Method for precise preparation of fluorinated soft carbon, and performance study of primary battery

Abstract

A preparation method of a fluorinated soft carbon material with adjustable crystallinity is disclosed, which can be used for a cathode of a primary lithium battery. A soft carbon material is subjected to high-energy ball milling in an alkane solvent, for example n-pentane or n-heptane,such that the solvent undergoes a certain degree of coating. Further, the soft carbon material whose surface is coated with the organic solvent such as n-pentane and n-heptane is annealed in a furnace to eliminate the organic solvent and form a carbonized structure on the surface of the soft carbon; further, the soft carbon material is fluorinated by use of fluorine in the presence of nitrogen.

Description

TECHNICAL FIELD

[0001] The present disclosure belongs to the technical field of new materials for primary batteries, and in particular relates to a method for precise preparation of fluorinated soft carbon, and a preparation method of a primary battery using an interface-regulated fluorinated carbon material as a cathode material of the primary battery. BACKGROUND

[0002] In the current energy crisis environment, clean energy and renewable energy, such as wind energy, solar energy, and geothermal energy, have become an urgent need. However, in order to facilitate the use, these energy sources need to be converted into electrical energy, and correspondingly, high-capacity electrochemical power sources are required to store the converted electrical energy. Lithium primary batteries are one of the most common and practical energy supply devices, mainly including lithium / sulfur dioxide batteries, lithium / manganese dioxide batteries, lithium / thionyl chloride batteries, and lithium / carbon fluoride batteries. At present, lithium / sulfur dioxide battery is the most widely used battery, but has low specific capacity and narrow applicable temperature range. The lithium / carbon fluoride battery has a highly wide operating temperature (-40°C to 170°C), and also has stable operating voltage, environmental friendliness, high safety, and low self-discharge, showing a wide range of applications in medical and other fields. However, as the cathode material of lithium / fluoride carbon batteries, carbon fluoride has a relatively high cost. It is an urgent need for the development of lithium / carbon fluoride batteries by preparation of new carbon fluoride materials. The patent 202110866336.6 of a fluorinated carbon material provided a method for preparing a new type of integrated fluorinated carbon-based cathode. A carbon nanotube and graphene are sieved, and transferred using a microporous filter membrane to a vacuum oven for drying. After drying, the microporous filter membrane is peeled off to obtain a graphene / carbon nanotube current collector. The graphene / carbon nanotube current collector is placed in a reaction container, and fluorination is conducted with a reaction gas composed of a gas fluorine source and a diluent gas at 600°C to 800°C, to obtain the new type of integrated fluorinated carbon-based cathode.

[0003] The present disclosure provides a simple method for precisely preparing fluorinated soft carbon with adjustable crystallinity at a relatively low fluorination temperature and a preparation method of a primary battery. Organic solvents such as n-pentane and n-heptane regulate the particle size, surface crystallinity, and wettability with an electrolyte of the soft carbon; meanwhile, the soft carbon material whose surface is coated with organic solvents such as n-pentane and n-heptane is annealed to eliminate impurities in the organic solvent and solvent gas molecules, and further form carbonized and graphitized structures on the surface of the soft carbon. The fluorinated soft carbon obtained after the soft carbon material is precisely fluorinated is used as a cathode material, and a prepared lithium / fluorinated soft carbon battery has an excellent performance. Therefore, in the present disclosure, based on the method for precise preparation of fluorinated soft carbon with adjustable crystallinity, and the preparation method of a primary battery, an obtained lithium / fluorinated soft carbon battery has excellent electrical properties. The method lays an important foundation for promoted application of the lithium / fluorinated soft carbon battery SUMMARY

[0004] In view of defects in the background, an objective of the present disclosure is to provide a method for precise preparation of fluorinated soft carbon, and a preparation method of a primary battery. In the present disclosure, the soft carbon material is subjected to high-energy ball milling in a solvent such as n-pentane and n-heptane, and coated and carbonized to a certain extent to form a soft carbon structure with amorphous carbon, so as to control a particle size, surface crystallinity, an interface, and wettability with an electrolyte of the soft carbon. The soft carbon material is further precisely fluorinated to obtain an adjustable fluorinated soft carbon material. The fluorinated soft carbon material after precise fluorination is used as a cathode material, to obtain a lithium / fluoride carbon battery with excellent electrochemical performances.

