Electrolyte for lithium secondary battery, secondary battery, and power consumption device

Abstract

The present application relates to an electrolyte for a lithium secondary battery, a secondary battery, and an electric power consumption device. The electrolyte for a lithium secondary battery contains an organic solvent, a first additive, a second additive, and an electrolyte salt dissolved in the organic solvent. The organic solvent contains a carboxylic acid ester-based solvent, and the mass percentage W1 of the carboxylic acid ester-based solvent in the organic solvent is 20% to 80%. The first additive contains one or more of monofluorophosphate, difluorophosphate, tetrafluoroborate, fluorosulfonate, oxalatoborate salt, malonic acid borate salt, oxalatophosphate salt, and (malonate) phosphate salt. The second additive contains one or more of vinylene carbonate and its derivatives, ethylene carbonate and its derivatives. The mass percentages of the first additive and the second additive in the electrolyte are W2 and W3, respectively, and 0.035 ≤ (W2 + W3) / W1 ≤ 0.15.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to electrolytes for lithium secondary batteries, secondary batteries, and power consumption devices.

[0002] Cross-reference to Related Applications This application claims the priority of a Chinese patent application with an application number of 2023105059142 and an invention title of "Electrolyte for Lithium Secondary Battery, Secondary Battery, and Power Consumption Device", which was filed with the Chinese Patent Office on May 8, 2023, and the entire content of the application is incorporated herein by reference.

Background Art

[0003] The description herein only provides background art related to the present application and does not necessarily constitute prior art.

[0004] In recent years, with the development of secondary battery technology, secondary batteries have been widely used in various fields such as energy storage power systems such as hydroelectric, thermal, wind, and solar power plants, power sources for electronic devices, power tools, electric bicycles, electric motorcycles, and electric vehicles.

[0005] With the development of science and technology and society, the performance of various products has been further improved. Therefore, the requirements for the fast charging performance, cycle performance, and storage performance of secondary batteries are also increasing. How to provide a secondary battery with excellent fast charging performance, cycle performance, and storage performance is one of the most concerned directions for those skilled in the art.

Summary of the Invention

Problems to be Solved by the Invention

[0006] In view of the above problems, the present application is made. One of the objectives is to provide an electrolyte for a lithium secondary battery so that a secondary battery employing the electrolyte of the present application has excellent fast charging performance, cycle performance, and power storage performance.

Means for Solving the Problems

[0007] To achieve the above object, a first aspect of the present application provides an electrolyte for a lithium secondary battery, which includes an organic solvent, and a first additive, a second additive, and an electrolyte salt dissolved in the organic solvent.

[0008] The organic solvent includes a carboxylic acid ester solvent, and based on the total mass of the organic solvent, the mass percentage W1 of the carboxylic acid ester solvent is 20% to 80%.

[0009] The first additive includes one or more of monofluorophosphate, difluorophosphate, tetrafluoroborate, fluorosulfonate, oxalatoborate salt, malonic acid borate, oxalatophosphate salt, and (malonato)phosphate salt.

[0010] The second additive includes one or more of the compounds shown in the following Formula I and Formula II. [Formula I] JPEG2025521103000002.jpg30130

[0011] In Formula I, R1 and R2 are each independently selected from a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 halogenated alkyl group, a C1-C6 alkoxy group, a C2-C6 alkenyl group, or a C2-C6 alkynyl group. [Formula II] JPEG2025521103000003.jpg30130

[0012] In Formula II, R3, R4, R5, and R6 are each independently selected from a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 halogenated alkyl group, a C1-C6 alkoxy group, a C2-C6 alkenyl group, or a C2-C6 alkynyl group, and R3, R4, R5, and R6 do not simultaneously represent hydrogen atoms.

[0013] However, the mass fractions of the first additive and the second additive in the electrolytic solution are W2 and W3 respectively, and 0.035 ≦ (W2 + W3) / W1 ≦ 0.15.

[0014] In this application, a carboxylic acid ester solvent is adopted in a specific content in the organic solvent of the electrolytic solution, and the first additive and the second additive are introduced in specific contents and types. By mixing the above components with each other in specific contents, the secondary battery has excellent rapid charging performance, cycle performance and storage performance, and the comprehensive performance of the secondary battery can be significantly improved.

[0015] In any embodiment, in formula I, R1 and R2 are each independently selected from a hydrogen atom, a halogen atom, a C1-C4 alkyl group, a C1-C4 halogenated alkyl group, a C1-C4 alkoxy group, a C2-C4 alkenyl group or a C2-C4 alkynyl group.

[0016] In any embodiment, in formula II, R3, R4, R5 and R6 are each independently selected from a hydrogen atom, a halogen atom, a C1-C4 alkyl group, a C1-C4 halogenated alkyl group, a C1-C4 alkoxy group, a C2-C4 alkenyl group or a C2-C4 alkynyl group.

[0017] In any embodiment, based on the total mass of the organic solvent, the mass percentage W1 of the carboxylic acid ester solvent is 30% - 70%. In this way, the rapid charging performance of the secondary battery can be further improved, and the secondary battery still has excellent cycle performance and storage performance.

[0018] In any embodiment, based on the total mass of the organic solvent, the mass percentage W1 of the carboxylic acid ester solvent is 40% - 60%. In this way, the comprehensive performance of the secondary battery can be further improved.

[0019] In any embodiment, 0.04 ≦ (W2 + W3) / W1 ≦ 0.10. Thus, the rapid charging performance of the secondary battery can be further improved, and the secondary battery still has good cycle performance and storage performance.

[0020] In any embodiment, 0.05 ≦ (W2 + W3) / W1 ≦ 0.075. Thus, the overall performance of the secondary battery can be further improved.

[0021] In any embodiment, based on the total mass of the electrolyte, the mass percentage W2 of the first additive is 0.01% - 10%. Thus, the cycle performance and storage performance of the secondary battery can be further improved, and the secondary battery has good rapid charging performance.

[0022] In any embodiment, based on the total mass of the electrolyte, the mass percentage W2 of the first additive is 0.05% - 5%. Thus, the overall performance of the secondary battery can be further improved.

[0023] In any embodiment, based on the total mass of the electrolyte, the mass percentage W3 of the second additive is 0.05% - 10%. Thus, the secondary battery has better cycle performance and storage performance, maintains good rapid charging performance, and has better overall performance.

[0024] In any embodiment, based on the total mass of the electrolyte, the mass percentage W3 of the second additive is 0.1% - 5%. Thus, the overall performance of the secondary battery can be further improved.

[0025] In any embodiment, the carboxylic acid ester solvent contains the compound represented by Formula III. [Formula III] JPEG2025521103000004.jpg26130

[0026] However, R7 and R8 are each independently selected from any one of C1-C3 alkyl groups and C1-C3 halogenated alkyl groups. In this way, the viscosity of the electrolyte can be maintained within an appropriate range, the electrolyte has a higher conductivity, and the secondary battery has better rapid charging performance.

[0027] In any embodiment, the carboxylic acid ester solvent contains one or more of the following compounds. JPEG2025521103000005.jpg57169

[0028] In any embodiment, the second additive contains one or more of vinylene carbonate, 4,5-diethyl vinylene carbonate, fluoroethylene carbonate, and vinyl ethylene carbonate.

[0029] In any embodiment, the monofluorophosphate contains lithium monofluorophosphate, the difluorophosphate contains lithium difluorophosphate, and the tetrafluoroborate contains lithium tetrafluoroborate.

[0030] In any embodiment, the oxalatoborate salt contains the compound represented by Formula IV. [Formula IV] JPEG2025521103000006.jpg30130

[0031] However, M1 is selected from one or more of Li, Na, K, Rb, Cs, Mg, Ca, Ba, Al, Fe, Cu, and Ni, X1 is a halogen, m1 is an integer from 1 to 3, n1 is an integer from 0 to 4, and a1, b1, and c1 are all positive integers. In this way, during the charging process of the secondary battery, the oxalatoborate salt can effectively form an organic-inorganic composite SEI film on the surface of the negative electrode together with the second additive, effectively preventing the carboxylic acid ester solvent from contacting the negative electrode interface, reducing gas generation, and improving the cycle performance and storage performance of the battery.

[0032] In any embodiment, the malonic acid borate includes a compound represented by Formula V. [Formula V] JPEG2025521103000007.jpg30130

[0033] However, M2 is selected from one or more of Li, Na, K, Rb, Cs, Mg, Ca, Ba, Al, Fe, Cu, and Ni; X2 is a halogen; m2 is an integer from 1 to 3; n2 is an integer from 0 to 4; and a2, b2, and c2 are all positive integers. Thus, in the charging process of the secondary battery, the malonic acid borate can form an organic-inorganic composite SEI film on the surface of the negative electrode together with the second additive, alleviate the problem of gas generation caused by the contact of the carboxylic acid ester-based solvent with the negative electrode, and improve the cycle performance and storage performance of the battery.

[0034] In any embodiment, the oxalato phosphate salt includes a compound represented by Formula VI. [Formula VI] JPEG2025521103000008.jpg30130

[0035] However, M3 is selected from one or more of Li, Na, K, Rb, Cs, Mg, Ca, Ba, Al, Fe, Cu, and Ni; X3 is a halogen; m3 is an integer from 1 to 3; n3 is an integer from 0 to 4; and a3, b3, and c3 are all positive integers. Thus, the above-described oxalato phosphate salt can form an organic-inorganic composite SEI film on the negative electrode surface together with the second additive, prevent the carboxylic acid ester-based solvent from contacting the negative electrode, and improve the cycle performance and storage performance of the battery.

[0036] In any embodiment, the (malonato) phosphate includes a compound represented by Formula VII. [Formula VII] JPEG2025521103000009.jpg35130

[0037] However, M4 is selected from one or more of Li, Na, K, Rb, Cs, Mg, Ca, Ba, Al, Fe, Cu, and Ni, X4 is a halogen, m4 is an integer from 1 to 3, n4 is an integer from 0 to 4, and a4, b4, and c4 are all positive integers. Thus, the above-mentioned (malonate) phosphate can form an organic-inorganic composite SEI film on the negative electrode surface together with the second additive, prevent the carboxylic acid ester-based solvent from contacting the negative electrode interface, and improve the cycle performance and storage performance of the battery.

