KR101340027B1 - Non-aqueous electrolyte and a rechargeable batter including the same - Google Patents

Abstract

The present invention relates to a lithium secondary battery electrolyte and a lithium secondary battery comprising the same, the present invention relates to a non-aqueous electrolyte for lithium secondary battery using a carbamate of formula (1) in which one of the oxygen atoms of the carbamate is substituted with N as an organic solvent And it relates to a lithium secondary battery comprising the same, provides a secondary battery with improved life characteristics, stability compared to the conventional DMC.

Secondary Battery, Dimethyl Carbamate, Oxazolidinone

Description

Non-aqueous electrolyte and a lithium secondary battery comprising the same {Non-aqueous electrolyte and a rechargeable batter including the same}

1 is a cross-sectional view of a rectangular lithium secondary battery shown as an embodiment of the present invention.

2 is a graph showing that overcharge safety of a lithium secondary battery manufactured using an electrolyte prepared according to Examples and Comparative Examples of the present invention is improved.

3A and 3B are graphs showing room temperature cycle life characteristics of a square lithium secondary battery manufactured using an electrolyte prepared according to Examples and Comparative Examples of the present invention.

The present invention relates to a lithium secondary battery electrolyte and a lithium secondary battery comprising the same, and more particularly, to improve the structural stability of the non-aqueous organic solvent to improve the stability and life characteristics of the battery, lithium secondary battery electrolyte and the same It relates to a secondary battery.

With the recent rapid development of the electronics, telecommunications, and computer industries, the use of portable electronic products such as camcorders, mobile phones, notebook PCs, etc., as well as the compactness, light weight, and high functionality of the devices are becoming common. The demand for this is increasing. In particular, the rechargeable lithium secondary battery has a high energy density per unit weight of about 3 times higher than conventional lead acid batteries, nickel-cadmium batteries, nickel-hydrogen batteries, and nickel-zinc batteries, and can be rapidly charged. Development is underway.

However, since the battery uses an organic solvent as an electrolyte, there are still many problems to be solved in the safety of the battery. The safety of the battery is the most important part in a lithium ion battery using a nonaqueous electrolyte as an electrolyte, and in particular, prevention of short circuit and overcharge is one of the most important factors.

In particular, the conventionally used DMC (dimethyl carbonate) electrolyte has been used to improve the performance at low temperatures, but has a low b.p. has a disadvantage in terms of high rate overcharge test or life characteristics due to rapid decomposition during battery performance evaluation.

Recently, various organic additives have been developed to prevent overcharging. In one method, a compound for forming a so-called Solid Electrolyte Interface (SEI) on a negative electrode, for example, as a means for inhibiting the reductive decomposition of lithium on a negative electrode in order to suppress the reductive decomposition of a solvent on a negative electrode, for example, VC (vinylene carbonate) is disclosed in VC (vinylene carbonate) in Japanese Patent Laid-Open No. 2001-6729, Japanese Patent Application Laid-open No. Hei 8-45545, and the like.

However, in the case of using such a film forming additive, since the conductivity of lithium ions is low and a high resistance SEI is formed on the negative electrode, when the discharge characteristic of the battery is remarkably lowered or is excessively added in the electrolyte, an excessive amount of the additive is added. There was a problem in that the battery was oxidized and decomposed at the anode at high temperature to generate gas, and the expansion of the battery was markedly due to the increase in the internal pressure.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an electrolyte solution for a lithium secondary battery having excellent lifespan characteristics while ensuring overcharge safety.

Another object of the present invention is to provide a lithium secondary battery comprising the electrolyte solution.

In order to achieve the above object,

Lithium salts; And

Including a compound of formula (1) as a non-aqueous organic solvent, the compound of formula (1) is characterized in that the non-aqueous electrolyte solution for a lithium secondary battery comprises 50% to 100% by weight relative to the total weight of the non-aqueous organic solvent:

Formula 1

　　　

Where R ¹ And R ² independently represents a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, 2-10 alkenyl group, 2-10 alkynyl group, 3-10 cyclic group, 3-10 unsaturated cyclic group , An aromatic group, and R ¹ and R ² may be connected to each other to form a ring.

