A high-rate sodium battery and its preparation method

Abstract

This application relates to the field of sodium-ion battery manufacturing technology, and particularly to a high-rate sodium battery and its preparation method. A high-rate sodium battery includes a positive electrode, a negative electrode, a separator, and an electrolyte; the positive electrode comprises, by mass percentage: 75-80% NVPF@C-N composite material, 10% positive electrode binder, and 10-15% conductive agent Super P, wherein the positive electrode binder is prepared by mixing sodium carboxymethyl cellulose and sodium polyacrylate in a 1:1 mass ratio; the negative electrode comprises, by mass percentage: 70-75% Fe7S8@N-C nanorod composite material, 15-20% conductive agent Super P, and 10% sodium hydroxymethyl cellulose; the separator is a glass fiber membrane. The technical solution of this application, through careful design of the structure and composition of key battery materials, achieves a comprehensive performance improvement in the high-rate sodium battery while maintaining the economy and scalability of the production process.

Description

Technical Field

[0001] This application relates to the field of sodium-ion battery manufacturing technology, and in particular to a high-rate sodium battery and its preparation method. Background Technology

[0002] With the advancement of technology, the demand for energy storage devices is constantly increasing, and high-rate lithium-ion batteries have become the preferred batteries for small power and small energy storage devices. However, in recent years, with the continuous rise in the price of lithium-ion battery raw materials, the manufacturing cost of lithium-ion batteries has also been increasing. Such high prices have made it impossible for most small and medium-sized enterprises to survive. Therefore, at this stage, most companies are turning to the research of sodium-ion batteries, which have a better cost performance.

[0003] The cost of lithium-ion batteries mainly lies in the positive electrode material and the copper foil current collector for the negative electrode. Lithium is a rare element in nature, making it expensive. Sodium ions belong to the same group as lithium ions, and sodium-ion batteries work similarly to lithium-ion batteries, utilizing the insertion and extraction of sodium ions between the positive and negative electrodes to achieve charging and discharging. Furthermore, the production equipment for sodium-ion batteries is essentially the same as that for lithium-ion batteries, eliminating the need for equipment replacement. Therefore, developing high-rate sodium-ion batteries with equivalent performance to replace lithium-ion batteries is highly necessary. Summary of the Invention

[0004] The purpose of this application is to address the shortcomings of current technology by providing a high-rate sodium battery and its preparation method. The preparation method of this application is simple, the reaction conditions are mild, the cost is low, and it is suitable for large-scale production. The high-rate sodium battery of this application has the advantages of effectively improving the excellent first discharge capacity, first coulombic efficiency, stable cycle performance, excellent high rate and long service life of sodium-ion batteries.

[0005] In a first aspect, this application provides a high-rate sodium battery, which adopts the following technical solution:

[0006] A high-rate sodium battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode comprises, by mass percentage: 75-80% NVPF@CN composite material, 10% positive electrode binder, and 10-15% conductive agent Super P. The positive electrode binder is prepared by mixing sodium carboxymethyl cellulose and sodium polyacrylate in a mass ratio of 1:1. The negative electrode comprises, by mass percentage: 70-75% Fe7S8@NC nanorod composite material, 15-20% conductive agent Super P, and 10% sodium hydroxymethyl cellulose. The separator is a glass fiber membrane.

[0007] By adopting the above technical solutions, this application's high-rate sodium battery utilizes a variety of materials and technologies to improve battery performance. Positive Electrode: The positive electrode is the main component of the battery, responsible for storing and releasing energy. The positive electrode in this application uses NVPF@CN composite material, with surface nitrogen-doped carbon coating to improve the electronic and ionic conductivity of the material, thereby improving the battery's reversible capacity and rate performance. Simultaneously, the positive electrode also contains a positive electrode binder and a conductive agent, Super P. The positive electrode binder is prepared by mixing sodium carboxymethyl cellulose and sodium polyacrylate, which helps improve the structural stability and conductivity of the positive electrode. Negative Electrode: The negative electrode is also an important component of the battery, participating in electrochemical reactions along with the positive electrode. The negative electrode in this application uses Fe7S8@NC nanorod composite material. Through the synergistic effect of Fe7S8 nanorods and the nitrogen-doped carbon layer, the cycle stability and high-rate performance of the sodium battery are improved. Simultaneously, the negative electrode also contains the conductive agent Super P and sodium carboxymethyl cellulose, which help improve the conductivity and structural stability of the negative electrode. Separator: The separator is a crucial component of the battery, used to isolate the positive and negative electrodes and prevent short circuits. The separator in this application uses a glass fiber membrane, which possesses excellent mechanical strength and chemical stability, effectively preventing short circuits between the positive and negative electrodes. Electrolyte: The electrolyte is another important component of the battery, responsible for transferring ions between the positive and negative electrodes. The electrolyte in this application uses a sodium-ion electrolyte, which helps improve the battery's ion transport efficiency, thereby enhancing its rate performance. In summary, the high-rate sodium battery of this application, through the use of high-performance materials such as NVPF@CN composite material and Fe7S8@NC nanorod composite material, achieves excellent initial discharge capacity, initial coulombic efficiency, stable cycle performance, high rate capability, and long service life, making it suitable for mass production.

