Electrolyte, battery, battery pack, and electric device

Abstract

The present application provides an electrolyte, a battery, a battery pack, and an electric device, the electrolyte comprising an additive, the additive comprising a fluorinated carbonate compound and a nitro organic compound. The electrolyte of the present application can improve the rate capability and the cycle stability of the battery simultaneously by introducing a specific additive, which can induce the formation of a thin and dense solid electrolyte interface film with good lithium ion conductivity.

Description

Technical Field

[0001] This invention relates to an electrolyte, and more particularly to an electrolyte, a battery, and an electrical device, belonging to the field of secondary batteries. Background Technology

[0002] Lithium-ion batteries are widely used in mobile phones, laptops, electric vehicles and other fields due to their advantages such as high energy density, long cycle life and low self-discharge. As an important component of lithium-ion batteries, the electrolyte has a significant impact on their performance.

[0003] Adding fluorinated ether diluents to the electrolyte has a positive effect on improving the battery's operating voltage window, cycle life, and safety. However, with the improvement of production levels, the demand for energy, range, and high power output is increasing, necessitating the search for electrolytes with superior rate performance and stability. Fluorinated ether diluents easily decompose at the battery's negative electrode interface to form a solid electrolyte interphase (SEI) film. This SEI film has drawbacks such as high impedance and a high lithium-ion transport barrier, which are detrimental to the battery's rate performance. Summary of the Invention

[0004] The present invention provides an electrolyte that can simultaneously improve the rate performance and cycle stability of a battery.

[0005] The present invention also provides a battery that, because it includes the above-mentioned electrolyte, has the advantages of low impedance and long cycle life.

[0006] The present invention also provides a battery pack, which has the advantages of high rate and long cycle life because it includes at least two of the above-mentioned batteries.

[0007] The present invention also provides an electrical device comprising the aforementioned battery, which has good electrochemical performance and a long service life.

[0008] In a first aspect, the present invention provides an electrolyte comprising additives, said additives including fluorocarbonate compounds and nitro organic compounds.

[0009] Optionally, the fluorocarbonate compound includes the compound shown in Formula 1 and / or the compound shown in Formula 2:

[0010] Formula 1,

[0011] Equation 2,

[0012] R1 and R2 are each independently a fluorinated or unsubstituted C1-C20 alkyl group, a fluorinated or unsubstituted C2-C20 alkenyl group, and at least one of R1 and R2 includes a fluorinated substituent; R3 and R4 are each independently a fluorinated or unsubstituted C1-C20 alkyl group, a fluorinated or unsubstituted C2-C20 alkenyl group, a fluorinated group, and at least one of R3 and R4 includes a fluorine atom.

[0013] Optionally, the nitro organic compound includes the compound shown in Formula 3:

[0014] Formula 3,

[0015] R4 to R9 are each independently one of nitro, H, cyano, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted alkenyl, and at least one of R4 to R9 is nitro.

[0016] Optionally, the fluorocarbonate compounds include one or more of methyl trifluoroethyl carbonate, ethyl trifluoroethyl carbonate, bis(2-fluoroethyl) carbonate, bis(2,2,2)-trifluoroethyl carbonate, propylene trifluorocarbonate, propylene difluorocarbonate, ethylene fluorocarbonate, and ethylene difluorocarbonate.

[0017] Optionally, the nitro organic compound includes one or more of the following: 3-nitrophthalonitrile, 4-nitrophthalonitrile, o-nitrobenzonitrile, m-nitrobenzonitrile, p-nitrobenzonitrile, 3,5-dinitrobenzonitrile, 4-methyl-3-nitrobenzonitrile, 2-methoxy-5-nitrobenzonitrile, 4-methoxy-2-nitrobenzonitrile, 2-amino-5-nitrobenzonitrile, o-nitrophenylacetonitrile, m-nitrophenylacetonitrile, p-nitrophenylacetonitrile, and 4-nitrobenzoylacetonitrile.

[0018] Optionally, the fluorocarbonate compound accounts for 1-5% of the total volume of the electrolyte;

[0019] And / or, the electrolyte further includes an electrolyte salt, wherein the nitro organic compound accounts for 0.2-10% of the molar percentage of the electrolyte salt.

[0020] Optionally, the electrolyte includes fluorinated lithium salts, ether solvents, and fluorinated ether diluents.

