JP2011258798A - Electrochemical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reliable electrochemical device having no self-discharge failure.SOLUTION: An electrochemical device comprises: an electrochemical element 5 including an electrolyte in which a positive electrode plate and a negative electrode plate are laminated via a separator so that the negative electrode plate is at an outermost part; an electrode plate for lithium insertion to supply lithium ions in advance by electrochemical contact, which is arranged oppositely to at least one negative electrode plate at the outermost part of the electrochemical device via a separate sheet of which the value of air permeability is larger than that of the separator; a positive-electrode external terminal plate 2 and a negative-electrode external terminal plate 3 that are electrically connected to the positive electrode plate and the negative electrode plate respectively; and an armoring film sheet 4 that incorporates the electrochemical element 5, the electrode plate for lithium insertion, and the separate sheet and that seals them at a periphery.

Description

  The present invention relates to electrochemical devices such as lithium ion capacitors and lithium ion secondary batteries.

  Electrochemical devices with a chargeable / dischargeable power supply function having an exterior structure made of a laminate film include electric double layer capacitors and lithium ion secondary batteries. Recently, positive electrodes and lithium ion secondary batteries of electric double layer capacitors are also included. A hybrid type capacitor (hereinafter referred to as a hybrid capacitor) in combination with a negative electrode of a battery is also known.

  Electrochemical devices such as those mentioned above are used as an energy source for driving motors such as electric vehicles, or as a key device for energy regeneration systems, and also as an uninterruptible power supply due to environmental concerns such as oil reserves and global warming. Application to various new uses such as application to wind power generation and solar power generation is being studied, and it is a highly promising device as a next-generation device.

  In recent years, there has been a demand for higher energy density and lower resistance for electrochemical devices in applications for energy sources and energy regeneration.

  Electric double layer capacitors are generally classified into aqueous electrolyte type and non-aqueous electrolyte type depending on the type of electrolyte used. The withstand voltage of a single electric double layer capacitor is that of the aqueous electrolyte type. In some cases, it is about 1.2V, and even in the case of a non-aqueous electrolyte type, it is about 2.7V. In order to increase the energy capacity that can be stored in the electric double layer capacitor, it is important to further increase the withstand voltage, but it is difficult to construct.

  On the other hand, a lithium ion secondary battery includes a positive electrode mainly composed of a lithium-containing transition metal oxide, a negative electrode mainly composed of a carbon material that can occlude and desorb lithium ions, and an organic electrolyte containing a lithium salt. It is composed of When the lithium ion secondary battery is charged, lithium ions are desorbed from the positive electrode and occluded in the carbon material of the negative electrode. Conversely, when discharged, lithium ions are desorbed from the negative electrode and occluded in the metal oxide of the positive electrode. Lithium ion secondary batteries have the properties of higher voltage and higher capacity than electric double layer capacitors, but have a problem that their internal resistance is high and resistance reduction is difficult.

  The hybrid capacitor uses activated carbon for the positive electrode and a carbon material that can occlude and desorb lithium ions for the negative electrode. Since the negative electrode is subjected to occlusion and desorption reactions in the negative electrode during charge and discharge, the potential difference between the two electrodes that actually occurs inside the capacitor changes at a lower value when lithium metal is used for the negative electrode. Therefore, the withstand voltage can be further increased as compared with the conventional electric double layer capacitor using activated carbon for the positive electrode and the negative electrode, and the amount of energy that can be stored is greatly increased compared to the electric double layer capacitor (high Energy) and low resistance, it is promising as a device for solving these problems.

  The hybrid capacitor normally needs to store lithium ions in a negative electrode material mainly composed of a carbon material capable of inserting and extracting lithium ions (hereinafter also referred to as lithium ion pre-doping). There is technology.

  Patent Document 1 proposes the following. An organic electrolyte battery comprising a positive electrode, a negative electrode, and an aprotic organic solvent solution of lithium salt as an electrolytic solution, the positive electrode current collector and the negative electrode current collector each having a hole penetrating the front and back surfaces, and a negative electrode active material Is capable of reversibly supporting lithium, and lithium derived from the negative electrode is supported by electrochemical contact with lithium arranged opposite to the negative electrode or the positive electrode, and the opposing area of the lithium is 40% or less of the negative electrode area An organic electrolyte battery is described.

  Moreover, there exists a technique of patent document 2 as a countermeasure for making dope uniform. From a positive electrode formed on a positive electrode current collector having holes penetrating the front and back surfaces, a negative electrode formed on a negative electrode current collector having holes penetrating the front and back surfaces, and an aprotic organic solvent liquid of lithium salt An electrolyte solution, a lithium ion supply source for supplying lithium ions previously supported on the negative electrode and / or the positive electrode by electrochemical contact, the lithium ion supply source (electrode plate for lithium insertion), the positive electrode, and the negative electrode A positive electrode active material of the positive electrode and reversible of lithium ions and / or anions, wherein the positive electrode and / or the negative electrode are alternately laminated in three or more layers. The negative electrode active material of the negative electrode includes a material capable of reversibly supporting lithium ions, and is disposed at a predetermined position. A lithium ion capacitor is proposed in which at least two separators are sandwiched between the positive electrode and / or the negative electrode adjacent to the lithium ion supply source in a range of 40 to 120 μm. Yes.

Japanese Patent No. 3485935 JP 2009-59732 A

  By using a current collector having a through hole, lithium ions move to each of the stacked electrodes through the through hole, and lithium ion pre-doping can be performed, which is a useful method. However, since the lithium ion supply source is arranged in the stacking direction, the resistance between the negative electrode and the lithium ion supply source is very small, and lithium is supported on the target electrode by electrical contact. The current flowing between the electrodes) (lithium pre-doping current) is very large, and the target electrode is doped with lithium ions, which may cause problems such as deterioration of the target electrode. In addition, there is a difference in the doping amount of lithium ions between the electrode to be carried closest to the lithium ion supply source (lithium insertion electrode plate) and the electrode farthest from the lithium ion, or lithium dendrite is deposited on the electrodes due to uneven doping. This may cause a short circuit or cause a problem such as deterioration of durability due to uneven dope.

