KR20190017477A - Non-aqueous electrolyte and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a non-aqueous electrolyte and a lithium secondary battery comprising the same. Specifically, the present invention relates to a non-aqueous electrolyte comprising a first lithium salt LiBF_4, a second lithium salt different from the first lithium salt, an organic solvent, a surfactant represented by chemical formula 1, and a first additive, wherein the concentration of the second lithium salt is 2-6 M, and to a secondary battery having high output and improved safety by comprising the same.

Description

TECHNICAL FIELD [0001] The present invention relates to a non-aqueous electrolytic solution and a lithium secondary battery comprising the same. BACKGROUND ART < RTI ID = 0.0 >

The present invention relates to a non-aqueous electrolytic solution containing a lithium salt of 2M or more and a surfactant, and a lithium secondary battery comprising the same.

BACKGROUND ART [0002] With the recent rapid development of electric, electronic, communication and computer industries, demand for high performance and high safety secondary batteries is increasing. In addition, as these electronic (communication) devices are becoming smaller and lighter, lithium secondary batteries, which are key components in this field, are required to be thinned and miniaturized.

Lithium secondary batteries are high performance, but they have a disadvantage that their discharge characteristics are low under a harsh environment such as low temperature and high temperature, or under a high output requiring a large amount of electricity in a short time. Furthermore, since the conventional lithium secondary battery uses a non-aqueous electrolytic solution as a main component, such as ethylene carbonate, which can cause side reactions at high voltage and the like, thermal runaway may occur or fire may occur.

Therefore, in order to improve the safety and high output characteristics of the lithium secondary battery, researches on the development of an electrolyte additive capable of improving the wetting property of the electrolyte have been made.

However, the electrolyte additives known so far have formed a film which easily breaks down in a high temperature environment on the negative electrode, and rather cause an increase in interfacial resistance between the electrode and the electrolyte.

Korean Patent Registration No. 1041127

In order to solve the above problems,

A first object of the present invention is to provide a non-aqueous electrolytic solution having a reduced surface tension and improved wettability.

A second object of the present invention is to provide a lithium secondary battery having improved output characteristics and safety by including the non-aqueous electrolyte solution.

Specifically, in one embodiment of the present invention

Claim 1 of a lithium salt LiBF _4,

A second lithium salt different from the first lithium salt,

Organic solvent,

A surfactant represented by the following formula (1), and

A first additive,

And the second lithium salt has a concentration of 2M to 6M.

[Chemical Formula 1]

In Formula 1,

R is a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms,

R ₁ and R ₂ are each independently a fluorine-substituted alkylene group having 1 to 5 carbon atoms,

R 'is an aliphatic, alicyclic or aromatic hydrocarbon group,

R "is hydrogen or an alkyl group having 1 to 3 carbon atoms,

n is an integer of 1 to 80, specifically 1 to 40,

m and o are each an integer of 1 to 3;

Specifically, in Formula 1, R is an alkylene group having 1 to 3 carbon atoms which is substituted or unsubstituted with at least one element selected from the group consisting of halogen, CN and oxygen.

The aliphatic hydrocarbon group is an alkylene group having 1 to 20 carbon atoms; An alkylene group having 1 to 20 carbon atoms containing an isocyanate group (NCO); An alkoxysilyl group having 1 to 20 carbon atoms; An alkenylene group having 2 to 20 carbon atoms; Or an alkynylene group having 2 to 20 carbon atoms; and the alicyclic hydrocarbon group is a substituted or unsubstituted cycloalkylene group having 4 to 20 carbon atoms; A substituted or unsubstituted C 4 -C 20 cycloalkylene group containing an isocyanate group (NCO); A cycloalkenylene group having 4 to 20 carbon atoms; Or a heterocycloalkylene group having 2 to 20 carbon atoms, and the aromatic hydrocarbon group is a substituted or unsubstituted arylene group having 6 to 20 carbon atoms; Or a heteroarylene group having 2 to 20 carbon atoms.

Also, the concentration of the second lithium salt may be 2M to 5M, specifically 2M to 4M, and the molar ratio of the first lithium salt: the second lithium salt may be 0.001: 1 to 1: 1.

Further, in one embodiment of the present invention, the second lithium salt is in, and anions including Li ⁺ as the cation ^{F -, Cl -, Br -} , I -, NO 3 -, N (CN) 2 -, _{^{ClO 4 -, AlO 4 -,}} AlCl 4 -, PF 6 -, SbF 6 -, AsF 6 -, BF 2 C 2 O 4 -, BC 4 O 8 -, (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 -, C 4 F 9 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 - , and _{(CF 3 CF 2 SO 2)} 2 N - consisting of And < / RTI >

The surfactant represented by Formula 1 may be at least one selected from the group consisting of compounds represented by Chemical Formulas 1a to 1c.

[Formula 1a]

In formula (1a)

n1 is an integer of 1 to 80, specifically 1 to 40;

[Chemical Formula 1b]

In the above formula (1b)

n2 is an integer of 1 to 80, specifically 1 to 40;

[Chemical Formula 1c]

In the above formula (1c)

n3 is an integer of 1 to 80, specifically 1 to 40;

The surfactant represented by Formula 1 may be contained in an amount of 0.5% by weight to 20% by weight, specifically 0.5% by weight to 15% by weight, more specifically 0.5% by weight to 10% by weight based on the total weight of the non-aqueous electrolytic solution.

In addition, the first additive may be selected from the group consisting of fluorobenzene (FB), lithium oxalyldifluoroborate (LiODFB), and lithium bis (oxalato) borate (LiBOB) At least one compound selected from the group consisting of:

The first additive may be contained in an amount of 0.1% by weight to 15% by weight, specifically 0.1% by weight to 10% by weight, more specifically 0.5% by weight to 7% by weight, based on the total weight of the non-aqueous electrolytic solution.

Wherein the non-aqueous electrolytic solution comprises at least one second additive selected from the group consisting of N, N'-dicyclohexylcarbodiimide (DCC), vinylene carbonate, saturated sulphone, and cyclic sulfite May be further included.

