KR101885906B1 - Positive electrode composition for rechargable lithium battery, positive electrode prepared from the composition, and recharable lithium battery including the positive electrode - Google Patents

Abstract

A positive electrode active material coated with vanadium pentoxide (V ₂ O ₅ ), and an aqueous binder, a positive electrode containing the negative electrode composition, and a lithium secondary battery employing the positive electrode.

Description

TECHNICAL FIELD [0001] The present invention relates to a positive electrode composition for a lithium secondary battery, a positive electrode containing the same, and a lithium secondary battery employing the positive electrode. BACKGROUND OF THE INVENTION [0002]

A positive electrode composition for a lithium secondary battery, a positive electrode obtained therefrom, and a lithium secondary battery employing the positive electrode.

The lithium secondary battery is composed of a positive electrode and a negative electrode containing an active material capable of inserting and desorbing lithium ions, and is filled with an organic electrolytic solution or a polymer electrolyte between the positive electrode and the negative electrode. At this time, electric energy is produced by oxidation and reduction reactions when lithium ions are inserted and removed from the positive electrode and the negative electrode.

Examples of the positive electrode active material of the lithium secondary battery include lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or lithium nickel cobalt manganese oxide (Li [NiCoMn] O ₂ , Li [Ni _1-xy Co _x M _y ] O ₂ ), and the like, oxides composed of lithium and a transition metal having a structure capable of intercalating lithium ions can be used.

When a positive electrode plate is manufactured using a positive electrode active material for a lithium secondary battery and an aqueous binder, the pH is remarkably increased due to an unreacted alkali metal ion or an alkali metal ion dissociated into water in the positive electrode active material, resulting in strong basicity.

When the slurry of the cathode active material for aqueous system having such strong basicity is coated on a metal substrate such as aluminum, the metal substrate is corroded due to the high pH, H ₂ gas is generated, pinholes are generated in a large amount on the electrode plate, There arises a problem that the resistance rises.

Japanese Patent No. 4,114,247 (Apr. 25, 2008) proposes a nonaqueous electrolyte secondary battery in which molybdenum trioxide (MoO ₃ ) is added to the anode as means for solving the above problems. However, molybdenum trioxide (MoO ₃ ) has a low electrical conductivity, thereby increasing the resistance of the electrode plate, which in turn deteriorates the charge / discharge characteristics of the lithium secondary battery.

Japanese Patent Application Laid-Open No. 2010-021027 (Jan. 28, 2010) proposes a method for coating various metal oxides on an aluminum substrate of a positive electrode as a method for solving the above problems. However, this requires a further process introduction in the production process, which is costly.

Therefore, there is a demand for a new aqueous anode composition capable of preventing corrosion of a metal substrate.

To provide a positive electrode composition for a lithium secondary battery which prevents corrosion of a metal substrate and has high electrical conductivity.

And to provide a positive electrode for a lithium secondary battery and a lithium secondary battery including the same, which can reduce an electrode plate resistance and secure an excellent high rate characteristic and a life characteristic.

One embodiment of the present invention relates to a method for producing an organic solvent, comprising mixing a cathode active material, vanadium pentoxide (V ₂ O ₅ ) and an organic solvent, stirring the mixture to evaporate the organic solvent, and calcining the mixture And a cathode active material coated with vanadium pentoxide.

The cathode active material may include at least one selected from the group consisting of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

The vanadium pentoxide may be contained in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the cathode active material.

The organic solvent may be a carbonate, an alcohol, an ester, an ether, a ketone, an aromatic hydrocarbon, an aprotic solvent, or a combination thereof.

The step of calcining the mixture in which the organic solvent is evaporated can be carried out at 620 to 730 캜.

Another embodiment of the present invention provides a cathode composition for a lithium secondary battery comprising a cathode active material coated with vanadium pentoxide (V ₂ O ₅ ) and an aqueous binder.

The vanadium pentoxide (V ₂ O ₅ ) may be coated in the form of an island on the surface of the cathode active material.

