Electrolyte additive, electrolyte, battery

Abstract

The application relates to the technical field of energy storage. Specifically, it relates to an electrolyte additive, an electrolyte and a battery. The electrolyte additive provided by the application comprises a halogenated imidazole additive and a halogenated benzene additive; the halogenated imidazole additive is selected from one or more of compounds with structural characteristics shown in formula (I) or formula (II); and the halogenated benzene additive is selected from one or more of compounds with structural characteristics shown in formula (III). The electrolyte additive can effectively improve the liquid absorption speed, efficiently infiltrate the electrode, and improve the cycle stability of the battery.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, specifically to an electrolyte additive, an electrolyte, and a battery. Background Technology

[0002] Portable electronic products, such as cameras, telephones, and laptops, have increasingly higher requirements for standby time and battery life, which places higher demands on the energy density of energy storage devices such as lithium-ion batteries. Currently, the main way to improve the energy density of lithium-ion batteries is to increase the compaction density of the positive and negative electrode materials. However, this increases the transport distance between lithium ions and electrons, leading to a deterioration in charge transport kinetics. At the same time, it also has the disadvantage that the electrodes are difficult to wet with electrolyte.

[0003] To improve the wetting properties of the electrolyte, additives are typically added. For example, one method involves adding fluoroethylene carbonate to the electrolyte. While this additive can effectively improve initial efficiency, the resulting SEI film is unstable, leading to poor cycle stability. Summary of the Invention

[0004] Based on this, this application provides an electrolyte additive, an electrolyte, and a battery. The electrolyte additive provided by this application can effectively improve the liquid absorption rate, efficiently wet the electrodes, and also improve the cycle stability of the battery.

[0005] A first aspect of this application provides an electrolyte additive, including haloimidazolium additives and halobenzene additives;

[0006] The haloimidazole additives are selected from one or more compounds having the structural features shown in formula (I) or formula (II):

[0007] or ;

[0008] Among them, X 11 X 12 and X 13 Each of the following is independently H, OH, a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an alkynyl group having 2 to 5 carbon atoms; and X 11 X 12 and X 13 At least one of them is a halogen atom; R 11 It is a single bond, an alkylene group with 1 to 5 carbon atoms, an alkenyl group with 2 to 5 carbon atoms, or an ynylene group with 2 to 5 carbon atoms; R 12 It is a ketone group; R 13It is an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an alkynyl group having 2 to 5 carbon atoms;

[0009] X 21 X 22 X 23 X 24 X 25 and X 26 Each of the following is independently H, OH, a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an alkynyl group having 2 to 5 carbon atoms; and X 21 X 22 X 23 X 24 X 25 and X 26 At least one of them is a halogen atom; R 21 and R 23 Each is independently a single bond, an alkylene group with 1 to 5 carbon atoms, an alkenyl group with 2 to 5 carbon atoms, or an ynylene group with 2 to 5 carbon atoms; R 22 It is a ketone group;

[0010] The halobenzene additives are selected from one or more compounds having the structural features shown in formula (III):

[0011] X3 is a halogen atom, and R3 is H, OH, halogen atom, alkyl with 1 to 5 carbon atoms, alkoxy with 1 to 5 carbon atoms, alkenyl with 2 to 5 carbon atoms, or alkynyl with 2 to 5 carbon atoms.

[0012] In one embodiment, X 11 X 12 and X 13 Each is independently H, F, Cl, Br, I, or an alkyl group having 1 to 3 carbon atoms; and X 11 X 12 and X 13 At least one of them is a halogen atom; R 11 It is a single bond or an alkylene group having 1 to 3 carbon atoms; R 12 It is a ketone group; R 13 It is an alkyl group having 1 to 3 carbon atoms;

[0013] X 21 X 22 X 23 X 24 X 25 and X 26 Each is independently H, F, Cl, Br, I or an alkyl group having 1 to 3 carbon atoms, and X 21 X22 X 23 X 24 X 25 and X 26 At least one of them is a halogen atom; R 21 and R 23 Each is an alkylene group with a single bond and 1 to 3 carbon atoms; R 22 It is a ketone group;

[0014] X3 is F, Cl, Br or I, and R3 is H, F, Cl, Br, I, an alkyl group with 1 to 3 carbon atoms or an alkoxy group with 1 to 3 carbon atoms.

[0015] In one embodiment, X 11 X 12 and X 13 Each is independently H, F, Cl, Br, or I, and X 11 X 12 and X 13 At least one of them is a halogen atom; R 11 For a single bond, R 12 It is a ketone group, R 13 It is methyl or ethyl;

[0016] X 21 X 22 X 23 X 24 X 25 and X 26 Each is independently H, F, Cl, Br, or I, and X 21 X 22 X 23 X 24 X 25 and X 26 At least one of them is a halogen atom; R 21 For a single bond, R 23 R is a single bond or an alkylene group having 1 to 3 carbon atoms. 22 It is a ketone group;

[0017] X3 is F, Cl, Br or I, and R3 is F, Cl, Br, I, methyl or ethyl.

