Phosphorus-carbon composite material with core-shell structure as well as preparation method and application of phosphorus-carbon composite material

Abstract

The invention provides a phosphorus-carbon composite material with a core-shell structure as well as a preparation method and application of the phosphorus-carbon composite material. The phosphorus-carbon composite material with the core-shell structure comprises a pre-sodium-modified phosphorus-carbon core material and a shell coating the surface of the pre-sodium-modified phosphorus-carbon core material, and the material of the shell comprises amorphous carbon and organic sulfonate. By regulating and controlling the structure and composition of the phosphorus-carbon composite material, the specific capacity, the first coulombic efficiency and the fast charging performance of the hard carbon material are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of negative electrode materials, and in particular relates to a phosphorus-carbon composite material with a core-shell structure, a preparation method and an application thereof. Background Art

[0002] As the energy density requirements of sodium-ion batteries continue to increase, the market requires that the negative electrode materials used in sodium-ion batteries need to have high specific capacity, high compaction density and high first coulombic efficiency. At present, commercial hard carbon materials are mainly biomass hard carbon or resin-based hard carbon, but they have the problems of low specific capacity and too high platform capacity, which leads to deviations in the kinetic performance of the materials.

[0003] Based on this, in order to further improve the specific capacity and kinetic performance of hard carbon materials, most researchers use technical means of doping or coating hard carbon materials to solve the above problems. For example, Chinese patent CN116487567A discloses a hard carbon-phosphorus composite negative electrode material. The specific preparation method includes: mixing white phosphorus and carbon source to obtain a mixed solution, then adding a catalyst to obtain a reaction solution to obtain a mixture; placing the mixture in a closed pressure reactor, heating it to 500-600℃ for reaction for 1h, obtaining a solid product, and obtaining a hard carbon-phosphorus composite negative electrode material. The negative electrode material obtained by the above technical scheme uses white phosphorus and carbon source as raw materials. Under the action of the catalyst, white phosphorus generates nano red phosphorus particles in situ in the carbon source, and finally improves the specific capacity of the negative electrode material. However, there are still defects such as a large full-charge expansion rate of the negative electrode material and deviation in fast charging performance.

[0004] Therefore, in the art, there is an urgent need to develop a hard carbon-based composite material to solve the above problems. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a phosphorus-carbon composite material with a core-shell structure and a preparation method and application thereof. The present invention improves the specific capacity, first coulombic efficiency and fast charging performance of hard carbon materials by regulating the structure and composition of the phosphorus-carbon composite material.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a phosphorus-carbon composite material with a core-shell structure, wherein the phosphorus-carbon composite material with a core-shell structure comprises a pre-sodiumized phosphorus-carbon core material and a shell coated on the surface of the pre-sodiumized phosphorus-carbon core material, wherein the material of the shell comprises amorphous carbon and organic sulfonate.

[0008] On the one hand, the present invention adopts a phosphorus-doped hard carbon core material, and utilizes the high specific capacity of phosphorus itself, thereby improving the specific capacity of the hard carbon material; at the same time, the present invention further pre-sodiumizes the phosphorus-carbon composite material, reduces the lattice defects of the phosphorus-carbon composite material by sodium ion doping, and improves the ion diffusivity and structural stability in the phosphorus-carbon composite material, thereby improving the first coulomb efficiency of the phosphorus-carbon composite material; on the other hand, the present invention coats a composite of amorphous carbon and organic sulfonate on the surface of the pre-sodiumized phosphorus-carbon core material, wherein the amorphous carbon can reduce the specific surface area and surface defects of the pre-sodiumized phosphorus-carbon core material, thereby improving the first coulomb efficiency and electronic conductivity of the phosphorus-carbon composite material, and improving its rate performance; the organic sulfonate in the shell material has a strong solvation ability, and can ultimately increase the insertion and extraction rate of sodium ions during the charge and discharge process, thereby improving the rate performance of the phosphorus-carbon composite material.

[0009] Preferably, based on the total mass of the pre-sodiumized phosphorus-carbon core material as 100%, the mass percentage of sodium in the pre-sodiumized phosphorus-carbon core material is 1wt.%-5wt.%, preferably 2wt.%-4wt.%, for example, it can be 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, 2wt%, 2.2wt%, 2.5wt%, 2.8wt%, 3wt%, 3.2wt%, 3.5wt%, 3.8wt%, 4wt%, 4.2wt%, 4.5wt%, 4.8wt%, 5wt%, etc. The present invention regulates the mass percentage of sodium so that the phosphorus-carbon composite material has a good first coulombic efficiency and ion diffusion performance, and takes into account the energy density. If the mass percentage of sodium is low, the first coulombic efficiency and rate performance of the phosphorus-carbon composite material will be improved less, otherwise the energy density of the phosphorus-carbon composite material will be reduced.

