WO2018028392A1 - Electrolyte solution and secondary battery - Google Patents

Abstract

Provided are an electrolyte solution and a secondary battery. The electrolyte solution comprises: an organic solvent; an electrolyte salt dissolved in the organic solvent; and an additive. The additive comprises: a silane compound, comprising one or more of compounds shown by formula 1; and one or more of dioxo-cyclic ethers. The electrolyte solution can comprehensively utilize a synergistic effect of the silane compound and the dioxo-cyclic ether to form a good protective film on the surfaces of a positive electrode and a negative electrode, able to reduce the reaction activity of the surface of the positive electrode, suppress the reduction of the electrolyte solution on the negative electrode and the oxidative decomposition of same at a high potential of the positive electrode, and suppress the elution of a transition metal element. At the same time, the impedance growth rate of the secondary battery during the cycle can be reduced. Therefore, the high-temperature cycle performance and the high-temperature storage performance of the secondary battery can be greatly improved simultaneously.

Description

Electrolyte and secondary battery Technical field

The present invention relates to the field of battery technologies, and in particular, to an electrolyte and a secondary battery.

Background technique

Increasing the operating voltage of the secondary battery is one of effective ways to increase the energy density of the secondary battery. At present, the negative electrode of a commercial lithium ion secondary battery mainly uses a graphite active material, and its lithium insertion potential is about 0.1 V (vs. Li/Li ⁺ ), which is very close to the theoretical lithium insertion potential of metallic lithium. Therefore, increasing the operating voltage of the lithium ion secondary battery can only improve the intercalation/deintercalation potential of the positive active material.

However, at high operating voltages, the positive electrode active material significantly enhances the oxidizing ability of the electrolyte, and with the dissolution of transition metal elements (especially manganese), lithium ion secondary batteries cause electrolysis during high temperature storage and cycle testing. The organic solvent of the liquid is continuously oxidized and decomposed, resulting in volume expansion of the lithium ion secondary battery, thereby causing capacity decay and safety hazard of the lithium ion secondary battery.

Summary of the invention

In view of the problems in the background art, an object of the present invention is to provide an electrolyte and a secondary battery which can simultaneously greatly improve the high temperature cycle performance and high temperature storage performance of the secondary battery.

In order to achieve the above object, in one aspect of the invention, the invention provides an electrolyte comprising: an organic solvent; an electrolyte salt dissolved in an organic solvent; and an additive. The additive includes a silane compound including one or more of the compounds represented by Formula 1; and one or more of dioxane ethers. Wherein R ₁ , R ₂ and R ₃ are each independently selected from the group consisting of H, F, Cl, Br, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, and a carbon number of 2 to 20 alkenyl groups, 2 to 20 alkenyloxy groups, 2 to 20 alkynyl groups, 2 to 20 alkynyloxy groups, and 6 to 26 carbon atoms; One of an aryl group and an aryloxy group having 6 to 26 carbon atoms; and R _{4 is} selected from the group consisting of an alkylene group having 1 to 20 carbon atoms, an alkenylene group having 2 to 20 carbon atoms, and a carbon number. And an alkylene group having 2 to 20 carbon atoms and 6 to 26 carbon atoms; and R _{5 is} selected from the group consisting of H, an alkyl group having 1 to 20 carbon atoms, and a carbon number of 1 to 20; An alkoxy group, an alkenyl group having 2 to 20 carbon atoms, an alkenyloxy group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkynyloxy group having 2 to 20 carbon atoms, or One of an aryl group having 6 to 26 carbon atoms and an aryloxy group having 6 to 26 carbon atoms; and a hydrogen atom on an alkoxy group, an alkenyloxy group, an alkynyloxy group or an aryloxy group may also be F , one or more substitutions of Cl, Br; alkyl, alkenyl, alkynyl, aryl, alkylene, alkenylene, alkynylene, Hydrogen atom on the aryl group may also be F, Cl, Br, a sulfonic acid group, a sulfonyl group, group, one or more cyano substituents.

In another aspect of the invention, the invention provides a secondary battery comprising an electrolyte according to an aspect of the invention.

Compared with the prior art, the beneficial effects of the present invention are:

The electrolyte of the invention can comprehensively utilize the coordination action of the silane compound and the dioxetane to form a good protective film on the surface of the positive and negative electrodes, thereby reducing the reactivity of the surface of the positive electrode, suppressing the reduction of the electrolyte at the negative electrode and the high potential at the positive electrode. The oxidative decomposition underneath inhibits the elution of the transition metal element and at the same time reduces the impedance growth rate of the secondary battery during the cycle, so that the high-temperature cycle performance and the high-temperature storage performance of the secondary battery can be greatly improved at the same time.

detailed description

Hereinafter, the electrolytic solution and the secondary battery according to the present invention will be described in detail.

First, the electrolytic solution according to the first aspect of the invention will be explained.

