KR20210054828A - Active material double layered electrode comprising active material particles having different sizes and secondary battery comprising the same - Google Patents

Abstract

The present invention relates to an electrode having a double-layer structure including different kinds of particulate active materials having different average particle diameters, and a secondary battery including the same. The present invention increases the mechanical strength and stability of the electrode, and the secondary battery using the same exhibits an excellent discharge capacity.

Description

A double-layered electrode containing heterogeneous particulate active materials with different average particle diameters, and a secondary battery including the same {ACTIVE MATERIAL DOUBLE LAYERED ELECTRODE COMPRISING ACTIVE MATERIAL PARTICLES HAVING DIFFERENT SIZES AND SECONDARY BATTERY COMPRISING THE SAME}

The present invention relates to an electrode having a double-layer structure including different types of particulate active materials having different average particle diameters, and a secondary battery including the same.

With the increase in technology development and demand for mobile devices, the demand for secondary batteries is also rapidly increasing. Among them, lithium secondary batteries are widely used as an energy source for various electronic products as well as various mobile devices because of their high energy density and high operating voltage and excellent storage and lifespan characteristics.

In addition, the secondary battery is attracting attention as an energy source such as an electric vehicle or a hybrid electric vehicle, which has been proposed as a solution for solving air pollution such as conventional gasoline vehicles and diesel vehicles using fossil fuels. To be applied as an energy source of an electric vehicle, a high-power battery is required.

The development of an electrode having a high energy density is drawing attention as a way to increase the output characteristics of a secondary battery. For example, in the case of a positive electrode, research on a high-content nickel (High-Ni)-based NCM positive electrode active material having a high energy density has been continued. However, a secondary battery to which a high-content nickel (High-Ni)-based NCM positive electrode active material is applied has poor battery cell stability, and is particularly vulnerable to exothermic reactions due to an internal short circuit.

In the case of a negative electrode, research on a silicon-based negative electrode active material having a high energy density has been continued. However, the electrode to which the silicon-based negative active material is applied exhibits a large volume change during the charging and discharging process, which causes the stability of the battery to be impaired.

Accordingly, there is a need to develop an electrode having a new structure capable of enhancing the output characteristics of the battery without impairing the stability of the battery cell.

Korean Patent Publication No. 2015-0049999

The present invention has been invented to solve the above problems, and an object of the present invention is to provide an electrode having a double layer structure including a different type of particulate active material having a different average particle diameter, and a secondary battery including the same.

The electrode for a secondary battery according to the present invention includes a current collector layer; A lower mixture layer formed on one or both surfaces of the current collector layer and including a particulate active material; And an upper mixture layer formed on a surface opposite to a surface in which the lower coalescence layer is in contact with the current collector layer, and includes a particulate active material. In addition, the lower mixture layer, based on 100% by weight of the total particulate active material of the lower mixture layer _{, the content of the small particle active material (D S} ) is 30 to 100% by weight, the upper mixture layer, the particulate active material of the upper mixture layer Based on the total 100% by weight _{, the content of the large} particle active material (D L) is in the range of 30 to 100% by weight.

In one example, the small particle active material (D _S ) has an average particle diameter of 1 to 10 μm, and the _large particle active material (D L) has an average particle diameter of 11 to 50 μm.

_{In a specific example, in the lower mixture layer, the content of the small particle active material (D S} ) is 55 to 90% by weight, based on 100% by weight of the total particulate active material of the lower mixture layer, and _{the content of the large particle active material (D L} ) is 10 to 45% by weight. In addition, the upper mixture layer, based on 100% by weight of the total particulate active material of the upper mixture layer _{, the content of the small particle active material (D S} ) is 10 to 45% by weight, the content of the large _{particle active material (D L} ) is 55 to 90% by weight.

_{In a specific example, in the lower mixture layer, the content of the small particle active material (D S} ) is 90 to 100% by weight, based on 100% by weight of the total particulate active material of the lower mixture layer. In addition, the upper mixture layer, based on 100% by weight of the total particulate active material of the upper mixture layer _{, the content of the small particle active material (D S} ) is 10 to 45% by weight, the content of the large _{particle active material (D L} ) is 55 to 90% by weight.

