JP2019029406A - Method for manufacturing sealed type power storage element - Google Patents

Abstract

To provide a method for manufacturing a sealed type alkali metal ion power storage element, by which the discharge of gas produced in an alkali metal ion-doping process and an aging process subsequent thereto can be performed.SOLUTION: As an outer package body 2 of a redox doped type alkali metal ion power storage element 1, a metal square can is used. A particular removable one-way valve 3 is attached to the metal square can, whereby gas produced in a doping step and an aging step which are arranged to apply a voltage between a positive electrode precursor including an alkali metal compound and a negative electrode is discharged.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a sealed power storage element.

  In recent years, midnight power storage systems, home-use distributed power storage systems based on solar power generation technology, power storage systems for electric vehicles, etc. have attracted attention from the viewpoint of global environment conservation and effective use of energy for resource saving. Yes. These power storage systems are required to have power storage elements having high energy density and high output characteristics.

  Development of alkali metal ion storage elements has been energetically promoted as a potential candidate for storage elements that satisfy the performance of high energy density and high output characteristics. The alkali metal ion storage element can store or use energy by the alkali metal ion acting between a plurality of electrodes. Typical examples of the alkali metal ion storage element include a lithium ion secondary battery and a lithium ion capacitor.

  In general, since a lithium ion secondary battery contains a non-aqueous electrolyte containing an electrolyte, gas is generated by decomposition of the electrolyte during charge / discharge or overcharge of the lithium ion secondary battery. The exterior body may swell.

  When the outer package of the lithium ion secondary battery is a laminate film, a protrusion for breaking the laminate film and releasing the internal pressure when the battery bulges due to internal gas generation may be provided near the side of the laminate film. It has been proposed (Patent Document 1).

  When the exterior body of a lithium ion secondary battery is a metal square or cylindrical can, it has been proposed to provide a film that selectively releases only hydrogen gas in a part of the can (Patent Literature). 2).

JP 2008-171579 A JP 2016-46021 A

  The exterior body described in Patent Document 1 or 2 is used for a lithium ion secondary battery, but, like a lithium ion capacitor, a redox-doped alkali metal ion accompanied by alkali metal ion doping in the manufacturing process. Application to a storage element has not been studied.

  Doping treatment of alkali metal ions is a step of delivering alkali metal ions from an alkali metal ion dopant source present in the outer package to the negative electrode and reducing the alkali metal ions at the negative electrode to dope the negative electrode active material layer with alkali metal ions Therefore, the mode of gas generation is different from the charge / discharge or overcharge of the lithium ion secondary battery.

  Therefore, the problem to be solved by the present invention is to provide a method for producing a sealed alkali metal ion storage element capable of discharging a gas generated by alkali metal ion doping and subsequent aging.

As a result of intensive studies, the present inventors have used the metal square can as the exterior body of the redox-doped alkali metal ion storage element, and attached the specific check valve to the metal square can. The inventors have found that the problem can be solved and completed the present invention. That is, the present invention is as follows.
[1]
The following steps:
(1) Reversibly occlude and release a positive electrode current collector, a positive electrode active material, a positive electrode precursor containing an alkali metal compound, a negative electrode current collector, and an alkali metal ion in a rectangular exterior body having an opening. Storing a negative electrode containing a negative active material;
(2) A nonaqueous electrolytic solution containing an alkali metal salt other than the alkali metal compound is injected from the opening, the opening is sealed, and a removable check valve is attached to the square exterior body. A step of forming an alkali metal ion storage element;
(3) A voltage is applied between the positive electrode precursor and the negative electrode to dope the alkali metal ions with respect to the negative electrode, and gas generated in the rectangular outer package is removed from the removable check valve. And (4) aging the alkali metal ion storage element and exhausting the gas generated in the rectangular outer package from the detachable check valve;
A method for producing a sealed alkali metal ion storage element including:
[2]
In addition, the following steps:
(5) The step of sealing the alkali metal ion storage element after removing the removable check valve from the rectangular outer package;
The method according to [1], comprising:
[3]
In addition, the following steps:
(6) discarding or recovering the removed removable check valve;
The method according to [2], comprising:
[4]
The method according to any one of [1] to [3], wherein the step (2) and / or the step (3) are performed under reduced pressure.
[5]
The method according to any one of [1] to [4], wherein in the step (2), the opening is sealed by attaching the removable check valve to the opening.
[6]
The method according to any one of [1] to [5], wherein the removable check valve is a sticker type or a screw type.
[7]
The method according to [6], wherein the removable check valve is a sticker type and includes a film, a discharge port, and a sticker part.
[8]
The method according to [7], wherein in the step (2), the detachable check valve is attached to the square exterior body via the sticker portion.
[9]
The method according to [6], wherein the detachable check valve is a screw type and includes a shaft, a weight, a spring, a discharge port, and a screw part.
[10]
The method according to any one of [1] to [9], wherein the rectangular outer package is made of metal.
[11]
The method according to any one of [1] to [10], wherein the rectangular outer package has a substantially hexahedral shape.
[12]
In the step (2), the detachable check valve has a surface on which the non-aqueous electrolyte does not leak from the prismatic exterior body even if the detachable check valve is removed from the prismatic exterior body. The method according to [11], wherein the method is attached.
[13]
The method according to [12], wherein the detachable check valve is attached to an upper surface of the rectangular outer casing.

  ADVANTAGE OF THE INVENTION According to this invention, in the redox dope type | mold alkali metal ion electrical storage element, the gas generated by the dope process of alkali metal ion and subsequent aging process can be discharged | emitted, and also the dope and aging method excellent in safety | security are provided. can do.

