KR100830611B1 - Hybrid capacitor, and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a hybrid capacitor, and more particularly, a positive electrode including a positive electrode active material; A negative electrode including a negative electrode active material; And an electrolyte present between them, and the cathode active material relates to a hybrid capacitor comprising a compound capable of reversible intercalation / deintercalation of lithium.

By using a compound capable of reversible intercalation / de-intercalation of lithium as the cathode active material, it is possible to conserve excess energy for a long time, thereby eliminating the problems caused when using activated carbon alone as a cathode active material of a conventional capacitor. As a result, the energy density and the output density are improved to enable the manufacture of a high-capacity, long-life and high-capacity hybrid capacitor.

Hybrid Capacitor, Coprecipitation Method, Carbonate Coprecipitation, Cathode Active Material, Energy Density, Power Density

Description

HYBRID CAPACITOR, AND METHOD FOR MANUFACTURING THE SAME

1 is a schematic diagram of a hybrid capacitor according to an embodiment of the present invention.

2 is a diagram illustrating the energy storage principle of a hybrid capacitor.

Figure 3 is an embodiment of _{Li [Ni 1/3 Co 1} /3 Mn 1/3] Field emission scanning electron micrograph of the O ₂ prepared in 1 (6000 times magnification).

Figure 4 is produced in Example 1, the Li _{[Ni 1/3 Co 1/} 3 Mn 1/3] The field emission scanning electron microscope (15,000 times enlarged) of O _2.

Figure 5 is a transmission electron micrograph of Li _{[Ni 1/3 Co 1/} 3 Mn 1/3] O 2 produced in Example 1.

Figure 6 is a X- ray diffraction patterns of the _{Li [Ni 1/3 Co 1} /3 Mn 1/3] O 2 produced in Example 1.

7 is prepared in Example 2 Li [Ni Mn _{0 .5 1 .5]} O _{3.95 0 .05} S of the field emission scanning electron micrograph (6000 times magnification).

8 is prepared in Example 2 Li [Ni Mn _{0 .5 1 .5]} O _{3.95 0 .05} S of the field emission scanning electron microscope (enlargement 7000 X).

Figure 9 is a Li [Ni Mn _{0 .5 1 .5]} O _3.95 X- ray diffraction pattern of S _{0 .05} prepared in Example 2.

10 is a graph showing charge and discharge curves of the first cycle of the hybrid capacitor prepared in Example 1 and the electric double layer capacitor prepared in Comparative Example 1. FIG.

11 is a graph showing the life characteristics according to the cycle change of the hybrid capacitors prepared in Example 2 and Comparative Example 2.

FIG. 12 is a graph showing specific discharge capacity according to a cycle of the hybrid capacitor prepared in Example 1 and the electric double layer capacitor prepared in Comparative Example 1. FIG.

FIG. 13 is a graph showing the self discharge amount with time of the hybrid capacitor prepared in Example 1 and the electric double layer capacitor prepared in Comparative Example 1. FIG.

14 is a graph showing a change in the leakage current with time of the hybrid capacitor prepared in Example 1 and the electric double layer capacitor prepared in Comparative Example 1. FIG.

[Industrial use]

The present invention relates to a hybrid capacitor, and more particularly, to a hybrid capacitor of high rate, long life, and high capacity by improving energy density and power density.

[Private Technology]

A nonaqueous electrolyte-based electric double layer capacitor is a capacitor that stores electric energy by using a principle of absorbing and desorbing electric charges at an electric double layer generated at an interface between an electrode and an electrolyte, and thus can be charged and discharged with a large current. Accordingly, it is promising as an energy storage device for electric vehicles and auxiliary power sources.

Conventional nonaqueous electrolyte-based electric double layer capacitors are composed of positive and negative polarizable electrodes and nonaqueous electrolyte mainly composed of carbonaceous materials such as activated carbon. Although the nonaqueous electrolyte-based electric double layer capacitor has a high voltage resistance, it is known that the composition of the non-aqueous electrolyte has a large influence on the capacitance. The non-aqueous electrolyte solution is composed of an electrolyte salt and a non-aqueous organic solvent, and various combinations of these electrolyte salts and non-aqueous organic solvents have been studied to date.

For example, as the electrolyte salt, a quaternary ammonium salt (Japanese Patent Application Laid-Open No. 61-32509, Japanese Patent Application Laid-Open No. 63-173312, Japanese Patent Application Laid-Open No. 10-55717, etc.) or a fourth phosphonium salt (Japanese Patent Laid-Open No. 62) -252927 and the like are widely used due to their wide solubility, dissociation degree and electrochemical stability in organic solvents. Moreover, the example which used the dialkyl imidazolium salt which is an ionic liquid as electrolyte salt is also reported (Japanese Unexamined-Japanese-Patent No. 6-61095, Japanese Unexamined-Japanese-Patent No. 2002-110472).

Conventional electric double layer capacitors are one type of capacitor, in which an electrode active material layer is formed on a metal foil current collector to form an electrode, and is wound between a pair of the electrodes via a separator. The electric double layer capacitor is advantageous in that it is small in size, large in capacity, can withstand charge discharge, and has a low environmental load in terms of materials used.

