Composite solid electrolyte containing zirconium oxide nanotube composite filler and preparation method of composite solid electrolyte

Abstract

The invention relates to a composite solid electrolyte containing a zirconia nanotube composite filler and a preparation method thereof, and belongs to the technical field of composite solid electrolyte materials. According to the composite solid electrolyte membrane, a composite ceramic filler and a zirconia nanotube are adopted as a first ceramic filler to reduce the crystallinity of a polymer, an active second ceramic filler can increase the transference number of lithium ions, and the polymer and a lithium salt are compounded by adopting a solvent evaporation method to prepare the composite solid electrolyte membrane. The composite solid electrolyte membrane provided by the invention not only has good ionic conductivity and thermal stability, but also generates greater energy dissipation under load due to the composition of organic-inorganic materials and abundant polymer-ceramic interfaces, thereby improving the mechanical properties of the traditional polymer solid electrolyte.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite solid electrolyte materials, and particularly relates to a composite solid electrolyte containing zirconia nanotube composite fillers and a preparation method thereof. Background Art

[0002] With the continuous growth of social power consumption, the new energy industry has developed rapidly, and secondary batteries as energy storage devices have highlighted their important status. Lithium-ion batteries occupy a large market in digital products, electric vehicles, and industrial and commercial energy storage due to their unique advantages. However, the organic liquid electrolyte in the battery is not only flammable but also has a risk of leakage. In addition, the organic separator is also flammable, which is not conducive to ensuring the safe storage of energy. At present, while ensuring the safety of the battery, pursuing a higher energy density of the battery core is the working direction of researchers in the industry. Therefore, the non-separable solid-state lithium metal battery has broad energy storage prospects due to its high energy density.

[0003] Solid electrolytes are the core of solid-state lithium metal batteries, and the ionic conductivity and lithium ion transference number of solid electrolytes are the key. As is well known, polymer solid electrolytes have been widely studied because of their good contact with electrodes and easy processability. At present, although it has a low conductivity at room temperature, it can be improved by adding inorganic fillers to increase the polymer region. In addition, inorganic fillers also play a role in enhancing the mechanical properties of polymer solid electrolytes, thus effectively resisting the puncture of lithium dendrites. Polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), etc. are often used to develop polymer solid electrolytes, and common inert ceramic fillers include Al2O3, SiO2, TiO2, ZrO2, and MgO, etc. In addition, adding Li7La3Zr2O 12 (LLZO), Li 1.3 Al 0.3 Ti l.7 P3O 12 (LATP) and Li 0.35 La 0.5 TiO3 (LLTO) and other active fillers can increase the lithium ion transference number. Many composite solid electrolytes are derived from their specific combinations.

[0004] Among common ceramic fillers, ZrO2 is expected to improve the ionic transport performance of polymer solid electrolytes due to its excellent chemical resistance and thermal stability. For example, Chinese Patent with Application No. 202310743617.1 discloses a preparation method of zirconia / PVDF-based polymer solid electrolyte. In this invention, in-situ synthesis, electrospinning, element doping, and solution casting methods are successively used to prepare a solid electrolyte membrane with uniformly distributed zirconia particles rich in oxygen vacancies. Although this method obtains a relatively high ionic conductivity, the preparation process is complex, and a simple and feasible preparation scheme still needs to be developed. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems existing in the existing solid electrolyte membranes, such as low room-temperature conductivity and complex preparation process. A composite solid electrolyte containing zirconia nanotube composite filler and its preparation method are provided. The prepared organic-inorganic composite solid electrolyte film has excellent thermal stability and mechanical properties, and at the same time has a relatively high ionic conductivity.

[0006] To achieve the above purpose, the technical solutions adopted by the present invention are as follows:

[0007] A composite solid electrolyte containing zirconia nanotube composite filler, the composite solid electrolyte includes a polymer matrix, a first ceramic filler, a second ceramic filler, and a lithium salt.

