Electrolyte of secondary battery, secondary battery and electronic device

Abstract

The invention provides an electrolyte of a secondary battery, the secondary battery and an electronic device. Wherein the electrolyte comprises a first component and a second component; the first component comprises a compound as shown in a formula I, and the second component comprises a compound as shown in a formula II. The electrolyte containing the first component and the second component at the same time is applied to the secondary battery, so that the cycle performance of the secondary battery is improved, and the electronic device has a relatively long service life. # imgabs0 #

Description

Technical Field

[0001] The present application relates to the field of electrochemistry technology, and particularly relates to an electrolyte for a secondary battery, a secondary battery, and an electronic device. Background Art

[0002] Secondary batteries, such as lithium-ion batteries, are widely used in mobile phones, laptops, tablets, drones, electric vehicles, power tools, power storage systems, etc. due to advantages such as high energy density, miniaturization, and lightweight.

[0003] With the development of modern information technology and the expansion of the application of electrochemical devices, the requirements for the cycle life of lithium-ion batteries are getting higher and higher. For example, it is required that lithium-ion batteries have high energy density, long life, and good cycle performance at the same time. However, while improving the energy density of lithium-ion batteries, the decomposition of the electrolyte is often accelerated, thereby affecting the service life and cycle performance of lithium-ion batteries. In view of this, developing a suitable electrolyte has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0004] The purpose of the present application is to provide an electrolyte for a secondary battery, a secondary battery, and an electronic device to improve the cycle performance of the secondary battery. The specific technical solutions are as follows:

[0005] In the first aspect of the present application, an electrolyte for a secondary battery is provided, which includes a first component and a second component;

[0006] The first component includes a compound represented by Formula I;

[0007]

[0008] Wherein, R is selected from unsubstituted or R-substituted C2-C6 alkyl, unsubstituted or R-substituted C2-C6 alkenyl, unsubstituted or R-substituted C2-C6 alkynyl, unsubstituted or R-substituted C5-C nitrogen-containing heteroaryl, unsubstituted or R-substituted C6-C aryl; the substituents R of each group are independently selected from fluorine or fluorine-substituted C1-C6 alkyl; a substituted C2-C6 alkyl, unsubstituted or R-substituted C2-C6 alkenyl, unsubstituted or R-substituted C2-C6 alkynyl, unsubstituted or R-substituted C5-C nitrogen-containing heteroaryl, unsubstituted or R-substituted C6-C aryl; the substituents R of each group are independently selected from fluorine or fluorine-substituted C1-C6 alkyl; a substituted C2-C6 alkenyl, unsubstituted or R-substituted C2-C6 alkynyl, unsubstituted or R-substituted C5-C nitrogen-containing heteroaryl, unsubstituted or R-substituted C6-C aryl; the substituents R of each group are independently selected from fluorine or fluorine-substituted C1-C6 alkyl; a substituted C2-C6 alkynyl, unsubstituted or R-substituted C5-C nitrogen-containing heteroaryl, unsubstituted or R-substituted C6-C aryl; the substituents R of each group are independently selected from fluorine or fluorine-substituted C1-C6 alkyl; a substituted C5-C nitrogen-containing heteroaryl, unsubstituted or R-substituted C6-C aryl; the substituents R of each group are independently selected from fluorine or fluorine-substituted C1-C6 alkyl; 12 nitrogen-containing heteroaryl, unsubstituted or R-substituted C6-C aryl; the substituents R of each group are independently selected from fluorine or fluorine-substituted C1-C6 alkyl; a substituted C6-C aryl; the substituents R of each group are independently selected from fluorine or fluorine-substituted C1-C6 alkyl; 12 aryl; the substituents R of each group are independently selected from fluorine or fluorine-substituted C1-C6 alkyl; a each independently selected from fluorine or fluorine-substituted C1-C6 alkyl;

[0009] The second component includes a compound represented by Formula II;

[0010]

[0011] R1 and R2 are each independently selected from unsubstituted or fluorine-substituted C1-C6 alkyl, unsubstituted or fluorine-substituted C2-C6 alkenyl, unsubstituted or fluorine-substituted C2-C6 alkynyl, unsubstituted or fluorine-substituted C6-C 12 aryl, unsubstituted or fluorine-substituted C1-C6 alkoxy, halogen, cyano, nitro, sulfonic acid group, aldehyde group, carboxyl group or silyl group.

[0012] In one embodiment of the present application, the first component comprises at least one of the following compounds;

[0013]

[0014] In one embodiment of the present application, R1 and R2 are each independently selected from unsubstituted or fluorine-substituted C1-C6 alkyl.

[0015] In one embodiment of the present application, the second component comprises at least one of the following compounds:

[0016]

[0017]

[0018]

[0019] In one embodiment of the present application, based on the mass of the electrolyte, the mass percentage content of the first component is A, 0.01% ≤ A ≤ 80%, preferably 0.5% ≤ A ≤ 60%.

[0020] In one embodiment of the present application, based on the mass of the electrolyte, the mass percentage content of the second component is B, 5% ≤ B ≤ 70%, preferably 10% ≤ B ≤ 50%.

[0021] In one embodiment of the present application, the electrolyte further comprises a first additive, and the first additive comprises at least one of ethylene sulfite, methyl ethylene sulfite, 1,4-butane sultone, 2,4-butane sultone, 1,3-propane sultone, vinylene carbonate or fluoroethylene carbonate.

[0022] In one embodiment of the present application, based on the mass of the electrolyte, the mass percentage content of the first additive is a, 0.1% ≤ a ≤ 10%.

