A fiber-succinic acid composite solid electrolyte and its preparation method

Abstract

This invention discloses a fiber-succinic acid composite solid electrolyte, the substrate of which is fiber cotton, coated with an electrolyte layer composed of succinic acid, polyethylene oxide, and lithium salt. The preparation method of the fiber-succinic acid composite solid electrolyte of this invention is as follows: 1) Soak the fiber cotton in acetone solution, wash and dry it, then soak it in a silane coupling agent, wash and dry it; 2) Weigh succinic acid, polyethylene oxide, and lithium salt, and mix them under heating and stirring to obtain an electrolyte solution; 3) Cut the fiber cotton from step 1) into discs with a diameter of 10-18 mm, immerse them in the electrolyte from step 2), and cool and solidify at room temperature. The fiber-succinic acid composite solid electrolyte of this invention uses modified fiber cotton, which can improve the mechanical properties of the polymer solid electrolyte. The composite solid electrolyte improves the conductivity of lithium ions, reduces the interfacial resistance, and enhances the cycle performance of all-solid-state batteries.

Description

Technical Field

[0001] This invention relates to battery materials, and more particularly to a fiber-succinic acid composite solid electrolyte and its preparation method. Background Technology

[0002] Lithium-ion batteries have garnered significant attention due to their widespread applications in various aspects of life, such as energy storage devices, portable electronic devices, and electric vehicles. This is attributed to the relatively low electrode potential and high theoretical specific capacity (3860 mAh / g) of lithium metal. However, the cycle life of these batteries is typically less than a few hundred cycles due to the high energy density and rapid growth of lithium dendrites on the negative electrode surface during cycling. Furthermore, when lithium metal is used as the negative electrode, the formed dendrites can penetrate the separator, causing short circuits and leading to serious safety issues. Replacing organic liquid electrolytes with solid electrolytes and developing all-solid-state batteries is considered a fundamental solution to the common safety problems of conventional batteries and the achievement of higher energy densities. This is because solid electrolytes offer numerous advantages over liquid electrolytes, such as high thermal stability, a wide electrochemical window, low flammability, and reduced volatility and leakage compared to liquid electrolytes. Moreover, the use of solid electrolytes enables the application of high-voltage positive electrodes and lithium metal negative electrodes, which not only prevents lithium dendrite growth but also increases the energy density of solid-state lithium batteries.

[0003] Generally, commonly used inorganic solid electrolytes are mainly of the NASICON type, garnet type, and perovskite type. Inorganic solid electrolytes have a wide voltage window and high ionic conductivity (>10). -4 S / cm) and Li + The migration number is approximately 1. However, poor interfacial contact between inorganic solid electrolytes and electrodes leads to high interfacial resistance, hindering their widespread application. Polymer electrolytes mainly include polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride, polyethylene oxide, and polyacrylonitrile. Solid polymer electrolytes are more flexible and easier to mass-produce than inorganic solid electrolytes. Polymer electrolytes typically exhibit low ionic conductivity (10⁻⁶) at room temperature. -7 (S / cm) and poor mechanical properties. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a fiber-butadiene nitrile composite solid electrolyte. The substrate of this fiber-butadiene nitrile composite solid electrolyte is fiber cotton, on which an electrolyte layer is coated. The electrolyte layer is composed of butadiene nitrile, polyethylene oxide, and lithium salt. The fiber cotton is made of basalt fiber cotton, sodium hexatitanate fiber cotton, or potassium hexatitanate fiber cotton. The thickness of the electrolyte layer is 500–800 μm, and the weight ratio of butadiene nitrile, polyethylene oxide, and lithium salt is (3–20):(1–5):1. The lithium salt is selected from one or more of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium dioxalatoborate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonic acid)imide, and lithium tri(trifluoromethanesulfonic acid)methyl.

[0005] The preparation method of the fiber-succinic acid composite solid electrolyte of the present invention is as follows: 1) Soak the fiber cotton in acetone solution for 100-200 min, take it out, wash it, dry it at 100-150℃, soak it in KH550, KH560 or KH570 coupling agent for 10-15 h, take it out, wash it, dry it at 100-150℃ to complete the modification of the fiber cotton; 2) Weigh succinic acid, polyethylene oxide and lithium salt according to the weight ratio, stir and mix them evenly with magnetic force at 40-70℃ to obtain electrolyte solution, and keep it warm for later use; 3) Cut the fiber cotton in step 1) into discs with a diameter of 10-18 mm, soak the fiber cotton in the electrolyte in step 2), take it out and cool and solidify it at room temperature to obtain the final product.

