KR102167590B1 - Non-aqueous electrolyte solution and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention provides i) a non-aqueous organic solvent comprising propylene carbonate (PC) and ethylene carbonate (EC); And ii) lithium bis (fluorosulfonyl) imide (Lithium bis (fluorosulfonyl) imide, LiFSI) and tetravinylsilane (tetravinylsilane, TVS) containing an electrolyte additive containing a non-aqueous electrolyte and a lithium secondary battery comprising the same do.
The non-aqueous electrolyte of the present invention can improve low and room temperature output characteristics by forming a solid SEI film at the negative electrode during initial charging of a lithium secondary battery including the same, as well as high temperature and room temperature cycle characteristics, and capacity characteristics after high temperature storage. Can improve.

Description

Non-aqueous electrolyte and lithium secondary battery containing the same {NON-AQUEOUS ELECTROLYTE SOLUTION AND LITHIUM SECONDARY BATTERY COMPRISING THE SAME}

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

As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing, and among these secondary batteries, lithium secondary batteries having a high energy density and voltage are commercialized and widely used.

Lithium metal oxide is used as a positive electrode active material of a lithium secondary battery, and lithium metal, a lithium alloy, crystalline or amorphous carbon or a carbon composite is used as the negative electrode active material. The active material is applied to a current collector with an appropriate thickness and length, or the active material itself is coated in a film shape and wound or stacked together with a separator as an insulator to form an electrode group, and then placed in a can or similar container, and then an electrolyte is injected. Manufacture a secondary battery.

In such a lithium secondary battery, charging and discharging are performed while repeating a process in which lithium ions are intercalated and deintercalated from the lithium metal oxide of the positive electrode to the graphite electrode of the negative electrode. At this time, since lithium is highly reactive, it reacts with the carbon electrode to generate Li ₂ CO ₃ , LiO, LiOH, etc. to form a film on the surface of the negative electrode. Such a film is called a solid electrolyte (SEI) film, and the SEI film formed at the beginning of charging prevents the reaction between lithium ions and carbon negative electrodes or other materials during charging and discharging. It also acts as an ion tunnel, allowing only lithium ions to pass. This ion tunnel serves to prevent the collapse of the structure of the carbon negative electrode through co-intercalation of the organic solvents of the high molecular weight electrolyte that move together by solvating lithium ions. do.

Therefore, in order to improve the high-temperature cycle characteristics and low-temperature output of the lithium secondary battery, a solid SEI film must be formed on the negative electrode of the lithium secondary battery. Once the SEI film is formed at the time of initial charge, it prevents the reaction between lithium ions and negative electrodes or other materials when charging and discharging is repeated after using the battery, and acts as an ion tunnel through which only lithium ions pass between the electrolyte and the negative electrode. Will perform.

Until now, in the non-aqueous electrolyte solution, various non-aqueous organic solvents have been used, and propylene carbonate is used as the non-aqueous organic solvent, but this has a problem that may cause an irreversible decomposition reaction with the graphite material. To replace this, two/three-component non-aqueous organic solvents have been used including ethylene carbonate (EC) as a basis. However, since ethylene carbonate has a high melting point, its use temperature is limited, and there is a problem that can lead to significant battery performance degradation at low temperatures.

KR 2009-0030237 A

The problem to be solved of the present invention is that it is possible to improve low and room temperature output characteristics, as well as reduce the initial resistance of the lithium secondary battery, and to improve the room temperature and high temperature cycle characteristics, and capacity characteristics after high temperature storage. To provide an electrolyte, and a lithium secondary battery including the same.

In order to solve the problem to be solved, the present invention provides i) a non-aqueous organic solvent including propylene carbonate (PC) and ethylene carbonate (EC); And ii) an electrolyte additive including lithium bis (fluorosulfonyl) imide (LiFSI) and tetravinylsilane (TVS).

In addition, the present invention includes a positive electrode including a positive electrode active material; A negative electrode including a negative active material; A separator interposed between the positive electrode and the negative electrode; And it provides a lithium secondary battery including the non-aqueous electrolyte.

