KR101812625B1 - Multilayer Electrode for Secondary Battery Having Different Volume of Conductive Materials and Preparation Method Thereof - Google Patents

Abstract

The present invention provides a plasma display panel comprising a first electrode mixture layer coated on a surface of a current collector and a second electrode mixture layer coated on the first electrode composite layer, wherein the first electrode mixture layer includes a first electrode active material Wherein the second electrode mixture layer comprises a second electrode active material and the porosity of the first electrode material mixture layer is relatively larger than the porosity of the second electrode material mixture layer and the porosity of the second electrode material mixture layer is not less than 15% Wherein the first electrode mixture layer includes a first conductive material located in a gap between the first electrode active materials and the second electrode mixture layer includes a second conductive material located in a gap between the second electrode active materials, Wherein the volume of the first conductive material is relatively larger than the volume of the second conductive material, and a method of manufacturing the same.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for a secondary battery having a multi-

The present invention relates to a multi-layered electrode for a secondary battery having different conductive materials and a method of manufacturing the same.

As technology development and demand for mobile devices have increased, the demand for secondary batteries as energy sources is rapidly increasing. In recent years, the use of secondary batteries as a power source for electric vehicles (EV) and hybrid electric vehicles (HEV) Among such secondary batteries, there is a high demand for a lithium secondary battery having a high energy density, a high discharge voltage and an output stability.

The lithium secondary battery is manufactured by using a metal oxide such as LiCoO ₂ as a cathode active material and a carbon material as a negative electrode active material and a polyolefin porous separator between the anode and the cathode and a nonaqueous electrolytic solution containing a lithium salt such as LiPF ₆ . During charging, lithium ions of the positive electrode active material are released and inserted into the carbon layer of the negative electrode. In discharging, lithium ions of the negative electrode carbon layer are released and inserted into the positive electrode active material. In this case, As a medium for transporting the liquid. Such a lithium secondary battery should basically be stable in the operating voltage range of the battery, and have a capability of transferring ions at a sufficiently high speed.

The non-aqueous electrolytic solution is introduced into the battery at the final stage of the lithium secondary battery. At this time, the electrode needs to be quickly and completely wetted by the electrolytic solution to shorten the time consumed in manufacturing the battery and optimize the battery performance.

However, when the electrode is compressed by rolling or the like in order to manufacture the electrode, the electrode density is increased, but the porosity of the electrode is decreased due to the reduction in volume, and the impregnation characteristic of the electrolyte is deteriorated. In this case, since the electrolyte can not penetrate into the electrode well and the contactability with the electrode is lowered, the substantial contact area with the electrolyte is relatively reduced. Therefore, the transfer path of the lithium ions is limited, so that a sufficient battery capacity can not be obtained, and the performance is deteriorated at the time of high-speed charging and discharging.

Conventional techniques for solving the poor impregnation characteristics of such electrodes include the following.

Japanese Patent Laid-Open Publication No. 1994-060877 discloses a method for improving the impregnating property of an electrolyte by plasma treatment or adsorption of a wetting agent on the surface of the anode. By plasma treatment, the surface of the electrode is roughened or the wetting agent is adsorbed, To improve the impregnation property.

Japanese Patent Application Laid-Open No. 1999-086849 discloses that when the electrode material is expanded due to temperature rise during operation, the electrolyte solution becomes insufficient. Therefore, the electrode material is assembled by using a high-temperature electrolytic solution and an electrode material at the time of manufacturing the electrode, Impregnation of the electrolytic solution was also improved.

The above-mentioned prior arts have their own effects as modifying the surface of the electrode or improving the impregnation property by changing the temperature. However, there is a disadvantage that there is no countermeasure in the case where the porosity itself decreases due to rolling or the like, have.

However, in this case, it is easy to penetrate the electrolytic solution from the surface portion having a large porosity to a portion where the porosity is small. However, as the inside of the electrode becomes more and more porous There is a problem in that the penetration of the electrolyte solution is not easy due to the viscosity and the surface tension of the electrolyte solution in the electrode which does not directly contact with the electrolyte solution because the porosity is rather low even though the amount of the penetrated electrolyte solution and the infiltration pressure are decreased.

At this time, the volume of the conductive material existing in the surface portion and the inside of the electrode is the same, and the electron conductivity of the surface portion of the electrode having a large porosity is relatively low compared with the electronic conductivity inside the electrode having a small porosity.

