Electrolyte additive, electrolyte and secondary battery

Abstract

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 represented by formula I, and the second component is selected from a compound represented by 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 cycle life of secondary batteries.

Description

Electrolyte additive, electrolyte and secondary battery

[0001] The present application claims priority to the Chinese patent application No. 202411105029.6, filed on August 13, 2024, and entitled "Electrolyte additive, electrolyte and secondary battery", the whole content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the field of electrochemistry, in particular to an electrolyte additive, an electrolyte and a secondary battery. BACKGROUND

[0003] Lithium ion batteries are widely used in electronic products, electric vehicles and other fields due to their high voltage, large capacity, no memory effect and long service life. Despite the many advantages of lithium ion batteries, the low energy density and the performance decline when working in high temperature environment have always plagued the development of lithium ion batteries. Increasing the working voltage of lithium ion batteries is an effective method to improve the energy density of the battery. However, when the working voltage of lithium ion batteries is increased, the decomposition of the electrolyte and the occurrence of side reactions are often accelerated, thereby affecting the service life and cycle performance of the lithium ion battery. Therefore, it is an urgent technical problem for those skilled in the art to develop a suitable electrolyte. SUMMARY

[0004] The present application aims 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 solutions are as follows:

[0005] The first aspect of the present application provides an electrolyte additive comprising a first component and a second component.

[0006] The first component is selected from the compound shown in Formula I;

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

[0008] wherein R1 is selected from halogen, C1-C6 alkyl unsubstituted or substituted with halogen;

[0009] R2 is selected from nitrogen or C6-C 12 arylene;

[0010] R3 or R4 is each independently selected from hydrogen, halogen, C1-C6 alkyl unsubstituted or substituted with R a , C6-C a aryl unsubstituted or substituted with R 12 ;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;

[0011] 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;

[0012] R5 is selected from

[0013] 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;

[0014] 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.

[0015] 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.

[0016] In one embodiment of this application, R1 is selected from fluorine, unsubstituted or fluorine-substituted C1-C4 alkyl groups;

[0017] R2 is selected from nitrogen or phenylene;

[0018] 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 Rc each independently selected from the group consisting of C1-C4 alkyl unsubstituted or substituted with fluorine, C2-C4 alkenyl unsubstituted or substituted with fluorine, C2-C4 alkynyl unsubstituted or substituted with fluorine, cyano, phenyl unsubstituted or substituted with fluorine;

[0019] R6is selected from the group consisting of hydrogen, C1-C4 alkyl unsubstituted or substituted with fluorine, C2-C4 alkenyl unsubstituted or substituted with fluorine, C2-C4 alkynyl unsubstituted or substituted with fluorine, cyano, phenyl unsubstituted or substituted with fluorine;

[0020] R d or R e each independently selected from the group consisting of hydrogen, C1-C4 alkyl unsubstituted or substituted with fluorine, C2-C4 alkenyl unsubstituted or substituted with fluorine, C2-C4 alkynyl unsubstituted or substituted with fluorine, cyano, phenyl unsubstituted or substituted with fluorine;

[0021] R f is selected from the group consisting of C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl; n is 0, 1, 2 or 3.

[0022] In an embodiment of the present application, the first component is selected from at least one of the following compounds:

[0023] In an embodiment of the present application, the second component is selected from at least one of the following compounds:

[0024] In an embodiment of the present application, the electrolyte additive further comprises a third component selected from at least one of vinylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, ethylene sulfate, 1,3-propane sultone, 1,3-propene sultone, ethylene sulfite, tris(trimethylsilyl)borate, lithium bis(oxalato)borate, lithium bisfluoride oxalate borate and lithium difluoride dioxalate phosphate.

[0025] In an embodiment of the present application, the mass ratio of the second component and the third component is (0.01-1.5):1, preferably (0.1-0.5):1.

[0026] The second aspect of the present application provides an electrolyte comprising the electrolyte additive of the first aspect of the present application; the mass percentage of the electrolyte additive in the electrolyte is 1% to 15%, preferably 3% to 8%, based on the mass of the electrolyte.

[0027] In an embodiment of the present application, at least one of the following features is satisfied:

[0028] (1) the mass percentage of the first component is A, 0.1%≤A≤2%, preferably 0.5%≤A≤1.5%, based on the mass of the electrolyte;

[0029] (2) the mass percentage of the second component is B based on the mass of the electrolyte, 0.1%≤B≤1.5%, preferably 0.5%≤B≤1%;

[0030] (3) the mass percentage of the third component is C based on the mass of the electrolyte, 1%≤C≤10%, preferably 3%≤C≤5%.

[0031] The third aspect of the present application provides a secondary battery, which comprises a positive electrode sheet, a negative electrode sheet, a separator and the electrolyte of the second aspect of the present application; wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode material layer arranged on at least one surface of the negative electrode current collector, the negative electrode material layer comprises a negative electrode active material selected from at least one of a silicon-based material, a carbon-based material and a lithium-containing metal composite oxide; the positive electrode sheet comprises a positive electrode current collector and a positive electrode material layer arranged on at least one surface of the positive electrode current collector, the positive electrode material layer comprises a positive electrode active material selected from at least one of lithium manganate, lithium nickel cobalt manganate ternary material, lithium nickel manganate, lithium-rich manganese-based material and lithium cobaltate.

