KR20150049893A - A method for manufacturing cathode, a cathode manufactured thereby and a lithium secondary battery including the same - Google Patents

Abstract

The present invention relates to a method for manufacturing an anode, which can replace a high-voltage activation process for an anode active material that is represented by the following chemical formula 1 and stabilize the surface of the anode active material, an anode manufactured thereby, and a lithium secondary battery including the same. The chemical formula 1 is Li(Li_xM_y-y′M′_y′)O_2-zA_z, wherein 0 < x < 0.5; 0.6 < y < 1.1; 0 <= y′ < 0.2; 0 <= z < 0.2; M includes one or more elements selected from the group consisting of Mn, Ni, Co, Fe, Cr, V, Cu, Zn and Ti; M′ is one or more elements selected from the group consisting of Al, Mg and B; and A is one or more elements selected from the group consisting of F, S and N. According to the present invention, the high-voltage activation can be omitted in a mixing process of anode active material slurry by performing chemical activation for the anode active material, which is represented by the chemical formula 1. The present invention is capable of stabilizing the surface of the anode active material by coating a silane coupling agent on the surface of the anode active material after the chemical activation and preventing deterioration of a battery life by reducing the surface reactivity with an electrolyte solution.

Description

[0001] The present invention relates to a positive electrode, a positive electrode manufactured by the method, and a lithium secondary battery including the same,

[0001] The present invention relates to a positive electrode and a lithium secondary battery comprising the same, and more particularly, to a positive electrode prepared by the method of manufacturing the positive electrode, and a lithium secondary battery comprising the positive electrode. A positive electrode prepared by the production method, and a lithium secondary battery containing the same.

Recently, interest in energy storage technology is increasing. As the application fields are expanded to mobile phones, camcorders, notebook PCs, and even middle- or large-sized batteries of electric vehicles, there is a growing demand for high energy density of batteries used as power sources for such electronic devices. Lithium secondary batteries are the ones that can best meet these demands, and researches on them are actively under way.

However, such a lithium secondary battery has safety problems such as ignition and explosion when using an organic electrolytic solution, and it is disadvantageous in that it is difficult to manufacture. In particular, with the recent expansion of the application range of lithium secondary batteries, lithium secondary batteries have been used under various conditions and environments, and the demand for lithium secondary batteries of higher capacity has been gradually increasing. In order to provide a high capacity lithium secondary battery, the operating range of the battery is gradually expanding. The shift to high voltage can benefit from the capacity but the safety problem is also made more remarkable than before.

In particular, the lithium compound having a layered structure represented by the following general formula (1), unlike other conventional cathode materials, is prepared in a range of 4.3 V to 4.8 V And a high capacity is required to be exhibited through the structural change of the active material when the activation step is performed at a high voltage higher than the flat level region. During the activation process, a large amount of gas is generated due to a side reaction at the interface between the positive electrode and the electrolyte due to the structural variation and high voltage in the positive electrode active material. When the generated gas remains in the battery, And may cause adverse effects on the battery, such as localized lithium deposition (Li plating). Therefore, it is inconvenient to remove such gas during the activation process or after the activation process.

[Chemical Formula 1]

Li (Li _x M _{y - y '} M' _{y '} ) O _{2 - z} A _z

Wherein M is at least one element selected from the group consisting of Mn, Ni, Co, Fe, Cr, V, Cu, Zn, Ti, M 'is at least one element selected from the group consisting of Al, Mg and B, and A is at least one element selected from the group consisting of F, S and N .)

Accordingly, a problem to be solved by the present invention is to provide a method for preparing a positive electrode capable of stabilizing the surface of a positive electrode active material while replacing high-voltage activation treatment for the positive electrode active material of Formula 1, a positive electrode prepared by the method, And a lithium secondary battery.

According to an aspect of the present invention, there is provided a method of preparing a slurry comprising mixing (S1) a cathode active material represented by the following formula (1), an organic solvent, and an acidity adjusting agent, Chemically activating the cathode active material; (S2) coating the surface of the activated cathode active material with the silane coupling agent by adding a silane coupling agent to the result of the step (S1) and then mixing the resultant; (S3) coating the resultant product after the step (S2) on the positive electrode current collector; And (S4) crosslinking the silane coupling agent coated on the surface of the positive electrode active material while vacuum drying the result obtained in the step (S3). In the step (S1), the conductive material, the polymer binder, The conductive agent, the polymer binder and the thickening agent are further added and mixed in the step (S2), or after the step (S2), the conductive agent, the polymer binder and the thickener are further added There is provided a process for producing an anode which is mixed with the anode.

