Preparation method of potassium ion positive electrode material and application of potassium ion positive electrode material in potassium ion battery
By preparing three-dimensional ordered porous potassium-ion cathode materials, the problem of slow electrochemical kinetics during the insertion/extraction process of potassium-ion battery cathode materials was solved, achieving high specific capacity, excellent rate performance, and long cycle life.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHAOXING INST OF NEW ENERGY & MOLECULAR ENG SHANGHAI JIAO TONG UNIV
- Filing Date
- 2024-05-23
- Publication Date
- 2026-07-14
Smart Images
Figure CN118545735B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing a potassium-ion cathode material and its application in potassium-ion batteries, and relates to the field of potassium-ion battery technology. Background Technology
[0002] Currently, in the field of new energy battery technology, lithium-ion batteries (LIBs) are the undisputed energy storage system for commercial applications. The cathode material of a lithium-ion battery releases lithium ions during charging, and the type and performance of this material directly affect the rated voltage, energy density, and cycle life of the power battery. The mainstream lithium-ion battery cathode materials include lithium iron phosphate (low cost, high safety, and long lifespan) and ternary materials such as lithium nickel cobalt manganese oxide (NCM) or lithium nickel cobalt aluminum oxide (NCA) (high specific energy).
[0003] However, due to the declining lithium resources in the Earth's crust, lithium-ion batteries have consistently faced the threat of raw material shortages. In recent years, sodium-ion batteries (SIBs) and potassium-ion batteries (KIBs) have attracted increasing attention due to their abundant resources, low cost, and electrochemical characteristics similar to lithium-ion batteries. Among them, potassium metal possesses an ultra-low redox potential (-2.93V vs. standard hydrogen electrode) to provide high operating voltage and energy density. Despite these advantages, potassium-ion batteries still face many significant challenges. For example, the large size of potassium ions leads to slow electrochemical kinetics during the insertion / extraction process of the cathode material, easily causing structural damage. Furthermore, most existing KIB cathode materials are non-porous bulk materials, and their obstructed ion channels limit the rapid transport of potassium ions within the cathode material, severely reducing the rate performance of KIBs. Therefore, one of the key issues for KIBs is the lack of cathode materials with high rate capability and long cycle life. Summary of the Invention
[0004] The first objective of this invention is to provide a method for preparing a potassium ion cathode material.
[0005] The technical solution adopted in this invention is as follows:
[0006] A method for preparing a potassium ion cathode material includes the following steps:
[0007] (1) Preparation of potassium ion cathode material template:
[0008] The amphiphilic diblock copolymer was dissolved in a mixed solvent and stirred at room temperature until the copolymer was completely dissolved. Then, deionized water was added, and the resulting sample was washed and dried in an oven at 60°C for 6 hours to obtain a potassium ion cathode material template.
[0009] (2) Preparation of potassium ion cathode material:
[0010] The potassium ion cathode material template prepared above was placed on vacuum filter paper, and then a potassium ferrocyanide precursor solution was prepared. The prepared potassium ferrocyanide precursor solution was added to the filter paper containing the potassium ion cathode material template, and vacuum treatment was performed. Then hydrochloric acid was added, and the reaction was carried out in an oven at 70°C for 48 hours. After the reaction was completed, the template was washed off and dried to obtain the potassium ion cathode material.
[0011] Further settings include:
[0012] In step (1):
[0013] The amphiphilic biblock copolymer is selected from polystyrene-b-polyethylene oxide block copolymer PS. 205～240 -b-PEO 45 Any one of them, preferably PS 209 -b-PEO 45 PS 220 -b-PEO 45 Or PS 226 -b-PEO 45 .
[0014] The preferred mixed solvent is a dioxane / N,N-dimethylformamide (v / v 9:1) mixed solvent.
[0015] Deionized water is added at a rate of 1 mL / h. -1 The dripping speed is increased.
[0016] In step (2):
[0017] The concentration of the potassium ferrocyanide precursor solution is preferably 100 mg / mL. -1 .
[0018] The vacuuming time is 10 minutes. Preferably, the filter paper containing the potassium ion positive electrode material template and the potassium ferrocyanide precursor solution is placed on a vacuum filtration device, and a vacuum pump is used to evacuate for 10 minutes. This vacuuming process removes the precursor solution between the template gaps, reducing the possibility of large impurities forming. The precursor solution within the template channels remains due to capillary action, which helps improve the purity of the ordered porous structure.
[0019] The hydrochloric acid has a mass concentration of 37%.