[0008] Further, the polymer matrix is one or more of polymethacrylate (PMMA), polyacrylonitrile (PAN), and polyvinylidene fluoride (PVDF); the first ceramic filler is zirconia ceramic nanotube (ZNT); the second ceramic filler is one or more of Li7La3Zr2O 12 (LLZO), Li 1.3 Al 0.3 Ti l.7 P3O 12 (LATP), and Li 0.35 La 0.5 TiO3 (LLTO); the lithium salt is one or more of lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), and lithium bis(fluorosulfonyl)imide (LiFSI).

[0009] Further, the mass percentage of the polymer matrix is 70%-90%, the mass percentage of the first ceramic filler is 3%-10%, the mass percentage of the second ceramic filler is 2%-10%, and the mass percentage of the lithium salt is 5%-10%.

[0010] Furthermore, the zirconia ceramic nanotubes are self-made. First, amorphous zirconia nanotubes with a length of (25 - 30 μm) and a diameter of (60 - 75 nm) are prepared by a two-step anodic oxidation method, and then annealed in a tube furnace under a nitrogen protection atmosphere at 600 °C for 2 h.

[0011] A preparation method of the above-mentioned composite solid electrolyte containing zirconia nanotube composite filler is prepared by a solvent evaporation method, and the method is as follows:

[0012] (1) Weigh 5 g of zirconia ceramic nanotubes, place them in 100 mL of absolute ethanol, ultrasonically clean for 20 min, centrifuge to obtain the precipitate, and place it in a vacuum drying oven at 60 °C for drying;

[0013] (2) The polymer matrix is added to the solvent according to the mass percentage, heated and stirred until completely dissolved to obtain a mixed solution A;

[0014] (3) In a glove box, the first ceramic filler, the second ceramic filler and the lithium salt are added to the mixed solution A according to the mass percentage, stirred for 12 - 24 h to form a mixed solution B, and the solid content of the mixed solution B is 5 - 30%;

[0015] (4) Place the mixed solution B in an evaporating dish with a length, width and height of 10 cm × 10 cm × 3 cm, and place it in a vacuum drying oven at 60 °C for 48 h;

[0016] (5) Peel off the film material and cut it into thin films of the same size for standby.

[0017] Furthermore, the thickness of the film can be controlled in the range of micrometers to centimeters. The first method is to control the solid content of the mixed solution; the second method is to control the volume of the mixed solution used during evaporation; the third method is to use a hot pressing method to press multiple thin films together, and the hot pressing parameters are a temperature of 80 - 100 °C and a pressure of 10 - 20 kg.

[0018] Furthermore, in step (2), the solvent is one or more of N, N-dimethylformamide and N-methylpyrrolidone.

[0019] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0020] (1) For the composite ceramic filler adopted in the present invention, the zirconia nanotubes, as the first ceramic filler, play a role in reducing the crystallinity of the polymer, and the second ceramic filler can increase the lithium ion transference number, thereby improving the ionic conductivity of the traditional polymer solid electrolyte.

[0021] (2) The composite ceramic filler used in the present invention enables the polymer solid electrolyte membrane to contain ceramic nanotubes of the first ceramic filler and nanospheres of the second ceramic filler. Such an organic-inorganic material composition and the rich polymer-ceramic interface result in greater energy dissipation under load, thereby improving the mechanical properties of traditional polymer solid electrolytes.

[0022] (3) The application of a high proportion of inorganic materials (the first ceramic filler / the second ceramic filler / lithium salt) is beneficial to improving the thermal stability of traditional polymer solid electrolytes. Description of the Drawings

[0023] Figure 1 It is a schematic structural diagram of the solid electrolyte membrane.

[0024] Figure 2 It is a process flow chart for the preparation of the solid electrolyte membrane.

[0025] Figure 3 It is an XRD diagram of amorphous zirconia nanotubes and crystalline zirconia nanotubes.

[0026] Figure 4 It is a contact depth-modulus diagram of the solid electrolyte membrane of Example 1 and Comparative Example 1.

[0027] Figure 5 It is a contact depth-hardness diagram of the solid electrolyte membrane of Example 1 and Comparative Example 1. Detailed Embodiments

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the following further details the present application with reference to examples. It can be understood that the examples are only for helping to understand the present invention and do not limit the invention. All other examples obtained by those of ordinary skill in the art based on the examples in the present invention without creative efforts fall within the scope of protection of the present invention.

