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

Abstract

The invention provides a polymer electrolyte as well as a preparation method and application thereof. The polymer electrolyte is a PVDF-HFP (Polyvinylidene Fluoride-Hexafluoropropylene) polymer film which takes LLZTO treated by a plasma enhanced chemical vapor deposition method as a filler. The preparation method of the polymer electrolyte comprises the following steps: S1, preparing PVDF-HFP-based solid electrolyte slurry; s2, the LLZTO is subjected to plasma enhanced chemical vapor deposition treatment, and P-LLZTO is obtained; and S3, adding the P-LLZTO into the PVDF-HFP-based solid electrolyte slurry, coating a mold with the P-LLZTO slurry in a casting manner, and performing vacuum drying to obtain the polymer electrolyte. And the polymer electrolyte is arranged between the positive electrode and the lithium metal negative electrode to form the solid-state lithium metal battery. The polymer electrolyte has excellent ionic conductivity and relatively strong lithium dendrite inhibition capability.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state lithium metal battery polymer electrolytes, and in particular to a solid-state battery polymer electrolyte and a preparation method and application thereof. Background Art

[0002] With the global energy crisis and environmental issues becoming increasingly severe, the development of high-energy-density, high-safety energy storage systems has become a research priority. Among numerous energy storage devices, lithium metal batteries (LiM) have attracted significant attention due to their high theoretical energy density. The LiM anode, with its theoretical specific capacity of up to 3860 mAh g⁻¹ and low redox potential of -3.04 V (vs. standard hydrogen electrode), is considered an ideal candidate for next-generation anode materials. However, LiM batteries still face numerous challenges in practical application. In liquid electrolyte systems, LiM ions readily form LiDs during repeated deposition / dissolution processes. This not only leads to the production of "dead lithium," but can also cause battery short circuits and even serious safety incidents such as combustion and explosion. Furthermore, the inherent flammability and leakage of traditional liquid electrolytes further limit the commercial application of LiM batteries.

[0003] To solve the above problems, researchers have proposed a strategy to replace liquid organic electrolytes with solid electrolytes. Compared with liquid electrolytes, solid electrolytes have a wider electrochemical stability window and can be used with high-voltage positive electrode materials, while effectively avoiding the risk of electrolyte leakage and volatilization. More importantly, the excellent mechanical strength of solid electrolytes can effectively inhibit the growth of lithium dendrites, ensure the stable transmission and uniform deposition of lithium ions, and thus significantly improve the cycle stability of all-solid-state lithium batteries. Among the many solid electrolyte materials, although solid inorganic electrolytes have excellent ionic conductivity and mechanical properties, their poor interface contact performance and harsh processing conditions limit their practical applications. In contrast, solid polymer electrolytes have attracted much attention due to their excellent flexibility, processability and good interface contact characteristics.

[0004] Among various polymer matrices, PVDF-HFP-based polymer electrolytes exhibit unique advantages: First, the highly polar -CF and -CF3 units in the PVDF-HFP molecule effectively promote lithium salt dissociation, providing a high concentration of charge carriers. Second, the high bond energy of the CF bond imparts excellent chemical stability and corrosion resistance to the material. Furthermore, PVDF-HFP exhibits a wide electrochemical window (>4.5V), good thermal stability, and excellent film-forming properties. Compared with polyethylene oxide (PEO)-based electrolytes, which have lower dielectric constants, PVDF-HFP's higher relative dielectric constant further facilitates lithium salt dissociation. Although PVDF-HFP-based solid polymer electrolytes exhibit outstanding flexibility, mechanical strength, and electrochemical stability, their ionic conductivity remains to be improved. Therefore, the design and development of high-performance PVDF-HFP-based polymer electrolytes is of great scientific significance and application value for promoting the development of solid-state lithium batteries. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a solid-state battery polymer electrolyte with excellent ionic conductivity and strong lithium dendrite inhibition ability.

[0006] The technical solution adopted to solve the above technical problems is: a polymer electrolyte, wherein the polymer electrolyte is LLZTO (Li 6.5 La3Zr 1.5 Ta 0.5 O 12 ) as filler PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene copolymer) polymer film.

