CN118922976A - Lithium secondary battery - Google Patents

Abstract

The present invention aims to provide a lithium secondary battery with improved high temperature storage characteristics and high temperature cycle characteristics. The lithium secondary battery of the present invention comprises a positive electrode, a negative electrode comprising a silicon-based negative electrode active material, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte containing a lithium salt, an organic solvent and an additive, wherein the additive may include a compound represented by Formula 1.

Description

Lithium secondary battery

Technical Field

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Korean Patent Application No. 10-2022-0033019 filed on March 16, 2022 and No. 10-2023-0031448 filed on March 9, 2023, the disclosures of which are incorporated herein by reference.

Technical Field

The present invention relates to a lithium secondary battery having improved high temperature storage characteristics and high temperature cycle characteristics.

Background Art

As modern society's reliance on electric energy has gradually increased and the production of electric energy has been required to be increased, research and development has been conducted on large-capacity power storage devices that can stably supply electricity.

Lithium-ion batteries have attracted much attention as devices that exhibit the highest energy density among commercial power storage devices.

A lithium-ion battery is composed of a positive electrode formed of a transition metal oxide containing lithium, a negative electrode capable of storing lithium, an electrolyte containing an organic solvent containing a lithium salt, and a separator.

Regarding the positive electrode therein, energy is stored through the redox reaction of transition metals, which leads to the fact that transition metals must be contained in the positive electrode material.

However, the problem is that transition metals dissolve due to the collapse of a specific positive electrode structure during repeated charge and discharge, or transition metals are dissolved due to the acid formed by hydrolysis/thermal decomposition of lithium salts, or side reactions of the electrolyte at high working potentials. It is known that the dissolved transition metals can not only increase the resistance of the positive electrode by redepositing on the positive electrode, but also cause the negative electrode to self-discharge by electro-depositing on the negative electrode through the electrolyte, increase the interface resistance of the negative electrode, and promote additional electrolyte decomposition reactions by destroying the solid electrolyte interface (SEI) film on the negative electrode surface.

In addition, when silicon-based negative electrode active materials are used as negative electrode components of lithium-ion batteries, since the SEI film will be lost due to electrode expansion as the cycle progresses, which may lead to increased resistance and increased electrolyte side reactions, such problems may cause damage to the electrode structure.

Therefore, there is a need to develop a method capable of preventing secondary batteries from deteriorating by forming a robust passivation film on the surface of an electrode.

Summary of the invention

Technical issues

One aspect of the present invention provides a lithium secondary battery in which high-temperature storage characteristics and high-temperature cycle characteristics are improved by including a nonaqueous electrolyte containing an additive capable of forming a stable film on an electrode surface.

Technical Solution

In an embodiment of the present invention, a lithium secondary battery is provided, comprising:

positive electrode,

A negative electrode comprising a silicon-based negative electrode active material,

a separator disposed between the positive electrode and the negative electrode, and

A non-aqueous electrolyte comprising a lithium salt, an organic solvent and an additive,

The additive includes a compound represented by Formula 1.

[Formula 1]

Among them, in formula 1,

_R1 to _R3 are each independently hydrogen or an alkyl group having 1 to 10 carbon atoms.

The silicon-based negative electrode active material may be at least one selected from the group consisting of silicon, silicon chloride, silicon oxide (SiO _x 0<x<2), and silicon carbon composite (SiC). Specifically, the silicon-based negative electrode active material may be silicon oxide.

The negative electrode may also include a carbon-based negative electrode active material.

In this case, the mixing ratio (weight ratio) of the silicon-based negative electrode active material and the carbon-based negative electrode active material may be 1:99 to 20:80, specifically 1:99 to 10:90.

The positive electrode may include a positive electrode active material including lithium and at least one metal selected from the group consisting of nickel (Ni), cobalt (Co), manganese (Mn), and aluminum (Al).

In Formula 1, _R1 to _R3 may each independently be an alkyl group having 1 to 8 carbon atoms. Specifically, in Formula 1, _R1 may be an alkyl group having 1 to 5 carbon atoms, and _R2 and _R3 may each independently be an alkyl group having 2 to 6 carbon atoms. More specifically, in Formula 1, _R1 may be an alkyl group having 1 to 3 carbon atoms, and _R2 and _R3 may each independently be an alkyl group having 2 to 5 carbon atoms.

The compound represented by Formula 1 may be present in an amount of 0.1 wt % to 5.0 wt % based on the total weight of the non-aqueous electrolyte.

Beneficial Effects

The present invention aims to provide a lithium secondary battery, wherein, by using a negative electrode containing a silicon-based negative electrode active material in combination with a non-aqueous electrolyte (containing a compound containing a phosphonate (-PO(OR) ₂ ) functional group in its structure as an additive), a stable inorganic component film can be formed on the surface of the negative electrode containing the silicon-based active material to prevent battery degradation, thereby achieving excellent cycle characteristics and high-temperature storage stability.

DETAILED DESCRIPTION

Hereinafter, the present invention will be described in more detail.

The words and terms used in the description and claims are for describing exemplary embodiments only and are not intended to be limiting of the invention.

For example, the terms “include”, “comprises” or “has” in this specification stipulate the existence of the features, numbers, steps, elements or a combination thereof, and other parts may also be added unless “only” is used.

Furthermore, in this specification, unless otherwise specifically stated, the expression "%" means weight %.

Unless otherwise defined in the specification, the expression "substituted" means that at least one hydrogen bonded to carbon is replaced by an element other than hydrogen, for example, an alkyl group having 1 to 5 carbon atoms or a fluorine element.

Generally, the passivation performance of the solid electrolyte interface (SEI) film formed on the surface of the negative electrode by the decomposition of the electrolyte and the positive electrode electrolyte interface (CEI) film formed on the surface of the positive electrode under high potential conditions is a factor that greatly affects the improvement of the storage performance of the secondary battery. It is known that the Lewis acid material formed by the thermal decomposition of the lithium salt (LiPF ₆ ) widely used in lithium-ion batteries will cause the negative electrode film (SEI) and the positive electrode film (CEI) to deteriorate. That is, when the positive electrode surface deteriorates due to the attack of the Lewis acid material, it will react with the electrolyte, and the local structure of the positive electrode surface will be changed accordingly due to the dissolution of the transition metal, the surface resistance of the electrode may increase, and the capacity may decrease. In addition, due to the change in the positive electrode structure caused by repeated charge and discharge, the transition metal ions are dissolved from the positive electrode. Since the dissolved transition metal ions move to the negative electrode through the electrolyte and then are deposited on the negative electrode, the negative electrode self-discharges and destroys the film (SEI), which promotes additional electrolyte decomposition reactions, thereby increasing the interface resistance of the negative electrode and the positive electrode.

