An organic-inorganic hybrid material, a method for preparing the same, and an application thereof

Abstract

The present application relates to an organic-inorganic hybrid material and a preparation method and application thereof. The organic-inorganic hybrid positive electrode material has a chemical formula of XTM L; wherein X is an alkali metal ion, TM is a 3d transition metal, and L is an organic ligand of 2-hydroxyphosphonooxyacetic acid ((C2H2O6P) 3‑ ).

Description

Technical Field

[0001] This invention relates to an organic-inorganic hybrid material, specifically to a method for preparing and applying an organic-inorganic hybrid cathode material that can achieve full charge and discharge of sodium ions, exhibiting high rate capability and long cycle life, belonging to the energy field. Background Technology

[0002] Compared to lithium-ion batteries, sodium-ion batteries benefit from the widespread availability, abundant quantity, and lower cost of sodium resources, leading to significant attention in large-scale electrochemical energy storage technologies. The cathode material, as the core of a sodium-ion battery, determines its electrochemical performance, thus influencing the battery's quality. Cathode materials, including transition metal oxides, organic compounds, polyanionic compounds, and Prussian blue compounds, have been studied and made considerable progress, but several challenges remain. For example, the limited number of Na ions inserted / extracted, irreversible phase transitions, and even structural collapse can lead to low capacity, high polarization, and rapid capacity decay during cycling. Therefore, developing novel cathode materials, especially those based on open structures, is crucial.

[0003] Olivine-structured LiFePO4 has been successfully used as a cathode material in commercial lithium-ion batteries, exhibiting remarkable stability during charge and discharge cycles. Therefore, the corresponding sodium iron phosphate compound, NaFePO4, has also been considered as a cathode material for sodium-ion batteries. However, stable olivine-structured NaFePO4 does not exist in nature; it is typically obtained from olivine-shaped LiFePO4 via electrochemical ion exchange reactions because it is not a thermodynamically stable phase. The thermodynamic instability of the NaFePO4 olivine structure and its large volume expansion (Vo) during charge-discharge processes contribute to this problem. FePO4 →V NaFePO4 This results in poor cycle performance, thus hindering the practical application of olivine-NaFePO4. On the other hand, the thermodynamically stable phase of NaFePO4 is the sodium phosphate rock structure, but due to the high Na content... + The ion migration barrier, which hinders the extraction and insertion of sodium ions, results in the thermodynamically stable sodium phosphate rock structure NaFePO4, which is generally considered to be electrochemically inactive. Currently, methods such as high-potential charging, ball milling, melt quenching, and amorphization have been employed to expand or construct sodium ion migration channels and lower the migration barrier, thereby activating the electrochemical activity of the NaFePO4 sodium phosphate rock structure. However, these methods typically cannot achieve a balance between rate performance and cycle stability in cathode materials. Summary of the Invention

[0004] To address the incompatibility between rate performance and cycle life inherent in inorganic sodium phosphate compounds, this invention provides an organic-inorganic hybrid cathode material, its preparation method, and its applications. When used as an electrode, this organic-inorganic hybrid material enables completely reversible extraction and insertion of sodium ions, exhibiting high rate capability and long cycle life. Furthermore, its preparation method is simple and easy to implement.

[0005] In a first aspect, the present invention provides an organic-inorganic hybrid material, wherein the chemical formula of the organic-inorganic hybrid cathode material is XTML; wherein X is an alkali metal ion, TM is a 3d transition metal, and L is an organic ligand of 2-hydroxyphosphonoacetic acid ((C2H2O6P)). 3- ).

[0006] In this invention, the organic-inorganic hybrid material, with its flexible organic portion, can provide a variable structural framework, which is beneficial for Na... + K + Li + Rapid migration without disrupting the channel structure, while the inorganic portion provides electrochemical activity. Based on metal phosphonates with 2-hydroxyphosphonoacetic acid (HPAA=H2O3PCH(OH)CO2H) as the organic ligand, these belong to organic-inorganic hybrid materials with an open structural framework. Therefore, the organic-inorganic hybridization of this invention enhances the electrochemical activity of sodium phosphate compounds.

[0007] Preferably, the organic-inorganic hybrid material has a tetragonal crystal system and a space group of [missing information]. Pbca The unit cell parameters are α=β=γ=90°.

[0008] Preferably, the 3d transition metal is coordinated with the phosphonoyl group and is selected from Mn. 2+ Fe 2+ Co 2+ Ni 2+ Cu 2+ Zn 2+ At least one of the following; the alkali metal ion is selected from Li + Na + K + At least one of them has a charge compensation function.