[0007] Preferably, the thickness of the polymer electrolyte is 80 μm-100 μm.

[0008] A method for preparing a polymer electrolyte comprises the following steps:

[0009] S1 prepares PVDF-HFP based solid electrolyte slurry;

[0010] S2 treated LLZTO with plasma enhanced chemical vapor deposition to obtain P-LLZTO (modified Li 6.5 La3Zr 1.5 Ta 0.5 O 12 );

[0011] S3 adds P-LLZTO to PVDF-HFP-based solid electrolyte slurry, coats it on the mold by casting, and obtains polymer electrolyte after vacuum drying.

[0012] Preferably, step S1 is specifically: adding PVDF-HFP polymer to DMA c (N,N-dimethylacetamide) solvent was stirred for 5 h, wherein DMA c The mass ratio of lithium salt to PVDF-HFP polymer is 80:3, and then lithium salt is added, the mass ratio of lithium salt (LiTFSI) to PVDF-HFP polymer is 1:2, after stirring for 10 minutes, it is placed in an ultrasonic instrument for 15 minutes, and then stirred for 8-12 hours to obtain a PVDF-HFP-based solid electrolyte slurry.

[0013] Preferably, step S2 specifically comprises: placing LLZTO in a PECVD device for plasma enhanced chemical vapor deposition treatment at a temperature of 400-700° C., a power of 50 W, and an Ar / H 2 atmosphere for 2 hours.

[0014] Preferably, the heating rate of the PECVD equipment is 5°C / min.

[0015] Preferably, the temperature is 550° C. and the power is 50W.

[0016] Preferably, the P-LLZTO added in step S3 is 5-20% of the total mass of the polymer electrolyte.

[0017] Preferably, the amount of P-LLZTO added in step S3 is 15% of the total mass of the polymer electrolyte.

[0018] The invention relates to an application of a polymer electrolyte, wherein the polymer electrolyte is installed between a positive electrode and a lithium metal negative electrode to form a solid-state lithium metal battery.

[0019] The beneficial effects of the present invention are:

[0020] Plasma-enhanced chemical vapor deposition technology modifies the high-performance structure of LLZTO, creating oxygen vacancies. This gives the polymer electrolyte excellent ionic conductivity and strong lithium dendrite suppression capabilities, resolving the problem of unsatisfactory ionic conductivity caused by the high crystallinity of PVDF-HFP at room temperature, which limits the movement of chain segments and the diffusion of ions. PVDF-HFP polymer films have good flexibility and mechanical strength, and when mixed with lithium salts and other plasticizers, they exhibit high mechanical properties and can reduce dendrite formation. PVDF-HFP-based polymer electrolytes with P-LLZTO inorganic fillers can effectively inhibit lithium dendrites from penetrating the electrolyte membrane, forming an electrolyte structure with stable ion / electron transport, improving the interfacial contact between the electrode and the electrolyte, and significantly improving the low ionic conductivity and high impedance of the polymer electrolyte. This solves the problem of insufficient interfacial contact between the electrode and the electrolyte, which is detrimental to ion transport and easily induces polarization.

[0021] Therefore, a technical problem also solved by the present invention is the application of the above-mentioned polymer electrolyte, which is installed between the positive electrode and the lithium metal negative electrode to form a solid-state lithium metal battery, so as to promote the development of solid-state lithium metal batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be derived from these drawings without inventive effort. Among them:

[0023] Figure 1 This is a cross-sectional scanning electron microscope image of Example 1;

[0024] Figure 2 The lithium symmetric battery assembled in Example 1 was -2 Cyclic test diagram under current density;

[0025] Figure 3 This is a cycle diagram of the solid-state lithium metal battery assembled in Example 1 at 0.5C;

[0026] Figure 4 The ionic conductivity of the polymer electrolyte membranes prepared in Example 1, Comparative Example 1 and Comparative Example 2 at 30° C.

