JP2007067097A - Wound type lithium ion capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-capacity and highly safe lithium ion capacitor having high energy density and output density. <P>SOLUTION: The lithium ion capacitor is provided with a positive electrode consisting of a positive electrode active substance capable of reversibly carrying lithium ions and/or anions, a negative electrode consisting of a negative electrode active substance capable of reversibly carrying lithium ions, and an aprotic organic solvent electrolytic solution of a lithium salt as an electrolyte. In the wound type lithium ion capacitor, the positive and negative electrodes are formed as electrode layers on one surface of an electric collector having holes each piercing front and rear surfaces, positive and negative pole terminals are connected to electric collector surfaces of the positive and negative electrodes where electrode layers are not formed, the positive and negative poles are wound via a separator to form an electrode wound unit, lithium ions are doped into the negative and/or positive electrodes by electrical chemical contact of negative and/or positive electrodes with a lithium ion supply source, and the potential of the positive electrode after short-circuiting the positive and negative electrodes becomes 2.0 V or low. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a high-capacity wound lithium ion capacitor having high energy density and high output density.

In recent years, a battery using a carbon material such as graphite for the negative electrode and a lithium-containing metal oxide such as LiCoO _{2 for} the positive electrode has been proposed. This battery is a so-called rocking chair type battery in which lithium ions are supplied from the lithium-containing metal oxide of the positive electrode to the negative electrode by charging after the battery is assembled, and lithium ions are returned from the negative electrode to the positive electrode in the discharge. This is called a lithium ion secondary battery and is distinguished from a lithium battery using lithium metal because only lithium ions are involved in charging and discharging without using metallic lithium. This battery is characterized by high voltage, high capacity, and high safety.

  In addition, while environmental issues are being highlighted, development of a clean energy storage system using solar power generation or wind power generation, and a power source for an electric vehicle or a hybrid electric vehicle that replaces a gasoline vehicle are being actively conducted. Furthermore, recently, in-vehicle devices and equipment such as power windows and IT-related equipment have become more sophisticated and functional, and new power sources are being demanded in terms of energy density and output density.

  In recent years, a power storage device called a hybrid capacitor, which combines the power storage principles of a lithium ion secondary battery and an electric double layer capacitor, has been attracting attention as a power storage device for such applications that require high energy density and high output characteristics. . As one of them, a lithium ion can be occluded and desorbed in advance by occlusion and support (hereinafter sometimes referred to as doping) of lithium ions by a chemical method or an electrochemical method to lower the negative electrode potential. An organic electrolyte capacitor using a carbon material that can significantly increase the energy density as a negative electrode has been proposed (see, for example, Patent Document 1).

  Although this type of organic electrolyte capacitor is expected to have high performance, there are problems in that it takes a very long time when lithium ions are doped in advance on the negative electrode and that lithium ions are uniformly supported on the entire negative electrode. In particular, it has been considered difficult to put into practical use in a large-sized high-capacity cell such as a cylindrical battery in which electrodes are wound or a square battery in which a plurality of electrodes are stacked.

  As a method for solving such a problem, the positive electrode current collector and the negative electrode current collector each have a hole penetrating the front and back surfaces, the negative electrode active material can reversibly carry lithium ions, and faces the negative electrode or the positive electrode. There has been proposed an organic electrolyte battery in which lithium ions are supported on a negative electrode by electrochemical contact with lithium metal disposed in a row (see, for example, Patent Document 2).

  In the above-mentioned organic electrolyte battery, since the electrode current collector is provided with holes that penetrate the front and back surfaces, lithium ions can move between the front and back surfaces of the electrode current collector without being blocked by the electrode current collector. Also in the power storage device having the configuration, lithium ions can be electrochemically supported not only on the negative electrode arranged in the vicinity of the lithium metal but also on the negative electrode arranged away from the lithium metal through the through hole.

JP-A-8-107048 (page 2, column 2, lines 38 to 47) International Publication No. WO98 / 033227 (page 11, line 4 to page 12, line 27)

  As described above, the negative electrode in which lithium ions are previously occluded in a carbon material that can occlude and desorb lithium ions has a lower potential than the activated carbon used in the electric double layer capacitor, so it is combined with the positive activated carbon. In addition, since the withstand voltage of the cell is improved and the capacity of the negative electrode is much larger than that of the activated carbon, the organic electrolyte capacitor (lithium ion capacitor) provided with the negative electrode has a high energy density.

  In the lithium ion capacitor, the cell is configured as an electrode winding unit in which a positive electrode and a negative electrode are alternately stacked via a separator, and the negative electrode is disposed outside the electrode winding unit so as to face the positive electrode and / or the negative electrode. Lithium ions are sequentially doped through the through holes of the electrode current collector from the lithium metal. In this case, it is preferable that all of the lithium metal previously set according to the amount of lithium ions doped in the negative electrode is uniformly doped as lithium ions in the negative electrode.

  An electrode winding unit of a wound lithium ion capacitor is configured by winding a ribbon-like positive electrode and a negative electrode through a separator. In this case, the ribbon-like positive electrode and the negative electrode can be obtained by forming an electrode layer on the current collecting surface of a ribbon-like electrode current collector having holes penetrating the front and back surfaces. FIG. 7 shows a typical conventional negative electrode thus obtained. As shown in FIG. 7, the conventional negative electrode 2 is provided with an uncoated portion 12 by intermittent coating when an electrode layer is applied to the front and back current collecting surfaces of a ribbon-shaped negative electrode current collector 2a. The electrode terminals are connected. Although not shown, such an electrode structure in which an uncoated portion is provided on a ribbon-like current collector is exactly the same as the negative electrode. The wound type lithium ion capacitor is assembled by winding the electrode terminals in which the ribbon-like positive electrode and the negative electrode formed in this way are connected to the uncoated portion 12 while aligning them.

  In a wound type lithium ion capacitor, providing an uncoated portion for attaching an electrode terminal to a current collector in this way requires that the electrode layer be coated so that it does not shift on both sides of the current collector. In particular, in the case of a porous body (for example, a porous foil) like the current collector of the present invention, the coating work becomes complicated, the productivity of the cell deteriorates, and the cost increases.

  The present invention solves such a problem, and the capacitor is formed by connecting the electrode terminal to the current collector without intermittently applying the electrode layer to the ribbon-shaped current collector to provide the electrode uncoated portion. An object of the present invention is to provide a wound lithium ion capacitor that can be assembled.

The present invention has been made to solve the above problems, and provides the following wound type lithium ion capacitor.
(1) A positive electrode made of a positive electrode active material capable of reversibly carrying lithium ions and / or anions, a negative electrode made of a negative electrode active material capable of reversibly carrying lithium ions, and an aprotic lithium salt as an electrolyte A lithium ion capacitor comprising an organic solvent electrolyte solution, wherein the positive electrode and the negative electrode are each formed as an electrode layer on one side of a current collector having holes penetrating the front and back surfaces, and each of the positive electrode and the negative electrode The positive electrode terminal and the negative electrode terminal are connected to the current collector surface on which no electrode layer is formed, and the positive electrode and the negative electrode are wound through a separator to form an electrode winding unit. Or the positive electrode after lithium ion is doped to the negative electrode and / or the positive electrode by electrochemical contact between the positive electrode and the lithium ion supply source, and the positive electrode and the negative electrode are short-circuited The wound type lithium ion capacitor is characterized in that the potential of the battery becomes 2.0 V or less.
(2) The wound lithium ion capacitor according to (1), wherein the positive electrode terminal and the negative electrode terminal are connected to the current collector by stitching or cold welding.
(3) The negative electrode active material has a capacitance per unit weight of 3 times or more as compared with the positive electrode active material, and the weight of the positive electrode active material is larger than the weight of the negative electrode active material. The wound type lithium ion capacitor according to the above (1) or (2).
(4) The negative electrode current collector is disposed on the outermost periphery of the electrode winding unit with the current collector surface on which no electrode layer is formed facing outside, and a lithium ion supply source is brought into contact with the negative electrode current collector. The wound type lithium ion capacitor according to any one of (1) to (3) above, wherein
(5) The wound type lithium ion capacitor according to any one of (1) to (4), wherein the electrode winding unit has a negative electrode layer and a positive electrode layer facing each other with a separator interposed therebetween.
(6) The wound type lithium according to any one of (1) to (5), wherein a lithium ion supply source and / or a separator is disposed on the outside of the electrode winding unit, or is fixed with a tape from the outside without being disposed. Ion capacitor.
(7) The wound lithium ion capacitor according to (6), wherein the outer periphery of the electrode winding unit is fastened with an adhesive tape to which a predetermined lithium ion supply source is attached.

  According to the present invention, as described above, since the positive electrode and the negative electrode are formed as electrode layers only on one side of the ribbon-like current collector having holes penetrating the front and back surfaces, the electrode layers are intermittently provided on the current collector. Even without providing an electrode uncoated portion for connecting the electrode terminal by coating, the positive electrode terminal and the negative electrode terminal are connected to the current collector surface on which the respective electrode layers of the positive electrode and the negative electrode are not formed. A wound type lithium ion capacitor can be assembled.

