Non-aqueous electrolyte solution and secondary battery

Abstract

The invention provides a non-aqueous electrolyte solution and a secondary battery. The non-aqueous electrolyte comprises an electrolyte salt, a non-aqueous organic solvent and an additive. The additive comprises a compound A shown as a structural formula I, R is selected from C1-C5 alkyl, C1-C5 halogenated alkyl, aromatic hydrocarbon, halogenated aromatic hydrocarbon, pyridyl or halogenated pyridyl, and n is selected from an integer of 0-4. The compound A as shown in the structural formula I has relatively high stability at high temperature and high pressure, and can effectively inhibit continuous decomposition of a solid electrolyte membrane so as to significantly reduce the problem of gas production. And meanwhile, the Schiff base structure can be preferentially reduced to form a thin and compact positive electrode solid electrolyte interface film (CEI), so that the stability of the CEI is improved, an electrolyte and an active material are more effectively isolated, and unnecessary side reactions are prevented. The sulfonyl groups in the compound A can be relatively and neatly arranged between the electrolyte and the electrode under the action of affinity, so that the interface contact between the electrolyte and the electrode is optimized, and the oxidation resistance of the electrolyte at the membrane is improved. # imgabs0 #

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy batteries, and particularly relates to a non-aqueous electrolyte and a secondary battery. Background Art

[0002] At present, the technology of sodium-ion secondary batteries is experiencing a rapid development momentum. Not only has a series of important breakthroughs been achieved in technological innovation, but also a significant expansion has been realized in the application scope. It has strongly promoted the transformation from theoretical research to commercial practice, and has become a highly competitive alternative in the field of lithium-ion batteries. At the technical level, significant progress has been made in aspects such as the positive and negative electrode materials, electrolytes, and battery structures of sodium-ion batteries. The research on positive electrode materials has gradually expanded from early sodium metal oxides to multi-component composite materials and nanostructured materials, effectively improving the energy density and cycle life of the battery. At the same time, the optimization of electrolytes has also provided strong support for the performance improvement of sodium-ion batteries. At the application level, sodium-ion batteries have gradually expanded from energy storage systems to diversified fields such as electric vehicles, power tools, and mobile devices, showing broad market prospects.

[0003] However, under high-temperature cycling and high-temperature storage conditions, sodium-ion batteries still face many technical challenges. On the one hand, the high-temperature environment will accelerate the rate of chemical reactions inside the battery, which may lead to structural changes and capacity loss of the electrode materials, thereby affecting the cycle stability and service life of sodium-ion batteries. On the other hand, the performance of the electrolyte will also change under high-temperature conditions, such as possible volatilization, decomposition, or reduction in conductivity, thereby affecting the safety and performance of the battery. Therefore, it is urgent to develop a non-aqueous electrolyte suitable for sodium-ion batteries. Summary of the Invention

[0004] Based on the above problems, the purpose of the present invention is to provide a non-aqueous electrolyte and a secondary battery. The non-aqueous electrolyte contains compound A, which can effectively improve the high-temperature cycling performance and safety performance of sodium-ion batteries.

[0005] To achieve the above purpose, the present invention provides a non-aqueous electrolyte on the one hand. The non-aqueous electrolyte includes an electrolyte salt, a non-aqueous organic solvent, and an additive. The additive includes compound A shown in Structural Formula Ⅰ, wherein R is selected from a C1-C5 hydrocarbon group, a C1-C5 halogenated hydrocarbon group, an aromatic hydrocarbon group, a halogenated aromatic hydrocarbon group, a pyridyl group, or a halogenated pyridyl group, and n is an integer selected from 0-4.

[0006]

[0007] In the electrolyte of the present invention, the additive of the non-aqueous electrolyte includes Compound A, which can maintain a solid electrolyte interface (SEI) film under high temperature and high pressure. The Compound A shown in Structural Formula I has relatively high stability under high temperature and high pressure, can effectively inhibit the continuous decomposition of the solid electrolyte interface film, and thus significantly reduce the gas generation problem caused by the repeated loss of the solid electrolyte interface film, thereby ensuring the high-temperature cycle performance and safety performance of the sodium-ion battery. At the same time, the Schiff base structure in Compound A can be preferentially reduced to form a thin and dense cathode solid electrolyte interface film (CEI), improving the stability of the CEI, being able to more effectively isolate the electrolyte from the active material, preventing unnecessary side reactions, and further ensuring the high-temperature cycle performance of the sodium-ion battery. Moreover, the sulfonyl groups in Compound A can be relatively neatly arranged between the electrolyte and the electrode under the action of affinity, optimizing the interfacial contact between the electrolyte and the electrode and improving the antioxidant performance of the electrolyte at the film, thereby further ensuring the high-temperature cycle performance and safety performance of the sodium-ion battery.

