KR20170110995A - Non-aqueous electrolyte solution and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a process for the production of a polymer electrolyte membrane comprising: i) a nonaqueous organic solvent comprising propylene carbonate (PC) and ethylene carbonate (EC); And ii) an electrolyte additive comprising an electrolyte additive comprising lithium bis (fluorosulfonyl) imide, LiFSI and tetravinylsilane (TVS), and a lithium secondary battery comprising the same do.
The nonaqueous electrolytic solution of the present invention can improve the low temperature and room temperature output characteristics by forming a solid SEI film in the cathode at the time of initial charging of the lithium secondary battery including the same, Can be improved.

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 organic solvent comprising propylene carbonate (PC) and ethylene carbonate (EC); And an electrolyte additive including lithium bis (fluorosulfonyl) imide (LiFSI) and tetravinylsilane (TVS), and a lithium secondary battery comprising the non-aqueous electrolyte, .

As technology development and demand for mobile devices are increasing, the demand for secondary batteries as energy sources is rapidly increasing. Among these secondary batteries, lithium secondary batteries having high energy density and voltage have been commercialized and widely used.

Lithium metal oxide is used as the positive electrode active material of the lithium secondary battery, and lithium metal, lithium alloy, crystalline or amorphous carbon or carbon composite material is used as the negative electrode active material. The active material is coated on the current collector with an appropriate thickness and length, or the active material itself is coated in a film form and wrapped or laminated with a separator as an insulator to form an electrode group. The electrode group is then placed in a can or similar container, Thereby manufacturing a secondary battery.

This lithium secondary battery is charged and discharged while repeating the process of intercalating lithium ions from the lithium metal oxide of the anode into the graphite electrode of the cathode and deintercalating the lithium ions. At this time, since lithium is highly reactive, it reacts with the carbon electrode to form Li ₂ CO ₃ , LiO, LiOH and the like to form a film on the surface of the cathode. This film is called Solid Electrolyte Interface (SEI) film. The SEI film formed at the beginning of charging prevents the reaction between lithium ion and carbon anode or other materials during charging and discharging. It also acts as an ion tunnel, allowing only lithium ions to pass through. This ion tunnel serves to prevent the collapse of the structure of the carbon anode by co-intercalating the organic solvent of the electrolyte with the high molecular weight, which is solvated by lithium ion, together with the carbon anode do.

Therefore, in order to improve the high-temperature cycle characteristics and the low-temperature output of the lithium secondary battery, a solid SEI film must always be formed on the cathode of the lithium secondary battery. Once the SEI membrane is formed at the time of initial charging, it is used as an ion tunnel to prevent the reaction between the lithium ion and the negative electrode or other materials during repetition of charging and discharging by using the battery and passing only lithium ions between the electrolyte and the negative electrode .

Until now, a variety of non-aqueous organic solvents have been used in non-aqueous electrolytic solutions, and propylene carbonate has been used as a non-aqueous organic solvent. However, this has the problem of causing irreversible decomposition reaction with graphite materials. In order to replace this, an ethylene / 3-component nonaqueous organic solvent including ethylene carbonate (EC) has been used. However, since ethylene carbonate has a high melting point, the use temperature is limited, and there is a problem that battery performance may be considerably deteriorated at a low temperature.

KR 2009-0030237 A

It is an object of the present invention to provide a nonaqueous electrolyte secondary battery which can improve low temperature and room temperature output characteristics as well as reduce the initial resistance of the lithium secondary battery and improve the room temperature and high temperature cycle characteristics, An electrolyte, and a lithium secondary battery comprising the same.

In order to solve the problems to be solved, the present invention relates to a process for producing a polymer electrolyte membrane, comprising: i) a nonaqueous organic solvent comprising propylene carbonate (PC) and ethylene carbonate (EC); And ii) an electrolyte additive comprising lithium bis (fluorosulfonyl) imide (LiFSI) and tetravinylsilane (TVS).

The present invention also relates to a positive electrode comprising a positive electrode active material; A negative electrode comprising a negative electrode active material; A separator interposed between the anode and the cathode; And a lithium secondary battery comprising the non-aqueous electrolyte.

