A non-aqueous electrolyte and secondary battery

Abstract

In order to overcome the problem that the existing lithium-ion batteries cannot take into account both high-temperature performance and low-temperature performance, the present invention provides a non-aqueous electrolyte, including a non-aqueous organic solvent, an electrolyte salt and an additive, wherein the additive includes a compound shown in Structural Formula 1 and a compound shown in Structural Formula 2: Structural Formula 1, Structural Formula 2. At the same time, the present invention also discloses a secondary battery including the non-aqueous electrolyte. The non-aqueous electrolyte provided by the present invention can effectively improve the high and low temperature cycle performance of lithium-ion batteries.

Description

Technical Field

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

[0002] As the protagonist of new energy electric vehicles, lithium-ion batteries have been widely used for their wide operating voltage range, high operating voltage, high specific energy, no pollution, and long service life. With the rapid development of the new energy electric vehicle industry, the market has put forward higher requirements on the performance of lithium-ion batteries. Not only do batteries need to have high energy density to support longer driving range, but they also need to ensure the stability and safety of batteries in different environments. In order to meet these needs, researchers have been exploring how to further optimize the performance of lithium-ion batteries.

[0003] One of the common performance improvement methods is to add specific additives to the non-aqueous electrolyte. These additives can change the chemical properties of the non-aqueous electrolyte, thereby affecting the electrochemical reaction process inside the battery and improving certain performance indicators of the battery. However, existing additive technology has certain limitations. For example, when trying to enhance the high-temperature performance of the battery, some additives may cause the battery's performance to deteriorate under low-temperature conditions; and vice versa. This phenomenon shows that the current additive technology cannot yet take into account the excellent performance of lithium-ion batteries in both high and low temperature environments. Therefore, how to take into account the high and low temperature performance of lithium-ion batteries is a technical problem that needs to be urgently solved in the field of electric vehicles. Summary of the invention

[0004] In view of the problem that existing lithium-ion batteries cannot achieve both high-temperature performance and low-temperature performance, the present invention provides a non-aqueous electrolyte and a secondary battery.

[0005] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0006] In one aspect, the present invention provides a non-aqueous electrolyte, comprising a non-aqueous organic solvent, an electrolyte salt and an additive, wherein the additive comprises a compound represented by structural formula 1 and a compound represented by structural formula 2:

[0007] ;

[0008] Wherein n is 0 or 1, A is selected from C or O, and X is selected from , R1, R2 are each independently selected from H, or , R1 and R2 are not simultaneously selected from H, and X, R1 and R2 contain at least one sulfur atom;

[0009] ;

[0010] Wherein, R3 and R4 are each independently selected from a substituted or unsubstituted alkyl group of 1 to 5 carbon atoms, a substituted or unsubstituted cyclic carbonate group of 3 to 6 carbon atoms, a silicon-containing group of 3 to 16 carbon atoms, an alkenyl group of 2 to 5 carbon atoms, an alkynyl group of 2 to 5 carbon atoms or a cyano group of 1 to 5 carbon atoms.

[0011] Optionally, based on the total mass of the non-aqueous electrolyte being 100%, the mass percentage of the compound represented by structural formula 1 is 0.01% to 3%; and / or

[0012] Based on the total mass of the non-aqueous electrolyte being 100%, the mass percentage of the compound represented by the structural formula 2 is 0.01% to 1.5%.

[0013] Optionally, the total mass of the compound represented by Structural Formula 1 and the compound represented by Structural Formula 2 added to the non-aqueous electrolyte is X, and X satisfies 0.05≤X≤4; and / or

[0014] The mass ratio of the compound represented by the structural formula 1 to the compound represented by the structural formula 2 is Y, and Y satisfies 1≤Y≤10.

[0015] Optionally, in the compound represented by structural formula 1, R1 and R2 are each independently selected from , and X, R1 and R2 contain at least one sulfur atom.

[0016] Optionally, in the compound represented by structural formula 1, X, R1 and R2 do not contain sulfur atoms at the same time.

[0017] Optionally, in the compound represented by the structural formula 1, R1 is selected from H, and X is selected from , R2 is selected from , or R1 is selected from H, X is selected from , R2 is selected from .

[0018] Optionally, in the compound shown in structural formula 2, R3 is selected from a substituted or unsubstituted cyclic carbonate of 3 to 6 carbon atoms, a silicon-containing group of 3 to 16 carbon atoms, an alkenyl of 2 to 5 carbon atoms, an alkynyl of 2 to 5 carbon atoms or a cyano group of 1 to 5 carbon atoms, and R4 is selected from a substituted or unsubstituted alkyl of 1 to 5 carbon atoms, a substituted or unsubstituted cyclic carbonate of 3 to 6 carbon atoms, a silicon-containing group of 3 to 16 carbon atoms, an alkenyl of 2 to 5 carbon atoms, an alkynyl of 2 to 5 carbon atoms or a cyano group of 1 to 5 carbon atoms.

[0019] Optionally, the compound represented by structural formula 1 is selected from at least one of the following compounds:

[0020] And / or, the compound represented by the structural formula 2 is selected from at least one of the following compounds: .

[0021] Optionally, the additive further includes at least one of a cyclic sulfate compound, a sultone compound, a cyclic carbonate compound, a phosphate compound, a borate compound and a nitrile compound;

[0022] The cyclic sulfate ester compound is selected from vinyl sulfate, propylene sulfate, methyl vinyl sulfate, At least one of; and / or

[0023] The sultone compound is selected from at least one of 1,3-propane sultone, 1,4-butane sultone and 1,3-propylene sultone; and / or

[0024] The cyclic carbonate compound is selected from at least one of vinylene carbonate, ethylene carbonate, methylene carbonate, fluoroethylene carbonate, trifluoromethylethylene carbonate, bisfluoroethylene carbonate or the compound shown in formula 3.

