High-rate negative electrode-free sodium metal battery electrolyte, preparation method and application thereof

Abstract

The application discloses a high-rate anode-free sodium metal battery electrolyte and a preparation method and application thereof, and belongs to the technical field of energy storage batteries. The high-rate anode-free sodium metal battery electrolyte provided by the application comprises an organic solvent and a sodium salt dissolved in the organic solvent; and the organic solvent is prepared by mixing diglyme and methyl perfluorobutyl ether (MPE). The electrolyte prepared by the application changes the preferential reduction sequence by reconfiguring the molecular arrangement of the solvation cluster through the dipole-dipole interaction formed by the diglyme and the MPE, can spontaneously perform a chemical reaction, directly participates in the construction of the original SEI dominated by NaF, ensures that the dense NaF SEI can be effectively generated before the battery cycle, realizes the Na + The uniform distribution of flux and the optimized migration path promote the dense and uniform metal sodium deposition and effectively inhibit the dendrite growth. The application has excellent cycle stability and wide application prospect in the anode-free sodium metal battery.

Description

Technical Field

[0001] This application belongs to the field of energy storage battery technology, and in particular relates to a high-rate sodium metal battery electrolyte without negative electrode, its preparation method and application. Background Technology

[0002] Based on the sodium metal battery system, the anode-less sodium metal battery eliminates the traditional pre-placed sodium anode structure, instead depositing sodium metal in situ on the surface of a metal current collector such as copper or aluminum foil during charging. This design not only significantly improves the battery's volumetric and gravimetric energy density but also simplifies the manufacturing process, reducing safety hazards and production costs. However, it is important to note that during the first charge and discharge cycle, the anode interface of the anode-less sodium metal battery consumes a large amount of active sodium provided by the cathode to form the SEI film. The accompanying irreversible side reactions directly lead to battery capacity decay and shortened cycle life. Therefore, constructing an electrolyte with high chemical stability and efficient sodium replenishment capability is key to overcoming the performance bottleneck of anode-less sodium metal batteries.

[0003] Currently used electrolytes for anode-free sodium metal batteries include ether-based electrolytes, carbonate-based electrolytes, and high-concentration electrolytes. However, ether-based electrolytes tend to form organic SEI films, which are porous and unstable. Especially under high-rate charge-discharge conditions, the accelerated sodium deposition rate leads to insufficient SEI film repair, exacerbating dendrite growth and capacity decay. Carbonate-based electrolytes react strongly with sodium metal, easily forming dendrites and a large number of byproducts. High-concentration electrolytes have high viscosity, high cost, and low ion mobility, which is not conducive to fast charging. Therefore, there is an urgent need to develop electrolytes with excellent overall performance to improve the electrochemical performance of anode-free sodium metal batteries and thus enhance their application effectiveness. Summary of the Invention

[0004] This application discloses a high-rate, electrodeless sodium metal battery electrolyte, its preparation method, and its application, aiming to solve the technical problems of poor electrochemical performance and poor cycle stability of existing electrolytes.

[0005] To achieve the above objectives, the technical solution of this application is:

[0006] The first aspect of this application provides a high-rate, electrodeless sodium metal battery electrolyte, comprising: an organic solvent and a sodium salt dissolved in the organic solvent;

[0007] The organic solvent is a mixture of diethylene glycol dimethyl ether and methyl perfluorobutyl ether.

[0008] Preferably, in conjunction with the first aspect, the sodium salt is sodium hexafluorophosphate.

[0009] Preferably, in conjunction with the first aspect, the concentration of the sodium salt is 0.9-1 mol / L.

[0010] Preferably, in conjunction with the first aspect, the concentration of the sodium salt is 1 mol / L.

[0011] Preferably, in conjunction with the first aspect, the volume ratio of diethylene glycol dimethyl ether to methyl perfluorobutyl ether is (7:3)-(8:2).

[0012] Preferably, in conjunction with the first aspect, the volume ratio of diethylene glycol dimethyl ether to methyl perfluorobutyl ether is (7:3).

[0013] The second aspect of this application provides a method for preparing the high-rate, negative-electrode-free sodium metal battery electrolyte described in the first aspect, the preparation method comprising:

[0014] The sodium salt is dissolved in a mixed solvent made of diethylene glycol dimethyl ether and methyl perfluorobutyl ether to obtain the negative electrode-free sodium metal battery electrolyte.