[0018] In one embodiment, the halogenated imidazole additive includes , and One or more of the following; wherein X is independently F, Cl, Br or I;

[0019] The halogenated benzene additives include , , , , and One or more of them.

[0020] In one embodiment, the mass ratio of the halogenated imidazole additive to the halogenated benzene additive is (0.8~1.2):1.

[0021] A second aspect of this application provides an electrolyte comprising a lithium salt, a solvent, and an additive, wherein the additive is the electrolyte additive described in any embodiment of the first aspect of this application.

[0022] In one embodiment, the electrolyte comprises 1% to 5% of the haloimidazole additive and 1% to 5% of the halobenzene additive, by mass percentage of the electrolyte.

[0023] In one embodiment, the lithium salt has a mass fraction of 10% to 14% as a percentage of the mass of the electrolyte.

[0024] In one embodiment, the lithium salt includes one or more of lithium hexafluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium difluorophosphate.

[0025] In one embodiment, the solvent comprises cyclic carbonates and chain carbonates; the electrolyte comprises 20% to 30% of the cyclic carbonates and 46% to 68% of the chain carbonates by mass percentage.

[0026] A third aspect of this application provides a battery that includes the electrolyte additive described in any embodiment of the first aspect of this application or the electrolyte described in any embodiment of the second aspect of this application.

[0027] The electrolyte additives provided in this application, by selecting haloimidazole and halobenzene additives with specific structures, achieve the following: Firstly, halobenzene additives can effectively adsorb onto the surface of the negative electrode to form a film, while haloimidazole additives can remove trace amounts of water and HF present in the electrolyte. The two work synergistically to continuously reduce byproducts of the SEI film and effectively improve the stability of the negative electrode SEI film, thereby suppressing lithium dendrite formation, reducing lithium-ion battery capacity decay, and improving cycle performance. Secondly, haloimidazole and halobenzene additives can reduce the surface tension of the electrolyte, improve the wettability of the electrolyte to the separator and electrode, and reduce the contact angle, thus effectively increasing the liquid absorption rate and efficiently wetting the electrode to improve lithium-ion transport and reduce battery internal resistance. Attached Figure Description

[0028] Figure 1This is a schematic diagram of the liquid absorption rate testing device selected in this application.

[0029] In the diagram, 10 is the capillary tube, 20 is the negative electrode sheet, 30 is the adhesive layer, 40 is the acrylic sheet, 50 is the bolt, and 60 is the nut. Detailed Implementation

[0030] The electrolyte additive, electrolyte, and battery of this application are further described in detail below with reference to specific embodiments. This application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0031] In this application, "alkyl" can refer to straight-chain, branched, and / or cyclic alkyl groups. Phrases containing this term, such as "alkyl group having 1 to 5 carbon atoms," refer to alkyl groups containing 1 to 5 carbon atoms, and each occurrence can independently be a C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, or C5 alkyl group. Non-limiting examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, isobutyl, 2-ethylbutyl, 3,3-dimethylbutyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, and cyclopentyl.

[0032] In this application, "alkoxy" refers to a group having an -O-alkyl group, i.e., an alkyl group as defined above connected to a parent nucleus via an oxygen atom. Phrases containing this term, such as "alkoxy group having 1 to 5 carbon atoms," mean that the alkyl moiety contains 1 to 5 carbon atoms, and each occurrence can be independently C1 alkoxy, C4 alkoxy, or C5 alkoxy. Suitable examples include, but are not limited to: methoxy (-O-CH3 or -OMe), ethoxy (-O-CH2CH3 or -OEt), and tert-butoxy (-OC(CH3)3 or -OtBu).

[0033] "Alkenyl" refers to a group containing at least one unsaturated site, i.e., carbon-carbon sp. 2 Hydrocarbons with a double bond consisting of a positive, secondary, tertiary, or cyclic carbon atom. Phrases containing this term, such as "alkenyl with 2 to 5 carbon atoms," refer to alkenyl groups containing 2 to 5 carbon atoms, which, each time appearing, can independently be C2-alkenyl, C3-alkenyl, C4-alkenyl, or C5-alkenyl. Suitable examples include, but are not limited to, vinyl (-CH=CH2), allyl (-CH2CH=CH2), and cyclopentenyl (-C5H7).

[0034] "Alynyl" refers to a hydrocarbon containing at least one unsaturated carbon atom, i.e., a carbon-carbon sp triple bond, or a cyclic carbon atom. Phrases containing this term, such as "alkynyl with 2 to 5 carbon atoms," refer to alkynyl groups containing 2 to 5 carbon atoms, and each occurrence can be independently C2-alkynyl, C3-alkynyl, C4-alkynyl, or C5-alkynyl. Suitable examples include, but are not limited to, ethynyl (-C≡CH) and propynyl (-CH2C≡CH).

