KR20080062671A - Nonaqueous electrolyte for li-secondary battery and li secondary battery thereby - Google Patents

Abstract

A nonaqueous electrolyte solution for a lithium secondary battery, and a lithium secondary battery containing the nonaqueous electrolyte solution are provided to improve high temperature storage characteristics and lifetime without the deterioration of battery performance. A nonaqueous electrolyte solution comprises a nonaqueous organic solvent comprising at least one solvent selected from the group consisting of a carbonate-based solvent, an ester-based solvent, an ether-based solvent and a ketone-based solvent; a lithium salt dissolved in the nonaqueous organic solvent; and 0.1-10 parts by weight of the trimethoxyboroxine represented by the formula 1 based on 100 parts by weight of the nonaqueous organic solvent.

Description

Non-aqueous electrolyte for lithium secondary battery and lithium secondary battery comprising the same {Nonaqueous electrolyte for Li-secondary battery and Li secondary battery

1 shows that aluminum (Al) is used as the positive electrode (100) metal, copper (Cu) is used as the negative electrode metal, LiCoO ₂ is used as the positive electrode active material, and carbon (C) is used as the negative electrode active material. It is a schematic diagram which shows the used lithium secondary battery.

<Explanation of symbols for the main parts of the drawings>

100: positive electrode 110: negative electrode

130: electrolyte solution 140: separator

The present invention relates to a non-aqueous electrolyte for lithium secondary batteries and a lithium secondary battery comprising the same, and more particularly, to the conventional non-aqueous electrolyte (nonnaqueous electrolyte) for a lithium secondary battery without affecting the battery characteristics And it relates to a non-aqueous electrolyte lithium secondary battery and a lithium secondary battery comprising the same that can improve the storage characteristics.

Secondary battery is a chemical battery that can be used semi-permanently because it can be recharged unlike primary battery. Recently, the market size is growing exponentially due to the mass distribution of notebooks, mobile communication devices, and digital cameras. In addition to semiconductors and displays, it is rapidly growing as one of the three parts industries in the 21st century.

Secondary batteries include lead-acid batteries, nickel-cadmium (Ni-Cd) batteries, nickel-hydrogen (Ni-MH) batteries, and lithium batteries, depending on the cathode and anode materials. The potential and energy density are determined by Among them, especially lithium secondary batteries are used as a driving power source for portable electronic devices because of their high energy density due to the low redox potential and molecular weight of lithium.

Among these lithium secondary batteries, a lithium secondary battery using a nonaqueous electrolyte, in particular, is coated with a lithium metal mixed oxide as a cathode active material on a metal as an anode, and as a cathode active material on a metal as a cathode. A carbon material or a metal lithium is coated and used, and an electrolyte in which lithium salt is appropriately dissolved in an organic solvent is disposed between these anodes and cathodes.

In brief, the operation principle of the lithium secondary battery, lithium ions (Li +) present in the ionic state in the electrolyte is moved from the positive electrode to the negative electrode during charging, and from the negative electrode to the positive electrode during discharge. The electrons then move along the wire that connects the anode and cathode to the lithium ion.

As described above, in the state of charge of the lithium ion battery, lithium ions (Li ⁺ ) from the lithium metal oxide used as the positive electrode are moved to the carbon electrode used as the negative electrode and intercalated, where lithium ions are highly reactive. As a result, materials such as Li ₂ CO ₃ , LiO, LiOH, etc. are generated on the surface of the negative electrode by reacting with the carbon negative electrode, which forms a film on the surface of the negative electrode.

The film thus produced is called a solid electrolyte interface (SEI), and these SEI films serve as a kind of passivation to protect the cathode surface.

That is, the SEI film prevents the reaction between lithium ions and the negative electrode or other materials during charge and discharge, and serves to pass only lithium ions by acting as an ion tunnel.

The ion tunnel effect is characterized by co-intercalation of organic solvents (e.g. ethylene carbonate, dimethyl carbonate, diethyl carbonate, etc.) of high molecular weight electrolytes that solvate lithium ions and move together. This prevents the structure of the negative electrode from collapsing.

