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

Abstract

The invention discloses a sodium ion battery electrolyte additive, an electrolyte and a sodium ion battery, and belongs to the technical field of battery energy storage. The sodium ion battery electrolyte additive provided by the invention has a chemical structure as shown in a formula (1): # imgabs0 # R <-> is an anion; hexafluorophosphate radical, hexafluoroarsenate radical, tetrafluoroborate radical, perchlorate radical, trifluoromethanesulfonate radical, bis (fluorosulfonyl) imine radical, bis (trifluoromethylsulfonyl) imine radical, difluoro oxalato borate radical, bis (oxalato) borate radical, bis (salicylic acid-2-) borate radical, salicylic benzenediol borate radical, tetraphenylborate radical, 4, 5-dicyano-2-(trifluoromethyl) imidazolate radical, 4, 5-dicyano-2-(trifluoromethyl) imidazolate radical, 4, 5-dicyano-2-(trifluoromethyl) imidazolate radical, 4, 5-dicyano-2-(trifluoromethyl) imidazolate radical, 4, 5-dicyano-2-(trifluoromethyl) imidazolate radical, 4, 5-dicyano-2-(trifluoromethyl) imidazolate radical, 4, 5- The compound is one of 2, 3, 5-dicyano-2-(pentafluoroethyl) imidazolate radical and 2, 5-dicyano-2-(pentafluoroethyl) imidazolate radical. By introducing the additives, the cycling stability of the sodium-ion battery under high voltage can be realized, the electrochemical performance of the sodium-ion battery is improved, meanwhile, the mechanical performance of a positive electrode / electrolyte interface can be improved, and the sodium-ion battery has a good industrial application prospect.

Description

Technical Field

[0001] The present application belongs to the field of battery energy storage technology, and in particular relates to a sodium ion battery electrolyte additive, an electrolyte and a sodium ion battery. Background Art

[0002] As the next generation of rechargeable batteries, sodium-ion batteries have the advantages of abundant resources and low cost, and their working principle is similar to that of lithium-ion batteries, which has attracted more and more attention and research. However, due to the large molecular weight of sodium (22.99g / mol vs. 6.94g / mol) and higher potential (-2.71V vs. -3.04V relative to standard hydrogen electrode), the energy density of sodium-ion batteries is severely restricted. In order to obtain high energy density, the positive electrode needs to be charged to a high voltage region (>4.0V vs. Na + / Na) to release more sodium ions, but conventional electrolytes are prone to oxidative decomposition on the surface of the cathode with strong catalytic activity under high voltage, producing byproducts such as CO2, H2O, and polymers, causing problems such as thickening of the cathode / electrolyte interface (CEI) film and increased impedance. At the same time, the volume change of the cathode material is large under high voltage, which further aggravates the rupture of the CEI film and the occurrence of electrode / electrolyte parasitic reactions, leading to interface reconstruction and capacity decay. Therefore, a stable cathode / electrolyte interface under high voltage is constructed to improve the electrochemical performance of the battery.

[0003] Existing electrolyte additives generally form an interfacial film through preferential oxidation decomposition to improve the cycle stability of the battery. However, during long-term high-voltage cycles, the continuous volume change of the positive electrode particles and the corrosion of acid species under high pressure will create the risk of CEI rupture. Therefore, the consumption of electrolyte exposed on the positive electrode surface is aggravated, accelerating the capacity decay. At the same time, the electrochemical window of the electrolyte prepared by existing additives is narrow, which in turn affects its application. Therefore, it is necessary to develop additives with excellent comprehensive performance to expand the scope of application. Summary of the invention

[0004] The present 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] In order to achieve the above purpose, the technical solution of this application is:

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

[0007]

[0008] In formula (1), R -It is an anion, which is one of hexafluorophosphate, hexafluoroarsenate, tetrafluoroborate, perchlorate, trifluoromethylsulfonate, bis(fluorosulfonyl)imide, bis(trifluoromethylsulfonyl)imide, difluorooxalatoborate, bisoxalatoborate, bis(salicylic acid-2-)borate, salicylic acid benzenediol borate, tetraphenylborate, 4,5-dicyano-2-(trifluoromethyl)imidazolate, and 4,5-dicyano-2-(pentafluoroethyl)imidazolate.

