A sodium ion solid-state electrolyte, a sodium ion solid-state battery and a preparation method thereof

Abstract

The application relates to a sodium ion solid-state electrolyte, a sodium ion solid-state battery and a preparation method thereof, and belongs to the technical field of batteries. The sodium ion solid-state electrolyte comprises a sodium salt, an electrolyte base material and a tin salt additive. The wettability and stability between a sodium metal negative electrode and an interface between the sodium ion solid-state electrolyte can be effectively improved, so that the cycle performance of the solid-state sodium ion battery is improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a sodium-ion solid electrolyte, a sodium-ion solid battery, and a method for preparing the same. Background Technology

[0002] All-solid-state sodium metal batteries are considered a promising energy storage technology due to their advantages such as low cost, abundant sodium resources, and high energy density. Solid-state electrolytes are a key component of all-solid-state sodium metal batteries. Compared with inorganic solid-state electrolytes, polymer-based solid-state electrolytes have significant advantages, such as improved interfacial contact, flexibility, processability, and good film-forming properties. However, polymer-based solid-state electrolytes still suffer from low ionic conductivity and interfacial degradation, which greatly hinders their practical application.

[0003] To address these issues, numerous methods have been employed, such as increasing operating temperature and introducing inorganic fillers. While these methods can improve ionic conductivity to some extent, they cannot fully resolve interface problems, resulting in limited cycle life for all-solid-state sodium metal batteries. Interface degradation is caused by interfacial side reactions at the negative electrode, leading to increased interfacial impedance, sodium dendrite growth, and ultimately, short-circuit failure of the battery.

[0004] Current traditional methods, whether adding inorganic fillers to form composite electrolytes or surface modification, mainly suppress electrolyte interface damage by blocking dendrite growth. These methods do not fundamentally change the dendrite growth kinetics; they can only delay battery failure and cannot fundamentally improve the stability of the sodium metal-electrolyte interface. Furthermore, some methods require expensive materials or precision equipment, resulting in high costs and complex operations; some interface modification methods may also alter the intrinsic electrochemical properties of the electrolyte material, leading to a decrease in battery energy density. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present application aims to provide a sodium-ion solid electrolyte, a sodium-ion solid battery, and a method for preparing the same. This can effectively improve the wettability and stability of the interface between the sodium metal anode and the sodium-ion solid electrolyte, thereby improving the cycle performance of the solid sodium-ion battery.

[0006] In a first aspect, embodiments of this application provide a sodium-ion solid electrolyte, comprising a sodium salt, an electrolyte substrate, and a tin salt additive.

[0007] The sodium-ion solid electrolyte provided in this application contains tin salt additives. On the one hand, the tin salt additives can fill the pores and voids on the surface of the original sodium-ion solid electrolyte, thereby effectively preventing sodium dendrites from penetrating. On the other hand, when the sodium-ion solid electrolyte is applied to a sodium-ion solid battery, the added tin salt additives can react with sodium metal in situ to form a sodium-tin alloy layer on the surface between the sodium-ion solid electrolyte and the sodium metal. This sodium-tin alloy layer has high stability, significantly suppresses interfacial side reactions, and effectively increases the ion transference number, thereby effectively improving the wettability and stability between the sodium metal anode and the sodium-ion solid electrolyte interface, and thus improving the cycle performance of the solid sodium-ion battery.

[0008] In some embodiments of this application, the sodium-ion solid electrolyte is composed of sodium salt, electrolyte substrate and tin salt additive.

[0009] The sodium-ion solid electrolyte provided in this application, in addition to the basic sodium salt and electrolyte substrate, only contains tin salt additives. The tin salt additives help fill the pores and voids on the surface of the original sodium-ion solid electrolyte, thereby effectively preventing sodium dendrites from penetrating. Furthermore, when this sodium-ion solid electrolyte is applied to a sodium-ion solid battery, it facilitates the in-situ reaction between the tin salt additives and sodium metal to form a stable sodium-tin alloy layer, reducing interference from other substances in the reaction between the tin salt additives and sodium metal to form a stable sodium-tin alloy layer.

[0010] In some embodiments of this application, the sodium salt includes at least one of NaTFSI, NaFSI, NaPF6, NaClO4, and NaBF4.

[0011] This application uses a suitable sodium salt to facilitate the formation of a high-performance sodium ion solid electrolyte.

[0012] In some embodiments of this application, the electrolyte substrate includes at least one selected from polyethylene oxide, polyvinylidene fluoride, polyvinyl alcohol, polyacrylonitrile, ethyl polyacrylate, and polyethylene glycol.

[0013] This application employs a suitable electrolyte substrate to facilitate the formation of a high-performance polymer-based sodium-ion solid electrolyte.