Accordingly, electric double layer capacitors are used for backing up memory of electronic devices such as video and audio, auxiliary power when replacing batteries in mobile devices, and storage power for clocks and indicator devices using solar cells. In recent years, small size, high capacity, and large current are utilized, and it is expected as a starting power source for small motors and cell motors of automobiles and electronic devices.

The electrode of the electric double layer capacitor having such various uses has high energy through a large specific surface area, high power through a low specific resistance, and electrochemical stability through suppression of an electrochemical reaction at an interface.

To this end, Korean Patent Publication Nos. 10-2005-0088181 and 10-2006-0001658 propose polarizable electrodes prepared by coating activated carbon in a predetermined pattern. In addition, Korean Patent Publication No. 10-2005-0056971 suggested that an ionic liquid of a quaternary ammonium salt and a quaternary phosphonium salt having at least one alkoxyalkyl group as a substituent is used as an electrolyte.

Therefore, the inventors of the present invention do not use the above-described approach, but a hybrid of a positive electrode similar to a lithium secondary battery and a negative electrode of an electric double layer capacitor type by using a cathode active material for a lithium secondary battery in which one electrode has high capacity and high rate characteristics. Propose a capacitor.

An object of the present invention is to provide a hybrid capacitor having a high rate, a long life and a high capacity characteristic by not only the excess energy can be maintained for a long time, but also the energy density and the output density are improved.

In order to achieve the above object, the present invention

A positive electrode including a positive electrode active material; A negative electrode including a negative electrode active material; And an electrolyte present between them,

The cathode active material provides a hybrid capacitor including a compound capable of reversible intercalation / deintercalation of lithium.

Compounds capable of reversible intercalation / deintercalation of lithium are lithium composite metal oxides or lithium-containing chalcogenide compounds.

Preferably, the positive electrode active material comprises at least one metal of Ni, Co or Mn, optionally Mg, Al, Cr, V, Ti, Cr, Fe, Zr, Zn, Si, Y, Nb, Ga, It includes one metal selected from the group consisting of Sn, Mo, W, and combinations thereof.

At this time, the positive electrode active material in the presence of carbonic acid gas at least one of a nickel salt, cobalt or manganese solution containing a metal salt aqueous solution, a basic chelating agent and a basic aqueous solution simultaneously to prepare a metal carbonate precipitate;

Drying or heat treating the metal carbonate precipitate to prepare a metal precursor; And

After mixing the metal precursor and the lithium salt, it is prepared through a heat treatment step.

Hereinafter, the present invention will be described in more detail.

As the active material of the positive electrode and the negative electrode of the conventional capacitor, a carbon material such as activated carbon is most widely used. The carbon material has a characteristic of long life in fast charging and discharging, but has a property of not storing a lot of energy, and has a disadvantage of not storing the stored energy for a long time. Accordingly, in the present invention, a hybrid capacitor including a cathode active material which can not only store excess energy but also preserve stored energy for a long time by supplementing the shortcomings of the carbon material is manufactured.

1 is a schematic diagram of a hybrid capacitor according to an embodiment of the present invention. Referring to FIG. 1, a capacitor 3 is prepared by arranging a separator 3 between a positive electrode 6, a negative electrode 8, and a positive electrode 6 and a negative electrode 8. 5) is injected so that the positive electrode 6, the negative electrode 8, and the separator 3 are impregnated with the electrolyte 5. At this time, the positive electrode 6 and the negative electrode 8 serve to collect current generated during the action of the battery, and the conductive lead members 2 and 4 are attached to the positive electrode 6 and the negative electrode 6 and 8, respectively. The generated current is induced to the positive and negative terminals.

The hybrid capacitor shown in FIG. 1 is one embodiment, and the hybrid capacitor of the present invention is not limited to this shape, and any shape capable of acting as a capacitor is possible.

The hybrid capacitor according to the present invention includes a positive electrode including a positive electrode active material; A negative electrode including a negative electrode active material; And an electrolyte present therebetween, and a compound capable of reversible intercalation / deintercalation of lithium is used as the cathode active material. At this time, a carbon material is used as the negative electrode active material.

Preferably, the compound capable of reversible intercalation / deintercalation of lithium is a lithium composite metal oxide or a lithium-containing chalcogenide compound.

More preferably, the positive electrode active material comprises at least one metal of Ni, Co or Mn, optionally Mg, Al, Cr, V, Ti, Cr, Fe, Zr, Zn, Si, Y, Nb, One metal selected from the group consisting of Ga, Sn, Mo, W, and combinations thereof.

Most preferably, the cathode active material may be a compound represented by Formula 1 or 2 below:

[Formula 1]

Li _a Ni _{1 -xy- z} Co _x Mn _y M _z O _{2 -δ} P _δ

(In Formula 1, M is one element selected from the group consisting of Mg, Al, Cr, V, Ti, Cr, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo and W, P is an element selected from F or S, and 0.95 ≦ a ≦ 1.2, 0 ≦ x ≦ 0.5, 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.3, and 0 ≦ δ ≦ 0.1.)

