JP2010283116A - Method of manufacturing electrochemical capacitor, and electrochemical capacitor manufactured using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an electrochemical capacitor capable of restraining the potential of a negative electrode from becoming high when manufacturing the electrochemical capacitor. <P>SOLUTION: The method of manufacturing the electrochemical capacitor is constituted to form lithium films 8 on obverse and reverse faces of the negative electrode 3 in a predoping process, and to form a protection layer 9 comprising oil containing saturated hydrocarbon as a main component, or oil containing silicone with a side chain of an alkyl group as a main component on the lithium film 8. The protection layer 9 becomes chemically inactive thereby, the lithium film 8 is thereby restrained from being deactivated due to a reaction of a surface of the lithium film 8 with a compound in an atmosphere in a period until the predoping process, and the potential of the negative electrode 3 is thereby restrained from becoming high in the predoping process. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an electrochemical capacitor used for regeneration or storage of a hybrid car or a fuel cell vehicle, and a battery for electronic equipment, and an electrochemical capacitor manufactured using the method.

  Conventionally, a capacitor has been used as a battery for many electronic devices because of its high charge / discharge response.

  During the development, capacitors with high energy density also appeared, and electric double layer capacitors that play the role of auxiliary power for storage batteries mounted as power sources in hybrid cars, etc., and improved versions of this electric double layer capacitor Therefore, an electrochemical capacitor having an energy density superior to that of an electric double layer capacitor has attracted attention.

  FIG. 4A is a top view of an element used in an electrochemical capacitor shown as an example of a conventional capacitor, and FIG. 4B is a part of the element (electrode winding unit 100) in the electrochemical capacitor. It is a notch front view.

  In FIG. 4 (a), this conventional electrochemical capacitor is formed by alternately laminating positive electrodes 101 and negative electrodes 102 with separators 103 therebetween and winding them concentrically to form an electrode winding unit 100. Foil-like lithium metals (lithium electrodes) 104 and 105 having a thickness of 50 to 300 μm are arranged as lithium ion supply sources on the outer periphery and center of the winding unit 100, respectively, and these are made of aluminum or iron. It was accommodated in 106 and filled with electrolyte.

  Further, the positive electrode 101 and the negative electrode 102 are formed on a current collector, which will be described later, made of a porous material provided with holes penetrating the front and back surfaces. Thus, by using a porous material for the current collector, lithium metal Even if 104 and 105 are arranged at the outer periphery and the center of the electrode winding unit 100, lithium ions can freely pass from the lithium metal 104 and 105 through the through holes of the current collector of the electrode winding unit 100 to each electrode. The lithium ions can be pre-doped into all the negative electrodes 102 of the electrode winding unit 100.

  In FIG. 4B, the electrode terminals 107 and 108 are connected to the respective current collectors of the positive electrode 101 and the negative electrode 102 as a method of taking out the electrodes of the positive electrode 101 and the negative electrode 102. The electrode terminals 107 and 108 are cylindrical. The electrode winding unit 100 is pulled out in the opposite direction to the winding axis direction. In particular, the lithium metal 105 formed at the winding center is supported by a tube rod 109, and this tube rod 109 also serves as a shaft rod for supporting the electrode winding unit 100.

  Further, the outermost periphery of the electrode winding unit 100 is fixed with a tape 110 in order to maintain the winding shape.

  As described above, the conventional electrochemical capacitor is provided with lithium metals 104 and 105, which are lithium ion supply sources, at two locations, the outer peripheral portion and the central portion of the electrode winding unit 100, so that lithium ions can be supplied from one lithium ion supply source. The lithium ion was pre-doped into the negative electrode 102 earlier than the method of pre-doping ions.

  As prior art document information relating to this application, for example, Patent Document 1 is known.

  However, even if pre-doping is performed using a lithium ion supply source such as the lithium metal 104 or 105, the lithium thickness of the lithium metal 104 or 105 is as high as 50 to 300 μm as described in Patent Document 1. When trying to pre-dope this thick lithium ion supply source, it took a long time to pre-dope many lithium ions into the negative electrode 102.

  Therefore, in order to shorten the time required for this pre-doping process, it has been studied to reduce the amount of lithium ions pre-doped to the negative electrode while maintaining the low potential of the negative electrode.

