Electrolyte Additive, Non-Aqueous Electrolyte and Sodium-Ion Battery

Abstract

The present invention provides an electrolyte additive, a non-aqueous electrolyte and a sodium ion battery. The electrolyte additive of the present invention has a structure shown in Formula I, wherein R1 to R3 are each independently selected from saturated or unsaturated, substituted or unsubstituted, straight-chain, branched-chain or cyclic hydrocarbon groups having 1 to 12 carbon atoms. The electrolyte additive of the present invention can accelerate the dissociation of sodium ions and acid radical ions in sodium salts, thereby improving the ionic conductivity of the non-aqueous electrolyte; moreover, the additive of the present invention can in-situ generate stable S-Na bonds when forming the SEI film, increasing the stability of the SEI film; in addition, the electrolyte additive of the present invention can also make the structure of the positive electrode material more stable. Therefore, the non-aqueous electrolyte containing the electrolyte additive of the present invention can improve the high and low temperature performance of the sodium ion battery.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and particularly to an electrolyte additive, a non-aqueous electrolyte and a sodium ion battery thereof. Background Art

[0002] Sodium ion batteries (SIBs) have been widely studied due to the abundant resources of sodium, the low cost of the battery system, and the similar working mechanism to lithium ion batteries (LIBs). They are a promising alternative to lithium ion batteries. Similar to the structure of lithium ion batteries, sodium ion batteries are also composed of key materials such as a positive electrode, a negative electrode, an electrolyte, and a separator. During charging, under the action of an electric field, sodium ions are removed from the positive electrode material, pass through the ion transport of the electrolyte, and reach the negative electrode material for insertion; correspondingly, electrons flow from the positive electrode to the negative electrode through the external circuit; the discharging process is opposite to the above charging process. Therefore, such batteries are also called "rocking chair batteries". As important components in the battery, the positive electrode material and the negative electrode material determine the overall performance indicators of the battery. However, as the connection between the two, the electrolyte is also a very important link for sodium ion transport, undertaking the role of transporting ions between the positive and negative electrodes, and having an important impact on the performance of the battery such as cycle life, rate performance, safety, and self-discharge. However, in a low-temperature environment, due to problems such as a decrease in ionic conductivity, poor compatibility between the electrolyte and the positive and negative electrodes, an increase in the desolvation energy, and a deterioration of the electrode / electrolyte interface properties, it is difficult for sodium ion batteries to exhibit ideal performance.

[0003] Therefore, there is an urgent need to develop new electrolyte additives, non-aqueous electrolytes and sodium ion batteries to solve the above problems. Summary of the Invention

[0004] The purpose of the present invention is to provide an electrolyte additive, a non-aqueous electrolyte and a sodium ion battery thereof that can significantly improve the high-temperature cycle performance, high-temperature storage performance and low-temperature discharge performance.

[0005] To achieve the above purpose, in the first aspect of the present invention, an electrolyte additive is provided, which has the structure shown in Formula I:

[0006]

[0007] Wherein, R1 to R3 are each independently selected from a C1-C12 saturated or unsaturated, substituted or unsubstituted, straight-chain, branched-chain or cyclic hydrocarbon group.

[0008] Compared with the prior art, the electrolyte additive of the present invention is an amphoteric ionic compound. The structure of the electrolyte additive contains a fluorosulfonyl group, a negatively charged nitrogen atom and a positively charged phosphorus atom. The negative charge is mainly concentrated on the nitrogen atom connected to the sulfur atom, while the positive charge is concentrated on the phosphorus atom connected to different substituents. The sulfonylimide group is connected to the phosphorus atom through a carbonyl group, which enables the additive to interact with sodium salts in the electrolyte, accelerating the dissociation of sodium ions and acid radical ions in the sodium salts, thereby improving the ionic conductivity of the non-aqueous electrolyte. Moreover, due to the instability of the S-N bond in the structure of the electrolyte additive, a stable S-Na bond can be in-situ generated when forming the SEI film, increasing the stability of the SEI film. In addition, the nitrogen atom in the additive structure has a certain degree of complexing effect with the positive electrode material, making the structure of the positive electrode material more stable. Therefore, the additive of the present invention can significantly improve the high-temperature cycling performance, high-temperature storage performance and low-temperature discharge performance of sodium-ion batteries.

