Non-aqueous electrolyte and secondary battery

Abstract

The invention provides a non-aqueous electrolyte and a secondary battery, and belongs to the technical field of secondary batteries. The non-aqueous electrolyte comprises an electrolyte salt, an organic solvent, a first additive and a second additive, the second additive comprises one or more of a compound A, a compound B or a compound C, the second additive is a compound with a sulfonyl vinyl nitrile functional group, the voltage window and the interface stability can be improved, and the performance of the non-aqueous electrolyte is improved. According to the present invention, the compound can effectively inhibit the oxidation and the dissolution of transition metal ions, can effectively inhibit the oxygenolysis of the electrolyte, has high reaction activity, can rapidly participate in the reaction, can cooperate with other components to form the stable polymer film, has characteristics of small molecule, small molecular tension, easy dispersion, and more stable compound after complexation. Especially for the lithium ion battery with the negative electrode material being a graphite material, a composite material of monocrystalline silicon and graphite or a composite material of silicon monoxide and graphite, the lithium ion battery has excellent performance.

Description

Technical Field

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

[0002] As the earliest commercialized positive electrode material, lithium cobalt oxide has the advantages of high voltage platform and high compaction density. However, the capacity of conventional lithium cobalt oxide materials is only 140mAh / g, which is about 50% of its theoretical capacity, restricting the improvement of lithium-ion battery energy density. Increasing voltage is an effective way to increase the capacity of lithium cobalt oxide materials. However, since the Fermi level of Co element overlaps with O, the increase of charging voltage will cause O 2- The oxidation of Co leads to the decrease of the stability of lattice oxygen and causes the oxidative decomposition of electrolyte. At the same time, the dissolution of transition metal Co also seriously endangers the stability of electrolyte and electrolyte electrode interface. Especially in high voltage and high temperature environment, this harmful effect will be more prominent.

[0003] Structural doping and interface modification are the most effective strategies to improve the stability of high-voltage LCO cathodes. Among them, in-situ formation of a relatively stable CEI film through electrolyte additives is a low-cost, simple and efficient approach. Without changing the currently used commercial carbonate-based electrolyte, the method of using a very small amount of electrolyte additives to achieve a breakthrough in the high-voltage performance of lithium cobalt oxide lithium-ion batteries is very simple and affordable.

[0004] Currently, nitrile (-C≡N) electrolyte additives are widely used, which contain lone pairs of electrons and easily react with Co 4+ Coordination forms RC≡Nδ--Co(4+δ) bonds, which can delay the oxidation and dissolution of transition metal ions, making them have good antioxidant properties. The nitrogen-containing groups can also act as Lewis bases to adsorb HF, and can also participate in the formation of a denser and thinner CEI film. The CEI film with excellent performance can more effectively protect the stability of the electrode material structure. The comprehensive use of additives can greatly improve the high voltage performance of cobalt oxide lithium ion batteries.

[0005] Therefore, in this field, additives suitable for lithium cobalt oxide systems are sought, hoping to develop an electrolyte that can solve the problems of instability of the solid electrolyte interface film in lithium-ion batteries and low capacity retention during long cycles. Summary of the invention

[0006] In view of the deficiencies of the prior art, the present invention aims to provide a non-aqueous electrolyte and a secondary battery.

[0007] One of the objects of the present invention is to provide a non-aqueous electrolyte solution, the electrolyte solution comprising an electrolyte salt, an organic solvent, a first additive and a second additive.

[0008] The first additive includes fluoroethylene carbonate, 1,3-propane sultone, vinylene carbonate and vinyl sulfate.

[0009] The second additive includes one or more of compound A as shown in formula I, compound B as shown in formula II, or compound C as shown in formula III;

[0010]

[0011] wherein R1, R4, and R7 are each independently selected from a substituted or unsubstituted C1-C6 alkyl group, a substituted or unsubstituted phenyl group, a furyl group, a thienyl group, a pyrrolyl group, a piperidinyl group, a piperazinyl group, a naphthyl group, or a decalinyl group;

[0012] R2 and R3 are each independently selected from H or a substituted or unsubstituted C1-C6 alkyl group;

[0013] R5 and R6 are each independently selected from H, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C6 alkenyl, substituted or unsubstituted C2-C6 alkynyl, substituted or unsubstituted phenyl;

[0014] R8 is a substituted or unsubstituted C1-C6 alkyl group, a C1-C6 sulfur-containing group or a C1-C6 nitrogen-containing group.