[0014] In some embodiments of this application, the tin salt additive includes at least one of anhydrous tin tetrachloride, tin dichloride, tin bromide, tin fluoride, and stannous trifluoromethanesulfonate.

[0015] This application employs suitable tin salt additives to facilitate the in-situ reaction with sodium metal to form a highly stable sodium-tin alloy layer, which can effectively improve the wettability and stability between the sodium metal anode and the sodium ion solid electrolyte interface, thereby improving the cycle performance of solid sodium-ion batteries.

[0016] In some embodiments of this application, the molar ratio of tin salt additive to sodium salt is 1:10~50.

[0017] This application uses an appropriate amount of tin salt additive, which facilitates the in-situ reaction with sodium metal to form a relatively stable sodium-tin alloy layer with low electrochemical impedance, thereby improving the cycle performance of solid-state sodium-ion batteries.

[0018] Secondly, embodiments of this application provide a method for preparing a sodium-ion solid electrolyte as provided in the first aspect, comprising: S1, Dissolve the electrolyte substrate in an organic solvent to obtain an electrolyte substrate solution; S2, add tin salt additive and sodium salt to the electrolyte substrate solution in a molar ratio, heat and stir to obtain a mixed solution; S3, the mixed solution is coated onto the surface of the carrier and dried to form an electrolyte sheet, thus obtaining a sodium ion solid electrolyte.

[0019] This application obtains a sodium-ion solid electrolyte by adding tin salt additives and sodium salts in a molar ratio to an electrolyte substrate solution, heating and stirring to obtain a mixed solution, coating the mixed solution onto the surface of a carrier, and drying to form an electrolyte layer. The sodium-ion solid electrolyte contains an appropriate amount of tin salt additive, which can fill the pores and voids on the original surface of the sodium-ion solid electrolyte, thereby effectively preventing sodium dendrite penetration. Furthermore, when applied to sodium-ion solid batteries, the added tin salt additives can react in situ with sodium metal to form a stable sodium-tin alloy layer on the surface between the sodium-ion solid electrolyte and the sodium metal. This effectively improves the wettability and stability between the sodium metal anode and the sodium-ion solid electrolyte interface, thereby improving the cycle performance of the solid sodium-ion battery.

[0020] In some embodiments of this application, dissolving the electrolyte substrate in an organic solvent includes: mixing the electrolyte substrate and the organic solvent at a mass ratio of 1:5~20, and stirring at 80~90 °C for 12~36 h.

[0021] This application dissolves the electrolyte substrate in a suitable amount of organic solvent under appropriate conditions, which facilitates the more complete dissolution of the electrolyte substrate and thus facilitates the subsequent preparation of sodium ion solid electrolyte.

[0022] In some embodiments of this application, the molar ratio of electrolyte substrate monomer to sodium salt is 5~30:1.

[0023] This application uses an appropriate amount of electrolyte substrate and sodium salt to facilitate the formation of a high-performance polymer-based sodium ion solid electrolyte.

[0024] Thirdly, embodiments of this application provide a method for preparing a sodium-ion solid-state battery, comprising: bonding and combining the sodium-ion solid electrolyte provided in the first aspect with a sodium metal anode, and reacting at 60~100 ℃ for 1~12 h, so that a sodium-tin alloy layer is formed in situ on the surface between the sodium-ion solid electrolyte and the sodium metal anode.

[0025] This application combines the sodium-ion solid electrolyte with tin salt additives provided in the first aspect with a sodium metal anode and reacts them under suitable conditions to facilitate the in-situ formation of a dense sodium-tin alloy layer on the surface between the sodium-ion solid electrolyte and the sodium metal anode. This can effectively improve the wettability and stability between the sodium metal anode and the sodium-ion solid electrolyte interface, thereby improving the cycle performance of the solid sodium-ion battery.

[0026] Fourthly, embodiments of this application provide a sodium-ion solid-state battery, including a positive electrode, a negative electrode, and a sodium-ion solid electrolyte; the negative electrode is sodium metal; the surface between the sodium-ion solid electrolyte and the negative electrode has a sodium-tin alloy layer; the sodium-ion solid electrolyte includes a sodium salt and an electrolyte substrate.

[0027] The sodium-ion solid-state battery provided in this application has a sodium-tin alloy layer with high stability on the surface between the sodium-ion solid electrolyte and the negative electrode. This layer can significantly suppress interfacial side reactions and effectively increase the ion transference number, thereby effectively improving the wettability and stability between the sodium metal negative electrode and the sodium-ion solid electrolyte interface, and thus improving the cycle performance of the solid sodium-ion battery.

[0028] In some embodiments of this application, the thickness of the sodium-tin alloy layer is less than 20 nm.

