CN111416146A - A kind of modified nano-silica and its preparation method and application - Google Patents

Abstract

The invention discloses a modified nano-silicon dioxide and a preparation method thereof. The modified nano-silica is prepared by the following method: the silica nanoparticles bridged by the pyromellitic acid diimide are obtained by reacting amino-functional silica nanoparticles with dianhydride compounds. The modified nano-silica provided by the present invention and the preparation method and application thereof have the following advantages: 1. The silica nanoparticles of the pyromellitic acid diimide bridge are synthesized by an efficient and simple amidation reaction, which is simple to operate, and Equipment requirements are low. 2. The silica nanoparticles bridged by the pyromellitic acid diimide prepared by this method have good compatibility in polymers, and the composite solid polymer electrolyte prepared therefrom has good ionic conductivity Rate.

Description

A kind of modified nano-silica and its preparation method and application

Technical field:

The invention belongs to the technical field of solid polymer electrolyte materials, in particular to a solid polymer electrolyte doped with modified nano-fillers and a preparation method thereof.

Background technique:

Lithium-ion battery electrolyte material refers to a material system that has excellent ionic conductivity, while taking into account functional properties such as interface properties, electrochemical stability, thermal stability, safety, and mechanical properties. At present, LiPF ₆ -carbonate-based electrolytes widely used in commercial lithium-ion batteries have high ionic conductivity and good wettability, but they have defects such as flammability, volatility, and insufficient oxidation resistance, which seriously restrict lithium-ion batteries. Further improvements in safety and energy density. In contrast, solid electrolyte materials contain no or only a small amount of liquid components, which are expected to fundamentally solve the safety problem of batteries.

Organic-inorganic composite solid-state electrolytes are a class of electrolytes formed by introducing inorganic particles into traditional polymer electrolytes. The polymer-based electrolyte can compensate for the volume change of the electrode during charging and discharging through elastic and plastic deformation; while the introduction of inorganic fillers into the polymer electrolyte can inhibit the crystallization of the polymer substrate, the interaction of the reconstituted polymer and lithium ions, Thus, the ionic conductivity, interface properties and mechanical strength of the electrolyte can be effectively improved. However, the compatibility between the inorganic filler and the polymer matrix needs to be improved, and the filler is prone to agglomeration in the polymer matrix, which affects the performance of the electrolyte. The related patented technology is CN03136183.3 which discloses a composite solid polymer electrolyte prepared from a polymer matrix, a lithium salt and modified or unmodified inorganic nanoparticles, wherein the inorganic nanoparticles are made of amino groups, epoxy groups, Acrylate-based silane coupling agents (KH550, KH560, KH570, KH792) are modified; CN03119735 discloses a composite solid polymer electrolyte prepared from polymer matrix, lithium salt and modified inorganic nanoparticles, wherein, The surface groups of inorganic silica nanoparticles can be hydroxyl, trimethylsilyl, polydimethylsilane; CN201710059631 discloses that a mercapto group-containing silane coupling agent is mixed with a polymer substrate to form a film, and then the mercapto group is oxidized to sulfonic acid base, re-in-situ polymerization and lithiation to make composite solid polymer electrolyte membrane containing lithium salt; CN201810072837.5 discloses a composite gel polymer electrolyte membrane with ionic liquid modified nano-silica as filler; CN201910269774 .7 discloses the preparation of self-healing polymer electrolytes by compounding UPy-functionalized silica nanoparticles and copolymers of UpyMA and PEGMA with self-healing function. The above patents all use inorganic silica nanoparticles as composite solid polymer electrolyte fillers. By introducing inorganic silica nanoparticles or surface functionalized modified inorganic nanoparticles, not only the inorganic silica nanoparticles are in the polymer matrix It has good dispersibility and can also endow the composite solid polymer electrolyte with more functional properties.

The polymers prepared by the reaction of diamine compounds and dianhydride monomers are used as binder materials and are used in lithium-ion batteries (CN201410591508.3) or lithium-sulfur batteries (CN201510422483.9) and exhibit excellent electrochemical properties. In this application, amino-functionalized nano-silica is prepared by reacting a commercial amino-functional silane coupling agent with nano-silica particles, and then reacting with dianhydride monomers to prepare pyromellitic acid bisulfite with a three-dimensional structure. Imide-bridged silica nanoparticles, and composited with polyethylene oxide and lithium salts to prepare solid electrolyte materials; pyromellitic acid imide-bridged silica nanoparticles help to improve the performance of such materials. Salt solubility, dispersibility and compatibility in polyethylene oxide polymers, in order to develop composite solid electrolyte materials with high ionic conductivity and excellent mechanical properties.