[0005] To achieve the above objective, the present disclosure adopts the following technical solutions.

[0006] The present disclosure provides a method for precise preparation of fluorinated soft carbon, including the following steps:

[0007] step 1, dissolving a soft carbon powder in a n-alkane solvent to form a mixed solution;

[0008] step 2, placing the mixed solution in a high-energy ball mill tank, adding 5 mm zirconia balls, 8 mm zirconia balls, and 10 mm zirconia balls at a mass ratio of 5:3:2, and conducting ball milling at 500 r / min to 900 r / min for 0.5 h to 2 h to obtain a mixed slurry;

[0009] step 3, annealing the mixed slurry at l,000°C to l,750°C for 1 h to 4 h to obtain a mixed powder, grinding the mixed powder, and drying in a vacuum oven at 60°C to 80°C for 6 h to 12 h to obtain a soft carbon material; and

[0010] step 4, conducting fluorination on the soft carbon material in a mixed gas of fluorine and nitrogen at 300°C to 500°C for 0.5 h to 2 h to obtain a fluorinated soft carbon material.

[0011] Further, in step 1, the soft carbon and the n-alkane solvent such as n-pentane and n-heptane that form the mixed solution have a mass ratio of (3-5): 1.

[0012] Further, in step 2, the ball milling is conducted for 0.5 h to 1 h.

[0013] Further, in step 4, the fluorination is conducted at 350°C to 450°C under a volume fraction of the fluorine in mixed gas of the fluorine and the nitrogen at 8% to 11%.

[0014] The present disclosure further provides use of the fluorinated soft carbon obtained by precise fluoridation as a cathode material of a primary lithium / carbon fluoride battery, where the primary lithium / carbon fluoride battery includes a fluorinated soft carbon-based cathode material, a lithium metal anode, an electrolyte, and a diaphragm.

[0015] Further, the fluorinated carbon fluoride-based cathode material is formed by coating a mixed slurry of the fluorinated soft carbon obtained by precise fluoridation, SP, and polyvinylidene fluoride (PVDF) at 8:8:1 on an aluminum foil current collector.

[0016] Compared with the prior art, the present disclosure has the following beneficial effects.

[0017] The present disclosure provides a method for precise preparation of fluorinated soft carbon, and a preparation method of a primary battery. Organic solvents such as n-pentane and n-heptane regulate a particle size, surface crystallinity, an interplanar spacing, an interface, a density, and wettability with an electrolyte of the soft carbon; meanwhile, the soft carbon material whose surface is coated with organic solvents such as n-pentane and n-heptane is annealed to eliminate organic solvent gas molecules, and further form carbonized and graphitized structures on the surface of the soft carbon. The fluorinated soft carbon obtained after the soft carbon material is precisely fluorinated is used as a cathode material, and a prepared lithium / fluorinated soft carbon battery has an excellent performance. Therefore, in the present disclosure, based on the precise preparation of fluorinated soft carbon with adjustable crystallinity, and the preparation method of a primary lithium battery, an obtained lithium / fluorinated soft carbon battery has certain electrical properties. The method lays an important foundation for promoted application of the lithium / fluorinated soft carbon battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 shows an high-resolution transmission electron microscopy (HRTEM) image of fluorinated soft carbon prepared by Example 3 and an appearance of a button battery assembled;

[0019] FIG. 2 shows a field-emission scanning electron microscopy (FESEM) image of soft carbon prepared by mixing soft carbon obtained in Example 1 with n-pentane;

[0020] FIG. 3 shows a FESEM image of soft carbon prepared by mixing soft carbon obtained in Example 2 with n-heptane;

[0021] FIG. 4 shows a FESEM image of fluorinated soft carbon annealed at l,350°C and fluorinated at 300°C obtained in Example 3;

[0022] FIG. 5 shows a FESEM image of fluorinated soft carbon annealed at l,550°C and fluorinated at 300°C obtained in Example 8;

[0023] FIG. 6 shows an HRTEM image of soft carbon prepared by mixing soft carbon obtained in Example 1 with n-pentane;

