KR20110017219A - Coin cell lithium metal capacitor and manufacturing method of the same - Google Patents

Abstract

PURPOSE: A coin cell lithium metal capacitor and a manufacturing method of the same are provided to implement high energy density by applying a lithium metal to a thin film cathode. CONSTITUTION: An anode case(300) and a cathode case are mutually interlocked to form a coin shape. . An anode(305) comprises an activated carbon inducing adsorption/desorption of lithium ions to/from the anode case. The cathode case comprises alkali metal or alkali metal or alkaline earth metals containing lithium metal or lithium alloy. The thin film cathode guides adsorption of lithium ions, causing solution or extraction of the lithium ions An electrolyte is interposed between the thin film cathode and the anode.

Description

Coin cell lithium metal capacitor and manufacturing method of the same}

The present invention relates to an energy storage device, and more particularly, to a coin cell lithium metal capacitor (LMC) and a manufacturing method.

As the electrical, electronics, telecommunications, computer industry, and automobile industry spread, and portable devices developed, the importance of energy storage devices capable of repeatedly charging and discharging electricity is increasing. As energy storage devices, capacitors are being developed in various forms depending on the type of electrolyte, whether the anode and cathode are symmetrical and the charge storage characteristics. For example, an electric double layer capacitor (EDLC) has a high output and a long life, but has a relatively high power, but is used as a backup power supply or an auxiliary power supply for a secondary battery due to a low specific energy density and a low use voltage limit. It is becoming. In order to achieve high voltage by connecting capacitors in series with low withstand voltage characteristics, deterioration of capacitor characteristics is accompanied by reduction of capacitance.

Research is underway to improve the capacitor with high energy density, high output, long life and stability. For example, attempts have been made to increase the breakdown voltage and increase the energy density by lowering the cathode potential by using a polarizable electrode for the positive electrode and introducing a prior process such as a lithium pre-doping process for the negative electrode. Nevertheless, a considerable long time is required for lithium doping of the negative electrode, and uniform lithium doping of the entire negative electrode is difficult. In addition, it has been difficult to put a high capacity capacitor into practical use, such as a cylindrical capacitor in which an electrode is wound, or a multilayer capacitor in which a plurality of electrodes are stacked.

The present invention is to propose a coin cell lithium metal capacitor and a manufacturing method having a high voltage characteristic, an output characteristic and a high energy density, which can improve the stability and reliability.

One aspect of the present invention, the positive electrode case and the negative electrode case which is mutually fastened to form a coin (coin); A cathode including activated carbon capable of inducing and adsorbing lithium ions on the cathode case; A thin-film negative electrode including an alkali metal or an alkaline earth metal including lithium metal or a lithium alloy on the negative electrode case, wherein the lithium ion is dissolved or precipitated to cause adsorption of the lithium ions to the positive electrode; And a coin cell lithium metal capacitor including an electrolyte introduced between the thin film anode and the anode.

The electrolyte includes a liquid electrolyte or a polymer electrolyte containing a salt of the lithium ions, and the lithium ion concentration in the electrolyte is increased by dissolution of the lithium ions from the negative electrode in a voltage range of less than or equal to an open circuit voltage, thereby allowing the positive electrode. Adsorption of the lithium ions is induced, the lithium ions and anions are dielectrically separated in the electrolyte in the voltage range above the open circuit voltage, the lithium ions are deposited on the negative electrode and the negative ions are adsorbed on the positive electrode and discharged The lithium ions may be dissolved into the electrolyte from the negative electrode and the anions may be released from the positive electrode to maintain a ratio of the lithium ions and the ions in the electrolyte.

A separator introduced into the electrolyte; And the thin film cathode presents a coin cell lithium metal capacitor deposited on the separator surface.

The separator may include a porous polymer film or a porous nonwoven fabric.

The lithium alloy may be an alloy in which lithium is alloyed with aluminum (Al), calcium (Ca), potassium (K), or sodium (Na).

The thin film cathode may be formed to a thickness of several μm to several tens of μm.

The anode may be formed of high specific surface area activated carbon having a specific surface area of 100 m ² / g to 3000 m ² / g.

The positive electrode is a non-porous activated carbon having a specific surface area of 100 m ² / g or less including a conductive polymer active material capable of adsorption or desorption of lithium ions, single-walled carbon nanotubes (SWNT), multi-walled carbon nanotubes (MWNT) or It may include an active material of double-walled carbon nanotubes (DWNT).

