An aromatic fluoronitrile-based electrolyte material, an electrolyte and a battery

Abstract

The present application relates to the technical field of electrolyte, and particularly relates to an aromatic fluoronitrile electrolyte material, an electrolyte and a battery. The aromatic fluoronitrile electrolyte material comprises aromatic hydrocarbon and ether group, fluorine group and nitrile group, and the rest of the groups are selected from at least one of hydrogen group, alkyl group and alkenyl group. Through the cooperation of the aromatic hydrocarbon structure fragment, the nitrile group structure fragment, the fluorine group structure fragment and the ether group structure fragment, the electrolyte material with high pressure resistance, high ionic conductivity and good long cycle performance is obtained, the types of the high pressure resistant fluoronitrile electrolyte are expanded, and the electrical performance of the fluoronitrile electrolyte is further improved. Meanwhile, the battery designed based on the above electrolyte has higher safety performance and allows higher charging voltage. In addition, the improvement of the ionic conductivity and the reduction of the interface resistance can effectively improve the fast charging capacity of the battery, and the stable SEI film impedance can effectively improve the cycle performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of electrolyte technology, and more particularly to an aromatic fluoronitrile electrolyte material, an electrolyte, and a battery. Background Technology

[0002] Improving the energy density, fast charging, and long cycle performance of lithium-ion batteries is a current research focus. High-energy-density cathode materials (such as ternary lithium and lithium nickel manganese oxide) generally require high charging voltages. However, traditional carbonate electrolytes are prone to oxidation and decomposition when charged above 4.3V, leading to electrolyte consumption, increased interfacial resistance, and increased gas production, thus limiting the capacity utilization of the cathode material and the battery's fast charging and cycle capabilities. Furthermore, ester electrolytes have drawbacks such as difficulty in forming a stable interfacial film at the positive and negative electrode interfaces, further inhibiting the battery's fast charging and cycle performance. Therefore, developing an electrolyte with high voltage resistance, high ionic conductivity, and the ability to easily form excellent interfacial films is essential.

[0003] Studies have found that aliphatic or aromatic nitrile electrolytes possess advantages such as high voltage resistance, non-flammability, high flash point, wide liquid range, low gas generation, and high ionic conductivity, making them a promising choice for battery systems with higher charging cut-off voltages. However, further research has revealed that nitrile electrolytes struggle to form excellent SEI films with electrode materials, are incompatible with negative electrode materials, and cannot guarantee long-term battery cycling, thus limiting their application.

[0004] To address this, numerous modifications have been made to nitrile electrolytes. For example, patent document CN116632358A discloses an electrolyte containing aromatic hydrocarbon nitrile compounds, comprising an electrolyte lithium salt, an organic solvent, and additives. The organic solvent is at least selected from aromatic hydrocarbon nitrile compounds, and the additives include fluoroethylene carbonate and lithium difluorooxalate borate, with the additives accounting for 1-20 wt% of the total amount of the electrolyte lithium salt and organic solvent. The aromatic hydrocarbon nitrile compound has a structural formula including an aromatic hydrocarbon, a nitrile group, and R1, R2, R3, R4, and R5 selected from at least one of hydrogen, a hydrocarbon group, a halogenated hydrocarbon group, and a halogen. For example, patent document CN117903001A discloses a type of partially fluorinated nitrile electrolyte material with the structural formula Rf-O-CH2CH2CN, wherein the -Rf group is selected from partially fluorinated C1-C10 alkyl groups; the -Rf group is selected from -CH2CH2F, -CH2CHF2, -CH2CH2CH2F, and -CH2CF2CHFCF2.

[0005] These existing technologies address the incompatibility of nitrile electrolytes with anode materials by replacing hydrogen atoms in aliphatic or aromatic nitrile electrolytes with fluorine, leveraging the excellent SEI film formation properties of fluorides. However, fluorination can reduce the solvation capacity of the solvent, making ion transport in the solvent more difficult and weakening the interaction between ions and solvent molecules. This reduces ion migration rate and ionic conductivity, affecting the electrolyte's electrical performance. Furthermore, the ability of fluorine substitution alone to improve the performance of nitrile electrolytes is limited. Summary of the Invention

[0006] The present invention aims to solve the above-mentioned problems by providing a fluoronitrile electrolyte material, electrolyte, and battery that has good compatibility with the negative electrode, excellent solvation ability, and good performance in terms of long-term cycling performance and ionic conductivity.

