Alkali metal ion battery electrolyte additive, electrolyte and preparation method and application thereof

Abstract

The invention relates to the technical field of alkali metal ion batteries, in particular to an alkali metal ion battery electrolyte additive, an electrolyte and a preparation method and application thereof. The alkali metal ion battery electrolyte additive has a chemical structure as shown in a formula (1): in the formula (1), anions are tetrafluoroborate, cations are cations containing 2, 4, 6-triphenylpyridinium salt, and the formula (1) is shown in the description. R represents one of 2-fluorophenyl, 3-fluorophenyl, 4-fluorophenyl, 4-trifluoromethylphenyl, cyclopentane, epoxyhexane, 4-phenylacetonitrile and phenyl methanesulfonate, and n represents an integer from 1 to 8. When the electrolyte containing the electrolyte additive is applied to the alkali metal ion battery, the growth of alkali metal dendrites can be inhibited, the cycle life of the alkali metal battery is prolonged, and the working performance of the alkali metal battery is improved.

Description

Technical Field

[0001] This invention relates to the field of alkali metal ion battery technology, and in particular to an alkali metal ion battery electrolyte additive, electrolyte, preparation method and application thereof. Background Technology

[0002] In alkali metal batteries, sodium-ion batteries and lithium-ion batteries are highly similar in structure and working principle, both belonging to the "rocking chair" type of battery composed of a positive electrode, a negative electrode, an electrolyte, and a separator. The positive and negative electrode materials, as the core components of the battery, directly determine its overall performance indicators; while the electrolyte, as the key medium for alkali metal ion transport, also has a significant impact on battery performance and lifespan. Especially when the positive electrode is charged to a high-voltage region to pursue high energy density, conventional electrolytes are prone to oxidative decomposition on the highly catalytically active positive electrode surface, generating byproducts such as CO2, H2O, and polymers, leading to thickening of the positive electrode / electrolyte interface film and increased impedance. Simultaneously, the significant volume change of the positive electrode material under high voltage further exacerbates the rupture of the positive electrode / electrolyte interface film and the occurrence of parasitic reactions between the electrode and electrolyte, ultimately causing interface reconstruction and capacity decay. Therefore, constructing a stable positive electrode / electrolyte interface under high voltage is one of the core directions for improving battery electrochemical performance.

[0003] Existing electrolyte additives typically improve battery cycle stability by preferentially oxidizing and decomposing to form an interfacial film. However, during long-term high-voltage cycling, the continuous volume change of the cathode particles and the corrosive effect of acidic species under high voltage increase the risk of cathode / electrolyte interfacial film rupture, leading to accelerated electrolyte consumption exposed on the cathode surface and increased capacity decay. Simultaneously, the complex side reactions of additives can easily result in excessively thick interfacial films or fragile nanostructured interfacial layers, leading to the growth of alkali metal dendrites and causing battery short circuits. Furthermore, the narrow electrochemical window of existing additives limits their application scenarios. Therefore, developing novel additives with superior overall performance is crucial for expanding their application range. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned shortcomings of the prior art by providing an alkali metal ion battery electrolyte additive, an electrolyte, its preparation method, and its application.

[0005] The first objective of this invention is to provide an additive for an alkali metal ion battery electrolyte, the additive having the chemical structure shown in formula (1):

[0006] In formula (1), the anion is tetrafluoroborate, the cation is a cation containing 2,4,6-triphenylpyridinium salt, R represents one of 2-fluorophenyl, 3-fluorophenyl, 4-fluorophenyl, 4-trifluoromethylphenyl, cyclopentane, epoxide, 4-phenylacetonitrile, and phenylmethylsulfonate, and n represents an integer from 1 to 8.

[0007] A second objective of this invention is to provide an alkali metal ion battery electrolyte, characterized in that it comprises an organic solvent, an alkali metal salt dissolved in the organic solvent, and an additive as described in claim 1.

[0008] Furthermore, the additive content is 0.5 mg / mL to 20 mg / mL.

[0009] Furthermore, the alkali metal salt is a lithium salt, a sodium salt, or a potassium salt.

[0010] Furthermore, the concentration of the alkali metal salt is 0.5 mol / L to 2 mol / L.