[0015] Preferably, the substituent of the C1-C6 alkyl group includes halogen, furyl, thienyl, pyrrolyl, piperidinyl, piperazinyl and naphthyl.

[0016] Preferably, the substituents of the phenyl group include halogen, alkyl or halogen-substituted alkyl.

[0017] Preferably, R1 is -C6H5, -CH3 or -CH2C4H4O.

[0018] Preferably, R4 is -C6H5, -C6H4CH3, -CH3 or -C(CH3)3.

[0019] Preferably, R7 is -CH3 or -CH2CH3.

[0020] Preferably, R2 and R3 are each independently H or -CH2CH3.

[0021] Preferably, R5 and R6 are each independently -C6H5, -CH3, -C6H4CF3 or -CH2C2H.

[0022] Preferably, R8 is =CHCH(CH2)2, =CHC5H 11 , =CH2, =CHNC5H 10 , =CHCH(SCH3)2 or a sulfur-containing heterocycle.

[0023] Preferably, compound A comprises one or more of the following compounds:

[0024]

[0025] Preferably, compound B comprises one or more of the following compounds:

[0026]

[0027]

[0028] Preferably, compound C comprises one or more of the following compounds:

[0029]

[0030] Preferably, based on the total mass of the electrolyte being 100%, the mass percentage of the second additive is 0.5-4%.

[0031] Preferably, the mass percentage of the first additive is 8-15%.

[0032] Preferably, the mass ratio of the first additive to the second additive is 2 to 30:1.

[0033] Preferably, in the first additive, the mass ratio of fluoroethylene carbonate, 1,3-propane sultone, vinylene carbonate and vinyl sulfate is 8:3:0.3:1.

[0034] Preferably, the electrolyte salt includes one or more of XPF6, XClO4, XBF4, XAsF6, XFSI, XTFSI, XBOB, XODFB, XCF3SO3, XPO2F2 or XOTFB.

[0035] Wherein, X includes any one of Li, Na or K, and X is preferably Li.

[0036] Preferably, based on the total mass of the electrolyte being 100%, the mass percentage of the electrolyte salt is 10-30%.

[0037] Preferably, the electrolyte salt comprises LiPF6.

[0038] Preferably, the organic solvent is one or more of carbonates, halogenated carbonates, carboxylates, propionates, fluoroethers, aromatic hydrocarbons or halogenated aromatic hydrocarbons.

[0039] Preferably, the carbonate includes one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate or ethyl methyl carbonate.

[0040] Preferably, the carboxylic acid ester comprises one or more of propyl butyrate, propyl acetate, isopropyl acetate, butyl propionate, isopropyl propionate, ethyl butyrate, methyl propionate, ethyl propionate or propyl propionate.

[0041] Preferably, based on the total mass of the electrolyte being 100%, the mass percentage of the organic solvent is 40% to 85%.

[0042] A second object of the present invention is to provide a secondary battery, wherein the secondary battery comprises the lithium ion non-aqueous electrolyte described above.

[0043] Preferably, the battery comprises a lithium ion battery, a sodium ion battery, a potassium ion battery or a supercapacitor.

[0044] Preferably, the negative electrode material of the lithium-ion battery is graphite, a composite material of single crystal silicon and graphite, a composite material of silicon oxide and graphite, lithium titanate or Nb2O5.

[0045] Beneficial effects of the present invention:

[0046] The present invention provides a non-aqueous electrolyte, including an electrolyte salt, an organic solvent, a first additive and a second additive. The second additive includes one or more of compound A, compound B or compound C, and compound A, compound B and compound C have sulfonyl alkene nitrile functional groups, wherein the sulfonyl group can increase the voltage window and interface stability; and the C≡N group can well play a role in delaying the oxidation and dissolution of transition metal ions, and at the same time, can hydrolyze and remove trace amounts of water in the electrolyte, prevent further reaction of PF5, effectively inhibit the oxidative decomposition of the electrolyte, and enhance the stability of the interface; and the role of the carbon-carbon double bond helps to form a stable and dense organic polymer film at the positive and negative electrode interfaces. The second additive compound A, compound B and compound C used in the present invention all belong to chain sulfonyl alkene nitrile substances. In this linear structure, the electron cloud density is unevenly distributed, the molecular polarity is large, and it has higher reactivity, can participate in the reaction faster, and cooperate with other components to form a stable polymer film. And compared with cyclic sulfonyl alkene nitrile substances, the molecules are small, the molecular tension is small, it is conducive to dispersion, and the compound after complexation tends to be more stable. In particular, the lithium-ion battery whose negative electrode material is a graphite material, a composite material of single crystal silicon and graphite, or a composite material of silicon oxide and graphite has excellent performance. DETAILED DESCRIPTION

