Nanohomogeneous phosphorus-doped hard carbon sodium-ion battery negative electrode material, preparation method and application thereof

Abstract

The embodiment of the present application relates to a preparation method of a nano-uniform phosphorus-doped hard carbon sodium ion battery negative material, comprising: dissolving a soluble phosphorus-containing compound in water to prepare a solution with a mass concentration of 1% to 30%; adding a polymer containing an exchange group to the solution to form a mixed solution, and fully stirring at a speed of 100 rpm to 1000 rpm until ion exchange is completed; filtering and cleaning the mixed solution; drying the filtered product to obtain a polymer containing phosphorus-containing groups; performing carbonization treatment on the polymer containing phosphorus-containing groups in stages according to temperature to obtain the nano-uniform phosphorus-doped hard carbon sodium ion battery negative material; wherein, during the carbonization treatment, at the temperature of the first stage, the phosphorus-containing groups are decomposed to form phosphorus oxide, and then at the temperature of the second stage, the phosphorus oxide is reduced to nano-phosphorus particles, so that the nano-phosphorus particles have a pore structure formed during the reduction of the phosphorus oxide.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery materials technology, and in particular to a method for preparing a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material, as well as the prepared material and its application. Background Technology

[0002] With the development and popularization of new energy sources, secondary batteries, represented by lithium-ion batteries, are widely used in electric vehicles, consumer electronics, and energy storage due to their advantages such as high energy density, long cycle life, and high energy conversion efficiency. However, lithium mineral resources are scarce, and the price increase of lithium mineral resources this year has greatly increased the application cost of lithium-ion batteries.

[0003] Sodium, an element in the same group as lithium, has similar physicochemical properties to lithium, especially its widespread availability and low cost. However, the radius of sodium ions is much larger than that of lithium ions, making them unable to be embedded in existing graphite anode materials. Currently, hard carbon materials have a much larger interlayer spacing than graphite and a microporous structure, enabling the insertion and extraction of sodium ions, and therefore have attracted much attention.

[0004] Currently, much research has been conducted in the industry on pore-forming processes for hard carbon materials, with acid washing or the addition of pore-forming agents being the mainstream methods. However, these methods only address the sodium ion insertion / extraction problem. This invention aims to research an industrially feasible method that not only achieves pore formation but also positively impacts other performance characteristics of sodium-ion batteries through the pore-forming process. Summary of the Invention

[0005] The purpose of this invention is to provide a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material, its preparation method, and its application. The preparation equipment is simple, the production cost is low, and the reproducibility is good. The prepared nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material has uniformly distributed phosphorus at the nanoscale. Simultaneously, the pores formed during the phosphorus oxidation-reduction process around the nano-phosphorus particles provide a buffer space for the volume expansion of the phosphorus particles. Furthermore, the resin-carbonized hard carbon itself possesses an extremely stable amorphous structure, ensuring structural stability during the sodium insertion / extraction process and guaranteeing high cycle stability.

[0006] Therefore, in a first aspect, embodiments of the present invention provide a method for preparing a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material, the preparation method comprising:

[0007] A solution with a mass concentration of 1% to 30% is prepared by dissolving a soluble phosphate compound in water.

[0008] A polymer containing exchange groups is added to the solution to form a mixture. The mixture is stirred thoroughly at a speed of 100 rpm to 1000 rpm until ion exchange is completed. The mixture is then filtered and washed. The filtered product is dried to obtain a polymer containing phosphate groups.

[0009] The phosphate-containing polymer was carbonized in stages according to temperature to obtain a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material.

[0010] During the carbonization process, at the first set of temperatures, phosphate ions decompose to form phosphorus oxide, and then at the second set of temperatures, phosphorus oxide is reduced to nano-phosphorus particles, resulting in a porous structure around the nano-phosphorus particles formed during the reduction of phosphorus oxide.