The non-aqueous electrolyte solution of the present invention can improve low and room temperature output characteristics by forming a solid SEI film at the negative electrode during initial charging of a lithium secondary battery including the same, as well as reducing the initial resistance of the lithium secondary battery, and It is possible to improve the room temperature cycle characteristics, and the capacity characteristics after high temperature storage.

Hereinafter, the present invention will be described in more detail to aid understanding of the present invention. The terms or words used in this specification and claims should not be construed as being limited to their usual or dictionary meanings, and the inventor may appropriately define the concept of terms in order to describe his own invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

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

[Formula 1]

According to an example of the present invention, by adjusting the mixing ratio of propylene carbonate (PC) and ethylene carbonate (EC), which are non-aqueous organic solvents, problems arising when using each of propylene carbonate (PC) and ethylene carbonate (EC) are solved. , Taking advantage of the advantages of each of these solvents, it is possible to express a synergistic effect by mixing non-aqueous organic solvents. In addition, since lithium bisfluorosulfonylimide is included in these mixed non-aqueous organic solvents, a solid SEI film is formed at the negative electrode during initial charging, so that the positive electrode can be generated during operation at a high temperature cycle of 45℃ or higher as well as low temperature and room temperature output characteristics. By suppressing the decomposition of the surface and preventing the oxidation reaction of the electrolyte, the capacity characteristics of the lithium secondary battery can be improved at the same time, and since it contains tetravinylsilane, the tetravinylsilane is decomposed during the initial activation of the battery and thus the SEI of the negative electrode. By participating in the formation of the film, it helps to form a solid film, thereby reducing low-temperature resistance and improving cell performance at high temperatures.

In general, ethylene carbonate (EC) as a non-aqueous organic solvent used in a non-aqueous electrolyte solution has been mainly used in lithium secondary batteries because of its excellent affinity with a carbon material. However, if too much EC is used, CO ₂ gas is generated due to EC decomposition, so that not only may adversely affect the performance of the secondary battery, but also have poor low temperature characteristics due to high melting point characteristics and low conductivity. Therefore, there is a problem with low high output characteristics.

In contrast, the non-aqueous electrolyte solution containing propylene carbonate has excellent low-temperature characteristics and high output characteristics due to high conductivity. However, since propylene carbonate causes an irreversible decomposition reaction with a graphite material, there is a problem of being limited in use with graphite. In addition, depending on the thickness of the electrode, there is a problem in that the capacity of the lithium secondary battery decreases due to electrode exforiation caused by propylene carbonate during a high-temperature cycle.

In particular, when propylene carbonate is used as a non-aqueous organic solvent with a lithium salt such as LiPF ₆ , propylene carbonate is a process of forming an SEI film in a lithium secondary battery using a carbon electrode, and lithium ions solvated by propylene carbonate. In the process of being inserted between the carbon layers, an irreversible reaction of an enormous capacity may occur. This may cause a problem of deteriorating battery performance, such as cycle characteristics.

In addition, when lithium ions solvated by propylene carbonate are inserted into the carbon layer constituting the negative electrode, exfoliation of the carbon surface layer may proceed. This exfoliation may be caused by 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 decomposition of the electrolyte may be continuously performed. Accordingly, when the propylene carbonate electrolyte is used in combination with the carbon-based negative electrode material, an effective SEI film may not be formed and lithium ions may not be inserted.

Accordingly, in the present invention, in order to overcome the problems of ethylene carbonate and propylene carbonate, and to maximize the above advantages, by mixing the amount of propylene carbonate with the existing ethylene carbonate as a non-aqueous organic solvent in an appropriate composition, the non-aqueous electrolyte By improving the conductivity characteristics, the output characteristics of the lithium secondary battery are improved, and the low-temperature characteristics are improved to provide a non-aqueous electrolyte having excellent electrochemical affinity with the carbon layer.

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

The lithium bisfluorosulfonylimide is added to the non-aqueous electrolyte as a lithium salt to form a strong and stable SEI film on the negative electrode, thereby improving low-temperature output characteristics and suppressing decomposition of the positive electrode surface that may occur during high-temperature cycle operation. And it can prevent the oxidation reaction of the electrolyte.

