Carbon fluoride halogenated graphene quantum dot composite material, and preparation method and application thereof

Abstract

This invention discloses a fluorinated carbon / halogenated graphene quantum dot composite material, its preparation method, and its applications, belonging to the field of lithium / fluorinated carbon batteries. In this invention, powdered halolated graphene quantum dots and carbon materials are separately dispersed in an organic solvent. A microwave solvothermal method is used, followed by solvent removal to obtain the carbon material / halogenated graphene quantum dot composite material. Then, a gas-phase fluorination method is used to prepare the fluorinated carbon / halogenated graphene quantum dot composite material. The resulting composite material can be used as the positive electrode active material for lithium / fluorinated carbon primary batteries. This invention can improve the capacity performance and discharge capability under high current of lithium fluorinated carbon batteries, while also improving their shelf stability.

Description

Technical Field

[0001] This invention relates to the field of lithium / fluorinated carbon batteries, specifically to a fluorinated carbon halo-based graphene quantum dot composite material, its preparation method, and its application. Background Technology

[0002] In recent years, lithium / carbon fluoride batteries have attracted widespread attention among primary lithium batteries due to their ultra-high theoretical specific energy (2180Wh / kg). However, lithium carbon fluoride batteries suffer from problems such as increased internal resistance, significant voltage drop, severe electrode polarization, and low discharge specific capacity during high-rate discharge. In addition, due to side reactions between the electrolyte and electrode materials, the capacity of lithium carbon fluoride batteries decays during storage, which to some extent limits the widespread application of lithium carbon fluoride batteries.

[0003] The aforementioned problems can be effectively improved by modifying the electrode active material—fluorinated carbon. For example, Chinese patent application CN 114583128 A discloses a controllable preparation method for highly conductive fluorinated carbon, which reduces the fluorine content on the material surface by using a defluorinating agent and utilizes the defects generated during the defluorination process to achieve a high proportion of nitrogen doping. Chinese patent application CN113299912A provides a method for preparing a fluorinated carbon composite positive electrode active material for lithium-fluorinated carbon batteries. This material is prepared by ball milling fluorinated carbon and Ketjen black. Although using the above-mentioned highly conductive fluorinated carbon and fluorinated carbon composite positive electrode active materials in lithium-fluorinated carbon batteries improves the rate performance of the battery to some extent and alleviates the voltage hysteresis phenomenon in the early stage of discharge, the improvement in specific capacity and rate performance is not significant. In addition, it does not improve the shelf stability of lithium-fluorinated carbon batteries. Summary of the Invention

[0004] To address the aforementioned shortcomings, this invention provides a fluorinated carbon halo-based graphene quantum dot composite material, its preparation method, and its application, thereby improving the capacity performance and discharge capability under high current of the corresponding lithium fluorinated carbon battery, while also improving the storage stability of the lithium fluorinated carbon battery.

[0005] In terms of dimensionality, graphene is a two-dimensional material, while graphene quantum dots, with dimensions at the nanometer level in all three dimensions, are quasi-zero-dimensional materials. Graphene quantum dots are artificial nanoscale crystals capable of transporting electrons, composed of one or several layers of graphene, with dimensions less than 100 nm. They are chemically and physically stable, possess a large surface-to-mass ratio, and are easily dispersed in water due to functional groups at their edges. Graphene quantum dots exhibit good electrical and thermal conductivity. Halogenated graphene quantum dots, due to the presence of substituents, are more easily composited with fluorinated carbon materials, while simultaneously possessing the excellent electrical and thermal conductivity and water solubility of graphene quantum dots.

[0006] This invention introduces halo-based graphene quantum dots into fluorinated carbon electrode materials, which can improve the conductivity of the fluorinated carbon materials themselves. At the same time, because halo-based graphene quantum dots have good water solubility, they are more compatible with the microwave hydrothermal method for preparing fluorinated carbon materials of this invention, and have technical effects that ordinary graphene cannot achieve.

[0007] The first aspect of this invention protects a method for preparing a fluorinated carbon / halogenated graphene quantum dot composite material, comprising the following steps:

[0008] (1) Disperse halo-based graphene quantum dots in an organic solvent, add carbon material, and carry out a hydrothermal reaction for 30-90 minutes. After the temperature drops to room temperature, take out the mixture, remove the solvent and dry it to obtain a carbon material / halo-based graphene quantum dot composite material.