[0038] In any embodiment, the fluorosulfonate includes a compound represented by Formula VIII. [VIII] (FSO3) y M y+

[0039] However, y is a positive integer, and M y+ is a metal ion or an organic cation. The metal ion includes one or more of Li + , Na + , K + , Rb + , Cs + , Mg 2+ , Ca 2+ , Ba 2+ , Al 3+ , Fe 2+ , Cu 2+ , Fe 3+ , Ni 2+ , and Ni 3+ . Thus, the fluorosulfonate can form an organic-inorganic composite SEI film on the negative electrode surface together with the second additive, prevent the carboxylic acid ester-based solvent from contacting the negative electrode interface, and improve the cycle performance and storage performance of the battery.

[0040] In any embodiment, the organic solvent further includes one or more of a chain carbonate and a cyclic carbonate.

[0041] In any embodiment, the chain carbonate includes one or more of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate.

[0042] In any embodiment, the cyclic carbonate includes one or more of ethylene carbonate, propylene carbonate, and butylene carbonate.

[0043] In any embodiment, the electrolyte salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bistrifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorooxalatoborate, lithium bis(oxalato)borate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluorooxalatophosphate.

[0044] The second aspect of the present application provides a secondary battery, which includes the electrolyte for a lithium secondary battery in the first aspect of the present application. Thus, the secondary battery not only has good rapid charging performance, but also has good cycle performance and storage performance, and has good comprehensive performance.

[0045] In any embodiment, the secondary battery further includes a negative electrode tab, the negative electrode tab includes a negative electrode active material, and the lithium ion solid phase diffusion coefficient Ds of the negative electrode active material is 10 -13 cm 2 / S~10 -10 cm 2 / S. Thus, the rapid charging ability of the secondary battery can be further improved.

[0046] In any embodiment, the lithium ion solid phase diffusion coefficient Ds of the negative electrode active material is 10 -12 cm 2 / S~10 -11 cm 2 / S. Thus, the rapid charging ability of the secondary battery can be further improved.

[0047] In any embodiment, the volume average particle diameter Dv50 of the negative electrode active material is ≧ 6 μm. Thus, the cycle performance and storage performance of the secondary battery can be further improved.

[0048] In any embodiment, the volume average particle diameter Dv50 of the negative electrode active material is 15 μm to 20 μm. Thus, not only can the battery have good cycle performance, but also the battery can have excellent kinetic performance.

[0049] In any embodiment, the BET specific surface area of the negative electrode active material is 0.5 m 2 / g to 2.0 m 2 / g. Thus, the cycle performance of the secondary battery can be further improved.

[0050] In any embodiment, the BET specific surface area of the negative electrode active material is 0.8 m 2 / g to 1.5 m 2 / g. Thus, not only can the secondary battery have good cycle performance, but also the secondary battery can have excellent kinetic performance.

[0051] In any embodiment, the negative electrode active material contains one or more of graphite and silicon-based materials.

[0052] The third aspect of the present application provides a power consumption device including the secondary battery of the second aspect of the present application.

Effect of the Invention

[0053] The electrolyte for a lithium secondary battery of the present application employs a carboxylic acid ester-based solvent in a specific content in an organic solvent, and introduces a first additive and a second additive in specific contents and types. By mixing the above components with each other in specific contents, the secondary battery has excellent rapid charging performance, cycle performance, and storage performance, and the overall performance of the secondary battery can be improved.

[0054] Details of one or more embodiments of the present application are provided in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the specification, drawings, and claims.

Brief Description of the Drawings

[0055] To better describe or explain an embodiment or example according to the present application, one or more drawings can be referred to. Additional details or examples for describing the drawings should not be considered as limiting any one of the disclosed application, the currently described embodiment or example, and the optimal mode of these applications currently understood. And in all the drawings, similar members are denoted by similar reference numerals.

[0056]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0057] Hereinafter, embodiments of the electrolyte for a lithium secondary battery, the secondary battery, and the power consumption device of the present application will be described in detail with appropriate reference to the drawings. However, detailed descriptions that are more detailed than necessary may be omitted. For example, detailed descriptions of matters that are already well-known or repeated descriptions of substantially the same structure may be omitted. This is to avoid making the following description unnecessarily long and to facilitate the understanding of those skilled in the art. Note that the drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand the present application and are not intended to limit the theme described in the claims.

[0058] The "range" disclosed in this application can be limited in the form of a lower limit and an upper limit. When a predetermined range is limited by selecting one lower limit and one upper limit, the selected lower limit and upper limit define the boundaries of a specific range. The range thus limited may or may not include the end values, and either one of the end values may or may not be independently included, and they may be combined in any way, that is, one range may be formed by combining any lower limit with any upper limit. For example, when ranges such as 60 - 120 and 80 - 110 are listed for a specific parameter, it should be understood that ranges of 60 - 110 and 80 - 120 are also envisioned. In addition, when the minimum range values 1 and 2 are listed and the maximum range values 3, 4, and 5 are further listed, ranges of 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5 are all possible. In this application, unless otherwise specified, the numerical range "a - b" represents an abbreviated expression of any combination of real numbers between a and b, and both a and b are real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are listed in this specification, and "0 - 5" is merely an abbreviated expression of the combination of these numerical values. Also, when a certain parameter is expressed as an integer greater than or equal to 2, it corresponds to listing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when a certain parameter is expressed as an integer selected from "2 - 10", it corresponds to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0059] In this application, unless otherwise specified, when it comes to "a plurality", "a plurality of types", etc., it means that the number is two or more. For example, "one or more" represents one or two or more.

[0060] Unless otherwise specified, new technical solutions can be formed by combining all the embodiments and alternative embodiments of this application with each other.

[0061] When "embodiments" are mentioned in this specification, it means that the specific features, structures, or characteristics described in connection with the embodiments may be included in at least one embodiment or implementation form of this application. The word appearing at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. It is explicitly or implicitly understood by those skilled in the art that the embodiments described in this specification can be combined with other embodiments. The "implementation forms" mentioned in this specification may be understood in the same way.

[0062] As can be understood by those skilled in the art, in the method of each implementation form or embodiment, the described order of each step does not constitute any limitation to the implementation process meaning a strict execution order, and the detailed execution order of each step should be determined by their functions and possible internal logic. Unless otherwise specified, all steps of this application may be performed in sequence or randomly, preferably in sequence. For example, the fact that the method includes steps (a) and (b) means that the method may include steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the fact that the method may further include step (c) means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or steps (a), (c), and (b), or steps (c), (a), and (b), etc.

[0063] In this application, for open-ended technical features or technical solutions described by terms such as "containing", "including", and "comprising", unless otherwise specified, additional elements existing other than the recited elements are not excluded, and a closed feature or solution composed of the recited elements is provided, and it may also be regarded that an open-ended feature or solution further including additional elements other than the recited elements is provided. For example, when A is represented as including a1, a2, and a3, unless otherwise specified, it may further include other elements or may not include additional elements, and a feature or solution of "A consists of a1, a2, and a3" is provided, and it may also be regarded that a feature or solution of "A not only includes a1, a2, and a3, but also further includes other elements" is further provided. In this application, unless otherwise specified, A (for example, B) represents that B is one non-limiting exemplification of A, and it may be understood that A is not limited to B.

[0064] In this application, "optionally", "optional", and "selectable" mean that it may or may not be present, that is, it means any one selected from two parallel solutions of "present" or "absent". When multiple "selectables" appear in one technical solution, unless otherwise explained and there is no contradiction or mutual restrictive relationship, each "selectable" is independent of each other.

[0065] The weights described in the specification of the embodiments of this application may be weight units well-known in the chemical industry field such as μg, mg, g, kg, etc.

[0066] At present, with the great development of secondary batteries, the requirements for the comprehensive performance of secondary batteries, such as rapid charging performance, cycle performance, and storage performance, are also increasing further. The electrolyte, which is an important component of secondary batteries, plays an irreplaceable role in improving the rapid charging performance, cycle performance, and storage performance of secondary batteries. Therefore, how to provide an electrolyte that enables secondary batteries to have excellent rapid charging performance, cycle performance, and storage performance is one of the most concerned directions for those skilled in the art. In this regard, the present application provides an electrolyte containing a carboxylic acid ester-based solvent, a first additive, and a second additive in specific contents, enabling secondary batteries to have excellent rapid charging performance, cycle performance, and storage performance, and improving the comprehensive performance of secondary batteries.

[0067] The first aspect of the present application provides an electrolyte for a lithium secondary battery, which includes an organic solvent, and a first additive, a second additive, and an electrolyte salt dissolved in the organic solvent.

[0068] The organic solvent includes a carboxylic acid ester-based solvent, and based on the total mass of the organic solvent, the mass percentage W1 of the carboxylic acid ester-based solvent is 20% - 80%.

[0069] The first additive includes one or more of monofluorophosphate, difluorophosphate, tetrafluoroborate, fluorosulfonate, oxalatoborate salt, malonic acid borate salt, oxalatophosphate salt, and (malonato)phosphate salt.

[0070] The second additive includes one or more of the compounds shown in the following Formula I and Formula II. [Formula I] JPEG2025521103000010.jpg30130

[0071] In Formula I, R1 and R2 are each independently selected from a hydrogen atom, a halogen atom, a C1 - C6 alkyl group, a C1 - C6 halogenated alkyl group, a C1 - C6 alkoxy group, a C2 - C6 alkenyl group, or a C2 - C6 alkynyl group. [Formula II] JPEG2025521103000011.jpg30130

[0072] In Formula II, R3, R4, R5, and R6 are each independently selected from a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 halogenated alkyl group, a C1-C6 alkoxy group, a C2-C6 alkenyl group, or a C2-C6 alkynyl group, and R3, R4, R5, and R6 do not simultaneously represent a hydrogen atom.

[0073] However, the mass percentages of the first additive and the second additive in the electrolyte are W2 and W3, respectively, and 0.035 ≤ (W2 + W3) / W1 ≤ 0.15.

[0074] This application employs a carboxylic acid ester solvent in a specific content in the organic solvent of the electrolyte for a lithium secondary battery, and introduces the first additive and the second additive in specific contents and types. By blending the above components with each other in specific contents, the secondary battery has excellent rapid charging performance, cycle performance, and storage performance, and can significantly improve the comprehensive performance of the secondary battery.