[0025] ;

[0026] In the structural formula 3, R 21 , R 22 , R 23 , R 24 , R 25 , R 26 Each is independently selected from a hydrogen atom, a halogen atom, a C1-C5 group; and / or

[0027] The phosphate compound is selected from at least one of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite or the compound shown in structural formula 4:

[0028] ;

[0029] In the structural formula 4, R 31 , R 32 , R 33 Each independently selected from a C1-C5 saturated hydrocarbon group, an unsaturated hydrocarbon group, a halogenated hydrocarbon group, -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and R 31 , R32 , R 33 At least one of them is an unsaturated hydrocarbon group; and / or

[0030] The borate compound is selected from at least one of tris(trimethylsilyl)borate and tris(triethylsilyl)borate; and / or

[0031] The nitrile compound is selected from at least one of succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrinitrile, adiponitrile, pimelonitrile, suberonitrile, azelaic acid dinitrile and sebacononitrile.

[0032] In another aspect, the present invention provides a secondary battery comprising a positive electrode, a negative electrode and the non-aqueous electrolyte as described above.

[0033] According to the non-aqueous electrolyte provided by the present invention, the compound shown in structural formula 1 and the compound shown in structural formula 2 are added as additives, wherein the compound shown in structural formula 1 is a sulfur-containing multi-ring structure, and its intrinsic structure film-forming activity (LUMO potential) is relatively high. After the sulfur-containing structure is cyclized, the lonely electron on O is more exposed and easy to coordinate and complex with Li ions, occupying the lithium ion solvation sheath, and migrating to the positive / negative electrode interface under the action of the electric field to preferentially form a film. The formed stable interface film inhibits the dissolution of positive electrode metal ions and the decomposition of non-aqueous electrolyte at the positive / negative electrode interface, and has a significant improvement in the compatibility of non-aqueous electrolyte with electrodes, and is also beneficial to improving the electrochemical and thermal stability of the positive / negative electrode interface. In addition, the improvement of the positive electrode by the additive is more optimized than that of general additives. However, after the structure of this type of additive is cyclized, the molecular structure is larger, especially when it has multiple ring structures, when occupying After the solvent sheath, the lithium ion migration rate is slow, and the desolvation ability is relatively poor. Under low temperature conditions, the lithium ion conduction efficiency at the interface of the electrode and the non-aqueous electrolyte is significantly affected, resulting in relatively poor low temperature performance of the entire battery. In order to solve the adverse effect of the film formation of the compound shown in Structural Formula 1 on the lithium ion conduction efficiency, the present invention also adds a compound shown in Structural Formula 2 to the non-aqueous electrolyte. The above situation can be significantly improved by introducing the compound shown in Structural Formula 2. The compound of Structural Formula 2 has the same active central atom as the compound shown in Structural Formula 1, but its chain structure has small steric hindrance, and competes with the compound shown in Structural Formula 1 to occupy the solvation sheath. Under the condition that the film formation amount of the sulfur central atom remains unchanged, more compounds shown in Structural Formula 1 act on the positive electrode, and at the same time, the lithium ion migration rate is improved, and the improvement of high temperature performance is taken into account. If the compound shown in Structural Formula 2 is used alone, the reduction potential is high after being solvated and transferred to the negative electrode due to the structural characteristics, and it cannot be quickly reduced at the negative electrode. Although it will improve the low temperature performance and impedance, it will be unfavorable for high temperature cycling and storage performance. Therefore, the combination of the first additive is the best choice. DETAILED DESCRIPTION

[0034] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0035] An embodiment of the present invention provides a non-aqueous electrolyte, including a non-aqueous organic solvent, an electrolyte salt and an additive, wherein the additive includes a compound shown in Structural Formula 1 and a compound shown in Structural Formula 2:

[0036] ;

[0037] Wherein n is 0 or 1, A is selected from C or O, and X is selected from , R1, R2 are each independently selected from H,

[0038] , R1 and R2 are not simultaneously selected from H, and X, R1 and R2 contain at least one sulfur atom;

[0039] ;

[0040] Wherein, R3 and R4 are each independently selected from a substituted or unsubstituted alkyl group of 1 to 5 carbon atoms, a substituted or unsubstituted cyclic carbonate group of 3 to 6 carbon atoms, a silicon-containing group of 3 to 16 carbon atoms, an alkenyl group of 2 to 5 carbon atoms, an alkynyl group of 2 to 5 carbon atoms or a cyano group of 1 to 5 carbon atoms.

[0041] The compound shown in structural formula 1 is a sulfur-containing multi-ring structure, and its intrinsic structure has a high film-forming activity (LUMO potential). After the sulfur-containing structure is cyclized, the lonely electron on O is more exposed and easy to coordinate and complex with Li ions, occupying the lithium ion solvation sheath, and migrating to the positive / negative electrode interface under the action of the electric field to preferentially form a film. The formed stable interface film inhibits the dissolution of positive electrode metal ions and the decomposition of non-aqueous electrolytes at the positive / negative electrode interface, and has a significant improvement in the compatibility of non-aqueous electrolytes and electrodes, and is also beneficial to improving the electrochemical and thermal stability of the positive / negative electrode interface. In addition, the improvement of the positive electrode by this additive is more optimized than that of general additives. However, after the structure of this type of additive is cyclized, the molecular structure is larger, especially when it has multiple ring structures. After occupying the solvent sheath layer, the lithium ion migration rate is slow, and the desolvation energy The force is also relatively poor. Under low temperature conditions, it significantly affects the conduction efficiency of lithium ions at the interface of the electrode and the non-aqueous electrolyte, resulting in relatively poor low-temperature performance of the entire battery. In order to solve the adverse effect of the film formation of the compound shown in Structural Formula 1 on the lithium ion conduction efficiency, the present invention also adds a compound shown in Structural Formula 2 to the non-aqueous electrolyte. The above situation can be significantly improved by introducing the compound shown in Structural Formula 2. The compound of Structural Formula 2 has the same active central atom as the compound shown in Structural Formula 1, but its chain structure has small steric hindrance, and competes with the compound shown in Structural Formula 1 to occupy the solvation sheath. Under the condition that the film formation amount of the sulfur central atom remains unchanged, more compounds shown in Structural Formula 1 act on the positive electrode, and at the same time, the lithium ion migration rate is improved, taking into account the improvement of high-temperature performance. If the compound shown in Structural Formula 2 is used alone, the reduction potential is high after being solvated and transferred to the negative electrode due to the structural characteristics, and it cannot be quickly reduced at the negative electrode. Although it will improve the low-temperature performance and impedance, it will be unfavorable for high-temperature cycling and storage performance, so the combination of the first additive is the best choice.