Once the SEI film is formed, the lithium ions do not react side-by-side with the negative electrode or any other material, thereby reversibly maintaining the amount of lithium ions.

That is, the carbon material of the negative electrode reacts with the electrolyte during overcharging to form a protective film SEI film on the surface of the negative electrode, thereby maintaining stable charge and discharge without further decomposition of the electrolyte.

The average discharge voltage of the lithium secondary battery is about 3.6 to 3.7 V, and high power can be obtained as compared with other alkaline batteries, Ni-MH batteries, Ni-Cd batteries and the like.

However, in order to produce such a high driving voltage, an electrochemically stable electrolyte composition is required in the charge and discharge voltage range of 0 to 4.2 V. For this reason, an organic electrolyte solution in which lithium salts are dissolved in a non-aqueous organic solvent is used as an electrolyte for a lithium secondary battery. In this case, it is preferable to use an organic solvent having high ionic conductivity and high dielectric constant and low viscosity.

However, since there is no single non-aqueous organic solvent that satisfies all of these conditions, a mixed solvent of a high dielectric constant organic solvent and a low dielectric constant organic solvent or a mixture of a high dielectric constant organic solvent and a low viscosity organic solvent is used. Solvents are used. Recently, high voltage batteries of 4.2 V or higher have been developed, and the safety of the electrolyte is becoming more important for such high voltage batteries.

In US Pat. Nos. 6,114,070 and 6,048,637, ionic conductivity of an organic solvent is prepared by mixing dimethyl carbonate or diethyl carbonate and ethylene carbonate or propylene carbonate as a mixed solvent of chain carbonate and cyclic carbonate. A method of improving is disclosed.

However, these mixed solvents can usually be used below 120 ℃ but when the temperature is higher than the gas generated by the vapor pressure there is a problem that the battery is swelled and can not be used.

U.S. Patent Nos. 5,352,548, 5,712,059 and 5,714,281 disclose electrolyte solutions comprising an organic solvent having a vinylene carbonate (VC) content of at least 20%.

However, vinylene carbonate has a low dielectric constant compared to ethylene carbonate, propylene carbonate, and gamma butyrolactone, and thus has a problem in that charge and discharge characteristics and high rate characteristics of a battery are significantly reduced when used as a main solvent.

In addition, U.S. Patent No. 1 improves the service life by adding VC, but as the addition amount increases, the film resistance increases, thereby increasing the resistance, thereby decreasing the capacity at low temperatures and decreasing the capacity even at high rates. There is a problem that the battery swells due to the generation of gas.

On the other hand, in order to suppress the reductive decomposition of the solvent on the negative electrode, as a means of suppressing the reductive decomposition of lithium on the negative electrode, a method of adding a compound that forms a so-called Solid Electrolyte Interface (SEI) on the negative electrode to the electrolyte solution. This is proposed in Japanese Patent Laid-Open No. 2001-6729.

However, in the case of using such a film forming additive, since the conductivity of lithium ions is low and a high resistance SEI is formed on the negative electrode, when the discharge characteristic of the battery is remarkably lowered or is excessively added in the electrolyte, an excessive amount of the additive is added. There is a problem in that the battery is oxidized and decomposed at the anode at high temperature to generate gas, and the expansion of the battery is markedly increased due to an increase in the internal pressure.

Japanese Laid-Open Patent Publication No. 1992-087156 improves the life of a battery by adding vinyl ethylene carbonate (VEC), but when it is added 1% or more, there is a problem in that the capacity decreases due to a large film resistance.

To compensate for this, Japanese Patent Laid-Open Publication No. 2 has been mixed with VEC and VC to improve its properties. However, if the added amount is 2% or more, the film resistance also increases, which does not solve the problem of decreasing capacity at high rate.

Japanese Patent Application Laid-Open No. 1995-006786 improves the battery life by adding fluoroethylene carbonate (FEC), but has a problem of decreasing the life at high temperatures.

In addition, US Pat. No. 6,650,624 describes that it is possible to form a stable protective film against the electrolyte on the surface of the graphite negative electrode material by using a solvent composed of fluoro ethylene carbonate and propylene carbonate as the electrolyte solvent.