[0015] The third aspect of this application provides the application of the high-rate, electrodeless sodium metal battery electrolyte prepared by the preparation method described in the second aspect in an electrodeless sodium metal battery.

[0016] The fourth aspect of this application provides a non-negative electrode sodium metal battery, comprising the high-rate non-negative electrode sodium metal battery electrolyte described in the first aspect or the high-rate non-negative electrode sodium metal battery electrolyte prepared by the preparation method described in the second aspect.

[0017] Compared with the prior art, the advantages or beneficial effects of the embodiments of this application include at least the following:

[0018] The negative electrode-free sodium metal battery electrolyte provided in this application is prepared by dissolving sodium salt in diethylene glycol dimethyl ether (Diglyme) and methyl perfluorobutyl ether (MPE). On the one hand, based on the dipole-dipole interaction formed by Diglyme and MPE, the molecular arrangement of the solvated cluster is reconstructed, changing its preferential reduction sequence, which can carry out spontaneous chemical reactions and directly participate in the construction of the NaF-dominated primary SEI, ensuring that a dense NaF SEI can be effectively generated before battery cycling. On the other hand, through the uniform interfacial properties of the NaF-rich SEI layer, the NaF-rich SEI layer achieves Na… + The uniform distribution of flux and the optimization of migration paths promote dense and uniform sodium metal deposition, effectively suppressing dendrite growth. At the same time, the formed SEI layer has an ultra-dense microstructure and dual stability against solvent decomposition and moisture erosion, providing additional protection for the high-activity sodium metal anode, giving it excellent cycle stability and broad application prospects in anode-free sodium metal batteries. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 Coulombic efficiency diagrams of A1-non-negative-electrode sodium metal battery electrolyte (NGMPE), A2-non-negative-electrode sodium metal battery electrolyte (NGMPE(8:2)) and B1-non-negative-electrode sodium metal battery electrolyte (NGMPE(9:1)) in sodium copper half-cells provided in the embodiments of this application;

[0021] Figure 2 The first charge-discharge curves of A1-non-negative-electrode sodium metal battery electrolyte (NGMPE), A2-non-negative-electrode sodium metal battery electrolyte (NGMPE(8:2)) and B1-non-negative-electrode sodium metal battery electrolyte (NGMPE(9:1)) in sodium copper half-cells provided in the embodiments of this application;

[0022] Figure 3 Coulombic efficiency diagrams of the following electrolytes provided in embodiments of this application in sodium-copper half-cells: A1-sodium metal battery electrolyte without negative electrode (NGMPE), A3-sodium metal battery electrolyte without negative electrode (0.9M NGMPE), B2-sodium metal battery electrolyte without negative electrode (0.8M NGMPE), B3-sodium metal battery electrolyte without negative electrode (0.7M NGMPE), B4-sodium metal battery electrolyte without negative electrode (0.6M NGMPE), and B5-sodium metal battery electrolyte without negative electrode (0.5M NGMPE).

[0023] Figure 4 The first charge-discharge curves of the following electrolytes provided in this application for the present invention (A1-sodium metal battery electrolyte without negative electrode (NGMPE), A3-sodium metal battery electrolyte without negative electrode (0.9M NGMPE), B2-sodium metal battery electrolyte without negative electrode (0.8M NGMPE), B3-sodium metal battery electrolyte without negative electrode (0.7M NGMPE), B4-sodium metal battery electrolyte without negative electrode (0.6M NGMPE) and B5-sodium metal battery electrolyte without negative electrode (0.5M NGMPE)) in a sodium-copper half-cell are shown in the diagram.

