CN101924246A - Preparation method of composite solid electrolyte based on carbonized polyphosphazene micro-nano material - Google Patents

Abstract

A method for preparing a composite solid electrolyte based on carbonized polyphosphazene micro-nano material in the technical field of lithium batteries, by dispersing the carbonized polyphosphazene micro-nano material in acetonitrile, adding polyethylene oxide and lithium hypochlorite in sequence, and stirring uniformly , and then cast the mixed solution into a polytetrafluoroethylene template to obtain a composite solid polymer electrolyte. Compared with the existing electrolyte, the conductivity and lithium ion migration number of the product of the present invention are improved, and at the same time, the mechanical properties are good, and there is good electrochemical performance. stability.

Description

Preparation method of composite solid electrolyte based on carbonized polyphosphazene micro-nano material

technical field

The invention relates to a dielectric in the technical field of lithium batteries and a preparation method thereof, in particular to a preparation method of a composite solid electrolyte based on carbonized polyphosphazene micro-nano materials.

Background technique

All-solid-state lithium-ion polymer batteries are expected to become one of the most promising advanced power sources in the future due to their high energy density, excellent cycle performance, processability into arbitrary shapes, and safety and reliability. PEO-based polymer electrolytes have long received widespread attention because they may replace liquid electrolytes in traditional lithium-ion batteries as electrolyte materials in all-solid-state lithium-ion polymer batteries. Actively developing polymer electrolytes with high room temperature ionic conductivity and lithium ion migration number TLi ⁺ , good electrode interface stability, excellent mechanical and processing properties, and a wide electrochemical stability window is the key to the development of all-solid-state lithium-ion polymer batteries. important basis. A large number of studies have shown that the above properties can be appropriately improved after the composite polymer electrolyte is obtained by mixing inorganic fillers into the PEO-based polymer electrolyte. However, the traditional inorganic ceramic fillers and layered fillers reported in the current literature have little effect on improving the ionic conductivity and lithium ion migration number of polymer electrolytes. Therefore, the development can more effectively improve the ionic conductivity of PEO-based polymer electrolytes. The new filler with lithium ion transfer number is of great significance to the practical application of all solid-state lithium ion polymer batteries.

Since the 1980s, with the discovery of some new carbon materials with nanometer size, such as C ₂₀ , C ₆₀ and other fullerenes, carbon nanotubes, carbon nanofibers, etc., carbon materials have become increasingly popular due to their morphological diversity. caused widespread concern in the world. In recent years, spherical carbon materials with sizes ranging from nanometer to micrometer and different structures have been successfully prepared by different methods, greatly enriching the research field of carbon materials. Carbon microspheres, carbon nanotubes, and carbon fibers usually have high specific surface area, large pore volume, chemical stability, and good mechanical properties, so they have broad application prospects. The pore size of most porous carbons is less than 2nm, and they are microporous materials. Their microporous properties can be well applied in adsorption, separation, supercapacitors and small molecule catalytic reactions. At present, such materials are mainly obtained from precursors through carbonization and then activation.

Polyphosphazene micro-nano materials are a novel type of organic-inorganic hybrid micro-nano materials based on ring-crosslinked polyphosphazenes. Polyphosphazene micro-nano materials have different shapes, and their constituent units are mainly organic components. It has good compatibility and affinity with various polymer materials, and has many advantages over inorganic nanomaterials. Moreover, polyphosphazene micro-nano materials also have the advantage of easy chemical modification of polyphosphazene materials, and surfaces with various chemical properties can be obtained through simple nucleophilic substitution reactions. Using polyphosphazene micro-nano materials as fillers to design composite polymer electrolytes is expected to obtain new composite polymer electrolytes that combine the advantages of polyphosphazene electrolytes, and obtain better electrochemical performance than traditional inorganic nanoparticle-doped composite polymer electrolytes. performance, greatly expanding the development and application of composite polymer electrolytes.

