A sodium ion composite polymer solid-state electrolyte and a preparation method thereof

Abstract

The application provides a sodium ion composite polymer solid-state electrolyte and a preparation method thereof. The preparation method can include the following steps: mixing active filler powder with a citric acid solution to obtain modified active filler powder; mixing the modified active filler powder, a polymer and a sodium salt to obtain precursor powder; dispersing the precursor powder on a polypropylene film, hot-pressing into a film, and drying to obtain the sodium ion composite polymer solid-state electrolyte. The preparation method of the application uses citric acid as a dispersant for the active filler, can inhibit the agglomeration of the active filler, make the active filler uniformly dispersed in the electrolyte, and improve the ionic conductivity.

Description

Technical Field

[0001] This invention relates to the field of solid electrolytes, and more specifically, to a sodium ion composite polymer solid electrolyte and its preparation method. Background Technology

[0002] In an era of decarbonized energy, electrified transportation, and intelligent equipment, developing renewable energy not only provides a sustainable and secure energy supply for humanity but also mitigates problems such as climate change and environmental pollution. Since its commercialization, lithium-ion batteries have seen continuous optimization in energy density and output power, meeting the demand for high energy density and high power. However, lithium resources are scarce and unevenly distributed on Earth, and as human society moves towards electrification, lithium resources are gradually becoming insufficient to meet demand. Therefore, sodium-ion batteries, with their abundant resources, low cost, similar structure and working principle to lithium-ion batteries, and equipment compatibility, have become the most ideal alternative to lithium-ion batteries.

[0003] Over the past decade, the research and development of sodium-ion batteries has progressed rapidly, gradually maturing and moving towards application. Currently, commercially available sodium-ion batteries based on organic liquid electrolytes have achieved success due to their high ionic conductivity and ability to form stable contacts with the electrodes. However, they still suffer from safety issues similar to lithium-ion batteries, such as easy leakage, volatility, flammability, explosiveness, and poor thermal stability, which limit their further development. Developing solid-state sodium-ion batteries, using solid electrolytes to replace liquid electrolytes, holds the promise of fundamentally solving battery safety problems.

[0004] An ideal solid electrolyte should have high ionic conductivity (>10 at room temperature). -4 S cm -1 Solid-state electrolytes (SSEs) possess several advantages, including electronic insulation, chemical / electrochemical stability, good electrode / electrolyte interface contact, sufficient mechanical strength, good flexibility, and high safety. Currently, SSEs are mainly classified into three categories: inorganic oxide solid electrolytes (ISEs), polymer solid electrolytes (SPEs), and composite polymer solid electrolytes (CPEs). Among these, polymer solid electrolytes are considered to have better application prospects due to their good safety performance, flexibility, ease of processing into films, and excellent interfacial contact. However, the low room-temperature ionic conductivity and limited oxidation potential window of polymer solid electrolytes hinder their practical application in batteries. Summary of the Invention

[0005] In view of the shortcomings of the prior art, one of the objectives of this invention is to solve one or more problems existing in the prior art. For example, one objective of this invention is to provide a sodium ion composite polymer solid electrolyte with high ionic conductivity, high flexibility, lightweight, and high mechanical strength.

[0006] One aspect of the present invention provides a method for preparing a sodium ion composite polymer solid electrolyte, which may include the following steps: mixing an active filler powder with a citric acid solution to obtain a modified active filler powder; mixing the modified active filler powder, a polymer, and a sodium salt to obtain a precursor powder; dispersing the precursor powder on a polypropylene film, hot-pressing it into a film, and drying it to obtain a sodium ion composite polymer solid electrolyte.

[0007] Furthermore, the concentration of the citric acid solution can be from 0.2 mol / L to 1 mol / L.

[0008] Furthermore, the molar ratio of the polymer to the sodium salt can be (10–30):1.

[0009] Furthermore, the sodium salt can be one or more combinations of sodium perchlorate, sodium hexafluorophosphate, sodium bis(trifluoromethanesulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide.

[0010] Furthermore, the polymer can be one or more combinations of polyethylene oxide, polyvinylidene fluoride, and poly(vinylidene fluoride-co-hexafluoropropylene) / polyethylene glycol.

[0011] Furthermore, the modified active filler powder, polymer, and sodium salt can be uniformly mixed by ball milling to obtain precursor powder, and the ball milling speed can be 10 r / min to 200 r / min.