However, when the solvent of the composition is used as the electrolyte solvent, the dielectric constant of fluoroethylene carbonate and propylene carbonate is high, but the viscosity is high, the ion conductivity of the inhibitor is lowered to less than 7mS / cm, there is a problem that the battery performance deteriorates.

Accordingly, research and development of a non-aqueous electrolyte for lithium secondary batteries that can improve life characteristics and storage characteristics without affecting battery characteristics are required.

The technical problem to be achieved by the present invention is a lithium secondary battery, in particular lithium secondary battery using a non-aqueous electrolyte, lithium 2 which can improve the life characteristics and high temperature storage characteristics of the battery by adding a certain additive to the non-aqueous electrolyte The present invention provides a nonaqueous electrolyte solution for a battery.

Another object of the present invention is to provide a lithium secondary battery including the non-aqueous electrolyte of the present invention.

Technical problems to be achieved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

Non-aqueous electrolyte lithium secondary battery according to an embodiment of the present invention for solving the above technical problem includes at least one solvent selected from the group consisting of carbonate solvent, ester solvent, ether solvent, and ketone solvent. A basic electrolyte containing a non-aqueous organic solvent and a lithium salt dissolved in the non-aqueous organic solvent; To the basic electrolyte is characterized in that the trimethoxy boroxine (Trimethoxyboroxine) represented by the formula (1) is added.

Lithium secondary battery according to an embodiment of the present invention for solving the above other technical problem is an electrolytic solution of the present invention, an electrode portion composed of a positive electrode and a negative electrode which are disposed to face each other with the electrolyte therebetween, and the positive electrode and the negative electrode electrically It includes a separator that separates it.

Specific details of other embodiments are included in the detailed description and the accompanying drawings.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, only the present embodiments to make the disclosure of the present invention complete, and common knowledge in the art to which the present invention pertains. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

A nonaqueous electrolyte for a lithium secondary battery according to an embodiment of the present invention does not include water (H ₂ O) as it is, and only an organic solvent is used as a solvent, and a lithium salt is dissolved in such a non-aqueous organic solvent. To the basic electrolyte, additives are added to improve the life and storage characteristics of the lithium secondary battery, which is a technical problem of the present invention.

The basic electrolyte solution contains a non-aqueous organic solvent and a lithium salt.

Non-aqueous organic solvents act as a medium through which ions involved in the electrochemical reaction of a battery can move. It is recommended to use a material having a high dielectric constant (polarity) and a low viscosity to increase ion dissociation and facilitate ion conduction. In general, it is preferable to use two or more mixed solvents composed of a solvent having a high dielectric constant and a high viscosity and a solvent having a low dielectric constant and a low viscosity.

The non-aqueous organic solvent used in the present invention includes at least one solvent selected from the group consisting of carbonate-based, ester-based, ether-based, and ketone-based solvents.

The carbonate solvent may be ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate (BC), 2,3-butylene carbonate, 1,2-pentylene carbonate, 2, One or more cyclic carbonate organic solvents of 3-pentylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC) ) And one or more chain carbonate organic solvents of ethyl propyl carbonate (EPC) are mixed.

In this case, the cyclic carbonate organic solvent and the chain carbonate organic solvent are mixed in a ratio of 1: 1 to 1: 9 based on the volume ratio, and preferably mixed in a volume ratio of 1: 1.5 to 1: 4. It is most preferable in view of the life characteristics and storage characteristics of the battery.

In particular, in the cyclic carbonate organic solvent, ethylene carbonate and propylene carbonate having a high dielectric constant are used, and when artificial graphite is used as the negative electrode active material, ethylene carbonate is preferably used. In the chain carbonate organic solvent, Preference is given to using dimethyl carbonate, ethylmethyl carbonate and diethyl carbonate having a low viscosity.

The ester organic solvent is methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone, ε-capro One or more selected from the group consisting of lactones are used, and one or more selected from tetrahydrofuran, 2-methyltetrahydrofuran, and dibutyl ether is used as the ether organic solvent, and as the ketone organic solvent, Methylvinyl ketone is used.

