JP2012253072A - Lithium ion capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve high energy density, excellent high output characteristics and long life, in a lithium ion capacitor high in discharge capacity and excellent in durability.SOLUTION: A lithium ion capacitor includes: a negative electrode formed by filling a material, as an active material, into a metal porous body having a three dimensional structure and serving as a negative electrode collector, the material being capable of adsorbing/desorbing lithium and having a capacity of 800 mAh/g or more; a positive electrode formed by filling active carbon into a metal porous body having a three dimensional structure and serving as a positive electrode collector; and a nonaqueous electrolyte including a lithium salt. In the lithium ion capacitor, a ratio (N/P value) between the charge/discharge capacity of the negative electrode and the charge/discharge capacity of the positive electrode is 50-400. A potential of the negative electrode is preferably 0.05 V or less based on lithium.

Description

  The present invention relates to a lithium ion capacitor.

  In recent years, capacitors, in particular lithium ion capacitors, have been used together with lithium ion batteries as power sources for mobile phones and laptop computers for small portable use, and as power sources for distributed power storage systems for household use. Further, from the viewpoints of environmental protection, oil removal, and energy saving, the use of mobile vehicles such as hybrid vehicles and electric vehicles is expanding.

  There are many types of capacitors. For example, aluminum electrolytic capacitors, ceramic capacitors, and tantalum capacitors are used for power supply circuits. In recent years, large-capacity capacitors such as electric double layer capacitors have been developed for use as the power supply itself and are increasingly used as power storage devices. In addition, hybrid capacitors that use activated carbon for the negative electrode and the same active material as the lithium ion battery for the positive electrode have appeared. As these capacitors increase in capacity, they can be used as power sources for notebook computers, hybrid vehicles and electric vehicles as well as secondary batteries such as lithium ion batteries.

  Originally, capacitors have been developed and put to practical use mainly for the purpose of high output and long life. On the other hand, lithium-based secondary batteries have many uses that require high energy density. However, high power density is often required along with high energy density. For example, in applications such as power tools, heavy machinery, and charging regenerative energy in a hybrid vehicle, it is required to repeatedly charge and discharge a large current frequently even when the depth of charging and discharging is shallow. For such applications, it is necessary to further enhance the capability of capacitors along with secondary batteries. In this case, especially by reducing the internal resistance, it is necessary to instantaneously input and output a large current, to suppress excessive heat generation and reduce power loss, and at the same time to have a long life.

  Aiming at these high output, high energy density, low cost, and safety improvement, the lithium secondary battery and the positive electrode oxide and negative electrode carbon-based material of the lithium-based capacitor are being improved. In particular, graphite is widely used as a negative electrode material, but silicon, tin, germanium, indium, and the like, which have a lithium storage capacity much larger than the theoretical capacity of graphite (372 mAh / g), or alloy materials of lithium or silicon, An oxide-based material such as an oxide such as tin, germanium, or indium has attracted attention (see, for example, Patent Document 1).

  Among the capacitors, in general, activated carbon is often used for both electrodes in the electric double layer lithium-based capacitor. For example, Patent Document 2 discloses a positive electrode composed of a polarizable electrode containing activated carbon as a lithium ion capacitor having the characteristics of an electric double layer capacitor and a lithium ion secondary battery, and a negative electrode active material capable of inserting and extracting lithium ions. A lithium ion capacitor comprising a negative electrode containing, and an organic electrolyte containing lithium ions is described.

  As the electrode current collector, an aluminum foil for the positive electrode and a copper foil for the negative electrode are used in any of general-purpose lithium ion batteries and capacitors. Patent Document 2 also describes this. However, due to the extension of the electrode technology for alkaline secondary batteries, two-dimensional porous bodies such as screens and expanded metals and current collectors having a three-dimensional structure such as foamed metals have attracted attention. For example, Patent Document 3 describes a foamed nickel-chrome current collector in which the content of chromium in the foamed nickel is 25% by mass or more.