The compound of Formula 1 is preferably dimethyl carbamate or oxazolidinon.

The non-aqueous organic solvent is at least one of linear carbamate consisting of dimethyl carbamate, diethyl carbamate, dipropyl carbamate, methyl propyl carbamate, ethyl propyl carbamate and ethyl methyl carbamate and ethylene carbamate, propylene carbamate And cyclic carbamates composed of butylene carbamates.

In addition, the nonaqueous electrolyte according to the present invention may be used by further adding an electrolyte additive which is usually used for secondary batteries. Such additives include aromatic compounds having a methoxy group and a halogen group, biphenyls, thiophenes, aromatic ether compounds and the like.

To the lithium salt is _{LiPF 6, LiBF 4, LiSbF 6} , LiAsF 6, LiClO 4, LiCF 3 SO 3, LiN (SO 2 CF 3) 2, LiN (SO 2 C 2 F 5) 2, LiC (SO 2 CF ₃ ) ₃ , LiN (SO ₃ CF ₃ ) ₂ , LiC ₄ F ₉ SO ₃ , LiAlO ₄ , LiAlCl ₄ , LiCl and LiI may be mixed and used. The concentration of the lithium salt is preferably in the range of 0.6 to 2.0M, more preferably in the range of 0.7 to 1.6M.

The present invention also provides an electrolyte prepared according to one embodiment of the present invention; A positive electrode including a positive electrode active material capable of inserting and detaching lithium ions; And it provides a lithium secondary battery comprising a negative electrode comprising a negative electrode active material capable of inserting and detaching lithium ions.

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

The present invention is excellent in overcharge stability and life characteristics, it is possible to provide a secondary battery of high efficiency by increasing the Li ion mobility.

The present invention is a lithium salt; And a nonaqueous electrolyte solution for a lithium secondary battery comprising the compound of formula 1 as a nonaqueous organic solvent:

Formula 1

　　　

　　　

Wherein R ¹ and R ² are independently substituted or unsubstituted alkyl of 1 to 10 carbon atoms, alkenyl of 2-10, alkynyl of 2-10, cyclic group of 3-10, unsaturated of 3-10 It is a cyclic group, an aromatic group, and R ¹ and R ² may be connected to each other to form a cyclic carbamate.

Conventionally, when the EC-based non-aqueous electrolyte is used, the DMC electrolyte has a low melting point and a solid at room temperature, so it is mixed and used to improve the performance at low temperature. There was this. Therefore, most of the structure of the electrolyte solution currently used has a carbonate structure, but this structure has a disadvantage that the decomposition can easily occur, but the structure is stable in the case of the carbamate structure in which one oxygen atom in the carbonate structure is replaced with N As a result, even in the continuous charging and discharging process, the mobility of Li ions can be increased or maintained at a low temperature by maintaining the skeleton structure without being easily decomposed as compared with the electrolyte of the carbonate skeleton structure.

Also referring to Formulas 2 and 3

(2)

(3)

Since oxygen has two unshared electrons and nitrogen has one unshared electrons, the electrolyte of the carbonate skeleton having two oxygens has a symmetrical structure, whereas carbamate has one oxygen atom and two unshared electron pairs with two unshared electron pairs. It has an asymmetrical structure by nitrogen atom. Therefore, the unshared electron pair in nitrogen is located in a specific direction to the outside, and as a result, the unshared electron pair of the oxygen atom in the C═O double bond and the unshared electron pair of nitrogen share Li advantageously. That is, Li ions may be located at a specific position and in the form of Formula 3 rather than the form of Formula 2, compared to the symmetric DMC structure due to the nature of the nitrogen atom.

In addition, when looking at the mobility of Li ions, conventionally, Li ions are not located at a specific position, but Li ions are randomly moved. Randomly moving lithium ions are not only time-consuming when passing through a separator. The extent of receiving partial Li ions in the cathode is different. This may result in the formation of dentite in which Li ions are deposited on the surface of the cathode during overcharging. However, using a non-aqueous organic solvent in which Li ions can be positioned at a specific position, as in the present invention, maintains this tendency even during charging and discharging, so that the speed of passage through the separator can be constant, thereby concentrating current on the surface of the separator. This can reduce the likelihood of dendrites.