Another aspect of the invention, forming a positive electrode including activated carbon that can induce the adsorption-desorption of lithium ions on the positive electrode case; A thin film including an alkali metal or an alkaline earth metal including lithium metal or a lithium alloy on a cathode case corresponding to the cathode case, wherein the lithium ions are dissolved or precipitated to induce adsorption of the lithium ions to the anode. Forming a cathode; Introducing an electrolyte between the positive electrode and the thin film negative electrode; And forming a coin-type cell by sealing and fastening the cathode case and the anode case with a gasket to form a coin cell lithium metal capacitor.

The forming of the thin film cathode may include directly depositing the thin film cathode on the cathode case.

The forming of the thin film cathode may include preparing a separator to be inserted on the cathode case and the cathode case; Depositing the thin film cathode directly on the separator; And introducing the separator onto the cathode case such that the thin film anode contacts the anode case.

The introducing of the electrolyte may include impregnating the positive electrode and the thin film negative electrode with a liquid electrolyte; And inserting a separator into the liquid electrolyte.

The electrolyte may be inserted as a solid electrolyte or a gel electrolyte between the anode and the thin film cathode.

According to the present invention, a coin cell lithium metal capacitor having a high voltage characteristic, a high output characteristic, and a high energy density can be implemented. By applying lithium metal as a thin film cathode, a high cell voltage can be realized by a low reduction potential of lithium. By depositing lithium on a foil, case or separator itself, contact resistance can be greatly reduced. By depositing the negative electrode on a material that is not reactive with lithium, the negative electrode manufacturing process can be simplified, and the negative electrode can be manufactured in a uniform thin film to suppress local dendritic precipitation.

In addition, by applying the lithium metal to the thin film anode, it is possible to omit the lithium ion pre-doping process can reduce the process step, it is possible to form a cell without being limited in size and shape. In addition, the magnetic discharge is low, the stability during use is high, and the mechanical and chemical bonding between the interface is superior to the energy storage device using the lithium bulk electrode, the resistance is low and the charge and discharge efficiency is high.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

A coin cell lithium metal capacitor according to an embodiment of the present invention includes an activated carbon-based positive electrode in which lithium ions are adsorbed and desorbed, and a negative electrode of a lithium thin film in which lithium ions are dissolved to provide lithium ions to an electrolyte. The negative electrode is made of a thin film of lithium metal, and is used as a matrix for supplying lithium ions to an electrolyte by application of a voltage or for depositing lithium ions from the electrolyte on a thin film. Lithium ions dissolved from the negative electrode of the lithium metal thin film are supplied to the electrolyte to increase the lithium ion concentration in the electrolyte, and lithium ions are adsorbed on the positive electrode by the increased lithium ion concentration gradient. As lithium ions are deposited on the lithium metal thin film, lithium ion concentration in the electrolyte is decreased, and thus lithium ions adsorbed on the positive electrode are desorbed and refluxed into the electrolyte. The adsorption and desorption of lithium ions at the anode causes discharge and charging of the capacitor.

In the lithium metal capacitor according to the embodiment of the present invention, the charging in the initial open circuit is performed by, for example, when Li ⁺ ₆ electrolyte is used, Li ⁺ and PF ₆ ⁻ of the electrolyte are deposited on the cathode and adsorbed on the anode, respectively. When discharged in a voltage range of approximately 3V to 2.2V that is less than an open circuit voltage (OCV: 3.0V), Li ⁺ ions are transferred from the lithium cathode to the activated carbon anode, that is, Li ⁺ ions alone Ions move in a shuttlecock fashion that shuttles the anode. That is, in the voltage range above the open circuit voltage OVC, for example, in the range of approximately 3.0V to 4.3V, it shows the electrolyte behavior of a typical capacitor due to the dielectric (or separation) of the electrolyte, and the voltage range below OVC, for example approximately 2.2V. In the range of 3.0 to 3.0V, ionic behavior on the electrolyte is exhibited in the same form as a lithium ion secondary battery.

Hereinafter, a coin cell lithium metal capacitor and a manufacturing method according to the present invention will be described with reference to the drawings.

1A to 1D are schematic views illustrating a lithium metal capacitor of an energy storage device according to an embodiment of the present invention. 2 to 3b are views showing a vacuum deposition apparatus.

Referring to FIG. 1A, a lithium metal capacitor includes an electrolyte 117 including a salt of lithium ions 119 and a thin film anode 105 of lithium or lithium alloy introduced into the electrolyte 117 to dissolve or precipitate lithium ions. And a thin film cathode 105, which is opposite to the thin film cathode 105 and includes a positive electrode 100 that physically adsorbs or desorbs lithium ions for charging / discharging behavior (see FIG. 1A).

