Linear-chain ether and cyclic ether mixed electrolyte for wide-temperature-range sodium-ion battery as well as preparation method and application of linear-chain ether and cyclic ether mixed electrolyte
By designing a mixed electrolyte of linear ethers and cyclic ethers, the problem of low electrolyte ionic conductivity at low temperatures in sodium-ion batteries was solved, achieving high efficiency and wide temperature range performance, which is suitable for the industrial production of sodium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-20
- Publication Date
- 2026-04-14
AI Technical Summary
Existing sodium-ion batteries exhibit low electrolyte ion conductivity and high desolvation energy at low temperatures, resulting in slow sodium ion transport rates and affecting the battery's low-temperature and wide-temperature-range performance.
A mixed electrolyte of linear and cyclic ethers, containing sodium trifluoromethanesulfonate and ether-based solvents such as diethylene glycol dimethyl ether and tetrahydrofuran, was designed to improve ionic conductivity and sodium ion transport number by adjusting the ratio and concentration of these solvents and by optimizing the electrode-electrolyte interface.
It achieves high ionic conductivity and rapid sodium ion insertion and extraction in sodium-ion batteries over a wide temperature range, improving the battery's charge-discharge specific capacity, cycle stability, and high-rate performance, making it suitable for industrial production.
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Figure CN121862850A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to wide-temperature-range electrolytes, their preparation methods, and applications. Background Technology
[0002] Sodium-ion batteries, as a potential alternative to lithium-ion batteries, have broad application prospects in large-scale grid energy storage, mopeds, and other fields due to their similar electrochemical performance. Sodium metal resources are abundant and inexpensive. The increasingly mature sodium-ion battery technology will inevitably face broader application areas and harsher operating environments, especially extreme temperature conditions, particularly at extremely low temperatures, such as in high-latitude or high-altitude regions and outer space exploration. Currently, research on wide-temperature-range sodium-ion battery technology is still in its early stages; therefore, in-depth understanding and research of this technology are necessary.
[0003] Solving the technical challenges of sodium-ion batteries operating over a wide temperature range hinges on addressing several key difficulties at low temperatures, including: reduced electrode reaction rates, alterations to electrode material properties, high electrolyte freezing point, decreased electrolyte ionic conductivity, and reduced sodium ion migration. Currently, research on low-temperature sodium-ion batteries largely focuses on electrode material design, including the construction of three-dimensional ion channels, optimization of electronic conductivity, and enhancement of electrode kinetics. All these strategies aim to promote the slow solid-state diffusion of sodium ions and improve the contact between electrode materials and the electrolyte at low temperatures. However, optimizing the low-temperature performance of sodium-ion batteries through electrode material modification has very limited effectiveness. Furthermore, designing the electrode / electrolyte interface can also improve the low-temperature performance of sodium-ion batteries to some extent. Clearly, electrode optimization is not only difficult to implement but also significantly increases the production cost of sodium-ion batteries, making industrial production challenging. Inspired by low-temperature sodium-ion battery technology, the slow ion transport associated with the electrolyte at low temperatures is one of the main reasons limiting the battery's low-temperature performance. Moreover, the design of low-temperature electrolytes should be more suitable for the industrial production of sodium-ion batteries, with controllable costs.
[0004] For low-temperature sodium-ion batteries, the main challenges at low temperatures include low ionic conductivity of the electrolyte, high desolution energy, and slow sodium-ion diffusion kinetics at the electrode / electrolyte interface. Specifically, at low temperatures, the viscosity of the electrolyte inevitably increases, and the ionic conductivity decreases accordingly, resulting in slow sodium-ion transport within the electrolyte. Then, the solvated sodium ions undergo desolution before entering the electrode material. The high desolution energy at low temperatures significantly reduces the ion transport rate, which is the main factor limiting ion transport rates at low temperatures.