  With respect to Patent Document 2, the distance between the lithium ion supply source and the adjacent electrode is set to 40 to 120 μm by using two or more separators disposed between the lithium ion supply source and the adjacent electrode, and lithium ion pre-doping is laminated. It is said that the dope between the target electrodes is made uniform. However, there are separators as many as the number of stacked electrodes between the target electrodes that are stacked, and depending on the stacking position of the target electrodes, the distance from the lithium ion source and the number of separators through which ions permeate also differ. It becomes uneven, and it cannot be denied that the technical basis is unclear. Patent Document 2 states that the distance between the lithium supply source and the electrode to be supported is 40 μm to 120 μm, but the described examples are only described as 70 μm to 100 μm.

  In the technique of performing lithium ion pre-doping described in Patent Document 1 or 2, there is no influence on the deterioration of the target electrode to be doped with lithium ions, and there is no uneven doping between the stacked electrode plates and in the electrode plane. In addition, it has been difficult to provide an electrochemical device having no lithium dendrite precipitation and excellent quality and reliability. That is, an object of the present invention is to provide an electrochemical device capable of pre-doping lithium ions uniformly between electrode plates and within an electrode surface.

  The electrochemical device according to the present invention includes a positive electrode plate and a negative electrode plate laminated via a separator so that the negative electrode plate is the outermost part, an electrochemical element containing an electrolyte, and a value of air permeability of the separator An electrode plate for lithium insertion that supplies lithium ions in advance by electrochemical contact disposed opposite to the outermost negative electrode plate of at least one of the electrochemical elements through a separator sheet having a larger value; A positive external terminal plate and a negative external terminal plate that are electrically connected to the positive electrode plate and the negative electrode plate, respectively, and an exterior that contains the electrochemical element, a lithium insertion electrode plate, and a separate sheet, and is sealed at the periphery. And a film sheet.

  Furthermore, the electrochemical device of the present invention is characterized in that the air permeability of the separate sheet is not less than 5 times and not more than 2000 times the air permeability of the separator used in the electrochemical element.

  Furthermore, the electrochemical device of the present invention is characterized in that the thickness of the separate sheet is 10 μm or more and 200 μm or less.

  Furthermore, the electrochemical device of the present invention is a lithium ion secondary battery or a hybrid capacitor.

  According to the present invention, a lithium ion pre-doping can be uniformly applied to a target electrode, and an electrochemical device having high quality and reliability can be provided.

FIG. 1A is a plan view, FIG. 1B is a side view, and FIG. 1C is a cross-sectional view taken along line AA in FIG. 1A. . 2A and 2B are diagrams showing the configuration of an electrochemical element inside the hybrid capacitor of the present invention, FIG. 2A is a plan view of a positive electrode plate, FIG. 2B is a plan view of a separator, and FIG. 2C is a negative electrode. FIG. 2D is a plan view of a separate sheet, and FIG. 2E is a plan view of a lithium insertion electrode plate for inserting lithium into the negative electrode. The perspective view of the electrochemical element of the hybrid capacitor of this invention. The perspective view of the electrochemical element of the hybrid capacitor of this invention which set the separate sheet | seat on the uppermost surface. The perspective view of the electrochemical element of the conventional hybrid capacitor which set the separator on the uppermost surface. The perspective view which set the electrode plate for lithium insertion to the electrochemical element of the hybrid capacitor of this invention.

  Hereinafter, embodiments of the electrochemical device of the present invention will be described with reference to the drawings, taking a hybrid capacitor as an example.

  The hybrid capacitor as an electrochemical device of the present invention comprises a positive electrode plate laminated with a separator and a positive electrode plate comprising a current collector, a negative electrode active material electrode sheet capable of reversibly inserting and extracting lithium, and a collector. A negative electrode plate provided with an electric conductor, an electrochemical element including an organic electrolyte containing a lithium salt, and lithium ions are supplied in advance to the negative electrode plate by electrochemical contact with the negative electrode plate. Built-in electrode plate for lithium insertion, separate sheet placed between the electrochemical element and the electrode plate for lithium insertion, and a positive external terminal plate and a negative external terminal plate electrically connected to the positive electrode plate and the negative electrode plate, respectively The exterior film sheet is hermetically sealed at the peripheral edge. The separate sheet disposed between the lithium insertion electrode plate and the electrochemical element is composed of a sheet having a larger air permeability than that of the separator used for the electrochemical element, that is, a sheet having low ion permeability.

  Furthermore, the air permeability of the separator sheet of the hybrid capacitor of the present invention is 5 to 2000 times that of the separator used in the electrochemical device, and the thickness is 10 μm to 200 μm. preferable.

  In the hybrid capacitor of the present invention, the doping current is controlled by a separate sheet that is disposed between the electrochemical element and the electrode plate for lithium insertion and has a larger air permeability value than that of the separator, that is, low ion permeability, so that the multi-layered negative electrode Even in the active material electrode sheet, the lithium capacitor can be uniformly doped within the electrode surface and between the laminated electrode plates, so that high quality and high reliability of the hybrid capacitor can be achieved. According to the present invention, it is possible to provide a hybrid capacitor that solves the conventional problems and achieves high quality and high reliability.

  FIG. 6 is a perspective view in which a separate sheet having a larger air permeability than the separator is disposed between the electrochemical element 5 of the hybrid capacitor of the present invention and the lithium insertion electrode plate 12. This shows an example of the configuration of the electrochemical device according to the embodiment of the present invention, and particularly shows the case of a hybrid capacitor. However, even in the case of lithium ion secondary batteries that are other electrochemical devices, the arrangement of the positive electrode active material electrode sheet, the arrangement of the negative electrode active material electrode sheet, the configuration provided on the external terminal plate, and the built-in metal foil There is no particular difference in the configuration of the exterior film sheet, which can be applied in any case.

