Electrode for secondary battery and secondary battery comprising the same

Abstract

The present application provides a secondary battery electrode including a current collector, an electrode active material layer containing an electrode active material formed on the current collector, satisfying the following relational expressions 1 and 2, the relational expression 1 being 7 ≤ total surface area of active material particles per unit volume of the electrode active material layer ≤ 10, the relational expression 2 being 20 ≤ total surface area of effective pores per unit volume of the electrode active material layer ≤ 29, the total surface area of active material particles per unit volume of the electrode active material layer in the relational expression 1 (m 2 / cc) being defined as the product of the surface area A (m 2 / g) of the electrode active material layer and the density D (g / cc) of the electrode, the total surface area of effective pores per unit volume of the electrode active material layer in the relational expression 2 (m 2 / ml) being defined as the product of the surface area A (m 2 / g) of the electrode active material layer and the effective pore volume V P (ml / g) in the electrode active material layer. The secondary battery electrode of the present application improves the high power characteristics of a secondary battery.

Description

TECHNICAL FIELD

[0001] The present application relates to an electrode for a secondary battery having improved rapid charging performance and a secondary battery including the same. BACKGROUND

[0002] Recently, as the demand for electronic devices such as mobile devices increases, in order to improve the portability of electronic devices, the development of lightweight and small-sized electrochemical cells (secondary batteries) is expanding. In addition to this trend, global automobile fuel efficiency and exhaust-related regulations are becoming stronger, and thus the electric vehicle (EV) market is also growing rapidly, and thus the development of high-power large-capacity lithium secondary batteries for these electric vehicles is required.

[0003] It is known that the development of pores in an electrode is important for the high performance of a lithium secondary battery, and thus the development of a pore structure that is advantageous for an electrode exhibiting high performance is being researched. Specifically, the diffusion of lithium ions in an electrode can be increased by adjusting factors such as the pore amount, the size of pores, etc. in the electrode. However, in the case where the pores in the electrode are not uniformly formed, it is difficult to achieve the purpose of improving the performance of a lithium secondary battery.

[0004] For this reason, there is a need to develop an electrode for a secondary battery that reduces the difference in reaction amount at different electrode positions by uniform distribution of pores in the electrode and suppresses the polarization phenomenon caused by uneven current to achieve high performance of a lithium secondary battery. SUMMARY

[0005] TECHNICAL PROBLEM

[0006] The present application relates to an electrode for a secondary battery having improved rapid charging performance and a secondary battery including the same.

[0007] TECHNICAL SOLUTION

[0008] The present application provides an electrode for a secondary battery, comprising:

[0009] a current collector; and

[0010] an electrode active material layer formed on the current collector and containing an electrode active material,

[0011] satisfying the following relational expressions 1 and 2:

[0012] [Relational expression 1]

[0013] 7 ≤ total surface area of active material particles per unit volume of the electrode active material layer ≤ 10,

[0014] [Relational expression 2]

[0015] 20 ≤ total surface area of effective pores per unit volume of the electrode active material layer ≤ 29,

[0016] the total surface area of active material particles per unit volume of the electrode active material layer (m 2 / cc) in the above-described relationship 1 is defined as the surface area A (m 2 / g) of the electrode active material layer * the density D (g / cc) of the electrode, and the total surface area of effective pores per unit volume of the electrode active material layer (m 2 / ml) in the above-described relationship 2 is defined as the surface area A (m 2 / g) of the electrode active material layer / the effective pore volume V P (ml / g) within the electrode active material layer.

[0017] The surface area A of the electrode active material layer can be 4 m 2 / g to 6 m 2 / g.

[0018] The density D of the electrode can be 1.6 g / cc to 1.8 g / cc.

[0019] The effective pore volume V P within the electrode active material layer can be 0.15 ml / g to 0.25 ml / g.

[0020] The electrode for secondary batteries can also satisfy the following relationships 3 and 4:

[0021] [Relationship 3]

[0022] 7.3 ≤ total surface area of active material particles per unit volume of the electrode active material layer ≤ 9.5,

[0023] [Relationship 4]

[0024] 20.5 ≤ total surface area of effective pores per unit volume of the electrode active material layer ≤ 28.5,

[0025] the total surface area of active material particles per unit volume of the electrode active material layer (m 2 / cc) in the above-described relationship 3 is defined as the surface area A (m 2 / g) of the electrode active material layer * the density D (g / cc) of the electrode, and the total surface area of effective pores per unit volume of the electrode active material layer (m 2 / ml) in the above-described relationship 4 is defined as the surface area A (m 2 / g) of the electrode active material layer / the effective pore volume V P (ml / g) within the electrode active material layer.