Invention content:

The purpose of the present invention is to provide a composite solid polymer electrolyte doped with modified silica nanofillers and a preparation method thereof. The silica nanofillers bridged by pyromellitic acid diimide have better dispersion It has good compatibility with polyethylene oxide and good dissociation ability for lithium salts; the composite solid electrolyte material exhibits good ionic conductivity and mechanical properties. The preparation method has simple process and low cost, and is favorable for large-scale production.

To achieve the above object, the technical scheme adopted in the present invention is:

A composite solid-state polymer electrolyte is composed of silica nanoparticles bridged by pyromellitic acid diimide, lithium salt and polyethylene oxide with lithium-conducting ability.

The mass fraction of the silica nanoparticles bridged by the pyromellitic acid diimide in the electrolyte is 1-30%, and the mass fraction of the lithium salt in the electrolyte is 15-50%. The mass fraction of ethylene oxide in the electrolyte is 30-80%.

Further, the silica nanoparticles bridged by the pyromellitic acid diimide are prepared according to a method comprising the following steps:

Step 1: Disperse nano-silica particles in a solvent, wherein the mass fraction of nano-silica in the solvent is 0.1%-10%, add amino-functional silane coupling agent to prepare amino-functional silica Nanoparticles;

Step 2: adding pyromellitic dianhydride to the above reaction solution, according to the mass ratio of amino-functionalized silica nanoparticles and pyromellitic dianhydride is 10:1-1:10, at 60 ℃-120 The reaction is carried out for 0.5-12 hours under the temperature condition of ℃, and the silica nanoparticles bridged by the pyromellitic acid diimide are obtained after centrifugal separation and washing with absolute ethanol and then drying.

Further, in step 1, the nano-silica is hydrophilic nano-silica, the particle size is 7-40 nm, and the specific surface area is 380 m ² /g.

Further, in step 1, the commercial amino-containing silane coupling agent is: γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-2-aminoethyl- γ-aminopropyltrimethoxysilane, γ-diethylenetriaminopropylmethyldimethoxysilane, polyaminoalkyltriethoxysilane.

Further, in step 1, the solvent is one or more of methanol, ethanol, tetrahydrofuran, toluene, xylene, and dichloromethane.

Further, in step 2, the conditions of the centrifugal separation are 8000-14000 r/min.

The lithium salt is lithium perchlorate (LiClO ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium bistrifluoromethanesulfonimide ( LiTFSI), Lithium Bisfluorosulfonimide (LiFSI), Lithium Trifluoromethanesulfonate (LiCF ₃ SO ₃ ), Lithium Bisoxalate Borate (LiBOB), Lithium Difluorooxalate Borate (LiODFB), Lithium Chloride (LiCl) ) one or more of them.

In order to achieve the above purpose, the present invention provides a preparation method of a composite solid polymer electrolyte, the preparation method comprising the following steps:

Step 1: dissolving polyethylene oxide in a solvent to prepare a polymer solution with a mass percentage concentration of 2%-20%, and adding lithium salt;

Step 2: Disperse the silica nanoparticles bridged by the pyromellitic acid diimide into the polymer solution obtained in Step 1, disperse at 20-90° C. for 0.5-24 hours, and cast evenly after the dispersion The film is formed, and the polymer film is obtained after the solvent is volatilized, which is the composite solid electrolyte film of the lithium ion battery;

The solvents in the steps 1 and 2 include acetonitrile, acetone, N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP) or water.

After the composite solid polymer electrolyte is formed into a membrane, the thickness of the membrane is between 50-200um.

The composite solid-state polymer electrolyte is characterized in that its ionic conductivity is 1.9×10 ^-5 S/cm under the temperature condition of 30°C.

The invention has simple operation and high safety, and is suitable for continuous scale production of composite solid polymer electrolytes. In addition, the solid polymer electrolyte prepared by the invention has high ionic conductivity, wide electrochemical stability window, and good compatibility with electrodes, which is beneficial to improve the safety performance of lithium ion batteries. The solid polymer electrolyte membrane prepared from the electrolyte of the present invention has high mechanical strength and good chemical stability, and is also suitable for the design and production of flexible batteries.

The present invention has the following beneficial effects:

The modified silica nano-filler of the present invention can further promote the dissociation of the lithium salt through the bridge of the pyromellitic acid diimide, which is beneficial to the improvement of the ionic conductivity of the solid polymer electrolyte.

