KR101256066B1 - Electrod and method of manufacturing the same and rechargeable battery including the same - Google Patents

Abstract

A metal substrate and a coating layer disposed on at least one surface of the metal substrate and including carbon nanotubes, wherein the carbon nanotubes are chemically etched to have a current collector having a length of 10 μm or less, and a method of manufacturing the same and the current collectors It relates to an electrode and a secondary battery.

Description

The electrode, the manufacturing method, and the secondary battery containing the said electrode TECHNICAL FIELD

An electrode, a manufacturing method thereof, and a secondary battery including the electrode are provided.

A battery is a device that converts chemical energy generated during the electrochemical redox reaction of chemical substances into electrical energy. A primary battery that needs to be discarded when all the energy inside the battery is exhausted, and a rechargeable battery that can be charged many times Can be divided into Among them, the secondary battery may be charged and discharged many times using reversible mutual conversion of chemical energy and electrical energy.

On the other hand, the recent development of the high-tech electronic industry is possible to reduce the size and weight of the electronic equipment is increasing the use of portable electronic devices. As a power source for such portable electronic devices, the necessity of a battery having a high energy density has been increased, and research on lithium secondary batteries has been actively conducted.

The lithium secondary battery includes a positive electrode, a negative electrode, and a separator, and the positive electrode and the negative electrode each include a current collector and an active material layer formed on one surface of the current collector.

In this case, the electrical characteristics between the current collector and the active material layer may affect the characteristics of the secondary battery. In particular, in the case of a high output battery, the resistance between the current collector and the active material layer may be increased, and thus the output characteristics of the electrode may be deteriorated.

One aspect of the present invention provides an electrode for a secondary battery capable of improving electrical characteristics between a current collector and an active material layer.

Another aspect of the present invention provides a method of manufacturing the electrode.

Another aspect of the invention provides a secondary battery comprising the electrode.

According to an aspect of the present invention, a metal substrate and a coating layer including carbon nanotubes located on at least one surface of the metal substrate, wherein the carbon nanotubes are chemically etched to have a length of about 10 ㎛ or less Current collector; And an active material layer formed on at least one surface of the current collector.

The carbon nanotubes may have a plurality of chemical functional groups on the surface.

The chemical functional group may be observed in an infrared spectroscopic analysis in the range of about 1400 to 1800 cm ^-1 , a peak in the range of about 3000 to 3500 cm ^-1 or a combination thereof.

The chemical functional group may include a carboxyl group, a carbonyl group or a combination thereof.

The carbon nanotubes may have a length of about 0.01 to 5㎛.

The carbon nanotubes may include single walled nanotubes, multi walled nanotubes, or a combination thereof.

The metal substrate may include aluminum foil, copper foil, nickel foil, stainless steel foil, titanium foil, silver foil, conductive polymer substrate, or a combination thereof.

The coating layer may have a thickness of about 0.1 to 1㎛.

The active material layer may be formed on the coating layer.

According to another aspect of the present invention, preparing a carbon nanotube, chemically etching the carbon nanotube to form a carbon nanotube having a length of 10 ㎛ or less, coating the carbon nanotube on a metal substrate And it provides a method for producing an electrode comprising the step of forming an active material layer by applying an active material to the current collector.

Chemically etching the carbon nanotubes may include ultrasonically decomposing the carbon nanotubes in a strong acid solution.

The carbon nanotubes may have a length of about 0.01 to 5㎛.

In the chemical etching of the carbon nanotubes, a chemical functional group may be introduced to the surface of the carbon nanotubes.

The chemical functional group may be observed in an infrared spectroscopic analysis in the range of about 1400 to 1800 cm ^-1 , a peak in the range of about 3000 to 3500 cm ^-1 or a combination thereof.

The chemical functional group may include a carboxyl group, a carbonyl group or a combination thereof.

The method may further include purifying the carbon nanotubes to remove catalyst particles and impurities before chemically etching the carbon nanotubes.

Coating the carbon nanotubes on the metal substrate may be performed by a slurry method or an electrophoretic deposition method.

According to another aspect of the invention, there is provided a secondary battery comprising the electrode.

The performance of the secondary battery may be improved by improving electrical characteristics of the current collector.

1 is a cross-sectional view illustrating a current collector that may be included in an electrode according to an embodiment;
2 is a schematic view showing a secondary battery according to another embodiment;
3 is a cross-sectional view illustrating an electrode in the rechargeable battery of FIG. 2;
4A and 4B are transmission electron microscope (TEM) photographs before and after chemical etching of multi-ply carbon nanotubes used in manufacturing a current collector according to Example 3;
5A and 5B are transmission electron microscope (TEM) photographs before and after chemical etching of the multi-ply carbon nanotubes used in manufacturing the current collector according to Example 6;
FIG. 6 is an infrared spectral spectrum showing a production peak of chemical functional groups as the chemical etching proceeds for 0, 5, 10 and 20 hours in preparing the current collector according to Example 1,
7 is a graph showing charge and discharge characteristics of secondary battery cells manufactured using the current collectors according to Examples 1 to 6 and Comparative Examples 1 to 3. FIG.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

In the drawings, the thickness is enlarged to clearly represent the layers and regions. Like parts are designated with like reference numerals throughout the specification. Whenever a portion of a layer, film, region, plate, or the like is referred to as being "on" another portion, it includes not only the case where it is "directly on" another portion, but also the case where there is another portion in between. Conversely, when a part is "directly over" another part, it means that there is no other part in the middle.