  Thereby, electrode coating should just be performed to the single side | surface of the electrical power collector which consists of porous materials, and while the workability | operativity of coating can be improved, an electrode terminal can be favorably connected also to electrical power collectors, such as porous foil. Furthermore, since the electrode terminal can be connected to the current collector surface on which no electrode layer is formed, the internal resistance can be reduced. Further, as described above, since the electrode uncoated portion is not provided on the current collector, it is easy to reduce the size of the wound lithium ion capacitor, and a high performance capacitor can be obtained.

  The wound lithium ion capacitor of the present invention (hereinafter sometimes referred to as LIC) includes a positive electrode made of a material capable of reversibly supporting lithium ions and / or anions and a material capable of reversibly supporting lithium ions. And an aprotic organic electrolyte solution of lithium salt as the electrolyte solution. In the LIC of the present invention, the potential of the positive electrode and the negative electrode after the positive electrode and the negative electrode are short-circuited is 2.0 V or less.

  In conventional electric double layer capacitors, the same active material (mainly activated carbon) is usually used in substantially the same amount for the positive electrode and the negative electrode. This active material has a potential of about 3 V when the cell is assembled. When the capacitor is charged, an anion forms an electric double layer on the positive electrode surface, and the positive electrode potential rises, while the negative electrode surface has a cation. Forms an electric double layer and the potential drops. Conversely, during discharge, anions are released from the positive electrode and cations from the negative electrode into the electrolyte, respectively, and the potential decreases and rises to return to around 3V. As described above, since the normal carbon material has a potential of about 3 V, the organic electrolyte capacitor using the carbon material for both the positive electrode and the negative electrode has both the positive electrode and negative electrode potentials after the positive electrode and the negative electrode are short-circuited. It becomes about 3V.

On the other hand, in the LIC of the present invention, as described above, the potential of the positive electrode after short-circuiting the positive electrode and the negative electrode is 2.0 V (Li / Li ⁺ , the same shall apply hereinafter) or less. That is, in the present invention, after using an active material capable of reversibly supporting lithium ions and / or anions for the positive electrode and using an active material capable of reversibly supporting lithium ions for the negative electrode, the positive electrode and the negative electrode are short-circuited. Lithium ions are previously supported on the negative electrode and / or the positive electrode so that the potential between the positive electrode and the negative electrode is 2.0 V or less.

  In the present invention, the potential of the positive electrode after the positive electrode and the negative electrode are short-circuited is 2 V or less. The potential of the positive electrode determined by one of the following two methods (A) or (B) is 2 V or less. Refers to cases. That is, (A) After doping with lithium ions, the positive electrode terminal and the negative electrode terminal of the capacitor cell are directly coupled with a conductive wire and left for 12 hours or more, then the short circuit is released, and within 0.5 to 1.5 hours Measured positive electrode potential, (B) Charge-discharge tester discharges constant current to 0V over 12 hours and then leaves positive electrode terminal and negative electrode terminal connected with lead wire for 12 hours or more, then releases short circuit The positive electrode potential measured within 0.5 to 1.5 hours is 2 V or less.

  In the present invention, the positive electrode potential after the positive electrode and the negative electrode are short-circuited is 2.0 V or less, not only immediately after the lithium ions are doped, but in the charged state, discharged state or charged state. The positive electrode potential after short-circuiting is 2.0 V or less in any state, such as when short-circuiting after repeating discharge.

In the present invention, the fact that the positive electrode potential after the positive electrode and the negative electrode are short-circuited is 2.0 V or less will be described in detail below. As described above, activated carbon and carbon materials usually have a potential of about 3 V (Li / Li ⁺ ), and when the cell is assembled using activated carbon for both the positive electrode and the negative electrode, both potentials are about 3 V. Even if it is short-circuited, the positive electrode potential is about 3 V regardless. The same applies to a so-called hybrid capacitor using activated carbon as the positive electrode and carbon material such as graphite or non-graphitizable carbon used in the lithium ion secondary battery as the negative electrode. Therefore, even if a short circuit occurs, the positive electrode potential is about 3 V regardless. Although depending on the weight balance between the positive electrode and the negative electrode, when charged, the potential of the negative electrode transitions to around 0 V, so that the charging voltage can be increased, so that the capacitor has a high voltage and a high energy density. Generally, the upper limit of the charging voltage is determined to be a voltage at which the electrolyte solution does not decompose due to the increase in the positive electrode potential. Therefore, when the positive electrode potential is set as the upper limit, the charging voltage can be increased by the amount of decrease in the negative electrode potential. .

  However, in the above-described hybrid capacitor in which the positive electrode potential is about 3 V at the time of short circuit, when the upper limit potential of the positive electrode is 4.0 V, for example, the positive electrode potential at the time of discharge is up to 3.0 V, and the potential change of the positive electrode is 1. The capacity of the positive electrode of about 0 V is not fully utilized. Furthermore, when lithium ions are inserted (charged) and desorbed (discharged) into the negative electrode, the initial charge / discharge efficiency is often low, and it is known that there are lithium ions that cannot be desorbed during discharge. This is explained when it is consumed in the decomposition of the electrolyte solution on the negative electrode surface or trapped in the structural defect part of the carbon material. In this case, the charge / discharge of the negative electrode is compared with the charge / discharge efficiency of the positive electrode. When the efficiency is lowered and the cell is short-circuited after repeated charging and discharging, the positive electrode potential becomes higher than 3 V, and the utilization capacity further decreases. That is, the positive electrode can be discharged from 4.0 V to 2.0 V. However, when only 4.0 V to 3.0 V can be used, only half of the usage capacity is used. It will not be.

  In order to increase not only high voltage and high energy density but also high capacity and energy density of the hybrid capacitor, it is necessary to improve the capacity of the positive electrode.

  If the positive electrode potential after the short circuit falls below 3.0V, the utilization capacity increases and the capacity increases. In order to be 2.0 V or less, it is preferable to charge not only the amount charged by charging / discharging the cell but also separately charging lithium ions from a lithium ion supply source such as lithium metal to the negative electrode. Since lithium ions are supplied from other than the positive electrode and the negative electrode, the positive electrode, the negative electrode, and the lithium metal have an equilibrium potential when they are short-circuited, so that both the positive electrode potential and the negative electrode potential are 3.0 V or less. As the amount of lithium metal increases, the equilibrium potential decreases. If the negative electrode material and the positive electrode material change, the equilibrium potential also changes. Therefore, it is necessary to adjust the amount of lithium ions supported on the negative electrode in view of the characteristics of the negative electrode material and the positive electrode material so that the positive electrode potential after the short circuit becomes 2.0 V or less. It is.

  In the LIC of the present invention, the positive electrode potential after the positive electrode and the negative electrode are short-circuited is 2.0 V or less, as described above, lithium ions are supplied to the positive electrode and / or the negative electrode from other than the positive electrode and the negative electrode of the LIC. It is that it has been. The supply of lithium ions may be either one or both of the negative electrode and the positive electrode. For example, when activated carbon is used for the positive electrode, if the amount of lithium ion supported increases and the positive electrode potential decreases, the lithium ion is irreversibly consumed. Since problems such as a reduction in cell capacity may occur, the amount of lithium ions supplied to the negative electrode and the positive electrode needs to be appropriately controlled so as not to cause problems. In any case, since the lithium ions previously supplied to the positive electrode and / or the negative electrode are supplied to the negative electrode by charging the cell, the negative electrode potential decreases.

When the positive electrode potential after the positive electrode and the negative electrode are short-circuited is higher than 2.0 V, the energy density of the cell is small because the amount of lithium ions supplied to the positive electrode and / or the negative electrode is small. As the supply amount of lithium ions increases, the potential of the positive electrode after the positive electrode and the negative electrode are short-circuited becomes lower and the energy density is improved. In order to obtain a high energy density, 2.0 V or less is preferable, and in order to obtain a higher energy density, 1.0 V (Li / Li ⁺ ) or less is preferable. In other words, the positive electrode potential after the positive electrode and the negative electrode are short-circuited is reduced, which means that the amount of lithium ions supplied to the negative electrode by charging the cell increases, and the capacitance of the negative electrode increases. At the same time, the potential change amount of the negative electrode is reduced, and as a result, the potential change amount of the positive electrode is increased, the capacitance and capacity of the cell are increased, and a high energy density is obtained.

  Further, when the positive electrode potential is less than 1.0 V, although depending on the positive electrode active material, problems such as gas generation and irreversible consumption of lithium ions occur, so that it is difficult to measure the positive electrode potential. On the other hand, when the positive electrode potential becomes too low, the negative electrode weight is excessive, and the energy density is decreased. Therefore, in general, the positive electrode potential is 0.1 V or more, preferably 0.3 V or more.

  In the present invention, the capacitance and capacitance are defined as follows. The capacitance of the cell indicates the slope of the discharge curve of the cell, the unit is F (farad), and the capacitance per unit weight of the cell is the positive electrode active material in which the capacitance of the cell is filled in the cell It is the value divided by the total weight of the weight and the weight of the negative electrode active material, the unit is F / g, the capacitance of the positive electrode is the slope of the discharge curve of the positive electrode, the unit is F, the electrostatic capacity per unit weight of the positive electrode The capacity is a value obtained by dividing the capacitance of the positive electrode by the weight of the positive electrode active material filled in the cell. The unit is F / g. The capacitance of the negative electrode is the capacitance of the negative electrode in the cell. The value is divided by the weight of the filled negative electrode active material, and the unit is F / g.

