WO2018086378A1

WO2018086378A1 - Electrolyte and secondary battery

Info

Publication number: WO2018086378A1
Application number: PCT/CN2017/093746
Authority: WO
Inventors: 冯俊敏; 陈培培; 张昌明; 周艳; 付成华
Original assignee: 宁德时代新能源科技股份有限公司
Priority date: 2016-11-10
Filing date: 2017-07-20
Publication date: 2018-05-17
Also published as: CN108075187B; CN108075187A

Abstract

An electrolyte and a secondary battery. The electrolyte comprises: an electrolyte salt, an organic solvent, and an additive. The additive comprises one or more of compounds as expressed in Formula (1). After applied to a secondary battery, the electrolyte can effectively enhance charge cycle performance of the secondary battery in a room temperature and low temperature, and enhance power storage performance in a high temperature and safety performance in a heat-stress test chamber.

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

In recent years, with the rapid development of secondary batteries, especially lithium ion secondary batteries, in the field of portable electric appliances, there is an increasing demand for small, lightweight, thin and high-performance secondary batteries that supply power to these portable electronic devices. increase. Due to the continuous pursuit of high energy density of secondary batteries, the use of high-pressure solid-density positive and negative electrodes or high-capacity anode materials with poor cycle performance is a commonly used strategy in the industry. The problem that comes with it is that the electrolyte cannot fully wet the electrode, which causes the charging platform of the secondary battery to rise and the discharge platform to decrease, which affects the output performance of the secondary battery. Especially in the low-temperature cycle, due to the poor dynamic performance of the secondary battery, lithium is easily precipitated during low-temperature charge and discharge, thereby seriously affecting the capacity retention rate after the secondary battery is cycled.

When the secondary battery is formed, a layer of SEI film (solid electrolyte interface film) is formed on the surface of the electrode. This layer of SEI film controls the passage of ions in and out, which is an important factor controlling the reaction kinetics of the electrode. Taking the charging and discharging process of a lithium ion secondary battery as an example, a dense and stable SEI film can ensure the cycle performance of a lithium ion secondary battery, otherwise the SEI film is gradually destroyed as the number of times of charge and discharge increases, so that the organic solvent and the electrode The sheet is subjected to barrier-free contact and chemical and electrochemical reactions occur, so that the organic solvent is consumed indefinitely, resulting in a sudden decrease in the cycle life of the lithium ion secondary battery. At low temperatures, the generated SEI film is too thick, and the large impedance causes the lithium ions to fail to migrate, which greatly reduces the capacity retention rate after the lithium ion secondary battery is cycled. The stability of the interface film formed by the positive and negative electrodes during high-temperature storage largely determines the high-temperature storage performance of the lithium ion secondary battery, and has a great influence on the safety performance of the hot-box 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 effectively improve the normal temperature of a secondary battery when the electrolyte is applied to a secondary battery. Low temperature cycle performance, high temperature storage performance and hot box safety.

In order to achieve the above object, in one aspect of the invention, the present invention provides an electrolyte comprising: an electrolyte salt, an organic solvent, and an additive. The additive includes one or more of the compounds represented by Formula 1; wherein R _{1 is} selected from a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, and the substituted or unsubstituted carbon atom is 1 An alkoxy group of ～12, a substituted or unsubstituted aryl group having 6 to 10 carbon atoms; and R _{2 is} selected from the group consisting of a substituted or unsubstituted alkylene group having 0 to 6 carbon atoms. R _{3 is} selected from H, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, and a substituted or unsubstituted carbon atom; The acyloxy group having 1 to 12, the substituted or unsubstituted aryl group having 6 to 10 carbon atoms, the substituted or unsubstituted aryl group having 5 to 10 carbon atoms, and the substituted or unsubstituted carbon atom are One of 1 to 6 nitrile groups; R _{4 is} selected from H, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, a substituted or unsubstituted acyloxy group having 1 to 12 carbon atoms, a substituted or unsubstituted aryl group having 6 to 10 carbon atoms, a substituted or unsubstituted aryl group having 5 to 10 carbon atoms, Replace or not a substituted one of the nitrile groups having 1 to 6 carbon atoms, and R ₃ and R _{4 are} not simultaneously selected from a substituted or unsubstituted nitrile group having 1 to 6 carbon atoms; and the substituent is selected from a halogen. One or several.

