KR20160009952A - Electrolyte solution for lithium secondary battery and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to an electrolyte for a lithium secondary battery and a lithium secondary battery comprising the same and, more specifically, to an electrolyte for a lithium secondary battery having excellent cycle properties by having high capacity maintaining rate and having improved preservative properties at high temperature by having high recovery capacity by comprising a pyrazol compound including a halogen atom and a sulfonyl group, a lithium salt, and an organic solvent, and to a lithium secondary battery comprising the same.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an electrolyte for a lithium secondary battery, and a lithium secondary battery having the same.

The present invention relates to an electrolyte for a lithium secondary battery and a lithium secondary battery having the same. More particularly, the present invention relates to an electrolyte for a lithium secondary battery improved in cycle characteristics and storage characteristics at high temperatures, and a lithium secondary battery having the same.

Recently, interest in energy storage technology is increasing. As the application fields of cell phones, camcorders, notebook PCs, and electric vehicles further expand, there is a growing demand for higher energy density of batteries used as power sources for such electronic devices. Lithium secondary batteries are the ones that can best meet these demands, and researches on them are actively under way.

Among the currently applied secondary batteries, the lithium secondary battery developed in the early 1990s is composed of a negative electrode made of a carbon material capable of absorbing and desorbing lithium ions, a positive electrode made of lithium-containing oxide, and a non-aqueous solution It is composed of electrolytic solution.

The average discharge voltage of the lithium secondary battery is about 3.6 to 3.7 V, which is one of merits that the discharge voltage is higher than other alkaline batteries and nickel-cadmium batteries. In order to achieve such a high driving voltage, an electrochemically stable electrolyte composition is required at a charge / discharge voltage range of 0 to 4.2V. For this purpose, a mixed solvent in which a cyclic carbonate compound such as ethylene carbonate or propylene carbonate and a linear carbonate compound such as dimethyl carbonate, ethylmethyl carbonate or diethyl carbonate are appropriately mixed is used as a solvent for the electrolyte solution. LiPF ₆ , LiBF ₄ , and LiClO ₄ are generally used as a lithium salt as a solute of an electrolytic solution, and these act as a source of lithium ions in the battery to enable operation of the lithium battery.

During the initial charging of the lithium secondary battery, lithium ions from the cathode active material such as lithium metal oxide migrate to the anode active material such as graphite and are inserted between the layers of the anode active material. At this time, since lithium is highly reactive, the electrolyte composing the anode active material reacts with carbon on the surface of the anode active material such as graphite to generate compounds such as Li ₂ CO ₃ , Li ₂ O, and LiOH. These compounds form a SEI (Solid Electrolyte Interface) film on the surface of the anode active material such as graphite.

The SEI film acts as an ion tunnel, allowing only lithium ions to pass through. The SEI film is an effect of such an ion tunnel and prevents an organic solvent molecule moving together with lithium ions in the electrolyte from being interposed between the layers of the anode active material and destroying the cathode structure. Therefore, the electrolytic solution is not decomposed by preventing the contact between the electrolytic solution and the negative electrode active material, and the amount of lithium ions in the electrolytic solution is reversibly maintained, so that stable charge / discharge is maintained.

On the other hand, the produced SEI film is not stably present until the battery life is over, and may be destroyed by repeated shrinkage and expansion of the electrode according to the progress of the cycle, and may be easily dissolvable due to external heat shock It is also destroyed. The passivation film thus destroyed is restored during the subsequent charge and discharge processes. In addition, the charge and discharge capacities of the battery are reduced and the efficiency is lowered due to the irreversible charge and the decomposition of the electrolyte.

In order to solve such problems, studies have been made to change the composition of the solvent component of the carbonate organic solvent or to change the shape of the SEI film formation reaction by mixing specific additives. However, as is well known, when the solvent component is changed or the specific compound is added to the electrolyte to improve battery performance, the performance of some items is improved, but the performance of other items is often decreased.

Korean Unexamined Patent Publication No. 2004-0023870 discloses a lithium secondary battery using a non-aqueous electrolyte, Korean Patent Publication No. 2007-7014671 discloses a lithium secondary battery comprising an additive containing 1,3-propanesultone and ethanesulfonylbenzene Discloses an electrolyte for a secondary battery, but fails to provide an alternative to the above problems.