[0032] The beneficial effects of the present application are as follows:

[0033] The present application provides an electrolyte additive, an electrolyte and a secondary battery. The electrolyte additive of the present application comprises a first component and a second component. When applied to an electrolyte, the first component alone generates a large amount of lithium-containing inorganic components (including lithium fluoride, lithium sulfate, etc.), which improves the high-temperature stability of the solid electrolyte interface film, but also causes the impedance of the solid electrolyte interface film to increase. However, the addition of the second component in the electrolyte additive can eliminate part of the lithium-containing inorganic components, and the silicon-oxygen component in the second component can replace the negative effects of the reduced stability caused by the reduction of lithium-containing inorganic components, thereby reducing the impedance without affecting the stability of the solid electrolyte interface film, and also providing a lithium ion channel to accelerate the transport of lithium ions. In addition, the second component can also eliminate by-products in the electrolyte and reduce the gas production problem caused by the first component. The electrolyte additive of the present application comprises the first component and the second component, and the synergistic effect of the first component and the second component can improve the high-temperature storage performance and cycle life of the secondary battery.

[0034] Preferably, the electrolyte additive of the present application can further comprise a third component, which can generate a flexible solid electrolyte interface film with good compatibility with the lithium-containing inorganic components formed by the first component, thereby improving the flexibility and stability of the solid electrolyte interface film (the third component can generate a flexible solid electrolyte interface film, and a large amount of lithium-containing inorganic components generated by the first component can serve as a skeleton to improve stability), and can better isolate the side reactions at the interface of the battery. At the same time, the second component can eliminate part of the lithium-containing inorganic components, and the silicon-oxygen component in the second component can replace the negative effects of the reduced stability caused by the reduction of lithium-containing inorganic components, thereby reducing the impedance without affecting the stability of the solid electrolyte interface film, and also providing a lithium ion channel to accelerate the transport of lithium ions. Preferably, the electrolyte additive of the present application comprises the first component, the second component and the third component, and the synergistic effect of the first component, the second component and the third component can better improve the high-temperature storage performance and cycle life of the secondary battery.

[0035] Of course, implementing any product or method of the present application does not necessarily require achieving all the advantages described above at the same time. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the present application are within the scope of protection of the present application.

[0037] The first aspect of the present application provides an electrolyte additive comprising a first component and a second component;

[0038] The first component is selected from the compound shown in formula I;

[0039] The second component is selected from the compound shown in formula II;

[0040] wherein R1 is selected from halogen, C1-C6 alkyl which is unsubstituted or substituted by halogen;

[0041] R2 is selected from nitrogen or C6-C 12 arylene;

[0042] R3 or R4 is each independently selected from hydrogen, halogen, C1-C6 alkyl which is unsubstituted or substituted by R a , C6-C a aryl which is unsubstituted or substituted by R 12 , sulfonyl which is unsubstituted or substituted by R a ; the substituents R aeach independently selected from the group consisting of halogen, unsubstituted or halogen-substituted Ci-C6-alkyl, C6-Cio-aryl, 12 aryl, Ci-C2-alkoxy, C2-C6-alkenyl, cyano, substituents R b or R c each independently selected from the group consisting of unsubstituted or halogen-substituted Ci-C6-alkyl;

[0043] R6is selected from the group consisting of hydrogen, unsubstituted or halogen-substituted Ci-C6-alkyl, unsubstituted or halogen-substituted C2-C6-alkenyl, unsubstituted or halogen-substituted C2-C6-alkynyl, cyano, unsubstituted or halogen-substituted C6-Cio-aryl; 12 aryl;

[0044] R5is selected from the group consisting of

[0045] R d or R e each independently selected from the group consisting of hydrogen, unsubstituted or halogen-substituted Ci-C6-alkyl, unsubstituted or halogen-substituted C2-C6-alkenyl, unsubstituted or halogen-substituted C2-C6-alkynyl, cyano, unsubstituted or halogen-substituted C6-Cio-aryl; 12 aryl;

[0046] R f selected from the group consisting of unsubstituted or halogen-substituted Ci-C6-alkyl, unsubstituted or halogen-substituted C2-C6-alkenyl, unsubstituted or halogen-substituted C2-C6-alkynyl; n is 0, 1, 2, 3, 4 or 5.

[0047] The first component of the present application is a sulfonyl additive, the S-C bond or S-N bond in the additive is easy to break, generating lithium-containing inorganic components (including LiF and Li2SO4 components) that are beneficial to improve the solid electrolyte interface film. The solid electrolyte interface film can also prevent the dissolution of transition metal ions and reduce the side reactions between the battery interfaces; but the additive is prone to hydrolysis, which can generate components that destroy the solid electrolyte interface film. In addition, the breaking of the S-N bond or S-C bond also generates by-products that are easy to decompose and produce gas, which greatly affects the high-temperature performance of the battery. The second component of the present application is an effective film-forming additive that can participate in the construction of a stable solid electrolyte interface film, eliminate HF / H2O in the electrolyte, and reduce the destructive effect of HF on the electrode material. The additive molecule contains a silane component, which can eliminate the LiF component in the interface film, remove excess LiF components to reduce battery impedance, and the large number of Si-O bonds in the second component have good stability, so the negative effects caused by the elimination of LiF can also be offset. The electrolyte additive of the present application simultaneously includes the first component and the second component, the second component can eliminate part of the lithium-containing inorganic components generated by the first component, and the silicon-oxygen component in the second component can replace the negative effects of the reduced stability caused by the reduction of lithium-containing inorganic components, thereby improving the high-temperature storage performance and cycle life of the secondary battery without affecting the stability of the solid electrolyte interface film, while also providing lithium ion channels and accelerating the transport of lithium ions. In addition, the second component can also eliminate by-products in the electrolyte and reduce the gas production problem caused by the first component. In summary, the electrolyte additive of the present application simultaneously includes the first component and the second component, and the synergistic effect of the first component and the second component can improve the high-temperature storage performance and cycle life of the secondary battery.

