A sodium battery composite solid electrolyte, its preparation method and application

Abstract

This invention discloses a method for preparing a sodium battery composite solid electrolyte, comprising the following steps: S1, preparing a modified solid sodium electrolyte; S2: completely dissolving a polymer in an organic solvent, adding sodium salt and the modified solid sodium electrolyte prepared in S1, stirring to obtain a mixed solution; S3, coating the prepared mixed solution onto the surface of an electrode sheet, and obtaining the sodium battery composite solid electrolyte after drying and hot pressing. The modified solid sodium electrolyte of this invention contains active functional groups such as hydroxyl and amino groups on its surface, which can react with the isocyanate active groups of the polymer solid electrolyte to form urethane and urea covalent bonds, improving the dispersibility of the solid sodium electrolyte in the polymer solid electrolyte. Simultaneously, the composite solid electrolyte forms a cross-linked network structure, reducing the regularity of the polymer molecular chain arrangement, significantly reducing the crystallinity of the polymer solid electrolyte, improving the ionic conductivity of the electrolyte, and also improving the mechanical strength and thermal stability of the composite solid electrolyte.

Description

Technical Field

[0001] This invention belongs to the field of solid-state sodium battery technology, specifically relating to a sodium battery composite solid electrolyte, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries have been widely used in mobile phones, laptops, digital cameras, and power tools due to their outstanding advantages such as high energy density, high operating voltage, long cycle life, low self-discharge rate, and environmental friendliness. They are also gradually expanding into new energy vehicles and energy storage. However, the Earth's lithium resources are extremely scarce and unevenly distributed, resulting in very high costs for lithium-ion batteries, which to some extent limits their large-scale application in new energy vehicles and energy storage.

[0003] Sodium-ion batteries have garnered significant attention in recent years due to their abundant resources, low cost, environmental friendliness, and electrochemical properties similar to lithium-ion batteries, offering a new option for electrochemical energy storage. However, traditional liquid sodium batteries contain organic liquid electrolytes, which have poor thermal stability and are flammable, posing safety hazards such as leakage, fire, and explosion when overheated due to misuse. Compared to traditional liquid sodium batteries, solid-state sodium batteries use non-flammable, thermally stable solid electrolytes instead of organic electrolytes, offering better safety and higher energy density. However, existing solid-state sodium batteries still face numerous challenges, with the relatively low ionic conductivity and high interfacial impedance of solid electrolytes at room temperature being key obstacles to technological development. Summary of the Invention

[0004] To solve the above problems, the present invention will adopt the following technical solution:

[0005] This invention provides a method for preparing a sodium battery composite solid electrolyte, comprising the following specific steps:

[0006] S1. Preparation of modified solid sodium electrolyte;

[0007] S2: The polymer is completely dissolved in an organic solvent, sodium salt and modified solid sodium electrolyte prepared in S1 are added, the temperature is raised to 60-100℃, and the mixture is stirred to obtain a mixture.

[0008] S3. The above-prepared mixture is coated on the surface of the electrode sheet, and after drying and hot pressing, a sodium battery composite solid electrolyte can be obtained.

[0009] Furthermore, the preparation method of the modified solid sodium electrolyte in step S1 includes the following steps:

[0010] a. Preparation of initial modified solid sodium electrolyte: Mix solid sodium electrolyte and dopamine hydrochloride buffer evenly, adjust pH, stir at room temperature for 2-10 h, and obtain initial modified solid sodium electrolyte after washing and filtration.

[0011] b. Add the initial modified solid sodium electrolyte and diisocyanate to an organic solvent at a mass ratio of 1:(2.5-9), heat to 50-100℃, and continue stirring for 2-25 hours to obtain the modified solid sodium electrolyte.

[0012] Furthermore, the polymer is selected from any one or more of polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polycarbonate, and polyacrylamide.

[0013] Furthermore, the solid sodium electrolyte is selected from Na2Zr2Si2PO4. 12 NaFeO2, Na 2 / 3 MnO2, Na 2 / 3 Mn 1 / 2 Fe 1 / 2O2, Na 7 / 9 Cu 2 / 9 Mn 2 / 3 Fe 1 / 3 Any one or more of the following: O2, Na2MnP2O7, Na2FeP2O7, Na3V2(PO4)3, Na3V2(PO4)2F3, NaFePO4, Na2MnFe(CN)6, and Na2CoFe(CN)6.

[0014] Furthermore, the sodium salt is selected from any one or more of sodium hexafluorophosphate, sodium bis(trifluoromethanesulfonyl)imide, sodium difluoromethanesulfonylimide, sodium perchlorate, sodium tetrafluoroborate, and sodium dioxolaneborate.