Korean Patent Publication No. 2004-0023870 Korea Patent Publication No. 2007-7014671

An object of the present invention is to provide an electrolyte solution for a lithium secondary battery in which the capacity retention rate is high and the cycle characteristics of the lithium secondary battery are improved.

An object of the present invention is to provide an electrolyte solution for a lithium secondary battery which has a large recovery capacity and can improve storage characteristics at high temperatures.

It is another object of the present invention to provide a lithium secondary battery comprising the above-described electrolyte solution for a lithium secondary battery.

1. An electrolyte solution for a lithium secondary battery comprising a pyrazole compound containing a halogen atom and a sulfonyl group, a lithium salt and an organic solvent.

2. The electrolytic solution for a lithium secondary battery according to 1 above, wherein the pyrazole compound having a halogen atom and a sulfonyl group is represented by the following formula (1)

[Chemical Formula 1]

(Wherein R ₁ , R ₂ , R ₃ and R ₄ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 12 carbon atoms, at least one of which is a halogen atom;

The alkyl group having 1 to 10 carbon atoms or the aryl group having 6 to 12 carbon atoms may be substituted with a halogen atom, an alkyl group having 1 to 10 carbon atoms substituted with a halogen atom, or an aryl group having 6 to 12 carbon atoms substituted with a halogen atom.

3. A compound according to item 1, wherein the pyrazole compound having a halogen atom and a sulfonyl group is 1-difluoromethyl-3-methyl-1H-pyrazole-4-sulfonyl chloride, 1-difluoromethyl- Methyl-3-trifluoromethyl-1H-pyrazole-4-sulfonyl chloride and 4-bromo-1- [4-bromo 3- (trifluoromethyl) phenyl] sulfonyl-pyrazole.

4. The electrolytic solution for a lithium secondary battery according to 1 above, wherein the halogen atom is a fluorine atom.

5. The electrolytic solution for a lithium secondary battery according to 1 above, wherein the pyrazole compound containing a halogen atom and a sulfonyl group is present in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the organic solvent.

6. A lithium secondary battery comprising an electrolyte solution according to any one of 1 to 5 above.

The electrolyte solution for a lithium secondary battery of the present invention has a high capacity retention rate and can improve the cycle characteristics of the lithium secondary battery.

In addition, the electrolyte solution for a lithium secondary battery of the present invention has a large recovery capacity and can improve the storage characteristics at high temperatures.

Disclosed is an electrolyte solution for a lithium secondary battery, which comprises a pyrazole compound containing a halogen atom and a sulfonyl group, a lithium salt, and an organic solvent and having excellent capacity retention and excellent cycle characteristics, And a lithium secondary battery having the same.

Hereinafter, the present invention will be described in detail.

The electrolyte solution for a lithium secondary battery of the present invention includes a pyrazole compound containing a halogen atom and a sulfonyl group, a lithium salt and an organic solvent.

The present invention can improve the cycle characteristics of a lithium secondary battery by increasing the capacity retention rate as the pyrazole compound includes a halogen atom and a sulfonyl group and can improve the recovery capacity at a high temperature, have.

The pyrazole compound containing a halogen atom and a sulfonyl group according to the present invention can be represented by the formula (1).

[Chemical Formula 1]

Wherein R ₁ , R ₂ , R ₃ and R ₄ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 12 carbon atoms, at least one of which is a halogen atom, An alkyl group having 6 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms may be substituted with a halogen atom, an alkyl group having 1 to 10 carbon atoms substituted with a halogen atom, or an aryl group having 6 to 12 carbon atoms substituted with a halogen atom.

The pyrazole compound containing a halogen atom and a sulfonyl group is not particularly limited as long as it is a compound having a halogen atom and a sulfonyl group bonded to the pyrazole compound. Specific examples of the pyrazole compound containing a halogen atom and a sulfonyl group include 1-difluoromethyl-3-methyl-1H-pyrazole-4-sulfonyl chloride, 1-difluoromethyl- Dimethyl-1H-pyrazole-4-sulfonyl chloride, 1-methyl-3-trifluoromethyl-1H-pyrazole- (Trifluoromethyl) phenyl] sulfonyl-pyrazole, and the like, but not limited thereto, and they may be used singly or in combination of two or more.