[0026] The electrode for a secondary battery can satisfy at least two of the following relationships 5 to 7:

[0027] [Relationship 5]

[0028] 4.4 ≤ A ≤ 5.6,

[0029] [Relationship 6]

[0030] 0.18 ≤ V P ≤ 0.21,

[0031] [Relationship 7]

[0032] 1.68 ≤ D ≤ 1.75,

[0033] A in the relationship 5 is a surface area (m 2 / g) of the electrode active material layer, V p is an effective pore amount (ml / g) in the electrode active material layer, and D is a density (g / cc) of the electrode.

[0034] A ratio of a difference between a D90 particle diameter and a D10 particle diameter and a D50 particle diameter ((D90-D10) / D50) of the active material particles in the electrode active material layer can be 1 or less.

[0035] An average size of the effective pores in the electrode active material layer can be 10 μm or less.

[0036] The electrode can be a cathode.

[0037] The electrode active material can include a carbon-based active material.

[0038] The present application also provides a secondary battery including the electrode according to one embodiment of the present application, a separator, and an electrolyte.

[0039] Technical Effects

[0040] The electrode for a secondary battery according to the present application can ensure a uniform pore structure in the electrode, thereby allowing lithium ions to smoothly diffuse in the electrode, and thus can improve high-power characteristics of the secondary battery.

[0041] Also, uniformity of an energy density in the electrode can be improved, and thus life characteristics of the secondary battery can be significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1a , Figure 1b is a schematic view of an internal structure of an electrode based on whether or not uniformity of a pore distribution in the electrode is reflected. Figure 1a shows a schematic view of an internal structure of an electrode in a case where uniformity of a pore distribution in the electrode is not reflected, Figure 1b is a schematic view of an internal structure of an electrode in a case where the uniformity of the pore distribution in the electrode is reflected. DETAILED DESCRIPTION

[0043] The advantages, features and implementation methods of the present application will become apparent from the following embodiments described with reference to the accompanying drawings. The present application is not limited to the embodiments disclosed below, but can be implemented in various ways. The embodiments are provided only to completely disclose the present application and to completely inform those skilled in the art to which the present application pertains of the scope of the application, which is defined only by the scope of the claims. The specific contents for implementing the present application are described in detail below with reference to the accompanying drawings. The same reference numerals are used throughout the drawings and like constituent elements are designated by like reference numerals regardless of the drawings, and "and / or" includes each of the terms mentioned and all combinations of two or more of the terms.

[0044] All terms used in the specification, including technical and scientific terms, have the same meanings as commonly understood by those skilled in the art unless otherwise defined in the specification. The terms "include" and "comprise" when used in this specification, specify the presence of the stated elements but do not preclude the presence of other elements. Also, the singular forms "a," "an" and "the" include plural references unless the context clearly dictates otherwise.

[0045] In the specification, when a part, such as a layer, a film, a region, a plate, or the like, is said to be "on" or "above" another part, it can be "directly on" or "directly above" the other part, or there can be intervening parts.

[0046] One embodiment of the present application provides an electrode for a secondary battery. The electrode includes a current collector; and an electrode active material layer containing an electrode active material formed on the current collector, and satisfies the following relational expressions 1 and 2.

[0047] [Relational Expression 1]

[0048] 7 ≤ total surface area of active material particles per unit volume of the electrode active material layer ≤ 10,

[0049] [Relational Expression 2]

[0050] 20 ≤ total surface area of effective pores per unit volume of the electrode active material layer ≤ 29,

[0051] The total surface area of active material particles per unit volume of the electrode active material layer (m 2 / cc) in the relational expression 1 is defined as the surface area A (m 2 / g) of the electrode active material layer * the density D (g / cc) of the electrode, and the total surface area of effective pores per unit volume of the electrode active material layer (m 2 / ml) in the relational expression 2 is defined as the surface area A (m 2V (ml / g) P (ml / g).