[Formula 2]

Li _a Ni _x Co _y Mn _{2 -xy- z} M _z O _{4 -δ} P _δ

(In Formula 2, M is one element selected from the group consisting of Mg, Al, Cr, V, Ti, Cr, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo and W, P is an element selected from F or S, and 0.95≤a≤1.2, 0≤x≤0.5, 0≤y≤0.5, 0≤z≤0.3 and 0≤δ≤0.1.)

At this time, the positive electrode active material is a spinel compound having a cubic crystal structure.

The cathode active material has a particle size of 20 to 500 nm, thereby increasing the surface area of particles of the cathode active material and the electrolyte, thereby improving capacity and life characteristics even when rapid charging and discharging is achieved. If the particle size of the positive electrode active material is less than the above range, the particles aggregate to increase the particle size, and if the particle size exceeds the above range, the low specific surface area decreases the high rate characteristic and the service life characteristics, making it inappropriate for use as an active material of a capacitor. .

Such a positive electrode active material has a specific surface area of at least 3 m ² / g or more, and preferably has a specific surface area of 3 to 100 m ² / g. If the size of the specific surface area is less than the range, the high rate characteristic and the service life characteristic are significantly degraded.

Therefore, the positive electrode active material of the present invention is a lithium transition metal composite oxide containing Ni, Co, or Mn, and greatly improves the low specific discharge and self discharge rate, which are disadvantages of the activated carbon of the conventional electric double layer capacitor, to design a hybrid capacitor with excellent performance. can do.

Such a positive electrode active material,

Simultaneously mixing an aqueous metal salt solution, a basic chelating agent and a basic aqueous solution containing at least one nickel, cobalt or manganese in the presence of carbonic acid gas to a reactor to prepare a metal carbonate precipitate;

Drying or heat treating the metal carbonate precipitate to prepare a precursor; And

After mixing the precursor and the lithium salt, it is prepared through a heat treatment step.

First, carbon dioxide gas is injected into the reactor in the step of preparing a metal carbonate precipitate, and then, a metal precipitate solution, a basic chelating agent and a basic aqueous solution containing at least one of nickel, cobalt or manganese are mixed in the reactor to obtain a metal precipitate. .

The aqueous metal salt solution is prepared by adding at least one nickel salt, cobalt salt and manganese salt to a solvent. At this time, the aqueous metal salt solution is optionally selected from the group consisting of Mg, Al, Cr, V, Ti, Cr, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W and combinations thereof It may further comprise a salt comprising.

As the metal salt, sulfates, nitrates, acetates, halides, and the like may be used, and are not particularly limited, as long as they can be dissolved in water.

In addition, the aqueous metal salt solution is nickel, cobalt, manganese, and Mg, Al, Cr, V, Ti, Cr, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W and The molar ratio of one metal selected from the group consisting of these is adjusted and mixed. This molar ratio can be easily calculated according to the metal composition of the positive electrode active material to be obtained.

It is preferable that the density | concentration of the said metal salt aqueous solution is 1M-3M. As the basic chelating agent, an aqueous ammonia solution, an aqueous ammonium sulfate solution, a mixture thereof, and the like may be used. It is preferable that the molar ratio of the said basic chelating agent and the metal salt aqueous solution is 0.05-0.5: 1.

When the molar ratio of the basic chelating agent is 0.05 to 0.5 moles with respect to 1 mole of the metal aqueous solution, the basic chelating agent reacts with the metal at least 1 to 1 to form a complex, but the complex is mixed with a basic aqueous solution such as caustic soda. This is because the basic chelating agent remaining after the reaction can be converted into an intermediate product and recovered and used as a basic chelating agent, which is also an optimal condition for increasing and stabilizing crystallinity of the positive electrode active material.

As the basic aqueous solution, one or more selected from the group consisting of Na ₂ CO ₃ , K ₂ CO ₃ , and NH ₄ HCO ₃ can be used.

It is preferable to use the thing of 2M-4M as the density | concentration of the said basic aqueous solution.

The aqueous metal salt solution, the basic chelating agent and the basic aqueous solution as described above are mixed in the presence of carbon dioxide gas to be converted to the metal carbonate, which is precipitated to the bottom of the reactor to prepare a metal carbonate precipitate. The carbon dioxide gas injected at this time creates an atmosphere in which the metal precipitate is made of carbonate.

At this time, the reaction is adjusted to a pH of 5 to 9, and carried out at a temperature of 30 to 80 ℃ to obtain a high-density composite metal carbonate. The reaction is carried out for 4 to 30 hours, preferably 4 to 12 hours, and the coprecipitation reaction gives a steady state duration for the reactants after the reaction reaches steady state to obtain a denser complex metal carbonate precipitate. Can be. At this time, the stirring is performed at a speed of 500 to 2000 rpm, and the pH is adjusted by further adding a basic solution.

The reactor in which such co-precipitation reaction is carried out may be a conventional reactor used in this field, but is not limited in the present invention. Typically, a reactor having 1 to 4 baffles inside the reactor, a cylinder for uniformly mixing the upper and lower portions of the reactor core portion, and a reactor equipped with a stirring device having a reverse wing rotary blade. desirable. The baffle is to control the intensity and direction of the material when mixing the respective reactants, to increase the turbulent effect to solve the local non-uniformity of the reaction solution, located 2 to 3 cm from the inside of the reactor. By using such a reactor, the tap density of the composite metal carbonate coprecipitation compound obtained after the coprecipitation reaction is improved by about 10% or more. As a result, the tap density of the prepared composite metal carbonate is 1.0 g / cm 3 or more, preferably 1.25 g / cm 3 or more, and more preferably 1.5 g / cm 3 or more.