  FIG. 1 is a diagram showing the shape and internal configuration of a hybrid capacitor of the present invention, in which FIG. 1 (a) is a plan view, FIG. 1 (b) is a side view, and FIG. 1 (c) is A in FIG. FIG. The upper and lower sides of the hybrid capacitor 1 are covered with an exterior film sheet 4, and the positive external terminal plate 2 and the negative external terminal plate 3 extend from one short side, respectively, as shown in FIG. The positive external terminal plate 2 and the negative external terminal plate 3 are led out from between the upper and lower exterior film sheets 4, respectively. Further, as shown in FIG. 1C, an electrochemical element 5 described later is built in the hybrid capacitor 1. In the electrochemical element, the positive electrode plate has a positive electrode current collector coated with a positive electrode active material electrode sheet. In the negative electrode plate, a negative electrode active material electrode sheet is coated on a negative electrode current collector. A positive electrode external terminal plate 2 and a negative electrode external terminal plate 3 are connected to the positive electrode plate and the negative electrode plate, respectively. An electrolyte solution is filled between the upper and lower exterior film sheets 4, and the electrochemical element 5 is immersed in the electrolyte solution. As the exterior film sheet, a laminated film obtained by bonding a metal foil and a polyolefin film can be used. A thermoplastic resin is formed inside the exterior film sheet, and polyethylene, polypropylene, acid-modified propylene, an ethylene-methacrylic acid copolymer, and the like can be used as the thermoplastic resin.

  The exterior film sheet 4 wraps the electrochemical element 5 from the upper side and the lower side, but at the peripheral part, the upper and lower exterior film sheets 4 adhere to each other to seal the contents containing the electrolyte, It is configured to prevent leakage. In addition, at the position where the positive electrode external terminal plate 2 and the negative electrode external terminal plate 3 lead out to the outside (joining portion), the periphery of each external terminal plate is covered and sealed. Therefore, the hybrid capacitor 1 is completely sealed by adhesion between the exterior film sheets 4 and covering around the joint between the positive external terminal plate 2 and the negative external terminal plate 3 by the external film sheet 4.

  2A and 2B are diagrams showing the structure of the electrochemical element inside the hybrid capacitor of the present invention. FIG. 2A is a plan view of the positive electrode plate, FIG. 2B is a plan view of the separator, and FIG. ) Is a plan view of the negative electrode plate, FIG. 2D is a plan view of a separate sheet, and FIG. 2E is a plan view of a lithium insertion electrode plate for inserting lithium into the negative electrode. The positive electrode plate 6 shown in FIG. 2 (a) is composed of a positive electrode active material electrode sheet 8 and a positive electrode current collector, of which the positive electrode current collector is generally composed of a metal foil such as aluminum or aluminum alloy, and has a surface. The positive electrode active material electrode sheet 8 is an electrode mixture layer containing a large amount of an active material mainly composed of a carbon material on one side or both sides of the current collector. Often includes a binder and a conductive agent. The positive electrode plate 6 of the terminal portion is generally a part of the current collector on which the positive electrode active material electrode sheet 8 is applied, but some thin metal body is welded or crimped to the positive electrode current collector. It may be fixed by the above method.

  The separator 10 shown in FIG. 2 (b) is an insulating porous film, and is generally configured to be slightly larger than the positive electrode active material electrode sheet 8 and the negative electrode active material electrode sheet 9, and has a relatively small air permeability value. It is necessary for the material to be easily penetrated by the liquid, to maintain the insulation between the positive electrode and the negative electrode and to have high ion permeability.

  The negative electrode plate shown in FIG. 2 (c) is composed of a negative electrode active material electrode sheet 9 and a negative electrode current collector. Of these, the negative electrode current collector is generally composed of a metal foil such as copper or copper alloy, A current collector having holes penetrating the back surface, the negative electrode active material electrode sheet 9 is an electrode mixture layer containing a large amount of an active material mainly composed of a carbon material on one or both surfaces of the current collector, Often contains a binder and a conductive agent. The negative electrode plate 7 of the terminal portion is generally a part of the current collector on which the negative electrode active material electrode sheet 9 is applied, but some thin metal body is welded or crimped to the negative electrode current collector. It may be fixed by the above method. In addition, although the case where it is set as the same shape as the positive electrode active material electrode sheet 8 is shown in FIG.2 (c), the area and shape of both may not be the same.

  A separate sheet 11 shown in FIG. 2 (d) is an insulating porous film, is configured to be slightly larger than the positive electrode active material electrode sheet 8 and the negative electrode active material electrode sheet 9, has a large air permeability, and is used for lithium insertion. It is necessary to maintain the insulation between the electrode plate 12 and the negative electrode plate and to have low ion permeability. In addition, the air permeability conforms to the term of 19.2 air permeability defined in JIS C2111 (insulating paper test method), and 100 ml of air measured by a B-type tester (Gurley densometer) passes through the measurement sheet. It is the value of the time required for

  In the lithium insertion electrode plate 12 shown in FIG. 2 (e), metallic lithium 13 is bonded and fixed to a current collector made of a metal foil such as copper. After inserting lithium into the negative electrode active material electrode sheet, it is desirable to take out the electrode plate for lithium insertion. However, if lithium metal is consumed using the amount of insertion, it may be placed inside.

  FIG. 6 is a perspective view of the electrode laminate of the hybrid capacitor of the present invention. From above, the lithium insertion electrode plate 12 shown in FIG. 2 (e), the separate sheet shown in FIG. 2 (d), the negative electrode plate 7 shown in FIG. 2 (c), the separator 10 shown in FIG. 2 (b), FIG. The positive electrode plates 6 shown in FIG. That is, the structure of the electrochemical element 5 in the exterior film sheet is lithium insertion electrode plate / separate sheet / negative electrode plate / separator / positive electrode plate / separator /.../ separator / positive electrode plate / separator / negative electrode plate. / Separator or electrode plate for lithium insertion / separate sheet / negative electrode plate / separator / positive electrode plate / separator /.../ separator / positive electrode plate / separator / negative electrode plate / separate sheet / The electrode plate for lithium insertion and the separate sheet / sheet for lithium insertion are arranged above and below. If the number of laminated layers is further increased, the electrode plate for lithium insertion / separate sheet / negative electrode plate / separator / positive electrode plate / separator /.// negative electrode plate / separate sheet / electrode plate for lithium insertion / separate sheet / Negative electrode plate ... / Separator / Positive electrode plate / Separator / Negative electrode plate / Separate sheet / Lithium insertion electrode plate Lithium insertion electrode plate with lithium metal bonded on both sides of Cu foil Separate sheets may be arranged above and below. Be sure to place a separate sheet between the lithium insertion electrode plate and the negative electrode plate.