  Further, the cell capacity is the difference between the discharge start voltage and the discharge end voltage of the cell, that is, the product of the voltage change amount and the cell capacitance, and the unit is C (coulomb). 1C is 1 A current per second. Therefore, in this patent, it was converted to mAh and displayed. The positive electrode capacity is the product of the difference between the positive electrode potential at the start of discharge and the positive electrode potential at the end of discharge (amount of change in positive electrode potential) and the capacitance of the positive electrode. The unit is C or mAh. Is the product of the difference between the negative electrode potential and the negative electrode potential at the end of discharge (amount of change in negative electrode potential) and the capacitance of the negative electrode, and the unit is C or mAh. These cell capacity, positive electrode capacity, and negative electrode capacity coincide with each other.

  Next, the configuration of the wound lithium ion capacitor of the present invention will be described with reference to the drawings. The drawings shown below illustrate preferred embodiments of the present invention, and the present invention is not limited thereto. FIG. 1 is a sectional view of a typical cylindrical (cylindrical) type cell of a wound lithium ion capacitor (hereinafter also referred to as a cell) according to the present invention.

In the cell of this example, as shown in FIG. 1, positive electrodes 1 and negative electrodes 2 are alternately stacked via separators 3 and wound concentrically to form an electrode winding unit 6. For example, lithium metal (lithium electrode) 4 is disposed on the outside as a lithium ion supply source, and these are housed in an outer container 5 and filled with an electrolyte. The positive electrode 1 and the negative electrode 2 are formed in a current collector made of a porous material provided with holes penetrating the front and back surfaces as will be described later. By using the current collector as a porous material in this way, lithium metal 4 is arranged, for example, on the outer periphery of the electrode winding unit 6, lithium ions freely move between the electrodes through the through holes of the current collector of the electrode winding unit 6 from the lithium metal 4. All negative electrodes and / or positive electrodes of the winding unit 6 can be doped with lithium ions.
The outer container 5 is not particularly limited, and a cylindrical type, a square type, a laminate type, or the like can be used as appropriate. The wound type lithium ion capacitor is a lithium ion capacitor having an electrode winding unit in the outer container. The electrode winding unit also includes an electrode unit in which a ribbon-like positive electrode and a negative electrode are laminated via a separator and folded in a staggered manner.

  The lithium metal 4 can be formed by pressing and bonding a lithium metal to a lithium electrode current collector. The lithium electrode current collector is preferably of the same porous structure as the current collectors of the positive electrode 1 and the negative electrode 2 so that lithium metal can be easily crimped and lithium ions can pass through if necessary. Further, the lithium electrode current collector is provided with a lithium electrode terminal, and the lithium electrode terminal is electrically connected to, for example, a negative electrode terminal.

  When an electrolyte (electrolyte) capable of transporting lithium ions is injected into the thus configured cell and sealed, and left in this state for a predetermined time (for example, 10 days), the lithium metal 4 and the anode 2 Are short-circuited, so that the negative electrode 2 can be preliminarily doped with lithium ions. In the present invention, the “positive electrode” means that a current flows out during discharging, the electrode into which current flows during charging, and the “negative electrode” refers to a current flowing during discharging, and during charging. It means the pole where the current flows out.

  Since the electrode structure of the positive electrode 1 and the negative electrode 2 in the electrode winding unit 6 is substantially the same, the negative electrode 2 will be described below. FIG. 2 is a plan view of the negative electrode 2 when the electrode winding unit 6 is unwound and unfolded, and is partially cut away. FIG. 3 is an enlarged cross-sectional view taken along line AA in FIG. As shown in the figure, the negative electrode 2 is an electrode layer formed by applying a negative electrode active material to be described later on one side (upper surface in FIGS. 1 and 2) of a ribbon-like negative electrode current collector 2a (the negative electrode layer is shown in FIG. The negative electrode terminal 9 is connected to the current collector surface on which the electrode layer of the negative electrode current collector 2a is not formed.

  The negative electrode current collector 2a is a porous material having holes 7 penetrating the front and back surfaces, and the negative electrode terminal 9 is stitched or cold welded to the current collector surface of the negative electrode current collector 2a where the negative electrode 2 is not formed. It is preferable to be connected. The negative electrode terminal 9 can be connected even on the current collector surface on which the negative electrode 2 is formed, that is, the electrode layer surface, but the internal resistance increases because the terminal is connected via the electrode layer. In the present invention, since the negative electrode terminal 2 is directly connected to the current collector surface on which the negative electrode 2 is not formed by stitching or cold welding, the connecting operation of the negative electrode terminal 9 is easy and the internal resistance can be reduced. The position where the negative electrode terminal 9 is connected to the negative electrode current collector 2a is determined and not limited by the position where the negative electrode terminal 9 is taken out of the electrode winding unit 6, but usually from, for example, the end of the ribbon-shaped current collector It is preferable to connect to the current collector surface that enters the inside by a predetermined distance.

  The negative electrode terminal and the positive electrode terminal may be provided separately at both ends of the electrode winding unit 6, or may be provided so as to be taken out together at one end. Further, the number of electrode terminals provided on one ribbon-like current collector (electrode) can be determined as appropriate depending on the size of the cell and is not limited. For example, in a small cell, it is sufficient to provide one for each current collector. However, in a large cell, a larger number of terminals can reduce the internal resistance. As the material of the electrode terminals of the negative electrode and the positive electrode, the same material as the negative electrode current collector and the positive electrode current collector can be preferably used from the viewpoint of connectivity and expandability, but is not limited to the same material.

  When the negative electrode active material is applied to the negative electrode current collector 2a to form the negative electrode 2, it is preferable to form a base layer 8 of a conductive material on the coated surface of the negative electrode current collector 2a as shown in FIG. Since the negative electrode current collector 2a is a porous material, if the negative electrode active material is applied directly to the current collector, the negative electrode active material leaks from the holes 7 of the current collector or the coated surface is not smooth. There is a possibility that the negative electrode 2 cannot be formed with a uniform thickness. If the undercoat layer 8 is formed on the current collector coating surface, the holes 7 can be closed with the undercoat layer 8 and the coating surface can be smoothed, so that the anode active material can be easily applied and the anode has a uniform thickness. 2 can be obtained. Although not shown, the positive electrode 1 is similarly coated with a positive electrode active material on one surface of a porous positive electrode current collector to form an electrode layer, and a positive electrode terminal is connected to the other surface where the electrode layer is not formed. Can be obtained.

  FIG. 4 is a partially enlarged view of a portion X of the electrode winding unit 6 shown in FIG. In the wound type lithium ion capacitor of this example, the negative electrode 2 is disposed on the outermost periphery (outermost layer) of the electrode winding unit 6 with the negative electrode current collector 2a facing outside, and lithium ions are disposed outside the negative electrode current collector 2a. As a supply source, a lithium metal 4 is fitted and crimped on, for example, a current collector surface. Thus, the lithium metal 4 pressure-bonded to the negative electrode current collector 2 a is short-circuited to the negative electrode 2, so that lithium ions are doped into the negative electrode 2 by electrochemical contact between the negative electrode 2 and the lithium metal 4.

  The wound lithium ion capacitor of the present invention is arranged with the outermost periphery of the electrode winding unit 6 as the negative electrode 2 and the current collector surface on which the electrode layer of the negative electrode 2 is not formed as shown in this example. The lithium metal 4 is preferably brought into contact with the current collector surface. By using the negative electrode 2 as the outermost periphery of the electrode winding unit 6, it is possible to prevent problems even if the negative electrode 2 and the lithium metal 4 are short-circuited, and the arrangement of the lithium metal in the cell becomes simple. Etc. are obtained. Further, the negative electrode current collector 2a on which the negative electrode 2 is not formed is disposed on the outside, and the lithium metal 4 is directly bonded to the negative electrode current collector 2a, whereby the lithium electrode current collector is attached to the negative electrode current collector 2a. This also makes it possible to eliminate the need for a lithium electrode current collector, and at the same time eliminates the need to connect lithium metal and the negative electrode, thereby improving energy density, simplifying the cell structure, and simplifying the process. Is made. However, the lithium metal 4 may be used by being pressure-bonded to a lithium electrode current collector.

  In the electrode winding unit 6, the electrode layer of the negative electrode 2 and the electrode layer of the positive electrode 1 are preferably opposed to each other with the separator 2 interposed therebetween as shown in FIG. 4. By disposing the negative electrode 2 and the positive electrode 1 in this way, the electrode layers of both electrodes are faced to both sides of the separator 3, so that the detachment and occlusion of lithium ions during charging / discharging of the cell are smoother and more reliable. . However, the arrangement of the negative electrode 2 and the positive electrode 1 in the electrode winding unit 6 is not limited to this, and the electrode layer of the negative electrode 2 and the positive electrode current collector 1a of the positive electrode 1 are opposed to each other with the separator 3 interposed therebetween. Also good.

  The lithium metal 4 may be provided outside the outermost negative electrode 2 (exactly, the negative electrode current collector 2a) of the electrode winding unit 6 via the separator 3, or the electrode winding unit 6 as necessary. Alternatively, the separator 3 may be provided outside the lithium metal 4 that has been wound around.

