Electrolyte and lithium battery

Abstract

The present disclosure provides an electrolyte and a lithium battery. Specifically, the electrolyte comprises an additive; wherein the additive comprises at least one compound of formula (I): wherein R1 is selected from at least one of H, halogen, substituted or unsubstituted alkyl, and substituted or unsubstituted alkenyl. Such electrolyte can meet the fast charging performance requirement of the battery cell while taking into account the high temperature performance.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of batteries, and in particular to an electrolyte and a lithium battery. BACKGROUND

[0002] With the widespread use of electrochemical energy storage in portable electronic products and electric vehicles, the requirements and dependence on lithium ion batteries have become higher than ever. After decades of development, the main challenge for the widespread use of electric vehicles compared to traditional internal combustion engine vehicles is "range anxiety". In order to provide a similar experience to traditional internal combustion engine vehicles, it is usually required to be able to charge about 400 kilometers of range in 15 minutes. However, ultra-fast charging brings new challenges to battery materials, which require further improvement of lithium ion transport in electrolyte and charge transfer kinetics at the electrode / electrolyte interface. SUMMARY

[0003] Therefore, the purpose of the present disclosure is to provide an electrolyte and a lithium battery.

[0004] To achieve the above purpose, the present disclosure provides an electrolyte, comprising an additive; wherein the additive comprises at least one compound of formula (I):

[0005]

[0006] wherein R1 is selected from at least one of H, halogen, substituted or unsubstituted alkyl, and substituted or unsubstituted alkenyl.

[0007] In some embodiments, the substituents of the alkyl and the alkenyl are each independently selected from halogen, -OH, -NO2, -CN, and -NH2.

[0008] In some embodiments, the alkyl is selected from C1-C8 alkyl; and / or the alkenyl is selected from C2-C8 alkenyl.

[0009] In some embodiments, the content of the additive is 0.1%-3%, optionally 0.3%-1%, based on the total mass of the electrolyte.

[0010] In some embodiments, further comprising a carboxylic acid ester; the content of the carboxylic acid ester is >50%, based on the total mass of the electrolyte.

[0011] In some embodiments, further comprising a cyclic carbonate; the content of the cyclic carbonate is <5%, based on the total mass of the electrolyte.

[0012] In some embodiments, further comprising a fluorinated cyclic carbonate; the content of the fluorinated cyclic carbonate is 4%-9%, based on the total mass of the electrolyte.

[0013] Optionally, the fluorinated cyclic carbonate includes fluorinated ethylene carbonate.

[0014] In some embodiments, the electrolyte further includes a lithium salt, the lithium salt including at least one of LiPF6 and LiFSI.

[0015] Optionally, the content of LiFSI is greater than the content of LiPF6, based on the total mass of the electrolyte.

[0016] Based on the same inventive concept, the second aspect of the present disclosure further provides a lithium battery including the electrolyte according to any one of the preceding embodiments.

[0017] In some embodiments, the positive active material of the lithium battery includes at least one of lithium iron phosphate, lithium nickel manganese oxide, lithium-rich manganese-based, lithium manganese iron phosphate, lithium cobalt oxide and ternary material; and / or

[0018] The negative electrode of the lithium battery includes at least one of graphite, silicon and silicon oxide.

[0019] As can be seen from the above, the present disclosure provides an electrolyte and a lithium battery, wherein the electrolyte includes an additive; wherein the additive includes at least one compound of formula (I): wherein R1 is selected from at least one of H, halogen, substituted or unsubstituted alkyl and substituted or unsubstituted alkenyl. In such a technical solution, the compound of formula (I) can be combined with the lithium salt, change the solvation structure of lithium ions, and improve the lithium ion conductivity; at the same time, the compound of formula (I) can be preferentially decomposed over other solvents, which is conducive to the formation of an interface composition rich in inorganic Li3N and Li-S compounds in the electrode interface film. These inorganic components can improve the ion conductivity and thermal stability of the interface, improve the kinetic performance of the battery cell, and thus meet the fast charging performance requirements of the battery cell while improving the interface stability at high temperatures. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the present disclosure more clear, the present disclosure is further described in detail below in combination with specific embodiments.