[0035] "Alkylene" refers to a hydrocarbon group derived from an alkyl group by removing one hydrogen atom, forming a group with two monovalent groups. It can be a saturated branched alkyl group or a saturated straight-chain alkyl group. For example, "alkylene with 1 to 5 carbon atoms" means that the alkyl part contains 1 to 5 carbon atoms, and each occurrence can be independently C1 alkylene, C4 alkylene, or C5 alkylene. Suitable examples include, but are not limited to: methylene (-CH2-), 1,1-ethyl (-CH(CH3)-), 1,2-ethyl (-CH2CH2-), 1,1-propyl (-CH(CH2CH3)-), 1,2-propyl (-CH2CH(CH3)-), 1,3-propyl (-CH2CH2CH2-), and 1,4-butyl (-CH2CH2CH2CH2-).

[0036] "Alkenyl" refers to a hydrocarbon group derived from an alkenyl group by removing one hydrogen atom, forming a group with two monovalent groups at its center. This can be an unsaturated branched hydrocarbon group or an unsaturated straight-chain hydrocarbon group. For example, "alkenyl with 2 to 5 carbon atoms" means that the alkenyl moiety contains 2 to 5 carbon atoms, and each occurrence can be independently of a C2-alkenyl, C4-alkenyl, or C5-alkenyl. Suitable examples include, but are not limited to, 1,2-vinyl (-CH=CH-).

[0037] "Imyynyl" refers to a hydrocarbon group derived from an alkynyl group by removing one hydrogen atom, forming a group with two monovalent groups. It can be an unsaturated branched hydrocarbon group or an unsaturated straight-chain hydrocarbon group. For example, "Imyynyl with 2 to 5 carbon atoms" means that the alkynyl moiety contains 2 to 5 carbon atoms, and each occurrence can be independently C2-Imyynyl, C4-Imyynyl, or C5-Imyynyl. Suitable examples include, but are not limited to: ethynylene (-C≡C-), propynyl (-CH2C≡C-), and 4-pentynyl (-CH2CH2CH2C≡C-).

[0038] In this application, the single bonds connecting the substituents extend through the corresponding ring, indicating that the substituent can be connected to any position on the ring, for example... R is attached to any substituted site on the benzene ring. For example... R is attached to any substituted site on the benzene ring. For example, " "Refers to the presence of 1 to 6 R functional groups on the benzene ring. Suitable examples include, but are not limited to: , , , , , , , or .

[0039] A first aspect of this application provides an electrolyte additive, including haloimidazolium additives and halobenzene additives;

[0040] The haloimidazole additives are selected from one or more compounds having the structural features shown in formula (I) or formula (II):

[0041] or ;

[0042] Among them, X 11 X 12 and X 13 Each of the following is independently H, OH, a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an alkynyl group having 2 to 5 carbon atoms; and X 11 X 12 and X 13 At least one of them is a halogen atom; R 11 It is a single bond, an alkylene group with 1 to 5 carbon atoms, an alkenyl group with 2 to 5 carbon atoms, or an ynylene group with 2 to 5 carbon atoms; R 12 It is a ketone group; R 13 It is an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an alkynyl group having 2 to 5 carbon atoms;

[0043] X 21 X 22 X 23 X 24 X 25 and X 26 Each of the following is independently H, OH, a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an alkynyl group having 2 to 5 carbon atoms; and X 21 X 22 X 23 X 24 X 25 and X 26 At least one of them is a halogen atom; R 21 and R 23Each is independently a single bond, an alkylene group with 1 to 5 carbon atoms, an alkenyl group with 2 to 5 carbon atoms, or an ynylene group with 2 to 5 carbon atoms; R 22 It is a ketone group;

[0044] The halobenzene additives are selected from one or more compounds having the structural features shown in formula (III):

[0045] X3 is a halogen atom, and R3 is H, OH, halogen atom, alkyl with 1 to 5 carbon atoms, alkoxy with 1 to 5 carbon atoms, alkenyl with 2 to 5 carbon atoms, or alkynyl with 2 to 5 carbon atoms.

[0046] The halogenated imidazole additives of this application include halogenated imidazole groups and ketone groups. The hygroscopic properties of these groups can remove trace amounts of water present in the electrolyte. Simultaneously, the halogenated imidazole groups can react with trace amounts of HF in the electrolyte to generate relatively stable halogenated imidazole derivatives, preventing HF corrosion of the electrode material and damage to the SEI film. Furthermore, the ketone groups can participate in the construction of the SEI film on the electrode surface to form a dense SEI film, thereby suppressing lithium dendrite formation and improving the battery's cycle performance. Additionally, the halogenated benzene additives contain electron-withdrawing groups and benzene rings, which can adsorb onto the negative electrode surface, contributing to the formation of a stable SEI film. Therefore, the synergistic effect of the halogenated imidazole and halogenated benzene additives can improve the stability of the SEI film and enhance the battery's cycle stability.