Next, a current collector according to one embodiment will be described with reference to FIG. 1.

1 is a cross-sectional view illustrating a current collector that may be included in an electrode according to an embodiment.

The current collector 110 that may be included in an electrode according to an embodiment includes a metal substrate 110a and a coating layer 110b disposed on at least one surface of the metal substrate 110a. As shown in FIG. 1, the coating layer 110b may be formed on one surface of the metal substrate 110a or may be formed on both surfaces of the metal substrate 110a.

The metal substrate 110a may be made of, for example, aluminum foil, copper foil, nickel foil, stainless steel foil, titanium foil, silver foil, conductive polymer substrate, or a combination thereof.

The coating layer 110b includes carbon nanotubes.

Carbon nanotubes may include single walled nanotubes, multi walled nanotubes, or a combination thereof.

Carbon nanotubes are conductors having high conductivity and are formed on one surface of the metal substrate 110a to lower the resistance between the metal substrate 110a and an active material layer (not shown) formed on the current collector 110. The electrical conductivity of the current collector 110 may be improved.

In addition, since carbon nanotubes have high strength and oxidation resistance, the current collector may be prevented from being deformed by external impact or repeated charging and discharging, and the surface of the metal substrate may be prevented from being oxidized.

The coating layer 110b including the carbon nanotubes may be coated in the form of a solution dispersed in a dispersion medium. In this case, the degree of dispersion of the carbon nanotubes may affect the electrical properties of the carbon nanotubes.

According to the present embodiment, the carbon nanotubes may be chemically etched to have a short length of about 10 μm or less. Here, the chemical etching refers to removing or cutting a part of the surface of the carbon nanotubes using a chemical solution such as a strong acid.

As such, by including carbon nanotubes having a short length of about 10 μm or less, the dispersibility of carbon nanotubes may be increased to uniformly form a thin coating layer, and the adhesion of the coating layer may be improved. As a result, the electrical conductivity of the current collector 110 may be further improved, thereby improving output characteristics.

The carbon nanotubes may have a length of about 0.001 to 10㎛, and may have a length of about 0.01 to 5㎛ within the above range.

On the other hand, the carbon nanotubes may be chemically etched to have a plurality of chemical functional groups on the surface. The amount of chemical functional groups produced varies depending on the degree of etching, and the greater the degree of etching, the greater the amount of chemical functional groups generated.

The chemical functional group may be, for example, a carboxyl group, a carbonyl group, or the like.

The production of chemical functional groups can be confirmed by Fourier transform infrared spectroscopy (FT-IR spectroscopy). For example, when a carboxyl group is generated by chemical etching, a peak in the range of about 1400 to 1800 cm ^-1 (C = O bond ), Peaks in the range of about 3000 to 3500 cm ⁻¹ (CH bonds) or combinations thereof can be observed.

The chemical functional group may increase the electrical conductivity by increasing the adhesion of the metal substrate 110a as well as increasing the density of states above the Fermi energy level of the carbon nanotubes.

The coating layer 110b may have a thickness of about 0.1 μm to 1 μm.

An active material layer 111 is formed on at least one surface of the current collector 110 including the metal substrate 110a and the coating layer 110b to form an electrode (see FIG. 3 to be described later). Preferably, the active material layer 111 is formed on the coating layer (110b). 3 illustrates a case in which the active material layer 111 is formed on the coating layer 110b in the current collector 110 including the metal substrate 110a having the coating layer 110b formed on one surface thereof, but is not limited thereto. This is possible. As another example, the active material layer 111 may be formed on both surfaces of the coating layer 110b again in the current collector 110 having the coating layers 110b formed on both surfaces of the metal substrate 110a.

Hereinafter, the current collector 110 described above may be manufactured according to the manufacturing method described below.

First, carbon nanotubes are synthesized.

The carbon nanotubes can be synthesized by various methods such as a method using an arc discharge, a method using a carbon-containing gas, or a method using a laser. In the case of using an arc discharge, for example, a current may flow between two carbon rods, and then carbonized to form carbon nanotubes to recondense. In the case of using a carbon-containing gas, for example, carbon-containing gas may be supplied onto a substrate on which catalyst particles are formed at a high temperature of about 600 ° C., and the carbon-containing gas may be thermally decomposed to form carbon nanotubes. As a method of using a carbon-containing gas, for example, thermal chemical vapor deposition may be mentioned. In the case of using a laser, carbon nanotubes may be formed by cooling a carbon atom that is ejected after injecting a laser pulse into a carbon rod.

Subsequently, carbon nanotubes are purified.

Purification of carbon nanotubes is a step for removing impurities such as catalyst particles and amorphous carbon remaining in the carbon nanotubes during the synthesis of carbon nanotubes, for example, by using a strong acid or oxidizing in an air or an inert atmosphere. .

Purified carbon nanotubes are washed with deionized water and dried.

Subsequently, the carbon nanotubes are chemically etched.

