KR102147925B1 - Electrolyte for lithium ion battery and lithium ion battery including the same - Google Patents

Abstract

The present invention is a lithium salt; Ether solvent; Fluorinated solvent; And a functional additive. Even if lithium metal is used as a negative electrode material, it prevents the growth of dendrite on the surface of the lithium metal during charging and discharging of the lithium ion battery, and uniform lithium electrodeposition (plating) ) Makes it possible.
In addition, by suppressing side reactions with the lithium metal negative electrode and the electrolyte, it is possible to provide a lithium ion battery with remarkably improved stability and lifespan performance.

Description

Electrolyte for lithium-ion battery and lithium-ion battery including the same {ELECTROLYTE FOR LITHIUM ION BATTERY AND LITHIUM ION BATTERY INCLUDING THE SAME}

The present invention relates to an electrolyte for a lithium ion battery and a lithium ion battery including the same, and more particularly, to an electrolyte for a lithium ion battery that can use lithium metal as a negative electrode material, and a lithium ion battery using the same.

The lithium metal secondary battery is the first commercially available lithium secondary battery, and uses lithium metal as a negative electrode. However, in lithium metal secondary batteries, the volume expansion of the cell, the gradual decrease in capacity and energy density due to the lithium resin formed on the surface of the lithium metal anode, the occurrence of short circuit due to continuous dendritic growth, reduction in cycle life and cell stability problems (explosion and ignition ), production ceased after only a few years of commercialization.

Instead of such lithium metal, a carbon-based negative electrode that is safer and capable of stably storing lithium in an ionic state in a lattice or empty space was used, and the use of the carbon-based negative electrode has led to full-scale commercialization and dissemination of lithium secondary batteries. .

To date, lithium secondary batteries are mainly made of carbon-based or non-carbon-based anode materials. Most anode material developments are focused on carbon-based (graphite, hard carbon, soft carbon, etc.) and non-carbon-based (silicon, tin, titanium oxide, etc.) materials.

However, carbon-based materials have a theoretical capacity of not exceeding 400mAh per gram, and non-carbon-based materials are materials exceeding 1000 mAh per gram, but they have not yet solved the problem of volume expansion and performance during charging and discharging.

In addition, as medium and large-sized lithium secondary batteries have recently been activated, high capacity and high energy density characteristics are required, but there are many limitations in meeting these performances of existing materials.

Recently, researches to re-use metallic lithium like lithium-air batteries are being actively conducted.

Lithium is very light and has the potential to realize a very good energy density with the theoretical capacity per gram exceeding 3,860mAh. Therefore, along with the research and development of the lithium-air battery, a movement to re-research the lithium metal secondary battery itself is actively progressing.

However, there are numerous problems to be overcome in order to apply lithium metal as a negative electrode material for secondary batteries. Unlike graphite-based anode materials, lithium metal anodes change into neutral lithium through electrochemical reactions with electrons from external conductors, so that very irregular lithium lumps appear on the lithium surface during charging. It is easily formed into a dendritic shape. The uneven surface formed in this way provides an overall expanded volume, and when discharging, ions do not selectively separate from the lithium resin and are more often dissociated directly from the lithium metal. The surface of the cathode is not only subject to a very severe volume change, but also the formed dendritic is irregular and has a complex morphology.

The complex aspect of such a surface is not stabilized at all as the cycle progresses, and the generation and extinction are continuously repeated, resulting in a very irregular cycle life. In addition, as the lithium resin phase formed during discharge dissociates, it may fall into the electrolyte area as a whole, and the resin phase continues to grow in the vertical direction, causing a hard short or soft short by directly or indirectly contacting the anode surface located on the opposite side through the separator. do.

Accordingly, even if lithium metal is used as a negative electrode material, it is necessary to develop an electrolyte for a lithium ion battery in order to suppress the formation of dendritic phases to improve the life of the lithium ion battery and to exhibit high capacity and high energy density characteristics.

