Preparation method of sheet-shaped sodium-ion battery positive electrode material sodium copper iron manganese oxide

Abstract

The application discloses a preparation method of a sheet-shaped sodium-ion battery positive electrode material sodium copper iron manganese oxygen, which comprises the following steps: step one, accurately weighing raw materials required for synthesizing the sodium-ion positive electrode material by using an electronic analytical balance, and adding the raw materials into a mixed solution of acrylic acid and water under the condition of magnetic stirring; step two, placing the mixed solution into a constant-temperature magnetic stirrer, and heating to perform constant-temperature reaction under the condition of magnetic stirring, and adding an ammonium peroxodisulfate solution as an initiator during the constant-temperature reaction; step three, after the constant-temperature reaction is completed, the solution gradually changes into a gelatin-like gel, the reaction-completed gel is placed into an oven for drying, the dried material is loaded into a pot for pyrolysis, and the pyrolyzed material is subjected to crushing treatment to obtain a semi-finished product powder; step four, loading the semi-finished product powder into a pot and sintering; and step five, after the sintered material is discharged, the material is subjected to crushing, magnetic removal, packaging and detection to obtain a finished product.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, specifically to a method for preparing a sheet-like sodium-copper-iron-manganese-oxygen cathode material for sodium-ion batteries. Background Technology

[0002] Since the beginning of the 21st century, lithium-ion batteries, with their high energy density, superior cycle stability compared to other batteries, and high volumetric energy density, have become the primary power source for mobile phones, laptops, and even electric vehicles. However, in recent years, lithium-ion batteries have also encountered serious cost problems due to rising lithium salt prices, making the development of new energy devices as a supplement to lithium-ion batteries increasingly urgent. Among the many next-generation energy storage devices available, sodium-ion batteries, which have a similar energy storage mechanism to lithium-ion batteries, have become a competitive candidate. In fact, research on sodium-ion batteries began almost simultaneously with that of lithium-ion batteries in the 1960s. However, sodium-ion batteries suffer from shortcomings in transport dynamics and discharge specific capacity due to the larger size of the sodium ions they transport. Sodium-ion batteries also have significant advantages. The price of sodium carbonate and metallic sodium used in them is much lower than that of lithium carbonate and metallic lithium, giving them a cost advantage compared to lithium-ion batteries, with an estimated cost saving of around 30%. Therefore, sodium-ion batteries can be widely used in fields such as power batteries for electric bicycles and batteries for energy storage power stations.

[0003] Similar to lithium-ion batteries, the performance of sodium-ion batteries also depends mainly on the electrode materials, especially the cathode materials. There are many cathode materials to choose from, but the commercially viable ones are mainly polyanionic materials (represented by sodium vanadium phosphate, etc.), layered oxide materials, and Prussian blue materials (Science Bulletin, 2022, 67(30): 3546-3564). Among them, layered oxide cathode materials have a structure similar to that of lithium-ion battery layered cathode materials, and are currently the most mature in research and application. The sodium-ion batteries released by pioneering domestic sodium-ion battery companies such as Zhongke Haina and Zhejiang Nachuang all use layered oxides as cathode materials. Among the many layered oxides, the representative one is the P2 structure Na 2 / 3 Ni 1 / 3 Mn 2 / 3 NaNi with O2 and O3 structures 1 / 3 Fe 1 / 3 Mn 1 / 3 O2. Na 2 / 3 Ni 1 / 3 Mn 2 / 3 O2 materials have relatively low capacity (2.0-4.0 V, below 90 mAh / g), but exhibit relatively stable structure, minimal capacity decay during cycling, and excellent rate performance. NaNi 1 / 3 Fe 1 / 3Mn1 / 3 O2 has a higher discharge specific capacity, reaching 120 mAh / g, and its cycle stability is acceptable.

