WO2013062177A1

WO2013062177A1 - Electrode including a graphene layer and a self-assembled electrode active material aggregate layer, and secondary battery using same, and method for manufacturing same

Info

Publication number: WO2013062177A1
Application number: PCT/KR2011/009933
Authority: WO
Inventors: 최진훈; 김일두
Original assignee: 한국과학기술원
Priority date: 2011-10-28
Filing date: 2011-12-21
Publication date: 2013-05-02
Also published as: KR20130046851A; KR101357241B1

Abstract

The present invention relates to: an electrode including a graphene layer, for improving the adhesion properties between a self-assembled electrode active nanoparticle aggregate layer and a collector; a secondary battery including same; an electrochemical capacitor including same; and a method for manufacturing same. More particularly, the graphene layer covers the self-assembled electrode active nano particle aggregate layer, and the graphene layer and the electrode active nano particle aggregate layer form an alternating multilayer so that fast electron transfer is achieved through the graphene layer and lithium ions can move quickly through the empty spaces between the aggregates. Thus, a thin battery suitable for fast charging and discharging can be realized. In particular, mechanical stability can be increased to provide good long lasting characteristics.

Description

【Specification】

[Name of invention]

An electrode comprising a graphene layer and a self-assembled electrode active material collector layer, a secondary battery using the same, and a method of manufacturing the same

Technical Field

The present invention relates to an electrode including a graphene layer, a secondary battery including the same, an electrochemical capacitor including the same, and a method of manufacturing the same, in order to improve adhesion characteristics between the self-assembled electrode active material layer and the current collector. . More specifically, the graphene layer covers the self-assembled electrode active material nanoparticle aggregate layer, and the graphene layer and the electrode active material nanoparticle aggregate layer alternately form a multilayer film, thereby providing fast electrons through the graphene layer. The transfer occurs, and lithium ions may move rapidly through the empty spaces between the collectors, thereby implementing a thin battery suitable for high-speed layer discharge. In particular, the mechanical stability is increased, the long life characteristics can be excellent.

Background Art

With the development of advanced technologies, secondary batteries used as power sources for electronic devices are also required to have high output, high stability, and long life characteristics, and thin film batteries are receiving great attention from the viewpoint of miniaturization. In the case of a thin film battery, a battery having a thickness of several to several tens of microns or less is manufactured and has an advantage that it can be applied to a wireless sensor, RFID, healthcare, and the like. However, such a thin film battery uses a vacuum deposition method to produce a thin positive electrode active material layer such as 1 ^) ¾, and solid electrolytes such as UPON are also deposited as a thin film, which leads to restrictions in selecting materials. In particular, in the case of the positive electrode active material, it is difficult to manufacture by chemical vapor deposition because a lot of materials having a complicated composition ratio and structure are used. In current technology, thin films are deposited using an RF sputtering apparatus, and it is also difficult to uniformly manufacture a ceramic target having a complex composition.

The spray technique is an easy technique for forming thin layers of 2-10 microns thick. However, in the case where a thin layer crystallized from the precursor solution is formed by coating the thin layer using a solvent in which the precursor is dissolved as a spray solution and then performing heat treatment at a high temperature, it may be difficult to obtain a thin crystal layer having excellent crystallinity. Can be. In addition, Al, Cu, or stainless steel used as the current collector substrate is oxidized during the high temperature heat treatment, thereby greatly increasing the resistance of the current collector.

In order to solve this problem, a colloidal solution in which fine nanoparticles having a crystalline property of 100 nm or less are well dispersed is prepared and sprayed therefrom. There is a need for a technique for forming a thin layer. In particular, high capacity electrode active materials of SK4200 mAh / g) and Sn (991 mAh / g) series having a higher theoretical capacity than carbon materials (372 mAh / g) or Li ₄ Ti ₅ 0 ₁₂ ( 175 mAh / g) material and the like by forming a colloidal solution for spray to form a thin layer, it is possible to significantly reduce the process cost compared to the vacuum deposition process. In the case of the thin layer obtained by spray coating from such a colloidal nanoparticle dispersion solution, since it does not contain a binder, a problem of easily detaching from the current collector substrate may occur. Therefore, it is important to manufacture an electrode active material layer capable of maintaining high adhesive strength with a current collector substrate without using a binder, and thus, a thin film type secondary battery electrode having excellent life characteristics can be manufactured.

Detailed description of the invention

[Technical Challenges]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrode and a method for manufacturing the electrode, in which the self-assembled electrode active material nanoparticle aggregate layer and the graphene layer are deposited alternately.

Specifically, the object of the present invention,

First, the present invention provides an electrode active material nanoparticle aggregate layer self-assembled in at least one shape selected from spherical, elliptical, and donut shapes, an electrode having a graphene layer inserted in an upper layer and a lower layer thereof, and a method of manufacturing the same.

