Non-aqueous electrolyte for secondary battery and secondary battery thereof

Abstract

The present invention discloses a non-aqueous electrolyte for a secondary battery and a secondary battery thereof, the electrolyte comprises an electrolyte salt, a non-aqueous solvent and an additive, the additive at least comprises: a nitrogen-containing heterocyclic compound as a first additive, a film-forming additive with a film-forming potential of less than 1.5 V (vs. Li + / Li) as a second additive, the specific structure of the additive is shown in the specification. The nitrogen-containing heterocyclic compound and the film-forming additive with the film-forming potential lower than 1.5 V (vs.Li < + > / Li) are combined for use, and the nitrogen-containing heterocyclic compound and the film-forming additive are regulated in a specific content ratio range to fully generate a synergistic effect, so that water catching and acid inhibition can be effectively realized, decomposition and gas production can be effectively inhibited at high temperature and high voltage, the stability of the electrolyte is greatly improved, and the service life of the electrolyte is prolonged. And an SEI film with excellent ion transmission capability and structure / thermal stability can be formed on the surface of the electrode, so that the first efficiency of the battery is effectively improved, and the low-temperature performance and the cycle performance of the battery are further improved.

Description

Technical Field

[0001] This invention relates to the field of electrolytes, and in particular to a non-aqueous electrolyte for secondary batteries that achieves long-term storage stability while maintaining good high and low temperature performance, and the secondary battery thereof. Background Technology

[0002] Electrolyte additives, as an indispensable component of secondary battery electrolytes, are mainly responsible for constructing a stable electrode / electrolyte interface film to achieve electronic insulation and facilitate lithium-ion / sodium-ion transport. Although their content is small, different types of additives have different functional groups, which alter the composition and structure of the battery interface film, resulting in different battery performance improvements. This helps lithium batteries achieve excellent characteristics such as high energy density, long cycle life, high rate performance, wide temperature range, and high safety, playing a significant role in the differentiated competition of electrolytes.

[0003] To achieve long cycle life in lithium metal anode batteries, Massachusetts Solid Energy Holdings Inc. (SSE) patent CN116075959A discloses a sulfonyl-based solvent system that is compatible with lithium metal anodes, effectively passivates them, and maintains oxidation stability at high-voltage cathodes. In lithium metal battery systems, reversible lithium intercalation and deintercalation are achieved through the deposition and stripping of lithium metal. However, in secondary battery systems using conventional commercial anode materials such as graphite, silicon-carbon, and hard carbon, the anode material itself does not provide lithium. + Li extracted from the positive electrode + Intercalation (e.g., graphite converted from C to Li) x C6) or a phase transformation mechanism (Li4Ti5O4 with spinel structure) 12 Li7Ti5O transformed into rock salt structure 17 This process facilitates the reversible insertion and extraction of active lithium. Although the interface formed on the electrode surface by both is collectively referred to as "SEI (solid electrode electrolyte interface film)," the construction strategies for the SEI of the two electrodes are fundamentally different. Sulfonyl compounds exhibit effective passivation capabilities for lithium metal anodes, which differs significantly from the key control factors for constructing the excellent ion-permeable interface required for graphite-based anode SEIs. During the research process, this invention discovered that fluorosulfonyl nitrogen-containing heterocyclic compounds, when used as additives in secondary batteries with conventional commercial anode materials, can effectively achieve water capture and acid suppression. Even at high temperatures and high voltages, they can effectively suppress decomposition and gas production, greatly improving electrolyte stability. However, using nitrogen-containing heterocyclic compounds as the primary additive alone will degrade the initial battery efficiency and affect the overall battery performance.

[0004] With the continuous development of the new energy industry, higher requirements are being placed on the storage performance, cycle life, and high and low temperature performance of secondary batteries. Therefore, developing an electrolyte with good overall performance to achieve long-term storage stability of batteries while also ensuring good high and low temperature performance is an urgent problem to be solved. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a fluorosulfonyl nitrogen-containing heterocyclic compound as a first additive and a film-forming potential below 1.5V (vs. Li). + The non-aqueous electrolyte for secondary batteries and the secondary battery thereof, which is used in combination with the second additive of / Li, can not only effectively achieve water capture and acid suppression, but also effectively suppress electrolyte decomposition and gas production under high temperature and high voltage, significantly improving the stability of the electrolyte. In addition, it can effectively improve the initial efficiency of the battery and further improve the low temperature performance and high temperature cycle performance of the battery, so as to achieve long-term storage stability of the battery while taking into account good high and low temperature performance.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] The first additive is selected from at least one nitrogen-containing heterocyclic compound represented by structural formula (I):

[0008]

[0009] In formula (I), R1 and R2 are independently selected from C1-C3 alkylene groups, or C1-C3 alkylene groups substituted with halogen, cyano or nitro groups; X is selected from one of N, O or S.