[0052] In the above equation 1, the total surface area (m 2 (cc) of the active material particles per unit volume of the electrode active material layer is defined as the surface area A (m 2 (g / cc) of the electrode.

[0053] Specifically, the surface area A of the electrode active material layer can represent the total surface area of the active material in the electrode active material layer, and can be measured by a mercury intrusion method. From the viewpoint of providing sufficient reaction sites in the electrode, the surface area A of the electrode active material layer can be 4 m 2 / g to 6 m 2 / g, preferably 4.2 m 2 / g to 5.8 m 2 / g.

[0054] The density D of the electrode refers to the density of the electrode after rolling, and from the viewpoint of increasing the energy density by increasing the content of the active material in the same volume of the electrode, the density D of the electrode can be 1.6 g / cc to 1.8 g / cc, preferably 1.65 g / cc to 1.8 g / cc, and for example, 1.7 g / cc.

[0055] In the above equation 2, the total surface area (m 2 / ml) of the effective pores per unit volume of the electrode active material layer is defined as the surface area A (m 2 V (ml / g) P (ml / g).

[0056] The surface area A of the electrode active material layer is as described above.

[0057] V (ml / g) P The effective pore content V in the electrode active material layer refers to the content of the effective pores present in the electrode active material layer, and specifically can be measured by a mercury intrusion method. Here, the effective pores refer to open-end pores having an average pore size of 10 μm or less, specifically 10 nm to 10 μm, and are distinguished from pores formed by cracking or peeling of the electrode.

[0058] V (ml / g) pIt can be 0.15 ml / g to 0.25 ml / g, preferably 0.16 ml / g to 0.24 ml / g. In the case of the range, "effective pores" which are pores substantially contributing to ion conduction can be sufficiently provided, and thus ion diffusion paths in the electrode can be improved.

[0059] The total surface area of active material particles and the total surface area of effective pores per unit volume of the electrode active material layer according to the present application reflect the uniformity of the distribution of pores in the electrode, and can provide information on the structure of pores in the electrode with high accuracy, compared to the prior art in which the size of pores in the electrode, the porosity, and the like are used to adjust the structure of pores in the electrode. In addition, the size of pores in the electrode, the porosity, and the like according to the prior art do not provide information on the uniformity of the distribution of pores in the electrode, and thus it can be difficult to accurately evaluate the performance of a secondary battery. Furthermore, measuring performance without explaining the uniformity of the distribution of pores in the electrode can provide false information, and thus can lead to misinterpretation.

[0060] Specifically, Figure 1a To illustrate a schematic diagram of the internal structure of an electrode in the case where the uniformity of the distribution of pores in the electrode is not reflected. As a non-limiting example, as shown in Figure 1a In the case where pores in the electrode are not uniformly formed in a dendritic shape, the contact area of active material / electrolyte per unit volume of the electrode active material layer can be different at different positions of the electrode, as shown in

[0061] On the contrary, an electrode for a secondary battery satisfying both the relationships 1 and 2 improves the uniformity of the distribution of pores in the electrode, and thus the contact area of electrolyte and active material particles can have a similar value regardless of the position of the electrode.

[0062] Specifically, as shown in Figure 1b In the case where the structure of pores in the electrode is uniform, the contact area of active material / electrolyte per unit volume of the electrode active material layer is similar regardless of the position of the electrode, and thus an optimal structure for uniform current distribution in the electrode can be provided. Thus, the polarization phenomenon in the electrode can be reduced under high-rate charge and discharge conditions, and thus excellent performance can be exhibited.

[0063] The electrode can satisfy the above-mentioned relations 1 and 2, and more preferably satisfy the following relations 3 and 4:

[0064] [Relation 3]

[0065] 7.3 ≤ total surface area of active material particles per unit volume of electrode active material layer ≤ 9.5,

[0066] [Relation 4]

[0067] 20.5 ≤ total surface area of effective pores per unit volume of electrode active material layer ≤ 28.5,