The vanadium pentoxide (V ₂ O ₅ ) may be contained in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the cathode active material.

The vanadium pentoxide (V ₂ O ₅ ) may be included in an amount of 0.1 to 1 part by weight based on 100 parts by weight of the cathode active material.

The cathode active material coated with the vanadium pentoxide may be one prepared by the above-described production method.

The cathode active material may include at least one selected from the group consisting of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

The aqueous binders may be selected from the group consisting of carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, polybutadiene, polyethylene oxide, polyvinyl Polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, polyvinylpyridine, chlorosulfonated polyethylene, polyester resin, acrylic resin, phenol A resin, an epoxy resin, a polymer of propylene and an olefin having 2 to 8 carbon atoms, a copolymer of (meth) acrylic acid and a (meth) acrylic acid alkyl ester, and combinations thereof.

The aqueous binder may be included in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the cathode active material.

The cathode composition for a lithium secondary battery may further include a conductive material.

Wherein the conductive material comprises at least one selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanotube, metal powder, metal fiber and conductive polymer.

In another embodiment of the present invention, a metal substrate having corrosion resistance to strong alkali; And a positive electrode composition for a lithium secondary battery according to any one of claims 6 to 15 disposed on at least one side of the metal base.

The metal substrate may be aluminum.

In another embodiment of the present invention, the above-described anode; A negative electrode comprising a negative electrode active material; A separator existing between the anode and the cathode; And a lithium secondary battery comprising the electrolyte.

The positive electrode composition according to the present invention prevents corrosion of the metal base material in the lithium secondary battery and has high electric conduction characteristics. The lithium secondary battery including the positive electrode composition can reduce the resistance of the electrode plate and secure high-rate characteristics and life characteristics.

1 is a schematic view of a lithium secondary battery according to an embodiment of the present invention.
2 is an X-ray diffraction (XRD) pattern of a cathode active material according to an embodiment of the present invention.
3 is an X-ray diffraction (XRD) pattern of a cathode active material according to a comparative example of the present invention.
4 is a scanning electron microscope (SEM) image of an anode surface according to an embodiment of the present invention.
5 is a scanning electron microscope (SEM) image of the anode surface according to a comparative example of the present invention.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

In one embodiment of the present invention, there is provided a cathode composition for a lithium secondary battery comprising a cathode active material coated with vanadium pentoxide (V ₂ O ₅ ), and an aqueous binder.

The vanadium pentoxide (V ₂ O ₅ ) may specifically be coated on the surface of the cathode active material in the form of an island.

The cathode composition is a water-based cathode composition which can use water as a solvent.

Generally, an aluminum substrate serving as a current collector in the anode structure of a lithium secondary battery has a thin oxide film of aluminum oxide (Al ₂ O ₃ ) on its surface. This oxidation film inhibits the reaction between aluminum metal and water in a neutral aqueous solution so that the reaction of the following reaction formula 1 in which hydrogen gas is generated is not caused.

(Reaction 1) 2Al + 3H ₂ O -> Al ₂ O ₃ + 3H ₂ ↑

However, in the alkaline aqueous solution, the aluminum oxide (Al ₂ O ₃ ) causes the reaction of the following reaction formula 2 to be eluted into the solution with the aluminate ion (AlO ₂ ^- ). The hydrogen gas generated at this time generates pinholes on the surface of the electrode.

(Reaction 2) Al ₂ O ₃ + H ₂ O + 2OH ^- -> 2AlO ₂ ^- + 2H ₂ O

(Reaction Scheme 3) 2Al + 6OH ^- + 6H ₂ O -> 2 [Al (OH) ₆ ] ^3- + 3H ₂

On the other hand, In the case of vanadium pentoxide (V ₂ O ₅₎ is the coated positive electrode active material, a vanadium pentoxide (V ₂ O ₅₎ up the strong oxidizing agent is due to the reaction to form the following the reaction of Scheme 3 is suppressed and the oxide film as shown in Scheme 4 .