As shown in FIG. 1A (b), when a voltage is applied to the anode 100 and the thin film cathode 105, the lithium metal capacitor is dissolved in lithium ions from the thin film cathode 105, thereby forming lithium in the electrolyte 117. The concentration of ions 119 is increased. As the concentration of the lithium ions 119 in the electrolyte 117 increases, the lithium ions 119 move in the direction of the anode 100, so that adsorption is induced to the anode 100. In addition, as the lithium ions 119 are deposited on the thin film cathode 105, desorption of the lithium ions 119 adsorbed to the positive electrode 100 is induced, thereby causing the charge and discharge of the capacitor. By the adsorption and desorption action of the lithium ions 119, the anode 100 has a potential of 2.2V to 4.3V.

In this case, the electrolyte 117 includes a liquid electrolyte or a polymer electrolyte including a salt of lithium ions 119. Carbonate based liquid electrolytes including, for example, propylene carbonate, ethylene carbonate, dimethyl carbonate or methyl ethyl carbonate, polyethylene oxide (PEO), PVdF copolymers including PVdF or PVdF-HFP, polymethylmethacrylate (PMMA), Gel-type electrolyte which adds a plasticizer to solid matrices, such as a polyoxo metalate (POM), a polypropylene oxide (PPO), and a polysiloxane system, can be used. The electrolyte may use a lithium salt, a metal salt or an organic salt electrolyte, and is not affected by the form of the electrolyte, such as a liquid electrolyte, a gel type electrolyte, a solid electrolyte, or an ionic electrolyte. In this case, the electrolyte 117 may further include a separator 115.

The thin film cathode 105 is formed on a foil or a current collector 120 (see FIG. 1B) or on a surface of the separator 115 (see FIG. 1C). Specifically, the thin film cathode 105 includes an alkali metal or an alkaline earth metal including lithium or a lithium alloy, and is formed by a deposition method. Here, the alkaline earth metal may include calcium, and the alkali metal may include potassium. The lithium alloy is selected from the group consisting of lithium and aluminum (Al), calcium (Ca), potassium (K) and sodium (Na) to maintain the cathode temperature characteristics in the reflow process in subsequent energy storage device fabrication. A lithium alloy alloyed with the material can be used. In this case, it is preferable that the alloy composition ratio keep the content of lithium more than 0% and less than 100%.

The thin film cathode 105 is deposited by a physical vapor deposition (PVD) method or a chemical vapor deposition (CVD) method using the deposition apparatus of FIGS. For example, sputtering method, ion-beam method, electrochemical vapor deposition (EVD) method, electron beam method, thermal evaporation and plasma spraying You can proceed by applying the method selected from the group.

In the case of using the thermal evaporation deposition apparatus of the physical vapor deposition method of FIG. 2, the lithium metal foil 210 is disposed on the boat 205 in the chamber 200, and the upper portion of the chamber 200 facing the boat 205 is disposed. The vapor deposition material 215 is disposed. A shutter 220 is disposed between the material to be deposited 215 and the boat 205. Next, after vacuuming the inside of the chamber 200, when the lithium metal foil 210 is heated, lithium atoms generated from the lithium metal foil 210 disposed on the boat 205 are adsorbed onto the deposition target material 215 to form lithium. A metal thin film is formed. The chamber 200 is vacuumed using a vacuum pump 225 connected to the chamber 200.

In addition, the thin film cathode 105 may be formed using a chemical vapor deposition apparatus including a vertical reactor (see FIG. 3A) or a horizontal reactor (see FIG. 3B). For example, the deposition material S is disposed on the susceptor 235 in the reactor 230, and a lithium-based reaction gas is supplied into the reactor 230. A lithium-based reaction gas is supplied to deposit a lithium metal thin film on the material to be deposited (S). During the supply of the reaction gas, the deposition material S inside the reactor 230 is heated from the resistance heating source 240. Then, the supplied reaction gas is pyrolyzed near the deposition material heated to a high temperature or chemical reaction occurs between the reaction gases, so that lithium material is adsorbed onto the deposition material S to form a lithium metal thin film. After the reaction, by-products or unreacted substances are discharged to the outside through the exhaust port. The thin film cathode 105 formed through the physical vapor deposition method or the chemical vapor deposition method may be formed in a single layer and a multi-layer structure to control the thickness of the cathode to be thick or thin.

The thin film cathode 105 of the present invention may be deposited by using the separator 115, the current collector 120, or a case of aluminum and stainless steel (SUS) as deposition materials. For example, referring back to FIG. 1B, the thin film cathode 105 may be formed by depositing the thin film cathode 105 on the surface of the current collector 120. Here, the current collector 120 includes copper (Cu) or nickel (Ni), which is not reactive with lithium, and the thin film cathode 105 is deposited on one or both surfaces of the current collector 120. When the thin film cathode 105 is formed on copper or nickel which is not reactive with lithium, it may be formed uniformly and simply. In addition, when forming a coin-type cell may be deposited directly on the case (SUS) material. Specific embodiments thereof will be described later.

