WO2017030416A1 - Electrolyte for lithium secondary battery and lithium secondary battery comprising same - Google Patents

Abstract

The present invention relates to an electrolyte for a lithium secondary battery, comprising an additive for forming a stable SEI film and a protective layer on the surface of an electrode to prevent a chemical reaction between the electrolyte and the electrode, and to a lithium secondary battery comprising the electrolyte, which has improved lifespan properties and high temperature safety.

Description

Electrolyte for lithium secondary battery and lithium secondary battery comprising same

Cross Citation with Related Application (s)

This application claims the benefit of priority based on Korean Patent Application No. 10-2015-0116637 dated August 19, 2015 and Korean Patent Application No. 10-2016-0104607 dated August 18, 2016. All content disclosed in the literature is included as part of this specification.

Technical Field

The present invention relates to a lithium secondary battery electrolyte and a lithium secondary battery comprising the same, which can ensure cycle life characteristics and high temperature durability.

Recently, as the miniaturization and light weight of electronic equipment are possible due to the development of the high-tech electronic industry, the use of portable electronic devices is increasing, and the need for a battery having a high energy density as a power source for such portable electronic devices is increasing.

A battery is a device that converts chemical energy generated during the electrochemical redox reaction of chemical substances into electrical energy. A primary battery that needs to be discarded when all the energy inside the battery is consumed and a rechargeable battery that can be recharged many times Can be divided into:

The secondary battery has an advantage of being able to be charged and discharged many times using reversible mutual conversion of chemical energy and electrical energy. In particular, the lithium secondary battery is rechargeable, and has an advantage that the energy density per unit weight is three times higher than that of a conventional lead storage battery, nickel-cadmium battery, nickel hydrogen battery, and nickel zinc battery, and enables fast charging. It is widely used as a driving power source for portable electronic devices such as video cameras, mobile phones, and notebook computers.

The lithium secondary battery includes a cathode including a cathode active material capable of intercalation and deintercalation of lithium, and a cathode including a cathode active material capable of intercalating and deintercalating lithium. It is used by injecting an electrolyte solution into a containing battery cell.

Since the lithium secondary battery operates at a high driving voltage, a non-aqueous organic solvent in which lithium salt is dissolved is used instead of an aqueous electrolyte having high reactivity with lithium. The organic solvent is preferably stable at high voltage, has high ion conductivity, high dielectric constant, and low viscosity.

For example, when a carbonate polar non-aqueous solvent is used in a lithium secondary battery, an irreversible reaction in which an excessive amount of charge is used by side reactions between the negative electrode / anode and the electrolyte during initial charging proceeds. By the irreversible reaction, a passivation layer such as a solid electrolyte interface (hereinafter referred to as an 'SEI film') is formed on the surface of the cathode, and a protection layer is formed on the surface of the anode.

The SEI membrane and the protective layer prevent the decomposition of the electrolyte during charging and discharging and serve as an ion tunnel. Therefore, as the SEI film and the protective layer have high stability and low resistance, the lifespan of the lithium secondary battery may be improved.

Accordingly, in order to improve battery performance, there is a need for an organic electrolyte solution capable of forming an SEI film and a protective layer having excellent stability and low resistance.

Prior art literature

Republic of Korea Patent Publication No. 10-2007-0031807

In order to solve the above problems, the present invention provides a lithium secondary battery electrolyte comprising an electrolyte additive that can improve the battery performance.

In addition, the present invention provides a lithium secondary battery comprising the electrolyte solution for the lithium secondary battery.

In one embodiment of the present invention

An electrolyte solution for a lithium secondary battery containing an electrolyte salt and an organic solvent,

The electrolyte provides a lithium secondary battery electrolyte further comprising a compound represented by the following formula (1) as an electrolyte additive.

[Formula 1]

In the above formula,

R is a linear or branched alkylene group having 1 to 3 carbon atoms,

R ₁ is a linear or branched alkylene group having 1 to 5 carbon atoms or an arylene group having 5 to 8 carbon atoms,

n is an integer of 0-10.

The compound represented by Chemical Formula 1 may be included in an amount of 0.05 wt% to 7 wt% based on the total weight of the electrolyte.