[0024] Figure 5 The A1-anode-free sodium metal battery electrolyte (NGMPE) and B6-anode-free sodium metal battery electrolyte (NG2) provided in the embodiments of this application are used at 5.0 mA / cm 2 and 5.0mAh / cm 2 SEM image after looping;

[0025] Figure 6 The A1-anode-free sodium metal battery electrolyte (NGMPE) and B6-anode-free sodium metal battery electrolyte (NG2) provided in the embodiments of this application are used at 8.0 mA / cm 2 and 4.0mAh / cm 2 Scanning electron microscope image after circulation;

[0026] Figure 7 The A1-anode-free sodium metal battery electrolyte (NGMPE) and B6-anode-free sodium metal battery electrolyte (NG2) provided in the embodiments of this application are used at 8.0 mA / cm 2 and 4.0mAh / cm 2 Micro-CT 3D reconstruction image;

[0027] Figure 8 Cryo-TEM image of Al-Negative Electrolyte (NGMPE) for a battery without negative electrode provided in an embodiment of this application;

[0028] Figure 9 HRTEM image of Al-Non-Negative Electrode Sodium Metal Battery Electrolyte (NGMPE) provided in the embodiments of this application;

[0029] Figure 10 Estimated energy density diagrams of different batteries provided in embodiments of this application;

[0030] Figure 11 C@Al||NVP full cells prepared using A1-sodium metal battery electrolyte without negative electrode (NGMPE) and B6-sodium metal battery electrolyte without negative electrode (NG2) respectively, in 10 mg cm⁻¹ -2 Coulomb efficiency diagram under 3C conditions;

[0031] Figure 12 C@Al||NVP full cells prepared using A1-sodium metal battery electrolyte without negative electrode (NGMPE) and B6-sodium metal battery electrolyte without negative electrode (NG2) respectively, in 15 mg cm⁻¹ -2 Coulomb efficiency diagram under 1C condition;

[0032] Figure 13 Voltage capacity distribution diagrams of A1-non-negative electrode sodium metal battery electrolyte (NGMPE) and B6-non-negative electrode sodium metal battery electrolyte (NG2) provided in the embodiments of this application;

[0033] Figure 14The coulombic efficiency diagram of the C@Al||NVP full cell prepared by adding water to the A1-non-negative electrode sodium metal battery electrolyte (NGMPE) and B6-non-negative electrode sodium metal battery electrolyte (NG2) provided in the embodiments of this application;

[0034] Figure 15 Water was added to the A1-anode-free sodium metal battery electrolyte (NGMPE) and B6-anode-free sodium metal battery electrolyte (NG2) provided in the embodiments of this application to prepare C@Al||NVP full cells. The results were obtained at 3 mg cm⁻¹. -2 Coulomb efficiency diagram at 10°C and 60°C;

[0035] Figure 16 SEM images of A1-sodium metal battery electrolyte without negative electrode (NGMPE) and B6-sodium metal battery electrolyte without negative electrode (NG2) after full-cell cycling in C@Al||NVP provided in the embodiments of this application;

[0036] Figure 17 The NVP||Na full cells prepared using A1-anode-free sodium metal battery electrolyte (NGMPE) and B6-anode-free sodium metal battery electrolyte (NG2) provided in the embodiments of this application, at 5 mg cm⁻¹ -2 Coulomb efficiency diagram under 10C conditions;

[0037] Figure 18 SEM images of A1-sodium metal battery electrolyte without negative electrode (NGMPE) and B6-sodium metal battery electrolyte without negative electrode (NG2) after NVP||Na full cell cycling provided in the embodiments of this application. Detailed Implementation

[0038] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0039] In the following description of this embodiment, the term "and / or" is used to describe the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, B existing alone, and A and B existing simultaneously. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0040] In the following description of this embodiment, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0041] Those skilled in the art should understand that, in the following description of the embodiments of this application, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0042] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0043] It should be noted that all raw materials and reagents in the embodiments of this application were purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0044] In a first aspect, embodiments of this application provide a high-rate, negative-electrode-free sodium metal battery electrolyte, comprising: an organic solvent and a sodium salt dissolved in the organic solvent;

[0045] The organic solvent is a mixture of diethylene glycol dimethyl ether and methyl perfluorobutyl ether.

[0046] On the one hand, the molecular arrangement of the solvated clusters is reconstructed based on the dipole-dipole interactions formed by Diglyme and MPE, changing their preferential reduction sequence. This allows for spontaneous chemical reactions, directly participating in the construction of the NaF-dominated primary SEI, ensuring the effective generation of a dense NaF SEI before battery cycling. On the other hand, the NaF-rich SEI layer, with its uniform interfacial properties, enables the formation of NaF-rich SEI layers. + The uniform distribution of flux and the optimization of migration paths promote dense and uniform sodium metal deposition, effectively suppressing dendrite growth. At the same time, the formed SEI layer has an ultra-dense microstructure and dual stability against solvent decomposition and moisture erosion, providing additional protection for the high-activity sodium metal anode, giving it excellent cycle stability and broad application prospects in anode-free sodium metal batteries.

