Carbon fluoride material, method for preparing the same, and use thereof

Abstract

The application discloses a kind of carbon fluoride material and its preparation method and application, belong to lithium / carbon fluoride battery technical field.The application is by carbon material into fixed bed reactor, after vacuumizing, heated to 200~1000 DEG C, inert gas is passed into, after keeping the pressure of reaction system stable, then inert gas containing halogenated reagent is passed into and carries out halogenation reaction, obtains halogenated carbon, continuously passes into inert gas containing fluorinated reagent, under 100~1000 DEG C, the product obtained is soaked by lye, deionized water is cleaned, after drying, obtains carbon fluoride material.The application is first by halogenation reaction, so that halogen atom is located between carbon layer, interval is larger, is conducive to the fluorination reaction of subsequent, also makes the heterogeneity of each place of carbon reduce, avoids invalid structure caused by excessive fluorination of edge carbon, and the specific capacity of prepared carbon fluoride is higher, and the wider interval of carbon material can make electrolyte fully infiltrate, guarantees the power characteristics of battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium / fluorinated carbon battery technology, specifically relating to a fluorinated carbon material, its preparation method, and its application. Background Technology

[0002] Primary batteries have long lifespan, high energy density, and high operating voltage. Even with the widespread use of lithium-ion secondary battery technology today, they still have broad application prospects. In particular, lithium / carbon fluoride batteries with higher energy density have attracted much attention and are widely used in aerospace, automotive, smart instrumentation and other fields.

[0003] To obtain lithium / carbon fluoride batteries with high energy density, researchers have tried to increase the specific capacity of carbon fluoride while reducing the weight of inactive materials, but technical bottlenecks still exist.

[0004] Fluorination mainly occurs through high-temperature and low-temperature methods. In high-temperature fluorination, carbon materials are mixed with fluorine-containing gases (such as F2 / HF mixtures) or other fluorine sources and undergo a fluorination reaction at 300℃–650℃. However, the C and C bonds are predominantly sp3 hybridized, while the CF bonds have high covalent bond energies and poor electrical conductivity. Low-temperature fluorination primarily prepares fluorinated graphite intercalation compounds (CF). x However, the low fluorine content results in a low specific capacity for the battery. Industrially, high-temperature fluorination is the primary method used, but as the degree of fluorination increases, a large number of inactive groups such as CF2 are formed. This not only fails to provide capacity but also reduces the conductivity of the fluorinated carbon material, which is detrimental to the battery's rate performance. Summary of the Invention

[0005] To address the aforementioned problems in the background art, the purpose of this invention is to provide a fluorocarbon material, its preparation method, and its application. The preparation method of this invention enables the fluorocarbon bonds in the fluorocarbon material to be uniformly distributed, the carbon interlayer spacing to be increased, and thus improves the specific capacity of the fluorocarbon material.

[0006] The objective of this invention is achieved through the following means:

[0007] This invention provides a method for preparing fluorinated carbon materials, mainly comprising the following steps:

[0008] (1) Place the carbon material into a fixed-bed reactor and evacuate to 0.005-0.1 kPa;

[0009] (2) After heating to 200-1000℃, an inert gas is introduced to maintain the pressure of the reaction system at 10kPa-95kPa. Then, an inert gas containing a halogenating reagent is introduced to carry out the halogenation reaction for 4-96 hours to obtain carbon halide. The molar ratio of halogen atoms to C in the carbon halide is 0.4-1.4:1, preferably 0.6-1.2:1.

[0010] (3) Continuously introduce an inert gas containing a fluorinated reagent into the reactor of step (2) and react at 100-1000°C for 4-96 hours;

[0011] (4) The product obtained in step (3) is soaked in an alkaline solution, washed with deionized water until neutral, and dried to obtain fluorocarbon material.

[0012] Based on the above technical solution, further, the particle size of the carbon material in step (1) is 1 to 100 μm, preferably 3 to 30 μm.