[0012] Furthermore, the hot pressing temperature for hot pressing film formation can be 60℃~100℃, the hot pressing time can be 10min~90min, and the hot pressing pressure can be 0.5MPa~5MPa.

[0013] Furthermore, drying can be carried out under vacuum conditions for a period of 1 hour to 24 hours at a temperature of 40°C to 80°C.

[0014] Furthermore, the modified active filler powder, polymer, and sodium salt can be ball-milled for 1 to 24 hours.

[0015] Another aspect of the present invention provides a sodium ion composite polymer solid electrolyte, which can be prepared by the sodium ion composite polymer solid electrolyte preparation method described above.

[0016] Furthermore, the thickness of the sodium ion composite polymer solid electrolyte can be 30 μm to 200 μm.

[0017] Another aspect of the present invention provides a solid-state sodium-ion battery, which may include a sodium-ion composite polymer solid-state electrolyte prepared by the sodium-ion composite polymer solid-state electrolyte preparation method described above, or a sodium-ion composite polymer solid-state electrolyte prepared by the sodium-ion composite polymer solid-state electrolyte described above.

[0018] Compared with the prior art, the beneficial effects of the present invention include at least one of the following:

[0019] (1) The preparation method of the present invention uses citric acid as a dispersant for active fillers, which can inhibit the agglomeration of active fillers, make the active fillers uniformly dispersed in the electrolyte, and improve the ionic conductivity.

[0020] (2) The preparation method and solid electrolyte of the present invention use polypropylene as the composite polymer solid electrolyte skeleton, fills the polymer, sodium salt and modified active filler into it, and prepares it by solvent-free hot pressing method, so that the obtained composite polymer solid electrolyte has a dense structure, good interfacial stability and greatly increased sodium ion transference number.

[0021] (3) The preparation process of the present invention is simple, does not involve complex reaction processes, has low energy consumption, and low production cost. Attached Figure Description

[0022] The above and other objects and features of the present invention will become clearer from the following description taken in conjunction with the accompanying drawings, in which:

[0023] Figure 1 This is a comparison of scanning electron microscope (SEM) images of the composite polymer solid electrolyte obtained in Example 1 of the present invention and the composite polymer solid electrolyte obtained in Comparative Example 1.

[0024] Figure 2 This is the X-ray diffraction (XRD) pattern of the composite polymer solid electrolyte with modified active filler obtained in Example 1 of the present invention;

[0025] Figure 3 This is a cycle diagram of a symmetrical cell (Na / composite polymer solid electrolyte / Na) of the composite polymer solid electrolyte with added active filler obtained in Example 1 of the present invention;

[0026] Figure 4 This is the electrochemical impedance spectroscopy (EIS) spectrum of the composite polymer solid electrolyte with added active filler obtained in Example 1 of the present invention;

[0027] Figure 5 This is a cycle diagram of a symmetrical cell (Na / composite polymer solid electrolyte / Na) of the composite polymer solid electrolyte with added active filler obtained in Example 2 of the present invention;

[0028] Figure 6 This is the electrochemical impedance spectroscopy (EIS) of the composite polymer solid electrolyte with added active filler obtained in Example 3 of the present invention. Detailed Implementation

[0029] In the following, a sodium-ion composite polymer solid electrolyte and its preparation method according to the present invention will be described in detail with reference to the accompanying drawings and exemplary embodiments.

[0030] Specifically, the preparation method of this invention adds citric acid to the active filler, using citric acid as a dispersant to inhibit the aggregation of the active filler, ensuring uniform dispersion of the active filler in the electrolyte and improving ionic conductivity. Adding sodium salt and modified active filler to a polymer electrolyte with a polypropylene backbone improves the electrochemical stability, ionic conductivity, and electrochemical performance of the composite polymer solid electrolyte. The resulting composite polymer solid electrolyte possesses advantages such as high ionic conductivity, high flexibility, lightweight, high mechanical strength, good adhesion, and uniformity. This allows for optimization of the cycle life and electrochemical performance of solid-state sodium-ion batteries using the aforementioned composite polymer solid electrolyte, achieving a fully solid-state sodium-ion battery.

[0031] One aspect of the present invention provides a method for preparing a sodium ion composite polymer solid electrolyte. In some embodiments, the preparation method may include the following steps:

[0032] S01, the active filler powder is mixed with citric acid solution to obtain the modified active filler powder;

[0033] S02, the modified active filler powder, polymer and sodium salt are mixed to obtain precursor powder;

[0034] S03, the precursor powder is dispersed on a polypropylene membrane, hot-pressed into a film, and dried to obtain a sodium ion composite polymer solid electrolyte.

