Preparation method of sodium ion battery Prussian blue positive electrode material

Abstract

The invention discloses a preparation method of a sodium ion battery Prussian blue positive electrode material. Comprising the following steps: dissolving ferric salt, sodium citrate and ascorbic acid in deionized water to obtain a solution A; dissolving ferrocyanide, sodium citrate and ascorbic acid in deionized water to obtain a solution B; sodium salt and polyvinylpyrrolidone are dissolved in deionized water, and a solution C is obtained; slowly adding the solution A and the solution B into the solution C, and centrifugally collecting precipitates after reaction; drying the precipitate in a vacuum drying oven to obtain initial Prussian blue powder; and further putting the obtained powder sample into a tubular furnace, and carrying out high-temperature annealing in an argon atmosphere to finally obtain the high-stability sodium ion battery Prussian blue positive electrode material. The required raw materials are simple, the cost is low, the process repeatability is high, the equipment requirement is relatively low, batch production is easy to realize, the obtained product is an optimized sodium ion battery Prussian blue positive electrode material, and the sodium storage specific capacity and the cycling stability are obviously improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of novel secondary battery sodium ion batteries, and relates to a preparation method of a sodium ion battery Prussian blue positive electrode material. BACKGROUND

[0002] With the aggravation of environmental pollution and climate change, the demand for renewable resources is growing globally. However, the unstable production capacity and poor controllability of renewable resources such as wind energy and solar energy have become important factors restricting their development. How to efficiently store renewable resources has become a difficult problem to be solved in the current energy field. At present, the main energy storage technologies include the following several categories: mechanical energy storage based on water storage, compressed air, etc., thermal energy storage, capacitor, supercapacitor energy storage, chemical energy storage based on hydrogen storage, and electrochemical energy storage based on secondary batteries. Among them, the lithium ion battery system has occupied the main market of electrochemical energy storage due to its high energy density, excellent stability and high efficiency and flexibility, and is widely used in portable intelligent devices and electric vehicles and other fields. However, lithium resources are scarce and unevenly distributed in the global range, and 70% of lithium in China depends on imports, which greatly increases the cost. In addition, the energy density of lithium ion batteries gradually reaches the limit, which limits their application in large-scale energy storage. In order to meet the sustainable development of energy, and better cope with the challenge of energy storage, researchers have begun to look for "emerging" alternative technologies. Sodium resources are abundant in the earth's crust and easy to obtain, and sodium and lithium are in the same main group, and have similar electrochemical properties. These characteristics make sodium ion batteries have unique advantages in the field of large-scale energy storage, and become the best candidate to replace lithium ion batteries.

[0003] The positive electrode material is an important factor affecting the energy density, service life and cost of the battery, and the development of high-efficiency and stable positive electrode materials is crucial for promoting the commercialization of sodium ion batteries. The positive electrode materials of sodium ion batteries mainly include layered oxides, polyanion and Prussian blue. The oxide positive electrode material usually has a theoretical specific capacity of 200 mAhg -1 The above theoretical specific capacity, but the transformation between the multiple phases during sodium storage easily causes poor structural stability and short cycle life; the polyanion positive electrode material has a more stable structure, but its theoretical specific capacity is low and the conductivity is poor, which also limits its further development. The Prussian blue positive electrode material has a unique 3D open structure, which can provide a large sodium ion insertion space and a fast transmission channel, and has a stable structure and a high theoretical specific capacity. In addition, it has low cost and is suitable for large-scale preparation and production. These advantages have attracted widespread attention from researchers.