[0021] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present disclosure should be understood as the usual meaning understood by those skilled in the art to which the present disclosure belongs.

[0022] The "range" used in the embodiments of the present disclosure is defined in the form of lower limit and 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 the specific range. The range defined in this way can include or not include the end value, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if the ranges of 60-130 and 70-120 are listed for a specific parameter, it is understood that the ranges of 60-120 and 70-130 are also expected. In addition, if the minimum range values of 1 and 2 are listed, and if the maximum range values of 3, 4 and 5 are listed, the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present disclosure, unless otherwise specified, the numerical range "a-b" represents a shorthand notation for any real 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" have been listed herein, and "0-5" is only a shorthand notation for these numerical combinations. In addition, when it is stated that a parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0023] Unless otherwise specified, all embodiments and optional embodiments of the present disclosure can be combined with each other to form new technical solutions.

[0024] Unless otherwise specified, all technical features and optional technical features of the present disclosure can be combined with each other to form new technical solutions.

[0025] Unless otherwise specified, the "includes" and "contains" mentioned in the present disclosure represent open-ended and closed-ended. For example, the "includes" and "contains" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0026] Unless otherwise specified, in the present disclosure, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B".

[0027] In the related art, in order to improve the charging efficiency of the lithium battery and realize super-fast charging, a common method is to introduce carboxylate into the electrolyte. However, the introduction of carboxylate is easy to cause the decline of high-temperature performance, such as the decline of high-temperature storage performance and high-temperature cycle performance.

[0028] Electrolyte

[0029] Therefore, the embodiments of the present disclosure provide an electrolyte, the electrolyte comprises an additive; wherein the additive comprises at least one compound of formula (I): wherein R1 is selected from at least one of H, halogen, substituted or unsubstituted alkyl, and substituted or unsubstituted alkenyl. Here, the halogen can be F, Cl, Br, I, etc., which are not limited by the present disclosure. The alkyl can be a straight-chain alkyl, a branched-chain alkyl, or a cyclic alkyl. Exemplarily, the straight-chain alkyl can be methyl, ethyl, butyl, etc.; the branched-chain alkyl can be isopropyl, isobutyl, tert-butyl, etc.; the cyclic alkyl can be cyclohexyl, cyclopropyl, cyclobutyl, etc., which are not limited by the present disclosure. Here, the alkenyl can be vinyl, propenyl, etc., which are not limited by the present disclosure.

[0030] The electrolyte provided by the present disclosure can improve the fast-charging performance of the lithium battery while taking into account the high-temperature cycling and high-temperature storage performance, which is conducive to the long-term stable operation of the lithium battery. Here, the lithium battery can be a primary lithium battery or a secondary lithium battery, which are not limited by the present disclosure.

[0031] The compound of formula (I) containing S, N, and O can be combined with a lithium salt to change the solvation structure of lithium ions and improve the lithium ion conductivity. Meanwhile, the compound of formula (I) can be preferentially decomposed over other solvents, which is conducive to the formation of an interface component rich in inorganic Li3N and Li-S compounds in the electrode interface film. These inorganic components can improve the ion conductivity and thermal stability of the interface and improve the kinetic performance of the battery cell, thereby meeting the demand of the battery cell for fast-charging performance while improving the interface stability at high temperatures.

[0032] In some embodiments, the substituents of the alkyl and the alkenyl are each independently selected from halogen, -OH, -NO2, -CN, and -NH2.

[0033] In some embodiments, the alkyl is selected from C1-C8 alkyl, such as C1-C6 alkyl, C1-C4 alkyl. In some embodiments, the alkenyl is selected from C2-C8 alkenyl, such as C2-C6 alkenyl, C2-C5 alkenyl, C2-C4 alkenyl.

[0034] It should be understood that the more the number of carbon atoms of the alkyl or alkenyl, the lower the relative content of S, N, and O in formula (I), and the lower the number of inorganic components formed in the electrode interface film. The C1-C8 alkyl and alkenyl are conducive to ensuring that the compound of formula (I) effectively improves the fast-charging performance and takes into account the high-temperature performance.