[0007] The technical solution to the problem solved by this invention is, first An aromatic fluoronitrile electrolyte material is provided, selected from compounds with the following general structural formula:

[0008]

[0009] Among them, at least one of R1, R2, R3, R4, R5, and R6 is selected from an ether-containing group, at least one is selected from a fluorine-containing group, at least one is selected from a nitrile-containing group, and the rest are selected from at least one of hydrogen-based, alkyl-based, and alkenyl-based groups.

[0010] In this application, the performance of the electrolyte is improved by the aromatic hydrocarbon and the substituted ether-containing, fluorine-containing, and nitrile-containing groups:

[0011] Aromatic hydrocarbon structural fragments can improve the ionic conductivity of electrolytes by enhancing their solvation structure and reducing viscosity. Nitrile-containing structural fragments effectively improve the electrolyte's high-voltage resistance, high-temperature resistance, low gas production, and high ionic conductivity. Fluorine-containing structural fragments can form excellent interfacial films and reduce interfacial resistance. Ether-containing structural fragments can improve the dissociation degree of electrolyte salts and the compatibility between the electrolyte and the negative electrode. Specifically, introducing ether-containing structural fragments into aromatic hydrocarbons with fluorine and nitrile structural fragments gives the molecule stronger polarity. Regarding compatibility with negative electrode materials, the higher electronegativity of the oxygen atoms may allow for dipole-dipole interactions with the negative electrode surface or react with active sites on the negative electrode surface to form chemical bonds, further increasing the interaction and compatibility between the two materials. This also improves the dissociation degree of electrolyte salts, or in other words, the degree of dissociation... Regarding conductivity, due to its strong polarity, it may more easily form a solvation shell with ions in the electrolyte, which helps reduce interactions and collisions between ions, lowers the resistance to ion migration, and improves ion solubility and mobility. Oxygen atoms may also form intramolecular or intermolecular hydrogen bonds or other interactions with fluorine atoms, which helps stabilize the microstructure of the electrolyte, reduce disordered ion movement and energy loss, thereby improving ion migration efficiency and conductivity. In addition, it may also affect the viscosity of the electrolyte, which helps reduce resistance to ion migration, making it more suitable for ion migration.

[0012] The choice of ether-containing, fluorine-containing, or nitrile-containing groups is not restricted, as long as ether-based, fluorine-based, or nitrile-based structural fragments can be provided.

[0013] As a preferred embodiment of the present invention, the fluorinated group is selected from fluorinated (-F) and fluorinated alkyl (-C) groups. x H y F z ), fluorinated alkenyl (-C x H y F z ), fluorinated alkoxy (-OC) x H y F z ), fluorinated olefins (-OC) x H y F z At least one of the following;

[0014] The nitrile group is selected from nitrile (-CN) and alkyl nitrile (-C). x H y CN), alkenyl nitrile (-C) x H y CN), alkoxynitrile (-OC) x H yCN), alkenoxynitrile (-OC) x H y At least one of CN);

[0015] The ether-containing group is selected from alkoxy (-OC) groups. x H y ), olefin (-OC) x H y ), fluorinated alkoxy (-OC) x H y F z ), fluorinated olefins (-OC) x H y F z ), alkoxynitrile (-OC) x H y CN), alkenoxynitrile (-OC) x H y At least one of CN).

[0016] It is understandable that ether-containing, fluorine-containing, and nitrile-containing groups are not necessarily three different groups. For example, fluorine-containing alkoxy groups and fluorine-containing olefinic groups (-OC) can be combined. x H y F z All of these contain both ether and fluorine structural segments, belonging to both fluorine-containing and ether-containing groups. When one of R1, R2, R3, R4, R5, and R6 is selected as a fluorine-containing alkoxy or fluorine-containing alkenoxy group, it can be considered that at this time, it satisfies the condition that "at least one is selected from a fluorine-containing group and at least one is selected from an ether-containing group." Similarly, alkoxynitriles and alkenoxynitriles (-OC) x H y CN) all contain ether group and nitrile group structural segments, belonging to both ether-containing and nitrile-containing groups. When one of R1, R2, R3, R4, R5, and R6 is selected as an alkoxynitrile or an alkenoxynitrile, it can be considered that at this time it satisfies "at least one is selected from an ether-containing group and at least one is selected from a nitrile-containing group".

