Lithium-ion battery

Abstract

The present application provides a lithium-ion battery, comprising a positive electrode, a negative electrode and a non-aqueous electrolyte. The negative electrode comprises a negative electrode material layer. The non-aqueous electrolyte comprises a non-aqueous organic solvent, an electrolyte salt and an additive; the additive comprises a first additive; the first additive comprises a compound represented by structural formula 1 and / or a compound represented by structural formula 2; and a second additive comprises a fluorobenzene compound and / or a cycloalkane compound. [Structural formula 1] [Structural formula 2]. The lithium-ion battery satisfies the following conditions: 3≤[formula (3)]≤60, 0.005≤a≤1, 0.1≤b≤10, and 10≤φ≤40.

Description

A lithium-ion battery

[0001] This application claims priority to Chinese Patent Application No. 202510120110.X, filed on January 25, 2025, entitled “A Lithium-ion Battery”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application belongs to the field of energy storage device technology, specifically relating to a lithium-ion battery. Background Technology

[0003] Lithium-ion batteries are widely used in digital products, energy storage, and new energy vehicles due to their long cycle life, high operating voltage, and lack of memory effect. As consumer demands increase, standards for thinner, lighter batteries and higher energy density are constantly rising. There are many methods to improve battery energy density, such as using new positive and negative electrode materials, replacing materials with lighter ones, and solid-state batteries. However, most of these technologies require long-term R&D investment and modifications to existing production lines, resulting in excessive resource investment. Increasing electrode compaction density does not introduce new processes, and its manufacturing process has gradually improved. However, it also faces the problem of reduced porosity due to high compaction density, leading to insufficient electrolyte wetting on the electrodes and deteriorating battery cycle and storage performance. Summary of the Invention

[0004] To address the problem of insufficient cycle performance and high-temperature storage performance in existing lithium-ion batteries due to reduced porosity, this application provides a lithium-ion battery.

[0005] The technical solution adopted in this application to solve the above-mentioned technical problems is as follows:

[0006] This application provides a lithium-ion battery, including a positive electrode, a negative electrode, and a non-aqueous electrolyte. The negative electrode includes a negative electrode material layer. The non-aqueous electrolyte includes a non-aqueous organic solvent, an electrolyte salt, and an additive. The additive includes a first additive, which includes a compound shown in structural formula 1 and / or a compound shown in structural formula 2. The second additive includes fluorobenzene and / or cycloalkanes.

[0007] Wherein, n is 0 or 1; R1 and R2 are each independently selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C1-C12 acyl, substituted or unsubstituted C2-C12 alkoxyacyl, substituted or unsubstituted C2-C12 ether, and R1 and R2 are not... Both are hydrogen, and R1 and R2 can be linked together to form a ring or not; R3 is selected from substituted or unsubstituted C1-C12 alkylene groups, substituted or unsubstituted C2-C12 alkenyl groups, substituted or unsubstituted C2-C12 alkyne groups, substituted or unsubstituted C6-C20 aryl groups, and substituted or unsubstituted C2-C12 ether groups; when R1, R2, and R3 are substituted, the substituents are alkoxy, hydroxyl, acyl, ester, cyano, or halogen.

[0008] R4 and R5 are each independently selected from substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C6 alkenyl, substituted or unsubstituted C2-C6 alkynyl or substituted or unsubstituted C1-C6 alkyl hydroxyl groups. R4 and R5 may be linked together to form a ring or not. R6 is selected from hydrogen, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C6 alkenyl or substituted or unsubstituted C2-C6 alkynyl, C1-C6 cyano, C2-C6 ester, substituted or unsubstituted C2-C6 amide or substituted or unsubstituted C1-C6 amidine.

[0009] The lithium-ion battery meets the following conditions:

[0010] And 0.005≤a≤1, 0.1≤b≤10,

[0011] Where a is the mass percentage of the first additive in the non-aqueous electrolyte, in %;

[0012] b represents the mass percentage of the second additive in the non-aqueous electrolyte, in %;

[0013] Porosity of the negative electrode material layer, in percentage (%).

[0014] Optionally, the lithium-ion battery satisfies the following conditions:

[0015] Optionally, the lithium-ion battery satisfies at least one of the following conditions:

[0016] (1) 0.005 ≤ a ≤ 0.6;

[0017] (2) 0.5 ≤ b ≤ 5;

[0018] (3)

[0019] Optionally, the compound represented by structural formula 1 satisfies at least one of the following conditions:

[0020] (1) R1 is selected from hydrogen, and R2 is selected from… Substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, wherein R 10 Selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, and substituted or unsubstituted C6-C20 aryl.

[0021] (2) R1 and R2 are each independently selected from substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, or substituted or unsubstituted C6-C20 aryl.

[0022] (3) R1 is selected from R2 is selected from substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, or... Among them, R 11 Selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, substituted or unsubstituted C6-C20 aryl, and substituted or unsubstituted C2-C12 ether.

[0023] (4) R1 is selected from Among them, R 12 R2 is selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, and substituted or unsubstituted C2-C11 alkynyl; R2 is selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, and substituted or unsubstituted C6-C20 aryl or... Among them, R 13 Selected from substituted or unsubstituted C1-C11 alkyl groups, substituted or unsubstituted C2-C11 alkenyl groups, and substituted or unsubstituted C2-C11 alkynyl groups.

[0024] Optionally, the compound represented by structural formula 1 includes one or more of the following compounds:

[0025] Optionally, the compound represented by Structural Formula 2 satisfies at least one of the following conditions:

[0026] (1) When R4 and R5 are substituted, the substituents are carboxyl, hydroxyl, halogen or cyano; when R6 is substituted, the substituents are hydroxyl, halogen or alkoxy;

[0027] (2) R6 is selected from cyano;

[0028] (3) R4 and R5 are each independently selected from substituted or unsubstituted C1-C6 alkyl groups.

[0029] Optionally, the compound represented by Structural Formula 2 includes one or more of the following compounds:

[0030] Optionally, the fluorobenzene includes at least one of fluorobenzene, difluorobenzene and trifluorobenzene; and / or

[0031] The cycloalkane compound includes at least one of cyclopentane, cyclohexane, cycloheptane, methylcyclopentane, ethylcyclopentane, 1,3-dimethylcyclopentane, 1,4-dimethylcyclopentane, methylcyclohexane, ethylcyclohexane, propylcyclohexane, butylcyclohexane, pentylcyclohexane, cis-1-methyl-3-ethylcyclohexane, trans-1-methyl-3-ethylcyclohexane, 1,3-dimethylcyclohexane, 1,4-dimethylcyclohexane, 1,3,5-trimethylcyclohexane, bromocyclohexane, 1-chloro-2-ethylcyclohexane and perfluoro(ethylcyclohexane). ]>

[0032] Optionally, the negative electrode material layer includes a negative electrode active material, and the negative electrode active material includes at least one of artificial graphite, natural graphite, silicon-carbon composite material, soft carbon and hard carbon.

[0033] Optionally, the non-aqueous electrolyte does not include a polymerizable monomer and / or a prepolymer obtained by polymerization of a polymerizable monomer.