[0009] Secondly, the present invention provides a method for preparing an organic-inorganic hybrid material, comprising:

[0010] (1) Mix the metal salt compound, 2-hydroxyphosphonoacetic acid, mineralizing agent and deionized water and adjust the pH of the solution to between 2 and 7 to obtain a mixed solution;

[0011] (2) The mixed solution is placed in a hydrothermal reactor and subjected to hydrothermal reaction. Then it is subjected to ultrasonic or filtration, washed and dried to obtain the organic-inorganic hybrid material.

[0012] Preferably, the metal salt compound includes at least one of the following: metal sulfate, metal nitrate, metal acetate, metal carbonate, and metal chloride;

[0013] The molar ratio of the metal salt compound to 2-hydroxyphosphonoacetic acid is 1:1 to 1:6.

[0014] Preferably, the mineralizing agent is selected from at least one of LiF, NaF, KF, Na2CO3, Na2SiF6, and Na2SO4; the molar ratio of the mineralizing agent to the metal salt compound is (0.5-20):1.

[0015] Preferably, the pH adjuster used to adjust the solution includes at least one of NH4Cl, NaOH, LiOH, KOH, (NH4)2HPO4, urea, and acetic acid.

[0016] Preferably, the temperature of the hydrothermal reaction is 80–200 °C, and the reaction time is 48–200 h; more preferably, the heating rate of the hydrothermal reaction is 2–6 °C / min.

[0017] Thirdly, the present invention provides an active electrode material, comprising: the above-mentioned organic-inorganic hybrid material XTML, and a carbon material coated on the surface of XTML, denoted as C@XTML;

[0018] Preferably, the carbon material includes at least one of carbon black, graphene, carbon nanotubes, and graphite;

[0019] Preferably, the mass ratio of the carbon material to XTML is y:(10-y), where 7≤y<10.

[0020] Fourthly, the present invention provides a method for preparing an active electrode material, wherein carbon material and XTML are weighed and ball-milled according to a mass ratio to obtain C@XTML material; preferably, the ball milling speed is 300-500 rpm and the ball milling time is 4-24 h.

[0021] Fifthly, the present invention provides an electrode, characterized in that it comprises: a current collector and an electrode layer coated on the surface of the current collector;

[0022] The electrode layer comprises the above-mentioned active electrode material, Super P, and a binder;

[0023] Preferably, the current collector is an Al foil, a carbon-coated Al foil, or a Cu foil;

[0024] Preferably, the mass ratio of the active electrode material, Super P and binder is z:(9-z):1, where 6≤z<9.

[0025] In a sixth aspect, the present invention provides a method for preparing an electrode, characterized in that C@XTML is used as the active material, and the active electrode material: Super P: binder mass ratio = z:(9-z):1 is weighed and mixed in an organic solution, coated on the surface of a current collector, and then dried to obtain the electrode;

[0026] Preferably, the organic solvent includes at least one of NMP, DMF, DMSO, and DMAc;

[0027] The drying process is vacuum drying, with a temperature of 100–120°C and a duration of 8–12 hours.

[0028] In a seventh aspect, the present invention provides an application of the above-mentioned organic-inorganic hybrid material in a secondary battery, the secondary battery including a lithium-ion battery, a sodium-ion battery, and a potassium-ion battery.

[0029] Eighthly, the present invention provides an application of the above-mentioned active electrode material in a secondary battery, the secondary battery including a lithium-ion battery, a sodium-ion battery, and a potassium-ion battery.

[0030] Ninthly, the present invention provides an application of the above-mentioned electrode in a secondary battery, the secondary battery including a lithium-ion battery, a sodium-ion battery, and a potassium-ion battery.

[0031] The present invention has the following beneficial effects:

[0032] 1. This invention pioneers the application of phosphonyl-based organic-inorganic hybrid materials as cathode materials for sodium-ion batteries. Polyanionic inorganic compounds possess structural rigidity, enabling long-cycle stability. However, the stable sodium phosphate rock structure NaFePO4 exhibits inactivity due to the high sodium ion migration barrier. Currently, amorphization of NaFePO4 is achieved through high-energy ball milling, melting, and high-potential charging to enhance its electrochemical activity. Essentially, the amorphization of sodium phosphate rock structure NaFePO4 aims to reduce the sodium ion migration barrier. + The migration barrier forms a distinct and continuous sodium ion migration channel. For example, in the amorphous NaFePO4 cathode, Na... + The migration barrier decreased from 2.68 eV to 0.73 eV, and a reversible capacity of 134.9 mAh / g was achieved at 0.05 C after 200 cycles. Organic-inorganic hybrid materials with open structural frameworks can achieve Na… +Rapid migration along the channel provides a new method for achieving high electrochemical activity of sodium phosphate compounds;