[0009] In combination with the first aspect, preferably, the additive has a chemical structure shown in formula (1): R - It is an anion, one of hexafluorophosphate, tetrafluoroborate, and difluorooxalatoborate.

[0010] The second aspect of the present 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 according to the first aspect;

[0011] Wherein, the content of the additive is 0.5-5.0wt%;

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

[0013] In combination with the second aspect, preferably, the content of the additive is 1.0-3.0 wt%.

[0014] In combination with the second aspect, preferably, the sodium salt concentration is 1.0-1.2 mol / L.

[0015] In combination with the second aspect, preferably, the sodium salt is one or more of sodium hexafluorophosphate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium trifluoromethanesulfonate, sodium bis(oxalatoborate), and sodium difluorooxalatoborate.

[0016] In combination with the second aspect, preferably, the sodium salt is one of sodium hexafluorophosphate and sodium perchlorate or a combination thereof.

[0017] In combination with the second aspect, preferably, the organic solvent is one or more of ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl formate, methyl acetate, methyl butyrate, ethyl propionate, ethyl butyrate, butyl acetate, methyl propionate, propyl butyrate, trimethyl phosphate, triethyl phosphate, cyclopentane, dimethyl sulfone, 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 the present application provides the application of the sodium ion battery electrolyte of the second aspect in a sodium ion battery.

[0019] The fourth aspect of the present application provides a sodium ion battery, comprising a positive electrode sheet, a negative electrode sheet, 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 the present application include at least:

[0021] The sodium ion battery electrolyte additive provided by the present application is composed of tetrabutylammonium cations and anions. On the one hand, the tetrabutylammonium cations in the additive can capture and fix the active oxygen released by the positive electrode material under high pressure conditions, inhibit the nucleophilic attack or catalytic decomposition of the active components in the positive electrode material on the solvent, reduce the parasitic reaction at the interface, and improve the high-voltage cycle stability of the sodium ion battery; on the other hand, the anions in the additive compete with the anions in the sodium salt, break the strong interaction between the ion pairs, and help improve the electrochemical performance of the sodium ion battery; thirdly, it can form an interface film rich in inorganic components such as F and N on the positive electrode surface, which can not only inhibit the continuous decomposition of the electrolyte, but also prevent the destruction of the electrode structure and the dissolution of metal ions, and improve the mechanical properties of the positive electrode / electrolyte interface. At the same time, the additive provided by the present application has an accurate and stable structure, rich variety, good solubility, high economic benefits, and good prospects for industrial application under high pressure conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 Electrochemical window diagram of the A1-sodium ion battery electrolyte and the B1-electrolyte prepared in the examples of the present application;

[0024] Figure 2 The sodium ion button battery (NaNi) prepared by the A1-sodium ion battery electrolyte and the B1-electrolyte in the embodiment of the present application 1 / 3 Fe 1 / 3 Mn 1 / 3 O2||Na) long cycle performance diagram at 1C rate;

[0025] Figure 3 The sodium ion button battery (NaNi) prepared by the A2-sodium ion battery electrolyte and the B1-electrolyte in the embodiment of the present application 1 / 3 Fe 1 / 3 Mn1 / 3 O2||Na) long cycle performance diagram at 1C rate;

[0026] Figure 4 The sodium ion button battery (NaNi) prepared by the A3-sodium ion battery electrolyte and the B1-electrolyte in the embodiment of the present application 1 / 3 Fe 1 / 3 Mn 1 / 3 O2||Na) long cycle performance diagram at 1C rate;

