Composite materials, methods of making and using the same

Abstract

The application discloses a composite material and a preparation method and application thereof. The composite material comprises: a porous carbon skeleton, wherein nano red phosphorus is attached in the porous carbon skeleton; and a carbon coating layer, which is coated on the surface of the porous carbon skeleton. According to the composite material of the first aspect of the application, the following beneficial effects are achieved: the porous carbon skeleton has a large number of pores, which can effectively solve the volume expansion problem of the nano red phosphorus attached therein, shorten the electron transmission distance, accelerate the electron transfer and the embedding and stripping of cations therein and the transmission between the electrode and the electrolyte interface. The outer carbon coating layer can isolate the nano red phosphorus in the carbon skeleton and the phosphorus salt generated in the working state from direct contact with the electrolyte, thereby avoiding the occurrence of side reactions; the carbon coating layer can also improve the conductivity of the material, reduce the polarization and ensure the stability of the electrode structure. Therefore, the composite material as a negative active material can bring excellent cycle performance.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to composite materials, their preparation methods, and applications. Background Technology

[0002] Currently, the theoretical specific capacity of graphite anodes used in commercially available lithium-ion batteries is only 372 mAh / g, while the theoretical specific capacity of elemental red phosphorus is as high as 2596 mAh / g, far exceeding that of graphite and second only to silicon. Therefore, red phosphorus is a lithium-ion anode material with advantages such as abundant reserves, low price, and non-toxicity, making it a material with great application potential. However, red phosphorus has poor conductivity, and like silicon, it exhibits a volume expansion effect during charging and discharging, which has seriously affected its application in lithium batteries.

[0003] To address this, common solutions involve combining red phosphorus with carbon materials through methods such as ball milling, sublimation condensation, thermal reduction, and chemical precipitation. While the resulting phosphorus-carbon composites possess high theoretical capacity, severe volume expansion remains unavoidable, resulting in poor cycle performance and significantly limiting their commercialization. Therefore, it is necessary to provide a phosphorus-carbon composite material with excellent overall performance, capable of mitigating expansion, controlling capacity decay, and improving cycle stability. Summary of the Invention

[0004] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a composite material with small volume expansion and good cycle performance, as well as its preparation method and application.

[0005] A first aspect of this application provides a composite material, the composite material comprising:

[0006] Porous carbon framework, with nano-red phosphorus attached to the porous carbon framework;

[0007] Carbon coating layer, which is coated on the surface of a porous carbon skeleton.

[0008] The composite material according to the first aspect of this application has the following beneficial effects:

[0009] The porous carbon framework, with its numerous pores, effectively addresses the volume expansion issue of the attached nano-red phosphorus, shortens electron transport distances, accelerates electron transfer, and facilitates the insertion and extraction of cations, as well as their transport between the electrode and electrolyte interfaces. The outer carbon coating layer isolates the nano-red phosphorus within the carbon framework and the phosphate salts generated during operation from direct contact with the electrolyte, preventing side reactions. It also improves the material's conductivity, reduces polarization, and ensures the stability of the electrode structure. Therefore, this composite material, as a negative electrode active material, offers excellent cycle performance.

[0010] In some embodiments of this application, the porosity of the porous carbon skeleton is 40% or more, for example, it can be 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80% or more.

[0011] In some embodiments of this application, the nano-red phosphorus accounts for more than 50% of the porous carbon skeleton by mass, for example, 50%, 55%, 60%, 65%, 70%, 75%, 80% or more.

[0012] In some embodiments of this application, the raw material for the porous carbon skeleton includes at least one of graphite and hard carbon.

[0013] In some embodiments of this application, graphite includes at least one of single particles and secondary particles.

[0014] In some embodiments of this application, graphite includes at least one of artificial graphite and natural graphite.