[0029] The sodium-ion solid-state battery provided in this application has a thinner sodium-tin alloy layer on the surface between the sodium-ion solid electrolyte and the negative electrode. This layer can improve the interface wettability and reduce the interface charge conduction impedance while suppressing interfacial side reactions, thereby improving the cycle performance of the solid sodium-ion battery.

[0030] In some embodiments of this application, the sodium-tin alloy layer is Na 15 Sn4 alloy layer.

[0031] The sodium-ion solid-state battery provided in this application has a sodium-tin alloy layer on the surface between the sodium-ion solid electrolyte and the negative electrode, which is further composed of Na... 15 Sn4 alloy layer, Na 15 Sn4 forms a low-resistance interface with the sodium-ion solid electrolyte, reducing the interface resistance and promoting the uniform distribution and rapid transport of sodium ions. This reduces sodium dendrite formation and inhibits sodium dendrite penetration, thereby improving the cycle performance of solid sodium-ion batteries. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a SEM image of the sodium-ion solid electrolyte provided in Example 1 of Test Example 1 of this application.

[0034] Figure 2 This is an EDS diagram of the Sn element in the sodium-ion solid electrolyte provided in Example 1 of Test Example 1 of this application.

[0035] Figure 3 The image shows a SEM image of the sodium-ion solid electrolyte provided in Comparative Example 1 of Test Example 1 of this application.

[0036] Figure 4 The image shows the XRD pattern of the sodium-ion solid electrolyte and sodium metal anode alloyed in Example 1 of Test Example 2 of this application.

[0037] Figure 5 This is the impedance data diagram provided in Test Example 4 of this application.

[0038] Figure 6 The impedance data diagram provided in Test Example 5 of this application is shown; wherein, PEO-SnCl4 5% - Example 1; PEO-SnCl4 2% - Example 6; PEO-SnCl4 10% - Example 7.

[0039] Figure 7 This is the long-cycle voltage distribution diagram provided in Test Example 6 of this application.

[0040] Figure 8 The diagram shows the cyclic charge-discharge performance provided in Test Example 6 of this application; where (a) - Comparative Example 1; (b) - Example 1. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0042] To fundamentally improve the stability of the sodium metal-electrolyte interface, this application provides a sodium-ion solid electrolyte, comprising a sodium salt, an electrolyte substrate, and a tin salt additive.

[0043] The sodium-ion solid electrolyte provided in this application contains tin salt additives. On the one hand, the tin salt additives can fill the pores and voids on the surface of the original sodium-ion solid electrolyte, thereby effectively preventing sodium dendrites from penetrating. On the other hand, when the sodium-ion solid electrolyte is applied to a sodium-ion solid battery, the added tin salt additives can react with sodium metal in situ to form a sodium-tin alloy layer on the surface between the sodium-ion solid electrolyte and the sodium metal. This sodium-tin alloy layer has high stability, significantly suppresses interfacial side reactions, and effectively increases the ion transference number, thereby effectively improving the wettability and stability between the sodium metal anode and the sodium-ion solid electrolyte interface, and thus improving the cycle performance of the solid sodium-ion battery.

[0044] In some embodiments of this application, the sodium-ion solid electrolyte is composed of sodium salt, electrolyte substrate, and tin salt additive. Besides the basic sodium salt and electrolyte substrate, only the tin salt additive is added. This allows the tin salt additive to fill the pores and voids on the surface of the original sodium-ion solid electrolyte, effectively preventing sodium dendrite penetration. Furthermore, when this sodium-ion solid electrolyte is applied to a sodium-ion solid battery, it facilitates the in-situ reaction between the tin salt additive and sodium metal to form a stable sodium-tin alloy layer, reducing interference from other substances in the reaction between the tin salt additive and sodium metal to form a stable sodium-tin alloy layer.

[0045] In some embodiments of this application, the sodium salt includes at least one selected from NaTFSI (sodium bis(trifluoromethanesulfonyl)imide), NaFSI (sodium bis(fluorosulfonyl)imide), NaPF6 (sodium hexafluorophosphate), NaClO4 (sodium perchlorate), and NaBF4 (sodium tetrafluoroborate). A suitable sodium salt is used to facilitate the formation of a high-performance sodium-ion solid electrolyte.

[0046] In some embodiments of this application, the electrolyte substrate includes at least one selected from polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), ethyl polyacrylate (PEA), and polyethylene glycol (PEG). Using a suitable electrolyte substrate facilitates the formation of a high-performance polymer-based sodium-ion solid electrolyte.

[0047] In some embodiments of this application, the tin salt additive includes at least one of anhydrous tin tetrachloride (SnCl4), tin dichloride (SnCl2), tin bromide (SnBr2), tin fluoride (SnF2), and stannous trifluoromethanesulfonate (Sn(OTf)2). Using a suitable tin salt additive facilitates the in-situ reaction with sodium metal to form a highly stable sodium-tin alloy layer, effectively improving the wettability and stability between the sodium metal anode and the sodium-ion solid electrolyte interface, thereby improving the cycle performance of the solid-state sodium-ion battery.