[0008] As a technical solution of the present invention, R is selected from alkyl groups having 1 to 3 carbon atoms, alkenyl groups having 2 to 3 carbon atoms, alkynyl groups having 2 to 3 carbon atoms, fluoroalkyl groups having 1 to 3 carbon atoms, fluoroalkenyl groups having 2 to 3 carbon atoms, fluoroalkynyl groups having 2 to 3 carbon atoms, phenyl, fluorophenyl, pyridyl or fluoropyridyl, and n is 1 or 2.

[0009] As a technical solution of the present invention, Compound A is selected from at least one of Compound 1 to Compound 3.

[0010]

[0011] As a technical solution of the present invention, the mass percentage of Compound A in the non-aqueous electrolyte is 0.01 to 0.50%.

[0012] As a technical solution of the present invention, the mass percentage of the electrolyte salt in the non-aqueous electrolyte is 6.5 to 15.5%, the electrolyte salt is a sodium salt, and the sodium salt is selected from at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium trifluoromethanesulfonate, sodium bis(trifluoromethanesulfonyl)imide, sodium bis(oxalato)borate, sodium difluorophosphate, sodium difluorooxalate borate, sodium difluorodioxalate phosphate and sodium bis(fluorosulfonyl)imide.

[0013] As a technical solution of the present invention, the non-aqueous organic solvent is selected from at least one of ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, butyl acetate, γ-butyrolactone, propyl propionate, ethyl propionate, ethyl acetate and ethyl butyrate.

[0014] The second aspect of the present invention provides a secondary battery, which includes a positive electrode material, a negative electrode material and the aforementioned non-aqueous electrolyte, and the highest charging voltage is 4.1V.

[0015] As a technical solution of the present invention, the chemical formula of the positive electrode material is Na x M (1-y-z) Fe y Mn z O2, where M is 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.

[0016] As a technical solution of the present invention, the negative electrode material includes at least one of a carbon-based negative electrode material, a titanium-based oxide negative electrode material, and an alloy-based negative electrode material.

[0017] As a technical solution of the present invention, the negative electrode material includes at least one of soft carbon, hard carbon, sodium titanate, FeS x , Cu x O, MoS2, Sn x O, CoS x , Fe2O3, Fe3O4, ZnS, Sb, and SbSn. Detailed implementation manners

[0018] The secondary battery of the present invention has good high-temperature cycle performance and safety performance at a high voltage of 4.1V. The secondary battery can be a sodium-ion battery, including a positive electrode material, a negative electrode material, and a non-aqueous electrolyte, and the highest charging voltage is 4.1V.

[0019] The chemical formula of the positive electrode material is Na x M (1-y-z) Fe y Mn z O2, where M is 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 negative electrode material includes at least one of a carbon-based negative electrode material, a titanium-based oxide negative electrode material, and an alloy-based negative electrode material. Further, the negative electrode material includes at least one of soft carbon, hard carbon, sodium titanate, FeS x , Cu x O, MoS2, Sn x O, CoS x , Fe2O3, Fe3O4, ZnS, Sb, and SbSn. Soft carbon is amorphous carbon that can be graphitized at a high temperature above 2500°C. In contrast, hard carbon is difficult to graphitize even in a similar high-temperature environment, thus showing stronger sodium storage capacity and lower working potential. Therefore, the negative electrode material is preferably hard carbon.

[0020] The non-aqueous electrolyte includes an electrolyte salt, a non-aqueous organic solvent, and an additive. This non-aqueous electrolyte can maintain the stability of the solid electrolyte interface (SEI) and the cathode solid electrolyte interface (CEI) under high temperature and high pressure, and can also optimize the interfacial contact between the electrolyte and the electrode and improve the antioxidant performance of the electrolyte at the membrane, thus improving the high-temperature cycling performance and safety performance of the sodium-ion battery.