[0047] In this embodiment, the sodium salt is preferably sodium hexafluorophosphate. This sodium salt, when mixed with diethylene glycol dimethyl ether and methyl perfluorobutyl ether, can rapidly and in-situ construct an ultra-dense inorganic-phase-dominated primary solid-state electrolyte interface, promoting the rapid formation of a NaF-rich inorganic-dominated SEI and accelerating the Na+-phase polymerization process. + The uniform distribution and migration path optimization promote dense and uniform sodium deposition, thereby improving its electrochemical performance.

[0048] In this embodiment, the sodium salt concentration is preferably 0.9-1 mol / L, more preferably 1 mol / L. By controlling the sodium salt concentration in the electrolyte, excessively high concentrations prevent the sodium salt from dissolving, while excessively low concentrations fail to provide a sufficient number of ion carriers and thus a sufficiently high electrolyte ionic conductivity.

[0049] In this embodiment, the volume ratio of diethylene glycol dimethyl ether to methyl perfluorobutyl ether is preferably (7:3)-(8:2), more preferably 7:3. By using diethylene glycol dimethyl ether as the main solvent and methyl perfluorobutyl ether as the diluent, and by controlling the volume ratio of diethylene glycol dimethyl ether to methyl perfluorobutyl ether, the main solvent is ensured to dominate, providing sufficient electrolyte solubility and salt dissociation, thus ensuring the electrolyte's ionic conductivity. A certain proportion of fluorinated solvent is also ensured, guaranteeing appropriate solvent-solvent interactions and providing sufficient fluorine source to induce suitable fluorination of the sodium metal surface.

[0050] It should be noted that the NaF-rich inorganic-dominated SEI layer achieves Na+ ionization through its uniform interfacial properties. + The uniform distribution of flux and optimization of migration paths facilitate the deposition of dense and uniform metallic sodium. Experiments show that this system can effectively suppress dendrite growth under high current density and large area capacity conditions. Furthermore, it effectively stabilizes the electrode / electrolyte interface layer, enabling ultra-high rate charge / discharge and ultra-long cycling of anode-free sodium metal batteries. Simultaneously, the formed SEI layer possesses an ultra-dense microstructure, exhibiting dual stability against solvent decomposition and moisture erosion, providing additional protection for the high-activity sodium metal anode.

[0051] Secondly, embodiments of this application also provide a method for preparing the high-rate sodium metal battery electrolyte without a negative electrode as described in the first aspect, the preparation method comprising:

[0052] The sodium salt is dissolved in a mixed solvent made of diethylene glycol dimethyl ether and methyl perfluorobutyl ether to obtain the high-rate sodium metal battery electrolyte without negative electrode.

[0053] The third aspect of this application provides the application of the high-rate, electrode-free sodium metal battery electrolyte prepared by the method described in the first aspect in electrode-free sodium metal batteries. Based on the excellent rate capability and cycle stability of the electrolyte, it endows electrode-free sodium metal batteries with superior electrochemical performance and has broad market application prospects.

[0054] The fourth aspect of this application provides a non-negative electrode sodium metal battery, comprising the high-rate non-negative electrode sodium metal battery electrolyte described in the first aspect or the high-rate non-negative electrode sodium metal battery electrolyte prepared by the preparation method described in the second aspect.

[0055] The technical solution of this application will be further described below with reference to specific embodiments.

[0056] Example 1

[0057] This embodiment provides a method for preparing Al-anode-free sodium metal battery electrolyte (NGMPE), specifically including:

[0058] Electrolyte preparation process: In an argon-filled glove box (O2<0.1PPM, H2O<0.1PPM), 1M NaPF6 was dissolved in a mixed solvent of diethylene glycol dimethyl ether and methyl perfluorobutyl ether in a volume ratio of 7:3. The mixture was slowly stirred at room temperature for 10 hours to obtain Al-anode-free sodium metal battery electrolyte (NGMPE).

