Non-aqueous electrolyte and secondary battery

Abstract

The application relates to a nonaqueous electrolyte and a secondary battery, which comprises a solvent, an alkali metal salt, a first additive, and a second additive; the first additive is at least one of substance 1, substance 2 and substance 3; and the second additive is a multiple bond additive. In the second additive of the application, the C connected with the multiple bond can accept the O free radical of the ring opening in the first additive, and a stable organic SEI component is synchronously formed; the SEI simultaneously contains S-O, R-C-Se-O groups or sulfite or sulfate, and a composite film component is formed, wherein the S-O component or the R-C-Se-O component can improve the kinetics and transmission capacity of the SEI, and the long-chain film component of the multiple bond can provide stability.

Description

Technical Field

[0001] This invention belongs to the field of secondary batteries, specifically relating to a non-aqueous electrolyte and a secondary battery. Background Technology

[0002] Rechargeable batteries, characterized by large capacity, fast charging speed, high energy density, and long cycle life, are widely used in daily life and production equipment, such as consumer electronics, new energy electric vehicles, and energy storage products for homes and businesses. Extensive academic and industrial research has found that the static storage degradation and dynamic cycle degradation of batteries under high-temperature environments are strongly correlated with the stability of the SEI film on the negative electrode. Poor SEI film stability leads to the loss of active lithium, SEI film damage, and exacerbated side reactions. It may also be accompanied by gas release causing cell expansion, thereby degrading battery performance and significantly reducing the overall battery life.

[0003] Existing technologies typically use various additives to improve the stability of the SEI film. Different additives can significantly improve the composition of the SEI film and enhance cycle life; examples include vinylene carbonate, fluoroethylene carbonate, vinyl sulfate, 1,3-propanesulfonate lactone, and methanedisulfonate. However, the SEI films formed by these additives still have some drawbacks. They cannot effectively inhibit SEI stripping and decomposition, cannot significantly suppress potential side reactions between the positive and negative electrodes and the electrolyte, and cannot effectively balance the simultaneous requirements of low-temperature performance, low impedance, and high cycle life. The overall battery performance remains poor. Therefore, it is crucial to develop additives with excellent low impedance, superior low-temperature performance, good high-temperature performance, and long cycle life, as well as their corresponding non-aqueous electrolyte systems and batteries. Summary of the Invention

[0004] The purpose of this invention is to address the problems existing in the prior art by providing a non-aqueous electrolyte and a secondary battery that can form a low-impedance and stable SEI film, enabling the battery to simultaneously achieve low impedance and good long-cycle performance, as well as low-temperature and high-temperature performance, thus achieving excellent overall performance.

[0005] The objective of this invention can be achieved through the following methods:

[0006] This invention provides a non-aqueous electrolyte, which contains a solvent, an alkali metal salt, a first additive, and a second additive; The first additive is at least one of substance 1, substance 2, and substance 3; the structural formulas of substance 1, substance 2, and substance 3 are as follows: ; The second additive is one or more of the following: 1,3-propenylsulfonate lactone, 2,4-butanesulfonate lactone, ethylene ethylene carbonate, triargyl phosphate, trimethyl phosphite, tripropylene phosphite, trimethyl phosphate, tetravinylsilane, tetramethyltetravinylcyclotetrasiloxane, tris(vinyldimethylsilane) phosphate, succinic anhydride, maleic anhydride, citric acid anhydride, and 2-propynyl-1-methanesulfonic acid.

[0007] As one embodiment of the present invention, the first additive is substance 1, or a combination of substance 1 with one or two of substances 2 and 3.

[0008] The first additive can form an SEI film mainly composed of sulfates, selenates, and organic sulfur / selenium compounds on the negative electrode surface (substance 2 can also form sulfites), which can reduce side reactions on the negative electrode surface. At the same time, the SEI film mainly composed of sulfates and selenates has good ion transport capacity and chemical kinetic performance.