[0048] In some preferred embodiments of this application, the tin salt additive is anhydrous tin tetrachloride, tin dichloride, or tin bromide. Further employing more suitable tin salt additives to facilitate in-situ reaction with sodium metal to form a denser sodium-tin alloy layer can further improve the cycle performance of solid-state sodium-ion batteries.

[0049] In some embodiments of this application, the molar ratio of the tin salt additive to the sodium salt is 1:10 to 50. As an example, the molar ratio of the tin salt additive to the sodium salt may be, but is not limited to, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, or 1:50. Preferably, the molar ratio of the tin salt additive to the sodium salt is 1:10 to 20. As an example, the molar ratio of the tin salt additive to the sodium salt may be, but is not limited to, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, or 1:20. Using an appropriate amount of tin salt additives facilitates the in-situ reaction with sodium metal to form a relatively stable sodium-tin alloy layer with low electrochemical impedance, thereby improving the cycle performance of solid-state sodium-ion batteries.

[0050] Secondly, embodiments of this application provide a method for preparing the above-mentioned sodium ion solid electrolyte, comprising: S1, Dissolve the electrolyte substrate in an organic solvent to obtain an electrolyte substrate solution; S2, add tin salt additive and sodium salt to the electrolyte substrate solution in a molar ratio, heat and stir to obtain a mixed solution; S3, the mixed solution is coated onto the surface of the carrier and dried to form an electrolyte sheet, thus obtaining a sodium ion solid electrolyte.

[0051] This application prepares a sodium-ion solid electrolyte with an appropriate amount of tin salt additive, which can fill the pores and voids on the surface of the original sodium-ion solid electrolyte, thereby effectively preventing sodium dendrite penetration. When applied to sodium-ion solid batteries, the added tin salt additive can react with sodium metal in situ to form a stable sodium-tin alloy layer on the surface between the sodium-ion solid electrolyte and the sodium metal. This can effectively improve the wettability and stability between the sodium metal anode and the sodium-ion solid electrolyte interface, thereby improving the cycle performance of solid sodium-ion batteries.

[0052] In some embodiments of this application, dissolving the electrolyte substrate in an organic solvent includes: mixing the electrolyte substrate and the organic solvent at a mass ratio of 1:5 to 20, and stirring at 80 to 90°C for 12 to 36 hours. As an example, the mass ratio of the electrolyte substrate to the organic solvent can be, but is not limited to, 1:5, 1:10, 1:15, or 1:20. Dissolving the electrolyte substrate in a suitable amount of organic solvent under suitable conditions facilitates more complete dissolution of the electrolyte substrate, thereby facilitating the subsequent preparation of sodium-ion solid electrolytes.

[0053] It should be noted that, in order to dissolve the electrolyte substrate more evenly and completely, an appropriate mass of organic solvent is added first, followed by an appropriate mass of electrolyte substrate added to the organic solvent. For example, the organic solvent may be, but is not limited to, acetonitrile.

[0054] As an example, the carrier may be, but is not limited to, a silicone paper sheet, a silicone sheet, or a polytetrafluoroethylene (PTFE) sheet. It is understood that the carrier may also be other similar objects with non-polar surfaces.

[0055] In some embodiments of this application, the thickness of the scraper used when coating the mixed solution on the carrier is 50~2000μm.

[0056] In some embodiments of this application, the heating and stirring are carried out at 80~90°C for 12~36 hours.

[0057] In some embodiments of this application, drying is carried out at 80~90℃ for 12~36 hours.

[0058] In some embodiments of this application, the molar ratio of electrolyte substrate monomer to sodium salt is 5-30:1. As an example, the molar ratio of electrolyte substrate to sodium salt may be, but is not limited to, 5:1, 10:1, 15:1, 20:1, 25:1, or 30:1. Using appropriate amounts of electrolyte substrate and sodium salt facilitates the formation of a high-performance polymer-based sodium-ion solid electrolyte.

[0059] Thirdly, this application provides a method for preparing a sodium-ion solid-state battery, comprising: bonding the above-mentioned sodium-ion solid electrolyte with a sodium metal anode and reacting at 60~100 ℃ for 1~12 h, so that a sodium-tin alloy layer is formed in situ on the surface between the sodium-ion solid electrolyte and the sodium metal anode.