[0015] Further, the diisocyanate is selected from any one or more of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, naphthalene diisocyanate, tetramethylphenyldimethyl diisocyanate, hexamethylene diisocyanate, and hexamethylene diisocyanate; the organic solvent is N-methylpyrrolidone.

[0016] Furthermore, in step S2, the mass ratio of the polymer, modified solid sodium electrolyte, and sodium salt is 50–85:10–30:5–20.

[0017] Furthermore, the electrode sheet in step S3 includes a positive electrode sheet and a negative electrode sheet, and the porosity of the electrode sheet is 35-50%; the drying process of the electrode sheet in step S3 is as follows: first, dry at room temperature for 5-30 minutes, and then dry at 60-100°C.

[0018] The present invention also provides a sodium battery composite solid electrolyte, which is prepared by the above-described method for preparing sodium battery composite solid electrolyte.

[0019] The present invention provides a solid sodium battery having the above-mentioned sodium battery composite solid electrolyte.

[0020] The beneficial effects of this invention are as follows:

[0021] 1. The modified solid sodium electrolyte of the present invention has a highly adhesive coating layer on its surface, which can effectively improve the contact between the electrolyte and the electrode sheet, reduce the interfacial impedance, and improve the electrical performance of the solid sodium battery.

[0022] 2. The modified solid sodium electrolyte of the present invention contains active functional groups such as hydroxyl and amino groups on its surface, which can react with the isocyanate active groups of the polymer solid electrolyte to form urethane and urea covalent bonds, thereby improving the dispersibility of the solid sodium electrolyte in the polymer solid electrolyte. At the same time, the composite solid electrolyte forms a cross-linked network structure, reducing the regularity of the polymer molecular chain arrangement, significantly reducing the crystallinity of the polymer solid electrolyte, further improving the ionic conductivity of the electrolyte, and also improving the mechanical strength and thermal stability of the composite solid electrolyte.

[0023] 3. The composite solid electrolyte mixture of the present invention is directly coated on the surface of the electrode sheet and dried at room temperature for a certain period of time, which allows the mixture to fully penetrate into the interior of the electrode sheet. Then, it is dried at high temperature, which can promote the cross-linking of the mixture, improve the mechanical strength of the electrode sheet, and at the same time, make full contact between the composite solid electrolyte and the materials in the electrode sheet. Furthermore, through hot pressing, the interfacial impedance is further reduced, and the electrical performance of the solid sodium battery is improved. Detailed Implementation

[0024] The technical solution of the present invention will be described in detail below with reference to several embodiments, so that those skilled in the art can more clearly understand the content of the technical solution. Furthermore, the description in this section is merely illustrative and explanatory, and should not be construed as limiting the scope of protection of the present invention in any way.

[0025] Example 1:

[0026] In this embodiment, the following steps are used to prepare the sodium battery composite solid electrolyte:

[0027] S1, Add 5g of Na2Zr2Si2PO4 12 Mix thoroughly with 10g of dopamine hydrochloride buffer, adjust the pH to 8.5, stir at room temperature for 2 hours, and obtain the initial modified Na2Zr2Si2PO after washing and filtration. 12 ; 5g of initial Na2Zr2Si2PO 12Add 20g of isophorone diisocyanate to 500mL of N-methylpyrrolidone, heat to 80℃, and continue stirring for 25h to obtain modified Na2Zr2Si2PO4. 12 ;

[0028] S2. Dissolve 50g of polyethylene oxide completely in 500mL of N-methylpyrrolidone, add 20g of sodium trifluoromethanesulfonyl imide and 30g of the modified Na2Zr2Si2PO4 prepared in S1. 12 Stir well, heat to 80℃, and continue stirring for 5 hours to obtain a mixture;

[0029] S3. The prepared mixture is coated onto the surface of the electrode sheet, dried at room temperature for 10 minutes, then dried at 60°C, and hot-pressed to obtain the sodium battery composite solid electrolyte. The electrode sheet used here includes a positive electrode sheet and a negative electrode sheet, and the porosity of the electrode sheet is 35%.