[0009] The second additive (bonding additive) can protect the negative and positive electrodes, inhibit the dissolution and deposition of transition metals, and at the same time, it can synergistically form a composite SEI film with the sulfate and selenium components on the negative electrode surface, further enhancing the stability of the SEI film. Meanwhile, the composite film can balance good lithium-ion transport kinetics and structural stability.

[0010] The interaction mechanism between the first and second additives: The C bonds in the second additive, which are connected by multiple bonds, can accept the open-ring O radicals from the first additive (O... . Simultaneously, a stable organic SEI component (a long-chain membrane component with multiple bonds) is formed, which provides stability; in addition, the Se-containing ring first undergoes ring-opening to form RC-Se. . Free radicals can react with CO. . Combination or O . Complexation occurs, forming RC-Se-O groups, which further enrich the SEI component. The resulting composite SEI membrane contains SO, selenate, organic sulfur / selenium compounds, RC-Se-O groups, and sulfate ions. The SO or RC-Se-O components can improve the kinetics and transport capacity of the SEI.

[0011] As one embodiment of the present invention, the alkali metal salt is a lithium salt, which includes any one or a combination of at least two of LiPF6 (lithium hexafluorophosphate), LiTFSI (lithium bis(trifluoromethanesulfonyl)imide), LiFSI (lithium bis(fluorosulfonyl)imide), and LiOTF (lithium trifluoromethanesulfonate).

[0012] As one embodiment of the present invention, the solvent includes carbonates and / or carboxylic esters; the carbonates include cyclic carbonates and / or chain carbonates; wherein, the cyclic carbonates include at least one of EC (ethylene carbonate), PC (propylene carbonate), and DFEC (difluoroethylene carbonate); the chain carbonates include at least one of DMC (dimethyl carbonate), EMC (ethyl methyl carbonate), DEC (diethyl carbonate), and FEMC (fluoroethyl methyl carbonate); and the carboxylic esters include at least one of EA (ethyl acetate), EP (ethyl propionate), PP (propyl propionate), MA (methyl acetate), MP (methyl propionate), PA (propyl acetate), and DFEA (ethyl difluoroacetate).

[0013] Cyclic ester solvents provide conductivity, while chain ester solvents provide solubility. Carboxylic esters are chain-like and belong to low-viscosity solvents. Their main function is to reduce viscosity. At the same time, carboxylic esters have low desolvation energies, allowing alkali metal salts to dissociate more effectively.

[0014] In one embodiment of the present invention, the mass fraction of alkali metal salt in the non-aqueous electrolyte is 7-18 wt.%, preferably 10-18 wt.%, and more preferably 10-15 wt.%. In one embodiment of the present invention, the mass fraction of the solvent in the non-aqueous electrolyte is 70-88 wt.%, preferably 76-85 wt.%; wherein the content of carboxylic acid ester is ≥4.5 wt.%, preferably 6-26 wt.%. As one embodiment of the present invention, the mass fraction of the first additive in the non-aqueous electrolyte is 0.01-3 wt.%, preferably 0.2-1.5 wt.%, more preferably 0.5-1.5 wt.%; when the first additive is a combination of substance 1 and one or two of substance 2 and substance 3, the mass percentage of substance 1 in the first additive is not less than 40%, preferably not less than 50%.

[0015] As one embodiment of the present invention, the mass fraction of the second additive in the non-aqueous electrolyte is 0.001-1 wt.%, preferably 0.2-1.5 wt.%, and more preferably 0.2-0.5 wt.%.

[0016] As one embodiment of the present invention, the non-aqueous electrolyte further comprises a lithium salt additive, which includes at least one of LiBF4 (lithium tetrafluoroborate), LiPO2F2 (lithium difluorophosphate), LiFS (lithium fluorosulfonate), LiSA (lithium aminosulfonate), LiODFP (lithium difluorooxalate phosphate), LiOTFP (lithium trifluoromethanesulfonylimide), LiODFB (lithium difluorooxalate borate), and LiBOB (lithium bis(oxalate borate)). The content of the lithium salt additive in the non-aqueous electrolyte is 0.01-2.5 wt.%.

