A lithium-ion battery

Abstract

In order to overcome the problem of unstable SEI film formation quality on the negative electrode surface of existing lithium ion batteries, the present invention provides a lithium ion battery comprising a positive electrode, a negative electrode and a non-aqueous electrolyte, wherein the non-aqueous electrolyte comprises a non-aqueous organic solvent, an electrolyte salt and an additive, wherein the additive comprises a compound represented by structural formula 1: #imgabs0# structural formula 1; an X-ray photoelectron spectrometer is used to test the surface of the negative electrode: an Ar ion gun is used for etching at a speed of 10 nm / min and an etching power of 1 kV; the etching time is 5 min, and the peak at the binding energy position of 528±1.0 eV is used as the O 1s The peak at the binding energy position of 685±1.0eV is taken as F 1s Peak, O 1s Peak and F 1s The peak area ratio Y is 0.3 to 0.6. The lithium-ion battery provided by the present invention can provide excellent protection for the lithium-intercalated negative electrode, reduce the generation of interface side reactions, and thus achieve excellent long-cycle stability.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage electronic components, and in particular to a lithium ion battery. Background Art

[0002] As secondary battery technology matures, demand for electric vehicles and large-scale energy storage systems is booming. Major manufacturers are understood to have mastered the key technologies to enable batteries to last more than 10,000 charge and discharge cycles, steadily moving toward the long-term goals of higher energy density, longer cycle life, and greater safety and reliability. Technically, the key to achieving long-cycle lithium-ion batteries lies in optimizing the electrochemical stability of the solid electrolyte interface (SEI) through electrolyte design.

[0003] The underlying logic of an excellent SEI film lies in its chemical composition and distribution model. Existing SEI films formed with different additives exhibit significant variations in composition and film quality stability. Unstable SEI films can break down and then repair and thicken during charge and discharge cycles, leading to increased battery impedance and decreased capacity. Regulating the SEI film composition to achieve a stable SEI film is an urgent issue. Summary of the Invention

[0004] Aiming at the problem of unstable film formation quality of SEI film on the negative electrode surface of existing lithium ion batteries, the present invention provides a lithium ion battery.

[0005] The technical solutions adopted by the present invention to solve the above technical problems are as follows:

[0006] The present invention provides a lithium-ion battery comprising a positive electrode, a negative electrode and a non-aqueous electrolyte, wherein the non-aqueous electrolyte comprises a non-aqueous organic solvent, an electrolyte salt and an additive, wherein the additive comprises a compound represented by structural formula 1:

[0007] ;

[0008] wherein n is 0 or 1; R1 and R2 are each independently selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C1-C12 acyl, substituted or unsubstituted C2-C12 alkoxyacyl, substituted or unsubstituted C2-C12 ether, and R1, R2 are not hydrogen at the same time; R1 and R2 may be linked to form a ring or not; R3 is selected from substituted or unsubstituted C1-C12 alkylene, substituted or unsubstituted C2-12 alkenylene, substituted or unsubstituted C2-12 alkynylene, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C2-C12 ether; when R1, R2, and R3 are substituted, the substituent is an alkoxy group, a hydroxyl group, an acyl group, an ester group, a cyano group, or a halogen group;

[0009] The surface of the negative electrode was tested by X-ray photoelectron spectroscopy: an Ar ion gun was used to etch at a speed of 10 nm / min and an etching power of 1 kV; the etching time was 5 min, and the peak at the binding energy position of 528 ± 1.0 eV was used as the O 1s The peak at the binding energy position of 685±1.0eV is taken as F 1s Peak, O 1s Peak and F 1s The peak area ratio Y is 0.3~0.6.

[0010] Optionally, in the compound shown in structural formula 1, R1 is selected from hydrogen, R2 is selected from , substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, wherein R 10 Selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, and substituted or unsubstituted C6-C20 aryl.

[0011] Optionally, in the compound shown in structural formula 1, R1 and R2 are each independently selected from a substituted or unsubstituted C1-C12 alkyl, a substituted or unsubstituted C2-C12 alkenyl, a substituted or unsubstituted C2-C12 alkynyl, or a substituted or unsubstituted C6-C20 aryl.

[0012] Optionally, in the compound shown in structural formula 1, R1 is selected from R2 is selected from substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl or , where R 11 Selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C2-C12 ether.

[0013] Optionally, in the compound shown in structural formula 1, R1 is selected from , where R 12 R2 is selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl or , where R 13 is selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, and substituted or unsubstituted C2-C11 alkynyl.

[0014] Optionally, the compound represented by structural formula 1 includes one or more of the following compounds:

[0015] .

[0016] Optionally, based on the total mass of the non-aqueous electrolyte being 100%, the mass content of the compound represented by Structural Formula 1 is 10 ppm to 1000 ppm.

[0017] Optionally, the non-aqueous electrolyte does not include a polymerizable monomer and / or a prepolymer obtained by polymerizing a polymerizable monomer.

[0018] Optionally, the additive further comprises at least one of a cyclic sulfate compound, a sultone compound, a cyclic carbonate compound, a phosphate compound, a nitrile compound, a lithium salt additive or an alkane compound; and / or

[0019] The cyclic sulfate compound includes at least one of vinyl sulfate, propylene sulfate, and methyl vinyl sulfate; and / or

[0020] The sultone compound includes at least one of 1,3-propane sultone, 1,4-butane sultone, 1,3-propylene sultone, and methylene methanedisulfonate; and / or

[0021] The cyclic carbonate compound includes at least one of vinylene carbonate, vinyl ethylene carbonate, methylene carbonate or the compound shown in structural formula 2:

[0022] ;

[0023] In the structural formula 2, R 21 、R 22 、R 23 、R 24 、R 25 、R 26 Each independently selected from a hydrogen atom, a halogen atom, a C1-C5 group; and / or

[0024] The phosphate compound includes at least one of tris(trimethylsilyl)phosphate, tris(triethylsilyl)phosphate or the compound shown in structural formula 3:

[0025] ;

[0026] In the structural formula 3, R 31 、R 32 、R 33 Each independently selected from C1-C5 saturated hydrocarbon group, C1-C5 unsaturated hydrocarbon group, C1-C5 halogenated hydrocarbon group, C6-C12 aryl group, C6-C12 halogenated aryl group, -Si(C m H 2m+1 )3, m is a natural number from 1 to 3; and / or

[0027] The nitrile compound includes at least one of succinonitrile, glutaronitrile, hexanetrinitrile, adiponitrile, pimelonitrile, suberonitrile, azelaic acid dinitrile and sebacononitrile; and / or

