Non-aqueous electrolyte and secondary battery

Abstract

A non-aqueous electrolyte and a secondary battery. The non-aqueous electrolyte comprises a saturated carbonate, an electrolyte salt and an additive, wherein the additive comprises a first additive, and the first additive comprises a compound as represented by structural formula 1 and / or a compound as represented by structural formula 2. The non-aqueous electrolyte satisfies the following conditions: 0.0001≤a / b×η≤0.09, 0.001≤a≤1, 50≤b≤90, and 2≤η≤6, 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 saturated carbonate in the non-aqueous electrolyte, with the unit thereof being %; and η is the viscosity of the non-aqueous electrolyte at 25°C, with the unit thereof being mPa·s.

Description

A non-aqueous electrolyte and a secondary battery

[0001] This application claims priority to Chinese Patent Application No. 202510109069.6, filed on January 23, 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 energy storage electronic components technology, specifically relating to a non-aqueous electrolyte and a secondary battery. Background Technology

[0003] Due to their environmental friendliness and stable performance, lithium-ion batteries are widely used in energy storage, new energy vehicles, and portable electronic devices. Currently, lithium-ion batteries are developing towards higher energy density and larger cell capacity to meet end-user demands for long lifespan, extended range, and low cost. Cell design is improving performance limits by increasing material utilization and internal space utilization, while also further reducing redundant design. This places greater challenges on materials; for example, in large-capacity cells, issues such as electrolyte penetration, charging / discharging heat generation, and internal side reactions become more stringent, altering the role of the electrolyte. With the upgrading of application terminal demands, higher requirements are being placed on the low-temperature cycle performance and high-rate discharge performance of lithium-ion batteries. The key to improving the low-temperature cycle performance and high-rate discharge performance of lithium-ion batteries lies in reducing the impedance of lithium-ion batteries. The diffusion efficiency of lithium ions in non-aqueous electrolytes is particularly critical. However, the ion diffusion performance of existing non-aqueous electrolytes is difficult to meet the requirements of low temperature and high-rate charge and discharge. The significant capacity reduction of lithium-ion batteries under low temperature conditions and the heat generation and capacity reduction under high-rate discharge conditions have become bottlenecks restricting the development of lithium-ion batteries. Summary of the Invention

[0004] To address the shortcomings of existing lithium-ion batteries in low-temperature performance and rate discharge performance, this application provides a non-aqueous electrolyte and a secondary battery.

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

[0006] On one hand, this application provides a non-aqueous electrolyte comprising a saturated carbonate, an electrolyte salt, and an additive, wherein the additive comprises a first additive comprising a compound represented by structural formula 1 and / or a compound represented by structural formula 2:

[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, and R4 and R5 are 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 non-aqueous electrolyte meets the following conditions:

[0010] 0.0001≤a / b×η≤0.09, and 0.001≤a≤1, 50≤b≤90, 2≤η≤6;

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

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

[0013] η is the viscosity of the non-aqueous electrolyte at 25°C, in mPa·s.

[0014] Optionally, the non-aqueous electrolyte satisfies at least one of the following conditions:

[0015] (1) 0.015 ≤ a / b × η ≤ 0.06;

[0016] (2) 0.005 ≤ a ≤ 0.8;

[0017] (3) 55≤b≤85;

[0018] (4) 2.5≤η≤5.2.

[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 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.

[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 groups;

[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 saturated carbonate includes one or more of chain carbonates and cyclic carbonates, wherein 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, and the cyclic carbonate includes one or more of ethylene carbonate, propylene carbonate, and fluorinated ethylene carbonate, and / or

[0031] The non-aqueous organic solvent also includes cyclic carboxylic esters and their halogenated derivatives and / or chain carboxylic esters and their halogenated derivatives.

[0032] Optionally, the non-aqueous electrolyte further includes unsaturated carbonates, including vinylene carbonate;

[0033] The non-aqueous electrolyte meets the following conditions:

[0034] 0.01≤(a+c) / b≤0.09, and 0.1≤c≤5.5;

[0035] Where a is the mass percentage of the first additive in the non-aqueous electrolyte, in %;

[0036] b represents the mass percentage of saturated carbonate in the non-aqueous electrolyte, in %;

[0037] c represents the mass percentage of unsaturated carbonates in the non-aqueous electrolyte, expressed as %.