[0006] This invention utilizes modified fiber cotton, which exhibits improved tensile strength and serves as a skeletal support, thus enhancing the mechanical properties of polymer solid electrolytes. As a battery material, the composite solid electrolyte improves lithium-ion conductivity, reduces interfacial resistance, and is completely flame-retardant, thereby improving the cycle performance of all-solid-state batteries. The fiber composite solid electrolyte prepared by this invention not only addresses the problems of poor electrolyte mechanical properties and high grain boundary impedance but also maintains high ionic conductivity, while simultaneously possessing low cost and extremely high flame-retardant properties. Attached Figure Description

[0007] Figure 1 This is a SEM image of the basalt fiber cotton used in Example 1.

[0008] Figure 2 This is a SEM image of the basalt fiber cotton-succinic acid composite solid electrolyte of Example 1.

[0009] Figure 3 The AC impedance spectra of the composite solid electrolytes of Examples 1 and 2 used in symmetrical blocking batteries are shown.

[0010] Figure 4 Examples 1 and 2 illustrate the use of composite solid electrolytes in constant current charge-discharge cycle testing of solid-state lithium-ion batteries.

[0011] Figure 5 The stress-strain curves of the composite solid electrolytes in Examples 1 and 2 are shown.

[0012] Figure 6 Example 1: Combustion test of basalt fiber-succinic acid composite solid electrolyte under flame. Detailed Implementation

[0013] The present invention will be described below with reference to examples. These examples are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0014] Example 1

[0015] A basalt fiber-butadiene nitrile composite solid electrolyte is disclosed. The substrate of the basalt fiber-butadiene nitrile composite solid electrolyte is basalt fiber cotton. An electrolyte layer is coated on the basalt fiber cotton. The electrolyte layer is composed of butadiene nitrile, polyethylene oxide and lithium bis(trifluoromethanesulfonic acid)imide in a weight ratio of 15:4:1. The thickness of the electrolyte layer is 800μm.

[0016] The preparation method of the basalt fiber-succinic acid composite solid electrolyte in this embodiment is as follows: 1) Soak the basalt fiber cotton in acetone solution for 120 min, take it out, wash it, dry it at 120℃, soak it in KH550 coupling agent for 12 h, take it out, wash it, dry it at 120℃ to complete the modification of the basalt fiber cotton; 2) Weigh succinic acid, polyethylene oxide and lithium bis(trifluoromethanesulfonic acid)imide according to the proportion, stir it magnetically at 60℃ to mix it evenly to obtain the electrolyte solution, and keep it warm for later use; 3) Cut the basalt fiber cotton in step 1) into a disc with a diameter of 16 mm, put the fiber cotton into the electrolyte in step 2) to wet it, take it out and cool it at room temperature to solidify, and then obtain the electrolyte solution.

[0017] Example 2

[0018] A sodium hexatite fiber-succinic acid composite solid electrolyte is disclosed. The substrate of the sodium hexatite fiber-succinic acid composite solid electrolyte is sodium hexatite fiber cotton. An electrolyte layer is coated on the sodium hexatite fiber cotton. The electrolyte layer is composed of succinic acid, polyethylene oxide and lithium tetrafluoroborate in a weight ratio of 4:1:1. The thickness of the electrolyte layer is 500 μm.

[0019] The preparation method of the sodium hexatite fiber-succinic acid composite solid electrolyte in this embodiment is as follows: 1) Soak the sodium hexatite fiber cotton in acetone solution for 150 min, take it out, wash it, dry it at 100℃, soak it in KH560 coupling agent for 15 h, take it out, wash it, dry it at 100℃ to complete the modification of sodium hexatite fiber; 2) Weigh succinic acid, polyethylene oxide and lithium tetrafluoroborate according to the proportion, stir them magnetically at 70℃ to mix them evenly to obtain electrolyte solution, and keep it warm for later use; 3) Cut the basalt fiber cotton in step 1) into a disc with a diameter of 16 mm, put the fiber cotton into the electrolyte in step 2) to wet it, take it out and cool it at room temperature to solidify, and then obtain the electrolyte solution.

