Sodium-ion solid electrolyte, sodium-ion solid battery and preparation method of sodium-ion solid electrolyte and sodium-ion solid battery

Abstract

The invention 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. A sodium ion solid electrolyte comprises a sodium salt, an electrolyte substrate and a tin salt additive. And the wettability and stability between the sodium metal negative electrode and the sodium ion solid electrolyte interface can be effectively improved, so that the cycle performance of the solid sodium ion battery is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, and in particular to a sodium ion solid-state electrolyte, a sodium ion solid-state battery and a preparation method thereof. BACKGROUND

[0002] All-solid-state sodium metal batteries have the advantages of low cost, abundant sodium resources and high energy density, and are considered as a promising energy storage technology. Among them, the solid-state electrolyte is 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 effectively improving the interface contact, flexibility, processability and good film-forming performance. However, the polymer-based solid-state electrolyte still has the problems of low ionic conductivity and interface degradation, which greatly hinders their practical application.

[0003] In order to solve these problems, many methods are currently used, such as increasing the working temperature and introducing inorganic fillers, although these methods can improve the ionic conductivity to some extent, but they cannot fully solve the interface problem, resulting in limited cycle life of all-solid-state sodium metal. Interface degradation is caused by the interface side reaction of the negative electrode, which leads to the increase of interface impedance, the growth of sodium dendrites, and finally the short circuit failure of the battery.

[0004] The current traditional methods, whether adding inorganic fillers to form composite electrolytes or surface modification, mainly block the growth of dendrites, thereby inhibiting the damage of the electrolyte interface. Such methods do not fundamentally change the dendrite growth kinetics, can only delay the failure of the battery, and cannot fundamentally improve the stability of the sodium metal and electrolyte interface. In addition, some methods require expensive materials or precise equipment, which has high cost and complex operation. Some interface modification methods may also change the intrinsic electrochemical properties of the electrolyte material, resulting in the reduction of the energy density of the battery. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the embodiments of the present application includes providing a sodium ion solid-state electrolyte, a sodium ion solid-state battery and a preparation method thereof. The wettability and stability between the sodium metal negative electrode and the sodium ion solid-state electrolyte interface can be effectively improved, thereby improving the cycle performance of the solid-state sodium ion battery.

[0006] In a first aspect, the embodiments of the present application provide a sodium ion solid-state electrolyte, which comprises a sodium salt, an electrolyte substrate and a tin salt additive.

[0007] The sodium ion solid-state electrolyte provided in the application adds tin salt additives, on the one hand, the tin salt additives can fill the holes and pores on the surface of the original sodium ion solid-state electrolyte, thereby effectively preventing sodium dendrites from penetrating; on the other hand, when the sodium ion solid-state electrolyte is applied to a sodium ion solid-state battery, the tin salt additives added therein can react in situ with sodium metal, forming a sodium-tin alloy layer on the surface between the sodium ion solid-state electrolyte and the sodium metal, the sodium-tin alloy layer has high stability, significantly inhibits the interface side reaction, and effectively improves the ion migration number, thereby effectively improving the wettability and stability between the sodium metal anode and the interface of the sodium ion solid-state electrolyte, thereby improving the cycle performance of the solid-state sodium ion battery.

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

[0009] The sodium ion solid-state electrolyte provided in the application adds only tin salt additives in addition to the basic sodium salt and electrolyte substrate, which is conducive to the tin salt additives filling the holes and pores on the surface of the original sodium ion solid-state electrolyte, thereby effectively preventing sodium dendrites from penetrating; and when the sodium ion solid-state electrolyte is applied to a sodium ion solid-state battery, the tin salt additives are conducive to reacting in situ with sodium metal to form a stable sodium-tin alloy layer, reducing the interference of other substances with the tin salt additives and sodium metal reacting to form a stable sodium-tin alloy layer.

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

[0011] The application adopts a suitable sodium salt to facilitate the formation of a sodium ion solid-state electrolyte with good performance.

[0012] In some embodiments of the application, the electrolyte substrate includes at least one of polyethylene oxide, polyvinylidene fluoride, polyvinyl alcohol, polyacrylonitrile, polyethyl acrylate, and polyethylene glycol.

[0013] The application adopts a suitable electrolyte substrate to facilitate the formation of a polymer-based sodium ion solid-state electrolyte with good performance.