Next, the metal carbonate precipitate obtained in the above step is filtered using a conventional filtration apparatus and then dried or heat treated to obtain a metal precursor. In this case, when only drying is performed, the metal precursor maintains a carbonate form, and when the heat treatment is performed, the metal precursor is converted into an oxide form.

The drying is performed for 5 to 18 hours at 50 to 120 ℃, the heat treatment is carried out for 5 to 15 hours at 400 to 600 ℃.

Next, the cathode active material according to the present invention is prepared by heat-treating the mixture obtained from the metal precursor and the lithium salt obtained in the above step.

In this case, the lithium salt may be one selected from the group consisting of lithium nitrate, lithium acetate, lithium carbonate, lithium hydroxide, and combinations thereof.

The lithium salt is mixed with the metal precursor in a molar ratio of 0.4: 1 to 2.5: 1, in which the mixing is not particularly limited in the present invention and may be both conventional wet mixing or dry mixing.

Optionally a salt comprising sulfur or fluoride is further mixed in addition to the metal precursor and lithium salt. Salts containing the fluoride may be NH ₄ F, HF, AHF (Anhydrous hydrogen fluoride) and the like.

The sulfur or fluoride added is mixed with a metal precursor: lithium salt: sulfur or fluoride in a molar ratio of 1: 0.4: 0 to 1: 2.5: 0.05.

The heat treatment is performed for 10 to 30 hours in an oxidizing atmosphere of 700 to 1100 ℃, it may further comprise a pre-baking and annealing process if necessary. At this time, the oxidizing atmosphere during the heat treatment is performed by introducing oxygen or air containing oxygen.

The prebaking may be performed for 2 to 5 hours at 300 to 550 ° C. for a mixture of the metal precursor and the lithium salt before the heat treatment process. In addition, the annealing process may be performed at 600 to 750 ° C. for 5 to 20 hours after the heat treatment process.

The cathode active material manufactured through the above steps is prepared by mixing a conductive agent and a binder to prepare a composition for forming a cathode, and then applying the composition to a cathode current collector such as aluminum foil and rolling the hybrid capacitor according to the present invention. It is made of anode.

In this case, the conductive agent may be used as long as it is an electron conductive material without causing chemical change, and examples thereof include metals such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, copper, nickel, aluminum, and silver. Powder, metal fiber or the like.

In addition, the binder is not particularly limited in the present invention, it is possible to be commonly used in this field. Typically, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylene (PE), polypropylene (PP), fluororubber, and the like are possible.

Meanwhile, the negative electrode of the hybrid capacitor according to the present invention includes a negative electrode active material, a conductive agent, and a binder, and is manufactured in the same process as the positive electrode.

At this time, activated carbon is used as the negative electrode active material. The activated carbon is preferably activated carbon in which a carbon material is modified by steam activating treatment, molten KOH activating treatment, or the like, and examples thereof include palm shell activated carbon, phenol based activated carbon, petroleum coke based activated carbon, and the like. May be used alone or in combination of two or more thereof.

The separator usable in the hybrid capacitor according to the present invention is polyethylene nonwoven fabric, polypropylene nonwoven fabric, polyester nonwoven fabric, polyacrylonitrile porous separator, poly (vinylidene fluoride) hexafluoropropane copolymer porous separator, cellulose porous separator, kraft If the separator is generally used in the field of batteries and capacitors, such as paper or rayon fibers, it is not particularly limited.

Meanwhile, as the electrolyte to be charged in the hybrid capacitor according to the present invention, a nonaqueous electrolyte or a known solid electrolyte may be used, and a lithium salt is used.

The lithium salt is not particularly limited as a lithium salt commonly used in capacitors, for example, LiPF ₆ , LiBF ₄ , LiClO ₄ , Li (CF ₃ SO ₂ ) ₂ , LiCF ₃ SO ₃ , LiSbF _6, or LiAsF ₆ Etc.

Although the solvent of the said non-aqueous electrolyte is not specifically limited, Cyclic carbonates, such as ethylene carbonate, a propylene carbonate, butylene carbonate, vinylene carbonate; Chain carbonates such as dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate; Esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate and γ-butyrolactone; Ethers such as 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,2-dioxane and 2-methyltetrahydrofuran; Nitriles such as acetonitrile; Amides, such as dimethylformamide, etc. can be used.

As the electrolyte, a gel polymer electrolyte in which an electrolyte solution is impregnated with a polymer electrolyte such as polyethylene oxide or polyacrylonitrile, or an inorganic solid electrolyte such as LiI and Li ₃ N can be used.

2 is a diagram illustrating an energy storage principle of a hybrid capacitor.