(Patent Document 1) KR 10-2017-0116464 A1

An object of the present invention is to provide an electrolyte for a lithium ion battery and a lithium ion battery including the same.

Another object of the present invention is to prevent the growth of dendrite on the surface of lithium metal when charging and discharging a lithium ion battery, even if lithium metal is used as a negative electrode material, and for a lithium ion battery capable of uniform lithium plating. It is to provide an electrolyte.

Another object of the present invention is to provide an electrolyte for a lithium ion battery capable of enhancing the stability of a lithium ion battery by suppressing side reactions with a lithium metal negative electrode and an electrolyte.

Another object of the present invention can provide a lithium ion battery with remarkably improved stability and lifetime performance.

In order to achieve the above object, the electrolyte for a lithium ion battery according to an embodiment of the present invention is a lithium salt; Ether solvent; Fluorinated solvent; And a functional additive represented by the following Chemical Formula 1:

[Formula 1]

here,

n is an integer from 1 to 5,

R ₁ is selected from the group consisting of hydrogen, deuterium, a halogen group, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a substituted or unsubstituted alkene group having 2 to 5 carbon atoms and a substituted or unsubstituted alkoxy group having 1 to 5 carbon atoms,

The substituted R ₁ may be substituted with a substituent selected from the group consisting of deuterium, a halogen group and an alkyl group having 1 to 5 carbon atoms.

The functional additive represented by Formula 1 may be a functional additive represented by the following Formula 2:

[Formula 2]

here,

R ₁ is as defined in Chemical Formula 1.

The functional additive represented by Formula 1 may be selected from the group consisting of compounds represented by the following Formulas 3 to 6:

[Formula 3]

[Formula 4]

[Formula 5]

[Formula 6]

The lithium salt may be selected from the group consisting of LiPF ₆ , LiBF ₄ , LiFSI, LiTFSI, LiSO ₃ CF ₃ , LiBOB and LiDFOB.

The ether solvent is 1,2-dimethoxyethane, 1,3-dioxolane, Diethylene glycol dimethyl ether, tetraethylene glycol dimethyl It may be selected from the group consisting of ether (tetraethylene glycol dimethyl ether) and mixtures thereof.

The ether solvent is 1,2-dimethoxyethane.

The fluorinated solvent is represented by the following formula (7):

[Formula 7]

The lithium ion battery electrolyte may include an ether-based solvent as a main solvent, and a fluorinated ether-based solvent as an auxiliary solvent. In addition, a carbonate-based solvent may be additionally included as a selective solvent.

The carbonate-based solvent is selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, and mixtures thereof. Can be.

The electrolyte for a lithium ion battery may increase reversibility of an electrochemical lithium plating/stripping reaction in a negative electrode including lithium metal as a negative electrode active material.

A lithium ion battery according to another embodiment of the present invention includes a positive electrode including a positive electrode active material; A negative electrode disposed to face the positive electrode and including a negative electrode active material; It may include an ion-permeable separator and an electrolyte according to claim 1 interposed between the anode and the cathode.

The negative active material is lithium metal.

The electrolyte includes a functional additive to increase the reversibility of the electrochemical lithium plating/stripping reaction of the negative electrode, and suppress side reactions of the lithium metal negative electrode and the electrolyte, thereby improving stability and lifespan.

A battery module according to another embodiment of the present invention may include the lithium ion battery as a unit battery.

A battery pack according to another embodiment of the present invention may include the battery module.

A device according to another embodiment of the present invention may include the battery pack.

The device is a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a system for power storage.

The present invention is an electrolyte for a lithium ion battery and a lithium ion battery including the same. Even if lithium metal is used as a negative electrode material, during charging and discharging of the lithium ion battery, the growth of dendrite on the lithium metal surface is prevented, and uniform Lithium plating is possible.

In addition, it provides a lithium ion battery with significantly improved stability and life performance by suppressing side reactions with a lithium metal negative electrode and an electrolyte.

