Electrolyte additive, electrolyte and secondary battery

Abstract

The invention provides an electrolyte additive, an electrolyte and a secondary battery. The electrolyte additive comprises a first component and a second component, wherein the first component is selected from a compound as shown in a formula I; and the second component is selected from a compound as shown in a formula II. The synergistic effect of the first component and the second component in the electrolyte additive can improve the high-temperature storage performance and the cycle life of the secondary battery.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to an electrolyte additive, an electrolyte, and a secondary battery. Background Technology

[0002] Lithium-ion batteries are widely used in electronic products, electric vehicles, and other fields due to their advantages such as high voltage, large capacity, no memory effect, and long lifespan. Despite these advantages, issues such as energy density and performance degradation at high temperatures continue to hinder the development of lithium-ion batteries. Increasing the operating voltage of lithium-ion batteries is an effective way to improve energy density; however, increasing the operating voltage often accelerates electrolyte decomposition and exacerbates side reactions, thus affecting the battery's lifespan and cycle performance. Therefore, developing a suitable electrolyte has become a pressing technical problem for those skilled in the art. Summary of the Invention

[0003] The purpose of this application is to provide an electrolyte additive, an electrolyte, and a secondary battery to improve the high-temperature storage performance and cycle life of the secondary battery. The specific technical solution is as follows:

[0004] A first aspect of this application provides an electrolyte additive comprising a first component and a second component;

[0005] The first component is selected from the compounds shown in Formula I;

[0006]

[0007] The second component is selected from the compounds shown in Formula II;

[0008]

[0009] R1 is selected from halogens, unsubstituted or halogen-substituted C1-C6 alkyl groups;

[0010] R2 is selected from nitrogen or C6-C. 12 Alpha-aryl;

[0011] R3 or R4 are each independently selected from hydrogen, halogen, unsubstituted or R-substituted. a Substituted C1-C6 alkyl, unsubstituted or R a Replacement C6-C 12 aryl, unsubstituted or R a Substituted sulfonyl group; substituent R a Each is independently selected from halogens, unsubstituted or halogenated C1-C6 alkyl groups, C6-C 12 Aryl, C1-C2 alkoxy, C2-C6 alkenyl, cyano Substituent R b Or R c Each is independently selected from unsubstituted or halogen-substituted C1-C6 alkyl groups;

[0012] R6 is selected from hydrogen, unsubstituted or halogenated C1-C6 alkyl, unsubstituted or halogenated C2-C6 alkenyl, unsubstituted or halogenated C2-C6 alkynyl, cyano, unsubstituted or halogenated C6-C 12 Aryl;

[0013] R5 is selected from

[0014] R d Or R e Each is independently selected from hydrogen, unsubstituted or halogenated C1-C6 alkyl, unsubstituted or halogenated C2-C6 alkenyl, unsubstituted or halogenated C2-C6 alkynyl, cyano, unsubstituted or halogenated C6-C 12 Aryl;

[0015] R f Selected from unsubstituted or halogenated C1-C6 alkyl, unsubstituted or halogenated C2-C6 alkenyl, unsubstituted or halogenated C2-C6 alkynyl; n is 0, 1, 2, 3, 4 or 5.

[0016] In one embodiment of this application, the mass ratio of the first component to the second component is (0.05-20):1, preferably (0.5-3):1.

[0017] In one embodiment of this application, R1 is selected from fluorine, unsubstituted or fluorine-substituted C1-C4 alkyl groups;

[0018] R2 is selected from nitrogen or phenylene;

[0019] R3 or R4 are each independently selected from hydrogen, fluorine, unsubstituted or R-substituted. a Substituted C1-C4 alkyl, unsubstituted or R a Substituted phenyl, unsubstituted or R a Substituted sulfonyl group; substituent R a Each is independently selected from fluorine, unsubstituted or fluorinated C1-C4 alkyl, phenyl, C1-C2 alkoxy, C2-C4 alkenyl, cyano, Substituent R b Or R c Each is independently selected from unsubstituted or fluorinated C1-C4 alkyl groups;

[0020] R6 is selected from hydrogen, unsubstituted or fluorinated C1-C4 alkyl, unsubstituted or fluorinated C2-C4 alkenyl, unsubstituted or fluorinated C2-C4 alkynyl, cyano, and unsubstituted or fluorinated phenyl.

[0021] R d Or R e Each is independently selected from hydrogen, unsubstituted or fluorinated C1-C4 alkyl, unsubstituted or fluorinated C2-C4 alkenyl, unsubstituted or fluorinated C2-C4 alkynyl, cyano, and unsubstituted or fluorinated phenyl.

[0022] R f Selected from C1-C4 alkyl, C2-C4 alkenyl, and C2-C4 alkynyl; n is 0, 1, 2, or 3.

[0023] In one embodiment of this application, the first component is selected from at least one of the following compounds;

[0024]

[0025] In one embodiment of this application, the second component is selected from at least one of the following compounds;

[0026]

[0027]

[0028] In one embodiment of this application, the electrolyte additive further includes a third component selected from at least one of vinylene carbonate, fluoroethylene carbonate, ethylene ethylene carbonate, ethylene sulfate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, vinyl sulfite, tris(trimethylsilane)borate, lithium bis(oxalato)borate, lithium difluorooxalatoborate, and lithium difluorodioxalatophosphate.

[0029] In one embodiment of this application, the mass ratio of the second component to the third component is (0.01 to 1.5):1, preferably (0.1 to 0.5):1.

[0030] A second aspect of this application provides an electrolyte comprising the electrolyte additive described in the first aspect of this application; the electrolyte additive has a mass percentage content of 1% to 15%, preferably 3% to 8%, based on the mass of the electrolyte.

[0031] In one embodiment of this application, at least one of the following features is satisfied:

[0032] (1) Based on the mass of the electrolyte, the mass percentage of the first component is A, 0.1% ≤ A ≤ 2%, preferably 0.5% ≤ A ≤ 1.5%;

[0033] (2) Based on the mass of the electrolyte, the mass percentage of the second component is B, 0.1% ≤ B ≤ 1.5%, preferably 0.5% ≤ B ≤ 1%;

[0034] (3) Based on the mass of the electrolyte, the mass percentage of the third component is C, 1% ≤ C ≤ 10%, preferably 3% ≤ C ≤ 5%.

