Electrolyte for regulating and controlling stability mechanism of sodium metal battery as well as preparation method and application of electrolyte

Abstract

The invention discloses an electrolyte for regulating and controlling a stability mechanism of a sodium metal battery as well as a preparation method and application of the electrolyte. The electrolyte comprises an organic solvent, electrolyte sodium salt and an additive, wherein the additives are fluoro carbonates and sulfones. According to the invention, additives are added into the electrolyte, and the two additives are subjected to division and cooperation at the positive electrode side and the negative electrode side: a fluoro-carbonic ester reinforced solid electrolyte interface (SEI) and a sulfone stable positive electrode electrolyte interface (CEI), and complementation and cooperation are realized through solvation regulation and interface adsorption; by using the electrolyte added with the additive, the overall interface stability of the sodium metal battery can be remarkably improved, good electrochemical performance is ensured, the battery can efficiently and stably circulate, and excellent rate capability is shown. The electrolyte is prepared by adopting a low-cost and simple method, and the extremely stable sodium metal battery is obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery energy storage, and in particular relates to an electrolyte for regulating the stabilization mechanism of a sodium metal battery, and a preparation method and application thereof. Background Art

[0002] Since their commercialization in 1991, lithium-ion batteries have powered the ubiquitous electric vehicles and portable transportation in our lives. However, due to the limited distribution and low abundance of key raw materials such as cobalt (Co) and lithium (Li), they still cannot meet the needs of large-scale grid storage. In fact, recent concerns about the increasing production costs of lithium-ion batteries and the availability of raw material supplies have promoted the development of low-cost, sustainable and more environmentally friendly alternatives such as sodium-ion batteries (SIBs) or SMBs. Despite the significant advantages of sodium metal batteries, their commercial application still faces multiple technical barriers. In particular, the technical bottlenecks are prominent in issues such as the stability of the negative electrode interface layer and the control of sodium dendrite growth during cycling. Specifically, during the battery charge and discharge cycle, due to the high chemical activity of metallic sodium and the instability of the electrolyte, a series of side reactions occur between the sodium anode and the electrolyte, forming an unstable and poorly conductive solid electrolyte interface (SEI), which seriously restricts the cycle life of the battery. Furthermore, the sodium metal anode is prone to irregular sodium dendrite growth during the charge-discharge cycle, which not only increases the battery's internal resistance and reduces its Coulombic efficiency, but can also pierce the separator, causing internal short circuits and even safety accidents. Therefore, how to construct a stable and dense interfacial layer and effectively inhibit the growth of sodium dendrites is key to achieving safe, reliable, and efficient energy storage applications in sodium metal batteries.

[0003] At present, the strategy of adding specific functional additives to the electrolyte to regulate the interfacial chemical properties, inhibit dendrite growth, and construct a stable interfacial layer has become one of the important research directions in the field of batteries. However, whether the organic-based SEI can provide sufficient passivation effect for the active Na negative electrode remains a question. It is understood that the electrolyte dissolution structure largely determines the interfacial chemical properties. Huang et al. selected an anion receptor additive tris(trimethylsilyl)borate with strong anion affinity to weaken the coupling of cations and anions and enhance the transport kinetics. However, it cannot change the Na + The dissolution structure of the cathode is still unclear. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an electrolyte for regulating the stability mechanism of sodium metal batteries, as well as a preparation method and application thereof. The prepared sodium metal battery significantly improves the overall interface stability of the sodium metal battery, ensures good electrochemical performance, and enables the battery to cycle efficiently and stably, and exhibits excellent rate performance.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] An electrolyte for regulating the stability mechanism of a sodium metal battery comprises: an organic solvent, an electrolyte sodium salt, and additives; the additives are fluorocarbonates and sulfones; wherein the mass fraction of the organic solvent in the electrolyte is 60%-95%, the mass fraction of the electrolyte sodium salt is 3%-15%, and the concentration is 0.5-5 mol / L; the mass fractions of the additives in the sodium metal battery electrolyte are as follows: 0.1%-10% for the fluorocarbonate; and 0.1%-10% for the sulfone.

[0007] Preferably, the organic solvent is a carbonate organic solvent; the carbonate organic solvent includes one or more of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, and propylene carbonate. When two or more organic solvents are mixed, the volume ratio is 1:1 to 9:1, and the total volume accounts for 60% to 95% of the total electrolyte volume.