[0059] Example 2

[0060] The composition ratio, preparation operation, and process parameters of the A2-anode-free sodium metal battery electrolyte (NGMPE(9:1)) prepared in this embodiment are basically the same as those in Example 1. The difference is that the preparation materials in this embodiment are a mixed solvent of diethylene glycol dimethyl ether and methyl perfluorobutyl ether with a volume ratio of 8:2, and the A2-anode-free sodium metal battery electrolyte (NGMPE(8:2)) is prepared.

[0061] Example 3

[0062] The composition ratio, preparation operation, and process parameters of the A3-anode-free sodium metal battery electrolyte (0.9M NGMPE) prepared in this embodiment are basically the same as those in Example 1. The difference is that the concentration of NaPF6 used in this embodiment is 0.9M, and the A3-anode-free sodium metal battery electrolyte (0.9M NGMPE) is prepared.

[0063] Meanwhile, to verify the comprehensive performance of the electrolytes prepared in the above embodiments, this application provides the following comparative examples for detailed illustration.

[0064] Comparative Example 1

[0065] The composition ratio, preparation operation, and process parameters of the B1-anode-free sodium metal battery electrolyte (NGMPE(9:1)) prepared in this comparative example are basically the same as those in Example 1. The difference is that the raw materials used in this comparative example are a mixed solvent of diethylene glycol dimethyl ether and methyl perfluorobutyl ether with a volume ratio of 9:1, which is used to prepare the B1-anode-free sodium metal battery electrolyte (NGMPE(9:1)).

[0066] Comparative Example 2

[0067] The composition ratio, preparation operation, and process parameters of the B2-anode-free sodium metal battery electrolyte (0.8M NGMPE) prepared in this comparative example are basically the same as those in Example 1. The difference is that the concentration of NaPF6 used in this comparative example is 0.8M, and the B2-anode-free sodium metal battery electrolyte (0.8M NGMPE) is prepared.

[0068] Comparative Example 3

[0069] The composition ratio, preparation operation, and process parameters of the B3-anode-free sodium metal battery electrolyte (0.7M NGMPE) prepared in this comparative example are basically the same as those in Example 1. The difference is that the concentration of NaPF6 used in this comparative example is 0.7M, and the B3-anode-free sodium metal battery electrolyte (0.7M NGMPE) is prepared.

[0070] Comparative Example 4

[0071] The composition ratio, preparation operation, and process parameters of the B4-anode-free sodium metal battery electrolyte (0.6M NGMPE) prepared in this comparative example are basically the same as those in Example 1. The difference is that the concentration of NaPF6 used in this comparative example is 0.6M, and the B4-anode-free sodium metal battery electrolyte (0.6M NGMPE) is prepared.

[0072] Comparative Example 5

[0073] The composition ratio, preparation operation, and process parameters of the B5-anode-free sodium metal battery electrolyte (0.5M NGMPE) prepared in this comparative example are basically the same as those in Example 1. The difference is that the concentration of NaPF6 used in this comparative example is 0.5M, and the B5-anode-free sodium metal battery electrolyte (0.5M NGMPE) is prepared.

[0074] Comparative Example 6

[0075] The composition ratio, preparation operation, and process parameters of the B6-anode-free sodium metal battery electrolyte (0.5M NGMPE) prepared in this comparative example are basically the same as those in Example 1. The difference is that only diethylene glycol dimethyl ether (Diglyme) is used in the preparation of this comparative example to prepare the B6-anode-free sodium metal battery electrolyte (NG2).

[0076] To verify the optimal ratio of the electrolyte prepared in the embodiments of this application, sodium-copper half-cells were fabricated using the electrolytes prepared in the embodiments for characterization and comparison. The results are as follows: Figures 1-4 As shown.

[0077] Sodium-copper half-cell: Carbon-coated aluminum foil was used as the current collector, cut into 10 mm diameter discs as electrode plates, and vacuum dried at 80°C for 6 h as the working electrode. A 12 mm sodium sheet was used as the negative electrode, and the electrolyte prepared above was used as the electrolyte. The separator was Celgard 2325, and the battery casing was CR2032. The Na||Cu half-cell was assembled and its electrochemical performance was tested.