Therefore, there is a high need for a technique capable of improving the performance of the battery by maximizing the electronic conductivity in the electrode while increasing the impregnation property of the electrolyte to the inside of the electrode.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and the technical problems required from the past.

The inventors of the present application have conducted intensive research and various experiments and have found that the electrode mixture layers having different porosities are arranged in a two-layer structure and the porosity of the electrode mixture layer located far away from the current collector is positioned near the current collector When the electrode is manufactured such that the volume of the conductive material of the electrode material mixture layer having a larger porosity is larger than the volume of the conductive material of the electrode material mixture layer having a smaller porosity, The present invention has been accomplished by confirming that the electronic conductivity of the electrode is improved overall and the performance of the secondary battery including the same is improved.

According to an aspect of the present invention,

A first electrode mixture layer coated on the surface of the current collector and a second electrode mixture layer coated on the first electrode coalescence layer,

Wherein the first electrode material mixture layer includes a first electrode active material, the second electrode material mixture layer includes a second electrode active material,

The porosity of the first electrode material mixture layer is relatively larger than the porosity of the second electrode material mixture layer, and the porosity of the second electrode material mixture layer is 15%

Wherein the first electrode material mixture layer includes a first conductive material located in a gap between the first electrode active material and the second electrode material mixture layer includes a second conductive material located in a gap between the second electrode active material,

And the volume of the first conductive material is relatively larger than the volume of the second conductive material.

At this time, the porosity of the second electrode material mixture layer may be 40% to 95% of the porosity of the first electrode material mixture layer, and the porosity of the second electrode material mixture layer may be, 60% to 95%.

The inventors of the present application have conducted intensive research and have found that even when the porosity of the electrode mixture layer far from the current collector is set to a predetermined range or more as described above, When the volume of the conductive material located in the gap between the electrode active materials differs according to the porosity of the electrode mixture layers, the surface area of the electrode also has a porosity of more than a predetermined range, The permeability of the electrolyte solution is easy, and the porosity of the electrolyte solution is higher than the amount of the electrolyte solution and the permeation pressure of the electrolyte solution. Therefore, the path through which the electrolyte solution can permeate is widened to enhance the impregnability of the electrolyte solution to the inside of the electrode. Respectively.

The porosity of the second electrode material mixture layer for achieving such an effect may be in the range of 15% to 30%, more specifically 20% to 25%, and the porosity of the first electrode material mixture layer The porosity may be 20% to 40% in a range larger than the porosity of the second electrode compound mixture layer, and more specifically, it may be 25% to 30%.

If the porosity of the second electrode material mixture layer is less than 15%, the porosity is too small to sufficiently penetrate the electrolyte solution into the first electrode material mixture layer. If the porosity exceeds 30%, the electrode density becomes very low, So it is not preferable.

When the porosity of the first electrode material mixture layer is less than 20%, the electrolyte solution having a smaller amount and a lower pressure is hardly penetrated to the surface of the collector. When the porosity is more than 40%, the electrode density is lowered, The capacity and the output of the battery may be lowered, which is undesirable.

Further, the volume of the second conductive material may be in the range of 50% to 95% of the space between the second electrode active material, and more specifically, 50% to 70%, and the volume of the first conductive material And may be in the range of 50% to 95%, and more specifically, 50% to 70% of the gap between the first electrode active material in a larger range.

If the volume of the second conductive material is less than 50% of the gap between the second electrode active materials, a desired level of electronic conductivity can not be obtained. If the volume of the second conductive material exceeds 95%, the electrolyte solution is hardly penetrated into the first electrode material mixture layer.

If the volume of the first conductive material is less than 50% of the gap between the first electrode active materials, a desired level of electronic conductivity can not be obtained. If the volume of the first conductive material is more than 95% I do not.

The first electrode material mixture layer and the second electrode material mixture layer may have an interface therebetween without being mixed with each other. The first electrode material mixture layer and the second electrode material mixture layer may have a thickness of 4: A thickness ratio of 7: 3 can be obtained.

When the first electrode material mixture layer is applied in an excessively large thickness over the above range, there is a problem that the overall electrode density is lowered. When the second electrode material mixture layer is out of the above-described range and is coated relatively too thick, The thickness of the layer is too thick to penetrate the electrolyte solution into the electrode, which is not preferable.

Meanwhile, in one specific example, the first electrode active material may be in the form of a spherical particle or a vertical cross-section, and may be in the form of an elliptical particle whose long diameter is parallel to the surface of the current collector, and the second electrode active material, And when the first electrode active material and the second electrode active material are all in the form of elliptical particles, the particle diameter of the first electrode active material may be smaller than the particle diameter of the second electrode active material.

