Polymer solid electrolyte and preparation method thereof

Abstract

This invention provides a polymer solid electrolyte and its preparation method, belonging to the field of lithium metal battery technology. The preparation method includes the following steps: Step 1, mixing polyethylene oxide, lithium salt, and an organic solvent to obtain a first mixed solution; Step 2, loading oxide nanoparticles onto nitride nanosheets to obtain a filler; Step 3, adding the filler to the first mixed solution and stirring, then pouring the mixture into a PTFE mold and placing it in a vacuum oven at a first predetermined temperature for vacuum drying to obtain the polymer solid electrolyte. This polymer solid electrolyte exhibits high conductivity, high toughness, inhibits lithium dendrite growth, and possesses excellent thermal stability to prevent battery thermal failure, resulting in high safety.

Description

Technical Field

[0001] This invention relates to the field of lithium metal battery technology, specifically to a polymer solid electrolyte and its preparation method. Background Technology

[0002] Lithium-ion batteries, due to their high energy density, long cycle life, low self-discharge, and environmental friendliness, have been widely used in mobile phones, digital cameras, electric vehicles, and many other fields, greatly promoting social progress. However, currently, liquid lithium-ion batteries are commonly used, and their electrolytes contain highly flammable carbonate organic solvents. These solvents can cause a series of safety problems during battery use due to organic solvent decomposition, electrolyte leakage, and combustion. Furthermore, current lithium-ion batteries mainly use polyethylene or polypropylene separators to prevent contact between the positive and negative electrodes. These separators have relatively low strength, and lithium dendrites generated during battery cycling can easily puncture the separator, leading to short circuits and further increasing safety concerns. Therefore, replacing traditional electrolyte and separator systems with solid-state electrolytes is of great significance.

[0003] Solid-state electrolytes are generally classified into two categories: polymer solid-state electrolytes and inorganic solid-state electrolytes. Compared to inorganic solid-state electrolytes, polymer solid-state electrolytes have greater advantages in large-scale production due to their high flexibility and low cost. Among polymer solid-state electrolytes, polyethylene oxide (PEO) has a high dielectric constant, facilitating the dissociation of lithium salts; therefore, its combination with lithium salts is the most commonly used polymer solid-state electrolyte system. However, because the chain segments used for lithium ion transport in the crystalline regions of PEO move slowly, its intrinsic lithium-ion conductivity is not high (around 10⁻⁶). -7 ~10 -6 S cm -1 (25℃). In addition, polyethylene oxide has low strength, cannot suppress lithium dendrite growth, and is flammable, which further hinders its application. Summary of the Invention

[0004] This invention is made to solve the above-mentioned problems, and its purpose is to provide a polymer solid electrolyte and a method for preparing the same.

[0005] This invention provides a method for preparing a polymer solid electrolyte, characterized by the following steps: Step 1, mixing polyethylene oxide, lithium salt, and organic solvent to obtain a first mixed solution; Step 2, loading oxide nanoparticles onto nitride nanosheets to obtain a filler; Step 3, adding the filler to the first mixed solution and stirring, then pouring it into a PTFE mold and placing it in a vacuum oven at a first predetermined temperature for vacuum drying to obtain the polymer solid electrolyte.

[0006] The method for preparing polymer solid electrolytes provided by the present invention may also have the following characteristics: in step 1, the lithium salt is any one of lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, and lithium perchlorate, and the organic solvent is any one of acetonitrile, ethylene carbonate, diethyl carbonate, and dimethyl carbonate.

[0007] The preparation method of polymer solid electrolyte provided by the present invention may also have the following features: in step 1, the molar ratio of polyethylene oxide to lithium salt is (8-15):1, and the mass ratio of the sum of the masses of polyethylene oxide and lithium salt to the mass ratio of organic solvent is 1:(6-9).

[0008] The preparation method of polymer solid electrolyte provided by the present invention may also have the following features: Step 2 includes the following sub-steps: Step 2-1, take an appropriate amount of boron-containing nitride, dissolve it in an organic solvent, put it in a beaker for ultrasonic treatment, centrifuge it after ultrasonication, and then put it in a vacuum oven for vacuum drying at a second predetermined temperature to obtain a precursor; Step 2-2, grind the precursor evenly and add it to ethanol, add silicate ester, adjust the pH of the solution to a predetermined pH range with ammonia, stir evenly and then vacuum dry it at a third predetermined temperature to obtain a filler.

[0009] The preparation method of polymer solid electrolyte provided by the present invention may also have the following features: in step 2-1, the boron-containing nitride is one of boron nitride, boron-nitrogen benzene, and ternary boron-carbon-nitrogen; the ultrasonic treatment power is 2000-3000W, the time is 10-30h, the centrifugation speed is 3000-5000rpm, and the second predetermined temperature is 60-80℃.