[0011] Preferably, the step-by-step carbonization treatment of the phosphate-containing polymer according to temperature specifically involves:

[0012] The phosphate-containing polymer is heated to 500℃~900℃ in a protective atmosphere for the first stage of carbonization, and held at that temperature for 5 hours~20 hours. Then, it is heated to 1000℃~1600℃ for the second stage of carbonization, and held at that temperature for 0.5 hours~10 hours.

[0013] More preferably, the heating rate of the first carbonization process is 1℃ / min to 5℃ / min, and the heating rate of the second carbonization process is 3℃ / min to 10℃ / min.

[0014] Preferably, the exchange group includes one or a combination of more than one of the following: quaternary ammonium group (-NR3OH, where R is a hydrocarbon group), primary amine group (-NH2), secondary amine group (-NHR), or tertiary amine group (-NR2);

[0015] The polymer includes one or a combination of several of the following: polystyrene resin, epoxy resin, urea-formaldehyde resin, and acrylic resin.

[0016] The soluble phosphorus-containing compounds include one or a combination of potassium phosphate, sodium phosphate, and ammonium phosphate.

[0017] Preferably, in the mixture, the molar ratio of phosphorus in the soluble phosphate-containing compound to the exchange groups in the polymer containing exchange groups is 0.1:1 to 1:1.

[0018] Preferably, the time for thorough stirring until ion exchange is completed is 12 to 72 hours.

[0019] Preferably, the protective atmosphere is a nitrogen or argon atmosphere. During the first carbonization process, the gas flow rate of the protective atmosphere is 10 L / min to 20 L / min, and during the second carbonization process, the gas flow rate of the protective atmosphere is 2 L / min to 5 L / min.

[0020] Secondly, embodiments of the present invention provide a sodium-ion battery anode material, which is prepared by the preparation method described in the first aspect above.

[0021] Thirdly, embodiments of the present invention provide a sodium-ion battery negative electrode, wherein the negative electrode comprises the sodium-ion battery negative electrode material described in the second aspect above.

[0022] Fourthly, embodiments of the present invention provide a sodium-ion battery, the sodium-ion battery comprising the sodium-ion battery negative electrode described in the third aspect above.

[0023] The method for preparing nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material provided in this invention uses simple equipment, has low production cost, and good reproducibility. The nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material prepared by this method has uniformly distributed phosphorus nanoparticles. The high sodium storage capacity of phosphorus enhances the sodium storage capacity of the anode material. Simultaneously, the pores formed during the phosphorus oxidation-reduction process around the nano-phosphorus particles provide a buffer space for the volume expansion of the phosphorus particles. Furthermore, the amorphous structure of the resin-carbonized hard carbon itself is extremely stable, ensuring structural stability during the sodium insertion / extraction process and guaranteeing high cycle stability. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating the preparation method of a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material provided in an embodiment of the present invention.

[0025] Figure 2 This is a scanning electron microscope (SEM) image of the material prepared in Example 1 of the present invention;

[0026] Figure 3 The image shows the energy dispersive spectroscopy (EDS) spectrum of the material prepared in Example 1 of this invention. Detailed Implementation

[0027] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0028] This invention provides a method for preparing a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material, the main steps of which are as follows: Figure 1 As shown, it includes:

[0029] Step 110: Dissolve the soluble phosphate-containing compound in water to prepare a solution with a mass concentration of 1% to 30%;

[0030] Soluble phosphorus-containing compounds may preferably include one or a combination of potassium phosphate, sodium phosphate, and ammonium phosphate.

[0031] Step 120: Add a polymer containing exchange groups to the solution to form a mixture. Stir the mixture thoroughly at a speed of 100 rpm to 1000 rpm until ion exchange is completed. Filter and wash the mixture. Dry the filtered product to obtain a polymer containing phosphate groups.

