Nano red phosphorus-porous carbon composite material and its preparation method and application

Abstract

The present invention relates to a nano red phosphorus-porous carbon composite material and its preparation method and application. The preparation method comprises: mixing a pore-forming agent, a solvent, an ethylenediamine solution and red phosphorus to obtain a first mixed solution, then mixing chlorella with the first mixed solution and adding a first acidic solution, and obtaining a first product through separation, wherein the solvent is selected from water and / or a hydrophilic solvent; carbonizing the first product under protective gas conditions to obtain a second product; mixing the second product with a second acidic solution and adding a second mixed solution, wherein the second mixed solution is a mixed solution of an ethylenediamine solution and red phosphorus, and obtaining a nano red phosphorus-porous carbon composite material through separation. The preparation method of the present invention improves the deposition amount and dispersion uniformity of nano red phosphorus particles, significantly reduces the problem of red phosphorus being converted into white phosphorus during the preparation process, improves production efficiency and safety, and also reduces costs, which is conducive to large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a nano red phosphorus-porous carbon composite material and a preparation method and application thereof. Background Art

[0002] Phosphorus has a high theoretical specific capacity (2596 mAh / g) and a safe operating voltage (-0.45 V), and has high electrochemical activity in both lithium-ion batteries and sodium-ion batteries. Phosphorus has multiple allotropes such as red phosphorus, white phosphorus, black phosphorus, and purple phosphorus. Among them, red phosphorus not only has the advantages of abundant content, low market cost, and low environmental pollution, but also has better chemical stability at room temperature than white phosphorus, black phosphorus, and purple phosphorus, and can be used as phosphorus-based negative electrode materials in lithium-ion batteries and sodium-ion batteries. However, red phosphorus has three problems: (1) It has electronic insulation (conductivity is only 10S / cm-14S / cm); (2) The volume change during the cycle is large (more than 490%); (3) The particle size of commercial red phosphorus is too large. These problems make red phosphorus poor in conductivity when used as a negative electrode material, and the particles are easily crushed during long cycles, resulting in the inability to achieve optimal energy storage.

[0003] To address the above problems, traditional technologies usually use the evaporation-condensation method to compound nano-sized red phosphorus with a carbon matrix. Although this can improve the electrical conductivity and structural stability during the cycle, on the one hand, the evaporation-condensation method will produce a portion of white phosphorus due to incomplete conversion, which will not only cause capacity loss of the composite material, but also have problems such as low yield and safety, making it impossible to apply to large-scale production; on the other hand, traditional carbon matrices mainly include graphene, carbon nanotubes, microporous carbon made from metal-organic frameworks, etc., but these carbon matrices are relatively expensive and not conducive to large-scale production. Summary of the Invention

[0004] Based on this, it is necessary to provide a nano red phosphorus-porous carbon composite material and its preparation method and application to address the above problems; the preparation method enables the nano red phosphorus particles to be fully deposited on the bio-based porous carbon, which not only improves the deposition amount and dispersion uniformity of the nano red phosphorus particles and effectively inhibits the agglomeration of the nano red phosphorus particles, but also significantly reduces the problem of the nano red phosphorus being converted into white phosphorus during the preparation process, thereby improving production efficiency and safety, while also reducing costs and facilitating large-scale production.

[0005] A method for preparing a nano red phosphorus-porous carbon composite material comprises the following steps:

[0006] Mixing a pore-forming agent, a solvent, an ethylenediamine solution, and red phosphorus to obtain a first mixed solution, then mixing Chlorella with the first mixed solution and adding a first acidic solution, and separating to obtain a first product, wherein the solvent is selected from water and / or a hydrophilic solvent;

[0007] Carbonizing the first product under protective gas conditions to obtain a second product;

[0008] The second product is mixed with a second acidic solution and added into a second mixed solution, wherein the second mixed solution is a mixed solution of ethylenediamine solution and red phosphorus, and a nano red phosphorus-porous carbon composite material is obtained through separation.

[0009] In one embodiment, the step of preparing the first product satisfies at least one of the following conditions:

[0010] (1) The mass ratio of the chlorella to the pore-forming agent and the hydrophilic solvent is 2:(4-15):(1-3);

[0011] (2) In the first mixed solution, the mass fraction of the red phosphorus is 2%-8%;

[0012] (3) In the first mixed solution, the mass fraction of the ethylenediamine solution is 6%-40%;

[0013] (4) the first acidic solution is added in batches;

[0014] (5) The pore-forming agent is selected from at least one of sodium carbonate, potassium carbonate, zinc chloride, potassium acetate, sodium bicarbonate, potassium bicarbonate, potassium hydroxide, sodium hydroxide, calcium carbonate, and calcium chloride;

[0015] (6) The hydrophilic solvent is selected from at least one of sodium chloride solution, glucose syrup, and ethanol.

