A composite polymer solid electrolyte membrane and its preparation method and application

Abstract

The present invention discloses a composite polymer solid electrolyte membrane and its preparation method and application, which belongs to the technical field of solid electrolyte membrane preparation. The components of the composite polymer solid electrolyte membrane include: a polymer matrix, a lithium salt and an inorganic filler; wherein the inorganic filler is CoMoO4 nanoparticles or CoMoO4 nanorods. The present invention significantly improves the performance of the composite polymer solid electrolyte membrane by introducing inorganic filler-CoMoO4 nanoparticles or CoMoO4 nanorods, which is macroscopically reflected in the improvement of tensile properties and microscopically reflected in the electrolyte interface being more stable, accelerating ion transmission, effectively improving ionic conductivity, and improving lithium ion mobility. The composite polymer solid electrolyte membrane provided by the present invention has good ionic conductivity, mechanical properties and electrochemical stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid electrolyte membrane preparation, and in particular relates to a composite polymer solid electrolyte membrane and a preparation method and application thereof. Background Art

[0002] Composite polymer solid electrolytes have become a hot topic in solid-state battery research due to their ability to circumvent safety concerns such as flammable and explosive electrolytes while also addressing the poor mechanical properties of polymer electrolytes and the brittleness of inorganic electrolytes, which hinder their commercialization. However, composite polymer electrolytes face multiple challenges, including poor compatibility between the polymer matrix and inorganic fillers, and the difficulty in balancing mechanical properties and ionic conductivity, which have hindered their commercialization.

[0003] Faced with these challenges, the following measures are generally adopted to address the corresponding issues: ① Selecting inorganic fillers with strong morphological plasticity as the matrix material (surface morphologies include but are not limited to spherical, rod-like, flaky, or porous structures); ② Manipulating the surface morphology of the inorganic filler by controlling the crystallization growth conditions; ③ Differentiated interfacial compatibilities between inorganic fillers with different surface morphologies and the polymer matrix (this interfacial compatibility influences the filler-polymer interaction strength and lithium salt dissociation efficiency); and ④ The optimized filler morphology constructs continuous lithium ion transport channels. This results in simultaneous improvements in the mechanical strength, lithium ion transference number, and ionic conductivity of the composite electrolyte. Currently, inactive inorganic fillers in composite polymer solid electrolytes are primarily unit oxides, which offer limited performance improvements and poor cycling performance, failing to meet the requirements for improving the comprehensive electrochemical performance of composite polymer solid electrolytes. Unit oxides are unstable, and the significant difference in chemical properties between the unit oxides and the polymer matrix results in poor interfacial wettability. In addition, there is a large obstruction when electrons and ions are transmitted between the unit oxide and the polymer electrolyte interface, which leads to higher interface resistance, reducing the overall electrochemical performance of the battery, and causing problems such as lower charge and discharge efficiency and rate performance. Summary of the Invention

[0004] In response to the above technical problems, the present invention provides a composite polymer solid electrolyte membrane and its preparation method and application. By using nano-scale binary transition metal oxides as inactive fillers in composite polymer solid electrolytes, the inactive fillers and polymers are mixed more evenly and interact more strongly, which can better promote the dissociation of lithium salts and accelerate the Li + transmission.

[0005] The binary transition metal oxide molybdate of the present invention possesses the advantages of complex oxides, such as bimetallic ion pairs and an octahedral network structure. Furthermore, it features a simple crystal structure, high packing ratio, structural stability, and readily obtainable, stable, and highly catalytically active surface. Furthermore, the molybdate exhibits a high degree of morphological plasticity, allowing for tailored manipulation of its morphology to achieve desired catalytic performance.

[0006] The synergistic effect of different metal ions in binary transition metal oxide molybdates can optimize the local electronic structure and form more efficient ion transport pathways. This synergy not only reduces the activation energy of ion migration through interfacial charge redistribution, but also produces stronger interactions with the polymer matrix, thereby improving the overall ionic conductivity of the composite electrolyte. The crystal structure diversity of the binary system can improve the uniformity of filler dispersion in the polymer and reduce interfacial defects. Its complementary redox potential characteristics broaden the electrochemical window of the electrolyte. In addition, the electronic interaction between the two metals can reduce the activity of interfacial side reactions and reduce the uneven growth of the SEI film, thereby achieving a comprehensive improvement in the electrochemical performance of solid-state batteries.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] One of the technical solutions of the present invention is to provide a composite polymer solid electrolyte membrane, the components of which include: a polymer matrix, a lithium salt and an inorganic filler; the inorganic filler is CoMoO4 nanoparticles or CoMoO4 nanorods (binary transition metal oxide).