Referring to FIG. 2, the hybrid capacitor according to the present invention includes a positive electrode 10 similar to a lithium secondary battery and a negative electrode 20 in the form of an electric double layer capacitor, so that the lithium ion 40 is formed on the positive electrode 10. Energy charging and discharging is performed by a Faraday reaction allowing insertion and desorption by redox and redox, and the negative electrode 20 allows the negative electrode 50 to accumulate in the electrolyte.

Specifically, during discharge, lithium ions 40 in the electrolyte are present in the bulk of the positive electrode 10, and when charging is performed, the lithium ions 40 emerge from the bulk and form a double layer at the interface of the negative electrode 20. To form.

In the conventional electric double layer capacitor, both the negative electrode and the positive electrode are activated carbon, and when charged, cations in the electrolyte move to the surface of the negative electrode and the negative ions move to the surface of the positive electrode to store energy.

In contrast, the hybrid capacitor according to the present invention deintercalates lithium ions 40 inside the cathode active material at the time of charging and moves to the surface of the cathode 20 through the electrolyte. The lithium ions 40 thus moved are adsorbed on the surface of the cathode 20 to store energy.

Accordingly, the positive electrode active material of the present invention can store high energy by deintercalation reaction of lithium ions with adsorption reaction of a conventional electric double layer capacitor with a high specific surface area, and can also lower the self-discharge rate.

As described above, the present invention uses a compound capable of reversible intercalation / deintercalation of lithium as a positive electrode active material to increase the reaction area with the electrolyte, thereby increasing capacity and life characteristics even when fast charging and discharging is achieved. It is preferably used as.

Hereinafter, although an Example of this invention is given and this invention is demonstrated in detail, this invention is not limited to these Examples.

EXAMPLE

( Example  One) Li [ Ni _{One / 3} Co _{One / 3} Mn _{One / 3} ] O ₂  Containing a positive electrode active material hybrid  Capacitor

Positive electrode active material

Nickel sulfate, cobalt sulfate and manganese sulfate were mixed in a molar ratio of 1: 1: 1 to prepare an aqueous metal solution of 2.4 M concentration. In addition, the aqueous ammonia solution was 4.8 M, Na ₂ CO ₃ aqueous solution was prepared at a concentration of 2.4 M.

4L of distilled water was added to the coprecipitation reactor (capacity 4L, the output of the rotary motor more than 80W), and carbon dioxide gas was supplied to the reactor at a rate of 0.5 liter / min to remove dissolved oxygen and to maintain the reactor temperature at 50 ° C. Stirred at rpm.

In the coprecipitation reactor, a metal aqueous solution was continuously added to the reactor at 0.3 liter / hour and an aqueous ammonia solution at 0.03 liter / hour. At this time, the pH was adjusted to maintain a pH of 7.5 by supplying a Na ₂ CO ₃ aqueous solution.

Subsequently, co-precipitation reaction was performed by adjusting the impeller speed of the reactor to 1000 rpm. At this time, the flow rate was adjusted so that the average residence time of the solution in the reactor was about 6 hours. After the reaction had reached a steady state, a steady state duration was given to the reactant for 10 hours to obtain a metal carbonate precipitate having a higher density.

The obtained metal carbonate precipitate was filtered, washed with water and dried in a warm air dryer at 110 ° C. for 15 hours. After continuously heating at a temperature increase rate of 1 ° C./min, the mixture was maintained at 500 ° C. for 10 hours to obtain a metal precursor.

Next, the mixture was mixed with lithium nitrate (LiNO ₃ ) in a 1: 1.15 molar ratio with the metal precursor and the lithium salt, and then heated at a temperature increase rate of 2 ° C./min, followed by primary firing at 280 ° C. for 10 hours. Next, to prepare a laminate was dried at 850 ℃ 20 sigan calcined, Li lithium composite metal oxide of _{[Ni 1/3 Co 1/} 3 Mn 1/3] O 2 for 10 hours annealing at 600 ℃.

Capacitor

The lithium composite metal oxide prepared in _{(Li [Ni 1/3 Co} 1/3 Mn 1/3] O 2) , and a conductive agent of acetylene black, a binder a 80:10 polyvinylidene fluoride (PVDF): Slurry was prepared by mixing at a weight ratio of 10. The slurry was uniformly applied to an aluminum foil having a thickness of 20 μm, and vacuum dried at 120 ° C. to prepare a positive electrode for a hybrid capacitor.

The capacitor anode prepared above was used, activated carbon was used as a counter electrode, a porous polyethylene membrane (Celgard ELC, Celgard 2300, thickness: 25 µm) was used as a separator, and LiBF ₄ was 1 in propylene carbonate solvent. Coin-type hybrid capacitors were manufactured according to a commonly known manufacturing process using a liquid electrolyte dissolved in M concentration.

( Example  2) Li [ Ni _{0 .5} Mn _{One .5} ] O _3.95 S _{0 .05}  Containing a positive electrode active material hybrid  Capacitor

Positive electrode active material

Nickel sulfate and manganese sulfate were mixed in a molar ratio of 1: 3 to prepare an aqueous metal solution of 2.4 M concentration.

4L of distilled water was added to the coprecipitation reactor (capacity 4L, the output of the rotary motor more than 80W), and carbon dioxide gas was supplied to the reactor at a rate of 0.5 liters / minute, thereby removing dissolved oxygen and maintaining the temperature of the reactor at 50 ° C. Stir at 1000 rpm.