FIG. 1 is a perspective view of an alkali metal ion storage element including a square outer package with a check valve attached thereto. FIG. 2 is a schematic cross-sectional view of a sticker type check valve when attached to a square type exterior body. FIG. 2 (a) shows an oil seal inside the check valve and an opening sealed with a film. And (b) represents a state where the gas pushes up the film and flows to the discharge port. FIG. 3 is a schematic cross-sectional view of a screw type check valve when attached to a square type exterior body, (a) represents a state in which a spring in the check valve is dropped, (b) The state where the gas pushes up the spring in the check valve and flows to the discharge port is shown, and (c) is an enlarged sectional view of the shaft.

  Hereinafter, a mode for carrying out the present invention (hereinafter also referred to as “the present embodiment”) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

The manufacturing method of the sealed alkali metal ion storage element according to this embodiment includes the following steps:
Cell assembly process (1): A positive electrode current collector, a positive electrode active material, a positive electrode precursor containing an alkali metal compound, a negative electrode current collector, and alkali metal ions are reversibly applied to a rectangular outer package having an opening. Storing a negative electrode containing a negative electrode active material capable of occlusion and release;
Injection / impregnation / temporary sealing step (2): A non-aqueous electrolyte containing an alkali metal salt other than an alkali metal compound is injected from the opening of the rectangular outer casing, and the opening is sealed and removable. Attaching the check valve to the square exterior body to form an alkali metal ion storage element;
Doping step (3): a step of applying a voltage between the positive electrode precursor and the negative electrode to dope alkali metal ions to the negative electrode, and exhausting gas generated in the rectangular outer package from the removable check valve ;
Aging step (4): a step of aging the alkali metal ion storage element and exhausting gas generated in the rectangular outer package from a removable check valve;
Air bleed and main sealing step (5) if desired: Step of sealing the alkali metal ion storage element after removing the detachable check valve from the rectangular outer casing; and discarding the check valve / Recovery step (6): discarding or recovering the removed removable check valve;
including.

  In this specification, the positive electrode state before the doping step (3) described later is defined as the positive electrode precursor, and the positive electrode state after the doping step (3) is defined as the positive electrode. Further, the positive electrode precursor according to the present embodiment is simply an electrode before doping, a one-sided electrode before doping, a half cell, a coating electrode, a dry electrode, etc., depending on the desired configuration of the sealed alkali metal ion storage element. Sometimes called.

<Representative examples of sealed alkali metal ion storage elements>
As a typical example of a sealed alkali metal ion storage element, a case of a lithium ion capacitor will be described in the present embodiment, but the sealed storage element according to the present embodiment is not limited to lithium ions and exhibits a similar behavior. The present invention can also be applied to alkali metal ions such as Na ions, K ions, Rb ions, and Cs ions.
In general, a lithium ion capacitor mainly includes a positive electrode, a negative electrode, a separator, and an electrolytic solution. As the electrolytic solution, an organic solvent containing lithium ions (hereinafter also referred to as “non-aqueous electrolytic solution”) is used. In addition, the manufacturing process of the lithium ion capacitor according to this embodiment includes the cell assembly process (1), the liquid injection / impregnation / temporary sealing process (2), the doping process (3), the aging process (4), The sealing step (5) and the check valve exhaust / recovery step (6) are preferably performed in this order. The components and manufacturing process of the sealed alkali metal ion storage element will be described below.

[Positive electrode]
The positive electrode has a positive electrode current collector and a positive electrode active material layer present on one side or both sides thereof. In addition, the positive electrode includes an alkali metal compound as a positive electrode precursor before assembly of the power storage element. As will be described later, in this embodiment, since the negative electrode is doped with alkali metal ions in the doping step (3), the alkali metal compound is contained in the positive electrode active material layer formed on the positive electrode current collector of the positive electrode precursor. It is preferable.

[Positive electrode active material layer]
The positive electrode active material layer preferably contains a positive electrode active material containing a carbon material, and may contain other optional components such as a conductive filler, a binder, and a dispersion stabilizer in addition to this. .
Moreover, it is preferable that an alkali metal compound is contained in the positive electrode active material layer of the positive electrode precursor or on the surface of the positive electrode active material layer.

[Positive electrode active material]
As the positive electrode active material, a carbon material is preferable. As this carbon material, it is preferable to use a carbon nanotube, a conductive polymer, or a porous carbon material, more preferably activated carbon. One or more kinds of materials may be mixed and used for the positive electrode active material, and a material other than a carbon material (for example, a composite oxide of lithium and a transition metal) may be included.

[Alkali metal compounds]
Examples of the alkali metal compound according to this embodiment include lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, lithium oxide, and lithium hydroxide, and decomposes in the positive electrode precursor to release a cation, One or more alkali metal carbonates selected from lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, and cesium carbonate, which can be pre-doped by reduction at the negative electrode, are preferably used. Among these, lithium carbonate is preferably used from the viewpoint of high capacity per unit weight. The alkali metal compound contained in the positive electrode precursor may be one kind or may contain two or more kinds of alkali metal compounds. The positive electrode precursor only needs to contain at least one alkali metal compound, and M is one or more selected from Li, Na, K, Rb, and Cs, an oxide such as M ₂ O, MOH, and the like. Or a carboxylate such as RCOOM (wherein R is H, an alkyl group, or an aryl group). _{Further, BeCO 3, MgCO 3, CaCO} 3, SrCO 3, alkaline earth metal carbonate or selected from BaCO _3, alkaline earth metal oxides, alkaline earth metal hydroxides, alkaline earth metal halides, alkali One or more earth metal carboxylates may be included.
When two or more kinds of alkali metal compounds or alkaline earth metal compounds are included in addition to the alkali metal compound, the total amount of the alkali metal compound and the alkaline earth metal compound is in the positive electrode active material layer per one side of the positive electrode precursor. It is preferable that the positive electrode precursor is prepared so that the amount of 5 g / m ² or more and 35 g / m ^{2 is} included.