[0035] In some embodiments, in step S01, the active filler powder and citric acid solution can be ball-milled and mixed, and then dried to obtain the modified active filler powder.

[0036] In some embodiments, the concentration of the citric acid solution can be from 0.2 mol / L to 1 mol / L. If the concentration of the citric acid solution is less than 0.2 mol / L, a good dispersion effect cannot be achieved; if the concentration of the citric acid solution is greater than 1 mol / L, it will lead to a reduction in the content of active filler. By mixing the active filler powder with a citric acid solution of 0.2 mol / L to 1 mol / L concentration, the active filler powder particles can be evenly dispersed, thereby ensuring uniform distribution of the active filler in the polymer matrix under solvent-free conditions. This reduces the polarization of the solid electrolyte after battery fabrication and makes the electroplating stripping process more stable. For example, the concentration of the citric acid solution can be a combination of 0.3 mol / L to 0.9 mol / L, 0.4 mol / L to 0.8 mol / L, 0.5 mol / L to 0.7 mol / L, or higher.

[0037] In some embodiments, the mass-to-volume ratio of the active filler to the citric acid solution can be 5 g:(4-9) ml. Under the conditions of the above mass-to-volume ratio and a citric acid solution concentration of 0.2 mol / L to 1 mol / L, the addition of citric acid can achieve optimal dispersibility of the active filler in the electrolyte, further improving the ionic conductivity. For example, the mass-to-volume ratio of the active filler to the citric acid solution can be 5 g:(4-6.5) ml, 5 g:(5.5-8.5) ml, or a combination thereof. Preferably, under the conditions of a citric acid solution concentration of 0.4 mol / L and a mass-to-volume ratio of the active filler to the citric acid solution of 5 g:6.5 ml, the dispersibility of the active filler in the electrolyte and the ionic conductivity are optimal.

[0038] In some embodiments, in step S02, the polymer and sodium salt can be dried before being mixed with the modified active filler powder.

[0039] In some embodiments, the sodium salt can be one or more combinations of sodium perchlorate, sodium hexafluorophosphate, sodium bis(trifluoromethanesulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide. By uniformly mixing the above-mentioned sodium salt with the polymer and modified active filler, for example by ball milling for 1 to 24 hours, the ionic conductivity of the resulting sodium ion composite polymer electrolyte can be increased, further increasing the sodium ion transport number.

[0040] In some embodiments, the molar ratio of polymer to sodium salt can be (10–30):1. At these polymer-to-sodium salt molar ratios, the flexibility of the sodium-ion composite polymer solid electrolyte can be improved, polymer crystallization can be effectively suppressed, the glass transition temperature can be lowered, and better mechanical and ionic conductivity properties can be exhibited. The resulting sodium-ion composite polymer solid electrolyte membrane has high mechanical properties and ionic conductivity, and the battery exhibits excellent cycle performance. For example, the molar ratio of polymer to sodium salt can be a combination of 12:1, 17:1, 20:1, 23:1, 26:1, or higher.

[0041] In some embodiments, the polymer can be one or more combinations of polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), and poly(vinylidene fluoride-co-hexafluoropropylene) / polyethylene glycol (PVDF-HFP / PEG). Using the above polymers offers advantages such as good electrochemical stability, high dielectric constant, good thermodynamic stability, and a structure conducive to rapid ion migration, resulting in a sodium ion composite solid electrolyte membrane with superior ionic conductivity, mechanical properties, and electrochemical performance.

[0042] In some embodiments, the active filler powder can be NASICON (Na3Zr2Si2PO4). 12Of course, it should be known that other active fillers in this field can also be used.

[0043] In some embodiments, the modified active filler powder, polymer, and sodium salt can be ball-milled to obtain a precursor powder, with the ball milling speed ranging from 10 r / min to 200 r / min. For example, the ball milling speed can be a combination of 25 r / min to 180 r / min, 45 r / min to 165 r / min, 67 r / min to 142 r / min, 81 r / min to 122 r / min, 92 r / min to 114 r / min, or a range above.