(Reaction Scheme 4) 2Al + 3V ₂ O ₅ ? Al ₂ O ₃ + 3V ₂ O ₄

In this manner, corrosion of aluminum is prevented by vanadium pentoxide (V ₂ O ₅ ), so that formation of pinholes in the electrode plate can be suppressed, thereby suppressing an increase in electrode resistance.

In addition, vanadium pentoxide (V ₂ O ₅ ) has a low electrical resistivity of 197 nΩm High electric conduction characteristics can be imparted to the anode material, so that the electrode plate resistance can be reduced, and excellent high-rate characteristics and life characteristics can be secured.

The cathode active material coated with vanadium pentoxide is produced by mixing a cathode active material, vanadium pentoxide (V ₂ O ₅ ) and an organic solvent, stirring the mixture to evaporate the organic solvent, ≪ / RTI >

The organic solvent may be an organic solvent having high volatility. Specifically, it may be a carbonate, alcohol, ester, ether, ketone, aromatic hydrocarbon, aprotic solvent or a combination thereof.

More specifically, examples of the solvent include methanol, ethanol, n-propanol, isopropanol, n-butanol, t-butyl alcohol, ethylene glycol dimethacrylate (EGDME), methyl ethyl ketone ), Methylisobutyl ketone (MIBK), benzene, toluene, or combinations thereof.

The step of stirring the mixture to evaporate the organic solvent may be performed at 30 to 90 ° C, specifically 30 to 70 ° C, and 30 to 50 ° C.

The step of calcining the mixture in which the organic solvent is evaporated can be carried out at 620 to 730 캜. In the case of firing in the above-mentioned temperature range, vanadium pentoxide (V ₂ O ₅ ) can be properly adhered to the surface of the cathode active material without being decomposed. Since the vanadium pentoxide (V ₂ O ₅ ) has a melting point of 650 to 700 ° C, if the calcination temperature is lower than 620 ° C, chemical bonding can not be made, and vanadium pentoxide (V ₂ O ₅ ) may be eliminated during the production of the active material. When the firing temperature is higher than 730 ° C, vanadium pentoxide (V ₂ O ₅ ) is doped into the active material and the effect of suppressing corrosion of the substrate can not be obtained.

In the cathode composition, the content of vanadium pentoxide (V ₂ O ₅ ) is not particularly limited, but if the content of vanadium pentoxide (V ₂ O ₅ ) is too low, it may be difficult to obtain an effect of preventing corrosion of the aluminum current collector And if the content is too high, the proportion of the cathode active material in the electrode plate is reduced, and the capacity can be reduced. Further, the active material having an increased amount of vanadium pentoxide (V ₂ O ₅ ) may have a lower density per unit capacity of the entire electrode plate.

According to one embodiment, vanadium pentoxide (V ₂ O ₅ ) is used in an amount of 0.1 to 5 parts by weight, specifically 0.1 to 4 parts by weight, 0.1 to 3 parts by weight, 0.1 to 2 parts by weight, 0.1 to 2 parts by weight, To 1 part by weight.

If the cathode active material is not vulnerable to an aqueous binder and an aqueous solvent and does not release metal ions, any cathode active material available in the art may be used.

