KR102046418B1 - Cathode active materials for lithium ion capacitor - Google Patents

Abstract

The present invention relates to a lithium ion capacitor having excellent capacity characteristics and a high energy density. In particular, a cathode active material for a lithium ion capacitor using a carbon nanotube composite having a specific lithium metal oxide dispersed on a surface of a carbon nanotube as a cathode additive And a method for manufacturing the same, and a lithium ion capacitor including the same.

Description

Cathode active material for lithium ion capacitor {CATHODE ACTIVE MATERIALS FOR LITHIUM ION CAPACITOR}

The present invention relates to a lithium ion capacitor having excellent capacity characteristics and high energy density, and more particularly, using a carbon nanotube composite having a specific lithium metal oxide dispersed on its surface as an anode lithium source as a cathode additive. The present invention relates to a cathode active material for a lithium ion capacitor capable of electrochemically doping lithium, and a method of manufacturing the same.

With the proliferation of small portable electronic devices, new secondary batteries such as nickel-metal hydride batteries, lithium secondary batteries, super capacitors, and lithium ion capacitors have been actively developed.

Among these, a lithium ion capacitor (LIC) is a new concept of a secondary battery system combining the high power / long life characteristics of an existing electric double layer capacitor (EDLC) and the high energy density of a lithium ion battery.

Electrical double layer capacitors that use physical adsorption reactions of electrical charges in electrical double layers have limited application to a variety of applications because of their low energy density, despite their excellent output and lifetime characteristics. As a means of solving the problems of the electric double layer capacitor, a hybrid capacitor using a carbon-based material capable of inserting and desorbing lithium ions as a cathode active material has been proposed, and a carbon-based material capable of inserting and detaching lithium ions as a cathode active material is proposed. Lithium ion capacitors have been proposed.

For example, as shown in FIG. 1, an electric double layer capacitor exhibits excellent output characteristics by using adsorption and desorption of electric charge using an activated carbon material having a large specific surface area symmetrically on the anode and the cathode, but has a low energy density (Ea). There is a disadvantage of having. In contrast, hybrid capacitors use a high-capacity transition metal oxide as the anode material to increase the capacity (Eb), and lithium-ion capacitors use a carbon-based material capable of reversible insertion and removal of lithium ions as the cathode material. It is characterized by improving (Ed).

Among these, lithium ion capacitors have a greater energy density improvement than hybrid capacitors due to the use of a negative electrode material capable of inserting and detaching lithium at low potential. In particular, the lithium ion capacitor can be pre-doped the lithium ion with high ionization tendency in the negative electrode to significantly lower the potential of the negative electrode, the cell voltage is also possible to implement a high voltage of 3.8 V or more improved significantly compared to the 2.5 V of the conventional electric double layer capacitor High energy density can be expressed.

Looking at the reaction mechanism of the lithium ion capacitor constituting the negative electrode using a carbon-based material doped with lithium ions, the electrons are transferred to the carbon-based material of the negative electrode during charging, and the carbon-based material becomes negatively charged. The lithium ions inserted into the carbonaceous material of the negative electrode and, conversely, the lithium ions inserted into the carbonaceous material of the negative electrode are released during discharge, and the negative ions are again adsorbed to the positive electrode. By using such a reaction mechanism, it is possible to realize a lithium ion capacitor having a high energy density by controlling the doping amount of lithium ions at the cathode. In addition, the lithium ion capacitor is a system that combines the energy storage capacity of the lithium ion battery with the output characteristics of the capacitor. The lithium ion capacitor adopts a material capable of expressing both functions at the same time. Is a future battery system that expands to the level of lithium ion batteries.