[0044] In some embodiments, the hot-pressing temperature for film formation can be 60℃ to 100℃, the hot-pressing time can be 10 min to 90 min, and the hot-pressing pressure can be 0.5 MPa to 5 MPa. By setting the above hot-pressing film formation conditions and mixing the modified active filler powder, polymer, and sodium salt at a ball milling speed of 10 r / min to 200 r / min, the polymer, sodium salt, and modified active filler can be mixed more uniformly, reducing agglomeration. The hot-pressing process results in a more uniform and dense structure, and the sodium ion composite polymer solid electrolyte exhibits lower impedance, better microstructure, density, mechanical properties, long-cycle performance, chemical stability, and superior electrochemical performance. For example, the hot-pressing temperature for film formation can be 75℃ to 96℃, the hot-pressing time can be 20 min to 75 min, and the hot-pressing pressure can be 0.9 MPa to 4.2 MPa. For example, the hot pressing temperature for hot pressing film formation can be 82℃~91℃, the hot pressing time can be 42min~60min, and the hot pressing pressure can be 1.6MPa~3.8MPa.

[0045] In some implementations, the film formed by hot pressing can be dried under vacuum conditions for a time of 1 to 24 hours at a temperature of 40°C to 80°C. For example, the drying time can be 15 hours at a temperature of 60°C.

[0046] In some embodiments, the present invention uses polypropylene as the composite electrolyte framework, and fills it with polymer, sodium salt and modified active filler. The polymer is hot-pressed into a film using a solvent-free hot pressing method, so that the obtained sodium ion composite polymer solid electrolyte forms a dense structure, which enhances the solid-solid interface compatibility and electrochemical stability of the electrolyte, has good electrochemical performance, greatly increases the sodium ion transference number, and extends the cycle life of solid batteries using the above-mentioned composite solid electrolyte film, and has stable cycle performance.

[0047] Another aspect of the present invention provides a sodium ion composite polymer solid electrolyte, which can be prepared by the sodium ion composite polymer solid electrolyte preparation method described above.

[0048] In some embodiments, the thickness of the sodium-ion composite polymer solid electrolyte can be from 30 μm to 200 μm. Within this thickness range, the composite solid electrolyte membrane exhibits superior performance, including better sodium-ion transport and battery cycle performance.

[0049] Another aspect of the present invention provides a solid-state sodium-ion battery, which may include the sodium-ion composite polymer solid-state electrolyte prepared by the above-described sodium-ion composite polymer solid-state electrolyte preparation method or the sodium-ion composite polymer solid-state electrolyte described above.

[0050] To better understand the present invention, specific examples are provided below to further illustrate the content of the present invention, but the content of the present invention is not limited to the examples below.

[0051] Example 1

[0052] Step 1, Precursor Powder Preparation: The active filler powder was ball-milled and dried in a 0.2 mol / L citric acid solution; according to the EO (ethylene oxide):Na... + PEO (polyethylene oxide) and sodium perchlorate were weighed in a ratio of 10:1, and ball-milled for 5 hours at a speed of 10 r / min to obtain a precursor powder in which the polymer, sodium salt and active filler were completely and uniformly mixed.

[0053] Step 2, Preparation of sodium ion composite polymer solid electrolyte: The precursor powder obtained in step 1 is slowly dispersed onto a polypropylene film and placed in an aluminized mold. It is then hot-pressed at 70°C and 0.5 MPa for 20 min and placed in a vacuum drying oven at 40°C for 24 h to obtain a sodium ion composite polymer solid electrolyte membrane with a thickness of 100 μm.

[0054] Comparative Example 1

[0055] Compared with Example 1, in Comparative Example 1, the active filler powder was not added to the 0.2 mol / L citric acid solution, but was directly mixed with the polymer and sodium salt. Everything else was the same as in Comparative Example 1.

[0056] The dispersibility of the active filler in the polymer in Comparative Example 1 and Comparative Example 1 is as follows: Figure 1 As shown, Figure 1 (b) is the sodium ion composite polymer solid electrolyte obtained in Example 1. Figure 1(a) is the sodium ion composite polymer solid electrolyte obtained in Comparative Example 1. The comparison shows that after adding citric acid modification, the active filler is more uniformly dispersed in the polymer and there is no obvious agglomeration.

[0057] The X-ray diffraction (XRD) pattern of the composite polymer solid electrolyte obtained in this embodiment is as follows: Figure 2 As shown, Figure 2 The XRD pattern shows only characteristic peaks of the polymer, indicating that the sodium salt is completely dissolved in the polymer and the active filler is encapsulated by the polymer. A comparison of cycling patterns of a battery (Na / composite polymer solid electrolyte / Na) made using this method is shown below. Figure 3 As shown, Figure 3 This indicates that the electrolyte in this embodiment exhibits relatively stable electroplating / stripping properties when applied to a symmetrical battery (Na / composite polymer solid electrolyte / Na). Comparison of electrochemical impedance spectroscopy (EIS) spectra of the composite polymer solid electrolyte. Figure 4 As shown, Figure 4 This indicates that the composite polymer solid electrolyte of this embodiment has low impedance.