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:

When the electrolytic solution of the present invention is applied to a secondary battery, the normal temperature and low temperature cycle performance, high temperature storage performance, and hot box safety performance of the secondary battery can be effectively improved.

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 electrolyte salt, an organic solvent, and an additive. The additive includes one or more of the compounds represented by Formula 1.

In Formula 1, R _{1 is} selected from a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, and a substituted or unsubstituted carbon atom. Is one of 6 to 10 aryl groups; R _{2 is} selected from one of substituted or unsubstituted alkylene groups having 0 to 6 carbon atoms; and R _{3 is} selected from H, substituted or unsubstituted carbon atoms. The alkyl group having 1 to 12, a substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, a substituted or unsubstituted acyloxy group having 1 to 12 carbon atoms, a substituted or unsubstituted carbon atom The aryl group having 6 to 10, the substituted or unsubstituted aryl group having 5 to 10 carbon atoms, and the substituted or unsubstituted nitrile group having 1 to 6 carbon atoms; and R _{4 are} selected from the group consisting of aryl groups having 6 to 10 carbon atoms; H, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, a substituted or unsubstituted acyloxy group having 1 to 12 carbon atoms a substituted, unsubstituted or substituted aryl group having 6 to 10 carbon atoms, a substituted or unsubstituted aryl group having 5 to 10 carbon atoms, a substituted or unsubstituted nitrile group having 1 to 6 carbon atoms One of them, and R ₃ and R _{4 is} not selected from the group consisting of a substituted or unsubstituted nitrile group having 1 to 6 carbon atoms; and the substituent is selected from one or more of halogens. Wherein "substituted" means substituted or wholly substituted by one or more of the halogens. Preferably, the substituent is selected from one or both of F and Cl.

In the electrolytic solution according to the first aspect of the present invention, the sulfonate structure in the compound represented by Formula 1 can form an alkyl sulfonate having good conductivity in electrochemical redox, thereby being used in a secondary battery The surface of the positive and negative electrodes forms a low-impedance, organic-inorganic composite protective film. At the same time, the double bond structure in the compound represented by Formula 1 contributes to the formation of a denser polymer protective film on the surface of the positive and negative electrodes, so that the secondary battery has good cycle performance. In addition, -CN in the compound of Formula 1 can complex with a transition metal ion on the surface of the positive electrode, and the resulting complex adheres to the surface of the positive electrode to form a stable CEI protective film, thereby significantly improving the high temperature storage of the secondary battery. performance. Therefore, by adding the compound represented by Formula 1 to the electrolyte, an interface protective film having a small impedance and a uniform density can be formed on the surface of the positive and negative electrodes, thereby improving the stability of the electrolyte and the dynamic properties of the electrode piece, thereby Secondary battery is high Good performance at low temperatures, specifically, can effectively improve the normal temperature and low temperature cycle performance of the secondary battery, high temperature storage performance and hot box safety performance.

In the electrolytic solution according to the first aspect of the present invention, if R _{2 is} selected from an alkylene group having 0 carbon atoms, it means that the double bond carbon atom in the formula 1 is directly bonded to the oxygen atom in the sulfonate structure. Specifically, it can be expressed by Formula 2.

In the electrolytic solution according to the first aspect of the present invention, the alkyl group having 1 to 12 carbon atoms may be a chain alkyl group or a cycloalkyl group, and hydrogen at a ring of the cycloalkyl group may be used. Replaced by an alkyl group. The lower limit of the number of carbon atoms in the alkyl group is preferably 2, 3, 4, and 5. The preferred upper limit is 3, 4, 5, 6, 8, and 10. Preferably, an alkyl group having 1 to 10 carbon atoms is selected, and more preferably, a chain alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 8 carbon atoms is selected, and 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 12 carbon atoms may be selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl Base, isopentyl, neopentyl, hexyl, 2-methyl-pentyl, 3-methyl-pentyl, 1,1,2-trimethyl-propyl, 3,3,-dimethyl- One of butyl, heptyl, 2-heptyl, 3-heptyl, 2-methylhexyl, 3-methylhexyl, isoheptyl, octyl, decyl, fluorenyl.

In the electrolytic solution according to the first aspect of the present invention, the alkoxy group having 1 to 12 carbon atoms is preferably an alkoxy group having 1 to 10 carbon atoms, and more preferably, the number of carbon atoms is selected. It is more preferably an alkoxy group having 1 to 6 carbon atoms, and still more preferably an alkoxy group having 1 to 4 carbon atoms. Specifically, the alkoxy group having 1 to 12 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. One of a group, a n-pentyloxy group, an isopentyloxy group, a cyclopentyloxy group, and a cyclohexyloxy group.