The present invention aims to provide a lithium secondary battery in which excellent high-temperature cycle characteristics and high-temperature storage stability can be achieved by combining a negative electrode containing a silicon-based negative electrode active material and a non-aqueous electrolyte containing an additive that can form a stable film on the surface of the negative electrode and the surface of the positive electrode to inhibit the degradation of the positive electrode and the negative electrode during rapid charging.

Lithium secondary battery

According to one embodiment of the present invention, the lithium secondary battery of the present invention includes:

positive electrode,

A negative electrode comprising a silicon-based negative electrode active material,

a separator disposed between the positive electrode and the negative electrode, and

A non-aqueous electrolyte comprising a lithium salt, an organic solvent and an additive,

The additive may include a compound represented by Formula 1 below.

[Formula 1]

Among them, in formula 1,

_R1 to _R3 are each independently hydrogen or an alkyl group having 1 to 10 carbon atoms.

Hereinafter, the configuration of the lithium secondary battery of the present invention will be described in detail.

(1) Positive electrode

The positive electrode of the present invention may include a positive electrode active material and, if necessary, may further include a conductive agent and/or a binder.

The positive electrode active material is a compound capable of reversibly inserting and deinserting lithium, wherein the positive electrode active material may specifically include a lithium transition metal oxide represented by the following formula 2, which contains lithium and at least one metal selected from the group consisting of nickel (Ni), cobalt (Co), manganese (Mn) and aluminum (Al).

[Formula 2]

Li _1+a Ni _x Co _y M ¹ _z M ² _w O ₂

In formula 1,

^M1 is Mn, Al or a combination thereof,

^M2 is at least one selected from the group consisting of Al, zirconium (Zr), tungsten (W), titanium (Ti), magnesium (Mg), calcium (Ca) and strontium (Sr), and 0≤a≤0.5, 0<x≤0.6, 0<y≤0.4, 0<z≤0.4 and 0≤w≤0.1.

1+a represents the atomic fraction of lithium in the lithium transition metal oxide, wherein a may satisfy 0≤a≤0.5, preferably 0≤a≤0.2, and more preferably 0≤a≤0.1. When the atomic fraction of lithium satisfies the above range, the crystal structure of the lithium transition metal oxide may be stably formed.

x represents the atomic fraction of nickel in all transition metal elements in the lithium transition metal oxide, wherein x may satisfy 0<x≤0.6, particularly 0.55<x<1.0, more particularly 0.6≤x≤0.98, for example 0.6≤x≤0.95. When the atomic fraction of nickel satisfies the above range, high energy density may be exhibited and high capacity may be achieved.

y represents the atomic fraction of cobalt in all transition metal elements in the lithium transition metal oxide, wherein y may satisfy 0<y≤0.4, particularly 0<y≤0.3, and more particularly 0.05≤y≤0.3. When the atomic fraction of cobalt satisfies the above range, good resistance characteristics and output characteristics may be achieved.

z represents the atomic fraction of the ^M1 element in all transition metal elements in the lithium transition metal oxide, wherein z may satisfy 0<z≤0.4, preferably 0<z≤0.3, and more preferably 0.01≤z≤0.3. When the atomic fraction of the element ^M1 satisfies the above range, the structural stability of the positive electrode active material is excellent.

w represents the atomic fraction of the ^M2 element in all transition metal elements in the lithium transition metal oxide, wherein w may satisfy 0<w≤0.1, preferably 0<w≤0.05, and more preferably 0<w≤0.02.

Specifically, the positive electrode active material may include a lithium composite transition metal oxide having a Ni content of _0.55 (atomic _fraction ) or more, such as Li( _{Ni0.6Mn0.2Co0.2} ) _O2 , Li( _{Ni0.7Mn0.15Co0.15 ) O2} , _Li ( _{Ni0.7Mn0.2Co0.1} ) _{O2 , Li(Ni0.8Mn0.1Co0.1)O2, Li(Ni0.8Co0.15Al0.05 ) O2 , Li ( Ni0.86Mn0.07Co0.05Al0.02 ) O2 , or Li} ( _{Ni0.90Mn0.05Co0.05 ) O2 ,} to achieve _{a high} -capacity battery _.

In addition, the positive electrode active material of the present invention can be lithium manganese oxide (for example, _LiMnO2 , _{LiMn2O4 ,} etc.), lithium cobalt oxide (for example, LiCoO2 _, etc.), lithium nickel oxide (for example, LiNiO2 _, etc.), lithium nickel manganese oxide (for example, _{LiNi1- YMnYO2} (0<Y< ₁ ), LiMn2 _{- ZNiZO4} (0<Z<2)), lithium nickel _{cobalt oxide} (for example, LiNi1 _{- Y1CoY1O2} (0<Y1<1)), lithium manganese _cobalt oxide (for example, LiCo1 _{- Y2MnY2O2} (0<Y2<1), LiMn2 _{- Z1CoZ1O4} (0<Z1<2) ₎ or Li(Ni _{p1Coq1Mn r2} ) _{O4 .} (0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2) is used in combination with the lithium transition metal oxide represented by Formula 2.

Next, the conductive agent is used to provide conductivity to the electrode, wherein any conductive agent can be used without particular limitation, as long as it has suitable electronic conductivity and does not cause adverse chemical changes in the battery. Specific examples of the conductive agent can be the following conductive materials, for example: carbon powder, such as carbon black, acetylene black (or Denka black), Ketjen black, channel black, furnace black, lamp black or thermal black; graphite powder, such as natural graphite, artificial graphite or graphite with a well-developed crystal structure; conductive fibers, such as carbon fibers or metal fibers; conductive powders, such as fluorocarbon powders, aluminum powders and nickel powders; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium oxide; or polyphenylene derivatives, one or a mixture of two or more thereof can be used.