[0023] In one embodiment of the present application, the electrolyte further includes a second additive, and the second additive includes at least one of succinonitrile, glutaronitrile, methylglutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelaonitrile, sebaconitrile, 1,3,6-hexanetricarbonitrile, 1,2,3-tris(2-cyanooxy)propane, ethylene glycol bis(propionitrile) ether, or fumarodinitrile.

[0024] In one embodiment of the present application, based on the mass of the electrolyte, the mass percentage content of the second additive is b, and 0.5% ≤ b ≤ 6%.

[0025] In one embodiment of the present application, the electrolyte further includes a third additive, and the third additive includes at least one of lithium tetrafluoroborate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, or bis(trifluoromethylsulfonyl)imide lithium.

[0026] In one embodiment of the present application, based on the mass of the electrolyte, the mass percentage content of the third additive is c, and 0.01% ≤ c ≤ 3%.

[0027] The second aspect of the present application provides a secondary battery, which includes the electrolyte described in the first aspect of the present application.

[0028] The third aspect of the present application provides an electronic device, which includes the secondary battery described in the second aspect of the present application.

[0029] Advantages of the present application:

[0030] The present application provides an electrolyte for a secondary battery, a secondary battery, and an electronic device. The electrolyte includes a first component and a second component. The second component is a better solvent for dissolving lithium salts, but its oxidation stability on the positive electrode side is insufficient. The ester functional groups contained in it are easily decomposed to generate CO2 during the charging process, destroying the stability of the positive electrode interface and the adhesion of the battery interface. The first component can decompose at the positive electrode interface to form an inorganic cathode electrolyte interface (CEI) containing sulfide, preventing the decomposition of the second component at the positive electrode interface. When the second component and the first component are used in combination, a passivation layer can be formed on the positive electrode surface, which not only retains the good lithium transport characteristics of the second component but also reduces the oxidative decomposition of the second component at the positive electrode interface. The combination of the first component and the second component enables the secondary battery to have a higher cycle capacity retention rate, thereby improving the cycle performance of the secondary battery.

[0031] Of course, it is not necessary for any product or method implementing the present application to achieve all the above-mentioned advantages simultaneously. Detailed implementation manners

[0032] The technical solutions in the embodiments of the present application will be clearly and completely described below. 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 belong to the scope of protection of the present application.

[0033] In the first aspect of the present application, an electrolyte for a secondary battery is provided, which includes a first component and a second component;

[0034] The first component includes a compound represented by Formula I;

[0035]

[0036] Wherein, R is selected from unsubstituted or R a substituted C2-C6 alkyl, unsubstituted or R a substituted C2-C6 alkenyl, unsubstituted or R a substituted C2-C6 alkynyl, unsubstituted or R a substituted C5-C 12 nitrogen-containing heteroaryl, unsubstituted or R a substituted C6-C 12 aryl; the substituents R a of each group are each independently selected from fluorine or C1-C6 alkyl substituted by fluorine;

[0037] The second component includes a compound represented by Formula II;

[0038]

[0039] R1 and R2 are each independently selected from unsubstituted or fluorine-substituted C1-C6 alkyl, unsubstituted or fluorine-substituted C2-C6 alkenyl, unsubstituted or fluorine-substituted C2-C6 alkynyl, unsubstituted or fluorine-substituted C6-C 12 aryl, unsubstituted or fluorine-substituted C1-C6 alkoxy, halogen, cyano, nitro, sulfonic acid group, aldehyde group, carboxyl group or silicon group.

[0040] In this application, a first component and a second component are added to the electrolyte simultaneously. The second component is a solvent that can better dissolve lithium salts, but its oxidation stability on the positive electrode side is insufficient. The ester functional groups it contains are prone to decompose into CO2 during the charging process, damaging the stability of the positive electrode interface and the adhesion of the battery interface. The first component can decompose at the positive electrode interface to form an inorganic CEI containing sulfide, preventing the decomposition of the second component at the positive electrode interface. When the second component is used in combination with the first component, a passivation layer can be formed on the positive electrode surface, which not only retains the good lithium transport characteristics of the second component but also reduces the oxidative decomposition of the second component at the positive electrode interface. The combined use of the first component and the second component enables the secondary battery to have a higher cycle capacity retention rate, thereby improving the cycle performance of the secondary battery.

[0041] In one embodiment of this application, the first component includes at least one of the following compounds;

[0042]

[0043] Applying the electrolyte including the above-mentioned first component to the secondary battery can, without affecting other performances, enable the secondary battery to have a higher cycle capacity retention rate and further improve the cycle performance of the secondary battery.

[0044] In one embodiment of this application, R1 and R2 each independently selected from unsubstituted or fluorine-substituted C1-C6 alkyl groups.

[0045] In one embodiment of this application, the second component includes at least one of the following compounds:

[0046]

[0047]

[0048] Applying the electrolyte including the second component within the above range to the secondary battery can, without affecting other performances, enable the secondary battery to have a higher cycle capacity retention rate and further improve the cycle performance of the secondary battery.

[0049] In an embodiment of the present application, based on the mass of the electrolyte, the mass percentage content of the first component is A, 0.01% ≤ A ≤ 80%, preferably 0.5% ≤ A ≤ 60%, and more preferably 10% ≤ A ≤ 55%. For example, the mass percentage content A of the first component can be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80% or a range composed of any two of these values. By controlling the mass percentage content of the first component within the above range, it can better cooperate with the second component, enabling the secondary battery to have a higher cycle capacity retention rate and further improving the cycle performance of the secondary battery.

[0050] In an embodiment of the present application, based on the mass of the electrolyte, the mass percentage content of the second component is B, 5% ≤ B ≤ 70%, preferably 10% ≤ B ≤ 50%, and more preferably 15% ≤ A ≤ 40%. For example, the mass percentage content B of the second component is 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or a range composed of any two of these values. By controlling the mass percentage content of the second component within the above range, it can better cooperate with the first component, enabling the secondary battery to have a higher cycle capacity retention rate and further improving the cycle performance of the secondary battery.