Next, as the electrolytic solution to be used, a non-aqueous organic electrolytic solution in which a salt is dissolved in an organic solvent is used. As the organic electrolyte, it is common to use an organic solvent such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate or the like, in which a lithium salt such as LiCl ₄ , LiBF ₄ , or LiPF ₆ is dissolved. Is.

  In addition, the capacity ratio (so-called N / P value) between the negative electrode and the positive electrode obtained by dividing the amount of the negative electrode active material by the amount of the active material of the positive electrode, which is the subject of the present invention, is also important in designing lithium ion batteries and capacitors. Is described in Patent Document 4.

  Usually, in secondary batteries that use general-purpose aqueous electrolytes such as nickel cadmium batteries, nickel metal hydride batteries, and lead acid batteries, the capacity ratio of the negative electrode to the positive electrode, that is, the N / P value, is extremely important in order to enable sealing. It is essential that it is at least 1 or more. That is, sealing is possible by decomposing water in the electrolyte during overcharge and returning oxygen generated from the positive electrode to water at the negative electrode. When charging of the positive electrode is completed, if there is no uncharged capacity in the negative electrode, hydrogen is generated from the negative electrode, and water in the electrolytic solution is lost due to electrolysis of water, and sealing is impossible. From this point, it is preferable to increase the N / P value as much as possible in order to keep hermetically sealed, but there is a limit in terms of reduction in energy density and price as a battery. About 0.0 is adopted.

  On the other hand, capacitors and lithium secondary batteries that use organic electrolytes are designed to be cut off when a certain charge potential is reached because organic solvents are used and the decomposition of the solvent must be avoided. Yes. Therefore, the N / P value is not as important as the aqueous electrolyte secondary battery. Nevertheless, Patent Document 4 states that it is normal in the battery and capacitor industry to maintain a capacity ratio N / P value of the negative electrode to the positive electrode of 1.2 to 1.4. The reason for this is that, in a lithium secondary battery or a lithium-based capacitor, anode ions released from the positive electrode during charging / discharging are sufficiently reserved to be absorbed by the negative electrode. For example, if the capacity ratio between the positive electrode and the negative electrode is 1 or less, the lithium metal is deposited inside the battery or the capacitor, and the charge / discharge performance is deteriorated due to the leakage of the electrolytic solution. It is said that it includes the danger of

  Furthermore, when manufacturing a capacitor or a lithium ion battery, a process of supporting (doping) lithium ions in advance in the active material is employed in order to increase the capacity, increase the voltage, and extend the life. This technique has been used for a long time. For example, Patent Document 5 describes that a lithium ion battery or a capacitor is manufactured using an electrode carrying lithium. As the method, lithium metal powder and an electrode material are mixed in advance, or an electrode is brought into contact with a lithium metal foil after production. The latter is a kind of short circuit method. In Patent Document 2, as a lithium doping method, a negative electrode and a lithium metal foil are sandwiched between separators (polypropylene nonwoven fabric) and set in a beaker cell, and a predetermined amount of lithium ions is occluded in the negative electrode over about 10 hours. I let you. It is described that the doping amount of lithium is about 75% of the negative electrode capacity.

JP 2009-76372 A JP 2009-130066 A JP 2009-176516 A JP-A-11-214027 JP-A-3-233860

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an organic electrolyte lithium ion capacitor in which energy density and discharge voltage are improved and good high rate discharge characteristics are obtained.
At present, activated carbon is widely used for capacitors and carbon-based materials such as graphite materials are widely used for lithium ion batteries. On the other hand, materials having lithium storage capacity far exceeding the theoretical capacity of graphite (372 mAh / g) and compounds thereof, such as silicon, tin, titanium, germanium, aluminum, indium and lithium alloy materials or silicon, tin, titanium, Oxide-based materials such as germanium, aluminum, and indium have attracted attention for quite some time, and some have been put into practical use.