In the electrolytic solution according to the first aspect of the present invention, the acyloxy group having 1 to 12 acyloxy groups is preferably an acyloxy group having 1 to 10 carbon atoms, and more preferably, the number of carbon atoms is selected. The acyloxy group of 1 to 6 is more preferably an acyloxy group having 1 to 4 carbon atoms. Specifically, the carbonyl group having 1 to 12 acyloxy groups may be selected from the group consisting of formyloxy, acetoxy, n-propionyloxy, isopropionyloxy, n-butyryloxy, and sec-butyryloxy. , tert-butyryloxy, n-pentanoyloxy, isovaleryloxy One of them.

In the electrolytic solution according to the first aspect of the invention, the alkylene group having 1 to 6 carbon atoms may be a linear alkylene group or a branched alkylene group. The lower limit of the number of carbon atoms in the alkylene group having 1 to 6 carbon atoms is preferably 2, 3, 4 or 5, and the preferred upper limit is 3, 4, 5 or 6. Specifically, the alkylene group having 1 to 6 carbon atoms may be selected from the group consisting of methylene, ethylene, propylene, isopropylidene, butylene, isobutylene, sec-butylene, and sub- One of a pentyl group and a hexylene group.

In the electrolytic solution according to the first aspect of the invention, the aryl group having 6 to 10 carbon atoms may be a phenyl group, a phenylalkyl group or an alkylphenyl group. Specifically, the aryl group having a carbon number of 6 to 10 may be selected from one of a phenyl group, a benzyl group, a p-tolyl group, an o-tolyl group, and an m-tolyl group.

In the electrolytic solution according to the first aspect of the invention, the aryl group having 5 to 10 carbon atoms may be selected from the group consisting of a furyl group, a thienyl group, a pyrrolyl group, a thiazolyl group, an imidazolyl group, a pyridyl group, and a pyrazine. One of a group, a pyrimidinyl group, a pyridazinyl group, a fluorenyl group, or a quinolyl group.

In the electrolytic solution according to the first aspect of the invention, preferably, the substituent for carrying out the substitution may be selected from one or more of -CN, F, Cl, Br, I.

In the electrolytic solution according to the first aspect of the present invention, specifically, the compound represented by Formula 1 is selected from one or more of the following compounds;

In the electrolytic solution according to the first aspect of the invention, the mass of the compound represented by Formula 1 is from 0.1% to 15% by mass based on the total mass of the electrolytic solution. The upper limit of the compound represented by Formula 1 is 5%, 6%, 7%, 8%, 9%, and 10%, and the lower limit of the compound represented by Formula 1 is 0.2%, 0.5%, 1%, 2 %, 3%. Preferably, the mass of the compound represented by Formula 1 is from 1% to 10% by mass based on the total mass of the electrolyte. Further preferably, the mass of the compound represented by Formula 1 is 3% to 7% of the total mass of the electrolytic solution. Still more preferably, the mass of the compound represented by Formula 1 is 3% of the total mass of the electrolyte.

In the electrolytic solution according to the first aspect of the invention, the organic solvent is selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and ethyl methyl carbonate (EMC). ), methyl propyl carbonate (MPC), methyl formate (MF), ethyl formate (EF), methyl acetate (MA), ethyl acetate (EA), propyl propionate (PP), ethyl butyrate (EB), ethyl propionate (EP), propyl butyrate (PB), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), One or more of vinyl sulfite (ES), propylene sulfite (1,3-PS), γ-butyrolactone (BL), and tetrahydrofuran (THF). Further, the organic solvent may further include different classes of ionic liquids and the like. In addition, the organic solvent used in the present invention may be used alone or in combination of two or more kinds in any combination and in any ratio depending on the application. Among them, the organic solvent is preferably propylene carbonate (PC), ethylene carbonate (EC), or carbonic acid from the viewpoints of electrochemical stability of its redox and chemical stability associated with heat and reaction of the above solute. One or more of ethyl ester (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC).