For example, a compound capable of reversible intercalation and deintercalation of lithium (a lithiated intercalation compound) can be used. Specifically, at least one of cobalt, manganese, nickel, or a composite oxide of a metal and lithium in combination thereof can be used. As specific examples, a compound represented by any one of the following formulas can be used: Li _a A _1-b R _b D ₂ wherein, in the formula, 0.90? A? 1.8 and 0? B? 0.5; Li _a E _1-b R _b O _{2 -c} D _c wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, and 0? C? 0.05; LiE (in the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05) 2-b R b O 4-c D c; Li _a Ni _{1- b c} Co _b R _c D _? Wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _{1- b c} Co _b R _c O _{2 -?} Z _? Wherein 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _{1- b c} Co _b R _c O _2-α Z ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 <α <2; Li _a Ni _1-bc Mn _b R _c D _? Wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _1-bc Mn _b R _c O _{2 -?} Z _? Wherein 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _1-bc Mn _b R _c O _2-α Z ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, and 0 <α <2; Li _a Ni _b E _c G _d O ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, and 0.001 ≤ d ≤ 0.1; Li _a Ni _b Co _c Mn _d GeO ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, and 0.001 ≤ e ≤ 0.1; Li _a NiG _b O ₂ (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); Li _a CoG _b O ₂ (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); Li _a MnG _b O ₂ wherein, in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1; Li _a Mn ₂ G _b O ₄ (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); QO _2; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiTO ₂ ; LiNiVO _4; Li _(3-f) J ₂ (PO ₄ ) ₃ (0? F? 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0? F? 2); And LiFePO _4.

In the above formulas, A is Ni, Co, Mn, or a combination thereof; R is at least one element selected from the group consisting of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; Z is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or combinations thereof; Q is Ti, Mo, Mn, or a combination thereof; T is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

Since the cathode composition is an aqueous system, it includes a binder for an aqueous system which can use water as a solvent. The aqueous binders serve to adhere the positive electrode active materials to each other well, adhere the positive electrode active material to the current collector, and act as thickeners for increasing the viscosity of the positive electrode composition.

Unlike the non-aqueous binders such as NMP (N-methyl-pyrrolidone), the water-based binders do not require a dry room because moisture may be present. Since it does not require a recycle treatment process, it is eco-friendly and can shorten mass production facilities. In addition, since the water-based binder has a binding mechanism that is not greatly affected by the specific surface area of the electrode material, it can be applied to various materials having a large specific surface area, and has low reactivity with an electrolytic solution.

Representative examples of the binder for a water-based binder include carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, polybutadiene, polyethylene oxide, Polyvinyl alcohol, polyacrylic acid and salts thereof, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, polyvinylpyridine, chlorosulfonated polyethylene, polyester resin, acrylic resin , A phenol resin, an epoxy resin, a polymer of propylene and an olefin having 2 to 8 carbon atoms, a copolymer of (meth) acrylic acid and an alkyl (meth) acrylate, and the like, but the present invention is not limited thereto. Anything that can be used is possible.

In the present invention, one kind of the binder may be used, or two or more kinds of the binders may be used in combination.

The aqueous binder may be used in an appropriate content range so as to impart the binding force between the cathode active material particles and the binding force between the cathode active material particles and the current collector and the viscosity of the cathode composition, and the content thereof is not particularly limited . For example, it may be used in a range of 0.1 to 10 parts by weight based on 100 parts by weight of the positive electrode active material, specifically 1 to 8 parts by weight, more specifically 4 to 8 parts by weight based on 100 parts by weight of the positive electrode active material.

The positive electrode slurry composition for a lithium secondary battery may further include a conductive material. The conductive material is used for imparting conductivity to the electrode, and any material can be used as long as it is an electron conductive material without causing any chemical change in the battery constituted.

Examples of the conductive material include metal powders such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, copper, nickel, aluminum and silver, and metal fibers. One or more conductive materials may be used in combination.

The conductive material may be suitably used within a range of 1 to 20 parts by weight based on 100 parts by weight of the positive electrode active material.

In another embodiment of the present invention, there can be provided a positive electrode for a lithium secondary battery comprising a metal base material having corrosion resistance to a strong alkali and a positive electrode composition for a lithium secondary battery described above disposed on at least one side of the metal base material.

In the anode, the metal substrate serves as a current collector, and may be used without particular limitation, as long as it has high conductivity without causing chemical changes in the battery. For example, the surface of stainless steel, aluminum, nickel, titanium, sintered carbon, aluminum or stainless steel can be used with surface treatment with carbon, nickel, titanium, silver, or the like. Among them, examples of the metal substrate that is corroded by the strong alkali include an aluminum substrate. In this case, corrosion of the aluminum substrate can be effectively prevented by applying the above-mentioned positive electrode composition. The thickness of the metal substrate may range from 3 to 500 mu m, but is not particularly limited.