  In particular, silicon-based oxides have a high lithium storage capacity per mass and are considered promising materials for increasing the energy density of batteries. However, since the initial efficiency is low and the volume change during lithium occlusion is larger than that of carbon-based materials, the energy density of the fabricated batteries is the same as that of lithium-based capacitors and lithium-based secondary batteries using activated carbon or graphite-based materials as negative electrodes. In comparison, there was a problem that the effect of improving the energy density was small and the charge / discharge characteristics were inferior. That is, the main cause of these materials and their compounds is that an increase in volume or pulverization of the materials due to repeated charge and discharge is unavoidable. For the improvement, there is a proposal of a method of using a current collector made of a porous metal body having a three-dimensional structure excellent in electrolytic solution resistance and oxidation resistance shown in Patent Document 3 as a mixture with a carbon material. The use of the compound became possible. However, there are further expectations for lithium ion capacitors in terms of high energy density, long life, and material resources.

  In particular, a lithium ion capacitor using a material or compound having a charge or discharge capacity (hereinafter also simply referred to as “capacity”) of 800 mAh / g or more as a positive electrode with activated carbon as a positive electrode has energy density, output characteristics, If the discharge cycle characteristics can be obtained, further expansion of application as a capacitor can be expected.

In the lithium ion capacitor having a negative electrode and a positive electrode in which a three-dimensional porous metal body is filled with an active material, a charge / discharge capacity capable of inserting and extracting lithium is 800 mAh / g or more. A negative electrode filled with a substance, a positive electrode filled with activated carbon, and a non-aqueous electrolyte containing a lithium salt, and a ratio (N / P value) between the charge / discharge capacity of the negative electrode and the charge / discharge capacity of the positive electrode The present invention was completed by finding that a lithium ion capacitor having an A of 50 to 400 can solve the above problems.
That is, the present invention is a lithium ion capacitor having the following configuration.

(1) A negative electrode in which a porous metal body having a three-dimensional structure as a negative electrode current collector is filled with a material capable of occluding and releasing lithium and having a capacity of 800 mAh / g or more as an active material, and a positive electrode A lithium ion capacitor comprising a positive electrode formed by filling activated carbon in a three-dimensional porous metal body as a current collector, and a non-aqueous electrolyte containing a lithium salt, the charge / discharge capacity of the negative electrode and the positive electrode A lithium ion capacitor having a ratio (N / P value) to a charge / discharge capacity of 50 to 400.
(2) The lithium ion capacitor according to (1), wherein the ratio (N / P value) between the charge / discharge capacity of the negative electrode and the charge / discharge capacity of the positive electrode is 55 to 200.
(3) The lithium ion capacitor according to (1), wherein the ratio (N / P value) between the charge / discharge capacity of the negative electrode and the charge / discharge capacity of the positive electrode is 60 to 160.
(4) The lithium ion capacitor according to any one of (1) to (3), wherein lithium is supported (doped) on the negative electrode active material before constituting the lithium ion capacitor.
(5) The lithium ion capacitor according to any one of (1) to (4), wherein the material of the three-dimensional porous metal body used for the positive electrode current collector is a nickel chromium alloy.
(6) The material having a capacity of 800 mAh / g or more is selected from the group consisting of silicon (Si), tin (Sn), germanium (Ge), oxides of these elements, and alloys of these elements and lithium. The lithium ion capacitor according to any one of (1) to (5), wherein the lithium ion capacitor is at least one kind.
(7) The lithium ion capacitor according to any one of (1) to (6), wherein the negative electrode potential is 0.05 V or less based on lithium.
(8) The lithium ion capacitor according to (6) or (7), wherein the material having a capacity of 800 mAh / g or more is silicon oxide (SiO).

  The lithium ion capacitor of the present invention has high energy density and discharge voltage, and exhibits good high rate discharge characteristics.