[0008] Preferably, the preparation method of the Fe7S8@NC nanorod composite material includes the following steps:

[0009] S21. Preparation of ferric hydroxy oxide: Ferric chloride hexahydrate and hexadecyltrimethylammonium bromide are placed in a reactor, deionized water is added, and the mixture is magnetically stirred at room temperature for 30-60 min to obtain solution A. Solution A is then transferred to a polytetrafluoroethylene-lined reactor and reacted at 75-80℃ for 12-16 h. After the reactor is cooled to room temperature, the precipitate is collected and washed three times by alternating centrifugation with ethanol and deionized water. The precipitate is then placed in a vacuum drying oven at 60℃ and vacuum dried for 8-12 h to obtain ferric hydroxy oxide.

[0010] S22. Preparation of polydopamine-coated iron hydroxy oxide: Iron hydroxy oxide is placed in a reactor and mixed with 0.05 mol / L tris(hydroxymethyl)aminomethane buffer solution. The mixture is ultrasonicated for 30-60 min to disperse it evenly. Then, dopamine hydrochloride is added to the reactor. After stirring in an oil bath at 30℃ for 8-10 h, the mixture is filtered, washed, dried, and placed in a vacuum drying oven at 60℃ for 6-8 h to obtain polydopamine-coated iron hydroxy oxide.

[0011] S23. Preparation of nitrogen-doped carbon-coated Fe7S8 nanorod composite material: Polydopamine-coated iron hydroxide and sublimed sulfur powder were mixed evenly and transferred to a corundum quartz boat. The mixture was carbonized and sulfurized at high temperature under an argon atmosphere. After natural cooling to room temperature in the furnace, nitrogen-doped carbon-coated Fe7S8 nanorod composite material was obtained, which was labeled as Fe7S8@NC nanorod composite material.

[0012] Using the above technical solution, step S21 prepares iron hydroxyl oxide, which serves as a precursor for the Fe7S8@NC nanorod composite material. The morphology and purity of the iron hydroxyl oxide significantly influence the structure and properties of Fe7S8 in subsequent steps. By using ferric chloride hexahydrate and hexadecyltrimethylammonium bromide as raw materials and reacting them at specific temperatures and times, the particle size and morphology of the iron hydroxyl oxide can be controlled, resulting in a uniform Fe7S8@NC nanorod composite material with good electrochemical performance in subsequent steps. Step S22 prepares polydopamine-coated iron hydroxyl oxide: Polydopamine is an organic compound with good adhesion and easy polymerization, which can form a uniform coating layer on the surface of iron hydroxyl oxide. This layer not only serves as a nitrogen source, providing a basis for subsequent nitrogen doping, but also transforms into a highly conductive carbon material during high-temperature carbonization, thereby improving the electronic conductivity of the composite material. S23 prepares nitrogen-doped carbon-coated Fe7S8 nanorod composites. This step involves high-temperature carbonization and sulfidation to transform polydopamine-coated iron hydroxide into nitrogen-doped carbon-coated Fe7S8 nanorod composites. The high-temperature treatment converts polydopamine into carbon material, and sulfur reacts with iron to generate Fe7S8 nanorods. The nitrogen-doped carbon layer and Fe7S8 nanorods work synergistically. The nitrogen-doped carbon layer provides excellent electronic conductivity, while the Fe7S8 nanorods provide high ion storage capacity. This structure is beneficial for improving the high-rate performance and cycle stability of sodium batteries because electron and ion transport channels are effectively constructed while maintaining structural stability. In summary, the preparation method of the Fe7S8@NC nanorod composite material in this application achieves control over the morphology, structure, and composition of the material by precisely controlling the synthesis of the precursor and subsequent coating and heat treatment processes, thereby obtaining a sodium battery anode material with excellent electrochemical performance.

[0013] Preferably, in step S21, the ratio of ferric chloride hexahydrate, hexadecyltrimethylammonium bromide, and deionized iron is 1.08 g: 1 g: 40 mL.

[0014] Preferably, in step S22, the ratio of the amount of ferric hydroxide, tris(hydroxymethyl)aminomethane buffer solution and dopamine hydrochloride is 1g:500mL:0.4g.

[0015] Preferably, in step S23, the ratio of polydopamine-coated ferric hydroxide to sublimed sulfur powder is 1g:4g.

[0016] Preferably, in step S23, the process conditions for high-temperature carbonization and sulfurization are: heating to 150°C at a heating rate of 5°C / min and holding for 2 hours, and then heating to 550-560°C at a heating rate of 5°C / min and holding for 3-3.5 hours.

[0017] Preferably, the preparation method of the NVPF@CN composite material includes the following steps:

[0018] S71. According to the molar ratio, dissolve 3 parts NaF, 2 parts NH4H2PO4 and 2 parts NH4VO3 in 100 parts deionized water. At the same time, add 0.15 parts citric acid as a chelating agent and carbon source, and add 0.12 parts urea as a nitrogen source. Mix and stir evenly to obtain a mixed solution.

[0019] S72. The mixed solution is continuously stirred at 70℃ for 0.5-0.8h, then transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene, and the reactor is placed in an oven at 110-120℃ for 7-8h to obtain a hydrothermal product. The hydrothermal product is then frozen at -20℃ for 24h, freeze-dried, and ground to obtain the reaction precursor powder.

