JP6911460B2 - Exterior and electrochemical elements - Google Patents

Description

The present invention relates to exterior bodies and electrochemical elements.

For the purpose of reducing the weight of the battery and increasing the degree of freedom in battery design, a laminate cell using a laminate film obtained by laminating a metal foil and a resin as an exterior body has been put into practical use. The laminated film covers the power generation element of the battery and prevents the power generation element from coming into contact with water or air.

The power generation element needs to be electrically connected to the outside. Therefore, in Patent Document 1, the lead terminal connected to the power generation element is pulled out from one end side of the peripheral edge portion of the exterior body. The power generation element and the outside are electrically connected via the lead terminal.

On the other hand, the lead terminal causes various problems. For example, a step of connecting the lead terminal and the electrode by welding or the like is required, and the number of steps of manufacturing the electrochemical element increases. In addition, the lead terminal may come off from the electrode, causing poor contact. In addition, the portion bonded via the lead terminal of the exterior body is liable to cause a problem. Further, the thickness of the entire power generation element is increased by the thickness of the lead terminal, which hinders the miniaturization and high density of the battery.

Therefore, Patent Documents 2 and 3 describe a method of making an electrical connection with the outside without using a lead terminal. Patent Document 2 describes a method of forming a metal exposed portion in which a metal layer is exposed on a part of a laminated exterior body and connecting the metal exposed portion and a power generation element. Further, Patent Document 3 describes a method of forming a conductive window by providing a conductive coating layer on one surface of a metal foil constituting the metal layer.

Japanese Unexamined Patent Publication No. 2004-31909 Japanese Unexamined Patent Publication No. 2015-228365 Japanese Unexamined Patent Publication No. 2016-207542

However, the method described in Patent Document 2 removes a part of the resin layer in order to expose the metal layer, which may reduce the strength of the exterior body.

Further, in the method described in Patent Document 3, a conductive coating layer is provided on the entire surface of the metal foil on one side. In this case, in order to maintain the insulating property of the portion other than the conductive window, it is necessary to further provide a thermoplastic resin layer on the portion other than the conductive window. That is, in the method described in Patent Document 3, a large step is formed between the portion of the exterior body provided with the thermoplastic resin layer and the portion provided with the conductive window.

When there is a step, it becomes necessary to pull out a part of the current collector constituting the power generation element to the conductive window to connect the power generation element and the conductive window of the exterior body. It is work-wise difficult to pull out a part of the current collector and connect it to the conductive window of the exterior body by welding or the like. Therefore, while the electrochemical element is being operated, the connection between the conductive window and the current collector is disconnected, resulting in poor contact.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an electrochemical element that does not need to be provided with a lead terminal and an exterior body used for the electrochemical element.

As a result of diligent studies, the present inventors have made a configuration in which the inner layer has a conductive portion and a non-conductive portion penetrating in the thickness direction in the same plane, so that a lead terminal is unnecessary and stable. It has been found that an electrochemical device that can operate in the same manner can be obtained.
That is, in order to solve the above problems, the following means are provided.

(1) The exterior body according to the first aspect is an exterior body that covers a power generation element, and is a metal layer, an inner layer provided on the power generation element side of the metal layer, and the inside of the metal layer. It has an outer layer provided on the opposite side of the layer, and the inner layer has a conductive portion and a non-conductive portion penetrating in the thickness direction in the same plane.

(2) The average thickness of the conductive portion in the exterior body according to the above aspect may be 0.5 times or more and 2.0 times or less the average thickness of the non-conductive portion.

(3) The conductive portion and the non-conductive portion in the exterior body according to the above aspect may contain the same resin, and the conductive portion may contain a conductive material.

(4) The outer layer of the exterior body according to the above aspect may have a second conductive portion and a second non-conductive portion penetrating in the thickness direction in the same plane.

(5) The average thickness of the second conductive portion in the exterior body according to the above aspect may be 0.5 times or more and 2.0 times or less the average thickness of the second non-conductive portion.

(6) The second conductive portion in the exterior body according to the above aspect may be provided at a position overlapping with the conductive portion when viewed from a direction perpendicular to the in-plane direction of the outer layer.

(7) The electrochemical element according to the second aspect includes an exterior body according to the above aspect and a power generation element covered with the exterior body, and the power generation element and the conductive portion of the exterior body are electrically connected. Is connected.

(8) In the electrochemical device according to the above aspect, the area of the conductive portion may be smaller than the area of one surface of the power generation element on the exterior body side.

(9) In the electrochemical device according to the above aspect, the average thickness of the conductive portion may be 1.0 times or more and 1.5 times or less the average thickness of the non-conductive portion.

(10) The power generation element in the electrochemical element according to the above aspect has a first surface with an exposed positive electrode and a second surface with an exposed negative electrode, and the metal layer of the exterior body covering the first surface. Is Al, and the metal layer of the exterior body covering the second surface may be any one selected from the group consisting of Cu, Ni, Pt and SUS.

