WO2018043419A1

WO2018043419A1 - Layered electrode body and power storage element

Info

Publication number: WO2018043419A1
Application number: PCT/JP2017/030771
Authority: WO
Inventors: 祐輔沖; 篤哉石橋; 稲益　徳雄
Original assignee: リチウムエナジーアンドパワーゲゼルシャフトミットベシュレンクテルハフッングウントコンパニーコマンディトゲゼルシャフト; 株式会社Ｇｓユアサ
Priority date: 2016-08-29
Filing date: 2017-08-28
Publication date: 2018-03-08
Also published as: DE112017004317T5; CN110088966A; JPWO2018043419A1; JP2022024044A

Abstract

The present invention addresses the problem of providing a layered electrode body and a power storage element that are able to effectively suppress electrodeposition. The layered electrode body according to one embodiment of the present invention is provided with: a positive electrode plate having a tab protruding from a first edge; at least one pair of separators which have a resin layer and a heat resistant layer formed on the resin layer, and which cover first and second surfaces of the positive electrode plate in a state in which the heat resistant layer faces the positive electrode plate; and a negative electrode plate which is disposed so as to face the positive electrode plate across the separator, wherein an outer peripheral side of the positive electrode plate has a plurality of welding regions where the at least one pair of separators are welded together; and the plurality of welding regions include a first welding region which extends intermittently and approximately parallel to the first edge of the positive electrode plate, and a second welding region which extends continuously and approximately perpendicular to the first edge.

Description

LAMINATED ELECTRODE BODY AND STORAGE ELEMENT

The present invention relates to a laminated electrode body and a storage element.

For example, secondary batteries that can be charged and discharged are used in various devices such as mobile phones and electric vehicles. In recent years, with higher output and higher performance of these devices, a secondary battery having a smaller size and a higher energy density (electric capacity per volume) has been demanded.

Generally, a secondary battery is formed by alternately laminating a positive electrode plate having an active material layer formed on a surface and a negative electrode plate having an active material layer formed on a surface through an electrically insulating separator. In order to increase the energy density in such a secondary battery, it is effective to make the separator thinner. For this reason, the secondary battery which formed the separator with the resin film is put into practical use.

However, since the separator formed from the resin film is relatively weak against heat, when the energy density of the secondary battery is increased, the separator is damaged by heat, and metal precipitates (for example, lithium dendrite) generated by electrodeposition are generated. There is a possibility that the positive electrode plate and the negative electrode plate may be short-circuited through the separator. For this reason, a secondary battery has been proposed in which a heat-resistant layer (inorganic coating layer) is formed on the surface of the separator that contacts the electrode plate to improve the heat resistance of the separator (see JP 2013-143337 A).

In the secondary battery described in the publication, a packaged positive electrode plate in which a positive electrode plate is sandwiched between two separators and an unpacked negative electrode plate that is larger than the positive electrode plate and smaller than the separator are alternately stacked. The laminated electrode body is accommodated in an exterior material. In the secondary battery described in this publication, a positive electrode plate is held between two separators by forming a plurality of dotted adhesive portions at intervals on the outer edges of the two separators.

JP 2013-143337 A

In the secondary battery described in the above publication, the electrolyte can pass relatively easily between the bonded portions of the two separators sandwiching the positive electrode plate. For this reason, in the secondary battery described in the above publication, metal species that generate metal ions capable of generating precipitates are mixed in the electrolyte near the positive electrode plate, or metal ions generated in the positive electrode move to the negative electrode. Electrodeposition by contact cannot be sufficiently suppressed.

In view of this situation, an object of the present invention is to provide a laminated electrode body and a storage element that can effectively suppress electrodeposition.

The laminated electrode body which concerns on 1 aspect of this invention has a positive electrode plate which has the tab which protrudes from a 1st edge, a resin layer, and the heat resistant layer formed on the said resin layer, The said heat resistant layer is said positive electrode plate At least a pair of separators covering the first surface and the second surface of the positive electrode plate in a state of being opposed to each other, and a negative electrode plate facing the positive electrode plate through the separator, and the outer peripheral side of the positive electrode plate A plurality of welding regions in which at least a pair of separators are welded to each other, the plurality of welding regions extending substantially in parallel and intermittently with the first side of the positive electrode plate, and the first side; A second welding region extending substantially vertically and continuously.

The laminated electrode body according to one embodiment of the present invention can effectively suppress electrodeposition.