It is a figure which shows the discharge curve of the lithium ion capacitor A (N / P value: 110) which combined the positive electrode 2 and the negative electrode 1. FIG. It is a figure which shows the discharge curve of the lithium ion capacitor B (N / P value: 7) which combined the positive electrode 3 and the negative electrode 4. FIG.

The lithium ion capacitor of the present invention is a lithium ion capacitor using a non-aqueous electrolyte containing a lithium salt and having improved energy density, output characteristics, and charge / discharge cycle characteristics.
That is, the feature of the present invention is to pay attention to the capacity ratio (N / P value) between the negative electrode and the positive electrode of the lithium ion capacitor and to make the value significantly larger than the conventional one. Specifically, 50 to 400 is selected as a specific preferable value of the N / P value. A more preferable value of the N / P value is 55 to 200, and more preferably 60 to 160. As a result, the lithium ion capacitor of the present invention can enable a high output and a long life while having an energy density close to that of a lithium-based secondary battery while being a capacitor. Further, as a resource, cobalt, rare earth, etc. It has the advantage that it is not necessary to use noble or rare metals.

In order to exert the features of the present invention, in the present invention, a three-dimensional metal porous body is used as a current collector for both the positive electrode and the negative electrode. That is, an aluminum foil as a current collector of a positive electrode that has been conventionally used as a current collector that is filled with activated carbon that is an active material of the positive electrode and a material such as silicon or tin that is an active material of the negative electrode or an oxide thereof, Instead of the copper foil as the current collector for the negative electrode, a three-dimensional metal porous body is used as the current collector for both the positive electrode and the negative electrode.
As the metal porous body having a three-dimensional structure, those based on foamed urethane or nonwoven fabric, such as foamed nickel and nonwoven fabric nickel, can be preferably used in terms of the filling property and porosity of the active material. Other three-dimensional structures include a metal plate with a large number of small holes, a metal plate with irregularities and a pseudo three-dimensional structure, and a structure with a sintered body and continuous air holes. However, a three-dimensional porous metal body obtained using urethane foam or nonwoven fabric as a base material is optimal.

  The active material may be filled into the three-dimensional metal porous body by making the active material into a slurry and filling the slurry by a known method such as a press-fitting method. In addition, for example, a method of immersing the current collector in the slurry, adding a decompression step as necessary, and filling the slurry while pressurizing with a pump or the like from one side of the current collector can be employed.

First, activated carbon, which is an active material for a positive electrode, is most preferably a method in which carbon black, a thickener, and a binder are usually added as conductive aids and filled into a current collector as a slurry. There is a proposal to use a metal foil as an active material as one of the negative electrodes, but in the present invention, a metal powder or a metal oxide and carbon black, a thickener, and a binder are added to the three-dimensional structure current collector in the same manner as the positive electrode. Thus, a method of filling the current collector as a slurry is suitable.
In addition to carbon black (Ketjen black, acetylene black, etc.), carbon fiber, natural graphite, artificial graphite, etc. can be used as the conductive agent. However, ketjen black is most preferable from the viewpoint of conductivity. The addition amount of the conductive assistant is preferably about 0.1 to 10 parts by weight.

  As the binder, an NMP solution of PVdF can be used, but polytetrafluoroethylene, polyvinyl pyrrolidone, polyethylene, polypropylene, styrene butadiene rubber, polyvinyl alcohol, carboxymethyl cellulose, and the like can also be used. These are attracting attention because they can be used as emulsions or aqueous solutions. The amount of the binder added is preferably about 0.5 to 10% by weight although it depends on the material. If it is less than 0.5%, the retention of the active material is inferior. If it exceeds 10%, the capacity decreases and the electrical resistance also increases.

  Both the positive electrode and the negative electrode are preferably filled with the active material slurry and then dried to remove the organic solvent. Then, after filling the slurry, compression molding is preferably performed by pressurizing with a roller press or the like. The thickness before and after pressing is not limited, but the thickness before compression is preferably about 250 to 1500 μm, and the thickness after pressing is usually preferably about 100 to 800 μm. The capacitor is preferably provided with a lead terminal. As a structure of the capacitor, a general-purpose structure such as a plate shape, a button shape, a square shape, or a cylindrical shape may be employed depending on the application.