[0075] Compared with carbonate solvents, carboxylic acid ester solvents have a lower freezing point and a smaller viscosity, can significantly improve the conductivity of the electrolyte, and can improve the rapid charging performance of the secondary battery. However, carboxylic acid ester solvents are prone to obtaining electrons at the negative electrode of the battery, generating a series of reduction gases such as CH4 and H2, leading to an increase in the internal pressure of the cell. After long-term cyclic use, carboxylic acid ester solvents cause serious cell swelling problems, especially at high temperatures, extrude the electrolyte between the tabs, reduce the ion conduction ability inside the battery, cause deterioration of the cycle performance and storage performance of the battery, and affect the service life of the battery.

[0076] In contrast, in the present application, by introducing a first additive and a second additive into the electrolyte for a lithium secondary battery in specific types and usage amounts, during the charging process of the secondary battery, the first additive and the second additive preferentially form an organic-inorganic composite SEI film on the surface of the negative electrode, preventing the carboxylic acid ester-based solvent from contacting the interface of the negative electrode and reducing the generation of gas. And when the mass percentage W1 of the carboxylic acid ester-based solvent in the organic solvent, the mass percentage W2 of the first additive, and the mass percentage W3 of the second additive are within the above ranges, the rapid charging performance, cycle performance, and storage performance of the secondary battery are all excellent.

[0077] As can be understood, the mass percentage W1 of the carboxylic acid ester-based solvent in the organic solvent may be, but is not limited to, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78%, 80%. The value of (W2 + W3) / W1 may be, but is not limited to, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06, 0.065, 0.07, 0.075, 0.08, 0.085, 0.09, 0.095, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15.

[0078] In some embodiments, in formula I, R1 and R2 are each independently selected from a hydrogen atom, a halogen atom, a C1-C4 alkyl group, a C1-C4 halogenated alkyl group, a C1-C4 alkoxy group, a C2-C4 alkenyl group, or a C2-C4 alkynyl group.

[0079] In some embodiments, in formula II, R3, R4, R5, and R6 are each independently selected from a hydrogen atom, a halogen atom, a C1-C4 alkyl group, a C1-C4 halogenated alkyl group, a C1-C4 alkoxy group, a C2-C4 alkenyl group, or a C2-C4 alkynyl group.

[0080] In some embodiments, based on the total mass of the organic solvent, the mass percentage W1 of the carboxylic acid ester solvent is 30% to 70%. By controlling the mass percentage W1 of the carboxylic acid ester solvent in the organic solvent within the above range, the rapid charging performance of the secondary battery can be further improved, and the secondary battery still has good cycle performance and storage performance.

[0081] In some embodiments, based on the total mass of the organic solvent, the mass percentage W1 of the carboxylic acid ester solvent is 40% to 60%. In this way, the overall performance of the secondary battery can be further improved.

[0082] In some embodiments, the mass percentage W1 of the carboxylic acid ester solvent in the organic solvent, the mass percentage W2 of the first additive in the electrolyte, and the mass percentage W3 of the second additive satisfy 0.04 ≦ (W2 + W3) / W1 ≦ 0.10. In this way, the rapid charging performance of the secondary battery can be further improved, and the secondary battery still has good cycle performance and storage performance.

[0083] In some embodiments, the mass percentage W1 of the carboxylic acid ester solvent in the organic solvent, the mass percentage W2 of the first additive in the electrolyte, and the mass percentage W3 of the second additive satisfy 0.05 ≦ (W2 + W3) / W1 ≦ 0.075. In this way, the overall performance of the secondary battery can be further improved.

[0084] In some embodiments, the carboxylic acid ester solvent contains the compound represented by Formula III. [Formula III] JPEG2025521103000012.jpg26130

[0085] However, R7 and R8 are each independently selected from any one of C1-C3 alkyl groups and C1-C3 halogenated alkyl groups. By selecting the above carboxylic acid ester-based solvent as the organic solvent of the electrolyte, the viscosity of the electrolyte can be maintained within an appropriate range, the electrolyte has a higher conductivity, and the secondary battery has better rapid charging performance.

[0086] In some embodiments, R7 and R8 in Formula III are each independently selected from any one of a methyl group, an ethyl group, a propyl group, a fluoromethyl group, a fluoroethyl group, and a fluoropropyl group.

[0087] In some embodiments, the carboxylic acid ester-based solvent contains one or more of the following compounds. JPEG2025521103000013.jpg241132

[0088] In some embodiments, the carboxylic acid ester-based solvent contains one or more of the following compounds. JPEG2025521103000014.jpg50132

[0089] In some embodiments, the organic solvent further contains one or more of a chain carbonate and a cyclic carbonate. In the present application, the types of other solvents, such as chain carbonates and cyclic carbonates, are not particularly limited and may be selected according to actual needs.

[0090] In some embodiments, the chain carbonate may be selected from at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate.

[0091] In some embodiments, the cyclic carbonate may be selected from at least one of substances such as ethylene carbonate (or ethyl carbonate), propylene carbonate (or propyl carbonate), and butylene carbonate (or butyl carbonate).

[0092] In some embodiments, based on the total mass of the electrolyte, the mass percentage W2 of the first additive is 0.01% to 10%. In this way, the cycle performance and storage performance of the secondary battery can be further improved, and the secondary battery has good rapid charging performance.

[0093] As can be understood, the mass percentage W2 of the first additive in the electrolyte may be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, but is not limited thereto.

[0094] In some embodiments, based on the total mass of the electrolyte, the mass percentage W2 of the first additive is 0.05% to 5%. In this way, the cycle performance and storage performance of the secondary battery can be further improved, and the secondary battery still has good rapid charging performance and obtains better comprehensive performance.

[0095] In some embodiments, the monofluorophosphate contains lithium monofluorophosphate, the difluorophosphate contains lithium difluorophosphate, and the tetrafluoroborate contains lithium tetrafluoroborate.

[0096] In some embodiments, the oxalatoborate salt contains the compound shown in Formula IV. [Formula IV] JPEG2025521103000015.jpg30130

[0097] However, M1 is selected from one or more of Li, Na, K, Rb, Cs, Mg, Ca, Ba, Al, Fe, Cu, and Ni, X1 is a halogen, m1 is an integer from 1 to 3, n1 is an integer from 0 to 4, and a1, b1, and c1 are all positive integers. The above-mentioned oxalate borate salt can effectively form an organic-inorganic composite SEI film on the surface of the negative electrode together with the second additive during the charging process of the secondary battery, effectively preventing the carboxylic acid ester-based solvent from contacting the negative electrode interface and reducing the generation of gas.

[0098] In some embodiments, the malonate borate contains a compound represented by Formula V. [Formula V] JPEG2025521103000016.jpg30130

[0099] However, M2 is selected from one or more of Li, Na, K, Rb, Cs, Mg, Ca, Ba, Al, Fe, Cu, and Ni, X2 is a halogen, m2 is an integer from 1 to 3, n2 is an integer from 0 to 4, and a2, b2, and c2 are all positive integers. Similarly, the above-mentioned malonate borate can form an organic-inorganic composite SEI film on the surface of the negative electrode together with the second additive during the charging process of the secondary battery, alleviating the problem of gas generation caused by the contact of the carboxylic acid ester-based solvent with the negative electrode.

[0100] In some embodiments, the oxalatophosphate salt contains a compound represented by Formula VI. [Formula VI] JPEG2025521103000017.jpg30130

[0101] However, M3 is selected from one or more of Li, Na, K, Rb, Cs, Mg, Ca, Ba, Al, Fe, Cu, and Ni; X3 is a halogen; m3 is an integer from 1 to 3; n3 is an integer from 0 to 4; and a3, b3, and c3 are all positive integers. Similarly, the above-mentioned oxalate phosphate salt can form an organic-inorganic composite SEI film on the negative electrode surface together with the second additive, and alleviate the problem of gas generation due to the contact of the carboxylic acid ester-based solvent with the negative electrode.

[0102] In some embodiments, the (malonato) phosphate salt includes a compound represented by Formula VII. [Formula VII] JPEG2025521103000018.jpg35130

[0103] However, M4 is selected from one or more of Li, Na, K, Rb, Cs, Mg, Ca, Ba, Al, Fe, Cu, and Ni; X4 is a halogen; m4 is an integer from 1 to 3; n4 is an integer from 0 to 4; and a4, b4, and c4 are all positive integers. Similarly, the above-mentioned (malonato) phosphate salt can form an organic-inorganic composite SEI film on the negative electrode surface together with the second additive, prevent the carboxylic acid ester-based solvent from contacting the negative electrode interface, and alleviate the problem of gas generation due to the contact of the carboxylic acid ester-based solvent with the negative electrode.

[0104] In some embodiments, the fluorosulfonate salt includes a compound represented by Formula VIII. [Formula VIII] (FSO3) y M y+

[0105] However, y is a positive integer, and M y+ is a metal ion or an organic cation. The metal ion is Li + , Na + , K + , Rb + , Cs + , Mg 2+ , Ca 2+ , Ba 2+ , Al3+ 、 Fe 2+ 、 Cu 2+ 、 Fe 3+ 、 Ni 2+ and Ni 3+ It contains one or more of them. The fluorosulfonate adopting the above structure can effectively form an organic-inorganic composite SEI film on the negative electrode surface together with the second additive, prevent the carboxylic acid ester-based solvent from contacting the negative electrode interface, and reduce the generation of gas.

[0106] In some embodiments, based on the total mass of the electrolyte, the mass percentage W3 of the second additive is 0.05% to 10%. In this way, the secondary battery has better cycle performance and storage performance, maintains good rapid charging performance, and has better comprehensive performance.

[0107] As can be understood, the mass percentage W3 of the second additive in the electrolyte may be 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 10%, but is not limited thereto.

[0108] In some embodiments, based on the total mass of the electrolyte, the mass percentage W3 of the second additive is 0.1% to 5%. In this way, the cycle performance and storage performance of the secondary battery can be further improved, good rapid charging performance is maintained, and the comprehensive performance of the secondary battery is further improved.

[0109] In some embodiments, the electrolyte salt contains one or more of lithium hexafluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bistrifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluorooxalatophosphate.

[0110] In some embodiments, the concentration of the electrolyte salt in the electrolytic solution is 0.3 mol / L (moles per liter) or more, may be selected to be 0.7 mol / L or more, may be selected to be 1.7 mol / L or less, and may further be selected to be 1.2 mol / L or less.

