Non-aqueous electrolyte and secondary battery

Abstract

A non-aqueous electrolyte and a secondary battery. The non-aqueous electrolyte comprises a non-aqueous organic solvent, an electrolyte salt and an additive, wherein the additive comprises a first additive and a second additive, the first additive comprises a compound as represented by structural formula 1 and / or a compound as represented by structural formula 2, and the second additive comprises a C2-C4 cyclic sulfonate. The non-aqueous electrolyte satisfies the following conditions: 0.001≤a≤1, 0.01≤b≤1, and 7≤σ≤12, wherein a is the mass percentage content of the first additive in the non-aqueous electrolyte, with the unit thereof being %; b is the mass percentage content of the second additive in the non-aqueous electrolyte, with the unit thereof being %; and σ is the conductivity of the non-aqueous electrolyte at 25°C, with the unit thereof being mS / cm.

Description

A non-aqueous electrolyte and a secondary battery

[0001] This application claims priority to Chinese Patent Application No. 202510120111.4, filed on January 25, 2025, entitled “A Non-Aqueous Electrolyte and a Secondary Battery”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application belongs to the field of battery materials technology, specifically relating to a non-aqueous electrolyte and a secondary battery. Background Technology

[0003] Lithium-ion batteries have wide applications in the energy storage, transportation, and consumer electronics industries. To adapt to harsher environmental temperatures and charging / discharging conditions, lithium-ion batteries need to have longer lifespans and calendar lives. Taking renewable energy storage electrochemical devices as an example, in deserts or high-temperature regions, these devices often experience high-temperature environments. Under high temperatures, the electrodes or electrolytes inside lithium-ion batteries undergo a series of side reactions, leading to battery performance degradation.

[0004] Patent CN109873206A discloses an electrolyte in which cyclic sulfonates are added to decompose on the positive electrode surface to form a protective film, inhibiting the dissolution of transition metals and improving the high-temperature storage performance of lithium-ion batteries with ternary high-nickel positive electrode materials. However, the application of sulfur-containing additives in batteries also faces the problem of performance degradation. A paper published in Nature Energy in 2024, "High lithium oxide prevalence in the lithium solid-electrolyte interphase for high Coulombic efficiency," shows that the sulfur content on the negative electrode surface is negatively correlated with the coulombic efficiency of the battery, while the content of N, O, etc., is positively correlated with the coulombic efficiency. Therefore, the sulfur content in the negative electrode interface layer may reduce the charge-discharge efficiency of the battery, thereby reducing the stability of the battery cycle charge-discharge and shortening the battery life. Cyclic sulfonates participate in the film formation of both the positive and negative electrodes. How to promote the formation of more cyclic sulfonates on the positive electrode while ensuring the improvement of battery performance is a technical problem that needs to be solved. Summary of the Invention

[0005] To address the problem that existing cyclic sulfonates cannot simultaneously achieve film formation effects on both positive and negative electrodes, this application provides a non-aqueous electrolyte and a secondary battery.

[0006] The technical solution adopted in this application to solve the above-mentioned technical problems is as follows:

[0007] On one hand, this application provides a non-aqueous electrolyte, comprising a non-aqueous organic solvent, an electrolyte salt, and an additive, wherein the additive comprises a first additive and a second additive, the first additive comprising a compound represented by structural formula 1 and / or a compound represented by structural formula 2, and the second additive comprising a C2-C4 cyclic sulfonate ester.

[0008] 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.

[0009] Structural Formula 2

[0010] 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.

[0011] The non-aqueous electrolyte meets the following conditions:

[0012] And 0.001≤a≤1, 0.01≤b≤1, 7≤σ≤12;

[0013] Where a is the mass percentage of the first additive in the non-aqueous electrolyte, in %;

[0014] b represents the mass percentage of the second additive in the non-aqueous electrolyte, in %;

[0015] σ is the conductivity of the non-aqueous electrolyte at 25℃, in mS / cm.

[0016] Optionally, the non-aqueous electrolyte meets the following conditions:

[0017] 0.01≤a / b≤10.

[0018] Optionally, the non-aqueous electrolyte satisfies at least one of the following conditions:

[0019] (1)

[0020] (2) 0.005 ≤ a ≤ 0.8;

[0021] (3) 0.02 ≤ b ≤ 0.8;

[0022] (4) 7.5≤σ≤11.