[0068] The total surface area of active material particles per unit volume of electrode active material layer (m2 / ml) in the above-mentioned relation 3 is defined as the surface area A (m2 / g) of the electrode active material layer * the density D (g / cc) of the electrode, and the total surface area of effective pores per unit volume of the electrode active material layer (m2 / ml) in the above-mentioned relation 4 is defined as the surface area A (m2 / g) of the electrode active material layer / the amount of effective pores V (ml / g) in the electrode active material layer. 2 (cc) of the electrode, and the total surface area of effective pores per unit volume of the electrode active material layer (m2 / ml) in the above-mentioned relation 4 is defined as the surface area A (m2 / g) of the electrode active material layer / the amount of effective pores V (ml / g) in the electrode active material layer. 2 (cc) of the electrode, and the total surface area of effective pores per unit volume of the electrode active material layer (m2 / ml) in the above-mentioned relation 4 is defined as the surface area A (m2 / g) of the electrode active material layer / the amount of effective pores V (ml / g) in the electrode active material layer. 2 (cc) of the electrode, and the total surface area of effective pores per unit volume of the electrode active material layer (m2 / ml) in the above-mentioned relation 4 is defined as the surface area A (m2 / g) of the electrode active material layer / the amount of effective pores V (ml / g) in the electrode active material layer. 2 (cc) of the electrode, and the total surface area of effective pores per unit volume of the electrode active material layer (m2 / ml) in the above-mentioned relation 4 is defined as the surface area A (m2 / g) of the electrode active material layer / the amount of effective pores V (ml / g) in the electrode active material layer. P (cc) of the electrode, and the total surface area of effective pores per unit volume of the electrode active material layer (m2 / ml) in the above-mentioned relation 4 is defined as the surface area A (m2 / g) of the electrode active material layer / the amount of effective pores V (ml / g) in the electrode active material layer.

[0069] Under the condition that the above-mentioned relations 3 and 4 are satisfied at the same time, sufficient effective pores in the electrode can be provided and the pore distribution uniformity can be improved. Thus, not only the amount of reaction sites per unit volume in the electrode can be maximized, but also the reaction sites can be uniformly distributed. Here, the reaction sites can represent the contact area of the active material particles in the electrode with the electrolyte formed in the pores in the electrode, and the uniform distribution of the reaction sites can represent that the contact area of the active material / electrolyte per unit volume of the electrode active material layer is large, and that the contact area has a similar value regardless of the position of the electrode.

[0070] The electrode can satisfy at least two of the following relations 5 to 7:

[0071] [Relation 5]

[0072] 4.4 ≤ A ≤ 5.6,

[0073] [Relation 6]

[0074] 0.18 ≤ V P ≤ 0.21,

[0075] [Relation 7]

[0076] 1.68 ≤ D ≤ 1.75.

[0077] A in the relational expression 5 is a surface area (m 2 / g) of the electrode active material layer, p V is an effective pore volume (ml / g) in the electrode active material layer, and D is a density (g / cc) of the electrode.

[0078] The electrode for secondary batteries according to one embodiment of the present application satisfies at least two of the relational expressions 5 to 7, and thus can exhibit a uniform pore structure in the electrode, and particularly, can provide a uniform lithium ion diffusion path even under a high-rate charge condition, and thus can significantly improve high-power characteristics.

[0079] The Dspan of the ratio of the difference between the D90 particle diameter and the D10 particle diameter to the D50 particle diameter ((D90-D10) / D50) of the active material particles in the electrode active material layer according to one embodiment of the present application can be 0.9 or less, preferably 0.7 to 0.9, and more preferably 0.75 to 0.89. In the case of the range, the particle size deviation of the active material particles in the electrode active material layer can be reduced, and thus an electrode active material layer containing uniform active material particles can be implemented, and a uniform pore can be formed in the electrode active material layer.

[0080] The D10, D50, and D90 refer to particle diameters at which the cumulative volume reaches 10%, 50%, and 90%, respectively, from a small particle diameter when the particle size distribution is measured by a laser scattering method, and specifically, the electrode active material particles can be collected according to the KSA ISO 13320-1 standard, and the particle size distribution can be measured using a Mastersizer 3000 of Malvern. As an example, ethanol can be used as a solvent and, if necessary, dispersed using an ultrasonic disperser, and then the volume density can be measured, but the present application is not limited thereto.

[0081] The electrode can include a current collector and an electrode active material layer formed by coating an electrode slurry containing an electrode active material on at least one side of the current collector.