[0005] Furthermore, the wide-temperature-range performance of sodium-ion batteries is also affected by the slow diffusion of ions at the solid electrolyte interface, and its composition and structure mainly depend on the electrolyte formulation. Clearly, the design of a wide-temperature-range electrolyte plays a crucial role in improving the wide-temperature-range performance of sodium-ion batteries. Given the above, developing suitable electrolyte formulations is urgently needed to obtain high-performance sodium-ion batteries with a wide temperature range. Summary of the Invention
[0006] To address the aforementioned technical problems, this invention provides a wide-temperature-range sodium-ion battery electrolyte consisting of a straight-chain ether and a cyclic ether mixture, its preparation method, and its application.
[0007] The present invention provides a wide-temperature-range sodium-ion battery electrolyte consisting of a straight-chain ether and a cyclic ether mixture, which has a low melting point, ideal ionic conductivity, and a sodium fluoride-rich solid electrolyte interface.
[0008] A wide-temperature-range sodium-ion battery electrolyte consisting of a straight-chain ether and a cyclic ether, comprising a sodium salt and an ether-based solvent;
[0009] The sodium salt is sodium trifluoromethanesulfonate (NaOTf); the ether solvent is a mixture of straight-chain ether and cyclic ether; the straight-chain ether is diethylene glycol dimethyl ether (DEGDME); and the cyclic ether is tetrahydrofuran (THF) or dimethyltetrahydrofuran (MeTHF).
[0010] The wide-temperature-range sodium-ion battery provided by this invention uses a mixed electrolyte of linear and cyclic ethers. By adjusting the ratio, an electrolyte with low melting point, low viscosity, low desolvation energy, and a sodium fluoride-rich solid electrolyte interface is selected. This allows the electrolyte to maintain high ionic conductivity over a wide temperature range, ensuring rapid insertion and extraction of sodium ions at the positive electrode. Furthermore, the low desolvation energy enables high-rate charge and discharge of sodium ions over a wide temperature range. This results in a wide-temperature-range sodium-ion battery with excellent electrochemical performance, including high rate and constant current cycling.
[0011] Compared with the prior art, the present invention has the following advantages:
[0012] The wide-temperature-range sodium-ion battery electrolyte, a mixture of linear and cyclic ethers, provided by this invention, has a low freezing point and low viscosity. It also exhibits high ionic conductivity and high sodium ion transport number over a wide temperature range, along with low desolvation energy. This reduces the charge transfer impedance at the electrode-electrolyte interface, allowing sodium ions to rapidly insert and extract upon reaching the electrode. Consequently, it improves the wide-temperature-range performance of the sodium-ion battery. The resulting sodium-ion battery possesses excellent wide-temperature-range charge-discharge specific capacity, cycle stability, and high-rate performance. Attached Figure Description
[0013] Figure 1The image shows the sodium-symmetric cycling performance of Na|NaOTf DEGDME|Na batteries assembled using electrolytes of different concentrations of sodium salt prepared in Comparative Examples 1-7 at -40°C, with a current density of 0.5 mA cm⁻¹. -2 ;
[0014] Figure 2 To test the HC|0.5M NaOTf DEGDME:THF|Na half-cells assembled using the electrolytes prepared in Examples 1-5 and Comparative Example 1 at different temperature gradients, 0.1 A g -1 Discharge tests were conducted at current densities ranging from 0.01 to 3V.
[0015] Figure 3 To test the low-temperature rate performance of HC|0.5M NaOTf DEGDME:THF|Na half-cells assembled using the electrolytes prepared in Examples 1-5 and Comparative Example 1, the current densities were 0.1 A g. -1 0.2 A g -1 0.5 A g -1 1 A g -1 and 2 A g -1 Obtain the rate performance diagram;
[0016] Figure 4 The HC|0.5M NaOTf DEGDME:THF|Na half-cells assembled using the electrolytes prepared in Examples 1-5 and Comparative Example 1 were subjected to low-temperature cycling performance testing at -40°C with a current density of 0.1 A g. -1 Obtain the cycle performance graph;
[0017] Figure 5 The HC|0.5M NaOTf DEGDME:THF|Na half-cell assembled using the electrolyte prepared in Example 3 was subjected to low-temperature cycling performance testing at -40°C with a current density of 0.1 A g. -1 The obtained charge-discharge curves with different numbers of cycles;
[0018] Figure 6 To test the HC|0.5M NaOTf DEGDME:MeTHF|Na half-cells assembled using the electrolytes prepared in Examples 6-8 and Comparative Example 1 at different temperature gradients, 0.1 A g -1 Discharge tests were conducted at current densities ranging from 0.01 to 3V.