[0023] Optionally, the compound represented by structural formula 1 satisfies at least one of the following conditions:

[0024] (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.

[0025] (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.

[0026] (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.

[0027] (4) R1 is selected from Among them, R 12R2 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.

[0028] Optionally, the compound represented by structural formula 1 includes one or more of the following compounds:

[0029] Optionally, the compound represented by structural formula 2 satisfies at least one of the following conditions:

[0030] (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.

[0031] (2) R6 is selected from cyano groups;

[0032] (3) R4 and R5 are each independently selected from substituted or unsubstituted C1-C6 alkyl groups.

[0033] Optionally, the compound represented by structural formula 2 includes one or more of the following compounds:

[0034] Optionally, the second additive includes one or more of 1,3-propanesulfonyl lactone, 2,4-butanesulfonyl lactone, 1,4-butanesulfonyl lactone, 1,3-propenesulfonyl lactone, and methylene disulfonate.

[0035] Optionally, the non-aqueous electrolyte does not include polymerizable monomers and / or prepolymers obtained by polymerizing polymerizable monomers.

[0036] In another embodiment, this application provides a secondary battery, including a positive electrode, a negative electrode, and a non-aqueous electrolyte as described above.

[0037] According to the non-aqueous electrolyte provided in this application, compounds represented by structural formula 1 and / or structural formula 2 are used as the first additive, and C2-C4 cyclic sulfonates are used as the second additive. The inventors have discovered 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 conductivity σ of the non-aqueous electrolyte at 25°C satisfy the following conditions… When 0.001≤a≤1, 0.01≤b≤1, and 7≤σ≤12, the resulting non-aqueous electrolyte, when applied to secondary batteries, significantly improves both room-temperature and high-temperature electrochemical performance. This is presumably due to the high electron cloud density of the oxygen-oxygen and nitrogen-nitrogen bonds in the first additive. Simultaneously, by regulating the conductivity of the non-aqueous electrolyte to provide a large number of mobile ions for charge transport, the electron cloud density of the oxygen-oxygen and nitrogen-nitrogen bonds in the first additive shifts slightly under the induction of the positive charge of lithium ions. This promotes the interaction between the first additive and the sulfonate groups exposed by ring strain in the second additive. This process reduces the reduction of sulfonate groups at the negative electrode interface, reduces the participation of low-valence sulfur components in the negative electrode surface coating, and thus reduces the sulfur content of the solid electrolyte interface film on the negative electrode surface. The first additive forms an appropriate solvation structure with migratable ions to participate in the formation of the solid electrolyte interface film on the negative electrode surface, resulting in the formation of a solid electrolyte interface film containing oxygen and nitrogen on the negative electrode surface, which is beneficial to improving the charge and discharge efficiency of the negative electrode. At the same time, this combination can promote more second additives to participate in the formation of the solid electrolyte interface film at the positive electrode, inhibit the dissolution of transition metal elements at the positive electrode under high temperature storage conditions, and improve the charge and discharge stability of the positive electrode. Detailed Implementation

[0038] 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.

[0039] One embodiment of this application provides a non-aqueous electrolyte, comprising a non-aqueous organic solvent, an electrolyte salt, and an additive. The additive includes a first additive and a second additive. The first additive includes a compound represented by structural formula 1 and / or a compound represented by structural formula 2. The second additive includes a C2-C4 cyclic sulfonate ester.

[0040]

[0041] 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.

[0042] 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.

[0043] The non-aqueous electrolyte meets the following conditions:

[0044] And 0.001≤a≤1, 0.01≤b≤1, 7≤σ≤12;

[0045] Where a is the mass percentage of the first additive in the non-aqueous electrolyte, in %;

[0046] b represents the mass percentage of the second additive in the non-aqueous electrolyte, in %;

[0047] σ is the conductivity of the non-aqueous electrolyte at 25℃, in mS / cm.

