Preparation method of sodium-rich Prussian blue positive electrode material

Abstract

The invention discloses a preparation method of a sodium-rich Prussian blue positive electrode material, which comprises the following steps: carrying out ball milling, centrifuging, washing and drying on sodium ferrocyanide, manganese salt and a lubricating grinding aid to obtain the sodium-rich Prussian blue positive electrode material. The lubricating grinding aid disclosed by the invention is obtained by carrying out a reaction on trans-1-propenyl boronic acid pinacol ester, acrylonitrile, 6-(ferrocenyl) hexanethiol, triethanolamine and (Z)-3-tributyltin alkyl ethyl acrylate. The borane is used as a catalyst in the grinding aid and can activate the electronic structure of the material, so that the electron cloud density of the C3 site is enhanced, and the conductivity of the positive electrode material is improved; the addition of stannane is helpful for adjusting the electron distribution of the positive electrode material and further optimizing the electron transfer path, so that the electron flow of the battery in the charging and discharging process is smoother; the introduction of ferrocene can improve the chemical stability of the positive electrode material, reduce the voltage platform attenuation in the cycle process, and prolong the service life of the positive electrode material.

Description

Technical Field

[0001] The invention relates to the technical field of sodium ion batteries, in particular to a method for preparing a sodium-rich Prussian blue positive electrode material. Background Art

[0002] PBAs have the characteristics of reversible sodium ion intercalation and deintercalation, high theoretical capacity, and high average voltage platform. They are considered to be one of the most promising cathode materials due to their low price and easy synthesis.

[0003] Chinese patent CN103474659B: discloses a method for preparing a type of Prussian blue complex material and its application as a positive electrode material for sodium ion batteries. The method for preparing a Prussian blue complex composite material provided by the present invention at least comprises: uniformly dispersing a transition metal salt, an acid and a reducing agent in water to obtain a reaction solution, and heating the solution under a protective atmosphere for a period of time to obtain the Prussian blue complex material.

[0004] Chinese patent CN109273682B: discloses a sodium ion battery positive electrode material and a preparation method thereof. This sodium ion battery positive electrode material is prepared by the following preparation method: dissolving an iron salt in a fluorine-containing ionic liquid, stirring the obtained mixed solution with a carbon source and a Prussian blue-based sodium ion positive electrode material, and performing a solvothermal reaction to obtain an iron-based fluoride and carbon in-situ coated modified Prussian blue-based composite sodium ion battery positive electrode material.

[0005] Chinese patent CN108258239B: Provides a sodium ion battery positive electrode material and a preparation method and use thereof. The positive electrode material provided by the present invention includes doped Prussian blue, the Prussian blue contains sodium element, and the positive electrode material does not contain water. The positive electrode material preparation method provided by the present invention comprises the following steps: (1) mixing solution A and solution B to obtain a suspension, wherein solution A is a mixed solution of sodium ferrocyanide and sodium chloride, and solution B is a mixed solution of a doping source and a complexing agent; (2) performing solid-liquid separation on the suspension obtained in step (1), taking the solid and drying it to obtain the positive electrode material.