[0010] Preferably, the pre-sodiumated phosphorus-carbon core material also includes an inorganic carbon material.

[0011] Preferably, the inorganic carbon material includes at least one of carbon nanotubes, graphene or carbon black.

[0012] Preferably, based on the total mass of the pre-sodiumized phosphorus-carbon core material as 100%, the mass percentage of the inorganic carbon material is 60wt.%-95wt.%, preferably 80wt.%-90wt.%, for example, it can be 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 82wt%, 85wt%, 88wt%, 90wt%, 95wt%, etc. The present invention makes the phosphorus-carbon composite material have a high specific capacity and a high electronic conductivity by regulating the mass percentage of the inorganic carbon material. If the mass percentage of the inorganic carbon material is low, the first coulomb efficiency of the phosphorus-carbon composite material will be reduced, and vice versa, the specific capacity of the phosphorus-carbon composite material will be reduced.

[0013] Preferably, the mass ratio of amorphous carbon to organic sulfonate in the material of the shell is (90-99):(1-10), preferably (95-98):(2-5), for example, it can be 90:10, 91:9, 92:8, 93:7, 94:6, 95:5, 96:4, 97:3, 98:2, 99:1, etc. The present invention adjusts the mass ratio of amorphous carbon to organic sulfonate so that the phosphorus-carbon composite material has high first efficiency, fast charging performance and compaction density. If the mass ratio of amorphous carbon to organic sulfonate is relatively low, the compaction density of the phosphorus-carbon composite material will be reduced, and vice versa, the improvement of the first coulombic efficiency of the phosphorus-carbon composite material will be limited.

[0014] Preferably, the organic sulfonate comprises a sodium sulfamate derivative.

[0015] Preferably, the sodium aminosulfonate derivative includes any one of sodium aminosulfonate, sodium 3-aminobenzenesulfonate, sodium m-aminobenzenesulfonate or sodium 4-aminobenzenesulfonate, or a combination of at least two thereof.

[0016] Preferably, the mass ratio of the pre-sodiumized phosphorus-carbon core material and the shell material is 100:(1-15), preferably 100:(5-10), for example, it can be 100:1, 100:2, 100:3, 100:4, 100:5, 100:6, 100:7, 100:8, 100:9, 100:10, 100:11, 100:12, 100:13, 100:14, 100:15, etc. The present invention regulates the mass ratio of the pre-sodiumized phosphorus-carbon core material and the shell material so that the phosphorus-carbon composite material has a good first coulombic efficiency and its specific capacity. If the mass ratio of the pre-sodiumized phosphorus-carbon core material and the shell material is relatively low, the specific capacity of the phosphorus-carbon composite material will be low.

[0017] In a second aspect, the present invention provides a method for preparing the phosphorus-carbon composite material having a core-shell structure according to the first aspect, the method comprising the following steps:

[0018] S1. preparing a reaction solution of a pre-sodiumizing agent, red phosphorus and a resin, subjecting the reaction solution to a hydrothermal reaction to obtain a pre-sodiumized phosphorus-carbon precursor material; carbonizing the pre-sodiumized phosphorus-carbon precursor material to obtain a pre-sodiumized phosphorus-carbon material;

[0019] S2. vapor-depositing the pre-sodiumized phospho-carbon material and the carbon source obtained in step S1 to obtain a pre-sodiumized phospho-carbon material coated with amorphous carbon;

[0020] S3. Mix the pre-sodiumized phosphorus-carbon material coated with amorphous carbon obtained in step S2, an organic sulfonate and a solvent to obtain a mixed solution; spray-dry the mixed solution to obtain the phosphorus-carbon composite material with a core-shell structure.

[0021] Preferably, the pre-sodiumizing agent in step S1 includes any one of sodium acetate, sodium pyruvate, sodium m-aminobenzenesulfonate, sodium hydroxybenzenesulfonate, sodium naphthalenesulfonate, sodium tetradecenesulfonate, sodium p-hydroxybenzoate or sodium ascorbate, or a combination of at least two thereof.

[0022] Preferably, the resin in step S1 includes any one of benzoxazine, sulfonated phenolic resin, rosin-modified phenolic resin, amino resin, polysulfone resin or furan resin, or a combination of at least two thereof.

[0023] Preferably, the reaction solution in step S1 further comprises an inorganic carbon material and an organic solvent.

[0024] Preferably, the organic solvent comprises at least one of ethanol, methanol, glycerol or 1,4-butanediol.