In addition, as illustrated in FIG. 1C, the thin film cathode 105 may be deposited on one surface of the separator 115 while supplying an ion source of an alkali metal or alkaline earth metal including lithium or a lithium alloy metal. Here, the separator 115 includes a porous polymer film or a porous nonwoven fabric. In addition, as the separator 115, as shown in FIG. 1D, a solid solid electrolyte 125 may be used.

The lithium metal capacitor of the present invention of FIGS. 1A to 1D may be effectively implemented in a coin cell structure. 4A and 4B, to form a coin cell, a positive electrode 305 may be formed on the positive electrode case 300 to induce adsorption and desorption of lithium ions. Next, on the negative electrode case 315, an alkali metal or alkaline earth metal including lithium or a lithium alloy is included, and a thin film negative electrode 310 in which lithium moves to the positive electrode 305 by dissolution and precipitation reaction is formed. The thin film cathode 310 is formed to a thickness of several micrometers to several tens of micrometers by vacuum deposition, and is preferably formed to a thickness of 2 micrometers to 10 micrometers. When the thickness of the thin film anode 310 is formed to a thickness of 10 μm or less, the energy density can be improved, and the output of the cathode can be increased while suppressing dendritic precipitation of lithium. Subsequently, the separator 320 is disposed between the anode 305 and the thin film cathode 310, and the inner space 330 provided by the cathode case 300 and the cathode case 315 is sealed with a gasket 325. It is fastened to construct a coin cell.

The thin film cathode 310 may be deposited on the cathode case 315 including sus (SUS) by physical vapor deposition or chemical vapor deposition while supplying an alkali or alkaline earth metal including lithium or lithium alloy to an ion source. Can be. In this case, the lithium alloy is selected from the group consisting of lithium and aluminum (Al), calcium (Ca), potassium (K) and sodium (Na) in order to maintain the temperature characteristics of the cathode 310 in the high temperature reflow process to be performed in a subsequent process. Alloying with the selected material, the alloy composition ratio is preferably made the content of lithium more than 0%, less than 100%.

Meanwhile, the thin film cathode 310 may be formed on the surface of the separator 320 by physical vapor deposition or chemical vapor deposition to form a separator. When the thin film cathode 310 is deposited on the surface of the cathode case 315 or the separator 320, the cell may be completed by assembling only the anode 305, thereby reducing the unit cost by reducing the size of the cell. .

The separator 320 impregnates the anode 305 and the thin film cathode 310 with a liquid electrolyte, and inserts the separator 320 including a polyolefin-based material or pulp paper having a single layer or multilayer structure including polyethylene or polypropylene. 305 and the thin film cathode 310 may be opposed to each other. Alternatively, the solid electrolyte may be formed in place of the separator 320. Specifically, a gel type solid electrolyte may be disposed between the anode 305 and the thin film cathode 310 at the position of the separator 320.

Solid electrolyte is solid such as polyethylene oxide (PEO), PVdF copolymer including PVdF or PVdF-HFP, polymethyl methacrylate (PMMA), polyoxometallate (POM), polypropylene oxide (PPO), polysiloxane Gel-type electrolytes in which plasticizers are added to the matrix can be used. The electrolyte may use a lithium salt, a metal salt or an organic salt electrolyte, and is not affected by the form of the electrolyte, such as a liquid electrolyte, a gel type electrolyte, a solid electrolyte, or an ionic electrolyte.

Meanwhile, the thin film cathode 310 formed by the deposition method is deposited to a thickness of several μm to several tens of μm, and preferably to a thickness of 2 μm to 10 μm. As such, when the thin film cathode 310 is deposited to a thickness of several μm to several tens of μm, a uniform thin film surface may be realized. When lithium is used in bulk, dendrite is formed by lithium, and stability problems such as explosion and ignition occur due to internal short circuit caused by dendritic growth. In contrast, the lithium metal capacitor according to the present invention realizes a uniform thin film surface by using a thin film cathode 310 having a few μm to several tens of μm, and thus maintains a low thickness, thereby suppressing the growth of dendritic growth of lithium on the thin film surface. It can improve the stability. When the thin film anode 310 is experimentally formed to a thickness of less than 1 μm to 10 μm, dendritic growth of lithium may be suppressed.