[0024] FIG. 7 shows an HRTEM image of soft carbon prepared by mixing soft carbon obtained in Example 2 with n-heptane;

[0025] FIG. 8 shows an HRTEM image of fluorinated soft carbon annealed at l,350°C and fluorinated at 300°C obtained in Example 3;

[0026] FIG. 9 shows an X-ray diffraction (XRD) pattern of fluorinated soft carbon annealed at l,350°C and fluorinated at 300°C obtained in Example 3;

[0027] FIG. 10 shows a Raman spectrum of fluorinated soft carbon annealed at l,350°C and fluorinated at 300°C obtained in Example 3;

[0028] FIG. 11 shows a particle size distribution of fluorinated soft carbon annealed at l,350°C and fluorinated at 300°C obtained in Example 3;

[0029] FIG. 12 shows discharge curves of batteries assembled with the fluorinated soft carbon annealed at l,350°C and fluorinated at 300°C to 500°C obtained in Examples 3 to 7 at a rate of 0.01 C;

[0030] FIG. 13 shows discharge curves of batteries assembled with the fluorinated soft carbon annealed at l,550°C and fluorinated at 300°C to 500°C obtained in Examples 8 to 12 at a rate of 0.01 C; and

[0031] FIG. 14 shows discharge curves of batteries assembled with the fluorinated soft carbon annealed at l,750°C and fluorinated at 300°C to 500°C obtained in Examples 13 to 17 at a rate of 0.01 C. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The technical solutions of the present disclosure will be further described below through specific examples.

[0033] Example 1

[0034] A method for precise preparation of fluorinated soft carbon with adjustable crystallinity, and a performance study of a primary battery were provided, where the method included the following steps:

[0035] step 1, a soft carbon powder was dissolved in a n-pentane solvent to form a mixed solution;

[0036] step 2, the mixed solution was placed in a high-energy ball mill tank, 5 mm zirconia balls, 8 mm zirconia balls, and 10 mm zirconia balls were added at a mass ratio of 5:3:2, and ball milling was conducted at 900 r / min for 0.5 h to obtain a mixed slurry; and

[0037] step 3, the mixed slurry was annealed at l,350°C for 4 h to obtain a mixed powder, the mixed powder was ground, and dried in a vacuum oven at 80°C for 12 h to obtain a fluorinated soft carbon material with adjustable crystallinity.

[0038] Example 2

[0039] Compared with Example 1, this example differed in that: step 1, a soft carbon powder was dissolved in a n-heptane solvent to form a mixed solution.

[0040] Example 3

[0041] A method for precise preparation of fluorinated soft carbon with adjustable crystallinity, and a performance study of a primary battery were provided, where the method included the following steps:

[0042] step 1, a soft carbon powder was dissolved in a n-pentane solvent to form a mixed solution;

[0043] step 2, the mixed solution was placed in a high-energy ball mill tank, 5 mm zirconia balls, 8 mm zirconia balls, and 10 mm zirconia balls were added at a mass ratio of 5:3:2, and ball milling was conducted at 900 r / min for 0.5 h to obtain a mixed slurry; and

[0044] step 3, the mixed slurry was annealed at l,350°C for 4 h to obtain a mixed powder, the mixed powder was ground, and dried in a vacuum oven at 80°C for 12 h to obtain a fluorinated soft carbon material with adjustable crystallinity.

[0045] step 4, fluorination was conducted on the fluorinated soft carbon material with adjustable crystallinity in a mixed gas of fluorine and nitrogen at 300°C for 1 h to obtain a fluorinated soft carbon material.

[0046] Example 4

[0047] This example differed from Example 3 in that: step 4, fluorination was conducted on the fluorinated soft carbon material with adjustable crystallinity in a mixed gas of fluorine and nitrogen at 350°C for 1 h to obtain a fluorinated soft carbon material.

[0048] Example 5

[0049] This example differed from Example 3 in that: step 4, fluorination was conducted on the fluorinated soft carbon material with adjustable crystallinity in a mixed gas of fluorine and nitrogen at 400°C for 1 h to obtain a fluorinated soft carbon material.

[0050] Example 6

[0051] This example differed from Example 3 in that: step 4, fluorination was conducted on the fluorinated soft carbon material with adjustable crystallinity in a mixed gas of fluorine and nitrogen at 450°C for 1 h to obtain a fluorinated soft carbon material.

