A perfluorinated electrolyte for sodium-ion batteries and methods and applications thereof

Abstract

The application discloses a kind of for sodium ion battery perfluorinated electrolyte and method and application, belong to sodium ion battery electrolyte technical field.The preparation method of perfluorinated electrolyte for sodium ion battery disclosed in the application comprises the following steps: sodium hexafluorophosphate is dissolved in fluoroethylene carbonate, carbonic acid bis (2,2,2-trifluoroethyl) ester and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, after stirring, perfluorinated electrolyte for sodium ion battery is obtained;The volume ratio of fluoroethylene carbonate, carbonic acid bis (2,2,2-trifluoroethyl) ester and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether is 3:2:1.The electrolyte gives system high pressure stability and safety, and promotes the formation of dense, solid and inorganic solid electrolyte interface film on the positive electrode surface, solves the degradation problem of electrode-electrolyte interface in long-term cycle, and obtains excellent cycle stability.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery electrolyte technology, specifically relating to a perfluorinated electrolyte, method, and application for sodium-ion batteries. Background Technology

[0002] To meet the demands of sustainable development, developing energy storage batteries that are both economical and energy-efficient, thereby reducing dependence on non-renewable energy and mitigating the impacts of climate change, is becoming an important direction in the energy sector. Sodium-ion batteries, due to the abundance, wide distribution, and low cost of sodium resources, are considered an important supplement and potential alternative to lithium-ion batteries in some application scenarios, particularly showing broad application prospects in large-scale energy storage and low-speed electric vehicles. However, compared to lithium-ion batteries, sodium-ion batteries still face key technological bottlenecks in areas such as high voltage stability, fast-charging rate performance, and safety, significantly hindering their large-scale industrial application. The electrolyte, as a crucial medium for ion transport and interfacial reactions in the battery system, directly determines the battery's electrochemical stability window, ion conduction efficiency, cycle life, and safety performance. Therefore, targeted optimization of the electrolyte system is one of the core approaches to overcoming the performance and application barriers of sodium-ion batteries.

[0003] Traditional sodium-ion battery electrolytes often use carbonate-based organic solvents (such as ethylene carbonate and dimethyl carbonate) combined with sodium salts. This type of electrolyte system has significant drawbacks, primarily due to the low flash point and flammability of carbonate solvents. Under conditions of overcharging, short circuits, or high temperatures, these solvents can easily cause combustion, explosions, and other safety accidents, making it difficult to meet the high safety requirements of scenarios such as energy storage power stations. Traditional electrolytes also have low ion conductivity and high interfacial impedance. Under fast-charging (high-rate) conditions, the sodium ion insertion / extraction kinetics are sluggish, resulting in poor rate performance. When paired with a high-voltage cathode, carbonate-based electrolytes undergo severe oxidative decomposition on the cathode surface. This uncontrolled decomposition leads to the formation of a thick, non-uniform, and organic-rich cathode-electrolyte interface (CEI). Such a CEI exhibits ionic resistivity, hindering sodium ion transport and causing significant polarization and capacity decay. More seriously, at voltages exceeding 4.5 V, the decomposition process particularly involves the parasitic oxidation of fluorinated electrolyte components (such as fluoroethylene carbonate and sodium hexafluorophosphate). This generates corrosive substances such as hydrogen fluoride (HF) and phosphorus pentafluoride (PF5), which continuously attack the CEI and the cathode substrate. This chemical cross-linking effect is extremely harmful: it disrupts the stability of the interface, accelerates the dissolution of transition metal ions from the cathode lattice, and causes these dissolved metals to migrate to the negative electrode, further damaging the integrity of the solid electrolyte interface (SEI). Therefore, the positive electrode continuously consumes electrolyte, suffers structural degradation, and loses active materials, ultimately leading to rapid battery failure. Thus, the exploration of high-voltage sodium-ion batteries is essentially closely related to developing electrolytes capable of forming thin, dense, ionicly conductive, and chemically stable cathode electrolyte interfaces (CEIs) that can suppress these cascading failure mechanisms. Summary of the Invention

[0004] The purpose of this invention is to provide a perfluorinated electrolyte, method, and application for sodium-ion batteries, in order to solve the technical problem that existing high-safety, high-voltage, fast-charging sodium-ion battery electrolytes are difficult to achieve long-term cycle stability.