[0051] In an embodiment of the present application, the electrolyte further includes a first additive, and the first additive includes at least one of vinylene sulfate, methyl vinylene sulfate, 1,4-butane sultone, 2,4-butane sultone, 1,3-propane sultone, vinylene carbonate or fluoroethylene carbonate. The electrolyte includes the first additive. During the first charging process, the first additive can form a solid electrolyte interface (SEI) at the negative electrode interface prior to the first component and the second component, effectively passivating the negative electrode interface and reducing the side reactions at the negative electrode interface. At the same time, during the cycling process, it can continuously decompose and repair the SEI, thereby enabling the secondary battery to have a higher cycle capacity retention rate and further improving the cycle performance of the secondary battery.

[0052] In an embodiment of the present application, based on the mass of the electrolyte, the mass percentage content of the first additive is a, where 0.1% ≤ a ≤ 10%. For example, the mass percentage content a of the first additive is 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range composed of any two of these values. Controlling the mass percentage content of the first additive within the above range can better passivate the negative electrode interface, further reduce the side reactions at the negative electrode interface, enable the secondary battery to have a higher cycle capacity retention rate, and further improve the cycle performance of the secondary battery.

[0053] In an embodiment of the present application, the electrolyte further includes a second additive, and the second additive includes at least one of succinonitrile, glutaronitrile, methylglutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelaonitrile, sebaconitrile, 1,3,6-hexanetricarbonitrile, 1,2,3-tris(2-cyanooxy)propane, ethylene glycol bis(propionitrile) ether, or fumarodinitrile. The electrolyte including the second additive can better passivate the positive electrode interface through adsorption, reduce the side reactions at the positive electrode interface, enable the secondary battery to have a higher cycle capacity retention rate, and further improve the cycle performance of the secondary battery.

[0054] In an embodiment of the present application, based on the mass of the electrolyte, the mass percentage content of the second additive is b, where 0.5% ≤ b ≤ 6%. For example, the mass percentage content b of the second additive is 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, or a range composed of any two of these values. Controlling the mass percentage content of the second additive within the above range can better passivate the positive electrode interface, further reduce the side reactions at the positive electrode interface, enable the secondary battery to have a higher cycle capacity retention rate, and further improve the cycle performance of the secondary battery.

[0055] In an embodiment of the present application, the electrolyte further includes a third additive, and the third additive includes at least one of lithium tetrafluoroborate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, or lithium bis(trifluoromethylsulfonyl)imide. The electrolyte including the third additive can better passivate the positive electrode interface, reduce the side reactions at the positive electrode interface, enable the secondary battery to have a higher cycle capacity retention rate, and further improve the cycle performance of the secondary battery.

[0056] In an embodiment of the present application, based on the mass of the electrolyte, the mass percentage content of the third additive is c, where 0.01% ≤ c ≤ 3%. For example, the mass percentage content b of the third additive is 0.01%, 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, or a range composed of any two of these values. Controlling the mass percentage content of the third additive within the above range can better passivate the positive electrode interface, further reduce the side reactions at the positive electrode interface, enable the secondary battery to have a higher cycle capacity retention rate, and further improve the cycle performance of the secondary battery.

[0057] In an embodiment of the present application, the electrolyte further includes a lithium salt. The present application places no particular limitation on the lithium salt, as long as the object of the present application can be achieved. For example, the lithium salt may include, but is not limited to, at least one of LiPF6, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiC(SO2CF3)3, Li2SiF6, or lithium difluoroborate. The present application places no particular limitation on the content of the lithium salt in the electrolyte, as long as the object of the present application can be achieved. For example, based on the mass of the electrolyte, the mass percentage content of the lithium salt is 8% to 15%.

[0058] In an embodiment of the present application, the electrolyte further contains other non-aqueous solvents. The present application places no particular limitation on the non-aqueous solvents, as long as the object of the present application can be achieved. For example, the non-aqueous solvents may include, but are not limited to, at least one of carbonate compounds, carboxylate compounds, ether compounds, or other organic solvents.

[0059] The above-mentioned carbonate compounds may include, but are not limited to, at least one of chain carbonate compounds, cyclic carbonate compounds, or fluorinated carbonate compounds. The above-mentioned chain carbonate compounds may include, but are not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or methyl ethyl carbonate (MEC). The above-mentioned cyclic carbonates may include, but are not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), or vinylene ethylene carbonate (VEC). The fluorinated carbonate compounds may include, but are not limited to, at least one of fluorinated ethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethyl ethylene carbonate. The above-mentioned carboxylic ester compounds may include, but are not limited to, at least one of γ-butyrolactone, decanolide, valerolactone, or caprolactone. The above-mentioned ether compounds may include, but are not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The above-mentioned other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate. The present application does not particularly limit the content of the non-aqueous solvent in the electrolyte as long as the object of the present application can be achieved. For example, based on the mass of the electrolyte, the mass percentage content of the non-aqueous solvent is 0% to 86%, preferably 0% to 81%, and more preferably 0% to 67%.

[0060] The second aspect of the present application provides a secondary battery, which includes the electrolyte described in the first aspect of the present application.

[0061] It should be noted that in the specific embodiments of the present application, lithium-ion batteries are used as examples of secondary batteries to explain the present application, but the secondary batteries of the present application are not limited to lithium-ion batteries. The specific technical solutions are as follows:

[0062] The present application has no particular limitation on the conductive agent, as long as the object of the present application can be achieved. For example, the conductive agent may include, but is not limited to, at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metal materials, or conductive polymers. The conductive carbon black may include, but is not limited to, at least one of acetylene black or Ketjen black. The above carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The above carbon fibers may include, but are not limited to, vapor-grown carbon fibers (VGCF) and / or nanofibers. The above metal materials may include, but are not limited to, metal powders and / or metal fibers. Specifically, the metal may include, but is not limited to, at least one of copper, nickel, aluminum, or silver. The above conductive polymers may include, but are not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, or polypyrrole.

