KR20190053363A - Multilayer lithium-ion capacitor comprising graphene electrode - Google Patents

Abstract

The present invention relates to a multi-layered lithium-ion capacitor applying a graphene electrode. According to the present invention, the multi-layered lithium-ion capacitor comprises: a plurality of cathode electrode units formed on at least one side of a cathode, and having a plate-shaped anode current collector having a cathode terminal unit protruding to one side and previously doped with a lithium ion; a plurality of anode electrode units having an anode formed on at least one surface, and a plate-shaped anode current collector having an anode terminal unit protruding to one side, wherein the anode is a graphene electrode including reduced graphene powder as an anode active material inducing absorption and desorption of the lithium ion; and a plurality of separators each interposed between the cathode electrode units and the anode electrode units which are alternately stacked.

Description

[0001] The present invention relates to a multi-layer lithium-ion capacitor having a graphene electrode,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a super capacitor, and more particularly, to a stacked lithium ion capacitor (LIC) using a graphene electrode.

In addition to various portable electronic devices, there is a demand for electric power storage devices for electric vehicles and electric energy storage devices for systems for controlling or supplying instantaneous overload. Ni-MH Secondary batteries such as batteries, Ni-Cd batteries, lead acid batteries and lithium secondary batteries, and super capacitors, aluminum electrolytic capacitors, and ceramic capacitors having high output densities and close to unlimited charge / discharge life.

In particular, the super capacitor includes an electric double layer capacitor (EDLC), a pseudo capacitor, and a hybrid capacitor such as a lithium ion capacitor (LIC).

Here, the electric double layer capacitor is a capacitor using an electrostatic charge phenomenon occurring in an electric double layer formed at the interface of different phases, and has a faster charging / discharging speed, a higher charge / discharge efficiency than the battery in which the energy storage mechanism depends on the oxidation and reduction process, Is widely used for backup power supply, and the potential as an auxiliary power source for electric vehicles in the future is also unlimited.

A pseudocapacitor is a capacitor that converts a chemical reaction into electric energy by using an oxidation-reduction reaction of an electrode and an electrochemical oxide reactant. The pseudocapacitor has a storage capacity about 5 times larger than that of the electric double layer capacitor because the electric double layer capacitor can store the electric charge near the surface of the electrode material as compared with the electric double layer capacitor formed on the surface of the electrochemical double layer type electrode. As the metal oxide electrode material, RuOx, IrOx, MnOx and the like are used.

And the lithium ion capacitor is a new concept secondary battery system which combines the high output and long life characteristics of the existing electric double layer capacitors and the high energy density of the lithium ion battery. Electric double layer capacitors using the physical adsorption reaction of electric charges in the electric double layer have been limited in their application to various applications due to their low energy density despite excellent power characteristics and lifetime characteristics. As a means for solving the problem of such an electric double layer capacitor, a lithium ion capacitor using a carbon-based material capable of inserting and separating lithium ions as a negative electrode active material has been proposed. The lithium ion capacitor has a structure in which lithium ions, And the cell voltage can realize a high voltage of 3.8 V or more, which is much higher than that of the conventional electric double layer capacitor by 2.5 V, and can exhibit a high energy density.

When the charge mechanism of the lithium ion capacitor constituting the cathode using the lithium-ion-doped carbonaceous material is examined, electrons move from the cathode to the carbonaceous material and the carbonaceous material becomes negatively charged. Thus, In contrast, when discharging, the lithium ions inserted in the carbonaceous material are removed from the negative electrode, and anions are adsorbed to the positive electrode. By using such a mechanism, it is possible to realize a lithium ion capacitor having a high energy density by controlling the doping amount of lithium ions in the cathode.

This lithium ion capacitor is a system that combines the energy storage capacity of a lithium ion battery and the output characteristics of a capacitor. By applying a material capable of simultaneously exhibiting two functions, it exhibits capacitor characteristics when using high output power, It is a future battery system that extends to ion battery level.