  In a preferred embodiment of the present invention, it is preferable to fix the electrode winding unit 6 and the lithium metal 4 with a tape 11 from the outside as shown in FIG. When a separator is provided at the outermost part of the electrode winding unit 6, the tape 11 is stopped from above the separator. By fixing the outside of the electrode winding unit 6 with the tape 11 in this way, the insertion into the outer container 5 is facilitated, and the cell assembly workability is improved. In FIG. 5, the negative electrode terminal 9 and the positive electrode terminal 10 are provided separately at both ends of the electrode winding unit 6.

  In the present invention, the above-described tape fastening can be performed by the following method. That is, although not shown, the outermost periphery of the electrode winding unit 6 can be taped, for example, in order to prevent the electrode winding unit 6 from being unwound during or after manufacture. It is preferable to arrange so that the lithium metal surface is on the inner side (the lithium electrode current collector is on the outer side) so as not to overlap the winding tape of the electrode winding unit 6. The other method is to wind the electrode winding unit 6 with an adhesive tape to which the lithium metal 4 is attached, and the advantage that the winding of the electrode winding unit and the arrangement of the lithium metal 4 can be performed simultaneously is obtained. It is done.

  The material of the tape 11 is not particularly limited as long as it is durable to the electrolytic solution and does not adversely affect the cell, but a tape made of the same material as the separator is optimal. Further, the thickness and width of the tape 11 are preferably about 50 to 100 μm in thickness and about 5 to 10 mm in width because the electrode winding unit can be stably fixed and workability is good. The position and number of the tapes 11 to be fixed are appropriately determined mainly according to the dimensions of the electrode winding unit 6, but when the height T (see FIG. 5) of the electrode winding unit 6 is, for example, 50 to 100 mm, 2 is used. Or it can stop stably in three places.

  FIG. 6 is a cross-sectional view of an electrode winding unit 6 according to another embodiment of the present invention. The electrode winding unit 6 of this example is a flat wound layered body in which a ribbon-like positive electrode 1 and a negative electrode 2 are wound with a separator 3 interposed therebetween. A separator 3 is provided between them and a lithium metal 4 is provided. Each of the positive electrode 1 and the negative electrode 2 of the electrode winding unit 6 has an electrode layer formed on one side of a porous electrode current collector in the same manner as the electrode in the cylindrical electrode winding unit 6 of FIG. The electrode terminals are connected to the current collector surface on which the respective electrode layers are not formed. The lithium metal 4 is formed on both sides of a plate-like lithium electrode current collector 4a, and the lithium metal 4 is short-circuited with, for example, the negative electrode 2 through an extraction terminal provided on the lithium electrode current collector 4a. Lithium ions extracted from the lithium metal 4 disposed in the part move outward through the holes of the positive and negative current collectors, and are doped into the negative electrode 2 of the wound electrode winding unit 6. Yes.

  In this example, the lithium metal 4 is provided at the core of the flat electrode winding unit 6, but the lithium metal 4 may be provided at the outer periphery of the electrode winding unit 6. Further, the outside of the electrode winding unit 6 may be taped with or without a separator as required, and when the lithium metal 4 is disposed on the outer periphery of the electrode winding unit 6 Can be taped from above the lithium metal 4.

Below, the main elements which comprise the lithium ion capacitor of this invention are demonstrated one by one.
As the positive electrode current collector and the negative electrode current collector of the present invention, various materials generally proposed for applications such as organic electrolyte batteries can be used. The positive electrode current collector is made of aluminum, stainless steel, or the like. Stainless steel, copper, nickel and the like can be suitably used for the body, and various shapes such as foil and net can be used. In particular, in order to support lithium ions in advance on the negative electrode and / or the positive electrode, those having holes penetrating the front and back surfaces are preferable. For example, expanded metal, punching metal, metal net, foam, or through holes are provided by etching. A porous foil etc. can be mentioned. The through-hole of the electrode current collector can be appropriately set to be round, square, or the like.

More preferably, before forming the electrode, at least a part of the through hole of the electrode current collector is blocked with a conductive material that does not easily fall off, and the positive electrode and the negative electrode are formed thereon, thereby forming the electrode In addition to improving the productivity of the capacitor, it solves the problem of reduced reliability of the capacitor due to electrode dropping, and furthermore, the electrode including the current collector can be made thinner to achieve high energy density and high output density. .
The shape and number of through-holes in the electrode current collector are blocked by a conductive material so that lithium ions in the electrolyte described later can move between the front and back of the electrode without being blocked by the electrode current collector. It can be set as appropriate so as to facilitate.

  The porosity of this electrode current collector is defined as that obtained by converting the ratio of {1- (current collector weight / current collector true specific gravity) / (current collector apparent volume)} into a percentage. The porosity of the electrode current collector used in the present invention is usually 10 to 79%, preferably 20 to 60%. It is desirable that the porosity and the pore diameter of the electrode current collector are appropriately selected within the above-mentioned range in consideration of the cell structure and productivity.

  The negative electrode active material is not particularly limited as long as it can reversibly carry lithium ions, and is, for example, a heat-treated product of graphite, non-graphitizable carbon, aromatic condensation polymer, and hydrogen atoms / carbon atoms. A polyacene organic semiconductor (PAS) having a polyacene skeleton structure having a number ratio (hereinafter referred to as H / C) of 0.50 to 0.05 can be given. Among these, PAS is more preferable in that a high capacity can be obtained. For example, if a PAS with H / C = 0.2 is loaded (charged) with 400 mAh / g of lithium ions, and then discharged, a capacitance of 650 F / g or more is obtained, and a lithium ion of 500 mAh / g or more is obtained. Is charged, a capacitance of 750 F / g or more is obtained. From this, it can be seen that PAS has a very large capacitance.

  In a preferred embodiment of the present invention, when an active material having an amorphous structure such as PAS is used for the negative electrode, the potential decreases as the amount of lithium ions to be carried increases, so that the withstand voltage (charging voltage) of the obtained power storage device In addition, the rate of increase in voltage during discharge (the slope of the discharge curve) decreases, so that the amount of lithium ions is within the range of lithium ion storage capacity of the active material, depending on the required operating voltage of the power storage device. It is desirable to set appropriately.

  In addition, since PAS has an amorphous structure, there is no structural change such as swelling / shrinkage with respect to insertion / extraction of lithium ions, so that cycle characteristics are excellent, and isotropic to insertion / extraction of lithium ions. Since it has a molecular structure (higher order structure), it is suitable as a negative electrode material because it has excellent characteristics in rapid charge and rapid discharge.

  The aromatic condensation polymer that is a precursor of PAS is a condensate of an aromatic hydrocarbon compound and an aldehyde. As the aromatic hydrocarbon compound, so-called phenols such as phenol, cresol, xylenol and the like can be suitably used. For example, the following formula

(Where x and y are each independently 0, 1 or 2)
Or a biphenyl or a hydroxynaphthalene. Among these, phenols, particularly phenol, are preferable for practical use.

  As the aromatic condensed polymer, a part of the aromatic hydrocarbon compound having a phenolic hydroxyl group is substituted with an aromatic hydrocarbon compound having no phenolic hydroxyl group, such as xylene, toluene, aniline, etc. It is also possible to use a modified aromatic condensation polymer such as a condensate of phenol, xylene and formaldehyde. Furthermore, a modified aromatic polymer substituted with melamine or urea can be used, and a furan resin is also suitable.

  In the present invention, PAS is used as an insoluble and infusible substrate, and the insoluble and infusible substrate can also be produced, for example, from the aromatic condensation polymer as follows. That is, by gradually heating the aromatic condensation polymer to an appropriate temperature of 400 to 800 ° C. in a non-oxidizing atmosphere (including vacuum), H / C is 0.5 to 0.05. Preferably, an insoluble and infusible substrate of 0.35 to 0.10 can be obtained.

However, the method for producing an insoluble and infusible substrate is not limited to this, and is, for example, a method described in Japanese Patent Publication No. 3-24024, etc., and has the above H / C and 600 m ² / g It is also possible to obtain an insoluble and infusible substrate having a specific surface area by the above BET method.

  According to X-ray diffraction (CuKα), the insoluble and infusible substrate used in the present invention has a main peak position represented by 2θ of 24 ° or less, and 41 to 46 ° in addition to the main peak. There are other broad peaks in between. That is, the insoluble infusible substrate has a polyacene skeleton structure in which an aromatic polycyclic structure is appropriately developed, has an amorphous structure, and can be stably doped with lithium. Suitable as an active material.

  In the present invention, the negative electrode active material preferably has a pore diameter of 3 nm or more and a pore volume of 0.10 mL / g or more, and the upper limit of the pore diameter is not limited, but is usually in the range of 3 to 50 nm. Moreover, although it does not specifically limit about the range of pore volume, Usually, it is 0.10-0.5 mL / g, Preferably it is 0.15-0.5 mL / g.

