KR102525619B1 - Rechargeable lithium battery - Google Patents

Abstract

(상기 화학식 1에서, R은 명세서에 정의된 바와 같다.)A negative electrode including a negative electrode active material including a silicon-based material and a carbon-based material, and an electrolyte solution, wherein the negative electrode includes a compound represented by the following Chemical Formula 1 in an amount of 0.01 part by weight or more and 1 part by weight or less based on 100 parts by weight of the negative electrode active material. A lithium secondary battery further comprising, wherein at least one of the electrolyte and the negative electrode contains lithium fluorosulfonate or lithium bis(fluorosulfonyl)imide in an amount of 0.1% by weight or more and 2% by weight or less based on the total weight of the electrolyte. is provided.
[Formula 1]

(In Formula 1, R is as defined in the specification.)

Description

Lithium secondary battery {RECHARGEABLE LITHIUM BATTERY}

It relates to a lithium secondary battery.

Recently, as a power source for various portable devices, high-voltage and high-capacity lithium ion secondary batteries have been widely adopted. In addition, there is a strong movement to adopt such lithium ion secondary batteries for large-sized devices such as power tools, electric bicycles, and electric vehicles. Therefore, in order to ensure sufficient continuous operating time even in such large-sized devices, lithium secondary batteries are increasingly required to have higher capacity.

For example, it is proposed to increase the capacity of a lithium secondary battery by using a material capable of intercalating and releasing more lithium ions, such as silicon (Si) or tin (Sn), as an anode active material. However, since these materials have a large volume change accompanying lithium ion occlusion and release, cycle characteristics when charging and discharging are repeated are not good.

Therefore, for example, Japanese Patent Laid-Open Nos. 2008-210618 and 2014-32802 disclose techniques for improving cycle characteristics of lithium secondary batteries by adding specific additives to an electrolyte solution. However, there is a problem in that the improvement of cycle characteristics of lithium secondary batteries is insufficient with the additives disclosed in the patent documents.

One embodiment is to provide a lithium secondary battery with improved cycle life characteristics.

One embodiment is a negative electrode including a negative electrode active material including a silicon-based material and a carbon-based material; and an electrolyte, wherein the negative electrode further includes 0.01 part by weight or more and 1 part by weight or less, based on 100 parts by weight of the negative electrode active material, of a compound represented by Formula 1 below, and at least one of the electrolyte and the negative electrode is fluorosulfonic acid A lithium secondary battery comprising lithium or lithium bis(fluorosulfonyl)imide in an amount of 0.1% by weight or more and 2% by weight or less based on the total weight of the electrolyte solution is provided.

[Formula 1]

(In Formula 1 above,

R is a single bond, a substituted or unsubstituted C1 to C4 alkylene group, a substituted or unsubstituted C1 to C4 haloalkylene group, a substituted or unsubstituted C2 to C4 alkenylene group, or a substituted or unsubstituted C2 to C4 alkyne group. It is a Nylene group.)

In Formula 1, R may be a single bond or a substituted or unsubstituted C1 to C4 alkylene group.

The electrolyte solution may include a halogen-substituted cyclic carbonate.

The halogen-substituted cyclic carbonate may include 4-fluoro-1,3-dioxolan-2-one.

Details of other implementations are included in the detailed description below.

A lithium secondary battery with improved cycle life characteristics may be implemented.

1 is a schematic diagram showing the configuration of a lithium secondary battery according to an embodiment.

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, and the present invention is not limited thereby, and the present invention is only defined by the scope of the claims to be described later.

Unless otherwise specified herein, when a part such as a layer, film, region, plate, etc. is said to be “on” another part, this is not only the case where it is “directly on” the other part, but also the case where there is another part in the middle. include

Hereinafter, a lithium secondary battery according to an embodiment will be schematically described.

A lithium secondary battery according to an embodiment includes a compound represented by Formula 1 as a first additive in a negative electrode, and also includes lithium fluorosulfonate (LiSO ₃ F) or lithium bis(fluorosulfonyl) as a second additive. LiFSI (also called "LiFSI") can be included in the cathode or in the electrolyte.

