Electrolyte, secondary battery and power consumption device

Abstract

The electrolyte, secondary battery, and power consumption device include a first additive, a second additive, and a third additive. The first additive includes an inorganic salt containing a fluorine element, and the second additive includes a compound containing an unsaturated bond, and the compound containing an unsaturated bond has a reduction potential of 0.8 V(Li + / Li), and the third additive includes a compound containing an amide group. By adding the first additive, the second additive, and the third additive to the electrolyte, the high-temperature performance and the low-temperature performance of the secondary battery can be improved simultaneously.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application references a Chinese patent application filed on September 28, 2023, with application number 202311276886.8, entitled "Electrolyte, Secondary Battery and Power Consumption Device," the entire contents of which are incorporated herein by reference.

[0002] The present application relates to the technical field of secondary batteries, and more particularly to electrolytes, secondary batteries, and power consuming devices. [Background technology]

[0003] This statement is intended only to provide background information related to the present application and may not necessarily constitute prior art.

[0004] Lithium-ion batteries have advantages such as high open-circuit voltage, high energy density, long service life, no memory effect, no pollution, and low self-discharge. Therefore, in recent years, they have been widely used in energy storage power systems such as hydroelectric, thermal, wind, and solar power plants, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. With the advancement of lithium-ion batteries, higher performance requirements have been put forward. However, related technologies have difficulty achieving both high-temperature and low-temperature performance, which has imposed certain limitations on the applications of lithium-ion batteries. Summary of the Invention

[0005] The present application has been made in consideration of the above-mentioned problems, and its purpose is to provide an electrolyte solution that can achieve both high-temperature and low-temperature performance of a secondary battery, and further to provide a secondary battery and a power consuming device.

[0006] In order to achieve the above object, according to a first aspect of the present application, a first additive containing an inorganic salt containing elemental fluorine; The compound containing an unsaturated bond has a reduction potential of ≥ 0.8 V(Li + / Li), and and a third additive including a compound containing an amide group.

[0007] The second additive has a reduction potential of ≥ 0.8 V (Li + The electrolyte contains a compound containing an unsaturated bond, which generates a polymer through a reduction reaction on the anode surface during battery formation, forming an SEI film and passivating the anode. This prevents direct contact between the solvent and the anode and subsequent side reactions, achieving excellent anode passivation and improving high-temperature battery performance. The first additive contains a fluorine-containing compound that decomposes at the anode to form an SEI film containing an Fluorine-containing inorganic compound. This SEI film has a wider bandgap and higher ionic conductivity, improving the ionic conduction capacity of the SEI film, lowering the energy barrier for lithium ion diffusion and facilitating lithium ion transport. This reduces the charge transfer resistance at the low-temperature interface, thereby improving low-temperature performance. Lithium ions in the electrolyte combine with solvent molecules and anions to form solvated lithium ions. During charging, the solvated lithium ions migrate to the anode and, upon reaching the SEI film, are desolvated and penetrate the SEI film to embed themselves in the anode. The third additive contains an amide group-containing compound, which can also participate in the formation of a solvation structure. The negatively charged N in the amide group strongly interacts with lithium ions. The third additive can replace the cyclic ester, reducing the amount of cyclic ester used in the solvation structure and significantly reducing the activation energy in the desolvation process of lithium ions, making desolvation easier and thereby improving low-temperature dynamic performance. Therefore, by adding the first additive, second additive, and third additive to the electrolyte of the present application, the three additives can exert a synergistic effect, simultaneously improving the high-temperature and low-temperature performance of the secondary battery.

[0008] In some embodiments, the mass ratio of the first additive in the electrolyte solution is A%, the mass ratio of the second additive in the electrolyte solution is B%, and the mass ratio of the third additive in the electrolyte solution is C%, and A, B, and C satisfy 2%≦(A+C) / B≦120%; Optionally, 5%≦(A+C) / B≦55%.

[0009] In some embodiments, 0.01≦A≦1.

[0010] In some embodiments, 0.5≦B≦10.

[0011] In some embodiments, 0.01≦C≦0.1.

[0012] In some embodiments, the mass ratio of the fluorine element in the inorganic salt is ≧8%; Optionally, the first additive includes one or more of difluorophosphate, tetrafluoroborate, and fluorosulfonate containing an M element, and the M element includes one or more of Li, Na, K, and Cs.

[0013] In some embodiments, the second additive comprises a cyclic compound containing an unsaturated bond; Optionally, the second additive comprises one or more of vinylene carbonate, 1,3-propane sultone, vinyl sulfate, and vinyl disulfate.

[0014] In some embodiments, the third additive comprises one or more of the compounds shown in formulas (I) and (II): JPEG2026505077000002.jpg38166R1 and R2 each independently comprise one of a hydrogen atom, a methyl group, and an ethyl group; R3 comprises a C3-C6 alkylene group; Optionally, the third additive comprises one or more of N,N-dimethylformamide and N-methylpyrrolidone.

[0015] In some embodiments, the electrolyte further comprises a cyclic ester solvent; Optionally, the cyclic ester solvent comprises one or more of ethylene carbonate and propylene carbonate; Further optionally, the mass ratio of the ethylene carbonate in the electrolytic solution is D%, and C and D satisfy 0.01%≦C / D≦1%; More preferably, 5≦D≦35.

[0016] In some embodiments, the electrolyte further comprises a lithium salt; Optionally, the lithium salt comprises one or more of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, and lithium bistrifluoromethylsulfonylimide; Optionally, the mass ratio of the lithium salt in the electrolyte solution is 5% to 15%.

[0017] According to a second aspect of the present application, there is provided a secondary battery containing the electrolytic solution of the first aspect of the present application.

[0018] The secondary battery of the present invention has excellent high-temperature performance and low-temperature performance at the same time.

[0019] In some embodiments, the secondary battery includes a negative electrode sheet, the negative electrode sheet includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, and the areal density of the negative electrode active material layer is Eg / m 2 and the specific surface area of ​​the negative electrode active material is Fm 2 / g, the mass ratio of the negative electrode active material in the negative electrode active material layer is L, The mass ratio of the second additive in the electrolytic solution is B%, The B, E, F, and L satisfy the relationship 0.5%≦B / (E*F*L)≦12%.

[0020] In some embodiments, 80≦E≦150.

[0021] In some embodiments, 0.5≦F≦5.

[0022] In some embodiments, 93%≦L≦98%.

[0023] According to a third aspect of the present application, there is provided a power consuming device including at least one of the electrolyte solution of the first aspect of the present application and the secondary battery of the second aspect of the present application.