In addition, in one embodiment of the present invention

An anode, a cathode, a separator interposed between the anode and the cathode, and

Provided is a lithium secondary battery including an electrolyte solution for a lithium secondary battery of the present invention.

According to the present invention, by providing a more stable SEI film and a protective layer on the electrode surface to provide an electrolyte solution for a lithium secondary battery containing an additive that can prevent a chemical reaction between the electrolyte and the electrode, life characteristics and high temperature safety is improved A lithium secondary battery can be manufactured.

The following drawings, which are attached to this specification, illustrate exemplary embodiments of the present invention, and together with the contents of the present invention serve to further understand the technical idea of the present invention, the present invention is limited to the matters described in such drawings. It is not to be construed as limited.

1 is a graph showing a result of maintaining a high temperature (60 ° C.) storage capacity of a lithium secondary battery according to Experimental Example 1 of the present invention.

Figure 2 is a graph showing the results of the change in the thickness of the cell at high temperature (60 ℃) storage of the lithium secondary battery according to Experimental Example 1 of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail. In this case, the terms or words used in the present specification and claims are appropriately defined in order to explain the invention in the best way for the understanding of the invention, and the scope of the present invention is limited to the scope of the following description. It doesn't happen.

On the other hand, prior to explaining the present invention, in the description of "carbon number a to b" in the specification, "a" and "b" means the number of carbon atoms in the specific functional group. That is, the functional group may include "a" to "b" carbon atoms. For example, "carbon atoms, linear or branched alkylene group of 1 to 3" is an alkyl group containing carbon atoms of 1 to 3 carbon atoms, i.e. _{-CH 2 -, -CH 2 CH 2} -, -CH 2 CH 2 CH 2 -, -CH ₂ CH (CH ₃ )-, and -CH (CH ₃ ) CH _2- .

In addition, in this specification, the term "alkyl group" or "alkylene group" means a branched or unbranched aliphatic hydrocarbon group. The alkyl group or alkylene group may be substituted or unsubstituted. In one embodiment, the alkylene group, methylene group, ethylene group, propylene r, isopropylene group, butylene group, isobutylene group, tert-butylene group, pentylene group, 3-pentylene group, hexylene group, cyclopropylene group, Cyclopentylene groups, cyclohexylene groups, cycloheptylene groups, and the like, but are not limited to these, each of which may be optionally substituted in other embodiments.

In addition, the term "aryl group" or "arylene group" herein means an aromatic ring or aromatic ring system (i.e., a ring sharing adjacent atom pairs) containing only carbon in the ring backbone. When aryl is a ring system, all rings in the system are aromatic. In one embodiment, the arylene group is a phenylene group, biphenylene group, naphthylene group, phenanthrenylene group, naphthacenylene group and the like, but is not limited thereto. In other embodiments, aryl groups may be substituted or unsubstituted.

Lithium secondary batteries known to date are difficult to prevent corrosion of metal materials, and in particular, there are insufficient points in maintaining performance at effective levels under extreme conditions such as overcharge, overdischarge, and high temperature storage. Accordingly, the present invention provides a lithium secondary battery electrolyte comprising an additive capable of preventing chemical reaction between the electrolyte and the electrode by forming an SEI film and a protective layer on the electrode surface, respectively, to improve the life characteristics and high temperature safety lithium secondary The battery can be manufactured.

Hereinafter, the present invention will be described in detail with reference to embodiments.

Non-aqueous electrolyte solution for secondary battery

Specifically, in one embodiment of the present invention

An electrolyte solution for a lithium secondary battery containing an electrolyte salt and an organic solvent,

The electrolyte provides a lithium secondary battery electrolyte further comprising a compound represented by the following formula (1) as an electrolyte additive.

[Formula 1]

In the above formula,

R is a linear or branched alkylene group having 1 to 3 carbon atoms,

R ₁ is a linear or branched alkylene group having 1 to 5 carbon atoms or an arylene group having 5 to 8 carbon atoms,

n is an integer of 0-10.