[0011] Further, the alkali metal salt is a lithium salt, a sodium salt, or a potassium salt; wherein the lithium salt is one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium bis(oxalate-borate), and lithium difluorooxalate-borate; the sodium salt is one or more of sodium hexafluorophosphate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium trifluoromethanesulfonate, sodium bis(oxalate-borate), and sodium difluorooxalate-borate; and the potassium salt is one or more of potassium hexafluorophosphate, potassium perchlorate, potassium bis(fluorosulfonyl)imide, potassium bis(trifluoromethanesulfonyl)imide, potassium trifluoromethanesulfonate, potassium bis(oxalate-borate), and potassium difluorooxalate-borate.

[0012] Further, the organic solvent is one or more of the following: ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl formate, methyl acetate, methyl butyrate, ethyl propionate, ethyl butyrate, butyl acetate, methyl propionate, propyl butyrate, trimethyl phosphate, triethyl phosphate, sulfolane, dimethyl sulfone, dimethyl sulfoxide, ethyl methyl sulfone, vinyl sulfite, propylene sulfite, dimethyl sulfite, diethyl sulfite, methyl (2,2,2-trifluoroethyl) carbonate, methyl trifluoroacetate, acetonitrile, 1,3-dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and tetrahydrofuran.

[0013] A third objective of this invention is to provide a method for preparing the alkali metal ion battery electrolyte according to the above-described method, comprising the following steps: S1. In an inert gas atmosphere where the oxygen and water content are both less than 5 ppm, add the alkali metal salt to the organic solvent and mix them evenly to obtain a mixed solvent. S2. Continue to add the additive to the mixed solvent in the above inert gas atmosphere, shake and mix evenly, dissolve and clarify, and let stand for 10 min to 60 min to obtain the electrolyte.

[0014] A fourth object of the present invention is to provide an alkali metal ion battery, comprising a positive electrode, a negative electrode, a separator, and an alkali metal ion battery electrolyte according to the above description. The alkali metal ion electrolyte containing the additives is assembled with the matching positive electrode, negative electrode, and separator to form a battery.

[0015] Furthermore, before electrochemical cycling, the alkali metal ion battery is aged at 20-65℃ for 0.5-10 hours to form an in-situ solid electrolyte interface film on the electrode surface.

[0016] This invention provides an additive for alkali metal ion battery electrolytes. The tetrafluoroborate anion in the additive is compatible with alkali metal ion battery electrolyte systems and facilitates the provision of additional fluorine and boron elements for the solid electrolyte interfacial film formation process. This invention introduces inorganic components NaF and boron salts through the tetrafluoroborate anion in the additive, while simultaneously introducing organic components through the cation containing 2,4,6-triphenylpyridinium salt. Utilizing the benzene ring-rich characteristics of 2,4,6-triphenylpyridinium, a benzene ring π-π dislocation stacking is formed as the core, supplemented by CH…π interactions, providing a diverse organic structure capable of accommodating one-dimensional chains to three-dimensional networks of inorganic salts. This simultaneously and efficiently constructs a uniform, high-mechanical-strength, and highly stable solid electrolyte composite interface rich in organic-inorganic components, effectively inhibiting the growth of alkali metal dendrites. Furthermore, the ordered layered stacking of pyridinium enhances the ion migration rate of alkali metal ions, thereby improving the battery's cycle performance.

[0017] This invention provides an electrolyte containing the electrolyte additives described in this invention. Therefore, when applied to alkali metal ion batteries, this electrolyte can inhibit the growth of alkali metal dendrites and improve the cycle life and performance of the alkali metal batteries. Attached Figure Description

[0018] Figure 1 These are the chemical structural formulas of additives T1, T2, T3, T4, T5, T6, T7, and T8 used in specific embodiments 1-8.

[0019] Figure 2 This is a graph showing the cycle test results of button sodium batteries assembled from the experimental group electrolyte using additive T1 and the control group electrolyte using B1.

[0020] Figure 3This is a graph showing the cycle test results of button sodium batteries assembled from the experimental group electrolyte using additive T2 and the control group electrolyte using B1.

[0021] Figure 4 This is a graph showing the cycle test results of button sodium batteries assembled from the experimental group electrolyte using additive T3 and the control group electrolyte using B1.

[0022] Figure 5 This is a graph showing the cycle test results of button sodium batteries assembled from the experimental group electrolyte using additive T5 and the control group electrolyte using B1.