Chemical etching is to remove or cut a portion of the surface of the carbon nanotubes using a chemical solution such as a strong acid, and form a carbon nanotube having a length of about 10 μm or less by chemical etching. At this time, the chemical etching may be performed by ultrasonic decomposition of carbon nanotubes in a strong acid solution such as nitric acid, sulfuric acid, hydrochloric acid.

By the chemical etching, a plurality of chemical functional groups such as, for example, a carboxyl group and / or a carbonyl group may be introduced to the surface of the carbon nanotubes. The amount of chemical functional groups introduced at this time is determined by the degree of chemical etching, and the degree of chemical etching may be determined by, for example, the concentration of a chemical liquid such as a strong acid, an etching time, an etching temperature, and the like.

Chemical functional groups may include, for example, carboxyl groups, peaks in the range of about 1400 to 1800 cm ⁻¹ (C═O bonds), peaks in the range of about 3000 to 3500 cm ⁻¹ (CH bonds) or their Combinations can be observed.

Chemically etched carbon nanotubes are washed with deionized water and dried.

In this way it is possible to produce the carbon nanotubes as described above.

After forming the carbon nanotubes by etching as described above, the current collector may be prepared by coating the carbon nanotubes on a current collector such as a metal substrate.

Coating the carbon nanotubes on the metal substrate may be performed by slurry method (dispersing and coating carbon nanotubes in an organic solvent in which a binder is dissolved) or electrophoretic deposition (charger: NaOH or MgCl ₂ ). Is dispersed by dispersing carbon nanotubes in a dissolved organic solvent and applying electricity.

As described above, an electrode may be manufactured by forming an active material layer by applying an active material to a current collector formed by coating the carbon nanotubes on a metal substrate.

Hereinafter, a rechargeable battery including the electrode described above will be described with reference to FIGS. 2 and 3 along with FIG. 1.

2 is a schematic view of a rechargeable battery according to an exemplary embodiment, and FIG. 3 is a cross-sectional view of an electrode in the rechargeable battery including the current collector 110 of FIG. 2.

Referring to FIG. 2, the secondary battery 100 according to an embodiment includes a positive electrode 114, a negative electrode 112 facing the positive electrode 114, and a separator disposed between the positive electrode 114 and the negative electrode 112 ( 113, and a battery cell comprising an electrolyte solution (not shown) impregnating the positive electrode 114, the negative electrode 112, and the separator 113, the battery container 120 containing the battery cell, and the battery container ( And a sealing member 140 for sealing 120.

The negative electrode 112, the positive electrode 114, or both the negative electrode 112 and the positive electrode 114 may be formed to include the current collector described above. For example, since the oxide-based negative electrode such as Li ₄ Ti ₅ O ₁₂ or TiO ₂ has very low conductivity, electrical properties may be improved by introducing the coating layer 110b including the carbon nanotubes of the current collector described above.

3 illustrates that the positive electrode 114 and / or the negative electrode 112 includes the current collector 110 and the active material layer 111 formed on the current collector 110.

First, the anode 114 will be described.

As described above, the current collector 110 may include a metal substrate 110a and a coating layer 110b disposed on one surface of the metal substrate 110a.

The metal substrate 110a may be made of, for example, aluminum foil, copper foil, nickel foil, stainless steel foil, titanium foil, silver foil, conductive polymer substrate, or a combination thereof.

The coating layer 110b includes carbon nanotubes including single-ply carbon nanotubes, multi-ply carbon nanotubes, or a combination thereof.

The coating layer 110b including the carbon nanotubes may be coated in the form of a solution dispersed in a dispersion medium, for example, may be formed to a thickness of about 0.1 to 1㎛.

As described above, the carbon nanotubes may be chemically etched to have a short length of about 10 μm or less. As such, by including carbon nanotubes having a short length of about 10 μm or less, the dispersibility of carbon nanotubes may be increased to uniformly form a thin coating layer, and the adhesion of the coating layer may be improved. As a result, the electrical conductivity of the current collector 110 may be further improved, thereby improving output characteristics.

The carbon nanotubes may have a length of about 0.001 to 10㎛, and may have a length of about 0.01 to 5㎛ within the above range.

On the other hand, the carbon nanotubes may be chemically etched to have a plurality of chemical functional groups on the surface. The amount of chemical functional groups produced varies depending on the degree of etching, and the greater the degree of etching, the greater the amount of chemical functional groups generated.

The chemical functional group may be, for example, a carboxyl group, a carbonyl group, or the like.

The production of chemical functional groups can be confirmed by FT-IR spectroscopy, for example, when a carboxyl group is produced by chemical etching, a peak in the range of about 1400 to 1800 cm ^-1 (C = O bond), 3000 to 3500 Peaks in the range of cm ⁻¹ (CH bonds) or combinations thereof may be observed.

The active material layer 111 includes a positive electrode active material, a binder, and a conductive material.

The positive electrode active material is not particularly limited as long as lithium is a compound capable of reversibly intercalating and deintercalating. Specifically, lithium (Li), cobalt (Co), manganese (Mn), nickel (Ni), and combinations thereof It may be a complex oxide of a metal selected from.