More specifically, R is a linear alkylene group having 1 to 3 carbon atoms, R ₁ is an arylene group having 5 to 8 carbon atoms, n is an integer of 0 to 5.

In the electrolyte solution of the present invention, when the electrolyte solution contains a compound containing a sulfonate group as a substituent, such as the compound represented by the formula (1), by the coordination bond between the sulfonate group and the electrode current collector metal on the electrode surface A stable film can be formed to prevent corrosion of the electrode, particularly the anode surface. That is, when the electrode surface of the lithium secondary battery is exposed to the electrolyte under extreme conditions such as overcharge, overdischarge, and high temperature storage, it reacts with the sulfonate group and the hydroxyl group of the electrode surface of the compound included in the electrolyte additive as shown in Scheme 1 below. While water molecules are detached and oxygen of the sulfonate group forms coordination bonds with sites having a positive charge on the surface of the metal component of the electrode current collector, a film is formed on the surface of the electrode. The chemical reaction of the electrode can be suppressed.

Scheme 1

In addition, in the case of including the compound containing an unsaturated functional group such as a triple bond or a polar functional group at the terminal as an electrolyte additive, since it accepts electrons more easily from the negative electrode than the polar solvent, it is reduced at a voltage lower than that of the polar solvent and thus polarized. The solvent may be reduced before it is reduced. That is, the unsaturated or polar functional groups contained in the compound represented by Formula 1 may be more easily reduced and / or decomposed into radicals and / or ions upon charging. These radicals and / or ions may precipitate or form insoluble compounds by bonding with lithium ions, and the insoluble compounds react with various functional groups present on the surface of the carbon-based negative electrode or the carbon-based negative electrode itself to form covalent bonds. Or adsorbed on the cathode surface. In conclusion, due to such bonding and / or adsorption, a modified SEI film having improved stability capable of maintaining a solid state even after prolonged charging and discharging is formed on the cathode surface. Such a rigid modified SEI membrane can effectively reduce or prevent the penetration of the electrolyte can reduce the gas generated during high temperature storage.

In addition, a compound containing an isocyanate group or a nitrile group as a substituent, such as the compound represented by Chemical Formula 1, may be easily oxidized and / or decomposed into radicals and / or ions at the time of charging as compared to a polar solvent. Therefore, when the electrolyte additive of the present invention includes a compound containing the isocyanate group or the nitrile group as a substituent, the complex is formed on the electrode surface by reacting with various transition metal ions or hydroxyl groups present on the electrode surface as shown in Scheme 2 below. It can form a modified protective film consisting of a complex (complex). The coating formed by such a composite can ensure stability by maintaining a solid state for a long time even after high temperature, charging and discharging, compared to the coating (protective layer) formed only by decomposition of the organic solvent.

Scheme 2

This robust modified protective layer can more effectively block the entry of the organic solvent solvated by the lithium ions into the electrode during the intercalation of the lithium ions. Therefore, since the modified protective film more effectively blocks direct contact between the organic solvent and the positive electrode, reversibility of lithium ion occlusion / release can be further improved, and consequently, a high temperature stability improvement effect of the battery can be realized.

In conclusion, in the case of the secondary battery electrolyte of the present invention, the compound represented by the formula (1) containing a triple bond structure, both a sulfonate group and an isocyanate group (-NCO) in the compound as an electrolyte additive, the positive and negative electrode surface By forming stable SEI films and protective films on the substrates, high temperature life characteristics and high temperature durability of the lithium secondary battery can be remarkably improved even under extreme conditions such as high temperature storage.

Specifically, the compound represented by Formula 1 may be represented by the following Formula 1a or 1b.

[Formula 1a]

[Formula 1b]

In this case, the compound represented by Formula 1 may be included in 0.05 wt% to 7 wt%, preferably 0.1 wt% to 5 wt% based on the total weight of the electrolyte. If the additive is contained in less than 0.05% by weight, since the effect of forming the SEI film and the protective film on the electrode surface is inadequate, the capacity deteriorates with a longer storage period, and when the additive content exceeds 7% by weight, such as side reactions. Since the gas generation suppression effect is insufficient due to the generation, it may cause a problem that the battery thickness increases with the interpolation period.