[0010] The second additive is selected from those with a film-forming potential below 1.5V (vs. Li). + Film-forming additives (Li).

[0011] The first additive accounts for A1 of the total mass of the electrolyte, and 0.001% ≤ A1 ≤ 5.0%;

[0012] The second additive accounts for A2 of the total mass of the electrolyte, and 0.05% ≤ A2 ≤ 4.0%.

[0013] During the research process, this invention discovered that when the proposed nitrogen-containing heterocyclic fluorosulfonyl compound is used as an additive, it effectively achieves water capture and acid suppression, inhibiting electrolyte decomposition and gas production. This is because the N / O / S atoms with lone pairs of electrons on the nitrogen-containing heterocycle in its structure can act as electron donors to coordinate with acidic substances such as PF5 and HF generated during the thermal decomposition and hydrolysis of electrolyte salts, as well as H2O generated in the electrolyte. Furthermore, the N atom with lone pairs of electrons and the F atom with strong electron-withdrawing properties in the -NSO2F structure work synergistically to create a more uniform electron cloud density distribution, effectively improving the oxidation stability of the structure. This allows it to effectively suppress decomposition and gas production even at high temperatures and voltages, significantly improving the stability of the electrolyte. However, using the nitrogen-containing heterocyclic compound as the first additive alone will degrade the battery's initial efficiency. Research suggests that when this nitrogen-containing heterocyclic compound is used alone, excessive decomposition occurs during battery charging and discharging, leading to excessive consumption of reversible active lithium and electrons in the battery, resulting in a decrease in initial efficiency.

[0014] This invention further introduces a film formation potential lower than 1.5V (vs. Li). + The second additive (LiF / Li) further enhances the synergistic effect of the first and second additives by adjusting their amounts and ratios. This not only improves the initial battery efficiency and effectively inhibits the decomposition and gas generation of electrolyte salts and the second additive, thus improving electrolyte stability, but also significantly improves the battery's low-temperature and cycle performance. Although the synergistic mechanism by which the two additives improve the battery's low-temperature and cycle performance is not fully understood, experimental results suggest that when used together, the second additive preferentially forms a film on the electrode surface, delaying the excessive consumption of the first additive and improving the initial battery efficiency. Furthermore, by controlling the amounts and ratios of both additives, the reaction intensity at the negative electrode can be regulated, forming an organic-inorganic multi-component composite SEI film rich in inorganic salts such as LiF and Li2SO3, as well as -NSO- cross-linked network organic components. This results in an SEI film with excellent ion transport capabilities and structural / thermal stability, further improving the battery's low-temperature and cycle performance—an effect that would not have been anticipated by those skilled in the art.

[0015] Therefore, regarding the amount of the first additive and the second additive, preferably, 0.01% ≤ A1 ≤ 3.0%; 0.1% ≤ A2 ≤ 3.0%. More preferably, 0.1 ≤ A2 / A1 ≤ 50; even more preferably, 0.2 ≤ A2 / A1 ≤ 30.

[0016] Regarding the structure of the first additive and the second additive, preferably, in structural formula (I), R1 and R2 are independently selected from methylene, -(CH2)2-, methylene substituted with halogen, cyano or nitro or -(CH2)2-.

[0017] More preferably, the first additive is selected from at least one of the compounds shown in the following structures:

[0018]

[0019]

[0020] The second addition is preferably fluoroethylene carbonate and / or vinylene carbonate.

[0021] The electrolyte for secondary batteries described above can be used in both lithium-ion and sodium-ion batteries.

[0022] When the electrolyte is used in a lithium-ion battery, the electrolyte salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(oxalate)borate, lithium difluorooxalateborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluorooxalate phosphate, lithium tri(oxalate) phosphate, or lithium difluorobis(oxalate) phosphate.

[0023] When the electrolyte is used in a sodium-ion battery, the electrolyte salt is selected from at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, or sodium difluorophosphate.

[0024] The amount of electrolyte salt added accounts for 6.0 to 22.5 wt% of the total mass of the electrolyte, preferably 10.0 to 18.0 wt%.