  The alkali metal compound contained in the positive electrode precursor is oxidatively decomposed by applying a high voltage when a non-aqueous hybrid capacitor is formed to release alkali metal ions, and the negative electrode is reduced to proceed to dope into the negative electrode. To do. Therefore, the doping step (3) can be performed in a short time by promoting the oxidation reaction. In order to promote the oxidation reaction, it is important to contact the alkali metal compound, which is an insulator, with the positive electrode active material to ensure electronic conduction and to diffuse the cations released by the reaction into the electrolyte. It is. Therefore, it is preferable that the surface of the positive electrode active material is appropriately covered with an alkali metal compound.

[Positive electrode current collector]
The material constituting the positive electrode current collector in the present invention is not particularly limited as long as it is a material that has high electron conductivity and does not deteriorate due to elution into the electrolytic solution and reaction with the electrolyte or ions. Is preferred. As the positive electrode current collector in the non-aqueous hybrid capacitor of the present embodiment, an aluminum foil is particularly preferable.
The metal foil may be a normal metal foil having no irregularities or through holes, or a metal foil having irregularities subjected to embossing, chemical etching, electrolytic deposition, blasting, etc., expanded metal, punching metal Alternatively, a metal foil having a through hole such as an etching foil may be used.

[Negative electrode]
The negative electrode in the present embodiment includes a negative electrode current collector and a negative electrode active material layer including a negative electrode active material provided on one or both surfaces thereof.

  The negative electrode active material layer includes a negative electrode active material that can occlude and release lithium ions, and may include optional components such as a conductive filler, a binder, and a dispersion stabilizer as necessary.

  Specific examples of the negative electrode active material include carbon materials, titanium oxide, silicon, silicon oxide, silicon alloys, silicon compounds, tin, and tin compounds. Among these, carbon materials are preferable, for example, non-graphitizable carbon materials; graphitizable carbon materials; carbon black; carbon nanoparticles; activated carbon; artificial graphite; natural graphite; graphitized mesophase carbon microspheres; Amorphous carbonaceous materials such as substances; carbonaceous materials obtained by heat treatment of carbon precursors such as petroleum pitch, coal pitch, mesocarbon microbeads, coke, synthetic resin (eg phenol resin); furfuryl Examples include thermal decomposition products of alcohol resins or novolak resins; fullerenes; carbon nanophones; and composite carbon materials thereof.

[Negative electrode current collector]
The material constituting the negative electrode current collector in the present invention is preferably a metal foil that has high electron conductivity and does not deteriorate due to elution into the electrolytic solution and reaction with the electrolyte or ions. There is no restriction | limiting in particular as such metal foil, For example, aluminum foil, copper foil, nickel foil, stainless steel foil, etc. are mentioned. The negative electrode current collector in the non-aqueous hybrid capacitor of the present embodiment is preferably a copper foil.
The metal foil may be a normal metal foil having no irregularities or through holes, or a metal foil having irregularities subjected to embossing, chemical etching, electrolytic deposition, blasting, etc., expanded metal, punching metal Alternatively, a metal foil having a through hole such as an etching foil may be used.

[Separator]
The positive electrode precursor and the negative electrode are preferably laminated or wound via a separator to form an electrode laminate or an electrode winding body having the positive electrode precursor, the negative electrode and the separator.
As the separator, a polyethylene microporous film or a polypropylene microporous film used in a lithium ion secondary battery, a cellulose nonwoven paper used in an electric double layer capacitor, or the like can be used. A film made of organic or inorganic fine particles may be laminated on one side or both sides of these separators. Further, organic or inorganic fine particles may be contained inside the separator.

[Non-aqueous electrolyte]
The non-aqueous electrolyte solution according to this embodiment includes a non-aqueous solvent. Further, the non-aqueous electrolyte solution contains an alkali metal salt other than the alkali metal compound described above on the basis of the total amount of the non-aqueous electrolyte solution, and preferably contains 0.5 mol / L or more alkali metal salt.

As the alkali metal salt, for example, MFSI, MBF ₄ , MPF ₆ or the like can be used, where M is Li, Na, K, Rb, Cs. The non-aqueous electrolyte solution in the present embodiment only needs to contain at least one kind of alkali metal ion, and may contain two or more kinds of alkali metal salts, alkali metal salts and beryllium salts, magnesium. An alkaline earth metal salt selected from a salt, a calcium salt, a strontium salt, and a barium salt may be contained. When two or more kinds of alkali metal salts are contained in the non-aqueous electrolyte solution, the presence of cations having different Stokes radii in the non-aqueous electrolyte solution can suppress an increase in viscosity at low temperatures. The low temperature characteristics of water-based hybrid capacitors are improved. When alkaline earth metal ions other than the above alkali metal ions are contained in the nonaqueous electrolyte, beryllium ions, magnesium ions, calcium ions, strontium ions, and barium ions are divalent cations. The capacity can be increased.

The method for containing the two or more alkali metal salts in the non-aqueous electrolyte solution or the method for containing the alkali metal salt and the alkaline earth metal salt in the non-aqueous electrolyte solution is not particularly limited, but in the non-aqueous electrolyte solution In addition, an alkali metal salt composed of two or more kinds of alkali metal ions can be dissolved in advance, or an alkali metal salt and an alkaline earth metal salt can be dissolved. In the positive electrode precursor, M in the following formula is one or more selected from Na, K, Rb, and Cs.
Carbonates such as M ₂ CO ₃ ,
Oxides such as M ₂ O,
Hydroxides such as MOH,
Halides such as MF and MCl,
Carboxylates such as RCOOM (wherein R is H, an alkyl group, or an aryl group),
And / _{or, BeCO 3, MgCO 3, CaCO} 3, SrCO 3, or an alkaline earth metal carbonate selected from BaCO _3, as well as alkaline earth metal oxides, alkaline earth metal hydroxides, alkaline earth metal halide Examples thereof include a method of containing at least one chemical compound and an alkaline earth metal carboxylate and decomposing in a pre-doping step described later.
The electrolyte salt concentration in the electrolytic solution is preferably in the range of 0.5 to 2.0 mol / L. At 0.5 mol / L or more, there are sufficient anions, and the capacity of the sealed alkali metal ion storage element is maintained. On the other hand, at 2.0 mol / L or less, the salt is sufficiently dissolved in the electrolytic solution, and appropriate viscosity and conductivity of the electrolytic solution are maintained.
When two or more kinds of alkali metal salts are contained in the non-aqueous electrolyte solution, or when alkali metal salts and alkaline earth metal salts are contained, the total value of these salt concentrations should be 0.5 mol / L or more. Is preferable, and the range of 0.5 to 2.0 mol / L is more preferable.