[0063] The present application has no particular limitation on the binder, as long as the object of the present application can be achieved. For example, the binder may include, but is not limited to, at least one of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyvinyl alcohol, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyimide, polyamideimide, styrene-butadiene rubber, or polyvinylidene fluoride.

[0064] In the present application, the secondary battery further includes a positive electrode plate, which includes a positive electrode current collector and a positive electrode material layer provided on at least one surface of the positive electrode current collector. The above "positive electrode material layer provided on at least one surface of the positive electrode current collector" means that the positive electrode material layer may be provided on one surface of the positive electrode current collector along its own thickness direction, or may be provided on two surfaces of the positive electrode current collector along its own thickness direction. It should be noted that the "surface" here may be the entire area of the surface of the positive electrode current collector, or may be a partial area of the surface of the positive electrode current collector. The present application has no particular limitation as long as the object of the present application can be achieved.

[0065] The present application has no particular limitation on the positive electrode current collector, as long as the object of the present application can be achieved. For example, it may include aluminum foil, aluminum alloy foil, or a composite current collector (such as an aluminum-carbon composite current collector), etc.

[0066] The positive electrode material layer includes a positive electrode active material. The present application has no particular limitation on the positive electrode active material, as long as the object of the present application can be achieved. For example, the positive electrode active material may include, but is not limited to, at least one of lithium nickel cobalt manganate (such as NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminate, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium manganese iron phosphate, or lithium titanate.

[0067] The positive electrode material layer may further include a conductive agent and a binder. The present application does not particularly limit the types of the conductive agent and the binder, as long as the purpose of the present application can be achieved. For example, it may be at least one of the above-mentioned conductive agent and the above-mentioned binder. The present application does not particularly limit the mass ratio of the positive electrode active material, the conductive agent, and the binder in the positive electrode material layer, and those skilled in the art can select according to actual needs as long as the purpose of the present application can be achieved.

[0068] The present application does not particularly limit the thickness of the positive electrode current collector and the positive electrode material layer, 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 30 μm to 120 μm.

[0069] Optionally, the positive electrode sheet may 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 may be a commonly used conductive layer in the art. The conductive layer includes a conductive agent and a binder. The present application does not particularly limit the conductive agent and the binder in the conductive layer. For example, it may be at least one of the above-mentioned conductive agent and the above-mentioned binder.

[0070] In the present application, the secondary battery further includes a separator. The present application does not particularly limit the separator, as long as the purpose of the present application can be achieved. For example, the material of the separator may include, but is not limited to, at least one of polyolefins (PO) mainly composed of polyethylene (PE) and polypropylene (PP), polyester (for example, polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex or aramid. The type of the separator may include at least one of a woven film, a non-woven film, a microporous film, a composite film, a rolled film or a spun film.

[0071] In some embodiments of the present application, the separator may include a substrate layer and a surface treatment layer. The substrate layer may be a non-woven fabric, a film or a composite film having a porous structure, and the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate or polyimide. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film may be used.

[0072] Optionally, a surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer may be a polymer layer, an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance.

[0073] In some embodiments of the present application, the inorganic layer includes inorganic particles and a binder. There are no particular limitations on the inorganic particles in the present application. For example, the inorganic particles may include at least one of alumina, silica, magnesia, titania, hafnium dioxide, tin dioxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. There are no particular limitations on the binder in the present application. For example, the binder may be at least one of the above-mentioned binders. In some embodiments of the present application, the polymer layer includes a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene ether, or polyvinylidene fluoride or poly(vinylidene fluoride - hexafluoropropylene).

[0074] In some embodiments of the present application, a thickener and a wetting agent may also be included. There are no particular limitations on the types of the thickener and the wetting agent in the present application, as long as the objects of the present application can be achieved. For example, the thickener may include, but is not limited to, at least one of sodium carboxymethyl cellulose or lithium carboxymethyl cellulose; the wetting agent may include, but is not limited to, at least one of dimethyl silicone, sodium dodecyl sulfate, trialkyl phosphate, methyl decanoate, or dodecyl acetate.

[0075] In the present application, there are no particular limitations on the thickness of the separator, as long as the objects of the present application can be achieved. For example, the thickness of the separator may be 4 μm to 30 μm.

[0076] In the present application, the secondary battery further includes a negative electrode sheet, and the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector. The above-mentioned "the negative electrode material layer is provided on at least one surface of the negative electrode current collector" means that the negative electrode material layer may be provided on one surface of the negative electrode current collector along its own thickness direction, or may be provided on both surfaces of the negative electrode current collector along its own thickness direction. It should be noted that the "surface" here may be the entire area of the surface of the negative electrode current collector, or may be a partial area of the surface of the negative electrode current collector. There are no particular limitations in the present application, as long as the objects of the present application can be achieved.

[0077] There are no particular limitations on the negative electrode current collector in the present application, as long as the objects of the present application can be achieved. For example, it may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or a composite current collector. Exemplarily, the composite current collector may be a lithium - copper composite current collector, a carbon - copper composite current collector, a nickel - copper composite current collector, a titanium - copper composite current collector, etc.

[0078] The negative electrode material layer includes a negative electrode active material. There is no particular limitation on the negative electrode active material in this application, as long as the purpose of this application can be achieved. For example, the negative electrode active material can include, but is not limited to, natural graphite, artificial graphite, mesophase carbon microspheres, hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, lithiated TiO2-Li4Ti5O with a spinel structure 12 or at least one of Li-Al alloys.