[0025] The non-aqueous solvent used in this invention can be any solvent commonly used in electrolytes. Preferably, the non-aqueous solvent is selected from at least one of C3-C6 carbonates or fluorocarbonates, C3-C8 carboxylic acids or fluorocarboxylic acids, sulfones, or ethers.

[0026] Specifically, the C3-C6 carbonate or fluorocarbonate compound is selected from at least one of ethylene carbonate (EC), propylene carbonate, butene carbonate, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, fluoroethylene carbonate (FEC), fluoropropylene carbonate, fluoromethyl ethyl carbonate, fluorodimethyl carbonate, or fluorodiethyl carbonate; the C3-C8 carboxylic acid ester or fluorocarboxylic acid ester compound is selected from... The compound is selected from at least one of γ-butyrolactone, methyl acetate, methyl propionate (MP), methyl butyrate, ethyl acetate, ethyl propionate (EP), ethyl butyrate, propyl acetate, propyl propionate (PP), and 2,2-difluoroethyl acetate; the sulfone compound is selected from at least one of sulfolane, dimethyl sulfoxide, dimethyl sulfone, or diethyl sulfone; the ether compound is selected from at least one of triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol dimethyl ether (DME), dioxolane (DOL), and tetrahydrofuran (THF).

[0027] Preferably, the non-aqueous solvent is selected from one of the following: a mixed solvent of EC and DMC; a mixed solvent of EC and EMC; a mixed solvent of EC, EMC, and DEC; a mixed solvent of FEC and EMC; a mixed solvent of methyltrifluoroethyl carbonate and EMC; a mixed solvent of EC, FEC, and EMC; a mixed solvent of EC, FEC, and DEC; a mixed solvent of FEC, methyltrifluoroethyl carbonate, and 2,2-difluoroethyl acetate; a mixed solvent of EC, DEC, and EP; a mixed solvent of EC, DEC, and PP; a mixed solvent of EC, EMC, and MP; a mixed solvent of EC, EMC, and 2,2-difluoroethyl acetate; a mixed solvent of PC and DEC; a mixed solvent of EMC and PC; a mixed solvent of DEC, EMC, and PC; a mixed solvent of PC and DME; a mixed solvent of PC, DME, and DOL; or a mixed solvent of PC, DME, and THF.

[0028] To further improve the overall performance of the battery, the additive also includes a basic additive, which is different from the electrolyte salt and is selected from at least one of vinyl sulfate, 4,4'-divinyl sulfate, 1,4-dioxane disulfate, tris(trimethylsilyl)phosphate or tris(trimethylsilyl)borate, 1,3-propane sulpholactone, 1,3-propene sulpholactone, lithium difluorophosphate, lithium difluorosulfonylimide, adiponitrile, cyclohexylbenzene, lithium difluorophosphate bis(oxalate), lithium difluorooxalate borate, sodium difluorooxalate borate, sodium difluorophosphate, sodium difluorosulfonylimide, and sodium difluorophosphate bis(oxalate). Each basic additive accounts for 0.1 to 5.0 wt% of the total electrolyte mass, and is used to meet the application scenarios and electrochemical performance requirements of different electrolytes.

[0029] In one specific embodiment, a lithium-ion battery electrolyte is provided, wherein the electrolyte salt is preferably LiPF6, and the amount used accounts for 3.0 to 15.0 wt% of the total mass of the electrolyte; the non-aqueous solvent is preferably at least one of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), more preferably a mixed solvent of EC, EMC, and DEC, and the mass ratio of the three is EC:EMC:DEC = 3:5:2; the first additive, a nitrogen-containing heterocyclic compound, is preferably I-1, and the amount used accounts for 0.001 to 5.0 wt% of the total mass of the electrolyte; the second additive is preferably FEC, and the amount used accounts for 0.05 to 4.0 wt% of the total mass of the electrolyte; the basic additive includes 1,3-propanesulfonyl lactone and lithium difluorooxalate borate, and the amount used accounts for 0.5 to 2.0 wt% of the total mass of the electrolyte.

[0030] In another specific embodiment, a sodium-ion battery electrolyte is provided, wherein the electrolyte salt is preferably NaPF6, and the amount used accounts for 3.0 to 18.0 wt% of the total mass of the electrolyte; the non-aqueous solvent is preferably at least one of diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and propylene carbonate (PC), more preferably a mixed solvent of DEC, EMC, and PC, and the mass ratio of the three is PC:EMC:DEC = 3:5:2; the first additive, a nitrogen-containing heterocyclic compound, is preferably I-1, and the amount used accounts for 0.001 to 5.0 wt% of the total mass of the electrolyte; the second additive is preferably FEC, and the amount used accounts for 0.05 to 4.0 wt% of the total mass of the electrolyte; the basic additive includes 1,3-propenyl sulfonyl lactone and sodium difluorosulfonyl imide, and the amount used accounts for 0.5 to 2.0 wt% of the total mass of the electrolyte.