The electrolytic solution according to the first aspect of the invention includes: an organic solvent; an electrolyte salt dissolved in an organic solvent; and an additive. The additive includes a silane compound, including one or more of the compounds represented by Formula 1, and one or more of dioxane ethers. Wherein R ₁ , R ₂ and R ₃ are each independently selected from the group consisting of H, F, Cl, Br, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, and a carbon number of 2 to 20 alkenyl groups, 2 to 20 alkenyloxy groups, 2 to 20 alkynyl groups, 2 to 20 alkynyloxy groups, and 6 to 26 carbon atoms; One of an aryl group and an aryloxy group having 6 to 26 carbon atoms; and R _{4 is} selected from the group consisting of an alkylene group having 1 to 20 carbon atoms, an alkenylene group having 2 to 20 carbon atoms, and a carbon number. alkynylene group having 2 to 20 carbon atoms as a arylene group having 6 to 26 in; R ₅ is selected from H, an alkyl group having a carbon number of 1 to 20 carbon atoms and 1 to 20 An alkoxy group, an alkenyl group having 2 to 20 carbon atoms, an alkenyloxy group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkynyloxy group having 2 to 20 carbon atoms, or One of an aryl group having 6 to 26 carbon atoms and an aryloxy group having 6 to 26 carbon atoms; and a hydrogen atom on an alkoxy group, an alkenyloxy group, an alkynyloxy group or an aryloxy group may also be F , one or more substitutions of Cl, Br; alkyl, alkenyl, alkynyl, aryl, alkylene, alkenylene, alkynylene, The hydrogen atom on the aryl group may also be substituted by one or more of F, Cl, Br, a sulfonic acid group, a sulfonyl group, an amine group (which may be a primary amine, a secondary amine, a tertiary amine or a combination thereof) or a cyano group. .

In the electrolytic solution according to the first aspect of the present invention, the dioxane ether can preferentially decompose on the positive electrode side during initial charging of the secondary battery and form a uniform and stable protective film on the surface of the positive electrode active material, the protective film It can inhibit the decomposition of the electrolyte (organic solvent or electrolyte salt) at a high potential, and can also inhibit the dissolution of the transition metal at a high potential, thereby effectively improving the high-temperature storage gas production of the secondary battery. The silylation reaction between the silane compound and the electrolyte on the surface of the negative electrode effectively improves the surface of the negative electrode, and the introduced silicon-oxygen bond is more flexible, which helps to form a more elastic SEI film on the surface of the negative electrode active material, which is better. Adapt to the change in volume of the negative active material during charge and discharge. The simultaneously formed SEI film maintains the film thickness constant during the cycle, and the SEI film is advantageous for improving ion conduction. At the same time, the fluorosilane formed by the reaction of the silane compound with a trace amount of hydrofluoric acid in the electrolyte can be adsorbed on the surface of the positive electrode to further protect the interface of the positive electrode. When a silane compound and a dioxane ether are simultaneously added to the electrolyte, the synergistic action of the silane compound and the dioxane ether can be comprehensively utilized to form a good protective film on the surface of the positive and negative electrodes, which can reduce the reactivity of the surface of the positive electrode and inhibit electrolysis. The reduction of the liquid in the negative electrode and the oxidative decomposition at the high potential of the positive electrode inhibits the elution of the transition metal element and reduces the impedance growth rate of the secondary battery during the cycle, thereby simultaneously improving the high-temperature cycle performance and the high temperature of the secondary battery at the same time. Storage performance.

In the electrolytic solution according to the first aspect of the present invention, the alkyl group having 1 to 20 carbon atoms may be a chain alkyl group or a cycloalkyl group, and hydrogen located on the ring of the cycloalkyl group may be further Alkyl substitution. Place The lower limit of the number of carbon atoms in the alkyl group is preferably 2, 3, 4, and 5. The preferred upper limits are 3, 4, 5, 6, 8, 10, 12, 14, 16, and 18. Preferably, an alkyl group having 1 to 10 carbon atoms is selected. More preferably, a chain alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 8 carbon atoms is selected. Still more preferably, a chain alkyl group having 1 to 4 carbon atoms or a cycloalkyl group having 5 to 7 carbon atoms is selected. Specifically, the alkyl group having 1 to 20 carbon atoms may be selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, Isoamyl, neopentyl, cyclopentyl, cyclohexyl, dodecyl, hexadecyl or octadecyl.

In the electrolytic solution according to the first aspect of the present invention, the alkenyl group having 2 to 20 carbon atoms may be a cyclic alkenyl group or a chain alkenyl group. Further, the number of double bonds in the alkenyl group is preferably one. The lower limit of the number of carbon atoms in the alkenyl group is preferably 3, 4, and 5. The preferred upper limits are 3, 4, 5, 6, 8, 10, 12, 14, 16, and 18. Preferably, an alkenyl group having 2 to 10 carbon atoms is selected, and more preferably an alkenyl group having 2 to 6 carbon atoms is selected, and more preferably an alkenyl group having 2 to 5 carbon atoms is selected. Specifically, the alkenyl group having 2 to 20 carbon atoms may be selected from a vinyl group, an allyl group, an isopropenyl group, a pentenyl group, a cyclohexenyl group, a cycloheptenyl group or a cyclooctenyl group.

In the electrolytic solution according to the first aspect of the present invention, the alkynyl group having 2 to 20 carbon atoms may be a cyclic alkynyl group or a chain alkynyl group. Further, the number of double bonds in the alkynyl group is preferably one. The lower limit of the number of carbon atoms in the alkynyl group is preferably 3, 4, and 5. The preferred upper limits are 3, 4, 5, 6, 8, 10, 12, 14, 16, and 18. Preferably, an alkynyl group having 2 to 10 carbon atoms is selected, and an alkynyl group having 2 to 6 carbon atoms is more preferably selected, and an alkynyl group having 2 to 5 carbon atoms is more preferably selected. Specifically, the alkynyl group having 2 to 20 carbon atoms may be selected from an ethynyl group, a propargyl group, an isopropynyl group, a pentynyl group, a cyclohexynyl group, a cycloheptynyl group or a cyclooctynyl group.

