Solid-state battery polymer electrolyte membrane and preparation method and application thereof

Abstract

The invention discloses a solid-state battery polymer electrolyte membrane as well as a preparation method and application thereof. The polymer electrolyte membrane is a PVDF-TRFE-CFE polymer membrane which is prepared by an electrostatic spinning method and is added with inorganic filler LLZTO and YSZ (Yttria Stabilized Zirconia) subjected to plasma enhanced chemical vapor deposition treatment. The YSZ nanoparticles with high dielectric constant can effectively induce the formation of a high dielectric state in PVDF, and promote the dissociation of lithium salt and the rapid transportation of Li < + >; the YSZ / P produces surface defects, the surface property of the YSZ / P is optimized, lithium salt dissociation can be further promoted, and meanwhile the interfacial compatibility with a polymer electrolyte membrane is effectively improved; by adding LLZTO, the movement of a polymer chain segment can be promoted, and the ion transmission capability is further improved; and YSZ / P and LLZTO are added at the same time, so that the tolerance of the polymer electrolyte membrane to the environment can be further improved, the interface impedance is reduced, and the side reaction is reduced, thereby prolonging the service life of the solid-state battery.

Description

Technical Field

[0001] The present invention belongs to the field of solid-state battery polymer electrolytes, and specifically relates to a PVDF-based solid-state battery polymer electrolyte membrane prepared by electrospinning and simultaneously adding YSZ and LLZTO inorganic fillers modified by PECVD plasma technology, as well as a preparation method and application thereof. Background Art

[0002] With the rapid development of energy technology and the booming new energy industry, electrochemical devices such as lithium-ion batteries, capacitors, and fuel cells have become the key force driving the application of modern energy technology. At the same time, the energy industry's demand for sustainable high-energy density storage is also growing. Lithium-ion batteries using traditional graphite anodes have a low theoretical capacity (300mAh g -1 ) limit, and gradually cannot meet the growing demand for energy storage. Therefore, it has a low electrochemical potential of -3.04V (vs. standard hydrogen electrode) and 3860mAh g -1 Lithium metal, with its high specific capacity, is considered an ideal anode material. However, liquid electrolyte lithium metal batteries face numerous issues during cycling, such as volume expansion caused by lithium dendrite growth and poor electrochemical stability due to interfacial compatibility, which severely impact their safety, electrochemical stability, and energy density. Finding a suitable electrolyte system is key to achieving good electrochemical performance in lithium metal batteries.

[0003] Polymer electrolytes have unique performance advantages in solid-state battery energy systems. Polymer electrolytes not only provide efficient ion conduction channels, but also significantly improve battery safety and cycle stability. They also have excellent designability and processing performance, and are electrolyte materials that researchers focus on.

[0004] Compared with other polymers, polymer electrolytes based on PVDF (polyvinylidene fluoride) have significant advantages, including good electrochemical stability, good film-forming properties, wide electrochemical window, good mechanical properties and good thermal stability. PVDF-based polymers have a highly polar -CF group, which can promote the dissociation of lithium salts and provide a high concentration of ion carriers. PVDF molecules contain a large number of fluorine atoms, and the strong covalent bonds formed by these fluorine atoms and carbon atoms make PVDF have good chemical inertness and corrosion resistance. There is still a lot of room for improvement in the combined performance of polyvinylidene fluoride-based solid polymer electrolytes (PVDF-SPE), especially in terms of ionic conductivity. Therefore, it is of great significance to design a high-performance PVDF-based polymer electrolyte membrane. Summary of the Invention

[0005] A technical problem to be solved by this application is to overcome the defects of the above-mentioned related technologies and provide a PVDF-based three-dimensional solid-state battery polymer electrolyte membrane with high ionic conductivity and low interface impedance to reduce side reactions and improve the service life of solid-state batteries.

[0006] The technical solution adopted by this polymer electrolyte membrane to solve the above technical problems is: a solid-state battery polymer electrolyte membrane, which is a polymer electrolyte membrane obtained by electrospinning, comprising a polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene polymer film, which is filled with inorganic filler lithium lanthanum zirconium tantalum oxide and yttrium-doped zirconium oxide modified by plasma enhanced chemical vapor deposition treatment.

