KR20160069996A - Rechargeable lithium battery - Google Patents

Abstract

Provided is a rechargeable lithium battery including a cathode that has a cathode active material which has a silicon-based material or a carbon-based material and an electrolyte, the cathode further having 0.01 part by weight to 1 part by weight of compound expressed by the following Chemical Formula 1 with respect to 100 parts by weight of the cathode active material and one or both of the electrolyte and the cathode having 0.1 wt% to 2 wt% of lithium fluorosulfonate or lithium bis(fluorosulfonyl)imide with respect to the total weight of the electrolyte. [Chemical Formula 1] (In the chemical formula, R is as defined in the specification)

Description

[0002] Lithium secondary batteries {RECHARGEABLE LITHIUM BATTERY}

To a lithium secondary battery.

BACKGROUND ART [0002] Recently, a lithium ion secondary battery having a high voltage and a high capacity has been widely used as a power source for various portable apparatuses. In addition, the use of such lithium ion secondary batteries in large-sized devices such as power tools, electric bicycles, and electric vehicles is becoming stronger. Therefore, in order to ensure a sufficient continuous running time even in such a large-sized apparatus, the lithium rechargeable battery is required to have a higher capacity.

For example, it has been proposed to increase the capacity of a lithium secondary battery by using a material capable of storing and storing more lithium ions such as silicon (Si) and tin (Sn) in the negative electrode active material. However, since such a material has a large volume change accompanying insertion and extraction of lithium ions, cycle characteristics when repeated charging and discharging were not good.

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

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

One embodiment includes a negative electrode comprising a negative electrode active material comprising a silicon-based material and a carbon-based material; Wherein the negative electrode further comprises a compound represented by the following general formula (1) in an amount of 0.01 part by weight to 1 part by weight based on 100 parts by weight of the negative electrode active material, and at least one of the electrolyte solution and the negative electrode is fluorosulfonic acid Lithium or lithium bis (fluorosulfonyl) imide in an amount of 0.1 wt% or more and 2 wt% or less based on the total weight of the electrolytic solution.

[Chemical Formula 1]

(In the formula 1,

R represents 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 alkynylene 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 electrolytic solution may contain a halogen-substituted cyclic carbonate.

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

The details of other embodiments are included in the detailed description below.

A lithium secondary battery having improved cycle life characteristics can be realized.

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

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

It is to be understood that where a layer, film, region, plate, or the like is referred to as being "on" another portion, unless stated otherwise in this specification, .

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

The lithium secondary battery according to an embodiment includes a compound represented by the following formula (1) as a first additive in a negative electrode, and lithium fluorosulfonate (LiSO ₃ F) or lithium bis (fluorosulfonyl) imide (Also referred to as "LiFSI") may be included in the cathode or in the electrolyte.

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

[Chemical Formula 1]

In Formula 1, R represents 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, Lt; RTI ID = 0.0 > C2-C4 < / RTI > alkynylene group.

The lithium secondary battery according to one embodiment can decompose the compound represented by Chemical Formula 1 selectively on the negative electrode by containing the compound represented by Chemical Formula 1, that is, the first chemical additive in the negative electrode, specifically, the negative electrode slurry. Further, the decomposed compound represented by the formula (1) can be mixed with LiSO ₃ F or LiFSI, that is, the second additive contained in the negative electrode or the electrolyte to form a good coat having ion conductivity on the negative electrode. With such a mechanism, the lithium secondary battery according to one embodiment can selectively form a good film having ion conductivity on the cathode. Accordingly, the lithium secondary battery according to one embodiment can improve cycle life characteristics.

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

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

Referring to FIG. 1, the lithium secondary battery 10 may include an anode 20, a cathode 30, and a separator layer 40.

The shape of the lithium secondary battery 10 is not particularly limited, and may be cylindrical, angular, laminate, button, or the like.

The anode 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 conductive material such as aluminum, stainless steel, nickel coated steel, or the like.

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

The positive electrode 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 is a material capable of occluding and releasing lithium ions electrochemically.

As the transition metal oxide containing lithium, LiCoO ₂ , A lithium nickel cobalt manganese composite oxide such as LiNi _x Co _y Mn _z O ₂ , a lithium nickel composite oxide such as LiNiO ₂ , or a lithium manganese composite oxide such as LiMn ₂ O ₄ , . The solid solution oxides include, 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 , and the like Ni _{0 .5} O _4. The cathode active material may be used alone or in combination of two or more thereof.

