A sodium-ion battery electrolyte additive, electrolyte and sodium-ion battery

Abstract

The application discloses a kind of sodium ion battery electrolyte additive, electrolyte and sodium ion battery, belong to battery energy storage technical field.The sodium ion battery electrolyte additive provided in the application has the chemical structure shown in formula (1):R ‑ Anion, hexafluorophosphate, hexafluoroarsenate, tetrafluoroborate, perchlorate, trifluoromethylsulfonate, bis (fluorosulfonyl) imide, bis (trifluoromethylsulfonyl) imide, difluoroboric acid oxalate, bisoxalate borate, bis (salicylic acid-2-) borate, salicylic acid hydroquinone borate, tetraphenylborate, 4, 5-dicyano-2- (trifluoromethyl) imidazole acid, 4, 5-dicyano-2- (pentafluoroethyl) imidazole acid. Through the introduction of these additives, not only can realize the cycle stability of sodium ion battery under high pressure, but also improve the electrochemical performance of sodium ion battery, at the same time, can improve the mechanical properties of positive electrode / electrolyte interface, has good industrial application prospect.

Description

Technical Field

[0001] This application belongs to the field of battery energy storage technology, and particularly relates to a sodium-ion battery electrolyte additive, electrolyte and sodium-ion battery. Background Technology

[0002] Sodium-ion batteries, as a next-generation rechargeable battery, have the advantages of abundant resources and low cost, and their working principle is similar to that of lithium-ion batteries, attracting increasing attention and research. However, the energy density of sodium-ion batteries is severely limited by the larger molecular weight of sodium (22.99 g / mol vs. 6.94 g / mol) and the higher potential (-2.71 V vs. -3.04 V relative to the standard hydrogen electrode). To obtain high energy density, the positive electrode needs to be charged to a high voltage region (>4.0 V vs. Na). + While electrolytes can facilitate the removal of more sodium ions (using a 'Na' combination), conventional electrolytes at high voltages are prone to oxidative decomposition on the highly catalytically active cathode surface, producing byproducts such as CO2, H2O, and polymers. This leads to problems like cathode / electrolyte interface (CEI) film thickening and increased impedance. Furthermore, the significant volume change of the cathode material at high voltages further exacerbates CEI film rupture and parasitic electrode / electrolyte reactions, resulting in interface reconstruction and capacity decay. Therefore, constructing a stable cathode / electrolyte interface under high voltage is crucial for improving battery electrochemical performance.

[0003] Existing electrolyte additives generally 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 corrosion of acid species under high voltage pose a risk of CEI (electrolyte interface) rupture. Consequently, electrolyte consumption exposed on the cathode surface intensifies, accelerating capacity decay. Furthermore, electrolytes prepared with existing additives have a narrow electrochemical window, thus limiting their application. Therefore, there is a need to develop additives with superior overall performance to broaden their application range. Summary of the Invention

[0004] This application discloses a sodium-ion battery electrolyte additive, an electrolyte, and a sodium-ion battery, aiming to solve the technical problem of instability of existing sodium-ion electrolyte additives under high voltage.

[0005] To achieve the above objectives, the technical solution of this application is:

[0006] The first aspect of this application provides a sodium-ion battery electrolyte additive, the additive having the chemical structure shown in formula (1):

[0007]

[0008] In equation (1), R -It is an anion, and is one of the following: hexafluorophosphate, hexafluoroarsinate, tetrafluoroborate, perchlorate, trifluoromethanesulfonate, bis(fluorosulfonyl)imide, bis(trifluoromethanesulfonyl)imide, difluorooxalateborate, bis(salicylic acid-2-)borate, salicylic acid hydroquinone borate, tetraphenylborate, 4,5-dicyano-2-(trifluoromethyl)imidazolium, and 4,5-dicyano-2-(pentafluoroethyl)imidazolium.

[0009] Preferably, in conjunction with the first aspect, the additive has the chemical structure shown in formula (1): R - It is an anion, one of hexafluorophosphate, tetrafluoroborate, and difluorooxalate borate.

[0010] The second aspect of this application provides a sodium-ion battery electrolyte, comprising an organic solvent, a sodium salt dissolved in the organic solvent, and the sodium-ion battery electrolyte additive described in the first aspect.

[0011] The additive content is 0.5-5.0 wt%.

[0012] The sodium salt concentration is 0.5-2.0 mol / L.

[0013] Preferably, in conjunction with the second aspect, the additive content is 1.0-3.0 wt%.

