JP6218191B2 - Electric double layer capacitor - Google Patents

Description

 The present invention relates to an electric double layer capacitor.

The electric double layer capacitor includes a pair of polarizable electrodes, a separator interposed between the pair of polarizable electrodes, and the pair of polarizable electrodes and separator in a storage container sealed by a lid and a container body. And an electrolytic solution impregnated in the container. Such an electric double layer capacitor is used as a backup power source for a memory, a backup power source for a clock function, etc. in various small electronic devices such as a mobile phone, a PDA, and a portable game machine. As such, a disk-shaped button type is often used.
The button-type electric double layer capacitor has a structure in which a lid is caulked on a container body and sealed. For this reason, the airtightness is not perfect, and moisture and the like easily enter the inside due to moisture and the like, and the polarizable electrode and the electrolytic solution deteriorate due to the infiltrated moisture, making it difficult to store and use for a long time. In addition, electric double layer capacitors have been required to be further reduced in size and thickness.

In order to solve such a problem, a rectangular chip-type electric double layer capacitor has been proposed (for example, Patent Document 1).
In general, a chip-type electric double-layer capacitor has a lid called a sealing plate, after a polarizable electrode, a separator, and an electrolyte are accommodated in a container body having a metal ring at the periphery of the opening. It is manufactured by closing with a body and heating to join the lid and the container body. In the electric double layer capacitor described in Patent Document 1, the metal ring provided on the periphery of the opening of the container body and the lid are joined by a brazing material such as nickel or silver brazing. Is excellent in airtightness. The heating temperature by this joining method is set to 300 ° C. or higher.
In addition, for example, as a method of joining the lid and the container body, a metal plated lid body and a metal ring are used, the opening of the container body is closed with the lid body and heated to a temperature at which the metal plating melts. Can be mentioned. The heating temperature in this joining method is set to 800 to 1500 ° C. when the metal plating is nickel plating.

JP 2001-216852 A

By the way, in general, an electrolyte used for an electric double layer capacitor has a low melting point and low viscosity ethyl methyl carbonate (EMC) or dimethyl carbonate (DMC) in order to improve the impregnation of the polarizable electrode and the separator and reduce the internal resistance. A symmetric or asymmetric linear alkyl carbonate solvent such as EMC and DMC have a relatively low boiling point (less than 200 ° C.) and thus have low heat resistance, and when the lid of the chip-type electric double layer capacitor and the container body are joined, the vapor pressure is easily evaporated. It becomes high or bumps. For this reason, there has been a problem that the remaining amount of the electrolytic solution becomes large and the quality such as the discharge capacity of the electric double layer capacitor becomes unstable. In addition, when the lid and the container body are welded, since the boiling point of the solvent is low, the vapor pressure of the electrolytic solution increases, so that the internal pressure increases and the storage container may be damaged.
The button-type and chip-type electric double layer capacitors are surface-mounted on the substrate by reflow soldering. Since the electric double layer capacitor is heated at about 240 to 260 ° C. in reflow soldering, the sealing portion is weakened due to an increase in vapor pressure, and the electrolytic solution may leak, resulting in unstable quality.
In addition, the electric double layer capacitor is often used in a state where it is always applied with a voltage of 2.0 V or higher or a high voltage of 3.0 V or higher from the main power supply. When an electrolytic solution is applied at a high voltage, the decomposition of the solute or solvent of the electrolytic solution is promoted, and the function is likely to deteriorate. In particular, when the ambient temperature to which the voltage is applied is high, the function is significantly reduced. For this reason, an electric double layer capacitor to be applied at a high voltage requires an increase in the amount of the electrolyte, but when the amount of the electrolyte is increased, the electrolyte can be used when welding the lid and the container body or when reflow soldering. There is a problem that the quality becomes unstable due to easy leakage.
Accordingly, an object of the present invention is to provide an electrolytic solution for an electric double layer capacitor from which a stable quality electric double layer capacitor can be obtained, an electric double layer capacitor using the same, and a method for manufacturing the same.

The electric double layer capacitor of the present invention contains at least a pair of polarizable electrodes arranged opposite to each other via a separator, a supporting salt, sulfolane and chain sulfone in a storage container sealed by a lid and a container body The separator is formed with an interposition part sandwiched between the pair of polarizable electrodes and an outer peripheral part extending outside the interposition part, and the separator coarse density represented by the following formula is: 1 to 4 or less.
Separator coarse density = peripheral part porosity / intervening part porosity The interstitial part porosity is expressed by the following formula (ii), and the outer peripheral part porosity is expressed by the following formula (iii).
Interstitial part porosity (volume%) = [(volume of interstitial part void) / (volume of interstitial part)] × 100 (ii)
Peripheral porosity (volume%) = [(volume of void in outer periphery) / (volume of outer periphery)] × 100 (iii)

  The inside of the storage container preferably has a porosity represented by [(volume of void in the storage container) / (volume of storage container)] × 100, and the interstitial space porosity is 10-30% by volume. The intervening portion preferably has a thickness of 40 to 70 μm, and the separator is a polytetrafluoroethylene microporous film or a glass fiber laminate. preferable.

The electrolytic solution preferably contains an organic fluorine compound, and the supporting salt contains 5-azoniaspiro [4.4] nonanetetrafluoroborate, and 5-azoniaspiro [4.4] nonane in the electrolytic solution. The tetrafluoroborate content is preferably 1.5 to 3.6 mol / dm ³ , and the pair of polarizable electrodes preferably have a negative electrode side surface area greater than a positive electrode side electrode surface area.

 According to the present invention, an electric double layer capacitor having a stable quality can be obtained.

It is sectional drawing of the electric double layer capacitor concerning one Embodiment of this invention. It is sectional drawing of the electric double layer capacitor concerning one Embodiment of this invention.

An electric double layer capacitor according to an embodiment of the present invention will be described below with reference to the drawings.
The electric double layer capacitor 1 shown in FIG. 1 is a so-called chip-type capacitor having a substantially rectangular parallelepiped shape with a length of 2 to 3 mm, a width of 2 to 3 mm, and a height of 0.2 to 1 mm. In the electric double layer capacitor 1, a pair of polarizable electrodes 40 including a negative electrode side electrode 42 and a positive electrode side electrode 44 are disposed opposite to each other with a separator 46 in the storage container 2, and the electrolytic solution 50 is stored therein. . The polarizable electrode 40 and the separator 46 are impregnated with the electrolytic solution 50 stored in the storage container 2.

The storage container 2 includes a bottomed square cylindrical container body 20, a lid 10 that is a flat sealing plate that closes the opening of the container body 20, and a seal ring 30 provided at the periphery of the opening of the container body 20. And the lid 10 and the container body 20 are sealed through a seal ring 30. Although the thickness of the wall of the storage container 2 is not specifically limited, For example, it is 0.15-0.25 mm.
The container body 20 is erected on the bottom wall portion 21 including a flat base plate 22 having a substantially rectangular shape in plan view and an intermediate layer 26 provided on one surface of the base plate 22, and the periphery of the bottom wall portion 21. A square cylindrical side wall portion 24 is provided.
A protective layer 27 penetrating the intermediate layer 26 is provided in the approximate center of the intermediate layer 26.
The seal ring 30 is joined to the peripheral edge of the opening of the container body 20, that is, to the upper end surface 23 of the side wall 24 by a brazing material 32.

  The negative electrode side electrode 42 only needs to be electrically connected to the lid body 10. For example, the negative electrode current collector 43 made of a conductive resin adhesive having amorphous carbon or graphite as a conductive filler is used for the lid body 10. It is preferable that it is adhered to. The positive electrode 44 is electrically connected to a positive current collector 45 similar to the negative current collector 43.

  A first external terminal 60 and a second external terminal 70 are provided on the outer bottom surface and the outer side surface of the container body 20. The first external terminal 60 is connected to a first metal layer 62 provided between the brazing material 32 and the side wall portion 24, whereby the first metal layer 62, the brazing material 32, the seal ring 30, and the negative electrode are connected. It is electrically connected to the negative electrode 42 via the current collector 43. The second external terminal 70 is connected to a second metal layer 72 provided between the base material 22 and the intermediate layer 26 and connected to the protective layer 27, whereby the second metal layer 72 and the protective layer are connected. 27 and the positive electrode current collector 45, and are electrically connected to the positive electrode 44.

  The electrolytic solution 50 is obtained by dissolving a supporting salt in a non-aqueous solvent, and the non-aqueous solvent contains sulfolane and chain sulfone. Sulfolane (tetrahydrothiophene 1,1-dioxide) and chain sulfone, which are solid at room temperature (25 ° C.), become a non-aqueous solvent of liquid (ionic liquid) by mixing, and an electrolytic solution 50 using this non-aqueous solvent Can be impregnated into the polarizable electrode 40 and the separator 46.

