A phosphorus-carbon-aluminum fluoride composite material, a preparation method and application thereof, and a lithium ion battery negative electrode

Abstract

The application discloses a phosphorus-carbon-aluminum fluoride composite material, a preparation method and application thereof, and a lithium ion battery negative electrode. The phosphorus-carbon-aluminum fluoride composite material comprises a phosphorus-carbon matrix and aluminum fluoride crystals dispersed in the phosphorus-carbon matrix, stable phosphorus-carbon covalent bonds are formed in the phosphorus-carbon matrix, and the mass ratio of the aluminum fluoride crystals to the phosphorus-carbon matrix is 5-20:80-95. Through mechanical force action of high-energy ball milling, the phosphorus source and the carbon material are promoted to form phosphorus-carbon covalent bonds, and meanwhile, the aluminum fluoride crystals are uniformly dispersed in the phosphorus-carbon matrix. The carbon material improves the conductivity of the material, the phosphorus-carbon bond enhances the interface bonding force and inhibits volume expansion, and the aluminum fluoride optimizes the interface structure, inhibits the dissolution and oxidation of polyphosphorus compounds. The three components synergistically make the material have high conductivity, structural stability and interface stability. The aluminum fluoride as an additive can significantly improve the fast-charging performance and long cycle life of the lithium ion battery.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and in particular to a phosphorus-carbon-aluminum fluoride composite material, its preparation method and application, and a lithium-ion battery anode. Background Technology

[0002] With the rapid development of electric vehicles and large-scale energy storage industries, the demand for high energy density, high-rate fast charging performance, and long cycle life in lithium-ion batteries is becoming increasingly urgent. Phosphorus-based materials (black phosphorus, red phosphorus, purple phosphorus, etc.) have become highly promising anode materials for lithium-ion batteries due to their advantages such as ultra-high theoretical specific capacity (2596 mAh / g), environmental friendliness, and abundant resource reserves. However, phosphorus-based materials have inherent defects: firstly, their electronic conductivity is extremely poor (only 10 mAh / g at room temperature). -14 The high charge transfer resistance (S / cm) limits fast charging performance; secondly, the volume expansion rate during charging and discharging is over 300%, which easily leads to electrode structure collapse and active material shedding, resulting in a sharp decline in cycle stability; thirdly, phosphorus-based materials readily react with the electrolyte to form soluble lithium polyphosphide (Li₂S / cm), resulting in high charge transfer resistance and limited fast charging performance; fourthly, the high volume expansion rate during charging and discharging (over 300%) easily causes electrode structure collapse and active material shedding, leading to a sharp decline in cycle stability; and fifthly, phosphorus-based materials readily react with the electrolyte to form soluble lithium polyphosphide (Li₂S / cm). x Ps), which leads to the loss of active materials and an increase in interfacial impedance, further deteriorating battery performance.

[0003] To address these issues, existing technologies often employ a strategy of combining phosphorus and carbon materials, leveraging the high conductivity and structural support of carbon materials (graphene, carbon nanotubes, etc.) to enhance the conductivity and structural stability of phosphorus-based materials. However, traditional phosphorus-carbon composites still have shortcomings: the chemical affinity between phosphorus and carbon materials is weak, resulting in mostly physical mixing, poor interfacial bonding, and a tendency for interfacial separation during long-term cycling; simultaneously, carbon materials cannot effectively suppress Li-. x The dissolution and oxidation of Ps and the interfacial stability still need to be improved. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a phosphorus-carbon-aluminum fluoride composite material, its preparation method, and its applications. This method utilizes the mechanical force of high-energy ball milling to achieve uniform compounding of the phosphorus source, carbon material, and aluminum fluoride powder, promoting the formation of phosphorus-carbon bonds and the uniform dispersion of aluminum fluoride, thereby significantly improving the material's conductivity, structural stability, and interfacial stability.

[0005] A further technical problem to be solved by the present invention is to provide a lithium-ion battery negative electrode comprising the above-mentioned phosphorus-carbon-aluminum fluoride composite material.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A phosphorus-carbon-aluminum fluoride composite material includes a phosphorus-carbon matrix and aluminum fluoride powder dispersed in the phosphorus-carbon matrix, wherein stable phosphorus-carbon covalent bonds are formed in the phosphorus-carbon matrix, and the mass ratio of aluminum fluoride crystals to phosphorus-carbon matrix is ​​5~20:80~95.