[0019] Figure 7To test the low-temperature rate performance of the HC|0.5M NaOTf DEGDME:MeTHF|Na half-cells assembled using the electrolytes prepared in Examples 6-8 and Comparative Example 1, the current densities were 0.1 A g. -1 0.2 A g -1 0.5 A g -1 1 A g -1 and 2 A g -1 Obtain the rate performance diagram;
[0020] Figure 8 The HC|0.5M NaOTf DEGDME:MeTHF|Na half-cells assembled using the electrolytes prepared in Examples 6-8 and Comparative Example 1 were subjected to low-temperature cycling performance testing at -40°C with a current density of 0.1 A g. -1 Obtain the cycle performance graph;
[0021] Figure 9 The HC|0.5M NaOTf DEGDME:MeTHF|Na half-cell assembled using the electrolyte prepared in Example 7 was subjected to low-temperature cycling performance testing at -40°C with a current density of 0.1 A g. -1 The obtained charge-discharge curves for different number of cycles. Detailed Implementation
[0022] Specific implementation method 1: This implementation method is a wide temperature range sodium-ion battery electrolyte consisting of a mixed electrolyte of linear ether and cyclic ether, including sodium salt and ether-based solvent;
[0023] The sodium salt is sodium trifluoromethanesulfonate; the ether solvent is a mixture of straight-chain ether and cyclic ether; the straight-chain ether is diethylene glycol dimethyl ether; and the cyclic ether is tetrahydrofuran or dimethyltetrahydrofuran.
[0024] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the concentration of sodium salt in the electrolyte is 0.4 mol / L to 1 mol / L. The other steps are the same as in Specific Implementation Method One.
[0025] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that the volume ratio of straight-chain ether to cyclic ether in the ether-based solvent is (5~9):(1~5). Other steps are the same as in Specific Implementation Method 1 or 2.
[0026] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the volume ratio of straight-chain ether to cyclic ether in the ether-based solvent is 9:1. The other steps are the same as in Specific Implementation Methods One to Three.
[0027] Specific Implementation Method 5: This implementation method differs from Specific Implementation Methods 1 to 4 in that the volume ratio of straight-chain ether to cyclic ether in the ether-based solvent is 8:2. The other steps are the same as in Specific Implementation Methods 1 to 4.
[0028] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the volume ratio of straight-chain ether to cyclic ether in the ether-based solvent is 7:3. The other steps are the same as in Specific Implementation Methods One to Five.
[0029] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the volume ratio of straight-chain ether to cyclic ether in the ether-based solvent is 6:4. The other steps are the same as in Specific Implementation Methods One to Six.
[0030] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the volume ratio of straight-chain ether to cyclic ether in the ether-based solvent is 5:5. The other steps are the same as in Specific Implementation Methods One to Seven.
[0031] Specific Implementation Method Nine: This implementation method is a method for preparing a mixed electrolyte of linear ether and cyclic ether for a wide-temperature-range sodium-ion battery, specifically completed according to the following steps:
[0032] In an argon-filled glove box, straight-chain ethers and cyclic ethers are added to a container to form a binary solvent. The mixture is stirred until homogeneous to obtain an ether-based solvent. Sodium salt is then added and the mixture is stirred until the sodium salt is completely dissolved in the ether-based solvent to obtain a wide-temperature-range sodium-ion battery electrolyte consisting of straight-chain ethers and cyclic ethers.
[0033] Specific Implementation Method 10: This implementation method is an application of a wide-temperature-range sodium-ion battery using a mixed electrolyte of linear ethers and cyclic ethers.