[0048] The inventors discovered 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 conductivity σ of the non-aqueous electrolyte at 25°C meet the following conditions... When 0.001≤a≤1, 0.01≤b≤1, and 7≤σ≤12, the resulting non-aqueous electrolyte, when applied to secondary batteries, significantly improves both room-temperature and high-temperature electrochemical performance. This is presumably due to the high electron cloud density of the oxygen-oxygen and nitrogen-nitrogen bonds in the first additive. Simultaneously, by regulating the conductivity of the non-aqueous electrolyte to provide a large number of mobile ions for charge transport, the electron cloud density of the oxygen-oxygen and nitrogen-nitrogen bonds in the first additive shifts slightly under the induction of the positive charge of lithium ions. This promotes the interaction between the first additive and the sulfonate groups exposed by ring strain in the second additive. This process reduces the reduction of sulfonate groups at the negative electrode interface, reduces the participation of low-valence sulfur components in the negative electrode surface coating, and thus reduces the sulfur content of the solid electrolyte interface film on the negative electrode surface. The first additive forms an appropriate solvation structure with migratable ions to participate in the formation of the solid electrolyte interface film on the negative electrode surface, resulting in the formation of a solid electrolyte interface film containing oxygen and nitrogen on the negative electrode surface, which is beneficial to improving the charge and discharge efficiency of the negative electrode. At the same time, this combination can promote more second additives to participate in the formation of the solid electrolyte interface film at the positive electrode, inhibit the dissolution of transition metal elements at the positive electrode under high temperature storage conditions, and improve the charge and discharge stability of the positive electrode.

[0049] In a preferred embodiment, the non-aqueous electrolyte satisfies the following conditions:

[0050] 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 conductivity σ of the non-aqueous electrolyte at 25°C further meet the above conditions, it is beneficial to further improve the battery's cycle capacity retention rate, high-temperature cycle performance, and high-temperature storage performance.

[0051] In some embodiments, the non-aqueous electrolyte meets the following conditions:

[0052] 0.01≤a / b≤10.

[0053] When the first additive and the second additive satisfy the condition 0.01≤a / b≤10, it is beneficial to promote the interaction between the first additive and the second additive and the reaction rate on the electrode surface. A sulfur-containing positive electrode protective layer is formed on the positive electrode to inhibit the dissolution of transition metal elements, reduce the increase of high-temperature storage impedance and capacity loss of the battery, and form an oxygen-containing and nitrogen-containing interface layer on the negative electrode to improve the negative electrode charge and discharge efficiency and lithium diffusion efficiency, improve charge and discharge stability, and improve the cycle performance of the battery.

[0054] In a preferred embodiment, the non-aqueous electrolyte satisfies the following conditions:

[0055] 0.02≤a / b≤6.

[0056] In a specific embodiment, the mass percentage 'a' of the first additive in the non-aqueous electrolyte can be any two of the following: 0.001%, 0.003%, 0.006%, 0.009%, 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%.

[0057] In a preferred embodiment, 0.005 ≤ a ≤ 0.8.

[0058] The oxygen-oxygen bonds and nitrogen-nitrogen bonds in the first additive have a high electron cloud density, which interacts with the sulfonate groups exposed by ring strain in the second additive, reducing the reduction of sulfonate groups at the negative electrode interface, reducing the participation of low-valence S components in the negative electrode surface coating, and improving the charge and discharge efficiency of the negative electrode. If the content of the first additive is too low, it is difficult to suppress the generation of S-containing components in the solid electrolyte interface film on the negative electrode surface, affecting the ion diffusion efficiency of the negative electrode surface. If the content of the first additive is too high, due to the instability of the properties of the first additive itself, it will promote the generation of too many free radicals in the non-aqueous electrolyte, increasing the probability of side reactions with impurities in the non-aqueous electrolyte, leading to the instability of the properties of the non-aqueous electrolyte itself.

[0059] In a specific embodiment, the mass percentage b of the second additive in the non-aqueous electrolyte can be any two of the following: 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%.

[0060] In a preferred embodiment, 0.02 ≤ b ≤ 0.8.

[0061] The second additive is used to participate in the formation of a solid electrolyte interface film at the positive electrode, inhibiting the dissolution of transition metal elements at the positive electrode under high-temperature storage conditions and improving the charge-discharge stability of the positive electrode. If the content of the second additive is too low, it will be difficult to improve the high-temperature stability of the positive electrode material; if the content of the second additive is too high, it will easily lead to an increase in the sulfur content on the surface of the negative electrode, affecting the charge-discharge efficiency of the negative electrode.