[0017] Although the choice of ether-containing, fluorine-containing, and nitrile-containing groups is not restricted, further optimization in selection can further improve the electrical performance of electrolyte materials.

[0018] In fluorinated groups, the fluorine group can be on the aromatic ring or on an alkyl or alkoxy group outside the aromatic ring. In some Implementation To further reduce the adverse effects of fluorine groups on solvation, it is preferable to place the fluorine group on an alkyl or alkoxy group outside the aromatic ring. As a preferred embodiment of the present invention, the fluorine-containing group is selected from at least one of fluorinated alkyl, fluorinated alkenyl, fluorinated alkoxy, and fluorinated alkenyloxy groups.

[0019] In some implementation methods To further improve cycle performance, as a preferred embodiment of the present invention, at least one of R1, R2, R3, R4, R5, and R6 is selected from alkoxynitrile and alkenoxynitrile (-OC). x H y One of the CN). That is to say, by selecting a group containing both ether group and nitrile group structural segments, and by combining the ether group structural segment to the nitrile group structural segment, the compatibility of the ether group with the nitrile group and the negative electrode material can be further improved.

[0020] In this embodiment, at least one of R1, R2, R3, R4, R5, and R6 is selected from fluorinated groups. The fluorinated group can be a group containing only a fluorinated structural segment, or a group containing both a fluorinated structural segment and an ether structural segment; preferably, it is a group containing both a fluorinated structural segment and an ether structural segment. Specifically, at least one of R1, R2, R3, R4, R5, and R6 is selected from fluorinated alkoxy groups and fluorinated olefinic groups (-OC groups). x H y F z One of them.

[0021] The alkoxynitrile or alkenoxynitrile (-OC) x H y CN), and the position of the fluorine-containing group are not restricted; the alkoxynitrile or alkenoxynitrile (-OC) x H y CN) can be located at the ortho, meta, or para position of the fluorinated group. Preferably, the alkoxynitrile or alkenoxynitrile (-OC) is... x H y CN) represents the ortho or para position of the fluorinated group.

[0022] In this embodiment, for example, the aromatic fluoronitrile electrolyte material may be selected from at least one of 2 / 3 / 4-(fluoromethyl)phenoxyacetonitrile, 2 / 3 / 4-(difluoromethyl)phenoxyacetonitrile, 2 / 3 / 4-(trifluoromethyl)phenoxyacetonitrile; 2 / 3 / 4-(2-fluoroethoxy)phenoxyacetonitrile, 2 / 3 / 4-(2,2,2-difluoroethoxy)phenoxyacetonitrile, and 2 / 3 / 4-(2,2,2-trifluoroethoxy)phenoxyacetonitrile. Wherein, "2 / 3 / 4" means that the group within the parentheses can be ortho, meta, or para-positioned in the oxyacetonitrile group.

[0023] In other implementations To further improve cycle performance and ionic conductivity, as a preferred embodiment of the present invention, at least one of R1, R2, R3, R4, R5, and R6 is selected from fluoroalkoxy and fluoroolefin (-OC) compounds. x H y F zOne of them. That is to say, a group containing both fluorine-based and ether-based structural segments is selected. By combining the ether-based structural segment with the fluorine-based structural segment, the polarity of the group is adjusted, the solvation ability of the fluorine-containing group is improved, and the compatibility between the fluorine group and the negative electrode material is further promoted.

[0024] In this embodiment, at least one of R1, R2, R3, R4, R5, and R6 is selected from groups containing nitrile groups. The nitrile group can be a group containing only a nitrile structural segment, or a group containing both a nitrile and an ether structural segment; preferably, it is a group containing both a nitrile and an ether structural segment. Specifically, at least one of R1, R2, R3, R4, R5, and R6 is selected from alkoxynitriles and alkenoxynitriles (-OC). x H y One of the CN).