[0015] In some embodiments of this application, the composite material satisfies 0.1 < 7a 2 b / (10(1-a) 2 (×c×d)<1.1; where a is the mass percentage of the nano-red phosphorus in the porous carbon framework; b is the average particle size D of the nano-red phosphorus. V 50, in μm; c is the average particle size D of the porous carbon framework. V 50, in μm; d is the porosity of the porous carbon skeleton. When the nano-red phosphorus and the porous carbon skeleton satisfy the above relationship, the composite material can be ensured to have both high capacity and low expansion.

[0016] In some embodiments of this application, the average particle size D of graphite and hard carbon is... V 50 represents 100nm to 20μm, specifically 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 800nm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, and 10μm.

[0017] In some embodiments of this application, the average particle size D of the nano-red phosphorus V 50 represents a particle size ranging from 1 to 1000 nm, specifically 1 nm, 2 nm, 4 nm, 5 nm, 6 nm, 8 nm, 10 nm, 20 nm, 40 nm, 50 nm, 60 nm, 80 nm, 100 nm, 200 nm, 400 nm, 500 nm, 600 nm, 800 nm, and 1000 nm. It is understandable that, under normal circumstances, the average particle size D of graphite and hard carbon... V50 is greater than the average particle size D of nano red phosphorus V 50, for example, the former is 2 to 200 times the latter, specifically 2 times, 3 times, 4 times, 5 times, 6 times, 8 times, 10 times, 15 times, 20 times, 25 times, 30 times, 40 times, 50 times, 60 times, 80 times, 100 times, 150 times, and 200 times.

[0018] In some embodiments of this application, the average particle size D of the porous carbon framework V The value 50 ranges from 2 to 50 μm, specifically 2 μm, 4 μm, 5 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, and 50 μm. In some embodiments, the outer surface of the porous carbon framework can be, for example, spherical or ellipsoidal.

[0019] In this application, the average particle size Dv50 refers to the particle size corresponding to a volume distribution of 50%.

[0020] A second aspect of this application provides a method for preparing a composite material, the method comprising the following steps:

[0021] S100: Take red phosphorus, the first carbon source and the self-sacrificing template agent, mix them, pressurize them under a protective atmosphere and heat them to 100-200℃ to obtain a mixed solid;

[0022] S200: The mixed solids are heated to 250-400°C to pulverize them into mixed particles;

[0023] S300: Mix the mixed particles with the second carbon source and carbonize them at 420-500℃ to obtain an intermediate;

[0024] S400: The intermediate is cooled to 240-280℃ to obtain the composite material.

[0025] In the above preparation method, red phosphorus, a first carbon source, and a template agent are first mixed, and then heated and pressurized to produce a mixed solid with a large number of micropores in the mixture, which is conducive to heating and pulverizing. The mixed solid is heated and pulverized, and a second carbon source is introduced on the surface of the resulting mixed particles. The first and second carbon sources are transformed into a porous carbon skeleton and a carbon coating layer by a one-time carbonization method. At the same time, the template agent is pyrolyzed to generate pore spaces, and the red phosphorus mixed in it will sublimate. The phosphorus vapor is adsorbed by the pore spaces of the porous carbon skeleton through capillary force and pressure difference to obtain an intermediate. Finally, white phosphorus is transformed into nano-red phosphorus by cooling, forming a composite material in which nano-red phosphorus is distributed in the pore spaces of the porous carbon skeleton and the outer surface is coated with a carbon coating.

[0026] In some embodiments of this application, the self-sacrificing template agent includes at least one of polystyrene, polymethyl methacrylate, and polyetherimide. The aforementioned template agent can be completely pyrolyzed during heating, maximizing the resulting void space to accommodate more red phosphorus, increasing specific capacity, and controlling volume expansion.

[0027] In some embodiments of this application, the first carbon source includes at least one of graphite and hard carbon.

[0028] In some embodiments of this application, graphite includes at least one of single particles and secondary particles.

[0029] In some embodiments of this application, graphite includes at least one of artificial graphite and natural graphite.