[0047] In addition, halogenated imidazole additives, including halogenated imidazole groups and halogenated benzenes, can change the surface tension of the electrolyte. Halogenated imidazole additives, including ketone groups, also exhibit surfactant properties. Therefore, under the synergistic effect of multiple functional groups, the electrolyte can spread more easily at the interface, change its wettability, increase the liquid absorption rate, and reduce the contact angle, thereby improving conductivity and reducing battery internal resistance.

[0048] In summary, the electrolyte additives provided in this application, by selecting halogenated imidazole and halogenated benzene additives with specific structures, achieve the following: Firstly, halogenated benzene additives can effectively adsorb onto the surface of the negative electrode to form a film, while halogenated imidazole additives can remove trace amounts of water and HF present in the electrolyte. These two additives work synergistically to continuously reduce byproducts of the SEI film and effectively improve the stability of the negative electrode SEI film, thereby suppressing lithium dendrite formation, reducing lithium-ion battery capacity decay, and improving cycle performance. Secondly, halogenated imidazole and halogenated benzene additives can reduce the surface tension of the electrolyte, improve the wettability of the electrolyte to the separator and electrode, reduce the contact angle, thereby improving lithium-ion transport and reducing battery internal resistance.

[0049] In one example, X11 X 12 and X 13 Each is independently H, F, Cl, Br, I, or an alkyl group having 1 to 3 carbon atoms; and X 11 X 12 and X 13 At least one of them is a halogen atom.

[0050] Furthermore, X 11 X 12 and X 13 Each is independently H, F, Cl, Br, or I, and X 11 X 12 and X 13 At least one of them is a halogen atom.

[0051] In one example, R 11 It is a single bond or an alkylene group having 1 to 3 carbon atoms; R 12 It is a ketone group; R 13 It is an alkyl group with 1 to 3 carbon atoms.

[0052] Furthermore, R 11 For a single bond, R 12 It is a ketone group, R 13 The methyl or ethyl group is directly attached to the ketone group, which helps to improve the overall stability of the molecule. At the same time, the compact structure of the compound at this time can also form a more stable SEI film, reduce interfacial resistance, reduce interfacial loss during battery cycling, and thus improve the cycle stability of the battery.

[0053] In one example, X 21 X 22 X 23 X 24 X 25 and X 26 Each is independently H, F, Cl, Br, I or an alkyl group having 1 to 3 carbon atoms, and X 21 X 22 X 23 X 24 X 25 and X 26 At least one of them is a halogen atom.

[0054] Furthermore, X 21 X 22 X 23 X 24 X 25 and X 26 Each is independently H, F, Cl, Br, or I, and X 21 X 22 X 23X 24 X 25 and X 26 At least one of them is a halogen atom.

[0055] In one example, R 21 and R 23 Each is an alkylene group with a single bond and 1 to 3 carbon atoms; R 22 It has a ketone group.

[0056] Specifically, R 21 For a single bond, R 23 R is a single bond or an alkylene group having 1 to 3 carbon atoms. 22 The ketone group is directly attached to the imidazole ring, which helps to improve the overall stability of the molecule. At the same time, the compact structure of the compound at this time can also form a more stable SEI film, reduce interfacial resistance, reduce interfacial loss during battery cycling, and thus improve the cycle stability of the battery.

[0057] More specifically, R 21 For a single bond, R 23 For a single bond, R 22 It has a ketone group.

[0058] In one example, the halogenated imidazole additive includes , , , and One or more of the following; wherein X is independently F, Cl, Br or I.

[0059] The haloimidazole ring exhibits good solubility, which can increase the stability of the electrolyte. Preferably, the haloimidazole additive is selected from one or more compounds having the structural features shown in formula (II). For example, the haloimidazole additive includes... , and One or more of the following; wherein X is independently F, Cl, Br or I.

[0060] Due to its high electronegativity, fluorine possesses oxidation potential and high ionization energy. When fluorine bonds to carbon atoms on an imidazole ring, the high bond energy of the carbon-fluorine bond stabilizes its structure. Furthermore, the fluorine atoms in this structure are difficult to polarize, making the carbon-fluorine bond not only hydrophobic but also oleophobic. In addition, the presence of carbon-fluorine bonds in different molecules weakens intermolecular forces, allowing them to oriented and assemble into molecular films at the interface, thus improving wettability. Preferably, X is F.

[0061] For example, the halogenated imidazole additives include , and One or more of the following.

[0062] Specifically, the halogenated imidazole additives include, but are not limited to, those mentioned above. , , , , , , , or .

[0063] In one example, X3 is F, Cl, Br, or I.