  FIG. 3 is a perspective view of the electrochemical element of the hybrid capacitor of the present invention before setting a separate sheet and a lithium insertion electrode plate. The electrochemical element 5 is configured by laminating a positive electrode plate 6 and a negative electrode plate 7 via a separator. From one short side of the positive electrode plate 6 and the negative electrode plate 7, a positive electrode extension portion and a negative electrode extension portion are respectively drawn out.

  FIG. 4 is a perspective view of the electrochemical element 5 of the hybrid capacitor of the present invention in which a separate sheet 11 is set on the electrochemical element of FIG.

  FIG. 5 is a perspective view of an electrochemical element of a conventional hybrid capacitor in which a separator 10 is set on the electrochemical element of FIG.

  FIG. 6 shows a lithium insertion electrode plate 12 set in the electrochemical element of the hybrid capacitor of the present invention. The positive external terminal plate 2 is a positive electrode plate, the negative external terminal plate 3 is a negative electrode plate and a lithium insertion electrode plate 12. 2 is a perspective view of an electrochemical element 5 that is ultrasonically welded to each other. It arrange | positioned so that the surface which bonded the lithium metal of the electrode plate 12 for lithium insertion, and the electrochemical element 5 may oppose. If a punching metal or an expanded metal having a through hole is used as the current collector of the lithium insertion electrode plate 12, the surface on which the metallic lithium is bonded does not necessarily have to face the electrochemical element. Opposite the chemical element is preferable for inserting lithium. When the lithium insertion electrode is arranged in the middle of the laminate, a punching metal or an expanded metal having a through hole is used, or lithium metal is used as the lithium insertion electrode. What was bonded to both the front and back surfaces of the current collector of the plate 12 is used. The joining method of each external terminal and each electrode plate is not limited to ultrasonic welding, and may be resistance welding, laser welding, or the like.

Here, an example of a manufacturing method of the multilayer hybrid capacitor in the embodiment of the present invention will be described below. The positive electrode plate is formed by pressing a metal foil made of aluminum foil, stainless steel foil, or the like, and a current collector having holes penetrating the front and back surfaces of the foil, so-called punching foil and an active material and a binder mainly composed of a carbon material, And a positive electrode active material electrode sheet mixed with a conductive agent to form a sheet. The current collector having the through holes is not limited to the punching foil, but may be any one having holes penetrating the front and back surfaces, such as an expanded metal, a through foil by electrolytic etching, and a foil having a three-dimensional microstructure. The carbon raw material used as the active material includes plant materials such as wood, sawdust, coconut husk and pulp waste liquid, coal, heavy petroleum oil, coal-based and petroleum-based pitch obtained by pyrolyzing them, and petroleum coke. Various materials such as fossil fuel materials such as carbon aerogel and tar pitch, and synthetic polymer materials such as phenol resin, polyvinyl chloride resin, and polyvinylidene chloride are used. These carbon material after carbonization, and activating the gas activation method or chemical activation method, the specific surface area to obtain a carbon-based active material of 700m ² / g~3000m ² / g. The specific surface area of the active material is particularly preferred if the 1000m ² / g~2000m ² / g. As the binder, fluorine-containing resins such as polytetrafluoroethylene, polyvinylidene fluoride and fluoroolefin copolymer cross-linked polymers, rubber binders such as styrene-butadiene rubber, thermoplastic resins such as polypropylene and polyethylene, etc. are used. It is preferable that the positive electrode active material electrode sheet is made to contain about 3% by mass to 20% by mass of the binder. Among these substances, polytetrafluoroethylene is particularly preferable as the binder from the viewpoint of heat resistance, chemical resistance, and strength of the sheet-like polarizable electrode layer to be produced. Further, as the conductive agent, a material selected from carbon black such as acetylene black and ketjen black, natural graphite, thermally expanded graphite carbon fiber, etc., is about 5% by mass to 30% by mass of the whole positive electrode active material electrode sheet. It is preferable to add.

  The negative electrode plate is formed by pressing a metal foil made of copper foil, nickel foil, stainless steel foil, or the like, and a current collector having holes penetrating the front and back surfaces of the foil, so-called punching foil. A negative electrode active material electrode sheet in which a substance, a binder, and a conductive agent are mixed to form a sheet is integrated. The current collector having a through hole is not limited to the punching foil, but may be any one having a hole penetrating the front and back surfaces, such as an expanded metal and a foil having a three-dimensional microstructure. As an active material mainly composed of a carbon material, a carbon-based material such as graphite or amorphous carbon that can be doped or dedoped with lithium ions can be used. As the conductive agent, carbon black such as acetylene black and ketjen black, natural graphite, and thermally expanded graphite carbon fiber are preferable, and it is preferable to add about 5 to 30% by mass of the entire negative electrode active material electrode sheet. As binders, fluorine-containing resins such as polytetrafluoroethylene, polyvinylidene fluoride and fluoroolefin copolymer crosslinked polymers, rubber-based binders such as polybutadiene rubber and styrene-butadiene rubber, thermoplastic resins such as polypropylene and polyethylene, etc. In particular, polyvinylidene fluoride is preferable from the viewpoints of heat resistance, chemical resistance, and sheet strength. It is preferable that the negative electrode active material electrode sheet is made to contain about 3 to 20% by mass of the binder. Although described here for carbon materials, the energy density of next-generation lithium-ion secondary batteries using next-generation anode materials such as Si, which has a theoretical capacity much larger than the theoretical capacity per unit weight of the cathode active material It has been studied as a technique, and a negative electrode material such as Si may be used.

