KR20160072769A - Electrode for rechargeable lithium battery, rechargeable lithium battery, and method of fabricating electrode for rechargeable lithium battery - Google Patents

Abstract

Provided are an electrode for a lithium secondary battery, a lithium secondary battery comprising the same, and a producing method thereof. The electrode for a lithium secondary battery comprises: a current collector; and an active material layer disposed on the current collector, wherein the active material layer comprises: a plurality of active material patterns extended in a band-shape; and a plurality of carbon layers disposed between the neighboring active material patterns. In addition, gaps between the carbon layers are greater than 1 mm and less than 10 mm.

Description

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

An electrode for a lithium secondary battery, a lithium secondary battery, and a method for manufacturing an electrode for a lithium secondary battery.

2. Description of the Related Art In recent years, a lithium ion secondary battery having a high energy density and a high capacity as a power source for portable electronic devices, electric vehicles, and electric power storage has been widely used.

Particularly, the power consumption of the apparatus is increased due to miniaturization and multifunctionalization of the apparatus and the like, and a high capacity of the lithium ion secondary battery is strongly demanded. In accordance with this demand, in order to increase the capacity of the lithium ion secondary battery, it is necessary to increase the ratio of the active material in the battery.

Specifically, in order to increase the ratio of the active material in the battery, the active material is thickly applied to the current collector, and the active material layer is densified to manufacture the electrode.

However, when the active material is thickly applied to the current collector, the following problems arise.

A stress is applied to the current collector due to a change in the volume of the active material in the charge-discharge cycle, and the active material tends to peel off from the current collector.

On the other hand, in Japanese Patent Laid-Open Publication No. 2014-038795 (Patent Document 1), the active material is applied to the current collector in a striped shape to relax the stress by the space located between the active materials in the stripe form, .

In addition, when the active material is thickly applied to the current collector and then dried to produce an electrode, the active material shrinks when dried and cured, and cracks are likely to occur in the active material layer.

On the other hand, Japanese Laid-Open Patent Application No. 2014-022220 (Patent Document 2) discloses that the active material coating liquid having different viscosity is divided into two portions and applied to the current collector, and the active material coating liquid is dried to suppress cracking.

When the active material layer is made thick and dense, there is a problem that the lithium ion conductivity in the active material layer is lowered. When the lithium ion conductivity is lowered, the transfer of lithium ions is rate-controlled particularly on the collector side of the active material layer, and the charge / discharge reaction does not proceed and the capacity decreases. In addition, the charging / discharging reaction in the depth direction of the active material layer becomes more uneven, and particularly irreversible reaction such as lithium precipitation occurs on the surface of the negative electrode at the time of charging in the negative electrode.

In order to solve this problem, researches for improving ion conduction in the active material layer of the electrode are underway.

For example, Japanese Laid-Open Patent Application No. 2007-250510 (Patent Document 3) improves ion conductivity in the active material layer by forming voids in the active material layer and smoothly moving lithium ions through the voids.

Japanese Laid-Open Patent Application No. 2013-251147 (Patent Document 4) discloses a method of improving ion conductivity in the active material layer by inserting an oblique cutout into the active material layer and increasing the amount of the electrolyte capable of being absorbed into the active material layer.

However, in the lithium ion secondary batteries disclosed in the above Patent Documents 1 to 4, a satisfactory value for the cycle life could not be obtained.

Specifically, when a gap is formed in the active material layer as in Patent Document 3, the charge / discharge reaction is not uniformly performed in the electrode opposed to the active material layer in which the gap is formed, so that local deterioration of the electrode occurs in the charge- And a value that can be satisfied as the cycle life could not be obtained.

In addition, in the case of the active material layer in which the cutout is inclined as in the case of Patent Document 4, the electron conductivity is lowered in the benching portion, so that the charging / discharging reaction is not uniformly performed.

Therefore, as in the case of Patent Document 3, local deterioration of the electrode occurs in the charge-discharge cycle, and a value that can be satisfied as the cycle life can not be obtained.

One embodiment is to provide an electrode for a lithium secondary battery that improves cycle life characteristics.

Another embodiment is to provide a lithium secondary battery including the electrode for the lithium secondary battery.

Another embodiment is to provide a method for manufacturing the electrode for a lithium secondary battery.

One embodiment includes a current collector; And an active material layer disposed on the current collector, wherein the active material layer includes a plurality of active material patterns extending in a strip shape, and a plurality of carbon layers disposed between the adjacent active material patterns, The electrode for a lithium secondary battery is more than 1 mm but less than 10 mm.

The carbon layer may be disposed across the active material layer in the film thickness direction.

The carbon layer may include at least one of acetylene black, Ketjen black, and carbon black.