The non-aqueous organic solvent may further include an aromatic hydrocarbon organic solvent represented by Formula 2 below.

(R is a halogen or an alkyl group having 1 to 10 carbon atoms, q is an integer of 0 to 6)

Specifically, the aromatic hydrocarbon-based organic solvent may be one or more of benzene, fluorobenzene, bromobenzen, chlorobenzene, toluene, xylene, mesitylene, fluorotoluene, difluorotoluene, and trifluorotoluene. .

The amount of the aromatic hydrocarbon compound and the carbonate solvent is determined in the range of 1: 1 to 1:30 based on the volume ratio.

Lithium salt is dissolved in the non-aqueous organic solvent to form a basic electrolyte.

At this time, the lithium salt serves as a source of lithium ions in the battery to enable the operation of the basic lithium battery.

Lithium salts include LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiN (C ₂ F ₅ SO ₃ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiSbF ₆ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiAlO ₄ , LiAlCl ₄ , LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ , wherein x and y are natural numbers), LiCl, and At least one selected from LiI is used.

The amount of lithium salt added is 0.6 to 2.0M in the total electrolyte, and considering the properties related to the electrical conductivity of the electrolyte and the viscosity related to the mobility of lithium ions, it is preferable to be in the range of 0.7 to 1.6M, and 0.7 to More preferably, it is in the range of 1.6M.

As described above, trimethoxyboroxine represented by Formula 1 is added as an additive to the basic electrolyte in which lithium salt is dissolved in the non-aqueous organic solvent.

The amount of trimethoxyboroxine added is 0.1 to 10 parts by weight based on 100 parts by weight of the nonaqueous organic solvent.

The reason why the amount of trimethoxyboroxine used as an additive has such a range is that the capacitance exhibits an optimized value in that range.

Further, the non-aqueous electrolyte solution of the present invention may further contain propyl acetate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate, and the like, as necessary.

The electrolyte of the lithium secondary battery of the present invention is excellent in storage characteristics and can maintain a long life in the temperature range of -20 to 60 ℃ usually improves the safety and reliability of the lithium secondary battery. The electrolyte solution of the present invention can be applied to all lithium secondary batteries such as lithium ion batteries and lithium polymer batteries.

1 shows that aluminum (Al) is used as the positive electrode 100 metal, copper (Cu) is used as the negative electrode 110 metal, LiCoO ₂ is used as the positive electrode 100 active material, and carbon (C) is used as the negative electrode active material. It is a schematic diagram which shows the lithium secondary battery which used the nonaqueous electrolyte solution as electrolyte solution 130. FIG.

As shown in FIG. 1, a lithium secondary battery according to an exemplary embodiment of the present invention includes a positive electrode 100, a negative electrode 110, an electrolyte 130, and a separator 140.

However, since the electrolyte 130 used in the lithium secondary battery according to the embodiment of the present invention is used, the non-aqueous electrolyte according to the embodiment of the present invention has been described above. .

The positive electrode 100 and the negative electrode 110 are disposed to face each other with the electrolyte 130 interposed therebetween.

The positive electrode 100 is an active material in a metal, and the positive electrode is Li _x Mn _{1 - y} M _y A ₂ , Li _x Mn ₂ O _4-z X _z , Li _x Mn _{2 - y} M _y M ' _z A ₄ , Li _x Co _{1 - y} M _y A ₂ , Li _x Co _{1 - y} M _y O _{2 - z} X _z , Li _x Ni _{1 - y} M _y O _{2 - z} X _z , Li _x Ni _{1 - y} Co _{y O 2 -z x z, Li x} Ni 1 -y- z Co y M z A α, Li x Ni 1 -y- z Co y M z O 2 -α x α, Li x Ni 1 -y- z Mn _y M _z a _α, there are one or more active materials selected from _{Li x Ni 1 -y- z Mn y} M z O 2 -α x α is coated.