The exterior body according to the above aspect does not require a lead terminal, and the electrochemical element can operate stably by using this exterior body.

It is sectional drawing of the cross section of the electrochemical element which concerns on 1st Embodiment. It is sectional drawing of another example of the electrochemical element which concerns on 1st Embodiment. It is sectional drawing of the electrochemical element which concerns on 1st Embodiment which has a sealing part. It is sectional drawing of the electrochemical element which concerns on 1st Embodiment which has a protrusion. FIG. 5 is a schematic cross-sectional view of the electrochemical element according to the first embodiment in which the power generation element is a laminated body. FIG. 5 is a schematic cross-sectional view of another example of the electrochemical element according to the first embodiment in which the power generation element is a laminated body. FIG. 5 is a schematic cross-sectional view of the electrochemical element according to the first embodiment in which the power generation element is a wound body. FIG. 5 is a schematic cross-sectional view of another example of the electrochemical element according to the first embodiment in which the power generation element is a wound body. It is sectional drawing of the cross section of the electrochemical element which concerns on 2nd Embodiment.

Hereinafter, the present embodiment will be described in detail with reference to the drawings as appropriate. The drawings used in the following description may be enlarged for convenience in order to make the features of the present invention easy to understand, and the dimensional ratios of the respective components may differ from the actual ones. be. The materials, dimensions, etc. exemplified in the following description are examples, and the present invention is not limited thereto, and the present invention can be appropriately modified without changing the gist thereof.

"First embodiment"
[Electrochemical element]
FIG. 1 is a schematic cross-sectional view of the electrochemical device according to the first embodiment. As shown in FIG. 1, the electrochemical element has a power generation element 10 and an exterior body 20. The power generation element 10 is impregnated with an electrolytic solution. The exterior body 20 prevents the electrolytic solution from leaking to the outside and prevents external air and moisture from reaching the power generation element 10.

(Power generation element)
The power generation element 10 has a positive electrode 1, a negative electrode 2, and a separator 3. In the power generation element 10 shown in FIG. 1, a pair of positive electrodes 1 and 2 negative electrodes are arranged so as to face each other with the separator 3 interposed therebetween.

<Positive electrode>
The positive electrode 1 has a positive electrode current collector 1A and a positive electrode active material layer 1B provided on one surface thereof. The positive electrode current collector 1A may be made of a conductive material, and for example, a thin metal plate of aluminum, copper, or nickel foil can be used.

The positive electrode active material used for the positive electrode active material layer 1B is occlusion of lithium ions and release, desorption and insertion of lithium ions (intercalation), or counter anions of the lithium ions and the lithium ions (e.g., PF 6 ^_-) and An electrode active material capable of reversibly advancing the doping and dedoping of the above can be used.

For example, lithium cobalt oxide (LiCoO _2), lithium nickelate (LiNiO _2), lithium manganate (LiMnO _2), lithium manganese spinel (LiMn ₂ O _4), and the general _{formula: LiNi x Co y Mn z M} a O ₂ (x + y + z + a = 1, 0 ≦ x <1, 0 ≦ y <1, 0 ≦ z <1, 0 ≦ a <1, M is one type selected from Al, Mg, Nb, Ti, Cu, Zn, Cr. Composite metal oxide represented by the above elements), lithium vanadium compound (LiV ₂ O ₅ ), olivine type LiMPO ₄ (however, M is Co, Ni, Mn, Fe, Mg, Nb, Ti, Al, Zr. more shows one or more elements or VO selected), lithium titanate _{(Li 4 Ti 5 O 12)} , LiNi x Co y Al z O 2 (0.9 <x + y + z <1.1) mixed metal oxide, such as Examples include substances, polyacetylene, polyaniline, polypyrrole, polythiophene, polyacene and the like.

Further, the positive electrode active material layer 1B may have a conductive material. Examples of the conductive material include carbon powder such as carbon black, carbon nanotubes, carbon material, metal fine powder such as copper, nickel, stainless steel and iron, a mixture of carbon material and metal fine powder, and conductive oxide such as ITO. Be done. When sufficient conductivity can be ensured only by the positive electrode active material, the power generation element 10 does not have to contain the conductive material.

The positive electrode active material layer 1B contains a binder. A known binder can be used. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoro Fluororesin such as ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride (PVF) can be mentioned.

In addition to the above, as binders, for example, vinylidene fluoride-hexafluoropropylene-based fluororubber (VDF-HFP-based fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-HFP-) TFE-based fluorine rubber), vinylidene fluoride-pentafluoropropylene-based fluorine rubber (VDF-PFP-based fluorine rubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene-based fluorine rubber (VDF-PFP-TFE-based fluorine rubber), Vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene-based fluororubber (VDF-PFMVE-TFE-based fluororubber), vinylidene fluoride-chlorotrifluoroethylene-based fluororubber (VDF-CTFE-based fluororubber), etc. Fluoroethylene rubber may be used.