[0082] The electrode active material can be used without limitation as long as it is generally used for electrodes of secondary batteries. For the anode active material, an anode active material known in the art can be used, for example, a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof can be used, but is not limited thereto.

[0083] In the case where the electrode active material is a cathode active material, at least one carbon-based active material can be contained, and preferably, two or more carbon-based active materials can be contained. For example, the cathode active material can be at least one carbon-based active material, and more preferably, at least two carbon-based active materials. The carbon-based active material can include one or more selected from the group consisting of natural graphite, artificial graphite, graphitized carbon fiber, graphitized mesocarbon microbeads, and amorphous carbon.

[0084] The cathode active material can further include a metal-based active material, which refers to an active material containing a metal, and generally refers to an active material having an element capable of intercalating lithium in the structure, and having a theoretical capacity per unit mass of 500 mAh / g or more when intercalating lithium. The metal-based active material can be, for example, lithium metal, a single metal capable of forming a lithium alloy (e.g., Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn, Sr, Zn, Ti, etc.), an alloy thereof, and oxides, sulfides, nitrides, silicides, carbides, phosphides, etc. thereof.

[0085] Among the metal-based cathode active materials, a silicon-containing active material is preferred. By using a silicon-based cathode active material, a high capacity of a lithium ion secondary battery can be achieved. The silicon-based cathode active material can be, for example, silicon (Si), an alloy of silicon and cobalt, nickel, iron, etc., SiOx (0 < x < 2), a mixture of a silicon-containing material and a carbon material, a composite of a silicon-containing material and a conductive carbon obtained by coating or compounding the silicon-containing material with the conductive carbon, etc.

[0086] The electrode active material layer contains the electrode active material, and can optionally contain a binder and a conductive material.

[0087] The binder can be a water-soluble binder. Specifically, it can be styrene-butylvinyl rubber, acrylated styrene-butylvinyl rubber, polyvinyl alcohol, sodium polyacrylate, a copolymer of propylene and an olefin having 2 to 8 carbon atoms, polyacrylamide, a copolymer of (meth)acrylic acid and (meth)acrylic alkyl ester, or a combination thereof.

[0088] In the case of using the water-soluble binder, the water-soluble binder does not affect the viscosity of the slurry and can well adhere the electrode active material to the current collector, and thus is very good, but the electrode active material and the conductive material as fine particles cause the slurry to easily gel, and thus a thickening agent for imparting viscosity to the slurry to form a stable slurry can be further contained. As an example, one or more of a cellulose series compound, specifically, hydroxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or an alkali metal salt thereof, etc. can be mixed to be used as the thickening agent. Na, K, or Li can be used as the alkali metal.

[0089] The conductive material is used to impart conductivity to the cathode, and is not particularly limited as long as it is an existing electron conductive material that does not cause chemical changes within the battery. As an example, it can be natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanotube, and combinations thereof, but is not limited thereto.

[0090] The current collector can be a material selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof, but is not limited thereto.

[0091] The electrode for a secondary battery according to one embodiment of the present application can be a cathode. Specifically, the cathode for a secondary battery satisfies the above conditions, thereby being able to secure uniformity of pore distribution within the cathode to reduce polarization within the cathode, to improve uniformity of energy density within the electrode, and thus to significantly improve high power performance.

[0092] The present application also provides a secondary battery including the electrode, a separator, and an electrolyte.

[0093] The electrode is as described above.

[0094] The separator, for example, can be a separator selected from glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene, or combinations thereof, and can be in the form of a nonwoven fabric or a woven fabric. For example, in a lithium secondary battery, a polyolefin-based polymer separator such as polyethylene or polypropylene can be mainly used, and to secure heat resistance or mechanical strength, a separator coated with a composition containing a ceramic component or a polymer material can also be used, and optionally, can be used in a single layer structure or a multi-layer structure, and there is no problem in using a separator known in the art, but the present application is not limited thereto.

[0095] The electrolyte includes an organic solvent and a lithium salt.

[0096] The organic solvent functions as a medium that enables ions participating in an electrochemical reaction of the battery to migrate, and for example, a carbonate-type, ester-type, ether-type, ketone-type, alcohol-type, or aprotic solvent can be used, and the organic solvent can be used alone or in a mixture of two or more, and in the case of using a mixture of two or more, the mixing ratio can be appropriately adjusted according to the desired battery performance. In addition, there is no problem in using an organic solvent known in the art, but the present application is not limited thereto.