[0013] Based on the above technical solution, further, the heating temperature in step (2) is 250-450℃.

[0014] Based on the above technical solution, further, in step (2), the volume percentage of the halogenated reagent in the inert gas containing the halogenated reagent is 30-70%; the halogenated reagent is one or more of the chlorination reagent, bromination reagent, and iodination reagent.

[0015] Based on the above technical solution, further, the reaction temperature in step (3) is 200-400℃.

[0016] Based on the above technical solution, further, in step (3), the volume percentage of the fluorinated reagent in the inert gas containing the fluorinated reagent is 10-30%; the fluorinated reagent is one or more of hydrogen fluoride, fluorine gas, and gaseous fluorides.

[0017] Based on the above technical solution, the gaseous fluoride is one or both of nitrogen trifluoride and xenon difluoride.

[0018] Based on the above technical solution, the inert gas is one or more of nitrogen, argon, and helium.

[0019] Based on the above technical solution, further, the alkaline solution mentioned in step (4) is an aqueous solution of sodium hydroxide or potassium hydroxide with a concentration of 5-20 wt%.

[0020] In another aspect, the present invention provides a fluorinated carbon material prepared by the above-described preparation method.

[0021] Based on the above technical solution, further, the molar ratio of fluorine atoms to C in the fluorinated carbon material is 0.4 to 1.4:1, preferably 0.6 to 1.2:1.

[0022] The present invention also provides the application of the above-mentioned fluorinated carbon materials in lithium-ion batteries.

[0023] Based on the above technical solution, the fluorinated carbon material is further used as the positive electrode material of a lithium-ion battery.

[0024] The advantages of this invention over the prior art are as follows:

[0025] This invention first uses a halogenation reaction to position halogen atoms between carbon layers, increasing the spacing and facilitating subsequent fluorination. This also reduces the anisotropy of carbon, preventing ineffective structures caused by excessive fluorination of edge carbons. The resulting fluorinated carbon has a higher specific capacity, and the wider interlayer spacing of the carbon material allows for sufficient electrolyte wetting, ensuring the battery's power characteristics. Essentially, this invention provides a method for achieving a uniform distribution of fluorinated carbon bonds in fluorinated carbon materials. Detailed Implementation

[0026] The present invention will be described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments can be obtained without creative effort and all fall within the protection scope of the present invention.

[0027] The battery manufacturing and testing process is as follows:

[0028] The prepared fluorinated carbon material, conductive carbon black, and polyvinylidene fluoride were thoroughly mixed with N-methylpyrrolidone at a mass ratio of 8:1:1, coated onto aluminum foil, and dried. The fluorinated carbon material was used as the positive electrode, and the areal density of the active material was controlled at 8 mg / cm³. 2 The negative electrode material was lithium metal, the electrolyte was propylene carbonate / dimethyl carbonate (V:V = 1:1) in 1 mol / L LiClO4 solution, and the separator was a 25 μm polyethylene membrane. These materials were assembled into a sandwich structure with the positive electrode, separator, and negative electrode, and after sufficient electrolyte was injected, a CR2032 coin cell was formed. After the battery was allowed to stand at room temperature for 12 hours, constant current discharge tests were conducted at 0.1 A / g, 0.5 A / g, 1 A / g, and 2 A / g (mass based on fluorinated carbon), respectively, until the discharge cutoff voltage of 1.5 V. The test and statistical results are recorded in Table 1.

[0029] Example 1

[0030] 100g of carbon powder (6μm particle size) was placed in a fixed-bed reactor and evacuated to 0.01kPa. After heating to 350℃, nitrogen gas was introduced to maintain the reaction system pressure at 80kPa. Then, a chlorine / nitrogen mixture (chlorine volume percentage 50%) was introduced for chlorination reaction for 24 hours, followed by 2 hours of nitrogen gas introduction. After adjusting the temperature to 300℃, a fluorine / nitrogen mixture (fluorine volume percentage 20%) was introduced and reacted for 12 hours. After the reaction, the product was soaked in a 10% alkaline solution, washed with deionized water until neutral, and dried to obtain fluorinated carbon material. The F:C ratio in the material was determined to be 1:1 by oxygen flask combustion method. The prepared fluorinated carbon was subjected to battery testing, and the results are recorded in Table 1.