[0062] In a specific embodiment, the conductivity σ of the non-aqueous electrolyte at 25°C can be 7 mS / cm, 7.5 mS / cm, 8 mS / cm, 8.5 mS / cm, 9 mS / cm, 9.5 mS / cm, 10 mS / cm, 10.5 mS / cm, 11 mS / cm, 12 mS / cm, or any two of the above.

[0063] In a preferred embodiment, 7.5 ≤ σ ≤ 11.

[0064] The conductivity σ of the non-aqueous electrolyte at 25°C affects the interaction between the first additive and the second additive. When the conductivity σ of the non-aqueous electrolyte at 25°C is within the above range, it is beneficial to provide a large number of migratable ions, which can form an appropriate solvation structure with the first additive, promote the film formation of the first additive on the negative electrode surface, and at the same time inhibit the film formation of the second additive on the negative electrode surface.

[0065] The ionic conductivity of the electrolyte at 25°C can be controlled, for example, by adjusting the non-aqueous solvent and the lithium salt. More specifically, the ionic conductivity of the electrolyte can be controlled to a higher value by mixing a low-viscosity solvent and / or a high-polarity solvent, by using a low-viscosity solvent with high polarity, by using a higher content of lithium salt, or by using a lithium salt with high dissociation capacity.

[0066] 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.

[0067] 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 R 15 Each is independently selected from a single bond or a C1-C11 alkyl group.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] As an example, the compound represented by structural formula 1 may be selected from the following compounds:

[0073] 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.

[0074] 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.

[0075] As an example, the compound represented by structural formula 1 may be selected from the following compounds:

[0076] 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.

[0077] 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.

[0078] 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.

[0079] As an example, the compound represented by structural formula 1 may be selected from the following compounds:

[0080] 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 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.

[0081] 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.

[0082] As an example, the compound represented by structural formula 1 may be selected from the following compounds:

[0083] 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.

[0084] 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.

[0085] As an example, the compound represented by structural formula 1 may be selected from the following compounds:

[0086] In some embodiments, the compound represented by structural formula 1 includes one or more of the following compounds:

[0087] 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.

[0088] 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.

[0089] In some embodiments, in the compound represented by structural formula 2, R6 is selected from cyano.

[0090] 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.

[0091] The C1-C6 alkyl groups include methyl, ethyl, n-propyl, isopropyl, isobutyl, tert-butyl, tert-amyl, etc.

[0092] In some embodiments, the compound represented by structural formula 2 includes one or more of the following compounds:

[0093] In some embodiments, the second additive includes one or more of 1,3-propanesulfonyl lactone, 2,4-butanesulfonyl lactone, 1,4-butanesulfonyl lactone, 1,3-propenesulfonyl lactone, and methylene disulfonate.

[0094] In some embodiments, the additive further includes a third additive, which includes at least one of cyclic sulfate compounds, cyclic carbonate compounds, phosphate compounds, phosphite compounds, borate compounds, nitrile compounds, lithium salt additives, or alkane compounds.

[0095] In some embodiments, the cyclic sulfate compound includes at least one of vinyl sulfate, propylene sulfate, and methyl vinyl sulfate.

[0096] 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:

[0097] 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.

[0098] 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:

[0099] 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 halohydrocarbon groups, and -Si(C m H2m+1 )3, where m is a natural number from 1 to 3.

[0100] 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, triargylpropyl phosphate, diargylpropyl methyl phosphate, diargylpropyl ethyl phosphate, diargylpropyl propyl phosphate, diargylpropyl-2,2,2-trifluoroethyl phosphate, diargylpropyl-3,3,3-trifluoropropyl phosphate, diargylpropyl hexafluoroisopropyl 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.

[0101] 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.

[0102] In some embodiments, the borate ester compound includes at least one of tris(trimethylsilane)borate and tris(triethylsilane)borate.

[0103] In some embodiments, the nitrile compound includes at least one selected from succinic acid, glutaronitrile, hexanetrionitrile, adiponitrile, heptacyanide, octadionitrile, nonadionitrile, and sebaconitrile.

[0104] In some embodiments, the alkane 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, and perfluoro(ethylcyclohexane).

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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%.

[0109] 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.

[0110] In some embodiments, the non-aqueous organic solvent includes at least one of ether solvents, nitrile solvents, carbonate solvents, carboxylic acid ester solvents, and sulfone solvents.

[0111] 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.

