A method for modifying carbon fluoride, modified carbon fluoride and lithium / carbon fluoride batteries

Abstract

The application provides a modification method of carbon fluoride, modified carbon fluoride and a lithium / carbon fluoride battery, and the modification method comprises the following steps: mixing carbon fluoride and a composite solvent, performing modification treatment, and then performing solid-liquid separation to obtain modified carbon fluoride, wherein the composite solvent comprises water and an ether solvent. The carbon fluoride is modified by using the composite solvent, and under the synergistic action of the water and the ether solvent, unstable components in the carbon fluoride material can be reacted and removed, the chemical stability of the carbon fluoride material itself is improved, the problem of side reactions between the carbon fluoride and an electrolyte is solved, and the storage stability of the lithium / carbon fluoride battery is improved. Moreover, the modification method is simple and feasible, does not need pre-charging, is easy to realize, and is suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and relates to a method for modifying fluorinated carbon, modified fluorinated carbon, and lithium / fluorinated carbon batteries. Background Technology

[0002] Lithium / carbon fluoride batteries are currently the type of primary lithium battery with the highest energy density. Compared to other primary lithium batteries, lithium / carbon fluoride batteries have advantages such as stable discharge, safe storage, and low self-discharge rate, making them applicable to many aspects of production and daily life. Lithium / carbon fluoride batteries have shown wide application in medical devices and military weaponry. Furthermore, these batteries are environmentally friendly and pollution-free, making recycling easier and reducing environmental pollution, making them an environmentally friendly battery.

[0003] However, in lithium / carbon fluoride batteries, the positive electrode active material, carbon fluoride, is prone to side reactions with the electrolyte, especially with the organic solvents in the electrolyte, which directly affects the battery's storage stability. To address this issue, CN112993289A discloses a lithium / carbon fluoride battery, its electrolyte, and a method of use. This method involves adding a cyclic phosphate ester to the electrolyte. This phosphate ester can form a passivation layer at the positive electrode, preventing direct contact between the electrolyte and carbon fluoride. Furthermore, the phosphate ester can decompose to generate phosphorus radicals, which quench hydrogen radicals in the electrolyte, thereby reducing side reactions between the electrolyte and the electrode and improving the battery's storage performance.

[0004] CN114628670A discloses the application of nitrogen-doped carbon-coated fluorinated carbon in lithium / carbon fluoride batteries. An aqueous solution of tris(hydroxymethyl)aminomethane is used as a buffer solution. A polydopamine-fluorinated carbon composite material is first obtained through the self-polymerization reaction of dopamine hydrochloride. This composite material is then calcined under an inert atmosphere to obtain a nitrogen-doped carbon-coated fluorinated carbon electrode material. The carbon layer coating on the surface serves to prevent direct contact between the electrolyte and the fluorinated carbon, thereby reducing self-discharge and improving the battery's shelf life.

[0005] However, the above technologies have the following problems: 1) The oxidation potential of phosphate ester additives is higher than the open circuit voltage of lithium / carbon fluoride batteries, and the battery needs to be pre-charged to form a passivation layer of cyclic phosphate esters on the positive electrode. This charging process may affect the safety performance of the battery and may generate lithium dendrites that puncture the separator; 2) The preparation process of fluoride surface coating is complex and costly, which is not conducive to large-scale production; 3) Both of the above technical methods reduce the side reactions between the positive electrode and the electrolyte by blocking the direct contact between the positive electrode and the electrolyte, but do not solve the problem of side reactions between fluoride and the electrolyte from the root.

[0006] Therefore, there is an urgent need to provide a method that can fundamentally solve the problem of side reactions between fluorinated carbon and electrolytes, without the need for a pre-charging step, and is suitable for large-scale production. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a method for modifying fluorinated carbon, modified fluorinated carbon, and a lithium / carbon fluoride battery. This invention employs a composite solvent to modify fluorinated carbon. With the synergistic effect of water and ether solvents, unstable components in the fluorinated carbon material can be reacted away, improving the material's chemical stability and resolving the side reaction problem between fluorinated carbon and the electrolyte, thereby enhancing the storage stability of the lithium / carbon fluoride battery. Furthermore, the modification method of this invention is simple and feasible, requires no pre-charging, is easy to implement, and is suitable for large-scale production.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for modifying fluorinated carbon, the modification method comprising:

[0010] Fluorinated carbon and a composite solvent are mixed and modified, and then separated into solid and liquid components to obtain modified fluorinated carbon. The composite solvent includes water and ether solvents.