[Chemical Formula 1]

Li (Li _x M _{y - y '} M' _{y '} ) O _{2 - z} A _z

Wherein M is at least one element selected from the group consisting of Mn, Ni, Co, Fe, Cr, V, Cu, Zn, Ti, M 'is at least one element selected from the group consisting of Al, Mg and B, and A is at least one element selected from the group consisting of F, S and N .)

At this time, the organic solvent may be selected from the group consisting of N-methyl pyrrolidone (NMP), dimethylsulfoxide (DMSO), methyl alcohol, ethyl alcohol, isopropyl alcohol alcohol and distilled water, or a mixture of two or more thereof.

The slurry may exhibit acidity by hydrogen ions generated by ionization of the acidity regulator.

The slurry may have a hydrogen ion concentration of pH 3 to pH 7.

The acidity regulator may be any one of acetic acid, oxalic acid, formic acid, hydrochloric acid, sulfuric acid and nitric acid, or a mixture of two or more thereof.

In step (S2), the silane coupling agent may be added in an amount of 0.01 to 5% by weight based on the weight of the cathode active material.

The drying temperature in the step (S4) may be 80 to 250 ° C.

According to another aspect of the present invention, there is provided a cathode produced by the above-described production method of the present invention.

According to still another aspect of the present invention, there is provided an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; A nonaqueous electrolytic solution for impregnating the electrode assembly; And a battery case containing the electrode assembly and the non-aqueous electrolyte, wherein the positive electrode is the positive electrode of the present invention as described above.

Here, the negative electrode may include a negative electrode active material containing lithium metal, a carbon material, a metal compound, or a mixture thereof.

The metal compound may be at least one selected from the group consisting of Si, Ge, Sn, Pb, P, Sb, Bi, Al, Ga, In, Ti, Mn, Fe, Co, Ni, Cu, Zn, Ag, Or a mixture of two or more thereof.

The separator may be made of any one of high density polyethylene, low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polypropylene, polybutylene, polypentene, polyethyleneterephthalate, polybutyleneterephthalate, ), Polyacetals, polyamides, polycarbonates, polyimides, polyetheretherketones, polyethersulfone, polyphenylene oxides, poly (phenylene oxides), poly A porous substrate formed of any one selected from the group consisting of polyphenylene sulfide and polyethylene naphthalene or a mixture of two or more thereof.

According to the present invention, in the mixing process of the positive electrode active material slurry, chemical activation is performed on the positive electrode active material represented by the above formula (1) so that the high voltage activation process can be omitted, and a silane coupling agent It is possible to stabilize the surface of the positive electrode active material and reduce the interfacial reactivity with the electrolytic solution, thereby preventing deterioration of the service life of the battery.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments of the invention and, together with the description of the invention, It should not be construed as limited.
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a graph comparing discharging capacities of a coin type battery including an anode manufactured in an embodiment of the present invention and a comparative example; FIG.
FIG. 2 is a graph showing a comparison of the capacity retention ratios of the polymer pouch type batteries manufactured in the example of the present invention and the comparative example.

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

In addition, since the configurations disclosed in the embodiments disclosed herein are only the most preferred embodiments of the present invention, they are not intended to represent all of the technical ideas of the present invention, and therefore, various equivalents It should be understood that variations can be made.

A method of manufacturing an anode according to an aspect of the present invention is as follows.

First, a slurry is prepared by mixing a cathode active material represented by the following Chemical Formula 1, an organic solvent, and an acidity regulator, and the cathode active material is chemically activated with hydrogen ions generated by ionization of the acidity regulator (S1).

[Chemical Formula 1]

Li (Li _x M _{y - y '} M' _{y '} ) O _{2 - z} A _z

Wherein M is at least one element selected from the group consisting of Mn, Ni, Co, Fe, Cr, V, Cu, Zn, Ti, M 'is at least one element selected from the group consisting of Al, Mg and B, and A is at least one element selected from the group consisting of F, S and N .)

In the case of the above-mentioned cathode active material, in order to obtain high capacity, an activation process is required to induce a structural change of the cathode active material under a high voltage (approximately 4.4 V or more). However, during the activation process, a large amount of gas is generated in the cathode active material, and side reactions may occur between the electrolyte and the electrode interface due to the high voltage. Therefore, in the present invention, to prevent such a phenomenon, a chemical activation method using a hydrogen ion is used instead of activation under a high voltage.