The positive electrode can be produced, for example, by molding the positive electrode composition into a predetermined shape or by applying the positive electrode composition to a metal base such as an aluminum foil.

Specifically, the positive electrode composition described above can be directly coated on a metal substrate and dried to form a positive electrode layer. Alternatively, the slurry composition may be cast on a separate support, and then the film obtained by peeling from the support may be laminated on a metal substrate to produce a cathode layer. In addition, the anode can be manufactured in a variety of ways using methods well known to those skilled in the art.

According to another embodiment of the present invention, there can be provided a lithium secondary battery including the above-described cathode, a cathode including the anode active material, a separator existing between the cathode and the anode, and an electrolyte.

FIG. 1 schematically shows a representative structure of the lithium secondary battery of the present invention. 1, the lithium secondary battery 1 includes a positive electrode 3, a negative electrode 2, and a battery 4 including an electrolyte solution impregnated in the separator 4 existing between the positive electrode 3 and the negative electrode 2, And a sealing member (6) for sealing the battery container (5).

The negative electrode of the lithium secondary battery includes a current collector and a negative electrode active material layer formed on the current collector, and the negative electrode active material layer includes a negative electrode active material.

The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, a lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

As a material capable of reversibly intercalating / deintercalating lithium ions, any of carbonaceous anode active materials generally used in lithium ion secondary batteries can be used. Representative examples of the carbon-based negative electrode active material include crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in an amorphous, plate-like, flake, spherical or fibrous form. Examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, fired coke and the like.

As the alloy of lithium metal, it is preferable that lithium is mixed with the metal of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Alloys may be used.

As the material capable of doping and dedoping lithium, Si, SiO _x (0 <x <2), Si-C composite, Si-Q alloy (Q is an alkali metal, an alkaline earth metal, A transition metal, a rare earth element or a combination thereof and not Si), Sn, SnO ₂ , Sn-C composite, Sn-R (wherein R is an alkali metal, an alkaline earth metal, A rare earth element or a combination thereof, but not Sn). Specific elements of Q and R include Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, , Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, Bi, S, Se, Te, Po, or a combination thereof.

Examples of the transition metal oxide include vanadium oxide, lithium vanadium oxide, and the like.

The negative electrode active material layer also includes a binder, and may optionally include a conductive material.

The binder serves to adhere the anode active material particles to each other and to adhere the anode active material to the current collector. Representative examples of the binder include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinyl pyrrolidone, poly But are not limited to, urethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin and nylon.

The conductive material is used for imparting conductivity to the electrode. Any conductive material can be used without causing any chemical change in the battery. Specific examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black and carbon fiber; Metal powders such as copper, nickel, aluminum, and silver, or metal-based materials such as metal fibers; Conductive polymers such as polyphenylene derivatives; Or a mixture thereof may be used.

The current collector may be a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foil, a copper foil, a polymer substrate coated with a conductive metal, or a combination thereof.

The negative electrode and the positive electrode can be produced by mixing an active material, a conductive material and a binder in a solvent to prepare an active material composition, and applying the composition to a current collector. The method of manufacturing the electrode is well known in the art, and therefore, a detailed description thereof will be omitted herein. As the solvent, N-methylpyrrolidone or the like can be used, but it is not limited thereto.

The separator separates the negative electrode and the positive electrode and provides a passage for lithium ion. Any separator commonly used in a lithium battery can be used. That is, it is possible to use an electrolyte having a low resistance to the ion movement and an excellent ability to impregnate the electrolyte. For example, selected from glass fibers, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and may be nonwoven fabric or woven fabric. For example, a polyolefin-based polymer separator such as polyethylene, polypropylene and the like is mainly used for a lithium ion battery, and a coated separator containing a ceramic component or a polymer substance may be used for heat resistance or mechanical strength, Structure.

