Sulfide modified carbon fluoride composite electrode and preparation method thereof

Abstract

The invention relates to a sulfide modified carbon fluoride composite electrode and a preparation method thereof, and belongs to the technical field of battery material preparation. Sulfide and a carbon fluoride material are subjected to ball milling to obtain a sulfide modified carbon fluoride composite material; adding the composite material and a conductive agent into a polymer binder solution to obtain sulfide modified carbon fluoride composite electrode slurry; and coating a current carrier with the slurry, and carrying out vacuum drying to obtain the sulfide modified carbon fluoride composite electrode. According to the invention, the surface morphology and conductive structure of the carbon fluoride material particles are modified by the high-conductive sulfide through a simple ball milling method. The sulfide has multivalent states and structural defect vacancies, not only stabilizes a high discharge platform of the carbon fluoride material at the initial stage of discharge, but also increases a reaction platform at the final stage of discharge, so that the discharge capacity of the carbon fluoride material is effectively improved. And meanwhile, the conductivity and the ion migration rate of the carbon fluoride material are improved, so that the composite electrode has a high working voltage platform and energy output performance under a high-rate discharge condition.

Description

Technical Field

[0001] This invention relates to the field of battery material preparation technology, specifically to a sulfide-modified fluorinated carbon composite electrode and its preparation method. Background Technology

[0002] Fluorocarbon (CF) x The high theoretical specific capacity and excellent stability of this material make it a high-safety lithium / carbon fluoride (Li / CF) material. x The key characteristic of Li / CF core cathode material in primary batteries is attributed to the high bond energy of the CF bond. However, its high stability also severely limits the performance of Li / CF core cathode materials. x The battery's power output performance, especially with the increase of fluorine content, is characterized by a low operating voltage platform (≤3.0 V), high internal resistance leading to large heat generation, and significant polarization accompanied by significant voltage hysteresis. As a result, the actual energy density of this battery system is far lower than the theoretical value, limiting its practical application range.

[0003] To fully utilize CF x Superior specific capacity while also improving power performance is currently achieved primarily through technical strategies such as optimizing carbon source materials, controlling material fluorination degree, and preparing composite materials, without affecting CF3. x Achieving CF under the premise of actual energy density of materials x Improved material conductivity. Carbon source material optimization primarily involves morphology design and particle size optimization, but mass production faces challenges in industrialization. Fluorination control includes designing the fluorine content of the carbon source material and pyrolysis reprocessing of the fluorinated carbon material, requiring a balance between capacity and rate performance. (For use in CF...) x Composite material preparation strategies mainly involve coating or mixing with conductive carbon, metal oxides with high theoretical discharge platforms, etc. However, the introduction of conductive carbon cannot directly improve the capacity of the composite material. Although metal oxides have the advantage of high voltage platforms such as manganese dioxide (≥3.5 V) and vanadium pentoxide (≥3.2 V), and are often used in lithium primary battery cathode materials, they can improve the initial discharge platform voltage of fluorinated carbon materials to some extent. However, due to the strong ionic bonds that restrict the movement of electrons or holes, the intrinsic conductivity of these metal oxides is not high (10). -4 ~10 -6 (S / cm), cannot fundamentally improve CF x The electrical conductivity of composite materials, thereby synergistically improving CF x Rate performance of composite materials.

[0004] Therefore, there is an urgent need to develop a method that can improve CF x A novel composite electrode structure that combines conductivity with high capacity. Summary of the Invention

[0005] The purpose of this invention is to provide a sulfide-modified fluorinated carbon composite electrode and its preparation method, so as to solve the problems of poor conductivity, low discharge platform and poor rate performance of existing fluorinated carbon electrodes.

[0006] In a first aspect, to achieve the above objectives, the present invention adopts the following technical solution: a sulfide-modified fluorinated carbon composite electrode, comprising a sulfide-modified fluorinated carbon composite material, a conductive agent and a polymer binder, wherein the composite material is obtained by ball milling sulfide and fluorinated carbon.

[0007] Furthermore, by weight percentage, the sulfide-modified fluorinated carbon composite material accounts for 80% to 95% of the total mass of the electrode, the polymer binder accounts for 3% to 10%, and the conductive agent accounts for 2% to 10%.

[0008] Furthermore, the fluorinated carbon material is one of fluorinated carbon nanotubes, fluorinated graphite, fluorinated carbon nanofibers, fluorinated graphene, and fluorinated carbon nanospheres, with a fluorination degree of... x It is 0.8~1.

[0009] Furthermore, the sulfide is one of cobalt disulfide, iron disulfide, nickel disulfide, manganese disulfide, and molybdenum disulfide.

[0010] Furthermore, the conductive agent is one or two of graphene, carbon nanotubes, Ketjen black, conductive carbon black, acetylene black, and activated carbon.

[0011] Furthermore, the polymeric binder is one of polyvinylidene fluoride, polyethersulfone, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, polyvinylpyrrolidone, polystyrene, polyvinyl alcohol, and polyethylene glycol.