[0020] S73. The reaction precursor powder was heated to 300℃ and sintered for 3-4 hours under an argon atmosphere at a heating rate of 5℃ / min. Then, it was heated to 650℃ and sintered for 8-10 hours at a heating rate of 5℃ / min. After being naturally cooled to room temperature in the furnace, nitrogen-doped carbon-coated Na3V2(PO4)2F3 composite material was obtained, which was labeled as NVPF@CN composite material.

[0021] By adopting the above technical solution, the preparation of the S71 precursor solution is achieved. The purpose of this step is to prepare a solution containing NaF and NH4H2PO4. 4、A mixed solution of NH4VO3, citric acid, and urea. Citric acid, acting as a chelating agent and carbon source, helps form a homogeneous solution and control the uniform distribution of metal ions. Urea, as a nitrogen source, provides the necessary element for nitrogen doping in subsequent steps. Precise control of the raw material ratios and mixing process ensures the homogeneity of the precursor solution, which is crucial for controlling the morphology and particle size of NVPF in the subsequent hydrothermal reaction. S72 hydrothermal reaction and freeze-drying: Heating in a high-pressure reactor at 110-120°C promotes the growth and morphology formation of NVPF crystals. Freeze-drying preserves the structure of the hydrothermal products, preventing structural collapse due to capillary forces during drying. Hydrothermal reaction conditions (temperature and time) significantly affect the crystal structure and morphology of the products, while freeze-drying helps maintain these structural characteristics, thus playing a key role in the final battery performance. S73 Heat Treatment and Nitrogen-Doped Carbon Coating: The heat treatment process involves two stages of temperature rise. First, pretreatment at 300℃ removes residual moisture and organic matter, followed by high-temperature sintering at 650℃ to form the NVPF crystal structure. During this process, the nitrogen source generated from urea decomposition and the carbon source derived from citric acid work together to form a nitrogen-doped carbon coating layer. This nitrogen-doped carbon coating layer not only improves the electronic conductivity of the material but also enhances its structural stability. This structural design enables the NVPF@CN composite material to exhibit excellent electrochemical performance in high-rate sodium batteries, including high reversible capacity and good cycle stability. In summary, the preparation method of the NVPF@CN composite material in this application achieves the regulation of the material's morphology, structure, and composition through precise control of the synthesis conditions and subsequent processing, thereby obtaining a sodium battery cathode material with excellent electrochemical performance.

[0022] Preferably, the electrolyte composition has the following mass percentages: 15% NaPF6, 81% solvent, and 4% additives.

[0023] Preferably, the solvent composition comprises 45% ethylene carbonate, 8% methyl ethyl carbonate, and 47% diethyl carbonate by mass percentage; the additive composition comprises 25% vinylene carbonate, 37.5% propylene sulfite, 12.5% ​​dithiodiimidazoline, 12.5% ​​sodium difluorooxalate borate, and 12.5% ​​sodium difluorophosphate by mass percentage.

[0024] Secondly, this application provides a method for preparing a high-rate sodium battery, which adopts the following technical solution:

[0025] As a general technical concept, this application also provides a method for preparing a high-rate sodium battery, including the following steps: S101, NVPF@CN composite material, positive electrode binder and conductive agent Super P are mixed in proportion and a positive electrode slurry is obtained by using a planetary stirrer;

[0026] S102. Fe7S8@NC nanorod composite material, conductive agent Super P and sodium hydroxymethyl cellulose are mixed in proportion by a mixer to obtain negative electrode slurry;

[0027] S103. Use a coating machine to coat according to the designed process standards. Low-temperature coating is required. The coating temperature of the positive electrode is below 140℃ and the coating temperature of the negative electrode is below 115℃.

[0028] S104. The coated positive and negative electrode rolls are vacuum baked separately. The positive electrode baking conditions are 100-115℃ for 6-10 hours with a vacuum degree of less than -0.085MPa. The negative electrode baking conditions are 80-100℃ for 6-10 hours with a vacuum degree of less than -0.085MPa.

[0029] S105. Prepare the electrolyte by mixing NaPF6, solvent and additives in proportion.

[0030] S106, high-rate sodium batteries are manufactured through a process of rolling, sheet making, winding, assembly, baking, and liquid injection.

[0031] In summary, the beneficial technical effects of this application are as follows:

[0032] 1. Improved initial discharge capacity: By using NVPF@CN composite material as the positive electrode material, the surface nitrogen-doped carbon coating of this material improves the electronic conductivity and ion diffusion rate of the electrode, thereby enabling a higher initial discharge capacity.

[0033] 2. Improved initial coulombic efficiency: Initial coulombic efficiency refers to the ratio of the battery's charge capacity to its discharge capacity during the first charge-discharge cycle. The presence of a nitrogen-doped carbon coating reduces electrolyte decomposition and irreversible sodium ion loss, thereby improving initial coulombic efficiency.

[0034] 3. Stable cycling performance: The specific structural design of the Fe7S8@NC nanorod composite material, including the synergistic effect of Fe7S8 nanorods and nitrogen-doped carbon layers, provides a stable electrochemical reaction platform, reduces material degradation during cycling, and thus maintains the cycling stability of the battery.