In the electrolytic solution according to the first aspect of the invention, the concentration of the electrolyte salt is from 0.5 mol/L to 2.5 mol/L, preferably, the concentration of the electrolyte salt is from 0.7 mol/L to 2.0 mol/L. Further preferably, the concentration of the electrolyte salt is from 0.9 mol/L to 1.5 mol/L. When the concentration of the electrolyte salt is less than 0.5 mol/L, the ionic conductivity of the electrolytic solution is lowered, so that the cycle performance and the electrical conductivity of the secondary battery tend to be lowered. On the other hand, when the concentration of the electrolyte salt exceeds 2.5 mol/L, the viscosity of the electrolytic solution rises, and the electrical conductivity of the secondary battery is too low, whereby there is still a risk of deteriorating the dynamic performance of the secondary battery.

In the electrolytic solution according to the first aspect of the invention, the additive may further include fluoroethylene carbonate and/or adiponitrile.

Next, a secondary battery according to a second aspect of the invention will be described.

A secondary battery according to a second aspect of the invention, which comprises the electrolytic solution of the first aspect of the invention.

In the secondary battery according to the second aspect of the invention, the secondary battery further includes a positive electrode sheet, a negative electrode sheet, and a separator.

In the secondary battery according to the second aspect of the invention, the positive electrode sheet includes a positive electrode current collector and a positive electrode active slurry layer on the positive electrode current collector, wherein the positive electrode active slurry layer includes a positive electrode active layer material. The specific type of the positive electrode active material is not particularly limited and can be selected according to requirements.

In the secondary battery according to the second aspect of the invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode active slurry layer on the negative electrode current collector. The negative active slurry layer includes a negative active material. The specific type of the negative active material is not particularly limited and can be selected according to requirements.

In the secondary battery according to the second aspect of the present invention, the specific kind of the separator is not particularly limited, and may be any separator material used in the existing secondary battery, such as polyethylene, polypropylene, poly Vinylidene fluoride and their multilayer composite films are not limited to these.

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

When the secondary battery is a lithium ion secondary battery, the electrolyte salt may be a lithium salt, and the lithium salt may be selected from the group consisting of LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiSbF ₆ , LiCF ₃ SO ₃ , LiN ( CF ₃ SO ₂ ) ₂ , LiN(FSO ₂ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ )(C ₄ F ₉ SO ₂ ), LiC(CF ₃ SO ₂ ) ₃ , LiPF ₃ (C ₃ F ₇ ) ₃ , LiB(CF ₃ ) ₄ , LiBF ₃ (C ₂ F ₅ ), LiPO ₂ F ₂ , LiPF ₄ (C ₂ O ₄ ), LiPF ₂ (C ₂ O ₄ ) ₂ , One or more of LiBF ₂ (C ₂ O ₄ ) and LiB(C ₂ O ₄ ) ₂ . Preferably, LiPF _{6 is} added as an essential component.

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.

In the following examples, the reagents, materials, and instruments used are commercially available unless otherwise specified.

In the examples and comparative examples, the compound 1 used was prepared as follows:

(1) First step reaction:

(2) The second step reaction:

Operation steps: adding methanol solution of sodium methoxide to a dry and nitrogen-filled reaction flask, cooling to 0 ° C, adding isoxazole and stirring at 0 ° C for two hours; monitoring the raw materials by TLC thin layer chromatography silica gel plate, in vacuum The solvent in the reaction system was removed by a rotary evaporator, and the residue was dried using a vacuum oil pump to obtain sodium 2-acrylonitrile-1-olate; sodium 2-acrylonitrile-1-olate was dissolved in anhydrous dry tetrahydrofuran, and the temperature was lowered to Methanesulfonyl chloride was slowly added dropwise to the reaction system at 0 ° C, and the reaction was completed for one hour after completion; the reaction solution was suction filtered to give a colorless filtrate, which was subjected to distillation under reduced pressure to give Compound 1.

The lithium ion secondary batteries of Examples 1 to 24 and Comparative Examples 1 to 5 were each prepared in the following manner.

(1) Preparation of positive electrode sheets

The positive electrode active material lithium cobaltate (LiCoO ₂ ), the binder polyvinylidene fluoride, and the conductive agent acetylene black are mixed at a weight ratio of 94:3:3, and N-methylpyrrolidone (NMP) is added under the action of a vacuum mixer. Stir the system to a uniform transparency to obtain a positive electrode slurry; uniformly apply the positive electrode slurry to a positive electrode current collector aluminum foil having a thickness of 12 μm; dry the aluminum foil at room temperature, transfer it to an oven at 120 ° C for 1 hour, and then pass cold pressing. The positive electrode sheets were obtained by slitting.

