KR20190001406A - Lithium Secondary Battery and Preparation Method Thereof - Google Patents

Abstract

The present invention provides a lithium secondary battery and a method for manufacturing the same. The lithium secondary battery comprises: a dry-manufactured first electrode; a wet-manufactured second electrode; a separator interposed between the dry-manufactured first electrode and the wet-manufactured second electrode; and an electrolyte, wherein the dry-manufactured first electrode comprises a first electrode active material, a binder, and a conductive material, and the wet-manufactured second electrode comprises a second electrode active material, a binder, and a conductive material. The interface resistance of the dry-manufactured first electrode is equal to or greater than the interface resistance of the wet-manufactured second electrode. The lithium secondary battery according to the present invention comprises two electrodes having a small difference in the interfacial resistance to secure the kinetic balance, and the lithium secondary battery employing the same can exhibit excellent cycle characteristics.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium secondary battery,

The present invention relates to a lithium secondary battery having improved cycle performance and a method of manufacturing the same.

As technology development and demand for mobile devices increase, the demand for secondary batteries that can be recharged and can be miniaturized and increased in capacity is rapidly increasing. In addition, among secondary batteries, lithium secondary batteries having high energy density and voltage are commercialized and widely used.

The lithium secondary battery has a structure in which an electrode including lithium salt is impregnated in an electrode assembly in which an active material is coated on a current collector, that is, an electrode assembly having a porous separator interposed between an anode and a cathode. The electrode has been manufactured by a wet process in which a slurry is prepared by dispersing an active material, a binder, a conductive material, and the like in a solvent, coating the slurry on a current collector, and removing the solvent through drying. As another method, there has recently been proposed a dry method in which an active material, a binder and a conductive material are mixed with each other without using a solvent, and the mixture is supplied to a current collector and passed through a rolling roll to produce an electrode.

On the other hand, in the lithium secondary battery, the portion that has the greatest effect on the characteristics such as the capacity and the cycle life can be referred to as a positive electrode and a negative electrode in which an electrochemical reaction takes place substantially. In particular, the cycle characteristics are influenced by the reaction rate of the positive electrode and the negative electrode in the course of lithium ion (Li ⁺ ) migration through the electrolyte by the redox reaction in the electrode. That is, when the kinetic balance in which the reaction speed between the anode and the cathode is balanced is secured, the cyclic characteristics are improved, and such kinetic balance can be dependent on the resistance due to the active material of each electrode.

Therefore, in order to improve the cycle characteristics of the battery, it is necessary to secure a kinetic balance between the two electrodes.

An object of the present invention is to provide a lithium secondary battery having excellent cycle characteristics by securing a kinetic balance between electrodes.

Another object of the present invention is to provide a method of manufacturing the lithium secondary battery.

According to an aspect of the present invention, there is provided a method of manufacturing a semiconductor device, including the steps of: preparing a dry-made first electrode, a wet-made second electrode, a separator interposed between the dry- And an electrolyte, wherein the dry fabrication first electrode comprises a first electrode active material, a binder and a conductive material, the wet fabrication second electrode comprises a second electrode active material, a binder and a conductive material, The interface resistance of the first electrode is greater than or equal to the interface resistance of the wet-made second electrode.

When the first electrode active material contained in the dry electrode manufacturing first electrode and the electrode active material same as the conductive material and the conductive material are dispersed in the dispersion medium and then the binder is added so that the wet electrode is referred to as a wet first electrode, The manufacturing first electrode may have a lower interface resistance than the wet manufacturing first electrode.

The binder included in the dry-made first electrode may be the same as or different from the binder of the wet-made first electrode.

The dry-fabrication first electrode may have a coverage of the binder and the conductive material to less than 50% of the total surface of the active material particle.

The wet-made second electrode may have a covering ratio of the binder and the conductive material to the entire surface of the active material particles of 50% or more.

Wherein the dry fabrication first electrode is a cathode, the wet fabrication second electrode is an anode, or the dry fabrication first electrode is an anode and the wet fabrication second electrode is a cathode.

