KR102143100B1 - Non-aqueous liquid electrolyte, lithium secondary battery comprising the same and preparation method thereof - Google Patents

Abstract

The present invention provides i) a fluorine-containing ether compound, ii) a fluorine-containing sulfone compound, iii) a non-aqueous organic solvent, and iv) a non-aqueous electrolyte containing a lithium salt, a lithium secondary battery including the same, and a method for manufacturing the same do.
The non-aqueous electrolyte of the present invention can improve the stability of the SEI film and the life characteristics of a secondary battery by including two types of fluorine-containing compounds.
In addition, by performing the high-temperature activation process in a specific temperature range using the non-aqueous electrolyte solution containing the two fluorine-containing compounds, the amount of gas generated after the activation process and the thickness of the battery cell can be reduced, thereby reducing the secondary battery. The capacity characteristics of can be further improved.

Description

Non-aqueous electrolyte, lithium secondary battery including the same, and manufacturing method thereof {NON-AQUEOUS LIQUID ELECTROLYTE, LITHIUM SECONDARY BATTERY COMPRISING THE SAME AND PREPARATION METHOD THEREOF}

The present invention relates to a non-aqueous electrolyte, a lithium secondary battery containing the same, and a method for manufacturing the same, and more specifically, a non-aqueous electrolyte containing a fluorine-containing ether compound and a fluorine-containing sulfone compound as two additives, including the same It relates to a lithium secondary battery and a manufacturing method thereof.

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 high energy density and voltage are commercialized and widely used.

Lithium metal oxide is used as a positive electrode active material for 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 the process of intercalating and deintercalating lithium ions from the lithium metal oxide of the positive electrode into 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 or LiOH 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. In addition, it performs the role of an ion tunnel to pass only lithium ions. The ion tunnel serves to prevent disintegration of the structure of the carbon negative electrode by solvating lithium ions so that organic solvents of an electrolytic solution having a high molecular weight that move together are co-tuned with the carbon negative electrode.

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 the negative electrode 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.

Conventionally, in the case of an electrolyte that does not contain an electrolyte additive or contains a non-aqueous organic solvent having poor characteristics or an electrolyte additive, it has been difficult to expect an improvement in the performance of a secondary battery due to the formation of an uneven SEI film. In particular, if the type or amount of the non-aqueous organic solvent, electrolyte additive, or lithium salt contained in the electrolyte cannot be adjusted to the required amount, the electrolyte causes an oxidation reaction during high-temperature reaction, ultimately increasing the irreversible capacity of the secondary battery and lowering the output characteristics. There was a problem.

Therefore, it is possible to improve the stability and uniformity of the SEI film by improving the conventional problems, while minimizing the increase in gas generation rate and thickness of the secondary battery, thereby improving the capacity and life characteristics of the secondary battery. There is a need to develop a secondary battery.

Korean Patent Application Publication No. 10-2009-0100249A

The present invention is devised to solve the problem of the prior art.

The first technical problem to be solved of the present invention is to provide a non-aqueous electrolyte solution capable of securing stability and uniformity of the SEI film.

A second technical problem to be solved of the present invention is to provide a lithium secondary battery having improved life characteristics and capacity characteristics by including the non-aqueous electrolyte.

A third technical problem to be solved by the present invention is to provide a method of manufacturing a lithium secondary battery capable of reducing the amount of gas generated and the thickness of the battery cell after the activation process.

The present invention is devised to solve the problem of the prior art.

The first technical problem to be solved of the present invention is to provide a non-aqueous electrolyte solution comprising i) a fluorine-containing ether compound, ii) a fluorine-containing sulfone compound, iii) a non-aqueous organic solvent, and iv) a lithium salt.

A second technical problem to be solved of the present invention is to provide a lithium secondary battery including the non-aqueous electrolyte.

The third technical problem to be solved of the present invention is (a) inserting an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode into a battery case to manufacture a battery cell; (b) injecting and sealing a non-aqueous electrolyte solution containing a fluorine-containing ether compound and a fluorine-containing sulfone compound into the battery case; And (c) to provide a method of manufacturing a lithium secondary battery comprising the step of performing the activation process of the battery cell at a temperature of 45 ℃ to 60 ℃.

The non-aqueous electrolyte of the present invention can improve the stability and uniformity of the SEI film and the life characteristics of a secondary battery by including two types of fluorine-containing compounds, such as a fluorine-containing ether compound and a fluorine-containing sulfone compound.