The amount of the electrolytic solution 50 in the storage container 2 is not particularly limited. For example, the porosity represented by the following formula (i) is preferably 10 to 30% by volume, more preferably 15 to 30% by volume. Can be determined. If it is less than 10% by volume, the storage container 2 may be damaged due to a change in the internal pressure due to the expansion of the electrolytic solution 50 during manufacture of the electric double layer capacitor 1. If it exceeds 30% by volume, the discharge capacity tends to decrease in a short period of time. This is considered due to the following causes. For example, when charged with a voltage exceeding 3 V, the supporting salt and the nonaqueous solvent of the electrolytic solution 50 are decomposed, and the electrolytic solution remaining in the separator 46 between the negative electrode side electrode 42 and the positive electrode side electrode 44 (between the electrodes). 50 decreases, and the electrolytic solution 50 decreases remarkably near the surface of the separator 46. When the electrolytic solution 50 in the vicinity of the surface of the separator 46 is significantly reduced, the cross-sectional area of the liquid junction formed between the electrodes is reduced, and an overvoltage is generated between the electrodes due to current concentration in charging / discharging. This overvoltage further promotes the decomposition of the supporting salt and the non-aqueous solvent, and the electrolytic solution 50 is significantly deteriorated. And the decomposition component which arises with decomposition | disassembly of the electrolyte solution 50 is considered to form a film on the surface of the separator 46, promote further increase in resistance and increase in overvoltage, and decrease discharge capacity in a short period of time. .
For example, the porosity is adjusted by adjusting the injection amount of the electrolytic solution 50 in the injection step described later, or by previously blending a low boiling point (less than 200 ° C.) solvent or water into the electrolytic solution 50, and in the preliminary heating step described later. It can be adjusted by evaporating the low boiling point solvent.

  Porosity (volume%) = [(volume of void in storage container) / (volume of storage container)] × 100 (i)

  In the above formula (i), the “volume of the storage container” is the volume of the space surrounded by the lid body 10 and the container body 20. The “volume of the void of the storage container” is the volume of the void 3 generated inside the storage container 2.

 Sulfolane is a substance represented by the following formula (a) and has a boiling point (bp) of 285 ° C.

 The content of sulfolane in the non-aqueous solvent can be determined in consideration of the heating conditions in the preheating step or the sealing step in the production of the electric double layer capacitor 1, the heating conditions in use, and the like. % Is preferable, 50 to 80% by mass is more preferable, and 55 to 70% by mass is further preferable. If it is less than 25% by mass, the electrolyte solution 50 will increase in viscosity and lower in fluidity. For this reason, for example, in the injection process described later, the injection amount of the electrolytic solution 50 varies, the remaining amount of the electrolytic solution 50 becomes unstable, and it becomes difficult to obtain the electric double layer capacitor 1 of stable quality. If it exceeds 90% by mass, the amount of the supporting salt in the non-aqueous solvent becomes insufficient, and there is a possibility that the discharge capacity of the electric double layer capacitor 1 cannot be secured sufficiently. In addition, when it exceeds 90% by mass, the content of the chain sulfone or the supporting salt becomes insufficient, and it may be difficult to ensure the discharge capacity under a low temperature environment (−20 ° C. or lower).

The chain sulfone has a structure in which a total of two linear or branched aliphatic alkyl groups are bonded to sulfur (S) of tetrahydrothiophene 1,1-dioxide. The two alkyl groups constituting the chain sulfone may be the same or different.
The chain sulfone can be determined in consideration of the heat resistance and the like required for the electrolytic solution 50. For example, dimethyl sulfone (DMS) represented by the following formula (b), ethyl methyl sulfone (D) represented by the following formula (c) ( EMS) is preferable, and among them, ethyl methyl sulfone having a melting point lowered by making the alkyl group asymmetric is preferable.
These can be used individually by 1 type or in combination of 2 or more types.

 The content of the chain sulfone in the non-aqueous solvent can be determined in consideration of the heating conditions in the preheating step or the sealing step in the production of the electric double layer capacitor 1, the heating conditions in use, etc. 80 mass% is preferable, 10-50 mass% is more preferable, 15-25 mass% is further more preferable. When it is less than 10% by mass, the non-aqueous solvent is solidified, the viscosity is remarkably increased, and the fluidity becomes insufficient. For example, it is difficult to inject the electrolytic solution 50 in the injecting step described later. For this reason, the amount of the electrolytic solution 50 is insufficient, and the performance of the electric double layer capacitor 1 cannot be ensured sufficiently, and it becomes difficult to obtain the electric double layer capacitor 1 with stable quality. If it exceeds 80% by mass, the non-aqueous solvent is solidified, the viscosity is remarkably increased and the fluidity becomes insufficient, and it becomes difficult to inject the electrolytic solution 50 in the injecting step described later. For this reason, the amount of the electrolytic solution 50 is insufficient, and the performance of the electric double layer capacitor 1 cannot be ensured sufficiently, and it becomes difficult to obtain the electric double layer capacitor 1 with stable quality.

 The total amount of sulfolane and chain sulfone in the non-aqueous solvent can be determined in consideration of the heating conditions in the preheating step or the sealing step in the production of the electric double layer capacitor 1, the heating conditions in use, etc. 40-90 mass% is preferable, 65-90 mass% is more preferable, 75-85 mass% is further more preferable. If it is less than 40% by mass, the electrolyte solution 50 has an increased viscosity and low fluidity. For this reason, for example, in the injection process described later, the injection amount of the electrolytic solution 50 varies, the remaining amount of the electrolytic solution 50 becomes unstable, and it becomes difficult to obtain the electric double layer capacitor 1 of stable quality. If it exceeds 90% by mass, the amount of the supporting salt in the non-aqueous solvent becomes insufficient, and there is a possibility that the discharge capacity of the electric double layer capacitor 1 cannot be secured sufficiently. In addition, if it exceeds 90% by mass, the content of the supporting salt becomes insufficient, and it may be difficult to ensure the discharge capacity under a low temperature environment (−20 ° C. or lower).

  As the content of sulfolane and chain sulfone in the non-aqueous solvent is increased, the heat resistance is improved as the sulfolane is increased. It will be enough. Therefore, it can be determined in consideration of the heating conditions and the use conditions in the production of the electric double layer capacitor 1, for example, sulfolane: chain sulfone = 1: 9 to 9: 1 (mass ratio) is preferable, and 5: 5 9: 1 is more preferable, and 7: 3 to 9: 1 is more preferable.

The non-aqueous solvent can contain other solvent (arbitrary solvent) as needed in addition to sulfolane and chain sulfone. The type of the arbitrary solvent can be determined in consideration of the heat resistance and viscosity required for the electrolytic solution 50, and an aprotic polar solvent having an oxygen atom in the structure is preferable. Examples of the optional solvent include aliphatic monocarboxylic acids such as formic acid esters such as ethyl formate, propyl formate and n-propyl formate, propionic acid esters such as methyl propionate and ethyl propionate, and butyric acid esters such as methyl butyrate and ethyl butyrate. Examples include chain esters such as esters, chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, chain ethers, and glycol ethers.
When the nonaqueous solvent contains an arbitrary solvent, the content of the arbitrary solvent in the nonaqueous solvent is preferably 0.1 to 50% by mass, and more preferably 1 to 30% by mass.

Examples of the supporting salt include a quaternary ammonium salt and a quaternary phosphonium salt. Examples of the quaternary ammonium salt include a compound having only an aliphatic chain, an alicyclic compound having an aliphatic chain and an alicyclic ring, or a fatty acid. Examples include spiro compounds having only a ring. A spiro compound is one in which two rings share one atom of a tetrahedral structure.
Examples of the counter ion constituting the salt include PF ₆ ⁻ , BF ₄ ⁻ , N (CF ₃ SO ₃ ) ₂ ⁻ , C (CF ₃ SO ₃ ) ₃ ^{− and the} like.
Among such quaternary ammonium salts, compounds having only fatty chains include triethylmethylammonium (TEMA) salts represented by the following formula (1) and tetraethylammonium (TEA) salts represented by the following formula (2): (In formulas (1) and (2), X ⁻ represents a counter ion). Examples of the spiro compound include 5-azonia spiro [4,4] nonanetetrafluoroborate (spiro- (1,1 ′)-bipyrrolidinium: SBP-BF ₄ ), represented by the following formula (3): 6-azonia spiro [5,5] undecane tetrafluoroborate represented by the formula, 3-azonia spiro [2,6] nonanetetrafluoroborate represented by the formula (5), 4-azonia spiro [6] represented by the formula (6) 3,5] nonanetetrafluoroborate and the like. Examples of the quaternary phosphonium salt include 5-phosphonspiro [4,4] nonanetetrafluoroborate represented by the following formula (7). As the supporting salt, a quaternary ammonium salt is preferable, a spiro compound is more preferable, and 5-azonia spiro [4,4] nonanetetrafluoroborate is more preferable. Since the quaternary ammonium salt spiro compound has high electrical conductivity, the discharge capacity can be increased.