These compounds include, for example, Li _a A _{1 - b} D _b E ₂ (Wherein 0.90 ≦ a ≦ 1.8 and 0 ≦ b ≦ 0.5); Li _a G _{1 - b} D _b O _{2 - c} J _c (Wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05); LiG _{2 - b} D _b O _{4 - c} J _c (Wherein 0 ≦ b ≦ 0.5 and 0 ≦ c ≦ 0.05); Li _a Ni _1-bc Co _b D _c E _α (wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α ≦ 2); Li _a Ni _{1 -b - c} Co _b D _c O _{2 -α} J _α (wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α <2); Li _a Ni _{1 -b- c} Co _b D _c O _{2 -α} J ₂ (Wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α <2); Li _a Ni _{1 -b - c} Mn _b D _c E _α (wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α ≦ 2); Li _a Ni _1-bc Mn _b D _c O _2-α J _α (wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α <2); Li _a Ni _{1 -b- c} Mn _b D _c O _{2 -α} J ₂ (Wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α <2); Li _a Ni _b G _c L _d O ₂ (Wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.9, 0 ≦ c ≦ 0.5, and 0.001 ≦ d ≦ 0.1); Li _a Ni _b Co _c Mn _d L _e O ₂ (wherein 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.9, 0 ≦ c ≦ 0.5, 0 ≦ d ≦ 0.5, and 0.001 ≦ e ≦ 0.1); Li _a NiL _b O ₂ (Wherein 0.90 ≦ a ≦ 1.8 and 0.001 ≦ b ≦ 0.1); Li _a CoL _b O ₂ (Wherein 0.90 ≦ a ≦ 1.8 and 0.001 ≦ b ≦ 0.1); Li _a MnL _b O ₂ (Wherein 0.90 ≦ a ≦ 1.8 and 0.001 ≦ b ≦ 0.1); Li _a Mn ₂ L _b O ₄ (Wherein 0.90 ≦ a ≦ 1.8 and 0.001 ≦ b ≦ 0.1); QO _2; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiRO ₂ ; LiNiVO _4; Li _(3-f) Z ₂ (PO ₄ ) ₃ (0 ≦ f ≦ 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0? F? 2); And LiFePO ₄ .

Wherein A is selected from the group consisting of Ni, Co, Mn, and combinations thereof; D is selected from the group consisting of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements and combinations thereof; E is selected from the group consisting of O, F, S, P and combinations thereof; G is selected from the group consisting of Co, Mn and combinations thereof; J is selected from the group consisting of F, S, P and combinations thereof; L is selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V and combinations thereof; Q is selected from the group consisting of Ti, Mo, Mn and combinations thereof; R is selected from the group consisting of Cr, V, Fe, Sc, Y and combinations thereof; Z may be selected from the group consisting of V, Cr, Mn, Co, Ni, Cu, and combinations thereof.

The positive electrode active material may be included in an amount of about 60 to 95 wt% based on the total content of the composition.

The binder increases the cohesion between the positive electrode active material particles and at the same time allows the positive electrode active material to adhere well to the current collector. The binder is not particularly limited as long as it is an adhesive material without affecting the chemical properties of the positive electrode active material. Such binders include, for example, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropylene cellulose, diacetylene cellulose, polyvinyl chloride, carboxylated polyvinylchloride, polyvinyldifluoride, polymers including ethylene oxide, polyvinylpi Ralidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, poly (vinylidene fluoride-hexafluoropropylene) (P (VdF-HFP)), polyethylene, polypropylene, styrene-butadiene rubber, acrylic Graded styrene-butadiene rubbers, epoxy resins and nylons. Of these, poly (vinylidene fluoride-hexafluoropropylene) (P (VdF-HFP)) is preferable, and when hexafluoropropylene (HFP) is contained in about 4 to 20 mol%, adhesion of the positive electrode active material Sex can be further improved.

The binder may be included in about 0.1 to 20% by weight relative to the total content of the composition.

The conductive material is used to impart conductivity to the positive electrode, and is not particularly limited as long as it is a conductive material without affecting the chemical properties of the positive electrode active material. For example, polyphenylene derivatives, natural graphite, artificial graphite, carbon black, acetylene And metal powders such as black, ketjen black, carbon fiber, copper, nickel, aluminum, silver, and the like.

The conductive material may be included in about 0.1 to 20% by weight based on the total content of the composition.

The separator 113 may be a single film or a multilayer film, and may be made of, for example, polyethylene, polypropylene, polyvinylidene fluoride, or a combination thereof.

The negative electrode 112 includes a current collector 110 and an active material layer 111 formed on the current collector 110.

As described above, the current collector 110 may include a metal substrate 110a and a coating layer 110b disposed on one surface of the metal substrate 110a.

The metal substrate 110a may be made of, for example, aluminum foil, copper foil, nickel foil, stainless steel foil, titanium foil, silver foil, conductive polymer substrate, or a combination thereof.

The coating layer 110b includes carbon nanotubes including single-ply carbon nanotubes, multi-ply carbon nanotubes, or a combination thereof.

The coating layer 110b including the carbon nanotubes may be coated in the form of a solution dispersed in a dispersion medium, for example, may be formed to a thickness of about 0.1 to 1㎛.