[0011] This invention provides a method for modifying fluorinated carbon, which uses a composite solvent to pretreat the fluorinated carbon. Water reacts with and removes unstable components from the fluorinated carbon, such as unstable CF bonds, atomic fluorine in the carbon interlayer, residual fluorinating agents and catalysts from the fluorination process, and some active defect structures on the material surface. In particular, the side reaction between the oxidizing fluorine of the fluorinated carbon and the solvent DME plays a role in removing unstable components from the fluorinated carbon. Ether solvents have good affinity with fluorinated carbon, wetting the fluorinated carbon material and allowing for more thorough treatment of unstable components, thus cleaning the material. Furthermore, ethers can also react with unstable components in the fluorinated carbon. Therefore, with the synergistic effect of water and ether solvents, unstable components in fluorinated carbon are removed, improving the chemical stability of the material. This solves the problem of side reactions between fluorinated carbon and the electrolyte, especially the side reactions of unstable organic solvents (such as ethylene glycol dimethyl ether) in fluorinated carbon. This improves the storage stability of lithium / fluorinated carbon batteries and avoids capacity loss caused by side reactions during storage. In addition, the modification method of this invention is simple and feasible, requires no pre-charging, is easy to implement, has low cost, and is suitable for large-scale production.

[0012] Preferably, the ether solvent includes at least one of dimethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and tetrahydrofuran, and is preferably ethylene glycol dimethyl ether.

[0013] Preferably, in the composite solvent, the mass ratio of water to ether solvent is (10-90):(10-90), wherein the range of water (10-90) can be, for example, 10, 20, 30, 40, 50, 60, 70, 80 or 90, and the range of ether solvent (10-90) can be, for example, 10, 20, 30, 40, 50, 60, 70, 80 or 90, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0014] In this invention, if the mass ratio of water to ether solvent is too low, the modification effect will be poor; if the mass ratio of water to ether solvent is too high, the fluorinated carbon will not be able to be wetted and cannot be modified because the water content in the composite solvent is too high and the fluorinated carbon is a hydrophobic material.

[0015] Preferably, the solid-liquid mass ratio of the fluorinated carbon and the composite solvent is (1 / 10-1 / 2):1, for example, it can be 0.1:1, 0.2:1, 0.3:1, 0.4:1 or 0.5:1, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0016] In this invention, if the solid-liquid ratio of fluorinated carbon and composite solvent is too low, it will lead to waste of resources; if the solid-liquid ratio of fluorinated carbon and composite solvent is too high, it will lead to insufficient treatment and the unstable components in fluorinated carbon will not be completely eliminated.

[0017] Preferably, the temperature of the modification treatment is 0-90℃, for example, it can be 0℃, 10℃, 20℃, 30℃, 40℃, 50℃, 60℃, 70℃ or 80℃, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 40-60℃.

[0018] This invention preferably performs the modification treatment at 40-60℃. This is because modification at high temperatures can increase the reactivity of unstable structures in fluorinated carbon, improve the wettability of the solvent with fluorinated carbon, and make the pretreatment reaction more thorough, which is beneficial to the structural stability of the material. If the modification temperature is too low, the wettability of the solvent with fluorinated carbon is poor, and the reactivity between the solvent and the active structures in fluorinated carbon is also poor, which will result in the unstable components in fluorinated carbon not being completely eliminated, and the material remaining unstable. If the modification temperature is too high, for power-type fluorinated hard carbon materials, the carbon-fluorine bonds on the surface of the fluorinated carbon will be destroyed, the wettability of the electrolyte with fluorinated carbon will improve, the release of half-ionic bonds in the fluorinated carbon will be aggravated, the self-discharge of the battery will be aggravated, and the storage performance will deteriorate.

[0019] Preferably, the modification treatment time is greater than 0.01h, for example, it can be 0.02h, 0.05h, 0.1h, 0.5h, 1h, 2h, 4h, 6h, 8h, 10h, 15h, 20h, 25h, 30h, 40h, 45h or 48h, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 4h-48h.