[0038] Optionally, the non-aqueous electrolyte does not include polymerizable monomers and / or prepolymers obtained by polymerizing polymerizable monomers.

[0039] On the other hand, this application provides a secondary battery, including a positive electrode, a negative electrode, and a non-aqueous electrolyte as described above.

[0040] According to the non-aqueous electrolyte provided in this application, a first additive containing oxygen-oxygen bonds and nitrogen-nitrogen bonds is added, and saturated carbonate is used as the non-aqueous organic solvent. Through extensive research, the inventors discovered that, based on the aim of improving the low-temperature performance and high-rate discharge performance of lithium-ion batteries, when the mass percentage of the first additive *a* in the non-aqueous electrolyte, the mass percentage of saturated carbonate in the non-aqueous electrolyte *b*, and the viscosity *η* of the non-aqueous electrolyte at 25°C satisfy the conditions 0.0001≤a / b×η≤0.09, and 0.001≤a≤1, 50≤b≤90, 2≤η≤6, the resulting lithium-ion battery exhibits excellent performance under low-temperature conditions and high-rate discharge. Under the given conditions, all exhibited high capacity retention, presumably due to the higher electron cloud density of the oxygen-oxygen and nitrogen-nitrogen bond groups in the first additive. This facilitates interaction with positively charged lithium ions, promoting the solvation of saturated carbonate and shielding the binding of lithium ions by anions. By controlling the relative ratio of the first additive and saturated carbonate, the ion conductivity and diffusion kinetics of the non-aqueous electrolyte can be improved. Due to its interaction with lithium ions, the first additive has a chance to participate in the lithium-ion solvation inner layer dominated by saturated carbonate, reaching the electrode surface and participating in the formation of the electrode surface coating during the ion desolvation stage, thus improving the interface composition and structure. Simultaneously, the viscosity control of the non-aqueous electrolyte affects the interaction between the first additive, saturated carbonate, and lithium ions, influencing the first additive's role in promoting ion diffusion and participating in electrode coating. When the mass percentage of the first additive (a), the mass percentage of saturated carbonate (b), and the viscosity (η) of the non-aqueous electrolyte at 25°C are in a synergistic state, it is beneficial to comprehensively consider the influence of various factors and obtain a non-aqueous electrolyte with high ion conductivity under low temperature and high discharge conditions. Detailed Implementation

[0041] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0042] In the description of this application, the term "unsaturated carbonate" refers to a carbonate containing carbon-carbon double bonds or carbon-carbon triple bonds, such as vinylene carbonate; the term "saturated carbonate" is the counterpart to "unsaturated carbonate" and refers to a carbonate that does not contain carbon-carbon double bonds or carbon-carbon triple bonds.

[0043] One embodiment of this application provides a non-aqueous electrolyte, comprising a saturated carbonate, an electrolyte salt, and an additive, wherein the additive comprises a first additive, the first additive comprising a compound represented by structural formula 1 and / or a compound represented by structural formula 2:

[0044] 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.

[0045] 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, and R4 and R5 are 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;

[0046] The non-aqueous electrolyte meets the following conditions:

[0047] 0.0001≤a / b×η≤0.09, and 0.001≤a≤1, 50≤b≤90, 2≤η≤6;

[0048] Where a is the mass percentage of the first additive in the non-aqueous electrolyte, in %;

[0049] b represents the mass percentage of saturated carbonate in the non-aqueous electrolyte, in %;

[0050] η is the viscosity of the non-aqueous electrolyte at 25°C, in mPa·s.

