Fluorine-doped long-cycle silicon-based negative electrode material, and preparation method and application thereof

Abstract

The application belongs to the technical field of lithium ion battery electrode materials, and particularly relates to a fluorine-doped long-cycle silicon-based negative electrode material and a preparation method and application thereof. The application realizes the doping modification of the fluorine to the silicon-based particles by using a simple and convenient dry mixing and heat treatment method, the introduction of the fluorine can realize the F doping to the silicon-based particles, continuously forms a high-strength solid-state electrolyte interface (SEI) rich in LiF in the expansion and pulverization process of the silicon-based particles, relieves the expansion and inhibits the pulverization, reduces the occurrence of the side reaction, simultaneously improves the mass transfer rate by the bulk doping element, reduces the inhomogeneous lithiation and stress concentration, and comprehensively improves the cycle stability of the silicon-based composite negative electrode material. The preparation method is simple in operation, low in raw material cost and easy to scale, has a good application prospect in the lithium ion battery negative electrode material, and has a high commercial value.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of lithium ion battery electrode materials, and particularly relates to a silicon-based negative electrode material, a preparation method thereof, and a lithium ion battery or lithium ion secondary battery comprising the same, and specifically relates to a fluorine-doped long-cycle silicon-based negative electrode material, a preparation method and application thereof. BACKGROUND

[0002] Lithium ion batteries or lithium ion secondary batteries have been widely used in various electronic products, electric vehicles and large-scale energy storage devices due to their stable performance, mature process and other characteristics, and have been rapidly iterated with the rapid development of related markets. The safety and environmental pollution and other negative problems have been greatly reduced. Compared with traditional batteries, lithium ion secondary batteries have high energy density and good cycle performance, and their market demand is still increasing, and they have become the backbone of the energy storage field.

[0003] Lithium ion secondary batteries mainly provide capacity by positive and negative electrode materials that can cycle lithium intercalation and deintercalation. The preparation of electrodes and the assembly process of batteries are also continuously optimized and improved with the development of technology. At the same time, based on the continuous replacement of various raw materials for lithium ion batteries, developing new materials that are more suitable for market development needs is one of the current research directions.

[0004] Silicon-based materials have become one of the current research hotspots for lithium ion secondary battery negative electrode materials due to their high specific capacity. The theoretical specific capacity of elemental silicon can reach 4200mAh / g, and the theoretical specific capacity of silicon monoxide can also reach 2600mAh / g, which is much higher than the low theoretical specific capacity of 372mAh / g of commercial graphite negative electrode. Therefore, developing commercial silicon-based negative electrode materials can meet the current market demand for high specific energy batteries. However, although silicon-based materials have the advantage of high specific capacity, they also face the problems of severe pulverization, multiple side reactions, poor rate performance, short cycle life, and other defects caused by large volume expansion rate and poor mass transfer ability. In addition, the introduction of oxygen alleviates the volume expansion of silicon monoxide, but worsens its electrical conductivity and first-cycle coulombic efficiency.

[0005] Therefore, the above defects seriously restrict the large-scale commercial application of silicon-based materials. How to alleviate the problems of large volume expansion rate and low mass transfer rate of silicon-based materials to improve the cycle performance of silicon-based materials is a key and difficult point for promoting the industrial application of silicon-based negative electrode materials. SUMMARY

[0006] To address the shortcomings of existing technologies, this invention proposes a fluorine-doped long-cycle silicon-based anode material and its preparation method. By using fluorides to modify the silicon-based material through doping, the doping of fluorine can continuously form a high-strength LiF-rich solid electrolyte interface (SEI) during the expansion and pulverization of silicon-based particles, thus alleviating expansion and inhibiting pulverization, reducing the occurrence of side reactions. At the same time, the fluorine doping inside can also improve the mass transfer rate, reduce uneven lithiation and stress concentration problems, and comprehensively improve the cycle stability of the silicon-based anode.

[0007] Furthermore, the present invention also provides the application of the fluorine-doped long-cycle silicon-based anode material in the preparation of lithium-ion batteries or lithium-ion secondary batteries.

[0008] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0009] A method for preparing a fluorine-doped long-cycle silicon-based anode material involves selecting a suitable fluorine-containing precursor and silicon-based material, and then performing doping modification through grinding and annealing to obtain a fluorine-doped modified silicon-based anode material.