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

The mixing ratio of the propylene carbonate and ethylene carbonate (EC) may be, for example, 1:0.1 to 1:2 weight ratio, preferably 1:0.3 to 1:1, more preferably 1:0.4 to 1:0.9, When satisfying the range of the mixing ratio, a synergistic effect may be expressed by mixing two non-aqueous organic solvents.

As a non-aqueous organic solvent according to an embodiment of the present invention, propylene carbonate may be included in 5 parts by weight to 60 parts by weight, specifically 10 parts by weight to 40 parts by weight based on 100 parts by weight of the non-aqueous organic solvent. If the content of propylene carbonate is less than 5 parts by weight, gas is continuously generated due to decomposition of the positive electrode surface during a high-temperature cycle, resulting in a swelling phenomenon that increases the thickness of the battery, and if it exceeds 60 parts by weight, the initial rechargeable battery negative electrode It is difficult to form a solid SEI film at, and high temperature properties may be deteriorated.

According to an embodiment of the present invention, by appropriately adjusting ethylene carbonate within the range of the mixing ratio within the amount of propylene carbonate used, not only the low temperature and room temperature output characteristics of the lithium secondary battery of the present invention, but also the capacity characteristics after high temperature storage, etc. To achieve the optimum effect.

According to an embodiment of the present invention, as a non-aqueous organic solvent that may be further included in the non-aqueous electrolyte in addition to the ethylene carbonate (EC) and propylene carbonate, decomposition due to oxidation reactions during the charging and discharging process of the battery may be minimized. In addition, there is no limitation as long as it can exhibit the desired properties with additives.

Non-aqueous organic solvents that may be further included in the non-aqueous electrolyte according to an embodiment of the present invention include, for example, 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 (EPC) any selected from the group consisting of One, or a mixture of two or more of them may be mentioned.

Meanwhile, according to an embodiment of the present invention, the lithium bisfluorosulfonylimide may have a concentration of 0.1 mol/ℓ to 2 mol/ℓ in the non-aqueous electrolyte solution, and specifically 0.5 mol/ℓ to 1.5 mol/ℓ. Can be If the concentration of the lithium bisfluorosulfonylimide is less than 0.1 mol/L, the effect of improving the low-temperature output and high-temperature cycle characteristics of the battery may be insignificant, and the concentration of the lithium bisfluorosulfonylimide is 2 If mol/L is exceeded, side reactions in the electrolyte solution may occur excessively during charging and discharging of the battery, resulting in a swelling phenomenon.

In order to further prevent such side reactions, the non-aqueous electrolyte solution of the present invention may further contain a lithium salt. The lithium salt may be a lithium salt commonly used in the art, for example, 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 It} may be any one selected from the group consisting of or a mixture of two or more of them.

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 lithium bisfluorosulfonylimide is out of the range of the molar ratio, side reactions in the electrolyte solution excessively occur during charging and discharging of the battery, resulting in a swelling phenomenon.

Specifically, the mixing ratio of the lithium salt and lithium bisfluorosulfonylimide is a molar ratio, and may be 1:6 to 1:9. For example, when the mixing ratio of the lithium salt and lithium bisfluorosulfonylimide is 1:6 or more in a molar ratio, the process of forming an SEI film in a lithium ion battery, and lithium ions solvated by propylene carbonate and ethylene carbonate It can prevent irreversible reaction of enormous capacity during the process of being inserted between the cathodes, and suppress the peeling of the anode surface layer (for example, carbon surface layer) and decomposition of the electrolyte, improving the low-temperature output of the secondary battery, and storing at high temperature. After that, the effect of improving the cycle characteristics and capacity characteristics can be exhibited.

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

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

The content of the tetravinylsilane can be adjusted according to the amount of lithium bis fluoro sulfonyl imide, and thus the lithium bis fluoro sulfonyl imide and the tetravinylsilane may be used in a weight ratio of 1:0.001 to 1:1. And, specifically, it may be used in a weight ratio of 1:0.002 to 0.5, more specifically, it may be used in a weight ratio of 1:0.01 to 1:0.3.

When the lithium bis fluoro sulfonyl imide and the tetravinyl silane are used in a weight ratio of 1:0.001 to 1:1, at room temperature of a lithium secondary battery that may be generated by the addition of the lithium bis fluorosulfonyl imide The tetravinylsilane can appropriately inhibit side reactions in the electrolyte during charging and discharging of the battery.

