Fluorine-containing microporous material, fluorine-doped microporous hard carbon coated carbon negative electrode material and lithium ion battery
By synthesizing fluorine-containing microporous materials and fluorine-doped microporous hard carbon-coated carbon anode materials, the problem of increased battery impedance caused by high organic content in the SEI of carbon anode materials was solved, and the performance of high-efficiency lithium-ion batteries was improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HEBEI UNIV OF SCI & TECH
- Filing Date
- 2025-12-30
- Publication Date
- 2026-04-14
AI Technical Summary
Existing carbon anode materials form a solid electrolyte interphase (SEI) film in lithium-ion batteries with a high organic content, which leads to increased battery impedance. Furthermore, common methods for constructing lithium fluoride-rich SEIs face challenges in terms of uniformity and efficiency, affecting battery performance.
Fluorine-containing microporous materials and fluorine-doped microporous hard carbon are used to coat carbon anode materials. Fluorine-containing microporous materials are synthesized through superacid-catalyzed polycondensation reaction, and then mixed with graphite and subjected to high-temperature carbonization treatment to form a uniform LiF coating, thereby controlling the formation of SEI.
Uniform fluoride coating is achieved, which improves electronic conductivity and lithium-ion transport, reduces electrolyte consumption, and increases the reversible capacity and initial coulombic efficiency of lithium-ion batteries. It is suitable for lithium-ion batteries and other secondary battery systems.
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Figure CN121851297A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery anode material technology, and more specifically, relates to a fluorine-containing microporous material and a fluorine-doped microporous hard carbon-coated carbon anode material and a lithium-ion battery. Background Technology
[0002] Carbon anode materials have a long history of application in batteries and received significant attention from the very beginning of lithium-ion battery development. Their excellent performance and safety have surpassed many other materials, making them one of the most widely used electrode materials today. However, carbon anode materials also have some drawbacks. For example, during the operation of a lithium-ion battery, the carbon anode reacts with the electrolyte to form a solid electrolyte interphase (SEI) film. The SEI mainly consists of organic and inorganic components. Organic components possess a certain degree of toughness but have poor ionic conductivity, while inorganic components have relatively high ionic conductivity but are generally rigid and cannot form a continuous film. Ideally, the SEI should be an excellent conductor of lithium ions and an electronic insulator. The formation of the SEI can effectively prevent the co-intercalation of solvent molecules, avoiding the damage caused by co-intercalation to the electrode material, and can greatly improve the cycle performance of the electrode, playing a crucial role in the normal operation of the battery.
[0003] In commercial carbonate-based electrolytes, the SEI formed on the carbon anode contains a relatively high amount of organic components, leading to increased battery impedance and significantly hindering battery performance. Increasing the ionic conductivity of inorganic lithium-containing components (such as LiF, Li₂CO₃) in the SEI can greatly improve performance. Lithium fluoride is widely considered to have high interfacial energy and lithium-ion conductivity, making it an indispensable component of the SEI. Therefore, constructing a lithium fluoride-rich SEI film is crucial for the efficient operation of lithium-ion batteries. Common methods for constructing fluoride-rich SEIs include modifying the electrolyte or modifying the electrode surface, among which: Modified electrolytes can be achieved by changing the electrolyte composition and introducing additives. However, during the electrochemical reaction, the electrolyte composition inevitably forms a non-uniform organic / inorganic layer at the interface, resulting in uneven SEI growth. This leads to excess electrolyte consumption before a sufficient LiF passivation film can be formed during long cycles. Constructing an artificial LiF SEI by directly coating a LiF layer on the negative electrode surface not only requires high-end equipment, but also presents a significant challenge in forming a uniform coating on commonly used porous electrodes. Furthermore, an uneven LiF coating can lead to battery failure during long-term cycling.
[0004] Therefore, designing a simple and effective coating strategy to prepare uniformly fluoride-coated anode materials is crucial for improving battery performance. Thus, there is an urgent need to propose a fluorine-containing microporous material and a fluorine-doped microporous hard carbon-coated carbon anode material, as well as a lithium-ion battery. Summary of the Invention
[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a fluorine-containing microporous material, a fluorine-doped microporous hard carbon-coated carbon anode material, and a lithium-ion battery. The fluorine-doped microporous hard carbon-coated carbon anode material prepared by this invention has a low specific surface area and a large interlayer spacing, and the resulting lithium-ion battery exhibits high reversible capacity and initial coulombic efficiency.