[0009] (2) The carbon material / halogenated graphene quantum dot composite material is placed in a reactor and protected by an inert gas.

[0010] (3) Fluorinated carbon / halogenated graphene quantum dot composite material was prepared by gas phase fluorination.

[0011] This invention improves the conductivity of fluorinated carbon materials by introducing highly conductive and easily dispersible halo-based graphene quantum dots; the in-situ composite of fluorinated carbon onto halo-based graphene quantum dots improves both conductivity and high-temperature storage stability.

[0012] Further, the halo-based graphene quantum dots in step (1) include one or more of fluorinated graphene quantum dots, chlorolated graphene quantum dots, brominated graphene quantum dots, and iodinated graphene quantum dots; the mass percentage of the halo-based graphene quantum dots in the organic solvent is 0.5-5 wt%.

[0013] Further, the carbon material in step (1) includes one or more of graphite, carbon nanotubes, carbon fibers, activated carbon, Ketjen black (KB), conductive carbon black (superP), and mesophase carbon microspheres; the mass ratio of the carbon material to halo-based graphene quantum dots is (50-200):1, preferably (100-150):1.

[0014] Further, the organic solvent in step (1) includes one or more of water, ethanol, ethylene glycol, N,N-dimethylpyrrolidone, N,N-dimethylformamide and N,N-dimethylacetamide.

[0015] Furthermore, the method for dispersing halo-based graphene quantum dots in an organic solvent in step (1) includes ultrasonic dispersion; the ultrasonic power is 400-600W, and the ultrasonic time is 2-5h; the hydrothermal reaction adopts microwave-assisted hydrothermal synthesis, the microwave power is 200-350W, and the temperature of microwave-assisted hydrothermal synthesis is 150-250℃.

[0016] Furthermore, the inert gas in step (2) includes one or more of argon, helium, neon and nitrogen.

[0017] Further, in step (3), the gas phase in the gas phase fluorination method includes one or more of fluorine gas, fluorine / argon mixture, fluorine / nitrogen mixture and nitrogen fluoride (NF3); the fluorination temperature of the gas phase fluorination method is 400-600℃, and the fluorination time of the gas phase fluorination method is 4-10h; the fluorine-carbon molar ratio in the obtained fluorinated carbon material is 0.7-1.

[0018] The second aspect of this invention protects the fluorinated carbon / halogenated graphene quantum dot composite material prepared by the above preparation method.

[0019] A third aspect of this invention protects the application of the above-mentioned fluorinated carbon / halogenated graphene quantum dot composite material in electrode active materials.

[0020] Furthermore, its application in lithium / carbon fluoride primary batteries.

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

[0022] (1) In this invention, halogenated graphene quantum dots are the conductive matrix of fluorinated carbon materials. Compared with commonly used graphene materials, halogenated graphene quantum dots are easier to disperse and less prone to agglomeration. They also have excellent conductivity, which can improve the conductivity of fluorinated carbon materials, increase the conductivity of fluorinated carbon materials, and alleviate the voltage hysteresis phenomenon in the discharge of lithium fluorinated carbon batteries.

[0023] (2) The halogen groups in graphene quantum dots are lithium-loving, which improves the high-rate discharge capability of fluorinated carbon materials.

[0024] (3) Halogenated graphene quantum dots are loaded on the surface of fluorinated carbon materials, which reduces the side reactions between fluorinated carbon electrode materials and electrolytes and improves the shelf stability of lithium fluorinated carbon batteries. Detailed Implementation

[0025] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0026] Example 1

[0027] (1) 1g of powdered chloro-based graphene quantum dots were ultrasonically dispersed in 19g of DMF solvent at an ultrasonic power of 500W for 3h. Then, 50g of graphite material was slowly added multiple times while stirring to form a uniform dispersion. The dispersion was transferred to a hydrothermal reactor and sealed before being placed in a microwave-assisted hydrothermal synthesizer. The reaction was carried out at a microwave power of 300W and a temperature of 200℃ for 60 minutes. After the temperature dropped to room temperature, the mixture in the reactor was removed, the solvent was removed, and the mixture was dried to obtain a graphite / halogenated graphene quantum dot composite material.

