JP2009188395A - Manufacturing method of electrochemical capacitor, and electrochemical capacitor manufactured by the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an electrochemical capacitor, which improves productivity furthermore and pre-dopes a negative electrode with lithium ion. <P>SOLUTION: A release agent and a lithium film are laminated on a substrate 8 in order to form a lithium film 9 on a surface of a carbon electrode layer 3b of a negative electrode 3, and the lithium film 9 is stuck and transferred to the surface of the negative electrode 3 by using the substrate 8, wherein a silicone 3c is used as the release agent, so that the thin lithium film 9 can be easily formed on the carbon electrode layer 3b. Even if the silicone remains on the lithium film 9 after the substrate 8 is peeled from the lithium film 9, the possibility that the silicone 3c reacts with a driving electrolyte due to charge/discharge after assembling of the electrochemical capacitor can be reduced because of chemical inactivity of the silicone. Thus the productivity and reliability of the electrochemical capacitor can be improved. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an electrochemical capacitor used as a regenerative brake or a power storage device for a backup power source of an electronic device, a hybrid vehicle, a fuel cell vehicle, or the like, and an electrochemical capacitor manufactured thereby.

  Conventionally, an electric double layer capacitor has excellent reliability with respect to rapid charging and rapid discharging as a power storage device, and thus has been mainly used as a power source for backup in a wide range of fields. In general, an electric double layer capacitor mainly uses activated carbon for a positive electrode and a negative electrode, and is impregnated with a driving electrolyte to absorb and desorb ions contained in the driving electrolyte on the surface of the activated carbon. Discharge. The type of driving electrolyte can be classified into aqueous and non-aqueous. Water-based drive electrolytes have the characteristics of high capacitance but low withstand voltage, and non-aqueous drive electrolytes have a certain trade-off, with low capacitance but high withstand voltage. There were characteristics. However, in general, since the amount of energy stored in a capacitor is proportional to the square of the withstand voltage of the capacitor, a non-aqueous organic driving electrolyte has been used. In recent years, in order to develop new application fields, development of capacitors with higher withstand voltage has been active.

  The capacitor developed in the development flow was an electrochemical capacitor having a higher withstand voltage than the conventional electric double layer capacitor.

  This electrochemical capacitor uses a positive electrode used for an electric double layer as a positive electrode, and has a crystal structure of a multilayer structure having a current collector made of a metal foil such as copper and layers formed on the front and back surfaces of the current collector. A negative electrode composed of a carbon electrode layer mainly composed of a material was used.

  Further, in the electrochemical capacitor, a step of preliminarily inserting (pre-doping) a certain amount of lithium ions into the carbon electrode layer formed on the negative electrode after the preparation of the negative electrode is provided in the manufacturing stage.

  By pre-doping with this lithium ion, the potential of the negative electrode of the electrochemical capacitor can be lowered, and the potential difference from the positive electrode can be made wider than that of the electric double layer capacitor.

  Thereby, the withstand voltage of the electrochemical capacitor was improved.

  The following three methods are disclosed as methods for pre-doping lithium ions into the negative electrode in a conventional electrochemical capacitor.

  1) A carbon material and powdered lithium are mixed to produce a negative electrode, and the negative electrode is immersed in a driving electrolyte solution to ionize lithium and chemically occlude the carbon material.

  2) A lithium foil is brought into contact with a negative electrode produced using a carbon material and immersed in a driving electrolyte solution, and the lithium foil is ionized and chemically occluded in the carbon material.

  3) A negative electrode produced using a carbon material and an electrode containing lithium are immersed in a driving electrolyte, and a current is passed between them to electrochemically occlude lithium ions in the carbon material.

As prior art document information relating to this application, for example, Patent Document 1 is known.
Japanese Patent No. 3689948

  However, in the lithium ion pre-doping method for the negative electrode mentioned above, the work of preliminarily inserting lithium ions by a chemical method or an electrochemical method into a carbon material capable of absorbing and desorbing lithium ions is complicated and requires many man-hours. Or cost. In addition, it has been difficult to stably obtain excellent performance.

  Accordingly, an object of the present invention is to provide a method for producing an electrochemical capacitor that can further improve productivity and pre-dope lithium ions into the negative electrode.