After searching the literature of the prior art, it was found that Zhang Jiawei, Huang Xiaobin, Tang Xiaozhen, etc. mentioned the use of PEO ₈ -LiClO ₄ PEO ₈ -LiClO ₄ -PZSMS (x%) series composite polymer electrolytes were prepared using polyphosphazene microspheres as the matrix, and the conductivity, lithium ion migration number and electrochemical stability window of the electrolyte were measured. The results show that the polyphosphazene micro-nano filler has good compatibility with the PEO matrix, and the introduction of polyphosphazene microspheres significantly improves the conductivity of the composite solid electrolyte, reaching 1.2×10 ^-5 S cm at 25°C ^-1 , the lithium ion migration number is also increased, reaching 0.29, and the electrochemical stability window is 5.0V. However, the polyphosphazene micro-nanomaterials generated by in-situ polymerization have a small surface area and fewer voids, which limits the further improvement of the electrical properties of the solid composite polymer electrolyte. Therefore, using high porosity but still containing polyphosphazene Particles that hybridize atoms to promote the electrical properties of solid composite polymer electrolytes have become a valuable research direction as fillers. Polyphosphazene micro-nanoparticles can not only prepare polymorphic polyphosphazene nanotubes, nanofibers and polyphosphazene microspheres under mild and simple conditions, but also facilitate surface chemical modification and elemental analysis. The results show that these micro-nano materials have a carbon content as high as about 45%. These polymer materials can be carbonized at high temperature under inert atmosphere conditions to drive out non-carbon components, quickly obtain carbonized materials, and obtain porous carbon nanotubes, carbon nano fibers and carbon microspheres. This provides a new way for the development of nanocomposite polymer electrolytes.

Contents of the invention

Aiming at the above-mentioned deficiencies in the prior art, the present invention provides a method for preparing a composite solid electrolyte based on carbonized polyphosphazene micro-nano materials, using polyphosphazene nanofibers, polyphosphazene nanotubes and polyphosphazene microspheres as precursors body, carbon nanofibers, carbon nanotubes and carbon microspheres were prepared by high-temperature carbonization, and a composite polymer electrolyte was prepared with the carbonized material as a filler, and a solid composite polymer with improved conductivity and lithium ion migration number was obtained. electrolyte. The composite solid electrolyte of the invention has high electrical conductivity, good mechanical properties and good electrochemical stability.

The present invention is achieved through the following technical scheme. The present invention disperses the carbonized polyphosphazene micro-nano material in acetonitrile, then adds polyoxyethylene and lithium hypochlorite in sequence and stirs evenly with magnetic force, and then casts the mixed solution onto polytetrafluoroethylene A composite solid polymer electrolyte is obtained in the template.

The mass percentage of polyethylene oxide and carbonized polyphosphazene micro-nano material is 0.1% to 1%;

The molar percentage of the oxygen atoms in the polyethylene oxide and the lithium atoms in the lithium hypochlorite is: 8% to 20%;

The dispersion refers to: ultrasonic dispersion for 10 to 60 minutes;

The magnetic stirring time is 5-25 hours.

The said casting into the polytetrafluoroethylene template refers to: casting the mixed solution onto the polytetrafluoroethylene template to volatilize acetonitrile, and then drying in a vacuum environment at 50° C. for 24 to 48 hours.

The molecular weight Mw of the polyethylene oxide is 100,000-1000,000;

The molecular weight Mw of described lithium hypochlorite is 106.5;

The filler molecular weight Mw of the carbonized polyphosphazene micro-nano material is 500-1380, specifically polyphosphazene microspheres, nanotubes or nanofibers carbonized at high temperature in an inert atmosphere.

The invention emphasizes the improvement effect of different carbonized polyphosphazene micro-nano materials on composite solid polymer electrolyte (CPE). The morphology and content of carbonized polyphosphazene micro-nanomaterials have an important impact on the conductivity, lithium ion migration number and electrochemical stability window of the composite polymer electrolyte.

The composite solid polymer electrolyte prepared according to the present invention, especially the composite solid polymer electrolyte using carbonized polyphosphazene micro-nano material as filler, not only has high room temperature conductivity, but also has good mechanical properties, does not contain any liquid components, and has a smooth and flat surface , with uniform internal composition, high lithium ion migration number and electrochemical stability window.

Description of drawings

Figure 1 is a scanning electron microscope SEM photo of carbonized polyphosphazene microspheres.

Fig. 2 is a scanning electron microscope SEM photo of carbonized polyphosphazene nanotubes.

Fig. 3 is a scanning electron microscope SEM picture of carbonized polyphosphazene nanofibers.

4 is a scanning electron microscope SEM photo of the composite solid polymer electrolyte doped with carbonized polyphosphazene microspheres in Example 1.

Fig. 5 is the conductivity-temperature curve of adding different amounts of carbonized polyphosphazene microspheres into the PEO ₁₀ -LiClO ₄ system. X=0.5 means that the added carbonized polyphosphazene microspheres are 0.5%, and X=1 means that the added carbonized polyphosphazene microspheres are 1%.