[0048] In an embodiment of the present application, the mass ratio of the first component and the second component is (0.05-20):1, preferably (0.5-3):1. For example, the mass ratio of the first component and 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 composed of any two of the above values. By limiting the mass ratio of the first component and the second component within the above range, the first component and the second component can better play a synergistic effect, further improving the high-temperature storage performance and cycle life of the secondary battery.

[0049] In the present application, the term "halogen" means a fluorine, chlorine, bromine or iodine atom.

[0050] In an embodiment of the present application, R1 is selected from fluorine, C1-C4 alkyl unsubstituted or substituted with fluorine;

[0051] R2 is selected from nitrogen or phenylene;

[0052] 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;

[0053] 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.

[0054] 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.

[0055] R f Selected from C1-C4 alkyl, C2-C4 alkenyl, and C2-C4 alkynyl; n is 0, 1, 2, or 3.

[0056] 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.

[0057] In one embodiment of this application, the first component is selected from at least one of the following compounds;

[0058] 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.

[0059] In one embodiment of this application, the second component is selected from at least one of the following compounds;

[0060] 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.

[0061] In an embodiment of the present application, the electrolyte additive further comprises a third component selected from at least one of vinylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, ethylene sulfate, 1,3-propane sultone, 1,3-propene sultone, ethylene sulfite, tris(trimethylsilyl)borate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, and lithium difluorophosphate bis(oxalate).

[0062] The electrolyte additive of the present application further comprises a third component, the ester additive of the third component can generate a flexible solid electrolyte interface film, which can better isolate the side reactions of the battery interface, and also can reduce the expansion of silicon particles, improve the stability of the cycle, the salt additive can generate more lithium-containing components on the surface of the interface film, which is conducive to the transport of lithium ions, and also fills the interface film, making it more dense. The first component, the second component and the third component are used together to form a dense interface film which can better isolate the dissolution of transition metal ions. In summary, the electrolyte additive of the present application simultaneously comprises the first component, the second component and the third component, and the synergistic effect of the first component, the second component and the third component can better improve the high-temperature storage performance and cycle life of the secondary battery.

[0063] In an embodiment of the present 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 formed by any two of the above values. By limiting the mass ratio of the first component, the second component and the third component within the above range, the first component, the second component and the third component can better play a synergistic effect, and further improve the high-temperature storage performance and cycle life of the secondary battery.

[0064] The second aspect of the present application provides an electrolyte comprising the electrolyte additive of the first aspect of the present 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 formed by any two of the above values, based on the mass of the electrolyte. The amount of electrolyte additive within the above range can make the secondary battery have higher high-temperature storage performance and cycle life without affecting other performances.

[0065] In an embodiment of the present application, the first component has a mass percentage A based on the mass of the electrolyte, and 0.1%≤A≤2%, preferably 0.5%≤A≤1.5%. For example, the mass percentage A of the first component based on the mass of the electrolyte can be 0.1%, 0.5%, 1%, 1.5%, or a range defined by any two of these values.

[0066] In an embodiment of the present application, the second component has a mass percentage B based on the mass of the electrolyte, and 0.1%≤B≤1.5%, preferably 0.5%≤B≤1%. 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 defined by any two of these values.

[0067] In an embodiment of the present application, the third component has a mass percentage C based on the mass of the electrolyte, and 1%≤C≤10%, preferably 3%≤C≤5%. For example, the mass percentage C of the third component based on the mass of the electrolyte can be 1%, 3%, 5%, 8%, 10%, or a range defined by any two of these values.

[0068] In addition to the first additive and the second additive, the third additive is further added and limited in the scope of the present application, which can better play the synergistic effect between the components while not affecting other properties, and further improve the high-temperature storage performance and cycle life of the secondary battery.

[0069] In an embodiment of the present application, the electrolyte further comprises a lithium salt, which is not particularly limited in the present application as long as the purpose of the present application can be achieved. For example, the lithium salt can include, but is not limited to, at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bisfluorosulfonylimide, and lithium bistrifluoromethanesulfonylimide.

[0070] The content of the lithium salt in the electrolyte is not particularly limited in the present application as long as the purpose of the present application can be achieved. For example, the mass percentage of the lithium salt based on the mass of the electrolyte is 10% to 15%, preferably 12% to 15%.

[0071] In an embodiment of the present application, the electrolyte further comprises a non-aqueous solvent. The present application does not have a particular limitation on the non-aqueous solvent as long as the purpose of the present application can be achieved. For example, the non-aqueous solvent can be selected from, but is not limited to, at least one of propylene carbonate, methyl ethyl 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.

[0072] The present application does not have a particular limitation on the content of the non-aqueous solvent in the electrolyte as long as the purpose of the present application can be achieved. For example, the mass percentage of the non-aqueous solvent is 72% to 88%, preferably 78% to 84%, based on the mass of the electrolyte.

[0073] The preparation method of the electrolyte of the present application does not have a particular limitation as long as the purpose of the present application can be achieved. For example, the various solvents in the electrolyte can be mixed, and then the electrolyte lithium salt and additives and other substances are added and uniformly mixed.

[0074] The third aspect of the present application provides a secondary battery, which comprises a positive electrode sheet, a negative electrode sheet, a separator, and the electrolyte of the second aspect of the present application; wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode material layer arranged on at least one surface of the negative electrode current collector, the negative electrode material layer comprises a negative electrode active material, and the negative electrode active material is selected from at least one of a silicon-based material, a carbon-based material, and a lithium-containing metal composite oxide; the positive electrode sheet comprises a positive electrode current collector and a positive electrode material layer arranged on at least one surface of the positive electrode current collector, the positive electrode material layer comprises a positive electrode active material, and the positive electrode active material is selected from at least one of lithium manganate, lithium nickel cobalt manganate ternary material, lithium nickel manganate, lithium-rich manganese-based material, and lithium cobaltate.