[0034] The beneficial effects of the present invention are verified using the following embodiments:
[0035] Example 1: A method for preparing a mixed electrolyte of linear ether and cyclic ether for a wide-temperature-range sodium-ion battery, specifically comprising the following steps:
[0036] In a glove box filled with argon (oxygen <0.01ppm, water <0.01ppm), straight-chain ethers and cyclic ethers were added to a container to form a binary solvent. The mixture was stirred until homogeneous to obtain an ether-based solvent. Sodium salt was then added, and stirring continued until the sodium salt was completely dissolved in the ether-based solvent to obtain a wide-temperature-range sodium-ion battery electrolyte of mixed straight-chain ethers and cyclic ethers (denoted as 0.5M NaOTf DEGDME:THF 9:1).
[0037] The sodium salt mentioned is sodium trifluoromethanesulfonate (NaOTf);
[0038] The straight-chain ether is diethylene glycol dimethyl ether (DEGDME); the cyclic ether is tetrahydrofuran (THF).
[0039] The volume ratio of diethylene glycol dimethyl ether (DEGDME) to tetrahydrofuran (THF) in the ether-based solvent is 9:1.
[0040] The concentration of sodium trifluoromethanesulfonate (NaOTf) in the wide-temperature-range sodium-ion battery mixed electrolyte of linear ether and cyclic ether is 0.5 mol / L.
[0041] Example 2: The difference between this example and Example 1 is that the volume ratio of diethylene glycol dimethyl ether (DEGDME) to tetrahydrofuran (THF) in the ether-based solvent is 8:2; the resulting wide-temperature-range sodium-ion battery straight-chain ether and cyclic ether mixed electrolyte is denoted as 0.5M NaOTf DEGDME:THF 8:2. All other steps and parameters are the same as in Example 1.
[0042] Example 3: The difference between this example and Example 1 is that the volume ratio of diethylene glycol dimethyl ether (DEGDME) to tetrahydrofuran (THF) in the ether-based solvent is 7:3; the resulting wide-temperature-range sodium-ion battery straight-chain ether and cyclic ether mixed electrolyte (denoted as 0.5M NaOTf DEGDME:THF 7:3) is the same as in Example 1. All other steps and parameters are the same as in Example 1.
[0043] Example 4: The difference between this example and Example 1 is that the volume ratio of diethylene glycol dimethyl ether (DEGDME) to tetrahydrofuran (THF) in the ether-based solvent is 6:4; the resulting wide-temperature-range sodium-ion battery straight-chain ether and cyclic ether mixed electrolyte (denoted as 0.5M NaOTf DEGDME:THF 6:4) is the same as in Example 1. All other steps and parameters are the same as in Example 1.
[0044] Example 5: The difference between this example and Example 1 is that the volume ratio of diethylene glycol dimethyl ether (DEGDME) to tetrahydrofuran (THF) in the ether-based solvent is 5:5; the resulting wide-temperature-range sodium-ion battery straight-chain ether and cyclic ether mixed electrolyte (denoted as 0.5M NaOTf DEGDME:THF 5:5) is the same as in Example 1. All other steps and parameters are the same as in Example 1.
[0045] Example 6: A method for preparing a mixed electrolyte of linear ether and cyclic ether for a wide-temperature-range sodium-ion battery, specifically comprising the following steps:
[0046] In a glove box filled with argon (oxygen <0.01ppm, water <0.01ppm), straight-chain ethers and cyclic ethers were added to a container to form a binary solvent. The mixture was stirred until homogeneous to obtain an ether-based solvent. Sodium salt was then added, and stirring continued until the sodium salt was completely dissolved in the ether-based solvent to obtain a wide-temperature-range sodium-ion battery electrolyte of mixed straight-chain ethers and cyclic ethers (denoted as 0.5M NaOTf DEGDME:MeTHF 9:1).