Fig. 6 is the conductivity-temperature curve of adding different amounts of carbonized polyphosphazene nanotubes into the PEO ₁₀ -LiClO ₄ system. X=0.5 means that the added carbonized polyphosphazene nanotube is 0.5%, and X=1 means that the added carbonized polyphosphazene nanotube is 1%.

Fig. 7 is the conductivity-temperature curve of adding different amounts of carbonized polyphosphazene nanofibers into the PEO ₁₀ -LiClO ₄ system. X=0.5 means that the added carbonized polyphosphazene nanofiber is 0.5%, and X=1 means that the added carbonized polyphosphazene nanofiber is 1%.

Detailed ways

The embodiments of the present invention are described in detail below. This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operating procedures are provided, but the protection scope of the present invention is not limited to the following implementation example.

Example 1

Step 1, weighing 0.005g of carbonized polyphosphazene microspheres (the mass of carbonized polyphosphazene microspheres is 0.5% of the mass of PEO) was added to 30ml of acetonitrile, and ultrasonically dispersed for 15 minutes;

Step 2, weigh 1.0 g of PEO (Mw ~ 300,000) and 0.242 g of LiClO ₄ (the O/Li molar ratio of PEO to LiClO ₄ is 10:1) and add them to the acetonitrile dispersion of carbonized polyphosphazene microspheres , stirring and dissolving with a magnetic stirrer for 8 hours;

Step 3, casting the obtained mixed solution onto a polytetrafluoroethylene template, and volatilizing the solvent for 6 hours;

Step 4, transfer the polymer electrolyte membrane obtained in Step 3 to a vacuum drying oven, and continue drying at 50° C. for 24 hours to obtain a composite solid polymer electrolyte.

Implementation effect of this example: Figure 1 is a scanning electron microscope SEM photo of the prepared carbonized polyphosphazene microspheres. It can be seen from the figure that the diameter distribution of polyphosphazene microspheres is uniform and the degree of dispersion is very good; Fig. 4 is a scanning electron microscope SEM photo of the prepared composite solid polymer electrolyte doped with carbonized polyphosphazene microspheres. It can be seen from the figure that the surface of the membrane is smooth and uniform, which proves that the carbonized polyphosphazene microspheres and the PEO polymer electrolyte matrix have good compatibility. Fig. 5 is the conductivity-temperature curve of adding different amounts of carbonized polyphosphazene microspheres into the PEO ₁₀ -LiClO ₄ system. The room temperature conductivity calculated through the characterization of the composite polymer electrolyte is 2.7×10 ^-5 S cm ^-1 , which is two orders of magnitude higher than that of pure PEO, the lithium ion migration number is 0.44, and the electrochemical stability window is 5.0V . The above characterization results show that the composite polymer electrolyte has high room temperature conductivity, high electrochemical stability window, and high lithium ion migration number, and can be used as a solid electrolyte material for lithium ion batteries.

Example 2

Step 1, weighing 0.0025g of carbonized polyphosphazene nanotubes (the mass of carbonized polyphosphazene nanotubes is 0.25% of the mass of PEO) was added to 40ml of acetonitrile, and ultrasonically dispersed for 20 minutes;

Step 2, weigh 1.0 g of PEO (Mw ~ 400,000) and 0.3025 g of LiClO ₄ (the O/Li molar ratio of PEO to LiClO ₄ is 8:1) and add them to the acetonitrile dispersion of carbonized polyphosphazene nanotubes , stirring and dissolving with a magnetic stirrer for 9 hours;

Step 3, casting the obtained mixed solution on a polytetrafluoroethylene template, volatilizing the solvent for 7 hours,

Step 4, transfer the polymer electrolyte membrane obtained in Step 3 to a vacuum drying oven, and continue drying at 50° C. for 28 hours to obtain a composite solid polymer electrolyte.

Implementation effect of this example: the characterization of the composite solid polymer electrolyte is as in Example 1. Fig. 2 is a scanning electron microscope SEM photo of the prepared carbonized polyphosphazene nanotubes. It can be seen from the figure that the diameter distribution of carbonized polyphosphazene nanotubes is uniform, the length of polyphosphazene nanotubes after carbonization is several microns, the outer diameter of both ends is about 150 nanometers, and the dispersion is very good; Conductivity-temperature curves of different amounts of carbonized polyphosphazene nanotubes added to PEO ₁₀ -LiClO ₄ system. The room temperature conductivity of the composite polymer electrolyte is 2.67×10 ^-5 S cm ^-1 , the lithium ion migration number is 0.5, and the electrochemical stability window is 5.0V. The composite polymer electrolyte also has high room temperature conductivity, high electrochemical stability window, and high lithium ion migration number, and can be used as a solid electrolyte material for lithium ion batteries.