[0024] The power consuming device of the present application includes the secondary battery provided by the present application, and therefore has at least the same advantages as said secondary battery.

[0025] The details of one or more embodiments of the application are set forth in the drawings and description below. Other features, objects, and advantages of the application will become apparent from the description, drawings, and claims. [Brief explanation of the drawings]

[0026] To better explain the embodiments or examples provided herein, reference may be made to one or more drawings. Any additional details or examples used to explain the drawings should not be considered to limit the scope of the disclosed application, the presently described embodiments and / or examples, or any of the best modes of those applications as currently understood. In the drawings, like elements use like reference numerals. The drawings are as follows:

[0027] [Figure 1] 1 is a schematic diagram of a battery cell according to an embodiment of the present application; [Figure 2] FIG. 2 is an exploded view of the battery cell shown in FIG. 1 according to the embodiment of the present application. [Figure 3] 1 is a schematic diagram of a battery module according to an embodiment of the present application; [Figure 4] 1 is a schematic diagram of a battery pack according to an embodiment of the present application; [Figure 5] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to the embodiment of the present application. [Figure 6]1 is a schematic diagram of a power consumption device that uses a secondary battery as a power source according to an embodiment of the present application. [Explanation of symbols]

[0028] 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 battery cell, 51 housing, 52 electrode assembly, 53 cover plate, 6 power consumption device. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, several embodiments of the electrolyte, secondary battery, and power consuming device of the present application will be described in detail with reference to the drawings as appropriate. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters or redundant description of substantially identical structures may be omitted. This is to avoid unnecessarily lengthening the following description and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.

[0030] "Ranges" disclosed herein can be defined in terms of lower and upper limits. A given range is defined by selecting one lower limit and one upper limit, with the selected lower and upper limits defining the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, or either endpoint may be independently inclusive or exclusive, and may be arbitrarily combinable; i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are recited for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Also, if minimum range values ​​of 1 and 2 are recited and maximum range values ​​of 3, 4, and 5 are further recited, then the ranges of 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all contemplated. In this application, unless otherwise specified, the numerical range "a to b" is meant as shorthand for any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0 to 5" means that all real numbers between "0 and 5" are fully recited herein, with "0 to 5" merely being shorthand for combinations of these numerical values. Furthermore, when a parameter is expressed as an integer ≧2, this is equivalent to reciting the parameter as, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when a parameter is expressed as being selected from the integers "2 to 10," this is equivalent to reciting the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0031] Unless otherwise specified, the terms "plurality," "plurality of species," and the like, as used herein, refer to a number greater than or equal to 2. For example, "one or more" means one or more than two.

[0032] All embodiments and alternative embodiments of the present application can be combined with each other to form new technical solutions, unless otherwise specified.

[0033] References to "examples" herein mean that a particular feature, structure, or characteristic described in connection with an example may be included in at least one example or embodiment of the present application. Appearances of the term "example" in various places in this specification do not necessarily refer to the same example, nor do they refer to examples that are mutually exclusive, independent, or alternative to other examples. Those skilled in the art will understand, both explicitly and implicitly, that examples described herein can be combined with other examples. References to "embodiments" herein have the same understanding.

[0034] As will be understood by those skilled in the art, the order of steps described in each embodiment or example method does not limit the implementation process to a strict execution order, and the detailed execution order of each step should be determined by its function and possible internal logic. All steps in this application can be performed sequentially or randomly, preferably sequentially, unless otherwise specified. For example, when a method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, when a method may further include step (c), it means that step (c) may be added to the method in any order, such as the method may include steps (a), (b), and (c), or steps (a), (c), and (b), or steps (c), (a), and (b), etc.

[0035] In this application, open-ended technical features or technical solutions described using terms such as "comprise," "include," or "comprise," unless otherwise specified, do not exclude additional elements other than the enumerated elements, and can be considered to provide not only closed-ended features or solutions consisting of the enumerated elements, but also open-ended features or solutions including additional elements other than the enumerated elements. For example, if A includes a1, a2, and a3, other elements may be included or not, unless otherwise specified, and it can be considered to provide not only a feature or solution "A consists of a1, a2, and a3," but also a feature or solution "A not only includes a1, a2, and a3, but also includes other elements." In this application, unless otherwise specified, A (e.g., B) indicates that B is a non-limiting example of A, and A is not limited to B.

[0036] In this application, "optionally", "selectable" and "optional" refer to something that may or may not exist, that is, to selecting one of two alternative solutions, "yes" or "no". When multiple "options" appear in one technical solution, each "option" is independent of the other, unless otherwise specified and there is no contradiction or mutual constraint.

[0037] In related technologies, it is difficult to achieve both high-temperature and low-temperature performance of lithium-ion batteries, which imposes certain limitations on the application of lithium-ion batteries.

[0038] Based on the above problem, the present application provides an electrolyte solution, to which a first additive, a second additive and a third additive are simultaneously added, thereby simultaneously improving the high-temperature performance and low-temperature performance of a secondary battery.

[0039] According to a first aspect of the present application, there is provided an electrolytic solution comprising a first additive, a second additive, and a third additive, wherein the first additive comprises an inorganic salt containing a fluorine element, and the second additive comprises a compound containing an unsaturated bond, and the compound containing an unsaturated bond has a reduction potential of ≥ 0.8 V(Li + / Li), and the third additive comprises a compound containing an amide group.

[0040] As can be seen, the second additive has a reduction potential of ≥ 0.8 V (Li + The electrolyte contains a compound containing an unsaturated bond, which generates a polymer through a reduction reaction on the anode surface during battery formation, forming an SEI film and passivating the anode. This prevents direct contact between the solvent and the anode and subsequent side reactions, achieving excellent anode passivation and improving high-temperature battery performance. The first additive contains a fluorine-containing compound that decomposes at the anode to form an SEI film containing an Fluorine-containing inorganic compound. This SEI film has a wider bandgap and higher ionic conductivity, improving the ionic conduction capacity of the SEI film, lowering the energy barrier for lithium ion diffusion and facilitating lithium ion transport. This reduces the charge transfer resistance at the low-temperature interface, thereby improving low-temperature performance. Lithium ions in the electrolyte combine with solvent molecules and anions to form solvated lithium ions. During charging, the solvated lithium ions migrate to the anode and, upon reaching the SEI film, are desolvated and penetrate the SEI film to embed themselves in the anode. The third additive contains an amide group-containing compound, which can also participate in the formation of a solvation structure. The negatively charged N in the amide group strongly interacts with lithium ions. The third additive can replace the cyclic ester, reducing the amount of cyclic ester used in the solvation structure and significantly reducing the activation energy in the desolvation process of lithium ions, making desolvation easier and thereby improving low-temperature dynamic performance. Therefore, by adding the first additive, the second additive, and the third additive to the electrolyte of the present application, the high-temperature performance and low-temperature performance of the secondary battery can be simultaneously improved.