The nonaqueous electrolytic solution of the present invention can improve the low temperature and room temperature output characteristics by forming a solid SEI film in the cathode at the time of initial charging of the lithium secondary battery including the lithium ion secondary battery of the present invention, The cycle characteristics at room temperature, and the capacity characteristics after high temperature storage can be improved.

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

The non-aqueous electrolytic solution of the present invention comprises i) a non-aqueous organic solvent comprising propylene carbonate (PC) and ethylene carbonate (EC); And ii) an electrolyte additive comprising lithium bis (fluorosulfonyl) imide (LiFSI) and tetravinylsilane (TVS) represented by the following formula (1).

[Chemical Formula 1]

According to one example of the present invention, problems caused when propylene carbonate (PC) and ethylene carbonate (EC) are respectively used are solved by controlling the mixing ratio of propylene carbonate (PC) and ethylene carbonate (EC) , The synergistic effect by mixing the non-aqueous organic solvent can be manifested by utilizing the advantages of each of these solvents. In addition, since they contain lithium bifluorosulfonylimide in these mixed non-aqueous organic solvents, by forming a solid SEI film at the cathode at the time of initial charging, the low temperature and room temperature output characteristics as well as the anode The capacity of the lithium secondary battery can be improved at the same time by suppressing the decomposition of the surface and preventing the oxidation reaction of the electrolytic solution. Further, since the tetravinylsilane is decomposed upon initial activation of the battery, the SEI Contributing to the formation of a film to form a solid film, thereby reducing the low-temperature resistance and improving the cell performance at a high temperature.

In general, ethylene carbonate (EC) as a non-aqueous organic solvent used in a non-aqueous electrolyte has been mainly used for a lithium secondary battery because of its excellent affinity with a carbon material. However, when EC is used too much, CO ₂ gas is generated due to EC decomposition, which may adversely affect the performance of the secondary battery. In addition, low-temperature characteristics are poor due to high melting point characteristics, There is a problem that the high output characteristic is low.

On the other hand, the nonaqueous electrolytic solution containing propylene carbonate has characteristics of excellent low temperature characteristics and high output characteristics due to high conductivity. However, propylene carbonate causes irreversible decomposition reaction with graphite material, and thus has a problem in use with graphite. In addition, there has been a problem that the capacity of the lithium secondary battery is lowered due to electrode refraction due to propylene carbonate at high temperature cycles depending on the electrode thickness.

Particularly, when propylene carbonate is used as a non-aqueous organic solvent together with a lithium salt such as LiPF ₆ , propylene carbonate is used in a process of forming a SEI film in a lithium secondary battery using a carbon electrode and a process of forming a lithium ion solvated by propylene carbonate An immense amount of irreversible reaction may occur during the insertion between the carbon layers. This may cause problems such as deterioration of battery performance such as cycle characteristics.

Further, when lithium ion solvated by propylene carbonate is inserted into the carbon layer constituting the negative electrode, exfoliation of the carbon surface layer may proceed. This exfoliation can be caused by the gas generated when the solvent is decomposed between the carbon layers causing a large distortion between the carbon layers. The peeling of the surface layer and the decomposition of the electrolyte can proceed continuously. Therefore, when the propylene carbonate electrolyte is used in combination with the carbonaceous anode material, an effective SEI film is not formed and lithium ions may not be inserted.

Therefore, in order to overcome the problems of ethylene carbonate and propylene carbonate and to maximize the above advantages, the present invention uses a non-aqueous organic solvent and a propylene carbonate in a proper composition in combination with ethylene carbonate, It is possible to provide a nonaqueous electrolytic solution having improved conductivity characteristics and improved output characteristics of the lithium secondary battery and improved low temperature characteristics and also excellent electrochemical affinity with the carbon layer.

In addition, in the present invention, the above-mentioned problems in using a lithium salt such as propylene carbonate and LiPF ₆ together can be solved by combining them using lithium bisfluorosulfonylimide.

The lithium bisfluorosulfonylimide is added to a non-aqueous electrolytic solution as a lithium salt to improve a low-temperature output characteristic by forming a stable and stable SEI film on a negative electrode, as well as to suppress decomposition of an anode surface And the oxidation reaction of the electrolytic solution can be prevented.