[0004] Whether it is Na 2 / 3 Ni 1 / 3 Mn 2 / 3 O2, or NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, with the exception of nickel, consists of relatively economical metals. Minimizing or eliminating nickel usage would significantly reduce material costs. Current experiments and theoretical calculations have demonstrated that divalent copper ions can pass through Cu during charging and discharging. 2+ / Cu 3+ The redox reactions between copper and nickel allow for energy storage, and the copper's potential is between 3.3 and 4.0 V, making it a suitable main active metal ion for sodium-ion battery layered materials. Considering that the price of copper is approximately one-third or less of that of nickel, using copper to replace nickel as the active component of the layered material is feasible. Subsequently, a sodium-ion battery layered material with copper as the main active component was prepared using a solid-state method, and its structure and electrochemical performance were systematically studied. It was found to have an O3 phase layered structure and exhibited a discharge specific capacity exceeding 90 mAh / g and good cycle stability, suggesting this material as a potential commercial cathode material (Advanced Materials, 2015, 27: 6928-6933). Given the large number of chemical components in this material, direct solid-state reactions involve multi-component diffusion and recrystallization, requiring high reaction temperatures and making pure phase preparation difficult. Therefore, this invention employs a polymer gelation method to disperse the corresponding ions at the molecular level in the gel, followed by decomposition and high-temperature sintering to obtain Na+. 0.9 Cu 0.22 Fe 0.3 Mn 0.48 O2 is used as a cathode material in sodium-ion batteries. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing sheet-like sodium-copper-iron-manganese-oxygen cathode materials for sodium-ion batteries, thus solving the problems mentioned in the background.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a sheet-like sodium-copper-iron-manganese-oxygen cathode material for sodium-ion batteries includes the following steps:

[0008] Step 1: Synthesize the molecular formula Na 0.9 Cu 0.22 Fe 0.3 Mn0.48 The raw materials required for the sodium ion cathode material of O2 were accurately weighed using an electronic analytical balance and added to a mixed solution of acrylic acid and water under magnetic stirring.

[0009] Step 2: Place the above mixed solution into a thermostatic magnetic stirrer, heat it to 80°C under magnetic stirring, and carry out the reaction at a constant temperature for 2-8 hours. During the reaction at a constant temperature, add ammonium persulfate solution as an initiator.

[0010] Step 3: After the constant temperature reaction is completed, the solution gradually turns into a jelly-like gel. The gel after the reaction is completed is placed in an oven at 120℃ and dried for 8-12 hours. The dried material is then placed in a pot for pyrolysis at a temperature of 350-450℃ for 2-4 hours. The pyrolyzed material is then pulverized to obtain a semi-finished powder.

[0011] Step 4: Place the semi-finished powder into a mortar and sinter it at a temperature of 800-900℃ for 8-10 hours.

[0012] Step 5: After sintering, the material is crushed, demagnetized, packaged, and tested to obtain the finished product.

[0013] Preferably, the raw materials required in step one are anhydrous sodium carbonate, copper acetate tetrahydrate, manganese acetate tetrahydrate, and ferric nitrate nonahydrate.

[0014] Preferably, the mixed solution of acrylic acid and water in step one is an aqueous solution of acrylic acid with a mass fraction of 50-60%.

[0015] Preferably, in step two, a total mass of 0.1-0.5% ammonium persulfate solution is added as an initiator.

[0016] Preferably, the ammonium persulfate solution with a mass fraction of 1-5% is added in step two.

[0017] Preferably, in step four, the heating rate is 3-5℃ / min, and the cooling method is to allow the sample to cool naturally to room temperature within the furnace. To prevent the sample from absorbing moisture, the powder is stored in a vacuum bag.

[0018] Preferably, the finished material, as determined by XRD, exhibits a layered structure, and as observed by scanning electron microscopy, it has a sheet-like morphology.

[0019] The present invention adopts the above technical solution and has the following beneficial effects:

[0020] Compared with existing technologies, this invention prepares Na by employing a polymer gel decomposition method. 0.9 Cu 0.22 Fe 0.3 Mn 0.48In the initial stage, metal ions dissolve in a mixed solution of acrylic acid and water. Then, at an appropriate temperature, acrylic acid undergoes active free radical polymerization under the action of an initiator to form a polyacrylic acid gel, which "freezes" the metal ions in the gel in a form similar to that in an aqueous solution, achieving a molecular-level dispersion effect.