1 is a related to the formation of a protective film of a negative electrode using an electrolyte according to an embodiment of the present invention.
2 is a voltage graph of a lithium electrodeposition/desorption reaction according to an embodiment of the present invention.
3 is a result showing the efficiency of the initial lithium electrodeposition/desorption reaction according to an embodiment of the present invention.
Figure 4 is a result showing the life of the lithium electrodeposition / desorption reaction according to an embodiment of the present invention.
5 is a graph of Li/NCM conversion charge/discharge voltage according to an embodiment of the present invention.
6 is a graph of Li/NCM conversion charge/discharge voltage according to an embodiment of the present invention.
7 is a life graph of Li/NCM according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

The electrolyte for a lithium ion battery according to an embodiment of the present invention includes a lithium salt; Ether solvent; Fluorinated solvent; And a functional additive represented by the following Chemical Formula 1:

[Formula 1]

here,

n is an integer from 1 to 5,

R ₁ is selected from the group consisting of hydrogen, deuterium, a halogen group, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a substituted or unsubstituted alkene group having 2 to 5 carbon atoms and a substituted or unsubstituted alkoxy group having 1 to 5 carbon atoms,

The substituted R ₁ may be substituted with a substituent selected from the group consisting of deuterium, a halogen group and an alkyl group having 1 to 5 carbon atoms.

Lithium metal is attracting attention as a negative electrode material for lithium-ion batteries due to its high capacity per weight of 3,860 mAh/g and a low standard electrode potential (-3.04 V vs. Normal hydrogen electrode). However, lithium metal is highly reactive, and an extremely reducing atmosphere is created during the charging process, so that an irreversible decomposition reaction occurs between the lithium metal and the electrolyte.

Electrolyte depletion occurs due to the decomposition reaction, and the decomposition product forms a non-uniform film on the surface of the lithium metal.

In addition, as charging and discharging are repeated, lithium grows in a dendrite form. Such dendritic lithium causes an electrical short inside the battery and induces ignition of the battery, thereby causing safety problems.

Therefore, in order to apply lithium metal that has high stability and can realize high capacity, the reactivity of lithium metal should be relaxed, and uniform lithium plating, not dendritic lithium growth, should be possible.

The electrolyte for a lithium ion battery of the present invention reduces the reactivity of lithium metal so that lithium metal can be applied as a negative electrode active material, and enables uniform lithium electrodeposition rather than dendritic lithium growth.

FIG. 1 relates to the formation of a protective film of a negative electrode by an electrolyte, and when a conventional electrolyte for a lithium ion battery is used and lithium metal is used as a negative electrode active material, a decomposition reaction between the electrolyte and lithium occurs, so that an electrolyte depletion problem may occur. do. In addition, as a product of the decomposition reaction forms a non-uniform film on the surface of the lithium metal, it may cause an electrical short inside the battery and induce ignition of the battery, thereby causing safety problems.

On the other hand, when the electrolyte of the present invention is included, a uniform film may be formed on the surface of the lithium metal according to the decomposition of the functional additive, and a decomposition reaction of lithium with other components of the electrolyte may be suppressed.

The functional additive represented by Formula 1 may be preferably a functional additive represented by the following Formula 2:

[Formula 2]

here,

R ₁ is as defined in Chemical Formula 1.

Preferably, R ₁ may be selected from the group consisting of H, F, CF ₃ and OCF ₃ .

More specifically, the functional additive represented by Formula 1 may be selected from the group consisting of functional additives represented by the following Formulas 3 to 6:

[Formula 3]

[Formula 4]

[Formula 5]

[Formula 6]

As the functional additive contained in the electrolyte of the present invention is decomposed to form a uniform film on the surface of the lithium metal, which is a negative electrode electrolyte, a lithium metal protective film may be formed.

This is because the functional additives represented by Chemical Formulas 3 to 6 contain an excess of fluorinated elements, and the functional additives are decomposed by lithium metal to form a LiF-based film. LiF has a higher shear modulus than Li, so it can suppress the formation of dendritic lithium.