[0006] Although there are many types of PBAs, the common ones are iron-manganese-based Prussian blue, iron-nickel-based Prussian blue, iron-copper-based Prussian blue, iron-cobalt-based Prussian blue, iron-iron-based Prussian blue, iron-zinc-based Prussian blue, and Prussian blue derivatives formed by doping different transition metal ions corresponding to these Prussian blue compounds, but the specific capacity of these materials in liquid sodium-ion batteries is uneven, and the cycle performance is also very different. The main reason is that the material often forms too much interstitial water and lattice defects during synthesis, resulting in low Na content and unstable structure, which leads to low capacity and poor cycle performance, especially for the full battery performance with hard carbon as the negative electrode, so it has been difficult to apply. To this end, people have explored a variety of methods to synthesize low-defect, low-water-content PBAs, such as adding complexing agents such as sodium citrate during the synthesis process of coprecipitation or hydrothermal method, which can reduce the reaction rate by complexing with metal ions to reduce the defects of the material, thereby increasing the Na content and reducing the water content; or increasing the coprecipitation temperature during the coprecipitation process; and the ball milling method can reduce the participation of water from the source during the synthesis process, and can optimize the sodium content and interstitial water content of the product by regulating the crystal water content of the raw materials, changing the type of raw materials, adjusting the mechanical ball milling speed, ball milling time, etc. In addition, the product can be dried by high vacuum and increasing the temperature to reduce the water content of Prussian blue. In summary, the current solutions mainly include removing interstitial water, lattice doping, or surface coating and modification of conductive materials to obtain sodium-rich PBAs with stable structure, low water content and few defects. Therefore, it is urgent to develop a simple synthesis strategy for sodium-rich low-defect PBAs to promote their industrial application. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a method for preparing a sodium-rich Prussian blue positive electrode material, which belongs to the technical field of sodium ion batteries.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] A method for preparing a sodium-rich Prussian blue positive electrode material, the operating steps of which are:

[0010] S1: 40-50 parts of sodium ferrocyanide and 15-25 parts of manganese salt are mixed evenly, and ball-milled for 20-30 minutes in a three-dimensional oscillating ball mill at room temperature, and 5-10 parts of lubricating grinding aid are added to the ball mill;

[0011] S2: After ball milling, the mixture is placed in a centrifuge and centrifuged at a speed of 6000-8000 rpm for 4-7 minutes. The mixture is washed alternately with water and ethanol for 3 times. The obtained product is placed in a vacuum drying oven and dried at 100-120° C. for 10-20 hours to obtain a sodium-rich Prussian blue positive electrode material.

[0012] In the present invention, the molecular formula of the sodium ferrocyanide is Na4Fe(CN)6.xH2O (0<x<10).

[0013] In the present invention, the molecular formula of the sodium-rich Prussian blue positive electrode material is Na 2-x Mn 1-y AyFe(CN)6.H2O (A=Fe, Ni, 0≤x≤1, 0≤y≤1).

[0014] In the present invention, the preparation method of the lubricating grinding aid is:

[0015] By mass, 0.05-0.5 parts of trans-1-propenylboronic acid pinacol ester, 70-100 parts of acrylonitrile, 3-8 parts of 6-(ferrocenyl)hexanethiol, 12-18 parts of triethanolamine, and 0.05-0.5 parts of (Z)-3-tributyltin ethyl acrylate are added into a reaction kettle, and the mixture is reacted at 70-80° C. for 30-80 minutes to obtain a lubricating grinding aid.

[0016] In the present invention, the manganese salt is one of manganese sulfate, manganese acetate, manganese chloride and manganese nitrate.

[0017] In the present invention, the ball milling time is 90-120 minutes.

[0018] In the present invention, the rotation speed of the ball mill is 300-1200r / min.

[0019] Reaction materials and conditions: trans-1-propenylboronic acid pinacol ester, acrylonitrile, 6-(ferrocenyl)hexanethiol, triethanolamine and (Z)-3-tributyltin ethyl acrylate. These substances are mixed in proportion and reacted at 70-80° C. for 30-80 minutes.

[0020] Addition reaction pathway: The reaction between trans-1-propenylboronic acid pinacol ester and acrylonitrile proceeds through a Michael addition reaction mechanism, in which the electron-rich double bond of acrylonitrile undergoes a nucleophilic attack on the electron-deficient double bond of boronic acid pinacol ester; at the same time, the thiol group in 6-(ferrocenyl)hexanethiol reacts with triethanolamine to form a thioether bond.

[0021] The present invention discloses a method for preparing a sodium-rich Prussian blue positive electrode material. Compared with the prior art, the present invention has the following significant effects:

[0022] 1. Enhance the efficiency of electron transfer:

[0023] Borane acts as a catalyst in the grinding aid, which can activate the electronic structure of the material, thereby enhancing the electron cloud density at the C3 position; this change promotes the efficiency of electron transfer and improves the conductivity of the positive electrode material;

[0024] The addition of stannane helps to adjust the electron distribution of the positive electrode material and further optimize the electron transfer path, making the electron flow smoother during the charging and discharging process of the battery.