The nonaqueous organic solvents according to the invention also include, for example, compounds of formula 4:

Formula 4

Where R ₂ =-(CH ₂ ) nC ₆ H ₆ (n = 0-10), or R ₂ =-(CH ₂ ) nC ₆ H ₁₂ (n = 0-10),

R ₁ =-(CH ₂ ) nCH ₃ (n = 0-10).

As shown here, substituted R ₁ and R ₂ are nonpolar and the oxazolidinone moiety plays a polar role such that the cyclic moiety at the end of the alkyl functional group, the nonpolar moiety, forms a stacking with the negative electrode. Can serve to protect the Since this is done without decomposition of the electrolyte, it is advantageous compared to forming a coating (SEI) by the decomposition of the electrolyte by adding a stabilizing additive such as VC before.

Other non-aqueous organic solvents in the present invention are preferably dimethyl carbamate or oxazolidinone.

The non-aqueous organic solvent is at least one of linear carbamate consisting of dimethyl carbamate, diethyl carbamate, dipropyl carbamate, methyl propyl carbamate, ethyl propyl carbamate and ethyl methyl carbamate and ethylene carbamate, propylene carbamate And cyclic carbamates composed of butylene carbamates. At this time, the mixing ratio is preferably 1: 1 to 3: 1.

In addition, the nonaqueous electrolyte according to the present invention may be used by further adding an electrolyte additive which is usually used for secondary batteries. Such additives include aromatic compounds having a methoxy group and a halogen group, biphenyls, thiophenes, aromatic ether compounds and the like. The additive is preferably added at 1 to 1000 ppm with respect to the non-aqueous organic solvent.

The electrolyte solution of the present invention contains a lithium salt. The lithium salt acts as a supply source of lithium ions in the battery to enable operation of a basic lithium battery, and the non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

To the lithium salt is _{LiPF 6, LiBF 4, LiSbF 6} , LiAsF 6, LiClO 4, LiCF 3 SO 3, LiN (SO 2 CF 3) 2, LiN (SO 2 C 2 F 5) 2, LiC (SO 2 CF ₃ ) ₃ , LiN (SO ₃ CF ₃ ) ₂ , LiC ₄ F ₉ SO ₃ , LiAlO ₄ , LiAlCl ₄ , LiCl and LiI may be mixed and used. The concentration of the lithium salt is preferably in the range of 0.6 to 2.0M, more preferably in the range of 0.7 to 1.6M. If the concentration of the lithium salt is less than 0.6M, the conductivity of the electrolyte decreases and the performance of the electrolyte deteriorates. If the concentration exceeds 2.0M, the viscosity of the electrolyte increases and the mobility of the lithium ion decreases.

The lithium salt acts as a supply source of lithium ions in the battery to enable operation of a basic lithium battery, and the non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

The non-aqueous organic solvent may include a carbamate according to the present invention alone, or a mixture of esters, ethers, or ketones. Organic solvents should be used to have high dielectric constant (polarity) and low viscosity to increase ion dissociation and smooth ion conduction. Generally, solvents having high dielectric constant, high viscosity and low dielectric constant and low viscosity are used. It is preferable to use two or more mixed solvents configured.

In the case of the carbamate solvent, it is preferable to use a cyclic carbamate and a chain carbamate. In this case, the cyclic carbamate and the chain carbamate are preferably used by mixing in a volume ratio of 1: 1 to 1: 9, and more preferably used by mixing in a volume ratio of 1: 1 to 1: 3. The performance of the electrolyte is preferable when mixed in the above volume ratio.