In an embodiment of the present invention,

Anode, cathode,

A separator interposed between the anode and the cathode, and

A non-aqueous electrolytic solution,

The non-aqueous electrolyte solution provides a lithium secondary battery comprising the non-aqueous electrolyte solution of the present invention.

As described above, according to the present invention, a high concentration lithium salt of 2M or more and a first additive as a cathode protecting agent capable of forming a passivation layer on the surface of a cathode are included in combination with an electrochemically stable oligomer type surfactant , It is possible to provide a non-aqueous electrolytic solution having reduced surface tension and improved wettability. In addition, safety and initial irreversible capacity can be reduced by using it, and a lithium secondary battery having improved high output characteristics can be manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and together with the description of the invention serve to further the understanding of the technical idea of the invention, It is not limited.
1 is a photograph of a cathode surface of a secondary battery of Comparative Example 3 after charge and discharge in Experimental Example 1 of the present invention.
FIG. 2 is a photograph of a cathode surface of a secondary battery of Example 1 after charge and discharge in Experimental Example 1 of the present invention. FIG.
FIG. 3 is a graph showing the exothermic characteristics of the non-aqueous electrolyte according to the concentration of the lithium salt in Experimental Example 2 of the present invention.
4 is a graph showing an initial discharge capacity of a secondary battery in Experimental Example 3 of the present invention.
5 is a graph showing resistance characteristics of a secondary battery according to time (sec) in Experimental Example 5 of the present invention.
6 is a graph showing a change in capacity of a secondary battery in Experimental Example 6 of the present invention.

Hereinafter, the present invention will be described in detail in order to facilitate understanding of the present invention. Herein, terms and words used in the present specification and claims should not be construed to be limited to ordinary or dictionary meanings, and the inventor may appropriately define the concept of the term to describe its own invention in the best way. It should be construed as meaning and concept consistent with the technical idea of the present invention.

Specifically, in one embodiment of the present invention

Claim 1 of a lithium salt LiBF _4,

A second lithium salt different from the first lithium salt,

Organic solvent,

A surfactant represented by the following formula (1), and

A first additive,

And the second lithium salt has a concentration of 2M to 6M.

[Chemical Formula 1]

In Formula 1,

R is a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms,

R ₁ and R ₂ are each independently a fluorine-substituted alkylene group having 1 to 5 carbon atoms,

R 'is an aliphatic, alicyclic or aromatic hydrocarbon group,

R "is hydrogen or an alkyl group having 1 to 3 carbon atoms,

n is an integer of 1 to 80, specifically 1 to 40,

m and o are each an integer of 1 to 3;

Specifically, in Formula 1, R is an alkylene group having 1 to 3 carbon atoms which is substituted or unsubstituted with at least one element selected from the group consisting of halogen, CN and oxygen. More specifically, R is substituted or halogenated with halogen And an optionally substituted alkylene group having 1 to 3 carbon atoms. At this time, the halogen is preferably fluorine.

The aliphatic hydrocarbon group may be an alkylene group having 1 to 20 carbon atoms; An alkylene group having 1 to 20 carbon atoms containing an isocyanate group (NCO); An alkoxysilyl group having 1 to 20 carbon atoms; An alkenylene group having 2 to 20 carbon atoms; Or an alkynylene group having 2 to 20 carbon atoms; and the alicyclic hydrocarbon group is a substituted or unsubstituted cycloalkylene group having 4 to 20 carbon atoms; A substituted or unsubstituted C 4 -C 20 cycloalkylene group containing an isocyanate group (NCO); A cycloalkenylene group having 4 to 20 carbon atoms; Or a heterocycloalkylene group having 2 to 20 carbon atoms, and the aromatic hydrocarbon group is a substituted or unsubstituted arylene group having 6 to 20 carbon atoms; Or a heteroarylene group having 2 to 20 carbon atoms.

In addition, the non-aqueous electrolyte of the present invention may contain LiBF ₄ , which is known to participate in the SEI film formation reaction on the initial cathode surface with the first lithium salt under a high-concentration lithium salt system in which ethylene carbonate is not contained as an organic solvent . The LiBF ₄ has a lower ionic conductivity than other lithium salts, but is thermally stable and less susceptible to moisture, so that stabilization of the electrolyte solution can be improved. Therefore, it is expected that the cycle performance of the secondary battery is improved and the output characteristic is improved at low temperature.

Further, in the non-aqueous electrolytic solution of the present invention according to one embodiment, the first lithium salt and different compounds in a second lithium salt including Li ⁺ as the cation and the anion F ^-, Cl ^-, Br ^-, I _{^{-, NO 3 -, N (}} CN) 2 -, ClO 4 -, AlO 4 -, AlCl 4 -, PF 6 -, SbF 6 -, AsF 6 -, BF 2 C 2 O 4 -, BC 4 O 8 - _{, (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 -, ^{_{C 4 F 9 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 - and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- . More specifically, the second lithium salt are _{LiClO 4, LiPF 6, LiCF 3} CF 2 SO 3, Li (CF 3 SO 2) 2 N, Li (FSO 2) 2 N, LiCF 3 (CF 2) 7 SO 3, and (CF ₃ CF ₂ SO ₂ ) ₂ N, and more specifically, the second lithium salt may include at least one selected from the group consisting of LiPF ₆ , Li (CF ₃ SO ₂ ) ₂ N, Li (FSO _{2) 2} N, and _{Li (CF 3 CF 2 SO 2} ) may include at least one selected from the group consisting of N _2.

In this case, the concentration of the second lithium salt may be 2M to 6M, specifically 2M to 5M, more specifically 2M to 4M.

When the concentration of the second lithium salt satisfies the range of 2M to 6M, the ion transfer characteristic (i.e., the cationic charge transference number) of the lithium cation (Li ⁺ ) is increased due to the increase of the lithium cation present in the non- And the effect of decreasing the diffusion resistance of lithium ions can be achieved, thereby achieving the effect of improving the cycle capacity characteristics and the output characteristics. At this time, when the maximum concentration of the lithium salt exceeds 6M, the viscosity of the non-aqueous electrolytic solution increases to lower the low-temperature characteristics and wetting characteristics of the secondary battery, thereby deteriorating the battery performance.