[0010] The method for preparing polymer solid electrolytes provided by the present invention may also have the following features: in step 2-2, the silicate ester is any one of tetraethyl orthosilicate, tetrabutyl orthosilicate and methyl orthosilicate, the predetermined pH range is 10-12, and the third predetermined temperature is 50-80°C.

[0011] The preparation method of polymer solid electrolyte provided by the present invention may also have the following feature: in step 2-2, the mass ratio of the precursor to the silicate ester is 1:3.

[0012] The preparation method of polymer solid electrolyte provided by the present invention may also have the following features: in step 3, the mass ratio of filler to first mixed solution is 1:(90-100), the stirring time is 10-20h, the first predetermined temperature is 50-80℃, and the vacuum drying time is 10-20h.

[0013] This invention provides a polymer solid electrolyte, characterized by being prepared using the above-described method for preparing polymer solid electrolytes.

[0014] The polymer solid electrolyte provided by the present invention may also have the following characteristics: wherein the polymer electrolyte is composed of polyethylene oxide and lithium salt, and the interior of the polymer electrolyte is filled with filler formed by oxide nanoparticles supported on nitride nanosheets.

[0015] The role and effect of invention

[0016] According to the polymer solid electrolyte and its preparation method of the present invention, the method utilizes the properties of oxide nanoparticles and nitride nanosheets to reduce the crystallinity of polyethylene oxide, thereby improving the ionic conductivity of polyethylene oxide. The polymer solid electrolyte prepared by the method has high conductivity, high toughness, can inhibit lithium dendrite growth, and has excellent thermal stability to prevent battery thermal failure, thus ensuring high safety.

[0017] In addition, the polymer solid electrolyte prepared by this invention also has excellent flexibility and can quickly recover its original shape after extreme deformation such as bending and twisting. Attached Figure Description

[0018] Figure 1 A scanning electron microscope image of the packing material prepared in Example 1;

[0019] Figure 2 This demonstrates the morphology and flexibility of the polymer solid electrolyte sheet prepared in Example 1.

[0020] Figure 3 Impedance diagram of the polymer solid electrolyte prepared in Example 1;

[0021] Figure 4 The electrochemical stability window test results are for the polymer solid electrolyte prepared in Example 1;

[0022] Figure 5 The electrochemical cycling performance of the polymer solid electrolyte prepared in Example 1 at 60°C and 1C.

[0023] Figure 6 The electrochemical cycling performance of the polymer solid electrolyte prepared in Example 1 at 0.2C and 60°C is shown. Detailed Implementation

[0024] This invention provides a polymer solid electrolyte and its preparation method, which includes the following steps:

[0025] Step 1: Mix polyethylene oxide, lithium salt, and organic solvent to obtain a first mixed solution. The lithium salt is any one of lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, and lithium perchlorate; the organic solvent is any one of acetonitrile, ethylene carbonate, diethyl carbonate, and dimethyl carbonate. The molar ratio of polyethylene oxide to lithium salt is (8–15):1, and the mass ratio of the sum of the masses of polyethylene oxide and lithium salt to the mass of the organic solvent is 1:(6–9).

[0026] Step 2: Load oxide nanoparticles onto nitride nanosheets to obtain filler.

[0027] Step 2 includes the following sub-steps:

[0028] Step 2-1: Dissolve 1g of boron-containing nitride in N-methylpyrrolidone and place it in a beaker for ultrasonic treatment. The ultrasonic power is 2000-3000W, and the time is 10-30h. After ultrasonication, centrifuge at 3000-5000rpm and then place it in a vacuum oven at 60-80℃ for vacuum drying to obtain the precursor. The boron-containing nitride is one of boron nitride, boron-nitrogen benzene, or a ternary boron-carbon-nitrogen compound.

[0029] Step 2-2: After grinding the precursor evenly, add it to 70 ml of ethanol, along with the silicate ester. Adjust the pH of the solution to 10-12 with ammonia, stir evenly, and then vacuum dry at 50-80℃ to obtain the filler. The silicate ester can be any one of tetraethyl orthosilicate, tetrabutyl orthosilicate, or methyl orthosilicate, and the mass ratio of precursor to silicate ester is 1:3.

[0030] Step 3: Add the filler to the first mixed solution and stir for 10-20 hours. Then pour the mixture into a PTFE mold and place it in a vacuum oven at 50-80°C for vacuum drying for 10-20 hours to obtain the polymer solid electrolyte. The mass ratio of the filler to the first mixed solution is 1:(90-100).

[0031] The polymer solid electrolyte is composed of polyethylene oxide and lithium salt, and its interior is filled with filler formed by oxide nanoparticles supported on nitride nanosheets.

