Sodium-ion battery electrolyte as well as preparation method and application thereof

Abstract

The invention discloses a sodium-ion battery electrolyte as well as a preparation method and application thereof, and belongs to the technical field of batteries. The fast-charging electrolyte for the sodium-ion battery comprises sodium salt and an ether solvent, the mixing ratio of the sodium salt to the ether solvent is 0.2-6 mol / L, based on the molar weight of the sodium element in the sodium salt. According to the invention, the advantages of low melting point and low viscosity of the ether solvent are utilized, and proper sodium salt is selected, so that the characteristics that the electronic structure of the ether solvent is relatively dispersed, molecules of the ether solvent and cations (sodium ions) have relatively low binding energy, and a solid electrolyte interface which is rich in inorganic, thin and uniform and has rapid Na < + > transmission kinetics can be generated are exerted; and the rapid charging capability of the battery is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a sodium ion battery electrolyte and a preparation method and application thereof. Background Art

[0002] Due to the current abundant sodium resources and similar working mechanisms to lithium-ion batteries, sodium-ion batteries are considered to be ideal candidates for lithium-ion batteries in large-scale energy storage. Compared with lithium-ion batteries, sodium-ion batteries have advantages in fast charging, and how to further improve the fast charging capability of sodium-ion batteries is a current research hotspot. Among the many factors that affect the fast charging capability of batteries, the electrode / electrolyte interface process is very important. It not only determines the rate and cycle performance of the battery, but also determines the operating voltage, operating temperature range and safety performance. In fact, the electrode / electrolyte interface process includes two key steps: ion desolvation and ion transport in the solid electrolyte interface (SEI). They are both affected by the electrolyte solvation coordination structure and energy, and are crucial to the rate performance of the electrode material. Therefore, achieving interface chemical regulation of the electrode / electrolyte is the key to improving the performance of sodium-ion batteries. Developing a thin and uniform, inorganic-rich, fast Na + The transport kinetics of the SEI electrolyte are extremely important. Summary of the invention

[0003] In view of this, the present invention provides a sodium ion battery electrolyte and a preparation method and application thereof, the main purpose of which is to solve the technical problem of poor electrochemical performance of sodium ion batteries.

[0004] In one aspect, the present invention provides a sodium ion battery electrolyte, wherein components of the sodium ion battery electrolyte include a sodium salt and an ether solvent.

[0005] Optionally, in the sodium ion battery electrolyte, the molar concentration of the sodium salt is 0.2 to 6 mol / L, measured by the molar amount of the sodium element in the sodium salt.

[0006] Optionally, the molar concentration is selected from any value among 0.2 mol / L, 0.3 mol / L, 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, 3.5 mol / L, 4.0 mol / L, 4.5 mol / L, 5.0 mol / L, 5.5 mol / L, 6.0 mol / L or any range value between two of them.

[0007] Optionally, the sodium salt is selected from at least one of phosphate sodium salts, chlorate sodium salts, amine sodium salts and borate sodium salts.

[0008] Optionally, the sodium salt is selected from at least one of sodium hexafluorophosphate, sodium perchlorate, sodium bis(trifluoromethanesulfonyl)imide, sodium bis(pentafluoroethylsulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium bis(oxalatoborate), sodium difluorooxalatoborate and sodium tetrafluoroborate.

[0009] Optionally, the ether solvent is selected from at least one of 1,3-dioxolane, 1,4-dioxolane, tetrahydrofuran, 2-chlorotetrahydrofuran, 3-bromotetrahydrofuran, 3-chlorotetrahydrofuran, 2-methyltetrahydrofuran, 3-hydroxytetrahydrofuran, 3-tetrahydrofuranmethanol, 3-tetrahydrofurancarboxylic acid, 2-chloromethyltetrahydrofuran, octafluorotetrahydrofuran, 3,3,4,4-tetrafluorotetrahydrofuran, 2,5-dihydrofuran, 2,3-dihydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethyl ether, dipropyl ether and dibutyl ether.