[0025] Similarly, the fluorinated alkoxy or fluorinated olefin (-OC) x H y F z The position of the fluorinated alkoxy group or the fluorinated olefin group is not limited, and the fluorinated alkoxy group or the fluorinated olefin group (-OC) is not limited. x H y F z The ) can be ortho, meta, or para of the nitrile-containing group. Preferably, the fluorinated alkoxy or fluorinated olefin (-OC) group is... x H y F z () represents the ortho or para position of the nitrile-containing group.

[0026] In this embodiment, for example, the aromatic fluoronitrile electrolyte material may be selected from at least one of 2 / 3 / 4-(2-fluoroethoxy)benzonitrile, 2 / 3 / 4-(2,2-difluoroethoxy)benzonitrile, 2 / 3 / 4-(2,2,2-trifluoroethoxy)benzonitrile; 2 / 3 / 4-(2-fluoroethoxy)phenoxyacetonitrile, 2 / 3 / 4-(2,2-difluoroethoxy)phenoxyacetonitrile, 2 / 3 / 4-(2,2,2-trifluoroethoxy)phenoxyacetonitrile; 2,3 / 2,4 / 2,5 / 2,6 / 3,5-di-(2,2,2-trifluoroethoxy)benzonitrile. Wherein, "2 / 3 / 4" means that the group within the parentheses can be ortho, meta, or para-positioned in benzonitrile or phenoxyacetonitrile. "2,3 / 2,4 / 2,5 / 2,6 / 3,5-bis-(2,2,2-trifluoroethoxy)benzonitrile" means that when formonitrile is at the first position on benzene, the two 2,2,2-trifluoroethoxy groups can be at positions 2 and 3, or positions 2 and 4, or positions 2 and 5, or positions 2 and 6, or positions 3 and 5.

[0027] In some implementation methodsTo further improve cycle performance, based on the role of fluorides in forming excellent SEI films and the fact that the unfavorable solvation problem of fluorination has been solved through ether-based structural fragments, as a preferred embodiment of the present invention, the fluorinated group includes at least two fluorine substituents, thereby improving cycle performance by increasing the number of fluorine substituents. For example, the material may be selected from at least one of 2 / 3 / 4-(difluoromethyl)phenoxyacetonitrile, 2 / 3 / 4-(trifluoromethyl)phenoxyacetonitrile, 2 / 3 / 4-(2,2-difluoroethoxy)benzonitrile, 2 / 3 / 4-(2,2,2-trifluoroethoxy)benzonitrile, 2 / 3 / 4-(2,2-difluoroethoxy)phenoxyacetonitrile, 2 / 3 / 4-(2,2,2-trifluoroethoxy)phenoxyacetonitrile, and 2,3 / 2,4 / 2,5 / 2,6 / 3,5-bis-(2,2,2-trifluoroethoxy)benzonitrile.

[0028] More preferably, the fluorinated group is perfluorinated; for example, the material may be selected from 2 / 3 / 4-(trifluoromethyl)phenoxyacetonitrile, 2 / 3 / 4-(2,2,2-trifluoroethoxy)benzonitrile, 2 / 3 / 4-(2,2,2-trifluoroethoxy)phenoxyacetonitrile, 2,3 /

[0029] At least one of 2,4 / 2,5 / 2,6 / 3,5-bis-(2,2,2-trifluoroethoxy)benzonitrile.

[0030] Secondly Another object of the present invention is to provide an electrolyte, comprising an electrolyte salt and a solvent, wherein the solvent comprises any of the aromatic fluoronitrile electrolyte materials described above.

[0031] The solvent may also include at least one of other commonly used additives, such as cyclic carbonates, cyclic sulfates, sulfonates, phosphates, borates, nitriles, and ionic additives. Alternatively, no additives may be used. Preferably, the solvent is composed of any of the above-mentioned aromatic fluoronitrile electrolyte materials.