Second, the electron transfer with the self-assembled electrode active material nanoparticle aggregates occurs quickly due to the excellent electrical conduction characteristics of the graphene layer, and the graphene holds the electrode active material nanoparticle aggregate layer, resulting in high mechanical strength. The present invention provides an electrode and a method of manufacturing the same. Third, an electrode is free to move an electrolyte through an open space between the self-assembled electrode active material nanoparticle aggregates, and thus has excellent high power characteristics and can serve as a complete layer for volume expansion. And a method of manufacturing the same,

Fourth, after forming a graphene layer on the current collector, and a self-assembled electrode active material nanoparticle aggregate layer on the graphene layer, and finally on the self-assembled electrode active material nanoparticle aggregate layer graphene or carbon nano Provides a method of an electrode that can produce a thin layer formed by the network (net) of the tube with a large yield in a large yield by using an electrostatic spray method using a plurality of nozzles,

Fifth, the current collector / graphene layer / self-assembled electrode active material nanoparticle aggregate layer / electrode on which the self-assembled electrode active material nanoparticle aggregate layer and the carbon layer is formed a plurality of times and a secondary battery using the same Providing supercapacitors ，

Sixth, the electrode active material nanoparticle aggregates networked by the carbon layer. The layer is thermally compressed to provide an electrode having high mechanical and electrical stability and a secondary battery and a supercapacitor using the same.

Technical Solution

An electrode of an aspect of the present invention is a current collector; Graphene stacked on the current collector

(graphene) layer; A collector layer of electrode active material nanoparticles laminated on the graphene layer; And it may include a carbon layer laminated on the collector layer.

In another aspect of the present invention, a secondary battery or a supercapacitor may include the electrode.

According to another aspect of the present invention, there is provided a method of manufacturing an electrode, the method comprising: forming a laminated structure by electrospraying a graphene dispersion solution, an electrode active material nanoparticle dispersion solution, and a carbon layer dispersion solution in order on a current collector; And it may include a step of compressing the laminated structure.

Advantageous Effects

According to the present invention, the collector prepared by electrospraying a solution in which the electrode active material nanoparticles for secondary batteries is dispersed is coated on the current collector in at least one shape selected from spherical, donut-shaped, or elliptical. By introducing a graphene layer on the upper and lower portions of the foam layer consisting of these bubbles, the problem of separation between the cubes is solved, and due to the fast electron transfer characteristics of the graphene, the resistance of the entire electrode It is greatly reduced. Alternatively, the electrode active material nanoparticle aggregate layer and the graphene layer may be alternately coated with a multilayer to prepare a thick multilayer thin film having a thickness of 10 microns or more. In this case, the carbon layer coated on the electrode active material nanoparticle coagulation layer may be a carbon nano-lever layer instead of the graphene layer. The graphene layer wraps the electrode active material collector layer, thereby enhancing the mechanical stability of the nanoparticle aggregates, and in the case of carbon nano-lube, networking and dyeing the aggregates between the aggregates increases mechanical durability. In addition, the graphene layer and the carbon nanotube layer have very fast electron transfer characteristics, and may provide an electrode active material nanoparticle aggregate layer that is advantageous for high-speed charging and discharging.

In particular, by having at least one form selected from the group consisting of spherical, donut and elliptic, it has an aggregate characteristic rather than individual nanoparticles, and facilitates electron and Li transfer characteristics between particles.

Since the self-assembled aggregate of the electrode active material of the present invention is manufactured from the nanoparticles of the positive electrode active material, the negative electrode active material or a mixture thereof, the secondary battery full cell (full cel l) Since the polymer binder is not used in the preparation of the electrode active material nanoparticle aggregate layer, the electron transfer can be performed quickly, and the mechanical stability problem that can be caused by not using the binder is the graphene layer or the carbon layer. By introducing the nanotube layer on top of the self-assembled electrode active material nanoparticle aggregate layer, the stability can be increased, and excellent long-life characteristics can be expected. In addition, through the single-axis thermocompression and compression process, it is possible to increase the adhesive strength between the graphene layer and the electrode active material nanoparticle enclosure layer, improve the layer density and contact characteristics, Can be configured. In addition, the thickness of the thin layer can be controlled by controlling the electrostratic spray time used in the preparation of the electrode active material, and the current collector-graphene layer (A) -electrode active material nanoparticles carrier layer (B) —carbon layer (C By stacking sequentially, a graphene layer or a carbon nanotube layer), a multilayer thin film can be realized. In this case, the electrode active material nanoparticle layer (B) -carbon layer (C) may be laminated one to five times more successively. Through the lamination process, the thickness of the electrode active material layer may be increased.

[Drawing and brief description]

1 shows a laminated structure of an electrode according to an embodiment of the present invention. 2 shows a laminated structure of an electrode according to another embodiment of the present invention. 3 is a scanning electron micrograph of Li ₄ Ti ₅ 0 ₁₂ nanofibers obtained from the embodiment of the present invention.

4 is a scanning electron micrograph of Li ₄ Ti ₅ 0 ₁₂ colloidal nanoparticles obtained from the embodiment of the present invention.

5 is a scanning electron micrograph of the self-assembled spherical nanoparticle pools obtained by electrostatic spraying Li ₄ Ti ₅ 0 ₁₂ nanoparticle colloidal dispersion solution.

6 is a scanning electron micrograph of an electrode active material in which a carbon nanotube network layer is formed on a Li ₄ Ti ₅ 0 ₁₂ nanoparticle aggregate layer.

FIG. 7 is an enlarged scanning electron micrograph of a selected region of FIG. 6.