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

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

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

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

The content of the binder is not particularly limited and may be a content applicable to the positive electrode active material layer of the lithium secondary battery.

The cathode active material layer 22 can be produced, for example, in the following manner. First, a positive electrode slurry is prepared by dispersing a positive electrode active material, a conductive material and a binder in an appropriate organic solvent such as N-methyl-2-pyrrolidone or the like, applying the positive electrode slurry on the current collector 21, And rolled to produce a positive electrode active material layer. The density of the cathode active material layer 22 after the rolling is not particularly limited and may be a density applicable to the cathode active material layer of the lithium secondary battery.

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

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

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

The first additive represented by Formula 1 may be contained in the negative electrode 30 in an amount of 0.01 to 1 part by weight based on 100 parts by weight of the negative active material.

[Chemical Formula 1]

In Formula 1, R represents 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, Lt; RTI ID = 0.0 > C2-C4 < / RTI > 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 specifically a single bond or a substituted or unsubstituted C1 to C4 alkylene group.

More specifically, the compound represented by Formula 1 may be lithium oxalate, lithium succinate, or the like.

The negative electrode active material layer 32 contains a compound represented by the following formula 1 to selectively decompose the compound represented by the formula 1 on the negative electrode 30 and selectively form a coating film on the negative electrode 30 .

The negative electrode active material may be a carbon-based material, a silicon-based material, a tin-based material, a lithium metal oxide, a metal lithium, or the like, or a mixture of two or more thereof. The carbon-based material may be, for example, graphite based materials such as artificial graphite, natural graphite, a mixture of artificial graphite and natural graphite, and natural graphite coated with artificial graphite. The silicon-based material may be, for example, silicon, a silicon oxide, a silicon-containing alloy, or a mixture of these with a graphite-based material. 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 thereof with a graphite-based material, or the like. The lithium metal oxide includes, for example, a titanium oxide-based compound such as Li ₄ Ti ₅ O ₁₂ .

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

The silicon-based material and the negative electrode active material including the carbon-based material can absorb and release more lithium ions to improve the capacity of the battery. However, since the volume change during insertion and extraction of lithium ions is large, . According to one embodiment, the lithium secondary battery 10 contains the compound represented by the formula (1) as the first additive and includes LiSO ₃ F or LiFSI as the second additive, so that the battery capacity can be maintained when the charge and discharge are repeated have. Accordingly, in the lithium secondary battery 10 according to an embodiment, a high battery capacity can be realized by appropriately using the anode active material including the silicon-based material and the carbon-based material.

The binder may be of the same kind as the binder constituting the positive electrode active material layer (22).

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

The cathode 30 may be manufactured as follows. First, a slurry is prepared by dispersing an anode active material, a compound represented by the formula (1), LiSO ₃ F or LiFSI, and a binder in a suitable solvent such as water, applying the slurry on the current collector 31, . 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 43.

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

As the separator 41, a porous film or nonwoven fabric exhibiting excellent high rate discharge performance can be used singly or in combination.

The separator 41 may be coated with an inorganic material such as Al ₂ O ₃ , Mg (OH) ₂ or SiO _2, or may contain the inorganic material as a filler.

Examples of the material constituting the separator 41 include a polyolefin resin, a polyester resin, polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride Vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride- Vinylidene fluoride-ethylene copolymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride- Copolymer, a vinylidene fluoride-ethylene-tetrafluoroethylene copolymer, etc. The can. Examples of the polyolefin-based resin include polyethylene and polypropylene. Examples of the polyester-based resin include polyethylene terephthalate and polybutylene terephthalate.

The porosity of the separator of the conventional lithium secondary battery can be arbitrarily applied without particular limitation.

The electrolyte 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 contained in the electrolyte solution 43 in an amount of 0.1 wt% or more and 2 wt% or less based on the total weight of the electrolytic solution. Further, when not include LiSO ₃ F or LiFSI in the electrolyte (43), LiSO ₃ F or LiFSI the negative electrode active material layer 32, the electrolyte less than of 2 wt% to 0.1 wt% based on the weight of (43) in the &Lt; / RTI &gt; 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 solution 43 and the anode active material layer 32 in an amount of 0.1 wt% to 2 wt% &Lt; / RTI &gt;

The LiSO ₃ F or LiFSI may be incorporated into the coating formed on the cathode 30 by the decomposition product of the compound represented by the formula 1 as the first additive, thereby imparting excellent ion conductivity to the coating. Therefore, the lithium secondary battery 10 according to one embodiment can selectively form a film having excellent ion conductivity on the cathode 30, so that the influence of volume change of the negative electrode active material upon repeated charging and discharging is ensured, . Accordingly, the lithium secondary battery 10 according to one embodiment can improve cycle life characteristics.