[0047] The sodium salt mentioned is sodium trifluoromethanesulfonate (NaOTf);
[0048] The straight-chain ether is diethylene glycol dimethyl ether (DEGDME); the cyclic ether is dimethyltetrahydrofuran (MeTHF).
[0049] The volume ratio of diethylene glycol dimethyl ether (DEGDME) to dimethyl tetrahydrofuran (MeTHF) in the ether-based solvent is 9:1;
[0050] The concentration of sodium trifluoromethanesulfonate (NaOTf) in the wide-temperature-range sodium-ion battery mixed electrolyte of linear ether and cyclic ether is 0.5 mol / L.
[0051] Example 7: The difference between this example and Example 6 is that the volume ratio of diethylene glycol dimethyl ether (DEGDME) to dimethyltetrahydrofuran (MeTHF) in the ether-based solvent is 8:2; thus, a wide-temperature-range sodium-ion battery mixed electrolyte of straight-chain ether and cyclic ether (denoted as 0.5M NaOTf DEGDME:MeTHF 8:2) is obtained. All other steps and parameters are the same as in Example 6.
[0052] Example 8: The difference between this example and Example 6 is that the volume ratio of diethylene glycol dimethyl ether (DEGDME) to dimethyltetrahydrofuran (MeTHF) in the ether-based solvent is 7:3; thus, a wide-temperature-range sodium-ion battery mixed electrolyte of straight-chain ether and cyclic ether (denoted as 0.5M NaOTf DEGDME:MeTHF 7:3) is obtained. All other steps and parameters are the same as in Example 6.
[0053] Comparative Example 1: The preparation method of the electrolyte is carried out according to the following steps:
[0054] In a glove box filled with argon (oxygen <0.01ppm, water <0.01ppm), diethylene glycol dimethyl ether (DEGDME) was added to a container, followed by sodium salt. The mixture was stirred until the sodium salt was completely dissolved in the DEGDME, resulting in an electrolyte (denoted as 0.5M NaOTf DEGDME).
[0055] The sodium salt mentioned is sodium trifluoromethanesulfonate (NaOTf);
[0056] The concentration of sodium trifluoromethanesulfonate (NaOTf) in the electrolyte is 0.5 mol / L.
[0057] Comparative Example 2: The difference between this example and Comparative Example 1 is that the concentration of sodium trifluoromethanesulfonate (NaOTf) in the electrolyte is 0.4 mol / L; the resulting electrolyte is denoted as 0.4 M NaOTf DEGDME. All other steps and parameters are the same as in Comparative Example 1.
[0058] Comparative Example 3: The difference between this example and Comparative Example 1 is that the concentration of sodium trifluoromethanesulfonate (NaOTf) in the electrolyte is 0.6 mol / L; the resulting electrolyte is denoted as 0.6 M NaOTf DEGDME. All other steps and parameters are the same as in Comparative Example 1.
[0059] Comparative Example 4: The difference between this example and Comparative Example 1 is that the concentration of sodium trifluoromethanesulfonate (NaOTf) in the electrolyte is 0.7 mol / L; the resulting electrolyte is denoted as 0.7 M NaOTf DEGDME. All other steps and parameters are the same as in Comparative Example 1.
[0060] Comparative Example 5: The difference between this example and Comparative Example 1 is that the concentration of sodium trifluoromethanesulfonate (NaOTf) in the electrolyte is 0.8 mol / L; the resulting electrolyte is denoted as 0.8 M NaOTf DEGDME. All other steps and parameters are the same as in Comparative Example 1.
[0061] Comparative Example 6: The difference between this example and Comparative Example 1 is that the concentration of sodium trifluoromethanesulfonate (NaOTf) in the electrolyte is 0.9 mol / L; the resulting electrolyte is denoted as 0.9 M NaOTf DEGDME. All other steps and parameters are the same as in Comparative Example 1.
[0062] Comparative Example 7: The difference between this example and Comparative Example 1 is that the concentration of sodium trifluoromethanesulfonate (NaOTf) in the electrolyte is 1 mol / L; the resulting electrolyte is denoted as 1M NaOTf DEGDME. All other steps and parameters are the same as in Comparative Example 1.