[0007] Preferably, the polymer electrolyte membrane has a thickness of 80 μm to 120 μm. This thickness is most suitable for polymer electrolyte membranes. A thicker thickness will limit the energy density of solid-state batteries; a thinner thickness will reduce mechanical properties, weaken the polymer electrolyte membrane's resistance to lithium dendrites, and increase the possibility of short circuits.

[0008] Preferably, the mass fraction of the yttrium-doped zirconia modified by plasma enhanced chemical vapor deposition treatment is 5 mass%.

[0009] Another technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned solid-state battery polymer electrolyte membrane, which specifically comprises the following steps:

[0010] S1. performing plasma enhanced chemical vapor deposition on yttrium-doped zirconia nanopowder to obtain modified yttrium-doped zirconia powder;

[0011] S2, adding lithium lanthanum zirconium tantalum oxide powder and modified yttrium-doped zirconium oxide powder simultaneously to a mixed solution containing polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene to obtain an electrospinning solution, and obtaining an electrospinning membrane by an electrospinning method;

[0012] S3, soaking the electrospun membrane in a yttrium-doped zirconia solution, and drying the electrospun membrane to obtain a polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene polymer film;

[0013] S4. Immersing the polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene polymer film in a mixed lithium salt solution based on polyvinylidene fluoride, and drying the immersed polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene polymer film to obtain a polymer electrolyte membrane.

[0014] Preferably, the mixed solution containing polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene in step S2 is obtained by dissolving the same weight of polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene and polyurethane in a ratio of 1:1 wt% in a mixed solvent of dimethylformamide and tetrahydrofuran in a volume ratio of 1:1, heating and stirring at 60°C until dissolved.

[0015] Preferably, the parameters of the electrospinning method in step S2 are: 2.5 ml / h, 14 KV, roller rotation speed of 50 rpm, the distance between the collector tip and the collector is 15 cm, and the environmental conditions during the spinning process are maintained in the relative humidity of 50-60% and the temperature range of 20-23°C; and glossy paper is used for collection.

[0016] Preferably, the preparation process of the mixed lithium salt solution based on polyvinylidene fluoride in step S4 is: SN, PVDF and LiTFSI are mixed in a mass ratio of 3:2:2 and dissolved in a certain amount of acetonitrile solution, and 2% volume of fluoroethylene carbonate is added, and stirred at room temperature overnight.

[0017] Compared with the existing technology, the advantages of this solid-state battery polymer electrolyte membrane and its preparation method are: it is prepared by electrospinning and simultaneously adds a high-performance three-dimensional porous network structure of YSZ and LLZTO modified by plasma chemical vapor deposition, so that this solid-state battery polymer electrolyte membrane has excellent ionic conductivity and strong lithium dendrite inhibition ability, solving the problem of unsatisfactory ionic conductivity caused by the high crystallinity of PVDF at room temperature limiting the movement of chain segments and the diffusion ability of ions; the PVDF-TRFE-CFE polymer film inherits the flexibility and mechanical strength of PVDF, and when mixed with lithium salts and other plasticizers, has high mechanical properties, which can reduce the formation of dendrites and consume electrolytes; the YSZ modified by PECVD creates surface defects, and its surface properties are optimized, which can further promote the dissociation of lithium salts, while effectively improving the interfacial compatibility with the polymer electrolyte membrane, effectively inhibiting lithium dendrites from penetrating the electrolyte membrane, forming a three-dimensional structural electrolyte membrane with stable ion / electron transport, and improving the interfacial contact between the electrode and the electrolyte membrane. At the same time, electrospinning is an important method for preparing composite electrolyte membranes with three-dimensional porous network structures. It provides strong mechanical support for the composite of CPE membranes with polymers and lithium salts, and prepares high-performance composite polymer electrolytes with high ionic conductivity and excellent mechanical properties.

[0018] Another technical problem solved by the present invention is the application of the above-mentioned solid-state battery polymer electrolyte membrane, which is installed between the positive electrode and the lithium metal negative electrode to form a solid-state battery, so as to promote the development of quasi-solid-state batteries.

[0019] Preferably, the solid-state battery is a lithium symmetric solid-state battery with a critical current density (CCD) of 1.6 mA cm at 25°C. -2 . BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 These are the AC impedance spectra of electrospinning membranes prepared by electrospinning without adding inorganic fillers and filled with different inorganic fillers.

[0021] Figure 2 This is a step current density diagram of the lithium symmetric solid-state battery assembled with the polymer electrolyte membrane of Verification Example 1 of the present invention.