However, such a lithium ion capacitor requires a lithium doping process for the insertion and desorption reaction of lithium as well as the electrochemical adsorption and desorption reaction. In order to realize such a lithium ion capacitor, a conventional technique of doping lithium to a negative electrode is a metal laminated by the potential difference between the negative electrode and the metal lithium only by laminating metal lithium on the electrode and then adding an electrolyte to short the negative electrode and the metal lithium. Lithium is melted into the cathode. However, in the case of the lithium doping method of laminating metal lithium on the electrode, it is difficult to control the amount of lithium doped to the negative electrode, it is difficult to secure the safety according to the lithium metal generated in the doping process, and thus difficult to apply to mass production There is a problem.

Therefore, research on the development of materials and processes for manufacturing lithium ion capacitors, which exhibits excellent energy characteristics, high output density, and lifetime characteristics as well as high energy density at high power usage and is secured to be suitable for mass production, is required.

The present invention provides a cathode active material for a lithium ion capacitor using a carbon nanotube composite including a specific lithium metal oxide as a cathode additive as a lithium source so that lithium can be doped to the cathode in an electrochemical manner without using metal lithium. To provide.

The present invention also provides a method of manufacturing the cathode active material for a lithium ion capacitor.

The present invention also provides a lithium ion capacitor including the cathode active material.

The present invention provides a cathode active material for a lithium ion capacitor including a carbon nanotube composite in which a lithium metal oxide represented by Formula 1 below is dispersed on a carbon nanotube surface.

[Formula 1]

Li _x M _y O _z

In the formula,

x, y, and z satisfy 0 <x ≦ 6, 0 <y ≦ 5, and 0 <z ≦ 10, respectively.

M is Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Tc, Ru, Rh, Pd, Ag, Cd, B, Al, Si, Ge, Sn, P, Ir, At least one member selected from the group consisting of Pt, Nb, Sb, and S

The present invention also provides a method for producing a cathode active material for a lithium ion capacitor comprising the step of forming a carbon-based nanocomposite containing lithium metal oxide by solid phase reaction, hydrothermal synthesis or chemical reduction method.

The present invention also provides a lithium ion capacitor including the cathode active material.

Hereinafter, a cathode active material for a lithium ion capacitor and a method of manufacturing the same, and a lithium ion capacitor including the same according to a specific embodiment of the present invention will be described in detail. However, this is presented as an example of the invention, whereby the scope of the invention is not limited, it is apparent to those skilled in the art that various modifications to the embodiments are possible within the scope of the invention.

In addition, unless otherwise indicated throughout the specification, "including" or "containing" refers to the inclusion of any component (or component) without particular limitation and refers to the addition of another component (or component). It cannot be interpreted as excluding.

In the present invention, the term "lithium ion capacitor" refers to the use of different asymmetric electrodes for the positive electrode and the negative electrode so that one pole uses a high capacity electrode material and the opposite pole uses a high output electrode material to improve the capacitance characteristics. The secondary battery system. Such lithium ion capacitors generally use a cathode material as a cathode material of an existing electric double layer capacitor and a carbon-based material capable of inserting and detaching lithium ions as a cathode active material, such as graphite, hard carbon, Since soft carbon and the like are used for the insertion and desorption reaction of lithium as well as the electrochemical adsorption and desorption reaction, it has the characteristics of improving the energy density per unit weight.

However, as described above, the lithium ion capacitor requires a lithium doping process not only for the electrochemical adsorption and desorption reaction but also for the insertion and desorption reaction of lithium. It is difficult to control the amount doped in, it is difficult to maintain the safety due to the lithium metal generated in the doping process.

Accordingly, the present invention significantly improves the capacity and energy density of lithium ion capacitors by efficiently adding a carbon nanotube composite containing a specific lithium metal oxide as a lithium source, and efficiently doping lithium to the cathode. It is possible to obtain a process improvement effect that is guaranteed to be safe enough for mass production.

In particular, the experimental results of the present inventors, as a lithium ion capacitor using a cathode active material comprising a carbon nanotube composite having a lithium metal oxide having a predetermined characteristic dispersed on the surface as a cathode additive, excellent capacitor characteristics at high power use As a result, it shows excellent output characteristics and lifetime characteristics with high energy density, and can replace the doping process using lithium metal, thereby ensuring excellent process safety.