[0017] In one embodiment of the present invention, the non-aqueous electrolyte further comprises an organic film-forming additive, which includes at least one of VC (vinylene carbonate), FEC (fluorovinyl carbonate), DTD (vinyl sulfate), MMDS (dimethyl methanedisulfonate), and PS (1,3-propanesulfonyl lactone). The content of the organic film-forming additive in the non-aqueous electrolyte is 0.01-5.5 wt.%.

[0018] The present invention also provides a secondary battery, comprising a positive electrode, a negative electrode, and the electrolyte.

[0019] The secondary battery is one of lithium battery, sodium battery, or potassium battery.

[0020] When the secondary battery is a lithium battery, the alkali metal salt in the non-aqueous electrolyte is a lithium salt. The active material in the positive electrode is any one or a combination of at least two of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium nickel oxide, lithium iron phosphate, lithium cobalt phosphate, and lithium nickel cobalt manganese aluminum oxide. The active material in the negative electrode is any one or a combination of at least two of graphite, silicon, silicon-carbon, and silicon-oxygen.

[0021] The electrolyte of the present invention can be used in both sodium and potassium battery systems, and the corresponding alkali metal salt can be sodium or potassium salt.

[0022] Substance 1 is obtained by adding substance A5 (structure 1.5) to dichloromethane, adding sodium hypochlorite dropwise, and reacting. The substance A5 (structure 1.5) is obtained by reacting substance A4 (structure 1.4) with thionyl chloride; The substance A4 (structure 1.4) is obtained by reacting substance A3 (structure 1.3) with sodium selenide; The substance A3 (structure 1.3) is obtained by dissolving substance A2 (structure 1.2), adding hydrochloric acid dropwise, and heating to react. The substance A2 (structure 1.2) is obtained by reacting substance A1 (structure 1.1) with p-toluenesulfonyl chloride.

[0023] Synthesis method of substance 1: (1) Add substance A1 (structure 1.1) to pyridine, add 2.2 eq of p-toluenesulfonyl chloride at -10 °C, and then raise to room temperature overnight. Post-treatment: add ice water, filter the solid, wash the filter cake with water, and wash with ethanol. Dry to obtain substance A2 (structure 1.2).

[0024] (2) Substance A2 (structure 1.2) was added to methanol, 1 eq of 1N hydrochloric acid was added dropwise, and the mixture was heated under reflux for 5 hours. The reaction was monitored by TLC until complete. The solution was evaporated to dryness, dissolved in chloroform, dried over magnesium sulfate, and the filtrate was evaporated to dryness to obtain substance A3 (structure 1.3).

[0025] (3) The obtained substance A3 (i.e., structure 1.3 in the following formula) was added to ethanol, and then 2.5 eq of sodium selenide was added to react and filtered. The filtrate was collected, evaporated to dryness, and subjected to column chromatography to obtain substance A4 (structure 1.4).

[0026] (4) Substance A4 (structure 1.4) was added to anhydrous dichloromethane, purged with nitrogen, and continuously purged with gas. Thionyl chloride was added dropwise between 0 and 10 degrees Celsius. After the addition was complete, the mixture was slowly brought to room temperature. GC monitoring was performed until the reaction was complete. Post-treatment: Concentration and distillation were performed to obtain substance A5 (structure 1.5).

[0027] (5) Substance A5 (structure 1.5) was added to dichloromethane. Sodium hypochlorite solution was added dropwise at -10°C, with the temperature controlled below 0°C. After the addition was complete, the reaction was carried out at 0°C for 4 hours. The reaction was monitored by GC until complete. Post-processing: extraction, concentration, and distillation. Finally, substance 1 (structure 1.6) was obtained.

