WO2023072084A1 - Secondary-battery electrolyte and preparation method therefor, secondary battery, and electronic device - Google Patents

Abstract

A secondary-battery electrolyte provided in the embodiments of the present application, which electrolyte comprises an electrolyte salt, an organic solvent and a flame retardant, wherein the flame retardant comprises pentafluorocyclotriphosphazene, tetrafluorocyclotriphosphazene and trifluorocyclotriphosphazene. In the electrolyte, pentafluorocyclotriphosphazene, tetrafluorocyclotriphosphazene and trifluorocyclotriphosphazene are added at the same time as flame retardants, such that the electrolyte is endowed with excellent flame retardancy, so that a battery has both high safety performance and good electrochemical performance. The embodiments of the present application further provide a secondary battery and an electronic device which comprise the secondary-battery electrolyte.

Description

Secondary battery electrolyte and preparation method thereof, secondary battery and electronic equipment

This application claims the priority of the Chinese patent application with the application number 202111260515.1 and the application title "Secondary Battery Electrolyte and Its Preparation Method, Secondary Battery and Electronic Equipment" submitted to the China Patent Office on October 27, 2021, The entire contents of which are incorporated by reference in this application.

technical field

The present application relates to the technical field of battery electrolyte, in particular to a secondary battery electrolyte and a preparation method thereof, a secondary battery and electronic equipment.

Background technique

The wide application of secondary batteries in consumer electronics (such as mobile phones, tablet computers) and electric vehicles has made people put forward higher requirements for the energy density and safety performance of secondary batteries. At present, the electrolytes of secondary batteries are mainly non-aqueous organic electrolytes (conventional carbonate or carboxylate electrolytes). , easy to burn and other hidden dangers, which can easily cause battery combustion and explosion accidents.

The mainstream strategy to improve the safety of secondary battery electrolytes is to add flame retardant additives to conventional electrolytes. Although there are many kinds of flame retardant additives reported so far, such as phosphate compounds, halogenated compounds, etc., most of them are not compatible with normal electrolytes. The compatibility of negative electrode materials is poor. Even if a phosphazene flame retardant with good compatibility with positive and negative electrode materials is used, in order to ensure the safety of high energy density batteries, it is still necessary to achieve good flame retardant effect at a relatively high dosage, which will damage the battery. Electrochemical properties such as high rate performance and low temperature cycle performance.

Contents of the invention

In view of this, the embodiment of the present application provides a secondary battery electrolyte, by adding three flame retardants pentafluorocyclotriphosphazene, tetrafluorocyclotriphosphazene and trifluorocyclotriphosphazene to the electrolyte at the same time, it can The battery has both high safety performance and good electrochemical performance.

Specifically, the first aspect of the embodiment of the present application provides a secondary battery electrolyte, including lithium salts, organic solvents and flame retardants, the flame retardants include pentafluorocyclotriphosphazene, tetrafluorocyclotriphosphazene and Trifluorocyclotriphosphazene.

In the secondary battery electrolyte solution provided by the first aspect of the embodiment of the present application, three flame retardants, pentafluorocyclotriphosphazene, tetrafluorocyclotriphosphazene and trifluorocyclotriphosphazene are added to the electrolyte at the same time. Under the synergistic effect of two kinds of flame retardants, the electrolyte can be endowed with flame retardant ability in the electrolyte volatilization range and flammable gas generation range, and their addition in a small amount makes the electrolyte have excellent flame retardant effect, and avoids a large amount of The problem of poor electrochemical performance of the battery caused by adding the phosphazene flame retardant can make the battery have both high safety performance and good electrochemical performance.

In the embodiment of the present application, the chemical structural formula of the pentafluorocyclotriphosphazene is shown in formula (I), the chemical structural formula of the tetrafluorocyclotriphosphazene is shown in formula (II), and the trifluorocyclotriphosphazene is shown in formula (II). The chemical structural formula of phosphazene is shown in formula (Ⅲ):

Wherein, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , and R ₆ are independently selected from alkoxy, haloalkoxy, aryloxy, haloaryloxy, alkyl, haloalkyl, alkenyl, Haloalkenyl, alkenyloxy, haloalkenyloxy, aryl, haloaryl, epoxy, haloepoxy, phosphate, substituted phosphate, carbonate, substituted carbonate , Sulfonate, Substituted Sulfonate, Alkyl Keto, Haloalkyl Keto, Alkoxysiloxy, Haloalkoxysiloxy, Substituted Imide, Substituted Sulfonimide, Nitrile any of the bases.

In the embodiment of the present application, the halogen in the halogenated alkoxy, halogenated aryloxy, halogenated alkyl, halogenated alkenyl, halogenated alkenyloxy, halogenated aryl, halogenated epoxy, and halogenated alkylketo group Both are fluorine; the phosphate group is an alkyl phosphate group, and the substituted phosphate group is a fluoroalkyl phosphate group; the carbonate group is an alkyl carbonate group, and the substituted carbonate group is fluorine carbonate Substituted alkyl ester group; the sulfonate group is a sulfonate alkyl ester group, and the substituted sulfonate group is a sulfonate fluoroalkyl ester group; the alkoxysilyloxy group is a trialkoxysiloxane The haloalkoxysilyloxy group is a fluorotrialkoxysilyloxy group.

In the embodiment of the present application, the number of carbon atoms of the alkoxy, haloalkoxy, alkyl, and haloalkyl is 1-10; the alkenyl, haloalkenyl, alkenyloxy, haloalkenyloxy, The number of carbon atoms of the epoxy group and the halogenated epoxy group is 2-10, and the number of carbon atoms of the aryl group, the halogenated aryl group, the aryloxy group, and the halogenated aryloxy group is 6-15; the phosphoric acid ester The number of carbon atoms in the group, substituted phosphate group, carbonate group, substituted carbonate group, sulfonate group, and substituted sulfonate group is 1-10. A smaller number of carbon atoms is beneficial to control the molecular weight of each flame retardant, thereby better controlling the viscosity of the electrolyte and ensuring the solubility of the flame retardant in the electrolyte.

In the embodiment of the present application, the total mass percentage of the pentafluorocyclotriphosphazene, tetrafluorocyclotriphosphazene and trifluorocyclotriphosphazene in the electrolyte is 0.1%-20%. The total addition amount of these flame retardants is relatively low, and can effectively improve the flame retardant performance of the electrolyte without significantly affecting the ion conductivity and viscosity of the electrolyte.

In some embodiments, the mass percentage of the pentafluorocyclotriphosphazene in the secondary battery electrolyte is 1%-10%, and the tetrafluorocyclotriphosphazene is electrolyzed in the secondary battery The mass percentage in the liquid is 1%-5%, and the mass percentage of the trifluorocyclotriphosphazene in the secondary battery electrolyte is 1%-5%. At this time, the electrolyte better balances good flame retardancy and electrochemical performance.

In some embodiments of the present application, the mass percentages of the pentafluorocyclotriphosphazene, the tetrafluorocyclotriphosphazene, and the trifluorocyclotriphosphazene in the secondary battery electrolyte are independently In the range of 1%-5%. At this time, the flame retardant performance of the above-mentioned electrolyte is better, and the high-voltage cycle performance, high-temperature storage performance and rate performance of the battery using the electrolyte are better, and thus the safety performance and electrochemical performance are better balanced.

In the embodiment of the present application, the average fluorine substitution degree DS of the flame retardant satisfies the following relationship:

DS=5×ω ₁ +4×ω ₂ +3×ω ₃ , where ω ₁ , ω ₂ , and ω ₃ represent pentafluorocyclotriphosphazene, tetrafluorocyclotriphosphazene and trifluorocyclotriphosphazene respectively in The mole percentage in the flame retardant; wherein, the value range of the DS is: 3<DS<5. At this time, the electrolytic solution simultaneously contains pentafluorocyclotriphosphazene, tetrafluorocyclotriphosphazene and trifluorocyclotriphosphazene in an appropriate proportion.

In some embodiments of the present application, the _ω3 is less than or equal to 50%. At this time, the molar ratio of trifluorocyclotriphosphazene in the flame retardant will not be too high to significantly increase the viscosity of the electrolyte, and it can ensure that the above flame retardant can play a good role in time during the solvent volatilization stage of the electrolyte. flame retardant effect.

In the embodiment of the present application, the organic solvent includes linear esters and cyclic esters.

In some embodiments of the present application, the linear ester includes linear carbonate and/or linear carboxylate, and the cyclic ester includes cyclic carbonate and/or cyclic carboxylate.

In the embodiment of the present application, the cyclic carbonate includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, and γ-butyrolactone; the linear carbonate includes but is not limited to dicarbonate One or more of methyl ester, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate; the linear carboxylate includes methyl acetate, ethyl acetate, propyl acetate, butyl acetate, propionic acid One or more of methyl ester, ethyl propionate, propyl propionate, and butyl propionate; the cyclic carboxylic acid ester includes α-acetone, β-propiolactone, γ-butyrolactone , δ-valerolactone, caprolactone or one or more.

In some embodiments of the present application, the mass ratio between the pentafluorocyclotrinitrile and tetrafluorocyclotriphosphazene is close to the mass ratio between the linear ester and the cyclic ester. This facilitates the flame retardant to maximize the flame retardancy of the electrolyte.

