High-voltage wide-temperature-range electrolyte suitable for sodium-ion battery and application of high-voltage wide-temperature-range electrolyte

Abstract

The invention belongs to the technical field of sodium-ion battery electrolyte, and particularly relates to high-voltage wide-temperature-range electrolyte suitable for a sodium-ion battery and application of the high-voltage wide-temperature-range electrolyte. The electrolyte consists of electrolyte salt, a solvent and a functional additive, wherein the electrolyte salt is sodium tetrafluoroborate; the functional additive comprises a negative electrode film-forming additive; the solvent comprises a high-dielectric-constant organic carbonate solvent, a low-viscosity organic carbonate solvent and an anti-solvent, and the volume of the anti-solvent accounts for 5-25% of the total volume of the solvent; and the anti-solvent is a fluoro-ether organic solvent. Through the synergistic effect of components in an electrolyte system, the problems that an existing electrolyte is poor in thermal stability, low in ion transmission capacity at low temperature and low in electrode interface stability are effectively solved, and meanwhile the electrolyte can be compatible with high-energy-density positive electrode materials such as ferric sodium pyrophosphate and the like; and excellent electrochemical performance is shown in a relatively wide temperature range from-40 DEG C to 80 DEG C.

Description

Technical Field

[0001] This application belongs to the field of sodium-ion battery electrolyte technology, and more specifically, relates to a high-voltage, wide-temperature-range electrolyte suitable for sodium-ion batteries and its application. Background Technology

[0002] With the development of new energy technologies, sodium metal batteries, due to their abundant raw materials, low cost, and high specific capacity, are gradually becoming a potential alternative to lithium batteries, particularly suitable for large-scale energy storage and energy supply in extreme environments. However, the practical application of sodium metal batteries under extreme conditions remains limited, especially in terms of stability and safety under high and low temperatures and high pressures. Among these factors, the electrolyte, as a core component of the battery, has key characteristics affecting battery performance, including its thermal stability, electrochemical window, and interfacial compatibility with sodium metal.

[0003] Existing electrolytes mostly use a combination of carbonate solvents and sodium hexafluorophosphate (NaPF6). Although they have a certain ability to form interfacial films, they are prone to decomposition under high temperature and high pressure environments, producing HF and other corrosive byproducts, which seriously affect the stability of the electrode interface and cycle life. At the same time, the ion conductivity of this system decreases at low temperatures, limiting sodium ion migration and battery capacity release, making it difficult to meet the wide temperature range requirements of high-performance energy storage devices.

[0004] Therefore, there is an urgent need to develop high-voltage electrolyte systems with excellent thermal stability and wide temperature adaptability to enable the reliable application of sodium metal batteries in various complex environments. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this application is to provide a high-voltage, wide-temperature-range electrolyte suitable for sodium-ion batteries and its application. The aim is to solve the problems of existing electrolytes in wide-temperature-range, high-voltage applications, such as difficulty in simultaneously achieving high-temperature thermal stability, low-temperature kinetics, and electrode interface compatibility. This solution enables sodium-ion batteries to operate stably in a wide temperature range of -40℃ to 80℃ and exhibits excellent cycle performance.

[0006] To achieve the above objectives, in a first aspect, this application provides a high-voltage, wide-temperature-range electrolyte suitable for sodium-ion batteries, comprising an electrolyte salt, a solvent, and functional additives; wherein the electrolyte salt is sodium tetrafluoroborate; and the functional additives include a negative electrode film-forming additives. The solvents mentioned above include high dielectric constant organic carbonate solvents, low viscosity organic carbonate solvents and fluorinated ether organic solvents, and the volume ratio of fluorinated ether organic solvents is 5% to 25% of the total volume of the solvents mentioned above.

[0007] Preferably, the concentration of the sodium tetrafluoroborate is 0.1 mol / L to 0.4 mol / L.