<Negative electrode>
The negative electrode 2 has a negative electrode current collector 2A and a negative electrode active material layer 2B provided on one surface thereof. As the negative electrode current collector 2A, the conductive material and the binder, the same ones as those of the positive electrode can be used. As the binder used for the negative electrode, for example, cellulose, styrene / butadiene rubber, ethylene / propylene rubber, polyimide resin, polyamide-imide resin, acrylic resin and the like may be used in addition to those listed for the positive electrode.

The negative electrode active material used for the negative electrode active material layer 2B may be any compound that can occlude and release lithium ions, and a known negative electrode active material can be used. Examples of the negative electrode active material include carbon materials such as metallic lithium, graphite capable of storing and releasing lithium ions (natural graphite, artificial graphite), carbon nanotubes, non-graphitizable carbon, easily graphitized carbon, and low-temperature calcined carbon. Metals that can be combined with lithium such as aluminum, silicon, and tin, SiO _x (0 <x <2), amorphous compounds mainly composed of oxides such as tin dioxide, lithium titanate (Li ₄ Ti ₅₎ Examples _{include particles containing O 12} ) and the like.

<Separator>
The separator 3 may be formed from an electrically insulating porous structure, for example, a monolayer of a film made of polyethylene, polypropylene or polyolefin, a laminate or a stretched film of a mixture of the above resins, or cellulose, polyester and Examples thereof include fibrous nonwoven fabrics made of at least one constituent material selected from the group consisting of polypropylene.

<Electrolytic solution>
As the electrolyte solution, an electrolyte solution containing a lithium salt or the like (electrolyte aqueous solution, electrolyte solution using an organic solvent) can be used. However, since the decomposition voltage of the aqueous electrolyte solution is electrochemically low, the withstand voltage during charging is low and limited. Therefore, it is preferable that the electrolyte solution uses an organic solvent (non-aqueous electrolyte solution).

The non-aqueous electrolyte solution has an electrolyte dissolved in a non-aqueous solvent, and may contain a cyclic carbonate and a chain carbonate as the non-aqueous solvent.

As the cyclic carbonate, one capable of solvating an electrolyte can be used. For example, ethylene carbonate, propylene carbonate, butylene carbonate and the like can be used.

The chain carbonate can reduce the viscosity of the cyclic carbonate. For example, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate can be mentioned. In addition, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane and the like may be mixed and used.

The ratio of cyclic carbonate to chain carbonate in the non-aqueous solvent is preferably 1: 9 to 1: 1 in volume.

Examples of the electrolyte include LiPF ₆ , LiClO ₄ , LiBF ₄ , LiCF ₃ SO ₃ , LiCF ₃ CF ₂ SO ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiN (CF ₃ SO ₂ ) ₂ , and LiN (CF ₃ CF). ₂ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiN (CF ₃ CF ₂ CO) ₂ , LiBOB and other lithium salts can be used. One of these lithium salts may be used alone, or two or more thereof may be used in combination. In particular, from the viewpoint of the degree of ionization, it is preferable to contain _{LiPF 6.}

When dissolving LiPF ₆ in a non-aqueous solvent, it is preferable to adjust the concentration of the electrolyte in the non-aqueous electrolyte solution to 0.5 to 2.0 mol / L. When the concentration of the electrolyte is 0.5 mol / L or more, the lithium ion concentration of the non-aqueous electrolyte solution can be sufficiently secured, and a sufficient capacity can be easily obtained during charging / discharging. Further, by suppressing the concentration of the electrolyte to 2.0 mol / L or less, it is possible to suppress an increase in the viscosity of the non-aqueous electrolyte solution, to sufficiently secure the mobility of lithium ions, and to obtain a sufficient capacity during charging and discharging. It will be easier.

Even when LiPF ₆ is mixed with other electrolytes, it is preferable to adjust the lithium ion concentration in the non-aqueous electrolyte solution to 0.5 to 2.0 mol / L, and the lithium ion concentration from _{LiPF 6 is 50 mol% thereof.} It is more preferable that the above is contained.

(Exterior body)
The exterior body 20 seals the power generation element 10 and the electrolytic solution. The exterior body 20 has a metal layer 21, an inner layer 22, and an outer layer 23.

The metal layer 21 blocks moisture and air that enter from the outside. The metal layer 21 is not particularly limited as long as it is a conductive metal. For example, Al, Cu, Ni, Pt, SUS and the like can be used.

The metal layer 21 is electrically connected to the power generation element 10 via an inner layer 22, which will be described later. The metal layer 21 electrically connected to the positive electrode 1 of the power generation element 10 is preferably made of a material that is not easily corroded at the positive electrode potential, and specifically, Al is preferably used. On the other hand, the metal layer 21 electrically connected to the negative electrode 2 of the power generation element 10 is preferably a material that does not easily react with lithium ions, and specifically, any one of Cu, Ni, Pt, and SUS is used. Is preferable.