In the embodiment of the present application, the electrolyte solution also includes other additives, the other additives include fluoroethylene carbonate, difluoroethylene carbonate, trifluoromethyl ethylene carbonate, vinylene carbonate, ethylene ethylene carbonate Esters, 1,3-propane sultone, 1,4-butane sultone, vinyl sulfite, propylene sulfite, butenyl sulfite, 4-methyl vinyl sulfite, disulfite Methyl ester, diethyl sulfite, vinyl sulfate, 4-methyl vinyl sulfate, 4-propyl vinyl sulfate, 1,4-butanediol sulfate, 4-fluorophenyl acetate, tri(tri Methylsilyl)phosphate, tris(trimethylsilane)borate, methylene methanedisulfonate, N,N-sulfuryldiimidazole, succinonitrile, adiponitrile, 1,3,6-hexane Alkanetrinitrile, 1,3,5-pentanetricarbonitrile, 1,2-bis(2-cyanoethoxy)ethane, ethylene glycol bispropionitrile ether, fluoroether D2, N,N-dimethyl One or more of trifluoroacetamide, biphenyl and benzene derivatives.

In the implementation manner of the present application, the mass percentage content of the other additives in the electrolyte is 0.2%-15%.

In some embodiments of the present application, the electrolyte salt is a lithium salt, and the lithium salt includes lithium perchlorate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium difluorophosphate, lithium bisoxalate borate, difluoro Lithium oxalate borate, lithium bisfluorosulfonyl imide, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(perfluoroethylsulfonyl)imide, lithium trifluoromethanesulfonate, perfluorobutylsulfonic acid One or more of lithium.

In the embodiment of the present application, the molar concentration of the lithium salt in the secondary battery electrolyte is 0.01 mol/L-2.0 mol/L.

The second aspect of the embodiment of the present application provides a secondary battery, including a positive electrode, a negative electrode, a separator and an electrolyte, and the electrolyte adopts the secondary battery electrolyte described in the first aspect of the embodiment of the present application.

The secondary battery provided by the embodiment of the present application, because the above-mentioned specific flame retardant is added to its electrolyte, and the flame retardant has good compatibility with positive and negative electrode materials, and the flame retardant can have The excellent flame retardant effect makes the secondary battery have both excellent safety performance and electrochemical performance.

The third aspect of the embodiments of the present application provides an electronic device, which includes the secondary battery described in the first aspect of the embodiments of the present application.

By using the secondary battery provided by the embodiment of the present application as the power supply, the electronic device can improve the user experience and market competitiveness of the product.

Description of drawings

FIG. 1 is a schematic structural diagram of a secondary battery provided in an embodiment of the present application.

Fig. 2 is a schematic diagram of the mechanism of action of the flame retardant provided in the examples of the present application.

FIG. 3 is a schematic structural diagram of an electronic device provided by an embodiment of the present application.

FIG. 4 is another schematic structural diagram of an electronic device provided by an embodiment of the present application.

Detailed ways

Embodiments of the present application are described below with reference to the drawings in the embodiments of the present application.

As shown in FIG. 1 , FIG. 1 is a schematic structural diagram of a secondary battery 100 provided in an embodiment of the present application, and the secondary battery 100 may specifically be a lithium secondary battery. The lithium secondary battery includes a positive electrode 101, a negative electrode 102, a separator 103, an electrolyte 104, and corresponding communication accessories and circuits. Among them, the positive electrode 101 and the negative electrode 102 can deintercalate active metal ions (for lithium secondary batteries, the active metal ions are lithium ions) to realize energy storage and release: driven by an external battery, lithium ions are extracted from the positive electrode and migrate To the negative electrode, the battery is charged; when an external electrical load is connected, lithium ions come out of the negative electrode and migrate back to the positive electrode for the discharge process. The separator 103 plays the role of separating the positive and negative electrodes, and avoids the occurrence of internal short circuit. The electrolyte 104 is the medium for lithium ions to be transmitted between the positive and negative electrodes, and plays an important role in the electrochemical performance and safety performance of the battery. The electrolyte solution 104 is mainly composed of lithium salts, non-aqueous organic solvents (usually carbonate solvents or carboxylate solvents) and additives. With the development of high-energy-density batteries, when the battery is continuously overcharged, overheated, externally short-circuited, or internally short-circuited due to external force damage (such as extrusion, puncture, collision), etc., its electrolyte is volatile, It is easy to burn and other hidden dangers, which can easily cause thermal runaway of the battery and cause safety problems.

In order to reduce the flammability of the electrolyte and improve the safety performance of the secondary battery, the industry adds flame retardants to conventional electrolytes, among which phosphazene flame retardants are favored due to their good compatibility with positive and negative electrode materials and good flame retardancy. followed. However, in order to ensure the safety of high-energy-density batteries, a good flame-retardant effect needs to be achieved at a relatively high addition amount (eg, ≥20wt.%). However, the addition of a large amount of a single type of phosphazene flame retardant will damage the electrochemical performance of the battery. In order to solve this problem, the industry is committed to improving its flame retardant efficiency and reducing the impact of a large number of additives on the electrical performance of batteries by designing and optimizing the structure of phosphazene molecules (such as introducing fluorine-containing groups, alkoxy groups, etc.). However, none of these methods can effectively improve the flame retardant effect of the electrolyte. In addition, the industry also adds phosphazene flame retardants in combination with other non-phosphazene flame retardants or non-flammable co-solvents to reduce the amount of phosphazene flame retardants used, but non-phosphazene flame retardants not only have poor flame retardancy These compounding strategies have not significantly improved the flame retardant effect of the electrolyte. In view of this, the present application provides a secondary battery electrolyte that can make the battery have both high safety performance and good electrochemical performance.

Specifically, the secondary battery electrolyte provided by the embodiment of the present application includes lithium salt, an organic solvent and a flame retardant, wherein the flame retardant includes pentafluorocyclotriphosphazene, tetrafluorocyclotriphosphazene and trifluorocyclotriphosphazene Cyclotriphosphazene.

The secondary battery electrolyte solution provided in the embodiment of the present application, by adding three types of fluorocyclotriphosphazene as a flame retardant to the conventional electrolyte solution, can realize the full range of each component of the conventional electrolyte solution and its decomposition products. effective flame retardant. Specifically, the electrolyte solvent generally contains linear esters and cyclic esters, and the linear esters and cyclic esters have different volatilization ranges. Fluorocyclotriphosphazenes with different degrees of fluorine substitution also have different volatilization characteristics, as shown in Figure 2 (the ordinate is the volatilization ratio of linear esters and cyclic esters in the electrolyte with increasing temperature, and the combustible gas in the electrolyte generation ratio), the volatility characteristic curve of pentafluorocyclotriphosphazene is close to the linear ester in the electrolyte, and it can be co-volatilized with the linear ester to inhibit the combustion of the electrolyte vapor and realize the flame retardancy of the linear ester; tetrafluorocyclotriphosphazene The volatilization characteristic curve of phosphazene is close to the cyclic ester in the electrolyte, and it can volatilize with most of the cyclic esters to realize the flame retardancy of the cyclic esters. During the thermal runaway process of the secondary battery, the electrolyte may undergo irreversible oxidative decomposition to generate a large amount of flammable gases (such as H ₂ , CO, etc.). Trifluorocyclotriphosphazene can effectively cover the temperature range where flammable gases are generated in thermal runaway of batteries, and improve the flame retardancy of flammable gases. Therefore, through the synergistic effect of three types of fluorocyclic triphosphazenes with different fluorine substitution degrees, the effective flame retardant ability of the flame retardant to the electrolyte volatilization range and the flammable gas generation range can be broadened, and the use of a single (pentafluoro) ring The problem caused by triphosphazene is that the thermal runaway of the battery will volatilize in the early stage, and the electrolyte cannot be effectively protected against flames for a long time. Moreover, the addition of a small amount of the above-mentioned flame retardant can make the electrolyte have an excellent flame-retardant effect, and avoid the problem of poor electrochemical performance of the battery caused by adding a large amount of phosphazene flame retardant, so that the battery can have both High safety performance and good electrochemical performance.

In addition, the above-mentioned pentafluorocyclotriphosphazene, tetrafluorocyclotriphosphazene and trifluorocyclotriphosphazene can not only co-volatize with the electrolyte solvent/flammable gas, but also have positive electrode film-forming properties, which can inhibit the electrolyte from forming on the positive electrode. Oxidation, inhibition of electrolyte decomposition to produce active O and active H, reduce the flammability of the electrolyte; and they can also capture the H, OH and other active free radicals generated by the decomposition of the electrolyte to inhibit the occurrence of combustion. In addition, their positive film-forming ability can also improve the high-voltage capability of the electrolyte, inhibit the decomposition of the electrolyte at high voltage, inhibit the destruction of the positive electrode at high potential, improve the high-voltage and high-temperature resistance of the battery, and improve the high-voltage cycle. performance.

Therefore, through the synergistic effect of three types of fluorinated cyclotriphosphazenes with different degrees of fluorine substitution, the flame retardancy of the electrolyte of the secondary battery can be effectively improved, the safety performance of the secondary battery can be improved, and the rate performance and cycle performance of the secondary battery can be improved. The electrochemical properties such as characteristics are still relatively good.