[0023] Figure 6 This is a graph showing the cycle test results of button sodium batteries assembled from the experimental group electrolyte using additive T6 and the control group electrolyte using B1.

[0024] Figure 7 This is a graph showing the cycle test results of button sodium batteries assembled from the experimental group electrolyte using additive T7 and the control group electrolyte using B1.

[0025] Figure 8 This is a graph showing the cycle test results of button sodium batteries assembled from the experimental group electrolyte using additive T8 and the control group electrolyte using B1.

[0026] Figure 9 The graph shows the rate test results of button sodium batteries assembled using electrolytes from experimental groups (using additives T1, T2, and T4) and control group (using electrolyte B1).

[0027] Figure 10 The NaNi prepared before cycling. 1 / 3 Fe 1 / 3 Mn 1 / 3 Morphology of O2 cathode at 10,000, 20,000, and 30,000x magnification under scanning electron microscopy and EDS elemental analysis results.

[0028] Figure 11 The morphology of the positive electrode of a button cell assembled using the B1 control electrolyte after cycle testing is obtained by scanning electron microscopy at magnifications of 10,000, 20,000, and 30,000 times, along with EDS elemental analysis results.

[0029] Figure 12 The morphology of the positive electrode of a button cell assembled with electrolyte containing additive T8 after cycle testing is obtained by scanning electron microscopy at magnifications of 10,000, 20,000, and 30,000 times, along with the results of EDS elemental analysis.

[0030] Figure 13 It is NaNi before the cycle 1 / 3 Fe 1 / 3 Mn1 / 3 The normalized sodium and fluorine content of the O2 positive electrode, the positive electrode after electrolyte cycling test in the B1 control group, and the positive electrode after electrolyte cycling test in the experimental group using additive T8.

[0031] Figure 14 The graph shows the LSV test results of button sodium batteries assembled from the experimental group electrolyte using additive T8 and the control group electrolyte using B2.

[0032] Figure 15 This is a graph showing the cycle test results of button lithium batteries assembled from the experimental group electrolyte using additive T1 and the control group electrolyte using B2.

[0033] Figure 16 This is a graph showing the cycle test results of button lithium batteries assembled from the experimental group electrolyte using additive T2 and the control group electrolyte using B2.

[0034] Figure 17 This is a graph showing the cycle test results of button lithium batteries assembled from the experimental group electrolyte using additive T6 and the control group electrolyte using B2.

[0035] Figure 18 This is a graph showing the cycle test results of button lithium batteries assembled from the experimental group electrolyte using additive T7 and the control group electrolyte using B2.

[0036] Figure 19 This is a graph showing the cycle test results of button lithium batteries assembled from the experimental group electrolyte using additive T8 and the control group electrolyte using B2.

[0037] Figure 20 The graph shows the LSV test results of button lithium batteries assembled from the electrolyte of the experimental group using additive T1 and the electrolyte of the control group using B2.

[0038] Figure 21 The graph shows the LSV test results of button lithium batteries assembled from the experimental group electrolyte using additive T2 and the control group electrolyte using B2.

[0039] Figure 22 The graph shows the LSV test results of button lithium batteries assembled from the experimental group electrolyte using additive T6 and the control group electrolyte using B2.

[0040] Figure 23 The graph shows the LSV test results of button lithium batteries assembled from the experimental group electrolyte using additive T7 and the control group electrolyte using B2.

[0041] Figure 24The graph shows the LSV test results of button lithium batteries assembled from the experimental group electrolyte using additive T8 and the control group electrolyte using B2.

[0042] Figure 25 The graph shows the rate test results of button lithium batteries assembled from electrolytes using additives T6, T7, and T8, and the control group B2. Detailed Implementation

[0043] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0044] Example 1 This embodiment provides a method for preparing T1-sodium ion battery electrolyte, specifically including: NaPF6 was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 7:3 to make a solution of 1 mol / L. Then, additive T1 (e.g., ...) was added at a ratio of 10 mg / mL. Figure 1 Add the above organic solvent (as shown) and stir at room temperature for 1 hour to obtain the T1-sodium ion battery electrolyte.