Accordingly, according to one embodiment of the present invention, a cathode active material for a lithium ion capacitor including a cathode additive having predetermined characteristics is provided. The cathode active material for a lithium ion capacitor includes a carbon nanotube composite in which a lithium metal oxide represented by Chemical Formula 1 is dispersed on a surface of a carbon nanotube.

[Formula 1]

Li _x M _y O _z

In the formula,

x, y, and z satisfy 0 <x ≦ 6, 0 <y ≦ 5, and 0 <z ≦ 10, respectively.

M is Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Tc, Ru, Rh, Pd, Ag, Cd, B, Al, Si, Ge, Sn, P, Ir, Pt, Nb, Sb, and S is one or more selected from the group consisting of.

Carbon nanotubes in the present invention refers to a carbon structure having a one-dimensional structure. The carbon nanotubes have an effect of increasing dispersibility of lithium metal oxides and maintaining electrical conductivity.

The carbon nanotubes may have an average outer diameter of 500 μm or less, preferably 200 μm, more preferably 100 μm or less. The average particle size of the carbon nanotubes may be less than 10 mm in terms of length.

In addition, the carbon nanotubes may have a conductivity of 10 ¹ S / cm or more, preferably 10 ² S / cm or more, more preferably 10 ⁴ S / cm or more. The conductivity of the carbon nanotubes including the lithium metal oxide may be 10 ¹ S / cm or more.

In the cathode active material for a lithium ion capacitor of the present invention, the carbon nanotube composite has a lithium metal oxide of 0.1 to 80 parts by weight, preferably 0.2 to 80 parts by weight, and more preferably 0.3 to 40 parts by weight, based on 100 parts by weight of carbon nanotubes. It may be dispersed in the content of parts by weight.

In addition, x, y, and z in Formula 1 of the lithium metal oxide are 0 <x≤6, 0 <y≤5, and 0 <z≤10, respectively, preferably 0 <x≤6, 0 <y≤. 4, and 0 <z ≦ 4, more preferably 0 <x ≦ 6, 0 <y ≦ 2, and 0 <z ≦ 4. In addition, the metal component M which forms an oxide together with lithium in the lithium metal oxide is Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Tc, Ru, Rh, Pd, Ag, Cd, B, Al, Si, Ge, Sn, P, Ir, Pt, Nb, Sb, S and the like. Of the M, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Ni, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Ir, Pt, Nb represents a transition metal, Anode additives containing such transition metals are transition metal oxides. Among these, Mn, Ni, Fe, Co, Mo, Ru, Sn, Zr, Ir, Pt and the like are preferable for the structural aspects.

Such lithium metal oxides include Li ₂ MoO ₃ , Li ₂ MnO ₃ , Li ₂ NiO ₂ , Li ₂ PtO ₃ , Li ₂ IrO ₃ , Li ₂ RuO ₃ , Li ₂ SnO ₃ , Li ₂ ZrO ₃ , Li ₅ FeO ₄ , Li ₆ CoO ₄ , Li ₅ MnO ₄ It may be used at least one selected from the group consisting of, Li ₂ MoO ₃ , Li ₂ MnO ₃ , Li ₂ NiO _{2 ,} Li ₅ FeO ₄ , Li ₆ CoO ₄ , Li ₅ MnO ₄ Etc. are preferable in terms of cost.

The positive electrode active material for a lithium ion capacitor of the present invention is a lithium source by adding a carbon nanotube composite including a specific lithium metal oxide having a large initial irreversible capacity as a positive electrode additive and doping lithium ions to the negative electrode in an electrochemical manner. It improves the process safety according to the generation, characterized in that to improve the capacity and energy density of the capacitor.