[0064] In one example, R3 is H, F, Cl, Br, I, an alkyl group having 1 to 3 carbon atoms, or an alkoxy group having 1 to 3 carbon atoms.

[0065] Furthermore, R3 can be F, Cl, Br, I, methyl, or ethyl.

[0066] In one example, the halogenated benzene additive includes , , , , and One or more of them.

[0067] For example, the halogenated benzene additives include, but are not limited to, those mentioned above. , , , , , , , , , , , , , , , , , or .

[0068] In this configuration, the halogen atom is directly bonded to the carbon atom on the aromatic ring. The high energy of the halogen-C bond makes it difficult to break, and the halogen atom also protects against potential C / C bond disruption, thus ensuring the stability of the halobenzene additive. Furthermore, the carbon atom on the aromatic ring has more π-electron characteristics than the carbon atom in alkyl groups, making it easier for the halogen atom bonded to it to interact with other polar substances. This, in turn, facilitates the interaction between the halobenzene additive and the solid surface or other polar molecules, promoting its extension to the interface and improving wettability. Additionally, this structure of halobenzene additive exhibits good compatibility with haloimidazole additives, which is beneficial for forming a homogeneous electrolyte system.

[0069] To fully leverage the synergistic effect of halogenated imidazole and halogenated benzene additives, in one example, the mass ratio of the halogenated imidazole to halogenated benzene additive is (0.8~1.2):1. Understandably, the mass ratio of the halogenated imidazole to halogenated benzene additive includes, but is not limited to, 0.8:1, 0.85:1, 0.9:1, 0.91:1, 0.93:1, 0.95:1, 0.97:1, 0.98:1, 0.99:1, 1:1, 1.01:1, 1.03:1, 1.05:1, 1.08:1, 1.1:1, 1.15:1, 1.18:1, or 1.2:1.

[0070] More preferably, the mass ratio of the halogenated imidazole additive to the halogenated benzene additive is (0.95~1.05):1.

[0071] A second aspect of this application provides an electrolyte comprising a lithium salt, a solvent, and an additive, wherein the additive is an electrolyte additive as described in any example of the first aspect of this application.

[0072] In one example, the electrolyte comprises 1% to 5% of the haloimidazolium additive and 1% to 5% of the halobenzene additive, by mass percentage. Limiting the mass percentage of the electrolyte ensures its wetting properties at the interface, helps increase the contact area between the electrode and the electrolyte, and promotes the electrochemical reaction. It effectively avoids the problem of poor wetting that may result from insufficient additives, affecting battery performance; it also avoids the problem of increased diffusion resistance and internal resistance caused by excessive coating on the electrode surface, which in turn affects battery cycle performance.

[0073] Specifically, the mass percentage of the halogenated imidazole additives includes, but is not limited to, 1%, 1.1%, 1.2%, 1.3%, 1.5%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.5%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.5%, 3.8%, 3.9%, 4%, 4.1%, 4.2%, 4.5%, 4.8%, 4.9%, or 5%.

[0074] Specifically, the mass percentage of the halogenated benzene additives includes, but is not limited to, 1.1%, 1.2%, 1.3%, 1.5%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.5%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.5%, 3.8%, 3.9%, 4%, 4.1%, 4.2%, 4.5%, 4.8%, 4.9%, or 5%.

[0075] In one example, the lithium salt has a mass fraction of 10% to 14% as a percentage of the electrolyte. Specifically, the mass fraction of the lithium salt includes, but is not limited to, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, or 14%.

[0076] In one example, the lithium salt includes one or more of lithium hexafluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium difluorophosphate.

[0077] In one example, the solvent comprises cyclic carbonates and linear carbonates; the electrolyte comprises 20% to 30% of the cyclic carbonates and 46% to 68% of the linear carbonates by mass percentage. Specifically, the mass fraction of the cyclic carbonates includes, but is not limited to, 20%, 20.5%, 21%, 21.5%, 22%, 22.5%, 23%, 23.5%, 24%, 24.5%, 25%, 25.5%, 26%, 26.5%, 27%, 27.5%, 28%, 28.5%, 29%, 29.5%, or 30%. The mass fraction of the linear carbonates includes, but is not limited to, 46%, 48%, 50%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, or 68%.

[0078] In one specific example, the electrolyte comprises, by mass percentage: 1% to 5% of haloimidazolium additives, 1% to 5% of halobenzene additives, 10% to 14% of lithium salts, 20% to 30% of cyclic carbonates, and 46% to 68% of chain carbonates.

[0079] In one example, the chain carbonate comprises one or more of methyl ethyl carbonate and dimethyl carbonate. Preferably, the chain carbonate comprises methyl ethyl carbonate and dimethyl carbonate in a mass ratio of (2-3):1. Specifically, the mass ratio of methyl ethyl carbonate to dimethyl carbonate includes, but is not limited to, 2:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.62:1, 2.625:1, 2.63:1, 2.4:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, or 3:1.