In this way, activated carbon is used for the positive electrode, lithium is occluded / desorbed for the negative electrode, and a lithium ion capacitor is formed by filling a negative electrode active material mainly composed of a material having a capacity of 800 mAh / g or more or its oxide. To do. Here, in this lithium ion capacitor, by constructing a lithium ion capacitor using a non-aqueous electrolyte containing a lithium salt, the calculated capacity of the negative electrode is 50 to 400 times the calculated capacity of the positive electrode, It achieves high output and long life.
In order to achieve the object of the present invention with such a large N / P which has not been considered in the past, a metal porous body having a three-dimensional structure is used as a positive electrode current collector, not a metal foil or a two-dimensional current collector. It is necessary to use nickel-chromium alloy as the three-dimensional porous metal body from the viewpoint of oxidation resistance and electrolytic solution resistance. As the negative electrode current collector, a nickel porous body having a three-dimensional structure can also be used.

  The positive electrode active material in the capacitor does not need to be a lithium-containing transition metal oxide as used in a lithium ion battery, and activated carbon is sufficient. Thus, in order to increase the capacity of the lithium ion capacitor, it is preferable that the capacity of the positive electrode is large, and it is preferable to use activated carbon filled in a porous metal body, particularly a foamed nickel chrome current collector, similarly to the negative electrode.

As the active carbon used as the active material of the positive electrode, as well known, waste wood, coconut husk, pulp waste liquid, coal, heavy petroleum oil, coal / petroleum pitch and various resins are used as well known. Yes. The obtained activated carbon is generally subjected to an activation treatment. As the activation method, a method of reacting with water vapor, carbon dioxide gas, oxygen in an inert gas, or the like at a high temperature, or a method of treating with a chemical such as zinc chloride or sodium hydroxide is common. Moreover, as a particle size of activated carbon, 20 micrometers or less and a specific surface area of about 1000-3000 m < ² > / g are desirable.
On the other hand, as materials having a capacity of 800 mAh / g or more capable of occluding and desorbing lithium used for the negative electrode, silicon (Si), tin (Sn), germanium (Ge), oxides of these elements, and these elements and lithium An alloy etc. are mentioned.

  In addition, it is important that lithium is supported (doped) on the negative electrode active material before constituting the lithium ion capacitor. In general, occlusion of lithium ions in the negative electrode is a preferable means for sufficiently supplying lithium ions to the positive electrode by discharge, and the cell voltage can be increased. Occlusion of lithium ions in the negative electrode is a process necessary to enable high capacity by using a current collector having a three-dimensional structure for the positive electrode. As the method, there are a method in which lithium metal powder and an electrode material are mixed in advance, and an electrode is brought into contact with a lithium metal foil after the electrode is manufactured. The latter is a kind of short circuit method.

The lithium ion capacitor according to the present invention can be manufactured by the following method. The basic structure of the capacitor is the same as that of the prior art, and is composed of a pair of positive and negative electrodes and a separator impregnated with an electrolyte solution disposed between the electrodes, and is accommodated in a battery case.
In addition, as a separator, well-known porous bodies, such as polyethylene, a polypropylene, a polyethylene terephthalate, polyamide, a polyimide, a cellulose, glass fiber, can be used, for example. The average pore size of the separator is not particularly limited, but a pore size of about 0.01 μm to 5 μm, a porosity of 30 to 70%, and a thickness of 10 μm to 100 μm can be employed.

  Examples of the lithium ion capacitor of the present invention are shown below. However, these examples are illustrative, and the present invention is not limited by these examples. The scope of the present invention is indicated by the scope of the claims, and the scope of the claims and All changes within an equivalent meaning and scope are included.