[0045] Example 2 This embodiment provides a method for preparing a T2-sodium ion battery electrolyte, specifically including: NaPF6 was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 7:3 to make a solution of 1 mol / L. Then, additive T2 (such as...) was added at a ratio of 10 mg / mL. Figure 1 Add the above organic solvent (as shown) and stir at room temperature for 1 hour to obtain the T2-sodium ion battery electrolyte.

[0046] Example 3 This embodiment provides a method for preparing T3-sodium ion battery electrolyte, specifically including: NaPF6 was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 7:3 to make a solution of 1 mol / L. Then, additive T3 (such as...) was added at a ratio of 10 mg / mL. Figure 1 Add the above organic solvent (as shown) and stir at room temperature for 1 hour to obtain the T3-sodium ion battery electrolyte.

[0047] Example 4 This embodiment provides a method for preparing a T4-sodium ion battery electrolyte, specifically including: NaPF6 was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 7:3 to make a solution concentration of 1 mol / L. Then, additive T4 (such as...) was added at a ratio of 10 mg / mL. Figure 1 (As shown) Add to the above organic solvent, stir at room temperature for 1 hour, and mix evenly to obtain T4-sodium ion battery electrolyte.

[0048] Example 5 This embodiment provides a method for preparing T5-sodium ion battery electrolyte, specifically including: NaPF6 was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 7:3 to make a solution of 1 mol / L. Then, additive T5 (such as...) was added at a ratio of 10 mg / mL. Figure 1 (As shown) Add to the above organic solvent, stir at room temperature for 1 hour, and mix evenly to obtain T5-sodium ion battery electrolyte.

[0049] Example 6 This embodiment provides a method for preparing a T6-sodium ion battery electrolyte, specifically including: NaPF6 was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 7:3 to make a solution of 1 mol / L. Then, additive T6 (such as...) was added at a ratio of 10 mg / mL. Figure 1 Add the above organic solvent (as shown) and stir at room temperature for 1 hour to obtain the T6-sodium ion battery electrolyte.

[0050] Example 7 This embodiment provides a method for preparing a T7-sodium ion battery electrolyte, specifically including: NaPF6 was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 7:3 to make a solution of 1 mol / L. Then, additive T7 (such as...) was added at a ratio of 10 mg / mL. Figure 1 (As shown) Add to the above organic solvent, stir at room temperature for 1 hour, and mix evenly to obtain T7-sodium ion battery electrolyte.

[0051] Example 8 This embodiment provides a method for preparing T8-sodium ion battery electrolyte, specifically including: NaPF6 was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 7:3 to make a solution of 1 mol / L. Then, additive T8 (such as...) was added at a ratio of 10 mg / mL. Figure 1 Add the above organic solvent (as shown) and stir at room temperature for 1 hour to obtain the T8-sodium ion battery electrolyte.

[0052] Meanwhile, to verify the comprehensive performance of the sodium-ion battery electrolyte prepared in the above embodiments, this application provides the following comparative examples for detailed illustration.

[0053] Comparative Example 1 The proportions, preparation operations, and process parameters of Comparative Example 1 are basically the same as those of Example 1, except that no electrolyte additives are added to obtain B1-electrolyte.

[0054] To verify the overall performance of the sodium-ion battery electrolytes prepared in the embodiments and comparative examples of this application, the sodium-ion battery electrolytes were used to make corresponding sodium-ion half-cells for performance testing.

[0055] The sodium-ion battery electrolytes prepared in Examples 1-8 and Comparative Example 1 were used to prepare corresponding sodium-ion half-cells: using NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 is the working electrode (where NaNi is used). 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, conductive agent SuperP, and binder PVDF in a mass ratio of 7:2:1 were used to assemble sodium-ion coin cells by adding 110 μL of the electrolyte from Examples 1-8 or Comparative Example 1 to sodium sheet as the counter electrode.

[0056] This application presents electrochemical cycle performance tests on the fabricated sodium-ion coin cells. The test conditions were constant current charge-discharge, with a voltage range of 2.0V-4.0V. The assembled cells were pre-cycled for 5 cycles at a current density of 0.2C at room temperature, followed by long-cycle charge-discharge testing at a current density of 1C. The test results are shown in Table 1 and Appendix. Figures 2-8 As shown: Table 1. Battery Long Cycle Performance Test Results

[0057] according to Figure 2 As shown in Table 1, compared with the battery assembled with B1-electrolyte, the sodium-ion coin cell assembled with T1-sodium-ion battery electrolyte showed an increase in discharge specific capacity retention from 7.2% to 59.6% after 150 cycles, indicating that the addition of additive T1 at a content of 10 mg / mL can significantly improve the cycling stability of sodium-ion half-cells under high voltage.

