and the time is 48 h; the material obtained through the vacuum freeze drying is sequentially washed by using water and ethanol to obtain the Prussian blue type positive electrode material.

[0053] Example 6

[0054] The embodiment provides a preparation method of a Prussian blue type positive electrode material, and the preparation method comprises the following steps:

[0055] Example 7

[0056] The embodiment provides a preparation method of a Prussian blue type positive electrode material, and the preparation method of the Prussian blue type positive electrode material in the embodiment is different from that in the embodiment 1 only in that the volume of the ethylene glycol is 84% of the volume of the first solvent.

[0057] Embodiment 8

[0058] The embodiment provides a preparation method of a Prussian blue type positive electrode material, and the preparation method of the Prussian blue type positive electrode material in the embodiment is different from that in the embodiment 1 only in that the volume of the ethylene glycol is 20% of the volume of the first solvent.

[0059] Embodiment 9

[0060] The embodiment provides a preparation method of a Prussian blue type positive electrode material, and the preparation method of the Prussian blue type positive electrode material in the embodiment is different from that in the embodiment 1 only in that the volume of the ethylene glycol is 95% of the volume of the first solvent.

[0061] Embodiment 10

[0062] The embodiment provides a preparation method of a Prussian blue type positive electrode material, and the preparation method of the Prussian blue type positive electrode material in the embodiment is different from that in the embodiment 1 only in that the dimethyl sulfoxide is used instead of the ethylene glycol.

[0063] Comparative example 1

[0064] The comparative example provides a preparation method of a Prussian blue type positive electrode material, and the preparation method of the Prussian blue type positive electrode material in the comparative example is different from that in the embodiment 1 only in that the sodium chloride is not contained.

[0065] Comparative example 2

[0066] The comparative example provides a preparation method of a Prussian blue type positive electrode material, and the preparation method of the Prussian blue type positive electrode material in the comparative example is different from that in the embodiment 1 only in that the sodium chloride is not contained.

[0067] 5g of the Prussian blue material Na 1.6 FeFe[(CN)6]·4.2H2O is placed in a freeze dryer for vacuum freeze drying, and the vacuum freeze drying is carried out under the following conditions: the temperature is -40 DEG C, the vacuum degree is 3 Pa, and the time is 24 h; the material obtained by the vacuum freeze drying is washed with water and ethanol in sequence to obtain the Prussian blue type positive electrode material.

[0068] Comparative example 3

[0069] The comparative example provides a preparation method of a Prussian blue type positive electrode material, and the preparation method of the Prussian blue type positive electrode material in the comparative example is different from that in the embodiment 1 only in that the sodium chloride is not contained.

[0070] 0.02mol of sodium chloride is added into 200mL of a first solvent, and stirred for 1h to obtain a first solution; the first solvent is a mixture of deionized water and ethylene glycol, and the volume of the ethylene glycol is 66% of the volume of the first solvent.

[0071] To the first solution, 5 g of Prussian blue material Na 1.6 FeFe[(CN)6]·4.2H2O, stirring and dispersing for 1 h, the obtained second solution was dried at 60℃ for 24 h, the dried material was washed with water and ethanol in sequence to obtain the Prussian blue type positive electrode material.

[0072] Comparative Example 4

[0073] The present comparative example provides a preparation method of a Prussian blue type positive electrode material, comprising the following steps:

[0074] 0.02 mol of sodium chloride was added to 200 mL of deionized water, stirring for 1 h to obtain a first solution;

[0075] To the first solution, 5 g of Prussian blue material Na 1.6 FeFe[(CN)6]·4.2H2O, stirring and dispersing for 1 h, the obtained second solution was placed in a freeze dryer for vacuum freeze drying, the conditions of vacuum freeze drying were as follows: temperature was -40℃, vacuum degree was 3 Pa, and time was 24 h; the vacuum freeze-dried material was washed with water and ethanol in sequence to obtain the Prussian blue type positive electrode material.