[0111] The second aspect of the present application provides a secondary battery, which includes the electrolytic solution for a lithium secondary battery in the first aspect of the present application. By adopting the electrolytic solution for a lithium secondary battery in the first aspect of the present application, the secondary battery of the present application has good rapid charging performance, and the first additive and the second additive form an organic-inorganic composite SEI film on the surface of the negative electrode during the charging process of the battery, and the carboxylic acid ester-based solvent prevents contact with the negative electrode interface. As a result, the secondary battery has good cycle performance and storage performance.

[0112] In some embodiments, the secondary battery further includes a negative electrode tab, the negative electrode tab contains a negative electrode active material, and the lithium ion solid-phase diffusion coefficient Ds of the negative electrode active material is 10 -11 cm 2 / S to 10 -12 cm 2 / S. That is, the negative electrode active material has a large lithium ion solid-phase diffusion coefficient Ds. When the lithium ion solid-phase diffusion coefficient Ds of the negative electrode active material in the negative electrode tab is too small, it is disadvantageous for the movement of lithium ions in the negative electrode material, the kinetic performance of the material is insufficient, and the rapid charging ability of the battery is insufficient. In addition, due to the insufficient kinetic performance of the material, charging at a high rate may lead to the risk of lithium precipitation, the battery performance deteriorates rapidly, and there is also a risk of gas generation in the battery. By controlling the lithium ion solid-phase diffusion coefficient Ds of the negative electrode active material within the above range, the movement speed of lithium ions in the negative electrode material can be made faster, the kinetic performance of the negative electrode material is excellent, and the rapid charging ability of the secondary battery is further improved.

[0113] In some embodiments, the volume average particle size Dv50 of the negative electrode active material is ≧6 μm. During the charging process of the battery, the first additive and the second additive form an SEI film with a certain thickness on the negative electrode surface. By controlling the volume average particle size Dv50 of the negative electrode active material to be ≧6 μm, the contact area between the negative electrode material and the electrolyte can be reduced, further preventing the carboxylic acid ester-based solvent from causing side reactions on the negative electrode surface, reducing gas generation, and suppressing the deterioration of cycle performance.

[0114] As can be understood, the volume average particle size Dv50 of the negative electrode active material may be 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, but is not limited thereto.

[0115] In some embodiments, the volume average particle size Dv50 of the negative electrode active material is 15 μm to 20 μm. In this way, the battery can have good cycle performance and excellent kinetic performance.

[0116] In some embodiments, the BET specific surface area of the negative electrode active material is 0.5 m 2 / g to 2.0 m 2 / g. During the charging process of the battery, the first additive and the second additive form an SEI film with a certain thickness on the negative electrode surface. By controlling the BET specific surface area of the negative electrode active material within the range of 0.5 m 2 / g to 2.0 m 2 / g, the contact area between the negative electrode material and the electrolyte can be reduced, the side reactions caused by the carboxylic acid ester-based solvent on the negative electrode surface can be reduced, gas generation can be reduced, and the cycle performance of the battery can be improved.

[0117] As can be understood, the BET specific surface area of the negative electrode active material is 0.5 m 2 / g, 0.6 m 2 / g, 0.7 m 2 / g, 0.8 m 2 / g, 0.9 m 2 / g, 1.0 m 2 / g, 1.1 m 2 / g, 1.2 m 2 / g, 1.3 m 2 / g, 1.4 m 2 / g, 1.5 m 2 / g, 1.6 m 2 / g, 1.7 m 2 / g, 1.8 m 2 / g, 1.9 m 2 / g, 2.0 m 2 It may be / g, but is not limited thereto.

[0118] In some embodiments, the BET specific surface area of the negative electrode active material is 0.8 m 2 / g to 1.5 m 2 / g. Thus, the secondary battery can have good cycle performance, and the secondary battery can have excellent kinetic performance.

[0119] The third aspect of the present application provides a power consumption device, and the power consumption device includes the secondary battery in the second aspect of the present application.

[0120] Hereinafter, the secondary battery and the power consumption device of the present application will be described with appropriate reference to the drawings.

[0121] Unless otherwise specified, the battery assemblies, types of materials or contents mentioned are also applicable to lithium-ion secondary batteries and sodium-ion secondary batteries.

[0122] In one embodiment of the present application, a secondary battery is provided.

[0123] Generally, a secondary battery includes a positive electrode tab, a negative electrode tab, an electrolyte, and a separator. In the charge and discharge process of the battery, active ions repeatedly intercalate and desorb between the positive electrode tab and the negative electrode tab. The electrolyte serves to transfer ions between the positive electrode tab and the negative electrode tab. The separator is provided between the positive electrode tab and the negative electrode tab, mainly serving to prevent short circuit between the positive electrode and the negative electrode and allowing ions to pass through.

[0124] Positive electrode tab The positive electrode tab includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector.

[0125] As a non-limiting example, the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is provided on either one or both of the two opposing surfaces of the positive electrode current collector.

[0126] In some embodiments, the positive electrode current collector may employ a metal foil sheet or a composite current collector. For example, an aluminum foil may be employed as the metal foil sheet. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be obtained by forming a metal material on a polymer material substrate. In the positive electrode current collector, non-limiting examples of the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. In the positive electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0127] In some embodiments, the positive electrode active material may include well-known positive electrode active materials used in batteries in this field.

[0128] As a non-limiting example, the positive electrode active material of the lithium-ion secondary battery may include one or more of materials such as lithium-containing phosphates having an olivine structure, lithium transition metal oxides, and modified compounds thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as the positive electrode active material of the battery may also be used. These positive electrode active materials may be used alone or in combination of two or more. However, examples of the lithium transition metal oxide may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide and modified compounds thereof. Non-limiting examples of the lithium-containing phosphate having an olivine structure may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon. Non-limiting examples of lithium cobalt oxide may include LiCoO2, non-limiting examples of lithium nickel oxide may include LiNiO2, non-limiting examples of lithium manganese oxide may include LiMnO2, LiMn2O4, etc., and non-limiting examples of lithium nickel cobalt manganese oxide may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (which may simply be called NCM 333 for short), LiNi 0.5 Co 0.2 Mn 0.3 O2 (which may simply be called NCM 523 for short), LiNi 0.5 Co 0.25 Mn 0.25 O2 (which may simply be called NCM 211 for short), LiNi 0.6 Co 0.2 Mn 0.2 O2 (which may simply be called NCM 622 for short), LiNi 0.8 Co 0.1 Mn0.1 O2 (which may also be simply referred to as NCM 811 etc.) may be included, and non-limiting examples of lithium nickel cobalt aluminum oxide are LiNi 0.85 Co 0.15 Al 0.05 O2 may also be included.

[0129] As can be understood, during the charge and discharge process of the battery, the desorption and consumption of lithium (Li) are involved, and the Li content in the positive electrode tab varies when the battery is discharged to different states. In the enumeration of the positive electrode materials in this application, unless otherwise specified, the Li content is the initial state of the material. When the positive electrode material is applied to the positive electrode tab in the battery system and undergoes charge and discharge cycles, the Li content in the positive electrode material contained in the tab usually changes. However, the Li content can be measured in terms of molar content, but is not limited thereto. Regarding "the Li content is the initial state of the material", the initial state of the material refers to the state before being put into the positive electrode slurry. As can be understood, new materials obtained by performing appropriate modifications based on the enumerated positive electrode materials are also included in the scope of the positive electrode materials. The appropriate modifications described above refer to modification methods that are possible to be allowed for the positive electrode materials, and as non-limiting examples, for example, it refers to coating modification.

[0130] In the enumeration regarding the positive electrode materials in this application, the oxygen (O) content is only the theoretical state value. Due to the release of oxygen by the lattice, the molar content of oxygen changes, and the actual O content fluctuates. However, the O content can be measured in terms of molar content, but is not limited thereto.

[0131] As a non-limiting example, the positive electrode active material of the sodium-ion secondary battery may include one or more of materials such as sodium transition metal oxides, polyanion-type compounds, and Prussian blue-based compounds. However, this application is not limited to these materials, and other conventionally well-known materials that can be used as the positive electrode active material of the sodium-ion battery may also be used.

[0132] As an alternative technical solution of the present application, in the sodium transition metal oxide, the transition metal may be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The sodium transition metal oxide is, for example, Na x MO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0 < x ≦ 1.

[0133] As an alternative technical solution of the present application, the polyanion-type compound may be a compound having sodium ions, transition metal ions, and tetrahedral (YO4) n- anion units. The transition metal may be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, Y may be one or more of P, S, and Si, and n represents the valence of (YO4) n- .

[0134] The polyanion-type compound may be a compound having sodium ions, transition metal ions, tetrahedral (YO4) n- anion units, and halogen anions. The transition metal may be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, Y may be one or more of P, S, and Si, n represents the valence of (YO4) n- , and the halogen may be one or more of F, Cl, and Br.

[0135] The polyanion-type compound may be a compound having sodium ions, tetrahedral (YO4) n- anion units, polyhedral units (ZO y ) m+ and optional halogen anions. Y may be one or more of P, S, and Si, n represents the valence of (YO4) n- , Z represents a transition metal, which may be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, and m represents (ZO y ) m+represents the valence, and the halogen may be one or more of F, Cl, and Br.

[0136] The polyanion-type compound is, for example, NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM’PO4F (M’ is one or more of V, Fe, Mn, and Ni), and Na3(VO y )2(PO4)2F 3-2y is one or more of (0≦y≦1).

[0137] The Prussian blue-based compound may be a compound having sodium ions, transition metal ions, and cyanur ions (CN - ). The transition metal may be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The Prussian blue-based compound is, for example, Na a Me b Me’ c (CN)6, provided that Me and Me’ are each independently one or more of Ni, Cu, Fe, Mn, Co, and Zn, and 0 < a ≦ 2, 0 < b < 1, 0 < c < 1.

[0138] The weight ratio of the positive electrode active material in the positive electrode film layer is 80 to 100% by weight based on the total weight of the positive electrode film layer.

[0139] In some embodiments, the positive electrode film layer further includes a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin. The weight ratio of the binder in the positive electrode film layer is 0 to 20% by weight based on the total weight of the positive electrode film layer.

[0140] In some embodiments, the positive electrode film layer further contains a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon spot, carbon nanotube, graphene, and carbon nanofiber. Based on the total weight of the positive electrode film layer, the weight ratio of the conductive agent in the positive electrode film layer is 0 to 20 wt%.