[0032] Among the polymers containing exchange groups, the polymers include one or a combination of several of the following: polystyrene resin, epoxy resin, urea-formaldehyde resin, and acrylic resin; the exchange groups include one or a combination of several of the following: quaternary ammonium group (-NR3OH, where R is a hydrocarbon group), primary amine group (-NH2), secondary amine group (-NHR), or tertiary amine group (-NR2).

[0033] In the mixture, the molar ratio of phosphorus in the soluble phosphate-containing compound to the exchange groups in the polymer containing exchange groups is 0.1:1 to 1:1.

[0034] The time for thorough stirring until ion exchange is complete is 12 to 72 hours.

[0035] Step 130: Carbonize the phosphate-containing polymer in stages according to temperature to obtain a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material.

[0036] Specifically, the phosphate-containing polymer is subjected to a first-stage carbonization process under a protective atmosphere, with the temperature increased at a rate of 1°C / min to 5°C / min to 500°C to 900°C, and held at this temperature for 5 to 20 hours. Then, a second-stage carbonization process is carried out by increasing the temperature at a rate of 3°C / min to 10°C / min to 1000°C to 1600°C, and held at this temperature for 0.5 to 10 hours. That is, the temperature for the first-stage carbonization process is 500°C to 900°C, and the temperature for the second-stage carbonization process is 1000°C to 1600°C.

[0037] The protective atmosphere is nitrogen or argon. During the first carbonization process, the gas flow rate of the protective atmosphere is 10 L / min to 20 L / min, and during the second carbonization process, the gas flow rate of the protective atmosphere is 2 L / min to 5 L / min.

[0038] In the carbonization process, during the first temperature gradient, phosphate ions decompose to form phosphorus oxide. The resin-based polymer slowly completes low-temperature carbonization to prevent the rapid growth of large amounts of decomposition gases caused by high temperatures from expanding and destroying the carbon matrix, resulting in numerous large pores. Then, during the second temperature gradient, the phosphorus oxide is reduced to nano-phosphorus particles by the surrounding carbon matrix. This results in the nano-phosphorus particles being surrounded by the porous structure formed during the phosphorus oxide reduction process. Simultaneously, the high temperature adjusts the interlayer spacing of the carbon matrix to approximately 0.39 nm, achieving a microcrystalline interlayer spacing more suitable for sodium ion intercalation.

[0039] To better understand the technical solution provided by the present invention, the following uses several specific examples to illustrate the specific process of preparing nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material using the method provided in the above embodiments of the present invention, as well as the characteristics of applying it to sodium-ion batteries.

[0040] Example 1

[0041] This embodiment provides a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material, and the preparation method is as follows:

[0042] Step 1: Dissolve 200g of potassium phosphate in 1800ml of water to prepare a solution with a mass concentration of about 10%. Add 315g of polystyrene containing quaternary ammonium (-NR3OH, R is a hydrocarbon group) exchange groups (exchange capacity of about 3mmol / g) at a molar ratio of 1:1 between phosphorus and the exchange groups in the polymer. Stir thoroughly at 100r / min for 12 hours until the ion exchange is completed. Filter and wash the mixture three times, and dry it to obtain a polymer with phosphate groups.

[0043] Step 2: Place the dried sample into the reaction apparatus, and perform the first carbonization at 900℃ with an argon gas flow rate of 10L / min and a heating rate of 1℃ / min. Hold the temperature for 5 hours, then heat the sample again to 1000℃ with a heating rate of 3℃ / min and adjust the argon gas flow rate to 5L / min for the second carbonization. Hold the temperature for 10 hours to obtain a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material.

[0044] The scanning electron microscope (SEM) image of the uniformly doped phosphorus-doped sodium carbon anode material particles prepared in Example 1 is shown below. Figure 2 As shown, the energy dispersive spectroscopy (EDS) spectrum of the material is as follows: Figure 3 As shown, phosphorus nanoparticles are uniformly distributed within the hard carbon particles, with no obvious particle precipitation.