The negative electrode comprises a graphite as an anode active material, and the positive electrode is as _{LiNi 1 -xy- z Co x M1 y} M2 z O 2 (M1 and M2 are, independently from each other as a positive electrode active material Al, Ni, Co, Fe, Mn, V X, y and z are independently selected from the group consisting of Cr, Ti, W, Ta, Mg and Mo, Lt; z < 0.5, 0 < x + y + z &amp;le; 1).

According to another aspect of the present invention,

(i) coating and drying a slurry containing a first electrode active material, a binder, a conductive material, and a dispersion medium on at least one surface of a current collector to prepare a wet preformed first spare electrode;

(ii) coating and drying a slurry containing a second electrode active material, a binder, a conductive material, and a dispersion medium on at least one surface of the current collector to prepare a wet-prepared second spare electrode;

(iii) measuring an interface resistance between the first preliminary electrode and the second preliminary electrode to compare their relative sizes;

(iv) the same electrode active material and conductive material as the electrode active material and the conductive material included in the spare electrode, which has been found to have a relatively large interfacial resistance in the step (iii), and a binder, which is the same or different from the binder contained in the spare electrode &Lt; / RTI &gt; at least one side of the current collector to provide an electrode;

 (v) selecting the electrode provided in the step (iv) as the dry-made first electrode and the spare electrode as the wet-made second electrode in the step (iii), the interface electrode having a relatively low interfacial resistance; And

(vi) fabricating an electrode assembly between the dry-made first electrode and the wet-made second electrode via a separator,

The interface resistance of the dry-made first electrode is greater than or equal to the interface resistance of the wet-made second electrode.

The interfacial resistance measurement in the step (iii) may be performed in a three-electrode system battery circuit configured by combining the reference electrode with the first spare electrode and the second spare electrode.

Since the lithium secondary battery according to the present invention includes the first dry electrode and the second wet electrode with small differences in the interface resistance, it is possible to maintain the kinetic balance and to exhibit excellent cycle characteristics.

FIG. 1 is a SEM (scanning electron microscope) photograph showing the distribution of a binder with respect to an active material in a wet-type second electrode included in a lithium secondary battery according to an embodiment of the present invention.
FIG. 2 is a scanning electron microscope (SEM) photograph showing the distribution of the binder to the active material in the dry-type first electrode included in the lithium secondary battery according to an embodiment of the present invention.
3 is a graph showing the cycle life at room temperature of the lithium secondary battery produced in Examples and Comparative Examples.

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

An embodiment of the present invention includes a dry-made first electrode, a wet-made second electrode, a separator interposed between the first and second electrodes, and a non-aqueous electrolyte, And the second electrode comprises an active material, a binder and a conductive material, respectively, and the interface resistance of the dry-made first electrode is greater than or equal to the interface resistance of the wet-made second electrode.

In an embodiment of the present invention, the first electrode active material and the conductive material, which are the same as the components contained in the dry-made first electrode, are dispersed in a dispersion medium, and then a binder is added to prepare a wet electrode. The dry-made first electrode has a lower interface resistance than the wet-made first electrode, and the binder included in the dry-made first electrode and the binder of the wet-made first electrode may be the same or different.

The term "interfacial resistance" used in the present invention means a resistance caused by an electrode active material in a lithium secondary battery, that is, a resistance that interferes with the charge transfer of Li ^{+ on} the surface of the active material particle. The interfacial resistance is affected by the distribution state of the binder and the conductive material on the surface of the active material particle, and the degree of distribution of the binder and the conductive material may vary depending on the method of manufacturing the electrode.

For example, the electrode may be formed by a wet process using a dispersion medium, that is, a slurry is prepared by dispersing an active material, a binder, a conductive material or the like in a dispersion medium, coating the slurry on at least one surface of the current collector, The binder dissolved and dispersed in the dispersion medium in the slurry coating layer is wrapped around the surface of the active material particles together with the conductive material. When the dispersion medium is dried in this state, the interface between the binder / conductive material and the active material And the charge movement of Li ⁺ is interfered with, thereby increasing the resistance.