[0010] The preparation method specifically includes the following steps:

[0011] Step 1): A certain amount of fluorine-containing precursor and a certain amount of silicon-based material are mixed and then physically ground to obtain mixture I;

[0012] Step 2): Place mixture I into a tube furnace and heat it at a constant rate to a certain temperature under an inert atmosphere and a certain pressure for high-temperature doping heat treatment. Then, allow it to cool naturally to room temperature (25±5℃) to obtain fluorine-doped long-cycle silicon-based anode material.

[0013] Furthermore, the silicon-based material mentioned in step 1) is pure silicon or silicon suboxide (SiO2). x The powder materials include pure silicon powder with a median particle size D50 of 0.05-10 μm and silicon suboxide (SiO2). x The median particle size D50 of the powder is 0.5-20 μm, and the silicon suboxide (SiO) content is... x The atomic ratio of silicon and oxygen in the silicon oxide is (0.2-5):1, preferably (0.2-0.9):1; or, the silicon suboxide SiO x Silicon accounts for 61% to 64% of the total atomic composition.

[0014] Furthermore, the fluorine-containing precursors mentioned in step 1) include, but are not limited to, one or more of the following: tin tetrafluoride, stannous fluoride, magnesium fluoride, aluminum fluoride, antimony fluoride, lanthanum fluoride, yttrium fluoride, iron fluoride, nickel fluoride, ammonium fluoride, and ammonium fluoroborate.

[0015] Furthermore, in step 1), the molar ratio of the silicon-based material to the fluorine-containing precursor is 200:1 to 1:20.

[0016] Furthermore, the equipment used for physical grinding and mixing in step 1) is a high-speed ball mill, a horizontal ball mill, a stirred ball mill, a VC-type mixing equipment, or a V-type mixing equipment, etc., with a mixing time of 0.02 to 12 hours and a rotation speed of 50 to 2000 rpm.

[0017] Furthermore, the high-temperature doping heat treatment described in step 2) is modified calcination.

[0018] Furthermore, during the high-temperature doping heat treatment described in step 2), the inert atmosphere is formed by one or more mixed gases selected from nitrogen, argon, and helium; the gas flow rate under the inert atmosphere is 0.2–10 L / min, and the ventilation time is 0.2–20 h.

[0019] Furthermore, the high-temperature doping heat treatment described in step 2) is to hold at a temperature of 200℃ to 1000℃ for 0.01 to 5 hours.

[0020] Furthermore, the heating rate during the high-temperature doping heat treatment described in step 2) is 1–10 °C / min.

[0021] More preferably, the high-temperature doping heat treatment procedure in step 2) can also be as follows: first, hold at 200℃~600℃ for 0.01h~3h, then raise the temperature to 600℃~1000℃ and hold for 0.01h~5h, with a heating rate of 1~10℃ / min.

[0022] More preferably, the pressure during the high-temperature doping heat treatment in step 2) is (0.9 to 1.2) atmospheres, preferably atmospheric pressure.

[0023] As another preferred technical solution, the preparation method of the fluorine-doped long-cycle silicon-based anode material of this application includes the following steps:

[0024] Step (1): Mix a certain amount of fluorine-containing precursor and a certain amount of silicon-based material and then perform physical grinding to obtain mixture II;

[0025] Step (2): Mix the mixture II from step (1) with a certain amount of carbon-containing precursor and then perform physical grinding to obtain mixture III;

[0026] Step (3): Place mixture III into a tube furnace, and heat it at a constant rate to a certain temperature under an inert atmosphere and a certain pressure to perform high-temperature doping heat treatment. Then, let it cool naturally to room temperature (25±5℃) to obtain fluorine-doped long-cycle silicon-based anode material.

[0027] Furthermore, the silicon-based material mentioned in step (1) is pure silicon or silicon suboxide (SiO2). x The powder materials include pure silicon powder with a median particle size D50 of 0.05-10 μm and silicon suboxide (SiO2). x The median particle size D50 of the powder is 0.5-20 μm, and the silicon suboxide (SiO) content is... x The atomic ratio of silicon and oxygen in the silicon oxide is (0.2-5):1, preferably (0.2-0.9):1; or, the silicon suboxide SiO x Silicon accounts for 61% to 64% of the total atomic composition.