[0010] Optionally, the operating voltage range of the sodium ion battery electrolyte is 0.001 ~ 4.5 V.

[0011] The present invention utilizes the advantages of low melting point and low viscosity of ether solvents, selects appropriate sodium salts, takes advantage of the dispersed electronic structure of ether solvents, and the low binding energy between ether solvent molecules and cations (sodium ions), and can produce inorganic-rich, thin and uniform, fast Na + The transfer kinetics of the SEI are characterized, thereby increasing the battery's fast charging capability and improving the battery's cycling performance.

[0012] In a second aspect, the present invention provides a method for preparing the above-mentioned sodium ion battery electrolyte, the method comprising the following steps: The raw materials containing sodium salt and ether solvent are mixed according to a proportion to obtain the sodium ion battery electrolyte.

[0013] In a third aspect, the present invention provides a sodium ion battery, comprising an electrolyte, wherein the electrolyte is the above-mentioned sodium ion battery electrolyte.

[0014] In a fourth aspect, the present invention provides the use of the above-mentioned sodium ion battery electrolyte in the preparation of a sodium ion battery.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1) The present invention utilizes the advantages of low melting point and low viscosity of ether solvents, selects appropriate sodium salts, takes advantage of the dispersed electronic structure of ether solvents, and the low binding energy between ether solvent molecules and cations (sodium ions), and can produce inorganic-rich, thin and uniform, fast Na + The transfer kinetics of the SEI are characterized, thereby increasing the battery's fast charging capability and improving the battery's cycling performance.

[0016] 2) The electrolyte provided by the present invention solves the problems of poor rate performance and short life of sodium ion batteries, improves the wetting performance of the electrolyte on the electrode, reduces the internal resistance of the battery, reduces the electrode polarization during the charge and discharge process, significantly improves the fast charging performance and improves the cycle performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The test diagram of the contact angle between the electrolyte and the electrode of Example 1 of the present invention and the comparative example; Figure 2 It is a rate performance diagram of Example 1 of the present invention and a comparative example; Figure 3 This is a rate performance diagram of Example 2 of the present invention; Figure 4 This is a rate performance diagram of Example 3 of the present invention; Figure 5 It is a cycle performance diagram of Example 1 of the present invention and a comparative example. DETAILED DESCRIPTION

[0018] The present application is further described below in conjunction with specific embodiments. The following are only a few embodiments of the present application, and are not intended to limit the present application in any form. Although the present application discloses the following preferred embodiments, they are not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the above disclosed technical content to make some changes or modifications are equivalent to equivalent implementation cases and are within the scope of the technical solution.

[0019] Unless otherwise specified, the raw materials in the examples of the present application were purchased from commercial sources and used directly without any special treatment.

[0020] Unless otherwise specified, the analysis methods in the examples all adopt conventional settings and conventional analysis methods of instruments or equipment.

[0021] Example 1 In a glove box filled with argon (H2O≤0.01ppm, O2≤0.01ppm), 0.168g of sodium hexafluorophosphate (NaPF6) was dissolved in 1mL of diethylene glycol dimethyl ether and stirred for 20min to obtain a sodium ion battery electrolyte with a sodium salt molar concentration of 1mol / L (i.e., 1 mol of sodium salt and 1L of ether solvent).

[0022] Example 2 In a glove box filled with argon (H2O≤0.01ppm, O2≤0.01ppm), 0.168g of sodium hexafluorophosphate (NaPF6) was dissolved in 1mL of ethylene glycol dimethyl ether and stirred for 20min to obtain a sodium ion battery electrolyte with a sodium salt molar concentration of 1mol / L (i.e., 1mol of sodium salt and 1L of ether solvent).