[0021] This invention prepares Na by polymer gelation. 0.9 Cu 0.22 Fe 0.3 Mn 0.48 As can be seen from the XRD spectrum of O2 material, the intensity of the XRD diffraction peaks increases with the increase of sintering temperature (as shown in the comparison of sample 1 and sample 3), indicating that the increase of temperature helps to improve the crystallinity of the material. As a cathode material for sodium-ion batteries, it mainly stores energy through the mechanism of extracting and inserting sodium ions. Good crystallinity is closely related to structural stability. In a sense, the improvement of crystallinity will improve the cycle stability of the material. Attached Figure Description

[0022] Figure 1 This invention relates to the preparation of Na by the polymer gelation method. 0.9 Cu 0.22 Fe 0.3 Mn 0.48 XRD patterns of O2 material, where samples 1-3 correspond to sintering temperatures of 800℃, 850℃ and 900℃ respectively.

[0023] Figure 2 This invention relates to the preparation of Na by the polymer gelation method. 0.9 Cu 0.22 Fe 0.3 Mn 0.48 SEM images of O2 materials: (a, b) 800℃, (c) 850℃, (d) 900℃.

[0024] Figure 3 Na obtained at different sintering temperatures according to the present invention 0.9 Cu 0.22 Fe 0.3 Mn 0.48 Electrochemical performance of O2 material as a cathode in sodium-ion batteries: (a) initial charge-discharge curve, (b) cycle stability curve (current density 15 mA / g (initial), voltage range 2.0-4.0 V). Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] 1. Na 0.9 Cu 0.22 Fe 0.3 Mn 0.48 O2 preparation:

[0027] The present invention provides a method for preparing a sheet-like sodium-copper-iron-manganese-oxygen cathode material for sodium-ion batteries, comprising the following steps:

[0028] Step 1: Synthesize the molecular formula Na 0.9 Cu 0.22 Fe 0.3 Mn 0.48 The total amount of substance required for the sodium ion positive electrode material of O2 is 0.03 mol of anhydrous sodium carbonate, copper acetate tetrahydrate, manganese acetate tetrahydrate, and ferric nitrate nonahydrate. These are accurately weighed using an electronic analytical balance and added to a mixed solution of 5 mL acrylic acid and 10 mL water under magnetic stirring. This mixed solution is a 50-60% mass fraction aqueous solution of acrylic acid.

[0029] Step 2: Place the above mixed solution into a thermostatic magnetic stirrer and heat it to 80°C under magnetic stirring. Maintain the temperature for 2-8 hours. Once the temperature has stabilized, add 0.1-0.5% (by mass) of ammonium persulfate solution as an initiator; the mass fraction of the ammonium persulfate solution is 1-5%.

[0030] Step 3: After the constant temperature reaction is completed, the solution gradually turns into a jelly-like gel. The gel after the reaction is completed is placed in an oven at 120℃ and dried for 8-12 hours. The dried material is then pyrolyzed in a pot at a temperature of 350-450℃ for 2-4 hours. The pyrolyzed material is then pulverized to obtain a semi-finished powder.

[0031] Step 4: After the semi-finished powder is carefully ground, it is transferred to a corundum porcelain boat and then placed in a muffle furnace for sintering. The heating rate is 3-5℃ / min, the sintering temperature is 800-900℃, the sintering time is 8-10 hours, and the cooling method is to let it cool naturally to room temperature in the furnace.

[0032] Step 5: After sintering, the material is removed from the furnace and subjected to crushing, demagnetization, packaging, and testing to obtain the finished product. To prevent the sample from absorbing moisture, the powder is stored in vacuum bags.

[0033] The finished material was examined by XRD and found to have a layered structure, and its microstructure was observed by scanning electron microscopy and found to be plate-like.

