A dehydration method for Prussian blue compounds

Abstract

The present invention provides a dehydration method for Prussian blue compounds, comprising the steps of: S1, drying the prepared Prussian blue compounds to remove free water therein; S2, mixing the Prussian blue compounds dried in step S1 with metal powders in a certain proportion and stirring evenly; S3, adding the powders stirred in step S2 to a ball mill, extracting a vacuum environment for ball milling; S4, transferring the material after ball milling in step S3 to a vacuum oven for heating and dehydration. The present invention allows unstable metal powders to react with water molecules in the crystal structure of the Prussian blue compounds during the ball milling process after mixing, so that the water that is difficult to remove in the Prussian blue compounds can be removed well, and the composite material finally obtained has a larger specific capacity, improves the electrical properties of the Prussian blue compounds, has a larger capacity during the charge and discharge process, and has a better cycle effect.

Description

Technical Field

[0001] The invention relates to the technical field of Prussian blue compounds, in particular to a dehydration method of Prussian blue compounds. Background Art

[0002] At present, the application of lithium-ion batteries in electric vehicles, 3C products, energy storage and other fields is growing rapidly, but the global available lithium resources are expected to be unable to meet the demand in the future, so it is necessary to find battery technologies that are not limited by resources. Sodium is abundant in the earth's crust and there is no limit to resource depletion. In addition, sodium-ion batteries are similar to lithium-ion batteries in principle and can use the same manufacturing equipment. At the same time, they have the advantage of low material cost. They are one of the most promising battery technologies for industrial application and have broad application prospects in large-scale energy storage, low-speed vehicles and other fields.

[0003] The positive electrode material is the most important component of the sodium ion battery and directly determines the capacity of the battery. At present, Prussian blue compounds are one of the most valuable materials for the positive electrode of sodium ion batteries. They have the characteristics of simple synthesis process, low raw material cost, high voltage platform, long cycle life and excellent low temperature performance. Prussian blue compounds, whose chemical formula is NaxM 1 [M 2 (CN)6]y,M 1 、M 2 As a transition metal element, Fe, Mn, Cu, Ni, Co and the like may be used.

[0004] The existing method for synthesizing Prussian blue is to use a co-precipitation method, in which a solution containing a divalent metal salt is slowly added dropwise to a sodium ferrocyanide solution to generate a Prussian blue precipitate. Since a stepwise substitution reaction is used in an aqueous solution during the preparation of the Prussian blue material, when metal ions are produced from an aqueous solution, the complexed water molecules in the metal ions will quickly enter the Prussian blue structure, and the water molecules will always exist in the Prussian blue material.

[0005] After the Prussian blue material is prepared, it is extremely difficult to dry out the water molecules inside the material during the dehydration process, because the Prussian blue structure is a relatively spacious lattice structure, and the water molecules will always exist in the lattice structure. After this material is used to prepare sodium-ion batteries, on the one hand, the water molecules occupy the lattice structure, resulting in a low specific capacity, and on the other hand, the water molecules will decompose and produce gas during the electrochemical process, causing the battery performance to decay rapidly. Traditional Prussian blue dehydration measures are mostly carried out at high temperature and low pressure, but this method is difficult to remove water molecules inside the lattice, and the removal efficiency is low.

[0006] Therefore, it is necessary to provide a new dehydration method for Prussian blue compounds to overcome the above problems. Summary of the invention

[0007] The purpose of the present invention is to overcome the defects of the prior art and provide a method for dehydrating Prussian blue compounds.

[0008] The present invention provides the following technical solutions:

[0009] The present invention provides a method for dehydrating a Prussian blue compound, comprising the steps of:

[0010] S1, drying the prepared Prussian blue compound to remove free water therein;

[0011] S2, mixing the Prussian blue compound dried in step S1 with the metal powder in a certain proportion and stirring evenly;

[0012] S3, adding the powder mixed in step S2 into a ball mill, and performing ball milling in a vacuum environment;

[0013] S4, transferring the material after ball milling in step S3 to a vacuum oven for heating and dehydration.

[0014] Unstable metal powder has a strong ability to compete for water. It reacts with water molecules in the crystal structure to remove the water that is difficult to remove from Prussian blue compounds.

[0015] Furthermore, the Prussian blue compound is Na 2 Fe[Fe(CN) 6 ]、Na 2 Mn[Fe(CN) 6 ] or Na 2 Ni 0.3 Mn 0.7 [Fe(CN) 6 ] is one of the following.

[0016] Furthermore, the metal powder is one of copper powder, aluminum powder, magnesium powder or iron powder.