[0045] To test the electrochemical performance of the obtained material, the prepared nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material was used as the active material. The ratio of active material: conductive carbon black (SP): polyvinylidene fluoride (PVDF) was 90.0:5.0:5.0, with a total material weight of 15g as an example. 0.75g of PVDF was added to 24.25g of N-methylpyrrolidone (NMP), and the dispersion was carried out at 2000 rpm for 30 minutes until the solution was clear. 0.75g of SP was added to the solution, and the dispersion was carried out at 2000 rpm for 40 minutes. 13.5g of active material was added to the slurry, and the dispersion was carried out at 2000 rpm for 40 minutes. An appropriate amount of NMP was added to adjust the viscosity to 2000 mPa·s. The slurry was sieved through an 180-mesh sieve before coating. The coated electrode was dried at 110℃. After drying, it was cut into circular electrode sheets with a diameter of 8mm. The electrodes were dried at 120°C for 6 hours under vacuum and then transferred to a glove box for later use. The simulated battery was assembled in an Ar atmosphere glove box, using metallic sodium as the counter electrode and 1 mole of NaPF6 dissolved in 1 L of a 1:1 volume ratio solution of ethylene carbonate and diethyl carbonate as the electrolyte to prepare a coin cell. The coin cell testing procedure was as follows: 1. Stand for 8 hours; 2. Rate discharge (0.1C, 0V), rate discharge (0.02C, 0V), stand for 5 minutes; 3. Rate charge (0.1C, 2V), stand for 5 minutes. The structure and electrochemical performance were evaluated through testing.

[0046] To facilitate a better comparison, we prepared the comparison samples using the following method.

[0047] Comparative Example 1

[0048] Step 1: Take 315g of polystyrene containing quaternary ammonium (-NR3OH, R is a hydrocarbon group) exchange groups (exchange capacity of about 3mmol / g) and put it into the reaction apparatus. Under an argon gas flow rate of 10L / min, heat to 900℃ at 1℃ / min for the first stage of carbonization and hold for 5 hours. Then heat to 1000℃ again at 3℃ / min and adjust the protective atmosphere gas flow rate to 5L / min for the second stage of carbonization and hold for 10 hours to obtain the sodium-ion battery anode material of the required control sample.

[0049] Example 2

[0050] This embodiment provides a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material, and the preparation method is as follows:

[0051] Step 1: Dissolve 200g of potassium phosphate in 19800ml of water to prepare a solution with a mass concentration of about 1%. Add 315g of polystyrene containing quaternary ammonium (-NR3OH, R is a hydrocarbon group) exchange groups (exchange capacity of about 3mmol / g) at a molar ratio of 1:1 between phosphorus and the exchange groups in the polymer. Stir thoroughly at 100r / min for 72 hours until ion exchange is completed. Filter and wash the mixture three times, and dry it to obtain a polymer with phosphate groups.

[0052] Step 2: Place the dried sample into the reaction apparatus and perform a first-stage carbonization at 500℃ / min under an argon gas flow rate of 20L / min, heating at 5℃ / min and holding for 20 hours. Then, heat the sample again to 1600℃ at 10℃ / min and adjust the protective atmosphere gas flow rate to 2L / min for a second-stage carbonization, holding for 0.5 hours to obtain a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material.

[0053] Example 3

[0054] This embodiment provides a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material, and the preparation method is as follows:

[0055] Step 1: Dissolve 200g of potassium phosphate in 667ml of water to prepare a solution with a mass concentration of approximately 30%. Add 315g of polystyrene containing quaternary ammonium (-NR3OH, R is a hydrocarbon group) exchange groups (exchange capacity of approximately 3mmol / g) at a molar ratio of 1:1 between phosphorus and the exchange groups in the polymer. Stir thoroughly at 100r / min for 12 hours until ion exchange is completed. Filter and wash the mixture three times, and dry to obtain a polymer with phosphate groups.