[0012] Secondly, the present invention also provides a method for preparing the sulfide-modified fluorinated carbon composite electrode, comprising the following steps: (1) Mix sulfide and fluorinated carbon materials at a mass ratio of 1:1 to 1:10 and ball mill for 6 to 12 hours to obtain sulfide-modified fluorinated carbon composite material; (2) Add the polymer binder to the organic solvent to prepare a solution with a viscosity of 12000–18000 mPa·s. -1 Adhesive solution; (3) Add the composite material to the binder solution, stir and disperse for 30 to 60 minutes, add the conductive agent, and continue vacuum stirring for 4 to 12 hours to obtain the electrode slurry; (4) The slurry is coated on the carrier fluid, dried at 60-100℃ for 0.5-1 hour, and then transferred to a vacuum oven at 100-120℃ for 10-12 hours to obtain the composite electrode.

[0013] Furthermore, the organic solvent is one of N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethyl sulfoxide.

[0014] Furthermore, the carrier fluid is one of carbon-coated aluminum foil, carbon-coated copper foil, copper foil, aluminum foil, carbon cloth, and carbon fiber paper.

[0015] The principles and beneficial technical effects of this solution are as follows: This invention utilizes a simple ball milling method, employing highly conductive sulfides to process fluorinated carbon (CF2). x The surface morphology and conductive structure of the cathode material were modified and controlled to achieve the preparation of high-conductivity sulfide-modified fluorinated carbon composite cathode materials. Sulfides contain numerous sulfur vacancies or interstitial metal atoms, which provide additional ion-carrying storage sites and multiple discharge plateaus, thereby improving the CF2 performance. x The discharge capacity of the composite material at the initial and final stages of discharge. Furthermore, due to the inherently low electronegativity of sulfur (2.58 eV), the chemical bonds in metal sulfides exhibit stronger covalent properties, which facilitates electron delocalization and migration, thus resulting in high intrinsic conductivity (10⁻⁶ eV). 2 ~10 5 S / cm). Through metal sulfides on CF x The surface of the cathode material is modified to alter the electron cloud arrangement of the CF bonds, thereby achieving control over the CF bonds. x The reconstruction of the particle conductive structure results in excellent rate performance. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the preparation process of the sulfide-modified fluorinated carbon composite electrode of the present invention.

[0017] Figure 2 SEM images of the sulfide-modified fluorinated carbon composite material in Example 1: (a) shows the overall morphology; (b) shows the magnified morphology of a single particle.

[0018] Figure 3 XRD of the crystal structure of the sulfide-modified fluorinated carbon composite electrode in Example 1.

[0019] Figure 4 The discharge curves of the sulfide-modified fluorinated carbon composite electrode and the modified fluorinated carbon electrode at 0.2C in Example 1 are shown. Detailed Implementation

[0020] The following detailed description illustrates the specific implementation method: Example 1, a method for preparing a sulfide-modified fluorinated carbon composite electrode, includes the following steps: (1) Take cobalt disulfide and fluorinated graphite (fluorination degree) x=0.9) were mixed at a mass ratio of 10:90 and ball-milled for 8 hours to obtain CoS2 / CF x Composite materials; (2) Add the PVDF binder to the NMP solvent to prepare a solution with a viscosity of approximately 15000 mPa·s. -1 The solution; (3) Add the composite material to the binder solution, stir for 40 minutes, then add the carbon nanotube conductive agent and stir under vacuum for 6 hours; (4) The slurry is coated on carbon-coated aluminum foil, dried at 80°C for 40 minutes, and then dried at 100°C for 11 hours in a vacuum oven to obtain a composite electrode.

[0021] Example 2: A method for preparing a sulfide-modified fluorinated carbon composite electrode, comprising the following steps: (1) Take ferric disulfide and fluorinated graphite (fluorination degree) x =0.8) Mix at a mass ratio of 10:90 and ball mill for 12 hours; (2) Add the polyvinylpyrrolidone binder to the N-methylpyrrolidone solvent to prepare a solution with a viscosity of approximately 18000 mPa·s. -1 The solution; (3) Add the composite material to the binder solution, stir for 60 minutes, then add the carbon nanotube conductive agent and stir under vacuum for 12 hours; (4) The slurry is coated on aluminum foil, dried at 60°C for 60 minutes, and then dried at 120°C in a vacuum oven for 12 hours to obtain a composite electrode.

[0022] Example 3: A method for preparing a sulfide-modified fluorinated carbon composite electrode, comprising the following steps: (1) Take molybdenum disulfide and fluorinated graphite (fluorination degree) x =1) Mix at a mass ratio of 20:80 and ball mill for 6 hours; (2) Add the polyvinyl alcohol binder to N,N-dimethyl sulfoxide solvent to prepare a solution with a viscosity of approximately 12000 mPa·s. -1 The solution; (3) Add the composite material to the binder solution, stir for 30 minutes, then add the carbon nanotube conductive agent and stir under vacuum for 4 hours; (4) The slurry is coated on carbon cloth, dried at 100°C for 30 minutes, and then dried at 110°C for 10 hours in a vacuum oven to obtain a composite electrode.