  In the present invention, the negative electrode is formed on the negative electrode current collector from the above-mentioned carbon material or negative electrode active material powder such as PAS, but the method is not specified and a known method can be used. Specifically, the negative electrode active material powder, the binder and, if necessary, the conductive powder are dispersed in an aqueous or organic solvent to form a slurry, and the slurry is applied to the current collector, or the slurry is preliminarily sheeted. It can form by shape | molding in a shape and sticking this on a collector. As the binder used here, for example, a rubber-based binder such as SBR, a synthetic fluorine-based resin such as polytetrafluoroethylene or polyvinylidene fluoride, or a thermoplastic resin such as polypropylene or polyethylene can be used. Among them, a fluorine-based binder is preferable, and it is particularly preferable to use a fluorine-based binder having a fluorine atom / carbon atom ratio (hereinafter referred to as F / C) of 0.75 or more and less than 1.5. More preferred is a fluorine-based binder of less than 1.3. Although the usage-amount of a binder changes with kinds, electrode shape, etc. of a negative electrode active material, it is 1-20 weight% with respect to a negative electrode active material, Preferably it is 2-10 weight%.

Moreover, as an electroconductive material used as needed, acetylene black, a graphite, a metal powder, etc. are mentioned. The amount of the conductive material used varies depending on the electrical conductivity of the negative electrode active material, the electrode shape, etc., but it is appropriate to add it in a proportion of 2 to 40% by weight with respect to the negative electrode active material.
In addition, the thickness of the negative electrode active material is designed with a balance of the thickness with the positive electrode active material so that the energy density of the cell can be secured, but considering the output density and energy density of the cell, industrial productivity, etc. The thickness of one side of the current collector is usually 15 to 100 μm, preferably 20 to 80 μm.

  In the LIC of the present invention, the positive electrode contains a positive electrode active material capable of reversibly supporting lithium ions and / or anions such as tetrafluoroborate.

  The positive electrode active material is not particularly limited as long as it can reversibly carry lithium ions and / or anions. For example, the positive electrode active material is a heat-treated product of activated carbon, conductive polymer, aromatic condensation polymer, and H / Examples thereof include a polyacene organic semiconductor (PAS) having a polyacene skeleton structure in which C is 0.05 to 0.50.

  The method for forming the positive electrode on the positive electrode current collector using the positive electrode active material is substantially the same as in the case of the negative electrode described above, and a detailed description thereof will be omitted.

  Further, in the LIC of the present invention, the capacitance per unit weight of the negative electrode active material has more than three times the capacitance per unit weight of the positive electrode active material, and the positive electrode active material weight is more than the negative electrode active material weight. Is also preferably large. In consideration of the capacitance of the positive electrode to be used, by appropriately controlling the filling amount (pre-doping amount) of lithium ions into the negative electrode, a capacitance more than three times the capacitance per unit weight of the positive electrode is secured, In addition, the weight of the positive electrode active material can be heavier than the weight of the negative electrode active material. Thereby, a capacitor having a higher voltage and a higher capacity than the conventional electric double layer capacitor can be obtained. Furthermore, when a negative electrode having a capacitance per unit weight larger than the capacitance per unit weight of the positive electrode is used, the negative electrode active material weight can be reduced without changing the potential change amount of the negative electrode. Therefore, the filling amount of the positive electrode active material is increased, and the capacitance and capacity of the cell can be increased. The weight of the positive electrode active material is preferably larger than the weight of the negative electrode active material, but more preferably 1.1 times to 10 times. If it is less than 1.1 times, the capacity difference becomes small, and if it exceeds 10 times, the capacity may be reduced, and the thickness difference between the positive electrode and the negative electrode becomes too large, which is not preferable in terms of the cell structure.

  As the electrolyte of the present invention, an electrolyte capable of transporting lithium ions is used. Such an electrolyte is preferably a liquid that can be impregnated in a separator. As the electrolyte solvent, an aprotic organic solvent capable of forming an aprotic organic solvent electrolyte solution can be preferably used. Examples of the aprotic organic solvent include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, acetonitrile, dimethoxyethane, tetrahydrofuran, dioxolane, methylene chloride, sulfolane and the like. Furthermore, a mixed solution in which two or more of these aprotic organic solvents are mixed can also be used.

As an electrolyte to be dissolved in such a solvent, any electrolyte can be used as long as it can transfer lithium ions, does not cause electrolysis even at a high voltage, and can stably exist. As such an electrolyte, lithium salts such as LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiPF _{6, and} Li (C ₂ F ₅ SO ₂ ) ₂ N can be preferably used.

  The electrolyte and solvent are mixed in a sufficiently dehydrated state to obtain an electrolytic solution. The concentration of the electrolyte in the electrolytic solution is at least 0.1 mol / L or more in order to reduce the internal resistance due to the electrolytic solution. It is preferable to make it within a range of 0.5 to 1.5 mol / L.

  Further, as the separator, a non-electrically conductive porous body having continuous vent holes that are durable against an electrolytic solution or an electrode active material can be used. Examples of the material of the separator include cellulose (paper), polyethylene, and polypropylene, and known materials can be used. Among these, cellulose (paper) is excellent in terms of durability and economy. Although the thickness of a separator is not limited, Usually, about 20-50 micrometers is preferable.

  In the present invention, the lithium metal is preferably formed on a lithium electrode current collector made of a conductive porous body. Here, it is preferable to use a porous metal body that does not react with a lithium ion supply source, such as a stainless mesh, as the conductive porous body serving as the lithium electrode current collector. For example, when lithium metal is used as the lithium ion supply source and a conductive porous material such as stainless steel mesh is used as the lithium electrode current collector, at least a portion of the lithium metal, preferably 80% by weight or more, is a pore of the lithium electrode current collector. It is preferably embedded in the part. Thereby, even after lithium ions are supported on the negative electrode, gaps generated between the electrodes due to the disappearance of the lithium metal are reduced, and the reliability of the LIC can be more reliably maintained.

  The thickness of the lithium metal to be pressure-bonded to the lithium electrode current collector is not limited because it can be appropriately determined in consideration of the amount of lithium ions supported in advance on the negative electrode, but is usually preferably about 50 to 300 μm.

  In the wound capacitor of the present invention, the material of the outer container is not particularly limited, and various materials generally used for batteries or capacitors can be used. For example, metal materials such as iron and aluminum, plastic materials, or those materials The composite material etc. which laminated | stacked can be used. Further, the shape of the outer container is not particularly limited, and can be appropriately selected depending on the application, such as a cylindrical shape or a rectangular shape as described above, but the columnar electrode winding unit is a cylindrical, flat electrode. The winding unit is preferably square. From the viewpoint of reducing the size and weight of the LIC, a film-type exterior container using a laminate film of aluminum and a polymer material such as nylon or polypropylene can also be used.

  Hereafter, an example of the manufacturing method of LIC of this invention is shown. The through hole of the electrode collector of the LIC may or may not be blocked with a conductive material, but in this example, the case of blocking will be described. The through hole of the electrode current collector can be closed by a known method such as a spray method using, for example, a carbon-based conductive material.

  Next, a positive electrode and a negative electrode are formed on one surface of the electrode current collector in which the through hole is closed with a conductive material. In the positive electrode, a positive electrode active material is mixed with a binder resin to form a slurry, which is coated on a positive electrode current collector and dried to form an electrode layer. Similarly, the negative electrode is formed by mixing a negative electrode active material with a binder resin to form a slurry, coating the negative electrode current collector, and drying.

  The lithium ion supply source is formed by pressure bonding lithium metal on a lithium electrode current collector made of a conductive porous body. The thickness of the lithium current collector is about 10 to 200 μm, and the thickness of the lithium metal is generally about 50 to 300 μm, although it depends on the amount of the negative electrode active material used.

  Each electrode is dried and then cut into a predetermined size, and an electrode terminal is connected by stitching, for example, to the current collector surface where the electrode layer of the cut electrode is not formed.

  Next, the electrode current collector on which the electrode is formed is wound while sandwiching the separator so that the positive electrode and the negative electrode are opposed to each other, and a cylindrical electrode winding unit is assembled. At this time, the negative electrode current collector is positioned on the outermost periphery of the electrode winding unit so that the current collector surface on which no electrode layer is formed is on the outside, and lithium metal is placed on the outer side of the electrode winding unit. Place it in contact with the electrical body and tape the outside. The electrode terminals of the positive electrode and the negative electrode are taken out at both ends of the electrode winding unit, and the terminals provided on the lithium metal lithium electrode current collector are connected to the electrode terminals of the negative electrode.

  Next, the electrode winding unit fixed with tape is inserted into the outer container, and the electrolytic solution is injected. Thereafter, the electrode terminal is taken out from the rubber gasket, and then the outer container is sealed and caulked with the gasket, whereby the wound type (cylindrical) lithium ion capacitor of the present invention is obtained.

  When the electrolyte is injected, all the negative electrode and lithium metal are in electrochemical contact, and the lithium ions eluted from the lithium metal into the electrolyte move to the negative electrode over time, and a predetermined amount of lithium ion is carried on the negative electrode. Is done. When lithium ions are supported on the negative electrode, even if distortion occurs due to the penetration of lithium ions into the negative electrode, the negative electrode can be prevented from being deformed because it is fixed with tape.

  Thus, the LIC of a preferred embodiment of the present invention uses an active material capable of reversibly supporting lithium ions and / or anions for the positive electrode, and uses an aprotic organic solvent solution of lithium salt for the electrolyte. The negative electrode is a lithium metal having a capacitance more than three times the capacitance per unit weight of the positive electrode active material, the positive electrode active material weight is larger than the negative electrode active material weight, and the lithium is previously supported on the negative electrode Is provided in the cell, and the negative electrode before charging can be previously doped with lithium ions.