[0035] A third aspect of this application provides a secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte as described in the second aspect of this application; wherein the negative electrode comprises a negative current collector and a negative electrode material layer disposed on at least one surface of the negative current collector, the negative electrode material layer comprising a negative electrode active material selected from at least one of silicon-based materials, carbon-based materials, and lithium-containing metal composite oxides; the positive electrode comprises a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector, the positive electrode material layer comprising a positive electrode active material selected from at least one of lithium manganese oxide, lithium nickel cobalt manganese oxide ternary materials, lithium nickel manganese oxide, lithium-rich manganese-based materials, and lithium cobalt oxide.

[0036] The beneficial effects of this application are:

[0037] This application provides an electrolyte additive, an electrolyte, and a secondary battery. The electrolyte additive comprises a first component and a second component. When used alone in an electrolyte, the first component generates a large amount of lithium-containing inorganic components (including lithium fluoride, lithium sulfate, etc.). While this improves the high-temperature stability of the solid electrolyte interfacial membrane, it also increases the impedance of the solid electrolyte interfacial membrane. Adding the second component to the electrolyte additive simultaneously eliminates some of the lithium-containing inorganic components. Furthermore, the silicon-oxygen components in the second component can compensate for the reduced stability caused by the decrease in lithium-containing inorganic components. Thus, without affecting the stability of the solid electrolyte interfacial membrane, it can reduce impedance and provide lithium-ion channels, accelerating lithium-ion transport. In addition, the second component can eliminate byproducts in the electrolyte and reduce the gas generation problem caused by the first component. The electrolyte additive of this application, comprising both the first and second components, works synergistically to improve the high-temperature storage performance and cycle life of the secondary battery.

[0038] Preferably, the electrolyte additive of this application may further include a third component. The third component can generate a flexible solid electrolyte interface film with good compatibility with the lithium-containing inorganic components formed by the first component. While improving the flexibility of the solid electrolyte interface film, it also improves its stability (the third component generates a flexible solid electrolyte interface film, and the large amount of lithium-containing inorganic components generated by the first component can serve as a framework to improve stability), thus better isolating side reactions at the battery interface. Simultaneously, the second component can eliminate some of the lithium-containing inorganic components, and the silicon-oxygen components in the second component can replace the negative effect of reduced stability caused by the reduction of lithium-containing inorganic components. Therefore, without affecting the stability of the solid electrolyte interface film, it reduces impedance and provides lithium-ion channels to accelerate lithium-ion transport. Preferably, the electrolyte additive of this application simultaneously includes the first, second, and third components. The synergistic effect of the first, second, and third components can better improve the high-temperature storage performance and cycle life of the secondary battery.

[0039] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Detailed Implementation

[0040] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0041] A first aspect of this application provides an electrolyte additive comprising a first component and a second component;

[0042] The first component is selected from the compounds shown in Formula I;

[0043]

[0044] The second component is selected from the compounds shown in Formula II;

[0045]

[0046] R1 is selected from halogens, unsubstituted or halogen-substituted C1-C6 alkyl groups;

[0047] R2 is selected from nitrogen or C6-C. 12 Alpha-aryl;

[0048] R3 or R4 are each independently selected from hydrogen, halogen, unsubstituted or R-substituted. a Substituted C1-C6 alkyl, unsubstituted or R a Replacement C6-C 12 aryl, unsubstituted or Ra Substituted sulfonyl group; substituent R a Each is independently selected from halogens, unsubstituted or halogenated C1-C6 alkyl groups, C6-C 12 Aryl, C1-C2 alkoxy, C2-C6 alkenyl, cyano Substituent R b Or R c Each is independently selected from unsubstituted or halogen-substituted C1-C6 alkyl groups;

[0049] R6 is selected from hydrogen, unsubstituted or halogenated C1-C6 alkyl, unsubstituted or halogenated C2-C6 alkenyl, unsubstituted or halogenated C2-C6 alkynyl, cyano, unsubstituted or halogenated C6-C 12 Aryl;

[0050] R5 is selected from

[0051] R d Or R e Each is independently selected from hydrogen, unsubstituted or halogenated C1-C6 alkyl, unsubstituted or halogenated C2-C6 alkenyl, unsubstituted or halogenated C2-C6 alkynyl, cyano, unsubstituted or halogenated C6-C 12 Aryl;

[0052] R f Selected from unsubstituted or halogenated C1-C6 alkyl, unsubstituted or halogenated C2-C6 alkenyl, unsubstituted or halogenated C2-C6 alkynyl; n is 0, 1, 2, 3, 4 or 5.

[0053] The first component of this application is a sulfonyl additive. The SC or SN bonds in this additive are easily broken, generating lithium-containing inorganic components (including LiF and Li₂SO₄) that are beneficial for improving the solid electrolyte interfacial film. A robust solid electrolyte interfacial film can also prevent the dissolution of transition metal ions and reduce side reactions at the battery interface. However, this additive is prone to hydrolysis, generating components that damage the solid electrolyte interfacial film. Furthermore, the breaking of SN or SC bonds can generate easily decomposed gaseous byproducts, which significantly affect the high-temperature performance of the battery. The second component of this application is an effective film-forming additive that can participate in the construction of a stable solid electrolyte interfacial film. It can eliminate HF / H₂O in the electrolyte, reducing the destructive effect of HF on electrode materials. This additive molecule contains silane components, which eliminate LiF components in the interfacial film, removing excess LiF and reducing battery impedance. Simultaneously, the numerous Si-O bonds in the second component have good stability, thus offsetting the negative impact of LiF elimination. The electrolyte additive of this application comprises both a first component and a second component. The second component can eliminate some of the lithium-containing inorganic components generated by the first component, and the silicon-oxygen component in the second component can replace the negative effect of reduced stability caused by the reduction of lithium-containing inorganic components. Thus, without affecting the stability of the solid electrolyte interfacial film, it reduces impedance and provides lithium-ion channels, accelerating lithium-ion transport. Furthermore, the second component can eliminate byproducts in the electrolyte and reduce gas generation problems caused by the first component. In summary, the electrolyte additive of this application comprises both a first component and a second component, and the synergistic effect of the first and second components can improve the high-temperature storage performance and cycle life of the secondary battery.

