A method for preparing illite-polyvinyl alcohol gel electrolyte

Abstract

The present invention discloses a method for preparing an illite-polyvinyl alcohol gel electrolyte, wherein the raw materials and mass percentages of the gel electrolyte are: 1-50% illite, 5-15% polyvinyl alcohol, and 35-94% deionized water. The present invention relates to the technical field of gel materials, and the beneficial effects of the present invention are that, firstly, the synthesis process of the traditional polymer gel electrolyte requires the participation of an organic solvent, the synthesis process is complicated, and an initiator is required to initiate crosslinking. As natural clay, illite can reduce the cost of raw materials on the one hand, and on the other hand, the characteristic of not requiring the participation of an organic solvent and an initiator in the synthesis reduces the pollution to the environment during the synthesis process.

Description

Technical Field

[0001] The invention relates to the field of gel materials, in particular to a method for preparing illite-polyvinyl alcohol gel electrolyte. Background Art

[0002] As one of the core technologies of new battery, solid electrolyte has great development potential. Through the research and application of solid electrolyte technology, the energy density of batteries can be improved, the cycle life can be extended, and the safety can be improved, thus promoting my country's new energy storage technology to a higher level. Among them, gel polymer is a research hotspot that has both the high ionic conductivity of liquid electrolytes and the safety of solid electrolytes. So far, the polymer materials in gel polymer electrolytes are still mainly dependent on fossil energy production. Due to the poor mechanical properties and narrow working window temperature of traditional polymer gel electrolytes, how to improve the mechanical properties of gel electrolytes is a very important part of ensuring the safety of energy storage devices and extending battery life. The structure of the gel is composed of a cross-linked network of polymer chains and interstitial spaces filled with solvent water. The on-demand regulation of the mechanical properties of the gel is mainly achieved by controlling the structure, cross-linking points and water content of the polymer chains.

[0003] In order to improve the mechanical properties of gel polymers, the introduction of inorganic fillers is a common method. The addition of inorganic fillers reduces the crystallinity of the polymer, thereby directly and effectively improving the ionic conductivity. Usually, fillers are divided into inert fillers and active fillers according to their ionic conductivity. Inert fillers such as Al2O3, SiO2, and montmorillonite are more common inert fillers. Too little addition has limited effect on crystallinity, but too much addition will hinder it. Active fillers include Li7La3Zr2O 12 In traditional high ionic conductivity inorganic ceramic electrolytes such as fluorocarbons, ions are generally preferentially transported through the interface between polymers and fillers, while the intrinsic ionic conductivity of active fillers has a very limited effect on ion transport. Montmorillonite is a two-dimensional layered silicate with high specific surface area and adsorption. Ma Zhonghua and others from the Department of Materials Science and Engineering at Jilin University reported a gel electrolyte synergistically reinforced with montmorillonite and hydroxyethyl cellulose. The montmorillonite-cellulose-PVA gel electrolyte prepared by simple hydrothermal synthesis achieved a 78.6% increase in elongation at break and a higher ionic conductivity (24.6 mScm -1). Lu Chao and others from Columbia University’s Department of Earth and Environmental Engineering used the lamellar structure of montmorillonite to form a directional conductive path that is conducive to ion transport. At the same time, the thermal stability of montmorillonite enhances the heat resistance of the gel electrolyte. At the same time, it exhibits excellent stable energy capacity. Although the mechanical strength and ion transport capacity of the gel polymer electrolyte have been improved to a certain extent, there are still problems such as difficulty in dispersing mineral powders, high cost, complex preparation process, and the need for organic solvents. Compared with montmorillonite, illite has a stronger lattice, and the Al in the silicon-aluminum tetrahedron is 3+ More, there is the possibility of bringing better mechanical properties and ion transport capabilities. In view of the above situation, we propose a method for preparing illite-polyvinyl alcohol gel electrolyte with high ionic conductivity. Summary of the invention

[0004] The purpose of the present invention is to solve the above problems and to design a method for preparing illite-polyvinyl alcohol gel electrolyte.

[0005] The technical solution of the present invention to achieve the above object is a method for preparing illite-polyvinyl alcohol gel electrolyte, wherein the raw materials and their mass percentages of the gel electrolyte are: 1-50% illite, 5-15% polyvinyl alcohol, and 35-94% deionized water.

[0006] The preparation method comprises the following steps:

[0007] Step S1. The illite powder and polyvinyl alcohol are mixed and ground using a mortar for 0.5-2h to obtain a preliminary mixed material;

[0008] Step S2. Mix the water and the preliminary mixed material evenly with a stirrer at a stirring speed of 1000 rpm for 2 to 6 hours to obtain a mixture solution with a uniform texture.