[0032] The choice of electrolyte salt is not limited; for example, lithium salts, sodium salts, potassium salts, etc., can be used. Preferably, the electrolyte salt is a lithium salt. More preferably, the electrolyte salt is selected from at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium difluorophosphate.

[0033] The amounts of electrolyte salt and aromatic fluoronitrile electrolyte material are not limited. Preferably, the ratio of the electrolyte salt to the aromatic fluoronitrile electrolyte material is 0.1–3 mol / L. Examples include 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L, 2.5 mol / L, 2.8 mol / L, and 3 mol / L.

[0034] The preparation method of this electrolyte is not limited. As a preferred embodiment of the present invention, the preparation of the electrolyte includes the following steps:

[0035] S1. Mix the aromatic fluoronitrile electrolyte material with the electrolyte salt in a certain proportion;

[0036] S2. Stir the mixture to fully dissolve the electrolyte salts.

[0037] at last Another object of the present invention is to provide a battery comprising any of the electrolytes described above. The components of other battery structures are not limited.

[0038] The beneficial effects of this invention are:

[0039] 1. This application provides an aromatic fluoronitrile electrolyte material and an electrolyte, wherein the nitrile structural segment effectively improves the electrolyte's high voltage resistance, high temperature resistance, low gas generation, and high ionic conductivity; the aromatic hydrocarbon structural segment can improve the electrolyte's ionic conductivity by enhancing its solvation structure and reducing its viscosity; the fluorine structural segment can form an excellent interfacial film and reduce interfacial resistance; and the ether structural segment can improve the lithium salt's dissociation degree and the compatibility between the electrolyte and the lithium anode. Thus, an electrolyte material with high voltage resistance, high ionic conductivity, and good long-cycle performance is obtained, which not only expands the types of high-voltage fluoronitrile electrolytes but also further improves the electrical performance of fluoronitrile electrolytes.

[0040] 2. This application provides a battery based on the electrolyte design described above, which has higher safety performance, allows for higher charging voltage, and the improved ionic conductivity and reduced interface resistance can effectively improve the battery's fast charging capability. The stable SEI film impedance can effectively improve the battery's cycle performance. Detailed Implementation

[0041] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described, but the present invention is not limited to these embodiments.

[0042] Example 1

[0043] An aromatic fluoronitrile electrolyte material 2-Fluoro-4-methoxyphenylacetonitrile (C9H8FNO) was selected, specifically including -CH2CN at position 1, -F at position 2, and -OCH3 at position 4.

[0044] An electrolyte The electrolyte is composed of lithium bis(fluorosulfonyl)imide as the electrolyte salt and the aforementioned aromatic fluoronitrile electrolyte material as the solvent. This electrolyte is prepared by the following steps: In a glove box filled with high-purity argon, lithium bis(fluorosulfonyl)imide and the aromatic fluoronitrile electrolyte material are mixed at a ratio of 1 mol / L and stirred until the lithium salt is fully dissolved, thus obtaining the electrolyte.

[0045] A type of battery The electrode was prepared by the following steps: 0.93g of LiNi0.8Co0.1Mn0.1O2 powder, 0.04g of conductive carbon black, and 0.03g of binder PVDF were added to an agate mortar, and an appropriate amount of NMP solvent was added. The mixture was then ground until homogeneous. The slurry was then uniformly coated onto the surface of an aluminum foil (i.e., the positive electrode current collector) and vacuum dried at 60°C for 12 hours. The dried electrode sheet was cut into 12mm diameter discs and compacted to obtain the positive electrode. Using a lithium foil as the counter electrode and the electrolyte obtained above as the electrolyte, a coin cell (NCM / LE / Li) composed of graphite and lithium foil was assembled.

[0046] Example 2

[0047] This embodiment is basically the same as Embodiment 1, except that the aromatic fluoronitrile electrolyte material is 2-(fluoromethyl)phenoxyacetonitrile (C9H8FNO), specifically, it includes aromatic hydrocarbons, ortho-CH2F and -OCH2CN.

[0048] Example 3

[0049] This embodiment is basically the same as Embodiment 1, except that the aromatic fluoronitrile electrolyte material is 2-(2-fluoroethoxy)benzonitrile (C9H8FNO), specifically, it includes aromatic hydrocarbons, ortho-OCH2CH2F and -CN.