[0025] Preferably, the mass ratio of the pre-sodiumizing agent, red phosphorus, inorganic carbon material and resin is (1-5):(1-5):(1-5):100, preferably 3:3:3:100, for example, it can be 1:1.2:1:100, 1.2:1:1:100, 1:1:1.2:100, 1.5:1:1.5:100, 1:1.5:1:100, 1.8:1.8:1:100, 1:1:1.8:100, 2:2:1:100, 1:2:2:100, 2.2:1:2.2:100, 2.5:2:1:100, 2: : 2.5:2.5:100, 2.8:1:2.8:100, 2.5:2.8:2.8:100, 3:1:3:100, 3:3:3:100, 3.2:3:2:100, 3:3.2:3.2:100, 3.5:1:3.5:100, 3.8:3.5:3.8:100, 4:3.8:3:100, 4.2:4:4:100, 4:4.2:4.2:100, 4.5:4.5:3:100, 4.8:1:4.5:100, 5:1:5:100, 3:5:3:100, etc. The present invention adjusts the mass ratio of the pre-sodium agent, red phosphorus, inorganic carbon material and resin so that the prepared phosphorus-carbon composite material has higher specific capacity, first coulomb efficiency, compaction density and power performance. If the mass ratio of the pre-sodium agent, red phosphorus, inorganic carbon material and resin is relatively low, the specific capacity of the phosphorus-carbon composite material will be reduced, and vice versa, the power performance and compaction density of the phosphorus-carbon composite material will be reduced.

[0026] In the present invention, the process of preparing the reaction solution of the pre-sodium agent, red phosphorus and resin in step S1 includes: mixing the pre-sodium agent and the organic solvent for the first time to obtain a pre-sodium agent solution; and mixing the pre-sodium agent solution with red phosphorus, an inorganic carbon material dispersion and a resin for a second time to obtain a reaction solution.

[0027] In the present invention, the mass concentration of the pre-sodium agent solution is 1wt.%-5wt.%, for example, it can be 1wt.%, 2wt.%, 3wt.%, 4wt.%, 5wt.%, etc.

[0028] In the present invention, the mass concentration of the inorganic carbon material dispersion is 1wt.%-5wt.%, for example, 1wt.%, 2wt.%, 3wt.%, 4wt.%, 5wt.%, etc. The solvent of the inorganic carbon material dispersion includes N-methylpyrrolidone.

[0029] Preferably, the temperature of the hydrothermal reaction in step S1 is 100-200°C, for example, it can be 100°C, 120°C, 150°C, 180°C, 200°C, etc.; the pressure is 1.5-5.5Mpa, for example, it can be 1.5Mpa, 2Mpa, 2.5Mpa, 3Mpa, 3.5Mpa, 4Mpa, 4.5Mpa, 5Mpa, 5.5Mpa, etc.; the time is 2-12h, for example, it can be 2h, 4h, 6h, 8h, 10h, 12h, etc.

[0030] Preferably, the carbonization temperature in step S1 is 1000-1400°C, for example, 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, etc.; the time is 1-6h, for example, 1h, 2h, 3h, 4h, 5h, 6h, etc.

[0031] Preferably, the carbon source in step S2 includes at least one of methane, ethane, ethylene or acetylene.

[0032] Preferably, the flow rate of the carbon source in step S2 is 100-500mL / min, for example, it can be 100mL / min, 120mL / min, 150mL / min, 180mL / min, 200mL / min, 220mL / min, 250mL / min, 280mL / min, 300mL / min, 320mL / min, 350mL / min, 380mL / min, 400mL / min, 420mL / min, 450mL / min, 480mL / min, 500mL / min, etc.

[0033] Preferably, the temperature of the vapor deposition in step S2 is 800-1100°C, for example, it can be 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, etc.; the time is 60-600min, for example, it can be 60min, 80min, 100min, 200min, 300min, 400min, 500min, 600min, etc.

[0034] Preferably, the mass ratio of the pre-sodiumized phosphocarbon material coated with amorphous carbon and the organic sulfonate in step S3 is 100:(1-10), preferably 100:5, for example, it can be 100:1, 100:1.5, 100:2, 100:2.5, 100:3, 100:3.5, 100:4, 100:4.5, 100:5, 100:5.5, 100:6, 100:6.5, 100:7, 100:7.5, 100:8, 100:8.5, 100:9, 100:9.5, 100:10, etc. The present invention adjusts the mass ratio of the pre-sodiumized phospho-carbon material coated with amorphous carbon and the organic sulfonate so that the phospho-carbon composite material has a high first efficiency and fast charging performance while taking into account the specific capacity. If the mass ratio of the pre-sodiumized phospho-carbon material coated with amorphous carbon and the organic sulfonate is relatively low, the specific capacity of the phospho-carbon composite material will be reduced. Conversely, the improvement of the first coulombic efficiency and fast charging performance of the phospho-carbon composite material will be limited.

[0035] Preferably, the solvent in step S3 is water.

[0036] Preferably, the mixed solution in step S3 further comprises a dispersant, and the dispersant exemplarily comprises an aqueous solution of sodium carboxymethyl cellulose with a mass concentration of 1 wt%.