According to one embodiment of the present invention, the mixing ratio of the propylene carbonate and the ethylene carbonate (EC) solvent as the non-aqueous organic solvent may have an important effect on improving both the low temperature and the room temperature output, and the high temperature storage capacity characteristics.

The mixing ratio of propylene carbonate to ethylene carbonate (EC) may be, for example, 1: 0.1 to 1: 2 by weight, preferably 1: 0.3 to 1: 1, more preferably 1: 0.4 to 1: When the mixing ratio is satisfied, a synergistic effect by mixing the two non-aqueous organic solvents can be exhibited.

As the non-aqueous organic solvent according to one embodiment of the present invention, propylene carbonate may be included in an amount of 5 to 60 parts by weight, specifically 10 to 40 parts by weight, based on 100 parts by weight of the non-aqueous organic solvent. If the amount of the propylene carbonate is less than 5 parts by weight, the swelling phenomenon may be generated in which the thickness of the battery is increased due to the decomposition of the surface of the anode during the high-temperature cycling, It is difficult to form a solid SEI film and the high-temperature characteristics may be deteriorated.

According to one embodiment of the present invention, by appropriately controlling the ethylene carbonate within the mixing ratio within the amount of the propylene carbonate used, not only the low temperature and normal temperature output characteristics of the lithium secondary battery of the present invention but also the high temperature storage capacity characteristics So that an optimum effect can be achieved.

According to an embodiment of the present invention, in addition to the ethylene carbonate (EC) and the propylene carbonate, the non-aqueous organic solvent which can be further contained in the non-aqueous electrolyte solution can minimize the decomposition due to the oxidation reaction or the like during the charge- , As long as it can exhibit the desired properties together with the additives.

Examples of the non-aqueous organic solvent that can be further included in the non-aqueous electrolyte according to an embodiment of the present invention include ethyl propionate (EP), methyl propionate (MP), butylene carbonate BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC) and ethyl propyl carbonate One, or a mixture of two or more thereof.

According to an embodiment of the present invention, the concentration of the lithium bisfluorosulfonylimide in the non-aqueous electrolytic solution may be from 0.1 mol / L to 2 mol / L, and more preferably from 0.5 mol / L to 1.5 mol / L Lt; / RTI > If the concentration of the lithium bis-fluorosulfonylimide is less than 0.1 mol / l, the effect of improving the low-temperature power and improving the high-temperature cycle characteristics of the battery may be insignificant. If the lithium bisfluorosulfonylimide concentration is less than 2 mol / l, side reactions within the electrolyte may occur excessively during charging and discharging of the battery, and swelling may occur.

In order to further prevent such side reactions, the non-aqueous electrolytic solution of the present invention may further include a lithium salt. Examples of the lithium salt include lithium salts such as LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN ₃ SO ₂ ) ₂ , CF ₃ SO ₃ Li, LiC (CF ₃ SO ₂ ) ₃ and LiC ₄ BO ₈ , or a mixture of two or more thereof.

The mixing ratio of the lithium salt and lithium bisfluorosulfonylimide may be 1: 1 to 1: 9 in a molar ratio. When the mixing ratio of the lithium salt and the lithium bisfluorosulfonylimide is out of the range of the molar ratio, a side reaction in the electrolyte may occur excessively during charging and discharging of the battery, resulting in swelling.

Specifically, the molar ratio of the lithium salt to the lithium bisfluorosulfonylimide may be 1: 6 to 1: 9. For example, when the mixing ratio of the lithium salt and the lithium bisfluorosulfonylimide is 1: 6 or more, the process of forming the SEI film in the lithium ion battery and the process of forming the lithium ion solvated by propylene carbonate and ethylene carbonate It is possible to prevent a large amount of irreversible reaction from occurring in the process of inserting between the negative electrodes and to prevent the peeling of the negative electrode surface layer (for example, carbon surface layer) and the decomposition of the electrolyte solution to improve the low temperature output of the secondary battery, The cycle characteristics and the capacity characteristics can be improved.

The content of the tetravinylsilane may be 0.01 to 3% by weight, specifically 0.05 to 2% by weight, more specifically 0.1 to 1.5% by weight based on the total weight of the nonaqueous electrolyte solution.