[0008] The mass ratio of phosphorus to carbon in the phosphorus-carbon matrix is ​​(0.6-3):1.

[0009] The particle size of the phosphorus-carbon-fluorinated aluminum composite material is 5-200 micrometers, and the preferred particle size of the phosphorus-carbon-fluorinated aluminum composite material is 5-100 micrometers.

[0010] The preparation method of the above-mentioned phosphorus-carbon-aluminum fluoride composite material includes the following steps:

[0011] (1) Raw material mixing: Weigh phosphorus source, carbon material and aluminum fluoride powder in a mass ratio of (30-60):(20-50):(5-20), and put the above raw materials into a ball mill jar; add ball milling media and control the ball-to-material ratio to be (10-100):1; the oxygen content in the ball mill jar is less than 1 ppm;

[0012] (2) High-energy ball milling: The ball milling jar is installed on a high-energy ball mill for high-energy ball milling treatment. The high-energy ball milling speed is 300-800 r / min and the ball milling time is 12-36 h.

[0013] (3) Post-processing: Place the ball milling product obtained in step (2) in a vacuum drying oven and dry it for 6-12 hours at a temperature of 80-120℃ and a vacuum degree of <1Pa to obtain the phosphorus carbon-fluoride aluminum composite material.

[0014] The phosphorus source and carbon materials in the raw materials need to be pre-dried before being added to the ball mill jar. The pre-drying temperature is 60-100℃, the vacuum degree is <1Pa, and the pre-drying time is 4-8h.

[0015] The particle size of the aluminum fluoride powder in the raw material is 100-500 nm.

[0016] The heating rate of the high-energy ball milling process is 5-10℃ / h, and the temperature inside the ball mill jar is maintained at 25-80℃.

[0017] The high-energy ball milling process employs an intermittent ball milling mode, specifically involving milling for 30-60 minutes followed by a 10-15 minute pause.

[0018] The process of placing the ball-milled product in a vacuum drying oven also includes a step of sieving the ball-milled product, with the standard sieve used for sieving having a mesh size of 200-400.

[0019] The above-mentioned phosphorus-carbon-aluminum fluoride composite material is used in lithium-ion batteries.

[0020] A lithium-ion battery anode is prepared by incorporating an active additive into a negative electrode slurry at a mass fraction of 5-15%, followed by stirring, coating, rolling, and drying. The active additive is the aforementioned phosphorus-carbon-aluminum fluoride composite material.

[0021] The beneficial effects of this invention are as follows:

[0022] (1) Excellent performance: This invention promotes the formation of phosphorus-carbon covalent bonds between the phosphorus source and carbon materials through the mechanical force of high-energy ball milling, while simultaneously ensuring that aluminum fluoride crystals are uniformly dispersed in the phosphorus-carbon matrix. The carbon materials improve the conductivity of the material, the phosphorus-carbon bonds enhance the interfacial bonding force and suppress volume expansion, while the aluminum fluoride optimizes the interfacial structure and suppresses Li. x P s Dissolution and oxidation work synergistically to give the material high conductivity, structural stability, and interfacial stability. As an additive, it can significantly improve the fast-charging performance and long cycle life of lithium-ion batteries.

[0023] (2) Wide range of raw material compatibility: The phosphorus source covers allotropes such as black phosphorus, red phosphorus, and purple phosphorus, and the carbon materials cover graphene, carbon nanotubes, soft carbon, and porous carbon. The raw material ratio can be flexibly selected according to actual performance requirements and cost control, making it highly practical.

[0024] (3) Significant process advantages: This invention uses high-energy ball milling to prepare the product, which does not require high temperature and high pressure, has simple process steps, is controllable, and the intermittent ball milling can avoid phosphorus source oxidation, making it suitable for large-scale industrial production. Compared with traditional roasting and solution methods, the preparation cycle is short, the cost is low, and it is environmentally friendly.

[0025] (4) Broad application prospects: The material prepared by this invention can be used as an additive for the negative electrode of lithium-ion batteries, which is suitable for electric vehicles, large-scale energy storage and other scenarios with high requirements for fast charging performance and cycle life. It can also be extended to energy storage systems such as sodium-ion batteries and potassium-ion batteries, with a wide range of applications. Attached Figure Description

[0026] Figure 1 The elemental distribution diagram of the black phosphorus-graphene-aluminum fluoride composite material prepared in Example 1 is shown below.