In addition, by applying lithium metal to the thin film anode 310, the process step is reduced, and there is no limitation on the shape of the cathode, thereby improving the characteristics of the cathode itself. For example, a lithium ion capacitor is a lithium ion capacitor that uses activated carbon at the positive electrode, and graphite-based and amorphous carbon at the negative electrode. It is expected that the increase can be implemented. However, since the lithium predoping process must be preceded to cause intercalation and deintercalation of lithium ions into the graphite material, which is a negative electrode material, the production process is increased and the charge and discharge action is increased. Even if there is a problem that the stability is lowered. In contrast, the lithium metal capacitor according to the present invention can simplify the production process because the lithium pre-doping process can be omitted by applying lithium metal to the negative electrode. In addition, the lithium metal capacitor according to the present invention implements a withstand voltage of 4V to 4.3V has improved withstand voltage characteristics than the lithium ion capacitor.

In addition, in the case of a lithium ion capacitor, there was a limitation in using propylene carbonate (PC) having the lowest viscosity and high dielectric constant characteristics among carbonate electrolytes by using graphite as a negative electrode material. However, the lithium metal capacitor of the present invention may use propylene carbonate as lithium metal is used as the negative electrode material.

The thin film anode 310 formed of lithium thus formed increases the total potential of the cell by lithium having the lowest reduction potential among all metals while maintaining the potential of the anode 305 including activated carbon. For example, the lithium metal capacitor of the present invention has a 4.3 V-class potential characteristic formed by the potential difference between the positive electrode and the negative electrode during charge and discharge. The energy density calculated by this is the voltage is improved by the formula of 1/2 * CV ² can be obtained more than twice the energy density improvement compared to the existing 2.7V class. In addition, it is possible to make the thickness of the cathode remarkably thin through the capacity balancing of lithium having a specific capacity of 3861 mAh / g and an activated carbon anode having a specific capacity of 50 mAh / g to 70 mAh / g, so that most of the electrode volume of the actual cell can be filled with the positive electrode. The size of the cell can be reduced. Thereby, regardless of the cell shape, it can be formed in a chip shape, a cylindrical shape, or a pouch type in addition to the coin shape.

In addition, the capacitance of the electric double layer capacitor (EDLC) having a symmetrical electrode is ^{_{C total = 1 / 2C + =}} 1 / 2C - a. On the other hand, the lithium metal capacitor of the present invention has a very high specific capacity and the capacitance becomes C _total = C ⁺ according to the application of lithium having a flat potential to the cathode, so the capacitance of the conventional double layer capacitor (EDLC) is improved by 2 times. Has a capacity value. Thus, the problem of the electric double layer capacitor can be improved while having an improved capacitance value than the electric double layer capacitor. For example, the cathode of an electric double layer capacitor exhibits capacity by inducing adsorption and desorption of ions using porous activated carbon having a large specific surface area. In this case, the negative electrode needs a binder, and as the binder deteriorates at a high voltage, a lifespan decreases and a resistance increases. However, since the lithium metal capacitor of the present invention does not use a binder by depositing lithium metal as a cathode, such a problem may be prevented.

Next, the anode 305 includes activated carbon having a surface area from which metal ions are adsorbed or desorbed from 100 m ² / g to 3000 m ² / g, non-porous activated carbon or carbon nanotube having a surface area of 100 m ² / g or less. Here, the non-porous activated carbon has a specific surface area of 100 m ² / g or less and exhibits capacitive expression by defects in the grain boundaries of carbon and by the edges of the hexagonal mesh layer formed on the defects. In this case, the activated carbon is activated carbon that has been reactivated for phenol, palm or coal tar pitch carbon material, carbon material, graphite material, amorphous carbon material, carbon nanotube, petroleum or coal carbon material. It may include. Carbon nanotubes include single-walled carbon nanotubes (SWNT; Single-wall NanoTube), multi-walled carbon nanotubes (MWNT; Multi-wall Nanotube) or double-walled carbon nanotubes (DWNT). In addition, the anode 305 is an active material material capable of inducing ions by using a carbon material or a conductive polymer and a mixture thereof having a particle diameter of carbon nanotubes or a layer between the carbon nanotubes as an ion storage structure. It may include.

The positive electrode 305 is adhered onto a sheet or coated with a positive electrode active material selected from the above materials on an aluminum foil or a mesh type current collector by using a slurry coating method. It is produced in the form. When formed on the current collector, 50% to 100% by weight of the positive electrode active material, 0% to 30% by weight of carbon black-based conductive material, and 0% to 30 by weight of polymer binder involved in binding and formation of the electrode It is desirable to adjust the ratio to%.