Next, the binder improves adhesion between positive electrode active material particles and between the positive electrode active material and a current collector.

As examples of adhesives, any of the following can be used: fluororesin adhesives, including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber adhesives, including styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber or styrene-isoprene rubber; cellulose adhesives, including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose or regenerated cellulose; polyol adhesives, such as polyvinyl alcohol; polyolefin adhesives, including polyethylene or polypropylene; polyimide adhesives; polyester adhesives; and silane adhesives, or a mixture of two or more thereof.

The positive electrode of the present invention can be prepared by a method for preparing a positive electrode known in the art. For example, the positive electrode can be prepared by the following method: coating the positive electrode current collector with a positive electrode slurry prepared by dissolving or dispersing a positive electrode active material, a binder and/or a conductive agent in a solvent, drying and then rolling, or casting the positive electrode slurry on a separate carrier to form a film, and then laminating the film separated from the carrier on the positive electrode current collector.

The positive electrode active material may be contained in an amount of 80 wt % to 98 wt %, more specifically 85 wt % to 98 wt %, based on the total weight of the positive electrode slurry. When the content of the positive electrode active material is within the above range, excellent capacity characteristics may be exhibited.

Based on the total weight of the positive electrode slurry, the content of the conductive agent can be 0.1 wt % to 10 wt %, preferably 0.1 wt % to 5 wt %, and based on the total weight of the positive electrode active material layer, the content of the binder is 0.1 wt % to 15 wt %, preferably 0.1 wt % to 10 wt %.

The positive electrode current collector is not particularly limited as long as it has conductivity without causing adverse chemical changes in the battery, and can use, for example, stainless steel, aluminum, nickel, titanium, fired carbon, or aluminum or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc. In addition, the thickness of the positive electrode current collector is generally 3 μm to 500 μm, and fine irregularities can be formed on the surface of the current collector to improve the adhesion of the positive electrode material. For example, the positive electrode current collector can be used in various shapes, such as a film, a sheet, a foil, a mesh, a porous body, a foam body, a non-woven fabric body, etc.

The solvent may be a commonly used solvent in the art, and may include dimethyl sulfoxide (DMSO), isopropanol, N-methylpyrrolidone (NMP), acetone or water, and any one or a mixture of two or more thereof may be used. If the coating thickness, manufacturing yield and processability of the positive electrode material mixture are taken into consideration, the positive electrode material mixture may be adjusted to have an appropriate viscosity, and the amount of the solvent used may be sufficient without particular limitation.

(2) Negative electrode

The negative electrode of the present invention includes a negative electrode active material and, if necessary, may further include a conductive agent and/or a binder.

As the negative electrode active material, a silicon-based negative electrode active material commonly used in the art may be used. In addition, a mixture of a carbon-based negative electrode active material and a silicon-based negative electrode active material may also be used.

For example, the silicon (Si)-based negative electrode active material may include at least one selected from the group consisting of silicon (Si), silicon carbide (SiC), silicon chloride, silicon oxide (SiO _x , where 0<x<2), and Si-Y alloy (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, but not Si). Element Y may be selected from the group consisting of Mg, Ca, Sr, barium (Ba), radium (Ra), scandium (Sc), yttrium (Y), Ti, Zr, hafnium (Hf), (Rf), vanadium (V), niobium (Nb), tantalum (Ta), (Db), chromium (Cr), molybdenum (Mo), W, (Sg), technetium (Tc), rhenium (Re), (Bh), iron (Fe), lead (Pb), ruthenium (Ru), osmium (Os), (Hs), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), boron (B), Al, gallium (Ga), tin (Sn), indium (In), Ti, germanium (Ge), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S), selenium (Se), tellurium (Te), polonium (Po), and combinations thereof.

Specifically, the negative active material may include silicon oxide (SiO) composed of silicon dioxide (SiO ₂ ) and amorphous silicon at a mixing ratio of 1:1 (based on a weight ratio).

Compared with carbon-based negative electrode active materials, silicon-based negative electrode active materials can obtain higher capacity characteristics. However, for the negative electrode containing silicon-based negative electrode active materials, by reacting with the non-aqueous electrolyte during the initial charge and discharge, a SEI film containing more oxygen-rich (O) components than the graphite negative electrode is formed on its surface, wherein when a Lewis acid (such as HF or PF ₅ ) is present in the electrolyte, the SEI film may be easily decomposed, resulting in side reactions of the electrolyte or consumption of the electrolyte. Therefore, in the case of using silicon-based negative electrode active materials as negative electrode components, it is important to form a stable SEI film containing inorganic components to inhibit the degradation of Si caused by HF. That is, in the case of using a negative electrode containing silicon-based negative electrode active materials, the non-aqueous electrolyte used in combination must contain an additive that can inhibit the formation of Lewis acids (such as HF or PF ₅ ) in the electrolyte or remove the Lewis acids that have been formed and simultaneously form an inorganic film to stably maintain the SEI film.

In addition, as a carbon-based negative electrode active material that can be used in combination with a silicon-based negative electrode active material, various carbon-based negative electrode active materials used in the art can be used, for example, graphite-based materials such as natural graphite, artificial graphite, and Kish graphite; pyrolytic carbon, mesophase pitch-based carbon fibers, mesophase carbon microbeads, mesophase pitch, high-temperature sintered carbon (e.g., coke derived from petroleum or coal tar pitch), soft carbon, and hard carbon. The shape of the carbon-based negative electrode active material is not particularly limited, and materials of various shapes can be used, such as irregular, planar, flaky, spherical, or fibrous.

Silicon-based negative electrode active materials and carbon-based negative electrode active materials can be mixed and used in a weight ratio of 1:99 to 20:80. When the mixing ratio of silicon-based negative electrode active materials to carbon-based negative electrode active materials is satisfied, since the volume expansion of silicon-based negative electrode active materials is suppressed and the capacity characteristics are improved at the same time, the excellent cycle performance of the battery can be ensured and high capacity can be achieved. If the mixing ratio (weight ratio) of the silicon-based negative electrode active materials is less than 1, it is difficult to achieve a high-capacity battery because it is difficult to increase the energy density. If the mixing ratio (weight ratio) of the silicon-based negative electrode active materials is greater than 20, the volume expansion of the negative electrode may be increased. Specifically, the mixing ratio (weight ratio) of the silicon-based negative electrode active materials and the carbon-based negative electrode active materials can be 1:99 to 10:90, particularly 3:97 to 5:95, and more particularly 5:95 to 3:9.