When the content of the tetravinylsilane is 0.01 wt% or more, an appropriate effect due to the addition of tetravinylsilane can be expected. When the content of the tetravinylsilane is 3 wt% or less, It is possible to prevent problems such as increasing the irreversible capacity of the battery while exhibiting a synergistic effect of the storage characteristics and the high-temperature cycle characteristics.

The content of the tetravinylsilane can be controlled according to the amount of lithium bisfluorosulfonylimide added, and thus the lithium bisfluorosulfonylimide and tetravinylsilane can be used in a weight ratio of 1: 0.001 to 1: 1 Specifically, it can be used in a weight ratio of 1: 0.002 to 0.5, more specifically, in a weight ratio of 1: 0.01 to 1: 0.3.

When the lithium bisfluorosulfonylimide and the tetravinylsilane are used in a weight ratio of 1: 0.001 to 1: 1, the lithium secondary battery, which can be generated by the addition of the lithium bisfluorosulfonylimide, The tetravinylsilane can appropriately suppress the side reaction in the electrolyte when the battery is charged and discharged.

Meanwhile, a lithium secondary battery according to an embodiment of the present invention includes a cathode including a cathode active material; A negative electrode comprising a negative electrode active material; A separator interposed between the anode and the cathode; And the non-aqueous electrolytic solution.

Here, the cathode active material may include a manganese spinel-based active material, a lithium metal oxide, or a mixture thereof. Further, the lithium metal oxide may be selected from the group consisting of a lithium-manganese-based oxide, a lithium-nickel-manganese-based oxide, a lithium-manganese-cobalt oxide, and a lithium-nickel-manganese-cobalt oxide, is _{LiCoO 2, LiNiO 2, LiMnO 2} , LiMn 2 O 4, Li (Ni a Co b Mn c) O 2 ( where, 0 <a <1, 0 <b <1, 0 <c <1, a + b + c = 1), LiNi 1 - Y Co Y O 2, LiCo 1 - Y Mn Y O 2, LiNi 1 - Y Mn Y O 2 ( here, 0≤Y <1), Li ( Ni a Co b _{Mn c) O 4 (0 <} a <2, 0 <b <2, 0 <c <2, a + b + c = 2), LiMn 2 - z Ni z O 4, LiMn 2 - z Co z O 4 (Where 0 &lt; Z &lt; 2).

In particular, in one embodiment of the present invention, the lithium-nickel-manganese-cobalt-based oxide may include an oxide represented by the following formula (2).

(2)

Li _{1 + x} (Ni _a Co _b Mn _c ) O ₂

0.55? A? 0.65, 0.18? B? 0.22, 0.18? C? 0.22, -0.2? X? 0.2, and x + a + b + c + = 1.

As the negative electrode active material, a carbonaceous anode active material such as a crystalline carbon, an amorphous carbon, or a carbon composite may be used alone or in combination of two or more. Preferably, the carbonaceous active material may be a crystalline carbon and a graphite such as natural graphite and artificial graphite (graphite) carbon.

Specifically, in the lithium secondary battery, the positive electrode or negative electrode is prepared by mixing a mixture of a positive electrode or a negative electrode active material, a conductive agent and a binder with a predetermined solvent on a positive electrode or negative electrode current collector to prepare a slurry, Applying the slurry on the current collector, and then drying the slurry.

According to an embodiment of the present invention, the cathode current collector generally has a thickness of 3 to 500 mu m. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery, and may be formed of a material such as stainless steel, aluminum, nickel, titanium, sintered carbon, or a surface of aluminum or stainless steel Treated with carbon, nickel, titanium, silver or the like may be used.

The cathode current collector may have fine irregularities on the surface thereof to increase the adhesive force of the cathode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

The negative electrode current collector is generally made to have a thickness of 3 [mu] m to 500 [mu] m. Such an anode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery, and may be formed of a material such as copper, stainless steel, aluminum, nickel, titanium, fired carbon, surface of copper or stainless steel A surface treated with carbon, nickel, titanium, silver or the like, an 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.

The conductive agent used for the positive electrode or negative electrode slurry is usually added in an amount of 1 to 20 wt% based on the total weight of the mixture including the positive electrode or negative electrode active material. Such a conductive agent is not particularly limited as long as it has electrical conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The binder is a component that assists in bonding of the positive electrode or negative electrode active material with the conductive agent and bonding to the current collector, and is usually added in an amount of 1 to 20 wt% based on the total weight of the mixture containing the positive electrode or negative electrode active material. Examples of such binders include polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HEP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate ), Polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer ), Sulfonated EPDM, styrene butylene rubber (SBR), fluorine rubber, various copolymers, and the like.