The organic solvent may be selected from the group consisting of N-methyl pyrrolidone (NMP), dimethylsulfoxide (DMSO), methyl alcohol, ethyl alcohol, isopropyl alcohol alcohol, and distilled water, or a mixture of two or more thereof. However, it is not limited as long as it can disperse without reacting with the cathode active material.

At this time, the slurry may exhibit acidity by hydrogen ions generated by ionization of the acidity controlling agent, and the slurry may have a pH of from 3 to 7.

The pH adjusting agent may be, for example, acetic acid, oxalic acid, formic acid, hydrochloric acid, sulfuric acid, or nitric acid, or a mixture of two or more thereof. have. However, it is preferable to use a weak acid which is easy to handle.

Subsequently, a silane coupling agent is added to the resultant product after the step (S1), followed by mixing, and the surface of the activated cathode active material is coated with the silane coupling agent (S2).

This can stabilize the surface of the cathode active material, reduce interfacial reactivity with the electrolyte, and prevent deterioration of the service life of the battery.

At this time, the silane coupling agent may be added in an amount of 0.01 to 5 wt% based on the weight of the cathode active material.

Meanwhile, in the step (S1), the conductive material, the polymer binder and the thickening agent may be further added and then mixed. In the step (S2), the conductive material, the polymer binder and the thickening agent may be further added and mixed, After the step (S2), the conductive material, the polymer binder, and the thickener are further added and mixed.

Here, the conductive material is not particularly limited as long as it is an electron conductive material that does not cause a chemical change in the lithium secondary battery. In general, carbon black, graphite, carbon fiber, carbon nanotube, metal powder, conductive metal oxide, organic conductive material and the like can be used. Commercially available products as the conductive material include acetylene black series (manufactured by Chevron Chemical Co., (Chevron Chemical Company or Gulf Oil Company products), Ketjen Black EC series (Armak Company), Vulcan XC-72 (Cabot Company) and Super P (MM (MMM)). For example, acetylene black, carbon black and graphite.

The polymer binder has a function of holding the positive electrode active material on the positive electrode collector and connecting the active materials, and a commonly used binder may be used without limitation.

For example, it is possible to use vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, styrene -Butadiene rubber (SBR, styrene butadiene rubber) may be used.

Examples of the thickener include cellulosic compounds such as carboxymethylcellulose, carboxymethylcellulose, compounds in which they are substituted with cations such as ammonium ions and monovalent metal ions, and the like.

Subsequently, the resultant product after step (S2) is coated on the positive electrode current collector (S3).

At this time, the cathode current collector is a metal having high conductivity and can be easily adhered to the slurry containing the cathode active material, and any material can be used as long as it is not reactive in the voltage range of the battery. Specifically, a foil manufactured by aluminum, nickel, or a combination thereof may be used.

Subsequently, the silane coupling agent coated on the surface of the cathode active material is crosslinked while vacuum drying the resultant material obtained in the step (S3) (S4).

At this time, the drying temperature may be 80 to 250 ° C. If the temperature is satisfied, the crosslinking reaction of the silane coupling agent can proceed more easily and the cathode active material slurry can be properly dried.

According to another aspect of the present invention, there is provided a lithium secondary battery including: an electrode assembly including a cathode, a cathode, and a separator interposed between the anode and the cathode; A nonaqueous electrolytic solution for impregnating the electrode assembly; And a battery case containing the electrode assembly and the non-aqueous electrolyte. The positive electrode is a positive electrode manufactured by the manufacturing method of the present invention described above.

Here, the negative electrode has a structure in which a negative electrode active material layer including a negative electrode active material and a polymeric binder is coated on one surface or both surfaces of the current collector.

As the negative electrode active material, a lithium metal, a carbonaceous material, a metal compound, or a mixture of lithium metal, a carbonaceous material, and a metal compound, in which lithium ions can be occluded and released, may be used.

Concretely, as the carbon material, low-crystallinity carbon and high-crystallinity carbon may be used. Examples of the low crystalline carbon include soft carbon and hard carbon. Examples of highly crystalline carbon include natural graphite, Kish graphite, pyrolytic carbon, liquid crystal pitch carbon fiber high temperature sintered carbon such as mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches and petroleum or coal tar pitch derived cokes.

