Electrolyte and use thereof

Abstract

The application provides an electrolyte and application thereof, and relates to the technical field of secondary batteries. Specifically, the electrolyte comprises an alternating copolymer, a first solvent, a second solvent, a third solvent, a lithium salt and an additive; the alternating copolymer is obtained by polymerization of a first monomer and a second monomer; the first monomer comprises a terminal alkenyl group, a terminal halogen atom and an ether bond, and the second monomer comprises at least one of maleic anhydride, citraconic anhydride, itaconic anhydride, maleimide and 2,5-thiophenedione. The electrolyte of the application has high-temperature safety and high low-temperature ionic conductivity; the electrolyte of the application is in a liquid state at low temperature, has high ionic conductivity, is in a solid state after reversible phase transition with the increase of temperature, has safety and stability at high temperature, and has a good application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of secondary batteries, in particular to an electrolyte and application thereof. BACKGROUND

[0002] Lithium ion batteries have high specific energy, lightweight, long cycle life and other advantages, and dominate in application fields such as consumer electronics, new energy vehicles and energy storage. The current mainstream lithium battery uses organic solvents as electrolytes, which will cause a series of safety problems in high temperature environment, such as electrolyte decomposition, gasification, etc., and these electrolytes are flammable, which makes the liquid lithium ion battery face serious safety challenges in high temperature environment.

[0003] Solid-state batteries are considered as a solution to improve battery safety. Solid-state batteries use non-flammable solid electrolytes instead of flammable organic solvents, which can greatly reduce the safety hazards related to high-temperature thermal runaway and electrolyte combustion. In addition to this, solid-state batteries have other advantages, such as solid-state electrolytes that can resist lithium dendrites, so solid-state batteries can also match metal lithium with ultra-high theoretical specific capacity (3860 mAh / g) as negative electrode material. However, solid-state batteries face the challenge of significant decrease in ionic conductivity in low temperature environment, which is one of the key bottlenecks restricting the application of solid-state batteries in low temperature scenarios. For example, the ionic conductivity of sulfide solid-state electrolyte is only 0.1~0.2 ms / cm at-20℃.

[0004] Therefore, the present application is proposed. SUMMARY

[0005] The first object of the present application is to provide an electrolyte, which is mainly used to solve the technical defects that the conventional electrolyte cannot balance the high temperature safety and low temperature ionic conductivity performance.

[0006] The second object of the present application is to provide a secondary battery.

[0007] The third object of the present application is to provide an electric device.

[0008] In order to achieve the above objects of the present application, the following technical solutions are adopted:

[0009] An electrolyte, comprising an alternating copolymer, a first solvent, a second solvent, a third solvent, a lithium salt and an additive;

[0010] The alternating copolymer is obtained by polymerization of a first monomer and a second monomer;

[0011] The first monomer comprises terminal alkenyl, terminal halogen atom and ether bond, and the second monomer comprises at least one of maleic anhydride, citraconic anhydride, itaconic anhydride, maleimide and 2,5-thiophenedione.

[0012] In an embodiment, the alternating copolymer has a degree of polymerization of 10,000 to 60,000.

[0013] In an embodiment, the content of the alternating copolymer in the electrolyte is 6 wt.% to 24 wt.%.

[0014] In an embodiment, the first monomer includes at least one of compounds (I) to (VIII) below:

[0015] (I); (II);

[0016] (III); (IV);

[0017] (V); (VI);

[0018] (VII); (VIII).

[0019] In an embodiment, the first solvent includes at least one of ethyl propionate, propyl acetate, methyl acetate, ethyl butyrate, butyl acetate, tetrahydrofuran, dimethoxyethane, N,N-dimethylformamide, dimethyl sulfoxide.

[0020] In an embodiment, the content of the first solvent in the electrolyte is 50 wt.% to 70 wt.%.

[0021] In an embodiment, the second solvent is an alkane compound, and the alkane compound includes at least one of n-octane, n-heptane, n-hexane, cyclohexane.

[0022] In an embodiment, the content of the second solvent in the electrolyte is 5 wt.% to 10 wt.%.

[0023] In an embodiment, the third solvent is an amphiphilic solvent, and the amphiphilic solvent includes at least one of compounds (a) to (e) below:

[0024] (a); (b);

[0025] (c); (d);

[0026] (e); R is -C n H2n+1 n is independently selected from 4 to 8.