  In order to solve this problem, in the present invention, in the method for producing an electrochemical capacitor, a release agent is applied on a substrate, a lithium film is formed on the release agent, and the lithium film Is transferred to the surface of the negative electrode to dispose a lithium film on the surface of the negative electrode, and the release agent is made of silicone.

  In the method for producing an electrochemical capacitor according to the present invention, since the lithium film is provided on the carbon electrode layer by using transfer in the lithium disposing step, the lithium can be fixed and supported on the base material. It can be simply arranged on the negative electrode surface.

  Then, by making this pre-doped lithium film thinner, the carbon electrode layer pre-doped with lithium ions can also be made thinner.

  Therefore, the path for the lithium ions to permeate the carbon electrode layer can be shortened, the pre-doping can be accelerated, and the productivity of the electrochemical capacitor can be improved.

  Furthermore, by using silicone as the release agent coated on the base material, even if the release agent remains on the lithium film disposed on the negative electrode surface after transfer, the silicone is chemically inert. Taking advantage of this property, it is possible to reduce the possibility that the release agent remaining after the transfer reacts with the driving electrolyte solution or the like through pre-doping or charging / discharging of the electrochemical capacitor to generate gas.

  Therefore, the release agent remaining at the time of transfer can be advanced to the next step without paying attention to a process of removing it from the negative electrode, and the reliability and productivity of the electrochemical capacitor can be further improved.

  Hereinafter, embodiments of the present invention and the invention described in claims 1 to 4 will be described with reference to the drawings. However, the present invention is not limited to the contents described in the following embodiments.

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

  In FIG. 1, the electrochemical capacitor according to the present embodiment has a positive electrode 2 in which a polarizable electrode layer 2b is formed on the front and back surfaces of a current collector 2a made of metal foil and a front and back surface of a current collector 3a made of metal foil. The negative electrode 3 on which the carbon electrode layer 3b is formed is used as a pair of electrodes, and the wound element 1, the positive electrode 2 and the negative electrode 3 so that the separator 4 is interposed between the positive electrode 2 and the negative electrode 3 facing each other. Lead wires 5a and 5b, one ends of which are electrically connected to each other, an exterior case 6 as an exterior body that houses the element 1 and the driving electrolyte, and an opening of the exterior case 6 is connected to lead wires 5a, The sealing member 7 is sealed so that the other end of 5b is exposed.

  The positive electrode 2 is obtained by applying a polarizable electrode layer 2b composed of activated carbon, a binder, and a conductive additive on the front and back surfaces of a current collector 2a of a high-purity aluminum foil having a thickness of 30 μm. For the polarizable electrode layer 2b, a mixed solution in which, for example, carboxymethylcellulose (CMC) is dissolved in water as a binder in phenol resin-based activated carbon having an average particle diameter of 5 μm, and acetylene black, for example, as a conductive auxiliary agent is 10: 2: 1. What was mixed in the amount of is applied and dried.

  Incidentally, since it is shown as the polarizable electrode layer 2b in FIG. 1 and FIG. 2, none of the activated carbon, the binder, and the conductive auxiliary agent constituting it is shown in the drawings.

  The negative electrode 3 is obtained by forming a carbon electrode layer 3b composed of a carbon material, a binder, and a conductive additive on the front and back surfaces of a copper foil current collector 3a having a thickness of 15 μm. The carbon electrode layer 3b uses non-graphitizable carbon such as a phenol resin raw material as a carbon material, and polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), or the like as a binder. And CMC are used at a weight ratio of 4: 1, and acetylene black is used as the conductive auxiliary agent in the same manner as the positive electrode 2. When these materials are mixed, the mixing ratio of the carbon material, the conductive additive and the binder is used at a ratio of about 8: 1: 1. And this mixture is apply | coated to the front and back of a collector and dried so that the thickness of the layer after application | coating may be about 50 micrometers by methods, such as a comma coater.

  Incidentally, since it is shown as the carbon electrode layer 3b in FIG. 1, none of the carbon material, the binder, and the conductive auxiliary agent constituting the carbon electrode layer 3b are shown in the drawing.

As the separator 4, for example, a cellulose resin paper having a thickness of about 35 μm and a density of 0.45 g / cm ³ is used.