[0008] Preferably, the fluorinated ether organic solvent is selected from one or more of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl-1,1,2,3,3,3-hexafluorobutyl ether, 1,1,2,2-tetrafluoroethyl-4-methylphenyl ether, 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane, and 1,1,2,2-tetrafluoroethylphenyl ether.

[0009] Preferably, the dielectric constant of the high dielectric constant organic carbonate solvent is greater than 60; and / or, the viscosity of the low viscosity organic carbonate solvent is less than 1 mPa·s.

[0010] Preferably, the volume ratio of the high dielectric constant organic carbonate solvent to the low viscosity organic carbonate solvent is (1~3):1.

[0011] Preferably, the high dielectric constant organic carbonate solvent is selected from one or more of ethylene carbonate, propylene carbonate, and fluoroethylene carbonate.

[0012] Preferably, the low-viscosity organic carbonate solvent is selected from one or more of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0013] Preferably, the above-mentioned negative electrode film-forming additive is selected from one or more of fluoroethylene carbonate, ethylene sulfate, and tetravinylsilane.

[0014] Preferably, the amount of the above-mentioned negative electrode film-forming additive is 0.5% to 5% of the total mass of the electrolyte.

[0015] Preferably, the above-mentioned additives also include positive electrode film-forming additives.

[0016] Preferably, the above-mentioned positive electrode film-forming additive is selected from one or more of sodium hexafluorosilicate and sodium hexafluoroaluminate.

[0017] Secondly, this application provides a sodium-ion battery, which includes a positive electrode, a negative electrode, and the aforementioned high-voltage, wide-temperature-range electrolyte.

[0018] Preferably, the material of the above-mentioned positive electrode includes one or more of polyanionic positive electrode materials and layered transition metal oxides.

[0019] In summary, the technical solutions conceived in this application have the following main technical advantages compared with the prior art: (1) The high-voltage, wide-temperature-range electrolyte for sodium-ion batteries provided in this application is composed of electrolyte salt, solvent, and functional additives; wherein, the electrolyte salt is sodium tetrafluoroborate; the functional additives include negative electrode film-forming additives; the solvents include high dielectric constant organic carbonate solvents, low viscosity organic carbonate solvents, and fluorinated ether organic solvents, and the volume ratio of fluorinated ether organic solvents is 5% to 25% of the total volume of solvents. Through the electrostatic synergistic effect of fluorinated ether organic solvents and sodium tetrafluoroborate, not only can the stability of carbonate solvents at high temperatures be improved, but also the binding force between solvents and sodium ions can be weakened, significantly reducing the desolvation energy barrier at low temperatures, improving ion transport power, and guiding more BF4. - Anions enter the solvation inner layer, promoting the formation of a solvation structure rich in contact ion pairs and aggregates, constructing a more stable electrode interface and further improving the thermal stability of the electrolyte. Furthermore, the addition of negative electrode film-forming additives preferentially constructs a dense, robust SEI film rich in inorganic fluorides on the electrode surface, effectively inhibiting continuous electrolyte decomposition and dendrite growth, and improving interfacial reversibility and safety. Combining these effects, the problems of poor electrolyte conductivity at low temperatures and compatibility between the electrolyte and electrode materials are effectively solved, resulting in an electrolyte with excellent high-temperature stability, low-temperature ion transport capability, and electrode interface compatibility. This ensures that the battery achieves long-term stable operation under wide temperature range (-40℃ to 80℃) and high voltage (1.7V to 4.3V), expanding the application potential of sodium-ion batteries in extreme environments.

[0020] (2) In terms of solvent design, the electrolyte provided in this application is constructed by compounding organic carbonate solvents with high dielectric constant and low viscosity and adjusting their ratio to create a solvent environment with both strong dissociation ability and high fluidity. This ensures that the electrolyte salt NaBF4 is fully dissociated to maintain high ionic conductivity, while significantly reducing the viscosity of the system, thus providing a guarantee for the rapid migration of ions in a wide temperature range, especially at extreme low temperatures of -40℃.

