KR20160040020A - Electrode assembly and lithium secondary battery comprising thereof - Google Patents

Abstract

The present invention relates to an electrode assembly that one or more from a cathode or a separation film has lithium, a manufacturing method thereof, and a lithium secondary battery comprising the same. Accordingly, the electrode assembly can restrain a transition metal component from being deposited inside an anode active material, and a solid electrolyte interphase (SEI) can be stably formed on the cathode.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an electrode assembly and a lithium secondary battery including the electrode assembly,

The present invention relates to an electrode assembly, a method of manufacturing the same, and a lithium secondary battery including the same, wherein at least one of the cathode and the separator includes lithium.

Recently, in response to the rapid development of the communication industry such as electronic industry and various information communication including mobile communication, in order to meet the demand of light and short life of electronic devices, a variety of products such as notebooks, netbooks, tablet PCs, mobile phones, smart phones, PDAs, Portable electronic products, and communication terminal devices have been widely used, and development of a battery, which is a driving power source for these devices, is also getting more attention.

In addition, with the development of electric vehicles such as hydrogen electric vehicles, hybrid electric vehicles and fuel cell vehicles, great attention has been paid to the development of batteries having high performance, large capacity, high density, high output and high stability, The development of batteries is also a big issue.

Batteries that convert chemical energy into electrical energy are divided into primary cells, secondary cells, fuel cells, and solar cells depending on the type and characteristics of basic materials.

The dual primary cells produce energy through irreversible reactions such as manganese batteries, alkaline batteries, and mercury batteries. However, they have a disadvantage in that they are large in capacity but can not be recycled, and thus have various problems such as energy inefficiency and environmental pollution.

The secondary battery includes a lead-acid battery, a nickel-metal hydride battery, a nickel-cadmium battery, a lithium ion battery, a lithium polymer battery, and a lithium metal battery and repeats charge and discharge using reversible mutual conversion of chemical energy and electric energy. As a chemical cell that can be operated by reversible reaction, it has advantages of recycling and environment-friendly. Double lithium secondary batteries are being actively studied.

Lithium secondary batteries have four basic components: a positive electrode and a negative electrode, a separator and an electrolyte.

Specifically, the lithium secondary battery has a structure in which an electrolyte is injected into an electrode assembly in which an anode, a separator, and a cathode are sequentially stacked.

The negative electrode includes an anode current collector for collecting electrons generated by a chemical reaction and transferring the generated electrons to an external circuit, a negative electrode active material layer coated on one side or both sides of the negative electrode current collector and capable of absorbing or desorbing lithium ions Respectively. The negative electrode active material layer includes a negative electrode active material. As the negative electrode active material, a compound capable of intercalating lithium metal, its alloy or lithium ion may be used. A polymer material or a carbon material may be used. Graphite carbon, soft-carbon, carbon nanotube (CNT), carbon (graphite), and graphite, such as natural graphite, non-grachite carbon or hard- A carbon nanofiber (CNF), a carbon nanowall (CNW), or the like can be used.

The anode includes a cathode current collector for collecting electrons generated by a chemical reaction and transferring the generated electrons to an external circuit, a cathode active material layer coated on one side or both sides of the cathode current collector and capable of intercalating or deintercalating lithium ions Respectively. The cathode active material layer contains a cathode active material. As the cathode active material, most of the materials capable of intercalating lithium ions are used. The lithium cobalt oxide (Li _x CoO ₂ ), lithium nickel oxide (Li _x NiO ₂ ), lithium nickel cobalt Oxides such as oxides (Li _x (NiCo) O ₂ ), lithium nickel cobalt manganese oxide (Li _x (NiCoMn) O ₂ ), spinel type lithium manganese oxide (Li _x Mn ₂ O ₄ ), manganese dioxide (MnO ₂ ) Olivine type or polymer materials such as lithium iron phosphate (Li _x FePO ₄ ), lithium manganese phosphate (Li _x MnPO ₄ ) and the like can be used.

On the other hand, a lot of research has been carried out to realize a high capacity characteristic of a lithium secondary battery. For example, a silicate-based material has been considered as a cathode active material, but its initial irreversible capacity is very high, There is a problem that the capacity retention is very poor due to the expression of irreversible capacity.

In addition, in the case of a composite transition metal cathode active material such as a manganese-rich material that is attracting attention as a high capacity cathode active material, manganese (or transition metal) eluted due to problems such as dissolution of manganese (or transition metal) And there is a problem that stable solid electrolyte interphase (SEI) formation on the cathode is restricted.