8 shows Li ₄ Ti ₅ 0 ₁₂ electrode active material nanoparticle aggregate layer, graphene layer / Li ₄ Ti ₅ 0 ₁₂ electrode active material nanoparticle aggregate layer / graphene layer, graphene layer / Li ₄ Ti ₅ 0 ₁₂ Characterization of secondary battery characteristics (10 C rate discharge) of electrode active material nanoparticle aggregate layer / graphene layer / Li ₄ Ti ₅ 0 ₁₂ electrode active material nanoparticle aggregate layer / graphene layer. 9 is a graph of 1C rate discharge versus cycle number of an electrode in which Li ₄ Ti ₅ 0 ₁₂ electrode active material nanoparticle aggregate layers and graphene layers are repeatedly stacked three times.

FIG. 10 is a graph of a 0.2C to 20C rate discharge versus a cycle number of electrodes in which Li ₄ Ti ₅ 0 ₁₂ electrode active material nanoparticle aggregate layers and graphene layers are repeatedly stacked three times.

[Form for implementation of invention]

An electrode of one aspect of the present invention

Current collector;

A graphene layer stacked on the current collector;

A collector layer of electrode active material nanoparticles laminated on the graphene layer; And it may include a carbon layer laminated on the collector layer.

1 shows an embodiment of the electrode of the present invention. According to FIG. 1, the electrode may include a current collector 100, a graphene layer 200, an ion collector layer 300 of an electrode active material nanoparticle, and a carbon layer 400. A graphene layer is formed on the current collector, an electrode active material nanoparticle coagulator layer is formed on the graphene layer, and a carbon layer is formed on the nanoparticle coagulator layer.

The collector layer and the carbon layer of the electrode active material nanoparticles may be formed in multiple layers on the carbon layer in order. Figure 2 shows another embodiment of the electrode of the present invention. According to FIG. 2, the electrode includes a graphene layer 200, a collector layer 300 of electrode active material nanoparticles, and a carbon layer 400 sequentially stacked on the current collector 100, and on the carbon layer 400. The collector layer 300 and the carbon layer 400 of the electrode active material nanoparticles are further formed. According to FIG. 2, although the multilayer structure of the collector layer 300 and the carbon layer 400 of the electrode active material nanoparticles is additionally formed once, it may be formed into a multilayer structure. It may preferably be formed once to 10 times, more preferably once to seven times, most preferably once to five times.

As the current collector, at least one selected from the group consisting of nickel (Ni), stainless steel (SUS), aluminum (A1), copper (Cu), and titanium (TO) can be used. The graphene layer improves the adhesion properties between the electrode active material nanoparticle coarse layer coated on the top and the current collector on the bottom.The graphene layer is graphene, graphene oxide, reduced graphene. Oxide, or a mixture thereof, because graphene, graphene oxide, reduced graphene oxide, or a mixture thereof has a high surface energy, which greatly increases the bonding strength with the electrode active material coated thereon. The electrode active material nano on the current collector without the graphene layer When the particle aggregate layer is coated, the adhesive strength with the current collector is weak, and the electrode active material nanoparticle aggregate layer can be easily detached.

Electrode active material nanoparticle aggregate layer is composed of aggregates in which nanoparticles are self-assembled. The electrode active material nanoparticle aggregate layer may be generated by spraying a dispersion solution in which the electrode active material nanoparticles are dispersed under an electric field. The nanoparticles charged by the polar solution are spawned in order to minimize the surface energy during the spraying process. This cohort process is referred to herein as 'self-assembly'.

In addition, since the spray process is a simple process, the graphene layer and the electrode active material nanoparticle aggregate layer may be laminated alternately. At this time, the thickness of the foam layer going up to the multilayer film does not need to be the same, and the graphene layer may be applied to the uppermost portion. In order to maintain a sufficient energy density, the graphene layer-electrode active material nanoparticle aggregate layer is preferably laminated at least once to five times, preferably two to three times.

The electrode active material nanoparticle aggregate layer is sandwiched between the graphene layer and the carbon layer. The aggregate may have at least one shape selected from the group consisting of a spherical shape, a donut shape, and an oval shape.

In the aggregate layer, nanoparticles having electrode active material properties are self-assembled to form a aggregate layer. As a result, the pore structure is very well developed between the collectors, which facilitates the penetration of the electrolyte.

The electrode active material nanoparticle aggregate layer and the thickness may be 500 nm to 20. If the thickness of the collector layer is 500 nm or less, the energy density becomes low. When the thickness of the foam layer is 20 or more, the bonding force between the foam and the graphene layer is weakened, causing a problem that the foam falls off from the current collector during battery cell operation. Preferably, the thickness of the male layer may be 2 / Hi ~ 10 // m.

The nanoparticles constituting the electrode active material nanoparticle aggregate layer may be selected from a cathode active material for a secondary battery, a cathode active material, or a mixture thereof. For example, Si, Sn, Li ₄ Ti ₅ 0 ₁₂ , Sn 0 ₂ , Ti 0 ₂ , Fe ₂ 0 ₃ , Fe ₃ 0 ₄ , Co ₃ 0 ₄ , or a combination thereof; Si, Sn, Ti, Cu,

At least one alloy selected from the group consisting of Al, Ce and La; LiMn ₂ 0 ₄ , V ₂ 0 ₅ ,

LiCo0 ₂ , LiNi0 ₂ , LiFeP0 ₄ , LiFeP0 ₄ . LiNii- _y Co _y 0 ₂ , Li [Ni _1/2 Mn _1/2 ] 0 ₂ or a combination thereof; Mg ²⁺ , Al ³⁺ , Ti ⁺ , Zr ⁺ , Nb ⁵⁺ , doped with lithium in place of LiFeP0 ₄ , Li [Ni _1/3 Co _1/3 Mn _1/3 ] 0 ₂ , Li [Ni _1/2 Mn _1/2 ] 0 ₂ , LiNi ^^, LiNi— _x Ti _{x / 2} Mg _{x / 2} 0 ₂ or their marks It may be one or more selected from the group consisting of compounds, but is not limited thereto. Preferably the said doping amount is 0.01-weight? May be ¾-1% by weight.