[0027] Figure 2 High-resolution transmission electron microscopy image of the black phosphorus-graphene-aluminum fluoride composite material prepared in Example 1;

[0028] Figure 3 XRD patterns of the black phosphorus-graphene-aluminum fluoride composite material prepared in Example 1, the phosphorus-carbon material prepared in Comparative Example 1, and aluminum fluoride.

[0029] Figure 4 The cycle performance diagrams of the composite materials prepared in Example 1 and Comparative Example 1 when used as negative electrodes of lithium-ion batteries are shown.

[0030] Figure 5 The rate performance diagrams are for the composite materials prepared in Example 1 and Comparative Example 1 when used as negative electrodes of lithium-ion batteries.

[0031] Figure 6 X-ray photoelectron spectroscopy of the black phosphorus-graphene-aluminum fluoride composite material prepared in Example 1;

[0032] Figure 7 The cycle performance diagrams of the composite materials prepared in Example 2 and Comparative Example 2 when used as negative electrodes of lithium-ion batteries are shown.

[0033] Figure 8 The cycle performance diagrams of the composite materials prepared in Example 3 and Comparative Example 3 when used as negative electrodes of lithium-ion batteries are shown.

[0034] Figure 9 The graph shows the cycle performance of the composite materials prepared in Example 4 and Comparative Example 4 when used as negative electrodes of lithium-ion batteries.

[0035] Figure 10 The graph shows the cycle performance of the composite materials prepared in Example 5 and Comparative Example 5 when used as the negative electrode of a lithium-ion battery. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0037] This invention uses a high-energy ball milling method to prepare phosphorus-carbon-aluminum fluoride composite materials, specifically including the following steps:

[0038] (1) Raw material pretreatment: The phosphorus source and carbon material are placed in a vacuum drying oven and dried for 4-8 hours at a temperature of 60-100℃ and a vacuum degree of <1Pa to remove moisture and impurities; the aluminum fluoride powder is placed in a planetary ball mill and ground to a particle size of 100-500nm to ensure uniform dispersion in the future; the phosphorus source is at least one of black phosphorus, red phosphorus, and purple phosphorus, which can be used alone or in combination; the carbon material is at least one of graphene, carbon nanotubes, soft carbon, and porous carbon, and a single carbon material or a composite carbon material can be selected according to the conductivity requirements.

[0039] (2) Raw material mixing ratio: Weigh the pretreated phosphorus source, carbon material and aluminum fluoride powder in a mass ratio of (30-60):(20-50):(5-20) and put them into a high-energy ball milling jar; add ball milling media (zirconia balls, stainless steel balls or tungsten carbide balls, ball diameter 2-10mm), and control the ball-to-material ratio to be (10-30):1; introduce inert reaction gas (argon or nitrogen) into the ball milling jar and replace the air in the jar at least 3 times to avoid the phosphorus source being oxidized during the ball milling process.

[0040] (3) High-energy ball milling: The ball milling jar is installed on a high-energy ball mill, and the ball milling speed is set to 200-500 r / min. Intermittent ball milling mode is adopted (ball milling for 30-60 min, pause for 10-15 min), and the ball milling time is 12-36 h. During the ball milling process, the heating rate is controlled at 5-10℃ / h, and the temperature inside the jar is maintained at 25-80℃ to prevent the phosphorus source from oxidizing or the structure from being damaged due to excessive temperature. Through the mechanical impact and shear force of high-energy ball milling, the phosphorus source, carbon material and aluminum fluoride crystals are fully mixed and refined, promoting the formation of PC covalent bonds between phosphorus atoms and carbon atoms, while making the aluminum fluoride crystals uniformly dispersed in the phosphorus-carbon matrix.

[0041] (4) Post-processing: Take out the ball milled product and pass it through a 200-400 mesh standard sieve to remove large particulate impurities that are not completely dispersed; place the sieved product in a vacuum drying oven and dry it for 6-12 hours at a temperature of 80-120℃ and a vacuum degree of <1Pa to remove residual moisture and inert gas adsorbates, and obtain phosphorus carbon-fluoride aluminum composite material.

[0042] In the phosphorus-carbon-aluminum fluoride composite material prepared by the above method, aluminum fluoride crystals are uniformly dispersed in the phosphorus-carbon matrix without obvious agglomeration; stable phosphorus-carbon covalent bonds are formed in the phosphorus-carbon matrix, and the interface is tightly bonded; the particle size of the material is 5-200 micrometers, the mass fraction of aluminum fluoride is 5-20%, and the mass ratio of phosphorus to carbon is (0.6-3):1.