In the electrolytic solution according to the first aspect of the present invention, the aryl group having 6 to 26 carbon atoms may be a phenyl group, a phenylalkyl group, an aryl group having at least one phenyl group (e.g., a biphenyl group), a fused ring. The aromatic hydrocarbon group (e.g., naphthyl, anthracenyl, phenanthryl), the biphenyl group and the fused ring aromatic hydrocarbon group may be further substituted by an alkyl group or an alkenyl group. Preferably, an aryl group having 6 to 16 carbon atoms is selected, and more preferably, an aryl group having 6 to 14 carbon atoms is selected, and even more preferably an aryl group having 6 to 9 carbon atoms is selected. Specifically, the aryl group having 6 to 26 carbon atoms may be selected from a phenyl group, a benzyl group, a biphenyl group, a p-tolyl group, an o-tolyl group, a m-tolyl group, a naphthyl group, an anthracenyl group or a phenanthryl group.

In the electrolytic solution according to the first aspect of the present invention, when the above-mentioned alkyl group having 1 to 20 carbon atoms contains an oxygen atom, an alkoxy group having 1 to 20 carbon atoms can be formed. Preferably, The alkoxy group having 1 to 10 carbon atoms is selected, and more preferably, an alkoxy group having 1 to 6 carbon atoms is selected, and more preferably, an alkoxy group having 1 to 4 carbon atoms is selected. Specifically, the alkoxy group having 1 to 20 carbon atoms may be selected from the group consisting of a methoxy group, an ethoxy group, a n-propoxy group, an isopropoxy group, a n-butoxy group, a sec-butoxy group, and a t-butoxy group. N-pentyloxy, isopentyloxy, cyclopentyloxy or cyclohexyloxy.

In the electrolytic solution according to the first aspect of the present invention, when the above-mentioned alkenyl group having 2 to 20 carbon atoms contains an oxygen atom, an alkenyloxy group having 2 to 20 carbon atoms can be formed. Preferably, an alkenyloxy group having 2 to 10 carbon atoms is selected, and more preferably, an alkenyloxy group having 2 to 6 carbon atoms is selected, and even more preferably, an alkenyloxy group having 2 to 5 carbon atoms is selected. . Specifically, the alkenyloxy group having 2 to 20 carbon atoms may be selected from a vinyloxy group, an allyloxy group, an isopropenyloxy group, a pentenyloxy group, a cyclohexenyloxy group, a cycloheptenyloxy group or a cyclooctyl group. Alkenyloxy.

In the electrolytic solution according to the first aspect of the present invention, when the alkynyl group having 2 to 20 carbon atoms as mentioned above contains an oxygen atom, an alkyne group having 2 to 20 carbon atoms can be formed. Preferably, the alkynyloxy group having 2 to 10 carbon atoms is selected, and more preferably, the alkynyloxy group having 2 to 6 carbon atoms is selected, and more preferably, the alkynyloxy group having 2 to 5 carbon atoms is selected. . Specifically, the alkynyloxy group having 2 to 20 carbon atoms may be selected from the group consisting of an ethynyloxy group, a propargyloxy group, an isopropynyloxy group, a pentynyloxy group, a cyclohexynyloxy group, a cycloheptynyloxy group or a ring. Octenyloxy.

In the electrolytic solution according to the first aspect of the present invention, when the aryl group having 6 to 26 carbon atoms as mentioned above contains an oxygen atom, an aryloxy group having 6 to 26 carbon atoms can be formed. Preferably, an aryloxy group having 6 to 16 carbon atoms is selected, and more preferably, an aryloxy group having 6 to 14 carbon atoms is selected, and still more preferably an aryloxy group having 6 to 10 carbon atoms is selected. Specifically, the aryloxy group having 6 to 26 carbon atoms may be selected from the group consisting of a phenoxy group, a benzyloxy group, a 4-methylphenoxy group, a 3,5-dimethylphenoxy group, and a 4-methylbenzyloxy group. Base, 3-methylbenzyloxy, 2,6-diisopropylbenzyloxy or 1-naphthyloxy.

In the electrolytic solution according to the first aspect of the present invention, the above-mentioned alkyl group having 1 to 20 carbon atoms, alkenyl group having 2 to 20 carbon atoms, and alkyne having 2 to 20 carbon atoms are mentioned. a group, an aryl group having 6 to 26 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkenyloxy group having 2 to 20 carbon atoms, an alkynyloxy group having 2 to 20 carbon atoms, or carbon When a hydrogen atom on an aryloxy group having 6 to 26 atoms is substituted by a halogen atom F, Cl or Br, a halogenated alkyl group having 1 to 20 carbon atoms and a halogenated group having 2 to 20 carbon atoms are sequentially formed. An alkenyl group, a haloalkynyl group having 2 to 20 carbon atoms, a halogenated aryl group having 6 to 26 carbon atoms, a halogenated alkoxy group having 1 to 20 carbon atoms, or a halogen having 2 to 20 carbon atoms. a substituted alkenyloxy group, a haloalkynyloxy group having 2 to 20 carbon atoms, and a carbon number of 6 to 26 The halogenated aryloxy group wherein the halogen atom is preferably F or Cl. In the halogen group to be formed, one or more of the halogen atoms F, Cl, and Br are substituted for a part of hydrogen atoms or all hydrogen atoms, and the number of halogen atoms to be substituted is not limited, and preferably It is 1, 2, 3 or 4.

