Electrochemical device and method for producing same

Abstract

This electrochemical device comprises: a first electrode; a second electrode; a separator interposed between the first electrode and the second electrode; an electrolytic solution; a lead terminal electrically connected to one of the first electrode and the second electrode; and a protection tape that covers the lead terminal. One of the electrodes comprises a current collector foil 20 and a mixture layer 21 provided to the current collector foil. The current collector foil 20 is provided with a first region 20A covered by the mixture layer 21, and a second region 20B which is not covered by the mixture layer 21 and in which the surface of the current collector foil 20 is exposed. The protection tape 24a is adhered to the lead terminal 5a provided in the second region 20B of the current collector foil, and is adhered to at least a part of a third region 20C which is a part of the second region and which is not covered by the lead terminal 5a.

Description

Electrochemical device and method for manufacturing the same

[0001] The present invention relates to an electrochemical device and a method for manufacturing the same.

[0002] An electrochemical device comprises a pair of electrodes and an electrolyte, at least one of which contains an active material capable of adsorbing and desorbing ions. A separator is interposed between the pair of electrodes. An electric double layer capacitor, which is an example of an electrochemical device, has a longer life, is capable of rapid charging, and has superior output characteristics compared to secondary batteries, and is therefore widely used as a backup power source, etc.

[0003] Patent Document 1 proposes covering the negative electrode terminal with a protective tape in order to prevent lithium from being deposited on the negative electrode terminal during pre-doping in a lithium ion capacitor.

[0004] JP 2018-67595 A

[0005] In recent years, there has been a demand for electrochemical devices with high capacities. To achieve this, attempts have been made to reduce the thickness of the current collector and the separator. On the other hand, attempts have also been made to increase the thickness of the mixture layer (active material layer) supported on the current collector.

[0006] As current collectors and separators become thinner, the strength of the electrodes decreases, making them more susceptible to damage or short circuits due to external impacts. To address this issue, applying protective tape to terminal connections, which are particularly susceptible to loads, is expected to improve impact resistance. However, poor adhesion between the electrodes and the protective tape may result in insufficient impact resistance.

[0007] In view of the above, one aspect of the present invention relates to an electrochemical device comprising: a first electrode, a second electrode, a separator interposed between the first electrode and the second electrode, an electrolyte, a lead terminal electrically connected to at least one of the first electrode and the second electrode, and a protective tape covering the lead terminal, wherein the at least one electrode comprises a current collecting foil and a mixture layer provided on the current collecting foil, the current collecting foil having a first region covered with the mixture layer and a second region not covered by the mixture layer and in which a surface of the current collecting foil is exposed, the protective tape comprising a base layer and an adhesive layer, and the protective tape is adhered to the lead terminal provided in the second region of the current collecting foil, and also to at least a part of a third region that is part of the second region and is not covered by the lead terminal.

[0008] In view of the above, another aspect of the present invention relates to a method for manufacturing an electrochemical device including a first electrode, a second electrode, a separator interposed between the first electrode and the second electrode, and an electrolyte solution, the method including the steps of: preparing, as at least one of the first electrode and the second electrode, an electrode including a current collecting foil and a mixture layer provided on the current collecting foil, wherein the current collecting foil of the at least one electrode has a first region covered with the mixture layer and a second region not covered by the mixture layer and in which a surface of the current collecting foil is exposed; electrically connecting a lead terminal to the second region of the current collecting foil; arranging a protective tape to cover at least a portion of the lead terminal, and adhering the protective tape to the one of the electrodes over at least a part of the surface of the lead terminal and at least a part of a third region that is part of the second region and is not covered by the lead terminal; and pressurizing the third region of the one of the electrodes via the protective tape during or after adhering the protective tape.

[0009] According to the present invention, it is possible to improve the impact resistance of an electrochemical device while maintaining a high capacity.

[0010] Fig. 1A is a layout diagram showing an example of an electrode used in an electrochemical device according to one embodiment of the present invention. Fig. 1B is a cross-sectional view showing an example of an electrode used in an electrochemical device according to one embodiment of the present invention. Fig. 2 is a partially cut-out perspective view of an electrochemical device according to one embodiment of the present invention.