The content of the compound represented by Formula 1 as the first additive may be 0.01 part by weight or more and 1 part by weight or less based on 100 parts by weight of the negative electrode active material in the negative electrode, and the content of the second additive LiSO ₃ F or LiFSI may be in the negative electrode. 0.1% by weight or more and 2% by weight or less based on the total weight of the electrolyte in or in the electrolyte.

[Formula 1]

In Formula 1, R is a single bond, a substituted or unsubstituted C1 to C4 alkylene group, a substituted or unsubstituted C1 to C4 haloalkylene group, a substituted or unsubstituted C2 to C4 alkenylene group, or a substituted or unsubstituted C1 to C4 alkenylene group. may be a C2 to C4 alkynylene group.

The lithium secondary battery according to an embodiment may selectively decompose the compound represented by Formula 1 on the negative electrode by including the compound represented by Chemical Formula 1, that is, the first additive, in the negative electrode, specifically, the negative electrode slurry. In addition, the decomposed compound represented by Formula 1 may be mixed with LiSO ₃ F or LiFSI, ie, the second additive, contained in the negative electrode or the electrolyte to form a good film having ion conductivity on the negative electrode. By this mechanism, a lithium secondary battery according to an embodiment may selectively form a good film having ion conductivity on the negative electrode. Accordingly, the lithium secondary battery according to an embodiment may improve cycle life characteristics.

Hereinafter, each configuration of a lithium secondary battery according to an embodiment will be described in detail with reference to FIG. 1 .

1 is a schematic diagram showing the configuration of a lithium secondary battery according to an embodiment.

Referring to FIG. 1 , the rechargeable lithium battery 10 may include a positive electrode 20 , a negative electrode 30 and a separator layer 40 .

The shape of the lithium secondary battery 10 is not particularly limited, that is, it may be cylindrical, prismatic, laminated, or button-shaped.

The cathode 20 may include a current collector 21 and a cathode active material layer 22 formed on the current collector.

The current collector 21 may be any conductor, and may be made of, for example, aluminum, stainless steel, nickel coated steel, or the like.

The cathode active material layer 22 may include a cathode active material, and may further include a conductive material and a binder. Contents of the positive electrode active material, the conductive material, and the binder are not particularly limited.

The cathode active material is, for example, a transition metal oxide or a solid solution oxide containing lithium, but is not particularly limited as long as it can electrochemically occlude and release lithium ions.

As the transition metal oxide containing lithium, LiCoO ₂ lithium cobalt-based composite oxides such as LiNi _x Coy _{Mn z} O ₂ , lithium nickel-cobalt-manganese composite oxides such as LiNiO ₂ , or lithium manganese-based composite oxides such as LiMn ₂ O ₄ , etc. can be heard The solid solution oxide is, for example, Li _a Mn _x Co _y Ni _z O ₂ (1.150≤a≤1.430, 0.45≤x≤0.6, 0.10≤y≤0.15, 0.20≤z≤0.28), LiMn _x Co _y Ni _z O ₂ (0.3≤x≤0.85, 0.10≤y≤0.3, 0.10≤z≤0.3), _{LiMn 1.5} Ni _0.5 O ₄ and _the like. The positive electrode active material may be used alone or in combination of two or more.

The content of the cathode active material is not particularly limited, and may be an amount applicable to a cathode active material layer of a lithium secondary battery.

The conductive material is, for example, carbon black such as Ketjen black and acetylene black, fibrous carbon such as natural graphite, artificial graphite, carbon nanotube, graphene, and carbon nanofiber, and these fibrous A composite of carbon and carbon black may be used, but it is not particularly limited as long as it is for increasing the conductivity of the anode.

The content of the conductive material is not particularly limited, and may be a content applicable to the cathode active material layer of a lithium secondary battery.

The binder is, for example, polyvinylidene fluoride, ethylene-propylene-diene terpolymer, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, fluoro rubber (fluoroelastomer), polyvinyl acetate, polymethyl methacrylate, polyethylene, nitrocellulose, etc. may be mentioned, but the positive electrode active material and the conductive material are placed on the current collector 21 It is not particularly limited as long as it can be bound and at the same time has oxidation resistance and electrolyte stability that can withstand a high potential of the anode.