In the electrolytic solution according to the first aspect of the present invention, preferably, a halogenated alkyl group having 1 to 10 carbon atoms, a halogenated alkenyl group having 2 to 10 carbon atoms, and a carbon number of 2 to 10 are selected. a haloalkynyl group, a halogenated aryl group having 6 to 16 carbon atoms, a halogenated alkoxy group having 1 to 10 carbon atoms, a halogenated alkenyloxy group having 2 to 10 carbon atoms, and 2 to 2 carbon atoms. A haloalkynyloxy group of 10 or a halogenated aryloxy group having 6 to 16 carbon atoms. Further preferably, a halogenated chain alkyl group having 1 to 6 carbon atoms, a halogenated cycloalkyl group having 3 to 8 carbon atoms, a halogenated alkenyl group having 2 to 6 carbon atoms, and a carbon number are selected. a halogenated alkynyl group of 2 to 6, a halogenated aryl group having 6 to 14 carbon atoms, a halogenated alkoxy group having 1 to 6 carbon atoms, a halogenated alkoxy group having 2 to 6 carbon atoms, or carbon The haloalkynyloxy group having 2 to 6 atoms and the halogenated aryloxy group having 6 to 14 carbon atoms. Still more preferably, a halogenated chain alkyl group having 1 to 4 carbon atoms, a halogenated cycloalkyl group having 5 to 7 carbon atoms, a halogenated alkenyl group having 2 to 5 carbon atoms, and a carbon atom are selected. a halogenated alkynyl group having 2 to 5, a halogenated aryl group having 6 to 10 carbon atoms, a halogenated alkoxy group having 1 to 4 carbon atoms, a halogenated alkoxy group having 2 to 5 carbon atoms, or carbon The haloalkynyloxy group having 2 to 5 atoms and the halogenated aryloxy group having 6 to 10 carbon atoms.

In the electrolytic solution according to the first aspect of the present invention, specific examples of the halogenated group include trifluoromethyl (-CF ₃ ), 2-fluoroethyl, 3-fluoro-n-propyl, 2-fluoroisopropyl, 4-fluoro-n-butyl, 3-fluorosec-butyl, 5-fluoro-n-pentyl, 4-fluoroisopentyl, 1-fluorovinyl, 3-fluoroallyl, 6- Fluoro-4-hexenyl, o-fluorophenyl, p-fluorophenyl, m-fluorophenyl, 4-fluoromethylphenyl, 2,6-difluoromethylphenyl, 2-fluoro-1-naphthyl , fluoromethoxy, 1-fluoroethoxy, 2-fluoro-n-propoxy, 1-fluoro-isopropoxy, 3-fluoro-n-butoxy, 4-fluoro-n-pentyloxy, 2,2-Difluoromethylpropoxy, 5-fluoro-n-hexyloxy, 1,1,2-trifluoromethylpropoxy, 6-fluoro-n-heptyloxy, 7-fluoro-n-octyl Alkoxy, 3-fluoro-cyclopentyloxy, 4-fluoro-2-methylcyclopentyloxy, 3-fluoro-cyclohexyloxy, 3-fluorocycloheptyloxy, 4-fluoro-2-methyl Cycloheptyloxy, 3-fluorocyclooctyloxy, 4-fluorophenoxy, 3-fluorophenoxy, 2-fluorophenoxy, 3,5-difluorophenoxy, 2,6-di Fluorophenoxy, 2,3-difluorophenoxy, 2,6-difluoro-4-methylphenoxy, 3-(2-fluoroethyl)phenoxy, 2-(1-fluoroethyl Phenoxy, 3,5-di Fluobenzyloxy, 2-fluorobenzyloxy, 2-fluoro-1-naphthyloxy. In the above specific examples, F may be substituted by Cl and/or Br.

In the electrolytic solution according to the first aspect of the present invention, the number of carbon atoms is 1 to 20 alkyl groups, the number of carbon atoms is 2 to 20, the alkynyl group having 2 to 20 carbon atoms, and the number of carbon atoms is 6 to 26 aryl groups After the hydrogen atom is substituted by a sulfonic acid group or a sulfonyl group, the corresponding sulfonic acid alkyl group, sulfonic acid alkenyl group, sulfonic acid alkynyl group, sulfonic acid aryl group, alkylsulfonyl group, alkenylsulfonyl group, Alkynylsulfonyl, arylsulfonyl. The sulfonic acid group may be substituted with a part of hydrogen atoms or all hydrogen atoms in the above alkyl group, alkenyl group, alkynyl group or aryl group, and the number of the sulfonic acid groups may be one or two. Similarly, the sulfonyl group may be substituted with a part of hydrogen atoms or all hydrogen atoms in the above alkyl group, alkenyl group, alkynyl group or aryl group, and the number of the sulfonyl group may be one or two.

In the electrolytic solution according to the first aspect of the present invention, examples of the sulfonyl group include methylsulfonyl group, ethylsulfonyl group, n-propylsulfonyl group, isopropylsulfonyl group and n-butyl group. Sulfonyl, isobutylsulfonyl, tert-butylsulfonyl, n-pentylsulfonyl, isopentylsulfonyl, neopentylsulfonyl, 2,3-dimethylpropylsulfonyl, 1-ethyl Propylsulfonyl, n-hexylsulfonyl, cyclopentylsulfonyl, cyclohexylsulfonyl, cycloheptylsulfonyl, cyclooctylsulfonyl, n-heptylsulfonyl, n-octylsulfonyl, cycloheptylsulfonyl , cyclooctylsulfonyl, propenylsulfonyl, butenylsulfonyl, pentenylsulfonyl, hexenylsulfonyl, heptenylsulfonyl, octenylsulfonyl, phenylsulfonyl, 4-methyl Benzosulfonyl or 4-ethylbenzenesulfonyl.