Currently, the reaction heat generated by electrochemical (eg, overcharge) or chemical (eg, hot box) reactions in most secondary batteries increases the internal temperature of the battery. When the temperature reaches the temperature above the ignition point, There is a problem that the secondary battery is ignited due to a thermal runaway phenomenon. Therefore, it is very important to lower the calorific value of the electrolyte in order to improve the high-temperature safety of the secondary battery.

Therefore, in the present invention, by including the high-concentration lithium salt of 2M or more, flame retardancy can be improved and an exothermic reaction at a high temperature can be prevented from appearing at the beginning of the reaction. That is, as shown in FIG. 3, in the case of a secondary battery having a non-aqueous electrolyte containing a high-concentration lithium salt of 2M or more, an endothermic reaction appears first and then an exothermic reaction occurs. Since the secondary battery having the conventional non-aqueous electrolyte containing the low-concentration lithium salt is at a low level, the safety of the secondary battery can be improved.

In this case, the molar ratio of the first lithium salt: the second lithium salt may be 0.001: 1 to 1: 1, specifically 0.01: 1 to 0.5: 1.

When the first lithium salt concentration is in the range of 0.001 to 1 with respect to 1 mole of the second lithium salt, improvement in cycle performance and improvement in low temperature output characteristics can be expected, and a high lithium ion transport rate effect can be obtained.

In addition, in the non-aqueous electrolyte according to an embodiment of the present invention, the organic solvent may minimize decomposition due to an oxidation reaction or the like during charging and discharging of the secondary battery, And may contain at least one or more selected from the group consisting of a linear carbonate compound, a cyclic ester compound and a linear ester compound, except for ethylene carbonate.

Examples of the linear carbonate compound are selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate and ethyl propyl carbonate Or a mixture of two or more of them may be used. However, the present invention is not limited thereto.

Specific examples of the linear ester compound include any one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate, And mixtures thereof, but the present invention is not limited thereto.

Specific examples of the cyclic ester compound include any one selected from the group consisting of? -Butyrolactone,? -Valerolactone,? -Caprolactone,? -Valerolactone,? -Caprolactone, The above mixture may be used, but is not limited thereto.

Conventionally, a cyclic carbonate compound such as ethylene carbonate, which can form a passivation layer on the surface of a negative electrode, is used as a main component of a non-aqueous electrolyte solvent in a secondary battery. However, such a solvent such as ethylene carbonate is not suitable for use as an organic solvent of the non-aqueous electrolytic solution of the present invention because it is known that the oxidation stability is poor, the heat generation characteristic is very high, and side reactions occur at high voltage.

The non-aqueous electrolyte according to one embodiment of the present invention may include a surfactant represented by Formula 1 to lower the viscosity and surface tension of the non-aqueous electrolyte according to the present invention.

Normally In the case of a surfactant, its own reduction stability is deteriorated to form a film which easily breaks down in a high temperature environment on the surface of the negative electrode at the time of initial charging, and the interface resistance between the electrode and the electrolyte is increased. On the other hand, since the surfactant represented by the above formula (1) used in the present invention simultaneously contains an acrylate group as a hydrophilic group and a tetrafluoroether group as a hydrophobic group in the molecular structure, the reduction reaction on the surface of the negative electrode is minimized, The surface tension of the aqueous electrolytic solution is reduced, and consequently the wettability of the electrolytic solution to the electrode can be improved.

As described above, in the non-aqueous electrolyte of the present invention, since the surface tension is significantly reduced by including the surfactant represented by Chemical Formula 1 in spite of the increase in viscosity including the high concentration lithium salt of 2M or more, The wetting property of the electrolytic solution can be improved. Therefore, the output characteristics and safety of the secondary battery can be improved.

In the non-aqueous electrolytic solution according to one embodiment of the present invention, the surfactant represented by Formula 1 may be at least one selected from the group consisting of compounds represented by Chemical Formulas 1a to 1c.

[Formula 1a]

In formula (1a)

n1 is an integer of 1 to 80, specifically 1 to 40;

[Chemical Formula 1b]

In the above formula (1b)

n2 is an integer of 1 to 80, specifically 1 to 40

[Chemical Formula 1c]

In the above formula (1c)

n3 is an integer of 1 to 80, specifically 1 to 40

The weight average molecular weight (Mw) of the surfactant represented by Formula 1 is 1,000 g / mol to 20,000 g / mol, specifically 1,000 g / mol to 10,000 g / mol, more specifically 1,000 g / mol to 5,000 g / mol Lt; / RTI >

When the weight average molecular weight (Mw) of the surfactant is in the range of 1,000 g / mol to 20,000 g / mol, the surface tension reduction effect to be realized by incorporating the surfactant can be obtained and affinity with the electrolyte solution can be maintained.

At this time, the weight average molecular weight can be measured by Gel Permeation Chromatography (GPC). For example, after a sample of a certain concentration is prepared, the GPC measurement system alliance 4 apparatus is stabilized. When the instrument is stabilized, the standard and sample are injected into the instrument to obtain a chromatogram, and the molecular weight is calculated according to the analytical method (System: Alliance 4, column: Ultrahydrogel linear x 2, eluent: 0.1M NaNO ₃ phosphate buffer, flow rate: 0.1 mL / min, temp: 40 ° C, injection: 100 μl)

The surfactant represented by Formula 1 may be contained in an amount of 0.5% by weight to 20% by weight, specifically 0.5% by weight to 15% by weight, more specifically 0.5% by weight to 10% by weight based on the total weight of the non-aqueous electrolytic solution. When the surfactant represented by Formula 1 is contained in the range of 0.5 wt% to 20 wt%, the viscosity increase can be suppressed and the surface tension can be lowered to further improve the wetting property.