[0035] In some embodiments, the additive is present in an amount of 0.1% to 3%, for example 0.1%, 0.14%, 0.2%, 0.52%, 1.13%, 1.5%, 2.15%, 2.4%, 3%, or optionally 0.3% to 1%, based on the total mass of the electrolyte. If the additive is present in an amount less than 0.1%, it is difficult to improve the fast-charging performance and ensure the high-temperature cycle performance. If the additive is present in an amount greater than 3%, the improvement of the high-temperature performance is weakened.

[0036] In some embodiments, the electrolyte further comprises a cyclic carbonate. The cyclic carbonate is present in an amount of less than 5%, for example 2%, 3%, 4%, or the like, based on the total mass of the electrolyte.

[0037] For example, the cyclic carbonate comprises at least one of propylene carbonate (PC) and ethylene carbonate (EC). The cyclic carbonate has a high dielectric constant, which helps to dissolve lithium salt and make it uniformly distributed in the electrolyte, thereby improving the kinetic performance of the lithium battery. A low amount of EC can reduce the viscosity of the electrolyte and also improve the kinetic performance of the lithium battery. If the cyclic carbonate is present in an amount greater than 5%, for example 10%, the direct current resistance of the lithium battery is still reduced, and the high-temperature cycle stability and storage performance of the lithium battery are improved, but the improvement effect is weaker than when the cyclic carbonate is present in an amount less than 5%.

[0038] In some embodiments, the electrolyte further comprises a fluorinated cyclic carbonate. Optionally, the fluorinated cyclic carbonate comprises fluorinated ethylene carbonate (FEC). Further, the fluorinated cyclic carbonate is present in an amount of 4% to 9%, for example 4%, 5%, 7%, 9%, or the like, based on the total mass of the electrolyte. The FEC in the above amount can compensate for the problem of lithium salt dissolution caused by a low amount of EC, and the FEC can also participate in film formation to improve the cycle performance of the lithium ion battery.

[0039] In some embodiments, the electrolyte further comprises a carboxylic acid ester, for example methyl acetate (MA), ethyl acetate (EA), ethyl propionate (EP), propyl acetate (PA), and propyl propionate (PP). Further, the carboxylic acid ester is present in an amount of greater than 50%, for example 60%, 70%, 75%, 80%, or the like, based on the total mass of the electrolyte. Here, a high amount of carboxylic acid ester can further reduce the viscosity of the electrolyte and improve the conductivity, thereby improving the kinetic performance of the lithium ion battery.

[0040] It should be noted that different carboxylic acid esters can be added alone or in combination to the electrolyte, and the present disclosure does not limit the same.

[0041] In some embodiments, the electrolyte further comprises a lithium salt, the lithium salt comprising at least one of LiPF6and LiFSI. Optionally, the content of LiFSI is greater than the content of LiPF6, based on the total mass of the electrolyte. Here, the use of LiFSI in place of part of LiPF6can effectively improve the kinetic performance of the lithium ion battery.

[0042] Lithium battery

[0043] The second aspect of the present disclosure provides a lithium battery comprising the electrolyte provided in the foregoing aspects of the present disclosure.

[0044] In some embodiments, the lithium battery comprises a positive electrode sheet, a negative electrode sheet, a separator between the positive electrode sheet and the negative electrode sheet, and an electrolyte. During the charging and discharging of the battery, active ions are inserted and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent short circuiting between the positive and negative electrodes, while allowing ions to pass through.

[0045] Positive electrode sheet

[0046] The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, the positive electrode film layer comprising a positive electrode active material.

[0047] Exemplarily, the positive electrode current collector has two opposite surfaces in the thickness direction thereof, and the positive electrode film layer is arranged on either one or both of the two opposite surfaces of the positive electrode current collector.

[0048] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be used. The composite current collector can comprise a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base material (such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0049] In some embodiments, the positive electrode active material comprises at least one of lithium iron phosphate (LiFePO4), lithium nickel manganese phosphate, lithium-rich manganese-based, lithium manganese iron phosphate, lithium cobalt oxide (LCO), and ternary material.

[0050] For ternary material, it can be lithium nickel cobalt manganese oxide (LiNi x Co y Mn z O2, and x+y+z=1), for example, LiNi 1 / 3Co 1 / 3 Mn 1 / 3 O2(also can be referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(also can be referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2(also can be referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2(also can be referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(also can be referred to as NCM811).