  After the study, the lithium film formed by vapor deposition on a foil-like substrate such as polypropylene was transferred to the surface of the negative electrode layer, and the negative electrode to which this lithium film was transferred was impregnated with an electrolytic solution to form a lithium film. A method of pre-doping lithium ions into a negative electrode by ionizing constituent metallic lithium is disclosed.

  By pre-doping lithium ions using a lithium film, the amount of metallic lithium per unit area of the negative electrode current collector is reduced, so the volume (thickness) of the carbon electrode layer that stores the metallic lithium can also be reduced. It becomes. Therefore, the path of lithium ions moving inside the carbon electrode layer due to pre-doping is shortened, and the effect of accelerating the pre-doping of lithium ions is achieved.

  As prior art document information relating to this application, for example, Patent Document 2 is known.

JP 2007-0667105 A JP 2008-21901 A

  However, the metallic lithium used in any of the above pre-dope is chemically active in terms of physical properties, and the substance contained in the atmosphere in which the metallic lithium is stored immediately after being disposed on the negative electrode A part of the metallic lithium reacted, and the lithium ion became an inactivated lithium compound that did not contribute to the pre-doping.

  By generating this deactivated lithium compound, the amount of metallic lithium that contributes to the pre-doping of lithium ions is reduced, so that the potential drop of the negative electrode due to occlusion of lithium ions in the negative electrode is inhibited, As an electrochemical capacitor, it was a factor causing a decrease in energy density.

  Accordingly, an object of the present invention is to provide an electrochemical capacitor manufacturing method capable of realizing improvement in energy density and reliability and an electrochemical capacitor manufactured using the method.

  In order to solve this problem, a method for manufacturing an electrochemical capacitor according to the present invention includes a positive electrode manufacturing step in which a positive electrode layer for adsorbing and desorbing anions is formed on the surface of a current collector made of metal to manufacture a positive electrode; Forming a negative electrode layer on the surface of a current collector made of a metal to create a negative electrode, and facing the positive electrode and the negative electrode so that a separator is interposed between the positive electrode and the negative electrode An element manufacturing process for manufacturing an element, a lithium preparation process for preparing a lithium ion supply source, an electrolytic solution containing the element and lithium ions, a housing process for storing the lithium ion supply source in an exterior body, and lithium ions A pre-doping process that occludes the negative electrode layer, and the lithium ion source prepared in this lithium preparation process is metallic lithium It is characterized by comprising a protective layer formed on the surface of the metallic lithium.

  In the electrochemical capacitor according to the present invention produced by the above production method, the protective layer is provided between the atmosphere and lithium by providing the protective layer on the surface of metallic lithium provided as a lithium ion supply source. This prevents the lithium metal that is chemically active from reacting with moisture or nitrogen contained in the atmosphere before pre-doping and is deactivated, and the lithium ions stored in the negative electrode layer by pre-doping are suppressed. Suppress the amount to decrease.

  As a result, when a predetermined amount of lithium ions is occluded in the negative electrode in the pre-doping process, the capacity deterioration as an electrochemical capacitor is suppressed, the reliability of the electrochemical capacitor is improved, and deactivation before pre-doping is performed. Since the amount of the metallic lithium that has not been stabilized is stabilized, the electrochemical capacitor according to the present invention can further stabilize the occlusion amount of lithium ions in the negative electrode layer during pre-doping. Thereby, the energy density of the electrochemical capacitor can be increased.

Partially cutaway perspective view of electrochemical capacitor in the present embodiment Schematic showing the vapor deposition equipment used for the negative electrode of the electrochemical capacitor in the present embodiment Partial enlarged view showing a front cross section of the negative electrode immediately before the pre-doping step in the present embodiment (A) A top view showing an element used in a conventional electrochemical capacitor, (b) a partially cutaway front view showing the element.

  The present invention and the invention described in all claims will be described below with reference to the drawings.

(Embodiment)
FIG. 1 is a partially cutaway perspective view of an electrochemical capacitor according to an embodiment of the present invention.