The electrolyte includes a non-aqueous organic solvent and a lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

As the non-aqueous organic solvent, a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based or aprotic solvent may be used. Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC) EC), propylene carbonate (PC), and butylene carbonate (BC) may be used. As the ester solvent, methyl acetate, ethyl acetate, n-propyl acetate, 1,1-dimethyl ethyl acetate, methyl propionate , Ethyl propionate,? -Butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone and the like can be used. Examples of the ether solvent include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran. As the ketone solvent, cyclohexanone may be used have. As the alcoholic solvent, ethyl alcohol, isopropyl alcohol and the like can be used. As the aprotic solvent, R-CN (R is a C2 to C20 linear, branched or cyclic hydrocarbon group, An amide such as nitriles such as dimethylformamide, and dioxolanes such as 1,3-dioxolane, sulfolanes, and the like can be used.

The non-aqueous organic solvent may be used alone or in admixture of one or more. If the non-aqueous organic solvent is used in combination, the mixing ratio may be appropriately adjusted according to the desired cell performance. .

In the case of the carbonate-based solvent, it is preferable to use a mixture of a cyclic carbonate and a chain carbonate. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1: 1 to about 1: 9, the performance of the electrolytic solution may be excellent.

The non-aqueous organic solvent may be used by mixing the aromatic hydrocarbon-based organic solvent with the carbonate-based solvent. In this case, the carbonate-based solvent and the aromatic hydrocarbon-based organic solvent may be mixed in a volume ratio of about 1: 1 to about 30: 1.

The aromatic hydrocarbon-based organic solvent may be an aromatic hydrocarbon-based compound represented by the following formula (1).

[Chemical Formula 1]

In Formula 1, R ₁ to R ₆ are independently hydrogen, halogen, a C1 to C10 alkyl group, a C1 to C10 haloalkyl group, or a combination thereof.

The aromatic hydrocarbon-based organic solvent is selected from the group consisting of benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3- , 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 4-trichlorobenzene, iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, 1,2,4 - triiodobenzene, toluene, fluorotoluene, 1,2-difluorotoluene, 1,3-difluorotoluene, 1,4-difluorotoluene, 1,2,3-trifluorotoluene, 1,2,4-trifluorotoluene, chlorotoluene, 1,2-dichlorotoluene, 1,3-dichlorotoluene, 1,4-dichlorotoluene, 1,2,3-trichlorotoluene, 1,2,4 - trichlorotoluene, iodotoluene, 1,2-diiodotoluene, 1,3-diiodotoluene, 1,4-diiodotol Ene, 1,2,3-tree-iodo toluene, 1,2,4-iodo toluene, xylene, or may be a combination thereof.

The non-aqueous electrolyte may further include vinylene carbonate or an ethylene carbonate-based compound represented by the following formula (2) to improve battery life.

(2)

In Formula 2, R ₇ and R ₈ are, independently, an alkyl group of hydrogen, halogen, cyano (CN), fluoro nitro group (NO _2), or a C1 to C5, the R ₇ and R ₈ of At least one is a halogen group, a cyano group (CN), a nitro group (NO ₂ ), or a C1 to C5 fluoroalkyl group.

Representative examples of the ethylene carbonate-based compound include, for example, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, fluoroethylene carbonate, . When the vinylene carbonate or the ethylene carbonate compound is further used, the amount of the vinylene carbonate or the ethylene carbonate compound can be appropriately controlled to improve the life.

The lithium salt dissolves in the non-aqueous organic solvent to act as a source of lithium ions in the cell to enable operation of a basic lithium secondary battery and to promote the movement of lithium ions between the positive electrode and the negative electrode. The lithium salt Representative examples include _{LiPF 6, LiBF 4, LiSbF 6} , LiAsF 6, LiC 4 F 9 SO 3, LiClO 4, LiAlO 2, LiAlCl 4, LiN (C x F 2x + 1 SO 2) (C y F 2y ₊₁ SO ₂₎ (where, x and y are natural numbers), LiCl, LiI, LiB ( C 2 O 4) 2 ( lithium bis oxalate reyito borate (lithium bis (oxalato) borate; LiBOB), or a combination thereof The concentration of the lithium salt is preferably in the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity, Performance, and lithium ions can move efficiently.