Another embodiment provides a lithium secondary battery including a positive electrode and a negative electrode, wherein at least one of the positive electrode and the negative electrode is the electrode.

Another embodiment provides a lithium secondary battery comprising a positive electrode and a negative electrode, wherein the negative electrode is the electrode.

According to another embodiment, a method of manufacturing a semiconductor device includes: forming a plurality of first active material patterns by applying a slurry containing an active material on a current collector in a strip shape at predetermined intervals; Coating a carbon dispersion to cover at least sides of the first active material pattern to form a carbon layer on a side surface of each first active material pattern; And forming a plurality of second active material patterns by applying a slurry containing an active material on the current collector positioned between the first active material patterns.

The details of other embodiments are included in the detailed description below.

The cycle life characteristics of the lithium secondary battery can be improved.

1 is a cross-sectional view showing a schematic configuration of a lithium secondary battery according to one embodiment.
2 is a perspective view schematically showing an electrode for a lithium secondary battery according to one embodiment.
3 is an enlarged cross-sectional view schematically showing an electrode for a lithium secondary battery according to an embodiment.
FIG. 4 is a view showing the manufacturing process of the electrode for a lithium secondary battery according to an embodiment in order.

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

It is to be understood that where a layer, film, region, plate, or the like is referred to as being "on" another portion, unless stated otherwise in this specification, .

Hereinafter, a lithium secondary battery according to one embodiment will be described with reference to FIG.

1 is a cross-sectional view showing a schematic configuration of a lithium secondary battery according to one embodiment. Specifically, FIG. 1 is a diagram schematically showing a cross section of a lithium secondary battery 10 according to an embodiment when it is cut in the thickness direction.

1, the lithium secondary battery 10 includes an anode 20, a cathode 30, and a separator layer 40. The charging reached voltage (redox potential) of the lithium secondary battery 10 is, for example, 4.3 V (vs. Li / Li ⁺ ) to 5.0 V or less.

The shape of the lithium secondary battery 10 is not particularly limited and may be, for example, a cylindrical shape, a square shape, a laminate shape, a button shape, or the like.

Hereinafter, the cathode 30 will be described with reference to FIG.

2 is a perspective view schematically showing an electrode for a lithium secondary battery according to one embodiment. 2 is a perspective view schematically showing a case where the cathode 30 according to an embodiment is cut in the thickness direction.

The cathode 30 includes a current collector 31 and a negative electrode active material layer 32 disposed on the current collector 31.

The current collector 31 may be any conductor, for example, copper, stainless steel, nickel-plated steel, or the like.

The negative electrode active material layer 32 may include a plurality of negative electrode active material patterns 33 and 34 extending in a strip shape in the plane direction of the current collector 31. Specifically, the negative electrode active material pattern 33 and the negative electrode active material pattern 34 may be alternately arranged in stripes on the current collector 31 in parallel.

A carbon layer 35 may be disposed between the negative electrode active material pattern 33 and the negative electrode active material pattern 34. In addition, the carbon layer 35 may be disposed on the upper surface of the negative electrode active material pattern 33 and on the lower surface of the negative electrode active material pattern 34. According to one embodiment, a carbon layer 35 may be disposed between at least the negative electrode active material pattern 33 and the negative electrode active material pattern 34. [

The carbon layer 35 disposed between the negative electrode active material pattern 33 and the negative electrode active material pattern 34 may be disposed so that the negative electrode active material layer 32 is tilted in the film thickness direction.

The gap A between the carbon layers 35 positioned between the negative electrode active material pattern 33 and the negative electrode active material pattern 34 may be more than 1 mm but less than 10 mm.

The negative active material patterns 33 and 34 may be aggregates of a particulate negative active material and a binder.

The negative electrode active material may include a carbon-based material. The carbon-based material is a material that contains carbon atoms and can simultaneously store and release lithium ions electrochemically.

Examples of the carbon-based material include graphite such as artificial graphite, natural graphite, a mixture of artificial graphite and natural graphite, and natural graphite coated with artificial graphite.

The binder may well adhere the negative electrode active material particles to each other and adhere the negative electrode active material to the current collector in a satisfactory manner. Examples of the binder include polyvinyl alcohol, carboxymethyl cellulose (CMC), hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride , Polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride, polyvinylidene fluoride, (PVDF), polyethylene, polypropylene, styrene-butadiene rubber (SBR), acrylic styrene-butadiene rubber, epoxy resin, and nylon. .

The negative electrode active material patterns 33 and 34 may further include a conductive auxiliary agent. The conductive auxiliary may include at least one of acetylene black, ketjen black, and carbon nanotubes.

The carbon layer 35 may include at least one of acetylene black, ketjen black, and carbon black having conductivity.

Hereinafter, the anode active material layer 32 will be described with reference to FIG.