[0058] Example 2

[0059] Step 1, Precursor Powder Preparation: The active filler powder was ball-milled and dried in a 0.4 mol / L citric acid solution; according to EO:Na + PEO and sodium perchlorate were weighed in a ratio of 20:1, and ball-milled for 5 hours at a speed of 10 r / min to obtain a mixed powder in which the polymer, sodium salt and active filler were completely and uniformly mixed.

[0060] Step 2, Preparation of sodium ion composite polymer solid electrolyte: The mixed powder obtained in step 1 is slowly dispersed onto a polypropylene film and placed in an aluminized mold. It is then hot-pressed at 70°C and 0.5 MPa for 20 min and placed in a vacuum drying oven at 50°C for 12 h to obtain a composite solid electrolyte membrane with a thickness of 150 μm.

[0061] The cycling diagram of the symmetric cell (Na / composite polymer solid electrolyte / Na) with added active filler obtained in this embodiment is shown in the figure below. Figure 5 As shown, Figure 5 This indicates that the sodium electroplating / stripping process of the symmetric cell (Na / composite polymer solid electrolyte / Na) with the addition of modified active filler is relatively stable.

[0062] Example 3

[0063] Step 1, Precursor Powder Preparation: The active filler powder was ball-milled and dried in a 0.6 mol / L citric acid solution; according to EO:Na +PEO and sodium perchlorate were weighed in a ratio of 30:1 and ball-milled for 5 hours at a speed of 10 r / min to obtain a precursor powder in which the polymer, sodium salt and active filler were completely and uniformly mixed.

[0064] Step 2, Preparation of composite polymer solid electrolyte: The precursor powder obtained in step (1) is slowly dispersed onto a polypropylene film and placed in an aluminum-plated mold. It is then hot-pressed at 70°C and 0.5MPa for 20 minutes and placed in a vacuum drying oven at 50°C for 20 hours to obtain a composite solid electrolyte membrane with a thickness of 150μm.

[0065] In this embodiment, the obtained composite polymer solid electrolyte is subjected to AC impedance testing, such as... Figure 6 As shown, Figure 6 This indicates that the composite polymer solid electrolyte with added active filler has a significant advantage in low impedance.

[0066] Example 4

[0067] Step 1, Precursor Powder Preparation: The active filler powder was ball-milled and dried in a 1 mol / L citric acid solution; according to EO:Na... + PEO and sodium perchlorate were weighed in a ratio of 10:1 and ball-milled for 10 hours at a speed of 20 r / min to obtain a precursor powder in which the polymer, sodium salt and active filler were completely and uniformly mixed.

[0068] Step 2, Preparation of composite polymer solid electrolyte: The precursor powder obtained in step (1) is slowly dispersed onto a polypropylene film and placed in an aluminum-plated mold. It is then hot-pressed at 80°C and 2MPa for 60 min and placed in a vacuum drying oven at 60°C for 10 h to obtain a composite solid electrolyte membrane with a thickness of 120 μm.

[0069] Physical and electrochemical tests were performed on the composite polymer solid electrolyte obtained in this embodiment, which showed relatively low impedance and polarization, as well as a long cycle life.

[0070] Example 5

[0071] Step 1, Precursor Powder Preparation: The active filler powder was ball-milled and dried in a 0.4 mol / L citric acid solution; according to EO:Na + PEO and sodium perchlorate were weighed in a ratio of 20:1 and ball-milled for 10 hours at a speed of 20 r / min to obtain a precursor powder in which the polymer, sodium salt and active filler were completely and uniformly mixed.

[0072] Step 2, Preparation of composite polymer solid electrolyte: The precursor powder obtained in step (1) is slowly dispersed onto a polypropylene film and placed in an aluminum-plated mold. It is then hot-pressed at 80°C and 2MPa for 60 min and placed in a vacuum drying oven at 70°C for 15 h to obtain a composite solid electrolyte membrane with a thickness of 120 μm.

[0073] Physical and electrochemical tests were performed on the composite polymer solid electrolyte obtained in this embodiment, which showed relatively low impedance and polarization, as well as a long cycle life.