[0028] The lithium salt additive includes at least one of lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorophosphate, lithium tetrafluorophosphate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethylsulfonyl imide, lithium bispentafluoroethylsulfonyl imide, lithium trifluoromethanesulfonate, lithium monofluorosulfonate, lithium trioxalatophosphate, lithium difluorobisoxalatophosphate, lithium tetrafluorooxalatophosphate, lithium dicyanamide or a lower aliphatic lithium carboxylate having 4 or less carbon atoms; and / or

[0029] The alkane compound includes at least one of cyclopentane, cyclohexane, cycloheptane, methylcyclopentane, ethylcyclopentane, 1,3-dimethylcyclopentane, 1,4-dimethylcyclopentane, methylcyclohexane, ethylcyclohexane, propylcyclohexane, butylcyclohexane, pentylcyclohexane, cis-1-methyl-3-ethylcyclohexane, trans-1-methyl-3-ethylcyclohexane, 1,3-dimethylcyclohexane, 1,4-dimethylcyclohexane, 1,3,5-trimethylcyclohexane and perfluoro(ethylcyclohexane).

[0030] Optionally, the negative electrode includes a negative electrode material layer, the negative electrode material layer includes a negative electrode active material, and the negative electrode active material includes one or more of soft carbon, hard carbon, artificial graphite, natural graphite, intermediate phase microcarbon beads, silicon, silicon oxides, silicon-carbon composites, metallic lithium or lithium titanate.

[0031] According to the lithium-ion battery provided by the present invention, the compound shown in structural formula 1 is added to the non-aqueous electrolyte as an additive. The peroxide group -OO- can provide [O] to promote the increase of Li2O content in SEI. In addition, the inventors have found through extensive research that in a battery system with the compound shown in structural formula 1, when the lithium-ion battery meets the O detected by the negative electrode 1s Peak and F 1s Under the additional condition that the peak area ratio Y is between 0.3 and 0.6, the inorganic components of the SEI have an appropriate ratio of Li2O and LiF components, which can provide excellent protection for the lithium-intercalated negative electrode, reduce the occurrence of interfacial side reactions, and thus achieve excellent long-term cycle stability. However, when the Y value is less than 0.3, the Li2O content is low, the lithium ion diffusion barrier is high, and the interfacial film impedance increases, which is not conducive to battery rate discharge. When the Y value is greater than 0.6, the LiF content is low, and the formed SEI film interface is relatively loose, resulting in increased side reactions, accelerated consumption of solvents and additives, and deterioration of battery cycle life. DETAILED DESCRIPTION

[0032] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0033] An embodiment of the present invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte comprises a non-aqueous organic solvent, an electrolyte salt, and an additive, wherein the additive comprises a compound represented by structural formula 1;

[0034] ;

[0035] wherein n is 0 or 1; R1 and R2 are each independently selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C1-C12 acyl, substituted or unsubstituted C2-C12 alkoxyacyl, substituted or unsubstituted C2-C12 ether, and R1, R2 are not hydrogen at the same time; R1 and R2 may be linked to form a ring or not; R3 is selected from substituted or unsubstituted C1-C12 alkylene, substituted or unsubstituted C2-12 alkenylene, substituted or unsubstituted C2-12 alkynylene, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C2-C12 ether; when R1, R2, and R3 are substituted, the substituent is an alkoxy group, a hydroxyl group, an acyl group, an ester group, a cyano group, or a halogen group;

[0036] The surface of the negative electrode was tested by X-ray photoelectron spectroscopy: an Ar ion gun was used to etch at a speed of 10 nm / min and an etching power of 1 kV; the etching time was 5 min, and the peak at the binding energy position of 528 ± 1.0 eV was used as the O 1s The peak at the binding energy position of 685±1.0eV is taken as F 1s Peak, O 1s Peak and F 1s The peak area ratio Y is 0.3~0.6.

[0037] According to the lithium-ion battery provided by the present invention, the compound shown in structural formula 1 is added to the non-aqueous electrolyte as an additive. The peroxide group -OO- can provide [O] to promote the increase of Li2O content in SEI. In addition, the inventors have found through extensive research that in a battery system with the compound shown in structural formula 1, when the lithium-ion battery meets the O detected by the negative electrode 1s Peak and F 1s Under the additional condition that the peak intensity ratio Y is between 0.3 and 0.6, the inorganic components of the SEI have an appropriate ratio of Li2O and LiF components, which can provide excellent protection for the lithium-intercalated negative electrode, reduce the occurrence of interfacial side reactions, and thus achieve excellent long-term cycle stability. However, when the Y value is less than 0.3, the Li2O content is low, the lithium ion diffusion barrier is high, and the interfacial film impedance increases, which is not conducive to battery rate discharge. When the Y value is greater than 0.6, the LiF content is low, and the formed SEI film interface is relatively loose, resulting in increased side reactions, accelerated consumption of solvents and additives, and deterioration of battery cycle life.

[0038] In the description of the present invention, the term "C1-C12 alkyl" includes straight-chain alkyl, branched-chain alkyl and cycloalkyl. Similarly, the term "C2-C12 alkenyl" includes straight-chain alkenyl, branched-chain alkenyl and cycloalkenyl. The term "C2-C12 alkynyl" includes straight-chain alkynyl, branched-chain alkynyl and cycloalkynyl. The term "C1-C12 alkylene" includes straight-chain alkylene, branched-chain alkylene and cycloalkylene. The term "C2-C12 alkenylene" includes straight-chain alkenylene, branched-chain alkenylene and cycloalkenylene. The term "C2-C12 alkynylene" includes straight-chain alkynylene, branched-chain alkynylene and cycloalkynylene.

[0039] In the description of the present invention, the term "C1-C12 acyl group" should be understood in a broad sense. Specifically, it can be understood as a C1-C12 alkyl group in which a single or multiple carbon atoms are replaced by a carbonyl group. The position of the substituted carbon atom is not particularly limited. In a preferred embodiment, the C1-C12 acyl group is selected from , where R 14 Selected from a single bond or a C1-C11 alkyl group, R 15 An alkyl group selected from C1-C11.

[0040] In the description of the present invention, the term "C2-C12 alkoxy acyl" should be understood in a broad sense. Specifically, it can be understood that a single or multiple carbon atoms in a C2-C12 alkyl group are replaced by an ester group. The position of the substituted carbon atom is not particularly limited. In a preferred embodiment, the C2-C12 alkoxyacyl group is selected from , where R 16 Selected from a single bond or a C1-C11 alkyl group, R 17 An alkyl group selected from C1-C11.