[0017] Furthermore, the mass ratio of the Lushi blue compound to the metal powder is 99.2:0.8 to 96.8:3.2.

[0018] Furthermore, step S3 also includes adding zirconium oxide balls into a ball mill and milling for 2-6 hours at a ball mill speed of 200-400 r / min.

[0019] Furthermore, step S4 also includes heating to 100-150° C. in a vacuum oven for 6 hours to dehydrate to obtain a composite material of a Prussian blue compound and a metal oxide.

[0020] The present invention also aims to provide a Prussian blue compound sodium ion battery positive electrode material, which is a composite material of a Prussian blue compound and a metal oxide obtained by dehydration using the above method.

[0021] The metal oxide generated after vacuum heating by the above method is coated on the surface of the Prussian blue compound, which has a larger specific capacity, further improves the electrical properties of the Prussian blue compound, has a larger capacity during the charge and discharge process, and has a better cycle effect.

[0022] The present invention has the following beneficial effects:

[0023] 1. Unstable metal powder has a strong ability to compete for water. After being mixed with Prussian blue compounds, it can react with water molecules in the crystal structure during the ball milling process, which can effectively remove the water in the Prussian blue compounds that is difficult to remove;

[0024] 2. In the generated composite material, the metal oxide is coated on the surface of the Prussian blue compound, which has a larger specific capacity, further improving the electrical properties of the Prussian blue compound, and having a larger capacity during the charge and discharge process and a better cycle effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 The thermogravimetric analysis diagrams of the materials obtained in Example 3 and Comparative Example 1 of the present invention are shown. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] The present invention provides a method for dehydrating a Prussian blue compound, comprising the steps of:

[0029] S1, drying the prepared Prussian blue compound to remove free water therein;

[0030] S2, mixing the Prussian blue compound dried in step S1 with the metal powder in a certain proportion and stirring evenly;

[0031] S3, adding the powder mixed in step S2 into a ball mill, and performing ball milling in a vacuum environment;

[0032] S4, transferring the material after ball milling in step S3 to a vacuum oven for heating and dehydration.

[0033] Among them, Prussian blue compound is Na 2 Fe[Fe(CN) 6 ]、Na 2 Mn[Fe(CN) 6 ] or Na 2 Ni 0.3 Mn 0.7 [Fe(CN) 6 ] is one of the following.

[0034] The metal powder is one of copper powder, iron powder, aluminum powder or magnesium powder.

[0035] The mass ratio of the Prussian blue material to the metal powder is 99.2:0.8 to 96.8:3.2.

[0036] Reactions involved include:

[0037] (1) Ball milling reaction of Prussian blue compounds and metal powders:

[0038] NaxF 1 [M 2 (CN)6]y·zH 2 O+Cu→NaxM 1 [M 2 (CN)6]y+Cu(OH) 2

[0039] NaxF 1 [M 2 (CN)6]y·zH 2 O+Al→NaxM 1 [M 2 (CN)6]y+Al(OH) 3

[0040] NaxF 1 [M 2 (CN)6]y·zH 2 O+Mg→NaxM 1 [M 2 (CN)6]y+Mg(OH) 2

[0041] NaxF 1 [M 2 (CN)6]y·zH2 O+Fe→NaxM 1 [M 2 (CN)6]y+Fe(OH) 3

[0042] (2) Vacuum environment heating after ball milling:

[0043] Cu(OH) 2 →CuO+H 2 O↑

[0044] Al(OH) 3 →Al 2 O 3 +H 2 O↑

[0045] Mg(OH) 2 →MgO+H 2 O↑

[0046] Fe(OH) 3 →Fe 2 O 3 +H 2 O↑

[0047] As a preferred solution, step S3 further comprises adding zirconium oxide balls into a ball mill and milling for 2-6 hours at a ball mill speed of 200-400 r / min.

[0048] As a preferred embodiment, step S4 further comprises heating to 100-150° C. in a vacuum oven for 6 hours to dehydrate and obtain a composite material of a Prussian blue compound and a metal oxide.

[0049] The following specific examples are used to illustrate:

[0050] Example 1

[0051] Dehydration of Prussian Blue compounds was performed by the following steps:

[0052] (1) The Na prepared by coprecipitation 2 Fe[Fe(CN) 6 ] Simple drying is performed to remove free water;

[0053] (2) To the dried Na 2 Fe[Fe(CN) 6 ] 1.5wt% copper powder was added and stirred evenly by simple powder mixing;

[0054] (3) Add the stirred powder into a ball mill, add zirconium oxide balls, draw a vacuum environment, adjust the speed of the ball mill to 200 r / min, and ball mill for 6 h;

[0055] (4) After ball milling, the material was transferred out and placed in a vacuum oven, heated to 100°C for 6 hours to obtain Na 2 Fe[Fe(CN) 6 ] and CuO composites.