[0054] In one embodiment of this application, the mass ratio of the first component to the second component is (0.05–20):1, preferably (0.5–3):1. For example, the mass ratio of the first component to the second component can be 0.05:1, 0.08:1, 0.1:1, 0.3:1, 0.5:1, 0.8:1, 1:1, 3:1, 5:1, 8:1, 10:1, 13:1, 15:1, 18:1, 20:1, or a range consisting of any two of these values. By limiting the mass ratio of the first component and the second component to the above range, the first component and the second component can better exert their synergistic effect, further improving the high-temperature storage performance and cycle life of the secondary battery.

[0055] In this application, the term "halogen" refers to a fluorine, chlorine, bromine, or iodine atom.

[0056] In one embodiment of this application, R1 is selected from fluorine, unsubstituted or fluorine-substituted C1-C4 alkyl groups;

[0057] R2 is selected from nitrogen or phenylene;

[0058] R3 or R4 are each independently selected from hydrogen, fluorine, unsubstituted or R-substituted. a Substituted C1-C4 alkyl, unsubstituted or R a Substituted phenyl, unsubstituted or R a Substituted sulfonyl group; substituent R a Each is independently selected from fluorine, unsubstituted or fluorinated C1-C4 alkyl, phenyl, C1-C2 alkoxy, C2-C4 alkenyl, cyano, Substituent R b Or R c Each is independently selected from unsubstituted or fluorinated C1-C4 alkyl groups;

[0059] R6 is selected from hydrogen, unsubstituted or fluorinated C1-C4 alkyl, unsubstituted or fluorinated C2-C4 alkenyl, unsubstituted or fluorinated C2-C4 alkynyl, cyano, and unsubstituted or fluorinated phenyl.

[0060] R d Or R e Each is independently selected from hydrogen, unsubstituted or fluorinated C1-C4 alkyl, unsubstituted or fluorinated C2-C4 alkenyl, unsubstituted or fluorinated C2-C4 alkynyl, cyano, and unsubstituted or fluorinated phenyl.

[0061] R f Selected from C1-C4 alkyl, C2-C4 alkenyl, and C2-C4 alkynyl; n is 0, 1, 2, or 3.

[0062] Applying an electrolyte comprising the first and second components to a secondary battery can further improve the high-temperature storage performance and cycle life of the secondary battery through the synergistic effect of the first and second components without affecting other performance characteristics.

[0063] In one embodiment of this application, the first component is selected from at least one of the following compounds;

[0064]

[0065] Applying an electrolyte containing the first component mentioned above to a secondary battery can improve the secondary battery's high-temperature storage performance and cycle life without affecting other performance characteristics.

[0066] In one embodiment of this application, the second component is selected from at least one of the following compounds;

[0067]

[0068]

[0069] Applying an electrolyte containing the second component mentioned above to a secondary battery can improve the secondary battery's high-temperature storage performance and cycle life without affecting other performance characteristics.

[0070] In one embodiment of this application, the electrolyte additive further includes a third component selected from at least one of vinylene carbonate, fluoroethylene carbonate, ethylene ethylene carbonate, ethylene sulfate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, vinyl sulfite, tris(trimethylsilane)borate, lithium bis(oxalato)borate, lithium difluorooxalatoborate, and lithium difluorodioxalatophosphate.

[0071] The electrolyte additive of this application also includes a third component. The ester additives in the third component can form a flexible solid electrolyte interface film, which can better isolate side reactions at the battery interface, reduce silicon particle expansion, and improve cycle stability. The salt additives can generate more lithium-containing components on the interface film surface, which is beneficial for lithium-ion transport and also fills the interface film, making it more dense. The first, second, and third components are used together, and the resulting dense interface film can better isolate the dissolution of transition metal ions. In summary, the electrolyte additive of this application simultaneously includes a first, second, and third component. The synergistic effect of the first, second, and third components can better improve the high-temperature storage performance and cycle life of the secondary battery.

[0072] In one embodiment of this application, the mass ratio of the second component to the third component is (0.01–1.5):1, preferably (0.1–0.5):1. For example, the mass ratio of the second component to the third component can be 0.01:1, 0.03:1, 0.05:1, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, or a range consisting of any two of these values. By limiting the mass ratio of the first component, the second component, and the third component to the above range, the first component, the second component, and the third component can better exert their synergistic effect, further improving the high-temperature storage performance and cycle life of the secondary battery.

[0073] A second aspect of this application provides an electrolyte comprising the electrolyte additive described in the first aspect of this application; the mass percentage of the electrolyte additive is 1% to 15%, preferably 3% to 8%, based on the mass of the electrolyte. For example, the mass percentage of the electrolyte additive can be 1%, 3%, 5%, 8%, 10%, 13%, 15%, or a range of any two of these values, based on the mass of the electrolyte. Using electrolyte additives within the above range, without affecting other performance characteristics, enables the secondary battery to have higher high-temperature storage performance and cycle life.

[0074] In one embodiment of this application, the mass percentage of the first component is A, based on the mass of the electrolyte, where 0.1% ≤ A ≤ 2%, preferably 0.5% ≤ A ≤ 1.5%. For example, based on the mass of the electrolyte, the mass percentage A of the first component can be 0.1%, 0.5%, 1%, 1.5%, 2%, or a range consisting of any two of these values.

[0075] In one embodiment of this application, the mass percentage of the second component, B, is 0.1% ≤ B ≤ 1.5%, preferably 0.5% ≤ B ≤ 1%, based on the mass of the electrolyte. For example, the mass percentage B of the second component, based on the mass of the electrolyte, can be 0.1%, 0.5%, 1%, 1.5%, or a range of any two of these values.

[0076] In one embodiment of this application, the mass percentage of the third component, C, is based on the mass of the electrolyte, wherein 1% ≤ C ≤ 10%, preferably 3% ≤ C ≤ 5%. For example, the mass percentage of the third component, C, based on the mass of the electrolyte, can be 1%, 3%, 5%, 8%, 10%, or a range consisting of any two of these values.

[0077] When the contents of the first component and / or the second component and / or the third component are within the above range, the synergistic effect between the components can be better utilized without affecting other properties, thereby further enabling the secondary battery to have higher high-temperature storage performance and cycle life.

[0078] In one embodiment of this application, the electrolyte further includes a lithium salt. This application does not impose any particular limitation on the lithium salt, as long as it achieves the purpose of this application. For example, the lithium salt may include, but is not limited to, at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide.