[0041] In the description of the present invention, the term "C2-C12 ether group" should be understood in a broad sense. Specifically, it can be understood as a group connecting two adjacent carbon atoms in a C2-C12 alkyl group. The number of oxygen atoms in the resulting group may be single or multiple.

[0042] In some embodiments, in the compound represented by structural formula 1, R1 is selected from hydrogen, R2 is selected from , substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, wherein R 10 is selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, and substituted or unsubstituted C6-C20 aryl.

[0043] In this case, the compound represented by Structural Formula 1 is a hydroperoxide or an organic peracid. When the compound represented by Structural Formula 1 is a hydroperoxide or an organic peracid, the high oxygen content can preemptively remove reducing impurities in the electrolyte, thereby reducing the amount of gas produced by the formation, improving the initial coulombic efficiency, and increasing the initial discharge capacity of the secondary battery.

[0044] As an example, the compound represented by the structural formula 1 can be selected from the following compounds:

[0045] .

[0046] In some embodiments, in the compound represented by structural formula 1, R1 and R2 are each independently selected from a substituted or unsubstituted C1-C12 alkyl, a substituted or unsubstituted C2-C12 alkenyl, a substituted or unsubstituted C2-C12 alkynyl, or a substituted or unsubstituted C6-C20 aryl.

[0047] In this case, the compound represented by the structural formula 1 is a dialkyl peroxide. When the compound represented by the structural formula 1 is a dialkyl peroxide, the co-embedding of solvent molecules can be suppressed, thereby improving the interfacial compatibility between the electrolyte and the negative electrode.

[0048] As an example, the compound represented by the structural formula 1 can be selected from the following compounds:

[0049] .

[0050] In some embodiments, in the compound represented by structural formula 1, R1 is selected from R2 is selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl or , where R 11 Selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C2-C12 ether.

[0051] In some embodiments, in the compound represented by structural formula 1, R1 is selected from ; R2 is selected from , where R 11 Selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C2-C12 ether.

[0052] In this case, the compound represented by Structural Formula 1 is a diacyl peroxide. When the compound represented by Structural Formula 1 is a diacyl peroxide, in addition to improving the battery cycle life, it can also decompose to form inert carbon dioxide during thermal runaway to dilute the explosion limit of the combustible gas, thereby improving battery safety.

[0053] As an example, the compound represented by the structural formula 1 can be selected from the following compounds:

[0054] .

[0055] In some embodiments, in the compound represented by structural formula 1, R1 is selected from R2 is selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, wherein R 11 Selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C2-C12 ether.

[0056] In this case, the compound represented by the structural formula 1 is a peroxy ester. When the compound represented by the structural formula 1 is a peroxy ester, the wettability of the electrolyte to the electrode can be improved, the ohmic internal resistance of the battery can be reduced, and the discharge performance of the battery can be improved.

[0057] As an example, the compound represented by the structural formula 1 can be selected from the following compounds:

[0058] .

[0059] In some embodiments, in the compound represented by structural formula 1, R1 is selected from , where R 12 R2 is selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl or , where R 13 is selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, and substituted or unsubstituted C2-C11 alkynyl.

[0060] In this case, the compound represented by the structural formula 1 is a peroxycarbonate or a peroxydicarbonate. When the compound represented by the structural formula 1 is a peroxycarbonate or a peroxydicarbonate, it has the effect of promoting the solvation of lithium ions and improving the lithium diffusion performance inside the battery.

[0061] As an example, the compound represented by the structural formula 1 can be selected from the following compounds:

[0062] .

[0063] In some embodiments, the compound represented by Structural Formula 1 includes one or more of the following compounds:

[0064] .

[0065] In a preferred embodiment, O 1s Peak and F 1s The peak area ratio Y is 0.4~0.5.

[0066] After lithium-ion batteries undergo the film-forming process of formation-aging-capacity separation, the non-aqueous electrolyte forms an organic-inorganic hybrid solid electrolyte interface film (SEI) at the solid-liquid interface of the negative electrode material. Li2O and LiF are two key inorganic components. LiF has a more critical influence on the protection of the SEI film, while Li2O has a lower lithium ion diffusion energy barrier and relatively high ionic conductivity. Increasing the Li2O component is beneficial to improving the coulomb efficiency and cycle life. In the XPS test of the SEI film on the negative electrode surface, the active component corresponding to the O1s peak with a binding energy of 528±1.0eV is Li2O, and the active component corresponding to the F1s peak with a binding energy of 685±1.0eV is LiF. When O 1s Peak and F 1s When the peak area ratio Y is within the above range, Li2O and LiF play a role in protecting the electrolyte from decomposition in an appropriate ratio.

[0067] In some embodiments, based on the total mass of the non-aqueous electrolyte being 100%, the mass content of the compound represented by Structural Formula 1 is 10 ppm to 1000 ppm.

[0068] In a specific embodiment, based on the total mass of the non-aqueous electrolyte as 100%, the mass content of the compound represented by structural formula 1 can be 10ppm, 20ppm, 30ppm, 40ppm, 50ppm, 60ppm, 70ppm, 80ppm, 90ppm, 100ppm, 110ppm, 120ppm, 130ppm, 140ppm, 150ppm, 160ppm, 170ppm, 180ppm, 190ppm, 200ppm, 210ppm, 220ppm, 230ppm m, 240ppm, 250ppm, 270ppm, 290ppm, 300ppm, 310ppm, 320ppm, 330ppm, 340ppm, 350ppm, 370ppm, 390ppm, 400ppm, 410ppm, 420ppm, 430ppm, 440ppm, 450ppm, 470ppm, 490ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm or a range consisting of any two of these values.

[0069] In a preferred embodiment, based on 100% of the total mass of the non-aqueous electrolyte, the mass content of the compound represented by Structural Formula 1 is 20 ppm to 500 ppm.