The halogen atom in the present invention may preferably be a fluorine atom.

The pyrazole compound having a halogen atom and a sulfonyl group according to the present invention may be contained in an amount of 0.1 to 5 parts by weight, preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the organic solvent. When the content is 0.1 to 5 parts by weight, the capacity retention rate of the electrolyte for a lithium secondary battery is high, thereby improving the cycle characteristics of the lithium secondary battery, and the recovery capacity is high, and the storage characteristics at a high temperature are excellent.

The lithium salt can be expressed as Li ⁺ X ^- as an electrolyte salt. In this lithium salt anion is not particularly ^{limited, F -, Cl -, Br} -, I -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) _{^{2 PF 4 -, (CF 3}} ) 3 PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO _{^{3 -, (CF 3 SO 2}} ) 2 N -, (FSO 2) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C - _{, (CF 3 SO 2) 3} C -, CF 3 (CF 2) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN ^- , (CF ₃ CF ₂ SO ₂ ) ₂ N ^- , SbF ₆ ^- , AsF ₆ ^- and the like.

The concentration of the lithium salt may be 0.6 to 2.0M, preferably 0.8 to 1.6M. If the concentration is less than 0.6M, the conductivity of the electrolyte may be lowered and the electrolyte performance may be deteriorated. If the concentration is more than 2.0M, the viscosity of the electrolyte may increase and the mobility of the lithium ion may decrease.

The organic solvent is not particularly limited as long as it is an organic solvent ordinarily used in an electrolyte of a lithium secondary battery. For example, a cyclic carbonate, a linear carbonate, or a mixture thereof can be used.

Examples of the cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), fluoroethylene carbonate (FEC), gamma butyrolactone (GBL) The halogen derivatives may be used alone or in combination of two or more, but the present invention is not limited thereto.

Examples of linear carbonates include diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC) But the present invention is not limited thereto.

In the present invention, ethylene carbonate and propylene carbonate, which are cyclic carbonates in the carbonate-based organic solvent, are high-viscosity organic solvents having a high dielectric constant and can dissociate the lithium salt in the electrolyte. Therefore, dimethyl carbonate and When a low viscosity, low dielectric constant linear carbonate such as diethyl carbonate is mixed in an appropriate ratio, an electrolytic solution having a high electric conductivity can be prepared, which is more preferably used.

When cyclic carbonate and linear carbonate are mixed and used, they are preferably mixed in a volume ratio of 1: 1-9, more preferably mixed in a volume ratio of 1: 1.5-4. When mixing in the volume ratio, the performance of the electrolyte may be more preferable.

In addition to the above-described carbonate-based solvents, solvents known in the art may be used without limitation, for example, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane and the like, but are not limited thereto.

The electrolyte for a lithium secondary battery of the present invention described above is injected into an electrode structure composed of a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode to manufacture a lithium secondary battery. The positive electrode, the negative electrode and the separator constituting the electrode structure may be any of those conventionally used in the production of lithium secondary batteries.

The positive electrode and the negative electrode are manufactured by applying the slurry of the positive electrode active material and the slurry of the negative electrode active material to each electrode current collector.

As the cathode active material, a cathode active material capable of inserting and desorbing lithium ions known in the art can be used without any particular limitation. For example, at least one kind selected from cobalt, manganese, and nickel, and at least one type of lithium complex oxide And as a representative example thereof, the lithium-containing compound described below can be preferably used.

Li _x Mn _{1 - y} M _y A ₂ (1)

Li _x Mn _{1 - y} M _y O _{2 - z} X _z (2)

Li _x Mn ₂ O _{4 - z} X _z (3)

Li _x Mn _{2 - y} M _y M ' _z A ₄ (4)

Li _x Co _{1 - y} M _y A ₂ (5)

Li _x Co _{1 - y} M _y O _{2 - z} X _z (6)

Li _x Ni _{1 - y} M _y A ₂ (7)

Li _x Ni _{1 - y} M _y O _{2 - z} X _z (8)

Li _x Ni _{1 - y} Co _y O _{2 - z} X _z (9)

Li _x Ni _{1- y- z} Co _y M _z A _? (10)

Li _x Ni _{1 - y - z} Co _y M _z O _{2 - ?} X _? (11)

Li _x Ni _{1- y- z} Mn _y M _z A _? (12)