Accordingly, there is a need to develop a lithium secondary battery that can easily apply a cathode active material having a high capacity characteristic by suppressing the deposition of metal ions contained in the cathode active material on the anode to form a stable SEI on the anode .

KR 2002-0097000 A

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and it is an object of the present invention to provide an electrode assembly in which at least one of a cathode and a separator contains lithium.

Another object of the present invention is to provide a method of manufacturing the electrode assembly.

It is still another object of the present invention to provide a lithium secondary battery including the electrode assembly.

According to an aspect of the present invention, there is provided an electrode assembly comprising an anode, a cathode, and a separator interposed between the anode and the cathode, wherein at least one of the anode and the separator comprises lithium .

The present invention also relates to a method of manufacturing a positive electrode, comprising the steps of: (a) preparing a positive electrode; Producing a negative electrode (step 2); And a step (step 3) of interposing a separation membrane between the anode and the cathode, wherein at least one of the cathode and the separation membrane comprises lithium.

In addition, the present invention provides a lithium secondary battery including the electrode assembly.

The electrode assembly according to the present invention can suppress the deposition of a transition metal component in the cathode active material by containing lithium in at least one of the cathode and the separator, and a solid electrolyte interphase (SEI) is stably formed on the cathode .

Therefore, a composite transition metal cathode active material having a high capacity characteristic can be used, the capacity characteristics of the lithium secondary battery including the lithium secondary battery can be excellent, and the lifetime characteristics can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and together with the description of the invention serve to further the understanding of the technical idea of the invention, It should not be construed as limited.
1 schematically shows a lamination structure of a separator having a lithium layer and a cathode according to an embodiment of the present invention.
FIG. 2 schematically shows a structure in which a negative electrode having a lithium layer, a separator, and an anode are sequentially stacked according to an embodiment of the present invention.
FIG. 3 is a graphical representation of a phenomenon occurring on the surface of a negative electrode in an electrode assembly during charging and discharging of a lithium secondary battery according to an embodiment of the present invention. FIG. 3 (a) 1 shows an electrode assembly having a lithium layer according to an embodiment.
FIG. 4 is a graph illustrating the capacity characteristics of a mono cell according to an embodiment of the present invention.
FIG. 5 is a graph illustrating the capacity maintenance ratio of a mono cell according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail in order to facilitate understanding of the present invention.

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.

The present invention provides an electrode assembly having high capacity characteristics and excellent stability.

The electrode assembly according to an embodiment of the present invention includes a cathode, a cathode, and a separator interposed between the anode and the cathode, and at least one of the cathode and the separator includes lithium.

That is, the electrode assembly according to the present invention may include lithium in the cathode, lithium in the separator, or lithium in the cathode and separator.

Specifically, the negative electrode comprises a negative electrode collector; And a negative electrode active material layer formed on the negative electrode current collector, wherein the lithium is formed on the surface of the negative active material layer or diffused into the surface of the negative active material layer, And may be diffused into the inside. That is, the cathode may further include a lithium layer on its surface. The lithium layer may have a thickness of several tens of nanometers or more, specifically, 10 nm to 100 nm. At this time, the surface of the negative electrode active material layer may be a negative electrode surface.

The lithium may be formed to have a concentration gradient from the surface of the negative electrode active material layer to the inside of the negative electrode active material layer. The concentration gradient may indicate that the concentration of lithium gradually decreases from the surface of the negative electrode active material layer toward the inside.

Specifically, lithium has a concentration gradient in which the concentration of lithium decreases from the surface of the negative electrode active material layer into the surface of the negative electrode active material layer, and the concentration of lithium in the surface of the negative electrode active material layer, The ratio of the lithium concentration at the point may be 1: 0.5 to 0.7.

The separator may include lithium, the lithium may be formed in a layer on one surface of the separator, may be diffused from one surface of the separator to the inside, or may be formed in a layer on the surface of the separator, It may be diffused from one surface to the other. At this time, the one surface may be a surface facing the cathode (see FIG. 1).

The lithium may be formed to have a concentration gradient from one surface to the inside of the separator, wherein the concentration gradient may have a meaning as described above.

Specifically, the ratio of the lithium concentration on the surface of the separator to the lithium concentration on the internal point 1/3 thickness of the separator from the surface of the separator may be 1: 0.5 to 0.7.

On the other hand, the anode includes a positive electrode collector; And a cathode active material layer formed on the cathode current collector, and the cathode active material layer may include a cathode active material.