[0041] In some embodiments, the weight percentage of the first additive in the electrolyte is A%, the weight percentage of the second additive in the electrolyte is B%, and the weight percentage of the third additive in the electrolyte is C%, and A, B, and C satisfy the relationship 2%≦(A+C) / B≦120%. For example, (A+C) / B may be 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, 120%, or a range between any two of the above values, but is not limited thereto. When A, B, and C satisfy the above relationship, the high-temperature performance and low-temperature performance of the secondary battery are significantly improved simultaneously. If (A+C) / B is lower than the above range, the improvement in the low-temperature performance of the secondary battery is limited, and if (A+C) / B is higher than the above range, the improvement in the high-temperature performance of the secondary battery is limited.

[0042] In some alternative embodiments, 5%≦(A+C) / B≦55%.

[0043] Here, A% means the mass ratio of the first additive in the electrolyte in a battery cell obtained after chemical formation or in a battery cell that has undergone continuous charge-discharge cycling. B% means the mass ratio of the second additive in the electrolyte in a battery cell obtained after chemical formation or in a battery cell that has undergone continuous charge-discharge cycling. C% means the mass ratio of the third additive in the electrolyte in a battery cell obtained after chemical formation or in a battery cell that has undergone continuous charge-discharge cycling. "Battery cell obtained after chemical formation" refers to a new battery cell manufactured after chemical formation that has not undergone continuous charge-discharge cycling.

[0044] In some possible embodiments, 0.01≦A≦1, where A may be, for example, but not limited to, 0.01, 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, 1, or a range between any two of the above values. If the mass percentage (A%) of the first additive in the electrolyte is lower than 0.01%, the low-temperature performance of the secondary battery may not be effectively improved. This is because, during the battery cycling process, as lithium insertion and extraction from the negative electrode progresses, the negative electrode expands and contracts accordingly, resulting in a significant change in the volume of the negative electrode. Because the inorganic SEI film has low mechanical stability, it is prone to rupture when there is a large change in the volume of the negative electrode, exposing new active sites and continuously inducing side reactions. Therefore, if the mass proportion (A%) of the first additive in the electrolyte is higher than 1%, the effect of improving the high-temperature cycle characteristics of the secondary battery tends to decrease.

[0045] In some possible embodiments, 0.5≦B≦10, for example, B may be 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, or a range between any two of the above values, but is not limited thereto. If the mass percentage (B%) of the second additive in the electrolyte is lower than 0.5%, the high-temperature performance of the secondary battery may not be effectively improved. If the mass percentage (B%) of the second additive in the electrolyte is higher than 10%, the low-temperature discharge performance may be adversely affected because the second additive causes an increase in battery resistance after forming an SEI film, especially a significant increase in low-temperature resistance.

[0046] In some possible embodiments, 0.01≦C≦0.1, for example, C may be 0.01, 0.015, 0.02, 0.025, 0.03, 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, 0.1, or a range between any two of the above values, but is not limited thereto. If the mass percentage (C%) of the third additive in the electrolyte is lower than 0.01%, it may not be possible to effectively improve the low-temperature performance of the secondary battery. This is because the third additive itself has low electrical and chemical stability, which makes it prone to reduction side reactions at the anode, affecting the stability of the SEI film. Reduction side reactions at high temperatures may worsen. If the mass percentage (C%) of the third additive in the electrolyte is higher than 0.1%, it may affect the high-temperature cycle life of the battery.

[0047] For example, the mass proportion (A%) of the first additive in the electrolyte mentioned above can be measured with reference to the ion chromatography method of JY / T 0575-2020.

[0048] The mass percentage (B%) of the second additive in the electrolyte and the mass percentage (C%) of the third additive in the electrolyte mentioned above can be measured with reference to GB / T9722-2006 Chemical Reagent Gas Chromatography Method.

[0049] In some embodiments, the mass percentage of elemental fluorine in the inorganic salt is ≥ 8%, such as, but not limited to, 8%, 10%, 13%, 15%, 17%, 20%, 23%, 25%, 27%, 30%, 40%, 50%, 60%, 70%, 80%, or a range between any two of the above values. When the mass percentage of elemental fluorine in the inorganic salt is within the above range, the fluoride content in the SEI film can be effectively increased, which helps to improve the ionic conductivity of the SEI film.

[0050] For example, the mass proportion of the fluorine element in the inorganic salt mentioned above can be measured with reference to JY / T 0567-2020 inductively coupled plasma optical emission spectrometry.

[0051] In some embodiments, the first additive comprises one or more of a difluorophosphate, a tetrafluoroborate, and a fluorosulfonate containing an M element, wherein the M element comprises one or more of Li, Na, K, and Cs.

[0052] In some embodiments, the first additive comprises one or more of lithium difluorophosphate, lithium tetrafluoroborate, and lithium fluorosulfonate.

[0053] In some embodiments, the second additive comprises a cyclic compound containing an unsaturated bond, which is susceptible to reduction at the negative electrode to form oligomers.

[0054] In possible embodiments, the second additive includes one or more of vinylene carbonate, 1,3-propane sultone, vinyl sulfate, and vinyl disulfate.

[0055] In some embodiments, the third additive comprises one or more of the compounds shown in formulas (I) and (II): JPEG2026505077000003.jpg39166R1 and R2 each independently include one of hydrogen, a methyl group, and an ethyl group, and R3 includes a C3-C6 alkylene group.

[0056] In a possible embodiment, the third additive comprises one or more of N,N-dimethylformamide and N-methylpyrrolidone.

[0057] In some embodiments, the electrolyte further comprises a cyclic ester solvent.

[0058] In some possible embodiments, the cyclic ester solvent comprises one or more of ethylene carbonate and propylene carbonate.

[0059] Ethylene carbonate has a high dielectric constant and can dissociate lithium salts, improving the conductivity of the electrolyte. At the same time, ethylene carbonate can cause a reduction reaction, and the resulting product, Li2CO3, has good thermal stability and can improve the high-temperature cycling properties of the battery to a certain extent.