[0141] In some embodiments, the positive electrode tab can be manufactured as follows. The components for manufacturing the positive electrode tab described above, such as the positive electrode active material, the conductive agent, the binder, and any other components, are dispersed in a solvent (for example, N-methylpyrrolidone) to form a positive electrode slurry, provided that the solid content of the positive electrode slurry is 40 wt% to 80 wt%, and the viscosity at room temperature is adjusted to 5000 mPa·s to 25000 mPa·s. The positive electrode slurry is applied to the surface of the positive electrode current collector and dried, and then cold pressed by a cold rolling machine to form a positive electrode tab. The unit area density of the application of the positive electrode slurry is 150 mg / m 2 ~350 mg / m 2 and the press density of the positive electrode tab is 3.0 g / cm 3 ~3.6 g / cm 3 It may be selected as 3.3 g / cm 3 ~3.5 g / cm 3

[0142] The calculation formula for the press density is as follows.

[0143] Press density = coating surface density / (thickness of the tab after extrusion - thickness of the current collector).

[0144] The mass M of the positive electrode active material in the positive electrode film per unit area is obtained by weighing using a standard balance.

[0145] ​The thickness T of the positive electrode film is obtained by measuring with a micrometer. For example, it is obtained by measuring with a micrometer with a model number of Mitutoyo 293-100 and an accuracy of 0.1 μm. It should be noted that the thickness of the positive electrode film described in this application refers to the thickness of the positive electrode film in the positive electrode tab for assembling the battery after being extruded by cold pressing.

[0146] Negative electrode tab The negative electrode tab includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, and the negative electrode film layer contains a negative electrode active material.

[0147] As a non-limiting example, the negative electrode current collector has two surfaces facing each other in its own thickness direction, and the negative electrode film layer is provided on either one or both of the two opposing surfaces of the negative electrode current collector.

[0148] In some embodiments, the negative electrode current collector may employ a metal foil sheet or a composite current collector. For example, a copper foil may be employed as the metal foil sheet. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be obtained by forming a metal material on a polymer material substrate. However, in the negative electrode current collector, non-limiting examples of the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. In the negative electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0149] In some embodiments, the negative electrode active material may employ well-known negative electrode active materials used in batteries in this field.

[0150] As a non-limiting example, the negative electrode active material of a lithium-ion secondary battery may include one or more of materials such as artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based materials may include one or more of elemental silicon, silicon oxide, silicon carbon composite, silicon nitride composite, and silicon alloy. The tin-based materials may include one or more of elemental tin, tin acid compounds, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of the battery may be used. These negative electrode active materials may be used alone or in combination of two or more kinds.

[0151] As a non-limiting example, the negative electrode active material of a sodium-ion secondary battery is usually a hard carbon material, a two-dimensional metal carbide or nitride. Preferably, the negative electrode active material of a sodium-ion secondary battery is usually a hard carbon material.

[0152] In some embodiments, the negative electrode film layer further includes a binder. The binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0153] In some embodiments, the negative electrode film layer further includes a conductive agent. The conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon spot, carbon nanotube, graphene, and carbon nanofiber.

[0154] In some embodiments, the negative electrode film layer further includes other auxiliaries, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)), etc.

[0155] In some embodiments, the negative electrode tab can be manufactured as follows. Components for manufacturing the negative electrode tab described above, such as a negative electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (a non-limiting example of the solvent is, for example, deionized water) to form a negative electrode slurry. The negative electrode slurry is applied to the surface of at least one side of the negative electrode current collector, and through processes such as drying and cold pressing, a negative electrode tab can be obtained. The surface of the negative electrode current collector to which the negative electrode slurry is applied may be a single surface of the negative electrode current collector or two surfaces of the negative electrode current collector. The solid content of the negative electrode slurry may be 40 wt% to 60 wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000 mPa·s to 10000 mPa·s. When applying the negative electrode slurry, the unit area density of the application on a dry weight basis (excluding the solvent) is 75 g / m 2 ~220 g / m 2 It may be. The press density of the negative electrode tab may be 1.0 g / cm 3 ~ 1.8 g / cm 3 It may be.

[0156] Electrolyte The electrolyte plays a role in transmitting ions between the positive electrode tab and the negative electrode tab. In the secondary battery of the present application, the electrolyte in the first aspect of the present application is adopted.

[0157] In some embodiments, the electrolyte includes an electrolyte salt and an organic solvent.

[0158]

[0159] In some embodiments, the electrolyte salt of the lithium-ion secondary battery may be selected from one or more of lithium hexafluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bistrifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluorooxalatophosphate.In some embodiments, the organic solvent contains a carboxylic acid ester solvent that accounts for 20% to 80% of the mass percentage of the organic solvent.

[0160] The electrolyte salt of the sodium-ion secondary battery may be selected from one or more of lithium hexafluorophosphate, sodium bis(fluorosulfonyl)amide, sodium bis(trifluoromethanesulfonyl)imide, sodium trifluoromethanesulfonate, sodium tetrafluoroborate, sodium difluorophosphate, sodium perchlorate, and sodium chloride.

[0161] The concentration of the electrolyte salt is usually 0.5 mol / L to 5 mol / L.

[0162] Separator In some embodiments, the secondary battery further includes a separator. In the present application, there is no particular limitation on the type of the separator, and any well-known separator with a porous structure having excellent chemical and mechanical stability may be selected and used.

[0163] In some embodiments, the material of the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, and there is no particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, and there is no particular limitation.

[0164] In some embodiments, the thickness of the separator is 6 μm to 40 μm, and it may be selected as 12 μm to 20 μm.

[0165] In some embodiments, the positive electrode tab, the negative electrode tab, and the separator can be used to manufacture an electrode assembly by a winding process or a lamination process.

[0166] In some embodiments, the secondary battery may include an exterior body. The exterior body may be used to package the electrode assembly and the electrolyte.

[0167] In some embodiments, the exterior body of the secondary battery may be a hard case, for example, a hard plastic case, an aluminum case, a steel case, etc. The exterior body of the secondary battery may be a soft pack, for example, a pouch-type soft pack. The material of the soft pack may be plastic, and further, non-limiting examples of the plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0168] The secondary battery includes at least one battery cell. The secondary battery may include one or more battery cells.

[0169] In this application, unless otherwise specified, the "battery cell" refers to a basic unit capable of mutually converting chemical energy and electrical energy, and further, usually includes at least a positive electrode tab, a negative electrode tab, and an electrolyte. During the charge and discharge process of the battery, active ions are repeatedly occluded and desorbed between the positive electrode tab and the negative electrode tab. The electrolyte serves to transfer active ions between the positive electrode tab and the negative electrode tab.

[0170] This application does not particularly limit the shape of the battery cell, and it may be cylindrical, rectangular, or any other arbitrary shape. For example, FIG. 1 shows a rectangular-shaped battery cell 5 as an example.

[0171] In some embodiments, referring to FIG. 2, the exterior body may include a case 51 and a cover 53. However, the case 51 may include a bottom plate and side plates connected to the bottom plate, and an accommodation chamber is formed by being surrounded by the bottom plate and the side plates. The case 51 has an opening communicating with the accommodation chamber, and the cover 53 can be crowned on the opening to close the accommodation chamber. The positive tab, the negative tab, and the separator can form the electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the accommodation chamber. The electrolyte is infiltrated into the electrode assembly 52. The number of electrode assemblies 52 included in the battery cell 5 may be one or more, and those skilled in the art can select according to actual needs.

[0172] In some embodiments, the battery cell 5 can be assembled into a battery module, and the number of battery cells 5 included in the battery module may be one or more. Those skilled in the art can select a specific number according to the application and capacity of the battery module.

[0173] In the battery module, the plurality of battery cells 5 may be arranged in sequence along the longitudinal direction of the battery module. Of course, they may be distributed in any other way. Further, the plurality of battery cells 5 may be fixed by a fastener.

[0174] In some embodiments, the battery module may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0175] In some embodiments, the above battery module may be assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more. Those skilled in the art can select a specific number according to the application and capacity of the battery pack.

[0176] The battery pack may include a battery box and a plurality of battery modules provided in the battery box. The battery box includes an upper housing and a lower housing, and the upper housing is crowned on the lower housing to form a closed space for accommodating the battery modules. The plurality of battery modules may be distributed in the battery box in any manner.

[0177] Furthermore, the present application further provides a power consumption device, and the power consumption device includes at least one of a secondary battery, a battery module, or a battery pack according to the present application. The secondary battery, the battery module, or the battery pack may be used as a power source of the power consumption device, and may also be used as an energy storage unit of the power consumption device. The power consumption device may include, but is not limited to, mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric motorcycles, electric scooters, electric golf carts, electric trucks, etc.), trains, ships, artificial satellites, energy storage systems, and the like.

[0178] As the power consumption device, a secondary battery, a battery module, or a battery pack can be selected according to the needs of its use.

[0179] FIG. 3 shows a power consumption device 6 as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the power consumption device for the secondary battery, a battery pack or a battery module may be adopted.

[0180] Another example of the device may be a mobile phone, a tablet, a notebook computer, etc. Such a device is usually required to be thin and light, and a secondary battery may be adopted as the power source.

[0181] The following are some examples.

[0182] In order to more clearly illustrate the problems, technical solutions, and beneficial effects to be solved by this application, the present application will be further described in detail below with reference to the embodiments and drawings. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Hereinafter, the description of at least one exemplary embodiment is merely illustrative and does not constitute any limitation to the present application and its application. Based on the embodiments in the present application, all other embodiments obtained without creative efforts by those skilled in the art shall fall within the protection scope of the present application.

[0183] In the case where specific technologies or conditions are not clearly indicated in the embodiments, the technologies or conditions described in the literature in this field are implemented in accordance with the product specifications. When the manufacturers of the reagents or equipment used are not indicated, they are commercially available general-purpose products.

[0184] Example 1 1) Regarding the manufacture of the positive electrode tab The positive electrode material of lithium iron phosphate, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are put into the solvent N-methylpyrrolidone (NMP) at a weight ratio of 90:5:5, and stirred and mixed sufficiently and uniformly to obtain a positive electrode slurry (the solid content is 67%), and then the positive electrode slurry is uniformly coated on the positive electrode current collector, and a positive electrode tab with the weight of the one-sided positive electrode tab film layer being 350 mg / 1540.25 mm 2 is obtained, and further through drying, cold pressing, and slitting, a positive electrode tab is obtained.