In the coprecipitation reactor, a metal aqueous solution was continuously added to the reactor at 0.3 liter / hour, and a 4.8 M aqueous ammonia solution at 0.03 liter / hour. At this time, the pH was adjusted to maintain a pH of 7.5 by supplying an aqueous solution of Na ₂ CO ₃ for pH adjustment.

Subsequently, co-precipitation reaction was performed by adjusting the impeller speed of the reactor to 1000 rpm. At this time, the flow rate was adjusted so that the average residence time of the solution in the reactor was about 6 hours. After the reaction had reached a steady state, a steady state duration was given to the reactant for 10 hours to obtain a metal carbonate precipitate having a higher density.

The obtained metal carbonate precipitate was filtered, washed with water and dried in a warm air dryer at 110 ° C. for 15 hours. After continuously heating at a temperature increase rate of 1 ° C./min, the mixture was maintained at 500 ° C. for 10 hours to obtain a metal precursor.

Next, the metal precursor, lithium nitrate (LiNO ₃ ) and sulfur were mixed at a molar ratio of 1.05: 2: 0.05, and then heated at a temperature increase rate of 2 ° C./min, followed by primary firing at 500 ° C. for 10 hours. It was. Next, it was prepared 12 hours after baking, by 20 hours annealing at 700 ℃ Li of the lithium complex _{[Ni 1/3 Co 1/} 3 Mn 1/3] O 2 metal oxide in 1000 ℃.

Capacitor

Prepared in the above as a cathode active material _{Li [Ni 0 .5 Mn 1 .5} ] O 3.95 S 0. _A hybrid capacitor was manufactured in the same manner as in Example 1, except that ₀₅ was used.

( Comparative example  1) electricity Double layer  Capacitor

Using two activated carbons as electrodes, a porous polyethylene membrane (Celgard LLC, Celgard 2300, thickness: 25 µm) was used as a separator, and a liquid electrolyte in which LiBF ₄ was dissolved at a concentration of 1 M in a propylene carbonate solvent was used. A coin type electric double layer capacitor was manufactured in the same manner as in Example 1.

( Comparative example  2) hybrid  Capacitor

This was carried out in the same manner as in Example 2, except that nitrogen gas was used instead of carbon dioxide, 4.8 M aqueous NaOH solution instead of 2.4 M aqueous Na ₂ CO ₃ solution, and the pH was maintained at 11 instead of 7.5. by co-precipitation _{Li [Ni 0 .5 Mn 1 .5} ] O 3.95 S 0. ₀₅ was manufactured, and a hybrid capacitor was manufactured using the same.

( Experimental Example  One) Li [ Ni _{One / 3} Co _{One / 3} Mn _{One / 3} ] O ₂  Physical property analysis

The physical properties of the compound prepared in Example 1 were measured using a field emission scanning electron microscope (FE-SEM), a transmission electron microscope (TEM) and an X-ray diffractometer.

3 is performed, and Example 1, _{Li [Ni 1/3 Co 1} /3 Mn 1/3] The field emission of O ₂ a scanning electron microscope manufactured by picture (6000-fold magnification), Figure 4 is an enlarged photograph 15,000 times. 5 is a transmission electron microscopic photo of _{Li [Ni 1/3 Co 1} /3 Mn 1/3] O 2 produced in Example 1.

A 3 to Referring to Figure 5, prepared in Example _{1 Li [Ni 1/3 Co} 1/3 Mn 1/3] O 2 is to check that it has particles of a spherical, nano-scale of 100 to 500 nm It can be seen that it has a particle size of. The specific surface area at this time was measured to be about 5.3 m ² / g.

Figure 6 is a X- ray diffraction patterns of the _{Li [Ni 1/3 Co 1} /3 Mn 1/3] O 2 produced in Example 1.

6, (006) and (102) peak separation, (018) and (110) peak separation are well shown in the diffraction peaks of the powder, and the compound from the (003) and (104) peak ratios of 1 or more. Has a hexagonal-NaFeO ₂ structure having a space group R-3m, and it can be seen that it is a layered compound having excellent crystallinity.

( Experimental Example  2) Li [ Ni _{0 .5} Mn _{One .5} ] O _3.95 S _{0 .05} Physical property analysis

The physical properties of the compound prepared in Example 2 were measured using a field emission scanning electron microscope (FE-SEM) and an X-ray diffractometer.

7 is a second embodiment of Li prepared from _{[Ni 0 .5 Mn 1 .5]} O 3.95 _{0 .05} S of the field emission scanning electron micrograph (6000 times magnification), Figure 8 is an enlarged photograph 15,000 times.

7, the Li prepared in Example 2, and when referring to Fig. _{8 [Ni 0 .5 Mn 1 .5} ] O 3.95 S 0. ₀₅ may be confirmed to have spherical particles as in Example 1, it can be seen that the particle size of the nano-level to 100 to 500 nm. The specific surface area at this time was measured to be about 4.8 m ² / g.