[Production of negative electrode]
(Current collector)
The current collector of a three-dimensional porous metal body is foamed nickel produced by chromizing treatment using a powder pack method in which foamed nickel is filled with a penetrating material containing chromium and heated in a reducing atmosphere. A chromium alloy current collector was used.
The foamed nickel is conductively treated on a urethane sheet (commercially available product with an average pore diameter of 90 μm, thickness of 1.4 mm, and porosity of 96%), and then 350 g / m ² of nickel plating is applied. It was made as.

In the chromizing treatment, the foamed nickel base material is filled with a penetrating material (chromium: 90%, NH ₄ Cl: 1%, Al ₂ O ₃ : 9%) mixed with chromium powder, halide and alumina. The heating was performed at 800 ° C. in a hydrogen gas atmosphere. The resulting foamed nickel chromium base had a chromium content of 30% by weight and a thickness of 1.4 mm.
The current collector was made of foamed nickel chrome having a porosity of 96%, a pore diameter of 100 to 400 μm, a thickness of which was previously adjusted to 250, 500, 1000, and 1300 μm, and punched into a 11 mm diameter circle with a mold.

(Negative electrode active material)
As the negative electrode active material, silicon oxide SiO 2 (calculated capacity density 1500 mAh / g) which is an oxide type material was used. Commercially available SiO having an average particle diameter of about 5 μm is 80 in weight ratio, Ketjen black (KB) 5 as a conductive agent, polyvinylidene fluoride (PVdF) 15 as a binder, solvent N-methyl-2-pyrrolidone (NMP) While stirring 100 with a mixer, the binder was dissolved in a solvent to obtain a slurry.

(Filling current collector with negative electrode active material)
The slurry obtained above was filled by press-fitting the slurry, dried and pressurized to obtain a negative electrode.

(Lithium doping to the negative electrode)
The negative electrode obtained above was contacted with a lithium foil having a diameter of 13 mm and a thickness of 100 μm and left at 50 ° C. overnight. By this operation, lithium pressure-bonded to the negative electrode is ionized and occluded in the silicon oxide of the negative electrode.
The negative electrode potential after lithium doping was 0.05 V or less based on lithium.

[Production of positive electrode]
(Current collector)
As the current collector for the positive electrode, the same foamed nickel chromium porous material as that used for the negative electrode was used.
In the positive electrode, the foamed nickel chrome porous body was adjusted to a thickness of 500, 780, and 1300 μm, and punched in a circular shape with a diameter of 11 mm with a mold in the same manner as the negative electrode to obtain a current collector for the positive electrode.

(Positive electrode active material)
Activated carbon (commercially available product) having a surface area (1500 m ² / g) activated by alkali treatment and an average particle size of 15 μm was used.
Further, with respect to the active material weight ratio of 80, KB was used as a conductive agent, 15 PVdF, 15 NMP100 was stirred with a mixer, and the binder was dissolved in a solvent to obtain a positive electrode slurry.

(Filling current collector with negative electrode active material)
The positive electrode current collector was filled with the positive electrode slurry by a press-fitting method, dried and pressurized to obtain a positive electrode.

[Manufacture of capacitors]
Using the circular positive electrode and negative electrode having a diameter of 11 mm obtained above, a polypropylene separator (thickness 25 μm) was sandwiched between the two electrodes to constitute a cell, and stored in a coin cell case of R2032 size, Electrodes and separators were impregnated using an electrolytic solution in which 1 mol / l LiPF ₆ was dissolved in ethylene carbonate (EC) and diethyl carbonate (DEC) having a volume ratio of 1: 1. Further, the case lid was tightened and sealed through an insulating gasket made of propylene to produce a coin-shaped lithium ion capacitor A.