  In addition, by using a negative electrode having a capacitance per unit weight that is larger than the capacitance per unit weight of the positive electrode, the weight of the negative electrode active material can be reduced without changing the potential change amount of the negative electrode. Therefore, the filling amount of the positive electrode active material is increased, and the capacitance and capacity of the cell are increased. In addition, since the negative electrode has a large capacitance, the potential change amount of the negative electrode is reduced, and as a result, the potential change amount of the positive electrode is increased, and the capacitance and capacitance of the cell are increased.

  Further, in the conventional electric double layer capacitor, the potential of the positive electrode drops only to about 3V at the time of discharge, but in the lithium ion capacitor of the present invention, the negative electrode potential is low, so that the positive electrode potential can be lowered to 3V or less. The capacity is higher than that of the double layer capacitor.

Furthermore, in order to obtain a required capacity as a negative electrode capacity, a predetermined amount of lithium ions is supported on the negative electrode in advance, so that the operating voltage of a normal capacitor is about 2.3 to 2.7 V, whereas 3 V or more The energy density is improved.
Details will be described below with reference to specific examples.

Example 1
(Production method of negative electrode 1)
A 0.5 mm thick phenolic resin molded plate is placed in a siliconite electric furnace, heated to 500 ° C. at a rate of 50 ° C./hour, and further at a rate of 10 ° C./hour to 660 ° C. in a nitrogen atmosphere, followed by heat treatment. PAS was synthesized. The PAS plate thus obtained was pulverized with a disk mill to obtain a PAS powder. The H / C ratio of this PAS powder was 0.21.

Next, 100 parts by weight of the PAS powder and a solution prepared by dissolving 10 parts by weight of polyvinylidene fluoride powder in 80 parts by weight of N-methylpyrrolidone were sufficiently mixed to obtain a slurry. The slurry was applied on one side of a 18 μm thick copper foil to a solid content of about 7 mg / cm ² , dried and pressed to obtain a PAS negative electrode 1.

(Method for producing positive electrode 1)
A slurry was obtained by thoroughly mixing 100 parts by weight of a commercially available specific surface area of 1950 m ² / g activated carbon powder and 10 parts by weight of polyvinylidene fluoride powder in 100 parts by weight of N-methylpyrrolidone. The slurry was applied on one side of an aluminum foil having a thickness of 20 μm coated with a carbon-based conductive paint to a solid content of about 7 mg / cm ² , dried and pressed to obtain a positive electrode 1.

(Capacitance measurement per unit weight of positive electrode 1)
The positive electrode was cut into a size of 1.5 × 2.0 cm ² and used as a positive electrode for evaluation. Using a lithium metal of 1.5 × 2.0 cm ² size and a thickness of 200 μm as a positive electrode and a counter electrode, a simulated cell was assembled through a non-woven fabric made of polyethylene having a thickness of 50 μm as a separator. Metallic lithium was used as a reference electrode. As the electrolytic solution, a solution obtained by dissolving LiPF ₆ in propylene carbonate at a concentration of 1 mol / l was used.

  The battery was charged to 3.6 V at a charging current of 1 mA and then charged at a constant voltage. After a total charging time of 1 hour, the battery was discharged to 2.5 V at 1 mA. The capacitance per unit weight of the positive electrode 1 was determined from the discharge time between 3.5 V and 2.5 V and found to be 92 F / g.

(Capacitance measurement per unit weight of negative electrode 1)
Four negative electrodes were cut into 1.5 × 2.0 cm ² sizes, and used as negative electrodes for evaluation. Using a lithium metal of 1.5 × 2.0 cm ² size and a thickness of 200 μm as a negative electrode and a counter electrode, a simulated cell was assembled through a non-woven fabric made of polyethylene having a thickness of 50 μm as a separator. Metallic lithium was used as a reference electrode. As the electrolytic solution, a solution obtained by dissolving LiPF ₆ in propylene carbonate at a concentration of 1 mol / l was used.

  Lithium ions for 280 mAh / g, 350 mAh / g, 400 mAh / g, and 500 mAh / g were charged with respect to the weight of the negative electrode active material at a charging current of 1 mA, and then discharged to 1.5 V at 1 mA. The electrostatic capacity per unit weight of the negative electrode 1 was determined from the discharge time during which the potential of the negative electrode changed by 0.2 V from the potential of the negative electrode one minute after the start of discharge. The results are shown in Table 1.

  The amount of charge here is a value obtained by dividing the integrated value of the charging current flowing through the negative electrode by the weight of the negative electrode active material, and the unit is mAh / g.

(Production method of negative electrode 2)
The slurry of the negative electrode 1 is formed on one side of a copper expanded metal (manufactured by Nippon Metal Industry Co., Ltd.) having a thickness of 32 μm (porosity 50%) by a die coater, and the thickness of the negative electrode as a whole (negative electrode layer on one side) The negative electrode 2 having a total thickness of 82 μm was obtained.

(Method for producing positive electrode 2)
A non-aqueous carbon-based conductive paint (Nippon Acheson Co., Ltd .: EB-815) is coated on one side of an aluminum expanded metal (manufactured by Nippon Metal Industry Co., Ltd.) with a thickness of 35 μm (porosity 50%) by a spray method. The positive electrode current collector on which the conductive layer was formed was obtained by drying. The total thickness (the sum of the current collector thickness and the conductive layer thickness) was 45 μm, and the through holes were almost blocked by the conductive paint. The positive electrode 1 slurry is formed on the surface of the positive electrode current collector on which the conductive paint is formed using a roll coater, and the thickness of the positive electrode after pressing (the thickness of the positive electrode layer on one side, the thickness of the conductive layer on one side, and the positive electrode collector). A positive electrode 2 having a total thickness (electrical body thickness) of 175 μm was obtained.

(Production of electrode winding unit 1)
The negative electrode 2 having a thickness of 82 μm is cut into a width of 3.0 × a length of 58.0 cm ² , a copper terminal is placed on a negative electrode current collector on which the negative electrode layer is not formed, and the terminal is collected by stitching. Connected to electrical body. Further, the positive electrode 2 having a thickness of 175 μm was cut into a width of 3.0 × length of 56.0 cm ² , an aluminum terminal was placed on a positive electrode current collector on which no positive electrode layer was formed, and the terminal was formed by stitching. Was connected to the positive electrode current collector. Using a cellulose / rayon mixed nonwoven fabric with a thickness of 35 μm as a separator, three electrode winding units 1 are wound and taped so that the positive and negative terminals are in the same direction and the outermost periphery is a separator. Produced.

(Production of cell 1)
As a lithium electrode, a lithium metal foil (128 μm, 3.0 × 4.0 cm ² , equivalent to 400 mAh / g) is bonded to a copper expanded metal having a thickness of 32 μm (porosity 50%) as a lithium electrode current collector. The lithium electrode is placed on the outermost circumference so that it does not overlap the winding tape of the electrode winding unit 1 and the lithium metal surface of the lithium electrode is on the inside, and the terminal weld of the lithium electrode current collector is the negative electrode Resistance welding was performed on the terminal welded portion to obtain a three-pole wound unit.

The triode winding unit is inserted into an aluminum outer can having an outer diameter of 18 mmΦ and a height of 40 mm, and a mixed solvent in which ethylene carbonate, diethyl carbonate, and propylene carbonate are used at a weight ratio of 3: 4: 1 as an electrolytic solution. Three impregnated lithium ion capacitor cells 1 were assembled by vacuum impregnating a solution of LiPF ₆ at a concentration of 1 mol / l and then covering the outer can with a cap made of butyl rubber. In addition, the lithium metal arrange | positioned in a cell is equivalent to 400 mAh / g per negative electrode active material weight.

(Initial evaluation of the cell)
When one cell was disassembled after being left for 20 days after cell assembly, all the lithium metal was completely lost. Therefore, lithium ions for obtaining a capacitance of 660 F / g or more per unit weight of the negative electrode active material were preliminarily used. Judged that it was charged. The capacitance of the negative electrode is 7.2 times that of the positive electrode.

(Characteristic evaluation of cells)
The battery was charged at a constant current of 400 mA until the cell voltage reached 3.6 V, and then a constant current-constant voltage charge in which a constant voltage of 3.6 V was applied was performed for 1 hour. Next, the battery was discharged at a constant current of 40 mA until the cell voltage reached 1.9V. This cycle of 3.6V-1.9V was repeated, and the cell capacity, energy density, and internal resistance in the 10th discharge were evaluated. The results are shown in Table 2. However, the data is an average of two cells.

  When the positive electrode and negative electrode of one cell were short-circuited after the measurement was completed, and the potential of the positive electrode was measured, it was about 0.95 V, and was 2.0 V or less. A capacitor having a high energy density was obtained by previously supporting lithium ions on the negative electrode and / or the positive electrode so that the positive electrode potential when the positive electrode and the negative electrode were short-circuited was 2.0 V or less. In addition, it is preferable to continuously form an electrode layer on one side of a current collector having through holes on the front and back surfaces because this is an extremely simple process and an inexpensive lithium ion capacitor can be provided.