[0078] according to Figure 1 It is known that A1-anode-free sodium metal battery electrolyte (NGMPE), A2-anode-free sodium metal battery electrolyte (NGMPE(8:2)), and B1-anode-free sodium metal battery electrolyte (NGMPE(9:1)) prepared using different solvent ratios, at a current density of 5 mA / cm², 2 And deposition capacity of 5mAh / cm 2 The coulombic efficiency diagram of the sodium-copper half-cell is shown. The coulombic efficiency of NGMPE in the Na||Cu half-cell after 200 cycles is 99.98%, that of NGMPE (9:1) in the Na||Cu half-cell after 200 cycles is 90.5%, and that of NGMPE (8:2) in the Na||Cu half-cell after 200 cycles is 99.16%.

[0079] according to Figure 2 To date, A1-anode-free sodium metal battery electrolyte (NGMPE), A2-anode-free sodium metal battery electrolyte (NGMPE(8:2)), and B1-anode-free sodium metal battery electrolyte (NGMPE(9:1)) prepared using different solvent ratios, at a current density of 8.0 mA / cm², 2 The deposition capacity is 4.0 mAh / cm³. 2 The first charge-discharge curves of the sodium-copper half-cell are shown. The abnormal peaks or fluctuations in the NGMPE (9:1) curve may be a precursor to a local short circuit before sodium dendrites pierce the separator. However, the NGMPE (8:2) curve is slightly smoother, and the NGMPE curve is significantly smoother, indicating that the electrochemical performance is more stable.

[0080] according to Figure 3 To date, the following electrolytes prepared using different solvent ratios—A1-sodium metal battery electrolyte without a negative electrode (NGMPE), A3-sodium metal battery electrolyte without a negative electrode (0.9M NGMPE), B2-sodium metal battery electrolyte without a negative electrode (0.8M NGMPE), B3-sodium metal battery electrolyte without a negative electrode (0.7M NGMPE), B4-sodium metal battery electrolyte without a negative electrode (0.6M NGMPE), and B5-sodium metal battery electrolyte without a negative electrode (0.5M NGMPE)—achieved the desired effect at a current density of 8.0 mA / cm². 2 The deposition capacity is 4.0 mAh / cm³. 2 The coulombic efficiency diagram of the sodium-copper half-cell is shown. The coulombic efficiencies of A1-anode-free sodium metal battery electrolyte (NGMPE) and A3-anode-free sodium metal battery electrolyte (0.9M NGMPE) are significantly better than those of the comparative example.

[0081] according to Figure 4 To date, the following electrolytes prepared using different solvent ratios—A1-sodium metal battery electrolyte without a negative electrode (NGMPE), A3-sodium metal battery electrolyte without a negative electrode (0.9M NGMPE), B2-sodium metal battery electrolyte without a negative electrode (0.8M NGMPE), B3-sodium metal battery electrolyte without a negative electrode (0.7M NGMPE), B4-sodium metal battery electrolyte without a negative electrode (0.6M NGMPE), and B5-sodium metal battery electrolyte without a negative electrode (0.5M NGMPE)—achieved the desired effect at a current density of 8.0 mA / cm². 2 The deposition capacity is 4.0 mAh / cm³. 2 The first charge-discharge curves of the sodium-copper half-cell are shown. As the concentration of NaPF6 decreases, abnormal peaks or fluctuations appear in the curves, while the curves of NGMPE and 0.9M NGMPE are significantly smoother, indicating more stable electrochemical performance.

[0082] To further verify the microscopic characteristics of the electrolyte during battery operation, the SEI film formed after battery operation was microscopically characterized.

[0083] according to Figure 5 In the case of a current density of 5.0 mA / cm², 2 And the deposition capacity is 5.0 mAh / cm³. 2 The deposition morphology of the Na||Cu half-cell after 50 cycles is shown. In the B6-anode-free sodium metal battery electrolyte (NG2), bulk sodium deposition was observed on the copper foil surface, and cracks appeared on the deposition surface. The non-uniform electric field at the protrusions and the pores at the copper foil-electrolyte interface further induced dendrite growth. In contrast, the copper foil surface of the NGMPE showed no obvious dendrite protrusions, forming a uniform and ordered layer, which significantly suppressed dendrite growth.