[0009] Preferably, each of R1 to R3 is independently selected from a straight-chain or branched-chain alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 3 to 6 carbon atoms, a cyclic unsaturated alkyl group having 3 to 6 carbon atoms and containing a heteroatom, an aryl group, an aryl group containing a methyl group, an aryl group containing a methoxy group, or an aryl group containing a halogen.

[0010] More preferably, R1, R2, and R3 are the same, and R1, R2, and R3 are selected from a n-butyl group, a tert-butyl group, a cyclohexyl group, a 2-furyl group, an aryl group, a methyl aryl group, a methoxy aryl group, a fluoro aryl group, or a pentafluoro aryl group.

[0011] Preferably, the electrolyte additive is selected from at least one of Compound 1 to Compound 9:

[0012]

[0013] Specifically, the preparation method of Compound 1 includes the steps: 1) Anhydrous potassium fluoride and isocyanatochlorosulfonic acid are subjected to a reflux reaction and post-treatment under certain conditions to obtain isocyanato fluorosulfonic acid ester (reaction substrate A); 2) The isocyanato fluorosulfonic acid ester (reaction substrate A) and triphenylphosphine (reaction substrate B) are reacted in a solvent, and after post-treatment, Compound 1 is obtained.

[0014] The preparation methods of Compound 2 to Compound 9 are the same as that of Compound 1, except that the reaction substrate B used is different. The structures of the reaction substrates B of Compound 1 to Compound 9 are shown as follows:

[0015]

[0016] On the other hand, the present invention provides a non-aqueous electrolyte, which includes a non-aqueous solvent and a sodium salt, and also includes the above-mentioned electrolyte additive.

[0017] Preferably, the mass percentage of the electrolyte additive in the non-aqueous electrolyte is 0.1% to 2%, specifically but not limited to 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%.

[0018] Preferably, the sodium salt is selected from at least one of sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium difluoro(oxalato)borate (NaODFB), sodium bis(oxalato)borate (NaBOB), sodium difluorophosphate (NaPO2F2), and sodium difluorobis(oxalato)phosphate (NaDFBP).

[0019] Preferably, the mass percentage of the sodium salt in the non-aqueous electrolyte is 5 to 25%, specifically but not limited to 5%, 7.5%, 8%, 10%, 13%, 15.6%, 16%, 17%, 19%, 21%, 23%, 24%, 25%.

[0020] Preferably, the sodium salt of the present invention is sodium hexafluorophosphate (NaPF6). Compared with other sodium salts, the interaction between the electrolyte additive and sodium hexafluorophosphate of the present invention is the strongest, and the electrolyte additive can significantly accelerate the dissociation of sodium ions and hexafluorophosphate ions, thereby improving the ionic conductivity of the electrolyte.

[0021] Preferably, the non-aqueous solvent is at least one of a chain carbonate, a cyclic carbonate, and a carboxylic acid ester.

[0022] Specifically, the non-aqueous solvent of the present invention is at least one of ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), propylene carbonate (PC), n-butyl acetate (n-Ba), γ-butyrolactone (γ-Bt), propyl propionate (PP), ethyl propionate (EP), and ethyl butyrate (Eb).

[0023] Preferably, the non-aqueous electrolyte of the present invention further includes a film-forming auxiliary agent, and the film-forming auxiliary agent is selected from at least one of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), ethylene sulfite (ES), 1,3-propane sultone (PS), and disulfuric acid ethylene ester (DTD).

[0024] Preferably, the mass percentage of the film-forming auxiliary agent in the non-aqueous electrolyte is 0.1 to 6%, specifically but not limited to 0.1%, 0.8%, 1.2%, 1.5%, 2%, 2.5%, 3%, 3.6%, 4%, 4.2%, 4.5%, 4.8%, 5.2%, 5.5%, 5.8%, 6%.

[0025] The third aspect of the present invention provides a sodium ion battery, which includes a positive electrode and a negative electrode, and also includes the above-mentioned non-aqueous electrolyte.

[0026] Preferably, the positive electrode includes a positive electrode material, the positive electrode material includes a layered oxide, and the chemical formula of the layered oxide is Na x M (1-y-z) Fe y Mn z O2, where M is selected from at least one of Co, Ni, Cu, Mg, Zn, Al, Sn, Ga, Cr, Sr, V, and Ti, 0 < x ≤ 1, 0 ≤ y < 1, 0 ≤ z < 1, and y + z ≤ 1. The electrolyte additive of the present invention has a certain degree of complexation with Na + , Ni 2 + , Co 3+ , Mn 4+ etc. in the positive electrode material, which can make the structure of the positive electrode material more stable.