[0051] The non-aqueous electrolyte contains a first additive with oxygen-oxygen bonds and nitrogen-nitrogen bonds, and saturated carbonate is used as the non-aqueous organic solvent. Through extensive research, the inventors discovered that, to improve the low-temperature performance and high-rate discharge performance of lithium-ion batteries, when the mass percentage of the first additive *a*, the mass percentage of saturated carbonate in the non-aqueous electrolyte *b*, and the viscosity *η* of the non-aqueous electrolyte at 25°C satisfy the conditions 0.0001 ≤ a / b × *η* ≤ 0.09, and 0.001 ≤ a ≤ 1, 50 ≤ b ≤ 90, 2 ≤ *η* ≤ 6, the resulting lithium-ion battery exhibits superior performance under low-temperature and high-rate discharge conditions. The high capacity retention of the non-aqueous electrolyte is attributed to the higher electron cloud density of the oxygen-oxygen and nitrogen-nitrogen bond groups in the first additive, which facilitates interaction with positively charged lithium ions, promotes the solvation of saturated carbonate, and shields the lithium ions from anion binding. Adjusting the relative ratio of the first additive to saturated carbonate improves the ion conductivity and diffusion kinetics of the non-aqueous electrolyte. Due to its interaction with lithium ions, the first additive has a chance to participate in the lithium-ion solvation inner layer dominated by saturated carbonate, reaching the electrode surface and participating in the formation of the electrode surface coating during the ion desolvation stage, thus improving the interface composition and structure. Simultaneously, the viscosity control of the non-aqueous electrolyte affects the interaction between the first additive, saturated carbonate, and lithium ions, influencing the first additive's role in promoting ion diffusion and participating in electrode coating. When the mass percentage of the first additive (a), the mass percentage of saturated carbonate (b), and the viscosity (η) of the non-aqueous electrolyte at 25°C are in a synergistic state, it is beneficial to comprehensively consider the influence of various factors, resulting in a non-aqueous electrolyte with high ion conductivity under low temperature and high discharge rate conditions.

[0052] In some embodiments, the non-aqueous electrolyte meets the following conditions:

[0053] (1) 0.015 ≤ a / b × η ≤ 0.06.

[0054] When the non-aqueous electrolyte further meets the above conditions, the first additive enhances the solvation of saturated carbonate, improves lithium-ion diffusion kinetics, and increases the rate charge / discharge capability. The first additive also increases its efficiency in participating in the electrode surface coating during the ion desolvation stage, forming a thinner interface layer, reducing battery internal resistance, and improving low-temperature discharge capability and room-temperature cycle life.

[0055] In a specific embodiment, the mass percentage 'a' of the first additive in the non-aqueous electrolyte can be 0.001%, 0.002%, 0.005%, 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%, 0.24%, 0.25%, 0.28%, 0.3%, 0.32%, 0.34%, 0.35%, 0.38%, 0.4%, 0.42%, 0.44%, 0.45%, 0.48%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or a range of any two of these values.

[0056] In a preferred embodiment, 0.005 ≤ a ≤ 0.8.

[0057] When the content of the first additive is too low, it is difficult to promote the solubilization of saturated carbonates; when the content of the first additive is too high, it increases the probability of side reactions in the electrolyte, which is not conducive to improving the storage performance of non-aqueous electrolytes.

[0058] In a specific embodiment, the mass percentage b of saturated carbonate in the non-aqueous electrolyte can be 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, or any combination of these values.

[0059] In a preferred embodiment, 55 ≤ b ≤ 85.

[0060] In non-aqueous electrolytes, saturated carbonates dissociate lithium salts through solvation. The lithium salts exist as free ions, loose ion pairs, and tightly packed ion pairs, thereby providing charge transport within the battery. When the content of the saturated carbonates is within the above range, it is beneficial to cooperate with the first additive to improve the ionic conductivity of the non-aqueous electrolyte.

[0061] In a specific embodiment, the viscosity η of the non-aqueous electrolyte at 25°C can be 2.0 mPa·s, 2.3 mPa·s, 2.6 mPa·s, 2.9 mPa·s, 3.0 mPa·s, 3.3 mPa·s, 3.6 mPa·s, 3.9 mPa·s, 4.0 mPa·s, 4.3 mPa·s, 4.6 mPa·s, 4.9 mPa·s, 5.0 mPa·s, 5.3 mPa·s, 5.6 mPa·s, 5.9 mPa·s, 6.0 mPa·s, or a range of any two of these values.