(Wherein 0.9≤x≤1.1, 0≤y≤0.5, 0≤z≤0.5, 0≤α≤2,

M and M 'are the same or different and include Mg, Al, Co, K, Na, Ca, Si, Ti, Sn, V, Ge, Ga, B, As, Zr, Mn, Cr, Fe, Sr, V and rare earths Selected from the group of elements,

A is selected from the group consisting of O, F, S and P,

X is selected from the group consisting of F, S and P)

The negative electrode 110 is coated with a carbon active material capable of inserting and detaching lithium ions into a metal (both crystalline carbon and amorphous carbon), but in addition, carbon composite, carbon fiber, lithium metal, lithium alloy, and lithium composite At least one active material selected from among may be coated.

For example, amorphous carbons include hard carbon, coke, mesocarbon microbeads (MCMB) fired at 1500 ° C. or lower, mesophase pitch-based carbon fibers (MPCF), and the like.

Graphite-based materials are used as the crystalline carbon, and specific examples thereof include natural graphite, graphitized coke, graphitized MCMB, and graphitized MPCF. The carbonaceous material is preferably a material having an d002 interplanar distance of 3.35 to 3.38 kPa and an Lc (crystallite size) of at least 20 nm by X-ray diffraction. As the lithium alloy, an alloy of lithium with aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium or indium may be used.

The positive electrode or the negative electrode may be prepared by dispersing an electrode active material, a binder and a conductive material, and, if necessary, a thickener in a solvent to prepare an electrode slurry composition, and applying the slurry composition to an electrode current collector.

Aluminum or an aluminum alloy may be used as the positive electrode current collector, and copper or a copper alloy may be used as the negative electrode current collector. Examples of the positive electrode current collector and the negative electrode current collector include a foil, a film, a sheet, a punched one, a porous body, a foam, and the like.

The binder is a material that plays a role of pasting the active material, mutual adhesion of the active material, adhesion with the current collector, buffering effect on the expansion and contraction of the active material, and the like, for example, polyvinylidene fluoride and polyhexafluoropropylene-poly Copolymers of vinylidene fluoride (P (VdF / HFP)), poly (vinylacetate), polyvinyl alcohol, polyethylene oxide, polyvinylpyrrolidone, alkylated polyethylene oxide, polyvinyl ether, poly (methylmethacryl) Rate), poly (ethylacrylate), polytetrafluoroethylene, polyvinylchloride, polyacrylonitrile, polyvinylpyridine, styrene-butadiene rubber, acrylonitrile-butadiene rubber and the like.

The content of the binder is 0.1 to 30% by weight, preferably 1 to 10% by weight based on the electrode active material. When the content of the binder is too small, the adhesion between the electrode active material and the current collector is insufficient, and when the content of the binder is too high, the adhesion is improved, but the content of the electrode active material decreases by that amount, which is disadvantageous in increasing battery capacity.

The conductive material may be at least one selected from the group consisting of a graphite-based conductive agent, a carbon black-based conductive agent, a metal or a metal compound-based conductive agent as a material for improving electronic conductivity. Examples of the graphite conductive agent include artificial graphite and natural graphite, and examples of the carbon black conductive agent include acetylene black, ketjen black, denka black, thermal black, and channel. And black or the like, and examples of the metal or metal compound conductive agent include perovskite such as tin, tin oxide, tin phosphate (SnPO ₄ ), titanium oxide, potassium titanate, LaSrCoO ₃ , and LaSrMnO _3. ) There is a substance.

However, it is not limited to the conductive agents listed above. The content of the conductive agent is preferably 0.1 to 10% by weight based on the electrode active material. When the content of the conductive agent is less than 0.1% by weight, the electrochemical properties are lowered, and when the content of the conductive agent is greater than 10% by weight, the energy density per weight decreases.

The thickener is not particularly limited as long as it can play a role of controlling the viscosity of the active material slurry. For example, carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, or the like may be used.

As a solvent in which an electrode active material, a binder, a conductive material, etc. are disperse | distributed, a non-aqueous solvent or an aqueous solvent is used. Examples of the non-aqueous solvent include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N, N-dimethylaminopropylamine, ethylene oxide and tetrahydrofuran.