[0008] Preferably, the electrolyte sodium salt includes one or more of sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide. When multiple components are mixed, the mass percentage of each component is 1% to 99%, and the total mass accounts for 3% to 15% of the electrolyte.

[0009] The present invention also provides a method for preparing an electrolyte for regulating the stabilization mechanism of a sodium metal battery, comprising the following steps:

[0010] (1) Pretreatment of the organic solvent: taking an appropriate amount of the organic solvent, first drying it with a molecular sieve to remove water impurities, and then deoxygenating it under an inert gas protection environment to obtain a high-purity organic solvent that is anhydrous and oxygen-free for use;

[0011] (2) Pretreatment of electrolyte sodium salt: Dry the electrolyte sodium salt in a vacuum drying oven for 6-12 hours to completely remove moisture and other volatile impurities in the sodium salt. The drying temperature is controlled in the range of 80-120°C.

[0012] (3) preparing an initial electrolyte solution: slowly adding the pretreated electrolyte sodium salt to the above-mentioned anhydrous and oxygen-free organic solvent under the protection of an inert gas, controlling the stirring speed and temperature during the addition process, wherein the stirring speed is 200-500 rpm and the ambient temperature is controlled between 20-30°C, so that the sodium salt is completely dissolved and a uniform and transparent electrolyte mother solution is formed;

[0013] (4) Adding fluorocarbonate additives: Slowly add an appropriate amount of fluorocarbonate dropwise under continuous stirring at a rate of 0.5-1 mL / min and stir for 30-60 minutes to ensure that the FEC is evenly dispersed and fully mixed with the mother liquor;

[0014] (5) Adding sulfone additives: Slowly add the sulfone at a controlled addition rate of about 0.5-1 mL per minute while continuously stirring for 60-90 minutes to ensure that the sulfolane is evenly dispersed in the solution;

[0015] (6) Homogenization and stabilization: After mixing, the obtained electrolyte is continuously stirred at room temperature for 1-3 hours to ensure that the solution reaches a fully uniform and stable state, and is allowed to stand for 12-24 hours under an inert gas protection environment to obtain the final electrolyte for regulating the stability mechanism of sodium metal batteries.

[0016] The present invention also provides an extremely stable sodium metal battery, comprising a positive electrode material, a negative electrode material and an electrolyte.

[0017] The positive electrode material includes any one of sodium vanadium phosphate, sodium cobalt oxide, sodium nickel oxide, and sodium iron oxide;

[0018] The sodium metal negative electrode is a pure sodium metal sheet or an active material modified on other substrates with sodium metal as the main body, specifically a commercial sodium metal sheet, an electrodeposited titanium metal sheet, etc.

[0019] The present invention also provides an electrical device, comprising a sodium metal battery.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. The present invention adopts a method of adding additives to the electrolyte to change the performance of the sodium metal battery, and the operation is simple.

[0022] 2. Introducing two additives, fluorocarbonates and sulfones, into the electrolyte allows the two additives to "divide the work and cooperate" on the positive and negative electrode sides: fluorocarbonates strengthen the solid electrolyte interface (SEI), and sulfones stabilize the positive electrode electrolyte interface (CEI), and achieve complementary synergy through solvation regulation and interfacial adsorption. The use of electrolytes with added additives can significantly improve the overall interfacial stability of sodium metal batteries.

[0023] 3. The present invention controls the stability mechanism of sodium metal batteries by adding additives to the electrolyte, thereby improving the electrode-electrolyte interface properties of sodium metal batteries, forming a stable protective layer on the surface of the negative electrode of the sodium metal battery, and achieving uniform deposition of sodium ions at the interface. It can enable sodium vanadium phosphate positive electrode materials to stably cycle for more than 1,200 cycles under conditions with a capacity retention rate of more than 80%, thus solving the problem of sodium metal batteries being easily decomposed during charge and discharge, leading to decreased battery cycle performance, storage performance, and safety performance, and meeting the performance requirements of secondary batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0025] Figure 1 The Na||Na symmetric cell composed of the electrolyte containing additives in Example 1 is at 0.5 mA cm -2 , 0.5mAhcm -2 Image of the sodium metal surface after 60 cycles under these conditions.