[0025] 2. Improve cycle life:

[0026] The introduction of ferrocene can improve the chemical stability of the positive electrode material and reduce the voltage platform decay during the cycle process; this means that the battery can maintain high performance for a longer period of time and extend its service life;

[0027] The presence of stannane helps to inhibit the phase change of the positive electrode material during the cycle process, which often reduces the performance of the battery; by stabilizing the material structure, stannane helps maintain the long-term stability of the battery. DETAILED DESCRIPTION

[0028] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description in combination with embodiments and comparative examples:

[0029] The sodium-rich Prussian blue positive electrode material prepared in the embodiment and the comparative example was used as an active material, and the active material: ultrafine carbon powder (SP): polyvinylidene fluoride were mixed in a mass ratio of 90:5:5, and N-methylpyrrolidone (NMP) was added to make a viscous glue, which was coated on an aluminum foil and baked in a vacuum drying oven at 120°C for 12 hours to obtain a positive electrode; a metallic sodium sheet was used as a counter negative electrode; glass fiber (Waterman) was used as a diaphragm, 1 mol / LNaPF6 (EC and PC with a solvent mass ratio of 1:1) was used as an electrolyte, and a 2032 button-type sodium ion battery was assembled in an Ar protective glove box; a constant current charge and discharge mode was used in the voltage range of 2.0-4.0V, and electrochemical performance tests were carried out on a NEWARE tester: the discharge specific capacity at a current density of 2000mA / g, and the battery capacity retention rate after 100 cycles.

[0030] Example 1

[0031] A method for preparing a sodium-rich Prussian blue positive electrode material, the operating steps of which are:

[0032] S1: 40g sodium ferrocyanide and 15g manganese salt were mixed evenly, and ball-milled for 20min at room temperature using a three-dimensional oscillating ball mill. 5g lubricating grinding aid was added to the ball mill;

[0033] S2: After ball milling, the mixture was placed in a centrifuge and centrifuged at 6000 rpm for 4 min. The mixture was washed alternately with water and ethanol for 3 times. The obtained product was placed in a vacuum drying oven and dried at 100°C for 10 h to obtain a sodium-rich Prussian blue positive electrode material.

[0034] The molecular formula of the sodium ferrocyanide is Na4Fe(CN)6.2H2O.

[0035] The molecular formula of the sodium-rich Prussian blue positive electrode material is Na2MnFe(CN)6.H2O.

[0036] The preparation method of the lubricating grinding aid is:

[0037] 0.05 g of trans-1-propenylboronic acid pinacol ester, 70 g of acrylonitrile, 3 g of 6-(ferrocenyl)hexanethiol, 12 g of triethanolamine, and 0.05 g of (Z)-3-tributyltin ethyl acrylate were added to a reaction kettle and reacted at 70° C. for 30 minutes to obtain a lubricating grinding aid.

[0038] The manganese salt is manganese sulfate.

[0039] The ball milling time is 90 minutes.

[0040] The ball mill has a rotating speed of 300 r / min.

[0041] After testing, the button-type sodium ion battery prepared with the positive electrode material in this example has a discharge specific capacity of 137 mAh / g, and a 100-week capacity retention rate of 94.5%.

[0042] Example 2

[0043] A method for preparing a sodium-rich Prussian blue positive electrode material, the operating steps of which are:

[0044] S1: 43g of sodium ferrocyanide and 18g of manganese salt were mixed evenly, and ball-milled for 25min at room temperature using a three-dimensional oscillating ball mill. 6g of lubricating grinding aid was added to the ball mill;

[0045] S2: After ball milling, the mixture was placed in a centrifuge and centrifuged at 6500 rpm for 5 min. The mixture was washed alternately with water and ethanol for 3 times. The obtained product was placed in a vacuum drying oven and dried at 105°C for 14 h to obtain a sodium-rich Prussian blue positive electrode material.