[0080] In one example, the cyclic carbonate includes one or more of ethylene carbonate, fluoroethylene carbonate, and vinylene carbonate.

[0081] The viscosity of the electrolyte has a significant impact on the wetting rate. Solvent, as a major component of the electrolyte, directly affects its performance through its composition and content. The solvent in this application comprises specific mass percentages of linear and cyclic carbonates. The linear carbonates allow for flexible adjustment of the electrolyte viscosity, while the cyclic carbonates ensure the formation of a relatively stable solid electrolyte interphase (SEI) film during battery cycling, helping to reduce electrolyte decomposition and electrode material loss, thereby extending the battery's cycle life.

[0082] A third aspect of this application provides a battery that includes the electrolyte additive described in any embodiment of the first aspect of this application or the electrolyte described in any embodiment of the second aspect of this application.

[0083] In one example, the battery includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and the electrolyte.

[0084] Without limitation, the positive electrode sheet can be selected from commonly used positive electrode sheets known to those skilled in the art. For example, the positive electrode sheet includes a positive current collector and a layer of positive active material located on the positive current collector. Specifically, the positive current collector includes an aluminum foil current collector. Further, the composition of the positive active material layer includes a positive active material, a conductive agent, and a binder. Examples of positive active materials include, for example, lithium cobalt oxide (LiCoO2), lithium nickel manganese cobalt ternary materials, lithium manganese oxide (LiMn2O4), and lithium nickel manganese oxide (LiNi). 0.5 Mn 1.5One or more of O4 and lithium iron phosphate (LiFePO4). For example, the conductive agent includes one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0085] Without limitation, the negative electrode sheet can be selected from commonly used negative electrode sheets known to those skilled in the art. For example, the negative electrode sheet includes a negative current collector and a layer of negative active material located on at least one surface of the negative current collector. Specifically, the negative current collector can be a metal foil or a composite current collector. For example, copper foil can be used as the metal foil. The composite current collector may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.). Further, the composition of the negative active material layer includes a negative active material, for example, such as artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The composition of the negative electrode active material layer may optionally include a binder. The binder may be selected from one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). The composition of the negative electrode active material layer may also optionally include a conductive agent. The conductive agent may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0086] Without limitation, the separator can be any type of separator commonly used in lithium-ion secondary batteries, such as polyolefin films, including microporous membranes made of polyethylene and polypropylene; multilayer membranes of porous polyethylene and polypropylene; nonwoven fabrics formed of polyester fibers, aramid fibers, glass fibers, etc.; and substrate membranes formed by attaching ceramic particles such as silica, alumina, and titanium dioxide to their surfaces. In some embodiments, the separator is a three-layer PP / PE / PP membrane coated with alumina on both sides.

[0087] In one specific example, the battery is a lithium-ion battery.

[0088] This application also provides an electrical device, including the battery described in the third aspect of this application. Specifically, the electrical device may include, for example, a smart wearable device, a computer, a smartphone, a camera, a drone, an electric vehicle, etc.

[0089] The following detailed embodiments illustrate this application in more detail. It should also be understood that the following embodiments are for further explanation only and should not be construed as limiting the scope of protection of this application. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of this application fall within the scope of protection of this application. The specific process parameters, etc., in the following embodiments are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the range based on the description herein, and are not necessarily limited to the specific values ​​in the embodiments below.

[0090] [raw material]

[0091] [Haloimidazole additives]

[0092] Compound number: I-1, preparation method is as follows: ;

[0093] At room temperature, after purging the four-necked flask with nitrogen, 100 ml of dichloromethane was added, and the temperature was maintained at 25°C with stirring. Then, 10 g of triphosgene, 18.85 g of 4-fluoroimidazole, and 22.17 g of triethylamine were added sequentially, and the temperature was maintained at 25°C with stirring for another 2 hours. After the reaction was completed, the reaction solution was concentrated to dryness at 45°C, slurried with 60 ml of toluene, filtered, and dried under nitrogen to obtain 18.56 g of compound I-1, with a yield of 92.66%.

[0094] Compound number: I-2. The preparation method is similar to that of I-1, the main difference being that 4-fluoroimidazole in the raw material is replaced with 4-bromoimidazole.

[0095] [Halogenated benzene additives]

[0096] Compound number: II-1, commercially available, CAS: 95-52-3.

[0097] [Cyclic carbonates]

[0098] Ethylene carbonate (EC) Commercially available, CAS: 96-49-1.

[0099] Fluorinated ethylene carbonate (FEC) Commercially available, CAS: 114435-02-8.

[0100] Vinyl carbonate (VC) Commercially available, CAS: 872-36-6.

[0101] [Chain carbonates]

[0102] Ethyl methyl carbonate (EMC), commercially available, CAS: 623-53-0.