3 is an enlarged cross-sectional view schematically showing an electrode for a lithium secondary battery according to an embodiment. 3 is an enlarged view of a part of a cross section when the cathode 30 is cut in the thickness direction according to one embodiment.

3, the negative electrode active material pattern 33 and the negative electrode active material pattern 34 disposed on the negative electrode active material layer 32 may be formed by overlapping and compressing the negative electrode active material 37, respectively. As can be seen from FIG. 3, between the negative electrode active material pattern 33 and the negative electrode active material pattern 34, there is less overlap between the negative electrode active materials 37 as compared to the inside of the negative electrode active material pattern. The ions passing through the carbon layer 35 between the negative electrode active material pattern 33 and the negative electrode active material pattern 34 are not disturbed by the negative electrode active material 37 and are scattered along the thickness direction of the negative electrode active material layer 32. [ It is possible to move linearly smoothly. As a result, ions can smoothly move, ion conduction in the negative electrode active material layer 32 is increased, and the charge / discharge reaction in the negative electrode active material layer 32 proceeds rapidly. As a result, the charging / discharging reaction is performed more uniformly in the cathode 30, so that the reduction in capacity of the lithium secondary battery 10 due to the irreversible reaction such as lithium precipitation in the cathode 30 can be avoided, The cycle life characteristics of the secondary battery 10 can be improved.

A carbon layer 35 may be disposed between the negative electrode active material pattern 33 and the negative electrode active material pattern 34. There is a possibility that there is little overlap between the negative electrode active material 37 between the negative electrode active material pattern 33 and the negative electrode active material pattern 34 and the electronic conductivity in the negative electrode active material layer 32 may be lowered. However, according to one embodiment, since the carbon layer 35 including acetylene black or the like having conductivity is disposed between the negative electrode active material pattern 33 and the negative electrode active material pattern 34, the overlapping between the negative electrode active materials 37 is small The deterioration of the electron conductivity of the negative electrode active material layer 32 caused by the negative electrode active material layer 32 can be avoided.

Also, since the carbon layer 35 contains acetylene black or the like having a large specific surface area, the carbon layer 35 has a property of being easily wetted with the electrolyte solution. Therefore, the electrolytic solution is induced in the carbon layer 35 and can smoothly penetrate between the negative electrode active material pattern 33 and the negative electrode active material pattern 34. As a result, the ions contained in the electrolytic solution reach the negative electrode active material pattern 33 It is possible to move smoothly between the negative electrode active material patterns 34 and to further increase the ion conductivity in the negative electrode active material layer 32.

In the inside of the negative electrode active material patterns 33 and 34, minute gaps are spotted between the fine-particle-type negative electrode active materials 37, and these minute gaps are connected to each other, 38 are formed.

Since the ion movement path 38 inside the negative electrode active material patterns 33 and 34 has a shape that meanders along the contour of the fine particle type negative electrode active material 37, Ions move in the direction of the thickness of the negative electrode active material layer 32 through the negative electrode active material patterns 33 and 34 through the negative electrode active material layer 37 and the negative electrode active material layer 37. It is difficult for the ions to move smoothly as compared with the case where the ions pass through the ion movement path 38 and pass through the carbon layer 35 between the negative electrode active material pattern 33 and the negative electrode active material pattern 34. On the contrary, in one embodiment, the carbon layer 35 is disposed in the anode active material layer 32 as a diffusion path of ions and an electron movement path. In this carbon layer 35, the overlapping of the anode active materials 37 is small The ions are not disturbed by the negative electrode active material 37 and can move linearly smoothly.

The thickness of the active material layer is not particularly limited and may be appropriately selected.

Hereinafter, a method of manufacturing the cathode 30 will be described with reference to FIG.

FIG. 4 is a view showing the manufacturing process of the electrode for a lithium secondary battery according to an embodiment in order. 4 is a diagram schematically showing a cross section when the cathode 30 is cut in the thickness direction in each manufacturing process of the cathode 30 according to one embodiment.

First, a negative electrode material mixture is prepared by dry mixing the negative electrode active material 37 and a binder, and then the negative electrode material mixture is dispersed in an appropriate solvent to adjust the viscosity to prepare a slurry-type negative electrode material mixture slurry.

Further, a carbon dispersion for forming the carbon layer 35 can be produced. Specifically, a carbon material such as acetylene black can be dispersed in a suitable solvent to prepare a carbon dispersion.

4 (a), the negative electrode material mixture slurry can be applied in a striped pattern on a surface of the current collector 31 with a predetermined gap therebetween. At this time, it may be applied using a nozzle, or it may be coated on the current collector 31 as if drawn with a brush. At this time, the negative electrode material mixture slurry can be applied in a stripe shape so that the interval is larger than 1 mm and less than 10 mm.