The content of the binder is not particularly limited, and may be an amount applicable to the cathode active material layer of a lithium secondary battery.

The positive electrode active material layer 22 can be manufactured, for example, by the following method. First, a positive electrode active material, a conductive material, and a binder are dispersed in an appropriate organic solvent such as N-methyl-2-pyrrolidone to prepare a positive electrode slurry, and the positive electrode slurry is applied on a current collector 21 and dried And rolling may be performed to prepare a positive electrode active material layer. The density of the positive electrode active material layer 22 after the rolling is not particularly limited, and may be a density applicable to the positive electrode active material layer of a lithium secondary battery.

The negative electrode 30 may include a current collector 31 and an anode active material layer 32 formed on the current collector 31 .

The current collector 31 may be any conductive material, and may be, for example, copper (Cu), a copper alloy, aluminum, stainless steel, or nickel-plated steel.

The negative active material layer 32 may include at least a negative active material and a compound represented by Formula 1 as a first additive, and may further include a binder and LiSO ₃ F or LiFSI as a second additive.

The compound represented by Chemical Formula 1 as the first additive may be included in the negative electrode 30 in an amount of 0.01 part by weight or more and 1 part by weight or less based on 100 parts by weight of the negative electrode active material.

[Formula 1]

In Formula 1, R is a single bond, a substituted or unsubstituted C1 to C4 alkylene group, a substituted or unsubstituted C1 to C4 haloalkylene group, a substituted or unsubstituted C2 to C4 alkenylene group, or a substituted or unsubstituted C1 to C4 alkenylene group. may be a C2 to C4 alkynylene group. Here, the haloalkylene group represents a substituent in which at least one of the hydrogen atoms of the alkylene group is substituted with a halogen atom.

In Formula 1, R may be a single bond or a substituted or unsubstituted C1 to C4 alkylene group.

More specifically, examples of the compound represented by Chemical Formula 1 include lithium oxalate, lithium succinate, and the like.

The negative electrode active material layer 32 includes a compound represented by Formula 1 below, so that the compound represented by Formula 1 is selectively decomposed on the negative electrode 30, and a film formed by the decomposition product is selectively formed on the negative electrode 30. can

The negative electrode active material may be used alone or in combination of two or more of a carbon-based material, a silicon-based material, a tin-based material, a lithium metal oxide, and metal lithium. The carbon-based material may be, for example, a graphite-based material such as artificial graphite, natural graphite, a mixture of artificial graphite and natural graphite, or natural graphite coated with artificial graphite. The silicon-based material may be, for example, silicon, silicon oxide, a silicon-containing alloy, a mixture of these and a graphite-based material, or the like. The silicon oxide may be represented by SiOx (0<x≤2). The tin-based material may be, for example, tin, tin oxide, a tin-containing alloy, a mixture of these and a graphite-based material, or the like. Examples of the lithium metal oxide include titanium oxide-based compounds such as Li ₄ Ti ₅ O ₁₂ .

Specifically, the negative active material according to one embodiment may include the silicon-based material and the carbon-based material.

The negative electrode active material including the silicon-based material and the carbon-based material can occlude and release more lithium ions, thereby improving battery capacity. can According to one embodiment, the lithium secondary battery 10 includes the compound represented by Formula 1 as a first additive and LiSO ₃ F or LiFSI as a second additive, thereby maintaining battery capacity when charging and discharging are repeated. there is. For this reason, in the lithium secondary battery 10 according to an embodiment, a high battery capacity can be implemented by appropriately using an anode active material including a silicon-based material and a carbon-based material.

The binder may be the same type as the binder constituting the positive electrode active material layer 22 .

The content of the binder is not particularly limited, and may be any content as long as it is applied to the negative electrode active material layer of a lithium secondary battery.

The cathode 30 may be manufactured as follows. First, a slurry is prepared by dispersing a negative electrode active material, a compound represented by Formula 1, optionally LiSO ₃ F or LiFSI, and a binder in an appropriate solvent such as water, and applying the slurry on a current collector 31, followed by drying and rolling can be formed by The density of the negative electrode active material layer 32 after rolling is not particularly limited.

The separator layer 40 includes a separator 41 and an electrolyte solution 43 .