In addition, by using the non-aqueous electrolyte solution containing the two fluorine-containing compounds and performing a high-temperature activation process in a specific temperature range, the amount of gas generated after the activation process and the thickness of the battery cell can be reduced, thereby reducing secondary The capacity characteristics of the battery can be further improved.

Hereinafter, the present invention will be described in more detail to aid understanding of the present invention. The terms or words used in the specification and claims should not be interpreted as being limited to ordinary or dictionary meanings, and the inventor can appropriately define the concept of terms in order to best describe his or her invention. Based on the principle of being present, it should be interpreted as meanings and concepts consistent with the technical spirit of the present invention.

Specifically, in one embodiment of the present invention

i) fluorine-containing ether compounds,

ii) fluorine-containing sulfone compounds,

iii) a non-aqueous organic solvent, and

iv) It provides a non-aqueous electrolyte solution containing a lithium salt.

According to an embodiment of the present invention, the non-aqueous electrolyte may secure stability and uniformity of the SEI film by including two types of fluorine-containing compounds, thereby further improving the life characteristics and capacity characteristics of the lithium secondary battery. I can.

More specifically, the non-aqueous electrolyte solution includes i) a fluorine-containing ether compound and ii) a fluorine-containing sulfone compound as two kinds of fluorine-containing compound additives.

The i) fluorine-containing ether compounds are 1H, 1H, 5H-perfluoropentyl-1,1,2,2-tetrafluoroethyl ether, nonafluorobutyl methyl ether, (2-(difluoromethoxymethyl )-1,1,1,2,3,3,3-heptafluoro propane, and perfluoro-[15]-crown-5-ether, any one selected from the group consisting of, or a mixture of two or more thereof Can include.

In particular, when i) 1H, 1H, 5H-perfluoropentyl-1,1,2,2-tetrafluoroethyl ether among the fluorine-containing ether compounds is included as an additive, compared to other fluorine-containing ether compounds The high boiling point (> 100℃) makes it easy to use in high-temperature processes and has good solubility in solvents, so it is particularly excellent in terms of uniformity and stability of the SEI film .

The fluorine-containing ether-based compound may be included in an amount of 2% by weight to 5% by weight, preferably 3% by weight to 5% by weight, based on the total weight of the non-aqueous electrolyte.

If the fluorine-containing ether-based compound is less than the above range, the stability effect of the SEI film may be insignificant and the capacity characteristics and life characteristics of the secondary battery may be deteriorated. If the amount exceeds the above range, the viscosity of the non-aqueous electrolyte solution is caused by an excessive amount. As is increased, the life of the secondary battery may decrease.

In addition, ii) the fluorine-containing sulfone-based compound includes any one selected from the group consisting of 1,2-ethandisulfonyl difluoride, ethanesulfonyl fluoride, and phenylmethylsulfonyl fluoride, or a mixture of two or more thereof. can do.

In particular, ii) in the case of containing 1,2-ethanedisulfonyl difluoride as an additive among the fluorine-containing sulfone-based compounds, the reactivity at the negative electrode is superior to that of other fluorine-containing sulfone-based compounds. great.

The fluorine-containing sulfone-based compound may be included in an amount of 0.5% to 5% by weight, preferably 0.5% to 3% by weight, more preferably 0.5% to 1.5% by weight based on the total weight of the non-aqueous electrolyte. .

If the fluorine-containing sulfone-based compound is less than the above range, the stability effect of the SEI film may be insignificant, resulting in a problem that the capacity characteristics and life characteristics of the secondary battery are deteriorated. can do.

As described above, according to an embodiment of the present invention, as a non-aqueous electrolyte additive, i) a fluorine-containing ether compound, particularly 1H, 1H, 5H-perfluoropentyl-1,1,2,2-tetrafluoroethyl When the ether and ii) a fluorine-containing sulfone-based compound, particularly 1,2-ethandisulfonyl difluoride, are included in the above content range, the optimum stability effect of the SEI film can be achieved. Accordingly, the life characteristics of the secondary battery and The capacity characteristics can be remarkably improved.

In addition, the non-aqueous electrolyte solution according to an embodiment of the present invention may include (iii) a non-aqueous organic solvent.