In the non-aqueous electrolytic solution according to an embodiment of the present invention, the first additive is at least one selected from the group consisting of fluorobenzene (FB), lithium oxalyldifluoroborate (LiODFB), and lithium bis (oxalato) And at least one compound selected from the group consisting of lithium bis (oxalato) borate (LiBOB).

The first additive may be contained in an amount of 0.1% by weight to 15% by weight, specifically 0.1% by weight to 10% by weight, more specifically 0.5% by weight to 7% by weight, based on the total weight of the non-aqueous electrolytic solution.

The first additive is a compound capable of contributing to the passivation layer forming reaction on the surface of the negative electrode at a low SOC. When the first additive satisfies the above-mentioned content range condition, a high concentration It is possible to form a stable film on the surface of the negative electrode even under the electrolytic salt condition, and to act as a protective agent for protecting the negative electrode surface. Particularly, in the case of fluorobenzene among the first additives, the wettability of the separator can be further improved due to its hydrophobic property.

In addition, the non-aqueous electrolytic solution of the present invention according to an embodiment may further comprise at least one second additive selected from the group consisting of N, N'-dichlorohexylcarbodiimide (DCC), vinylene carbonate, saturated sulphone, and cyclic sulfite . ≪ / RTI >

The second additive may be contained in an amount of 10 wt% or less, specifically 0.1 wt% to 7 wt%, more specifically 0.5 wt% to 5 wt%, based on the total weight of the non-aqueous electrolytic solution.

The second additive is a compound capable of inhibiting side reactions in the positive electrode and the negative electrode coating. When the second additive is contained in an amount of 10% by weight or less, the stability of the electrolyte and the electrolyte decomposition reaction (including both Faradaic and Non- And it is mostly consumed and decomposed in order to protect the surface of the negative electrode at the time of initial activation.

Among the second additives, the dichlorohexylcarbodiimide (DCC) does not directly form a cathode passivation layer, but suppresses the formation of by-products caused by the suppression of HF formation and salt anions, and ultimately, The side effect can be suppressed and the resistance improving effect can be expected.

Examples of the saturated sultone include 1,3-propane sultone (PS) and 1,4-butane sultone. Unsaturated sultones include ethene sultone, 1,3-propenesultone, 1,4-butene sultone , Or 1-methyl-1,3-propanesultone.

Examples of the cyclic sulfite include ethylene sulfite (Esa), methyl ethylene sulfite, ethyl ethylene sulfite, 4,5-dimethylethylene sulfite, 4,5-diethyl ethylene sulfite, propylene sulfite, 5-dimethylpropylene sulfite, 4,5-diethylpropylene sulfite, 4,6-dimethylpropylene sulfite, 4,6-diethylpropylene sulfite or 1,3-butylene glycol sulfite. have.

The non-aqueous electrolytic solution of the present invention according to one embodiment may further include at least one additive for forming at least one SEI film selected from the group consisting of noncyclic sulfones, alkylsilyl compounds and inorganic compounds, if necessary.

As the non-cyclic sulfone, representative examples thereof include divinyl sulfone, dimethyl sulfone, diethyl sulfone, methyl ethyl sulfone, and methyl vinyl sulfone.

The alkylsilyl compound is exemplified by tri (trimethylsilyl) phosphate, tri (trimethylsilyl) phosphite, tri (triethylsilyl) phosphate, tri (triethylsilyl) phosphite, Triethylsilyl) borate, and the like.

Examples of the inorganic compound include lithium difluoro (bisoxalate) phosphate, lithium difluorophosphate, lithium tetrafluorooxalatophosphate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoro Methylsulfonyl) imide, and the like.

These additives are preferably included in an amount of 10% by weight or less based on the total weight of the non-aqueous electrolytic solution in order to prevent side reactions.

Conventionally, a non-aqueous electrolytic solution containing a high-concentration electrolyte salt is disadvantageous in that it has low wettability (or impregnability) to the electrode and the separator because of its high viscosity.

On the other hand, as described above, the non-aqueous electrolytic solution of the present invention can improve the wettability by lowering the surface tension of the electrolytic solution by introducing the electrochemically stable oligomer type surfactant together with the high concentration electrolyte salt of 2M or more. In addition, since the non-aqueous electrolytic solution of the present invention uses a lithium salt having a flame-retarding property at a high concentration of 2M or more, the effect of improving flame retardancy can be further expected.

Further, since the non-aqueous electrolyte of the present invention does not contain ethylene carbonate known as a solvent capable of causing a side reaction at a high voltage (EC Free system), it can prevent disadvantages caused by ethylene carbonate, And the first additive capable of forming a passivation layer on the surface of the negative electrode by electrolysis may be provided to provide a negative electrode surface protection effect and reduce the initial irreversible reaction and the interfacial resistance to realize a high rate property improving effect. In addition, the oxidation stability can be improved, and the amount of heat generated by decomposition of the electrolyte can be reduced, so that the safety of the secondary battery can be further improved. Therefore, utilization of automotive batteries, which require high output and safety, can be increased.

Further, in an embodiment of the present invention,

Anode, cathode,

A separator interposed between the anode and the cathode, and

There is provided a lithium secondary battery comprising the non-aqueous electrolytic solution of the present invention.

Specifically, the lithium secondary battery of the present invention can be manufactured by injecting the non-aqueous electrolyte solution of the present invention into an electrode assembly in which a cathode, a cathode, and a separator selectively interposed between the anode and the cathode are sequentially laminated. At this time, the positive electrode, negative electrode, and separator forming the electrode assembly may be those conventionally used in the manufacture of the lithium secondary battery.

The positive electrode and the negative electrode constituting the lithium secondary battery of the present invention can be manufactured and used by a conventional method.

First, the positive electrode may be manufactured by forming a positive electrode mixture layer on the positive electrode current collector. The positive electrode mixture layer may be formed by coating a positive electrode slurry containing a positive electrode active material, a binder, a conductive material and a solvent on a positive electrode collector, followed by drying and rolling.