[0043] The application of the above-mentioned phosphorus-carbon-aluminum fluoride composite material in lithium-ion batteries is as follows: the material is used as a negative electrode active additive and is added to the negative electrode slurry (containing negative electrode active material, binder, conductive agent and solvent) at a mass fraction of 5-15%. After stirring evenly, coating, rolling and drying, the negative electrode of lithium-ion battery is prepared. After being assembled into a lithium-ion battery, the fast charging performance, cycle stability and interface stability of the battery can be significantly improved.

[0044] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0045] Example 1

[0046] Under an argon atmosphere, black phosphorus crystal powder, aluminum fluoride powder, and graphene were placed in a ball mill jar, and grinding balls were added simultaneously. The mass ratio of phosphorus powder, aluminum fluoride powder, and graphene was 6:0.5:3.5. The ball milling was performed using a planetary ball mill. Both the ball mill jar and the grinding balls were made of stainless steel, and the diameters of the grinding balls were 5 mm and 10 mm, respectively. The mass ratio of the mixed powder to the grinding balls was 1:10. The mixture was ball-milled at 500 rpm for 24 hours to obtain the phosphorus-carbon-aluminum fluoride composite material.

[0047] A phosphorus-carbon-aluminum fluoride composite material, conductive carbon black, and PVDF binder were mixed with an organic solvent (NMP) in a mass ratio of 7:2:1. The resulting electrode slurry (solid content 20%) was coated onto the surface of a current collector with a thickness of 10 μm and then dried in a vacuum oven at 100°C for 8 hours at a vacuum degree <1 Pa to obtain a phosphorus-based electrode sheet. The areal loading of the electrode active material was 1 mg·cm³. -2 .

[0048] Example 2

[0049] Under an argon atmosphere, black phosphorus crystal powder, aluminum fluoride powder, and artificial graphite were placed in a ball mill jar, and grinding balls were added simultaneously. The mass ratio of phosphorus powder, aluminum fluoride powder, and artificial graphite was 6:0.5:3.5. The ball milling was performed using a planetary ball mill. Both the ball mill jar and the grinding balls were made of stainless steel, and the diameters of the grinding balls were 5 mm and 10 mm, respectively. The mass ratio of the mixed powder to the grinding balls was 1:20. The mixture was ball-milled at 500 rpm for 24 hours to obtain the phosphorus-carbon-aluminum fluoride composite material.

[0050] A phosphorus-carbon-aluminum fluoride composite material, conductive carbon black, and PVDF binder were mixed with an organic solvent (NMP) in a mass ratio of 7:2:1. The resulting electrode slurry (solid content 20%) was coated onto the surface of a current collector with a thickness of 10 μm and then dried in a vacuum oven at 100°C for 8 hours at a vacuum degree <1 Pa to obtain a phosphorus-based electrode sheet. The areal loading of the electrode active material was 1 mg·cm³. -2 .

[0051] Example 3

[0052] Under an argon atmosphere, black phosphorus crystal powder, aluminum fluoride powder, and carbon nanotubes were placed in a ball mill jar, and grinding balls were added simultaneously. The mass ratio of phosphorus powder, aluminum fluoride powder, and carbon nanotubes was 6:0.5:3.5. The ball milling was performed using a planetary ball mill. Both the ball mill jar and the grinding balls were made of stainless steel, and the diameters of the grinding balls were 5 mm and 10 mm, respectively. The mass ratio of the mixed powder to the grinding balls was 1:30. The mixture was ball-milled at 500 rpm for 24 hours to obtain the phosphorus-carbon-aluminum fluoride composite material.

[0053] A phosphorus-carbon-aluminum fluoride composite material, conductive carbon black, and PVDF binder were mixed with an organic solvent (NMP) in a mass ratio of 7:2:1. The resulting electrode slurry (solid content 20%) was coated onto the surface of a current collector with a thickness of 10 μm and then dried in a vacuum oven at 100°C for 8 hours at a vacuum degree <1 Pa to obtain a phosphorus-based electrode sheet. The areal loading of the electrode active material was 1 mg·cm³. -2 .