[0056] Step 2: Place the dried sample into the reaction apparatus, and perform the first carbonization at 600℃ with an argon gas flow rate of 20L / min and a heating rate of 5℃ / min. Hold the temperature for 6 hours, then heat the sample again to 1400℃ with a heating rate of 10℃ / min and adjust the argon gas flow rate to 5L / min for the second carbonization. Hold the temperature for 2 hours to obtain a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material.

[0057] Example 4

[0058] This embodiment provides a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material, and the preparation method is as follows:

[0059] Step 1: Dissolve 200g of potassium phosphate in 1800ml of water to prepare a solution with a mass concentration of about 10%. Add 3150g of polystyrene containing quaternary ammonium (-NR3OH, R is a hydrocarbon group) exchange groups (exchange capacity of about 3mmol / g) at a molar ratio of phosphorus to exchange groups in the polymer of 0.1:1. Stir thoroughly at 100r / min for 12 hours until ion exchange is completed. Filter and wash the mixture 3 times, and dry to obtain a polymer with phosphate groups.

[0060] Step 2: Place the dried sample into the reaction apparatus, and perform the first carbonization at 600℃ with an argon gas flow rate of 10 L / min and a temperature increase of 5℃ / min. Hold the temperature for 10 hours, then raise the temperature again to 1200℃ with a temperature increase of 10℃ / min and adjust the protective atmosphere gas flow rate to 5 L / min for the second carbonization. Hold the temperature for 0.5 hours to obtain a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material.

[0061] Example 5

[0062] This embodiment provides a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material, and the preparation method is as follows:

[0063] Step 1: Dissolve 200g of potassium phosphate in 1800ml of water to prepare a solution with a mass concentration of approximately 10%. Add 630g of polystyrene containing quaternary ammonium (-NR3OH, R is a hydrocarbon group) exchange groups (exchange capacity of approximately 3mmol / g) at a molar ratio of phosphorus to exchange groups in the polymer of approximately 0.5:1. Stir thoroughly at 100r / min for 12 hours until ion exchange is completed. Filter and wash the mixture three times, and dry to obtain a polymer with phosphate groups.

[0064] Step 2: Place the dried sample into the reaction apparatus, and perform the first carbonization at 600℃ with an argon gas flow rate of 10L / min and a heating rate of 4℃ / min. Hold the temperature for 7 hours, then heat the sample again to 1600℃ with a heating rate of 5℃ / min and adjust the argon gas flow rate to 4L / min for the second carbonization. Hold the temperature for 7 hours to obtain a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material.

[0065] Example 6

[0066] This embodiment provides a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material, and the preparation method is as follows:

[0067] Step 1: Dissolve 200g of sodium phosphate in 1800ml of water to prepare a solution with a mass concentration of approximately 10%. Add 410g of polystyrene containing quaternary ammonium (-NR3OH, R is a hydrocarbon group) exchange groups (exchange capacity of approximately 3mmol / g) at a molar ratio of 1:1 between phosphorus and the exchange groups in the polymer. Stir thoroughly at 100r / min for 12 hours until ion exchange is completed. Filter and wash the mixture three times, and dry it to obtain a polymer with phosphate groups.

[0068] Step 2: Place the dried sample into the reaction apparatus, and perform a first-stage carbonization at 700℃ with an argon gas flow rate of 10L / min and a heating rate of 5℃ / min. Hold the temperature for 5 hours, then heat the sample again to 1100℃ with a heating rate of 5℃ / min and adjust the argon gas flow rate to 5L / min for a second-stage carbonization. Hold the temperature for 8 hours to obtain a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material.

[0069] Example 7

[0070] This embodiment provides a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material, and the preparation method is as follows:

[0071] Step 1: Dissolve 200g of sodium phosphate in 1800ml of water to prepare a solution with a mass concentration of approximately 10%. Add 820g of polystyrene containing quaternary ammonium (-NR3OH, R is a hydrocarbon group) exchange groups (exchange capacity of approximately 3mmol / g) at a molar ratio of phosphorus to exchange groups in the polymer of approximately 0.5:1. Stir thoroughly at 100r / min for 12 hours until ion exchange is completed. Filter and wash the mixture three times, and dry to obtain a polymer with phosphate groups.