[0062] In a preferred embodiment, 2.5 ≤ η ≤ 5.2.

[0063] Viscosity of non-aqueous electrolytes is a parameter describing the frictional forces and resistance between fluid molecules. Essentially, it reflects the result of molecular thermal motion; the lower the viscosity, the faster the molecular thermal motion, and the faster the diffusion of ions and other substances in the electrolyte. This characteristic of viscosity is essentially related to factors such as van der Waals forces and other interactions between the molecules of the fluid components, as well as the frequency of molecular thermal collisions. When the viscosity of the non-aqueous electrolyte is within the above-mentioned range, it is beneficial for the interaction with saturated carbonates and lithium ions, promoting lithium ion diffusion and the participation of the first additive in the electrode coating process.

[0064] The viscosity of the non-aqueous electrolyte at 25°C can be controlled, for example, by adjusting the non-aqueous solvent and lithium salt. More specifically, the viscosity of the electrolyte can be controlled to a lower 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 ability.

[0065] 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 alkyl, branched alkyl, and cycloalkyl; the term "C2-C12 alkenyl" includes straight-chain alkenyl, branched alkenyl, and cycloalkenyl; and the term "C2-C12 alkenylene" includes straight-chain alkynyl, branched alkynyl, and cycloalkenyl.

[0066] 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 alkyl group is independently selected from C1-C11.

[0067] 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 16Selected from single-bonded or C1-C11 alkyl groups, R 17 Alkyl groups selected from C1-C11.

[0068] 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.

[0069] 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.

[0070] 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.

[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 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.

[0073] At this point, the compound represented by structural formula 1 is a dihydrocarbon peroxide. When the compound represented by structural formula 1 is a dihydrocarbon peroxide, it inhibits solvent molecule co-intercalation and improves the interfacial compatibility between the electrolyte and the negative electrode.

[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... 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.

[0076] 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.

[0077] 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.

[0078] As an example, the compound represented by structural formula 1 may be selected from the following compounds:

[0079] 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.

[0080] 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.

[0081] As an example, the compound represented by structural formula 1 may be selected from the following compounds:

[0082] 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.

[0083] 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.

[0084] As an example, the compound represented by structural formula 1 may be selected from the following compounds:

[0085] In some embodiments, the compound represented by structural formula 1 includes one or more of the following compounds:

[0086] 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.

[0087] 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.

[0088] In some embodiments, in the compound shown in structural formula 2, R6 is selected from cyano.

[0089] 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.

[0090] The C1-C6 alkyl groups include methyl, ethyl, n-propyl, isopropyl, isobutyl, tert-butyl, tert-amyl, etc.

[0091] In some embodiments, the compound represented by structural formula 2 includes one or more of the following compounds:

[0092] In some embodiments, the saturated carbonate includes one or more of chain carbonates and cyclic carbonates, wherein 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, and the cyclic carbonate includes one or more of ethylene carbonate, propylene carbonate, and fluorinated ethylene carbonate.

[0093] In some embodiments, the mass ratio of the chain carbonate to the cyclic carbonate is 1 to 9.

[0094] In some embodiments, the saturated carbonate includes ethylene carbonate, and the non-aqueous electrolyte contains ≤50% by mass of ethylene carbonate.

[0095] In some embodiments, the non-aqueous electrolyte further includes unsaturated carbonates, including vinylene carbonate;

[0096] The non-aqueous electrolyte meets the following conditions:

[0097] 0.01≤(a+c) / b≤0.09, and 0.1≤c≤5.5;

[0098] Where a is the mass percentage of the first additive in the non-aqueous electrolyte, in %;

[0099] b represents the mass percentage of saturated carbonate in the non-aqueous electrolyte, in %;

[0100] c represents the mass percentage of unsaturated carbonates in the non-aqueous electrolyte, expressed as %.