[0028] Furthermore, the fluorine-containing precursors mentioned in step (1) include, but are not limited to, one or more of the following: tin tetrafluoride, tin fluoride, magnesium fluoride, aluminum fluoride, antimony fluoride, lanthanum fluoride, yttrium fluoride, iron fluoride, nickel fluoride, ammonium fluoride, and ammonium fluoroborate.

[0029] Furthermore, the molar ratio of the silicon-based material and the fluorine-containing precursor in step (1) is 200:1 to 1:20.

[0030] Furthermore, the equipment used for physical grinding and mixing in steps (1) and (2) is a high-speed ball mill, a horizontal ball mill, a stirred ball mill, a VC type mixing equipment, or a V type mixing equipment, etc., with a mixing time of 0.02 to 12 hours and a rotation speed of 50 to 2000 rpm.

[0031] Furthermore, the carbon-containing precursors mentioned in step (2) include, but are not limited to, one or more of the following: asphalt (coal-based mesophase asphalt, coal tar pitch, petroleum pitch, etc.), biomass and its derivatives (cellulose, lignin, glucose, starch, chitosan, sucrose, humic acid, etc.), and chemical materials (phenolic resin, urea, citric acid, etc.).

[0032] Furthermore, in step (2), the mass ratio of the carbon-containing precursor to the silicon-based material is (0.01-5):1.

[0033] Furthermore, the high-temperature doping heat treatment described in step (3) is modified calcination.

[0034] Furthermore, during the high-temperature doping heat treatment described in step (3), the inert atmosphere is formed by one or more mixed gases selected from nitrogen, argon, and helium; the gas flow rate under the inert atmosphere is 0.2 to 10 L / min, and the ventilation time is 0.2 to 20 h.

[0035] Furthermore, the high-temperature doping heat treatment in step (3) is to keep the temperature at 200℃~1000℃ for 0.01~5h.

[0036] Furthermore, the heating rate during the high-temperature doping heat treatment in step (3) is 1 to 10 °C / min.

[0037] More preferably, the high-temperature doping heat treatment procedure in step (3) can also be as follows: first, hold at 200℃~600℃ for 0.01h~3h, then raise the temperature to 600℃~1000℃ and hold for 0.01h~5h, with a heating rate of 1~10℃ / min.

[0038] More preferably, the pressure during the high-temperature doping heat treatment in step 2) is (0.9 to 1.2) atmospheres, preferably atmospheric pressure.

[0039] Furthermore, the present invention also provides a fluorine-doped long-cycle silicon-based anode material prepared by the above method. The anode material has a morphology similar to that of the silicon-based material precursor. Fluorine is uniformly doped inside the silicon-based particles. At the same time, there may be some other elements in the precursor that are doped in the bulk phase and loaded on the surface of the silicon-based particles, forming a synergistic effect with the fluorine doping.

[0040] Furthermore, based on a general inventive concept, the present invention also provides the application of the fluorine-doped long-cycle silicon-based anode material in the preparation of lithium-ion batteries or lithium-ion secondary batteries.

[0041] Furthermore, based on a general inventive concept, the present invention also provides a method for preparing lithium-ion batteries or lithium-ion secondary batteries using the aforementioned fluorine-doped long-cycle silicon-based anode material, comprising the following steps:

[0042] a) Preparation of mixed powder: A certain amount of active material, binder, conductive agent and single-walled carbon nanotubes are placed in a container to obtain mixed powder;

[0043] b) Preparation of the mixed slurry: Then, solvent is added to the mixed powder in step a), and ultrasonically dispersed at a power of 80-100W for 8-12 minutes. Polytetrafluoroethylene magnets are placed in a container and stirred at a speed of 300-400r / min for 8-12 hours to make the fluorine-doped long-cycle silicon-based anode material, binder, conductive agent and single-walled carbon nanotubes dispersed evenly to obtain the mixed slurry;

[0044] c) Button cell assembly: The mixed slurry from step b) is coated onto copper foil (current collector) and dried at 60-80°C for 8-12 hours. Then, it is made into a button cell electrode disc with a diameter of 12 mm. The electrode disc is then used as the working electrode and the lithium metal sheet is used as the counter electrode. The electrode disc, lithium metal sheet, separator, and electrolyte are assembled into a button cell. The battery model is a CR2032 type button cell.

[0045] Specifically, in step a), the active material is a fluorine-doped silicon-based anode material, or a composite anode material formed by fluorine-doped silicon-based material and graphite, wherein the mass ratio of fluorine-doped silicon-based material to graphite in the fluorine-doped silicon-based material / graphite composite anode material is 1:(1-10).