_{In a specific example, in the lower mixture layer, the content of the small particle active material (D S} ) is 55 to 90% by weight, based on 100% by weight of the total particulate active material of the lower mixture layer, and _{the content of the large particle active material (D L} ) is 10 to 45% by weight. _{In addition, in the upper mixture layer, the content of the large particle active material (D L} ) is 90 to 100% by weight, based on 100% by weight of the total particulate active material of the upper mixture layer.

In one example, the ratio of the average thickness of the lower mixture layer and the upper mixture layer is in the range of 3:7 to 7:3.

In another example, the ratio of the average thickness of the lower mixture layer and the upper mixture layer is in the range of 1:9 to 4.5:5.5.

In one example, in the electrode for a secondary battery according to the present invention, the ratio of the content of the binder contained in the upper mixture layer (B _Top ) to the _{content of the binder contained in the lower mixture layer (B Under ) ((B Top} ) /(B _Under )) is in the range of 0.1 to 1.0.

In addition, the present invention provides a secondary battery including the electrode described above.

In one example, the secondary battery, a positive electrode; And a cathode and a separator interposed between the anode and the cathode, wherein at least one of the anode and the cathode has the same structure as the electrode described above.

In a specific example, the positive electrode and the negative electrode of the secondary battery have the same structure as the electrode described above.

In addition, the present invention provides a vehicle including the secondary battery described above.

The electrode for a secondary battery according to the present invention has excellent mechanical strength, and a secondary battery to which it is applied exhibits excellent discharge capacity.

1 to 5 are views each schematically showing a cross section of an electrode for a secondary battery according to an embodiment of the present invention.
6 is a result of comparing and measuring the discharge capacity of a secondary battery according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail. Prior to this, terms or words used in the present specification and claims are not limited to their usual or dictionary meanings and should not be construed, and the inventors appropriate the concept of terms to describe their own invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention on the basis of the principle that it can be defined.

The present invention provides an electrode for a secondary battery. The secondary battery electrode may include a current collector layer; A lower mixture layer formed on one or both surfaces of the current collector layer and including a particulate active material; And an upper mixture layer formed on a surface opposite to a surface in which the lower coalescence layer is in contact with the current collector layer, and includes a particulate active material. _{In addition, in the lower mixture layer, the content of the small particle active material (D S} ) is 30 to 100% by weight, based on 100% by weight of the total particulate active material of the lower mixture layer, and the upper mixture layer has a total of 100% by weight of the particulate active material of the upper mixture layer. Based on the weight %, _{the content of the large} particle active material (D L) is 30 to 100% by weight.

The electrode for a secondary battery according to the present invention has a structure in which a double-layered mixture layer is formed on one or both surfaces of a current collector layer. The double-layered mixture layer includes a lower mixture layer formed on the current collector layer and an upper mixture layer formed on the lower mixture layer. The lower mixture layer has a high content of small particle active material, and the upper mixture layer has a high content of large particle active material.

In the present invention, the term'antiparticle active material' refers to a case where a particle diameter is relatively large as a particulate active material, and includes, for example, a case in which the average particle diameter is in the range of 11 to 50 μm. In addition, "small particle active material" refers to a case where a particle diameter is relatively small as a particulate active material, and includes, for example, a case in which the average particle diameter is in the range of 1 to 10 µm.

The electrode for a secondary battery according to the present invention can be applied in various shapes or structures according to the mixing ratio of the large particle active material and the small particle active material.