The content of the supporting salt in the electrolytic solution 50 can be determined in consideration of the type of the supporting salt. For example, when the supporting salt is SBP-BF ₄ , the content of the supporting salt in the electrolytic solution 50 used in the injection step described later is preferably 1.0 to 3.6 mol / dm ³ , more preferably 1. 5 to 3.6 mol / dm ³ . When it is less than 1.0 mol / dm ³ , when charged with a voltage exceeding 3 V, the electrolyte solution 50 is significantly deteriorated, and the discharge capacity is likely to be reduced in a short period of time. If it exceeds 3.6 mol / dm ^{3, the} amount of SBP-BF ₄ dissolved in the non-aqueous solvent is saturated, and there is a risk of manufacturing problems such as nozzle clogging in the injection step described later.
Further, the non-aqueous solvent and the supporting salt are evaporated in a preheating process and a sealing process described later. At this time, since sulfolane, chain sulfone, and optional solvent in the non-aqueous solvent evaporate more easily than the supporting salt, the content of the supporting salt in the electrolytic solution 50 in the electric double layer capacitor 1 of the final product is increased. . For this reason, the content of the supporting salt in the electrolytic solution 50 that is filled in the injection step is determined based on the type of the non-aqueous solvent and the like, and the content of the supporting salt in the electrolytic solution 50 in the electric double layer capacitor 1 of the final product. The amount may be adjusted so as to be preferably 1.0 to 3.6 mol / dm ³ , more preferably 1.5 to 3.6 mol / dm ³ .
The supporting salt decomposes and decreases when a voltage is applied to the electric double layer capacitor 1. For this reason, in applications where a high voltage is applied, the supporting salt may be in an excessive (supersaturated) state. Alternatively, the supporting salt in the electrolytic solution 50 sealed in the storage container 2 may be temporarily precipitated without being dissolved after passing through the supersaturated state depending on the heating conditions of the preheating step and the sealing step described later. Also good. At this time, the electrolytic solution 50 is changed in the solubility of the supporting salt due to the supersaturated supporting salt and the decomposition product, the supporting salt is re-dissolved, the concentration of the supporting salt is increased, and a high discharge in a low temperature environment. Capacity can be secured. Thus, the supporting salt can be replenished by bringing the supporting salt into a supersaturated state.

The electrolytic solution 50 can contain an organic fluorine compound. In the sealing process described later, the organic fluorine compound reacts with the nickel plating of the lid 10 or the seal ring 30 to generate nickel fluoride that is passive on the surface of the lid 10 or the seal ring 30. For this reason, elution of nickel into the electrolytic solution 50 is suppressed, and deterioration of the electrolytic solution 50 due to mixing of impurities (nickel) is suppressed. As a result, the electric double layer capacitor 1 can maintain a high discharge capacity for a long time.
Examples of the organic fluorine compound include those in which some or all of the substituents of the organic compound are substituted with fluorine. For example, a compound in which fluorine is introduced into an aromatic hydrocarbon (fluorinated aromatic compound), saturated Fluorine introduced into hydrocarbons (fluorinated saturated hydrocarbons), chain unsaturated hydrocarbons introduced with fluorine, ester compounds such as formate ester, acetate ester, butyrate ester, etc. Fluorine introduced into products (fluorinated esters), ether compounds with fluorine introduced (fluorinated ethers), ketone compounds with fluorine introduced (fluorinated ketones), ethylene carbonate, propylene carbonate, butylene carbonate, etc. Fluorinated carbonate and the like.
Examples of the fluorinated aromatic compound include decafluorobenzophenone (bp: 206 ° C., mp (melting point): 92 to 94 ° C.), 1,3-bis (trifluoromethyl) benzene (bp: 116, mp: −35). ° C), 4,4'-difluorobenzophenone (bp: 170 ° C (10 torr), mp: 106-109 ° C), octafluoronaphthalene (bp: 209 ° C, mp: 87-88 ° C), 1-fluoronaphthalene (bp : 215 to 217 ° C, mp: -13 ° C), octafluorotoluene (bp: 104 ° C, mp: -65.6 ° C), allyl pentafluorobenzene (bp: 148 to 149 ° C, mp: -64 ° C), 1,2,3,4-tetrafluorobenzene (bp: 95, mp: -42 ° C), 1,2,3,5-tetrafluorobenzene (bp: 83 ° C) , Mp: -48 ° C), 1,2,4,5-tetrafluorobenzene (bp: 90 ° C, mp: 4 ° C), 1,2,3-trifluorobenzene (bp: 94-95 ° C), 1 , 2,4-trifluorobenzene (bp: 88-91 ° C., mp: −12 ° C.), 1,3,5-trifluorobenzene (bp: 75-76 ° C., mp: −5.5 ° C.), 1 , 2-difluorobenzene (bp: 92 ° C., mp: −34 ° C.), 1,3-difluorobenzene (bp: 83 ° C., mp: −59 ° C.), 1,4-difluorobenzene (bp: 88-89 ° C.) , Mp: −13 ° C.), α, α, α-trifluorotoluene (bp: 102 ° C., mp: −29 ° C.), fluorobenzene (bp: 85 ° C., mp: −42 ° C.), (trifluoromethoxy) Benzene (bp: 102 ° C.), 1-ethynyl-4 fluor Benzene (bp: 55 ° C. (40 mmHg), mp: 27 to 28 ° C.), 1,4-bis (difluoromethyl) benzene (bp: 70 ° C. (2.7 KPa)), 1-acetoxy-4-fluorobenzene (bp 197 ° C.), 2,4,6-trimethylfluorobenzene (bp: 163 to 165 ° C.), 2,6-difluorotoluene (bp: 112 ° C.), o-fluorotoluene (bp: 114 ° C., mp: −62) ° C), m-fluorotoluene (bp: 115 ° C, mp: -87 ° C), p-fluorotoluene (bp: 116 ° C, mp: -53 ° C), 2,4-difluorotoluene (bp: 114-116 ° C) ), 3-fluoro-o-xylene (bp: 148-152 ° C.), 2-fluorostyrene (bp: 29-30 ° C.), 4-fluorostyrene (bp: 67 ° C. (50 mHg), mp: -36 ℃), as perfluorodecalin (mixture of cis and trans, bp: 142 ℃, mp: include -10 ° C.) and the like.
The fluorinated saturated hydrocarbon may be either cyclic or chain-like, for example, 1-fluorohexane (bp: 93 ° C.), perfluoro-1,3-dimethylcyclohexane (bp: 101 to 102 ° C., mp: -55 ° C), 1-fluoropentane (bp: 62-63 ° C), 1-fluorononane (bp: 166-169 ° C), perfluoro-2-methyl-2-pentene (bp: 53-61 ° C) ) And the like.
Examples of the compound in which fluorine is introduced into a chain-like unsaturated hydrocarbon include (perfluorobutyl) ethylene (bp: 58 ° C.).
Examples of the fluorinated ester include ethyl fluoroacetate (bp: 117 ° C), ethyl 4,4,4-trifluoroacetoacetate (bp: 131 ° C, mp: -39 ° C), and methyl 2-fluorophenylacetate. .
The fluorinated ether may have a symmetric shape centered on oxygen or an asymmetric shape, but an asymmetric shape is preferred. Examples of the fluorinated ether include 2,2,2-trifluoroethyl methyl ether (bp: 30 ° C.), 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether ( bp: 92 ° C), 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (bp: 50 ° C, mp: -94 ° C), 1,1,2,2-tetrafluoro Ethyl ethyl ether (bp: 57.5 ° C, mp: -90.8 ° C), 1,1,2,2-tetrafluoroethyl methyl ether (bp: 36-37 ° C, mp: -107 ° C), F- Perfluoropolyether represented by (CF ₂ CF ₂ CF ₂ O) _n CF ₂ CF ₃ (where n is a number representing the number of repetitions of (CF ₂ CF ₂ CF ₂ O)), and the like. . Commercially available fluorinated ethers include Novec ^TM 7000 (C ₃ F ₇ OCH ₃ ), Novec ^TM 7100 (C ₄ F ₉ OCH ₃ ), Novec ^TM 7200 (C ₄ F ₉ OC ₂ H ₅ ), Novec ^TM 7300. (C ₂ F ₅ CF (OCH ₃ ) C ₃ F ₇ ) (manufactured by Perfluoroether Sumitomo 3M Limited) and the like.
Examples of commercially available perfluoropolyethers include demnum ^TM S-20 (average molecular weight: 2700, pour point: -75 ° C), demnum ^TM S-65 (average molecular weight: 4500, pour point: -65 ° C), Demnum ^TM S-200 (average molecular weight: 8400, pour point: -53 ° C.) (above, perfluoropolyether, manufactured by Daikin Industries, Ltd.) and the like.
Examples of the fluorinated ketone include 1,1,1-trifluoroacetone (bp: 22 ° C., mp: −78 ° C.), cyclopropyl-4-fluorophenyl ketone (bp: 119 to 120 ° C., mp: −15). ° C), cyclobutyl-4-fluorophenyl ketone (bp: 125-127 ° C), and the like.