[0054] Example 4

[0055] Under an argon atmosphere, black phosphorus crystal powder, aluminum fluoride powder, and soft carbon were placed in a ball mill jar, and grinding balls were added simultaneously. The mass ratio of phosphorus powder, aluminum fluoride powder, and soft carbon was 6:0.5:3.5. The ball milling was performed using a planetary ball mill. Both the ball mill jar and the grinding balls were made of stainless steel, with diameters of 5 mm and 10 mm, and the mass ratio of the mixed powder to the grinding balls was 1:10. The mixture was ball-milled at 500 rpm for 24 hours to obtain the phosphorus-carbon-aluminum fluoride composite material.

[0056] A phosphorus-carbon-aluminum fluoride composite material, conductive carbon black, and PVDF binder were mixed with an organic solvent (NMP) in a mass ratio of 7:2:1. The resulting electrode slurry (solid content 20%) was coated onto the surface of a current collector with a thickness of 10 μm and then dried in a vacuum oven at 100°C for 8 hours at a vacuum degree <1 Pa to obtain a phosphorus-based electrode sheet. The areal loading of the electrode active material was 1 mg·cm³. -2 .

[0057] Example 5

[0058] Under an argon atmosphere, black phosphorus crystal powder, aluminum fluoride powder, and porous carbon were placed in a ball mill jar, and grinding balls were added simultaneously. The mass ratio of phosphorus powder, aluminum fluoride powder, and porous carbon was 6:0.5:3.5. The ball milling was performed using a planetary ball mill. Both the ball mill jar and the grinding balls were made of stainless steel, and the diameters of the grinding balls were 5 mm and 10 mm, respectively. The mass ratio of the mixed powder to the grinding balls was 1:10. The mixture was ball-milled at 500 rpm for 24 hours to obtain the phosphorus-carbon-aluminum fluoride composite material.

[0059] A phosphorus-carbon-aluminum fluoride composite material, conductive carbon black, and PVDF binder were mixed with an organic solvent (NMP) in a mass ratio of 7:2:1. The resulting electrode slurry (solid content 20%) was coated onto the surface of a current collector with a thickness of 10 μm and then dried in a vacuum oven at 100°C for 8 hours at a vacuum degree <1 Pa to obtain a phosphorus-based electrode sheet. The areal loading of the electrode active material was 1 mg·cm³. -2 .

[0060] Comparative Example 1

[0061] The difference between this comparative example and Example 1 is that aluminum fluoride powder is not added, and the mass ratio of phosphorus powder to graphene is 6:4.

[0062] Comparative Example 2

[0063] The difference between this comparative example and Example 2 is that aluminum fluoride powder is not added, and the mass ratio of phosphorus powder to artificial graphite is 6:4.

[0064] Comparative Example 3

[0065] The difference between this comparative example and Example 3 is that aluminum fluoride powder is not added, and the mass ratio of phosphorus powder to carbon nanotubes is 6:4.

[0066] Comparative Example 4

[0067] The difference between this comparative example and Example 4 is that aluminum fluoride powder is not added, and the mass ratio of phosphorus powder to soft carbon is 6:4.

[0068] Comparative Example 5

[0069] The difference between this comparative example and Example 5 is that aluminum fluoride powder is not added, and the mass ratio of phosphorus powder to porous carbon is 6:4.

[0070] Structural characterization and performance testing

[0071] Figure 1 This is the elemental distribution diagram of the black phosphorus-graphene-aluminum fluoride composite material prepared in Example 1. Figure 1 It can be seen that in the black phosphorus-graphene-aluminum fluoride composite material prepared by high-energy ball milling, the distribution profiles of the four elements, carbon, phosphorus, fluorine and aluminum, are highly overlapping and uniform overall. This not only confirms the effective composite and tight bonding of each component at the microscale, but also shows that the aluminum fluoride particles are well dispersed on the substrate without obvious agglomeration or phase separation. This reflects that the high-energy ball milling process can effectively achieve uniform mixing of multiple components, laying a good microstructure foundation for the subsequent performance of the material.

[0072] Figure 2 This is a high-resolution transmission electron microscope (TEM) image of the black phosphorus-graphene-aluminum fluoride composite material prepared in Example 1. From... Figure 2 It can be seen that aluminum fluoride crystals are uniformly dispersed in the phosphorus-carbon matrix.