  Since the separator 4 is interposed between the positive electrode 2 and the negative electrode 3 and prevents a short circuit due to contact between the positive electrode 2 and the negative electrode 3, in the wound element 1 in the present embodiment, the positive electrode 2 or the negative electrode 3 It is preferable that one sheet is provided on at least one of the front and back surfaces.

  The lead wires 5a and 5b, which are external connection terminals, are connected to unformed portions of the polarizable electrode layer 2b and the carbon electrode layer 3b of the positive electrode 2 and the negative electrode 3, that is, the exposed surfaces of the current collectors 2a and 3a. Connecting.

  Therefore, in order to reduce the connection resistance with the current collectors 2a and 3a as much as possible, for example, the lead wire 5a is made of aluminum, and the lead wire 5b is made of copper, nickel, or nickel-plated copper. .

  The outer case 6 has a bottomed cylindrical shape, and houses the element 1 connected to the lead wires 5a and 5b and the driving electrolyte (not shown) impregnated in the element 1.

  For example, aluminum is used as the material of the outer case 6 from the viewpoint of workability.

Incidentally The driving electrolyte, for example, Li ⁺ as electrolyte cations, BF ₄ as an electrolyte anion ^- a, as a solvent and a high permittivity ethylene carbonate (EC) low viscosity ^{- -} or PF ₆ and diethyl carbonate (DEC) A mixed solvent mixed at a weight ratio of 1: 1 was used.

  The shape of the exterior case 6 is not limited to the above shape and material, and may be, for example, a rectangular tube shape or a laminate type.

  The sealing member 7 was disposed so as to be in close contact with the inner peripheral surface of the outer case 6 inside the opening end of the outer case 6. The sealing member 7 was subjected to drawing processing from the outer peripheral surface of the outer case 6 toward the inside of the outer case 6 with respect to a part of the inner peripheral surface of the outer end of the outer case 6 in contact with the sealing member 7. The sealing member 7 was fixed to the arrangement location by this drawing process.

  Further, a part of the opening end portion of the exterior case 6 protruding outward from the sealing member 7 was bent toward the inside of the exterior case 6 to enhance the fixing strength of the sealing member 7. In the embodiment of the present invention, a through hole is provided in a part of the sealing member 7 so that the lead wires 5a and 5b connected to the element 1 penetrate the sealing member 7 and connect to an external circuit. For the sealing member 7, for example, butyl rubber was used.

  FIG. 2 is a schematic sectional view of the element 1 used in the electrochemical capacitor according to the present embodiment cut in the vertical direction.

  As shown in FIG. 2, the electrochemical capacitor according to the embodiment of the present invention has a configuration in which silicone 3c is provided on the outer surface of the carbon electrode layer 3b of the negative electrode 3.

  This is because the lithium film 9 is disposed on the carbon electrode layer 3b formed on the negative electrode 3 in order to pre-doped lithium ions to the negative electrode 3 in manufacturing the electrochemical capacitor in the present embodiment. This is because the lithium film 9 is provided using transfer using silicone 3c as a release agent.

  Incidentally, since the lithium film 9 becomes lithium ions and is pre-doped into the carbon material of the carbon electrode layer 3b, it is not shown in FIGS.

  Below, the lithium film arrangement | positioning method to the negative electrode 3 in the manufacturing method of the electrochemical capacitor in this Embodiment is demonstrated.

  FIG. 3 is a front view showing the base material 8 used for transferring the lithium film 9 to the carbon electrode layer 3b of the negative electrode 3 of the electrochemical capacitor in the present embodiment.

  As shown in FIG. 3, in the present embodiment, for the transfer, for example, a release agent made of silicone 3c is applied to the surface of a sheet-like substrate 8 made of polyphenylene sulfide (PPS) having an excellent heat resistance and a thickness of about 150 μm. In addition, a material obtained by forming a lithium film 9 having a thickness of about 2 μm with lithium by vapor deposition on the release agent was used.

  And the base material 8 which has the lithium film 9 and the mold release agent is affixed to the negative electrode 3 so that the lithium film 9 and the carbon electrode layer 3b surface may oppose, and the laminated body which consists of this negative electrode 3 and the base material 8 is made. .

