Preparation method of anion modified Prussian blue positive electrode material
By introducing carboxylic functional groups into the Prussian blue structure, the gap water content is reduced, and the problems of the impact of defective positions and high gap water in Prussian blue materials are solved, and its electrochemical cycling performance and conductivity are significantly improved.
Patent Information
- Application Number
- CN202411985003.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2025-04-11
AI Technical Summary
There are many defects and high gap water content in the Prussian blue structure, which affects its discharge specific capacity and cycling performance.
Using ferrous acetate as raw material, a Prussian blue material modified with carboxyl functional group was prepared in one step by ball milling. The carboxyl group was used to inhibit the binding of water molecules with Prussian blue and reduce the gap water content.
The electrochemical cycling performance of the material is improved, the conductivity and electrochemical activity are enhanced, and the battery maintains a high reversible capacity and excellent rate performance under high load conditions.
Abstract
Description
Technical Field
[0001] The invention belongs to the field of preparation of novel sodium ion battery positive electrode materials, and specifically relates to a preparation method of an anion-modified Prussian blue positive electrode material. Background Art
[0002] Prussian blue analogues have the characteristics of easily regulated skeleton structure, simple synthesis process, low cost and environmental friendliness, and are suitable as positive electrode materials for sodium ion batteries.
[0003] Patent CN118380542A discloses a sodium ion battery positive electrode, a preparation method and application thereof, and relates to the technical field of sodium ion batteries. A highly conductive hydrophobic positive electrode can be constructed by growing a Prussian blue analogue on a metal foam substrate and coating the Prussian blue analogue with reduced graphene oxide.
[0004] Patent CN118439630A discloses a Prussian blue cathode material and a preparation method and application thereof; the preparation method comprises the following steps: S1, weighing an appropriate amount of a chelating agent and dissolving it in a ferric chloride solution to obtain a first mixed solution; S2, weighing an appropriate amount of sodium ferrocyanide decahydrate and dissolving it in a saturated sodium chloride solution to obtain a second mixed solution; S3, freezing and crushing the first mixed solution and the second mixed solution in turn to obtain a first powder and a second powder; S4, mixing the first powder and the second powder in a low temperature environment, stirring the reaction under the protection of an inert gas and centrifuging; S5, washing and freeze-drying the precipitate obtained by centrifugation to obtain a Prussian blue cathode material.
[0005] However, the presence of many defects and high interstitial water content in the structure of Prussian blue still affects its discharge specific capacity and cycle performance. In the liquid phase synthesis of dual iron sources, the nucleation rate of Prussian blue is affected by the anion radicals of ferrous salts, resulting in different structural morphologies, interstitial water and defect content of the materials, which results in significant differences in their electrochemical performance. Acetic acid can passivate the prepared Prussian blue, thereby improving the electrochemical cycle performance of the material. Summary of the invention
[0006] The invention aims to provide a method for preparing an anion-modified Prussian blue positive electrode material. Ferrous acetate is used as a raw material and a carboxyl functional group-modified Prussian blue material is prepared in one step by a ball milling method. The carboxyl group is used to inhibit the combination of water molecules and Prussian blue, and the interstitial water content in the Prussian blue structure is reduced, so as to improve the electrochemical cycle performance of the material.
[0007] The technical solution of the present invention is: a method for preparing an anion-modified Prussian blue positive electrode material, comprising the following steps:
[0008] A. Ferrous acetate containing crystal water is placed in a tube furnace according to a certain molar ratio, and heated in a tube furnace under an inert atmosphere to remove the crystal water. Then the anhydrous ferrous acetate obtained above, sodium ferrocyanide decahydrate, ascorbic acid and a reducing synergist are placed in a ball mill jar and sealed in a glove box protected by an inert atmosphere, and then ball milled with a planetary ball mill. After the ball milling reaction, a product (blue powder) is obtained at the bottom of the ball mill jar, and the ball milled product is scraped off the jar wall, and the precipitated product is washed with a detergent for multiple times, and finally vacuum dried to obtain the final sample Prussian blue.
[0009] B. Assemble the battery and test its discharge capacity and cycle performance at a current density of 1C.