[0034] According to the lithium-ion battery provided in this application, compounds represented by structural formula 1 and / or structural formula 2 are added to the non-aqueous electrolyte as a first additive. During the battery formation stage, this first additive can participate in regulating the formation of the solid electrolyte interphase (SEI) film on the surface of the negative electrode, protecting the negative electrode material and preventing the decomposition and gas generation of the non-aqueous electrolyte at the negative electrode interface. However, with the increasing demand for energy density in lithium-ion batteries, the porosity of the negative electrode sheet is decreasing. Low porosity leads to poor wettability of the non-aqueous electrolyte. During the film formation process at the negative electrode, the first additive consumed internally cannot be replenished in time. After formation begins, an SEI film with uneven distribution and thickness is formed inside and outside the negative electrode. Due to the uneven thickness of the SEI film, it is prone to recombination and regeneration during long-term cycling or storage. This process consumes active lithium and increases impedance, which is detrimental to long-term cycling and high-temperature storage of the battery. To address this issue, this application further adds fluorobenzene and / or cycloalkanes as a second additive to the non-aqueous electrolyte and discovers that when the mass percentage a of the first additive in the non-aqueous electrolyte, the mass percentage b of the second additive in the non-aqueous electrolyte, and the porosity of the negative electrode material layer are all considered to be optimal, the following additives can be added: Meet the conditions And 0.005≤a≤1, 0.1≤b≤10, The resulting lithium-ion battery exhibits a long cycle life and high capacity retention after high-temperature storage. This is primarily due to the fact that the addition of the second additive enhances the diffusion efficiency of the first additive in the negative electrode material layer. During battery formation, this effectively promotes the decomposition and replenishment of the first additive at each interface of the negative electrode, ensuring the uniformity of film thickness at each location. Simultaneously, the porosity of the negative electrode material layer affects the wettability of the non-aqueous electrolyte within it, indirectly influencing the conductivity of the first additive. Therefore, by controlling the content of the first and second additives and the porosity of the negative electrode material layer, and ensuring their synergistic effect, the uniformity of the solid electrolyte interface film on the negative electrode surface can be effectively improved, reducing interface impedance and enhancing the protection against the negative electrode and non-aqueous electrolyte. This shortens the ion transport path, reduces impedance, and ultimately achieves stable battery cycling and storage. Detailed Implementation

[0035] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0036] This application provides a lithium-ion battery, including a positive electrode, a negative electrode, and a non-aqueous electrolyte. The negative electrode includes a negative electrode material layer. The non-aqueous electrolyte includes a non-aqueous organic solvent, an electrolyte salt, and an additive. The additive includes a first additive, which includes a compound shown in structural formula 1 and / or a compound shown in structural formula 2. The second additive includes fluorobenzene and / or cycloalkanes.

[0037] Wherein, n is 0 or 1; R1 and R2 are each independently selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C1-C12 acyl, substituted or unsubstituted C2-C12 alkoxyacyl, substituted or unsubstituted C2-C12 ether, and R1 and R2 are not... Both are hydrogen, and R1 and R2 can be linked together to form a ring or not; R3 is selected from substituted or unsubstituted C1-C12 alkylene groups, substituted or unsubstituted C2-C12 alkenyl groups, substituted or unsubstituted C2-C12 alkyne groups, substituted or unsubstituted C6-C20 aryl groups, and substituted or unsubstituted C2-C12 ether groups; when R1, R2, and R3 are substituted, the substituents are alkoxy, hydroxyl, acyl, ester, cyano, or halogen.

[0038] R4 and R5 are each independently selected from substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C6 alkenyl, substituted or unsubstituted C2-C6 alkynyl or substituted or unsubstituted C1-C6 alkyl hydroxyl groups. R4 and R5 may be linked together to form a ring or not. R6 is selected from hydrogen, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C6 alkenyl or substituted or unsubstituted C2-C6 alkynyl, C1-C6 cyano, C2-C6 ester, substituted or unsubstituted C2-C6 amide or substituted or unsubstituted C1-C6 amidine.

[0039] The lithium-ion battery meets the following conditions:

[0040] And 0.005≤a≤1, 0.1≤b≤10,

[0041] Where a is the mass percentage of the first additive in the non-aqueous electrolyte, in %;

[0042] b represents the mass percentage of the second additive in the non-aqueous electrolyte, in %;

[0043] Porosity of the negative electrode material layer, in percentage (%).

[0044] The first additive, during the battery formation stage, can participate in regulating the formation of the solid electrolyte interphase (SEI) film on the negative electrode surface, protecting the negative electrode material and preventing the decomposition and gas generation of the non-aqueous electrolyte at the negative electrode interface. However, with the increasing energy density requirements of lithium-ion batteries, the porosity of the negative electrode sheet has decreased. Low porosity leads to poor wettability of the non-aqueous electrolyte, and the first additive consumed during the negative electrode film formation process cannot be replenished in time. After formation begins, an SEI film with uneven distribution and thickness is formed inside and outside the negative electrode. Due to the uneven thickness of the SEI film, it is prone to recombination and regeneration during long-term cycling or storage. This process consumes active lithium and increases impedance, which is detrimental to long-term cycling and high-temperature storage of the battery. To solve this problem, this application further adds fluorobenzene and / or cycloalkanes as a second additive to the non-aqueous electrolyte and finds that when the mass percentage of the first additive in the non-aqueous electrolyte (a), the mass percentage of the second additive in the non-aqueous electrolyte (b), and the porosity of the negative electrode material layer are... Meet the conditions And 0.005≤a≤1, 0.1≤b≤10, The resulting lithium-ion battery exhibits a long cycle life and high capacity retention after high-temperature storage. This is primarily due to the fact that the addition of the second additive enhances the diffusion efficiency of the first additive in the negative electrode material layer. During battery formation, this effectively promotes the decomposition and replenishment of the first additive at each interface of the negative electrode, ensuring the uniformity of film thickness at each location. Simultaneously, the porosity of the negative electrode material layer affects the wettability of the non-aqueous electrolyte within it, indirectly influencing the conductivity of the first additive. Therefore, by controlling the content of the first and second additives and the porosity of the negative electrode material layer, and ensuring their synergistic effect, the uniformity of the solid electrolyte interface film on the negative electrode surface can be effectively improved, reducing interface impedance and enhancing the protection against the negative electrode and non-aqueous electrolyte. This shortens the ion transport path, reduces impedance, and ultimately achieves stable battery cycling and storage.

[0045] In a preferred embodiment, the lithium-ion battery satisfies the following conditions:

[0046] When the mass percentage a of the first additive in the non-aqueous electrolyte, the mass percentage b of the second additive in the non-aqueous electrolyte, and the porosity of the negative electrode material layer are considered... Meeting the above conditions further will help improve the storage capacity retention rate, room temperature cycle life, and reduce the impedance of lithium-ion batteries.

[0047] In a specific embodiment, the mass percentage a% of the first additive in the non-aqueous electrolyte can be 0.005%, 0.006%, 0.008%, 0.01%, 0.02%, 0.04%, 0.05%, 0.08%, 0.1%, 0.12%, 0.14%, 0.15%, 0.18%, 0.2%, 0.22%, 0.28%, 0.3%, 0.32%, 0.38%, 0.4%, 0.42%, 0.48%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or a range of any two of these values.