[0028]

[0029] The synthesis method of substance 2 is as follows: The overall steps are similar to those of Substance 1, with the following differences: (1) Substance B3 (structure 1.3, i.e., structure 2.3 in the following formula) was added to ethanol, followed by 2.5 eq of sodium sulfide nonahydrate, and heated to reflux. After the reaction was complete, the mixture was filtered, the filtrate was evaporated to dryness, and then dissolved in chloroform. The mixture was filtered again, and the filter cake was washed with a large amount of chloroform. The filtrate was collected, evaporated to dryness, and subjected to column chromatography to obtain substance B4 (structure 2.4).

[0030] (4) Substance B4 (structure 2.4) was added to anhydrous dichloromethane, purged with nitrogen, and continuously purged with gas. Thionyl chloride was added dropwise between 0 and 10 degrees Celsius. After the addition was complete, the mixture was slowly brought to room temperature. GC monitoring was performed until the reaction was complete. Post-treatment: Concentration and distillation were performed to obtain substance B5 (structure 2.5).

[0031] (5) Substance B5 (structure 2.5) was added to dichloromethane. Sodium hypochlorite solution was added dropwise at -10°C, keeping the temperature below 0°C. After the addition was complete, the reaction was carried out at 0°C for 4 hours. The reaction was monitored by GC until complete. Post-processing: extraction, concentration, and distillation. Substance 2 (structure 2.6) was obtained.

[0032]

[0033] The synthesis method of substance 3 is as follows: (1) Add 1 eq of substance C1 (structure 3.1) to anhydrous dichloromethane, purge with nitrogen, and continuously purge. Add thionyl chloride dropwise between 0 and 10 °C. After the addition is complete, slowly raise the temperature to room temperature. Monitor the reaction by GC until it is complete. Post-treatment: concentrate and distill to obtain substance C2 (structure 3.2).

[0034] (2) Dichloromethane was added to substance C2 (structure 3.2), and sodium hypochlorite solution was added dropwise at -10℃, keeping the temperature below 0℃. After the addition was complete, the reaction was carried out at 0℃ for 4 hours. The reaction was monitored by GC until complete. Post-processing: extraction, concentration, and distillation. Substance 3 (structure 3.3) was obtained.

[0035]

[0036] Compared with the prior art, the present invention has the following beneficial effects: (1) The first additive can form an SEI film mainly composed of sulfates and organic sulfides on the surface of the negative electrode (the SEI film formed by substance 1 also includes selenate and organic selenium compounds; the SEI film formed by substance 2 also includes sulfite), which reduces side reactions on the surface of the negative electrode. At the same time, the SEI mainly composed of sulfates and selenium has good ion transport ability and chemical kinetics.

[0037] (2) The second additive (bond additive) can protect both the negative and positive electrodes at the same time, inhibit the dissolution and deposition of transition metals, and can also synergistically form a composite SEI film with the sulfate and selenium components of the negative electrode, further enhancing the stability of the SEI film. At the same time, the composite film can take into account good ion transport capacity, chemical kinetic performance and structural stability.

[0038] (3) The C-chains in the second additive, which are linked by multiple bonds, can accept the O-chain radicals from the first additive, and simultaneously form a stable organic SEI component (a long-chain membrane component with multiple bonds). The long-chain membrane component with multiple bonds can provide structural stability. In addition, the SEI membrane will contain SO, RC-Se-O groups, or sulfite or sulfate groups. Among them, the SO component or RC-Se-O component can improve the kinetics and ion transport capacity of the SEI. Detailed Implementation

[0039] The present invention will now be described in detail with reference to specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0040] Example 1 The lithium iron phosphate battery system is used. The electrolyte formulation is 10 wt.% LiPF6 and 3 wt.% LiFSI dissolved in EC / EMC / EA (24:34:24 wt.%). The first additive is substance 1 with a content of 0.8 wt.%, the second additive is tris(vinyldimethylsilane) phosphate with a content of 0.3 wt.%, and other additives are VC, FEC, and LiODFB.