[0032] To make the technical means, creative features, objectives and effects of the present invention easy to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate the polymer solid electrolyte and its preparation method of the present invention.

[0033] <Example 1>

[0034] Example 1 provides a polymer solid electrolyte and its preparation method, which includes the following steps:

[0035] Step 1: Mix polyethylene oxide, lithium bis(trifluoromethanesulfonyl)imide, and anhydrous acetonitrile to obtain a first mixed solution. The molar ratio of polyethylene oxide to lithium bis(trifluoromethanesulfonyl)imide is 10:1; the mass ratio of the sum of the masses of polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide to the mass ratio of anhydrous acetonitrile is 1:6.

[0036] Step 2: Load oxide nanoparticles onto nitride nanosheets to obtain filler.

[0037] Step 2 includes the following sub-steps:

[0038] Step 2-1: Dissolve 1g of boron nitride in N-methylpyrrolidone and place it in a beaker for ultrasonic treatment. The ultrasonic treatment power is 2000W and the time is 24h. After ultrasonic treatment, centrifuge at 3000rpm for 15min. Then place it in a vacuum oven and vacuum dry at 70℃ for 12h to obtain the precursor.

[0039] Step 2-2: After grinding the precursor evenly, add it to 70 ml of ethanol and tetraethyl orthosilicate. Adjust the pH of the solution to 10-12 with ammonia, stir evenly, and then vacuum dry at 60℃ for 12 h to obtain the filler. The mass ratio of precursor to silicate ester is 1:3.

[0040] Step 3: Add the filler to the first mixed solution and stir for 16 hours. Then pour the mixture into a PTFE mold and place it in a vacuum oven at 60°C for 12 hours to allow the solvent to evaporate, obtaining the polymer solid electrolyte. The mass ratio of the filler to the first mixed solution is 1:90.

[0041] The polymer solid electrolyte is composed of polyethylene oxide and lithium salt, and its interior is filled with filler formed by oxide nanoparticles supported on nitride nanosheets.

[0042] Figure 1 The image shows a scanning electron microscope image of the packing material prepared in Example 1.

[0043] Figure 2 This demonstrates the morphology and flexibility of the polymer solid electrolyte sheet prepared in Example 1. Figure 2 As shown, the polymer solid electrolyte prepared in Example 1 has good flexibility.

[0044] A stainless steel blocking battery (stainless steel / electrolyte / stainless steel) was assembled using the polymer solid electrolyte obtained in Example 1, and its electrochemical impedance spectroscopy was tested at 60°C. The test results are shown in [Figure 1]. Figure 3 .

[0045] Figure 3 Impedance spectroscopy for the polymer solid electrolyte prepared in Example 1. Figure 3The calculated ionic conductivity at 60℃ is 4.97 × 10⁻⁶. -4 S cm -1 .

[0046] The polymer solid electrolyte obtained in Example 1 was used to assemble a lithium / stainless steel battery. Its electrochemical stability against lithium metal was tested using a linear sweep voltammetry method (voltage range 1V–6V). The test results are shown in [Figure number missing]. Figure 4 .

[0047] Figure 4 The electrochemical stability window test results are for the polymer solid electrolyte prepared in Example 1. Figure 4 The electrochemical window for lithium was found to be approximately 5.2V, which meets the requirement of matching higher voltage positive electrode active materials for lithium-ion batteries.

[0048] The polymer solid electrolyte obtained in Example 1 was used to assemble lithium / electrolyte / lithium iron phosphate batteries, and their 1C and 0.2C cycle performance tests were conducted at 60°C. The test results are shown in the figures below. Figure 5 and Figure 6 .

[0049] Figure 5 The electrochemical cycling performance of the polymer solid electrolyte prepared in Example 1 at 60°C and 1C. Figure 6 The electrochemical cycling performance of the polymer solid electrolyte prepared in Example 1 at 0.2C and 60°C is shown.

[0050] like Figure 5 As shown, the battery assembled using the prepared polymer solid electrolyte exhibits high cycle stability at 1C. After 200 cycles, the discharge specific capacity remains at 132 mAh / g, and the coulombic efficiency is close to 100%. Figure 6 In the test, the battery exhibited a high initial coulombic efficiency (94%) at 0.2C. After 200 cycles, it maintained a high coulombic efficiency and its capacity remained relatively stable.

[0051] Functions and effects of Example 1

[0052] The results of Example 1 show that the conductivity of the polymer solid electrolyte prepared in this invention is 4.97 × 10⁻⁶. -4 Scm -1 The chemical stability window for lithium-ion batteries is approximately 5.2V, which meets the requirements for high-voltage cathode active materials in lithium-ion batteries. Because the nitride nanosheets used possess high mechanical strength, the prepared polymer solid electrolyte exhibits high strength, effectively suppressing lithium dendrite growth; coupled with high thermal stability, this enhances battery safety.