In this case, the metal used in the positive electrode 100 and the negative electrode 110 is a portion to which a voltage is applied from the outside during charging and supplies a voltage to the outside during discharge, and the positive electrode active materials are a collector and a negative electrode that collect positive charges. The active material serves as a current collector for collecting negative charges.

The separator 140 electrically separates the positive electrode 100 and the negative electrode 110 to prevent a short and serve as a movement path of lithium ions.

As the separator 140, one of a single layer separator made of polyethylene or polypropylene, a two layer separator laminated with polyethylene / polypropylene, polyethylene / polypropylene / polyethylene, or a three layer separator laminated with polypropylene / polyethylene / polypropylene is used. It may be used in the form of a multi-layer, microporous film, woven fabric and nonwoven fabric. In addition, a film coated with a resin having excellent stability may be used for the porous polyolefin film.

The electrode assembly manufactured as described above is accommodated in a can-shaped housing together with an electrolyte, and the upper end of the can is sealed with a cap assembly to complete a lithium secondary battery.

In this case, the cap assembly includes a cap plate, an insulating plate, a terminal plate, and an electrode terminal.

At this time, the cap assembly is combined with the insulating case serves to seal the can. In addition, a terminal through-hole having an electrode terminal inserted therein is formed at the center of the cap plate. When the electrode terminal is inserted into the terminal through-hole, a tubular gasket is coupled to the outer surface of the electrode terminal for insertion of the electrode terminal and the cap plate. .

After the cap assembly is assembled to the upper end of the can, the electrolyte is injected through the electrolyte injection hole and the electrolyte injection hole is closed by a cap. In this case, the electrode terminals are connected to the negative electrode tab of the negative electrode and the positive electrode tab of the positive electrode, respectively, and act as negative electrode terminals or positive electrode terminals.

However, the lithium secondary battery of the present invention is not limited to the above shape, and any shape, such as a cylindrical shape or a pouch type, including the cathode active material of the present invention and capable of operating as a battery is possible.

Hereinafter, the life characteristics and the storage characteristics of the lithium secondary battery are improved by using the nonaqueous electrolyte solution for the lithium secondary battery according to the embodiments of the present invention with reference to specific examples and comparative examples. However, the content not described herein is omitted because it can be inferred technically sufficient by those skilled in the art.

< Example  1>

LiCoO ₂ as a positive electrode active material, polyvinylidene fluoride (PVdF) as a binder and carbon as a conductive agent were mixed in a weight ratio of 92: 4: 4, and then dispersed in N-methyl-2-pyrrolidone to prepare a positive electrode slurry. It was. The slurry was coated on an aluminum foil having a thickness of 20 μm, dried, and rolled to prepare a positive electrode.

Artificial graphite as a negative electrode active material, styrene-butadiene rubber (SBR) as a binder, and carboxymethyl cellulose as a thickener were mixed in a weight ratio of 96: 2: 2, and then dispersed in water to prepare a negative electrode active material slurry. The slurry was coated on a copper foil having a thickness of 15 μm, dried, and rolled to prepare a negative electrode.

A film separator made of a polyethylene (PE) material having a thickness of 20 μm was inserted between the prepared electrodes, and then rolled and compressed to be inserted into a cylindrical can. An electrolyte was injected into the cylindrical can to prepare a lithium secondary battery.

As described above, the lithium secondary battery was manufactured by injecting the electrolyte solution of the present invention into a cylindrical can into which a positive electrode and a negative electrode were inserted.

In this case, the electrolyte solution is ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / dimethyl carbonate (DMC) mixed solvent were dissolved so that a 1.3M LiPF ₆ in (1: 1 volume ratio: 1) and then, vinyl ethylene carbonate, and fluoro It was prepared by adding ethylene carbonate, wherein the additive trimethoxyboroxine was added 0.1 parts by weight based on 100 parts by weight of the non-aqueous organic solvent.

< Example  2>

The same procedure as in Example 1 was carried out except that trimethoxyboroxine, an additive, was added in an amount of 1 part by weight based on 100 parts by weight of the non-aqueous organic solvent.