Example 3

Step 1: Weigh 0.0075g of carbonized polyphosphazene nanofibers (the mass of carbonized polyphosphazene nanofibers is 0.75% of the mass of PEO) and add it to 45ml of acetonitrile, and ultrasonically disperse for 30 minutes;

Step 2, weigh 1.0 g of PEO (Mw ~ 500,000) and 0.2017 g of LiClO ₄ (the O/Li molar ratio of PEO to LiClO ₄ is 12:1) and add them to the acetonitrile dispersion of carbonized polyphosphazene nanofibers , stirring and dissolving with a magnetic stirrer for 10 hours;

Step 3, casting the obtained mixed solution on the polytetrafluoroethylene template, volatilizing the solvent for 8 hours,

Step 4, transfer the polymer electrolyte membrane obtained in Step 3 to a vacuum drying oven, and continue drying at 50° C. for 32 hours to obtain a composite solid polymer electrolyte.

Implementation effect of this example: the characterization of the composite solid polymer electrolyte is as in Example 1. Figure 3 is a scanning electron microscope SEM photo of the prepared carbonized polyphosphazene nanofibers. It can be seen from the figure that the diameter distribution of polyphosphazene nanofibers is uniform, the length of polyphosphazene nanofibers after carbonization is several microns, the outer diameter of both ends is about 200-500 nanometers, and the dispersion is very good; Conductivity-temperature curves of different amounts of carbonized polyphosphazene nanofibers added to PEO ₁₀ -LiClO ₄ system. The room temperature conductivity of the composite polymer electrolyte is 3.25×10 ^-5 S cm ^-1 , the lithium ion migration number is 0.51, and the electrochemical stability window is 5.0V. The composite polymer electrolyte also has high room temperature conductivity, high electrochemical stability window, and high lithium ion migration number, and can be used as a solid electrolyte material for lithium ion batteries.

Claims (10)

1. A method for preparing a composite solid electrolyte based on carbonized polyphosphazene micro-nano material, characterized in that, after the carbonized polyphosphazene micro-nano material is dispersed in acetonitrile, polyethylene oxide and lithium hypochlorite are added successively and magnetically stirred uniform, and then cast the mixed solution into a polytetrafluoroethylene template to obtain a composite solid polymer electrolyte. 2. The preparation method of the composite solid electrolyte based on carbonized polyphosphazene micro-nano material according to claim 1, characterized in that, the mass percentage of polyethylene oxide and carbonized polyphosphazene micro-nano material is 0.1%～1 %. 3. the preparation method of the composite solid electrolyte based on carbonized polyphosphazene micro-nano material according to claim 1, is characterized in that, the mole of the lithium atom in the oxygen atom in described polyethylene oxide and lithium hypochlorite The percentage is: 8% to 20%. 4 . The method for preparing a composite solid electrolyte based on carbonized polyphosphazene micro-nano material according to claim 1 , wherein the dispersion refers to ultrasonic dispersion for 10 to 60 minutes. 5 . The method for preparing a composite solid electrolyte based on carbonized polyphosphazene micro-nano material according to claim 1 , wherein the magnetic stirring is performed for 5 to 25 hours. 6 . 6. The method for preparing a composite solid electrolyte based on carbonized polyphosphazene micro-nano materials according to claim 1, wherein said casting into a polytetrafluoroethylene template means: casting the mixed solution into a polytetrafluoroethylene template Acetonitrile was volatilized on the vinyl fluoride template, and then dried in a vacuum environment at 50° C. for 24 to 48 hours. 7. The method for preparing composite solid electrolyte based on carbonized polyphosphazene micro-nano material according to claim 1, characterized in that the molecular weight Mw of the polyethylene oxide is 100,000-1,000,000. 8 . The method for preparing a composite solid electrolyte based on carbonized polyphosphazene micro-nano material according to claim 1 , wherein the molecular weight Mw of the lithium hypochlorite is 106.5. 9. The method for preparing a composite solid electrolyte based on carbonized polyphosphazene micro-nano material according to claim 1, characterized in that the filler molecular weight Mw of the carbonized polyphosphazene micro-nano material is 500-1380, specifically Polyphosphazene microspheres, nanotubes or nanofibers carbonized at high temperature in an inert atmosphere. 10. A composite solid electrolyte, characterized in that it is obtained by the preparation method according to any one of the preceding claims.

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