[0053] <Example 2>

[0054] Example 2 provides a polymer solid electrolyte and its preparation method. The only difference between this preparation method and the preparation method in Example 1 is the amount of some raw materials used; the rest of the process is exactly the same.

[0055] The specific difference in the preparation method of Example 2 is that:

[0056] In step 1, the molar ratio of polyethylene oxide to lithium bis(trifluoromethanesulfonylimide) is 8:1; the sum of the masses of polyethylene oxide and lithium bis(trifluoromethanesulfonylimide) is in the mass ratio of anhydrous acetonitrile to 1:7.

[0057] In step 3, the mass ratio of the filler to the first mixed solution is 1:92.

[0058] <Example 3>

[0059] Example 3 provides a polymer solid electrolyte and its preparation method. The only difference between this preparation method and the preparation method in Example 1 is the amount of some raw materials used; the rest of the process is exactly the same.

[0060] The specific difference in the preparation method of Example 3 is as follows:

[0061] In step 1, the molar ratio of polyethylene oxide to lithium bis(trifluoromethanesulfonyl)imide is 12:1; the mass ratio of the sum of the masses of polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide to the mass of anhydrous acetonitrile is 1:8.

[0062] In step 3, the mass ratio of the filler to the first mixed solution is 1:94.

[0063] <Example 4>

[0064] Example 4 provides a polymer solid electrolyte and its preparation method. The only difference between this preparation method and the preparation method in Example 1 is the amount of some raw materials used; the rest of the process is exactly the same.

[0065] The specific difference in the preparation method of Example 4 is that:

[0066] In step 1, the molar ratio of polyethylene oxide to lithium bis(trifluoromethanesulfonylimide) is 15:1; the sum of the masses of polyethylene oxide and lithium bis(trifluoromethanesulfonylimide) is in a mass ratio of 1:9 to that of anhydrous acetonitrile.

[0067] In step 3, the mass ratio of the filler to the first mixed solution is 1:96.

[0068] The above embodiments are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention.

Claims

1. A method for preparing a polymer solid electrolyte, characterized in that, Includes the following steps: Step 1: Mix polyethylene oxide, lithium salt and organic solvent to obtain a first mixed solution; Step 2: Load oxide nanoparticles onto nitride nanosheets to obtain the filler; Step 3: Add the filler to the first mixed solution and stir for 10-20 hours. The mass ratio of the filler to the first mixed solution is 1:(90-100). Then pour the mixture into a PTFE mold and place it in a vacuum oven at 50-80°C for vacuum drying for 10-20 hours to obtain a polymer solid electrolyte. Step 2 includes the following sub-steps: Step 2-1: Dissolve an appropriate amount of boron-containing nitride in an organic solvent and place it in a beaker for ultrasonic treatment. The ultrasonic treatment power is 2000-3000W and the time is 10-30h. After ultrasonic treatment, centrifuge at a speed of 3000-5000rpm and then place it in a vacuum oven at 60-80℃ for vacuum drying to obtain the precursor. Step 2-2: After grinding the precursor evenly, add it to ethanol, and then add silicate ester. The mass ratio of the precursor to the silicate ester is 1:

3. Adjust the pH of the solution to 10-12 with ammonia water, stir evenly, and then vacuum dry at 50-80℃ to obtain the filler. The boron-containing nitride is one of boron nitride, boron-nitrogen benzene, and ternary boron-carbon-nitrogen compounds, and the silicate ester is any one of tetraethyl orthosilicate, tetrabutyl orthosilicate, and methyl orthosilicate.

2. The method for preparing the polymer solid electrolyte according to claim 1, characterized in that: in, In step 1, the lithium salt is any one of lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, and lithium perchlorate. The organic solvent is any one of acetonitrile, ethylene carbonate, diethyl carbonate, and dimethyl carbonate.

3. The method for preparing the polymer solid electrolyte according to claim 1, characterized in that: in, In step 1, the molar ratio of the polyethylene oxide to the lithium salt is (8-15):

1. The mass ratio of the sum of the masses of the polyethylene oxide and the lithium salt to the mass of the organic solvent is 1:(6-9).

4. A polymer solid electrolyte, characterized in that: It is prepared by the method of any one of claims 1-3 for preparing polymer solid electrolyte.

5. The polymer solid electrolyte according to claim 4, characterized in that: in, The polymer electrolyte is composed of polyethylene oxide and lithium salt, and its interior is filled with filler formed by oxide nanoparticles supported on nitride nanosheets.

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