[0035] 4. Excellent high-rate performance: High-rate performance refers to the battery's performance under high-rate charge and discharge conditions. The nitrogen-doped carbon coating and nanorod structure in this application facilitate rapid electron transport and ion diffusion, enabling the battery to maintain good performance even at high rates.

[0036] 5. Long service life: By optimizing the positive and negative electrode materials, the chemical stability and mechanical strength of the materials are improved, and the loss of active materials and structural damage during long-term cycling are reduced, thereby extending the service life of the battery.

[0037] 6. Simple and mild preparation method: The preparation method of this application is simple and the reaction conditions are mild. It does not require expensive equipment or harsh reaction conditions, which helps to reduce production costs and is suitable for large-scale production. Detailed Implementation

[0038] The embodiments of this application will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of this application. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0039] Preparation Example 1: Preparation of Fe7S8@NC Nanorod Composite Material

[0040] The preparation method of Fe7S8@NC nanorod composite material includes the following steps:

[0041] S21. Preparation of ferric hydroxyoxide: 10.8g of ferric chloride hexahydrate and 10g of hexadecyltrimethylammonium bromide were placed in a reactor, and 400mL of deionized water was added. The mixture was magnetically stirred at room temperature for 30min to obtain solution A. Solution A was then transferred to a polytetrafluoroethylene-lined reactor and reacted at 75℃ for 16h. After the reactor cooled to room temperature, the precipitate was collected and washed three times by alternating centrifugation with ethanol and deionized water. The precipitate was then vacuum dried in a 60℃ vacuum drying oven for 8h to obtain ferric hydroxyoxide. S22. Preparation of polydopamine-coated ferric hydroxyoxide: 10g of ferric hydroxyoxide was placed in a reactor and mixed with 5L of 0.05mol / L tris(hydroxymethyl)aminomethane buffer solution. The mixture was sonicated for 30min to disperse it evenly. Then, 4g of dopamine hydrochloride was added to the reactor and stirred in an oil bath at 30℃ for 8h. The mixture was then filtered, washed, dried, and vacuum dried in a 60℃ vacuum drying oven for 6h to obtain polydopamine-coated ferric hydroxyoxide.

[0042] S23. Preparation of nitrogen-doped carbon-coated Fe7S8 nanorod composite material: 10g of polydopamine-coated iron hydroxide and 40g of sublimed sulfur powder were mixed evenly and transferred to a corundum quartz boat. The mixture was then carbonized and vulcanized at high temperature under an argon atmosphere. The high-temperature carbonization and vulcanization process conditions were as follows: heating to 150℃ at a heating rate of 5℃ / min and holding for 2h, then heating to 550℃ at a heating rate of 5℃ / min and holding for 3.5h, and then naturally cooling to room temperature with the furnace to obtain nitrogen-doped carbon-coated Fe7S8 nanorod composite material, labeled as Fe7S8@NC nanorod composite material.

[0043] Preparation Example 2: Preparation of Fe7S8@NC Nanorod Composite Material

[0044] The preparation method of Fe7S8@NC nanorod composite material includes the following steps:

[0045] S21. Preparation of ferric hydroxyoxide: 10.8 g of ferric chloride hexahydrate and 10 g of hexadecyltrimethylammonium bromide were placed in a reactor, and 400 mL of deionized water was added. The mixture was magnetically stirred at room temperature for 60 min to obtain solution A. Solution A was then transferred to a polytetrafluoroethylene-lined reactor and reacted at 80 °C for 12 h. After the reactor cooled to room temperature, the precipitate was collected and washed three times by alternating centrifugation with ethanol and deionized water. The precipitate was then placed in a vacuum drying oven at 60 °C and vacuum dried for 12 h to obtain ferric hydroxyoxide.

[0046] S22. Preparation of polydopamine-coated iron hydroxyoxide: 10g of iron hydroxyoxide was placed in a reactor, and 5L of 0.05mol / L tris(hydroxymethyl)aminomethane buffer solution was added to the reactor and mixed. The mixture was sonicated for 60min to disperse it evenly. Then, 4g of dopamine hydrochloride was added to the reactor, and the mixture was stirred in an oil bath at 30℃ for 10h. After filtration, washing and drying, the mixture was placed in a vacuum drying oven at 60℃ and vacuum dried for 8h to obtain polydopamine-coated iron hydroxyoxide.

[0047] S23. Preparation of nitrogen-doped carbon-coated Fe7S8 nanorod composite material: 10g of polydopamine-coated iron hydroxide and 40g of sublimed sulfur powder were mixed evenly and transferred to a corundum quartz boat. The mixture was then carbonized and vulcanized at high temperature under an argon atmosphere. The high-temperature carbonization and vulcanization process conditions were as follows: heating to 150℃ at a heating rate of 5℃ / min and holding for 2h, then heating to 560℃ at a heating rate of 5℃ / min and holding for 3h, and then naturally cooling to room temperature with the furnace to obtain nitrogen-doped carbon-coated Fe7S8 nanorod composite material, labeled as Fe7S8@NC nanorod composite material.