The separator 41 is not particularly limited, and any one may be used as long as it is used as a separator for a lithium secondary battery.

As the separator 41, a porous film or non-woven fabric exhibiting excellent high-rate discharge performance may be used alone or in combination.

Also, the separator 41 may be coated with an inorganic material such as Al ₂ O ₃ , Mg(OH) ₂ , or SiO ₂ , and may include the inorganic material as a filler.

Materials constituting the separator 41 include, for example, polyolefin-based resin, polyester-based resin, polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer, and vinylidene fluoride. -Perfluorovinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-fluoroethylene copolymer, vinylidene fluoride-hexa Fluoroacetone copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymers, vinylidene fluoride-ethylene-tetrafluoroethylene copolymers, and the like. Examples of the polyolefin-based resin include polyethylene and polypropylene, and examples of the polyester-based resin include polyethylene terephthalate and polybutylene terephthalate.

The porosity of the separator is not particularly limited, and a porosity of a separator of a conventional lithium secondary battery may be arbitrarily applied.

The electrolyte solution 43 may include a lithium salt and a solvent, and may further include LiSO ₃ F or LiFSI as a second additive.

The LiSO ₃ F or LiFSI may be included in the electrolyte 43 in an amount of 0.1% by weight or more and 2% by weight or less based on the total weight of the electrolyte. In addition, when LiSO ₃ F or LiFSI is not included in the electrolyte 43, LiSO ₃ F or LiFSI is present in the negative electrode active material layer 32 in an amount of 0.1% by weight or more and 2% by weight or less based on the total weight of the electrolyte 43. can be included as In other words, in the lithium secondary battery 10 according to one embodiment, LiSO ₃ F or LiFSI is added to at least one of the electrolyte 43 and the negative electrode active material layer 32 in an amount of 0.1% by weight or more and 2% by weight based on the total weight of the electrolyte. may be included below.

The LiSO ₃ F or LiFSI may be incorporated into the film formed on the negative electrode 30 by the decomposition product of the compound represented by Formula 1, which is the first additive, to impart excellent ion conductivity to the film. Therefore, since the lithium secondary battery 10 according to an embodiment can selectively form a film having excellent ion conductivity on the negative electrode 30, the effect of volume change of the negative electrode active material during repeated charging and discharging while securing ion conductivity is reduced. can be suppressed Accordingly, the lithium secondary battery 10 according to an embodiment may improve cycle life characteristics.

The lithium salt may be an electrolyte of the electrolyte solution 43 . The lithium salt may be, for example, LiPF ₆ , LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ , LiSO ₃ CF ₃ , LiN(SO ₂ CF ₃ ), LiN(SO ₂ CF ₂ CF ₃ ), LiC(SO ₂ CF ₂ CF ₃ ) ₃ , LiC(SO ₂ CF ₃ ) ₃ , LiI, LiCl, LiF, LiPF ₅ (SO ₂ CF ₃ ), LiPF ₄ (SO ₂ CF ₃ ) ₂ and the like. One or two or more of these lithium salts may be dissolved.

The concentration of the lithium salt is not particularly limited, and may be used in a concentration of 0.5 to 2.0 mol/L, for example.

The solvent may be a non-aqueous solvent that dissolves the lithium salt and each of the additives.

Examples of the solvent include cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate, and vinylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethylmethyl carbonate; cyclic esters such as γ-butyrolactone and γ-valerolactone; chain esters such as methyl formate, methyl acetate, and methyl butyric acid; tetrahydrofuran or its derivatives; ethers such as 1,3-dioxane, 1,4-dioxane, 1,2-dimethoxyethane, 1,4-dibutoxyethane, and methyl diglyme; nitriles such as acetonitrile and benzonitrile; dioxolane or a derivative thereof; Ethylene sulfide, sulfolane, sultone or a derivative thereof may be used alone or in a mixture of two or more, but is not limited thereto. When two or more non-aqueous solvents are mixed and used, the mixing ratio of each solvent can be applied as a mixing ratio usable in a conventional lithium secondary battery.

In addition, in the lithium secondary battery 10 according to an embodiment, a halogen-substituted cyclic carbonate may be included as the solvent. The halogen-substituted cyclic carbonate may specifically include 4-fluoro-1,3-dioxolan-2-one.