In one embodiment, the lower electrode material mixture layer is, based on the total 100% by weight of particulate active material of the lower electrode material mixture layer, the content of small-particle active material, the content of (D _S) and 55 to 90 wt%, Coarse active material (D _L) Is 10 to 45% by weight, the upper mixture layer, based on 100% by weight of the total particulate active material of the upper mixture layer, the content of the _{small particle active material (D S ) is 10 to 45% by weight, large particle active material (D L} ) The content of is 55 to 90% by weight. In a specific example, the lower mixture layer has a small particle active material (D _S ) content of 70 to 90% by weight, a large _{particle active material (D L} ) content of 10 to 30% by weight, and the upper mixture layer is a particulate form of the upper mixture layer. Based on 100% by weight of the total active material _{, the content of the small particle active material (D S} ) is 20 to 35% by weight, and the content of the large _{particle active material (D L} ) is 65 to 80% by weight. In this case, the lower mixture layer has a _{high content of the small particle active material (D S} ), and the upper mixture layer has a high content _{of the large particle active material (D L} ). By controlling the content of the small particle active material in the lower mixture layer high, there is an effect of increasing the capacity of the battery by applying the small particle active material having a large specific surface area. In addition, by controlling the content of the counterparticulate active material in the upper mixture layer high, there is an effect of enhancing the stability of the battery and supplementing the mechanical strength. In addition, it was experimentally confirmed that, by mixing small particles and large particle active materials in each mixture layer, an improved dose expression rate was exhibited at a high C-rate.

_{In another embodiment, the lower mixture layer has a content of the small particle active material (D S} ) of 90 to 100% by weight, based on 100% by weight of the total particulate active material of the lower mixture layer, and the upper mixture layer is Based on 100% by weight of the total particulate active material of the mixture layer _{, the content of the small particle active material (D S} ) is 10 to 45% by weight, and the content of the large _{particle active material (D L} ) is 55 to 90% by weight. In a specific example, the lower mixture layer has _{a content of the small particle active material (D S} ) of 95 to 100% by weight, the upper mixture layer has _{a content of the small particle active material (D S} ) of 20 to 35% by weight, and the large _{particle active material (D L} ) Content is 65 to 80% by weight. In this case, the content of the small particle active material (D _S ) in the lower mixture layer is controlled very high or the counterpart active material (D _L ) is not included, and the upper mixture layer has a _{high content of the large particle active material (D L} ). It is a controlled structure. By controlling the content of the small particle active material in the lower mixture layer very high, there is an effect of increasing the capacity of the battery by applying the small particle active material having a large specific surface area. Furthermore, the lower mixture layer also serves as a buffer layer to prevent damage to the current collector by the large particle active material included in the upper mixture layer when the electrode mixture layer is pressed. In addition, by controlling the content of the counterparticulate active material in the upper mixture layer high, there is an effect of enhancing the stability of the battery and supplementing the mechanical strength.

_{In another embodiment, the lower mixture layer has a content of the small particle active material (D S} ) of 55 to 90% by weight, based on 100% by weight of the total particulate active material of the lower mixture layer, and the large particle active _{material (D L} ) The content of is 10 to 45% by weight, the upper mixture layer, based on the total 100% by weight of the particulate active material of the upper mixture layer, the content of the large particle active material (D _L ) is 90 to 100% by weight. In a specific example, the lower mixture layer has a small particle active material (D _S ) content of 70 to 90% by weight, a large _{particle active material (D L} ) content of 10 to 30% by weight, and the upper mixture layer is a large particle active material (D _{The content of L} ) is 95 to 100% by weight. In this case, the lower mixture layer _{controls the content of the small particle active material (D S} ) high, and the upper mixture layer controls the content of the large particle active _{material (D L} ) very high or does not contain the _{small particle active material (D S)} to be. By controlling the content of the small particle active material in the lower mixture layer high, there is an effect of increasing the capacity of the battery by applying the small particle active material having a large specific surface area. In addition, by controlling the content of the opposing active material to a very high level in the upper mixture layer, the stability of the battery is improved and the mechanical strength is complemented, and further, pores are formed relatively large between the opposing active materials, and these pores induce smooth flow of the electrolyte. do.

In another embodiment, in the electrode for a secondary battery according to the present invention, the ratio of the average thickness of the lower mixture layer and the upper mixture layer is in the range of 3:7 to 7:3. Specifically, the ratio of the average thickness of the lower mixture layer and the upper mixture layer is in the range of 3:7 to 5:5, 3:7 to 4:6, or 4:6 to 4.5:5.5. The thickness of the lower mixture layer may be formed equal to that of the upper mixture layer, or the thickness of the lower mixture layer may be slightly smaller than that of the upper mixture layer. In another example, in the electrode for a secondary battery according to the present invention, the ratio of the average thickness of the lower mixture layer and the upper mixture layer is in the range of 1:9 to 4.5:5.5. Specifically, the ratio of the average thickness of the lower mixture layer and the upper mixture layer is in the range of 1:9 to 4:6, 1:9 to 3:7, or 1:9 to 2:8. The thickness of the lower mixture layer can be made smaller than the upper mixture layer. In the present invention, an upper mixture layer including a large particle active material in a relatively high content is formed thick, and a lower mixture layer including a small particle active material in a relatively high content is formed thin. Since the small particle active material has a small particle diameter, the impregnation rate of the electrolyte solution is slow, and the flow rate or ionic conductivity of the electrolyte solution is low due to the small pore size. Accordingly, by forming the upper mixture layer to be relatively thick, smooth ion conductivity can be realized.