[0005] To achieve the above objectives, the present invention employs the following technical solution: This invention discloses a method for preparing a perfluorinated electrolyte for sodium-ion batteries, comprising the following steps: Sodium hexafluorophosphate was dissolved in fluoroethylene carbonate, bis(2,2,2-trifluoroethyl) carbonate and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and stirred to obtain a perfluorinated electrolyte for sodium-ion batteries. The volume ratio of the fluoroethylene carbonate, bis(2,2,2-trifluoroethyl) carbonate, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether is 3:2:1.

[0006] Furthermore, the concentration of sodium hexafluorophosphate in the perfluorinated electrolyte for sodium-ion batteries is 1M.

[0007] Furthermore, the electrolyte preparation is carried out in an inert environment.

[0008] Furthermore, the stirring is performed on a stirring table for 6-8 hours.

[0009] The present invention also discloses a perfluorinated electrolyte for sodium-ion batteries prepared by the above preparation method.

[0010] The present invention also discloses the application of the above-mentioned perfluorinated electrolyte in sodium-ion batteries, wherein the sodium-ion battery is a high-safety, high-voltage, fast-charging NVPF||HC battery or NVPF||HC battery.

[0011] Furthermore, the NVPF‖HC battery retains 77% of its capacity and has an average coulombic efficiency of 99.77% after 2000 cycles at a voltage range of 2-4.6 V, a rate of 10 C, and room temperature.

[0012] Furthermore, the NVPF‖HC battery retains 80% of its capacity after 800 cycles at a voltage range of 2-4.6 V, a rate of 10 C, and a temperature of 60 °C.

[0013] Furthermore, the NVPF‖HC battery exhibits a capacity retention of 74.3% after 600 cycles in the 2-4.2 V voltage range.

[0014] Furthermore, the NVPF‖HC battery exhibits an average coulombic efficiency of 99.86% after 600 cycles in the 2-4.2 V voltage range.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method for preparing a perfluorinated electrolyte for sodium-ion batteries. The method uses sodium hexafluorophosphate and a mixed solvent consisting of fluoroethylene carbonate, bis(2,2,2-trifluoroethyl) carbonate, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether as raw materials. This method reconstructs the solvation structure and interface formation mechanism of the electrolyte, achieving a breakthrough in overall performance. The fluorinated solvent imparts high-voltage stability and safety to the system. The synergistic effect of FEC (fluoroethylene carbonate) and TTE (1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether) guides the formation of a solvation environment dominated by preferential anion reduction, promoting the formation of a dense and robust inorganic solid electrolyte interface film on the positive electrode surface. This interface film effectively inhibits the continuous decomposition of the electrolyte, buffers electrode volume changes, and prevents sodium dendrite growth. Thus, while meeting the requirements of high voltage window, fast charging kinetics, and high safety, it completely solves the problem of electrode-electrolyte interface degradation during long-term cycling, achieving excellent cycle stability.

[0016] The present invention also discloses a perfluorinated electrolyte prepared by the above method, which exhibits good flame retardant properties in ignition tests; batteries assembled using the perfluorinated electrolyte of the present invention have good rate performance and long-term cycle stability at high cutoff voltage, and achieve good operating performance in a high-temperature environment of 60°C. Attached Figure Description

[0017] Figure 1 The results of the flame retardancy verification experiment for different electrolytes.