[0042] In the description of the present invention, the term "substituted or unsubstituted" in "substituted" means that the hydrogen atom is replaced by a hydrocarbon group or a group with a heteroelement (oxygen, nitrogen, halogen). In a specific embodiment, the substituted group can be a C1~C3 hydrocarbon group, a fluorinated hydrocarbon group, an oxygen-containing hydrocarbon group, a cyano group, a halogen, etc.

[0043] In some embodiments, based on the total mass of the non-aqueous electrolyte being 100%, the mass percentage of the compound represented by Structural Formula 1 is 0.01% to 3%.

[0044] In a specific embodiment, based on the total mass of the non-aqueous electrolyte as 100%, the mass percentage of the compound represented by Structural Formula 1 can be 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, 0.2%, 0.4%, 0.5%, 0.7%, 0.9%, 1.0%, 1.1%, 1.3%, 1.5%, 1.8%, 2.0%, 2.3%, 2.7%, 3.0% or a range therebetween.

[0045] In a preferred embodiment, based on the total mass of the non-aqueous electrolyte being 100%, the mass percentage of the compound represented by the structural formula 1 is 0.05% to 2%.

[0046] The compound shown in the structural formula 1 participates in the formation of the positive and negative electrode interface film. The interface film formed by the compound has good high-temperature stability, can better protect the positive and negative electrode structures, and avoid unnecessary side reactions of non-aqueous electrolytes on the positive and negative electrode surfaces. If the amount of the compound shown in the structural formula 1 added is too low, it is difficult to improve the high-temperature performance of the battery; if the amount of the compound shown in the structural formula 1 added is too high, due to its influence on lithium ion conduction, it will lead to an increase in battery impedance, which is not conducive to improving the low-temperature capacity retention rate of the battery.

[0047] In some embodiments, based on the total mass of the non-aqueous electrolyte being 100%, the mass percentage of the compound represented by Structural Formula 2 is 0.01% to 1.5%.

[0048] In a specific embodiment, based on the total mass of the non-aqueous electrolyte as 100%, the mass percentage of the compound represented by Structural Formula 2 can be 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, 0.2%, 0.4%, 0.5%, 0.7%, 0.9%, 1.0%, 1.1%, 1.3%, 1.5% or a range therebetween.

[0049] In a preferred embodiment, based on the total mass of the non-aqueous electrolyte being 100%, the mass percentage of the compound represented by Structural Formula 2 is 0.1% to 1%.

[0050] The compound shown in Structural Formula 2 has a chain structure and has the same active central atom as the compound shown in Structural Formula 1, and can form a film on the surface of the positive and negative electrodes together with the compound shown in Structural Formula 1, so as to improve the conductivity efficiency of the interface film for lithium ions without deteriorating the high temperature performance of the battery; if the addition amount of the compound shown in Structural Formula 2 is too low, it is difficult to improve the low temperature performance of the battery; if the addition amount of the compound shown in Structural Formula 2 is too high, the proportion of the decomposition products of the compound shown in Structural Formula 1 in the interface film is reduced due to the competition relationship, resulting in a decrease in the high temperature stability of the interface film, affecting the high temperature performance of the battery.

[0051] In some embodiments, the total mass of the compound represented by Structural Formula 1 and the compound represented by Structural Formula 2 added to the non-aqueous electrolyte is X, and X satisfies 0.05≤X≤4.

[0052] In a preferred embodiment, X satisfies 0.1≤X≤3.

[0053] The addition amount of the compound shown in Structural Formula 1 and the compound shown in Structural Formula 2 is related to the film quality on the surface of the positive and negative electrodes. When the total added mass X is too small, it is difficult to form a continuous and complete interface film on the surface of the positive and negative electrodes, resulting in the decomposition of the non-aqueous electrolyte on the surface of the positive and negative electrodes under high temperature conditions, resulting in problems such as decreased battery capacity and gas production; when the total added mass X is too large, the film thickness on the surface of the positive and negative electrodes will be too large, which will in turn lead to an increase in battery impedance.

[0054] In some embodiments, the mass ratio of the compound represented by Structural Formula 1 to the compound represented by Structural Formula 2 is Y, and Y satisfies 1≤Y≤10.

[0055] In a preferred embodiment, Y satisfies 2≤Y≤5.

[0056] Due to the interaction between the compound shown in Structural Formula 1 and the compound shown in Structural Formula 2, the synergistic effect produced by the compound shown in Structural Formula 1 and the compound shown in Structural Formula 2 is more obvious when the above addition ratio is met, which is conducive to forming a positive and negative electrode interface film that takes into account both high temperature stability and lithium ion conduction efficiency.

[0057] In some embodiments, in the compound represented by structural formula 1, R1 and R2 are each independently selected from , and X, R1 and R2 contain at least one sulfur atom.

[0058] When the compound shown in Structural Formula 1 satisfies the above conditions, the compound shown in Structural Formula 1 has a tricyclic structure. Compared with the bicyclic structure, the tricyclic structures each open their rings to participate in the formation of the interface film on the electrode surface, which has the effect of improving the strength of the interface film structure, thereby helping to improve its high temperature stability.

[0059] As an example, the compound represented by the structural formula 1 is selected from one or more of the following compounds:

[0060]

[0061] In some embodiments, in the compound represented by Structural Formula 1, X, R1 and R2 do not contain sulfur atoms at the same time.

[0062] When the compound shown in the structural formula 1 satisfies the above conditions, the compound shown in the structural formula 1 has a tricyclic structure, and the compound shown in the structural formula 1 includes both a sulfur-containing cyclic structure and a carbonate-containing cyclic structure, wherein the carbonate cyclic structure is conducive to the formation of a lithium carbonate component in the electrode interface film, and compared with simple sulfur-containing decomposition products, the interface film component formed by the carbonate cyclic structure and the sulfur-containing cyclic structure is more stable and dense.