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

[0015] The application adopts a suitable tin salt additive to facilitate in-situ reaction with sodium metal to form a sodium-tin alloy layer with high stability, which can effectively improve the wettability and stability between the sodium metal anode and the interface of the sodium ion solid-state electrolyte, thereby improving the cycle performance of the solid-state sodium ion battery.

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

[0017] The present application uses a suitable amount of tin salt additive to facilitate in-situ reaction with sodium metal to form a relatively stable sodium-tin alloy layer, and has a relatively small electrochemical impedance, thereby improving the cycle performance of the solid-state sodium ion battery.

[0018] In a second aspect, the present application provides a preparation method of the sodium ion solid-state electrolyte provided in the first aspect, comprising: S1, dissolving the electrolyte base material in an organic solvent to obtain an electrolyte base material solution; S2, adding a tin salt additive and a sodium salt to the electrolyte base material solution according to a molar ratio, and heating and stirring to obtain a mixed solution; S3, coating the mixed solution on the surface of the carrier, and drying to form an electrolyte sheet to obtain the sodium ion solid-state electrolyte.

[0019] The present application adds a tin salt additive and a sodium salt to an electrolyte base material solution according to a molar ratio, and obtains a mixed solution by heating and stirring, then coats the mixed solution on the surface of a carrier, and dries to form an electrolyte layer to obtain a sodium ion solid-state electrolyte. The sodium ion solid-state electrolyte has a suitable amount of tin salt additive, which can fill the holes and pores on the surface of the original sodium ion solid-state electrolyte, thereby effectively preventing sodium dendrites from penetrating. When the sodium ion solid-state electrolyte is applied to a sodium ion solid-state battery, the added tin salt additive can react in-situ with sodium metal to form a stable sodium-tin alloy layer on the surface between the sodium ion solid-state electrolyte and the sodium metal, which can effectively improve the wettability and stability between the sodium metal anode and the sodium ion solid-state electrolyte interface, thereby improving the cycle performance of the solid-state sodium ion battery.

[0020] In some embodiments of the present application, dissolving the electrolyte base material in the organic solvent comprises: mixing the electrolyte base material and the organic solvent according to a mass ratio of 1:5-20, and stirring at 80-90°C for 12-36h.

[0021] The present application dissolves the electrolyte base material in a suitable amount of organic solvent under suitable conditions, which facilitates the complete dissolution of the electrolyte base material, thereby facilitating the subsequent preparation of the sodium ion solid-state electrolyte.

[0022] In some embodiments of the present application, the molar ratio of the electrolyte base material monomer to the sodium salt is 5-30:1.

[0023] The present application uses a suitable amount of electrolyte base material and sodium salt to facilitate the formation of a polymer-based sodium ion solid-state electrolyte with good performance.

[0024] In a third aspect, the embodiments of the present application provide a preparation method of a sodium ion solid-state battery, comprising: bonding and compounding the sodium ion solid-state electrolyte provided in the first aspect with a sodium metal negative electrode, and reacting at 60-100 DEG C for 1-12 h to form a sodium-tin alloy layer in situ on the surface between the sodium ion solid-state electrolyte and the sodium metal negative electrode.

[0025] The present application can effectively improve the wettability and stability between the sodium metal negative electrode and the sodium ion solid-state electrolyte interface, and thus improve the cycle performance of the solid-state sodium ion battery.

[0026] In a fourth aspect, the embodiments of the present application provide a sodium ion solid-state battery, comprising a positive electrode sheet, a negative electrode sheet and a sodium ion solid-state electrolyte; the negative electrode sheet is a sodium metal; the sodium ion solid-state electrolyte has a sodium-tin alloy layer on the surface between the sodium ion solid-state electrolyte and the negative electrode sheet; and the sodium ion solid-state electrolyte comprises a sodium salt and an electrolyte base material.

[0027] The sodium ion solid-state battery provided by the present application has a sodium-tin alloy layer with high stability on the surface between the sodium ion solid-state electrolyte and the negative electrode sheet, can significantly inhibit the interface side reaction, and effectively improve the ion migration number, thereby effectively improving the wettability and stability between the sodium metal negative electrode and the sodium ion solid-state electrolyte interface, and thus improving the cycle performance of the solid-state sodium ion battery.