Next, the conductive agent is a component for further improving the conductivity of the negative electrode active material, wherein any conductive agent can be used without particular limitation, as long as it has conductivity and does not cause adverse chemical changes in the battery. Specifically, as the conductive agent, the following conductive materials can be used, for example: carbon powder, such as carbon black, acetylene black (or Denka black), Ketjen black, channel black, furnace black, lamp black or thermal black; graphite powder, such as natural graphite, artificial graphite or graphite with a well-developed crystal structure; conductive fibers, such as carbon fibers or metal fibers; conductive powders, such as fluorocarbon powders, aluminum powders and nickel powders; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium oxide; or polyphenylene derivatives, and the conductive agent can be the same as or different from the conductive agent used in the positive electrode.

The binder is a component that helps to bond between the conductive agent, the active material and the current collector, wherein representative examples of the binder can be fluororesin binders, including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber binders, including styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber or styrene-isoprene rubber; cellulose binders, including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose or regenerated cellulose; polyol binders, including polyvinyl alcohol; polyolefin binders, including polyethylene or polypropylene; polyimide binders; polyester binders; and silane binders, and the binder can be the same as or different from the binder used for the positive electrode.

The negative electrode can be prepared by a method for preparing a negative electrode known in the art. For example, the negative electrode can be prepared by a method in which a negative electrode current collector is coated with a negative electrode slurry prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive agent in a solvent, followed by drying and roll pressing, or a method in which the negative electrode slurry can be cast on a separate support to form a film, and then the film separated from the support is laminated on the negative electrode current collector.

The negative electrode active material may be contained in an amount of 80 wt % to 99 wt % based on the total weight of the negative electrode slurry. When the amount of the negative electrode active material satisfies the above range, excellent capacity characteristics and electrochemical performance may be obtained.

Based on the total weight of the negative electrode slurry, the added amount of the conductive agent may be 10 wt % or less, preferably 5 wt % or less, and based on the total weight of the negative electrode slurry, the content of the binder is 0.1 wt % to 15 wt %, preferably 0.1 wt % to 10 wt %.

The negative electrode current collector is not particularly limited as long as it has high conductivity without causing adverse chemical changes in the battery, and can use, for example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, copper or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy. In addition, the thickness of the negative electrode current collector can generally be 3 μm to 500 μm, and similar to the positive electrode current collector, fine irregularities can be formed on the surface of the current collector to improve the adhesion of the negative electrode active material. For example, the negative electrode current collector can be used in various shapes, such as a film, a sheet, a foil, a mesh, a porous body, a foam body, a non-woven fabric body, etc.

The solvent may be a commonly used solvent in the art, and may include dimethyl sulfoxide (DMSO), isopropanol, N-methylpyrrolidone (NMP), acetone or water, and any one or a mixture of two or more thereof may be used. If the coating thickness, manufacturing yield and processability of the negative electrode material mixture are taken into consideration, the negative electrode slurry may be adjusted to have an appropriate viscosity, and the amount of the solvent used may be sufficient without particular limitation.

(3) Diaphragm

The lithium secondary battery of the present invention includes a separator between a positive electrode and a negative electrode.

The separator separates the negative electrode and the positive electrode and provides a path for the movement of lithium ions. Any separator commonly used in lithium secondary batteries can be used as the separator without special restrictions. In particular, a separator with higher moisture retention capacity for the electrolyte and lower resistance to the transfer of lithium salt ions is preferred.

Specifically, porous polymer film can be used, for example, a porous polymer film prepared by polyolefin polymers (such as ethylene homopolymers, propylene homopolymers, ethylene/butene copolymers, ethylene/hexene copolymers and ethylene/methacrylate copolymers) or a laminated structure of more than two layers thereof. In addition, common porous nonwoven fabrics can be used, for example, nonwoven fabrics formed by high melting point glass fibers or polyethylene terephthalate fibers. In addition, the coated diaphragm comprising ceramic components or polymer materials can be used to ensure heat resistance or mechanical strength, and a diaphragm with a monolayer or multilayer structure can be optionally used.

(4) Non-aqueous electrolyte

The lithium secondary battery of the present invention comprises a non-aqueous electrolyte containing a lithium salt, an organic solvent and an additive.

(4-1) Lithium Salt

First, in the non-aqueous electrolyte of the present invention, any lithium salt commonly used in non-aqueous electrolytes for lithium secondary batteries can be used as the lithium salt without particular limitation. For example, the lithium salt can include Li ⁺ as a cation and can include at least one selected from the group consisting of: F ^- , Cl ^- , Br ^- , I ^- , NO ₃ ^- , N(CN) ₂ ^- , BF ₄ ^- , ClO ₄ ^- , B ₁₀ Cl ₁₀ ^- , AlCl ₄ ^- , AlO ₂ ^- , PF ₆ ^- , CF ₃ SO ₃ ^- , CH ₃ CO ₂ ^- , CF ₃ CO ₂ ^- , AsF ₆ ^- , SbF ₆ ^- , CH ₃ SO ₃ ^- , (CF ₃ CF ₂ SO ₂ ) ₂ N ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- , BF ₂ C ₂ O ₄ ^-, or a mixture thereof. , BC ₄ O ₈ ^- , PF ₄ C ₂ O ₄ ^- , PF ₂ C ₄ O ₈ ^- , (CF ₃ ) ₂ PF ₄ ^- , (CF ₃ ) ₃ PF ₃ ^- , (CF ₃ ) ₄ PF ₂ ^- , (CF ₃ ) ₅ PF ^- , (CF ₃ ) ₆ P ^- , C ₄ F ₉ SO ₃ ^- , CF ₃ CF ₂ SO ₃ ^- , CF ₃ CF ₂ (CF ₃ ) ₂ CO ^- , (CF ₃ SO ₂ ) ₂ CH ^- , CF ₃ (CF ₂ ) ₇ SO ₃ ^- and SCN ^- .