In the embodiment of the present application, the chemical structural formula of the pentafluorocyclotriphosphazene can be represented by the following formula (I), the chemical structural formula of the tetrafluorocyclotriphosphazene can be represented by the following formula (II), and the trifluorocyclotriphosphazene can be represented by the following formula (II). The chemical structural formula of phosphazene can be represented by following formula (Ⅲ):

Wherein, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , and R ₆ are independently selected from alkoxy, haloalkoxy, aryloxy, haloaryloxy, alkyl, haloalkyl, alkenyl, Haloalkenyl, alkenyloxy, haloalkenyloxy, aryl, haloaryl, epoxy, haloepoxy, phosphate, substituted phosphate, carbonate, substituted carbonate , Sulfonate, Substituted Sulfonate, Alkyl Keto, Haloalkyl Keto, Alkoxysiloxy, Haloalkoxysiloxy, Substituted Imide, Substituted Sulfonimide, Nitrile any of the bases.

In this application, the number of carbon atoms of the alkoxy, haloalkoxy, alkyl, and haloalkyl involved in R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , and R ₆ can be 1-10, and further , the number of carbon atoms can be 1-6, preferably 1-4; the number of carbon atoms of alkenyl, haloalkenyl, alkenyloxy, haloalkenyloxy, epoxy, and haloepoxy can be 2 -10, further, the number of carbon atoms can be 2-6; the number of carbon atoms of aryl, halogenated aryl, aryloxy, halogenated aryloxy is 6-15, further, the number of carbon atoms can be 6 -10, the specific number of carbon atoms is, for example, 6, 7, 8, 9, or 10. Less number of carbon atoms is beneficial to control the molecular weight of each fluorocyclotriphosphazene, thereby better controlling the viscosity of the electrolyte and the solubility of the flame retardant in the electrolyte. In the embodiment of the present application, the halogen in the haloalkyl, haloalkoxy, haloalkenyl, haloalkenyloxy, haloaryl, haloaryloxy, and haloepoxy can be fluorine, chlorine, bromine Or iodine, and further can be fluorine, which can help improve the film-forming ability of each flame retardant. Wherein, halogenation may be full halogenation or partial halogenation. Alkyl, haloalkyl, alkenyl, haloalkenyl, alkenyloxy, haloalkenyloxy, alkoxy, haloalkoxy may be linear or branched.

In this application, both the phosphate group and the substituted phosphate group can be expressed as -OP(=O)(OR) ₂ , when R is a hydrocarbon group, it is a phosphate group, and when R includes a substituted hydrocarbon group, it is a substituted phosphoric acid Ester group. The substituted or unsubstituted phosphate group forms a PO bond with the phosphorus atom in the six-membered ring structure of cyclotriphosphazene through the oxygen atom. Wherein, hydrocarbyl includes alkyl, alkenyl, aryl, etc.; substituted hydrocarbyl may include halohydrocarbyl (including haloalkyl, haloalkenyl, haloaryl, etc.), hydrocarbyloxy (that is, hydrocarbyl substituted by oxygen atoms, Including alkoxy, alkenyloxy, aryloxy), halogenated alkoxy (including halogenated alkoxy, halogenated alkenyloxy, halogenated aryloxy, etc.) and the like.

Similarly, carbonate groups and substituted carbonate groups can be expressed as -O-C(=O)-T, when T is a hydrocarbon group, it is a carbonate group, and when T includes a substituted hydrocarbon group, it is a substituted carbonate group. Among them, hydrocarbon groups include alkyl, alkenyl, aryl, etc.; substituted hydrocarbon groups can include halogenated hydrocarbon groups (including halogenated alkyl, halogenated alkenyl, halogenated aryl, etc.), alkoxy groups (including alkoxy, alkenyloxy, etc.) , aryloxy), halogenated alkoxy (including halogenated alkoxy, halogenated alkenyloxy, halogenated aryloxy, etc.), etc.

Similarly, both the sulfonate group and the substituted sulfonate group can be expressed as -OS(=O) ₂ -Q, when Q is a hydrocarbon group, it is a sulfonate group, and when Q includes a substituted hydrocarbon group, it is a substitution Sulfonate group. Wherein, hydrocarbyl includes alkyl, alkenyl, aryl; substituted hydrocarbyl may include halogenated hydrocarbyl, hydrocarbyloxy, halogenated hydrocarbyloxy, etc.

In the embodiment of the present application, the halogen-containing substituting group (such as halogenated hydrocarbon group, halogenated hydrocarbon oxygen group) in the substituted phosphate group, substituted carbonate group, and substituted sulfonate group can be fluorine, chlorine, Bromine or iodine is preferably fluorine, and the halogenation can be perhalogenation or partial halogenation. Alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, alkenyloxy, haloalkenyloxy may be linear or branched.

In some embodiments of the present application, the phosphate group is an alkyl phosphate group (that is, R is an alkyl group), and the substituted phosphate group is a fluoroalkyl phosphate group (that is, R is a fluoroalkyl group). The carbonate group is an alkyl carbonate group (ie, T is an alkyl group), and the substituted carbonate group is a fluoroalkyl carbonate group (ie, T is a fluoroalkyl group). The sulfonate group is an alkyl sulfonate group (ie, Q is an alkyl group), and the substituted sulfonate group is a fluoroalkyl sulfonate group (ie, Q is a fluoroalkyl group).

In the present application, the alkoxysilyloxy group can be represented by the general formula -O-Si(R ₇ )(R ₈ )(R ₉ ), and at least one of R ₇ , R ₈ and R ₉ is an alkoxy group. The alkoxysilyloxy group forms a PO bond with the phosphorus atom in the six-membered ring structure of cyclotriphosphazene through its own oxygen atom. The alkoxysilyloxy group can be a monoalkoxysilyloxy group (one of R ₇ , R ₈ and R ₉ is an alkoxy group, and the other two are alkyl or aryl groups, etc.), dialkoxy groups Siloxy (two of R ₇ , R ₈ and R ₉ are alkoxy, the other is alkyl or aryl, etc.) or trialkoxysilyloxy (R ₇ , R ₈ and R ₉ are all alkyl oxygen). In some embodiments of the present application, R ₇ , R ₈ and R ₉ are all alkoxy groups. That is, the alkoxysiloxy group is a trialkoxysiloxy group. The number of carbon atoms of R ₇ , R ₈ and R ₉ may be the same or different, and the number of carbon atoms is independently 1-10, further, the number of carbon atoms may be 1-6, preferably 1-4. In some embodiments, R ₇ , R ₈ and R ₉ may all be alkoxy groups with 1-6 carbon atoms. Haloalkoxysilyloxy can also be represented by the general formula -O-Si(R ₇ )(R ₈ )(R ₉ ), and at least one of R ₇ , R ₈ and R ₉ is halogenated or unhalogenated The alkoxy group, at least one of R ₇ , R ₈ and R ₉ is a halo group (specifically, it can be a haloalkoxy group, a haloalkyl group, or a haloaryl group, etc.). For example, it may be that R ₇ , R ₈ and R ₉ are all haloalkoxy; or one of R ₇ , R ₈ and R ₉ is haloalkoxy, and the other two are independently selected from alkyl, haloalkyl, alkoxy or two of R ₇ , R ₈ and R ₉ are haloalkoxy, and the remaining one is alkyl or haloalkyl or alkoxy; or one of R ₇ , R ₈ and R ₉ is alkoxy, The remaining two are haloalkyl, or haloalkyl + alkyl; or two of R ₇ , R ₈ and R ₉ are alkoxy, and the remaining one is haloalkyl. In some embodiments, the haloalkoxysiloxy is trihaloalkoxysiloxy, further trifluoroalkoxysiloxy.

In this application, both the alkylketo group and the halogenated alkylketo group can be represented by the general formula -R ₁₀ -C(=O)-R _11. When it is an alkyl ketone group, R ₁₀ is an alkylene group, and R ₁₁ is Alkyl; when it is a haloalkyl ketone group, R ₁₀ is an alkylene group and/or a haloalkylene group, R ₁₁ is an alkyl group and/or a haloalkyl group, and at least one of R ₁₀ and R ₁₁ contains a halogen. Halogen may be fluorine, chlorine, bromine or iodine, preferably fluorine. Haloalkylene and haloalkyl can be fully or partially halogenated. In some embodiments, R ₁₀ and R ₁₁ are respectively an alkylene group and an alkyl group with 1-10 carbon atoms, and further, the number of carbon atoms is 1-4. In other embodiments, R ₁₀ and R ₁₁ are respectively a fluoroalkylene group and a fluoroalkyl group with 1-10 carbon atoms, and further, the number of carbon atoms is 1-4.

In the present application, the substituted imide group can be represented as -NH-C(=O)-X, wherein X can be selected from alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, Any of alkenyloxy, haloalkenyloxy, aryl, haloaryl, aryloxy, and haloaryloxy.

In this application, the substituted sulfonylimide group can be represented as -NH-S(=O) ₂ -Z, wherein Z can be selected from alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkene Any one of radical, alkenyloxy, haloalkenyloxy, aryl, haloaryl, aryloxy, haloaryloxy.

Wherein, the nitrile group (-CN) can be directly connected with the phosphorus atom in the six-membered ring structure of cyclotriphosphazene, or can be connected with the phosphorus atom in the six-membered ring structure of cyclotriphosphazene through the alkylene group with 1-6 carbon atoms. Phosphorus atoms are linked.