[0027] Figure 5 The long cycle performance diagram of the sodium ion button battery (Na3V2(PO4)2F3||Na) made of the A4-sodium ion battery electrolyte and the B1-electrolyte prepared in the examples of the present application at a rate of 1C;

[0028] Figure 6 The long cycle performance diagram of the sodium ion button battery (Na3V2(PO4)2F3||Na) made of the A5-sodium ion battery electrolyte and the B1-electrolyte prepared in the examples of the present application at a rate of 1C;

[0029] Figure 7 This is a long cycle performance diagram of sodium ion button batteries (Na3V2(PO4)2F3||Na) made of A6-sodium ion battery electrolyte and B1-electrolyte prepared in the examples of this application at 1C rate. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work 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 of associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, B exists alone, and A and B exist at the same time. A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship.

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

[0033] Those skilled in the art should understand that in the following description of the embodiments of the present application, the order of serial numbers does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and 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 the present application.

[0034] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

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

[0036] In a first aspect, an embodiment of the present application provides a sodium ion battery electrolyte additive, wherein the additive has a chemical structure shown in formula (1):

[0037]

[0038] In formula (1), R - It is an anion, which is one of hexafluorophosphate, hexafluoroarsenate, tetrafluoroborate, perchlorate, trifluoromethylsulfonate, bis(fluorosulfonyl)imide, bis(trifluoromethylsulfonyl)imide, difluorooxalatoborate, bisoxalatoborate, bis(salicylic acid-2-)borate, salicylic acid benzenediol borate, tetraphenylborate, 4,5-dicyano-2-(trifluoromethyl)imidazolate, and 4,5-dicyano-2-(pentafluoroethyl)imidazolate.

[0039] Among them, on the one hand, the tetrabutylammonium cation in the additive can capture and fix the active oxygen in the electrolyte under high pressure conditions, which can reduce the oxidation of the electrolyte caused by active oxygen, inhibit the nucleophilic attack or catalytic decomposition of the active components in the positive electrode material on the solvent, reduce the parasitic reaction of the interface, and help to achieve the stable cycle performance of the sodium ion battery under high pressure; on the other hand, the anions in the additive compete with the anions in the sodium salt, break the strong interaction between the ion pairs, and help to improve the electrochemical performance of the sodium ion battery; thirdly, it can form an interface film rich in inorganic components such as F and N on the positive electrode surface, which can not only inhibit the continuous decomposition of the electrolyte, but also prevent the destruction of the electrode structure and the dissolution of metal ions, and improve the mechanical properties of the positive electrode / electrolyte interface. At the same time, the additive provided by this application has an accurate and stable structure, rich variety, good solubility, and high economic benefits under high pressure conditions, and has good prospects for industrial application.

[0040] It should be noted that R - is an anion, preferably hexafluorophosphate (PF6 - ), hexafluoroarsenate (AsF6 - ), tetrafluoroborate (BF4 - ), perchlorate (ClO4 - ), trifluoromethanesulfonate (OTF - ), bis(fluorosulfonyl)imide (FSI - ), bis(trifluoromethylsulfonyl)imide (TFSI - ), difluorooxalate borate (DFOB - ), bis(oxalatoborate) (BOB - ), bis(salicylic acid-2-)borate (BSB - ), benzyl salicylate borate (BDSB - ), tetraphenylborate (BPh4 - )、4,5-dicyano-2-(trifluoromethyl)imidazolate (TDI - ) and 4,5-dicyano-2-(pentafluoroethyl)imidazolate (PDI - ), more preferably one of hexafluorophosphate, tetrafluoroborate, and difluorooxalatoborate. The additive provided in the present application can increase the operating voltage window of the electrolyte, so that the electrolyte can work normally in a wide voltage range of 0-5V. Since the operating voltage of the sodium ion battery is generally 1.5-4.5V, the electrolyte prepared by adding the additive is more compatible with the sodium ion battery.