[0075] The present application does not have a particular limitation on the silicon-based material, the carbon-based material, or the lithium-containing metal composite oxide as long as the purpose of the present application can be achieved. For example, the silicon-based material can include, but is not limited to, at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys; the carbon-based material can include, but is not limited to, at least one of artificial graphite, natural graphite, soft carbon, hard carbon, and mesophase carbon microbeads; and the lithium-containing metal composite oxide can include, but is not limited to, at least one of lithium titanate and metallic lithium.

[0076] The use of the positive electrode active material and the negative electrode active material of the present application matches the electrolyte additive of the present application, further improving the high-temperature storage performance and cycle life of the secondary battery.

[0077] It should be noted that in the specific embodiments of the present application, the present application is explained by taking lithium ion batteries as an example of secondary batteries, but the secondary batteries of the present application are not limited to lithium ion batteries. The specific technical solutions are as follows:

[0078] The conductive agent of the present application is not particularly limited as long as the purpose of the present application can be achieved, for example, the conductive agent can be selected from, but not limited to, at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. The above-mentioned carbon nanotubes can include, but not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The above-mentioned carbon fibers can include, but not limited to, vapor grown carbon fibers (VGCF) and / or nanocarbon fibers.

[0079] The binder of the present application is not particularly limited as long as the purpose of the present application can be achieved, for example, the binder can be selected from, but not limited to, at least one of 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), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.

[0080] In the present application, the above-mentioned "positive electrode material layer provided on at least one surface of the positive electrode current collector" means that the positive electrode material layer can be provided on one surface of the positive electrode current collector along the thickness direction of the positive electrode current collector, or can be provided on two surfaces of the positive electrode current collector along the thickness direction of the positive electrode current collector. It should be noted that the "surface" here can be the entire area of the surface of the positive electrode current collector, or can be part of the area of the surface of the positive electrode current collector, and the present application is not particularly limited as long as the purpose of the present application can be achieved.

[0081] The positive electrode current collector of the present application is not particularly limited as long as the purpose of the present application can be achieved, for example, the positive electrode current collector can adopt a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil, an aluminum alloy foil, a carbon-coated aluminum foil can be used. The composite current collector can include a high molecular material base layer and a metal layer formed on at least one surface of the high molecular material base layer. 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 high molecular material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0082] The positive electrode material layer can further include a conductive agent and a binder. The kind of the conductive agent and the binder is not particularly limited in the present application as long as the purpose of the present application can be achieved, for example, can be at least one of the above-mentioned conductive agent and the above-mentioned binder. The mass ratio of the positive electrode active material, the conductive agent, and the binder in the positive electrode material layer is not particularly limited in the present application, and can be selected by a person skilled in the art according to actual needs as long as the purpose of the present application can be achieved.

[0083] The thickness of the positive electrode current collector and the positive electrode material layer is not particularly limited in the present application as long as the purpose of the present application can be achieved. For example, the thickness of the positive electrode current collector is 5 μm to 20 μm, and the thickness of the single-sided positive electrode material layer is 20 μm to 90 μm.

[0084] Optionally, the positive electrode sheet can further include a conductive layer, and the conductive layer is located between the positive electrode current collector and the positive electrode material layer. The composition of the conductive layer is not particularly limited and can be a commonly used conductive layer in the art. The conductive layer includes a conductive agent and a binder. The conductive agent and the binder in the conductive layer are not particularly limited in the present application, for example, can be at least one of the above-mentioned conductive agent and the above-mentioned binder.

[0085] In an embodiment of the present application, the compaction density of the positive electrode sheet is 2 g / cm 3 ~ 5 g / cm 3 .

[0086] In the present application, the secondary battery further includes a separator. The separator is not particularly limited in the present application as long as the purpose of the present application can be achieved. For example, the material of the separator can be selected from, but not limited to, at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The number of layers of the separator is not particularly limited in the present application as long as the purpose of the present application can be achieved, for example, the separator can be a single-layer film or a multi-layer composite film.

[0087] In some embodiments of the present application, the separator can include a substrate layer and a surface treatment layer. The substrate layer is not particularly limited in the present application as long as the purpose of the present application can be achieved. For example, the substrate layer can be selected from, but not limited to, at least one of polyethylene, polypropylene, polyvinylidene fluoride, and polyacrylonitrile.

[0088] Optionally, a surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer is not particularly limited in the present application as long as the purpose of the present application can be achieved. For example, the surface treatment layer can be selected from, but not limited to, at least one of conductive carbon, aluminum trioxide, and Li 6.4 La3Zr 1.4 Ta 0.6 O 12 (LLZTO).

[0089] In the present application, the thickness of the separator is not particularly limited as long as the object of the present application can be achieved, for example, the thickness of the separator can be 5 μm to 10 μm.

[0090] In the present application, the above-mentioned "the negative electrode material layer provided on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be provided on one surface of the negative electrode current collector along the thickness direction of the negative electrode current collector, or can be provided on two surfaces of the negative electrode current collector along the thickness direction of the negative electrode current collector. It should be noted that the "surface" here can be the entire area of the surface of the negative electrode current collector, or can be part of the area of the surface of the negative electrode current collector, and the present application is not particularly limited as long as the object of the present application can be achieved.