[0041] Preparation of lithium iron phosphate batteries: Positive electrode sheet: Lithium iron phosphate (LiFePO4), PVDF (PVDF binder), and SP (SP conductive agent) are weighed in a mass ratio of 48.25:1:0.75. These components are mixed, and then N-methylpyrrolidone solvent is added and stirred until homogeneous to prepare the positive electrode slurry. The positive electrode slurry is coated onto the surface of aluminum foil, rolled and dried, and then sliced ​​to obtain the positive electrode sheet with an areal density of 460 g / m³. 2 Compacted to 2.7g / m 3 .

[0042] Negative electrode sheet: Artificial graphite (negative electrode active material), CMC (negative electrode binder), and SP (negative electrode conductive agent) are weighed according to a mass ratio of 120.25:3.75:1. These components are mixed and then added to deionized water and stirred until homogeneous to prepare the negative electrode slurry. The negative electrode slurry is coated onto the surface of copper foil, rolled and dried, and then sliced ​​to obtain the negative electrode sheet. The sheet surface density is 218 g / m². 2 Compacted to 1.63 g / m 3 .

[0043] Electrolyte: The electrolyte used in the examples is employed.

[0044] The separator is a 9µm PE separator. Facing the positive electrode side, an Al2O3 layer is first coated, followed by a PVDF adhesive layer with thicknesses of 2µm and 2µm, respectively.

[0045] Battery: The above-mentioned positive electrode, negative electrode, electrolyte and separator are assembled to form a battery, which is then processed through formation and aging processes to obtain the battery.

[0046] Example 2 The lithium iron phosphate battery system is used. The electrolyte formulation is 10 wt.% LiPF6 and 3 wt.% LiFSI dissolved in EC / EMC / EA (24:34.1:24 wt.%). The first additive is substance 2 with a content of 0.8 wt.%, the second additive is tetravinylsilane with a content of 0.2 wt.%, and the other additives are VC, FEC, and LiODFB.

[0047] The battery preparation steps are the same as in Example 1.

[0048] Example 3 The lithium iron phosphate battery system is used. The electrolyte formulation is 10 wt.% LiPF6 and 3 wt.% LiFSI dissolved in EC / EMC / EA (24:34.1:24 wt.%). The first additives are substances 1 and 3, with contents of 0.4 wt.% and 0.4 wt.% respectively. The second additive is ethylene ethylene carbonate with a content of 0.3 wt.%. Other additives are VC, FEC, and LiODFB.

[0049] The battery preparation steps are the same as in Example 1.

[0050] Example 4 The lithium iron phosphate battery system is used. The electrolyte formulation is 10 wt.% LiPF6 and 3 wt.% LiFSI dissolved in EC / EMC / EA (24:34.1:24 wt.%). The first additive is substance 3 with a content of 0.8 wt.%, the second additive is 1,3-propenylsulfonate lactone with a content of 0.3 wt.%, and other additives are VC, FEC, and LiODFB.

[0051] The battery preparation steps are the same as in Example 1.

[0052] Example 5 The lithium iron phosphate battery system is used. The electrolyte formula is 10 wt.% LiPF6 and 3 wt.% LiFSI dissolved in EC / EMC / EA (24:33.9:24 wt.%). The first additive is substance 2 with a content of 1 wt.% and the second additive is succinic anhydride with a content of 0.2 wt.%. Other additives are VC, FEC and LiODFB.

[0053] The battery preparation steps are the same as in Example 1.

[0054] Example 6 The lithium iron phosphate battery system is used. The electrolyte formulation is 10 wt.% LiPF6 and 3 wt.% LiFSI dissolved in EC / EMC / EA (24:34:24 wt.%). The first additive is substance 2 with a content of 0.8 wt.% and the second additive is tris(vinyldimethylsilane) phosphate with a content of 0.3 wt.%. Other additives are VC, FEC and LiODFB.