The bp of the organic fluorine compound is preferably lower than that of sulfolane (285 ° C.), more preferably 240 ° C. or less, and further preferably 150 ° C. or less. If the bp of the organic fluorine compound is lower than that of sulfolane, the viscosity of the electrolytic solution 50 can be reduced, and the polarizable electrode 40 or the separator 46 can be impregnated sufficiently and quickly. In addition, if the bp of the organic fluorine compound is lower than the bp of sulfolane, the organic fluorine compound easily evaporates in the preheating step described later. For this reason, the porosity can be easily adjusted by using an organic fluorine compound having bp equal to or less than the upper limit.
Although the minimum of bp of an organic fluorine compound is not specifically limited, 30 degreeC or more is preferable, 60 degreeC or more is more preferable, and 100 degreeC or more is further more preferable. If bp is 30 ° C. or higher, the remaining amount of the electrolytic solution 50 in the storage container 2 is not easily bumped when the preheating step, the sealing step, and the reflow soldering described later are performed. It becomes uniform.

 Although mp of an organic fluorine compound is not specifically limited, Room temperature (25 degreeC) or less is preferable and -30 degreeC or less is more preferable. If mp is room temperature or less, the viscosity of the electrolytic solution 50 can be reduced, and the polarizable electrode 40 or the separator 46 can be sufficiently and rapidly impregnated with the electrolytic solution 50. In addition, if mp is −30 ° C. or lower, it is easier to secure the discharge capacity in a low temperature environment.

  Among the organic fluorine compounds mentioned above, decafluorobenzophenone, 4,4′-difluorobenzophenone, 1-fluoronaphthalene, octafluoronaphthalene, 1,2,4,5-tetrafluorobenzene, 1,2,3-trifluorobenzene 1-ethynyl-4fluorobenzene, 2-fluorostyrene, perfluoro-2-methyl-2-pentene, (perfluorobutyl) ethylene, 1,2,3,4-tetrafluorobenzene, 1,2,3 5-tetrafluorobenzene, 1,2,4-trifluorobenzene, 1,3,5-trifluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, fluorobenzene, (Trifluoromethoxy) benzene, 1,4-bis (difluoromethyl) , 4-fluorostyrene, perfluorodecalin (a mixture of cis and trans), 1-fluorohexane, 1-fluoropentane, 1-fluorononane, 1,3-bis (trifluoromethyl) benzene, octafluorotoluene, Allyl pentafluorobenzene, α, α, α-trifluorotoluene, 1-acetoxy-4-fluorobenzene, 2,4,6-trimethylfluorobenzene, 2,6-difluorotoluene, o-fluorotoluene, m-fluorotoluene P-fluorotoluene, 2,4-difluorotoluene, 3-fluoro-o-xylene, perfluoro-1,3-dimethylcyclohexane, ethyl fluoroacetate, and ethyl 4,4,4-trifluoroacetoacetate are preferred. , 2,3,4-tetrafluorobenzene, 1 2,3,5-tetrafluorobenzene, 1,2,4-trifluorobenzene, 1,3,5-trifluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene , Fluorobenzene, (trifluoromethoxy) benzene, 1,4-bis (difluoromethyl) benzene, 4-fluorostyrene, perfluorodecalin (a mixture of cis and trans), 1-fluorohexane, 1-fluoropentane, -Fluorononane, 1,3-bis (trifluoromethyl) benzene, octafluorotoluene, allylpentafluorobenzene, α, α, α-trifluorotoluene, 1-acetoxy-4-fluorobenzene, 2,4,6- Trimethylfluorobenzene, 2,6-difluorotoluene, o-fluoro Rotoluene, m-fluorotoluene, p-fluorotoluene, 2,4-difluorotoluene, 3-fluoro-o-xylene, perfluoro-1,3-dimethylcyclohexane, ethyl fluoroacetate, 4,4,4-trifluoroacetate More preferred is ethyl acetate, 1,3-bis (trifluoromethyl) benzene, octafluorotoluene, allylpentafluorobenzene, α, α, α-trifluorotoluene, 1-acetoxy-4-fluorobenzene, 2,4, 6-trimethylfluorobenzene, 2,6-difluorotoluene, o-fluorotoluene, m-fluorotoluene, p-fluorotoluene, 2,4-difluorotoluene, 3-fluoro-o-xylene, perfluoro-1,3- Dimethylcyclohexane, ethyl fluoroacetate, 4,4, - trifluoroacetamido ethyl acetate is more preferable. With these organic fluorine compounds, it is possible to more easily balance the reduction in the viscosity of the electrolytic solution 50 and the securing of the discharge capacity in a low temperature environment.

The content of the organic fluorine compound in the electrolytic solution 50 used in the injection step described later can be determined in consideration of the viscosity and the like required for the electrolytic solution 50, and is preferably 0.1 to 50% by mass, for example, 0.1 to 20 mass% is preferable. If it is less than 0.1% by mass, the viscosity of the electrolytic solution 50 may not be sufficiently reduced, or the formation of nickel fluoride may be insufficient. If it exceeds 50% by mass, the amount of the supporting salt dissolved in the nonaqueous solvent may be reduced, and the discharge capacity may be reduced.
Moreover, 10 mass ppm-30 mass% are preferable, and, as for content of the organic fluorine compound in the electrolyte solution 50 in the electric double layer capacitor 1 of a final product, 10 mass ppm-10 mass% are more preferable. If it is less than 10 mass ppm, the discharge capacity under a low temperature environment may not be sufficiently increased. If it exceeds 30 mass%, the concentration of the supporting salt in the electrolytic solution 50 is lowered, and the charge / discharge characteristics are degraded. It is to do.

  The electrolytic solution 50 can be prepared, for example, by mixing sulfolane, chain sulfone, and optional solvent as necessary to make a non-aqueous solvent, adding a supporting salt to the non-aqueous solvent, stirring and dissolving. Furthermore, if necessary, the organic fluorinated compound may be added to a non-aqueous solvent together with the supporting salt and mixed.

The negative electrode 42 is, for example, a rolled roll of powdered activated carbon obtained by an activation process in which organic substances such as sawdust, coconut shell, pitch, coke, and phenol resin are used alone or in combination with water vapor or alkali. Or what was press-molded is mentioned. Also, for example, phenol, rayon, acrylic, pitch, etc. fibers are infusibilized and carbonized to form activated carbon or activated carbon fibers, which are made into a felt, fiber, paper, or sintered body. The thing which was done is mentioned.
The density of the negative electrode side electrode 42 is not particularly limited, but is preferably ^{0.1~0.9g / cm 3, 0.40~0.75g / cm} 3 is more preferable. If it is less than 0.1 g / cm ³ , the energy density of the negative electrode side electrode 42 decreases, and when the negative electrode side electrode 42 expands due to impregnation with the electrolytic solution 50, the distance between the electrode particles increases and the electrical resistance increases. There is a fear. If it exceeds 0.9 g / cm ³ , not only a great pressure is required when the negative electrode 42 is formed, but also the amount of the electrolyte solution 50 impregnated in the negative electrode 42 is significantly reduced.

The activated carbon that is the active material of the negative electrode 42 can have various pore distributions and surface states depending on the starting material, carbonization method, or activation conditions. Among the activated carbons having such various surface states and pore distributions, the specific surface area of the activated carbon used for the active material of the negative electrode 42 is preferably 1000 m ² / g or more, more preferably 1700 m ² / g or more, and 2400 m. ² / g or more is more preferable. If it is 1000 m < ² > / g or more, sufficient electrostatic capacity can be obtained.
The pore volume of the activated carbon is preferably from 0.4 cm ³ / g or more, 0.7 cm ³ / g or more is more preferable. If the pore volume is 0.4 cm ³ / g or more, sufficient electrostatic capacity can be obtained.
Further, the pores of the activated carbon are the ratio (fine pore ratio) of the pores having a pore radius of less than 1 nm in the total pores (number of pores having a pore radius of less than 1 nm) / (total number of pores). Is preferably 75% or less, more preferably 50% or less, and still more preferably 30% or less. This is because if it is 75% or less, a sufficient capacitance can be obtained.
Further, the pores of the activated carbon are the ratio of the pores having a pore radius of 1 to 3 nm to the total pores (medium pore ratio) (the number of pores having a pore radius of 1 to 3 nm) / (total pores). The value represented by the number) is preferably 20% or more, more preferably 50% or more, and still more preferably 70% or more. If it is 20% or more, a sufficient electrostatic capacity can be obtained, and if it is 70% or more, the deterioration preventing performance against continuous application of a high voltage of 3 V or more is further improved by combination with the electrolyte 50 containing sulfolane. To do.

