A prussian white-like material, its preparation and use in sodium-ion batteries
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DALIAN INSTITUTE OF CHEMICAL PHYSICS CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2022-10-14
- Publication Date
- 2026-07-21
Smart Images
Figure CN117923516B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of cathode materials for sodium-ion batteries, and specifically relates to the preparation of a Prussian white-like material with a stepped structure and its application in sodium-ion batteries. Background Technology
[0002] With the development of human society, fossil fuels are being depleted, and environmental problems are intensifying. The development of renewable energy is therefore crucial. However, renewable energy sources such as wind, solar, and tidal power are all dependent on weather conditions and highly uncertain. Therefore, large-scale energy storage technologies are needed to store electricity, thereby achieving a safe, continuous, and stable power supply. Among the many rapidly developing energy storage technologies, electrochemical energy storage holds a significant market share. Lithium-ion batteries, in particular, have wide applications in portable electronic devices and electric vehicles due to their advantages such as high energy density, high output voltage, low self-discharge, no memory effect, wide operating temperature range, and rapid charging and discharging capabilities. However, the low abundance and uneven distribution of lithium resources hinder its further development, especially in the field of large-scale energy storage.
[0003] Sodium resources are abundant and widely distributed globally. Their low price and similar working principle to lithium-ion batteries have made sodium-ion batteries a core research direction for large-scale energy storage technologies. However, due to the larger ionic radius of sodium ions compared to lithium ions, their occupancy in similar structures differs, thus requiring materials with larger pores to serve as cathode materials for sodium-ion batteries. Prussian blue and its analogues, as a class of MOF materials, possess advantages such as large gaps and wide pores, which can fully accommodate sodium ions and facilitate their insertion / extraction. They contain M... A and M B Both transition metal sites are active and can undergo reversible redox reactions, thus giving it a high theoretical specific capacity. However, in practical applications, the presence of defects leads to poor rate performance and cycle stability, thereby limiting its performance in sodium-ion batteries. Summary of the Invention
[0004] To address the problem of poor rate performance and cycle stability of Prussian blue-based sodium-ion battery cathode materials in existing technologies, this invention proposes a method for synthesizing a Prussian white-based material with a stepped structure, and applies it to sodium-ion batteries to improve the rate performance and cycle stability of Prussian blue-based sodium-ion battery cathode materials.
[0005] In sodium-ion batteries, the poor rate performance and cycle performance of Prussian blue-based cathode materials are mainly due to defects introduced during the synthesis process. B[CN]6] The presence of vacancies can disrupt the framework structure and cause lattice distortion, while also hindering electron conduction and increasing the ohmic polarization of the material. [M B [CN]6] Increased vacancies lead to increased bound water, which can cause side reactions with the electrolyte at high potentials, further deteriorating the material's stability. To address these issues, this invention proposes a synthetic method. On one hand, starting from the crystal structure, a low-vacancy crystal material with high integrity is synthesized using a slower reaction rate. The bound water content in the crystal structure is controlled by heating at several different temperatures to achieve the synthesis of a low-defect Prussian white-like material. On the other hand, from a morphological perspective, the presence of larger primary cubic structures increases the material's stability, while the use of chelating agents to synthesize cluster particles with a stepped structure increases its contact area with the electrolyte, promoting sodium ion transport. The balance between these two factors allows the Prussian white-like material to simultaneously exhibit excellent rate performance and cycle stability in sodium-ion batteries.
[0006] This invention relates to the preparation of a Prussian white-like material with a stepped structure and its application in sodium-ion batteries.
[0007] The Prussian white cathode material with a stepped structure is composed of Na. x Fe[Fe(CN)6] y ·□ 1-y ·mH2O (where 1.2 < x < 2, 0.7 < y < 1, 0 < m < 3, □ represents [Fe(CN)6] vacancy);
[0008] The preparation steps of the Prussian white-like cathode material with a stepped structure are as follows: Na4Fe(CN)6·10H2O is dissolved in 200mL of ultrapure water to form a solution A with a concentration of 15-25mM; 10-20g of sodium citrate is dissolved in a FeSO4·7H2O solution with a concentration of 25-35mM; after stirring for 1.5-3h, solution A is quickly poured into solution B, stirred for 15-25min, aged at room temperature for 5-8h, the supernatant is removed, centrifuged, washed with deionized water and ethanol, and transferred to a vacuum drying oven to be vacuum dried overnight at 60-180℃ to obtain the Prussian white-like material with a stepped structure.