[0027] Preferably, the negative electrode material is selected from at least one of carbon-based negative electrode materials, titanium-based oxide negative electrode materials, and alloy-based negative electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the 19 F-NMR spectrum of isocyanato fluorosulfonate (FSI) of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The sodium ion battery of the present invention includes a positive electrode, a negative electrode, and a non-aqueous electrolyte. The non-aqueous electrolyte may include a sodium salt, a non-aqueous solvent, an electrolyte additive, and a film-forming aid.

[0030] Among them, the positive electrode includes a positive electrode material, the positive electrode material includes a layered oxide, and the chemical formula of the layered oxide is Na x M (1-y-z) Fe y Mn z O2, where M is selected from at least one of Co, Ni, Cu, Mg, Zn, Al, Sn, Ga, Cr, Sr, V, and Ti, 0 < x ≤ 1, 0 ≤ y < 1, 0 ≤ z < 1, and y + z ≤ 1. As an example, the positive electrode material of the present invention is selected from NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2. The electrolyte additive and Na + , Ni 2+ , Mn 4+It has a certain degree of complexing effect, which can make the structure of the positive electrode material more stable. The negative electrode includes a negative electrode material, and the negative electrode material is at least one of a carbon-based negative electrode material, a titanium-based oxide negative electrode material, and an alloy-based negative electrode material. By way of example, the negative electrode material of the present invention is selected from hard carbon.

[0031] The sodium salt is selected from at least one of sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium difluoro(oxalato)borate (NaODFB), sodium bis(oxalato)borate (NaBOB), sodium difluorophosphate (NaPO2F2), and sodium difluorobis(oxalato)phosphate (NaDFBP). As a preferred example, the sodium salt of the present invention is sodium hexafluorophosphate (NaPF6). Compared with other sodium salts, the interaction between the electrolyte additive of the present invention and sodium hexafluorophosphate is the strongest, and the electrolyte additive can significantly accelerate the dissociation of sodium ions and hexafluorophosphate ions, thereby improving the ionic conductivity of the electrolyte. The mass percentage of the sodium salt in the non-aqueous electrolyte is 5-25%, specifically but not limited to 5%, 7.5%, 8%, 10%, 13%, 15.6%, 16%, 17%, 19%, 21%, 23%, 24%, 25%. Preferably, the mass of the sodium salt of the present invention accounts for 12.5% of the total mass of the non-aqueous electrolyte.

[0032] The non-aqueous solvent is selected from at least one of chain carbonates, cyclic carbonates, and carboxylic acid esters, specifically at least one of ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), propylene carbonate (PC), n-butyl acetate (n-Ba), γ-butyrolactone (γ-Bt), propyl propionate (PP), ethyl propionate (EP), and ethyl butyrate (Eb). By way of example, the non-aqueous solvent of the present invention is a mixture of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC). Preferably, the non-aqueous solvent of the present invention is composed of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a mass ratio of 1:5:6:8.

[0033] The film-forming auxiliary includes at least one of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), ethylene sulfite (ES), 1,3-propane sultone (PS), and divinyl sulfite (DTD). The film-forming auxiliary of the present invention is preferably any one or a mixture of two of 1,3-propane sultone (PS) and fluoroethylene carbonate (FEC). More preferably, the film-forming auxiliary of the present invention is composed of 1,3-propane sultone and fluoroethylene carbonate with a mass ratio of 1:2. The mass percentage of the film-forming auxiliary in the non-aqueous electrolyte is 0.1% to 6%, specifically but not limited to 0.1%, 0.8%, 1.2%, 1.5%, 2%, 2.5%, 3%, 3.6%, 4%, 4.2%, 4.5%, 4.8%, 5.2%, 5.5%, 5.8%, 6%.