[0046] Specifically, the conductive agent in step a) is carbon black (Super-P) or acetylene black.

[0047] The binder in step a) is one or more of carboxymethyl cellulose, sodium alginate, ammonium alginate, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid (PPA), lithium-ionized polyacrylic acid (lithium-ionized PPA), styrene-butadiene rubber, and polystyrene-butadiene copolymer.

[0048] More preferably, the adhesive is a mixture of carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) in a mass ratio of 1:(1-2), preferably 1:1.

[0049] Specifically, the solvent is selected from deionized water, ethanol, and NMP.

[0050] Specifically, the mass of the solvent is 2 to 12 times the mass of the mixed powder.

[0051] Specifically, in the mixed slurry obtained in step b), the weight ratio of active material, conductive agent, binder and single-walled carbon nanotubes is (80-95):(1-10):(3-10):(0.2-2).

[0052] Specifically, in step b), the loading of the mixed slurry on the prepared electrode disc is 1–10 mg / cm³. 2 .

[0053] Specifically, in step c), the separator type is a polypropylene separator Celgard2400, and the main component of the electrolyte used in the battery is lithium salt (lithium hexafluorophosphate); preferably, the electrolyte is 1M LiPF6 / EC+DMC (V / V = 1:1) with 5% fluoroethylene carbonate FEC added.

[0054] Furthermore, based on a general inventive concept, the present invention also provides a lithium-ion battery or lithium-ion secondary battery prepared by the above method.

[0055] Compared with the prior art, the advantages of the present invention are:

[0056] 1. This invention provides a method for preparing fluorine-doped long-cycle silicon-based anode materials that is easy to operate, uses inexpensive raw materials, and is easy to scale up, and has advantages such as high commercial value and ease of large-scale production.

[0057] 2. The silicon-based composite anode material prepared by the method described in this invention exhibits significant fluorine doping characteristics, enabling it to form a self-healing, high-strength solid electrolyte interface during cycling, ensuring excellent cycle stability. The partially fluorinated precursor also exhibits dual-element doping characteristics, combining solid phase doping and surface nanocluster loading, effectively improving the mass transfer rate of the material and reducing stress concentration, thereby significantly extending the cycle life of the material. This makes it show broad application prospects in the field of lithium-ion battery anode materials. Attached Figure Description

[0058] Figure 1 Fluorine-doped long-cycle SiO2 prepared in Example 1 x SEM structure of the composite anode material;

[0059] Figure 2 The graphs show the cycling performance of Examples 1-2 and Comparative Examples 1-2 of the present invention at 1 A / g.

[0060] Figure 3 The graph shows the cycling performance of Example 3 and Comparative Example 3 of the present invention at 1A / g. Detailed Implementation

[0061] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0062] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are conventional methods; unless otherwise specified, the reagents, raw materials, etc. used in the following examples are all commercially available products.

[0063] The micron-sized Si and micron-sized silicon suboxide SiO used in the following examples and comparative examples x All are in powder form and produced by Shanghai Xiangtian Nanomaterials Co., Ltd. The micron-sized Si is designated XT-SI-06, with a median particle size D50 of 5 μm; the micron-sized SiO... x The product number XT-SIO-5U has a median particle size D50 of 5μm and a silicon-oxygen atomic ratio of 6:4.

[0064] Stannous fluoride powder (item number T195033-100g) was purchased from Aladdin Biochemical Technology Co., Ltd. The argon gas used in the following examples and comparative examples had a purity of 99.99%.

[0065] Example 1

[0066] Example 1 provides a method for preparing a fluorine-doped long-cycle silicon-based anode material, the specific steps of which are as follows:

[0067] Step 1: Apply micron-sized silicon suboxide (SiO2) x The powder and stannous fluoride powder were mixed at a molar ratio of 100:1 and ground and mixed using an MSK-PCV-300 planetary vacuum centrifugal mixer from Kejing Company at a grinding speed of 800 rpm for half an hour to obtain mixture A.

[0068] Step 2: Place mixture A into a tube furnace, purge the air, and introduce high-purity argon gas at a flow rate of 0.8 L / min. In an atmospheric pressure argon atmosphere, heat the mixture at a rate of 5 °C / min until it reaches 600 °C. Hold the temperature at 600 °C for 2 hours for atmospheric pressure calcination and doping. Then allow it to cool naturally to room temperature (25 ± 5 °C) to obtain fluorine-doped long-cycle SiO₂. x Base anode material I.