  In FIG. 1, an element 1 includes a positive electrode 2 in which a polarizable electrode layer 2b mainly composed of activated carbon is formed as a positive electrode layer for absorbing and desorbing ions on the surface of a current collector 2a made of metal, and a current collector made of metal. A negative electrode 3 having a carbon material layer 3b mainly composed of a carbon material 3c having a multilayered crystal structure having an interlayer as a negative electrode layer occluded with lithium ions on the surface of 3a is used as a pair of electrodes, and a positive electrode facing each other The separator 4 is wound or laminated with the separator 4 interposed between the negative electrode 3 and the negative electrode 3. Lead wires 5 a and 5 b are connected to the surfaces of the positive electrode 2 and the negative electrode 3 as electrode lead terminals, respectively. In this state, the element 1 and an electrolytic solution (not shown) are accommodated in a bottomed cylindrical outer case 6 that is an outer body, and lead wires 5a and 5b are exposed at the open ends of the outer case 6. By the sealing member 7 It is sealed.

  Hereinafter, a method for manufacturing the electrochemical capacitor according to the present embodiment will be described.

  First, a positive electrode manufacturing process for manufacturing the positive electrode 2 will be described.

  For example, a high-purity aluminum foil having a thickness of about 30 μm (containing Al of 99.99% or more) is used as the current collector 2a, and the surface of the aluminum foil is roughened by electrolytic etching in a chlorine-based etching solution.

  Then, the polarizable electrode layer 2b is formed on the front and back surfaces of the roughened current collector 2a. Examples of the material constituting the polarizable electrode layer 2b include activated carbon, a binder and a conductive additive.

  The activated carbon is, for example, a phenol resin activated carbon having an average particle diameter of 5 μm, the binder is, for example, an aqueous solution of carboxymethyl cellulose (CMC), and the conductive assistant is, for example, acetylene black, mixed in a weight ratio of 10: 2: 1. Use things. This mixture is kneaded with a kneader to adjust to a predetermined viscosity.

  This paste is applied to the front and back surfaces of the current collector 2a and dried in an air atmosphere at 100 ° C. for 1 hour to form a polarizable electrode layer 2b having a thickness of 40 μm. Thereafter, the current collector 2a provided with the polarizable electrode layer 2b is slit so as to have a predetermined width.

  Further, a part of the polarizable electrode layer 2b formed on the front and back surfaces of the current collector 2a is removed, and the lead wire 5a is connected to the portion where the polarizable electrode layer 2b is not formed by a method such as needle caulking.

  As described above, the positive electrode 2 is completed.

  Next, a negative electrode manufacturing process for manufacturing the negative electrode 3 will be described.

  For example, a copper foil having a thickness of about 15 μm is used as the current collector 3a, and the carbon electrode layer 3b is formed on the front and back surfaces of the current collector 3a. As a material constituting the carbon electrode layer 3b, for example, graphitic carbon is used as the carbon material 3c capable of reversibly occluding and releasing lithium ions. As the conductive auxiliary agent, for example, acetylene black is used as in the positive electrode 2. As the binder, for example, a mixture of polytetrafluoroethylene (PTFE) and CMC at a weight ratio of 4: 1 is used. When these materials are mixed, the graphitic carbon, the conductive assistant, and the binder are mixed at a weight ratio of 8: 1: 1.

  When preparing the paste, CMC, acetylene black, graphitic carbon, and PTFE are added to water in this order, and the mixture is stirred and kneaded to prepare the paste.

This paste is formed on the front and back surfaces of the current collector 3a using a comma coater, a die coater, or the like so that the thickness of one surface is about 50 μm, and is dried in the air at 80 ° C. After drying, the current collector 3a having the carbon electrode layer 3b formed on the front and back surfaces is pressed at a linear pressure of 75 to 100 kgf / cm, and the thickness of one side of the carbon electrode layer 3b is 40 μm and the density is 0.4 to Adjust to 1.0 g / cm ³ . Then, the current collector 3a in which the carbon electrode layer 3b is formed on the front and back surfaces after pressing is slit to a predetermined width.

  Further, like the positive electrode 2, a part of the carbon electrode layer 3b formed on the surface of the current collector 3a is removed, and a lead wire 5b made of copper or the like is connected to the portion where the carbon electrode layer 3b is not formed by resistance welding or the like.

  Thus, the negative electrode 3 is completed.

  In addition, as the material of the carbon material 3c, in the present embodiment, graphitic carbon having a high breakdown voltage and low energy loss in the charge / discharge cycle is used. Carbon, low-temperature calcined carbon, non-graphitizable carbon, and the like are considered as candidate materials. When each material is compared in terms of physical properties, the specialized performance is different, and accordingly, selection is made as appropriate according to the purpose of use. For example, graphitizable carbon is superior in terms of low resistance and charge / discharge cycle life, low-temperature calcined carbon is superior in terms of high capacity and low resistance, and non-graphitizable carbon is superior in terms of high capacity and cycle loss. Is excellent in a small aspect.