  Next, an example of a method for producing a positive electrode plate will be described. In the following example, a phenol resin is used as a carbon raw material to be an active material, polytetrafluoroethylene is selected as a binder material, and ketjen black is selected as a conductive agent. First, the activated carbon powder obtained by carbonizing and activating the phenol resin, a binder made of polytetrafluoroethylene, and a ketjen black are kneaded and then rolled to form a sheet-like active material electrode layer . The positive electrode active material electrode sheet thus obtained is adhered to a current collector foil having aluminum or stainless steel through holes using a conductive carbon paste. Furthermore, it integrates by heating-drying and makes this a positive electrode plate. At this time, if one extension portion is formed in advance on the current collector foil and the positive electrode active material electrode sheet is not adhered thereto, a positive electrode plate connected to the external terminal plate can be formed. it can.

  In addition to the above method, the positive electrode plate may be produced by a method in which a positive electrode active material electrode sheet and a current collector having a through hole are stacked and rolled to bond them together. The positive electrode active material electrode sheet may be adhered to one side of the current collector or may be adhered to both sides. Furthermore, the active material and the conductive agent are mixed and dispersed in a solution in which a binder such as methylcellulose or polyvinylidene fluoride is dissolved in a solvent to form a slurry, and this slurry is applied to one or both sides of a current collector having a through hole. The positive electrode plate may be produced by the method of:

  Next, an example of a method for producing a negative electrode plate will be described. In the following example, a non-graphitizable carbon material is used as a carbon raw material as an active material, polytetrafluoroethylene is selected as a binder material, and ketjen black is selected as a conductive agent. First, the three components of the non-graphitizable carbon material powder, the binder made of the above polytetrafluoroethylene, and ketjen black are kneaded, and then rolled to form a sheet-like active material electrode layer. The negative electrode active material electrode sheet thus obtained is bonded to a current collector foil having copper, nickel, or stainless steel through-holes using a conductive carbon paste. Furthermore, it integrates by heating-drying and makes this a negative electrode plate. At this time, if one extension portion is formed in advance on the current collector foil and the negative electrode active material electrode sheet is not adhered thereto, a negative electrode plate connected to the external terminal plate can be formed. it can.

  In addition to the above method, the negative electrode plate may be produced by a method in which a negative electrode active material electrode sheet and a current collector having a through hole are stacked and rolled to bond them together. The negative electrode active material electrode sheet may be adhered to one side of the current collector or may be adhered to both sides. Furthermore, the active material and the conductive agent are mixed and dispersed in a solution in which a binder such as methylcellulose or polyvinylidene fluoride is dissolved in a solvent to form a slurry, and this slurry is applied to one or both sides of a current collector having a through hole. The negative electrode plate may be produced by the method of:

  Moreover, the separator installed between the positive electrode plate and the negative electrode plate or between the exterior film sheet and the negative electrode plate has a small thickness (for example, 10 to 40 μm) and a low air permeability value (for example, 50 to 300 sec / 100 ml). A material having high electronic insulation and ion permeability is preferred. The constituent material of the separator is not particularly limited. For example, a microporous sheet such as polyethylene, polypropylene, polyamide or polyimide, a nonwoven fabric of the resin, or papermaking of viscose rayon or natural cellulose is preferably used. The The constituent material of the separator is preferably selected according to the type of electrochemical device to be produced.

  Next, the separate sheet | seat installed between the positive electrode plate or negative electrode plate which opposes a lithium insertion electrode plate is demonstrated. The separate sheet is preferably made of a material having a high air permeability value (for example, 1500 to 150,000 sec / 100 ml), high electronic insulation, and low ion permeability. The constituent material of the separate sheet is not particularly limited, but for example, a stretching method in which an unstretched resin film made of polyethylene, polypropylene, polyamide or polyimide is made porous by stretching, an extractable filler, a plasticizer, etc. A microporous sheet produced by an extraction method in which a filler, a plasticizer, etc. are extracted from a non-rolled film blended with a solvent to make it porous, and uniaxially or biaxially stretched before or after extraction as necessary. A nonwoven fabric in which resin fibers are overlapped and bonded in a three-dimensional structure, or a papermaking of viscose rayon or natural cellulose is preferably used. It is preferable to select the constituent material of the separate sheet according to the type of electrochemical device to be produced.

  The dimensions and the number of active material electrode sheets of the positive electrode and the negative electrode are not necessarily the same.

  Hereinafter, examples and comparative examples will be described. In addition, Examples 1-18 and Comparative Examples 1-3 produced a hybrid capacitor as an electrochemical device, and Example 19 and Comparative Example 4 produced lithium ion secondary batteries, respectively, and performed various evaluations.

Example 1
With respect to a powder obtained by mixing 92 parts by mass of a phenol-based activated carbon powder having a specific surface area of 1500 m ² / g as a positive electrode active material and 8 parts by mass of graphite as a conductive agent, 3 parts by mass of styrene-butadiene rubber as a binder and 3 parts by mass of carboxymethyl cellulose And 200 parts by mass of water as a solvent and kneaded to obtain a slurry. Next, using a 20 μm-thick aluminum press, the punching foil having through holes formed thereon is used as a current collector, and the slurry is uniformly applied to both sides thereof, then dried and rolled and pressed. A positive electrode active material electrode sheet of 30 μm was obtained on each side. The thickness of this positive electrode plate was 80 μm. In addition, a part of the end face of the positive electrode active material electrode sheet is formed with an electrode plate so that the current collector can be taken out in a tab shape, and a positive electrode active material electrode sheet is formed on both sides of the current collector of that part. The aluminum foil was exposed.