Li _x Ni _{1 - y - z} Mn _y M _z O _{2 - ?} X _? (13)

In the formula, 0.9? X? 1.1, 0? Y? 0.5, 0? Z? 0.5, 0?? 2, M and M 'are the same or different, and Mg, Al, Co, K, Wherein A is selected from the group consisting of Si, Ti, Sn, V, Ge, Ga, B, As, Zr, Mn, Cr, Fe, Sr, V and rare earth elements. And X is selected from the group consisting of F, S and P. In addition to the lithium-containing compounds described above, LiCoPO ₄ and LiFePO _{4 may} also be used. In addition to the oxides, sulfides, selenides and halides may also be used.

As the negative electrode active material, a negative electrode active material capable of inserting and desorbing lithium ions known in the art can be used without any particular limitation. Examples of such negative electrode active material include crystalline carbon, low crystalline carbon, amorphous carbon, carbon composite, A material, a lithium metal, a lithium alloy, or the like can be used, and a carbon material is more preferable. Specific examples of the amorphous carbon include hard carbon, coke, mesocarbon microbead (MCMB) fired at 1500 ° C or lower, mesophase pitch-based carbon fiber (MPCF) Graphite materials, specifically natural graphite, artificial graphite, graphitized coke, graphitized MCMB, graphitized MPCF, and the like.

 Preferably, the carbonaceous material has a crystallite size (Lc) of at least 20 nm by d002 interplanar distance of 3.35-3.38 Å by X-ray diffraction. As the lithium alloy, an alloy of lithium and aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium or indium may be used.

The positive electrode active material and the negative electrode active material may be mixed with a binder and a solvent to prepare a slurry of the positive electrode active material and a negative electrode active material, respectively.

Examples of the binder include a paste acting as an active material, mutual adhesion of an active material, adhesion to a collector, buffering effect on expansion and contraction of an active material, and the like. Examples of the binder include polyvinylidene fluoride, polyhexafluoropropylene Polyvinylidene fluoride copolymer (P (VdF / HFP)), poly (vinyl acetate), polyvinyl alcohol, polyethylene oxide, polyvinylpyrrolidone, alkylated polyethylene oxide, polyvinyl ether, poly Methacrylate), poly (ethyl acrylate), polytetrafluoroethylene, polyvinyl chloride, polyacrylonitrile, polyvinylpyridine, styrene-butadiene rubber, and acrylonitrile-butadiene rubber. The content of the binder is 0.1 to 30% by weight, preferably 1 to 10% by weight, based on the electrode active material. If the content of the binder is too small, the adhesive force between the electrode active material and the current collector is insufficient. If the content of the binder is too large, the adhesive force is improved but the content of the electrode active material is reduced accordingly.

As the solvent of the active material slurry, a non-aqueous solvent or an aqueous solvent may be usually used. Examples of the non-aqueous solvent include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N, N-dimethylaminopropylamine, ethylene oxide and tetrahydrofuran And water, isopropyl alcohol, and the like may be used as the aqueous solvent, but the present invention is not limited thereto.

The electrode active material slurry may further include a conductive material, a thickener, and the like, if necessary.

The conductive material may be at least one material selected from the group consisting of a graphite conductive material, a carbon black conductive material, and a metal or metal compound conductive material, which improves the electronic conductivity. Examples of the black electroconductive material include artificial graphite and natural graphite. Examples of the carbon black conductive material include acetylene black, ketjen black, denka black, thermal black, channel black ( channel black). Examples of metal or metal compound conductive materials include perovskite materials such as tin, tin oxide, tin phosphate (SnPO ₄ ), titanium oxide, potassium titanate, LaSrCoO ₃ , and LaSrMnO ₃ have. However, the present invention is not limited to the above-mentioned conductive materials.

The content of the conductive material is preferably 0.1 to 10% by weight with respect to the electrode active material. If the content of the conductive material is less than 0.1% by weight, the electrochemical characteristics may be deteriorated, and if it exceeds 10% by weight, the energy density per weight may be decreased.

The thickening agent is not particularly limited as long as it can control the viscosity of the active material slurry. For example, carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose and the like can be used.