[0011] [Electrochemical Device] An electrochemical device according to one embodiment of the present invention comprises a first electrode, a second electrode, a separator interposed between the first electrode and the second electrode, an electrolyte, lead terminals, and a protective tape covering the lead terminals.

[0012] In the electrochemical device, at least one of the first electrode and the second electrode may be a polarizable electrode. The polarizable electrode may include an active material capable of adsorbing and desorbing ions. The electrochemical device exhibits capacitance when ions are adsorbed to the active material on the side of at least one of the electrodes. When ions are desorbed from the active material, a non-Faradaic current flows.

[0013] When both the first electrode and the second electrode are polarizable electrodes, the electrochemical device may be an electric double layer capacitor (EDLC) in which an electric double layer is formed by ions being adsorbed to the active material. When one of the first electrode and the second electrode is a non-polarizable electrode, the electrochemical device may be a lithium ion capacitor (LIC) in which capacitance is generated by the adsorption or desorption of lithium ions on one of the electrodes. In the case of an LIC, a negative electrode used in a lithium ion secondary battery may be used as the non-polarizable electrode.

[0014] A lead terminal is electrically connected to one of the first and second electrodes (which may be a polarizable electrode or a non-polarizable electrode). Similarly, another lead terminal may be electrically connected to the other of the first and second electrodes. The electrochemical device includes a protective tape covering the lead terminal of at least one of the electrodes. One of the electrodes includes a current collecting foil and a mixture layer provided on the current collecting foil.

[0015] In the following, a case where at least the first electrode is provided with a protective tape (first protective tape) will be described as an example. However, the electrochemical device according to this embodiment is not limited to this. The second electrode may be provided with a protective tape (second protective tape), or both the first electrode and the second electrode may be provided with a protective tape individually. The first electrode may be a positive electrode or a negative electrode. The first electrode may be a polarizable electrode or a non-polarizable electrode.

[0016] In the first electrode, the current collector foil has a first region covered with the mixture layer and a second region not covered with the mixture layer, where the surface of the current collector foil is exposed. A lead terminal is attached to the second region. A third region that is part of the second region but is not covered by the lead terminal is present between the lead terminal and the mixture layer.

[0017] The protective tape covers the lead terminal attached to the second region. The protective tape also covers at least a portion of the third region in the longitudinal direction of the current collecting foil (in the case where the first electrode and the second electrode form a wound electrode group, the direction perpendicular to the winding axis). The protective tape can be disposed so as to straddle the mixture layer beyond the third region between the lead terminal and the mixture layer.

[0018] The protective tape includes a base layer and an adhesive layer. The protective tape is adhered to the lead terminals provided in the second region of the current collector foil via the adhesive layer, and also to at least a portion of the third region via the adhesive layer. This strengthens the adhesion between the protective tape and the first electrode, improving impact resistance.

[0019] In order to ensure sufficiently strong adhesion between the protective tape and the first electrode, the width W2 of the second region in the longitudinal direction of the current collector foil is preferably 5000 μm or more.

[0020] In order to achieve high capacity, it is preferable that the thickness of the mixture layer is thicker than the thickness of the protective tape. Furthermore, in order to achieve high capacity, it is preferable that the area of ​​the third region, which is not used for attaching the lead terminal, in the second region where the current collecting foil is exposed is as small as possible. Meanwhile, a step is formed at the boundary between the third region where the current collecting foil is exposed and the lead terminal, and at the boundary between the third region and the mixture layer. The thicker the mixture layer, the higher the step at the boundary between the third region and the mixture layer. Furthermore, the narrower the width of the third region in the longitudinal direction of the current collecting foil, the greater the ratio of the height of the step to the width of the third region (the distance between the lead terminal and the mixture layer).

[0021] The higher the step and the greater the ratio of the step height to the width of the third region, the more difficult it becomes to stably adhere the protective tape to the first electrode in the third region. That is, it becomes more difficult to achieve strong adhesion between the protective tape and the first electrode. To achieve high capacity, even when the step height and / or the step height ratio are increased, pressure may be applied to the third region via the protective tape during or after adhesion of the protective tape so that the protective tape can be firmly adhered in the third region.