[0026] Figure 2 The Na||Na symmetric cell composed of the electrolyte without additives in Comparative Example 3 was -2 , 0.5mAh cm -2 Image of the sodium metal surface after 60 cycles under these conditions.

[0027] Figure 3 For example 1, the Na||Na symmetric battery with electrolyte composition in comparative examples 1, 2, and 3 is at 0.5 mA cm -2 , 0.5mAhcm -2 Conditional cycle diagram.

[0028] Figure 4 For Example 1, the Na||Cu half-cells with electrolyte compositions in Comparative Examples 1, 2, and 3 were tested at 0.5 mA cm -2 , 0.5mAhcm -2 Conditional cycle diagram.

[0029] Figure 5 The Na||NVP full battery composed of the sodium metal battery electrolyte containing additives in Example 1 is at 100mAg -1 Cycling performance under .

[0030] Figure 6The Na||NVP full battery composed of the sodium metal battery electrolyte containing only SUL additive in Comparative Example 1 is at 100mAg -1 Cycling performance under .

[0031] Figure 7 The Na||NVP full battery composed of the sodium metal battery electrolyte containing only FEC additive in Comparative Example 2 is at 100mAg -1 Cycling performance under .

[0032] Figure 8 The Na||NVP full battery composed of the sodium metal battery electrolyte without additives in Comparative Example 2 is 100mAg -1 Cycling performance under .

[0033] Figure 9 For example 1, the electrolyte compositions of the Na||NVP full cells in comparative examples 1, 2, and 3 were 0.05-1A g -1 Magnification diagram.

[0034] Figure 10 The Na||NVP full battery composed of the electrolyte containing additives in Example 1 is 80mAg -1 SEM image of the positive electrode surface after 180 cycles under the same conditions.

[0035] Figure 11 The Na||NVP full battery composed of the electrolyte containing additives in Comparative Example 3 was tested at 80 mAg -1 SEM image of the positive electrode surface after 180 cycles under the same conditions. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Example 1:

[0039] An embodiment of the present invention provides an electrolyte for regulating the stability mechanism of a sodium metal battery, comprising: an organic solvent, an electrolyte sodium salt, and an additive; the additive is a fluorocarbonate and a sulfone; wherein the mass fraction of the organic solvent in the electrolyte is 60%-95%, the mass fraction of the electrolyte sodium salt is 3%-15%, and the concentration is 0.5-5 mol / L; the mass fractions of the additives in the sodium metal battery electrolyte are as follows: 0.1%-10% for the fluorocarbonate; and 0.1%-10% for the sulfone.

[0040] As an implementation method of an embodiment of the present invention, the organic solvent is a carbonate organic solvent; the organic solvent is a carbonate organic solvent; the carbonate organic solvent includes one or more of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, and propylene carbonate. When two or more organic solvents are mixed, the volume ratio is 1:1 to 9:1, and the total volume accounts for 60% to 95% of the total amount of the electrolyte.

[0041] As an implementation method of an embodiment of the present invention, the organic solvent is a carbonate organic solvent; the electrolyte sodium salt includes one or more of sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide. When multiple components are mixed and used, the mass percentage of each component is 1% to 99%, and the total mass accounts for 3% to 15% of the electrolyte.

[0042] Example 2:

[0043] Example 1

[0044] An embodiment of the present invention provides a method for preparing an electrolyte for regulating the stability mechanism of a sodium metal battery, comprising:

[0045] The electrolyte was prepared in an argon-protected glove box (H2O, O2 concentration ≤ 0.01 ppm):

[0046] (1) Pretreatment of organic solvent: Ethylene carbonate (EC) and propylene carbonate (PC) were mixed in a volume ratio of 1:1. After dehydration treatment with molecular sieves for 72 hours, nitrogen bubbling deoxygenation treatment was performed in a glove box to obtain a mixed solvent matrix with a water content of <3 ppm;

[0047] (2) Pretreatment of electrolyte sodium salt: Dry the electrolyte NaClO4 in a vacuum drying oven for 6-12 hours to completely remove moisture and other volatile impurities in the sodium salt. The drying temperature is controlled in the range of 80-120°C.