[0031] Example 2

[0032] 100g of carbon powder (6μm particle size) was placed in a fixed-bed reactor and evacuated to 0.01kPa. After heating to 350℃, nitrogen gas was introduced to maintain the reaction system pressure at 80kPa. Then, a chlorine / nitrogen mixture (chlorine volume percentage 50%) was introduced for chlorination reaction for 12 hours, followed by nitrogen gas for 2 hours. After adjusting the temperature to 300℃, a fluorine / nitrogen mixture (fluorine volume percentage 20%) was introduced and reacted for 6 hours. After the reaction, the product was soaked in a 10% alkaline solution, washed with deionized water until neutral, and dried to obtain fluorinated carbon material. The F:C ratio of the material was measured to be 0.6:1 using the oxygen flask combustion method. The prepared fluorinated carbon was subjected to battery testing, and the results are recorded in Table 1.

[0033] Comparative Example 1

[0034] 100g of carbon powder (6μm particle size) was placed in a fixed-bed reactor and evacuated to 0.01kPa. After heating to 350℃, nitrogen gas was introduced, and the reaction system pressure was maintained at 80kPa. After adjusting the temperature to 300℃, a fluorine / nitrogen mixture (fluorine volume percentage of 20%) was introduced, and the reaction was carried out for 12 hours. After the reaction, the product was soaked in a 10% alkaline solution, washed with deionized water until neutral, and dried to obtain fluorinated carbon material. The F:C ratio in the material was determined to be 1:1 by the oxygen flask combustion method. The prepared fluorinated carbon was subjected to battery testing, and the results are recorded in Table 1.

[0035] Comparative Example 2

[0036] 100g of carbon powder (6μm particle size) was placed in a fixed-bed reactor and evacuated to 0.01kPa. After heating to 350℃, nitrogen gas was introduced to maintain the reaction system pressure at 80kPa. The temperature was then adjusted to 300℃, and a fluorine / nitrogen mixture (fluorine volume percentage 20%) was introduced. The reaction was carried out for 6 hours. After the reaction, the product was soaked in a 10% alkaline solution, washed with deionized water until neutral, and dried to obtain fluorinated carbon material. The F:C ratio in the material was determined to be 0.6:1 using the oxygen flask combustion method. The prepared fluorinated carbon was subjected to battery testing, and the results are recorded in Table 1.

[0037] Comparative Example 3

[0038] 100g of carbon powder (6μm particle size) was placed in a fixed-bed reactor, and the vacuum was evacuated to 0.01kPa. After heating to 350℃, nitrogen gas was introduced to maintain the reaction system pressure at 80kPa. Then, a mixture of chlorine / fluorine / nitrogen gas (chlorine accounting for 50% by volume and fluorine accounting for 20% by volume) was introduced to simultaneously carry out fluorination and chlorination reactions for 24 hours. After the reaction, the product was soaked in a 10% alkaline solution, washed with deionized water until neutral, and dried to obtain fluorinated carbon material. The F:C ratio in the material was determined to be 1:1 by the oxygen flask combustion method. The prepared fluorinated carbon was subjected to battery testing, and the results are recorded in Table 1.