The cathode active material may be at least one selected from oxides represented by the following general formulas (1) to (3).

 [Chemical Formula 1]

Li _{1 + x} [Ni _a Co _b Mn _c ] O ₂ (-0.5? X? 0.6, 0? A, b, c? 1, x + a + b + c = 1);

(2)

LiMn _{2 - x} M _x O ₄ (M is at least one element selected from the group consisting of Ni, Co, Fe, P, S, Zr, Ti and Al, 0? X? 2);

(3)

_{Li 1 + a Fe 1 - x} M x (PO 4 -b) X b (M is Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn , and Y X is at least one element selected from the group consisting of F, S and N, and -0.5? A? +0.5, 0? X? 0.5, 0? B? 0.1)

Preferably, the cathode active material is LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li [Ni _a Co _b Mn _c ] O ₂ (0 <a, b, c ≤ 1, a + b + c = 1), and LiFePO ₄ .

As described above, in the electrode assembly according to the present invention, at least one of the negative electrode and the separator included in the electrode assembly may include lithium, and when the separator includes lithium, the lithium may contact the negative electrode (Refer to Fig. 2).

Accordingly, the electrode assembly can prevent the transition metal component from being deposited on the cathode in the cathode active material, and the solid electrolyte interphase (SEI) can be stably formed on the cathode. Therefore, the above-described cathode active material having a high capacity characteristic can be used, and the capacity characteristics of the lithium secondary battery including the lithium secondary battery can be excellent and the lifetime characteristics can be improved (refer to FIG. 3).

Here, the SEI (solid electrolyte interphase) means a surface coating formed between the electrode and the electrolyte. By forming the SEI on the surface of the anode, it is possible to suppress the further reaction between the anode and the electrolyte, have.

Specifically, the SEI has such a characteristic that the electron conductivity is negligibly low, the lithium ion conductivity is high, and the electrolyte has porosity, so that only the lithium ion is permeated and the other components are not permeated. Therefore, when the SEI is formed on the surface of the negative electrode, electrolyte decomposition due to electron movement between the negative electrode and the electrolyte is suppressed and only insertion / desorption of lithium ions is possible, and direct contact between the electrolyte and the negative electrode can be prevented It can show high safety.

The present invention also provides a method of manufacturing the electrode assembly.

The manufacturing method according to an embodiment of the present invention includes the steps of manufacturing a positive electrode (step 1); Producing a negative electrode (step 2); And a step (step 3) of interposing a separation membrane between the anode and the cathode, wherein at least one of the cathode and the separation membrane has a lithium diffusion part.

The step 1 is a step for preparing the positive electrode, which can be performed by applying a positive electrode active material slurry containing a positive electrode active material on at least one surface of the positive electrode collector and drying the applied positive electrode active material slurry.

The cathode current collector generally has a thickness of 3 탆 to 500 탆, and is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, surfaces of copper, stainless steel, aluminum, nickel, titanium, sintered carbon or aluminum or stainless steel surface-treated with carbon, nickel, titanium or silver may be used.

The cathode active material slurry may contain additives such as a binder, a conductive material and a filler in addition to the cathode active material.

The cathode active material may be as described above.

The binder is not particularly limited as a component for assisting the bonding between the positive electrode collector and the positive electrode active material layer and may be a material commonly known in the art. For example, a binder such as vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co Polyvinylidenefluoride, chlorotrifluoroethylene, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), polyacrylonitrile, polyvinylidene fluoride, ), Starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butylene rubber SBR), and fluorine rubber.

The conductive material is not particularly limited as long as it has electrical conductivity without causing side reactions with other elements of the battery. Examples of the conductive material include graphite such as natural graphite and artificial graphite; Carbon black such as carbon black (super-p), acetylene black, ketjen black, channel black, furnace lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; And conductive materials such as polyphenylene derivatives can be used.

The filler is a component for inhibiting the expansion of the electrode. The filler may be used or not, depending on necessity. The filler is not particularly limited as long as it is a fibrous material without causing any chemical change in the battery. Examples of the filler include an olefin polymer such as polyethylene and polypropylene ; Glass fiber, carbon fiber, or the like.

The dispersion medium may be, for example, isopropyl alcohol, N-methylpyrrolidone (NMP), acetone or the like, although it is not particularly limited.

For example, the cathode active material slurry may be sprayed or distributed on at least one surface of the cathode current collector, and then may be applied using a doctor blade or the like Can be uniformly dispersed. In addition, it can be performed by a method such as die casting, comma coating, screen printing and the like.