[0101] During battery formation, vinylene carbonate participates in the formation of the solid electrolyte interfacial film on the negative electrode surface. The first additive and vinylene carbonate interact synergistically to participate in the lithium-ion solvation structure formed by saturated carbonate, inhibiting excessive vinylene carbonate film formation and regulating the formation of a lithium-dominant interfacial diffusion layer at the electrode interface, further improving room-temperature cycling performance. When (a+c) / b < 0.01, the core of the lithium-ion solvation structure contains less first additive and vinylene carbonate, resulting in a stronger interaction between anions and lithium ions and a larger impedance in the interfacial diffusion layer generated on the electrode surface. When (a+c) / b > 0.09, the content of first additive and vinylene carbonate is too high, and saturated carbonate is too low. Excessive first additive and vinylene carbonate have stronger van der Waals forces and other interactions, increasing the viscous resistance of the electrolyte and increasing ion concentration polarization, thereby degrading the low-temperature performance of the battery.

[0102] In some embodiments, the non-aqueous organic solvent includes at least one of ether solvents, nitrile solvents, carboxylic acid ester solvents, and sulfone solvents.

[0103] 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.

[0104] In some embodiments, the nitrile solvent may be, but is not limited to, at least one of acetonitrile, glutaronitrile, and malononitrile.

[0105] In some embodiments, carboxylic acid ester solvents include cyclic carboxylic acid esters and their halogenated derivatives and / or chain carbonates and their halogenated derivatives. 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.

[0106] 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.

[0107] In a preferred embodiment, the non-aqueous organic solvent further includes cyclic carboxylic esters and their halogenated derivatives and / or chain carboxylic esters and their halogenated derivatives.

[0108] Cyclic carboxylic esters and their halogenated derivatives and / or chain carboxylic esters and their halogenated derivatives act as diluents in non-aqueous electrolytes, and the viscosity of the non-aqueous electrolyte can be controlled by adjusting the content of cyclic carboxylic esters and their halogenated derivatives and / or chain carboxylic esters and their halogenated derivatives.

[0109] It is important to emphasize 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 compounds shown in structural formula 1 and structural formula 2 participating in the formation of the solid electrolyte interphase (SEI) film on the negative electrode surface during the battery charge-discharge formation stage, and the compounds shown in structural formula 1 and structural formula 2 remaining in the electrolyte continuously repairing the damaged solid electrolyte interphase (SEI) film during long-term battery cycling. However, as a precursor to a gel electrolyte or solid electrolyte, a polymerization reaction occurs before the battery charge-discharge formation to form a gel electrolyte. In this polymerization reaction, the compounds shown in structural formula 1 or structural formula 2 act as initiators and react with polymerizable monomers, leading to the consumption of the compounds shown in structural formula 1 and structural formula 2, thus preventing them from playing their corresponding roles in charge-discharge formation and battery charge-discharge cycling.

[0110] In some embodiments, the non-aqueous electrolyte does not include polymerizable monomers and / or prepolymers obtained by polymerizing polymerizable monomers.

[0111] 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.

[0112] In some embodiments, the non-aqueous electrolyte does not undergo polymerization under light or heating conditions.

[0113] In some embodiments, the non-aqueous electrolyte is in a liquid state after formation.

[0114] 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.

[0115] 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.

[0116] Another embodiment of this application provides a secondary battery, including a positive electrode, a negative electrode, and a non-aqueous electrolyte as described above.

[0117] In some embodiments, the secondary battery is a lithium-ion battery.

[0118] 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.

[0119] 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.

[0120] In a more preferred embodiment, the positive electrode active material is selected from LiFe. 1-x’ Mn x’ PO4, where 0 ≤ x' ≤ 0.5.

[0121] In some specific embodiments, the positive electrode active material may include LiCoO2, LiFePO4, LiFe 0.4 Mn 0.6PO4, 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] In some embodiments, the secondary battery further includes a separator located between the positive electrode and the negative electrode.

[0134] 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.

[0135] The present application will be further illustrated by the following examples.

[0136] Table 1

[0137] In Table 1, EC stands for ethylene carbonate, EMC stands for ethyl methyl carbonate, DMC stands for dimethyl carbonate, and PC stands for propylene carbonate.