[0033] 2. This invention utilizes the phosphonyl-based organic-inorganic hybrid material NaFe(O3PCH(OH)CO2) as the cathode material for sodium-ion batteries, exhibiting excellent rate performance and cycle stability. At a current density of 0.1C, the initial discharge specific capacities within voltage windows of 1.5–4.2V, 1.5–4.4V, and 1.5–4.6V are 135.2 mAh / g, 103.2 mAh / g, and 119.4 mAh / g, respectively. After 50 charge-discharge cycles within the 1.5–4.2V range, the specific capacity of the NaFe(O3PCH(OH)CO2) cathode material stabilizes at approximately 106.1 mAh / g, with a coulombic efficiency of 99.8%. At 0.2C, 0.3C, 0.4C, and 0.5C, the discharge specific capacities of the NaFe(O3PCH(OH)CO2) cathode material are 89.1, 85.9, 83.5, and 81.8, respectively. The reversible specific capacity was 106.1 mAh / g at 0.1C, with capacity retention rates of 83.9%, 80.9%, 78.6%, and 77.1% at 0.2C, 0.3C, 0.4C, and 0.5C, respectively. Furthermore, while the capacity gradually decreased as the current density increased to 1C, 2C, and 3C, it recovered to 94.0 mAh / g upon returning to 0.1C, demonstrating excellent rate performance. Moreover, at current rates of 1C and 2C, the NaFe(O3PCH(OH)CO2 cathode material achieved specific capacities of 70.7 mAh / g and 62.4 mAh / g after 200 and 400 cycles, respectively, exhibiting good cycling performance. Attached Figure Description

[0034] Figure 1 The crystal structure diagram of the NaFe(O3PCH(OH)CO2 material prepared in Example 1 is shown below.

[0035] Figure 2 The infrared spectrum of the NaFe(O3PCH(OH)CO2 material prepared in Example 1 is shown below.

[0036] Figure 3 The X-ray powder diffraction pattern of the NaFe(O3PCH(OH)CO2 material prepared in Example 1 is shown below.

[0037] Figure 4 This is a scanning electron microscope image of the NaFe(O3PCH(OH)CO2 material prepared in Example 1;

[0038] Figure 5The constant current charge-discharge diagrams of the NaFe(O3PCH(OH)CO2@C material prepared in Example 1 as a positive electrode material for sodium-ion batteries are shown in the voltage range of 1.5 to 4.2 V.

[0039] Figure 6 The constant current charge-discharge diagram shows the NaFe(O3PCH(OH)CO2@C material prepared in Example 1 as a positive electrode material for sodium-ion batteries in the voltage range of 1.5 to 4.4 V.

[0040] Figure 7 The constant current charge-discharge diagram of the NaFe(O3PCH(OH)CO2@C material prepared in Example 1 as a positive electrode material for sodium-ion batteries in the voltage range of 1.5 to 4.6 V is shown.

[0041] Figure 8 The cycling curves of the NaFe(O3PCH(OH)CO2@C material prepared in Example 1 as a positive electrode material for sodium-ion batteries are shown in the current density at 0.5C and the voltage range of 1.5 to 4.2V.

[0042] Figure 9 Cyclic voltammetry of the NaFe(O3PCH(OH)CO2@C material prepared in Example 1 as a cathode material for sodium-ion batteries in the voltage range of 1.5–4.2 V;

[0043] Figure 10 The constant current charge-discharge diagram of the NaMn(O3PCH(OH)CO2@C material prepared in Example 11 as a positive electrode material for sodium-ion batteries in the voltage range of 1.5 to 4.26.

[0044] Figure 11 The constant current charge-discharge diagram of the NaMn(O3PCH(OH)CO2 material prepared in Example 11 as a positive electrode material of sodium-ion battery in the voltage range of 1.5 to 4.26. Detailed Implementation

[0045] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0046] In this disclosure, based on a fully charge-discharge organic-inorganic hybrid material, and leveraging the flexibility of the organophosphonic framework structure and the redox activity of metal ions, Na… +The fully reversible de-entrapment and intercalation, coupled with high rate capability and long cycle life, solves the problem of incompatibility between rate performance and cycle life in inorganic sodium phosphate compounds. This invention's phosphonyl-containing organic-inorganic hybrid material, applied to sodium-ion batteries with sodium metal as the negative electrode and an organic electrolyte, achieves a reversible specific capacity of 106.1 mA h / g within a voltage range of 1.5-4.2 V, representing 93.4% of the theoretical specific capacity. After 200 and 400 cycles at 1C and 2C current densities, respectively, it still exhibits specific capacities of 70.7 and 62.4 mA h / g, demonstrating excellent rate performance and good cycle stability. The material used in this invention has a simple preparation process, abundant and inexpensive raw materials, and excellent electrochemical performance, thus showing great promise for energy storage applications.