[0047] In the following description, certain specific details are included to provide a comprehensive understanding of each disclosed embodiment. However, one skilled in the relevant art will recognize that the embodiments can be implemented without one or more of these specific details, but with other methods, components, materials, etc.

[0048] Unless otherwise required herein, the words "include" and "comprising" should be interpreted as having an open and inclusive meaning, ie, "including but not limited to".

[0049] References to "one embodiment" or "an embodiment" or "a preferred embodiment" or "certain embodiments" throughout this specification mean that the specific referenced elements, structures or features described in connection with the embodiment are included in at least one embodiment. Therefore, the phrases "in one embodiment" or "in an embodiment" or "in a preferred embodiment" or "in certain embodiments" appearing in different places throughout the specification do not necessarily all refer to the same embodiment. In addition, the specific elements, structures or features may be combined in any appropriate manner in one or more embodiments.

[0050] According to a first aspect of the present invention, there is provided a lithium ion non-aqueous electrolyte, the electrolyte comprising an electrolyte lithium salt, an organic solvent, a first additive and a second additive;

[0051] The first additive includes fluoroethylene carbonate, 1,3-propane sultone, vinylene carbonate and vinyl sulfate;

[0052] The second additive includes one or more of compound A as shown in formula I, compound B as shown in formula II, or compound C as shown in formula III;

[0053]

[0054] Wherein, R1, R4, and R7 are each independently a substituted or unsubstituted C1-C6 alkyl group or a substituted or unsubstituted phenyl group;

[0055] R2 and R3 are each independently a C1-C6 alkyl group or hydrogen;

[0056] R5 and R6 are each independently hydrogen, C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, or substituted or unsubstituted phenyl;

[0057] R8 is each independently a substituted or unsubstituted C1-C6 alkyl group, a C1-C6 sulfur-containing group or a C1-C6 nitrogen-containing group.

[0058] In the present invention, the second additive compound A, compound B and compound C carry sulfonyl alkene nitrile functional groups, wherein the presence of sulfonyl groups can increase the voltage window and interface stability; and the C≡N group can well play a role in delaying the oxidation and dissolution of transition metal ions, and at the same time, can hydrolyze and remove trace amounts of water in the electrolyte, prevent further reaction of PF5, effectively inhibit the oxidative decomposition of the electrolyte, and enhance the stability of the interface; and the effect of the carbon-carbon double bond helps the positive and negative electrode interfaces to form a stable and dense organic polymer film, thereby improving the cycle performance. The second additive compound A, compound B and compound C used in the present invention all belong to chain sulfonyl alkene nitrile substances, and in this linear structure, the electron cloud density is unevenly distributed, the molecular polarity is large, and it has a higher reactivity, can participate in the reaction faster, and cooperate with other components to form a stable polymer film. And relative to cyclic sulfonyl alkene nitrile substances, the molecules are small, the molecular tension is small, it is conducive to dispersion, and the compound after complexation tends to be more stable. In particular, the invention provides excellent performance for lithium-ion batteries whose negative electrode materials are graphite, a composite material of single crystal silicon and graphite, or a composite material of silicon oxide and graphite.

[0059] In the present invention, the second additive is, for example, compound A, compound B, compound C, compound A and compound B, compound A and compound C, compound B and compound C, or a combination of compound A, compound B and compound C.

[0060] Preferably, the second additive comprises compound A and compound B.

[0061] Preferably, the mass ratio of compound A to compound B is 0.3 to 3:1, preferably 1:1.

[0062] In a preferred embodiment of the present invention, the substituents of the C1-C6 alkyl group include halogen, furyl, thienyl, pyrrolyl, piperidinyl, piperazinyl and naphthyl.

[0063] Preferably, the substituents of the phenyl group include halogen, alkyl or halogen-substituted alkyl.