  As the binder, conventionally known substances can be used, and examples thereof include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), polyacrylic acid polymer, carboxymethyl cellulose, and the like. Among them, PTFE is most preferable. For example, the content of the binder in the negative electrode 42 is preferably 2 to 14% by mass, and more preferably 4 to 12% by mass from the viewpoint of improving durability and handling properties during production.

  A conductivity-imparting agent can be added to the negative electrode side electrode 42 as necessary. Examples of the conductivity-imparting agent include amorphous carbon such as carbon black such as furnace black, ketjen black, and acetylene black, , Carbon fiber (CF), carbon nanohorn (CNH), carbon nanotube (CNT), crystalline carbonaceous materials such as powdered graphite, and metal powder with high corrosion resistance such as Ni, Ti, etc. Furnace black is more preferable.

Examples of the positive electrode 44 include the same as the negative electrode 42.
The negative electrode side electrode 42 and the positive electrode side electrode 44 may be the same or different, and can be determined in consideration of the type of the supporting salt and the like. Here, when the applied voltage at the time of charging of the electric double layer capacitor 1 is high, cations in the supporting salt are adsorbed on the negative electrode 42 and decomposed on the electrode surface, and the concentration in the electrolytic solution 50 is reduced. It will be a thing. As the concentration of the supporting salt decreases, the discharge capacity of the electric double layer capacitor 1 decreases. Similarly, the anion in the supporting salt is adsorbed on the positive electrode 44 and decomposed on the electrode surface, and the concentration in the electrolytic solution 50 is lowered. As the concentration of the supporting salt decreases, the discharge capacity of the electric double layer capacitor 1 decreases. In the electric double layer capacitor 1, for example, when a quaternary ammonium salt or the like is used as a supporting salt, cation decomposition is significant, and the voltage applied to the negative electrode 42 needs to be lowered and operated within the potential window. There is. For this reason, the surface area ratio represented by [surface area of negative electrode side electrode 42] / [surface area of positive electrode side electrode 44] is preferably in the range of 1.0 to 1.2, and in the range of more than 1.05 and less than 1.15. Is more preferable.
If the surface area ratio is less than 1.0, it is difficult to reduce the voltage applied to the negative electrode 42. In addition, if the surface area ratio exceeds 1.05, the density of ion species adsorbed on the surface of the negative electrode 42 can be reduced to 5% or less, and the negative electrode side can be changed from a state where the positive and negative electrodes are at the same potential. The potential applied to the electrode 42 can be lowered by approximately 5% from the potential applied to the positive electrode 44. For this reason, the voltage applied to the negative electrode 42 can be reduced by about 5%, and the decomposition of cations in the supporting salt can be suppressed.
In addition, when the surface area ratio is more than 1.2, the voltage of the positive electrode 44 is increased compared to the negative electrode 42 and the non-aqueous solvent or the like is easily decomposed in addition to the supporting salt. It becomes easy to deteriorate. In addition, when the surface area ratio is less than 1.15, the voltage balance between the negative electrode 42 and the positive electrode 44 is improved, and deterioration of the electric double layer capacitor 1 can be suppressed.
For the surface area ratio, the volume of the negative electrode side electrode 42 is made larger than the volume of the positive electrode side electrode 44, or the material of the negative electrode side electrode 42 is made of a material having a specific surface area larger than the specific surface area of the positive electrode side electrode 44. Adjusted to greater than zero.

Although the thickness of the separator 46 is not specifically limited, For example, the thickness of the interposition part 46a which is the part pinched by the negative electrode side electrode 42 and the positive electrode side electrode 44 becomes like this. Preferably it is 30-100 micrometers, More preferably, it is 40-70 micrometers. Is done. When the thickness of the interposition part 46a is less than 30 μm, the function of separating the negative electrode side electrode 42 and the positive electrode side electrode 44 is impaired, and there is a risk of short circuit. When the thickness of the interposition part 46a is more than 100 μm, the resistance between the electrodes is increased, and the discharge capacity may be reduced.
40-94 volume% is preferable and, as for the porosity (interposition part porosity) in the interposition part 46a, 60-90 volume% is more preferable. If the porosity of the intervening portion is within the above range, the amount of the electrolytic solution 50 in the intervening portion 46a becomes a sufficient amount, and the discharge capacity is less likely to be reduced. This makes it easier to maintain the discharge capacity for a long time. In addition, the interstitial part porosity is represented by the following formula (ii).
Interstitial part porosity (volume%) = [(volume of interstitial part void) / (volume of interstitial part)] × 100 (ii)

The separator 46 is formed with an outer peripheral portion 46b that is a portion extending to the outside of the interposition portion 46a. The thickness of the outer peripheral part 46b may be the same as that of the interposition part 46a, and may differ. However, from the viewpoint of increasing the contact area with the electrolytic solution 50 and efficiently supplementing the intervening portion 46a with the electrolytic solution 50, the thickness of the outer peripheral portion 46b is preferably thicker than the thickness of the intervening portion 46a.
The porosity of the outer peripheral part 46b (peripheral part porosity) may be the same as or different from the interstitial part porosity. However, from the viewpoint of maintaining the discharge capacity for a long time, the separator coarse density represented by the outer peripheral portion porosity / intervening portion porosity is preferably more than 1, more preferably 1.5 or more, and further preferably 2.2 or more. . As the separator coarse density increases, the electrolytic solution 50 can be more efficiently replenished to the interposition part 46a, and the discharge capacity can be easily maintained for a long time. The upper limit of the separator coarse density is not particularly limited, but is preferably 4 or less, more preferably 3 or less, and even more preferably 2.5 or less. If the value exceeds the upper limit, the porosity of the interposition part 46a becomes too small, the amount of the electrolytic solution 50 in the interposition part 46a becomes insufficient, and the discharge capacity may be reduced. In addition, if the value exceeds the upper limit, the thickness of the interposition part 46a may become too thin, and a short circuit may occur due to breakage of the separator 46 or the like. Furthermore, if the value exceeds the upper limit value, a sealing failure may occur when the lid 46 is sealed by a repulsive force when the separator 46 is compressed. In addition, a peripheral part porosity is represented by the following (iii) type | formula.
Peripheral porosity (volume%) = [(volume of void in outer periphery) / (volume of outer periphery)] × 100 (iii)

  As the separator 46, those conventionally used for separators of electric double layer capacitors can be applied, for example, polytetrafluoroethylene (PTFE) microporous film, borosilicate glass, alkali glass, quartz glass, lead glass, soda lime silica. Examples thereof include glass fiber laminates (glass fiber laminates) such as glass and alkali-free glass, nonwoven fabrics made of resins such as polyphenylene sulfide, polyamide, and polyimide. Among them, a glass fiber laminate is preferable, a fiber laminate of borosilicate glass, alkali glass, and quartz glass is more preferable, and a fiber laminate of borosilicate glass is more preferable. Since the glass fiber laminate is excellent in mechanical strength and has a large ion permeability, the internal resistance can be reduced and the discharge capacity can be improved.

 In the glass fiber laminate, glass fibers are bonded together with a binder and integrated as a whole, and voids are formed. The glass fiber laminate is formed by molding a mixture of glass fibers (glass fibers) and a binder into an arbitrary shape and, for example, subjected to heat treatment at 25 to 250 ° C. The heating temperature is preferably 120 ° C. or lower when a water-soluble binder is used. If it exceeds 120 ° C., the binder is denatured and exhibits hydrophobicity, which is not preferable. However, this is not the case when the binder is completely carbonized in the separator heat treatment described below.

The separator 46 preferably contains no impurities as much as possible, and particularly preferably does not contain a metal such as cadmium, manganese, zinc, copper, nickel, chromium, and iron.
The content of each metal in the separator 46 is less than 1 μg / g cadmium, less than 0.5 μg / g manganese, less than 5 μg / g zinc, less than 4 μg / g copper, less than 1 μg / g nickel, less than 1 μg / g chromium, iron Less than 25 μg / g is preferred.

The glass fiber constituting the glass fiber laminate preferably has a fiber diameter of 10 μm or less, and more preferably a fiber diameter of 1 μm or less. When the fiber diameter is 10 μm or less, when laminating the fibers, the size of each gap formed in the separator 46 can be reduced, and the impregnation of the electrolyte solution 50 into the separator 46 by capillary action is more rapid. become. In addition, since the liquid retention of the separator 46 is increased and the ionic conductivity between the electrodes can be reduced, the resistance in the electric double layer capacitor 1 can be further reduced.
In addition, the glass fiber constituting the glass fiber laminate may be a mixture of a glass fiber having a fiber diameter of more than 1 μm and 10 μm or less and a glass fiber having a fiber diameter of 1 μm or less. In this case, the glass fiber preferably contains 80% by mass or more of glass fiber having a fiber diameter of 1 μm. By containing 80% by mass or more of glass fibers having a fiber diameter of 1 μm or less, the electrolyte solution 50 can be more easily impregnated into the separator 46 and the resistance between the electrodes can be further reduced.