[0060] In some possible embodiments, the mass proportion of ethylene carbonate in the electrolyte solution is D%, and C and D satisfy 0.01%≦C / D≦1%, and for example, C / D may be, but is not limited to, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 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%, 1%, or a range between any two of the above values. Because ethylene carbonate occupies the inner layer of the electrolyte's solvation structure, its high dielectric constant also increases the intermolecular orientation forces, thereby increasing the electrolyte's phase transition point and viscosity. The viscosity increases rapidly at low temperatures and affects the desolvation process of lithium ions. The desolvation process determines the rate of electrolytic migration of the electrolyte at low temperatures. Therefore, if the mass proportion of ethylene carbonate in the electrolyte is too high, the battery's low-temperature performance will deteriorate. The third additive also contributes to the formation of the solvation structure, thereby reducing the amount of ethylene carbonate in the solvation structure and improving low-temperature dynamic performance. Therefore, by controlling the amounts of ethylene carbonate and the third additive, it is possible to achieve both low-temperature and high-temperature performance of the battery. When the C / D ratio is within the above range, both low-temperature and high-temperature performance of the battery are good. When the C / D ratio is lower than the above range, the improvement in low-temperature performance may be limited. When the C / D ratio is higher than the above range, the improvement in high-temperature performance may be limited.

[0061] In some possible embodiments, the mass proportion of ethylene carbonate in the electrolyte is D%, where 5≦D≦35, and for example, D may be, but is not limited to, 5, 7, 10, 12, 15, 17, 20, 22, 25, 27, 30, 32, 35, or a range between any two of the above values. If the mass proportion of ethylene carbonate in the electrolyte is lower than 5%, the effect of increasing the conductivity of the electrolyte may be limited, and if the mass proportion of ethylene carbonate in the electrolyte is higher than 35%, the viscosity of the electrolyte is high and the low-temperature conductivity is low, which may deteriorate the low-temperature performance of the battery.

[0062] For example, the mass proportion (D%) of ethylene carbonate in the electrolyte and the mass ratio (C / D) of the third additive to ethylene carbonate mentioned above can be determined with reference to GB / T9722-2006.

[0063] The above-mentioned D% refers to the mass ratio of ethylene carbonate in the electrolyte in a battery cell obtained after chemical formation or in a battery cell that has undergone continuous charge-discharge cycling. C / D refers to the mass ratio of the third additive to ethylene carbonate in a battery cell obtained after chemical formation or in a battery cell that has undergone continuous charge-discharge cycling. The "battery cell obtained after chemical formation" refers to a new battery cell manufactured after chemical formation that has not undergone continuous charge-discharge cycling.

[0064] In some embodiments, the electrolyte further comprises a lithium salt.

[0065] Optionally, the lithium salt comprises one or more of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, and lithium bistrifluoromethylsulfonylimide.

[0066] In some possible embodiments, the mass proportion of the lithium salt in the electrolyte is 5% to 15%, for example, but not limited to, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or a range between any two of the above values. The lithium salt dissociates ions in the electrolyte and transports the medium during charge and discharge. As the lithium salt concentration increases, the number of lithium ions in the electrolyte increases, and the conductivity of the electrolyte increases. When the mass proportion of the lithium salt in the electrolyte is within the above range, the conductivity of the electrolyte is high. When the mass proportion of the lithium salt in the electrolyte is higher than the above range, the viscosity of the electrolyte becomes too high, increasing the lithium ion transport resistance and, conversely, decreasing the conductivity of the electrolyte.

[0067] The mass ratio of the lithium salt in the electrolyte referred to above means the mass ratio of the lithium salt in the electrolyte in a battery cell obtained after chemical formation or in a battery cell that has undergone continuous charge-discharge cycling. The "battery cell obtained after chemical formation" refers to a new battery cell manufactured after chemical formation, which has not undergone continuous charge-discharge cycling.

[0068] For example, the mass proportion of the above-mentioned lithium salt in the electrolyte can be measured by referring to the ion chromatography method of JY / T 0575-2020.

[0069] In some embodiments, the lithium salt in the electrolyte may include one or more of lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPOF), lithium difluorooxalatoborate (LiDFOB), lithium bis(oxalatoborate) (LiBOB), lithium difluorobis(oxalatophosphate) (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP).

[0070] In some embodiments, the solvent in the electrolyte is JPEG2026505077000004.jpg26170 Ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), JPEG2026505077000005.jpg25161 may include one or more of fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, ethyl methyl sulfone, and diethyl sulfone.

[0071] In some embodiments, the additives in the electrolyte may further include a negative electrode film-forming additive, a positive electrode film-forming additive, and may further include an additive that can improve specific battery properties, such as an additive that improves the overcharge characteristics of the battery, or an additive that improves the high-temperature or low-temperature performance of the battery.

[0072] In some embodiments, the additives in the electrolyte may further include, but are not limited to, one or more of difluoroethylene carbonate (DFEC), trifluoropropylene carbonate (TFPC), and the like.

[0073] According to a second aspect of the present application, there is provided a secondary battery containing the electrolyte solution according to the first aspect of the present application. The secondary battery of the present application simultaneously has excellent high-temperature performance and low-temperature performance.

[0074] Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charge and discharge process, active ions are inserted and removed between the positive and negative electrode sheets. The electrolyte in the electrolyte serves to conduct ions between the positive and negative electrode sheets. The separator, located between the positive and negative electrode sheets, primarily serves to prevent short circuits between the positive and negative electrodes while allowing ions to pass through.

[0075] Negative electrode sheet The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer that contains a negative electrode active material and is disposed on at least one surface of the negative electrode current collector.

[0076] As a non-limiting example, the negative electrode current collector has two surfaces facing each other in the thickness direction thereof, and the negative electrode active material is provided on either one or both of the two facing surfaces of the negative electrode current collector.

[0077] In some embodiments, the secondary battery includes a negative electrode sheet, the negative electrode sheet includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, and the areal density of the negative electrode active material layer is Eg / m 2 and the specific surface area of ​​the negative electrode active material is Fm 2 / g, the mass proportion of the negative electrode active material in the negative electrode active material layer is L, the mass proportion of the second additive in the electrolyte is B%, and B, E, F, and L satisfy 0.5%≦B / (E*F*L)≦12%. For example, B / (E*F*L) may be, but is not limited to, 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%, 10.5%, 11%, 11.5%, 12%, or a range between any two of the above values.

[0078] The mass proportion of the negative electrode active material in the negative electrode active material layer referred to above means the mass proportion of the negative electrode active material in the negative electrode active material layer in a battery cell obtained after chemical formation or in a battery cell that has undergone continuous charge-discharge cycling. The "battery cell obtained after chemical formation" refers to a new battery cell manufactured after chemical formation, which has not undergone continuous charge-discharge cycling.