[0020] Preferably, the modification process is accompanied by stirring at a rate of 100-1000 r / min, but not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0021] As a preferred technical solution of the present invention, the modification method specifically includes:

[0022] Fluorinated carbon is added to a composite solvent consisting of water and ether solvents, and then stirred to carry out the modification treatment. After solid-liquid separation, drying and dispersion, the modified fluorinated carbon is obtained.

[0023] Optionally, the solid-liquid separation method includes centrifugation, filtration, or natural sedimentation.

[0024] In a second aspect, the present invention provides a modified fluorinated carbon, which is prepared by the modification method described in the first aspect.

[0025] Preferably, the cyclic voltammetry (CV) curve of the modified fluorinated carbon exhibits one reduction peak in the voltage range of 2-3V. This reduction peak corresponds to the reduction peak of the lithium-fluorinated carbon reaction.

[0026] Preferably, compared to the infrared spectrum of unmodified fluorinated carbon, the infrared spectrum of the modified fluorinated carbon has a higher spectral density at 1332 cm⁻¹. -1 CF2 functional group and 1100-1200cm -1 The absorption peak of the half-ionic CF bond at 877-878 cm⁻¹ weakens, indicating that some unstable CF₂ and half-ionic CF bonds have been removed; and the absorption peak at 877-878 cm⁻¹ is also weakened. -1 and 1427-1697cm -1 Characteristic absorption peaks of structures without active defects within the wavelength range, such as 1697 cm⁻¹. -1 (C=O), 1631cm -1 (C=C), 1427cm -1 (CH2) and 877cm -1 (Substituents on the benzene ring)

[0027] Thirdly, the present invention provides a lithium / carbon fluoride battery, wherein the positive electrode of the lithium / carbon fluoride battery comprises the modified fluoride carbon described in the second aspect.

[0028] Preferably, the lithium / carbon fluoride battery further includes a lithium metal anode, an electrolyte, and a separator.

[0029] Optionally, the modified fluorinated carbon cathode, the lithium metal anode, and the separator are assembled into a battery cell by stacking or winding.

[0030] Preferably, the electrolyte comprises an organic solvent and an electrolyte salt.

[0031] Preferably, the electrolyte salt includes at least one of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium trifluoromethanesulfonate.

[0032] Preferably, the organic solvent includes at least one of ethylene glycol dimethyl ether, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

[0033] Preferably, the concentration of the electrolyte is 0.5-2 mol / L, for example, it can be 0.5 mol / L, 0.7 mol / L, 1 mol / L, 1.5 mol / L or 2 mol / L, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] Optionally, the electrolyte preparation process is as follows: in an argon-filled glove box, organic solvent components (such as propylene carbonate and ethylene glycol dimethyl ether) are mixed to obtain a mixed solvent, and an electrolyte salt is added to the mixed solvent to obtain the electrolyte.

[0035] Optionally, after assembling the battery cell, electrolyte is injected into the battery cell at an injection rate of 1.0-1.6 g / Ah (e.g., 1.0 g / Ah, 1.2 g / Ah, 1.4 g / Ah, or 1.6 g / Ah, etc.). After sealing, a lithium / carbon fluoride battery is obtained.

[0036] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] (1) This invention provides a method for modifying fluorinated carbon, which uses a composite solvent to pretreat the fluorinated carbon. Water reacts with and removes unstable components in the fluorinated carbon, such as unstable CF bonds, atomic fluorine in the carbon interlayer, residual fluorinating agents and catalysts from the fluorination process, and some active defect structures on the material surface. In particular, the side reaction between the oxidizing fluorine in the fluorinated carbon and the solvent DME plays a role in removing unstable components from the fluorinated carbon. Ether solvents have good affinity with fluorinated carbon, wetting the fluorinated carbon material and allowing the unstable components to be treated more thoroughly, thus cleaning the material. Ethers can also react with unstable components in the fluorinated carbon. Therefore, under the combined action of water and ether solvents, unstable components in the fluorinated carbon are removed, improving the chemical stability of the material and solving the side reaction problem between fluorinated carbon and the electrolyte, especially the side reaction of unstable organic solvents (such as ethylene glycol dimethyl ether) in the fluorinated carbon. This improves the storage stability of lithium / fluorinated carbon batteries and avoids capacity loss caused by side reactions during battery storage.