[0009] Optionally, the polymer matrix comprises polyethylene oxide (PEO) or polyvinylidene fluoride (PVDF).

[0010] Optionally, the lithium salt includes lithium bis(fluorosulfonyl)imide (LiTFSI).

[0011] Preferably, the mass ratio of the polymer matrix, lithium salt and inorganic filler is 1:0.3:(0.1-0.5) (most preferably 1:0.3:0.3).

[0012] Preferably, the preparation step of the CoMoO4 nanoparticles comprises: mixing a solution containing molybdate with a dispersion containing Co-ZIF, reacting at 50-80°C (most preferably 70°C), and calcining the resulting product to obtain CoMoO4 nanoparticles.

[0013] More preferably, the molar ratio of Mo in the molybdate-containing solution to Co in the Co-ZIF-containing dispersion is 1:1.

[0014] Optionally, the molybdate in the molybdate-containing solution is sodium molybdate.

[0015] Preferably, the CoMoO4 nanorods are obtained by calcining cobalt molybdate.

[0016] The second technical solution of the present invention: provides a method for preparing the above-mentioned composite polymer solid electrolyte membrane, comprising the following steps: preparing a casting liquid using a polymer matrix, a lithium salt and an inorganic filler as raw materials, and forming the casting liquid into a membrane, namely the composite polymer solid electrolyte membrane.

[0017] The third technical solution of the present invention is to provide an application of the above-mentioned composite polymer solid electrolyte membrane in the preparation of solid-state batteries.

[0018] The beneficial technical effects of the present invention are as follows:

[0019] The present invention uses nano-scale cobalt molybdate as an inorganic filler to prepare a composite polymer solid electrolyte membrane. After the addition of binary transition metal oxide cobalt molybdate with different nanostructures, the crystallinity of PEO is effectively reduced and its disorder is increased. Among them, the effect of nano-particle cobalt molybdate is more obvious.

[0020] The present invention significantly improves the performance of composite polymer solid electrolyte membranes by introducing an inorganic filler, nanoscale cobalt molybdate. This improvement is reflected in improved tensile properties on a macroscopic level and a more stable electrolyte interface on a microscopic level, enabling faster ion transfer and effectively increasing ionic conductivity. The composite polymer solid electrolyte membranes provided by the present invention exhibit excellent ionic conductivity, mechanical properties, and electrochemical stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 SEM images of CoMoO4 nanorods (a) prepared in Example 1 and CoMoO4 nanoparticles (b) prepared in Example 2.

[0022] Figure 2 These are macroscopic images of the composite polymer solid electrolyte membranes prepared in Comparative Example 1, Example 3, and Example 4, wherein a is the PEO composite polymer solid electrolyte membrane prepared in Comparative Example 1, b is the NRCMO-PEO composite polymer solid electrolyte membrane prepared in Example 3, and c is the NPCMO-PEO composite polymer solid electrolyte membrane prepared in Example 4.

[0023] Figure 3 These are SEM images of the composite polymer solid electrolyte membranes prepared in Comparative Example 1, Example 3, and Example 4, wherein a is the PEO composite polymer solid electrolyte membrane prepared in Comparative Example 1, b is the NRCMO-PEO composite polymer solid electrolyte membrane prepared in Example 3, and c is the NPCMO-PEO composite polymer solid electrolyte membrane prepared in Example 4.

[0024] Figure 41 and 2 are XRD patterns of the composite polymer solid electrolyte membranes prepared in Comparative Example 1, Example 3, and Example 4.

[0025] Figure 5 The tensile properties of the composite polymer solid electrolyte membranes prepared in Comparative Example 1, Example 3 and Example 4 are shown.

[0026] Figure 6 Graph showing the cycle performance of symmetrical batteries assembled using the composite polymer solid electrolyte membranes of Example 3, Example 4, and Comparative Example 1 as raw materials.

[0027] Figure 7 for Figure 6 A partial enlarged view, where a, b, and c are enlarged views of different cycle time periods.

[0028] Figure 8 This is a cycle performance diagram of a symmetrical battery assembled using the composite polymer solid electrolyte membranes of Comparative Examples 4 and 5 as raw materials.

[0029] Figure 9 This is a cycle performance diagram of an all-solid-state battery assembled using the composite polymer solid electrolyte membranes of Example 3, Example 4 and Comparative Example 1 as raw materials. DETAILED DESCRIPTION

[0030] Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention.

[0031] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention.

[0032] In addition, for numerical ranges in the present invention, it is understood that each intervening value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or stated range, and any other stated value or intervening value in the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention.