[0021] Optionally, the fluorinated lithium salt includes one or more of lithium difluorosulfonylimide, lithium trifluoromethylsulfonylimide, lithium difluorooxalateborate, and lithium difluorophosphate;

[0022] And / or, the ether solvent includes one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and 1,3-dioxolane;

[0023] And / or, the fluorinated ether diluent includes one or more of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, dichloromethane, dichlorobutane, and trifluoromethoxybenzene.

[0024] Optionally, the molar concentration of the fluorinated lithium salt in the electrolyte is 2-5 mol·L⁻¹. -1 ;

[0025] And / or, the volume ratio of the ether solvent to the fluorinated ether diluent is 1:(1-6).

[0026] In a second aspect, the present invention provides a battery comprising the electrolyte described in the first aspect.

[0027] Thirdly, the present invention provides a battery pack comprising at least two batteries as described in the second aspect.

[0028] Fourthly, the present invention provides an electrical device comprising the battery described in the second aspect or the battery pack described in the third aspect.

[0029] The electrolyte provided by this invention, by introducing specific additives, can induce the decomposition products to form a thin and dense solid electrolyte interface film with good lithium-ion conductivity, thereby simultaneously improving the rate performance and cycle stability of the battery. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0031] In this application, references to "an embodiment," "an example," or "an example" mean that a specific feature, structure, or characteristic described in connection with that embodiment, example, or example is included in at least one embodiment of the invention. Therefore, the phrases "an embodiment," "an example," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination.

[0032] Introducing fluorinated ether diluents and high-concentration fluorinated lithium salts into the electrolyte can create localized high-lithium-concentration regions on the electrode surface or in specific areas. These regions have a positive effect on improving the battery's operating voltage window and cycle stability. However, fluorinated ether diluents and fluorinated lithium salts are prone to decomposition during battery use. On the one hand, they decompose rapidly and produce a large amount of fluorinated compounds. These fluorinated compounds form a solid electrolyte interface film with high impedance, a high lithium-ion transport barrier, and unevenness on the negative electrode surface, limiting the application of the electrolyte in high-rate scenarios. On the other hand, as the battery is used, the fluorinated ether diluents gradually decompose completely, leading to the failure of the high-lithium-concentration regions.

[0033] To address the above problems, the present invention provides the following solution:

[0034] In a first aspect, the present invention provides an electrolyte comprising: a fluorocarbonate compound and a nitro organic compound.

[0035] In this invention, the introduction of fluorocarbonate compounds and nitro organic compounds into the electrolyte effectively improves the rate performance and cycle stability of the battery. The main reasons include: the introduction of fluorocarbonate compounds into the electrolyte affects the solvation structure of the electrolyte system, replacing the decomposition of other fluorinated reagents and inducing their decomposition products to deposit uniformly at the electrode interface, reducing the proportion of fluorinated compounds in the solid electrolyte interfacial film, and promoting the formation of a thin and dense solid electrolyte interfacial film. Simultaneously, nitro organic compounds exhibit superior redox reactions at the solid-liquid interface compared to other solvents, and their decomposition products also participate in the formation of the electrode solid electrolyte interfacial film, helping to increase the proportion of nitrogen-containing inorganic phases in the solid electrolyte interfacial film, thereby enhancing the lithium-ion conductivity and mechanical strength of the interfacial film and reducing interfacial side reactions. Furthermore, the organic nitro additives can react with trace amounts of water and hydrofluoric acid in the electrolyte, thereby mitigating the destructive effects of water and hydrofluoric acid on the battery system.

[0036] For the reasons mentioned above, the electrolyte of the present invention can improve both the rate performance and cycle stability of the battery by regulating the decomposition sequence of the components and inducing the decomposition products to form a thin and dense solid electrolyte interface film with good lithium-ion conductivity.

[0037] It should be noted that the electrolyte described above is universal and can be used not only in lithium-ion battery systems, but also in sodium-ion batteries and zinc-ion batteries.

[0038] When used in lithium-ion battery systems, fluorinated ether diluents and fluorinated lithium salts can be further introduced to form localized high lithium salt concentration regions on the electrode surface or in specific areas, improving lithium-ion transport at the electrode / electrolyte interface. At the same time, since fluorinated carbonate compounds and nitro organic compounds synergistically replace the decomposition of fluorinated ether diluents, the aforementioned high lithium salt concentration regions can be kept stable, thereby simultaneously improving the rate capability and cycle stability of the battery.