[0064] In a preferred embodiment of the present invention, R1 is -C6H5, -CH3 or -CH2C4H4O.

[0065] Preferably, R4 is -C6H5, -C6H4CH3, -CH3 or -C(CH3)3.

[0066] Preferably, R7 is -CH3 or -CH2CH3.

[0067] Preferably, R2 and R3 are each independently H or -CH2CH3.

[0068] Preferably, R5 and R6 are each independently -C6H5, -CH3, -C6H4CF3 or -CH2C2H.

[0069] Preferably, R8 is =CHCH(CH2)2, =CHC5H 11 , =CH2, =CHNC5H 10 , =CHCH(SCH3)2 or a sulfur-containing heterocycle.

[0070] In a preferred embodiment of the present invention, compound A comprises one or more of the following compounds;

[0071]

[0072] Preferably, compound B comprises one or more of the following compounds:

[0073]

[0074] Preferably, compound C comprises one or more of the following compounds:

[0075]

[0076] In a preferred embodiment of the present invention, the total mass of the electrolyte is 100%, and the mass percentage of the second additive is 0.5-4%;

[0077] Preferably, the mass percentage of the first additive is 8-15%;

[0078] Preferably, the mass ratio of the first additive to the second additive is 2 to 30:1.

[0079] In the present invention, the mass percentage of the second additive is, for example, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5% or 4.0%.

[0080] The mass percentage of the first additive is, for example, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%.

[0081] The mass ratio of the first additive to the second additive is, for example, 2:1, 4:1, 6:1, 8:1, 10:1, 12:1, 14:1, 16:1, 18:1, 20:1, 22:1, 24:1, 26:1, 28:1 or 30:1.

[0082] In a preferred embodiment of the present invention, in the first additive, the mass ratio of fluoroethylene carbonate, 1,3-propane sultone, vinylene carbonate and vinyl sulfate is 8:3:0.3:1.

[0083] In a preferred embodiment of the present invention, the electrolyte salt includes one or more of XPF6, XClO4, XBF4, XAsF6, XFSI, XTFSI, XBOB, XODFB, XCF3SO3, XPO2F2 or XOTFB;

[0084] Wherein, X includes any one of Li, Na or K, and X is preferably Li.

[0085] Preferably, the molar concentration of the electrolyte salt in the electrolyte is 0.5 to 3 mol / L, and the mass percentage of the electrolyte salt is 10 to 30% based on the total mass of the electrolyte as 100%.

[0086] Preferably, the electrolyte salt comprises LiPF6.

[0087] In the present invention, the molar concentration of the electrolyte salt in the electrolytic solution is, for example, 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L or 3.0 mol / L.

[0088] Preferably, the organic solvent is one or more of carbonates, halogenated carbonates, carboxylates, fluoroethers, aromatic hydrocarbons or halogenated aromatic hydrocarbons.

[0089] Preferably, the carbonate includes one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate or ethyl methyl carbonate.

[0090] Preferably, the carboxylic acid ester comprises one or more of propyl butyrate, propyl acetate, isopropyl acetate, butyl propionate, isopropyl propionate, ethyl butyrate, methyl propionate, ethyl propionate or propyl propionate.

[0091] Preferably, the organic solvent includes propyl propionate, ethyl propionate, ethylene carbonate and propylene carbonate.

[0092] Preferably, the mass ratio of propyl propionate, ethyl propionate, ethylene carbonate and propylene carbonate is 7:7:3:3.

[0093] Preferably, based on the total mass of the electrolyte being 100%, the mass percentage of the organic solvent is 40% to 85%.

[0094] In the present invention, the mass percentage of the organic solvent is, for example, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80% or 85%.

[0095] Specifically, the preparation method of the electrolyte includes:

[0096] Firstly, the organic solvent, the first additive and the second additive are mixed evenly, and then the electrolyte salt is added and mixed evenly to obtain the electrolyte solution.

[0097] According to a second aspect of the present invention, a secondary battery is provided. The secondary battery includes the electrolyte according to the first aspect.

[0098] In a preferred embodiment of the present invention, the secondary battery includes a lithium ion battery, a sodium ion battery, a potassium ion battery or a supercapacitor.

[0099] Preferably, the negative electrode material of the lithium-ion battery is graphite, a composite material of single crystal silicon and graphite, a composite material of silicon oxide and graphite, lithium titanate or Nb2O5.