[0046] The molecular formula of the sodium ferrocyanide is Na4Fe(CN)6.4H2O.

[0047] The molecular formula of the sodium-rich Prussian blue positive electrode material is NaMnFe(CN)6.H2O.

[0048] The preparation method of the lubricating grinding aid is:

[0049] 0.2 g of trans-1-propenylboronic acid pinacol ester, 75 g of acrylonitrile, 5 g of 6-(ferrocenyl)hexanethiol, 14 g of triethanolamine, and 0.2 g of (Z)-3-tributyltin ethyl acrylate were added to a reaction kettle and reacted at 75° C. for 50 minutes to obtain a lubricating grinding aid.

[0050] The manganese salt is manganese acetate.

[0051] The ball milling time is 100 min.

[0052] The ball mill has a rotating speed of 600 r / min.

[0053] After testing, the button-type sodium ion battery prepared with the positive electrode material in this example has a discharge specific capacity of 139 mAh / g, and a 100-week capacity retention rate of 95.1%.

[0054] Example 3

[0055] A method for preparing a sodium-rich Prussian blue positive electrode material, the operating steps of which are:

[0056] S1: 48g of sodium ferrocyanide and 23g of manganese salt were mixed evenly, and ball-milled for 25min at room temperature using a three-dimensional oscillating ball mill, and 8g of lubricating grinding aid was added to the ball mill;

[0057] S2: After ball milling, the mixture was placed in a centrifuge and centrifuged at 7500 rpm for 6 min. The mixture was washed alternately with water and ethanol for 3 times. The obtained product was placed in a vacuum drying oven and dried at 115°C for 18 h to obtain a sodium-rich Prussian blue positive electrode material.

[0058] The molecular formula of the sodium ferrocyanide is Na4Fe(CN)6.6H2O.

[0059] The molecular formula of the sodium-rich Prussian blue positive electrode material is Na2NiFe(CN)6.H2O.

[0060] The preparation method of the lubricating grinding aid is:

[0061] 0.4 g of trans-1-propenylboronic acid pinacol ester, 90 g of acrylonitrile, 7 g of 6-(ferrocenyl)hexanethiol, 16 g of triethanolamine, and 0.4 g of (Z)-3-tributyltin ethyl acrylate were added to a reaction kettle and reacted at 75° C. for 70 minutes to obtain a lubricating grinding aid.

[0062] The manganese salt is manganese chloride.

[0063] The ball milling time is 110 min.

[0064] The ball mill has a rotating speed of 900 r / min.

[0065] After testing, the button-type sodium ion battery prepared with the positive electrode material in this example has a discharge specific capacity of 140 mAh / g, and a 100-week capacity retention rate of 95.8%.

[0066] Example 4

[0067] A method for preparing a sodium-rich Prussian blue positive electrode material, the operating steps of which are:

[0068] S1: 50g of sodium ferrocyanide and 25g of manganese salt were mixed evenly, and ball-milled for 30min at room temperature using a three-dimensional oscillating ball mill. 10g of lubricating grinding aid was added to the ball mill;

[0069] S2: After ball milling, the mixture was placed in a centrifuge and centrifuged at 8000 rpm for 7 min. The mixture was washed alternately with water and ethanol for 3 times. The obtained product was placed in a vacuum drying oven and dried at 120°C for 20 h to obtain a sodium-rich Prussian blue positive electrode material.

[0070] The molecular formula of the sodium ferrocyanide is Na4Fe(CN)6.8H2O (0<x<10).

[0071] The molecular formula of the sodium-rich Prussian blue positive electrode material is Na2Fe2(CN)6.H2O.

[0072] The preparation method of the lubricating grinding aid is:

[0073] 0.5 g of trans-1-propenylboronic acid pinacol ester, 100 g of acrylonitrile, 8 g of 6-(ferrocenyl)hexanethiol, 18 g of triethanolamine, and 0.5 g of (Z)-3-tributyltin ethyl acrylate were added to a reaction kettle and reacted at 80° C. for 80 minutes to obtain a lubricating grinding aid.