[0006] To achieve the above objectives, the first aspect of the present invention provides a fluorinated microporous material, wherein the fluorinated microporous material is synthesized by superacid-catalyzed polycondensation reaction of a bifunctional aromatic nucleophilic monomer and a bifunctional electrophilic monomer under the conditions of solvent and catalyst. The bifunctional aromatic nucleophilic monomer is 4,4'-dihydroxybiphenyl and / or 4,4'-(hexafluoroisopropylidene)bisphenol (bisphenol AF). The bifunctional electrophilic monomer is 2,2,2-trifluoroacetophenone.
[0007] According to the present invention, preferably, the molar ratio of the bifunctional aromatic nucleophilic monomer and the bifunctional electrophilic monomer is (4-5):(4-6.5).
[0008] According to the present invention, preferably, the solvent is dichloromethane.
[0009] According to the present invention, preferably, the catalyst is trifluoromethanesulfonic acid.
[0010] According to the present invention, preferably, the fluorinated microporous material has a micropore diameter of 0.4-2.0 nm and a weight-average molecular weight of 220-300 kDa. The method and conditions for testing the weight-average molecular weight of the fluorinated microporous material include: determining the weight-average molecular weight (Mw) to be 220-300 kDa by gel permeation chromatography (GPC, THF as mobile phase, 30°C, polystyrene standard).
[0011] According to the present invention, preferably, the preparation method of the fluorine-containing microporous material includes the following steps: (1) Mix the bifunctional aromatic nucleophilic monomer, the bifunctional electrophilic monomer, the solvent and the catalyst, and stir until the mixture becomes viscous to obtain a viscous solution; (2) The viscous solution is mixed with a methanol-water system, filtered and washed to obtain the fluorine-containing microporous material.
[0012] According to the present invention, preferably, in step (1), the stirring temperature is 15-30°C and the stirring time is 3-4 hours.
[0013] The second aspect of the present invention provides a fluorine-doped microporous hard carbon-coated carbon anode material, wherein the anode material is prepared by mixing graphite, N-methylpyrrolidone and the fluorine-containing microporous material evenly, and then subjecting them to vacuum drying and high-temperature carbonization treatment in sequence.
[0014] According to the present invention, preferably, the mass ratio of the fluorine-containing microporous material to graphite is (0.005-0.25):1.
[0015] According to the present invention, preferably, the mixing and stirring time is 1.5-2.5 hours. In the present invention, as a preferred embodiment, the mixing and stirring is carried out by magnetic stirring.
[0016] According to the present invention, preferably, the operating conditions for the high-temperature carbonization treatment include: an inert gas atmosphere; a heating rate of 5-10°C / min from room temperature (15-30°C) to 900°C, a heating rate of 1.5-2.5°C / min from 900°C to 1100°C, and holding at 1100°C for 2-5 hours. In this invention, as a preferred embodiment, the equipment used for the high-temperature carbonization treatment is a tube furnace.
[0017] A third aspect of the present invention provides a lithium-ion battery, wherein the negative electrode of the lithium-ion battery comprises the aforementioned fluorine-doped microporous hard carbon-coated carbon negative electrode material.
[0018] The beneficial effects of the technical solution of the present invention are as follows: The fluorine-doped microporous hard carbon-coated carbon anode material of the present invention, after electrochemical reduction (battery formation process), irreversibly generates LiF on the carbon anode surface after fluoride lithiation, achieving the formation of a carbon anode material with in-situ uniform LiF coating. This strategy of the present invention not only ensures uniform fluoride coating but also regulates the formation of SEI on the carbon anode surface, providing an effective solution for achieving electrode materials and battery systems with long-term cycle stability.