[0097] The lithium salt is dissolved in an organic solvent and functions as a source of lithium ions in the battery to enable the basic operation of the lithium secondary battery and to facilitate the migration of lithium ions between the anode and the cathode. As examples of the lithium salt, LiPF6, LiBF4, LiSbF6, LiAsF6, LiN(SO3C2F5)2, LiN(CF3SO2)2, LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(x and y are natural numbers), LiCl, LiI, LiB(C2O4)2, or a combination thereof, but the present application is not limited thereto. y F 2y+1 SO2)(x and y are natural numbers), LiCl, LiI, LiB(C2O4)2, or a combination thereof, but the present application is not limited thereto.

[0098] The concentration of the lithium salt can be used in the range of 0.1 M to 2.0 M. In the case where the concentration of the lithium salt is in the range, the electrolyte has proper conductivity and viscosity, and thus can exhibit excellent electrolyte properties, and lithium ions can be efficiently migrated.

[0099] Further, in order to improve charge-discharge characteristics, flame retardant characteristics, etc., the electrolyte can further include, as necessary, pyridine, triethyl phosphate, triethanolamine, a cyclic ether, ethylenediamine, n-glyme, triamide hexaphosphate, a nitrobenzene derivative, sulfur, a quinonimine dye, an N-substituted oxazolidinone, an N,N-substituted imidazolidine, an ethylene glycol dialkyl ether, an ammonium salt, a pyrrole, 2-methoxyethanol, aluminum trichloride, etc. Depending on the case, in order to impart flame retardancy, a halogen-containing solvent such as carbon tetrachloride, ethylene trifluoride, etc. can be further included, and in order to improve high-temperature storage characteristics, fluoro-ethylene carbonate (FEC), propene sulfone (PRS), fluoropro-pylene carbonate (FPC), etc. can also be included.

[0100] The secondary battery can be a lithium secondary battery.

[0101] A method of manufacturing a secondary battery according to the present application for achieving the above object can form an electrode assembly by sequentially stacking a manufactured cathode, a separator, and an anode, and manufacture a battery by injecting an electrolyte into a cylindrical battery case or a square battery case after placing the manufactured electrode assembly therein. Alternatively, the electrode assembly can be manufactured by stacking the electrode assembly, immersing the same in an electrolyte, and sealing the resulting article in a battery case.

[0102] The battery case used in the present application can employ a battery case generally used in the art, and there is no limitation on the shape for the battery use, for example, it can be a cylindrical, a square, a pouch, or a coin shape using a can, etc.

[0103] The secondary battery according to the present application can be used not only as a battery cell used as a power source for a small device, but also preferably as a unit battery in a medium-large battery module including a plurality of battery cells. Preferred examples of the medium-large device include an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, a power storage system, etc., but are not limited thereto.

[0104] The present application is described in detail below by way of examples, but these are only for detailed description of the present application, and the scope of the present application is not limited to the following examples.

[0105] Example

[0106] (Examples 1 to 5 and Comparative Examples 1 to 5)

[0107] 1: Manufacturing cathode

[0108] An active material having a Dspan value shown in Table 1 below was manufactured using one or two graphite-based active materials, and a cathode slurry was prepared by adding water to 93.4 wt% of the manufactured active material, 3.0 wt% of a carbon black conductive agent, 2.4 wt% of an SBR binder, and 1.2% of CMC, and mixing at room temperature for 120 minutes. After the prepared cathode slurry was applied to a Cu foil current collector and dried, it was rolled to a cathode mixture density of 1.7 g / cc, thereby manufacturing a cathode.

[0109] The Dspan value refers to a ratio of a difference between a D90 particle size and a D10 particle size to a D50 particle size ((D90-D10) / D50), and can be obtained by measuring a particle size distribution using a Mastersizer 3000 of Malvern Company according to the KSA ISO 13320-1 standard. Specifically, in measuring the particle size distribution, the particle diameters at which the cumulative volume reaches 10%, 50%, and 90% from the small particle size are defined as D10, D50, and D90, respectively, and the ratio of a difference between a D90 particle size and a D10 particle size to a D50 particle size ((D90-D10) / D50) is calculated and shown in Table 1 below.