[0074] Example 6

[0075] Step 1, Precursor Powder Preparation: The active filler powder was ball-milled and dried in a 0.2 mol / L citric acid solution; according to EO:Na... + PEO and sodium perchlorate were weighed in a ratio of 30:1 and ball-milled for 10 hours at a speed of 20 r / min to obtain a precursor powder in which the polymer, sodium salt and active filler were completely and uniformly mixed.

[0076] Step 2, Preparation of composite polymer solid electrolyte: The precursor powder obtained in step (1) is slowly dispersed onto a polypropylene film and placed in an aluminum-plated mold. It is then hot-pressed at 80°C and 2MPa for 60 min and placed in a vacuum drying oven at 80°C for 24 h to remove the organic solvents, thus obtaining a composite solid electrolyte membrane with a thickness of 120 μm.

[0077] Physical and electrochemical tests were performed on the composite polymer solid electrolyte obtained in this embodiment, which showed relatively low impedance and polarization, as well as a long cycle life.

[0078] Example 7

[0079] Step 1, Precursor Powder Preparation: The active filler powder was ball-milled and dried in a 0.6 mol / L citric acid solution; according to EO:Na + PEO and sodium perchlorate were weighed in a ratio of 20:1 and ball-milled for 20 hours at a speed of 20 r / min to obtain a precursor powder in which the polymer, sodium salt and active filler were completely and uniformly mixed.

[0080] Step 2, Preparation of composite polymer solid electrolyte: The precursor powder obtained in step (1) is slowly dispersed onto a polypropylene film and placed in an aluminum-plated mold. It is then hot-pressed at 90°C and 3MPa for 70 min and placed in a vacuum drying oven at 60°C for 5 h to obtain a composite solid electrolyte membrane with a thickness of 100 μm.

[0081] Physical and electrochemical tests were performed on the composite polymer solid electrolyte obtained in this embodiment, which showed relatively low impedance and polarization, as well as a long cycle life.

[0082] Example 8

[0083] Step 1, Precursor Powder Preparation: The active filler powder was ball-milled and dried in a 0.8 mol / L citric acid solution; according to EO:Na + PEO and sodium perchlorate were weighed in a ratio of 30:1 and ball-milled for 20 hours at a speed of 10 r / min to obtain a precursor powder in which the polymer, sodium salt and active filler were completely and uniformly mixed.

[0084] Step 2, Preparation of composite polymer solid electrolyte: The precursor powder obtained in step (1) is slowly dispersed onto a polypropylene film and placed in an aluminum-plated mold. It is then hot-pressed at 90°C and 3MPa for 90 min and placed in a vacuum drying oven at 50°C for 20 h to obtain a composite solid electrolyte membrane with a thickness of 100 μm.

[0085] Physical and electrochemical tests were performed on the composite polymer solid electrolyte obtained in this embodiment, which showed relatively low impedance and polarization, as well as a long cycle life.

[0086] Example 9

[0087] Step 1, Precursor Powder Preparation: The active filler powder was ball-milled and dried in a 0.6 mol / L citric acid solution; according to EO:Na + PEO and sodium perchlorate were weighed in a ratio of 10:1, and ball-milled for 24 hours at a speed of 20 r / min to obtain a precursor powder in which the polymer, sodium salt and active filler were completely and uniformly mixed.

[0088] Step 2, Preparation of composite polymer solid electrolyte: The precursor powder obtained in step (1) is slowly dispersed onto a polypropylene film and placed in an aluminum-plated mold. It is then hot-pressed at 80°C and 2MPa for 80 min and placed in a vacuum drying oven at 40°C for 24 h to obtain a composite solid electrolyte membrane with a thickness of 120 μm.

[0089] Physical and electrochemical tests were performed on the composite polymer solid electrolyte obtained in this embodiment, which showed relatively low impedance and polarization, as well as a long cycle life.

[0090] Example 10

[0091] Step 1, Precursor Powder Preparation: The active filler powder was ball-milled and dried in a 0.4 mol / L citric acid solution; according to EO:Na +PEO and sodium perchlorate were weighed in a ratio of 10:1, and ball-milled for 20 hours at a speed of 20 r / min to obtain a precursor powder in which the polymer, sodium salt and active filler were completely and uniformly mixed.