As described above, the carbon nanotubes may be chemically etched to have a short length of about 10 μm or less. As such, by including carbon nanotubes having a short length of about 10 μm or less, the dispersibility of carbon nanotubes may be increased to uniformly form a thin coating layer, and the adhesion of the coating layer may be improved. As a result, the electrical conductivity of the current collector 110 may be further improved, thereby improving output characteristics.

The carbon nanotubes may have a length of about 0.001 to 10㎛, and may have a length of about 0.01 to 5㎛ within the above range.

On the other hand, the carbon nanotubes may be chemically etched to have a plurality of chemical functional groups on the surface. The amount of chemical functional groups produced varies depending on the degree of etching, and the greater the degree of etching, the greater the amount of chemical functional groups generated.

The chemical functional group may be, for example, a carboxyl group, a carbonyl group, or the like.

The production of chemical functional groups can be confirmed by FT-IR spectroscopy, for example, when a carboxyl group is produced by chemical etching, a peak in the range of about 1400 to 1800 cm ^-1 (C = O bond), 3000 to 3500 Peaks in the range of cm ⁻¹ (CH bonds) or combinations thereof may be observed.

The active material layer 111 includes a negative electrode active material, a binder, and a conductive material.

The negative electrode active material is not particularly limited as long as it is a compound capable of reversibly intercalating and deintercalating lithium ions, and specifically, a carbon-based negative electrode active material, a compound capable of alloying with lithium, a transition metal oxide, and a lithium It may be selected from the group consisting of dopeable compounds, compounds capable of reversibly reacting with lithium, and combinations thereof.

The carbon-based negative electrode active material may be selected from crystalline carbon, amorphous carbon, and combinations thereof, and examples of the crystalline carbon include graphite such as amorphous, plate, flake, spherical or fibrous natural graphite or artificial graphite. Examples of the amorphous carbon include soft carbon (low temperature calcined carbon) or hard carbon, mesophase pitch carbide, calcined coke, and the like.

Compounds that can be alloyed with lithium include Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Ti, Ag, Zn, Cd, Al, Ga, In, Si, Ge, Sn , Pb, Sb, Bi and combinations thereof may include an element selected from the group.

Examples of the transition metal oxide, a material capable of doping and undoping lithium, or a material capable of reversibly reacting with lithium to form a compound include vanadium oxide, lithium vanadium oxide, Si, SiO _x (0 <x <2) , Sn, SnO ₂ , composite tin alloys, and combinations thereof.

The binder and the conductive material are as described above.

The electrolyte contains a non-aqueous organic solvent and a lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move. The non-aqueous organic solvent may be selected from carbonate, ester, ether, ketone, alcohol and aprotic solvents.

Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), and ethylpropyl carbonate ( ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), ethylmethyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate , BC) and the like can be used.

In particular, when a mixture of the chain carbonate compound and the cyclic carbonate compound is used, the dielectric constant may be increased, and the solvent may be prepared with a low viscosity solvent. In this case, the cyclic carbonate compound and the chain carbonate compound may be mixed and used in a volume ratio of about 1: 1 to 1: 9.

The ester solvent may be, for example, n-methyl acetate, n-ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, decanolide, valerian Lolactone, mevalonolactone, caprolactone and the like can be used. As the ether solvent, for example, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc. may be used. As the ketone solvent, cyclohexanone may be used. have. In addition, ethyl alcohol, isopropyl alcohol, etc. may be used as the alcohol solvent.

The non-aqueous organic solvents may be used alone or in combination of one or more, and the mixing ratio in the case of mixing one or more may be appropriately adjusted according to the desired battery performance.

The non-aqueous electrolyte may further include an additive such as an overcharge inhibitor such as ethylene carbonate and pyrocarbonate.

Through the following examples will be described in more detail the embodiment of the present invention. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

House  Produce

Manufacturing example  One

Multi-layered carbon nanotubes (MWNTs) were synthesized using supported catalysts by thermal chemical vapor deposition. Subsequently, a purification process was performed to remove catalyst particles and impurities remaining on the surface of the synthesized multi-ply carbon nanotubes. Into a solution of concentrated hydrofluoric acid (HF, 50%) and distilled water in a 1: 3 mixture and stirred for 18 hours to dissolve the catalyst particles, and then in a 15% air-argon mixture at 550 ° C. Purification by burning gas phase oxidation for 1 hour to burn impurities such as amorphous carbon. The multi-ply carbon nanotubes were then ultrasonically decomposed in concentrated hydrochloric acid (HCl, 37%) for 10 minutes to dissolve the metal oxide and catalyst particles formed by gas phase oxidation. Then washed and filtered several times with demineralized water and then dried at 150 ℃ for 12 hours. The formed multi-ply carbon nanotubes had a length of about 10 μm.

Subsequently, after applying the coating solution in which the multi-ply carbon nanotubes were dispersed in a dispersion medium of NMP (N-methyl-2-pyrrolidone) in which PVDF binder (10 wt.%) Was dissolved on aluminum foil, 4 hours at 120 ° C. Dry to prepare a current collector.