[0091] The present application does not particularly limit the negative electrode current collector as long as the object of the present application can be achieved, for example, the negative electrode current collector can adopt a metal foil or a composite current collector. For example, as the metal foil, a copper foil, an aluminum alloy foil can be used. The composite current collector can include a high polymer material base layer and a metal layer formed on at least one surface of the high polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, etc.) on a high polymer material base layer (such as a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0092] In some embodiments of the present application, the negative electrode material layer can further include a conductive agent and a binder, and the present application does not particularly limit the types of the conductive agent and the binder as long as the object of the present application can be achieved, for example, at least one of the above-mentioned conductive agent and the above-mentioned binder. The mass ratio of the negative electrode active material, the conductive agent, and the binder in the negative electrode material layer is not particularly limited, and a person skilled in the art can select according to actual needs as long as the object of the present application can be achieved.

[0093] In some embodiments of the present application, the negative electrode material layer can further include a conductive agent, a binder, and a thickening agent, and the present application does not particularly limit the types of the conductive agent and the binder as long as the object of the present application can be achieved, for example, the conductive agent and the binder can be at least one of the above-mentioned conductive agent and the above-mentioned binder. The thickening agent can include but is not limited to at least one of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose. The mass ratio of the negative electrode active material, the conductive agent, the binder, and the thickening agent in the negative electrode material layer is not particularly limited, and a person skilled in the art can select according to actual needs as long as the object of the present application can be achieved.

[0094] The present application does not particularly limit the thickness of the negative electrode material layer as long as the object of the present application can be achieved, for example, the thickness of the single-sided negative electrode material layer is 30 μm to 125 μm.

[0095] The thickness of the negative current collector is not particularly limited in the present application, as long as the object of the present application can be achieved. For example, the thickness of the negative current collector is 4 μm to 10 μm.

[0096] Optionally, the negative electrode tab can further comprise a conductive layer, which is located between the negative current collector and the negative material layer. The composition of the conductive layer is not particularly limited in the present application, and can be a conductive layer commonly used in the art. For example, the conductive layer comprises a conductive agent and a binder. The conductive agent and the binder in the conductive layer are not particularly limited in the present application, and can be at least one of the above-mentioned conductive agent and the above-mentioned binder.

[0097] In some embodiments of the present application, the compaction density of the negative electrode tab is 1 g / cm 3 ~ 4 g / cm 3 .

[0098] The secondary battery further comprises a housing for accommodating the positive electrode tab, the separator, the negative electrode tab and the electrolyte, and other components known in the art of secondary batteries, which are not limited in the present application. The housing is not particularly limited in the present application, and can be a housing known in the art, as long as the object of the present application can be achieved. For example, the housing can be a hard-shell housing or a flexible housing. The material of the hard-shell housing can be metal, and the type of metal is not limited in the present application, and a metal hard-shell housing known in the art can be used, as long as the object of the present application can be achieved. The flexible housing can be a metal plastic film, such as an aluminum plastic film, a steel plastic film, etc.

[0099] The preparation process of the secondary battery of the present application is well known to those skilled in the art, and is not particularly limited in the present application. For example, the preparation process of the secondary battery can comprise, but is not limited to, the following steps: stacking the positive electrode tab, the separator and the negative electrode tab in order, and performing operations such as winding, folding, etc. according to the need to obtain a wound electrode assembly, placing the electrode assembly into the housing, injecting the electrolyte into the housing and sealing, forming, sorting to obtain the secondary battery.

[0100] In some embodiments of the present application, the secondary battery of the present application can be suitable for a high-voltage system, with a voltage range of 4.2-4.6 V.

[0101] The fourth aspect of the present application provides an electronic device comprising the secondary battery of the third aspect of the present application.

[0102] The electronic device of the present application is not particularly limited, and it can be any electronic device known in the art. In some embodiments, the electronic device can include, but is not limited to, a notebook computer, a pen input type computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile machine, a portable copying machine, a portable printer, a head-mounted stereo headphone, a video recorder, a liquid crystal television, a hand-held cleaner, a portable CD player, a mini disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable audio player, a radio, a backup power supply, an electric motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, a lighting appliance, a toy, a game machine, a timepiece, an electric power tool, a flash, a camera, a household large storage battery, or a lithium ion capacitor, etc.

[0103] Embodiments

[0104] Hereinafter, embodiments and comparative examples are presented to more specifically describe the embodiments of the present application. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are on a mass basis.

[0105] Test methods and apparatus:

[0106] Normal temperature cycle performance test

[0107] The lithium ion battery was placed in a 25°C constant temperature test chamber, and allowed to stand for 30 minutes to bring the lithium ion battery to a constant temperature. The lithium ion battery was charged at 1.0 C constant current to 4.4 V, and then charged at constant voltage of 4.4 V to a cutoff current of 0.05 C, allowed to stand for 5 minutes, and discharged at 1.0 C constant current to 2.75 V, and the discharge capacity C1 was recorded. This step was repeated for 500 cycles, and the discharge capacity C2 after 500 cycles was recorded, and the cycle capacity retention rate of the lithium ion battery was calculated. Normal temperature cycle capacity retention rate = C2 / C1 x 100%.

[0108] High temperature cycle performance test

[0109] The lithium ion battery was placed in a 45°C constant temperature test chamber, and allowed to stand for 60 minutes to bring the lithium ion battery to a constant temperature. The lithium ion battery was charged at 1.0 C constant current to 4.4 V, and then charged at constant voltage of 4.4 V to a cutoff current of 0.05 C, allowed to stand for 5 minutes, and discharged at 1.0 C constant current to 2.75 V, and the discharge capacity C3 was recorded. This step was repeated for 300 cycles, and the discharge capacity C4 after 300 cycles was recorded, and the cycle capacity retention rate of the lithium ion battery was calculated. High temperature cycle capacity retention rate = C4 / C3 x 100%.

[0110] High temperature storage performance test

[0111] 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%.