[0037] In the present invention, the preparation process of the mixed solution in step S3 includes: mixing the organic sulfonate and the dispersant solution for the first time to obtain a precursor solution; and then adding the pre-sodiumized phospho-carbon material coated with amorphous carbon to obtain the mixed solution.

[0038] In the present invention, the mass concentration of the organic sulfonate in the precursor solution is 1wt.%-10wt.%, for example, it can be 1wt.%, 2wt.%, 3wt.%, 4wt.%, 5wt.%, 6wt.%, 7wt.%, 8wt.%, 9wt.%, 10wt.%, etc.

[0039] Preferably, the inlet temperature of the spray drying in step S3 is 150-250°C (for example, it can be 150°C, 180°C, 200°C, 220°C, 250°C, etc.), the outlet temperature is 80-100°C (for example, it can be 80°C, 85°C, 90°C, 95°C, 100°C, etc.), the flow rate is 0.1-0.5kg / h (for example, it can be 0.1kg / h, 0.2kg / h, 0.3kg / h, 0.4kg / h, 0.5kg / h, etc.), and the time is 0.5-2h (for example, it can be 0.5h, 0.8h, 1h, 1.5h, 2h, etc.).

[0040] In a third aspect, the present invention provides a negative electrode, which includes a negative electrode active material, and the negative electrode active material includes the phosphorus-carbon composite material with a core-shell structure according to the first aspect.

[0041] In a fourth aspect, the present invention provides a secondary battery, comprising a positive electrode, a negative electrode and an electrolyte, wherein the negative electrode comprises the negative electrode according to the third aspect.

[0042] In the present invention, the secondary battery exemplarily includes a sodium ion battery.

[0043] In the present invention, the material of the positive electrode exemplarily includes a layered oxide positive electrode material.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The present invention provides a phosphorus-carbon composite material with a core-shell structure. On the one hand, the present invention adopts a phosphorus-doped hard carbon core material, and utilizes the high specific capacity of phosphorus itself, thereby improving the specific capacity of the hard carbon material; at the same time, the present invention further pre-sodiumizes the phosphorus-carbon composite material, reduces the lattice defects of the phosphorus-carbon composite material by sodium ion doping, and improves the ion diffusivity and structural stability in the phosphorus-carbon composite material, thereby improving the first coulomb efficiency of the phosphorus-carbon composite material; on the other hand, the present invention coats a composite of amorphous carbon and organic sulfonate on the surface of the pre-sodiumized phosphorus-carbon core material, wherein the amorphous carbon can reduce the specific surface area and surface defects of the pre-sodiumized phosphorus-carbon core material, thereby improving the first coulomb efficiency and electronic conductivity of the phosphorus-carbon composite material, and improving its rate performance; the organic sulfonate in the shell material has a strong solvation ability, and can ultimately improve the insertion and extraction rate of sodium ions during the charge and discharge process, thereby improving the rate performance of the phosphorus-carbon composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a SEM image of the phosphorus-carbon composite material with a core-shell structure provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further described below by combining the accompanying drawings and specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0048] Example 1

[0049] The present embodiment provides a phosphorus-carbon composite material with a core-shell structure. The phosphorus-carbon composite material with a core-shell structure includes a pre-sodiumized phosphorus-carbon core material and an outer shell coated on the surface of the pre-sodiumized phosphorus-carbon core material. The pre-sodiumized phosphorus-carbon core material also includes a carbon nanotube material, and the material of the outer shell includes amorphous carbon and sodium aminosulfonate.

[0050] Taking the total mass of the pre-sodium-treated phosphorus-carbon core material as 100%, the mass percentage of sodium element in the pre-sodium-treated phosphorus-carbon core material is 3wt.%, and the mass percentage of the carbon nanotube material is 85wt.%; the mass ratio of amorphous carbon to sodium aminosulfonate in the shell material is 95:5; and the mass ratio of the pre-sodium-treated phosphorus-carbon core material and the shell is 100:10.

[0051] This embodiment also provides a method for the above-mentioned phosphorus-carbon composite material with a core-shell structure, the method comprising the following steps:

[0052] S1. Add 3g of sodium acetate to 100g of ethanol organic solvent to prepare a 3wt.% solution, then add 3g of red phosphorus powder, 100g of carbon nanotube conductive agent solution with a mass concentration of 3wt.% and 100g of benzoxazine to disperse evenly to obtain a reaction solution; transfer the reaction solution to a high-pressure reactor, perform hydrothermal reaction at 150°C and a pressure of 3Mpa for 6h, and then filter to obtain a pre-sodium phosphorus-carbon precursor material; carbonize the pre-sodium phosphorus-carbon precursor material at 1200°C for 3h to obtain a pre-sodium phosphorus-carbon material;

[0053] S2. The pre-sodiumized phospho-carbon material was transferred to a tubular furnace, heated to 900°C and introduced into ethylene gas for vapor deposition at a flow rate of 300 mL / min for 300 min to form a pre-sodiumized phospho-carbon material coated with amorphous carbon;

[0054] S3. 5 g of sodium sulfamate was dissolved in 100 g of sodium carboxymethyl cellulose in an aqueous solvent with a mass concentration of 1 wt.% to prepare a mixed solution with a mass concentration of 5 wt.%, and then 100 g of pre-sodiumized phosphorus-carbon material coated with amorphous carbon was added and dispersed evenly. After spray drying, the inlet temperature of the spray drying was 200 ° C, the outlet temperature was 90 ° C, the flow rate was 0.3 kg / h, and the time was 1 h, and the following was obtained: Figure 1 The phosphorus-carbon composite material with a core-shell structure is shown.