The lithium salt may be selected from the group consisting of LiPF ₆ , LiBF ₄ , LiFSI, LiTFSI, LiSO ₃ CF ₃ , LiBOB and LiDFOB, but is not limited to the above example, and the lithium salt usable for preparing an electrolyte for a lithium ion battery is All can be used without limitation.

The ether solvent is 1,2-dimethoxyethane, 1,3-dioxolane, Diethylene glycol dimethyl ether, tetraethylene glycol dimethyl It is selected from the group consisting of ether (tetraethylene glycol dimethyl ether) and mixtures thereof, preferably 1,2-dimethoxyethane, but is not limited to the above example, and can be used in the preparation of an electrolyte. The ether solvent can be used without limitation.

The fluorinated solvent is represented by the following formula (7):

[Formula 7]

The fluorinated solvent is 1,1,2,2,-tetrafluoroethyl-1H,1H,5H-octafluoropentyl ether (1,1,2,2-Tetrafluoroethyl-1H,1H,5H-octafluoropentyl ether) , The ether solvent is a solvent in which the substituent is substituted with a fluorine substituent.

The electrolyte for a lithium ion battery includes an ether-based solvent as a main solvent, and may further include a carbonate-based solvent as a selective solvent.

The carbonate-based solvent is selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, and mixtures thereof. do.

The electrolyte for a lithium ion battery may increase reversibility of an electrochemical lithium plating/stripping reaction in a negative electrode including lithium metal as a negative electrode active material.

As described above, in the electrolyte for a lithium ion battery of the present invention, a uniform protective film is formed due to decomposition of functional additives in a negative electrode including lithium metal as a negative electrode active material.

In the process of forming the uniform protective layer, a decomposition reaction of lithium with other components of the electrolyte may be suppressed.

Through this process, it is possible to prevent lithium from growing in a dendrite form on the lithium metal surface, and to increase the reversibility of electrochemical lithium plating/stripping reactions.

A lithium ion battery according to another embodiment of the present invention includes a positive electrode including a positive electrode active material; A negative electrode disposed to face the positive electrode and including a negative electrode active material; Separator; And the electrolyte interposed between the positive electrode and the negative electrode.

More specifically, the lithium ion battery will be described in detail as follows.

Lithium ion batteries include a positive electrode manufactured by applying a mixture of the positive electrode active material, a conductive material, and a binder as described above on a positive electrode current collector, followed by drying and pressing, and a negative electrode manufactured using the same method. In some cases, additional fillers may be added to the mixture.

The positive electrode current collector is generally made to have a thickness of 3 micrometers to 500 micrometers. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel. Surface treatment of carbon, nickel, titanium, silver, or the like may be used on the surface of. The current collector may increase the adhesion of the positive electrode active material by forming fine irregularities on its surface, and various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics are possible.

The conductive material is typically added in an amount of 1% to 50% by weight based on the total weight of the mixture including the positive electrode active material. Such a conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery,

Graphite, such as natural graphite and artificial graphite, for example; Carbon blacks such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

The binder is a component that assists in bonding of an active material and a conductive material and bonding to a current collector, and is typically added in an amount of 1% to 50% by weight based on the total weight of the mixture including the positive electrode active material.

Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, recycled cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butyrene rubber, fluorine rubber, and various copolymers.

The filler is selectively used as a component that suppresses the expansion of the positive electrode, and is not particularly limited as long as it is a fibrous material without causing chemical changes to the battery, and examples thereof include olefinic polymerizers such as polyethylene and polypropylene; Fibrous materials such as glass fiber and carbon fiber are used.

The negative electrode current collector is generally made to have a thickness of 3 micrometers to 500 micrometers. Such a negative electrode current collector is not particularly limited as long as it has conductivity without causing a chemical change in the battery,

For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, surface-treated copper or stainless steel with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, and the like may be used.