[0072] Step 2: Place the dried sample into the reaction apparatus and perform a first-stage carbonization at 900℃ with a nitrogen gas flow rate of 10L / min and a temperature increase of 1℃ / min. Hold the temperature for 20 hours, then increase the temperature again to 1000℃ with a nitrogen gas flow rate of 3℃ / min and adjust the nitrogen gas flow rate to 2L / min for a second-stage carbonization. Hold the temperature for 0.5 hours to obtain a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material.

[0073] Example 8

[0074] This embodiment provides a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material, and the preparation method is as follows:

[0075] Step 1: Dissolve 200g of potassium phosphate in 1800ml of water to prepare a solution with a mass concentration of about 10%. Add 315g of polystyrene containing quaternary ammonium (-NR3OH, R is a hydrocarbon group) exchange groups (exchange capacity of about 3mmol / g) at a molar ratio of 1:1 between phosphorus and the exchange groups in the polymer. Stir thoroughly at 100r / min for 12 hours until the ion exchange is completed. Filter and wash the mixture three times, and dry it to obtain a polymer with phosphate groups.

[0076] Step 2: Place the dried sample into the reaction apparatus and perform a first-stage carbonization at 800℃ with a nitrogen gas flow rate of 10L / min and a temperature increase of 1℃ / min. Hold the temperature for 5 hours, then increase the temperature again to 1300℃ with a nitrogen gas flow rate of 6℃ / min and adjust the nitrogen gas flow rate to 5L / min for a second-stage carbonization. Hold the temperature for 9 hours to obtain a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material.

[0077] Example 9

[0078] This embodiment provides a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material, and the preparation method is as follows:

[0079] Step 1: Dissolve 200g of sodium phosphate in 19800ml of water to prepare a solution with a mass concentration of about 1%. Add 410g of polystyrene containing quaternary ammonium (-NR3OH, R is a hydrocarbon group) exchange groups (exchange capacity of about 3mmol / g) at a molar ratio of 1:1 between phosphorus and the exchange groups in the polymer. Stir thoroughly at 100r / min for 12 hours until the ion exchange is completed. Filter and wash the polymer three times, and dry it to obtain a polymer with phosphate groups.

[0080] Step 2: Place the dried sample into the reaction apparatus, and perform the first carbonization at 500℃ with a nitrogen gas flow rate of 10L / min and a temperature increase of 1℃ / min. Hold the temperature for 5 hours, then increase the temperature again to 1500℃ with a temperature increase of 7℃ / min and adjust the nitrogen gas flow rate to 2L / min for the second carbonization. Hold the temperature for 0.5 hours to obtain a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material.

[0081] Example 10

[0082] This embodiment provides a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material, and the preparation method is as follows:

[0083] Step 1: Dissolve 200g of potassium phosphate in 800ml of water to prepare a solution with a mass concentration of approximately 20%. Add 1260g of polystyrene containing quaternary ammonium (-NR3OH, R is a hydrocarbon group) exchange groups (exchange capacity of approximately 3mmol / g) at a molar ratio of phosphorus to exchange groups in the polymer of approximately 0.25:1. Stir thoroughly at 100r / min for 12 hours until ion exchange is completed. Filter and wash the mixture three times, and dry to obtain a polymer with phosphate groups.

[0084] Step 2: Place the dried sample into the reaction apparatus, and perform the first carbonization at 500℃ with an argon gas flow rate of 10L / min and a heating rate of 1℃ / min. Hold the temperature for 5 hours, then heat the sample again to 1600℃ with a heating rate of 3℃ / min and adjust the argon gas flow rate to 2L / min for the second carbonization. Hold the temperature for 0.5 hours to obtain a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material.