In some embodiments of the present application, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , and R ₆ are independently selected from alkoxy, fluoroalkoxy, aryloxy, fluoroaryloxy, and phosphoric alkyl Ester group, fluoroalkyl phosphate group, alkyl carbonate group, fluoroalkyl carbonate group, alkyl sulfonate group, fluoroalkyl sulfonate group, trialkoxysilyloxy group, Fluorotrialkoxysiloxy, alkylketo, fluoroalkylketo, nitrile. In some embodiments, _R2 is the same as _R3 . R ₄ , R ₅ , and R ₆ may all be the same.

In some specific implementations, the pentafluorocyclotriphosphazene may specifically be methoxypentafluorophosphazene shown in the following formula (i1), ethoxypentafluorophosphazene shown in the following formula (i2), Trifluoroethoxy pentafluorocyclotriphosphazene shown in the following formula (i3), perfluorobutoxy pentafluorocyclotriphosphazene shown in the following formula (i4), phenoxycyclotriphosphazene shown in the following formula (i5) Base pentafluorophosphazene, diethyl phosphate pentafluorophosphazene shown in the following formula (i6), ethyl carbonate-based pentafluorophosphazene shown in the following formula (i7), and the following formula (i8) Methanesulfonate-based pentafluorophosphazene, ethylsulfonate-based pentafluorocyclotriphosphazene represented by the following formula (i9), trimethoxysiloxy-pentafluorophosphazene represented by the following formula (i10) , one or more of ethyl ketonemethyl pentafluorophosphazene represented by the following formula (i11), acetonitrile pentafluorophosphazene represented by the following formula (i12), but not limited thereto.

In some specific embodiments, tetrafluorocyclotriphosphazene can specifically be bismethoxytetrafluorocyclotriphosphazene, bisethoxytetrafluorocyclotriphosphazene, bistrifluoroethoxytetrafluorocyclotriphosphazene , Bisperfluorobutoxytetrafluorocyclotriphosphazene, bisphenoxytetrafluorocyclotriphosphazene, bisphosphonate diethyl tetrafluorocyclotriphosphazene, diethylcarbonate tetrafluorocyclotriphosphazene, Bismethylsulfonate tetrafluorocyclotriphosphazene, bisethylsulfonate tetrafluorocyclotriphosphazene, bistrimethoxysiloxytetrafluorocyclotriphosphazene, diethylketonemethyltetrafluoro One or more of cyclotriphosphazene, bisacetonitrile tetrafluorocyclotriphosphazene, etc.

In some specific embodiments, the trifluorocyclotriphosphazene can specifically be trimethoxytrifluorocyclotriphosphazene shown in the following formula (ⅲ1), triethoxytrifluorocyclotriphosphazene shown in the following formula (ⅲ2) Phosphazene, three trifluoroethoxytrifluorocyclotriphosphazenes shown in the following formula (ⅲ3), three perfluorobutoxy trifluorocyclotriphosphazenes shown in the following formula (ⅲ4), the following formula (ⅲ5) The triphenoxytrifluorocyclotriphosphazene shown, the diethyl triphosphate trifluorocyclotriphosphazene shown in the following formula (ⅲ6), the triethylcarbonate group trifluorocyclotriphosphazene shown in the following formula (ⅲ7) Fluorocyclotriphosphazene, trimethylsulfonate group trifluorocyclotriphosphazene shown in the following formula (ⅲ8), triethylsulfonate group trifluorocyclotriphosphazene shown in the following formula (ⅲ9), Tristrimethoxysilyloxy trifluorocyclotriphosphazene shown in the following formula (ⅲ10), triethylketomethyl trifluorocyclotriphosphazene shown in the following formula (ⅲ11), and trifluorocyclotriphosphazene shown in the following formula (ⅲ12) One or more of the three acetonitrile trifluorocyclotriphosphazenes shown, but not limited thereto.

In the embodiment of the present application, the aforementioned trifluorocyclotriphosphazene can be prepared by a two-step substitution-fluorination method. When R ₄ , R ₅ , and R ₆ in the trifluorocyclotriphosphazene represented by formula (III) can be all the same (for example, all are R'), the preparation process of trifluorocyclotriphosphazene is exemplified. The specific preparation process is shown in the following formula:

Taking the triethoxytrifluorocyclotriphosphazene shown in formula (ⅲ2) as an example, its specific preparation process is as follows:

(1) Dissolve 1 mol of hexachlorocyclotriphosphazene in 300 mL of hexane, add 3 mol of sodium ethoxide (R'=-OCH ₂ CH ₃ ), condense and reflux at 50°C for 12 hours, and then generate The mixed solution is distilled and separated to obtain triethoxytrichlorocyclotriphosphazene;

(2) Dissolve 1 mol of triethoxytrichlorocyclotriphosphazene in 300 mL of acetonitrile, add 3 mol of sodium fluoride, condense and reflux at 50°C for 12 hours, and then distill and separate the resulting mixed solution , collected to obtain triethoxytrifluorocyclotriphosphazene; after dehydration treatment, sealed and preserved under dry conditions for future use.

In the embodiment of the present application, the mass percent content of the flame retardant in the electrolyte is 0.1%-20%. That is, the total mass percentage of the pentafluorocyclotriphosphazene, tetrafluorocyclotriphosphazene and trifluorocyclotriphosphazene in the electrolyte is 0.1%-20%. Specifically, the total mass percentage may be 1%, 3%, 5%, 8%, 10%, 12% or 15% and so on. The addition of a lower content of flame retardant facilitates the effective improvement of the flame retardant ability of the electrolyte, and at the same time ensures that the ion conductivity of the electrolyte will not be excessively reduced, and the viscosity will not be too high to affect battery performance. This avoids the problem of poor electrochemical performance of the battery caused by the addition of a large amount of phosphazene flame retardant, and enables the battery to have both high safety performance and good electrochemical performance. In some embodiments, the total mass percentage may be 2%-12%, further may be 5%-10%. At this time, the electrolyte can better balance good flame retardancy and electrochemical performance.

In some embodiments of the present application, the mass percentage of the pentafluorocyclotriphosphazene in the secondary battery electrolyte is 1%-10%, and further may be 1%-5%; the tetrafluorocyclotriphosphazene The mass percentage of nitrile in secondary battery electrolyte is 1%-5%, such as can be 1%, 2%, 3%, 4% or 5% etc.; The mass percent content in the battery electrolyte is 1%-5%. The mass percentages of the three in the electrolyte can be equal or different. The mass percentage of the three in the electrolyte is controlled within the above range, which can fully exert the synergistic effect between the three, so that the battery with the electrolyte has excellent safety performance and excellent high voltage. The cycle performance, high temperature storage performance and good rate performance make the overall performance of the battery at a better level.

In the embodiment of the present application, in the flame retardant system composed of pentafluorocyclotriphosphazene, tetrafluorocyclotriphosphazene and trifluorocyclotriphosphazene, the average fluorine substitution degree DS of the flame retardant satisfies the following relationship Formula: DS=5×ω ₁ +4×ω ₂ +3×ω ₃ , where ω ₁ , ω ₂ , and ω ₃ represent pentafluorocyclotriphosphazene, tetrafluorocyclotriphosphazene and trifluorocyclotriphosphazene, respectively The mole percentage of nitrile in the flame retardant; wherein, the value range of DS is: 3<DS<5. This means that the flame retardant of the present application contains an appropriate proportion of pentafluorocyclotriphosphazene, tetrafluorocyclotriphosphazene and trifluorocyclotriphosphazene at the same time, which can better improve the flame retardant effect of the electrolyte.

In some embodiments of the present application, the mole percentage of the moles of the trifluorocyclotriphosphazene in the total moles of the pentafluorocyclotriphosphazene, tetrafluorocyclotriphosphazene and trifluorocyclotriphosphazene ( That is, ω ₃ ) is less than or equal to 50%. The molar percentage of trifluorocyclotriphosphazene in the flame retardant will not be too high, which can ensure that the viscosity of the electrolyte will not be too high, and can ensure that the above-mentioned flame retardant can be activated in time during the solvent volatilization stage of the electrolyte. To a good flame retardant effect.

In the embodiment of the present application, according to different secondary battery systems, the electrolyte salt may be lithium salt, sodium salt, potassium salt, magnesium salt, zinc salt, aluminum salt, and the like. Specifically, lithium salt, sodium salt, potassium salt can be MClO ₄ , MBF ₄ , MPF ₆ , MAsF ₆ , MPF ₂ O ₂ , MB(C ₂ O ₄ ) ₂ (MBOB), MBF ₂ C ₂ O ₄ (MDFOB ), M[(FSO ₂ ) ₂ N], M[(CF ₃ SO ₂ ) ₂ N], M(C ₂ F ₅ SO ₂ ) ₂ N, MCF ₃ SO ₃ , MC ₄ F ₉ SO ₃ One or more, wherein, M is Li, Na or K. Similarly, magnesium salt, zinc salt, and aluminum salt can also be salts formed by magnesium ions, zinc ions, aluminum ions and anions in the above-mentioned lithium salts, sodium salts, and potassium salts.