In another embodiment, the ratio of the content of the binder contained in the upper mixture layer (B _{Top ) to the content of the binder contained in the lower mixture layer (B Under ) ((B Top} )/(B _Under )) is , In the range of 0.1 to 1.0. Specifically, the content ratio ((B _Top )/(B _Under )) is in the range of 0.1 to 0.9, 0.2 to 0.8, 0.3 to 0.6, 0.1 to 0.5, 0.4 to 0.9, or 0.25 to 0.55. The electrode for a secondary battery according to the present invention has a structure in which a double-layered mixture layer is formed on the collector body layer. In the present invention, in order to increase the bonding force between the current collector layer and the mixture layer, the content of the binder in the lower mixture layer is controlled to a high level. For example, the binder content (B _Under ) of the lower mixture layer may be controlled to a level of about 5% by weight, and the binder content (B _Top ) of the upper mixture layer may be controlled to a level of about 2.5% by weight. In this case, the ratio of the binder content ((B _Top )/(B _Under )) is 0.5.

In addition, the present invention provides a secondary battery including the electrode described above. For example, the secondary battery is a lithium secondary battery.

In one embodiment, the secondary battery includes a positive electrode; A cathode and a separator interposed between the anode and the cathode, wherein at least one of the anode and the cathode is the electrode according to claim 1. Specifically, in the secondary battery, the positive or negative electrode may have a structure in which a double-layered mixture layer is formed on the above-described current collector layer, or both the positive and negative electrode have a structure in which a double-layered mixture layer is formed on the above-described current collector layer. I can. For example, in the secondary battery, both the positive electrode and the negative electrode have a structure in which a double-layered mixture layer is formed on the current collector layer described above.

In the present invention, the secondary battery is, for example, a lithium secondary battery. The lithium secondary battery may include, for example, the electrode assembly described above; A non-aqueous electrolyte solution impregnating the electrode assembly; And a battery case containing the electrode assembly and the non-aqueous electrolyte.

The positive electrode has a structure in which a positive electrode mixture layer is laminated on one or both surfaces of a positive electrode current collector. The positive electrode active materials may each independently be a lithium-containing oxide, and may be the same or different. As the lithium-containing oxide, a lithium-containing transition metal oxide may be used. In one example, the positive electrode mixture layer includes a conductive material and a binder polymer in addition to the positive electrode active material, and if necessary, may further include a positive electrode additive commonly used in the art.

The positive electrode active material may be a lithium-containing oxide, and may be the same or different. As the lithium-containing oxide, a lithium-containing transition metal oxide may be used.

For example, the lithium-containing transition metal oxide is Li _x CoO ₂ (0.5<x<1.3), Li _x NiO ₂ (0.5<x<1.3), Li _x MnO ₂ (0.5<x<1.3), Li _x Mn ₂ O ₄ (0.5<x<1.3), Li _x (Ni _a Co _b Mn _c )O ₂ (0.5<x<1.3, 0<a<1, 0<b<1, 0<c<1, a +b+c=1), Li _x Ni _1-y Co _y O ₂ (0.5<x<1.3, 0<y<1), Li _x Co _1-y Mn _y O ₂ (0.5<x<1.3, 0 ≤y<1), Li _x Ni _1-y Mn _y O ₂ (0.5<x<1.3, O≤y<1), Li _x (Ni _a Co _b Mn _c )O ₄ (0.5<x<1.3, 0 <a<2, 0<b<2, 0<c<2, a+b+c=2), Li _x Mn _2-z Ni _z O ₄ (0.5<x<1.3, 0<z<2), Li _x Mn _2-z Co _z O ₄ (0.5<x<1.3, 0<z<2), Li _x CoPO ₄ (0.5<x<1.3) and Li _x FePO ₄ (0.5<x<1.3) It may be any one selected from or a mixture of two or more of them. In addition, the lithium-containing transition metal oxide may be coated with a metal or metal oxide such as aluminum (Al). In addition, in addition to the lithium-containing transition metal oxide, at least one of sulfide, selenide, and halide may be used.