[0063] In some embodiments, in the compound represented by the structural formula 1, R1 is selected from H, and X is selected from , R2 is selected from ;or

[0064] R1 is selected from H, X is selected from , R2 is selected from

[0065] When the compound shown in Structural Formula 1 satisfies the above conditions, the compound shown in Structural Formula 1 has a bicyclic structure, and the compound shown in Structural Formula 1 includes both a sulfur-containing cyclic structure and a carbonate-containing cyclic structure. Compared with simple sulfur-containing decomposition products, the interface film component formed by the carbonate cyclic structure and the sulfur-containing cyclic structure is more stable and dense.

[0066] In some embodiments, the compound represented by structural formula 1 is selected from at least one of the following compounds: .

[0067] In some embodiments, in the compound shown in Structural Formula 2, R3 is selected from substituted or unsubstituted cyclic carbonates of 3 to 6 carbon atoms, silicon-containing groups of 3 to 16 carbon atoms, alkenyls of 2 to 5 carbon atoms, alkynyls of 2 to 5 carbon atoms, or cyano groups of 1 to 5 carbon atoms, and R4 is selected from substituted or unsubstituted alkyls of 1 to 5 carbon atoms, substituted or unsubstituted cyclic carbonates of 3 to 6 carbon atoms, silicon-containing groups of 3 to 16 carbon atoms, alkenyls of 2 to 5 carbon atoms, alkynyls of 2 to 5 carbon atoms, or cyano groups of 1 to 5 carbon atoms.

[0068] When R3 in the compound shown in Structural Formula 2 is selected from the above groups, the R3 group is an electron-donating group, which makes the oxygen lone electron density on the sulfate group larger, and is easy to complex with lithium ions. It will compete with the compound shown in Structural Formula 1 to occupy a certain lithium ion solvation sheath. The overall lithium ion solvation structure sheath steric hindrance is reduced, which is conducive to the rapid transfer of lithium ions in the non-aqueous electrolyte. The part of the compound of Structural Formula 1 that is competed away will form a film on the positive electrode, further strengthening the protection of the positive electrode.

[0069] The silicon-containing group is selected from , where R 41 , R 42 , R 43 Each is independently selected from a C1~C5 alkyl group.

[0070] In some embodiments, in the compound shown in Structural Formula 2, R3 is selected from a substituted or unsubstituted cyclic carbonate of 3 to 6 carbon atoms, and R4 is selected from a substituted or unsubstituted alkyl of 1 to 5 carbon atoms, a substituted or unsubstituted cyclic carbonate of 3 to 6 carbon atoms, a silicon-containing group of 3 to 16 carbon atoms, an alkenyl of 2 to 5 carbon atoms, an alkynyl of 2 to 5 carbon atoms, or a cyano group of 1 to 5 carbon atoms.

[0071] When the R3 group in the compound shown in Structural Formula 2 is selected as a cyclic carbonate, a carbonate ring is introduced on the sulfate group. Compared with the above-mentioned compounds, the solvation hindrance increases, but this structure can enhance the film-forming activity of the overall structure at the positive electrode, thereby making the positive electrode protection better. Moreover, the carbonate ring is also an electron-donating group structure, which is beneficial for competing with the compound shown in Structural Formula 1 for the solvation sheath and participating in the positive / negative electrode film formation. It provides better protection for the positive electrode, so this type of combination can also take into account the improvement of both high-temperature performance and low-temperature performance.

[0072] In some embodiments, in the compound shown in structural formula 2, R3 is selected from a silicon-containing group of 3 to 16 carbon atoms, and R4 is selected from a substituted or unsubstituted alkyl group of 1 to 5 carbon atoms, a substituted or unsubstituted cyclic carbonate group of 3 to 6 carbon atoms, a silicon-containing group of 3 to 16 carbon atoms, an alkenyl group of 2 to 5 carbon atoms, an alkynyl group of 2 to 5 carbon atoms, or a cyano group of 1 to 5 carbon atoms.

[0073] When the R3 group in the compound shown in Structural Formula 2 is selected as a silicon-containing group, due to the activity of the silicon-oxygen group, the compound shown in Structural Formula 2 will react with the electrolyte salt to generate an inorganic lithium salt (LiF, lithium sulfate) at the interface after being added to the non-aqueous electrolyte, thereby reducing the interface impedance. At the same time, the Si group is also an electron-donating group, which also increases the density of lone pairs of oxygen electrons on the sulfate on the compound shown in Structural Formula 2, thereby improving the complexing ability with lithium ions, and further participating in the lithium ion solvation sheath. While improving the transfer ability of lithium ions in the non-aqueous electrolyte, more compounds shown in Structural Formula 1 can also act on the positive electrode. The silicon-containing group also has an action characteristic. The Si-O bond can react with the reduction product of the non-aqueous organic solvent to introduce the sulfate group into the negative electrode interface. Therefore, the combination of this type of compound with Structural Formula 1 can take into account the improvement of both high temperature performance and rate performance.

[0074] In some embodiments, in the compound shown in structural formula 2, R3 is selected from an alkenyl group of 2 to 5 carbon atoms or an alkynyl group of 2 to 5 carbon atoms, and R4 is selected from a substituted or unsubstituted alkyl group of 1 to 5 carbon atoms, a substituted or unsubstituted cyclic carbonate group of 3 to 6 carbon atoms, a silicon-containing group of 3 to 16 carbon atoms, an alkenyl group of 2 to 5 carbon atoms, an alkynyl group of 2 to 5 carbon atoms, or a cyano group of 1 to 5 carbon atoms.

[0075] When the R3 group in the compound shown in Structural Formula 2 is selected as an unsaturated hydrocarbon group, the unsaturated hydrocarbon group can undergo addition reaction on the surface of the negative electrode to improve the mechanical strength of the film formed on the surface of the negative electrode, and the double bond is also an electron-donating group, which can increase the electron density of the lone oxygen electrons on the sulfate ester and increase the coordination ability with ions. Therefore, this structure can also compete with the compound shown in Structural Formula 1 to occupy the lithium ion solvation sheath, and then more compounds shown in Structural Formula 1 form a film on the positive electrode, thereby protecting the positive electrode.

[0076] In some embodiments, the compound represented by structural formula 2 is selected from at least one of the following compounds: .