The anode and anode active material slurries thus prepared are applied to the electrode current collector and made of a positive electrode and a negative electrode. Aluminum or an aluminum alloy may be used as the positive electrode collector, and copper or a copper alloy may be used as the negative electrode collector. . The anode current collector and the anode current collector may be in the form of foil, film, sheet, punched, porous, foam or the like.

The prepared positive electrode and negative electrode are made of an electrode structure with a separator interposed therebetween, and then housed in a battery case, and an electrolytic solution is injected into the battery case to manufacture a lithium secondary battery. As the separator, a conventional porous polymer film conventionally used as a separator, such as a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer Or a nonwoven fabric made of conventional porous nonwoven fabric such as high melting point glass fiber or polyethylene terephthalate fiber can be used, but the present invention is not limited thereto .

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

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to be illustrative of the invention and are not intended to limit the scope of the claims. It will be apparent to those skilled in the art that such variations and modifications are within the scope of the appended claims.

Example  One

Ethylene carbonate (EC), propylene carbonate (PC) and ethyl methyl carbonate (EMC) were mixed at a weight ratio of 3: 2: 5 to prepare a solvent mixture. 0.5 part by weight of vinylene carbonate was added based on 100 parts by weight of the mixture. Then, 0.5 part by weight of 1-difluoromethyl-3-methyl-1H-pyrazole-4-sulfonyl chloride was further added based on 100 parts by weight of the prepared mixed solution, and 1 M LiPF ₆ was added and dissolved to prepare a non- Respectively.

Example  2

Except that 1-difluoromethyl-3, 5-dimethyl-1H-pyrazole-4-sulfonyl chloride was used instead of 1-difluoromethyl-3-methyl- A non-aqueous electrolyte was prepared in the same manner as in Example 1.

Example  3

Except that 1-methyl-3- (trifluoromethyl) -1H-pyrazole-4-sulfonyl chloride was used in place of 1-difluoromethyl-3-methyl-1H-pyrazole-4-sulfonyl chloride A nonaqueous electrolytic solution was prepared in the same manner as in Example 1.

Example  4

A nonaqueous electrolytic solution was prepared in the same manner as in Example 1 except that fluoroethylene carbonate (FEC), ethylene carbonate (EC) and ethylmethyl carbonate (EMC) were mixed at a weight ratio of 2: 3: Respectively.

Example  5

Except that 1-difluoromethyl-3, 5-dimethyl-1H-pyrazole-4-sulfonyl chloride was used instead of 1-difluoromethyl-3-methyl-1H-pyrazole-4-sulfonyl chloride A nonaqueous electrolytic solution was prepared in the same manner as in Example 4.

Example  6

Except that 1-methyl-3- (trifluoromethyl) -1H-pyrazole-4-sulfonyl chloride was used in place of 1-difluoromethyl-3-methyl-1H-pyrazole-4-sulfonyl chloride A nonaqueous electrolytic solution was prepared in the same manner as in Example 4.

Example  7

Except that 5-chloro-1,3-dimethyl-1H-pyrazole-4-sulfonyl chloride was used instead of 1-difluoromethyl-3-methyl-1H-pyrazole-4-sulfonyl chloride A nonaqueous electrolytic solution was prepared in the same manner as in Example 4.

Comparative Example  One

A nonaqueous electrolytic solution was prepared in the same manner as in Example 1, except that 1-difluoromethyl-3-methyl-1H-pyrazole-4-sulfonyl chloride was not used.

Comparative Example  2

A nonaqueous electrolytic solution was prepared in the same manner as in Example 1 except that pyrazole was used instead of 1-difluoromethyl-3-methyl-1H-pyrazole-4-sulfonyl chloride.

Comparative Example  3

A nonaqueous electrolytic solution was prepared in the same manner as in Example 1 except that 4-fluoro-1H-pyrazole was used instead of 1-difluoromethyl-3-methyl-1H-pyrazole-4-sulfonyl chloride .

Comparative Example  4

A nonaqueous electrolytic solution was prepared in the same manner as in Example 1, except that ethylsulfonylbenzene was used instead of 1-difluoromethyl-3-methyl-1H-pyrazole-4-sulfonyl chloride.