[0031] The present invention also provides a secondary battery, comprising a positive electrode, a negative electrode, and a separator, as well as an electrolyte for a secondary battery as described above.

[0032] Specifically, the positive electrode is selected from at least one of lithium cobalt oxide, lithium iron phosphate, lithium nickel manganese oxide, ternary materials of nickel cobalt manganese lithium, sodium-containing layered oxides, Prussian blue / white, and polyanions, and the negative electrode is selected from graphite, silicon-carbon composite materials, lithium titanate, hard carbon, anthracite soft carbon, hard-soft composite carbon, or composite materials thereof.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] This invention utilizes a fluorosulfonyl nitrogen-containing heterocyclic compound as a first additive and a film-forming potential below 1.5V (vs. Li). +The combined use of the second additive (Li) and the regulation of their content ratio within a specific range to fully generate a synergistic effect can not only effectively achieve water capture and acid suppression, but also effectively suppress decomposition and gas production under high temperature and high voltage, greatly improving the stability of the electrolyte. Moreover, it can form an organic-inorganic multi-component composite SEI film with excellent ion transport capability and structural / thermal stability on the electrode surface, effectively improving the battery's initial efficiency and further improving the battery's low-temperature performance and high-temperature cycling performance. Detailed Implementation

[0035] The present invention will be further described below with reference to specific embodiments, but the invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternatives, improvements, and equivalents that may be included within the scope of the claims.

[0036] I. Electrolyte Preparation

[0037] Mix the solvents in equal proportions according to the data in Table 1 below, then slowly add the electrolyte salt to the mixed solution. After mixing evenly, add the additive compound in a measured amount and mix evenly to form an electrolyte.

[0038] Table 1 Electrolyte Formulation

[0039]

[0040] Note: After adjusting the amount of additives, only the amount of solvent in the base electrolyte is adjusted, and the distribution ratio of each component in the solvent remains unchanged; in Comparative Examples 5 and 6, 4-methanesulfonylmorpholine (CAS: 1697-34-3), a comparative compound with a similar structure to the first additive, is used as a comparative compound to further illustrate the beneficial effects of the present invention.

[0041] II. Electrochemical Performance Testing

[0042] The electrolytes from Examples 1-18 and Comparative Examples 1-7 were used to fabricate 1260mAh lithium-ion batteries in soft-pack form. Each lithium-ion battery includes a positive electrode, a negative electrode, a separator, an electrolyte, and battery auxiliary materials. The positive electrode active material is a ternary positive electrode (LiNi). 0.6 Co 0.2 Mn 0.2 O2, the negative electrode active material is high-capacity graphite. The preparation process is as follows: the positive electrode sheet, separator and negative electrode sheet are wound together into a core, sealed with aluminum-plastic film and then baked to ensure that the electrode moisture meets the requirements. After baking, the cell is injected with electrolyte, and after standing, formation, capacity testing and aging processes, the finished lithium-ion battery soft pack cell is obtained.

[0043] The electrolytes from Examples 19-21 and Comparative Examples 8-10 were used to prepare 1000mAh capacity soft-pack sodium-ion batteries. Each sodium-ion battery includes a positive electrode, a negative electrode, a separator, an electrolyte, and battery auxiliary materials. The positive electrode active material is a ternary positive electrode (NaNi). 0.33 Fe 0.33 Mn 0.33 O2, with hard carbon as the negative electrode active material. The preparation process is as follows: the positive electrode, separator, and negative electrode are wound together into a core, sealed with aluminum-plastic film, and then baked to ensure that the electrode moisture content meets the requirements. After baking, the cell is injected with electrolyte, and after standing, formation, capacity testing, and aging processes, the finished sodium ion soft-pack cell is obtained.