[0030] Example 2:

[0031] In this embodiment, the following steps are used to prepare the sodium battery composite solid electrolyte:

[0032] S1, Add 5g of Na2Zr2Si2PO4 12 Mix thoroughly with 10g of dopamine hydrochloride buffer, adjust the pH to 8.5, stir at room temperature for 2 hours, and obtain the initial modified Na2Zr2Si2PO after washing and filtration. 12 ; 5g of initial Na2Zr2Si2PO 12 Add 45g of isophorone diisocyanate to 500mL of N-methylpyrrolidone, heat to 100℃, and continue stirring for 2h to obtain modified Na2Zr2Si2PO4. 12 ;

[0033] S2. Dissolve 50g of polymethyl methacrylate completely in 500mL of N-methylpyrrolidone, add 20g of sodium trifluoromethanesulfonyl imide and 20g of the modified Na2Zr2Si2PO4 prepared in S1. 12 Stir well, heat to 80℃, and continue stirring for 5 hours to obtain a mixture;

[0034] S3. The prepared mixture is coated onto the surface of the electrode sheet, dried at room temperature for 20 minutes, then dried at 70°C, and hot-pressed to obtain the sodium battery composite solid electrolyte. The electrode sheet used here includes a positive electrode sheet and a negative electrode sheet, and the porosity of the electrode sheet is 40%.

[0035] Example 3:

[0036] In this embodiment, the following steps are used to prepare the sodium battery composite solid electrolyte:

[0037] S1, Add 5g of Na 2 / 3 Mn 1 / 2 Fe 1 / 2 O2 and 10g of dopamine hydrochloride buffer were mixed thoroughly, the pH was adjusted to 8.5, and the mixture was stirred at room temperature for 2 hours. After washing and filtration, the initial modified Na was obtained. 2 / 3 Mn 1 / 2 Fe 1 / 2 O2; 5g of initial Na 2 / 3 Mn 1 / 2 Fe 1 / 2 O2 and 12.5 g of naphthalene diisocyanate were added to 500 mL of N-methylpyrrolidone, the mixture was heated to 80 °C, and stirring was continued for 10 h to obtain modified Na. 2 / 3 Mn 1 / 2Fe 1 / 2 O2;

[0038] S2. Dissolve 70g of polyethylene oxide completely in 500mL of N-methylpyrrolidone, add 20g of sodium (trifluoromethanesulfonyl)imide and 30g of the modified Na prepared in S1. 2 / 3 Mn 1 / 2 Fe 1 / 2 O2, stir evenly, heat to 80℃, continue stirring for 5 hours to obtain a mixture;

[0039] S3. The prepared mixture is coated onto the surface of the electrode sheet, dried at room temperature for 10 minutes, then dried at 100°C, and hot-pressed to obtain the sodium battery composite solid electrolyte. The electrode sheet used here includes a positive electrode sheet and a negative electrode sheet, and the porosity of the electrode sheet is 35%.

[0040] Example 4:

[0041] In this embodiment, the following steps are used to prepare the sodium battery composite solid electrolyte:

[0042] S1, Add 5g of Na2Zr2Si2PO4 12 Mix thoroughly with 10g of dopamine hydrochloride buffer, adjust the pH to 8.5, stir at room temperature for 2 hours, and obtain the initial modified Na2Zr2Si2PO after washing and filtration. 12 ; 5g of initial Na2Zr2Si2PO 12 Add 20g of isophorone diisocyanate to 500mL of N-methylpyrrolidone, heat to 80℃, and continue stirring for 25h to obtain modified Na2Zr2Si2PO4. 12 ;

[0043] S2. Dissolve 85g of polyethylene oxide completely in 500mL of N-methylpyrrolidone, add 10g of sodium trifluoromethanesulfonyl imide and 10g of the modified Na2Zr2Si2PO4 prepared in S1. 12 Stir well, heat to 80℃, and continue stirring for 5 hours to obtain a mixture;

[0044] S3. The prepared mixture is coated onto the surface of the electrode sheet, dried at room temperature for 10 minutes, then dried at 60°C, and hot-pressed to obtain the sodium battery composite solid electrolyte. The electrode sheet used here includes a positive electrode sheet and a negative electrode sheet, and the porosity of the electrode sheet is 35%.

[0045] Example 5:

[0046] In this embodiment, the following steps are used to prepare the sodium battery composite solid electrolyte:

[0047] S1, Add 5g Na 2 / 3 Mn 1 / 2 Fe 1 / 2 O2 and 10g of dopamine hydrochloride buffer were mixed thoroughly, the pH was adjusted to 8.5, and the mixture was stirred at room temperature for 5 hours. After washing and filtration, the initial modified Na was obtained. 2 / 3 Mn 1 / 2 Fe 1 / 2 O2; 5g of initial Na 2 / 3 Mn 1 / 2 Fe 1 / 2 O2 and 20g of toluene diisocyanate were added to 500mL of N-methylpyrrolidone, the mixture was heated to 80℃ and stirred for 10h to obtain modified Na. 2 / 3 Mn 1 / 2Fe 1 / 2 O2;

[0048] S2. Dissolve 60g of polyacrylonitrile completely in 500mL of N-methylpyrrolidone, then add 20g of sodium hexafluorophosphate and 20g of the modified Na prepared in S1. 2 / 3 Mn 1 / 2 Fe 1 / 2 O2, stir evenly, heat to 80℃, continue stirring for 5 hours to obtain a mixture;

[0049] S3. The prepared mixture is coated onto the surface of the electrode sheet, dried at room temperature for 10 minutes, then dried at 90°C, and hot-pressed to obtain the sodium battery composite solid electrolyte. The electrode sheet used here includes a positive electrode sheet and a negative electrode sheet, and the porosity of the electrode sheet is 50%.