[0019] The microporous structure of the fluorine-containing microporous material of the present invention (which still exists after high-temperature carbonization treatment) can improve the skeleton structure of the negative electrode material to a certain extent, increase the electronic conductivity of the negative electrode material, and reduce the charge transfer impedance of lithium ions on the surface of the negative electrode material. In addition, the microporous structure of the fluorine-containing microporous material of the present invention can also enhance the wetting ability of the electrolyte on the surface of the negative electrode material and improve the transport and transfer impedance of lithium ions inside the negative electrode material.
[0020] The fluorine-doped microporous hard carbon-coated carbon anode material prepared by this invention has a low specific surface area and a large interlayer spacing. This not only reduces the irreversible consumption of electrolyte and improves the coulombic efficiency of the first cycle, but also improves the intercalation kinetics of lithium ions (the fluorine-doped microporous hard carbon-coated carbon anode material of this invention is an anode material with an inner graphite layer and an outer hard carbon layer. The hard carbon layer is formed by high-temperature carbonization of the fluorine-containing microporous material of this invention. During the high-temperature carbonization process, the functional groups of the fluorine-containing microporous material of this invention and fluorine ions will form rich pore structures and defects, which can serve as fast channels for lithium ion transport. Hard carbon itself also has the characteristic of having a larger interlayer spacing, which reduces the resistance to lithium ion transport in the channels). As a result, the lithium-ion battery prepared by this invention has a high reversible capacity and initial coulombic efficiency.
[0021] This invention is applicable not only to lithium-ion batteries, but also to other secondary battery systems that use carbon materials as negative electrodes, such as sodium-ion batteries and potassium-ion batteries. It is highly versatile, simple and convenient, low in cost, and suitable for large-scale preparation.
[0022] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description
[0023] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings.
[0024] Figure 1 A schematic diagram of the process for preparing a fluorine-doped microporous hard carbon-coated carbon anode material according to the present invention is shown.
[0025] Figure 2 The image shows a transmission electron microscope (TEM) image of the fluorine-doped microporous hard carbon-coated carbon anode material prepared in Example 4 of the present invention (the hard carbon layer is formed by high-temperature carbonization treatment of the fluorine-containing microporous material of the present invention).
[0026] Figure 3 The first charge-discharge curves of the lithium-ion battery anode material prepared by fluorine-doped microporous hard carbon coated carbon and unmodified graphite powder as components of the lithium-ion battery anode prepared in Example 4 of the present invention are shown (i.e., the first charge-discharge curves of the lithium-ion batteries of Example 4 and Comparative Example 1).
[0027] Figure 4 The cycling performance diagrams of the fluorine-doped microporous hard carbon-coated carbon anode material prepared in Example 4 of the present invention and unmodified graphite powder as the components of the lithium-ion battery anode are shown (i.e., the cycling performance diagrams of the lithium-ion batteries of Example 4 and Comparative Example 1).
[0028] Figure 5The rate performance diagrams of the fluorine-doped microporous hard carbon-coated carbon anode material prepared in Example 4 of the present invention and unmodified graphite powder as the components of the lithium-ion battery anode are shown (i.e., the rate performance diagrams of the lithium-ion batteries of Example 4 and Comparative Example 1).
[0029] Figure 6 The image shows a SEM image of the microporous structure of a fluorine-containing microporous material after high-temperature carbonization, as provided in Embodiment 2 of the present invention. Detailed Implementation
[0030] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
[0031] In the following embodiments and comparative examples: The graphite powder was purchased from Shijiazhuang Shangtai Technology Co., Ltd. (ST-46).
[0032] Example 1
[0033] This embodiment provides a fluorinated microporous material, the preparation method of which includes: adding 0.9 g (4.8 mmol) of 4,4'-dihydroxybiphenyl, 0.8 g (4.8 mmol) of 2,2,2-trifluoroacetophenone, 7 mL of dichloromethane, and 1 mL of trifluoromethanesulfonic acid to a 20 mL round-bottom flask, stirring at room temperature for about 4 h until the mixture becomes viscous, obtaining a viscous solution. The viscous solution is poured into a methanol-water system, and the precipitated polymer is collected by filtration and thoroughly washed with methanol and water to obtain the fluorinated microporous material, namely white fiber PX-BP. The micropore diameter of the fluorinated microporous material is 0.4-2.0 nm, and the weight-average molecular weight is 300 kDa.