[0112] High-temperature storage DC internal resistance (DCIR) growth rate

[0113] 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 ).

[0114] 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... 2C Discharge 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 ).

[0115] DC internal resistance (DCIR) growth rate = (DCIR2 - DCIR1) / DCIR1 × 100%.

[0116] Example 1-1

[0117] <Preparation of Electrolyte>

[0118] In an argon atmosphere glove box (water content <10 ppm, oxygen content <1 ppm), non-aqueous organic solvents ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) were mixed uniformly in a mass ratio of 3:5:2, then the first component compound of formula I-1 and the second component compound of formula II-1 were mixed uniformly, and then lithium salt lithium hexafluorophosphate was added, dissolved and mixed uniformly to obtain an electrolyte; wherein the mass percentage of lithium salt lithium hexafluorophosphate in the electrolyte was 12.5%, the mass percentage of the first component compound of formula I-1 was A 0.05%, the mass percentage of the second component compound of formula II-1 was B 1%, and the balance was a non-aqueous organic solvent.

[0119] <Preparation of the positive electrode sheet>

[0120] The positive electrode active material lithium nickel cobalt manganese oxide (NCM613), the binder polyvinylidene fluoride (PVDF), the conductive agent acetylene black, and the conductive agent single-walled carbon nanotube (SWCNT) were mixed in a mass ratio of 95:1.5:3:0.5, N-methyl pyrrolidone (NMP) was added as a solvent, and a slurry with a solid content of 65 wt% was prepared. After uniform stirring in a vacuum, a positive electrode slurry was obtained. The positive electrode slurry was uniformly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 16 μm. After baking in an oven with different temperature gradients (90°C, 100°C, and 85°C in turn) at a speed of 2200 mm / min, the positive electrode slurry was dried at 120°C to obtain a positive electrode sheet with a single-coated positive electrode material layer. Then, the above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-coated positive electrode material layer. After cutting and welding the tabs, a positive electrode sheet with a size of 258 mm x 54 mm was obtained for use. The tap density of the positive electrode material layer was 3.4 g / cm 3 , and the thickness of the single-coated positive electrode material layer was 37 μm.

[0121] <Preparation of the negative electrode sheet>

[0122] The negative electrode active material artificial graphite (BTR S360-L1), the thickening agent sodium carboxymethyl cellulose (CMC-Na), the binder styrene-butadiene rubber, and the conductive agent acetylene black were mixed in a mass ratio of 95:1.5:2:1.5, deionized water was added as a solvent, and a slurry with a solid content of 49 wt% was prepared. After uniform stirring in a vacuum, a negative electrode slurry was obtained. The negative electrode slurry was uniformly coated on one surface of a negative electrode current collector copper foil with a thickness of 9 μm. After drying at 85°C, a negative electrode sheet with a single-coated negative electrode material layer was obtained. Then, the above steps were repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-coated negative electrode material layer. After cutting and welding the tabs, a negative electrode sheet with a size of 264 mm x 58 mm was obtained for use. The tap density of the negative electrode material layer was 1.5 g / cm 3The thickness of the single-sided negative electrode material layer is 50 μm.

[0123] <Preparation of the separator>

[0124] Polyethylene (provided by Star Source Material Co., Ltd.) with a thickness of 8 μm was used as the separator.

[0125] <Preparation of the lithium ion battery>

[0126] The positive electrode sheet, the separator, and the negative electrode sheet prepared above were stacked in order with the separator between the positive electrode sheet and the negative electrode sheet to play a role of isolation, and then were wound. The positive tab was connected to the positive electrode sheet, and the negative tab was connected to the negative electrode sheet to obtain an electrode assembly. The electrode assembly was put into an aluminum plastic film, and the positive tab and the negative tab were led out from the inside space of the aluminum plastic film to the outside space of the aluminum plastic film. After water was removed at 85°C, the electrolyte prepared above was injected. After vacuum sealing and standing for 24 hours, a pressure of 3 kg / cm2was applied at 45°C to perform formation by charging at 0.1C for 6.5 hours. Then, the lithium ion battery was obtained by sorting (charging at 0.1C to 4.4V, then charging at 4.4V to the cut-off current of 0.05C, standing for 5 minutes, discharging at 0.5C to 2.75V; charging at 0.5C to 4.4V, then charging at 4.4V to the cut-off current of 0.05C, standing for 5 minutes, discharging at 1.0C to 2.75V; charging at 1.0C to 4.4V, then charging at 4.4V to the cut-off current of 0.05C, standing for 5 minutes, discharging at 1.0C to 2.75V). 2

[0127] Examples 1-2 to 1-41

[0128] Except that the types and mass percentages of the first component and the second component were adjusted according to Table 1 in the preparation of the electrolyte, the mass percentage of the non-aqueous organic solvent changed accordingly, and the mass percentage of the lithium salt remained unchanged, the rest was the same as in Example 1-1.

[0129] Example 1-42

[0130] <Preparation of the electrolyte>

[0131] ​In an argon atmosphere glove box (water content <10 ppm, oxygen content <1 ppm), non-aqueous organic solvent ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) were mixed uniformly in a mass ratio of 3:5:2, then the first component compound of formula I-1 and the second component compound of formula II-1 were mixed uniformly, and then lithium salt lithium hexafluorophosphate was added, dissolved and mixed uniformly to obtain an electrolyte; wherein the mass percentage of lithium salt lithium hexafluorophosphate in the electrolyte is 12.5%, the mass percentage of the first component compound of formula I-1 is A 0.5%, the mass percentage of the second component compound of formula II-1 is B 0.5%, and the balance is a non-aqueous organic solvent.