[0048] (3) Preparation of an initial electrolyte solution: Under inert gas protection, slowly add 1 mol of pretreated NaClO4 to the above-mentioned anhydrous and oxygen-free organic solvent, controlling the stirring speed and temperature during the addition process, wherein the stirring speed is 200-500 rpm and the ambient temperature is controlled between 20-30°C, so that the NaClO4 is completely dissolved and a uniform and transparent electrolyte mother solution is formed;

[0049] (4) Adding 5% fluorocarbonate additive (FEC): Slowly add an appropriate amount of fluorocarbonate dropwise under continuous stirring at a rate of 0.5-1 mL / min and stir for 30-60 minutes to ensure that the FEC is evenly dispersed and fully mixed with the mother liquor;

[0050] (5) Adding 5% sulfone additive (SUL): Slowly add sulfone at a controlled rate of about 0.5-1 mL per minute while stirring continuously for 60-90 minutes to ensure that the sulfolane is evenly dispersed in the solution;

[0051] (6) Homogenization and stabilization: After mixing, the obtained electrolyte is continuously stirred at room temperature for 1-3 hours to ensure that the solution reaches a fully uniform and stable state, and is allowed to stand for 12-24 hours under an inert gas protection environment to obtain the final electrolyte for regulating the stability mechanism of sodium metal batteries.

[0052] Comparative Example 1

[0053] The electrolyte was prepared in an argon-protected glove box (H2O, O2 concentration ≤ 0.01 ppm):

[0054] (1) Pretreatment of organic solvent: Ethylene carbonate (EC) and propylene carbonate (PC) were mixed in a volume ratio of 1:1. After dehydration treatment with molecular sieves for 72 hours, nitrogen bubbling deoxygenation treatment was performed in a glove box to obtain a mixed solvent matrix with a water content of <3 ppm;

[0055] (2) Pretreatment of electrolyte sodium salt: Dry the electrolyte NaClO4 in a vacuum drying oven for 6-12 hours to completely remove moisture and other volatile impurities in the sodium salt. The drying temperature is controlled in the range of 80-120°C.

[0056] (3) Preparation of an initial electrolyte solution: Under inert gas protection, slowly add 1 mol of pretreated NaClO4 to the above-mentioned anhydrous and oxygen-free organic solvent, controlling the stirring speed and temperature during the addition process, wherein the stirring speed is 200-500 rpm and the ambient temperature is controlled between 20-30°C, so that the NaClO4 is completely dissolved and a uniform and transparent electrolyte is formed;

[0057] (4) Adding 5% sulfone additive (SUL): Slowly add sulfone at a controlled rate of about 0.5-1 mL per minute while stirring continuously for 60-90 minutes to ensure that the sulfolane is evenly dispersed in the solution;

[0058] (5) Homogenization and stabilization: After mixing, the obtained electrolyte is continuously stirred at room temperature for 1-3 hours to ensure that the solution reaches a fully uniform and stable state, and is allowed to stand for 12-24 hours under an inert gas protection environment to obtain the final electrolyte for regulating the stability mechanism of sodium metal batteries.

[0059] Comparative Example 2

[0060] The electrolyte was prepared in an argon-protected glove box (H2O, O2 concentration ≤ 0.01 ppm):

[0061] (1) Pretreatment of organic solvent: Ethylene carbonate (EC) and propylene carbonate (PC) were mixed in a volume ratio of 1:1. After dehydration treatment with molecular sieves for 72 hours, nitrogen bubbling deoxygenation treatment was performed in a glove box to obtain a mixed solvent matrix with a water content of <3 ppm;

[0062] (2) Pretreatment of electrolyte sodium salt: Dry the electrolyte NaClO4 in a vacuum drying oven for 6-12 hours to completely remove moisture and other volatile impurities in the sodium salt. The drying temperature is controlled in the range of 80-120°C.