[0092] Step 2, Preparation of composite polymer solid electrolyte: The precursor powder obtained in step (1) is slowly dispersed onto a polypropylene film and placed in a stainless steel mold. It is then hot-pressed at 90°C and 2MPa for 70 min and placed in a vacuum drying oven at 80°C for 24 h to obtain a composite solid electrolyte membrane with a thickness of 120 μm.

[0093] Physical and electrochemical tests were performed on the composite polymer solid electrolyte obtained in this embodiment, which showed relatively low impedance and polarization, as well as a long cycle life.

[0094] Example 11

[0095] Step 1, Precursor Powder Preparation: The active filler powder was ball-milled and dried in a 0.6 mol / L citric acid solution; according to EO:Na + PEO and sodium perchlorate were weighed in a ratio of 25:1 and ball-milled for 10 hours at a speed of 20 r / min to obtain a precursor powder in which the polymer, sodium salt and active filler were completely and uniformly mixed.

[0096] Step 2, Preparation of composite polymer solid electrolyte: The precursor powder obtained in step (1) is slowly dispersed onto a polypropylene film and placed in an aluminum-plated mold. It is then hot-pressed at 80°C and 3MPa for 80 min and placed in a vacuum drying oven at 60°C for 10 h to obtain a composite solid electrolyte membrane with a thickness of 100 μm.

[0097] Physical and electrochemical tests were performed on the composite polymer solid electrolyte obtained in this embodiment, which showed relatively low impedance and polarization, as well as a long cycle life.

[0098] Example 12

[0099] Step 1, Precursor Powder Preparation: The active filler powder was ball-milled and dried in a 0.2 mol / L citric acid solution; according to EO:Na... + PEO and sodium perchlorate were weighed in a ratio of 15:1 and ball-milled for 15 hours at a speed of 30 r / min to obtain a precursor powder in which the polymer, sodium salt and active filler were completely and uniformly mixed.

[0100] Step 2, Preparation of composite polymer solid electrolyte: The precursor powder obtained in step (1) is slowly dispersed onto a polypropylene film and placed in a stainless steel mold. It is then hot-pressed at 90°C and 2MPa for 70 min and placed in a vacuum drying oven at 70°C for 18 h to obtain a composite solid electrolyte membrane with a thickness of 120 μm.

[0101] Physical and electrochemical tests were performed on the composite polymer solid electrolyte obtained in this embodiment, which showed relatively low impedance and polarization, as well as a long cycle life.

[0102] Example 13

[0103] Step 1, Precursor Powder Preparation: The active filler powder was ball-milled and dried in a 0.8 mol / L citric acid solution; according to EO:Na + PEO and sodium perchlorate were weighed in a ratio of 25:1 and ball-milled for 5 hours at a speed of 30 r / min to obtain a precursor powder in which the polymer, sodium salt and active filler were completely and uniformly mixed.

[0104] Step 2, Preparation of composite polymer solid electrolyte: The precursor powder obtained in step (1) is slowly dispersed onto a polypropylene film and placed in a stainless steel mold. It is then hot-pressed at 80°C and 4MPa for 50 min and placed in a vacuum drying oven at 50°C for 15 h to obtain a composite solid electrolyte membrane with a thickness of 90 μm.

[0105] Physical and electrochemical tests were performed on the composite polymer solid electrolyte obtained in this embodiment, which showed relatively low impedance and polarization, as well as a long cycle life.

[0106] Example 14

[0107] Step 1, Precursor Powder Preparation: The active filler powder was ball-milled and dried in a 0.2 mol / L citric acid solution; according to EO:Na... + PEO and sodium perchlorate were weighed in a ratio of 20:1 and ball-milled for 15 hours at a speed of 15 r / min to obtain a precursor powder in which the polymer, sodium salt and active filler were completely and uniformly mixed.

[0108] Step 2, Preparation of composite polymer solid electrolyte: The precursor powder obtained in step (1) is slowly dispersed onto a polypropylene film and placed in a stainless steel mold. It is then hot-pressed at 80°C and 3MPa for 70 min and placed in a vacuum drying oven at 60°C for 10 h to obtain a composite solid electrolyte membrane with a thickness of 100 μm.

[0109] Physical and electrochemical tests were performed on the composite polymer solid electrolyte obtained in this embodiment, which showed relatively low impedance and polarization, as well as a long cycle life.

[0110] Example 15

[0111] Step 1, Precursor Powder Preparation: The active filler powder was ball-milled and dried in a 0.4 mol / L citric acid solution; according to EO:Na + PEO and sodium perchlorate were weighed in a ratio of 30:1 and ball-milled for 20 hours at a speed of 25 r / min to obtain a precursor powder in which the polymer, sodium salt and active filler were completely and uniformly mixed.