The non-aqueous organic solvent is propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, dipropyl carbonate, fluoro-ethylene carbonate, dimethyl sulfoxide, acetonitrile, dime. Oxyethane, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, tetrahydrofuran, methyl formate, methyl acetate, ethyl acetate, Isopropyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate ), methyl butylate, and ethyl butylate, or a mixture of two or more of them. In addition, preferably, the non-aqueous organic solvent may include propylene carbonate, ethylene carbonate and propyl propionate.

In addition, the non-aqueous electrolyte according to an embodiment of the present invention may further include a vinylidene carbonate-based compound as a second additive in some cases.

The vinylidene carbonate-based compound may play a role in helping to form an SEI film. The kind of the vinylidene carbonate-based compound is not limited as long as it can play the role, for example, vinylene carbonate (VC), vinylene ethylene carbonate (VEC), or a combination thereof Can be

In addition, in the non-aqueous electrolyte solution used in an embodiment of the present invention, the lithium salt (iv)) that may be included as an electrolyte may be used without limitation as long as it is commonly used in an electrolyte solution for a secondary battery. the lithium salt anion is ^{F -, Cl -, I -} , NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (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 -, 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 - use at least one member selected from the group consisting of I can.

The lithium salt is, 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( It may be any one selected from the group consisting of CF ₃ SO ₂ ) ₃ and LiC ₄ BO ₈ , or a mixture of two or more of them.

The lithium salt may be included in the range of 0.8M to 2.0M in the non-aqueous electrolyte.

In addition, in an embodiment of the present invention, a lithium secondary battery including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and the non-aqueous electrolyte solution of the present invention may be provided.

In addition, in an embodiment of the present invention, a method of manufacturing the lithium secondary battery may be provided.

Specifically, the method for manufacturing a lithium secondary battery of the present invention

(a) inserting an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode into a battery case to manufacture a battery cell (step a);

(b) injecting and sealing a non-aqueous electrolyte solution containing a fluorine-containing ether compound and a fluorine-containing sulfone compound into the battery case (step b); And

(c) performing the activation process of the battery cell at a temperature of 45°C to 60°C (step c).

According to the method of manufacturing a lithium secondary battery according to an exemplary embodiment of the present invention, a non-aqueous electrolyte solution containing two fluorine-containing compounds is used, and the gas of the battery cell includes a high-temperature activation process step in the specific range. It is possible to reduce the amount of emission and the thickness of the battery cell, thereby further improving the life characteristics and capacity characteristics of the secondary battery.

Specifically, in the manufacturing method of a lithium secondary battery according to an embodiment of the present invention, the (step a) includes an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode in a battery case. This is a step of manufacturing a battery cell by inserting it.

A battery cell 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; It may be prepared by a method commonly used in the art by using a separator interposed between the anode and the cathode.

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-nickel-manganese-cobalt-based oxides, lithium-manganese-based oxides, lithium-nickel-manganese-based oxides, and lithium-manganese-cobalt-based oxides, and more specifically 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).

Meanwhile, as the negative electrode 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 material, and a binder on a positive or negative current collector to prepare a slurry, It can be prepared by applying this 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. The negative electrode current collector is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surfaces The surface treatment with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. may be used. In addition, like the positive electrode current collector, it is also possible to form a fine unevenness on the surface to enhance the bonding force of the negative electrode active material, and may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

The conductive material 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. The conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, graphite such as natural graphite or artificial 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 fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder, 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 bonding of a positive or negative active material to a conductive material and bonding 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 vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HEP), polyvinylidenefluoride, polyacrylonitrile, polymethylmethacrylate , Polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM) , Sulfonated EPDM, styrene butadiene rubber (SBR), fluorine rubber, 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 in the drying process.

As the separator, a conventional porous polymer film conventionally used as a separator, for example, ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer and ethylene/methacrylate copolymer, etc. A porous polymer film made of a polymer may be used alone or by laminating them, or a conventional porous nonwoven fabric, such as a high melting point glass fiber, a polyethylene terephthalate fiber, or the like, may be used, but is not limited thereto. no.

In addition, in the method of manufacturing a lithium secondary battery of the present invention, in (step b), a non-aqueous electrolyte solution including a fluorine-containing ether compound and a fluorine-containing sulfone compound is injected into the battery case obtained in (step a), It may include sealing.

Specifically, the non-aqueous electrolyte may include i) a fluorine-containing ether compound, ii) a fluorine-containing sulfone compound, iii) a non-aqueous organic solvent; And iv) a lithium salt, and the types and contents of each component are as described above.