[0056] Example 2

[0057] Dehydration of Prussian Blue compounds was performed by the following steps:

[0058] (1) The Na prepared by coprecipitation 2 Fe[Fe(CN) 6 ] Simple drying is performed to remove free water;

[0059] (2) To the dried Na 2 Fe[Fe(CN) 6 ] add 0.8wt% aluminum powder and stir evenly by simple powder mixing;

[0060] (3) Add the stirred powder into a ball mill, add zirconium oxide balls, draw a vacuum environment, adjust the speed of the ball mill to 400 r / min, and ball mill for 2 h;

[0061] (4) The ball-milled material was transferred out and placed in a vacuum oven, heated to 150°C for 6 h to obtain Na 2 Fe[Fe(CN) 6 ] and Al 2 O 3 of composite materials.

[0062] Example 3

[0063] Dehydration of Prussian Blue compounds was performed by the following steps:

[0064] (1) The Na prepared by coprecipitation 2 Fe[Fe(CN) 6 ] Simple drying is performed to remove free water;

[0065] (2) To the dried Na 2 Fe[Fe(CN) 6 ] add 2.2wt% magnesium powder, and stir evenly by simple powder mixing;

[0066] (3) Add the stirred powder into a ball mill, add zirconium oxide balls, draw a vacuum environment, adjust the speed of the ball mill to 200 r / min, and ball mill for 6 h;

[0067] (4) After the ball milling, the material was transferred out and placed in a vacuum oven, heated to 130°C for 6 hours to obtain Na 2 Fe[Fe(CN) 6 ] and MgO composite materials.

[0068] Example 4

[0069] Dehydration of Prussian Blue compounds was performed by the following steps:

[0070] (1) The Na prepared by coprecipitation 2 Mn[Fe(CN) 6 ] Simple drying is performed to remove free water;

[0071] (2) To the dried Na 2 Mn[Fe(CN) 6 ] add 1.2wt% iron powder and stir evenly by simple powder mixing;

[0072] (3) Add the stirred powder into a ball mill, add zirconium oxide balls, draw a vacuum environment, adjust the speed of the ball mill to 300 r / min, and ball mill for 4 h;

[0073] (4) After the ball milling, the material was transferred out and placed in a vacuum oven, heated to 110°C for 6 hours to obtain Na 2 Mn[Fe(CN) 6 ] and Fe 2 O 3 of composite materials.

[0074] Example 5

[0075] Dehydration of Prussian Blue compounds was performed by the following steps:

[0076] (1) The Na prepared by coprecipitation 2 Mn[Fe(CN) 6 ] Simple drying is performed to remove free water;

[0077] (2) To the dried Na 2 Mn[Fe(CN) 6 ] 1.2wt% aluminum powder was added and stirred evenly by simple powder mixing;

[0078] (3) Add the stirred powder into a ball mill, add zirconium oxide balls, draw a vacuum environment, adjust the speed of the ball mill to 300 r / min, and ball mill for 4 h;

[0079] (4) After the ball milling, the material was transferred out and placed in a vacuum oven, heated to 125°C for 6 hours to obtain Na2 Mn[Fe(CN) 6 ] and Al 2 O 3 of composite materials.

[0080] Example 6

[0081] Dehydration of Prussian Blue compounds was performed by the following steps:

[0082] (1) The Na prepared by coprecipitation 2 Mn[Fe(CN) 6 ] Simple drying is performed to remove free water;

[0083] (2) To the dried Na 2 Mn[Fe(CN) 6 ] add 2.5wt% magnesium powder, and stir evenly by simple powder mixing;

[0084] (3) Add the stirred powder into a ball mill, add zirconium oxide balls, draw a vacuum environment, adjust the speed of the ball mill to 200 r / min, and ball mill for 6 h;

[0085] (4) The ball-milled material was transferred out and placed in a vacuum oven, heated to 150°C for 6 h to obtain Na 2 Mn[Fe(CN) 6 ] and MgO composite materials.

[0086] Example 7

[0087] Dehydration of Prussian Blue compounds was performed by the following steps:

[0088] (1) The Na prepared by coprecipitation 2 Ni 0.3 Mn 0.7 [Fe(CN) 6 ] Simple drying is performed to remove free water;

[0089] (2) To the dried Na 2 Ni 0.3 Mn 0.7 [Fe(CN) 6 ] add 2.5wt% copper powder, and stir evenly by simple powder mixing;

[0090] (3) Add the stirred powder into a ball mill, add zirconium oxide balls, draw a vacuum environment, adjust the speed of the ball mill to 200 r / min, and ball mill for 6 h;

[0091] (4) After the ball milling, the material was transferred out and placed in a vacuum oven, heated to 110°C for 6 hours to obtain Na 2 Ni 0.3 Mn 0.7 [Fe(CN) 6 ] and CuO composites.