[0014] Preferably, in conjunction with the second aspect, the sodium salt concentration is 1.0-1.2 mol / L.

[0015] Preferably, in conjunction with the second aspect, the sodium salt is one or more of sodium hexafluorophosphate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium trifluoromethanesulfonate, sodium bis(oxalato)borate, and sodium difluorooxalato)borate.

[0016] Preferably, in conjunction with the second aspect, the sodium salt is one or a combination of sodium hexafluorophosphate and sodium perchlorate.

[0017] Preferably, in conjunction with the second aspect, 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 sulfoxide, ethyl methyl sulfone, vinyl sulfite, propylene sulfite, dimethyl sulfite, diethyl sulfite, methyl (2,2,2-trifluoroethyl) carbonate, methyl trifluoroacetate, acetonitrile, and 1,3-dioxolane.

[0018] The third aspect of this application provides the application of the sodium-ion battery electrolyte of the second aspect in sodium-ion batteries.

[0019] The fourth aspect of this application provides a sodium-ion battery, including a positive electrode, a negative electrode, a separator, and the sodium-ion battery electrolyte described in the third aspect.

[0020] Compared with the prior art, the advantages or beneficial effects of the embodiments of this application include at least the following:

[0021] The sodium-ion battery electrolyte additive provided in this application is composed of tetrabutylammonium cations and anions. Firstly, the tetrabutylammonium cations in the additive can capture and fix the active oxygen released by the cathode material under high-voltage conditions, inhibiting the nucleophilic attack or catalytic decomposition of the solvent by the active components in the cathode material, reducing interfacial parasitic reactions, and improving the high-voltage cycle stability of the sodium-ion battery. Secondly, the anions in the additive compete with the anions in the sodium salt, breaking the strong interaction between ion pairs and helping to improve the electrochemical performance of the sodium-ion battery. Thirdly, it can form an interfacial film rich in inorganic components such as F and N on the cathode surface, which can not only inhibit the continuous decomposition of the electrolyte but also prevent electrode structure damage and metal ion dissolution, improving the mechanical properties of the cathode / electrolyte interface. Meanwhile, the additive provided in this application has an accurate and stable structure under high-voltage conditions, is diverse in type, has good solubility, and is economically efficient, showing good prospects for industrial application. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 Electrochemical window diagrams of the A1-sodium ion battery electrolyte and B1-electrolyte prepared for embodiments of this application;

[0024] Figure 2 Sodium-ion coin cells (NaNi) made from the Al-sodium-ion battery electrolyte and B1-electrolyte prepared in the embodiments of this application 1 / 3 Fe 1 / 3 Mn 1 / 3 Long-cycle performance of O2||Na) at 1C rate;

[0025] Figure 3 Sodium-ion coin cells (NaNi) made from A2-sodium-ion battery electrolyte and B1-electrolyte prepared according to embodiments of this application 1 / 3 Fe 1 / 3 Mn1 / 3 Long-cycle performance of O2||Na) at 1C rate;

[0026] Figure 4 Sodium-ion coin cells (NaNi) made from the A3-sodium-ion battery electrolyte and B1-electrolyte prepared in the embodiments of this application 1 / 3 Fe 1 / 3 Mn 1 / 3 Long-cycle performance of O2||Na) at 1C rate;

[0027] Figure 5 The long-cycle performance of sodium-ion coin cells (Na3V2(PO4)2F3||Na) prepared with A4-sodium-ion battery electrolyte and B1-electrolyte prepared for the embodiments of this application at 1C rate;

[0028] Figure 6 The long-cycle performance of sodium-ion coin cells (Na3V2(PO4)2F3||Na) prepared with A5-sodium-ion battery electrolyte and B1-electrolyte prepared for the embodiments of this application at 1C rate;

[0029] Figure 7 The image shows the long-cycle performance of a sodium-ion coin cell (Na3V2(PO4)2F3||Na) made from the A6-sodium-ion battery electrolyte and B1-electrolyte prepared for the embodiments of this application at a 1C rate. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0031] In the following description of this embodiment, the term "and / or" is used to describe the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, B existing alone, and A and B existing simultaneously. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0032] In the following description of this embodiment, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0033] Those skilled in the art should understand that, in the following description of the embodiments of this application, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0034] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0035] It should be noted that all raw materials and reagents in the embodiments of this application were purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0036] In a first aspect, embodiments of this application provide a sodium-ion battery electrolyte additive, the additive having the chemical structure shown in formula (1):

[0037]

[0038] In equation (1), R - It is an anion, and is one of the following: hexafluorophosphate, hexafluoroarsinate, tetrafluoroborate, perchlorate, trifluoromethanesulfonate, bis(fluorosulfonyl)imide, bis(trifluoromethanesulfonyl)imide, difluorooxalateborate, bis(salicylic acid-2-)borate, salicylic acid hydroquinone borate, tetraphenylborate, 4,5-dicyano-2-(trifluoromethyl)imidazolium, and 4,5-dicyano-2-(pentafluoroethyl)imidazolium.