[0112] In some embodiments, the nitrile solvent may be, but is not limited to, at least one of acetonitrile, glutaronitrile, and malononitrile.

[0113] 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.

[0114] 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.

[0115] Carboxylic acid ester solvents include 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 (PA), butyl acetate, propyl propionate (PP), and butyl propionate.

[0116] 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.

[0117] In a preferred embodiment, the non-aqueous organic solvent includes the carbonate solvent, which includes one or more of chain carbonates and cyclic carbonates.

[0118] In some embodiments, the chain carbonate includes one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, fluorinated dimethyl carbonate, fluorinated diethyl carbonate, and fluorinated methyl ethyl carbonate; the cyclic carbonate includes one or more of ethylene carbonate, propylene carbonate, and fluorinated ethylene carbonate; and / or

[0119] In some embodiments, the carbonate solvent includes ethylene carbonate, and the non-aqueous electrolyte contains ≤50% by mass of ethylene carbonate.

[0120] In some embodiments, the mass ratio of the chain carbonate to the cyclic carbonate is 1 to 9.

[0121] By controlling the ratio of chain carbonates to cyclic carbonates and adjusting the polarity of the solvent to change the solvation structure, it is beneficial to further improve the structure of the solid electrolyte film on the negative electrode surface and enhance the high-temperature storage performance of the battery.

[0122] 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 10At least one of lithium chloroborane, lithium trioxazophosphate, lithium lower aliphatic carboxylic acid having four or fewer carbon atoms, or lithium tetraphenylborate.

[0123] 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.

[0124] 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.

[0125] In some embodiments, the non-aqueous electrolyte does not include polymerizable monomers and / or prepolymers obtained by polymerizing polymerizable monomers.

[0126] 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.

[0127] In some embodiments, the non-aqueous electrolyte does not undergo polymerization under light or heating conditions.

[0128] In some embodiments, the non-aqueous electrolyte is in a liquid state after formation.

[0129] Another embodiment of this application provides a secondary battery, including a positive electrode, a negative electrode, and a non-aqueous electrolyte as described above.

[0130] In some embodiments, the secondary battery is a lithium-ion battery.

[0131] 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 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 thereof. 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-z At 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.

[0132] 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.

[0133] In a more preferred embodiment, the positive electrode active material is selected from LiFe. 1-x’ Mn x’ PO4, where 0 ≤ x' ≤ 0.5.

[0134] 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 Mn 0.2 Al 0.1 O2, LiNi 0.5 Co 0.2 Al 0.3 One or more of O2.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] 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.

[0139] In some embodiments, the negative electrode includes a negative electrode material layer, the negative electrode material layer includes a negative electrode active material, and the negative electrode active material includes at least one of carbon-based negative electrode, silicon-based negative electrode, tin-based negative electrode, and lithium negative electrode. The carbon-based negative electrode may include graphite, hard carbon, soft carbon, graphene, mesophase carbon microspheres, etc.; the silicon-based negative electrode may include silicon materials, silicon oxides, silicon-carbon composite materials, and silicon alloy materials, etc.; the tin-based negative electrode may include tin, tin-carbon, tin oxide, and tin metal compounds; the lithium negative electrode may include metallic lithium or lithium alloys. Specifically, the lithium alloy may be at least one of lithium-silicon alloy, lithium-sodium alloy, lithium-potassium alloy, lithium-aluminum alloy, lithium-tin alloy, and lithium-indium alloy.

[0140] In a more preferred embodiment, the negative electrode active material includes at least one of graphite, hard carbon, soft carbon, graphene, and silicon-carbon composite materials.

[0141] In some embodiments, the silicon material is one or more of silicon nanoparticles, silicon nanowires, silicon nanotubes, silicon thin films, 3D porous silicon, and hollow porous silicon.

[0142] 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.

[0143] 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.

[0144] 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.

[0145] 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.

[0146] In some embodiments, the secondary battery further includes a separator located between the positive electrode and the negative electrode.

[0147] 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.

[0148] The present application will be further illustrated by the following examples.

[0149] Table 1

[0150] In Table 1, VC stands for vinylene carbonate; EC stands for ethylene carbonate; PC stands for propylene carbonate; DMC stands for dimethyl carbonate; EMC stands for ethyl methyl carbonate; DEC stands for diethyl carbonate; and EP stands for ethyl propionate.