Manufacturing example  2

Multi-layered carbon nanotubes (MWNTs) were synthesized using supported catalysts by thermal chemical vapor deposition. Subsequently, a purification process was performed to remove catalyst particles and impurities remaining on the surface of the synthesized multi-ply carbon nanotubes. Into a solution mixed with concentrated hydrofluoric acid (HF, 50%) and distilled water 1: 3, mixed with multiple layers of carbon nanotubes and stirred for 18 hours to dissolve the catalyst particles, and then in a 15% air-argon mixture at 550 ° C. Purification by burning gas phase oxidation for 1 hour to burn impurities such as amorphous carbon. The multi-ply carbon nanotubes were then ultrasonically decomposed in concentrated hydrochloric acid (HCl, 37%) for 10 minutes to dissolve the metal oxide and catalyst particles formed by gas phase oxidation. Then washed and filtered several times with demineralized water and then dried at 150 ℃ for 12 hours.

remind Purified multi-ply carbon nanotubes were ultrasonically decomposed for 5 hours in a strong acid mixed solution of concentrated sulfuric acid (H ₂ SO ₄ , 96%) and nitric acid (70%) in a 3: 1 chemical etching process. Subsequently, the chemically etched multi-ply carbon nanotubes were washed and filtered several times with deionized water and then dried at 150 ° C. for 12 hours. Then dried at 150 ° C. under 5 × 10 ⁻⁶ Torr vacuum for 5 hours. The formed multi-ply carbon nanotubes had a length of about 5 μm.

Subsequently, after applying the coating solution in which the multi-ply carbon nanotubes were dispersed in a dispersion medium of NMP (N-methyl-2-pyrrolidone) in which PVDF binder (10 wt.%) Was dissolved on aluminum foil, 4 hours at 120 ° C. Dry to prepare a current collector.

Manufacturing example  3

Multi-layered carbon nanotubes (MWNTs) were synthesized using supported catalysts by thermal chemical vapor deposition. Subsequently, a purification process was performed to remove catalyst particles and impurities remaining on the surface of the synthesized multi-ply carbon nanotubes. Into a solution mixed with concentrated hydrofluoric acid (HF, 50%) and distilled water 1: 3, mixed with multiple layers of carbon nanotubes and stirred for 18 hours to dissolve the catalyst particles, and then in a 15% air-argon mixture at 550 ° C. The gas phase was oxidized for 1 hour to purify the 순 ¶ pure product such as amorphous carbon by burning. The multi-ply carbon nanotubes were then ultrasonically decomposed in concentrated hydrochloric acid (HCl, 37%) for 10 minutes to dissolve the metal oxide and catalyst particles formed by gas phase oxidation. Then washed and filtered several times with demineralized water and then dried at 150 ℃ for 12 hours.

The purified multi-ply carbon nanotubes were ultrasonically decomposed for 10 hours in a strong acid mixed solution of concentrated sulfuric acid (H ₂ SO ₄ , 96%) and nitric acid (70%) in a 3: 1 chemical etching process. Subsequently, the chemically etched multi-ply carbon nanotubes were washed and filtered several times with deionized water and then dried at 150 ° C. for 12 hours. Then dried at 150 ° C. under 5 × 10 ⁻⁶ Torr vacuum for 5 hours. The formed multi-ply carbon nanotubes had a length of about 1 μm.

Subsequently, after applying the coating solution in which the multi-ply carbon nanotubes were dispersed in a dispersion medium of NMP (N-methyl-2-pyrrolidone) in which PVDF binder (10 wt.%) Was dissolved on aluminum foil, 4 hours at 120 ° C. Dry to prepare a current collector.

Manufacturing example  4

Multi-layered carbon nanotubes (MWNTs) were synthesized using supported catalysts by thermal chemical vapor deposition. Subsequently, a purification process was performed to remove catalyst particles and impurities remaining on the surface of the synthesized multi-ply carbon nanotubes. Into a solution mixed with concentrated hydrofluoric acid (HF, 50%) and distilled water 1: 3, mixed with multiple layers of carbon nanotubes and stirred for 18 hours to dissolve the catalyst particles, and then in a 15% air-argon mixture at 550 ° C. Purification by burning gas phase oxidation for 1 hour to burn impurities such as amorphous carbon. The multi-ply carbon nanotubes were then ultrasonically decomposed in concentrated hydrochloric acid (HCl, 37%) for 10 minutes to dissolve the metal oxide and catalyst particles formed by gas phase oxidation. Then washed and filtered several times with demineralized water and then dried at 150 ℃ for 12 hours.

The purified multi-ply carbon nanotubes were ultrasonically decomposed for 20 hours in a strong acid mixed solution of concentrated sulfuric acid (H ₂ SO ₄ , 96%) and nitric acid (70%) in a 3: 1 chemical etching process. Subsequently, the chemically etched multi-ply carbon nanotubes were washed and filtered several times with deionized water and then dried at 150 ° C. for 12 hours. Then dried at 150 ° C. under 5 × 10 ⁻⁶ Torr vacuum for 5 hours. The formed multi-ply carbon nanotubes had a length of about 0.2 μm.

Subsequently, after applying the coating solution in which the multi-ply carbon nanotubes were dispersed in a dispersion medium of NMP (N-methyl-2-pyrrolidone) in which PVDF binder (10 wt.%) Was dissolved on aluminum foil, 4 hours at 120 ° C. Dry to prepare a current collector.