[0022] The second region may be pressurized via the protective tape during or after the bonding of the protective tape. By pressurizing the second region via the protective tape, the protective tape can be firmly bonded to the lead terminals and the protective tape can be firmly bonded to the current collecting foil in the third region.

[0023] The pressure applied to the second or third region is 4 N / cm ２ More than 6N / cm is preferable. ２ The pressure (linear pressure) applied by the roll press is preferably 2 N / cm or more, more preferably 4 N / cm or more.

[0024] By adhering the second region while applying pressure, a portion of the adhesive layer of the protective tape that was on the adhesive surface with the lead terminal can flow to the adhesive surface with the current collector foil in the third region, and as a result, the average thickness of the adhesive layer interposed between the current collector foil and the base layer in the third region can be formed to be thicker than the average thickness of the adhesive layer interposed between the lead terminal and the base layer in the second region.

[0025] The protective tape may be provided on both sides of the current collecting foil. In this case, when the current collecting foil is viewed from the normal direction of one side, the second region on the other side (the back side of the one side) may have an overlapping portion with the second region on the one side. In this case, by pressing the second region of the first electrode from both sides, it is easy to press the protective tape against the first electrode during or after bonding.

[0026] When protective tape is provided on both sides of the current collector foil, each of the protective tapes provided on both sides may protrude from the first electrode in the short direction of the current collector foil (in the case where the first electrode and the second electrode form a wound electrode group, in the direction parallel to the winding axis). In this case, the protective tapes provided on both sides may be bonded to each other at their protruding portions. This can further strengthen the bond between the protective tape and the first electrode, and further improve impact resistance.

[0027] The materials for the base layer and adhesive layer of the protective tape are not particularly limited, but the base layer may contain polypropylene (PP) in order to suppress deterioration of the base layer due to the electrolyte.

[0028] As a solvent for an electrolyte solution used in an electrochemical device, a lactone compound such as gamma-butyrolactone (GBL) can be used because of its low viscosity. When an electrolyte solution containing a lactone compound is used, if a protective tape containing commonly used polyethylene terephthalate (PET) in a substrate layer is used, the PET may dissolve in the electrolyte solution due to the high affinity between PET and lactone compounds, leading to deterioration of the substrate layer. In contrast, a protective tape containing polypropylene in a substrate layer is less likely to dissolve in lactone compounds, and therefore deterioration of the substrate layer can be suppressed.

[0029] For the base layer, a compound whose Hildebrand solubility parameter (SP value) is sufficiently different from the SP value of the lactone compound can be used. The SP value of the lactone compound γ-butyrolactone (GBL) is 12.6 [(cal / cm) 1 / 2 ], and is easily soluble in PET, which has an SP value of 10.7, but is hardly soluble in PP, which has an SP value of 8.0. In terms of suppressing deterioration of the base layer of the protective tape, the SP value of the material constituting the base layer is preferably 2.5 or more, more preferably 3.0 or more, different from the SP value of the lactone compound. The SP value of the material constituting the base layer may be 10.0 or less, or may be 9.0 or less.

[0030] According to the present invention, even when the thickness of the current collecting foil is reduced to, for example, 20 μm or less and / or the thickness of the mixture layer is increased to, for example, 60 μm or more in order to increase capacity, the impact resistance can be improved and breakage of the current collecting foil can be suppressed by adhering the protective tape to the lead terminals and also to the current collecting foil in the third region.

[0031] The current collecting foil may be an etched foil. Etched foil has reduced strength compared to unetched foil and is easily broken by external impact, etc. However, by adhering the protective tape to the lead terminals and also to the current collecting foil in the third region, it is possible to improve impact resistance and prevent the current collecting foil from breaking.

[0032] DETAILED DESCRIPTION OF THE INVENTION Electrochemical devices according to embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the configurations shown in the drawings.

[0033] Fig. 1 shows an example of an electrode used in an electrochemical device according to an embodiment of the present invention. Fig. 1A is a layout diagram that schematically shows a first electrode 2 used in a wound electrochemical device in a state before being wound. In Fig. 1A, the X direction is the longitudinal direction of the first electrode, which is perpendicular to the winding axis, and the Y direction is the lateral direction of the first electrode, which is parallel to the winding axis. Fig. 1B shows the X direction of Fig. 1A. １ -X ２1A and 1B, the connection portion with the lead terminal, which is a key feature of the present invention, is emphasized, and the scale of each component in the drawings does not necessarily match the scale of each component in the actual electrode.