[0039] Comparative Example 4

[0040] 100g of carbon powder (6μm particle size) was placed in a fixed-bed reactor and evacuated to 0.01kPa. After heating to 350℃, nitrogen gas was introduced to maintain the reaction system pressure at 80kPa. Then, a chlorine / nitrogen mixture (chlorine volume percentage 50%) was introduced for chlorination reaction for 30 hours, followed by nitrogen gas for 2 hours. After adjusting the temperature to 300℃, a fluorine / nitrogen mixture (fluorine volume percentage 20%) was introduced and reacted for 24 hours. After the reaction, the product was soaked in a 10% alkaline solution, washed with deionized water until neutral, and dried to obtain fluorinated carbon material. The F:C ratio of the material was determined to be 1.4:1 using the oxygen flask combustion method. The prepared fluorinated carbon was subjected to battery testing, and the results are recorded in Table 1.

[0041] Comparative Example 5

[0042] 100g of carbon powder (6μm particle size) was placed in a fixed-bed reactor and evacuated to 0.01kPa. After heating to 350℃, nitrogen gas was introduced to maintain the reaction system pressure at 80kPa. Then, a chlorine / nitrogen mixture (50% chlorine by volume) was introduced for chlorination for 10 hours, followed by 2 hours of nitrogen gas introduction. After adjusting the temperature to 300℃, a fluorine / nitrogen mixture (20% fluorine by volume) was introduced and reacted for 4 hours. After the reaction, the product was soaked in a 10% alkaline solution, washed with deionized water until neutral, and dried to obtain fluorinated carbon material. The F:C ratio of the material was measured to be 0.4:1 using the oxygen flask combustion method. The prepared fluorinated carbon was tested for batteries, and the results are recorded in Table 1.

[0043] Example 3

[0044] 100g of carbon powder (6μm particle size) was placed in a fixed-bed reactor and evacuated to 0.1kPa. After heating to 450℃, nitrogen gas was introduced to maintain the reaction system pressure at 80kPa. Then, a chlorine / nitrogen mixture (chlorine volume percentage 50%) was introduced for chlorination reaction for 28 hours, followed by 2 hours of nitrogen gas introduction. After adjusting the temperature to 400℃, a fluorine / nitrogen mixture (fluorine volume percentage 20%) was introduced and reacted for 12 hours. After the reaction, the product was soaked in a 10% alkaline solution, washed with deionized water until neutral, and dried to obtain fluorinated carbon material. The F:C ratio of the material was determined to be 1.2:1 using the oxygen flask combustion method. The prepared fluorinated carbon was subjected to battery testing, and the results are recorded in Table 1.

[0045] Example 4

[0046] 100g of carbon powder (6μm particle size) was placed in a fixed-bed reactor and evacuated to 0.01kPa. After heating to 250℃, nitrogen gas was introduced to maintain the reaction system pressure at 80kPa. Then, a chlorine / nitrogen mixture (chlorine volume percentage 50%) was introduced for chlorination reaction for 18 hours, followed by nitrogen gas for 2 hours. After adjusting the temperature to 200℃, a fluorine / nitrogen mixture (fluorine volume percentage 20%) was introduced and reacted for 10 hours. After the reaction, the product was soaked in a 10% alkaline solution, washed with deionized water until neutral, and dried to obtain fluorinated carbon material. The F:C ratio of the material was measured to be 0.6:1 using the oxygen flask combustion method. The prepared fluorinated carbon was subjected to battery testing, and the results are recorded in Table 1.

[0047] Example 5

[0048] 100g of carbon powder (particle size 28μm) was placed in a fixed-bed reactor and evacuated to 0.01kPa. After heating to 300℃, nitrogen gas was introduced to maintain the reaction system pressure at 80kPa. Then, a chlorine / nitrogen mixture (chlorine volume percentage 50%) was introduced for chlorination reaction for 24 hours, followed by nitrogen gas for 2 hours. After adjusting the temperature to 275℃, a fluorine / nitrogen mixture (fluorine volume percentage 20%) was introduced and reacted for 12 hours. After the reaction, the product was soaked in a 10% alkaline solution, washed with deionized water until neutral, and dried to obtain fluorinated carbon material. The F:C ratio of the material was measured to be 0.95:1 using the oxygen flask combustion method. The prepared fluorinated carbon was tested for batteries, and the results are recorded in Table 1.