[0009] The prepared Prussian white-like material with a stepped structure was used as the positive electrode active material. It was mixed with Super P (superconducting carbon black) and PVDF (polyvinylidene fluoride) in a mass ratio of 7:2:1. After adding an appropriate amount of NMP and stirring, the slurry was coated on Al foil and dried overnight at 60°C. The resulting discs were then cut into round pieces to serve as the positive electrode. A sodium metal sheet was used as the negative electrode. A glass fiber membrane was used as the separator. A 1M NaClO4 solution in EC / DEC (1:1 volume ratio) was used as the electrolyte. A CR2016 coin cell was used. The positive electrode shell, positive electrode sheet, separator, electrolyte, negative electrode sheet, gasket, spring sheet, and negative electrode shell were stacked in sequence, pressed together, and assembled into a sodium-ion battery for performance testing.
[0010] Advantages and beneficial effects of this invention: This invention is prepared by a co-precipitation method with the addition of an appropriate amount of chelating agent, and obtained through a high-temperature vacuum drying process. The stepped-structured Prussian white-like material has abundant contact surfaces, allowing for good contact with the electrolyte, thereby shortening the migration path of sodium ions. Appropriate temperature drying reduces the interstitial water content in the Prussian white-like material, which on the one hand weakens the side reactions with the electrolyte, and on the other hand, fewer defects stabilize the framework structure of the Prussian white-like material. Therefore, as a cathode material for sodium-ion batteries, it exhibits high rate performance and cycle stability. Furthermore, this method is simple, low-cost, and has excellent application prospects. Attached Figure Description
[0011] Figure 1 The images are scanning electron microscope images of Examples 1-6, where the scale bar of ac is 100 nm and the scale bar of bd is 1 μm.
[0012] Figure 2 The images shown are scanning electron microscope images of comparative examples 1-4, where the scale bar is 1 μm.
[0013] Figure 3 The images shown are scanning electron microscope images of comparative examples 5-6, where the scale bar is 1 μm.
[0014] Figure 4 These are images showing the rate performance tests of Examples 1-6 and Comparative Examples 1-6.
[0015] Figure 5 Images show the cycle performance test results of Examples 1-6 and Comparative Examples 1-6 at 1C. Detailed Implementation
[0016] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.
[0017] Examples 1-3:
[0018] 1. Investigate the effects of different sodium citrate addition amounts on the morphology and battery performance of Prussian white-like materials.
[0019] 4 mmol Na₄Fe(CN)₆·10H₂O was dissolved in 200 mL of deionized water to form solution A; 6 mmol FeSO₄·7H₂O and ng sodium citrate were dissolved in 200 mL of deionized water to form solution B (where n was 12, 15, and 18 g respectively). The solutions were stirred for 2 h. Solution A was directly poured into solution B, stirred for 15 min, and then aged at room temperature for 6 h. The supernatant was then removed by filtration. The solid filter was washed successively with deionized water and ethanol. The solid was then placed in a vacuum drying oven and dried overnight at 160 °C to obtain a Prussian white-like material. This material was named PW-12-160 (its composition is Na₄Fe(CN)₆·10H₂O). 1.23 Fe[Fe(CN)6] 0.76 ·1.80H2O), PW-15-160 (its composition is Na) 1.41 Fe[Fe(CN)6] 0.82 ·1.74H2O), PW-18-160 (its composition is Na) 1.39 Fe[Fe(CN)6] 0.80 ·1.77H2O).
[0020] The products obtained in Examples 1-3 were used as positive electrode active materials, respectively, and were mixed with Super P (superconducting carbon black) and PVDF (polyvinylidene fluoride) in a mass ratio of 7:2:1. After adding an appropriate amount of NMP and stirring to form a slurry, the mixture was coated onto Al foil (active material loading 1-2 mg / cm³). -2 After drying, the material was cut into 14mm diameter discs as the positive electrode. A 1M NaClO4 solution in EC / DEC (1:1 volume ratio) was used as the electrolyte. A glass fiber membrane served as the separator, and 16mm diameter discs of metallic sodium were used as the negative electrode. The positive electrode shell, positive electrode sheet, separator, electrolyte, negative electrode sheet, gasket, spring sheet, and negative electrode shell were stacked sequentially and compressed to form a coin cell. The battery's rate performance was tested by cycling 5 times each at 0.2C, 0.5C, 0.8C, 1C, 2C, 5C, 8C, 10C, and 0.2C. Cycle stability was tested by cycling 200 times at 1C. The Prussian white-like material synthesized with the addition of 15g of sodium citrate showed the best performance.