[0058] according to Figure 3As shown in Table 1, compared with the battery assembled with B1-electrolyte, the sodium-ion coin cell assembled with T2-sodium-ion battery electrolyte showed an increase in discharge specific capacity retention from 7.2% to 67.5% after 150 cycles, indicating that the addition of additive T2 at a content of 10 mg / mL can significantly improve the cycling stability of sodium-ion half-cells under high voltage.

[0059] according to Figure 4 As shown in Table 1, compared with the battery assembled with B1-electrolyte, the sodium-ion coin cell assembled with T3-sodium-ion battery electrolyte showed an increase in discharge specific capacity retention from 7.2% to 65.2% after 150 cycles, indicating that the addition of additive T3 at a content of 10 mg / mL can significantly improve the cycling stability of sodium-ion half-cells under high voltage.

[0060] according to Figure 5 As shown in Table 1, compared with the battery assembled with B1-electrolyte, the sodium-ion coin cell assembled with T5-sodium-ion battery electrolyte showed an increase in discharge specific capacity retention from 7.2% to 89.6% after 150 cycles, indicating that the addition of additive T5 at a content of 10 mg / mL can significantly improve the cycling stability of sodium-ion half-cells under high voltage.

[0061] according to Figure 6 As shown in Table 1, compared with the battery assembled with B1-electrolyte, the sodium-ion coin cell assembled with T6-sodium-ion battery electrolyte showed an increase in discharge specific capacity retention from 7.2% to 82.5% after 150 cycles, indicating that the addition of additive T6 at a content of 10 mg / mL can significantly improve the cycling stability of sodium-ion half-cells under high voltage.

[0062] according to Figure 7 As shown in Table 1, compared with the battery assembled with B1-electrolyte, the sodium-ion coin cell assembled with T7-sodium-ion battery electrolyte showed an increase in discharge specific capacity retention from 7.2% to 90.6% after 150 cycles, indicating that the addition of additive T7 at a content of 10 mg / mL can significantly improve the cycling stability of sodium-ion half-cells under high voltage.

[0063] according to Figure 8 As shown in Table 1, compared with the battery assembled with B1-electrolyte, the sodium-ion coin cell assembled with T8-sodium-ion battery electrolyte showed an increase in discharge specific capacity retention from 7.2% to 94.3% after 150 cycles, indicating that the addition of additive T8 at a content of 10 mg / mL can significantly improve the cycling stability of sodium-ion half-cells under high voltage.

[0064] This application describes electrochemical rate performance testing of the fabricated sodium-ion coin cells. The test conditions were constant current charge-discharge, with a voltage range of 2.0V-4.1V. The assembled cells were cycled five times at current densities of 0.2C, 1C, 2C, 5C, and 0.2C at room temperature. Test results are attached. Figure 9 As shown, under high current density, the experimental groups containing additives T1, T2, and T4 have a higher capacity retention rate than the B1 control group, indicating that the SEI film formed by the experimental groups containing additives is rich in inorganic components such as NaF and has good ionic conductivity.

[0065] This application presents the morphology of the positive electrode sheets of T8 and B1 sodium-ion coin cells after cycle performance testing, as well as the morphology of the uncycled positive electrode sheets, under scanning electron microscopy and EDS energy dispersive spectroscopy. Test results are attached. Figures 10-13 As shown, the electrode of the B1 control group after cycling showed obvious sodium dendrite growth in morphological characterization, and elemental analysis showed that the sodium content increased by 4.3%. The electrode of the T8 experimental group after cycling showed no sodium dendrite growth in morphological characterization and the surface was smoother than that of the uncycled electrode. Elemental analysis showed that the sodium content increased by 3.8% and the fluorine content increased by 4.3%, proving that the SEI film formed on the positive electrode surface by the electrolyte with additives is rich in inorganic components such as NaF.

[0066] This application describes the LSV testing of the fabricated T8-sodium-ion coin cell: the test range is 0-6V, and the scan rate is 1 mV / s. Test results are attached. Figure 14 As shown, the addition of T8 additive can increase the oxidation potential of the electrolyte from 4.0V in B1 to over 4.5V.