[0103] Dimethyl carbonate (DMC), commercially available, CAS: 616-38-6.

[0104] Examples 1-8 and Comparative Examples 1-3

[0105] Electrolyte preparation:

[0106] (1) Electrolyte additives: Select electrolyte additives according to Table 1 below. The preparation process of lithium-ion batteries in Examples 1-8 and Comparative Examples 1-3 is the same, the difference lies in the composition of the electrolyte additives, as shown in Table 1.

[0107] (2) Prepare lithium-ion battery electrolyte in a glove box under the conditions of moisture <0.01ppm and oxygen content <0.01ppm: Mix cyclic carbonate and chain carbonate according to the mass ratio in Table 1 below to obtain a solvent; dissolve lithium hexafluorophosphate in the solvent to obtain a mixture of lithium salt and solvent; add electrolyte additives according to Table 1, mix evenly to obtain electrolyte.

[0108] Preparation of lithium-ion batteries:

[0109] A bare cell is made by winding a lithium iron phosphate positive electrode, an artificial graphite negative electrode, and a separator. The cell is then packaged with an aluminum-plastic film, vacuum dried at 85°C, and injected with 12g of the electrolyte prepared above after the water content reaches the standard. The cell is then vacuum-sealed using known technology and processed through steps such as standing, hot and cold pressing, formation, liquid extraction, capacity testing, and aging to obtain a lithium-ion battery.

[0110] Table 1

[0111]

[0112] The lithium-ion batteries assembled in the examples and comparative examples were subjected to the following tests:

[0113] Cycle capacity retention and recovery: The lithium-ion batteries were placed in a 35°C constant temperature chamber and left to stand for 6 hours to allow them to reach a constant temperature. The lithium-ion batteries that had reached a constant temperature were then cycled at 1P within the range of 3.65V-2V. The corresponding cycle data were recorded, and the capacity retention rate of the lithium-ion batteries after 500 cycles was calculated.

[0114] High-temperature storage capacity retention: Lithium-ion batteries were placed in a 60°C constant temperature chamber and left to stand for 6 hours to allow them to reach a constant temperature. Storage cycles were: 1 week ~ 1 week ~ 1 week ~ 1 week ~ 15 days ~ 15 days ~ 15 days ~ 1 month ~ 1 month. At the fixed storage time, a cycle of 0.5P was performed, and the capacity retention and recovery rates were obtained by comparing the cell capacity with the initial capacity measured during storage.

[0115] EIS Impedance Testing: The impedance of the battery cell at 50% SOC after formation was tested using an electrochemical workstation with a voltage of 5mV and a frequency of 106-0.01HZ.

[0116] Aspiration rate test: Selected Figure 1 The liquid absorption rate testing device uses a capillary tube 10 to draw electrolyte to the same height, selects the same 4cm*4cm negative electrode sheet 20 as the substrate, and records the time it takes for the electrolyte to be completely absorbed by the negative electrode sheet.

[0117] Contact angle test: Using the negative electrode sheet as the substrate, a contact angle device is used to take pictures starting from the 1st second of the droplet. The first picture after the first droplet separates from the syringe is selected as the judgment, and the size of the contact angle is compared.

[0118] The performance test results of the lithium-ion batteries assembled in the examples and comparative examples are shown in Table 2.

[0119] Table 2

[0120]

[0121] As shown in Table 2, in Examples 1 to 5, as the amount of halogenated imidazole and halogenated benzene additives gradually increased, the liquid absorption time and contact angle showed a trend of first decreasing and then increasing. Furthermore, the capacity retention rate, capacity recovery rate, and cycle capacity retention rate of the lithium-ion battery at 35°C also showed a trend of first increasing and then decreasing. This indicates that the cycle performance and wetting performance of Example 4 were the best when the content of halogenated imidazole and halogenated benzene additives was 2%.

[0122] Compared to Example 6, the main difference in Example 4 lies in the content of ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) in the chain carbonate. The lithium-ion battery in Example 4 exhibits superior overall performance, indicating that a higher EMC content results in better synergistic effects with halogenated imidazole and halogenated benzene additives. Compared to Example 7, the main difference lies in the content of chain and cyclic carbonates. In Example 4, the chain carbonate content is higher than the cyclic carbonate content, while in Example 7, the chain carbonate content is lower than the cyclic carbonate content. This suggests that a higher chain carbonate content leads to better synergistic effects with halogenated imidazole and halogenated benzene additives. In Example 8, the halogenated imidazole additive I-2 was selected, resulting in lower capacity retention and capacity recovery rates compared to Example 2.

[0123] In Comparative Example 1, only a single halogenated imidazole additive, the same as in Example 8, was used. Because Comparative Example 1 did not use a halogenated benzene additive, it could not effectively suppress the occurrence of lithium dendrites, leading to capacity decay in the lithium-ion battery. Compared to Example 2, Comparative Examples 2 and 3 both contained a single additive, resulting in a decrease in the overall performance of the lithium-ion battery.