[0027] In an embodiment, the content of the third solvent in the electrolyte is 5wt.% to 10wt.%.

[0028] In an embodiment, the lithium salt comprises at least one of LiPF6, LiBF4, LiFSI, LiTFSI, LiAsF6, LiBOB, LiCF3SO3, LiClO4.

[0029] In an embodiment, the content of the lithium salt in the electrolyte is 5wt.% to 15wt.%.

[0030] In an embodiment, the additive comprises at least one of the following compounds (A) to (D):

[0031] (A); (B);

[0032] (C); (D).

[0033] In an embodiment, the content of the additive in the electrolyte is 1wt.% to 3wt.%.

[0034] A secondary battery comprising the electrolyte.

[0035] An electrical equipment comprising the secondary battery.

[0036] Compared with the prior art, the present application has the following beneficial effects:

[0037] The present application provides an electrolyte material capable of reversible phase change in an organic solvent, which has high temperature safety and can achieve high low-temperature ionic conductivity at low temperature. The electrolyte comprises a specific alternating copolymer as a phase change polymer material, and three solvents, a lithium salt and other additives. The electrolyte is in a liquid state at low temperature and has high ionic conductivity like an electrolyte. With the increase of temperature, the electrolyte is in a solid state after reversible phase change, and has safety and stability at high temperature.

[0038] (1) High low-temperature ionic conductivity: by adjusting the content of the alternating copolymer, the content of the amphiphilic solvent, the type and content of the additive, the electrolyte of the present application can achieve high ionic conductivity at low temperature, which is 5 to 10 times of that of conventional sulfide solid electrolyte.

[0039] (2) High temperature safety: when the lithium battery using the electrolyte of the application is in the normal working temperature range of 20-30℃, the electrolyte is in a liquid state; when the battery temperature rises, the electrolyte undergoes a phase transition, and the phase transition temperature is between 20-70℃, which has not reached the decomposition temperature of the SEI film. After phase transition, the capacity of the battery decreases, slowing down the continuous rise of the battery temperature, and preventing the battery from thermal runaway.

[0040] (3) Low cost: the existing temperature phase transition electrolyte usually uses ionic liquid as the carrier, which has a high cost, for example, the cost of imidazole ionic liquid is as high as 500-1500 yuan / kg; compared with the ionic liquid, the application uses low-cost organic solvents to realize the phase transition of the electrolyte in a wide temperature range of 20-70℃, and the cost is much lower than that of the ionic liquid under the condition of similar performance. BRIEF DESCRIPTION OF DRAWINGS

[0041] In order to more clearly illustrate the specific embodiments of the application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or the prior art description. Obviously, the drawings described below are some embodiments of the application, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0042] Figure 1 Cycle capacity performance chart for each embodiment of the application;

[0043] Figure 2 Transmittance result chart for embodiment 1 of the application. DETAILED DESCRIPTION

[0044] The technical solutions of the application will be described clearly and completely in combination with the drawings and specific embodiments, but those skilled in the art will understand that the following described embodiments are part of the embodiments of the application, not all the embodiments, and are only used to illustrate the application, and should not be regarded as limiting the scope of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application. The specific conditions are not specified in the embodiments, and the conventional conditions or the conditions recommended by the manufacturer are used. The reagents or instruments used are not specified by the manufacturer, and are conventional products that can be purchased on the market. In addition, the terms "first", "second", "third" are only used for description purposes, and cannot be understood as indicating or implying relative importance.

[0045] The first aspect of the application is to provide an electrolyte.

[0046] The electrolyte of the present invention comprises an alternating copolymer, a first solvent, a second solvent, a third solvent, a lithium salt, and an additive; wherein the alternating copolymer is obtained by polymerization of a first monomer and a second monomer; the first monomer comprises a terminal alkenyl group, a terminal halogen atom, and an ether bond, and the second monomer comprises at least one of maleic anhydride, citraconic anhydride, itaconic anhydride, maleimide, and 2,5-thiophenedione.

[0047] The alternating copolymer described in this invention primarily satisfies the conventional definition in the art, namely, that the two monomer units in the macromolecular chain are arranged in a strictly alternating manner, and must meet the conditions of containing only two monomers, at least one monomer being unable to homopolymerize, and heteropolymer copolymerization being necessary; in this invention, the alternating copolymer is obtained by alternating polymerization of the first monomer and the second monomer.