[0079] Because the active material is porous, its actual surface and specific surface area are larger. E*F*L represents the actual surface area of ​​the active material on the polar sheet per unit area. The secondary additive primarily obtains electrons on the specific surface of the anode active material and is reduced to form a film. The larger the specific surface area, the more secondary additive is required. However, excessive secondary additive use can adversely affect low-temperature charge / discharge performance, so the B, E, F, and L values ​​must be controlled. When the B / (E*F*L) value is within the above range, the secondary battery simultaneously exhibits good high-temperature cycling performance and low-temperature performance. When the B / (E*F*L) value is higher than the above range, the secondary additive content is too high, resulting in an excessively thick SEI film, which may affect the battery's low-temperature performance. When the B / (E*F*L) value is lower than the above range, the secondary additive content is insufficient to form a film on the specific surface of the anode material. This exposes the active sites, which may continuously react with the electrolyte and affect the high-temperature cycling performance of the battery.

[0080] In some embodiments, 80≦E≦150, for example, but not limited to, E can be 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, or a range between any two of the foregoing numbers.

[0081] For example, the areal density of the negative electrode active material layer mentioned above can be measured by the following method: The battery is discharged at 0.1 C to 2.0 V, disassembled, and the unit area V (100 cm 2The negative electrode sheet (100%) is removed and immersed in DMC for 48 hours. The polar sheet is then dried at 60°C and -80 kPa, and its mass (m1) is weighed. The paste is then scraped off, and the substrate mass (m2) is weighed. If the negative electrode sheet is coated on one side, the surface density of the negative electrode active material layer is (m1 - m2) / V. If the negative electrode sheet is coated on both sides, the surface density of the negative electrode active material layer is (m1 - m2) / V.

[0082] In some embodiments, 0.5≦F≦5, for example, but not limited to, F can be 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, or a range between any two of the foregoing numbers.

[0083] For example, the specific surface area of ​​the negative electrode active material mentioned above can be measured with reference to GB / T 19587-2017 gas adsorption BET method.

[0084] In some embodiments, 95%≦L≦99%, for example, L can be, but is not limited to, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or a range between any two of the foregoing numbers.

[0085] For example, the mass proportion of the above-mentioned negative electrode active material in the negative electrode active material layer can be measured by the method described below.

[0086] The battery was charged at a constant current of 0.1C to 3.8V, and then charged at a constant voltage of 0.05C, at which point the negative active material was graphite with the maximum amount of lithium absorbed, forming a LiC6 compound. The lithium content in the negative electrode film layer was measured using the EPA6010D-2018 inductively coupled plasma optical emission spectrometry method, and the content of the negative electrode active material in the negative electrode film layer was calculated based on the result, and its mass proportion in the negative electrode active material layer was obtained.

[0087] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. The metal foil may be, for example, copper foil. The composite current collector may include a polymer substrate layer and a metal layer formed on at least one surface of the polymer substrate layer. The composite current collector may be obtained by forming a metal material on a polymer substrate. Non-limiting examples of the metal material in the negative electrode current collector may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc. Non-limiting examples of the polymer substrate in the negative electrode current collector may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0088] In some embodiments, the negative electrode active material may be any negative electrode active material known in the art. Non-limiting examples of the negative electrode active material include one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials may include one or more of silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of tin, tin oxide, and tin alloys. However, the present application is not limited to these materials, and other conventional materials usable as negative electrode active materials in batteries may also be used. These negative electrode active materials may be used alone or in combination.

[0089] In some embodiments, the negative electrode active material layer optionally further includes a binder, which 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).

[0090] In some embodiments, the negative electrode active material layer optionally further includes a conductive agent, which may include one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0091] In some embodiments, the negative electrode active material layer optionally further includes other additives such as a thickener (eg, carboxymethylcellulose sodium (CMC-Na)).

[0092] In some embodiments, a negative electrode sheet can be manufactured by the following method. Components for manufacturing the negative electrode sheet, 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 deionized water) to form a negative electrode paste. The negative electrode paste is then coated on at least one surface of a negative electrode current collector, followed by drying, cold pressing, and other steps to obtain a negative electrode sheet. The negative electrode paste may be coated on one surface of the negative electrode current collector, or may be coated on both surfaces of the negative electrode current collector. The solid content of the negative electrode paste may be 40 wt% to 60 wt%. The viscosity of the negative electrode paste at room temperature can be adjusted to 2000 mPa·s to 10000 mPa·s. The compressed density of the negative electrode sheet is 1.0 g / cm. 3 ~2.0 g / cm 3 may be.

[0093] Positive electrode sheet The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector.

[0094] In some embodiments, the active cathode material can further include one or more of a ternary material and a lithium manganese iron phosphate material, where the ternary material includes Li(NiaCobMnc)1-dMdO2-yAy (x is 0.2 to 1.2) and / or LixAa(NiaCobMnc)1-dMdO2-yAy (x + a is 0.2 to 1.2), and the lithium manganese iron phosphate material includes LiaMn1-yByP1-zCzO4-nDn (a is 0 to 1.1) and / or LiaAxMn1-yByP1-zCzO4-nDn (a + x is 0 to 1.1).

[0095] It should be noted that the above limitations on x include the molar content of Li at different charge and discharge states of the battery (typically the battery voltage is between 2 and 5 V).

[0096] Note that batteries undergo lithium (Li) desorption, insertion, and consumption during the charge / discharge process, and the Li content in the positive electrode sheet will vary when the battery is discharged to different states. In the list of positive electrode materials in this application, unless otherwise specified, the Li content refers to the initial state of the material. When a positive electrode material is used in a positive electrode sheet in a battery system and undergoes charge / discharge cycles, the Li content in the positive electrode material contained in the polar sheet generally changes. The Li content can be measured using, but is not limited to, the molar content. Regarding the phrase "Li content refers to the initial state of the material," the initial state of the material refers to the state before being added to the positive electrode paste. As can be understood, new materials obtained by appropriate modification of the listed positive electrode materials also fall within the category of positive electrode materials. The appropriate modification refers to an acceptable modification method for the positive electrode material, including, but not limited to, coating modification.

[0097] In the enumeration of positive electrode materials in this application, the oxygen (O) content is merely a theoretical value, and the release of lattice oxygen causes a change in the molar content of oxygen, so that the molar content of O actually fluctuates. The O content can be measured using the molar content, but is not limited to this.

[0098] As a non-limiting example, the positive electrode current collector has two surfaces facing each other in the thickness direction thereof, and the positive electrode active material layer is provided on either one or both of the two facing surfaces of the positive electrode current collector.