< Example  3>

Except for adding trimethoxyboroxine additive 2.0 parts by weight to 100 parts by weight of the non-aqueous organic solvent was carried out in the same manner as in Example 1.

< Example  4>

Trimethoxyboroxine, an additive, was added in the same manner as in Example 1 except that 5.0 parts by weight of trimethoxyboroxine was added based on 100 parts by weight of the non-aqueous organic solvent.

< Example  5>

The same procedure as in Example 1 was carried out except that trimethoxyboroxine, an additive, was added in an amount of 10 parts by weight based on 100 parts by weight of the non-aqueous organic solvent.

< Comparative example  1>

The same procedure as in Example 1 was conducted except that trimethoxyboroxine was not added as an additive.

< Comparative example  2>

Trimethoxyboroxine, an additive, was added in the same manner as in Example 1 except that 0.01 parts by weight of trimethoxyboroxine was added based on 100 parts by weight of the non-aqueous organic solvent.

< Comparative example  3>

The same procedure as in Example 1 was conducted except that 15 parts by weight of trimethoxyboroxine, an additive, was added to 100 parts by weight of the nonaqueous organic solvent.

<Standard capacity>

Table 1 shows standard capacities when the batteries prepared according to Examples 1 to 5 and Comparative Examples 1 to 3 were charged for 3 hours under 0.5 C / 4.2 V constant current-constant voltage conditions.

<Room temperature life characteristics>

The cells prepared according to Examples 1 to 5 and Comparative Examples 1 to 3 were charged with 0.5 C / 4.2 V CC-CV for 3 hours at 25 ° C., and then cut-off at 3 V by 1 C CC discharge. ) After repeating this process 300 times, the capacity retention rate (%) was calculated at room temperature 300 cycles, and the results are shown in Table 1 below.

 * 300th cycle  Capacity Retention Rate (%) = ( 300th cycle  Discharge capacity) / ( 1st cycle  Discharge capacity) * 100 (%)

<High temperature preservation characteristic>

The cells prepared according to Examples 1 to 5 and Comparative Examples 1 to 3 were charged with 0.5 C / 4.2 V CC-CV for 3 hours at 25 ° C., and the amount of change in battery thickness after standing at 85 ° C. for 4 days was measured.

TMBXIN: Trimethoxyboroxine

Referring to Table 1, the electrolyte solution of Examples 1 to 5 in which trimethoxyboroxine was added in the range of 0.1 to 10 parts by weight based on 100 parts by weight of the non-aqueous organic solvent had a 300-cycle capacity retention rate at room temperature. All show about 80% of the value, and it can be seen that the high temperature life characteristics are also excellent.

On the other hand, Comparative Example 1 and Comparative Example 3, in which trimethoxyboroxine as an additive was not added, and Comparative Example 2 and Comparative Example 3, which were added so as to deviate from the range of addition amount of Trimethoxyboroxine, as presented in the present invention, were added. In the case of not only the standard capacity was small, but the 300-cycle capacity retention ratio was less than 60%, which is lower than that of the example, and it was found that the high temperature storage characteristics were not good.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings and tables, the present invention is not limited to the above embodiments, but may be manufactured in various forms, and common knowledge in the art to which the present invention pertains. Those skilled in the art can understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features of the present invention. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

According to the non-aqueous electrolyte lithium secondary battery and the lithium secondary battery including the same according to an embodiment of the present invention can maintain the performance of the battery as it is applied at high voltage while excellent in high temperature storage characteristics and can improve the life.

Claims (14)

Basic electrolyte containing a non-aqueous organic solvent containing at least one solvent selected from the group consisting of a carbonate solvent, an ester solvent, an ether solvent, and a ketone solvent, and a lithium salt dissolved in the non-aqueous organic solvent. ; A non-aqueous electrolyte solution for lithium secondary batteries, characterized in that trimethoxyboroxine represented by the following general formula (1) is added to the basic electrolyte solution.