[Nonaqueous solvent]
The nonaqueous electrolytic solution of the present embodiment preferably contains a cyclic carbonate as a nonaqueous solvent. The nonaqueous electrolytic solution containing a cyclic carbonate is advantageous in that a lithium salt having a desired concentration is dissolved and an appropriate amount of a lithium compound is deposited on the positive electrode active material layer. Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, and fluoroethylene carbonate.

  The non-aqueous electrolyte solution of the present embodiment preferably contains a chain carbonate as a non-aqueous solvent. The nonaqueous electrolytic solution containing chain carbonate is advantageous in that it exhibits high lithium ion conductivity. Examples of the chain carbonate include dialkyl carbonate compounds represented by dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, dibutyl carbonate and the like. The dialkyl carbonate compound is typically unsubstituted.

[Additive]
The non-aqueous electrolyte solution of this embodiment may further contain an additive. Although it does not restrict | limit especially as an additive, For example, using a sultone compound, cyclic phosphazene, acyclic fluorine-containing ether, a fluorine-containing cyclic carbonate, cyclic carbonate ester, cyclic carboxylate ester, cyclic acid anhydride, etc. independently. In addition, two or more kinds may be mixed and used.

[Cell assembly process (1)]
In the cell assembling step (1), a positive electrode terminal and a negative electrode terminal are connected to a laminate formed by laminating a positive electrode precursor and a negative electrode cut into a single sheet through a separator to produce an electrode laminate. Alternatively, a positive electrode terminal and a negative electrode terminal are connected to a wound body obtained by laminating and winding a positive electrode precursor and a negative electrode via a separator to produce an electrode wound body. The shape of the electrode winding body may be a cylindrical shape or a flat shape.

  Although the connection method of a positive electrode terminal and a negative electrode terminal is not specifically limited, It can carry out by methods, such as resistance welding and ultrasonic welding.

[Square exterior body]
The square-shaped exterior body according to the present embodiment has a cornered shape, for example, a box shape or a can shape. In the cell assembly step (1), the exterior body has an opening for accommodating the electrode laminate or the electrode winding body and the non-aqueous electrolyte therein. The opening area of the opening is not limited as long as the electrode laminate or the electrode winding body and the non-aqueous electrolyte can pass through.

  In order to prevent the non-aqueous electrolyte from leaking out of the rectangular exterior body even if the non-aqueous electrolyte is injected into the rectangular exterior body in the liquid injection / impregnation / temporary sealing step (2) described later, It is preferable to form in an exterior body.

  When the rectangular outer package is a box shape, the outer package has a bottomed rectangular parallelepiped shape in which one surface corresponding to the upper surface in the normal use state of the sealed alkali metal ion storage element is opened from the viewpoint of the opening area. It is preferable.

  In the case where the rectangular exterior body has a substantially hexahedral shape, it is preferable that an opening having an opening area smaller than the area of at least one of the six faces is formed in the corresponding one face.

  The rectangular exterior body is preferably made of metal from the viewpoint of impact resistance and dimensional stability, and is more preferably made of a metal material that is lightweight and has good thermal conductivity. Examples of the material of the rectangular exterior body include aluminum, stainless steel, and nickel-plated steel.

[Liquid injection / impregnation / temporary sealing process (2)]
After the assembly process is completed, a non-aqueous electrolyte solution is injected into the electrode laminate or the electrode winding body housed in the exterior body. It is desirable that further impregnation is performed after the injection, and the positive electrode precursor, the negative electrode, and the separator are sufficiently immersed in the nonaqueous electrolytic solution. In a state where the non-aqueous electrolyte is not immersed in at least a part of the positive electrode precursor, the negative electrode, and the separator, the resistance of the obtained alkali metal ion storage element is increased or the durability is decreased. The impregnation method is not particularly limited. For example, after injecting a non-aqueous electrolyte solution, it is placed in a decompression chamber with the exterior material opened, and the inside of the chamber is decompressed using a vacuum pump, and is again at atmospheric pressure. The method of returning to (1) etc. can be used.

  After the impregnation, the pressure reduction of the electrode laminated body or the electrode winding body is started with the exterior material opened, and then the alkali metal ion storage element formed by sealing the opening is temporarily sealed. Is preferred. In addition to liquid injection and impregnation, temporary sealing may be performed under reduced pressure.

  In step (2), a removable check valve is attached to the rectangular outer package. When the rectangular outer casing has a polyhedral shape such as a substantially six-sided shape, the removable check valve is a surface on which the non-aqueous electrolyte does not leak from the rectangular outer casing even if it is removed from the rectangular outer casing. It is preferable to be attached to the upper surface of the exterior body corresponding to the upper surface in the normal use state of the sealed alkali metal ion storage element.

  When the attachment position of the detachable check valve corresponds to the opening of the square outer package, the opening can be sealed by attaching the detachable check valve to the opening. When the attachment position of the detachable check valve does not correspond to the opening of the rectangular outer package, the temporary sealing of the alkali metal ion storage element described above is the attachment of the detachable check valve. As another embodiment, the opening of the exterior body can be closed by screwing, sticking a seal, welding a metal sealing plate, or the like.