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

[0029] The sodium ion solid-state battery provided by the present application has a sodium-tin alloy layer with high stability on the surface between the sodium ion solid-state electrolyte and the negative electrode sheet, can significantly inhibit the interface side reaction, and effectively improve the ion migration number, thereby effectively improving the wettability and stability between the sodium metal negative electrode and the sodium ion solid-state electrolyte interface, and thus improving the cycle performance of the solid-state sodium ion battery.

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

[0031] The sodium ion solid-state battery provided by the present application has a sodium-tin alloy layer with high stability on the surface between the sodium ion solid-state electrolyte and the negative electrode sheet, can significantly inhibit the interface side reaction, and effectively improve the ion migration number, thereby effectively improving the wettability and stability between the sodium metal negative electrode and the sodium ion solid-state electrolyte interface, and thus improving the cycle performance of the solid-state sodium ion battery. 15 Sn4 alloy layer, Na 15 Sn4 and the sodium ion solid-state electrolyte form a low-resistance interface, reduce the interface resistance, and promote the uniform distribution and rapid transmission of sodium ions, thereby reducing the formation of sodium dendrites and inhibiting the penetration of sodium dendrites, and thus improving the cycle performance of the solid-state sodium ion battery. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0033] Figure 1 SEM image of the sodium ion solid-state electrolyte provided for Example 1 in Test Example 1 of the present application.

[0034] Figure 2 EDS image of Sn element of the sodium ion solid-state electrolyte provided for Example 1 in Test Example 1 of the present application.

[0035] Figure 3 SEM image of the sodium ion solid-state electrolyte provided for Comparative Example 1 in Test Example 1 of the present application.

[0036] Figure 4 XRD image of the sodium ion solid-state electrolyte provided for Example 1 in Test Example 2 of the present application after alloying with sodium metal.

[0037] Figure 5 Impedance data graph provided in Test Example 4 of the present application.

[0038] Figure 6 Impedance data graph provided in Test Example 5 of the present application; wherein PEO-SnCl45%-Example 1; PEO-SnCl42%-Example 6; PEO-SnCl410%-Example 7.

[0039] Figure 7 Long cycle voltage distribution graph provided in Test Example 6 of the present application.

[0040] Figure 8 Cycle charge-discharge performance graph provided in Test Example 6 of the present application; wherein (a)-Comparative Example 1; (b)-Example 1. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely. The specific conditions not mentioned in the embodiments are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments not mentioned by the manufacturer are all conventional products that can be obtained by market purchase.

[0042] In order to fundamentally improve the stability of the interface between sodium metal and electrolyte. On the one hand, the present application provides a sodium ion solid-state electrolyte, which comprises a sodium salt, an electrolyte substrate and a tin salt additive.

[0043] The sodium ion solid-state electrolyte provided by the present application, wherein a tin salt additive is added. On the one hand, the tin salt additive can fill the holes and pores on the surface of the sodium ion solid-state electrolyte, thereby effectively preventing the penetration of sodium dendrites. On the other hand, when the sodium ion solid-state electrolyte is applied to a sodium ion solid-state battery, the tin salt additive can react in situ with sodium metal to form a sodium-tin alloy layer on the surface between the sodium ion solid-state electrolyte and the sodium metal. The sodium-tin alloy layer has high stability, significantly inhibits the interface side reaction, and effectively improves the ion migration number, thereby effectively improving the wettability and stability between the sodium metal anode and the interface of the sodium ion solid-state electrolyte, and improving the cycle performance of the solid-state sodium ion battery.

[0044] In some embodiments of the present application, the sodium ion solid-state electrolyte is composed of a sodium salt, an electrolyte substrate and a tin salt additive. In addition to the basic sodium salt and the electrolyte substrate, only the tin salt additive is added, which is conducive to the tin salt additive filling the holes and pores on the surface of the sodium ion solid-state electrolyte, thereby effectively preventing the penetration of sodium dendrites; and when the sodium ion solid-state electrolyte is applied to a sodium ion solid-state battery, the tin salt additive is conducive to the tin salt additive reacting in situ with sodium metal to form a stable sodium-tin alloy layer, reducing the interference of other substances with the tin salt additive and sodium metal reacting to form a stable sodium-tin alloy layer.

[0045] In some embodiments of the present application, the sodium salt includes at least one of NaTFSI (sodium bis(trifluoromethylsulfonyl)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 sodium ion solid-state electrolyte with good performance.

[0046] In some embodiments of the present application, the electrolyte substrate includes at least one of polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polyethyl acrylate (PEA), and polyethylene glycol (PEG). A suitable electrolyte substrate is used to facilitate the formation of a polymer-based sodium ion solid-state electrolyte with good performance.