The metal compound may be at least one selected from the group consisting of Si, Ge, Sn, Pb, P, Sb, Bi, Al, Ga, In, Ti, Mn, Fe, Co, Ni, Cu, Zn, Ag, Of at least one metal element. These metal compounds may be a single substance, an alloy, an oxide (TiO ₂ , SnO ₂ Or the like), a nitride, a sulfide, a boride, an alloy with lithium, or the like, but an alloy with a single substance, an alloy, an oxide, and lithium can be increased in capacity. Among them, it may contain at least one element selected from Si, Ge and Sn, and it may further increase the capacity of the battery including at least one element selected from Si and Sn.

The current collector used for the negative electrode is a metal having high conductivity and can easily adhere to the slurry of the active material, and any material can be used as long as it is not reactive in the voltage range of the battery. Specifically, non-limiting examples of the current collector for a negative electrode include a foil manufactured by copper, gold, nickel or a copper alloy or a combination thereof. In addition, the current collector may be used by laminating the substrates made of the above materials.

On the other hand, the separator used in the present invention can be any porous substrate commonly used in the art. For example, a polyolefin porous membrane or a nonwoven fabric may be used, but the present invention is not limited thereto.

Examples of the polyolefin-based porous film include polyolefin-based polymers such as polyethylene, polypropylene, polybutylene, and polypentene, such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene and ultra-high molecular weight polyethylene, One membrane can be mentioned.

The nonwoven fabric may include, in addition to the polyolefin nonwoven fabric, for example, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate ), Polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylenesulfide, and polyethylene naphthalene, which may be used alone or in combination, And nonwoven fabrics formed by mixing these polymers. The structure of the nonwoven fabric may be a spun bond nonwoven fabric or a meltblown nonwoven fabric composed of long fibers.

The thickness of the porous substrate is not particularly limited, but may be 5 to 50 μm, and the pore size and porosity present in the porous substrate are also not particularly limited, but may be 0.01 to 50 μm and 10 to 95%, respectively.

Meanwhile, the non-aqueous electrolyte used in the present invention may include an organic solvent and an electrolyte salt, and the electrolyte salt is a lithium salt. The lithium salt may be any of those conventionally used for non-aqueous electrolytes for lithium secondary batteries. For example is the above lithium salt anion ^{F -, Cl -, Br -} , 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 ^- , or two or more of them.

Examples of the organic solvent included in the non-aqueous electrolyte include those commonly used in non-aqueous electrolytes for lithium secondary batteries, such as ether, ester, amide, linear carbonate, cyclic carbonate, etc., Two or more of them may be used in combination.

Among them, a carbonate compound which is typically a cyclic carbonate, a linear carbonate, or a mixture thereof may be included.

Specific examples of the cyclic carbonate compound include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, Propylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, vinylethylene carbonate, and halides thereof, or a mixture of two or more thereof. Examples of such halides include, but are not limited to, fluoroethylene carbonate (FEC) and the like.

Specific examples of the linear carbonate compound include any one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate and ethyl propyl carbonate And mixtures of two or more of them may be used as typical examples, but the present invention is not limited thereto.

In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates in the carbonate-based organic solvent, are high-viscosity organic solvents having a high dielectric constant and can dissociate the lithium salt in the electrolyte more easily. In addition, such cyclic carbonates can be used as dimethyl carbonate and diethyl carbonate When a low viscosity, low dielectric constant linear carbonate is mixed in an appropriate ratio, an electrolyte having a higher electric conductivity can be produced.

As the ether in the organic solvent, any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether and ethyl propyl ether or a mixture of two or more thereof may be used , But is not limited thereto.

Examples of the ester in the organic solvent include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate,? -Butyrolactone,? -Valerolactone,? -Caprolactone,? -Valerolactone and? -Caprolactone, or a mixture of two or more thereof, but the present invention is not limited thereto.

The injection of the non-aqueous electrolyte may be performed at an appropriate stage of the production process of the lithium secondary battery, depending on the manufacturing process and required properties of the final product. That is, it can be applied before assembling the lithium secondary battery or in the final stage of assembling the lithium secondary battery.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

One. Example

(1) Preparation of positive electrode

In N- methylpyrrolidone solvent of money (NMP), Li was charged into the positive electrode active material _{(Li 0 .2 Mn 0 .55 Ni} 0 .15 Co 0 .1) O 2, and mixed for 30 minutes. Subsequently, acetic acid was added to the mixture to adjust the pH to 5.2, followed by further mixing for 24 hours to induce chemical activation of the cathode active material while preparing the slurry.