[0028] (2) Place the composite material obtained in step (1) into a tube furnace and introduce an inert gas at room temperature to remove the air from the tube furnace.

[0029] (3) Fluorine gas was introduced and the reaction was carried out at 500°C for 7 hours to prepare fluorinated graphite / halogenated graphene quantum dot composite material.

[0030] Preparation of positive electrode sheet of fluorinated graphite / halogenated graphene quantum dot composite material: Fluorinated graphite / halogenated graphene quantum dot composite material: polyvinylidene fluoride (PVDF): acetylene black conductive agent = 90:5:5 by mass. The mixture is homogenized with N-methylpyrrolidone (NMP) solvent and stirred for 10 hours to form a modified fluorinated graphite slurry. This slurry is then coated onto a composite aluminum foil current collector, with the fluorinated graphite loading controlled at ~11 mg / cm³. 2 The modified fluorinated graphite positive electrode was obtained by drying at 100℃. This electrode was then vacuum-dried at 85℃ for 24 hours and used as the positive electrode. Lithium / carbon fluoride batteries were assembled using lithium metal strips as the negative electrode, with Celgard 2400 as the separator and a 1 mol / L potassium perchlorate / propylene carbonate / dimethyl carbonate / ethyl methyl carbonate / sulfolane (25:40:20:15V / V) electrolyte. The discharge performance of the batteries at 0.1C and 20C rates was tested, and the corresponding discharge specific capacity and discharge specific energy were obtained. Three prepared lithium / carbon fluoride batteries were placed in a 60℃ oven for 30 days, and their discharge specific capacity at 0.1C rate at room temperature was tested.

[0031] Example 2

[0032] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the mass ratio of graphite to chloro-based graphene quantum dots was 200:1.

[0033] Example 3

[0034] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the mass ratio of graphite to chloro-based graphene quantum dots was 100:1.

[0035] Example 4

[0036] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the mass ratio of graphite to chloro-based graphene quantum dots was 150:1.

[0037] Example 5

[0038] Fluorinated graphene / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the halo-based graphene quantum dots were fluorinated graphene quantum dots.

[0039] Example 6

[0040] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the halo-based graphene quantum dots were iodine-based graphene quantum dots.

[0041] Example 7

[0042] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the microwave power in the microwave hydrothermal method was 200W.

[0043] Example 8

[0044] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the microwave power in the microwave hydrothermal method was 350W.

[0045] Example 9

[0046] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the hydrothermal temperature in the microwave hydrothermal method was 150°C.

[0047] Example 10

[0048] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the hydrothermal temperature in the microwave hydrothermal method was 250°C.

[0049] Example 11

[0050] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the hydrothermal time in the microwave hydrothermal method was 30 min.

[0051] Example 12

[0052] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the hydrothermal time in the microwave hydrothermal method was 90 min.

[0053] Example 13

[0054] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the fluorination temperature was 400°C.

[0055] Example 14

[0056] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the fluorination temperature was 600°C.

[0057] Example 15

[0058] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the fluorination time was 4 hours.

[0059] Example 16

[0060] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the fluorination time was 10 hours.

[0061] Comparative Example 1

[0062] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the mass ratio of graphite to halo-based graphene quantum dots was 40:1.

[0063] Comparative Example 2

[0064] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the mass ratio of graphite to halo-based graphene quantum dots was 201:1.

[0065] Comparative Example 3

[0066] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the microwave power in the microwave solvothermal method was 150W.

[0067] Comparative Example 4

[0068] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the microwave power in the microwave solvothermal method was 400W.

[0069] Comparative Example 5

[0070] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the microwave solvent reaction temperature in the microwave solvothermal method was 100°C.

[0071] Comparative Example 6

[0072] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the microwave solvent reaction temperature in the microwave solvothermal method was 350°C.

[0073] Comparative Example 7

[0074] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the fluorination temperature in the gas-phase fluorination method was 650°C.

[0075] Comparative Example 8

[0076] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the fluorination temperature in the gas-phase fluorination method was 350°C.