[0016] In one embodiment, the pH of the first acidic solution and the second acidic solution are independently selected from 1.3-1.6.

[0017] In one embodiment, the first acidic solution and the second acidic solution are independently selected from an ethanol solution containing dilute hydrochloric acid, and in the ethanol solution containing dilute hydrochloric acid, the volume ratio of ethanol to dilute hydrochloric acid is 1:(0.5-30);

[0018] And / or, the concentration of the dilute hydrochloric acid is 0.025 mol / L-0.1 mol / L.

[0019] In one embodiment, the step of mixing the second product with the second acidic solution and adding the second mixed solution satisfies at least one of the following conditions:

[0020] (1) In the second mixed solution, the concentration of red phosphorus is 4 g / L-50 g / L;

[0021] (2) The second mixed solution is added in batches.

[0022] In one embodiment, the carbonization temperature is 400° C.-1100° C., and the time is 0.5 h-30 h.

[0023] A nano red phosphorus-porous carbon composite material is prepared by the above-mentioned preparation method of the nano red phosphorus-porous carbon composite material. The nano red phosphorus-porous carbon composite material comprises a porous carbon matrix and nano red phosphorus particles distributed in the porous carbon matrix.

[0024] In one embodiment, the nano red phosphorus-porous carbon composite material satisfies at least one of the following conditions:

[0025] (1) The particle size of the nano red phosphorus-porous carbon composite material is 2 μm-10 μm;

[0026] (2) The particle size of the nano red phosphorus particles is 5nm-10nm;

[0027] (3) The deposition amount of nano red phosphorus particles in the nano red phosphorus-porous carbon composite material is 38%-45%.

[0028] A negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer, wherein the negative electrode active material layer comprises the nano red phosphorus-porous carbon composite material as described above.

[0029] A battery comprises the negative electrode sheet as described above.

[0030] The preparation method of the present invention, under the synergistic effects of liquid phase phosphorus source acid precipitation of nano red phosphorus clusters and two-step deposition, not only significantly reduces the problem of red phosphorus being converted into white phosphorus during the preparation process, but also can quickly control the size of the generated nano red phosphorus clusters, and is also beneficial to improving the production rate and yield of red phosphorus, and improving the safety during red phosphorus synthesis. On the other hand, it fully utilizes the pore space of the porous carbon, not only increasing the deposition amount of nano red phosphorus particles to about 38%-45%, making the nano red phosphorus particles more evenly dispersed and effectively limiting the agglomeration of the nano red phosphorus particles, but also after the nano red phosphorus particles are deposited, the composite material can still maintain a large number of pores, providing a buffer space for the expansion of the nano red phosphorus particles, and is beneficial to improving cycle stability. At the same time, because the nano red phosphorus particles fully fill the pores on the porous carbon surface, the pores on the porous carbon surface are reduced or closed, which is beneficial to increasing the number of closed pores, thereby improving the sodium storage capacity and low voltage platform.

[0031] In addition, since Chlorella is rich in amino acids and proteins, it will form porous carbon doped with nitrogen and phosphorus elements after carbonization as a biological template, which will make the composite material have certain defects, which is beneficial to enhance the surface wettability and catalytic activity of the composite material, and can provide more active sites during the charging and discharging process, thereby further improving the electrochemical performance of the composite material.

[0032] Therefore, the nano red phosphorus-porous carbon composite material prepared by the preparation method of the present invention, when used as a negative electrode material in a battery, not only has a high initial charge and discharge efficiency and discharge specific capacity, but also has excellent cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 Schematic diagram of the preparation method according to one embodiment of the present invention;

[0035] Figure 2 Schematic diagram of the cross-sectional structure of the nano red phosphorus-porous carbon composite material in one embodiment of the present invention;

[0036] Figure 3 A long cycle curve of a sodium ion battery prepared using Example 1 as the negative electrode material at a current density of 0.5 A / g for 500 cycles, where A is the discharge capacity after 500 cycles and B is the first charge and discharge efficiency after 500 cycles;

[0037] Figure 4 The long cycle curve of the sodium ion battery prepared as the negative electrode material in Example 1 was cycled 200 times at a current density of 0.2 A / g, where A is the discharge capacity after 200 cycles and B is the first charge and discharge efficiency after 200 cycles.