That is, as shown in FIG. 2, the conventional lithium ion capacitor laminates lithium metal on an electrode to form a lithium source for transferring lithium ions to the cathode. However, the lithium ion capacitor of the present invention, as shown in Figure 3, by using a carbon nanotube composite in which a specific lithium metal oxide, for example, Li ₂ MoO ₃ or the like is dispersed in the positive electrode active material, a separate lithium metal laminate It is characterized in that the lithium ions can be effectively transferred to the cathode side without forming a layer.

In this respect, the lithium metal oxide used as the positive electrode additive according to the present invention may be one having various crystal structures so that lithium can be inserted and desorbed electrochemically. The lithium metal oxide is characterized by a large initial irreversible capacity can effectively dope lithium to the cathode.

In addition, the lithium metal oxide has a property of reversibly inserting or detaching lithium ions in a voltage range of 0V to 5V, preferably 2V to 5V, and more preferably 2.5V to 5V. In particular, the lithium metal oxide has a large initial irreversible capacity to supply lithium ions to the cathode in an electrochemical manner without using metal lithium.

Accordingly, the lithium metal oxide may have an initial charge and discharge efficiency (Q _E ) of 50% or less, preferably 40% or less, and more preferably 30% or less, according to Formula 1 below.

[Calculation 1]

Q _E = (Q _D / Q _C ) × 100

In the formula,

Q _E is the initial charge and discharge efficiency of the lithium metal oxide,

Q _D represents discharge capacity (mAh / g) at Li / Li + cut-off at a discharge voltage of 2.3 V,

Q _C represents the charge capacity (mAh / g) at Li / Li + cut-off at a charge voltage of 4.7 V.

As shown in FIG. 4, the initial charge / discharge efficiency (Q _E ) of the lithium metal oxide may be determined by a constant current or constant voltage method by electrochemical method under a half cell condition of lithium as a counter electrode, and at a voltage of 2.3 V. Measure discharge capacity (Q _D , mA / hr) at / Li + cut-off and charge capacity (Q _C , mA / hr) at Li / Li + cut-off at 4.7 V Can be calculated according to the above formula (1).

Here, the carbon nanotube additive including the lithium metal oxide has a discharge capacity per weight Q _D at Li / Li + cut-off at a voltage of 2.3 V of 100 mAh / g or less or 0 to 100 mAh / g , Preferably 80 mAh / g or less or 0 to 80 mAh / g, more preferably 60 mAh / g or less or 0 to 60 mAh / g. In addition, at a voltage of 4.7 V of the carbon nanotube composite including lithium metal oxide, the charge capacity per weight (Q _C ) at Li / Li + cut-off is 100 mAh / g or more or 100 to 120 mAh / g , Preferably 120 mAh / g or more or 120 to 150 mAh / g, more preferably 150 mAh / g or more or 150 to 300 mAh / g.

Initial charge and discharge efficiency (Q _E ) of the carbon nanotube composite including the lithium metal oxide and the discharge capacity per weight (Q _D , mAh / g) during Li / Li + cut-off at a voltage of 2.3 V The charge capacity per weight (Q _C , mAh / g) at Li / Li + cut-off at an overvoltage of 4.7 V is preferably maintained in the range described above in terms of capacity.

In addition, the lithium metal oxide dispersed on the surface of the carbon nanotubes may have an average particle size of 10 μm or less, preferably 1 μm or less, and more preferably 500 nm or less.

On the other hand, the carbon-based material used as the positive electrode active material for lithium ion capacitors of the present invention is characterized by a specific surface area of activated carbon, characterized in that the specific surface area is 500 m ² / g or more. The carbon-based material may be used at least one of activated carbon, activated carbon and metal oxide composite, activated carbon and conductive polymer composite, and among these, activated carbon is preferable for the conductive aspect.