[0049] Example 6

[0050] 100g of carbon powder (particle size 12μm) was placed in a fixed-bed reactor and evacuated to 0.01kPa. After heating to 350℃, nitrogen gas was introduced to maintain the reaction system pressure at 80kPa. Then, a bromine / nitrogen mixture (bromine volume percentage 50%) was introduced for bromination reaction for 24 hours, followed by nitrogen gas for 2 hours. After adjusting the temperature to 275℃, a fluorine / nitrogen mixture (fluorine volume percentage 20%) was introduced and reacted for 12 hours. After the reaction, the product was soaked in a 10% alkaline solution, washed with deionized water until neutral, and dried to obtain fluorinated carbon material. The F:C ratio of the material was measured to be 0.97:1 using the oxygen flask combustion method. The prepared fluorinated carbon was tested for batteries, and the results are recorded in Table 1.

[0051] Example 7

[0052] 100g of carbon powder (particle size 12μm) was placed in a fixed-bed reactor and evacuated to 0.01kPa. After heating to 400℃, nitrogen gas was introduced to maintain the reaction system pressure at 80kPa. Then, an iodination reaction was carried out for 24 hours by introducing a mixture of iodine and nitrogen gas (iodine vapor volume percentage of 50%), followed by 2 hours of nitrogen gas introduction. After adjusting the temperature to 275℃, a fluorine / nitrogen gas mixture (fluorine gas volume percentage of 20%) was introduced and reacted for 16 hours. After the reaction, the product was soaked in a 10% alkaline solution, washed with deionized water until neutral, and dried to obtain fluorinated carbon material. The F:C ratio of the material was measured to be 1.1:1 by oxygen flask combustion method. The prepared fluorinated carbon was subjected to battery testing, and the results are recorded in Table 1.

[0053] Table 1. Specific capacity of fluorinated carbon assembled batteries in the examples and comparative examples

[0054]

[0055] In Examples 1-2, fluorinated carbon materials with different fluorine / carbon ratios were obtained by adjusting the halogenation temperature and time as well as the fluorination temperature and time. It was found that the capacity of materials with different fluorine / carbon ratios differed greatly at low currents. As the current increased, the capacities of the two materials gradually approached each other, indicating that materials with low fluorine / carbon ratios are more suitable for use under high currents.

[0056] Compared with Comparative Example 1, Example 1 has the same fluorine-carbon ratio, but the performance is significantly different. This indicates that the method of halogenation followed by fluorination can achieve higher electrochemical energy conversion efficiency of fluorine under the same fluorine-carbon ratio. This is because in Example 1, after halogenation, the interlayer spacing of the halogenated carbon is larger and the halogen-carbon bond distribution is more uniform. After fluorine replaces the halogen, the resulting fluorinated carbon layer can still maintain a large spacing, making it easier for the electrolyte to wet, reducing battery polarization, and increasing capacity. In contrast, the fluorinated carbon prepared in Comparative Example 1 without the halogenation step has a smaller interlayer spacing, uneven fluorine-carbon bond distribution, and poor capacity performance, especially at higher currents, where it can hardly perform.

[0057] Example 2 and Comparative Example 2 have a lower fluorine-to-carbon ratio than Example 1 and Comparative Example 1. They also show that the method of first halogenating and then fluorinating can achieve a higher electrochemical energy conversion efficiency of fluorine under the same fluorine-to-carbon ratio, resulting in a higher capacity of fluorinated carbon.

[0058] Comparative Example 3, which involves simultaneous fluorination and chlorination reactions, yielded a battery assembled with fluorinated carbon materials. The battery's specific capacity was slightly better than that of the battery assembled with fluorinated carbon materials in Comparative Example 1 under the same fluorine-carbon ratio conditions. However, it was significantly worse than that of the battery assembled with fluorinated carbon materials in Example 1 under the same fluorine-carbon ratio conditions. This may be because the simultaneous fluorination and chlorination reactions resulted in irregular interlayer spacing and uneven distribution of fluorinated carbon bonds, leading to poor capacity performance.