[0185] 2) Regarding the manufacture of the negative electrode tab The artificial graphite of the negative electrode active material, the carbon black of the conductive agent, the styrene-butadiene rubber (SBR) of the binder, and the sodium carboxymethyl cellulose (CMC-Na) of the thickening agent are dissolved in the deionized water of the solvent at a weight ratio of 90:4:4:2, and after being uniformly mixed, a negative electrode slurry (the solid content is 48%) is manufactured. The negative electrode slurry is uniformly coated on the copper foil of the negative electrode current collector once or multiple times, and through drying, cold pressing, and slitting, a negative electrode tab is obtained. The lithium ion solid-phase diffusion coefficient Ds of the negative electrode active material is 5×10 -12 cm2 / S, the volume-average particle size Dv50 is 17 μm, and the BET specific surface area is 1 m 2 / g.

[0186] 3) Separator A commercially available polypropylene membrane is used as the separator.

[0187] 4) Electrolyte In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC) / ethyl methyl carbonate (EMC) is uniformly mixed at a volume ratio of 3:7. Based on the total weight of the solvent, the ratio of the total weight of ethylene carbonate and ethyl methyl carbonate is 80%. 20% by weight of methyl acetate is added thereto. Then, lithium hexafluorophosphate (LiPF6) lithium salt, the first additive (lithium difluorophosphate), and the second additive (vinylene carbonate) are put into an organic solvent and dissolved to make the concentration of LiPF6 12.5%, the mass percentage of the first additive is 1%, and the mass percentage of the second additive is 2%. It is uniformly stirred to obtain an electrolyte.

[0188] 5) Battery assembly The positive electrode tab (width 87 mm × length 605 mm), the separator (width 98 mm × length 1896 mm), and the negative electrode tab (width 93 mm × length 735 mm) are laminated in sequence, with the separator positioned between the positive and negative tabs to play a role in separation, and then wound to obtain an electrode assembly. The electrode assembly is placed in a battery case, and after drying, 12.0 g of electrolyte is injected (3 Ah, injection coefficient 4.0 g / Ah). Further, a lithium-ion secondary battery is manufactured through processes such as formation and standing.

[0189] Example 2 The manufacturing method of the secondary battery in this example is almost the same as that in Example 1, except that the mass percentage W1 of the carboxylic acid ester-based solvent in the organic solvent of the electrolyte in this example is 30%, and correspondingly, (W2 + W3) / W1 is 0.1.

[0190] Example 3 The manufacturing method of the secondary battery of this example is almost the same as that of Example 1. The only difference is that the mass percentage W1 of the carboxylic acid ester solvent in the organic solvent of the electrolyte solution in this example is 40%, and correspondingly, (W2 + W3) / W1 is 0.075.

[0191] Example 4 The manufacturing method of the secondary battery of this example is almost the same as that of Example 1. The only difference is that the mass percentage W1 of the carboxylic acid ester solvent in the organic solvent of the electrolyte solution in this example is 50%, and correspondingly, (W2 + W3) / W1 is 0.06.

[0192] Example 5 The manufacturing method of the secondary battery of this example is almost the same as that of Example 1. The only difference is that the mass percentage W1 of the carboxylic acid ester solvent in the organic solvent of the electrolyte solution in this example is 60%, and correspondingly, (W2 + W3) / W1 is 0.05.

[0193] Example 6 The manufacturing method of the secondary battery of this example is almost the same as that of Example 1. The only difference is that the mass percentage W1 of the carboxylic acid ester solvent in the organic solvent of the electrolyte solution in this example is 70%, and correspondingly, (W2 + W3) / W1 is 0.04.

[0194] Example 7 The manufacturing method of the secondary battery of this example is almost the same as that of Example 1. The only difference is that the mass percentage W1 of the carboxylic acid ester solvent in the organic solvent of the electrolyte solution in this example is 80%, and correspondingly, (W2 + W3) / W1 is 0.0375.

[0195] Example 8 The manufacturing method of the secondary battery of this example is almost the same as that of Example 5. The only difference is that the carboxylic acid ester solvent in the organic solvent of the electrolyte solution in this example is ethyl acetate.

[0196] Example 9 The manufacturing method of the secondary battery of this example is almost the same as that of Example 5, and the only difference is that the carboxylic acid ester solvent of the organic solvent in the electrolytic solution in this example is ethyl difluoroacetate.

[0197] Example 10 The manufacturing method of the secondary battery of this example is almost the same as that of Example 5, and the only difference is that the carboxylic acid ester solvent of the organic solvent in the electrolytic solution in this example is methyl difluoroacetate.

[0198] Example 11 The manufacturing method of the secondary battery of this example is almost the same as that of Example 5, and the only difference is that the mass percentage W2 of lithium difluorophosphate, which is the first additive in the electrolytic solution in this example, is 5%, and correspondingly, (W2 + W3) / W1 is 0.117.

[0199] Example 12 The manufacturing method of the secondary battery of this example is almost the same as that of Example 5, and the only difference is that the type of the first additive in the electrolytic solution in this example is lithium difluorooxalate borate.

[0200] Example 13 The manufacturing method of the secondary battery of this example is almost the same as that of Example 5, and the only difference is that the type of the first additive in the electrolytic solution in this example is lithium tetrafluoroborate.

[0201] Example 14 The manufacturing method of the secondary battery of this example is almost the same as that of Example 5, and the only difference is that the type of the first additive in the electrolytic solution in this example is lithium fluorosulfonate.

[0202] Example 15 The manufacturing method of the secondary battery of this example is almost the same as that of Example 5, and the only difference is that the mass percentage W3 of the second additive in the electrolytic solution in this example is 5%, and correspondingly, (W2 + W3) / W1 is 0.1.

[0203] Example 16 The manufacturing method of the secondary battery of this example is almost the same as that of Example 5, and the only difference is that the type of the second additive in the electrolyte of this example is JPEG2025521103000019.jpg2036.

[0204] Example 17 The manufacturing method of the secondary battery of this example is almost the same as that of Example 5, and the only difference is that the type of the second additive in the electrolyte of this example is JPEG2025521103000020.jpg2032.

[0205] Example 18 The manufacturing method of the secondary battery of this example is almost the same as that of Example 5, and the only difference is that the type of the second additive in the electrolyte of this example is JPEG2025521103000021.jpg2043.

[0206] Example 19 The manufacturing method of the secondary battery of this example is almost the same as that of Example 5, and the only difference is that the carboxylic acid ester solvent of the organic solvent in the electrolyte of this example is methyl formate.

[0207] Example 20 The manufacturing method of the secondary battery of this example is almost the same as that of Example 5, and the only difference is that the carboxylic acid ester solvent of the organic solvent in the electrolyte of this example is propyl propionate.

[0208] Example 21 The manufacturing method of the secondary battery of this example is almost the same as that of Example 5, and the only difference is that the lithium ion solid-phase diffusion coefficient Ds of the negative electrode active material of the secondary battery of this example is 10 -11 cm 2 / S.

[0209] Example 22 The manufacturing method of the secondary battery of this example is almost the same as that of Example 5, and the only difference is that the lithium ion solid-phase diffusion coefficient Ds of the negative electrode active material of the secondary battery in this example is 10 -12 cm 2It only differs in that it is / S.

[0210] Example 23 The method for manufacturing a secondary battery in this example is almost the same as that in Example 5, and the lithium-ion solid-phase diffusion coefficient Ds of the negative electrode active material of the secondary battery in this example is 10 -10 cm 2 It only differs in that it is / S.

[0211] Example 24 The method for manufacturing a secondary battery in this example is almost the same as that in Example 5, and the lithium-ion solid-phase diffusion coefficient Ds of the negative electrode active material of the secondary battery in this example is 10 -13 cm 2 It only differs in that it is / S.

[0212] Example 25 The method for manufacturing a secondary battery in this example is almost the same as that in Example 5, and it only differs in that the volume average particle diameter Dv50 of the negative electrode active material of the secondary battery in this example is 15 μm.

[0213] Example 26 The method for manufacturing a secondary battery in this example is almost the same as that in Example 5, and it only differs in that the volume average particle diameter Dv50 of the negative electrode active material of the secondary battery in this example is 20 μm.

[0214] Example 27 The method for manufacturing a secondary battery in this example is almost the same as that in Example 5, and it only differs in that the volume average particle diameter Dv50 of the negative electrode active material of the secondary battery in this example is 10 μm.

[0215] Example 28 The method for manufacturing a secondary battery in this example is almost the same as that in Example 5, and it only differs in that the volume average particle diameter Dv50 of the negative electrode active material of the secondary battery in this example is 25 μm.

[0216] Example 29 The method for manufacturing a secondary battery in this example is almost the same as that in Example 5, and the BET specific surface area of the negative electrode active material of the secondary battery in this example is 0.5 m 2It is only different in that it is / g.

[0217] Example 30 The manufacturing method of the secondary battery of this example is almost the same as that of Example 5, and the BET specific surface area of the negative electrode active material of the secondary battery in this example is 2 m 2 It is only different in that it is / g.

[0218] Example 31 The manufacturing method of the secondary battery of this example is almost the same as that of Example 5, and the BET specific surface area of the negative electrode active material of the secondary battery in this example is 0.1 m 2 It is only different in that it is / g.

[0219] Example 32 The manufacturing method of the secondary battery of this example is almost the same as that of Example 5, and the BET specific surface area of the negative electrode active material of the secondary battery in this example is 3 m 2 It is only different in that it is / g.

[0220] Comparative Example 1 The manufacturing method of the secondary battery of this comparative example is almost the same as that of Example 5. The mass percentage W2 of potassium difluorophosphate, which is the first additive of the electrolytic solution in this comparative example, is 0.005%, and correspondingly, it is only different in that (W2 + W3) / W1 is 0.0334.

[0221] Comparative Example 2 The manufacturing method of the secondary battery of this comparative example is almost the same as that of Example 5. The mass percentage W2 of potassium difluorophosphate, which is the first additive of the electrolytic solution in this comparative example, is 0.01%, and correspondingly, it is only different in that (W2 + W3) / W1 is 0.0335.