[0021] (3) When the electrolyte provided in this application is used in sodium-ion batteries, it can be used to simultaneously support the metallic sodium anode and the high-energy-density sodium iron pyrophosphate cathode, thus broadening the applicability of the electrolyte system. Attached Figure Description

[0022] Figure 1 The cycling performance of a Na4Fe3(PO4)2(P2O7)||Na coin cell (REF) assembled using commercial electrolyte at 80℃ and 1C rate is shown. Figure 2 The cycling performance of Na4Fe3(PO4)2(P2O7)||Na coin cells assembled using commercial electrolytes, electrolytes prepared in Example 1 of this application, and Comparative Example 5, respectively, at -40°C and 0.1C rate. Figure 3 The cycling performance of Na4Fe3(PO4)2(P2O7)||Na coin cells assembled using the electrolytes prepared in Examples 1-3 and Comparative Example 6 of this application is shown at 80°C and 1C rate. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0024] In the description of this application, it should be understood that the term "and / or" describes a relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The symbol " / " in this document indicates that the related objects are in an "or" relationship; for example, A / B means A or B.

[0025] In the description of the embodiments in this application, the words "exemplary" or "for example" are used to indicate that they are examples, illustrations, or descriptions. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design options. Specifically, the use of the words "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0026] In the description of the embodiments in this application, unless otherwise stated, "multiple" means two or more.

[0027] This application provides a high-voltage, wide-temperature-range electrolyte suitable for sodium-ion batteries, which is composed of electrolyte salt, solvent and functional additives; The electrolyte salt mentioned above is sodium tetrafluoroborate (NaBF4). The solvents mentioned above include high dielectric constant organic carbonate solvents, low viscosity organic carbonate solvents, and antisolvents, and the volume ratio of antisolvents is 5% to 25% of the total volume of the solvents. The antisolvents mentioned above are fluorinated ether organic solvents; The aforementioned functional additives include negative electrode film-forming additives.

[0028] This application achieves stable performance and efficient ion transport of electrolyte under extreme high and low temperature and high voltage conditions by compounding appropriate types of electrolyte salts, appropriate amounts of antisolvents, negative electrode film-forming additives, high dielectric constant organic carbonate solvents, and low viscosity organic carbonates. Through the synergistic effect between components, an electrolyte system with good thermal stability, strong ion transport capability, good electrode compatibility, and the ability to form a stable interfacial film at the electrode interface is constructed within a voltage range of 1.7V to 4.3V and a wide temperature range of -40℃ to 80℃.

[0029] Currently, commercially available electrolytes mainly use sodium hexafluorophosphate as the sodium salt. However, in practical applications, sodium hexafluorophosphate exhibits poor electrochemical performance at low temperatures and decomposes at high temperatures. This application uses sodium tetrafluoroborate as the electrolyte salt, whose anion (BF4) - The high bond energy of the BF chemical bonds in the electrolyte makes it difficult to break at high temperatures, and the low Lewis acidity of the decomposition product (BF3) makes it less likely to trigger solvent chain decomposition. This fundamentally ensures the high-temperature thermal and chemical stability of the electrolyte, laying the foundation for the stable operation of the entire system at high temperatures. In some embodiments, the concentration of sodium tetrafluoroborate in the above electrolyte is 0.1 mol / L to 0.4 mol / L.

[0030] In some embodiments, the antisolvent is selected from one or more of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE-458), 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether (HFE-6512), 1,1,2,2-tetrafluoroethyl-1,1,2,3,3,3-hexafluorobutyl ether (HFE-5510), 1,1,2,2-tetrafluoroethyl-4-methylphenyl ether (TFET), 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane (HFE-578), and 1,1,2,2-tetrafluoroethylphenyl ether (TFTB).