[0022] Figure 3 This is a critical current density diagram of the lithium symmetric solid-state battery test assembled with the polymer electrolyte membrane of Verification Example 1 of the present invention.

[0023] Figure 4 This is a scanning electron microscope image of a polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene polymer film with an inorganic filler of 5% YSZ / P 1h + 1% LLZTO.

[0024] Figure 5 This is a critical current density diagram of a lithium symmetric solid-state battery assembled with a polymer electrolyte membrane according to Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0025] First, those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the embodiments of the present application and are not intended to limit the scope of protection of the embodiments of the present application. Those skilled in the art may adjust them as needed to suit specific application scenarios.

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] The present invention provides a solid-state battery polymer electrolyte membrane, specifically a polymer electrolyte membrane obtained by electrospinning, with a thickness of 80 to 120 μm. The membrane comprises a polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene (PVDF-TRFE-CFE) polymer film filled with lithium lanthanum zirconium tantalum oxide (LLZTO) and plasma-enhanced chemical vapor deposition (PECVD)-modified yttrium-doped zirconia (YSZ) inorganic filler. The mass fraction of the PECVD-modified yttrium-doped zirconia is 5 mass%.

[0028] The above-mentioned method for preparing the solid-state battery polymer electrolyte membrane specifically comprises the following steps:

[0029] S1. performing plasma enhanced chemical vapor deposition on yttrium-doped zirconia nanopowder to obtain modified yttrium-doped zirconia powder, denoted as YSZ / P or YSZ,P;

[0030] Among them, the method of PECVD modification of YSZ is specifically as follows:

[0031] YSZ nanopowder was placed in a magnetic boat, and then placed in a PECVD tube. The temperature was raised to 500°C at a rate of 5°C / min at 500W, and kept at this temperature for 1 hour. The temperature was then naturally cooled to room temperature to obtain PECVD-modified YSZ powder.

[0032] S2, adding lithium lanthanum zirconium tantalum oxide powder and modified yttrium-doped zirconium oxide powder simultaneously to a mixed solution containing polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene to obtain an electrospinning solution, and obtaining an electrospinning membrane by an electrospinning method;

[0033] The mixed solution is prepared by dissolving polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene and polyurethane (TPU) in a 1:1 wt% ratio in a 1:1 volume ratio of dimethylformamide and tetrahydrofuran, heating and stirring at 60° C. until dissolved.

[0034] LLZTO powder and YSZ / P powder were added to the mixed solution and stirred at room temperature overnight to obtain an electrospinning solution;

[0035] The parameters of the electrospinning method were: 2.5 ml / h, 14 kV, roller rotation speed of 50 rpm, the distance between the collector tip and the collector was 15 cm, the environmental conditions during the spinning process were maintained in the relative humidity range of 50-60% and the temperature range of 20-23 ° C; and glossy paper was used for collection.

[0036] S3, soaking the electrospun membrane in a yttrium-doped zirconia solution, and drying the electrospun membrane to obtain a polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene polymer film;

[0037] S4, soaking the polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene polymer film in a mixed lithium salt solution based on polyvinylidene fluoride, and drying the soaked polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene polymer film to obtain a polymer electrolyte membrane;

[0038] Preparation of a polyvinylidene fluoride-based mixed lithium salt solution: SN, PVDF, and LiTFSI were mixed in a mass ratio of 3:2:2 and dissolved in a certain amount of acetonitrile solution. 2% by volume of fluoroethylene carbonate (FEC) was added and stirred at room temperature overnight. This mixed lithium salt solution was designated as PVDF-TRFE-CFE / SN / LiTFSI.

[0039] The mixed lithium salt solution was uniformly infiltrated into the YSZ-soaked polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene polymer film, and then placed in an oven and dried at 50° C. for 10 hours.