  FIG. 1 shows an example of an alkali metal ion storage element including a square outer package with a check valve attached thereto. The rectangular outer package 2 accommodates an electrode laminate or an electrode winding body (not shown). After the electrode laminate or electrode winding body and the electrolyte are stored in the exterior body 2a, the opening of the exterior body is sealed so that the metal terminals (4, 4) are drawn out of the rectangular exterior body 2. The body 2b is welded and sealed. A detachable check valve 3 is attached to the upper surface of the rectangular outer casing 2 corresponding to the outer surface of the sealing body 2b.

[Removable check valve]
The check valve according to the present embodiment is a valve that is attached to a vent or a gas pipe of a rectangular exterior body, and has a structure in which the valve body operates in a form that prevents backflow due to a back pressure of gas. It is detachable for the air bleeding / main sealing step (5). In general, the check valve is sometimes called a check valve, a check valve, or a check.

  The check valve prevents the gas such as water, air, and water vapor existing outside the exterior body from flowing into the exterior body, while the exterior of the exterior during the dope process (3) and / or the aging process (4). The gas generated inside the body is exhausted to the outside of the exterior body. Examples of the check valve degassing method include a spring and an oil seal.

  The check valve attaching / detaching method is preferably a sticker type or a screw type from the viewpoint of the air venting / main sealing step (5) performed later.

(Sticker type check valve)
The sticker type check valve includes a film (seal part), a discharge port, and a sticker part. The interior of the sticker check valve can usually be oil sealed.

  The sticker type check valve can be attached to the square type exterior body via the sticker portion so that the film closes the vent or gas piping port of the square type exterior body and the discharge port in the check valve. If necessary, the sticker type check valve can be removed from the square type outer casing due to the stickiness of the sticker part.

  The film (seal part) is preferably formed of a material that is easily moved by the gas generated in the outer layer, and more preferably formed of a mixture of PET and adipic acid dihydrazide (ADH), PET, or the like.

  For the sticker type check valve, the operating pressure may be 5 to 9 hPa, the closing pressure may be 1 to 3 hPa, the gas passing amount may be 0.3 Norm · l / hour when the internal pressure is 12 hPa, and the operating temperature is − It may be in the range of 30 ° C. to + 80 ° C., and the shape may be circular or square.

  FIG. 2 shows an example of a schematic cross section of a sticker type check valve when attached to a square type exterior body. There is a film (seal part) 5 and a discharge port 6 inside the fixing part 8 of the sticker type check valve 3 a, and a sticker part 9 outside the fixing part 8. The sticker type check valve 3 a is attached to the can wall 4 via the sticker portion 9 so as to close the opening of the can wall 4. The discharge port 6 is provided in the fixing portion 8 in the depth direction in FIGS. Normally, since no gas is generated inside the can wall 4, the discharge port 6 is blocked by the film 5 (FIG. 2 (a)). When gas is generated inside the can wall 4, the space 7 generated by the gas pushing up the film 5 is in fluid communication with the discharge port 6, so that the gas flows along the direction x to the discharge port 6 (FIG. 2). (B)).

(Screw check valve)
A screw type check valve can be attached to a square type exterior body by being screwed into a square type exterior body or by being inserted into a screw receptacle provided in the square type exterior body. It can be removed from the prismatic exterior body by rotating in the opposite direction to the time or insertion. The screw type check valve may be at least one selected from the group consisting of a ball check valve, a screw check valve, and a butterfly check valve.

  FIG. 3 shows an example of a schematic cross-sectional view of the screw type check valve when attached to the square type outer package. The screw type check valve 3 b includes a discharge port 6, a fixing part 8, a shaft 10, a weight 11, a spring 12, and a screw part (screw type) 13, and is screwed into the can wall 4 via the screw part 13. As shown in the partially enlarged view of FIG. 3C, the shaft 10 is hollow and has a gas inlet and a gas outlet provided at both ends in the longitudinal direction, and a gas outlet provided at the side wall. Usually, since no gas is generated inside the can wall 4, the spring 12 is extended downward by the weight 11, and the weight 11 closes the discharge port 6 that is a gas discharge path (FIG. 3A). When gas is generated inside the can wall 4, the gas pushes up the shaft 10, the weight 11 and the spring 12, and flows from the gas outlet of the shaft 10 to the discharge port 6 along the direction x (FIG. 3B).

[Doping process (3)]
In this embodiment, the positive electrode active material and alkali metal carbonate containing alkali metal ions function as a dopant source of alkali metal ions to the negative electrode active material. In the alkali metal ion doping process, a voltage is applied between the positive electrode precursor and the negative electrode, the alkali metal carbonate in the positive electrode precursor is decomposed to release alkali metal ions, and the alkali metal ions are reduced at the negative electrode. By doing so, it is preferable to pre-dope alkali metal ions in the negative electrode active material layer.

  The application of the voltage between the positive and negative electrodes can be performed by a method of connecting an external power source to the positive electrode terminal and the negative electrode terminal, a method of self-discharge by storing a precharged alkali metal ion storage element, or the like. . The dope time is preferably within 24 hours, more preferably 1 hour to 24 hours, still more preferably 1 hour to 20 hours.

In the alkali metal ion doping step, gas such as CO ₂ is generated with the oxidative decomposition of the alkali metal compound in the positive electrode precursor. Therefore, when applying a voltage, a check valve attached to the exterior body is used as means for releasing the generated gas to the outside of the rectangular exterior body.

From the viewpoint of degassing a gas such as CO ₂ from the outer package, the doping step (3) may be performed under reduced pressure. The pressure reduction in the dope process (3) is performed continuously from the liquid injection / impregnation / temporary sealing process (2), or sequentially separately from the pressure reduction in the liquid injection / impregnation / temporary sealing process (2). It can be carried out.