(2) Preparation of negative electrode sheets

The negative active material artificial graphite, the conductive agent acetylene black, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are mixed at a weight ratio of 95:2:2:1, and deionized. Water, the negative electrode slurry was obtained under the action of a vacuum mixer; the negative electrode slurry was uniformly coated on the negative electrode current collector copper foil having a thickness of 8 μm; the copper foil was air-dried at room temperature, transferred to an oven at 120 ° C for 1 hour, and then cooled. The negative electrode sheet was obtained by pressing and slitting.

(3) Electrolyte preparation

In an argon atmosphere glove box having a water content of <10 ppm, EC and DEC are mixed at a volume ratio of EC:DEC=3:7, followed by dissolving the sufficiently dried lithium salt LiPF ₆ in a mixed organic solvent, followed by adding an additive. After mixing, the electrolyte is obtained. Among them, the concentration of LiPF ₆ was 1 mol/L. The specific types and contents of the additives used in the electrolyte are shown in Table 1. In Table 1, the content of the additive is a mass percentage calculated based on the total mass of the electrolyte.

(4) Preparation of separator

A 16 μm thick polyethylene (PE) separator was used.

(5) Preparation of lithium ion secondary battery

The positive electrode sheet, the separator film and the negative electrode sheet are stacked in order, so that the separator is in a role of isolation between the positive and negative electrode sheets, and then wound to obtain a bare cell; the bare cell is placed in the outer packaging foil, The prepared electrolyte solution is injected into the dried bare cell, and subjected to vacuum encapsulation, standing, formation, shaping, and the like to obtain a lithium ion secondary battery.

Table 1 Parameters of the electrolytes of Examples 1-24 and Comparative Examples 1-5

Next, the test process of the lithium ion secondary battery will be described.

(1) Cyclic performance test of lithium ion secondary battery

The lithium ion secondary battery was charged at a constant current of 0.5 C to a voltage of 4.45 V at 0 ° C and 25 ° C, respectively, and further charged at a constant voltage of 4.45 V until the current was 0.05 C, and then discharged at a constant current of 0.5 C to a voltage of 3.0V, this is a charge and discharge cycle process, this discharge capacity is the discharge capacity of the first cycle. The lithium ion secondary battery was subjected to 300 cycles of charge/discharge test in accordance with the above method.

The capacity retention ratio (%) of the lithium ion secondary battery after N times of cycle = (discharge capacity N times of discharge / discharge capacity of first cycle) × 100%.

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

The lithium ion secondary battery was charged at a constant current of 1 C to a voltage of 4.45 V at 25 ° C, and then charged at a constant voltage of 4.45 V until the current was 0.05 C. At this time, the volume of the lithium ion secondary battery was tested and recorded as V _{0 .} Then, the lithium ion secondary battery was placed in an incubator at 60 ° C, and stored for 10 days, 20 days, and 30 days, respectively, and the volume of the lithium ion secondary battery was measured and recorded as V _n .

The volume expansion ratio of the lithium ion secondary battery after storage for n days at 60 ° C = [(V _n - V ₀ ) / V ₀ ] × 100%, where n is the number of days in which the lithium ion secondary battery is stored.

(3) Hot box safety performance test of lithium ion secondary battery

The lithium ion secondary battery was charged at a constant current of 1 C to a voltage of 4.45 V at 25 ° C, further charged at a constant voltage of 4.45 V until the current was 0.05 C, the charging was stopped, and the lithium ion secondary battery was placed in a hot box. The temperature of the hot box was raised from 25 ° C to 130 ° C at a rate of 5 ° C / min. After the temperature reached 130 ° C, the temperature was maintained unchanged, and the timing was started. The state of the lithium ion secondary battery was observed after 1 h. Five lithium ion secondary batteries were tested in each group.

The standard for the lithium ion secondary battery to pass the test is: no smoke, no fire, no explosion.

Table 2 Performance test results of Examples 1-24 and Comparative Examples 1-5

From the analysis of the test results in Table 2, it was found that Comparative Example 1 did not contain any additives, and the normal temperature cycle performance, low temperature cycle performance, high temperature storage performance, and hot box safety performance of the lithium ion secondary battery were inferior.