(Comparative Example 1)
(Method for producing negative electrode 3)
The slurry of the negative electrode 1 was formed on both sides of a copper expanded metal (manufactured by Nippon Metal Industry Co., Ltd.) having a thickness of 32 μm (porosity 50%) with a die coater, and the thickness of the whole negative electrode after pressing (the negative electrode layers on both sides) The negative electrode 3 having a thickness of 148 μm was obtained.

(Production method of positive electrode 3)
Non-aqueous carbon conductive paint (Nippon Acheson Co., Ltd .: EB-815) is coated on both sides of an aluminum expanded metal (manufactured by Nippon Metal Industry Co., Ltd.) with a thickness of 35 μm (porosity 50%) by a spray method. The positive electrode current collector on which the conductive layer was formed was obtained by drying. The total thickness (the sum of the current collector thickness and the conductive layer thickness) was 52 μm, and the through-hole was almost blocked by the conductive paint. The positive electrode 1 slurry is formed on both sides of the positive electrode current collector with a roll coater, and the thickness of the entire positive electrode after pressing (the total thickness of the positive electrode layer on both sides, the thickness of the conductive layer on both sides, and the thickness of the positive electrode collector) ) Obtained a positive electrode 3 of 312 μm.

(Preparation of electrode winding unit 2)
A negative electrode 3 having a thickness of 148 μm was cut into a width of 3.0 × a length of 36.0 cm ² , a copper terminal was placed on the negative electrode layer, and the terminal was connected to the negative electrode by stitching. Further, the positive electrode 3 having a thickness of 312 μm was cut into a width of 3.0 × a length of 34.0 cm ² , an aluminum terminal was placed on the positive electrode layer, and the terminal was connected to the positive electrode by stitching. Using a cellulose / rayon mixed nonwoven fabric having a thickness of 35 μm as a separator, the positive and negative terminals were wound in the same direction, and the outermost periphery was taped to produce three electrode winding units 2.

(Production of cell 2)
As a lithium electrode, a lithium metal foil (159 μm, 3.0 × 4.0 cm ² , equivalent to 400 mAh / g) is bonded to a copper expanded metal having a thickness of 32 μm (porosity 50%) as a lithium electrode current collector. The lithium electrode is placed on the outermost periphery so that it does not overlap the winding tape of the electrode winding unit 2 and the lithium metal surface of the lithium electrode is on the inside, and the terminal weld of the lithium electrode current collector is the negative electrode Resistance welding was performed on the terminal welded portion to obtain a three-pole wound unit.

The triode winding unit is inserted into an aluminum outer can having an outer diameter of 18 mmΦ and a height of 40 mm, and a mixed solvent in which ethylene carbonate, diethyl carbonate, and propylene carbonate are used at a weight ratio of 3: 4: 1 as an electrolytic solution. Three impregnated lithium ion capacitor cells 2 were assembled by vacuum impregnating a solution of LiPF ₆ at a concentration of 1 mol / l and then covering the outer can with a cap made of butyl rubber. In addition, the lithium metal arrange | positioned in a cell is equivalent to 400 mAh / g per negative electrode active material weight.

(Initial evaluation of the cell)
When one cell was disassembled after being left for 20 days after cell assembly, all the lithium metal was completely lost. Therefore, lithium ions for obtaining a capacitance of 660 F / g or more per unit weight of the negative electrode active material were preliminarily used. Judged that it was charged. The capacitance of the negative electrode is 7.2 times that of the positive electrode.

(Characteristic evaluation of cells)
The battery was charged at a constant current of 300 mA until the cell voltage reached 3.6 V, and then a constant current-constant voltage charge in which a constant voltage of 3.6 V was applied was performed for 1 hour. Next, the battery was discharged at a constant current of 30 mA until the cell voltage reached 1.9V. This cycle of 3.6V-1.9V was repeated, and the cell capacity, energy density, and internal resistance in the 10th discharge were evaluated. The results are shown in Table 3. However, the data is an average of two cells.

  When the positive electrode and negative electrode of one cell were short-circuited after the measurement was completed, and the potential of the positive electrode was measured, it was about 0.95 V, and was 2.0 V or less. A capacitor having a high energy density was obtained by previously supporting lithium ions on the negative electrode and / or the positive electrode so that the positive electrode potential when the positive electrode and the negative electrode were short-circuited was 2.0 V or less. In addition, it is preferable to continuously form electrode layers on both sides of a current collector having through holes on the front and back surfaces because it is a simple process and an inexpensive lithium ion capacitor can be provided, but it is formed on the current collector. Even if the terminal is welded from above the electrode, the internal resistance of the cell increases, which is not preferable. In order to reduce internal resistance, it is particularly preferable to place and connect terminals on a current collector that is coated on one side and on which no electrode layer is formed.

(Comparative Example 2)
(Method for producing negative electrode 4)
The slurry of the negative electrode 1 is intermittently applied with a die coater on both sides of a copper expanded metal (manufactured by Nippon Metal Industry Co., Ltd.) having a thickness of 32 μm (porosity 50%), and the coated part length is 35.5 cm, uncoated. The negative electrode was patterned so as to have a portion of 10.0 cm, and the negative electrode 4 having a total thickness of the negative electrode after pressing (total thickness of the negative electrode layers on both sides and the negative electrode current collector thickness) of 148 μm was obtained.

(Method for producing positive electrode 4)
A non-aqueous carbon-based conductive paint (Nippon Acheson Co., Ltd .: EB-815) is applied to both sides of an aluminum expanded metal (manufactured by Nippon Metal Industry Co., Ltd.) having a thickness of 35 μm (porosity 50%) on both sides using a die coater. The positive electrode current collector was obtained by intermittently coating, patterning the conductive layer so that the coated part length was 33.5 cm, and the uncoated part was 10.0 cm, and drying. The total thickness (the total of the current collector thickness and the conductive layer thickness) was 52 μm, and the through-holes in the coating part were almost blocked by the conductive paint. Furthermore, the slurry of the positive electrode 1 is intermittently coated on the conductive layers on both sides with a die coater, and the positive electrode layer is pattern-formed so that the coated part length is 33.5 cm and the uncoated part is 10.0 cm. The positive electrode 4 having a total thickness of the rear positive electrode (total thickness of the positive electrode layers on both sides, the thickness of the conductive layers on both sides and the thickness of the positive electrode current collector) of 312 μm was obtained.

(Preparation of electrode winding unit 3)
The negative electrode 4 having a thickness of 148 μm is cut into a width of 3.0 × length of 36.5 cm ² so as to include an uncoated portion at a position 10 mm from the end, and a copper terminal is placed on the uncoated portion current collector. The terminals were connected to the negative electrode current collector by stitching. Further, the positive electrode 4 having a thickness of 312 μm is cut into a width of 3.0 × length of 34.5 cm ² so as to include an uncoated portion at a position 10 mm from the end, and an aluminum terminal is used to collect the uncoated portion of the current collector. It arrange | positioned on the body and the terminal was connected to the positive electrode electrical power collector by stitching. Using a cellulose / rayon mixed nonwoven fabric with a thickness of 35 μm as a separator, the positive electrode and negative electrode terminals were wound in the same direction, and the outermost periphery was taped to produce three electrode winding units 3.

(Production of cell 3)
As a lithium electrode, a lithium metal foil (159 μm, 3.0 × 4.0 cm ² , equivalent to 400 mAh / g) is bonded to a copper expanded metal having a thickness of 32 μm (porosity 50%) as a lithium electrode current collector. The lithium electrode is placed on the outermost circumference so that it does not overlap the winding tape of the electrode winding unit 3 and the lithium metal surface of the lithium electrode is on the inside, and the terminal weld of the lithium electrode current collector is the negative electrode Resistance welding was performed on the terminal welded portion to obtain a three-pole wound unit.

The triode winding unit is inserted into an aluminum outer can having an outer diameter of 18 mmΦ and a height of 40 mm, and a mixed solvent in which ethylene carbonate, diethyl carbonate, and propylene carbonate are used at a weight ratio of 3: 4: 1 as an electrolytic solution. Three cylindrical lithium ion capacitor cells 3 were assembled by vacuum impregnating a solution in which LiPF ₆ was dissolved at a concentration of 1 mol / l, and then covering the outer can with a cap made of butyl rubber. In addition, the lithium metal arrange | positioned in a cell is equivalent to 400 mAh / g per negative electrode active material weight.

(Initial evaluation of the cell)
When one cell was disassembled after being left for 20 days after cell assembly, all the lithium metal was completely lost. Therefore, lithium ions for obtaining a capacitance of 660 F / g or more per unit weight of the negative electrode active material were preliminarily used. Judged that it was charged. The capacitance of the negative electrode is 7.2 times that of the positive electrode.

(Characteristic evaluation of cells)
The battery was charged at a constant current of 300 mA until the cell voltage reached 3.6 V, and then a constant current-constant voltage charge in which a constant voltage of 3.6 V was applied was performed for 1 hour. Next, the battery was discharged at a constant current of 30 mA until the cell voltage reached 1.9V. This cycle of 3.6V-1.9V was repeated, and the cell capacity, energy density, and internal resistance in the 10th discharge were evaluated. The results are shown in Table 4. However, the data is an average of two cells.