[0050] Example 6:

[0051] In this embodiment, the following steps are used to prepare the sodium battery composite solid electrolyte:

[0052] S1. Mix 5g Na2MnFe(CN)6 and 10g dopamine hydrochloride buffer solution evenly, adjust the pH to 8.5, stir at room temperature for 3h, and obtain the initial modified Na2MnFe(CN)6 after washing and filtration; add 5g initial Na2MnFe(CN)6 and 20g diphenylmethane diisocyanate to 500mL N-methylpyrrolidone, heat to 80℃, and continue stirring for 10h to obtain modified Na2MnFe(CN)6.

[0053] S2. Dissolve 60g of polycarbonate completely in 500mL of N-methylpyrrolidone, add 20g of sodium tetrafluoroborate and 20g of modified Na2MnFe(CN)6 prepared in S1, stir evenly, heat to 80℃, and continue stirring for 5h to obtain a mixture.

[0054] S3. The prepared mixture is coated onto the surface of the electrode sheet, dried at room temperature for 30 minutes, then dried at 100°C, and hot-pressed to obtain the sodium battery composite solid electrolyte. The electrode sheet used here includes a positive electrode sheet and a negative electrode sheet, and the porosity of the electrode sheet is 45%.

[0055] Example 7:

[0056] In this embodiment, the following steps are used to prepare the sodium battery composite solid electrolyte:

[0057] S1. Mix 5g Na3V2(PO4)2F3 and 10g dopamine hydrochloride buffer solution evenly, adjust the pH to 8.5, stir at room temperature for 10h, and obtain the initial modified Na2Zr2Si2PO after washing and filtration. 12 Add 5g of initial Na3V2(PO4)2F3 and 20g of diphenylmethane diisocyanate to 500mL of N-methylpyrrolidone, heat to 80℃, and continue stirring for 8h to obtain modified Na3V2(PO4)2F3.

[0058] S2. Dissolve 60g of polyacrylamide completely in 500mL of N-methylpyrrolidone, add 20g of sodium trifluoromethanesulfonyl imide and 20g of modified Na3V2(PO4)2F3 prepared in S1, stir evenly, heat to 80℃, and continue stirring for 5h to obtain a mixture.

[0059] S3. The above-prepared mixture is coated on the surface of the electrode sheet, dried at room temperature for 5 minutes, and then dried at 70°C. After hot pressing, the sodium battery composite solid electrolyte can be obtained.

[0060] It should be noted that in the above embodiments, the polymer can be selected from any one or more of polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polycarbonate, and polyacrylamide. The solid sodium electrolyte is selected from Na2Zr2Si2PO4. 12 NaFeO2, Na 2 / 3 MnO2, Na 2 / 3 Mn 1 / 2 Fe 1 / 2 O2, Na 7 / 9 Cu 2 / 9 Mn 2 / 3 Fe 1 / 3 O2, Na2MnP2O7, Na2FeP2O7, Na3V2(PO4)3, Na3V2(PO4)2F3, NaFePO4, Na2MnFe(CN)6, Na2CoFe(CN)6. The sodium salt is selected from any one or more of sodium hexafluorophosphate, sodium bis(trifluoromethanesulfonyl)imide, sodium difluoromethanesulfonylimide, sodium perchlorate, sodium tetrafluoroborate, and sodium dioxolaneborate. The diisocyanate is selected from any one or more of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, naphthalene diisocyanate, tetramethylphenyldimethyl diisocyanate, hexamethylene diisocyanate, and hexamethylene diisocyanate.

[0061] Comparative Example 1:

[0062] S1. Dissolve 60g of polyethylene oxide completely in 500mL of N-methylpyrrolidone, add 20g of sodium trifluoromethanesulfonyl imide and 20g of Na2Zr2Si2PO4 prepared in S1. 12 Stir well, heat to 80℃, and continue stirring for 5 hours to obtain a mixture;

[0063] S2. The above-prepared mixture is coated on the surface of the electrode sheet, dried at room temperature for 10 minutes, and then dried at 90°C. After hot pressing, the sodium battery composite solid electrolyte can be obtained.