[0023] Example 3 In a glove box filled with argon (H2O≤0.01ppm, O2≤0.01ppm), 0.168g of sodium hexafluorophosphate (NaPF6) was dissolved in 1mL of tetrahydrofuran and stirred for 20min to obtain a sodium ion battery electrolyte with a sodium salt molar concentration of 1mol / L (i.e., 1mol of sodium salt and 1L of ether solvent).

[0024] Comparative Example In a glove box filled with argon (H2O≤0.01ppm, O2≤0.01ppm), 0.172g of sodium trifluoromethanesulfonate (NaCF3SO3) was dissolved in 1mL of diethylene glycol dimethyl ether and stirred for 20min to obtain a sodium ion battery electrolyte with a sodium salt molar concentration of 1mol / L (i.e., 1 mol of sodium salt and 1L of ether solvent).

[0025] Example 4 (Battery) The assembly process of the sodium||hard carbon button battery is carried out in the order of positive electrode shell, electrolyte, hard carbon electrode sheet, electrolyte, diaphragm, electrolyte, metal sodium sheet, gasket, and negative electrode shell. After the battery is completed, it is packaged and left to stand at room temperature for 6 hours before the electrochemical performance test.

[0026] Among them, the preparation method of the hard carbon electrode is to uniformly disperse hard carbon, conductive agent Super P, and sodium carboxymethyl cellulose in deionized water in a mass ratio of 80:10:10 to make a negative electrode slurry; apply the dispersed negative electrode slurry on a copper foil with a thickness of 12μm, place it in an 80℃ forced air oven to dry, and die-cut it into a hard carbon electrode with a diameter of 12mm.

[0027] The contact angles of Example 1 and Comparative Example were measured as follows: Figure 1 As shown, the contact angle of Example 1 is 18.12, which is less than 23.16 of the comparative example, indicating that the electrolyte prepared by the present invention has better wettability than the comparative electrolyte; further illustrating that the electrolyte prepared by the specific sodium salt and ether solvent selected in Example 1 of the present invention has better wettability.

[0028] The sodium||hard carbon button cells prepared by the electrolytes prepared in Example 1 and the comparative example were tested for rate performance. The test results are as follows: Figure 2 As shown, Example 1 room temperature 3 A g -1At the fast charge and discharge rate, the discharge capacity is still as high as 113 mAhg -1 , while the comparative example is only 25mAhg -1 ; It further illustrates that the electrolyte prepared by the specific sodium salt and ether solvent selected in Example 1 of the present invention has better rate performance.

[0029] The sodium||hard carbon button cell prepared by the electrolyte prepared in Example 2 was tested for rate performance. The test results are as follows: Figure 3 As shown, Example 2 room temperature 2 A g -1 At a fast charge and discharge rate, the discharge capacity is still as high as 207 mAhg -1 ; It further illustrates that the electrolyte prepared by the specific sodium salt and ether solvent selected in Example 2 of the present invention has better rate performance.

[0030] The sodium||hard carbon button cell prepared by the electrolyte prepared in Example 3 was tested for rate performance. The test results are as follows: Figure 4 As shown, Example 3 room temperature 2 A g -1 At fast charge and discharge rates, the discharge capacity is still as high as 191 mAhg -1 ; It further illustrates that the electrolyte prepared by the specific sodium salt and ether solvent selected in Example 3 of the present invention has better rate performance.

[0031] The sodium||hard carbon button cells prepared by the electrolytes prepared in Example 1 and the comparative example were subjected to cycle performance tests. The test results are as follows: Figure 5 As shown, Example 1 room temperature 3 A g -1 The discharge capacity is as high as 118 mAhg after 1000 cycles at a fast charge and discharge rate. -1 , the capacity retention rate is 86%; this further illustrates that the sodium ion battery prepared by the electrolyte prepared by the specific sodium salt and ether solvent selected in Example 1 of the present invention has more stable electrochemical performance and longer life.