The negative electrode active material layer 33 may be formed by drying the negative electrode material mixture slurry using an air blow type drier or the like.

The carbon dispersion may then be applied. The carbon dispersion can be applied by using a nozzle or the like so as to cover at least the side surface of the negative electrode active material pattern 33. [ At this time, as shown in Fig. 4 (b), the entire surface of the current collector 31, that is, the upper surface and the side surface of the negative electrode active material pattern 33, The carbon dispersion may be applied on one surface of the whole body 31. [

Further, the carbon layer 35 can be formed at least on the side surface of the negative electrode active material pattern 33 by drying the carbon dispersion by using a blower-type dryer or the like.

4C, the negative electrode material mixture slurry is striped so as not to overlap the negative electrode active material pattern 33 on one surface of the current collector 31 located between the negative electrode active material patterns 33 Can be applied.

Further, the negative electrode active material pattern 34 may be formed between the negative electrode active material patterns 33 by drying using a blower-type dryer or the like.

Further, the negative electrode active material patterns 33 and 34 may be rolled to a desired density and then dried using a blower dryer to form the negative electrode 30.

Hereinafter, the anode 20 will be described.

The anode 20 may be constructed in the same manner as the cathode 30 according to one embodiment except for the following description. Therefore, the description of the elements common to the cathode 30 is omitted here.

The shape of the anode 20 is the same as that of the cathode 30, and can be represented by FIG. 2 and FIG.

2 and 3, the current collector 21 of the anode 20 corresponds to the current collector 31 of the cathode 30, the cathode active material layer 22 corresponds to the anode active material layer 32, The pattern corresponds to the negative electrode active material patterns 33 and 34. The carbon layer in the positive electrode 20 corresponds to the carbon layer 35 in the negative electrode 30 and the positive electrode active material corresponds to the negative electrode active material 37 .

The current collector 21 of the anode 20 may be any conductive material, and examples thereof include aluminum, stainless steel, nickel-plated steel, and the like.

The positive electrode active material pattern includes at least a particulate positive electrode active material, and may further include at least one of a conductive material and a binder.

The cathode active material is, for example, a solid solution oxide containing lithium, but is not particularly limited as long as it is a material capable of occluding and releasing lithium ions electrochemically.

The solid solution oxides include, for example, Li _a Mn _x Co _y Ni _z O ₂ (1.150? A? 1.430, 0.45? X? 0.6, 0.10? Y? 0.15, 0.20 = _z? 0.28), LiMn _x Co _y Ni _z O ₂ (0.3? X? 0.85, 0.10? Y? 0.3, 0.10? Z? 0.3), LiMn _1.5 Ni _0.5 O ₄ , Li _1.20 Mn _0.55 Co _0.10 Ni _0.15 O ₂ .

Examples of the conductive material include carbon black such as ketjen black and acetylene black, natural graphite, and artificial graphite. However, the conductive material is not particularly limited as long as it enhances the conductivity of the anode.

The binder may be selected from, for example, polyvinylidene fluoride, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, acrylonitrile-butadiene rubber, fluor rubber, polyvinyl acetate, polymethyl methacrylate, polyethylene, Cellulose, and the like. However, it is not particularly limited as long as it can bind the positive electrode active material and the conductive material on the current collector, and at the same time, has oxidation resistance and electrolyte stability to withstand the high potential of the positive electrode.

Although the positive electrode active material layer 22 of the positive electrode 20 has a plurality of positive electrode active material patterns extending in a strip shape like the negative electrode 30, the positive electrode 20 may not be of such a shape, At least one of the anode 20 and the cathode 30 may have an active material layer having the above-described pattern.

Hereinafter, a method of manufacturing the anode 20 will be described.

The manufacturing method of the anode 20 may be the same as the manufacturing method of the cathode 30. [ That is, the cathode mixture may be prepared by dry mixing the cathode active material, the binder and the like, and then the cathode mixture may be dispersed in an appropriate organic solvent to prepare the cathode mixture slurry. The subsequent steps are the same as the method for manufacturing the negative electrode 30, and the description thereof is omitted here.

Hereinafter, the separator layer 40 will be described.

The separator layer 40 may include a separator and an electrolytic solution.

The separator is not particularly limited, and any separator may be used as long as it is used as a separator of a lithium secondary battery. For example, a porous film or nonwoven fabric exhibiting excellent high rate discharge performance can be used singly or in combination.