[0079] This application does not impose any particular limitation on the content of lithium salt in the electrolyte, as long as the purpose of this application is achieved. For example, based on the mass of the electrolyte, the mass percentage of lithium salt is 10% to 15%, preferably 12% to 15%.

[0080] In one embodiment of this application, the electrolyte further includes a non-aqueous solvent. This application does not impose any particular limitation on the non-aqueous solvent, as long as it achieves the purpose of this application. For example, the non-aqueous solvent may be selected from, but is not limited to, propylene carbonate, ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, fluoroethylene carbonate, γ-butyrolactone, sulfolane, methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, and butyl butyrate.

[0081] This application does not impose any particular limitation on the content of non-aqueous solvents in the electrolyte, as long as the purpose of this application is achieved. For example, based on the mass of the electrolyte, the mass percentage of non-aqueous solvents is 72% to 88%, preferably 78% to 84%.

[0082] The preparation method of the electrolyte in this application is not particularly limited, as long as it can achieve the purpose of this invention. For example, various solvents in the electrolyte can be mixed, and then electrolyte lithium salt and additives can be added and mixed evenly.

[0083] A third aspect of this application provides a secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte as described in the second aspect of this application; wherein the negative electrode comprises a negative current collector and a negative electrode material layer disposed on at least one surface of the negative current collector, the negative electrode material layer comprising a negative electrode active material selected from at least one of silicon-based materials, carbon-based materials, and lithium-containing metal composite oxides; the positive electrode comprises a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector, the positive electrode material layer comprising a positive electrode active material selected from at least one of lithium manganese oxide, lithium nickel cobalt manganese oxide ternary materials, lithium nickel manganese oxide, lithium-rich manganese-based materials, and lithium cobalt oxide.

[0084] This application does not impose any particular restrictions on silicon-based materials, carbon-based materials, or lithium-containing metal composite oxides, as long as they can achieve the purpose of this application. For example, the silicon-based materials may include, but are not limited to, at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys; the carbon-based materials may include, but are not limited to, at least one of artificial graphite, natural graphite, soft carbon, hard carbon, and mesophase microcarbon spheres; and the lithium-containing metal composite oxides may include, but are not limited to, at least one of lithium titanate and lithium metal.

[0085] By using the positive and negative active materials of this application and matching them with the electrolyte additives of this application, the high-temperature storage performance and cycle life of the secondary battery are further improved.

[0086] It should be noted that, in the specific embodiments of this application, a lithium-ion battery is used as an example of a secondary battery to explain this application; however, the secondary battery in this application is not limited to lithium-ion batteries. The specific technical solution is as follows:

[0087] This application does not impose any particular limitation on the conductive agent, as long as it can achieve the purpose of this application. For example, the conductive agent may be selected from, but is not limited to, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The aforementioned carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The aforementioned carbon fibers may include, but are not limited to, vapor-grown carbon fibers (VGCF) and / or carbon nanofibers.

[0088] This application does not impose any particular limitation on the adhesive, as long as it can achieve the purpose of this application. For example, the adhesive may be selected from, but is not limited to, styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), terpolymer of vinylidene fluoride-tetrafluoroethylene-propylene, terpolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, terpolymer of tetrafluoroethylene-hexafluoropropylene, and fluorinated acrylate resin.

[0089] In this application, the aforementioned "positive electrode material layer disposed on at least one surface of the positive electrode current collector" means that the positive electrode material layer can be disposed on one surface of the positive electrode current collector along its own thickness direction, or it can be disposed on two surfaces of the positive electrode current collector along its own thickness direction. It should be noted that the "surface" here can be the entire area of ​​the surface of the positive electrode current collector, or it can be a part of the surface of the positive electrode current collector. This application has no particular limitation, as long as the purpose of this application can be achieved.

[0090] This application does not impose any particular limitation on the positive electrode current collector, as long as it can achieve the purpose of this application. For example, the positive electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, aluminum foil, aluminum alloy foil, or carbon-coated aluminum foil can be used. The composite current collector can include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0091] The positive electrode material layer may also include a conductive agent and a binder. This application does not impose any particular restrictions on the types of conductive agents and binders, as long as they achieve the purpose of this application. For example, it may include at least one of the aforementioned conductive agents and binders. This application does not impose any particular restrictions on the mass ratio of the positive electrode active material, conductive agent, and binder in the positive electrode material layer. Those skilled in the art can select according to actual needs, as long as the purpose of this application is achieved.

[0092] This application does not impose any particular limitations on the thickness of the positive electrode current collector and the positive electrode material layer, as long as the purpose of this application can be achieved. For example, the thickness of the positive electrode current collector can be 5 μm to 20 μm, and the thickness of the single-sided positive electrode material layer can be 20 μm to 90 μm.

[0093] Optionally, the positive electrode may further include a conductive layer located between the positive current collector and the positive electrode material layer. The composition of the conductive layer is not particularly limited and can be any conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer; for example, it can be at least one of the aforementioned conductive agents and binders.

[0094] In one embodiment of this application, the compaction density of the positive electrode sheet is 2 g / cm³. 3 ~5g / cm 3 .

[0095] In this application, the secondary battery also includes a separator. This application does not impose any particular limitation on the separator, as long as it achieves the purpose of this application. For example, the material of the separator can be selected from, but is not limited to, at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. This application does not impose any particular limitation on the number of layers in the separator, as long as it achieves the purpose of this application; for example, the separator can be a single-layer thin film or a multi-layer composite thin film.

[0096] In some embodiments of this application, the diaphragm may include a substrate layer and a surface treatment layer. This application does not impose any particular limitation on the substrate layer, as long as it achieves the purpose of this application. For example, the substrate layer may be selected from, but is not limited to, at least one of polyethylene, polypropylene, polyvinylidene fluoride, and polyacrylonitrile.

[0097] Optionally, a surface treatment layer is provided on at least one surface of the substrate layer. This application does not impose any particular limitation on the surface treatment layer, as long as it achieves the purpose of this application. For example, the surface treatment layer may be selected from, but is not limited to, conductive carbon, alumina, and Li. 6.4 La3Zr 1.4 Ta 0.6 O 12 At least one of (LLZTO).