[0222] Comparative Example 3 The manufacturing method of the secondary battery of this comparative example is almost the same as that of Example 5. The mass percentage W2 of potassium difluorophosphate, which is the first additive of the electrolytic solution in this comparative example, is 0.05%, and correspondingly, it is only different in that (W2 + W3) / W1 is 0.034.

[0223] Comparative Example 4 The manufacturing method of the secondary battery of this comparative example is almost the same as that of Example 5. The mass percentage W2 of potassium difluorophosphate, which is the first additive in the electrolytic solution in this comparative example, is 10%. Accordingly, the only difference is that (W2 + W3) / W1 is 0.2.

[0224] Comparative Example 5 The manufacturing method of the secondary battery of this comparative example is almost the same as that of Example 5. The mass percentage W2 of potassium difluorophosphate, which is the first additive in the electrolytic solution in this comparative example, is 11%. Accordingly, the only difference is that (W2 + W3) / W1 is 0.217.

[0225] Comparative Example 6 The manufacturing method of the secondary battery of this comparative example is almost the same as that of Example 5. The mass percentage W3 of the second additive in the electrolytic solution in this comparative example is 0.04%. Accordingly, the only difference is that (W2 + W3) / W1 is 0.0173.

[0226] Comparative Example 7 The manufacturing method of the secondary battery of this comparative example is almost the same as that of Example 5. The mass percentage W3 of the second additive in the electrolytic solution in this comparative example is 0.05%. Accordingly, the only difference is that (W2 + W3) / W1 is 0.0175.

[0227] Comparative Example 8 The manufacturing method of the secondary battery of this comparative example is almost the same as that of Example 5. The mass percentage W3 of the second additive in the electrolytic solution in this comparative example is 0.1%. Accordingly, the only difference is that (W2 + W3) / W1 is 0.018.

[0228] Comparative Example 9 The manufacturing method of the secondary battery of this comparative example is almost the same as that of Example 5. The mass percentage W3 of the second additive in the electrolytic solution in this comparative example is 10%. Accordingly, the only difference is that (W2 + W3) / W1 is 0.183.

[0229] Comparative Example 10 The manufacturing method of the secondary battery of this comparative example is almost the same as that of Example 5. The mass percentage W3 of the second additive in the electrolytic solution in this comparative example is 11%, and correspondingly, the only difference is that (W2 + W3) / W1 is 0.2.

[0230] Comparative Example 11 The manufacturing method of the secondary battery of this comparative example is almost the same as that of Example 5. No second additive is added to the electrolytic solution in this comparative example, that is, W3 is 0, and correspondingly, the only difference is that (W2 + W3) / W1 is 0.0167.

[0231] Comparative Example 12 The manufacturing method of the secondary battery of this comparative example is almost the same as that of Example 5. No first additive is added to the electrolytic solution in this comparative example, that is, W2 is 0, and correspondingly, the only difference is that (W2 + W3) / W1 is 0.033.

[0232] Comparative Example 13 The manufacturing method of the secondary battery of this comparative example is almost the same as that of Example 5. The mass percentage W1 of methyl acetate as the organic solvent in the electrolytic solution in this comparative example is 10%, and correspondingly, the only difference is that (W2 + W3) / W1 is 0.3.

[0233] Comparative Example 14 The manufacturing method of the secondary battery of this comparative example is almost the same as that of Example 5. The mass percentage W1 of methyl acetate as the organic solvent in the electrolytic solution in this comparative example is 90%, and correspondingly, the only difference is that (W2 + W3) / W1 is 0.033.

[0234] Performance Test 1) Rapid Charging Performance Test At 25 °C, a charge-discharge test was performed on the battery after the capacity grading at 2.5 V to 3.65 V. The test steps were as follows. First, it was charged at a constant current of 3 C until SOC30%, then charged at a constant current of 2 C until SOC60%, then charged at a constant current of 1 C and constant voltage until SOC80%, with a cut-off current of 0.01 C, left to stand for 5 minutes, discharged at a constant current of 1 C until 2.0 V, and left to stand for 5 minutes. The time taken to charge the battery to SOC80% was measured.

[0235] 2) Cycle performance test At 45 °C, the secondary battery was charged at a constant current of 0.5 C until 3.65 V, and then charged at a constant voltage of 3.65 V until the current was less than 0.05 C, and then the secondary battery was discharged at a constant current of 0.5 C until 2.5 V. This was one charge-discharge process (i.e., 1 cycle). Charging and discharging were repeated in this way, and the number of cycles when the capacity retention rate was 80% was recorded.

[0236] 3) Storage performance test The lithium-ion secondary battery was charged at a constant current of 0.33 C until 3.65 V, and then charged at a constant voltage of 3.65 V until the current reached 0.05 C, fully charging the secondary battery. The volume of the battery was tested by the water replacement method, and this volume was taken as the volume before storage. Then, the secondary battery was placed at 60 °C for 30 days of storage. After the storage was completed, the secondary battery was placed in an environment of 25 °C, and the volume of the battery was tested by the water replacement method, and this volume was taken as the volume after storage. The volume expansion rate of the battery was calculated according to the following formula.

[0237] Volume expansion rate of the battery = (Volume after storage / Volume before storage - 1) × 100%.

[0238] 4) Lithium-ion solid-phase diffusion coefficient test Taking the GITT method as an example, the steps to test the lithium-ion solid-phase diffusion coefficient of the negative electrode active material were as follows.

[0239] The negative electrode active material was polished into a powder microelectrode, and the powder microelectrode was connected to an electrochemical station for coulometric titration. However, a pulse current of 20 μA, a titration time of 1 h (hour), an interval of 4 h (in addition, in order to compare the effects of the pulse current and time, parallel experiments may be carried out at 10 μA and 10 minutes), and a GITT curve was obtained. The lithium ion diffusion coefficient was calculated using the following formula.

[0240] JPEG2025521103000022.jpg18132

[0241] However, D is the lithium ion diffusion coefficient, I0 is the applied current of 20 μA, V m is the molar volume of the active material, F is the Faraday constant, A is the electrode surface area, dE / dx is the slope of the coulometric titration curve, that is, the slope at a specific concentration on the open circuit potential vs. Li concentration curve of the electrode, and dE / d(t 1 / 2 ) is the slope of the polarization voltage vs. t 1 / 2 curve. Specifically, references such as Xie et al., Solid State Ionics, 2007, 178: 1218-1224; Yang et al., Electrochimica Acta, 2012, 66: 88-93 can be referred to.

[0242] 5) Volume average particle size test "Dv50" represents the particle size until the volume accumulates to 50% when measured from the small particle size in the volume-based particle size distribution of the material. Usually, Dv50 may be tested by methods and instruments well-known in this field. For example, it can be measured by a laser diffraction particle size distribution analyzer (such as Malvern Mastersizer 3000).

[0243] 6) BET specific surface area test The test method referred to the standard GB / T19587-2004 "Measurement of Specific Surface Area of Solid Substances by Gas Adsorption BET Method". 8 g to 15 g of the sample to be measured was taken and placed in a sample tube, and the initial mass of the sample to be measured was recorded. The weighed sample to be measured was placed into the instrument NOVA2000e. Then, degassing was started, and after heating the sample to be measured to 200 °C, it was held for 2 h. And the mass of the sample to be measured after degassing was recorded. Then, the sample to be measured after degassing was placed into the instrument again, and liquid nitrogen was injected to conduct a BET test.

[0244] The rapid charging performance, cycle performance, and storage performance of the secondary batteries in each of the above examples and comparative examples were tested, and the specific test results are shown in Tables 1 to 9.

[0245]

Table 1

[0246]

Table 2

[0247]

Table 3

[0248]

Table 4

[0249]

Table 5

[0250] [Table 6] JPEG2025521103000034.jpg209169JPEG2025521103000035.jpg210169

[0251] [Table 7] JPEG2025521103000037.jpg159169

[0252] [Table 8] JPEG2025521103000039.jpg216169JPEG2025521103000040.jpg176169

[0253] [Table 9]

[0254] As can be seen from the data of the above manufacturing examples and comparative manufacturing examples, in Examples 1 to 7, W1 is in the range of 20% to 80%, (W2+W3) / W1 is in the range of 0.035 to 0.15, and as the mass fraction of the carboxylic acid ester solvent methyl acetate in the organic solvent gradually increases, the fast charging performance of the battery gradually improves, and the cycle performance and storage performance of the battery decrease to a certain extent, but all are at a good level.

[0255] In Examples 2 to 6, W1 is in the range of 30% to 70%, and (W2+W3) / W1 is in the range of 0.04 to 0.1. Compared with Examples 1 and 7, the secondary batteries of Examples 2 to 6 have better overall performance.

[0256] In Examples 3 to 5, W1 is in the range of 40% to 60%, (W2 + W3) / W1 is in the range of 0.05 to 0.075. Compared with Examples 1, 2, 6, and 7, the overall performance of the secondary batteries in Examples 3 to 5 is further improved.

[0257] Compared with Example 5, the amount of the first additive lithium difluorophosphate in Example 11 increases, and the storage performance of the secondary battery is significantly improved. Compared with Example 5, the amount of the second additive vinylene carbonate in Example 15 increases, and the storage performance of the secondary battery is also significantly improved.

[0258] Compared with Example 5, the amount of the first additive lithium difluorophosphate in Comparative Examples 1, 2, and 3 decreases, and the rapid charging performance is improved to a certain extent, but the cycle performance and storage performance are significantly reduced, and the overall performance is not good.

[0259] Compared with Example 5, the amount of the first additive lithium difluorophosphate in the electrolytes of Comparative Examples 4 and 5 increases, and the storage performance of the battery is improved to a certain extent, but the rapid charging performance and cycle performance of the battery both decrease significantly, and the overall performance is not good.

[0260] Compared with Example 5, the amount of the second additive vinylene carbonate in the electrolytes of Comparative Examples 6, 7, and 8 decreases, and the rapid charging performance of the battery is improved slightly, but the cycle performance and storage performance of the battery both decrease significantly.

[0261] Compared with Example 5, the amount of the second additive vinylene carbonate in the electrolytes of Comparative Examples 9 and 10 increases, and the storage performance of the battery is improved to a certain extent, but the rapid charging performance and cycle performance of the battery both decrease significantly.