[0084] according to Figure 6 In the case of a current density of 8.0 mA / cm², 2 The deposition capacity is 4.0 mAh / cm³. 2 The deposition morphology of the Na||Cu half-cell after 50 cycles was determined. In the B6-anode-free sodium metal battery electrolyte (NG2), the copper foil surface became rough and exhibited blocky deposits, while the copper foil surface of the NGMPE showed no obvious dendrite protrusions and formed a uniform and ordered layer. Meanwhile, to further verify the morphology of the prepared electrolyte, according to... Figure 7 As shown, the distribution and density of pores in sodium metal anodes were reconstructed using Micro-CT. The density of NG2 was 0.35%, while that of NGMPE was 0.002%.

[0085] according to Figure 8 It was found that a dense SEI layer (approximately 200 nm) existed on the surface of the in-situ formed SEI deposit, as revealed by cryo-TEM kinetic capture. Simultaneously, HRTEM testing was performed, based on... Figure 9 It can be seen that the dense SEI layer is mainly composed of various inorganic components, with NaF being the dominant component.

[0086] according to Figure 10 It is evident that predictable negative electrode-free sodium metal batteries have the potential for ultra-high energy density compared to traditional sodium-ion batteries and sodium metal batteries with excess sodium metal.

[0087] To further improve the overall performance of the electrolyte, this application used the electrolyte prepared above as the electrolyte to assemble a coin-shaped C@Al||NVP assembly full cell and conducted performance tests on different electrochemical properties.

[0088] according to Figure 11 It can be seen that the coulombic efficiency plots (horizontal axis: cycle number, vertical axis: coulombic efficiency, discharge capacity) of C@Al||NVP full cells prepared with A1-anode-free sodium metal battery electrolyte (NGMPE) and B6-anode-free sodium metal battery electrolyte (NG2) respectively, at 10 mg cm⁻¹, are as follows: -2 Under 3C conditions, the sodium metal battery without a negative electrode exhibits an ultra-long stable cycle time, retaining more than 80% of its capacity after more than 400 cycles.

[0089] according to Figure 12It can be seen that the coulombic efficiency plots (horizontal axis: cycle number, vertical axis: coulombic efficiency, discharge capacity, specific capacity) of C@Al||NVP full cells prepared with A1-anode-free sodium metal battery electrolyte (NGMPE) and B6-anode-free sodium metal battery electrolyte (NG2) respectively, at 15mg cm⁻¹, are as follows: -2 Under 1C conditions, the sodium metal battery without a negative electrode still provides an ultra-high initial discharge specific capacity of over 100 mAh / g, and under electrolyte-deficient conditions (1 μL / mg positive electrode), it still maintains an ultra-long cycle of over 480 cycles with more than 80% capacity.

[0090] according to Figure 13 As can be seen from the voltage-capacity distribution diagrams (horizontal axis: specific capacity, vertical axis: voltage) of A1-sodium metal battery electrolyte without negative electrode (NGMPE) and B6-sodium metal battery electrolyte without negative electrode (NG2), compared with the traditional NG2 electrolyte, NGMPE provides a stable voltage-capacity curve for the battery, which proves that short circuits occur very rarely and sodium metal deposition / stripping occurs in an orderly manner.

[0091] according to Figure 14 It can be seen that the coulombic efficiency plots (horizontal axis: cycle number, vertical axis: coulombic efficiency, discharge capacity, specific capacity) of C@Al||NVP full cells prepared by adding A1-anode-free sodium metal battery electrolyte (NGMPE) and B6-anode-free sodium metal battery electrolyte (NG2) to 5000ppm of water respectively are shown in the figure at 10mg cm⁻¹. -2 Under 1C conditions, the dense SEI formed by the NGMPE electrolyte effectively resists the corrosion and reaction of trace water on the sodium metal anode, ensuring the reversible cycling of the sodium metal during the cycling process, and ensuring that the anode-free sodium metal battery can still retain 83% of its initial capacity after 200 cycles.

[0092] according to Figure 15 It can be seen that the coulombic efficiency plots (horizontal axis: cycle number, vertical axis: coulombic efficiency, discharge capacity, specific capacity) of C@Al||NVP full cells made with A1-anode-free sodium metal battery electrolyte (NGMPE) and B6-anode-free sodium metal battery electrolyte (NG2) are as follows: At 3mg cm⁻¹ -2At 10°C and 60°C, the N / P ratio is 5. Even under high temperature conditions, the reactivity of sodium metal with electrolyte increases. The dense SEI formed by NGMPE still effectively resists excessive solvent-sodium metal side reactions. Even with a small amount of excess sodium metal and ultra-high rate, the sodium metal battery still ensures more than 1000 cycles.