[0031] In some embodiments, the volume percentage of the antisolvent is 5% to 25% of the total volume of the supersolvent, specifically 5% to 20%, 10% to 20%, 10% to 15%, 10% to 12.5%, etc.

[0032] In some embodiments, the dielectric constant of the above-mentioned high dielectric constant organic carbonate solvent is greater than 60, and it can be selected from one or more of ethylene carbonate, propylene carbonate, and fluoroethylene carbonate.

[0033] In some embodiments, the viscosity of the aforementioned low-viscosity organic carbonate solvent is less than 1 mPa·s, and it can be selected from one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC).

[0034] In some embodiments, the volume ratio of the high-dielectric-constant organic carbonate solvent to the low-viscosity organic carbonate solvent is (1~3):1. This application constructs an organic solvent system that can synergistically optimize the basic performance of the electrolyte by compounding high-dielectric-constant and low-viscosity organic carbonate solvents and adjusting their ratio. The high-dielectric-constant organic carbonate solvent can effectively weaken the Na+... + With BF4 - The electrostatic attraction between the electrolyte salt NaBF4 ensures its full dissociation, helping to maintain a high bulk ionic conductivity. Secondly, the introduced low-viscosity organic carbonate solvent significantly reduces the overall viscosity of the system. This counteracts the negative impact of high viscosity caused by the high-dielectric-constant solvent, maximizing ion migration rate and improving battery rate performance. Furthermore, it improves the low-temperature fluidity of the electrolyte, preventing it from becoming too viscous or even solidifying at extreme temperatures of -40°C, ensuring effective ion transport even in low-temperature environments. In addition, this optimized solvent environment synergizes with the introduced antisolvent, creating favorable conditions for optimizing the solvation structure and stabilizing the interface of the entire electrolyte system. This allows for more efficient induction of solvation structures rich in contact ion pairs (CIPs) and aggregates (AGGs), thereby promoting the formation of a more stable and dense electrode interface film on the electrode surface.

[0035] The negative electrode film-forming additive added to the electrolyte system provided in this application can preferentially undergo a reduction reaction at the sodium metal negative electrode interface to form a dense, robust SEI film rich in inorganic fluorides. This SEI film not only effectively inhibits the continuous consumption of electrolyte and the uncontrolled growth of sodium dendrites, but also ensures the rapid and uniform deposition / stripping of sodium ions, thereby significantly improving the cycle reversibility and safety of the battery over a wide temperature range. In some embodiments, the above-mentioned negative electrode film-forming additive is selected from one or more of fluoroethylene carbonate (FEC), ethylene sulfate (DTD), and tetravinylsilane. FEC can also inhibit the decomposition and gas generation of the electrolyte at high temperatures to a certain extent, improving the high-temperature stability and safety of the battery. In some embodiments, the amount of the above-mentioned negative electrode film-forming additive is 0.5% to 5% of the total mass of the electrolyte.

[0036] In some embodiments, the high-voltage, wide-temperature-range electrolyte further includes a positive electrode film-forming additive, which, in conjunction with the negative electrode film-forming additive, preferentially decomposes at the positive / negative electrode-electrolyte interface during the first charge / discharge process to form an interfacial film. This stabilizes the electrode-electrolyte interface, enabling the electrolyte system to match high-energy-density positive electrode materials, while simultaneously reducing the dissolution of transition metals in the layered oxide positive electrode material, thus contributing to improved cycle life of the layered oxide sodium-ion battery. In some embodiments, the positive electrode film-forming additive is selected from one or more of sodium hexafluorosilicate (NaSiF6) and sodium hexafluoroaluminate (NaAlF6), and its addition amount is 0.5% to 5% of the total mass of the electrolyte.

[0037] On the other hand, this application also provides a sodium-ion battery, characterized in that it includes a positive electrode, a negative electrode, and the aforementioned high-voltage wide-temperature-range electrolyte.