[0064] Test method:

[0065] Ionic conductivity testing: The ionic conductivity of the electrolyte was measured on an electrochemical workstation using symmetrical cells assembled with steel sheets as blocking electrodes, at frequencies ranging from 0.1 Hz to 10 Hz. 6 Hz, the ionic conductivity is calculated according to the following working time: σ=L / (R*S), where σ is the ionic conductivity of the composite solid electrolyte membrane, L is the thickness of the composite solid electrolyte membrane, S is the area of ​​the composite solid electrolyte membrane, and R is the bulk resistance of the composite solid electrolyte membrane.

[0066] The ionic conductivity at room temperature of each embodiment and comparative example was tested and the results are as follows:

[0067]

[0068]

[0069] The above results show that the sodium battery composite solid electrolyte prepared by the method of the present invention has a much higher ionic conductivity at room temperature than that of sodium battery solid electrolytes prepared by existing methods, and its mechanical strength is also much higher than that of sodium battery solid electrolytes prepared by existing methods.

[0070] The technical solution of the present invention has been described in detail above. Obviously, the present invention is not limited to the described content. Those skilled in the art can make various modifications based on this, but any modifications that are equivalent or similar to the present invention fall within the scope of protection of the present invention.

Claims

1. A method for preparing a sodium battery composite solid electrolyte, characterized in that, The specific steps include: S1, preparing modified solid sodium electrolyte, the preparation method of modified solid sodium electrolyte includes the following steps: a. Preparation of initial modified solid sodium electrolyte: Mix solid sodium electrolyte and dopamine hydrochloride buffer evenly, adjust pH, stir at room temperature for 2-10 h, and obtain initial modified solid sodium electrolyte after washing and filtration. b. Add the initial modified solid sodium electrolyte and diisocyanate to an organic solvent at a mass ratio of 1:(2.5~9), heat to 50~100℃, and continue stirring for 2~25h to obtain the modified solid sodium electrolyte. S2: The polymer is completely dissolved in an organic solvent, sodium salt and modified solid sodium electrolyte prepared in S1 are added, the temperature is raised to 60-100℃, and the mixture is stirred to obtain a mixture. S3. The above-prepared mixture is coated on the surface of the electrode sheet, and after drying and hot pressing, a sodium battery composite solid electrolyte can be obtained.

2. The method for preparing a sodium battery composite solid electrolyte as described in claim 1, characterized in that, The polymer is selected from any one or more of polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polycarbonate, and polyacrylamide.

3. The method for preparing a sodium battery composite solid electrolyte as described in claim 1, characterized in that, The solid sodium electrolyte is selected from Na₂Zr₂Si₂PO₁₂, NaFeO₂, Na₂ / ₃MnO₂. Na2 / 3Mn1 / 2Fe1 / 2O2, Na7 / 9Cu2 / 9Mn2 / 3Fe1 / 3O2, Na2MnP2O7, Na2FeP2O7, Any one or more of Na3V2(PO4)3, Na3V2(PO4)2F3, NaFePO4, Na2MnFe(CN)6, and Na2CoFe(CN)6.

4. The method for preparing a sodium battery composite solid electrolyte as described in claim 1, characterized in that, The sodium salt is selected from any one or more of sodium hexafluorophosphate, sodium bis(trifluoromethanesulfonyl)imide, sodium difluoromethanesulfonylimide, sodium perchlorate, sodium tetrafluoroborate, and sodium dioxolaneborate.

5. The method for preparing a sodium battery composite solid electrolyte as described in claim 1, characterized in that, The diisocyanate is selected from any one or more of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, naphthalene diisocyanate, tetramethylphenyldimethyl diisocyanate, hexamethylene diisocyanate, and hexamethylene diisocyanate; the organic solvent is N-methylpyrrolidone.

6. The method for preparing a sodium battery composite solid electrolyte as described in claim 1, characterized in that, In step S2, the mass ratio of the polymer, modified solid sodium electrolyte, and sodium salt is 50–85:10–30:5–20.

7. The method for preparing a sodium battery composite solid electrolyte as described in claim 1, characterized in that, The electrode sheet in step S3 includes a positive electrode sheet and a negative electrode sheet, and the porosity of the electrode sheet is 35-50%. The drying process of the electrode sheet in step S3 is as follows: first, dry at room temperature for 5-30 minutes, and then dry at 60-100°C.

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

9. A solid-state sodium battery, characterized in that: The solid sodium battery has the sodium battery composite solid electrolyte of claim 8.

Images