[0004] Currently, the preparation methods of Prussian blue cathode material mainly include hydrothermal method and precipitation method. The hydrothermal method is usually carried out at high temperature, using sodium ferrocyanide Na4Fe(CN)6 solution as a single iron source, and reacting with hydrochloric acid solution. Its characteristics are slow reaction speed, high purity of synthesis, and the disadvantages are low yield of hydrothermal method, which is not suitable for industrial production, and toxic hydrogen cyanide is easily produced during the synthesis process. The precipitation method is the most commercially potential in the preparation and research of Prussian blue cathode material, and its characteristics are safe synthesis process, high yield, and suitable for large-scale production. However, due to the fast chemical reaction in the precipitation process, the crystallinity of the generated Prussian blue material is low, and serious vacancy defects are generated. Therefore, further technical adjustment is needed to prepare Prussian blue cathode material with more excellent structure. SUMMARY

[0005] In view of the problems in the prior art, the application provides a preparation method of sodium ion battery Prussian blue cathode material, which improves the crystallinity of Prussian blue powder and exhibits significantly improved sodium storage kinetics and stability.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the application is: The preparation method of sodium ion battery Prussian blue cathode material, characterized by comprising the following process steps: (1) A certain amount of iron salt, sodium citrate and ascorbic acid are dissolved in deionized water, and stirred for 3 hours under the condition of continuous argon gas to make them fully dissolved, and recorded as solution A; (2) A certain amount of ferrocyanide, sodium citrate and ascorbic acid are dissolved in deionized water, and stirred for 3 hours under the condition of continuous argon gas to make them fully dissolved, and recorded as solution B; (3) A certain amount of sodium salt and polyvinylpyrrolidone are dissolved in deionized water, and fully stirred to make them dissolved, and recorded as solution C; (4) The obtained solutions A and B are slowly added to solution C through a peristaltic pump, and stirred for a certain time under the condition of continuous argon gas to make them fully react; (5) The solution obtained in step (4) is centrifuged to collect the precipitate, and deionized water and alcohol are used for full washing; (6) The precipitate prepared in step (5) is placed in a vacuum drying box for drying; (7) The dried sample in step (6) is placed in a tube furnace for high-temperature annealing under argon atmosphere, to obtain a high-stability sodium ion battery Prussian blue cathode material.

[0007] According to the preparation method of sodium ion battery Prussian blue cathode material, in step (1), the iron salt is ferrous chloride or ferrous sulfate, and the molar ratio of the iron salt, sodium citrate and ascorbic acid is 1:1:0.5.

[0008] According to the preparation method of the sodium ion battery Prussian blue positive material, in step (2), the ferrocyanide is sodium ferrocyanide with ten water, the molar ratio of the ferrocyanide to the iron salt in step (1) is 1:1, and the molar ratio of the ferrocyanide, sodium citrate and ascorbic acid is 1:1:0.5.

[0009] According to the preparation method of the sodium ion battery Prussian blue positive material, in step (3), the sodium salt is sodium chloride, the molar ratio of the sodium salt to the iron salt in step (1) is 1:0.1, and the molar ratio of the sodium salt to polyvinylpyrrolidone is 1:0.5.

[0010] According to the preparation method of the sodium ion battery Prussian blue positive material, in step (4), the solution A and B are added at a rate of 10 mL / min by a peristaltic pump. -1 The reaction time is not less than 6 hours.

[0011] According to the preparation method of the sodium ion battery Prussian blue positive material, in step (5), the product is washed with deionized water and alcohol for 3 times respectively.

[0012] According to the preparation method of the sodium ion battery Prussian blue positive material, in step (6), the product is dried in a vacuum drying oven at 120°C for 24h.

[0013] According to the preparation method of the sodium ion battery Prussian blue positive material, in step (7), the high-temperature annealing temperature is 270-300°C, and the annealing time is 2-3h.

[0014] The present application is first based on the preparation of Prussian blue powder by regulating co-precipitation method, and then high-temperature annealing is carried out to obtain high-stability Prussian blue positive material.

[0015] Advantages: (1) The co-precipitation method is used to prepare Prussian blue powder, and the synthesis process is safe, easy to operate and suitable for large-scale production.

[0016] (2) In the synthesis process, the modifiers such as sodium citrate, ascorbic acid and sodium salt are added in a certain proportion to effectively reduce the reaction rate in the precipitation process, reduce the oxidation of Fe 2+ / [Fe(CN)6] 4- and improve the sodium content, so as to improve the crystallinity of Prussian blue powder, and the synthesis process is controllable and easy to operate.

[0017] (3) Further high-temperature annealing of Prussian blue powder at a suitable temperature can effectively reduce the content of crystalline water and further improve the structure of Prussian blue material.