The difference in particle shape between the first electrode active material and the second electrode active material may be caused by differences in the manufacturing method of the active material and the like. However, even if the same active material is manufactured in the same manner, the porosity of each electrode material mixture layer The different strengths of the electrodes can be adjusted by varying the rolling strength of the electrodes.

That is, since the shape of the active material depends on the magnitude of the pressure applied during the rolling process, the first electrode material mixture layer having a large porosity is rolled at a low pressure to maintain the original particle shape of the first electrode active material, The second electrode mixture layer, which should be small, is rolled at a higher pressure to change the shape of the second electrode active material to an elliptical shape.

As described above, the electrode of the present invention can be manufactured as a two-layer electrode having different porosity by a rolling process. The first electrode active material and the second electrode active material may have the same kind and / or different particle volume, Or the like, but the details may be the same.

Here, the particle volume means a volume in which the particle is autonomous regardless of whether it is spherical or elliptical.

Similar to the electrode active material, the first conductive material located in the gap between the first electrode active materials may be in the form of spherical particles or elliptical particles having a long cross section and having a long diameter parallel to the surface of the current collector, The second conductive material located in the gap between the first conductive material and the second conductive material may be in the form of elliptical particles whose longitudinal diameter is parallel to the surface of the current collector. In this case, the shape of the first conductive material may be the same as that of the first electrode active material.

This is because, as described above, the shape of the materials in each mixed layer varies depending on the magnitude of the applied pressure as the electrode active materials in the rolling process.

However, also in this case, the first conductive material and the second conductive material may be configured so that the volume of the first conductive material is larger than the volume of the second conductive material regardless of the form thereof.

In this case, the first conductive material and the second conductive material may be the same or different, and the volume difference may be caused by a difference in kind of the conductive materials, and even if the kinds of the conductive materials are the same, Or the difference in order. The surface structure such as the specific surface area (BET) of the conductive material particles is different according to the method and order of synthesis of the conductive material. As a result, the degree of impregnation of the electrolyte and the physical contact with the active material .

Meanwhile, in one specific example, the first electrode material mixture layer and the second electrode material mixture layer may include a binder for assisting the bonding of the active material and the conductive material to the gap and the bonding to the current collector, respectively .

At this time, the composition of the first electrode material mixture layer and the composition of the second electrode material mixture layer, which are mixing ratios of the active material, the conductive material, and other binders, may be the same or different.

The present invention also provides a method of manufacturing an electrode using the difference in rolling strength as described above.

Specifically, in the electrode according to the present invention,

(a) preparing a second electrode slurry including a first electrode slurry including a first electrode active material and a first conductive material, a second electrode active material, and a second conductive material;

(b) applying a first electrode slurry to the surface of the electrode current collector, followed by drying and rolling to form a first electrode mixture layer;

(c) applying a second electrode slurry to the surface of the first electrode material mixture layer, followed by drying and rolling to form a second electrode material mixture layer;

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or,

(a) preparing a second electrode slurry including a first electrode slurry including a first electrode active material and a first conductive material, a second electrode active material, and a second conductive material;

(b) applying a first electrode slurry to the surface of the electrode current collector, followed by drying and rolling to form a first electrode mixture layer;

(c) applying a second electrode slurry on a separate substrate, drying and rolling the green film for a second electrode composite layer; And

(d) separating the green film from the base material, adding the green film to the surface of the first electrode material mixture layer, and further drying and rolling to form a second electrode material mixture layer;

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Here, the green film means an intermediate for completing the preparation of the electrode.

In order to make the porosity of the first electrode material mixture layer larger than the porosity of the second electrode material mixture layer in the above-described manufacturing method, the rolling strength of the first electrode slurry in the step (b) It is preferably from 40% to 95%, more specifically from 60% to 95%.

As described above, the electrode according to the present invention can be manufactured by coating and rolling the first electrode slurry, applying and rolling the second electrode slurry again, or applying the second electrode slurry to another substrate and rolling the same, The first electrode material mixture layer and the second electrode material mixture layer are separately prepared at different rolling ratios so that the electrode material mixture layer is coated and rolled at one time, The porosity of each layer can be easily controlled, the porosity of the surface portion is excessively small, and the porosity of the interior portion is prevented from becoming excessively large, unlike the structure in which the porosity of the first electrode material mixture layer and the second electrode material mixture The ratio of the porosity of the layer can be easily controlled, so that the intended effect of the present invention can be achieved.