[0050] Example 4

[0051] This embodiment is basically the same as Embodiment 1, except that the aromatic fluoronitrile electrolyte material is 2-(fluoromethoxy)phenylacetonitrile (C9H8FNO), specifically: including aromatic hydrocarbons, ortho-OCH2F and -CH2CN.

[0052] Example 5

[0053] This embodiment is basically the same as Embodiment 1, except that the aromatic fluoronitrile electrolyte material is 2-(difluoromethyl)phenoxyacetonitrile (C9H7F2NO), specifically: including aromatic hydrocarbons, ortho-CHF2 and -OCH2CN.

[0054] Example 6

[0055] This embodiment is basically the same as Embodiment 1, except that the aromatic fluoronitrile electrolyte material is 2-(trifluoromethyl)phenoxyacetonitrile (C9H6F3NO), specifically, it includes aromatic hydrocarbons, ortho-CF3 and -OCH2CN.

[0056] Example 7

[0057] This embodiment is basically the same as Embodiment 1, except that the aromatic fluoronitrile electrolyte material is 2-fluorophenoxypropionitrile (i.e., 3-(2-fluorophenoxy)propionitrile, C9H8FNO), specifically: including aromatic hydrocarbons, ortho-F and -OCH2CH2CN.

[0058] Example 8

[0059] This embodiment is basically the same as Embodiment 1, except that: the aromatic fluoronitrile electrolyte material is 2-fluoro-4,5-dimethoxyphenylacetonitrile (C... 10 H 10 Specifically, FNO2 includes aromatic hydrocarbons, -CH2CN at position 1, -F at position 2, and -OCH3 at positions 4 and 5.

[0060] Example 9

[0061] This embodiment is basically the same as Embodiment 1, except that: the aromatic fluoronitrile electrolyte material is 2-(2-fluoroethoxy)phenoxyacetonitrile (C 10 H 10 FNO2), specifically: including aromatic hydrocarbons, ortho-OCH2CH2F and -OCH2CN.

[0062] Example 10

[0063] This embodiment is basically the same as Embodiment 2, except that the aromatic fluoronitrile electrolyte material is 3-(fluoromethyl)phenoxyacetonitrile (C9H8FNO), specifically, it includes aromatic hydrocarbons, meta-CH2F and -OCH2CN.

[0064] Example 11

[0065] This embodiment is basically the same as Embodiment 2, except that the aromatic fluoronitrile electrolyte material is 4-(fluoromethyl)phenoxyacetonitrile (C9H8FNO), specifically: including aromatic hydrocarbons, para-CH2F and -OCH2CN.

[0066] Example 12

[0067] This embodiment is basically the same as Embodiment 1, except that the aromatic fluoronitrile electrolyte material is 2-fluoro-4-methoxybenzonitrile (C8H6FNO), specifically: including -CN at position 1, -F at position 2, and -OCH3 at position 4.

[0068] Comparative Example 1

[0069] This comparative example is basically the same as Example 1, except that the electrolyte material used is a commercially available ester.

[0070] Comparative Example 2

[0071] This comparative example is basically the same as Example 1, except that the electrolyte material used is phenylacetonitrile, which does not have fluorine-containing groups or ether-containing groups.

[0072] Comparative Example 3

[0073] This comparative example is basically the same as Example 1, except that the electrolyte material used is 2-fluorophenylacetonitrile, which does not have an ether group.

[0074] Comparative Example 4

[0075] This comparative example is basically the same as Example 1, except that the electrolyte material used is p-methoxyphenylacetonitrile, which does not have fluorine-containing groups.

[0076] Comparative Example 5

[0077] This comparative example is basically the same as Example 1, except that the electrolyte material is a mixture of 2-fluorophenylacetonitrile and tetrahydrofuran in a mass ratio of 3:7.

[0078] Performance testing was performed on the electrolytes or batteries obtained in the examples and comparative examples.

[0079] Electrolyte ionic conductivity: The ionic conductivity of the electrolyte is measured using an ionic conductivity meter.