[0018] (4) The Prussian blue powder prepared by the technology has significantly improved sodium storage kinetics and stability, and has a broad application prospect in sodium ion batteries. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The X-ray diffraction pattern of the Prussian blue powder obtained by the coprecipitation method (before high-temperature annealing) of the present application example 1. The abscissa is the angle, and the ordinate is the intensity.

[0020] Figure 2 The X-ray diffraction pattern of the Prussian blue powder obtained after high-temperature annealing of the present application example 1. The abscissa is the angle, and the ordinate is the intensity.

[0021] Figure 3 The scanning electron microscope photo of the Prussian blue powder obtained by the coprecipitation method of the present application example 1.

[0022] Figure 4 The scanning electron microscope photo of the Prussian blue powder obtained after high-temperature annealing of the present application example 1. DETAILED DESCRIPTION

[0023] The present application will be further described below in conjunction with specific examples, and it should be understood that the following description is only for the purpose of explaining the present application and does not limit its content.

[0024] The preparation method of the sodium ion battery Prussian blue positive material of the present application comprises the following steps, (1) A certain amount of iron salt, sodium citrate and ascorbic acid are dissolved in deionized water, and stirred for 3 hours under the condition of continuous argon gas to make them fully dissolved, which is recorded as solution A; (2) A certain amount of ferrocyanide, sodium citrate and ascorbic acid are dissolved in deionized water, and stirred for 3 hours under the continuous argon gas to make them fully dissolved, which is recorded as solution B; (3) A certain amount of sodium salt and polyvinylpyrrolidone are dissolved in deionized water, and fully stirred to make them dissolved, which is recorded as solution C; (4) The obtained solutions A and B are slowly added to solution C through a peristaltic pump, and stirred for a certain time under the condition of continuous argon gas to make them fully react; (5) The solution obtained in step (4) is centrifuged to collect the precipitate, and deionized water and alcohol are fully washed; (6) The precipitate prepared in step (5) is placed in a vacuum drying oven for drying; (7) The dried sample in step (6) is placed in a tube furnace for high-temperature annealing under argon atmosphere to obtain a high-stability sodium ion battery Prussian blue positive material.

[0025] The following specific parameters are used as examples to explain the content of the present application in detail: Example 1

[0026] The steps are as follows: (1) Dissolve 0.99g ferrous chloride tetrahydrate, 1.29g sodium citrate and 0.44g ascorbic acid in 25mL of deionized water and stir continuously for 3 hours under argon gas to ensure complete dissolution, to obtain solution A; (2) Dissolve 2.42g sodium ferrocyanide decahydrate, 1.29g sodium citrate and 0.44g ascorbic acid in 25mL of deionized water and stir continuously for 3 hours under argon gas to ensure complete dissolution, to obtain solution B; (3) Dissolve 2.91g of sodium chloride and 2.88g of polyvinylpyrrolidone in 100mL of deionized water and stir thoroughly to obtain solution C; (4) The obtained solutions A and B are pumped through a peristaltic pump at a rate of 10 mL / min. -1 The solution was added to solution C at a rate of , and stirred for 6 hours under continuous argon gas to allow it to react fully. The solution was then centrifuged to collect the precipitate, and washed three times each with deionized water and alcohol. (5) The precipitate obtained in step (4) was dried in a vacuum drying oven at 120°C for 24 hours. Then the dried sample was placed in a tube furnace and annealed at 270°C for 2 hours under an argon atmosphere to finally obtain highly stable Prussian blue powder.

[0027] X-ray diffraction was performed on the Prussian blue powder obtained by the co-precipitation method in step (4) (before high-temperature annealing) to obtain... Figure 1 The spectral density of the sample shows that it is a typical cubic Prussian blue. The scanning electron microscope (SEM) image of the obtained Prussian blue powder shows that the initial sample was a stacked cubic Prussian blue cathode material.