The self-assembled aggregates may have a size of 100 nm to 3000 nm.

Nanoparticles constituting the self-assembled aggregates may have a size of 2 nm ~ 100 nm.

The electrode of the present invention does not use a separate polymeric binder in the nanoparticle aggregate layer. Since the binder is not used, the conductivity characteristics can be maximized. On the other hand, because the self-assembled coagulation is weakly bonded by van der Waals attraction, it may fall from the current collector through the repeated electrochemical reaction process, or separation between aggregates may occur.

In order to minimize the problems of bonding stability resulting from the absence of such a binder, a carbon layer is formed on the self-assembled electrode active material collector layer.

The carbon layer is formed on the collector layer of the electrode active material nanoparticles. The carbon layer may be a graphene layer, a carbon nanotube layer, or a mixed layer in which graphene and carbon nanotubes are mixed. Graphene and carbon nanotubes have excellent electrical conductivity, which can improve the conductivity of electrode active material nanoparticle aggregate layers.

The carbon layer may be networked with each other between graphene or carbon nanotubes to surround the electrode active material aggregates or to connect the aggregates.

The carbon layer may be a single layer or a plurality of layers, but is not limited thereto. ᅳ

The carbon layer may preferably be a graphene layer. If the graphene layer is coated on the electrode layer of the electrode active material nanoparticles, the electrode active material layer is coated by a graphene layer having a wide plate-like structure, the adhesion strength with the substrate is greatly improved.

Since the size of graphene ¾ is generally greater than 1, when the graphene layers are well spread, the electrode active material nanoparticle aggregate layer may be well wrapped. Therefore, since the electrode active material collector layer is formed by sandwiching between the graphene filling, mechanical stability may be higher than when only the single electrode active material aggregate layer is formed. In addition, graphene is excellent in electrical conductivity as a material for transparent electrodes. The graphene layer is formed on the upper and lower portions of the electrode active material nanoparticle aggregate layer, thereby providing a fast electron transfer passage. Therefore, a battery having excellent output characteristics can be constituted. In addition, carbon nanotubes can improve adhesion strength by holding nanoparticle aggregates as straws.

As shown in FIGS. 1 and 2, the graphene layers are connected to each other while covering the self-assembled nanoparticle aggregate layers.

The electrode active material nanoparticle aggregate layer-graphene layer in which a graphene layer is continuously stacked on the self-assembled nanoparticle electrode active material layer is a nanoparticle aggregate self-assembled with a graphene layer having excellent conductivity characteristics. By enclosing and enclosing the aggregates, the electron conduction characteristics are excellent, and the wide graphene layer captures the aggregates, thereby improving mechanical stability. In the absence of a graphene layer, the collector layer formed by self-assembly of nanoparticles can be relatively well detached from the current collector during cell assembly or layer discharge cycle.

Electrode active material nanoparticle aggregate layer-graphene layer through the compression and heat treatment process to increase the layer density, it is possible to reduce the contact resistance between the nanoparticles or aggregates and graphene. A secondary battery according to another aspect of the present invention may include the electrode.

Specifically, the secondary battery may be composed of the electrode, the electrolyte, the separator, the case and the terminal. The electrolyte is not limited as long as it is a composite electrode active material having a continuous stacked structure of a graphene layer / self-assembled nanoparticle aggregate layer / carbon layer and an electrolyte capable of causing electrochemical reaction. An example is LiPF ₆ . Another aspect of the invention a method for producing an electrode

(1) forming a laminated structure by electrospraying a graphene dispersion solution, an electrode active material nanoparticle dispersion solution, and a dispersion solution for forming a carbon layer on a current collector in order; And

(2) may comprise pressing the laminated structure.

As the current collector, at least one selected from the group consisting of nickel (Ni), stainless steel (SUS), aluminum (A1), copper (Cu), and titanium (Ti) may be used.

Electrode active material nanoparticles may have a size of 1 nm ~ 100 nm.

The electrode active material may be a negative electrode active material, a positive electrode active material or a combination thereof. As a solvent for dispersing the electrode active material nanoparticles, graphene or carbon nanotubes, a solvent having a boiling point (volatile point) of 80 ° C or lower, or a solvent having a boiling point (volatile point) of 80 or lower can be It may be a solvent mixture containing at least% by weight. Such solvents include ethanol, methanol, propanol, butanol, IPA (isopropyl alcohol), dimethyl formamide (DMF), acetone, detrahydrofuran, toluene, water, and combinations thereof. It can be one species selected from. The boiling point may preferably be 56 ^° C.-80 ° C. In addition, the manufacturing method may further include forming a multilayer structure by electrospraying the electrode active material nanoparticle dispersion solution and the carbon layer-forming dispersion solution in sequence a plurality of times before the pressing step.

In addition, the manufacturing method may further include a step of heat-treating the compressed laminated structure in order to increase the density of the laminated layer and improve the adhesive strength with the current collector after the pressing step. The manufacturing method of the electrode of the present invention will be described in detail step by step.