Examples of the cyclic carbamate include ethylene carbamate, propylene carbamate, 1,2-butylene carbamate, 2,3-butylene carbamate, 1,2-pentylene carbamate, 2,3-pentylene carbamate, and the like. This can be used. Ethylene carbamate and propylene carbamate having a high dielectric constant are preferred, and ethylene carbamate is preferred when artificial graphite is used as the negative electrode active material. As the chain carbamate, dimethyl carbamate, diethyl carbamate, dipropyl carbamate, methylpropyl carbamate, ethylmethyl carbamate, ethylpropyl carbamate, and the like may be used, and among these, dimethyl carbamate having a low viscosity Preference is given to ethylmethyl carbamate and diethyl carbamate.

The ester is methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone, ε-caprolactone, and the like. There may be used as the ether, tetrahydrofuran, 2-methyltetrahydrofuran, dibutyl ether and the like. As the ketone, polymethylvinyl ketone may be used.

The electrolyte solution of the present invention may further include an aromatic hydrocarbon organic solvent in the carbamate solvent. As the aromatic hydrocarbon organic solvent, an aromatic hydrocarbon compound of Formula 5 may be used.

Formula 5

In the above formula, R is halogen or an alkyl group having 1 to 10 carbon atoms and q is an integer of 0 to 6.

Specific examples of the aromatic hydrocarbon-based organic solvent may be used such as benzene, fluorobenzene, bromobenzene, chlorobenzene, toluene, xylene, mesitylene, etc., these may be used alone or in combination. The volume ratio of the carbamate solvent / aromatic hydrocarbon-based organic solvent in the electrolyte solution containing the aromatic hydrocarbon-based organic solvent is preferably 1: 1 to 30: 1. The performance of the electrolyte solution may be desirable to be mixed in the volume ratio.

The lithium secondary battery including the electrolyte solution of the present invention includes a positive electrode and a negative electrode.

The positive electrode includes a positive electrode active material capable of inserting and detaching lithium ions, and the positive electrode active material is preferably at least one selected from cobalt, manganese, nickel, and at least one of a composite oxide with lithium. As examples, the lithium-containing compound described below can be preferably used.

Li_xMn_{One - y}M_yA₂ (One)

Li_xMn_{One - y}Myo_{2 - z}X_z (2)

Li_xMn₂O_{4 - z}X_z (3)

Li_xMn_{2 - y}M_yM '_zA₄ (4)

Li_xCo_{One - y}M_yA₂ (5)

Li_xCo_{One - y}M_yO_{2 - z}X_z (6)

Li_xNi_{One - y}M_yA₂ (7)

Li_xNi_{One - y}M_yO_{2 - z}X_z (8)

Li_xNi_{One - y}Co_yO_{2 - z}X_z (9)

Li_xNi_{One -y- z}Co_yM_zA_α (10)

Li_xNi_{One -y- z}Co_yM_zO_{2 -α}X_α (11)

Li_xNi_{One -y- z}Mn_yM_zA_α (12)

Li_xNi_{One -y- z}Mn_yM_zO_{2 -α}X_α (13)

(Wherein 0.9≤x≤1.1, 0≤y≤0.5, 0≤z≤0.5, 0≤α≤2, M and M 'are the same or different, Mg, Al, Co, K, Na, Ca, Si, Ti, Sn, V, Ge, Ga, B, As, Zr, Mn, Cr, Fe, Sr, V and rare earth elements, A is selected from the group consisting of O, F, S and P And X is selected from the group consisting of F, S and P.)

The negative electrode includes a negative electrode active material capable of inserting and detaching lithium ions, and the negative electrode active material may be a carbon material such as crystalline carbon, amorphous carbon, carbon composite, carbon fiber, lithium metal, lithium alloy, or the like. Examples of the amorphous carbon include hard carbon, coke, mesocarbon microbead (MCMB) calcined at 1500 ° C. or lower, and mesophase pitch-based carbon fiber (MPCF). The crystalline carbon is a graphite-based material, specifically natural graphite, graphitized coke, graphitized MCMB, and graphitized MPCF. The carbonaceous material is preferably a material having an d002 interplanar distance of 3.35 to 3.38 Å and an Lc (crystallite size) of at least 20 nm by X-ray diffraction. As the lithium alloy, an alloy of lithium with aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium or indium may be used.