[0047] Using (NaFe(O3PCH(OH)CO2)) as an example, this invention illustrates a method for preparing a high-performance organic-inorganic hybrid cathode material for sodium-ion batteries. The organic-inorganic hybrid material prepared by the above method has the molecular formula NaFe(O3PCH(OH)CO2), a tetragonal crystal system, and a space group of [missing information]. Pbca The unit cell parameters are α=β=γ=90°.

[0048] The solution was prepared using a hydrothermal method. Ferrous salt and 2-hydroxyphosphorylated acetic acid solution were mixed at a specific molar ratio, and 20 ml of deionized water was added at room temperature. The mixture was stirred for 2 hours, and a mineralizing agent was added to adjust the pH value, resulting in a mixed solution. The ferric salts included FeSO4·7H2O, FeCl2·4H2O, and Fe(CH3COO)2. The molar ratio of ferrous salt to 2-hydroxyphosphorylated acetic acid solution was between 1:1 and 1:4. The mineralizing agents were NaF and NaCO3. The pH was adjusted using NH4Cl and acetic acid.

[0049] The mixed solution was reacted in a hydrothermal reactor under high temperature and high pressure for a period of time. After the reaction, it was naturally cooled to room temperature, and then subjected to ultrasonication or filtration, multiple washings, and drying to obtain the organic-inorganic hybrid material NaFe(O3PCH(OH)CO2). The reaction temperature was 80–180 °C, the heating rate was 2–6 °C / min, and the reaction time was 48–200 h.

[0050] Using (NaFe(O3PCH(OH)CO2)) as the active material, an example is given to illustrate the preparation process of the electrode material.

[0051] The high-performance organic lithium-ion battery cathode material provided by this invention uses iron-based 2-hydroxyphosphorylacetate sodium (NaFe(O3PCH(OH)CO2)) as the active material, which is directly used as a self-supporting electrode material after being ball-milled with conductive agent carbon.

[0052] In this invention, iron-based organic-inorganic hybrid materials are used as positive electrode materials in sodium-ion batteries.

[0053] Preparation of the working electrode: The prepared organic-inorganic hybrid material NaFe(O3PCH(OH)CO2) was dried in a vacuum oven at 60–100 °C for 824 h. Then, the dried active material (NaFe(O3PCH(OH)CO2)) and conductive agent (Super P) were weighed at a mass ratio of 7.5:2.5, mixed, and ball-milled at a speed of 300–500 rpm for 4–24 h to obtain NaFe(O3PCH(OH)CO2@C material. The dried NaFe(O3PCH(OH)CO2@C), conductive agent (Super P), and binder (polyvinylidene fluoride: PVDF) were weighed at a mass ratio of 8:1:1, ground and mixed evenly, and slurried with solvent (N-methylpyrrolidone) to form a paste. The paste was coated on aluminum foil to make an electrode sheet. The electrode sheet was dried in a forced-air drying oven at 70–100 °C for a period of time, and then dried in a vacuum drying oven at 100–120 °C for 10–12 hours. h; Select an MSKT10 manual slicing machine with a mold diameter of 8-14 mm to cut the dried electrode sheets into circular electrode sheets, and weigh them for later use.

[0054] Battery assembly: In an argon-filled glove box, the obtained circular electrode sheet is used as the positive electrode of the battery, and the sodium disc is used as the negative electrode. The battery casing is a CR2032 button cell, the separator is Whatman glass fiber, and the electrolyte is a 1 mol / L NaClO4 (EC+DMC+5.0% FEC) mixed solution, where EC is ethylene carbonate, DMC is dimethyl carbonate, FEC is fluoroethylene carbonate, and the volume ratio of EC to DEC is 1:1.

[0055] Electrochemical performance testing: The battery was tested in a constant temperature chamber at 25 ℃ using a LAND testing system. Charge-discharge curves were tested under constant current conditions at 0.1C (1C=110 mAh / g) for voltage windows of 1.5–4.2 V, 1.5–4.4 V, and 1.5–4.6 V. Within the voltage window of 1.5–4.2 V, constant current charge-discharge was performed at current densities of 0.1C, 0.5C, 1C, 2C, 3C, 2C, 1C, 0.5C, and 0.1C, with 6 cycles at each rate. The number of charge-discharge cycles was 200 at a current density of 1C and 400 at a current density of 2C. Cyclic voltammetry measurements were performed on an electrochemical workstation with voltages between 1.5V and 4.2V and a scan rate of 0.5 mV / s.