As described above, since the first electrode material mixture layer and the second electrode material mixture layer are not mixed with each other and form an interface with each other, And the composition of the first electrode slurry and the composition of the second electrode slurry can be made the same, and the process can be simplified as well.

Meanwhile, the electrode according to the present invention can be applied to both the positive electrode and the negative electrode.

When the electrode is a positive electrode, the first electrode mixture layer and the second electrode mixture layer coated on the surface of the positive electrode collector are coated with the first electrode active material and the first electrode active material A two-electrode active material, a first conductive material and a second conductive material as a conductive material, and a mixture of a binder and, if necessary, a filler.

The cathode active material may be a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Lithium manganese oxides such as Li _{1 + x} Mn _{2 - x} O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ and LiMnO ₂ ; Lithium copper oxide (Li ₂ CuO ₂ ), vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; A Ni-site type lithium nickel oxide expressed by the formula LiNi _1-x M _x O ₂ (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga and x = 0.01 to 0.3); Formula _{LiMn 2-x M x O 2} ( where, M = Co, Ni, Fe , Cr, and Zn, or Ta, x = 0.01 ~ 0.1 Im) or Li ₂ Mn ₃ MO ₈ (where, M = Fe, Co, Ni, Cu, or Zn); A lithium manganese composite oxide having a spinel structure represented by LiNi _x Mn _2-x O ₄ ; A LiMn ₂ O ₄ disulfide compound in which a part of Li in the formula is substituted with an alkaline earth metal ion; Fe ₂ (MoO ₄ ) ₃ , and the like. However, the present invention is not limited to these.

The cathode current collector generally has a thickness of 3 to 500 mu m. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, sintered carbon, aluminum or stainless steel A surface treated with carbon, nickel, titanium, silver or the like may be used. The current collector may have fine irregularities on the surface thereof to increase the adhesive force of the cathode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

The conductive material is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture including the cathode active material. The conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, but the material used as the first conductive material is preferably larger than the material used as the second conductive material. For example, the materials that can be used as the first conductive material and the second conductive material include graphite such as natural graphite and artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, 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 whiskey 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.

The binder is a component which assists in bonding of the active material and the conductive material and bonding to the current collector, and is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture containing the cathode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like.

The filler is optionally used as a component for suppressing the expansion of the anode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. Examples of the filler include olefin polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

In the case where the electrode is a negative electrode, the first electrode mixture layer coated on the surface of the negative electrode collector and the second electrode mixture layer coated on the first electrode mixture layer are composed of the first electrode active material and the first electrode active material Electrode active material, a first conductive material and a second conductive material as conductive materials, and may optionally further include a binder, a filler, and the like as described above.

The negative electrode active material may include, for example, carbon such as non-graphitized carbon or graphite carbon; _{Li x Fe 2 O 3 (0≤x≤1} ), Li x WO 2 (0≤x≤1), Sn x Me 1 - x Me 'y O z (Me: Mn, Fe, Pb, Ge; Me' : Metal complex oxides such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, Halogen, 0 < x < Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{SnO, SnO 2, PbO, PbO} 2, Pb 2 O 3, Pb 3 O 4, Sb 2 O 3, Sb 2 O 4, Sb 2 O 5, GeO, GeO 2, Bi 2 O 3, Bi 2 O 4, and Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials; Titanium oxide; Lithium titanium oxide, and the like.

The negative electrode current collector is generally made to have a thickness of 3 to 500 mu m. Such an anode current collector is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and examples of the anode current collector include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, a surface of copper or stainless steel A surface treated with carbon, nickel, titanium, silver or the like, an aluminum-cadmium alloy, or the like can be used. In addition, like the positive electrode collector, fine unevenness can be formed on the surface to enhance the bonding force of the negative electrode active material, and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams and nonwoven fabrics.

The present invention also provides a lithium secondary battery comprising the electrode.

The lithium secondary battery may be composed of the positive electrode, the negative electrode, the separator, and the non-aqueous electrolyte containing a lithium salt, and may be manufactured by putting a porous separator between the positive electrode and the negative electrode by a conventional method known in the art, .

Other components of the secondary battery according to the present invention will be described below.