The positive electrode or the negative electrode may be prepared by dispersing an electrode active material, a binder and a conductive material, if necessary, a thickener in a solvent to prepare an electrode slurry composition, and applying the slurry composition to an electrode current collector. Aluminum or an aluminum alloy may be used as the positive electrode current collector, and copper or a copper alloy may be used as the negative electrode current 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 binder is a material that serves to paste the active material, the mutual adhesion of the active material, the adhesion with the current collector, the buffering effect on the expansion and contraction of the active material, and the like, for example, polyvinylidene fluoride, polyhexafluoropropylene- Copolymer of polyvinylidene fluoride (PVdF / HFP)), poly (vinylacetate), polyvinyl alcohol, polyethylene oxide, polyvinylpyrrolidone, alkylated polyethylene oxide, polyvinyl ether, poly (methyl methacrylate) ), Poly (ethyl acrylate), polytetrafluoroethylene, polyvinylchloride, polyacrylonitrile, polyvinylpyridine, styrene-butadiene rubber, acrylonitrile-butadiene rubber and the like. The content of the binder is 0.1 to 30% by weight, preferably 1 to 10% by weight based on the electrode active material. When the content of the binder is too small, the adhesion between the electrode active material and the current collector is insufficient, and when the content of the binder is too high, the adhesion is improved, but the content of the electrode active material decreases by that amount, which is disadvantageous in increasing battery capacity.

The conductive material may be at least one selected from the group consisting of a graphite-based conductive agent, a carbon black-based conductive agent, a metal or a metal compound-based conductive agent as a material for improving electronic conductivity. Examples of the graphite conductive agent include artificial graphite and natural graphite, and examples of the carbon black conductive agent include acetylene black, ketjen black, denka black, thermal black, and channel. Channel black and the like, and examples of the metal or metal compound conductive agent include perovskite such as tin, tin oxide, tin phosphate (SnPO ₄ ), titanium oxide, potassium titanate, LaSrCoO ₃ , and LaSrMnO _3. ) There is a substance. However, it is not limited to the conductive agents listed above. The content of the conductive agent is preferably 0.1 to 10% by weight based on the electrode active material. When the content of the conductive agent is less than 0.1% by weight, the electrochemical properties are lowered, and when the content of the conductive agent is greater than 10% by weight, the energy density per weight decreases.

The thickener is not particularly limited as long as it can play a role of controlling the viscosity of the active material slurry, and for example, carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose and the like can be used.

As the solvent in which the electrode active material, the binder, the conductive material and the like are dispersed, a non-aqueous solvent or an aqueous solvent is used. Examples of the non-aqueous solvent include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N, N-dimethylaminopropylamine, ethylene oxide and tetrahydrofuran.

The lithium secondary battery may include a separator that prevents a short circuit between the positive electrode and the negative electrode and provides a passage for lithium ions, and such separators include polypropylene, polyethylene, polyethylene / polypropylene, polyethylene / polypropylene / polyethylene, poly Polyolefin polymer membranes, such as propylene / polyethylene / polypropylene, or a multilayer of these, a microporous film, a woven fabric, and a nonwoven fabric can be used. Further, a film coated with a resin having excellent stability may be used for the porous polyolefin film.

1 is a cross-sectional view of a rectangular lithium secondary battery shown as one embodiment of the present invention.

Referring to FIG. 1, in a lithium secondary battery, an electrode assembly 12 including an anode 13, a cathode 15, and a separator 14 is accommodated in a can 10 together with an electrolyte solution. It is formed by sealing the upper end with the cap assembly 20. The cap assembly 20 includes a cap plate 40, an insulating plate 50, a terminal plate 60, and an electrode terminal 30. The cap assembly 20 is combined with the insulating case 70 to seal the can 10.