In some embodiments of the present application, the secondary battery is a lithium secondary battery, and the electrolyte salt in the electrolyte is a lithium salt, which specifically includes but is not limited to lithium perchlorate LiClO ₄ , lithium tetrafluoroborate LiBF ₄ , lithium hexafluorophosphate LiPF ₆ , lithium hexafluoroarsenate LiAsF ₆ , lithium difluorophosphate LiPF ₂ O ₂ , lithium bisoxalate borate LiB(C ₂ O ₄ ) ₂ (LiBOB), lithium difluorooxalate borate LiBF ₂ C ₂ O ₄ (LiDFOB), bis Lithium fluorosulfonyl imide Li[(FSO ₂ ) ₂ N, LiFSI], lithium bistrifluoromethylsulfonyl imide (Li(CF ₃ SO ₂ ) ₂ N, LiTFSI), bis(perfluoroethylsulfonyl ) lithium imide (Li(C ₂ F ₅ SO ₂ ) ₂ N), lithium trifluoromethanesulfonate LiCF ₃ SO ₃ , lithium perfluorobutylsulfonate (LiC ₄ F ₉ SO ₃ ) or Various. In some embodiments of the present application, the molar concentration of the lithium salt in the electrolyte may be 0.01 mol/L-2.0 mol/L, and further may be 0.1 mol/L-1.5 mol/L.

In the embodiment of the present application, the organic solvent in the electrolyte generally includes linear esters and cyclic esters. The ester may include at least one of carbonates and carboxylates. Wherein, the linear ester includes at least one of linear carbonate and linear carboxylate, and the cyclic ester includes at least one of cyclic carbonate and cyclic carboxylate. This facilitates sufficient dissolution of the above-mentioned flame retardant and electrolyte salt.

Specifically, cyclic carbonates may include, but are not limited to, one or more of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC); linear carbonates may include, but are not limited to It is one or more of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dipropyl carbonate (DPC). Wherein, carboxylate solvents can include linear carboxylates, which specifically can include but not limited to methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), butyl acetate, methyl propionate One or more of propionate (MP), ethyl propionate (EP), propyl propionate (PP), butyl propionate (BP), etc. Cyclic carboxylic acid esters may include, but are not limited to, α-acetone (CAS: 42879-41-4), β-propiolactone, γ-butyrolactone, δ-valerolactone, caprolactone and other lactones or one or more of its derivatives. In some embodiments, the organic solvent is a mixed solvent composed of linear carbonates and cyclic carbonates.

The above organic solvents can be mixed in any proportion. In some embodiments of the present application, the mass ratio between the above-mentioned pentafluorocyclotriphosphazene and tetrafluorocyclotriphosphazene (denoted as a) and the mass ratio between the linear ester and the cyclic ester (denoted as b) approach. In some embodiments, the degree of deviation between a and b (denoted as k) is within 40%, that is, k=|a-b|/b, k≤40%. Optionally, k≤35%, or k≤30%, or k≤25%, or even k=0. As mentioned above in this application, the volatility characteristics of pentafluorocyclotriphosphazene and linear ester are close, and the volatility characteristics of tetrafluorocyclotriphosphazene and cyclic ester are close. In this case, the pentafluorocyclotriphosphazene containing such mass ratio The aforementioned flame retardants of phosphazene and tetrafluorocyclotriphosphazene can maximize the flame retardancy of the electrolyte and effectively improve safety.

In the embodiment of the present application, in addition to the above-mentioned flame retardant, other additives may be added to the electrolyte solution of the secondary battery according to different performance requirements. Specifically, other additives may include one or more of film-forming additives, high-voltage additives, anti-overcharge additives, and the like.

Among them, the film-forming additives can be but not limited to fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethylethylene carbonate (TFEC), vinylene carbonate (VC), ethylene carbonate Ethylene ester (VEC), 1,3-propane sultone (1,3-PS), 1,4-butane sultone, vinyl sulfite (ES), propylene sulfite (TMS), Butenyl sulfite (BS), 4-methylethylene sulfite (MeES), dimethyl sulfite (DS), diethyl sulfite, vinyl sulfate (DTD), 4-methylethylene sulfite (MeDTD), 4-propyl vinyl sulfate (PEGLST), 1,4-butanediol sulfate, 4-fluorophenyl acetate (FPA), tris(trimethylsilane) phosphate (TMSP), tris (Trimethylsilane) borate (TMSB), methylene disulfonate (MMDS), N,N-sulfuryldiimidazole (SDI), N,N-dimethyltrifluoroacetamide (DTA) one or more of these. Among them, DTA can form a film on the electrode surface to improve the low temperature performance additive of the battery. Among them, high voltage additives can be but not limited to succinonitrile (SN), adiponitrile (ADN), 1,3,6-hexanetrinitrile (HTCN), 1,3,5-pentanetricarbonitrile (PTCN) , 1,2-bis(2-cyanoethoxy)ethane (DENE), ethylene glycol bispropionitrile ether (DENE), fluoroether D2, etc. one or more. The anti-overcharge additive can be, for example, biphenyl and benzene derivatives. In some embodiments of the present application, other additives only include fluorocarbonate, vinylene carbonate (VC) and high voltage additives.

In the embodiment of the present application, the total mass percentage of other additives in the electrolyte may be 0.2%-15%, further may be 0.5%-10%.

In the secondary battery electrolyte provided by the embodiment of the present invention, three types of fluorocyclotriphosphazenes with different degrees of fluorine substitution are added to the electrolyte at the same time as flame retardants, and their synergistic effect can effectively improve the flame retardancy of the electrolyte The safety performance of the secondary battery is significantly improved, and at the same time, they have good compatibility with the positive and negative electrode materials, and do not deteriorate the electrochemical performance such as the rate performance and low-temperature cycle performance of the secondary battery. High temperature capability, with broader application prospects.

Correspondingly, the embodiment of the present application also provides a method for preparing the above secondary battery electrolyte, comprising the following steps:

In an inert environment or a closed environment (such as an argon-filled glove box), fully dry electrolyte salts and flame retardants (including pentafluorocyclotriphosphazene, tetrafluorocyclotriphosphazene, and trifluorocyclotriphosphazene) Add it into an organic solvent and mix uniformly to obtain a secondary battery electrolyte.

Among them, the specific selection of raw materials such as electrolyte salts, non-aqueous organic solvents, flame retardants, and other additives is as described above, and will not be repeated here. When the electrolyte solution also includes other additives, they can be added together with the flame retardant. In addition, the electrolyte salt and flame retardant can be added to the organic solvent simultaneously, or additives such as flame retardant and other additives can be added to the organic solvent first, and after mixing evenly, then add fully dried lithium salt and mix again After uniformity, an electrolyte solution for a secondary battery is obtained. Each operation in the above preparation method can be implemented according to the existing conventional electrolyte preparation process.

The preparation method of the secondary battery electrolyte provided in the embodiment of the present application has a simple process and is suitable for industrial production.

The embodiment of the present application also provides a secondary battery, as shown in Figure 1. The secondary battery includes a positive electrode 101, a negative electrode 102, a separator 103, and an electrolyte 104, wherein the electrolyte 104 adopts the method provided above in the embodiment of the application secondary battery electrolyte. The specific structure of the secondary battery is as described above, and will not be repeated here.

The secondary battery provided by the embodiment of the present application, because the above-mentioned specific flame retardant is added to its electrolyte, and the flame retardant has good compatibility with positive and negative electrode materials, and the flame retardant can have The excellent flame retardant effect makes the secondary battery have both excellent safety performance and electrochemical performance.

In the embodiment of the present application, the secondary battery can be not only the lithium secondary battery mentioned above, but also a potassium secondary battery, a sodium secondary battery, a magnesium secondary battery, a zinc secondary battery, an aluminum secondary battery, etc. . The secondary battery provided by the embodiment of this application can be used in terminal consumer products, such as mobile phones, tablet computers, mobile power supplies, portable computers, notebook computers, digital cameras, and other wearable or mobile electronic devices, as well as drones, automobiles, etc. and other products to improve product performance.

In the embodiment of the present application, the positive electrode 101 includes a positive electrode active material capable of reversibly intercalating/deintercalating metal ions (lithium ions, sodium ions, potassium ions, magnesium ions, zinc ions, aluminum ions, etc.). The selection is not particularly limited, and it can be a positive electrode active material conventionally used in existing secondary batteries. Taking lithium secondary battery as an example, the positive electrode active material can be but not limited to lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (NCM) , lithium nickel cobalt aluminate (NCA), lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium manganese phosphate, lithium cobalt phosphate, etc. Each positive active material may be undoped or doped modified.

In the embodiment of the present application, the negative electrode 102 includes a negative electrode active material capable of reversibly intercalating/deintercalating metal ions (lithium ions, sodium ions, potassium ions, magnesium ions, zinc ions, aluminum ions, etc.). The selection is not particularly limited, and it can be a negative electrode active material conventionally used in existing secondary batteries. Taking a lithium secondary battery as an example, the negative electrode active material may be, but not limited to, one or more of lithium titanate, lithium metal, lithium alloy, carbon-based material, silicon-based material, tin-based material, and the like. Among them, carbon-based materials can include graphite (such as natural graphite, artificial graphite), non-graphitized carbon (soft carbon, hard carbon, etc.); silicon-based materials can include elemental silicon, silicon-based alloys, silicon oxides, and silicon-carbon composite materials One or more of them; tin-based materials may include one or more of simple tin, tin alloys, etc.

In the embodiment of the present application, the separator can be an existing conventional separator, including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP/PE, double-layer PP/PP and three-layer PP/ PE/PP and other separators.