[0067] Therefore, the electrolyte prepared by the electrolyte additive selected in this application is compatible with NaNi. 1 / 3 Fe 1 / 3 Mn 1 / 3 The O2 system has good compatibility and can effectively form an excellent solid electrolyte interface rich in organic and inorganic components, inhibiting the growth of sodium dendrites, promoting sodium ion conduction in the SEI, and improving the cycle stability of sodium-ion batteries.

[0068] Example 9 This embodiment provides a method for preparing T1-lithium-ion battery electrolyte, specifically including: LiPF6 was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 6:4 to make the solution 2.0 mol / L. Then, additive T1 was added to the above organic solvent at a ratio of 20 mg / mL. The mixture was stirred at room temperature for 0.5 h and mixed evenly to obtain T1-lithium-ion battery electrolyte.

[0069] Example 10 This embodiment provides a method for preparing T2-lithium-ion battery electrolyte, specifically including: LiPF6 was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 6:4 to make the solution 1.5 mol / L. Then, additive T2 was added to the above organic solvent at a ratio of 20 mg / mL. The mixture was stirred at room temperature for 0.5 h and mixed evenly to obtain T12-lithium-ion battery electrolyte.

[0070] Example 11 This embodiment provides a method for preparing T6-lithium-ion battery electrolyte, specifically including: LiPF6 was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 1:1 to make the solution 1.2 mol / L. Then, additive T6 was added to the above organic solvent at a ratio of 20 mg / mL. The mixture was stirred at room temperature for 0.5 h and mixed evenly to obtain T6-lithium-ion battery electrolyte.

[0071] Example 12 This embodiment provides a method for preparing T7-lithium-ion battery electrolyte, specifically including: LiPF6 was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 1:1 to make the solution 1.2 mol / L. Then, additive T7 was added to the above organic solvent at a ratio of 20 mg / mL. The mixture was stirred at room temperature for 0.5 h and mixed evenly to obtain T7-lithium-ion battery electrolyte.

[0072] Example 13 This embodiment provides a method for preparing T8-lithium-ion battery electrolyte, specifically including: LiPF6 was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 1:1 to make the solution 1.2 mol / L. Then, additive T8 was added to the above organic solvent at a ratio of 20 mg / mL. The mixture was stirred at room temperature for 0.5 h and mixed evenly to obtain T8-lithium-ion battery electrolyte.

[0073] Comparative Example 2 The proportions, preparation operations, and process parameters of Comparative Example 1 are basically the same as those of Example 8, except that no electrolyte additives are added to obtain B2-lithium-ion battery electrolyte.

[0074] This application presents electrochemical cycle performance tests on the fabricated sodium-ion coin cells. The test conditions were constant current charge-discharge, with a voltage range of 3.0V-4.3V. The assembled cells were pre-cycled for 5 cycles at a current density of 0.2C at room temperature, followed by long-cycle charge-discharge testing at a current density of 1C. The test results are shown in Table 2 and Appendix. Figures 15-19 As shown: Table 2. Battery Long Cycle Performance Test Results

[0075] according to Figures 15-19 As shown in Table 2, compared with the battery assembled with B2-lithium-ion electrolyte, the sodium-ion coin cell assembled with T1, T2, T6, T7, and T8-lithium-ion battery electrolytes showed an increase in discharge specific capacity retention from 71.8% to over 91% after 150 cycles. This indicates that the addition of additives T1, T2, T6, T7, and T8 at a concentration of 20 mg / mL can significantly improve the cycling stability of lithium-ion half-cells under high voltage.

[0076] This application describes the LSV testing of fabricated T1, T2, T6, T7, and T8 lithium-ion coin cells: the test range is 0-6V, and the scan rate is 1 mV / s. Test results are attached. Figures 20-24 As shown, the addition of additives T1, T2, T6, T7, and T8 can increase the oxidation potential of the electrolyte from 3.2 V in B1 to over 4.5 V.