[0023] result: Comparative example: Unmodified fluorinated carbon electrodes were prepared. The difference from Example 1 is that the fluorinated graphite was not treated with sulfides (CF). x Specifically: Mix PVDF binder with NMP to prepare a solution with a viscosity of approximately 15000 mPa·s. -1The solution; fluorinated graphite (fluoride degree) x =0.9) was added to the binder solution, stirred for 40 minutes, and then carbon nanotube conductive agent was added. The mixture was stirred under vacuum for 6 hours. The slurry was coated on carbon-coated aluminum foil, dried at 80°C for 40 minutes, and then dried in a vacuum oven at 100°C for 11 hours to obtain the modified fluorinated carbon electrode.

[0024] Scanning electron microscopy (SEM) revealed that metal sulfide nanoparticles were uniformly distributed on the surface of fluorinated carbon particles in the sulfide-modified fluorinated carbon composite electrode. Figure 2 In addition, X-ray diffraction (XRD) analysis ( Figure 3 The crystal structure of the sulfide-modified fluorinated carbon composite electrode. XRD patterns show a typical CoS2 phase (JCPDS 04-003-1962, P21 / n), and CF... x The diffraction peaks at 13.60° and 41.20° (marked with black asterisks) correspond to CF, respectively. x The (002) and (100) crystal planes. The introduction of CoS2 particles significantly improved the CoS2 / CF ratio. x Electrical conductivity of composite materials. Under a pressure of 150 MPa, pure CF... x The sample's conductivity is much lower than the device's detection range (10). -15 S cm -1 This indicates that it is close to an insulating material; under the same pressure, CoS2 / CF x The electrical conductivity of the composite material is 5.12 × 10⁻⁶. -7 S cm -1 In lithium / carbon fluoride battery testing ( Figure 4 The composite electrode achieved a discharge specific capacity of 800.03 mAh / g at a 0.2C rate, which is 13.11% higher than that of the unmodified fluorinated carbon material (707.32 mAh / g). It also added a voltage plateau around 2.14V, significantly improving the energy density of the entire sulfide-modified fluorinated carbon composite electrode.

[0025] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A sulfide-modified fluorinated carbon composite electrode, characterized in that, It includes sulfide-modified fluorocarbon composite materials, conductive agents, and polymeric binders, wherein the sulfide-modified fluorocarbon composite materials are obtained by ball milling sulfides and fluorocarbons.

2. The sulfide-modified fluorinated carbon composite electrode according to claim 1, characterized in that: By weight percentage, the sulfide-modified fluorinated carbon composite material accounts for 80% to 95% of the total mass of the electrode, the polymer binder accounts for 3% to 10%, and the conductive agent accounts for 2% to 10%.

3. A sulfide-modified fluorinated carbon composite electrode according to claim 1 or 2, characterized in that: The fluorinated carbon material is one of the following: fluorinated carbon nanotubes, fluorinated graphite, fluorinated carbon nanofibers, fluorinated graphene, and fluorinated carbon nanospheres, with a fluorination degree of... x It is 0.8~1.

4. A sulfide-modified fluorinated carbon composite electrode according to claim 1 or 2, characterized in that: The sulfide is one of cobalt disulfide, iron disulfide, nickel disulfide, manganese disulfide, and molybdenum disulfide.

5. A sulfide-modified fluorinated carbon composite electrode according to claim 1 or 2, characterized in that: The conductive agent is one or two of graphene, carbon nanotubes, Ketjen black, conductive carbon black, acetylene black, and activated carbon.

6. A sulfide-modified fluorinated carbon composite electrode according to claim 1 or 2, characterized in that: The polymeric binder is one of polyvinylidene fluoride, polyethersulfone, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, polyvinylpyrrolidone, polystyrene, polyvinyl alcohol, and polyethylene glycol.

7. A method for preparing a sulfide-modified fluorinated carbon composite electrode as described in claim 2, characterized in that, Includes the following steps: (1) Mix sulfide and fluorinated carbon materials at a mass ratio of 1:1 to 1:10 and ball mill for 6 to 12 hours to obtain sulfide-modified fluorinated carbon composite material; (2) Add the polymer binder to the organic solvent to prepare a solution with a viscosity of 12000–18000 mPa·s. -1 Adhesive solution; (3) Add the composite material to the binder solution, stir and disperse for 30 to 60 minutes, add the conductive agent, and continue vacuum stirring for 4 to 12 hours to obtain the electrode slurry; (4) The slurry is coated on the carrier fluid, dried at 40-100℃ for 0.5-1 hour, and then transferred to a vacuum oven at 100-120℃ for 10-12 hours to obtain the composite electrode.

8. The preparation method according to claim 7, characterized in that, The organic solvent is one of N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylmethyl sulfoxide.

9. The preparation method according to claim 7, characterized in that, The carrier fluid is one of the following: carbon-coated aluminum foil, carbon-coated copper foil, copper foil, aluminum foil, carbon cloth, and carbon fiber paper.

Images