It is typical sectional drawing which shows the electrical storage element of one Embodiment of this invention. FIG. 2 is a schematic plan view of a laminated electrode body of the energy storage device in FIG. 1.

One embodiment of the present invention includes a positive electrode plate having a tab protruding from a first side, a resin layer and a heat resistant layer formed on the resin layer, and the heat resistant layer facing the positive electrode plate And at least a pair of separators covering the first surface and the second surface of the positive electrode plate, and a negative electrode plate facing the positive electrode plate via the separator, and the at least one pair of separators on the outer peripheral side of the positive electrode plate A plurality of welding regions welded to each other, the plurality of welding regions extending substantially parallel and intermittently to the first side of the positive electrode plate, and substantially perpendicular and continuous to the first side; A laminated electrode body including a second welding region extending in the direction.

The laminated electrode body has a plurality of welding regions in which the at least one pair of separators are welded to each other on the outer peripheral side of the positive electrode plate, and the plurality of welding regions are substantially parallel and intermittent to the first side of the positive electrode plate. By including the first welding region extending in the direction, the inside of the at least one pair of separators can be filled from between the first welding regions. Further, the multilayer electrode body includes a second welding region in which the plurality of welding regions extend substantially perpendicularly and continuously to the first side, so that the electrolyte is separated into two separators in a direction parallel to the first side. I can't go in and out. For this reason, since the movement of the electrolyte solution in contact with the positive electrode plate is suppressed, the laminated electrode body suppresses mixing of metal species that generate metal ions capable of generating precipitates in the electrolyte in the vicinity of the positive electrode plate. In addition, the metal ions generated at the positive electrode can be prevented from moving and coming into contact with the negative electrode for electrodeposition.

The second weld region may have a cut surface. Thus, the second welding region has a cut surface, that is, the second welding region is formed on the outer edges of the at least one pair of separators, so that the second welding in the width direction is performed on the long sheet-like separator. A plurality of packaged positive plates can be efficiently formed by forming a region and cutting the second welding region into two parts in the width direction.

The at least one pair of separators may have a translucent portion in the welding region, and the average width of the welding region may be 10 μm or more and 1000 μm or less. As described above, the at least one pair of separators has a light-transmitting portion in the welding region, and the average width of the welding region is within the range. Can be bigger.

The at least one pair of separators may include fragments of the heat-resistant layer in the welding region. As described above, since the at least one pair of separators includes the fragments of the heat-resistant layer in the welding region, it is not necessary to remove the fragments of the heat-resistant layer that is destroyed when the resin layers are welded to each other. The separator can be welded relatively easily.

Another aspect of the present invention is a power storage device including the multilayer electrode body and an exterior material that accommodates the multilayer electrode body.

The electrical storage element can be used safely by preventing the short circuit by including the laminated electrode body that can effectively suppress electrodeposition.

It is preferable that the exterior material is a metal case. Thus, the said laminated | stacked electrode body can be protected because the said exterior material is a metal case.

Note that “substantially parallel” means that the relative angle is 15 ° or less, and “substantially perpendicular” means that the relative angle is 75 ° or more. Further, “having translucency” means that the total light transmittance measured in accordance with JIS-K7375 (2008) is 20% or more.

Hereinafter, a power storage device according to an embodiment of the present invention will be described in detail with reference to the drawings as appropriate.

[Storage element]
The power storage device of FIG. 1 includes a laminated electrode body 1 that is another embodiment of the present invention, and an exterior material 2 that accommodates the laminated electrode body 1. In addition, the power storage element is filled with an electrolyte (electrolytic solution) in the exterior material 2.

(Laminated electrode body)
The laminated electrode body 1 includes a plurality of positive plates 3, a plurality of pairs of separators 4 that cover the first surface and the second surface of the positive plates 3, and a plurality of negative electrodes that face the positive plates 3 with the separators 4 interposed therebetween. And a plate 5.

<Positive electrode plate>
The positive electrode plate 3 includes a conductive foil-shaped or sheet-shaped positive electrode current collector 6 and a positive electrode active material layer 7 laminated on both surfaces of the positive electrode current collector 6. More specifically, as shown in FIG. 2, the positive electrode plate 3 includes an electrode portion 8 having a polygonal shape (usually rectangular shape) in plan view in which a positive electrode active material layer 7 is laminated on both surfaces of a positive electrode current collector 6. A tab 9 protrudes from the first side S of the electrode portion 8 and is electrically connected to the electrode terminal of the power storage element.