In the electrolytic solution according to the first aspect of the present invention, as an example containing a sulfonic acid group, a sulfonic acid methyl group, a 2-sulfonic acid ethyl group, a 3-sulfonic acid n-propyl group, and the like may be specifically mentioned. 4-sulfonic acid n-butyl, sulfonic acid tert-butyl, 2-sulfonic acid n-pentyl, 3-sulfonic acid isopentyl, 6-sulfonyl n-hexyl, 2-sulfonic acid cyclopentyl , 4-sulfonic acid cyclohexyl, sulfonic acid propenyl, sulfonic acid butenyl, sulfonic acid pentenyl, sulfonic hexenyl, sulfonyl heptyl, sulfonic acid octenyl, Sulfophenyl or 4-sulfonic acid methylphenyl.

In the electrolytic solution according to the first aspect of the present invention, the alkyl group having 1 to 20 carbon atoms, the alkenyl group having 2 to 20 carbon atoms, the alkynyl group having 2 to 20 carbon atoms, and the number of carbon atoms When an aryl group of 6 to 26 loses one hydrogen atom, an alkylene group having 1 to 20 carbon atoms, an alkenylene group having 2 to 20 carbon atoms, an alkynylene group having 2 to 20 carbon atoms, or the like, An arylene group having 6 to 26 carbon atoms.

In the electrolytic solution according to the first aspect of the present invention, the alkylene group having 1 to 20 carbon atoms, the alkenylene group having 2 to 20 carbon atoms, the alkynylene group having 2 to 20 carbon atoms, When a hydrogen atom on an arylene group having 6 to 26 carbon atoms is substituted by a halogen atom F, Cl or Br, a halogenated alkylene group having 1 to 20 carbon atoms is formed in order, and the number of carbon atoms is 2 to 2 A halogenated alkenylene group of 20, a halogenated alkynylene group having 2 to 20 carbon atoms, or a halogenated arylene group having 6 to 26 carbon atoms, wherein the halogen atom is preferably F or Cl. In the halogen group formed, one or more of the halogen atoms F, Cl, and Br are partially hydrogen atoms or All of the hydrogen atoms are substituted, and the number of halogen atoms to be substituted is not limited, and preferably one, two, three or four.

In the electrolytic solution according to the first aspect of the invention, the silane compound is selected from one or more of the following compounds;

In the electrolytic solution according to the first aspect of the present invention, the dioxane ether is one selected from the group consisting of 1,3-dioxolane, 1,3-dioxane, and 1,4-dioxane. Or several.

In the electrolytic solution according to the first aspect of the present invention, preferably, the silane compound is one or more selected from the group consisting of Compound 1, Compound 2, Compound 3, Compound 4, Compound 5, Compound 10, Compound 11, and Compound 16. Kind.

In the electrolytic solution according to the first aspect of the invention, the total mass of the additive may be 0.2% to 10% of the total mass of the electrolytic solution.

In the electrolytic solution according to the first aspect of the invention, the mass of the dioxane is from 0.1% to 5% by mass based on the total mass of the electrolyte.

In the electrolytic solution according to the first aspect of the present invention, the mass of the silane compound is an electrolyte 0.1% to 5% of the total mass.

In the electrolytic solution according to the first aspect of the invention, preferably, the organic solvent is a non-aqueous organic solvent. Specifically, the organic solvent may include a cyclic ester and a chain ester. The cyclic ester is selected from one or more of ethylene carbonate, propylene carbonate, butylene carbonate, and tetrahydrofuran. The chain ester is selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl formate, ethyl formate, propyl formate, acetic acid. One or more of methyl ester, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, dimethyl sulfite, diethyl sulfite.

In the electrolytic solution according to the first aspect of the invention, the mass of the cyclic ester is from 20% to 50% of the total mass of the electrolytic solution.

In the electrolytic solution according to the first aspect of the present invention, the mass of the chain ester is 40% to 80% of the total mass of the electrolytic solution.

In the electrolytic solution according to the first aspect of the invention, the total mass of the organic solvent may be from 60% to 85% of the total mass of the electrolytic solution.

In the electrolytic solution according to the first aspect of the invention, the electrolyte salt may be a lithium salt, a sodium salt or a zinc salt, which varies depending on the secondary battery to which the electrolyte is applied.

In the electrolytic solution according to the first aspect of the invention, the concentration of the electrolyte salt in the electrolytic solution is from 0.3 M to 1.8 M.

Next, a secondary battery according to a second aspect of the present invention, which comprises the electrolytic solution according to the first aspect of the invention, is explained.

The secondary battery according to the second aspect of the present invention may be a lithium ion secondary battery, a sodium ion secondary battery, or a zinc ion secondary battery.

The secondary battery according to the second aspect of the invention further includes a positive electrode sheet, a negative electrode sheet, a separator, and a packaging foil. The positive electrode sheet includes a positive electrode current collector and a positive electrode film containing a positive electrode active material provided on the positive electrode current collector. The negative electrode sheet includes a negative electrode current collector and an negative electrode film containing a negative electrode active material disposed on the negative electrode current collector. The separator is spaced between adjacent positive and negative sheets. The packaging foil can be aluminum foil.