[0138] Example 1

[0139] This embodiment illustrates the method for preparing the lithium-ion battery disclosed in this application, including the following steps:

[0140] 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 an aluminum foil, and after drying, calendering, and vacuum drying, aluminum leads were welded on using an ultrasonic welder to obtain the positive electrode sheet.

[0141] Preparation of the negative electrode: Artificial graphite (anode active material), Super-P conductive carbon black, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) binder were 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 was coated on both sides of a copper foil, dried, rolled, and vacuum dried, and then nickel leads were soldered on using an ultrasonic welder to obtain the negative electrode.

[0142] Cell preparation: 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 then vacuum baked at 75°C for 48 hours to obtain the cell to be injected with electrolyte.

[0143] Preparation of electrolyte: A non-aqueous organic solvent, additives, and lithium hexafluorophosphate were mixed. The non-aqueous organic solvent included saturated carbonate with the following composition: EC (ethylene carbonate): PC (propylene carbonate): DMC (dimethyl carbonate): EMC (ethyl methyl carbonate) = 3:0.5:3:3.5 (mass ratio). The selection and content of additives, lithium hexafluorophosphate content, and saturated carbonate content in the electrolyte are shown in Table 1. Meanwhile, a diluent and / or thickener were used to make up the balance in the non-aqueous organic solvent. The diluent was selected from n-hexane, and the thickener was selected from 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide salt. The viscosity of the electrolyte was tested and recorded in Table 1.

[0144] Electrolyte injection and formation of the battery cell: Electrolyte is injected into the battery cell, and after standing for 1 hour, it is sealed. After sealing, the battery is aged at 45°C for 48 hours. Then, the first charge is carried out according to the following steps: 0.05C constant current charging for 2 hours, 0.1C constant current charging for 1 hour, 0.2C constant current charging for 1 hour, resting for 1 hour, aging at 45°C for 48 hours, and then further charging at 0.2C constant current to 3.65V, and discharging at 0.2C constant current to 2.5V.

[0145] Examples 2-41

[0146] Examples 2-41 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:

[0147] In the preparation steps of the non-aqueous electrolyte:

[0148] With the total mass of the non-aqueous electrolyte being 100%, the components with the mass percentages shown in Examples 2 to 41 of Table 1 were added to the non-aqueous electrolyte, and the viscosity of the electrolyte was tested and recorded in Table 1.

[0149] Comparative Examples 1-14

[0150] Comparative Examples 1-14 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:

[0151] In the preparation steps of the non-aqueous electrolyte:

[0152] With the total mass of the non-aqueous electrolyte being 100%, the non-aqueous electrolyte was added to the components with the mass percentages shown in Comparative Examples 1 to 14 in Table 1, and the viscosity of the electrolyte was tested and recorded in Table 1.

[0153] Performance testing

[0154] The lithium-ion batteries prepared above were subjected to the following performance tests:

[0155] 1. Rate Capacity Retention Test: Place the battery at room temperature, charge it to 3.65V at a constant current and constant voltage of 0.2C, let it stand for 5 minutes, then discharge it to 2.5V at a constant current of 0.2C, and record the discharge capacity C1; let it stand for 5 minutes, charge it to 3.65V at a constant current and constant voltage of 0.2C, let it stand for 5 minutes, then discharge it to 2.5V at a constant current of 3C, and record the discharge capacity C2. Rate capacity retention (%) = C2 / C1 × 100%.

[0156] 2. Low-temperature discharge capacity retention rate: The battery was placed at room temperature and charged to 3.65V at a constant current and constant voltage of 0.5C. After standing for 5 minutes, it was discharged to 2.5V at a constant current of 0.5C and the discharge capacity C3 was recorded. After standing for 5 minutes, it was charged to 3.65V at a constant current and constant voltage of 0.5C and the discharge capacity C4 was recorded. The low-temperature discharge capacity retention rate (%) = C4 / C3 × 100%.