[0055] Example 2

[0056] The present embodiment provides a phosphorus-carbon composite material with a core-shell structure. The phosphorus-carbon composite material with a core-shell structure includes a pre-sodiumized phosphorus-carbon core material and an outer shell coated on the surface of the pre-sodiumized phosphorus-carbon core material. The pre-sodiumized phosphorus-carbon core material also includes a carbon nanotube material, and the material of the outer shell includes amorphous carbon and sodium aminosulfonate.

[0057] Taking the total mass of the pre-sodium-treated phosphorus-carbon core material as 100%, the mass percentage of sodium element in the pre-sodium-treated phosphorus-carbon core material is 1wt.%, and the mass percentage of the carbon nanotube material is 60wt.%; the mass ratio of amorphous carbon to sodium aminosulfonate in the shell material is 99:1; and the mass ratio of the pre-sodium-treated phosphorus-carbon core material and the shell is 100:1.

[0058] This embodiment also provides a method for the above-mentioned phosphorus-carbon composite material with a core-shell structure, the method comprising the following steps:

[0059] S1. Add 1g of sodium acetate to 100g of ethanol organic solvent to prepare a 1wt.% solution, then add 1g of red phosphorus powder, 100g of carbon nanotube conductive agent solution with a mass concentration of 1wt.% and 100g of benzoxazine to disperse evenly to obtain a reaction solution; transfer the reaction solution to a high-pressure reactor, perform a hydrothermal reaction at 150°C and a pressure of 3Mpa for 6h, and then filter to obtain a pre-sodium phosphorus-carbon precursor material; carbonize the pre-sodium phosphorus-carbon precursor material at 1200°C for 3h to obtain a pre-sodium phosphorus-carbon material;

[0060] S2. The pre-sodiumized phospho-carbon material was transferred to a tubular furnace, heated to 900°C and introduced into ethylene gas for vapor deposition at a flow rate of 300 mL / min for 300 min to form a pre-sodiumized phospho-carbon material coated with amorphous carbon;

[0061] S3. Dissolve 1g of sodium aminosulfonate in 100g of sodium carboxymethyl cellulose in an aqueous solvent with a mass concentration of 1wt.% to prepare a mixed solution with a mass concentration of 1wt.%, then add 100g of pre-sodiumized phosphorus-carbon material coated with amorphous carbon, disperse evenly, and after spray drying, the inlet temperature is 150°C, the outlet temperature is 80°C, the flow rate is 0.1kg / h, and the time is 2h to obtain the phosphorus-carbon composite material with a core-shell structure.

[0062] Example 3

[0063] The present embodiment provides a phosphorus-carbon composite material with a core-shell structure. The phosphorus-carbon composite material with a core-shell structure includes a pre-sodiumized phosphorus-carbon core material and an outer shell coated on the surface of the pre-sodiumized phosphorus-carbon core material. The pre-sodiumized phosphorus-carbon core material also includes a carbon nanotube material, and the material of the outer shell includes amorphous carbon and sodium aminosulfonate.

[0064] Taking the total mass of the pre-sodium-treated phosphorus-carbon core material as 100%, the mass percentage of sodium element in the pre-sodium-treated phosphorus-carbon core material is 5wt.%, and the mass percentage of the carbon nanotube material is 95wt.%; the mass ratio of amorphous carbon to sodium aminosulfonate in the shell material is 90:10; and the mass ratio of the pre-sodium-treated phosphorus-carbon core material and the shell is 100:15.