Specifically, the lithium _{salt may} include a single material selected from the group consisting _of LiCl, LiBr, LiI, _LiBF4 , _LiClO4 , _LiB10Cl10 , LiAlCl4, LiAlO2, _LiPF6 , _LiCF3SO3 , LiCH3CO2, _LiCF3CO2 , LiAsF6, _{LiSbF6 , LiCH3SO3} , _LiN ( _{SO2F ) 2} (lithium bis(fluorosulfonyl)imide, _LiFSI ), _LiN ( _{SO2CF2CF3 ) 2} (lithium bis( _{pentafluoroethanesulfonyl} )imide, LiBETI), and LiN( _{SO2CF3 ) 2} (lithium bis( _{trifluoromethanesulfonyl} )imide, LiTFSI), or a mixture of two or more thereof. In addition to them, lithium salts generally used in electrolytes for lithium secondary batteries may be used without limitation.

The lithium salt may be appropriately changed within the normal use range, but may be contained in the electrolyte at a concentration of 0.8 M to 4.0 M, specifically 1.0 M to 3.0 M, to obtain the best effect of forming a film for preventing corrosion of the electrode surface.

When the concentration of the lithium salt is within the above range, the viscosity of the nonaqueous electrolyte can be controlled to achieve optimal impregnation, and the mobility of lithium ions can be improved to obtain the effect of improving the capacity characteristics and cycle characteristics of the lithium secondary battery.

(4-2) Organic solvents

In addition, the description of the organic solvent is as follows.

Various organic solvents generally used in nonaqueous electrolytes may be used as the nonaqueous organic solvent without particular limitation, wherein the type thereof is not limited as long as decomposition caused by oxidation reaction during charge and discharge of the secondary battery can be minimized and desired characteristics can be exhibited together with additives.

Specifically, the nonaqueous organic solvent may include (i) a cyclic carbonate-based organic solvent, (ii) a linear carbonate-based organic solvent, or (iii) a mixed organic solvent thereof.

(i) Cyclic carbonate organic solvents are high-viscosity organic solvents and can dissociate lithium salts in non-aqueous electrolytes well due to their high dielectric constants, wherein specific examples of cyclic carbonate organic solvents can be at least one organic solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, wherein the cyclic carbonate organic solvent can include at least one of ethylene carbonate and propylene carbonate.

(ii) Linear carbonate organic solvents are organic solvents with low viscosity and low dielectric constant, wherein specific examples of the linear carbonate organic solvents may be at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate and ethyl propyl carbonate, and the linear carbonate organic solvent may specifically include one of dimethyl carbonate and ethyl methyl carbonate.

Furthermore, in order to ensure high ion conductivity, the (i) cyclic carbonate-based organic solvent and the (ii) linear carbonate-based organic solvent may be mixed and used in a volume ratio of 10:90 to 50:50, specifically 20:80 to 40:60.

In addition, the ionic conductivity of the non-aqueous electrolyte of the present invention can be further improved by additionally comprising at least one organic solvent of (iv) a linear ester organic solvent and (v) a cyclic ester organic solvent, wherein the ester organic solvent has a lower melting point and higher high temperature stability than the cyclic carbonate organic solvent and/or the linear carbonate organic solvent.

Representative examples of the (iv) linear ester organic solvent may be at least one organic solvent selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate and butyl propionate, and the (iv) linear ester organic solvent may specifically include at least one selected from ethyl propionate and propyl propionate.

(v) The cyclic ester organic solvent may include at least one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

If necessary, an organic solvent commonly used in an electrolyte of a lithium secondary battery may be added without limitation and used as the organic solvent. For example, at least one organic solvent of an ether organic solvent, an amide organic solvent, and a nitrile organic solvent may be included.

Unless otherwise specified, the rest of the non-aqueous electrolyte of the present invention except the lithium salt, the additives and other additives may be an organic solvent.

(4-3) Additives

A compound represented by the following Formula 1 may be included as an additive.

[Formula 1]

Among them, in formula 1,

_R1 to _R3 are each independently hydrogen or an alkyl group having 1 to 10 carbon atoms.

As described above, for the negative electrode containing silicon-based negative electrode active materials, a SEI film containing a large amount of oxygen-rich (O) components can be formed on the negative electrode surface by reacting with the electrolyte. Therefore, in order to stably maintain the SEI film, it is necessary to use an additive that can inhibit the formation of Lewis acid (such as HF or PF ₅ ) in the electrolyte or remove (or clear) the formed Lewis acid.

Since the compound represented by Formula 1 contains a phosphonate (-PO(OR) ₂ ) group in the structure, an inorganic component film can be formed on the surface of the negative electrode containing a silicon-based negative electrode active material, thereby preventing Si degradation caused by HF and the resulting capacity loss, and reducing the consumption of the electrolyte and the increase in film thickness caused by the decomposition and regeneration of the SEI film. In addition, since the compound represented by Formula 1 contains an alkoxy group that is not substituted by fluorine as an end group, the end group can be prevented from being removed at high temperature and high potential, thereby suppressing side reactions caused by the removed substituents, such as gas generation. In addition, since the compound represented by Formula 1 contains a cyano (-CN) functional group in the structure, a stable CEI film can be formed on the positive electrode surface by forming a ligand with a transition metal, thereby preventing side reactions between the positive electrode and the electrolyte during high temperature storage, and suppressing metal dissolution.

Therefore, in the case of using a non-aqueous electrolyte solution including the compound represented by Formula 1 as a non-aqueous electrolyte additive, a lithium secondary battery capable of achieving excellent cycle characteristics and high-temperature storage stability may be prepared.

In Formula 1, when _R1 to _R3 are each independently an alkyl group having more than 10 carbon atoms, the solubility in the organic solvent may increase due to the increase in the molecular structure and molecular weight of the compound, and the impregnation property of the electrolyte may decrease due to the increase in electrolyte viscosity. In addition, in Formula 1, when _R1 to _R3 are each independently an alkyl group having more than 10 carbon atoms, the amount of gas generated may increase when a decomposition reaction of an additive that breaks an oxygen-phosphorus bond, an oxygen-carbon bond, or a carbon-carbon bond occurs during charge and discharge.

Specifically, in Formula 1, _R1 to _R3 may each independently be an alkyl group having 1 to 8 carbon atoms.

In addition, _R1 may be an alkyl group having 1 to 5 carbon atoms, and _R2 and _R3 may each independently be an alkyl group having 2 to 6 carbon atoms.