9 is an X- ray diffraction patterns of the Li [Ni Mn _{0 .5 1 .5]} O S _{0 .05 3.95} prepared in Example 2. Referring to FIG. 9, (533) and (622) peak separations are well shown in the diffraction peaks of the powder, the peak ratio of (111) and (311) is close to 2, and the peaks of (311) and (400) are almost similar. It can be seen that the spinel compound having a cubic (Cubic) crystal structure having a space group Fd3m.

 ( Experimental Example  3) lifespan characteristics

(One) Example  1 lesson Comparative example  Comparison of 1

In order to determine the characteristics of the hybrid capacitor manufactured in Example 1 and the electric double layer capacitor manufactured in Comparative Example 1, an electrochemical analyzer (Toyo System, Toscat 3100U) was used in a 0.2 to 2.2 V region for a hybrid capacitor. In the case of the electric double layer capacitor, the characteristics of the capacitor were evaluated in the 0 to 2.7 V region, and the obtained results are shown in FIG. 10.

10 is a graph showing charge and discharge curves of the first cycle of the hybrid capacitor manufactured in Example 1 and the electric double layer capacitor prepared in Comparative Example 1. FIG.

10, a hybrid capacitor using a _{Li [Ni 1/3 Co 1} /3 Mn 1/3] O 2 as active materials for positive electrode in accordance with the present invention (Example 1) The electric double layer capacitor using activated carbon (Comparative Example It can be seen that it has a high energy density compared to 1). This result is because the cathode active material of the present invention has a high particle size compared to activated carbon as the nanoparticle size has a small capacity decrease even in a fast discharge.

(2) Example  2 and Comparative example  2, comparison

In order to determine the charge and discharge characteristics of the hybrid capacitors manufactured in Examples 2 and 2, the characteristics of the capacitors were evaluated in the 1.5 to 2.8 V region using an electrochemical analyzer (Toyo System, Toscat 3100U). Is shown in FIG. 11.

11 is a graph showing the life characteristics according to the cycle change of the hybrid capacitors prepared in Example 2 and Comparative Example 2.

Referring to FIG. 11, each cycle has a different discharge current density, and the value has a discharge current density of 32, 80, 160, 320, 800, and 1600 mA / g.

 Specifically, the hybrid capacitor using the positive electrode active material synthesized by the carbonate co-precipitation method according to the present invention (Example 2) is a hybrid capacitor using the positive electrode active material synthesized by the hydroxide co-precipitation method at a high discharge current density (Comparative Example 2) It is much better than that.

Furthermore, when the specific discharge capacity is 100% when discharged at a current density of 32 mA / g, the difference is low at low current density (80 to 320 mA / g) but high current density (800 to 1600 mA / g) It can be seen that the hybrid capacitor using the positive electrode active material synthesized by the carbonate coprecipitation method shows excellent performance.

These results show that the cathode active material synthesized by carbonate co-precipitation according to the present invention is more suitable for a hybrid capacitor than the cathode active material synthesized by the hydroxide co-precipitation method.

( Experimental Example  4) Capacity Characteristics

0.2 to 2.2 V region for a hybrid capacitor using an electrochemical analyzer (Toyo System, Toscat 3100U) to determine the capacitance characteristics of the hybrid capacitor prepared in Example 1 and the electric double layer capacitor prepared in Comparative Example 1 In the case of the electric double layer capacitor, charging and discharging were performed in the region of 0 to 2.7 V to evaluate the characteristics of the capacitor at 15C, and the obtained results are shown in FIG. 12.

FIG. 12 is a graph showing specific discharge capacity according to a cycle of the hybrid capacitor prepared in Example 1 and the electric double layer capacitor prepared in Comparative Example 1. FIG.

Referring to FIG. 12, it can be seen that the hybrid capacitor (Example 1) according to the present invention has an excellent capacity compared to the electric double layer capacitor (Comparative Example 1). Although there is a slight capacity reduction after 300 cycles in the hybrid capacitor, it is not significant.

( Experimental Example  5) Self discharge characteristic

In order to determine the self-discharge characteristics of the hybrid capacitor manufactured in Example 1 and the electric double layer capacitor manufactured in Comparative Example 1, an electrochemical analyzer (Toyo System, Toscat 3100U) was used, up to 2.2 V for the hybrid capacitor, After fully charged to 2.7 V in the case of the electric multilayer capacitor, self-discharge characteristics were observed for 72 hours without applying current, and the obtained results are shown in FIG. 13.

FIG. 13 is a graph showing the self discharge amount with time of the hybrid capacitor prepared in Example 1 and the electric double layer capacitor prepared in Comparative Example 1. FIG.

Referring to FIG. 13, the hybrid capacitor according to the present invention (Example 1) had a self-discharge of 11.6% with a voltage retention of 88.4% after 72 hours, but the voltage retention of an electric double layer capacitor (Comparative Example 1) was increased. At 60.3%, 39.7% of self-discharge occurred. This result means that the hybrid capacitor of Example 1 maintains its potential for a long time even after a long time.

( Experimental Example  6) Leakage current characteristic

To determine the leakage current characteristics of the hybrid capacitor manufactured in Example 1 and the electric double layer capacitor manufactured in Comparative Example 1, using an electrochemical analyzer (Toyo System, Toscat 3100U), up to 2.2 V for the hybrid capacitor, In the case of the electric double layer capacitor, after fully charging to 2.7 V, the current leakage degree was measured by maintaining the charging voltage for 3 hours, and the obtained result is shown in FIG. 14.