[0027] Figure 5 is the ionic conductivity of the polymer electrolyte membranes prepared in Example 1, Example 2 and Example 3 at 30°C;

[0028] Figure 6 is the ionic conductivity of the polymer electrolyte membranes prepared in Example 1, Example 4, Example 5 and Comparative Example 3 at 30° C.;

[0029] Figure 7 The XRD patterns of the polymer electrolytes of Example 1 and Comparative Example 4 are shown;

[0030] Figure 8 The XRD patterns of the polymer electrolytes of Example 1 and Comparative Example 5 are shown. DETAILED DESCRIPTION

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from the description. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0032] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0033] Example 1

[0034] A polymer electrolyte is a PVDF-HFP polymer film filled with LLZTO using plasma enhanced chemical vapor deposition (PECVD) technology.

[0035] A method for preparing a polymer electrolyte, which specifically comprises the following steps:

[0036] S1 Preparation of PVDF-HFP based solid electrolyte slurry; in a 20 mL glass bottle, add 8 g N, N-dimethylacetamide (DMA c ) as a solvent, 0.3g of PVDF-HFP was added to the solvent and stirred at room temperature for 5 hours. Subsequently, 0.15g of lithium salt (LiTFSI) was placed in a glass bottle and stirred with a magnetic stirrer for 10 minutes. The glass bottle was then transferred to an ultrasonicator and sonicated for 15 minutes. Finally, it was stirred thoroughly at room temperature for 10 hours to form a PVDF-HFP-based solid electrolyte slurry.

[0037] S2 placed LLZTO in a PECVD device for plasma-enhanced chemical vapor deposition treatment, using a power of 50 W, a heating rate of 5°C / min to 550°C, an Ar / H2 atmosphere for 2 hours, and kept warm for 2 hours, and then naturally cooled to room temperature to obtain P-LLZTO.

[0038] In step S3, the P-LLZTO obtained by the treatment is added to the PVDF-HFP-based solid electrolyte slurry prepared in step S1, coated on the mold by casting, and vacuum dried to obtain a polymer electrolyte, wherein P-LLZTO is 15% of the total mass of the polymer electrolyte, recorded as P-LLZTO-PHP.

[0039] Example 2

[0040] In step S2, the temperature is raised to 400° C. at a rate of 5° C. / min, and the rest is the same as in Example 1.

[0041] Example 3

[0042] In step S2, the temperature is raised to 700° C. at a rate of 5° C. / min, and the rest is the same as in Example 1.

[0043] Example 4

[0044] In step S3, the P-LLZTO accounts for 10% of the total mass of the polymer electrolyte, and the rest is the same as in Example 1.

[0045] Example 5

[0046] In step S3, the P-LLZTO accounts for 20% of the total mass of the polymer electrolyte, and the rest is the same as in Example 1.

[0047] Comparative Example 1

[0048] The power of the PECVD equipment in step S2 is 0 W, and the rest is the same as in Example 1.

[0049] Comparative Example 2

[0050] The power of the PECVD equipment in step S2 is 100 W, and the rest is the same as in Example 1.

[0051] Comparative Example 3

[0052] In step S3, the P-LLZTO accounts for 5% of the total mass of the polymer electrolyte, and the rest is the same as in Example 1.

[0053] Comparative Example 4

[0054] In a 20 mL glass bottle, add 8 g N,N-dimethylacetamide (DMA c ) as a solvent, 0.3g PVDF-HFP was added to the solvent and stirred at room temperature for 5h. Subsequently, 0.15g of lithium salt (LiTFSI) was placed in a glass bottle, and the solution was stirred for 10min by a magnetic stirrer. The glass bottle was then transferred to an ultrasonic instrument for 15min of ultrasonication. Finally, it was fully stirred at room temperature for 10h to form a PVDF-HFP-based solid electrolyte slurry. By a simple solution casting method, the PVDF-HFP-based solid electrolyte slurry was poured into a polytetrafluoroethylene mold and dried to form a film (denoted as PHP). After the film was formed, the electrolyte membrane was cut into small discs with a punch having a diameter of 14mm, and then vacuum packaged.

[0055] Comparative Example 5

[0056] In step S3, LLZTO replaces P-LLZTO, and the rest is the same as in Example 1.

[0057] Comparative Example 6

[0058] In step 2, Li5La3Nb2O 12 Replace LLZTO, and the rest is the same as in Example 1.

[0059] Material characterization and performance testing

[0060] like Figure 1 As shown, the polymer electrolyte of Example 1 is dense, and the P-LLZTO powder particles are evenly distributed in the matrix without agglomeration.