[0063] Application Example 1: The assembly of the HC||Na half-cell is carried out according to the following steps:
[0064] 1. The positive electrode uses a sodium plate;
[0065] II. Preparation of the Negative Electrode: In this experiment, commercial hard carbon (HC) powder, Super P, and CMC were mixed and ground thoroughly in a mass ratio of 8:1:1. After fine grinding, the mixture was placed in a slurry container, and a certain amount of deionized water was added gradually until it became relatively viscous. Then, the slurry container was placed on a magnetic stirring device and stirred thoroughly to ensure that the slurry was in a uniform state. Then, copper foil of appropriate size was cut, and the matte side of the copper foil was wiped clean with alcohol and deionized water in turn and placed flat on a glass plate. The slurry was evenly coated on the surface of the copper foil with a scraper. The electrode to be treated was dried in a vacuum drying device at 110°C for 12 hours to remove the residual volatile organic components and surface adsorbed water inside the material. To prevent burrs on the surface of the electrode sheet from causing unnecessary impact on subsequent battery testing, the prepared electrode sheet was placed between two appropriately sized weighing papers and rolled to uniformly cut into circular electrode sheets with a diameter of 12 mm to obtain the HC electrode, which is the negative electrode. Then, it was transferred to a glove box for storage and use.
[0066] III. Assembly: Due to the extremely reactive chemical properties of metallic sodium, which oxidizes upon contact with air and explodes upon contact with water, the HC||Na battery needs to be assembled in a glove box. The assembly steps are as follows: Place the spring plate, gasket, and sodium plate sequentially in the center of the negative electrode shell and add 40 μL of electrolyte. Then place the separator and add another 60 μL of electrolyte to wet it. Next, align the HC electrode with the positive electrode shell and place it under pressure in a battery sealing machine to obtain a CR2032 button cell. Place the assembled HC||Na half-cell in a 25°C constant temperature chamber for 24 hours before further testing.
[0067] Application Example 2: The difference between this application example and Application Example 1 is that the HC electrode is replaced with a sodium sheet to obtain a Na||Na battery. All other steps and parameters are the same as in Application Example 1.
[0068] Following the method in Application Example 2, Na|NaOTf DEGDME|Na half-cells were assembled using electrolytes of different concentrations of sodium salt prepared in Comparative Examples 1-7, and the cycle performance of the cells was tested. (See attached image.) Figure 1 As shown;
[0069] Figure 1 The figure shows the sodium-symmetric cycling performance of Na|NaOTf DEGDME|Na half-cells assembled using electrolytes of different concentrations of sodium salt prepared in Comparative Examples 1-7 at -40℃, with a current density of 0.5 mA cm⁻¹. -2 ;
[0070] from Figure 1 It can be seen that: at a current density of 0.5 mA cm -2The 0.5 M NaOTf DEGDME electrolyte exhibited the lowest voltage polarization, indicating lower interfacial impedance and faster ion transport. Furthermore, the curve was uniform, without abnormal fluctuations or short circuits, suggesting more uniform sodium deposition at -40°C and suppression of sodium dendrite growth. Therefore, this invention selected a sodium salt concentration of 0.5 M NaOTf.
[0071] Following the method of Application Example 1, HC|0.5MNaOTf DEGDME:THF|Na half-cells were assembled using the electrolytes prepared in Examples 1-5 and Comparative Example 1, and then tested.
[0072] Figure 2 To test the HC|0.5M NaOTf DEGDME:THF|Na batteries assembled using the electrolytes prepared in Examples 1-5 and Comparative Example 1 at different temperature gradients, 0.1 A g -1 Discharge tests were conducted at current densities ranging from 0.01 to 3V.