Tables 1 and 2 show the thickness after thickness adjustment, the thickness after pressurization, and the active material filling amount of the negative electrodes 1 to 3 and the positive electrodes 1 to 4 manufactured as described above (however, the negative electrode 4, the negative electrode 5, and Since the metal foil is used for the positive electrode 4, the thickness after thickness adjustment is not described. Table 1 also shows electrodes 4 and 5 using a copper foil as a current collector for comparison. Table 2 also shows a positive electrode 4 produced by using activated carbon slurry on an aluminum foil as a comparison.
Table 3 shows N / P values of lithium ion capacitors produced using the negative electrode and the positive electrode.
N / P was determined as follows. The capacity of SiO as the negative electrode active material is 1500 mAh / g, the capacity of the activated carbon as the positive electrode active material is 30 mAh / g, and the capacity of each electrode is obtained by multiplying the weight of SiO and activated carbon contained in each electrode. It was. The value obtained by dividing the negative electrode capacity thus obtained by the positive electrode capacity was defined as the N / P ratio. The N / P ratio was adjusted by changing the amount of active material filled in the current collector.

FIG. 1 shows a discharge curve of a lithium ion capacitor A (N / P value: 110) in which the positive electrode 2 and the negative electrode 1 are combined. As is apparent from FIG. 1, a linear discharge curve is drawn from 4V to 2V, and the lithium ion capacitor A functions normally as a capacitor. The capacity is about 1.0 mAh / cm ² .
FIG. 2 shows a discharge curve of a lithium ion capacitor B (N / P value: 7) in which the positive electrode 3 and the negative electrode 4 are combined. The discharge curve is bent from 4V to 2V, and it can be seen that the lithium ion capacitor B does not function normally as a capacitor.

  From the results of the above examples, both the positive electrode and the negative electrode are filled with a three-dimensional metal porous body, the positive electrode is filled with activated carbon, and the negative electrode is filled with silicon oxide having a capacity of 800 mAh / g or more. Ratio, that is, an N / P of 50 to 400, particularly 60 to 160, an energy density close to that of a lithium-based secondary battery, a high output density and a long life can be obtained, and a lithium ion capacitor having excellent resource properties was gotten.

Lithium ion capacitors incorporating the novel technology of the present invention will be able to be expanded in application as portable, mobile, emergency, other general and industrial power supplies.

Claims (8)

  A negative electrode formed by filling a porous metal body having a three-dimensional structure as a negative electrode current collector with a material capable of absorbing and desorbing lithium and having a capacity of 800 mAh / g or more as an active material, and a positive electrode current collector A lithium ion capacitor comprising a positive electrode formed by filling activated carbon in a three-dimensional metal porous body as a body, and a non-aqueous electrolyte containing a lithium salt, the charge / discharge capacity of the negative electrode and the charge / discharge of the positive electrode A lithium ion capacitor having a capacity ratio (N / P value) of 50 to 400. 2. The lithium ion capacitor according to claim 1, wherein a ratio (N / P value) between a charge / discharge capacity of the negative electrode and a charge / discharge capacity of the positive electrode is 55 to 200. 3.   2. The lithium ion capacitor according to claim 1, wherein the ratio (N / P value) between the charge / discharge capacity of the negative electrode and the charge / discharge capacity of the positive electrode is 60 to 160. 3.   The lithium ion capacitor according to claim 1, wherein lithium is supported (doped) on the negative electrode active material before constituting the lithium ion capacitor.   The lithium ion capacitor according to any one of claims 1 to 4, wherein the material of the three-dimensional porous metal body used for the positive electrode current collector is a nickel chromium alloy.   The material having a capacity of 800 mAh / g or more is at least one selected from the group consisting of silicon (Si), tin (Sn), germanium (Ge), oxides of these elements, and alloys of these elements and lithium The lithium ion capacitor according to claim 1, wherein the capacitor is a lithium ion capacitor.   The lithium ion capacitor according to claim 1, wherein the negative electrode potential is 0.05 V or less based on lithium. The lithium ion capacitor according to claim 6 or 7, wherein the material having a capacity of 800 mAh / g or more is silicon oxide (SiO).

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