[0100] Preferably, the negative electrode material of the lithium-ion battery includes a graphite negative electrode material.

[0101] Preferably, the positive electrode material of the lithium-ion battery includes a lithium cobalt oxide positive electrode material.

[0102] Specifically, the positive electrode of the secondary battery includes a binder PVDF-900, a composite conductive agent Super-P, a lithium cobalt oxide positive electrode material and a solvent NMP (N-methyl-2-pyrrolidone).

[0103] The negative electrode raw materials of the secondary battery include graphite, a conductive agent Super-P, a solvent CMC, H2O and a binder SBR.

[0104] Specifically, the positive electrode and the negative electrode are coated, sliced, rolled, striped, dried, taped, wound, and dried at 80° C. for 48 hours, and then the electrolyte is added to seal the lithium-ion battery, which is left for 24 hours and then formed. Then, a final sealing, aging, and a second final sealing are performed in sequence to prepare a lithium-ion soft-pack battery.

[0105] Example

[0106] The present invention is further described in detail below in conjunction with the embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0107] In the following examples, unless otherwise specified, all raw materials are commercially available products.

[0108] According to the electrolyte compositions of Examples 1 to 25 and Comparative Example 1 shown in Table 1, the organic solvent, the first additive and the second additive were mixed evenly, and then the electrolyte salt was added and mixed evenly again.

[0109] The lithium cobalt oxide positive electrode and the graphite negative electrode are coated, sliced, rolled, striped, dried, taped, wound up and dried at 80°C for 48 hours in sequence, and then a non-aqueous electrolyte is added. After the lithium-ion battery is filled and sealed, it is placed for 24 hours and then formed. Then, a primary final sealing, aging and a secondary final sealing are carried out in sequence to prepare a lithium-ion soft-pack battery.

[0110] The electrolyte compositions of Examples 1 to 25 and Comparative Example 1 are shown in Table 1.

[0111] Table 1 Electrolyte compositions of Examples 1 to 25 and Comparative Example 1

[0112]

[0113]

[0114]

[0115]

[0116] Then, the battery was tested for high temperature cycle performance and high temperature storage performance.

[0117] (1) Cycle performance: The charge and discharge voltage range is 2.75V to 4.48V, the charging current is 1C (2.0A) to 4.48V, 4.48V constant voltage charging to a cut-off current ≤ 0.05C (0.1A), after standing for 5 minutes, 1C (2.0A) discharge to 2.75V, and stand for 5 minutes; the cycle is repeated (the high temperature cycle test needs to be carried out in a 45℃ oven, and the battery is clamped and left for 2h), and the capacity retention rate of different cycles is calculated.

[0118] (2) High temperature storage performance: Fully charge capacity C1 at 0.2C constant current and constant voltage at room temperature, and measure thickness d1 at the same time. Then stand at 60℃ for 7 days, take out and immediately test hot thickness d2, cool to room temperature and leave for 4 hours to test cold thickness d3. Then discharge capacity at 1C (2.0A) at room temperature is recorded as C2, and the average discharge capacity is calculated by three cycles and recorded as C3. The capacity retention rate is C2 / C1, the capacity recovery rate is C3 / C1, the thermal expansion rate is d2 / d1, and the cold expansion rate is d3 / d1.

[0119] The lithium-ion batteries prepared by the electrolyte formulations of Examples 1 to 25 and Comparative Example 1 were tested for normal temperature, high temperature cycle performance and high temperature storage performance. The test results are shown in Tables 2 to 4:

[0120] Table 2 Room temperature cycle performance of lithium ion batteries prepared in Examples 1 to 25 and Comparative Example 1

[0121]

[0122]

[0123] Table 3 High temperature cycle performance of lithium ion batteries prepared in Examples 1 to 25 and Comparative Example 1

[0124]

[0125]

[0126] Table 4 High temperature storage performance of lithium ion batteries prepared in Examples 1 to 25 and Comparative Example 1

[0127]

[0128]

[0129]