[0124] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0125] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. An electrolyte additive, characterized in that, Including halogenated imidazole additives and halogenated benzene additives; The haloimidazole additives are selected from one or more compounds having the structural features shown in formula (I) or formula (II): or ; Among them, X 11 X 12 and X 13 Each of the following is independently H, OH, a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an alkynyl group having 2 to 5 carbon atoms; and X 11 X 12 and X 13 At least one of them is a halogen atom; R 11 It is a single bond, an alkylene group with 1 to 5 carbon atoms, an alkenyl group with 2 to 5 carbon atoms, or an ynylene group with 2 to 5 carbon atoms; R 12 It is a ketone group; R 13 It is an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an alkynyl group having 2 to 5 carbon atoms; X 21 X 22 X 23 X 24 X 25 and X 26 Each of the following is independently H, OH, a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an alkynyl group having 2 to 5 carbon atoms; and X 21 X 22 X 23 X 24 X 25 and X 26 At least one of them is a halogen atom; R 21 and R 23 Each is independently a single bond, an alkylene group with 1 to 5 carbon atoms, an alkenyl group with 2 to 5 carbon atoms, or an ynylene group with 2 to 5 carbon atoms; R 22 It is a ketone group; The halobenzene additives are selected from one or more compounds having the structural features shown in formula (III): X3 is a halogen atom, and R3 is H, OH, halogen atom, alkyl with 1 to 5 carbon atoms, alkoxy with 1 to 5 carbon atoms, alkenyl with 2 to 5 carbon atoms, or alkynyl with 2 to 5 carbon atoms.

2. The electrolyte additive according to claim 1, characterized in that, X 11 X 12 and X 13 Each is independently H, F, Cl, Br, I, or an alkyl group having 1 to 3 carbon atoms; and X 11 X 12 and X 13 At least one of them is a halogen atom; R 11 It is a single bond or an alkylene group having 1 to 3 carbon atoms; R 12 It is a ketone group; R 13 It is an alkyl group having 1 to 3 carbon atoms; X 21 X 22 X 23 X 24 X 25 and X 26 Each is independently H, F, Cl, Br, I or an alkyl group having 1 to 3 carbon atoms, and X 21 X 22 X 23 X 24 X 25 and X 26 At least one of them is a halogen atom; R 21 and R 23 Each is an alkylene group with a single bond and 1 to 3 carbon atoms; R 22 It is a ketone group; X3 is F, Cl, Br or I, and R3 is H, F, Cl, Br, I, an alkyl group with 1 to 3 carbon atoms or an alkoxy group with 1 to 3 carbon atoms.

3. The electrolyte additive according to claim 1, characterized in that, X 11 X 12 and X 13 Each is independently H, F, Cl, Br, or I, and X 11 X 12 and X 13 At least one of them is a halogen atom; R 11 For a single bond, R 12 It is a ketone group, R 13 It is methyl or ethyl; X 21 X 22 X 23 X 24 X 25 and X 26 Each is independently H, F, Cl, Br, or I, and X 21 X 22 X 23 X 24 X 25 and X 26 At least one of them is a halogen atom; R 21 For a single bond, R 23 R is a single bond or an alkylene group having 1 to 3 carbon atoms. 22 It is a ketone group; X3 is F, Cl, Br or I, and R3 is F, Cl, Br, I, methyl or ethyl.

4. The electrolyte additive according to claim 1, characterized in that, The halogenated imidazole additives include , and One or more of the following; wherein X is independently F, Cl, Br or I; The halogenated benzene additives include , , , , and One or more of them.

5. The electrolyte additive according to any one of claims 1 to 3, characterized in that, The mass ratio of the halogenated imidazole additive to the halogenated benzene additive is (0.8~1.2):

1.

6. An electrolyte, characterized in that, It includes lithium salt, solvent and additive, wherein the additive is the electrolyte additive according to any one of claims 1 to 5.

7. The electrolyte according to claim 6, characterized in that, The electrolyte comprises 1% to 5% of the haloimidazole additive and 1% to 5% of the halobenzene additive, by mass percentage.

8. The electrolyte according to claim 6 or 7, characterized in that, The lithium salt has one or more of the following characteristics: (1) The lithium salt has a mass fraction of 10% to 14% based on the mass percentage of the electrolyte; (2) The lithium salt includes one or more of lithium hexafluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide and lithium difluorophosphate.

9. The electrolyte according to claim 6 or 7, characterized in that, The solvent includes cyclic carbonates and chain carbonates; The electrolyte comprises 20% to 30% of the cyclic carbonate and 46% to 68% of the chain carbonate, by mass percentage.

10. A battery, characterized in that, It includes the electrolyte additive according to any one of claims 1 to 5 or the electrolyte according to any one of claims 6 to 9.

Images