The separation membrane is interposed between the anode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally 0.01 to 10 mu m and the thickness is generally 5 to 300 mu m. Such separation membranes include, for example, olefinic polymers such as polypropylene, which are chemically resistant and hydrophobic; A sheet or nonwoven fabric made of glass fiber, polyethylene or the like is used. When a solid electrolyte such as a polymer is used as an electrolyte, the solid electrolyte may also serve as a separation membrane.

The lithium salt-containing nonaqueous electrolyte is composed of a nonaqueous electrolyte and lithium. Nonaqueous organic solvents, organic solid electrolytes, inorganic solid electrolytes, and the like are used as the nonaqueous electrolyte, but the present invention is not limited thereto.

Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma -Butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane , Acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate Nonionic organic solvents such as tetrahydrofuran derivatives, ethers, methyl pyrophosphate, ethyl propionate and the like can be used.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, A polymer containing an ionic dissociation group and the like may be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides and sulfates of Li such as Li ₄ SiO ₄ -LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

The lithium salt is a material that is readily soluble in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO 4, LiBF 4, LiB 10 Cl 10, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF _{6, LiSbF 6, LiAlCl 4,} CH 3 SO 3 Li, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate and imide.

For the purpose of improving the charge / discharge characteristics and the flame retardancy, the electrolytic solution is preferably mixed with an organic solvent such as pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, Benzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, . In some cases, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further added to impart nonflammability. In order to improve the high-temperature storage characteristics, carbon dioxide gas may be further added. FEC (Fluoro-Ethylene Carbonate, PRS (Propene sultone), and the like.

In a preferred _{embodiment, LiPF 6, LiClO 4, LiBF} 4, LiN (SO 2 CF 3) 2 , such as a lithium salt, a highly dielectric solvent of DEC, DMC or EMC Fig solvent cyclic carbonate and a low viscosity of the EC or PC of And then adding it to a mixed solvent of linear carbonate to prepare a lithium salt-containing non-aqueous electrolyte.

The present invention also provides a battery pack comprising the lithium secondary battery as a unit battery and a device including the battery pack. The manufacturing method of the secondary battery, the battery pack, and the like are well known in the art, and a detailed description thereof will be omitted.

The device may be a small device including a smart phone, a mobile phone, a notebook, and a tablet PC; Electric Vehicle (EV); An electric vehicle including a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and an extended range electric vehicle (EREV); And an electric motorcycle including an E-bike and an E-scooter.

As described above, the electrode according to the present invention has an electrode mixture layer which is larger than the porosity of the electrode material mixture layer located at a portion far from the porosity of the electrode material mixture layer located near the current collector, The porosity of the electrolyte layer is 15% or more, so that the surface of the electrode has a porosity of more than a predetermined range to easily penetrate the electrolyte into the electrode, while the porosity of the electrolyte is higher than that of the electrolyte. It is possible to increase the penetration path so that the impregnation property of the electrolytic solution to the inside of the electrode can be enhanced and also the volume of the conductive material of the electrode material mixture layer having a large porosity is made larger than the volume of the conductive material of the electrode material mixture layer having a small porosity As a result, the electronic conductivity in the electrode is improved as a whole, and the charge of the lithium secondary battery based thereon is improved. The discharge characteristic is improved.

1 is a schematic diagram of an electrode according to one embodiment of the present invention;
2 is a schematic view of an electrode according to another embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings according to the embodiments of the present invention, but the scope of the present invention is not limited thereto.

For a better understanding of the construction of the electrode according to the invention, FIGS. 1 and 2 show schematically the electrodes according to one embodiment of the invention.

Referring to FIG. 1, the electrode 100 has a structure in which a first electrode compound layer 110 and a second electrode compound layer 120 are coated on each current collector 10, The layer 110 includes the first electrode active material 130 and the second electrode mixture layer 120 includes the second electrode active material 140. The first electrode active material 130 has a spherical shape On the other hand, the second electrode active material 140 has an elliptical shape, so that the porosity of the second electrode material mixture layer 120 is smaller than that of the first electrode material mixture layer 110.

The volume of the first conductive material 150 located in the gap between the first electrode active materials 130 is relatively larger than the volume of the second conductive material 160 located in the gap between the second electrode active materials 140 .