[0070] The content of the compound shown in structural formula 1 in the non-aqueous electrolyte will affect the relative content of Li2O and LiF components in the SEI film. When the content of the compound shown in structural formula 1 in the non-aqueous electrolyte is too low, the Li2O content in the SEI film will decrease, thereby increasing the negative electrode interface impedance. When the content of the compound shown in structural formula 1 in the non-aqueous electrolyte is too high, O 1s Peak and F 1s The increase of the area ratio Y of the peaks can easily lead to loose interface of SEI film and increase of interface side reactions. However, it should be noted that the content of the compound shown in structural formula 1 does not affect the O 1s Peak and F 1s The only factor affecting the area ratio Y of the peaks, for example, the wettability of the non-aqueous electrolyte to the negative electrode material layer affects the formation of the negative electrode solid electrolyte membrane. Under different compaction densities, the ratio of Li2O and LiF components in the obtained negative electrode solid electrolyte membrane is different; for example, the composition of the non-aqueous electrolyte, additives or impurities, etc., will cause changes in the components of the negative electrode SEI film; furthermore, the formation conditions of the lithium-ion battery will also affect the content ratio of different components in the SEI film. For example, adding a small amount of fluoroethylene carbonate to the non-aqueous electrolyte can promote the SEI to generate more LiF. For example, increasing the current density during the formation of the lithium-ion battery can induce the additive to undergo a two-electron reaction to form more Li2O. Furthermore, by controlling O1s Peak and F 1s The peak area ratio Y and the content of the compound represented by structural formula 1 can comprehensively consider the combined effects of the two on the performance of lithium-ion batteries and play a synergistic role in improving them.

[0071] In some embodiments, the formation conditions of the lithium-ion battery are: formation temperature of 40-50° C., formation pressure of 3-6 kg / cc, and charging current of 0.05-0.2C.

[0072] It should be emphasized that the non-aqueous electrolyte provided in the present application is not a precursor of a gel electrolyte or a solid electrolyte, nor is it suitable as a precursor of a gel electrolyte or a solid electrolyte. The reason is that the improvement of the electrochemical performance of the secondary battery in the present application depends on the regulation of the SEI film composition by the compound shown in Structural Formula 1 during the battery charge and discharge formation process, and the continued effect of the compound shown in Structural Formula 1 remaining in the electrolyte on lithium ion conduction during the long-term cycle of the battery. As a precursor of a gel electrolyte or a solid electrolyte, a polymerization operation will be performed to form a gel electrolyte before the battery charge and discharge formation. In this polymerization operation, the compound shown in Structural Formula 1 reacts with the polymerizable monomer as an initiator, resulting in the consumption of the compound shown in Structural Formula 1, and thus cannot play a corresponding role in the charge and discharge formation and battery charge and discharge cycle process.

[0073] In some embodiments, the non-aqueous electrolyte does not include a polymerizable monomer and / or a prepolymer obtained by polymerizing a polymerizable monomer.

[0074] In some embodiments, the polymerizable monomers include one or more of acrylate monomers (such as methyl acrylate, ethyl acrylate, butyl acrylate), acrylamide monomers (such as acrylamide, N,N'-methylenebisacrylamide), vinyl compound monomers (such as polyvinyl alcohol, vinyl pyrrolidone, vinyl imidazole), epoxy resin monomers (such as bisphenol A epoxy resin), polyethylene oxide monomers, polyacrylonitrile monomers, and siloxane monomers.

[0075] In some embodiments, the non-aqueous electrolyte does not undergo polymerization reaction under light or heating conditions.

[0076] In some embodiments, the non-aqueous electrolyte is in liquid state after formation.

[0077] In some embodiments, the viscosity of the non-aqueous electrolyte is 2 mPa·s to 10 mPa·s.

[0078] In some embodiments, the additive further comprises at least one of a cyclic sulfate compound, a sultone compound, a cyclic carbonate compound, a phosphate compound, a nitrile compound, a lithium salt additive, or an alkane compound.

[0079] In some embodiments, the cyclic sulfate ester compound includes at least one of vinyl sulfate, propylene sulfate, and methyl vinyl sulfate.

[0080] In some embodiments, the sultone compound includes at least one of 1,3-propane sultone, 1,4-butane sultone, 1,3-propene sultone, and methylene methanedisulfonate.

[0081] In some embodiments, the cyclic carbonate compound includes at least one of vinylene carbonate, vinyl ethylene carbonate, methylene carbonate, or a compound represented by Structural Formula 2:

[0082] ;

[0083] In the structural formula 2, R 21 、R 22 、R 23 、R 24 、R 25 、R 26 Each is independently selected from a hydrogen atom, a halogen atom, and a C1-C5 group.

[0084] In some embodiments, the phosphate compound includes a compound represented by structural formula 3:

[0085] ;

[0086] In the structural formula 3, R 31 、R 32 、R 33 Each independently selected from C1-C5 saturated hydrocarbon group, C1-C5 unsaturated hydrocarbon group, C1-C5 halogenated hydrocarbon group, C6-C12 aryl group, C6-C12 halogenated aryl group, -Si(C m H 2m+1 )3, m is a natural number from 1 to 3.

[0087] In some embodiments, the nitrile compound includes at least one of succinonitrile, glutaronitrile, hexanetrionitrile, adiponitrile, pimelonitrile, suberonitrile, azelaic acid dinitrile, and sebacononitrile.

[0088] In some embodiments, the lithium salt additive includes at least one of lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorophosphate, lithium tetrafluorophosphate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethylsulfonyl imide, lithium bispentafluoroethylsulfonyl imide, lithium trifluoromethanesulfonate, lithium monofluorosulfonate, lithium trioxalatophosphate, lithium difluorobisoxalatophosphate, lithium tetrafluorooxalatophosphate, lithium dicyanamide, or a lower aliphatic lithium carboxylate having 4 or fewer carbon atoms.

[0089] In some embodiments, the alkane compound includes at least one of cyclopentane, cyclohexane, cycloheptane, methylcyclopentane, ethylcyclopentane, 1,3-dimethylcyclopentane, 1,4-dimethylcyclopentane, methylcyclohexane, ethylcyclohexane, propylcyclohexane, butylcyclohexane, pentylcyclohexane, cis-1-methyl-3-ethylcyclohexane, trans-1-methyl-3-ethylcyclohexane, 1,3-dimethylcyclohexane, 1,4-dimethylcyclohexane, 1,3,5-trimethylcyclohexane and perfluoro(ethylcyclohexane).

[0090] In some embodiments, based on the total mass of the non-aqueous electrolyte being 100%, the total content of the additives is 1% to 12%.

[0091] In some embodiments, the mass content of any one of the optional substances in the additive is 0.01% to 10%. Specifically, the content of any one of the optional substances in the additive can be 0.01%, 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5%, 10% or a range consisting of any two of these values.

[0092] In some embodiments, the non-aqueous organic solvent includes at least one of an ether solvent, a nitrile solvent, a carbonate solvent, a carboxylate solvent, and a sulfone solvent.