[0077] Comparative Example 9

[0078] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the fluorination time in the gas-phase fluorination method was 3 hours.

[0079] Comparative Example 10

[0080] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the fluorination time in the gas-phase fluorination method was 12 hours.

[0081] Comparative Example 11

[0082] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the reaction time in the microwave solvothermal method was 20 min.

[0083] Comparative Example 12

[0084] Fluorinated graphite / halogenated graphene quantum dot composite materials and batteries were prepared using the same method as in Example 1, except that the reaction time in the microwave solvothermal method was 100 min.

[0085] Comparative Example 13

[0086] Fluorinated graphite composite material and battery were prepared using the same method as in Example 1, except that graphene and fluorinated graphite were combined in the above composite material.

[0087] Comparative Example 14

[0088] Fluorinated graphite composite material and battery were prepared using the same method as in Example 1, except that chloro-based graphene was combined with fluorinated graphite in the composite material.

[0089] Table 1

[0090]

[0091]

[0092]

[0093] The specific capacity, capacity retention, specific energy of the corresponding battery cells, and capacity retention (%) of the materials or electrodes prepared in Examples 1-16 and Comparative Examples 1-14 at different rates (0.1C and 20C) are listed in Table 2 below:

[0094] Table 2 Performance of Lithium / Fluorocarbon Battery Cells

[0095]

[0096]

[0097]

[0098] Note: The 20C / 0.1C capacity retention rate (%) in the appendix refers to the discharge specific capacity of a single battery cell at 20C rate / discharge specific capacity of a single battery cell at 0.1C rate * 100%; the capacity retention rate (%) after 30 days of storage at 60℃ refers to the discharge specific capacity of a battery after 30 days of storage at 55℃ and discharge at 0.1C rate, divided by the discharge specific capacity of an unstored battery at the same rate * 100%.

[0099] Analysis of test results: As can be seen from Table 2, in the preparation process of fluorinated carbon / halogenated graphene quantum dot composite materials, the type of halogenated graphene quantum dot material, the mass ratio of carbon material to halogenated graphene quantum dots, microwave power, microwave hydrothermal reaction temperature, hydrothermal reaction time, fluorination temperature, and fluorination reaction time all have a significant impact on the capacity performance, rate performance, and high-temperature storage performance of the final lithium fluorinated carbon battery. Among these, the halo-based graphene quantum dot material is chloro-based graphene quantum dots (as in Examples 1, 5-6, Comparative Examples 13-14), the mass ratio of carbon material to halo-based graphene quantum dots is in the range of (100-150):1 (as in Examples 1-4, Comparative Examples 1-2), the microwave power is in the range of 200-350W (as in Examples 1, 7-8, Comparative Examples 3-4), the hydrothermal reaction temperature is in the range of 150-250℃ (as in Examples 1, 9-10, Comparative Examples 5-6), the reaction time is in the range of 30-90min (as in Examples 1, 11-12, Comparative Examples 11-12), and the fluorination temperature is in the range of 40℃. When the temperature is between 0-600℃ (e.g., Examples 1, 13-14, Comparative Examples 7-8) and the fluorination time is within the range of 4-10h (e.g., Examples 1, 15-16, Comparative Examples 9-10), the corresponding batteries exhibit excellent overall performance, namely, high specific capacity and consequently high specific energy at discharge rates of 0.1C and 20C; a high 20C / 0.1C capacity retention rate (%) indicates that the corresponding batteries have excellent rate performance; furthermore, after being stored at 55℃ for 30 days, the corresponding batteries exhibit a capacity retention rate of over 90%, indicating excellent storage stability. However, when the above conditions are outside the scope of this invention, the corresponding storage performance is poor, with a capacity retention rate of only slightly over 80% (e.g., Comparative Examples 1-12); when graphene or halo-based graphene is used, the corresponding storage performance is even worse, with a capacity retention rate of less than 70%, and similarly, both rate performance and specific energy are poor (e.g., Comparative Examples 13-14).