  With respect to the powder obtained by mixing 88 parts by mass of the non-graphitizable material powder as the negative electrode active material and 6 parts by mass of acetylene black as a conductive agent, 5 parts by mass of styrene-butadiene rubber, 4 parts by mass of carboxymethyl cellulose, and 200 parts by mass of water as a solvent. And kneaded to obtain a slurry. Next, a copper foil having a thickness of 10 μm is pressed by a punching machine, and the slurry is uniformly applied to both sides of the punching foil having through holes formed therein, and then dried and rolled and pressed to obtain a thickness of the polarizable electrode layer. Produced negative electrode active material electrode sheets of 20 μm on both sides. The thickness of this negative electrode plate was 50 μm. In addition, a part of the end face of the negative electrode active material electrode sheet is formed with an electrode plate so that the current collector can be taken out in a tab shape, and a negative electrode active material electrode sheet is formed on both sides of the current collector of that part The copper foil was not exposed.

  As a separator, a thin plate of natural cellulose material having a thickness of 35 μm and an air permeability of 150 sec / 100 ml was used. The size and shape of the separator was configured to be slightly larger than the shape excluding the extended portion of the electrode plate.

  As a separate sheet, a polyethylene microporous sheet having a thickness of 38 μm and an air permeability of 45000 sec / 100 ml was used. The size and shape of this separate sheet was configured to be slightly larger than the shape excluding the extended portion of the electrode plate, and to be the same size as the separator.

  Subsequently, these three members were stacked in the order of a separator, a negative electrode plate, a separator, a positive electrode plate, and a separator, and a separate sheet was stacked on the top to obtain a stacked body. In this example, four positive electrode plates, five negative electrode plates, nine separators, and one separate sheet were stacked per sample, and the dimensions of the positive electrode active material excluding the extension were The electrode sheet was 53 mm × 70 mm, the negative electrode active material electrode sheet was 55 mm × 72 mm, the separator was 57 mm × 74 mm, and the separate sheet was 57 mm × 74 mm. Moreover, the extension part formed in the electrode plate extended from the same short side of each active material electrode sheet, and the dimension of the extension part was 9 mm x 12 mm, respectively.

  The positive electrode external terminal plate was made of an aluminum material having a length of 20 mm, a width of 10 mm, and a thickness of 0.2 mm, and the negative electrode external terminal plate was made of a nickel material having a length of 20 mm, a width of 10 mm, and a thickness of 0.2 mm. The region derived from the exterior film sheet was 10 mm long and 10 mm wide. As the surface to be thermally bonded to the exterior film sheet, one having a sealant made of an acid-modified polyolefin resin on both sides was used.

  Next, metallic lithium was bonded to the copper foil to prepare an electrode plate for lithium insertion, which was placed on the upper surface of the electrochemical element separate sheet so that the metallic lithium was opposed to the electrochemical element separate sheet.

  Next, the positive electrode extension part and the negative electrode extension part extending from the electrochemical element and the extension part of the lithium insertion electrode plate were bundled, and fixed to the end of the external terminal board by ultrasonic welding in a lump. . An electrochemical element in which a lithium insertion electrode plate is welded with two exterior film sheets is wrapped, and the peripheral edge of three sides including the short side of one side where the positive electrode / negative electrode external terminal plate is arranged is thermocompression bonded to the inner surface. The formed thermoplastic resin layer made of acid-modified polyolefin resin was joined to form a bag. The thickness of the thermoplastic resin layer on the inner surface of this exterior film sheet was 40 μm.

  An electrolytic solution was injected into the two exterior film sheets having a built-in electrochemical element and formed into a bag shape. As the electrolytic solution, a solution prepared by dissolving lithium hexafluorophosphate in a mixed solvent in which propylene carbonate and diethyl carbonate were mixed at a ratio of 1: 1 and adjusted to a concentration of 1.0 mol / l was used. After injecting the electrolytic solution, the remaining one side of the two exterior film sheets was sealed by thermocompression bonding in a vacuum atmosphere. Lithium was inserted from the lithium insertion electrode plate into the negative electrode active material electrode sheet by electrical contact between the negative electrode plate and the lithium insertion electrode plate. The amount of insertion was 400 mAh / g based on the weight of the negative electrode active material. After completion of lithium insertion, aging was performed at a predetermined voltage. After the aging was performed, the laminate was opened once, the gas generated by the aging was taken out, and the opened laminate side was again heat-pressed and sealed in a vacuum atmosphere.

  A multilayer hybrid capacitor was obtained by the above method. There were 50 hybrid capacitors produced by this method.

(Comparative Examples 1-3: Case of conventional technology)
In the same manner as in Example 1, 50 hybrid capacitors were produced for each condition described below. The dimensions and shape of the fabricated hybrid capacitor are exactly the same as in the first embodiment.

  In Comparative Example 1, a similar configuration described in Patent Document 1 as a prior art is applied, and in Comparative Examples 2-3, a similar configuration described in Patent Document 2 as a prior art is applied to manufacture of a hybrid capacitor. is there. FIG. 5 is a perspective view of an electrochemical element of a conventional hybrid capacitor in which a separator is set on the uppermost surface. Regarding Comparative Example 2 and Comparative Example 3, two separate sheets were used on the uppermost surface.

  In Comparative Example 1, a thin sheet of natural cellulose material having a thickness of 35 μm and an air permeability of 150 sec / 100 ml was used in place of the separate sheet of Example 1. In Comparative Example 2, two sheets of a natural cellulose material having a thickness of 35 μm and an air permeability of 150 sec / 100 ml were used instead of the separate sheet of Example 1, and in Comparative Example 3, natural cellulose having a thickness of 50 μm and an air permeability of 200 sec / 100 ml was used. Two thin plates of the material were used, and 50 hybrid capacitors were produced under the same conditions as in the present invention except for the separator on the uppermost surface of the electrochemical element.

(Examples 2-9: Comparison of air permeability ratio between separate sheet and separator)
In the same manner as in Example 1, 50 hybrid capacitors were produced for each condition described below. The dimensions and shape of the fabricated hybrid capacitor were exactly the same as those in Example 1.