The drying is not particularly limited, but may be carried out within one day in a vacuum oven at 50 ° C to 200 ° C.

The step 2 is a step for preparing a negative electrode, and the manufacturing method of the negative electrode may be different depending on whether the negative electrode contains lithium.

When the negative electrode does not contain lithium, the negative electrode may be prepared by coating a negative electrode active material slurry on at least one surface of the negative electrode collector and drying the coated negative electrode active material slurry.

When the cathode contains lithium, the cathode can be prepared by the following steps:

a. Coating at least one negative electrode active material slurry of the negative electrode current collector and drying to form a first negative electrode having a negative electrode active material layer; And

b. Depositing the first negative electrode, the separator, and the counter electrode sequentially, injecting an electrolyte, and applying a charge.

At this time, the counter electrode may include a lithium source, and the lithium source may be lithium foil, lithium metal powder, or the like.

Specifically, the step (a) is a step of coating a negative electrode active material slurry on at least one surface of the negative electrode collector and drying to form a first negative electrode (a conventional negative electrode).

The negative electrode current collector may be the same as or included in the positive electrode current collector.

The negative electrode active material slurry includes a negative electrode active material, and in addition to the negative electrode active material, additives such as a binder, a conductive material, and a filler may be included.

The additives such as the binder, the conductive material and the filler may be as described above or may be included.

The negative electrode active material is not particularly limited and a carbonaceous material, lithium metal, silicon, or tin, which is commonly known in the art, into which lithium ions can be inserted and removed can be used. Preferably, the carbonaceous material may be used. As the carbonaceous material, both low-crystalline carbon and highly crystalline normal carbon may be used. Examples of the low-crystalline carbon include soft carbon and hard carbon. Examples of the cemented carbon include natural graphite, kish graphite, pyrolytic carbon, High temperature sintered carbon such as mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches and petroleum or coal tar pitch derived cokes. More preferably, it may be graphite, softened carbon and hardened carbon, or may be the above-described negative electrode active material having a carbon coating layer having a thickness of 10 nm to 100 nm, particularly preferably graphite. In the case of using the negative electrode active material having graphite, softened carbon, hardened carbon or carbon coating layer, lithium may be uniformly diffused in the negative electrode active material layer or may be formed as a uniform thickness layer.

The above coating and drying can be carried out by the method as described above.

The step b is a step for containing lithium on the first negative electrode prepared in the step a, and may be performed by sequentially laminating the first negative electrode, the separation membrane, and the counter electrode, injecting an electrolyte, and applying an electric charge.

At this time, the separation membrane and the electrolyte are not particularly limited, and those commonly known in the art may be used, and specifically, the separation membrane and the electrolyte may be as described below.

The voltage is not particularly limited and can be adjusted according to the thickness of the desired lithium layer and the degree of diffusion of lithium. For example, when the potential of the negative electrode alone is 0.05 V (relative to the lithium source) Or less.

That is, in the method of manufacturing a negative electrode containing lithium, a conventional negative electrode is manufactured, a half cell is manufactured using the negative electrode manufactured, and a charge is applied in the negative direction to form a lithium ion Is deposited and diffused on the negative electrode active material layer of the negative electrode.

Step 3 is a step for manufacturing an electrode assembly, which can be performed by sequentially laminating the negative electrode, the separator, and the positive electrode.

At this time, the separation membrane may be an insulating thin film having high ion permeability and mechanical strength, and may generally have a pore diameter of 0.01 μm to 10 μm and a thickness of 5 μm to 300 μm. As such a separation membrane, a porous polymer film such as a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer and an ethylene / methacrylate copolymer may be used alone Or they may be laminated. Alternatively, nonwoven fabrics made of conventional porous nonwoven fabrics such as high melting point glass fibers, polyethylene terephthalate fibers and the like may be used, but the present invention is not limited thereto.

Meanwhile, when the separator includes lithium as described above, the separator may be manufactured by depositing a lithium source on one surface of the separator described above. The deposition may be performed by one or more methods selected from the group consisting of chemical vapor deposition, electrochemical reaction, and physical adsorption.

In addition, the present invention provides a lithium secondary battery including the electrode assembly.

The lithium secondary battery according to an embodiment of the present invention includes the electrode assembly and the electrolyte.

The electrolyte may include an organic solvent and a lithium salt ordinarily used in an electrolyte, and is not particularly limited.