[0063] (3) Preparation of an initial electrolyte solution: Under inert gas protection, slowly add 1 mol of pretreated NaClO4 to the above-mentioned anhydrous and oxygen-free organic solvent, controlling the stirring speed and temperature during the addition process, wherein the stirring speed is 200-500 rpm and the ambient temperature is controlled between 20-30°C, so that the NaClO4 is completely dissolved and a uniform and transparent electrolyte is formed;

[0064] (4) Adding 5% sulfone additive (SUL): Slowly add sulfone at a controlled rate of about 0.5-1 mL per minute while stirring continuously for 60-90 minutes to ensure that the sulfolane is evenly dispersed in the solution;

[0065] (5) Homogenization and stabilization: After mixing, the obtained electrolyte is continuously stirred at room temperature for 1-3 hours to ensure that the solution reaches a fully uniform and stable state, and is allowed to stand for 12-24 hours under an inert gas protection environment to obtain the final electrolyte for regulating the stability mechanism of sodium metal batteries.

[0066] Comparative Example 3

[0067] The electrolyte was prepared in an argon-protected glove box (H2O, O2 concentration ≤ 0.01 ppm):

[0068] (1) Pretreatment of organic solvent: Ethylene carbonate (EC) and propylene carbonate (PC) were mixed in a volume ratio of 1:1. After dehydration treatment with molecular sieves for 72 hours, nitrogen bubbling deoxygenation treatment was performed in a glove box to obtain a mixed solvent matrix with a water content of <3 ppm;

[0069] (2) Pretreatment of electrolyte sodium salt: Dry the electrolyte NaClO4 in a vacuum drying oven for 6-12 hours to completely remove moisture and other volatile impurities in the sodium salt. The drying temperature is controlled in the range of 80-120°C.

[0070] (3) Preparation of an initial electrolyte solution: Under inert gas protection, slowly add 1 mol of pretreated NaClO4 to the above-mentioned anhydrous and oxygen-free organic solvent, controlling the stirring speed and temperature during the addition process, wherein the stirring speed is 200-500 rpm and the ambient temperature is controlled between 20-30°C, so that the NaClO4 is completely dissolved and a uniform and transparent electrolyte is formed;

[0071] (4) Homogenization and stabilization: After mixing, the obtained electrolyte is continuously stirred at room temperature for 1-3 hours to ensure that the solution reaches a fully uniform and stable state, and is allowed to stand for 12-24 hours under an inert gas protection environment to obtain the final electrolyte for regulating the stability mechanism of sodium metal batteries.

[0072] Electrochemical performance tests were conducted by injecting the electrolytes prepared in the above examples and comparative examples into Na||Na symmetric cells, where both the positive and negative electrodes were sodium metal and the separator was glass fiber. The electrolytes were evaluated for their stability at the sodium metal interface, their ability to form a stable and dense SEI film to reduce side reactions, and their ability to inhibit sodium dendrite formation. The electrolytes were then cycled for extended periods at specific current densities and capacities to examine their protective effect on the sodium negative electrode and their long-term stability in sodium metal use.

[0073] The optical microscopy of the Na negative electrode surface after 60 cycles is a strong evidence that the electrolyte containing SUL and FEC additives inhibits the formation of sodium dendrites. The Na negative electrode of the battery assembled with the electrolyte of Example 1 appears smooth and flat (such as Figure 1 As shown), while the Na negative electrode of the battery assembled with the electrolyte of Comparative Example 3 showed large and small protrusions and depressions (as shown Figure 2 shown).

[0074] At a current density of 0.5 mA cm -2 , with a capacity of 0.5 mAh cm -2Under these conditions, the symmetrical battery assembled with the electrolyte of Example 1 can be stably cycled for more than 1400 hours. The polarization voltage of the battery assembled with the electrolyte of Comparative Example 1 begins to increase significantly after about 200 hours of cycling. The battery assembled with the electrolyte of Comparative Example 2 can only be cycled for less than 500 hours, and the battery assembled with the electrolyte of Comparative Example 3 can only be cycled for about 250 hours (e.g. Figure 3 shown).

[0075] The electrolyte of Example 1 has high stability at the metal interface and can form a stable and dense SEI film. It can inhibit the formation of sodium dendrites and regulate the stability mechanism of the sodium metal battery.

[0076] The electrolytes prepared in the above examples and comparative examples were injected into a Na||Cu half-cell for electrochemical performance testing, wherein the Na||Cu half-cell had a positive electrode of nanographene-coated copper foil, a negative electrode of metallic sodium, and a separator of glass fiber.

[0077] Evaluation of the coulombic efficiency and cycling stability of the electrolyte during the sodium metal deposition / stripping process.

