An electrolyte, a lithium-ion battery, and an electrical device

Abstract

This application belongs to the technical field of secondary batteries, and particularly relates to an electrolyte, a lithium-ion battery and an electrical device. The electrolyte includes a lithium salt, an organic solvent and a negative electrode film-forming additive. The negative electrode film-forming additive includes a compound having a structure represented by formula (I) or formula (II). Among them, the B element in the negative electrode film-forming additive is connected to an unsaturated cyclic structure containing a double bond, which can improve the compatibility of the electrolyte, and can preferentially form a film on the negative electrode. In the presence of B and a five-membered or six-membered ring containing a double bond, etc., a B / P composite layer is formed, optimizing the film-forming impedance and enhancing the fast charging performance. At the same time, the negative electrode film-forming additive has high stability at high temperatures, can avoid the deterioration of the SEI film or gas generation, and improve the comprehensive performance of the battery.

Description

Technical Field

[0001] This application belongs to the technical field of secondary batteries, and particularly relates to an electrolyte, a lithium-ion battery, and an electrical device. Background Art

[0002] In the past few decades, lithium-ion batteries have become a research hotspot in social development. However, industries such as electric vehicles, logistics vehicles, and mobile phones have put forward more stringent requirements for battery performance, such as long cycle life, fast charging ability, etc. Among them, the excessively long charging time has been plaguing end-users.

[0003] Due to the slow kinetics of the negative electrode electrochemical reaction, the negative electrode side is regarded as one of the key factors restricting fast charging performance. The insertion of Li ions into the graphite electrode mainly includes four steps: (1) the diffusion and transport of Li ions in the bulk phase of the electrolyte; (2) the desolvation of solvated Li ions at the SEI; (3) the passage of Li ions through the SEI film; (4) the charge transfer at the SEI-graphite interface; (5) the diffusion of Li ions in the graphite bulk phase. To improve the fast charging ability of the graphite negative electrode, existing modification methods mainly include developing graphite composites, developing fast charging electrolytes, etc. Among them, developing fast charging electrolytes is one of the most effective methods to improve the fast charging ability and has become the main research direction in the field.

[0004] Adding a suitable additive to the electrolyte can form a film on the surface of the graphite negative electrode, which is beneficial to improving the transport ability of Li ions and thus improving the fast charging performance of the battery cell. However, negative electrode film-forming additives in the prior art, such as borates, have low solubility in the electrolyte or uneven film formation due to uneven distribution of polar groups, affecting the transport of Li ions; in addition, boron-containing additives (such as borate LiDFOB, LiBOB, etc.) are easily decomposed at high temperatures, which can cause deterioration of the SEI film or gas generation, affecting battery performance. Summary of the Invention

[0005] Therefore, the technical problem to be solved by this application is to overcome the defects such as the fast charging performance of lithium-ion batteries in the prior art needs to be further improved, so as to provide an electrolyte, a lithium-ion battery, and an electrical device.

[0006] To this end, this application provides the following technical solutions:

[0007] According to one aspect of this application, there is provided an electrolyte, including a lithium salt, an organic solvent, and a negative electrode film-forming additive, wherein the negative electrode film-forming additive includes a compound represented by the following formula (I) or formula (II):

[0008] Formula (I), Formula (II)

[0009] Wherein, R is independently selected from at least one of hydrogen, alkyl with 1 - 4 carbons, fluoroalkyl with 1 - 4 carbons, alkenyl with 2 - 4 carbons, siloxanyl with 1 - 4 carbons, and ester group with 2 - 4 carbons.

[0010] In some alternative embodiments, R is independently selected from at least one of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, tert - butyl, vinyl, propenyl, trifluoromethyl, (CH3)3SiO -, and CH3OCO -.

[0011] In some alternative embodiments, the negative electrode film - forming additive includes any of the following structures:

[0012]

[0013] In some alternative embodiments, based on the total mass of the electrolyte, the mass percentage content of the negative electrode film - forming additive is 0.2% - 1.5%. As an example, based on the total mass of the electrolyte, the mass percentage content of the negative electrode film - forming additive can be 0.2%, 0.4%, 0.5%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.5%, or within the range composed of any of the above values.