[0110] 2. Manufacturing half-cell

[0111] CR2016 coin cells were manufactured by inserting a PE separator between the manufactured cathode and lithium metal anode and then injecting electrolyte. The assembled coin cells were then left at room temperature for 24 hours to produce half-cells. Here, an electrolyte was prepared by mixing 1.0 M lithium salt LiPF6 with an organic solvent (EC:EMC = 1:4 vol%) and adding 1 vol% of electrolyte additive FEC.

[0112] 3. Evaluating physical properties

[0113] 1) measuring the surface area A (m2 / g) of the cathode active material layer 2 / g)

[0114] The surface area A(m²) of the active material layer of the cathodes manufactured in Examples 1-5 and Comparative Examples 1-5 was measured using mercury intrusion porosimetry. 2 / g). Specifically, the manufactured cathode was placed in the cylinder of a mercury porosimetry (Micromeritics Auto Pore IV 9505), and the pressure change was measured as mercury was filled into the cylinder and the cylinder was gradually pressurized. Then, the surface area A (m²) of the cathode active material layer was calculated using the following formula 1. 2 / g) and shown in Table 1.

[0115] [Equation 1]

[0116]

[0117] In formula 1, A is the surface area (m²) of the cathode active material layer. 2 / g), P is the applied pressure (psi), V is the volume of mercury permeating into the cathode active material layer (ml), and Vmax is the cumulative permeation volume under maximum pressure (ml). K2 is represented by –γcosθ, where γ is the surface tension of mercury (dynes / cm), and θ is the contact angle (°) between the active material particles and mercury in the cathode active material layer. Here, the surface tension τ is 485 dynes / cm, and the contact angle θ is 130°.

[0118] 2) measuring the effective pore volume V within the cathode active material layer p (ml / g)

[0119] The total porosity (ml / g) within the cathode active material layer was confirmed using the mercury intrusion porosimetry method, which is the same as the method used to measure the surface area A of the cathode active material layer described above, for the cathodes manufactured in Examples 1-5 and Comparative Examples 1-5. Here, the porosity Vp of pores with an average pore size of 10 nm or more and 10 μm or less, i.e., the effective pores, was calculated and is shown in Table 1 below.

[0120] 3) Evaluating high-rate charge characteristics of half-cell

[0121] After the half-cells produced in Examples 1 to 5 and Comparative Examples 1 to 5 were stabilized by charging and discharging at a low rate (0.1 C) for the first 3 to 5 cycles, the high-rate chargeability was evaluated by charging at a high rate (2 C), and the results are shown in Table 1 below. Here, the high-rate charge efficiency (%) was calculated from the ratio of the high-rate charge amount to the low-rate charge amount.

[0122] Evaluation Example

[0123] [Example 1 of evaluation]: Comparing high-rate charge characteristics of secondary batteries corresponding to the relationship formula 1

[0124] The cathodes and half-cells produced in Examples 1 to 5 and Comparative Examples 1 to 5 were evaluated for cathode physical properties and charge efficiency (%), and the results are shown in Table 1 below.

[0125] [Table 1]

[0126]

[0127] The A*D value in Table 1 means the total surface area (m2 / cc) of the cathode active material particles per unit volume of the cathode active material layer. 2 P The A / V value means the total surface area (ml / ml) of the effective pores per unit volume of the cathode active material layer. 2

[0128] As shown in Table 1, it was analyzed that Examples 1 to 4 and Comparative Examples 1 to 5 all used cathode active materials having a Dspan value of 1 or less, and the cathodes produced had a binder density of 1.7 g / cc, but differed in the uniformity of the pore distribution within the electrode, and thus the half-cells of the respective examples and comparative examples differed in high-rate chargeability. This result indicates that the uniformity of the pore distribution within the electrode is an important factor in improving the high-rate chargeability.

[0129] Specifically, it was analyzed that Examples 1 to 5 satisfying the relational expressions 1 and 2 of the present application ensured the uniformity of the pore distribution as compared to Comparative Examples 1 to 5, and thus not only had lithium ion diffusion performance, but also had the effect of reducing the uniformity of the energy density within the electrode and the polarization within the electrode, which manifested as an improvement in high-rate characteristics and other additional electrochemical performance.