[0038] Among them, 10, porous carbon matrix; 101, pores; 20, nano red phosphorus particles. DETAILED DESCRIPTION

[0039] To facilitate understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in this specification of the present invention are only for the purpose of describing specific embodiments or examples and are not intended to limit the present invention.

[0041] Combine Figure 1 FIG. 1 is a flow chart of a method for preparing a nano red phosphorus-porous carbon composite material provided by the present invention, comprising the following steps:

[0042] S1, mixing a pore-forming agent, a solvent, an ethylenediamine solution, and red phosphorus to obtain a first mixed solution, then mixing Chlorella with the first mixed solution and adding a first acidic solution, and obtaining a first product through separation, wherein the solvent is selected from water and / or a hydrophilic solvent;

[0043] S2, carbonizing the first product under protective gas conditions to obtain a second product;

[0044] S3, mixing the second product with a second acidic solution and adding the mixture into a second mixed solution, wherein the second mixed solution is a mixed solution of ethylenediamine solution and red phosphorus, and obtaining a nano red phosphorus-porous carbon composite material through separation.

[0045] It is understandable that the red phosphorus is mainly selected from commercial red phosphorus, and the present invention does not limit the selection of commercial red phosphorus in terms of specific brands, etc.; the ethylenediamine solution is preferably an anhydrous ethylenediamine solution.

[0046] In step S1, red phosphorus is dissolved in an ethylenediamine solution as a liquid phase phosphorus source and Chlorella as a carbon source, and a pore-forming agent and a hydrophilic solvent are added. On the one hand, the pore-forming agent utilizes the hydrophilic properties of Chlorella itself and can enter the interior of the Chlorella along with water and / or the hydrophilic solvent, which is beneficial for forming pores inside the Chlorella during the subsequent carbonization process, thereby forming porous carbon with high porosity. On the other hand, since red phosphorus is highly soluble in ethylenediamine, red phosphorus mainly exists in the ethylenediamine solution in the form of phosphorus ions and phosphorus radical ions. By regulating the hydrogen ion concentration provided by the first acidic solution, not only can the size of the generated nano-red phosphorus clusters be quickly regulated, but it is also beneficial to increase the production rate and yield of red phosphorus, thereby improving the safety of red phosphorus synthesis.

[0047] The synthesis principle of the nano red phosphorus clusters includes the following: during the process of red phosphorus dissolving in ethylenediamine, ethylenediamine generates amino anions through self-ionization. The amino anions act as nucleophiles and attack the 3d orbitals of the red phosphorus molecules, causing the PP bonds to cleave and generate polyphosphorus amine anions. The reaction formula is shown below:

[0048] H2N-CH2-CH2-NH2+P n →(H2N-CH2-CH2-NH3+ )(H2N-CH2-CH2-NH-P n - );

[0049] When hydrogen ions react with polyphosphorus amine anions, P n Ring closure can be used to recover P from a mixed solution of red phosphorus and ethylenediamine. n Cluster, then P n The clusters aggregate and grow to form nano red phosphorus clusters. The reaction formula is as follows: (H2N-CH2-CH2-NH3 + )(H2N-CH2-CH2-NH-P n - )+H + →2(H2N-CH2-CH2-NH3 + )+P n ↓.

[0050] In one embodiment, the mass ratio of the Chlorella to the pore-forming agent and the solvent is 2:(4-15):(1-3), more preferably 2:(6-10):(1-3), wherein the pore-forming agent includes but is not limited to at least one of sodium carbonate, potassium carbonate, zinc chloride, potassium acetate, sodium bicarbonate, potassium bicarbonate, potassium hydroxide, sodium hydroxide, calcium carbonate, and calcium chloride, more preferably sodium carbonate; the hydrophilic solvent includes but is not limited to at least one of sodium chloride solution, glucose syrup, and ethanol, and the water is more preferably deionized water.

[0051] In one embodiment, in the first mixed solution, the mass fraction of the red phosphorus is 2%-8%.

[0052] In one embodiment, in the first mixed solution, the mass fraction of the ethylenediamine solution is 6%-40%.

[0053] By regulating the ratio of the first mixed solution and Chlorella, it is beneficial for Chlorella to form a rich and uniform pore structure during the subsequent carbonization process, and at the same time, the nano red phosphorus particles can reach a certain deposition amount in the porous carbon.

[0054] It should be noted that the pore-forming agent, solvent, ethylenediamine solution and red phosphorus can be directly mixed, or the pore-forming agent and solvent can be mixed first and then the ethylenediamine solution and red phosphorus are added. The present invention does not limit the order of mixing the components.