[0021] Examples 4-6:
[0022] 2. Investigate the effects of different drying temperatures on the morphology and battery performance of the Prussian white-like material.
[0023] 4 mmol Na₄Fe(CN)₆·10H₂O was dissolved in 200 mL of deionized water to form solution A; 6 mmol FeSO₄·7H₂O and 15 g sodium citrate were dissolved in 200 mL of deionized water to form solution B. The mixture was stirred for 2 h. Solution A was then directly poured into solution B, and the mixture was stirred for 15 min. The mixture was then aged at room temperature for 6 h. The supernatant was removed by filtration. The solid filter was washed successively with deionized water and ethanol. The solid was then placed in a vacuum drying oven and dried overnight at 60 °C, 120 °C, and 180 °C, respectively, to obtain Prussian white material. This material was named PW-15-60 (its composition is Na₄Fe(CN)₆·10H₂O). 1.27 Fe[Fe(CN)6] 0.74 ·2.33H2O), PW-15-120 (its composition is Na) 1.26 Fe[Fe(CN)6] 0.76 ·2.13H2O), PW-15-180 (its composition is Na) 1.20 Fe[Fe(CN)6] 0.72 ·1.46H2O).
[0024] The products obtained in Examples 4-6 were used as positive electrode active materials, respectively, and were mixed with Super P (superconducting carbon black) and PVDF (polyvinylidene fluoride) in a mass ratio of 7:2:1. After adding an appropriate amount of NMP and stirring to form a slurry, the mixture was coated onto Al foil (active material loading 1-2 mg / cm³). -2 After drying, the material is cut into 14mm diameter discs as the positive electrode. A 1M NaClO4 solution in EC / DEC (1:1 volume ratio) is used as the electrolyte. A glass fiber membrane serves as the separator, and 16mm diameter discs of metallic sodium are used as the negative electrode. The positive electrode shell, positive electrode sheet, separator, electrolyte, negative electrode sheet, gasket, spring sheet, and negative electrode shell are stacked sequentially and compressed to form a coin cell. The battery's rate performance is tested by cycling 5 times each at 0.2C, 0.5C, 0.8C, 1C, 2C, 5C, 8C, 10C, and 0.2C. Cycle stability is tested by cycling 200 times at 1C.
[0025] Figure 1 These are scanning electron microscope images from Examples 1-6. Figure 1It can be seen that as the sodium citrate content increases from 12g to 15g, the stepped structure of Prussian white becomes more abundant. When it increases from 15g to 18g, the cubic size of Prussian white increases from 500nm-1.2μm to 800nm-1.5μm. The morphology of Prussian white samples at different drying temperatures does not show significant differences, indicating that drying temperature has little effect on its morphology. Overall, Examples 1-6 all exhibit abundant stepped structures, with primary particle sizes (single cubic shapes) between 500nm and 1.5μm, forming a cubic structure. Due to the chelating effect of sodium citrate, Fe... 2+ With [Fe(CN)6] 4- Slow bonding occurs as new cubic primary particles grow sequentially, layer upon layer, on the surface of a single cubic primary particle. This eventually forms layered secondary particles with a stepped structure, composed of multiple primary particles. The size of these secondary particles ranges from 2 μm to 5 μm. This abundant stepped structure is beneficial to Na… + The transmission.
[0026] Comparative Examples 1-4:
[0027] Investigating the effects of different sodium citrate addition amounts on the morphology and battery performance of Prussian white-like materials.
[0028] 4 mmol Na₄Fe(CN)₆·10H₂O was dissolved in 200 mL of deionized water to form solution A; 6 mmol FeSO₄·7H₂O and ng sodium citrate were dissolved in 200 mL of deionized water to form solution B (where n = 0, 3.75, 7.5, 30 g). The mixture was stirred for 2 h. Solution A was then directly poured into solution B, and the mixture was stirred for 15 min. The mixture was then aged at room temperature for 6 h. The supernatant was removed by filtration. The solid filter was washed successively with deionized water and ethanol. The solid was then placed in a vacuum drying oven and dried overnight at 160 °C to obtain Prussian white material. This material was named PW-1 (its composition is Na₄Fe(CN)₆·10H₂O). 0.68 Fe[Fe(CN)6] 0.60 ·2.41H2O), PW-2 (its composition is Na) 0.97 Fe[Fe(CN)6] 0.72 ·2.01H2O), PW-3 (its composition is Na) 1.24 Fe[Fe(CN)6] 0.76 ·1.80H2O), PW-4 (its composition is Na) 1.25 Fe[Fe(CN)6] 0.76 ·1.77H2O).