[0073] Depend on Figure 2 It can be seen that the half-cell assembled using 0.5M NaOTf DEGDME:THF 7:3 has the highest discharge specific capacity, which is 255.6 mAh g⁻¹ under different temperature gradients. -1 (50℃), 226.8 mAh g -1 (25℃), 204.2 mAh g -1 (0℃), 187.7 mAh g -1 (-20℃), 174.5 mAh g -1 (-40℃) and 139.9 mAh g -1 (-60℃), it still retains 61.7% of its room temperature capacity when the temperature drops to the extremely low temperature of -60℃.
[0074] Figure 3 To test the low-temperature rate performance of HC|0.5M NaOTf DEGDME:THF|Na half-cells assembled using the electrolytes prepared in Examples 1-5 and Comparative Example 1, the current densities were 0.1 A g. -1 0.2 A g -1 0.5 A g -1 1 A g -1 and 2 A g -1 Obtain the rate performance diagram;
[0075] Depend on Figure 3It can be seen that the half-cell assembled using 0.5M NaOTf DEGDME: THF 7:3 has the highest discharge specific capacity at different current densities, which is 179.9 mAh g⁻¹. -1 164 mAh g -1 146.9 mAh g -1 128.9 mAh g -1 and 105.8 mAh g -1 Finally, it returned to 163.8 mAh g. -1 It exhibits excellent rate performance.
[0076] Figure 4 The HC|0.5M NaOTf DEGDME:THF|Na half-cells assembled using the electrolytes prepared in Examples 1-5 and Comparative Example 1 were subjected to low-temperature cycling performance testing at -40°C with a current density of 0.1 A g. -1 Obtain the cycle performance graph;
[0077] Depend on Figure 4 It can be seen that the half-cell assembled using 0.5M NaOTf DEGDME:THF 7:3 has the highest discharge specific capacity, with a discharge specific capacity of 161.6 mAh g after 50 cycles. -1 It exhibits excellent cycle performance.
[0078] Figure 5 The HC|0.5M NaOTf DEGDME:THF|Na half-cell assembled using the electrolyte prepared in Example 3 was subjected to low-temperature cycling performance testing at -40°C with a current density of 0.1 A g. - The obtained charge-discharge curves with different numbers of cycles;
[0079] Depend on Figure 5 It can be seen that even at -40℃, the charge-discharge plateau remains unchanged, indicating that there is no excess negative reaction or sodium precipitation.
[0080] Figure 6 To test the HC|0.5M NaOTf DEGDME:MeTHF|Na half-cells assembled using the electrolytes prepared in Examples 6-8 and Comparative Example 1 at different temperature gradients, 0.1 A g -1 Discharge tests were conducted at current densities ranging from 0.01 to 3V.
[0081] Depend on Figure 6 It can be seen that the half-cell assembled using 0.5M NaOTf DEGDME:MeTHF 8:2 has the highest discharge specific capacity, which is 260.9 mAh g⁻¹ under different temperature gradients. -1(50℃), 224.8 mAh g -1 (25℃), 215.3 mAh g -1 (0℃), 199 mAh g -1 (-20℃), 175.3 mAh g -1 (-40℃) and 154.2 mAh g -1 (-60℃), it still retains 68.6% of its room temperature capacity when the temperature drops to the extremely low temperature of -60℃.
[0082] Figure 7 To test the low-temperature rate performance of the HC|0.5M NaOTf DEGDME:MeTHF|Na half-cells assembled using the electrolytes prepared in Examples 6-8 and Comparative Example 1, the current densities were 0.1 A g. -1 0.2 A g -1 0.5 A g -1 1 A g -1 and 2 A g -1 Obtain the rate performance diagram;
[0083] Depend on Figure 7 It can be seen that the half-cell assembled using 0.5M NaOTf DEGDME:MeTHF 8:2 has the highest discharge specific capacity at different current densities, which is 182.4 mAh g⁻¹. -1 165.7 mAh g -1 146.9 mAh g -1 127.8 mAhg -1 and 105.6 mAh g -1 Finally, it returned to 166.8 mAh g -1 It exhibits excellent rate performance.