[0048] In a preferred embodiment, 0.005 ≤ a ≤ 0.6.

[0049] The first additive is used to regulate the formation of the solid electrolyte interface film on the negative electrode surface. If the content of the first additive is too low, it will be difficult to effectively improve the film quality of the carboxylic acid ester, resulting in insufficient long-term cycle life of the secondary battery. If the content of the second additive is too high, the excess first additive will easily trigger unnecessary side reactions in the non-aqueous electrolyte due to the high reactivity of the first additive, thereby affecting the service life of the non-aqueous electrolyte.

[0050] In a specific embodiment, the mass percentage b% of the second additive in the non-aqueous electrolyte can be 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5%, 10%, or any combination of these values.

[0051] In a preferred embodiment, 0.5 ≤ b ≤ 5.

[0052] The second additive is used to improve the diffusion efficiency of the first additive in the non-aqueous electrolyte, ensuring that the first additive consumed at the film formation site during the battery formation process is replenished in a timely manner, and ensuring the uniformity of the negative electrode solid electrolyte interface film. If the content of the second additive is too low, the improvement on the uniformity of the negative electrode solid electrolyte interface film will not be significant. If the content of the second additive is too high, it will destroy the original solvation structure of the electrolyte, affect ion transport, reduce the viscosity of the electrolyte, and at the same time, the low viscosity of the electrolyte will reduce the internal stability of the battery.

[0053] In a specific embodiment, the porosity of the negative electrode material layer It can be a range of 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, or any combination of these values.

[0054] In a preferred embodiment,

[0055] Porosity of the negative electrode material layer Porosity is related to the energy density of lithium-ion batteries. Theoretically, lower porosity is more conducive to improving energy density. However, in practice, lower porosity makes it difficult for non-aqueous electrolytes to wet the material, affecting ion conduction efficiency. Therefore, if the porosity of the negative electrode material layer is low... If the porosity is too low, the electrolyte storage and permeation space will be too small, making it difficult to fully wet the electrode even with wettability-improving additives, resulting in insufficient uniformity of the negative electrode solid electrolyte interface film formed during the formation stage; if the porosity of the negative electrode material layer is too low... If the temperature is too high, it will be detrimental to the improvement of battery energy density. At the same time, the electrode structure is loose, and the negative electrode is prone to deformation and powder shedding during battery manufacturing and operation. In addition, the contact area between the active materials of the negative electrode is reduced, the transmission performance is reduced, and the battery capacity is affected.

[0056] Porosity of the negative electrode material layer This can be obtained through testing in the following ways:

[0057] The porosity of the lithium-ion battery anode material layer was tested using the gas adsorption method. The anode material layer was ground into powder, and the sample was kept dry. The sample was placed in a gas adsorption analyzer, and nitrogen gas was used at -77K to test the gas adsorption capacity under different pressures. Based on the adsorption test data, adsorption isotherms were plotted, and the porosity of the anode material layer was determined using BET theory.

[0058] In the description of this application, the term "C1-C12 alkyl" includes straight-chain alkyl, branched alkyl, and cycloalkyl; similarly, the term "C2-C12 alkenyl" includes straight-chain alkenyl, branched alkenyl, and cycloalkenyl; the term "C2-C12 alkynyl" includes straight-chain alkynyl, branched alkynyl, and cycloalkenyl; the term "C1-C12 alkylene" includes straight-chain alkylene, branched alkylene, and cycloalkenyl; the term "C2-C12 alkenyl" includes straight-chain alkenyl, branched alkenyl, and cycloalkenyl; and the term "C2-C12 alynyl" includes straight-chain alynyl, branched alynyl, and cycloalynyl.

[0059] In the description of this application, the term "C1-C12 acyl" should be interpreted broadly. Specifically, it can be understood as one or more carbon atoms in a C1-C12 alkyl group being surrounded by a carbonyl group. The substitution group is obtained, and the position of the substituted carbon atom is not particularly limited. In a preferred embodiment, the acyl group of C1-C12 is selected from... Among them, R 14 and R15 Each is independently selected from a single bond or a C1-C11 alkyl group.

[0060] In the description of this application, the term "C2-C12 alkoxyacyl" should be interpreted broadly, specifically, it can be understood as one or more carbon atoms in a C2-C12 alkyl group being... The substituted group is obtained, and the position of the substituted carbon atom is not particularly limited. In a preferred embodiment, the C2-C12 alkoxyacyl group is selected from... Among them, R 16 Selected from single-bonded or C1-C11 alkyl groups, R 17 Alkyl groups selected from C1-C11.

[0061] In the description of this application, the term "C2-C12 ether group" should be interpreted broadly. Specifically, it can be understood as a group formed by connecting -O- between two adjacent carbon atoms in a C2-C12 alkyl group, where the number of oxygen atoms can be single or multiple.

[0062] In some embodiments, in the compound represented by structural formula 1, R1 is selected from hydrogen, and R2 is selected from… Substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, wherein R 10 Selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, and substituted or unsubstituted C6-C20 aryl.

[0063] At this point, the compound represented by structural formula 1 is a hydroperoxide or an organic peroxy acid. When the compound represented by structural formula 1 is a hydroperoxide or an organic peroxy acid, its high oxygen content can remove reducing impurities in the electrolyte in advance, reduce the amount of gas generated during formation, improve the initial coulombic efficiency, and increase the initial discharge capacity of the secondary battery.

[0064] As an example, the compound represented by structural formula 1 may be selected from the following compounds:

[0065] In some embodiments, in the compound represented by structural formula 1, R1 and R2 are each independently selected from substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, and substituted or unsubstituted C6-C20 aryl.

[0066] At this point, the compound represented by structural formula 1 is a dialkyl peroxide. When the compound represented by structural formula 1 is a dialkyl peroxide, it is beneficial to suppress solvent molecule co-intercalation and improve the interfacial compatibility between the electrolyte and the negative electrode.

[0067] As an example, the compound represented by structural formula 1 may be selected from the following compounds:

[0068] In some embodiments, in the compound represented by structural formula 1, R1 is selected from... R2 is selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, or... Among them, R 11 Selected from substituted or unsubstituted C1-C11 alkyl groups, substituted or unsubstituted C2-C11 alkenyl groups, substituted or unsubstituted C2-C11 alkynyl groups, substituted or unsubstituted C6-C20 aryl groups, and substituted or unsubstituted C2-C12 etheryl groups.

[0069] In some embodiments, in the compound represented by structural formula 1, R1 is selected from... R2 is selected from Among them, R 11 Selected from substituted or unsubstituted C1-C11 alkyl groups, substituted or unsubstituted C2-C11 alkenyl groups, substituted or unsubstituted C2-C11 alkynyl groups, substituted or unsubstituted C6-C20 aryl groups, and substituted or unsubstituted C2-C12 etheryl groups.

[0070] At this point, the compound represented by structural formula 1 is a diacyl peroxide. When the compound represented by structural formula 1 is a diacyl peroxide, in addition to improving battery cycle life, it can also decompose to form inert carbon dioxide during battery thermal runaway to dilute the explosion limits of flammable gases, which is beneficial to improving battery safety performance.