[0073] Figure 3 XRD patterns of the black phosphorus-graphene-aluminum fluoride composite material prepared in Example 1, the phosphorus-carbon material prepared in Comparative Example 1, and aluminum fluoride. From... Figure 3It can be seen that both black phosphorus-graphene@aluminum fluoride (prepared in Example 1) and black phosphorus-graphene (prepared in Comparative Example 1) exhibit a broad diffuse scattering background and no obvious sharp characteristic diffraction peaks, indicating that both samples are amorphous or low-crystallinity structures. The signal intensity of the black phosphorus-graphene@aluminum fluoride sample is generally higher than that of black phosphorus-graphene, reflecting that the introduction of aluminum fluoride may have improved the electron density or scattering ability of the sample. The similar slow decreasing trend of both indicates that neither composite system has formed highly crystalline black phosphorus or other crystalline phases, and both exhibit typical XRD characteristics of amorphous composite materials.

[0074] The electrochemical performance of the electrode sheets prepared in the examples and comparative examples was tested sequentially:

[0075] Using the electrode sheets prepared in the application examples and comparative application examples as negative electrodes, lithium metal sheets as counter and reference electrodes, polypropylene microporous membranes (Celgard 2400) as separators, and 1.0 mol / L LiPF6 solution (a mixture of ethylene carbonate EC, dimethyl carbonate DMC, and diethyl carbonate DEC in a volume ratio of 2:2:1, with 10% fluoroethylene carbonate FEC additive added) as the electrolyte, CR2025 coin cells were assembled in a glove box. Specifically, the electrode sheets, separator, and lithium metal sheets were stacked sequentially into a layered structure, then placed in a battery case, and the electrolyte was added to assemble the CR2025 coin cell. The assembled CR2025 coin cells were then transferred to a Xinwei charge-discharge tester for constant current charge-discharge cycle testing at a current density of 0.5 A·g. -1 The cutoff voltage is set to 0.01~3.0V.

[0076] Figure 4 The graph shows the cycle performance of the composite materials prepared in Example 1 and Comparative Example 1 when used as negative electrodes in lithium-ion batteries. Figure 4 It can be seen that the sample of Example 1 at 1 A·g -1 After 500 cycles, maintain 1527 mA hg -1 The high specific capacity. In stark contrast, the capacity of Comparative Example 1 is only 877 mA hg after 500 cycles. -1 Reversible capacity.

[0077] Figure 5 The graph shows the rate performance of the composite materials prepared in Example 1 and Comparative Example 1 when used as negative electrodes in lithium-ion batteries. Figure 5 It can be seen that the sample of Example 1 showed better performance at current densities of 0.1, 0.2, 0.5, 1.0, 2.0, and 5.0 A·g. -1 The stable capacities at different times were 1848, 1723, 1612, 1541, 1466 and 1323 mA hg, respectively. -1When the current density gradually decreases to 0.1 A·g -1 At that time, the capacity was almost completely recovered. This is because the interface is stable after aluminum fluoride modification, and the electrode has higher electronic conductivity and faster ion diffusion capability. However, the performance of the sample in Comparative Example 1 was lower than that in Example 1.

[0078] Figure 6 The X-ray photoelectron spectroscopy (XPS) of the black phosphorus-graphene-aluminum fluoride composite material prepared in Example 1 shows that the black phosphorus-graphene-aluminum fluoride composite material prepared by high-energy ball milling not only achieved physical mixing among the components, but also underwent significant interfacial chemical interactions: the PC bonds in the C 1s and P 2p spectra prove that black phosphorus and graphene have formed a covalent bond, and the P 2p, O 1s, and Al 2p spectra together reveal that black phosphorus and aluminum fluoride have formed Al-OP bonds through oxygen bridges. At the same time, the Al-F peak retained in the Al 2p spectrum indicates that the main structure of aluminum fluoride has not been destroyed. The formation of these interfacial chemical bonds not only improves the structural stability of the composite material, but also provides key chemical support for its performance optimization.

[0079] Figures 7-10 Samples from Example 2 and Comparative Example 2, Example 3 and Comparative Example 3, Example 4 and Comparative Example 4, and Example 5 and Comparative Example 5 were tested at 1 A·g. -1 The following is a comparison chart of cycles. From Figures 7 to 10 It can be seen that the performance of the samples with added aluminum fluoride is better than that of the samples without added aluminum fluoride.