  Next, unlike the positive electrode 2, the negative electrode 3 stores lithium ions 8 (not shown) serving as a lithium ion supply source using a physical vapor phase method in order to occlude lithium ions into the carbon material 3c during the pre-doping step. It forms on the outer surface of the electrode layer 3b. In the present embodiment, as a method for forming the lithium film 8 on the front and back surfaces of the negative electrode 3, for example, a vacuum vapor deposition apparatus may be used.

  In this embodiment, a protective layer 9 (not shown) made of a compound having a lower reactivity with the atmosphere than metallic lithium constituting the lithium film 8 is formed on the surface of the lithium film 8 formed on the negative electrode 3 by vapor deposition. To do. The thickness of the protective layer 9 to be formed is preferably 10 nm to 100 nm.

  The lithium disposing process will be described in detail later.

  Next, an element manufacturing process for manufacturing the element 1 will be described.

The positive electrode 2 and the negative electrode 3 are opposed to each other, and a separator 4 made of, for example, a cellulose paper having a thickness of about 35 μm and a density of 0.45 g / cm ³ is used. The element 1 is completed by winding so that 4 is interposed.

  From the above, the element 1 is completed.

  Next, a housing process for housing the element 1 and the electrolytic solution in the outer case 6 will be described.

Electrolyte, for example, lithium ions as electrolyte cations, BF ₄ as an electrolyte anion ^- or PF ₆ ^-, and a high dielectric constant of ethylene carbonate (EC) and low viscosity diethyl carbonate (DEC) weight ratio as a solvent 1: 1 A mixed solvent mixture is used.

  The electrolyte solution in the present invention is not limited to the above configuration, and the same effect can be obtained as long as it contains lithium ions.

  For example, a metal such as aluminum, copper, or nickel is used for the outer case 6 from the viewpoint of heat dissipation. However, the outer case 6 is not particularly limited as long as it has a low risk of causing a reaction with the electrolytic solution, and may be a prismatic case or a laminate type.

  Here, a pre-doping process applied to the negative electrode 3 constituting the element 1 will be described.

  In this step, an operation called pre-doping is performed for the purpose of preliminarily occluding lithium ions in the negative electrode 3. In this case, the term “occlusion” means that the lithium ions in the vicinity of the negative electrode 3 have an interlayer that the carbon material 3 c has. This refers to a phenomenon in which lithium ions enter between layers of a multilayered crystal structure to form an intercalation compound of lithium and carbon.

  When the lithium ions are occluded in the negative electrode 3, the electrode potential of the negative electrode 3 decreases due to the electrochemical reaction of the lithium ions, and the electrochemical capacitor expands the potential difference between the positive electrode 2 and the negative electrode 3, thereby increasing the energy density of the electrochemical capacitor. Can be improved.

  Incidentally, the pre-doping performed on the negative electrode 3 is also performed in the field of lithium ion secondary batteries, but the purpose of pre-doping in the lithium ion secondary battery is to reduce the irreversible capacity of the negative electrode in the charge / discharge cycle, and to charge / discharge It is to improve capacity.

  On the other hand, the purpose of the pre-doping of the electrochemical capacitor in the present invention is to improve the withstand voltage due to the potential drop of the negative electrode 3. Depending on this purpose, the amount of occlusion of lithium ions during each pre-doping is also different, and the amount of occlusion of lithium ions in the lithium ion secondary battery only needs to be the irreversible capacity of the negative electrode 3, so it is clear from the amount of occlusion of lithium ions in the electrochemical capacitor Very few.

  In the present embodiment, the negative electrode 3 having the lithium film 8 formed on the surface thereof is impregnated with an electrolytic solution having lithium ions as a cation, so that the metallic lithium constituting the lithium film comes into contact with the electrolytic solution. Ionize. The lithium ions are inserted between the layers of the multilayered crystal structure of the carbon material 3 c and inserted in the carbon material 3 c of the negative electrode 3, and the potential of the negative electrode 3 is lowered.

  Then, by impregnating the negative electrode 3 with the electrolytic solution for a certain time, a certain amount of metallic lithium in the lithium film formed on the negative electrode 3 is occluded in the carbon material 3c, and the pre-doping step is completed.