When the electrode is prepared by mixing the dry powders of the active material, the binder and the conductive material without using the dispersion medium and supplying the mixture to the current collector and passing the high-temperature rolling roll, the binder and the conductive material are dispersed while being mixed with the active material is not dissolved or dispersed mothamyeo not completely surround the active material, a certain amount of the surface part only a binder and a conductive material is attached to the distribution of the active material particles Let it passes through the rolling rolls in this state, the active material particle surface is in the form that is exposed in the Li ⁺ The charge transfer becomes more smooth and the interface resistance of the active material becomes lower.

As described above, the degree of distribution of the binder and the conductive material on the surface of the active material particle varies depending on the electrode manufacturing method. The degree of distribution of the binder and the conductive material on the surface of the active material particle, that is, the coverage rate, Can be calculated.

In one embodiment of the present invention, the dry-fabrication first electrode may have a coverage of less than 50%, preferably less than 40%, of the binder and conductive material to the entire surface of the active material particle, The covering ratio of the binder and the conductive material to the entire surface of the particles may be 50% or more, preferably 60% or more. When the dry-type first electrode and the wet-type second electrode satisfy the coverage of the binder and the conductive material in the above range, the difference in the interface resistance between the two electrodes can be minimized.

In one embodiment of the present invention, the dry fabrication first electrode is a cathode and the wet fabrication second electrode is a cathode. Conversely, the dry fabrication first electrode may be an anode and the wet fabrication second electrode may be a cathode.

In the dry-type first electrode and the wet-type second electrode, components commonly used for the positive electrode and the negative electrode of the lithium secondary battery may be used. Examples of usable examples of the positive electrode active material include LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiCoPO ₄ , LiFePO ₄ and LiNi _{1 -xy- z} Co _x M _y M2 _z O ₂ Wherein x, y and z are independently selected from the group consisting of Al, Ni, Co, Fe, Mn, V, Cr, Ti, W, Ta, Mg and Mo; x <0.5, 0? y <0.5, 0? z <0.5, 0 <x + y + z? 1), or a mixture of two or more thereof. Examples of usable examples of the negative electrode active material include lithium metal or a lithium alloy such as lithium alloy, carbon, petroleum coke, activated carbon, graphite or other carbon materials.

Particularly, when a cathode _containing LiNi _{1 -xy- z} Co _x M _{y y} M2 _z O ₂ as a cathode active material and a graphite-containing anode active material is used, the reaction rate of lithium ions to the cathode active material The reaction rate of lithium ions to the negative electrode active material is faster. This is caused by the fact that the interface resistance of the anode is smaller than the interface resistance of the cathode. The wet electrode method is used for the anode and the dry resistance method is used for the cathode. .

Considering this aspect, when the three-component cathode active material and the graphite anode active material are used, the interface resistance magnitude of the electrode according to the manufacturing method is in the order of 'dry manufacturing anode', 'wet manufacturing anode', 'dry manufacturing cathode' .

Therefore, in one embodiment of the present invention, the dry-made first electrode includes graphite as a negative electrode active material, and the wet-made second electrode is a three-component active material LiNi _{1 -xy- z} Co _x M1 _y M2 _z O ₂ (M1 and M2 are each independently selected from Al, Ni, Co, Fe, Mn, V, Cr, Ti, W, Ta, at least one selected from the group consisting of Mg and Mo, and, x, y and z are independent from each other 0 < y < 0.5, 0 < z < 0.5, and 0 &lt; x + y + z &lt; 1) as atomic fractions of the oxide composition elements. Specifically, examples of the graphite include artificial graphite, natural graphite, hard carbon, and soft carbon. Examples of the three-component type active material include Li-NiCoMn, Li-CoMnAl, and Li-NiCoAl. In addition, lithium iron phosphate (LFE, LiFePO ₄ ), lithium titanium oxide (LTO), or the like can be used as the positive electrode active material.