[0034] The experimental reagents include: anhydrous sodium carbonate, copper acetate tetrahydrate, manganese acetate tetrahydrate, ferric nitrate nonahydrate, acrylic acid, ammonium persulfate, polyvinylidene fluoride, acetylene black, anhydrous ethanol, and N-methylpyrrolidone; the experimental equipment includes: electronic balance, constant temperature magnetic stirrer, forced air drying oven, vacuum drying oven, benchtop film processor, super clean glove box, and battery testing system.

[0035] Example 1

[0036] The present invention provides a method for preparing a sheet-like sodium-copper-iron-manganese-oxygen cathode material for sodium-ion batteries, comprising the following steps:

[0037] Step 1: Synthesize the molecular formula Na 0.9 Cu 0.22 Fe 0.3 Mn 0.48 The total amount of substance required for the sodium ion positive electrode material of O2 is 0.03 mol of anhydrous sodium carbonate, copper acetate tetrahydrate, manganese acetate tetrahydrate, and ferric nitrate nonahydrate. These are accurately weighed using an electronic analytical balance and added to a mixed solution of 5 mL acrylic acid and 10 mL water under magnetic stirring.

[0038] Step 2: Place the above mixed solution into a thermostatic magnetic stirrer, heat to 80°C under magnetic stirring, and maintain the temperature for 2-8 hours until the temperature is basically stable. Add 0.1% by mass of ammonium persulfate solution as an initiator; wherein the mass fraction of ammonium persulfate solution is 1-5%.

[0039] Step 3: After the constant temperature reaction is completed, the solution gradually turns into a jelly-like gel. The gel after the reaction is completed is placed in an oven at 120°C and dried for 10 hours. The dried material is then pyrolyzed in a pot at 400°C for 2 hours. The pyrolyzed material is then pulverized to obtain a semi-finished powder.

[0040] Step 4: After the semi-finished powder is carefully ground, it is transferred to a corundum porcelain boat and then placed in a muffle furnace for sintering. The heating rate is 5℃ / min, the sintering temperature is 800℃, the sintering time is 10 hours, and the cooling method is to let it cool naturally to room temperature in the furnace.

[0041] Step 5: After sintering, the material is removed from the furnace and subjected to crushing, demagnetization, packaging, and testing to obtain the finished product. To prevent the sample from absorbing moisture, the powder is stored in vacuum bags.

[0042] Example 2

[0043] The present invention provides a method for preparing a sheet-like sodium-copper-iron-manganese-oxygen cathode material for sodium-ion batteries, comprising the following steps:

[0044] Step 1: Synthesize the molecular formula Na 0.9 Cu 0.22 Fe 0.3 Mn 0.48 The total amount of substance required for the sodium ion positive electrode material of O2 is 0.03 mol of anhydrous sodium carbonate, copper acetate tetrahydrate, manganese acetate tetrahydrate, and ferric nitrate nonahydrate. These are accurately weighed using an electronic analytical balance and added to a mixed solution of 5 mL acrylic acid and 10 mL water under magnetic stirring.

[0045] Step 2: Place the above mixed solution into a thermostatic magnetic stirrer, heat to 80°C under magnetic stirring, and maintain the temperature for 2-8 hours until the temperature is basically stable. Add 0.1% by mass of ammonium persulfate solution as an initiator; wherein the mass fraction of ammonium persulfate solution is 1-5%.

[0046] Step 3: After the constant temperature reaction is completed, the solution gradually turns into a jelly-like gel. The gel after the reaction is completed is placed in an oven at 120°C and dried for 10 hours. The dried material is then pyrolyzed in a pot at 400°C for 2 hours. The pyrolyzed material is then pulverized to obtain a semi-finished powder.

[0047] Step 4: After the semi-finished powder is carefully ground, it is transferred to a corundum porcelain boat and then placed in a muffle furnace for sintering. The heating rate is 5℃ / min, the sintering temperature is 850℃, the sintering time is 10 hours, and the cooling method is to let it cool naturally to room temperature in the furnace.