[0085] The battery was assembled and tested in the same manner as in the previous example. The results are shown in Table 1 below.

[0086]

[0087] Table 1

[0088] Based on the comparison of the above embodiments and comparative examples, it can be seen that by uniformly incorporating phosphorus, the capacity of the sodium-ion battery composite hard carbon material obtained in each embodiment is greatly improved compared to Comparative Example 1, which uses carbonized resin material without phosphorus doping, resulting in a significantly higher specific charge capacity. Therefore, this invention utilizes phosphorus's high sodium storage capacity to enhance the sodium storage capacity of the negative electrode material. Simultaneously, the pores formed during the phosphorus oxidation-reduction process around the nano-phosphorus particles provide a buffer space for the volume expansion of the phosphorus particles. Furthermore, the amorphous structure of the resin-carbonized hard carbon itself is extremely stable, ensuring structural stability during the sodium insertion / extraction process and guaranteeing high cycle stability.

[0089] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material, characterized in that, The preparation method includes: A solution with a mass concentration of 1% to 30% is prepared by dissolving a soluble phosphate compound in water. A polymer containing exchange groups is added to the solution to form a mixture. The mixture is stirred thoroughly at a speed of 100 rpm to 1000 rpm until ion exchange is completed. The mixture is then filtered and washed. The filtered product is dried to obtain a polymer containing phosphate groups. The phosphate-containing polymer was carbonized in stages according to temperature to obtain a nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material. During the carbonization process, at the first set of temperatures, phosphate ions decompose to form phosphorus oxide, and then at the second set of temperatures, phosphorus oxide is reduced to nano-phosphorus particles, so that the nano-phosphorus particles have a porous structure formed during the reduction of phosphorus oxide. The specific steps of carbonizing the phosphate-containing polymer according to temperature gradients are as follows: The phosphate-containing polymer is heated to 500℃~900℃ in a protective atmosphere for the first stage of carbonization, and held at that temperature for 5 hours~20 hours. Then, it is heated to 1000℃~1600℃ for the second stage of carbonization, and held at that temperature for 0.5 hours~10 hours. The heating rate of the first carbonization process is 1℃ / min to 5℃ / min, and the heating rate of the second carbonization process is 3℃ / min to 10℃ / min. The exchange group includes one or more combinations of quaternary ammonium group, primary amino group, secondary amino group or tertiary amino group; wherein the quaternary ammonium group is -NR3OH, and R is a hydrocarbon group; The polymer includes one or a combination of several of the following: polystyrene resin, epoxy resin, urea-formaldehyde resin, and acrylic resin. The soluble phosphate-containing compounds include one or a combination of potassium phosphate, sodium phosphate, and ammonium phosphate.

2. The method for preparing the nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material according to claim 1, characterized in that, In the mixture, the molar ratio of phosphorus in the soluble phosphate compound to the exchange groups in the polymer containing exchange groups is 0.1:1 to 1:

1.

3. The method for preparing the nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material according to claim 1, characterized in that, The time required for thorough stirring until ion exchange is complete is 12 to 72 hours.

4. The method for preparing the nano-uniform phosphorus-doped hard carbon sodium-ion battery anode material according to claim 1, characterized in that the protective atmosphere is a nitrogen or argon atmosphere, the gas flow rate of the protective atmosphere is 10 L / min to 20 L / min during the first carbonization process, and the gas flow rate of the protective atmosphere is 2 L / min to 5 L / min during the second carbonization process.

5. A sodium-ion battery anode material, characterized in that, The negative electrode material is prepared by any one of the preparation methods described in claims 1 to 4.

6. A sodium-ion battery negative electrode, characterized in that, The negative electrode comprises the sodium-ion battery negative electrode material as described in claim 5.

7. A sodium-ion battery, characterized in that, The sodium-ion battery includes the sodium-ion battery negative electrode as described in claim 6.

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