In the positive electrode current collector 6, the tab 9 is preferably formed in a belt shape extending vertically from the first side S of the electrode portion 8 and having a width smaller than that of the electrode portion 8. In addition, the tab 9 is preferably disposed offset to one end side of the first side S of the electrode portion 8.

The width of the separator 4 in the direction along the first side S of the positive electrode plate 3 is preferably equal to or less than the width of the negative electrode plate 5. More specifically, in the multilayer electrode body 1, the separator 4 has a shape that does not protrude from the negative electrode plate 5 in the direction along the first side S in a plan view. Thus, the positive electrode plate 3 held between the paired separators 4 is opposed to the negative electrode plate 5 without protruding from the negative electrode plate 5 in plan view. Thereby, in the said laminated electrode body 1 and by extension, the said electrical storage element, since a current density becomes large in the outer edge part of the negative electrode plate 5, and electrodeposition is not promoted locally, the short circuit by electrodeposition is prevented.

Thus, the lower limit of the difference between the average length in the direction along the first side S of the separator 4 and the average length in the direction along the first side S of the negative electrode plate 5 is preferably 0 mm. The upper limit of the difference between the average length in the direction along the side S and the average length in the direction along the first side S of the negative electrode plate 5 is preferably 1 mm, and more preferably 0.5 mm. By making the difference between the average length in the direction along the first side S of the separator 4 and the average length in the direction along the first side S of the negative electrode plate 5 equal to or greater than the lower limit, the positive electrode plate 3 is sandwiched between the pair of separators 4. It becomes easy to laminate the packaged positive electrode plate and the negative electrode plate 5 so that the positive electrode plate 3 does not protrude from the negative electrode plate 5. Moreover, by making the difference of the average length of the direction along the 1st edge | side S of the separator 4 and the average length of the direction along the 1st edge | side S of the negative electrode plate 5 below the said upper limit, the positive electrode plate 3 and the negative electrode plate 5 Thus, the difference in area between the stacked electrode body 1 and the energy density of the power storage element can be sufficiently increased.

In the laminated electrode body 1, the positive electrode plate 3 can be relatively easily positioned with respect to the negative electrode plate 5 by positioning the separator 4 of the positive electrode plate 3 with respect to the negative electrode plate 5. For this reason, in the laminated electrode body 1, even if the ratio of the area of the positive electrode plate 3 to the area of the negative electrode plate 5 is relatively large, the electrodeposition is not promoted at the outer edge portion of the negative electrode plate 5. can do.

Further, since the separator 4 is disposed on the inner side in the width direction of the negative electrode plate 5 in the laminated electrode body 1, the clearance between the negative electrode plate 5 and the exterior material 2 can be reduced. For this reason, the said electrical storage element can make the dead space in the exterior material 2 comparatively small, and can make energy density comparatively large.

(Positive electrode current collector)
As a material of the positive electrode current collector 6, a metal such as aluminum, copper, iron, nickel, or an alloy thereof is used. Among these, aluminum, an aluminum alloy, copper, and a copper alloy are preferable from the balance between high conductivity and cost, and aluminum and an aluminum alloy are more preferable. Moreover, as a formation form of the positive electrode electrical power collector 6, foil, a vapor deposition film, etc. are mentioned, A foil is preferable from the surface of cost. That is, the positive electrode current collector 6 is preferably an aluminum foil. Examples of aluminum or aluminum alloy include A1085P and A3003P defined in JIS-H4000 (2014).

The lower limit of the average thickness of the positive electrode current collector 6 is preferably 5 μm, more preferably 10 μm. On the other hand, the upper limit of the average thickness of the positive electrode current collector 6 is preferably 50 μm, more preferably 40 μm. By setting the average thickness of the positive electrode current collector 6 to be equal to or more than the lower limit, sufficient strength of the positive electrode current collector 6 can be obtained. In addition, by setting the average thickness of the positive electrode current collector 6 to be equal to or lower than the above upper limit, the volume of the positive electrode active material layer 7 is not relatively decreased, and the energy density of the power storage element can be sufficiently increased.

(Positive electrode active material layer)
The positive electrode active material layer 7 is formed from a so-called positive electrode mixture containing a positive electrode active material. In addition, the positive electrode mixture forming the positive electrode active material layer 7 includes optional components such as a conductive agent, a binder (binder), a thickener, and a filler as necessary.