In addition, 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, rectangular, pouch type using a can Or it can be a coin (coin) type, etc.

In addition, in the method of manufacturing a lithium secondary battery of the present invention, the (step c) may include an activation process step for the battery cell obtained in (step b) at a temperature of 45°C to 60°C.

According to an embodiment of the present invention, by performing the activation process at a high temperature within the above range, the negative electrode film reaction can be quickly formed, thereby reducing side reactions at the negative electrode interface, and finally, the gas emission amount and the battery cell of the secondary battery. The thickness of the can be reduced. In addition, due to this, the capacity characteristics of the secondary battery can be improved.

In particular, when the activation process is performed at a temperature of 45° C. to 60° C. according to an exemplary embodiment of the present invention, the thickness of the battery cell is smallest and optimum capacity characteristics may be achieved.

Further, according to an embodiment of the present invention, performing the activation process may include charging the battery cell to a voltage of 3.6V to 4.2V.

In general, when the activation process is performed at a high temperature or a high voltage, the impregnability of the electrolyte solution to the electrode is increased, so that a uniform SEI film can be formed. However, when the oxidation stability of the additive included in the non-aqueous electrolyte is not secured, the additive decomposes at the anode interface to cause side reactions such as electrolyte decomposition, which may adversely affect the performance of the secondary battery.

Accordingly, in the present invention, a battery cell is prepared at a high temperature of 45°C to 60°C by using a non-aqueous electrolyte solution containing two types of fluorine-containing compounds, a fluorine-containing ether compound and a fluorine-containing sulfone compound. The activation process can be easily performed, and by this method, the thickness of the battery cell and the amount of gas generated can be reduced, thereby remarkably improving the life characteristics and capacity characteristics of the secondary battery.

If, in the manufacturing method of the lithium secondary battery of the present invention, when the activation process is performed at a temperature of less than 45°C, impregnation of the electrolyte solution to the electrode is poor, making it difficult to form a uniform SEI film, and the activity of the active material is reduced. Cell activation may not be possible. In addition, if the activation process is performed at an excessively high temperature exceeding 60°C, a burden may be placed on the electrode material, etc., and there is a concern that a side reaction of the electrolyte solution may be caused due to the high temperature.

In addition, according to an embodiment of the present invention, after the activation process step, a degassing step of removing gas such as oxygen may be further required. The method of degassing is not particularly limited, and a method known in the art may be used.

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 as a unit battery for a medium-to-large battery module including a plurality of battery cells. Preferred examples of the medium and large-sized devices include an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage system, but are not limited thereto.

Hereinafter, examples will be described in detail to specifically describe the present invention. However, the embodiments according to the present invention can be modified in many different 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 more fully describe the present invention to those skilled 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 One.

(Step a) Battery cell Manufacturing steps

89% by weight of a mixture of LiCoO ₂ as a positive electrode active material, 8% by weight of carbon black as a conductive material, 3% by weight of polyvinylidene fluoride (PVdF) as a binder, 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 of a positive electrode current collector having a thickness of about 20 μm, dried, and then roll pressed to prepare a positive electrode.

In addition, a negative electrode mixture slurry was prepared by adding graphite powder as a negative active material, PVdF as a binder, and carbon black as a conductive material in 97% by weight, 2% by weight, and 1% by weight, respectively, to NMP as a solvent. The negative electrode mixture slurry was applied to a copper (Cu) thin film of a negative electrode current collector having a thickness of 10 μm, dried, and then roll pressed to prepare a negative electrode.

A battery cell was manufactured by inserting the electrode assembly including the prepared positive electrode, negative electrode, and polyolefin separator into a battery case.

(Step b) Non-aqueous Electrolyte injection step

As shown in Table 1 below, ethylene carbonate (EC). LiPF ₆ based on the total weight of the non-aqueous electrolyte solution in a non-aqueous organic solvent having a composition of 3:1:6 by weight of propylene carbonate (PC) and propyl propionate 1 mol/l and 1H, 1H, 5H-perfluoropentyl-1,1,2,2-tetrafluoroethyl ether as a fluorine-containing ether compound and 1,2-ethanedisulfonyl di as a fluorine-containing sulfone compound. A fluoride additive was added in an amount of 3% by weight and 0.5% by weight, respectively, and vinylene carbonate was added in an amount of 1% by weight to prepare a non-aqueous electrolyte.