The embodiment of the present application also provides an electronic device, the electronic device is equipped with the above-mentioned secondary battery. The electronic equipment can include various consumer electronic products, such as mobile phones, tablet computers, mobile power supplies, portable computers, notebook computers and other wearable or mobile electronic equipment, TV sets, DVD players, video recorders, camcorders, Radios, tape recorders, stereos, record players, CD players, home office equipment, home electronic health care equipment, and electronic products such as automobiles and energy storage equipment.

In some implementations, referring to FIG. 3 , the embodiment of the present application provides an electronic device 300, which includes a casing 301, electronic components (not shown in the figure) contained in the casing 301, and a battery 302. The battery 302 is The electronic device 300 supplies power, and the battery 302 includes the secondary battery described above in the embodiment of the present application. In some embodiments, the housing 301 may include a front cover assembled on the front side of the terminal and a rear case assembled on the rear side, and the battery 302 may be fixed inside the rear case. The electronic device 300 shown in FIG. 3 is usually a small portable electronic device, such as a mobile phone.

In other implementations, referring to FIG. 4, the embodiment of the present application provides an electronic device 400, which may be various mobile devices for loading, transportation, assembly, disassembly, security, etc., and may be in various forms vehicle. Specifically, the electronic device 400 may include a car body 401, a moving assembly 402, and a driving assembly. The driving assembly includes a motor 403 and a battery system 404 for supplying power to the motor 403. The battery system 404 includes the above-mentioned secondary Battery. Wherein, the moving component 402 may be a wheel; the battery system 404 may be a battery pack of the above-mentioned secondary battery 100 , which is accommodated at the bottom of the vehicle body and electrically connected to the motor 403 . The battery system 404 supplies power to the motor 403 , and the motor 403 provides power to drive the moving component 402 of the electronic device 400 to move.

The technical solution of the present application will be further described below through specific examples.

Example 1

Electrolyte preparation: In a glove box filled with dry argon, mix dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethylene carbonate (EC) in a mass ratio of 1:1:1 to form An organic solvent, adding additives to the organic solvent, stirring thoroughly, then adding fully dried lithium salt LiPF ₆ to the organic solvent, and mixing uniformly to obtain an electrolyte solution for lithium secondary batteries. Wherein, the concentration of LiPF ₆ in the electrolytic solution is 1mol/L, and the above-mentioned additives include the following components in the electrolytic solution in mass percent: 3wt% of methoxypentafluorocyclotriphosphazene, 2wt% of Dimethoxytetrafluorocyclotriphosphazene, 5wt% trimethoxytrifluorocyclotriphosphazene, 1wt% ethylene carbonate (VC), 5wt% fluoroethylene carbonate (FEC) and 2wt% Hexanetrinitrile (HTCN).

Production of lithium secondary batteries:

Preparation of the positive electrode sheet: the positive active material lithium cobaltate (LiCoO ₂ ), the conductive agent Super P, and the binder polyvinylidene fluoride (PVDF) were added to N-methylpyrrolidone (NMP ), the positive electrode slurry was obtained by vacuum stirring; the positive electrode slurry was coated on the aluminum foil current collector, and the positive electrode sheet was obtained by drying, rolling, and slicing, and was vacuum-dried at 85°C and then moved into a glove box for standby.

Preparation of negative electrode sheet: Negative active material - graphite, conductive agent Super P, binder sodium carboxymethyl cellulose (CMC), binder styrene-butadiene rubber (SBR) in a mass ratio of 95:2:1:2 Add in deionized water, stir in vacuum to obtain negative electrode slurry; coat the negative electrode slurry on the copper foil current collector, dry, roll, and slice to obtain the negative electrode sheet, after vacuum drying at 120°C, move it into the glove box for later use.

Stack the above-mentioned positive pole piece, commercial ceramic-coated PE diaphragm, and negative pole piece in order to make a square cell, and coat it with commercial ceramics, and use aluminum-plastic film as the packaging material to prepare the above-mentioned Example 1. The electrolyte solution is injected into the above-mentioned batteries, and after packaging, standing, forming, and capacity separation, a soft-packed lithium secondary battery is made.

Example 2

The preparation method of the electrolyte is basically the same as in Example 1, except that the additives used in the electrolyte include the following components in the electrolyte in mass percentages: 3wt% ethoxypentafluorocyclotri Phosphazene, 3 wt% diethoxytetrafluorocyclotriphosphazene, 4 wt% triethoxytrifluorocyclotriphosphazene, 1 wt% VC, 5 wt% FEC and 2 wt% HTCN.

The electrolyte solution prepared in Example 2 was used to prepare a lithium secondary battery, and the preparation method was the same as in Example 1.

Example 3

The preparation method of the electrolyte is basically the same as in Example 1, except that the additives used in the electrolyte include the following components in the electrolyte in mass percentages: 4wt% of phenoxy pentafluorocyclotri Phosphazene, 3 wt% diphenoxytetrafluorocyclotriphosphazene, 3 wt% triphenoxytrifluorocyclotriphosphazene, 1 wt% VC, 5 wt% FEC and 2 wt% HTCN.

The electrolyte solution prepared in Example 3 was used to prepare a lithium secondary battery, and the preparation method was the same as in Example 1.

Example 4

The preparation method of the electrolyte is basically the same as in Example 1, except that the additives used in the electrolyte include the following components in the electrolyte in mass percentages: 4wt% ethyl ketone methyl pentafluoro Cyclotriphosphazene, 3wt% diethylketonemethyltetrafluorocyclotriphosphazene, 3wt% triethylketonemethyltrifluorocyclotriphosphazene, 1wt% VC, 5wt% FEC and 2wt% HTCN.

The electrolyte solution prepared in Example 4 was used to prepare a lithium secondary battery, and the preparation method was the same as in Example 1.

Example 5

The preparation method of the electrolyte is basically the same as that of Example 1, except that the additives used in the electrolyte include the following components in the electrolyte in percentage by mass: 4wt% diethyl phosphate pentafluoro Cyclotriphosphazene, 3wt% diethyl diphosphate diethyl tetrafluorocyclotriphosphazene, 3wt% diethyltriphosphate trifluorocyclotriphosphazene, 1wt% VC, 5wt% FEC and 2wt% HTCN.

The electrolyte solution prepared in Example 5 was used to prepare a lithium secondary battery, and the preparation method was the same as in Example 1.

Example 6

The preparation method of the electrolyte is basically the same as that of Example 1, except that the additive used in the electrolyte contains the following components in the electrolyte in percentage by mass: 4wt% of ethyl carbonate-based pentafluoro Cyclotriphosphazene, 3wt% diethylcarbonate-tetrafluorocyclotriphosphazene, 3wt% triethylcarbonate-trifluorocyclotriphosphazene, 1wt% VC, 5wt% FEC and 2wt% HTCN.

The electrolyte solution prepared in Example 6 was used to prepare a lithium secondary battery, and the preparation method was the same as in Example 1.

Example 7

The preparation method of the electrolyte is basically the same as that of Example 1, except that the additive used in the electrolyte contains the following components in the electrolyte in percentage by mass: 4wt% of methylsulfonate group five Fluorocyclotriphosphazene, 3wt% bismethylsulfonate tetrafluorocyclotriphosphazene, 3wt% trimethylsulfonate trifluorocyclotriphosphazene, 1wt% VC, 5wt% FEC and 2 wt% of HTCN.

The electrolyte solution prepared in Example 7 was used to prepare a lithium secondary battery, and the preparation method was the same as in Example 1.

Example 8

The preparation method of the electrolyte is basically the same as in Example 1, except that the additives used in the electrolyte include the following components in the electrolyte in mass percentages: 4wt% of trimethoxysiloxypenta Fluorocyclotriphosphazene, 3wt% bistrimethoxysiloxytetrafluorocyclotriphosphazene, 3wt% tristrimethoxysiloxytrifluorocyclotriphosphazene, 1wt% VC, 5wt% FEC and 2 wt% of HTCN.

The electrolyte solution prepared in Example 8 was used to prepare a lithium secondary battery, and the preparation method was the same as in Example 1.

Example 9

The preparation method of the electrolyte is basically the same as in Example 1, except that the additives used in the electrolyte include the following components in the electrolyte in mass percentages: 4wt% of acetonitrile pentafluorocyclotriphosphorus Nitrile, 3 wt% bisacetonitrile tetrafluorocyclotriphosphazene, 3 wt% triacetonitrile trifluorocyclotriphosphazene, 1 wt% VC, 5 wt% FEC and 2 wt% HTCN.

The electrolyte solution prepared in Example 9 was used to prepare a lithium secondary battery, and the preparation method was the same as in Example 1.

Example 10

The preparation method of the electrolyte is basically the same as in Example 1, except that the additives used in the electrolyte include the following components in the electrolyte in mass percentages: 2wt% of ethoxylated pentafluorocyclotri Phosphazene, 2 wt% diphenoxytetrafluorocyclotriphosphazene, 1 wt% triacetonitriletrifluorocyclotriphosphazene, 1 wt% VC, 5 wt% FEC and 2 wt% HTCN.

The electrolyte solution prepared in Example 10 was used to prepare a lithium secondary battery, and the preparation method was the same as in Example 1.