[0093] In some embodiments, the ether solvent includes a cyclic ether or a chain ether, preferably a chain ether with 3 to 10 carbon atoms and a cyclic ether with 3 to 6 carbon atoms. The cyclic ether may be, but is not limited to, at least one of 1,3-dioxolane, 1,4-dioxane, crown ether, tetrahydrofuran, 2-methyltetrahydrofuran, and 2-trifluoromethyltetrahydrofuran; the chain ether may be, but is not limited to, dimethoxymethane, diethoxymethane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether. Since chain ethers have high solvation ability with lithium ions and can improve ion dissociation, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane, which have low viscosity and can impart high ionic conductivity, are particularly preferred. The ether compound can be used alone or in any combination and ratio. The content of the ether compound is not particularly limited and is arbitrary within a range that does not significantly impair the effect of the high-density lithium-ion battery of the present invention. The volume ratio is usually 1% or more, preferably 2% or more, and more preferably 3% or more, based on 100% by volume of the non-aqueous solvent. In addition, the volume ratio is usually 30% or less, preferably 25% or less, and more preferably 20% or less.

[0094] In some embodiments, the nitrile solvent may be, but is not limited to, at least one of acetonitrile, glutaronitrile, and malononitrile.

[0095] In some embodiments, the carbonate solvent includes a cyclic carbonate or a chain carbonate. The cyclic carbonate may be, but is not limited to, at least one of ethylene carbonate, propylene carbonate, γ-butyrolactone, and butylene carbonate; the chain carbonate may be, but is not limited to, at least one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and dipropyl carbonate. The content of the cyclic carbonate is not particularly limited and is arbitrary within the range that does not significantly damage the effect of the lithium-ion battery of the present invention. However, when using one alone, the lower limit of its content is generally 3% or more by volume, preferably 5% or more by volume, relative to the total amount of solvent in the non-aqueous electrolyte. By setting this range, the decrease in conductivity caused by the decrease in the dielectric constant of the non-aqueous electrolyte can be avoided, and it is easy to achieve good high-current discharge characteristics, stability relative to the negative electrode, and cycle characteristics of the non-aqueous electrolyte battery. In addition, the upper limit is generally 90% or less by volume, preferably 85% or less by volume, and more preferably 80% or less by volume. By setting this range, the oxidation / reduction resistance of the non-aqueous electrolyte can be improved, thereby helping to improve stability during high-temperature storage. The content of linear carbonate is not particularly limited, and with respect to the total amount of solvent of nonaqueous electrolytic solution, is generally volume ratio and is more than 15%, preferred volume ratio and is more than 20%, more preferably volume ratio and is more than 25%.In addition, usually volume ratio is below 90%, preferred volume ratio and is below 85%, more preferably volume ratio and is below 80%.By making the content of linear carbonate in above-mentioned scope, easily make the viscosity of nonaqueous electrolytic solution reach appropriate range, suppress the reduction of ionic conductivity, and then contribute to make the output characteristics of nonaqueous electrolyte battery reach good scope.When using in combination two or more linear carbonates, make the total amount of linear carbonate satisfy above-mentioned scope and get final product.

[0096] In certain embodiments, also can preferably use the linear carbonates with fluorine atoms (hereinafter referred to as " fluorinated linear carbonate ").The number of the fluorine atoms possessed by fluorinated linear carbonate is as long as being more than 1 then has no particular restrictions, but is generally below 6, preferably below 4.When fluorinated linear carbonate has a plurality of fluorine atoms, these fluorine atoms can be bonded on the same carbon, also can be bonded on different carbons.As fluorinated linear carbonate, can enumerate, fluorinated dimethyl carbonate derivatives, fluorinated ethyl methyl carbonate derivatives, fluorinated diethyl carbonate derivatives etc.

[0097] Carboxylate solvents include cyclic carboxylates and / or chain carbonates. Examples of cyclic carboxylates include at least one of γ-butyrolactone, γ-valerolactone, and δ-valerolactone. Examples of chain carbonates include at least one of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, propyl propionate, and butyl propionate.

[0098] In some embodiments, the sulfone solvent includes a cyclic sulfone and a chain sulfone. Preferably, in the case of a cyclic sulfone, it is generally a compound having 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms; in the case of a chain sulfone, it is generally a compound having 2 to 6 carbon atoms, preferably 2 to 5 carbon atoms. The content of the sulfone solvent is not particularly limited and is arbitrary within the range that does not significantly damage the effect of the lithium ion battery of the present invention. Relative to the total amount of solvent in the non-aqueous electrolyte, the volume ratio is generally 0.3% or more, preferably 0.5% or more, more preferably 1% or more. In addition, the volume ratio is generally 40% or less, preferably 35% or less, more preferably 30% or less. When two or more sulfone solvents are used in combination, the total amount of the sulfone solvent is sufficient to meet the above range. When the content of the sulfone solvent is within the above range, a non-aqueous electrolyte with excellent high-temperature storage stability tends to be obtained.

[0099] In a preferred embodiment, the non-aqueous organic solvent comprises a mixture of cyclic carbonate and chain carbonate.

[0100] In some embodiments, the electrolyte salt is selected from lithium salts, including LiPF6, LiBOB, LiPO2F2, LiBF4, LiSbF6, LiAsF6, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, LiClO4, LiAlCl4, LiCF3SO3, LiSO3F, Li2B 10 Cl 10 , lithium chloroborane, lithium trioxalophosphate, a lower aliphatic carboxylic acid lithium having 4 or less carbon atoms, or at least one of lithium tetraphenylborate.

[0101] In some embodiments, the concentration of the lithium salt in the non-aqueous electrolyte is 0.1 mol / L to 4 mol / L. In a preferred embodiment, the concentration of the lithium salt in the non-aqueous electrolyte is 0.5 mol / L to 2.5 mol / L. Specifically, in the non-aqueous electrolyte, the concentration of the lithium salt can be 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, 0.65 mol / L, 0.7 mol / L, 0.8 mol / L, 0.85 mol / L, 0.9 mol / L, 0.95 mol / L, 1.0 mol / L, 1.1 mol / L, 1.15 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.45 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2.0 mol / L, 2.1 mol / L, 2.2 mol / L, 2.3 mol / L, 2.4 mol / L, 2.5 mol / L or a range consisting of any two of these values.

[0102] In some embodiments, the positive electrode comprises a positive electrode material layer, the positive electrode material layer comprises a positive electrode active material, and the positive electrode active material is selected from LiFe 1-x’ M' x’ PO4、LiMn 2-y’ M y’ O4 and LiNi x Co y Mn z M 1-x-y-z At least one of O2, wherein M' is selected from at least one of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V or Ti, M is selected from at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V or Ti, and 0≤x'<1, 0≤y'≤1, 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1.