[0020] After the reaction was complete, the template was washed three times with tetrahydrofuran (THF) solution, and then washed three more times with ethanol and water, respectively.
[0021] The drying process is preferably carried out in a vacuum oven at 100°C for 12 hours to finally obtain the potassium ion cathode material.
[0022] Particularly preferred, a method for preparing a potassium ion cathode material includes the following steps:
[0023] (1) Preparation of potassium ion cathode material template:
[0024] 90 mg of amphiphilic diblock copolymer (PS) 209 -b-PEO 45 The copolymer was dissolved in 6 mL of a dioxane / N,N-dimethylformamide (v / v 9:1) mixed solvent and stirred at room temperature for 3 hours until completely dissolved; subsequently, the copolymer was added to the above solution at a rate of 1 mL·h -1 5 mL of deionized water was added dropwise at a certain rate; the obtained sample was washed three times with water and three times with ethanol, and then the sample was collected and dried in an oven at 60 °C for 6 hours to finally prepare a powdered potassium ion cathode material template.
[0025] (2) Preparation of potassium ion cathode material:
[0026] The potassium ion cathode material template powder prepared above was placed on vacuum filter paper, and then a concentration of 100 mg / mL was prepared. -1 A potassium ferrocyanide precursor solution was prepared, and then the prepared potassium ferrocyanide precursor solution was added to filter paper containing potassium ion cathode material template powder. The filter paper containing potassium ion cathode material template powder and potassium ferrocyanide precursor solution was placed on a vacuum suction filter and vacuumed for 10 minutes. Then the filter paper was placed in a sealed device with 100% humidity, and 2 mL of 37% hydrochloric acid was added. The sealed device was then placed in an oven at 70°C for 48 hours. Finally, the template was removed by washing three times with tetrahydrofuran, and then washed three more times with ethanol and water respectively. Finally, it was dried in a vacuum oven at 100°C for 12 hours to obtain the potassium ion cathode material.
[0027] A second objective of the present invention is the application of the aforementioned potassium-ion cathode material in a potassium-ion battery.
[0028] The beneficial effects of this invention are as follows:
[0029] (1) This invention prepares a novel potassium-ion battery cathode material with a three-dimensional ordered porous topology, a uniform pore size of 48 nm, and a specific surface area (SSA) of 65 m². 2 g -1 Its chemical formula was calculated to be K through ICP and TGA testing. 1.42 Fe[Fe(CN)6] 0.92 0.55H2O.
[0030] (2) Upon testing, the potassium-ion battery cathode material prepared in this invention, when applied to a potassium-ion battery, exhibits performance at 20 mA g⁻¹. -1A 123.3 mAh gg was achieved at a current density of [value missing]. -1 The material exhibits high specific capacity, maintaining a coulombic efficiency greater than 99% after 50 stable cycles. Simultaneously, it achieves excellent rate performance at current densities of 20, 50, 200, 500, and 2000 mA g. -1 At that time, 120.2, 116.7, 110.4, 101.2, and 92.2 mAh g were achieved. -1 The specific capacity, when the current density returns to 20 mA g -1 At that time, the specific capacity of the material rebounded to 114.5 mAh g. -1 This result demonstrates that three-dimensionally ordered porous Prussian blue exhibits outstanding rate performance. Furthermore, at a high current of 2A g... -1 Even at this speed, it can still cycle 300 times, showing only a slight decrease in cycle frequency.
[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Attached image description:
[0032] Figure 1 The image shows the SEM morphology of the potassium ion cathode material template prepared in Example 1.
[0033] Figure 2 The image shows the XRD pattern of the potassium ion cathode material prepared in Example 1.
[0034] Figure 3 SEM and TEM images of the potassium ion cathode material prepared in Example 1: (a) SEM image; (b) TEM image.
[0035] Figure 4 This is a SEM image of the material prepared in Example 2.
[0036] Figure 5 This is a SEM image of the material prepared in Example 3.
[0037] Figure 6 This is a SEM image of the material prepared in Example 4.
[0038] Figure 7 This is a SEM image of the material prepared in Example 5.