[0029] The composite solid electrolyte membrane of the present invention uses a composite ceramic filler. As Figure 1 shown, zirconia nanotubes, as the first ceramic filler, play a role in reducing the crystallinity of the polymer, and the active second ceramic filler can increase the lithium ion transference number. The composite polymer, lithium salt, is prepared by the solvent evaporation method. The composite solid electrolyte membrane described in the present invention not only has good ionic conductivity and thermal stability, but also due to the organic-inorganic material composition and the rich polymer-ceramic interface, greater energy dissipation occurs under load, thereby improving the mechanical properties of traditional polymer solid electrolytes.

[0030] The main reagents used in the examples and comparative examples of the present invention are as follows:

[0031] Table 1

[0032]

[0033]

[0034] Example 1:

[0035] (ZNT-LLZO / PMMA / LiPF6) The preparation process of the composite solid electrolyte film is as follows Figure 2 shown: Amorphous zirconia nanotubes were prepared by a two-step anodization method. Weigh 5 g of amorphous zirconia ceramic nanotubes, place them in 100 mL of absolute ethanol, ultrasonically clean for 20 min, centrifuge to obtain the precipitate, and place it in a vacuum drying oven at 60 °C to dry. Then, anneal it in a tube furnace under a nitrogen protection atmosphere at 500 °C for 2 h. The XRD patterns of the nanotubes before and after annealing are as follows Figure 3 shown; Weigh poly(methyl methacrylate) solid particles according to 5.0 wt.%, place them in a beaker containing 200 mL of N,N-dimethylformamide, heat in a water bath at a temperature of 80 °C, stir continuously. After the solid particles are completely dissolved, cool to obtain mixture A; Weigh ZNT according to 0.8 wt.%, weigh LLZO according to 0.5 wt.%, weigh LiPF6 according to 0.4 wt.%. Add ZNT, LLZO ceramic fillers and LiPF6 to mixture A, stir for 12 - 24 h and record it as mixture B, and place it in an evaporating dish with dimensions of 10 cm × 10 cm × 3 cm, and place it in a vacuum drying oven at 60 °C for 48 h; Peel off the film material and cut it into uniformly sized thin films for standby. The film thickness is about 150 μm.

[0036] The mechanical properties of the composite solid electrolyte film were tested using a nanoindentation instrument. The nanoindentation test method is the continuous stiffness test method, which is carried out in 20 segments with a loading force of 1000 μN - 10000 μN to measure the Young's modulus and nano-hardness at different depths. The modulus test results are as follows Figure 4 shown, and the hardness test results are as follows Figure 5 shown. The ionic conductivity test was carried out using a symmetric blocking cell assembled with stainless steel sheet SS / composite solid electrolyte film / stainless steel sheet SS. The specific process is as follows: 1. Place the lower electrode steel sheet at the bottom of the button cell case to ensure it is flat and without deviation; 2. Clamp the solid electrolyte film and place it on the stainless steel sheet; 3. Drop the electrolyte; 4. Place the upper stainless steel sheet and align it in the center; 5. Place the gasket; 6. Press and fit.

[0037] Example 2:

[0038] (ZNT-LLZTO / PVDF / LiClO4) The preparation process of the composite solid electrolyte film is as follows: The pretreatment of ZNT is the same as that in Example 1; Weigh PVDF powder at 5.0 wt.%, place it in a beaker containing 200 mL of N-methylpyrrolidone, and continuously stir at a water bath temperature of 60 °C. After the powder is completely dissolved, it is recorded as mixture A; Weigh ZNT at 0.8 wt.%, weigh LLZTO at 0.5 wt.%, and weigh LiClO4 at 0.4 wt.%. Add ZNT, LLZTO ceramic filler and LiClO4 to mixture A, stir for 12 - 24 h and then record it as mixture B. Place it in an evaporating dish with dimensions of 10 cm × 10 cm × 3 cm and put it in a 60 °C vacuum drying oven for 48 h; Peel off the film material and cut it into uniformly sized thin films for standby. The mechanical properties and ionic conductivity tests are the same as those in Example 1.