[0103] In a preferred embodiment, the positive electrode active material is selected from LiFe 1-x’ M' x’ PO4, wherein M' is selected from at least one of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V or Ti, and 0≤x'<1.

[0104] In a more preferred embodiment, the positive electrode active material is selected from LiFe 1-x’ Mn x’ PO4, where 0≤x'≤0.5.

[0105] In some embodiments, the positive electrode material layer further includes a positive electrode binder and a positive electrode conductor, and the positive electrode active material, the positive electrode binder and the positive electrode conductor are blended to obtain the positive electrode material layer.

[0106] The positive electrode binder includes polyvinylidene fluoride, a copolymer of vinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, a copolymer of tetrafluoroethylene-perfluoroalkyl vinyl ether, a copolymer of ethylene-tetrafluoroethylene, a copolymer of vinylidene fluoride-tetrafluoroethylene, a copolymer of vinylidene fluoride-trifluoroethylene, a copolymer of vinylidene fluoride-trichloroethylene, a copolymer of vinylidene fluoride-fluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, a thermoplastic resin such as polyethylene and polypropylene; an acrylic resin; and at least one of styrene butadiene rubber.

[0107] The positive electrode conductive agent includes at least one of conductive carbon black, conductive carbon balls, conductive graphite, conductive carbon fibers, carbon nanotubes, graphene, or reduced graphene oxide.

[0108] In some embodiments, the positive electrode current collector includes a metal material that can conduct electrons. Preferably, the positive electrode current collector includes at least one of Al, Ni, tin, copper, and stainless steel. In a more preferred embodiment, the positive electrode current collector is selected from aluminum foil.

[0109] In some embodiments, the negative electrode includes a negative electrode material layer, the negative electrode material layer including a negative electrode active material, and the negative electrode active material includes at least one of a carbon-based negative electrode, a silicon-based negative electrode, a tin-based negative electrode, and a lithium negative electrode. Carbon-based negative electrodes may include graphite, hard carbon, soft carbon, graphene, mesocarbon microbeads, and the like; silicon-based negative electrodes may include silicon materials, silicon oxides, silicon-carbon composites, and silicon alloys; tin-based negative electrodes may include tin, tin-carbon, tin-oxygen, and tin metal compounds; and lithium negative electrodes may include metallic lithium or a lithium alloy. Specifically, the lithium alloy may be at least one of a lithium-silicon alloy, a lithium-sodium alloy, a lithium-potassium alloy, a lithium-aluminum alloy, a lithium-tin alloy, and a lithium-indium alloy.

[0110] In a more preferred embodiment, the negative electrode active material includes at least one of graphite, hard carbon, soft carbon, graphene, and silicon-carbon composite materials.

[0111] In some embodiments, the silicon material is one or more of silicon nanoparticles, silicon nanowires, silicon nanotubes, silicon thin films, and porous silicon.

[0112] In some embodiments, the negative electrode further comprises a negative electrode current collector, and the negative electrode material layer covers the surface of the negative electrode current collector. The negative electrode current collector comprises an electron-conducting metal material, preferably comprising at least one of Al, Ni, tin, copper, and stainless steel. In a more preferred embodiment, the negative electrode current collector is selected from copper foil.

[0113] In some embodiments, the negative electrode material layer further includes a negative electrode binder and a negative electrode conductor, and the negative electrode active material, the negative electrode binder and the negative electrode conductor are blended to obtain the negative electrode material layer.

[0114] The negative electrode binder includes polyvinylidene fluoride, a copolymer of vinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, a copolymer of tetrafluoroethylene-perfluoroalkyl vinyl ether, a copolymer of ethylene-tetrafluoroethylene, a copolymer of vinylidene fluoride-tetrafluoroethylene, a copolymer of vinylidene fluoride-trifluoroethylene, a copolymer of vinylidene fluoride-trichloroethylene, a copolymer of vinylidene fluoride-fluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, a thermoplastic resin such as polyethylene and polypropylene; an acrylic resin; and at least one of styrene butadiene rubber.

[0115] The negative electrode conductive agent includes at least one of conductive carbon black, conductive carbon balls, conductive graphite, conductive carbon fibers, carbon nanotubes, graphene, or reduced graphene oxide.

[0116] In some embodiments, the secondary battery further includes a separator, and the separator is located between the positive electrode and the negative electrode.

[0117] The diaphragm can be an existing conventional diaphragm, which can be a ceramic diaphragm, a polymer diaphragm, a non-woven fabric, an inorganic-organic composite diaphragm, etc., including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP / PE, double-layer PP / PP and triple-layer PP / PE / PP diaphragms.

[0118] Example

[0119] The following examples and comparative examples are provided to more specifically illustrate the embodiments of the present invention. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0120] Example 1

[0121] This embodiment is used to illustrate the preparation method of the lithium ion battery disclosed in the present invention, which includes the following steps:

[0122] (1) Preparation of non-aqueous electrolyte:

[0123] The solvents ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) were mixed in a mass ratio of 5:2:5:8, and then lithium hexafluorophosphate (LiPF6) was added as an electrolyte salt and the additives shown in Table 1. After oscillation and homogenization, the mixture was filtered and allowed to stand for use. The content of lithium hexafluorophosphate in the non-aqueous electrolyte was 1 mol / L, and the content of each additive was as shown in Table 1.

[0124] (2) Injection and formation of battery cells:

[0125] In a glove box with a water content of <10 ppm and an oxygen content of <50 ppm, the prepared electrolyte was injected into a lithium iron phosphate / graphite dry cell and maintained at a vacuum of 20 kPa for 10 minutes. The encapsulated cell was then aged at 45°C for 48 hours. Formation was then carried out as shown in Table 1. After formation, the cell was evacuated and sealed, and then further charged at a constant current of 0.2C to 3.65V, then charged at a constant voltage to a cutoff of 0.03C, and then discharged at a constant current of 0.2C to 2.5V to obtain a lithium-ion battery.

[0126] Examples 2 to 24

[0127] Examples 2 to 24 are used to illustrate the lithium-ion batteries and preparation methods disclosed in the present invention, and include most of the steps in Example 1, except that:

[0128] The types and contents of the additives and the formation conditions in Examples 2 to 24 are shown in Table 1.

[0129] Comparative Examples 1 to 8

[0130] Comparative Examples 1 to 8 are used to illustrate the lithium ion battery and the preparation method thereof disclosed in the present invention, and include most of the operating steps in Example 1, except that:

[0131] The types and contents of the additives and the formation conditions in Comparative Examples 1 to 8 are shown in Table 1.