[0151] Example 1

[0152] This embodiment illustrates the lithium-ion battery and its preparation method disclosed in this application, and includes the following steps:

[0153] (1) Preparation of non-aqueous electrolyte: A solution was prepared by mixing a solvent, a first additive, a second additive, lithium hexafluorophosphate, and vinylene carbonate. The solvent composition, the content of the first additive, the second additive, lithium hexafluorophosphate, and vinylene carbonate are shown in Table 1. The conductivity of the non-aqueous electrolyte was measured and recorded in Table 1.

[0154] (2) Preparation of the positive electrode sheet: The positive electrode active material LiFePO4, conductive carbon black Super-P and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 96:2:2, and then dispersed in N-methyl-2-pyrrolidone (NMP) to obtain the positive electrode slurry. The slurry was uniformly coated on both sides of aluminum foil, and after drying, rolling and vacuum drying, aluminum leads were welded on using an ultrasonic welding machine to obtain the positive electrode sheet.

[0155] (3) Preparation of negative electrode sheet: The negative electrode active material artificial graphite, conductive carbon black Super-P, binder styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) are mixed in a mass ratio of 94:1:2.5:2.5, and then dispersed in deionized water to obtain a negative electrode slurry. The slurry is coated on both sides of copper foil, dried, rolled and vacuum dried, and nickel leads are welded on using an ultrasonic welding machine to obtain the negative electrode sheet.

[0156] (4) Preparation of the cell: Three layers of separator are placed between the positive electrode and the negative electrode. Then, the sandwich structure composed of the positive electrode, the negative electrode and the separator is wound up. The wound body is flattened and placed in an aluminum foil packaging bag. It is vacuum baked at 75°C for 48 hours to obtain the cell to be injected with electrolyte.

[0157] (5) Electrolyte injection and formation of the battery cell: In a glove box with the dew point controlled below -40°C, the electrolyte prepared above is injected into the battery cell, which is then vacuum sealed and left to stand for 24 hours. Then the first charging formation is carried out.

[0158] Examples 2-34

[0159] Examples 2-34 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:

[0160] In the preparation steps of the non-aqueous electrolyte:

[0161] Using the non-aqueous electrolyte composition shown in Table 1, the conductivity of the non-aqueous electrolyte was tested and recorded in Table 1.

[0162] Comparative Examples 1-20

[0163] Comparative Examples 1-20 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:

[0164] In the preparation steps of the non-aqueous electrolyte:

[0165] Using the non-aqueous electrolyte composition shown in Table 1, the conductivity of the non-aqueous electrolyte was tested and recorded in Table 1.

[0166] Performance testing

[0167] The lithium-ion batteries prepared above were subjected to the following performance tests:

[0168] 1. Cyclic life at room temperature:

[0169] Place the battery at room temperature and let it stand for 5 minutes. Then charge it at a constant current and constant voltage of 0.33C to 3.65V, let it stand for 5 minutes, and then discharge it at a constant current of 0.33C to 2.5V. Record the discharge capacity C1. Repeat this charge and discharge cycle. After n charge and discharge cycles, record the charging capacity C2 of the nth cycle.

[0170] When C2 / C1 = 70%, the cycle life at room temperature is n cycles.

[0171] 2. High-temperature storage capacity retention and internal resistance growth rate:

[0172] Place the battery at room temperature for 2 hours, then charge it at a constant current and voltage of 0.5C to 50% SOC. Let it stand for 40 minutes, and test the battery's internal resistance R1 using an internal resistance test. Charge it at a constant current and voltage of 0.5C to 3.65V, let it stand for 5 minutes, then discharge it at a constant current of 0.5C to 2.5V, let it stand for 5 minutes, then charge it at a constant current and voltage of 0.5C to 3.65V, let it stand for 5 minutes, and record the charging capacity C1. Store the battery at 60℃ for 45 days. Place the battery at room temperature for 2 hours, then discharge it at a constant current of 0.5C to 2.5V, let it stand for 5 minutes, and record the discharge capacity C2. Test the battery's internal resistance R2 using an internal resistance test. Calculate using the following formula:

[0173] High-temperature storage capacity retention rate (%) = C2 / C1 * 100%;

[0174] The rate of increase in internal resistance at high temperatures (%) = R2 / R1 * 100%.