[0034] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0035] Unless otherwise specified, the room temperature in the examples and comparative examples of the present invention refers to a temperature of 20±10°C.

[0036] Example 1

[0037] Preparation of CoMoO4 nanorods (NRCMO):

[0038] 2.142 g CoCl2·6H2O and 2.42 g Na2MoO4·2H2O were dissolved in 40 / 60 mL deionized water, respectively, to obtain a solution containing a Co source and a solution containing a Mo source. The solution containing a Mo source was added to the solution containing a Co source, stirred in a 70°C water bath for 3 h, centrifuged, and the precipitate was washed with deionized water and alcohol in sequence. It was then dried in an oven at 80°C for 24 h, then heated to 400°C at a rate of 2°C / min, kept warm for 3 h, and calcined. The temperature was naturally cooled to room temperature to obtain CoMoO4 nanorods.

[0039] Example 2

[0040] Preparation of CoMoO4 nanoparticles (NPCMO):

[0041] 2.142 g of CoCl2·6H2O and 1.64 g of dimethylimidazole (C4H6N2) were dissolved in 40 mL of deionized water, mixed, and stirred at room temperature for 7 h to obtain a Co-ZIF dispersion; 2.42 g of Na2MoO4·2H2O was dissolved in 60 mL of deionized water and added to the Co-ZIF dispersion with a molar ratio of Mo to Co of 1:1. The mixture was stirred in a 70°C water bath for 3 h, centrifuged, and the precipitate was washed with deionized water and alcohol in sequence, then dried in an 80°C oven for 24 h, then heated to 400°C at a rate of 2°C / min, kept warm for 3 h, and calcined, and then cooled to room temperature naturally to obtain CoMoO4 nanoparticles.

[0042] The SEM images of the CoMoO4 nanorods prepared in Example 1 and the CoMoO4 nanoparticles prepared in Example 2 are shown in FIG. Figure 1 .

[0043] Depend on Figure 1 It can be seen that the nano-granular CoMoO4 has a smaller particle size and a larger specific surface area, which can expose more active sites. It is more evenly mixed with the polymer and has a stronger interaction, which can better promote the dissociation of lithium salts and accelerate Li + The composite polymer solid electrolyte prepared by the inorganic filler with this morphology will have better electrochemical performance.

[0044] Example 3

[0045] Preparation of composite polymer solid electrolyte membrane using CoMoO4 nanorods:

[0046] 1 g of PEO, 0.3 g of LiTFSI, and 0.3 g of NRCMO prepared in Example 1 were weighed, dissolved in 10 mL of anhydrous acetonitrile, and stirred at room temperature for 24 h to obtain a casting solution;

[0047] The obtained casting liquid was added to a round hole polytetrafluoroethylene template with a diameter of 19 mm and a depth of 0.5 mm. After evaporating the solvent in a glove box with an argon atmosphere, the electrolyte membrane was peeled off and placed in a vacuum drying oven at 60°C for 24 hours to obtain an NRCMO-PEO composite polymer solid electrolyte membrane, which was then stored in an argon atmosphere glove box.

[0048] Example 4

[0049] Preparation of composite polymer solid electrolyte membrane using CoMoO4 nanoparticles:

[0050] 1 g of PEO, 0.3 g of LiTFSI, and 0.3 g of NPCMO prepared in Example 2 were weighed, dissolved in 10 mL of anhydrous acetonitrile, and stirred at room temperature for 24 h to obtain a casting solution;

[0051] The obtained casting liquid was added to a round hole polytetrafluoroethylene template with a diameter of 19 mm and a depth of 0.5 mm. After evaporating the solvent in a glove box with an argon atmosphere, the electrolyte membrane was peeled off and placed in a vacuum drying oven at 60°C for 24 hours to obtain an NPCMO-PEO composite polymer solid electrolyte membrane, which was then stored in an argon atmosphere glove box.

[0052] Comparative Example 1

[0053] Preparation of PEO composite polymer solid electrolyte membrane:

[0054] Weigh 1 g of PEO and 0.3 g of LiTFSI, dissolve them in 7 mL of anhydrous acetonitrile, and stir at room temperature for 24 h to obtain a casting solution;

[0055] The obtained casting liquid was added to a round hole polytetrafluoroethylene template with a diameter of 19 mm and a depth of 0.5 mm. The solvent was evaporated in a glove box with an argon atmosphere. After 24 hours, the electrolyte membrane was peeled off and placed in a vacuum drying oven at 60°C for 24 hours to obtain a PEO composite polymer solid electrolyte membrane, which was then stored in an argon atmosphere glove box.

