A method for heat treatment of PBAs material using active screen plasma technology
By using active screen plasma technology to perform low-temperature heat treatment on PBA materials at a suspended potential, the problems of rapid dehydration and structural protection in existing technologies are solved, achieving efficient and low-energy removal of crystal water and improving the electrochemical stability of the materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SOUTHEAST UNIV
- Filing Date
- 2024-04-17
- Publication Date
- 2026-06-02
AI Technical Summary
Existing technologies struggle to rapidly remove water of crystallization from Prussian blue analogues (PBAs) at low temperatures while avoiding structural collapse and material damage caused by high temperatures. Furthermore, high-temperature heat treatment is energy-intensive and inefficient.
By employing active screen plasma technology, low-temperature heat treatment is performed on a sample stage with a suspended potential. High-energy electrons in the plasma excite H+ ions in the water of crystallization to reduce them to hydrogen gas. Combined with a vacuum environment, the boiling point of the water of crystallization is lowered, avoiding direct bombardment of the material by high-energy particles. The plasma collision frequency is controlled, achieving rapid dehydration without damaging the crystal structure.
This method effectively removes the water of crystallization from PBA materials at low temperatures, maintains the integrity of the crystal structure, improves processing efficiency, reduces energy consumption, avoids material damage, and has high controllability and environmental friendliness.
Smart Images
Figure CN118359209B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of PBA materials, and particularly relates to a method for heat treatment of PBA materials using active screen plasma technology. Background Technology
[0002] Among the many cathode materials for aqueous zinc-ion batteries, Prussian blue analogues (PBAs) show great promise due to their three-dimensional porous framework structure, high voltage plateau, and simple synthesis methods. However, the synthesis of PBAs often employs co-precipitation methods, which are limited by the solubility product constant K of PBAs. sp The crystals are very small, which makes the nucleation and grain growth rates extremely fast. The crystals contain a large number of ferricyanide vacancies, and these vacancies are easily occupied by water molecules, resulting in a large amount of water of crystallization in the material. During the ion insertion / extraction process, the high concentration of water of crystallization can cause the material structure to be distorted or even collapse, reducing the electrochemical stability.
[0003] Currently, the main method for removing crystal water from Prussian blue materials is high-temperature heat treatment under an inert atmosphere. However, the dehydration of PBAS is a staged process; only adsorbed water can be removed at 120°C, while most interstitial water is difficult to remove at 150°C. Furthermore, PBAs have a narrow thermal stability range; above 250°C, cyanide ions may flip, leading to structural collapse. In addition, current high-temperature heat treatment mainly relies on muffle furnaces or tube furnaces, which have long reaction times and require large flow rates of the reaction atmosphere, resulting in significant energy consumption.
[0004] Plasma technology generates heat through the collision of electrons and ions, where energy is lost during the transfer between them, thus releasing heat and producing a heating effect. It offers advantages such as high efficiency, low processing temperature, and environmental friendliness. However, because the high-energy active particles in the plasma directly contact the material surface, problems such as arc discharge and high-energy bombardment inevitably occur, which can damage the surface morphology and crystal structure of nanomaterials. Therefore, it is necessary to develop a new heat treatment process that can rapidly remove the water of crystallization from PBAs at low temperatures without damaging the material itself. Summary of the Invention
[0005] Purpose of the invention: The purpose of this invention is to provide a method for heat-treating PBA materials using active screen plasma technology, which has a low reaction temperature, a fast reaction rate, does not damage the morphology and crystal structure of PBA materials, and can reduce the water of crystallization content of PBA materials.
[0006] Technical solution: The method for heat-treating PBAs materials using active screen plasma technology according to the present invention includes the following steps:
[0007] (1) First, PBAs material is made into PBAs powder and then spread on the sample stage of the active screen plasma device. The sample stage is at a floating potential through an insulating support. Then, the active screen conductive metal mesh cover is arranged so that the sample stage is placed inside it.
[0008] (2) Close the cavity of the active screen plasma equipment, turn on the active screen plasma equipment, evacuate and then introduce the working atmosphere. The vacuum furnace wall is grounded as the anode and the active screen is the cathode. Apply voltage to ionize the gas in the working atmosphere.