The separators 115 and 320 contained in the electrolyte (117 of FIG. 1A) and inserted between the anodes 100 and 305 and the cathodes 105 and 310 include a porous polymer film or a porous nonwoven fabric. For example, the separators 115 and 320 have a thickness of 5 μm to 50 μm, a pore size of 0.03 μm to 1 μm, and a single layer or multilayer structure including polyethylene or polypropylene having 20% to 60% porosity. Polyolefin separator and pulp paper. Furthermore, a copolymer containing crosslinked polyvinylidene fluoride or crosslinked polyvinylidene fluoride (PVdF), a porous membrane made of acrylonitrile resin, a vinylidene fluoride hexafluoropropylene (PVdF-HFP) copolymer, and a polyolefin resin Materials containing cation exchange resins, paraamide polymer-based porous films, para-aromatic polyamides, materials containing heat-resistant nitrogenous aromatic polymers and ceramic powders, and polyolefin resins containing atactic polypropylene. Selected from the group consisting of a porous film as an essential component, a composition containing a low molecular weight polyethylene and a high melting point polymer, a polyphenylene sulfide nonwoven fabric, a hydrophilic polyolefin microporous membrane and a fiber melt-spun from polyvinyl alcohol and polyolefin containing an alkali metal Material may be included.

As described above, the coin cell lithium metal capacitor to which the positive electrode including the activated carbon of the present invention and the thin film negative electrode including the lithium or the lithium alloy are applied has the following characteristics.

First, the anode has a high voltage value of 3.0V to 3.3V in the open circuit compared to the cathode potential, and shows a stable voltage curve up to 4.3V during charging after capacitor formation. Referring to Figure 5 showing the data measured the voltage capacity of the lithium metal capacitor according to the present invention, stable electric double layer capacity expression behavior by the cyclic voltammetry at a scan rate of 10mV / sec in the 2V to 4V region This appears, it can be confirmed that the physical adsorption, desorption of activated carbon occurs. The weak point of horizontal inflection point around 3V depending on the potential can be seen as the phenomenon that the adsorption and desorption behavior of lithium (Li +) ions to the anode at the potential of 3V or less and the anion behavior at the potential after 3V are separated. . This voltage value is 1V or more higher than the threshold voltage of 2.7V to 2.8V of the supercapacitor. Accordingly, when most capacitors are used in a power system combined with a lithium secondary battery, a voltage drop circuit should be formed or used as a series module of two cells or more, but the lithium metal capacitor of the present invention can be implemented as a single cell. Therefore, a small cell structure can be formed.

Next, the lithium metal capacitor of the present invention has a high energy density. Lithium has a specific capacity of 3861 mAh / g and activated carbon has a specific capacity of about 50 to 70 mAh / g in the 3.0 V to 4.2 V range. Since the negative electrode is substantially made of lithium, it is possible to suppress a decrease in specific amount due to incorporation into activated carbon, so that a significant large specific amount of lithium can be directly used to contribute to an increase in energy density and an increase in capacitance. . That is, the capacity (C-) of the cathode is considerably larger than that of the anode (C +), and the capacitance (Ctotal) of the entire cell is C + by the formula 1 / Ctotal = 1 / C + + 1 / C-. have.

Accordingly, the total cell capacitance (Ctotal) of the electric double layer capacitor applying activated carbon to both the positive electrode and the negative electrode becomes 1 / 2C, whereas the lithium metal capacitor of the present invention has twice the capacity. In addition, by maximizing the cathode / anode ratio (N / P Ratio) in which the anode is formed 55 to 75 times thicker than the cathode due to the large specific capacity difference, the capacitance value is nearly doubled as the ratio of the anode increases. have. Therefore, the lithium metal capacitor of the present invention can obtain a capacitance value four times higher than that of an electric double layer capacitor (EDLC), and the energy density of about 8 times is approximated by an energy density equation (E = 1/2 * CV ² ). Has

As described above, lithium metal capacitors have a high capacity retention capability. Referring to FIG. 6, which shows data of measuring capacity retention ratio of a lithium metal capacitor according to an exemplary embodiment of the present invention, even when the lithium metal capacitor is operated up to 1000 cycles, it may be confirmed that a capacity reduction phenomenon hardly occurs.

Subsequently, the lithium metal capacitor of the present invention has a low resistance characteristic. In EDLC, a polymer binder is used as a binder and a binder for both the positive electrode and the negative electrode, which acted as a resistance. In addition, activated carbon, which is an active material of a positive electrode and a negative electrode, causes a decrease in electron conductivity of the material itself due to the development of countless pores. On the other hand, the lithium metal capacitor of the present invention does not use a binder for the negative electrode, and uses an alkali metal or alkaline earth metal containing lithium or lithium alloy as the negative electrode material and deposits metal ions on the case or the separator itself. Greatly decreases. In addition, it is possible to lower the electrical resistance in the horizontal axis direction by forming a thin layer of the cathode through the thinning of the electrode. Thin film technology can promote adhesion of the electrode-electrolyte interface, which keeps the surface of the compound clean, thereby reducing the interface resistance, and facilitates the deposition of thin films of alkali metals such as lithium.