[0055] In one embodiment, the pH of the first acidic solution is 1.3-1.6, and is preferably an ethanol solution containing dilute hydrochloric acid, wherein the volume ratio of ethanol to dilute hydrochloric acid is 1:(0.5-30), preferably 1:(10-20), and more preferably 1:20; the concentration of dilute hydrochloric acid is 0.025 mol / L-0.1 mol / L, preferably 0.025 mol / L-0.05 mol / L, and more preferably 0.05 mol / L.

[0056] In one embodiment, the first acidic solution is added in batches, preferably dropwise.

[0057] By regulating the ratio and addition method of the first acidic solution, the growth of nano red phosphorus clusters can be more accurately controlled, making the size of the nano red phosphorus clusters controllable.

[0058] In one embodiment, before the Chlorella is mixed with the first mixed solution, the Chlorella is pretreated, specifically including: washing the Chlorella with deionized water to remove impurities, and centrifugally drying.

[0059] In step S2, on the basis of acid precipitation of nano red phosphorus clusters by liquid phase phosphorus source, the chlorella loaded with nano red phosphorus clusters is carbonized. When the chlorella is completely decomposed into carbon, the pore-forming agent inside the chlorella decomposes to generate pores and form active sites, thereby forming bio-based porous carbon. Then, the nano red phosphorus clusters are gasified into the pores with active sites inside. At high temperature, gaseous phosphorus begins to deposit from the inside of the porous carbon through physical adsorption or chemical adsorption of the carbon matrix, and the amount of nano red phosphorus deposited in the direction extending from the inside of the porous carbon to the surface shows a decreasing trend. This not only significantly reduces the problem of red phosphorus being converted into white phosphorus during the preparation process, but also makes full use of the pore space of the porous carbon. While increasing the amount of nano red phosphorus particle deposition, the porous carbon can still maintain a large number of pores, providing a buffer space for the expansion of the nano red phosphorus particles, thereby improving the cycle stability.

[0060] In addition, the nitrogen and phosphorus elements converted from Chlorella's own proteins and amino acids are doped into the porous carbon, which gives the composite material certain defects, which is beneficial to enhancing the surface wettability and catalytic activity of the composite material, and can provide more active sites during the charging and discharging process, thereby further improving the electrochemical performance of the composite material.

[0061] In one embodiment, the carbonization temperature is 400°C-1100°C, and the time is 0.5h-30h. Preferably, the carbonization temperature is 500°C-1000°C, and the time is 2h-24h. More preferably, the carbonization temperature is 700°C-1000°C, and the time is 6h-12h. By controlling the temperature and time of carbonization, it can not only ensure that the carbon source is completely decomposed into carbon, but also the decomposition of the pore-forming agent can also produce pores, thereby forming porous carbon with rich pores, but also facilitates the precise control of the nano red phosphorus particles to be mainly deposited in the internal pores, thereby effectively reducing the problem of red phosphorus being converted into white phosphorus during the preparation process.

[0062] In one embodiment, the protective gas includes but is not limited to nitrogen, preferably nitrogen.

[0063] Since the pores of the porous carbon are interconnected, in step S3, further liquid-phase impregnation treatment is performed to allow the nano-red phosphorus clusters to infiltrate and deposit from the surface of the porous carbon to the interior. Considering the space-occupying effect of the deposited nano-red phosphorus clusters, the deposition amount of the nano-red phosphorus clusters in the direction extending from the surface of the porous carbon to the interior shows a decreasing trend. Moreover, since the nano-red phosphorus clusters fully fill the pores on the surface of the porous carbon, the pores on the surface of the porous carbon are reduced or closed, which is beneficial to increase the number of closed pores, thereby improving the sodium storage capacity and the low-voltage platform.

[0064] Furthermore, under the synergistic effect of liquid phase phosphorus source acid precipitation of nano red phosphorus clusters and two-step deposition, the pore space of porous carbon is fully utilized, which not only increases the deposition amount of nano red phosphorus particles to about 38%-45%, making the nano red phosphorus particles more evenly dispersed and effectively limiting the agglomeration of nano red phosphorus particles, but also after the deposition of the nano red phosphorus particles, the composite material can still maintain a large number of pores, which can provide a buffer space for the expansion of the nano red phosphorus particles. While improving the conductivity of the composite material, it can also make the composite material have excellent cycle stability.