[0038] In some embodiments, the material of the positive electrode includes one or more of polyanionic positive electrode materials, layered transition metal oxides, etc. Specifically, the polyanionic positive electrode material includes phosphate polyanionic, phosphate pyrophosphate polyanionic, sulfate polyanionic, etc. The phosphate pyrophosphate polyanionic material may specifically include sodium iron phosphate pyrophosphate or doped sodium iron phosphate pyrophosphate. In some specific embodiments, the material of the positive electrode includes sodium iron phosphate pyrophosphate (such as Na4Fe3(PO4)2P2O7).

[0039] The aforementioned layered transition metal oxides may specifically include O3-type layered transition metal oxides (O3-Na) x TMO2) or P2-type layered transition metal oxides (P2-Na) x TMO2), where TM is a transition metal selected from one or more of Ni, Mn, Fe, Co, and Cu, and x is 0.7 to 1.

[0040] When the high-voltage wide-temperature-range electrolyte provided in this application is assembled with positive and negative electrodes to form a sodium-ion battery, the interfacial stability of the electrodes can be improved, the long-cycle performance of the battery can be enhanced, and the capacity of the battery at high and low temperatures can be increased. This enables the sodium-ion battery to operate stably in a wide temperature range of -40℃ to 80℃, effectively solving the problems of decreased ion conductivity of existing electrolytes at low temperatures (-40℃ and below), low battery capacity and rapid decay, low thermal stability under high temperature and high pressure environments, poor electrode interfacial stability, and battery cycle performance that does not meet the requirements of high-performance energy storage devices. This greatly expands the applicable scenarios of the electrolyte system.

[0041] It should be understood that materials of the same or similar type, model, quality, properties, or function as the reagents and instruments used in the following embodiments can be used to implement this application. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the materials and reagents used in the following embodiments are commercially available.

[0042] The following are examples and comparative examples: The components of the high-voltage, wide-temperature-range electrolytes suitable for sodium-ion batteries provided in the embodiments and comparative examples of this application are shown in Table 1. " / " indicates that the component was not added.

[0043] Table 1. Composition of high-voltage, wide-temperature-range electrolyte

[0044] The preparation method of the above-mentioned high-voltage wide-temperature-range electrolyte includes the following steps: The electrolyte is obtained by mixing anhydrous organic solvent and antisolvent, then adding electrolyte salt and functional additives and stirring until homogeneous. The anhydrous organic solvent is prepared by adding a dehydrating agent to an organic solvent and allowing it to stand for 2-4 days; the dehydrating agent is a molecular sieve, of any type 3Å, 4Å, or 5Å.

[0045] The electrolyte prepared above was assembled with the positive electrode material Na4Fe3(PO4)2(P2O7) and the negative electrode material sodium metal sheet to form a Na4Fe3(PO4)2(P2O7)||Na coin cell, and its cycle performance was tested according to the following steps: The button cell half-cells were placed in the Xinwei Battery Testing System for charge / discharge capacity and cycle life testing. High-temperature performance testing was conducted in a forced-air drying oven at a constant temperature of 60℃ / 80℃, with a long-cycle charge / discharge rate of 1C and a voltage range of 1.7~4.3V. Low-temperature performance testing was conducted in a low-temperature constant-temperature chamber at a constant temperature of -20℃ / -40℃, with a low-temperature charge / discharge rate of 0.1C and a voltage range of 1.7~4.3V. Room-temperature performance testing was conducted in a 25℃ constant-temperature chamber with a discharge rate of 1C and a voltage range of 1.7~4.3V.

[0046] The performance test results are shown in Table 2. Figure 1 , Figure 2 , Figure 3 As shown.

[0047] Table 2. Electrochemical performance of Na₄Fe₃(PO₄)₂(P₂O₇)||Na coin cells assembled in the examples and comparative examples.