[0132] Table 1

[0133]

[0134] In Table 1, the formation conditions of "45°C, 0.1C cc for 60 minutes, 3kg / cc; 45°C, 0.2C cc for 90 minutes, 5kg / cc" indicate that the formation was divided into two stages: the first stage: temperature 45°C, charging current 0.1C, charging time 60 minutes, pressure 3kg / cc; the second stage: temperature 45°C, charging current 0.2C, charging time 90 minutes, pressure 5kg / cc.

[0135] VC is vinylene carbonate, MMDS is methylene methanedisulfonate, DTD is vinyl sulfate, PS is propane sultone, FPS is fluoropropane sultone, TVS is tetravinylsilane, SN is succinonitrile, FEC is fluoroethylene carbonate, HTCN is hexanetrinitrile, ECH is ethylcyclohexane, and TBMPi is triphenyl phosphite.

[0136] Performance Testing

[0137] 1. O on the negative electrode surface 1s Peak and F 1s Peak area ratio test:

[0138] The lithium-ion batteries prepared in the Examples and Comparative Examples were disassembled in an argon-filled glove box to obtain the negative electrode sheets. The resulting negative electrode sheets were cut into 8mm x 8mm test samples and soaked and cleaned in a low-boiling-point dimethyl carbonate (DMC) solvent for half an hour. After complete drying, they were attached to the XPS sample stage with the negative electrode material layer facing away from the current collector. The samples were vacuum degassed and then transferred to an X-ray photoelectron spectrometer (XPS) for measurement without exposure to the atmosphere. The specific test conditions and steps are as follows:

[0139] Ar ion gun etching was performed at a rate of 10 nm / min and an etching power of 1 kV; the etching time was 5 min, and the peak at the binding energy position of 528 ± 1.0 eV was used as the O 1s The peak at the binding energy position of 685±1.0eV is taken as F 1s Peak, O 1s Peak and F 1s The peak area ratio is recorded in Table 1

[0140] 2. Battery cycle test at room temperature:

[0141] After the capacity is divided, the battery is placed in a constant temperature environment at 25°C. After a short period of rest, it is charged at a constant current and constant voltage of 1C to 3.65V, with a cut-off current of 0.05C. After a short period of rest, it is discharged at a constant current of 1.5C to 2.5V. This charge and discharge cycle is repeated for 2000 cycles. The initial battery impedance and the battery impedance at the 2000th cycle are recorded, and the discharge capacity of each cycle is recorded.

[0142] Capacity retention rate (%) = 2000th cycle discharge capacity / first cycle discharge capacity * 100%, and calculate the average value of parallel samples;

[0143] Impedance growth rate (%) = (battery impedance at the 2000th cycle - battery initial impedance) / battery initial impedance * 100%.

[0144] (1) The test results obtained in Examples 1 to 10 and Comparative Examples 1 to 8 are shown in Table 2.

[0145] Table 2

[0146]

[0147] The test results of Examples 1-10 and Comparative Examples 1-8 show that in a battery system incorporating the compound represented by Structural Formula 1, when the lithium-ion battery satisfies the additional condition that the intensity ratio Y of the O1s peak to the F1s peak detected at the negative electrode is between 0.3 and 0.6, the resulting lithium-ion battery exhibits excellent long-cycle stability. This indicates that the inorganic components of the SEI film have an appropriate ratio of Li2O and LiF components, and in combination with the compound represented by Structural Formula 1, they can provide excellent protection for the lithium-intercalated negative electrode and reduce the occurrence of interfacial side reactions. However, when the Y value is less than 0.3, the Li2O content is low, the lithium ion diffusion barrier is high, and the interfacial film impedance increases, which is not conducive to the battery's rate discharge. When the Y value exceeds 0.6, the LiF content is low, the formed SEI film interface is relatively loose, resulting in increased side reactions, accelerated consumption of solvents and additives, and thus deteriorating the battery's cycle life.

[0148] At the same time, based on Examples 1 to 10, it can be seen that at low content, as the content of the compound represented by Structural Formula 1 increases, the Y value gradually increases, indicating that the Li2O component in the SEI film gradually increases at this time. When the content of the compound represented by Structural Formula 1 reaches a certain amount, the effect on the Y value is not obvious. When the intensity ratio Y of the O1s peak to the F1s peak is controlled between 0.3 and 0.6, and the content of the compound represented by Structural Formula 1 is controlled between 20 and 500 ppm, the cycle performance of the lithium ion battery is most significantly improved. The test results of Comparative Examples 2 to 5 and Comparative Examples 6 to 8 show that even under the condition of appropriate content of the compound represented by Structural Formula 1, when other additives or formation conditions are changed to cause the intensity ratio Y of the O1s peak to the F1s peak of the negative electrode to be too large or too small, the improvement effect of the compound represented by Structural Formula 1 on the lithium ion battery will not be exerted. This shows that in terms of improving the cycle performance of lithium ion batteries, the addition of the compound represented by Structural Formula 1 and the control of the intensity ratio Y of the O1s peak to the F1s peak of the negative electrode are both necessary.

[0149] (2) The test results obtained in Examples 4, 11 to 16 are entered in Table 3.

[0150] Table 3

[0151]

[0152] It can be seen from the test results of Examples 4 and 11 to 16 that in the battery system provided by the present invention, when the intensity ratio Y of the O1s peak to the F1s peak of the negative electrode satisfies 0.3 to 0.6, the use of different compounds represented by Structural Formula 1 as additives has a significant effect on improving the cycle capacity retention rate of the lithium-ion battery, and is also beneficial for reducing the cycle internal resistance. This shows that the battery system provided by the present invention is suitable for different types of compounds represented by Structural Formula 1, and the peroxide group -OO- shared by the compounds represented by different Structural Formula 1 is related to the performance improvement of the lithium-ion battery.

[0153] (3) The test results obtained in Examples 4, 17 to 20 are entered in Table 4.

[0154] Table 4

[0155]

[0156] It can be seen from the test results of Examples 4 and 17 to 20 that when the content of the compound represented by Structural Formula 1 is constant, adjusting the type and content of other additives in the electrolyte system will cause the intensity ratio Y of the O1s peak to the F1s peak at the negative electrode to change, thereby affecting the cycle capacity retention rate and impedance growth rate of the lithium-ion battery. This shows that the intensity ratio Y of the O1s peak to the F1s peak at the negative electrode is affected not only by the content of the compound represented by Structural Formula 1, but also by the composition of other additives in the non-aqueous electrolyte.

[0157] (4) The test results obtained in Examples 4 and 21 to 24 are entered in Table 5.