[0078] The Na||Cu half-cell assembled with the electrolyte of Example 1 can be cycled for more than 550 cycles and has an average coulombic efficiency of up to 95.7%. The Na||Cu half-cell assembled with the electrolyte of Comparative Example 2 short-circuited after only 200 cycles. The Na||Cu half-cells assembled with the electrolytes of Comparative Examples 1 and 3 not only have a small number of cycles, but also have a coulombic efficiency below 70% (e.g. Figure 4 shown).

[0079] The electrolyte of Example 1 can regulate the sodium metal stabilization mechanism, enhance the reversibility of sodium metal and the stability of the deposition / stripping process, reduce irreversible capacity loss, and effectively improve the capacity retention and recovery capabilities of the battery at different rates, demonstrating great potential application value.

[0080] Electrolytes prepared in the above examples and comparative examples were injected into sodium metal full cells for electrochemical performance testing. The electrolytes were evaluated in full cells using sodium vanadium phosphate as the positive electrode, sodium metal as the negative electrode, and a glass fiber separator. The electrolytes were evaluated for actual cycling stability, capacity retention, and rate performance in sodium metal cells.

[0081] The sodium metal battery assembled with the electrolyte of Example 1 showed the best cycle stability. After 1200 charge and discharge cycles, the capacity decay was small and the discharge capacity remained at about 85 mAh g -1 Above, the coulomb efficiency is maintained above 99% for a long time (such as Figure 5 The sodium metal battery assembled with the electrolyte of Comparative Example 1 showed a rapid capacity decay trend. The capacity dropped rapidly from the initial cycle stage. After 1200 cycles, the capacity was only about 30 mAh g-1 The coulombic efficiency also showed large fluctuations. The electrolyte in Comparative Example 1 could not form a sufficiently stable CEI film and could not effectively suppress the side reactions and uneven deposition on the surface of sodium metal (such as Figure 6 The capacity of the sodium metal battery assembled with the electrolyte of Comparative Example 2 was relatively stable at the beginning of the cycle, but it began to decrease rapidly around 300 cycles, and the final discharge capacity dropped to about 25 mAh g -1 The following coulombic efficiency fluctuates significantly in the later period, indicating that although the electrolyte of Comparative Example 2 can provide a certain stability in the early cycle, it is not enough to maintain a stable interface during the long cycle (e.g. Figure 7 As shown). The sodium metal battery assembled with the electrolyte of Comparative Example 3 performed the worst. The capacity decayed rapidly in the early stage of the cycle, and the coulombic efficiency fluctuated significantly and decreased rapidly. This shows that the electrolyte without additive system is difficult to form an effective protective film on the surface of the sodium metal negative electrode, resulting in serious irreversible side reactions and consumption of active sodium, which in turn caused serious capacity decay and extremely poor battery stability (as shown). Figure 8 shown).

[0082] The sodium metal battery assembled with the electrolyte of Example 1 showed the best rate performance under different rate conditions. It could cycle stably at low current and the rate performance increased with the current density gradually increasing to 1Ag. -1 , the capacity only decreased slightly and still maintained at about 90mAh g -1 The sodium metal batteries assembled with the electrolytes of Comparative Examples 1 and 2, at 1Ag -1 The capacity dropped to about 30 mAh g at the rate -1 , the capacity after rate recovery cannot return to the initial level (such as Figure 9 shown).

[0083] Example 1: Sodium metal battery assembled with electrolyte at 80mAg -1 After 180 cycles at the same current density, the cathode particles are evenly distributed and dense, the crack phenomenon is significantly suppressed, the overall microstructure is more complete and compact, and the interface between the particles is well connected (such as Figure 10 As shown). The positive electrode of the sodium metal battery assembled with the electrolyte of Comparative Example 3 shows cracks running through the entire electrode surface under SEM observation, reflecting serious structural damage and particle shedding of the electrode material (as shown). Figure 11 shown).

[0084] The combined effect of FEC and SUL additives in the electrolyte of Example 1 significantly improved the interfacial stability of the sodium metal battery, effectively inhibited side reactions, and promoted the formation of a uniform and stable CEI film.

[0085] Example 3:

[0086] An embodiment of the present invention further provides an extremely stable sodium metal battery, comprising a positive electrode material, a negative electrode material and an electrolyte.