[0034] The reaction equation for preparing the fluorine-containing microporous material PX-BP in this embodiment is as follows: .
[0035] Example 2
[0036] This embodiment provides a fluorinated microporous material, the preparation method of which includes: adding bisphenol AF (4,4'-(hexafluoroisopropylidene)bisphenol, 1.7 g, 4.8 mmol), 2,2,2-trifluoroacetophenone (1.1 g, 6.28 mmol), dichloromethane (5 mL), and trifluoromethanesulfonic acid (4 mL) to a 20 mL round-bottom flask, stirring at room temperature for about 4 hours until the mixture becomes viscous, obtaining a viscous solution. The viscous solution is poured into a methanol-water system, and the precipitated polymer is collected by filtration and thoroughly washed with methanol and water to obtain the fluorinated microporous material, namely white fiber PX-HFP. The micropore diameter of the fluorinated microporous material is 0.4-2.0 nm, and the weight-average molecular weight is 300 kDa.
[0037] The reaction equation for preparing the fluorine-containing microporous material PX-HFP in this embodiment is as follows: .
[0038] Example 3
[0039] This embodiment provides a fluorine-doped microporous hard carbon-coated carbon anode material, the preparation method of which includes the following steps: (1) Add 0.05g of PX-HFP (prepared in Example 2) to 30mL of N-methylpyrrolidone and stir until the solution is clear and transparent. Then weigh 2.5g of graphite powder and pour it into the solution. Continue stirring until no graphite powder floats on the surface of the solution. Then place it in a magnetic stirrer and mix evenly for 2h to obtain the product.
[0040] (2) The product obtained in step (1) is dried under vacuum to obtain a precursor; the precursor is transferred to a tube furnace and subjected to high-temperature carbonization under a nitrogen atmosphere to obtain a fluorine-doped microporous hard carbon-coated carbon anode material; wherein, in the high-temperature carbonization process, the heating rate is 10℃ / min between room temperature and 900℃, the heating rate is 2℃ / min between 900℃ and 1100℃, and the temperature is held at 1100℃ for 4h.
[0041] This embodiment also utilizes the obtained fluorine-doped microporous hard carbon-coated carbon anode material to prepare a lithium-ion battery, including: A negative electrode slurry was prepared by uniformly mixing 80 mg of the fluorine-doped microporous hard carbon-coated carbon anode material prepared in this example, 10 mg of conductive carbon black, 10 mg of PVDF (polyvinylidene fluoride), and an appropriate amount of NMP (N-methylpyrrolidone) solution. The negative electrode slurry was then uniformly coated onto a copper foil, and the copper foil coated with the negative electrode slurry was subsequently dried in a vacuum oven at 60°C for 24 hours to obtain the negative electrode.
[0042] Using lithium metal foil as the working electrode, and 1 M LiPF6 dissolved in a solvent with a volume ratio of EC, DEC, and FEC of 9:9:2, the CR2032 button cell was assembled in an argon-filled glove box (H2O, O2 < 0.1ppm).
[0043] Example 4
[0044] The only difference between this embodiment and embodiment 3 is that: Replace “PX-HFP (prepared in Example 2)” with “PX-BP (prepared in Example 1)”; In the high-temperature carbonization process, the heating rate is 10℃ / min between room temperature and 900℃, and the heating rate is 2℃ / min between 900℃ and 1100℃. The temperature is then maintained at 1100℃ for 2 hours.
[0045] Comparative Example 1
[0046] This comparative example provides a lithium-ion battery, the preparation method of which includes: A negative electrode slurry was prepared by uniformly mixing 80 mg of graphite powder, 10 mg of conductive carbon black, 10 mg of PVDF (polyvinylidene fluoride), and an appropriate amount of NMP (N-methylpyrrolidone) solution. The negative electrode slurry was then uniformly coated onto a copper foil, which was subsequently dried in a vacuum oven at 60°C for 24 hours to obtain the negative electrode.
[0047] Using lithium metal foil as the working electrode, and 1 M LiPF6 dissolved in a solvent with a volume ratio of EC, DEC, and FEC of 9:9:2, the CR2032 button cell was assembled in an argon-filled glove box (H2O, O2 < 0.1ppm).