[0056] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0057] Example 1:

[0058] Example 1 describes a method for preparing the organic-inorganic hybrid material NaFe(O3PCH(OH)CO2), and the steps are as follows:

[0059] 1.0 mmol of FeSO4·7H2O, 2.0 mmol of 2-hydroxyphosphorylic acid solution, 19 mmol of NaF, 90 mmol of NH4Cl, and 20 ml of deionized water were mixed and stirred at room temperature for 2 h. The pH of the resulting solution was around 3.4. The solution was then poured into a 50 ml polytetrafluoroethylene hydrothermal reactor and heated at 150 °C for 96 h at a heating rate of 5 °C / min. After the reaction was completed, the solution was allowed to cool naturally to room temperature, filtered, and washed several times with deionized water. The solution was then dried in a 70 °C forced-air drying oven for 24 h to obtain the light-colored organic-inorganic hybrid material NaFe(O3PCH(OH)CO2).

[0060] Structural analysis:

[0061] Figure 1 The crystal structure diagram of NaFe(O3PCH(OH)CO2), an organic-inorganic hybrid material containing phosphonyl groups, prepared in Example 1, is shown. The Fe group in its structure... 2+ Ions and L from three different ligands 3- The phosphate oxygen atom in (L=O3PCH(OH)CO2) comes from two different ligands L 3- The carboxylic acid oxygen atom and a hydroxyl oxygen atom form a twisted [FeO6] octahedron. Therefore, from L 3- All oxygen atoms in the ligand participate in coordination, monodentately connecting to the iron ion. The length of the Fe-O bond in [FeO6] ranges from 2.031 to 2.271 Å, which is close to the bond length range in inorganic iron phosphate. Unlike the [FeO6] octahedron, in the [NaO6] octahedron, four oxygen atoms come from the phosphate, and the remaining two come from the carboxylic acid and hydroxyl groups, respectively. These polyhedra ([FeO6], [NaO6], [CPO3]) are interconnected by sharing edges and vertices, with channels extending along the a-axis, and charge-compensated Na… +Located at the intersection of these channels, it forms a complex three-dimensional open framework structure.

[0062] Figure 2 The infrared spectrum of NaFe(O3PCH(OH)CO2), an organic-inorganic hybrid material containing phosphonoyl groups, prepared in Example 1, is shown in the 3300-3600 cm⁻¹ range. -1 The vibrational peak in the range corresponds to the stretching vibration of -OH in the organic ligand, 1576 cm⁻¹. -1 A very strong absorption peak nearby corresponds to the stretching vibration of O=CO- in the organic ligand, at 1363 and 1268 cm⁻¹. -1 A moderately strong absorption band nearby is caused by the tensile vibrations of O=CO-, CH, and CP. Tensile and bending bands of P=O and PO appear at 1195–998 cm⁻¹. -1 Within the region. Therefore, during the synthesis process, not only are the functional groups of the organic ligands not destroyed, but phosphoryl groups are also introduced into NaFe[O3PCH(OH)CO2] by combining with metal atoms.

[0063] Morphological characteristics:

[0064] Figure 3 The X-ray powder diffraction pattern of NaFe(O3PCH(OH)CO2), an organic-inorganic hybrid material containing phosphonyl groups prepared in Example 1, is shown, and the experimental spectrum is compared with the calculated simulated XRD. Figure 3 It can be observed that the three strongest diffraction peaks calculated are at 19.95°, 30.42°, and 31.97°, corresponding to crystal planes (021), (222), and (213), respectively. These three diffraction peaks were shifted to 19.98°, 30.19°, and 31.62° in the experimental XRD. The small shift of the diffraction peaks in the XRD (∆2θmax = 0.35°) is related to the error in calculating the crystal parameters. Therefore, based on the intensity of the diffraction peaks and the peak positions of the small differences between the experimental and calculated XRD patterns, it can be determined that the sample obtained through a one-step hydrothermal method is of high purity.

[0065] Figure 4 The scanning electron microscope image of NaFe(O3PCH(OH)CO2), an organic-inorganic hybrid material containing phosphonyl groups prepared in Example 1, shows that the material has a layered structure.

[0066] Example 2:

[0067] Example 2 describes a method for preparing the organic-inorganic hybrid material NaFe(O3PCH(OH)CO2), and the steps are as follows:

[0068] 1.0 mmol FeCl2·4H2O, 2.0 mmol 2-hydroxyphosphorylic acid solution, 19 mmol Na2CO3, 90 mmol NH4Cl, and 20 ml deionized water were mixed and stirred at room temperature for 2 h. The pH of the resulting solution was 3.8. The solution was then poured into a 50 ml polytetrafluoroethylene hydrothermal reactor and heated at 160 °C for 72 h at a heating rate of 6 °C / min. After the reaction was completed, the solution was allowed to cool naturally to room temperature, filtered, and washed several times with deionized water. The solution was then dried in a 70 °C forced-air drying oven for 24 h to obtain the light-colored organic-inorganic hybrid material NaFe(O3PCH(OH)CO2).