The positive electrode active material for a lithium ion capacitor according to the present invention may have a composition in which a carbon-based material has a specific positive electrode additive, that is, a carbon nanotube composite in which the lithium metal oxide is dispersed on a surface thereof. In particular, the cathode active material for a lithium ion capacitor according to the present invention may include 0.5 to 80% by weight of the carbon nanotube composite and 20 to 99.5% by weight of the carbonaceous material. Preferably, the carbon nanotube composite may include 1.0 to 60% by weight of the carbon-based material and 40 to 99% by weight, and more preferably, 1.5 to 50% by weight of the carbon nanotube composite and 50 to 50% by weight of the carbonaceous material. 98.5 weight percent. Herein, the carbon nanotube composite and the carbon-based lithium may be included in an amount of 0.5 wt% or more and 99.5 wt% or less, respectively, in terms of doping amount control, and may be included in an amount of 50 wt% or less and 50 wt% or more, respectively, in terms of conductivity. The carbon nanotube composite may be uniformly mixed throughout the carbon-based material or locally mixed only in part depending on the amount added to the carbon-based material.

As described above, the cathode additive according to the present invention, that is, the carbon nanotube composite in which the lithium metal oxide of Formula 1 is dispersed on the surface may be electrochemically doped with lithium on the carbon-based anode active material, and doped lithium The ions contribute to the capacitor characteristics, lowering the cell voltage to improve the capacity and energy density of the lithium ion capacitor.

On the other hand, according to another embodiment of the present invention, a method of manufacturing a cathode active material for the lithium ion capacitor is provided. The method of manufacturing a cathode active material for a lithium ion capacitor may include forming a carbon-based nanocomposite including a lithium metal oxide by a solid phase reaction or a chemical chemical method.

In the method of manufacturing a cathode active material for a lithium ion capacitor according to the present invention, a lithium metal oxide, a carbon nanotube and a composite thereof, and a carbon-based material as a cathode active material may be applied as described above with respect to the cathode active material for a lithium ion capacitor. have.

The method of manufacturing a cathode active material for a lithium ion capacitor according to the present invention may further include mixing a carbon nanotube composite having a lithium metal oxide of Formula 1 dispersed on a surface thereof with a carbon-based material.

The mixing process of the carbon nanotube composite and the carbon-based material may be performed by various physical mixing methods. At this time, the carbon-based material as the carbon nanotube composite and the positive electrode active material is 0.5 to 50% by weight and 50 to 99.5% by weight, preferably 1.0 to 35% by weight and 65 to 99% by weight, more preferably 1.5 to 20 Weight percent and 80-98.5 weight percent.

On the other hand, according to another embodiment of the present invention, there is provided a lithium ion capacitor using a cathode active material for a lithium ion capacitor including the carbon nanotube composite. The lithium ion capacitor uses a carbon nanotube composite having a specific lithium metal oxide having a large initial irreversible capacity dispersed on its surface as a positive electrode additive to effectively transfer lithium ions to a negative electrode without forming a separate lithium metal layer. It is done.

In particular, the lithium ion capacitor of the present invention includes a cathode including a cathode active material; An anode including an anode active material; And a separator between the positive electrode and the negative electrode, wherein the negative electrode may be supplied with lithium ions only from the positive electrode.

At this time, "receiving only lithium ions from the positive electrode" is, as shown in Figure 3, a separate lithium ion supply layer for supplying lithium ions to the negative electrode, for example, included in the negative electrode or on the negative electrode A separate lithium metal layer stacked (coated or laminated) is not included in the capacitor, and the negative electrode may mean that only lithium ions derived from lithium metal oxide included in the positive electrode active material are supplied.

The lithium ion capacitor of the present invention may include a carbon-based negative electrode active material reversibly inserting or detaching lithium ions in the voltage range of 0V to 5V.

The lithium ion capacitor according to the present invention has an excellent performance of charging and discharging capacity of 50 F / g or more, preferably 70 F / g or more, more preferably 100 F / g or more, measured by an electrochemical method.

The lithium ion capacitor according to the present invention can be manufactured without using lithium metal as a lithium source.