[0051] In some embodiments, the positive electrode film layer further optionally includes a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0052] In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent can include at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0053] In some embodiments, the positive electrode tab can be prepared by dispersing the above-mentioned components for preparing the positive electrode tab, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on a positive electrode current collector, and after processes such as drying, cold pressing, etc., the positive electrode tab can be obtained.

[0054] Negative electrode sheet

[0055] The negative electrode tab includes a negative electrode current collector and optionally a film layer disposed on at least one surface of the negative electrode current collector.

[0056] As an example, the film layer can include a negative electrode active material, a conductive agent, a thickening agent, a binder.

[0057] In some embodiments, the negative electrode active material can be at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon, and silicon oxide, for example, a graphite and silicon mixture, a graphite and silicon oxide mixture.

[0058] In some embodiments, the negative electrode sheet can be prepared by dispersing the negative electrode active material, the conductive agent, the thickening agent, the binder and any other components in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on a negative electrode current collector, and then drying, cold-pressing, etc. to obtain the negative electrode sheet.

[0059] Separator film

[0060] In some embodiments, the secondary battery further comprises a separator. The type of the separator is not particularly limited in the present disclosure, and any known porous separator having good chemical stability and mechanical stability can be used.

[0061] In some embodiments, the separator can be made of at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0062] Examples

[0063] Hereinafter, examples of the present disclosure will be described. The examples described below are exemplary and are intended to explain the present disclosure, and should not be construed as limiting the present disclosure. In the examples, specific techniques or conditions not described are performed according to the techniques or conditions described in the literature in the art or according to the product manual. The reagents or instruments not described by the manufacturer are all conventional products that can be obtained commercially.

[0064] Examples 1 to 22

[0065] (1) Preparation of the positive electrode:

[0066] The positive electrode active material LiFePO4, the conductive agent acetylene black and the binder polyvinylidene fluoride were dissolved in NMP at a mass ratio of 95:3:2, mixed uniformly, coated on an aluminum foil, dried, rolled, cut to obtain the positive electrode sheet.

[0067] (2) Preparation of the graphite negative electrode:

[0068] The negative electrode active material was artificial graphite, the conductive agent was acetylene black, and the binder was sodium carboxymethyl cellulose (CMC-Na). The negative electrode active material, the conductive agent and the binder were added to deionized water at a mass ratio of 96:2:2, mixed uniformly, coated on a copper foil, dried, rolled, cut to obtain the negative electrode sheet.

[0069] (3) Preparation of the electrolyte:

[0070] In an argon atmosphere glove box with water content <10 ppm, the solvents were mixed and stirred according to the proportions in Examples 1-22 to form the total organic solvent, the lithium salt was added to the mixed solvent under stirring, and the stirring was continued until the lithium salt was completely dissolved, and finally the additive was added to the solution and stirred uniformly.

[0071] Here, the proportional relationship of the lithium salt, the additive and the solvent in Examples 1-22 is shown in Table 1.

[0072] It should be noted that the additive of Example 1-Example 19 is as follows: Formula (I-1);

[0073] The additive of Example 20 is as follows:

[0074] The additive of Example 21 is as follows:

[0075] The additive of Example 22 is as follows:

[0076] The mass percentage of the lithium salt and the additive in Table 1 is the mass percentage calculated based on the total mass of the electrolyte. EMC in Table 1 represents methyl ethyl carbonate.

[0077] (4) Preparation of the battery:

[0078] The above prepared negative electrode, separator and positive electrode were sequentially stacked in order with polypropylene film as the separator film, and were packed in an aluminum plastic film to obtain a dry cell, and the dry cell was baked at 80°C to remove water. The electrolyte was injected into the dry cell to obtain a finished lithium ion battery.

[0079] Comparative examples 1 and 2

[0080] Comparative Examples 1-4 and Example 1 differ in the composition of the electrolyte in step (3), as shown in Table 1.