Furthermore, _R1 may be an alkyl group having 1 to 3 carbon atoms, and _R2 and _R3 may each independently be an alkyl group having 2 to 5 carbon atoms.

More specifically, the compound represented by Formula 1 may include a compound represented by the following Formula 1a.

[Formula 1a]

The compound of Formula 1 may be present in an amount of 0.1 wt % to 5.0 wt % based on the total weight of the non-aqueous electrolyte.

If the compound represented by Formula 1 is within the above range, since the compound can effectively prevent the degradation of the negative electrode during rapid charge and discharge by forming a stable film on the negative electrode and the positive electrode, and prevent the side reaction caused by the additive, a secondary battery with improved overall performance can be prepared. Specifically, if the amount of the compound represented by Formula 1 is 0.1% by weight or more, the effect of forming a film on the surface of the negative electrode and the positive electrode, and the effect of removing the thermal decomposition products of the lithium salt (such as HF or PF ₅ ) during battery operation can be more stably maintained. In addition, when the content of the compound represented by Formula 1 is 5.0% by weight or less, the viscosity of the non-aqueous electrolyte can be controlled to obtain the best impregnation, the increase in battery resistance caused by the decomposition of the additive can be effectively suppressed, and since the ionic conductivity of the electrolyte will not be reduced, the degradation of the rate performance or low temperature life characteristics can be prevented.

Specifically, the compound represented by Formula 1 may be present in an amount of 0.1 wt % to 3.0 wt %, more preferably 0.3 wt % to 1.0 wt %.

(4-4) Other additives

If necessary, the non-aqueous electrolyte may also contain other additives to prevent the occurrence of negative electrode collapse due to decomposition of the non-aqueous electrolyte in a high power environment, or to further improve low temperature high rate discharge characteristics, high temperature stability, prevent overcharge, and inhibit the expansion of the battery at high temperature.

As a representative example, other additives may include at least one other additive selected from the group consisting of: cyclic carbonate compounds, halogenated carbonate compounds, sultone compounds, sulfate ester/salt compounds, phosphate ester/salt compounds, borate ester/salt compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds and lithium salt compounds.

The cyclic carbonate-based compound may include vinylene carbonate (VC) or vinyl ethylene carbonate.

The halogenated carbonate compounds may include fluoroethylene carbonate (FEC).

The sultone compound may include at least one compound selected from the group consisting of 1,3-propane sultone (PS), 1,4-butane sultone, ethane sultone, 1,3-propene sultone (PRS), 1,4-butene sultone, and 1-methyl-1,3-propene sultone.

The sulfate compound may include ethylene sulfate (Esa), trimethylene sulfate (TMS) or tripropylene methyl sulfate (MTMS).

The phosphate compound may include at least one compound selected from the group consisting of lithium difluoro(bisoxalato)phosphate, lithium difluorophosphate, tris(trimethylsilyl)phosphate, tris(2,2,2-trifluoroethyl)phosphate, and tris(trifluoroethyl)phosphate.

The borate compounds may include tetraphenylborate and lithium oxalyldifluoroborate.

The nitrile compound may include at least one compound selected from the group consisting of succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, octanonitrile, heptanecarbonitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, benzyl cyanide, 2-fluorophenyl cyanide and 4-fluorophenyl cyanide.

The benzene compound may include fluorobenzene, the amine compound may include triethanolamine or ethylenediamine, and the silane compound may include tetravinylsilane.

The lithium salt compound is a compound other than the lithium salt contained in the non-aqueous electrolyte, wherein the lithium salt compound may include at least one compound selected from the group consisting of LiPO ₂ F ₂ , LiODFB, LiBOB (lithium bis(oxalatoborate) (LiB(C ₂ O ₄ ) ₂ ) and LiBF ₄ .

In the case where vinylene carbonate, vinyl ethylene carbonate, or succinonitrile is included in these other additives, a more robust SEI film may be formed on the negative electrode surface during the initial activation of the secondary battery.

Two or more other additives may be mixed and used, and based on the total weight of the non-aqueous electrolyte, the amount of the other additives present may be 50% by weight or less, particularly 0.01% by weight to 10% by weight, preferably 0.05% by weight to 5% by weight. If the amount of the other additives is less than 0.01% by weight, the improvement effect on the low temperature output, high temperature storage characteristics and high temperature life characteristics of the battery is not obvious; if the amount of the other additives is greater than 50% by weight, side reactions in the electrolyte may occur excessively during battery charging and discharging. In particular, since the additives used to form the SEI film may not be fully decomposed at high temperatures when an excess of additives for forming the SEI film is added, the additives used to form the SEI film may be present in the electrolyte in the form of unreacted materials or precipitates at room temperature. Therefore, side reactions that deteriorate the life or resistance characteristics of the secondary battery may occur.

The lithium secondary battery of the present invention can be prepared according to conventional methods known in the art. Specifically, it can be prepared by forming an electrode assembly (in which a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode are stacked in sequence), storing the electrode assembly in a battery case, and then injecting a non-aqueous electrolyte.

The shape of the lithium secondary battery of the present invention is not particularly limited, but a cylindrical shape using a can, a prismatic shape, a pouch shape, or a coin shape may be used.

In addition, the lithium secondary battery of the present invention can be used not only in a battery cell used as a power source for small devices, but also as a unit cell of a large and medium-sized battery module containing a plurality of battery cells. Specifically, the lithium secondary battery of the present invention can be applied to portable devices such as mobile phones, notebook computers and digital cameras, and electric vehicles such as hybrid electric vehicles (HEV).

Hereinafter, the present invention will be described in more detail according to the embodiments. However, the present invention can be implemented in many different forms and should not be interpreted as being limited to the embodiments set forth herein. On the contrary, these exemplary embodiments are provided to make this specification thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

Example

Example 1.

(Preparation of non-aqueous electrolyte)

After dissolving _LiPF6 in an organic solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 30:70 so that the concentration of _LiPF6 was 1.0 M, a non-aqueous electrolyte was prepared by adding 0.1 wt% of the compound represented by Formula 1a and 1.0 wt% of vinylene carbonate (VC) and 0.5 wt% of 1,3-propane sultone (PS) (see Table 1 below).