14 is a graph showing a change in the leakage current with time of the hybrid capacitor manufactured in Example 1 and the electric double layer capacitor prepared in Comparative Example 1. FIG.

Referring to FIG. 14, the hybrid capacitor according to the present invention (Example 1) required a current close to 0% of the initial current compared to the initial current for maintaining the voltage for 3 hours, but the electric double layer capacitor (Comparative Example 1 ) Maintained about 25% of the initial current after 3 hours to maintain the charging voltage. These results show that the hybrid capacitor of Example 1 has an excellent energy storage preservation characteristic compared to the electric double layer capacitor, and also has a small current required to maintain a charged potential.

All simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

As described above, according to the present invention, a hybrid capacitor using a compound capable of reversible intercalation / deintercalation of lithium as a cathode active material and using activated carbon as a cathode active material was prepared. As the cathode active material has a particle size of nano level and has a large specific surface area and excellent high rate characteristics, a hybrid capacitor having high capacity, high efficiency, and long lifespan can be manufactured.

Claims (18)

A positive electrode including a positive electrode active material; A negative electrode including a negative electrode active material; And an electrolyte present between them, Hybrid electrode comprising a compound capable of reversible intercalation / deintercalation of lithium represented by the formula (1) or (2). [Formula 1] Li _a Ni _1-xyz Co _x Mn _y M _z O _2-δ P _δ (In Formula 1, M is one element selected from the group consisting of Mg, Al, Cr, V, Ti, Cr, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo and W, P is an element selected from F or S, and 0.95 ≦ a ≦ 1.2, 0 ≦ x ≦ 0.5, 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.3, and 0 ≦ δ ≦ 0.1.) [Formula 2] Li _a Ni _x Co _y Mn _2-xyz M _z O _4-δ P _δ (In Formula 2, M is one element selected from the group consisting of Mg, Al, Cr, V, Ti, Cr, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo and W, P is an element selected from F or S, and 0.95≤a≤1.2, 0≤x≤0.8, 0≤y≤0.8, 0≤z≤0.3, and 0≤δ≤0.3.) The method of claim 1, The compound capable of reversible intercalation / deintercalation of lithium is a lithium composite metal oxide or a lithium-containing chalcogenide compound. The method of claim 2, And the compound capable of reversible intercalation / deintercalation of lithium comprises at least one Ni, Co or Mn. The method of claim 2, Compounds capable of reversible intercalation / deintercalation of lithium include Mg, Al, Cr, V, Ti, Cr, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W and these Hybrid capacitor further comprising one metal selected from the group consisting of. delete The method of claim 1, The lithium composite metal oxide has a particle size of 20 to 500 nm hybrid capacitor. The method of claim 1, The lithium composite metal oxide has a specific surface area of 3 to 100 m ² / g hybrid capacitor. Preparing a metal carbonate precipitate by simultaneously mixing an aqueous metal salt solution, a basic chelating agent and a basic aqueous solution containing at least one nickel, cobalt or manganese in the presence of carbonic acid gas into a reactor; Drying or heat treating the metal carbonate precipitate to prepare a metal precursor; And After mixing the metal precursor and the lithium salt, a method of manufacturing a hybrid capacitor for producing a positive electrode active material through a process comprising the step of heat treatment. The method of claim 8, The metal salt aqueous solution is a method of producing a hybrid capacitor having a concentration of 1 M to 3 M. The method of claim 8, The metal salt aqueous solution may further include one element selected from the group consisting of Mg, Al, Cr, V, Ti, Cr, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, and combinations thereof. Method for producing a hybrid capacitor comprising a salt comprising a. The method of claim 8, The metal salt aqueous solution is a method for producing a hybrid capacitor comprising a salt selected from the group consisting of sulfate, nitrate, acetate, halide, hydroxide and combinations thereof. The method of claim 8, The basic aqueous solution is a method for producing a hybrid capacitor comprising one selected from the group consisting of Na ₂ CO ₃ , K ₂ CO ₃ , NH ₄ HCO ₃ and combinations thereof. The method of claim 8, The basic aqueous solution is a method for producing a hybrid capacitor having a concentration of 2 M to 4 M. The method of claim 8, The manufacturing method of the metal carbonate precipitate is a pH of 5 to 9 is a method for producing a hybrid capacitor. The method of claim 8, The metal carbonate precipitate is dried at 50 to 120 ℃, or a method for producing a hybrid capacitor is optionally carried out from the heat treatment at 400 to 600 ℃. The method of claim 8, The lithium salt is a method for producing a hybrid capacitor is one selected from the group consisting of lithium nitrate, lithium acetate, lithium carbonate, lithium hydroxide and combinations thereof. The method of claim 8, The heat treatment of the mixture of the metal precursor and the lithium salt comprises the steps of pre-firing at 300 to 550 ℃, firing at 700 to 1100 ℃, and annealing at 600 to 750 ℃. The method of claim 1, The negative active material is a hybrid capacitor is activated carbon.

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