[0074] The manganese salt is manganese nitrate.

[0075] The ball milling time is 120 min.

[0076] The ball mill has a rotating speed of 1200 r / min.

[0077] After testing, the button-type sodium ion battery prepared with the positive electrode material in this example has a discharge specific capacity of 142 mAh / g, and a 100-week capacity retention rate of 96.3%.

[0078] Comparative Example 1

[0079] This example is the same as Example 1 except that no lubricating grinding aid is added.

[0080] After testing, the button-type sodium ion battery prepared with the positive electrode material in this example has a discharge specific capacity of 106 mAh / g, and a 100-week capacity retention rate of 80.8%.

[0081] Comparative Example 2

[0082] This example is the same as Example 1 except that trans-1-propenylboronic acid pinacol ester is not added.

[0083] After testing, the button-type sodium ion battery prepared with the positive electrode material in this example has a discharge specific capacity of 118 mAh / g, and a 100-week capacity retention rate of 85.7%.

[0084] Comparative Example 3

[0085] This example is the same as Example 1 except that (Z)-3-tributyltin ethyl acrylate is not added.

[0086] After testing, the button-type sodium ion battery prepared with the positive electrode material in this example has a discharge specific capacity of 123 mAh / g, and a 100-week capacity retention rate of 88.4%.

[0087] Through the data analysis of the above examples and comparative examples, the sodium-rich Prussian blue positive electrode material prepared by the present invention has a higher discharge specific capacity and excellent cycle stability.

[0088] Although the present invention has been described in detail above by means of general description, specific implementation methods and tests, it is obvious to those skilled in the art that some modifications or improvements may be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a sodium-rich Prussian blue positive electrode material, the operating steps of which are: S1: Mix 40-50 parts of sodium ferrocyanide and 15-25 parts of manganese salt by weight, and mill them in a three-dimensional oscillating ball mill for 20-30 minutes at room temperature, and add 5-10 parts of lubricating grinding aid into the ball mill; S2: After ball milling, the mixture is placed in a centrifuge and centrifuged at a speed of 6000-8000 rpm for 4-7 minutes. The mixture is washed alternately with water and ethanol for 3 times. The obtained product is placed in a vacuum drying oven and dried at 100-120° C. for 10-20 hours to obtain a sodium-rich Prussian blue positive electrode material.

2. The method for preparing a sodium-rich Prussian blue positive electrode material according to claim 1, characterized in that: The molecular formula of the sodium ferrocyanide is Na4Fe(CN)6.xH2O (0<x<10).

3. The method for preparing a sodium-rich Prussian blue positive electrode material according to claim 1, characterized in that: The molecular formula of the sodium-rich Prussian blue positive electrode material is Na 2-x Mn 1-y AyFe(CN)6.H2O (A=Fe, Ni, 0≤x≤1, 0≤y≤1).

4. The method for preparing a sodium-rich Prussian blue positive electrode material according to claim 1, characterized in that: The preparation method of the lubricating grinding aid is: By mass, 0.05-0.5 parts of trans-1-propenylboronic acid pinacol ester, 70-100 parts of acrylonitrile, 3-8 parts of 6-(ferrocenyl)hexanethiol, 12-18 parts of triethanolamine, and 0.05-0.5 parts of (Z)-3-tributyltin ethyl acrylate are added into a reaction kettle, and the mixture is reacted at 70-80° C. for 30-80 minutes to obtain a lubricating grinding aid.

5. The method for preparing a sodium-rich Prussian blue positive electrode material according to claim 1, characterized in that: The manganese salt is one of manganese sulfate, manganese acetate, manganese chloride and manganese nitrate.

6. The method for preparing a sodium-rich Prussian blue positive electrode material according to claim 1, characterized in that: The ball milling time is 90-120 minutes.

7. The method for preparing a sodium-rich Prussian blue positive electrode material according to claim 1, characterized in that: The ball mill has a rotating speed of 300-1200 r / min.