[0060] This application combines the sodium-ion solid electrolyte with tin salt additives provided above with a sodium metal anode and reacts them under suitable conditions to facilitate the in-situ formation of a dense sodium-tin alloy layer on the surface between the sodium-ion solid electrolyte and the sodium metal anode. This can effectively improve the wettability and stability between the sodium metal anode and the sodium-ion solid electrolyte interface, thereby improving the cycle performance of the solid sodium-ion battery.

[0061] In some preferred embodiments of this application, a sodium-ion solid electrolyte is bonded and composited with a sodium metal anode, and reacted at 80-100 °C for 1-2 h to form a sodium-tin alloy layer in situ on the surface of the electrolyte layer of the sodium-ion solid electrolyte. Further, by bonding and composited the sodium-ion solid electrolyte with tin salt additives provided in the first aspect with the sodium metal anode under more suitable conditions, it is more conducive to the in-situ formation of a dense sodium-tin alloy layer on the surface between the sodium-ion solid electrolyte and the sodium metal anode.

[0062] Fourthly, embodiments of this application provide a sodium-ion solid-state battery, including a positive electrode, a negative electrode, and a sodium-ion solid electrolyte; the negative electrode is sodium metal; the surface between the sodium-ion solid electrolyte and the negative electrode has a sodium-tin alloy layer; the sodium-ion solid electrolyte includes a sodium salt and an electrolyte substrate.

[0063] The sodium-ion solid-state battery provided in this application has a sodium-tin alloy layer with high stability on the surface between the sodium-ion solid electrolyte and the negative electrode. This layer can significantly suppress interfacial side reactions and effectively increase the ion transference number, thereby effectively improving the wettability and stability between the sodium metal negative electrode and the sodium-ion solid electrolyte interface, and thus improving the cycle performance of the solid sodium-ion battery.

[0064] In some embodiments of this application, the thickness of the sodium-tin alloy layer is less than 20 nm. Exemplarily, the thickness of the sodium-tin alloy layer can be, but is not limited to, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, or 19 nm. In sodium-ion solid-state batteries, the sodium-tin alloy layer on the surface between the sodium-ion solid electrolyte and the negative electrode is relatively thin. This allows for the suppression of interfacial side reactions, improved interfacial wettability, and reduced interfacial charge conduction impedance, thereby improving the cycle performance of the solid-state sodium-ion battery.

[0065] In some embodiments of this application, the sodium-tin alloy layer is Na 15 Sn4 alloy layer. In sodium-ion solid-state batteries, the surface between the sodium-ion solid electrolyte and the negative electrode has a sodium-tin alloy layer, further modified by Na... 15 Sn4 alloy layer, Na15 Sn4 forms a low-resistance interface with the sodium-ion solid electrolyte, reducing the interface resistance and promoting the uniform distribution and rapid transport of sodium ions. This reduces sodium dendrite formation and inhibits sodium dendrite penetration, thereby improving the cycle performance of solid sodium-ion batteries.

[0066] Example 1 This embodiment provides a sodium-ion solid electrolyte, comprising: S1, first add acetonitrile to the reactor, then add the corresponding mass of polyethylene oxide (PEO) electrolyte substrate. The mass ratio of polyethylene oxide electrolyte substrate to acetonitrile is 1:10. Control the temperature inside the reactor at 80 ℃ and stir for 12 hours to obtain a fully dissolved electrolyte substrate solution. S2, tin salt additive SnCl4 and NaTFSI (Macklin, >98%) were added to the electrolyte substrate solution. The molar ratio of PEO monomer to NaTFSI was 20:1, and the molar ratio of SnCl4 to NaTFSI was 1:20. The mixture was stirred at 80 °C for 24 h until a homogeneous mixed solution was formed. S3. Pour the mixed solution onto silicone paper, spread it with a scraper, and dry it at 80 °C for 24 h to form an electrolyte sheet. After cooling, cut it into round pieces of appropriate size to obtain a sodium ion solid electrolyte.

[0067] The sodium-ion solid electrolyte provided in this embodiment is PEO-SnCl4.

[0068] Example 2 This embodiment provides a method for preparing a sodium ion solid electrolyte, which differs from Example 1 in that the tin salt additive is tin dichloride (SnCl2).

[0069] The sodium-ion solid electrolyte provided in this embodiment is PEO-SnCl2.

[0070] Example 3 This embodiment provides a method for preparing a sodium ion solid electrolyte, which differs from Example 1 in that the tin salt additive is tin bromide (SnBr2).

[0071] The sodium-ion solid electrolyte provided in this embodiment is PEO-SnBr2.

[0072] Example 4 This embodiment provides a method for preparing a sodium ion solid electrolyte, which differs from Example 1 in that the tin salt additive is tin fluoride (SnF2).

[0073] The sodium-ion solid electrolyte provided in this embodiment is PEO-SnF2.

[0074] Example 5 This embodiment provides a method for preparing a sodium ion solid electrolyte, which differs from Example 1 in that the tin salt additive is stannous trifluoromethanesulfonate (Sn(OTF)2).