[0099] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. The metal foil may be, for example, aluminum foil. The composite current collector may include a polymer substrate layer and a metal layer formed on at least one surface of the polymer substrate layer. The composite current collector may be obtained by forming a metal material on a polymer substrate. Non-limiting examples of the metal material in the positive electrode current collector may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc. Non-limiting examples of the polymer substrate in the positive electrode current collector may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0100] In some embodiments, the positive electrode active material may further include positive electrode active materials for batteries known in the art. Non-limiting examples of the positive electrode active material include one or more of an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials usable as positive electrode active materials in batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, one or more of lithium cobalt oxide (e.g., LiCoO), lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Non-limiting examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composite, lithium manganese phosphate, lithium manganese phosphate and carbon composite, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composite. Non-limiting examples of lithium cobalt oxides may include LiCoO2, non-limiting examples of lithium nickel oxides may include LiNiO2, non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc., and non-limiting examples of lithium nickel cobalt manganese oxides include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM 333 (also called LiNi) 0.5 Co 0.2 Mn 0.3 O2(NCM 523 (also called LiNi) 0.5 Co 0.25 Mn 0.25 O2(NCM 211 (also called LiNi) 0.6 Co 0.2 Mn 0.2 O2(NCM 622(also called LiNi) 0.8 Co 0.1 Mn 0.1 O2(NCM 811 A non-limiting example of lithium nickel cobalt aluminum oxide is LiNi 0.85 Co 0.15 Al 0.05 O2 may also be included.

[0101] In some embodiments, the positive electrode active material layer preferably further comprises a binder. Non-limiting examples of the binder include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0102] In some embodiments, the positive electrode active material layer optionally further includes a conductive agent, which may include, by non-limiting example, one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0103] In some embodiments, a positive electrode sheet can be manufactured by the following method. The components for manufacturing the positive electrode sheet, such as a positive electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent to form a positive electrode paste. The positive electrode paste is then coated on at least one surface of a positive electrode current collector, followed by processes such as drying and cold pressing to obtain a positive electrode sheet. The type of solvent can be any one of those in the above embodiments, such as, but not limited to, N-methylpyrrolidone (NMP). The positive electrode paste can be coated on one surface of the positive electrode current collector or on both surfaces of the positive electrode current collector. The solid content of the positive electrode paste can be 40 wt% to 80 wt%. The viscosity of the positive electrode paste at room temperature can be adjusted to 5000 mPa·s to 25000 mPa·s. When coating the positive electrode paste, the surface density per coating unit in terms of dry weight (excluding the solvent) is 15 mg / cm. 2 ~35mg / cm 2 The compressed density of the positive electrode sheet may be 2 g / cm 3 ~3g / cm 3 may be.

[0104] Separator The present application does not particularly limit the type of separator, and any known porous structure separator having good chemical stability and mechanical stability can be selected.

[0105] In some embodiments, the separator may be made of one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, and are not particularly limited.

[0106] In some embodiments, the thickness of the separator is between 6 μm and 40 μm, and optionally between 12 μm and 20 μm.

[0107] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be fabricated into an electrode assembly via a winding or lamination process.

[0108] In some embodiments, the secondary battery may include a housing material, which is used to encapsulate the electrode assembly and electrolyte.

[0109] In some embodiments, the exterior material of the secondary battery may be a hard case such as a hard plastic case, an aluminum case, a steel case, etc. The exterior material of the secondary battery may be a soft pack such as a pouch-type soft pack. The material of the soft pack may be plastic, and non-limiting examples of the plastic may be one or more of polypropylene, polybutylene terephthalate, polybutylene succinate, etc.

[0110] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0111] In this application, unless otherwise specified, the term "battery cell" refers to a basic element capable of converting chemical energy into electrical energy and vice versa, and generally includes at least a positive electrode sheet, a negative electrode sheet, and an electrolyte. During the charge and discharge process of a battery, active ions are inserted and removed between the positive electrode sheet and the negative electrode sheet. The electrolyte serves to conduct the active ions between the positive electrode sheet and the negative electrode sheet.

[0112] The present application does not particularly limit the shape of the battery cell, and it may be cylindrical, rectangular, or any other shape. For example, Figure 1 shows an example of a rectangular battery cell 5.

[0113] In some embodiments, referring to FIG. 2 , the exterior material may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, forming a receiving cavity surrounded by the bottom plate and side plates. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 may cover the opening and seal the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator may form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is sealed in the receiving cavity. An electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 included in the battery cell 5 may be one or more, and can be selected by those skilled in the art according to actual requirements.

[0114] The secondary battery may be a battery module or a battery pack.

[0115] A battery module includes at least one battery cell. The number of battery cells included in a battery module may be one or more, and those skilled in the art can select an appropriate number depending on the application and capacity of the battery module.

[0116] FIG. 3 shows an example of a battery module 4. Referring to FIG. 3, in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the plurality of battery cells 5 can be fixed by fasteners.

[0117] Optionally, the battery module 4 may further include an outer case having an accommodating space for accommodating the plurality of battery cells 5.

[0118] In some embodiments, the battery modules can be further assembled into a battery pack, and the number of battery modules included in the battery pack can be one or more, and those skilled in the art can select an appropriate number depending on the application and capacity of the battery pack.

[0119] 4 and 5 show an example of a battery pack 1. Referring to FIGS. 4 and 5, the battery pack 1 may include a battery case and a plurality of battery modules 4 installed in the battery case. The battery case includes an upper housing 2 and a lower housing 3, and the upper housing 2 is covered by the lower housing 3, forming an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery case in any manner.

[0120] The present application also provides a power consuming device including a secondary battery according to the present application. The secondary battery may be used as a power source for the power consuming device or as an energy storage element for the power consuming device. The power consuming device may include, but is not limited to, a mobile device, an electric vehicle, a train, a ship, a satellite, an energy storage system, etc. The mobile device may be, for example, a mobile phone, a laptop, etc., and the electric vehicle may be, for example, a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., but is not limited to these.

[0121] As a power consuming device, a secondary battery can be selected depending on the requirements for its use.

[0122] 6 shows an example of a power consuming device 6. The power consuming device may be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. To meet the demand for high power output and high energy density of the secondary battery of the power consuming device, a battery pack or a battery module may be used.

[0123] Other examples of the device may be a mobile phone, a tablet computer, a laptop computer, etc. These devices are generally required to be lightweight and can use a secondary battery as a power source.

[0124] Example The following examples of the present application are described. The examples described below are illustrative and are intended to illustrate the present application only and should not be construed as limiting the present application. If no techniques or conditions are specified in the examples, they are carried out according to the techniques or conditions described in the literature in this field or according to the product instructions. If no manufacturer is specified for the reagents or equipment used, they are all commercially available general products.