Specifically, the substrate constituting the raw material of the separator is, for example, a polyolefin resin, a polyester resin, polyvinylidene fluoride (PVDF), a vinylidene fluoride-hexafluoropropylene copolymer, a vinylidene fluoride- Vinylidene fluoride-fluoroethylene copolymers, vinylidene fluoride-tetrafluoroethylene copolymers, vinylidene fluoride-trifluoroethylene copolymers, vinylidene fluoride-fluoroethylene copolymers, vinylidene fluoride-hexafluoro Vinylidene fluoride-ethylene copolymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride- , Vinylidene fluoride-ethylene-tetrafluoroethylene There may be mentioned polymers. Examples of the polyolefin-based resin include polyethylene and polypropylene. Examples of the polyester-based resin include polyethylene terephthalate and polybutylene terephthalate.

The electrolytic solution may have a composition containing an electrolytic salt in a non-aqueous solvent.

Examples of the non-aqueous solvent include cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate and vinylene carbonate; Chain carbonates such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate; cyclic esters such as? -butyrolactone and? -valerolactone; Chain esters such as methyl formate, methyl acetate and butyric acid methyl; Tetrahydrofuran or a derivative thereof; Ethers such as 1,3-dioxane, 1,4-dioxane, 1,2-dimethoxyethane, 1,4-dibutoxyethane and methyl diglyme; Nitriles such as acetonitrile and benzonitrile; Dioxolane or derivatives thereof; Ethylene sulfide, sulfolane, sultone or a derivative thereof may be used alone or as a mixture of two or more thereof, but is not limited thereto.

The electrolyte salt may be, for _{example, LiClO 4, LiBF 4, LiAsF} 6, LiPF 6, LiPF 6 - x (CnF 2n + 1) x (1 <x <6, n = 1 or 2), LiSCN, LiBr, LiI, Li ₂ SO _4, Li ₂ B ₁₀ Cl _10, NaClO _4, NaI, NaSCN, NaBr, KClO _4, an inorganic ion salt containing lithium, sodium or potassium, such as one type of KSCN; _{LiCF 3 SO 3, LiN (CF} 3 SO 2) 2, LiN (C 2 F 5 SO 2) 2, LiN (CF 3 SO 2) (C 4 F 9 SO 2), LiC (CF 3 SO 2) 3, _{LiC (C 2 F 5 SO 2} ) 3, (CH 3) 4 NBF 4, (CH 3) 4 NBr, (C 2 H 5) 4 NClO 4, (C 2 H 5) 4 NI, (C 3 H 7 _{) 4 NBr, (nC 4 H} 9) 4 NClO 4, (nC 4 H 9) 4 NI, (C 2 H 5) 4 N- _{maleate, (C 2 H 5) 4} N- benzoate, (C ₂ H ₅ ) ₄ N-phthalate, lithium stearylsulfonate, lithium octylsulfonate, and lithium dodecylbenzenesulfonate. These ionic compounds may be used singly or in combination of two or more.

The concentration of the electrolyte salt is not particularly limited and may be, for example, 0.8 to 1.5 mol / L.

Various additives may be added to the electrolytic solution. Examples of the additives include an anode active additive, an anode active additive, an ester based additive, a carbonic acid ester additive, a sulfuric acid ester additive, a phosphate ester additive, a boric acid ester additive, an acid anhydride additive and an electrolyte additive. Any one or more of these additives may be added to the electrolytic solution.

Hereinafter, a method of manufacturing the lithium secondary battery 10 will be described.

The separator is disposed between the anode 20 and the cathode 30 to prepare an electrode structure and then the electrode structure is processed into a desired shape such as a cylindrical shape, a square shape, a laminate shape, a button shape, Lt; / RTI &gt; Subsequently, the electrolyte is injected into the container to impregnate the pores in the separator with an electrolytic solution, whereby a lithium secondary battery can be manufactured.

The positive electrode 20 and the negative electrode 30 according to one embodiment are used as the positive and negative electrodes in the lithium secondary battery 10, but the positive electrode 20 and the negative electrode 30 according to one embodiment, ) Can be used.

Hereinafter, specific embodiments of the present invention will be described. However, the embodiments described below are only intended to illustrate or explain the present invention, and thus the present invention should not be limited thereto. In addition, contents not described here can be inferred sufficiently technically if they are skilled in the art, and a description thereof will be omitted.

(Cathode manufacture)

Example 1

Water was added to 98 wt% of natural graphite, 1 wt% of carboxymethyl cellulose (CMC) and 1 wt% of styrene-butadiene rubber (SBR) to adjust the viscosity suitable for application, and an anode mix slurry was prepared.

Further, a carbon dispersion comprising 5% by weight of acetylene black, 75% by weight of water and 20% by weight of ethanol was prepared.

The negative electrode mixture slurry was coated on one surface of a copper foil as a current collector 31 in a striped pattern and dried for 15 minutes by an air blower dryer set at 80 캜 to form a negative electrode active material pattern 33. At this time, the intervals of stripes, that is, the intervals of the negative electrode active material patterns 33 were 2 mm.