As the positive electrode collector, aluminum, nickel, or a foil produced by a combination of these may be used depending on whether the dry-made first electrode and the wet-made second electrode are positive electrodes or negative electrodes, Copper, gold, nickel or copper alloy, or a combination thereof, may be used, but is not limited thereto.

In addition, the dry fabrication first electrode, the wet fabrication first electrode, and the wet fabrication second electrode may all include a binder and a conductive material. Meanwhile, the binders used for the dry and wet production electrodes may be the same or different.

Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HEP), polyvinylidene fluoride, polyacrylonitrile, Polyvinylpyrrolidone, polyethylene, polypropylene, polyacrylic acid, styrene butylene rubber (SBR), polyvinylpyrrolidone, polyvinylpyrrolidone, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, ) May be used.

Particularly, when the microfibrillatable polymer as the binder is used in the production of the dry electrode, the microfibrillable polymer is physically stretched when a high shear force is applied in the mixing process of the active material, the binder and the conductive material, Can form a web-like fiber network by collecting active materials. In addition, when the adhesive force between the binder and the conductive material is stronger than the adhesive force between the binder and the active material, the binder and the conductive material may be mixed to form a conductive binding aggregate between the active material particles. A space is filled to form a conductive path, thereby facilitating insertion and removal of lithium ions from the active material. A representative example of such a microfibrillated polymer is polytetrafluoroethylene (PTFE). In addition, polyethylene (PE), polypropylene (PP), and the like may be used.

The conductive material is not particularly limited as long as it has electrical conductivity without causing chemical change in the lithium secondary battery. Examples of the conductive material include carbon black, acetylene black, ketjen black, channel black, panes black, lamp black, Of carbon black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as aluminum and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

In the present invention, the wet-type first electrode and the wet-type second electrode may be prepared by dispersing an active material, a binder, a conductive material or the like in a solvent such as N-methylpyrrolidone, acetone or water to prepare a slurry, And coating with a current collector, followed by drying to remove the solvent. The coating method commonly used in the art, for example, a coating method using a slot die, a Meyer bar coating method, a gravure coating method, an immersion coating method , A spray coating method, or the like.

Also, the dry-type first electrode may be manufactured by mixing each dry powder of the active material, the binder and the conductive material, supplying the mixture to the current collector, and passing the mixture through a high-temperature rolling roll, And the pressure applied at the time of rolling can be controlled in such a manner that the gap between the two rolls is adjusted in accordance with the thickness of the current collector passing between the rolls. Further, a high strength or high energy mixer may be used to uniformly mix the active material, the binder and the dry powder of the conductive material, and if necessary, a dry mill may be used by means of a jet mill using a high shear technique, Fibrosis step can be performed. In addition, high voltage electrostatic spray deposition may be used to supply the dry mixture to the current collector.

Another embodiment of the present invention relates to a method of manufacturing a lithium secondary battery as described above. Specifically,

(i) coating and drying a slurry containing a first electrode active material, a binder, a conductive material, and a dispersion medium on at least one surface of a current collector to prepare a wet preformed first spare electrode;

(ii) coating and drying a slurry containing a second electrode active material, a binder, a conductive material, and a dispersion medium on at least one surface of the current collector to prepare a wet-prepared second spare electrode;

(iii) measuring an interface resistance between the first preliminary electrode and the second preliminary electrode to compare their relative sizes;

(iv) the same electrode active material and conductive material as the electrode active material and the conductive material included in the spare electrode, which has been found to have a relatively large interfacial resistance in the step (iii), and a binder, which is the same or different from the binder contained in the spare electrode &Lt; / RTI &gt; at least one side of the current collector to provide an electrode;

(v) selecting the electrode provided in the step (iv) as the dry-made first electrode and the spare electrode as the wet-made second electrode in the step (iii), the interface electrode having a relatively low interfacial resistance; And

(vi) fabricating an electrode assembly between the dry-made first electrode and the wet-made second electrode via a separator,

At this time, the interface resistance of the dry-type first electrode is equal to or greater than the interface resistance of the wet-type second electrode.