  After this laminated body is pressure-bonded using a rolling roller heated to about 80 ° C., the base material 8 is peeled from the laminated body, whereby the transfer of the lithium film 9 onto the carbon electrode layer 3b is completed.

  After the lithium film 9 is pasted together with the base material 8 to the carbon electrode layer 3b, when the base material 8 is peeled from the lithium film 9, a peeling interface is generated in the layer of the silicone 3c due to the physical properties of the silicone, and peeling is performed therefrom. Is called. And it becomes the form which remained so that the silicone 3c might be scattered on the lithium film 9 surface arrange | positioned to the carbon electrode layer 3b.

  In this way, by disposing the lithium film 9 on the negative electrode 3 by transfer, very thin lithium, which is difficult to handle, such as moving alone, such as the lithium film 9 formed by vapor deposition, is applied to the substrate 8. It can be fixed and carried and can be attached to the negative electrode 3.

  Next, a method for disposing the silicone 3c and the lithium film 9 on the base material 8 will be described.

  Silicone 3c used as a mold release agent has a specific gravity of 0.88 to 0.99 and a viscosity at 25 ° C. of 10,000 to 20000 cp. This silicone 3c was previously dissolved in a solvent such as toluene to give a platinum catalyst curing agent. A mixed solution was prepared, and the mixed solution was applied to the surface of the substrate 8 using a wire bar, and then processed with a hot-air circulating dryer. The mixing ratio of silicone 3c, platinum catalyst, and toluene constituting the mixed solution was approximately 100: 1: 499.

  If this release agent remains on the lithium film 9 after transfer, gas may be generated by reacting with the influence of the driving electrolyte solution impregnated in the element 1 or the electrochemical reaction that occurs during charge / discharge by the element 1. There is sex. Therefore, in some cases, it is necessary to darely remove the release agent remaining on the negative electrode 3 in order to further improve the reliability.

  Therefore, by using the silicone 3c as a release agent in the embodiment of the present invention, the pre-dope or electrochemical capacitor is attached to the lithium film 9 using the characteristic that the silicone 3c is chemically inactive. Even if charging / discharging is repeated, the possibility of generating gas by reacting with the driving electrolyte or the like can be reduced, and the reliability of the electrochemical capacitor can be further increased.

  Moreover, since the peeling strength between the base material 8 and a mold release agent is low when peeling the base material 8 from the lithium film | membrane 9 from the physical property of the silicone 3c, it becomes possible to peel easily.

  As described above, the substrate 8 can be easily peeled off without having to consider the residual of the silicone 3c on the lithium film 9 at the time of transfer, and the lithium film 9 can be applied to the negative electrode 3 more simply than the conventional electrochemical capacitor. It becomes possible to transfer, and the productivity of the electrochemical capacitor can be improved.

  In addition, the electrochemical capacitor in this Embodiment is not limited to the structure by which the silicone 3c is provided on the carbon electrode layer 3b of the negative electrode 3.

  For example, the wound element 1 may be provided on the surface of the separator 4 that is in close contact with the negative electrode 3, or may be peeled off from the carbon electrode layer 3b and included in the driving electrolyte. It is also possible that

Silicone 3c used in the present embodiment has a siloxane bond composed of a silicon atom and an oxygen atom, and is represented by the chemical formula X ₃ SiO (Y ₂ SiO) _n SiZ ₃ .

  The atom or molecule represented by X, Y, or Z appearing in this chemical formula is generally an alkyl group, but there is no particular limitation, and a plurality of X, Y, and Z are the same. It is not necessary to be a functional group composed of the following atoms or molecules. Further, n in the chemical formula is not particularly limited as long as it is a natural number.

  In the present embodiment, in the silicone 3c, a carbonate group represented by the following (Chemical Formula 1) is included in at least one functional group of the above-mentioned chemical formulas X, Y, and Z of the silicone as represented by (Chemical Formula 2). A thing may be used. Here, (Chemical Formula 2) shows a configuration in which one of the functional groups of Y is a carbonate group.

  Incidentally, A shown in (Chemical Formula 1) is an arbitrary atom or molecule and is not particularly limited, and the constituent elements shown by other alphabets indicate elements based on the periodic table. Generally, a hydrogen atom is provided in the portion A to form a hydrogen carbonate group.