Preparation of Graphite Dispersion and Tasonanotube Dispersion Solution ^''

First, in order to coat the graphene layer on the current collector, a dispersion solution in which graphene is dispersed is prepared. Commercially available graphene can be used and it does not matter if the graphene is not composed of a single layer. Graphene can be purchased from commercially available XG-SCIENCE or other manufacturers.

Carbon nanotubes may use single-walled, double-walled, multi-walled carbon nanotubes, and a small amount of surfactant may be used for uniform dispersion. These surfactants can be removed through repeated washing or high temperature heat treatment after assembling the layer of all active material nanoparticle aggregates.

Preparation of Low Cathode Dispersion Solution

Prepare a colloidal dispersion solution in which the electrode active material nanoparticles are uniformly dispersed in a solvent. Electrode active material nanoparticle dispersion solution may comprise 0.5 to 20 wt% of the electrode active material.

For the stable dispersion of nanoparticles, microbead milling can be used to remove pores between nanoparticles, and microbead milling can be performed so that fine particle dispersion can be achieved in a solution without a binder. The milling method is not limited, but milling can be performed in a wet atmosphere using zirconia balls (or beads) of 0.1 mm to 0.015 mm in size.

Graphite layer. Low electrode active material nanoparticles collector layer and carbon filler red aggregate Collecting the graphene dispersion solution prepared above using an air-spray coating machine Coating on top. Then, the electrode active material nanoparticle dispersion solution is installed in an electrostatic spray (electrospray) apparatus to perform spraying.

The electric spray device used here is composed of a spray nozzle, a high voltage generator, a grounded conductive substrate, and the like connected to a metering pump capable of quantitatively dispersing the dispersion solution. By applying a voltage of 8 to 30 kV and adjusting the solution discharge rate to 10 to 300 minutes, the thickness of the insecticide can be sprayed on the current collector until a thickness of 500 nm-20 mi is formed, but is not limited thereto.

The graphene dispersion solution is sprayed to cover the whole house. Since graphene is a very high surface energy material, it can be strongly bound on the current collector.

Nanoparticles tend to condense with each other because of their large surface energy, reducing the surface energy. Especially in the electrostatic spray injection process used in the present invention

Since solvents lower than 80 ° C are used, the solvent easily volatilizes during electrostatic spray injection, and pure particles are coated on the current collector as they accelerate under an electric field.

Since the gap between the current collector and the nozzle is 10 to 20 cm apart, the nanoparticles are spun together as the nanoparticles accelerate toward the current collector, thereby spontaneously forming a spherical coarse body. The size of the bubble may have a size of 100nm ~ 3000nm, the size of the bubble is determined according to the concentration of the nanoparticles contained in the dispersion solution.

The shape of these enclosures can be influenced by the volatilization rate, scattering distance and applied voltage of the solution. The spherical shape is most preferable for regular pore distribution and the formation of a rigid form, but may have an elliptical or donut shaped form, and some may reach the current collector with a non-formed form, and form spherical aggregates and nanoparticles. Particles may be common to form a coated thin layer.

The carbon layer is coated on the electrode active material nanoparticle aggregate prepared by using an air-spray method. Since graphene has a wide plate-like structure, it is possible to wrap the electrode active material nanoparticle aggregate layer to prevent the aggregates from falling off the substrate. In the case of carbon nano hubs, the mechanical binding strength is greatly increased by connecting the coarse bodies to each other by carbon nanotubes having a very high aspect ratio.

The above-mentioned electrode active material nanoparticle aggregate layer and the carbon layer stacked thereon may be continuously stacked to form a thicker thin layer. This continuous stacking structure repeats the electrode active material nanoparticle coarse layer and the carbon layer several times in succession. By doing so, it is helpful to construct an electrode active material layer having excellent mechanical binding force and fast electrical electron transfer. The thick film cell may be constituted by at least two times from a single stack, preferably 1 to 10 times, more preferably 1 to 7 times, and most preferably 1 to 5 times. have. However, considering the price of nanoparticles and the efficiency of the process, a thin film battery of less than 10 is expected to have the greatest effect.

Pressing may include compressing the current collector / graphene layer / electrode active material nanoparticle coarse layer / carbon layer to increase the density and improve the adhesive strength with the current collector. Compression may be possible and the compressive strength can be adjusted. For example, it can be 5-15 MPa, but it is not limited to this.

Heat treatment

The method may further include heat treating the composite electrode active material formed by networking the self-assembled nanoparticle aggregate layer and the carbon layer formed through the pressing step. The heat treatment may increase the binding force between the nanoparticles, and may increase the mechanical stability by increasing the binding force between the self-assembled nanoparticle aggregate layer and the carbon layer.

The heat treatment can be carried out at a temperature range in the range of 300-500 ^° C, in which the carbon layer does not decompose by carbonization. In another aspect of the present invention, a secondary battery or an electrochemical capacitor may include the electrode. Secondary batteries or electrochemical capacitors can be prepared by conventional methods.