[Aging process (4)]
After the doping step (3), it is preferable to perform aging on the electrode laminate or the electrode winding body. In aging, the solvent in the non-aqueous electrolyte is decomposed at the negative electrode, and an alkali metal ion permeable solid polymer film is formed on the negative electrode surface. In the aging process, gas of the organic electrolyte is generated due to decomposition of the solvent in the non-aqueous electrolyte. Therefore, also in the aging process, a check valve attached to the exterior body is used as means for releasing the generated gas to the outside of the exterior body.

  The aging method is not particularly limited. For example, a method of reacting a solvent in the electrolytic solution under a high temperature environment can be used.

[Air bleeding / main sealing process (5)]
It is preferable that after aging, further degassing is performed to reliably remove the gas remaining in the electrolytic solution, the positive electrode, and the negative electrode (so-called air bleeding). In a state where gas remains in at least a part of the electrolytic solution, the positive electrode, and the negative electrode, ion conduction is inhibited, and thus the resistance of the obtained alkali metal ion storage element is increased.

  The air bleeding can be performed by removing the removable check valve described above from the rectangular outer casing. In addition, the storage device with the check valve removed may be installed in a decompression chamber, and the inside of the chamber may be decompressed using a vacuum pump to facilitate air bleeding.

  After the degassing as described above, the exterior body is sealed by sealing the exterior body, whereby a sealed alkali metal ion storage element can be obtained. This sealing can be performed by attaching the check valve to the exterior body again, or by closing the opening of the exterior body by screwing, sticking a seal, welding a metal sealing plate, or the like.

[Check valve disposal / recovery process (6)]
From the viewpoint of productivity and environmental considerations, it is preferable to discard or collect the check valve removed in the air venting / main sealing step (5). The collected detachable check valve can be reused when manufacturing the sealed alkali metal ion storage element.

<Lithium ion capacitor>
A lithium ion capacitor can be manufactured by the above method. In one embodiment, the lithium ion capacitor includes a positive electrode having a porous positive electrode active material layer having pores that are traces of decomposition and dissipation of the lithium compound contained in the positive electrode precursor, and a lithium compound as a dopant. And a negative electrode having a negative electrode active material layer doped as a source. The positive electrode may contain a lithium compound that has not been decomposed in the lithium doping step.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. The present invention is not limited in any way by the following examples.

<Preparation of positive electrode active material>
The phenol resin was placed in a firing furnace, carbonized at 600 ° C. for 2 hours in a nitrogen atmosphere, pulverized with a ball mill, and classified to obtain a carbide having an average particle diameter of 7 μm. The obtained carbide and KOH were mixed at a mass ratio of 1: 5, put into a firing furnace, and activated by heating at 800 ° C. for 1 hour in a nitrogen atmosphere. Activated charcoal 1 was obtained by taking out the activated carbide, stirring and washing in dilute hydrochloric acid adjusted to a concentration of 2 mol / L for 1 hour, boiling and washing with distilled water until it was stabilized between pH 5 and 6, and then drying.
It was 7.0 micrometers as a result of measuring the average particle diameter of the activated carbon 1 using the Shimadzu Corporation laser diffraction type particle size distribution measuring apparatus (SALD-2000J). Moreover, the pore distribution of the activated carbon 1 was measured using a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. As a result, the BET specific surface area was 3627 m ² / g, the mesopore volume (V ₁ ) was 1.50 cc / g, the micropore volume (V ₂ ) was 2.28 cc / g, and V ₁ / V ₂ = 0.66. there were.

<Production of positive electrode precursor>
A positive electrode precursor was manufactured using activated carbon 1 as a positive electrode active material.
50.0 parts by mass of activated carbon 1, 38.5 parts by mass of lithium carbonate 1, 3.0 parts by mass of ketjen black, 1.5 parts by mass of PVP (polyvinylpyrrolidone), and 7 parts of PVDF (polyvinylidene fluoride) 0.0 parts by mass and NMP (N-methylpyrrolidone) are mixed and dispersed using a thin film swirl type high speed mixer film mix manufactured by PRIMIX under the condition of a peripheral speed of 17 m / s to obtain a coating liquid. It was.
The viscosity (ηb) and TI value of the obtained coating solution were measured using an E-type viscometer TVE-35H manufactured by Toki Sangyo Co., Ltd. As a result, the viscosity (ηb) was 2,650 mPa · s, and the TI value was 4.1. Moreover, the dispersion degree of the obtained coating liquid was measured using the grain gauge made from Yoshimitsu Seiki. As a result, the particle size was 32 μm.
Using a die coater manufactured by Toray Engineering Co., Ltd., the coating liquid was applied on both surfaces of a 15 μm thick aluminum foil at a coating speed of 1 m / s and dried at a drying temperature of 120 ° C. Obtained. The obtained positive electrode precursor 1 was pressed using a roll press machine under conditions of a pressure of 6 kN / cm and a surface temperature of the pressing part of 25 ° C. The total thickness of the pressed positive electrode precursor 1 was measured at any 10 locations of the positive electrode precursor 1 using a thickness gauge Linear Gauge Sensor GS-551 manufactured by Ono Keiki Co., Ltd. The film thickness of the positive electrode active material layer of the positive electrode precursor 1 was determined by subtracting the thickness of the aluminum foil from the average value of the measured total thickness. As a result, the film thickness of the positive electrode active material layer was 59 μm per side.