[0052] Example 7

[0053] This example differed from Example 3 in that: step 4, fluorination was conducted on the fluorinated soft carbon material with adjustable crystallinity in a mixed gas of fluorine and nitrogen at 500°C for 1 h to obtain a fluorinated soft carbon material.

[0054] Examples

[0055] A method for precise preparation of fluorinated soft carbon with adjustable crystallinity, and a performance study of a primary battery were provided, where the method included the following steps:

[0056] step 1, a soft carbon powder was dissolved in a n-pentane solvent to form a mixed solution;

[0057] step 2, the mixed solution was placed in a high-energy ball mill tank, 5 mm zirconia balls, 8 mm zirconia balls, and 10 mm zirconia balls were added at a mass ratio of 5:3:2, and ball milling was conducted at 900 r / min for 0.5 h to obtain a mixed slurry; and

[0058] step 3, the mixed slurry was annealed at 1550°C for 4 h to obtain a mixed powder, the mixed powder was ground, and dried in a vacuum oven at 80°C for 12 h to obtain a fluorinated soft carbon material with adjustable crystallinity.

[0059] step 4, fluorination was conducted on the fluorinated soft carbon material with adjustable crystallinity in a mixed gas of fluorine and nitrogen at 300°C for 1 h to obtain a fluorinated soft carbon material.

[0060] Example 9

[0061] This example differed from Example 3 in that: step 4, fluorination was conducted on the fluorinated soft carbon material with adjustable crystallinity in a mixed gas of fluorine and nitrogen at 350°C for 1 h to obtain a fluorinated soft carbon material.

[0062] Example 10

[0063] This example differed from Example 3 in that: step 4, fluorination was conducted on the fluorinated soft carbon material with adjustable crystallinity in a mixed gas of fluorine and nitrogen at 400°C for 1 h to obtain a fluorinated soft carbon material.

[0064] Example 11

[0065] This example differed from Example 3 in that: step 4, fluorination was conducted on the fluorinated soft carbon material with adjustable crystallinity in a mixed gas of fluorine and nitrogen at 450°C for 1 h to obtain a fluorinated soft carbon material.

[0066] Example 12

[0067] This example differed from Example 3 in that: step 4, fluorination was conducted on the fluorinated soft carbon material with adjustable crystallinity in a mixed gas of fluorine and nitrogen at 500°C for 1 h to obtain a fluorinated soft carbon material.

[0068] Example 13

[0069] A method for precise preparation of fluorinated soft carbon with adjustable crystallinity, and a performance study of a primary battery were provided, where the method included the following steps:

[0070] step 1, a soft carbon powder was dissolved in a n-pentane solvent to form a mixed solution;

[0071] step 2, the mixed solution was placed in a high-energy ball mill tank, 5 mm zirconia balls, 8 mm zirconia balls, and 10 mm zirconia balls were added at a mass ratio of 5:3:2, and ball milling was conducted at 900 r / min for 0.5 h to obtain a mixed slurry; and

[0072] step 3, the mixed slurry was annealed at 1750°C for 4 h to obtain a mixed powder, the mixed powder was ground, and dried in a vacuum oven at 80°C for 12 h to obtain a fluorinated soft carbon material with adjustable crystallinity.

[0073] step 4, fluorination was conducted on the fluorinated soft carbon material with adjustable crystallinity in a mixed gas of fluorine and nitrogen at 300°C for 1 h to obtain a fluorinated soft carbon material.

[0074] Example 14

[0075] This example differed from Example 3 in that: step 4, fluorination was conducted on the fluorinated soft carbon material with adjustable crystallinity in a mixed gas of fluorine and nitrogen at 350°C for 1 h to obtain a fluorinated soft carbon material.

[0076] Example 15

[0077] This example differed from Example 3 in that: step 4, fluorination was conducted on the fluorinated soft carbon material with adjustable crystallinity in a mixed gas of fluorine and nitrogen at 400°C for 1 h to obtain a fluorinated soft carbon material.