[0069] Example 3:

[0070] Example 3 describes a method for preparing the organic-inorganic hybrid material NaFe(O3PCH(OH)CO2), and the steps are as follows:

[0071] 1.0 mmol of Fe(CH3COO)2, 2.0 mmol of 2-hydroxyphosphorylic acid solution, 19 mmol of NaF, 25 mmol of NH4Cl, and 35 mmol of acetic acid were mixed together with 20 ml of deionized water and stirred at room temperature for 2 h. The mixture was then poured into a 50 ml polytetrafluoroethylene hydrothermal reactor and heated at 140 °C for 96 h at a heating rate of 4 °C / min. After the reaction was completed, the mixture was allowed to cool naturally to room temperature, filtered, and washed several times with deionized water. Finally, it was dried in a 70 °C forced-air drying oven for 24 h to obtain a light green organic-inorganic hybrid material NaFe(O3PCH(OH)CO2).

[0072] Example 4:

[0073] Example 4 describes the fabrication of a positive electrode for a sodium-ion battery using an organic-inorganic hybrid material NaFe(O3PCH(OH)CO2) combined with a conductive agent, carbon. The steps are as follows:

[0074] The organic-inorganic hybrid material NaFe(O3PCH(OH)CO2) prepared in Example 1 was dried in a vacuum oven at 70°C for 24 h. Then, the dried active material (NaFe(O3PCH(OH)CO2)) and conductive agent (Super P) were weighed at a mass ratio of 7.5:2.5, mixed and ball-milled at 400 rpm for 20 h to obtain NaFe(O3PCH(OH)CO2@C material. The dried NaFe(O3PCH(OH)CO2@C), conductive agent (Super P) and binder (polyvinylidene fluoride: PVDF) were weighed at a mass ratio of 8:1:1, ground and mixed evenly, and slurried with solvent (N-methylpyrrolidone) to form a paste. The paste was coated on aluminum foil to make an electrode sheet. The electrode sheet was dried in a forced-air drying oven at 70°C for 1 h and then dried in a vacuum drying oven at 100°C for 12 h. The dried electrode sheet was cut into circular electrode sheets using an MSKT10 manual slicing machine with a mold diameter of 14 mm.

[0075] Example 5:

[0076] Example 5 describes the fabrication of a positive electrode for a sodium-ion battery using an organic-inorganic hybrid material NaFe(O3PCH(OH)CO2) combined with a conductive agent, carbon. The steps are as follows:

[0077] The organic-inorganic hybrid material NaFe(O3PCH(OH)CO2) prepared in Example 1 was dried in a vacuum oven at 70°C for 24 h. Then, the dried active material (NaFe(O3PCH(OH)CO2)) and conductive agent (SuperP) were weighed at a mass ratio of 8:2, mixed and ball-milled at 450 rpm for 20 h to obtain NaFe(O3PCH(OH)CO2@C material. The dried NaFe(O3PCH(OH)CO2@C), conductive agent (Super P) and binder (polyvinylidene fluoride: PVDF) were weighed at a mass ratio of 8:1:1, ground and mixed evenly, and slurried with solvent (N-methylpyrrolidone) to form a paste. The paste was coated on aluminum foil to make an electrode sheet. The electrode sheet was dried in a forced-air drying oven at 70°C for 1 h and then dried in a vacuum drying oven at 100°C for 12 h. The dried electrode sheet was cut into circular electrode sheets using an MSKT10 manual slicing machine with a mold diameter of 14 mm.

[0078] Example 6:

[0079] Example 6 presents the electrochemical performance test of the organic-inorganic hybrid material NaFe(O3PCH(OH)CO2@C as a cathode material for sodium-ion batteries:

[0080] The positive electrode prepared in Example 4 was placed in an argon-filled glove box, with a sodium disc as the negative electrode and Whatman glass fiber as the diaphragm, and 150 μL of 1mol / L NaClO4 (EC+DMC+5.0% FEC, V) was dropped on it. EC :V DMC A sodium-ion coin cell was assembled using an electrolyte solution with a 1:1 electrolyte ratio and a CR2032 coin cell casing. The cells were then tested using a LAND testing system in a 25°C constant temperature chamber. Figure 5 This indicates that under constant current conditions of 0.1C (1C=110 mAh / g) and a voltage window of 1.5 to 4.2 V, the battery's first discharge specific capacity is 119.4 mAh / g, and the charge-discharge specific capacity after 10 cycles is 98.8 mAh / g.