[0039] In one specific embodiment, the fluorocarbonate compound includes the compound shown in Formula 1 and / or the compound shown in Formula 2:

[0040] Formula 1,

[0041] Equation 2,

[0042] R1 and R2 are each independently a fluorinated or unsubstituted C1-C20 alkyl group, a fluorinated or unsubstituted C2-C20 alkenyl group, and at least one of R1 and R2 includes a fluorinated substituent; R3 and R4 are each independently a fluorinated or unsubstituted C1-C20 alkyl group, a fluorinated or unsubstituted C2-C20 alkenyl group, a fluorinated group, and at least one of R3 and R4 includes a fluorine atom.

[0043] Fluorocarbonate compounds with the structure described above can not only affect the solvation structure of the electrolyte system, replace the decomposition of other fluorinated reagents, and induce their decomposition products to be uniformly deposited at the electrode interface, promoting the formation of a thin and dense solid electrolyte interface film, but also maintain good solubility in a variety of solvents, thereby ensuring the consistency of the electrolyte.

[0044] In some embodiments, the C1-C20 alkyl group can be a C1-C20 straight-chain alkyl group or a C3-C20 straight-chain alkyl group.

[0045] In one specific embodiment, the nitro organic compound includes the compound shown in Formula 3:

[0046] Formula 3,

[0047] R4 to R9 are each independently one of nitro, H, cyano, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted alkenyl, and at least one of R4 to R9 is nitro.

[0048] Nitro organic compounds with the structure described above can maintain good solubility in a variety of solvents, thus ensuring the consistency of the electrolyte. Furthermore, as additives, they readily decompose during battery charging and discharging to participate in SEI formation, thereby regulating the SEI composition.

[0049] In some embodiments, the C1-C20 alkyl group can be a C1-C20 straight-chain alkyl group or a C3-C20 straight-chain alkyl group.

[0050] In some embodiments, at least one of R4 to R9 is a cyano group. When at least one of R4 to R9 is a cyano group, the cyano group and the nitro group can together increase the proportion of nitrogen-containing inorganic phase (such as Li3N, LiN) in the solid electrolyte interfacial film. x O y (Inorganic components, etc.), thereby further enhancing the lithium-ion conductivity of the interfacial film, which helps to further improve the rate performance of the battery. In addition, cyano groups have a strong binding ability with water and HF, which can alleviate the destructive effect of HF on the battery system.

[0051] In one specific embodiment, the fluorocarbonate compound includes one or more of methyl trifluoroethyl carbonate, ethyl trifluoroethyl carbonate, bis(2-fluoroethyl) carbonate, bis(2,2,2)-trifluoroethyl carbonate, propylene trifluorocarbonate, propylene difluorocarbonate, ethylene fluorocarbonate, and ethylene difluorocarbonate.

[0052] As described above, fluorinated carbonate compounds not only ensure the decomposition of other fluorinated reagents and induce and promote the formation of thin and dense solid electrolyte interfacial films from the decomposition products, but also have the advantages of being inexpensive and readily available, which can further reduce the cost of electrolytes.

[0053] In one specific embodiment, the nitro organic compound includes one or more of the following: 3-nitrophthalonitrile, 4-nitrophthalonitrile, o-nitrobenzonitrile, m-nitrobenzonitrile, p-nitrobenzonitrile, 3,5-dinitrobenzonitrile, 4-methyl-3-nitrobenzonitrile, 2-methoxy-5-nitrobenzonitrile, 4-methoxy-2-nitrobenzonitrile, 2-amino-5-nitrobenzonitrile, o-nitrophenylacetonitrile, m-nitrophenylacetonitrile, p-nitrophenylacetonitrile, and 4-nitrobenzoylacetonitrile.

[0054] As mentioned above, nitro organic compounds can further enhance the lithium-ion conductivity and mechanical strength of solid electrolyte interfacial membranes, while also having the advantages of being inexpensive and readily available, which can further reduce the cost of electrolytes.

[0055] In one specific embodiment, the fluorocarbonate compound accounts for 1-5% of the total volume of the electrolyte.