Hereinafter, examples and comparative examples of the present invention will be described. The following examples are illustrative of the present invention only, and the present invention is not limited by these examples.

Manufacture of anode

Production Example 1

10 g (10 wt%) of V ₂ O ₅ solution, 200 g of Li [Ni _0.5 Co _0.2 Mn _0.3 ] O ₂ and 12 g of ethanol were mixed and stirred at 40 ° C to evaporate the ethanol. Heated at a rate of 1 占 폚 / min and baked for 120 minutes while maintaining a constant temperature at 650 占 폚 and cooled at 300 占 폚 for 300 minutes to coat V ₂ O ₅ on Li [Ni _0.5 Co _0.2 Mn _0.3 ] O ₂ . 100 g of Li [Ni _0.5 Co _0.2 Mn _0.3 ] O ₂ coated with V ₂ O ₅ , 13.4 g of acetylene black, and 3.3 g of carboxymethyl cellulose were added to 75 g of water and mixed. Thereafter, 70 g of water and 25 g (40 wt%) of an acrylic copolymer emulsion (Xeon Co., ax-4069) were added and then mixed to prepare a cathode composition. The positive electrode composition was coated on an aluminum foil and dried at 100 DEG C for 10 minutes to prepare a positive electrode.

Production Example 2

Except that ₅ g (10 wt%) of a V ₂ O ₅ solution was used instead of ₅ g (10 wt%) of a V ₂ O ₅ solution.

Production Example 3

Except that 15 g (10 wt%) of a V ₂ O ₅ solution was used as a cathode active material.

Comparative Preparation Example 1

Except that Li [Ni _0.5 Co _0.2 Mn _0.3 ] O ₂ not coated with V ₂ O ₅ was used.

Manufacture of Lithium Secondary Battery (Coin Cell)

Example 1

A coin cell (CR2032 type) having a diameter of 20 mm was prepared by using the positive electrode plate prepared in Production Example 1. In the cell preparation, 97.5 g of graphite, 1 g of carboxymethylcellulose (CMC) and 50 g of water were mixed first, and then a binder (BM400B 1.5 g (solid content 40%)) and 50 g of water were further added to prepare a slurry. The membrane was coated with a dried plate and a PE / PP separator was used as the electrolyte. A 1.3: 1 mixture of ethylene carbonate (EC): diethyl carbonate (DEC): dimethyl carbonate (DMC) M &lt; / RTI &gt; LiPF ₆ dissolved therein was used to prepare a coin cell of the CR-2032 standard.

Examples 2 and 3

Coin cells were prepared in the same manner as in Example 1, except that the positive electrode plates prepared in Production Examples 2 and 3 were used, respectively.

Comparative Example 1

A coin cell was produced in the same manner as in Example 1 except that the positive electrode plate prepared in Comparative Production Example 1 was used.

Evaluation Example 1: Evaluation of X-ray Diffraction (XRD)

An X-ray diffraction pattern of Li [Ni _0.5 Co _0.2 Mn _0.3 ] O ₂ coated with V ₂ O _{5, which} is the cathode active material prepared in Preparation Example 1, is shown in FIG. 3 shows an X-ray diffraction pattern of Li [Ni _0.5 Co _0.2 Mn _0.3 ] O ₂ , which is the cathode active material prepared in the above comparative production and was not coated with V ₂ O ₅ .

In Fig. 2, the circled portion is a peak indicating vanadium (V). 2 and 3, it can be seen that the cathode active material prepared in Preparation Example 1 contains vanadium.