[0034] The first electrode 2 includes a current collector foil 20 and a mixture layer (active material layer) 21 provided on the current collector foil 20. The current collector foil 20 is covered with the mixture layer 21 in a first region 20A, while the surface of the current collector foil is exposed in a second region 20B without being covered with the mixture layer 21. In the example of Fig. 1A , the mixture layer 21 is formed on both sides of the current collector foil 20 so as to cover the entire surface of the current collector foil 20 except for the second region 20B (the unhatched region in Fig. 1A ).

[0035] The current collector foil 20 has a first main surface 20X and a second main surface 20Y opposite to the first main surface. The second region 20B is provided on both the first main surface 20X and the second main surface 20Y. The second region 20B on the first main surface 20X is arranged to overlap the second region 20B on the second main surface 20Y when viewed in the normal direction of the first main surface 20X.

[0036] A lead terminal 5a is attached to the second region 20B of the first main surface 20X, and the first electrode 2 and the lead terminal 5a are electrically connected to each other.

[0037] A third region 20C, which is part of the second region 20B and is not covered with the lead terminal 5a, exists between the lead terminal 5a and the mixture layer 21. In the third region 20C, the surface of the current collector foil 20 is exposed even after the lead terminal 5a is attached.

[0038] 1B , a step S1 is formed at the boundary between the lead terminal 5a and the third region 20C by the side end surface of the lead terminal 5a. A step S2 is formed at the boundary between the mixture layer 21 and the third region 20C by the side end surface of the mixture layer 21. The thicker the lead terminal 5a in the second region 20B, the higher the step S1, and the thicker the mixture layer 21, the higher the step S2. To prevent the step S1 from becoming higher, the thickness of the lead terminal 5a in the region in the second region 20B where the lead terminal 5a is attached is preferably 450 μm or less, and more preferably 350 μm or less or 300 μm or less.

[0039] The lead terminal 5a may have, for example, a columnar first portion and a flatter second portion that is continuous with the first portion, but is not limited thereto. In the example of FIG. 1A , the lead terminal 5a includes a round bar portion 52, which is the first portion, and a flat portion 53, which is continuous with the round bar portion 52 and is formed flatter than the round bar portion 52. For example, the second portion (flat portion 53) can be formed by flattening one end of a single cylindrical metal member by pressing, and the first portion (round bar portion 52) can be formed on the other end that is not pressed. In the example of FIG. 1A , the lead terminal 5a further includes a copper-coated steel wire (CP wire) 51 that connects to the round bar portion 52. The CP wire 51 is used for electrical connection to an external circuit.

[0040] The flat portion 53 overlaps the current collector foil 20 in the second region 20B. The current collector foil 20 has a through hole 22 that communicates between the first main surface 20X and the second main surface 20Y in a region of the second region 20B that overlaps the flat portion 53. By overlapping the flat portion 53 and the current collector foil 20 and drilling them together, a needle-shaped protrusion is formed at a predetermined position of the flat portion 53, protruding from the flat portion 53, and a through hole 22 is formed that penetrates both. The lead terminal 5a is attached to the first electrode 2 by crimping the protrusion that passes through the through hole 22 along the second main surface 20Y. Note that while the entire through hole 22 is filled with the protrusion in FIG. 1B , if only a portion of the through hole 22 is filled with the protrusion, an opening that communicates between the lead terminal 5a (flat portion 53) and the second main surface 20Y can be formed along the through hole 22.

[0041] The thicker the flat portion 53, the larger the diameter of the wound electrode group, which hinders achieving a high capacity. Also, the step S1 formed between the flat portion 53 and the third region 20C becomes higher, making it difficult to bond the protective tape 24a to the first electrode 2 in the third region 20C. In order to maintain a high capacity and a good bond between the protective tape 24a and the first electrode 2, the thickness of the flat portion 53 is preferably 450 μm or less, and more preferably 350 μm or less or 300 μm or less.