[0021] Among them, the mass percentage of the electrolyte salt in the non-aqueous electrolyte is 6.5-15.5%. As an example, the mass percentage can be but is not limited to 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, 10.0%, 10.5%, 11.0%, 11.5%, 12.0%, 12.5%, 13.0%, 13.5%, 14.0%, 14.5%, 15.0%, 15.5%. The electrolyte salt is a sodium salt, and the sodium salt is selected from at least one of sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium trifluoromethanesulfonate (NaCF3SO3), sodium bis(trifluoromethanesulfonyl)imide (NaN(CF3SO2)2), sodium bis(oxalato)borate (C4BNaO8), sodium difluorophosphate (NaPO2F2), sodium difluoro(oxalato)borate (C2BF2NaO4), sodium difluoro bis(oxalato)phosphate (NaDFBP), and sodium bis(fluorosulfonyl)imide (NaFSI). Preferably, the sodium salt is selected from sodium hexafluorophosphate (NaPF6) or sodium bis(fluorosulfonyl)imide (NaFSI).

[0022] The mass ratio of the non-aqueous organic solvent in the electrolyte is more than 80%, preferably more than 85%. As an example, the mass ratio of the non-aqueous organic solvent is 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%. The content of the non-aqueous organic solvent is not limited to the listed values, and other unlisted values within this numerical range are also applicable. The non-aqueous organic solvent includes at least one of carbonate compounds, carboxylic ester compounds, and ether compounds. Further, the carbonate compounds include but are not limited to 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), n-propyl propionate (n-Pp), ethyl propionate (EP), and ethyl butyrate (Eb). Preferably, the non-aqueous organic solvent includes a combination of propylene carbonate (PC), ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) to achieve relatively stable cycling performance.

[0023] The additive includes compound A as shown in structural formula I, and the mass proportion of compound A in the electrolyte is 0.01-0.50%. Preferably, the mass proportion of compound A is 0.05-0.50%. As an example, the mass proportion of compound A can be, but is not limited to, 0.01%, 0.03%, 0.05%, 0.07%, 0.09%, 0.1%, 0.15%, 0.18%, 0.2%, 0.22%, 0.24%, 0.26%, 0.28%, 0.3%, 0.33%, 0.36%, 0.38%, 0.41%, 0.44%, 0.46%, 0.48%, 0.5%.

[0024] In the compound A shown in the structural formula I, R is selected from a C1-C5 hydrocarbon group, a C1-C5 halogenated hydrocarbon group, an aromatic hydrocarbon group, a halogenated aromatic hydrocarbon group, a pyridyl group or a halogenated pyridyl group, and n is selected from an integer of 0 to 4. Further, R is selected from a C1-C3 alkyl group, a C2-C3 alkenyl group, a C2-C3 alkynyl group, a C1-C3 fluoroalkyl group, a C2-C3 fluoroalkenyl group, a C2-C3 fluoroalkynyl group, a phenyl group, a fluorophenyl group, a pyridyl group or a fluoropyridyl group, and n is 1 or 2. Furthermore, R is selected from methyl, ethyl, propyl, isopropyl, butyl, pentyl, vinyl, propenyl, isopropenyl, butenyl, pentenyl, ethynyl, propynyl, isopropynyl, butynyl, pentynyl, a fluoromethyl, a fluoroethyl, a fluoropropyl, a fluoroisopropyl, a fluorobutyl, a fluoropentyl, a fluorovinyl, a fluoropropenyl, a fluoroisopropenyl, a fluorobutenyl, a fluoropentenyl, a fluoroethynyl, a fluoropropynyl, a fluoroisopropynyl, a fluorobutynyl, a fluoro substituted pentynyl, polyfluoromethyl, polyfluoroethyl, polyfluoropropyl, polyfluoroisopropyl, polyfluorobutyl, polyfluoropentyl, polyfluorovinyl, polyfluoropropenyl, polyfluoroisopropenyl, polyfluorobutenyl, polyfluoropentenyl, polyfluoroethynyl, polyfluoropropynyl, polyfluoroisopropynyl, polyfluorobutynyl, polyfluoropentynyl, phenyl, tolyl, ethylphenyl, monofluorophenyl, monofluorotolyl, monofluoroethylphenyl, polyfluorophenyl, polyfluorotolyl, polyfluoroethylphenyl, pyridyl, fluoropyridyl. n can be, but is not limited to, 0, 1, 2, 3, 4.