That is, the metal layer 21 that covers the first surface of the power generation element 10 with the exposed positive electrode 1 is preferably Al, and the metal layer 21 that covers the second surface of the power generation element 10 with the negative electrode 2 exposed is Cu, Ni, Pt, and It is preferably one selected from the group consisting of SUS.

The inner layer 22 has a conductive portion 22A penetrating in the thickness direction perpendicular to the in-plane direction in which the inner layer 22 extends, and a non-conductive portion 22B other than the conductive portion 22A. The conductive portion 22A and the non-conductive portion 22B are integrally formed in the same plane. The inner layer 22 may be a single layer or a plurality of layers.

The conductive portion 22A electrically connects the metal layer 21 and the power generation element 10. A resin in which a conductive material is dispersed can be used for the conductive portion 22A. Examples of the conductive material include carbon materials, metals, conductive polymers and the like. As the resin, it is preferable to use a heat-sealing resin, and for example, polyethylene (PE), polypropylene (PP) and the like can be used.

The non-conductive portion 22B prevents the power generation element 10 from coming into contact with an external element or the like and causing a short circuit. A resin can be used for the non-conductive portion 22B. The resin constituting the non-conductive portion 22B is preferably the same as the resin constituting the conductive portion 22A.

The average thickness of the conductive portion 22A is preferably 0.5 times or more and 2.0 times or less, and more preferably 0.7 times or more and 1.5 times or less of the average thickness of the non-conductive portion 22B. It is more preferably 0.0 times. Here, the "average thickness" means the average thickness in the state before laminating the power generation element 10 (the state in which the exterior body 20 is peeled off from the power generation element 10), and is a plane perpendicular to one surface 10A of the power generation element 10. It means the average of 5 points in the cut section.

If the average thickness of the conductive portion 22A and the average thickness of the non-conductive portion 22B are significantly different, a step is formed between the conductive portion 22A and the non-conductive portion 22B. The step causes a decrease in the adhesion between the exterior body 20 and the power generation element 10 and a poor connection between the conductive portion and the non-conductive portion. On the other hand, if the thickness difference between the conductive portion 22A and the non-conductive portion 22B is about twice, the step can be relaxed by the pressure when laminating the exterior body 20.

Further, as shown in FIG. 1, when the area of one surface 10A on the exterior body 20 side of the power generation element 10 is larger than the area of the conductive portion 22A, the average thickness of the conductive portion 22A is 1 of the average thickness of the non-conductive portion 22B. More preferably, it is 0.0 times or more and 1.5 times or less. If the thickness of the conductive portion 22A is thicker than the thickness of the non-conductive portion 22B, the power generation element 10 and the non-conductive portion 22B do not come into contact first, and the contact state between the power generation element 10 and the conductive portion 22A can be further improved. ..

FIG. 2 is a schematic cross-sectional view of another example of the electrochemical device according to the first embodiment. In the electrochemical element 101 shown in FIG. 2, the thickness of the conductive portion 22A is thinner than the thickness of the non-conductive portion 22B. In this case, it differs from the electrochemical element 100 according to FIG. 1 in that the area of the conductive portion 22A is made wider than the area of one surface 10A of the power generation element 10 in order to bring the power generation element 10 into contact with the conductive portion 22A.

As shown in FIG. 2, when the area of the conductive portion 22A is larger than the area of one surface 10A of the power generation element 10, it is necessary to widen the space between the side surface of the power generation element 10 and the exterior body 20, and the energy of the electrochemical element 101 is increased. It causes a decrease in density.

When the thickness of the conductive portion 22A is the same as or thicker than the thickness of the non-conductive portion 22B, the area of the conductive portion 22A is preferably smaller than the area of one surface 10A on the exterior body 20 side of the power generation element 10. On the other hand, if the area of the conductive portion 22A is too small with respect to the area of one surface 10A on the exterior body 20 side of the power generation element 10, an excessive current is concentrated on the conductive portion 22A. Therefore, the area of the conductive portion 22A is preferably 0.1 times or more and 1.0 times or less the area of one surface 10A on the exterior body 20 side of the power generation element 10.

The outer layer 23 has a second conductive portion 23A and a second non-conductive portion 23B that penetrate in the thickness direction perpendicular to the in-plane direction in which the outer layer 23 extends. The second conductive portion 23A and the second non-conductive portion 23B are integrally formed in the same plane.

The second conductive portion 23A electrically connects the metal layer 21 and the external element. That is, the power generation element 10 and the external element are electrically connected by the conductive portion 22A of the inner layer 22 and the second conductive portion 23A of the outer layer 23. The outer layer 23 may be a single layer or a plurality of layers.