[0048] Performance test results (Table 2) show that the high-voltage, wide-temperature-range electrolyte provided in this application, through the synergistic design of electrolyte salt, antisolvent, and functional additives, enables the Na4Fe3(PO4)2(P2O7)||Na coin cells assembled using the high-voltage, wide-temperature-range electrolyte prepared in the examples to exhibit excellent cycle stability and reliability within a wide temperature range of -40℃ to 80℃. The reason for this may be the existence of multiple synergistic effects among the components in the electrolyte system. By selecting NaBF4 as the electrolyte salt, its anion (BF4... - The high bond energy of the BF4 chemical bonds in the electrolyte makes them difficult to break at high temperatures, and the low Lewis acidity of the decomposition product (BF3) makes it less likely to trigger solvent chain decomposition. This fundamentally ensures the high-temperature thermal and chemical stability of the electrolyte, laying the foundation for the stable operation of the entire system at high temperatures. Simultaneously, this application introduces hydrofluoroether organic solvents as antisolvents and optimizes their dosage. Through the electrostatic interaction between the strongly electronegative fluorine atoms in the antisolvent molecules and the solvents (PC, DEC), the stability of the solvent at high temperatures is improved, and the binding force between the solvent and sodium ions is effectively weakened. This significantly reduces the desolvation energy barrier at low temperatures, improves ion transport dynamics, and effectively addresses the problems of poor conductivity at low temperatures and poor compatibility with electrode materials. This process also guides more BF4... - Anions enter the solvation inner layer, forming a solvation structure rich in contact ion pairs and aggregates. This helps to construct a more stable electrode interface and improve the thermal stability of the electrolyte. Furthermore, to ensure the construction of a stable solid electrolyte interphase (SEI) film on the negative electrode surface, functional additives such as fluoroethylene carbonate (FEC) are added to the system. This additive can preferentially reduce at the electrode interface to form a dense, robust SEI film rich in inorganic fluorides. This not only effectively inhibits the continuous consumption of electrolyte and the uncontrolled growth of sodium dendrites, but also ensures the rapid and uniform deposition / stripping of sodium ions, thereby significantly improving the cycle reversibility and safety of the battery over a wide temperature range.

[0049] Depend on Figure 1 , Figure 2 It can be seen that the Na4Fe3(PO4)2(P2O7)||Na coin cell assembled with commercial electrolyte is extremely prone to failure at 80℃, and its capacity drops sharply after 100 cycles, with an average coulombic efficiency of less than 90% during the cycle; the cycle life at a low temperature of -40℃ is only 70 cycles.

[0050] The Na4Fe3(PO4)2(P2O7)||Na coin cells assembled with electrolytes prepared using NaPF6 and NaFSI as electrolyte salts (Comparative Examples 1-2) exhibited poor cycle performance at room temperature and failed under high-temperature conditions (60℃, 80℃). The Na4Fe3(PO4)2(P2O7)||Na coin cells assembled with electrolytes prepared using NaTFSI as electrolyte salts (Comparative Example 3) could not be charged and discharged normally at -40℃, failing to meet the requirements of the application scenario. Therefore, no further performance tests were conducted, and these results were marked as "-".

[0051] The Na4Fe3(PO4)2(P2O7)||Na coin cell assembled using the electrolyte prepared in Comparative Example 4 also failed to charge and discharge normally at -40℃. The reason for this may be that the concentration of the electrolyte salt NaBF4 was too high, leading to deterioration of the electrolyte's fluidity at -40℃, increased ion migration resistance, and decreased conductivity. Simultaneously, the high concentration of Na... + With BF4 - It easily forms an overly dense solvation shell and may even lead to salting out, which is detrimental to Na+. + The rapid desolvation and interfacial transport, as well as the exacerbation of side reactions on the electrode surface, affect interfacial stability, ultimately causing the battery to fail to function properly at a low temperature of -40°C.