[0079] In some embodiments of this application, the negative electrode material layer can further include a conductive agent and a binder. There is no particular limitation on the types of the conductive agent and the binder in this application, as long as the purpose of this application can be achieved. For example, it can be at least one of the above-mentioned conductive agent and the above-mentioned binder. There is no particular limitation on the mass ratio of the negative electrode active material, the conductive agent, and the binder in the negative electrode material layer, and those skilled in the art can select according to actual needs as long as the purpose of this application can be achieved.

[0080] In some embodiments of this application, it can further include a conductive agent, a binder, and a thickening agent. There is no particular limitation on the types of the conductive agent and the thickening agent in this application, as long as the purpose of this 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 or lithium carboxymethyl cellulose. There is no particular limitation on the mass ratio of the negative electrode active material, the conductive agent, the binder, and the thickening agent in the negative electrode material layer, and those skilled in the art can select according to actual needs as long as the purpose of this application can be achieved.

[0081] There is no particular limitation on the thickness of the negative electrode material layer in this application, as long as the purpose of this application can be achieved. For example, the thickness of the single-sided negative electrode material layer is 30 μm to 120 μm.

[0082] There is no particular limitation on the thickness of the negative electrode current collector in this application, as long as the purpose of this application can be achieved. For example, the thickness of the negative electrode current collector is 4 μm to 15 μm.

[0083] Optionally, the negative electrode sheet can further include a conductive layer, and the conductive layer is located between the negative electrode current collector and the negative electrode material layer. There is no particular limitation on the composition of the conductive layer in this application, and it can be a commonly used conductive layer in the art. For example, the conductive layer includes a conductive agent and a binder. There is no particular limitation on the conductive agent and the binder in the conductive layer in this application. For example, it can be at least one of the above-mentioned conductive agent and the above-mentioned binder.

[0084] The secondary battery further includes a housing for accommodating the positive electrode plate, the separator, the negative electrode plate, and the electrolyte, as well as other components known in the field of secondary batteries. The present application does not limit the above-mentioned other components. The present application has no particular limitation on the housing, and it can be a housing well-known in the art as long as it can achieve the purpose of the present application. 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 present application does not limit the type of metal. Any known metal hard shell housing in the art can be used as long as it can achieve the purpose of the present application. The flexible housing can be a metal plastic film, such as an aluminum plastic film, a steel plastic film, etc.

[0085] The preparation process of the secondary battery of the present application is well-known to those skilled in the art, and the present application has no particular limitation. For example, the preparation process of the secondary battery can include but is not limited to the following steps: stacking the positive electrode plate, the separator, and the negative electrode plate in sequence, and performing operations such as winding and folding according to needs to obtain a wound electrode assembly. Then, placing the electrode assembly into the housing, injecting the electrolyte into the housing and sealing it to obtain the secondary battery. Or, stacking the positive electrode plate, the separator, and the negative electrode plate in sequence, and then fixing the four corners of the entire laminated structure with tape to obtain a laminated electrode assembly. Placing the electrode assembly into the housing, injecting the electrolyte into the housing and sealing it to obtain the secondary battery. In addition, an overcurrent protection element, a guide plate, etc. can also be placed in the housing according to needs to prevent the pressure inside the secondary battery from rising and overcharging / discharging.

[0086] The third aspect of the present application provides an electronic device, which includes the secondary battery described in the second aspect of the present application. The secondary battery provided in the second aspect of the present application has good cycle performance, so that the electronic device of the present application has a long service life.

[0087] The electronic device of the present application is not particularly limited, and it can be any electronic device known in the prior art. In some embodiments, the electronic device can include but is not limited to a laptop computer, a pen input computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, a liquid crystal TV, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a moped, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flash, a camera, a large household battery, or a lithium-ion capacitor, etc.

[0088] Examples

[0089] Hereinafter, examples and comparative examples are given to more specifically illustrate the embodiments of the present application. Various tests and evaluations are carried out according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0090] Test methods and equipment

[0091] Cyclic performance test:

[0092] Place the lithium-ion battery in a constant-temperature test chamber at 25 °C and let it stand for 30 minutes to reach a constant temperature. Charge it at a constant current of 0.5C to 4.45V, then charge it at a constant voltage until the current is 0.025C, let it stand for 5 minutes, and discharge it at a constant current of 0.5C to 3.0V. Record the initial discharge capacity C1. Repeat this step 200 cycles, record the discharge capacity C2 after 200 cycles, and calculate the cyclic capacity retention rate of the lithium-ion battery. Cyclic capacity retention rate = C2 / C1 × 100%.

[0093] Example 1-1

[0094] <Preparation of electrolyte>

[0095] In an argon atmosphere glove box with a water content < 10 ppm, add propylene carbonate as a non-aqueous organic solvent, the first component of formula I-1 and the second component of formula II-3, mix them evenly, then add lithium salt LiPF6, dissolve and mix evenly to obtain an electrolyte; wherein, based on the mass of the electrolyte, the mass percentage content of lithium salt LiPF6 is 15%, the mass percentage content A of the first component of formula I-1 is 0.01%, the mass percentage content B of the second component of formula II-3 is 70%, and the balance is propylene carbonate as a non-aqueous organic solvent.