[0039] (2) The modification method of the present invention is simple and feasible, requires no pre-charging, is easy to implement, has low cost, and is suitable for large-scale production. Attached Figure Description

[0040] Figure 1 The CV curves are for the modified fluorinated carbon provided in Example 1 of the present invention and the unmodified fluorinated carbon provided in Comparative Example 1.

[0041] Figure 2 The infrared spectra of the modified fluorinated carbon provided in Example 1 of the present invention and the unmodified fluorinated carbon provided in Comparative Example 1 are shown. Detailed Implementation

[0042] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0043] Example 1

[0044] This embodiment provides a method for modifying fluorinated carbon, including:

[0045] Fluorocarbon material was added to a composite solvent consisting of water and an ether solvent, with the ether solvent being ethylene glycol dimethyl ether. The mass ratio of water to ethylene glycol dimethyl ether was 50:50, and the solid-liquid mass ratio of fluorocarbon to the composite solvent was 1:5. Then, stirring was started at a rate of 500 r / min, and the mixture was modified at 40°C for 24 h. After that, solid-liquid separation was performed, and the separated product was placed in a forced-air drying oven for drying. Finally, the dried modified fluorocarbon granules were dispersed using a powder disperser to obtain modified fluorocarbon powder.

[0046] Example 2

[0047] This embodiment provides a method for modifying fluorinated carbon, including:

[0048] Fluorocarbon material was added to a composite solvent consisting of water and an ether solvent, with tetrahydrofuran as the ether solvent and a water-to-tetrahydrofuran mass ratio of 60:40. The solid-liquid mass ratio of fluorocarbon to the composite solvent was 1 / 3:1. The mixture was then stirred at a rate of 300 r / min and modified at 60 °C for 10 h. After solid-liquid separation, the separated product was dried in a forced-air drying oven. Finally, the dried modified fluorocarbon granules were dispersed using a powder disperser to obtain modified fluorocarbon powder.

[0049] Example 3

[0050] This embodiment provides a method for modifying fluorinated carbon, including:

[0051] Fluorocarbon material was added to a composite solvent consisting of water and an ether solvent, with diethylene glycol dimethyl ether as the ether solvent. The mass ratio of water to diethylene glycol dimethyl ether was 50:50, and the solid-liquid ratio of fluorocarbon to the composite solvent was 1 / 5:1. The mixture was then stirred at a rate of 400 r / min and modified at 70 °C for 24 h. After solid-liquid separation, the separated product was dried in a forced-air drying oven. Finally, the dried modified fluorocarbon granules were dispersed using a powder disperser to obtain modified fluorocarbon powder.

[0052] Example 4

[0053] The difference between this embodiment and Embodiment 1 is that ethylene glycol dimethyl ether is replaced by tetrahydrofuran.

[0054] The remaining parameters and operating steps are exactly the same as in Example 1.

[0055] Example 5

[0056] The difference between this embodiment and Embodiment 1 is that the solid-liquid mass ratio of fluorinated carbon and composite solvent is adjusted to 0.05:1.

[0057] The remaining parameters and operating steps are exactly the same as in Example 1.

[0058] Example 6

[0059] The difference between this embodiment and Embodiment 1 is that the solid-liquid mass ratio of fluorinated carbon and composite solvent is adjusted to 0.55:1.

[0060] The remaining parameters and operating steps are exactly the same as in Example 1.

[0061] Example 7

[0062] The difference between this embodiment and Embodiment 1 is that the modification temperature is adjusted to -5℃.

[0063] The remaining parameters and operating steps are exactly the same as in Example 1.

[0064] Example 8

[0065] The difference between this embodiment and Embodiment 1 is that the modification temperature is adjusted to 95°C.

[0066] The remaining parameters and operating steps are exactly the same as in Example 1.

[0067] Comparative Example 1

[0068] This comparative example provides the same fluorinated carbon material as in Example 1, without the composite solvent modification treatment.

[0069] Comparative Example 2

[0070] The difference between this comparative example and Example 1 is that water is omitted from the composite solvent, so that the composite solvent contains only ether solvent (i.e., ethylene glycol dimethyl ether).