[0028] The Prussian blue powder from step (5) was irradiated with X-ray diffraction to obtain Figure 2 The spectrum shows that the obtained sample underwent a certain phase transition. The scanning electron microscope image of the obtained Prussian blue powder shows that the Prussian blue particles became finer and the surface became rougher after high-temperature annealing. Example 2

[0029] (1) Dissolve 1.39g ferrous sulfate heptahydrate, 1.29g sodium citrate and 0.44g ascorbic acid in 25mL of deionized water and stir continuously for 3 hours under argon gas to ensure complete dissolution, to obtain solution A; (2) Dissolve 2.42g sodium ferrocyanide decahydrate, 1.29g sodium citrate and 0.44g ascorbic acid in 25mL of deionized water and stir continuously for 3 hours under argon gas to ensure complete dissolution, to obtain solution B; (3) 2.91 g of sodium chloride and 2.88 g of polyvinylpyrrolidone were dissolved in 100 mL of deionized water, and stirred to dissolve, to obtain solution C; (4) The obtained solutions A and B were added to solution C at a rate of 10 mL / min by using a peristaltic pump, and stirred for 6 hours under continuous argon flow to allow the reaction to proceed completely, and then the solution was centrifuged to collect the precipitate, and washed with deionized water and alcohol for 3 times, respectively; -1 (5) The precipitate obtained in step (4) was dried in a vacuum drying oven at 120°C for 24 h, and then the dried sample was placed in a tube furnace and annealed at 270°C for 2 h under argon atmosphere, to obtain Prussian blue powder. Example 3

[0030] (1) 0.99 g of ferrous chloride tetrahydrate, 1.29 g of sodium citrate and 0.44 g of ascorbic acid were dissolved in 25 mL of deionized water, and continuously stirred for 3 hours under continuous argon flow to allow the reaction to proceed completely, to obtain solution A; (2) 2.42 g of sodium ferrocyanide decahydrate, 1.29 g of sodium citrate and 0.44 g of ascorbic acid were dissolved in 25 mL of deionized water, and continuously stirred for 3 hours under continuous argon flow to allow the reaction to proceed completely, to obtain solution B; (3) 2.91 g of sodium chloride and 2.88 g of polyvinylpyrrolidone were dissolved in 100 mL of deionized water, and stirred to dissolve, to obtain solution C; (4) The obtained solutions A and B were added to solution C at a rate of 10 mL / min by using a peristaltic pump, and stirred for 6 hours under continuous argon flow to allow the reaction to proceed completely, and then the solution was centrifuged to collect the precipitate, and washed with deionized water and alcohol for 3 times, respectively; -1 (5) The precipitate obtained in step (4) was dried in a vacuum drying oven at 120°C for 24 h, and then the dried sample was placed in a tube furnace and annealed at 270°C for 3 h under argon atmosphere, to obtain Prussian blue powder. Example 4

[0031] Compared with Example 1, in step (5), the further high-temperature annealing temperature under argon atmosphere in the tube furnace was 280°C, and the annealing time was 2 h, and the rest was the same as Example 1. Example 5

[0032] Compared with Example 1, in step (5), the further high-temperature annealing temperature under argon atmosphere in the tube furnace was 280°C, and the annealing time was 3 h, and the rest was the same as Example 1. Example 6

[0033] ​​Compared with Example 1, the further high temperature annealing temperature in step (5) is 290°C under argon atmosphere in a tube furnace, the annealing time is 2h, and the rest is the same as Example 1. Example 7

[0034] Compared with Example 1, the further high temperature annealing temperature in step (5) is 290°C under argon atmosphere in a tube furnace, the annealing time is 3h, and the rest is the same as Example 1. Example 8

[0035] Compared with Example 1, the further high temperature annealing temperature in step (5) is 300°C under argon atmosphere in a tube furnace, the annealing time is 2h, and the rest is the same as Example 1. Example 9

[0036] Compared with Example 1, the further high temperature annealing temperature in step (5) is 300°C under argon atmosphere in a tube furnace, the annealing time is 3h, and the rest is the same as Example 1. Example 10

[0037] Compared with Example 2, the further high temperature annealing temperature in step (5) is 270°C under argon atmosphere in a tube furnace, the annealing time is 3h, and the rest is the same as Example 2. Example 11