[0071] As an example, the compound represented by structural formula 1 may be selected from the following compounds:

[0072] In some embodiments, in the compound represented by structural formula 1, R1 is selected from... R2 is selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, and substituted or unsubstituted C6-C20 aryl, wherein R 11Selected from substituted or unsubstituted C1-C11 alkyl groups, substituted or unsubstituted C2-C11 alkenyl groups, substituted or unsubstituted C2-C11 alkynyl groups, substituted or unsubstituted C6-C20 aryl groups, and substituted or unsubstituted C2-C12 etheryl groups.

[0073] At this point, the compound represented by structural formula 1 is a peroxy ester. When the compound represented by structural formula 1 is a peroxy ester, it can improve the wettability of the electrolyte to the electrode, reduce the ohmic internal resistance of the battery, and improve the discharge performance of the battery.

[0074] As an example, the compound represented by structural formula 1 may be selected from the following compounds:

[0075] In some embodiments, in the compound represented by structural formula 1, R1 is selected from... Among them, R 12 R2 is selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, and substituted or unsubstituted C2-C11 alkynyl; R2 is selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, and substituted or unsubstituted C6-C20 aryl or... Among them, R 13 Selected from substituted or unsubstituted C1-C11 alkyl groups, substituted or unsubstituted C2-C11 alkenyl groups, and substituted or unsubstituted C2-C11 alkynyl groups.

[0076] At this point, the compound represented by structural formula 1 is a peroxycarbonate or a peroxydicarbonate. When the compound represented by structural formula 1 is a peroxycarbonate or a peroxydicarbonate, it promotes lithium-ion solvation and improves lithium diffusion performance inside the battery.

[0077] As an example, the compound represented by structural formula 1 may be selected from the following compounds:

[0078] In some embodiments, the compound represented by structural formula 1 includes one or more of the following compounds:

[0079] It should be noted that the compound shown in Structural Formula 2 has a symmetrical structure, that is, the compound shown in Structural Formula 2 is based on left-right symmetry of -N=N-. Under the constraints of this application, this symmetrical structure is beneficial to the function of the compound shown in Structural Formula 2. At the same time, the C connected to N needs to be sp3 hybridized to ensure the stability of the -N=N- structure.

[0080] In some embodiments, in the compound shown in Formula 2, when R4 and R5 are substituted, the substituents are carboxyl, hydroxyl, halogen, or cyano; when R6 is substituted, the substituents are hydroxyl, halogen, or alkoxy.

[0081] In some embodiments, in the compound represented by structural formula 2, R6 is selected from cyano.

[0082] In some embodiments, in the compound shown in Formula 2, R4 and R5 are each independently selected from substituted or unsubstituted C1-C6 alkyl groups.

[0083] The C1-C6 alkyl groups include methyl, ethyl, n-propyl, isopropyl, isobutyl, tert-butyl, tert-amyl, etc.

[0084] In some embodiments, the compound represented by structural formula 2 includes one or more of the following compounds:

[0085] In some embodiments, the additive further includes a second additive, the second additive comprising at least one of cyclic sulfate compounds, sulfonyl lactone compounds, cyclic carbonate compounds, phosphate compounds, phosphite compounds, borate compounds, nitrile compounds, lithium salt additives, or alkane compounds.

[0086] In some embodiments, the cyclic sulfate compound includes at least one of vinyl sulfate, propylene sulfate, and methyl vinyl sulfate.

[0087] In some embodiments, the sulfonyl lactone compound includes at least one of 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, 1,3-propenesulfonyl lactone, and methylene disulfonate.

[0088] In some embodiments, the cyclic carbonate compound includes at least one of vinylene carbonate, ethylene ethylene carbonate, methylene ethylene carbonate, or the compound shown in structural formula 3:

[0089] In structural formula 3, R 21 R 22 R 23 R 24 R 25 R 26 Each is independently selected from one of the following: hydrogen atom, halogen atom, or C1-C5 group.

[0090] In some embodiments, the phosphate compound includes at least one of tris(trimethylsilane) phosphate, tris(triethylsilane) phosphate, or the compound shown in structural formula 4:

[0091] In structural formula 4, R 31 R 32 R 33 Each is independently selected from C1-C5 saturated hydrocarbon groups, C1-C5 unsaturated hydrocarbon groups, C1-C5 haloalkyl groups, C6-C12 aryl groups, C6-C12 haloaryl groups, -Si(C m H 2m+1 )3, where m is a natural number from 1 to 3.

[0092] In a preferred embodiment, the phosphate ester compound represented by structural formula 4 may be at least one of the following: triphenyl phosphate, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, triargylpropyl phosphate, diargylpropyl methyl phosphate, diargylpropyl ethyl phosphate, diargylpropyltrifluoromethyl phosphate, diargylpropyl-2,2,2-trifluoroethyl phosphate, diargylpropyl-3,3,3-trifluoropropyl phosphate, diargylpropylhexafluoroisopropyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, diallyl trifluoromethyl phosphate, diallyl-2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate, and diallyl hexafluoroisopropyl phosphate.

[0093] In some embodiments, the phosphite compounds include at least one of trimethyl phosphite, triethyl phosphite, tributyl phosphite, triphenyl phosphite, tri-toluene phosphite, tri-o-toluene phosphite, tri(trimethylsilane) phosphite, and tri(triethylsilane) phosphite.

[0094] In some embodiments, the borate ester compound includes at least one of tris(trimethylsilane)borate and tris(triethylsilane)borate.

[0095] In some embodiments, the nitrile compound includes at least one selected from succinic acid, glutaronitrile, hexanetrionitrile, adiponitrile, heptacyanide, octadionitrile, nonadionitrile, and sebaconitrile.

[0096] In other embodiments, the additive may also include other additives that can improve battery performance: for example, additives that improve battery safety performance, such as flame retardant additives like fluorophosphates and cyclophosphonitriles, or overcharge prevention additives like tert-amylbenzene and tert-butylbenzene.

[0097] It should be noted that, unless otherwise specified, the content of any optional substance in the additive in the non-aqueous electrolyte is generally less than 10%, preferably 0.01-5%, and more preferably 0.1% to 2%. Specifically, the content of any optional substance in the additive can be 0.01%, 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5%, 10%, or any combination of these values.

[0098] In some embodiments, the additive includes fluoroethylene carbonate, and the content of the fluoroethylene carbonate is 0.01% to 30% based on 100% of the total mass of the non-aqueous electrolyte.

[0099] In some embodiments, the fluorobenzene includes at least one of fluorobenzene, difluorobenzene, and trifluorobenzene.

[0100] In some embodiments, the difluorobenzene includes at least one of ortho-difluorobenzene, m-difluorobenzene, and p-difluorobenzene.

[0101] In some embodiments, the trifluorobenzene includes at least one of 1,2,3-trifluorobenzene, 1,3,5-trifluorobenzene, and 1,2,4-trifluorobenzene.