In addition, like the positive electrode current collector, it is possible to enhance the bonding strength of the negative electrode active material by forming fine irregularities on the surface thereof, and may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

The lithium ion battery may have a structure in which a lithium salt-containing electrolyte is impregnated in an electrode assembly having a structure in which a separator is interposed between a positive electrode and a negative electrode.

The separator is interposed between the anode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally 0.01 micrometers to 10 micrometers, and the thickness is generally 5 micrometers to 300 micrometers. Examples of such separation membranes include olefin-based polymers such as polypropylene having chemical resistance and hydrophobicity; Sheets or non-woven fabrics made of glass fiber or polyethylene are used. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separator.

The electrolyte according to the present invention includes the lithium salt described above; Ether solvent; Fluorinated solvent; And a functional additive represented by the following Formula 1 may be included, but is not limited thereto:

[Formula 1]

here,

n is an integer from 1 to 5,

R ₁ is selected from the group consisting of hydrogen, deuterium, a halogen group, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a substituted or unsubstituted alkene group having 2 to 5 carbon atoms and a substituted or unsubstituted alkoxy group having 1 to 5 carbon atoms,

The substituted R ₁ may be substituted with a substituent selected from the group consisting of deuterium, a halogen group and an alkyl group having 1 to 5 carbon atoms.

The present invention provides a battery module comprising the lithium ion battery as a unit cell, and a battery pack including the battery module.

The battery pack can be used as a power source for devices that require high temperature stability, long cycle characteristics, and high rate characteristics.

Examples of the device may be an electric vehicle including an electric vehicle, a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), etc., but the secondary battery according to the present invention Since exhibits excellent room temperature and low temperature output characteristics, in detail, can be preferably used in a hybrid electric vehicle.

In addition, recently, research has been actively conducted to use a lithium secondary battery in a power storage device that converts unused power into physical or chemical energy and stores it and then uses it as electrical energy when necessary.

Preparation Example 1. Preparation of electrolyte for lithium ion battery

Preparation Example 1-1. 1,2-dimethoxyethane was prepared as an organic solvent, and lithium bis(fluorosulfonyl)imide (LiFSI) was dissolved in the organic solvent to a concentration of 3M, and the organic electrolytic solution was Was prepared.

Preparation Example 1-2. In the organic electrolyte solution obtained in Preparation Example 1-1, 4-benzyloxy-2,2,3,3-tetrafluoro-1-trifluoromethoxybutane (4-benzyloxy-2,2,3,3-tetrafluoro-1 -trifluoromethoxybutane, JS02) was added in 1% by weight to prepare an organic electrolyte.

Preparation Example 1-3. Instead of 1,2-dimethoxyethane as an organic solvent, 1,2-dimethoxyethane and 1,1,2,2,-tetrafluoroethyl-1H ,1H,5H-octafluoropentyl ether (1,1,2,2-Tetrafluoroethyl-1H,1H,5H-octafluoropentyl ether), except that a mixed solvent was used in a volume ratio of 80:20 An organic electrolyte was prepared in the same manner as in Example 1-1.

Preparation Example 1-4. In the organic electrolyte solution obtained in Preparation Example 1-3, 4-benzyloxy-2,2,3,3-tetrafluoro-1-trifluoromethoxybutane (4-benzyloxy-2,2,3,3-tetrafluoro-1 -trifluoromethoxybutane, JS02) was added in 1% by weight to prepare an organic electrolyte.