[0065] This embodiment also provides a method for the above-mentioned phosphorus-carbon composite material with a core-shell structure, the method comprising the following steps:

[0066] S1. Add 5g of sodium acetate to 100g of ethanol organic solvent to prepare a 5wt.% solution, then add 5g of red phosphorus powder, 100g of carbon nanotube conductive agent solution with a mass concentration of 5wt.% and 100g of benzoxazine to disperse evenly to obtain a reaction solution; transfer the reaction solution to a high-pressure reactor, perform hydrothermal reaction at 150°C and a pressure of 3Mpa for 6h, and then filter to obtain a pre-sodium phosphorus-carbon precursor material; carbonize the pre-sodium phosphorus-carbon precursor material at 1200°C for 3h to obtain a pre-sodium phosphorus-carbon material;

[0067] S2. The pre-sodiumized phospho-carbon material was transferred to a tubular furnace, heated to 900°C and introduced into ethylene gas for vapor deposition at a flow rate of 300 mL / min for 300 min to form a pre-sodiumized phospho-carbon material coated with amorphous carbon;

[0068] S3. Dissolve 10g of sodium aminosulfonate in 100g of sodium carboxymethyl cellulose with a mass concentration of 1wt.% in an aqueous solvent to prepare a mixed solution with a mass concentration of 10wt.%, then add 100g of pre-sodiumized phosphorus-carbon material coated with amorphous carbon, disperse evenly, and after spray drying, the inlet temperature is 250°C, the outlet temperature is 100°C, the flow rate is 0.5kg / h, and the time is 0.5h to obtain the phosphorus-carbon composite material with a core-shell structure.

[0069] Example 4

[0070] The difference between this embodiment and embodiment 1 is that no carbon nanotube conductive agent solution is added in step S1 , and the rest is the same as embodiment 1.

[0071] Example 5

[0072] The difference between this embodiment and embodiment 1 is that the mass ratio of the pre-sodiumized phospho-carbon material coated with amorphous carbon to sodium aminosulfonate in step S3 is 100:0.5, and the rest is the same as embodiment 1.

[0073] Example 6

[0074] The difference between this embodiment and embodiment 1 is that the mass ratio of the pre-sodiumized phospho-carbon material coated with amorphous carbon to sodium aminosulfonate in step S3 is 100:15, and the rest is the same as embodiment 1.

[0075] Example 7

[0076] The difference between this embodiment and embodiment 1 is that in step S3, sodium sulfamate is replaced by sodium dodecyl sulfonate of the same content, and the rest is the same as embodiment 1.

[0077] Comparative Example 1

[0078] The difference between this comparative example and Example 1 is that sodium acetate is not added in step S1, and the rest is the same as Example 1.

[0079] Comparative Example 2

[0080] The difference between this comparative example and Example 1 is that red phosphorus and carbon nanotube conductive agent are not added in step S1, and the other steps are the same as those in Example 1.

[0081] Comparative Example 3

[0082] The difference between this comparative example and Example 1 is that the treatments of step S2 and step S3 are not performed, and the pre-sodiumized phosphorus-carbon material obtained in step S1 is used, and the rest is the same as Example 1.

[0083] Comparative Example 4

[0084] The difference between this comparative example and Example 1 is that the processing of step S3 is not performed, and the rest is the same as Example 1.

[0085] Test conditions

[0086] The phosphorus-carbon composite materials with core-shell structure provided by Examples 1 to 7 and Comparative Examples 1 to 4 were subjected to relevant tests, and the test methods are as follows:

[0087] (1) Morphological characterization:

[0088] The core-shell structured phosphorus-carbon composite material obtained in Example 1 was subjected to SEM testing. Figure 1 As shown, from Figure 1 It can be seen that the phosphorus-carbon composite material with a core-shell structure prepared in Example 1 presents a granular structure, has a uniform size distribution, has a microporous structure on the surface, and has a particle size between 3-7 μm.

[0089] (2) Physical and chemical properties and button battery testing:

[0090] The tap density, specific surface area, specific capacity and initial efficiency of the phosphorus-carbon composite materials with core-shell structure prepared in Examples 1-7 and Comparative Examples 1-4 were tested. The test method reference standard: GBT-43114-2023 "Hard Carbon". At the same time, the diffusion coefficient of the material was tested by GITT; the powder resistivity was tested by a four-probe tester.

[0091] The core-shell phosphorus-carbon composite materials obtained in Examples 1-7 and Comparative Examples 1-4 are respectively assembled into button batteries, and the preparation method thereof is as follows: a binder, a conductive agent and a solvent are added to the negative electrode material, stirred to make a slurry, coated on a copper foil, and dried and rolled to obtain the battery. The binder used is LA132 binder, the conductive agent is Super P, the negative electrode material is the phosphorus-carbon composite material with a core-shell structure prepared in Examples 1-7 and Comparative Examples 1-4, and the solvent is double distilled water, and its content is specifically: the negative electrode material of the phosphorus-carbon composite material with a core-shell structure, Super P, LA132 and double distilled water are: 90g, 3g, 6g and 220mL, respectively, and the negative electrode sheet is prepared; the electrolyte is NaPF6 / EC+DEC (volume ratio 1:1, concentration 1.1mol / L), the metal sodium sheet is the counter electrode, the diaphragm is a polypropylene film, the simulated battery assembly is carried out in an argon-filled glove box, and the electrochemical performance is carried out on a Wuhan Blue Electric CT2001A battery tester, the charge and discharge voltage range is 0.00V to 2.0V, and the charge and discharge rate is 0.1C. At the same time, the charging DCR (50% SOC) of its button battery is tested.