The current collector used for the positive electrode may be a metal having high conductivity, and may be used as long as it is a metal to which the positive electrode active material slurry can be easily adhered, and has no reactivity in the voltage range of the secondary battery. Specifically, non-limiting examples of the current collector for the positive electrode include a foil manufactured by aluminum, nickel, or a combination thereof. Specifically, the current collector for the positive electrode is formed of the metal component described above, and includes a metal plate having a through hole in the thickness direction, and an ion conductive porous reinforcing material filled in the through hole of the metal plate.

The negative electrode may include a carbon material, lithium metal, silicon or tin as a negative electrode mixture layer. When a carbon material is used as the negative electrode active material, both low crystalline carbon and high crystalline carbon may be used. Typical low crystalline carbons include soft carbon and hard carbon, and high crystalline carbons include natural graphite, kish graphite, pyrolytic carbon, and liquid crystal pitch-based carbon fiber. High-temperature calcined carbons such as (mesophase pitch based carbon fiber), mesocarbon microbeads, mesophase pitches, and petroleum orcoal tar pitch derived cokes are typical.

Non-limiting examples of the current collector used for the negative electrode include copper, gold, nickel, or a foil manufactured by a copper alloy or a combination thereof. In addition, the current collector may be used by stacking substrates made of the above materials. Specifically, the current collector for the negative electrode includes a metal plate formed of the described metal component and having a through hole in the thickness direction, and an ion conductive porous reinforcing material filled in the through hole of the metal plate.

In addition, the negative electrode may include a conductive material and a binder commonly used in the art.

The first and second separators may be any porous substrate used in a lithium secondary battery, and for example, a polyolefin-based porous membrane or a nonwoven fabric may be used, but the present invention is not particularly limited thereto. Examples of the polyolefin-based porous membrane include polyolefin-based polymers such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene, polyolefin-based polymers such as polypropylene, polybutylene, and polypentene, respectively, alone or as a mixture of them. There is one membrane.

According to an embodiment of the present invention, the electrolyte may be a non-aqueous electrolyte including a non-aqueous electrolyte. Examples of the non-aqueous electrolyte solution include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and gamma-butyl. Lactone, 1,2-dimethoxyethane, tetrahydroxy franc (franc), 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolone, formamide, dimethylformamide, dioxolone, acetonitrile , Nitromethane, methyl formate, methyl acetate, phosphate tryester, trimethoxy methane, dioxolone derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, Aprotic organic solvents such as tetrahydrofuran derivatives, ethers, methyl pyropionate, and ethyl propionate may be used. However, it is not particularly limited thereto, and a number of electrolyte components commonly used in the field of lithium secondary batteries may be added or subtracted within an appropriate range.

In addition, the present invention provides a vehicle including the secondary battery described above. In a specific example, the vehicle is a hybrid or electric vehicle.

Hereinafter, the present invention will be described in more detail through examples and the like. However, since the configurations described in the embodiments described in the present specification are only one embodiment of the present invention and do not represent all the technical spirit of the present invention, various equivalents and modifications that can replace them at the time of the present application It should be understood that there may be.

Examples and Comparative Examples

Example 1

_{NCM (LiNi 0.8} Co _0.1 Mn _0.1 O ₂ ) 100 parts by weight as a positive electrode active material, carbon black (FX35, Denka, spherical, average diameter (D50) 15 to 40 nm) 1.5 parts by weight as a conductive material and polyvinylidene as a binder polymer 3.5 parts by weight of fluoride (KF9700, Kureha) was added to NMP (N-methyl-2-pyrrolidone) as a solvent to prepare a slurry for the lower mixture layer. The positive electrode active material is obtained by mixing a small particle active material having an average particle diameter of 6 µm and a large particle active material having an average particle diameter of 25 µm in a ratio of 70:30 parts by weight.