[0047] In some embodiments of the present 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 triflate (Sn(OTf)2). A suitable tin salt additive is used to facilitate the in-situ reaction with sodium metal to form a sodium-tin alloy layer with high stability, which can effectively improve the wettability and stability between the sodium metal anode and the interface of the sodium ion solid-state electrolyte, thereby improving the cycle performance of the solid-state sodium ion battery.

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

[0049] In some embodiments of the present application, the molar ratio of the tin salt additive to the sodium salt is 1:10-50. As an example, the molar ratio of the tin salt additive to the sodium salt can 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 1:10-20. As an example, the molar ratio of the tin salt additive to the sodium salt can 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. The use of a suitable amount of tin salt additive facilitates in-situ reaction with sodium metal to form a more stable sodium-tin alloy layer with smaller electrochemical impedance, thereby improving the cycle performance of the solid-state sodium ion battery.

[0050] In a second aspect, the embodiments of the present application provide a preparation method of the above-mentioned sodium ion solid-state electrolyte, comprising: S1, dissolving the electrolyte substrate in an organic solvent to obtain an electrolyte substrate solution; S2, adding the tin salt additive and the sodium salt into the electrolyte substrate solution according to a molar ratio, and heating and stirring to obtain a mixed solution; S3, coating the mixed solution on the surface of a carrier and drying to form an electrolyte sheet, thereby obtaining the sodium ion solid-state electrolyte.

[0051] The present application can fill the holes and pores on the surface of the original sodium ion solid-state electrolyte by preparing a sodium ion solid-state electrolyte with a suitable amount of tin salt additive, thereby effectively preventing sodium dendrites from penetrating; and when the sodium ion solid-state electrolyte is applied to a sodium ion solid-state battery, the tin salt additive added therein can react in-situ with sodium metal to form a stable sodium-tin alloy layer on the surface between the sodium ion solid-state electrolyte and the sodium metal, which can effectively improve the wettability and stability between the sodium metal anode and the sodium ion solid-state electrolyte interface, thereby improving the cycle performance of the solid-state sodium ion battery.

[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 an NVP (sodium vanadium phosphate) | sodium-ion solid-state electrolyte | sodium metal structure sodium-ion all-solid-state battery, bonding and compositing the sodium-ion solid-state electrolytes provided in Examples 1-7 and Comparative Example 1 with NVP and sodium metal respectively, 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. Long-cycle voltage distribution tests were conducted on sodium-symmetric batteries; cycle charge-discharge tests were conducted on sodium-ion all-solid-state batteries prepared with the sodium-ion solid electrolytes provided in Example 1 and Comparative Example 1 of Case 2; 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 sodium-ion solid electrolyte, characterized in that, Including sodium salts, electrolyte base materials, and tin salt additives.

2. The sodium-ion solid electrolyte 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 sodium-ion solid electrolyte according to claim 1, characterized in that, The sodium salt includes at least one of NaTFSI, NaFSI, NaPF6, NaClO4, and NaBF4; And / or, the electrolyte substrate includes at least one of polyethylene oxide, polyvinylidene fluoride, polyvinyl alcohol, polyacrylonitrile, ethyl polyacrylate, and polyethylene glycol; And / or, the tin salt additive includes at least one of anhydrous tin tetrachloride, tin dichloride, tin bromide, tin fluoride, and stannous trifluoromethanesulfonate.

4. The sodium-ion solid electrolyte according to any one of claims 1 to 3, characterized in that, The molar ratio of the tin salt additive to the sodium salt is 1:10~50.

5. A method for preparing a sodium-ion solid electrolyte as described in any one of claims 1 to 4, characterized in that, include: 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.

7. A method for preparing a sodium-ion solid-state battery, characterized in that, include: The sodium-ion solid electrolyte according to any one of claims 1 to 4 is bonded and composited with a sodium metal anode, and reacted at 60 to 100 °C for 1 to 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.

8. A sodium-ion solid-state battery, characterized in that, It includes 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.

9. The sodium-ion solid-state battery according to claim 8, characterized in that, The thickness of the sodium-tin alloy layer is less than 20 nm.

10. The sodium-ion solid-state battery according to claim 8, characterized in that, The sodium-tin alloy layer is Na 15 Sn4 alloy layer.

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