Next, the lithium metal capacitor according to the present invention can simplify the manufacturing process. For example, an electric double layer capacitor (EDLC) is a process in which both the negative electrode and the positive electrode are coated with a binder, a conductive material, a mixed slurry of an active material or a high viscosity paste, and a sheet-shaped electrode is bonded to form an electrode. On the other hand, the present invention can be formed by a large-scale quantitative deposition method using a copper or nickel that is not reactive with lithium, it is possible to simply form a uniform thin film. In addition, as the lithium metal is applied, the lithium ion pre-doping process, which causes intercalation of lithium ions into the graphite, such as a lithium ion capacitor, is omitted, thereby lowering the process cost and advantageous for mass production as the process step is reduced. Because of its size and shape constraints, it is possible to produce not only medium and large capacitors but also small capacitors. In addition, the lithium metal capacitor of the present invention may be formed in a coin cell structure, a chip or a pouch cell structure.

Table 1 shows the results of comparing the energy density, output density and voltage of the lithium metal capacitor according to the embodiment of the present invention with the super capacitor, the lithium ion capacitor, and the lithium ion battery.

division  Super capacitor  Lithium ion capacitor  Lithium ion battery  Lithium metal capacitors Applicable size   Small to large   Medium to Large  Small to large  Small to large Energy density [Wh / kg]     5   20    150    30 Power density [kW / kg]    3.8   3.8 or higher   1.7   4.0 or higher Voltage [V]   0 to 2.7   2.2 to 3.8   3.7  2.2 to 4.3

Referring to Table 1, the lithium metal capacitor according to the present invention exhibits a working voltage of 2.2V to 4.3V compared to other storage devices. This is higher than the threshold voltage value of 0V to 2.7V for supercapacitors, 2.2V to 3.8V for lithium ion capacitors and 3.7V for lithium ion batteries. Accordingly, when most capacitors are used in a power system combined with a lithium secondary battery, a voltage drop circuit is formed or two or more cells are used as a series module. However, the lithium metal capacitor according to the present invention may be implemented as a single cell.

For example, the capacity of an electric double layer capacitor when manufacturing X series modules is 1 cell by 1 / C _total = 1 / C ₁ + 1 / C ₂ + 1 / C ₃ ... + 1 / C _x Has a 1 / X value of capacitance. The lithium metal capacitor of the present invention requires the number of cells at the level of 1/2 of the existing cells when the same voltage is generated in the module by the high voltage of 4.3V. This reduces the volume of the serial module system by nearly half and achieves twice the energy density of the serial module in the same volume. In other words, compared to an electric double layer capacitor, the energy density can be improved by 16 times or more when manufacturing a module, thereby reducing the amount of auxiliary materials consumed when manufacturing the module, and saving both the design cost and the process cost of the series circuit.

The lithium metal capacitor according to the present invention has a capacitance higher than that of an electric double layer capacitor in which both the positive electrode and the negative electrode are both activated carbon, as the specific capacity of lithium is directly applied to the negative electrode.

In addition, the lithium metal capacitor according to the present invention has a small capacity change rate according to the current. Referring to FIG. 7, which is a graph measuring a potential profile of time and voltage according to a discharge rate, a potential profile of a lithium metal capacitor (FIG. 7B) is equal to a potential profile of an electric double layer capacitor (FIG. 7A). It shows the change rate of discharge time according to similar discharge rate. The measurement graph of FIG. 7 shows that the lithium metal capacitor according to the embodiment of the present invention may exhibit an effect that can be realized in the electric double layer capacitor. That is, since the discharge time is constantly maintained in proportion to the current increase ratio according to the applied current, it can be predicted that the capacity change rate according to the current is small.

Experimental results shown in Figures 5 to 7 are the results measured by the test lithium metal capacitor according to an embodiment of the present invention. The test lithium metal capacitor used for the measurement is manufactured by introducing a 100 μm thick positive electrode and a 2 μm thick negative electrode. In this case, the cathode is prepared by depositing a thin film by a deposition method using an electron beam (E-beam) using a lithium-aluminum alloy containing lithium in a range of 90% to 100%.

The electrolyte is prepared by dissolving a salt of LiPF ₆ in 1.0 M propylene carbonate (PC). The anode electrode is manufactured using 87 wt% of activated carbon, 10 wt% of Super P Black (SPB), and 3 wt% of binder of polytetrafluoroethylene (PFTE). In the case of coin cell type capacitors, a sheet electrode using a kneading method using dough is manufactured. In the case of a chip type capacitor, a slurry using 85 wt% activated carbon, 10 wt% conductive material, and 5% wt binder is used. The slurry is mixed and coated to prepare an electrode. In this case, polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), polyvinylpyrrolidone (PVP), or the like is used as the binder.