[0098] In this application, there is no particular limitation on the thickness of the diaphragm, as long as it can achieve the purpose of this application. For example, the thickness of the diaphragm can be 5 μm to 10 μm.

[0099] In this application, the aforementioned "negative electrode material layer disposed on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be disposed on one surface of the negative electrode current collector along its own thickness direction, or it can be disposed on two surfaces of the negative electrode current collector along its own thickness direction. It should be noted that the "surface" here can be the entire area of ​​the surface of the negative electrode current collector, or it can be a part of the surface of the negative electrode current collector. This application has no particular limitation, as long as the purpose of this application can be achieved.

[0100] This application does not impose any particular limitation on the negative electrode current collector, as long as it can achieve the purpose of this application. For example, the negative electrode current collector can be a metal foil or a composite current collector. For example, copper foil or aluminum alloy foil can be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0101] In some embodiments of this application, the negative electrode material layer may further include a conductive agent and a binder. This application does not impose any particular restrictions on the types of conductive agents and binders, as long as they achieve the purpose of this application. For example, it may be at least one of the aforementioned conductive agents and binders. This application does not impose any particular restrictions on the mass ratio of the negative electrode active material, conductive agent, and binder in the negative electrode material layer. Those skilled in the art can select according to actual needs, as long as the purpose of this application is achieved.

[0102] In some embodiments of this application, the negative electrode material layer may further include a conductive agent, a binder, and a thickener. This application does not particularly limit the types of conductive agents and binders, as long as they achieve the purpose of this application. For example, the conductive agent and binder may be at least one of the aforementioned conductive agents and binders. The thickener may include, but is not limited to, at least one of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose. This application does not particularly limit the mass ratio of the negative electrode active material, conductive agent, binder, and thickener in the negative electrode material layer; those skilled in the art can select them according to actual needs, as long as the purpose of this application is achieved.

[0103] This application does not impose any particular limitation on the thickness of the negative electrode material layer, as long as it can achieve the purpose of this application. For example, the thickness of the single-sided negative electrode material layer is 30 μm to 125 μm.

[0104] This application does not impose any particular limitation on the thickness of the negative electrode current collector, as long as it can achieve the purpose of this application. For example, the thickness of the negative electrode current collector is 4 μm to 10 μm.

[0105] Optionally, the negative electrode sheet may further include a conductive layer located between the negative electrode current collector and the negative electrode material layer. This application does not impose any particular limitation on the composition of the conductive layer, which can be a conductive layer commonly used in the art. For example, the conductive layer may include a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer; for example, it can be at least one of the aforementioned conductive agents and binders.

[0106] In some embodiments of this application, the compaction density of the negative electrode sheet is 1 g / cm³ to 4 g / cm³. 3 .

[0107] The secondary battery also includes a casing for housing the positive electrode, separator, negative electrode, and electrolyte, as well as other components known in the field of secondary batteries. This application does not limit the scope of these other components. This application does not impose any particular limitation on the casing; it can be a casing known in the art, as long as it achieves the purpose of this application. For example, the casing can be a rigid casing or a flexible casing. The material of the rigid casing can be metal; this application does not limit the type of metal and can use known metal rigid casings, as long as they achieve the purpose of this application. The flexible casing can be a metal plastic film, such as aluminum-plastic film, steel-plastic film, etc.

[0108] The preparation process of the secondary battery in this application is well known to those skilled in the art, and this application has no particular limitations. For example, the preparation process of the secondary battery may include, but is not limited to, the following steps: stacking the positive electrode sheet, the separator and the negative electrode sheet in sequence, and winding, folding and other operations as needed to obtain the wound electrode assembly, placing the electrode assembly into the housing, injecting the electrolyte into the housing and sealing it, forming, capacity testing and sorting to obtain the secondary battery.

[0109] In some embodiments of this application, the secondary battery of this application can be used in high-voltage systems with a voltage range of 4.2 to 4.6V.

[0110] A fourth aspect of this application provides an electronic device comprising the secondary battery described in the third aspect of this application.

[0111] The electronic device described in this application is not particularly limited and can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries or lithium-ion capacitors, etc.

[0112] Example

[0113] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0114] Test methods and equipment:

[0115] ambient temperature cycling performance test

[0116] The lithium-ion battery was placed in a 25°C constant temperature test chamber and left to stand for 30 minutes to allow it to reach a constant temperature. It was then charged at a constant current of 1.0C to 4.4V, followed by constant voltage charging at 4.4V until the cutoff current reached 0.05C. After standing for 5 minutes, it was discharged at a constant current of 1.0C to 2.75V, and this discharge capacity was recorded as C1. This process was repeated for 500 cycles, and the discharge capacity C2 after 500 cycles was recorded. The cycle capacity retention rate of the lithium-ion battery was calculated. The cycle capacity retention rate at room temperature = C2 / C1 × 100%.

[0117] High-temperature cycling performance test

[0118] The lithium-ion battery was placed in a 45°C constant temperature test chamber and left to stand for 60 minutes to allow it to reach a constant temperature. It was then charged at a constant current of 1.0C to 4.4V, followed by constant voltage charging at 4.4V until the cutoff current reached 0.05C. After standing for 5 minutes, it was discharged at a constant current of 1.0C to 2.75V, and this discharge capacity was recorded as C3. This process was repeated for 300 cycles, and the discharge capacity C4 after 300 cycles was recorded. The cycle capacity retention rate of the lithium-ion battery was calculated. High-temperature cycle capacity retention rate = C4 / C3 × 100%.

[0119] High-temperature storage performance test

[0120] The lithium-ion battery was placed in a 25°C constant temperature test chamber and left to stand for 30 minutes to allow it to reach a constant temperature. It was then charged at a constant current of 1.0C to 4.4V, followed by constant voltage charging at 4.4V until the cutoff current was 0.05C. After standing for 5 minutes, it was discharged at a constant current of 1.0C to 2.75V, and this discharge capacity was recorded as C5. The battery was then charged again at a constant current of 1.0C to 4.4V, followed by constant voltage charging at 4.4V until the cutoff current was 0.05C. The thickness of the lithium-ion battery was measured and recorded as h1. The battery was then transferred to 60°C and left to stand for 28 days. The thickness of the battery was measured and recorded as h2. Finally, it was discharged at a constant current of 1.0C to 2.75V, and the discharge capacity was recorded as C6. High-temperature storage capacity retention rate = C6 / C5 × 100%, high-temperature storage thickness expansion rate = (h2 - h1) / h1 × 100%.