[0018] Figure 2 Linear scan voltammetry (LSV) curves of Al‖Na cells at a scan rate of 1.0 mV / s; Figure 3 The cyclic voltammetry (CV) curves of the NVPF‖Na cell at a scan rate of 0.1 mV / s are shown. Figure 4 The long-cycle performance curves of NVPF‖Na batteries in the voltage range of 2~4.6 V and at a rate of 10C are shown. Figure 5 Typical charge-discharge curves of NVPF‖Na batteries during cycling; Figure 6 The electrochemical impedance spectroscopy (EIS) spectrum of the NVPF‖Na battery after 200 cycles; Figure 7 The long-cycle performance curves of NVPF‖Na batteries at 60℃, 2~4.6 V voltage range, and 10C rate are shown. Figure 8 The cycling performance curves of NVPF‖Na batteries at different rates in the voltage range of 2~4.6 V are shown. Figure 9 Energy efficiency and energy density curves of NVPF‖Na batteries assembled with FDT electrolyte at different rates; Figure 10 Energy efficiency and energy density curves of NVPF‖Na batteries assembled with FD electrolyte at different rates; Figure 11 Energy efficiency and energy density curves of NVPF‖Na batteries assembled with ED electrolyte at different rates; Figure 12 The voltage drop curve of an NVPF||Na battery after 75 hours of rest in a fully charged state; Figure 13 The long-cycle performance curves of NVPF‖HC full cells in the voltage range of 2~4.2 V and at a rate of 0.5 C are shown. Figure 14 The rate performance curves of NVPF‖HC full cells in the voltage range of 2~4.2 V are shown. Detailed Implementation

[0019] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0020] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0021] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0022] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0023] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0024] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0025] This invention discloses a method for preparing a perfluorinated electrolyte for sodium-ion batteries. Sodium hexafluorophosphate (NaPF6) is dissolved in a mixed solution of fluoroethylene carbonate (FEC), bis(2,2,2-trifluoroethyl) carbonate (DFDEC), and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) in a volume ratio of 3:2:1. The solution is stirred and dissolved on a stirring table for 6-8 hours to obtain FDT electrolyte (a perfluorinated electrolyte for sodium-ion batteries).

[0026] The entire preparation process was carried out in an argon-atmospheric glove box, with water and oxygen content both <0.1 ppm.

[0027] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0028] Example 1 A method for preparing a perfluorinated electrolyte for sodium-ion batteries includes the following steps: Sodium hexafluorophosphate (NaPF6) was dissolved in a mixed solution of fluoroethylene carbonate (FEC), bis(2,2,2-trifluoroethyl) carbonate (DFDEC), and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) in a volume ratio of 3:2:1, and stirred on a stirring table for 6 hours to obtain a 1 M FDT electrolyte (a perfluorinated electrolyte for sodium-ion batteries).

[0029] Comparative Example 1 500 μL of fluoroethylene carbonate (FEC), 333 μL of bis(2,2,2-trifluoroethyl) carbonate (DFDEC) and 167 μL of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) were thoroughly mixed and stirred on a stirring table for 20 min to obtain mixed solvent C. Mixed solvent C was added to 0.1679 g of sodium hexafluorophosphate (NaPF6) and the volume was adjusted to 1 mL. The mixture was stirred on a stirring table for 6 h to obtain a 1 M sodium hexafluorophosphate (NaPF6)-fluoroethylene carbonate (FEC), bis(2,2,2-trifluoroethyl) carbonate (DFDEC), and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) (volume ratio 3:2:1) electrolyte, namely perfluorinated electrolyte FDT (perfluorinated electrolyte for sodium-ion batteries).

[0030] Comparative Example 1 Mix 500 μL of ethylene carbonate (EC) and 500 μL of diethyl carbonate (DEC) thoroughly and stir on a stirring table for 20 min to obtain mixed solvent A.

[0031] Add mixed solvent A to 0.1679 g of sodium hexafluorophosphate (NaPF6) and bring the volume to 1 mL; stir on a stirring table for 6-8 h to obtain a 1 M sodium hexafluorophosphate (NaPF6)-ethylene dicarbonate (EC) / diethyl carbonate (DEC) (volume ratio 1:1) electrolyte, i.e., basic electrolyte ED.

[0032] Comparative Example 2 600 μL of fluoroethylene carbonate (FEC) and 400 μL of bis(2,2,2-trifluoroethyl) carbonate (DFDEC) were thoroughly mixed and stirred on a stirring table for 20 min to obtain mixed solvent B. Mixed solvent B was added to 0.1679 g of sodium hexafluorophosphate (NaPF6) and the volume was adjusted to 1 mL. The mixture was stirred on a stirring table for 6 h to obtain a 1 M sodium hexafluorophosphate (NaPF6)-fluoroethylene carbonate (FEC) / bis(2,2,2-trifluoroethyl) carbonate (DFDEC) (volume ratio 3:2) electrolyte, namely the intermediate sample electrolyte FD.