[0056] Comparative Example 2

[0057] Preparation of Co3O4 nanoparticles:

[0058] 2.142g of CoCl2·6H2O and 1.64g of dimethylimidazole were dissolved in 40mL of deionized water, mixed, and stirred at room temperature for 7 hours. The solution was placed in a reactor and reacted in a 120°C oven for 12 hours. The precipitate was then filtered, washed with deionized water and then ethanol, dried in an 80°C oven for 24 hours, and then calcined at 400°C at a rate of 2°C / min, held for 3 hours, and cooled to room temperature to produce Co3O4 nanoparticles.

[0059] Comparative Example 3

[0060] Preparation of MoO3 nanoparticles:

[0061] 2.42g of Na2MoO4·2H2O and 1.64g of dimethylimidazole were dissolved in 60 / 40 mL of deionized water, respectively. The mixture was stirred at room temperature for 7 hours, then placed in a reactor and reacted in a 120°C oven for 12 hours. The precipitate was then filtered, washed with deionized water and then ethanol, and dried in an 80°C oven for 24 hours. The temperature was then increased to 400°C at a rate of 2°C / min, held for 3 hours, and then cooled to room temperature to produce MoO3 nanoparticles.

[0062] Comparative Example 4

[0063] Preparation of composite polymer solid electrolyte membrane using Co3O4 nanoparticles:

[0064] Weigh 1 g of PEO, 0.3 g of LiTFSI, and 0.3 g of Co3O4 nanoparticles prepared in Comparative Example 2, dissolve them in 10 mL of anhydrous acetonitrile, and stir at room temperature for 24 h to obtain a casting solution;

[0065] The obtained casting liquid was added to a round hole polytetrafluoroethylene template with a diameter of 19 mm and a depth of 0.5 mm. The solvent was evaporated in a glove box with an argon atmosphere. After 24 hours, the electrolyte membrane was peeled off and placed in a vacuum drying oven at 60°C for 24 hours to obtain a Co3O4-PEO composite polymer solid electrolyte membrane, which was then stored in an argon atmosphere glove box.

[0066] Comparative Example 5

[0067] Preparation of composite polymer solid electrolyte membrane using MoO3 nanoparticles:

[0068] Weigh 1 g of PEO, 0.3 g of LiTFSI, and 0.3 g of MoO3 nanoparticles prepared in Comparative Example 3, dissolve them in 10 mL of anhydrous acetonitrile, and stir at room temperature for 24 h to obtain a casting solution;

[0069] The obtained casting liquid was added to a round hole polytetrafluoroethylene template with a diameter of 19 mm and a depth of 0.5 mm. The solvent was evaporated in a glove box with an argon atmosphere. After 24 hours, the electrolyte membrane was peeled off and placed in a vacuum drying oven at 60°C for 24 hours to obtain a MoO3-PEO composite polymer solid electrolyte membrane, which was stored in an argon atmosphere glove box.

[0070] The macroscopic images of the composite polymer solid electrolyte membranes prepared in Comparative Example 1, Example 3 and Example 4 are shown in FIG. Figure 2 , wherein a is the PEO composite polymer solid electrolyte membrane prepared in Comparative Example 1, b is the NRCMO-PEO composite polymer solid electrolyte membrane prepared in Example 3, and c is the NPCMO-PEO composite polymer solid electrolyte membrane prepared in Example 4.

[0071] The SEM images of the composite polymer solid electrolyte membranes prepared in Comparative Example 1, Example 3 and Example 4 are shown in FIG. Figure 3 , wherein a is the PEO composite polymer solid electrolyte membrane prepared in Comparative Example 1, b is the NRCMO-PEO composite polymer solid electrolyte membrane prepared in Example 3, and c is the NPCMO-PEO composite polymer solid electrolyte membrane prepared in Example 4.

[0072] from Figure 3 It can be seen that compared with PEO and NPCMO-PEO composite polymer solid electrolyte membranes, the surface of NPCMO-PEO composite polymer solid electrolyte membrane is smoother and flatter, which helps it to better contact with the positive and negative electrodes and reduce the interface impedance; on the other hand, it helps Li + Uniform deposition and stripping.

[0073] The XRD patterns of the composite polymer solid electrolyte membranes prepared in Comparative Example 1, Example 3 and Example 4 are shown in FIG. Figure 4 .

[0074] from Figure 4 It can be seen that the introduction of nano binary transition metal oxides can significantly reduce the crystallinity of PEO; and the effect of NPCMO is more obvious than that of NRCMO.

[0075] The tensile properties of the composite polymer solid electrolyte membranes prepared in Comparative Example 1, Example 3 and Example 4 are shown in FIG. Figure 5 .