On the other hand, l class commonly used in the powder of the positive electrode active material comprising the carbon nanotube composite according to the present invention as a positive electrode additive, a conductive agent, a binder, a thickener, a filler, a dispersant, an ion conductive agent, a pressure enhancer, etc. Or 2 or more types of addition components are added, and it slurry-pastes with suitable solvents, such as water and an organic solvent. The slurry or paste thus obtained is coated and dried on an electrode support substrate using a doctor blade method or the like, and then pressed using a rolling roll or the like is used as the positive electrode plate.

The binder may be, for example, a rubber binder such as styrene butadiene rubber (SBR), a fluorine resin such as polyethylene tetrafluoride, polyvinylidene fluoride (PVdF, polyvinylidene fluoride), polypropylene, polyethylene, or the like. Thermoplastic resin, acrylic resin, etc. can be used. The amount of the binder may vary depending on the electrical conductivity of the cathode active material, the electrode shape, etc., but may be used in an amount of 2 to 40 parts by weight based on 100 parts by weight of the cathode active material.

If necessary, examples of the conductive agent include graphite, carbon black, acetylene black, Ketjen Black, carbon fiber, and metal powder. The amount of the conductive material used varies depending on the electrical conductivity, the electrode shape, and the like of the positive electrode active material, but may be used in an amount of 2 to 40 parts by weight based on 100 parts by weight of the positive electrode active material.

In addition, carboxymethyl cellulose (CMC) may be used as the thickener.

At this time, the electrode support substrate (also referred to as 'current collector') may be made of foil, sheet, mesh or carbon fiber such as copper, nickel, stainless steel, aluminum, or the like.

A lithium ion capacitor is manufactured using the anode prepared as described above. The form of the lithium ion capacitor may be any one of a coin, a button, a sheet, a pouch, a cylinder, a square, and the like. At this time, the negative electrode, the electrolyte, the separator of the lithium ion capacitor can be used in the existing lithium secondary battery.

The electrolyte solution may be a non-aqueous electrolyte solution in which lithium salt is dissolved in an organic solvent, an inorganic solid electrolyte, a composite material of an inorganic solid electrolyte, and the like, but is not limited thereto.

Here, carbonate, ester, ether or ketone can be used as a solvent of the non-aqueous electrolyte. The carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC) ethylene carbonate (EC), Propylene carbonate (PC), butylene carbonate (BC) and the like can be used. Esters include butyrolactone (BL), decanolide, valerolactone, mevalonolactone, caprolactone, n-methyl acetate, n-ethyl acetate, n- Propyl acetate and the like can be used. Dibutyl ether or the like may be used as the ether. As the ketone, polymethylvinyl ketone may be used. In addition, the non-aqueous electrolyte according to the present invention is not limited to the type of non-aqueous organic solvent.

Examples of the lithium salt of the non-aqueous electrolyte solution include LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiAlO ₄ At least one selected from the group consisting of LiAlCl ₄ , LiN (CxF2x + 1SO2) (CyF2x + 1SO2), wherein x and y are natural water, and LiSO ₃ CF ₃ .

As the separator, a porous film made from polyolefin such as polypropylene (PP) or polyethylene (PE), or a porous material such as nonwoven fabric can be used.

In the present invention, matters other than those described above can be added or subtracted as necessary, and therefore the present invention is not particularly limited.

According to the present invention, by using a carbon nanotube composite having a large initial irreversible lithium metal oxide dispersed on the surface as a lithium source as a positive electrode additive, by doping lithium to the carbon-based negative active material in an electrochemical manner, a lithium ion capacitor Improved charge and discharge capacity can be ensured.

In addition, the doping of lithium using the positive electrode additive according to the present invention has the effect of improving the energy density of the lithium ion capacitor by lowering the potential of the negative electrode.

In addition, due to the simple lithium doping process there is an effect that can also improve the production efficiency of the lithium ion capacitor.