[0014] In some alternative embodiments, based on the total mass of the electrolyte, the electrolyte further includes other additives with a mass percentage content of 2.0% - 8.0%. The other additives include at least one of fluoroethylene carbonate, vinylene carbonate, and ethylene sulfate; as an example, based on the total mass of the electrolyte, the mass percentage content of the other additives in the electrolyte can be 2.0%, 2.5%, 3%, 4%, 5%, 5.5%, 6%, 7%, 8%, or within the range composed of any of the above values.

[0015] And / or, based on the total mass of the electrolyte, the mass percentage content of the lithium salt is 12.5% - 18%;

[0016] And / or, the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(oxalato)borate, lithium trioxalatophosphate (CAS: 321201 - 33 - 6), lithium difluoro(oxalato)borate, lithium tetrafluoro(oxalato)phosphate, and lithium difluoro - bis(oxalato)phosphate.

[0017] And / or, the organic solvent includes at least one of chain - like esters and cyclic esters.

[0018] In some alternative embodiments, the other additives are a mixture of fluoroethylene carbonate (FEC), vinylene carbonate (VC), and ethylene sulfate (DTD);

[0019] And / or, the lithium salt is a mixture of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide;

[0020] And / or, the chain ester includes at least one of ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, ethyl acetate, n-propyl acetate, ethyl propionate, and propyl propionate;

[0021] And / or, the cyclic ester includes at least one of ethylene carbonate and propylene carbonate.

[0022] In some alternative embodiments, the other additives include vinylene carbonate accounting for 1.0% - 4.0% of the total mass of the electrolyte, vinylene sulfate accounting for 0.5% - 1.5% of the total mass of the electrolyte, and fluoroethylene carbonate accounting for 0.5% - 1.5% of the total mass of the electrolyte;

[0023] And / or, the lithium salt includes lithium hexafluorophosphate accounting for 8% - 12% of the total mass of the electrolyte, and lithium bis(fluorosulfonyl)imide accounting for 4% - 8% of the total mass of the electrolyte; as an example, lithium hexafluorophosphate (LiPF6) in the lithium salt accounts for 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12% of the total mass of the electrolyte, or within the range composed of any of the above values; lithium bis(fluorosulfonyl)imide (LiFSI) in the lithium salt accounts for 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8% of the total mass of the electrolyte, or within the range composed of any of the above values.

[0024] And / or, the organic solvent is a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and ethyl acetate (EA).

[0025] In some alternative embodiments, the mass ratio of ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and ethyl acetate (EA) in the organic solvent is 25 - 45:10 - 20:10 - 40:15 - 45.

[0026] According to another aspect of the present application, a lithium-ion battery is provided, including the above-mentioned electrolyte.

[0027] According to another aspect of the present application, an electrical device is provided, including the above-mentioned lithium-ion battery.

[0028] Those skilled in the art can understand that the lithium-ion battery provided in this application, in addition to the above-mentioned electrolyte, further includes structural components such as a positive electrode plate, a negative electrode plate, a separator, and a housing. During the charging and discharging process of the battery, lithium ions are inserted and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The separator is disposed between the positive electrode plate and the negative electrode plate, mainly to prevent short circuit between the positive and negative electrodes, and at the same time allows lithium ions to pass through.

[0029] As an example, the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer. The positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material layer is disposed on either or both of the two surfaces opposite to the negative electrode current collector. The materials, compositions, and manufacturing methods of the positive electrode plates used in the lithium-ion batteries of this application can include any technologies disclosed in the prior art.

[0030] As an example, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer. The negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two surfaces opposite to the negative electrode current collector. The materials, compositions, and manufacturing methods of the negative electrode plates used in the lithium-ion batteries of this application can include any technologies disclosed in the prior art.

[0031] There is no particular limitation on the material shape of the separator used in the lithium-ion batteries of this application, and it can include any technologies disclosed in the prior art.

[0032] The electrolyte used in the lithium-ion batteries of this application can also include any technologies disclosed in the prior art.

[0033] This application does not specifically limit the preparation method of the lithium-ion battery, and the lithium-ion battery can be prepared by using conventional preparation methods in the art. For example, the positive electrode plate, the separator, and the negative electrode plate are stacked in sequence, with the separator located between the positive electrode plate and the negative electrode plate, and the battery core is obtained through the stacking or winding process. Then, through processes such as baking, liquid injection, formation, and encapsulation, the lithium-ion battery of this application can be obtained.