[0078] Example 16

[0079] This example differed from Example 3 in that: step 4, fluorination was conducted on the fluorinated soft carbon material with adjustable crystallinity in a mixed gas of fluorine and nitrogen at 450°C for 1 h to obtain a fluorinated soft carbon material.

[0080] Example 17

[0081] This example differed from Example 3 in that: step 4, fluorination was conducted on the fluorinated soft carbon material with adjustable crystallinity in a mixed gas of fluorine and nitrogen at 500°C for 1 h to obtain a fluorinated soft carbon material.

[0082] FIG. 2 and FIG. 3 were a FESEM image of the soft carbon prepared by mixing the soft carbon obtained in Example 1 with the n-pentane solvent, and a FESEM image of the soft carbon prepared by mixing the soft carbon obtained in Example 2 with the n-heptane solvent, respectively. It was seen that the prepared soft carbon samples were in a block shape.

[0083] FIG. 4 and FIG. 5 were a FESEM image of the fluorinated soft carbon annealed at l,350°C and fluorinated at 300°C obtained in Example 3, and a FESEM image of the fluorinated soft carbon annealed at l,550°C and fluorinated at 300°C obtained in Example 8, respectively. It was seen that the fluorinated soft carbon samples prepared after fluorination were layered.

[0084] FIG. 6 and FIG. 7 were an HRTEM image of the soft carbon prepared by mixing the soft carbon obtained in Example 1 with the n-pentane solvent, and an HRTEM image of the soft carbon prepared by mixing the soft carbon obtained in Example 2 with the n-heptane solvent. It was seen that the edges of the samples had thin walls, indicating that the surface crystallinity of the soft carbon was regulated by the organic solvent.

[0085] FIG. 8 showed an HRTEM image of fluorinated soft carbon annealed at l,350°C and fluorinated at 300°C obtained in Example 3. It was seen that after the organic solvent regulated the particle size, surface crystallinity, interplanar spacing, density, and wettability of the soft carbon, the fluorinated soft carbon material after fluorination had a denser edge.

[0086] FIG. 9 showed an XRD pattern of fluorinated soft carbon annealed at l,350°C and fluorinated at 300°C obtained in Example 3. The diffraction peak at 20=26° corresponded to a (002) plane of the graphite structure, indicating that the fluorinated soft carbon annealed at l,350°C and fluorinated at 300°C still had a graphite structure.

[0087] FIG. 10 showed a Raman spectrum of fluorinated soft carbon annealed at l,350°C and fluorinated at 300°C obtained in Example 3. As shown in the figure, the peaks at 1,341 cm1 and 1,587 cm1 were characteristic peaks of carbon, corresponding to peak D and peak G, respectively, and an Id / Ig value was 1.05, indicating that the fluorinated soft carbon material structure was still orderly after fluorination.

[0088] FIG. 11 showed a particle size distribution of fluorinated soft carbon annealed at l,350°C and fluorinated at 300°C obtained in Example 3. It was seen that the fluorinated soft carbon samples had a particle size mainly concentrated in 0 pm to 20 pm, and most of them were the fluorinated soft carbon samples with a particle size of 0 pm to 10 pm.

[0089] Assembly of a battery:

[0090] The fluorinated soft carbon samples obtained in Examples 3 to 17, a conductive agent Ketjen black, and a binder PVDF were prepared in a mass ratio of 8:1:1 to obtain a slurry separately; the slurry was evenly coated on an aluminum foil current collector, and vacuum-dried at 80°C for 12 h to obtain a cathode sheet. In a glove box, metal lithium was used as an anode, and the electrode sheet prepared from fluorinated ginkgo leaf was used as a cathode. A button battery was assembled in the glove box, and then allowed to stand for 24 h for the test.

[0091] FIG. 12 showed discharge curves of batteries assembled with the fluorinated soft carbon annealed at l,350°C and fluorinated at 300-500°C obtained in Examples 3 to 7 at a rate of 0.01 C. ft was seen that the fluorinated soft carbon sample obtained by fluorinating the soft carbon material at 500°C and annealing at l,350°C had a specific capacity of not less than 800 mAh / g at a discharge rate of 0.01C, but had a low voltage plateau and an unstable discharge curve. The fluorinated soft carbon sample obtained by fluorinating the soft carbon material at 400°C and annealing at l,350°C had a better discharge performance at a discharge rate of 0.01 C, showing a specific capacity of about 700 mAh / g at 1.5 V.