Subsequently, the carbon dispersion was applied to the entire upper surface of the current collector 31 and dried for 15 minutes by a blower dryer set at 80 DEG C to form a carbon layer 35. [

The negative electrode mixture slurry was applied between the negative electrode active material patterns 33 so as not to overlap with the negative electrode active material pattern 33 and dried for 15 minutes in an air blower dryer set at 80 DEG C to form the negative electrode active material pattern 33 The negative electrode active material pattern 34 was formed.

The negative electrode active material patterns 33 and 34 were rolled so as to have a predetermined density and then vacuum dried at 150 ° C for 6 hours to prepare a negative electrode 30. The packing density of the negative electrode active material layer 32 of the prepared negative electrode 30 was 1.60 g / cc.

Example 2

The negative electrode 30 was formed in the same manner as in Example 1 except that the interval of the stripe, that is, the distance between the negative electrode active material patterns 33 was 3 mm.

Example 3

The negative electrode 30 was prepared in the same manner as in Example 1, except that the interval of the stripe, that is, the distance between the negative electrode active material patterns 33 was 5 mm.

Comparative Example 1

A negative electrode (30) was prepared in the same manner as in Example 1, except that the negative electrode material mixture slurry was uniformly coated on one surface of the copper foil as the current collector (31) and dried.

Comparative Example 2

A negative electrode 30 was prepared in the same manner as in Example 1, except that the carbon dispersion was not applied.

Comparative Example 3

The negative electrode 30 was prepared in the same manner as in Example 1, except that the carbon dispersion was not applied and the interval of the stripe, that is, the distance between the negative electrode active material patterns 33 was 10 mm.

Comparative Example 4

The negative electrode 30 was prepared in the same manner as in Example 1 except that the interval of the stripe, that is, the distance between the negative electrode active material patterns 33 was 10 mm.

Comparative Example 5

The negative electrode 30 was produced in the same manner as in Example 1, except that the interval of the stripe, that is, the distance between the negative electrode active material patterns 33 was 1 mm.

Evaluation 1: Intensity of cathode

The strength of the negative electrode active material layer 32 was evaluated for the negative electrode 30 according to Examples 1 to 3 and Comparative Examples 4 and 5 by using the cross-cut method of JIS K5600.

The classification of the evaluation results is shown in Table 1 below.

Classification Explanation 0 The edge of the cut is perfectly smooth and there is no peeling in the eye of any grid One There is a small peeling point of the coating film at the intersection of the cut. It is clearly not more than 5% that it is affected by the closscut part 2 The coating is peeled off along the edges of the cut and / or at the point of intersection. Affected by crosscuts clearly exceeds 5% but not above 15% 3 The coating film has partially or wholly peeled off along the edges of the cut, and / or various parts of the eye are partially or entirely peeled off. The effect of crosscuts is clearly more than 15% but not more than 35% 4 The coating film has partially or wholly peeled off along the edges of the cut, and / or some of the eyes are partially or entirely peeled off. The effect of the crosscuts is clearly more than 35% but not more than 65%. 5 The extent to which the degree of exfoliation exceeds Classification 4.

As a result of the evaluation, results of "classification 2" were obtained in the cathode 30 according to Examples 1 to 3 and Comparative Example 4, and "classification 3" was obtained in the cathode 30 according to Comparative Example 5. In other words, it can be seen that the negative electrode according to Examples 1 to 3 and Comparative Example 4 having a stripe interval of 2 mm to 10 mm has a higher strength of the negative electrode active material layer as compared with the negative electrode of Comparative Example 5 having a striped interval of 1 mm.

The reasons are as follows.

Since the carbon layer 35 between the negative electrode active material pattern 33 and the negative electrode active material pattern 34 is less overlapped with the particulate negative electrode active material 37, the negative electrode active material layer 32 tends to collapse. Therefore, the distance A between the stripes, that is, the distance A between the carbon layer 35 between the negative electrode active material pattern 33 and the negative electrode active material pattern 34 is narrowed, and the carbon layer 35 is distributed in the negative active material layer 32 The strength of the negative electrode active material layer 32 is lowered because the negative electrode active material layer 32 is easily collapsed.

If the strength of the negative electrode active material layer 32 is lowered, the active material may fall off during the manufacturing process of the lithium secondary battery, which may increase the defective ratio in the manufacturing process of the lithium secondary battery. Further, since the strength of the negative electrode active material layer 32 is lowered, the negative electrode active material 37 is easily detached from the current collector 31 due to a change in the volume of the active material accompanying the charging and discharging,

The gap A between the anode active material pattern 33 and the anode active material pattern 34 can be made larger than 1 mm in order to prevent the strength of the anode active material layer 32 from lowering.