[0077] In some embodiments, the non-aqueous organic solvent includes at least one of an ether solvent, a nitrile solvent, a carbonate solvent, and a carboxylate solvent.

[0078] In some embodiments, the ether solvent includes cyclic ether or chain ether and fluorinated products thereof, preferably chain ether with 3 to 10 carbon atoms and cyclic ether with 3 to 6 carbon atoms, and the cyclic ether may be, but not limited to, at least one of 1,3-dioxolane (DOL), 1,4-dioxolane (DX), crown ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH3-THF), and 2-trifluoromethyltetrahydrofuran (2-CF3-THF); the chain ether may be, but not limited to, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether. Since chain ethers have high solvation ability with lithium ions and can improve ion dissociation, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane, which have low viscosity and can impart high ionic conductivity, are particularly preferred. Ether compounds can be used alone or in any combination and ratio. There is no special restriction on the amount of ether compounds added, which is arbitrary within the range that does not significantly damage the effect of the high-density lithium-ion battery of the present invention. In the non-aqueous solvent volume ratio of 100%, the volume ratio is usually 1% or more, preferably 2% or more, and more preferably 3% or more. In addition, the volume ratio is usually 30% or less, preferably 25% or less, and more preferably 20% or less. When two or more ether compounds are used in combination, the total amount of ether compounds is made to meet the above range. When the amount of ether compounds added is within the above-mentioned preferred range, it is easy to ensure the improvement of ionic conductivity brought about by the increase in the dissociation degree of lithium ions of the chain ether and the decrease in viscosity. In addition, when the negative electrode active material is a carbon-based material, the phenomenon of co-embedding of chain ethers and lithium ions can be suppressed, so that the input-output characteristics and the charge-discharge rate characteristics can reach an appropriate range.

[0079] In some embodiments, the nitrile solvent may specifically be but is not limited to at least one of acetonitrile, glutaronitrile, and malononitrile.

[0080] In some embodiments, the carbonate solvent includes a cyclic carbonate or a chain carbonate, and the cyclic carbonate may be, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), and butylene carbonate (BC); the chain carbonate may be, but is not limited to, at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dipropyl carbonate (DPC). The content of the cyclic carbonate is not particularly limited, and is arbitrary within the range that does not significantly damage the effect of the lithium ion battery of the present invention, but when one is used alone, the lower limit of its content is usually 3% or more by volume, preferably 5% or more by volume, relative to the total amount of solvent in the non-aqueous electrolyte. By setting this range, the conductivity can be reduced due to the reduction in the dielectric constant of the non-aqueous electrolyte, and it is easy to make the large current discharge characteristics, stability relative to the negative electrode, and cycle characteristics of the non-aqueous electrolyte battery reach a good range. In addition, the upper limit is usually 90% or less by volume, preferably 85% or less by volume, and more preferably 80% or less by volume. By setting this scope, the oxidation / reduction tolerance of nonaqueous electrolyte can be improved, thus contribute to the stability during high temperature storage. The content of linear carbonate is not particularly limited, and relative to the total amount of solvent of nonaqueous electrolyte, it is usually more than 15% by volume, preferably more than 20% by volume, and more preferably more than 25% by volume. In addition, usually the volume ratio is less than 90%, preferably less than 85% by volume, and more preferably less than 80% by volume. By making the content of linear carbonate in the above-mentioned scope, it is easy to make the viscosity of nonaqueous electrolyte reach appropriate range, suppress the reduction of ionic conductivity, and then contribute to make the output characteristics of nonaqueous electrolyte battery reach good scope. When two or more linear carbonates are used in combination, the total amount of linear carbonate is made to meet the above-mentioned scope.

[0081] In certain embodiments, it is also possible to preferably use chain carbonates with fluorine atoms (hereinafter referred to as "fluorinated chain carbonates"). The number of fluorine atoms possessed by the fluorinated chain carbonate is not particularly limited as long as it is more than 1, but is generally less than 6, preferably less than 4. When the fluorinated chain carbonate has a plurality of fluorine atoms, these fluorine atoms can be bonded to the same carbon or to different carbons. As the fluorinated chain carbonate, fluorinated dimethyl carbonate derivatives, fluorinated ethyl methyl carbonate derivatives, fluorinated diethyl carbonate derivatives, etc. can be listed.

[0082] The carboxylate solvent includes cyclic carboxylate and / or chain carbonate. Examples of cyclic carboxylate include at least one of γ-butyrolactone, γ-valerolactone, and δ-valerolactone. Examples of chain carbonate include at least one of methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, propyl propionate (PP), butyl propionate, and ethyl fluoroacetate.

[0083] In some embodiments, the sulfone solvent includes a cyclic sulfone and a chain sulfone. Preferably, in the case of a cyclic sulfone, it is usually a compound with 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms, and in the case of a chain sulfone, it is usually a compound with 2 to 6 carbon atoms, preferably 2 to 5 carbon atoms. There is no special restriction on the amount of sulfone solvent added, and it is arbitrary within the range that does not significantly damage the effect of the lithium ion battery of the present invention. Relative to the total amount of solvent of the non-aqueous electrolyte, the volume ratio is usually 0.3% or more, preferably 0.5% or more, and more preferably 1% or more. In addition, the volume ratio is usually 40% or less, preferably 35% or less, and more preferably 30% or less. In the case of using two or more sulfone solvents in combination, the total amount of sulfone solvents can be made to meet the above range. When the amount of sulfone solvent added is within the above range, a non-aqueous electrolyte with excellent high temperature storage stability tends to be obtained.

[0084] In a preferred embodiment, the non-aqueous organic solvent is a mixture of cyclic carbonate and chain carbonate.

[0085] In some embodiments, the additive further comprises at least one of a cyclic sulfate compound, a sultone compound, a cyclic carbonate compound, a phosphate compound, a borate compound, and a nitrile compound;

[0086] Preferably, based on the total mass of the non-aqueous electrolyte being 100%, the amount of the additive added is 0.01% to 30%.