Further, in the electrolytic solution of the present invention, the electrolyte salt is (i) Li ^+, Na ⁺ and K ⁺ cations and (ii) selected from the group consisting of _{^{PF 6 -, BF 4 -,}} Cl -, Br -, I - _{^{, ClO 4 -, AsF 6 -}} , B 10 Cl 10 -, CH 3 CO 2 -, CF 3 SO 3 -, CF 3 SO 3 -, SbF 6 -, AlCl 4 -, AlO 4 -, CH 3 SO 3 - , _{N (CF 3 SO 2) 2} - and _{C (CF 2 SO 2) 3} - can be made of a combination of an anion selected from the group, typically, examples of LiCl, LiBr, LiI, LiClO _4, LiBF _4, LiB ₁₀ consisting of Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCH ₃ CO ₂ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , LiAlO ₄ , LiCH ₃ SO ₃ , chloroborane lithium, lower aliphatic lithium carbonate, 4 phenyl It may include a single material or a mixture of two or more selected from the group consisting of lithium borate, in addition to these lithium bisperfluoroethanesulfonimide, LiN (C ₂ F ₅₎ commonly used in the electrolyte of the lithium secondary battery SO ₂ ) _{2 ,} LiBETI), lithium fluoromethanesulfonimide (LiFSI), or lithium (bis) trifluoromethanesulfonimide, LiN (CF ₃ SO ₂ ) ₂ , LiTFSI) without limiting electrolyte salts such as lithium imide salt It can be used. Specifically, the electrolyte salt may include a single substance or a mixture of two or more selected from the group consisting of LiPF ₆ , LiCH ₃ CO ₂ , LiCF ₃ CO ₂ , LiCH ₃ SO ₃ , LiFSI, LiTFSI, and (CF ₃ SO ₂ ) ₂ NLi. have.

The electrolyte salt may be appropriately changed within a usable range, but may be included in an electrolyte solution at a concentration of 0.8 M to 1.5 M in order to obtain an effect of forming an anti-corrosion coating on the surface of an electrode. If the concentration of the electrolyte salt exceeds 1.5M, it is difficult to realize a stable film forming effect.

In addition, in the non-aqueous electrolyte of the present invention, the non-aqueous organic solvent may include conventional organic solvents usable as non-aqueous organic solvents of lithium secondary batteries, such as cyclic carbonate solvent, linear carbonate solvent, ester solvent or ketone solvent. These may be used alone or in combination of two or more in an appropriate ratio.

The cyclic carbonate solvent may include one or two or more mixed solutions selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC) and butylene carbonate (BC). In addition, the linear carbonate solvent is dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), vinylene carbonate (VC), fluoroethylene carbonate (FEC), methyl 1 type, or 2 or more types of mixed solution chosen from the group which consists of propyl carbonate (MPC) and ethylpropyl carbonate (EPC). In addition, the ester solvent is methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone and ε -1 type, or 2 or more types of mixed solution chosen from the group which consists of caprolactone is mentioned. In addition, polymethylvinyl ketone or the like may be used as the ketone solvent.

Secondary battery

In addition, the present invention provides a lithium secondary battery including the positive electrode, the negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte solution, the lithium secondary battery comprising the electrolyte solution for the lithium secondary battery of the present invention as the electrolyte solution.

The positive electrode may be formed by coating a positive electrode active material on an electrode current collector, wherein the positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery, for example, stainless steel, Aluminum, nickel, titanium, calcined carbon, or a surface treated with carbon, nickel, titanium, silver, or the like on the surface of aluminum or stainless steel may be used. In this case, the positive electrode current collector may use various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric having fine irregularities formed on a surface thereof so as to increase the adhesion with the positive electrode active material.