  Next, the sealing process will be described.

  In a state where the lead wires 5a and 5b protruding from the element 1 are passed through the through holes provided in the sealing member 7, the sealing member 7 is disposed in the opening of the outer case 6 having a bottomed cylindrical shape, and the sealing member The sealing member 7 is crimped and clamped and fixed by drawing from the outer peripheral surface of the opening of the outer case 6 where 7 is located toward the inside of the outer case 6 and by curling the opening end of the outer case 6. To do. Thereby, sealing of the opening part of the exterior case 6 is completed. Then, the sealing process is completed.

  Finally, as a quality maintenance step, the assembled electrochemical capacitor is aged and then the initial operation is confirmed.

  Thus, the electrochemical capacitor is completed.

  FIG. 2 is a schematic diagram showing the configuration of the vapor deposition equipment used in the lithium disposing step in the present embodiment.

  In FIG. 2, the negative electrode 3 unwound from the unwinding portion 10 is first formed with a lithium film 8 (not shown) of about 7 to 10 μm by vapor deposition on the surface of the carbon electrode layer 3 b in the lithium film forming portion 11. A protective layer 9 (not shown) is formed on the lithium film 8 by vapor deposition in the protective layer forming unit 12, and finally wound up by the winding unit 13 and conveyed to the next step.

  In the lithium film forming portion 11, the carbon electrode layer on the other surface of the negative electrode 3 is formed by lithium vaporized from the evaporation source 11b while one surface of the foil-shaped negative electrode 3 is in contact with the can 11a in an atmosphere with a high degree of vacuum. It is sprayed on the surface of 3b. Then, after vaporized lithium adheres to the carbon electrode layer 3b, the can 11a in contact with the negative electrode 3 is cooled to cool the lithium, and the lithium is cooled from the can 11a using heat conduction.

  In the protective layer forming part 12, like the lithium film forming part 11, the oil vaporized from the vapor deposition source 12b is brought into contact with one surface of the foil-like negative electrode 3 in contact with the can 12a in an atmosphere with a high degree of vacuum. It is sprayed onto the surface of the lithium film 8 on the other surface of the negative electrode 3. A cooled can 12a is used to cool the oil adhering to the lithium film 8.

  In the present embodiment, the lithium film 8 and the protective layer 9 are thus formed.

  In the present embodiment, in order to form the lithium film 8, not only a physical vapor phase method such as vapor deposition but also a chemical vapor phase method or a liquid phase method, a direct transfer to the negative electrode 3 instead of the formation is performed. Alternatively, the lithium film 8 may be indirectly formed. Alternatively, a metallic lithium lump having the protective layer 9 together with the element 1 is impregnated in the electrolytic solution, and lithium ions are supplied to the carbon electrode layer 3b through the electrolytic solution. May be pre-doped. Also, the means for forming the protective layer 9 is not limited to vapor deposition, and coating equipment such as a die coater, comma coater, and gravure coater may be used, and any means that can form the protective layer 9 is not particularly limited.

  Further, in the method for manufacturing an electrochemical capacitor according to the present embodiment, metallic lithium that already has the protective layer 9 may be used without providing the step of forming the protective layer 9.

  FIG. 3 is a partially enlarged front sectional view showing a state immediately after the formation of the protective layer 9 of the negative electrode 3 used in the electrochemical capacitor according to the present embodiment.

  As shown in FIG. 3, immediately after the lithium disposing step, in the present embodiment, the protective layer 9 is formed on the lithium film 8 of the negative electrode 3.

  By impregnating the negative electrode 3 on which the protective layer 9 is formed with an electrolytic solution, a part of the lithium film 8 and a substance contained in the atmosphere to which the negative electrode 3 is exposed until the pre-doping process is performed. It is possible to suppress the generation of a deactivated lithium compound such as lithium nitride that does not contribute to the pre-doping of lithium ions by reacting with the metal lithium 8a. Thereby, since it can suppress that the quantity of the lithium ion pre-doped from the metallic lithium 8a arrange | positioned at the negative electrode 3 can be suppressed, it suppresses that the electric potential of the negative electrode 3 raises in a pre dope process, and this invention The energy density of such an electrochemical capacitor can be increased.