[0048] Preparation Example 3: Preparation of Fe7S8@NC Nanorod Composite Material

[0049] The preparation method of Fe7S8@NC nanorod composite material includes the following steps:

[0050] S21. Preparation of ferric hydroxyoxide: 10.8 g of ferric chloride hexahydrate and 10 g of hexadecyltrimethylammonium bromide were placed in a reactor, and 400 mL of deionized water was added. The mixture was magnetically stirred at room temperature for 40 min to obtain solution A. Solution A was then transferred to a polytetrafluoroethylene-lined reactor and reacted at 78 °C for 14 h. After the reactor cooled to room temperature, the precipitate was collected and washed three times by alternating centrifugation with ethanol and deionized water. The precipitate was then placed in a vacuum drying oven at 60 °C and vacuum dried for 10 h to obtain ferric hydroxyoxide.

[0051] S22. Preparation of polydopamine-coated iron hydroxyoxide: 10g of iron hydroxyoxide was placed in a reactor, and 5L of 0.05mol / L tris(hydroxymethyl)aminomethane buffer solution was added to the reactor and mixed. The mixture was sonicated for 45min to disperse it evenly. Then, 4g of dopamine hydrochloride was added to the reactor. After stirring in an oil bath at 30℃ for 9h, the mixture was filtered, washed and dried, and then placed in a vacuum drying oven at 60℃ for 7h to obtain polydopamine-coated iron hydroxyoxide.

[0052] S23. Preparation of nitrogen-doped carbon-coated Fe7S8 nanorod composite material: 10g of polydopamine-coated iron hydroxide and 40g of sublimed sulfur powder were mixed evenly and transferred to a corundum quartz boat. The mixture was then carbonized and vulcanized at high temperature under an argon atmosphere. The high-temperature carbonization and vulcanization process conditions were as follows: heating to 150℃ at a heating rate of 5℃ / min and holding for 2h, then heating to 555℃ at a heating rate of 5℃ / min and holding for 3.3h, and then naturally cooling to room temperature with the furnace to obtain nitrogen-doped carbon-coated Fe7S8 nanorod composite material, labeled as Fe7S8@NC nanorod composite material.

[0053] Preparation Example 4: Preparation of NVPF@CN Composite Material

[0054] The preparation method of NVPF@CN composite material includes the following steps:

[0055] S71. Dissolve 3 mol NaF, 2 mol NH4H2PO4 and 2 mol NH4VO3 in 100 mol deionized water according to the molar ratio. At the same time, add 0.15 mol citric acid as a chelating agent and carbon source, and add 0.12 mol urea as a nitrogen source. Mix and stir evenly to obtain a mixed solution.

[0056] S72. The mixed solution was continuously stirred at 70°C for 0.7 h, then transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene, and the reactor was placed in an oven at 115°C for 8 h to obtain a hydrothermal product. The hydrothermal product was then frozen at -20°C for 24 h, freeze-dried, and ground to obtain the reaction precursor powder.

[0057] S73. The reaction precursor powder was heated to 300℃ and sintered for 3.5h at a heating rate of 5℃ / min under an argon atmosphere, and then heated to 650℃ and sintered for 9h at a heating rate of 5℃ / min. After being naturally cooled to room temperature in the furnace, nitrogen-doped carbon-coated Na3V2(PO4)2F3 composite material was obtained, which was labeled as NVPF@CN composite material.

[0058] Preparation of Comparative Example 1: Preparation of NVPF@C Composite Material

[0059] Same as in Preparation Example 4, except that the amount of urea added is 0.

[0060] Preparation of Comparative Example 2: Preparation of NVPF Material

[0061] Same as in Preparation Example 4, except that the amount of urea and citric acid added is 0.

[0062] Preparation of Comparative Example 3Fe7S8 Nanorod Material

[0063] The preparation method of Fe7S8 nanorod materials includes the following steps:

[0064] S21. Preparation of ferric hydroxyoxide: 10.8 g of ferric chloride hexahydrate and 10 g of hexadecyltrimethylammonium bromide were placed in a reactor, and 400 mL of deionized water was added. The mixture was magnetically stirred at room temperature for 40 min to obtain solution A. Solution A was then transferred to a polytetrafluoroethylene-lined reactor and reacted at 78 °C for 14 h. After the reactor cooled to room temperature, the precipitate was collected and washed three times by alternating centrifugation with ethanol and deionized water. The precipitate was then placed in a vacuum drying oven at 60 °C and vacuum dried for 10 h to obtain ferric hydroxyoxide.

[0065] S23. Preparation of Fe7S8 nanorod composite material: 10g of iron hydroxyl oxide and 40g of sublimed sulfur powder were mixed evenly and transferred to a corundum quartz boat. The mixture was then carbonized and sulfurized at high temperature under an argon atmosphere. The high-temperature carbonization and sulfurization process conditions were as follows: heating to 150℃ at a heating rate of 5℃ / min and holding for 2h, then heating to 555℃ at a heating rate of 5℃ / min and holding for 3.3h, and then naturally cooling to room temperature with the furnace to obtain Fe7S8 nanorod material.