_{100 parts by weight of NCM (LiNi 0.8} Co _0.1 Mn _0.1 O ₂ ) as a positive electrode active material, 0.1 parts by weight of carbon black (FX35, Denka, spherical, average diameter (D50) 15 to 40 nm) as a conductive material, and KF9700 (Kureha) as a binder polymer ) 2 parts by weight of the solvent was added to NMP (N-methyl-2-pyrrolidone) to prepare a slurry for the upper mixture layer. The positive electrode active material is obtained by mixing a small particle active material having an average particle diameter of 6 µm and a large particle active material having an average particle diameter of 25 µm in a ratio of 30:70 parts by weight.

The slurry for the lower mixture layer was coated on the aluminum foil, and the slurry for the upper mixture layer was further coated thereon. Then, vacuum drying was performed to obtain a positive electrode. The average thickness of the lower mixture layer after drying is 50 µm, and the average thickness of the upper mixture layer is 50 µm.

The negative electrode is 100 parts by weight of artificial graphite (GT, Zichen (China)) as a negative electrode active material, 1.1 parts by weight of carbon black (Super-P) as a conductive material, 2.2 parts by weight of styrene-butadiene rubber, 0.7 parts by weight of carboxy methyl cellulose, water as a solvent After adding to to prepare a negative active material slurry, it was prepared by coating, drying, and pressing a copper current collector.

Meanwhile, polypropylene was uniaxially stretched using a dry method to prepare a separator having a microporous structure having a melting point of 165° C. and a width of 200 mm on one side. An electrode assembly was prepared by repeatedly collecting unit cells having a structure in which a separator was interposed between the positive electrode and the negative electrode. The electrode assembly has a structure in which 50 unit cells are radially assembled around a central axis based on a horizontal cross-sectional structure.

After the electrode assembly was built into a hollow cylindrical battery case, a 1M LiPF ₆ carbonate-based solution electrolyte was injected to complete a battery.

The cross-sectional structure of the prepared anode is shown in FIG. 1. Referring to FIG. 1, the electrode 100 according to the present embodiment has a structure in which a lower mixture layer 120 and an upper mixture layer 110 are sequentially stacked on a current collector layer 140 formed of aluminum foil. The lower mixture layer 120 has a structure in which the content of the small particle active material 132 is relatively high. In addition, the upper mixture layer 110 has a structure in which the content of the opposing active material 131 is high. The thickness ratio of the upper mixture layer 110 and the lower mixture layer 120 is 5:5.

Examples 2 to 5

A secondary battery was manufactured in the same manner as in Example 1, except that the content by particle size of the active material used in manufacturing the positive electrode, the content of the binder, and the thickness of each layer were different. In Example 3, the composition of the positive electrode mixture layer was formed in the same manner as in Example 2, but the mixture layer was formed on both sides of the current collector layer.

Using the prepared positive electrode, a secondary battery was manufactured in the same manner as in Example 1.

The types and contents of the components included in the positive electrode mixture layer for each example, and the layer thickness are shown in Table 1 below.

division Example 1 Example 2 Example 3 Example 4 Example 5 Lower mixture layer Large particle content (parts by weight) 30 15 15 0 15 Small particle content (parts by weight) 70 85 85 100 85 Layer thickness (㎛) 40 25 25 20 25 Binder content (parts by weight) 3.5 4 4 4.5 4 Upper mixture layer Large particle content (parts by weight) 70 80 80 85 100 Small particle content (parts by weight) 30 20 20 15 0 Layer thickness (㎛) 60 75 75 80 75 Binder content (parts by weight) 2 2 2 2 2

The structures of the anodes prepared in Examples 2 to 5 are shown in FIGS. 2 to 6.

Referring to FIG. 2, the electrode 200 according to the present embodiment has a structure in which a lower mixture layer 220 and an upper mixture layer 210 are sequentially stacked on a current collector layer 240 formed of aluminum foil. The lower mixture layer 220 has a content of the opposite particle active material 231 and the small particle active material 232 in the range of 15:80, and the upper mixture layer 210 has a content of the opposite particle active material 231 and the small particle active material 232 It's an 80:20 ratio.