  Further, A may be configured to be bonded to the left oxygen atom as well as the structure bonded to the right oxygen atom as in (Chemical Formula 1).

  By forming the silicone 3c having a carbonate group on the surface of the substrate 8 as a release agent, metallic lithium constituting the lithium film 9 formed on the silicone 3c by vapor deposition or the like, the silicone 3c and the lithium film Reacts at the interface with and produces lithium carbonate.

  This lithium carbonate has excellent conductivity.

  Conventionally, when pre-doping with lithium ions, the surface functional groups formed on the carbon material of the carbon electrode layer 3b, the driving electrolyte, and the like react with lithium ions to generate a compound with low conductivity.

  However, in the present embodiment, a part of the lithium ion is previously present as highly conductive lithium carbonate, so that a part of the reaction of the lithium ion with the surface functional group of the carbon electrode layer 3b is suppressed, The resistance can be reduced in the electrochemical capacitor according to the present embodiment.

  In addition, since the carbonic acid group of silicone 3c reacts only with highly reactive lithium ion, the low reactivity as silicone 3c is maintained.

  In (Chemical Formula 2), the oxygen atom contained in the carbonic acid group is bonded to the carbon atom of the side chain of the silicone 3c. However, the oxygen atom is bonded to the silicon atom of the main chain directly without any particular limitation. It may be a configuration.

  The composition of the silicone 3c used in the present embodiment can be confirmed by using NMR spectroscopy, infrared spectroscopy, or the like.

  Incidentally, in the present embodiment, the vapor deposition used when forming the lithium film 9 on the substrate 8 is used to form a metal film that is so thin that it is difficult to maintain its shape by itself. Is the method.

  By forming the thin lithium film 9 on the negative electrode 3, the total amount of lithium ions stored is reduced, and therefore the carbon electrode layer 3 b storing lithium ions can be made thinner than before. Since the carbon electrode layer 3b is thinned, the diffusion distance of lithium ions in the carbon electrode layer 3b can be reduced, so that lithium ions can be occluded more quickly and more uniformly.

  The lithium film 9 generated by using this vapor deposition forms a lithium metal thin film by spraying lithium atoms once vaporized by applying heat to the film formation target.

  Therefore, normally reactive lithium, which has received heat, further increases the reactivity, and when pre-doping is performed by applying a voltage to the element 1, it is possible to occlude lithium ions more quickly and more uniformly. It is.

  Here, it will be described that the effect of forming the lithium film 9 and preliminarily occluding lithium ions (giving lithium) to the negative electrode 3 is completely different between the lithium ion secondary battery and the electrochemical capacitor.

  The purpose of providing lithium ions to the negative electrode in a lithium ion secondary battery is to reduce the irreversible capacity of the negative electrode and improve the charge / discharge capacity. In the case of a general negative electrode using a graphite material as an active material, the ratio of the irreversible capacity to the negative electrode capacity is about 0% to 20%.

  Therefore, at most, lithium ions in an amount corresponding to about 20% of the negative electrode capacity may be applied to the negative electrode.

  On the other hand, in the case of an electrochemical capacitor using lithium ions, the purpose of preliminarily occluding lithium ions in the negative electrode 3 is to increase the voltage of the capacitor by lowering the potential of the negative electrode 3.

  In order to lower the potential of the negative electrode 3, it is necessary to store more lithium ions in the negative electrode 3. That is, it is necessary to occlude the negative electrode 3 in advance with an amount of lithium corresponding to at least 50% or more, preferably 70% or more of the capacity of the negative electrode 21.

  The lithium ions occluded in the carbon electrode layer 3b form an alloy with the carbon atoms of the carbon material mainly constituting the carbon electrode layer 3b.

  Thus, it is a problem peculiar to an electrochemical capacitor that the amount of lithium pre-doping needs to be significantly increased as compared with a lithium ion secondary battery.

  In addition to the silicone 3c, wax-based organic substances, wax-based organic substances, fatty acids, hydrocarbon esters, and the like can be used as a release agent. All are chemically inactive, but the peel strength is higher than that of silicone 3c.