[0030] In some embodiments of this application, the second carbon source includes at least one of phenolic resin, epoxy resin, urea-formaldehyde resin, melamine resin, polybutadiene resin, polydopamine, citric acid, glucose, fructose, sucrose, maltose, dextrin, starch, sorbitol, tartaric acid, ethylenediaminetetraacetic acid, polyethylene glycol, polyvinyl alcohol, polyvinyl butyral, polyacrylic acid, carboxymethyl cellulose, coal tar pitch, and needle tar pitch.

[0031] In some embodiments of this application, the pressure conditions for the pressurization process are 2 to 6 kPa, for example, 2 kPa, 3 kPa, 4 kPa, 5 kPa, or 6 kPa.

[0032] Red phosphorus, a first carbon source, and a template agent are mixed, heated, and pressurized to maintain micropores in the mixture. After stabilization and cooling, a mixed solid is obtained. The mixed solid is then heated at high temperature and pulverized. A second carbon source is then introduced onto the surface of the mixed solid. A one-step carbonization process transforms the first and second carbon sources into a carbon skeleton and a coating layer. Simultaneously, the template agent undergoes pyrolysis, creating void spaces. The carbon skeleton transforms into a porous carbon skeleton, while the internal red phosphorus sublimates. Phosphorus vapor is adsorbed by the porous carbon skeleton through capillary forces and pressure differences. Cooling then converts white phosphorus into red phosphorus. Ultimately, a composite material is formed with nano-red phosphorus distributed on a porous carbon skeleton and a carbon coating on the outer surface.

[0033] A third aspect of this application provides a secondary battery comprising the aforementioned composite material.

[0034] In some embodiments of this application, the secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode includes a negative current collector and a negative active material layer. The raw material of the negative active material layer includes a negative active material, which includes the aforementioned composite material.

[0035] In some embodiments of this application, the raw materials for the negative electrode active material layer further include at least one of a conductive agent and a binder. The conductive agent includes, but is not limited to, conductive graphite (such as KS-6, KS-15, SFG-6, SFG-15, SO, etc.), conductive carbon black (such as Super P / SP, Super S, 350G, acetylene black, Ketjen black, etc.), conductive carbon fiber (such as vapor-grown carbon fiber VGCF, carbon nanotubes CNT), and graphene. The binder includes, but is not limited to, at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyurethane (PU), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), and lithium polyacrylate (PAALi).

[0036] In some embodiments of this application, the negative electrode active material layer comprises 70-99 wt% negative electrode active material, 0.5-6 wt% conductive agent and 0.5-20 wt% binder.

[0037] In some embodiments of this application, when the negative electrode active material, conductive agent and binder are made into a negative electrode active material layer, the negative electrode active material, conductive agent and binder are dispersed in a solvent and then coated on a negative electrode current collector and dried to obtain a negative electrode active material layer.

[0038] In some embodiments of this application, the positive electrode sheet includes a positive current collector and a positive active material layer.

[0039] In some embodiments of this application, the positive electrode active material layer includes a positive electrode active material, which is at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate (LFP), lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), lithium nickel manganese aluminum oxide (NMA), and lithium titanate (LTO).

[0040] In some embodiments of this application, the raw materials for the positive electrode active material layer further include at least one of a conductive agent and a binder. The conductive agent includes, but is not limited to, conductive graphite (such as KS-6, KS-15, SFG-6, SFG-15, SO, etc.), conductive carbon black (such as Super P, Super S, 350G, acetylene black, Ketjen black, etc.), conductive carbon fiber (such as VGCF, CNT), and graphene. The binder includes, but is not limited to, at least one of polyvinylidene fluoride, polytetrafluoroethylene, carboxymethyl cellulose, styrene-butadiene rubber, polyurethane, polyvinyl alcohol, and polyvinyl butyral.

[0041] In some embodiments of this application, the positive current collector and the negative current collector are each independently selected from at least one of the following metal materials: metal foil (such as aluminum foil, silver foil, tin foil, iron foil, titanium foil, nickel foil, copper foil or alloy foil of the above metals) and metal mesh (such as aluminum mesh, silver mesh, tin mesh, iron mesh, titanium mesh, nickel mesh, copper mesh or alloy mesh of the above metals).