(Preparation of Secondary Battery)

Lithium nickel cobalt manganese oxide (Li(Ni _0.8 Mn _0.1 Co _0.1 )O ₂ ) as positive electrode active material particles, carbon black as a conductive agent, and polyvinylidene fluoride as a binder were added to N-methyl-2-pyrrolidone (NMP) as a solvent at a weight ratio of 97.5:1:1.5 to prepare a positive electrode slurry (solid content: 85.0 wt %). A 15 μm thick positive electrode collector (aluminum (Al) thin film) was coated with the positive electrode slurry, dried, and roll-pressed to prepare a positive electrode.

The negative electrode active material (graphite: SiO = 95:5 weight ratio), the binder (SBR-CMC) and the conductive agent (carbon black) were added to water as a solvent at a weight ratio of 95:3.5:1.5 to prepare a negative electrode slurry (solid content: 60 weight %). A 6 μm thick copper (Cu) film as a negative electrode current collector was coated with the negative electrode slurry, dried and then rolled to prepare a negative electrode.

After an electrode assembly was prepared by placing a polypropylene porous separator between the prepared positive electrode and negative electrode, the electrode assembly was housed in a battery case, and the prepared nonaqueous electrolyte was injected to prepare a lithium secondary battery.

Example 2.

A lithium secondary battery was prepared in the same manner as in Example 1, except that after dissolving _LiPF6 in a non-aqueous organic solvent so that the concentration of _LiPF6 was 1.0 M, a non-aqueous electrolyte was prepared by adding 0.5 wt% of the compound represented by Formula 1a, 1.0 wt% of vinylene carbonate (VC), and 0.5 wt% of 1,3-propane sultone (PS) (see Table 1 below).

Example 3.

A lithium secondary battery was prepared in the same manner as in Example 1, except that after dissolving _LiPF6 in a non-aqueous organic solvent so that the concentration of _LiPF6 was 1.0 M, a non-aqueous electrolyte was prepared by adding 1.0 wt% of the compound represented by Formula 1a, 1.0 wt% of vinylene carbonate (VC), and 0.5 wt% of 1,3-propane sultone (PS) (see Table 1 below).

Example 4.

A lithium secondary battery was prepared in the same manner as in Example 1, except that after dissolving _LiPF6 in a non-aqueous organic solvent so that the concentration of _LiPF6 was 1.0 M, a non-aqueous electrolyte was prepared by adding 5.0 wt% of the compound represented by Formula 1a, 1.0 wt% of vinylene carbonate (VC), and 0.5 wt% of 1,3-propane sultone (PS) (see Table 1 below).

Example 5.

A lithium secondary battery was prepared in the same manner as in Example 1, except that after dissolving _LiPF6 in a non-aqueous organic solvent so that the concentration of _LiPF6 was 1.0 M, a non-aqueous electrolyte was prepared by adding 6.0 wt% of the compound represented by Formula 1a, 1.0 wt% of vinylene carbonate (VC), and 0.5 wt% of 1,3-propane sultone (PS) (see Table 1 below).

Comparative Example 1.

A lithium secondary battery was prepared in the same manner as in Example 1, except that after dissolving _LiPF6 in a non-aqueous organic solvent so that the concentration of _LiPF6 was 1.0 M, a non-aqueous electrolyte was prepared by adding 1.0 wt% of vinylene carbonate (VC), 0.5 wt% of 1,3-propane sultone (PS) (see Table 1 below).

Comparative Example 2.

A lithium secondary battery was prepared in the same manner as in Example 2, except that after dissolving _LiPF6 in a non-aqueous organic solvent so that the concentration of _LiPF6 was 1.0 M, a non-aqueous electrolyte was prepared by adding 0.5 wt% of a compound represented by the following formula 2 instead of the compound of formula 1a as an additive (see Table 1 below).

[Formula 2]

Comparative Example 3.

A lithium secondary battery was prepared in the same manner as in Example 3, except that after dissolving _LiPF6 in a non-aqueous organic solvent so that the concentration of _LiPF6 was 1.0 M, a non-aqueous electrolyte was prepared by adding 1.0 wt% of the compound represented by Formula 2 instead of the compound of Formula 1a as an additive (see Table 1 below).

Comparative Example 4.

(Preparation of lithium secondary battery)

Lithium nickel cobalt manganese oxide (Li(Ni _0.8 Mn _0.1 Co _0.1 )O ₂ ) as positive electrode active material particles, carbon black as a conductive agent, and polyvinylidene fluoride as a binder were added to N-methyl-2-pyrrolidone (NMP) as a solvent at a weight ratio of 97.5:1:1.5 to prepare a positive electrode slurry (solid content: 85.0 wt %). A 15 μm thick positive electrode collector (Al thin film) was coated with the positive electrode slurry, dried, and roll-pressed to prepare a positive electrode.

The negative electrode active material (graphite), binder (SBR-CMC) and conductive agent (carbon black) were added to water as a solvent at a weight ratio of 95:3.5:1.5 to prepare a negative electrode slurry (solid content: 60 wt%). A 6 μm thick copper (Cu) film as a negative electrode current collector was coated with the negative electrode slurry, dried and then rolled to prepare a negative electrode.

After preparing an electrode assembly by disposing a polypropylene porous separator between the positive electrode and the negative electrode prepared above, the electrode assembly was housed in a battery case.

Then, a lithium secondary battery was prepared in the same manner as in Example 1, except that the nonaqueous electrolyte prepared in Example 3 was injected.

[Table 1]

In Table 1, the abbreviation of each compound has the following meaning.

EC: Ethylene carbonate

EMC: Ethyl Methyl Carbonate

VC: Vinylene carbonate

PS: 1,3-propane sultone

Experimental example

Experimental Example 1. Performance evaluation after high temperature storage

Each lithium secondary battery of Examples 1 to 5 and each lithium secondary battery of Comparative Examples 1 to 4 was charged to 4.2V at 0.2C in constant current-constant voltage (CC-CV) mode, and then stored in a room at 60°C for 30 days. After measuring the open circuit voltage (OCV) before storage, the OCV after 30 days of storage was measured, and the change value was expressed as dOCV. Then, each secondary battery was discharged to 2.5V at 0.2C in CC mode, gas was extracted, and the total amount of gas generated after high temperature storage was set as the gas generation amount, which is listed in Table 2 below.