When the secondary battery is a lithium ion secondary battery, the positive electrode active material is selected from the group consisting of LiCoO ₂ , LiMnO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , One or more of LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , LiNi _0.4 Co _0.2 Mn _0.4 O ₂ , and LiFePO ₄ . The negative active material may be selected from one or more of natural graphite, artificial graphite, soft carbon, hard carbon, lithium titanate, and silicon. The upper limit cutoff voltage of the lithium ion secondary battery is 4.35 V to 4.6 V. The electrolyte salt is a lithium salt. The lithium salt is selected from the group consisting of LiPF ₆ , LiBF ₄ , LiBOB, LiDFOB, LiAsF ₆ , LiClO ₄ , LiFAP, LiCF ₃ SO ₃ , Li(FSO ₂ ) ₂ N, Li(SO ₂ (CF ₂ ) ₃ SO ₂ ) ₂ One or more of N, Li(SO ₂ R _F ) ₂ N, Li(SO ₂ F)(SO ₂ R _F )N, R _F is C _n F _2n+1 , n is an integer of 1-10 . Preferably, the lithium salt is selected from one or more of LiPF ₆ , LiBF ₄ , LiBOB, Li(FSO ₂ ) ₂ N. At this time, the upper limit cutoff voltage of the lithium ion secondary battery to which the electrolytic solution of the present invention is applied can reach 4.35 V to 4.6 V.

When the secondary battery is a sodium ion secondary battery or a zinc ion secondary battery, it is only necessary to change the corresponding positive electrode active material, negative electrode active material, and electrolyte salt.

The present application is further illustrated below in conjunction with the embodiments. It is to be understood that the examples are not intended to limit the scope of the application. Only the case where the secondary battery is a lithium ion secondary battery is shown in the embodiment, but the invention is not limited thereto.

Example 1

(1) Preparation of positive electrode sheet

The positive electrode active material LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , the conductive agent Super-P, and the binder PVDF are dissolved in a solvent N-methylpyrrolidone at a mass ratio of 97.2:1.3:1.5 to form a positive electrode slurry, and then The positive electrode slurry was uniformly coated on the double-sided current collector aluminum foil, and the coating amount was 0.0102 g/cm ² , followed by drying at 85 ° C, followed by cold pressing, trimming, cutting, and slitting, followed by vacuum at 85 ° C. After drying for 4 hours under conditions, the tabs were welded to form a positive electrode sheet.

(2) Preparation of negative electrode sheet

The negative electrode active material artificial graphite, conductive agent Super-P, thickener CMC, and binder SBR are mixed in a solvent deionized water at a mass ratio of 95.4:1.2:1.2:2.2 to form a negative electrode slurry, and then the negative electrode slurry is prepared. The material was uniformly coated on the double-sided current collector copper foil, and the coating weight was 0.0071 g/cm ² , followed by drying at 85 ° C, followed by cold pressing, trimming, cutting, and slitting, followed by vacuum at 110 ° C. After drying for 4 h, the tabs were welded to prepare a negative electrode sheet.

(3) Preparation of electrolyte

The electrolyte solution has a lithium salt of 1 mol/L of LiPF _{6 and} an organic solvent of a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC), wherein the mass ratio of EC and EMC is 30:70. Further, the electrolyte further contains an additive which is a 1,3-dioxolane which accounts for 1% of the total mass of the electrolyte and a compound 5 which accounts for 2% of the total mass of the electrolyte.

(4) Preparation of lithium ion secondary battery

The positive electrode sheet, the negative electrode sheet, and the separator (PE film, including the ceramic coating layer) are subjected to a winding process to form a battery core having a thickness of 5.7 mm, a width of 16 mm, and a length of 33 mm, wherein the battery core has a long air bag. In order to observe its gas production. And vacuum-bake at 85 ° C for 14h (vacuum degree <-0.08MPa), inject the electrolyte, let stand for 24h, then charge to 3.4V with a constant current of 0.05C (11mA), remove the battery and then perform a vacuum pre-emption The package is degassed, then charged to 4.5V with a constant current of 0.05C (11mA), and then the battery is removed for a second degassing, and then discharged to a constant current of 0.5C (110mA) to 2.8V, repeating 2 The charge and discharge were repeated, and finally charged to 3.8 V at a constant current of 0.5 C (110 mA) to complete the preparation of the lithium ion secondary battery.

Example 2

A lithium ion secondary battery was prepared according to the method of Example 1, except that in the preparation of the electrolytic solution (ie, step (3)), the additive was 1,3-dioxolane and 2% of the total mass of the electrolyte. The total mass of the liquid is 2% of compound 5.

Example 3

A lithium ion secondary battery was prepared according to the method of Example 1, except that in the preparation of the electrolytic solution (ie, step (3)), the additive was 1,3-dioxolane and occupies 3% of the total mass of the electrolyte. The total mass of the liquid is 2% of compound 5.

Example 4

A lithium ion secondary battery was prepared according to the method of Example 1, except that in the preparation of the electrolyte (ie, step (3)), the additive was 1,3-dioxolane and 4% of the total mass of the electrolyte. The total mass of the liquid is 2% of compound 5.

Example 5

A lithium ion secondary battery is prepared according to the method of Example 1, except that in the preparation of the electrolyte (ie, step (3)), the additive is 1,3-dioxolane and occupies 5% of the total mass of the electrolyte. Liquid Compound 5 with a total mass of 2%.

Example 6

A lithium ion secondary battery was prepared according to the method of Example 1, except that in the preparation of the electrolytic solution (ie, step (3)), the additive was 1,3-dioxolane and occupies 3% of the total mass of the electrolyte. The total mass of the liquid is 1% of compound 5.

Example 7

A lithium ion secondary battery was prepared according to the method of Example 1, except that in the preparation of the electrolytic solution (ie, step (3)), the additive was 1,3-dioxolane and occupies 3% of the total mass of the electrolyte. The total mass of the liquid was 3% of Compound 5.

Example 8

A lithium ion secondary battery was prepared according to the method of Example 1, except that in the preparation of the electrolytic solution (ie, step (3)), the additive was 1,3-dioxolane and occupies 3% of the total mass of the electrolyte. The total mass of the liquid is 4% of compound 5.