In addition to the second additive, LiSO ₃ F or LiFSI, the electrolyte solution 43 may contain other additives such as a solid electrolyte interface (SEI) forming agent and a surfactant.

Examples of such additives are succinic anhydride, lithium bis(oxalate)borate, lithium tetrafluoroborate, dinitrile compounds, propane sultone , butane sultone, propene sultone, 3-sulfone, fluorinated arylether, fluorinated methacrylate, and the like.

The content of the additive can be used as the content of the additive in a general lithium secondary battery.

Hereinafter, a method for manufacturing a lithium secondary battery will be described. However, the manufacturing method of the lithium secondary battery is not limited to the following method, and any manufacturing method can be applied.

The anode 20 can be manufactured as follows. First, a slurry is prepared by dispersing a mixture of a cathode active material, a conductive material, and a binder in a solvent, for example, N-methyl-2-pyrrolidone. Then, the slurry is applied on the current collector 21 and dried to form the positive electrode active material layer 22 . At this time, the method of application is not particularly limited, and examples thereof include a knife coater method and a gravure coater method. The application process below can be performed in the same way. Subsequently, the cathode 20 may be manufactured by compressing the cathode active material layer 22 to a desired density by using a compressor.

The negative electrode 3 may be manufactured in the same way as the positive electrode 20 . For example, first, a slurry is prepared by dispersing a mixture of a negative electrode active material, a compound represented by Formula 1 as a first additive, and a binder in a desired ratio in a solvent such as water. At this time, a second additive, LiSO ₃ F or LiFSI, may be added to the slurry. LiSO ₃ F or LiFSI may be added into the electrolyte solution 43 if not added into the slurry. Next, the slurry is applied on the current collector 31 and dried to form the negative electrode active material layer 32 . Subsequently, the negative electrode 30 may be formed by compressing the negative electrode active material layer 32 to have a density within the above range by using a compressor.

In addition, when metal lithium is used as the negative electrode active material layer 32 , a metal lithium foil may be overlapped on the current collector 31 .

Then, by inserting the separator 41 between the positive electrode 20 and the negative electrode 30, an electrode structure is manufactured. Then, the fabricated electrode structure is processed into a desired shape, for example, a cylindrical shape, a prismatic shape, a laminated shape, a button shape, etc., and inserted into a container of the above shape. Further, by injecting a desired electrolyte solution 43 into the container, the pores in the separator 41 are impregnated with the electrolyte solution 43 . Thus, the lithium secondary battery 10 is manufactured.

Hereinafter, specific embodiments of the present invention are presented. However, the embodiments described below are only intended to specifically illustrate or explain the present invention, and the present invention should not be limited thereto. In addition, since the content not described herein can be sufficiently technically inferred by those skilled in the art, the description thereof will be omitted.

Example One

97.5% by weight of LiCoO ₂ , 1% by weight of polyvinylidene fluoride, and 1.5% by weight of conductive carbon were dispersed in N-methyl-2-pyrrolidone to prepare a slurry, and then the slurry was coated on an aluminum current collector foil. By coating and drying, a positive electrode active material layer was formed. Then, by compressing the positive electrode active material layer with a compressor, the density of the positive electrode active material layer was set to 4.2 g/cm ³ , thereby manufacturing a positive electrode.

A slurry was prepared by dispersing 20% by weight of a silicon alloy (containing 70% by atom of silicon), 75% by weight of graphite, and 5% by weight of lithium polyacrylate in water. At this time, 0.01 part by weight of lithium oxalate was added to the slurry based on 100 parts by weight of the total amount of the silicon alloy and graphite. Subsequently, the slurry was applied onto a copper foil as a current collector and dried to form a negative electrode active material layer. Then, by compressing the negative electrode active material layer with a compressor, the density of the negative electrode active material layer was set to 1.6 g/cm ³ , thereby manufacturing a negative electrode.

A porous polyethylene film (thickness of 12 μm) was prepared as a separator, and an electrode structure was prepared by placing the separator between the positive electrode and the negative electrode, and then stored in a battery container.