[0084] Figure 8 The HC|0.5M NaOTf DEGDME:MeTHF|Na half-cells assembled using the electrolytes prepared in Examples 6-8 and Comparative Example 1 were subjected to low-temperature cycling performance testing at -40°C with a current density of 0.1 A g. -1 Obtain the cycle performance graph;
[0085] Depend on Figure 8 It can be seen that the half-cell assembled using 0.5M NaOTf DEGDME:MeTHF 8:2 has the highest discharge specific capacity, with a discharge specific capacity of 164.5 mAh g after 50 cycles. -1 It exhibits excellent cycle performance.
[0086] Figure 9The HC|0.5M NaOTf DEGDME:MeTHF|Na half-cell assembled using the electrolyte prepared in Example 7 was subjected to low-temperature cycling performance testing at -40°C with a current density of 0.1 A g. -1 The obtained charge-discharge curves with different numbers of cycles;
[0087] Depend on Figure 9 It can be seen that even at -40℃, the charge-discharge plateau remains unchanged, indicating that there is no excess negative reaction or sodium precipitation.
Claims
1. A wide-temperature-range sodium-ion battery electrolyte consisting of a straight-chain ether and a cyclic ether mixture, characterized in that... The electrolyte comprises sodium salt and ether-based solvent; The sodium salt is sodium trifluoromethanesulfonate; the ether solvent is a mixture of straight-chain ether and cyclic ether; the straight-chain ether is diethylene glycol dimethyl ether; and the cyclic ether is tetrahydrofuran or dimethyltetrahydrofuran.
2. The wide-temperature-range sodium-ion battery mixed electrolyte of linear ether and cyclic ether according to claim 1, characterized in that... The concentration of sodium salt in the electrolyte is 0.4 mol / L to 1 mol / L.
3. The wide-temperature-range sodium-ion battery mixed electrolyte of linear ether and cyclic ether according to claim 1, characterized in that... The volume ratio of straight-chain ether to cyclic ether in the ether-based solvent is (5~9):(1~5).
4. The wide-temperature-range sodium-ion battery mixed electrolyte of linear ether and cyclic ether according to claim 3, characterized in that... The volume ratio of straight-chain ethers to cyclic ethers in the ether-based solvent is 9:
1.
5. The wide-temperature-range sodium-ion battery mixed electrolyte of linear ether and cyclic ether according to claim 3, characterized in that... The volume ratio of straight-chain ethers to cyclic ethers in the ether-based solvent is 8:
2.
6. The wide-temperature-range sodium-ion battery mixed electrolyte of linear ether and cyclic ether according to claim 3, characterized in that... The volume ratio of straight-chain ethers to cyclic ethers in the ether-based solvent is 7:
3.
7. The wide-temperature-range sodium-ion battery mixed electrolyte of linear ether and cyclic ether according to claim 3, characterized in that... The volume ratio of straight-chain ethers to cyclic ethers in the ether-based solvent is 6:
4.
8. The wide-temperature-range sodium-ion battery mixed electrolyte of linear ether and cyclic ether according to claim 3, characterized in that... The volume ratio of straight-chain ethers to cyclic ethers in the ether-based solvent is 5:
5.
9. The method for preparing a wide-temperature-range sodium-ion battery mixed electrolyte of linear ether and cyclic ether as described in claim 1, characterized in that... The preparation method is specifically carried out according to the following steps: In an argon-filled glove box, straight-chain ethers and cyclic ethers are added to a container to form a binary solvent. The mixture is stirred until homogeneous to obtain an ether-based solvent. Sodium salt is then added and the mixture is stirred until the sodium salt is completely dissolved in the ether-based solvent to obtain a wide-temperature-range sodium-ion battery electrolyte consisting of straight-chain ethers and cyclic ethers.
10. The application of the wide-temperature-range sodium-ion battery electrolyte consisting of a straight-chain ether and a cyclic ether as described in claim 1, characterized in that... A wide-temperature-range sodium-ion battery electrolyte consisting of a straight-chain ether and a cyclic ether is applied in sodium-ion batteries.