[0065] In one embodiment, the pH of the second acidic solution is 1.3-1.6, and is preferably an ethanol solution containing dilute hydrochloric acid, wherein the volume ratio of ethanol to dilute hydrochloric acid is 1:(0.5-30), preferably 1:(10-20); the concentration of dilute hydrochloric acid is 0.025 mol / L-0.1 mol / L, preferably 0.025 mol / L-0.05 mol / L, and more preferably 0.05 mol / L.

[0066] In one embodiment, in the second mixed solution, the concentration of red phosphorus is 4 g / L-50 g / L, preferably 5 g / L-15 g / L; the ethylenediamine solution in the second mixed solution is preferably an anhydrous ethylenediamine solution.

[0067] In one embodiment, the second mixed solution is added in batches, preferably dropwise, and more preferably, the second mixed solution is added dropwise while the second product and the second acidic solution are stirred and mixed.

[0068] By regulating the ratio of the second acidic solution and the method of adding the second mixed solution, it is beneficial to more accurately control the growth of nano red phosphorus clusters, making the size of the nano red phosphorus clusters more uniform and the particle size smaller, which is more conducive to improving the cyclic stability of the composite material.

[0069] It should be noted that the types and proportions of the first acidic solution and the second acidic solution may be the same or different, and the present invention does not impose any limitation thereto.

[0070] In one embodiment, after the second product is mixed with the second acidic solution and the second mixed solution is added, the mixture is stirred sufficiently, and then separated, washed, dried, and the like to obtain the nano red phosphorus-porous carbon composite material.

[0071] Combine Figure 2 1 is a schematic diagram of the cross-sectional structure of a nano red phosphorus-porous carbon composite material prepared by the preparation method of the nano red phosphorus-porous carbon composite material provided by the present invention, wherein the nano red phosphorus-porous carbon composite material includes a porous carbon matrix 10 and nano red phosphorus particles 20 distributed in the porous carbon matrix 10.

[0072] Specifically, the porous carbon matrix 10 has abundant pores 101 , and the nano red phosphorus particles 20 are filled in the pores 101 inside and on the surface of the porous carbon matrix 10 .

[0073] It should be noted that the size of most of the pores 101 in the porous carbon matrix 10 is larger than the particle size of the nano red phosphorus particles 20, and most of the pores 101 are filled with the nano red phosphorus particles 20. In order to more comprehensively represent the filling condition of the nano red phosphorus-porous carbon composite material, Figure 2 Some smaller pores 101 and pores 101 not filled with nano red phosphorus particles 20 are also listed. Figure 2 The cross-sectional structure of the nano red phosphorus-porous carbon composite material provided by the present invention is only one example, and does not represent all nano red phosphorus-porous carbon composite materials.

[0074] In one embodiment, the particle size of the nano red phosphorus-porous carbon composite material is 2 μm-10 μm, and the particle size of the nano red phosphorus particles 20 is 5 nm-10 nm.

[0075] In one embodiment, the deposition amount of the nano red phosphorus particles 20 in the nano red phosphorus-porous carbon composite material is 38%-45%.

[0076] The nano red phosphorus-porous carbon composite material of the present invention is used as a negative electrode material in a battery, and not only has high initial charge and discharge efficiency and discharge specific capacity, but also has excellent cycle stability.

[0077] The present invention provides a negative electrode plate. The negative electrode plate comprises a negative electrode current collector and a negative electrode active material layer, wherein the negative electrode active material layer comprises the nano red phosphorus-porous carbon composite material described above. It is understood that the negative electrode active material layer may also include materials such as a binder, which is not limited in the present invention.

[0078] The present invention also provides a battery, which can be a lithium-ion battery or a sodium-ion battery. The battery includes the negative electrode sheet described above. It is understood that the battery also includes a positive electrode sheet, a separator, and an electrolyte, which are not limited in the present invention.

[0079] Below, described nano red phosphorus-porous carbon composite material and its preparation method and application are further described by following specific examples.But those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.If specific conditions are not specified in the embodiment, it is carried out according to normal conditions or the conditions recommended by the manufacturer.If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be obtained by commercial purchase.

[0080] Example 1

[0081] The Chlorella vulgaris was washed several times with deionized water to remove impurities and then centrifuged and dried. 1.28 g of sodium carbonate was mixed with 480 mL of deionized water, and 9 mL of ethylenediamine solution and 100 mg of commercial red phosphorus were added and dispersed evenly. 0.60 g of dried Chlorella vulgaris was then added, stirred, and a mixed solution of ethanol and 0.05 mol / L dilute hydrochloric acid (the volume ratio of ethanol to dilute hydrochloric acid was 1:20) was gradually added dropwise. The mixture was stirred evenly and separated to obtain the first product.