[0034] The mass percentage of the electrolyte additive of the present invention in the non-aqueous electrolyte is 0.1% to 2%, specifically but not limited to 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%. The electrolyte additive of the present invention is selected from at least one of Compound 1 to Compound 9:

[0035]

[0036] Specifically, the preparation method of Compound 1 includes the steps:

[0037] 1) Synthesize fluorosulfonyl isocyanate (FSI) with reference to Reaction Scheme 1

[0038]

[0039] Reaction Scheme 1

[0040] Add 68 g (1.2 mol) of anhydrous potassium fluoride to a dry three-necked flask, install a mechanical stirrer and a condenser, set the temperature of the condenser water to -20°C, install 141.5 g (1 mol) of chlorosulfonyl isocyanate (CSI) in the dropping funnel, and slowly drop it into the reaction flask for solvent-free reaction. Set the reaction temperature to 35°C, and finish dropping the chlorosulfonyl isocyanate within 2 h. Then raise the reaction temperature to 130°C and carry out a condensation reflux reaction for 6 h. After the reaction, cool down to room temperature. Set up an atmospheric distillation device on the three-necked reaction flask, slowly raise the temperature for distillation, and collect the fraction in the range of 85°C - 100°C to obtain 101 g of fluorosulfonyl isocyanate (reaction substrate A) with a yield of 80.7%. Identify the collected fraction by 19 19F-NMR, and the spectrum is as shown in Figure 1 shown, where trifluorotoluene is the added internal standard.

[0041] (2) Synthesize Compound 1 with reference to Reaction Scheme 2

[0042]

[0043] Reaction formula 2

[0044] Add 26.2 g of triphenylphosphine (reaction substrate B) and 100 g of dichloromethane into a three-necked flask, cool down to -10 °C. Load 12.5 g of isocyanatofluorosulfonate (reaction substrate A) and 55 g of dichloromethane in a dropping funnel, and slowly add them dropwise into the three-necked flask for reaction. During the reaction, the temperature of the reaction solution does not exceed 10 °C. White solid will continuously form during the reaction process. After the isocyanatofluorosulfonate is completely added dropwise, transfer the reaction to room temperature and react for 2 h. After the reaction, filter, and dry the filter cake in a vacuum oven at 40 °C for 10 h to obtain 34.8 g of white solid powder, denoted as Compound 1, with a yield of 90%.

[0045] The synthetic routes of Compound 2 to Compound 9 are shown in Reaction formula 3 to Reaction formula 10 respectively. Except for using different reaction substrates B, the specific synthesis methods are the same as that of Compound 1, and will not be elaborated in this invention.

[0046]

[0047] Reaction formula 3

[0048]

[0049] Reaction formula 4

[0050]

[0051] Reaction formula 5

[0052]

[0053] Reaction formula 6

[0054]

[0055] Reaction formula 7

[0056]

[0057] Reaction formula 8

[0058]

[0059] Reaction formula 9

[0060]

[0061] Reaction formula 10

[0062] To better illustrate the purpose, technical solution and beneficial effects of the present invention, the present invention will be further described below in conjunction with specific embodiments. It should be noted that the methods described in the following embodiments are further explanatory descriptions of the present invention and should not be regarded as limitations on the present invention.

[0063] Example 1

[0064] Preparation of non-aqueous electrolyte:

[0065] In a glove box filled with nitrogen (water content ≤ 1 ppm, oxygen content ≤ 1 ppm), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were dehydrated respectively using 4A molecular sieve activated by 5% solution mass to make the water content of the solution ≤ 1 ppm. Then, EC, PC, EMC, and DEC were mixed evenly according to the mass ratio of 1:5:6:8 to obtain solution A. Then, compound 1 was added to solution A, and sodium hexafluorophosphate was slowly added and stirred evenly until it was completely dissolved to form a non-aqueous electrolyte.

[0066] Preparation of the positive electrode:

[0067] NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 material, binder PVDF, and conductive agent Super P were mixed evenly according to the mass ratio of 97:1:2 to prepare a slurry. Then, the slurry was coated on both sides of the aluminum foil, and then dried and roll-pressed to obtain the positive electrode.

[0068] Preparation of the negative electrode:

[0069] Hard carbon, conductive agent SuperP, thickening agent CMC, and binder SBR (styrene-butadiene rubber latex) were mixed evenly according to the mass ratio of 95:2:1:2 to prepare a slurry. Then, the slurry was coated on both sides of the copper foil and then dried and roll-pressed to obtain the negative electrode.