<Preparation of negative electrode active material>
The BET specific surface area and pore distribution of commercially available artificial graphite were measured by the above-described method using a pore distribution measuring apparatus (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. As a result, the BET specific surface area was 3.1 m ² / g, and the average particle size was 4.8 μm.
300 g of this artificial graphite is placed in a stainless steel mesh jar, placed on a stainless steel bat containing 30 g of a coal-based pitch (softening point: 50 ° C.), and both are placed in an electric furnace (effective size in the furnace 300 mm × 300 mm × 300 mm). ). Artificial graphite and coal-based pitch were heated to 1000 ° C. in a nitrogen atmosphere over 12 hours and held at the same temperature for 5 hours to cause a thermal reaction to obtain a composite porous carbon material 2a. The obtained composite porous carbon material 2a was cooled to 60 ° C. by natural cooling and taken out from the electric furnace.
About the obtained composite porous carbon material 2a, the BET specific surface area and pore distribution were measured by the same method as described above. As a result, the BET specific surface area was 6.1 m ² / g, and the average particle size was 4.9 μm. Moreover, the mass ratio with respect to activated carbon of the carbonaceous material derived from coal pitch in the composite porous carbon material 2a was 2.0%.

<Manufacture of negative electrode>
A negative electrode was produced using the composite porous carbon material 2a as a negative electrode active material.
84 parts by mass of composite porous carbon material 2a, 10 parts by mass of acetylene black, 6 parts by mass of PVdF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) are mixed, and the mixture is a thin film made by PRIMIX. Using a swirl type high-speed mixer film mix, dispersion was performed under conditions of a peripheral speed of 17 m / s to obtain a coating liquid 1A.
The viscosity (ηb) and TI value of the resulting coating liquid 1A were measured using an E-type viscometer TVE-35H manufactured by Toki Sangyo Co., Ltd. As a result, the viscosity (ηb) was 2,520 mPa · s, and the TI value was 3.8.
Using a die coater manufactured by Toray Engineering Co., Ltd., a coating liquid 1A was applied on both surfaces of an electrolytic copper foil having a thickness of 10 μm at a coating speed of 2 m / s, and dried at a drying temperature of 120 ° C. to obtain negative electrode 1. It was. Using a roll press machine, pressing was performed under conditions of a pressure of 5 kN / cm and a surface temperature of the pressing part of 25 ° C. The total thickness of the pressed negative electrode 1 was measured at any 10 locations of the negative electrode 1 using a thickness gauge Linear Gauge Sensor GS-551 manufactured by Ono Keiki Co., Ltd. Thereafter, the negative electrode active material layer on one surface of the negative electrode 1 was removed, and the thickness was measured again. Then, all the negative electrode active material layers remaining on the negative electrode current collector were removed, and the thickness of the copper foil was measured. From the obtained measurement results, the thickness of the negative electrode active material layer of the negative electrode 1 was determined. As a result, the film thickness of the negative electrode active material layer was 59 μm per side.

<Preparation of electrolyte>
As an organic solvent, a mixed solvent of ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 33: 67 (volume ratio) is used, and the concentration ratio of LiN (SO ₂ F) ₂ and LiPF ₆ is relative to the total electrolyte. The non-aqueous electrolyte solution 1 is obtained by dissolving each electrolyte salt so that the sum of the concentrations of 75:25 (molar ratio) and LiN (SO ₂ F) ₂ and LiPF ₆ is 1.2 mol / L. It was. The concentrations of LiN (SO ₂ F) ₂ and LiPF ₆ in the nonaqueous electrolytic solution 1 were 0.9 mol / L and 0.3 mol / L, respectively.

[Example 1]
<Production of non-aqueous lithium storage element>
The positive electrode precursor 1 was cut into a size of 12.0 cm × 210.0 cm (the size of the positive electrode active material layer was 10.0 cm × 210.0 cm, and the positive electrode active material layer was coated on the positive electrode current collector) The negative electrode uncoated portion is 2.0 cm × 210.0 cm), and the negative electrode 1 is cut into a size of 12.1 × 220.0 cm (the size of the negative electrode active material layer is 10.1 cm × 220.cm). 0 cm, the negative electrode uncoated portion where the negative electrode active material layer is not coated on the negative electrode current collector is 2.0 cm × 220.0 cm.), And the cut positive electrode precursor 1 and negative electrode 1 are made of polyethylene A flat wound electrode body was produced by winding in a flat shape through a separator (manufactured by Asahi Kasei Corporation, thickness 10 μm). The obtained flat wound electrode body was ultrasonically welded with a positive electrode terminal and a negative electrode terminal, and housed in a metal cuboid can whose upper surface was open.

About 70 g of the non-aqueous electrolyte solution 1 was injected from the opening of the metal rectangular parallelepiped can under a dry air environment at a temperature of 25 ° C. and a dew point of −40 ° C. or less under atmospheric pressure. Subsequently, a metal rectangular parallelepiped can containing a flat wound electrode body and a non-aqueous electrolyte solution was placed in a vacuum chamber, the pressure was reduced from atmospheric pressure to -87 kPa, then returned to atmospheric pressure, and allowed to stand for 5 minutes. . Then, after reducing the pressure in the chamber from atmospheric pressure to -87 kPa, the process of returning to atmospheric pressure was repeated 4 times, and then allowed to stand for 15 minutes. Further, the pressure in the chamber was reduced from atmospheric pressure to -91 kPa, and then returned to atmospheric pressure. Similarly, the process of reducing the pressure and returning to atmospheric pressure was repeated a total of 7 times (reduced pressure from atmospheric pressure to −95, −96, −97, −81, −97, −97, and −97 kPa, respectively). Through the above steps, the flat wound electrode body was impregnated with the non-aqueous electrolyte solution 1.
Thereafter, the flat wound electrode body impregnated with the non-aqueous electrolyte solution 1 is put into a vacuum sealing machine, and in a state where the pressure is reduced to -95 kPa, the opening portion of the metal rectangular parallelepiped can is drawn out to the outside of the can Is sealed with a metal sealing body having an opening narrower than the opening at the top of the metal, and a sticker type check valve is provided on the upper surface of the opening of the metal sealing body so as not to contact the electrode terminal. Attached. At that time, the weight A (g) of the metal rectangular parallelepiped can was measured.