[0075] The sodium-ion solid electrolyte provided in this embodiment is PEO-Sn(OTF)2.

[0076] Example 6 This embodiment provides a method for preparing a sodium ion solid electrolyte, which differs from Example 1 in that the molar ratio of tin salt additive SnCl4 to sodium salt is 1:50.

[0077] The sodium-ion solid electrolyte provided in this embodiment is PEO-SnCl4.

[0078] Example 7 This embodiment provides a method for preparing a sodium ion solid electrolyte, which differs from Example 1 in that the molar ratio of tin salt additive SnCl4 to sodium salt is 1:10.

[0079] The sodium-ion solid electrolyte provided in this embodiment is PEO-SnCl4.

[0080] Comparative Example 1 This comparative example provides a method for preparing a sodium-ion solid electrolyte, which differs from Example 1 in that no additives are added.

[0081] The sodium-ion solid electrolyte provided in this comparative example is PEO.

[0082] The preparation methods of sodium ion solid electrolytes provided in Examples 1-7 and Comparative Example 1 are shown in Table 1.

[0083] Table 1. Preparation methods of sodium ion solid electrolytes

[0084] Note: In Table 1, " / " indicates that tin salt additives are not included.

[0085] Application Example 1 This application example provides a sodium-ion solid-state battery, including sodium-sodium symmetric batteries made from sodium-ion solid-state electrolytes provided in Examples 1-7 and Comparative Example 1.

[0086] This application example also provides a method for preparing a sodium-ion solid-state battery, comprising: using a sodium-sodium symmetric battery with a sodium metal | sodium-ion solid electrolyte | sodium metal sandwich structure, bonding and compositing the sodium-ion solid electrolytes provided in Examples 1-7 and Comparative Example 1 with sodium metal, and reacting at 80 °C for 1 h to form a sodium-tin alloy layer in situ on the surface of the electrolyte layer of the sodium-ion solid electrolyte.

[0087] Application Example 2 This application example provides a sodium-ion solid-state battery, including a sodium-ion all-solid-state battery made of sodium-ion solid-state electrolyte provided in Examples 1-7 and Comparative Example 1.

[0088] This application example also provides a method for preparing a sodium-ion solid-state battery, comprising: using a sodium-ion all-solid-state battery with an NVP (sodium vanadium phosphate) | sodium-ion solid-state electrolyte | sodium metal structure, bonding and compositing the sodium-ion solid-state electrolytes provided in Examples 1-7 and Comparative Example 1 with NVP and sodium metal, and reacting at 80 °C for 1 h.

[0089] Experimental Example 1 This experimental example characterizes the sodium ion solid electrolyte provided in Example 1 and the sodium ion solid electrolyte provided in Comparative Example 1 using SEM and EDS. The detection results are as follows: Figures 1-3 As shown.

[0090] Depend on Figures 1-3 As far as we know, Figure 1 The surface morphology of the PEO-SnCl4 sodium ion solid electrolyte provided in Example 1 is shown. Figure 2 The above are the EDS test results of Sn element in the PEO-SnCl4 sodium ion solid electrolyte provided in Example 1. Figure 3 The surface morphology of the sodium ion solid electrolyte provided for Comparative Example 1.

[0091] Depend on Figure 1 The results showed that the PEO-SnCl4 sodium ion solid electrolyte provided in Example 1 had no obvious pores or voids on its surface, but instead exhibited sheet-like deposits. Figure 2 The results show that the EDS characterization of the PEO-SnCl4 sodium ion solid electrolyte provided in Example 1 reveals that the sheet-like deposition contains Sn element. Figure 3 The results show that the PEO sodium-ion solid electrolyte provided in Comparative Example 1 exhibits obvious pores and voids on its surface. Therefore, this application demonstrates that by adding tin salt additives to the sodium-ion solid electrolyte, the surface of the sodium-ion solid electrolyte is significantly improved, effectively filling the pores and voids on the surface of the unmodified PEO sodium-ion solid electrolyte, thereby effectively preventing sodium dendrites from piercing the electrolyte and causing a battery short circuit.

[0092] Experimental Example 2 This experimental example examines the alloy phase of the sodium-tin alloy layer formed on the surface of the sodium-ion solid electrolyte in a sodium-sodium symmetric battery prepared with the sodium-ion solid electrolyte provided in Example 1. The results are as follows: Figure 4 As shown.