[0048] In this invention, the structure of the second monomer satisfies the conventional definition of a compound whose name implies it. Specifically, the structural formula of maleic anhydride is: The structural formula of citric acid anhydride is: The structural formula of itaconic anhydride is: The structural formula of maleimide is: The structural formula of 2,5-thiophenedionone is: .

[0049] In a preferred embodiment, the degree of polymerization of the alternating copolymer is 10,000 to 60,000, including but not limited to 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6 (×10⁻⁶). 4 The range of values ​​formed by any one or any two of the following.

[0050] In a preferred embodiment, the terminal halogen atom in the first monomer is at least one of a fluorine atom or a chlorine atom.

[0051] In a more preferred embodiment, the first monomer comprises at least one of the following compounds (I) to (VIII):

[0052] (I); (II);

[0053] (III); (IV);

[0054] (V); (VI);

[0055] (VII); (VIII).

[0056] As a preferred embodiment, the content of the alternating copolymer in the electrolyte is 6wt.%~24wt.%, including but not limited to any one of 6, 8, 10, 12, 15, 16, 18, 20, 22, 23, 24 (wt.%), or a numerical range constituted by any two of them.

[0057] As a preferred embodiment, the first solvent is a main dispersing solvent of the electrolyte, and the first solvent includes but is not limited to at least one of ethyl propionate, propyl acetate, methyl acetate, ethyl butyrate, butyl acetate, tetrahydrofuran, dimethoxyethane, N,N-dimethylformamide, dimethyl sulfoxide.

[0058] As a preferred embodiment, the content of the first solvent in the electrolyte is 50wt.%~70wt.%, including but not limited to any one of 50, 52, 54, 55, 56, 58, 60, 62, 64, 65, 66, 68, 70 (wt.%), or a numerical range constituted by any two of them.

[0059] As a preferred embodiment, the second solvent is an alkane compound, and the alkane compound includes at least one of n-octane, n-heptane, n-hexane, cyclohexane.

[0060] As a preferred embodiment, the content of the second solvent in the electrolyte is 5wt.%~10wt.%, including but not limited to any one of 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10 (wt.%), or a numerical range constituted by any two of them.

[0061] As a preferred embodiment, the third solvent is an amphiphilic solvent, i.e. a special solvent with hydrophilic (polar) and lipophilic (non-polar) groups; the amphiphilic solvent includes alkyl and ester groups.

[0062] As a more preferred embodiment, the amphiphilic solvent includes at least one of the following compounds (a)~(e):

[0063] (a); (b);

[0064] (c); (d);

[0065] (e);

[0066] and R in the compounds (a)~(e) is -C n H 2n+1n are independently selected from 4 to 8.

[0067] As a preferred embodiment, the content of the third solvent in the electrolyte is 5wt.% to 10wt.%, including but not limited to any one of 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10 (wt.%), or a numerical interval composed of any two of them.

[0068] It is worth noting that there are three solvents in the present application; among them, the first solvent is the commonly used solvent in lithium battery electrolyte, mainly ester, ether; the second solvent can produce LCST phenomenon with the alternating copolymer, that is, the alternating copolymer dissolves as a phase change polymer at low temperature, and precipitates at high temperature; the third solvent is a cosolvent, which has amphiphilic properties and can improve the solubility between the first solvent and the second solvent. Specifically, the second solvent contains alkanes, and the polarity of these solvents is small, which is quite different from the polarity of the ester in the first solvent; the present application solves the compatibility problem of the first solvent and the second solvent by adding the third solvent as a cosolvent.

[0069] Further, for the above-mentioned LCST (Lower Critical Solution Temperature) phenomenon, it is found through detection that there is an unfolding explanation as follows: at low temperature, hydrogen bonds are formed between the alternating copolymer and the second solvent molecules, and the alternating copolymer molecules are chain-like dissolved in the second solvent; when the temperature rises, the enthalpy change of the hydrogen bond breaking between the alternating copolymer and the second solvent molecules is enthalpy increase, the alternating copolymer precipitates from the second solvent, and the entropy change of the whole electrolyte system is entropy increase, and with the increase of temperature, the change of entropy increase dominates. According to ΔG=ΔH-TΔS, ΔG<0, the reaction of the alternating copolymer precipitating from the second solvent is spontaneous, and the effect shown is that the alternating copolymer becomes a group after precipitation, and the whole system changes from liquid to solid.