[0132] <Preparation of positive electrode sheet>

[0133] The positive active material lithium cobaltate, the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black were mixed in a mass ratio of 97.3:1.2:1.5, N-methyl pyrrolidone (NMP) was added as a solvent, and a slurry with a solid content of 68.4 wt% was prepared. After uniform vacuum stirring, a positive electrode slurry was obtained. The positive electrode slurry was uniformly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 16 μm. After baking in an oven with different temperature gradients (90°C, 100°C, 85°C in turn) at a speed of 2200 mm / min, the positive electrode slurry was dried at 120°C to obtain a positive electrode sheet with a single-coated positive electrode material layer. Then the above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-coated positive electrode material layer. After cutting and welding the tabs, a positive electrode sheet with a size of 558 mm x 55 mm was obtained for use. The tap density of the positive electrode material layer was 4.15 g / cm 3 , and the thickness of the single-coated positive electrode material layer was 36 μm.

[0134] <Preparation of negative electrode sheet>

[0135] The negative active material artificial graphite (BTR S360-L1), thickening agent carboxymethyl cellulose sodium (CMC-Na), binder styrene-butadiene rubber, conductive agent acetylene black, and conductive agent single-walled carbon nanotube (SWCNT) were mixed in a mass ratio of 95.9:1:2:1:0.1, deionized water was added as a solvent, and a slurry with a solid content of 49 wt% was prepared. After uniform vacuum stirring, a negative electrode slurry was obtained. The negative electrode slurry was uniformly coated on one surface of a negative electrode current collector copper foil with a thickness of 9 μm, and dried at 85°C to obtain a negative electrode sheet with a single-coated negative electrode material layer. Then the above steps were repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-coated negative electrode material layer. After cutting and welding the tabs, a negative electrode sheet with a size of 708 mm x 59 mm was obtained for use. The tap density of the negative electrode material layer was 1.6 g / cm 3The thickness of the single-sided negative electrode material layer is 63.5 μm.

[0136] <Preparation of the separator>

[0137] Polyethylene (provided by Star Source Material Co.) with a thickness of 8 μm was used as the separator.

[0138] <Preparation of the lithium ion battery>

[0139] The positive electrode sheet, the separator, and the negative electrode sheet prepared above were stacked in order with the separator between the positive electrode sheet and the negative electrode sheet to play a role of isolation, and then were wound. The positive tab was connected to the positive electrode sheet, and the negative tab was connected to the negative electrode sheet to obtain an electrode assembly. The electrode assembly was put into an aluminum plastic film, and the positive tab and the negative tab were led out from the inside space of the aluminum plastic film to the outside space of the aluminum plastic film. After water was removed at 85 °C, the electrolyte prepared above was injected. After vacuum sealing and standing for 24 hours, a pressure of 3 kg / cm2was applied at 45 °C to perform formation by charging at 0.1 C for 6.5 hours, and then the lithium ion battery was obtained by sorting (charging at 0.1 C to 4.4 V, then charging at 4.4 V to the cut-off current of 0.05 C, standing for 5 minutes, discharging at 0.5 C to 2.75 V; charging at 0.5 C to 4.4 V, then charging at 4.4 V to the cut-off current of 0.05 C, standing for 5 minutes, discharging at 1.0 C to 2.75 V; charging at 1.0 C to 4.4 V, then charging at 4.4 V to the cut-off current of 0.05 C, standing for 5 minutes, discharging at 1.0 C to 2.75 V). 2

[0140] Examples 2-1 to 2-23

[0141] Except that the third component was added in <Preparation of the electrolyte> according to Table 2, 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 was unchanged, the rest was the same as Example 1-7.

[0142] Comparative Example 1

[0143] Except that the second component was not added in <Preparation of the electrolyte>, and the mass percentage of the first component was adjusted according to Table 1, the mass percentage of the non-aqueous organic solvent was changed accordingly, and the mass percentage of the lithium salt was unchanged, the rest was the same as Example 1-1.

[0144] Comparative Example 2

[0145] ​The same as Example 1-1 except that the first component was not added in the preparation of the electrolyte, the mass percentage of the second component was adjusted according to Table 1, the mass percentage of the non-aqueous organic solvent was changed accordingly, and the mass percentage of the lithium salt was unchanged.

[0146] Comparative Example 3

[0147] The same as Example 1-42 except that the first component was not added in the preparation of the electrolyte, the mass percentage of the second component was adjusted according to Table 1, the mass percentage of the non-aqueous organic solvent was changed accordingly, and the mass percentage of the lithium salt was unchanged.

[0148] Comparative Example 4

[0149] The same as Example 1-42 except that the second component was not added in the preparation of the electrolyte, the mass percentage of the first component was adjusted according to Table 1, the mass percentage of the non-aqueous organic solvent was changed accordingly, and the mass percentage of the lithium salt was unchanged.

[0150] The preparation parameters and performance parameters of each example and comparative example are shown in Table 1 to Table 2.

[0151] As can be seen from Example 1-1 to Example 1-42 and Comparative Example 1 to Comparative Example 4, the electrolyte with only the first component or the second component added is applied to a lithium ion battery, and the lithium ion battery has a low room temperature cycle capacity retention rate, a high temperature cycle capacity retention rate, a high temperature storage capacity retention rate, a high high temperature storage thickness expansion rate, and a high high temperature storage DCIR increase rate. The electrolyte with the first component and the second component added is applied to a lithium ion battery, and the lithium ion battery has a high room temperature cycle capacity retention rate, a high temperature cycle capacity retention rate, a high temperature storage capacity retention rate, a low high temperature storage thickness expansion rate, and a low high temperature storage DCIR increase rate. The above results show that the combination of the first component and the second component can improve the high temperature storage performance and cycle life of the lithium ion battery.