For the second conductive portion 23A and the second non-conductive portion 23B, the same materials as the conductive portion 22A and the non-conductive portion 22B of the inner layer 22 can be used. On the other hand, the resin constituting the outer layer 23 does not require heat-sealing properties and is preferably a material having a high melting point. Specifically, polyethylene terephthalate (PET), polyamide and the like are preferable.

The second conductive portion 23A is preferably provided at a position where it overlaps with the conductive portion 22A when viewed from a direction perpendicular to the in-plane direction of the outer layer 23. By superimposing the positions of the conductive portion 22A and the second conductive portion 23A in a plan view, the conductive path from the power generation element 10 to the external element becomes linear. As a result, it is suppressed that the element resistance of the electrochemical element 100 becomes high.

Further, the area of the second conductive portion 23A is preferably 0.1 times or more the area of one surface 10A on the exterior body 20 side of the power generation element 10. If the area of the second conductive portion 23A is too small, an excessive current concentrates on the second conductive portion 23A. The area of the second conductive portion 23A is not particularly limited as long as it is large, but it is preferably 1.0 times or less the area of one surface 10A on the exterior body 20 side of the power generation element 10 in order to prevent a short circuit with the external element. ..

The average thickness of the second conductive portion 23A is preferably 0.5 times or more and 2.0 times or less, and 0.7 times or more and 1.5 times or less the average thickness of the second non-conductive portion 23B. More preferably, it is more preferably 1.0 times. If the average thickness of the conductive portion 23A and the average thickness of the non-conductive portion 23B are significantly different, a step is formed between the conductive portion 23A and the non-conductive portion 23B, and stress is concentrated on the boundary between the conductive portion 23A and the non-conductive portion 23B. It will be easier to do.

Further, it is preferable that the total thickness of the conductive portion 22A and the second conductive portion 23A is equal to the total thickness of the non-conductive portion 22B and the second non-conductive portion 23B, specifically, 0.5 times or more and 2.0 times or less. Is more preferable, 0.7 times or more and 1.5 times or less is more preferable, and 1.0 times or more is further preferable.

Even when the average thickness difference between the second conductive portion 23A and the second non-conductive portion 23B is large, it is possible to alleviate the difference in thickness as a whole due to the difference in thickness between the conductive portion 22A and the non-conductive portion 22B. As a result, it is possible to avoid forming a step on the outer surface of the exterior body 20.

As described above, the electrochemical element according to the present embodiment can be electrically connected to the external element via the conductive portion 22A, the metal layer 21, and the second conductive portion 23A. Therefore, it is not necessary to use the lead terminal, and it is possible to suppress an increase in the number of steps for providing the lead terminal, occurrence of poor contact due to the lead terminal, peeling of the outer body even at the portion via the lead terminal, and the like. Further, in the inner layer 22 and the outer layer 23, the conductive portion 22A and the non-conductive portion 22B, and the second conductive portion 23A and the second non-conductive portion 23B are integrally formed in the same plane, so that the exterior body 20 is formed. The sealing property of is improved.

Although the present embodiment has been described in detail with reference to the drawings, each configuration and a combination thereof are examples, and the configurations can be added, omitted, replaced, and other changes can be made.

For example, as shown in the electrochemical element 102 shown in FIG. 3, an insulating sealing portion 24 may be provided at an end portion where the exterior bodies 20 are joined to each other. Since the metal layer 21 has an equipotential potential, if the end portion of the metal layer 21 is exposed, it causes a short circuit. For example, when the metal layer 21 connected to the positive electrode 1 and the metal layer 21 connected to the negative electrode 2 come into contact with each other, the power generation element 10 is short-circuited.

Further, instead of completely sealing the end portion with the sealing portion 24, the non-conductive portion 22B of the inner layer 22 is projected from the metal layer 21 as in the electrochemical element 103 shown in FIG. 4, and the protruding portion 26 is projected. It may be provided. The protruding portion 26 can prevent the metal layers 21 from being short-circuited with each other.

Further, as in the electrochemical element 104 shown in FIG. 5, the power generation element 11 may be a laminated body. In the power generation element 11 shown in FIG. 5, a plurality of positive electrodes 1 and 2 negative electrodes are laminated via a separator 3. The positive electrode current collectors 1A of the plurality of positive electrodes 1 are connected to each other, and the negative electrode current collectors 2A of the plurality of negative electrodes 2 are connected to each other. Therefore, each positive electrode 1 and each negative electrode 2 are electrically connected to an external element via the positive electrode current collector 1A and the negative electrode current collector 2A.

Further, as in the electrochemical element 105 shown in FIG. 6, the stacking direction of the power generation element 12 which is a laminated body may be the extending direction of the exterior body 20. The power generation element 12 shown in FIG. 6 has a different stacking direction from the power generation element 11 shown in FIG. Also in the electrochemical element 105 shown in FIG. 6, the positive electrode current collectors 1A of the plurality of positive electrodes 1 are connected to each other, and the negative electrode current collectors 2A of the plurality of negative electrodes 2 are connected to each other. Therefore, each positive electrode 1 and each negative electrode 2 are electrically connected to an external element via the positive electrode current collector 1A and the negative electrode current collector 2A.