In addition, the positive electrode active material is not particularly limited as long as it is a lithium-containing transition metal oxide used as a positive electrode active material in the manufacture of a general lithium secondary battery. For example, LiCoO ₂ , Li _x NiO ₂ (0.5 <x <1.3), Li _x MnO ₂ (0.5 <x <1.3), Li _x Mn ₂ O ₄ (0.5 <x <1.3), Li _x (Ni _a Co _b Mn _c ) O ₂ (0.5 <x <1.3, 0 <a <1, 0 <b <1, 0 <c <1 , a + b + c = 1, NCM), Li x Ni 1 -y Co y O2 (0.5 <x <1.3, 0 <y <1), Li x Co 1 - y Mn _y O ₂ (0.5 <x <1.3, 0 ≦ y <1), Li _x Ni _{1- y} Mn _y O ₂ (0.5 <x <1.3, O ≦ y <1), Li _x (Ni _a Co _b Mn _c ) O ₄ (0.5 <x <1.3, 0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), Li _x Mn _{2 - z} Ni _z O ₄ (0.5 < x <1.3, 0 <z <2), Li _x Mn _{2 - z} Co _z O ₄ (0.5 <x <1.3, 0 <z <2), Li _x CoPO ₄ (0.5 <x <1.3) and Li _x FePO ₄ (0.5 <x <1.3) may be used any one selected from the group consisting of or a mixture of two or more thereof, specific examples Li _x (Ni _a Co _b Mn _c ) O ₂ (0.5 <x <1.3, 0 <a <1, 0 <b <1, 0 <c <1, a + b + c = 1, NCM), i.e., Li (Ni _1/3 Mn _1/3 Co _1/3 ) O ₂ , Li (Ni _0.6 Mn _0.2 Co _0.2 ) O ₂ , And a single substance selected from the group consisting of Li (Ni _0.5 Mn _0.3 Co _0.2 ) O ₂ and Li (Ni _0.8 Mn _0.1 Co _0.1 ) O ₂ or two or more of these lithium transition metal oxides.

The negative electrode may be formed by coating a negative electrode active material on a negative electrode current collector, and the negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical changes in the battery. For example, copper and stainless steel , Aluminum, nickel, titanium, calcined carbon, surface treated with carbon, nickel, titanium, silver, and the like on the surface of copper or stainless steel, aluminum-cadmium alloy and the like can be used. In addition, the negative electrode current collector, like the positive electrode current collector, may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven fabric having fine irregularities formed on a surface thereof.

In addition, the negative electrode active material may be a carbon material, lithium metal, silicon or tin that can be stored and released lithium ions in the manufacturing of a general lithium secondary battery, for example, low crystalline carbon and high crystallinity Both carbon and the like can be used. Soft crystalline carbon and hard carbon are typical low crystalline carbon, and high crystalline carbon is natural graphite, Kish graphite, pyrolytic carbon, liquid crystal pitch-based carbon fiber. high temperature calcined carbon such as mesophase pitch based carbonfiber, meso-carbon microbeads, mesophase pitches and petroleum or coal tar pitch derived cokes.

The positive electrode and the negative electrode active material may further include a binder and a conductive material.

In this case, the binder is a component that assists the bonding between the conductive material, the active material and the current collector, and is typically added in an amount of 1 to 50 wt% based on the total weight of the electrode mixture. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoro Low ethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, fluorine rubber, various copolymers thereof, and the like.

The conductive material is a component for further improving the conductivity of the electrode active material, and may be added in an amount of 1 to 20 wt% based on the total weight of the electrode mixture. Such a conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; Carbon blacks such as acetylene black, Ketjen black, channel black, furnace black, lamp black and thermal black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

In the present invention, after mounting a battery assembly consisting of a separator interposed between the positive electrode, the negative electrode, the positive electrode and the negative electrode in the battery case, the electrolyte solution containing the additive for preventing corrosion of the electrode of the present invention is impregnated with an electrolyte solution, the battery The formation process can be performed. In addition, by performing the aging process at room temperature or high temperature before and after activation, the urethane reaction efficiency between -NCO, which is the terminal group of the compound represented by Formula 1, and OH, which is an impurity on the electrode surface, is further increased, and thus the protective effect is more enhanced. I think it will increase.

At this time, as the electrolyte and the electrode surface react, a passivation film is formed on the electrode surface to prevent the electrode surface from being exposed even under extreme conditions such as overcharge, overdischarge, and high temperature storage, thereby preventing electrode corrosion. Various performances, such as the cycle life characteristic of a secondary battery, can be improved.