On the other hand, the lithium secondary battery according to an embodiment of the present invention includes a positive electrode including a positive electrode active material; A negative electrode including a negative active material; A separator interposed between the positive electrode and the negative electrode; And the non-aqueous electrolyte.

Here, the positive electrode active material may include a manganese spinel-based active material, lithium metal oxide, or a mixture thereof. Further, the lithium metal oxide may be selected from the group consisting of lithium-manganese-based oxide, lithium-nickel-manganese-based oxide, lithium-manganese-cobalt-based oxide, and lithium-nickel-manganese-cobalt-based oxide, and more specifically Is LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li(Ni _a Co _b Mn _c )O ₂ (here, 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 (Here, it may be 0<Z<2).

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

[Formula 2]

Li _1+x (Ni _a Co _b Mn _c )O ₂

In the above formula, 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.

On the other hand, as the negative active material, a carbon-based negative active material such as crystalline carbon, amorphous carbon, or carbon composite may be used alone or in combination of two or more, and graphite materials such as natural graphite and artificial graphite as crystalline carbon (graphite) May be carbon.

Specifically, in a lithium secondary battery, the positive or negative electrode is, for example, a mixture of a positive or negative active material, a conductive agent, and a binder on a positive or negative current collector to prepare a slurry, It can be prepared by applying the slurry on a current collector and then drying it.

According to an embodiment of the present invention, the positive electrode current collector is generally made to have a thickness of 3 μm to 500 μm. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or the surface of aluminum or stainless steel. For example, those treated with carbon, nickel, titanium, silver, or the like may be used.

The positive electrode current collector may increase the adhesion of the positive electrode active material by forming fine irregularities on its surface, and various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics are possible.

The negative electrode current collector is generally made to have a thickness of 3 μm to 500 μm. Such a negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical changes to the battery, for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel. For the surface treatment with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloys, etc. may be used. In addition, like the positive electrode current collector, it is possible to enhance the bonding strength of the negative electrode active material by forming fine irregularities on the surface thereof, and may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

The conductive agent used in the positive or negative electrode slurry is typically added in an amount of 1 to 20% by weight based on the total weight of the mixture including the positive or negative active material. Such a conductive agent is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; Carbon blacks such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride, 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 may be used.

The binder is a component that aids in binding of a positive or negative active material to a conductive agent and to a current collector, and is typically added in an amount of 1 to 20% by weight based on the total weight of the mixture including the positive or negative active material. Examples of such a binder include polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HEP), polyvinylidenefluoride, polyacrylonitrile, and polymethylmethacrylate. ), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM ), sulfonated EPDM, styrene butyrene rubber (SBR), fluorine rubber, and various kinds of binder polymers such as various copolymers may be used.

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

As the separator, a conventional porous polymer film conventionally used as a separator, for example, an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer, and an ethylene/methacrylate copolymer, etc. A porous polymer film made of a polymer may be used alone or by stacking them, or a conventional porous nonwoven fabric, for example, a nonwoven fabric made of a high melting point glass fiber, polyethylene terephthalate fiber, etc., may be used, but is limited thereto. no.

The battery case used in the present invention may be adopted that is commonly used in the art, and there is no limitation on the appearance according to the use of the battery, for example, a cylindrical shape using a can, a square shape, a pouch type, or a coin It can be (coin) type, etc.

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

Hereinafter, examples will be described in detail to illustrate the present invention in detail. However, the embodiments according to the present invention may be modified in various forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. Embodiments of the present invention are provided to more completely describe the present invention to those of ordinary skill in the art.

Example

Hereinafter, examples and experimental examples will be further described, but the present invention is not limited by these examples and experimental examples.

Example 1

[Preparation of non-aqueous electrolyte solution]

Propylene carbonate (PC):ethylene carbonate (EC):ethylmethyl carbonate (EMC) 2:1:7 (volume ratio) as a non-aqueous organic solvent and lithium salt based on the total amount of non-aqueous electrolyte LiPF ₆ 0.1 mol/l was added, and 0.9 mol/l of lithium bisfluorosulfonylimide and 0.2 wt% of tetravinylsilane were added to prepare a non-aqueous electrolyte.