[0100] In terms of dimensionality, graphene quantum dots, with their nanometer-scale dimensions in all three dimensions, belong to quasi-zero-dimensional materials and possess excellent electrical conductivity. Halogenated graphene quantum dots, due to the presence of substituents, are more easily composited with fluorinated carbon materials, while also exhibiting the excellent conductivity and water solubility of graphene quantum dots. This invention introduces halobased graphene quantum dots into fluorinated carbon electrode materials, which improves the conductivity of the fluorinated carbon material itself. Furthermore, the good water solubility of halobased graphene quantum dots makes them more compatible with the microwave hydrothermal method for preparing fluorinated carbon materials in this invention, achieving technical effects that ordinary graphene cannot achieve.

[0101] In summary, the preparation method of this invention, using halo-based graphene quantum dots as the conductive matrix of fluorinated carbon materials, improves the conductivity of fluorinated carbon materials, increases their electrical conductivity, and alleviates the voltage hysteresis phenomenon during the discharge of lithium fluorinated carbon batteries. The halo groups in the graphene quantum dots have affinity, improving the high-rate discharge capability of fluorinated carbon materials. The halo-based graphene quantum dots loaded on the surface of fluorinated carbon materials reduce side reactions between the fluorinated carbon electrode materials and the electrolyte, thereby improving the shelf stability of lithium fluorinated carbon batteries.

[0102] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for preparing a fluorinated carbon / halogenated graphene quantum dot composite material, characterized in that: Includes the following steps: (1) Disperse halo-based graphene quantum dots in a solvent, add carbon material, and carry out a hydrothermal reaction for 30-90 minutes. After the temperature drops to room temperature, take out the mixture, remove the solvent and dry it to obtain a carbon material / halo-based graphene quantum dot composite material. (2) The carbon material / halogenated graphene quantum dot composite material is placed in a reactor and protected by an inert gas. (3) Fluorinated carbon / halogenated graphene quantum dot composite material was prepared by gas phase fluorination.

2. The preparation method according to claim 1, characterized in that: The halo-based graphene quantum dots in step (1) include one or more of fluorinated graphene quantum dots, chlorolated graphene quantum dots, brominated graphene quantum dots, and iodinated graphene quantum dots; the mass percentage of the halo-based graphene quantum dots in the solvent is 0.5-5 wt%.

3. The preparation method according to claim 1, characterized in that: The carbon material mentioned in step (1) includes one or more of the following: graphite, carbon nanotubes, carbon fibers, activated carbon, conductive carbon black, acetylene black, Ketjen black, and mesophase carbon microspheres; the mass ratio of carbon material to halo-based graphene quantum dots is (50-200):

1.

4. The preparation method according to claim 1, characterized in that: The solvent in step (1) includes one or more of water, ethanol, ethylene glycol, N,N-dimethylpyrrolidone, N,N-dimethylformamide and N,N-dimethylacetamide.

5. The preparation method according to claim 1, characterized in that: The method for dispersing halo-based graphene quantum dots in an organic solvent in step (1) includes ultrasonic dispersion; the ultrasonic power is 400-600W and the ultrasonic time is 2-5h; the hydrothermal reaction adopts microwave-assisted hydrothermal synthesis, the microwave power is 200-350W and the temperature of microwave-assisted hydrothermal synthesis is 150-250℃.

6. The preparation method according to claim 1, characterized in that: The inert gas in step (2) includes one or more of argon, helium, neon and nitrogen.

7. The preparation method according to claim 1, characterized in that: The gas phase in the gas phase fluorination method in step (3) includes one or more of fluorine gas, fluorine / argon mixture, fluorine / nitrogen mixture and nitrogen fluoride; the fluorination temperature of the gas phase fluorination method is 400-600℃, and the fluorination time of the gas phase fluorination method is 4-10h; the fluorine-carbon molar ratio in the obtained fluorinated carbon material is 0.7-1.

8. A fluorinated carbon / halogenated graphene quantum dot composite material prepared by the preparation method according to any one of claims 1-7.

9. The application of the fluorinated carbon / halogenated graphene quantum dot composite material as described in claim 8 in electrode active materials.

10. The application of the fluorinated carbon / halogenated graphene quantum dot composite material according to claim 9 in electrode active materials, characterized in that, Applications in lithium / carbon fluoride primary batteries.

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