[0025] Furthermore, compound A is selected from at least one of compound 1 to compound 3. Among them, the CAS number of compound 2 is: 942505-03-5. Compound 1 can be obtained by reacting taurine and isobutyraldehyde.

[0026] Compound three can be obtained by the reaction of taurine and 2-fluoropyridine-5-carboxaldehyde.

[0027]

[0028] To better illustrate the objectives, technical solutions, 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.

[0029] For those not specifying specific conditions in the examples and comparative examples, they can be carried out according to conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments not indicating the manufacturer, they are all conventional products that can be obtained commercially.

[0030] Compound I in the example can be prepared in the following manner: Add 50 g of taurine and 800 g of absolute ethanol to a 1 L reaction flask, stir at room temperature, add 28.82 g of isobutyraldehyde, stir evenly, then add 21.58 g of sodium methoxide in batches, react at room temperature, detect isobutyraldehyde by GC-MS, stop the reaction after consumption, rotary evaporate under vacuum to obtain 76.5 g of a white solid, then slurry with dichloromethane, filter, and dry to obtain 72.4 g of the target compound with a yield of 90%. Perform mass spectrometry detection on the target compound. 1 HNMR(400 MHz, HD2O): δ 1.25 (6H, d, J = 6.8 Hz), 2.40 (1H, o, J = 6.8 Hz), 3.54 (2H, t, J = 6.7 Hz), 4.01 (2H, t, J = 6.7 Hz), 7.41 (1H, d, J = 6.7 Hz), indicating the synthesis of Compound I.

[0031] Compound III in the example can be prepared in the following manner: Add 50 g of taurine and 800 g of absolute ethanol to a 1 L reaction flask, stir at room temperature, add 50 g of 2-fluoropyridine-5-carbaldehyde, stir evenly, then add 21.58 g of sodium methoxide in batches, react at room temperature, detect 2-fluoropyridine-5-carbaldehyde by GC-MS, stop the reaction after consumption, rotary evaporate under vacuum to obtain 100.7 g of a white solid, then slurry with dichloromethane, filter, and dry to obtain 96.2 g of the target compound with a yield of 94.7%. Perform mass spectrometry detection on the target compound. 1 HNMR(400 MHz, HD2O): δ 3.59 (2H, t, J = 6.5 Hz), 3.96 (2H, t, J = 6.5 Hz), 7.27 (1H, dd, J = 7.6, 0.5 Hz), 7.76 (1H, dd, J = 7.6, 1.9 Hz), 8.27 - 8.41 (2H, 8.32 (s), 8.36 (dd, J = 1.9, 0.5 Hz)); 19 FNMR(376 MHz, HD2O): δ -57.7, indicating the synthesis of Compound III.

[0032] Example 1

[0033] (1) Preparation of Non-aqueous Electrolyte

[0034] In an argon atmosphere, a non-aqueous electrolyte was prepared in a vacuum glove box with a water content < 1 ppm. In a dry argon atmosphere glove box, propylene carbonate (PC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed at a weight ratio of PC:EMC:DEC = 1:1:1 to obtain 87 g of non-aqueous organic solvent. Then, 0.05 g of Compound I was added, dissolved and stirred well, and then 12.95 g of sodium salt was added. After mixing evenly, the non-aqueous electrolyte was obtained.

[0035] (2) Preparation of Positive Electrode

[0036] NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, binder PVDF, and conductive agent SuperP were mixed evenly at a mass ratio of 95:1:4 to prepare a sodium-ion battery positive electrode slurry with a certain viscosity. After the prepared slurry was coated on both sides of the aluminum foil, it was dried and rolled to obtain the positive electrode sheet.

[0037] (3) Preparation of Negative Electrode

[0038] Hard carbon, conductive agent SuperP, thickening agent CMC, and binder SBR (styrene-butadiene rubber latex) were made into a slurry at a mass ratio of 95:1.5:1.0:2.5, mixed evenly, and the prepared slurry was coated on both sides of the copper foil. After drying and rolling, the negative electrode sheet was obtained.