[0071] The remaining parameters and operating steps are exactly the same as in Example 1.

[0072] Performance testing

[0073] (1) Cyclic Voltammetry (CV) Test

[0074] The modified fluorinated carbon of Example 1 and the unmodified fluorinated carbon of Comparative Example 1 were used to make button cells. After being stored at 55°C for 14 days, CV tests were performed. The specific test conditions were: scan speed 0.05mV / s, scan from the full-charge open-circuit voltage of the cell to 1V.

[0075] Figure 1 The CV curves of unmodified fluorinated carbon in Comparative Example 1 and modified fluorinated carbon in Example 1 are shown. The figure shows that the unmodified fluorinated carbon material exhibits two reduction peaks in the CV curve. The peak at 2.3V represents the reduction peak of the side reaction between fluorinated carbon and the electrolyte, demonstrating the instability of the fluorinated carbon material and its susceptibility to side reactions with the electrolyte. Furthermore, the deterioration of the electrolyte reduces the reduction peak current of the lithium-fluorinated carbon reaction, causing the reduction peak to shift to the left and increasing polarization during battery discharge. The modification process stabilizes the fluorinated carbon material, essentially eliminating the side reactions with the electrolyte, and removing the reduction peak of the side reactions, thus improving the battery's storage stability.

[0076] (2) Infrared spectroscopy test

[0077] Infrared spectroscopy was performed on the modified fluorinated carbon material of Example 1 and the unmodified fluorinated carbon material of Comparative Example 1, with a test range of 4000-400 cm⁻¹. -1 ,like Figure 2As shown. Test results indicate that, after pretreatment, the fluorocarbon material at 1697 cm⁻¹... -1 (C=O), 1631cm -1 (C=C), 1427cm -1 (CH2), 877cm -1 The characteristic absorption peak at the (substituent on the benzene ring) disappears, and at 1332 cm⁻¹... -1 (CF2) and 1100-1200cm -1 The weakening at the (half-ionic CF bond) indicates that there are many defective structures in the unmodified fluorinated carbon material, and some carbon-fluorine bonds are unstable. Pretreatment can eliminate unstable components in the material, improve the stability of the material, and thus improve the storage stability of the battery.

[0078] (3) Storage stability test

[0079] The fluorinated carbon material provided in the above embodiments and comparative examples was used as the active material and mixed with the conductive agent Super P and the binder polyvinylidene fluoride (PVDF) respectively. A high-viscosity slurry with a viscosity of 12000 cp was prepared by mixing the active material, conductive agent, and binder in a mass ratio of 87:8:5. This slurry was coated onto carbon-coated aluminum foil, with one coating on side A and then one coating on side B, resulting in a coating thickness of 100 μm and an electrode loading of 120 g / m². 2 After drying at 100℃, it is rolled and compacted to a density of 1.26 g / cm³. 3 The modified fluorinated carbon positive electrode sheet is cut or die-cut to the corresponding size to obtain a fluorinated carbon positive electrode sheet with a porosity of 52%. The lithium strip is cut to the corresponding size to obtain a lithium negative electrode sheet with a thickness of 50 μm. The modified fluorinated carbon positive electrode sheet, the lithium metal negative electrode sheet and the separator are assembled into a battery cell by stacking. The primary lithium fluorinated carbon battery electrolyte is injected into the battery cell. The organic solvent in the electrolyte is propylene carbonate (PC) and dimethyl ethylene glycol (DME), the electrolyte salt is lithium trifluoromethanesulfonate (LiTFA) and lithium perchlorate (LiClO4), the electrolyte concentration is 1 mol / L, the injection coefficient is 1.2 g / Ah, and the battery is sealed to obtain a lithium / fluorinated carbon battery.

[0080] Test conditions: a) Discharge the lithium / carbon fluoride battery at 0.01C at room temperature with a discharge cutoff voltage of 1.5V and record the discharge capacity of the new battery; b) Store the new lithium / carbon fluoride battery of the same type at 55℃ for 14 days, then test and record the discharge capacity of the battery under the above conditions, and calculate the capacity retention rate = discharge capacity after high temperature storage / discharge capacity of the new battery * 100%.