[0096] <Preparation of positive electrode sheet>

[0097] Mix the positive electrode active material LiCoO2, binder polyvinylidene fluoride, and conductive agent conductive carbon black in a mass ratio of 96:2:2, add N-methylpyrrolidone as a solvent, and formulate a slurry with a solid content of 70 wt%. After vacuum stirring evenly, obtain a positive electrode slurry. Coat the positive electrode slurry evenly on one surface of a positive electrode current collector aluminum foil with a thickness of 14 μm, and dry it at 120 °C to obtain a positive electrode sheet with a single-sided coated positive electrode material layer. Then repeat the above steps on the other surface of the positive electrode current collector aluminum foil to obtain a positive electrode sheet with a double-sided coated positive electrode material layer. Dry it under vacuum at 120 °C, then cold press it, and then cut it into pieces and weld the tabs to obtain a positive electrode sheet with a specification of 74 mm × 867 mm for use. Among them, the compaction density of the positive electrode material layer is 4.15 g / cm 3 , and the thickness of the single-sided positive electrode material layer is 45 μm.

[0098] <Preparation of negative electrode sheet>

[0099] Mix artificial graphite as the negative electrode active material, sodium carboxymethyl cellulose as the thickener, and styrene-butadiene rubber as the binder in a mass ratio of 85:2:13. Add deionized water as the solvent and formulate a slurry with a solid content of 65 wt%. After stirring evenly with a vacuum mixer, obtain the negative electrode slurry. Uniformly coat the negative electrode slurry on one surface of a negative electrode current collector copper foil with a thickness of 12 μm, and dry it at 120 °C to obtain a negative electrode plate with a single-sided coated negative electrode material. Then repeat the above steps on the other surface of the copper foil to obtain a negative electrode plate with a double-sided coated negative electrode material layer. Dry it under vacuum at 120 °C, then cold press it, and then cut it into pieces and weld the electrode tabs to obtain a negative electrode plate with a specification of 76 mm × 875 mm. Among them, the compaction density of the negative electrode material layer is 1.6 g / cm 3 , and the thickness of the single-sided negative electrode material layer is 60 μm.

[0100] <Preparation of Separator>

[0101] Mix aluminum oxide as the inorganic particles, sodium carboxymethyl cellulose as the thickener, and dimethyl silicone as the wetting agent in a mass ratio of 95:0.5:4.5. Add deionized water as the solvent and formulate a slurry with a solid content of 5 wt%. After stirring evenly under the action of a vacuum mixer, obtain a porous coating slurry with a viscosity of 40 mPa·s. Uniformly coat the porous coating slurry on one surface of a polyethylene porous substrate with a thickness of 10 μm, and dry it at 85 °C to obtain 2 mg / 1540 mm 2 of a separator with a single-sided coated porous coating. Then repeat the above steps on the other surface of the polyethylene porous substrate to obtain a separator with a double-sided coated porous coating.

[0102] <Preparation of Lithium-Ion Battery>

[0103] Stack the positive electrode plate, separator, and negative electrode plate prepared above in sequence, with the separator in the middle between the positive electrode plate and the negative electrode plate to play a role in isolation, then wind it, connect the positive electrode tab to the positive electrode plate, and connect the negative electrode tab to the negative electrode plate to obtain an electrode assembly. Place the electrode assembly in an aluminum foil packaging bag, and lead the positive electrode tab and the negative electrode tab from the internal space of the aluminum foil packaging bag to the external space of the aluminum foil packaging bag. Remove the moisture at 80 °C, inject the electrolyte prepared above, and obtain a lithium-ion battery through processes such as vacuum packaging, standing, formation, degassing, and shaping. Among them, the upper limit voltage of formation is 4.15 V, the formation temperature is 70 °C, and the formation standing time is 2 h.

[0104] Examples 1-2 to Examples 1-20

[0105] Except that in the <preparation of electrolyte>, the types and mass percentage contents of the first component and the second component are adjusted according to Table 1, the mass percentage content of the non-aqueous organic solvent changes accordingly, and the mass percentage content of the lithium salt remains unchanged, the rest is the same as in Example 1-1.

[0106] Examples 2-1 to 2-9

[0107] Except that in the <preparation of electrolyte>, a first additive is further added according to Table 2, and the type and its mass percentage content of the first additive are adjusted according to Table 2, the mass percentage content of the non-aqueous organic solvent changes accordingly, and the mass percentage content of the lithium salt remains unchanged, the rest is the same as in Example 1-8.

[0108] Examples 3-1 to 3-10

[0109] Except that in the <preparation of electrolyte>, a second additive is further added according to Table 3, and the type and its mass percentage content of the second additive are adjusted according to Table 3, the mass percentage content of the non-aqueous organic solvent changes accordingly, and the mass percentage content of the lithium salt remains unchanged, the rest is the same as in Example 2-9.

[0110] Examples 4-1 to 4-10

[0111] Except that in the <preparation of electrolyte>, a third additive is further added according to Table 4, and the type and its mass percentage content of the third additive are adjusted according to Table 4, the mass percentage content of the non-aqueous organic solvent changes accordingly, and the mass percentage content of the lithium salt remains unchanged, the rest is the same as in Example 3-5.

[0112] Comparative Example 1

[0113] Except that in the <preparation of electrolyte>, the second component is not added, the mass percentage content of the non-aqueous organic solvent changes accordingly, and the mass percentage content of the lithium salt remains unchanged, the rest is the same as in Example 1-1.

[0114] Comparative Example 2

[0115] Except that in the <preparation of electrolyte>, the first component is not added, the mass percentage content of the non-aqueous organic solvent changes accordingly, and the mass percentage content of the lithium salt remains unchanged, the rest is the same as in Example 1-1.

[0116] The preparation parameters and performance parameters of each example and comparative example are shown in Tables 1 to 4.

[0117] Table 1

[0118]

[0119] Note: " / " in Table 1 indicates no relevant parameters.