The positive electrode collector is not particularly limited as long as it has electrical conductivity without causing chemical change in the battery. For example, the positive electrode collector may be formed of a metal such as carbon, stainless steel, aluminum, nickel, titanium, sintered carbon, , Nickel, titanium, silver, or the like may be used.

The cathode active material is a compound capable of reversibly intercalating and deintercalating lithium, and may specifically include a lithium composite metal oxide including lithium and at least one metal such as cobalt, manganese, nickel, or aluminum have. More specifically, the lithium composite metal oxide may be at least one selected from the group consisting of lithium-manganese-based oxides (for example, LiMnO ₂ and LiMn ₂ O ₄ ), lithium-cobalt oxides (for example, LiCoO ₂ ), lithium- (for example, LiNiO ₂ and the like), lithium-nickel-manganese-based oxide (for example, LiNi _1-Y Mn _Y O ₂ (where, 0 <Y <1), LiMn _2-z Ni _z O ₄ ( here, 0 <Z <2) and the like), lithium-nickel-cobalt oxide (e.g., LiNi _1-Y1 Co _Y1 O ₂ (here, 0 <Y1 <1) and the like), lithium-manganese-cobalt oxide (e. g., LiCo _1-Y2 Mn _Y2 O ₂ (here, 0 <Y2 <1), LiMn 2 - z1 Co z1 O 4 ( here, 0 <z1 <2) and the like), lithium-nickel -manganese-cobalt oxide (e.g., Ni _p Co _q Mn _r1 (Li) O ₂ (here, 0 <p <1, 0 <q <1, 0 <r1 <1, p + q + r1 = 1) or Li (Ni _p1 Co _q1 Mn _r2) O ₄ (here, 0 <p1 <2, 0 <q1 <2, 0 <r2 <2, p1 + q1 + r2 = 2) , etc.), or a lithium- nickel-cobalt-transition metal (M) oxide (e.g., Li (Ni Co _{p2 q2} Mn _r3 M _S2) O ₂ (here Wherein M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, p2, q2, r3 and s2 are atomic fractions of independent elements, 0 <p2 < (Q2 <1, 0 <r3 <1, 0 <s2 <1, p2 + q2 + r3 + s2 = 1)), and any one or two or more of these compounds may be included.

The lithium composite metal oxide may be LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , lithium nickel manganese cobalt oxide (for example, Li (Ni _1/3 Mn _1/3 Co _{1 / 3} ) O ₂ , Li (Ni _0.6 Mn _0.2 Co _0.2 ) O ₂ , _{Li (Ni 0.5 Mn 0.3 Co 0.2} ) O 2, Li (Ni 0.7 Mn 0.15 Co 0.15) O 2 and _{Li (Ni 0.8 Mn 0.1 Co 0.1} ) O 2 ), or lithium nickel cobalt aluminum oxide (e.g., Li (Ni _0.8 Co _0.15 Al _0.05 ) O _2, etc.).

The cathode active material may be contained in an amount of 80% by weight to 99% by weight based on the total weight of solids in the cathode slurry.

The binder is a component that assists in bonding of the active material to the conductive material and bonding to the current collector, and is usually added in an amount of 1 to 30 wt% based on the total weight of the solid content in the positive electrode slurry. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene (Ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluorine rubber, various copolymers and the like.

The conductive material is usually added in an amount of 1 to 30% by weight based on the total weight of the solid content in the positive electrode slurry.

Such a conductive material is not particularly limited as long as it has electrical conductivity without causing a chemical change in the battery, and includes, for example, graphite; Carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey 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. Concrete examples of commercially available conductive materials include acetylene black series such as Chevron Chemical Company, Denka Singapore Private Limited and Gulf Oil Company products), Ketjenblack, EC series (Available from Armak Company), Vulcan XC-72 (from Cabot Company) and Super P (from Timcal).

The solvent may include an organic solvent such as N-methyl-2-pyrrolidone (NMP), and may be used in an amount that provides a preferable viscosity when the positive electrode active material and optionally a binder and a conductive material are included. For example, the solid content in the slurry containing the positive electrode active material, and optionally the binder and the conductive material may be in the range of 50 wt% to 95 wt%, preferably 70 wt% to 90 wt%.

The negative electrode may be manufactured by forming a negative electrode mixture layer on the negative electrode collector. The negative electrode material mixture layer may be formed by coating a negative electrode current collector with a slurry containing a negative electrode active material, a binder, a conductive material, a solvent, and the like, followed by drying and rolling.

The anode current collector generally has a thickness of 3 to 500 mu m. The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery. Examples of the negative electrode current collector include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel Surface-treated with carbon, nickel, titanium, silver or the like, aluminum-cadmium alloy, or the like can be used. In addition, like the positive electrode collector, fine unevenness can be formed on the surface to enhance the bonding force of the negative electrode active material, and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams and nonwoven fabrics.

In addition, the negative electrode active material may include a lithium-containing titanium composite oxide (LTO); Carbon-based materials such as graphitized carbon and graphite carbon; Li _x Fe ₂ O ₃ (0? _X ?? 1), Li _x WO ₂ (0? _{X? 1} ), Sn _x Me _1-x Me _{y y z} (Me: Mn, Fe, Pb, Ge ; Me ': Al, B, P, Si, Group 1, Group 2 or Group 3 elements of the periodic table, Halogen; 0? X? 1; 1? Y? Metal complex oxides; Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{SnO, SnO 2, PbO, PbO} 2, Pb 2 O 3, Pb 3 O 4, Sb 2 O 3, Sb 2 O 4, Sb 2 O 5, GeO, GeO 2, Bi 2 O 3, Bi 2 O 4, And Bi ₂ O ₅ ; And conductive polymers such as polyacetylene, or a mixture of two or more thereof.

The negative active material may be contained in an amount of 80% by weight to 99% by weight based on the total weight of the solid content in the negative electrode slurry.

The binder is a component that assists in bonding between the conductive material, the active material and the current collector, and is usually added in an amount of 1 to 30% by weight based on the total weight of the solid content in the negative electrode slurry. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene Examples thereof include ethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, fluorine rubber and various copolymers thereof.