Examples of the positive electrode active material include complex oxides (Li _x CoO ₂ , Li _x NiO ₂ , Li _x Mn ₂ O ₄ , Li _x ) represented by Li _x MO _y (M represents at least one transition metal). MnO ₃ , Li _x Ni _α Co _(1-α) O ₂ , Li _x Ni _α Mn _β Co _(1-α-β) O ₂ , Li _x Ni _α Mn _(2-α) O ₄ ), Li _w A polyanion compound (LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ , LiCoPO ₄ ) represented by Me _x (XO _y ) _z (Me represents at least one transition metal, and X represents, for example, P, Si, B, V, etc.) Li ₃ V ₂ (PO ₄ ) ₃ , Li ₂ MnSiO ₄ , Li ₂ CoPO ₄ F, etc.). The elements or polyanions in these compounds may be partially substituted with other elements or anion species. In the positive electrode active material layer 7, one kind of these compounds may be used alone, or two or more kinds may be mixed and used. The crystal structure of the positive electrode active material is preferably a layered structure or a spinel structure.

The lower limit of the content of the positive electrode active material in the positive electrode active material layer 7 is preferably 50% by mass, more preferably 70% by mass, and still more preferably 80% by mass. On the other hand, as an upper limit of content of a positive electrode active material, 99 mass% is preferable and 94 mass% is more preferable. By setting the content of the positive electrode active material particles in the above range, the energy density of the power storage element can be increased.

The conductive agent is not particularly limited as long as it is a conductive material that does not adversely affect battery performance. Examples of such a conductive agent include carbon black such as natural or artificial graphite, furnace black, acetylene black, and ketjen black, metals, and conductive ceramics. Examples of the shape of the conductive agent include powder and fiber.

The lower limit of the content of the conductive agent in the positive electrode active material layer 7 is preferably 0.1% by mass, and more preferably 0.5% by mass. On the other hand, as an upper limit of content of a electrically conductive agent, 10 mass% is preferable and 5 mass% is more preferable. By setting the content of the conductive agent in the above range, the energy density of the power storage element can be increased.

Examples of the binder include thermoplastic resins such as fluororesin (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), polyethylene, polypropylene, polyimide; ethylene-propylene-diene rubber (EPDM), sulfonated EPDM. , Elastomers such as styrene butadiene rubber (SBR) and fluororubber; polysaccharide polymers and the like.

The lower limit of the binder content in the positive electrode active material layer 7 is preferably 1% by mass, and more preferably 2% by mass. On the other hand, as an upper limit of content of a binder, 10 mass% is preferable and 5 mass% is more preferable. By setting the content of the binder in the above range, the positive electrode active material can be stably held.

Examples of the thickener include polysaccharide polymers such as carboxymethylcellulose (CMC) and methylcellulose. When the thickener has a functional group that reacts with lithium, it is preferable to deactivate this functional group in advance by methylation or the like.

The filler is not particularly limited as long as it does not adversely affect battery performance. Examples of the main component of the filler include polyolefins such as polypropylene and polyethylene, silica, alumina, zeolite, glass, and carbon.

<Separator>
The separator 4 has a sheet-like resin layer 10 and a heat-resistant layer 11 laminated on the resin layer 10. The separators 4 are arranged in pairs on both sides of each positive electrode plate 3. More specifically, the pair of separators 4 cover the first surface and the second surface of the electrode portion 8 of the positive electrode plate 3 with the heat-resistant layer 11 facing the positive electrode plate 3.

In the separator 4 forming a pair sandwiching the positive electrode plate 3, the resin layers 10 are welded to each other on the outer peripheral side of the positive electrode plate 3, more specifically, in a range where the tab 9 near the outside of the electrode portion 8 does not exist in plan view. It has a plurality of welding regions (first welding region A1 and second welding region A2).

(Resin layer)
The resin layer 10 is formed from a porous resin film.

Examples of the main component of the resin layer 10 include polyethylene (PE), polypropylene (PP), ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, and chlorinated polyethylene. Polyolefins such as polyolefin derivatives, ethylene-propylene copolymers, and polyesters such as polyethylene terephthalate and copolymerized polyesters can be used. Among these, as the main component of the resin layer 10, polyethylene and polypropylene excellent in electrolytic solution resistance, durability, and weldability are preferably used. The “main component” means a component having the largest mass content.