[0102] In some embodiments, the cycloalkane compound includes at least one selected from cyclopentane, cyclohexane, cycloheptane, methylcyclopentane, ethylcyclopentane, 1,3-dimethylcyclopentane, 1,4-dimethylcyclopentane, methylcyclohexane, ethylcyclohexane, propylcyclohexane, butylcyclohexane, pentylcyclohexane, cis-1-methyl-3-ethylcyclohexane, trans-1-methyl-3-ethylcyclohexane, 1,3-dimethylcyclohexane, 1,4-dimethylcyclohexane, 1,3,5-trimethylcyclohexane, bromocyclohexane, 1-chloro-2-ethylcyclohexane, and perfluoro(ethylcyclohexane).

[0103] In some embodiments, the negative electrode material layer includes a negative electrode active material, which includes at least one of artificial graphite, natural graphite, silicon-carbon composite material, soft carbon, and hard carbon.

[0104] In some embodiments, the negative electrode further includes a negative electrode current collector, and the negative electrode material layer covers the surface of the negative electrode current collector. The negative electrode current collector includes a metallic material capable of conducting electrons. Preferably, the negative electrode current collector includes at least one of Al, Ni, tin, copper, and stainless steel. In a more preferred embodiment, the negative electrode current collector is selected from copper foil.

[0105] In some embodiments, the negative electrode material layer further includes a negative electrode binder and a negative electrode conductive agent, and the negative electrode active material, the negative electrode binder and the negative electrode conductive agent are blended to obtain the negative electrode material layer.

[0106] The negative electrode binder includes at least one of the following: polyvinylidene fluoride (PVDF), copolymers of PVDF, polytetrafluoroethylene (PTFE), copolymers of PVDF-hexafluoropropylene, copolymers of tetrafluoroethylene-hexafluoropropylene, copolymers of tetrafluoroethylene-perfluoroalkyl vinyl ethers, copolymers of ethylene-tetrafluoroethylene, copolymers of PVDF-tetrafluoroethylene, copolymers of PVDF-trifluoroethylene, copolymers of PVDF-trichloroethylene, copolymers of PVDF-fluorinated vinylidene, copolymers of PVDF-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, polyethylene, and polypropylene; acrylic resins; and styrene-butadiene rubber.

[0107] The negative electrode conductive agent includes at least one of conductive carbon black, conductive carbon spheres, conductive graphite, conductive carbon fiber, carbon nanotubes, graphene, or reduced graphene oxide.

[0108] In some embodiments, the positive electrode includes a positive electrode material layer, the positive electrode material layer includes a positive electrode active material, and the positive electrode active material includes one or more of the following: lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium nickel manganese oxide (e.g., lithium nickel manganese oxide), lithium nickel oxide (e.g., lithium nickel oxide), lithium manganese oxide (e.g., spinel-type lithium manganese oxide, layered lithium manganese oxide, etc.), lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, and doped / coated modified compounds. Preferably, the positive electrode active material includes LiFe... 1-x’ M' x’ PO4, LiMn 2-y’ M y’ O4 and LiNi x Co y Mn z M 1-x-y-zAt least one of O2, wherein M' is selected from at least one of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V or Ti, and M is selected from at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V or Ti, and 0≤x'<1, 0≤y'≤1, 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1.

[0109] In a preferred embodiment, the positive electrode active material is selected from LiFe. 1-x’ M' x’ PO4, wherein M' is selected from at least one of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V, or Ti, and 0 ≤ x' < 1. The lithium-ion battery described has a high specific capacity, thereby effectively improving the battery's energy density. Furthermore, the battery's charging cut-off voltage can reach 3.8V, exhibiting a high discharge plateau and good cycle stability within a conventional voltage window. Moreover, since iron is relatively abundant and inexpensive globally, compared to rare and expensive metals such as cobalt, nickel, and manganese, using the aforementioned positive electrode active material helps reduce costs and alleviate dependence on limited resources.

[0110] In a more preferred embodiment, the positive electrode active material is selected from LiFe. 1-x’ Mn x’ PO4, where 0 ≤ x' ≤ 0.5.

[0111] In some specific embodiments, the positive electrode active material may include LiCoO2, LiFePO4, LiFe 0.4 Mn 0.6 PO4, LiMn2O4, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.7 Co 0.1 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiNi 0.9 Co 0.05 Mn 0.05 O2, LiNi 0.5 Co 0.2 Mn0.2 Al 0.1 O2, LiNi 0.5 Co 0.2 Al 0.3 One or more of O2.

[0112] In some embodiments, the positive electrode material layer further includes a positive electrode binder and a positive electrode conductive agent, and the positive electrode active material, the positive electrode binder and the positive electrode conductive agent are blended to obtain the positive electrode material layer.

[0113] The positive electrode binder includes at least one of the following: polyvinylidene fluoride (PVDF), copolymers of PVDF, polytetrafluoroethylene (PTFE), copolymers of PVDF-hexafluoropropylene, copolymers of tetrafluoroethylene-hexafluoropropylene, copolymers of tetrafluoroethylene-perfluoroalkyl vinyl ethers, copolymers of ethylene-tetrafluoroethylene, copolymers of PVDF-tetrafluoroethylene, copolymers of PVDF-trifluoroethylene, copolymers of PVDF-trichloroethylene, copolymers of PVDF-fluorinated vinylidene, copolymers of PVDF-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, polyethylene, and polypropylene; acrylic resins; and styrene-butadiene rubber.

[0114] The positive electrode conductive agent includes at least one of conductive carbon black, conductive carbon spheres, conductive graphite, conductive carbon fiber, carbon nanotubes, graphene, or reduced graphene oxide.

[0115] In some embodiments, the positive current collector comprises a metallic material capable of conducting electrons. Preferably, the positive current collector comprises at least one of Al, Ni, tin, copper, and stainless steel. In a more preferred embodiment, the positive current collector is selected from aluminum foil.

[0116] In some embodiments, the non-aqueous organic solvent has a mass content of 65% to 90% based on the total mass of the non-aqueous electrolyte being 100%.

[0117] Specifically, based on the total mass of the non-aqueous electrolyte as 100%, the mass content of the non-aqueous organic solvent can be 65%, 68%, 71%, 74%, 76%, 78%, 79%, 80%, 81.5%, 82%, 84%, 85%, 86%, 87%, 89%, 90%, or any combination of these values.

[0118] In some embodiments, the non-aqueous organic solvent further includes at least one of ether solvents, nitrile solvents, carboxylic acid ester solvents, carbonate solvents, and sulfone solvents.

[0119] In some embodiments, the ether solvent includes cyclic ethers or chain ethers, preferably chain ethers with 3 to 10 carbon atoms and cyclic ethers with 3 to 6 carbon atoms. The cyclic ethers may specifically include, but are not limited to, at least one of 1,3-dioxolane (DOL), 1,4-dioxane (DX), crown ethers, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH3-THF), and 2-trifluoromethyltetrahydrofuran (2-CF3-THF). The chain ethers may specifically include, but are not limited to, dimethoxymethane, diethoxymethane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether. Because chain ethers have high solvation ability with lithium ions and can improve ion dissociation, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane, which have low viscosity and can impart high ionic conductivity, are particularly preferred. Ether compounds can be used alone or in any combination and ratio of two or more. There are no particular restrictions on the content of ether compounds, and it is arbitrary as long as it does not significantly impair the performance of the high-pressure lithium-ion battery of this application. In the case of a non-aqueous solvent volume ratio of 100%, the volume ratio is usually 1% or more, preferably 2% or more, and more preferably 3% or more. In addition, the volume ratio is usually 30% or less, preferably 25% or less, and more preferably 20% or less.