[0092] Example 8

[0093] Dehydration of Prussian Blue compounds was performed by the following steps:

[0094] (1) The Na prepared by coprecipitation 2 Ni 0.3 Mn 0.7 [Fe(CN) 6 ] Simple drying is performed to remove free water;

[0095] (2) To the dried Na 2 Ni 0.3 Mn 0.7 [Fe(CN) 6 ] add 1.8wt% aluminum powder, and stir evenly by simple powder mixing;

[0096] (3) Add the stirred powder into a ball mill, add zirconium oxide balls, draw a vacuum environment, adjust the speed of the ball mill to 300 r / min, and ball mill for 4 h;

[0097] (4) After the ball milling, the material was transferred out and placed in a vacuum oven, heated to 120°C for 6 hours to obtain Na 2 Ni 0.3 Mn 0.7 [Fe(CN) 6 ] and Al 2 O 3 of composite materials.

[0098] Example 9

[0099] Dehydration of Prussian Blue compounds was performed by the following steps:

[0100] (1) The Na prepared by coprecipitation 2 Ni 0.3 Mn 0.7 [Fe(CN) 6 ] Simple drying is performed to remove free water;

[0101] (2) To the dried Na 2 Ni 0.3 Mn 0.7 [Fe(CN) 6] 3.2wt% magnesium powder was added and stirred evenly by simple powder mixing;

[0102] (3) Add the stirred powder into a ball mill, add zirconium oxide balls, draw a vacuum environment, adjust the speed of the ball mill to 200 r / min, and ball mill for 6 h;

[0103] (4) The ball-milled material was transferred out and placed in a vacuum oven, heated to 150°C for 6 h to obtain Na 2 Ni 0.3 Mn 0.7 [Fe(CN) 6 ] and MgO composite materials.

[0104] Comparative Example 1

[0105] The difference from Examples 1 to 3 is that no metal powder is added.

[0106] Comparative Example 2

[0107] The difference from Examples 4 to 6 is that no metal powder is added.

[0108] Comparative Example 3

[0109] The difference from Examples 7 to 9 is that no metal powder is added.

[0110] Test example

[0111] The materials finally obtained from Example 3 (material after ball milling with metal powder) and Comparative Example 1 (material after ball milling without metal powder) were selected for TGA thermogravimetric analysis:

[0112] Results Figure 1 It can be seen that after ball milling with metal powder, the unstable metal powder has a strong ability to compete for water. By reacting with the water molecules in the crystal structure, the water that is difficult to remove in the Prussian blue compounds is removed. The water content of the material is significantly reduced, and the water content of the obtained material is lower.

[0113] The electrochemical performance of the above-prepared materials was analyzed:

[0114] Table 1

[0115]

[0116]

[0117] The results are shown in Table 1. It can be seen that the metal oxide generated after vacuum heating is coated on the surface of the Prussian blue compound, which has a larger specific capacity, further improving the electrical properties of the Prussian blue compound, and has a larger capacity during the charge and discharge process and a better cycle effect.

[0118] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for dehydrating a Prussian blue compound, characterized in that: Includes steps: S1, drying the prepared Prussian blue compound to remove free water therein; S2, mixing the Prussian blue compound dried in step S1 with the metal powder in a certain proportion and stirring evenly; S3, adding the powder mixed in step S2 into a ball mill, and performing ball milling in a vacuum environment; S4, transferring the material after ball milling in step S3 to a vacuum oven for heating and dehydration; The metal powder is one of copper powder, aluminum powder, magnesium powder or iron powder.

2. The method for dehydrating a Prussian blue compound as claimed in claim 1, wherein: The Prussian blue compound is Na2Fe[Fe(CN)6], Na2Mn[Fe(CN)6] or Na2Ni 0.3 Mn 0.7 One of [Fe(CN)6].

3. The method for dehydrating a Prussian blue compound according to any one of claims 1 to 2, characterized in that: The mass ratio of the Prussian blue compound to the metal powder is 99.2:0.8 to 96.8:3.

2.

4. A Prussian blue compound sodium ion battery positive electrode material, characterized in that: A composite material of a Prussian blue compound and a metal oxide prepared by the method of any one of claims 1 to 3.

Images