The prepared non-aqueous electrolyte was injected into the battery case obtained in (step a) and sealed to complete the manufacture of a lithium secondary battery.

(Step c) Activation process step

In the activation process step, the lithium secondary battery was CC charged to 4.0V at 60°C, and then discharged at 3V (C-rate = 0.2C). Thereafter, the cycle was operated between 4.4V and 3V.

Example 2.

As shown in Table 1 below, 1H, 1H, 5H-perfluoropentyl-1,1,2,2-tetrafluoroethyl ether and fluorine-containing sulfone-based as fluorine-containing ether compounds in (step b) of Example 1 A lithium secondary battery was carried out in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding 1,2-ethane disulfonyl difluoride additives as a compound in an amount of 5% by weight and 1.5% by weight, respectively. Got it.

Example 3.

As shown in Table 1 below, 1H, 1H, 5H-perfluoropentyl-1,1,2,2-tetrafluoroethyl ether and fluorine-containing sulfone compounds as fluorine-containing ether compounds in step b) of Example 1 As a lithium secondary battery was carried out in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding a 1,2-ethane disulfonyl difluoride additive in an amount of 3% by weight and 5% by weight, respectively. Got it.

Example 4.

As shown in Table 1 below, 1H, 1H, 5H-perfluoropentyl-1,1,2,2-tetrafluoroethyl ether and fluorine-containing sulfone compounds as fluorine-containing ether compounds in step b) of Example 1 A lithium secondary battery was obtained in the same manner as in Example 1, except that an ethanesulfonyl fluoride additive was added in an amount of 5% by weight and 1.5% by weight, respectively, to prepare a non-aqueous electrolyte.

Example 5.

As shown in Table 1, in step b) of Example 1, nonafluorobutyl methyl ether as a fluorine-containing ether compound and a 1,2-ethandisulfonyl difluoride additive as a fluorine-containing sulfone compound were respectively added in 5% by weight and A lithium secondary battery was obtained in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding it in an amount of 1.5% by weight.

Comparative example One.

As shown in Table 1 below, in the preparation of the non-aqueous electrolyte solution in step b) of Example 1, 1H, 1H, 5H-perfluoropentyl-1,1,2,2-tetrafluoro, which are fluorine-containing ether compounds as additives. A lithium secondary battery was obtained in the same manner as in Example 1, except that only 5% by weight of roethyl ether was used.

Comparative example 2.

As shown in Table 1 below, in the preparation of the non-aqueous electrolyte solution in step b) of Example 1, Example 1 except that only 1.5% by weight of 1,2-ethandisulfonyl difluoride, which is a fluorine-containing sulfone-based compound, was used. By performing the same method as to obtain a lithium secondary battery.

Comparative example 3.

As shown in Table 1 below, a lithium secondary battery was obtained in the same manner as in Example 2, except that the activation process in step c) of Example 1 was performed at 25°C.

Comparative example 4.

As shown in Table 1 below, 1H, 1H, 5H-perfluoropentyl-1,1,2,2-tetrafluoroethyl ether and fluorine-containing sulfone compounds as fluorine-containing ether compounds in step b) of Example 1 As a lithium secondary battery was carried out in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding a 1,2-ethane disulfonyl difluoride additive in an amount of 2% by weight and 6% by weight, respectively. Got it.

Comparative example 5.

As shown in Table 1 below, 1H, 1H, 5H-perfluoropentyl-1,1,2,2-tetrafluoroethyl ether and fluorine-containing sulfone compounds as fluorine-containing ether compounds in step b) of Example 1 As a lithium secondary battery was carried out in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding 1,2-ethane disulfonyl difluoride additives in amounts of 1% and 5% by weight, respectively. Got it.

Comparative example 6.

As shown in Table 1 below, 1H, 1H, 5H-perfluoropentyl-1,1,2,2-tetrafluoroethyl ether and fluorine-containing sulfone compounds as fluorine-containing ether compounds in step b) of Example 1 As a lithium secondary battery was carried out in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding a 1,2-ethane disulfonyl difluoride additive in an amount of 6% by weight and 0.5% by weight, respectively. Got it.

Comparative example 7.

As shown in Table 1 below, 1H, 1H, 5H-perfluoropentyl-1,1,2,2-tetrafluoroethyl ether and fluorine-containing sulfone compounds as fluorine-containing ether compounds in step b) of Example 1 As a lithium secondary battery was carried out in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding a 1,2-ethane disulfonyl difluoride additive in an amount of 5% by weight and 0.3% by weight, respectively. Got it.