[0010] As a preferred technical solution of the present invention, in step A, the molar ratio of ferrous acetate, sodium ferrocyanide decahydrate and ascorbic acid is 0.3-0.5:0.5-0.7:0.2-0.4.
[0011] As a preferred technical solution of the present invention, in step A, a reducing synergist is provided, and the added amount is 5-8% of the mass percentage content of ascorbic acid; and the preparation method thereof is:
[0012] T1: by weight, 20-40 parts of diglycerol ascorbic acid, 18-36 parts of 2,1,3-benzothiazol-4-yl isocyanate, CAS: 342411-14-7; 2-5 parts of stannous octoate, 300-400 parts of toluene, stirred at 60-80°C for 100-150 minutes;
[0013] T2: Add 0.003-0.05 parts of 2-mercapto-4-aminopyrimidine-5-carbonitrile, CAS: 16462-26-3, stir at 65-85° C. for 60-100 minutes, and distill to remove toluene to obtain a reduction synergist.
[0014] As a preferred technical solution of the present invention, in step A, the heating temperature of the tube furnace is 50-100° C., and the heating time is 20-40 min.
[0015] As a preferred technical solution of the present invention, in step A, the planetary ball mill is operated at a speed of 250 rpm for 1-3 hours.
[0016] As a preferred technical solution of the present invention, in step A, the detergent is one or both of deionized water and anhydrous ethanol.
[0017] As a preferred technical solution of the present invention, in step A, the washing times are 2-5 times.
[0018] As a preferred technical solution of the present invention, in step A, the precipitated product is dried in a vacuum oven at 50-100° C. for 6-12 hours.
[0019] Reaction mechanism
[0020] 1: The hydroxyl group in diglycerol ascorbic acid undergoes nucleophilic attack on the isocyanate group in 2,1,3-benzothiazol-4-yl isocyanate to generate an intermediate; this intermediate undergoes intramolecular rearrangement to form a more stable urea structure; and finally forms the target product containing a benzothiazole ring and an improved ascorbic acid structure.
[0021] 2: The amino group in 2-mercapto-4-aminopyrimidine-5-carbonitrile undergoes nucleophilic addition to the isocyanate portion of 2,1,3-benzothiazol-4-yl isocyanate to form an adduct that integrates the structural units of pyrimidine and benzothiazole.
[0022] Compared with the prior art, the present invention has the following advantages:
[0023] Enhanced reducing ability: The sulfur atom in the benzothiazole structure can provide lone pair electrons, thereby enhancing its reducing ability; Improved reaction selectivity: Through its specific structure and reactivity, benzothiazole can achieve selective reduction of specific functional groups, thereby improving the efficiency and selectivity of the reaction.
[0024] As a strong reducing group, pyrimidine-5-carbonitrile can effectively promote the related reduction reaction. Pyrimidine-5-carbonitrile shows high selectivity for specific functional groups during the reduction process, thus ensuring the specificity of the reaction. The internal structure of the highly crystalline Prussian blue material is regular, making the insertion and extraction of sodium ions smoother, thereby improving the stability of the battery cycle.
[0025] The optimized crystallinity effectively improves the conductivity and electrochemical activity of the material, allowing the battery to maintain a high reversible capacity and excellent rate performance under high loading conditions.
[0026] In the liquid phase synthesis of double iron sources, the nucleation rate of Prussian blue is affected by the anion radicals of ferrous salts, resulting in different structural morphologies, interstitial water and defect content of the materials, which leads to significant differences in their electrochemical performance. Acetic acid can passivate the prepared Prussian blue, thereby improving the electrochemical cycle performance of the material. DETAILED DESCRIPTION
[0027] The present invention is described in detail below in conjunction with specific implementation modes.
[0028] Embodiment 1,
[0029] A method for preparing an anion-modified Prussian blue positive electrode material comprises the following steps:
[0030] A. 69.6 g of ferrous acetate containing water of crystallization was placed in a tube furnace, and heated in an 80°C tube furnace for 30 min under an inert atmosphere to remove the water of crystallization. The anhydrous ferrous acetate obtained above was then placed in a ball mill jar and sealed in a glove box protected by an inert atmosphere. The ball mill was then milled with a planetary ball mill. The ball milling parameters were set to 250 rpm and the running time was 2 h. After the ball milling reaction, the product (blue powder) was obtained at the bottom of the ball mill jar. The ball milled product was scraped off the jar wall, and the precipitated product was centrifuged and washed 3 times with deionized water and anhydrous ethanol respectively, and finally dried in a vacuum drying oven at 80°C for 8 h to obtain the final sample Prussian blue.