[0052] The Na4Fe3(PO4)2(P2O7)||Na coin cell assembled using the electrolyte prepared in Comparative Example 6 exhibited deteriorating high-temperature cycling performance. Figure 3 The possible reasons are that excessive addition of antisolvent will over-dilute the concentration of active ions in the electrolyte, impairing the bulk ion transport capacity of the electrolyte, thus leading to a significant decrease in ionic conductivity. Furthermore, excessive antisolvent may cause the solvation shell to become too loose, disordered, or unstable, making Na+ more susceptible to degradation. + The energy barrier increases during the desolvation process, and the reduction and decomposition products generated by excessive antisolvents interfere with the formation of the interfacial film, leading to the deterioration of the SEI film composition and ultimately causing a sharp decline in the cycle performance of the battery under high temperature conditions.

[0053] This application effectively overcomes the performance defects of single components by using appropriate types of electrolyte salts, appropriate amounts of antisolvents and negative electrode film-forming additives, and solvent synergistic effects. Furthermore, through the mutual promotion between components, a synergistic gain effect is generated, thereby achieving high thermal stability, fast ion transport and high interfacial stability in a wide temperature range of -40℃ to 80℃, enabling the battery to exhibit excellent electrochemical performance.

[0054] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A high-voltage, wide-temperature-range electrolyte suitable for sodium-ion batteries, characterized in that, It is composed of electrolyte salt, solvent and functional additives; the electrolyte salt is sodium tetrafluoroborate; the functional additives include negative electrode film-forming additives; The solvents include high dielectric constant organic carbonate solvents, low viscosity organic carbonate solvents, and fluorinated ether organic solvents, and the volume percentage of fluorinated ether organic solvents is 5% to 25% of the total volume of the solvents.

2. The high-voltage, wide-temperature-range electrolyte according to claim 1, characterized in that, The concentration of sodium tetrafluoroborate is 0.1 mol / L to 0.4 mol / L.

3. The high-voltage, wide-temperature-range electrolyte according to claim 1, characterized in that, The fluorinated ether organic solvent is selected from one or more of the following: 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl-1,1,2,3,3,3-hexafluorobutyl ether, 1,1,2,2-tetrafluoroethyl-4-methylphenyl ether, 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane, and 1,1,2,2-tetrafluoroethylphenyl ether.

4. The high-voltage, wide-temperature-range electrolyte according to claim 1, characterized in that, The high dielectric constant organic carbonate solvent has a dielectric constant greater than 60; and / or, the low viscosity organic carbonate solvent has a viscosity less than 1 mPa·s.

5. The high-voltage, wide-temperature-range electrolyte according to claim 4, characterized in that, The volume ratio of the high dielectric constant organic carbonate solvent to the low viscosity organic carbonate solvent is (1~3):

1.

6. The high-voltage, wide-temperature-range electrolyte according to claim 4, characterized in that, The high dielectric constant organic carbonate solvent is selected from one or more of ethylene carbonate, propylene carbonate, and fluoroethylene carbonate; and / or, The low-viscosity organic carbonate solvent is selected from one or more of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

7. The high-voltage, wide-temperature-range electrolyte according to claim 1, characterized in that, The negative electrode film-forming additive is selected from one or more of fluoroethylene carbonate, ethylene sulfate, and tetravinylsilane; and / or, The amount of the negative electrode film-forming additive is 0.5% to 5% of the total mass of the electrolyte.

8. The high-voltage, wide-temperature-range electrolyte according to claim 1, characterized in that, The additives also include positive electrode film-forming additives; Preferably, the positive electrode film-forming additive is selected from one or more of sodium hexafluorosilicate and sodium hexafluoroaluminate.

9. A sodium-ion battery, characterized in that, The sodium-ion battery includes a positive electrode, a negative electrode, and a high-voltage, wide-temperature-range electrolyte as described in any one of claims 1 to 8.

10. The sodium-ion battery according to claim 9, characterized in that, The positive electrode material includes one or more of polyanionic positive electrode materials and layered transition metal oxides.

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