[0066] Example 1

[0067] A high-rate sodium battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode comprises, by mass percentage: 75% NVPF@CN composite material, 10% positive electrode binder, and 15% conductive agent Super P. The positive electrode binder is prepared by mixing sodium carboxymethyl cellulose and sodium polyacrylate in a 1:1 mass ratio. The negative electrode comprises, by mass percentage: 70% Fe7S8@NC nanorod composite material and 20% conductive agent Super P. P, 10% sodium hydroxymethyl cellulose; the separator is a glass fiber membrane; the electrolyte composition by mass percentage is: 15% NaPF6, 81% solvent and 4% additives; the solvent composition by mass percentage is: 45% ethylene carbonate, 8% methyl ethyl carbonate and 47% diethyl carbonate; the additive composition by mass percentage is: 25% vinylene carbonate, 37.5% propylene sulfite, 12.5% ​​dithiodiimidazoline, 12.5% ​​sodium difluorooxalate borate and 12.5% ​​sodium difluorophosphate; the Fe7S8@NC nanorod composite material was prepared in Preparation Example 1.

[0068] The above-mentioned method for preparing a high-rate sodium battery includes the following steps:

[0069] S101. NVPF@CN composite material, positive electrode binder and conductive agent Super P are mixed in proportion and obtained by planetary stirrer to obtain positive electrode slurry.

[0070] S102. Fe7S8@NC nanorod composite material, conductive agent Super P and sodium hydroxymethyl cellulose are mixed in proportion by a mixer to obtain negative electrode slurry;

[0071] S103. Use a coating machine to coat according to the designed process standards. Low-temperature coating is required, with the positive electrode coating temperature at 135℃ and the negative electrode coating temperature at 110℃.

[0072] S104. The coated positive and negative electrode rolls are vacuum baked separately. The positive electrode baking conditions are 100℃ for 10 hours with a vacuum degree of -0.09MPa, and the negative electrode baking conditions are 80℃ for 6 hours with a vacuum degree of -0.09MPa.

[0073] S105. Prepare the electrolyte by mixing NaPF6, solvent and additives in proportion.

[0074] S106, high-rate sodium batteries are manufactured through a process of rolling, sheet making, winding, assembly, baking, and liquid injection.

[0075] Example 2

[0076] A high-rate sodium battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode comprises, by mass percentage: 80% NVPF@CN composite material, 10% positive electrode binder, and 10% conductive agent Super P. The positive electrode binder is prepared by mixing sodium carboxymethyl cellulose and sodium polyacrylate in a 1:1 mass ratio. The negative electrode comprises, by mass percentage: 75% Fe7S8@NC nanorod composite material and 15% conductive agent Super P. P, 10% sodium hydroxymethyl cellulose; the separator is a glass fiber membrane; the electrolyte composition by mass percentage is: 15% NaPF6, 81% solvent and 4% additives; the solvent composition by mass percentage is: 45% ethylene carbonate, 8% methyl ethyl carbonate and 47% diethyl carbonate; the additive composition by mass percentage is: 25% vinylene carbonate, 37.5% propylene sulfite, 12.5% ​​dithiodiimidazoline, 12.5% ​​sodium difluorooxalate borate and 12.5% ​​sodium difluorophosphate; the Fe7S8@NC nanorod composite material was prepared in Preparation Example 2.

[0077] The above-mentioned method for preparing a high-rate sodium battery includes the following steps:

[0078] S101. NVPF@CN composite material, positive electrode binder and conductive agent Super P are mixed in proportion and obtained by planetary stirrer to obtain positive electrode slurry.

[0079] S102. Fe7S8@NC nanorod composite material, conductive agent Super P and sodium hydroxymethyl cellulose are mixed in proportion by a mixer to obtain negative electrode slurry;

[0080] S103. Use a coating machine to coat according to the designed process standards. Low-temperature coating is required, with the positive electrode coating temperature at 138℃ and the negative electrode coating temperature at 113℃.

[0081] S104. The coated positive and negative electrode rolls are vacuum baked separately. The positive electrode baking conditions are 115℃ for 6 hours with a vacuum degree of -0.09MPa, and the negative electrode baking conditions are 100℃ for 6 hours with a vacuum degree of -0.09MPa.

[0082] S105. Prepare the electrolyte by mixing NaPF6, solvent and additives in proportion.

[0083] S106, high-rate sodium batteries are manufactured through a process of rolling, sheet making, winding, assembly, baking, and liquid injection.

[0084] Example 3

[0085] A high-rate sodium battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode comprises, by mass percentage: 78% NVPF@CN composite material, 10% positive electrode binder, and 12% conductive agent Super P. The positive electrode binder is prepared by mixing sodium carboxymethyl cellulose and sodium polyacrylate in a 1:1 mass ratio. The negative electrode comprises, by mass percentage: 73% Fe7S8@NC nanorod composite material, and 17% conductive agent Super P. P, 10% sodium hydroxymethyl cellulose; the separator is a glass fiber membrane; the electrolyte composition by mass percentage is: 15% NaPF6, 81% solvent and 4% additives; the solvent composition by mass percentage is: 45% ethylene carbonate, 8% methyl ethyl carbonate and 47% diethyl carbonate; the additive composition by mass percentage is: 25% vinylene carbonate, 37.5% propylene sulfite, 12.5% ​​dithiodiimidazoline, 12.5% ​​sodium difluorooxalate borate and 12.5% ​​sodium difluorophosphate; the Fe7S8@NC nanorod composite material was prepared in Preparation Example 3.