The lithium salt may be an electrolyte of the electrolyte 43. The lithium salt is, 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 ), and LiPF ₄ (SO ₂ CF ₃ ) ₂ . One 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, for example, 0.5 to 2.0 mol / L.

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

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 ethyl methyl carbonate; cyclic esters such as? -butyrolactone and? -valerolactone; Chain esters such as methyl formate, methyl acetate and butyric acid methyl; Tetrahydrofuran or a derivative thereof; 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 derivatives thereof; Ethylene sulfide, sulfolane, sultone or a derivative thereof may be used alone or as a mixture of two or more thereof, but is not limited thereto. When a mixture of two or more nonaqueous solvents is used, the mixing ratio of each solvent can be applied at a mixing ratio that can be used in a conventional lithium secondary battery.

Also, in the lithium secondary battery 10 according to one embodiment, the solvent may include a halogen-substituted cyclic carbonate. 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 43 may be added with various other additives such as a negative electrode SEI (solid electrolyte interface) forming agent, a surfactant, and the like.

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

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

Hereinafter, a method for producing 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 mixture obtained by mixing a cathode active material, a conductive material and a binder is dispersed in a solvent, for example, N-methyl-2-pyrrolidone to prepare a slurry. Then, the slurry is coated on the current collector 21 and dried to form the positive electrode active material layer 22. The coating method is not particularly limited, and examples thereof include a knife coater method and a gravure coater method. The following application process can be carried out in the same way. Subsequently, the positive electrode active material layer 22 is compressed to a desired density by a compressor, so that the positive electrode 20 can be manufactured.

The cathode (3) can be manufactured in the same manner as the anode (20). For example, first, a negative electrode active material, a compound represented by the general formula (1) as a first additive, and a binder are mixed in a desired ratio and dispersed in a solvent such as water to prepare a slurry. At this time, the second additive LiSO ₃ F or LiFSI may be added to the slurry. If LiSO ₃ F or LiFSI is not added to the slurry, it may be added to the electrolyte 43. Then, the slurry is coated on the current collector 31 and dried to form a negative electrode active material layer 32. Next, as shown in FIG. Subsequently, the negative electrode 30 is formed by compressing the negative electrode active material layer 32 to a density within the above range by a compressor.

When metal lithium is used as the anode active material layer 32, a metal lithium foil can be overlapped with the current collector 31. [

Subsequently, the separator 41 is sandwiched between the positive electrode 20 and the negative electrode 30 to manufacture an electrode structure. Then, the produced electrode structure is processed into a desired shape, for example, a cylindrical shape, a square shape, a laminate shape, a button shape, or the like, and inserted into the container of the above-described shape. Further, by injecting the desired electrolyte 43 into the vessel, the electrolyte 43 is impregnated into each pore in the separator 41. [ Thus, the lithium secondary battery 10 is manufactured.

Hereinafter, specific embodiments of the present invention will be described. However, the embodiments described below are only intended to illustrate or explain the present invention, and thus the present invention should not be limited thereto. In addition, contents not described here can be inferred sufficiently technically if they are skilled in the art, and a description thereof will be omitted.

Example  One

97.5 wt% of LiCoO ₂ , 1 wt% of polyvinylidene fluoride, and 1.5 wt% of conductive carbon were dispersed in N-methyl-2-pyrrolidone to prepare a slurry. Then, the slurry was cast on an aluminum current collector Followed by coating and drying to form a positive electrode active material layer. Subsequently, the positive electrode active material layer was compressed by a compressor to obtain a positive electrode active material layer having a density of 4.2 g / cm &lt; ^{3 &} gt ;.

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 were dispersed in water to prepare a slurry. At this time, lithium oxalate was added to the slurry in an amount of 0.01 part by weight based on 100 parts by weight of the total amount of the silicon alloy and graphite. Subsequently, the slurry was coated on a copper foil as a current collector and dried to form a negative electrode active material layer. Subsequently, the negative electrode active material layer was compressed by a compressor to obtain a negative electrode active material layer having a density of 1.6 g / cm &lt; ^{3 &} gt ;.

As a separator, a polyethylene film (thickness: 12 mu m) was prepared, and a separator was disposed between the positive electrode and the negative electrode to prepare an electrode structure and housed in a battery container.