[0081] Table 1

[0082]

[0083]

[0084] analyze:

[0085] As shown in the results of Examples 1-3 and Comparative Example 1, the present invention uses a composite solvent consisting of water and ether solvents to modify fluorinated carbon materials. Under the synergistic effect of water and ether solvents, unstable components in the fluorinated carbon materials can be reacted off, improving the chemical stability of the material itself and solving the side reaction problem between fluorinated carbon and the electrolyte, especially the side reaction between oxidizing fluorine and ethylene glycol dimethyl ether in fluorinated carbon. This improves the storage stability of lithium / fluorinated carbon batteries and maintains stable capacity. Table 1 shows that Examples 1-3 have high capacity retention rates, indicating that the modified fluorinated carbon materials have good stability, the modified fluorinated carbon batteries have reduced self-discharge, and good storage stability. Comparative Example 1 has a low capacity retention rate, indicating that the unmodified fluorinated carbon assembled battery has a large self-discharge after 14 days of storage at high temperature, resulting in poor storage stability.

[0086] The results of Examples 1 and 4 show that using ethylene glycol dimethyl ether and water as a composite solvent for modification results in better capacity retention and storage stability of the corresponding battery.

[0087] The results of Examples 1 and 5-6 show that if the solid-liquid mass ratio of fluorinated carbon and composite solvent is too low, it will lead to waste of resources; if the solid-liquid ratio of fluorinated carbon and composite solvent is too high, it will lead to insufficient treatment, the unstable components in fluorinated carbon will not be completely eliminated, and the battery capacity retention rate will be low.

[0088] As can be seen from the results of Examples 1 and 7-8, if the modification temperature is too low, the wettability of the solvent with fluorinated carbon is poor, and the reaction ability of the solvent with the active structure in fluorinated carbon is poor, which will result in the unstable components in fluorinated carbon not being completely eliminated, and the battery capacity retention rate being low. If the modification temperature is too high, for power-type fluorinated hard carbon materials, the carbon-fluorine bonds on the surface of fluorinated carbon will be destroyed, the wettability of the electrolyte with fluorinated carbon will be improved, the release of half-ionic bonds in fluorinated carbon will be aggravated, the self-discharge of the battery will be aggravated, and the storage performance will deteriorate.

[0089] The results of Example 1 and Comparative Example 2 show that if only ether solvents are used for modification, the improvement on battery storage stability is limited, and ether solvents alone cannot significantly improve battery storage stability.

[0090] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for modifying fluorinated carbon, characterized in that, The modification method includes: Fluorinated carbon and a composite solvent are mixed and modified, and then the mixture is separated into solid and liquid components to obtain the modified fluorinated carbon. The composite solvent includes water and ether solvents. In the composite solvent, the mass ratio of water to ether solvent is (50-60):(40-50); The solid-liquid mass ratio of the fluorinated carbon and the composite solvent is (1 / 10-1 / 2):1; The modification treatment is performed at a temperature of 40-70℃ for 4-48 hours. The ether solvent is ethylene glycol dimethyl ether or diethylene glycol dimethyl ether.

2. The modification method according to claim 1, characterized in that, The modification treatment is performed at a temperature of 40-60℃.

3. The modification method according to claim 1, characterized in that, The modification process is accompanied by stirring at a rate of 100-1000 r / min.

4. The modification method according to claim 1, characterized in that, The modification method specifically includes: Fluorinated carbon is added to a composite solvent consisting of water and ether solvents, and then stirred to carry out the modification treatment. After solid-liquid separation, drying and dispersion, the modified fluorinated carbon is obtained.

5. A modified fluorinated carbon, characterized in that, The modified fluorinated carbon is prepared by the modification method according to any one of claims 1-4.

6. The modified fluorinated carbon according to claim 5, characterized in that, The cyclic voltammetry curve of the modified fluorinated carbon shows one reduction peak in the voltage range of 2-3V.

7. A lithium / carbon fluoride battery, characterized in that, The positive electrode of the lithium / fluorinated carbon battery comprises the modified fluorinated carbon as described in claim 5 or 6.

8. The lithium / carbon fluoride battery according to claim 7, characterized in that, The lithium / carbon fluoride battery also includes a lithium metal anode, an electrolyte, and a separator.

9. The lithium / carbon fluoride battery according to claim 8, characterized in that, The concentration of the electrolyte is 0.5-2 mol / L.

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