[0009] Step S3: Performing a hydrothermal reaction on the mixture solution to prepare the illite-polyvinyl alcohol gel electrolyte. The temperature of the hydrothermal reaction is 100-220° C., and the time of the hydrothermal reaction is 3-48 hours.

[0010] Step S4. Defoaming the illite-polyvinyl alcohol gel solution by centrifugation. The process parameters of the defoaming by centrifugation include: the rotation speed is set to 8000-12000 rpm.

[0011] Step S5. After removing the bubbles from the upper layer, the illite-polyvinyl alcohol gel solution is placed in a freeze dryer and frozen to obtain a semi-solid colloid with a flat and smooth surface. The process parameters of the vacuum freeze drying include: a freezing temperature of -10 to -80°C and a standing time of 5 to 72 hours.

[0012] Illite is a 2:1 type layered silicate mica clay mineral with a particle size of 0.1~0.5μm, consisting of two silicon-oxygen tetrahedra sandwiching an aluminum-oxygen octahedron.

[0013] The polyvinyl alcohol refers to a polyvinyl alcohol having a mass fraction ranging from 31000 to 124000.

[0014] A method for preparing an illite-polyvinyl alcohol gel electrolyte prepared by the technical solution of the present invention, firstly, the synthesis process of the traditional polymer gel electrolyte requires the participation of an organic solvent, the synthesis process is complicated, and an initiator is required to initiate crosslinking. Illite, as a natural clay, can reduce the cost of raw materials on the one hand, and on the other hand, the characteristic of not requiring the participation of an organic solvent and an initiator in the synthesis reduces the pollution to the environment during the synthesis process.

[0015] Secondly, the silanol groups on the surface of illite combine with the hydroxyl groups on the polyvinyl alcohol chain segments, which effectively improves the mechanical properties of the prepared illite-polyvinyl alcohol gel. Benefiting from the more stable lattice structure of illite, the synthesized illite-polyvinyl alcohol gel has good chemical stability. At the same time, the lamellar structure of illite provides more channels for ion transport, which directly improves the ion transport capacity.

[0016] Finally, since all components in the system are environmentally friendly materials, the problems of non-recyclability and environmental pollution of traditional polymer gel electrolytes are solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the SEM image of the illite-polyvinyl alcohol gel of Example 1;

[0018] Figure 2 This is a schematic diagram of XRD of illite-polyvinyl alcohol gel in Example 1;

[0019] Figure 3 is the stress-strain curve of illite-polyvinyl alcohol gel in Example 1;

[0020] Figure 4 Schematic diagram of the EIS curve of illite-polyvinyl alcohol gel electrolyte in Example 1. DETAILED DESCRIPTION

[0021] The present invention will be described in detail below in conjunction with the accompanying drawings. Figure 1-4 As shown, a method for preparing illite-polyvinyl alcohol gel electrolyte,

[0022] Embodiment 1:

[0023] The invention discloses a method for preparing an illite-polyvinyl alcohol gel electrolyte. The raw materials and mass percentages of the gel electrolyte are: 5% illite, 5% polyvinyl alcohol, the mass fraction of polyvinyl alcohol is 46000, and 90% deionized water.

[0024] Step S1. Take 10 g of illite powder and 10 g of polyvinyl alcohol powder and mix them in a mortar, grind for 0.5 h, and obtain a preliminary mixed material;

[0025] Step S2. Add 180 mL of deionized water to the preliminary mixed material and mix well using a stirrer at a stirring speed of 1000 rpm for 3 h;

[0026] Step S3. Performing a hydrothermal reaction on the aqueous solution of the mixture to prepare the illite-polyvinyl alcohol gel electrolyte. The temperature of the hydrothermal reaction is 120° C., and the time of the hydrothermal reaction is 8 hours;

[0027] Step S4. After cooling to room temperature, the prepared illite-polyvinyl alcohol gel solution is centrifuged to defoam, and the centrifugal speed is set to 10000 rpm;

[0028] Step S5. The defoamed illite-polyvinyl alcohol gel solution was placed in a freeze dryer and frozen for 36 hours at a freeze drying temperature of -70°C to obtain an illite-polyvinyl alcohol gel electrolyte.

[0029] Figure 1 , is a SEM image of the illite-polyvinyl alcohol gel electrolyte product of Example 1. As can be seen from the figure, the illite-polyvinyl alcohol gel electrolyte obtained under the conditions of Example 1 is rich in pores, providing channels for the ion transport process.

[0030] Figure 2 , is the XRD diagram of the illite-polyvinyl alcohol gel electrolyte of Example 1. As can be seen from the figure, the addition of illite effectively reduces the crystallinity of polyvinyl alcohol, which is beneficial to the establishment of ion channels.