[0034] It can be understood that in the electrical equipment provided in this application, the lithium-ion battery can be used as the power source of the electrical equipment or as the energy storage unit of the electrical equipment. The electrical equipment can be, but is not limited to, mobile devices (such as mobile phones, laptop computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc. The electrical equipment has the same advantages as the above-mentioned lithium-ion battery compared with the prior art, which will not be elaborated here.

[0035] The technical solution of the present application has the following advantages:

[0036] The electrolyte provided by the present application includes a lithium salt, an organic solvent, and a negative electrode film-forming additive, and the negative electrode film-forming additive includes a compound represented by formula (I) or formula (II). Among them, in the additive having the structure shown in formula (I) or formula (II), the B element is connected to an unsaturated cyclic structure containing a double bond, which improves the compatibility of the electrolyte and can preferentially form a film on the negative electrode. In the presence of the B element and a five-membered or six-membered ring containing a double bond, etc., a B / P composite layer is formed, optimizing the film-forming impedance and enhancing the fast-charging performance. At the same time, the negative electrode film-forming additive has high stability at high temperatures, can avoid the deterioration of the SEI film or gas generation, and improves the comprehensive performance of the battery.

[0037] For the electrolyte provided by the present application, based on the total mass of the electrolyte, the mass percentage content of the negative electrode film-forming additive is 0.2% - 1.5%. By limiting the content of the negative electrode film-forming additive in the present application, the rate performance can be improved while minimizing the cost of the electrolyte. If the addition amount is too low, it will affect the formation of the SEI film on the negative electrode. If it is too high, the SEI film will be too thick, hindering the lithium ion transmission, reducing the battery capacity and rate performance, and at the same time significantly increasing the cost of the electrolyte.

[0038] For the electrolyte provided by the present application, LiPF6 has good conductivity and low cost at room temperature, but its thermal stability is poor, and it is easy to react with trace amounts of moisture to generate corrosive HF, resulting in the deterioration of the electrode / electrolyte interface. While LiFSI has higher conductivity (about 20% - 30% higher than LiPF6) and thermal stability (decomposition temperature > 200°C), which can make up for the defect that LiPF6 is easily decomposed at high temperatures. By using the two in combination, LiFSI can make up for the high-temperature defect of LiPF6 and improve the overall performance of the electrolyte. Using lithium hexafluorophosphate as the main salt can avoid a significant increase in the cost of the electrolyte due to the high price of LiFSI.

[0039] For the electrolyte provided by the present application, through the optimization of other additives, the combined use of fluoroethylene carbonate, vinylene carbonate, and ethylene sulfate can balance the interfacial impedance. Among them, VC is a relatively important additive in the lithium iron phosphate cycle system, which can further effectively improve the cycle life of lithium iron phosphate. However, at the same time, VC has a large impedance. The combined addition of FEC and DTD can form film-forming components containing LiF / containing S, etc. on the negative electrode to achieve the balance of the interfacial impedance.

[0040] The electrolyte provided by the present application, through the optimization of organic solvents, uses ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and ethyl acetate (EA) in combination. In addition to the conventional carbonate solvent system, the present application additionally adds the carboxylic acid ester EA, further reducing the viscosity of the solvent system, improving the overall conductivity of the electrolyte, and being able to further enhance the fast charge cycle performance.

[0041] Additional aspects and advantages of the present application will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0043] Figure 1 It is a physical diagram of the negative electrode plate after the fast charge cycle of the battery in Example 6 of the present application;

[0044] Figure 2 It is a physical diagram of the negative electrode plate after the fast charge cycle of the battery in Comparative Example 2 of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] The following embodiments are provided to better further understand the present application, which is not limited to the described best embodiment, and does not limit the content and protection scope of the present application. Any product that is the same as or similar to the present application obtained by anyone under the inspiration of the present application or by combining the features of the present application with other prior art features falls within the protection scope of the present application.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "including" and "having" and any variations thereof in the text of the present application are intended to cover non-exclusive inclusion.

[0047] References herein to "embodiments" mean that the particular features, structures, or characteristics described in connection with the embodiments can be included in at least one embodiment of the present application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0048] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The ranges defined in this way can include or exclude the end values and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. In the present application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter can be, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0049] In the description of the embodiments of the present application, the term "and / or" is merely a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone.