 The binder is not particularly limited as long as it is water-soluble, and examples thereof include carboxymethyl cellulose (CMC), sodium polyacrylate (PAS), polyacrylic acid (PAA), polyvinyl alcohol (PVA), and modified polyacrylic resin. . When using polyacrylic acid as the binder, it is preferable to use cross-linked acrylic acid. The binder has hydrophilicity, but may exhibit water repellency after heat treatment.

The lid 10 is obtained by applying nickel plating to a conductive metal flat plate such as Kovar (alloy of iron, nickel and cobalt) or a nickel iron alloy containing about 50% by mass of nickel.
Examples of the seal ring 30 include those in which nickel plating is applied to Kovar or the like.
The lid 10 and the seal ring 30 have the same thermal expansion coefficient in order to prevent the sealing portion from being fragile due to the degree of expansion of the material at the time of joining and the stress at the time of shrinkage caused by cooling after joining. It is preferable to use a material. Similarly, for the seal ring 30 and the container main body 20, it is preferable to select materials having similar thermal expansion coefficients in order to prevent the container main body 2 from being damaged by the residual stress due to heat. Here, for example, alumina (Al ₂ O ₃ ) used as the main component of the storage container 2 has a representative value of linear expansion coefficient (400 ° C.) of 7.1 × 10 ⁻⁶ K ⁻¹ , and the lid 10 Alternatively, the Kovar used as the main component of the seal ring 30 has a representative value of linear expansion coefficient of 4.9 × 10 ⁻⁶ K ⁻¹ .
Examples of the brazing material 32 include conventionally known brazing materials such as gold brazing, silver brazing, and silver bronze brazing.

Examples of the base material 22 include a heat-resistant material having insulating properties such as ceramic, glass, plastic, and alumina.
The side wall 24 is made of the same material as the base material 22. The side wall part 24 is obtained by baking a green sheet, for example.
The intermediate layer 26 is made of the same material as the base material 22. The intermediate layer 26 is made of, for example, a green sheet similar to the side wall portion 24, and after the second metal layer 72 is provided on the base material 22, ceramic, glass, alumina or the like is covered so as to cover the second metal layer 72. It can also be provided by applying and firing a green sheet.
Examples of the protective layer 27 include conductive metals such as aluminum, tungsten, gold, and silver, or conductive resins containing carbon as a conductive filler. Among these, aluminum and conductive resins are preferable. When the intermediate layer 26 is provided, the protective layer 27 can be provided by providing an arbitrary quantity of conductive metal, conductive resin, or the like at any position and sintering.

The first external terminal 60 is a flat plate or thin film made of a conductive metal such as nickel or gold. For example, the first external terminal 60 is provided by conducting conductor printing on the container body 20 and baking it. A surface of the first external terminal 60 is preferably provided with a weld layer such as nickel, gold, or solder so that it can be welded onto the substrate. This weld layer can be provided by a vapor phase method such as plating or vapor deposition.
The second external terminal 70 is the same as the first external terminal 60.

  The first metal layer 62 is a flat plate or thin film of a conductive metal such as tungsten, nickel, gold, silver, and is provided by, for example, printing the metal on a green sheet and baking it. Among these, the first metal layer 62 is preferably tungsten. The second metal layer 72 is the same as the first metal layer 62.

Next, a method for manufacturing the electric double layer capacitor 1 will be described.
First, the container body 20 provided with the intermediate layer 26, the protective layer 27, the first external terminal 60, the first metal layer 62, the second external terminal 70, and the second metal layer 72 is prepared. The seal ring 30 is joined to the peripheral edge of the opening of the container body 20, that is, the upper end surface 23 of the side wall portion 24 by the brazing material 32. Next, nickel plating is performed so as to cover the seal ring 30, the brazing material 32, and the upper end surface 23. Examples of the nickel plating include electrolytic nickel plating and electroless nickel plating.

The positive electrode 44 is bonded to the inner bottom surface of the container body 20 with the positive electrode current collector 45, and the separator 46 is placed on the bonded positive electrode electrode 44, and an arbitrary amount of the electrolytic solution 50 is placed in the container body 20. Is injected (injection step). The injection amount of the electrolytic solution 50 can be determined in consideration of the type of the non-aqueous solvent, the porosity of the electric double layer capacitor 1, and the like.
Here, when using the glass fiber laminated body containing a binder as the separator 46, before inject | pouring the electrolyte solution 50, you may heat the separator 46 (separator heat processing). By heating the separator 46, the binder is carbonized to reduce or disappear. By reducing or disappearing the binder, the interstitial portion porosity and the outer peripheral portion porosity of the separator 46 are increased, and the electrolytic solution 50 can be impregnated in a large amount and quickly by the separator 46. The heating temperature in the separator heat treatment is preferably, for example, 250 to 350 ° C. If the temperature is lower than 250 ° C, the binder may not be sufficiently reduced. If the temperature is higher than 350 ° C, the polarizable electrode 40 using activated carbon may be impaired in mechanical strength and cannot maintain the shape.

  The negative electrode side electrode 42 is adhered to one surface of the lid body 10 by the negative electrode current collector 43, and the lid body 10 is placed on the seal ring 30 so that the negative electrode side electrode 42 contacts the separator 46. Alternatively, the negative electrode 42 is placed so as to be in contact with the separator 46, and the lid body 10 provided with the negative current collector 43 in advance is placed on the seal ring 30 (electrode placement step).

  Next, the lid 10 and the seal ring 30 are welded while being partially melted to form an unsealed body. The method of partial welding of the lid 10 and the seal ring 30 is, for example, by partially plating nickel on the lid 10 and nickel plating covering the seal ring 30 by resistance welding, laser welding, thermal welding, or the like. What is welded is mentioned, and resistance welding is preferable among them. “Partially welded” means that the lid 10 and the seal ring 30 are welded by spot welding or the like where the welded portions are spaced apart.

The non-sealed body in which the lid body 10 and the seal ring 30 are partially welded is heated at 200 ° C. or higher and lower than 900 ° C. (preheating step). In the preheating step, impurities such as moisture can be removed from the electrolytic solution 50, or a nonaqueous solvent or a part of the organic fluorine compound can be evaporated to increase the concentration of the supporting salt in the electrolytic solution 50. In addition, the viscosity of the electrolytic solution 50 can be reduced by heating, and the polarizable electrode 40 or the separator 46 can be sufficiently impregnated with the electrolytic solution 50. The heating method in the preheating step is not particularly limited, and examples thereof include a method by energizing the lid body 10 and a heating method by infrared rays, laser irradiation, and warm air. Among these, a method of energizing the lid body 10 is preferable. . By energizing the lid 10, the temperature of the electrolytic solution 50 rises in a short time, and the impurities in the electrolytic solution 50 can be efficiently removed. Moreover, since the energization to the lid body 10 can also serve as partial welding of the lid body 10 and the seal ring 30 described above, the manufacturing efficiency of the electric double layer capacitor 1 can be improved.
The heating time can be determined in consideration of the type of the nonaqueous solvent, the heating method, and the like, and for example, 1 msec or more is preferable. At this time, since the electrolytic solution 50 contains sulfolane having a high boiling point, the remaining amount of the electrolytic solution 50 in the storage container 2 becomes uniform without being easily bumped. In addition, by removing the low boiling point impurities in the preheating step, it is possible to prevent the electric double layer capacitor 1 from being damaged due to the vaporization of the low boiling point impurities in the sealing step and reflow soldering described later.

The non-sealed lid 10 and the seal ring 30 are welded, and the inside of the storage container 2 is sealed by the lid 10 and the container main body 20 (sealing process). The welding method of the lid 10 and the seal ring 30 is not particularly limited, and examples thereof include seam welding by resistance welding. In seam welding, nickel plating of the lid 10 and nickel plating covering the seal ring 30 are welded. At this time, if the electrolytic solution 50 contains an organic fluorine compound, a nickel fluoride film is formed on the surface of the lid 10 or the seal ring 30.
In the sealing step, the electrolytic solution 50 is exposed to the melting point of nickel plating (800 to 1455 ° C.), but contains a high boiling point sulfolane, so that the electrolytic solution 50 in the storage container 2 is not easily bumped. The remaining amount of is uniform. In addition, since the electrolytic solution 50 does not easily bump, it is possible to prevent the storage container 2 from being damaged during the sealing process. Furthermore, when the electrolytic solution 50 contains an organic fluorine compound, it is impregnated quickly by the polarizable electrode 40 or the separator 46.
Thus, the electric double layer capacitor 1 with a uniform amount of the electrolytic solution 50 can be obtained.