[0070] As a preferred embodiment, the lithium salt includes at least one of LiPF6, LiBF4, LiFSI, LiTFSI, LiAsF6, LiBOB, LiCF3SO3, LiClO4.

[0071] As a preferred embodiment, the content of the lithium salt in the electrolyte is 5wt.% to 15wt.%, including but not limited to any one of 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 (wt.%), or a numerical interval composed of any two of them.

[0072] As a preferred embodiment, the additive includes at least one of the following compounds (A) to (D):

[0073] (A); (B);

[0074] (C); (D).

[0075] As a preferred embodiment, the content of the additive in the electrolyte is 1wt.%~3wt.%, including but not limited to any one of 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3 (wt.%), or a numerical interval composed of any two of them.

[0076] As a preferred embodiment, the electrolyte can undergo reversible phase transition according to temperature, and the phase transition temperature of the electrolyte is 20℃~70℃; it is detected that the electrolyte has good phase transition reversibility, and can realize reversible cycle for at least 100 times within the above temperature range.

[0077] It is worth noting that the phase transition temperature window of the electrolyte in the application can be adjusted; by adjusting the types, contents and molecular weights of the first monomer and the second monomer, the types and contents of the second solvent, and the types and contents of the third solvent, the phase transition temperature can be controlled.

[0078] As a preferred embodiment, the preparation method of the alternating copolymer comprises the following steps: stirring the first monomer, the second monomer, an initiator and a reaction solvent at 50℃~100℃ for 1h~6h, and then separating the precursor of the alternating copolymer in a poor solvent, drying, and obtaining the alternating copolymer.

[0079] As an optional embodiment, the drying is vacuum drying, the temperature is 80℃~120℃, and the time is 6h~10h.

[0080] As a more preferred embodiment, the molar ratio of the first monomer to the second monomer is 1:1; the molar amount of the initiator to the total molar amount is 1: (100~1000), and the ratio of the reaction solvent to the total molar amount is (5~15):1.

[0081] As a more preferred embodiment, the initiator comprises at least one of azobisisobutyronitrile (AIBN), azobisisoheptyl nitrile (ABVN), and dibenzoyl peroxide (BPO); the reaction solvent comprises at least one of methyl ethyl ketone, ethyl acetate, acetone, and toluene; as another more preferred embodiment, the poor solvent comprises at least one of diethyl ether, n-hexane, and petroleum ether, and the amount of the poor solvent is used in an amount sufficient to precipitate the precursor of the alternating copolymer to completion, and the amount can be adjusted by those skilled in the art.

[0082] As a preferred embodiment, the preparation method of the electrolyte comprises the following steps: mixing the alternating copolymer, the first solvent, the second solvent, the third solvent, the lithium salt, and the additive sufficiently to obtain the electrolyte.

[0083] As an optional embodiment, the sufficient mixing can be assisted by oscillation, stirring, a shaking table, centrifugation, ultrasonic, heating, etc., which helps to accelerate dispersion and obtain a relatively uniform dispersion system.

[0084] The second aspect of the present application is to provide a secondary battery comprising the electrolyte as described in the first aspect.

[0085] As a preferred embodiment, the secondary battery is a lithium ion battery.

[0086] As a more preferred embodiment, the positive electrode of the lithium ion battery comprises one of lithium iron phosphate, lithium cobaltate, lithium manganate, or a ternary material, and the negative electrode comprises one of natural graphite, artificial graphite, silicon, silicon-carbon composite material, or metallic lithium. In some optional embodiments, the separator of the lithium ion battery comprises one of polyethylene, polypropylene, polyimide, polyamide, polyvinylidene fluoride, or polytetrafluoroethylene.

[0087] The third aspect of the present application is to provide an electrical equipment comprising the secondary battery as described in the second aspect.

[0088] It can be understood that the electrical equipment can be any device or apparatus that relies on electrical energy for work or operation, including but not limited to new energy vehicles, building electrical equipment, industrial electrical equipment, household and agricultural electrical equipment, etc.; when comprising the secondary battery, any electrical equipment equipped with the secondary battery can belong to an embodiment of the present application.