[0056] In one specific embodiment, the electrolyte further includes an electrolyte salt, wherein the nitro organic compound accounts for 0.2-10% of the molar percentage of the electrolyte salt.

[0057] The addition of fluorocarbonate compounds, as described above, can further ensure a low overall viscosity of the electrolyte and avoid altering the properties of the SEI layer, making it too thick or uneven.

[0058] The addition of the nitro organic compound as described above can further enhance the lithium-ion conductivity and mechanical strength of the solid electrolyte interface film, while avoiding unnecessary side reactions with the electrode material.

[0059] In one specific embodiment, the electrolyte further includes a fluorinated lithium salt, an ether solvent, and a fluorinated ether diluent.

[0060] As described above, introducing ether solvents and fluorinated ether diluents into the electrolyte can create localized high lithium salt concentration regions on the electrode surface or in specific areas, further improving lithium-ion transport at the electrode / electrolyte interface. Meanwhile, since fluorinated carbonate compounds and nitro organic compounds synergistically replace the decomposition of fluorinated ether diluents, the aforementioned high lithium salt concentration regions can be kept stable, thereby further improving the rate capability and cycle stability of the battery.

[0061] It is understandable that the aforementioned fluorinated lithium salts are electrolyte salts.

[0062] In one specific embodiment, the fluorinated lithium salt includes one or more of lithium difluorosulfonylimide, lithium trifluoromethylsulfonylimide, lithium difluorooxalate borate, and lithium difluorophosphate.

[0063] And / or, the ether solvent includes one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and 1,3-dioxolane.

[0064] And / or, the fluorinated ether diluent includes one or more of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, dichloromethane, dichlorobutane, and trifluoromethoxybenzene.

[0065] As mentioned above, fluorinated lithium salts, ether solvents, and fluorinated ether diluents have the advantages of being inexpensive and readily available. Furthermore, electrolytes containing these components can form localized high lithium salt concentration regions on the electrode surface or in specific areas, further improving lithium-ion transport at the electrode / electrolyte interface.

[0066] In one specific embodiment, the molar concentration of the fluorinated lithium salt in the electrolyte is 2-5 mol·L⁻¹.-1 ;

[0067] And / or, the volume ratio of the ether solvent to the fluorinated ether diluent is 1:(1-6).

[0068] The electrolyte described above can further improve lithium-ion transport at the electrode / electrolyte interface while maintaining a low electrolyte viscosity.

[0069] For example, the molar concentration of the fluorinated lithium salt in the electrolyte is 2.0 mol·L⁻¹. -1 2.5 mol·L -1 3.0 mol·L -1 3.5 mol·L -1 4.0 mol·L -1 4.5 mol·L -1 5.0 mol·L -1 Any value in the range or a range consisting of both.

[0070] The volume ratio of the ether solvent to the fluorinated ether diluent is any one of 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, etc.

[0071] In a second aspect, the present invention provides a battery comprising the electrolyte described in the first aspect.

[0072] Because it contains the electrolyte mentioned above, this battery has excellent cycle performance and rate performance.

[0073] In one specific embodiment, in addition to the electrolyte provided by this invention, the battery also includes a positive electrode, a negative electrode, and a separator. During the charging and discharging process, active metal ions repeatedly insert and extract between the positive and negative electrode, while the electrolyte acts as a conductor of ions between them. The separator is disposed between the positive and negative electrode, primarily to prevent short circuits between them, while simultaneously allowing ions to pass through.

[0074] This application does not limit the type of separator, and any separator material in existing batteries can be used. For example, separators include, but are not limited to, single-layer PP (polypropylene) membranes, single-layer PE (polyethylene) membranes, double-layer PP / PE membranes, double-layer PP / PP membranes, and triple-layer PP / PE / PP membranes.

[0075] For example, the above-mentioned positive electrode sheet includes a positive electrode active material, which includes, but is not limited to: LiCoO2, LiMn2O4, LiMnO2, Li2MnO4, LiFePO4, Li 1+a Mn 1-b M b O2, LiCo1-b M b O2, LiFe 1-b M b PO4, Li2Mn 1-b O4, LiNi x Co y Mn z At least one of O2, M is selected from one or more of Ni, Co, Mn, Al, Cr, Mg, Zr, Mo, V, Ti, B, and F, 0≤a<0.2, 0≤b<1, and x+y+z=1.