[0038] Compared with Example 2, the further high temperature annealing temperature in step (5) is 280°C under argon atmosphere in a tube furnace, the annealing time is 2h, and the rest is the same as Example 2. Example 12

[0039] Compared with Example 2, the further high temperature annealing temperature in step (5) is 280°C under argon atmosphere in a tube furnace, the annealing time is 3h, and the rest is the same as Example 2. Example 13

[0040] Compared with Example 2, the further high temperature annealing temperature in step (5) is 290°C under argon atmosphere in a tube furnace, the annealing time is 2h, and the rest is the same as Example 2. Example 14

[0041] Compared with Example 2, the further high temperature annealing temperature in step (5) is 290°C under argon atmosphere in a tube furnace, the annealing time is 3h, and the rest is the same as Example 2. Example 15

[0042] Compared with Example 2, the further high temperature annealing temperature in step (5) is 300°C under argon atmosphere in a tube furnace, the annealing time is 2h, and the rest is the same as Example 2. Example 16

[0043] Compared with Example 2, the further high temperature annealing temperature in step (5) is 300 °C under the argon atmosphere in the tube furnace, the annealing time is 3 h, and the rest is the same as Example 2.

Claims

1. A method for preparing Prussian blue cathode material for sodium-ion batteries, characterized in that... The process includes the following steps: (1) Dissolve a certain amount of iron salt, sodium citrate and ascorbic acid in deionized water, and stir for 3 hours under continuous argon gas to ensure complete dissolution. This solution is denoted as solution A. (2) Dissolve a certain amount of ferrocyanide, sodium citrate and ascorbic acid in deionized water, and stir for 3 hours under continuous argon gas to ensure complete dissolution. This solution is called solution B. (3) Dissolve a certain amount of sodium salt and polyvinylpyrrolidone in deionized water and stir thoroughly until dissolved. This solution is denoted as solution C. (4) The obtained solutions A and B are slowly added to solution C through a peristaltic pump, and stirred for a certain period of time under continuous argon gas to allow them to react fully; (5) Centrifuge the solution obtained in step (4) to collect the precipitate, and wash thoroughly with deionized water and alcohol; (6) Place the precipitate obtained in step (5) in a vacuum drying oven to dry; (7) The dried sample from step (6) is placed in a tube furnace and annealed at high temperature under an argon atmosphere to obtain a high-stability Prussian blue cathode material for sodium-ion batteries.

2. The method for preparing a Prussian blue cathode material for a sodium-ion battery according to claim 1, characterized in that: In step (1), the iron salt is ferrous chloride or ferrous sulfate, and the molar ratio of iron salt, sodium citrate and ascorbic acid is 1:1:0.

5.

3. The method for preparing a Prussian blue cathode material for a sodium-ion battery according to claim 1, characterized in that: In step (2), the ferrocyanide is sodium ferrocyanide decahydrate, the molar ratio of ferrocyanide to the iron salt in step (1) is 1:1, and the molar ratio of ferrocyanide, sodium citrate and ascorbic acid is 1:1:0.

5.

4. The method for preparing a Prussian blue cathode material for a sodium-ion battery according to claim 1, characterized in that: In step (3), the sodium salt is sodium chloride, the molar ratio of sodium salt to iron salt in step (1) is 1:0.1, and the molar ratio of sodium salt to polyvinylpyrrolidone is 1:0.

5.

5. The method for preparing a Prussian blue cathode material for a sodium-ion battery according to claim 1, characterized in that: In step (4), solutions A and B are added at a rate of 10 mL / min using a peristaltic pump. -1 The reaction time shall be no less than 6 hours.

6. The method for preparing a Prussian blue cathode material for a sodium-ion battery according to claim 1, characterized in that: In step (5), the water is washed three times with deionized water and alcohol respectively.

7. The method for preparing a Prussian blue cathode material for a sodium-ion battery according to claim 1, characterized in that: In step (6), the product is dried at 120°C for 24 hours in a vacuum drying oven.

8. The method for preparing a Prussian blue cathode material for a sodium-ion battery according to claim 1, characterized in that: In step (7), the high-temperature annealing temperature is 270-300°C and the annealing time is 2-3h.

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