[0061] like Figure 2 As shown, the lithium symmetric battery assembled with the polymer electrolyte of Example 1 was subjected to a cycle test at 0.1 mA cm -2 Under high current density, it showed good cycle stability during the cycle process.

[0062] like Figure 3 As shown, the solid-state lithium metal full battery assembled with the polymer electrolyte of Example 1 was subjected to a 0.5C cycle test, and had good cycle performance and good electrochemical stability, thus ensuring the cycle stability of the battery.

[0063] like Figure 4 As shown, compared with Comparative Examples 1 and 2, the ionic conductivity of Example 1 at 30°C and 550°C and 50W is better (8.18×10 -4 S cm -1 ).

[0064] like Figure 5 As shown in the figure, the ionic conductivity of Examples 1, 2 and 3 is relatively good at 30°C, among which the ionic conductivity of Example 1 is the best (8.18×10 -4 S cm -1 ).

[0065] like Figure 6 As shown, compared with Comparative Example 3, Example 1, Example 4 and Example 5 have better ionic conductivity at 30° C., among which Example 1 has the best ionic conductivity.

[0066] like Figure 7 As shown in the figure, comparing the peak position changes before and after the composite P-LLZTO, it can be seen that no obvious changes were found in the synthesized composite electrolyte, which means that the P-LLZTO ceramic powder and PVDF-HFP have good stability during the preparation process and no chemical reaction occurs between the two. However, with the addition of P-LLZTO powder, the crystallinity of the PVDF-HFP polymer decreases.

[0067] like Figure 8 As shown in FIG, from the XRD data, it can be seen that after Ar / H2 atmosphere PECVD treatment, the diffraction angle of P-LLZTO is slightly shifted to the right compared with the untreated LLZTO powder, proving that the LLZTO powder is reduced.

[0068] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A polymer electrolyte, characterized in that The polymer electrolyte is a PVDF-HFP polymer film filled with LLZTO processed by plasma enhanced chemical vapor deposition.

2. A polymer electrolyte according to claim 1, characterized in that: The thickness of the polymer electrolyte is 80 μm-100 μm.

3. A method for preparing a polymer electrolyte according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1 prepares PVDF-HFP based solid electrolyte slurry; S2 processes LLZTO by plasma enhanced chemical vapor deposition to obtain P-LLZTO; S3 adds P-LLZTO to PVDF-HFP-based solid electrolyte slurry, coats it on the mold by casting, and obtains polymer electrolyte after vacuum drying.

4. The method for preparing a polymer electrolyte according to claim 3, wherein: Step S1 specifically includes: adding PVDF-HFP polymer to DMA c Stir in solvent for 5 h, wherein DMA c The mass ratio of lithium salt to PVDF-HFP polymer is 80:3, and then lithium salt is added, the mass ratio of lithium salt to PVDF-HFP polymer is 1:2, stirred for 10 minutes, and then placed in an ultrasonic instrument for 15 minutes, and then stirred for 8-12 hours to obtain a PVDF-HFP-based solid electrolyte slurry.

5. The method for preparing a polymer electrolyte according to claim 3, wherein: Step S2 specifically includes placing LLZTO in a PECVD device for plasma enhanced chemical vapor deposition treatment at a temperature of 400-700°C, a power of 50W, and an Ar / H2 atmosphere for 2 hours.

6. The method for preparing a polymer electrolyte according to claim 5, characterized in that: The heating rate of the PECVD equipment is 5°C / min.

7. The method for preparing a polymer electrolyte according to claim 5, wherein: The temperature is 550° C. and the power is 50W.

8. The method for preparing a polymer electrolyte according to claim 3, wherein: The amount of P-LLZTO added in step S3 is 5-20% of the total mass of the polymer electrolyte.

9. The method for preparing a polymer electrolyte according to claim 3, wherein: The amount of P-LLZTO added in step S3 is 15% of the total mass of the polymer electrolyte.

10. Use of the polymer electrolyte according to any one of claims 1 to 9, characterized in that: The polymer electrolyte is installed between the positive electrode and the lithium metal negative electrode to form a solid-state lithium metal battery.

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