In addition, preferred examples of the solvent include dimethyl sulfoxide (DMSO), alcohol, N-methylpyrrolidone (NMP), acetone or water, and are removed during drying.

As the separator, a conventional porous polymer film conventionally used as a separator, for example, 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 porous polymer film made of a polymer may be used alone or in a laminated form, or a nonwoven fabric made of a conventional porous nonwoven fabric such as a glass fiber having a high melting point, polyethylene terephthalate fiber or the like may be used. no.

The battery case used in the present invention may be of any type that is commonly used in the art, and is not limited in its external shape depending on the use of the battery. For example, a cylindrical case, a square type, a pouch type, (coin) type or the like.

The lithium secondary battery according to the present invention can be used not only in a battery cell used as a power source of a small device but also as a unit cell in a middle- or large-sized battery module including a plurality of battery cells. Preferable examples of the above medium and large-sized devices include, but are not limited to, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric power storage systems, and the like.

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

EXAMPLES The present invention will be further illustrated by the following examples and experimental examples, but the present invention is not limited by these examples and experimental examples.

Example 1

[Preparation of non-aqueous electrolytic solution]

Aqueous organic solvent having a composition of propylene carbonate (PC): ethylene carbonate (EC): ethyl methyl carbonate (EMC) 2: 1: 7 (volume ratio) and LiPF ₆ based on the total amount of non- And 0.1 mol / l of lithium bis-fluorosulfonylimide and 0.2 wt% of tetravinylsilane were added to prepare a non-aqueous electrolytic solution.

[Production of lithium secondary battery]

96% by weight of a mixture of LiMn ₂ O ₄ and Li (Ni _0.6 Co _0.2 Mn _0.2 ) O ₂ as a cathode active material, ₂ % by weight of carbon black as a conductive material, 2% by weight of polyvinylidene fluoride (PVdF) % Was added to the solvent N-methyl-2-pyrrolidone (NMP) to prepare a positive electrode mixture slurry. The positive electrode mixture slurry was applied to an aluminum (Al) thin film having a thickness of about 20 탆 and dried to prepare a positive electrode, followed by roll pressing to prepare a positive electrode.

Further, a negative electrode mixture slurry was prepared by adding carbon powder as a negative electrode active material, PVdF as a binder and carbon black as a conductive agent to 96 wt%, 3 wt% and 1 wt%, respectively, as a solvent. The negative electrode mixture slurry was applied to a copper (Cu) thin film as an anode current collector having a thickness of about 10 占 퐉 and dried to prepare a negative electrode, followed by roll pressing to prepare a negative electrode.

The thus prepared positive electrode and negative electrode were fabricated by polymerizing a polymer type cell with a separator composed of three layers of polypropylene / polyethylene / polypropylene (PP / PE / PP), and then the prepared non-aqueous electrolyte was injected, The preparation of the battery was completed.

Example 2

LiPF ₆ Except that the amount of lithium bisfluorosulfonylimide was changed to 0.17 mol / L and 0.83 mol / L (molar ratio of about 1: 5) of lithium bisfluorosulfonylimide, A battery was prepared.

Example 3

A non-aqueous electrolytic solution and a lithium secondary battery were prepared in the same manner as in Example 1 except that the tetravinylsilane was used in an amount of 0.5 wt%.

Comparative Example 1

A nonaqueous electrolytic solution and a lithium secondary battery were prepared in the same manner as in Example 1 except that LiFSI and tetravinylsilane were not used.

Comparative Example 2

A non-aqueous electrolytic solution and a lithium secondary battery were prepared in the same manner as in Example 1, except that LiFSI was not used.

Comparative Example 3

A nonaqueous electrolytic solution and a lithium secondary battery were prepared in the same manner as in Example 1 except that tetravinylsilane was not used.

Comparative Example 4

A non-aqueous electrolytic solution and a lithium secondary battery were prepared in the same manner as in Example 1, except that Li (Ni _0.5 Co _0.3 Mn _0.2 ) O ₂ was used as the cathode active material.