Such a lithium ion capacitor uses a porous current collector to facilitate pre-doping of lithium ions to the cathode. An external terminal is joined to an internal terminal formed in the porous current collector. Ultrasonic welding is mainly used as a method of joining external terminals.

As described above, since the ultrasonic welding method is used when connecting the external terminal to the porous current collector, the porous current collector may be damaged depending on the intensity of the energy used for the ultrasonic welding. If the porous collector is damaged, the cell resistance is increased, which may lead to deterioration of the performance of the lithium ion capacitor.

Also, there may be a break between the inner terminal and the outer terminal due to the stress acting in the process of ultrasonic welding the outer terminal to the inner terminal of the porous current collector.

Korean Registered Patent No. 10-0874199 (registered on December, 2008)

Accordingly, an object of the present invention is to provide a stacked lithium ion capacitor using a graphene electrode.

Another object of the present invention is to provide a stacked lithium ion capacitor to which a graphene electrode capable of solving the problem caused by the use of a porous current collector is applied.

In order to achieve the above object, the present invention provides a lithium ion secondary battery comprising: a plurality of cathode electrode parts formed on at least one surface of a cathode, having a cathode terminal part protruded to one side and having a platelike anode current collector pre-doped with lithium ions; A positive electrode active material for inducing adsorption / desorption of lithium ions, wherein a positive electrode which is a graphene electrode including reduced graphene powder is formed on at least one surface and a positive electrode terminal portion protruded to one side is formed, ; And a plurality of separators interposed between the alternately stacked negative electrode portions and the positive electrode portions, respectively, and a stacked lithium ion capacitor to which the graphene electrode is applied.

The negative electrode and the positive electrode current collector may be aluminum foil.

The negative electrode current collector may be an aluminum foil that is etched.

Wherein the negative terminal portion includes: a plurality of first internal terminals each projecting to one side of the negative electrode current collector of the plurality of negative electrode portions; And a first external terminal bonded to the plurality of first internal terminals by ultrasonic welding.

The positive electrode terminal portion includes: a plurality of second internal terminals each projecting to one side of the positive electrode collector of the plurality of positive electrode portions; And a second external terminal bonded to the plurality of second internal terminals by ultrasonic welding.

The positive electrode terminal portion and the negative electrode terminal portion may be formed to be offset from each other.

The cathode active material may include reduced graphene powder, conductive carbon, and a binder.

The composition ratio of the reduced graphene powder, the conductive carbon, and the binder may be 90: 5: 5.

Since the stacked lithium ion capacitor according to the present invention uses a graphene electrode as an anode and the graphene electrode includes a reduced graphene powder, the manufacturing cost of the stacked lithium ion capacitor can be lowered, and excellent electricity Chemical properties.

The stacked lithium ion capacitor according to the present invention pre-dopes lithium ions into the plate-shaped current collector, not by pre-doping lithium ions into the negative electrode, thereby preventing damage to the current collector during ultrasonic welding between the internal terminal and the external terminal, The external terminals can be stably bonded.

Further, by using the plate-shaped current collector, a large area between the electrode material and the current collector is high, and high output is easy.

Also, it is easy to coat the electrode material on the plate-shaped current collector according to the present invention, compared with coating the electrode material on the conventional porous current collector in the electrode implementation.

1 is a perspective view showing a stacked cell of a stacked lithium ion capacitor according to an embodiment of the present invention.
2 is a cross-sectional view of Fig.

In the following description, only parts necessary for understanding embodiments of the present invention will be described, and descriptions of other parts will be omitted to the extent that they do not disturb the gist of the present invention.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary meanings and the inventor is not limited to the meaning of the terms in order to describe his invention in the best way. It should be interpreted as meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely preferred embodiments of the present invention, and are not intended to represent all of the technical ideas of the present invention, so that various equivalents And variations are possible.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a perspective view showing a stacked cell of a stacked lithium ion capacitor according to an embodiment of the present invention. 2 is a cross-sectional view of Fig. 1, the illustration of the separator 50 formed at the uppermost portion is omitted.