[0070] Preparation of sodium-ion battery:

[0071] The positive electrode, separator, and negative electrode were stacked to form a square battery cell, which was packaged with a polymer. Then, the non-aqueous electrolyte was injected into the battery cell in the glove box, and after processes such as formation and grading, a sodium-ion battery with a capacity of 1400 mAh was made.

[0072] The electrolyte composition components of Examples 1 to 20 and Comparative Examples 1 to 3 are shown in Table 1. The preparation of the non-aqueous electrolyte, the positive and negative electrodes, and the sodium-ion battery in Examples 2 to 9 and Comparative Examples 1 to 2 are exactly the same as those in Example 1.

[0073] Table 1

[0074]

[0075]

[0076] In the comparative example, the CAS number of FSI is 1495-51-8, and the CAS number of triphenylphosphine is 603-35-0.

[0077] The sodium-ion batteries prepared in Examples 1 to 20 and Comparative Examples 1 to 6 were respectively subjected to high-temperature cycle tests, high-temperature storage tests, and low-temperature discharge performance tests according to the following test conditions, and the test results are shown in Table 2.

[0078] High-temperature cycle test:

[0079] Under the condition of high temperature (45 °C), the sodium-ion battery was charged at a constant current of 1C to 4.0V, then charged at a constant voltage of 4.0V until the current was 0.05C, and then discharged at a constant current of 1C to 4.0V. The initial discharge capacity of the battery was recorded as C0, and this was one charge-discharge cycle. Then, at 45 °C, 1C / 1C charging and discharging were carried out for 400 cycles, and the discharge capacity of the last cycle was recorded as C1. The capacity retention rate was calculated according to the following formula.

[0080] Capacity retention rate = (C1 / C0) * 100%.

[0081] High-temperature storage test:

[0082] Under the condition of normal temperature (25 °C), the sodium-ion battery was subjected to one 0.5C / 0.5C charge and discharge (the discharge capacity of the battery was recorded as C0), and the upper limit voltage was 4.0V; the battery was placed in an oven at 60 °C for storage for 30 days, then the battery was taken out and restored to room temperature, and then the battery was placed in an environment of 25 °C, and 0.5C discharge was carried out. The discharge capacity was recorded as C1, and then the sodium-ion battery was subjected to one 0.5C / 0.5C charge and discharge (the discharge capacity of the battery was recorded as C2).

[0083] Capacity retention rate = (C1 / C0) * 100%.

[0084] Capacity recovery rate = (C2 / C0) * 100%.

[0085] Low-temperature discharge test:

[0086] Under the condition of normal temperature (25 °C), the sodium-ion battery was subjected to one 0.3C / 0.3C charge and discharge (the discharge capacity of the battery was recorded as C0), and the upper limit voltage was 4.2V; the battery was placed in an environment of -20 °C for 4 hours, and 0.3C discharge was carried out on the battery. The discharge capacity was recorded as C1, and the cut-off voltage was 3.0V.

[0087] Capacity retention rate = (C1 / C0) * 100%.

[0088] Table 2

[0089]

[0090]

[0091] Comparing Examples 1 to 20 with Comparative Examples 1 - 6, it can be seen that the sodium-ion battery of the present invention has relatively good high-temperature cycling performance, low-temperature discharge performance, and high-temperature storage performance. This is because the additive of the present invention is an amphoteric ion compound, and the additive structure contains a sulfonylimide group and a phosphorus-carbon bond. The negative charge is mainly concentrated on the nitrogen atom connected to the sulfur atom, while the positive charge is concentrated on the phosphorus atom. The sulfonylimide group and the organophosphorus compound are connected by a carbonyl group, which enables the additive to interact with sodium salts in the electrolyte, accelerating the dissociation of sodium salts and acid radical ions, thereby improving the ionic conductivity of the electrolyte. Moreover, due to the instability of the C-P bond in the additive structure, stable P-Na and F-Na bonds can be formed in-situ when forming the SEI film, increasing the stability of the SEI film. In addition, the nitrogen atom in the additive structure has a certain degree of complexing effect on Ni 2+ , Mn 4+ in the nickel-manganese-based layered oxide cathode material, making the structure of the cathode material more stable. Therefore, the non-aqueous electrolyte of the present invention can significantly improve the high-temperature cycling performance, high-temperature storage performance, and low-temperature discharge performance of sodium-ion batteries. Specifically, it can be seen from Example 1 and Comparative Examples 2 and 3, and Example 18 and Comparative Examples 5 and 6 that using the amphoteric ion compound of the present invention as an additive has better electrochemical performance. Adding triphenylphosphine and isocyanato fluorosulfonate will deteriorate the high-temperature cycling performance, low-temperature discharge performance, and high-temperature storage performance of the battery. The main reason is that the addition of triphenylphosphine will hinder the transmission of sodium ions, thereby increasing the internal resistance of the battery. The reaction activity of isocyanato fluorosulfonate is very high, and the isocyanate will react with the SEI film on the surfaces of the positive and negative electrodes of the battery to destroy the structure of the SEI film, resulting in a decline in battery performance.