The electrode terminal 30 is inserted into the terminal through-hole 41 formed in the center of the cap plate 40. When the electrode terminal 30 is inserted into the terminal through-hole 41, the tubular gasket 46 is coupled to the outer surface of the electrode terminal 30 and inserted together to insulate the electrode terminal 30 and the cap plate 40. . After the cap assembly 20 is assembled to the upper end of the can 10, the electrolyte is injected through the electrolyte injection hole 42, and the electrolyte injection hole 42 is closed by a stopper 43. The electrode terminal 30 is connected to the negative electrode tab 17 of the negative electrode 15 or the positive electrode tab 16 of the positive electrode 13 to act as a negative electrode terminal or a positive electrode terminal.

The lithium secondary battery of the present invention is not limited to the above-described shape, and any shape such as a cylindrical shape, a pouch, etc., including the positive electrode active material of the present invention and capable of operating as a battery, is possible.

Hereinafter, preferred embodiments and comparative examples of the present invention will be described. However, the following examples are only a preferred embodiment of the present invention, and the present invention is not limited to the following examples.

Example 1

LiCoO ₂ as a positive electrode active material, polyvinylidene fluoride (PVDF) as a binder and carbon as a conductive agent were mixed in a weight ratio of 92: 4: 4, and then dispersed in N-methyl-2-pyrrolidone to prepare a positive electrode slurry. It was. 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. Synthetic graphite as a negative electrode active material, styrene-butadiene rubber as a binder, and carboxymethyl cellulose 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 a polyethylene (PE) material having a thickness of 20 μm was put between the prepared electrodes and then wound and compressed, and inserted into a rectangular can. An electrolyte solution was injected into the rectangular can to prepare a lithium secondary battery. The electrolyte solution was prepared by dissolving LiPF6 to 1.15M in a dimethylcarbamate solvent.

Example 2

Except for using oxazolidinone as the non-aqueous organic solvent in the electrolyte solution was carried out in the same manner as in Example 1.

Example 3

Except for using an ethylene carbamate / ethyl methyl carbamate / diethyl carbamate mixed solvent (3: 6: 1 volume ratio) as the non-aqueous organic solvent in the electrolyte solution was carried out in the same manner as in Example 1.

Example 4

Except for using an ethylene carbamate / ethylmethyl carbamate / dimethyl carbamate mixed solvent (3: 6: 1 volume ratio) as the non-aqueous organic solvent in the electrolyte solution was carried out in the same manner as in Example 1.

Example 5

The same method as in Example 1, except that ethylene carbamate / ethylmethyl carbamate / dimethylcarbamate / N-methyloxazolidinone mixed solvent (3: 2: 3: 2 by volume) was used as the non-aqueous organic solvent in the electrolyte. Was carried out.

Example 6

Except for using the ethylene carbamate / ethyl methyl carbamate / dimethyl carbamate / N- phenyl oxazolidinone mixed solvent (3: 2: 3: 2) as the non-aqueous organic solvent in the electrolyte solution in the same manner as in Example 1 Was carried out.

Example 7

Ethylene carbamate / ethylmethyl carbamate / dimethylcarbamate / N-phenyloxazolidinone mixed solvent (3: 2: 3: 2) was used as a non-aqueous organic solvent in the electrolyte, and LiPF6 was dissolved to 1.3M. Except that was carried out in the same manner as in Example 1.

Comparative Example 1

Except for using dimethyl carbonate as a non-aqueous organic solvent in the electrolyte solution was carried out in the same manner as in Example 1.

Comparative Example 2

Except for using an ethylene carbonate / ethyl methyl carbonate / diethyl carbonate mixed solvent (3: 6: 1 volume ratio) as the non-aqueous organic solvent in the electrolyte solution was carried out in the same manner as in Example 1.

Comparative Example 3

Except for using an ethylene carbonate / ethyl methyl carbonate / dimethyl carbonate mixed solvent (3: 6: 1 volume ratio) as the non-aqueous organic solvent in the electrolyte solution was carried out in the same manner as in Example 1.

Comparative Example 4

The same procedure as in Example 1 was carried out except that LiPF ₆ was dissolved to 1.3 M in an ethylene carbonate / ethylmethyl carbonate / dimethyl carbonate mixed solvent (3: 6: 1 volume ratio) in the electrolyte solution. .