[0093] To demonstrate the stability of the prepared electrolyte, the sodium metal anode in the cycled NVP||Na full cell was characterized by SEM.

[0094] according to Figure 16 It can be seen that in the C@Al||NVP full cell, the cathode loading is 15 mg cm⁻¹. -2 Scanning electron microscopy (SEM) images of the surface morphology of the sodium metal anode in NG2 and NGMPE electrolytes after 50 cycles at 1C show that the surface of the NGMPE electrolyte still exhibits a significantly uniform and smooth appearance, fully demonstrating its ultra-high cycling stability.

[0095] The NVP||Na full cell consists of an NVP positive electrode (5 mg cm⁻²) and a sodium metal negative electrode with an electrochemically deposited NP ratio of 1. According to Figure 17 It can be seen that, with an N / P ratio of 1, the Na||NVP full cell, using different electrolytes, operating at a high rate of 10C, and undergoing three charge-discharge cycles at 0.2C, can guarantee more than 1200 cycles for the NVP||Na full cell.

[0096] according to Figure 18 It can be seen that in the Na||NVP full cell, with a cathode loading of 5 mg cm-2, 10C, and after 1200 cycles, the surface morphology of the sodium metal anode in the post-cycle electrolytes of NG2 and NGMPE shows that the surface of the NGMPE electrolyte is obviously uniform and smooth.

[0097] Therefore, the negative electrode-free sodium metal battery electrolyte provided in this application is prepared by dissolving sodium salt in diethylene glycol dimethyl ether (Diglyme) and methyl perfluorobutyl ether (MPE). Through an intermolecular interaction regulation mechanism, by introducing the "non-coordinating" diluent methyl perfluorobutyl ether (MPE) into the diethylene glycol dimethyl ether solvent, the molecular arrangement of the solvated clusters is reconstructed based on specific dipole-dipole interactions, altering their preferential reduction sequence. The highly fluorinated MPE diluent directly participates in the construction of the NaF-dominated primary SEI through a spontaneous chemical reaction triggered by dipole-dipole complexes. Therefore, the SEI film formation is chemically spontaneous, rather than slowly formed during electrochemical cycling as in other electrolytes. This process differs from the electrochemical decomposition film formation mechanism of traditional electrolytes, achieving the rapid generation of an ultra-dense inorganic SEI.

[0098] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0099] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A high-rate, electrodeless sodium metal battery electrolyte, characterized in that, include: Organic solvents and sodium salts dissolved in said organic solvents; The organic solvent is a mixture of diethylene glycol dimethyl ether and methyl perfluorobutyl ether, and the volume ratio of the diethylene glycol dimethyl ether to the methyl perfluorobutyl ether is (7:3)-(8:2).

2. The high-rate, negative-electrode-free sodium metal battery electrolyte according to claim 1, characterized in that, The sodium salt is sodium hexafluorophosphate.

3. The high-rate, electrodeless sodium metal battery electrolyte according to claim 2, characterized in that, The concentration of the sodium salt is 0.9-1 mol / L.

4. The high-rate, negative-electrode-free sodium metal battery electrolyte according to claim 3, characterized in that, The concentration of the sodium salt is 1 mol / L.

5. The high-rate, negative-electrode-free sodium metal battery electrolyte according to claim 1, characterized in that, The volume ratio of diethylene glycol dimethyl ether to methyl perfluorobutyl ether is (7:3).

6. A method for preparing a high-rate, negative-electrode-free sodium metal battery electrolyte according to any one of claims 1-5, characterized in that, The preparation method includes: The sodium salt is dissolved in a mixed solvent made of diethylene glycol dimethyl ether and methyl perfluorobutyl ether to obtain the negative electrode-free sodium metal battery electrolyte.

7. The application of a high-rate sodium metal battery electrolyte without a negative electrode prepared by the preparation method of claim 6 in the preparation of sodium metal batteries without a negative electrode.

8. A sodium metal battery without a negative electrode, characterized in that, Includes the high-rate sodium metal battery electrolyte without negative electrode as described in any one of claims 1-5 or the high-rate sodium metal battery electrolyte without negative electrode prepared by the preparation method described in claim 6.

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