[0042] In some embodiments of this application, the positive current collector is aluminum foil and the negative current collector is copper foil.

[0043] In some embodiments of this application, the positive electrode active material layer comprises 70-99 wt% positive electrode active material, 0.5-6 wt% conductive agent, and 0.5-20 wt% binder.

[0044] In some embodiments of this application, the electrolyte may be at least one of a solid electrolyte or an electrolyte solution.

[0045] In some embodiments of this application, the positive electrode, negative electrode, and separator are formed into a secondary battery by at least one of the following methods, including but not limited to winding and stacking.

[0046] A fourth aspect of this application provides an electrical device that includes the aforementioned secondary battery.

[0047] Electrical equipment refers to any device that can utilize electrical energy and convert it into mechanical energy, thermal energy, light energy, or one or more other forms of energy, such as electric motors, electric heaters, and electric light sources. This includes mobile devices, electric vehicles, electric trains, ships and satellites, and energy storage systems. Mobile devices can be mobile phones, laptops, drones, robot vacuum cleaners, e-cigarettes, etc.; electric vehicles can be pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.

[0048] Compared with the prior art, the embodiments of this application have the following advantages:

[0049] 1) During the preparation of the composite material, self-sacrificing template agents such as polystyrene are used to generate a large number of pores in the primary carbon source, which serves as the carbon skeleton. This solves the problem of severe volume expansion in phosphorus-carbon materials, effectively shortens the electron transport distance, and accelerates electron transfer and Li + / Na + The insertion and extraction of cations in composite materials and their transport between the electrode and electrolyte interfaces.

[0050] 2) Since red phosphorus and a first carbon source are first mixed, and a mixed solid is synthesized by pressurization, more than 50 wt% of red phosphorus can be added during the process. After the mixed solid is pulverized, a second carbon source is coated to form a carbon coating layer. The red phosphorus is then uniformly distributed on the porous carbon framework by condensation. Compared with the low red phosphorus loading in the single condensation method, the energy density of the phosphorus-carbon composite material prepared by the method of this application embodiment is greatly improved.

[0051] 3) This composite material has a higher energy density than hard carbon. Whether used as a lithium-ion or sodium-ion battery anode, its specific capacity is more than four times that of hard carbon, and its initial efficiency can reach over 90%, with a significant cost advantage. Furthermore, as a lithium-ion battery anode, it has a moderate compaction density, and phosphorus has a high lithium intercalation potential. Even under high current charging, the phosphorus-carbon structure remains stable, safe, and reliable. Moreover, the lithium-phosphorus compound has a positive impact on lithium-ion diffusion.

[0052] 4) The outer carbon coating layer can prevent direct contact between phosphorus and electrolyte, effectively isolate the electrolyte from contact with lithium phosphide or sodium phosphide to avoid side reactions; and can improve the conductivity of the material, reduce polarization, and ensure the stability of the electrode structure.

[0053] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Detailed Implementation

[0054] The following will clearly and completely describe the concept and technical effects of this application in conjunction with embodiments, so as to fully understand the purpose, features and effects of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are all within the scope of protection of this application.

[0055] The embodiments of this application are described in detail below. The described embodiments are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0056] In the description of this application, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number, and "approximately" means within the range of ±20%, 10%, 8%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.2%, 0.1%, etc. of the stated number. The use of "first" and "second" is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0057] In the description of this application, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0058] The present application will be described below with reference to specific embodiments.

[0059] Example 1

[0060] This embodiment provides a composite material, including a porous carbon skeleton and a carbon coating layer covering the porous carbon skeleton, wherein nano-red phosphorus is attached to the surface and internal pores of the porous carbon skeleton.

[0061] The preparation method of this composite material is as follows:

[0062] (1) Take 54 kg of red phosphorus (D v 50 (800nm), 30kg single-particle graphite (D) v 50 (7μm) and 10kg of polystyrene were added to the reactor and stirred until homogeneous.