[0092] The test results are shown in Table 1:

[0093] Table 1

[0094]

[0095]

[0096] It can be seen from Table 1 that the phosphorus-carbon composite materials provided in Examples 1-3 are doped with phosphorus in the inner core to increase the specific capacity of the hard carbon material and its sodium salt to reduce the irreversible capacity of the phosphorus-carbon composite material and improve its first coulombic efficiency; at the same time, the organic sulfonate coated in the outer shell has a strong solvation ability, which can ultimately increase the insertion and extraction rate of sodium ions during the charge and discharge process and improve the diffusion coefficient of the phosphorus-carbon composite material, thereby reducing the direct current resistance (DCR) of the phosphorus-carbon composite material.

[0097] Examples 5-6 show that the present invention, by regulating the mass ratio range of the pre-sodiumized phosphorus-carbon material coated with amorphous carbon and sodium aminosulfonate, makes the phosphorus-carbon composite material have high initial efficiency and fast charging performance while taking into account the specific capacity; Example 7 shows that replacing sodium aminosulfonate with an equal content of sodium dodecyl sulfonate cannot achieve all the technical effects of the technical solution of the present invention.

[0098] Soft pack battery test:

[0099] The core-shell structured phosphorus-carbon composite materials in Examples 1-7 and Comparative Examples 1-4 were used as negative electrodes, and slurry mixing and coating were performed to prepare negative electrode sheets. 1 / 3 Mn 1 / 3 Ni 1 / 3 A 2Ah soft-pack battery was prepared using celegard 2400 as the separator, NaPF6 with a concentration of 1.3 mol / L, a mixed solvent of EC+DEC with a volume ratio of 1:1 as the electrolyte, and celegard 2400 as the cathode.

[0100] High temperature storage performance test:

[0101] Test method: Test the capacity of the battery at full charge at 60°C as X1, then place it at 60°C for 30 days, and then test the capacity of the battery again as X2, and calculate the charge retention = (X2 / X1) × 100%; then charge the battery to full charge (100% SOC), test the capacity of the battery as X3, and calculate the recovery capacity = (X3 / X1) × 100%;

[0102] Cycling performance: temperature is 25°C, voltage range is 1.5-3.95V, current density is 1C / 1C, and number of cycles is 500;

[0103] Rate performance: Charge at a rate of 2C+0.1C with constant current + constant voltage to 3.95C, and then calculate the constant current ratio of the battery = 2C constant current capacity / (2C constant current capacity+0.1C constant voltage capacity).

[0104] The test results are shown in Table 2:

[0105] Table 2

[0106] Examples Charge retention rate Capacity recovery rate Cycle performance Constant current ratio Example 1 94.2％ 97.4％ 92.7％ 86.4％ Example 2 94.8％ 97.9％ 93.1％ 85.9％ Example 3 93.7％ 96.8％ 91.3％ 87.8％ Example 4 93.2％ 96.2％ 90.7％ 84.7％ Example 5 93.5％ 96.6％ 89.9％ 83.9％ Example 6 92.7％ 95.1％ 92.7％ 89.7％ Example 7 92.9％ 95.5％ 91.9％ 88.9％ Comparative Example 1 91.2％ 94.3％ 88.2％ 75.3％ Comparative Example 2 90.3％ 93.2％ 90.7％ 79.4％ Comparative Example 3 89.4％ 92.1％ 89.5％ 77.1％ Comparative Example 4 89.6％ 92.3％ 89.6％ 77.6％

[0107] It can be seen from Table 2 that the phosphorus-carbon composite materials provided in Examples 1-3 have a high diffusion coefficient and improve their rate performance; at the same time, the organic sulfonate coated in the outer shell layer reduces the contact between the electrolyte and the core material, thereby reducing the occurrence of side reactions, thereby improving the high-temperature storage performance of the phosphorus-carbon composite material.

[0108] Examples 5-6 show that the present invention, by regulating the mass ratio range of the pre-sodiumized phosphorus-carbon material coated with amorphous carbon and sodium aminosulfonate, makes the phosphorus-carbon composite material have high rate performance and good high-temperature storage performance; Example 7 shows that replacing sodium aminosulfonate with an equal content of sodium dodecyl sulfonate cannot achieve all the technical effects of the technical solution of the present invention.

[0109] The applicant declares that the present invention illustrates the process method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned process steps, that is, it does not mean that the present invention must rely on the above-mentioned process steps to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A phosphorus-carbon composite material with a core-shell structure, characterized in that: The phosphorus-carbon composite material with a core-shell structure comprises a pre-sodiumized phosphorus-carbon core material and a shell coated on the surface of the pre-sodiumized phosphorus-carbon core material, wherein the material of the shell comprises amorphous carbon and organic sulfonate.