With the lithium salt of the anion is ^{F -, Cl -, I -} , NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF 4 -, (CF 3 ^{_{) 3 PF 3 -, (CF}} 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2 _{^{) 2 N -, (FSO 2}} ) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 CO 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 - may be at least one member selected from the group consisting of .

Examples of the organic solvent include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, methylpropyl carbonate, dipropyl carbonate, dimetal sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene And may be one or more selected from the group consisting of carbonates, sulfolane, gamma-butyrolactone, propylene sulfite and tetrahydrofuran.

In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates in the carbonate-based organic solvent, can be preferably used because they have a high dielectric constant as an organic solvent having a high viscosity and thus dissociate the lithium salt in the electrolyte well. These cyclic carbonates, When a low viscosity, low dielectric constant linear carbonate such as carbonate is mixed in an appropriate ratio, an electrolyte having a high electric conductivity can be prepared, and thus it can be more preferably used.

In order to improve the charge-discharge characteristics and the flame retardant characteristics, the electrolyte may further contain at least one selected from the group consisting of pyridine, triethylphosphate, triethanolamine, cyclic ether, ethylenediamine, glyme, hexaphosphoric triamide, , Sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride, . In some cases, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further added to impart nonflammability. In order to improve the high-temperature storage property, a carbon dioxide gas may be further added. FEC (fluoro-ethylene carbonate ), PRS (propene sulfone), FPC (fluoro-propylene carbonate), and the like.

The lithium secondary battery of the present invention can be manufactured by disposing a separator between an anode and a cathode to form an electrode assembly, inserting the electrode assembly into a cylindrical battery case or a prismatic battery case, and then injecting an electrolyte. Alternatively, the electrode assembly may be laminated, impregnated with the electrolyte, and the resultant may be sealed in a battery case.

The battery case used in the present invention may be of any type that is commonly used in the art, and is not limited in its external shape depending on the use of the battery. For example, a cylindrical case, a square type, a pouch type, (coin) type or the like.

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

Hereinafter, the present invention will be described in more detail with reference to Examples and Experimental Examples. However, the following examples and experimental examples are provided for illustrating the present invention, and the scope of the present invention is not limited thereto.

Example  One

1) Preparation of negative electrode containing lithium

An anode active material slurry obtained by mixing natural graphite, styrene-butadiene rubber, carboxymethyl cellulose and denka black in a ratio of 96.5: 1: 1.5: 1 was coated on a copper thin film having a thickness of 15 탆 and vacuum dried at 180 캜 for 24 hours, Thereby preparing a negative electrode.

A lithium thin film was used as an anode, and an electrode assembly was produced by laminating a cell guard, which is a separation membrane, between the first negative electrode and the positive electrode. Thereafter, an electrolytic solution prepared by dissolving 1 M of LiPF ₆ in a mixed solvent of propylene carbonate (PC), ethylmethyl carbonate (EMC) and ethylene carbonate (EC) (PC: EMC: EC = 2: 3: 5) And an anode including lithium at a level of 0.05 V or less with respect to the lithium thin film was prepared using an electrochemical charging method.

2) Manufacture of anode

96 wt% of LiNiCoMnO _{2, 2} wt% of carbon black and 2 wt% of polyfluorovinylidene were mixed as a cathode active material, and N-methyl-2-pyrrolidone (NMP) was further added and mixed to prepare a cathode active material slurry Which was coated on an aluminum foil to a thickness of 130 μm, rolled and dried to prepare a positive electrode.

3) Preparation of lithium secondary battery

The positive electrode, the porous polymer film, and the negative electrode having the lithium diffusion portion were sequentially laminated, followed by pulverization with a size of ³ x 4 cm ² , followed by the injection of a carbonate-based electrolyte in which 1 mol and 2 wt% of vinyl chloride (LiPF ₆ ) A polymer cell type mono cell was fabricated.

Comparative Example

1) Manufacture of cathode

An anode active material slurry obtained by mixing natural graphite, styrene-butadiene rubber, carboxymethyl cellulose and denka black in a ratio of 96.5: 1: 1.5: 1 was coated on a copper thin film having a thickness of 15 탆 and vacuum dried at 180 캜 for 24 hours, .

2) Manufacture of anode

96 wt% of LiNiCoMnO _{2, 2} wt% of carbon black and 2 wt% of polyfluorovinylidene were mixed as a cathode active material, and N-methyl-2-pyrrolidone (NMP) was further added and mixed to prepare a cathode active material slurry Which was coated on an aluminum foil to a thickness of 130 μm, rolled and dried to prepare a positive electrode.