[0055] Example 7 The lithium iron phosphate battery system is used. The electrolyte formulation is 10 wt.% LiPF6 and 3 wt.% LiFSI dissolved in EC / EMC / EA (24:34:24 wt.%). The first additive is substance 3 with a content of 0.8 wt.% and the second additive is tris(vinyldimethylsilane) phosphate with a content of 0.3 wt.%. Other additives are VC, FEC and LiODFB.

[0056] Example 8 The lithium iron phosphate battery system is used. The electrolyte formulation is 10 wt.% LiPF6 and 3 wt.% LiFSI dissolved in EC / EMC / EA (24:31.8:24 wt.%). The first additive is substance 1 with a content of 3 wt.%, the second additive is tris(vinyldimethylsilane) phosphate with a content of 0.3 wt.%, and the other additives are VC, FEC, and LiODFB.

[0057] Example 9 The lithium iron phosphate battery system is used. The electrolyte formulation is 10 wt.% LiPF6 and 3 wt.% LiFSI dissolved in EC / EMC / EA (24:33.3:24 wt.%). The first additive is substance 1 with a content of 1.5 wt.% and the second additive is tris(vinyldimethylsilane) phosphate with a content of 0.3 wt.%. Other additives are VC, FEC and LiODFB.

[0058] Example 10 The lithium iron phosphate battery system is used. The electrolyte formulation is 10 wt.% LiPF6 and 3 wt.% LiFSI dissolved in EC / EMC / EA (24:34.79:24 wt.%). The first additive is substance 1 with a content of 0.01 wt.% and the second additive is tris(vinyldimethylsilane) phosphate with a content of 0.3 wt.%. Other additives are VC, FEC and LiODFB.

[0059] The components and their mass percentages (wt.%) in the examples are shown in Table 1 below: Table 1

[0060] Comparative Example 1 The lithium iron phosphate battery system was used, and the electrolyte formulation was basically the same as in Example 1, except that only the first additive was used, the second additive was not used, and the total content remained unchanged. The battery preparation steps were the same as in Example 1.

[0061] Comparative Example 2 The lithium iron phosphate battery system was used, and the electrolyte formulation was basically the same as in Example 1, except that only the second additive was used, the first additive was not used, and the total content remained unchanged. The battery preparation steps were the same as in Example 1.

[0062] Comparative Example 3 The lithium iron phosphate battery system was used, and the electrolyte formulation was basically the same as in Example 1, except that the solvent contained no carboxylic acid esters, while the total content remained unchanged. The battery preparation steps were the same as in Example 1.

[0063] The composition of each component in the comparative example is shown in Table 2 below: Table 2

[0064] Test method: 1. 50% SOC DCR test method: (1) Charge the 1C CCCV to 3.65V, and cut off the current at 0.05C; (2) Let it sit for 30 minutes; (3) Discharge to 2.5V at 1C; (4) Let it sit for 30 minutes; (5) Repeat steps 1-4 for 3 cycles; (6) Charge the CCCV at 0.33C to 3.65V, and cut off the current at 0.05C; (7) Let it sit for 30 minutes; (8) Discharge at 0.3C for 100 minutes; (9) Let it sit for 30 minutes; (10) 3C discharge for 30s, and obtain the DCR value at 50% SOC.

[0065] 2. 45℃ high-temperature cycling test method: (1) The battery is placed in a 45°C constant temperature cabinet until the temperature is balanced and the battery temperature rises to the specified temperature; (2) Charge 1C CC to 3.65V; (3) Let it sit for 10 minutes; (4) Discharge to 2.5V at 1C; (5) Let it sit for 10 minutes; (6) Repeat steps 2-5 above for repeated testing; (7) Check the capacity retention rate when the cycle reaches 1500 times.

[0066] 3. 25℃ 4C Fast Charging Test: (1) Place the battery in a 25°C constant temperature cabinet until the temperature reaches the specified temperature; (2) Charge the 1C CCCV to 3.65V, and cut off the current at 0.05C; (3) Let it sit for 30 minutes; (4) Discharge to 2.5V at 1C; (5) Let it sit for 30 minutes; (6) Repeat steps 2-5 for 3 cycles; (7) Charge the 4C CC to 3.65V and check the percentage of 4C rate charge.