2. The phosphorus-carbon composite material with a core-shell structure according to claim 1, characterized in that: Taking the total mass of the pre-sodiumized phosphorus-carbon core material as 100%, the mass percentage of sodium element in the pre-sodiumized phosphorus-carbon core material is 1wt.%-5wt.%, preferably 2wt.%-4wt.%; Preferably, the pre-sodiumized phosphorus-carbon core material further comprises an inorganic carbon material; Preferably, the inorganic carbon material comprises at least one of carbon nanotubes, graphene or carbon black; Preferably, based on the total mass of the pre-sodiumized phosphorus-carbon core material as 100%, the mass percentage of the inorganic carbon material is 60wt.%-95wt.%, preferably 80wt.%-90wt.%; Preferably, the mass ratio of amorphous carbon to organic sulfonate in the material of the shell is (90-99):(1-10), preferably (95-98):(2-5); Preferably, the organic sulfonate comprises a sodium sulfamate derivative; Preferably, the sodium aminosulfonate derivative includes any one of sodium aminosulfonate, sodium 3-aminobenzenesulfonate, sodium m-aminobenzenesulfonate or sodium 4-aminobenzenesulfonate, or a combination of at least two thereof.

3. The phosphorus-carbon composite material with a core-shell structure according to claim 1 or 2, characterized in that: The mass ratio of the pre-sodiumized phosphorus-carbon core material to the shell material is 100:(1-15), preferably 100:(5-10).

4. A method for preparing a phosphorus-carbon composite material having a core-shell structure according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: S1. preparing a reaction solution of a pre-sodiumizing agent, red phosphorus and a resin, subjecting the reaction solution to a hydrothermal reaction to obtain a pre-sodiumized phosphorus-carbon precursor material; carbonizing the pre-sodiumized phosphorus-carbon precursor material to obtain a pre-sodiumized phosphorus-carbon material; S2. vapor-depositing the pre-sodiumized phospho-carbon material and the carbon source obtained in step S1 to obtain a pre-sodiumized phospho-carbon material coated with amorphous carbon; S3. Mix the pre-sodiumized phosphorus-carbon material coated with amorphous carbon obtained in step S2, an organic sulfonate and a solvent to obtain a mixed solution; spray-dry the mixed solution to obtain the phosphorus-carbon composite material with a core-shell structure.

5. The method according to claim 4, characterized in that The pre-sodiumizing agent in step S1 includes any one of sodium acetate, sodium pyruvate, sodium m-aminobenzenesulfonate, sodium hydroxybenzenesulfonate, sodium naphthalenesulfonate, sodium tetradecenesulfonate, sodium p-hydroxybenzoate or sodium ascorbate, or a combination of at least two thereof; Preferably, the resin in step S1 comprises any one or a combination of at least two of benzoxazine, sulfonated phenolic resin, rosin-modified phenolic resin, amino resin, polysulfone resin or furan resin; Preferably, the reaction solution in step S1 further comprises an inorganic carbon material and an organic solvent; Preferably, the organic solvent comprises at least one of ethanol, methanol, glycerol or 1,4-butanediol; Preferably, the mass ratio of the pre-sodiumizing agent, red phosphorus, inorganic carbon material and resin is (1-5):(1-5):(1-5):100, preferably 3:3:3:100; Preferably, the temperature of the hydrothermal reaction in step S1 is 100-200°C, the pressure is 1.5-5.5Mpa, and the time is 2-12h; Preferably, the carbonization temperature in step S1 is 1000-1400° C. and the time is 1-6 hours.

6. The method according to claim 4 or 5, characterized in that: The carbon source in step S2 includes at least one of methane, ethane, ethylene or acetylene; Preferably, the flow rate of the carbon source in step S2 is 100-500 mL / min; Preferably, the temperature of the vapor deposition in step S2 is 800-1100° C. and the time is 60-600 min.

7. The method according to any one of claims 4 to 6, characterized in that: The mass ratio of the pre-sodiumized phospho-carbon material coated with amorphous carbon to the organic sulfonate in step S3 is 100:(1-10), preferably 100:5; Preferably, the solvent in step S3 is water; Preferably, the mixed solution in step S3 further includes a dispersant.

8. The method according to any one of claims 4 to 7, characterized in that: The inlet temperature of the spray drying in step S3 is 150-250° C., the outlet temperature is 80-100° C., the flow rate is 0.1-0.5 kg / h, and the time is 0.5-2 h.

9. A negative electrode, characterized in that: The negative electrode comprises a negative electrode active material, and the negative electrode active material comprises the phosphorus-carbon composite material with a core-shell structure according to any one of claims 1 to 3.

10. A secondary battery, characterized in that: The secondary battery includes a positive electrode, a negative electrode, and an electrolyte, and the negative electrode includes the negative electrode according to claim 9.

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