<Overcharge Safety Experiment>

Experimental Method

The temperature and voltage changes of the batteries were observed while overcharging the charged batteries described in Examples 1 to 7 and Comparative Examples 1 to 4 for 2 hours under the conditions of 3.6C-16V. Among them, the battery manufactured according to Example 6 was tested three times and the results are shown in FIG. 2.

<Life characteristics>

Experimental Method

The batteries described in Examples 1 to 7 and Comparative Examples 1 to 4 were charged under 4.2 V-0.02 C cut-off conditions under 1 C constant current / constant voltage conditions. The battery thus discharged was discharged under a 3V cut-off condition at 1 C constant current, and the life characteristics test was performed 500 times. The results of three experiments for Comparative Examples 1 and 2 are shown in FIGS. 3A and 4, and the results for Examples 4 and 6 are shown in FIGS. 3A and 3B, respectively. The red dotted line indicates that the battery will generate an error if it falls below the battery's baseline.

As can be seen from Figure 2 and Figures 3a and 3b, it can be seen that the battery prepared according to the embodiment is improved overcharge characteristics, and also life characteristics improved compared to the comparative example.

As described above, the electrolyte according to the present invention provides a lithium secondary battery excellent in overcharge safety and lifespan characteristics.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the scope of the present invention . Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

Claims (10)

Lithium salts; And Including a compound of Formula 1 as a non-aqueous organic solvent, The compound of Formula 1 is a non-aqueous electrolyte lithium secondary battery, characterized in that it comprises 50 to 100% by weight relative to the total weight of the non-aqueous organic solvent: Formula 1

Wherein R ¹ and R ² are independently substituted or unsubstituted alkyl of 1 to 10 carbon atoms, alkenyl of 2-10, alkynyl of 2-10, cyclic group of 3-10, unsaturated of 3-10 It is a cyclic group, an aromatic group, and R ¹ and R ² may be connected to each other to form a ring. The non-aqueous electrolyte lithium secondary battery of claim 1, wherein the compound of Formula 1 is dimethyl carbamate or oxazolidone. The method of claim 1, wherein the non-aqueous organic solvent is at least one of linear carbamate consisting of dimethyl carbamate, diethyl carbamate, dipropyl carbamate, methyl propyl carbamate, ethyl propyl carbabate and ethylmethyl carbamate and ethylene A nonaqueous electrolyte solution for a lithium secondary battery, characterized in that it is used by mixing at least one of the cyclic carbamate consisting of carbamate, propylene carbamate and butylene carbamate. The nonaqueous lithium secondary battery of claim 1, wherein the electrolyte further comprises at least one stabilizing additive selected from the group consisting of an aromatic compound having a methoxy group and a halogen group, a biphenyl, a thiophene, or an aromatic ether compound. Electrolyte solution. The nonaqueous electrolyte solution for lithium secondary batteries according to claim 4, wherein the additive is 1 to 1000 ppm with respect to the nonaqueous organic solvent. The method of claim 1, wherein the lithium salt is LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , LiN (SO ₃ CF ₃ ) ₂ , LiC ₄ F ₉ SO ₃ , LiAlO ₄ , LiAlCl ₄ , LiCl and one or more selected from the group consisting of LiI Non-aqueous electrolyte solution for lithium secondary batteries, characterized in that. According to claim 1, wherein the concentration of the lithium salt is a non-aqueous electrolyte lithium secondary battery, characterized in that used in the range of 0.6 to 2.0M. The non-aqueous electrolyte solution for lithium secondary batteries according to claim 1, wherein the non-aqueous organic solvent is a mixture of a carbamate solvent and an ester, an ether or a ketone of 1 in chemistry. The non-aqueous electrolyte solution for lithium secondary batteries according to claim 8, wherein the carbamate solvent is used by mixing a cyclic carbamate and a chain carbamate in a volume ratio of 1: 1 to 1: 9. . The electrolyte according to any one of claims 1 to 9, A positive electrode including a positive electrode active material capable of inserting and detaching lithium ions; And a negative electrode including a negative electrode active material capable of inserting and detaching lithium ions.

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