[0076] For example, the aforementioned negative electrode sheet includes a negative electrode material, which can be a conventional material in the art, including but not limited to: carbonaceous materials, silicon-carbon materials, alloy materials, and one or more lithium-containing metal composite oxides. Furthermore, the negative electrode material can be one or more of graphite, soft carbon, hard carbon, silicon, silicon oxides, silicon-carbon composites, and lithium titanate.

[0077] For example, the battery described above can be prepared by a method including the following process: stacking the positive electrode, separator and negative electrode in sequence to obtain a battery cell, or stacking the positive electrode, separator and negative electrode in sequence and then winding them to obtain a battery cell; placing the battery cell in a battery packaging film shell (such as an aluminum-plastic film shell), injecting electrolyte into the outer packaging and sealing it to obtain the battery of the present invention.

[0078] Thirdly, the present invention provides a battery pack comprising at least two batteries as described in the second aspect.

[0079] Typically, a battery pack includes at least two of the aforementioned batteries, which are connected as individual cells to form a battery array. These batteries can be electrically connected using methods conventional in the art, such as series connection, parallel connection, or a combination of these connection methods.

[0080] Fourthly, the present invention provides an electrical device comprising the battery described in the second aspect or the battery pack described in the third aspect.

[0081] The electrical equipment used in the embodiments of the present invention can be conventional electrical equipment in the art, such as power equipment (e.g., electric vehicles, electric cars), electronic equipment (e.g., mobile phones, tablets, laptops, digital cameras, etc.), wearable devices (e.g., watches, bracelets, VR glasses, etc.), energy storage power stations, etc., and there are no particular limitations on this.

[0082] The technical solution of the present invention will be further illustrated below with reference to specific embodiments. All parts, percentages and ratios recorded in the following embodiments are based on weight. All reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing. The instruments used in the embodiments are also commercially available.

[0083] Example 1

[0084] This example provides an electrolyte, including additives: 3-nitrophthalonitrile and methyltrifluoroethyl carbonate;

[0085] Its preparation method includes the following steps:

[0086] (1) Mix 1 mol of battery-grade lithium difluoroformyl sulfonate, 0.05 mol of 3-nitrophthalonitrile, and 250 ml of ethylene glycol dimethyl ether containing 6 wt% methyl trifluoroethyl carbonate, and dissolve by vigorous stirring to form a transparent and uniform high-concentration electrolyte; the solvent needs to be dried by molecular sieve to a moisture content of less than 20 ppm before use.

[0087] (2) Add 750 ml of anhydrous 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether diluent to the above high-concentration electrolyte and stir until homogeneous to obtain the electrolyte.

[0088] Example 2

[0089] The only difference from Example 1 is that 3-nitrophthalonitrile is replaced with 2-methoxy-5-nitrobenzonitrile.

[0090] Example 3

[0091] The only difference from Example 1 is that 0.05 mol of 3-nitrophthalonitrile is replaced with 0.08 mol of 3-nitrophthalonitrile.

[0092] Examples 4-10

[0093] The only difference from Example 1 is that the type and / or content of additives are changed, as detailed in Table 1.

[0094] Comparative Example 1

[0095] The preparation method of the electrolyte in this example includes the following steps:

[0096] (1) Dissolve battery-grade lithium bisfluorosulfonylimide in anhydrous 1,2-dimethoxyethane solvent by vigorous stirring to form a transparent and uniform high-concentration electrolyte, and obtain a solution with a lithium salt concentration of 4M.

[0097] (2) Add 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether diluent to the above high-entropy high-concentration electrolyte, wherein the volume ratio of solvent to diluent is 1:3, and the electrolyte is obtained after stirring evenly.

[0098] Comparative Examples 2-3

[0099] The only difference from Example 1 is that the additive content has changed, as shown in Table 1.

[0100] Test case

[0101] The preparation of an NCM|Li half-cell using the above electrolyte includes the following steps:

[0102] Preparation of positive electrode sheet: NCM622 positive electrode powder (molecular formula LiNi) was prepared in a mass ratio of 90:5:5:100. 0.6 Mn 0.2 Co 0.2 O2), conductive carbon black, polyvinylidene fluoride (PVDF) and N-methylpyrrolidone. Add PVDF to N-methylpyrrolidone, stir evenly, then add conductive carbon black, stir evenly again, then add NCM622 in batches, stir evenly, then coat the slurry onto aluminum foil, vacuum dry at 90℃ for 6 hours, and press into a disc with a diameter of 14 mm.