Referring to FIG. 3, the electrode 300 according to the present embodiment has a structure in which a lower mixture layer 320 and an upper mixture layer 310 are sequentially stacked on both surfaces of a current collector layer 340 formed of aluminum foil. The lower mixture layer 320 has a content of the opposite particle active material 331 and the small particle active material 332 in the range of 15:80, and the upper mixture layer 310 has the content of the opposite particle active material 331 and the small particle active material 332 It's an 80:20 ratio. In addition, the electrode 300 has a structure in which a double-layered mixture layer is formed on both surfaces of the current collector layer 340.

Referring to FIG. 4, the electrode 400 according to the present embodiment has a structure in which a lower mixture layer 420 and an upper mixture layer 410 are sequentially stacked on a current collector layer 440 formed of aluminum foil. The lower mixture layer 420 includes a small particle active material 432 as an active material, and the upper mixture layer 410 has a content of the large particle active material 431 and the small particle active material 432 in a ratio of 85:15.

Further, referring to FIG. 5, the electrode 500 according to the present embodiment has a structure in which a lower mixture layer 520 and an upper mixture layer 510 are sequentially stacked on a current collector layer 540 formed of aluminum foil. The lower mixture layer 520 has a content of the opposite particle active material 531 and the small particle active material 532 in the range of 15:80, and the upper mixture layer 510 includes the opposite particle active material 531 as an active material.

Comparative Example 1

_{NCM (LiNi 0.8} Co _0.1 Mn _0.1 O ₂ ) 100 parts by weight as a positive electrode active material, carbon black (FX35, Denka, spherical, average diameter (D50) 15 to 40 nm) 1.5 parts by weight as a conductive material and polyvinylidene as a binder polymer A slurry for a mixture layer was prepared by adding 3 parts by weight of fluoride (KF9700, Kureha) to NMP (N-methyl-2-pyrrolidone) as a solvent. The positive electrode active material is obtained by mixing a small particle active material having an average particle diameter of 6 μm and a large particle active material having an average particle diameter of 25 μm in a ratio of 50:50 parts by weight.

The prepared slurry for the mixture layer was coated on an aluminum foil and dried in vacuum to obtain a positive electrode. The thickness of the mixture layer after drying is an average of 100 µm.

Using the prepared positive electrode, a secondary battery was manufactured in the same manner as in Example 1.

Comparative Example 2

_{100 parts by weight of NCM (LiNi 0.8} Co _0.1 Mn _0.1 O ₂ ) having an average particle diameter of 25 µm as a positive electrode active material, 1.5 parts by weight of carbon black (FX35, Denka, spherical, average diameter (D50) 15 to 40 nm) as a conductive material, and As a binder polymer, 3.5 parts by weight of polyvinylidene fluoride (KF9700, Kureha) was added to NMP (N-methyl-2-pyrrolidone) as a solvent to prepare a slurry for the lower mixture layer.

_{100 parts by weight of NCM (LiNi 0.8} Co _0.1 Mn _0.1 O ₂ ) having an average particle diameter of 6 µm as a positive electrode active material, 0.1 parts by weight of carbon black (FX35, Denka, spherical, average diameter (D50) 15 to 40 nm) as a conductive material, and As a binder polymer, 2 parts by weight of KF9700 (Kureha) was added to NMP (N-methyl-2-pyrrolidone) as a solvent to prepare a slurry for the upper mixture layer.

The slurry for the lower mixture layer was coated on the aluminum foil, and the slurry for the upper mixture layer was further coated thereon. Then, vacuum drying was performed to obtain a positive electrode. The average thickness of the lower mixture layer after drying was 40 µm, and the average thickness of the upper mixture layer was 60 µm.

Experimental Example 1: Evaluation of discharge capacity

For the secondary batteries prepared in Example 1 and Comparative Examples 1 and 2, the discharge capacity rate according to the charge/discharge cycle was evaluated.