1 is a schematic diagram showing general charge and discharge characteristics of an electric double layer capacitor (EDLC), a hybrid capacitor, and a lithium ion capacitor (LIC).
2 is a schematic diagram showing a general structure of a conventional lithium ion capacitor (LIC).
3 is a schematic diagram showing the structure of a lithium ion capacitor (LIC) according to the present invention.
Figure 4 is a reference graph for the initial charge and discharge efficiency of the positive electrode additive according to the present invention.

Hereinafter, preferred examples are provided to help understanding of the present invention, but the following examples are merely to illustrate the present invention, and the scope of the present invention is not limited to the following examples.

Example  One

LiOH and (NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ 0 were mixed in an aqueous solution so that Li and Mo were in a 2: 1 molar ratio, and the carbon nanotubes were dispersed in the aqueous solution at 200 ° C. through hydrothermal synthesis. Heat treatment was performed for 10 hours to synthesize a precursor in which the lithium metal oxide precursor Li ₂ MoO ₄ was dispersed on the carbon nanotube surface. The thus-synthesized Li ₂ MoO ₄ is a lithium metal oxide by heating the carbon nanotubes dispersed in 700 ℃ in the Ar atmosphere containing the 5% H ₂ gas for 10 hours, the surface Li ₂ MoO ₃ is distributed to the surface of carbon nanotubes Was synthesized.

Thus synthesized lithium metal oxide Li ₂ MoO ₃ 50% by weight of the carbon-based nanocomposites and 50% by weight of the activated carbon dispersed on the surface to prepare a cathode active material for a lithium ion capacitor. At this time, the activated carbon was used having an average particle size of 15㎛.

Meanwhile, the lithium metal oxide Li ₂ MoO ₃ synthesized by the method described above has an average particle size of 1 μm or less, and is analyzed by a XRD (X-ray diffraction) method to analyze the crystal structure of a Rombohedral (Hxagonal system). It was confirmed that it had a crystal structure of.

In addition, the lithium metal oxide Li ₂ MoO ₃ , the charge capacity (Q _D ) and the discharge capacity (Q _C ) by the constant current or constant voltage method by the electrochemical method under the half cell (half cell) conditions with lithium as a counter electrode The initial charge and discharge efficiency (Q _E ) was calculated according to the following equation 1.

[Calculation 1]

Q _E = (Q _D / Q _C ) × 100

In the formula,

Q _E is the initial charge and discharge efficiency of the lithium metal oxide, Q _D is the discharge capacity (mAh / g) at Li / Li + cut-off at a discharge voltage of 2.3 V, Q _C is charged The charge capacity (mAh / g) at Li / Li + cut-off at 4.7 V is shown.

At this time, the initial charge and discharge efficiency (Q _E ) of the carbon nanotube composite having the prepared lithium metal oxide Li ₂ MoO ₃ dispersed on the surface was 50%.

In addition, the carbon nanocomposite had a conductivity of 10 ² S / cm measured by a powder resistance measuring method.

Test Example

After the lithium ion capacitor was manufactured by the following method using the positive electrode active material prepared according to Example 1, battery performance evaluation thereof was performed.

a) Lithium-ion capacitor manufacturing

First, as the cathode active material, N-methylpyrrolidone (NMP) is used as a solvent by using 80 wt% of carbon nanotube composites in which activated carbon and lithium metal oxide are dispersed, Super P 10 wt% as a conductive material, and 10 wt% of binder PVdF. A slurry was prepared. The slurry was applied to an aluminum foil (Al foil) having a thickness of 20 μm, dried, compacted by a press, dried for 16 hours at 120 ° C. in a vacuum, and a cathode was prepared from a disc having a diameter of 12 mm.

As the anode, a lithium metal foil punched to a diameter of 12 mm was used, and a polyethylene (PE) film was used as the separator. At this time, the positive electrode active material of Example 1 was used as the positive electrode material, and a mixed solution containing 3 M of ethylene glycol / dimethyl chloride (EC / DMC) of 1 M LiPF ₆ was used as the electrolyte.