When the compound of Formula 1 was added to the electrolytic solution (Examples 1 to 15), the room temperature cycle performance, low-temperature cycle performance, high-temperature storage property, and hot box safety performance of the lithium ion secondary battery were all improved. In Example 8, since Formula 1 is a fluorinated compound, the fluorine atom increases the oxidation potential of Formula 1 so that it is not easily oxidized, so the performance of the lithium ion secondary battery is superior to that of other compounds. In Example 13, since the structure of Formula 1 contains two benzene rings, the viscosity of the electrolytic solution is slightly large, resulting in a slow migration rate of lithium ions, and thus the performance of the lithium ion secondary battery is slightly inferior to those of other compounds.

From the comparison of Examples 1-7 and Comparative Example 2-3, it is understood that when the amount of the compound represented by Formula 1 is too small (Comparative Example 2), the improvement in the performance of the lithium ion secondary battery is not remarkable, and Formula 1 shows When the amount of the compound added was too large (Comparative Example 3), the performance of the lithium ion secondary battery deteriorated.

In Comparative Example 4, fluoroethylene carbonate was separately added to the electrolytic solution, compared to Comparative Example 1, The cycle performance of the lithium ion secondary battery is improved, but the high temperature storage performance and the heat box safety performance are still poor. In Comparative Example 5, adiponitrile was separately added to the electrolytic solution, and the high-temperature storage performance and the heat box safety performance of the lithium ion secondary battery were improved as compared with Comparative Example 1, but the cycle performance was still poor. In Examples 16 to 24, when fluoroethylene carbonate and/or adiponitrile were further added to the electrolytic solution, the overall performance of the lithium ion secondary battery was further improved.

The present application is disclosed in the above preferred embodiments, but is not intended to limit the scope of the claims, and any of the possible changes and modifications may be made by those skilled in the art without departing from the scope of the present application. The scope of protection shall be determined by the scope defined in the claims of the present application.

Claims

An electrolyte comprising:

Electrolyte salt

Organic solvent;

additive;

It is characterized in that

The additive includes one or more of the compounds represented by Formula 1;

among them,

R 1 is selected from a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, and a substituted or unsubstituted carbon number of 6 to 10; One of the aryl groups;

R 2 is selected from the group consisting of substituted or unsubstituted alkylene groups having 0 to 6 carbon atoms;

R 3 is selected from H, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, and a substituted or unsubstituted carbon atom of 1 to 12 An acyloxy group of 12, a substituted or unsubstituted aryl group having 6 to 10 carbon atoms, a substituted or unsubstituted aryl group having 5 to 10 carbon atoms, and a substituted or unsubstituted carbon atom of 1 to 10 One of the nitrile groups of 6;

R 4 is selected from H, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, and a substituted or unsubstituted carbon atom of 1 to 12 An acyloxy group of 12, a substituted or unsubstituted aryl group having 6 to 10 carbon atoms, a substituted or unsubstituted aryl group having 5 to 10 carbon atoms, and a substituted or unsubstituted carbon atom of 1 to 10 One of 6 nitrile groups, and R 3 and R 4 are not simultaneously selected from substituted or unsubstituted nitrile groups having 1 to 6 carbon atoms;

The substituent is selected from one or more of halogens.
The electrolyte according to claim 1, wherein the substituent is selected from one or both of F and Cl.
The electrolyte according to claim 2, wherein the compound of Formula 1 is selected from one or more of the following compounds;
The electrolytic solution according to claim 1, wherein the mass of the compound represented by Formula 1 is from 0.1% to 15% by mass based on the total mass of the electrolytic solution.
The electrolyte according to claim 4, wherein the substance of the compound represented by Formula 1 is The amount is from 1% to 10% of the total mass of the electrolyte.
The electrolytic solution according to claim 5, wherein the mass of the compound represented by Formula 1 is from 3% to 7% based on the total mass of the electrolytic solution.
The electrolyte according to claim 1, wherein the organic solvent is selected from the group consisting of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl formate, and formic acid. Ethyl ester, methyl acetate, ethyl acetate, propyl propionate, ethyl butyrate, ethyl propionate, propyl butyrate, ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, sub One or more of vinyl sulfate, propylene sulfite, γ-butyrolactone, and tetrahydrofuran.
The electrolytic solution according to claim 1, wherein the concentration of the electrolyte salt is from 0.5 mol/L to 2.5 mol/L.
The electrolyte according to any one of claims 1 to 8, characterized in that the additive further comprises fluoroethylene carbonate and/or adiponitrile.
A secondary battery comprising the electrolytic solution according to any one of claims 1-9.