[0086] The above-mentioned method for preparing a high-rate sodium battery includes the following steps:

[0087] S101. NVPF@CN composite material, positive electrode binder and conductive agent Super P are mixed in proportion and obtained by planetary stirrer to obtain positive electrode slurry.

[0088] S102. Fe7S8@NC nanorod composite material, conductive agent Super P and sodium hydroxymethyl cellulose are mixed in proportion by a mixer to obtain negative electrode slurry;

[0089] S103. Use a coating machine to coat according to the designed process standards. Low-temperature coating is required, with the positive electrode coating temperature at 135℃ and the negative electrode coating temperature at 110℃.

[0090] S104. The coated positive and negative electrode rolls are vacuum baked separately. The positive electrode baking conditions are 110℃ for 8 hours with a vacuum degree of -0.09MPa, and the negative electrode baking conditions are 90℃ for 8 hours with a vacuum degree of -0.09MPa.

[0091] S105. Prepare the electrolyte by mixing NaPF6, solvent and additives in proportion.

[0092] S106, high-rate sodium batteries are manufactured through a process of rolling, sheet making, winding, assembly, baking, and liquid injection.

[0093] Comparative Example 1

[0094] Similar to Example 3, except that the NVPF@C composite material prepared in equal amounts as in Comparative Example 1 was used instead of the NVPF@CN composite material.

[0095] Comparative Example 2

[0096] Similar to Example 3, except that the NVPF material prepared in Comparative Example 2 was used in equal amounts instead of the NVPF@CN composite material.

[0097] Comparative Example 3

[0098] Similar to Example 3, except that Fe7S8 nanorods were prepared in equal quantities to replace the Fe7S8@NC nanorod composite material in Comparative Example 3.

[0099] Comparative Example 4

[0100] Similar to Example 3, except that an equal amount of 1 mol / L NaPF6 diethylene glycol dimethyl ether was used instead of the electrolyte.

[0101] Performance testing

[0102] The high-rate sodium batteries prepared in Examples 1-3 and Comparative Examples 1-4 were sampled and placed for 24 hours. Then, constant current charge / discharge tests were performed on the high-rate sodium batteries using the Land CT2001A from Wuhan Landian Technology Co., Ltd. The test results are shown in Table 1. Capacity test: The discharge capacity at 1C and 10C rates was tested using a voltage of 2-4V.

[0103] Cyclic testing: Using 2-4V voltage, 1C charging and 1C discharging; 1C charging and 10C discharging, cyclic testing is carried out in a normal temperature and humidity environment.

[0104] Table 1 Performance Tests

[0105]

[0106]

[0107] Analyzing the data in Table 1, we can see that:

[0108] 1) The high-rate sodium batteries prepared in Examples 1-3 have advantages such as excellent initial discharge capacity, initial coulombic efficiency, stable cycle performance, excellent high rate and long service life.

[0109] 2) A comparative analysis of the performance of high-rate sodium batteries prepared in Example 3 and Comparative Examples 1-2 shows that the high cycle stability of the NVPF@CN composite material is mainly due to the nitrogen-containing carbon coating layer. This coating layer can ensure effective contact between the electrode material and the electrolyte and reduce corrosion of the active material, while also stabilizing the NVPF in the Na+ electrolyte. + The structural stress changes caused by rapid insertion and extraction ensure effective electrical contact of the NVPF active material, thus enabling high-rate sodium batteries to have excellent cycle performance, stability, and high rate.

[0110] 3) A comparative analysis of the performance of the high-rate sodium batteries prepared in Example 3 and Comparative Example 3 shows that the polydopamine-modified Fe7S8 nanorod composite material utilizes the synergistic effect of the nitrogen-doped carbon layer and the Fe7S8 nanorods. The nitrogen-doped carbon layer provides good electronic conductivity, while the Fe7S8 nanorods provide high ion storage capacity. This structure is beneficial for improving the high-rate performance and cycle stability of high-rate sodium batteries because electron and ion transport channels are effectively constructed while maintaining structural stability.

[0111] 4) The performance comparison analysis of the high-rate sodium batteries prepared in Example 3 and Comparative Example 4 shows that the use of electrolyte (composed of 15% NaPF6, 81% solvent and 4% additive by mass percentage) is beneficial to improve the high-rate performance and cycle stability of high-rate sodium batteries.

[0112] The above embodiments are only used to explain the technical solutions of this application and are not intended to limit it. Although the above embodiments have provided specific descriptions of this application, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of this invention. Any modifications and equivalent substitutions that do not depart from the spirit and scope of this application should be covered within the protection scope of this application.

Claims

1. A high-rate sodium battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that, The positive electrode sheet is composed of the following mass percentages: 75-80% NVPF@CN composite material, 10% positive electrode binder, and 10-15% conductive agent SuperP. The positive electrode binder is prepared by mixing sodium carboxymethyl cellulose and sodium polyacrylate in a mass ratio of 1:

1. The negative electrode sheet is composed of the following mass percentages: 70-75% Fe7S8@N-C nanorod composite material, 15-20% conductive agent Super P, and 10% sodium hydroxymethyl cellulose. The isolation membrane is a glass fiber membrane; The NVPF@CN composite material is a nitrogen-doped carbon-coated Na3V2(PO4)2F3 composite material. The preparation method of the NVPF@CN composite material includes the following steps: S71, dissolve 3 parts NaF, 2 parts NH4H2PO4 and 2 parts NH4VO3 in 100 parts deionized water according to the molar ratio, and add 0.15 parts citric acid and 0.12 parts urea at the same time, mix and stir evenly to obtain a mixed solution; S72, continuously stir the mixed solution at 70 °C for 0.5-0.8 h, then transfer it to a stainless steel high-pressure reactor lined with polytetrafluoroethylene, and place the reactor in an oven at 110-120 °C for 7-8 h to obtain a hydrothermal product, then freeze the hydrothermal product at -20 °C for 24 h, freeze dry and grind it to obtain a reaction precursor powder; S73, heat the reaction precursor powder to 300 °C at a heating rate of 5 °C / min under an argon atmosphere. Sinter at ℃ for 3-4 hours, then heat to 650℃ at a heating rate of 5℃ / min and sinter for 8-10 hours. After natural cooling to room temperature in the furnace, nitrogen-doped carbon-coated Na3V2(PO4)2F3 composite material is obtained, which is labeled as NVPF@CN composite material. The Fe7S8@N-C nanorod composite material is a nitrogen-doped carbon-coated Fe7S8 nanorod composite material. The preparation method of the Fe7S8@N-C nanorod composite material includes the following steps: S21, Preparation of ferric hydroxide: Ferric chloride hexahydrate and hexadecyltrimethylammonium bromide are placed in a reactor, deionized water is added, and the mixture is magnetically stirred at room temperature for 30-60 min to obtain solution A. Then, solution A is transferred to a polytetrafluoroethylene-lined reactor and reacted at 75-80℃ for 12-16 h. After the reactor cools to room temperature... Collect the precipitate and wash it three times alternately by centrifugation with ethanol and deionized water. Then, place it in a vacuum drying oven at 60℃ and vacuum dry for 8-12 hours to obtain ferric hydroxide. S22. Preparation of polydopamine-coated ferric hydroxide: Place ferric hydroxide in a reactor, add 0.05 mol / L tris(hydroxymethyl)aminomethane buffer solution to the reactor and mix. Sonicate for 30-60 minutes to disperse it evenly. Then, add dopamine hydrochloride to the reactor and stir in an oil bath at 30℃ for 8-10 hours. After filtration, washing and drying, place... Vacuum drying in a vacuum drying oven at 60℃ for 6-8 h yields polydopamine-coated hydroxyl oxide; S23, Preparation of nitrogen-doped carbon-coated Fe7S8 nanorod composite material: Polydopamine-coated hydroxyl oxide and sublimed sulfur powder are mixed evenly and transferred to a corundum quartz boat, carbonized and sulfurized at high temperature under an argon atmosphere, and then naturally cooled to room temperature with the furnace to obtain nitrogen-doped carbon-coated Fe7S8 nanorod composite material, labeled as Fe7S8@N-C nanorod composite material; In step S21, ferric chloride hexahydrate and hexadecyltrimethyl bromide... The ratio of ammonium to deionized water is 1.08g:1g:40mL; the ratio of iron hydroxyoxide, tris(hydroxymethyl)aminomethane buffer solution and dopamine hydrochloride in step S22 is 1g:500mL:0.4g; the ratio of polydopamine-coated iron hydroxyoxide and sublimed sulfur powder in step S23 is 1g:4g. The high-temperature carbonization and sulfurization process conditions are: heating to 150℃ at a heating rate of 5℃ / min and holding for 2h, then heating to 550-560℃ at a heating rate of 5℃ / min and holding for 3-3.5h.

2. The high-rate sodium battery according to claim 1, characterized in that, The electrolyte composition is as follows (by mass percentage): 15% NaPF6, 81% solvent, and 4% additives.

3. A high-rate sodium battery according to claim 2, characterized in that, The solvent composition by mass percentage is: 45% ethylene carbonate, 8% methyl ethyl carbonate and 47% diethyl carbonate; the additive composition by mass percentage is: 25% vinylene carbonate, 37.5% propylene sulfite, 12.5% ​​dithiodiimidazoline, 12.5% ​​sodium difluorooxalate borate and 12.5% ​​sodium difluorophosphate.

4. A method for preparing a high-rate sodium battery as described in any one of claims 1-3, characterized in that, Includes the following steps: S101. NVPF@CN composite material, positive electrode binder and conductive agent Super P are mixed in proportion and obtained by planetary stirrer to obtain positive electrode slurry. S102. Fe7S8@N-C nanorod composite material, conductive agent Super P and sodium hydroxymethyl cellulose are mixed in proportion by a mixer to obtain negative electrode slurry; S103. Use a coating machine to coat according to the designed process standards. Low-temperature coating is required. The coating temperature of the positive electrode is below 140℃ and the coating temperature of the negative electrode is below 115℃. S104. The coated positive and negative electrode rolls are vacuum baked separately. The positive electrode baking conditions are 100-115℃ for 6-10 hours with a vacuum degree of less than -0.085MPa. The negative electrode baking conditions are 80-100℃ for 6-10 hours with a vacuum degree of less than -0.085MPa. S105. Prepare the electrolyte by mixing NaPF6, solvent and additives in proportion. S106, high-rate sodium batteries are manufactured through a process of rolling, sheet making, winding, assembly, baking, and liquid injection.

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