[0080] Electrolyte high voltage resistance: Assemble a coin cell (SS / LE / Li) consisting of lithium and steel sheets, and determine the electrochemical stability window of the electrolyte, i.e., the high voltage resistance of the electrolyte, by means of LSV.

[0081] Battery rate performance and cycle performance: 0.93g LiNi0.8Co0.1Mn0.1O2 powder, 0.04g conductive carbon black, and 0.03g binder PVDF were added to an agate mortar, and an appropriate amount of NMP solvent was added. The mixture was then ground until homogeneous. The slurry was then uniformly coated onto the surface of aluminum foil (i.e., the positive electrode current collector) and vacuum dried at 60℃ for 12h. The dried electrode sheet was cut into 12mm diameter discs and compacted to obtain the positive electrode. Using a lithium sheet as the counter electrode and the above solution as the electrolyte, a coin cell (NCM / LE / Li) consisting of graphite and lithium sheets was assembled. The rate performance and cycle performance of the battery were determined through testing.

[0082] The test results are shown in Table 1 below.

[0083] Table 1.

[0084]

[0085] As shown in Table 1, the comparative examples and Comparative Example 1 demonstrate that the aromatic fluoronitrile electrolyte material of this application exhibits good performance in terms of ionic conductivity, initial decomposition voltage, rate performance, and capacity retention after 500 cycles (i.e., long-term cycling performance).

[0086] Comparing Example 1 and Comparative Examples 2-5, it can be seen that in this application, the aromatic nitrile and its substituted fluorine and ether structural segments work synergistically to achieve improvements in ionic conductivity and long-term cycling performance. Specifically:

[0087] Regarding ionic conductivity, Comparative Example 2 used phenylacetonitrile, and Comparative Example 3 used 2-fluorophenylacetonitrile, which only added a fluorine-based structural fragment compared to Comparative Example 2, resulting in a decrease in ionic conductivity. Comparative Example 4 used p-methoxyphenylacetonitrile, which only added an ether-based structural fragment compared to Comparative Example 2. Although the ionic conductivity was improved to some extent, the improvement rate was less than that of Example 1, which used both fluorine-based and ether-based structural fragments. This may be because the combined effect of the ether-based and fluorine-based structural fragments helps to stabilize the microstructure of the electrolyte, reduce the disordered movement of ions and energy loss, thereby further improving the ionic conductivity.

[0088] Regarding long-term cycle performance, Comparative Example 2 used phenylacetonitrile, Comparative Example 3 used 2-fluorophenylacetonitrile, which only added a fluorine-based structural segment compared to Comparative Example 2, and Comparative Example 4 used p-methoxyphenylacetonitrile, which only added an ether-based structural segment compared to Comparative Example 2. Although Comparative Examples 3 and 4 could improve the long-term cycle performance of the battery to a certain extent, the improvement rate was less than that of Example 1, indicating that the ether-based structural segment and the fluorine-based structural segment can further synergistically improve the long-term cycle performance of the battery.

[0089] In Comparative Example 5, although it contains aromatic nitrile, fluorine-based structural fragments and ether-based structural fragments, the ether-based structural fragments are not on the aromatic nitrile, so its improvement in ionic conductivity and long-term cycling performance is not as good as that of Example 1. This may be because the ether-based structural fragments in Comparative Example 5 cannot adjust the polarity of the aromatic fluoronitrile.

[0090] Furthermore, the comparison within the examples also shows that by further optimizing the functional groups on the electrolyte material, a technical solution can be obtained that improves ionic conductivity and long-term cycling performance. Specifically:

[0091] Examples 1, 2, 3, and 4 have the same molecular formula, but Example 1 uses 2-fluoro-4-methoxyphenylacetonitrile, with the nitrile, fluorine, and ether segments distributed within three separate groups. Example 2 uses 2-(fluoromethyl)phenoxyacetonitrile, with the ether and nitrile segments within a single group. Compared to Example 1, Example 2 shows further improvements in ionic conductivity and long-term cycling performance, possibly because the ether segment is attached to the nitrile segment, further enhancing the compatibility between the ether and nitrile groups and the anode material. In Examples 3 and 4, the ether and fluorine segments are within the same group, also showing further improvements in ionic conductivity and long-term cycling performance compared to Example 1. This is likely because the ether segment is attached to the fluorine segment, further adjusting the polarity of the group, improving the solvation ability of the fluorine-containing group, and further promoting compatibility between the fluorine group and the anode material. Furthermore, a comparison of Examples 3 and 4 reveals that the position of the methyl group in the ether, fluorine, and nitrile groups has little impact on electrical performance.