[0029] The obtained products (Comparative Examples 1-4) were used as positive electrode active materials, respectively, and were mixed with Super P (superconducting carbon black) and PVDF (polyvinylidene fluoride) in a mass ratio of 7:2:1. An appropriate amount of NMP was added and stirred into a slurry, which was then coated onto Al foil (active material loading 1-2 mg / cm³). -2 After drying, the material is cut into 14mm diameter discs as the positive electrode. A 1M NaClO4 solution in EC / DEC (1:1 volume ratio) is used as the electrolyte. A glass fiber membrane serves as the separator, and 16mm diameter discs of metallic sodium are used as the negative electrode. The positive electrode shell, positive electrode sheet, separator, electrolyte, negative electrode sheet, gasket, spring sheet, and negative electrode shell are stacked sequentially and compressed to form a coin cell. The battery's rate performance is tested by cycling 5 times each at 0.2C, 0.5C, 0.8C, 1C, 2C, 5C, 8C, 10C, and 0.2C. Cycle stability is tested by cycling 200 times at 1C.
[0030] Figure 2 These are scanning electron microscope images for comparative examples 1-4. (The text appears to be incomplete and requires further context.) Figure 2 It can be seen that PW-1 exhibits a morphology of irregular agglomeration of very small particles; PW-2 has a regular cubic morphology with a particle size of about 500 nm and uniform particle size; PW-3 exhibits a cubic morphology, but there is agglomeration between the cubic particles, and the particle size is mainly concentrated at about 1 μm; PW-4 shows a certain degree of stepped structure, but most of the particles are about 2 μm, and there are fewer steps, so it tends to form complete large cubic particles.
[0031] Comparative Examples 5-6:
[0032] 10 mmol of Na₄Fe(CN)₆·10H₂O was dissolved in 200 mL of deionized water to form solution A; 10 mmol of FeSO₄·7H₂O was dissolved in 200 mL of deionized water to form solution B. After thorough stirring, solution A was rapidly added dropwise to solution B. The solutions were then allowed to stand and aged at room temperature for 6 hours. The solid filter was washed with deionized water and ethanol, and then the solid was placed in a vacuum drying oven and dried overnight at different temperatures to obtain Prussian blue material. The vacuum drying temperatures were 60℃ and 160℃. Based on the different vacuum drying temperatures, the obtained Prussian blue materials were named PB-60 (its composition is Na₄Fe(CN)₆·10H₂O). 0.80 Fe[Fe(CN)6] 0.62 ·2.66H2O), PB-160 (its composition is Na) 0.83 Fe[Fe(CN)6] 0.60 ·2.14H2O).
[0033] The obtained products, comparative examples 5 and 6, were used as positive electrode active materials, and were respectively mixed with Super P (superconducting carbon black) and PVDF (polyvinylidene fluoride) in a mass ratio of 7:2:1. An appropriate amount of NMP was added and stirred into a slurry, which was then coated onto Al foil (active material loading 1-2 mg / cm³). -2 After drying, the material is cut into 14mm diameter discs as the positive electrode. A 1M NaClO4 solution in EC / DEC (1:1 volume ratio) is used as the electrolyte. A glass fiber membrane serves as the separator, and 16mm diameter discs of metallic sodium are used as the negative electrode. The positive electrode shell, positive electrode sheet, separator, electrolyte, negative electrode sheet, gasket, spring sheet, and negative electrode shell are stacked sequentially and compressed to form a coin cell. The battery's rate performance is tested by cycling 5 times each at 0.2C, 0.5C, 0.8C, 1C, 2C, 5C, 8C, 10C, and 0.2C. Cycle stability is tested by cycling 200 times at 1C.
[0034] Figure 3 These are the scanning electron microscope images for comparative examples 5-6. (Through...) Figure 3 It can be seen that both PB-60 and PB-160 exhibit a morphology of irregular small particle agglomeration.