[0087] In some embodiments, the cyclic sulfate ester compound is selected from vinyl sulfate, propylene sulfate, methyl vinyl sulfate, At least one of;

[0088] The sultone compound is selected from at least one of 1,3-propane sultone, 1,4-butane sultone, and 1,3-propylene sultone;

[0089] The cyclic carbonate compound is selected from at least one of vinylene carbonate, ethylene carbonate, methylene carbonate, fluoroethylene carbonate, trifluoromethylethylene carbonate, bisfluoroethylene carbonate or the compound shown in formula 3.

[0090] ;

[0091] In the structural formula 3, R 21 , R 22 , R 23 , R 24 , R 25 , R 26 Each is independently selected from a hydrogen atom, a halogen atom, and a C1-C5 group;

[0092] The phosphate compound is selected from at least one of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite or the compound shown in structural formula 4:

[0093] ;

[0094] In the structural formula 4, R 31 , R 32 , R 33 Each independently selected from a C1-C5 saturated hydrocarbon group, an unsaturated hydrocarbon group, a halogenated hydrocarbon group, -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and R 31 , R 32 , R 33 At least one of them is an unsaturated hydrocarbon group;

[0095] In a preferred embodiment, the phosphate compound shown in the structural formula 4 may be at least one of tripropargyl phosphate, dipropargyl methyl phosphate, dipropargyl ethyl phosphate, dipropargyl propyl phosphate, dipropargyl trifluoromethyl phosphate, dipropargyl-2,2,2-trifluoroethyl phosphate, dipropargyl-3,3,3-trifluoropropyl phosphate, dipropargyl hexafluoroisopropyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, diallyl trifluoromethyl phosphate, diallyl-2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate, and diallyl hexafluoroisopropyl phosphate;

[0096] The borate compound is selected from at least one of tris(trimethylsilyl)borate and tris(triethylsilyl)borate;

[0097] The nitrile compound is selected from at least one of succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrinitrile, adiponitrile, pimelonitrile, suberonitrile, azelaic acid dinitrile and sebacononitrile.

[0098] In other embodiments, the additives may also include other additives that can improve battery performance: for example, additives that enhance battery safety performance, such as flame retardant additives such as fluorophosphates and cyclophosphazenes, or overcharge prevention additives such as tert-amylbenzene and tert-butylbenzene.

[0099] It should be noted that, unless otherwise specified, in general, the amount of any one of the optional substances in the additives added to the non-aqueous electrolyte is less than 10%, preferably, the amount added is 0.1%-5%, and more preferably, the amount added is 0.1%~2%. Specifically, the amount of any one of the optional substances in the additives can be 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5%, 10%.

[0100] In some embodiments, when the additive is selected from fluoroethylene carbonate, the amount of the fluoroethylene carbonate added is 0.05% to 30% based on the total mass of the non-aqueous electrolyte as 100%.

[0101] In some embodiments, the electrolyte salt is selected from a lithium salt, and the lithium salt is selected from LiPF6, LiBOB, LiDFOB, LiPO2F2, LiBF4, LiSbF6, LiAsF6, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, LiN(SO2F)2, LiClO4, LiAlCl4, LiCF3SO3, Li2B 10 Cl 10 , LiSO2F, LiTOP (lithium trioxalate phosphate), LiDODFP (lithium difluorodioxalate phosphate), LiOTFP (lithium tetrafluorooxalate phosphate) and at least one of a low aliphatic carboxylic acid lithium salt.

[0102] In some embodiments, the concentration of the lithium salt in the non-aqueous electrolyte is 0.1 mol / L to 8 mol / L. In a preferred embodiment, the concentration of the lithium salt in the non-aqueous electrolyte is 0.5 mol / L to 2.5 mol / L. Specifically, the concentration of the lithium salt in the non-aqueous electrolyte may be 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, or 2.5 mol / L.

[0103] Another embodiment of the present invention provides a secondary battery including a positive electrode, a negative electrode, and the non-aqueous electrolyte as described above.

[0104] The present invention is further described below by way of examples.

[0105] Table 1

[0106] .

[0107] Example 1

[0108] This example is used to illustrate the preparation method of the lithium ion battery disclosed in the present invention, which includes the following steps:

[0109] 1) Preparation of non-aqueous electrolyte

[0110] Ethylene carbonate (EC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) were mixed at a mass ratio of EC:DEC:EMC=1:1:1, and then lithium hexafluorophosphate (LiPF6) was added to a molar concentration of 1 mol / L. As shown in Table 1, additives were added based on the total mass of the electrolyte.

[0111] 2) Preparation of positive electrode

[0112] The positive electrode active material LiNi was mixed in a mass ratio of 93:4:3 0.6 Co 0.1 Mn 0.3 O2, conductive carbon black Super-P and binder polyvinylidene fluoride (PVDF), and then disperse them in N-methyl-2-pyrrolidone (NMP) to obtain positive electrode slurry. The slurry is evenly coated on both sides of the aluminum foil, dried, rolled and vacuum dried, and welded with aluminum lead wires using an ultrasonic welder to obtain a positive plate with a thickness of 120-150μm.

[0113] 3) Preparation of negative electrode

[0114] The negative electrode active material artificial graphite, conductive carbon black Super-P, binder styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) are mixed in a mass ratio of 94:1:2.5:2.5, and then dispersed in deionized water to obtain negative electrode slurry. The slurry is coated on both sides of the copper foil, dried, rolled and vacuum dried, and the nickel lead wire is welded with an ultrasonic welder to obtain the negative electrode plate, and the thickness of the plate is 120-150μm.

[0115] 4) Preparation of battery cells

[0116] A three-layer separator with a thickness of 20 μm was placed between the positive plate and the negative plate, and then the sandwich structure consisting of the positive plate, the negative plate and the separator was wound. The wound body was flattened and placed in an aluminum foil packaging bag, and vacuum-baked at 75°C for 48 hours to obtain a battery cell to be injected with liquid.

[0117] 5) Battery filling and formation

[0118] In a glove box with a dew point controlled below -40°C, the prepared electrolyte was injected into the battery cell, vacuum packaged, and left to stand for 24 hours. Then the first charge formation was carried out, and the formation conditions were: formation temperature of 40°C to 50°C, formation pressure of 2 to 8 kg / cm 2 , the charging current is 0.05C~0.12C, and the discharging current is 0.1C~0.3C.