[0112] Step 2, Preparation of composite polymer solid electrolyte: The precursor powder obtained in step (1) is slowly dispersed onto a polypropylene film and placed in a stainless steel mold. It is then hot-pressed at 75°C and 2MPa for 60 min and placed in a vacuum drying oven at 70°C for 20 h to obtain a composite solid electrolyte film with a thickness of 120 μm.

[0113] Physical and electrochemical tests were performed on the composite polymer solid electrolyte obtained in this embodiment, which showed relatively low impedance and polarization, as well as a long cycle life.

[0114] In summary, the preparation method of this invention utilizes citric acid as a dispersant for the active filler to inhibit its aggregation, ensuring uniform dispersion in the electrolyte and improving ionic conductivity. Furthermore, it employs polypropylene as the framework of the composite polymer solid electrolyte, incorporating the polymer, sodium salt, and modified active filler, and using a solvent-free hot-pressing method to obtain a composite polymer solid electrolyte with a dense structure, enhancing interfacial stability. The addition of sodium salt further improves the interfacial stability of the composite polymer electrolyte, resulting in excellent electrochemical performance; compared to known electrolytes, the sodium ion transport number is significantly increased. Moreover, the process flow for preparing the precursor powder and the composite polymer solid electrolyte is simple, involving minimal complex reactions, thus reducing energy consumption and equipment investment. Finally, the polypropylene membrane framework used in this invention is an environmentally friendly polymer, and virtually no waste is generated in any process step, aligning with green industry principles and demonstrating environmental friendliness.

[0115] Although the invention has been described above in conjunction with exemplary embodiments, those skilled in the art will understand that various modifications and changes can be made to the exemplary embodiments of the invention without departing from the spirit and scope defined by the claims.

Claims

1. A method for preparing a sodium-ion composite polymer solid-state electrolyte, characterized by, Includes the following steps: The active filler powder was mixed with citric acid solution to obtain the modified active filler powder. The modified active filler powder, polymer, and sodium salt are mixed to obtain the precursor powder; The precursor powder was dispersed on a polypropylene membrane, hot-pressed into a film, and dried to obtain a sodium ion composite polymer solid electrolyte. The concentration of the citric acid solution is 0.2 mol / L to 1 mol / L, and the active filler powder is Na3Zr2Si2PO 12 .

2. The method for preparing sodium ion composite polymer solid electrolyte according to claim 1, characterized in that, The molar ratio of polymer to sodium salt is (10~30):

1.

3. The method for preparing sodium ion composite polymer solid electrolyte according to claim 1 or 2, characterized in that, The sodium salt is one or more combinations of sodium perchlorate, sodium hexafluorophosphate, sodium bis(trifluoromethanesulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide. The polymer is one or more of polyethylene oxide, polyvinylidene fluoride, and poly(vinylidene fluoride-co-hexafluoropropylene) / polyethylene glycol.

4. The method for preparing sodium ion composite polymer solid electrolyte according to claim 1 or 2, characterized in that, The modified active filler powder, polymer, and sodium salt were uniformly mixed by ball milling to obtain precursor powder. The ball milling speed was 10 r / min to 200 r / min.

5. The method for preparing sodium ion composite polymer solid electrolyte according to claim 1 or 2, characterized in that, The hot pressing temperature for hot pressing film formation is 60 ℃~100 ℃, the hot pressing time is 10 min~90 min, and the hot pressing pressure is 0.5 MPa~5 MPa.

6. The method for preparing sodium ion composite polymer solid electrolyte according to claim 1 or 2, characterized in that, Drying is carried out under vacuum conditions for 1 h to 24 h at a temperature of 40 ℃ to 80 ℃.

7. A sodium-ion composite polymer solid electrolyte, characterized in that, It is prepared by the method for preparing sodium ion composite polymer solid electrolyte according to any one of claims 1 to 6.

8. The sodium ion composite polymer solid electrolyte according to claim 7, characterized in that, The thickness of the sodium ion composite polymer solid electrolyte is 30 µm to 200 µm.

9. A solid-state sodium-ion battery, characterized in that, This includes sodium ion composite polymer solid electrolytes prepared by the method for preparing sodium ion composite polymer solid electrolytes according to any one of claims 1 to 6, or sodium ion composite polymer solid electrolytes according to any one of claims 7 to 8.

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