Example 11

The preparation method of the electrolyte is basically the same as in Example 1, except that the additives used in the electrolyte include the following components in the electrolyte in mass percentages: 2wt% of ethoxylated pentafluorocyclotri Phosphazene, 1 wt% diphenoxytetrafluorocyclotriphosphazene, 2 wt% triacetonitriletrifluorocyclotriphosphazene, 1 wt% VC, 5 wt% FEC and 2 wt% HTCN.

The electrolyte solution prepared in Example 11 was used to prepare a lithium secondary battery, and the preparation method was the same as in Example 1.

Example 12

The preparation method of the electrolyte is basically the same as in Example 1, except that the additives used in the electrolyte include the following components in the electrolyte in mass percentages: 2wt% diethyl phosphate pentafluoro Cyclotriphosphazene, 1 wt% bismethoxytetrafluorocyclotriphosphazene, 2 wt% triacetonitrile trifluorocyclotriphosphazene, 1 wt% VC, 5 wt% FEC and 2 wt% HTCN.

The electrolyte solution prepared in Example 12 was used to prepare a lithium secondary battery, and the preparation method was the same as in Example 1.

Example 13

The preparation method of the electrolyte is basically the same as in Example 1, except that the additives used in the electrolyte include the following components in the electrolyte in mass percentages: 3wt% of phenoxy pentafluorocyclotri Phosphazene, 1 wt% diethylketonemethyltetrafluorocyclotriphosphazene, 1 wt% triethylcarbonatetrifluorocyclotriphosphazene, 1 wt% VC, 5 wt% FEC and 2 wt% HTCN.

The electrolyte solution prepared in Example 13 was used to prepare a lithium secondary battery, and the preparation method was the same as in Example 1.

In order to highlight the beneficial effects of the embodiments of the present application, the following comparative examples are provided.

Comparative example 1

The preparation method of the electrolytic solution of Comparative Example 1 is basically the same as that of Example 1, except that the additives used in the electrolytic solution only include the following components in the electrolytic solution in mass percentages: 1wt% of VC, 5 wt% FEC and 2 wt% HTCN. That is, the electrolyte solution does not contain a flame retardant.

The electrolyte solution prepared in Comparative Example 1 was used to prepare a lithium secondary battery, and the preparation method was the same as in Example 1.

Comparative example 2

The preparation method of the electrolytic solution of Comparative Example 2 is basically the same as that of Example 2, except that the additives used in the electrolytic solution only include the following components in the electrolytic solution in mass percentage: 10wt% ethoxy Pentafluorocyclotriphosphazene, 1 wt% VC, 5 wt% FEC and 2 wt% HTCN.

The electrolyte solution prepared in Comparative Example 2 was used to prepare a lithium secondary battery, and the preparation method was the same as in Example 1.

Comparative example 3

The preparation method of the electrolytic solution of Comparative Example 3 is basically the same as that of Example 2, except that the additives used in the electrolytic solution only include the components in the electrolytic solution with the following mass percentages: 10 wt% of diethyl Oxytetrafluorocyclotriphosphazene, 1 wt% VC, 5 wt% FEC and 2 wt% HTCN.

The electrolyte solution prepared in Comparative Example 3 was used to prepare a lithium secondary battery, and the preparation method was the same as in Example 1.

Comparative example 4

The preparation method of the electrolytic solution of Comparative Example 4 is basically the same as that of Example 2, except that the additives used in the electrolytic solution only include the following components in the electrolytic solution in mass percentage: 10wt% triethyl Oxytrifluorocyclotriphosphazene, 1 wt% VC, 5 wt% FEC and 2 wt% HTCN.

The electrolyte solution prepared in Comparative Example 4 was used to prepare a lithium secondary battery, and the preparation method was the same as in Example 1.

Comparative example 5

The preparation method of the electrolytic solution of Comparative Example 5 is basically the same as that of Example 2, except that the additives used in the electrolytic solution only include the following components in the electrolytic solution in mass percentage: 5wt% ethoxy phenyl pentafluorocyclotriphosphazene, 5wt% diethoxytetrafluorocyclotriphosphazene, 1wt% VC, 5wt% FEC and 2wt% HTCN.

The electrolyte solution prepared in Comparative Example 5 was used to prepare a lithium secondary battery, and the preparation method was the same as in Example 1.

Comparative example 6

The preparation method of the electrolytic solution of Comparative Example 6 is basically the same as that of Example 3, except that the additives used in the electrolytic solution only include the following components in the electrolytic solution in mass percentage: 10wt% of phenoxy Pentafluorocyclotriphosphazene, 1 wt% VC, 5 wt% FEC and 2 wt% HTCN.

The electrolyte solution prepared in Comparative Example 6 was used to prepare a lithium secondary battery, and the preparation method was the same as in Example 1.

Comparative example 7

The preparation method of the electrolytic solution of Comparative Example 7 is basically the same as that of Example 3, except that the additives used in the electrolytic solution only include the following components in the electrolytic solution in mass percentage: 5% phenoxy Pentafluorocyclotriphosphazene, 5% diphenoxytetrafluorocyclotriphosphazene, 1 wt% VC, 5 wt% FEC and 2 wt% HTCN.

The electrolyte solution prepared in Comparative Example 7 was used to prepare a lithium secondary battery, and the preparation method was the same as in Example 1.

Comparative example 8

The preparation method of the electrolytic solution of Comparative Example 8 is basically the same as that of Example 2, except that the additives used in the electrolytic solution only include the following components in the electrolytic solution in mass percent: 30 wt% ethoxy Pentafluorocyclotriphosphazene, 1 wt% VC, 5 wt% FEC and 2 wt% HTCN.

The electrolyte solution prepared in Comparative Example 8 was used to prepare a lithium secondary battery, and the preparation method was the same as in Example 1.

The electrolytes and lithium secondary batteries of Examples 1-12 and Comparative Examples 1-7 of the present application were subjected to the following performance tests, and the results are summarized in Table 1 below.

1. Electrolyte self-extinguishing performance test

Take 5g of electrolyte solution and place it in a 5.0ml crucible, use the ignition device to quickly ignite the electrolyte solution, and record the time from when the ignition device is removed until the flame is automatically extinguished. The extinguishment time corresponding to a unit mass of electrolyte solution is the electrolyte self-extinguishing time (SET). The SET of each electrolyte sample was tested 5 times, and the average value was taken. In addition, the combustion characteristics of each electrolyte on continuous exposure to flame were recorded.

2. Performance test of lithium secondary battery

2.1, cycle performance test

Under the condition of ambient temperature 25 ℃ 23 ℃, the lithium secondary battery is charged and discharged at the charge and discharge rate of 0.7/0.7C. The voltage range of the graphite/LiCoO ₂ battery is 3.0-4.5V, and the recording cycle is 300 cycles later. capacity retention.

2.2. Multiplier performance test

Under the condition of ambient temperature of 25°C and 22°C, the lithium secondary battery was charged and discharged at 0.2/0.2C and 0.2/2.0C charge and discharge rates, and the voltage range of the graphite/ _LiCoO2 battery was 3.0-4.5V. Record the 2C rate discharge capacity retention rate (2C discharge capacity/0.2C discharge capacity*100%).

2.3. High temperature storage performance test

Under the ambient temperature of 25°C and 22°C, the battery is charged and discharged once at 0.2C/0.2C, and the capacity this time is the initial capacity; the battery is fully charged again at 0.2C, and the charged battery is placed at 70°C. 72 hours, then leave it open circuit at room temperature for 2 hours, discharge to the cut-off voltage with a constant current of _0.2C , and record it as the remaining capacity. initial capacity*100%).

The test data summary of each embodiment and comparative example of table 1

In Table 1, from the comparison of Examples 1-9 and Comparative Example 1, it can be seen that the electrolyte that uses pentafluorocyclotriphosphazene, tetrafluorocyclotriphosphazene and trifluorocyclotriphosphazene as flame retardants is non-flammable. And there is no fire phenomenon in the whole heating process until the electrolyte is completely volatilized. This is mainly due to the fact that pentafluorocyclotriphosphazene can effectively cover the volatilization range of the linear ester solvent in the electrolyte, tetrafluorocyclotriphosphazene can effectively cover the volatilization range of the cyclic ester solvent, and trifluorocyclotriphosphazene can effectively cover the volatilization range of the cyclic ester solvent. Covering the generation interval of flammable gas generated by the decomposition of electrolyte, thus achieving a wider range of flame retardancy. In addition, the fluorocyclotriphosphazene flame retardant itself has high oxidation resistance and the ability to form a composite interfacial film on the surface of the positive electrode, which can effectively inhibit the damage of the positive electrode at high potential, thereby improving the cycle stability of the lithium secondary battery Therefore, the battery cycle performance of Examples 1-9 is also better than that of Comparative Example 1. However, the electrolyte of Comparative Example 1 that does not contain a flame retardant can be ignited by a flame immediately, and continues to burn, and the safety performance of the battery is relatively poor.