Example 9

A lithium ion secondary battery was prepared according to the method of Example 1, except that in the preparation of the electrolytic solution (ie, step (3)), the additive was 1,3-dioxolane and occupies 3% of the total mass of the electrolyte. The total mass of the liquid is 5% of compound 5.

Example 10

A lithium ion secondary battery was prepared according to the method of Example 1, except that in the preparation of the electrolytic solution (ie, step (3)), the additive was 1,3-dioxolane and occupies 3% of the total mass of the electrolyte. The total mass of the liquid was 2% of Compound 1.

Example 11

A lithium ion secondary battery was prepared according to the method of Example 1, except that in the preparation of the electrolytic solution (ie, step (3)), the additive was 1,3-dioxolane and occupies 3% of the total mass of the electrolyte. Liquid Compound 2 with a total mass of 2%.

Example 12

A lithium ion secondary battery was prepared according to the method of Example 1, except that in the preparation of the electrolytic solution (ie, step (3)), the additive was 1,3-dioxolane and occupies 3% of the total mass of the electrolyte. The total mass of the liquid is 2% of compound 3.

Example 13

A lithium ion secondary battery was prepared according to the method of Example 1, except that in the preparation of the electrolytic solution (ie, step (3)), the additive was 1,3-dioxolane and occupies 3% of the total mass of the electrolyte. The total mass of the liquid is 2% of compound 4.

Example 14

A lithium ion secondary battery was prepared according to the method of Example 1, except that in the preparation of the electrolytic solution (ie, step (3)), the additive was 1,4-dioxane and 3% of the total mass of the electrolyte. The total mass of the liquid is 2% of compound 13.

Example 15

A lithium ion secondary battery was prepared according to the method of Example 1, except that in the preparation of the electrolytic solution (ie, step (3)), the additive was 1,3-dioxane and 3% of the total mass of the electrolyte. The total mass of the liquid is 2% of compound 14.

Example 16

A lithium ion secondary battery was prepared according to the method of Example 1, except that in the preparation of the electrolytic solution (ie, step (3)), the additive was 1,4-dioxane and 3% of the total mass of the electrolyte. The total mass of the liquid is 2% of compound 5.

Example 17

A lithium ion secondary battery was prepared according to the method of Example 1, except that in the preparation of the electrolytic solution (ie, step (3)), the additive was 1,3-dioxane and 3% of the total mass of the electrolyte. Liquid Compound 5 with a total mass of 2%.

Comparative example 1

A lithium ion secondary battery was prepared in accordance with the method of Example 1, except that in the preparation of the electrolytic solution (i.e., the step (3)), no additive was added.

Comparative example 2

A lithium ion secondary battery is prepared according to the method of Example 1, except that in the preparation of the electrolyte (ie, step (3)), the additive is 0.05% of the total mass of the electrolyte, 1,3-dioxolane and electrolysis Compound 5 was 0.05% of the total mass of the liquid.

Comparative example 3

A lithium ion secondary battery was prepared according to the method of Example 1, except that in the preparation of the electrolyte (ie, step (3)), the additive was 1,3-dioxolane and occupies 6% of the total mass of the electrolyte. The total mass of the liquid was 6% of Compound 5.

Comparative example 4

A lithium ion secondary battery was prepared in accordance with the method of Example 1, except that in the preparation of the electrolytic solution (i.e., in the step (3)), the additive was 1,3-dioxolane in an amount of 3% by mass based on the total mass of the electrolytic solution.

Comparative example 5

A lithium ion secondary battery was prepared in accordance with the method of Example 1, except that in the preparation of the electrolytic solution (i.e., the step (3)), the additive was Compound 5 which was 2% by mass of the total mass of the electrolytic solution.

Finally, the test process and test results of the lithium ion secondary battery are explained.

(1) High temperature cycle performance test of lithium ion secondary battery

At 45 ° C, the lithium ion secondary battery was first charged to 4.5 V with a constant current of 0.5 C, further charged to a current of 0.025 C at a constant voltage of 4.5 V, and then discharged to a lithium ion secondary battery at a constant current of 0.5 C. To 2.8V, this is a charge and discharge cycle, and the discharge capacity of this time is the discharge capacity of the first cycle. The lithium ion secondary battery is subjected to a cyclic charge and discharge test in the above manner, and the first Discharge capacity of 100 cycles.

Capacity retention ratio (%) after 100 cycles of the lithium ion secondary battery = [discharge capacity at the 100th cycle / discharge capacity at the first cycle] × 100%.

(2) High-temperature storage performance test of lithium ion secondary battery

The lithium ion secondary battery was first charged to 4.5 V at a constant current of 0.5 C at 25 ° C, further charged to a current of 0.025 C at a constant voltage of 4.5 V, and then the lithium ion secondary battery was drained in deionized water. The initial volume (the volume before the high-temperature storage of the lithium ion secondary battery) was measured and stored at 60 ° C for 30 days. After the storage was completed, the volume of the lithium ion secondary battery after high-temperature storage was tested.

Volume expansion ratio (%) of lithium ion secondary battery after high temperature storage = [(volume after high temperature storage of lithium ion secondary battery - volume before high temperature storage of lithium ion secondary battery) / before high temperature storage of lithium ion secondary battery Volume] × 100%.

Table 1 Parameters and performance test results of Examples 1-17 and Comparative Examples 1-5

Next, the performance test results of Examples 1-17 and Comparative Examples 1-5 were analyzed.