[0009] (3) Adjust the voltage and duty cycle to heat the active screen and control the temperature of the sample stage. The PBAs powder is heat-treated on the sample stage.
[0010] Further, in step (1), the PBAs material is K x Mn[Fe(CN)6], Na x Fe[Fe(CN)6] or K x Cu[Fe(CN)6], wherein x is 0-2, preferably 1-2; the particle size of the PBAs powder is 500nm-1μm; the distance between the top of the active screen conductive metal mesh cover and the sample stage is 2-8cm, preferably 2cm; the material of the active screen conductive metal mesh cover is stainless steel or copper.
[0011] Further, in step (2), the flow rate of the working atmosphere is 50-200 sccm, preferably 100-200 sccm; the working atmosphere is one or more of hydrogen, argon or nitrogen.
[0012] Further, in step (3), the voltage is 300-1500V and the duty cycle is 30-85%, preferably 400-500V and the duty cycle is 85%.
[0013] Further, the heat treatment temperature is 100-220℃ and the heat treatment time is 0.5-2h; preferably, the heat treatment temperature is 130-200℃ and the heat treatment time is 0.5-1h; more preferably, the heat treatment temperature is 200℃; within this temperature range, the water of crystallization in the PBAs material lattice can be effectively removed without causing cyanide decomposition, thus ensuring the integrity of the crystal structure.
[0014] Invention Principle: In this invention, the activated screen plasma technology transfers plasma from the stage surface to the activated screen surface by adding a conductive mesh cover to the working platform and applying a cathode potential, thus avoiding direct bombardment of the PBAs material. Simultaneously, the insulating support of the working platform is suspended inside the activated screen, and the sample on the platform is at a floating potential, allowing for the processing of non-conductive substrate materials. The plasma energy partially passing through the mesh cover is significantly reduced, which can produce a certain activation effect on the material surface. High-energy electrons activate H+ in the crystal water. + The ions are reduced to hydrogen gas, leaving only hydroxyl groups inside the crystal, thereby reducing the water of crystallization content. In addition, the vacuum environment of the process effectively lowers the boiling point of the water of crystallization, and the heat generated by the collision of electrons and ions in the plasma enables the rapid removal of water of crystallization from PBAs at low temperatures without damaging the crystal structure and morphology of PBAs.
[0015] Beneficial effects: Compared with the prior art, the present invention has the following significant effects: (1) It avoids the direct bombardment of materials by high-energy particles in plasma, reducing the damage of plasma to materials; (2) The temperature of the processing process is low, avoiding the destruction of PBAs crystal structure by high temperature; (3) The excitation electron energy of the processing process is high, which will quickly transfer energy to the material, so the overall reaction time is shorter and the efficiency is higher; (4) The frequency of plasma collision can be further controlled by controlling or changing the working atmosphere, heat treatment temperature, distance between the sample stage and the conductive metal mesh, etc., and the controllability is high; (5) The processing process is low-cost, environmentally friendly and has no by-products. Attached Figure Description
[0016] Figure 1 The image shows the XRD pattern of the MnHCF-P material prepared in Example 1 of this invention.
[0017] Figure 2 This is a SEM image of the MnHCF-P material prepared in Example 1 of the present invention;
[0018] Figure 3 This is a comparison chart of the thermogravimetric curves of the materials prepared in Example 1 and Comparative Example 1 of the present invention;
[0019] Figure 4 The above are cycle stability diagrams of aqueous zinc-ion batteries measured using the materials prepared in Example 1 and Comparative Example 1 of this invention as positive electrode materials.
[0020] Figure 5 The image shows the cycle stability of an aqueous zinc-ion battery measured using the materials prepared in Example 2 and Comparative Example 2 as positive electrode materials.
[0021] Figure 6 The image shows the cycle stability of an aqueous zinc-ion battery measured using the material prepared in Example 4 of this invention as the positive electrode material. Detailed Implementation
[0022] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings.