[0082] The first product was carbonized at 1000° C. for 12 h under a nitrogen atmosphere to obtain a second product.

[0083] 400 mg of commercial red phosphorus was dissolved in 35 mL of ethylenediamine solution to obtain a second mixed solution. The second product was dispersed in a mixed solution of 5 mL of ethanol and 100 mL of dilute hydrochloric acid, stirred, and the second mixed solution was added dropwise. After sufficient stirring, the mixture was filtered and freeze-dried to obtain a nano red phosphorus-porous carbon composite material.

[0084] Example 2

[0085] The Chlorella vulgaris was washed several times with deionized water to remove impurities and then centrifuged and dried. 1.35 g of zinc chloride was mixed with 360 mL of deionized water, and 10 mL of ethylenediamine solution and 100 mg of commercial red phosphorus were added and dispersed evenly. 0.30 g of dried Chlorella vulgaris was then added, stirred, and a mixed solution of ethanol and 0.05 mol / L dilute hydrochloric acid (the volume ratio of ethanol to dilute hydrochloric acid was 1:20) was gradually added dropwise. The mixture was stirred evenly and separated to obtain the first product.

[0086] The first product was carbonized at 1000° C. for 12 h under a nitrogen atmosphere to obtain a second product.

[0087] 400 mg of commercial red phosphorus was dissolved in 35 mL of ethylenediamine solution to obtain a second mixed solution. The second product was dispersed in a mixed solution of 5 mL of ethanol and 100 mL of dilute hydrochloric acid, stirred, and the second mixed solution was added dropwise. After sufficient stirring, the mixture was filtered and freeze-dried to obtain a nano red phosphorus-porous carbon composite material.

[0088] Example 3

[0089] The Chlorella vulgaris was washed several times with deionized water to remove impurities and then centrifuged and dried. 1.28 g of sodium carbonate was mixed with 480 mL of deionized water, and 9 mL of ethylenediamine solution and 100 mg of commercial red phosphorus were added and dispersed evenly. 0.40 g of dried Chlorella vulgaris was then added, stirred, and a mixed solution of ethanol and 0.05 mol / L dilute hydrochloric acid (the volume ratio of ethanol to dilute hydrochloric acid was 1:20) was gradually added dropwise. The mixture was stirred evenly and separated to obtain the first product.

[0090] The first product was carbonized at 700° C. for 12 h under a nitrogen atmosphere to obtain a second product.

[0091] 400 mg of commercial red phosphorus was dissolved in 35 mL of ethylenediamine solution to obtain a second mixed solution. The second product was dispersed in a mixed solution of 5 mL of ethanol and 100 mL of dilute hydrochloric acid, stirred, and the second mixed solution was added dropwise. After sufficient stirring, the mixture was filtered and freeze-dried to obtain a nano red phosphorus-porous carbon composite material.

[0092] Comparative Example 1

[0093] The chlorella was washed several times with deionized water to remove impurities and centrifuged to dry. 1.28 g of sodium carbonate was mixed with 480 mL of deionized water, and 0.60 g of dried chlorella was added. The mixture was stirred and separated to obtain the first product.

[0094] The first product was carbonized at 1000°C for 12 h under a nitrogen atmosphere to obtain Chlorella-derived porous carbon.

[0095] 400 mg of commercial red phosphorus was dissolved in 35 mL of ethylenediamine solution to obtain a mixed solution. Chlorella-derived porous carbon was dispersed in a mixed solution of 5 mL of ethanol and 100 mL of dilute hydrochloric acid, stirred, and the mixed solution was added dropwise. After sufficient stirring, the mixture was filtered and freeze-dried to obtain a nano red phosphorus-porous carbon composite material.

[0096] Comparative Example 2

[0097] The chlorella was washed several times with deionized water to remove impurities and centrifuged to dry. 1.28 g of sodium carbonate was mixed with 480 mL of deionized water, and 0.60 g of dried chlorella was added. The mixture was stirred and separated to obtain the first product.

[0098] The first product was carbonized at 1000°C for 12 h under a nitrogen atmosphere to obtain Chlorella-derived porous carbon.

[0099] 400 mg of commercial red phosphorus was dissolved in 35 mL of ethylenediamine solution to obtain a mixed solution. Chlorella-derived porous carbon was dispersed in a mixed solution of 5 mL of ethanol and 100 mL of dilute hydrochloric acid, and the mixture was stirred and added dropwise. After sufficient stirring, the mixture was filtered to obtain an intermediate product.