The evaluation results are as shown in FIG. 7. Referring to FIG. 6, compared to the secondary battery of Example 1, it can be seen that in the secondary batteries of Comparative Examples 1 and 2, the discharge capacity decreases to a greater extent as the discharge C-rate increases. For example, when the discharge C-rate is 2C, the secondary battery of Example 1 shows a discharge capacity rate of about 60%, but the secondary batteries of Comparative Examples 1 and 2 show a discharge capacity rate of about 50%. have.

The above description is merely illustrative of the technical idea of the present invention, and those of ordinary skill in the art to which the present invention pertains will be able to make various modifications and variations without departing from the essential characteristics of the present invention. Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but to explain the technical idea, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

100, 200, 300, 400, 500: electrode
110, 210, 311, 312, 410, 510: upper mixture layer
120, 220, 321, 322, 420, 520: lower mixture layer
131, 231, 331, 431, 531: active material alleles
132, 232, 332, 432, 532: active material small particles
140, 240, 340, 440, 540: current collector

Claims (11)

Current collector layer;
A lower mixture layer formed on one or both surfaces of the current collector layer and including a particulate active material; And
The lower mixture layer is formed on a surface opposite to the surface in contact with the current collector layer, and includes an upper mixture layer containing a particulate active material,
_{The lower mixture layer has a content of the small particle active material (D S} ) of 30 to 100% by weight, based on 100% by weight of the total particulate active material of the lower mixture layer,
The upper mixture layer, based on 100% by weight of the total particulate active material of the upper mixture layer, the content of the large particle active material (D _L ) is 30 to 100% by weight of the secondary battery electrode.
The method of claim 1,
The particle diameter of the small particle active material (D _S ) is in the range of 1 to 10 μm on average,
The particle diameter of the large particle active material (D _L ) is an average of 11 to 50 ㎛ range of secondary battery electrode.
The method of claim 1,
_{In the lower mixture layer, the content of the small particle active material (D S} ) is 55 to 90% by weight, and the content of the large _{particle active material (D L} ) is 10 to 45% by weight, based on 100% by weight of the total particulate active material of the lower mixture layer. %ego,
_{In the upper mixture layer, the content of the small particle active material (D S} ) is 10 to 45% by weight, and the content of the large _{particle active material (D L} ) is 55 to 90% by weight, based on 100% by weight of the total particulate active material of the upper mixture layer. % Of secondary battery electrode.
The method of claim 1,
The lower mixture layer, based on 100% by weight of the total particulate active material of the lower mixture layer _{, the content of the small particle active material (D S} ) is 90 to 100% by weight,
_{In the upper mixture layer, the content of the small particle active material (D S} ) is 10 to 45% by weight, and the content of the large _{particle active material (D L} ) is 55 to 90% by weight, based on 100% by weight of the total particulate active material of the upper mixture layer. % Of secondary battery electrode.
The method of claim 1,
_{In the lower mixture layer, the content of the small particle active material (D S} ) is 55 to 90% by weight, and the content of the large _{particle active material (D L} ) is 10 to 45% by weight, based on 100% by weight of the total particulate active material of the lower mixture layer. %ego,
The upper mixture layer, based on 100% by weight of the total particulate active material of the upper mixture layer, the content of the large particle active material (D _L ) is 90 to 100% by weight of the secondary battery electrode.
The method of claim 1,
An electrode for a secondary battery in which the ratio of the average thickness of the lower mixture layer and the upper mixture layer is in the range of 3:7 to 7:3.
The method of claim 1,
An electrode for a secondary battery in which the ratio of the average thickness of the lower mixture layer and the upper mixture layer is in the range of 1:9 to 4.5:5.5.
The method of claim 1,
The ratio ((B _Top )/(B _{Under )) of the binder content (B Top} ) contained in the upper mixture layer to the binder content (B _Under ) contained in the lower mixture layer is in the range of 0.1 to 1.0 for secondary batteries. electrode.
anode; It includes a negative electrode and a separator interposed between the positive electrode and the negative electrode,
At least one of the positive and negative electrodes is a secondary battery, characterized in that the electrode according to claim 1.
The method of claim 9,
A secondary battery, characterized in that the positive and negative electrodes are the electrodes according to claim 1.
A vehicle comprising the secondary battery according to claim 9.

Images