[0023] Example 1: The method for heat treatment of PBA materials using active screen plasma technology provided in this example has the following specific steps:
[0024] Using an active screen plasma device, the processing platform and surrounding area were cleaned with alcohol, and impurities were removed with a vacuum cleaner. The obtained K2Mn[Fe(CN)6] was then evenly spread on the sample stage using a 100-mesh sieve. The sample stage was placed at a floating potential via an insulating support. A stainless steel active screen mesh was placed inside the vacuum chamber, positioning the sample stage within it, with a 2cm distance between the sample stage and the top of the mesh. After closing the chamber, the mechanical pump and Roots pump were sequentially activated to evacuate the vacuum to below 0.1 Pa. The Roots pump was then turned off, and argon gas was introduced at a flow rate of 100 sccm. The grounded vacuum furnace wall served as the anode, and the active screen as the cathode. High voltage was applied to ionize the argon gas, and the voltage was adjusted to 400V with a duty cycle of 85%. The active screen was heated, and the sample stage temperature was controlled at 150℃. After 30 minutes of treatment, the power was turned off for cooling, yielding K2Mn[Fe(CN)6] (denoted as MnHCF-P) after active screen plasma heat treatment.
[0025] Phase analysis was performed on the heat-treated MnHCF-P. Figure 1 The XRD diffraction pattern of MnHCF-P shows that the diffraction peaks at 2θ = 17.53, 24.89, 35.51, 39.99, and 44.71 are consistent with the standard PDF (JCPDS No. 51-1896) card, proving that MnHCF-P maintains its original crystal structure. Figure 2 The image shows the SEM pattern of MnHCF-P. The processed sample is a regular cubic block with a relatively smooth surface, indicating that the PBA material still retains its original crystal structure and microstructure after active screen plasma treatment.
[0026] Example 2: The method for heat treatment of PBA materials using active screen plasma technology provided in this example has the following specific steps:
[0027] Using an active screen plasma device, the processing platform and surrounding area were cleaned with alcohol, and impurities were removed with a vacuum cleaner. The obtained K2Cu[Fe(CN)6] was then evenly spread on the sample stage using a 100-mesh sieve. The sample stage was placed at a floating potential via an insulating support. A stainless steel active screen mesh was placed inside the vacuum chamber, positioning the sample stage within it, with a 2cm distance between the sample stage and the top of the mesh. After closing the chamber, the mechanical pump and Roots pump were sequentially activated to evacuate the vacuum to below 0.1 Pa. The Roots pump was then turned off, and argon gas was introduced at a flow rate of 100 sccm. The grounded vacuum furnace wall served as the anode, and the active screen as the cathode. High voltage was applied to ionize the argon gas, and the voltage was adjusted to 400V with a duty cycle of 85%. The active screen was heated, and the sample stage temperature was controlled at 150℃. After 1 hour of treatment, the power was turned off for cooling, yielding the active screen plasma-treated K2Cu[Fe(CN)6](CuHCF-P).
[0028] Example 3: The method for heat treatment of PBA materials using active screen plasma technology provided in this example has the following specific steps:
[0029] Using an active screen plasma device, the processing platform and surrounding area were cleaned with alcohol, and impurities were removed with a vacuum cleaner. The obtained NaFe[Fe(CN)6] was then evenly spread on the sample stage using a 100-mesh sieve. The sample stage was placed at a floating potential via an insulating support. A stainless steel active screen mesh was placed inside the vacuum chamber, positioning the sample stage within it, with a distance of 4 cm between the sample stage and the top of the mesh. After closing the chamber, the mechanical pump and the Roots pump were turned on sequentially to evacuate the vacuum to below 0.1 Pa. The Roots pump was then turned off, and nitrogen gas was introduced at a flow rate of 100 sccm. The grounded vacuum furnace wall served as the anode, and the active screen as the cathode. High voltage was applied to ionize the nitrogen gas, and the voltage was adjusted to 500V with a duty cycle of 85%. The active screen was heated, and the sample stage temperature was controlled at 130℃. After 1 hour of treatment, the power was turned off for cooling to obtain NaFe[Fe(CN)6] after active screen plasma heat treatment.