[0020] Figure 1 This is a SEM image of the basalt fiber cotton used in Example 1. Figure 2 The image shows the SEM image of the basalt fiber cotton-succinic acid composite solid electrolyte in Example 1. It can be seen that the electrolyte is uniformly impregnated into the pores of the fiber.

[0021] The basalt fiber-succinic acid composite solid electrolyte of Example 1 and the sodium hexatitanate fiber-succinic acid composite solid electrolyte of Example 2 were respectively assembled into symmetrical blocking batteries, with stainless steel gaskets as blocking electrodes. The resulting AC impedance spectra are shown below. Figure 3 As shown, the calculated ionic conductivity of the composite solid electrolyte is 9.4 × 10⁻⁶. -4 S / cm and 8.1×10 -4 S / cm.

[0022] The basalt fiber-succinic acid composite solid electrolyte of Example 1 and the sodium hexatitanate fiber-succinic acid composite solid electrolyte of Example 2 were respectively punched into discs with a diameter of 16 mm, and solid-state lithium-ion batteries were assembled. The positive electrode was composed of lithium iron phosphate, superconducting carbon black, polyvinylidene fluoride, polyethylene oxide, and lithium bis(trifluoromethanesulfonic acid)imide in a mass ratio of 80:10:7:1:2, and the negative electrode was a lithium metal sheet. The batteries were assembled in an argon-filled glove box. Constant current charge-discharge cycle tests were performed on the solid-state lithium-ion batteries, cycling 200 times at a current density of 0.1C. The results are as follows. Figure 4 As shown, the capacity of Example 1 is maintained at 137 mAh / g with a capacity efficiency of 96%, while the capacity of Example 2 is 87 mAh / g with a capacity efficiency of 93%.

[0023] Figure 5 The figures show the stress-strain curves of the composite solid electrolytes in Examples 1 and 2. The maximum stress of the basalt fiber-succinic acid composite solid electrolyte in Example 1 is 34.5 MPa, and the maximum stress of the sodium hexatitanate fiber-succinic acid composite solid electrolyte in Example 2 is 8.7 MPa.

[0024] The basalt fiber-succinic acid composite solid electrolyte of Example 1 was tested under flame. It was observed that under the outer flame of an alcohol lamp, it remained unignited for 5 seconds. After the combustion test, the remaining portion maintained its structural integrity. Figure 6 As shown, it demonstrates a high level of security performance.

[0025] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fiber-succinic acid composite solid electrolyte, characterized in that, The fiber-butadiene nitrile composite solid electrolyte substrate is fiber cotton, and an electrolyte layer is coated on the fiber cotton. The electrolyte layer is composed of butadiene nitrile, polyethylene oxide and lithium salt. The fiber cotton is either sodium hexatitanate fiber cotton or potassium hexatitanate fiber cotton. The thickness of the electrolyte layer is 500–800 μm; The weight ratio of succinic anionylene, polyethylene oxide and lithium salt is (3-4):(1-5):

1.

2. The fiber-succinic acid composite solid electrolyte according to claim 1, characterized in that, The lithium salt is one or more of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium dioxaborate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonic acid)imide, and lithium tri(trifluoromethanesulfonic acid)methyl.

3. The method for preparing the fiber-succinic acid composite solid electrolyte according to any one of claims 1 to 2, characterized in that, Includes the following steps: 1) Soak the fiber cotton in acetone solution for 100-200 minutes, take it out, wash it, dry it at 100-150℃, soak it in KH550, KH560 or KH570 coupling agent for 10-15 hours, take it out, wash it, and dry it at 100-150℃ to complete the modification of the fiber cotton. 2) Weigh out succinic acid, polyethylene oxide and lithium salt according to the weight ratio, and mix them evenly with magnetic stirring at 40-70℃ to obtain electrolyte solution, and keep it warm for later use; 3) Cut the fiber cotton from step 1) into discs with a diameter of 10-18 mm, immerse the fiber cotton in the electrolyte from step 2), remove it and cool and solidify at room temperature to obtain the final product.

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