[0040] Verification Example 1

[0041] This verification example provides a method for preparing a three-dimensional polymer electrolyte membrane of a solid-state battery prepared by electrospinning, and simultaneously adding YSZ and LLZTO modified by plasma chemical vapor deposition as fillers PVDF-TRFE-CFE polymer films, which specifically includes the following steps:

[0042] S1 performs plasma enhanced chemical vapor deposition on YSZ to obtain modified YSZ;

[0043] S2: adding the modified 5% YSZ and 1% LLZTO to a mixed solution to obtain an electrospinning solution, and electrospinning to obtain an electrospinning membrane; wherein the mixed solution is specifically: dissolving 0.75g of PVDF-TrFE-CFE and TPU in a 1:1wt% ratio in 6ml of a mixed solvent of dimethylformamide (DMF) and tetrahydrofuran (THF), and heating the mixture and stirring at 60°C until dissolved;

[0044] S3: immersing the electrospun membrane in a YSZ solution and drying it to obtain a PVDF-TRFE-CFE polymer film;

[0045] S4: Immerse the PVDF-TRFE-CFE polymer film in a mixed lithium salt solution, followed by drying to obtain a CPE film. The mixed lithium salt solution is prepared by mixing 0.3 g of SN, 0.2 g of PVDF, and 0.2 g of LiTFSI in 2 ml of acetonitrile, adding 2% fluoroethylene carbonate (FEC), and stirring at room temperature overnight.

[0046] Comparative Example 1

[0047] This comparative example provides a method for preparing a three-dimensional polymer electrolyte membrane using an electrospinning method and adding LLZTO as a filler to a PVDF-TRFE-CFE polymer film, which specifically includes the following steps:

[0048] Omit S1 to perform plasma enhanced chemical vapor deposition on YSZ;

[0049] S2: 1% LLZTO is added to the mixed solution to obtain an electrospinning solution, and electrospinning is performed to obtain an electrospinning membrane; the mixed solution is the same as the mixed solution of the verification example;

[0050] S3: immersing the electrospun membrane in a YSZ solution and drying it to obtain a PVDF-TRFE-CFE polymer film, which is recorded as PVDF-TRFE-CFE / 1% LLZTO;

[0051] S4: PVDF-TRFE-CFE / 1% LLZTO is immersed in a mixed lithium salt solution, and then dried to obtain a CPE film; the mixed lithium salt solution is the same as the mixed lithium salt solution of the verification example.

[0052] Material characterization and performance testing

[0053] The electrospinning membrane with 1% LLZTO prepared in Comparative Example 1 was subjected to an AC impedance test at room temperature. The AC impedance spectrum was as shown in FIG. Figure 1 As shown in the test results, the ionic conductivity of the prepared three-dimensional structured composite electrolyte is 2.5×10 -4 S / cm. Figure 1 In the figure, the PVDF line represents the AC impedance spectrum of the electrospun membrane without adding inorganic filler in step 2, the (5%) LLZTO line represents the AC impedance spectrum of the electrospun membrane with 5% by mass LLZTO added as inorganic filler in step 2, the (5%) YSZ line represents the AC impedance spectrum of the electrospun membrane with 5% by mass ordinary YSZ added as inorganic filler in step 2, the (5%) YSZ / P+(1%) LLZTO line represents the AC impedance spectrum of the electrospun membrane with 5% by mass modified YSZ and 1% by mass LLZTO added as inorganic filler in step 2, and the (5%) YS The Z / P+(2%)LLZTO line represents the AC impedance spectrum of the electrospun membrane in which 5% of modified YSZ by mass and 2% of LLZTO by mass are added as inorganic fillers in step 2, the (5%)YSZ / P+(5%)LLZTO line represents the AC impedance spectrum of the electrospun membrane in which 5% of modified YSZ by mass and 5% of LLZTO by mass are added as inorganic fillers in step 2, and the (5%)YSZ+(1%)LLZTO line represents the AC impedance spectrum of the electrospun membrane in which 5% of ordinary YSZ by mass and 1% of LLZTO by mass are added as inorganic fillers in step 2.

[0054] Depend on Figure 4 The modified 5% YSZ and 1% LLZTO electrospun membranes were subjected to AC impedance test at room temperature. The AC impedance spectrum is shown in Figure 1 As shown in the test results, the ionic conductivity of the prepared three-dimensional structured composite electrolyte is 6.1×10 -4 S / cm.

[0055] The lithium symmetric solid-state battery assembled with the modified 5% YSZ and 1% LLZTO polymer electrolyte membrane in Verification Example 1 was subjected to cycle testing. The test results are shown in Figure 2. Figure 2 As shown in Figure 3, the battery cycle stability is achieved at different current densities, proving that PECVD-modified YSZ and LLZTO ensure the battery cycle stability performance.