[0125] 1. Secondary battery manufacturing Example 1 1) Manufacturing of positive electrode sheets The positive electrode materials LiFePO4, polyvinylidene fluoride (PVDF), and carbon black (SP) are mixed with the solvent dimethyl sulfoxide in a mass ratio of 96:3:1, and stirred to obtain a uniformly dispersed positive electrode paste. The positive electrode paste is then evenly applied to two surfaces of aluminum foil, which is then dried, cold pressed, and cut to obtain a positive electrode sheet.

[0126] 2) Manufacturing of negative electrode sheets Artificial graphite, carbon black (SP), styrene butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC) are mixed in a mass ratio of 96:1.5:1.5:1, deionized water is added, and the mixture is stirred to obtain a uniformly dispersed negative electrode paste. The negative electrode paste is then evenly applied to the two surfaces of copper foil, which is then dried, cold pressed, and cut to obtain a negative electrode sheet. The specific surface area of ​​the negative electrode active material, artificial graphite, is 1 m 2 / g, and the surface density per coating unit of the negative electrode active material is 90 g / m 2 is.

[0127] 3) Separator A polyethylene film is used as the separator.

[0128] 4) Electrolyte production In an argon atmosphere glove box, ethylene carbonate (EC, solvent), dimethyl carbonate (DMC, solvent), ethyl methyl carbonate (EMC, solvent), diethyl carbonate (DEC, solvent), vinylene carbonate (VC, second additive), lithium difluorophosphate (LiPO2F2, first additive), N-methylpyrrolidone (NMP, third additive), and lithium hexafluorophosphate (LiPF6, lithium salt) are mixed and dissolved in a mass percent manner to obtain an electrolyte solution.

[0129] 5) Battery cell manufacturing The positive electrode sheet, the negative electrode sheet, and the separator are fabricated into an electrode assembly through a winding process or a lamination process, and then placed in an outer case made of an aluminum case, an aluminum laminate film, or the like. After the above-mentioned electrolyte is injected, the assembly is left standing at high temperature, chemically converted, and graded, a secondary battery is obtained.

[0130] The battery cell has a fluid retention coefficient of 3g / Ah.

[0131] Examples 2 to 24 The differences between the manufacturing method of the secondary battery in Examples 2-24 and that in Example 1 are mainly as follows: at least one of the mass percentage of the solvent in the electrolyte, the type and / or amount of the first additive, the type and / or amount of the second additive, the type and / or amount of the third additive, the specific surface area of ​​the negative electrode active material, the surface density per coating unit of the negative electrode active material, and the mass proportion of the negative electrode active material in the negative electrode active material layer is different, as shown in Table 1.

[0132] Comparative Example 1 In Comparative Example 1, the first additive, the second additive and the third additive were not added, and the specific results are as shown in Table 1.

[0133] Comparative Example 2 The electrolyte solution of Comparative Example 2 did not contain the second additive, but contained only the first and third additives, as shown in Table 1.

[0134] Comparative Example 3 The electrolyte solution of Comparative Example 3 did not contain the first additive, but contained only the second and third additives, as shown in Table 1.

[0135] Comparative Example 4 The electrolyte solution of Comparative Example 4 did not contain the third additive, but contained only the first and second additives, as shown in Table 1.

[0136] For the secondary batteries obtained in the above examples and comparative examples, parameter measurements including at least the following items are carried out.

[0137] From the mass percentages of EC, DMC, EMC, DEC, the first additive, the second additive, the third additive, and the lithium salt in the electrolyte, (A+C) / B, C / D, and B / (E*F*L) are calculated, as shown in Table 1.

[0138] The parameter settings for the above examples and comparative examples are as shown in Table 1.

[0139] [Table 1] JPEG2026505077000007.jpg191170

[0140] In Table 1, n represents the percentage by mass of the second lithium salt relative to the mass of the first lithium salt, T represents the thickness of the positive electrode sheet, A% represents the mass proportion of the first additive in the electrolyte, B% represents the mass proportion of the second additive in the electrolyte, C% represents the mass proportion of the third additive in the electrolyte, D% represents the mass proportion of ethylene carbonate in the electrolyte, VC represents vinylene carbonate, PS represents 1,3-propane sultone, DTD represents vinyl sulfate, BDTD represents vinyl disulfide, NMP represents N-methylpyrrolidone, DMP represents N,N-dimethylformamide, E represents the areal density per coating unit of the negative electrode active material, F represents the specific surface area of ​​the negative electrode active material, and L represents the mass proportion of the negative electrode active material in the negative electrode active material layer.

[0141] The mass proportion of the first additive in the electrolyte mentioned above is measured with reference to the ion chromatography method of JY / T 0575-2020.

[0142] The mass proportions of the second and third additives mentioned above in the electrolyte are measured in accordance with GB / T9722-2006 chemical reagent gas chromatography method.

[0143] The mass proportion of EC in the electrolyte and the mass ratio (C / D) of the third additive to ethylene carbonate mentioned above are measured in accordance with GB / T9722-2006 Chemical Reagent Gas Chromatography Method.

[0144] The mass proportion of the lithium salt in the electrolyte solution mentioned above is measured with reference to the ion chromatography method of JY / T 0575-2020.

[0145] The specific surface area of ​​the negative electrode active material mentioned above can be measured with reference to GB / T 19587-2017 gas adsorption BET method.

[0146] The surface density per unit of application of the negative electrode active material mentioned above is measured by the following method. The battery is discharged at 0.1 C to 2.0 V, disassembled, and the unit area V (100 cm 2 The negative electrode sheet (100%) is removed and immersed in DMC for 48 hours. The polar sheet is then dried at 60°C and -80 kPa, and its mass m1 is weighed. The paste is then scraped off, and the substrate mass m2 is weighed. The surface density of the negative electrode active material is calculated using the formula (m1 - m2) / 2 / V.

[0147] The mass proportion of the above-mentioned negative electrode active material in the negative electrode active material layer is measured as follows: The battery is charged at a constant current of 0.1 C to 3.8 V, and then charged at a constant voltage of ≦0.05 C. At this time, the negative electrode active material is graphite with the maximum amount of lithium absorbed, forming a LiC6 compound. The lithium content in the negative electrode film layer is measured using the inductively coupled plasma optical emission spectrometry method specified in EPA 6010D-2018, and the graphite content in the negative electrode film layer is calculated based on the result, and its mass proportion in the negative electrode active material layer is obtained.