The fabricated test capacitor deposits lithium on the lithium cathode through the discharge to the initial 2.2V and then charges and discharges in the 4.3V region to measure the capacitor behavior according to the charge and discharge. At this time, the charge and discharge current density is set to 1mA / F.

Lithium metal capacitor according to the present invention is not limited in size and shape, low self-discharge, high stability during use, excellent mechanical and chemical bonding between interfaces compared to lithium bulk electrode, very high battery efficiency, The thin film process can be applied, which is very advantageous for mass production.

1A to 1D are schematic views illustrating a lithium metal capacitor according to an embodiment of the present invention.

2 to 3b are views showing a vacuum deposition apparatus.

4A and 4B are diagrams illustrating a coin cell lithium metal capacitor and a manufacturing method.

5 is a graph measuring the capacity retention rate of a lithium metal capacitor.

6 is a graph measuring the capacity retention rate of a lithium metal capacitor.

7 is a graph measuring the potential profile of time and voltage according to discharge rate.

Claims (13)

An anode case and a cathode case fastened to each other to form a coin shape; A cathode including activated carbon capable of inducing and adsorbing lithium ions on the cathode case; A thin-film negative electrode including an alkali metal or an alkaline earth metal including lithium metal or a lithium alloy on the negative electrode case, wherein the lithium ion is dissolved or precipitated to cause adsorption of the lithium ions to the positive electrode; And A coin cell lithium metal capacitor comprising an electrolyte introduced between the thin film anode and the anode. The method of claim 1, The electrolyte includes a liquid electrolyte or a polymer electrolyte containing a salt of the lithium ions, The lithium ion concentration in the electrolyte is increased by dissolving the lithium ions from the negative electrode in the voltage range below the open circuit voltage, so that the adsorption of the lithium ions to the positive electrode is induced. Lithium ions and anions are dielectrically separated in the electrolyte in a voltage range above the open circuit voltage, and when charged, the lithium ions precipitate on the negative electrode and the anions adsorb on the positive electrode, and during discharge, the lithium ions are discharged from the negative electrode. The coin cell lithium metal capacitor is dissolved in the solution and the anion is released from the positive electrode to maintain the ratio of the lithium ion and the ion in the electrolyte. The method of claim 1, A separator introduced into the electrolyte; And And the thin film cathode is deposited on the surface of the separator. The method of claim 3, The separator is a coin cell lithium metal capacitor comprising a porous polymer film or a porous nonwoven fabric. The method of claim 1, The lithium alloy is a coin cell lithium metal capacitor in which lithium is alloyed with aluminum (Al), calcium (Ca), potassium (K) or sodium (Na). The method of claim 1, The thin film cathode is a coin cell lithium metal capacitor formed to a thickness of several ㎛ to several tens of ㎛. The method of claim 1, The anode is a coin cell lithium metal capacitor formed of high specific surface area activated carbon having a specific surface area of 100m ² / g to 3000m ² / g. The method of claim 1, The positive electrode is a non-porous activated carbon having a specific surface area of 100 m ² / g or less including a conductive polymer active material capable of adsorption or desorption of lithium ions, single-walled carbon nanotubes (SWNT), multi-walled carbon nanotubes (MWNT) or A coin cell lithium metal capacitor comprising an active material of double wall carbon nanotubes (DWNT). Forming a positive electrode including activated carbon on the positive electrode case to induce adsorption and desorption of lithium ions; A thin film anode including an alkali metal or an alkaline earth metal including lithium metal or a lithium alloy on a cathode case corresponding to the cathode case, wherein the lithium ions are dissolved or precipitated to induce adsorption of the lithium ions to the anode. Forming a; Introducing an electrolyte between the positive electrode and the thin film negative electrode; And Sealing the positive electrode case and the negative electrode case with a gasket and forming a coin-type cell by fastening. 10. The method of claim 9, Forming the thin film cathode is And depositing the thin film cathode directly on the cathode case. 10. The method of claim 9, Forming the thin film cathode is Preparing a separator to be inserted onto the cathode case and the anode case; Depositing the thin film cathode directly on the separator; And And introducing the separator on the positive electrode case such that the thin film negative electrode contacts the positive electrode case. 10. The method of claim 9, Introducing the electrolyte Impregnating the positive electrode and the thin film negative electrode into a liquid electrolyte; And A method of manufacturing a coin cell lithium metal capacitor comprising inserting a separator into the liquid electrolyte. 10. The method of claim 9, The electrolyte is A method of manufacturing a coin cell lithium metal capacitor inserted into a solid electrolyte or a gel electrolyte between the cathode and the anode.

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