The conductive material is a component for further improving the conductivity of the negative electrode active material and may be added in an amount of 1 to 20 wt% based on the total weight of the solid content in the negative electrode slurry. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey 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.

The solvent may include water or an organic solvent such as NMP, alcohol, etc., and may be used in an amount in which the negative electrode active material and, optionally, a binder, a conductive material, and the like are contained in a desired viscosity. For example, the slurry containing the negative electrode active material and, optionally, the binder and the conductive material may be contained to have a solid concentration of 50 wt% to 95 wt%, preferably 70 wt% to 90 wt%.

In addition, the separation membrane blocks the internal short circuit of both electrodes and impregnates the electrolyte. The separation membrane composition is prepared by mixing a polymer resin, a filler and a solvent, and then the separation membrane composition is directly coated on the electrode and dried Or may be formed by casting and drying the separation membrane composition on a support, and then laminating the separation membrane film peeled off from the support on the electrode.

The separator may be a porous polymer film commonly used, such as a porous polymer film made of 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 The polymer film may be used alone or as a laminate thereof, or may be a nonwoven fabric made of a conventional porous nonwoven fabric, for example, glass fiber of high melting point, polyethylene terephthalate fiber or the like, but is not limited thereto.

At this time, the pore diameter of the porous separation membrane is generally 0.01 to 50 μm, and the porosity may be 5 to 95%. The thickness of the porous separator may be generally in the range of 5 to 300 mu m.

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.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Example

Example 1

(Preparation of non-aqueous electrolytic solution)

2.5M LiPF ₆ and 0.2M LiBF ₄ were dissolved in dimethyl carbonate (DMC) to prepare a mixed solution. To 95.3 g of the mixed solution, the surfactant represented by Formula 1a (weight average molecular weight (Mw) = 5,000, n = 35), 4 g of fluorobenzene as the first additive and 0.2 g of dichlorohexylcarbodiimide (DCC) as the second additive were added to prepare a nonaqueous electrolytic solution of the present invention (see Table 1 below).

(Secondary Battery Manufacturing)

(Li (Ni _0.5 Mn _0.3 Co _0.2 ) O ₂ ) as a positive electrode active material, carbon black as a conductive material, and polyvinylidene fluoride (LiNbO ₃ ) as a binder were added to 100 parts by weight of N-methyl-2-pyrrolidone PVDF) in a ratio of 90: 5: 5 (wt%) was added to prepare a positive electrode active material slurry. The positive electrode active material slurry was applied to a positive electrode current collector (Al thin film) having a thickness of 100 m, dried, and roll pressed to prepare a positive electrode.

NMP was mixed with 100 parts by weight of a negative electrode active material mixed with natural graphite and SiO _x (0 <x <1), PVDF as a binder and carbon black as a conductive material in a ratio of 90: 5: 2: 3 (wt% 100 parts by weight were added to prepare a negative electrode active material slurry. The negative electrode active material slurry was coated on a negative electrode current collector (Cu thin film) having a thickness of 90 탆, dried, and rolled to produce a negative electrode.

A positive electrode and a negative electrode prepared by the above-described method were laminated together with a polyethylene porous film to prepare an electrode assembly, which was then placed in a pouch-type battery case, each of the prepared non-aqueous electrolyte solutions was injected, and sealed to produce a lithium secondary battery .

Example  2 to 6

A nonaqueous electrolytic solution and a nonaqueous electrolytic solution were prepared in the same manner as in Example 1, except that a lithium salt, a surfactant, and an additive were included in the composition ratios shown in Table 1 below in the preparation of the nonaqueous electrolytic solution in Example 1 (See Table 1 below). &Lt; tb &gt; &lt; TABLE &gt;

Comparative Example  One

1M LiPF ₆ was dissolved in EC (3: 7 vol%) to prepare a mixed solution. Then, 1.5 g, 0.5 g and 1 g of VC, PS and ESa were added to 97 g of the mixed solution as a second additive A non-aqueous electrolytic solution was prepared.

Then, a lithium secondary battery including the same was prepared in the same manner as in Example 1 (see Table 1 below).

Comparative Example  2

1M LiPF ₆ and 0.2M LiBF ₄ were dissolved in dimethyl carbonate (DMC) to prepare a mixed solution. To 97 g of the mixed solution, 1.5 g, 0.5 g and 1 g of VC, PS and ESa as the second additives were added A non-aqueous electrolytic solution was prepared.

Then, a lithium secondary battery including the same was prepared in the same manner as in Example 1 (see Table 1 below).

Comparative Example  3

2.5 M LiPF ₆ and 0.2 M LiBF ₄ were dissolved in dimethyl carbonate (DMC) to prepare a mixed solution. Then, 99.4 g of the mixed solution was mixed with 0.3 g, 0.2 g and 0.1 g of VC, PS and ESa To prepare a non-aqueous electrolytic solution.

Then, a lithium secondary battery including the same was prepared in the same manner as in Example 1 (see Table 1 below).

Experimental Example 1: Observation of a cathode surface

The cells were disassembled after charging / discharging of 0.1 C, 4.25 V-3 V to the secondary batteries manufactured in Example 1 and Comparative Example 3, and the surface of the negative electrode was visually observed. Then, the side reactions generated on the electrode surface and the lithium metal OCV measurement (0 V) confirmed that the side reactions formed on the cathode surface were plated lithium.

That is, even though charging and discharging proceeded at a low current value of 0.1 C, the surface of the negative electrode of the secondary battery of Comparative Example 3 having the non-aqueous electrolyte solution of the high concentration lithium salt not containing the surfactant and the first additive was dendritic (See FIG. 1), while the negative electrode surface of the secondary battery of Example 1 having the nonaqueous electrolyte solution containing the surfactant and the first additive was subjected to the wettability enhancement and the influence of the negative electrode surface protection It can be confirmed that dendrite is not formed (see Fig. 2).