  As for the base material 8, in addition to PPS, a material having a characteristic capable of withstanding a high temperature when the lithium film 9 is deposited on the base material 8, such as polypropylene (PP) and polyethylene terephthalate (PET), is preferable.

  Also for the carbon electrode layer 3b, in the embodiment of the present invention, non-graphitizable carbon having the characteristics of high capacity and low cycle loss in the charge / discharge cycle was used. Easily graphitized carbon, low-temperature calcined carbon, etc. are considered as candidate materials. Since these carbon-based materials have different physical properties, they are selected appropriately according to the purpose of use. For example, graphite materials are excellent in terms of high pressure resistance and low cycle loss of charge / discharge cycles, graphitizable carbon is excellent in terms of low resistance and charge / discharge cycle life, and low-temperature calcined carbon has high properties. Excellent in terms of capacity and low resistance.

  When a highly oriented graphite material is used as the material constituting the carbon electrode layer 3b, the sum of the thickness of the carbon electrode layer 3b before doping lithium and the thickness of the lithium film 9 provided on the carbon electrode layer Is substantially equal to the thickness of the lithium film 9 after being doped with lithium, so that the electrodes inside the electrochemical capacitor and the separator 4 can be easily fixed. Therefore, it is advantageous in that it is easy to produce a highly reliable electrochemical capacitor.

  This effect can be obtained in the same way when a stacked element is manufactured, but a more remarkable effect is obtained when a wound element is manufactured. That is, by providing the carbon electrode layer 3b with a lithium film in an amount corresponding to the expansion of the carbon electrode layer 3b after the lithium ion in the lithium film 9 is pre-doped, the pressure change inside the electrode can be reduced and the reliability is improved. It is possible to produce an electrochemical capacitor having a high height.

  As for the solvent for the driving electrolyte, in addition to the above, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), etc. can be used instead of DEC, or when mixing with EC, a plurality of solvents can be selected from DEC, DMC, EMC, etc. Can be mixed. In addition, it is conceivable to use polypropylene carbonate (PC) instead of EC. However, in the case of PC, since it has a characteristic of easily reacting with the graphite surface, PC uses non-graphitizable carbon as the carbon electrode layer 3b. It is preferable to use it.

  Further, the method of external connection is not limited to the lead wires 5a and 5b. For example, the polarizable electrode layer 2b and the electrode 2b at one end in the width direction of the current collectors 2a and 3a on the front and back surfaces of the current collectors 2a and 3a of the element 1 An unformed portion of the carbon electrode layer 3b is provided.

  When the element 1 is produced, when the separator 4 is wound between the positive electrode 2 and the negative electrode 3 facing each other, the unformed portions of the polarizable electrode layer 2b and the carbon electrode layer 3b are respectively The polarizable electrode layer 2b and the carbon electrode of the current collectors 2a and 3a are wound by winding the positive electrode 2 and the negative electrode 3 that are opposed to each other with a separator in a reverse direction so as to protrude in the reverse direction. The both end faces of the wound element 1 constituted by the unformed part of the layer 3b, the inner surface of the conductive terminal board used as a member for sealing the opening of the outer case 6, and the inner bottom of the outer case 6 are in contact with each other. Alternatively, a configuration called an end face current collector that is electrically connected may be used. In this case, for example, the outer surface of the terminal board and the outer surface of the outer case 6 are electrically connected to the external circuit.

  As a method for further improving the connection between the both end faces of the wound element 1 and the terminal plate and the inner bottom of the outer case 6 in order to reduce the resistance when the end face current collecting configuration is adopted, the element 1 is used. A configuration may be adopted in which current collecting plates, which are metal plates, are disposed on both end faces of the metal plate, and then end face current collection is performed.

  Further, the transfer method of the lithium film 9 using the silicone 3c is not limited to the case where the element 1 is wound, but can be used similarly when the element 1 is laminated.

(Performance evaluation test)
Ten wound electrochemical capacitors used in the above embodiment of the present invention are manufactured, and these are examples. Silicone was used as a release agent when transferring the lithium film to the carbon electrode layer of the negative electrode.

  In addition, 10 electrochemical capacitors having the same number of windings of the members and elements as those of the examples except that the carbon electrode layer was pre-doped using lithium ions contained in the driving electrolyte. These were prepared and used as comparative examples.