[0089] Examples 1~9

[0090] S1, stirring the first monomer, the second monomer, the initiator and the reaction solvent at a specific temperature for a specific time, ensuring that the molar ratio between the two monomers is 1:1; the sum of the molar amounts of the two monomers is the total molar amount, the molar amount of the initiator is M value with respect to the total molar amount, and the molar amount of the reaction solvent is N value with respect to the total molar amount. After the polymerization reaction is completed, a poor solvent is added to the reaction system, and after stirring, the solid phase is obtained by precipitation and centrifugation, and then vacuum drying at 100°C for 8h to obtain the alternating copolymer of the present embodiment.

[0091] In each embodiment, the reaction temperature, reaction time, M and N values, initiator type, reaction solvent type, and poor solvent type are shown in Table 1; in addition, the types of each monomer are shown in Table 2 below.

[0092] S2, in an argon-filled glove box, mix the alternating copolymer (obtained by alternating polymerization of the first monomer and the second monomer), the first solvent, the second solvent, the third solvent, the lithium salt, and the additive, and place it on a stirring device to stir at 800rpm for 30min to obtain the electrolyte of each embodiment.

[0093] In each embodiment, the types of each monomer, the degree of polymerization of the alternating copolymer, the amount of the alternating copolymer, the types and amounts of each solvent, the types and amounts of lithium salt, and the types and amounts of additives are all shown in Table 1. It is worth noting that the specific substances referred to in compounds (I)-(VIII), (a)-(e), (A)-(D) in Table 2 are consistent with the serial numbers in the specification of the present application; for compounds (a)-(e), there are R groups that are -C n H 2n+1 In Table 2, the n value is provided, and for the two R groups of compound (e), there is the same n value.

[0094] Table 1

[0095]

[0096] Table 2

[0097]

[0098] Comparative Example 1: substantially the same as Example 1, the only difference being that no alternating copolymer is added, and the content of the first solvent is changed to 73wt.%.

[0099] Comparative Example 2: substantially the same as Example 3, the only difference being that the alternating copolymer is replaced by a self-polymer of the first monomer.

[0100] Comparative Example 3: substantially the same as Example 3, the only difference being that no second solvent is added, and the content of the first solvent is changed to 72wt.%.

[0101] Comparative Example 4: substantially the same as Example 3, except that the third solvent is not added, and the content of the first solvent is changed to 72 wt.%.

[0102] Test Example

[0103] (1) Ionic conductivity test: 2 cm 2 The stainless steel gasket and the electrolyte are assembled into a battery, the battery is placed in a low-temperature test chamber at -20°C for 3 h, and then connected to an electrochemical workstation, the electrochemical workstation applies a sinusoidal voltage signal with an amplitude of 20 mV, the test frequency range is between 4 MHz and 100 MHz, the resistance of the electrolyte is recorded, and the ionic conductivity is calculated.

[0104] (2) Discharge capacity test: the electrolytes obtained in each example and comparative example are prepared into test batteries; specifically, lithium iron phosphate is used as the positive electrode, metal lithium is used as the negative electrode, and polyvinylidene fluoride is used as the separator, which is assembled into a battery shell to obtain lithium batteries corresponding to each example.

[0105] Each assembled battery is placed in a high and low temperature test chamber, the temperature is set to 25°C, and the battery is left to stand for 1 hour; then a charge-discharge instrument is connected, and the battery is discharged at a rate of 0.2 C, the discharge cut-off voltage is 2 V, the capacity at 25°C is recorded. The first discharge capacity (corresponding to the capacity value at cycle number 1 in Figure 1 ); then the battery is placed in a temperature chamber, the temperature chamber is raised from the test environment temperature to 75°C at a rate of 5°C / min, and maintained at this temperature for 30 min; then the temperature chamber is cooled to 25°C at a rate of 1°C / min, and maintained at this temperature for 30 min, then discharged at a rate of 0.2 C, the discharge cut-off voltage is 2 V, and the discharge capacity (corresponding to the capacity value at cycle number 2 in Figure 1 ) is recorded. Repeat the above steps until 5 cycles are generated, and plot the results to obtain the capacity performance graph shown in Figure 1 .