Thereafter, bis (triethoxy silyl) ethane was added to the slurry and mixed for 3 hours to perform a coupling treatment on the surface of the cathode active material. Thereafter, the PVDF binder, the dengan black conductive material and the NMP solvent were added and mixed (89.5 wt% of the positive electrode active material, 5 wt% of the denganic black conductive material, 5 wt% of the PVDF binder, 0.5% by weight of Ling.

Subsequently, the slurry was coated on an aluminum (Al) foil having a thickness of 20 탆, which was a positive electrode current collector, and rolled. Thereafter, the positive electrode was dried under a vacuum at a temperature of 150 캜 for 24 hours to form a coupling agent Crosslinking reaction.

(2) Manufacture of cathodes

96% by weight of natural graphite as a negative electrode active material, 3% by weight of PVDF as a binder, and 1% by weight of a conductive material rhodenk black were added to a solvent of deionized water (DI water) to prepare a slurry. This was coated on a copper foil having a thickness of 10 탆, which was an anode current collector, rolled and vacuum dried to prepare a negative electrode.

(3) Production of polymer pouch type battery

A polymer pouch-type battery having a 1 C discharge capacity of 25 mAh was produced by using the separator composed of the anode, the cathode and three layers of polypropylene / polyethylene / polypropylene (PP / PE / PP). A non-aqueous electrolyte (ethylene carbonate (EC): propylene carbonate (PC): diethyl carbonate (DEC) = 30: 20: 50 wt%, lithium hexafluorophosphate (LiPF ₆ ) 1 mol) .

2. Comparative Example  One

(1) Preparation of positive electrode

Except that bis (triethoxy silyl) ethane was not added to the positive electrode.

(2) Manufacture of cathodes

A negative electrode was prepared in the same manner as in Example.

(3) Production of polymer pouch type battery

A polymer pouch-type battery was prepared in the same manner as in Example except that the positive electrode prepared in Comparative Example 1 was used.

3. Comparative Example  2

(1) Preparation of positive electrode

In N- methylpyrrolidone solvent of money _{(NMP), Li (Li 0} .2 Mn 0 .55 Ni 0 .15 Co 0 .1) of the positive electrode active material O _2: Denka Black conductive material: the binder PVDF of 90: 5: To prepare a slurry. The slurry was coated on an aluminum (Al) foil having a thickness of 20 탆, which was a cathode current collector, rolled and dried to prepare a positive electrode.

(2) Manufacture of cathodes

A negative electrode was prepared in the same manner as in Example.

(3) Production of polymer pouch type battery

A polymer pouch-shaped battery was produced in the same manner as in Example except that the anode prepared in Comparative Example 2 was used.

4. Capacity evaluation of cathode material

A separator composed of three layers of polypropylene / polyethylene / polypropylene (PP / PE / PP) was interposed between the positive electrode prepared in each of Examples and Comparative Examples 1 and 2 and the negative electrode of metallic lithium, Coin-type batteries were prepared.

Each of the coin type batteries including the anode of Example and Comparative Example 1 was charged with CC / CV up to 4.35 V at a charge current of 0.1 C (cut-off current 0.05 C) and then discharged by CC to 2.5 V, The discharge capacity was measured. The coin type battery including the anode of Comparative Example 2 was charged with CC / CV to a voltage of 4.5 V at a charging current of 0.1 C (cut-off current of 0.05 C) and discharged at a voltage of 2.5 V to conduct high voltage activation, The cell was charged with CC / CV at a charge current of 0.1 C to 4.35 V (cut-off current 0.05 C), and discharged to 2.5 V by CC to measure the discharge capacity of the cathode material.

FIG. 1 is a graph showing discharge capacities of coin-type batteries each including a positive electrode of each of Examples and Comparative Examples 1 and 2. FIG.

Referring to FIG. 1, the capacity of the cathode active material of the coin type battery including the positive electrode active material of Example 1 and the positive electrode active material of Comparative Example 1 was about 183 mAh / g, 2 was expressed in a dose-dependent manner.

5. Polymer  Activation process of pouch type battery

The cells of Example and Comparative Example 1 were charged with CC / CV to a voltage of 4.35 V at a charge current of 0.1 C (cut-off current 0.05 C), then discharged at a voltage of 2.5 V, and a portion of the polymer pouch case was cut, 95 kPa) and the cuts were sealed again with heat and pressure. The battery of Comparative Example 2 was charged with CC / CV at a charging current of 0.1 C to a voltage of 4.5 V, discharged at a cut-off current of 0.05 C, discharged at 2.5 V, After charging with a CV (cut-off current 0.05 C), discharging was performed up to 2.5 V, and the gas was removed in the same manner. Thereafter, all of the cells of Examples, Comparative Examples 1 and 2 were operated at an operating voltage of 4.35 V to 2.5 V.