[0039] Figure 8 (a) Charge-discharge curves and (b) Cycle-specific capacity curves (current density 20 mA g) of the potassium-ion cathode material prepared in Example 1 as the cathode of a potassium-ion battery. -1 (c) Rate loop performance diagrams (current densities of 20, 50, 200, 500, 2000, and 20 mA respectively) -1(d) Long-cycle performance diagram (current density of 2A g) -1 ). Detailed implementation method:
[0040] Reagents and equipment used in the embodiments of this invention:
[0041] Regarding polystyrene (PS)-b-polyethylene oxide (PEO) block copolymer PS 209 -b-PEO 45 The synthesis can be prepared by referring to the following literature: Zhixing Lin, Shaohua Liu, Wenting Mao, Hao Tian, Nan Wang, NingheZhang, Feng Tian, Lu Han, Xinliang Feng, Yiyong Mai, Tunable Self-Assembly of Diblock Copolymers into Colloidal Particles with Triply Periodic MinimalSurfaces. Angew. Chem. Int. Ed. 2017, 56, 7135.
[0042] Example 1
[0043] A method for preparing a potassium ion cathode material includes the following steps:
[0044] (1) Preparation of potassium ion cathode material template:
[0045] First, 90 mg of amphiphilic diblock copolymer (PS) was added. 209 -b-PEO 45 The copolymer was dissolved in 6 mL of a dioxane / N,N-dimethylformamide (v / v 9:1) mixed solvent and stirred at room temperature for 3 hours until completely dissolved. Then, the copolymer was added to the above solution at a rate of 1 mL / h. -1 5 mL of deionized water was added dropwise. The obtained sample was washed three times each with water and ethanol, and then the sample was collected and dried in an oven at 60 °C for 6 hours to obtain a powdered potassium ion cathode material template.
[0046] Product confirmation: such as Figure 1 As shown, the potassium ion cathode material template has a three-dimensional ordered structure.
[0047] (2) Preparation of potassium ion cathode material:
[0048] 120 mg of potassium ion cathode material template powder was placed on vacuum filter paper, and then a concentration of 100 mg / mL was prepared. -1A potassium ferrocyanide precursor solution was prepared. Subsequently, the prepared potassium ferrocyanide precursor solution was added to filter paper containing potassium ion cathode material template powder. The filter paper containing the potassium ion cathode material template powder and potassium ferrocyanide precursor solution was placed on a vacuum filtration device and evacuated for 10 minutes. The filter paper was then placed in a sealed device with 100% humidity, and 2 mL (37% mass concentration) of hydrochloric acid was added. The sealed device was then placed in an oven at 70°C for 48 hours. Finally, the template was removed by washing three times with tetrahydrofuran (THF), and then washed three more times with ethanol and water respectively. Finally, the material was dried in a vacuum oven at 100°C for 12 hours to obtain the potassium ion cathode material.
[0049] Product confirmation:
[0050] XRD, SEM, and TEM images of the potassium ion cathode material are as follows: Figure 2 , Figure 3 As shown: The potassium-ion cathode material has a three-dimensional ordered porous topology with a uniform pore size of 48 nm and a specific surface area (SSA) of 65 m². 2 g -1 Its chemical formula was calculated using ICP and TGA testing: K 1.42 Fe[Fe(CN)6] 0.92 0.55H2O.
[0051] By analyzing the SEM morphology of the potassium-ion cathode material, we believe that due to its three-dimensional ordered porous topology, it has extremely high mass transfer efficiency and active site utilization when used as a cathode material for potassium-ion batteries, and can be used to prepare potassium-ion batteries with excellent electrochemical performance.
[0052] Example 2
[0053] The preparation method is the same as in Example 1, except that in step (2), the vacuuming time is 2 minutes, hydrochloric acid is added, and then the reaction is carried out in an oven at 70°C for 24 hours.
[0054] Product structure: such as Figure 4 As shown, the potassium ion cathode material prepared by the above method has a relatively disordered morphology and cannot form a three-dimensional ordered porous topology. The reason for this is that the vacuuming time is too short, which will cause the monomers between the polymer templates to not be completely dried. Therefore, in the subsequent reaction process, a large number of bulk impurities will be generated in the potassium ion cathode material, forming a disordered structure. In addition, the short reaction time will cause the potassium ion cathode material to grow incompletely.
[0055] Example 3
[0056] The preparation method is the same as in Example 1, except that in step (2), the vacuuming time is 2 minutes, hydrochloric acid is added, and then the reaction is carried out in an oven at 70°C for 48 hours.
[0057] Product structure: such as Figure 5 As shown, the potassium ion cathode material prepared by the above method has a relatively disordered morphology and cannot form a three-dimensional ordered porous topology.
[0058] Example 4
[0059] The preparation method is the same as in Example 1, except that in step (2), the vacuuming time is 10 minutes, hydrochloric acid is added, and then the reaction is carried out in an oven at 70°C for 24 hours.