[0059] Comparative Examples 4-5: By adjusting the halogenation temperature and time, as well as the fluorination temperature and time, fluorinated carbon materials with different fluorine / carbon ratios were prepared. The fluorine / carbon ratios of the obtained fluorinated carbons were not within the optimized range. This has a certain impact on the specific capacity of the battery under different discharge currents. This is because when the fluorine / carbon ratio is too high, the conductivity of the fluorinated carbon deteriorates and polarization increases; when the fluorine / carbon ratio is too low, the content of the active element fluorine decreases, and the battery capacity decreases. Therefore, a suitable fluorine / carbon ratio is necessary.

[0060] In Examples 3 and 4, the reaction temperature and fluorine-carbon ratio were both within a favorable range, and the specific capacity of the batteries assembled with fluorinated carbon materials remained at a high level. Therefore, the preferred fluorine-carbon ratio was 0.6-1.2:1.

[0061] Example 5 investigated the performance of fluorination of large carbon particles. Although the performance was lower than that of Example 1, it still showed good performance, indicating that the method provided by the present invention is also suitable for fluorination of large carbon particles.

[0062] Examples 6-7 examine the effects of bromine gas and iodine vapor, which are also applicable to the preparation process of this invention. They demonstrate that halogenation first, which increases the interlayer spacing, followed by fluorination, can improve the specific capacity and power characteristics of fluorinated carbon materials, making it a high-quality method for preparing fluorinated carbon.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for the production of a fluorinated carbon material, characterized by, The method comprises the following steps: (1) placing carbon material into a reactor, and vacuumizing to 0.005-0.1 kPa; (2) heating to 200-1000 ℃, then introducing inert gas to keep the pressure of the reaction system at 10-95 kPa, and then introducing inert gas containing halogenated reagent to carry out halogenation reaction, to obtain halogenated carbon, the molar ratio of halogen atom to C in the halogenated carbon being 0.4-1.4:1; (3) continuously introducing inert gas containing fluorinated reagent into the reactor of step (2) to react at 100-1000 ℃ for 4-96 hours; (4) soaking the product obtained in step (3) in alkaline solution, washing with deionized water until neutral, and drying to obtain fluorinated carbon material; The halogenated reagent is chlorine, bromine or iodine vapor.

2. The production method according to claim 1, characterized by, The particle size of the carbon material in step (1) is 1-100 μm.

3. The preparation method according to claim 2, characterized in that, The particle size of the carbon material in step (1) is 3-30 μm.

4. The method of claim 1, wherein, The molar ratio of halogen atom to C in the halogenated carbon in step (2) is 0.6-1.2:

1.

5. The preparation method according to claim 1, characterized in that, The heating temperature in step (2) is 250-450 ℃; the volume percentage of halogenated reagent in the inert gas containing halogenated reagent is 30-70%.

6. The method of claim 1, wherein, The reaction temperature in step (3) is 200-400 ℃; the volume percentage of fluorinated reagent in the inert gas containing fluorinated reagent is 10-30%; the fluorinated reagent is one or more than two of hydrogen fluoride, fluorine gas and gas-phase fluorinated substance.

7. The production method according to claim 6, characterized by, The gas-phase fluorinated substance is one or more than two of nitrogen trifluoride and xenon difluoride.

8. The method of claim 1, wherein, The inert gas is one or more than two of nitrogen, argon and helium.

9. The method of claim 1, wherein, The alkaline solution in step (4) is sodium hydroxide or potassium hydroxide aqueous solution with a concentration of 5-20 wt%.

10. The fluorinated carbon material prepared by the method of any one of claims 1-9.

11. The fluorinated carbon material of claim 10 for use in lithium ion battery.

12. Use according to claim 11, characterized in that, The fluorinated carbon material is used as positive electrode material of lithium ion battery.

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