Comparative example 8.

As shown in Table 1 below, in the preparation of the non-aqueous electrolyte solution of step b) of Example 1, 1H, 1H, 5H-perfluoropentyl-1,1,2,2-tetrafluoroethyl ether and ethyl methyl as additives A lithium secondary battery was obtained in the same manner as in Example 1, except that 5% by weight and 1.5% by weight of sulfone were used, respectively.

Experimental Example

Experimental Example 1: Analysis of capacity characteristics, life characteristics and thickness expansion rate

The lithium secondary batteries prepared in Examples 1 to 5 and Comparative Examples 1 to 8 were charged at 0.2C from 25 to 4.4V/38mA in a constant current/constant voltage (CC/CV) condition, and then 3.0V in a constant current (CC) condition. Discharge was carried out at 0.2 C until, and the discharge capacity was measured. This was repeated in 1 to 200 cycles, and the measured discharge capacity is shown in Table 1 below.

In addition, the initial thickness change rate was measured based on the initial cell thickness of Example 2, and the results are shown in Table 1 below.

Experimental Example 2: gas generation rate measurement

The gas generated from each of the cells in which the activation process was performed in Examples 1 to 5 and Comparative Examples 1 to 8 was analyzed through GC, and each of the gases generated by the method of Equation 1 was used based on the amount of gas generated in Example 2. The amount of gas remaining in the battery (%) was calculated. The results are shown in Table 1 below.

[Equation 1]

Gas generation rate (%) = volume of extracted gas/volume of extracted gas of Example 2 × 100

As can be seen in Table 1, in the case of the secondary batteries of Examples 1 to 5 using the non-aqueous electrolyte containing two additives of the present invention, a comparative example using a non-aqueous electrolyte containing only one of the additives It can be seen that the gas generation rate and the battery cell thickness are decreased compared to the secondary batteries of 1 and 2 and the secondary batteries of Comparative Examples 3 to 7 using the non-aqueous electrolyte solution containing more than or less than the critical range content of the additives. have.

Specifically, in the case of the secondary batteries of Examples 1 to 5 of the present invention, the gas generation rate after the activation process was 105% or less, whereas the battery of Comparative Examples 1 and 2 increased by more than 120%, and the comparative examples 3 to 7 In the case of secondary batteries, it can be seen that the increase is more than 110%.

In addition, the initial cell thickness ratio was about 101% or less in the case of the secondary batteries of Examples 1 to 5, whereas it increased to 103% of the cells of Comparative Examples 1 and 2, and 102% or more in the case of the batteries of Comparative Examples 3 to 7 You can see that it is rising.

In addition, in the case of the secondary batteries of Examples 1 to 5, it was found that the initial 0.2 C capacity ratio (%) and the capacity retention rate (%) at 25° C. increased to about 1% to 6% compared to the secondary batteries of Comparative Examples 1 to 7. I can.

In particular, 1H, 1H, 5H-perfluoropentyl-1,1,2,2-tetrafluoroethyl ether is included as a fluorine-containing ether compound, and 1,2-ethanedisulfonyl di In the case of the secondary battery of Examples 1 to 3 containing a non-aqueous electrolyte containing fluoride as an additive, the secondary battery of Example 5 containing nonafluorobutyl methyl ether as a fluorine-containing ether compound, or a fluorine-containing sulfone-based battery Compared to the secondary battery of Example 4 containing ethanesulfonyl fluoride as a compound and the secondary battery of Comparative Example 8 containing ethyl methyl sulfone, the gas generation rate and the battery cell thickness were reduced, and the initial 0.2 C capacity ratio (%) and It can be seen that the capacity retention rate (%) of 25°C is higher.