Further, as in the electrochemical element 106 shown in FIG. 7, the power generation element 13 may be a wound body. The power generation element 13 shown in FIG. 7 is obtained by stacking a positive electrode 1, a separator 3, a negative electrode 2, and a separator 3 in this order and winding them around one end side. The positive electrode 1 and the negative electrode 2 face each other via the separator 3 and carry out an electrochemical reaction.

Further, the winding axis direction of the wound body is not limited to the extending direction of the exterior body 20, and may be the thickness direction of the exterior body 20. In the electrochemical element 107 shown in FIG. 8, the winding axis direction of the power generation element 14 which is a wound body is the thickness direction of the exterior body 20. FIG. 8 is a cross-sectional view of the electrochemical element 107 cut along a plane passing through the center of the winding shaft of the power generation element 14. The power generation element 14 shown in FIG. 8 has a different winding axis direction from the power generation element 13 shown in FIG. 7. The power generation element 14 shown in FIG. 8 is obtained by stacking a positive electrode 1, a separator 3, a negative electrode 2, and a separator 3 in this order and winding them around one end side. At this time, the positive electrode current collector 1A of the positive electrode 1 projects to one end side in the winding axis direction, and the negative electrode current collector 2A of the negative electrode 2 projects to the other end side in the winding axis direction. When the power generation element 14 is covered with the exterior body 20, the protruding portion of the positive electrode current collector 1A and the protruding portion of the negative electrode current collector 2A are electrically connected to the conductive portion 22A of the inner layer 22, respectively.

"Second embodiment"
FIG. 9 is a schematic cross-sectional view of the electrochemical element 108 according to the second embodiment. In the electrochemical element 108 shown in FIG. 9, the configuration of the exterior body 30 is different from the configuration of the exterior body 20 of the electrochemical element 100 according to the first embodiment. The exterior body 30 is the same as the exterior body 20 according to the first embodiment in that it has a metal layer 21, an inner layer 22, and an outer layer 33, except that the outer layer 33 is composed of only a non-conductive portion. The same components as those in the first embodiment are designated by the same reference numerals.

When the outer layer 33 is composed of only the non-conductive portion, the power generation element 10 and the external element are connected by using the end portion of the metal layer 21. By connecting the external element to the end of the metal layer 21, the positive electrode 1 and the negative electrode 2 and the external element are connected via the metal layer 21 and the conductive portion 22A.

For the outer layer 33, the same material as the non-conductive portion 22B according to the first embodiment can be used. The outer layer 33 does not need to form a conductive portion. Therefore, the strength of the outer layer 33 is higher than that of the outer layer 23 according to the first embodiment. Further, since the outer layer 33 does not have conductivity, even if the external device and the electrochemical element 108 come into contact with each other, the short circuit between the external device and the electrochemical element 108 is further suppressed, and the safety is enhanced.

[Manufacturing method of electrochemical device]
The power generation element of the electrochemical element can be manufactured by a known method. Hereinafter, the manufacturing method will be specifically described by taking the power generation element 10 shown in FIG. 1 as an example.

First, the positive electrode 1 and the negative electrode 2 are manufactured. The positive electrode 1 and the negative electrode 2 differ only in the material used as the active material, and can be produced by the same manufacturing method.

A coating material is prepared by mixing a positive electrode active material, a binder and a solvent. If necessary, a conductive material may be further added. As the solvent, for example, water, N-methyl-2-pyrrolidone, N, N-dimethylformamide and the like can be used. The composition ratio of the positive electrode active material, the conductive material, and the binder is preferably 80 wt% to 98 wt%: 0.1 wt% to 10 wt%: 0.1 wt% to 10 wt% in terms of mass ratio. These mass ratios are adjusted so as to be 100 wt% as a whole.

The method of mixing these components constituting the paint is not particularly limited, and the mixing order is also not particularly limited. The above paint is applied to the positive electrode current collector 1A. The coating method is not particularly limited, and a method usually adopted when producing an electrode can be used. For example, the slit die coat method and the doctor blade method can be mentioned. Similarly, for the negative electrode, a paint is applied on the negative electrode current collector 2A.

Subsequently, the solvent in the paint applied on the positive electrode current collector 1A and the negative electrode current collector 2A is removed. The removal method is not particularly limited. For example, the positive electrode current collector 1A and the negative electrode current collector 2A coated with the paint may be dried in an atmosphere of 80 ° C. to 150 ° C. Then, the positive electrode 1 and the negative electrode 2 are completed.

Finally, the power generation element 10 is manufactured by sandwiching the positive electrode 1 and the negative electrode 2 with the separator 3 interposed therebetween.