[0030] Example 4: The method for heat treatment of PBAs materials using active screen plasma technology provided in this example has the following specific steps:
[0031] Using an active screen plasma device, the processing platform and surrounding area were cleaned with alcohol, and impurities were removed with a vacuum cleaner. The obtained K2Mn[Fe(CN)6] was then evenly spread on the sample stage using a 100-mesh sieve. The sample stage was placed at a floating potential via an insulating support. A stainless steel active screen mesh was placed inside the vacuum chamber, positioning the sample stage within it, with a 2cm distance between the sample stage and the top of the mesh. After closing the chamber, the mechanical pump and Roots pump were sequentially activated to evacuate the vacuum to below 0.1 Pa. The Roots pump was then turned off, and argon gas was introduced at a flow rate of 100 sccm. The grounded vacuum furnace wall served as the anode, and the active screen as the cathode. High voltage was applied to ionize the argon gas, and the voltage was adjusted to 400V with a duty cycle of 85%. The active screen was heated, and the sample stage temperature was controlled at 200℃. After 30 minutes of treatment, the power was turned off for cooling, yielding K2Mn[Fe(CN)6] after active screen plasma heat treatment.
[0032] Comparative Example 1: Manganese-based Prussian blue (K2Mn[Fe(CN)6]) synthesized in the same batch as in Example 1 was used. The difference from Example 1 was that the active screen plasma heat treatment was not performed. Instead, MnHCF-L was obtained by heat treatment in a tube furnace at 150°C for 30 min under an argon atmosphere.
[0033] Figure 3 Comparing the thermogravimetric curves of the manganese-based Prussian blue analogs obtained in Example 1 and Comparative Example 1, it can be found that the water content of MnHCF-P is 3.7 wt% and that of MnHCF-L is 7.7 wt% between 30℃ and 300℃. This indicates that compared with tube furnace, active screen plasma heat treatment can effectively remove the crystal water inside the Prussian blue analogs at low temperatures.
[0034] Comparative Example 2: The same batch of copper-based Prussian blue (CuHCF) synthesized in Example 3 was used. The difference from Example 3 was that the active screen plasma treatment was not performed. Instead, CuHCF-L was obtained by heat treatment in a tube furnace at 150°C for 1 hour under an argon atmosphere.
[0035] Comparative Example 3: The difference from Example 1 is that the heat treatment temperature is 60°C.
[0036] Comparative Example 4: The difference from Example 1 is that the heat treatment temperature is 250°C.
[0037] The materials obtained in Examples 1-4 and Comparative Examples 1-4 were used as positive electrode materials for electrical performance testing: Positive electrode material, conductive carbon black, and polyvinylidene fluoride (PDVF) binder were mixed in a mass ratio of 7:2:1, poured into an agate mortar, and ground thoroughly. Then, an appropriate amount of N-methylpyrrolidone (NMP) solution was added, and grinding continued until a uniform, particle-free slurry was formed. This slurry was then evenly coated onto a stainless steel mesh and dried in a vacuum oven at 80°C for 12 hours. Aqueous zinc-ion full cells were assembled in the following order: positive electrode shell, positive electrode material, 20 μL electrolyte, separator, 20 μL electrolyte, zinc metal, gasket, spring sheet, and negative electrode shell. The cells were tested at 1 Ag. -1 The long-cycle performance was tested at current densities, and the test results are shown in Table 1 and 2. Figures 4-6 .
[0038] Table 1. Electrical properties of the materials prepared in Examples 1-4 and Comparative Examples 1-5.
[0039]
[0040] Table 1 shows that the active screen plasma heat treatment method is applicable to different PBA materials (Examples 1-4). Compared with the conventional tube furnace heat treatment method (Examples 1-2 and Comparative Examples 1-2), the prepared PBA materials exhibit higher capacity retention after 400 cycles, indicating that the PBA materials treated with active screen plasma heat treatment have better cycle stability. Further analysis revealed that 130℃-200℃ is the suitable temperature range for active screen plasma heat treatment of PBA materials. Within this temperature range, the water of crystallization inside the PBA lattice can be effectively removed without cyanide decomposition due to excessively high temperatures, thus preventing damage to the crystal structure (Examples 1, 4, and Comparative Examples 3 and 4). Among these, the samples treated at 200℃ exhibited the lowest water of crystallization content, the highest capacity retention, and the best cycle stability.