Comparative Example 5

A non-aqueous electrolytic solution and a lithium secondary battery were prepared in the same manner as in Example 1, except that LiCoO ₂ was used as the cathode active material.

Experimental Example 1

<Capacity measurement after high temperature storage>

The lithium secondary batteries of Examples 1 to 3 and Comparative Examples 1 to 5 were charged at 1 C to 4.2 V / 38 mA at a constant current / constant voltage (CC / CV) condition at room temperature, , And the discharge capacity thereof was measured to obtain the capacity of the 0th battery. Then, the lithium secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 5 were stored at 60 占 폚 for 12 weeks and then charged to 1 C at 4.2 V / 38 mA under a constant current / constant voltage (CC / CV) Then, the battery was discharged at 2 C to 2.5 V under a constant current (CC) condition, and its discharge capacity was measured to obtain the capacity after 12 weeks.

The capacity after high-temperature storage is calculated by the capacity X100 of the capacity after 12 weeks / 0-th storage, and is shown in Table 1 as a percentage value.

Experimental Example 2

<Output measurement after high temperature storage>

The lithium secondary batteries of Examples 1 to 3 and Comparative Examples 1 to 5 were discharged at an SOC (charge depth) of 50 C at a room temperature for 10 seconds for 10 seconds to calculate a low temperature output, Respectively. Then, the lithium secondary batteries of Examples 1 to 3 and Comparative Examples 1 to 5 were stored at 60 DEG C for 12 weeks, discharged at SOC (charge depth) of 50% at 5 C for 10 seconds at room temperature, The output was calculated and the output was taken as the output after 12 weeks.

The output after high-temperature storage is calculated by the output X100 of the output / 0-th week after 12 weeks and is shown in Table 1 as a percentage value.

Experimental Example 3

&Lt; Measurement of cell thickness increase rate &

The thickness of the lithium secondary batteries of Examples 1 to 3 and Comparative Examples 1 to 5 was measured and the thickness after storage at 60 占 폚 for 12 weeks was measured to determine the rate of cell thickness increase (thickness after 16 weeks / -100, and the values are shown in Table 1 below.

Experimental Example 4

<Low Temperature Output Characteristics>

The low temperature output was calculated by the voltage difference generated by discharging the lithium secondary batteries of Examples 1 to 3 and Comparative Examples 1 to 5 at -30 ° C and 0.5 ° C for 10 seconds at SOC (charge depth) (Output of the secondary battery to be measured / output X100 of the secondary battery of Comparative Example 5) -100 based on the value of the secondary battery of Comparative Example 5, and is shown in Table 1 as a percentage value.

Experimental Example 5

<Room temperature output characteristics>

The room temperature output was calculated from the voltage difference generated by discharging the lithium secondary batteries of Examples 1 to 3 and Comparative Examples 1 to 5 at room temperature (25 ° C) at 0.5 C for 10 seconds at SOC (charge depth) (Output of the secondary battery to be measured / output X100 of the secondary battery of Comparative Example 5) -100 based on the value of the secondary battery of Comparative Example 5, and is shown in Table 1 as a percentage value.

LiPF ₆ : LiFSI additive
(weight%) High Temperature Storage Characteristics
(%) Print (%)
(Compared to Comparative Example 5) Volume Print Battery Thickness
increase Low temperature Room temperature Example 1 1: 9 0.2 93.5 96.5 11.0 6.5 15.1 Example 2 1: 5 0.2 93.1 96.1 10.6 5.2 8.2 Example 3 1: 9 0.5 94.5 97.8 8.2 3.9 12.2 Comparative Example 1 1: 0 0 81.2 85.7 25.9 -10.1 -11.0 Comparative Example 2 1: 0 0.2 83.9 86.3 17.5 -9.2 -7.1 Comparative Example 3 1: 9 0 88.5 88.8 23.7 0 0 Comparative Example 4 1: 9 0.2 89.1 89.9 18.0 0.3 10.7 Comparative Example 5 1: 9 0.2 87.9 87.9 19.1 -0.2 7.5

Referring to Table 1, the lithium secondary batteries of Examples 1 to 3 including LiFSI and tetravinylsilane as electrolyte additives were excellent in high temperature storage characteristics and excellent in low temperature and room temperature output characteristics. In contrast, the lithium secondary batteries of Comparative Examples 1 to 3, which did not contain any one of LiFSI and tetravinylsilane, had poorer high-temperature storage characteristics and lower-temperature and normal-temperature output characteristics than the lithium secondary batteries of Examples 1 to 3 .