[0050] In the description of the embodiments of the present application, the term "at least one" refers to one or more than two (including two).

[0051] For those embodiments where specific experimental steps or conditions are not indicated, the operations or conditions of the conventional experimental steps described in the literature in this field can be followed. For reagents or instruments whose manufacturers are not indicated, they are all conventional reagent products that can be obtained through commercial purchase.

[0052] The following describes the present application with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present application in any way.

[0053] Example 1

[0054] This example provides an electrolyte, and its specific composition and preparation method are as follows:

[0055] The electrolyte is prepared as follows: In a glove box filled with argon (moisture < 0.1 ppm, oxygen content < 0.1 ppm), ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and ethyl acetate (EA) are mixed evenly in a mass ratio of 30:15:30:25 to obtain a mixed organic solvent. To the mixed organic solvent, 10.0% of LiPF6 and 6.0% of LiFSI based on the total mass of the electrolyte are added, and stirred until completely dissolved. Then, 0.5% of a negative electrode film-forming additive (with a structure shown as Ad1) and 2.5% of vinylene carbonate (VC) based on the total mass of the electrolyte are added, and after stirring evenly, the electrolyte is obtained.

[0056] Examples 2 - 17

[0057] Examples 2 - 17 provide an electrolyte. Compared with Example 1, the differences are shown in Table 1, and its preparation method and parameters are the same as those of Example 1.

[0058] Comparative Examples 1 - 6

[0059] Comparative Examples 1 - 6 provide an electrolyte, whose composition is shown in Table 1, and its preparation method and parameters are the same as those of Example 1.

[0060] Table 1 Electrolyte Compositions in Each Example and Comparative Example

[0061]

[0062] Test Example

[0063] The electrolytes provided in each example and comparative example are used in the preparation of lithium-ion batteries for various performance tests. The specific operations are as follows:

[0064] Fabrication of lithium-ion battery:

[0065] The positive electrode active material lithium iron phosphate, conductive agent acetylene black, carbon nanotubes, and binder polyvinylidene fluoride (PVDF) are fully stirred and mixed evenly in an N-methylpyrrolidone solvent system in a mass ratio of 95.5:2:0.5:2, and then coated on a carbon-coated aluminum foil, dried, and cold-pressed to obtain a positive electrode plate with a compaction density of 2.40 g / cm 3 , and a single-sided areal density of 145 g / m 2 ;

[0066] The negative electrode active material graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are fully stirred and mixed evenly in a deionized water solvent system in a mass ratio of 96:2:0.5:1.5, and then coated on a Cu foil, dried, and cold-pressed to obtain a negative electrode plate with a compaction density of 1.50 g / cm3 , with a single-sided areal density of 70 g / m 2 ;

[0067] Using polyethylene (PE) as the base film (7 μm, 45% porosity) and coating a nano-aluminum oxide coating (2 μm) on the base film as the separator;

[0068] Stack the positive electrode sheet, separator, and negative electrode sheet in sequence, with the separator in the middle of the positive electrode sheet and the negative electrode sheet to play an isolation role, and wind to obtain a bare battery cell. Place the bare battery cell in the outer package, inject the electrolytes prepared in each example and comparative example, and go through processes such as encapsulation, shelving, formation, aging, secondary encapsulation, and grading to obtain a soft-pack lithium iron phosphate battery (designed capacity 2 Ah). Perform performance tests on the batteries in each example and comparative example respectively.

[0069] (1) Fast charge performance test

[0070] Fast charge test: Under the condition of 25 °C, discharge the lithium-ion battery at a constant current of 0.33C until the voltage reaches 2.5V, then charge it at a constant current and constant voltage of 0.33C until the voltage reaches 3.65V, with a cut-off current of 0.05C. Repeat the above steps, and the charging rate is changed from 0.33C to 1C, 2C, 3C, and 5C respectively. Record the capacity in the constant current charging stage as C1, the capacity in the constant voltage charging stage as C2, and the fast charge performance (%) = C1 / (C1 + C2) × 100%.