Experimental Example  2. Lithium salt  Depending on concentration Non-aqueous  Evaluation of heat generation characteristics of electrolyte

Using the differential scanning calorimeter (DSC), each of the secondary batteries prepared in Comparative Example 1, Comparative Example 2 and Example 1 was heated at a rate of 10 ° C / min from 25 ° C to 400 ° C. The results are shown in Fig.

As shown in Fig. 3, in the case of the secondary battery of Example 1 having a nonaqueous electrolyte solution containing a high-concentration lithium salt of 2M or more, an endothermic peak of -140 J / g appears first at a decomposition temperature of 240 deg. The secondary battery of Comparative Example 1 having a non-aqueous electrolyte at a normal concentration showed an exothermic peak of 230 J / g at 260 DEG C and a non-aqueous electrolyte solution containing a lithium salt having a low concentration of 1 M The secondary battery of Comparative Example 2 shows an exothermic peak of 238 J / g at 260 占 폚.

That is, the secondary battery of Example 1 does not include a cyclic solvent such as ethylene carbonate, but an endothermic reaction occurs first by increasing the concentration of the lithium salt, then an exothermic reaction occurs after 300 ° C, J / g) is also significantly lower than that of the secondary batteries of Comparative Examples 1 and 2, and thus the cell safety is improved. On the other hand, in the case of the secondary battery of Comparative Example 2 including the secondary battery of Comparative Example 1 containing the ethylene carbonate solvent and the secondary battery of Comparative Example 2, the exothermic reaction occurred at 300 ° C or lower, and the heat calories of 230 J / g and 238 J / g, which means that the safety of the battery is low.

Experimental Example 3: Initial  Discharge capacity measurement

The secondary batteries prepared in Examples 1 and 2 and Comparative Examples 1 to 3 were charged to 4.25 V at 0.1 C at room temperature (25 캜), discharged to 3 V at 0.1 C, and then measured for discharge capacity Respectively. Each experiment was repeated three times, and the result was calculated as an average value of three measurements and is shown in FIG.

As shown in FIG. 4, the capacity of the secondary battery of Comparative Example 1, which did not include the first lithium salt but had a nonaqueous electrolyte solution containing ethylene carbonate, was about 61.5 Ah, and the ratio including the low- The capacity of the secondary battery of Comparative Example 2 having the aqueous electrolyte solution is about 59.5 Ah and the capacity of the secondary battery of Comparative Example 3 having the nonaqueous electrolyte solution containing the high concentration lithium salt of 2M or more is about 61 Ah, The capacity of the secondary batteries of Examples 1 and 2 having the non-aqueous electrolyte solution containing the activator and the first additive was 63 Ah or more, which was improved by about 2 to 5% as compared with the capacity of the secondary batteries of Comparative Examples 1 to 3 .

Experimental Example  4. Surface tension and Li  Mobility measurement

The surface tension (mV / m) of each of the non-aqueous electrolytes prepared in Examples 1 to 6 and Comparative Examples 1 to 3 was measured at 25 占 폚 using a ring system measurement method (KRUSS tensiometer K11 model apparatus) The results are shown in Table 2 below.

Each of the non-aqueous electrolytes prepared in Examples 1 to 6 and Comparative Examples 1 to 3 was subjected to temperature stabilization in a chamber at 25 DEG C for 30 minutes using a VMP3 Multichannel potentiostat of Bio-logic Science Instruments Co., The cation transport rate (tLi ⁺ ) was measured, and the results are shown in Table 2 below.

In addition, for each of the non-aqueous electrolytes prepared in Examples 1 to 6 and Comparative Examples 1 to 3, Viscosity at 25 캜 was measured at 100 rpm using a viscometer (DV-III ULTRA, Brrokfield). For calibration, a viscometer calibration standard solution manufactured by Nippon Grizzlies Co., Ltd. was used. The results are shown in Table 2 below.

The concentration (M) of the second lithium salt Viscosity (cPs) Li ⁺ ion transport rate Surface tension (mN / m) Example 1 2.5 10.20 0.489 20.1 Example 2 2.5 10.10 0.488 20.5 Example 3 2.5 9.95 0.488 20.0 Example 4 3.5 12.50 0.529 21.2 Example 5 2 8.12 0.465 19.6 Example 6 5 24.2 0.598 23.2 Comparative Example 1 One 2.3 0.408 31.1 Comparative Example 2 One 1.56 0.406 29.9 Comparative Example 3 2.5 10.15 0.487 35.2

As shown in Table 2, in the case of the non-aqueous electrolytic solution of the present invention of Examples 1 to 6 including the high-concentration electrolyte salt and the surfactant, the surface tension was 23.2 mN / m And the Li ⁺ ion transport rate is as high as 0.465 or more.

On the other hand, the secondary battery of Comparative Example 1 having a non-aqueous electrolyte containing ethylene carbonate as a main component had a viscosity as low as 2.3 cPs, a surface tension as high as 31.1 mN / m and a Li ⁺ ion transport rate as low as 0.408 .

Also, the secondary battery of Comparative Example 2 having a non-aqueous electrolyte containing a low-concentration lithium salt containing no ethylene carbonate at a concentration of 1M or less had a low viscosity of 1.56 cPs, a low Li ⁺ ion transport rate of 0.406, Is 29.9 mN / m.

The secondary battery of Comparative Example 3 having a non-aqueous electrolyte containing a high concentration lithium salt containing no ethylene carbonate instead of 2M had a high Li ⁺ ion transport ratio of 0.487, a high viscosity of 10.15 cPs and a surface tension of 35.2 mN / m. &lt; / RTI &gt;

Experimental Example 5. Measurement of Resistance Characteristic

Each of the secondary batteries manufactured in Example 1 and Comparative Examples 1 to 3 was charged to 0.33 C and 4.25 V, and then, through a voltage drop caused by discharging at 2.5 C pulse for 30 seconds in a state where the SOC was adjusted to 50% sec) was measured. The measured resistance values are shown in Fig.