[0039] Example 3:

[0040] (ZNT-LATP / PAN / LiFSI) The preparation process of the composite solid electrolyte film is as follows: The pretreatment of ZNT is the same as that in Example 1; Weigh PAN powder at 5.0 wt.%, place it in a beaker containing 200 mL of N-methylpyrrolidone, and continuously stir at a water bath temperature of 60 °C. After the powder is completely dissolved, it is recorded as mixture A; Weigh ZNT at 0.8 wt.%, weigh LATP at 0.5 wt.%, and weigh LiFSI at 0.4 wt.%. Add ZNT, LATP ceramic filler and LiFSI to mixture A, stir for 12 - 24 h and then record it as mixture B. Place it in an evaporating dish with dimensions of 10 cm × 10 cm × 3 cm and put it in a 60 °C vacuum drying oven for 48 h; Peel off the film material and cut it into uniformly sized thin films for standby. The mechanical properties and ionic conductivity tests are the same as those in Example 1.

[0041] Example 4:

[0042] The (ZNT-LLZO / PMMA / LiPF6) composite solid electrolyte film of this example is different from that of Example 1 in that the addition ratios of ZNT and LLZO are different. Its preparation process is as follows: The pretreatment of ZNT is the same as that of Example 1; Weigh poly(methyl methacrylate) solid particles at 5.0 wt.%, place them in a beaker containing 200 mL of N,N-dimethylformamide, carry out water bath heating at the temperature of an 80°C water bath, stir continuously. After the solid particles are completely dissolved, cool to obtain mixture A; Weigh ZNT at 0.5 wt.%, weigh LLZO at 0.8 wt.%, weigh LiPF6 at 0.4 wt.%, add ZNT, LLZO ceramic fillers and LiPF6 to mixture A, stir for 12 - 24 h and record it as mixture B, and place it in an evaporating dish with dimensions of 10 cm × 10 cm × 3 cm, and place it in a 60°C vacuum drying oven for 48 h; Peel off the film material and cut it into uniformly sized thin films for standby. The mechanical property and ionic conductivity tests are the same as those of Example 1.

[0043] Example 5:

[0044] The (ZNT-LLZO / PMMA / LiPF6) composite solid electrolyte film of this example is different from that of Example 1 in that the addition amount of LiPF6 is different. Its preparation process is as follows: The pretreatment of ZNT is the same as that of Example 1; Weigh poly(methyl methacrylate) solid particles at 5.0 wt.%, place them in a beaker containing 200 mL of N,N-dimethylformamide, carry out water bath heating at the temperature of an 80°C water bath, stir continuously. After the solid particles are completely dissolved, cool to obtain mixture A; Weigh ZNT at 0.8 wt.%, weigh LLZO at 0.5 wt.%, weigh LiPF6 at 0.8 wt.%, add ZNT, LLZO ceramic fillers and LiPF6 to mixture A, stir for 12 - 24 h and record it as mixture B, and place it in an evaporating dish with dimensions of 10 cm × 10 cm × 3 cm, and place it in a 60°C vacuum drying oven for 48 h; Peel off the film material and cut it into uniformly sized thin films for standby. The mechanical property and ionic conductivity tests are the same as those of Example 1.

[0045] Comparative Example 1:

[0046] Preparation of (PMMA / LiPF6) composite solid electrolyte film without inorganic filler: Weigh poly(methyl methacrylate) solid particles at 5.0 wt.%. Place them in a beaker containing 200 mL of N,N-dimethylformamide and heat them in a water bath at 80 °C with continuous stirring. After the solid particles are completely dissolved and cooled, it is denoted as mixture A. Weigh LiPF6 at 0.4 wt.%, add it to mixture A, stir for 12 - 24 h and then denote it as mixture B. Place mixture B in an evaporating dish with dimensions of 10 cm × 10 cm × 3 cm and put it in a vacuum drying oven at 60 °C for 48 h. Then, peel off the film. The mechanical properties and ionic conductivity tests are the same as in Example 1. The modulus test results are as Figure 4 shown, and the hardness test results are as Figure 5 shown.