[0039] Firstly, the tetrabutylammonium cation in the additive can capture and fix reactive oxygen species in the electrolyte under high pressure, reducing electrolyte oxidation caused by reactive oxygen species, inhibiting nucleophilic attack or catalytic decomposition of the solvent by the active components in the cathode material, reducing interfacial parasitic reactions, and contributing to the stable cycle performance of sodium-ion batteries under high pressure. Secondly, the anions in the additive compete with the anions in the sodium salt, breaking the strong interaction between ion pairs and helping to improve the electrochemical performance of sodium-ion batteries. Thirdly, it can form an interfacial film rich in inorganic components such as F and N on the cathode surface, which can not only inhibit the continuous decomposition of the electrolyte, but also prevent electrode structure damage and metal ion dissolution, improving the mechanical properties of the cathode / electrolyte interface. Meanwhile, the additives provided in this application have accurate and stable structures under high pressure, are diverse in type, have good solubility, and are highly economical, showing good prospects for industrial application.

[0040] It should be noted that R - It is an anion, preferably hexafluorophosphate (PF6). - ), hexafluoroarsenate (AsF6) - ), tetrafluoroborate (BF4) - ), perchlorate (ClO4) - ), trifluoromethanesulfonate (OTF) - ), bis(fluorosulfonyl)imide (FSI) - ), bis(trifluoromethanesulfonyl)imide (TFSI) - ), difluorooxalate borate (DFOB) - ), bis(oxalate)borate (BOB) - ), bis(salicylic acid-2-)borate (BSB) - ), salicylic acid hydroquinone borate (BDSB) - ), tetraphenylborate (BPh4) - ), 4,5-dicyano-2-(trifluoromethyl)imidazolium (TDI) - ) and 4,5-dicyano-2-(pentafluoroethyl)imidazolium (PDI) - The additive is one of the following, more preferably one of hexafluorophosphate, tetrafluoroborate, and difluorooxalate borate. The additive provided in this application can improve the working voltage window of the electrolyte, enabling the electrolyte to operate normally within a wider voltage range of 0-5V. Since the working voltage of sodium-ion batteries is generally 1.5-4.5V, the electrolyte prepared by adding the additive has higher compatibility with sodium-ion batteries.

[0041] It should be noted that R in the additive provided in this application -Anions have strong electron-withdrawing properties, which can delocalize the negative charge on the N atom in the structure. The strong ion association and pairing makes sodium ions easy to dissociate, promotes the migration of sodium ions between the positive and negative electrodes, and is beneficial to the improvement of kinetic performance.

[0042] Secondly, this application provides a sodium-ion battery electrolyte, comprising an organic solvent, a sodium salt dissolved in the organic solvent, and the sodium-ion battery electrolyte additive described in the first aspect; the additive content is preferably 0.5-5.0 wt%, more preferably 1.0-3.0 wt%; the sodium salt concentration is preferably 0.5-2.0 mol / L, more preferably 1.0-1.2 mol / L. By limiting the amount of additive added, the electrolyte can be endowed with a wide electrochemical window and good thermal stability; by controlling the sodium salt concentration, the electrochemical performance and safety of the sodium-ion battery can be significantly improved, while reducing costs and enhancing the overall performance of the sodium-ion battery.

[0043] In this embodiment, the sodium salt is preferably one or more of sodium hexafluorophosphate (NaPF6), sodium perchlorate (NaClO4), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium trifluoromethanesulfonate (NaOTf), sodium bis(oxalatoborate) (NaBOB), and sodium difluorooxalatoborate (NaDFOB), more preferably sodium hexafluorophosphate and sodium perchlorate. The selection of these sodium salts ensures good ionic conductivity, and the raw materials are common, readily available, widely sourced, and inexpensive.