  The only difference between the sample of Example 1 and the samples of Examples 2 to 9 was the difference in transparency of the used separation sheet. In Example 2, a polyethylene microporous sheet having an air permeability of 450 sec / 100 ml, an air permeability of 750 sec / 100 ml in Example 3, an air permeability of 1500 sec / 100 ml in Example 4, and an air permeability of 7500 sec / in Example 5. 100 ml, air permeability of 15000 sec / 100 ml in Example 6, air permeability of 75000 sec / 100 ml in Example 7, air permeability of 150,000 sec / 100 ml in Example 8, air permeability of 300000 sec / 100 ml in Example 9, polyethylene microporous It was a quality sheet. These samples were evaluated based on the difference in the air permeability ratio between the separate sheet and the separator.

(Examples 10-14: Comparison of separate sheet materials)
In the same manner as in Example 1, 50 hybrid capacitors were produced for each condition described below. The dimensions and shape of the fabricated hybrid capacitor were exactly the same as those in Example 1.

  The only difference between the sample of Example 1 and the samples of Examples 10 to 14 was the difference in the material of the separate sheet. Example 10 is a polypropylene microporous sheet, Example 11 is a glass fiber sheet, Example 12 is a polyphenylene sulfide microporous sheet, Example 13 is a polyamide microporous sheet, and Example 14 is a polyimide microporous sheet. It was a quality sheet. With these samples, the difference due to the hole diameter was evaluated.

(Examples 15 to 18: thickness of separate sheet)
By the same method as in Example 11, 50 hybrid capacitors were produced for each condition described below. The dimensions and shape of the fabricated hybrid capacitor are exactly the same as those in Example 11. The only difference between the sample of Example 1 and the samples of Examples 15 to 18 was the difference in the thickness of the separate sheet. In Example 15, the thickness was 8 μm, in Example 16, the thickness was 10 μm, in Example 17, the thickness was 100 μm, and in Example 18, the thickness was 200 μm. With these samples, the difference due to the thickness of the separate sheet was evaluated.

(Example 19, Comparative Example 4: Type of electrochemical device)
In the same manner as in Example 1, 50 lithium ion secondary batteries were produced for each condition described below. The difference between the sample in Example 19 and the sample in Example 1 was the type of electrochemical device. Lithium cobaltate (LiCoO ₂ ) was used as the positive electrode active material instead of the phenol-based activated carbon of Example 1, and a polyethylene-based separator was used as the separator instead of the cellulose-based material of Example 1. Except for these, 50 lithium ion secondary batteries were produced in the same manner using the same materials as in Example 1, and Example 19 was obtained. Comparative Example 4 is different from Example 1 in the type of electrochemical device as in Example 19. The difference from Example 19 is that a separator is disposed between the lithium insertion electrode plate and the positive electrode or negative electrode plate.

(Evaluation methods)
The electrochemical devices produced in Examples 1 to 19 and Comparative Examples 1 to 4 were evaluated as follows. In other words, after three samples of DC resistance (hereinafter referred to as DC-R) measurement evaluation, capacity measurement evaluation, and self-discharge measurement evaluation, and after high temperature load test (80 ° C.-3.8 V / 1000 hours, 50 samples) Evaluation was performed after selecting 10 samples randomly. In Examples 1-19 and Comparative Examples 1-4, 50 electrochemical devices were produced.

  DC-R measurement evaluation measured DC-R at the time of discharging with the electric current value 20C, after charging an electrochemical device with the predetermined constant voltage for 1 hour with the charging / discharging apparatus. The selection standard of DC-R was set to be equal to or less than the average value of DC resistance values measured for 20 pieces extracted from Comparative Example 1 + 3σ. Those larger than the screening standard were regarded as defective, and the defect rate was calculated from the number of defects relative to the evaluation number. Moreover, the measurement after a float test was implemented, the raise rate of DC-R after sample preparation was computed, and the comparative evaluation was performed. Since Example 19 and Comparative Example 4 are lithium ion secondary batteries, defect selection and float test evaluation were excluded.

  In the capacity measurement evaluation, the electrochemical device was charged at a predetermined constant voltage for 1 hour with a charging / discharging device, and then the current capacity was measured at a current value of 20 C until it was discharged to the use lower limit voltage. The capacity selection standard was 90% or more of the average capacity value measured for 20 samples extracted from Comparative Example 1. Those smaller than the screening standard were regarded as defective, and the defect rate was calculated from the number of defects relative to the evaluation number. Moreover, the measurement after a float test was implemented, the change rate of the capacity | capacitance after sample preparation was computed, and the comparative evaluation was performed. Since Example 19 and Comparative Example 4 are lithium ion secondary batteries, the defect selection / float test evaluation was excluded.

  Self-discharge measurement evaluation is performed after charging an electrochemical device at a predetermined constant voltage with a charging / discharging device for 1 hour, and then leaving the terminals open circuited and leaving the terminals at 60 ° C. for 72 hours in a high temperature bath The inter-voltage was measured. The self-discharge selection standard was set to a value equal to or higher than the voltage average value −3σ measured for 10 samples extracted from Comparative Example 1. Those smaller than the screening standard were regarded as defective, and the defect rate was calculated from the number of defects relative to the evaluation number.

  According to the above method, four types of evaluations of DC-R measurement evaluation, capacity measurement evaluation, and self-discharge measurement evaluation were performed for each sample condition in Examples 1 to 19 and Comparative Examples 1 to 4, respectively. Table 1 shows the average capacity, average DC-R, overall failure rate, overall result and self-discharge (SD) failure, high temperature load test DC-R change rate, and high temperature load test capacity change rate.