[0081] Example 7:

[0082] Example 7 presents the electrochemical performance test of the organic-inorganic hybrid material NaFe(O3PCH(OH)CO2@C as a cathode material for sodium-ion batteries:

[0083] The positive electrode prepared in Example 4 was placed in an argon-filled glove box, with a sodium disc as the negative electrode and Whatman glass fiber as the diaphragm, and 150 μL of 1mol / L NaClO4 (EC+DMC+5.0% FEC, V) was dropped on it. EC :V DMC A sodium-ion coin cell was assembled using an electrolyte solution with a 1:1 electrolyte ratio and a CR2032 coin cell casing. The cells were then tested using a LAND testing system in a 25°C constant temperature chamber. Figure 6 This indicates that under constant current conditions of 0.1C (1C=110 mAh / g) and a voltage window of 1.5 to 4.4 V, the battery's first discharge specific capacity is 103.2 mAh / g, and the charge-discharge specific capacity after 10 cycles is 98.2 mAh / g.

[0084] Example 8:

[0085] Example 8 presents the electrochemical performance test of the organic-inorganic hybrid material NaFe(O3PCH(OH)CO2@C as a positive electrode material for sodium-ion batteries:

[0086] The positive electrode prepared in Example 4 was placed in an argon-filled glove box, with a sodium disc as the negative electrode and Whatman glass fiber as the diaphragm, and 150 μL of 1mol / L NaClO4 (EC+DMC+5.0% FEC, V) was dropped on it. EC :V DMCA sodium-ion coin cell was assembled using an electrolyte solution with a 1:1 electrolyte ratio and a CR2032 coin cell casing. The cells were then tested using a LAND testing system in a 25°C constant temperature chamber. Figure 7 This indicates that under constant current conditions of 0.1C (1C=110 mAh / g) and a voltage window of 1.5–4.6 V, the battery's first discharge specific capacity is 135.6 mAh / g, and the charge / discharge specific capacity after 10 cycles is 123.5 mAh / g.

[0087] Example 9:

[0088] Example 9 presents the electrochemical performance test of the organic-inorganic hybrid material NaFe(O3PCH(OH)CO2@C as a cathode material for sodium-ion batteries:

[0089] The positive electrode prepared in Example 4 was placed in an argon-filled glove box, with a sodium disc as the negative electrode and Whatman glass fiber as the diaphragm, and 150 μL of 1mol / L NaClO4 (EC+DMC+5.0% FEC, V) was dropped on it. EC :V DMC A sodium-ion coin cell was assembled using an electrolyte solution with a 1:1 electrolyte ratio and a CR2032 coin cell casing. The cells were then tested using a LAND testing system in a 25°C constant temperature chamber. Figure 8 This indicates that under constant current conditions of 0.5C (1C=110 mAh / g) and a voltage window of 1.5–4.2 V, the specific capacity of the battery after 150 cycles is 73.3 mAh / g, and the coulombic efficiency is 97.8%.

[0090] Example 10:

[0091] Example 10 presents the electrochemical performance test of the organic-inorganic hybrid material NaFe(O3PCH(OH)CO2@C as a cathode material for sodium-ion batteries:

[0092] The positive electrode prepared in Example 4 was placed in an argon-filled glove box, with a sodium disc as the negative electrode and Whatman glass fiber as the diaphragm, and 150 μL of 1mol / L NaClO4 (EC+DMC+5.0% FEC, V) was dropped on it. EC :V DMC A sodium-ion coin cell was assembled using an electrolyte solution with a 1:1 ratio (electrolyte ratio of 1:1) and a CR2032 coin cell casing. The cells were then tested in a 25°C incubator using an electrochemical workstation. Figure 9The cyclic voltammogram shows that when the voltage window is in the range of 1.5 to 4.2 V, the redox potential of the sodium-ion battery with NaFe(O3PCH(OH)CO2 as the cathode material is 2.39 / 3.01 V. The fact that the position of the redox peak remains unchanged with the increase of the number of cycles indicates the stability of the NaFe(O3PCH(OH)CO2 structure.

[0093] Example 11:

[0094] Example 11 describes the preparation of the organic-inorganic hybrid material NaMn(O3PCH(OH)CO2) and the electrochemical performance testing of NaMn(O3PCH(OH)CO2@C as a cathode material for sodium-ion batteries.