[0130] Thus, it was found that the preferable range of the Dspan value of the cathode active material particles was 0.75 to 0.89.

[0131] For Comparative Example 5, it was judged that although a cathode active material having a preferable Dspan value of the present application was used, the surface area A value of the cathode active material layer was too low, and thus the high-rate characteristics were significantly degraded.

[0132] In addition, it was found that the A*D value and the A / V P ​​The value simultaneously satisfies the preferred numerical range of the present invention (7.3~9.5m). 2 / cc and 20.5 to 28.5), therefore, compared to Examples 4 to 5 which are not like this, the above effects are further improved.

[0133] Furthermore, it simultaneously satisfies the requirement that the surface area A of the cathode active material layer is 4.4 m². 2 / g~5.6m 2 / g, Effective porosity V within the cathode active material layer p In Examples 1-3, under three conditions—0.18 ml / g to 0.21 ml / g and cathode compound density D of 1.68 g / cc to 1.75 g / cc—a uniform porous structure was observed within the cathode, and the significant effect of this was confirmed by the high-rate charging performance results. It was determined that this result was due to the uniform porous structure within the cathode providing a smooth lithium-ion diffusion path even under high-rate charging conditions, thus significantly improving high-power characteristics.

[0134] In addition, for Examples 4 and 5, it is expected that the energy density will be relatively lower than that of Examples 1 to 3 due to the relatively large amount of porosity in the cathode or the relatively small density of the compound.

Claims

1. An electrode for a secondary battery, comprising: current collector; as well as An electrode active material layer is formed on the current collector and contains electrode active material. Satisfy the following relations 1 and 2: [Relation 1] 7≤ Total surface area of ​​active material particles per unit volume of electrode active material layer ≤ 10, [Relationship 2] 20 ≤ Total surface area of ​​effective pores per unit volume of electrode active material layer ≤ 29, In Equation 1, the total surface area of ​​the active material particles per unit volume of the electrode active material layer is defined as the surface area A of the electrode active material layer. The electrode density D, and the total surface area of ​​effective pores per unit volume of the electrode active material layer in Equation 2, are defined as the surface area A of the electrode active material layer / the effective porosity V within the electrode active material layer. P ; The unit of the total surface area of ​​the active material particles per unit volume of the electrode active material layer is m. 2 / cc, where the unit of A is m 2 / g, where D is in g / cc, and the unit of the total surface area of ​​effective pores per unit volume of the electrode active material layer is m². 2 / ml, the V P The unit is ml / g. Wherein, the ratio of the difference between the D90 and D10 particle sizes of the active material particles in the electrode active material layer to the D50 particle size (D90-D10) / D50 is less than 0.

9.

2. The electrode for a secondary battery according to claim 1, wherein the surface area A of the electrode active material layer is 4m². 2 / g to 6m 2 / g.

3. The electrode for a secondary battery according to claim 1, wherein the density D of the electrode is from 1.6 g / cc to 1.8 g / cc.

4. The electrode for a secondary battery according to claim 2, wherein the effective porosity V in the electrode active material layer P The concentration ranges from 0.15 ml / g to 0.25 ml / g.

5. The electrode for a secondary battery according to claim 1 also satisfies the following relationships 3 and 4. [Relationship 3] 7.3 ≤ Total surface area of ​​active material particles per unit volume of the electrode active material layer ≤ 9.5, [Relationship 4] 20.5≤The total surface area of ​​effective pores per unit volume of the electrode active material layer≤28.

5.

6. The electrode for a secondary battery according to claim 1 further satisfies at least two of the following relationships 5 to 7: [Relation 5] 4.4≤A≤5.6， [Relationship 6] 0.18≤V P ≤0.21， [Relation 7] 1.68≤D≤1.75。 7. The electrode for a secondary battery according to claim 1, wherein the average size of the effective pores in the electrode active material layer is less than 10 μm.

8. The electrode for a secondary battery according to claim 1, wherein the electrode is a cathode.

9. The electrode for a secondary battery according to claim 8, wherein the electrode active material contains a carbon-based active material.

10. A secondary battery comprising the electrode according to any one of claims 1 to 9.

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