[0048] Step 5: After sintering, the material is removed from the furnace and subjected to crushing, demagnetization, packaging, and testing to obtain the finished product. To prevent the sample from absorbing moisture, the powder is stored in vacuum bags.

[0049] Example 3

[0050] The present invention provides a method for preparing a sheet-like sodium-copper-iron-manganese-oxygen cathode material for sodium-ion batteries, comprising the following steps:

[0051] Step 1: Synthesize the molecular formula Na 0.9 Cu 0.22 Fe 0.3 Mn 0.48 The total amount of substance required for the sodium ion positive electrode material of O2 is 0.03 mol of anhydrous sodium carbonate, copper acetate tetrahydrate, manganese acetate tetrahydrate, and ferric nitrate nonahydrate. These are accurately weighed using an electronic analytical balance and added to a mixed solution of 5 mL acrylic acid and 10 mL water under magnetic stirring.

[0052] Step 2: Place the above mixed solution into a thermostatic magnetic stirrer, heat to 80°C under magnetic stirring, and maintain the temperature for 2-8 hours until the temperature is basically stable. Add 0.1% by mass of ammonium persulfate solution as an initiator; wherein the mass fraction of ammonium persulfate solution is 1-5%.

[0053] Step 3: After the constant temperature reaction is completed, the solution gradually turns into a jelly-like gel. The gel after the reaction is completed is placed in an oven at 120°C and dried for 10 hours. The dried material is then pyrolyzed in a pot at 400°C for 2 hours. The pyrolyzed material is then pulverized to obtain a semi-finished powder.

[0054] Step 4: After the semi-finished powder is carefully ground, it is transferred to a corundum porcelain boat and then placed in a muffle furnace for sintering. The heating rate is 5℃ / min, the sintering temperature is 900℃, the sintering time is 10 hours, and the cooling method is to let it cool naturally to room temperature in the furnace.

[0055] Step 5: After sintering, the material is removed from the furnace and subjected to crushing, demagnetization, packaging, and testing to obtain the finished product. To prevent the sample from absorbing moisture, the powder is stored in vacuum bags.

[0056] II. Structural Characterization Analysis:

[0057] XRD patterns of the precursor and product were analyzed using an X-ray powder diffractometer (Panasco, Netherlands) (angle range 10-80 degrees, accelerating voltage and current 40 kV and 40 mA, respectively). The test results are as follows: Figure 1 As shown; the morphology and particle size of the material were observed and analyzed using a scanning electron microscope (SEM, Hitachi, Japan), and the results are as follows. Figure 2 As shown.

[0058] III. Electrochemical Performance Testing:

[0059] Na prepared as described above 0.9 Cu 0.22 Fe 0.3 Mn 0.48 O2 material is used as the active substance and is mixed evenly with acetylene black and PVDF (polyvinylidene fluoride) in a ratio of 8:1:1 (total mass about 0.2 g). Then, an appropriate amount of N-methylpyrrolidone (about 20 drops) is added to make a slurry. The slurry is coated onto the current collector aluminum foil and dried overnight in a vacuum drying oven at a constant temperature of 80°C. After rolling, the dried coated aluminum foil is punched into a circular sheet with a diameter of 14 mm using a punching machine.

[0060] In an argon-filled glove box, the working electrodes were assembled into a coin cell using a commercial electrolyte (NC-304, an ester solution of sodium perchlorate), a separator (Celgard lithium-ion separator), a sodium sheet (commercially available laboratory-grade aluminum-sodium composite sheet), a nickel sheet, and a battery casing. The assembled battery was then subjected to charge-discharge tests in a battery test system with a voltage range of 2.0 to 4.0 V and a current density of 15 mA / g.

[0061] 4. Na 0.9 Cu 0.22 Fe 0.3 Mn 0.48 O2 analysis:

[0062] Because of Na 0.9 Cu 0.22 Fe 0.3 Mn 0.48 O2 materials have a complex composition. Dispersing the metal ions at the molecular level before material formation is beneficial for the formation and crystallization of the pure phase. This invention uses a polymer gel decomposition method to prepare Na. 0.9 Cu 0.22 Fe 0.3 Mn 0.48 In the initial stage, metal ions dissolve in a mixed solution of acrylic acid and water. Then, at an appropriate temperature, acrylic acid undergoes active free radical polymerization under the action of an initiator to form a polyacrylic acid gel, which "freezes" the metal ions in the gel in a form similar to that in an aqueous solution, achieving molecular-level dispersion.