1 and 2, a stacked lithium ion capacitor 100 according to an embodiment of the present invention includes a cathode electrode unit 10, a separator 50, an anode electrode unit 20, And a stacked cell 80 in which a plurality of unit cells 70 are stacked. The cathode electrode portion 10 and the anode electrode portion 20 may further include a cathode terminal portion 19 and a cathode terminal portion 29, respectively. That is, the stacked lithium ion capacitor 100 includes a stacked cell 80 in which a plurality of cathode electrode portions 10, a plurality of anode electrode portions 20, and a plurality of separators 50 are stacked, (Not shown), and then sealed with the casing member 90. [0051] The stacked lithium ion capacitor 100 has a structure in which a separator 50 is interposed between the electrode portions 10 and 20 so that the cathode electrode portion 10 and the anode electrode portion 20 are not in contact with each other. A portion of the negative electrode terminal portion 19 and the positive electrode terminal portion 29 are protruded out of the sealing material 90 so as to be connected to an external device.

The cathode electrode unit 10 includes a cathode 12 and an anode current collector 14. The positive electrode portion 20 includes a positive electrode 22 and a positive electrode collector 24. The anode current collector 14 and the cathode current collector 24 may be made of an aluminum foil in a plate shape. In particular, the anode current collector 14 is pre-doped with lithium ions and an etched aluminum foil is used.

The negative electrode 12 includes a negative electrode active material capable of inserting and desorbing lithium ions, and is formed on the negative electrode current collector 14. The negative electrode 12 is formed on at least one layer on the negative electrode current collector 14 and one layer is formed on one side or both sides of the negative electrode current collector 14, respectively. The negative electrode current collector 14 located on both outsides of the laminated cell 80 is positioned on the inner side of the laminated cell 80 And the cathode 12 is formed on the surface facing the cathode 12, respectively. The negative electrode 12 is formed on both surfaces of the negative electrode collector 14 located inside the laminated cell 80. As the negative electrode active material, carbon-based materials such as hard carbon, soft carbon, artificial graphite, natural graphite, graphitized carbon fiber, graphitized mesocarbon microbead, petroleum coke, resinous material, carbon fiber or pyrolysis carbon can be used.

The positive electrode 22 includes a positive electrode active material capable of adsorbing and desorbing lithium ions, and is formed on the positive electrode collector 24. Since the anode 22 is formed on at least one layer on the anode current collector 24 and the anode current collector 24 is located inside the outermost cell of the stacked cell 80 in the present embodiment, An example in which one layer is formed on each of both surfaces of the support member 24 is disclosed. Here, the positive electrode 22 uses a graphene electrode containing a reduced-graphene oxide (rGO) powder as a positive electrode active material. For example, the cathode active material may include reduced graphene powder, conductive carbon, and a binder, and the composition ratio of the reduced graphene powder, the conductive carbon, and the binder may be 90: 5: 5. As the conductive carbon, an activated carbon-metal oxide composite material, a conductive polymer-activated carbon composite material, and a carbon nanotube may be used which are improved in the activated carbon material and the activated carbon material. One or more of the above cathode active materials may be used. Carbon nanotubes include single-wall carbon nanotubes (SWNTs), multi-wall nanotubes (MWNTs), or dual-wall nanotubes (DWNTs). The anode 22 is made of a carbon material or a conductive polymer that brings the layer of carbon nanotubes or a layer between the carbon nanotubes into an ion storage structure, and an active material . ≪ / RTI > On the other hand, the above-mentioned cathode active material is only one example, and the present invention is not limited thereto.

The separator 50 is interposed between the cathode electrode portion 10 and the anode electrode portion 20 to separate the cathode electrode portion 10 and the anode electrode portion 20 from each other. As the separator 50, there can be used a porous body having a communicating pore having durability against an electrolytic solution or an electrode active material, etc., and having no electron conductivity. For example, as the separator 50, a porous polymer film or a porous nonwoven fabric may be used.