[0121] High-temperature storage DC internal resistance (DCIR) growth rate

[0122] Place the lithium-ion battery in a 25°C constant temperature chamber and let it stand for 30 minutes to allow it to reach a constant temperature. Charge it to 4.4V at a constant current of 1.0C, let it stand for 5 minutes, then discharge it at a constant current of 1.0C for 30 minutes, let it stand for 1 hour, and then discharge it at the current corresponding to a 2C rate (IC). 2C Discharge for 10 seconds, record the voltage values ​​V1 and V2 before and after 2C rate discharge, respectively. Calculate the DCIR1 of the lithium-ion battery at 50% state of charge (SOC). (The formula for calculating DCIR1 is: DCIR1 = (V1 - V2) / I) 2C ).

[0123] Then, the lithium-ion battery was transferred to 60℃ and left to stand for 7 days. After 3 weeks of constant current charging and discharging at 1.0C (charged to 4.4V at 1.0C, then constant voltage at 4.4V until the cutoff current is 0.05C, left to stand for 5 minutes, then discharged at 1.0C at a constant current to 2.75V, cycled for 3 weeks), charged to 4.4V at 1.0C at a constant current, left to stand for 5 minutes, then discharged at 1.0C for 30 minutes, left to stand for 1 hour, and then discharged at the current corresponding to a 2C rate (I... 2CDischarge for 10 seconds, record the voltage values ​​V3 and V4 before and after 2C rate discharge, respectively, and calculate the DCIR2 of the battery at 50% SOC (the formula for calculating DCIR2 is: DCIR2=(V3-V4) / I). 2C ).

[0124] DC internal resistance (DCIR) growth rate = (DCIR2 - DCIR1) / DCIR1 × 100%.

[0125] Example 1-1

[0126] <Preparation of Electrolyte>

[0127] In an argon-atmospheric glove box (water content <10ppm, oxygen content <1ppm), non-aqueous organic solvents ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) are mixed uniformly in a mass ratio of 3:5:2. Then, the first component, formula I-1, and the second component, formula II-1, are added and mixed uniformly. Lithium hexafluorophosphate is then added, dissolved, and mixed uniformly to obtain the electrolyte. Based on the mass of the electrolyte, the mass percentage of lithium hexafluorophosphate is 12.5%, the mass percentage A of the first component, formula I-1, is 0.05%, the mass percentage B of the second component, formula II-1, is 1%, and the remainder is non-aqueous organic solvent.

[0128] <Preparation of the positive electrode>

[0129] Lithium nickel cobalt manganese oxide (NCM613), polyvinylidene fluoride (PVDF), acetylene black, and single-walled carbon nanotubes (SWCNTs) were mixed in a mass ratio of 95:1.5:3:0.5. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 65 wt%. The slurry was then uniformly stirred under vacuum to obtain the positive electrode slurry. The positive electrode slurry was uniformly coated onto one surface of a 16 μm thick aluminum foil current collector. The foil was then baked in an oven at different temperature gradients (90℃, 100℃, and 85℃) at a speed of 2200 mm / min, followed by drying at 120℃ to obtain a positive electrode sheet with a single-sided coating. The above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating. After cutting and welding tabs, a positive electrode sheet with dimensions of 258 mm × 54 mm was obtained for later use. The compaction density of the positive electrode material layer is 3.4 g / cm³. 3 The thickness of the single-sided positive electrode material layer is 37 μm.

[0130] <Preparation of Negative Electrode Sheets>

[0131] Artificial graphite (BTR S360-L1) as the negative electrode active material, sodium carboxymethyl cellulose (CMC-Na) as the thickener, styrene-butadiene rubber as the binder, and acetylene black as the conductive agent were mixed in a mass ratio of 95:1.5:2:1.5. Deionized water was added as a solvent to prepare a slurry with a solid content of 49 wt%. After vacuum stirring, the slurry was obtained. The negative electrode slurry was uniformly coated on one surface of a 9 μm thick copper foil current collector and dried at 85°C to obtain a negative electrode sheet with a single-sided negative electrode material layer. The above steps were repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided negative electrode material layer. After cutting and welding tabs, a negative electrode sheet with a size of 264 mm × 58 mm was obtained for use. The compaction density of the negative electrode material layer was 1.5 g / cm³. 3 The thickness of the single-sided negative electrode material layer is 50 μm.

[0132] <Preparation of the diaphragm>

[0133] The membrane is made of polyethylene with a thickness of 8μm (provided by Xingyuan Material Company).

[0134] <Preparation of Lithium-ion Batteries>

[0135] The prepared positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to act as a separator. They are then wound, with the positive tab connected to the positive electrode and the negative tab connected to the negative electrode, resulting in an electrode assembly. The electrode assembly is then placed in an aluminum-plastic film, with the positive and negative tabs extended from the interior to the exterior of the film. Moisture is removed at 85°C, and the prepared electrolyte is injected. After vacuum sealing and standing for 24 hours, an application of 3 kg / cm² is performed at 45°C. 2 The pressure was adjusted, and the cells were formed by constant current charging at 0.1C for 6.5 hours. Then, the cells were sorted by capacity (charged at 0.1C constant current to 4.4V, then charged at 4.4V constant voltage to the cutoff current of 0.05C, allowed to stand for 5 minutes, and discharged at 0.5C constant current to 2.75V; then charged at 0.5C constant current to 4.4V, then charged at 4.4V constant voltage to the cutoff current of 0.05C, allowed to stand for 5 minutes, and discharged at 1.0C constant current to 2.75V; then charged at 1.0C constant current to 4.4V, then charged at 4.4V constant voltage to the cutoff current of 0.05C, allowed to stand for 5 minutes, and discharged at 1.0C constant current to 2.75V) to obtain lithium-ion batteries.

[0136] Examples 1-2 to 1-41

[0137] Except for adjusting the types and mass percentages of the first and second components according to Table 1 in the <Preparation of Electrolyte>, changing the mass percentage of the non-aqueous organic solvent accordingly, and keeping the mass percentage of the lithium salt unchanged, the rest is the same as in Example 1-1.