[0063] Na prepared by polymer gelation method 0.9 Cu 0.22 Fe 0.3 Mn 0.48 The XRD pattern of O2 material is shown below. Figure 1 As shown in the figure, the positions of its XRD diffraction peaks remain basically unchanged. Since there is no standard indexing card for the diffraction peaks, references were used, along with similar O3 phase NaNi. 1 / 3 Mn 2 / 3 The O2 standard spectrum indicates that the desired material is an O3 layered structure. Furthermore, the diffraction peaks do not show single oxides such as CuO, Fe2O3, and Mn3O4 (these types of diffraction peaks often appear and maintain a certain intensity when a pure phase target product cannot be obtained), indicating that this method can be used to prepare pure-phase Na. 0.9 Cu 0.22 Fe 0.3 Mn 0.48 O2, in which the molecularly dispersed polymer gel is formed should be key.

[0064] As the sintering temperature increases, the intensity of the XRD diffraction peaks increases (as shown in the comparison between sample 1 and sample 3), indicating that increasing the temperature helps improve the crystallinity of the material. As a cathode material for sodium-ion batteries, it primarily stores energy through the mechanism of sodium ion extraction and insertion. Good crystallinity is closely related to structural stability; in a sense, improved crystallinity enhances the material's cycle stability. However, the higher sintering temperatures required to improve crystallinity can also cause particle growth, which may be detrimental to performance improvement. Therefore, optimizing the sintering temperature requires further clarification through electrochemical performance testing of the material.

[0065] Next, the prepared series of Na 0.9 Cu 0.22 Fe 0.3 Mn 0.48 The O2 material was observed using SEM, and typical photographs were taken as follows: Figure 2 As shown in the overall photograph of the low-temperature sample (800℃) Figure 2 a) Micron-sized sheet-like structures can be clearly observed. The formation of these sheet-like structures is typical of organic matter decomposition, similar to the morphology of products prepared by soft chemical methods reported in some literature, and may be related to the decomposition of the original polymeric network framework. In the magnified image of the sample, these sheet-like structures are observed to be composed of countless nanoparticles. These nanoparticles are relatively uniform in size, ranging from 200 to 500 nanometers. The well-dispersed metal ions in the organic matter readily nucleate due to the numerous nucleation sites, easily forming the nanoparticles shown in the figure. Furthermore, almost every particle has clear edges and corners, indicating that the material underwent good crystallization during high-temperature sintering, which is consistent with… Figure 1 The materials in the middle exhibit consistent XRD diffraction peaks.

[0066] As the sintering temperature increases, the material maintains good crystallinity while ( Figure 2 As shown in c and d), the particle size increases, which is due to the higher sintering temperature favoring particle crystallization and crystal production. At a higher sintering temperature (900℃), Na... 0.9 Cu 0.22 Fe 0.3 Mn 0.48 The fusion and aggregation between O2 material particles are also more pronounced, which is due to the fusion growth of particles at high temperatures. As described earlier, good crystallinity and particle size have a significant impact on the electrochemical performance of the material, requiring further testing and analysis.