Referring to FIG. 2, the first electrode active material 230, the first conductive material 250, the second electrode active material 240, and the second conductive material 260 are all elliptical, _{1 in that} the particle diameter D ₁ of the active material 230 is smaller than the particle diameter D ₂ of the second electrode active material 240. However, The first electrode mixture layer 210 and the second electrode mixture layer 220 are coated on the first electrode active material layer 20 and the first electrode active material layer 230. The first electrode active material layer 230 and the first electroconductive material layer The second electrode mixture layer 220 includes the second electrode active material 240 and the second conductive material 260 and the second electrode mixture layer 220 includes the first electrode mixture layer 210, And the volume of the first conductive material 250 is relatively larger than the volume of the second conductive material 260 is the same.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims (22)

A first electrode mixture layer coated on the surface of the current collector and a second electrode mixture layer coated on the first electrode coalescence layer,
Wherein the first electrode material mixture layer includes a first electrode active material, the second electrode material mixture layer includes a second electrode active material,
The porosity of the first electrode material mixture layer is relatively larger than the porosity of the second electrode material mixture layer, and the porosity of the second electrode material mixture layer is 15%
Wherein the first electrode material mixture layer includes a first conductive material located in a gap between the first electrode active material and the second electrode material mixture layer includes a second conductive material located in a gap between the second electrode active material,
The volume of the first conductive material is relatively larger than the volume of the second conductive material,
Wherein the first electrode material mixture layer and the second electrode material mixture layer are not mixed with each other but form an interface,
(a) preparing a second electrode slurry including a first electrode slurry including a first electrode active material and a first conductive material, a second electrode active material, and a second conductive material;
(b) applying a first electrode slurry to the surface of the electrode current collector, followed by drying and rolling to form a first electrode mixture layer;
(c) applying a second electrode slurry to the surface of the first electrode material mixture layer, followed by drying and rolling to form a second electrode material mixture layer; or
(c) applying a second electrode slurry on a separate substrate, drying and rolling the green film for a second electrode composite layer; And (d) separating the green film from the substrate, adding the green film to the surface of the first electrode material mixture layer, and further drying and rolling to form a second electrode material mixture layer;
Wherein the electrode is made of a metal. The method of manufacturing an electrode according to claim 1, wherein the first electrode material mixture layer and the second electrode material mixture layer each contain a binder in the respective voids. delete The method of claim 1, wherein the first electrode material mixture layer and the second electrode material mixture layer have a thickness ratio of 4: 6 to 7: 3. The method according to claim 1, wherein the porosity of the second electrode material mixture layer is 15% to 30%. The method of manufacturing an electrode according to claim 1, wherein the porosity of the first electrode material mixture layer is 20% to 40% in a range larger than the porosity of the second electrode material mixture layer. The method according to claim 1, wherein the porosity of the second electrode material mixture layer is in the range of 40 to 95% of the porosity of the first electrode material mixture layer. The method of claim 1, wherein the first electrode active material is in the form of spherical particles, and the second electrode active material is in the form of elliptical particles having a vertical cross-section and a long diameter parallel to the surface of the current collector. The method according to claim 8, wherein the first conductive material located in the gap between the first electrode active materials is in the form of spherical particles, and the second conductive material located in the gap between the second electrode active materials has a long longitudinal dimension parallel to the surface of the current collector Wherein the electrode is in the form of an elliptical particle. 2. The electrode active material according to claim 1, wherein the first electrode active material and the second electrode active material are each in the form of an elliptical particle having a vertical cross-section and a long diameter parallel to the surface of the current collector, Wherein the electrode is smaller than the long diameter. The method according to claim 10, wherein the second conductive material in a gap between the first conductive material and the second electrode active material in the gap between the first electrode active materials is in the form of an elliptical particle having a long longitudinal axis and parallel to the surface of the current collector Wherein the electrode is made of a metal. The method according to claim 1, wherein the first electrode active material and the second electrode active material have the same kind and / or different particle volume. The method according to claim 1, wherein the volume of the second conductive material ranges from 50% to 95% of the void between the second electrode active material. The method of claim 1, wherein the volume of the first conductive material ranges from 50% to 95% of the space between the first electrode active materials in a range larger than the volume of the second conductive material. The method of manufacturing an electrode according to claim 1, wherein the first conductive material and the second conductive material are the same or different. The electrode manufacturing method according to claim 1, wherein the composition of the first electrode material mixture layer and the composition of the second electrode material mixture layer are the same or different. delete delete The method of claim 1, wherein the rolling strength of the first electrode slurry in step (b) ranges from 40% to 95% of the rolling strength of the second electrode slurry in step (c). A lithium secondary battery comprising an electrode according to any one of claims 1, 2, 4 to 16, and 19. A battery pack comprising the lithium secondary battery according to claim 20 as a unit battery. A device comprising a battery pack according to claim 21.

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