[0148] 2. Battery cell performance test 1. Measurement of high temperature cycle characteristics at 60℃ At 60°C, the secondary batteries of each Example and Comparative Example were charged at a constant current of 0.5C up to a voltage limit of 3.8V, then further charged at a constant voltage until the current reached 0.05C. The batteries were then allowed to stand for 5 minutes and discharged at a constant current of 1 / 3C down to 2.0V. This was the initial charge-discharge cycle process for the batteries. The discharge capacity at this time was recorded as the initial cycle discharge capacity D1. The batteries were then subjected to a cycle charge-discharge test according to the above method, and the capacity Dn at the nth cycle was recorded. The capacity retention rate was Dn / D1. The number of cycles at which the capacity retention rate reached 80% was recorded.

[0149] 2. -10℃ low temperature cycle characteristic test At -10°C, the secondary batteries of each example and comparative example were charged at a constant current of 0.2 C up to a voltage upper limit of 3.8 V, then charged at a constant voltage of 0.05 C, allowed to stand for 5 minutes, and discharged at a constant current of 1 / 3 C down to 2.0 V. This was the initial charge-discharge cycle process for the battery, and the discharge capacity at this time was recorded as the initial cycle discharge capacity D1. The discharge capacity at the nth cycle was designated Dn, the capacity retention rate was Dn / D1, and the number of cycles at which the battery capacity retention rate was 80% was recorded.

[0150] The results of the performance tests for the above examples and comparative examples are shown in Table 2.

[0151] [Table 2]

[0152] As can be seen from a comparison of the results of Examples 1 to 24 and Comparative Examples 1 to 4, the electrolyte solution provided herein can simultaneously improve the high-temperature and low-temperature performance of a secondary battery by simultaneously adding the first additive, the second additive, and the third additive. Furthermore, as can be seen from a comparison of the results of Examples 1 to 21 and Examples 22 to 23, the high-temperature and low-temperature performance of a secondary battery can be simultaneously improved by adjusting the amounts of the first additive, the second additive, and the third additive so that the amounts of the three additives satisfy the relationship 2%≦(A+C) / B≦120%.

[0153] The main differences between Example 24 and Examples 1 and 10-11 are as follows: EC was not added to the electrolyte of Example 24. EC has a high dielectric constant and can dissociate lithium salts, improving the conductivity of the electrolyte. At the same time, it can also generate a reduction reaction to produce the product Li2CO3, which has good thermal stability, thereby improving the high-temperature cycle performance of the battery to some extent. Furthermore, the viscosity of EC increases rapidly at low temperatures, which can increase the viscosity of the electrolyte, reduce its conductivity, and potentially affect its low-temperature performance. However, the addition of EC and a third additive simultaneously improves the low-temperature performance of the battery. Therefore, as can be seen from a comparison of the results of Example 24 with those of Examples 1 and 10-11, the addition of EC to the electrolyte can further improve the high-temperature and low-temperature performance of the battery cell.

[0154] The above description of each embodiment focuses on highlighting the differences between each embodiment, and the same or similar points can be cross-referenced and will not be described in this specification for the sake of brevity.

[0155] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any embodiment that has substantially the same configuration as the technical idea and achieves the same effects within the scope of the technical solution of the present application is included within the technical scope of the present application. Furthermore, various modifications conceivable by those skilled in the art to the embodiments, as well as other forms constructed by combining some of the components of the embodiments, are also included within the scope of the present application, as long as they do not deviate from the gist of the present application.

Claims

1. a first additive containing an inorganic salt containing elemental fluorine; The compound containing an unsaturated bond has a reduction potential of 0.8 V (Li ＋ / Li), and and a third additive comprising a compound containing an amide group.

2. The mass ratio of the first additive in the electrolytic solution is A%, the mass ratio of the second additive in the electrolytic solution is B%, and the mass ratio of the third additive in the electrolytic solution is C%, and A, B, and C satisfy 2%≦(A+C) / B≦120%, Optionally, the electrolyte solution of claim 1, wherein 5%≦(A+C) / B≦55%.

3. 3. The electrolyte solution according to claim 2, wherein 0.01≦A≦1.

4. The electrolyte solution according to any one of claims 2 to 3, wherein 0.5≦B≦10.

5. The electrolyte solution according to any one of claims 2 to 4, wherein 0.01≦C≦0.

1.

6. the mass ratio of the fluorine element in the inorganic salt is ≧8%, 6. The electrolyte solution according to claim 1, wherein the first additive optionally includes one or more of a difluorophosphate, a tetrafluoroborate, and a fluorosulfonate containing an M element, and the M element includes one or more of Li, Na, K, and Cs.

7. the second additive comprises a cyclic compound containing an unsaturated bond, 7. The electrolyte solution according to claim 1, wherein the second additive optionally comprises one or more of vinylene carbonate, 1,3-propane sultone, vinyl sulfate, and vinyl disulfate.

8. The third additive comprises one or more of the compounds shown in the following formulas (I) and (II): However, R １ , R ２ each independently contains one of hydrogen, a methyl group, and an ethyl group; R ３ is C ３ -C ６ Contains an alkylene group, 8. The electrolyte solution according to claim 1, wherein the third additive optionally comprises one or more of N,N-dimethylformamide and N-methylpyrrolidone.

9. further comprising a cyclic ester solvent; Optionally, the cyclic ester solvent comprises one or more of ethylene carbonate and propylene carbonate; Further optionally, the mass ratio of the ethylene carbonate in the electrolytic solution is D%, and C and D satisfy 0.01%≦C / D≦1%; Further optionally, the electrolyte solution according to any one of claims 2 to 8, wherein 5≦D≦35.

10. further comprising a lithium salt; Optionally, the lithium salt comprises one or more of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, and lithium bistrifluoromethylsulfonylimide; Optionally, the mass ratio of the lithium salt in the electrolyte solution is 5% to 15%.

11. A secondary battery comprising the electrolytic solution according to any one of claims 1 to 10.

12. The secondary battery includes a negative electrode sheet, the negative electrode sheet includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, and the areal density of the negative electrode active material layer is Eg / m ２ and the specific surface area of ​​the negative electrode active material is Fm ２ / g, the mass ratio of the negative electrode active material in the negative electrode active material layer is L, The mass ratio of the second additive in the electrolytic solution is B%, The secondary battery according to claim 11 , wherein the B, the E, the F, and the L satisfy 0.5%≦B / (E*F*L)≦12%.

13. The secondary battery according to claim 12 , wherein 80≦E≦150.

14. The secondary battery according to any one of claims 12 to 13, wherein 0.5≦F≦5.

15. The secondary battery according to any one of claims 12 to 14, wherein 93%≦L≦98%.

16. A power consuming device comprising at least one of the electrolyte solution according to any one of claims 1 to 10 and the secondary battery according to any one of claims 11 to 15.

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