From the evaluation results of four types of tests for the conditions of each sample shown in Table 1, the following was found. That is, in the electrochemical device, as in the present invention, the self-discharge characteristic is excellent when the air permeability value between the lithium insertion electrode plate and the electrochemical element is larger than that of the separator. The DC-R increase rate and capacity degradation of the high temperature load test were small, and good results were obtained for both. The SD failure of Example 1 was 0%, the DC-R increase rate after the high temperature load test was 3.7%, the capacity change rate was -0.5%, the SD failure of Comparative Example 1 was 18%, and the DC-R increase rate. It can be seen that the reliability of the high temperature load is improved as compared with 23.4% and the capacity change rate of −5.3%. This is because, as shown in the doping time of Table 1, by using a separate sheet between the lithium insertion electrode plate and the electrochemical element, the lithium doping current is controlled, and the lithium doping is uniformly applied to the negative electrode with a minute current. It is thought that it was done. As a result of disassembling the defective SD product of Comparative Example 1, it was confirmed that there was a large variation in the potential of the negative electrode between the stacks, and that the sample in which the positive electrode potential was remarkably lowered could not be identified. Therefore, it is highly possible that lithium dendrite is deposited on the electrode and short-circuited with the positive electrode. On the other hand, when the sample of Example 1 was sampled and evaluated, it was confirmed that none of the decomposed samples had a variation in negative electrode potential between the layers as in Comparative Example 1, and lithium ions were uniformly distributed between the electrodes. It seems that the dope is made. Moreover, when the decomposition evaluation of Example 1 and Comparative Example 1 after the high temperature load test was performed, it can be confirmed that Comparative Example 1 tends to have a higher negative electrode potential than Comparative Example 1 (Comparative Example). 1: av. 0.05 V vs Li / Li ⁺ , Example 1: av. 0.4 V vs Li / Li ⁺ ), and the potential increase of the negative electrode is considered to be the cause of deterioration. The increase in the negative electrode potential under a high temperature load is considered to be due to the non-uniform doping of the negative electrode. Similarly, the same tendency is observed for Comparative Examples 2 and 3, which are considered to be the same factors. When comparing Comparative Example 1 with Comparative Examples 2 and 3, even if two separators were provided between the lithium insertion electrode plate and the electrochemical element, the doping time was almost 72 to 73 hours as shown in Table 1. Since it did not change, it was confirmed that the doping current did not change (Example 1 and Comparative Examples 1 to 3).

  When the separation sheet / separator air permeability ratio is 5 to 2000 times that of the separator, the SD defect does not occur, and the DC- It turned out that R rise rate and a capacity | capacitance change rate are small and suitable (Examples 1-9). When the air permeability ratio was 3, there was no SD failure, but in the high-temperature load test, the increase in DC-R was 10.5%, which was higher than other levels. The reason for the deterioration was that the lithium insertion was non-uniform due to the low air permeability (Example 2).

  In addition, as a result of comparative evaluation of polyethylene, polypropylene, glass fiber, polyphenylene sulfide, polyamide, and polyimide, the material of this separate sheet does not cause SD failure in any system, and in a high temperature load test for reliability evaluation It was confirmed that there was no difference in deterioration (Example 1, Examples 10 to 14).

  In addition, it turned out that SD defect does not generate | occur | produce as the thickness of a separate sheet is 10 micrometers or more, and the reliability evaluation test result is also favorable and suitable (Examples 16-18). When the separation sheet has a thickness of 8 μm, 2p of SD failure has occurred. As a result of the decomposition evaluation, the potential of the negative electrode facing the lithium insertion electrode plate through the separate sheet is lower than the other electrodes. Was confirmed. When the non-defective product was disassembled, it was confirmed that there was no potential variation between the laminated electrodes and it was stable. Although the location has not been specified yet, it is considered that an external pressure was applied during the trial production, and the short-circuited between the negative electrode plate opposed to the lithium insertion electrode plate via the separate sheet (Example 15).

  Furthermore, it was found that the present invention can be applied to both lithium ion secondary batteries and hybrid capacitors as long as they are electrochemical devices, and it is preferable that no self-discharge failure occurs as in the case of hybrid capacitors. . (Example 1, Example 19, Comparative Example 4).

  Thus, it was confirmed that the target electrode can be uniformly pre-doped with lithium ions, and an electrochemical device having high quality and reliability can be provided.

  As described above, in the electrochemical device of the present invention, the lithium doping current can be controlled by using a separator sheet larger than the air permeability value of the separator between the lithium insertion electrode plate and the electrochemical element. In addition, it was possible to dope uniformly into the electrodes during the stacking of the target electrodes, and it was possible to produce a high-quality electrochemical device by improving the SD characteristics and to improve the reliability. Further, the description of each of the above examples is for explaining the effect in the case of the embodiment of the present invention, thereby limiting the invention described in the scope of claims or the scope of claims. It does not reduce. Moreover, each part structure of this invention is not restricted to said embodiment, A various deformation | transformation is possible within the technical scope as described in a claim.

DESCRIPTION OF SYMBOLS 1 Hybrid capacitor 2 Positive electrode external terminal board 3 Negative electrode external terminal board 4 Exterior film sheet 5 Electrochemical element 6 Positive electrode board 7 Negative electrode board 8 Positive electrode active material electrode sheet 9 Negative electrode active material electrode sheet 10 Separator 11 Separate sheet 12 For lithium insertion Electrode plate 13 Metallic lithium

Claims (4)

  An electrochemical element that includes a positive electrode plate and a negative electrode plate that are laminated so that the negative electrode plate is disposed on the outermost side through a separator, and a separator sheet that has a value greater than the air permeability of the separator. A lithium insertion electrode plate that supplies lithium ions in advance by electrochemical contact disposed opposite to the outermost negative electrode plate of at least one of the electrochemical elements, the positive electrode plate, and the negative electrode A positive external terminal plate and a negative external terminal plate electrically connected to each of the plates; and an exterior film sheet containing the electrochemical element, a lithium insertion electrode plate, and a separate sheet and hermetically sealed at a peripheral portion. And electrochemical devices.   2. The electrochemical device according to claim 1, wherein an air permeability value of the separate sheet is not less than 5 times and not more than 2000 times an air permeability value of the separator used in the electrochemical element.   The electrochemical device according to claim 1 or 2, wherein the thickness of the separate sheet is 10 µm or more and 200 µm or less.   The electrochemical device according to any one of claims 1 to 3, wherein the electrochemical device is a lithium ion secondary battery or a hybrid capacitor.

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