Hereinafter, the present invention will be described in detail through examples. However, these examples are only presented to more clearly understand the present invention, but the present invention is not limited thereto. Example 1 Preparation of an Electrode of Graphene Layer / Self-assembled Li ₄ Ti ₅ 0 ₁₂ Nanoparticle Collector Layer / Graphene Layer

Li ₄ Ti ₅ 0 ₁₂ nanofibers were prepared by the electrospinning method. In order to prepare Li ₄ Ti ₅ 0 ₁₂ nanofibers, a lithium acetylacetonate precursor and a titanium tetraipropoxide precursor were prepared so that the ratio of Li: Ti was 4: 5, and polyvinylpyrrolidone (PVP, 1,300,000 g / mol ) Dissolve the polymer in DMP (dimethyl phthalate) solvent to prepare a spinning solution, Electrospinning was performed to prepare Li ₄ Ti ₅ 0 ₁₂ precursor / PVP composite nanofibers. Finally, the polymer was removed by heat treatment in air at 750 for 1 hour to prepare pure Li ₄ Ti ₅ 0 ₁₂ nanofibers. Referring to Figure 3, prepared by the electrospinning method

Li ₄ Ti ₅ 0i ₂ nanofibers have polycrystalline properties composed of fine nanoparticles.

In order to prepare a nanoparticle dispersion solution from the polycrystalline Li ₄ Ti ₅ 0 ₁₂ nanofibers obtained above, microbead milling was performed in a wet manner using 0.1 m zirconia balls. Microbeads (Kyotobuki) were run at a speed of 4000 rpm for 30 minutes. At this time, the dispersion solvent was ethanol, 10 g of Li ₄ Ti ₅ 0 ₁₂ nanofiber was added to 190 g of ethanol to prepare a 5% dispersion solution, and microbead milling was performed. 4 is a scanning electron micrograph of a nanoparticle dispersion solution obtained by grinding from nanofibers after microbead milling. A certain amount was extracted from the dispersion solution, sprinkled on a magnetoscopic microscope holder, and dried to observe the microstructure. As observed in FIG. 4, the Li ₄ Ti ₅ 0i ₂ nanofibers were completely pulverized, and it was confirmed that the pulverization was well performed with nanoparticles having a size of 20 to 50 nm. In the sample preparation process for scanning electron microscopic analysis, the size of some particles was observed, but the initial particle size was found to be very small at about 20 nm.

Graphene was purchased from XG Sciences for the preparation of graphene dispersions and ¾ sonanoleube dispersions used for the coating of carbon layers, and carbon nanotubes were purchased from Hanwha Nanotech in a single-walled structure. Graphene is dispersed in IPA solution, and carbon nanotubes are sodium dodecyl sul fate (C ₁₂ H ₂₅ 0 ₄ S. Na, FW

288.38) A uniformly dispersed carbon nanotube dispersion solution was prepared by adding a surfactant together by ultrasonication and centrifugation. And graphene dispersion solution and carbon nanotube dispersion solution was coated by air-spray method. The dispersion solution in which graphene and single-walled carbon or norebe were dispersed showed excellent dispersion even after 15 days. The graphene dispersion solution was spray-coated on a stainless steel substrate as a current collector by using an air-spray gun to form a graphene layer first. Then, the Li ₄ Ti ₅ 0 ₁₂ nanoparticle dispersion solution was electrosprayed onto the gurifin layer to coat the self-assembled nanoparticle aggregate layer.

Referring to FIG. 5, a spherical Li ₄ Ti ₅ 0 ₁₂ nanoparticle having a size of 300 nm to 1 an It can be seen that the male populations are well formed on the current collector. Li ₄ Ti ₅ 0 ₁₂ nanoparticle aggregates were close to the spherical shape, as shown in Figure 5, it can be seen that the fine nanoparticles are self-assembled as shown in FIG.

A graphene layer and a carbon nanotube network layer were introduced on top of the nanoparticle aggregate layer. After the laminated structure was continuously formed, compression was performed at a pressure of 10 MPa to increase the layer density between the electrode active materials and to increase the binding force between the carbon layer and the electrode active material layer. In the present embodiment, no post heat treatment was performed separately. In the case of the graphene layer, the white Li ₄ Ti ₅ 0 ₁₂ nanoparticle aggregate layer was found to be transformed to black after coating the graphene layer. FIG. 6 shows a scanning electron micrograph observed in a thin layer in which a single-walled carbon nanotube network layer was formed on a Li ₄ Ti ₅ 0 ₁₂ nanoparticle aggregate layer. As shown in Figure 6, it can be seen that the carbon nanotubes are connected to each other between the collectors can easily occur electron transfer between the collectors. FIG. 7 is an enlarged scanning electron micrograph of the region indicated in yellow in FIG. 6, and it can be seen that the globules themselves are also coated by carbon nanotubes. It can be seen that carbon nanotubes not only play a role of connecting the aggregates, but also surround the aggregates, thereby significantly lowering the resistance of the aggregates. Thus, by forming a carbon layer on the upper layer of the electrode active material nanoparticle aggregates, it is expected to ensure the mechanical stability of the electrode and a sharp decrease in the impedance resistance due to fast electron transfer. Example 2 Electrode Preparation of Graphene Layer / Self-assembled Li ₄ Ti ₅ 0 ₁₂ Nanoparticle Ensemble Layer / Graphene Layer / Self-assembled Li ₄ Ti ₅ 0 ₁₂ Nanoparticle Ensemble Layer / Graphene Layer Graphene layer / self-assembled Li ₄ Ti ₅ 0 ₁₂ nanoparticles sample layer / graphene layer / self-assembled by the pin layer, the sandwiching electrode active material nanoparticle aggregate layer is laminated twice in succession Li ₄ Ti ₅ 0 ₁₂ nanoparticle aggregate layer / graphene layer was prepared. The manufacturing conditions of each layer were the same as in Example 1, by coating the Li ₄ Ti ₅ 0 ₁₂ nanoparticle aggregate layer / graphene layer once more successively, to prepare a multilayer electrode active material shown in FIG. In the case of such a multi-layer structure, a carbon layer such as graphene or carbon nanotubes is introduced before two or three electrode active material layers are stacked, thereby maintaining excellent electrical conductivity in the thickness direction, and mechanical stability. It is a structure that is advantageous to realize a battery with high energy density and high thickness. Comparative Example 1 Preparation of Electrode Active Material Having Self-Assembled Li ₄ Ti ₅ 0 ₁₂ Nanoparticle Cumulus Layer