[0095] In this embodiment, 1.0 mmol of FeSO4·7H2O in Example 1 was replaced with 1.0 mmol of Mn(CH3COO)2·4H2O. The types and contents of other raw materials, synthesis conditions, and washing methods remained unchanged, resulting in a grayish-white organic-inorganic hybrid material NaMn(O3PCH(OH)CO2). Its electrochemical performance was further tested according to the methods in Examples 4 and 8. Figure 10 As shown, under constant current conditions of 0.1C (1C=110 mAh / g) and a voltage window of 1.5 to 4.6 V, the battery's first discharge specific capacity is 98.2 mAh / g, and the charge-discharge specific capacity after 10 cycles is 94.4 mAh / g.

[0096] Example 12:

[0097] Example 12 is an electrochemical performance test of the organic-inorganic hybrid material NaMn(O3PCH(OH)CO2) as a cathode material for sodium-ion batteries:

[0098] The NaMn(O3PCH(OH)CO2) prepared in Example 11 was directly weighed at a mass ratio of 6:3:1 without ball milling and compounding with a conductive agent. Super P and PVDF were ground and mixed evenly, and the mixture was prepared into a slurry with a solvent (N-methylpyrrolidone). This slurry was coated onto aluminum foil to form an electrode sheet. The electrode sheet was dried in a forced-air drying oven at 70°C for 1 hour, and then baked in a vacuum drying oven at 100°C for 12 hours. A 14 mm diameter MSKT10 manual slicing machine was used to cut the dried electrode sheet into circular electrode sheets. The electrochemical performance was then tested according to the method in Example 8. Figure 11As shown, under constant current conditions of 0.1C (1C=110 mAh / g) and a voltage window of 1.5 to 4.6 V, the battery's first discharge specific capacity is only 54.7 mAh / g, and the charge-discharge specific capacity after 5 cycles is only 26.2 mAh / g.

[0099] Comparative Example 1:

[0100] 1.0 mmol of FeSO4·7H2O, 2.0 mmol of 2-hydroxyphosphorylic acid solution, and 20 ml of deionized water were mixed and stirred at room temperature for 2 h. Then, 2 mol / L NaOH solution was added dropwise to bring the pH of the mixed solution to around 4. The mixed solution was then poured into a 50 ml polytetrafluoroethylene hydrothermal reactor and heated at 150 °C for 96 h at a heating rate of 5 °C / min. After the reaction was completed, the solution was allowed to cool naturally to room temperature, and almost no precipitate was formed.

Claims

1. An active electrode material, characterized in that, include: Organic-inorganic hybrid material, and carbon material coated on the surface of said organic-inorganic hybrid material, are denoted as C@XTML; The chemical formula of the organic-inorganic hybrid material is NaFe(O3PCH(OH)CO2); the crystal structure of the organic-inorganic hybrid material belongs to the tetragonal crystal system, and the space group is [missing information]. Pbca The unit cell parameters are α = β = γ = 90°; The carbon material includes at least one of carbon black, graphene, carbon nanotubes, and graphite. The mass ratio of the carbon material to the organic-inorganic hybrid material is y:(10-y), where 7≤y<10.

2. A method for preparing the active electrode material according to claim 1, characterized in that, Carbon materials and organic-inorganic hybrid materials are weighed and ball-milled according to a mass ratio to obtain C@XTML materials; the ball milling speed is 300-500 rpm and the ball milling time is 4-24 h.

3. An electrode, characterized in that, include: Current collector and electrode layer coated on the surface of current collector; The electrode layer comprises the active electrode material as described in claim 1, Super P, and a binder; The current collector is an Al foil, a carbon-coated Al foil, or a Cu foil; The mass ratio of the active electrode material, Super P and binder is z:(9-z):1, where 6≤z<9.

4. A method for preparing the electrode according to claim 3, characterized in that, Using C@XTML as the active electrode material, the active electrode material: Super P: binder mass ratio = z: (9-z): 1 was weighed and mixed in an organic solvent, then coated on the surface of the current collector, and then dried to obtain the electrode; The organic solvent is at least one of NMP, DMF, DMSO and DMAc; The drying process is vacuum drying, with a temperature of 100–120°C and a duration of 8–12 hours.

5. The application of an organic-inorganic hybrid material in a secondary battery, characterized in that, The chemical formula of the organic-inorganic hybrid material is NaFe(O3PCH(OH)CO2); the crystal structure of the organic-inorganic hybrid material belongs to the tetragonal crystal system, and the space group is [missing information]. Pbca The cell parameters are α=β=γ=90°; the secondary battery includes lithium-ion battery, sodium-ion battery and potassium-ion battery.

6. The application of the active electrode material as described in claim 1 in a secondary battery, characterized in that, The secondary battery includes lithium-ion batteries, sodium-ion batteries, and potassium-ion batteries.

7. The application of the electrode as described in claim 3 in a secondary battery, characterized in that, The secondary battery includes lithium-ion batteries, sodium-ion batteries, and potassium-ion batteries.

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