[0092] FIG. 13 showed discharge curves of batteries assembled with the fluorinated soft carbon annealed at l,550°C and fluorinated at 300°C to 500°C obtained in Examples 8 to 12 at a rate of 0.01 C. It was seen that the fluorinated soft carbon sample obtained by fluorinating the soft carbon material at 400°C and annealing at l,550°C had a higher voltage plateau in the discharge curve at a discharge rate of 0.01 C, but had a lower specific capacity of about 500 mAh / g. ft was seen that the fluorinated soft carbon sample obtained by fluorinating the soft carbon material at 500°C and annealing at l,550°C had a better specific capacity at a discharge rate of 0.01C, but had a low voltage plateau and an unstable discharge curve. The fluorinated soft carbon sample obtained by fluorinating the soft carbon material at 450°C and annealing at l,550°C had a better discharge performance at a discharge rate of 0.01 C, showing a voltage plateau exceeding 2.5 V, and a specific capacity of about 700 mAh / g at 1.5 V.

[0093] FIG. 14 showed discharge curves of batteries assembled with the fluorinated soft carbon annealed at l,750°C and fluorinated at 300°C to 500°C obtained in Examples 13 to 17 at a rate of 0.01 C. ft was seen that the fluorinated soft carbon sample obtained by fluorinating the soft carbon material at 400°C and annealing at l,750°C had a higher voltage plateau in the discharge curve at a discharge rate of 0.01 C, but had a lower specific capacity below 200 mAh / g. ft was seen that the fluorinated soft carbon sample obtained by fluorinating the soft carbon material at 500°C and annealing at l,750°C had a better specific capacity at a discharge rate of 0.01 C, but had a low voltage plateau and an unstable discharge curve. The fluorinated soft carbon sample obtained by fluorinating the soft carbon material at 450°C and annealing at l,750°C had a better discharge performance at a discharge rate of 0.01 C, showing a voltage plateau exceeding 2.6 V, and a specific capacity of about 700 mAh / g at 1.5 V. Compared with FIG. 12 and FIG. 13, it was seen that the fluorinated soft carbon sample obtained by fluorinating the soft carbon material at 450°C and annealing at l,750°C generally showed a more excellent discharge performance.

Claims

AMENDMENTS TO THE CLAIMS1. A method for precise preparation of fluorinated soft carbon, comprising the following steps:step 1, dissolving a soft carbon powder in a n-alkane solvent to form a mixed solution;step 2, placing the mixed solution in a high-energy ball mill tank, adding 5 mm zirconia balls, 8 mm zirconia balls, and 10 mm zirconia balls at a mass ratio of 5:3:2, and conducting ball milling at 500 r / min to 900 r / min for 0.5 h to 2 h to obtain a mixed slurry;step 3, annealing the mixed slurry at l,000°C to l,750°C for 1 h to 4 h to obtain a mixed powder, grinding the mixed powder, and drying in a vacuum oven at 60°C to 80°C for 6 h to 12 h to obtain a soft carbon material; andstep 4, conducting fluorination on the soft carbon material in a mixed gas of fluorine and nitrogen at 300°C to 500°C for 0.5 h to 2 h to obtain a fluorinated soft carbon material.

2. The method for precise preparation of fluorinated soft carbon according to claim 1, wherein in step 1, the soft carbon and the n-alkane have a mass ratio of (3-5): 1.

3. The method for precise preparation of fluorinated soft carbon according to claim 1, wherein in step 2, the ball milling is conducted for 0.5 h to 1 h.

4. The method for precise preparation of fluorinated soft carbon according to claim 1, wherein in step 4, the fluorination is conducted at 350°C to 450°C under a volume fraction of the fluorine in mixed gas of the fluorine and the nitrogen at 8% to 11%.

5. Use of the fluorinated soft carbon prepared by the method according to any one of claims 1 to 4 as a cathode material of a primary lithium battery.

6. The use acceding to claim 5, wherein the cathode material of a primary lithium battery is prepared by mixing the fluorinated soft carbon, a conductive agent, and a binder at a ratio of 8:1:1.

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