[0033] right Figure 1 Three glass fiber GF / D diaphragms were thoroughly soaked in 300 μL of electrolyte prepared in Examples 1 and 1-2, and then ignited with an igniter for 4 seconds before the igniter was removed. The conventional ED electrolyte exhibited high flammability, while the FD and FDT electrolytes rapidly self-extinguished after the igniter was removed, with a self-extinguishing time of 0 sg. -1It exhibits excellent flame retardant properties.

[0034] right Figure 2 The electrochemical stability window of the electrolyte was evaluated using linear voltammetry (LSV). The FDT electrolyte exhibited an oxidation stability voltage exceeding 5 V, sufficient to support a high cutoff voltage of 4.6 V. This high oxidation stability is mainly attributed to the introduction of fluorinated solvents.

[0035] right Figure 3 NVPF‖Na batteries were assembled using three different electrolytes, and cyclic voltammetry (CV) tests were conducted at a scan rate of 0.1 mV / s. The perfluorinated electrolyte system FDT exhibited the best electrochemical stability in the high-voltage range (above 3.5 V), indicating that it effectively suppressed electrolyte decomposition and side reactions under high voltage. Furthermore, compared to the intermediate sample FD (FEC:DFDEC), FDT, while maintaining the same stable current, further improved the electrode / electrolyte interfacial compatibility due to the introduction of TTE, exhibiting lower polarization and more stable interfacial kinetics. Therefore, the FDT system possesses a wider electrochemical stability window, lower polarization characteristics, and superior high-voltage stability, making it suitable for high-voltage fast-charging sodium-ion batteries.

[0036] right Figure 4 This electrolyte system uses an NVPF||Na battery system. Long-term cycling performance testing was conducted at a high cutoff voltage of 4.6 V and a high rate of 10 C. After 2000 cycles, the discharge specific capacity remained at approximately 84 mAh g⁻¹. -1 With a capacity retention rate of 77% and an average coulombic efficiency of 99.77%, it exhibits excellent high-rate long-cycle stability and coulombic efficiency retention characteristics. This indicates that the FDT electrolyte forms a more stable CEI during long-term charge / discharge processes, reducing continuous parasitic reactions and CEI dissolution.

[0037] right Figure 5 The re-discharge curves of NVPF‖Na batteries at different cycle numbers during long-term cycling in the 2-4.6 V voltage range and at a 10 C rate were extracted. The voltage curve of the battery using FDT electrolyte did not show significant distortion during 2000 long-term cycles, exhibiting good voltage plateau stability and low polarization growth, proving that FDT electrolyte has excellent interfacial compatibility and cycle stability under high voltage and high rate conditions.

[0038] right Figure 6 After 200 cycles, EIS tests were performed on NVPF||Na batteries assembled with the three electrolytes. Throughout the frequency range, the impedance of the FDT system was consistently lower than that of the FD and ED systems, especially in the low-to-mid-frequency region representing the charge transfer process. This indicates that the FDT system can form a more stable electrode / electrolyte interface film (SEI / CEI) with lower impedance, which is beneficial for Na…+ The efficient migration of FDT electrolytes is demonstrated. Compared to FD, FDT further reduces interfacial impedance due to the introduction of TTE, indicating that TTE may enhance interfacial compatibility and charge transfer kinetics by optimizing the solvation structure or promoting the formation of a uniform ion-conducting interfacial layer. The ED system exhibits the highest impedance across all frequency bands, confirming its issues of numerous interfacial side reactions and high transport resistance during high-voltage cycling. These results further confirm from an impedance perspective that FDT electrolytes can construct low-impedance, highly stable interfaces, which is one of the key reasons for their excellent cycling performance and stable electrochemical behavior under high voltage and high rate conditions.

[0039] right Figure 7 High temperatures significantly accelerate the oxidative decomposition of electrolytes under high voltages, interfacial film dissolution / reconstruction, and the resulting impedance increase and polarization intensification. NVPF‖Na batteries assembled using three electrolytes underwent long-term cycling tests at 60°C. Under harsh conditions of 60°C, 10 C, and 2.0–4.6 V, the initial capacity of the FDT electrolyte was approximately 125 mAh g⁻¹. -1 It then exhibits a slow, near-linear decay, remaining at ~100 mAh g even after 800 cycles. -1 The FDT electrolyte exhibits excellent high-temperature resistance and long-term stability. In contrast, the FD electrolyte shows a shorter cycle life. The ED electrolyte exhibits rapid capacity decay, demonstrating significant premature failure. The superior performance of the FDT electrolyte indicates that it is more conducive to the formation of a thermally stable interfacial phase that suppresses side reactions on the surfaces of the NVPF positive and Na negative electrodes, thereby effectively mitigating continuous parasitic reactions and impedance increases.