[0093] Depend on Figure 4The results show that the sodium-tin alloy layer formed on the surface of the sodium-ion solid electrolyte in the sodium-sodium symmetric battery prepared by the sodium-ion solid electrolyte provided in Example 1 is Na. 15 Sn4 alloy. This application demonstrates the in-situ formation of stable Na+ on the surface between the sodium-ion solid electrolyte and the sodium metal anode. 15 The Sn4 alloy layer forms a low-resistance interface with the sodium-ion solid electrolyte, reducing the interface resistance and promoting the uniform distribution and rapid transport of sodium ions. This reduces sodium dendrite formation and inhibits sodium dendrite penetration, thereby improving the cycle performance of solid sodium-ion batteries.

[0094] Experimental Example 3 This test example measures the thickness of the sodium-tin alloy layer formed on the surface of the sodium-ion solid electrolyte in a sodium-sodium symmetric battery made with the sodium-ion solid electrolyte provided in Example 1. The results are shown in Table 2.

[0095] Table 2 Thickness of Sodium-Tin Alloy Layer

[0096] As shown in Table 2, the thickness of the sodium-tin alloy layer formed on the surface of each sodium-ion solid electrolyte in the sodium-sodium symmetric battery prepared by the sodium-ion solid electrolyte provided in Example 1 is 10 nm, which is less than 20 nm. This indicates that the in-situ formation of a relatively thin sodium-tin alloy layer between the sodium-ion solid electrolyte and the sodium metal anode provided in this application can improve interface wettability and reduce interface charge conduction impedance, thereby improving the cycle performance of the solid sodium-ion battery, while suppressing interfacial side reactions.

[0097] Test Example 4 In this experimental example, sodium-ion batteries prepared with the sodium-ion solid electrolytes provided in Examples 1-5 and Comparative Example 1 were subjected to electrochemical impedance spectroscopy tests with a bias voltage of 10 mV applied within a frequency range of 1-7 MHz. The results are as follows: Figure 5 As shown.

[0098] Depend on Figure 5The results show that the sodium-sodium symmetric batteries prepared with the sodium-ion solid electrolytes provided in Examples 1-5 all exhibited lower impedance values ​​compared to the sodium-sodium symmetric batteries prepared with the sodium-ion solid electrolyte provided in Comparative Example 1. This indicates that by adding tin salt additives to the sodium-ion solid electrolyte, the electrochemical impedance of the sodium-ion solid battery is effectively reduced when applied to it. Because the tin salt additives added to the sodium-ion solid electrolyte react in situ with sodium metal, a stable sodium-tin alloy layer is formed on the surface between the sodium-ion solid electrolyte and sodium metal, which can significantly suppress interfacial side reactions and effectively increase the ion transference number, thereby effectively improving the wettability and stability between the sodium metal anode and the sodium-ion solid electrolyte interface.

[0099] Comparing Examples 1-5, the sodium-sodium symmetric battery prepared with the sodium-ion solid electrolyte provided in Example 1 exhibits the best resistance optimization effect. This is because the Sn in SnCl4 added to the sodium-ion solid electrolyte provided in Example 1 is a high-valence tetravalent Sn. 4+ It exhibits strong reduction reactivity and can generate relatively dense NaF and stable Na+ at the interface. 15 Sn4 alloy layer interface structure; SnCl2 and SnF2 have low reactivity, or directly provide F - The generated NaF layer may not be dense enough, and the alloying process is slow when forming the sodium-tin alloy layer, resulting in a low sodium content and poor gradient in the sodium-tin alloy layer; SnBr2 will generate NaBr with low ionic conductivity, and Sn(OTf)2 will form a complex organic-inorganic hybrid layer, which seriously hinders ion transport.

[0100] Experimental Example 5 In this experimental example, sodium-sodium symmetric batteries prepared with sodium-ion solid electrolytes provided in Examples 1 and 6-7 were subjected to electrochemical impedance spectroscopy tests with a bias voltage of 10 mV applied within a frequency range of 1-7 MHz. The results are as follows: Figure 6 As shown.

[0101] Depend on Figure 6 The results show that, comparing Examples 1 and 6-7, the sodium-ion solid electrolyte provided in Example 1, with a molar ratio of tin salt additive to sodium salt of 1:20, exhibits the best resistance optimization effect when applied to sodium-ion solid-state batteries. This indicates that the appropriate amount of tin salt additive used in this application facilitates the in-situ reaction with sodium metal to form a relatively stable sodium-tin alloy layer, which has lower electrochemical impedance, thereby improving the cycle performance of solid-state sodium-ion batteries.

[0102] Experimental Example 6 This test case corresponds to the sodium-ion solid electrolyte prepared from Example 1 and Comparative Example 1 in Case 1. Sodium-symmetric batteries were subjected to long-cycle voltage distribution tests; sodium-ion all-solid-state batteries prepared with sodium-ion solid electrolytes provided in Example 1 and Comparative Example 1 of Case 2 were subjected to cycle charge-discharge tests; the specific methods are as follows: (1) Long-cycle voltage distribution test: The above sodium A sodium-symmetric battery, at 60 °C, achieves a single cycle at 0.1 mA / cm². 2 Charge and discharge for 30 minutes each, and record the voltage distribution during the long-cycle test. The results are as follows: Figure 7 As shown.