The plurality of cathode electrode portions 10 and the plurality of anode electrode portions 10 are laminated via a plurality of separators 50 to form a laminated electrode portion. In the present embodiment, the laminated electrode portion has the four cathodes 12 and the positive electrodes 22, but the present invention is not limited thereto. The laminated electrode portion may include at least one layer of the cathode 12 and the anode 22 have. At this time, when the cathode 12 and the anode 22 of one layer are provided on both surfaces of the separator 50, the lithium ion capacitor of the unit cell 70 is used.

The electrolyte includes a liquid electrolyte or a polymer electrolyte containing a salt of lithium ion. As the lithium salt, LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiPF ₆ , Li (C ₂ F ₅ SO ₂ ) ₂ N and the like can be used. Examples of the solvent for dissolving the lithium salt include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate,? -Butyrolactone, acetonitrile, dimethoxymethane, tetrahydrofuran, dioxolane, The magnetic organic solvent may be used alone or in combination. (PVdF) or PVdF-HFP, polymethylmethacrylate (PMMA), polyvinylidene fluoride (PVDF), polyvinylidene fluoride (PVDF) , Polyoxometalate (POM), polypropylene oxide (PPO), and polysiloxane-based solid matrix may be used. The electrolyte may be a lithium salt, a metal salt or an organic salt electrolyte, and is not affected by the shape of the electrolyte, such as a liquid electrolyte, a gel electrolyte, a solid electrolyte or an ionic electrolyte. Here, when the electrolyte is in a liquid form, the electrolyte may further include a separator 50, but in the case of a gel electrolyte or a solid electrolyte, introduction of the separator 50 may be omitted.

The casing member 90 may be made of a metal material such as aluminum (Al), a plastic material, a composite material made of a combination of a metal material and a plastic material, and the like to protect the stacked cell 80 and prevent leakage of the electrolyte solution . In order to reduce the size and weight of the multilayer lithium ion capacitor 100, a composite material may be used as the casing member 90, and a laminate type composite film in which a polymer film such as aluminum and nylon or polypropylene is laminated may be used.

On the other hand, the negative electrode current collector 14 and the positive electrode current collector 24 each have a negative electrode terminal portion 19 and a positive electrode terminal portion 29 so as to protrude to one side. At this time, the negative electrode terminal portion 19 and the positive electrode terminal portion 29 are formed to be shifted from each other. The negative terminal portions 19 and the positive electrode terminal portions 29 formed on the plurality of the cathode electrode portions 10 and the plurality of the anode electrode portions 20 may be formed in a row at positions corresponding to each other. Wherein the internal terminals 16 and 26 include a first internal terminal 16 and a second internal terminal 26. [ The external terminal 18.28 includes a first external terminal 18 and a second external terminal 28 and one end of the external terminals 18 and 28 protrudes out of the casing member 90.

The negative electrode terminal portion 19 includes a first internal terminal 16 protruding from one side of the negative electrode current collector 14 and a first external terminal 18 bonded to the first internal terminal 16. At this time, the first internal terminal 16 is bonded to the first external terminal 18 by ultrasonic welding. The respective first internal terminals 16 formed on the plurality of cathode electrode portions 10 are collectively bonded to the first external terminals 18. [ The conductive paste may be applied to the first internal terminal 16 or the first external terminal 18.

The positive electrode terminal portion 29 includes a second internal terminal 26 protruding from one side of the positive electrode collector 24 and a second external terminal 28 bonded to the second internal terminal 26. At this time, the second internal terminal 26 is bonded to the second external terminal 28 by ultrasonic welding. Each of the second internal terminals 26 formed on the plurality of the anode electrode portions 20 is bonded to the second external terminal 28 collectively.

Since the cathode and anode current collectors 14 and 24 according to the present embodiment are plate-like, when the current collectors 14 and 24 are welded during ultrasonic welding between the internal terminals 16 and 26 and the external terminals 18 and 28, It is possible to stably bond the external terminals 18 and 28 to the internal terminals 16 and 26 while suppressing damage.

The stacked lithium ion capacitor 100 is not doped with lithium ions in the cathode 12 but is pre-doped in the plate-like anode current collector 14 so that the large area between the anode active material and the anode current collector 14 And high output is easy.