(Coin cell production)

Solid solution oxide Li _{1 . 20} Mn _{0 . 55} Co _{0 . 10} Ni _{0 .} 96% by weight of ₁₅ O ₂ , 2% by weight of Ketjenblack and 2% by weight of polyvinylidene fluoride were dispersed in N-methyl-2-pyrrolidone to prepare a positive electrode mixture slurry. The positive electrode material mixture slurry was uniformly applied to the entire aluminum foil as a current collector, and was dried for 15 minutes by a blower dryer set at 80 캜. Then, the current collector was rolled and vacuum-dried at 100 DEG C for 6 hours to prepare a positive electrode. The filling density of the positive electrode active material layer of the positive electrode was 3.0 g / cc.

The positive electrode was cut to a diameter of 13 mm and the negative electrode according to Examples 1 to 3 and Comparative Examples 1 to 5 was cut to a diameter of 15.5 mm and a separator made of a polyethylene microporous membrane having a diameter of 19 mm and a thickness of 25 占 퐉 was placed between the positive electrode and the negative electrode And then housed in a CR2032 coin cell battery case.

Next, an electrolyte solution in which 1.5 M LiPF ₆ was dissolved in a mixed solution of ethylene carbonate / diethyl carbonate / fluoro ethylene carbonate (10/70/20 volume ratio) was injected into the battery case and sealed to manufacture a lithium secondary battery.

Evaluation 2: Discharge rate characteristic of lithium secondary battery

The lithium secondary batteries according to Examples 1 to 3 and Comparative Examples 1 to 5 were charged to 4.2 V at a constant current of 5 mA at 25 캜 and charged until the current value reached 0.1 mA at a constant voltage of 4.2 V, The battery was discharged at a constant current of 5 mA until it reached 2.75 V with a rest (stop). Then, the battery was charged in the same manner as described above, and discharged at 2.9 V at a constant current of 10 mA to evaluate discharge rate characteristics. The results are shown in Table 2 below.

In the following Table 2, the discharge rate (%) is calculated as a percentage of the discharge capacity at a constant current of 10 mA to the discharge capacity at a constant current of 5 mA.

Evaluation 3: Cycle characteristics of lithium secondary battery

The lithium secondary batteries according to Examples 1 to 3 and Comparative Examples 1 to 5 were charged to 4.2 V at a constant current of 5 mA at 25 캜 and charged until the current value reached 0.1 mA at a constant voltage of 4.2 V, The battery was discharged at a constant current of 5 mA until it reached 2.75 V with a rest (stop). The discharge capacity at this time was regarded as the discharge capacity of the first cycle, and the cycle characteristics were evaluated by repeating a charge-discharge cycle 100 times. The results are shown in Table 2 below.

In the following Table 2, the capacity retention rate (%) is calculated as a percentage of the discharge capacity at the 100th cycle with respect to the discharge capacity at the first cycle.

The anode active material layer Discharge rate (%) Capacity retention rate (%) Comparative Example 1 No carbon layer
Negative electrode active material pattern not formed 70 67 Comparative Example 2 No carbon layer
Spacing of negative active material pattern 2 mm 75 73 Comparative Example 3 No carbon layer
Negative electrode active material pattern interval 10 mm 70 68 Comparative Example 4 With carbon layer
Gap of carbon layer A 10 mm 71 68 Example 1 With carbon layer
Spacing of carbon layer A 2 mm 82 81 Example 2 With carbon layer
Gap of carbon layer A 3 mm 80 77 Example 3 With carbon layer
Gap of carbon layer A 5 mm 76 74

Referring to Table 2, it can be seen that the discharge rate characteristics and cycle life characteristics of the lithium secondary batteries according to Examples 1 to 3 are improved compared to Comparative Examples 1 to 4.

Specifically, the discharge rate characteristics of Comparative Examples 1 to 3 were improved in Examples 1 to 3. This indicates that the charge-discharge reaction in the negative electrode active material layer of the negative electrode according to Examples 1 to 3 is progressing rapidly. In the negative electrode according to Examples 1 to 3, since the pattern and the carbon layer are formed in the negative electrode active material layer, the ion conductivity in the negative electrode active material layer is higher than that in Comparative Example 1, and the charge / discharge reaction seems to progress rapidly.

In addition, the charging / discharging reaction progresses rapidly, so that the charging and discharging reaction is more uniformly performed in the negative electrode according to Examples 1 to 3, and the capacity reduction of the lithium secondary battery caused by the irreversible reaction such as lithium precipitation in the negative electrode is suppressed do. As a result, the cycle life characteristics of the lithium secondary batteries of Examples 1 to 3 seem to be improved as compared with Comparative Example 1.