[0080] As can be seen from the above application examples and comparative examples, the present invention improves the performance of phosphorus-carbon composite materials by introducing aluminum fluoride into them. The core of this invention is that aluminum fluoride can form a dense and stable artificial solid electrolyte interface layer containing lithium fluoride on the material surface, which inhibits electrolyte side reactions and environmental degradation of phosphorus. At the same time, it can constrain the large volume expansion of phosphorus during charging and discharging with its excellent mechanical strength, enhance the stability of carbon skeleton and electrode structure, provide additional ion transport channels, reduce lithium ion migration and charge transfer impedance, and improve electrochemical kinetic characteristics. Through multi-faceted synergistic optimization, the electrochemical performance of the material, such as cycle life and rate capability, is improved.

[0081] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0082] The parts of this invention not described in detail are well-known in the art. The above embodiments are provided merely for the purpose of describing the invention and are not intended to limit the scope of the invention. The scope of the invention is defined by the appended claims. All equivalent substitutions and modifications made without departing from the spirit and principles of the invention should be covered within the scope of the invention.

Claims

1. A phosphorus-carbon-aluminum fluoride composite material, characterized in that, The phosphorus-carbon-aluminum fluoride composite material includes a phosphorus-carbon matrix and aluminum fluoride crystals dispersed in the phosphorus-carbon matrix. Stable phosphorus-carbon covalent bonds are formed in the phosphorus-carbon matrix, and the mass ratio of aluminum fluoride crystals to phosphorus-carbon matrix is ​​5~20:80~95.

2. The phosphorus-carbon-aluminum fluoride composite material according to claim 1, characterized in that, The mass ratio of phosphorus to carbon in the phosphorus-carbon matrix is ​​(0.6-3):

1.

3. The phosphorus-carbon-aluminum fluoride composite material according to claim 1, characterized in that, The particle size of the phosphorus-carbon-fluorinated aluminum composite material is 5-200 micrometers.

4. The method for preparing the phosphorus-carbon-aluminum fluoride composite material according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Raw material mixing: Weigh phosphorus source, carbon material and aluminum fluoride powder in a mass ratio of (30-60):(20-50):(5-20), and put the above raw materials into a ball mill jar; add ball milling media and control the ball-to-material ratio to be (10-100):1; the oxygen content in the ball mill jar is less than 1 ppm; (2) High-energy ball milling: The ball milling jar is installed on a high-energy ball mill for high-energy ball milling treatment. The high-energy ball milling speed is 300-800 r / min and the ball milling time is 12-36 h. (3) Post-processing: Place the ball milling product obtained in step (2) in a vacuum drying oven and dry it for 6-12 hours at a temperature of 80-120℃ and a vacuum degree of <1Pa to obtain the phosphorus carbon-fluoride aluminum composite material.

5. The method for preparing the phosphorus-carbon-aluminum fluoride composite material according to claim 4, characterized in that, The phosphorus source and carbon materials in the raw materials need to be pre-dried before being added to the ball mill jar. The pre-drying temperature is 60-100℃, the vacuum degree is <1Pa, and the pre-drying time is 4-8h. The particle size of the aluminum fluoride powder in the raw material is 100-500 nm.

6. The method for preparing the phosphorus-carbon-aluminum fluoride composite material according to claim 4, characterized in that, The heating rate of the high-energy ball milling process is 5-10℃ / h, and the temperature inside the ball mill jar is maintained at 25-80℃.

7. The method for preparing the phosphorus-carbon-aluminum fluoride composite material according to claim 4, characterized in that, The high-energy ball milling process adopts an intermittent ball milling mode, specifically a ball milling process of 30-60 minutes followed by a pause of 10-15 minutes.

8. The method for preparing the phosphorus-carbon-aluminum fluoride composite material according to claim 4, characterized in that, The process of placing the ball-milled product in a vacuum drying oven also includes a step of sieving the ball-milled product, with the standard sieve used for sieving having a mesh size of 200-400.

9. The application of the phosphorus-carbon-aluminum fluoride composite material according to any one of claims 1 to 3 in lithium-ion batteries.

10. A lithium-ion battery negative electrode, characterized in that, A negative electrode active additive is incorporated into the negative electrode slurry at a mass fraction of 5-15%, and after stirring evenly, coating, rolling and drying, a lithium-ion battery negative electrode is prepared, wherein the negative electrode active additive is the phosphorus-carbon-aluminum fluoride composite material as described in any one of claims 1 to 3.

Images