[0039] (4) Preparation of Sodium-ion Battery

[0040] The positive electrode sheet, separator, and negative electrode sheet were made into a square battery cell in a stacked manner, packaged with a polymer, and filled with the non-aqueous electrolyte of the sodium-ion battery prepared above. After processes such as formation and grading, a sodium-ion battery with a capacity of 1000 mAh was made.

[0041] The composition and content of the non-aqueous electrolytes of Examples 1 to 6 and Comparative Example 1 are shown in Table 1. Among them, the preparation processes of the non-aqueous electrolytes, positive electrode sheets, negative electrode sheets, and lithium-ion batteries of Examples 2 to 6 and Comparative Example 1 are the same as those of Example 1.

[0042] Table 1 Components of Non-aqueous Electrolytes in Examples and Comparative Examples

[0043] Group Non-aqueous organic solvent / mass (g) Sodium salt / mass (g) Additive (g) Example 1 PC / EMC / DEC = 1:1:1 (87 g) <![CDATA[NaPF6(12.95g)]]> Compound 1 (0.05 g) Example 2 PC / EMC / DEC = 1:1:1 (87 g) <![CDATA[NaPF6(12.95g)]]> Compound 2 (0.05 g) Example 3 PC / EMC / DEC = 1:1:1 (87 g) <![CDATA[NaPF6(12.95g)]]> Compound 3 (0.05 g) Example 4 PC / EMC / DEC = 1:1:1 (87 g) <![CDATA[NaPF6(12.9g)]]> Compound 3 (0.1 g) Example 5 PC / EMC / DEC = 1:1:1 (87 g) <![CDATA[NaPF6(12.5g)]]> Compound 3 (0.5 g) Example 6 EP / EMC / DEC = 1:3:2 (86 g) NaFSI (13.8 g) Compound 1 (0.2 g) Comparative Example 1 PC / EMC / DEC = 1:1:1 (87 g) <![CDATA[NaPF6(13g)]]> /

[0044] The sodium-ion batteries prepared in Examples 1 to 6 and Comparative Example 1 were respectively subjected to high-temperature cycle tests, high-temperature storage performance tests, and safety performance tests. The test results are shown in Table 2.

[0045] (1) High-temperature Cycle Performance Test

[0046] Place the sodium-ion battery in an incubator at 45 °C and let it stand for 30 min to make the sodium-ion battery reach a constant temperature. Charge it at a constant current of 1C until the voltage reaches 4.1V, then charge it at a constant voltage of 4.1V until the current reaches 0.05C, and then discharge it at a constant current of 1C until the voltage reaches 2.5V. Record the first-cycle discharge capacity of the battery, which is one charge-discharge cycle. Repeat this cycle 400 times, record the discharge capacity of the first cycle and the last cycle, and calculate the capacity retention rate according to the following formula.

[0047] Capacity retention rate = Discharge capacity of the last cycle / Discharge capacity of the first cycle × 100%

[0048] (2) High-temperature storage performance test

[0049] Under normal temperature (25 °C) conditions, perform one 0.5C / 0.5C charge and discharge on the lithium-ion battery (the discharge capacity of the battery is recorded as C0), with the upper limit voltage of 4.1V. Place the battery in an oven at 60 °C for 30 days, take out the battery, and then place the battery in an environment at 25 °C and perform 0.5C discharge. Record the discharge capacity as C1. Then perform one 0.5C / 0.5C charge and discharge on the lithium-ion battery (the discharge capacity of the battery is recorded as C2), and calculate the capacity retention rate and capacity recovery rate of the lithium-ion battery using the following formula.

[0050] Capacity retention rate = (C1 / C0) × 100%

[0051] Capacity recovery rate = (C2 / C0) × 100%

[0052] (3) Safety performance test

[0053] Place the sodium-ion battery in an oven at 60 °C and heat it to 60 °C at a heating rate of 5 °C / min, and keep it at 60 °C for 30 min. Perform 1C constant current and constant voltage charging on the sodium-ion battery, with the upper limit voltage of 10V, and observe whether there are any serious bulging, smoking, fire, explosion and other phenomena in the battery.