[0041] It should be noted that the additives provided in this application include -The anion has strong electron-withdrawing property, which can delocalize the negative charge on the N atom in the structure. The strong ion association and pairing effect makes it easy for the sodium ions to dissociate, which promotes the migration of sodium ions between the positive and negative electrodes and is beneficial to the improvement of kinetic performance.

[0042] In the second aspect, the present 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 0.5-5.0wt%, more preferably 1.0-3.0wt%; the sodium salt concentration is preferably 0.5-2.0mol / L, more preferably 1.0-1.2mol / L. Among them, by limiting the amount of additive added, the electrolyte can be given a wide electrochemical window and good thermal stability; by regulating and selecting the sodium salt concentration, the electrochemical performance and safety of the sodium ion battery can be significantly improved, while reducing costs and improving the overall performance of the sodium ion battery.

[0043] In the embodiment of the present application, 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(oxalyl)borate (NaBOB), sodium difluorooxalylborate (NaDFOB), more preferably one of sodium hexafluorophosphate and sodium perchlorate. Among them, by selecting these sodium salts, good ionic conductivity can be guaranteed, and the raw materials are common and easy to obtain, with a wide source and low price.

[0044] In the embodiment of the present application, the organic solvent is preferably ethylene carbonate (EC), fluoroethylene carbonate, vinylene carbonate, propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl 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, cyclopentane, 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, one or more. Among them, the selection of these organic solvents is conducive to improving the kinetic performance of sodium ion batteries, preventing sodium precipitation, and optimizing their impedance performance.

[0045] In the third aspect, the present application provides the application of the sodium ion battery electrolyte in the second aspect in a sodium ion battery. Among them, based on the excellent performance of the sodium ion battery electrolyte, the sodium ion battery is endowed with the advantages of high charge and discharge efficiency, good cycle performance, high safety, wide electrochemical window and low cost, and has broad application prospects.

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

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

[0048] It should be noted that the present application does not specifically limit the above-mentioned sodium ion battery electrolyte, the positive electrode, the separator and the negative electrode of the sodium ion battery, and the preparation method of the sodium ion battery, and the known technical solutions in the art can be adopted.

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

[0050] The technical solution of the present application will be further described below in conjunction with specific embodiments.

[0051] Example 1

[0052] This embodiment provides a method for preparing an A1-sodium ion battery electrolyte, which specifically includes:

[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, and then tetrabutylammonium hexafluorophosphate accounting for 1.0 wt% of the total mass of the above electrolyte was added, stirred at room temperature for 12 hours, and mixed evenly to obtain A1-sodium ion battery electrolyte.

[0054] Example 2

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

[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, and then tetrabutylammonium hexafluorophosphate accounting for 2.0 wt% of the total mass of the above electrolyte was added, stirred at room temperature for 12 hours, and mixed evenly to obtain A2-sodium ion battery electrolyte.

[0057] Example 3

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

[0059] 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, and then tetrabutylammonium hexafluorophosphate accounting for 3.0 wt% of the total mass of the above electrolyte was added, stirred at room temperature for 12 hours, and mixed evenly to obtain A3-sodium ion battery electrolyte.

[0060] Example 4

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

[0062] 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, and then tetrabutylammonium tetrafluoroborate accounting for 1.0 wt% of the total mass of the above electrolyte was added, stirred at room temperature for 12 hours, and mixed evenly to obtain A4-sodium ion battery electrolyte.

[0063] Example 5

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

[0065] 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, and then tetrabutylammonium tetrafluoroborate accounting for 2.0 wt% of the total mass of the above electrolyte was added, stirred at room temperature for 12 hours, and mixed evenly to obtain A5-sodium ion battery electrolyte.

[0066] Example 6

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

[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, and then tetrabutylammonium tetrafluoroborate accounting for 3.0 wt% of the total mass of the above electrolyte was added, stirred at room temperature for 12 hours, and mixed evenly to obtain A6-sodium ion battery electrolyte.