[0040] right Figure 8 NVPF‖Na batteries assembled with three different electrolytes were tested at different rates. The FDT electrolyte maintained relatively stable capacity output at medium to high rates. It exhibited the highest capacity and least capacity decay at all rates, and returned to 0.05 A g at the highest rate. -1 The increased capacity recovery and superior rate performance indicate faster sodium ion transport kinetics and reduced polarization.

[0041] right Figures 9-11 The energy density and energy efficiency of the three electrolytes prepared in Example 1 and Comparative Examples 1-2 all decreased with increasing rate, mainly due to the reduced discharge plateau and increased charge-discharge voltage difference caused by intensified polarization at high current. In contrast, the energy density of the traditional carbonate-based ED electrolyte decreased rapidly with increasing rate, and its energy efficiency also decreased significantly, indicating that polarization and irreversible losses were more severe under high-voltage fast charging conditions. The FDT electrolyte performed best across the entire rate range: at an extreme current density of 5 A g... -1 The energy density can still be maintained at 309 Wh kg.- ¹ Energy efficiency remains consistently high and only decreases slowly with increasing charging rate. FD maintains high energy output even at high rates, but is slightly lower overall than FDT. Overall, FDT / FD better balances energy density and energy efficiency at high rates, demonstrating better fast charging compatibility.

[0042] right Figure 12 Open-circuit self-discharge and interfacial stability were further evaluated by examining the capacity and voltage loss of the cycled cells under fully charged conditions. NVPF‖Na cells assembled with three different electrolytes were first cycled 15 times at 1C within a voltage range of 2.0–4.6V, then charged to 4.6V and paused for 75 h. The open-circuit voltage of all three electrolyte systems showed a rapid initial decrease followed by a slower decrease, reflecting the inevitable self-discharge and interfacial side reactions under high voltage and full charge conditions. In contrast, the FDT system maintained the highest voltage and the smallest voltage decrease throughout the resting period; FD followed; while the conventional carbonate system ED showed the most significant voltage decrease, with the difference widening further over time. This result indicates that the FDT electrolyte, with the introduction of a fluorinated solvent and the addition of TTE, can more effectively suppress persistent parasitic reactions (such as electrolyte oxidation / interfacial film dissolution and reconstruction) under high voltage and full charge conditions, thereby reducing the open-circuit self-discharge rate and maintaining a more stable interfacial state. Conversely, the ED system exhibited poor interfacial stability under high voltage and resting conditions, making it more prone to side reactions and resulting in faster voltage decay.

[0043] right Figure 13 Both FD and FDT electrolytes were used in an NVPF‖HC battery system for long-term cycling performance testing within a voltage range of 2-4.2 V and a rate of 0.5 C, further validating the application of the electrolytes in full cells. The FD electrolyte exhibited rapid capacity decay and premature failure in the early stages of cycling, showing significant reversible capacity loss. The FDT electrolyte, however, showed slower capacity decay, exhibiting a 74.3% capacity retention and a 99.86% average coulombic efficiency after 600 cycles, indicating its effective suppression of side reactions and maintenance of a stable interface in full-cell systems. The full-cell results further validated that the FDT formulation incorporating TTE has better practical application suitability and long-term cycling stability. right Figure 14 NVPF‖HC batteries assembled with FD and FDT electrolytes were tested at different rates. The battery using FDT electrolyte consistently exhibited higher capacity than the FD battery at all rates, and maintained higher capacity output even at high rates, demonstrating better fast-charging adaptability. In contrast, the FD system showed a more significant capacity drop at medium to high rates, and the recovered capacity was lower, suggesting greater polarization or faster increase in interfacial impedance under high-rate conditions. Overall, the introduction of TTE can significantly improve the rate performance of the entire battery.