[0031] Figure 3 , is the stress-strain curve of the illite-polyvinyl alcohol gel electrolyte of Example 1. As can be seen from the figure, the addition of illite improves the mechanical properties.

[0032] Figure 4 , is a schematic diagram of the EIS curve of the illite-polyvinyl alcohol gel electrolyte of Example 1. As shown in the figure, according to the intercept of the curve with the X-axis, the resistance of the illite-polyvinyl alcohol gel electrolyte of Example 1 is small, which is conducive to the transmission of ions.

[0033] The rest of Example 2 is the same as Example 1, except that the raw materials of the gel electrolyte and their mass percentages are: 5% illite, 15% polyvinyl alcohol, the mass fraction of polyvinyl alcohol is 46000, and 80% deionized water.

[0034] The rest of Example 3 is the same as Example 1, except that the grinding time in step S1 is 2 hours.

[0035] The rest of Example 4 is the same as Example 1, except that the stirring time of step S2 is 6 hours.

[0036] The rest of Example 5 is the same as Example 1, except that the hydrothermal temperature in step S3 is 150°C.

[0037] The rest of Example 6 is the same as Example 1, except that the freezing temperature in step S5 is -50°C.

[0038] Experimental data

[0039] serial number Stress(Mpa) <![CDATA[Ionic conductivity (mS·cm -1 )]]> Example 1 1.23 21.76 Example 2 0.79 19.87 Example 3 0.98 20.07 Example 4 1.13 21.53 Example 5 1.07 20.92 Example 6 1.15 20.85

[0040] Stress testing:

[0041] The illite-polyvinyl alcohol gel electrolyte was made into a cuboid with a length of 50 mm, a width of 7 mm, and a thickness of 3 mm. The strain rate was 50 mm min -1 , use a microcomputer-controlled universal mechanical testing machine to test its stress strength.

[0042] Ionic conductivity calculation:

[0043] The illite-polyvinyl alcohol gel electrolyte was sandwiched between two 50*20 mm copper sheets, and its EIS curve was tested using an electrochemical workstation. The resistance R was obtained based on the EIS curve.

[0044] The ionic conductivity of the sample is expressed in σ (mS·cm -1 ) indicates that it is calculated according to the formula σ=L / SR*1000.

[0045] Where: R is the resistance of illite-polyvinyl alcohol gel electrolyte, in ohm (Ω); S is the contact area between the copper sheet and the illite-polyvinyl alcohol gel electrolyte, in square centimeters (cm 2 ); L is the distance between the two copper sheets, in centimeters (cm). The arithmetic mean of the three parallel determination results was taken as the determination result.

[0046] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0047] The above technical solutions only reflect the preferred technical solutions of the technical solutions of the present invention. Some changes that may be made to certain parts thereof by technicians in this technical field all reflect the principles of the present invention and fall within the protection scope of the present invention.

Claims

1. A method for preparing illite-polyvinyl alcohol gel electrolyte, characterized in that: The raw materials of the gel electrolyte and their mass percentages are: illite 1-50%, polyvinyl alcohol 5-15%, deionized water 35-94%; The preparation method comprises the following steps: Step S1. The illite powder and polyvinyl alcohol are mixed and ground using a mortar for 0.5-2h to obtain a preliminary mixed material; Step S2. The water and the preliminary mixed material are mixed evenly using a stirrer at a stirring speed of 1000 rpm for a stirring time of 2 to 6 hours to obtain a mixture solution having a uniform texture; Step S3. performing a hydrothermal reaction on the mixture solution to prepare the illite-polyvinyl alcohol gel electrolyte, wherein the temperature of the hydrothermal reaction is 100-220° C. and the time of the hydrothermal reaction is 3-48 h; Step S4. The illite-polyvinyl alcohol gel solution prepared is centrifuged for defoaming, wherein the process parameters of the centrifugal defoaming include: the rotation speed is set to 8000~12000 rpm; Step S5. After removing the bubbles from the upper layer, the illite-polyvinyl alcohol gel solution is placed in a freeze dryer and frozen to obtain a semi-solid colloid with a flat and smooth surface. The process parameters of vacuum freeze drying include: a freezing temperature of -10 to -80°C and a standing time of 5 to 72 hours.

2. The method for preparing the illite-polyvinyl alcohol gel electrolyte according to claim 1, wherein the illite is a 2:1 type layered silicate mica clay mineral, i.e., two silicon-oxygen tetrahedra sandwich an aluminum-oxygen octahedron, and has a particle size of 0.1-0.5 μm.

3. The method for preparing the illite-polyvinyl alcohol gel electrolyte according to claim 1, characterized in that: The polyvinyl alcohol refers to a polyvinyl alcohol having a mass fraction ranging from 31000 to 124000.

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