[0069] Example 7

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

[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, and then tetrabutylammonium hexafluorophosphate accounting for 1.0 wt% of the total mass of the above electrolyte was added, stirred at room temperature for 12 hours, and mixed evenly to obtain A7-sodium ion battery electrolyte.

[0072] Example 8

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

[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, and then tetrabutylammonium hexafluorophosphate accounting for 3.0 wt% of the total mass of the above electrolyte was added, stirred at room temperature for 12 hours, and mixed evenly to obtain A8-sodium ion battery electrolyte.

[0075] Example 9

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

[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, and then tetrabutylammonium difluorooxalatoborate accounting for 5.0 wt% of the total mass of the above electrolyte was added, stirred at room temperature for 12 hours, and mixed evenly to obtain A9-sodium ion battery electrolyte.

[0078] At the same time, in order to verify the comprehensive performance of the sodium ion battery electrolyte prepared in the above embodiment, the present application provides the following comparative examples for detailed description.

[0079] Comparative Example 1

[0080] The distribution ratio, preparation operation and process parameters of Comparative Example 1 of the present application are basically the same as those of Example 1, except that no electrolyte additive is added to obtain B1-electrolyte.

[0081] In order to verify the comprehensive performance of the sodium ion battery electrolytes prepared in the examples and comparative examples of the present application, the sodium ion battery electrolytes were made into corresponding sodium ion half-cells for corresponding performance tests.

[0082] The electrolytes prepared in Example 1 and Comparative Example 1 of the present application were subjected to electrochemical window tests. 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 larger oxidation peak appears near 4.5V, indicating that the electrolyte is oxidized and decomposed, while the A1-sodium ion battery electrolyte prepared in Example 1 does not show an increase in current until the voltage exceeds 5V, indicating that the A1-sodium ion battery electrolyte does not undergo obvious decomposition below 5V, indicating that it has a higher antioxidant capacity and the voltage window is significantly widened.

[0083] The sodium ion battery electrolytes prepared in Examples 1-3, 7-9 and Comparative Example 1 were made into corresponding sodium ion half-cells: NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 is the working electrode (where NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 The mass ratio of O2, conductive agent Super P, and binder PVDF is 8:1:1), and the sodium sheet is used as the counter electrode. 60 μL of the electrolyte of Example 1-3 and Comparative Example 1 are added respectively, and the sodium ion button battery-1 is assembled together.

[0084] The sodium ion battery electrolytes prepared in Examples 4-6 and Comparative Example 1 were made into 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 a sodium sheet was used as the counter electrode. 60 μL of the electrolytes of Examples 4-6 and Comparative Example 1 were added respectively, and the cells were assembled into sodium ion button cell-2.

[0085] The electrochemical performance test of the sodium ion button battery prepared in this application is carried out: the test conditions are constant current charge and discharge, the voltage range is 2.0V-4.3V, the assembled battery is pre-circulated for 3 cycles at a current density of 0.1C at room temperature, and then a long cycle charge and discharge test is carried out 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 can be seen from Table 1, compared with the battery assembled with B1-electrolyte, the discharge capacity retention rate of the sodium ion button cell-1 assembled with A1-sodium ion battery electrolyte increased from 46.9% to 77.3% after 150 cycles, indicating that the addition of 1.0wt% tetrabutylammonium hexafluorophosphate can significantly improve the cycle stability of the sodium ion half-cell at high voltage.

[0089] according to Figure 3 As shown in Table 1, compared with the battery assembled with B2-electrolyte, the discharge capacity retention rate of the sodium ion button cell-1 assembled with A2-sodium ion battery electrolyte increased from 46.9% to 75.1% after 150 cycles, indicating that the addition of 2.0wt% tetrabutylammonium hexafluorophosphate can significantly improve the cycle stability of the sodium ion half-cell at high voltage.