[0119] Embodiments 2 to 30

[0120] Examples 2 to 30 are used to illustrate the lithium ion battery and the preparation method thereof disclosed in the present invention, and include most of the operation steps in Example 1, except that:

[0121] The types and mass percentages of additives in the non-aqueous electrolytes used in Examples 2 to 30 are shown in Table 1.

[0122] Comparative Examples 1 to 31

[0123] Comparative Examples 1 to 31 are used to compare and illustrate the lithium ion battery and the preparation method thereof disclosed in the present invention, and include most of the operation steps in Example 1, except that:

[0124] The types and mass percentages of additives in the non-aqueous electrolytes used in Comparative Examples 1 to 31 are shown in Table 1.

[0125] Performance Testing

[0126] The lithium-ion battery prepared above was subjected to the following performance tests:

[0127] 1. High temperature cycle performance test

[0128] The lithium-ion batteries prepared in the examples and comparative examples were placed in an oven at a constant temperature of 45°C, charged at a constant current of 4C to 80% SOC, then charged at a constant current of 1C to 4.4V, then charged at a constant voltage until the current dropped to 0.02C, and then discharged at a constant current of 1C to 3.0V, and this cycle was repeated, and the first discharge capacity and the last discharge capacity were recorded.

[0129] The capacity retention rate of high temperature cycle is calculated as follows:

[0130] Capacity retention rate = last discharge capacity / first discharge capacity × 100%.

[0131] 2. Normal temperature cycle performance test

[0132] The lithium-ion batteries prepared in the examples and comparative examples were placed in an oven at a constant temperature of 25°C, charged to 80% SOC at a constant current of 4C, then charged to 4.4V at a constant current and voltage of 1C, with a cut-off current of 0.05C, and then discharged to 3.0V at a constant current of 1C, and the cycle was repeated, and the first discharge capacity and the last discharge capacity were recorded.

[0133] The capacity retention rate of high temperature cycle is calculated as follows:

[0134] Capacity retention rate = last discharge capacity / first discharge capacity × 100%.

[0135] 3. High temperature storage performance test

[0136] The formed lithium-ion battery was charged to 4.4V at room temperature using a constant current and constant voltage of 0.5C, and the initial discharge capacity and initial battery thickness of the battery were measured. After being stored in a 60°C environment for 30 days, the battery was discharged to 3V at 1C, and the battery retention capacity and recovery capacity as well as the battery thickness after storage were measured. The calculation formula is as follows:

[0137] Battery capacity retention rate (%) = retention capacity / initial capacity × 100%;

[0138] Battery capacity recovery rate (%) = recovery capacity / initial capacity × 100%;

[0139] Thickness expansion rate (%) = (battery thickness after storage - initial battery thickness) / initial battery thickness × 100%.

[0140] 4. Low temperature performance test

[0141] At 25°C, the formed battery was charged to 4.4V with 1C constant current and constant voltage, and then discharged to 3.0V with 1C constant current, and the discharge capacity was recorded. Then, the battery was charged to 4.4V with 1C constant current and constant voltage, placed in a -20°C environment for 12 hours, and then discharged to 3.0V with 0.5C constant current, and the discharge capacity was recorded.

[0142] The low-temperature discharge efficiency value at -20℃ = 0.5C discharge capacity (-20℃) / 1C discharge capacity (25℃) × 100%.

[0143] (1) The test results obtained in Examples 1 to 16 and Comparative Examples 1 to 8 and 16 to 24 are entered in Table 2.

[0144] Table 2

[0145] .

[0146] It can be seen from the test results of Examples 1 to 16 and Comparative Examples 1 to 8 and 16 to 24 that, compared with adding the compound represented by Structural Formula 1 alone or adding the compound represented by Structural Formula 2 alone to the non-aqueous electrolyte in Comparative Examples 1 to 8 and 16 to 24, adding the compound represented by Structural Formula 1 and the compound represented by Structural Formula 2 simultaneously in Examples 1 to 16 significantly improves the various performances of the battery. In particular, even when the total addition amount is not much different, or when the total addition amount is lower, the combined addition of the compound represented by Structural Formula 1 and the compound represented by Structural Formula 2 is significantly better than adding them alone for improving the battery performance, indicating that the compound represented by Structural Formula 1 and the compound represented by Structural Formula 2 have a synergistic effect in the film formation stage of battery formation, and can better protect the positive and negative electrode structures, while avoiding unnecessary side reactions of the non-aqueous electrolyte on the positive and negative electrode surfaces, and at the same time improving the ion conduction efficiency of the solid electrolyte membrane on the positive and negative electrode surfaces, thereby taking into account the improvement of the high temperature storage performance, high temperature cycle performance and low temperature discharge performance of the battery.

[0147] It can be seen from the test results of Examples 1 to 16 that due to the interaction between the compound represented by Structural Formula 1 and the compound represented by Structural Formula 2 in the battery formation stage, the total addition amount X of the two and the mass ratio Y of the two have a significant correlation effect on the synergistic effect thereof. Specifically, when X satisfies 0.05≤X≤4 and Y satisfies 1≤Y≤10, the obtained lithium ion battery has better high temperature stability and low temperature discharge capacity; in particular, when X satisfies 0.1≤X≤3 and Y satisfies 2≤Y≤5, the obtained lithium ion battery has further improved high temperature stability and low temperature discharge capacity.

[0148] (2) The test results obtained in Examples 1, 17 to 30 and Comparative Examples 9 to 15, 25 to 31 are entered in Table 3.

[0149] Table 3

[0150] .

[0151] It can be seen from the test results of Examples 1, 17 to 30 and Comparative Examples 9 to 15, 25 to 31 that in the electrolyte system provided by the present invention, the combination of different compounds represented by Structural Formula 1 and different compounds represented by Structural Formula 2 can improve the high temperature performance and low temperature performance of lithium-ion batteries, indicating that the structural commonality of the compound represented by Structural Formula 1 and the compound represented by Structural Formula 2 is an influencing factor for their synergistic effect. Specifically, the polycyclic structure of the compound represented by Structural Formula 1, the chain structure of the compound represented by Structural Formula 2, and the same active central atom between the compound represented by Structural Formula 1 and the compound represented by Structural Formula 2 are all key factors affecting their interaction.