[0054] Table 2 Performance test results of sodium-ion batteries in examples and comparative examples

[0055]

[0056] As can be seen from the results in Table 2, compared with Comparative Example 1, the sodium-ion batteries of Examples 1 to 6 have better high-temperature storage, high-temperature cycling performance and safety performance. This is because the additives in the sodium-ion batteries of Examples 1 to 6 can maintain a solid electrolyte interface (SEI) film under high temperature and high pressure. The Schiff base structure contained in the compound of Structural Formula I can be preferentially reduced to form a thin and dense cathode solid electrolyte interface film (CEI), improving the stability of the CEI, which can more effectively isolate the electrolyte from the active material, prevent unnecessary side reactions, and the sulfonyl group in the structure can be relatively neatly arranged between the electrolyte and the electrode under the action of affinity, optimizing the interfacial contact between the electrolyte and the electrode and improving the antioxidant performance of the electrolyte at the film, thus further ensuring the high-temperature cycling performance and safety performance of the sodium-ion battery. In particular, the compound III shown in Structural Formula I exhibits the best performance. Under the synchronous action of the Schiff base, sulfonyl group and fluorine atom, it has relatively higher stability under high temperature and high pressure, can effectively inhibit the continuous decomposition of the solid electrolyte film, and thus significantly reduce the gas generation problem caused by the repeated loss of the solid electrolyte film, thereby ensuring the high-temperature cycling performance and safety performance of the sodium-ion battery.

[0057] 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 those listed in the embodiments. 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. A non-aqueous electrolyte comprising an electrolyte salt, a non-aqueous organic solvent and an additive, wherein the additive comprises a compound A as shown in structural formula I, wherein: R is selected from a C1-C5 hydrocarbon group, a C1-C5 halogenated hydrocarbon group, an aromatic hydrocarbon group, a halogenated aromatic hydrocarbon group, a pyridyl group or a halogenated pyridyl group, n is selected from an integer of 0 to 4, 2. The non-aqueous electrolyte according to claim 1, characterized in that R is selected from C1-C3 alkyl, C2-C3 alkenyl, C2-C3 alkynyl, C1-C3 fluoroalkyl, C2-C3 fluoroalkenyl, C2-C3 fluoroalkynyl, phenyl, fluorophenyl, pyridyl or fluoropyridyl, and n is 1 or 2.

3. The non-aqueous electrolyte according to claim 1, characterized in that The compound A is selected from at least one of compound 1 to compound 3, 4. The non-aqueous electrolyte according to claim 1, characterized in that The mass proportion of the compound A in the non-aqueous electrolyte is 0.01-0.50%.

5. The nonaqueous electrolyte according to claim 1, characterized in that The mass percentage of the electrolyte salt in the non-aqueous electrolyte is 6.5-15.5%, and the electrolyte salt is a sodium salt, which is selected from at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium trifluoromethanesulfonate, sodium bistrifluoromethanesulfonyl imide, sodium bisoxalatoborate, sodium difluorophosphate, sodium difluorooxalatoborate, sodium difluorobisoxalatophosphate and sodium bisfluorosulfonyl imide.

6. The nonaqueous electrolyte according to claim 1, characterized in that The non-aqueous organic solvent is at least one selected from ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, butyl acetate, γ-butyrolactone, propyl propionate, ethyl propionate, ethyl acetate and ethyl butyrate.

7. A secondary battery, characterized in that: The invention comprises a positive electrode material, a negative electrode material and the non-aqueous electrolyte according to any one of claims 1 to 6, and the maximum charging voltage is 4.1V.

8. The secondary battery according to claim 7, characterized in that: The chemical formula of the positive electrode material is Na x M (1-y-z) Fe y Mn z O2, wherein M is 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,y+z≤1。 9. The secondary battery according to claim 7, characterized in that: The negative electrode material includes at least one of a carbon-based negative electrode material, a titanium-based oxide negative electrode material and an alloy negative electrode material.

10. The secondary battery according to claim 7, characterized in that: The negative electrode material includes soft carbon, hard carbon, sodium titanate, FeS x , Cu x O, MoS2, Sn x O. CoS x , Fe2O3, Fe3O4, ZnS, Sb and SbSn.

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