[0092] Comparing Examples 1 to 9, it can be seen that by adjusting different substituents connected to the phosphorus atom, it will also have different degrees of influence on the various performances of sodium-ion batteries. More specifically, the various performances of the sodium-ion battery in Example 3 are the best, which indicates that introducing 3 pentafluorophenoxy groups on the substituent can greatly improve the high and low temperature performances of the battery. It may be because a SEI film with more NaF components can be formed during the formation stage of the battery, making the structure of the SEI film more stable and stronger, thereby maximizing the high-temperature cycling, low-temperature discharge, and high-temperature storage performances of sodium-ion batteries.

[0093] Comparing Example 1, Example 18 and Comparative Example 4, it can be seen that when Compound 1 is used in combination with PS, the high and low temperature performance of the battery is more significantly improved compared to the use of Compound 1 and PS alone. The reason may be that the mechanism of action of Compound 1 and PS is similar, and it is preferentially reduced at the negative electrode, forming a dense passivation film at the negative electrode, thereby improving the high and low temperature performance of the battery.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, it is not limited to only the embodiments listed. Those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. An electrolyte additive, characterized in that, It has the structure shown in Formula I: Wherein, R1 to R3 are each independently selected from saturated or unsaturated, substituted or unsubstituted, straight-chain, branched-chain or cyclic hydrocarbon groups having 1 to 12 carbon atoms.

2. The additive according to claim 1, characterized in that, R1 to R3 are each independently selected from straight-chain or branched-chain alkyl groups having 1 to 6 carbon atoms, cyclic alkyl groups having 3 to 6 carbon atoms, cyclic unsaturated alkyl groups containing heteroatoms having 3 to 6 carbon atoms, aryl groups, aryl groups containing methyl groups, aryl groups containing methoxy groups or aryl groups containing halogen atoms.

3. The additive according to claim 1, characterized in that The electrolyte additive is selected from at least one of Compound 1 to Compound 9:

4. A non-aqueous electrolyte, comprising a non-aqueous solvent and a sodium salt, characterized in that, It further includes the electrolyte additive according to any one of Claims 1 to 3.

5. The non-aqueous electrolyte according to claim 4, wherein The mass percentage of the electrolyte additive in the non-aqueous electrolyte is 0.1% to 2%.

6. The non-aqueous electrolyte according to claim 4, characterized in that, The sodium salt is selected from at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium difluorooxalate borate, sodium bis(oxalato)borate, sodium difluorophosphate and sodium difluorobis(oxalato)phosphate.

7. The non-aqueous electrolyte according to claim 4, characterized in that, The non-aqueous solvent is at least one of chain carbonates, cyclic carbonates and carboxylic acid esters.

8. A sodium-ion battery, comprising a positive electrode and a negative electrode, characterized in that, It further includes the non-aqueous electrolyte according to any one of Claims 4 to 7.

9. The sodium-ion battery according to claim 8, characterized in that, The positive electrode includes a positive electrode material, and the positive electrode material is selected from Na x M (1-y-z) Fe y Mn z O2, where M is selected from at least one of Co, Ni, Cu, Mg, Zn, Al, Sn, Ga, Cr, Sr, V, and Ti, 0 < x ≤ 1, 0 ≤ y < 1, 0 ≤ z < 1, and y + z ≤ 1.

10. The sodium-ion battery according to claim 8, characterized in that, The negative electrode includes a negative electrode material, and the negative electrode material is selected from at least one of carbon-based negative electrode materials, titanium-based oxide negative electrode materials and alloy-based negative electrode materials.

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