[0138] Examples 1-42

[0139] <Preparation of Electrolyte>

[0140] In an argon-atmospheric glove box (water content <10ppm, oxygen content <1ppm), non-aqueous organic solvents ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) are mixed uniformly in a mass ratio of 3:5:2. Then, the first component, formula I-1, and the second component, formula II-1, are added and mixed uniformly. Lithium hexafluorophosphate is then added, dissolved, and mixed uniformly to obtain the electrolyte. Based on the mass of the electrolyte, the mass percentage of lithium hexafluorophosphate is 12.5%, the mass percentage of the first component, formula I-1, is 0.5%, the mass percentage of the second component, formula II-1, is 0.5%, and the remainder is non-aqueous organic solvent.

[0141] <Preparation of the positive electrode>

[0142] Lithium cobalt oxide (CCO), polyvinylidene fluoride (PVDF), and acetylene black (HCO) were mixed in a mass ratio of 97.3:1.2:1.5. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 68.4 wt%. The slurry was then uniformly stirred under vacuum to obtain the positive electrode slurry. This slurry was uniformly coated onto one surface of a 16 μm thick aluminum foil used as a positive electrode current collector. The foil was then baked in an oven at different temperature gradients (90℃, 100℃, and 85℃) at a speed of 2200 mm / min, followed by drying at 120℃ to obtain a positive electrode sheet with a single-sided coating of the positive electrode material. The above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of the positive electrode material. After cutting and welding the tabs, positive electrode sheets with dimensions of 558 mm × 55 mm were obtained for use. The compaction density of the positive electrode material layer was 4.15 g / cm³. 3 The thickness of the single-sided positive electrode material layer is 36 μm.

[0143] <Preparation of Negative Electrode Sheets>

[0144] Artificial graphite (BTR S360-L1) as the negative electrode active material, sodium carboxymethyl cellulose (CMC-Na) as the thickener, styrene-butadiene rubber as the binder, acetylene black as the conductive agent, and single-walled carbon nanotubes (SWCNTs) as the conductive agent were mixed in a mass ratio of 95.9:1:2:1:0.1. Deionized water was added as a solvent to prepare a slurry with a solid content of 49wt%. After vacuum stirring, the slurry was obtained. The negative electrode slurry was uniformly coated on one surface of a 9μm thick copper foil as a negative electrode current collector and dried at 85℃ to obtain a negative electrode sheet with a single-sided coating of negative electrode material. The above steps were repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided coating of negative electrode material. After cutting and welding tabs, a negative electrode sheet with a size of 708mm×59mm was obtained for use. The compaction density of the negative electrode material layer was 1.6g / cm³. 3 The thickness of the single-sided negative electrode material layer is 63.5 μm.

[0145] <Preparation of the diaphragm>

[0146] The membrane is made of polyethylene with a thickness of 8μm (provided by Xingyuan Material Company).

[0147] <Preparation of Lithium-ion Batteries>

[0148] The prepared positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to act as a separator. They are then wound, with the positive tab connected to the positive electrode and the negative tab connected to the negative electrode, resulting in an electrode assembly. The electrode assembly is then placed in an aluminum-plastic film, with the positive and negative tabs extended from the interior to the exterior of the film. Moisture is removed at 85°C, and the prepared electrolyte is injected. After vacuum sealing and standing for 24 hours, an application of 3 kg / cm² is performed at 45°C. 2 The pressure was adjusted, and the cells were formed by constant current charging at 0.1C for 6.5 hours. Then, the cells were sorted by capacity (charged at 0.1C constant current to 4.4V, then charged at 4.4V constant voltage to the cutoff current of 0.05C, allowed to stand for 5 minutes, and discharged at 0.5C constant current to 2.75V; then charged at 0.5C constant current to 4.4V, then charged at 4.4V constant voltage to the cutoff current of 0.05C, allowed to stand for 5 minutes, and discharged at 1.0C constant current to 2.75V; then charged at 1.0C constant current to 4.4V, then charged at 4.4V constant voltage to the cutoff current of 0.05C, allowed to stand for 5 minutes, and discharged at 1.0C constant current to 2.75V) to obtain lithium-ion batteries.

[0149] Examples 2-1 to 2-23

[0150] Except that a third component was added as shown in Table 2 in the <Preparation of Electrolyte>, and the type and mass percentage of the third component were adjusted according to Table 2, the mass percentage of the non-aqueous organic solvent was changed accordingly, and the mass percentage of the lithium salt remained unchanged, the rest was the same as in Examples 1-7.

[0151] Comparative Example 1

[0152] Except that the second component is not added in the <Preparation of Electrolyte>, the mass percentage of the first component is adjusted according to Table 1, the mass percentage of the non-aqueous organic solvent is changed accordingly, and the mass percentage of the lithium salt remains unchanged, the rest is the same as in Example 1-1.

[0153] Comparative Example 2

[0154] Except that the first component is not added in the <Preparation of Electrolyte>, the mass percentage of the second component is adjusted according to Table 1, the mass percentage of the non-aqueous organic solvent is changed accordingly, and the mass percentage of the lithium salt remains unchanged, the rest is the same as in Example 1-1.

[0155] Comparative Example 3

[0156] Except that the first component is not added in the <Preparation of Electrolyte>, the mass percentage of the second component is adjusted according to Table 1, the mass percentage of the non-aqueous organic solvent is changed accordingly, and the mass percentage of the lithium salt remains unchanged, the rest is the same as in Examples 1-42.

[0157] Comparative Example 4

[0158] Except that the second component is not added in the <Preparation of Electrolyte>, the mass percentage of the first component is adjusted according to Table 1, the mass percentage of the non-aqueous organic solvent is changed accordingly, and the mass percentage of the lithium salt remains unchanged, the rest is the same as in Examples 1-42.

[0159] The preparation parameters and performance parameters of each embodiment and comparative example are shown in Tables 1 and 2.

[0160]

[0161]

[0162]

[0163] As can be seen from Examples 1-1 to 1-42 and Comparative Examples 1 to 4, when electrolytes with only the first or second component are added, lithium-ion batteries exhibit lower room-temperature cycle capacity retention, high-temperature cycle capacity retention, and high-temperature storage capacity retention, as well as higher high-temperature storage thickness expansion rate and high-temperature storage DCIR growth rate. When electrolytes with both the first and second components are added, lithium-ion batteries exhibit higher room-temperature cycle capacity retention, high-temperature cycle capacity retention, and high-temperature storage capacity retention, as well as lower high-temperature storage thickness expansion rate and high-temperature storage DCIR growth rate. These results demonstrate that the combined use of the first and second components can improve the high-temperature storage performance and cycle life of lithium-ion batteries.