On the other hand, the batteries of Comparative Examples 4 and 5 were excellent in high-temperature storage characteristics, or low-temperature and room-temperature output characteristics, compared with the batteries of Comparative Examples 1 to 3, including LiFSI and tetravinylsilane as electrolyte additive. However, these characteristics were not excellent as in the lithium secondary batteries of Examples 1 to 3, and it was confirmed that lithium nickel cobalt manganese oxide having a specific composition was more effective when used as the cathode active material.

Claims (16)

i) a non-aqueous organic solvent comprising propylene carbonate (PC) and ethylene carbonate (EC); And ii) an electrolyte additive comprising an electrolyte additive comprising lithium bis (fluorosulfonyl) imide (LiFSI) and tetravinylsilane (TVS).
The method according to claim 1,
Wherein the mixing ratio of the propylene carbonate to the ethylene carbonate is 1: 0.1 to 2 by weight.
The method according to claim 1,
Wherein the non-aqueous electrolytic solution further comprises a lithium salt.
The method of claim 3,
Wherein the mixing ratio of the lithium salt to lithium bisfluorosulfonylimide is 1: 1 to 9 in molar ratio.
5. The method of claim 4,
Wherein a mixing ratio of the lithium salt to lithium bisfluorosulfonylimide is 1: 6 to 9 in a molar ratio.
The method according to claim 1,
Wherein the lithium bisfluorosulfonylimide has a concentration of 0.1 mol / L to 2 mol / L in the non-aqueous electrolytic solution.
The method according to claim 1,
Wherein the content of the propylene carbonate is 5 parts by weight to 60 parts by weight based on 100 parts by weight of the non-aqueous organic solvent.
8. The method of claim 7,
Wherein the content of the propylene carbonate is 10 parts by weight to 40 parts by weight based on 100 parts by weight of the non-aqueous organic solvent.
The method according to claim 1,
Wherein the content of the tetravinylsilane is 0.01 wt% to 3 wt% based on the total weight of the nonaqueous electrolyte solution.
The method according to claim 1,
Wherein the lithium bis fluorosulfonyl imide and the tetravinyl silane are in a weight ratio of 1: 0.01 to 1.
The method according to claim 1,
The non-aqueous organic solvent may be at least one selected from the group consisting of ethyl propionate (EP), methyl propionate (MP), butylen carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate Wherein the electrolytic solution further comprises any one selected from the group consisting of carbonate (DPC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC) and ethyl propyl carbonate (EPC), or a mixture of two or more thereof.
The method of claim 3,
The lithium salt is _{LiPF 6, LiBF 4, LiSbF 6} , LiAsF 6, LiClO 4, LiN (C 2 F 5 SO 2) 2, LiN (CF 3 SO 2) 2, CF 3 SO 3 Li, LiC (CF 3 SO ₂ ) ₃ and LiC ₄ BO ₈ , or a mixture of two or more thereof.
A cathode comprising a cathode active material; A negative electrode comprising a negative electrode active material; A separator interposed between the anode and the cathode; And
A lithium secondary battery comprising the non-aqueous electrolytic solution of claim 1.
14. The method of claim 13,
Wherein the cathode active material is a manganese spinel-based active material, a lithium metal oxide, or a mixture thereof.
15. The method of claim 14,
Wherein the lithium metal oxide is selected from the group consisting of a lithium-manganese-based oxide, a lithium-nickel-manganese-based oxide, a lithium-manganese-cobalt oxide, and a lithium-nickel-manganese-cobalt oxide.
16. The method of claim 15,
Wherein the lithium-nickel-manganese-cobalt-based oxide comprises an oxide represented by the following formula (2).
(2)
Li _{1 + x} (Ni _a Co _b Mn _c ) O ₂
0.55? A? 0.65, 0.18? B? 0.22, 0.18? C? 0.22, -0.2? X? 0.2, and x + a + b + c + = 1.