[0041] Figure 4 The materials prepared in Example 1 and Comparative Example 1 were subjected to a reaction at 1 A g. -1 The long cycling curve below shows that the MnHCF-P prepared in Example 1 has a specific capacity of 44.4 mAh g after 400 cycles. -1 The capacity retention rate was 64.2%. However, the specific capacity of the MnHCF-L prepared in Comparative Example 1 was only 18 mAh g after 400 cycles. -1 The capacity retention rate was 28%, indicating that MnHCF treated with active screen plasma exhibits better cycle stability.
[0042] Figure 5 The materials prepared in Example 3 and Comparative Example 3 were in 1Ag -1The long cycling curve shows that the CuHCF-P prepared in Example 3 has a specific capacity of 19.2 mAh g after 400 cycles. -1 The capacity retention rate was 40.6%. However, the specific capacity of CuHCF-L after 400 cycles was only 5 mAh g. -1 The capacity retention rate was 11%, indicating that CuHCF treated with active screen plasma exhibits better cycle stability.
[0043] Figure 6 The material prepared in Example 4 is in 1Ag -1 The long cycling curve below shows that the MnHCF-200 prepared in Example 4 has a specific capacity of 49.7 mAh g after 400 cycles. -1 The capacity retention rate was 93.8%, indicating that 200℃ is the optimal temperature for heat treatment of PBA materials using active screen plasma technology. PBA materials prepared at this temperature have the best cycle stability.
[0044] In summary, the method of the present invention uses active screen plasma heat treatment technology, which not only avoids the direct bombardment of plasma on the surface of PBA materials, but also removes the internal water of crystallization of PBA materials at a lower temperature. It has the advantages of high efficiency, good controllability, simple process and environmental friendliness, and can be used for industrial production.
Claims
1. A method for heat treatment of PBAs materials with active screen plasma technology, characterized in that, Includes the following steps: (1) First, PBAs material is made into PBAs powder and then spread on the sample stage of the active screen plasma device. The sample stage is at a floating potential through an insulating support. Then, the active screen conductive metal mesh cover is arranged so that the sample stage is placed inside it. (2) Close the cavity of the active screen plasma equipment, turn on the active screen plasma equipment, evacuate and then introduce the working atmosphere. The vacuum furnace wall is grounded as the anode and the active screen is the cathode. Apply voltage to ionize the gas in the working atmosphere. (3) Adjust the voltage and duty cycle to heat the active screen and control the temperature of the sample stage. The PBAs powder is heat-treated on the sample stage; the temperature of the heat treatment is 100-220℃.
2. The method for heat treating PBAs materials with active screen plasma technology according to claim 1, characterized in that, In step (1), the PBA material is K x Mn[Fe(CN)6], Na x Fe[Fe(CN)6] or K x Cu[Fe(CN)6], wherein x has a value of 0-2.
3. The method of heat treating PBAs materials with active screen plasma technology according to claim 1, wherein, In step (1), the particle size of the PBAs powder is 500 nm-1 μm.
4. The method of heat treating PBAs materials with active screen plasma technology according to claim 1, wherein, In step (1), the distance between the top of the active screen conductive metal mesh cover and the sample stage is 2-8cm.
5. The method for thermal treatment of PBAs materials with active screen plasma technology according to claim 1, characterized in that, In step (1), the material of the conductive metal mesh cover of the active screen is stainless steel or copper.
6. The method of heat treating PBAs materials with active screen plasma technology according to claim 1, wherein, In step (2), the flow rate of the working atmosphere is 50-200 sccm.
7. The method of heat treating PBAs materials with active screen plasma technology according to claim 1, wherein, In step (2), the working atmosphere is one or more of hydrogen, argon or nitrogen.
8. The method for thermal treatment of PBAs materials with active screen plasma technology according to claim 1, characterized in that, In step (3), the voltage is 300-1500V and the duty cycle is 30-85%.
9. The method for thermal treatment of PBAs materials with active screen plasma technology according to claim 1, characterized in that, In step (3), the heat treatment time is 0.5-2 hours.
10. The method of heat treating PBAs materials with active screen plasma technology according to claim 9, wherein, The heat treatment temperature is 130-200℃, and the heat treatment time is 0.5-1h.