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

Subsequently, an electrolyte solution having the above composition was injected into the battery container, and each of the pores in the separator was impregnated with an electrolytic solution to prepare a lithium secondary battery.

Example  2 to 7 and Comparative Example  1 to 5

A lithium secondary battery was produced 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 from lithium succinate in that lithium succinate was added in an amount of 0.1 part by weight based on 100 parts by weight of the total amount of the negative electrode active material, that is, silicon alloy and graphite, in place of lithium oxalate.

Example  8 to 13 and Comparative Example  6 to 9

A lithium secondary battery was fabricated in the same manner as in Example 1 except that LiSO ₃ F was added instead of LiFSI in Example 8.

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

Evaluation 1: Cycle life test

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

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

The following Table 1 shows the results of the evaluation of Examples 1 to 7 and Comparative Examples 1 to 6 in which LiFSI was added as the second additive in the electrolytic solution and Examples 8 to 13 in which LiSO ₃ F was added as the second additive, And the evaluation results of Comparative Examples 6 to 9.

Addition amount (% 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 as the first additives are shown in terms of the weight ratio with respect to the total amount of 100 parts by weight of the negative electrode active material, and the addition amounts of LiFSI and LiSO ₃ F as the second additives are as follows: DMC + EMC + LiPF ₆ ). "-" indicates that no additive is added.

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

Further, referring to Examples 1 to 3 and 7 and Comparative Examples 2 and 3, in Examples 1 to 3 and 7, since the addition amount of the compound represented by Formula 1 as the first additive is within the range according to one embodiment, The retention ratio 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 the formula (1) is out of the range according to one embodiment, the discharge capacity retention rate is not improved and the cycle life characteristics are not good.

Also, referring to Examples 4 to 6 and Comparative Examples 4 and 5, in Examples 4 to 6, since the addition amount of LiFSI as the second additive is within the range according to one embodiment, the discharge capacity retention ratio is improved and cycle life characteristics are improved Able to know. On the other hand, in Comparative Examples 4 and 5, since the addition amount of LiFSI deviates from the range according to one embodiment, the discharge capacity retention rate is not improved and the cycle life characteristics are not good.

Addition amount (% 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 ratios of Examples 8 to 13 are improved compared to Comparative Examples 7 to 10. Therefore, it can be seen that the 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 in the negative electrode and LiSO ₃ F is added as the second additive in the negative electrode.

Further, 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 ratio is improved 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 the formula (1) is out of the range according to one embodiment, the discharge capacity retention ratio is not improved and the cycle life characteristics are not good.

Also, referring to Examples 11 to 13 and Comparative Examples 9 and 10, in Examples 11 to 13, since the addition amount of LiSO ₃ F as the second additive is within the range according to one embodiment, the discharge capacity retention ratio is improved, It can be seen that it is improved. On the other hand, in Comparative Examples 9 and 10, since the added amount of LiSO ₃ F is out of the range according to one embodiment, the discharge capacity retention ratio is not improved and the cycle life characteristics are not good.

From the above evaluation results, according to one embodiment, the compound represented by the general formula (1) is contained as the first additive in an amount of 0.01 to 1 part by weight based on 100 parts by weight of the total amount of the negative electrode active material, and LiFSI Or LiSO ₃ F is contained in at least one of the electrolyte solution and the cathode in an amount of 0.1 wt% to 2 wt% based on the total weight of the electrolytic solution, thereby improving the cycle characteristics of the lithium secondary battery.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, And falls within the scope of the invention.

10 lithium secondary battery
20 anode
21 Home
22 cathode active material layer
30 cathode
31 Home Full
32 Anode active material layer
40 Separator layer
41 Separator
43 electrolyte solution

Claims (4)

A negative electrode comprising a negative electrode active material including a silicon-based material and a carbon-based material; And
Comprising an electrolytic solution,
Wherein the negative electrode further comprises 0.01 to 1 part by weight of a compound represented by the following formula (1) based on 100 parts by weight of the negative electrode active material,
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 wt% or more and 2 wt% or less based on the total weight of the electrolytic solution.
[Chemical Formula 1]

(In the formula 1,
R represents 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 alkynylene group It is a nylene group.) The method of claim 1,
In Formula 1, R is a single bond or a substituted or unsubstituted C1 to C4 alkylene group. The method of claim 1,
Wherein the electrolytic solution comprises a halogen-substituted cyclic carbonate. 4. The method of claim 3,
The halogen-substituted cyclic carbonate includes 4-fluoro-1,3-dioxolan-2-one.

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