[0106] (3) Phase transition temperature test: the phase transition temperature of the electrolyte is determined by measuring the transmittance of the electrolyte solution; a variable temperature UV-visible spectrometer is used to determine the transmittance of the electrolyte solution; the solution is placed on the heating stage of the instrument, and the solution is heated at a heating rate of 1°C / min, the transmittance curve is recorded, and the temperature at which the transmittance reaches 0 is defined as the phase transition temperature.

[0107] (4) Phase reversibility test: the transmittance of each electrolyte was tested at 25°C, and the phase state was liquid when the transmittance was equal to 100%; the reagent bottle containing the electrolyte was placed on a heating table, the heating temperature was set to 70°C, the heating rate was 20°C / min, and the transmittance was tested at 70°C for 10 minutes. When the transmittance was <5%, the phase state was solid, the heater was turned off, and the electrolyte was cooled to 25°C, which was recorded as one cycle. A total of 100 cycles were performed, and after 100 cycles, the electrolyte material had a transmittance of 100% at 25°C and a transmittance of <5% at 70°C, which proved that the electrolyte had reversibility, otherwise it was not reversible.

[0108] Figure 2 The transmittance performance chart of the electrolyte corresponding to Example 1 in 100 cycles is provided.

[0109] The results of the above tests (1) to (4) are recorded in Table 3 below.

[0110] Table 3

[0111]

[0112] Although the present application has been illustrated and described with respect to specific embodiments, it should be understood that the above examples are merely illustrative of the present application and are not to be taken as limiting thereof. It is understood that various modifications can be made to the embodiments described above, and that such modifications, and any other modifications that come within the spirit and scope of the present application, are to be considered as falling within the scope of the present application. Accordingly, although specific embodiments have been illustrated and described herein, it should be appreciated that any arrangement which is calculated to achieve the same or similar result can be substituted for the specific embodiments shown.

Claims

1. An electrolyte, characterized in that, The electrolyte comprises an alternating copolymer, a first solvent, a second solvent, a third solvent, a lithium salt, and additives; The alternating copolymer is obtained by polymerization of a first monomer and a second monomer; The first monomer includes a terminal alkenyl group, a terminal halogen atom, and an ether bond, and the second monomer includes at least one of maleic anhydride, citraconic anhydride, itaconic anhydride, maleimide, and 2,5-thiophenedione. The first solvent includes at least one of ethyl propionate, propyl acetate, methyl acetate, ethyl butyrate, butyl acetate, tetrahydrofuran, dimethoxyethane, N,N-dimethylformamide, and dimethyl sulfoxide. The second solvent is an alkane compound, and the alkane compound includes at least one of n-octane, n-heptane, n-hexane, and cyclohexane; The third solvent is an amphiphilic solvent, which includes at least one of the following compounds (a) to (e): (a); (b); (c); (d); (e); R-based is -C n H 2n+1 n is independently selected from 4 to 8.

2. The electrolyte according to claim 1, characterized in that, The degree of polymerization of the alternating copolymer is 10,000 to 60,000; And / or, in the electrolyte, the content of the alternating copolymer is 6 wt.% to 24 wt.%.

3. The electrolyte according to claim 1, characterized in that, The first monomer comprises at least one of the following compounds (I) to (VIII): (AND); (II); (III)) (IV)) (V); (VI); (VII)? (VIII)。 4. The electrolyte according to claim 1, characterized in that, In the electrolyte, the content of the first solvent is 50 wt.% to 70 wt.%.

5. The electrolyte according to claim 1, characterized in that, In the electrolyte, the content of the second solvent is 5 wt.% to 10 wt.%.

6. The electrolyte according to claim 1, characterized in that, In the electrolyte, the content of the third solvent is 5 wt.% to 10 wt.%.

7. The electrolyte according to claim 1, characterized in that, The lithium salt includes at least one of LiPF6, LiBF4, LiFSI, LiTFSI, LiAsF6, LiBOB, LiCF3SO3, and LiClO4; And / or, in the electrolyte, the lithium salt content is 5 wt.% to 15 wt.%.

8. The electrolyte according to claim 1, characterized in that, The additive includes at least one of the following compounds (A) to (D): (A); (B); (C); (D); And / or, in the electrolyte, the content of the additive is 1 wt.% to 3 wt.%.

9. A secondary battery, characterized in that, Includes the electrolyte as described in any one of claims 1 to 8.

10. An electrical appliance, characterized in that, Includes the secondary battery as described in claim 9.

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