[0032] In Examples 1-3 of the present invention, sodium hexafluorophosphate is used as an example to prepare an electrolyte with good effect with a specific ether solvent; other specific salts of the present invention, such as sodium perchlorate, sodium bis(trifluoromethanesulfonyl)imide, sodium bis(pentafluoroethylsulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium bis(oxalatoborate), sodium difluorooxalatoborate and sodium tetrafluoroborate, also have the above-mentioned good electrical properties after being mixed with a specific ether solvent.

[0033] In Examples 1-3 of the present invention, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, and tetrahydrofuran are taken as examples, and are mixed with the above-mentioned specific sodium salt to prepare an electrolyte having good electrical properties; other specific ether solvents of the present invention such as 1,3-dioxolane, 1,4-dioxolane, tetrahydrofuran, 2-chlorotetrahydrofuran, 3-bromotetrahydrofuran, 3-chlorotetrahydrofuran, 2-methyltetrahydrofuran, 3-hydroxytetrahydrofuran, 3-tetrahydrofuranmethanol, 3-tetrahydrofurancarboxylic acid, 2-chloromethyltetrahydrofuran, octafluorotetrahydrofuran, 3,3,4,4-tetrafluorotetrahydrofuran, 2,5-dihydrofuran, 2,3-dihydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethyl ether, dipropyl ether, and dibutyl ether also have the above-mentioned good electrical properties.

[0034] In Examples 1-3 of the present invention, the electrolyte prepared with a mixing ratio of 1 mol / L of the specific sodium salt and the specific ether solvent has good electrochemical properties. Similarly, the electrolyte prepared with a mixing ratio of 0.2-6 mol / L also has good electrochemical properties.

[0035] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A sodium ion battery electrolyte, characterized in that: The components of the sodium ion battery electrolyte include sodium salt and ether solvent.

2. A sodium ion battery electrolyte according to claim 1, characterized in that: In the sodium ion battery electrolyte, the molar concentration of the sodium salt is 0.2 to 6 mol / L, calculated based on the molar amount of the sodium element in the sodium salt.

3. A sodium ion battery electrolyte according to claim 1, characterized in that: The sodium salt is selected from at least one of phosphate sodium salts, chlorate sodium salts, amine sodium salts and borate sodium salts.

4. A sodium ion battery electrolyte according to claim 1, characterized in that: The sodium salt is selected from at least one of sodium hexafluorophosphate, sodium perchlorate, sodium bis(trifluoromethanesulfonyl)imide, sodium bis(pentafluoroethylsulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium bis(oxalatoborate), sodium difluorooxalatoborate and sodium tetrafluoroborate.

5. A sodium ion battery electrolyte according to claim 1, characterized in that: The ether solvent is selected from at least one of 1,3-dioxolane, 1,4-dioxolane, tetrahydrofuran, 2-chlorotetrahydrofuran, 3-bromotetrahydrofuran, 3-chlorotetrahydrofuran, 2-methyltetrahydrofuran, 3-hydroxytetrahydrofuran, 3-tetrahydrofuranmethanol, 3-tetrahydrofurancarboxylic acid, 2-chloromethyltetrahydrofuran, octafluorotetrahydrofuran, 3,3,4,4-tetrafluorotetrahydrofuran, 2,5-dihydrofuran, 2,3-dihydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethyl ether, dipropyl ether and dibutyl ether.

6. A sodium ion battery electrolyte according to claim 1, characterized in that: The operating voltage range of the sodium ion battery electrolyte is 0.001 to 4.5V.

7. The method for preparing a sodium ion battery electrolyte according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: The raw materials containing sodium salt and ether solvent are mixed according to a proportion to obtain the sodium ion battery electrolyte.

8. A sodium ion battery comprising an electrolyte, characterized in that: The electrolyte is the sodium ion battery electrolyte according to any one of claims 1 to 6.

9. Use of the sodium ion battery electrolyte according to any one of claims 1 to 6 in the preparation of a sodium ion battery.

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