In the method of manufacturing a lithium secondary battery according to an embodiment of the present invention, the interface resistance in the step (iii) may be obtained by forming a three-electrode system battery circuit by combining the reference electrodes together with the two electrodes and then performing electrochemical impedance spectroscopy EIS) experiments.

According to the manufacturing method of the embodiment of the present invention, since the interface resistance of the dry first electrode is greater than or equal to the interface resistance of the wet second electrode, and the difference in the interface resistance between the two electrodes is minimized, The battery can be manufactured, and the cycle life of the battery can ultimately be improved.

In one embodiment of the present invention, the separator is a porous polymer film commonly used as a separator in a lithium secondary battery, such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / Methacrylate copolymer and the like can be used alone or in the form of a laminate thereof. Further, an insulating thin film having high ion permeability and mechanical strength can be used. The separator may include a safety reinforced separator (SRS) on the surface of which a ceramic material is thinly coated. In addition, nonwoven fabrics made of conventional porous nonwoven fabrics such as high melting point glass fibers, polyethylene terephthalate fibers and the like can be used, but the present invention is not limited thereto.

In one embodiment of the present invention, the non-aqueous electrolyte may include a lithium salt and an organic solvent for dissolving the lithium salt.

For example, the anion of the lithium salt may be an anion of F ^- , Cl ^- , I ^- , NO ₃ ^- , N (CN) ₂ ^- , and the like as the anion of the lithium salt. _{^{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 ^- can be used.

The organic solvent contained in the electrolyte may be any of those conventionally used, and examples thereof include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, methylpropyl carbonate, dipropyl carbonate, dimethyl sulfoxide At least one member selected from the group consisting of acetone, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite and tetrahydrofuran can be used.

In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates in the carbonate-based organic solvent, can be preferably used because they have high permittivity as a high-viscosity organic solvent and dissociate the lithium salt in the electrolyte well. To such a cyclic carbonate, dimethyl carbonate and diethyl 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.

Alternatively, the electrolyte to be stored in accordance with the present invention may further contain an additive such as an overcharge inhibitor or the like contained in a conventional electrolytic solution.

The lithium secondary battery manufactured by the method according to an embodiment of the present invention can be used in a battery cell which can be a stacked type, a winding type, a stacked and folded type, or a cable type, And may be suitably used as a unit cell in a middle- or large-sized battery module including a plurality of battery cells. Preferred examples of the middle- or large-sized device include an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, a power storage system, and the like, and particularly to a hybrid electric vehicle and a battery for storing a renewable energy Lt; / RTI &gt;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the following 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 following embodiments. Embodiments of the invention are provided to more fully describe the present invention to those skilled in the art.

Production Example 1: Preparation of a positive electrode by a wet process

(Ni _0.5 Mn _0.3 Co _0.2 ) O ₂ as a positive electrode active material, carbon black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder in a weight ratio of 95: 3: 2, (NMP) to prepare a cathode active material slurry. The slurry was coated on one surface of an aluminum current collector having a thickness of 20 mu m, followed by drying and rolling to prepare a positive electrode.

Production Example 2: Preparation of positive electrode by dry method

The cathode active material, the conductive material and the binder having the same components and contents as those in Production Example 1 were mixed in a V-blender equipped with a high-strength mixing rod for 60 minutes, and the resulting dry mixture was passed through a feeder, (Thickness: 20 mu m). The positive electrode was prepared by passing the current collector supplied with the dry mixture through rolling rolls.

Preparation Example 3: Preparation of positive electrode by dry method

A high strength mixing rod was mounted using Li (Ni _0.5 Mn _0.3 Co _0.2 ) O ₂ as a cathode active material, carbon black as a conductive material and polytetrafluoroethylene (PTFE) as a binder in a weight ratio of 95: 3: 2 Blended in a V-blender for 60 minutes, and the resulting dry mixture was jet-milled into microfibers.