[0090] according to Figure 4 As shown in Table 1, compared with the battery assembled with B3-electrolyte, the discharge capacity retention rate of the sodium ion button cell-1 assembled with A3-sodium ion battery electrolyte increased from 46.9% to 72.6% after 150 cycles, indicating that the addition of 3.0wt% tetrabutylammonium hexafluorophosphate can significantly improve the cycle stability of the sodium ion half-cell at high voltage.

[0091] according to Figure 5 As shown in Table 1, compared with the battery assembled with B4-electrolyte, the discharge capacity retention rate of the sodium ion button cell-2 assembled with A4-sodium ion battery electrolyte increased from 69.3% to 96.2% after 150 cycles, indicating that the addition of 1.0wt% tetrabutylammonium tetrafluoroborate can significantly improve the cycle stability of the sodium ion half-cell at high voltage.

[0092] according to Figure 6 As shown in Table 1, compared with the battery assembled with B4-electrolyte, the discharge capacity retention rate of the sodium ion button cell-2 assembled with A4-sodium ion battery electrolyte increased from 69.3% to 95.4% after 150 cycles, indicating that the addition of 2.0wt% tetrabutylammonium tetrafluoroborate can significantly improve the cycle stability of the sodium ion half-cell at high voltage.

[0093] according to Figure 7 As shown in Table 1, compared with the battery assembled with B4-electrolyte, the discharge capacity retention rate of the sodium ion button cell-2 assembled with A4-sodium ion battery electrolyte increased from 69.3% to 95.6% after 150 cycles, indicating that the addition of 3.0wt% tetrabutylammonium tetrafluoroborate can significantly improve the cycle stability of the sodium ion half-cell at high voltage.

[0094] Therefore, the electrolyte prepared by the electrolyte additive selected in the present application has good compatibility with the positive electrode under high voltage, thereby improving the cycle stability of the positive electrode under high voltage.

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

[0096] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions recorded in the aforementioned embodiments may still be modified, or some or all of the technical features therein may be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. A sodium ion battery electrolyte additive, characterized in that: The additive has a chemical structure shown in formula (1): In formula (1), R - It is an anion, which is one of hexafluorophosphate, hexafluoroarsenate, tetrafluoroborate, perchlorate, trifluoromethylsulfonate, bis(fluorosulfonyl)imide, bis(trifluoromethylsulfonyl)imide, difluorooxalatoborate, bisoxalatoborate, bis(salicylic acid-2-)borate, salicylic acid benzenediol borate, tetraphenylborate, 4,5-dicyano-2-(trifluoromethyl)imidazolate, and 4,5-dicyano-2-(pentafluoroethyl)imidazolate.

2. The sodium ion battery electrolyte additive according to claim 1, characterized in that: The additive has a chemical structure shown in formula (1): R - It is an anion, one of hexafluorophosphate, tetrafluoroborate, and difluorooxalatoborate.

3. A sodium ion battery electrolyte, characterized in that: Comprising an organic solvent, a sodium salt dissolved in the organic solvent, and the sodium ion battery electrolyte additive according to any one of claims 1 to 2; Wherein, the content of the additive is 0.5-5.0wt%; The sodium salt concentration is 0.5-2.0 mol / L.

4. The sodium ion battery electrolyte according to claim 3, characterized in that The content of the additive is 1.0-3.0 wt%.

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

6. The sodium ion battery electrolyte according to claim 3, 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(oxalatoborate), and sodium difluoro(oxalatoborate).

7. The sodium ion battery electrolyte according to claim 3, characterized in that: The sodium salt is one of sodium hexafluorophosphate and sodium perchlorate or a combination thereof.

8. The sodium ion battery electrolyte according to claim 3, characterized in that: The organic solvent is one or more of ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl 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, and 1,3-dioxolane.

9. Use of the sodium ion battery electrolyte according to any one of claims 3 to 8 as an electrolyte in a sodium ion battery.

10. A sodium ion battery, characterized in that: The invention comprises a positive electrode sheet, a negative electrode sheet, a separator and the sodium ion battery electrolyte according to any one of claims 3 to 8.

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