After the electrolyte was impregnated into the separator, the separator was sandwiched between the anode and the cathode, and then a case of stainless steel was manufactured as a test cell for electrode evaluation, that is, a non-aqueous lithium ion capacitor half cell. It was.

b) battery performance evaluation

The lithium ion capacitor was charged and discharged for 1 cycle with a current of 0.2C (10.6 mA / g) for lithium doping, followed by charging and discharging for 5 cycles with a current of 0.2C (10.6 mA / g). .

Claims (14)

On the surface of the carbon nanotubes, represented by the formula (1) below, the positive electrode active material comprising a tanyang nanotube composite, in which lithium metal oxide is dispersed in which lithium ions are reversibly inserted or detached in a voltage range of 2.5V to 5V An anode comprising;
A negative electrode including a negative electrode active material; And
A separator between the anode and the cathode;
Including, lithium ion capacitor:
[Formula 1]
Li _x M _y O _z
In the formula,
Satisfies 2 ≦ x ≦ 6, y = 1, and 2 ≦ z ≦ 4,
M is Ti, V, Cr, Co, Ni, Cu, Zn, Zr, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Ir, Pt, or Nb.
The method of claim 1,
The carbon nanotubes, characterized in that the average outer diameter size is 500 ㎛ or less, lithium ion capacitors.
The method of claim 1,
The carbon nanotube composite is lithium ion capacitor, characterized in that the content of 0.1 to 80 parts by weight of lithium metal oxide is dispersed with respect to 100 parts by weight of carbon nanotubes.
The method of claim 1,
The lithium metal oxide, the initial charge and discharge efficiency (QE) according to the following formula 1, characterized in that 50% or less, lithium ion capacitor:
[Calculation 1]
Q _E = (Q _D / Q _C ) Х100
In the formula,
Q _E is the initial charge and discharge efficiency of the lithium metal oxide,
Q _D represents discharge capacity (mAh / g) at Li / Li + cut-off at a discharge voltage of 2.3 V,
Q _C represents the charge capacity (mAh / g) at Li / Li + cut-off at a charge voltage of 4.7 V.
The method of claim 1,
The lithium metal oxide is Li ₂ MoO ₃ , Li ₂ NiO ₂ , Li ₂ PtO ₃ , Li ₂ IrO ₃ , Li ₂ RuO ₃ , Li ₂ SnO ₃ , Li ₂ ZrO ₃ , and Li ₆ CoO ₄ Lithium ion capacitor, characterized in that at least one selected.
The method of claim 1,
The lithium metal oxide has an average particle size of 10 μm or less, lithium ion capacitors.
The method of claim 1,
In Formula 1, M is Mo, Ir, or Pt, lithium ion capacitors.
The method of claim 1,
The negative electrode is lithium ion capacitor, characterized in that the lithium ion is supplied only from the positive electrode.
The method of claim 1,
The lithium metal oxide is Li ₂ MoO ₃ , Li ₂ PtO ₃ , or Li ₂ IrO ₃ , a lithium ion capacitor.
delete The method of claim 1,
The cathode active material further comprises a carbon-based material having a specific surface area of 500 m ² / g or more.
The method of claim 11,
The positive electrode active material, characterized in that it comprises 0.5 to 50% by weight of the carbon nanotube composite and 50 to 99.5% by weight of the carbon-based material, lithium ion capacitor.
The method of claim 1,
The negative electrode active material is a lithium ion capacitor, characterized in that the carbon-based negative electrode active material reversibly inserting or detaching lithium ions in the voltage range of 0V to 5V.
The method of claim 4, wherein
In Formula 1, Q _D is 0 to 60 mAh / g, Q _C is characterized in that 150 to 300 mAh / g, lithium ion capacitor.

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