[0100] The intermediate product was carbonized at 1000° C. for 12 h under a nitrogen atmosphere to obtain a nano red phosphorus-porous carbon composite material.

[0101] Comparative Example 3

[0102] The Chlorella vulgaris was washed several times with deionized water to remove impurities and then centrifuged and dried. 1.28 g of sodium carbonate was mixed with 480 mL of deionized water, and 9 mL of ethylenediamine solution and 100 mg of commercial red phosphorus were added and dispersed evenly. 0.60 g of dried Chlorella vulgaris was then added, stirred, and a mixed solution of ethanol and 0.05 mol / L dilute hydrochloric acid (the volume ratio of ethanol to dilute hydrochloric acid was 1:20) was gradually added dropwise. The mixture was stirred evenly and separated to obtain the first product.

[0103] The first product was carbonized at 1000° C. for 12 h under a nitrogen atmosphere to obtain a nano red phosphorus-porous carbon composite material.

[0104] Comparative Example 4

[0105] The difference between Comparative Example 4 and Example 1 is that sodium carbonate is not added.

[0106] Comparative Example 5

[0107] The difference between Comparative Example 5 and Example 1 is that 480 mL of n-butanol is added instead of 480 mL of deionized water.

[0108] Comparative Example 6

[0109] The difference between Comparative Example 6 and Example 1 is that 480 mL of ether is added instead of 480 mL of deionized water.

[0110] The composite materials prepared in Examples 1-3 and Comparative Examples 1-6 were tested, and the results are shown in Table 1.

[0111] Table 1

[0112]

[0113]

[0114] As shown in Table 1, the composite materials prepared in Examples 1-3 all achieved red phosphorus deposition of approximately 38%-45%. Compared with Example 1, Comparative Example 1 did not deposit nano-red phosphorus during carbonization, resulting in the nano-red phosphorus being primarily distributed on the surface of the porous carbon and having difficulty penetrating the interior. Consequently, the deposition amount was lower than that of Example 1, and some white phosphorus was present. Comparative Example 2 employed liquid phase deposition followed by carbonization. Due to the limited liquid phase deposition capacity, the deposition amount was not as high as that of Example 1. Comparative Example 3 utilized only carbonization to deposit nano-red phosphorus, resulting in insufficient nano-red phosphorus on the surface of the porous carbon, resulting in a lower deposition amount than that of Example 1. Comparative Example 4 did not incorporate a pore-forming agent, resulting in fewer pores in the carbon material, which affected the deposition amount of nano-red phosphorus. Comparative Examples 5 and 6 employed n-butanol or ether as solvents. Since n-butanol or ether are not hydrophilic, the interior of the porous carbon was essentially free of pores, preventing the nano-red phosphorus from penetrating the porous carbon interior, resulting in low nano-red phosphorus deposition.

[0115] Application Examples

[0116] The composite materials prepared in Examples 1-3 and Comparative Examples 1-6 were formulated into button-type sodium-ion battery anodes, specifically comprising: adding 90 wt% of the composite material, 5 wt% of a conductive agent, and 5 wt% of a binder to N-methylpyrrolidone (NMP), mixing them uniformly, coating them on aluminum foil, and drying them in a vacuum drying oven at 80°C for 12 hours. The baked electrode sheet was roll-cut and cut into 12 mm discs, weighed, and placed in a vacuum glove box for assembly into the button-type battery. A mixed solution of 1.0 mol / L NaPF6 and 3.0% FEC in propylene carbonate (PC) was used as the electrolyte, and the sodium metal sheet served as the counter electrode.

[0117] The electrochemical performance of the buckle batteries prepared in Examples 1-3 and Comparative Examples 1-6 was tested. The long cycle curve of Example 1 at a current density of 0.5 A / g for 500 cycles and the long cycle curve at a current density of 0.2 A / g for 200 cycles were as shown in FIG. Figure 3 and Figure 4 As shown, the test data of all embodiments and comparative examples after 200 cycles at a current density of 0.2 A / g are shown in Table 2.

[0118] Table 2

[0119]

[0120] according to Figure 3 As can be seen, after 500 cycles at a current density of 0.5 A / g, the discharge capacity of Example 1 dropped from 1438 mAh / g at the first cycle to 1211 mAh / g at the 20th cycle, then gradually stabilized. Even after 500 cycles, the discharge capacity still reached 1193 mAh / g. Its initial charge-discharge efficiency was 89.9%, and it remained stable at around 100% in subsequent cycles, demonstrating ultra-high discharge capacity and excellent cycling stability.