[0042] A pair of protective tapes 24a, 24b cover the second region 20B provided on the first main surface 20X and the second main surface 20Y. The protective tape 24a includes a base material layer 25a and an adhesive layer 26a. The protective tape 24b includes a base material layer 25b and an adhesive layer 26b. Of the pair of protective tapes, the protective tape 24a provided on the first main surface 20X covers the lead terminal 5a (flat portion 53), the third region 20C, and a portion of the mixture layer 21 beyond the boundary between the third region 20C and the mixture layer 21. The protective tape 24a is adhered to the lead terminal 5a via the adhesive layer 26a and is also adhered to the current collector foil 20 in the third region 20C.

[0043] When bonding the protective tape 24a to the current collector foil 20 in the third region 20C, since the third region 20C is a recessed region sandwiched between the step S1 formed by the lead terminal 5a and the step S2 formed by the mixture layer 21, it is difficult to achieve a strong bond in the third region 20C using a normal bonding method. To achieve a strong bond, it is preferable to apply pressure to the third region 20C during or after bonding the protective tape 24a. Pressurization can be performed by pressing at least the third region 20C from both the first main surface 20X and the second main surface 20Y. The entire second region 20B including the third region 20C may also be pressed. The applied pressure is 4 N / cm ２ More than 6N / cm is preferable. ２ The pressure may be applied by a roll press. When applying pressure by a roll press, the linear pressure is preferably 2 N / cm or more, more preferably 4 N / cm or more.

[0044] When the entire second region 20B is pressed, a portion of the adhesive layer of the protective tape 24a that was present on the adhesive surface with the lead terminal 5a (flat portion 53) may flow to the adhesive surface with the current collector foil 20 in the third region 20C. This allows the portion of the protective tape 24a that extends above the current collector foil 20 at an angle relative to the first main surface 20X of the current collector foil in the third region 20C to also contribute to adhesion, thereby increasing the adhesive area. Furthermore, the average thickness T3 of the adhesive layer interposed between the current collector foil 20 and the base layer in the third region 20C may be greater than the average thickness T2 of the adhesive layer interposed between the lead terminal 5a and the base layer. The thickness ratio T3 / T2 may be, for example, 1.01 or greater or 1.05 or greater.

[0045] In order to obtain a high capacity, the width W3 (the distance between the lead terminal and the mixture layer) of the third region 20C sandwiched between the lead terminal 5a and the mixture layer 21 in the longitudinal direction of the current collecting foil is preferably 2000 μm or less. On the other hand, in order to firmly bond the protective tape to the first electrode in the third region 20C, the width W3 of the third region is preferably 1000 μm or more, and more preferably 1200 μm or more.

[0046] In order to obtain a high capacity and to firmly adhere the protective tape to the first electrode in the third region 20C, the ratio of the thickness of the composite layer to the width W3 of the third region in the longitudinal direction of the current collecting foil (aspect ratio) is preferably 0.02 or more and 0.08 or less, and more preferably 0.04 or more and 0.06 or less.

[0047] Each of the protective tapes 24a and 24b has a portion 27 that protrudes from the first electrode 2 in the short-side direction of the current collector foil 20. The protruding portions 27 protrude on the same side in the short-side direction on both of the protective tapes 24a and 24b, and overlap each other when viewed from the normal direction of the first main surface 20X. The protective tapes 24a and 24b are bonded to each other at the protruding portions 27. This further strengthens the bond between the protective tapes 24a and 24b and the first electrode 2, further improving impact resistance.

[0048] FIG. 2 is a partially cutaway perspective view of an electrochemical device according to an embodiment of the present invention.

[0049] The electrochemical device 10 in Fig. 2 is an electric double layer capacitor and includes a wound capacitor element 1. The capacitor element 1 is configured by winding a sheet-like first electrode 2 and a sheet-like second electrode 3 with a separator 4 interposed therebetween. The first electrode 2 and the second electrode 3 each include a first current collector and a second current collector made of metal, respectively, and a first active layer and a second active layer carried on the surfaces thereof, and exhibit capacitance by adsorbing and desorbing ions. The first active layer and the second active layer contain, for example, porous carbon particles.