[0063] (2) After the reactor is evacuated, it is heated to 150°C, then nitrogen gas is introduced and pressurized to 4 kPa. It is kept for 4 hours to stabilize the micropores generated in the mixture, and then cooled to room temperature to obtain a mixed solid.

[0064] (3) Crush the mixed solids into D v 50 refers to mixed particles of 10 μm.

[0065] (4) Dissolve 6 kg of phenolic resin in ethanol, then add mixed particles, stir at room temperature for 5 h, then heat to 80 °C to remove solvent, dry and cure at 100 °C for 1 h under nitrogen atmosphere, then heat to 500 °C at a rate of 2 °C / min for 5 h to obtain an intermediate containing a porous carbon skeleton and a carbon coating layer with adsorbed white phosphorus.

[0066] (5) Cool the intermediate to 260°C to convert the white phosphorus adsorbed in the porous carbon skeleton into nano red phosphorus and obtain the composite material.

[0067] The mass fraction of nano-red phosphorus in the porous carbon framework is 54 / (54+30)×100%=64.3%, and the porosity of the porous carbon framework is 60%.

[0068] In this embodiment, 7a 2 b / (10(1-a)2 (×c×d)=7×0.643 2 ×0.8÷(10×(1-0.643) 2 (×7×0.6)=7×0.643 2 ×0.8÷5.35=0.43.

[0069] Example 2

[0070] This embodiment provides a composite material whose preparation method differs from that of Example 1 in that the amount of red phosphorus added is 36 kg, and the mass fraction of nano-red phosphorus in the porous carbon framework is 54.5%.

[0071] In this embodiment, 7a 2 b / (10(1-a) 2 (×c×d)=7×0.545 2 ×0.8÷(10×(1-0.545) 2 (×7×0.6)=7×0.545 2 ×0.8÷8.7=0.19.

[0072] Example 3

[0073] This embodiment provides a composite material whose preparation method differs from that of Example 1 in that the amount of red phosphorus added is 84 kg, and the mass fraction of nano-red phosphorus in the porous carbon framework is 73.7%.

[0074] In this embodiment, 7a 2 b / (10(1-a) 2 (×c×d)=7×0.737 2 ×0.8÷(10×(1-0.737) 2 (×7×0.6)=7×0.737 2 ×0.8÷2.91=1.05.

[0075] Comparative Example 1

[0076] This comparative example provides a composite material whose preparation method differs from that of Example 1 in that the addition of phenolic resin is omitted, and the mixed particles are directly subjected to pyrolysis reaction.

[0077] Comparative Example 2

[0078] This comparative example provides a composite material whose preparation method differs from that of Example 1 in that the addition of polystyrene is omitted.

[0079] The porous carbon framework has a porosity of 20%, 7a 2 b / (10(1-a) 2 (×c×d)=7×0.643 2×0.8÷(10×(1-0.643) 2 (×7×0.2)=7×0.643 2 ×0.8÷1.78=1.3.

[0080] Comparative Example 3

[0081] This comparative example provides a composite material whose preparation method differs from that of Example 1 in that the red phosphorus in the original step (1) is pulverized into mixed particles in step (3) and added by steam condensation, and then mixed and coated with phenolic resin. The red phosphorus mixing reaction process is as follows:

[0082] 54 kg of red phosphorus powder washed with deionized water was sealed in an argon-filled reactor and ground for 2 h. The temperature was then increased to 500 °C at a rate of 5 °C / h and held for 4 h. The mixture was then cooled to 300 °C and held for 20 h to complete the condensation process. After cooling to room temperature, the product was collected, washed with carbon disulfide to remove residual white phosphorus, and dried in a vacuum oven at 60 °C for 12 h.

[0083] Comparative Example 4

[0084] This embodiment provides a composite material whose preparation method differs from that of Example 1 in that red phosphorus is not added in step (1).

[0085] Comparative Example 5

[0086] This embodiment provides a composite material whose preparation method differs from that of Example 1 in that graphite is not added in step (1).