6. Polymer  Evaluation of cycle characteristics of pouch type battery

Each of the polymer pouch-type cells subjected to the activation process was charged / discharged at 45 ° C under 1 C charging (4.35 V CC / CV, cut-off 0.05 C) and 1 C discharge (2.5 V CC cut- Were repeated to measure the capacity retention rate according to the cycle.

Fig. 2 is a graph showing the capacity retention ratios of the polymer pouch type batteries of Examples and Comparative Examples 1 and 2. Fig.

Referring to FIG. 2, it can be confirmed that excellent life characteristics are shown in Examples, as compared with Comparative Examples 1 and 2.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Claims (12)

(S1) chemically activating the cathode active material with hydrogen ions generated by ionization of the acidity adjusting agent by mixing a cathode active material represented by the following Chemical Formula 1, an organic solvent, and an acidity adjusting agent to prepare a slurry;
(S2) coating the surface of the activated cathode active material with the silane coupling agent by adding a silane coupling agent to the result of the step (S1) and then mixing the resultant;
(S3) coating the resultant product after the step (S2) on the positive electrode current collector; And
(S4) crosslinking the silane coupling agent coated on the surface of the cathode active material while vacuum drying the result obtained in the step (S3)
In the step (S1), the conductive material, the polymer binder and the thickening agent are further added and then mixed, or the conductive material, the polymer binder and the thickening agent are further added and mixed in the step (S2) Thereafter, the conductive material, the polymer binder and the thickener are further added and then mixed.
[Chemical Formula 1]
Li (Li _x M _{y - y '} M' _{y '} ) O _{2 - z} A _z
Wherein M is at least one element selected from the group consisting of Mn, Ni, Co, Fe, Cr, V, Cu, Zn, Ti, M 'is at least one element selected from the group consisting of Al, Mg and B, and A is at least one element selected from the group consisting of F, S and N .) The method according to claim 1,
The organic solvent may be selected from the group consisting of N-methyl pyrrolidone (NMP), dimethylsulfoxide (DMSO), methyl alcohol, ethyl alcohol, isopropyl alcohol, And distilled water, or a mixture of two or more thereof. The method according to claim 1,
Wherein the slurry exhibits acidity by hydrogen ions generated by ionization of the acidity-regulating agent. The method according to claim 1,
Wherein the slurry has a hydrogen ion concentration of from 3 to 7. The method according to claim 1,
Wherein the acidity regulator is any one of acetic acid, oxalic acid, formic acid, hydrochloric acid, sulfuric acid and nitric acid, or a mixture of two or more thereof. The method according to claim 1,
In the step (S2), the silane coupling agent is added in an amount of 0.01 to 5 wt% based on the weight of the cathode active material. The method according to claim 1,
Wherein the drying temperature in the step (S4) is 80 to 250 占 폚. A positive electrode produced by the method of any one of claims 1 to 7. An electrode assembly including an anode, a cathode, and a separator interposed between the anode and the cathode;
A nonaqueous electrolytic solution for impregnating the electrode assembly; And
And a battery case having the electrode assembly and the nonaqueous electrolyte solution built therein, the lithium secondary battery comprising:
Wherein the positive electrode is the positive electrode of claim 8. 10. The method of claim 9,
Wherein the negative electrode comprises an anode active material comprising lithium metal, a carbon material, a metal compound, or a mixture thereof. 11. The method of claim 10,
The metal compound may be at least one selected from the group consisting of Si, Ge, Sn, Pb, P, Sb, Bi, Al, Ga, In, Ti, Mn, Fe, Co, Ni, Cu, Zn, Ag, , Or a mixture of two or more thereof. 10. The method of claim 9,
The separator may be at least one selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polypropylene, polybutylene, polypentene, polyethyleneterephthalate, polybutyleneterephthalate, But are not limited to, polyacetals, polyamides, polycarbonates, polyimides, polyetheretherketones, polyethersulfone, polyphenylene oxides, polyphenylene oxides, Wherein the porous substrate is a porous substrate formed of any one selected from the group consisting of polyphenylene sulfide and polyethylene naphthalene or a mixture of two or more thereof.

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