[0044] In this embodiment, the organic solvent is preferably one or more of the following: ethylene carbonate (EC), fluoroethylene carbonate, vinylene carbonate, propylene carbonate (PC), butenyl carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), methyl propyl carbonate (MPC), methyl formate, methyl acetate, methyl butyrate, ethyl propionate, ethyl butyrate, butyl acetate, methyl propionate, propyl butyrate, trimethyl phosphate, triethyl phosphate, sulfolane, dimethyl sulfoxide, dimethyl sulfoxide, ethyl methyl sulfone, vinyl sulfite, propylene sulfite, dimethyl sulfite, diethyl sulfite, methyl (2,2,2-trifluoroethyl) carbonate, methyl trifluoroacetate, acetonitrile, and 1,3-dioxolane. The selection of these organic solvents is beneficial for improving the kinetic performance of sodium-ion batteries, preventing sodium deposition, and optimizing their impedance performance.

[0045] Thirdly, this application provides the application of the sodium-ion battery electrolyte in sodium-ion batteries. The sodium-ion battery electrolyte possesses excellent performance, thus endowing sodium-ion batteries with advantages such as high charge-discharge efficiency, good cycle performance, high safety, a wide electrochemical window, and low cost, and has broad application prospects.

[0046] The fourth aspect of this application provides a sodium-ion battery, including a positive electrode, a negative electrode, a separator, and the sodium-ion battery electrolyte described in the third aspect.

[0047] It should be noted that the positive electrode material is selected from conventional positive electrode active materials in the art, namely one or more of transition metal layered oxides and their derivatives, polyanionic compounds, Prussian blue, and Prussian blue analogues. The negative electrode material is selected from conventional negative electrode active materials in the art, namely one or more of carbon materials, metallic sodium, alloy materials, transition metal oxides, transition metal sulfides, transition metal phosphides, and transition metal selenides. The separator is selected from conventional separator materials in the art, including one or more single-layer or multi-layer films of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.

[0048] It should be noted that this application does not impose any particular limitations on the sodium-ion battery electrolyte, the positive electrode, the separator and the negative electrode of the sodium-ion battery, or the preparation method of the sodium-ion battery; any technical solutions known in the art may be used.

[0049] The following examples and comparative examples were all prepared in a glove box filled with argon gas.

[0050] The technical solution of this application will be further described below with reference to specific embodiments.

[0051] Example 1

[0052] This embodiment provides a method for preparing an Al-sodium ion battery electrolyte, specifically including:

[0053] NaPF6 was dissolved in a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) in a volume ratio of 1:1 to make the solution 1 mol / L. Then, tetrabutylammonium hexafluorophosphate (1.0 wt%) of the total mass of the electrolyte was added, and the mixture was stirred at room temperature for 12 h until homogeneous to obtain the Al-sodium ion battery electrolyte.

[0054] Example 2

[0055] This embodiment provides a method for preparing an A2-sodium ion battery electrolyte, specifically including:

[0056] NaPF6 was dissolved in a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) in a volume ratio of 1:1 to make the solution 1 mol / L. Then, 2.0 wt% of tetrabutylammonium hexafluorophosphate was added and stirred at room temperature for 12 h. The mixture was stirred until homogeneous to obtain the A2-sodium ion battery electrolyte.

[0057] Example 3

[0058] This embodiment provides a method for preparing an A3-sodium ion battery electrolyte, specifically including:

[0059] NaPF6 was dissolved in a 1:1 mixture of ethylene carbonate (EC) and propylene carbonate (PC) to make a solution of 1 mol / L. Then, 3.0 wt% of tetrabutylammonium hexafluorophosphate was added and stirred at room temperature for 12 h until homogeneous to obtain the A3-sodium ion battery electrolyte.

[0060] Example 4

[0061] This embodiment provides a method for preparing an A4-sodium ion battery electrolyte, specifically including:

[0062] NaPF6 was dissolved in a 1:1 mixture of ethylene carbonate (EC) and propylene carbonate (PC) to make a solution of 1 mol / L. Then, 1.0 wt% of tetrabutylammonium tetrafluoroborate was added and stirred at room temperature for 12 h until homogeneous to obtain the A4-sodium ion battery electrolyte.

[0063] Example 5

[0064] This embodiment provides a method for preparing A5-sodium ion battery electrolyte, specifically including:

[0065] NaPF6 was dissolved in a 1:1 mixture of ethylene carbonate (EC) and propylene carbonate (PC) to make a solution of 1 mol / L. Then, 2.0 wt% of tetrabutylammonium tetrafluoroborate was added and stirred at room temperature for 12 h until homogeneous to obtain the A5-sodium ion battery electrolyte.