  Further, when the element 1 is impregnated with the electrolytic solution, a lithium compound deactivated as in the past remains in the carbon electrode layer 3b and the like, and when this is pre-doped with lithium ions, the produced electrochemical capacitor is charged and discharged. When performing, it is an obstacle to the movement of lithium ions that move because it is occluded by the carbon material 3c included in the carbon electrode layer 3b, and this has been one of the causes of the increase in resistance of the conventional electrochemical capacitor. The invention makes it possible to reduce the amount of metallic lithium that is deactivated, so that the electrochemical capacitor in this embodiment can have a low resistance.

  Therefore, in order to achieve the effect of the present invention, the material constituting the protective layer 9 in the present invention is a compound contained in the atmosphere to which the negative electrode 3 is exposed before entering the pre-doping step, or a material constituting the electrochemical capacitor. Low reactivity is required.

  The protective layer 9 may be made of oil or the like, and in particular, a hydrocarbon oil containing a large amount of paraffinic compounds or naphthenic compounds having a low reactivity or a silicone containing a lot of silicone compounds whose side chains are alkyl groups. Oil is preferred.

  In other words, hydrocarbon oils containing many unsaturated bonds, aromatic hydrocarbon oils, carboxyl, epoxy, amino silicone oils, other phenol groups and carboxyl groups, Oils with many compounds having highly reactive functional groups such as ester groups, sulfo groups, and nitrate ester groups are outside the scope of the present invention.

  However, oil is composed of a plurality of types of polymer compounds, and it is difficult to completely remove a polymer compound having a highly reactive functional group as described above from the oil used. Will be included.

  In consideration of the above contents, the oil used for producing the effects of the present invention has low reactivity as a physical property of the whole oil. Therefore, the hydrocarbon oil or side chain mainly containing the paraffinic compound or naphthenic compound is used. Is preferably a silicone oil mainly composed of a silicone compound comprising an alkyl group.

  Here, the expression “main component” means that the compound is the most contained among the plurality of compounds constituting the oil.

  By using such oil as the protective layer 9, it is possible to suppress the deactivation of the metallic lithium 8a located particularly on the surface portion of the lithium film 8.

  Further, many of these oils are very difficult to dissolve in the electrolytic solution used in the electrochemical capacitor in the present embodiment.

  Due to this property, a part of the compound constituting the protective layer 9 remaining in the outer case 6 of the electrochemical capacitor according to the present embodiment after the pre-doping step floats in the electrolytic solution, and the atmosphere present in the outer case 6 It is considered that there is an effect that a thin film is formed at the interface with the electrolytic solution, and that a highly reactive substance such as moisture is mixed from the atmosphere into the electrolytic solution.

  As specific examples of oils that satisfy such conditions, ULVOIL (registered trademark) of ULVAC TECHNO CORPORATION includes product number D-11 (hydrocarbon oil) and product number D-31 (silicone oil). Can be mentioned. However, the oil used in the present invention is not limited to these oils. In addition, the said product contains the inactive polymer compound which has the effect of this invention with the content rate of about 90% with respect to all the polymer compounds which comprise the said product.

  After the pre-doping step, the protective layer 9 remains on the surface or inside of the negative electrode 3 or the positive electrode 2 or in the electrolytic solution.

  Incidentally, the thickness of the protective layer 9 formed in this lithium disposing step is preferably 10 to 100 nm.

  This is because it is difficult to make the protective layer 9 thinner than 10 nm thinner than this because the protective layer 9 thinner than 10 nm is smaller than the size of a single molecule constituting the oil. Also, the protective layer 9 thicker than 100 nm is not suitable as an electrochemical capacitor because resistance increases when oil remains inside.

  Among the above oils, in particular, when metallic lithium is disposed on the carbon electrode layer, it is performed in a high vacuum atmosphere (about 0.01 to 0.001 Pa) in consideration of the reactivity of lithium. Often.

  For this reason, in consideration of productivity, when the protective layer 9 is continuously formed in the space where the lithium film 8 is disposed, the oil of the protective layer 9 should have a low vapor pressure in order to suppress volatilization. preferable. For example, it is preferable to use oil having a vapor pressure of 0.01 Pa or less at 40 ° C.

  The magnitude of the vapor pressure is considered to be due to the average molecular weight of the oil. For example, in order to satisfy the vapor pressure, there are saturated hydrocarbon oils with an average molecular weight of about 360, and the vapor pressure is An oil having an average molecular weight of about 200 to 1000 is preferable.