[0087] The composite materials from Examples 1-3 and Comparative Examples 1-5 were used as negative electrode active materials to prepare and assemble batteries. The specific process is as follows:

[0088] 1. Preparation of negative electrode sheet

[0089] The negative electrode active material, conductive agent (SP and CNT mixed in a mass ratio of 9:1), and binder (SBR and PAALi mixed in a mass ratio of 0.5:1.8) are mixed in a mass ratio of 97.7:1.1:1.2 to prepare a negative electrode active material slurry. The slurry is then uniformly coated onto the negative electrode current collector copper foil, and then cold-pressed and slit to obtain a negative electrode sheet.

[0090] 2. Preparation of the positive electrode sheet

[0091] The positive electrode active material NCM523, conductive agent acetylene black, and binder PVDF were mixed at a mass ratio of 97:2:1. NMP solvent was added, and the mixture was stirred under vacuum until homogeneous, yielding a positive electrode active material slurry. This slurry was then uniformly coated onto a positive electrode current collector aluminum foil, air-dried at room temperature, and then transferred to an oven for further drying. Finally, it was cold-pressed and slit to obtain the positive electrode sheet.

[0092] 3. Preparation of electrolyte

[0093] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0094] 4. Selection of diaphragm: Polyethylene film is selected as the diaphragm.

[0095] 5. Preparation of lithium-ion batteries

[0096] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained with a capacity of 5000mAh and a design of 1C = 5000mA.

[0097] The manufactured lithium-ion batteries were subjected to the following tests:

[0098] (1) Capacity retention rate and thickness expansion rate test:

[0099] S1. Discharge the battery at 0.2C to 3V and let it rest for 5 minutes.

[0100] S2. Charge the battery at 0.5C to 4.5V at 25℃, with a cutoff current of 0.05C, and let it rest for 5 minutes.

[0101] S3. Measure the battery's discharge capacity at this point and record it as D. 前 Measure the thickness of the battery at this point and record it as d. 前 .

[0102] S4. Discharge the battery to 3V at 0.2C and let it rest for 5 minutes.

[0103] S5. Charge the battery at 1.5C to 4.5V, with a cutoff current of 0.05C, and let it rest for 5 minutes.

[0104] S6. After repeating steps S1 to S4 300 times, measure the battery's discharge capacity at this point and record it as D.后 Measure the thickness of the battery at this point and record it as d. 后 ;

[0105] 300-cycle capacity retention rate = D 后 / D 前 ×100%;

[0106] Thickness expansion rate after 300 cycles = (d 后 -d 前 ) / d 前 ×100%.

[0107] (2) Gram volume test:

[0108] Assemble the button cell for testing. The positive and negative electrodes and separator of the button cell are the same as those of the aforementioned soft-pack battery. The button cell model is 2025. First, discharge the battery with a constant current to 5mV at a current of 0.1mA, let it stand for 10 minutes, then discharge it with a constant current to 5mV at a current of 0.05mA, let it stand for 10 minutes, and then charge it with a constant current to 2.0V at a current of 0.1mA. Record the charging capacity, and calculate the specific capacity and first efficiency according to the following formula:

[0109] Specific capacity = charging capacity / mass of composite material on negative electrode;

[0110] First-time efficiency = (First discharge capacity / First charge capacity) × 100%.

[0111] The results are shown in Table 1:

[0112] Table 1. Performance test results of the examples and comparative examples

[0113]

[0114] Compared with Example 1 and Comparative Example 1, although the carbon coating layer formed by adding phenolic resin caused a decrease in specific capacity, it could effectively isolate the nano red phosphorus from the electrolyte, avoid side reactions, and significantly improve the first-efficiency and cycle performance.

[0115] Compared with Example 1 and Comparative Example 2, the addition of polystyrene template agent pyrolysis resulted in a large number of pores in the carbon skeleton, which solved the serious volume expansion effect of phosphorus-carbon anode materials and greatly reduced the cycle thickness expansion rate.