[0092] Building upon this, Examples 8 and 9 were compared. Example 8 used 2-fluoro-4,5-dimethoxyphenylacetonitrile, adding a methoxy group compared to Example 1, which slightly improved ionic conductivity and long-term cycling performance, but the improvement was not significant. Example 9 had the same molecular formula as Example 8, but in Example 9, the ether and nitrile structural fragments were in the same group, and the ether and fluorine structural fragments were in the same group. As mentioned above, this significantly improved ionic conductivity and long-term cycling performance.

[0093] In Examples 2, 5, and 6, increasing the number of fluorine substitutions to two significantly improved long-term cycling performance; increasing it to three slightly improved long-term cycling performance. Furthermore, it was unexpectedly found that ionic conductivity also increased with the increase in the number of fluorine-driven substitutions. This may be because, under the ether-based structural segment, more fluorine groups can form more stable microstructures with it, thereby reducing the disordered movement of ions.

[0094] Example 7 has the same molecular formula as Example 2, but in Example 7, the fluorine group is directly attached to the aromatic hydrocarbon, while in Example 2, the fluorine group is attached to the methyl group. The ionic conductivity and long-term cycling performance of Example 2 are relatively high, indicating that the indirect attachment of the fluorine group to the aromatic hydrocarbon can reduce the adverse effects of fluorination on solvation.

[0095] In Examples 2, 10, and 11, the fluoromethyl groups were located at the ortho, meta, and para positions of the oxyacetonitrile, respectively. However, the changes in ionic conductivity and long-term cycling performance were not significant, indicating that the position of the group had little effect on its electrical properties. However, the electrical properties of the ortho and para positions were slightly better than those of the meta position.

[0096] Compared to Example 1, Example 12 had one less methyl group, but the changes in ionic conductivity and long-term cycling performance were minimal, indicating that the number of methyl groups had virtually no impact on its electrical properties. This, compared with Comparative Examples 2 and 3, demonstrates that the changes in ionic conductivity and long-term cycling performance in Comparative Examples 2 and 3 compared to Example 1 were mainly due to the addition of fluorine and ether groups, and were unrelated to the reduction of the methyl group.

[0097] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. An electrolyte comprising an electrolyte salt and a solvent, characterized in that: The solvent is composed of aromatic fluoronitrile electrolyte materials; the aromatic fluoronitrile electrolyte materials are selected from compounds with the following general structure: ， Among R1, R2, R3, R4, R5, R6, at least one is selected from ether groups, at least one is selected from fluorine-containing groups, at least one is selected from nitrile groups, and the rest are selected from hydrogen groups; The fluorine-containing group is selected from at least one of fluorine-containing alkyl groups and fluorine-containing alkoxy groups; The nitrile group is selected from at least one of nitrile groups, alkyl nitriles, and alkoxy nitriles; The ether group is selected from at least one of alkoxy groups, fluorine-containing alkoxy groups, and alkoxy nitriles.

2. An electrolyte according to claim 1, characterized in that: At least one of R1, R2, R3, R4, R5, and R6 is an alkoxy nitrile.

3. An electrolyte according to claim 2, wherein: The alkoxy nitrile is at the ortho position or para position of the fluorine-containing group.

4. An electrolyte according to claim 1 or 2, characterized in that: At least one of R1, R2, R3, R4, R5, and R6 is a fluorine-containing alkoxy group.

5. An electrolyte according to claim 1, characterized in that: The fluorine-containing group includes at least two fluorine substituents.

6. An electrolyte according to claim 1, characterized in that: The ratio of the electrolyte salt to the aromatic fluoronitrile electrolyte material is 0.1-3 mol / L.

7. A battery, characterized by: The electrolyte includes the electrolyte of any one of claims 1-6.

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