[0152] At the same time, according to the test results of Examples 1 and 17 to 23, it can be seen that among the compounds represented by Structural Formula 1, compared with the bicyclic structure, when the compound represented by Structural Formula 1 is selected as a tricyclic structure, it has the effect of improving the structural strength of the interfacial film, which is beneficial to improving its high temperature stability; and compared with the compound represented by Structural Formula 1 containing only a sulfur-containing cyclic structure, the interfacial film formed by the compound represented by Structural Formula 1 containing both a sulfur-containing cyclic structure and a carbonate-containing cyclic structure has a higher density, which is beneficial to improving stability.

[0153] According to the test results of Examples 1 and 24 to 30, it can be seen that in the compound shown in Structural Formula 2, compared with R3 being selected from an alkyl group, when the R3 group is selected from an electron-donating group, the oxygen lone electron density on the sulfate group can be made larger, which is easy to complex with lithium ions, and then competes with the compound of Structural Formula 1 to occupy a certain lithium ion solvation sheath, thereby playing a role in replacing the compound shown in Structural Formula 1 and strengthening the positive electrode protection.

[0154] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A non-aqueous electrolyte, characterized in that: It includes a non-aqueous organic solvent, an electrolyte salt and an additive, wherein the additive includes a compound shown in Structural Formula 1 and a compound shown in Structural Formula 2: Structural formula 1 Wherein n is 0 or 1, A is selected from C or O, and X is selected from or , R1, R2 are each independently selected from H, , , , or , R1 and R2 are not simultaneously selected from H, and X, R1 and R2 contain at least one sulfur atom; Structural formula 2 wherein R3 and R4 are each independently selected from a substituted or unsubstituted alkyl group of 1 to 5 carbon atoms, a substituted or unsubstituted cyclic carbonate group of 3 to 6 carbon atoms, a silicon-containing group of 3 to 16 carbon atoms, an alkenyl group of 2 to 5 carbon atoms, an alkynyl group of 2 to 5 carbon atoms, or a cyano group of 1 to 5 carbon atoms; The mass ratio of the compound represented by the structural formula 1 to the compound represented by the structural formula 2 is Y, and Y satisfies 1≤Y≤10; Based on the total mass of the non-aqueous electrolyte being 100%, the mass percentage of the compound represented by the structural formula 1 is 0.01% to 3%; and / or Based on the total mass of the non-aqueous electrolyte being 100%, the mass percentage of the compound represented by the structural formula 2 is 0.01% to 1.5%.

2. The non-aqueous electrolyte according to claim 1, characterized in that The total mass of the compound represented by the structural formula 1 and the compound represented by the structural formula 2 added to the non-aqueous electrolyte is X%, and X satisfies 0.05≤X≤4.

3. The non-aqueous electrolyte according to claim 1, characterized in that In the compound represented by the structural formula 1, R1 and R2 are each independently selected from , , , or , and X, R1 and R2 contain at least one sulfur atom.

4. The non-aqueous electrolyte according to claim 1 or 3, characterized in that In the compound represented by the structural formula 1, X, R1 and R2 do not contain sulfur atoms at the same time.

5. The non-aqueous electrolyte according to claim 1, characterized in that In the compound shown in the structural formula 1, R1 is selected from H, X is selected from , R2 is selected from ,or R1 is selected from H, X is selected from , R2 is selected from , , or .

6. The non-aqueous electrolyte according to claim 1, characterized in that In the compound shown in structural formula 2, R3 is selected from substituted or unsubstituted cyclic carbonates of 3 to 6 carbon atoms, silicon-containing groups of 3 to 16 carbon atoms, alkenyls of 2 to 5 carbon atoms, alkynyls of 2 to 5 carbon atoms or cyano groups of 1 to 5 carbon atoms, and R4 is selected from substituted or unsubstituted alkyls of 1 to 5 carbon atoms, substituted or unsubstituted cyclic carbonates of 3 to 6 carbon atoms, silicon-containing groups of 3 to 16 carbon atoms, alkenyls of 2 to 5 carbon atoms, alkynyls of 2 to 5 carbon atoms or cyano groups of 1 to 5 carbon atoms.

7. The non-aqueous electrolyte according to claim 1, characterized in that The compound represented by the structural formula 1 is selected from at least one of the following compounds: And / or, the compound represented by structural formula 2 is selected from at least one of the following compounds: 。 8. The non-aqueous electrolyte according to claim 1, characterized in that The additive further comprises at least one of a cyclic sulfate compound, a sultone compound, a cyclic carbonate compound, a phosphate compound, a borate compound and a nitrile compound; The cyclic sulfate ester compound is selected from vinyl sulfate, propylene sulfate, methyl vinyl sulfate, , At least one of; and / or The sultone compound is selected from at least one of 1,3-propane sultone, 1,4-butane sultone and 1,3-propylene sultone; and / or The cyclic carbonate compound is selected from at least one of vinylene carbonate, ethylene carbonate, methylene carbonate, fluoroethylene carbonate, trifluoromethylethylene carbonate, bisfluoroethylene carbonate or the compound shown in formula 3. Structural formula 3 In the structural formula 3, R 21 , R 22 , R 23 , R 24 , R 25 , R 26 Each is independently selected from a hydrogen atom, a halogen atom, a C1-C5 group; and / or The phosphate compound is selected from at least one of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite or the compound shown in structural formula 4: Structural formula 4 In the structural formula 4, R 31 , R 32 , R 33 Each independently selected from a C1-C5 saturated hydrocarbon group, an unsaturated hydrocarbon group, a halogenated hydrocarbon group, -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and R 31 , R 32 , R 33 At least one of them is an unsaturated hydrocarbon group; and / or The borate compound is selected from at least one of tris(trimethylsilyl)borate and tris(triethylsilyl)borate; and / or The nitrile compound is selected from at least one of succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrinitrile, adiponitrile, pimelonitrile, suberonitrile, azelaic acid dinitrile and sebacononitrile.

9. A secondary battery, characterized in that: It comprises a positive electrode, a negative electrode and the non-aqueous electrolyte as claimed in any one of claims 1 to 8.

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