[0069] Example 2

[0070] Example 2 provides a method for preparing a fluorine-doped long-cycle silicon-based anode material, the specific steps of which are as follows:

[0071] Step 1: Mix mixture A from Example 1 with coal-based mesophase pitch (Shandong Keneng New Carbon Materials Technology Co., Ltd., ash content <350ppm, coking value ≥90%, mesophase content ≥95%). The mass ratio of mixture A to coal-based mesophase pitch is 8:2. The mixture is ball-milled using an MSK-SFM-14-IVS rolling ball mill from Kejing Company. The ball milling speed is 300rpm and the ball milling time is 10h to obtain mixture B.

[0072] Step 2: Place mixture B into a tube furnace, purge the air, and introduce high-purity argon gas at a flow rate of 0.8 L / min. In an atmospheric argon atmosphere, heat the mixture at a rate of 5 °C / min until it reaches 310 °C. Hold this temperature for 2 hours to soften the asphalt. Then, continue heating at a rate of 5 °C / min to 900 °C and hold for 2 hours for carbonization and coating. Finally, allow it to cool naturally to room temperature (25 ± 5 °C) to obtain modified fluorine-doped long-cycle SiO₂. x Base anode material II.

[0073] Example 3

[0074] Example 3 provides a method for preparing a fluorine-doped long-cycle silicon-based anode material, the specific steps of which are as follows:

[0075] Step 1: Mix micron-sized silicon powder and tin fluoride powder at a molar ratio of 50:1. Grind and mix the powder using an MSK-PCV-300 planetary vacuum centrifugal mixer from Kejing Company at a grinding speed of 800 rpm for half an hour to obtain mixture C.

[0076] Step 2: Place mixture C into a tube furnace, remove the air, and introduce high-purity argon gas at a flow rate of 0.8 L / min. In an atmospheric argon atmosphere, heat the mixture at a rate of 5 °C / min until it reaches 900 °C. Hold the temperature for 2 hours for atmospheric calcination and doping, and then allow it to cool naturally to room temperature (25 ± 5 °C) to obtain modified fluorine-doped long-cycle Si-based anode material III.

[0077] The morphology and particle size of the product from Example 1 were observed using scanning electron microscopy. The obtained SEM images are shown below. Figure 1 As shown, micron-sized silica suboxide particles and a small amount of debris can be seen in the sample, while the surface remains intact.

[0078] Comparative Example 1

[0079] Raw, untreated micron-sized silicon suboxide (SiO2) x The powder is used directly as the negative electrode material.

[0080] Comparative Example 2

[0081] Original micron-sized silicon suboxide SiO x The powder was placed in a tube furnace, air was removed, and high-purity argon gas was introduced at a flow rate of 0.8 L / min. Under atmospheric pressure and argon atmosphere, the temperature was increased at a rate of 5 °C / min until it reached 600 °C. This temperature was then held for 2 hours for atmospheric pressure calcination, followed by natural cooling to room temperature (25 ± 5 °C) to obtain heat-treated SiO₂. x Material IV.

[0082] Comparative Example 3

[0083] Raw, unprocessed micron-sized silicon powder is used directly as the negative electrode material.

[0084] Performance testing

[0085] The products prepared in Examples 1-3 and Comparative Examples 1-3 were assembled into batteries and their electrochemical performance was tested (the test methods are referenced in Wang, Haolin, et al. "What Is the Real Origin of Single-Walled Carbon Nanotubes for the Performance Enhancement of Si-Based Anodes?" Journal of the American Chemical Society 2024, 146(25), 17041-17053). The specific methods are as follows:

[0086] a) Preparation of the mixed powder: The active material (the product prepared in Examples 1, 2, 3 or Comparative Examples 1, 2, 3), binder CMC:SBR (the mass ratio of CMC to SBR is 1:1, CMC model MAC500LC, SBR model JSR TRD104A, both purchased from Shenzhen Kejing Zhida Technology Co., Ltd.), carbon black Super P (carbon-based conductive agent, purchased from Shenzhen Kejing Zhida Technology Co., Ltd., grade CAS1333-86-4), and single-walled carbon nanotubes (purchased from Dongguan Kelude New Energy Technology Co., Ltd., item number MA-EN-CO-0010) were mixed in a mass ratio of 90:5:4:1 to obtain the mixed powder;