[0044] This invention provides a perfluorinated electrolyte for high-safety, high-voltage, fast-charging sodium-ion batteries, its preparation method, and its application. It exhibits the following significant advantages in electrochemical performance testing: In flame retardant safety tests, the electrolyte of this invention can quickly self-extinguish after the external ignition source is removed, which significantly reduces the flammability risk of conventional carbonate electrolytes, thereby improving the intrinsic safety of the battery system.

[0045] In LSV and high-voltage electrochemical tests, the electrolyte of this invention exhibits higher oxidation stability and a wider electrochemical stability window, which can meet the stable operation requirements under high cutoff voltage conditions and is beneficial to the application of high-voltage cathode systems.

[0046] In cyclic voltammetry, long-cycle and high-rate tests, the electrolyte of this invention can effectively suppress electrolyte decomposition and continuous side reactions under high voltage, reduce polarization and maintain more stable charge and discharge behavior, thereby significantly improving the battery's cycle stability, coulombic efficiency and fast-charge rate performance.

[0047] In electrochemical impedance spectroscopy and open-circuit static testing, the electrolyte of this invention can construct a more stable interface film (SEI / CEI) with lower impedance and better ion conduction, reducing the increase in interface impedance after cycling and suppressing self-discharge under full charge, thereby further ensuring long-term stable operation from the interface level.

[0048] In high-temperature and full-cell verification tests, the electrolyte of this invention can still maintain good capacity retention and reversibility under harsh conditions, and exhibits good adaptability and stability in the full-cell system, proving that it has comprehensive advantages for practical applications.

[0049] In summary, the perfluorinated electrolyte of this invention achieves synergistic improvements in flame retardant safety, high voltage stability, fast charge rate performance, and long-term cycle stability, providing a reliable electrolyte solution for high-safety, high-voltage, and fast-chargeable sodium-ion batteries.

[0050] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a perfluorinated electrolyte for sodium-ion batteries, characterized in that, Includes the following steps: Sodium hexafluorophosphate was dissolved in fluoroethylene carbonate, bis(2,2,2-trifluoroethyl) carbonate and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and stirred to obtain a perfluorinated electrolyte for sodium-ion batteries. The volume ratio of the fluoroethylene carbonate, bis(2,2,2-trifluoroethyl) carbonate, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether is 3:2:

1.

2. The method for preparing a perfluorinated electrolyte for sodium-ion batteries according to claim 1, characterized in that, The concentration of sodium hexafluorophosphate in the perfluorinated electrolyte used in sodium-ion batteries is 1M.

3. The method for preparing a perfluorinated electrolyte for sodium-ion batteries according to claim 1, characterized in that, The electrolyte preparation is carried out in an inert environment.

4. A method for preparing a perfluorinated electrolyte for sodium-ion batteries according to claim 1, characterized in that, The stirring is carried out on a stirring table for 6-8 hours.

5. A perfluorinated electrolyte for sodium-ion batteries, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 4.

6. The application of the perfluorinated electrolyte according to claim 5 in a sodium-ion battery, characterized in that, The sodium-ion battery is a high-safety, high-voltage, fast-charging NVPF||HC battery or NVPF||HC battery.

7. The application of the perfluorinated electrolyte according to claim 6 in a sodium-ion battery, characterized in that, The NVPF‖HC battery retains 77% of its capacity and has an average coulombic efficiency of 99.77% after 2000 cycles at a voltage range of 2-4.6 V, a rate of 10 C, and room temperature.

8. The application of the perfluorinated electrolyte according to claim 7 in a sodium-ion battery, characterized in that, The NVPF‖HC battery retains 80% of its capacity after 800 cycles at a voltage range of 2-4.6 V, a rate of 10 C, and a temperature of 60 °C.

9. The application of the perfluorinated electrolyte according to claim 6 in a sodium-ion battery, characterized in that, The NVPF‖HC battery exhibited a capacity retention of 74.3% after 600 cycles in the 2-4.2 V voltage range.

10. The application of the perfluorinated electrolyte according to claim 9 in a sodium-ion battery, characterized in that, The NVPF‖HC battery exhibits an average coulombic efficiency of 99.86% after 600 cycles in the 2-4.2 V voltage range.

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