[0044] The performance of the lithium-ion and sodium-ion batteries prepared above was tested, mainly including:

[0045] (1) Initial Coulomb efficiency:

[0046] The battery was left to stand at room temperature (25℃) for 2 hours, then charged at a constant current rate of 0.2C to the charging cutoff voltage, followed by constant voltage charging until the current reached 0.02C. Finally, it was discharged at a constant current rate of 0.2C to the discharge cutoff voltage. The initial coulombic efficiency was calculated using the following formula:

[0047] Initial coulombic efficiency = (Initial discharge capacity / Initial charge capacity) × 100%

[0048] (2) Low-temperature discharge performance test

[0049] The battery was discharged to 80% of its lower limit voltage at a discharge current of 1C in an oven at -20±1℃. This was taken as the low-temperature discharge capacity, and the percentage of this capacity to the 1C discharge capacity at 25℃ was calculated and recorded as the low-temperature discharge capacity retention rate.

[0050] (3) High-temperature storage volume expansion rate

[0051] At room temperature (25℃), the battery was charged at a constant current of 1C to the charging cutoff voltage, and then charged at a constant voltage until the current dropped to 0.05C. It was then placed in a 60℃ oven for 60 days. After storage, when the battery cooled to room temperature, the initial volume V1 and the volume V2 after storage were recorded. The high-temperature storage volume expansion rate and capacity retention rate were calculated using the following formula:

[0052] High-temperature storage volume expansion rate = (V2 / V1-1)×100%

[0053] (4) High-temperature cycling performance test

[0054] The battery was cycled in an oven at 45±1℃ with a charge / discharge current of 1C / 1C. The discharge capacity was calculated per cycle. The cycle was stopped after 500 cycles, and the capacity retention rate after the cycle was calculated.

[0055] The specific test results are shown in Table 2 below:

[0056] Table 2 Battery Electrochemical Test Results

[0057]

[0058]

[0059] Based on the data in Tables 1 and 2 above, a comparison of Comparative Examples 1 and 2 / 3 shows that using the first additive alone can suppress electrolyte gas generation during high-temperature storage and improve the battery's high-temperature cycle performance, but it reduces the battery's initial efficiency and degrades its low-temperature discharge performance. Using the second additive alone can slightly improve the battery's initial efficiency and enhance its low-temperature discharge and high-temperature cycle performance, but it increases gas generation during high-temperature storage and degrades its high-temperature storage performance. Furthermore, a comparison of Comparative Examples 8 and 9 / 10 shows that the first and second additives exhibit similar effects in sodium-ion batteries.

[0060] Comparing Comparative Examples 2 and 4, it can be seen that the comparative substance 4-methanesulfonylmorpholine (CAS: 1697-34-3), which has a similar structure to the first additive, has electron-donating groups in its -N-SO2-CH3 structure. Compared to the first additive containing fluorosulfonyl groups, its oxidative stability is reduced. Under high temperature and high voltage, this further exacerbates its excessive decomposition, leading to a significant degradation of the battery's initial efficiency and, to some extent, deteriorating high-temperature cycling, high-temperature storage performance, and low-temperature discharge rate. Furthermore, comparing Example 5 and Comparative Example 5, it can be seen that compared to the combined use of the first and second additives, the combined use of the comparative substance and the second additive significantly exacerbates gas generation during high-temperature storage, significantly deteriorating the initial efficiency and low-temperature discharge rate, and failing to achieve the improvement effect achieved by the combined use of the first and second additives of this invention.

[0061] Comparing Examples 1-8 with Comparative Examples 6 and 7, it can be seen that only when the first additive and the second additive satisfy the relationship 0.01%≤A1≤5.0%, 0.1%≤A2≤4.0%, and 0.1≤A2 / A1≤50, can the secondary battery possess good initial efficiency, low-temperature performance, high-temperature cycling performance, and high-temperature storage performance. When A2 / A1 is too small, the content of the first additive is much higher than that of the second additive, which will lead to excessive decomposition of the first additive during battery charging and discharging. On the one hand, this will excessively consume reversible active lithium and electrons in the battery, reducing the initial efficiency of the battery. On the other hand, it will result in poor thermal stability of the formed -NSO- crosslinked network SEI film structure, deteriorating the high-temperature cycling performance. When A2 / A1 is too large, the decomposition and gas production of the second additive during high-temperature cycling or storage will be aggravated, and the high-temperature storage performance and high-temperature cycling performance will be deteriorated.

[0062] Comparative Examples 1-8 show that controlling the content of the first additive and the second additive, especially when the two satisfy the relationship 0.2≤A1 / A2≤30, can further improve the battery's initial efficiency and high-temperature storage performance, while also exhibiting good low-temperature discharge and high-temperature cycling performance.