Next, the exterior body 20 is manufactured. The exterior body 20 includes a metal layer 21, an inner layer 22, and an outer layer 23. There are a method of directly forming an inner layer and an outer layer on a metal layer, a method of preparing each separately and laminating them, and a method of using these in combination. Lamination is performed by heating press or adhesive. When an adhesive is used for lamination, a conductive adhesive is used.

The inner layer 22 can be manufactured, for example, by using a two-color molding technique. A resin composition in which a resin and a conductive material are mixed is injection-molded in a predetermined pattern, and the peripheral portion thereof is injection-molded only with a resin composition containing no conductive material, whereby the conductive portion 22A and the non-conductive portion 22B are integrated. The inner layer 22 is formed.

The thickness of the conductive portion 22A and the non-conductive portion 22B constituting the inner layer 22 can be adjusted by adjusting the amount of each resin composition injected into the mold. The outer layer 23 can also be produced by the same means.

Then, the produced power generation element 10 is enclosed in the exterior body 20. The electrolytic solution may be injected into the exterior body 20, or the power generation element 10 may be impregnated with the electrolytic solution. The exterior body 20 is sealed by applying heat or the like and laminating.

"Example 1"
First, an exterior body was produced. The inner layer was made of polypropylene (PP) as a constituent resin, and carbon was mixed into the conductive portion as a conductive filler. In the outer layer, the constituent resin was polyethylene terephthalate (PET), and carbon was mixed in the second conductive portion as a conductive filler. The metal layer was made of Al on the side connected to the positive electrode and Cu on the side connected to the negative electrode.

The areas of the conductive portion and the second conductive portion are the same, and the area of the conductive region including the conductive portion and the second conductive portion is set to 4.3 cm ² in a plan view. The average thickness of the conductive portion and the non-conductive portion of the inner layer was set to 30 μm. Similarly, the average thickness of the second conductive portion and the second non-conductive portion of the outer layer was also set to 30 μm. That is, the average thickness of the non-conductive portion was 1.0 times the average thickness of the conductive portion, and the average thickness of the second non-conductive portion was 1.0 times the average thickness of the second conductive portion.

Next, a power generation element was manufactured. For the positive electrode, a positive electrode active material layer was applied to one surface of a positive electrode current collector made of aluminum foil. The positive electrode active material layer has 94 parts by mass of LiCoO ₂ (active material), 2 parts by mass of carbon (conductive material), and 4 parts by mass of polyvinylidene fluoride (PVDF, binder).

Similarly, a negative electrode active material layer was applied to one surface of a negative electrode current collector made of copper foil to prepare a negative electrode. The negative electrode active material layer consists of 95 parts by mass of graphite (active material), 1 part by mass of carbon (conductive material), 1.5 parts by mass of styrene-butadiene rubber (SBR, binder), and 2.5 parts by mass. It has carboxymethyl cellulose (CMC, binder).

Then, polyethylene was used as the separator, and the positive electrode active material layer and the negative electrode active material layer were arranged so as to face each other toward the separator side to manufacture a power generation element. The area of the laminated surface of the power generation element was 4.3 cm ² . That is, the area of the conductive region (conductive portion and the second conductive portion) of the exterior body was set to be the same as the area of the laminated surface of the power generation element.

The obtained power generation element and the electrolytic solution were sealed in the prepared exterior body to prepare an electrochemical device. The electrolytic solution is 1.0 M (mol / L) as a lithium salt in a solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) in a volume ratio of 3: 4: 3. The one to which LiPF ₆ was added was used.

In order to confirm the durability of the electrochemical element, charging and discharging were performed for 100 cycles. Then, the failure rate after 100 cycles was measured. In the cycle test, 100 samples were performed, and the sample in which a value of 80% or less was obtained with respect to the initial power generation capacity was treated as a failure.

Moreover, the resistance value of the electrochemical element was obtained by impedance measurement. The impedance measurement condition was an applied voltage of 10 mV, and the impedance was measured at 100 points while changing the AC frequency from 100 MHz to 100 kHz. Then, the values at 1 kHz were compared.

(Examples 2 to 4)
Examples 2 to 4 differ from Example 1 in that the conductive materials constituting the conductive portion of the inner layer and the second conductive portion of the outer layer are changed to the materials shown in Table 1. As shown in Examples 1 to 4, the resistance was sufficiently small when any of the conductive materials was used.

(Examples 5 and 6)
Examples 5 and 6 differ from Example 1 in that the thicknesses of the conductive portion and the non-conductive portion of the inner layer are changed. The thickness of the conductive part was fixed, and the thickness of the non-conductive part was changed.

If the thickness ratio was too small, the resistance value increased. It is considered that the conductive portion is too thin as the non-conductive portion, which makes it difficult to contact the internal power generation element. Further, if the thickness ratio was too small or too large, the failure rate after the 100-cycle test increased. This is because the expansion and contraction of the positive electrode active material layer and the negative electrode active material layer during charging and discharging cause poor contact between the power generation element and the conductive part of the inner layer, cracks at the joint between the conductive part and the non-conductive part, etc. It is probable that this occurred.