[0175] (1) The test results obtained from Examples 1-15 and Comparative Examples 1-20 are filled in Table 2.

[0176] Table 2

[0177] The test results of Examples 1-15 and Comparative Examples 1-20 show that in non-aqueous electrolytes using compounds of structural formula 1 and / or structural formula 2 as the first additive and cyclic sulfonates as the second additive, the conditions can be met by controlling 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 conductivity σ of the non-aqueous electrolyte at 25°C. When 0.001≤a≤1, 0.01≤b≤1, and 7≤σ≤12, the resulting lithium-ion battery has a longer cycle life, higher high-temperature storage capacity retention, and a lower impedance growth rate. It is speculated that the oxygen-oxygen bonds and nitrogen-nitrogen bonds in the first additive have a high electron cloud density. Simultaneously, by regulating the conductivity of the non-aqueous electrolyte to provide a large number of migrateable ions for charge transport, under the induction of the positive charge of lithium ions, the electron cloud density of the oxygen-oxygen bonds and nitrogen-nitrogen bonds in the first additive undergoes a slight shift. This promotes the interaction between the first additive and the sulfonate groups exposed by ring strain in the second additive, reducing the reduction of sulfonate groups at the negative electrode interface and decreasing the participation of low-valence sulfur components in the negative electrode surface coating. This, in turn, reduces the sulfur content in the solid electrolyte interfacial film on the negative electrode surface. The first additive and migrateable ions form an appropriate solvation structure to participate in the formation of the solid electrolyte interfacial film on the negative electrode surface, resulting in a solid electrolyte interfacial film containing oxygen and nitrogen components, which is beneficial to improving the charge-discharge efficiency of the negative electrode. At the same time, this combination can promote more participation of the second additive in the formation of the solid electrolyte interfacial film at the positive electrode, inhibiting the dissolution of transition metal elements at the positive electrode under high-temperature storage conditions and improving the charge-discharge stability of the positive electrode. Therefore, 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 conductivity σ of the non-aqueous electrolyte at 25°C are in a synergistic state, it can promote the formation of a more stable solid electrolyte interface film on the surfaces of the negative and positive electrodes, thereby improving the various performance characteristics of the lithium-ion battery.

[0178] The test results from Examples 1-15 show 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 conductivity σ of the non-aqueous electrolyte at 25°C further meet the conditions... Furthermore, when 0.005≤a≤0.8, 0.02≤b≤0.8, and 7.5≤σ≤11, it is beneficial to further improve the stability of the solid electrolyte interface film on the positive and negative electrode surfaces, and enhance the room temperature electrochemical performance and high temperature electrochemical performance of the secondary battery.

[0179] The test results of Comparative Examples 1 to 20 show that even if the mass percentage of the first additive a in the non-aqueous electrolyte, the mass percentage of the second additive b in the non-aqueous electrolyte, and the conductivity σ of the non-aqueous electrolyte at 25°C meet the conditions... Even when the limit of σ ≤ 90 is met, lithium-ion batteries still do not exhibit good room-temperature and high-temperature electrochemical performance when the values ​​of a, b, or σ do not meet these limits. This indicates a strong correlation between the values ​​of a, b, and σ in improving the cycle performance of lithium-ion batteries. Similarly, even when the values ​​of a, b, or σ meet these limits, lithium-ion batteries still do not exhibit good room-temperature and high-temperature electrochemical performance. The value does not meet the above preset conditions. At the same time, it does not have a good effect on improving battery performance, indicating that the synergistic effect of the three only exists under specific conditions.

[0180] (2) The test results obtained in Examples 16 to 23 are filled in Table 3.

[0181] Table 3

[0182] A comparison of the test results of Examples 1-15 in Table 2 and Examples 16-23 in Table 3 shows that when the mass percentage of the first additive 'a' in the non-aqueous electrolyte and the mass percentage of the second additive 'b' in the non-aqueous electrolyte further satisfy the condition 0.01≤a / b≤10, the interaction between the first additive and the second additive can be promoted, forming a sulfur-containing positive electrode solid electrolyte interface layer on the positive electrode side and an oxygen- and nitrogen-containing negative electrode solid electrolyte interface layer on the negative electrode side. This reduces the battery's high-temperature impedance growth and capacity loss, and improves the battery's cycle performance.