[0063] Comparing Examples 5 and Examples 9-16, it can be seen that compounds I-1, I-2, I-3, I-4, I-5, I-6, I-7, I-8, I-9, and compounds FEC and VC all have the functions of the additives they represent and can be used interchangeably.

[0064] Comparing Examples 5 with Examples 17 and 18, it can be seen that, based on the addition of the first and second additives, the combined use of basic additives such as PS and LiDFOB can further improve the battery's initial efficiency, high and low temperature performance, and storage performance. Meanwhile, comparing Examples 19 with Examples 20 and 21, it can be seen that adding basic additives to sodium-ion batteries can achieve the same effect.

Claims

1. A non-aqueous electrolyte for secondary batteries, comprising an electrolyte salt, a non-aqueous solvent, and additives, characterized in that: The additives include: The first additive is selected from at least one nitrogen-containing heterocyclic compound represented by structural formula (I): In formula (I), R1 and R2 are independently selected from C1-C3 alkylene groups, or C1-C3 alkylene groups substituted with halogen, cyano or nitro groups; X is selected from one of N, O or S. The second additive is selected from those with a film-forming potential below 1.5V (vs. Li). + Film-forming additives for / Li); The first additive accounts for A1 of the total mass of the electrolyte, and 0.001% ≤ A1 ≤ 5.0%; The second additive accounts for A2 of the total mass of the electrolyte, and 0.05% ≤ A2 ≤ 4.0%.

2. The non-aqueous electrolyte for secondary batteries according to claim 1, characterized in that: 0.01% ≤ A1 ≤ 3.0%; 0.1% ≤ A2 ≤ 3.0%.

3. The non-aqueous electrolyte for secondary batteries according to claim 1 or 2, characterized in that: 0.1≤A2 / A1≤50.

4. The non-aqueous electrolyte for secondary batteries according to claim 1, characterized in that: In formula (I), R1 and R2 are independently selected from methylene, -(CH2)2-, methylene substituted with halogen, cyano or nitro or -(CH2)2-.

5. The non-aqueous electrolyte for secondary batteries according to claim 4, characterized in that: The first additive is selected from at least one of the compounds shown in the following structures:

6. The non-aqueous electrolyte for secondary batteries according to claim 1, characterized in that: The second additive is selected from fluoroethylene carbonate and / or vinylene carbonate.

7. The non-aqueous electrolyte for secondary batteries according to claim 1, characterized in that: When the electrolyte is used in a lithium-ion battery, the electrolyte salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(oxalate)borate, lithium difluorooxalateborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluorooxalate phosphate, lithium tri(oxalate) phosphate, or lithium difluorobis(oxalate) phosphate. When the electrolyte is used in a sodium-ion battery, the electrolyte salt is selected from at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, or sodium difluorophosphate.

8. The non-aqueous electrolyte for secondary batteries according to claim 1, characterized in that: The non-aqueous solvent is selected from at least one of C3-C6 carbonates or fluorocarbonates, C3-C8 carboxylic esters or fluorocarboxylic esters, sulfones, or ethers.

9. The non-aqueous electrolyte for secondary batteries according to any one of claims 1-8, characterized in that: The additives also include a base additive selected from at least one of vinyl sulfate, 4,4'-divinyl sulfate, 1,4-dioxane disulfate, tris(trimethylsilyl)phosphate or tris(trimethylsilyl)borate, 1,3-propanesulfonyl lactone, 1,3-propenesulfonyl lactone, lithium difluorophosphate, lithium difluorosulfonylimide, adiponitrile, cyclohexylbenzene, lithium difluorophosphate bis(oxalate), lithium difluorooxalate borate, sodium difluorooxalate borate, sodium difluorophosphate, sodium difluorosulfonylimide, and sodium difluorophosphate bis(oxalate), and any one base additive accounts for 0.1 to 5.0 wt% of the total mass of the electrolyte; the base additive is different from the electrolyte salt.

10. A secondary battery, comprising a positive electrode, a negative electrode, and a separator, characterized in that: The secondary battery is filled with the non-aqueous electrolyte for secondary batteries as described in any one of claims 1-9.

11. The secondary battery according to claim 10, characterized in that: The active material of the positive electrode is selected from lithium cobalt oxide, lithium iron phosphate, lithium nickel manganese oxide, ternary materials of nickel cobalt manganese lithium, sodium-containing layered oxides, Prussian blue / white or polyanionic oxides, and the active material of the negative electrode is selected from graphite, silicon-carbon composite material, lithium titanate, hard carbon, anthracite soft carbon, hard-soft composite carbon or composite materials thereof.

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