[Lithium doping process]
The power storage element obtained after sealing was placed in a thermostatic bath at a temperature of 25 ° C. After connecting the electrode terminal outside the can to the power source (P4LT18-0.2) manufactured by Matsusada Precision Co., Ltd. and carrying out constant-current charging until the voltage reaches 4.5 V at a current value of 100 mA, continue Initial charging was performed by a method of continuing 4.5 V constant voltage charging for 72 hours, and lithium doping was performed on the negative electrode.

[Aging process]
The storage element after lithium doping was taken out from the argon box, and under a 25 ° C. environment, a constant current discharge was performed until the voltage reached 3.8 V at 100 mA, and then a 3.8 V constant current discharge was performed for 1 hour. Adjusted to 3.8V. Subsequently, the electricity storage element was stored in a constant temperature bath at 60 ° C. for 48 hours. Thereafter, the stored cell was taken out and cooled for 1 hour, and then the weight B (g) of the metal rectangular parallelepiped can was measured. Further, the difference between the weight B and the weight A was measured and summarized in Table 1.

[Degassing process]
The sticker-type check valve was removed from the can which is the outer package of the storage element after aging in a dry air environment at a temperature of 25 ° C. and a dew point of −40 ° C. Subsequently, the storage element was placed in a vacuum chamber, and the pressure was reduced from atmospheric pressure to −80 kPa over 3 minutes using a diaphragm pump (manufactured by KNF, N816.3KT.45.18). The process of returning to atmospheric pressure was repeated a total of 3 times. Thereafter, the storage element was put in a vacuum sealer and the pressure was reduced to -90 kPa, and then the storage element was sealed by sealing at 200 ° C. for 10 seconds with a pressure of 0.1 MPa, to produce a sealed lithium ion storage element. .

[Example 2]
A sealed lithium ion energy storage device was produced in the same manner as in Example 1 except that a screw type check valve was attached to the upper surface of the opening of the metal sealing body instead of the sticker type check valve.

[Comparative Example 1]
A sealed lithium ion storage element was produced in the same manner as in Example 1 except that the check valve was not attached to the opening of the metal sealing body.

[Comparative Example 2]
A sealed lithium ion storage element was produced in the same manner as in Example 1 except that no opening was formed in the upper part of the metal rectangular parallelepiped can.

[Confirmation of safety of lithium ion capacitor exterior]
In the lithium doping step of the lithium ion energy storage devices obtained in Example 1, Example 2, Comparative Example 1 and Comparative Example 2, the appearance of the exterior body during 4.5 V constant voltage charging was confirmed. In Comparative Example 2, the outer package was cleaved 48 hours after the start of constant voltage charging, and measurement of weight B was impossible.

From Table 1, it is possible to dope without volatilizing the electrolyte solution by using a metal square can as the exterior body of the redox-doped alkali metal ion storage element and attaching a specific check valve to the metal square can. It was found that gas such as CO ₂ produced by the above can be safely discharged.

DESCRIPTION OF SYMBOLS 1 Alkali metal ion electrical storage element 2 Square type exterior body 2a Exterior body main body 2b Sealing body 3 Detachable check valve 3a Sticker type check valve 3b Screw type check valve 4 Can wall 5 Film (seal part)
6 Discharge port 7 Space 8 Fixed part 9 Sticker part 10 Shaft 11 Weight 12 Spring 13 Screw (screw type)
x Gas flow direction

Claims (13)

The following steps:
(1) Reversibly occlude and release a positive electrode current collector, a positive electrode active material, a positive electrode precursor containing an alkali metal compound, a negative electrode current collector, and an alkali metal ion in a rectangular exterior body having an opening. Storing a negative electrode containing a negative active material;
(2) A nonaqueous electrolytic solution containing an alkali metal salt other than the alkali metal compound is injected from the opening, the opening is sealed, and a removable check valve is attached to the square exterior body. A step of forming an alkali metal ion storage element;
(3) A voltage is applied between the positive electrode precursor and the negative electrode to dope the alkali metal ions with respect to the negative electrode, and gas generated in the rectangular outer package is removed from the removable check valve. And (4) aging the alkali metal ion storage element and exhausting the gas generated in the rectangular outer package from the detachable check valve;
A method for producing a sealed alkali metal ion storage element including: In addition, the following steps:
(5) The step of sealing the alkali metal ion storage element after removing the removable check valve from the rectangular outer package;
The method of claim 1 comprising: In addition, the following steps:
(6) discarding or recovering the removed removable check valve;
The method of claim 2 comprising:   The method according to any one of claims 1 to 3, wherein the step (2) and / or the step (3) are performed under reduced pressure.   The method according to claim 1, wherein in the step (2), the opening is sealed by attaching the detachable check valve to the opening.   The method according to claim 1, wherein the removable check valve is a sticker type or a screw type.   The method according to claim 6, wherein the removable check valve is of a sticker type and includes a film, a discharge port, and a sticker part.   The method according to claim 7, wherein in the step (2), the detachable check valve is attached to the square exterior body via the sticker portion.   The method of claim 6, wherein the removable check valve is screw-type and includes a shaft, weight, spring, outlet, and screw portion.   The method according to claim 1, wherein the rectangular outer package is made of metal.   The method according to any one of claims 1 to 10, wherein the rectangular outer casing has a substantially hexahedral shape.   In the step (2), the detachable check valve has a surface on which the non-aqueous electrolyte does not leak from the prismatic exterior body even if the detachable check valve is removed from the prismatic exterior body. 12. A method according to claim 11 attached.   The method according to claim 12, wherein the removable check valve is attached to an upper surface of the square sheath.

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