[0103] Battery assembly: The positive electrode, polypropylene separator, and lithium metal sheet are assembled into a button cell in sequence, and an appropriate amount of the electrolyte obtained in each embodiment and comparative example is added.

[0104] The following performance characteristics of the NCM|Li half-cell were tested:

[0105] The NCM|Li half-cells of the examples and comparative examples were first subjected to a small current charge-discharge cycle of 0.1C / 0.1C for 3 cycles to form a stable SEI film. Then, their rate capability and cycle capability were tested in a 3-4.5V window. The discharge rates for the rate test were 0.2C, 0.5C, 1C, and 2C, and the number of cycles for the cycle test was 100 cycles (0.5C). The test results are shown in Table 1.

[0106] The test results are summarized in Table 1.

[0107] Table 1:

[0108]

[0109] As shown in Table 1, compared with the comparative example, the electrolyte used in the embodiment can significantly improve the cycle performance and rate performance of the battery.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrolyte, characterized in that, The additives include fluorinated ether diluents, fluorinated carbonate compounds, and nitro organic compounds; the nitro organic compounds include one or more of the following: 3-nitrophthalonitrile, 4-nitrophthalonitrile, o-nitrobenzonitrile, m-nitrobenzonitrile, p-nitrobenzonitrile, 3,5-dinitrobenzonitrile, 4-methyl-3-nitrobenzonitrile, 2-methoxy-5-nitrobenzonitrile, 4-methoxy-2-nitrobenzonitrile, 2-amino-5-nitrobenzonitrile, o-nitrophenylacetonitrile, m-nitrophenylacetonitrile, p-nitrophenylacetonitrile, and 4-nitrobenzoylacetonitrile.

2. The electrolyte according to claim 1, characterized in that, The fluorocarbonate compounds include the compounds shown in Formula 1 and / or the compounds shown in Formula 2: Formula 1, Equation 2, R1 and R2 are each independently a fluorinated or unsubstituted C1-C20 alkyl group, a fluorinated or unsubstituted C2-C20 alkenyl group, and at least one of R1 and R2 includes a fluorinated substituent; R3 and R4 are each independently a fluorinated or unsubstituted C1-C20 alkyl group, a fluorinated or unsubstituted C2-C20 alkenyl group, a fluorinated group, and at least one of R3 and R4 includes a fluorine atom.

3. The electrolyte according to claim 2, characterized in that, The fluorocarbonate compounds include one or more of the following: methyl trifluoroethyl carbonate, ethyl trifluoroethyl carbonate, di(2-fluoroethyl) carbonate, bis(2,2,2)-trifluoroethyl carbonate, propylene trifluorocarbonate, propylene difluorocarbonate, ethylene fluorocarbonate, and ethylene difluorocarbonate.

4. The electrolyte according to any one of claims 1-3, characterized in that, The fluorocarbonate compound accounts for 1-5% of the total volume of the electrolyte; And / or, the electrolyte further includes an electrolyte salt, wherein the nitro organic compound accounts for 0.2-10% of the molar percentage of the electrolyte salt.

5. The electrolyte according to claim 4, characterized in that, The electrolyte includes fluorinated lithium salts and ether solvents.

6. The electrolyte according to claim 5, characterized in that, The fluorinated lithium salt includes one or more of lithium difluorosulfonylimide, lithium trifluoromethylsulfonylimide, lithium difluorooxalate borate, and lithium difluorophosphate; And / or, the ether solvent includes one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and 1,3-dioxolane; And / or, the fluorinated ether diluent includes one or more of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, dichloromethane, dichlorobutane, and trifluoromethoxybenzene.

7. The electrolyte according to claim 6, characterized in that, The electrolyte contains a fluorinated lithium salt with a molar concentration of 2-5 mol·L⁻¹. -1 ; And / or, the volume ratio of the ether solvent to the fluorinated ether diluent is 1:(1-6).

8. A battery, characterized in that, Includes the electrolyte as described in any one of claims 1-7.

9. A battery pack, characterized in that, It includes at least two batteries as described in claim 8.

10. An electrical appliance, characterized in that, Includes the battery of claim 8 or the battery pack of claim 9.

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