[0164] As can be seen from Examples 1-7 and Examples 2-1 to 2-23, when an electrolyte containing the first, second, and third components is applied to a lithium-ion battery, the lithium-ion battery exhibits higher room-temperature cycle capacity retention, high-temperature cycle capacity retention, and high-temperature storage capacity retention, as well as lower high-temperature storage thickness expansion rate and high-temperature storage DCIR growth rate. These results demonstrate that the combined use of the first, second, and third components enables lithium-ion batteries to achieve better high-temperature storage performance and cycle life.

[0165] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or article.

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

Claims

1. An electrolyte additive, comprising a first component and a second component; The first component is selected from the compounds shown in Formula I; The second component is selected from the compounds shown in Formula II; in, R1 is selected from halogens, unsubstituted or halogenated C1-C6 alkyl groups; R2 is selected from nitrogen or C6-C. 12 Alpha-aryl; R3 or R4 are each independently selected from hydrogen, halogen, unsubstituted or R-substituted. a Substituted C1-C6 alkyl, unsubstituted or R a Replacement C6-C 12 aryl, unsubstituted or R a Substituted sulfonyl group; substituent R a Each is independently selected from halogens, unsubstituted or halogenated C1-C6 alkyl groups, C6-C 12 Aryl, C1-C2 alkoxy, C2-C6 alkenyl, cyano Substituent R b Or R c Each is independently selected from unsubstituted or halogen-substituted C1-C6 alkyl groups; R6 is selected from hydrogen, unsubstituted or halogenated C1-C6 alkyl, unsubstituted or halogenated C2-C6 alkenyl, unsubstituted or halogenated C2-C6 alkynyl, cyano, unsubstituted or halogenated C6-C 12 Aryl; R5 is selected from R d Or R e Each is independently selected from hydrogen, unsubstituted or halogenated C1-C6 alkyl, unsubstituted or halogenated C2-C6 alkenyl, unsubstituted or halogenated C2-C6 alkynyl, cyano, unsubstituted or halogenated C6-C 12 Aryl; R f Selected from unsubstituted or halogenated C1-C6 alkyl, unsubstituted or halogenated C2-C6 alkenyl, unsubstituted or halogenated C2-C6 alkynyl; n is 0, 1, 2, 3, 4 or 5.

2. The electrolyte additive according to claim 1, wherein, The mass ratio of the first component to the second component is (0.05-20):1, preferably (0.5-3):

1.

3. The electrolyte additive according to claim 1, wherein, R1 is selected from fluorine, unsubstituted or fluorine-substituted C1-C4 alkyl groups; R2 is selected from nitrogen or phenylene; R3 or R4 are each independently selected from hydrogen, fluorine, unsubstituted or R-substituted. a Substituted C1-C4 alkyl, unsubstituted or R a Substituted phenyl, unsubstituted or R a Substituted sulfonyl group; substituent R a Each is independently selected from fluorine, unsubstituted or fluorinated C1-C4 alkyl, phenyl, C1-C2 alkoxy, C2-C4 alkenyl, cyano, Substituent R b Or R c Each is independently selected from unsubstituted or fluorinated C1-C4 alkyl groups; R6 is selected from hydrogen, unsubstituted or fluorinated C1-C4 alkyl, unsubstituted or fluorinated C2-C4 alkenyl, unsubstituted or fluorinated C2-C4 alkynyl, cyano, and unsubstituted or fluorinated phenyl. R d Or R e Each is independently selected from hydrogen, unsubstituted or fluorinated C1-C4 alkyl, unsubstituted or fluorinated C2-C4 alkenyl, unsubstituted or fluorinated C2-C4 alkynyl, cyano, and unsubstituted or fluorinated phenyl. R f Selected from C1-C4 alkyl, C2-C4 alkenyl, and C2-C4 alkynyl; n is 0, 1, 2, or 3.

4. The electrolyte additive according to claim 1, wherein, The first component is selected from at least one of the following compounds; 5. The electrolyte additive according to claim 1, wherein, The second component is selected from at least one of the following compounds; 6. The electrolyte additive according to claim 1, wherein, The electrolyte additive further includes a third component selected from at least one of vinylene carbonate, fluoroethylene carbonate, ethylene ethylene carbonate, ethylene sulfate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, vinyl sulfite, tris(trimethylsilane)borate, lithium bis(oxalato)borate, lithium difluorooxalatoborate, and lithium difluorodioxalatophosphate.

7. The electrolyte additive according to claim 6, wherein, The mass ratio of the second component to the third component is (0.01 to 1.5):1, preferably (0.1 to 0.5):

1.

8. An electrolyte comprising an electrolyte additive according to any one of claims 1 to 7; wherein the electrolyte additive comprises, based on the mass of the electrolyte, 1% to 15% by mass, preferably 3% to 8% by mass.

9. The electrolyte according to claim 8, wherein it satisfies at least one of the following characteristics: (1) Based on the mass of the electrolyte, the mass percentage of the first component is A, 0.1% ≤ A ≤ 2%, preferably 0.5% ≤ A ≤ 1.5%; (2) Based on the mass of the electrolyte, the mass percentage of the second component is B, 0.1% ≤ B ≤ 1.5%, preferably 0.5% ≤ B ≤ 1%; (3) Based on the mass of the electrolyte, the mass percentage of the third component is C, 1% ≤ C ≤ 10%, preferably 3% ≤ C ≤ 5%.

10. A secondary battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte according to any one of claims 8 to 9; wherein, The negative electrode sheet includes a negative current collector and a negative electrode material layer disposed on at least one surface of the negative current collector. The negative electrode material layer includes a negative electrode active material, which is selected from at least one of silicon-based materials, carbon-based materials, and lithium-containing metal composite oxides. The positive electrode sheet includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The positive electrode material layer includes a positive electrode active material, which is selected from at least one of lithium manganese oxide, lithium nickel cobalt manganese oxide ternary materials, lithium nickel manganese oxide, lithium-rich manganese-based materials, and lithium cobalt oxide.

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