[0087] b) Preparation of the mixed slurry: Then, the mixed powder from step a) is added to the solvent (deionized water), placed in a mixing container and mixed evenly. The mass of the solvent is 2.5 times the mass of the mixed powder. Then, a polytetrafluoroethylene magnet is placed in the mixing container and stirred at a speed of 400 r / min for 10 h to disperse the active material, binder CMC+SBR, carbon black Super-P, and single-walled carbon nanotubes evenly, thus obtaining the mixed slurry.

[0088] c) Button cell assembly and performance testing: The mixed slurry from step b) was coated onto copper foil (current collector) and vacuum dried at 80°C for 12 hours to obtain a loading of 1.5 mg / cm³. 2 The negative electrode sheet is then prepared; and then a slicer is used to make the prepared negative electrode sheet into button electrode discs with a diameter of 12mm.

[0089] Using the CR2032 coin cell model, with a lithium metal sheet as the counter electrode, a Celgard2400 separator, and an electrolyte (Suzhou Duoduo Chemical Technology Co., Ltd., product number LB-007) of 1M LiPF6 / EC+DMC (V / V = 1:1) with 5% fluoroethylene carbonate FEC added, the prepared negative electrode disc, lithium metal sheet (as counter electrode), separator, and electrolyte were assembled into a coin cell.

[0090] Cyclic performance testing was conducted under the following conditions: the electrodes were activated by cycling 3 times at a current density of 0.1 A / g, and then constant current charge-discharge cycle testing was performed at a high current density of 1 A / g, with a charge-discharge voltage range of 0.01 to 2 V.

[0091] Following the assembly and testing methods described above, the cycling performance of the fluorine-doped long-cycle silicon-based anode materials prepared in Examples 1-3 of this invention and the cycling performance of Comparative Examples 1-3 were tested according to the same assembly and testing methods. The resulting performance comparison chart is shown below. Figure 2 , 3 As shown.

[0092] from Figure 2 , 3 As can be seen from the above, the fluorine-doped long-cycle SiO2 obtained in Example 1... x The initial efficiency of base anode material I is 80%, and the capacity retention after 300 cycles at 1 A / g is 83.8% (1126.3 mAh / g); the fluorine-doped long-cycle SiO2 obtained in Example 2... x The primary anode material II exhibits an initial efficiency of 84% and a capacity retention of 90.4% (1130 mAh / g) after 300 cycles at 1 A / g, while the comparative material shows a significant performance degradation. Figure 3 In the performance comparison between the fluorine-doped long-cycle Si-based anode material III (Example 3) and the original micron-sized silicon (Comparative Example 3), it can be seen that Example 3 also shows a relatively slow performance decline, with a capacity retention of 43.4% after 100 cycles, which is much higher than the 20.5% of Comparative Example 3. The above data indicate that the doping modification of silicon-based anodes such as silicon, silicon sub-silicon, and silicon-carbon using fluorine-containing precursors can effectively improve their cycle performance.

[0093] In summary, this invention modifies silicon-based materials by fluorine doping with fluorine-containing precursors. The doping of fluorine can continuously form a high-strength LiF-rich solid electrolyte interface (SEI) during the expansion and pulverization of silicon-based particles, thus alleviating expansion and inhibiting pulverization, reducing the occurrence of side reactions. At the same time, the fluorine and other elements doped into the silicon-based materials can further improve the mass transfer rate of the bulk phase of the silicon-based materials, reduce the problems of uneven lithiation and stress concentration, and comprehensively improve the cycle stability of silicon-based anodes.