[0066] Example 6

[0067] This embodiment provides a method for preparing an A6-sodium ion battery electrolyte, specifically including:

[0068] NaPF6 was dissolved in a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) in a volume ratio of 1:1 to make the solution 1 mol / L. Then, 3.0 wt% of tetrabutylammonium tetrafluoroborate was added and stirred at room temperature for 12 h to obtain the A6-sodium ion battery electrolyte.

[0069] Example 7

[0070] This embodiment provides a method for preparing an A7-sodium ion battery electrolyte, specifically including:

[0071] NaPF6 was dissolved in a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) in a volume ratio of 1:1 to make the solution 1.2 mol / L. Then, tetrabutylammonium hexafluorophosphate (1.0 wt%) of the total mass of the electrolyte was added and stirred at room temperature for 12 h. The mixture was stirred until homogeneous to obtain the A7-sodium ion battery electrolyte.

[0072] Example 8

[0073] This embodiment provides a method for preparing an A8-sodium ion battery electrolyte, specifically including:

[0074] NaClO4 was dissolved in a mixed solvent of vinylene carbonate and diethyl carbonate in a volume ratio of 1:1 to make the solution 1.0 mol / L. Then, tetrabutylammonium hexafluorophosphate (3.0 wt% of the total mass of the electrolyte) was added and stirred at room temperature for 12 h. The mixture was stirred until homogeneous to obtain the A8-sodium ion battery electrolyte.

[0075] Example 9

[0076] This embodiment provides a method for preparing an A9-sodium ion battery electrolyte, specifically including:

[0077] NaClO4 was dissolved in a mixed solvent of vinylene carbonate and diethyl carbonate in a volume ratio of 1:1 to make the solution 1.2 mol / L. Then, 5.0 wt% of tetrabutyldifluorooxalate-borate ammonium was added and stirred at room temperature for 12 h until the mixture was homogeneous to obtain the A9-sodium ion battery electrolyte.

[0078] 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.

[0079] Comparative Example 1

[0080] 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.

[0081] 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.

[0082] The electrolytes prepared in Example 1 and Comparative Example 1 of this application were subjected to electrochemical window testing, according to... Figure 1As shown, with the increase of voltage (horizontal axis), the B1- electrolyte prepared in Comparative Example 1 begins to show an oxidation peak near 4.3V, and with the increase of voltage, a large oxidation peak appears near 4.5V, indicating that the electrolyte is oxidized and decomposed. In contrast, the Al-sodium ion battery electrolyte prepared in Example 1 only shows an increase in current when the voltage exceeds 5V, indicating that the Al-sodium ion battery electrolyte does not undergo significant decomposition below 5V, demonstrating high antioxidant capacity and a significantly widened voltage window.

[0083] The sodium-ion battery electrolytes prepared in Examples 1-3, 7-9 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 as the working electrode). 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, conductive agent Super P, and binder PVDF were in a mass ratio of 8:1:1. Sodium sheet was used as the counter electrode. 60 μL of the electrolyte from Examples 1-3 and Comparative Example 1 were added to assemble a sodium-ion coin cell-1.

[0084] The sodium-ion battery electrolytes prepared in Examples 4-6 and Comparative Example 1 were used to prepare corresponding sodium-ion half-cells: sodium vanadium fluorophosphate Na3V2(PO4)2F3 (NVPF) was used as the working electrode (wherein, the mass ratio of sodium vanadium fluorophosphate, conductive agent Super P, and binder PVDF was 8:1:1), and sodium sheet was used as the counter electrode. 60 μL of the electrolytes from Examples 4-6 and Comparative Example 1 were added to each electrode, and the two were assembled into sodium-ion coin cell-2.

[0085] This application presents electrochemical performance tests on the fabricated sodium-ion coin cells. The test conditions were constant current charge-discharge, with a voltage range of 2.0V-4.3V. The assembled cells were pre-cycled for 3 cycles at a current density of 0.1C at room temperature, followed by long-cycle charge-discharge testing at a current density of 1C. The test results are shown in Table 1.

[0086] Table 1. Battery Long Cycle Performance Test Results

[0087]

[0088] according to Figure 2 As shown in Table 1, compared with the battery assembled with B1-electrolyte, the sodium-ion coin cell-1 assembled with A1-sodium-ion battery electrolyte showed an increase in discharge specific capacity retention from 46.9% to 77.3% after 150 cycles, indicating that the addition of 1.0wt% tetrabutylammonium hexafluorophosphate can significantly improve the cycling stability of sodium-ion half-cells under high voltage.