[0120] As can be seen from Examples 1-1 to 1-20 and Comparative Examples 1 to 2, when the electrolytes with only the first component or the second component added are applied to lithium-ion batteries, the cyclic capacity retention rates of the lithium-ion batteries are all poor; when both the first component and the second component are added to the electrolyte, where the second component is a better solvent for dissolving lithium salts but has insufficient oxidation stability on the positive electrode side, and the ester functional groups contained in it are prone to decompose into CO2 during the charging process, damaging the stability of the positive electrode interface and the adhesion of the battery interface. However, the first component can decompose at the positive electrode interface to form an inorganic CEI containing sulfide, preventing the decomposition of the second component at the positive electrode interface. When used in combination with the first component, a passivation layer can be formed on the positive electrode surface, which not only retains the good lithium transport characteristics of the second component but also reduces the oxidative decomposition of the second component at the positive electrode interface. The combined use of the first component and the second component enables the lithium-ion battery to have a higher cyclic capacity retention rate and thus better cycling performance.

[0121] Table 2

[0122] First additive a(％) Cyclic capacity retention rate (%) Examples 1 - 8 / / 46 Example 2 - 1 1,3 - Propane sultone 0.05 46 Example 2 - 2 1,3 - Propane sultone 0.1 50 Example 2 - 3 1,3 - Propane sultone 3 64 Example 2 - 4 1,3 - Propane sultone 5 70 Example 2 - 5 1,3 - Propane sultone 10 63 Example 2 - 6 1,3 - Propane sultone 11 45 Example 2 - 7 1,3 - Propane sultone + 1,4 - Butane sultone 0.5+2.5 65 Example 2 - 8 1,3 - Propane sultone + 2,4 - Butane sultone 0.5+2.5 67 Example 2 - 9 Vinylene carbonate + 1,3 - Propane sultone 0.1+2.9 69

[0123] Note: " / " in Table 2 indicates no relevant parameters.

[0124] As can be seen from Examples 1-8 and Examples 2-1 to 2-9, when the electrolyte with the first additive added is applied to lithium-ion batteries, during the first charging process, the first additive can form an SEI at the negative electrode interface prior to the first component and the second component, effectively passivating the negative electrode interface and reducing the side reactions at the negative electrode interface. At the same time, during the cycling process, it can continuously decompose to repair the SEI, thereby enabling the lithium-ion battery to have a higher cyclic capacity retention rate and thus better cycling performance.

[0125] Table 3

[0126]

[0127]

[0128] Note: " / " in Table 3 indicates no relevant parameters.

[0129] As can be seen from Examples 2-9 and Examples 3-1 to 3-10, when the electrolyte with the second additive added is applied to lithium-ion batteries, it can better passivate the positive electrode interface through adsorption, reduce the side reactions at the positive electrode interface, enable the lithium-ion battery to have a higher cyclic capacity retention rate, and thus better cycling performance.

[0130] Table 4

[0131] Third additive c(％) Cyclic capacity retention rate (%) Example 3 - 5 / / 78 Example 4 - 1 Lithium difluoro(oxalato)borate 0.005 78 Example 4 - 2 Lithium difluoro(oxalato)borate 0.01 79 Example 4 - 3 Lithium difluoro(oxalato)borate 0.1 80 Example 4 - 4 Lithium difluoro(oxalato)borate 0.5 82 Example 4 - 5 Lithium difluoro(oxalato)borate 1 79 Example 4 - 6 Lithium difluoro(oxalato)borate 2 79 Example 4 - 7 Lithium difluoro(oxalato)borate 3 79 Example 4 - 8 Lithium difluoro(oxalato)borate 4 73 Example 4 - 9 Lithium difluoro(oxalato)borate + Lithium difluorophosphate 0.3+0.3 81 Example 4 - 10 Lithium tetrafluoroborate + Lithium bis(fluorosulfonyl)imide 0.1+2 85

[0132] Note: " / " in Table 4 indicates no relevant parameters.

[0133] As can be seen from Examples 3-5, Examples 4-1 to 4-10, applying the electrolyte added with the third additive to the lithium-ion battery can better passivate the positive electrode interface through adsorption, reduce the side reactions at the positive electrode interface, enable the lithium-ion battery to have a higher cycle capacity retention rate, and thus have better cycle performance.

[0134] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method or article including a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method or article.

[0135] The above are only the preferred embodiments of the present application, and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included within the scope of protection of the present application.