In the detailed description of the invention as described above, specific embodiments have been described. However, many modifications are possible without departing from the scope of the invention. The technical spirit of the present invention should not be limited to the described embodiments of the present invention, but should be determined not only by the claims, but also by those equivalent to the claims.

Example

Example 1.

(Cathode production)

98% by weight of natural graphite, 1.0% by weight of styrene-butadiene rubber (SBR) binder and 1.0% by weight of carboxymethylcellulose (CMC, NIPPON A & L) are added to distilled water and stirred for 60 minutes using a mechanical stirrer. A negative electrode active material slurry was prepared. The slurry was applied on a 10 μm thick copper current collector using a doctor blade to a thickness of about 60 μm, dried for 0.5 hours in a hot air dryer at 100 ° C., and then dried again under vacuum, 120 ° C. for 4 hours, and rolled. (roll press) to prepare a negative electrode plate.

(Anode manufacturing)

Li (Ni _0.6 Mn _0.2 Co _0.2 ) O ₂ 97.45 wt%, artificial graphite (SFG6, Timcal) powder 0.5 wt%, carbon black (Ketjenblack, ECP) 0.7 wt%, modified acrylonitrile rubber (BM-720H, Zeon Corporation) 0.25 wt%, polyvinylidene fluoride ( PVdF, S6020, Sollvay) 1.1% by weight of the mixture was added to the N-methyl-2-pyrrolidone solvent and stirred for 30 minutes using a mechanical stirrer to prepare a cathode active material slurry. The slurry was applied on a 20 μm thick aluminum current collector using a doctor blade, dried about 0.5 μm in a hot air dryer at 100 ° C., and then dried again under vacuum, 120 ° C. for 4 hours, and rolled. (roll press) to prepare a positive electrode plate.

(Electrolyte preparation)

0.2 weight of a compound represented by Chemical Formula 1a as an additive to a non-aqueous solvent (ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) = 3: 5: 2 vol%) containing 1.0 M LiPF ₆ Organic electrolyte was prepared by adding%.

(Secondary Battery Manufacturing)

An electrode assembly is manufactured through a separator of porous polyethylene having a thickness of 14 μm coated with a ceramic between the negative electrode prepared above and the negative electrode, the electrode assembly is placed in a case, and the prepared electrolyte is transferred into the case. Injected to prepare a lithium secondary battery.

Example 2.

An electrolyte and a lithium secondary battery including the same were prepared in the same manner as in Example 1, except that 3 wt% of the compound of Formula 1b was used instead of the compound of Formula 1a as an electrolyte additive.

Comparative Example 1.

Except not including an electrolyte additive, an electrolyte and a lithium secondary battery including the same were prepared in the same manner as in Example 1.

Comparative Example 2.

An electrolyte solution and a lithium secondary battery including the same were prepared in the same manner as in Example 1, except that 0.02% by weight of the compound of Formula 1a was included as an electrolyte additive.

Comparative Example 3.

An electrolyte solution and a lithium secondary battery were manufactured in the same manner as in Example 1, except that 7.3 wt% of the compound of Formula 1a was included as an electrolyte additive.

Experimental Example

Experimental Example  1: Determination of capacity drop for high temperature storage (60 ℃)

After charging the lithium secondary batteries prepared in Examples 1 and 2 and Comparative Examples 1 to 3 with SOC 100% at 25 ° C, the cells were stored in a 60 ° C chamber and the capacity decay behavior was measured according to the storage period. The results are shown in Figure 1 below.

Referring to FIG. 1, it can be seen that the secondary batteries of Examples 1 and 2 have a lower capacity decay reduction rate according to storage periods than the secondary batteries of Comparative Examples 1 to 3.

Experimental Example  2: Measurement of gas generation at high temperature (60 ° C)

After charging the lithium secondary batteries prepared in Examples 1 and 2 and Comparative Examples 1 to 3 with 100% SOC at 25 ° C., the cells were stored in a 60 ° C. chamber, and cell thicknesses according to gas generation according to storage periods. The change was confirmed, and the result is shown in FIG.