Manufacturing example  - Manufacture of batteries

LiCoO ₂ as a positive electrode active material, polyvinylidene fluoride (PVdF) as a binder and carbon as a conductive material were mixed at a weight ratio of 92: 4: 4 and then dispersed in N-methyl-2-pyrrolidone to prepare a positive electrode active material slurry . This slurry was coated on an aluminum foil having a thickness of 20 mu m, followed by drying and rolling to prepare a positive electrode. Styrene-butadiene rubber as a binder and carboxymethylcellulose as a thickener were mixed in a weight ratio of 96: 2: 2 and then dispersed in water to prepare a negative electrode active material slurry. This slurry was coated on a copper foil having a thickness of 15 mu m, followed by drying and rolling to prepare a negative electrode. A film separator made of polyethylene (PE) having a thickness of 20 탆 was inserted between the electrodes thus prepared, wound and compressed, and inserted into a cylindrical can. An electrolyte solution of the example or comparative example prepared in the cylindrical can was injected to prepare a lithium secondary battery.

Experimental Example

(1) Evaluation of cycle characteristics (capacity retention rate)

The produced lithium secondary battery was charged at a constant current of 1.0 C at 4.2 V until the charging current reached 1/10 C, and discharged at 3.0 C at a constant current of 1.0 C for 5 cycles. The discharging capacity after the 5th cycle and the discharging capacity after the 100th cycle were measured, and the discharge capacity ratio was used as the capacity retention rate.

Capacity retention rate (%) = (100 cycle discharge capacity (mAh) / 5 cycle discharge capacity) * 100

(2) Evaluation of storage characteristics (recovery capacity) at high temperature

The battery was charged at a constant current of 1.0 C until the charge current reached 1/10 C at 4.2 V and discharged to 3.0 V at a constant current of 1.0 C to measure the discharge capacity. Thereafter, after being charged under the same charge / discharge condition, the battery was stored in a thermostatic chamber at 80 캜 for one day, discharged at a discharge voltage of 3 V at 25 캜, and then the remaining capacity was measured. Thereafter, the recovery capacity was measured once after the same charge / discharge condition. The recovery capacity was calculated by setting the discharge capacity before storage in a thermostatic chamber at 80 ° C to 100.

Capacity retention rate (%) Recovery capacity (%) Example 1 91 90 Example 2 92 91 Example 3 92 91 Example 4 90 93 Example 5 91 89 Example 6 90 90 Example 7 89 87 Comparative Example 1 83 82 Comparative Example 2 86 85 Comparative Example 3 87 85 Comparative Example 4 84 81

Referring to Table 1, it can be seen that the cyclic characteristics and the storage characteristics at high temperatures are improved as compared with the conventional electrolytes for lithium secondary batteries because the embodiments have higher capacity retention and recovery capacity than the comparative examples.

Claims (6)

An electrolyte solution for a lithium secondary battery comprising a pyrazole compound containing a halogen atom and a sulfonyl group, a lithium salt and an organic solvent.
The pyrazole compound according to claim 1, wherein the pyrazole compound having a halogen atom and a sulfonyl group is represented by the following Formula 1:
[Chemical Formula 1]

(Wherein R ₁ , R ₂ , R ₃ and R ₄ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 12 carbon atoms, at least one of which is a halogen atom;
The alkyl group having 1 to 10 carbon atoms or the aryl group having 6 to 12 carbon atoms may be substituted with a halogen atom, an alkyl group having 1 to 10 carbon atoms substituted with a halogen atom, or an aryl group having 6 to 12 carbon atoms substituted with a halogen atom.
[2] The method according to claim 1, wherein the pyrazole compound containing a halogen atom and a sulfonyl group is 1-difluoromethyl-3-methyl-1H-pyrazole-4-sulfonyl chloride, 1-difluoromethyl- -Methyl-3-trifluoromethyl-lH-pyrazole-4-sulfonyl chloride and 4-bromo-l- [4-bromo-3 - (trifluoromethyl) phenyl] sulfonyl-pyrazole, wherein the electrolyte is at least one selected from the group consisting of:
The electrolyte solution for a lithium secondary battery according to claim 1, wherein the halogen atom is a fluorine atom.
The electrolytic solution for a lithium secondary battery according to claim 1, wherein the pyrazole compound containing a halogen atom and a sulfonyl group is 0.1 to 5 parts by weight based on 100 parts by weight of the organic solvent.
A lithium secondary battery comprising the electrolyte solution according to any one of claims 1 to 5.