Lithium salt

Lithium bis(fluorosulfonyl)imide (LiFSI)

Ether solvent

1,2-dimethoxyethane (DME)

Fluorinated solvent

1,1,2,2-Tetrafluoroethyl-1H,1H,5H-octafluoropentyl ether (HFE6)

Functional additive

4-benzyloxy-2,2,3,3-tetrafluoro-1-trifluoromethoxybutane

(4-Benzyloxy-2,2,3,3-tetrafluoro-1-trifluoromethoxybutane, JS02)

Experimental Example 1. Measurement of efficiency of lithium electrodeposition/desorption reaction

<Experimental conditions>

-Counter electrode and reference electrode: lithium metal, working electrode: copper foil (Cu)

-Electrochemical evaluation (25℃)

(Lithium electrodeposition/desorption reaction: Mars charge/discharge)

Charging: Electrodeposition of lithium ions to the working electrode (-0.2 mA cm ^-2 for 10 hr, 2 mAh cm ^-2 )

Discharge: Desorption of lithium ion electrodeposited to the working electrode (0.2 mA cm ^-2 up to 1V)

(Implementation of lithium electrodeposition/desorption reaction: cycle)

Charging: Electrodeposition of lithium ions to the working electrode (-1 mA cm ^-2 for 2 hr, 2 mAh cm ^-2 )

Discharge: Desorption of lithium ion electrodeposited to the working electrode (1 mA cm ^-2 up to 1V)

Electrolyte: 3M LiFSI DME, 3M LiFSI DME+1% JS02

<Experiment result>

As shown in Figure 2, the voltage graph of the lithium electrodeposition / desorption reaction according to the introduction of the functional additive. Below 0V, lithium ions are reduced and electrodeposited to the copper working electrode.

After a capacity of 2.0 mAh cm ^-2 is electrodeposited on the copper working electrode, lithium electrodeposited on the copper is desorbed from a plateau of 0 V or higher.

3 is an initial efficiency of lithium electrodeposition/desorption reaction according to the introduction of a functional additive.

The initial coulomb efficiency was calculated in the following manner.

[Equation 1]

Initial Coulombic Efficiency = Lithium desorption capacity/lithium electrodeposition capacity × 100

3M LiFSI-DME has a low efficiency of 20.4%. This is because an irreversible decomposition reaction of the electrolyte solution occurred on the surface of the lithium metal during the lithium electrodeposition process. However, when the functional additive is introduced, the lithium electrodeposition/desorption reaction efficiency is improved by 49.9%.

This is because the functional additive effectively suppresses the reaction between the electrolyte and the lithium metal by forming a thin and uniform film (protective film) on the surface of the lithium metal as shown in FIG. 1, thereby increasing the reversibility of the lithium electrodeposition/desorption reaction.

In particular, since the functional additive contains an excessive amount of fluorinated elements, the additive decomposes into lithium metal to form a LiF-based film. LiF has a higher shear modulus than Li (Li: 4.2 GPa, LiF: 64.97 GPa) and can suppress the formation of dendritic lithium.

Experimental Example 2. Li/LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM) Full Cell Evaluation

<Experimental conditions>

-Cathode: Lithium metal

-Anode: LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM)

-Electrochemical evaluation (25℃)

-Capacity: 1.8 mAh cm ^-2

(Mars charge and discharge)

-charge

Constant current: +0.18 mA cm ^-2 up to 4.2 V

Constant voltage: 4.2 V, 0.02C

-Discharge

Constant current: -0.18 mA cm ^-2 up to 3.0 V

(Cycle)

-charge

Constant current: +1 mA cm ^-2 up to 4.2 V

-Discharge

Constant current: -1 mA cm ^-2 up to 3.0 V

-Electrolyte: 3M LiFSI DME,

3M LiFSI DME+1% JS02,

3M LiFSI DME/HFE6 (8/2),

3M LiFSI DME/HFE6 (8/2) + 1% JS02

<Experiment result>

The 3M LiFSI DME (reference electrolyte) has a charging capacity of 212.1 mAh g ^-1 and a discharge capacity of 185.9 mAh g ^-1 during Li/NCM conversion and initial coulomb efficiency of 87.6%. As shown in FIG. 5, when 1% of JS02 is added, the charging capacity is 209.9 mAh g ^-1 and the discharge capacity is 183.4 mAh g ^-1, and the initial coulomb efficiency is 87.4%, which is similar to the standard electrolyte.