[Manufacture 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 positive electrode active material, ₂ % by weight of carbon black as a conductive material, 2% by weight of polyvinylidene fluoride (PVdF) as a binder % Was added to N-methyl-2-pyrrolidone (NMP) as a solvent to prepare a positive electrode mixture slurry. The positive electrode mixture slurry was applied to an aluminum (Al) thin film of a positive electrode current collector having a thickness of about 20 μm, dried to prepare a positive electrode, and then roll press to prepare a positive electrode.

In addition, carbon powder as an anode active material, PVdF as a binder, and carbon black as a conductive material in 96% by weight, 3% by weight, and 1% by weight, respectively, were added to NMP as a solvent to prepare a negative electrode mixture slurry. The negative electrode mixture slurry was coated on a copper (Cu) thin film of a negative electrode current collector having a thickness of about 10 μm, dried to prepare a negative electrode, and then roll press to prepare a negative electrode.

The prepared positive electrode and negative electrode were prepared as a polymer battery by a conventional method together with a separator consisting of three layers of polypropylene/polyethylene/polypropylene (PP/PE/PP), and then the prepared non-aqueous electrolyte was injected to form a lithium secondary battery. The production of the battery was completed.

Example 2

LiPF ₆ In the same manner as in Example 1, except that the amount was changed to 0.17 mol/l and lithium bisfluorosulfonylimide 0.83 mol/l (molar ratio of about 1:5), a non-aqueous electrolyte and lithium secondary The battery was prepared.

Example 3

A non-aqueous electrolyte solution and a lithium secondary battery were prepared in the same manner as in Example 1, except that 0.5% by weight of tetravinylsilane was used.

Comparative Example 1

A non-aqueous electrolyte 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 electrolyte 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 non-aqueous electrolyte 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 electrolyte 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 positive electrode active material.

Comparative Example 5

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

Experimental Example 1

<Measure capacity after high temperature storage>

The lithium secondary batteries of Examples 1 to 3 and Comparative Examples 1 to 5 were charged at room temperature at constant current/constant voltage (CC/CV) to 4.2 V/38 mA at 1 C, and then 2.5 V under constant current (CC) conditions. The discharge was performed at 2 C until, and the discharge capacity was measured to obtain the capacity at week 0. Then, the lithium secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 5 were stored at 60° C. for 12 weeks, and then charged at 1 C to 4.2 V/38 mA under constant current/constant voltage (CC/CV) conditions at room temperature. Then, it was discharged at 2 C to 2.5 V under constant current (CC) conditions, and the discharge capacity was measured to obtain the capacity after 12 weeks.

The capacity after high-temperature storage was calculated as the capacity X100 at the capacity of the 0 weeks after 12 weeks, and is shown in Table 1 below as a% value.

Experimental Example 2

<Output measurement after high temperature storage>

The low-temperature output was calculated with the voltage difference generated by discharging the lithium secondary batteries of Examples 1 to 3 and Comparative Examples 1 to 5 at room temperature at SOC (depth of charge) 50 to 5 C for 10 seconds, and the output as the output of week 0 I did. Then, the lithium secondary batteries of Examples 1 to 3 and Comparative Examples 1 to 5 were stored at 60°C for 12 weeks, and then discharged at 50% SOC (depth of charge) at room temperature for 10 seconds. The output was calculated and the output was taken as the output after 12 weeks.

The output after high-temperature storage was calculated as output x 100 of output / 0 week after 12 weeks, and is shown in Table 1 below as a% value.

Experimental Example 3

<Measurement of battery 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° C. for 12 weeks was measured, and the rate of increase in the battery thickness was determined (thickness after 16 weeks/thickness at week 0×100). It was calculated as -100 and shown in Table 1 below as a% value.

Experimental Example 4

<Low temperature output characteristics>

The low-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 -30°C at 0.5 C at SOC (depth of charge) 50 for 10 seconds. Based on the value of the secondary battery of Comparative Example 3, (output of the secondary battery to be measured/output of the secondary battery of Comparative Example 3 X100) -100 was calculated as a% value and is shown in Table 1 below.