[0077] This application presents electrochemical rate performance tests on the fabricated T6, T7, T8, and B2-lithium-ion coin cells. The test conditions were constant current charge-discharge, with a voltage range of 3.0V-4.3V. The assembled cells were cycled five times at current densities of 0.2C, 1C, 2C, 5C, and 0.2C at room temperature. Test results are attached. Figure 25 As shown, under high current density, the experimental groups containing additives T6, T7, and T8 have a higher capacity retention rate than the B2 control group, indicating that the SEI film formed by the experimental groups containing additives is rich in inorganic components such as LiF and has good ionic conductivity.

[0078] The alkali metal ion battery electrolytes or alkali metal electrodes provided in other embodiments were tested using the same method described above. Compared to the unmodified electrolytes or electrodes, all showed an inhibitory effect on dendrite growth, as well as higher capacity retention and better cycle stability. This further demonstrates that the 2,4,6-triphenylpyridinium tetrafluoroborate proposed in this invention can enhance the mechanical strength of the solid electrolyte interface film and effectively inhibit the growth of alkali metal dendrites.

[0079] For any points not covered above, existing technologies shall apply.

[0080] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. An additive for alkali metal ion battery electrolyte, characterized in that, The additive possesses the chemical structure shown in formula (1): In formula (1), the anion is tetrafluoroborate, the cation is a cation containing 2,4,6-triphenylpyridinium salt, R represents one of 2-fluorophenyl, 3-fluorophenyl, 4-fluorophenyl, 4-trifluoromethylphenyl, cyclopentane, epoxide, 4-phenylacetonitrile, and phenylmethylsulfonate, and n represents an integer from 1 to 8.

2. An alkali metal ion battery electrolyte, characterized in that, It includes an organic solvent, an alkali metal salt dissolved in the organic solvent, and the additive as described in claim 1.

3. The alkali metal ion battery electrolyte according to claim 2, characterized in that, The additive content is 0.5 mg / mL to 20 mg / mL.

4. The alkali metal ion battery electrolyte according to claim 2, characterized in that, The alkali metal salt is a lithium salt, a sodium salt, or a potassium salt.

5. The alkali metal ion battery electrolyte according to claim 2, characterized in that, The concentration of the alkali metal salt is 0.5 mol / L to 2 mol / L.

6. The alkali metal ion battery electrolyte according to claim 2, characterized in that, The alkali metal salt is a lithium salt, sodium salt, or potassium salt; wherein the lithium salt is one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium bis(oxalate-borate), and lithium difluorooxalate-borate; the sodium salt is one or more of sodium hexafluorophosphate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium trifluoromethanesulfonate, sodium bis(oxalate-borate), and sodium difluorooxalate-borate; and the potassium salt is one or more of potassium hexafluorophosphate, potassium perchlorate, potassium bis(fluorosulfonyl)imide, potassium bis(trifluoromethanesulfonyl)imide, potassium trifluoromethanesulfonate, potassium bis(oxalate-borate), and potassium difluorooxalate-borate.

7. The alkali metal ion battery electrolyte according to claim 2, characterized in that, The organic solvent is one or more of the following: ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl formate, methyl acetate, methyl butyrate, ethyl propionate, ethyl butyrate, butyl acetate, methyl propionate, propyl butyrate, trimethyl phosphate, triethyl phosphate, sulfolane, dimethyl sulfone, dimethyl sulfoxide, ethyl methyl sulfone, ethylene sulfite, propylene sulfite, dimethyl sulfite, diethyl sulfite, methyl (2,2,2-trifluoroethyl) carbonate, methyl trifluoroacetate, acetonitrile, 1,3-dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and tetrahydrofuran.

8. A method for preparing an alkali metal ion battery electrolyte according to any one of claims 2 to 7, characterized in that, Includes the following steps: S1. In an inert gas atmosphere where the oxygen and water content are both less than 5 ppm, add the alkali metal salt to the organic solvent and mix them evenly to obtain a mixed solvent. S2. Continue to add the additive to the mixed solvent in the above inert gas atmosphere, shake and mix evenly, dissolve and clarify, and let stand for 10 min to 60 min to obtain the electrolyte.

9. An alkali metal ion battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and an alkali metal ion battery electrolyte according to claims 2 to 7.

10. An alkali metal ion battery as described in claim 9, characterized in that, Before electrochemical cycling, the alkali metal ion battery is aged at 20-65℃ for 0.5-10 h to form an in-situ solid electrolyte interface film on the electrode surface.

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