[0048] Test case
[0049] This test example performs electrochemical measurements on the fluorine-doped microporous hard carbon-coated carbon anode material obtained in the examples. Specifically, the coin cell obtained in Example 4 was left to stand for 12 hours and then placed on the blue battery test channel for electrochemical performance testing. The initial charge-discharge test was conducted in the 0.01-2V range to measure the 0.2C charge-discharge capacity. The long-cycle test measures the charge and discharge capacity at 1C in the 0.01-2V range, with 400 cycles. The rate test measures the charge and discharge capacity from 0.1 to 10C within the 0.01-2V range, with 70 test cycles. Test results are as follows Figure 3-5 As shown. By Figure 3-5It can be seen that: Example 4, namely the fluorine-doped microporous hard carbon coated carbon anode material, has excellent electrochemical performance as a lithium-ion battery anode material. Its first charge specific capacity and initial coulombic efficiency are 519.86 mAh / g and 85.47%, respectively. After 700 cycles at a current density of 1C, the specific capacity can be maintained at 350 mAh / g. At current densities of 0.1C-10C, the specific capacity is better than that of Comparative Example 1, namely the unfluorinated graphite powder, as a lithium-ion battery anode material.
[0050] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.
Claims
1. A fluorine-containing microporous material, characterized in that, The fluorine-containing microporous material is synthesized by superacid-catalyzed polycondensation reaction of bifunctional aromatic nucleophilic monomers and bifunctional electrophilic monomers under solvent and catalyst conditions. The bifunctional aromatic nucleophilic monomer is 4,4'-dihydroxybiphenyl and / or 4,4'-(hexafluoroisopropylidene)bisphenol; The bifunctional electrophilic monomer is 2,2,2-trifluoroacetophenone.
2. The fluorine-containing microporous material according to claim 1, wherein, The molar ratio of the bifunctional aromatic nucleophilic monomer to the bifunctional electrophilic monomer is (4-5):(4-6.5).
3. The fluorine-containing microporous material according to claim 1, wherein, The solvent is dichloromethane; The catalyst is trifluoromethanesulfonic acid.
4. The fluorine-containing microporous material according to claim 1, wherein, The fluorine-containing microporous material has a micropore diameter of 0.4-2.0 nm and a weight-average molecular weight of 220-300 kDa.
5. The fluorine-containing microporous material according to claim 1, wherein, The preparation method of the fluorine-containing microporous material includes the following steps: (1) Mix the bifunctional aromatic nucleophilic monomer, the bifunctional electrophilic monomer, the solvent and the catalyst, and stir until the mixture becomes viscous to obtain a viscous solution; (2) The viscous solution is mixed with a methanol-water system, filtered and washed to obtain the fluorine-containing microporous material.
6. The fluorine-containing microporous material according to claim 5, wherein, In step (1), the stirring temperature is 15-30℃ and the stirring time is 3-4h.
7. A fluorine-doped microporous hard carbon-coated carbon anode material, characterized in that, The negative electrode material is prepared by mixing and stirring graphite, N-methylpyrrolidone and the fluorine-containing microporous material according to any one of claims 1-6 until homogeneous, and then subjecting them to vacuum drying and high-temperature carbonization treatment in sequence.
8. The fluorine-doped microporous hard carbon-coated carbon anode material according to claim 7, wherein, The mass ratio of the fluorine-containing microporous material to graphite is (0.005-0.25):1; The mixing time is 1.5-2.5 hours.
9. The fluorine-doped microporous hard carbon-coated carbon anode material according to claim 7, wherein, The operating conditions for the high-temperature carbonization treatment include: an inert gas atmosphere; a heating rate of 5-10℃ / min from room temperature to 900℃, a heating rate of 1.5-2.5℃ / min from 900℃ to 1100℃, and holding at 1100℃ for 2-5 hours.
10. A lithium-ion battery, characterized in that, The negative electrode of the lithium-ion battery comprises the fluorine-doped microporous hard carbon-coated carbon negative electrode material as described in any one of claims 7-9.