[0050] The current collector may be made of, for example, aluminum foil. The surface of the current collector may be roughened by etching or other techniques. The separator 4 may be made of, for example, a microporous film primarily composed of polypropylene. A first lead wire 5a and a second lead wire 5b are connected to the first electrode 2 and the second electrode 3, respectively, as lead members (lead terminals). The capacitor element 1 is housed in a cylindrical outer case 6 together with an electrolyte (not shown). The outer case 6 may be made of a metal such as aluminum, stainless steel, copper, iron, or brass. The opening of the outer case 6 is sealed with a sealing member 7. The lead wires 5a and 5b extend to the outside, passing through the sealing member 7. The sealing member 7 may be made of, for example, a rubber material such as butyl rubber.

[0051] [Method for manufacturing an electrochemical device] A method for manufacturing an electrochemical device according to one embodiment of the present invention is the method for manufacturing the electrochemical device described above. The manufacturing method includes the step of preparing an electrode, as one of the first electrode and the second electrode, including a current collector foil and a mixture layer provided on the current collector foil. The current collector foil of the prepared one electrode has a first region covered with the mixture layer and a second region not covered with the mixture layer, where the surface of the current collector foil is exposed.

[0052] The manufacturing method further includes the steps of: (i) electrically connecting a lead terminal to the second region of the current collector foil; (ii) arranging a protective tape so as to cover at least a portion of the lead terminal and adhering the protective tape to the one electrode over at least a portion of the surface of the lead terminal and over at least a portion of a third region that is part of the second region and is not covered by the lead terminal; and (iii) applying pressure to the third region of the one electrode via the protective tape during or after adhering the protective tape. The applied pressure in step (iii) is 4 N / cm. ２ More than 6N / cm is preferable. ２ The pressure in step (iii) may be applied using a roll. In this case, the pressure (linear pressure) in the application is preferably 2 N / cm or more, more preferably 4 N / cm or more.

[0053] One electrode obtained in step (iii) is laminated with the other electrode via a separator to obtain a laminate. The laminate may be a wound body in which one electrode and the other electrode are wound with a separator interposed therebetween. The laminate is housed in an outer case, and an electrolyte solution is poured into the outer case. Thereafter, the outer case is sealed to produce an electrochemical device.

[0054] Each component of the electrochemical device will be described below.

[0055] (Electrodes) As the first and second electrodes of the electrochemical device, for example, electrodes including an active layer containing an active material and a current collector supporting the active layer are used as polarizable electrodes. The active material includes, for example, porous carbon particles. The active layer includes the porous carbon particles as the active material as an essential component, and may also include a binder, a conductive agent, and the like as optional components.

[0056] Porous carbon particles can be produced, for example, by heat-treating a raw material to carbonize it, and then activating the resulting carbonized material to make it porous. The carbonized material may be crushed and sized before the activation treatment. The porous carbon particles obtained by the activation treatment may be pulverized. After the pulverization treatment, classification may be performed. Examples of activation treatments include gas activation using a gas such as water vapor, and chemical activation using an alkali such as potassium hydroxide.

[0057] Examples of raw materials include wood, coconut shells, pulp waste liquid, coal or coal-based pitch obtained by thermal decomposition thereof, heavy oil or petroleum-based pitch obtained by thermal decomposition thereof, phenol resin, petroleum-based coke, coal-based coke, etc. Among these, petroleum-based coke and coal-based coke are preferred as raw materials.

[0058] Petroleum coke or coal-based coke may be heat-treated, the resulting carbonized product may be activated, and then the porous carbon particles may be pulverized. For example, a ball mill, a jet mill, or the like may be used for the pulverization. By the pulverization, fine porous carbon particles are obtained, and the average particle size (D50) thereof is, for example, 1 μm or more and 4 μm or less. In this specification, the average particle size (D50) refers to the particle size (median diameter) at which the volume-integrated value is 50% in a volume-based particle size distribution measured by a laser diffraction / scattering method.

[0059] The pore size distribution and particle size distribution of the porous carbon particles can be adjusted by the raw material, heat treatment temperature, gas activation temperature, degree of pulverization, etc. Alternatively, two types of porous carbon particles made from different raw materials may be mixed to adjust the pore size distribution and particle size distribution of the porous carbon particles. The average particle size and particle size distribution of the porous carbon particles are measured by a laser diffraction / scattering method. For example, a laser diffraction / scattering particle size distribution analyzer "MT3300EXII" manufactured by Microtrac Corporation is used as the measuring device.