Also, it is advantageous in terms of the process of coating the electrode active material on the plate-shaped current collector 14.24 according to the present embodiment, compared to coating the electrode material on the conventional porous current collector even in the case of implementing the electrode.

On the other hand, a conductive paste can be used for good bonding between the internal terminals 16 and 26 and the external terminals 18 and 28. For example, the first internal terminal 16 is bonded to the first external terminal 18 by ultrasonic welding via a conductive paste. The respective first internal terminals 16 formed on the plurality of cathode electrode portions 10 are bonded to the first external terminals 18 through the conductive paste collectively. The conductive paste may be applied to the first internal terminal 16 or the first external terminal 18. The conductive paste is also applied between the plurality of first internal terminals 16. The conductive paste forms the bonding layer 60 between the first internal terminals 16 and between the first internal terminal 16 and the first external terminal 18. [ At this time, the conductive paste includes at least one metal powder of silver (Ag), copper (Cu), gold (Au), platinum (Pt), nickel (Ni), lead (Pb) and aluminum (Al). The second internal terminal 18 is bonded to the second external terminal 18 by ultrasonic welding via a conductive face.

In this way, the inner terminals 16 and 26 and the outer terminals 18 and 28 of the current collectors 14 and 24 are connected to the external terminals 18 and 28 through the ultrasonic welding, 28 are bonded to each other, the conductive paste absorbs the energy transmitted to the current collectors 14, 24 in the process of ultrasonic welding, so that damage to the current collectors 14, 24 can be suppressed. Further, by using the conductive paste, the contact resistance between the internal terminals 16 and 26 and the external terminals 18 and 28 and between the electrodes is lowered and the bonding strength is improved, so that the disconnection of the terminals is suppressed, It is possible.

It should be noted that the embodiments disclosed in the present specification and drawings are only illustrative of specific examples for the purpose of understanding, and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

10: cathode electrode part 12: cathode
13: lithium ion 14: anode current collector
16: first internal terminal 20: anode electrode portion
22: positive electrode 24: positive electrode collector
26: second internal terminal 30: lithium electrode part
32: Lithium 34: Lithium collector
36: lithium terminal 42: first external terminal
44: second external terminal 50: separator
60: electrolyte 70: unit cell
80: laminated cell 90: exterior material
100: stacked lithium ion capacitor

Claims (8)

A plurality of cathode electrode portions formed on at least one side of the cathode, a cathode terminal portion protruding to one side and having a platelike anode current collector pre-doped with lithium ions;
A positive electrode active material for inducing adsorption / desorption of lithium ions, wherein a positive electrode which is a graphene electrode including reduced graphene powder is formed on at least one surface and a positive electrode terminal portion protruded to one side is formed, ;
A plurality of separators interposed between the cathode electrode portions and the cathode electrode portions alternately stacked;
Wherein the graphene electrode is formed of a metal. The method according to claim 1,
Wherein the negative electrode and the positive electrode current collector are aluminum foil. The method according to claim 1,
Wherein the cathode current collector is an aluminum foil that is etched. ≪ RTI ID = 0.0 > 8. < / RTI > The light emitting device according to claim 1,
A plurality of first internal terminals protruding from one side of the anode current collector of each of the plurality of cathode electrode portions;
A first external terminal bonded to the plurality of first internal terminals by ultrasonic welding;
Wherein the graphene electrode is formed of a metal. The semiconductor device according to claim 1,
A plurality of second internal terminals each projecting to one side of the positive electrode collector of the plurality of positive electrode portions;
A second external terminal bonded to the plurality of second internal terminals by ultrasonic welding;
Wherein the graphene electrode is formed of a metal. 6. The method of claim 5,
Wherein the positive electrode terminal portion and the negative electrode terminal portion are formed to be offset from each other. The method according to claim 1,
Wherein the positive electrode active material comprises reduced graphene powder, conductive carbon, and a binder. 8. The method of claim 7,
Wherein the composition ratio of the reduced graphene powder, the conductive carbon, and the binder is 90: 5: 5.

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