[0152] As can be seen from Example 1-7, Example 2-1 to Example 2-23, the electrolyte with the first component, the second component and the third component added is applied to a lithium ion battery, and the lithium ion battery has a higher room temperature cycle capacity retention rate, a higher temperature cycle capacity retention rate, and a higher temperature storage capacity retention rate, a lower high temperature storage thickness expansion rate, and a lower high temperature storage DCIR increase rate. The above results show that the combination of the first component, the second component and the third component makes the lithium ion battery have better high temperature storage performance and cycle life.

[0153] It is to be noted that, as used in this specification and the appended claims, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a component" can include a combination of two or more components, and the term "an element" can include comparable reference to a plurality of elements. Also, as used in this specification and the appended claims, the term "or" as used in the context of "A / B" or "A / B / C" means any of the possibilities; for example, the term "or" means "any of A, B, or C; or any of A, B, or C." Further, the term "comprising" or "comprises" as used in this specification and the appended claims, is inclusive or open and does not exclude additional, non-relevant elements or method steps. Thus, the term "comprising" or "comprises," as used in the claims, should not be interpreted as being restricted to security elements or steps referred to but should be interpreted to also cover the possibility of additional security elements or steps not referred to.

[0154] The foregoing is considered as illustrative only of the principles of the application. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the application to the exact construction and practice described. Accordingly, all such variations are intended to be included within the scope of the present application as defined in the following claims.

Claims

An electrolyte additive comprising a first component and a second component; said first component is selected from the group consisting of compounds of formula I; said second component is selected from the group consisting of compounds of formula II; wherein R1is selected from halogen, C1-C6alkyl unsubstituted or substituted with halogen; R2is selected from nitrogen or C6-Ci8-aryl; 12 heteroaryl; and R2is selected from nitrogen or C6-Ci8-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 substituents R b or R c each independently selected from C1-C6alkyl unsubstituted or substituted by halogen; 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; R5is 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 the group consisting of C1-C6alkyl, C2-C6alkenyl, C2-C6alkynyl, C3-C6cycloalkyl, C4-C8alkylcycloalkyl, C4-C8cycloalkylalkyl, C5-C10alkylcycloalkylalkyl, C6-C10cycloalkylcycloalkylalkyl, C3-C6cycloalkenyl, C4-C8alkylcycloalkenyl, C4-C8cycloalkylalkyl, C5-C10alkylcycloalkylalkyl, C6-C10cycloalkylcyc The electrolyte additive according to claim 1, wherein, The mass ratio of the first component and the second component is (0.05-20):1, preferably (0.5-3):

1. The electrolyte additive according to claim 1, wherein, R1is selected from fluorine, C1-C4alkyl unsubstituted or substituted with fluorine; R2is 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, substituents R b or R c each independently selected from C1-C4 alkyl unsubstituted or substituted by fluorine; R6is selected from hydrogen, C1-C4alkyl unsubstituted or substituted with fluorine, C2-C4alkenyl unsubstituted or substituted with fluorine, C2-C4alkynyl unsubstituted or substituted with fluorine, cyano, phenyl unsubstituted or substituted with fluorine; R d or R e each independently is selected from the group consisting of hydrogen, C1-C4-alkyl which is unsubstituted or substituted by fluorine, C2-C4-alkenyl which is unsubstituted or substituted by fluorine, C2-C4-alkynyl which is unsubstituted or substituted by fluorine, cyano, phenyl which is unsubstituted or substituted by fluorine; R f selected from the group consisting of C1-C4-alkyl, C2-C4-alkenyl, C2-C4-alkynyl; n is 0, 1, 2 or 3. The electrolyte additive according to claim 1, wherein, The first component is selected from at least one of the following compounds; The electrolyte additive according to claim 1, wherein, The second component is selected from at least one of the following compounds: The electrolyte additive according to claim 1, wherein, The electrolyte additive further comprises a third component selected from at least one of vinylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, ethylene sulfate, 1,3-propane sultone, 1,3-propene sultone, ethylene sulfite, tris(trimethylsilyl)borate, lithium bisoxalate borate, lithium difluoro oxalate borate, and lithium difluoro difoxalate phosphate. The electrolyte additive according to claim 6, wherein, The mass ratio of the second component and the third component is (0.01-1.5):1, preferably (0.1-0.5):

1. An electrolyte comprising the electrolyte additive according to any one of claims 1 to 7; the mass percentage content of the electrolyte additive is 1% to 15%, preferably 3% to 8%, based on the mass of the electrolyte. The electrolyte according to claim 8, which satisfies at least one of the following characteristics: (1) the mass percentage content of the first component is A, 0.1%≤A≤2%, preferably 0.5%≤A≤1.5%, based on the mass of the electrolyte; (2) the mass percentage content of the second component is B, 0.1%≤B≤1.5%, preferably 0.5%≤B≤1%, based on the mass of the electrolyte; (3) the mass percentage content of the third component is C, 1%≤C≤10%, preferably 3%≤C≤5%, based on the mass of the electrolyte. A secondary battery comprising a positive electrode sheet, a negative electrode sheet, a separator, and the electrolyte solution according to any one of claims 8 to 9; wherein, The negative electrode tab comprises a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, the negative electrode material layer comprising a negative electrode active material selected from at least one of silicon-based material, carbon-based material, and lithium-containing metal composite oxide; The positive electrode tab comprises a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector, the positive electrode material layer comprising a positive electrode active material selected from at least one of lithium manganate, lithium nickel cobalt manganese ternary material, lithium nickel manganate, lithium-rich manganese-based material, and lithium cobaltate.

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