Claims (20)

As a lithium secondary battery comprising a positive electrode, a negative electrode, a negative electrode, and a separator interposed between the positive and negative electrodes and a non-aqueous electrolyte,
The negative electrode includes a carbon-based negative electrode active material,
The non-aqueous electrolyte solution includes i) a fluorine-containing ether compound, ii) a fluorine-containing sulfone compound, iii) a non-aqueous organic solvent, and iv) a lithium salt,
The i) fluorine-containing ether compound is contained in an amount of 2% to 5% by weight based on the total weight of the non-aqueous electrolyte,
The ii) fluorine-containing sulfone-based compound is a lithium secondary battery contained in an amount of 0.5% to 5% by weight based on the total weight of the non-aqueous electrolyte.
The method according to claim 1,
The fluorine-containing ether compound is 1H, 1H, 5H-perfluoropentyl-1,1,2,2-tetrafluoroethyl ether, nonafluorobutyl methyl ether, (2-(difluoromethoxymethyl)- Containing a single substance selected from the group consisting of 1,1,1,2,3,3,3-heptafluoro propane, and perfluoro-[15]-crown-5-ether, or a mixture of two or more thereof Phosphorus lithium secondary battery.
The method according to claim 2,
The fluorine-containing ether-based compound is a lithium secondary battery that is 1H, 1H, 5H-perfluoropentyl-1,1,2,2-tetrafluoroethyl ether.
delete The method according to claim 1,
The fluorine-containing sulfone-based compound is a single material selected from the group consisting of 1,2-ethandisulfonyl difluoride, ethanesulfonyl fluoride, and phenylmethylsulfonyl fluoride, or a mixture of two or more of them.
The method according to claim 5,
The fluorine-containing sulfone-based compound is a lithium secondary battery that is 1,2-ethane disulfonyl difluoride.
delete The method according to claim 1,
The non-aqueous organic solvent is propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, methylpropyl carbonate, dipropyl carbonate, fluoroethylene carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane. , Vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, tetrahydrofuran, methyl formate, methyl acetate, ethyl acetate, isopropyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, A lithium secondary battery comprising a single substance selected from the group consisting of propyl propionate, butyl propionate, methyl butyrate, and ethyl butyrate, or a mixture of two or more of them.
The method according to claim 8,
The non-aqueous organic solvent is a lithium secondary battery comprising a single material selected from the group consisting of propylene carbonate, ethylene carbonate, and propyl propionate, or a mixture of two or more of them.
The method according to claim 1,
The non-aqueous electrolyte is a lithium secondary battery further comprising a vinylidene carbonate-based compound.
The method according to claim 10,
The vinylidene carbonate-based compound is a lithium secondary battery that is vinylene carbonate, vinylene ethylene carbonate, or a combination thereof.
delete (a) manufacturing a battery cell by inserting an electrode assembly including a positive electrode, a negative electrode including a carbon-based negative electrode, and a separator interposed between the positive electrode and the negative electrode into a battery case;
(b) injecting and sealing a non-aqueous electrolyte solution containing a fluorine-containing ether compound and a fluorine-containing sulfone compound into the battery case; And
(c) performing the activation process of the battery cell at a temperature of 45 ℃ to 60 ℃; includes,
The fluorine-containing ether-based compound is included in an amount of 2% to 5% by weight based on the total weight of the non-aqueous electrolyte,
The method of manufacturing a lithium secondary battery according to claim 1, wherein the fluorine-containing sulfone-based compound is contained in an amount of 0.5% to 5% by weight based on the total weight of the non-aqueous electrolyte.
The method according to claim 13,
The activation process step (c) is a method of manufacturing a lithium secondary battery that is performed while charging the battery cell at a voltage of 3.6V to 4.2V.
The method according to claim 13,
The fluorine-containing ether compound is 1H, 1H, 5H-perfluoropentyl-1,1,2,2-tetrafluoroethyl ether, nonafluorobutyl methyl ether, (2-(difluoromethoxymethyl)- 1,1,1,2,3,3,3-heptafluoro propane, and perfluoro-[15]-crown-5-ether containing any one selected from the group consisting of, or a mixture of two or more thereof The method of manufacturing a lithium secondary battery.
The method of claim 15,
The method of manufacturing a lithium secondary battery wherein the fluorine-containing ether-based compound is 1H, 1H, 5H-perfluoropentyl-1,1,2,2-tetrafluoroethyl ether.
delete The method according to claim 13,
The fluorine-containing sulfone-based compound is any one selected from the group consisting of 1,2-ethandisulfonyl difluoride, ethanesulfonyl fluoride) and phenylmethylsulfonyl fluoride 1,2-ethandisulfonyl difluoride, or Method for producing a lithium secondary battery comprising a mixture of two or more of.
The method according to claim 18,
The method of manufacturing a lithium secondary battery wherein the fluorine-containing sulfone-based compound is 1,2-ethanedisulfonyl difluoride.
delete