[0047] Comparative Example 2:

[0048] Preparation of (LLZO / PMMA / LiPF6) composite solid electrolyte film without the first inorganic filler: The preparation of mixture A is the same as in Comparative Example 1. The difference from Comparative Example 1 lies in the preparation of mixture B. Weigh LiPF6 at 0.4 wt.% and LLZO at 0.5 wt.%. Add LiPF6 and LLZO to mixture A, stir for 12 - 24 h and then denote it as mixture B.

[0049] Comparative Example 3:

[0050] Preparation of (ZNT / PMMA / LiPF6) composite solid electrolyte film without the second inorganic filler: The preparation of mixture A is the same as in Comparative Example 1 and Comparative Example 2. The difference from Comparative Example 1 and Comparative Example 2 lies in the preparation of mixture B. Weigh LiPF6 at 0.4 wt.% and ZNT at 0.5 wt.%. Add LiPF6 and ZNT to mixture A, stir for 12 - 24 h and then denote it as mixture B.

[0051] To better illustrate the effects of the embodiments of the present invention, the following provides the comparative test results of the composite solid electrolyte films of the examples and comparative examples. Table 2 shows the detailed test data.

[0052] Table 2

[0053]

[0054]

Claims

1. A composite solid electrolyte containing a zirconia nanotube composite filler, characterized in that: The composite solid electrolyte includes a polymer matrix, a first ceramic filler, a second ceramic filler, and a lithium salt.

2. The composite solid electrolyte containing the zirconia nanotube composite filler according to claim 1, wherein: The polymer matrix is one or more of polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), and polyvinylidene fluoride (PVDF); the first ceramic filler is zirconia ceramic nanotubes (ZNT); the second ceramic filler is one or more of Li7La3Zr2O 12 (LLZO), Li 1.3 Al 0.3 Ti l.7 P3O 12 (LATP), and Li 0.35 La 0.5 TiO3 (LLTO); the lithium salt is one or more of lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), and lithium bis(fluorosulfonyl)imide (LiFSI).

3. The composite solid electrolyte containing the zirconia nanotube composite filler according to claim 1 or 2, characterized in that: The mass percentage of the polymer matrix is 70%-90%, the mass percentage of the first ceramic filler is 3%-10%, the mass percentage of the second ceramic filler is 2%-10%, and the mass percentage of the lithium salt is 5%-10%.

4. A composite solid electrolyte containing a zirconia nanotube composite filler according to claim 1, characterized in that: The zirconia ceramic nanotubes are prepared by a two-step anodic oxidation method. The nanotubes have a length of (25-30 μm) and a diameter of (60-75 nm), and are then annealed in a tube furnace under a nitrogen protection atmosphere at 600 °C for 2 h.

5. A method for preparing a composite solid electrolyte containing a zirconia nanotube composite filler according to any one of claims 1 to 4, characterized in that: It is prepared by the solvent evaporation method. The method is as follows: (1) Weigh the zirconia ceramic nanotubes, place them in absolute ethanol, ultrasonically clean them, centrifuge to obtain the precipitate, and vacuum dry it. (2) Add the polymer matrix to the solvent by mass percentage, heat and stir until completely dissolved to obtain a mixed solution A. (3) In a glove box, add the first ceramic filler, the second ceramic filler, and the lithium salt to the mixed solution A by mass percentage, stir for 12-24 h to form a mixed solution B, and the solid content of the mixed solution B is 5%-30%. (4) Place the mixed solution B in an evaporating dish with a length, width, and height of 10 cm×10 cm×3 cm, and place it in a vacuum drying oven at 60 °C for 48 h. (5) Peel off the film material and cut it into thin films of the same size for standby.

6. The preparation method of a composite solid electrolyte containing a zirconia nanotube composite filler according to claim 5, characterized in that: The thickness of the film can be controlled in the range of micrometers to centimeters. The first method is to control the solid content of the mixed solution; the second method is to control the volume of the mixed solution used during evaporation; the third method is to laminate multiple thin films together by hot pressing. The hot pressing parameters are a temperature of 80-100 °C and a pressure of 10-20 kg.

7. The preparation method of a composite solid electrolyte containing a zirconia nanotube composite filler according to claim 1, characterized in that: In step (2), the solvent is one or more of N,N-dimethylformamide and N-methylpyrrolidone.

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