Lithium hexafluorophosphate (LiPF ₆ ) was added to a solvent in which ethylene carbonate (EC), diethyl carbonate (DEC) and ethylmethyl carbonate (EMC) were mixed in a volume ratio of 30:20:50 at a concentration of 1.0 mol/L. Dissolved to prepare an electrolyte solution. LiFSI as a second additive to the prepared electrolyte was added in an amount of 1% by weight based on the total weight of the electrolyte (EC+DMC+EMC+LiPF ₆ ).

Next, a lithium secondary battery was produced by injecting an electrolyte having the above composition into the battery container and impregnating each pore in the separator with the electrolyte.

Example 2 to 7 and comparative example 1 to 5

A lithium secondary battery was manufactured in the same manner as in Example 1, except that the content of the additive in Example 1 was changed as shown in Table 1 below. Example 7 is different only in that 0.1 part by weight of lithium succinate was added instead of lithium oxalate based on 100 parts by weight of the total amount of the negative electrode active material, that is, the silicon alloy and graphite.

Example 8 to 13 and comparative example 6 to 9

In Example 8, a lithium secondary battery was manufactured in the same manner as in Example 1, except that LiSO ₃ F was added instead of LiFSI.

In Examples 9 to 13 and Comparative Examples 6 to 9, lithium secondary batteries were manufactured in the same manner as in Example 8, except that the additive content was changed as shown in Table 2 below.

Evaluation 1: Cycle life test

The discharge capacity retention rates of the lithium secondary batteries according to Examples 1 to 13 and Comparative Examples 1 to 10 were evaluated.

Specifically, charging and discharging were performed twice at a temperature of 25° C. at a current density of 0.4 mA/cm ² and a cell voltage of 4.4 V to 3.0 V. Thereafter, charging and discharging was repeated at a temperature of 25° C., at a current density of 4.0 mA/cm ² , and at a cell voltage of 4.4 V to 3.0 V. Here, the discharge capacity retention rate was calculated by dividing the discharge capacity after 100 charge/discharge cycles by the discharge capacity at the first charge/discharge cycle. The results are shown in Table 1 and Table 2 below.

Table 1 below shows the evaluation results of Examples 1 to 7 and Comparative Examples 1 to 6 in which LiFSI was added as a second additive to the electrolyte solution, and Table 2 below shows Examples 8 to 13 in which LiSO ₃ F was added as a second additive and These are the evaluation results of Comparative Examples 6 to 9.

Amount added (% by weight) Discharge capacity retention rate (%) lithium oxalate lithium succinate LiFSI Example 1 0.01 - One 74 Example 2 0.1 - 78 Example 3 One - 76 Example 4 0.5 - 0.1 77 Example 5 - One 79 Example 6 - 2 78 Example 7 - 0.1 One 74 Comparative Example 1 - - - 62 Comparative Example 2 0.001 - One 65 Comparative Example 3 2 - 60 Comparative Example 4 0.5 - 0.05 64 Comparative Example 5 - 3 63 Comparative Example 6 One - - 64

In Table 1, the addition amounts of lithium oxalate and lithium succinate, which are the first additives, are expressed as a weight ratio with respect to 100 parts by weight of the total amount of the negative electrode active material, and the addition amounts of the second additives, LiFSI and LiSO ₃ F, are the total weight of the electrolyte (EC+ DMC+EMC+LiPF ₆ ) was expressed as a weight ratio. Also, "-" indicates that no additives are added.

Referring to Table 1, it can be seen that the discharge capacity retention rate of Examples 1 to 7 is improved compared to Comparative Examples 1 to 6. Accordingly, it can be seen that cycle life characteristics are improved in the lithium secondary batteries according to Examples 1 to 7 in which the compound represented by Chemical Formula 1 is added to the negative electrode as the first additive and LiFSI is added to the electrolyte as the second additive.

In addition, referring to Examples 1 to 3 and 7 and Comparative Examples 2 and 3, Examples 1 to 3 and 7 have a discharge capacity because the addition amount of the compound represented by Formula 1 as the first additive is within the range according to one embodiment. It can be seen that the maintenance rate is improved and the cycle life characteristics are improved. On the other hand, in Comparative Examples 2 and 3, since the addition amount of the compound represented by Formula 1 was out of the range according to the embodiment, the discharge capacity retention rate was not improved, and thus the cycle life characteristics were not good.