As can be seen from Table 1, the lithium ion secondary battery to which the dioxane ether and the silane compound of the present invention are added has better high-temperature cycle performance and high-temperature storage than the lithium ion secondary battery of Comparative Example 1 without adding any additive. performance. In Comparative Example 4, the addition of dioxane ether alone can only form a good interfacial film on the positive electrode side unilaterally, inhibiting the oxidative decomposition of the electrolyte on the positive electrode side, and the organic solvent can be continuously reduced and decomposed on the negative electrode side. The generation of gas also causes a decline in the capacity of the lithium ion secondary battery. In Comparative Example 5, the silane compound was separately added, since an excellent SEI film could be formed only on the negative electrode side unilaterally, and the organic solvent would continuously oxidize and decompose the gas at a high potential, resulting in accelerated decay of the capacity of the lithium ion secondary battery.

When the content of the dioxetane and the silane compound is more than 5% (Comparative Example 3), the high-temperature cycle performance of the lithium ion secondary battery is deteriorated, possibly because the additive occupies an excessive proportion of the organic solvent, so that the viscosity of the electrolyte is excessive. Large, leading to increased lithium ion migration resistance, while the protective film formed on the positive and negative electrodes is too thick, which affects the high temperature cycle performance of the lithium ion secondary battery. However, the high-temperature storage performance of the lithium ion secondary battery is still relatively improved, because the interface film formed on the surface of the positive and negative electrodes by the high content of the dioxetane and the silane compound lowers the reactivity of the surface of the positive electrode, thereby The reduction of the electrolyte at the negative electrode and the oxidation of the positive electrode are effectively suppressed. When the content of the dioxetane and the silane compound is less than 0.1% (Comparative Example 2), the improvement in the high-temperature cycle performance and the high-temperature storage property of the lithium ion secondary battery is not remarkable.

It can be seen from the comparison of Example 3 and Examples 10-15 that the larger the molecular weight of the substituent, the larger the spatial structure of the compound, and the more improved the high-temperature cycle performance and high-temperature storage performance of the lithium ion secondary battery. it is good. This may be due to the fact that in the silane compound, a larger substituent forms a larger steric hindrance on the surface of the negative electrode, which better prevents further contact reduction of the electrolyte at the negative electrode. Further, since the compound 4 and the compound 5 contain an unsaturated olefin, the negative electrode is more easily reduced, which is more advantageous for the stability of the SEI film.

The above is a detailed description of the preferred embodiments of the present invention, but the present invention is not limited to the embodiments, and some modifications or alternatives are included in the scope defined by the claims of the present application. In addition, the present invention has been described with certain specific terms, which are merely for convenience of description and do not limit the invention.

Claims (10)

An electrolyte comprising: Organic solvents; An electrolyte salt dissolved in an organic solvent; additive; It is characterized in that The additive includes: a silane compound, including one or more of the compounds of Formula 1; One or more of dioxane ethers;

among them, R ₁ , R ₂ and R ₃ are each independently selected from the group consisting of H, F, Cl, Br, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, and 2 to 2 carbon atoms. 20 alkenyl group, alkenyloxy group having 2 to 20 carbon atoms, alkynyl group having 2 to 20 carbon atoms, alkynyloxy group having 2 to 20 carbon atoms, or aryl group having 6 to 26 carbon atoms One of aryloxy groups having 6 to 26 carbon atoms; R _{4 is} selected from the group consisting of an alkylene group having 1 to 20 carbon atoms, an alkenylene group having 2 to 20 carbon atoms, an alkynylene group having 2 to 20 carbon atoms, and an aromatic group having 6 to 26 carbon atoms. One of the bases; R _{5 is} selected from the group consisting of H, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, and an oxyalkylene having 2 to 20 carbon atoms. One of a group, an alkynyl group having 2 to 20 carbon atoms, an alkynyloxy group having 2 to 20 carbon atoms, an aryl group having 6 to 26 carbon atoms, and an aryloxy group having 6 to 26 carbon atoms Species The hydrogen atom on the alkoxy group, the alkenyloxy group, the alkynyloxy group or the aryloxy group may also be substituted by one or more of F, Cl and Br; The hydrogen atom on the alkyl, alkenyl, alkynyl, aryl, alkylene, alkenylene, alkynylene, arylene group may also be represented by F, Cl, Br, sulfonate, sulfonyl, amine, One or several substitutions in the cyano group. The electrolyte according to claim 1, wherein the dioxane is selected from the group consisting of 1,3-dioxolane, 1,3-dioxane, and 1,4-dioxane. Or several. The electrolyte according to claim 1, wherein the silane compound is one or more selected from the group consisting of:

The electrolyte according to claim 1, wherein The mass of the dioxepane is from 0.1% to 5% of the total mass of the electrolyte; The mass of the silane compound is from 0.1% to 5% of the total mass of the electrolyte. The electrolyte according to claim 1, wherein the organic solvent comprises a cyclic ester and a chain ester. The electrolyte according to claim 5, wherein The cyclic ester is selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, tetrahydrofuran One or several; The chain ester is selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl formate, ethyl formate, propyl formate, acetic acid. One or more of methyl ester, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, dimethyl sulfite, diethyl sulfite. The electrolyte according to claim 5, wherein The mass of the cyclic ester is 20% to 50% of the total mass of the electrolyte; The mass of the chain ester is 40% to 80% of the total mass of the electrolyte. The electrolyte according to claim 7, wherein the total mass of the organic solvent is from 60% to 85% of the total mass of the electrolyte. A secondary battery comprising the electrolytic solution according to any one of claims 1-8. The secondary battery according to claim 9, wherein the secondary battery is a lithium ion secondary battery, a sodium ion secondary battery, or a zinc ion secondary battery.