Manufacturing example  5

Single layered carbon nanotubes (SWNTs) were synthesized using supported catalysts by thermal chemical vapor deposition. Subsequently, a purification process was performed as follows to remove catalyst particles and impurities remaining on the surface of the synthesized single-ply carbon nanotubes. Into a solution of concentrated hydrofluoric acid (HF, 50%) and distilled water 1: 3, single-ply carbon nanotubes were stirred for 18 hours to dissolve the catalyst particles, and then in a 15% air-argon mixture at 550 ° C. Purification by burning gas phase oxidation for 1 hour to burn impurities such as amorphous carbon. The single-ply carbon nanotubes were then ultrasonically decomposed in concentrated hydrochloric acid (HCl, 37%) for 10 minutes to dissolve the metal oxide and catalyst particles formed by gas phase oxidation. Then washed and filtered several times with demineralized water and then dried at 150 ℃ for 12 hours. The formed single-ply carbon nanotubes had a length of about 10 μm.

Subsequently, the coating solution obtained by dispersing the single-ply carbon nanotubes on the aluminum foil in a dispersion medium of NMP (N-methyl-2-pyrrolidone) in which PVDF binder (10 wt.%) Was dissolved was applied. Dry to prepare a current collector.

Manufacturing example  6

Single layered carbon nanotubes (SWNTs) were synthesized using supported catalysts by thermal chemical vapor deposition. Subsequently, a purification process was performed as follows to remove catalyst particles and impurities remaining on the surface of the synthesized single-ply carbon nanotubes. Into a solution of concentrated hydrofluoric acid (HF, 50%) and distilled water 1: 3, single-ply carbon nanotubes were stirred for 18 hours to dissolve the catalyst particles, and then in a 15% air-argon mixture at 550 ° C. Purification by burning gas phase oxidation for 1 hour to burn impurities such as amorphous carbon. The single-ply carbon nanotubes were then ultrasonically decomposed in concentrated hydrochloric acid (HCl, 37%) for 10 minutes to dissolve the metal oxide and catalyst particles formed by gas phase oxidation. Then washed and filtered several times with demineralized water and then dried at 150 ℃ for 12 hours.

The purified single-ply carbon nanotubes were ultrasonically decomposed for 10 hours in a strong acid mixed solution of concentrated sulfuric acid (H ₂ SO ₄ , 96%) and nitric acid (70%) in a 3: 1 chemical etching process. Subsequently, the chemically etched carbon nanotubes were washed and filtered several times with deionized water and then dried at 150 ° C. for 12 hours. Then dried at 150 ° C. under 5 × 10 ⁻⁶ Torr vacuum for 5 hours. The formed single-ply carbon nanotubes had a length of about 1 μm.

Subsequently, the coating solution obtained by dispersing the single-ply carbon nanotubes on the aluminum foil in a dispersion medium of NMP (N-methyl-2-pyrrolidone) in which PVDF binder (10 wt.%) Was dissolved was applied. Dry to prepare a current collector.

Fabrication of Lithium Secondary Cells

Example  One

On the current collector of Preparation Example 1 prepared as described above, a positive electrode slurry containing 94 wt% of LiCoO ₂ , 3 wt% of poly (vinylidene fluoride) (PVdF), and 3 wt% of acetylene black (conductive material) was applied to the cathode. To prepare a half-coin cell.

Example  2 to 6

94% by weight of LiCoO ₂ , 3% by weight of poly (vinylidene fluoride) (PVdF) and 3% by weight of acetylene black (conductive material) as in Example 1 on the current collectors of Preparation Examples 2 to 6 prepared as described above, respectively The positive electrode slurry was mixed to prepare a positive electrode to prepare a half-coin cell.

Comparative example  One

Aluminum foil was used as the current collector without forming a coating layer containing carbon nanotubes.

A positive electrode slurry was prepared by mixing 94 wt% of LiCoO ₂ , 3 wt% of poly (vinylidene fluoride) (PVdF), and 3 wt% of acetylene black (conductive material) on the current collector to prepare a positive electrode to prepare a half-coin cell. Prepared.

Evaluation-1

Before and after the chemical etching of the carbon nanotubes used in the current collector production of Preparation Examples 3 and 6.

4A and 4B are transmission electron microscope (TEM) photographs before and after chemical etching of the multi-ply carbon nanotubes used in manufacturing the current collectors of Preparation Examples 1 and 3, respectively, and FIGS. 5A and 5B. Are transmission electron microscope (TEM) photographs before and after chemical etching of the multi-ply carbon nanotubes used in the preparation of the current collectors of Preparation Example 5 and Preparation Example 6, respectively.

4A and 4B, it can be seen that the length of the multi-ply carbon nanotubes is shortened after chemical etching.

Similarly, comparing FIGS. 5A and 5B, it can be seen that the length of the single-ply carbon nanotubes is shortened after chemical etching.

It can be seen from this that the length of the carbon nanotubes can be controlled by chemically etching the carbon nanotubes.

Evaluation-2

In the preparation of the current collector of Preparation Example 1, the chemical functional groups generated as the chemical etching progresses are confirmed.

6 is an infrared spectral spectrum showing a production peak of chemical functional groups as the chemical etching proceeds for 0, 5, 10, and 20 hours in preparing the current collector of Preparation Example 1. FIG.