[0103] (2) Cyclic charge-discharge test: The sodium-ion all-solid-state battery described above was charged and discharged at 0.2 C for the first two cycles, and then at 0.5 C for the subsequent cycles. The cyclic charge-discharge performance graphs are shown below. Figure 8 As shown.

[0104] Depend on Figure 7 The results show that the sodium-sodium symmetric battery prepared with the sodium-ion solid electrolyte provided in Comparative Example 1 exhibited extremely unstable voltage during cycling, experiencing multiple micro-short circuits and significant voltage fluctuations. Ultimately, after 116 hours of cycling, it was penetrated by sodium dendrites, causing the voltage to plummet to 0V and resulting in a short circuit. In contrast, the sodium-sodium symmetric battery prepared with the sodium-ion solid electrolyte provided in Example 1 maintained stable cycling even after 400 hours of continuous charging, and its charge and discharge voltage remained essentially stable.

[0105] Depend on Figure 8 The results show that the sodium-ion all-solid-state battery prepared with the sodium-ion solid-state electrolyte provided in Comparative Example 1 exhibits extremely poor coulombic efficiency stability, with abrupt changes in coulombic efficiency at the beginning of the cycle, and the capacity begins to decay rapidly after 180 cycles. In contrast, the sodium-ion all-solid-state battery prepared with the sodium-ion solid-state electrolyte provided in Example 1 exhibits extremely stable cycle performance, showing a coulombic efficiency of nearly 99% per cycle, and can stably cycle for more than 300 cycles without significant capacity decay.

[0106] In summary, the results show that the sodium-ion solid-state battery provided in this application has relatively stable cycle performance. Since the sodium-ion solid-state battery provided in this application forms a stable sodium-tin alloy layer in situ on the surface between the sodium-ion solid electrolyte and the sodium metal anode, it can significantly suppress interfacial side reactions and effectively increase the ion transference number, thereby effectively improving the wettability and stability between the sodium metal anode and the sodium-ion solid electrolyte interface, thus improving the cycle performance of the solid sodium-ion battery.

[0107] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A method for preparing a sodium-ion solid-state battery, characterized in that, include: A sodium-ion solid electrolyte is provided, the sodium-ion solid electrolyte comprising a sodium salt, an electrolyte substrate, and a tin salt additive; the tin salt additive is anhydrous tin tetrachloride. The tin salt additive is dispersed in the sodium ion solid electrolyte; the molar ratio of the tin salt additive to the sodium salt is 1:20; The sodium-ion solid electrolyte is bonded and composited with a sodium metal anode, and reacted at 60~100 ℃ for 1~12 h to form a sodium-tin alloy layer in situ on the surface between the sodium-ion solid electrolyte and the sodium metal anode. Tin salt additives fill the pores and voids on the original sodium-ion solid electrolyte surface. The thickness of the sodium-tin alloy layer is 10 nm.

2. The method for preparing a sodium-ion solid-state battery according to claim 1, characterized in that, The sodium-ion solid electrolyte is composed of sodium salt, electrolyte substrate and tin salt additive.

3. The method for preparing a sodium-ion solid-state battery according to claim 2, characterized in that, The sodium salt includes at least one of NaTFSI, NaFSI, NaPF6, NaClO4, and NaBF4.

4. The method for preparing a sodium-ion solid-state battery according to any one of claims 1 to 3, characterized in that, The electrolyte substrate includes at least one of polyethylene oxide, polyvinylidene fluoride, polyvinyl alcohol, polyacrylonitrile, ethyl polyacrylate, and polyethylene glycol.

5. The method for preparing a sodium-ion solid-state battery according to any one of claims 1 to 3, characterized in that, The preparation method of the sodium ion solid electrolyte includes: S1, Dissolve the electrolyte substrate in an organic solvent to obtain an electrolyte substrate solution; S2, the tin salt additive and the sodium salt are added to the electrolyte substrate solution in a molar ratio, and the mixture is heated and stirred to obtain a mixed solution; S3, the mixed solution is coated onto the surface of the carrier and dried to form an electrolyte sheet, thus obtaining the sodium ion solid electrolyte.

6. The preparation method according to claim 5, characterized in that, Dissolving the electrolyte substrate in an organic solvent includes: mixing the electrolyte substrate and the organic solvent at a mass ratio of 1:5~20, and stirring at 80~90 °C for 12~36 h; And / or, the molar ratio of the electrolyte substrate monomer to the sodium salt is 5~30 : 1.

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