Claims

1. An electrolyte for a secondary battery, which comprises a first component and a second component; The first component comprises a compound represented by Formula I; Among them, R is selected from unsubstituted or R-substituted C2-C6 alkyl, unsubstituted or R-substituted C2-C6 alkenyl, unsubstituted or R-substituted C2-C6 alkynyl, unsubstituted or R-substituted C5-C nitrogen-containing heteroaryl, unsubstituted or R-substituted C6-C aryl; the substituent R of each group is independently selected from fluorine or C1-C6 alkyl substituted with fluorine; a R is selected from unsubstituted or R-substituted C2-C6 alkyl, unsubstituted or R-substituted C2-C6 alkenyl, unsubstituted or R-substituted C2-C6 alkynyl, unsubstituted or R-substituted C5-C nitrogen-containing heteroaryl, unsubstituted or R-substituted C6-C aryl; the substituent R of each group is independently selected from fluorine or C1-C6 alkyl substituted with fluorine; a R is selected from unsubstituted or R-substituted C2-C6 alkyl, unsubstituted or R-substituted C2-C6 alkenyl, unsubstituted or R-substituted C2-C6 alkynyl, unsubstituted or R-substituted C5-C nitrogen-containing heteroaryl, unsubstituted or R-substituted C6-C aryl; the substituent R of each group is independently selected from fluorine or C1-C6 alkyl substituted with fluorine; a R is selected from unsubstituted or R-substituted C2-C6 alkyl, unsubstituted or R-substituted C2-C6 alkenyl, unsubstituted or R-substituted C2-C6 alkynyl, unsubstituted or R-substituted C5-C nitrogen-containing heteroaryl, unsubstituted or R-substituted C6-C aryl; the substituent R of each group is independently selected from fluorine or C1-C6 alkyl substituted with fluorine; a R is selected from unsubstituted or R-substituted C2-C6 alkyl, unsubstituted or R-substituted C2-C6 alkenyl, unsubstituted or R-substituted C2-C6 alkynyl, unsubstituted or R-substituted C5-C nitrogen-containing heteroaryl, unsubstituted or R-substituted C6-C aryl; the substituent R of each group is independently selected from fluorine or C1-C6 alkyl substituted with fluorine; 12 R is selected from unsubstituted or R-substituted C2-C6 alkyl, unsubstituted or R-substituted C2-C6 alkenyl, unsubstituted or R-substituted C2-C6 alkynyl, unsubstituted or R-substituted C5-C nitrogen-containing heteroaryl, unsubstituted or R-substituted C6-C aryl; the substituent R of each group is independently selected from fluorine or C1-C6 alkyl substituted with fluorine; a R is selected from unsubstituted or R-substituted C2-C6 alkyl, unsubstituted or R-substituted C2-C6 alkenyl, unsubstituted or R-substituted C2-C6 alkynyl, unsubstituted or R-substituted C5-C nitrogen-containing heteroaryl, unsubstituted or R-substituted C6-C aryl; the substituent R of each group is independently selected from fluorine or C1-C6 alkyl substituted with fluorine; 12 R is selected from unsubstituted or R-substituted C2-C6 alkyl, unsubstituted or R-substituted C2-C6 alkenyl, unsubstituted or R-substituted C2-C6 alkynyl, unsubstituted or R-substituted C5-C nitrogen-containing heteroaryl, unsubstituted or R-substituted C6-C aryl; the substituent R of each group is independently selected from fluorine or C1-C6 alkyl substituted with fluorine; a R is selected from unsubstituted or R-substituted C2-C6 alkyl, unsubstituted or R-substituted C2-C6 alkenyl, unsubstituted or R-substituted C2-C6 alkynyl, unsubstituted or R-substituted C5-C nitrogen-containing heteroaryl, unsubstituted or R-substituted C6-C aryl; the substituent R of each group is independently selected from fluorine or C1-C6 alkyl substituted with fluorine; The second component comprises a compound represented by Formula II; R1 and R2 are each independently selected from unsubstituted or fluorine-substituted C1-C6 alkyl, unsubstituted or fluorine-substituted C2-C6 alkenyl, unsubstituted or fluorine-substituted C2-C6 alkynyl, unsubstituted or fluorine-substituted C6-C 12 aryl, unsubstituted or fluorine-substituted C1-C6 alkoxy, halogen, cyano, nitro, sulfo, aldehyde, carboxyl or silyl.

2. The electrolyte according to claim 1, wherein, The first component comprises at least one of the following compounds; 3. The electrolyte according to claim 1, wherein, R1 and R2 each independently selected from unsubstituted or fluorine-substituted C1-C6 alkyl groups.

4. The electrolyte according to claim 1, wherein, The second component comprises at least one of the following compounds:

5. The electrolyte according to claim 1, wherein, Based on the mass of the electrolyte, the mass percentage content of the first component is A, 0.01% ≤ A ≤ 80%.

6. The electrolyte according to claim 1, wherein Based on the mass of the electrolyte, the mass percentage content of the second component is B, 5% ≤ B ≤ 70%.

7. The electrolyte according to claim 1, which satisfies at least one of the following characteristics: (1) Based on the mass of the electrolyte, the mass percentage content of the first component is A, 0.5% ≤ A ≤ 60%; (2) Based on the mass of the electrolyte, the mass percentage content of the second component is B, 10% ≤ B ≤ 50%.

8. The electrolyte according to any one of claims 1 to 7, wherein, The electrolyte further comprises a first additive, and the first additive comprises at least one of vinylene sulfate, methyl vinylene sulfate, 1,4-butane sultone, 2,4-butane sultone, 1,3-propane sultone, vinylene carbonate or fluoroethylene carbonate.

9. The electrolyte according to claim 8, wherein, Based on the mass of the electrolyte, the mass percentage content of the first additive is a, 0.1% ≤ a ≤ 10%.

10. The electrolyte according to any one of claims 1 to 7, wherein, The electrolyte further comprises a second additive, and the second additive comprises at least one of butanedinitrile, pentanedinitrile, methylpentanedinitrile, hexanedinitrile, heptanedinitrile, octanedinitrile, nonanedinitrile, decanedinitrile, 1,3,6-hexanetricarbonitrile, 1,2,3-tris(2-cyanooxy)propane, ethylene glycol bis(propionitrile) ether or fumarodinitrile.

11. The electrolyte according to claim 10, wherein, Based on the mass of the electrolyte, the mass percentage content of the second additive is b, 0.5% ≤ b ≤ 6%.

12. The electrolyte according to any one of claims 1 to 7, wherein The electrolyte further comprises a third additive, and the third additive comprises at least one of lithium tetrafluoroborate, lithium difluorooxalate borate, lithium bis(oxalate) borate, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide or lithium bis(trifluoromethylsulfonyl)imide.

13. The electrolyte according to claim 12, wherein, Based on the mass of the electrolyte, the mass percentage content of the third additive is c, 0.01% ≤ c ≤ 3%.

14. A secondary battery, which comprises the electrolyte according to any one of claims 1 to 13.

15. An electronic device, which comprises the secondary battery according to claim 14.

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