[0183] (3) The test results obtained in Examples 3, 24 to 34 are filled in Table 4.

[0184] Table 4

[0185] A comparison of the test results from Examples 3 and 24-34 shows that, in the electrolyte system provided in this application, 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 conductivity σ of the non-aqueous electrolyte at 25°C meet the conditions. Under the premise that 0.001≤a≤1, 0.01≤b≤1, and 7≤σ≤12, the use of different first additives and different second additives can improve the cycle performance and high-temperature performance of lithium-ion batteries. This indicates that the electrolyte system of this application is suitable for different first additives and different second additives. In this electrolyte system, different first additives have similar effects, and different second additives have similar effects.

[0186] 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 nonaqueous electrolyte, wherein, comprise a non-aqueous organic solvent, an electrolyte salt, and additives, the additives comprising a first additive and a second additive, the first additive comprising a compound represented by Structural Formula 1 and / or a compound represented by Structural Formula 2, the second additive comprising a cyclic sulfonate ester of C2 to C4; wherein n is 0 or 1; R1, R2are 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 alkoxylacyl, substituted or unsubstituted C2-C12 ether group, and R1, R2are not simultaneously hydrogen, and R1, R2may or can not be connected to each other to form a ring; R3is selected from substituted or unsubstituted C1-C12 alkylene, substituted or unsubstituted C2-C12 alkenylene, substituted or unsubstituted C2-C12 alkynylene, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C2-C12 ether group; when R1, R2, R3are substituted, the substituents are alkoxy, hydroxyl, acyl, ester group, 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 non-aqueous electrolyte meets the following conditions: And 0.001≤a≤1, 0.01≤b≤1, 7≤σ≤12; 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 %; σ is the conductivity of the non-aqueous electrolyte at 25℃, in mS / cm.

2. The nonaqueous electrolyte according to claim 1, wherein The non-aqueous electrolyte meets the following conditions: 0.01≤a / b≤10.

3. The nonaqueous electrolyte according to claim 1 or 2, wherein The non-aqueous electrolyte satisfies at least one of the following conditions: (1) (2)0.005≤a≤0.8； (3)0.02≤b≤0.8； (4) 7.5≤σ≤11.

4. The nonaqueous electrolyte according to any one of claims 1 to 3, wherein The compound represented by structural formula 1 satisfies at least one of the following conditions: (1) R1is selected from hydrogen, R2is selected from substituted or unsubstituted C1-C12alkyl, substituted or unsubstituted C2-C12alkenyl, substituted or unsubstituted C2-C12alkynyl, substituted or unsubstituted C6-C20aryl, wherein R 10 substituted or unsubstituted C1-C11alkyl, substituted or unsubstituted C2-C11alkenyl, substituted or unsubstituted C2-C11alkynyl, substituted or unsubstituted C6-C20aryl; (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) R1is selected from R2is selected from substituted or unsubstituted C1-C12alkyl, substituted or unsubstituted C2-C12alkenyl, substituted or unsubstituted C2-C12alkynyl, substituted or unsubstituted C6-C20aryl, or wherein R 11 is 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, substituted or unsubstituted C2-C12 ether; (4) R1is selected from wherein R is selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl; R2is 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 12 wherein R is selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl; R2is 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 wherein R 13 is selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl.

5. The nonaqueous electrolyte according to any one of claims 1 to 4, wherein The compound of Structural Formula 1 includes one or more of the following compounds:

6. The nonaqueous electrolyte according to any one of claims 1 to 5, wherein 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 nonaqueous electrolyte according to any one of claims 1 to 6, wherein The compound of Structural Formula 2 includes one or more of the following compounds:

8. The nonaqueous electrolyte according to any one of claims 1 to 7, wherein The second additive includes one or more of 1,3-propanesulfonyl lactone, 2,4-butanesulfonyl lactone, 1,4-butanesulfonyl lactone, 1,3-propenesulfonyl lactone, and methylene disulfonate.

9. The nonaqueous electrolyte according to any one of claims 1 to 8, wherein The non-aqueous electrolyte does not contain polymerizable monomers and / or prepolymers obtained by polymerizing polymerizable monomers.

10. A secondary battery, wherein, It includes a positive electrode, a negative electrode, and a non-aqueous electrolyte as described in any one of claims 1 to 9.

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