[0116] Compared with Example 1 and Comparative Example 3, in the conventional steam condensation method, red phosphorus adheres to the surface after graphite is crushed, resulting in a low loading of red phosphorus and limited improvement in specific capacity.

[0117] Compared with Examples 1-3 and Comparative Example 4, the phosphorus-carbon anode material prepared by this method has little effect on the cycle capacity retention rate and thickness expansion rate compared with the pure graphite system, but the specific capacity is significantly improved.

[0118] Compared with Example 1 and Comparative Example 5, graphite was used as a carrier to act as a container for loading red phosphorus, thereby reducing expansion and playing a framework role for the entire phosphorus-carbon anode material.

[0119] Comparative Examples 1-3 and Comparative Example 2, the condition 0.1 < 7a is met. 2 b / (10(1-a) 2 ×c×d)<1.1 can simultaneously achieve both high capacity and low expansion.

[0120] Example 4

[0121] Referring to the aforementioned specific capacity experiment, the difference lies in using a sodium metal sheet as the positive electrode, a 1 mol / L NaPF6 electrolyte in the electrolyte solution, and identical negative electrode and separator, assembling a sodium ion cladding electrode. Specific capacity measurements showed a result exceeding 1500 mAh / g; initial efficiency measurements showed a result exceeding 90%.

[0122] The present application has been described in detail above with reference to the embodiments. However, the present application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present application. Furthermore, unless otherwise specified, the embodiments and features in the embodiments of the present application can be combined with each other.

Claims

1. A method for preparing composite materials, characterized in that, Includes the following steps: S100: Mix red phosphorus, the first carbon source and the self-sacrificing template agent, pressurize under a protective atmosphere and heat to 100~200 ℃, keep the mixture to generate micro-pores, stabilize and then cool to obtain a mixed solid; S200: The mixed solid is heated to 250~400 ℃ to pulverize it into mixed particles; S300: The mixed particles are mixed with a second carbon source and carbonized at 420~500 °C to obtain an intermediate; S400: Cool the intermediate to 240~280 ℃ to obtain the composite material; The composite material includes: A porous carbon framework in which nano-red phosphorus is attached; A carbon coating layer is applied to the surface of the porous carbon framework; the nano-red phosphorus accounts for more than 54.5% of the porous carbon framework by mass. The self-sacrificing template agent includes at least one of polystyrene, polymethyl methacrylate, and polyetherimide; the first carbon source includes at least one of graphite and hard carbon; the second carbon source includes at least one of phenolic resin, epoxy resin, urea-formaldehyde resin, melamine resin, polybutadiene resin, polydopamine, citric acid, glucose, fructose, sucrose, maltose, dextrin, starch, sorbitol, tartaric acid, ethylenediaminetetraacetic acid, polyethylene glycol, polyvinyl alcohol, polyvinyl butyral, polyacrylic acid, carboxymethyl cellulose, coal tar pitch, and needle tar pitch.

2. The preparation method according to claim 1, characterized in that, The pressure conditions for the pressurization process are 2~6 kPa.

3. A composite material, characterized in that, The composite material is prepared according to the preparation method described in any one of claims 1 to 2.

4. The composite material according to claim 3, characterized in that, The porosity of the porous carbon skeleton is above 40%.

5. The composite material according to claim 3, characterized in that, The composite material satisfies 0.1 < 7a 2 b / (10(1-a) 2 (×c×d)<1.1; where a is the mass percentage of the nano-red phosphorus in the porous carbon framework; b is the average particle size D of the nano-red phosphorus. V 50, in μm; c is the average particle size D of the porous carbon framework. V 50, in μm; d is the porosity of the porous carbon framework.

6. The composite material according to claim 3, characterized in that, The average particle size D of the porous carbon skeleton V 50 represents 2~50 μm, and the average particle size D of the nano-red phosphorus is... V 50 represents 1~1000 nm.

7. A secondary battery, characterized in that, Includes the composite material as described in any one of claims 3 to 6.

8. Electrical equipment, characterized in that, Includes the secondary battery as described in claim 7.

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