[0158] Table 5

[0159]

[0160] It can be seen from the test results of Examples 4 and 21 to 24 that when the content of the compound represented by Structural Formula 1 is constant, adjusting the formation conditions will cause the intensity ratio Y of the O1s peak to the F1s peak of the negative electrode to change, thereby affecting the cycle capacity retention rate and impedance growth rate of the lithium-ion battery. This shows that the intensity ratio Y of the O1s peak to the F1s peak of the negative electrode is affected not only by the content of the compound represented by Structural Formula 1, but also by the formation conditions.

[0161] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A lithium-ion battery, characterized in that: The invention comprises a positive electrode, a negative electrode and a non-aqueous electrolyte, wherein the non-aqueous electrolyte comprises a non-aqueous organic solvent, an electrolyte salt and an additive, wherein the additive comprises a compound shown in structural formula 1: Structural formula 1 wherein n is 0 or 1; R1 and R2 are each independently selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C1-C12 acyl, substituted or unsubstituted C2-C12 alkoxyacyl, substituted or unsubstituted C2-C12 ether, and R1, R2 are not hydrogen at the same time; R1 and R2 may be linked to form a ring or not; R3 is selected from substituted or unsubstituted C1-C12 alkylene, substituted or unsubstituted C2-12 alkenylene, substituted or unsubstituted C2-12 alkynylene, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C2-C12 ether; when R1, R2, and R3 are substituted, the substituent is an alkoxy group, a hydroxyl group, an acyl group, an ester group, a cyano group, or a halogen group; After the lithium-ion battery undergoes the film-forming process of formation-aging-capacity separation, the non-aqueous electrolyte forms an organic-inorganic hybrid solid electrolyte interface film at the solid-liquid interface of the negative electrode. The negative electrode surface is tested using an X-ray photoelectron spectrometer: an Ar ion gun is used to etch at a speed of 10 nm / min and an etching power of 1 kV; the etching time is 5 min, and the peak at the binding energy position of 528±1.0 eV is used as the O 1s The peak at the binding energy position of 685±1.0eV is taken as F 1s Peak, O 1s Peak and F 1s The peak area ratio Y is 0.3~0.

6.

2. The lithium-ion battery according to claim 1, wherein In the compound shown in the structural formula 1, R1 is selected from hydrogen, R2 is selected from , substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, wherein R 10 is selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, and substituted or unsubstituted C6-C20 aryl.

3. The lithium-ion battery according to claim 1, wherein In the compound represented by structural formula 1, R1 and R2 are each independently selected from a substituted or unsubstituted C1-C12 alkyl group, a substituted or unsubstituted C2-C12 alkenyl group, a substituted or unsubstituted C2-C12 alkynyl group, or a substituted or unsubstituted C6-C20 aryl group.

4. The lithium-ion battery according to claim 1, wherein In the compound shown in the structural formula 1, R1 is selected from R2 is selected from substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl or , where R 11 Selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C2-C12 ether.

5. The lithium-ion battery according to claim 1, wherein In the compound shown in the structural formula 1, R1 is selected from , where R 12 R2 is selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl or , where R 13 is selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, and substituted or unsubstituted C2-C11 alkynyl.

6. The lithium-ion battery according to claim 1, wherein The compound represented by the structural formula 1 includes one or more of the following compounds: 。 7. The lithium-ion battery according to claim 1, wherein Based on the total mass of the non-aqueous electrolyte being 100%, the mass content of the compound represented by structural formula 1 is 10 ppm to 1000 ppm.

8. The lithium-ion battery according to claim 1, wherein The non-aqueous electrolyte does not include a polymerizable monomer and / or a prepolymer obtained by polymerizing a polymerizable monomer.

9. The lithium-ion battery according to claim 1, wherein The additive further comprises at least one of a cyclic sulfate compound, a sultone compound, a cyclic carbonate compound, a phosphate compound, a nitrile compound, a lithium salt additive or an alkane compound; and / or The cyclic sulfate compound includes at least one of vinyl sulfate, propylene sulfate, and methyl vinyl sulfate; and / or The sultone compound includes at least one of 1,3-propane sultone, 1,4-butane sultone, 1,3-propylene sultone, and methylene methanedisulfonate; and / or The cyclic carbonate compound includes at least one of vinylene carbonate, vinyl ethylene carbonate, methylene carbonate or the compound shown in structural formula 2: Structural Formula 2 In the structural formula 2, R 21 、R 22 、R 23 、R 24 、R 25 、R 26 Each independently selected from a hydrogen atom, a halogen atom, a C1-C5 group; and / or The phosphate compound includes a compound shown in structural formula 3: Structural formula 3 In the structural formula 3, R 31 、R 32 、R 33 Each independently selected from C1-C5 saturated hydrocarbon group, C1-C5 unsaturated hydrocarbon group, C1-C5 halogenated hydrocarbon group, C6-C12 aryl group, C6-C12 halogenated aryl group, -Si(C m H 2m+1 )3, m is a natural number from 1 to 3; and / or The nitrile compound includes at least one of succinonitrile, glutaronitrile, hexanetrinitrile, adiponitrile, pimelonitrile, suberonitrile, azelaic acid dinitrile and sebacononitrile; and / or The lithium salt additive includes at least one of lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorophosphate, lithium tetrafluorophosphate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethylsulfonyl imide, lithium bispentafluoroethylsulfonyl imide, lithium trifluoromethanesulfonate, lithium monofluorosulfonate, lithium trioxalatophosphate, lithium difluorobisoxalatophosphate, lithium tetrafluorooxalatophosphate, lithium dicyanamide or a lower aliphatic lithium carboxylate having 4 or less carbon atoms; and / or The alkane compound includes at least one of cyclopentane, cyclohexane, cycloheptane, methylcyclopentane, ethylcyclopentane, 1,3-dimethylcyclopentane, 1,4-dimethylcyclopentane, methylcyclohexane, ethylcyclohexane, propylcyclohexane, butylcyclohexane, pentylcyclohexane, cis-1-methyl-3-ethylcyclohexane, trans-1-methyl-3-ethylcyclohexane, 1,3-dimethylcyclohexane, 1,4-dimethylcyclohexane, 1,3,5-trimethylcyclohexane and perfluoro(ethylcyclohexane).

10. The lithium-ion battery according to claim 1, wherein The negative electrode includes a negative electrode material layer, the negative electrode material layer includes a negative electrode active material, and the negative electrode active material includes one or more of soft carbon, hard carbon, artificial graphite, natural graphite, mesophase microcarbon beads, silicon, silicon oxides, silicon-carbon composites, metallic lithium or lithium titanate.

Images