Evaluation Example 2: Assessment of pinhole occurrence on the surface of the positive electrode plate

The positive electrode plates prepared in Preparation Examples 1 to 3 and Comparative Preparation Example 1 were observed for hydrogen gas pinholes on the surface, and the results are shown in Table 1 below.

A scanning electron microscope (SEM) photograph of the positive electrode plate prepared in Production Example 1 is shown in FIG. 4, and a scanning electron microscope photograph of the positive electrode plate prepared in Comparative Production Example 1 is shown in FIG.

H ₂ pinhole occurrence Production Example 1 X Production Example 2 X Production Example 3 X Comparative Preparation Example 1 O

As shown in Table 1, in the case of the positive electrode plate according to Comparative Production Example 1, hydrogen gas pinholes were generated, but in the case of the positive electrode plates prepared in Production Examples 1 to 3, hydrogen gas pinholes due to corrosion of the electrode plate did not occur.

Referring to FIG. 5, pinholes are clearly observed in the positive electrode plate according to Comparative Production Example 1. On the other hand, the positive electrode plate of Example 1 shown in FIG. 4 does not show any pinholes.

Evaluation Example 3: Life characteristic evaluation

The capacity retention (%) of the lithium secondary batteries manufactured in Examples 1 to 3 and Comparative Example 1 at the time of 100 cycles per cycle was evaluated. The results are shown in Table 2 below.

Capacity retention rate (%) Example 1 91.2 Example 2 87.9 Example 3 86.3 Comparative Example 1 73.7

Referring to Table 2, it can be confirmed that the capacity retention ratios of Examples 1 to 3 are 86.3 to 91.2%, which is superior to that of Comparative Example 1.

It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims and their equivalents. It will be understood that the invention may be practiced. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

1: Lithium secondary battery
2: cathode
3: anode
4: Separator
5: Battery container
6: sealing member

Claims (10)

A positive electrode composition for a lithium secondary battery comprising a positive electrode active material coated with vanadium pentoxide (V ₂ O ₅ ), and an aqueous binder,
Wherein the aqueous binder comprises carboxymethyl cellulose and an acrylic copolymer,
The positive electrode active material is a lithium nickel cobalt manganese oxide,
The vanadium pentoxide (V ₂ O ₅ ) is contained in an amount of 0.25 to 0.5 part by weight based on 100 parts by weight of the cathode active material,
Wherein the aqueous binder is contained in an amount of 4 to 8 parts by weight based on 100 parts by weight of the positive electrode active material. The method according to claim 1,
Wherein the vanadium pentoxide (V ₂ O ₅ ) is coated in the form of an island on the surface of the cathode active material. The method according to claim 1,
The cathode active material coated with vanadium pentoxide
Mixing the cathode active material, vanadium pentoxide (V ₂ O ₅ ) and an organic solvent to form a mixture,
Stirring the mixture to evaporate the organic solvent, and
And firing the mixture in which the organic solvent is evaporated. The cathode composition for a lithium secondary battery according to claim 1, The method of claim 3,
Wherein the organic solvent is a carbonate, alcohol, ester, ether, ketone, aromatic hydrocarbon, aprotic solvent or a combination thereof. The method of claim 3,
Wherein the step of firing the mixture in which the organic solvent is evaporated is performed at 620 to 730 캜. The method according to claim 1,
Wherein the positive electrode composition for a lithium secondary battery further comprises a conductive material. The method according to claim 6,
Wherein the conductive material comprises at least one selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanotube, metal powder, metal fiber and conductive polymer. Metal substrates that are corrosive to strong alkali; And
The positive electrode composition for a lithium secondary battery according to any one of claims 1 to 7, which is disposed on at least one surface of the metal substrate.
And a positive electrode for a lithium secondary battery. 9. The method of claim 8,
Wherein the metal substrate is aluminum. A positive electrode of claim 8;
A negative electrode comprising a negative electrode active material;
A separator existing between the anode and the cathode; And
Electrolyte;
&Lt; / RTI &gt;

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