[0076] Example 11

[0077] The present example tests the performance of the Prussian blue type positive electrode materials obtained in Examples 1-10 and Comparative Examples 1-4.

[0078] The Prussian blue type positive electrode materials obtained in Examples 1-10 and Comparative Examples 1-4 were respectively used as positive electrode materials, N-methyl pyrrolidone was used as a solvent, the positive electrode material, a conductive agent (Super P) and a binder polyvinylidene fluoride were mixed uniformly at a mass ratio of 7:2:1, and then uniformly coated on an aluminum foil into a thin layer, and then cut into a round piece after drying as a positive electrode material, a sodium metal sheet was used as a negative electrode, Whatman glass fiber was used as a separator, and 1.0 mol L NaPF6 / EC (ethylene carbonate) + PC (propylene carbonate) (the volume ratio of EC to PC was 1:1) was used as an electrolyte, and then CR2032 button cells were assembled in an argon glove box. The button cells were subjected to constant current charge and discharge test, the charge and discharge voltage interval was 2-4 V, and the current density was 0.1 C for continuous circulation for 200 cycles.

[0079] Table 1 shows the electrochemical performance of the batteries prepared from the Prussian blue type positive electrode materials prepared in Examples 1-10 and Comparative Examples 1-4.

[0080] Table 1

[0081]

[0082] From the performance test results of Table 1, it can be seen that the Prussian blue-based positive electrode material prepared in the application has excellent specific capacity and cycle stability.

[0083] From Comparative Example 1 and Examples 6-9, it can be seen that when the volume of the organic solvent is 52-84% of the volume of the first solvent, the obtained Prussian blue-based positive electrode material has higher specific capacity and cycle stability.

[0084] Finally, it should be noted that the above examples are used to illustrate the technical solutions of the present disclosure and are not a limitation on the protection scope of the present disclosure. Although the present disclosure has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present disclosure can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present disclosure.

Claims

1. A method for preparing a Prussian blue cathode material, characterized in that: The following steps are involved: Adding the repair agent to the first solvent and stirring evenly to obtain a first solution; Adding Prussian blue material to the first solution and stirring evenly, and performing vacuum freeze drying and washing on the obtained second solution to obtain a Prussian blue cathode material; Wherein, the repair agent is at least one of sodium salt, potassium salt, and transition metal salt; The first solvent is a mixture of water and an organic solvent, the volume of the organic solvent is 20-99% of the volume of the first solvent, and the organic solvent is at least one of ethylene glycol, glycerol, and dimethyl sulfoxide; The transition metal salt is at least one of transition metal nitrates, transition metal acetates, and transition metal sulfates; the transition metal includes at least one of iron, manganese, nickel, copper, zinc, chromium, vanadium, and cobalt.

2. The preparation method according to claim 1, wherein The volume of the organic solvent is 52-84% of the volume of the first solvent.

3. The preparation method according to claim 1, wherein The sodium salt is at least one of sodium chloride, sodium sulfate, sodium nitrate and sodium perchlorate.

4. The preparation method according to claim 1, wherein The potassium salt is at least one of potassium chloride and potassium sulfate.

5. The preparation method according to claim 1, wherein In the first solution, the molar concentration of the repair agent is 0.01-10 mol / L.

6. The preparation method according to claim 1, wherein The structural formula of the Prussian blue material is A x P y [R(CN)6] z nH2O, wherein 0≤x≤2, 0<y≤1, 0<z≤1, and 0<n≤4.5; A is an alkali metal element including at least one of lithium, sodium, and potassium; and P and R are transition metal elements including at least one of iron, manganese, nickel, copper, zinc, chromium, vanadium, and cobalt.

7. The preparation method according to claim 1, wherein The vacuum freeze-drying conditions are as follows: temperature of 0-(-100)°C, pressure of 0-101 kPa, and time of 0.5-168 h.

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

9. A sodium ion battery, characterized in that: The sodium ion battery comprises the Prussian blue-based positive electrode material according to claim 8.

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