Experimental Example 5

<Room temperature output characteristics>

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 0.5 C at room temperature (25° C.) at SOC (depth of charge) 50 for 10 seconds. Based on the value of the secondary battery of Comparative Example 3, (output of the secondary battery to be measured/output of the secondary battery of Comparative Example 3 X100) -100 was calculated as a% value and is shown in Table 1 below.

LiPF ₆ :LiFSI additive
(weight%) High temperature storage characteristics
(%) Print (%)
(Comparative Example 3) 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 containing LiFSI and tetravinylsilane as electrolyte additives have excellent high-temperature storage characteristics and excellent low-temperature and room-temperature output characteristics. In contrast, the lithium secondary batteries of Comparative Examples 1 to 3 that do not contain any one of LiFSI and tetravinylsilane were inferior to the lithium secondary batteries of Examples 1 to 3 in high-temperature storage characteristics and low-temperature and room-temperature output characteristics. .

On the other hand, the batteries of Comparative Examples 4 and 5 included LiFSI and tetravinylsilane as electrolyte additives, and were superior to the batteries of Comparative Examples 1 to 3 in high-temperature storage characteristics or low-temperature and room-temperature output characteristics. However, not all of the above characteristics were excellent as in the lithium secondary batteries of Examples 1 to 3, and through this, it was confirmed that it was more effective when lithium nickel cobalt manganese oxide having a specific composition was used as a positive electrode active material.

Claims (16)

i) a non-aqueous organic solvent comprising propylene carbonate (PC) and ethylene carbonate (EC); And ii) an electrolyte additive including lithium bis (fluorosulfonyl) imide (LiFSI) and tetravinylsilane (TVS), and
The lithium bis fluoro sulfonyl imide and the tetravinylsilane are 1: Non-aqueous electrolyte solution to be contained in a weight ratio of 0.01 to 1.
The method of claim 1,
The mixing ratio of the propylene carbonate and ethylene carbonate is 1:0.1 to 2 weight ratio of the non-aqueous electrolyte.
The method of claim 1,
The non-aqueous electrolyte solution further comprises a lithium salt.
The method of claim 3,
The mixing ratio of the lithium salt and lithium bisfluorosulfonylimide is 1:1 to 9 as a molar ratio.
The method of claim 4,
The mixing ratio of the lithium salt and lithium bisfluorosulfonylimide is a molar ratio of 1:6 to 9, a non-aqueous electrolyte.
The method of claim 1,
The lithium bisfluorosulfonylimide is a non-aqueous electrolyte having a concentration of 0.1 mol/L to 2 mol/L in the non-aqueous electrolyte.
The method of claim 1,
The content of propylene carbonate is 5 parts by weight to 60 parts by weight based on 100 parts by weight of the non-aqueous organic solvent.
The method of claim 7,
The content of 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 of claim 1,
The content of the tetravinylsilane is 0.01% by weight to 3% by weight based on the total weight of the non-aqueous electrolyte solution.
delete The method of claim 1,
The non-aqueous organic solvent is 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 (EPC) any one selected from the group consisting of, or a non-aqueous electrolyte further comprising a mixture of two or more of them.
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 ) Any one selected from the group consisting of ₃ and LiC ₄ BO ₈ or a mixture of two or more of them.
A positive electrode including a positive electrode active material; A negative electrode including a negative active material; A separator interposed between the positive electrode and the negative electrode; And
A lithium secondary battery comprising the non-aqueous electrolyte of claim 1.
The method of claim 13,
The positive electrode active material is a lithium secondary battery of a manganese spinel-based active material, lithium metal oxide, or a mixture thereof.
The method of claim 14,
The lithium metal oxide is a lithium secondary battery selected from the group consisting of a lithium-manganese-based oxide, a lithium-nickel-manganese-based oxide, a lithium-manganese-cobalt-based oxide, and a lithium-nickel-manganese-cobalt-based oxide.
The method of claim 15,
The lithium-nickel-manganese-cobalt-based oxide is a lithium secondary battery comprising an oxide represented by Formula 2 below.
[Formula 2]
Li _1+x (Ni _a Co _b Mn _c )O ₂
(In the above formula, 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.)