  The microfibrous dried material was fed through a feeder to an aluminum current collector (thickness 20 mu m) conveyed through a rolling roll. The positive electrode was prepared by passing the current collector supplied with the dry mixture through rolling rolls.

Production Example 4: Preparation of negative electrode by wet process

Stator diene rubber butadiene (SBR) and carboxymethyl cellulose (CMC) as a binder were added to water as a solvent at a weight ratio of 93: 1: 5: 1 to prepare a negative electrode active material slurry Were prepared. The slurry was coated on one surface of a copper current collector having a thickness of 20 mu m, followed by drying and rolling to prepare a negative electrode.

Production Example 5: Preparation of negative electrode by dry method

The negative active material, the conductive material and the binder of the same components and contents as in Production Example 3 were mixed in a V-blender equipped with a high-strength mixing rod for 60 minutes. The resulting dry mixture was fed through a feeder to a copper current collector (20 mu m) conveyed through a rolling roll. The negative electrode was prepared by passing the current collector supplied with the dry mixture through rolling rolls.

Production Example 6: Preparation of negative electrode by dry method

The mixture was mixed for 60 minutes in a V-blender equipped with a high-strength mixing rod using artificial graphite as a negative electrode active material, carbon black as a conductive material and polytetrafluoroethylene (PTFE) as a binder in a weight ratio of 95: 3: 2, The resulting dry mixture was jet milled into microfibers.

  The microfibrous dried material was fed through a feeder to a copper current collector (thickness 20 mu m) conveyed through a rolling roll. The negative electrode was prepared by passing the current collector supplied with the dry mixture through rolling rolls.

Example 1:

The interfacial resistance of the two electrodes prepared in Preparation Example 1 and Preparation Example 4 was measured using a three-electrode system battery circuit, and the relative sizes were compared. Specifically, measurements were made by analyzing the semicircular size of a Nyquiest plot obtained through an electrochemical impedance spectroscopy (EIS) experiment to analyze an electrochemical reaction occurring between two electrodes and an electrolyte.

As a result of the above resistance measurement, since the resistance of the wet-type manufacturing negative electrode manufactured in Production Example 4 was relatively large, the dry-type manufacturing negative electrode of Production Example 6 was selected as the first electrode instead of the wet- The manufacturing anode was selected as the second electrode.

The interfacial resistance between the selected dry-type first electrode and the wet-type second electrode was measured again using a three-component battery circuit. As a result, the interfacial resistance of the dry-type first electrode and the interface resistance of the wet- But it was almost similar.

A nonwoven fabric made of polyethyleneterephthalate as a separator was interposed between the dry-made first electrode and the wet-made second electrode to constitute an electrode assembly. Then, an electrode assembly was prepared by dissolving 1M LiPF ₆ dissolved in ethylene carbonate (3: 4: 3 EC), dimethyl carbonate (DMC), and ethyl acetate (EA) were injected to prepare a monocell.

To evaluate the cycle performance of the prepared monocell, the capacity according to the cycle progression was measured under the conditions of charging 1C, discharging 1C, and room temperature.

Comparative Examples 1 to 3:

Without considering the relative size of the interfacial resistance, two electrodes were arbitrarily selected with the configuration shown in Table 1 below, and an electrode assembly was formed between the two electrodes through a nonwoven fabric made of polyether terephthalate as a separator. Then, 1M LiPF _6. the solubilized volume ratio of 3: 4: 3 by injection of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl acetate is mixed electrolyte solution (EA) was prepared in each of the mono-cell. The cycle performance was evaluated in the same manner as in Example 1 for each mono cell.

anode cathode Interfacial resistance difference between two electrodes Example 1 Production Example 1 Production Example 6 Wet (+) Dry (-) Comparative Example 1 Production Example 1 Production Example 4 Not considered Comparative Example 2 Production Example 3 Production Example 6 Not considered Comparative Example 3 Production Example 3 Production Example 4 Not considered

3 shows the result of the cycle performance evaluation of each of the mono cells thus manufactured, showing that the cell of Example 1 comprising a combination of a dry cathode and a wet cathode having small or no difference in interfacial resistance is superior to the cells of Comparative Examples 1 to 3 Cycle performance.