In addition, from the comparison of Example 2 and Comparative Example 2, Example 3 and Comparative Example 6, it can be seen that when the total amount of flame retardant added is equal, adding a single pentafluorocyclotriphosphazene as a flame retardant In this case, the electrolyte did not catch fire at the initial stage, but after 60 seconds of continuous ignition, burning occurred, which also indicated that a single pentafluorocyclotriphosphazene could only cover the volatile range of the linear ester in the electrolyte and perform flame retardancy. From comparative examples 3-4, it can be seen that when the total amount of flame retardant added is equal, when a single tetrafluorocyclotriphosphazene or trifluorocyclotriphosphazene is added as the electrolyte, the electrolyte catches fire at the initial stage . This may be because a single tetrafluorocyclotriphosphazene or trifluorocyclotriphosphazene cannot cover the volatilization range of the early linear ester, so the electrolyte is ignited at the initial stage and then extinguished. From Comparative Example 5 or Comparative Example 7, it can be seen that when the total amount of flame retardants added is equal, when pentafluorocyclotriphosphazene and tetrafluorocyclotriphosphazene are added together as flame retardants, the initial stage of the electrolyte does not change. It caught fire and lasted longer than the single use of pentafluorocyclotriphosphazene, but in the later stage of continuous ignition, the electrolyte still caught fire, which may be because the flame retardant could not cover the flammable Gas generation interval. And the electrolytic solution that adopts single pentafluorocyclotriphosphazene as flame retardant, only when the addition amount of pentafluorocyclotriphosphazene is bigger (comparative example 8), the flame retardant performance of this electrolytic solution is just with the application implementation Examples 1-9 are similar, but the rate performance and cycle performance of the battery of Comparative Example 8 are greatly deteriorated.

In addition, in the electrolyte solution of Examples 10-12 of the present application, the total addition amount of the flame retardant system composed of pentafluorocyclotriphosphazene, tetrafluorocyclotriphosphazene and trifluorocyclotriphosphazene is reduced to 5% of the electrolyte solution. %, the flame retardant performance of each electrolyte is still good. In addition, from the comparison of Example 10 and Example 11, it can be seen that when the composition and total content of the flame retardant system are the same, when the mass ratio of pentafluorocyclotriphosphazene to tetrafluorocyclotriphosphazene in the electrolyte is the same as that of the electrolyte solvent When the mass ratio of linear ester and cyclic ester is 2:1 (Example 11), the flame retardancy of the electrolyte is better.

Claims (19)

1. An electrolyte solution for a secondary battery, characterized in that it includes an electrolyte salt, an organic solvent and a flame retardant, wherein the flame retardant includes pentafluorocyclotriphosphazene, tetrafluorocyclotriphosphazene and trifluorocyclotriphosphazene Nitrile.
2. The secondary battery electrolyte according to claim 1, wherein the total mass percentage of the pentafluorocyclotriphosphazene, tetrafluorocyclotriphosphazene and trifluorocyclotriphosphazene in the electrolyte is The content is 0.1%-20%.
3. The secondary battery electrolyte according to claim 2, wherein the total mass percentage of the pentafluorocyclotriphosphazene, tetrafluorocyclotriphosphazene and trifluorocyclotriphosphazene in the electrolyte is The content is 5%-20%.
4. The secondary battery electrolyte according to any one of claims 1-3, wherein the mass percentage of the pentafluorocyclotriphosphazene in the secondary battery electrolyte is 1%-10% , the mass percent of the tetrafluorocyclotriphosphazene in the secondary battery electrolyte is 1%-5%, and the mass percent of the trifluorocyclotriphosphazene in the secondary battery electrolyte is Min content is 1%-5%.
5. The secondary battery electrolyte according to any one of claims 1-4, wherein the average fluorine substitution degree DS of the flame retardant satisfies the following relational formula:

   DS=5×ω ₁ +4×ω ₂ +3×ω ₃ , where ω ₁ , ω ₂ , and ω ₃ represent pentafluorocyclotriphosphazene, tetrafluorocyclotriphosphazene and trifluorocyclotriphosphazene respectively in The mole percentage in the flame retardant;

   Wherein, the value range of the DS is: 3<DS<5.
6. The secondary battery electrolyte according to claim 5, wherein said _ω is less than or equal to 50%.
7. The secondary battery electrolyte as claimed in any one of claims 1-6, wherein the chemical structural formula of the pentafluorocyclotriphosphazene is as shown in formula (I), and the chemical structure of the tetrafluorocyclotriphosphazene The chemical structural formula is as shown in formula (II), and the chemical structural formula of the trifluorocyclotriphosphazene is as shown in formula (III):

   

   Wherein, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , and R ₆ are independently selected from alkoxy, haloalkoxy, aryloxy, haloaryloxy, alkyl, haloalkyl, alkenyl, Haloalkenyl, alkenyloxy, haloalkenyloxy, aryl, haloaryl, epoxy, haloepoxy, phosphate, substituted phosphate, carbonate, substituted carbonate , Sulfonate, Substituted Sulfonate, Alkyl Keto, Haloalkyl Keto, Alkoxysiloxy, Haloalkoxysiloxy, Substituted Imide, Substituted Sulfonimide, Nitrile any of the bases.
8. The secondary battery electrolyte according to claim 7, wherein the halogenated alkoxy, halogenated aryloxy, halogenated alkyl, halogenated alkenyl, halogenated alkenyloxy, halogenated aryl, halogenated The halogens in the epoxy group and the haloalkyl ketone group are all fluorine;

   The phosphate group is an alkyl phosphate group, the substituted phosphate group is a fluoroalkyl phosphate group; the carbonate group is an alkyl carbonate group, and the substituted carbonate group is a fluoroalkyl carbonate group The sulfonate group is an alkyl sulfonate group, and the substituted sulfonate group is a fluoroalkyl sulfonate group;

   The alkoxysiloxy is a trialkoxysiloxy, and the haloalkoxysiloxy is a fluorotrialkoxysiloxy.
9. The secondary battery electrolyte according to claim 7 or 8, wherein the number of carbon atoms of the alkoxy, haloalkoxy, alkyl, and haloalkyl is 1-10; the alkenyl, halo The number of carbon atoms of alkenyl, alkenyloxy, halogenated alkenyloxy, epoxy, and halogenated epoxy is 2-10, and the aryl, halogenated aryl, aryloxy, and halogenated aryloxy The number of carbon atoms is 6-15;

   The number of carbon atoms in the phosphate group, substituted phosphate group, carbonate group, substituted carbonate group, sulfonate group and substituted sulfonate group is 1-10.
10. The secondary battery electrolyte according to any one of claims 1-9, wherein the organic solvent includes linear esters and cyclic esters.
11. The secondary battery electrolyte according to claim 10, wherein the linear ester comprises at least one of a linear carbonate and a linear carboxylate, and the cyclic ester comprises a cyclic carbonate and a cyclic carboxylate at least one of acid esters.
12. The secondary battery electrolyte according to claim 11, wherein the cyclic carbonate comprises one or more of ethylene carbonate, propylene carbonate, butylene carbonate, and gamma-butyrolactone; Described linear carbonate includes but not limited to be one or more in dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate; Described linear carboxylate includes methyl acetate, ethyl acetate , one or more of propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate; the cyclic carboxylic acid ester includes α-acetone, One or more of β-propiolactone, γ-butyrolactone, δ-valerolactone, and caprolactone.
13. The secondary battery electrolyte according to any one of claims 10-12, wherein the mass ratio between the pentafluorocyclotrinitrile and tetrafluorocyclotriphosphazene is proportional to the ratio between the linear ester and the cyclic The mass ratio between the esters is close.
14. The secondary battery electrolyte solution according to any one of claims 1-13, wherein the electrolyte solution also includes other additives, and the other additives include fluoroethylene carbonate, difluoroethylene carbonate, trifluoroethylene carbonate, Fluoromethyl vinyl carbonate, vinylene carbonate, vinyl ethylene carbonate, 1,3-propane sultone, 1,4-butane sultone, vinyl sulfite, propylene sulfite, sulfurous acid Butenyl ester, 4-methyl vinyl sulfite, dimethyl sulfite, diethyl sulfite, vinyl sulfate, 4-methyl vinyl sulfate, 4-propyl vinyl sulfate, 1,4-butyl Glycol sulfate, 4-fluorophenyl acetate, tris(trimethylsilane) phosphate, tris(trimethylsilane) borate, methylene methanedisulfonate, N,N-sulfuryldiimidazole , succinonitrile, adiponitrile, 1,3,6-hexanetrinitrile, 1,3,5-pentanetricarbonitrile, 1,2-bis(2-cyanoethoxy)ethane, ethylene glycol bis One or more of propionitrile ether, fluoroether D2, N,N-dimethyltrifluoroacetamide, biphenyl and benzene derivatives.
15. The secondary battery electrolyte solution according to claim 14, characterized in that, the mass percentage of said other additives in said electrolyte solution is 0.2%-15%.
16. The secondary battery electrolyte according to any one of claims 1-15, wherein the electrolyte salt is a lithium salt, and the lithium salt includes lithium perchlorate, lithium tetrafluoroborate, lithium hexafluorophosphate, arsenic hexafluoro lithium difluorophosphate, lithium difluorooxalate borate, lithium difluorooxalate borate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethylsulfonyl imide, lithium bis(perfluoroethylsulfonyl)imide , one or more of lithium trifluoromethanesulfonate and lithium perfluorobutylsulfonate.
17. The secondary battery electrolyte according to claim 16, wherein the molar concentration of the lithium salt in the secondary battery electrolyte is 0.01mol/L-2.0mol/L.
18. A secondary battery, characterized in that it comprises a positive electrode, a negative electrode, a diaphragm and an electrolyte, and the electrolyte is the secondary battery electrolyte according to any one of claims 1-17.
19. An electronic device comprising the secondary battery according to claim 18.

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