[0157] 3. Capacity retention rate during room temperature cycling: Place the battery at room temperature, let it stand for 5 minutes, charge it at 1C constant current and constant voltage to 3.65V, let it stand for 5 minutes, discharge it at 1C constant current to 2.5V, and record the discharge capacity C5; repeat this charge and discharge cycle for 2000 cycles, and record the discharge capacity C6; the capacity retention rate (%) after 2000 cycles at room temperature = C6 / C5 × 100%.

[0158] (1) The test results obtained from Examples 1 to 22 and Comparative Examples 1 to 14 are filled in Table 2.

[0159] Table 2

[0160] The test results from Examples 1-22 and Comparative Examples 1-14 show that in a non-aqueous electrolyte containing an oxygen-oxygen bond and a nitrogen-nitrogen bond, and using saturated carbonate as a non-aqueous organic solvent, when the mass percentage of the first additive (a), the mass percentage of saturated carbonate, and the viscosity η of the non-aqueous electrolyte at 25°C satisfy the conditions 0.0001≤a / b×η≤0.09, and 0.001≤a≤1, 50≤b≤90, 2≤η≤6, the resulting lithium-ion battery exhibits higher rate capacity retention, low-temperature discharge capacity retention, and room-temperature cycle capacity retention. This is presumably because the oxygen-oxygen bond and nitrogen-nitrogen bond groups in the first additive have higher electron cloud density, making them more likely to interact with positively charged lithium ions, thereby promoting the solvation effect of the saturated carbonate and shielding the binding of lithium ions by anions. By adjusting the relative ratio of the first additive and saturated carbonate, the ionic conductivity and diffusion kinetics of the non-aqueous electrolyte can be improved. Due to its interaction with lithium ions, the first additive may participate in the lithium-ion solvation inner layer, which is mainly composed of saturated carbonate, and reach the electrode surface. During the ion desolvation stage, it participates in the formation of the coating on the electrode surface, thereby improving the interface composition and structure.

[0161] Furthermore, the viscosity control of the non-aqueous electrolyte affects the interaction between the first additive and saturated carbonate and lithium ions, thereby influencing the first additive's role in promoting ion diffusion and participating in electrode coating. When the mass percentage of the first additive (a), the mass percentage of saturated carbonate (b), and the viscosity (η) of the non-aqueous electrolyte at 25°C are in a synergistic state, the influence of various factors can be integrated to obtain a non-aqueous electrolyte with high ion conduction efficiency under low temperature and high-rate discharge conditions.

[0162] The test results of Examples 1 to 22 show that when the mass percentage of the first additive a in the non-aqueous electrolyte, the mass percentage of saturated carbonate in the non-aqueous electrolyte b, and the viscosity η of the non-aqueous electrolyte at 25°C further satisfy the conditions 0.015≤a / b×η≤0.06, 0.005≤a≤0.8, 55≤b≤85, and 2.5≤η≤5.2, the obtained lithium-ion battery has the best rate discharge performance and low-temperature discharge performance.

[0163] The test results of Comparative Examples 1 to 6 show that when one or more parameters of the mass percentage of the first additive 'a' in the non-aqueous electrolyte, the mass percentage of saturated carbonate in the non-aqueous electrolyte 'b', and the viscosity 'η' of the non-aqueous electrolyte at 25°C exceed the specified range, even if the requirement of the relationship 0.0001≤a / b×η≤0.09 is met, the rate discharge performance and cycle performance of the obtained lithium-ion battery are still insufficient. This indicates that when the value of a, the value of b, or the value of η are too high or too low, they will affect the lithium-ion conduction efficiency of the non-aqueous electrolyte. The test results from Comparative Examples 7 to 14 show that even if the values ​​of a, b, or η all meet their parameter range limits, excessively large or small a / b×η values ​​will lead to a deterioration in the rate discharge performance and cycle performance of the battery. This indicates that there is an interaction between the mass percentage of the first additive a in the non-aqueous electrolyte, the mass percentage of saturated carbonate in the non-aqueous electrolyte b, and the viscosity η of the non-aqueous electrolyte at 25°C. Only when the three reach a good balance can they significantly improve the rate discharge performance and cycle performance of the lithium-ion battery.

[0164] (2) The test results obtained in Examples 1, 23 to 33 are filled in Table 3.