In addition, referring to Examples 4 to 6 and Comparative Examples 4 and 5, Examples 4 to 6 show that the discharge capacity retention rate is improved and cycle life characteristics are improved because the addition amount of the second additive, LiFSI, is within the range according to one embodiment. Able to know. On the other hand, in Comparative Examples 4 and 5, since the amount of LiFSI added is out of the range according to the embodiment, the discharge capacity retention rate is not improved, so it can be seen that the cycle life characteristics are not good.

Amount added (% by weight) Discharge capacity retention rate (%) lithium oxalate LiSO ₃ F Example 8 0.01 One 74 Example 9 0.1 78 Example 10 One 76 Example 11 0.5 0.1 77 Example 12 One 79 Example 13 2 78 Comparative Example 7 0.001 One 65 Comparative Example 8 2 60 Comparative Example 9 0.5 0.05 64 Comparative Example 10 3 63

Referring to Table 2, it can be seen that the discharge capacity retention rate of Examples 8 to 13 is improved compared to Comparative Examples 7 to 10. Accordingly, it can be seen that cycle life characteristics are improved in the lithium secondary batteries according to Examples 8 to 13 in which the compound represented by Formula 1 is added as the first additive to the negative electrode and LiSO ₃ F is added to the negative electrode as the second additive.

In addition, referring to Examples 8 to 10 and Comparative Examples 7 and 8, in Examples 8 to 10, since the addition amount of the compound represented by Formula 1 as the first additive is within the range according to one embodiment, the discharge capacity retention rate is improved. It can be seen that the cycle life characteristics are improved. On the other hand, in Comparative Examples 7 and 8, since the addition amount of the compound represented by Formula 1 was out of the range according to the embodiment, the discharge capacity retention rate was not improved, and thus the cycle life characteristics were not good.

In addition, referring to Examples 11 to 13 and Comparative Examples 9 and 10, Examples 11 to 13 are within the range according to one embodiment of the second additive, LiSO ₃ F, so that the discharge capacity retention rate is improved and the cycle life characteristics are improved. improvement can be seen. On the other hand, in Comparative Examples 9 and 10, since the addition amount of LiSO ₃ F was out of the range according to one embodiment, the discharge capacity retention rate was not improved, and thus the cycle life characteristics were not good.

From the above evaluation results, according to one embodiment, the compound represented by Formula 1 as the first additive is included in an amount of 0.01 part by weight or more and 1 part by weight or less based on 100 parts by weight of the total amount of the negative electrode active material in the negative electrode, and LiFSI as the second additive. Alternatively, it can be seen that the cycle characteristics of the lithium secondary battery are improved by including LiSO ₃ F in at least one of the electrolyte and the negative electrode in an amount of 0.1% by weight or more and 2% by weight or less based on the total weight of the electrolyte.

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 of those skilled in the art using the basic concept of the present invention defined in the following claims are also present. It falls within the scope of the right of invention.

10 Lithium secondary battery
20 anode
21 whole house
22 cathode active material layer
30 cathode
31 whole house
32 negative electrode active material layer
40 separator layer
41 separator
43 Electrolyte

Claims (4)

a negative electrode including a negative electrode active material including a silicon-based material and a carbon-based material; and
contains an electrolyte,
The negative electrode further comprises 0.01 parts by weight or more and 1 part by weight or less based on 100 parts by weight of the negative electrode active material of the compound represented by Formula 1 below,
At least one of the electrolyte solution and the negative electrode includes lithium fluorosulfonate or lithium bis(fluorosulfonyl)imide in an amount of 0.1% by weight or more and 2% by weight or less based on the total weight of the electrolyte solution.
[Formula 1]

(In Formula 1,
R is a single bond or a substituted or unsubstituted C1 to C4 alkylene group.) delete In paragraph 1,
The electrolyte solution is a lithium secondary battery comprising a halogen-substituted cyclic carbonate. In paragraph 3,
The halogen-substituted cyclic carbonate is a lithium secondary battery comprising 4-fluoro-1,3-dioxolan-2-one.

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