[0067] 4. -20℃ Discharge Test: (1) Discharge at 1C to 2.5V; (2) Let it sit for 30 minutes; (3) Charge the 1C CCCV to 3.65V, and cut off the current at 0.05C; (4) Let it sit for 30 minutes; (5) Repeat steps 1-4 for 3 cycles; (6) Place the battery in a -20℃ constant temperature cabinet until the battery temperature drops and balances to the specified temperature; (7) Discharge to 2.0V at 0.2C and check the discharge energy retention rate.

[0068] The test results of the example are shown in Table 3 below: Table 3

[0069] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A non-aqueous electrolyte, characterized in that, The non-aqueous electrolyte contains a solvent, an alkali metal salt, a first additive, and a second additive; The first additive is at least one of substance 1, substance 2, and substance 3; the structural formulas of substance 1, substance 2, and substance 3 are as follows: ； The second additive is one or more of the following: 1,3-propenylsulfonate lactone, 2,4-butanesulfonate lactone, ethylene ethylene carbonate, triargyl phosphate, trimethyl phosphite, tripropylene phosphite, trimethyl phosphate, tetravinylsilane, tetramethyltetravinylcyclotetrasiloxane, tris(vinyldimethylsilane) phosphate, succinic anhydride, maleic anhydride, citric acid anhydride, and 2-propynyl-1-methanesulfonic acid.

2. The non-aqueous electrolyte according to claim 1, characterized in that, The first additive is substance 1, or a combination of substance 1 with one or two of substances 2 and 3.

3. The non-aqueous electrolyte according to claim 2, characterized in that, The mass percentage of substance 1 in the first additive shall not be less than 40%.

4. The non-aqueous electrolyte according to claim 1, characterized in that, The alkali metal salt is a lithium salt, which includes any one or a combination of at least two of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium trifluoromethanesulfonate.

5. The non-aqueous electrolyte according to claim 1, characterized in that, Solvents include carbonates and / or carboxylic esters; The carbonates include cyclic carbonates and / or chain carbonates; cyclic carbonates include at least one of EC, PC, and DFEC; chain carbonates include at least one of DMC, EMC, DEC, and FEMC. Carboxylic acid esters include at least one of EA, EP, PP, MA, MP, PA, and DFEA.

6. The non-aqueous electrolyte according to claim 1, characterized in that, The mass fraction of alkali metal salts in the non-aqueous electrolyte is 7-18 wt.%. And / or, the mass fraction of the solvent in the non-aqueous electrolyte is 70-88 wt.%; And / or, the mass fraction of the first additive in the non-aqueous electrolyte is 0.01-3 wt.%; And / or, the mass fraction of the second additive in the non-aqueous electrolyte is 0.001-1 wt.%.

7. The non-aqueous electrolyte according to claim 1, characterized in that, The electrolyte also contains lithium salt additives, including at least one of LiBF4, LiPO2F2, LiFS, LiFSA, LiODFP, LiOTFP, LiODFB, and LiBOB.

8. The non-aqueous electrolyte according to claim 1, characterized in that, The electrolyte also contains organic film-forming additives, including at least one of VC, FEC, DTD, MMDS, and PS.

9. A secondary battery, characterized in that, It includes a positive electrode, a negative electrode, and the non-aqueous electrolyte as described in claim 1.

10. The secondary battery according to claim 9, characterized in that, The secondary battery is a lithium battery, and the alkali metal salt in the non-aqueous electrolyte is a lithium salt. The active material in the positive electrode is any one or a combination of at least two of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium nickel oxide, lithium iron phosphate, lithium cobalt phosphate, and lithium nickel cobalt manganese aluminum oxide; and / or, the active material in the negative electrode is any one or a combination of at least two of graphite, silicon, silicon carbon, and silicon oxide.

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