However, as shown in FIG. 6, when using the fluorinated solvent HFE6 as a co-solvent (co-solvent), the initial coulomb efficiency was 89.0% (3M LiFSI DME/HFE6 (8/2)) to 89.5% (3M LiFSI DME/HFE6(8/2)+1% JS02) improved. The life characteristics are also improved compared to HFE6.

As shown in FIG. 7, 3M LiFSI DME/HFE6 (8/2) implements a 55.9% capacity retention rate in 76 cycles, but when JS02 is added, it is improved to 80.3% capacity retention rate in 91 cycles.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention defined in the following claims are also present. It belongs to the scope of rights of

Claims (17)

Lithium salt;
Ether solvent;
Fluorinated solvent; And
An electrolyte for a lithium-ion battery containing a functional additive represented by the following Formula 1:
[Formula 1]

here,
n is an integer from 1 to 5,
R ₁ is selected from the group consisting of hydrogen, deuterium, a halogen group, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a substituted or unsubstituted alkene group having 2 to 5 carbon atoms and a substituted or unsubstituted alkoxy group having 1 to 5 carbon atoms,
The substituted R ₁ may be substituted with a substituent selected from the group consisting of deuterium, a halogen group and an alkyl group having 1 to 5 carbon atoms. The method of claim 1,
The functional additive represented by Formula 1 is an electrolyte for a lithium ion battery, which is a compound represented by Formula 2 below:
[Formula 2]

here,
R ₁ is the same as in claim 1. The method of claim 1,
The functional additive represented by Formula 1 is an electrolyte for a lithium ion battery selected from the group consisting of compounds represented by the following Formulas 3 to 6:
[Formula 3]

[Formula 4]

[Formula 5]

[Formula 6]

The method of claim 1,
The lithium salt is an electrolyte for a lithium ion battery selected from the group consisting of LiPF ₆ , LiBF ₄ , LiFSI, LiTFSI, LiSO ₃ CF ₃ , LiBOB and LiDFOB. The method of claim 1,
The ether solvent is 1,2-dimethoxyethane, 1,3-dioxolane, Diethylene glycol dimethyl ether, tetraethylene glycol dimethyl An electrolyte for a lithium ion battery selected from the group consisting of ether (tetraethylene glycol dimethyl ether) and mixtures thereof. The method of claim 5,
The ether-based solvent is 1,2-dimethoxyethane (1,2-dimethoxyethane) electrolyte for a lithium ion battery. The method of claim 1,
The fluorinated solvent is an electrolyte for a lithium ion battery represented by the following formula (7):
[Formula 7]

The method of claim 1,
The lithium ion battery electrolyte includes an ether-based solvent as a main solvent, and further includes a carbonate-based solvent as a selective solvent. The method of claim 8,
The carbonate-based solvent is selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, and mixtures thereof. Lithium ion battery electrolyte. The method of claim 1,
The lithium ion battery electrolyte is an electrolyte for a lithium ion battery capable of increasing the reversibility of electrochemical lithium plating and stripping reactions in a negative electrode including lithium metal as a negative electrode active material. A positive electrode including a positive electrode active material;
A negative electrode disposed to face the positive electrode and including a negative electrode active material;
Ion permeable separation membrane; And
A lithium ion battery comprising the electrolyte according to claim 1 interposed between the positive electrode and the negative electrode. The method of claim 11,
The negative active material is a lithium ion battery of lithium metal. The method of claim 11,
The electrolyte includes a functional additive to increase the reversibility of the electrochemical lithium plating/stripping reaction of the negative electrode,
Lithium ion battery with improved stability and life by suppressing side reactions of lithium metal anode and electrolyte. A battery module comprising the lithium ion battery according to claim 11 as a unit cell. A battery pack comprising the battery module according to claim 14. A device comprising the battery pack according to claim 15. The method of claim 16,
The device is a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a power storage system.

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