[0120] In some embodiments, the nitrile solvent may be, but is not limited to, at least one of acetonitrile, glutaronitrile, and malononitrile.

[0121] In some embodiments, the carbonate solvent includes cyclic carbonates or chain carbonates. Cyclic carbonates may specifically include, but are not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC); chain carbonates may specifically include, but are not limited to, at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dipropyl carbonate (DPC). The content of cyclic carbonates is not particularly limited and is arbitrary as long as it does not significantly impair the performance of the lithium-ion battery described in this application. However, when using only one type, its content is typically 3% or more, preferably 5% or more, by volume relative to the total amount of solvent in the non-aqueous electrolyte. By setting this range, a decrease in conductivity due to a decrease in the dielectric constant of the non-aqueous electrolyte can be avoided, making it easier to achieve good high-current discharge characteristics, stability relative to the negative electrode, and cycle characteristics of the non-aqueous electrolyte battery. Furthermore, the upper limit is typically 90% or less by volume, preferably 85% or less, and more preferably 80% or less by volume. By setting this range, the oxidation / reduction resistance of the non-aqueous electrolyte can be improved, thereby contributing to enhanced stability during high-temperature storage. The content of the chain carbonate is not particularly limited, but relative to the total amount of solvent in the non-aqueous electrolyte, it is typically 15% or more by volume, preferably 20% or more, and more preferably 25% or more. Furthermore, it is typically 90% or less by volume, preferably 85% or less, and more preferably 80% or less. By keeping the chain carbonate content within the above range, it is easier to achieve an appropriate viscosity for the non-aqueous electrolyte, suppressing the decrease in ionic conductivity, and thus contributing to achieving a favorable range of output characteristics for the non-aqueous electrolyte battery. When using two or more chain carbonates in combination, it is sufficient to ensure that the total amount of chain carbonate meets the above range.

[0122] In some embodiments, fluorine-containing chain carbonates (hereinafter referred to as "fluorinated chain carbonates") are also preferably used. There is no particular limitation on the number of fluorine atoms in a fluorinated chain carbonate as long as it is 1 or more, but it is generally 6 or less, preferably 4 or less. When a fluorinated chain carbonate has multiple fluorine atoms, these fluorine atoms can be bonded to the same carbon atom or to different carbon atoms. Examples of fluorinated chain carbonates include dimethyl fluorinated carbonate derivatives, methyl ethyl fluorinated carbonate derivatives, and diethyl fluorinated carbonate derivatives.

[0123] In some embodiments, the carboxylic acid ester solvent includes cyclic carboxylic acid esters and / or chain carbonates. Examples of cyclic carboxylic acid esters include at least one of γ-butyrolactone, γ-valerolactone, and δ-valerolactone. Examples of chain carbonates include at least one of methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, propyl propionate (PP), and butyl propionate.

[0124] In some embodiments, the sulfone solvent includes cyclic sulfones and chain sulfones. Preferably, in the case of cyclic sulfones, it is typically a compound with 3 to 6 carbon atoms, more preferably 3 to 5 carbon atoms; in the case of chain sulfones, it is typically a compound with 2 to 6 carbon atoms, more preferably 2 to 5 carbon atoms. The content of the sulfone solvent is not particularly limited and is arbitrary within a range that does not significantly impair the performance of the lithium-ion battery of this application. Relative to the total amount of solvent in the non-aqueous electrolyte, it is typically 0.3% or more by volume, preferably 0.5% or more by volume, more preferably 1% or more by volume. Furthermore, it is typically 40% or less by volume, preferably 35% or less by volume, more preferably 30% or less by volume. When using two or more sulfone solvents in combination, the total amount of sulfone solvent should satisfy the above range. When the content of the sulfone solvent is within the above range, a non-aqueous electrolyte with excellent high-temperature storage stability is preferred.

[0125] In some embodiments, the electrolyte salt is selected from lithium salts, including LiPF6, LiODFP, LiODFB, LiBOB, LiPO2F2, LiBF4, LiSbF6, LiAsF6, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, LiClO4, LiAlCl4, LiCF3SO3, LiSO3F, and Li2B. 10 Cl 10 At least one of lithium chloroborane, lithium trioxazophosphate, lithium lower aliphatic carboxylic acid having four or fewer carbon atoms, or lithium tetraphenylborate.

[0126] In some embodiments, the concentration of the lithium salt in the non-aqueous electrolyte is 0.1 mol / L to 4 mol / L. In a preferred embodiment, the concentration of the lithium salt in the non-aqueous electrolyte is 0.5 mol / L to 2.5 mol / L. Specifically, in the non-aqueous electrolyte, the concentration of the lithium salt can be 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, 0.65 mol / L, 0.7 mol / L, 0.8 mol / L, 0.85 mol / L, 0.9 mol / L, 0.95 mol / L, 1.0 mol / L, 1.1 mol / L, 1.15 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.45 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2.0 mol / L, 2.1 mol / L, 2.2 mol / L, 2.3 mol / L, 2.4 mol / L, 2.5 mol / L, or any combination of these values.

[0127] It should be emphasized that the non-aqueous electrolyte provided in this application is not a precursor to a gel electrolyte or solid electrolyte, nor is it suitable as a precursor to a gel electrolyte or solid electrolyte. The reason is that the improvement of the electrochemical performance of the secondary battery in this application relies on the participation of the first additive in the formation of the solid electrolyte interphase (SEI) film on the negative electrode surface during the battery charge-discharge formation stage, and the continuous repair of the damaged solid electrolyte interphase (SEI) film by the first additive remaining in the electrolyte during the long-term cycling of the battery. However, as a precursor to a gel electrolyte or solid electrolyte, there is a polymerization operation to form a gel electrolyte before the battery charge-discharge formation. In this polymerization operation, the first additive reacts with polymerizable monomers as an initiator, resulting in the consumption of the first additive, thus it cannot play a corresponding role in the charge-discharge formation and battery charge-discharge cycling process.

[0128] In some embodiments, the non-aqueous electrolyte does not include polymerizable monomers and / or prepolymers obtained by polymerizing polymerizable monomers.

[0129] In some embodiments, the polymerizable monomers include one or more of the following: acrylate monomers (such as methyl acrylate, ethyl acrylate, butyl acrylate), acrylamide monomers (such as acrylamide, N,N'-methylenebisacrylamide), vinyl compound monomers (such as polyvinyl alcohol, vinylpyrrolidone, vinylimidazole), epoxy resin monomers (such as bisphenol A epoxy resin), polyethylene oxide monomers, polyacrylonitrile monomers, and siloxane monomers.

[0130] In some embodiments, the non-aqueous electrolyte does not undergo polymerization under light or heating conditions.

[0131] In some embodiments, the non-aqueous electrolyte is in a liquid state after formation.

[0132] In some embodiments, the secondary battery further includes a separator located between the positive electrode and the negative electrode.