[Table 2]

Referring to Table 2, for the secondary batteries of Examples 1 to 5 using the nonaqueous electrolyte containing the compound of Formula 1a, it can be confirmed that the dOCV and the amount of gas generated are reduced compared to the secondary battery of Comparative Example 1.

In addition, when the secondary batteries of Examples 2 and 3 containing the same amount of additives are compared with the secondary batteries of Comparative Examples 2 and 3, it can be determined that the dOCV and gas generation amount are reduced compared with the secondary batteries of Comparative Examples 2 and 3 in which the non-aqueous electrolyte containing the compound of Formula 1a of the present invention is used.

Considering these results, it appears that both dOCV and gas generation are reduced because the compound of Formula 1a of the present invention can suppress the side reaction of the electrolyte during high-temperature storage by forming a stable film on the surface of the negative electrode and the positive electrode.

In addition, when the secondary battery of Example 3 comprising a non-aqueous electrolyte containing an equal amount of additives is compared with the secondary battery of Comparative Example 4, for the secondary battery of Example 3 of the present invention in which a negative electrode comprising a silicon-based negative electrode active material is used, it can be determined that compared with the secondary battery of Comparative Example 4, the dOCV is reduced and the effect of suppressing gas generation is further improved.

Experimental Example 2. Performance evaluation after rapid charge and discharge

The lithium secondary batteries of Examples 1 to 5 and the secondary batteries of Comparative Examples 1 to 4 were charged to 4.2 V at 3 C in CC-CV mode, and the lithium secondary batteries were discharged to 2.5 V at 0.2 C in CC mode as 1 cycle. After 100 rapid charge and discharge cycles, the capacity retention rate (%) and the resistance increase rate (%) were calculated, and the results are shown in Table 3 below.

[Table 3]

Referring to Table 3, for the secondary batteries of Examples 1 to 4 in which the nonaqueous electrolyte containing the compound of Formula 1a is used, it can be understood that, compared with the secondary battery of Comparative Example 1, a better capacity retention rate can be ensured after rapid charge and discharge, and the resistance increase rate is also reduced.

For the secondary battery of Example 5 containing a non-aqueous electrolyte containing a relatively large amount of additives, it can be understood that due to the side reactions of the additives, the capacity retention rate is slightly reduced and the resistance increase rate is slightly increased compared with the lithium secondary batteries of Examples 1 to 4.

When the secondary batteries of Examples 2 and 3 containing the same amount of additives are compared with the secondary batteries of Comparative Examples 2 and 3, it can be determined that for the secondary batteries of Examples 2 and 3 in which a non-aqueous electrolyte containing a compound of Formula 1a of the present invention is used, the capacity retention rate after rapid charge and discharge is increased and the resistance increase rate is decreased compared with the secondary batteries of Comparative Examples 2 and 3.

In addition, when the secondary battery of Example 3 containing a non-aqueous electrolyte containing an equal amount of additives is compared with the secondary battery of Comparative Example 4, for the secondary battery of Example 3 of the present invention in which a negative electrode containing a silicon-based negative electrode active material is used, it can be determined that compared with the secondary battery of Comparative Example 4, the capacity retention rate after rapid charge and discharge is increased and the resistance increase rate is reduced.

Claims (14)

1. A lithium secondary battery, comprising:

A positive electrode, a negative electrode, a positive electrode,

A negative electrode comprising a silicon-based negative electrode active material,

A separator disposed between the positive electrode and the negative electrode, and

A nonaqueous electrolytic solution containing a lithium salt, an organic solvent and an additive,

Wherein the additive comprises a compound represented by formula 1:

[ 1]

Wherein, in the formula 1,

R ₁ to R ₃ are each independently hydrogen or alkyl having 1 to 10 carbon atoms.

2. The lithium secondary battery according to claim 1, wherein the silicon-based anode active material is at least one selected from the group consisting of: silicon, silicon chloride, silicon oxide, and silicon carbon composite (SiC), wherein silicon oxide is represented by SiO _x, 0< x <2.

3. The lithium secondary battery according to claim 2, wherein the silicon-based negative electrode active material is silicon monoxide (SiO).

4. The lithium secondary battery according to claim 3, wherein the silicon monoxide (SiO) comprises silicon dioxide (SiO ₂) and amorphous silicon in a weight ratio of 1:1.

5. The lithium secondary battery according to claim 1, wherein the anode further comprises a carbon-based anode active material.

6. The lithium secondary battery according to claim 5, wherein a mixing ratio of the silicon-based negative electrode active material and the carbon-based negative electrode active material is 1:99 to 20:80 in a weight ratio.

7. The lithium secondary battery according to claim 5, wherein a mixing ratio of the silicon-based negative electrode active material and the carbon-based negative electrode active material is 1:99 to 10:90 in a weight ratio.

8. The lithium secondary battery according to claim 1, wherein the positive electrode comprises a positive electrode active material containing lithium and at least one metal selected from the group consisting of nickel (Ni), cobalt (Co), manganese (Mn), and aluminum (Al).

9. The lithium secondary battery according to claim 1, wherein R ₁ to R ₃ are each independently an alkyl group having 1 to 8 carbon atoms.

10. The lithium secondary battery according to claim 1, wherein R ₁ is an alkyl group having 1 to 5 carbon atoms, and

R ₂ and R ₃ are each independently an alkyl group having 2 to 6 carbon atoms.

11. The lithium secondary battery according to claim 1, wherein R ₁ is an alkyl group having 1 to 3 carbon atoms, and

R ₂ and R ₃ are each independently an alkyl group having 2 to 5 carbon atoms.

12. The lithium secondary battery according to claim 1, wherein the compound represented by formula 1 is a compound represented by formula 1 a:

[ 1a ]

13. The lithium secondary battery according to claim 1, wherein the compound represented by formula 1 is present in an amount of 0.1 to 5.0 wt% based on the total weight of the nonaqueous electrolytic solution.

14. The lithium secondary battery according to claim 1, wherein the nonaqueous electrolyte further comprises at least one other additive selected from the group consisting of: cyclic carbonate compounds, halogenated carbonate compounds, sultone compounds, sulfate compounds, phosphate compounds, borate compounds, nitrile compounds, amine compounds, silane compounds, and lithium compounds.