[0121] according to Figure 4 As can be seen, after 200 cycles at a current density of 0.2 A / g, the discharge capacity of Example 1 rapidly decreases from 1673 mAh / g initially to 1366 mAh / g, then gradually stabilizes. Even after 200 cycles, the discharge capacity still reaches 1327 mAh / g. Its initial charge-discharge efficiency is 89.9%, and it stabilizes at 99.8% in subsequent cycles, demonstrating both ultra-high discharge capacity and excellent cycling stability.

[0122] As shown in Table 2, the initial discharge specific capacity and the specific capacity after 200 cycles of Examples 1-3 are better than those of Comparative Examples 1-6, indicating that the nano red phosphorus-porous carbon composite material provided by the present invention can significantly reduce the capacity attenuation phenomenon caused by the volume deformation effect of nano red phosphorus during the charge and discharge process, and can be used as a negative electrode material for batteries to improve the electrochemical performance.

[0123] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0124] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing a nano red phosphorus-porous carbon composite material, characterized in that: The steps include: Mixing a pore-forming agent, a solvent, an ethylenediamine solution, and red phosphorus to obtain a first mixed solution, then mixing Chlorella with the first mixed solution and adding a first acidic solution, and separating to obtain a first product, wherein the solvent is selected from water and / or a hydrophilic solvent; Carbonizing the first product under protective gas conditions to obtain a second product; The second product is mixed with a second acidic solution and added into a second mixed solution, wherein the second mixed solution is a mixed solution of ethylenediamine solution and red phosphorus, and a nano red phosphorus-porous carbon composite material is obtained through separation.

2. The method for preparing the nano red phosphorus-porous carbon composite material according to claim 1, characterized in that: The step of preparing the first product satisfies at least one of the following conditions: (1) The mass ratio of the chlorella to the pore-forming agent and the solvent is 2:(4-15):(1-3); (2) In the first mixed solution, the mass fraction of the red phosphorus is 2%-8%; (3) In the first mixed solution, the mass fraction of the ethylenediamine solution is 6%-40%; (4) the first acidic solution is added in batches; (5) The pore-forming agent is selected from at least one of sodium carbonate, potassium carbonate, zinc chloride, potassium acetate, sodium bicarbonate, potassium bicarbonate, potassium hydroxide, sodium hydroxide, calcium carbonate, and calcium chloride; (6) The hydrophilic solvent is selected from at least one of sodium chloride solution, glucose syrup, and ethanol.

3. The method for preparing the nano red phosphorus-porous carbon composite material according to claim 1, characterized in that: The pH of the first acidic solution and the second acidic solution are independently selected from 1.3-1.

6.

4. The method for preparing the nano red phosphorus-porous carbon composite material according to claim 3, characterized in that: The first acidic solution and the second acidic solution are independently selected from ethanol solutions containing dilute hydrochloric acid. In the ethanol solution containing dilute hydrochloric acid, the volume ratio of ethanol to dilute hydrochloric acid is 1:(0.5-30), and the concentration of the dilute hydrochloric acid is 0.025mol / L-0.1mol / L.

5. The method for preparing the nano red phosphorus-porous carbon composite material according to claim 1, characterized in that: The step of mixing the second product with the second acidic solution and adding the second mixed solution satisfies at least one of the following conditions: (1) In the second mixed solution, the concentration of red phosphorus is 4 g / L-50 g / L; (2) The second mixed solution is added in batches.

6. The method for preparing the nano red phosphorus-porous carbon composite material according to claim 1, characterized in that: The carbonization temperature is 400° C.-1100° C., and the carbonization time is 0.5 h-30 h.

7. A nano red phosphorus-porous carbon composite material prepared by the method for preparing a nano red phosphorus-porous carbon composite material according to any one of claims 1 to 6, characterized in that: The nano red phosphorus-porous carbon composite material comprises a porous carbon matrix and nano red phosphorus particles distributed in the porous carbon matrix.

8. The nano red phosphorus-porous carbon composite material according to claim 7, characterized in that: The nano red phosphorus-porous carbon composite material meets at least one of the following conditions: (1) The particle size of the nano red phosphorus-porous carbon composite material is 2 μm-10 μm; (2) The particle size of the nano red phosphorus particles is 5nm-10nm; (3) The deposition amount of nano red phosphorus particles in the nano red phosphorus-porous carbon composite material is 38%-45%.

9. A negative electrode plate, characterized in that: The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer comprises the nano red phosphorus-porous carbon composite material according to any one of claims 7 or 8.

10. A battery, characterized in that: Comprising the negative electrode sheet as claimed in claim 9.

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