[0133] The diaphragm can be a conventional diaphragm, such as a ceramic diaphragm, a polymer diaphragm, a non-woven fabric, or an inorganic-organic composite diaphragm, including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP / PE, double-layer PP / PP, and triple-layer PP / PE / PP diaphragms.

[0134] The present application will be further illustrated by the following examples.

[0135] Table 1

[0136] Example 1

[0137] This embodiment illustrates the lithium-ion battery and its preparation method disclosed in this application, and includes the following steps:

[0138] (1) Preparation of positive electrode: The positive active material LiFePO4, conductive agent carbon black (SP), conductive agent carbon nanotube (CNT), and polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 96:1.5:0.5:2. N-methylpyrrolidone (NMP) is added and stirred under vacuum until the mixture becomes a uniform and fluid positive electrode slurry. The slurry is evenly coated on both sides of aluminum foil, dried, rolled and vacuum dried, and aluminum leads are welded on using an ultrasonic welding machine to obtain the positive electrode plate. The thickness of the electrode plate is 120-150μm.

[0139] (2) Preparation of negative electrode sheet: The negative electrode active material graphite, conductive agent carbon black (SP), thickener sodium carboxymethyl cellulose (CMC) and binder styrene-butadiene rubber (SBR) are mixed in a weight ratio of 95:1:1.5:2.5, deionized water is added, and a negative electrode slurry is obtained under the action of a vacuum stirrer. The slurry is coated on both sides of copper foil, dried, rolled and vacuum dried, and nickel leads are welded on with an ultrasonic welding machine to obtain a negative electrode plate with a thickness of 120-150μm.

[0140] (3) Preparation of electrolyte: In an argon-filled glove box (moisture <10ppm, oxygen <10ppm), the solvent was mixed evenly at a mass ratio of ethylene carbonate (EC): ethyl methyl carbonate (EMC): dimethyl carbonate (DMC): propylene carbonate = 30:35:30:5. Fully dried lithium hexafluorophosphate was quickly added to the mixed solvent, and the following electrolyte additives were added, where the mass fraction of the corresponding substance is based on the mass fraction of the electrolyte: The electrolyte additives included 1 wt% ethylene sulfate, 3 wt% vinylene carbonate, and the first and second additives as shown in Table 1 by mass percentage. The mass fraction of lithium hexafluorophosphate was 12.8 wt%.

[0141] (4) Battery separator: 8µm polyethylene separator is selected.

[0142] (5) Preparation of lithium-ion batteries: A three-layer separator with a thickness of 20 μm is placed between the positive and negative plates. Then, the sandwich structure composed of the positive plate, negative plate and separator is wound up, flattened and placed in an aluminum foil packaging bag. It is then vacuum baked at 75°C for 48 h to obtain the cell to be injected with electrolyte. In a glove box with the dew point controlled below -40°C, the electrolyte prepared above is injected into the cell. After vacuum sealing, it is left to stand for 24 h. Then, the first charge formation is performed.

[0143] Examples 2-33

[0144] Examples 2-33 illustrate the lithium-ion battery and its preparation method disclosed in this application, including most of the operational steps in Example 1, with the following differences:

[0145] In the preparation steps of the non-aqueous electrolyte:

[0146] Using the first additive, the second additive, and their contents as shown in Table 1, the porosity of the negative electrode material layer is shown in Table 1.

[0147] Comparative Examples 1-21

[0148] Comparative Examples 1-21 are used to illustrate the lithium-ion battery and its preparation method disclosed in this application, including most of the operation steps in Example 1, the difference being:

[0149] In the preparation steps of the non-aqueous electrolyte:

[0150] Using the first additive, the second additive, and their contents as shown in Table 1, the porosity of the negative electrode material layer is shown in Table 1.

[0151] Performance testing

[0152] The lithium-ion batteries prepared above were subjected to the following performance tests:

[0153] 1. Storage Capacity Retention Test: 1) Before storage, perform room temperature constant-capacity setting: charge at 0.5C constant current and constant voltage to 3.65V (cutoff current 0.05C), let stand for 5 minutes, discharge at 0.5C constant current to 2.5V, record the discharge capacity before storage, and charge at 0.5C constant current and constant voltage to 3.65V (cutoff current 0.05C). 2) Store in a 60℃ oven for 30 days. After storage, place on a rack for constant-capacity setting, discharge at 0.5C constant current to 2.5V, and record the discharge capacity after storage.

[0154] Storage capacity retention rate (%) = (discharge capacity after storage / discharge capacity before storage) × 100%.

[0155] 2. Room temperature cycle test: At 25℃, the battery is charged and discharged at 1C. The cycle capacity retention rate (%) = (discharge capacity of the nth cycle / discharge capacity of the 1st cycle) × 100% until the capacity retention rate reaches 70%. Record the number of cycles n. The number of cycles n is the cycle life.

[0156] 3. Impedance growth rate (%) after 2000 cycles at room temperature = (Impedance after 2000 cycles at room temperature / Impedance before cycling at room temperature - 1) × 100%

[0157] Impedance test method: At 25℃, using a battery with a SOC of 50%, the test was conducted using an electrochemical workstation instrument. The frequency range was set to 1MHz-1mHz, and the constant voltage perturbation amplitude was 5mV. The experimental data were recorded. The first data point with an imaginary part of 0 corresponds to the real part R1, and the second data point with a slope of 0 corresponds to the real part R2. Impedance = R2-R1.

[0158] (1) The test results obtained from Examples 1 to 22 and Comparative Examples 1 to 21 are filled in Table 2.

[0159] Table 2

[0160] The test results of Examples 1-22 and Comparative Examples 1-21 show that the mass percentage a of the first additive in the non-aqueous electrolyte, the mass percentage b of the second additive in the non-aqueous electrolyte, and the porosity of the negative electrode material layer are all related to the content of the first additive. There is a clear correlation between the mass percentage of the first additive in the non-aqueous electrolyte (a), the mass percentage of the second additive in the non-aqueous electrolyte (b), and the porosity of the negative electrode material layer. Satisfying the relation: And 0.005≤a≤1, 0.1≤b≤10, The resulting lithium-ion battery exhibits high high-temperature storage capacity retention, long cycle life, and low impedance growth rate during cycling. This is presumably because the addition of the second additive enhances the diffusion efficiency of the first additive in the negative electrode material layer. During battery formation, this effectively promotes the decomposition and replenishment of the first additive at each interface of the negative electrode, ensuring uniformity of film thickness at each location. Simultaneously, the porosity of the negative electrode material layer affects the wettability of the non-aqueous electrolyte within it, indirectly influencing the conductivity of the first additive. This results in a more complete and uniform film formation of the first additive at each location on the negative electrode material, which is more conducive to lithium-ion conduction and exhibits higher interfacial stability.

[0161] The test results from Examples 1 to 22 show that when the mass percentage of the first additive in the non-aqueous electrolyte is a, the mass percentage of the second additive in the non-aqueous electrolyte is b, and the porosity of the negative electrode material layer is... Further meet the conditions And 0.005≤a≤0.6, 0.5≤b≤5, At this time, the resulting lithium-ion battery exhibits the best overall performance.