  When the positive electrode and negative electrode of one cell were short-circuited after the measurement was completed, and the potential of the positive electrode was measured, it was about 0.95 V, and was 2.0 V or less. A capacitor having a high energy density was obtained by previously supporting lithium ions on the negative electrode and / or the positive electrode so that the positive electrode potential when the positive electrode and the negative electrode were short-circuited was 2.0 V or less. Moreover, since the terminal was welded onto the current collector in the uncoated part, the internal resistance of the cell was also reduced. However, the process of intermittently applying an electrode layer to a current collector having through holes on the front and back surfaces is extremely difficult, and an inexpensive lithium ion capacitor cannot be provided.

(Example 2)
(Production of cell 4)
The electrode winding unit is wound so that the outermost periphery becomes a negative electrode current collector, and a lithium metal foil (equivalent to 128 μm, 3.0 × 4.0 cm ² , 400 mAh / g) is directly bonded to the outermost negative electrode current collector. Three cylindrical lithium ion capacitor cells 4 were assembled in the same manner as in Example 1 except that they were taped. In addition, the lithium metal arrange | positioned in a cell is equivalent to 400 mAh / g per negative electrode active material weight.

(Initial evaluation of the cell)
When one cell was disassembled after being left for 20 days after cell assembly, all the lithium metal was completely lost. Therefore, lithium ions for obtaining a capacitance of 660 F / g or more per unit weight of the negative electrode active material were preliminarily used. Judged that it was charged. The capacitance of the negative electrode is 7.2 times that of the positive electrode.

(Characteristic evaluation of cells)
The battery was charged at a constant current of 400 mA until the cell voltage reached 3.6 V, and then a constant current-constant voltage charge in which a constant voltage of 3.6 V was applied was performed for 1 hour. Next, the battery was discharged at a constant current of 40 mA until the cell voltage reached 1.9V. This cycle of 3.6V-1.9V was repeated, and the cell capacity, energy density, and internal resistance in the 10th discharge were evaluated. The results are shown in Table 5. However, the data is an average of two cells.

  When the positive electrode and negative electrode of one cell were short-circuited after the measurement was completed, and the potential of the positive electrode was measured, it was about 0.95 V, and was 2.0 V or less. A capacitor having a high energy density was obtained by previously supporting lithium ions on the negative electrode and / or the positive electrode so that the positive electrode potential when the positive electrode and the negative electrode were short-circuited was 2.0 V or less. Also, in the case of a single-sided electrode, the negative electrode current collector can be positioned on the outermost periphery by adjusting the length of the electrode. Since an ion capacitor can be provided, it is preferable.

(Example 3)
(Production of cell 5)
The electrode winding unit was wound so that the outermost periphery was a negative electrode current collector, and a lithium metal having a thickness of 128 μm, a width of 3.0 × a length of 4.0 cm ² was previously attached, and a width of 3.0 × length Three cylindrical lithium ion capacitor cells 5 were assembled in the same manner as in Example 1 except that the outermost periphery was taped with a 6.0 cm ² adhesive tape. In addition, the lithium metal arrange | positioned in a cell is equivalent to 400 mAh / g per negative electrode active material weight.

(Initial evaluation of the cell)
When one cell was disassembled after being left for 20 days after cell assembly, all the lithium metal was completely lost. Therefore, lithium ions for obtaining a capacitance of 660 F / g or more per unit weight of the negative electrode active material were preliminarily used. Judged that it was charged. The capacitance of the negative electrode is 7.2 times that of the positive electrode.

(Characteristic evaluation of cells)
The battery was charged at a constant current of 400 mA until the cell voltage reached 3.6 V, and then a constant current-constant voltage charge in which a constant voltage of 3.6 V was applied was performed for 1 hour. Next, the battery was discharged at a constant current of 40 mA until the cell voltage reached 1.9V. This cycle of 3.6V-1.9V was repeated, and the cell capacity, energy density, and internal resistance in the 10th discharge were evaluated. The results are shown in Table 6. However, the data is an average of two cells.

  When the positive electrode and negative electrode of one cell were short-circuited after the measurement was completed, and the potential of the positive electrode was measured, it was about 0.95 V, and was 2.0 V or less. A capacitor having a high energy density was obtained by previously supporting lithium ions on the negative electrode and / or the positive electrode so that the positive electrode potential when the positive electrode and the negative electrode were short-circuited was 2.0 V or less. In addition, the length of the single-sided electrode is adjusted, the negative electrode current collector is positioned on the outermost periphery, and is wound with an adhesive tape to which a predetermined lithium metal is attached, thereby preventing the winding of the electrode winding unit and the lithium Since it becomes possible to arrange | position metal simultaneously, since a cheaper lithium ion capacitor can be provided, it is especially preferable.

(Comparative Example 3)
(Production of cell 6)
Thickness 175 .mu.m, the positive electrode 2 having a width 30.0 × 44.0cm ^2, a thickness of 175 .mu.m as a negative electrode, a positive electrode 2 having a width 30.0 × 46.0cm ² used as the positive electrode, except that no place lithium electrode Example Two cylindrical lithium ion capacitor cells 6 were assembled in the same manner as in Example 1.

(Characteristic evaluation of cells)
The battery was charged with a constant current of 400 mA until the cell voltage reached 2.5 V, and then a constant current-constant voltage charge in which a constant voltage of 2.5 V was applied was performed for 1 hour. Next, the battery was discharged at a constant current of 40 mA until the cell voltage reached 0V. The cycle of 2.5V-0V was repeated, and the cell capacity, energy density, and internal resistance in the 10th discharge were evaluated. The results are shown in Table 7. However, the data is an average of two cells.

  When the positive electrode and negative electrode of one cell were short-circuited after the measurement was completed, and the potential of the positive electrode was measured, it was about 3 V, which was 2.0 V or more. The electric double layer capacitor using activated carbon for the positive electrode and the negative electrode has an upper limit voltage as low as 3.0 V or less, and the positive electrode potential when the positive electrode and the negative electrode are short-circuited is 2.0 V or less in advance. It can be seen that the energy density is lower than that of a lithium ion capacitor doped with ions.

  The lithium ion capacitor of the present invention is extremely effective as a drive or auxiliary storage power source for electric vehicles, hybrid electric vehicles and the like. Further, it can be suitably used as a storage power source for driving such as an electric bicycle or an electric wheelchair, a power storage device for various energy such as solar energy or wind power generation, or a storage power source for household electric appliances.

It is sectional drawing of the cylindrical lithium ion capacitor which is preferable embodiment of this invention. FIG. 2 is a development plan view of a negative electrode of the cylindrical lithium ion capacitor of FIG. 1. It is an expanded sectional view of the AA arrow part of FIG. FIG. 2 is an enlarged explanatory diagram of a portion X in FIG. 1. It is a top view when the electrode winding unit of the cylindrical lithium ion capacitor of FIG. 1 is fixed with a tape. It is sectional drawing of the electrode winding unit which concerns on other embodiment of this invention. It is explanatory drawing of the conventional electrode (negative electrode).

Explanation of symbols

1: Positive electrode 1a: Positive electrode current collector 2: Negative electrode 2a: Negative electrode current collector 3: Separator 4: Lithium metal 4a: Lithium electrode current collector 5: Exterior container 6: Electrode winding unit 7: Hole 8: Underlayer 9 : Negative terminal 10: Positive terminal 11: Tape 12: Uncoated part

Claims (7)

  A positive electrode composed of a positive electrode active material capable of reversibly supporting lithium ions and / or anions, a negative electrode composed of a negative electrode active material capable of reversibly supporting lithium ions, and an aprotic organic solvent electrolyte of a lithium salt as an electrolyte A positive electrode and a negative electrode, each of which is formed as an electrode layer on one side of a current collector having holes penetrating the front and back surfaces, and each of the positive and negative electrode layers A positive electrode terminal and a negative electrode terminal are connected to a current collector surface on which no electrode is formed, and the positive electrode and the negative electrode are wound through a separator to form an electrode winding unit, and the negative electrode and / or the positive electrode The potential of the positive electrode after lithium ions are doped into the negative electrode and / or positive electrode by electrochemical contact with the lithium ion source, and the positive electrode and the negative electrode are short-circuited Wound type lithium ion capacitor, characterized by comprising a 2.0V or less.   The wound lithium ion capacitor according to claim 1, wherein the positive electrode terminal and the negative electrode terminal are connected to the current collector by stitching or cold welding.   The negative electrode active material has a capacitance per unit weight of 3 times or more as compared with the positive electrode active material, and the weight of the positive electrode active material is larger than the weight of the negative electrode active material. The wound type lithium ion capacitor according to any one of -2.   A negative electrode current collector is disposed on the outermost periphery of the electrode winding unit with a current collector surface on which no electrode layer is formed facing outside, and a lithium ion supply source is provided in contact with the negative electrode current collector. The wound lithium ion capacitor according to any one of claims 1 to 3.   5. The wound lithium ion capacitor according to claim 1, wherein the electrode winding unit has a negative electrode layer and a positive electrode layer facing each other with a separator interposed therebetween.   The winding type according to any one of claims 1 to 5, wherein a lithium ion supply source and / or a separator is arranged on the outside of the electrode winding unit or fixed with a tape from the outside without being arranged. Lithium ion capacitor.   The wound type lithium ion capacitor according to claim 6, wherein the outer periphery of the electrode winding unit is fastened with an adhesive tape to which a predetermined lithium ion supply source is attached.

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