[0081] Table 1

[0082]

[0083] Test method

[0084] The lithium batteries prepared in the above examples and comparative examples can be tested by the following method:

[0085] (1) Cycle test, the test method is as follows:

[0086] The lithium ion battery was charged at 45°C with a constant current of 1 / 3C to 4.35V, and then charged with a constant voltage until the current was 0.05C. The battery was discharged with a constant current of 1 / 3C to 2.5V, and the capacity C0was recorded. The above charging and discharging steps were repeated 800 times, and the discharge capacity C1of 800 cycles was recorded. The capacity retention rate of the battery = C1 / C0x 100%.

[0087] (2) Direct Current Resistance (DCR) test, the test method is as follows:

[0088] The lithium ion battery was charged at 25°C with a constant current of 1 / 3C to 4.35V, and then charged with a constant voltage until the current was 0.05C. The battery was discharged with a constant current of 1 / 3C to 2.5V. The above charging steps were repeated, and the charging capacity was recorded as C2. The battery was discharged with a constant current of 1 / 3C to (50% x C2), and the initial voltage was recorded as V2. The battery was discharged with a constant current of 1C2for 30s, and the terminal voltage was recorded as V3. DCR = (V2-V3) / (C2x 1).

[0089] (3) High temperature storage test, the test method is as follows:

[0090] The lithium ion battery was stored at 60°C for 60 days. The battery was then discharged at 25°C with a constant current of 1 / 3C to 2.5V, and then charged with a constant current of 1 / 3C to 4.35V, and then charged with a constant voltage until the current was 0.05C. The battery was discharged with a constant current of 1 / 3C to 2.5V, and the discharge capacity C3was recorded. The capacity recovery rate was (C3 / C2) x 100%.

[0091] The test results are shown in Table 2.

[0092] Table 2

[0093]

[0094] Comparing Comparative Example 1, Example 1, and Examples 20-22, it can be seen that the addition of the compounds of formula (I-1) to (I-3) not only reduces the direct current resistance of the battery, but also helps to achieve fast charging, and improves the high temperature storage performance and high temperature cycle performance of the battery. The addition of the compound of formula (I-4) increases the ethylene substitution resistance, which increases the direct current resistance, but it also improves the high temperature storage performance and high temperature cycle performance of the battery.

[0095] Comparing Examples 1-4, it can be seen that, under the condition that the content of the cyclic carbonate does not exceed 4% of the total mass of the electrolyte, the addition of the cyclic carbonate helps to reduce the direct current resistance.

[0096] Comparing Comparative Example 2, Example 5 and Example 9, it can be seen that the addition of the compound of formula (I-1) can significantly improve the high-temperature storage performance and high-temperature cycle performance of the battery cell. Comparing Example 5 and Example 9, it can be seen that increasing the amount of LiFSI added increases the direct current resistance, but the level is close, and the high-temperature storage performance and high-temperature cycle performance of the battery cell remain basically unchanged, and the comprehensive performance is better.

[0097] Comparing Example 1 and Example 18, it can be seen that when the content of carboxylic acid ester is less than 50%, the direct current resistance of the battery cell increases significantly, which is not conducive to fast charging. This may be because the decrease in the content of carboxylic acid ester increases the viscosity of the electrolyte and reduces the conductivity, affecting the kinetic performance of the battery cell.

[0098] Comparing Example 5 to Example 8 and Example 18, it can be seen that when the mass percentage of carboxylic acid ester in the electrolyte is greater than 50%, the combination of different carboxylic acid esters can reduce the direct current resistance of the battery cell, and the degree of reduction of the direct current resistance of the battery cell is different for different combinations of carboxylic acid esters. Among them, the combination of EA and MA reduces the direct current resistance of the battery cell most significantly.

[0099] Comparing Comparative Example 2, Example 5 and Example 10 to Example 13, it can be seen that the addition of the compound of formula (I-1) helps to improve the high-temperature performance of the battery cell. Specifically, as the mass percentage of the compound of formula (I-1) increases, the degree of improvement of the high-temperature performance of the battery cell shows a trend of first increasing and then decreasing. When the mass percentage of the compound of formula (I-1) is 0.3% and 1%, the direct current resistance of the battery cell increases slightly, and the high-temperature storage performance and high-temperature cycle performance are significantly improved. When the mass percentage is 0.5%, the direct current resistance of the battery cell remains stable, and the high-temperature storage performance and high-temperature cycle performance are significantly improved.