On the other hand, examining the discharge rate characteristics and cycle life characteristics of the examples and comparative examples in which the intervals of the stripe patterns, that is, the intervals of the negative electrode active material patterns are the same, Example 1 and Comparative Example 2 show the intervals of stripes, Was 2 mm. However, in Example 1 having a carbon layer, discharge rate characteristics and cycle life characteristics were improved as compared with Comparative Example 2 in which there was no carbon layer.

This is because the carbon layer contains carbon black or the like having a large specific surface area, so that the carbon layer is easily wetted with the electrolyte solution, and therefore lithium ions in the electrolyte can smoothly move between the negative electrode active material patterns through the carbon layer. In addition, since the electrons can move smoothly between the anode active material patterns through the carbon layer, the discharge rate characteristics and the cycle life characteristics of the Example 1 having the carbon layer are improved as compared with Comparative Example 2 in which the carbon layer is not provided see. As described above, in the first embodiment, the carbon layer seems to function as an ion diffusion path and an electron transfer path.

Further, with reference to Comparative Example 3 and Comparative Example 4 in which the interval of the stripe, that is, the interval of the negative electrode active material pattern is 10 mm, the discharge rate characteristic and the cycle life characteristic of Comparative Example 4 having a carbon layer are comparative examples 3 &lt; / RTI &gt; The discharge rate characteristics and cycle life characteristics of Comparative Example 3 and Comparative Example 4 are the same as those of Comparative Example 1 in which the negative electrode active material pattern and the carbon layer are not present.

This is because the effect of the pattern formation and the effect of the carbon layer formation are reduced by increasing the interval of the stripe, that is, the interval of the negative electrode active material pattern to 10 mm.

Further, in Examples 1 to 3, the discharge rate characteristics and the cycle life characteristics are improved as the interval of the striations, that is, the interval A between the carbon layers between the negative electrode active material pattern and the negative electrode active material pattern is narrowed. This is because the ion conduction in the negative electrode active material layer becomes high due to the increase of the carbon diffusion layer and the electron transfer path of the ion, so that the charging / discharging reaction proceeds rapidly and the charging / discharging reaction in the negative electrode is performed more uniformly see.

The effect of the carbon layer becomes less noticeable when the gap A between the carbon layers between the negative electrode active material pattern 33 and the negative electrode active material pattern 34 is about 10 mm, so that the gap A between the carbon layers can be less than 10 mm.

As a result, as the gap A between the carbon layers becomes narrower, that is, as the carbon layer as the ion diffusion path and the electron movement path increases, the charging / discharging reaction of the electrode occurs uniformly and the discharge rate and cycle characteristics are improved . However, if the gap A between the carbon layers is narrowed, the strength of the negative electrode active material layer tends to decrease. Therefore, the gap A between the carbon layers may be larger than 1 mm to prevent the strength of the negative electrode active material layer from lowering.

The lithium secondary battery according to one embodiment has a high ion conductivity in the active material layer and can accelerate the charging / discharging reaction at the electrode because the carbon layer as the ion diffusion path and the electron migration path is provided in the active material layer . Therefore, the charging / discharging reaction can be performed more uniformly, and the capacity decrease due to the deterioration due to the non-uniformity of the reaction in the electrode can be suppressed, and as a result, the cycle life characteristics of the lithium secondary battery can be improved.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, And falls within the scope of the invention.

10 lithium secondary battery
20 anode
21,31 collection
22 cathode active material layer
30 cathode
32 Anode active material layer
33, 34 Active material pattern
35 carbon layer
37 active material
38 ion transport path
40 Separator layer

Claims (6)

Collecting house; And
And an active material layer disposed on the current collector,
Wherein the active material layer includes a plurality of active material patterns extending in a strip shape and a plurality of carbon layers disposed between the adjacent active material patterns,
Wherein the distance between the carbon layers is greater than 1 mm and less than 10 mm. The method of claim 1,
Wherein the carbon layer is disposed across the active material layer in the film thickness direction. The method of claim 1,
Wherein the carbon layer comprises at least one of acetylene black, ketjen black, and carbon black. An anode, and a cathode,
Wherein at least one of the positive electrode and the negative electrode is an electrode according to any one of claims 1 to 3. An anode, and a cathode,
Wherein the negative electrode is the electrode according to any one of claims 1 to 3. Forming a plurality of first active material patterns by applying a slurry containing an active material on a current collector in a strip shape at predetermined intervals;
Coating a carbon dispersion to cover at least sides of the first active material pattern to form a carbon layer on a side surface of each first active material pattern; And
Forming a plurality of second active material patterns by applying a slurry containing an active material on the collector positioned between the first active material patterns
And an electrode for a lithium secondary battery.

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