3) Preparation of lithium secondary battery

The positive electrode, the porous polymer film, and the negative electrode were sequentially laminated, followed by pulverizing to a size of 3 × ⁴ cm ^{2. Then} , a carbonate-based electrolyte in which 1 mol and 2 wt% of vinyl chloride (LiPF ₆ ) Monocell was prepared.

Experimental Example

The life characteristics of the mono cells prepared in Examples 1 and 2 and Comparative Example were compared and analyzed.

Each mono cell was charged and inverted in turn at 25 ° C under the conditions of 0.2C / 0.2C, 0.2C / 0.5C, 0.2C / 1.0C, and 0.2C / 2.0C in order to analyze the capacity retention rate Respectively. The results are shown in Fig. 4 and Fig.

As shown in FIG. 4 and FIG. 5, the monocells of Example 1 or Example 2 including a negative electrode containing lithium or a separator containing lithium according to the present invention had excellent capacity retention as a whole Respectively.

Claims (18)

A cathode, and a separator interposed between the anode and the cathode,
Wherein at least one of the cathode and the separator comprises lithium.
The method according to claim 1,
Wherein the cathode further comprises a lithium layer on the surface.
The method of claim 2,
Wherein the thickness of the lithium layer is from 10 nm to 100 nm.
The method according to claim 1,
Wherein the lithium has a concentration gradient in which the lithium concentration decreases from the surface of the negative electrode toward the inside thereof.
The method according to claim 1,
Wherein the ratio of the lithium concentration on the surface of the negative electrode to the lithium concentration in the internal point 1/3 thickness from the surface of the negative electrode is 1: 0.5 to 0.7.
The method according to claim 1,
Wherein the separator further comprises a lithium layer on one surface thereof,
Wherein the one surface is a surface facing the cathode.
The method of claim 6,
Wherein the thickness of the lithium layer is from 10 nm to 100 nm.
The method of claim 6,
Wherein the lithium has a concentration gradient in which the lithium concentration decreases from one surface of the separator to the interior thereof.
The method of claim 6,
Wherein the ratio of the lithium concentration on the surface of the separator to the lithium concentration on the internal point 1/3 thickness from the surface of the separator is 1: 0.5 to 0.7.
The method according to claim 1,
The positive electrode being a positive electrode collector; And
And a positive electrode active material layer formed on the positive electrode current collector.
The method according to claim 1,
Wherein the cathode active material layer comprises a cathode active material,
Wherein the cathode active material is at least one selected from the group consisting of oxides represented by the following general formulas (1) to (3)
[Chemical Formula 1]
Li _{1 + x} [Ni _a Co _b Mn _c ] O ₂ (-0.5? X? 0.6, 0? A, b, c? 1, x + a + b + c = 1);
(2)
LiMn _{2 - x} M _x O ₄ (M is at least one element selected from the group consisting of Ni, Co, Fe, P, S, Zr, Ti and Al, 0? X? 2);
(3)
_{Li 1 + a Fe 1 - x} M x (PO 4 -b) X b (M is Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn , and Y X is at least one element selected from the group consisting of F, S and N, and -0.5? A? +0.5, 0? X? 0.5, 0? B? 0.1)
The method of claim 11,
Wherein the positive electrode active material is LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li [Ni _a Co _b Mn _c ] O ₂ (0 <a, b, c ≤ 1, a + b + LiFePO _4, and LiFePO ₄ .
1) preparing an anode;
2) preparing a negative electrode; And
3) interposing a separation membrane between the anode and the cathode,
The method of claim 1, wherein at least one of the cathode and the separator comprises lithium.
14. The method of claim 13,
Wherein the step 2) comprises: coating a negative electrode active material slurry on at least one surface of the negative electrode collector and drying the same to produce a first negative electrode having a negative electrode active material layer; And
A first electrode, a separator, and a counter electrode, sequentially injecting an electrolyte, and applying an electric charge,
Wherein the counter electrode comprises a lithium source.
14. The method of claim 13,
Wherein the separation membrane is manufactured by depositing a lithium source on one surface of the separation membrane.
16. The method of claim 15,
Wherein the deposition is performed through at least one method selected from the group consisting of chemical vapor deposition, electrochemical reaction, and physical adsorption.
The method according to claim 14 or 15,
Wherein the lithium source is a lithium foil, a lithium metal powder, or a combination thereof.
A lithium secondary battery comprising the electrode assembly of claim 1.

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