Carried out in Example 1, the electrostatic directly the Li ₄ Ti ₅ 0 ₁₂ nano-particle dispersion solution was obtained by crushing the Li ₄ Ti ₅ 0 ₁₂ nanofibers obtained on the current collector in the injection Li ₄ Ti ₅ 0 ₁₂ nano Hung particles are made of self-assembled The aggregate layer was comprised. In Comparative Example 1, unlike Example 1, the graphene layer was not introduced between the current collector and the electrode active material retainer layer, and no carbon layer was introduced into the upper layer of the electrode active material nanoparticle aggregate layer. Experimental Example: Characterization of Self-Assembled Lithium Battery with Li ₄ Ti ₅ 0 ₁₂ Split Particle Layer and Graphene Layer

Two samples from Example 1

1. Graphene layer / self-assembled Li ₄ Ti ₅ 0 ₁₂ coarse layer / graphene layer (g / LTO / g notation)

2. Graphene layer / self-assembled Li ₄ Ti ₅ 0 ₁₂ coarse layer / graphene layer / self-assembled Li ₄ Ti ₅ 0 ₁₂ coarse layer / graphene layer (g / LTO / g / LTO / g notation) Electrodes composed of Li ₄ Ti ₅ 0 ₁₂ coarse layer (LTO notation) self-assembled on the current collector in Comparative Example 1 and the electrode having a continuous laminated structure of) were prepared, respectively, and compared with each other. Battery characteristics were evaluated by preparing a coin cell (CR2032—type coin cell). In the sal composition, an EC / DEC (1/1 volume%) solution in which 1 M LiPF ₆ was dissolved was used as an electrolyte. As a cathode used as the reference electrode and the counter electrode, metal lithium foil (Foote Mineral Co.) of purity 99.99) was used, and as a working electrode, 1. graphene layer / self-assembled Li ₄ Ti ₅ 0 ₁₂ coarse layer / Graphene layer, 2. graphene layer / self-assembled Li ₄ Ti ₅ 0 ₁₂ aggregate layer / graphene layer / self-assembled

A thin layer consisting of a Li ₄ Ti ₅ 0i ₂ aggregate layer / graphene layer, 3. self assembled Li ₄ Ti ₅ 0 ₁₂ aggregate layer was used. Polypropylene film (Celgard Inc.) was used as a separator to prevent the electrical short between the cathode and the anode. The cell was fabricated after creating an argon (Ar) atmosphere in a VAC glove box. It was.

The layer-discharge test apparatus used here was WonATech's WBCS3000 model, which examined the voltage change under constant current with Multi Potent Iost at System (MPS), which was able to measure 16 channels by adding 16 boards. Current mill used for charging and discharging The intensity of the figure was calculated by 50 cycles on the basis of 0.2 C-rate ~ 20 C-rate by calculating the theoretical capacity of each material. Cut off voltage was 0.01 ~ 3.0 V.

Figure 8 shows the negative electrode active material characteristics of the cell measured from the three samples, the characterization was made at a very high rate of 10 C-rate. An electrode made of pure LTO (Li ₄ Ti ₅ 0 ₁₂ ) aggregates (sample # 1) without a graphene (g) layer (175 mAh /), which is the theoretical value of LT0 at high rate characteristics, as shown in FIG. The value of 120 mAh / g, which is less than g, was observed initially, and as the cycle progressed, the capacity was reduced to about 100 mAh / g. On the other hand, when the graphene layer is sandwiched on the upper and lower surfaces of the LT0 coarse layer, the electroconductivity is greatly improved, and the capacity value is 20 mAh / g higher than that of the battery composed of the pure LT0 layer. I could confirm that it came out. In particular, the stacked structure (sample # 3) in which the graphene layer and the electrode active material layer were repeated twice consecutively showed the highest discharge capacity value. Therefore, it was confirmed that the graphene layer having excellent electron conduction characteristics was introduced into the upper and lower layers of the electrode active material collector, thereby greatly improving the battery performance.

9 is an LTO nanoparticle aggregate layer and a graphene layer stacked three times in succession. The cell performance of this thin layer (g / LTO / g / LTO / g / LTO / g) is shown. In particular, when manufacturing a thin layer having a three-layer structure, the LT0 layer was not prepared from the nanoparticle dispersion solution pulverized from the Li ₄ Ti ₅ 0 ₁₂ nanofibers used in Example 1, 20 nm ~ 60 nm In the form of a nano-nano (Nanoamor) to sell the nanopowder was purchased after the microbead milling to obtain a dispersion solution, it was electrostatically sprayed to form the LTO electrode active material layer.