[0162] The test results of Comparative Examples 2 to 13 show that when the mass percentage of the first additive in the non-aqueous electrolyte is a, the mass percentage of the second additive in the non-aqueous electrolyte is b, and the porosity of the negative electrode material layer is... If one or more parameters exceed the specified range, even if the relation can be satisfied: The requirements resulted in poor cycle life and high-temperature storage performance of the obtained lithium-ion battery, indicating that when the values ​​of a, b, and... When the value is too high or too low, it will affect the film density and stability of the first additive on the surface of the negative electrode material layer, leading to a continuous increase in the SEI film thickness during charge-discharge cycles, and affecting the lithium-ion exchange efficiency between the non-aqueous electrolyte and the negative electrode. The test results of Comparative Examples 14-21 show that even when the values ​​of a, b, and... The values ​​all satisfy the range limits of their parameters, but Both excessively large and small values ​​can lead to the deterioration of battery cycle performance and high-temperature storage performance, as well as the increase of impedance. This indicates that there is an interaction between the porosity of the first additive, the second additive, and the negative electrode material layer. Only when the three reach a good balance can they significantly improve the electrochemical performance of lithium-ion batteries.

[0163] (2) The test results obtained in Examples 1, 23 to 33 are filled in Table 3.

[0164] Table 3

[0165] As can be seen from the test results of Examples 23-33, in the lithium-ion battery system provided in this application, under the condition of... And 0.005≤a≤1, 0.1≤b≤10, Under the premise that different first additives and different second additives can improve the cycle life, low impedance performance and high temperature storage performance of lithium-ion batteries, it can be seen that the battery system provided in this application is applicable to different first additives and different second additives, and different first additives and different second additives play similar roles in this battery system.

[0166] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A lithium-ion battery, characterized in that, The electrolyte includes a positive electrode, a negative electrode, and a non-aqueous electrolyte. The negative electrode includes a negative electrode material layer. The non-aqueous electrolyte includes a non-aqueous organic solvent, an electrolyte salt, and an additive. The additive includes a first additive, which includes a compound shown in structural formula 1 and / or a compound shown in structural formula 2. The second additive includes fluorobenzene and / or cycloalkanes. Wherein, n is 0 or 1; R1 and R2 are each independently selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C1-C12 acyl, substituted or unsubstituted C2-C12 alkoxyacyl, substituted or unsubstituted C2-C12 ether, and R1 and R2 are not... Both are hydrogen, and R1 and R2 can be linked together to form a ring or not; R3 is selected from substituted or unsubstituted C1-C12 alkylene groups, substituted or unsubstituted C2-C12 alkenyl groups, substituted or unsubstituted C2-C12 alkyne groups, substituted or unsubstituted C6-C20 aryl groups, and substituted or unsubstituted C2-C12 ether groups; when R1, R2, and R3 are substituted, the substituents are alkoxy, hydroxyl, acyl, ester, cyano, or halogen. R4 and R5 are each independently selected from substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C6 alkenyl, substituted or unsubstituted C2-C6 alkynyl or substituted or unsubstituted C1-C6 alkyl hydroxyl groups. R4 and R5 may be linked together to form a ring or not. R6 is selected from hydrogen, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C6 alkenyl or substituted or unsubstituted C2-C6 alkynyl, C1-C6 cyano, C2-C6 ester, substituted or unsubstituted C2-C6 amide or substituted or unsubstituted C1-C6 amidine. The lithium-ion battery meets the following conditions: And 0.005≤a≤1, 0.1≤b≤10, Where a is the mass percentage of the first additive in the non-aqueous electrolyte, in %; b represents the mass percentage of the second additive in the non-aqueous electrolyte, in %; Porosity of the negative electrode material layer, in percentage (%).

2. The lithium-ion battery according to claim 1, characterized in that, The lithium-ion battery meets the following conditions:

3. The lithium-ion battery according to claim 1 or 2, characterized in that, The lithium-ion battery satisfies at least one of the following conditions: (1)0.005≤a≤0.6； (2)0.5≤b≤5； (3) 4. The lithium-ion battery according to any one of claims 1 to 3, characterized in that, The compound represented by structural formula 1 satisfies at least one of the following conditions: (1) R1 is selected from hydrogen, and R2 is selected from… Substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, wherein R 10 Selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, and substituted or unsubstituted C6-C20 aryl. (2) R1 and R2 are each independently selected from substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, or substituted or unsubstituted C6-C20 aryl. (3) R1 is selected from R2 is selected from substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, or... Among them, R 11 Selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, substituted or unsubstituted C6-C20 aryl, and substituted or unsubstituted C2-C12 ether. (4) R1 is selected from Among them, R 12 R2 is selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, and substituted or unsubstituted C2-C11 alkynyl; R2 is selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, and substituted or unsubstituted C6-C20 aryl or... Among them, R 13 Selected from substituted or unsubstituted C1-C11 alkyl groups, substituted or unsubstituted C2-C11 alkenyl groups, and substituted or unsubstituted C2-C11 alkynyl groups.

5. The lithium-ion battery according to any one of claims 1 to 4, characterized in that, The compound represented by structural formula 1 includes one or more of the following compounds:

6. The lithium-ion battery according to any one of claims 1 to 5, characterized in that, The compound represented by structural formula 2 satisfies at least one of the following conditions: (1) When R4 and R5 are substituted, the substituents are carboxyl, hydroxyl, halogen or cyano; when R6 is substituted, the substituents are hydroxyl, halogen or alkoxy. (2) R6 is selected from cyano groups; (3) R4 and R5 are each independently selected from substituted or unsubstituted C1-C6 alkyl groups.

7. The lithium-ion battery according to any one of claims 1 to 6, characterized in that, The compound represented by structural formula 2 includes one or more of the following compounds:

8. The lithium-ion battery according to any one of claims 1 to 7, characterized in that, The lithium-ion battery satisfies at least one of the following conditions: (1) The fluorobenzene includes at least one of fluorobenzene, difluorobenzene and trifluorobenzene; (2) The cycloalkane compounds include at least one of cyclopentane, cyclohexane, cycloheptane, methylcyclopentane, ethylcyclopentane, 1,3-dimethylcyclopentane, 1,4-dimethylcyclopentane, methylcyclohexane, ethylcyclohexane, propylcyclohexane, butylcyclohexane, pentylcyclohexane, cis-1-methyl-3-ethylcyclohexane, trans-1-methyl-3-ethylcyclohexane, 1,3-dimethylcyclohexane, 1,4-dimethylcyclohexane, 1,3,5-trimethylcyclohexane, bromocyclohexane, 1-chloro-2-ethylcyclohexane, and perfluoro(ethylcyclohexane).

9. The lithium-ion battery according to any one of claims 1 to 8, characterized in that, The negative electrode material layer includes a negative electrode active material, which includes at least one of artificial graphite, natural graphite, silicon-carbon composite material, soft carbon, and hard carbon.

10. The lithium-ion battery according to any one of claims 1 to 9, characterized in that, The non-aqueous electrolyte does not contain polymerizable monomers and / or prepolymers obtained by polymerizing polymerizable monomers.

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