[0087] The positive electrode material includes any one of sodium vanadium phosphate, sodium cobalt oxide, sodium nickel oxide, and sodium iron oxide;

[0088] The sodium metal negative electrode is a pure sodium metal sheet or an active material modified on other substrates with sodium metal as the main body, specifically a commercial sodium metal sheet, an electrodeposited titanium metal sheet, etc.

[0089] Example 4:

[0090] The present invention also provides an electrical device, comprising a sodium metal battery.

[0091] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. An electrolyte for regulating the stability mechanism of sodium metal batteries, characterized in that include: An organic solvent, an electrolyte sodium salt, and additives; the additives are fluorocarbonates and sulfones; wherein the mass fraction of the organic solvent in the electrolyte is 60%-95%, the mass fraction of the electrolyte sodium salt is 3%-15%, and the concentration is 0.5-5 mol / L; the mass fractions of the additives in the sodium metal battery electrolyte are as follows: 0.1%-10% for fluorocarbonates; and 0.1%-10% for sulfones.

2. The electrolyte for regulating the stabilization mechanism of sodium metal batteries according to claim 1, characterized in that: The organic solvent is a carbonate organic solvent; the carbonate organic solvent includes one or more of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, and propylene carbonate. When two or more organic solvents are mixed, the volume ratio is 1:1 to 9:1, and the total volume accounts for 60% to 95% of the total electrolyte volume.

3. The electrolyte for regulating the stabilization mechanism of sodium metal batteries according to claim 2, characterized in that: The electrolyte sodium salt includes one or more of sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide. When multiple components are mixed, the mass percentage of each component is 1% to 99%, and the total mass accounts for 3% to 15% of the electrolyte.

4. The method for preparing an electrolyte for regulating the stabilization mechanism of a sodium metal battery according to any one of claims 1 to 3, characterized in that: The steps include: (1) Pretreatment of the organic solvent: taking an appropriate amount of the organic solvent, first drying it with a molecular sieve to remove water impurities, and then deoxygenating it under an inert gas protection environment to obtain a high-purity organic solvent that is anhydrous and oxygen-free for use; (2) Pretreatment of electrolyte sodium salt: Dry the electrolyte sodium salt in a vacuum drying oven for 6-12 hours to completely remove moisture and other volatile impurities in the sodium salt. The drying temperature is controlled in the range of 80-120°C. (3) preparing an initial electrolyte solution: slowly adding the pretreated electrolyte sodium salt to the above-mentioned anhydrous and oxygen-free organic solvent under the protection of an inert gas, controlling the stirring speed and temperature during the addition process, wherein the stirring speed is 200-500 rpm and the ambient temperature is controlled between 20-30°C, so that the sodium salt is completely dissolved and a uniform and transparent electrolyte mother solution is formed; (4) Adding fluorocarbonate additives: Slowly add an appropriate amount of fluorocarbonate dropwise under continuous stirring at a rate of 0.5-1 mL / min and stir for 30-60 minutes to ensure that the FEC is evenly dispersed and fully mixed with the mother liquor; (5) Adding sulfone additives: Slowly add the sulfone at a controlled addition rate of about 0.5-1 mL per minute while continuously stirring for 60-90 minutes to ensure that the sulfolane is evenly dispersed in the solution; (6) Homogenization and stabilization: After mixing, the obtained electrolyte is continuously stirred at room temperature for 1-3 hours to ensure that the solution reaches a fully uniform and stable state, and is allowed to stand for 12-24 hours under an inert gas protection environment to obtain the final electrolyte for regulating the stability mechanism of sodium metal batteries.

5. An extremely stable sodium metal battery, characterized in that The electrolyte comprises a positive electrode material, a negative electrode material and the electrolyte as claimed in claim 1. The positive electrode material includes any one of sodium vanadium phosphate, sodium cobalt oxide, sodium nickel oxide, and sodium iron oxide; The sodium metal negative electrode is a pure sodium metal sheet or an active material modified on other substrates with sodium metal as the main body, specifically a commercial sodium metal sheet, an electrodeposited titanium metal sheet, etc.

6. An electrical equipment, characterized in that: Including the sodium metal battery according to claim 5.

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