Referring to FIG. 2, it can be seen that the secondary batteries of Examples 1 and 2 have a lower cell thickness increase (change) according to the storage period compared to those of Comparative Examples 1 to 3.

From the results obtained in Experimental Examples 1 and 2, since the secondary batteries of Examples 1 and 2 form a safe film on the surface of the electrode by the electrolyte additive, the penetration of the electrolyte can be effectively reduced or prevented, and thus, at high temperature storage. It can be seen that the effect of reducing the gas generated by the side reaction of the electrolyte can be implemented.

Claims (11)

1. An electrolyte solution for a lithium secondary battery containing an electrolyte salt and an organic solvent,

   The electrolyte solution is a lithium secondary battery electrolyte further comprises a compound represented by the following formula (1) as an additive:

   [Formula 1]

   

   In the above formula,

   R is a linear or branched alkylene group having 1 to 3 carbon atoms,

   R ₁ is a linear or branched alkylene group having 1 to 5 carbon atoms or an arylene group having 5 to 8 carbon atoms,

   n is an integer of 0-10.
2. The method according to claim 1,

   In the general formula (1), R is a linear alkylene group having 1 to 3 carbon atoms, R ₁ is an arylene group having 5 to 8 carbon atoms, n is an integer of 0 to 5, the electrolyte solution for lithium secondary batteries.
3. The method according to claim 1,

   The compound represented by Formula 1 includes a compound of Formula 1a or a compound of Formula 1b.

    [Formula 1a]

   

   [Formula 1b]

   
4. The method according to claim 1,

   The compound represented by Formula 1 is included in the lithium secondary battery electrolyte, characterized in that contained in 0.05 wt% to 7 wt% based on the total weight of the electrolyte.
5. The method according to claim 4,

   The compound represented by the formula (1) is a lithium secondary battery electrolyte, characterized in that it comprises 0.1 to 5% by weight based on the total weight of the electrolyte.
6. The method according to claim 1,

   The electrolyte salt is (i) Li ^+, Na ⁺ and K ⁺ at least one cation and, (ii) selected from the group consisting of _{^{PF 6 -, BF 4 -,}} Cl -, Br -, I -, ClO 4 -, _{^{AsF 6 -, B 10 Cl 10}} -, CH 3 CO 2 -, CF 3 SO 3 -, CF 3 SO 3 -, SbF 6 -, AlCl 4 -, AlO 4 -, CH 3 SO 3 -, _{N (CF 3 SO 2) 2} - and _{C (CF 2 SO 2) 3} - for a lithium secondary battery electrolyte, which is characterized by being a combination of at least one anion selected from the group consisting of.
7. The method according to claim 6,

   The electrolyte salt is LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCH ₃ CO ₂ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , LiAlO ₄ LiCH ₃ SO ₃ , chloroborane lithium, lower aliphatic lithium carbonate, and lithium phenyl borate a single material selected from the group consisting of or a mixture of two or more thereof.
8. The method according to claim 6,

   The electrolyte salts are lithium bisperfluoroethanesulfoimide (LiN (C ₂ F ₅ SO ₂ ) ₂ ), lithium fluoromethanesulfoimide and lithium (bis) trifluoromethanesulfoimide (LiN (CF ₃ SO ₂ ) ₂ ) A lithium secondary battery electrolyte, characterized in that it further comprises a single material or a mixture of two or more selected from the group consisting of.
9. The method according to claim 1,

   The electrolyte salt is a lithium secondary battery electrolyte, characterized in that it is contained in a concentration of 0.8M to 1.5M.
10. The method according to claim 1,

    The non-aqueous organic solvent is a lithium secondary battery electrolyte, characterized in that it comprises a single solution selected from the group consisting of cyclic carbonate solvent, linear carbonate solvent, ester solvent and ketone solvent or a mixture solution of two or more thereof.
11. In the lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte,

    Said nonaqueous electrolyte is a nonaqueous electrolyte for secondary batteries of Claim 1, The lithium secondary battery characterized by the above-mentioned.

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