The modified silica nanofiller of the present invention is bridged by pyromellitic acid diimide, which can effectively solve the problems of easy agglomeration of nanoparticles and poor compatibility with polymer substrates, and is beneficial to the filler in the matrix. uniform dispersion.

After the polymer film prepared by the invention is assembled into a battery, electrochemical tests show that the solid polymer electrolyte has good ionic conductivity, which is two times higher than that of the composite polymer electrolyte doped with silica nanoparticles without modification. order of magnitude, which can meet the practical application requirements of lithium-ion batteries.

Description of drawings:

FIG. 1 is an infrared contrast spectrum of the silica nanoparticles bridged by the pyromellitic acid diimide prepared in Example 1 of the present invention.

2 is a thermogravimetric diagram of the pyromellitic acid diimide bridged silica nanoparticles prepared in Example 1 of the present invention.

3 is a graph of the ionic conductivity of the silica nanoparticles-doped composite solid-state polymer electrolyte material bridged by pyromellitic acid diimide in Examples 3 and 7 (blank) of the present invention.

Detailed ways:

The following is a further description of the present invention, rather than a limitation of the present invention. After reading the present disclosure, those skilled in the art can make modifications to the various equivalent forms of the present disclosure within the scope defined by the appended claims of the present application.

Example 1

Silica nanoparticles bridged by pyromellitic acid diimide were prepared according to the following steps: Disperse 0.5 g of nano-silica particles in 50 mL of toluene solvent, and ultrasonically disperse uniformly: under stirring conditions, add 1.0 g of γ- Aminopropyltrimethoxysilane was reacted at 120°C for 0.5 hours, and then 1.0 g of pyromellitic dianhydride was added to react at 120°C for 6 hours. After the reaction, centrifuged at 10000r/min and used Washed with ethanol three times and dried at 80°C to obtain silica nanoparticles bridged by pyromellitic acid diimide.

Example 2

Silica nanoparticles bridged by pyromellitic acid diimide were prepared according to the following steps: Disperse 0.5 g of nano-silica particles in 20 mL of ethanol solvent, and ultrasonically disperse uniformly: under stirring conditions, add 2.0 g of N -2-Aminoethyl-γ-aminopropyltrimethoxysilane, reacted at 30°C for 12 hours, then added 4.0 g of pyromellitic dianhydride and reacted at 80°C for 12 hours, after the reaction Centrifuge at 10,000 r/min, wash three times with ethanol, and dry at 80° C. to obtain silica nanoparticles bridged by pyromellitic acid.

Example 3

In an argon glove box, the mass ratio of polyethylene oxide (PEO), the pyromellitic acid imide bridged silica nanoparticles prepared in Example 1, and lithium perchlorate were mixed in a mass ratio of 3:1:1. (LiClO ₄ ) was fully dissolved in acetonitrile, stirred for 24 hours to obtain a uniform viscous solution, then the electrolyte mixture was casted on a polytetrafluoroethylene plate, the solvent was evaporated, and then dried in a vacuum drying box at 80°C for 48 hours . The prepared solid polymer electrolyte membrane doped with nanofillers has a thickness of about 160um, an electrochemical window greater than 5.3V, and an ionic conductivity of 1.9×10 ^-5 S/cm at 30°C.

Example 4

In an argon glove box, the mass ratio of polyethylene oxide (PEO), the pyromellitic acid imide bridged silica nanoparticles prepared in Example 2, lithium bisoxalate borate was mixed in a mass ratio of 5:4:4. (LiBOB) was fully dissolved in acetonitrile, stirred for 24 hours to obtain a uniform viscous solution, and then the electrolyte mixture was casted on a polytetrafluoroethylene plate, the solvent was evaporated, and then dried in a vacuum drying oven at 80 °C for 48 hours. The prepared solid polymer electrolyte membrane doped with nanofillers has a thickness of about 100um, an electrochemical window greater than 5.0V, and an ionic conductivity of 5.3×10 ^-5 S/cm at 30°C.

Example 5

In an argon glove box, the mass ratio of polyethylene oxide (PEO), the pyromellitic acid imide bridged silica nanoparticles prepared in Example 1, lithium hexafluorophosphate (LiPF ₆ ) was fully dissolved in acetonitrile, stirred for 24 hours to obtain a uniform viscous solution, then the electrolyte mixture was casted on a polytetrafluoroethylene plate, the solvent was evaporated, and then dried in a vacuum drying box at 80 °C for 48 hours. The prepared solid polymer electrolyte membrane doped with nanofillers has a thickness of about 70um, an electrochemical window greater than 5.1V, and an ionic conductivity of 3.8×10 ^-5 S/cm at 30°C.