[0060] Examples of the binder include resin materials such as polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR), and examples of the conductive agent include carbon black such as acetylene black.

[0061] The electrode can be obtained by, for example, applying a slurry containing porous carbon particles, a binder and / or a conductive agent, and a dispersion medium to the surface of a current collector, drying the resulting coating, and rolling it to form an active layer. The current collector can be made of a metal foil such as aluminum foil.

[0062] When the electrochemical device is an electric double layer capacitor (EDLC), at least one of the first and second electrodes can be an electrode containing the porous carbon particles. When the electrochemical device is a lithium ion capacitor (LIC), one of the first and second electrodes (positive electrode) can be an electrode containing the porous carbon particles, and the other of the first and second electrodes (negative electrode) can be a negative electrode used in a lithium ion secondary battery. The negative electrode used in a lithium ion secondary battery contains, for example, a negative electrode active material (e.g., graphite) capable of absorbing and releasing lithium ions.

[0063] (Electrolyte) The electrolyte contains a solvent (non-aqueous solvent) and an ionic substance. The ionic substance is dissolved in the solvent and contains cations and anions. The ionic substance may contain, for example, a low-melting-point compound (ionic liquid) that can exist as a liquid at around room temperature. The concentration of the ionic substance in the electrolyte is, for example, 0.5 mol / L or more, 2.0 mol / L or more.

[0064] The solvent preferably has a high boiling point. The solvent may contain a lactone compound. Examples of lactone compounds include β-propiolactone, γ-butyrolactone, γ-valerolactone, and δ-valerolactone. The lactone compound preferably contains γ-butyrolactone (GBL), which has a low viscosity even at low temperatures, is electrochemically stable within the voltage range of the device, and emits a small amount of gas.

[0065] The solvent may contain a solvent other than the lactone compound. Examples of the other solvent that can be used include chain carboxylic acid esters such as methyl propionate, chain carbonate esters such as diethyl carbonate, cyclic carbonate esters such as propylene carbonate, polyhydric alcohols such as ethylene glycol and propylene glycol, cyclic sulfones such as sulfolane, amides such as N-methylacetamide, N,N-dimethylformamide, and N-methyl-2-pyrrolidone, ethers such as 1,4-dioxane, ketones such as methyl ethyl ketone, and formaldehyde.

[0066] When the solvent is a mixed solvent of a lactone compound and another solvent, the proportion of the lactone compound in the entire solvent may be, for example, 50% by volume or more and 85% by volume or less.

[0067] The solvent may include acetonitrile.

[0068] Ionic substances include, for example, organic salts. Organic salts are salts in which at least one of the anion and cation contains an organic substance. Examples of organic salts in which the cation contains an organic substance include quaternary ammonium salts. Examples of organic salts in which the anion (or both ions) contains an organic substance include trimethylamine maleate, triethylamine borodisalicylate, ethyldimethylamine phthalate, mono-1,2,3,4-tetramethylimidazolinium phthalate, and mono-1,3-dimethyl-2-ethylimidazolinium phthalate.

[0069] From the viewpoint of improving the withstand voltage characteristics, the anion preferably includes an anion of a fluorine-containing acid. Examples of the anion of a fluorine-containing acid include BF ４ － and / or PF ６ － The organic salt preferably contains, for example, a tetraalkylammonium cation and a fluorine-containing acid anion. Specifically, diethyldimethylammonium tetrafluoroborate (DEDMABF ４ ), triethylmethylammonium tetrafluoroborate (TEMABF ４ ) etc.

[0070] When the electrochemical device is a lithium ion capacitor (LIC), the ionic material includes a lithium salt. The lithium salt is preferably a salt having a fluorine-containing anion. Among the salts having a fluorine-containing anion, at least one selected from the group consisting of LiBF, LiPF, and lithium bis(fluorosulfonyl)imide (LiN(SOF) is more preferred. LiN(SOF) is also known as LiFSI or LFSI. Among the salts having a fluorine-containing anion, LFSI is less likely to produce by-products and has excellent stability.