[0035] Figure 4 The figures show the rate performance test results for Examples 1-6 and Comparative Examples 1-6. As can be seen from the figures, Examples 1-6 all exhibit excellent rate performance, with PW-15-160 showing the best rate performance. The reversible specific capacity of PW-15-160 at 0.2C in the first cycle is 107 mAh g. -1 At 2C and 5C, the specific capacity reaches 89.7% and 82.4% of the initial capacity, respectively. Even at 10C, it still has 78mAh capacity. -1 The reversible specific capacity. Excellent rate performance is mainly due to its moderate particle size and stepped structure; the abundant contact surface between the electrode and electrolyte is beneficial for Na… + The transfer of Na, thus enabling it to have faster Na... +The diffusion kinetics allow it to maintain a high level of reversible specific capacity even at high current densities, and its low bound water content results in a more complete structure. PW-12-160 has slightly fewer steps than PW-15-160, and PW-18-160 has a larger particle size, making its rate performance slightly worse than PW-15-160. PW-15-60 and PW-15-120 have more bound water, leading to more side reactions and slightly worse performance. The excessively high drying temperature of PW-15-180 damaged its structure. However, compared to comparative samples 1-6, the rate performance of Examples 1-6 is still superior. In contrast, PW-1, PW-60, and PW-160 have irregular morphologies and excessively large contact areas, resulting in too many irreversible reactions and thus poor performance. PW-2 has a regular cubic structure with a moderate contact area, and its performance is also at a medium level. PW-3 has a morphology closest to a stepped structure, therefore its performance is superior in the comparative examples. The PW-4 particles were too large, which affected the Na... + Diffusion occurs within the electrode material, resulting in poor performance.
[0036] Figure 5 The graphs show the cycling performance of Examples 1-6 and Comparative Examples 1-6 at 1C. After 200 cycles, Examples 1-6 all maintained a high capacity retention. This can be attributed to the rapid Na+ ionization. + Migration kinetics and low diffusion resistance were observed. PW-15-160 exhibited the highest specific capacity and excellent stability, primarily attributed to its abundant step-like morphology and lower bound water content. Furthermore, PW-2 and PW-3 showed superior cycling stability in the comparative examples, which is related to their moderate electrode / electrolyte contact area. PW-1, PB-60, and PB-160 all exhibited poor cycling performance due to severe side reactions caused by excessively large contact areas. PW-4, on the other hand, suffered from severe capacity decay due to its excessively large particle size and small contact area.
Claims
1. A method for preparing a Prussian white-like material, characterized in that: It was prepared using a co-precipitation method, and the specific process is as follows: 1) Dissolve Na4Fe(CN)6·10H2O in 100-300 mL of water to form solution A with a concentration of 15-25 mM; 2) Dissolve 10-20 g of sodium citrate in 100-300 mL of an aqueous solution with a concentration of 25-35 mMFeSO4·7H2O, and stir for 1.5-3 h to form solution B; 3) Mix solution A and solution B, stir for 15-25 min, age at room temperature for 5-8 h, remove the supernatant and centrifuge, wash the solid with deionized water and ethanol in sequence, and dry the solid under vacuum at 155-165 ℃ for 8-24 h to obtain Prussian white material. The Prussian white-like material obtained by the preparation method; Its composition is Na x Fe[Fe(CN)6] y ·□ 1-y ·mH2O, where 1.2 < x < 2, 0.7 < y < 1, 0 < m < 3, and □ represents [Fe(CN)6] vacancy.
2. The preparation method according to claim 1, characterized in that: The specific process is as follows: 1) Dissolve Na4Fe(CN)6·10H2O in 180-220 mL of water to form solution A with a concentration of 18-22 mM; 2) Dissolve 14-16 g of sodium citrate in 180-220 mL of an aqueous solution of 18-32 mM FeSO4·7H2O, and stir for 1.8-2.4 h to form solution B; 3) Mix solution A and solution B, stir for 15-25 min, age at room temperature for 5.5-6.5 h, remove the supernatant and centrifuge, wash the solid with deionized water and ethanol in sequence, and dry the solid under vacuum at 155-165 ℃ for 8-24 h to obtain Prussian white material; The Prussian white-like material obtained by the preparation method; Its composition is Na 1.41 Fe[Fe(CN)6] 0.82 ·1.74H2O.
3. The application of a Prussian white-like material prepared by the method of claim 1 in a sodium-ion battery.
4. The application according to claim 3, characterized in that: The Prussian white-like material is used as a positive electrode active material in sodium-ion batteries.