Example 6

Polyethylene oxide (PEO) with a mass ratio of 2:2:3, the silica nanoparticles bridged by the pyromellitic acid imide prepared in Example 1, lithium bistrifluoromethanesulfonimide (LiTFSI) was fully dissolved in distilled water, stirred for 24 hours to obtain a uniform viscous solution, and then the electrolyte mixture was casted on a polytetrafluoroethylene plate, the solvent was evaporated, and then dried in a vacuum drying box at 80 °C for 48 hours. The thickness of the prepared solid polymer electrolyte membrane doped with nano-filler is about 120um, the electrochemical window is greater than 5.0V, and the ionic conductivity is 5.7×10 ^-5 S/cm at 30℃.

Example 7

In an argon glove box, the mass ratio of polyethylene oxide (PEO), silica nanoparticles, and lithium perchlorate (LiClO ₄ ) with a mass ratio of 3:1:1 was fully dissolved in acetonitrile, and a uniform viscosity was obtained after stirring for 24 hours. Then, the electrolyte mixture was casted on a polytetrafluoroethylene plate, the solvent was evaporated, and then dried in a vacuum oven at 80 °C for 48 hours. The thickness of the prepared solid polymer electrolyte membrane doped with nanofillers is about 160um, the electrochemical window is greater than 5.0V, and the ionic conductivity is 3.5×10 ^-7 S/cm at 30°C.

Claims (5)

1. a modified nano-silica particle doped composite solid-state polymer electrolyte, consisting of: modified nano-silica particle, lithium salt and polyethylene oxide; it is characterized in that: the composite solid-state polymer electrolyte is made of The silica nanoparticles bridged by pyromellitic acid diimide are fillers, and the modified silica nanoparticles are beneficial to improve their dispersibility in polyethylene oxide and the interaction with lithium salts; The mass fraction of formic acid imide-bridged silica nanoparticles in the electrolyte is 1-30%, the mass fraction of lithium salt in the electrolyte is 15-50%, and the mass fraction of polyethylene oxide in the electrolyte is 30% -80%. 2. The composite solid-state polymer electrolyte according to claim 1, wherein the silica nanoparticles bridged by the pyromellitic acid diimide are prepared according to a method comprising the following steps: Step 1: Disperse nano-silica particles in a solvent, wherein the mass fraction of nano-silica in the solvent is 0.1%-10%, add amino-functional silane coupling agent to prepare amino-functional silica Nanoparticles; Step 2: adding pyromellitic dianhydride to the above reaction solution, according to the mass ratio of amino-functionalized silica nanoparticles and pyromellitic dianhydride is 10:1-1:10, at 60 ℃-120 The reaction is carried out for 0.5-12 hours under the temperature condition of ℃, and the silica nanoparticles bridged by the pyromellitic acid diimide are obtained after centrifugal separation and washing with absolute ethanol and then drying. 3. The composite solid-state polymer electrolyte according to claim 1, wherein the lithium salt is lithium perchlorate (LiClO ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), lithium tetrafluoroborate (LiBF ₄ ) ), Lithium Hexafluorophosphate (LiPF ₆ ), Lithium Bistrifluoromethanesulfonimide (LiTFSI), Lithium Bisfluoromethanesulfonimide (LiFSI), Lithium Trifluoromethanesulfonate (LiCF ₃ SO ₃ ), Bisoxaloboric Acid One or more of lithium (LiBOB), lithium difluorooxalate borate (LiODFB), and lithium chloride (LiCl). 4. a preparation method of composite solid polymer electrolyte, it is characterized in that this preparation method comprises the steps: Step 1: dissolving polyethylene oxide in a solvent to prepare a polymer solution with a mass percentage concentration of 2%-20%, and adding lithium salt; Step 2: Disperse the silica nanoparticles bridged by the pyromellitic acid diimide into the polymer solution obtained in Step 1, disperse at 20-90° C. for 0.5-24 hours, and cast evenly after the dispersion A film is formed, and a polymer film is obtained after the solvent is volatilized, which is a composite solid electrolyte film of a lithium ion battery. 5. The preparation method of composite solid polymer electrolyte according to claim 4, wherein the solvent in the step 1 and step 2 comprises acetonitrile, acetone, N,N-dimethylformamide (DMF) , N-methylpyrrolidone (NMP) or water.

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