[0071] (Separator) A separator is interposed between the first electrode and the second electrode. The separator has ion permeability and serves to physically separate the pair of electrodes to prevent short-circuiting. The form of the separator is not particularly limited, and may be, for example, a nonwoven fabric, a woven fabric, or a microporous film.

[0072] In the above embodiment, a wound type electrochemical device has been described, but the scope of application of the present invention is not limited to the above, and it can also be applied to devices with other structures, for example, stacked type electrochemical devices.

[0073] The electrochemical device according to the present invention is suitable for use in applications requiring large capacity and excellent impact resistance.

[0074] 1: capacitor element, 2: first electrode, 3: second electrode, 4: separator, 5a: first lead wire, 5b: second lead wire, 6: exterior case, 7: sealing member, 10: electrochemical device, 20: current collecting foil, 21: mixture layer, 22: through hole, 24a, 24b: protective tape, 25a, 25b: base layer, 26a, 26b: adhesive layer, 27: protruding portion, 51: CP wire, 52: round bar portion, 53: flat portion

Claims

1. A first electrode; A second electrode; a separator interposed between the first electrode and the second electrode; An electrolyte; a lead terminal electrically connected to at least one of the first electrode and the second electrode; a protective tape covering the lead terminals, The at least one electrode includes a current collecting foil and a mixture layer provided on the current collecting foil, the current collecting foil has a first region covered with the mixture layer and a second region that is not covered with the mixture layer and where a surface of the current collecting foil is exposed, The protective tape includes a base layer and an adhesive layer, an electrochemical device, wherein the protective tape is adhered to the lead terminal provided in the second region of the current collecting foil, and is also adhered to at least a portion of a third region that is part of the second region and is not covered by the lead terminal.

2. the lead terminal has a columnar first portion and a second portion continuous with the first portion and flatter than the first portion; the second portion is fixed to the second region of the current collecting foil; The electrochemical device according to claim 1 , wherein the second portion has a thickness of 450 μm or less.

3. At least a part of the second portion of the lead terminal overlaps with the current collecting foil in the second region, the current collecting foil has a through hole in a region overlapping at least a portion of the second portion, 3. The electrochemical device according to claim 2, wherein the lead terminal further has a protruding portion protruding from the second portion and inserted into the through hole, the protruding portion being crimped to the current collecting foil via the through hole.

4. 4. The electrochemical device according to claim 1, wherein the second region has a width of 5000 μm or more in the longitudinal direction of the current collecting foil.

5. 4. The electrochemical device according to claim 1, wherein the width of the third region sandwiched between the lead terminal and the mixture layer in the longitudinal direction of the current collecting foil is 2000 μm or less.

6. The protective tape is provided on both sides of the current collecting foil, The electrochemical device according to any one of claims 1 to 3, wherein the protective tape protrudes from the one electrode in a short-side direction of the current collecting foil, and the protective tapes provided on both sides are adhered to each other at the protruding portions.

7. The electrochemical device according to any one of claims 1 to 3, wherein an average thickness of the adhesive layer interposed between the current collecting foil and the base material layer in the third region is thicker than an average thickness of the adhesive layer interposed between the lead terminal and the base material layer.

8. 4. The electrochemical device according to claim 1, wherein the one electrode is a polarizable electrode.

9. The electrochemical device of claim 8 , wherein both the first electrode and the second electrode are polarizable electrodes.

10. The electrolyte solution contains a lactone compound, 4. The electrochemical device according to claim 1, wherein the base layer of the protective tape comprises polypropylene.

11. A method for manufacturing an electrochemical device comprising: a first electrode; a second electrode; a separator interposed between the first electrode and the second electrode; and an electrolyte solution, The method includes a step of preparing an electrode including a current collecting foil and a mixture layer provided on the current collecting foil as at least one of the first electrode and the second electrode, the current collecting foil of the at least one electrode has a first region covered with the mixture layer and a second region that is not covered with the mixture layer and in which a surface of the current collecting foil is exposed, electrically connecting a lead terminal to the second region of the current collecting foil; a step of placing a protective tape so as to cover at least a portion of the lead terminal, and adhering the protective tape to the one electrode in at least a portion of a surface of the lead terminal and in at least a portion of a third region that is a part of the second region and is not covered by the lead terminal; the third region of the one electrode being pressed via the protective tape during or after bonding of the protective tape.