[0089] according to Figure 3 As shown in Table 1, compared with the battery assembled with B2- electrolyte, the sodium-ion coin cell-1 assembled with A2- sodium-ion battery electrolyte showed an increase in discharge specific capacity retention from 46.9% to 75.1% after 150 cycles, indicating that the addition of 2.0 wt% tetrabutylammonium hexafluorophosphate can significantly improve the cycling stability of sodium-ion half-cells under high voltage.

[0090] according to Figure 4 As shown in Table 1, compared with the battery assembled with B3-electrolyte, the sodium-ion coin cell-1 assembled with A3-sodium-ion battery electrolyte showed an increase in discharge specific capacity retention from 46.9% to 72.6% after 150 cycles, indicating that the addition of 3.0wt% tetrabutylammonium hexafluorophosphate can significantly improve the cycling stability of sodium-ion half-cells under high voltage.

[0091] according to Figure 5 As shown in Table 1, compared with the battery assembled with B4-electrolyte, the sodium-ion coin cell-2 assembled with A4-sodium-ion battery electrolyte showed an increase in discharge specific capacity retention from 69.3% to 96.2% after 150 cycles, indicating that the addition of 1.0wt% tetrabutyltetrafluoroborate can significantly improve the cycling stability of sodium-ion half-cells under high voltage.

[0092] according to Figure 6 As shown in Table 1, compared with the battery assembled with B4-electrolyte, the sodium-ion coin cell-2 assembled with A4-sodium-ion battery electrolyte showed an increase in discharge specific capacity retention from 69.3% to 95.4% after 150 cycles, indicating that the addition of 2.0wt% tetrabutyltetrafluoroborate can significantly improve the cycling stability of sodium-ion half-cells under high voltage.

[0093] according to Figure 7 As shown in Table 1, compared with the battery assembled with B4-electrolyte, the sodium-ion coin cell-2 assembled with A4-sodium-ion battery electrolyte showed an increase in discharge specific capacity retention from 69.3% to 95.6% after 150 cycles, indicating that the addition of 3.0wt% tetrabutyltetrafluoroborate can significantly improve the cycling stability of sodium-ion half-cells under high voltage.

[0094] Therefore, the electrolyte prepared by the electrolyte additives selected in this application has good compatibility with the positive electrode under high voltage, which improves the cycle stability of the positive electrode under high voltage.

[0095] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0096] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A sodium-ion battery electrolyte, characterized in that, Includes organic solvents, sodium salts dissolved in said organic solvents, and sodium-ion battery electrolyte additives; The additive content is 0.5-5.0 wt%. The concentration of the sodium salt is 0.5-2.0 mol / L; The additive possesses the chemical structure shown in formula (1): ； In formula (1), R- is an anion, which is one of hexafluorophosphate, hexafluoroarsenate, tetrafluoroborate, perchlorate, trifluoromethanesulfonate, bis(fluorosulfonyl)imide, bis(trifluoromethanesulfonyl)imide, difluorooxalateborate, bis(oxalateborate), and tetraphenylborate.

2. The sodium-ion battery electrolyte according to claim 1, characterized in that, The additive content is 1.0-3.0 wt%.

3. The sodium-ion battery electrolyte according to claim 1, characterized in that, The sodium salt concentration is 1.0-1.2 mol / L.

4. The sodium-ion battery electrolyte according to claim 1, characterized in that, The sodium salt is one or more of sodium hexafluorophosphate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium trifluoromethanesulfonate, sodium bis(oxalato)borate, and sodium difluorooxalato)borate.

5. The sodium-ion battery electrolyte according to claim 1, characterized in that, The sodium salt is one or a combination of sodium hexafluorophosphate and sodium perchlorate.

6. The sodium-ion battery electrolyte according to claim 1, 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, and 1,3-dioxolane.

7. The sodium-ion battery electrolyte according to claim 6, characterized in that, The additive has the chemical structure shown in formula (1): R- is an anion, which is one of hexafluorophosphate, tetrafluoroborate, or difluorooxalate borate.

8. The application of the sodium-ion battery electrolyte according to any one of claims 1-7 as an electrolyte in a sodium-ion battery.

9. A sodium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and the sodium-ion battery electrolyte according to any one of claims 1-7.

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