[0060] Product structure: such as Figure 6 As shown, the potassium ion cathode material prepared by the above method has a small particle-like bicontinuous structure and cannot form a three-dimensional ordered porous topology. The reason for this is that the reaction time is less than 48 hours, so the growth of the potassium ion cathode material is not complete and the particles formed are small.
[0061] Example 5
[0062] The preparation method is the same as in Example 1, except that in step (2), the vacuuming time is 20 minutes, hydrochloric acid is added, and then the reaction is carried out in an oven at 70°C for 48 hours.
[0063] Product structure: such as Figure 7 As shown, the potassium ion cathode material prepared by the above method has a morphology of bicontinuous structural fragments and cannot form a three-dimensional ordered porous topology. The reason for this is that when the vacuuming time is too long, greater than 10 minutes, the monomers in the polymer template channels will also be filtered out. Therefore, the structure formed by the reaction is incomplete and more fragments are formed.
[0064] In summary, only by evacuating the vacuum for 10 minutes and reacting in an oven at 70°C for 48 hours can a potassium ion cathode material with a three-dimensional ordered porous topology be obtained.
[0065] Application Examples:
[0066] The application of a potassium-ion cathode material as a cathode in a potassium-ion battery includes the following steps.
[0067] The potassium-ion cathode material prepared in Example 1 was used to prepare a potassium-ion cathode and fabricated into a CR2016 coin battery. Its electrical performance was then tested.
[0068] Preparation of potassium ion cathode: Potassium ion cathode material, Ketjen black, and polyvinylidene fluoride binder (PVDF) were mixed in a mass ratio of 7:2:1 to prepare an electrode slurry. The uniformly mixed electrode slurry was coated onto aluminum foil and dried in a vacuum oven at 100°C for 6 hours to obtain the potassium ion cathode. The mass loading of the active material was approximately 2 mg / cm². -2 .
[0069] Assembly of the CR2016 coin cell battery: The atmosphere was filled with pure argon gas (H2O < 0.1 ppm, O2 < 0.1 ppm). First, potassium metal was processed. The oxide layer on the surface of the potassium metal was carefully removed with a utility knife, then it was flattened and prepared into a potassium metal sheet using a 10 mm punch. Subsequently, a 10 mm diameter potassium metal sheet was used as the negative electrode, and 0.5 M potassium hexafluorophosphate (KPF6) was dissolved in ethyl carbonate (EC) and diethyl carbonate (DEC) at a 1:1 volume ratio as the electrolyte. A 16 mm diameter glass fiber membrane (GF / D What-man) was used as the separator, and the CR2016 coin cell battery was assembled with the aforementioned potassium ion positive electrode.
[0070] Performance testing:
[0071] A multi-channel battery testing system (LAND CT2001A) was used to study constant current charge-discharge cycle performance and rate performance, such as... Figure 8 As shown.
[0072] Figure 8 (a) is a charge-discharge curve of the cathode material prepared in Example 1 as a potassium-ion battery cathode. It can be seen that, as a potassium-ion battery (KIB) cathode, the cathode material of the present invention has two relatively high voltage plateaus of 3.75 and 3.45 V and a relatively high specific capacity of 123.3 mAh g. -1 .
[0073] Figure 8 (b) Cycle-specific capacity diagram of the cathode material prepared in Example 1 as the cathode of a potassium-ion battery (current density 20 mA g). -1 It can be seen that at 20mA g -1 It still has a coulombic efficiency of nearly 100% after 50 cycles at a current density.
[0074] Figure 8 (c) Rate ring performance diagram of the cathode material prepared in Example 1 as the cathode of a potassium-ion battery (current densities of 20, 50, 200, 500, 2000, and 20 mA g). -1 As can be seen, the cathode material of this invention exhibits excellent rate performance as a potassium-ion battery (KIB) cathode: at current densities of 20, 50, 200, 500, and 2000 mA g -1At that time, the specific capacity reached 120.2, 116.7, 110.4, 101.2, and 92.2 mAh g. -1 When the current density returns to 20 mA g -1 At that time, the specific capacity of the material returned to 114.5 mAh g. -1 This proves that it has outstanding rate capability.
[0075] Figure 8 (d) shows the long-cycle performance of the cathode material prepared in Example 1 as the cathode of a potassium-ion battery (current density of 2A g). -1 It can be seen that: in 2A g -1 At the specified current density, the OP-PBA can still cycle stably for 300 times with only slight capacity decay.