[0071] (2) Fast charge cycle test

[0072] Under normal temperature (25 ± 2 °C) conditions, charge the lithium-ion battery at a constant current and constant voltage of 0.33C until the voltage reaches 3.65V, with a cut-off current of 0.05C, and discharge it at a constant current of 0.33C until the voltage reaches 2.5V. Take the discharge capacity as C0, and then perform 3C step charging and 0.5C discharging. The 3C step charging cycle steps are shown in Table 2. Record the discharge capacity (DC 200 ) and the first discharge capacity (DC0) after 200 cycles. The cycle life of the lithium-ion battery from the 200th cycle (%) = DC 200 / DC0 × 100%.

[0073] After 200 cycles, disassemble the battery cells in the examples and comparative examples, and observe the lithium deposition situation on the negative electrode sheet. Figure 1 It is a physical picture of the negative electrode sheet after the fast charge cycle of the battery in Example 6; Figure 2 It is a physical picture of the negative electrode sheet after the fast charge cycle of the battery in Comparative Example 2 of this application. As can be seen from the figure, there is no lithium deposition on the surface of the negative electrode sheet obtained by disassembling the example, while there is lithium deposition on the surface of the negative electrode sheet obtained by disassembling Comparative Example 2 (the position of the spots in the figure). There is no lithium deposition on the surface of the negative electrode sheets obtained by disassembling other examples, and the physical pictures are the same as Figure 1Close. There is lithium deposition on the surface of the negative electrode tab obtained by disassembling each other pair of ratios. The physical diagram is the same as Figure 2 Close, and will not be shown one by one.

[0074] Table 2 Step charging cycle process

[0075]

[0076] The specific test results are shown in the following table:

[0077] Table 3 Test results

[0078]

[0079] From the above data, it can be seen that the electrolyte provided by the embodiments of the present application can improve the fast charging performance and cycling performance by adopting a negative electrode film-forming additive with a specific structure.

[0080] Obviously, the above embodiments are only examples for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or variations derived therefrom are still within the protection scope of the present invention.

Claims

1. An electrolyte, characterized in that, It includes a lithium salt, an organic solvent and a negative electrode film-forming additive, and the negative electrode film-forming additive includes a compound represented by the following formula (I) or formula (II): Formula (I), Formula (II), Wherein, R is independently selected from at least one of hydrogen, an alkyl group with 1-4 carbons, a fluoroalkyl group with 1-4 carbons, an alkenyl group with 2-4 carbons, a siloxanyl group with 1-4 carbons, and an ester group with 2-4 carbons.

2. The electrolyte according to claim 1, wherein The R is independently selected from at least one of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, vinyl, propenyl, trifluoromethyl, (CH3)3SiO-, and CH3OCO-.

3. The electrolyte according to claim 2, characterized in that, The negative electrode film-forming additive includes a compound represented by any of the following structures: 。 4. The electrolyte according to any one of claims 1 to 3, characterized in that, Based on the total mass of the electrolyte, the mass percentage content of the negative electrode film-forming additive is 0.2% - 1.5%.

5. The electrolyte according to claim 1, characterized in that, Based on the total mass of the electrolyte, the electrolyte further includes other additives with a mass percentage content of 2.0% - 8.0%, and the other additives include at least one of fluoroethylene carbonate, vinylene carbonate, and ethylene sulfate; and / or, based on the total mass of the electrolyte, the mass percentage content of the lithium salt is 12.5% - 18%; and / or, the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(oxalato)borate, lithium trioxalatophosphate, lithium difluoro(oxalato)borate, lithium tetrafluoro(oxalato)phosphate, and lithium difluoro(bis(oxalato))phosphate; and / or, the organic solvent includes at least one of a chain ester and a cyclic ester.

6. The electrolyte according to claim 5, wherein The other additives are a mixture of fluoroethylene carbonate, vinylene carbonate, and ethylene sulfate; and / or, the lithium salt is a mixture of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide; and / or, the chain ester includes at least one of ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, ethyl acetate, n-propyl acetate, ethyl propionate, and propyl propionate; and / or, the cyclic ester includes at least one of ethylene carbonate and propylene carbonate.

7. The electrolyte according to claim 6, characterized in that, The other additives include 1.0% - 4.0% of vinylene carbonate, 0.5% - 1.5% of ethylene sulfate, and 0.5% - 1.5% of fluoroethylene carbonate based on the total mass of the electrolyte; ​ ​ 8. The electrolyte according to claim 7, characterized in that, ​ 9. A lithium-ion battery, characterized in that, ​ 10. An electrical device, characterized in that, ​

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