[0031] The present invention provides a reduction synergist, the addition amount is 3.4g, and the preparation method thereof is:
[0032] T1: According to weight, 30g diglycerol ascorbic acid, 24g 2,1,3-benzothiazol-4-yl isocyanate, CAS: 342411-14-7; 3.5g stannous octoate, 350g toluene, stirred at 70°C for 120 minutes;
[0033] T2: Add 0.025 g of 2-mercapto-4-aminopyrimidine-5-carbonitrile, CAS: 16462-26-3, stir at 65-85° C. for 80 minutes, and distill off toluene to obtain a reduction enhancer.
[0034] B. The battery was assembled and tested to have a discharge capacity of 113.7 mAh / g at a current density of 1 C. The capacity retention rate after 1000 cycles was 55%.
[0035] Embodiment 2,
[0036] A method for preparing an anion-modified Prussian blue positive electrode material comprises the following steps:
[0037] A. 52.2 g of ferrous acetate containing water of crystallization was placed in a tube furnace, and heated in a tube furnace at 50°C for 20 min under an inert atmosphere to remove the water of crystallization. The anhydrous ferrous acetate obtained above was then placed in a ball mill jar and sealed in a glove box protected by an inert atmosphere. The ball mill was then milled with a planetary ball mill. The ball milling parameters were set to 250 rpm and the running time was 1 h. After the ball milling reaction, the product (blue powder) was obtained at the bottom of the ball mill jar. The ball milled product was scraped off the jar wall, and the precipitated product was centrifuged and washed twice with deionized water and anhydrous ethanol, respectively. Finally, it was dried in a vacuum drying oven at 50°C for 6 h to obtain the final sample Prussian blue.
[0038] The present invention provides a reducing synergist, the addition amount is 1.76g, and the preparation method thereof is:
[0039] T1: According to weight, 20g diglycerol ascorbic acid, 18g 2,1,3-benzothiazol-4-yl isocyanate, CAS: 342411-14-7; 2g stannous octoate, 300g toluene, stirred at 60°C for 100 minutes;
[0040] T2: 0.003 g of 2-mercapto-4-aminopyrimidine-5-carbonitrile (CAS: 16462-26-3) was added, and the mixture was stirred at 65° C. for 60 minutes. Toluene was removed by distillation to obtain a reduction synergist.
[0041] B. The battery was assembled and tested to have a discharge capacity of 109.5 mAh / g at a current density of 1 C. The capacity retention rate after 1000 cycles was 52.5%.
[0042] Embodiment 3,
[0043] A method for preparing an anion-modified Prussian blue positive electrode material comprises the following steps:
[0044] A. 87 g of ferrous acetate containing water of crystallization was placed in a tube furnace, and heated in a tube furnace at 100 ° C for 40 min under an inert atmosphere to remove the water of crystallization. Then, the anhydrous ferrous acetate obtained above and 339 g of sodium ferrocyanide decahydrate, 70.4 g of ascorbic acid and 5.6 g of a reducing synergist were placed in a ball mill in a glove box protected by an inert atmosphere and sealed. The mixture was then ball milled with a planetary ball mill. The ball milling parameters were set to 250 rpm and the running time was 3 h. After the ball milling reaction, a product (blue powder) was obtained at the bottom of the ball mill. The ball milled product was scraped off the wall of the jar, and the precipitated product was centrifuged and washed 5 times with deionized water and anhydrous ethanol, respectively. Finally, it was dried in a vacuum drying oven at 100 ° C for 12 h to obtain the final sample Prussian blue.
[0045] The present invention provides a reduction synergist, the addition amount is 5.6g, and the preparation method thereof is:
[0046] T1: According to weight, 40g diglycerol ascorbic acid, 36g 2,1,3-benzothiazol-4-yl isocyanate, CAS: 342411-14-7, 5g stannous octoate, 400g toluene, stirred at 80°C for 150 minutes;
[0047] T2: Add 0.05 g of 2-mercapto-4-aminopyrimidine-5-yl, CAS: 16462-26-3, stir at 85° C. for 100 minutes, and distill off toluene to obtain a reduction enhancer.