[0076] The reason for this is that the potassium-ion battery cathode material of this invention has a three-dimensional ordered porous structure, allowing electrons to move along the 3D ordered framework, thereby achieving faster charge transfer. Furthermore, the shortest transport time of ions in a medium is proportional to the square of the diffusion distance and inversely proportional to the diffusion coefficient. Clearly, the potassium-ion battery cathode material of this invention has a much shorter ion migration path than conventional materials, thus enabling faster ion migration and significantly improving its electrochemical performance as a potassium-ion battery cathode.
Claims
1. A method for preparing a potassium ion cathode material, characterized in that, Includes the following steps: (1) Preparation of potassium ion cathode material template: The amphiphilic diblock copolymer was dissolved in a mixed solvent and stirred at room temperature until the copolymer was completely dissolved. Then, deionized water was added, and the resulting sample was washed and dried in an oven at 60°C for 6 hours to obtain a potassium ion cathode material template. In step (1), the amphiphilic diblock copolymer is selected from polystyrene-b-polyethylene oxide block copolymer PS 205～240 - b -PEO 45 Any one of them; (2) Preparation of potassium ion cathode material: The potassium ion cathode material template prepared above was placed on vacuum filter paper, and then a potassium ferrocyanide precursor solution was prepared. The prepared potassium ferrocyanide precursor solution was added to the filter paper containing the potassium ion cathode material template, and vacuum treatment was performed. Then hydrochloric acid was added, and the reaction was carried out in an oven at 70°C for 48 hours. After the reaction was completed, the template was washed off and dried to obtain the potassium ion cathode material. In step (2), the vacuuming time is 10 minutes.
2. The method for preparing a potassium ion cathode material according to claim 1, characterized in that: In step (1), the amphiphilic diblock copolymer is PS 209 - b -PEO 45 PS 220 - b -PEO 45 Or PS 226 - b -PEO 45 .
3. The method for preparing a potassium ion cathode material according to claim 1, characterized in that: In step (1), the mixed solvent is a dioxane / N,N-dimethylformamide mixed solvent with a v / v ratio of 9:
1.
4. The method for preparing a potassium ion cathode material according to claim 1, characterized in that: In step (1), deionized water is added at a rate of 1 mL / h. -1 The dripping speed is increased.
5. The method for preparing a potassium ion cathode material according to claim 1, characterized in that: In step (2), the concentration of the potassium ferrocyanide precursor solution is 100 mg / mL. -1 .
6. The method for preparing a potassium ion cathode material according to claim 1, characterized in that: In step (2), after the reaction is complete, the template is washed three times with tetrahydrofuran (THF) solution, and then washed three more times with ethanol and water respectively. Finally, it is dried in a vacuum oven at 100°C for 12 hours to obtain the potassium ion cathode material.
7. A method for preparing a potassium ion cathode material, characterized in that, Includes the following steps: (1) Preparation of potassium ion cathode material template: 90 mg of amphiphilic diblock copolymer PS 209 - b -PEO 45 Dissolved in 6 mL of a dioxane / N,N-dimethylformamide mixed solvent (v / v = 9:1), and stirred at room temperature for 3 hours until the copolymer was completely dissolved; subsequently, the above solution was added at a rate of 1 mL / h. -1 5 mL of deionized water was added dropwise at a certain rate; the obtained sample was washed three times with water and three times with ethanol, and then the sample was collected and dried in an oven at 60 °C for 6 hours to finally prepare a powdered potassium ion cathode material template. (2) Preparation of potassium ion cathode material: The potassium ion cathode material template powder prepared above was placed on vacuum filter paper, and then a concentration of 100 mg / mL was prepared. -1 The potassium ferrocyanide precursor solution was prepared, and then the prepared potassium ferrocyanide precursor solution was added to the filter paper containing potassium ion cathode material template powder. The filter paper containing potassium ion cathode material template powder and potassium ferrocyanide precursor solution was placed on a vacuum suction filter and vacuumed for 10 minutes. The filter paper was then placed in a sealed device with 100% humidity, and 2 mL of 37% hydrochloric acid was added. The sealed device was then placed in an oven at 70°C for 48 hours. Finally, the template was removed by washing three times with tetrahydrofuran, and then washed three more times with ethanol and water respectively. Finally, it was dried in a vacuum oven at 100°C for 12 hours to obtain the potassium ion cathode material.
8. The application of a potassium-ion cathode material prepared by any one of claims 1-7 in a potassium-ion battery.