  This is because when the average molecular weight is smaller than 200, the vapor pressure increases and the liquid is easily volatilized. When the average molecular weight is larger than 1000, the state of the oil becomes closer to a solid and it is difficult to form the protective layer 9.

  Incidentally, as a method for detecting oil used in the protective layer in the present embodiment, the electrolytic solution is taken out from the electrochemical capacitor and extracted with a separatory funnel using n-hexane. The extract is concentrated by evaporation and vacuum dried to the extent that n-hexane can be removed. The residue is identified by performing structural analysis using GC-MS, NMR, and IR.

  Finally, for confirmation, it is more preferable that the oil having the specified structure is measured with a liquid chromatography as a known sample and confirmed that the retention time is the same as that of the residue, so that the accuracy of the analysis is improved.

  Further, the protective layer 9 is required to be composed of a compound having a lower reactivity with the atmosphere than metal lithium in order to suppress deactivation of the metal lithium constituting the lithium film 8. Therefore, the determination of the reactivity of the protective layer 9 and the lithium film 8 can be made by, for example, preparing metallic lithium and a compound constituting the protective layer 9 as a sample, and leaving them in the atmosphere to determine the amount of air used. There is no particular limitation as long as a known measurement method such as measurement is used.

  In the present embodiment, vapor deposition was performed in order to provide the pre-doping lithium film 8 on the front and back surfaces of the negative electrode 3.

  As a result, a porous lithium film 8 can be formed. Thereby, when the element 1 is impregnated with the electrolytic solution, the contact area between the electrolytic solution and the metal lithium 8a is increased, and the effect of accelerating the ionization of the metal lithium 8a is achieved.

  Moreover, since the oil formed as the protective layer 9 is also liquid, even if the surface of the lithium film 8 or the like formed by vapor deposition has a complicated shape, the shape can be flexibly aligned with the lithium film 8. Thus, the protective layer 9 and the lithium film 8 can be closely adhered, and the effect of deactivation of lithium can be further enhanced.

  Further, the metal lithium 8a activated by vapor deposition further receives the radiant heat of the vapor deposition source 12b, so that part of the metal lithium 8a diffuses and penetrates from the surface of the carbon electrode layer 3b to the inside, and the internal carbon material 3c. And may be alloyed. Thereby, when the metal lithium 8a subjected to thermal diffusion is pre-doped with lithium ions, the distance that the metal lithium 8a is ionized and moves inside the carbon electrode layer 3b is reduced, so that the time required for pre-doping can be shortened.

  In particular, when the lithium film 8 is formed by vapor deposition, since the lithium film 8 is once vaporized in the formation process, the lithium film 8 is more chemically activated than at normal temperature and is more easily deactivated in the atmosphere. Since the lithium film obtained by vapor deposition is a thin film of about 20 μm or less, the amount of the metallic lithium 8a disposed per unit area of the current collector 3a is small. For this reason, the metal lithium 8a contributing to pre-doping is reduced as compared with a sheet-like metal lithium larger than 20 μm obtained by rolling or the like as in the prior art, and the potential increase of the negative electrode 3 becomes remarkable.

  Therefore, when the lithium film 8 or the like formed by vapor deposition on the pre-dope is used as a lithium supply source, the protective layer 9 of the present invention is particularly necessary for suppressing the potential increase of the negative electrode 3.

(Performance evaluation test)
In the examples and comparative examples, the negative electrode 3 used in the electrochemical capacitor according to the present embodiment is used as an example, and a negative electrode having the same configuration as the example except that the protective layer 9 is not formed is used as a comparative example. The potential of the negative electrode after the pre-doping step was measured using a lithium electrode. The results are shown in (Table 1).

  As can be seen from the above (Table 1), in the example, the protective layer 9 formed on the lithium film 8 suppresses the deactivation of the metal lithium 8a, and the potential drop effect of the negative electrode 3 due to the lithium ion pre-doping is sufficiently obtained. It has been.

  Note that the timing of pre-doping the negative electrode 3 may be immediately after the production of the negative electrode 3 or after the production of the element 1, and is not limited to the timing in the present embodiment.

  In the present embodiment, the lead wires 5a and 5b are used as the lead terminals. However, the present invention is not limited to this, and the positive and negative electrodes are not drawn from the same direction of the element 1 but may be drawn from the opposite direction. Good.