[0048] B. The battery was assembled and tested to have a discharge capacity of 103 mAh / g at a current density of 1 C. The capacity retention rate after 1000 cycles was 47.5%.
[0049] Comparative Example 1
[0050] A method for preparing an anion-modified Prussian blue positive electrode material comprises the following steps:
[0051] A. 69.6 g of ferrous acetate containing water of crystallization was placed in a tube furnace, and heated in an 80°C tube furnace for 30 min under an inert atmosphere to remove the water of crystallization. The anhydrous ferrous acetate obtained above, 290.4 g of sodium ferrocyanide decahydrate and 52.8 g of ascorbic acid were then placed in a ball milling jar and sealed in a glove box protected by an inert atmosphere. The ball milling was then performed using a planetary ball mill. The ball milling parameters were set to 250 rpm and the operating time was 2 h. After the ball milling reaction, a product (blue powder) was obtained at the bottom of the ball milling jar. The ball milling product was scraped off the jar wall, and the precipitated product was centrifuged and washed 3 times with deionized water and anhydrous ethanol, respectively. Finally, it was dried in a vacuum drying oven at 80°C for 8 h to obtain the final sample Prussian blue.
[0052] B. The battery was assembled and tested to have a discharge capacity of 97.7 mAh / g at a current density of 1 C, and a capacity retention rate of 44.2% after 1000 cycles.
Claims
1. A method for preparing an anion-modified Prussian blue positive electrode material, characterized in that: The following steps are involved: A. According to a certain molar ratio, ferrous acetate containing crystal water is placed in a tube furnace, and heated in a tube furnace under an inert atmosphere to remove the crystal water. Then, the anhydrous ferrous acetate obtained above, sodium ferrocyanide decahydrate, ascorbic acid and a reduction synergist are placed in a ball milling jar and sealed in a glove box protected by an inert atmosphere, and then ball milled with a planetary ball mill. After the ball milling reaction, a product is obtained at the bottom of the ball milling jar, and the ball milling product is scraped off the jar wall, and the precipitated product is washed with a detergent for multiple times, and finally vacuum dried to obtain the final sample Prussian blue; B. Assemble the battery and test its discharge capacity and cycle performance at a current density of 1C.
2. The method for preparing an anion-modified Prussian blue cathode material according to claim 1, characterized in that: In step A, the molar ratio of ferrous acetate, sodium ferrocyanide decahydrate and ascorbic acid is 0.3-0.5:0.5-0.7:0.2-0.
4.
3. The method for preparing an anion-modified Prussian blue cathode material according to claim 1, characterized in that: In step A, the amount of the reducing synergist added is 5-8% of the ascorbic acid content by mass percentage; the preparation method is: T1: by weight, 20-40 parts of diglycerol ascorbic acid, 18-36 parts of 2,1,3-benzothiazol-4-yl isocyanate; 2-5 parts of stannous octoate, 300-400 parts of toluene, stirring at 60-80°C for 100-150 minutes; T2: add 0.003-0.05 parts of 2-mercapto-4-aminopyrimidine-5-carbonitrile, stir at 65-85° C. for 60-100 minutes, and distill off toluene to obtain a reduction synergist.
4. The method for preparing an anion-modified Prussian blue cathode material according to claim 1, characterized in that: In step A, the heating temperature of the tubular furnace is 50-100° C., and the heating time is 20-40 minutes.
5. The method for preparing an anion-modified Prussian blue positive electrode material according to claim 1, characterized in that: In step A, the planetary ball mill is operated at a speed of 250 rpm for 1-3 h.
6. The method for preparing an anion-modified Prussian blue cathode material according to claim 1, characterized in that: In step A, the detergent is one or both of deionized water and anhydrous ethanol.
7. The method for preparing an anion-modified Prussian blue cathode material according to claim 1, characterized in that: In step A, the washing times are 2-5 times.
8. The method for preparing an anion-modified Prussian blue cathode material according to claim 1, characterized in that: In step A, the precipitated product is dried in a vacuum oven at 50-100° C. for 6-12 hours.