Referring to FIG. 6, when the current etching of the current collector of Preparation Example 1 was performed for 0 hours (a), 5 hours (b), 10 hours (c), and 20 hours (d), about 1400 to 1800 cm ^-1. It can be seen that the peak in the range (C═O bond), the peak in the range of about 3000 to 3500 cm ⁻¹ (CH bond) gradually increases.

As such, it can be seen that more chemical functional groups are generated on the surface of the carbon nanotubes depending on the degree of chemical etching, from which the degree of generation of chemical functional groups can be controlled.

Evaluation-3

The charge and discharge characteristics of the secondary battery cells prepared in Examples 1 to 6 and Comparative Example 1 are confirmed with reference to Table 1 and FIG. 7.

7 is a graph showing charge and discharge characteristics of the secondary battery cells of Examples 1 to 6 and Comparative Examples 1 to 3. FIG.

Charge and discharge conditions are as follows.

Charging: CC-CV mode 0.1C 4.2V 0.01C cut-off

Discharge: CC mode 0.1 / 0.2 / 0.5 / 1 / 2C 3.0V Cutoff

0.1C 0.2C 0.5C 1C 2C Example 1 100.0 98.3 93.9 89.4 84.2 Example 2 100.0 98.6 96.1 93.9 91.5 Example 3 100.0 98.8 97.1 95.3 93.7 Example 4 100.0 99.3 98.2 96.8 95.5 Example 5 100.0 98.4 94.9 90.9 86.5 Example 6 100.0 99.1 97.5 96.0 94.5 Comparative Example 1 100.0 96.1 90.4 85.4 78.4

Referring to Table 1 and Figure 7, it can be seen that the secondary battery cells of Examples 1 to 6 have a higher efficiency according to the charge and discharge than the secondary battery cells of Comparative Example 1.

In particular, when comparing the secondary battery cells of Examples 1 to 4, the charge and discharge efficiency is high in the order of shorter length of the multi-ply carbon nanotubes, that is, in the order of Examples 4, 3, 2 and 1 It can be seen that. Similarly, when comparing the secondary battery cells of Examples 5 and 6, it can be seen that the charge and discharge efficiency is high in the order of shorter length of the single-ply carbon nanotubes, that is, in the order of Examples 6 and 5.

From this, it can be seen that the shorter the length of the chemically etched carbon nanotubes, the better the charge and discharge efficiency.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of the invention.

100: secondary battery 110: current collector
110a: metal thin film 110b: coating layer
111: active material layer 112: negative electrode
113: separator 114: anode
120: battery container 140: sealing member

Claims (18)

Metal substrate, and
Located on at least one surface of the metal substrate and the coating layer comprising carbon nanotubes
Including,
The carbon nanotubes are chemically etched and have a length of 10 μm or less,
The coating layer will have a thickness of 0.1 to 1 ㎛
Current collector; And,
An active material layer formed on at least one surface of the current collector;
Electrode comprising a.
In claim 1,
The carbon nanotube electrode having a plurality of chemical functional groups on the surface.
In claim 2,
Wherein the chemical functional group is observed at an infrared spectroscopic analysis in a peak in the range of 1400 to 1800 cm ⁻¹ , a peak in the range of 3000 to 3500 cm ^−1, or a combination thereof.
In claim 2,
The chemical functional group comprises a carboxyl group, a carbonyl group or a combination thereof.
In claim 1,
The carbon nanotubes have a length of 0.01 to 5㎛.
In claim 1,
The carbon nanotubes include single walled nanotubes, multi walled nanotubes, or a combination thereof.
In claim 1,
The metal substrate comprises an aluminum foil, copper foil, nickel foil, stainless steel foil, titanium foil, silver foil, conductive polymer substrate or a combination thereof.
delete In claim 1,
And the active material layer is formed on the coating layer.
Preparing carbon nanotubes,
Chemically etching the carbon nanotubes to form carbon nanotubes having a length of 10 μm or less;
Coating a carbon nanotube on a metal substrate to form a current collector, and
Applying an active material to the current collector to form an active material layer
Method for producing an electrode comprising a.
11. The method of claim 10,
Chemically etching the carbon nanotubes
Ultrasonic decomposition of the carbon nanotubes in a strong acid solution
Method of manufacturing the electrode.
11. The method of claim 10,
The carbon nanotube is a method of manufacturing an electrode having a length of 0.01 to 5㎛.
11. The method of claim 10,
A method of manufacturing an electrode in which a chemical functional group is introduced to the surface of the carbon nanotubes in the step of chemically etching the carbon nanotubes.
In claim 13,
The chemical functional group is a method for producing an electrode in which the peak in the range of 1400 to 1800 cm ^-1 , the peak in the range of 3000 to 3500 cm ^-1, or a combination thereof is observed during infrared spectroscopy.
In claim 13,
Wherein said chemical functional group comprises a carboxyl group, a carbonyl group, or a combination thereof.
11. The method of claim 10,
Before chemical etching the carbon nanotubes
Purifying the carbon nanotubes to remove the catalyst particles and impurities further comprising the manufacturing method of the electrode.
11. The method of claim 10,
Coating the carbon nanotubes on the metal substrate
The manufacturing method of the electrode performed by the slurry method or the electrophoretic deposition method. A secondary battery comprising the electrode according to any one of claims 1 to 7.

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