5, the resistance value of the secondary battery of Example 1 of the present invention having a non-aqueous electrolyte solution containing a high concentration of lithium salt of 2M or more and a surfactant was 0.7 mohm and the resistance value was 1.5 mohm Whereas the secondary batteries of Comparative Examples 1 to 3 all had an initial resistance value exceeding 1.0 mohm and a resistance value after 30 seconds increased to about 2.0 mohm or more. In particular, it can be seen that the resistance value of the secondary battery of Comparative Example 1 having the non-aqueous electrolyte at a normal concentration containing ethylene carbonate is the highest.

Experimental Example 6. Measurement of Capacitance Change

The secondary battery of Example 1 and Comparative Examples 1 to 3 was subjected to 1 C / 1 C charging and discharging at 25 ° C in the 4.25 V-3 V voltage region, and the discharge capacity retention ratio was measured. The results are shown in FIG.

As shown in Fig. 6, the secondary battery of Example 1 of the present invention having a nonaqueous electrolyte solution containing a high-concentration lithium salt and a surfactant of 2M or more in comparison with the secondary batteries of Comparative Examples 1 to 3 has a cycle capacity characteristic It can be seen that it lasts for the longest time.

On the other hand, in the secondary battery of Comparative Example 2 having a non-aqueous electrolyte containing a low-concentration lithium salt not containing ethylene carbonate and having a concentration of 1M or lower, the decomposition reaction of the electrolyte on the surface of the negative electrode was promoted, (sudden death) occurs.

In the case of the secondary battery of Comparative Example 3 having a non-aqueous electrolyte containing a high-concentration lithium salt not containing ethylene carbonate instead of the high-concentration lithium salt of 2M or more, the nonaqueous electrolytic solution containing a low- It can be seen that the cycle capacity characteristics are better than that of the secondary battery of Comparative Example 2, while the poor SEI film is formed, and the cycle capacity performance rapidly deteriorates after 350 cycles.

Further, in the case of the secondary battery of Comparative Example 1 having a non-aqueous electrolyte containing ethylene carbonate as a main component, the SEI film formation reaction was induced on the surface of the negative electrode by ethylene carbonate, and the cycle capacity characteristics at room temperature did not include ethylene carbonate Which is superior to the secondary batteries of Comparative Examples 2 and 3 having a nonaqueous electrolyte solution.

Claims (11)

Claim 1 of a lithium salt LiBF _4,
A second lithium salt different from the first lithium salt,
Organic solvent,
A surfactant represented by the following formula (1), and
A first additive,
Wherein the concentration of the second lithium salt is 2M to 6M.
[Chemical Formula 1]

In Formula 1,
R is a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms,
R ₁ and R ₂ are each independently a fluorine-substituted alkylene group having 1 to 5 carbon atoms,
R 'is an aliphatic, alicyclic or aromatic hydrocarbon group,
R "is hydrogen or an alkyl group having 1 to 3 carbon atoms,
n is an integer of 1 to 80,
m and o are each an integer of 1 to 3;
In Formula 1,
The aliphatic hydrocarbon group is an alkylene group having 1 to 20 carbon atoms; An alkylene group having 1 to 20 carbon atoms containing an isocyanate group (NCO); An alkoxysilyl group having 1 to 20 carbon atoms; An alkenylene group having 2 to 20 carbon atoms; Or an alkynylene group having 2 to 20 carbon atoms,
The alicyclic hydrocarbon group is a substituted or unsubstituted cycloalkylene group having 4 to 20 carbon atoms; A substituted or unsubstituted C 4 -C 20 cycloalkylene group containing an isocyanate group (NCO); A cycloalkenylene group having 4 to 20 carbon atoms; Or a heterocycloalkylene group having 2 to 20 carbon atoms,
The aromatic hydrocarbon group is a substituted or unsubstituted arylene group having 6 to 20 carbon atoms; Or a heteroarylene group having 2 to 20 carbon atoms.
The method according to claim 1,
And the concentration of the second lithium salt is 2M to 5M.
The method according to claim 1,
Wherein the molar ratio of the first lithium salt: the second lithium salt is 0.001: 1 to 1: 1.
The method according to claim 1,
Wherein the second lithium salt comprises Li ^{&lt; +} &gt; as a cation,
Anion ^{F -, Cl -, Br -} , I -, NO 3 -, N (CN) 2 -, ClO 4 -, AlO 4 -, AlCl 4 -, PF 6 -, SbF 6 -, AsF 6 -, BF ^{_{2 C 2 O 4 -, BC}} 4 O 8 -, (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 -, C 4 F 9 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 ^-, and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- .
The method according to claim 1,
Wherein the surfactant represented by the formula (1) is at least one selected from the group consisting of compounds represented by the following formulas (1a) to (1c).
[Formula 1a]

In formula (1a)
n1 is an integer of 1 to 80, specifically 1 to 40;

[Chemical Formula 1b]

In the above formula (1b)
n2 is an integer of 1 to 80, specifically 1 to 40;

[Chemical Formula 1c]

In the above formula (1c)
n3 is an integer of 1 to 80, specifically 1 to 40;
The method according to claim 1,
Wherein the surfactant represented by Formula 1 is contained in an amount of 0.5 to 20% by weight based on the total weight of the non-aqueous electrolytic solution.
The method according to claim 1,
Wherein the first additive is at least one compound selected from the group consisting of fluorobenzene, lithium oxalyl difluoroborate, and lithium bis (oxalato) borate.
The method according to claim 1,
Wherein the first additive is contained in an amount of 0.1 wt% to 15 wt% based on the total weight of the non-aqueous electrolytic solution.
The method according to claim 1,
Wherein the non-aqueous electrolytic solution further comprises at least one second additive selected from the group consisting of N, N'-dicyclohexylcarbodiimide, vinylene carbonate, saturated sulphone, and cyclic sulfite.
Anode, cathode,
A separator interposed between the anode and the cathode, and
A non-aqueous electrolytic solution,
Wherein the non-aqueous electrolyte is the non-aqueous electrolyte according to claim 1.

Images