[0067] As a cathode material for sodium-ion batteries, the Na produced at different sintering temperatures was evaluated. 0.9 Cu 0.22Fe 0.3 Mn 0.48 The electrochemical properties of O2 materials, such as Figure 3 As shown, the sample obtained at 800℃ exhibits a charging capacity of approximately 79.5 mAh / g, while its initial discharge specific capacity is 65.6 mAh / g, resulting in a relatively low initial coulombic efficiency of only 82.5%. In contrast, the sample obtained at 850℃ demonstrates superior initial electrochemical performance, with an initial charging capacity of approximately 100.3 mAh / g and a discharge specific capacity reaching 94.3 mAh / g, achieving a coulombic efficiency close to 94%, both of which are quite ideal. For the sample obtained at 900℃, both its initial charging and discharging capacities exceed 100 mAh / g, but both its charging and discharging voltages are relatively low. This is presumably due to the presence of electrochemically active Mn in the material caused by sodium volatilization at high temperatures. 3+ The charge-discharge curves show a smaller difference between the charging and discharging voltages of the sample obtained at 850℃, indicating less polarization and demonstrating good electrochemical reversibility. The main capacity contribution occurs within the 3.0-3.8 V discharge voltage range, primarily attributed to the Cu content. 2+ / Cu 3+ The contribution of the redox couple, while the contribution of the Mn3+ / Mn4+ couple may mainly occur in the sample at 900℃.

[0068] Cyclic stability curves are as follows Figure 3 As shown in b, to improve testing efficiency, the current density was measured at 100 mA / g. The figure clearly shows that the capacity of the samples at 800℃ and 850℃ decreased less during 100 cycles, indicating good cycling stability. This may be attributed to its well-ordered layered structure and the close-packed spherical structure of the nanoparticles. The sample at 900℃ showed poor cycling stability, presumably because Mn ions began to participate in the reaction as active components, and the Jamin-Taylor distortion of Mn during cycling significantly affects the material's cycling stability.

[0069] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a sheet-like sodium-copper-iron-manganese-oxygen cathode material for sodium-ion batteries, characterized in that, Includes the following steps: Step 1: Synthesize the molecular formula Na 0.9 Cu 0.22 Fe 0.3 Mn 0.48 The raw materials required for the sodium ion cathode material of O2 were accurately weighed using an electronic analytical balance and added to a mixed solution of acrylic acid and water under magnetic stirring. The raw materials required in step one are anhydrous sodium carbonate, copper acetate tetrahydrate, manganese acetate tetrahydrate, and ferric nitrate nonahydrate; Step 2: Place the above mixed solution into a thermostatic magnetic stirrer, heat it to 80°C under magnetic stirring, and carry out the reaction at a constant temperature for 2-8 hours. During the reaction at a constant temperature, add ammonium persulfate solution as an initiator. Step 3: After the constant temperature reaction is completed, the solution gradually turns into a jelly-like gel. The gel after the reaction is completed is placed in an oven at 120℃ and dried for 8-12 hours. The dried material is then placed in a pot for pyrolysis at a temperature of 350-450℃ for 2-4 hours. The pyrolyzed material is then pulverized to obtain a semi-finished powder. Step 4: Place the semi-finished powder into a mortar and sinter it at a temperature of 800-900℃ for 8-10 hours. Step 5: After sintering, the material is crushed, demagnetized, packaged, and tested to obtain the finished product.

2. The method for preparing a sheet-like sodium-copper-iron-manganese-oxygen cathode material according to claim 1, characterized in that, In step one, the mixed solution of acrylic acid and water is a 50-60% by mass aqueous solution of acrylic acid.

3. The method for preparing a sheet-like sodium-copper-iron-manganese-oxygen cathode material according to claim 1, characterized in that, In step two, 0.1-0.5% of a total mass of ammonium persulfate solution is added as an initiator.

4. The method for preparing a sheet-like sodium-copper-iron-manganese-oxygen cathode material according to claim 1, characterized in that, In step two, a 1-5% persulfate solution is added.

5. The method for preparing a sheet-like sodium-copper-iron-manganese-oxygen cathode material according to claim 1, characterized in that, In step four, the heating rate is 3-5℃ / min, and the cooling method is to allow the sample to cool naturally to room temperature within the furnace. To prevent the sample from absorbing moisture, the powder is stored in a vacuum bag.

6. The method for preparing a sheet-like sodium-copper-iron-manganese-oxygen cathode material according to claim 1, characterized in that, The finished material was examined by XRD and found to have a layered structure, and its microstructure was observed by scanning electron microscopy and found to be plate-like.

Images