Figure 9 shows the characteristics of the negative active material g / LTO / g / LTO / g / LTO / g thin layer evaluated at 1 C rate. The initial discharge capacity value is 375 mAh / g, the second discharge capacity value is 282 mAh / g, the fifth discharge capacity value is 240 mAh / g, and slightly exceeds the theoretical capacity value of LTO 175 mAh / g over 10 times. The capacity value is higher than that.

This can be seen that even in the electrochemical cell evaluation measured according to the cycle change from 0.2 c rate to 20 C rate of FIG. 10 shows very good results. It can be seen that the high discharge capacity value of about 180 mAh / g is shown even at a very fast high rate characteristic of 20 C rate. This is a result of the increase in capacity due to the graphene, the electrode active material layer sandwiched between the graphene layer and the mechanical stability and electrical conduction properties are greatly improved.

In this embodiment, the graphene layer is used as the carbon layer, but the results are shown. The carbon nano-lever network layer can also have the same effect, and is an invention that can be applied to various negative electrode active material and positive electrode active material nanoparticle aggregate layers in addition to LTQ, and there are various types of electrode active materials used to obtain a thin layer. It is not limited to matter,

In the above, the present invention has been described with reference to the illustrated examples, which are only examples, and the present invention performs various modifications and other equivalent embodiments that are obvious to those skilled in the art. Understand that you can.

Industrial Applicability

The present invention is applied to the production of high performance secondary batteries suitable for high speed charging and charging.

Claims

[Range of request]

[Claim 1]

Current collector;

A graphene layer stacked on the current collector;

An aggregate layer of self-assembled electrode active material nanoparticles laminated on the graphene layer; An electrode comprising a carbon layer laminated on the collector layer.

[Claim 2]

The electrode according to claim 1, wherein a plurality of layers and a carbon layer of electrode active material nanoparticles are further stacked on the carbon layer.

[Claim 3]

The electrode according to claim 1, wherein the electrode active material nanoparticles have a diameter of 5 nm-100 nm.

[Window 4]

The electrode according to claim 1, wherein the size of the aggregates of the electrode active material nanoparticles included in the aggregate layer is 100 nm-3000 nm.

[Claim 5]

The electrode according to claim 1, wherein the thickness of the aggregate layer of the electrode active material nanoparticles is 500 nm to 20 mi.

[Claim 6]

The method according to claim 1, wherein the electrode active material is Si, Sn, Li ₄ Ti ₅ 0 ₁₂ , Sn0 ₂ , Ti0 _2> Fe ₂ 0 ₃₎ Fe ₃ 0 _4> C03O4, or a mixture thereof; At least one alloy selected from the group consisting of Si, Sn, Ti, Cu, Al, Ce and La; LiMn ₂ 0 ₄ , V ₂ 0 ₅ , LiCo0 ₂ , LiNi0 ₂ , LiFeP0 ₄ ,

LiFeP0 ₄ . LiNi _! _y Co _y 0 ₂ , Li [Ni _1/2 Mn _1/2 ] 0 ₂ or a combination thereof; Mg ²⁺ , Al ³⁺ ,

LiFeP0 ₄ , Li [Nii _/ sCoi _/ sMni _/ slOz, Li [Ni _1/2 Mn _1/2 ] 0 ₂ , LiNi doped with Ti ⁴⁺ , Zr ⁺ , Nb ⁵⁺ , W ⁶⁺ to below 1 ¾ _h CoA, LiNi-Ji ^ Mgx _/ or an electrode, characterized in that at least one selected from the group consisting of these.

[Claim 7]

The electrode of claim 1, wherein the carbon layer is a graphene layer, a carbon nanotube layer, or a mixed layer in which graphene and carbon nanotubes are mixed.

[Claim 8]

The electrode according to claim 1, wherein the aggregates of the electrode active material nanoparticles included in the aggregate layer are spherical, dough-shaped, elliptical, or a combination thereof.

[Claim 9]

The electrode according to claim 7, wherein the carbon nanotubes are single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, or a mixture thereof.

[Claim 10]

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

[Claim 11]

An electrochemical capacitor comprising the electrode of claim 1.

[Claim 12]

Forming a laminated structure by electrically spraying a graphene dispersion solution, an electrode active material nanoparticle dispersion solution, and a dispersion solution for forming a carbon layer on a current collector in order; And

A method of manufacturing an electrode comprising the step of pressing the laminated structure.

[Claim 13]

The method of manufacturing an electrode according to claim 12, further comprising forming a multilayer structure by electrospraying the electrode active material nanoparticle dispersion solution and the dispersion solution for forming a carbon layer in a plurality of times before the pressing step. .

[Claim 14]

The method of claim 12, further comprising, after the pressing step, heat treating the compressed laminated structure.

[Claim 15]

The solvent of claim 12, wherein the solvent of the graphene dispersion solution, the electrode active material nanoparticle dispersion solution, and the carbon layer-forming dispersion solution has a boiling point of 80 ° C. or lower, or a boiling point of 80

A method for producing an electrode, characterized in that the solvent mixture containing 50% by weight or more of the solvent of not more than ° C.

[Claim 16]

The method of claim 12, wherein the electrode active material nanoparticle injection solution comprises 0.5 to 20% of the electrode active material.