  As described above, in the method for producing an electrochemical capacitor according to the present invention, the main component is an oil mainly composed of a saturated hydrocarbon or a silicone whose side chain is an alkyl group on the lithium film formed in the lithium disposing step. A protective layer that is oil was formed, and in the pre-doping step, the negative electrode in a state where the protective layer was formed was impregnated with an electrolytic solution, and lithium ions were pre-doped to the negative electrode carbon material.

  With this protective layer that is chemically inert, the electrochemical capacitor according to the present invention reacts with the compound in the atmosphere, particularly the surface of the lithium film formed on the carbon electrode layer of the negative electrode until the pre-doping step. It can be suppressed that the lithium compound which does not contribute to pre-doping is deactivated.

  In the electrochemical capacitor according to the present invention, in the pre-doping process, lithium ions were pre-doped to the negative electrode using a metal lithium surface on which a protective layer that suppresses the formation of a compound by the metal lithium was formed. Since this protective layer suppresses the deactivation of the surface of metallic lithium, the potential of the negative electrode can be more stably lowered, and the reliability and energy density of the electrochemical capacitor can be improved. Therefore, it is useful as a power source for a hybrid vehicle used for regeneration or backup.

DESCRIPTION OF SYMBOLS 1 Element 2 Positive electrode 2a, 3a Current collector 2b Polarization electrode layer 3 Negative electrode 3b Carbon electrode layer 3c Carbon material 4 Separator 5a, 5b Lead wire 6 Exterior case 7 Sealing member 8 Lithium film 8a Metal lithium 9 Protective layer 10 Unwinding part DESCRIPTION OF SYMBOLS 11 Lithium film formation part 11a, 12a Can 11b, 12b Evaporation source 12 Protective layer formation part 13 Winding part

Claims (7)

Forming a positive electrode by forming a positive electrode layer that absorbs and desorbs anions on the surface of a current collector made of metal;
Forming a negative electrode by forming a negative electrode layer that occludes lithium ions on the surface of a current collector made of metal;
An element manufacturing step of manufacturing the element so that the positive electrode and the negative electrode face each other and a separator is interposed between the positive electrode and the negative electrode;
A lithium preparation process for preparing a lithium ion source;
A housing step of housing the element, an electrolytic solution containing lithium ions, and the lithium ion supply source in an exterior body;
A pre-doping step of occluding lithium ions into the negative electrode layer,
The method for producing an electrochemical capacitor, wherein the lithium ion supply source prepared in the lithium preparation step comprises metal lithium and a protective layer formed on the surface of the metal lithium. The method for producing an electrochemical capacitor according to claim 1, wherein the protective layer of the lithium ion supply source is made of oil mainly composed of saturated hydrocarbon or oil mainly composed of silicone whose side chain is an alkyl group. 2. The electrochemical capacitor according to claim 1, wherein the lithium ion supply source prepared in the lithium preparation step includes metal lithium formed on the negative electrode surface by vapor deposition and the protective layer formed on the surface of the metal lithium. Production method. The lithium ion supply source prepared in the lithium preparation step includes foil-like metal lithium and the protective layer formed on the surface of the metal lithium, and the lithium ion supply source is attached to the negative electrode surface. Item 2. A method for producing an electrochemical capacitor according to Item 1. 2. The method for producing an electrochemical capacitor according to claim 1, wherein the protective layer of the lithium ion supply source has a vapor pressure of 0.01 Pa or less in an atmosphere of 40 ° C. 3. A positive electrode having a positive electrode portion for adsorbing ions on a current collector made of metal and a negative electrode having a negative electrode portion having a lithium ion occluded on the surface of the current collector made of metal are opposed to each other as a pair of electrodes. An element in which a separator is interposed between the positive electrode and the negative electrode;
Consists of this element and an exterior body containing an electrolytic solution containing lithium ions,
An electrochemical capacitor in which at least one of the electrolyte and the element includes at least one of oil mainly composed of a saturated hydrocarbon and oil mainly composed of silicone whose side chain is an alkyl group. The electrochemical capacitor according to claim 6, wherein the oil mainly composed of saturated hydrocarbon and the oil mainly composed of silicone whose side chain is an alkyl group have a vapor pressure of 0.01 Pa or less in an atmosphere at 40 ° C. .

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