The method of claim 1, The trimethoxyboroxine is 0.1 to 10 parts by weight based on 100 parts by weight of the non-aqueous organic solvent. The method of claim 1, The carbonate solvent is ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate (BC), 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene One or more cyclic carbonate-based organic solvents of carbonates; The chain carbonate organic solvent of at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC) and ethyl propyl carbonate (EPC) A non-aqueous electrolyte solution for lithium secondary batteries, which is mixed. The method of claim 3, wherein The cyclic carbonate organic solvent and the chain carbonate organic solvent are non-aqueous electrolyte solution for lithium secondary batteries, characterized in that they are mixed in a volume ratio of 1: 1 to 1: 9. The method of claim 1, The ester solvent is methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone, ε-capro A non-aqueous electrolyte solution for lithium secondary batteries, characterized in that it comprises at least one selected from the group consisting of lactones. The method of claim 1, The ether solvent is at least one selected from tetrahydrofuran, 2-methyltetrahydrofuran, dibutyl ether, non-aqueous electrolyte for lithium secondary battery. The method of claim 1, The ketone solvent is a non-aqueous electrolyte lithium secondary battery, characterized in that the polymethyl vinyl ketone. The method of claim 1, The non-aqueous organic solvent is a non-aqueous electrolyte lithium secondary battery, characterized in that it further comprises an aromatic hydrocarbon compound represented by the formula (3).

(Wherein R is a halogen or an alkyl group having 1 to 10 carbon atoms and q is an integer of 0 to 6) The method of claim 8, The aromatic hydrocarbon compound is lithium secondary, characterized in that one of benzene, fluorobenzene, bromobenzene, chlorobenzene, toluene, xylene, mesitylene, fluoro toluene, difluoro toluene, trifluoro toluene Non-aqueous electrolyte solution for batteries. The method according to claim 8 or 9, The aromatic hydrocarbon compound and the carbonate solvent is a non-aqueous electrolyte solution for a lithium secondary battery, characterized in that mixed in a ratio of 1: 1 to 1:30. The method of claim 1, The lithium salt may be LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiN (C ₂ F ₅ SO ₃ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiSbF ₆ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiAlO ₄ , LiAlCl ₄ , LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ , wherein x and y are natural numbers), LiCl, and At least one selected from LiI, the concentration is 0.6 to 2.0M in the total electrolyte, characterized in that the non-aqueous electrolyte for lithium secondary battery. The electrolyte of claim 1; An electrode unit including positive and negative electrodes positioned to face each other with the electrolyte interposed therebetween; And Lithium secondary battery comprising a separator for electrically separating the positive electrode and the negative electrode. The method of claim 12, The positive electrode is Li _x Mn _{1 - y} M _y A ₂ , Li _x Mn ₂ O _{4 - z} X _z , Li _x Mn _{2 - y} M _y M ' _z A ₄ , Li _x Co _{1 - y} M _y A ₂ , _{Li x Co 1 - y M y} O 2 - z X z, Li x Ni 1 - y M y O 2 - z X z, Li x Ni 1 - y Co y O 2 - z X z, Li x Ni 1 - _{y- z} Co _y M _z A _α , Li _x Ni _{1 -y- z} Co _y M _z O _{2 -α} X _α , Li _x Ni _{1 -y- z} Mn _y M _z A _α , Li _x Ni _{1 -y - z} Mn _y M _z O _{2 -α} X _α lithium secondary battery, characterized in that you are in the coating at least one active material selected from. (Wherein 0.9≤x≤1.1, 0≤y≤0.5, 0≤z≤0.5, 0≤α≤2, M and M 'are the same or different and include Mg, Al, Co, K, Na, Ca, Si, Ti, Sn, V, Ge, Ga, B, As, Zr, Mn, Cr, Fe, Sr, V and rare earths Selected from the group of elements, A is selected from the group consisting of O, F, S and P, X is selected from the group consisting of F, S and P) The method of claim 12, The negative electrode is a lithium secondary battery characterized in that the metal is coated with at least one active material selected from crystalline carbon, amorphous carbon, carbon composite, carbon fiber, lithium metal, lithium alloy, lithium composite.

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