 Since the electrolyte solution of this embodiment contains a chain sulfone in a non-aqueous solvent, it is a liquid even if it contains solid sulfolane at room temperature, and can be impregnated into a separator or a polarizable electrode, and functions as an electric double layer capacitor. Can demonstrate.

 Since the electric double layer capacitor of this embodiment includes an electrolyte containing sulfolane in a non-aqueous solvent, the electrolyte is difficult to bump during the preheating step or the sealing step, the remaining amount of the electrolyte is stable, and the quality is high. Stabilize. In addition, at the time of reflow soldering, it is possible to prevent leakage of the electrolytic solution and damage to the storage container due to rapid vaporization of the electrolytic solution. Furthermore, since the amount of the electrolytic solution can be increased, the electric double layer capacitor can be used for a long period of time even under a condition where a high voltage of 3.0 V or higher is applied.

  According to the manufacturing method of the electric double layer capacitor of the present embodiment, since the electrolyte containing sulfolane is used, the electrolyte does not easily leak during welding of the lid and the container body, and stable quality electricity can be obtained. A double layer capacitor can be obtained. In addition, by providing a preheating step, it is possible to remove impurities such as moisture that cause deterioration of the electrolyte, or to evaporate excess nonaqueous solvent and increase the concentration of the supporting salt. Even under conditions where the multilayer capacitor is applied at a high voltage, the electric double layer capacitor can be used over a long period of time.

The present invention is not limited to the embodiment described above.
The electric double layer capacitor of the above-described embodiment is a chip type, but the present invention is not limited to this, and may be, for example, a button type.
However, the effect of the present invention is remarkably exhibited in a tip type in which the confidentiality is high and the lid and the container main body are welded at a high temperature.

  In the above-described embodiment, the bottomed square cylindrical container body and the flat lid body are chip-type ones provided with external terminals on the container body, but the present invention is not limited thereto, For example, the chip type shown in FIG. 2 may be used.

  In the electric double layer capacitor 100 shown in FIG. 2, a pair of polarizable electrodes 40 composed of a negative electrode 42 and a positive electrode 44 are disposed in a storage container 102 so as to face each other with a separator 46 interposed therebetween, and an electrolytic solution 50 is stored. It is a thing. The polarizable electrode 40 and the separator 46 are impregnated with the electrolytic solution 50 stored in the storage container 102.

The storage container 102 includes a covered rectangular tubular container body 110, a flat lid body 120 that closes the opening of the container body 110, and a seal ring 130 provided at the periphery of the opening of the container body 110. The lid 120 and the container main body 110 are sealed via the ring 130.
The container main body 110 includes a flat plate-like top wall portion 112 having a substantially rectangular shape in plan view, a rectangular cylindrical side wall portion 114 extending downward from the periphery of the top wall portion 112, and a side wall portion at the lower end of the side wall portion 114. 114 and a flange 116 extending in a direction away from the axis of 114.
The lid 120 has a two-layer structure including an upper layer 122 and a lower layer 124. A first conductor portion 145 having a substantially rectangular shape in plan view is provided in the approximate center of the upper layer 122 surface, and a second conductor portion 132 having a square shape is provided in the vicinity of the periphery of the upper layer 122. The lower layer 124 is provided with a first external terminal 160 and a second external terminal 170 from the side surface to the bottom surface, and extends from approximately the center of the lid 120 toward the periphery between the upper layer 122 and the lower layer 124. A lead conductor portion 172 is provided. The first external terminal 160 is connected to the second conductor portion 132, and the second external terminal 170 is connected to the lead conductor portion 172. The lead conductor portion 172 is connected to the first conductor portion 145 by a via conductor portion 174 that penetrates the upper layer 122.

The material of the container body 110 is the same as the material of the lid body 10.
The material of the lid 120 is the same as the material of the base material 22.
The material of the seal ring 130 is the same as the material of the seal ring 30.
The first external terminal 160 is the same as the first external terminal 60, and the second external terminal 170 is the same as the second external terminal 70.
The first conductor portion 145 is the same as the positive electrode current collector 45, and the second conductor portion 132 is the same as the first metal layer 62.
The lead conductor portion 172 is the same as the first metal layer 62.

 Examples of the chip type like the electric double layer capacitor 100 include an electrochemical device described in JP 2010-1441026 A.

 In the above embodiment, the second metal layer is provided between the intermediate layer and the base material, but the present invention is not limited to this, and the second metal layer is provided on the intermediate layer. Also good. However, if the electrolytic solution directly contacts the second metal layer, there is a risk of short-circuiting, so the second metal layer should not be in contact with the electrolytic solution, for example, by providing it between the intermediate layer and the substrate. Is preferred.

  In the above-described embodiment, the preheating step is provided, but the present invention is not limited to this, and the preheating step may not be provided. From the viewpoint of removing impurities and the like in the electrolytic solution and maintaining a high discharge capacity for a long period of time, it is preferable to provide a preheating step.

 In the above-described embodiment, the lid body and the seal ring are partially welded in the electrode arrangement step, but the present invention is not limited to this, and the lid body may simply be placed on the seal ring.

 In the above-described embodiment, the sealing between the lid and the container body is a method of welding the nickel plating of the lid and the nickel plating of the seal ring, but the present invention is not limited to this, for example, the lid and The seal ring may be joined with a brazing material.

 The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

(Reference Example 1-1)
Sulfolane (denoted as SL in the table): dimethylsulfone (denoted as DMS in the table) = 8: 2 (mass ratio) was mixed to make a non-aqueous solvent, and SBP-BF ₄ as a supporting salt was added to the non-aqueous solvent. Was dissolved to 1.5 mol / dm ³ to prepare an electrolytic solution.
Using the obtained electrolytic solution, an electric double layer capacitor similar to the electric double layer capacitor shown in FIG. 1 was produced as follows.
Commercially available activated carbon (specific surface area: 1900 m ² / g, pore volume: 0.85 cm ³ / g, fine pore ratio: 4%, medium pore ratio: 95%, number average particle diameter: 12 μm (measured by laser method) )) Was rolled into a sheet having a thickness of 0.25 mm ± 0.05 mm, and cut into 1.7 mm × 1.0 mm as a positive electrode and a negative electrode. The negative electrode was bonded to the lid body obtained by electrolytic nickel plating on the Kovar flat plate with a conductive adhesive. A Kovar seal ring was joined by silver brazing to the periphery of the opening of the container body provided with a bottom wall portion made of a ceramic base material and a ceramic intermediate layer, and a ceramic side wall portion. The positive electrode was bonded to the inner bottom surface of the container body with a conductive adhesive, and the microporous sheet (2.25 mm × 1.72 mm) made of polytetrafluoroethylene was placed on the positive electrode as a separator. . 2 μL of electrolyte solution was injected into the container body on the positive electrode, and the lid was placed on the seal ring so that the negative electrode was in contact with the separator. Subsequently, the lid body and the seal ring were partially welded by spot welding to form an unsealed body. At this time, the lid was heated at 250 ° C. for 5 msec (preheating step).
Next, the container was sealed by resistance welding seam welding to obtain an electric double layer capacitor. The obtained electric double layer capacitor had a porosity of 25% by volume and a surface area ratio = 1.0.

  Six electric double layer capacitors obtained were applied at a voltage of 3.3 V for 2 hours in a 24 ° C. environment. Thereafter, the battery was discharged at a constant current of 5 μA (discharge current) until it reached 2.0 V in a 24 ° C. environment, the discharge capacity was calculated according to the following formula (I), and the average value was taken as the initial capacity.

  Discharge capacity (μAh) = discharge current (5 μA) × discharge time (h) (I)

Further, six electric double layer capacitors were applied at a voltage of 3.3 V for 2 hours in an environment of 24 ° C. Thereafter, the battery was discharged at a constant current of 5 μA (discharge current) until it reached 2.0 V under an environment of −20 ° C., the discharge capacity was calculated by the above formula (I), and the average value was taken as the low temperature capacity.
From the obtained initial capacity and low temperature capacity, the low temperature capacity maintenance rate was calculated by the following formula (II).

 Low temperature capacity retention rate (%) = low temperature capacity / initial capacity × 100 (II)

(Reference Example 1-2)
An electric double layer capacitor was obtained in the same manner as in Reference Example 1-1 except that the non-aqueous solvent was sulfolane: ethyl methyl sulfone (EMS) = 8: 2 (mass ratio), and the low temperature capacity retention rate was determined.