[0165] Table 3

[0166] As can be seen from the test results of Examples 1 and 23-33, in the electrolyte system provided in this application, under the premise of satisfying the relationship 0.0001≤a / b×η≤0.09, and 0.001≤a≤1, 50≤b≤90, 2≤η≤6, different first additives can improve the rate capacity retention rate, low temperature discharge capacity retention rate and room temperature cycle capacity retention rate of lithium-ion batteries. This indicates that the electrolyte system provided in this application is suitable for different first additives, and the compounds shown in structural formula 1 and structural formula 2 play similar roles in the electrolyte system of this application.

[0167] (3) The test results obtained in Examples 34 to 41 are filled in Table 4.

[0168] Table 4

[0169] Comparing the test results of Examples 34-41 and Examples 1-22 in Table 2, it can be seen that when the mass percentage of the first additive (a) in the non-aqueous electrolyte, the mass percentage of saturated carbonate (b) in the non-aqueous electrolyte, and the mass percentage of unsaturated carbonate (c) in the non-aqueous electrolyte meet the condition 0.01 ≤ (a+c) / b ≤ 0.09, it is beneficial to reduce battery impedance and improve the battery's low-temperature and rate performance. This is because vinylene carbonate (unsaturated carbonate) participates in the formation of the solid electrolyte interface film on the negative electrode surface. The first additive and vinylene carbonate interact synergistically to participate in the lithium-ion solvation structure formed by saturated carbonate, inhibiting excessive film formation by vinylene carbonate. Furthermore, by regulating the relative ratio between the first additive and vinylene carbonate and saturated carbonate, the formation of a lithium-dominant interfacial diffusion layer at the electrode interface can be controlled, further improving the battery's low-temperature and rate performance.

[0170] 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 non-aqueous electrolyte, characterized in that, It includes saturated carbonates, electrolyte salts, and additives, wherein the additives include a first additive, the first additive comprising a compound shown in structural formula 1 and / or a compound shown in structural formula 2: 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, and R4 and R5 are 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: 0.0001≤a / b×η≤0.09, and 0.001≤a≤1, 50≤b≤90, 2≤η≤6; Where a is the mass percentage of the first additive in the non-aqueous electrolyte, in %; b represents the mass percentage of saturated carbonate in the non-aqueous electrolyte, in %; η is the viscosity of the non-aqueous electrolyte at 25°C, in mPa·s.

2. The non-aqueous electrolyte according to claim 1, characterized in that, The non-aqueous electrolyte satisfies at least one of the following conditions: (1) 0.015 ≤ a / b × η ≤ 0.06; (2)0.005≤a≤0.8； (3)55≤b≤85； (4) 2.5≤η≤5.

2.

3. The non-aqueous electrolyte according to claim 1 or 2, 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.

4. The non-aqueous electrolyte according to any one of claims 1 to 3, characterized in that, The compound represented by structural formula 1 includes one or more of the following compounds:

5. The non-aqueous electrolyte according to any one of claims 1 to 4, 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.

6. The non-aqueous electrolyte according to any one of claims 1 to 5, characterized in that, The compound represented by structural formula 2 includes one or more of the following compounds:

7. The non-aqueous electrolyte according to any one of claims 1 to 6, characterized in that, The saturated carbonate includes one or more of chain carbonates and cyclic carbonates; 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 The non-aqueous organic solvent also includes cyclic carboxylic esters and their halogenated derivatives and / or chain carboxylic esters and their halogenated derivatives.

8. The non-aqueous electrolyte according to any one of claims 1 to 7, characterized in that, The non-aqueous electrolyte also includes unsaturated carbonates, including vinylene carbonate. The non-aqueous electrolyte meets the following conditions: 0.01≤(a+c) / b≤0.09, and 0.1≤c≤5.5; Where a is the mass percentage of the first additive in the non-aqueous electrolyte, in %; b represents the mass percentage of saturated carbonate in the non-aqueous electrolyte, in %; c represents the mass percentage of unsaturated carbonates in the non-aqueous electrolyte, expressed as %.

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

10. A secondary battery, characterized in that, 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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