Claims

1. A non-aqueous electrolyte, characterized in that: The electrolyte comprises an electrolyte salt, an organic solvent, a first additive and a second additive; The first additive includes fluoroethylene carbonate, 1,3-propane sultone, vinylene carbonate and vinyl sulfate; The second additive includes one or more of compound A as shown in formula I, compound B as shown in formula II, or compound C as shown in formula III; wherein R1, R4, and R7 are each independently selected from a substituted or unsubstituted C1-C6 alkyl, a substituted or unsubstituted phenyl, a furyl, a thienyl, a pyrrolyl, a piperidinyl, a piperazinyl, a naphthyl, or a decalinyl; R2 and R3 are each independently selected from H or a substituted or unsubstituted C1-C6 alkyl group; R5 and R6 are each independently selected from H, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C6 alkenyl, substituted or unsubstituted C2-C6 alkynyl, substituted or unsubstituted phenyl; R8 is a substituted or unsubstituted C1-C6 alkyl group, a C1-C6 sulfur-containing group or a C1-C6 nitrogen-containing group.

2. The non-aqueous electrolyte according to claim 1, characterized in that The substituents of the alkyl group include one or more of halogen, furyl, thienyl, pyrrolyl, piperidinyl, piperazinyl and naphthyl; Preferably, the substituents of the phenyl group include halogen, alkyl or halogen-substituted alkyl.

3. The non-aqueous electrolyte according to claim 1, characterized in that R1 is -C6H5, -CH3 or -CH2C4H4O; Preferably, R4 is -C6H5, -C6H4CH3, -CH3 or -C(CH3)3; Preferably, R7 is -CH3 or -CH2CH3; Preferably, R2 and R3 are each independently H or -CH2CH3; Preferably, R5 and R6 are each independently -C6H5, -CH3, -C6H4CF3 or -CH2C2H; Preferably, R8 is =CHCH(CH2)2, =CHC5H 11 , =CH2, =CHNC5H 10 , =CHCH(SCH3)2 or a sulfur-containing heterocycle.

4. The non-aqueous electrolyte according to claim 1, characterized in that Compound A includes one or more of the following compounds: Preferably, compound B comprises one or more of the following compounds: Preferably, compound C comprises one or more of the following compounds:

5. The non-aqueous electrolyte according to claim 1, characterized in that Based on the total mass of the electrolyte being 100%, the mass percentage of the second additive is 0.5 to 4%; Preferably, the mass percentage of the first additive is 8-15%; Preferably, the mass ratio of the first additive to the second additive is 2 to 30:

1.

6. The non-aqueous electrolyte according to claim 1, characterized in that In the first additive, the mass ratio of fluoroethylene carbonate, 1,3-propane sultone, vinylene carbonate and vinyl sulfate is 8:3:0.3:

1.

7. The non-aqueous electrolyte according to claim 1, characterized in that The electrolyte salt includes one or more of XPF6, XClO4, XBF4, XAsF6, XFSI, XTFSI, XBOB, XODFB, XCF3SO3, XPO2F2 or XOTFB; Wherein, X includes any one of Li, Na or K, and X is preferably Li; Preferably, based on the total mass of the electrolyte being 100%, the mass percentage of the electrolyte salt is 10 to 30%; Preferably, the electrolyte salt comprises LiPF6.

8. The non-aqueous electrolyte according to claim 1, characterized in that The organic solvent is one or more of carbonate, halogenated carbonate, carboxylate, fluoroether, aromatic hydrocarbon or halogenated aromatic hydrocarbon; Preferably, the carbonate comprises one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate or ethyl methyl carbonate; Preferably, the carboxylic acid ester comprises one or more of propyl butyrate, propyl acetate, isopropyl acetate, butyl propionate, isopropyl propionate, ethyl butyrate, methyl propionate, ethyl propionate or propyl propionate; Preferably, the organic solvent comprises propyl propionate, ethyl propionate, ethylene carbonate and propylene carbonate; Preferably, the mass ratio of propyl propionate, ethyl propionate, ethylene carbonate and propylene carbonate is 7:7:3:3; Preferably, based on the total mass of the electrolyte being 100%, the mass percentage of the organic solvent is 40% to 85%.

9. A secondary battery, characterized in that: The battery comprises the electrolyte according to any one of claims 1 to 8.

10. The secondary battery according to claim 9, characterized in that The secondary battery includes a lithium ion battery, a sodium ion battery, a potassium ion battery or a supercapacitor; Preferably, the negative electrode material of the lithium-ion battery is graphite, a composite material of single crystal silicon and graphite, a composite material of silicon oxide and graphite, lithium titanate or Nb2O5.

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