(Comparative Example 1)
An electric double layer capacitor was obtained in the same manner as in Reference Example 1-1 except that the non-aqueous solvent was sulfolane: methyl propionate (MP) = 8: 2 (mass ratio), and the low temperature capacity retention rate was determined.

As shown in Table 1, all of Reference Examples 1-1 to 1-2 to which the present invention was applied had a low-temperature capacity retention rate of 80% or more. On the other hand, Comparative Example 1 using methyl propionate instead of chain sulfone had a low-temperature capacity retention rate of 54.3%.
From these results, it has been found that the electric double layer capacitor to which the present invention is applied can stably exhibit a sufficient function under an environment of -20 ° C.

(Reference Example 2-1)
An electric double layer capacitor was obtained in the same manner as in Reference Example 1-2 except that the concentration of SBP-BF ₄ was changed to 1.0 mol / dm ³ . Ten electric double layer capacitors obtained were applied at a voltage of 3.3 V under an environment of 70 ° C., and then stored at 60 ° C. for 20 days. The electric double layer capacitor after storage was discharged in a 24 ° C. environment at a constant current of 5 μA to 2.0 V to obtain a discharge capacity, and the average value was taken as the high temperature capacity. From the obtained high temperature capacity and the separately obtained initial capacity, the high temperature capacity retention rate was calculated by the following formula (III).

  High temperature capacity retention rate (%) = high temperature capacity ÷ initial capacity × 100 (III)

(Reference Example 2-2)
Except that the concentration of the SBP-BF ₄ was 1.5 mol / dm ^3, the resulting electric double layer capacitor in the same manner as in Reference Example 2-1, was determined hot capacity retention rate.

(Reference Example 2-3)
Except that the concentration of the SBP-BF ₄ was 3.6 mol / dm ^3, the resulting electric double layer capacitor in the same manner as in Reference Example 2-1, was determined hot capacity retention rate.

 As shown in Table 2, each of Reference Examples 2-1 to 2-3 to which the present invention was applied had a capacity retention rate of more than 80%. Moreover, as the concentration of the supporting salt increased, the high temperature capacity retention rate increased.

(Reference Examples 3-1 to 3-10)
Except for the temperature and time shown in Table 3, the preheating step was performed in the same manner as in Reference Example 2-1, 10 electric double layer capacitors of each example were manufactured, and the presence or absence of damage was confirmed. In addition, the high temperature capacity maintenance rate was calculated | required about the electric double layer capacitor which was not damaged.

(Comparative Example 2)
Except for the nonaqueous solvent being propylene carbonate (PC): dimethyl carbonate (DMC) = 8: 2 (mass ratio), 10 electric double layer capacitors were produced in the same manner as in Reference Example 3-2, with or without damage. Confirmed. In addition, the high temperature capacity maintenance rate was calculated | required about the electric double layer capacitor which was not damaged.

As shown in Table 3, in Reference Examples 3-1 to 3-10 to which the present invention was applied, the number of damaged parts was 2 or less, and the high-temperature capacity retention rate was 30% or more.
In addition, Reference Examples 3-1 to 3-6 provided with a preheating step at a heating temperature of 200 ° C. or 300 ° C. are relatively high temperature capacity retention rates compared to Reference Example 3-10 without a preheating step. Was high and there was little damage.
On the other hand, in Comparative Example 2 in which the nonaqueous solvent was PC-DMC, since the amount of evaporation of the nonaqueous solvent in the preheating step was large, no damage was observed, but the high temperature capacity retention rate was extremely low at 10%. It was a thing.

(Reference Examples 4-1 to 4-5)
Ten electric double layer capacitors were produced in the same manner as in Reference Example 2-1, except that the electrolyte solution was injected so that the porosity shown in Table 4 was obtained, and the presence or absence of damage was confirmed. In addition, the high temperature capacity maintenance rate was calculated | required about the electric double layer capacitor which was not damaged.

(Comparative Example 3)
Except that the nonaqueous solvent was PC: DMC = 8: 2 (mass ratio), ten electric double layer capacitors were produced in the same manner as in Reference Example 4-1, and the presence or absence of damage was confirmed. In addition, the high temperature capacity maintenance rate was calculated | required about the electric double layer capacitor which was not damaged.

As shown in Table 4, it was found that the higher the porosity, the more damage to the electric double layer capacitor can be prevented. In addition, all of Reference Examples 4-1 to 4-5 to which the present invention was applied had a high temperature capacity retention rate of 30% or more.
On the other hand, in Comparative Example 3 in which the nonaqueous solvent was PC-DMC, since the amount of nonaqueous solvent evaporated in the preheating step was large, no damage was observed, but the high temperature capacity retention rate was extremely low at 5%. It was a thing.

(Reference Examples 5-1 to 5-4)
According to the composition of Table 5, SBP-BF ₄ was dissolved in a mixture of a nonaqueous solvent and an organic fluorine compound so as to be 1.5 mol / dm ³ to prepare an electrolytic solution.
Commercially available activated carbon (specific surface area: 1900 m ² / g, pore volume: 0.85 cm ³ / g, fine pore ratio: 4%, medium pore ratio: 95%, number average particle diameter: 12 μm (measured by laser method) )) Was formed into a disk shape having a thickness of 0.2 mm and φ3.95 mm to obtain a test electrode.
To this test electrode, 1.5 μL of the electrolyte solution of each example was dropped, and the time until the dropped electrolyte solution was absorbed by the test electrode was measured. It was visually determined that the electrolytic solution was absorbed by the test electrode.
Further, an electric double layer capacitor was obtained in the same manner as in Reference Example 1-1 except that the electrolyte solution of each example was used. About the obtained electrical double layer capacitor, the low temperature capacity maintenance factor and the high temperature capacity maintenance factor were calculated | required.

 As shown in Table 5, in Reference Examples 5-2 to 5-4 containing an organic fluorine compound, the impregnation time was shortened compared to Reference Example 5-1 not containing an organic fluorine compound. In addition, Reference Examples 5-2 to 5-4 had higher low temperature capacity retention rates and higher temperature capacity retention rates than Reference Example 1.

(Examples 6-1 to 6-5)
An electric double layer capacitor was obtained in the same manner as in Reference Example 1-1 except that the separator was used as shown in Table 6. About the obtained electric double layer capacitor, the high temperature capacity retention rate was calculated | required.
However, Example 6-4 is a reference example.

 As shown in Examples 6-1 to 6-4 in Table 6, when the glass fiber laminate was used as a separator, the higher the separator coarse density, the higher the high-temperature capacity retention rate.

DESCRIPTION OF SYMBOLS 1,100 Electric double layer capacitor 2,102 Storage container 10,120 Lid body 20,110 Container main body 40 Polarized electrode 42 Negative electrode side electrode 44 Positive electrode side electrode 46 Separator 50 Electrolyte

Claims (7)

In a storage container sealed with a lid and a container main body, it is provided with at least a pair of polarizable electrodes arranged to face each other with a separator interposed therebetween, and an electrolyte containing a supporting salt, sulfolane and chain sulfone,
The pair of polarizable electrodes includes a negative electrode and a positive electrode,
The negative electrode includes an activated carbon or activated carbon fiber,
The separator is formed with an interposed portion sandwiched between the pair of polarizable electrodes, and an outer peripheral portion that spreads outside the interposed portion,
The porosity in the interposition part is 40 to 94% by volume,
The separator double density represented by a following formula is 1.5 or more and 4 or less, The electric double layer capacitor characterized by the above-mentioned.
Separator coarse density = peripheral part porosity / intervening part porosity The interstitial part porosity is expressed by the following formula (ii), and the outer peripheral part porosity is expressed by the following formula (iii).
Interstitial part porosity (volume%) = [(volume of interstitial part void) / (volume of interstitial part)] × 100 (ii)
Peripheral porosity (volume%) = [(volume of void in outer periphery) / (volume of outer periphery)] × 100 (iii)   2. The inside of the storage container has a porosity represented by [(volume of void in the storage container) / (volume of storage container)] × 100, 10 to 30% by volume. Electric double layer capacitor. When the thickness of the intervening portion, the electric double layer capacitor according to claim 1 or 2, characterized in that it is 40～70Myuemu. The separator, the electric double layer capacitor according to any one of claims 1 to 3, wherein the poly microporous film of tetrafluoroethylene, or a glass fiber laminate. The electrolyte, the electric double layer capacitor according to any one of claims 1 to 4, characterized in that it contains an organic fluorine compound. The supporting salt contains 5-azoniaspiro [4.4] nonanetetrafluoroborate,
The content of 5-azoniaspiro [4.4] nonanetetrafluoroborate in the electrolytic solution is 1.5 to 3.6 mol / dm ³ , according to any one of claims 1 to 5. The electric double layer capacitor as described. Electric double layer capacitor according to any one of claims 1 to 6, the surface area of the negative electrode side electrode being greater than the surface area of the cathode-side electrode.

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