Claims (11)

A dry-made first electrode, a wet-made second electrode, a separator interposed between the dry-made first electrode and the wet-made second electrode, and an electrolyte,
Wherein the dry-made first electrode includes a first electrode active material, a binder and a conductive material, the wet-made second electrode includes a second electrode active material, a binder, and a conductive material,
And the interface resistance of the dry-made first electrode is greater than or equal to the interface resistance of the wet-made second electrode. The method according to claim 1,
When the first electrode active material contained in the dry electrode manufacturing first electrode and the same electrode active material same as the conductive material and the conductive material are dispersed in the dispersion medium and then the binder is added to form a wet electrode, Wherein the dry-type first electrode has a lower interface resistance than the wet-type first electrode. 3. The method of claim 2,
Wherein the binder included in the dry-made first electrode is the same as that of the wet-made first electrode. 3. The method of claim 2,
Wherein the binder included in the dry-made first electrode is different from the binder included in the wet-made first electrode. The method according to claim 1,
Wherein the dry-type first electrode has a coating ratio of the binder and the conductive material to the entire surface of the active material particle is less than 50%. The method according to claim 1,
Wherein the wet-made second electrode has a covering ratio of a binder and a conductive material to an entire surface of the active material particle of 50% or more. The method according to claim 1,
Wherein the dry fabrication first electrode is a cathode, the wet fabrication second electrode is an anode, or
Wherein the dry-type first electrode is a positive electrode and the wet-type second electrode is a negative electrode. 8. The method of claim 7,
Ni, Co, Fe, Mn, V (where, M and M2 are independently of each other, LiNi _{1 -xy- z} Co _x M _{y y} M2 _z O ₂ as the positive electrode active material, and the negative electrode contains graphite as the negative active material. X, y and z are independently selected from the group consisting of Cr, Ti, W, Ta, Mg and Mo, 0 < x + y + z < / = 1). (i) coating and drying a slurry containing a first electrode active material, a binder, a conductive material, and a dispersion medium on at least one surface of a current collector to prepare a wet preformed first spare electrode;
(ii) coating and drying a slurry containing a second electrode active material, a binder, a conductive material, and a dispersion medium on at least one surface of the current collector to prepare a wet-prepared second spare electrode;
(iii) measuring an interface resistance between the first preliminary electrode and the second preliminary electrode to compare their relative sizes;
(iv) the same electrode active material and conductive material as the electrode active material and the conductive material included in the spare electrode, which has been found to have a relatively large interfacial resistance in the step (iii), and a binder, which is the same or different from the binder contained in the spare electrode &Lt; / RTI &gt; at least one side of the current collector to provide an electrode;
(v) selecting the electrode provided in the step (iv) as the dry-made first electrode and the spare electrode as the wet-made second electrode in the step (iii), the interface electrode having a relatively low interfacial resistance; And
(vi) fabricating an electrode assembly between the dry-made first electrode and the wet-made second electrode via a separator,
Wherein the interface resistance of the dry-type first electrode is greater than or equal to the interface resistance of the wet-type second electrode. 10. The method of claim 9,
Wherein the interfacial resistance measurement in the step (iii) is performed in a three-electrode system battery circuit comprising a combination of the first preliminary electrode and the second preliminary electrode together with the reference electrode. 10. The method of claim 9,
Wherein the dry fabrication first electrode is a cathode, the wet fabrication second electrode is a cathode, or
Wherein the dry-type first electrode is a positive electrode, and the wet-type second electrode is a negative electrode.

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