[0100] Comparing Comparative Example 1, Example 1 and Example 14, it can be seen that the electrolyte of Example 1 and Example 14 can reduce the direct current resistance of the battery cell and improve the high-temperature storage performance and high-temperature cycle performance of the battery cell. Compared to the electrolyte in Example 1, the content of the cyclic carbonate is less than 5%, and the content of the cyclic carbonate in the electrolyte in Example 14 is greater than 5%, the improvement of the direct current resistance and the high-temperature storage performance of the battery cell is weakened, and the improvement of the high-temperature cycle performance is slightly enhanced.

[0101] Comparing Example 1 and Example 15 to Example 17, it can be seen that the addition amount of FEC has a significant effect on the direct current resistance of the battery cell. Among them, when the addition amount of FEC in the electrolyte is between 4% and 9%, the direct current resistance of the battery cell decreases significantly, and beyond this range, the improvement of the direct current resistance decreases, and the improvement of the high-temperature performance also decreases slightly.

[0102] Comparing Example 1 and Example 19, it can be seen that LiFSI is more helpful to reduce the direct current resistance of the battery cell than LiPF6. This can be because the fluorine ion of LiFSI has strong electron-withdrawing property, which weakens the coordination between the anion and the cation of the lithium salt, and the lithium ion is more active.

[0103] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to suggest that the scope of the disclosure (including the claims) is limited to these examples; the embodiments of the disclosure or technical features between different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of the embodiments of the disclosure as described above, which are not provided in details for the sake of brevity.

[0104] The embodiments of the disclosure are intended to cover all such alternatives, modifications, and variations as fall within the broad scope of the appended claims. Accordingly, any one of the above-mentioned alternatives, modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the embodiments of the disclosure shall be included in the protection scope of the disclosure.

Claims

1. An electrolyte, characterized by, The electrolyte further comprises an additive; wherein the additive comprises at least one compound of Formula (I): Formula (I); wherein R1 is selected from at least one of H, halogen, substituted or unsubstituted alkyl, and substituted or unsubstituted alkenyl. The content of the additive is 0.1% to 3% based on the total mass of the electrolyte.

2. The electrolyte according to claim 1, characterized in that, The substituents of the alkyl and the alkenyl are each independently selected from halogen, -OH, -NO2, -CN, and -NH2.

3. The electrolyte according to claim 1 or 2, characterized in that, The alkyl is selected from C1-C8 alkyl; and / or the alkenyl is selected from C2-C8 alkenyl.

4. The electrolyte of claim 1, wherein The content of the additive is 0.3% to 1% based on the total mass of the electrolyte.

5. The electrolyte of claim 1, wherein The electrolyte further comprises a carboxylic acid ester; the content of the carboxylic acid ester is >50% based on the total mass of the electrolyte.

6. The electrolyte of claim 1, wherein The electrolyte further comprises a cyclic carbonate; the content of the cyclic carbonate is <5% based on the total mass of the electrolyte.

7. The electrolyte of claim 1, wherein The electrolyte further comprises a fluorinated cyclic carbonate; the content of the fluorinated cyclic carbonate is 4% to 9% based on the total mass of the electrolyte.

8. The electrolyte according to claim 7, characterized in that The fluorinated cyclic carbonate comprises fluorinated ethylene carbonate.

9. The electrolyte according to any one of claims 1 to 8, characterized in that, The electrolyte further comprises a lithium salt, the lithium salt comprises at least one of LiPF6 and LiFSI.

10. The electrolyte of claim 9, wherein, The content of LiFSI is greater than the content of LiPF6 based on the total mass of the electrolyte.

11. A lithium battery comprising the electrolyte of any one of claims 1-10.

12. The lithium battery of claim 11, wherein, The positive active material of the lithium battery comprises at least one of lithium iron phosphate, lithium nickel manganese oxide, lithium-rich manganese-based, lithium manganese iron phosphate, lithium cobalt oxide, and ternary material; and / or The negative electrode of the lithium battery comprises at least one of graphite, silicon, and silicon oxide.

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