[0056] Depend on Figure 5 It can be seen that the lithium symmetric solid-state battery assembled with the polymer electrolyte membrane of 1% LLZTO in Comparative Example 1 has a CCD of 0.7 mA / cm at 25°C. -2 .Depend on Figure 3 It can be seen that the lithium symmetric solid-state battery assembled with the polymer electrolyte membrane of Verification Example 2 has a CCD of 1.6 mA / cm at 25°C. -2 This demonstrates that altering the doping of LLZTO and PECVD-treated YSZ in Comparative Example 1 and Verification Example 1 significantly improves the ionic conductivity of the polymer electrolyte. However, since PECVD was not performed in Comparative Example 1, the electrolyte polarization impedance is relatively high. Therefore, PECVD-treated YSZ and the addition of an appropriate proportion of LLZTO achieve optimal interfacial impedance, excellent ionic conductivity, and stable CCD data.

[0057] Depend on Figure 4 The scanning electron microscope shown in the figure shows that the polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene polymer film used to prepare the polymer electrolyte membrane in Verification Example 1 has relatively uniform distribution between its electrospun fibers, and some white particles are relatively evenly loaded on the surface, which are YSZ inorganic filler nanoparticles.

[0058] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A solid-state battery polymer electrolyte membrane, characterized in that: The invention relates to a polymer electrolyte membrane obtained by electrostatic spinning, which comprises a polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene polymer film filled with inorganic fillers of lithium lanthanum zirconium tantalum oxide and yttrium-doped zirconium oxide modified by plasma enhanced chemical vapor deposition treatment.

2. A solid-state battery polymer electrolyte membrane according to claim 1, characterized in that: The thickness of the polymer electrolyte membrane is 80 μm to 120 μm.

3. A solid-state battery polymer electrolyte membrane according to claim 2, characterized in that: The mass fraction of the yttrium-doped zirconia modified by plasma enhanced chemical vapor deposition is 5 mass %.

4. The method for preparing a solid-state battery polymer electrolyte membrane according to claim 2 or 3, wherein: The specific steps include: S1. performing plasma enhanced chemical vapor deposition on yttrium-doped zirconia nanopowder to obtain modified yttrium-doped zirconia powder; S2, adding lithium lanthanum zirconium tantalum oxide powder and modified yttrium-doped zirconium oxide powder simultaneously to a mixed solution containing polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene to obtain an electrospinning solution, and obtaining an electrospinning membrane by an electrospinning method; S3, soaking the electrospun membrane in a yttrium-doped zirconia solution, and drying the electrospun membrane to obtain a polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene polymer film; S4. Immersing the polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene polymer film in a mixed lithium salt solution based on polyvinylidene fluoride, and drying the immersed polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene polymer film to obtain a polymer electrolyte membrane.

5. The method for preparing a solid-state battery polymer electrolyte membrane according to claim 4, characterized in that: The mixed solution containing polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene in step S2 is obtained by dissolving equal weights of polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene and polyurethane in a 1:1 wt% ratio in a mixed solvent of dimethylformamide and tetrahydrofuran in a 1:1 volume ratio, heating and stirring at 60° C. until dissolved.

6. The method for preparing a solid-state battery polymer electrolyte membrane according to claim 5, characterized in that: The parameters of the electrospinning method in step S2 were: 2.5 ml / h, 14 kV, a roller rotation speed of 50 rpm, a distance between the collector tip and the collector of 15 cm, and the environmental conditions during the spinning process were maintained in the range of 50-60% relative humidity and 20-23°C; and glossy paper was used for collection.

7. The method for preparing a solid-state battery polymer electrolyte membrane according to claim 6, characterized in that: The preparation process of the mixed lithium salt solution based on polyvinylidene fluoride in step S4 is as follows: SN, PVDF and LiTFSI are mixed in a mass ratio of 3:2:2 and dissolved in a certain amount of acetonitrile solution, and 2% volume of fluoroethylene carbonate is added, and stirred at room temperature overnight.

8. An application of a solid-state battery polymer electrolyte membrane as claimed in claim 2 or 3, characterized in that: Installed between the positive electrode and the lithium metal negative electrode to form a solid-state battery.

9. The use of the solid-state battery polymer electrolyte membrane according to claim 8, characterized in that: The solid-state battery is a lithium symmetric solid-state battery with a critical current density (CCD) of 1.6 mA cm at 25°C. -2 .

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