(Examples 7 and 8)
Examples 7 and 8 differ from Example 1 in that the thicknesses of the second conductive portion and the second non-conductive portion of the outer layer are changed. The thickness of the second conductive portion was fixed, and the thickness of the second non-conductive portion was changed.

If the thickness ratio was too small or too large, the failure rate after the 100 cycle test increased. It is considered that this is because a step is generated between the conductive portion and the non-conductive portion of the outer layer, and cracks and the like are generated at the joint portion due to the stress of expansion and contraction during charging and discharging. If the thickness ratio was too small, the resistance value increased. It is considered that the total thickness of the conductive portion including the outer layer and the inner layer is too thin than the total thickness of the non-conductive portion, so that the contact with the internal power generation element becomes difficult.

(Example 9)
Example 9 is different from Example 1 in that the thicknesses of the conductive portion and the non-conductive portion of the inner layer and the thicknesses of the second conductive portion and the second non-conductive portion of the outer layer are changed. The total thickness of the conductive part and the second conductive part was equal to the total thickness of the non-conductive part and the second non-conductive part.

In Example 9, since the difference in thickness between the inner layer and the outer layer was alleviated, the failure rate after the 100-cycle test was also small.

(Examples 10 and 11)
Examples 10 and 11 differ from Example 1 in that the area of the conductive region with respect to the area of the laminated surface of the power generation element is changed, and the thicknesses of the conductive portion and the non-conductive portion of the inner layer are changed.

In the tenth embodiment, since the thickness of the non-conductive portion is thicker than the thickness of the conductive portion, the power generation element comes into contact with the non-conductive portion before the conductive portion. Initial continuity could be ensured by the pressure during laminating, but the resistance value was high and the failure rate after the 100-cycle test increased. It is probable that the expansion and contraction during charging and discharging caused poor contact between the power generation element and the conductive portion of the inner layer. On the other hand, in Example 11 in which the thickness of the conductive portion was larger than the thickness of the non-conductive portion, both the resistance value and the failure rate were good results.

1 ... Positive electrode, 1A ... Positive electrode current collector, 1B ... Positive electrode active material layer, 2 ... Negative electrode, 2A ... Negative electrode current collector, 2B ... Negative electrode active material layer, 3 ... Separator, 10, 11, 12 ... Power generation element, 10A One side, 20 ... exterior body, 21 ... metal layer, 22 ... inner layer, 22A ... conductive part, 22B ... non-conductive part, 23 ... outer layer, 23A ... second conductive part, 23B ... second non-conductive part, 24 ... Sealing part, 26 ... Protruding part, 100, 101, 102, 103, 104, 105 ... Electrochemical element

Claims (8)

An exterior body that covers a power generation element
It has a metal layer, an inner layer provided on the power generation element side of the metal layer, and an outer layer provided on the side opposite to the inner layer of the metal layer.
The inner layer has a conductive portion and a non-conductive portion penetrating in the thickness direction in the same plane.
The outer layer has a second conductive portion and a second non-conductive portion penetrating in the thickness direction in the same plane.
The power generation element has a first surface with an exposed positive electrode and a second surface with an exposed negative electrode.
The metal layer of the exterior body covering the first surface is Al.
The metal layer of the outer package body covering the second face Ri der one selected from the group consisting of Cu, Ni, Pt and SUS,
In the inner layer, the average thickness of the conductive portion and the average thickness of the non-conductive portion are different.
The total thickness of the conductive portion of the inner layer and the average thickness of the second conductive portion of the outer layer, the average thickness of the non-conductive portion of the inner layer, and the second non-conductive portion of the outer layer. An exterior body that is equal to the total thickness of the average thickness of the part. The exterior body according to claim 1, wherein the average thickness of the conductive portion is 0.5 times or more and 2.0 times or less the average thickness of the non-conductive portion. The exterior body according to claim 1 or 2, wherein the conductive portion and the non-conductive portion contain the same resin, and the conductive portion contains a conductive material. The average thickness of the second conductive portion, the second is less than 2.0 times 0.5 times or more the average thickness of the non-conductive portion, the exterior body of claim 1. The second conductive portion according to any one of claims 1 to 4, wherein the second conductive portion is provided at a position where the second conductive portion overlaps with the conductive portion when viewed from a direction perpendicular to the in-plane direction of the outer layer. Exterior body. The exterior body according to any one of claims 1 to 5 and a power generation element covered with the exterior body are provided, and the power generation element and the conductive portion of the exterior body are electrically connected to each other. There is an electrochemical element. The electrochemical element according to claim 6 , wherein the area of the conductive portion is smaller than the area of one surface of the power generation element on the exterior body side. The electrochemical device according to claim 7 , wherein the average thickness of the conductive portion is 1.0 times or more and 1.5 times or less the average thickness of the non-conductive portion.

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