[0076] from Figure 5 It can be seen that the introduction of nano binary transition metal oxides can significantly enhance the mechanical properties of the electrolyte; and NPCMO-PEO is more stretchable than NRCMO-PEO.

[0077] Symmetrical batteries were assembled using the composite polymer solid electrolyte membranes prepared in Example 3, Example 4, Comparative Example 1, Comparative Example 4, and Comparative Example 5.

[0078] The assembly steps are as follows: assemble the CR2032 button battery from bottom to top in an argon glove box (H2O, O2 <0.01ppm) in the order of positive electrode shell, lithium sheet, composite polymer solid electrolyte, lithium sheet, gasket, spring, and negative electrode shell.

[0079] The cycle performance of the assembled symmetrical battery is shown in the figure Figure 6 (Using the composite polymer solid electrolyte membranes of Example 3, Example 4 and Comparative Example 1 as raw materials), Figure 7 (for Figure 6 Partially enlarged diagram, where a, b, and c are enlarged diagrams of different cycle time periods) and Figure 8 (Using the composite polymer solid electrolyte membranes of Comparative Examples 4 and 5 as raw materials), symmetrical battery cycle tests were carried out at room temperature.

[0080] from Figures 6 to 8 It can be seen that the introduction of nano-inorganic fillers (Co3O4, MoO3, NRCMO, NPCMO) can improve the cycle performance of symmetrical batteries. The introduction of binary oxides (NRCMO, NPCMO) has better cycle performance than the introduction of single oxides (Co3O4, MoO3) into polymer solid electrolytes. When binary oxides are also introduced, the cycle performance of the symmetrical battery assembled by NPCMO-PEO is better than that of NRCMO-PEO.

[0081] An all-solid-state battery was assembled using the composite polymer solid electrolyte membranes prepared in Example 3, Example 4 and Comparative Example 1.

[0082] The assembly steps are as follows: lithium iron phosphate (LiFePO4, LFP), Super P conductive agent, and polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 8:1:1, an appropriate amount of nitrogen methyl pyrrolidone (NMP) is added to form a slurry, and the mixture is stirred continuously for 12 hours. The uniform slurry is then slowly coated on the relatively rough surface of a clean aluminum foil current collector as the positive electrode material. The mixture is then placed in a vacuum drying oven at 80°C for 12 hours to remove water under vacuum. The positive electrode material loading is 1-1.25 mg·cm -2 After using a cutting machine to cut the positive electrode sheet into a circular shape with a diameter of 16 mm, CR2032 button cells were assembled from bottom to top in an argon glove box (H2O, O2 <0.01ppm) in the following order: positive electrode shell, positive electrode, composite polymer solid electrolyte, lithium sheet, gasket, spring, and negative electrode shell. After high-voltage sealing, the battery was left at room temperature for 6 hours before testing its electrochemical performance.

[0083] The cycle performance of the assembled all-solid-state battery is shown in Figure 9 , all-solid-state battery cycling tests were performed at room temperature.

[0084] from Figure 9 It can be seen that the introduction of nano-inorganic fillers (NRCMO, NPCMO) can improve the cycle performance of all-solid-state batteries, and the cycle performance of all-solid-state batteries assembled with NPCMO-PEO is better than that of NRCMO-PEO.

[0085] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A composite polymer solid electrolyte membrane, characterized in that: The components include: polymer matrix, lithium salt and inorganic filler; the inorganic filler is CoMoO4 nanoparticles; The mass ratio of the polymer matrix, lithium salt and inorganic filler is 1:0.3:(0.1~0.5); The preparation method of the composite polymer solid electrolyte membrane comprises the following steps: A casting solution is prepared with polymer matrix, lithium salt and inorganic filler as raw materials, and the casting solution is made into a membrane, which is the composite polymer solid electrolyte membrane.

2. The composite polymer solid electrolyte membrane according to claim 1, characterized in that The preparation steps of the CoMoO4 nanoparticles include: mixing a solution containing molybdate and a dispersion containing Co-ZIF, reacting at 50-80°C, and calcining the obtained product to obtain CoMoO4 nanoparticles.

3. The composite polymer solid electrolyte membrane according to claim 2, characterized in that The molar ratio of Mo in the molybdate-containing solution to Co in the Co-ZIF-containing dispersion is 1:

1.

4. A method for preparing the composite polymer solid electrolyte membrane according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: preparing a casting solution with polymer matrix, lithium salt and inorganic filler as raw materials, and forming the casting solution into a membrane, namely the composite polymer solid electrolyte membrane.

5. Use of the composite polymer solid electrolyte membrane according to any one of claims 1 to 3 in the preparation of solid-state batteries.

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