  The electrochemical capacitors of Examples and Comparative Examples were evaluated by the following methods.

The total 20 electrochemical capacitors are charged with a constant current of 1A until the charging voltage reaches 4.0V, then charged with a constant voltage of 4.0V for 10 minutes, and then 1A until the charging voltage reaches 2.0V. Discharge at a constant current of. When discharging, the initial voltage drop immediately after the start of discharge and the voltage drop between 3.5V and 3.0V during discharge are measured, and the internal resistance and capacitance of each electrochemical capacitor are calculated from them. did. And it evaluated based on the average value of those calculated values.

  The results are shown in (Table 1).

  As shown in (Table 1), even when compared with a comparative example in which lithium ions are occluded in the carbon electrode layer using a conventional method, an example in which silicone is used as a release agent for transfer is It can be confirmed that there is almost no change in the internal resistance. From this, it can be said that the silicone remaining on the negative electrode after the transfer does not affect the electrochemical reaction of the element after the transfer.

  As described above, the electrochemical capacitor according to the embodiment of the present invention uses silicone as a release agent between the base material and the lithium film when the lithium film is transferred to the surface of the carbon electrode layer of the negative electrode and pre-doped.

  As a result, after the base material on which the lithium film and the release agent are laminated is attached to the carbon electrode layer of the negative electrode, when the base material is peeled off from the lithium film, the peeling strength is lower than the physical properties of silicone, so that it can be easily peeled off. Is possible. And since silicone is chemically inert, even if silicone remains on the lithium film after peeling, it does not affect the charge and discharge performed by the electrochemical capacitor, and it is necessary to consider the remaining silicone when peeling The peeling work can be performed without any problems. Thereby, productivity and reliability can be improved as an electrochemical capacitor.

  According to the electrochemical capacitor according to the present invention, the pre-doping process of the lithium foil on the negative electrode carbon material has been simplified, and the working efficiency and reliability at the time of manufacturing the electrochemical capacitor have been improved. Thus, it is expected to be used as a backup power source or regenerative power for a hybrid vehicle or a fuel cell vehicle because of its high pressure resistance and resistance to rapid charge / discharge.

Cutaway perspective view showing a part of the electrochemical capacitor in the present embodiment Vertical sectional view showing elements used in the electrochemical capacitor Front view of the substrate used to transfer the lithium film to the negative electrode surface of the electrochemical capacitor

DESCRIPTION OF SYMBOLS 1 Element 2 Positive electrode 2a, 3a Current collector 2b Polarization electrode layer 3 Negative electrode 3b Carbon electrode layer 3c Silicone 4 Separator 5a, 5b Lead wire 6 Exterior case 7 Sealing member 8 Base material 9 Lithium film

Claims (4)

Forming a positive electrode by forming a polarizable electrode layer mainly composed of activated carbon on the surface of a current collector made of metal;
Forming a negative electrode by forming a carbon electrode layer mainly composed of a carbon material on the surface of a current collector made of metal;
Lithium which coats a release agent on a base material, forms a lithium film on the release agent, transfers the lithium film to the surface of the negative electrode, and disposes the lithium film on the surface of the negative electrode An arrangement process;
An element manufacturing step of manufacturing an element by making the positive electrode and the negative electrode face each other with a separator interposed therebetween, and winding or stacking;
It comprises a housing process for housing this element and the driving electrolyte in an exterior body,
A method for producing an electrochemical capacitor, wherein a release agent used in the lithium disposing step is made of silicone. The method for producing an electrochemical capacitor according to claim 1, wherein the silicone used in the lithium disposing step has a carbonate group in its chemical structural formula. A pair of electrodes includes a positive electrode in which a polarizable electrode layer mainly composed of activated carbon is formed on the surface of a current collector made of metal and a negative electrode in which a carbon electrode layer having occluded lithium ions is formed on the surface of the current collector made of metal. Facing each other, and an element wound or laminated in a state where a separator is interposed between the positive electrode and the negative electrode,
An exterior body containing the element and the driving electrolyte;
An electrochemical capacitor comprising silicone provided in at least one place on the negative electrode surface, the separator surface or the driving electrolyte. The electrochemical capacitor according to claim 3, wherein the silicone has a carbonate group in its chemical structural formula.

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