[0262] In Comparative Example 11, without adding the second additive to the electrolytic solution, both the cycle performance and storage performance of the battery are clearly reduced. In Comparative Example 12, without adding the first additive to the electrolytic solution, the cycle performance and storage performance of the battery are similarly clearly reduced. In Comparative Example 13, the amount of carboxylic acid ester in the organic solvent is lower than 20%, and the rapid charging performance of the battery is significantly reduced. In Comparative Example 14, the amount of carboxylic acid ester in the organic solvent exceeds 80%, and both the cycle performance and storage performance of the battery are significantly reduced.

[0263] It should be noted that the present application is not limited to the above embodiments. The above embodiments are merely illustrative, and any embodiments that have substantially the same configuration and the same effects within the scope of the technical concept of the present application are included in the technical scope of the present application. In addition, without departing from the spirit of the present application, other forms created by making various modifications that can be conceived by those skilled in the art to the embodiments or by combining some components of the embodiments are also considered to be included in the scope of the present application.

Explanation of Reference Numerals

[0264] 5 Battery Cell 51 Case 52 Electrode Assembly 53 Cover 6 Power Consumption Device

Claims

1. An electrolyte for a lithium secondary battery, comprising an organic solvent, a first additive, a second additive, and an electrolyte salt dissolved in the organic solvent, wherein the organic solvent includes a carboxylic acid ester solvent, and based on the total mass of the organic solvent, the mass percentage W1 of the carboxylic acid ester solvent is 20% to 80%, the first additive includes one or more of monofluorophosphate, difluorophosphate, tetrafluoroborate, fluorosulfonate, oxalatoborate salt, malonic acid borate, oxalatophosphate salt, and (malonate) phosphate, the second additive includes one or more of the compounds represented by the following Formula I and Formula II, [Formula I] In formula I, R １ and R ２ are each independently selected from a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 halogenated alkyl group, a C1-C6 alkoxy group, a C2-C6 alkenyl group, or a C2-C6 alkynyl group. [Formula II] In formula II, R ３ , R ４ , R ５ and R ６ are each independently selected from a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 halogenated alkyl group, a C1-C6 alkoxy group, a C2-C6 alkenyl group or a C2-C6 alkynyl group, and R ３ , R ４ , R ５ and R ６ do not simultaneously represent a hydrogen atom, However, the mass percentages of the first additive and the second additive in the electrolyte are W2 and W3, respectively, and 0.035 ≤ (W2 + W3) / W1 ≤ 0.

15. An electrolyte for a lithium secondary battery.

2. The electrolyte is (1) In formula (I), R １ and R ２ are each independently selected from a hydrogen atom, a halogen atom, a C1-C4 alkyl group, a C1-C4 halogenated alkyl group, a C1-C4 alkoxy group, a C2-C4 alkenyl group, or a C2-C4 alkynyl group. In formula (II), R ３ , R ４ , R ５ and R ６ each independently satisfy at least one of being selected from a hydrogen atom, a halogen atom, a C1-C4 alkyl group, a C1-C4 halogenated alkyl group, a C1-C4 alkoxy group, a C2-C4 alkenyl group, or a C2-C4 alkynyl group, and the electrolytic solution for a lithium secondary battery according to claim 1, characterized by this.

3. Based on the total mass of the organic solvent, the mass percentage W1 of the carboxylic acid ester solvent is 30% to 70%. The electrolyte for a lithium secondary battery according to Claim 1 or 2, characterized in that.

4. Based on the total mass of the organic solvent, the mass percentage W1 of the carboxylic acid ester solvent is 40% to 60%. The electrolyte for a lithium secondary battery according to any one of Claims 1 to 3, characterized in that.

5. 0.05 ≤ (W2 + W3) / W1 ≤ 0.

075. The electrolyte for a lithium secondary battery according to any one of Claims 1 to 4, characterized in that.

6. Based on the total mass of the electrolyte, the mass percentage W2 of the first additive is 0.01% to 10%. The electrolyte for a lithium secondary battery according to any one of Claims 1 to 5, characterized in that.

7. Based on the total mass of the electrolyte, the mass percentage W2 of the first additive is 0.05% to 5%. The electrolyte for a lithium secondary battery according to any one of Claims 1 to 6, characterized in that.

8. Based on the total mass of the electrolyte, the mass percentage W3 of the second additive is 0.05% to 10%. The electrolyte for a lithium secondary battery according to any one of Claims 1 to 7, characterized in that.

9. Based on the total mass of the electrolyte, the mass percentage W3 of the second additive is 0.1% to 5%, and the electrolyte for a lithium secondary battery according to any one of claims 1 to 8 is characterized in that.

10. The carboxylic acid ester solvent contains a compound represented by Formula III, [Formula III] However, R ７ and R ８ is independently selected from any one of C1-C3 alkyl groups and C1-C3 halogenated alkyl groups, respectively. The electrolyte for a lithium secondary battery according to any one of claims 1 to 9, characterized in that.

11. The carboxylic acid ester solvent contains one or more of the following compounds, and the electrolyte for a lithium secondary battery according to claim 10 is characterized in that.

12. The second additive contains one or more of vinylene carbonate, 4,5 - diethylvinylene carbonate, fluoroethylene carbonate and vinyl ethylene carbonate, and the electrolyte for a lithium secondary battery according to any one of claims 1 to 11 is characterized in that.

13. The electrolyte, (3)the monofluorophosphate contains lithium monofluorophosphate, (4)the difluorophosphate contains lithium difluorophosphate, (5)satisfies at least one of the following: the tetrafluoroborate contains lithium tetrafluoroborate, and the electrolyte for a lithium secondary battery according to any one of claims 1 to 12 is characterized in that.

14. The oxalatoborate salt contains a compound represented by Formula IV, [Formula IV] However, M １ is selected from one or more of Li, Na, K, Rb, Cs, Mg, Ca, Ba, Al, Fe, Cu, and Ni, and X １ is a halogen, m1 is an integer from 1 to 3, n1 is an integer from 0 to 4, and a1, b1, and c1 are all positive integers. The electrolyte for a lithium secondary battery according to any one of claims 1 to 13, characterized in that.

15. The malonic acid borate contains a compound represented by Formula V, [Formula V] However, M ２ is selected from one or more of Li, Na, K, Rb, Cs, Mg, Ca, Ba, Al, Fe, Cu, and Ni, X ２ is a halogen, m2 is an integer of 1 to 3, n2 is an integer of 0 to 4, and a2, b2, and c2 are all positive integers. The electrolyte for a lithium secondary battery according to any one of claims 1 to 14, characterized by this.

16. The oxalatophosphate salt contains a compound represented by Formula VI, [Formula VI] However, M ３ is selected from one or more of Li, Na, K, Rb, Cs, Mg, Ca, Ba, Al, Fe, Cu, and Ni, and X ３ is a halogen, m3 is an integer of 1 to 3, n3 is an integer of 0 to 4, and a3, b3, and c3 are all positive integers. The electrolyte for a lithium secondary battery according to any one of claims 1 to 15, characterized in that.

17. The (malonato) phosphate contains a compound represented by Formula VII, [Formula VII] However, M ４ is selected from one or more of Li, Na, K, Rb, Cs, Mg, Ca, Ba, Al, Fe, Cu, and Ni, X ４ is a halogen, m4 is an integer of 1 to 3, n4 is an integer of 0 to 4, and a4, b4, and c4 are all positive integers. The electrolyte for a lithium secondary battery according to any one of claims 1 to 16, characterized in that.

18. The fluorosulfonate contains a compound represented by Formula VIII, [Formula VIII] (FSO ３ ) ｙ M ｙ＋ However, y is a positive integer, and M ｙ＋ is a metal ion or an organic cation, and the metal ion is Li ＋ , Na ＋ , K ＋ , Rb ＋ , Cs ＋ , Mg ２＋ , Ca ２＋ , Ba ２＋ , Al ３＋ , Fe ２＋ , Cu ２＋ , Fe ３＋ , Ni ２＋ and Ni ３＋ The electrolyte for a lithium secondary battery according to any one of claims 1 to 17, characterized by comprising one or more of the above.

19. The organic solvent further contains one or more of a chain carbonate and a cyclic carbonate, and the electrolyte for a lithium secondary battery according to any one of claims 1 to 18 is characterized in that.

20. The electrolyte, (6)the chain carbonate contains one or more of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate and ethyl propyl carbonate, The electrolytic solution for a lithium secondary battery according to claim 19, wherein (7) the cyclic carbonate satisfies at least one of the following conditions: including one or more of ethylene carbonate, propylene carbonate, and butylene carbonate.

21. The electrolyte salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bistrifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorooxalatoborate, lithium bis(oxalato)borate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluorooxalatophosphate. The electrolytic solution for a lithium secondary battery according to any one of claims 1 to 20 is characterized by this.

22. A secondary battery containing the electrolytic solution for a lithium secondary battery according to any one of claims 1 to 21.

23. The secondary battery further includes a negative electrode tab, the negative electrode tab contains a negative electrode active material, and the lithium ion solid phase diffusion coefficient Ds of the negative electrode active material is 10 －１３ cm ２ / S to 10 －１０ cm ２ / S, and Optionally, the lithium ion solid phase diffusion coefficient Ds of the negative electrode active material is 10 －１２ cm ２ / S to 10 －１１ cm ２ / S, and the secondary battery according to claim 22, characterized in that.

24. The secondary battery further includes a negative electrode tab, the negative electrode tab contains a negative electrode active material, and the volume average particle diameter Dv50 of the negative electrode active material is ≧ 6 μm. Optionally, the volume average particle diameter Dv50 of the negative electrode active material is 15 μm to 20 μm. The secondary battery according to claim 22 or 23 is characterized by this.

25. The secondary battery further includes a negative electrode tab, the negative electrode tab contains a negative electrode active material, and the BET specific surface area of the negative electrode active material is 0.5 m ２ / g to 2.0 m ２ / g, and Optionally, the BET specific surface area of the negative electrode active material is 0.8 m ２ / g to 1.5 m ２ / g, and the secondary battery according to any one of claims 22 to 24, characterized in that.

26. The secondary battery further includes a negative electrode tab, the negative electrode tab contains a negative electrode active material, and the negative electrode active material includes one or more of graphite and a silicon-based material. The secondary battery according to any one of claims 22 to 25 is characterized by this.

27. An electric power consumption device containing the secondary battery according to any one of claims 22 to 26.

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