[0094] The foregoing has shown and described the basic principles and main features of the present invention, as well as its advantages. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A fluorine-doped long-cycle silicon-based anode material, characterized in that, It is prepared through the following steps: Step 1): A certain amount of fluorine-containing precursor and a certain amount of silicon-based material are mixed and then physically ground to obtain mixture I; Step 2): Mixture I is heated to a certain temperature under an inert atmosphere and a certain pressure to perform high-temperature doping heat treatment, and then naturally cooled to room temperature to obtain fluorine-doped long-cycle silicon-based anode material. Alternatively, it can be prepared by the following steps: Step 1): A certain amount of fluorine-containing precursor and a certain amount of silicon-based material are mixed and then physically ground to obtain mixture II; Step 2): Mix mixture II from step 1) with a certain amount of carbon-containing precursor and then perform physical grinding to obtain mixture III; Mixture III is heated to a certain temperature under an inert atmosphere and a certain pressure to perform high-temperature doping heat treatment, and then naturally cooled to room temperature to obtain fluorine-doped long-cycle silicon-based anode material. The silicon-based material mentioned in step 1) is a powder material of pure silicon or silicon suboxide, wherein the median particle size D50 of the pure silicon powder is 0.05-10 μm, the median particle size D50 of the silicon suboxide powder is 0.5-20 μm, and the atomic percentage of silicon in the silicon suboxide is 61%~64%. The fluorine-containing precursor mentioned in step 1) is stannous fluoride; Step 1) The molar ratio of the silicon-based material to the fluorine-containing precursor is 200:1 to 1:20; The carbon-containing precursor mentioned in step 2) is coal-based mesophase pitch; In step 2), the mass ratio of the carbon-containing precursor to the silicon-based material is (0.01–5):

1. The high-temperature doping heat treatment mentioned in step 2) is calcination; During the high-temperature doping heat treatment described in step 2), the inert atmosphere is formed by one or more mixed gases selected from nitrogen, argon, and helium; the gas flow rate under the inert atmosphere is 0.2–10 L / min, and the ventilation time is 0.2–20 h. The high-temperature doping heat treatment described in step 2) is to keep the temperature at 200℃~1000℃ for 2 hours.

2. The fluorine-doped long-cycle silicon-based anode material as described in claim 1, characterized in that, The procedure for the high-temperature doping heat treatment in step 2) is as follows: first, hold at 200℃~600℃ for 0.01 h~3 h, then raise the temperature to 600℃~1000℃ and hold for 0.01 h~5 h, with a heating rate of 1~10℃ / min.

3. The application of the fluorine-doped long-cycle silicon-based anode material according to claim 1 in the preparation of lithium-ion batteries or lithium-ion secondary batteries, characterized in that, When applying, the following steps are included: a) Preparation of mixed powder: A certain amount of active material, binder, conductive agent and single-walled carbon nanotubes are placed in a container to obtain mixed powder; b) Preparation of mixed slurry: Then, solvent is added to the mixed powder in step a), and ultrasonically dispersed at a power of 80~100 W for 8~12 min. Polytetrafluoroethylene magnets are placed in a container and stirred at a speed of 300~400 r / min for 8~12 h to make the active material, binder, conductive agent and single-walled carbon nanotubes dispersed evenly to obtain mixed slurry; c) Button cell assembly: The mixed slurry from step b) is coated onto copper foil and dried at 60~80℃ for 8~12h. Then it is made into a button cell electrode disc with a diameter of 12 mm. Then, the prepared electrode disc is used as the working electrode and the lithium metal sheet is used as the counter electrode. The prepared electrode disc, lithium metal sheet, separator and electrolyte are assembled into a button cell. The battery model is a CR2032 type button cell. In step a), the active material is a fluorine-doped silicon-based anode material; In step a), the conductive agent is either carbon black Super-P or acetylene black; The binder in step a) is one or more of carboxymethyl cellulose, sodium alginate, ammonium alginate, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, lithium-ionized polyacrylic acid, styrene-butadiene rubber, and polystyrene-butadiene copolymer.

4. The application as described in claim 3, characterized in that, The adhesive is a mixture of carboxymethyl cellulose and styrene-butadiene rubber in a mass ratio of 1:(1~2). The solvent is selected from deionized water, ethanol, and NMP; The mass of the solvent is 2 to 12 times the mass of the mixed powder.

5. The application as described in claim 3, characterized in that, In the mixed slurry obtained in step b), the weight ratio of active material, conductive agent, binder and single-walled carbon nanotubes is (80-95): (1-10): (3-10): (0.2-2).

6. The application as described in claim 3, characterized in that, In step b), the loading of the mixed slurry on the prepared electrode disc is 1~10 mg / cm². 2 .

7. The application as described in claim 3, characterized in that, In step c), the separator type is a polypropylene separator Celgard2400, and the electrolyte used in the battery is 1M LiPF6 / EC+DMC with 5wt% added fluoroethylene carbonate FEC, wherein the volume ratio of EC to DMC is 1:1.

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