The lower limit of the average thickness of the resin layer 10 is preferably 5 μm and more preferably 10 μm. On the other hand, the upper limit of the average thickness of the resin layer 10 is preferably 50 μm, and more preferably 30 μm. By setting the average thickness of the resin layer 10 to be equal to or greater than the lower limit, the separator 4 can be welded without the resin layer 10 breaking. Further, by setting the average thickness of the resin layer 10 to be equal to or less than the above upper limit, the capacity per volume of the power storage element can be made sufficiently large without unnecessarily increasing the thickness of the separator 4.

(Heat resistant layer)
The heat-resistant layer 11 includes a large number of inorganic particles and a binder that connects the inorganic particles.

As the main component of the inorganic particles, for example, oxides such as alumina, silica, zirconia, titania, magnesia, ceria, yttria, zinc oxide, iron oxide, nitrides such as silicon nitride, titanium nitride, boron nitride, silicon carbide, carbonate Calcium, aluminum sulfate, aluminum hydroxide, potassium titanate, talc, kaolin clay, kaolinite, halloysite, pyrophyllite, montmorillonite, sericite, mica, amicite, bentonite, asbestos, zeolite, calcium silicate, magnesium silicate Etc. Among these, alumina, silica and titania are particularly preferable as the main component of the inorganic particles of the heat-resistant layer 11.

The lower limit of the average particle diameter of the inorganic particles of the heat-resistant layer 11 is preferably 1 nm, and more preferably 7 nm. On the other hand, the upper limit of the average particle diameter of the inorganic particles is preferably 5 μm and more preferably 1 μm. By setting the average particle diameter of the inorganic particles to the above lower limit or more, the ratio of the binder in the heat resistant layer 11 does not increase, and the heat resistant layer 11 having sufficient heat resistance can be obtained. Moreover, the uniform heat resistant layer 11 can be easily formed by making the average particle diameter of an inorganic particle below the said upper limit. The “average particle diameter” is a value measured according to JIS-R1670 using a transmission electron microscope (TEM) or a scanning electron microscope (SEM).

Examples of the main component of the binder of the heat-resistant layer 11 include fluorine resins such as polyvinylidene fluoride and polytetrafluoroethylene, fluororubbers such as vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, and styrene-butadiene copolymers. And its hydride, acrylonitrile-butadiene copolymer and its hydride, acrylonitrile-butadiene-styrene copolymer and its hydride, methacrylic acid ester-acrylic acid ester copolymer, styrene-acrylic acid ester copolymer, acrylonitrile -Synthetic rubber such as acrylic acid ester copolymer, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), cellulose derivatives such as ammonium salt of carboxymethyl cellulose, polyether imi , Polyimides such as polyamideimide, polyamide and precursors thereof (polyamic acid), ethylene-acrylic acid copolymers such as ethylene-ethyl acrylate copolymer, polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone ( PVP), polyvinyl acetate, polyurethane, polyphenylene ether, polysulfone, polyether sulfone, polyphenylene sulfide, polyester and the like.

The lower limit of the average thickness of the heat-resistant layer 11 is preferably 0.5 μm, and more preferably 1 μm. On the other hand, the upper limit of the average thickness of the heat-resistant layer 11 is preferably 10 μm, and more preferably 6 μm. By making the average thickness of the heat-resistant layer 11 equal to or more than the lower limit, the separator 4 can be welded without the heat-resistant layer 11 breaking. Further, by setting the average thickness of the heat-resistant layer 11 to be equal to or less than the above upper limit, the capacity per volume of the power storage element can be sufficiently increased without unnecessarily increasing the thickness of the separator 4.

(Welding area)
As shown in FIG. 2, the plurality of welding regions include a first welding region A <b> 1 that extends approximately in parallel and intermittently with the first side S on which the tab 9 of the positive electrode plate 3 is provided, and is substantially perpendicular to and continuous with the first side S. And a second welding region A2 extending in the direction. In other words, the first welding region A1 is discontinuously spaced along a pair of outer edges (edges on both sides in the short direction in FIG. 2) of the electrode portion 8 substantially perpendicular to the extending direction of the tab 9. The second welding region A2 is formed continuously along a pair of outer edges (edges on both sides in the longitudinal direction in FIG. 2) of the electrode portion 8 substantially parallel to the extending direction of the tab 9.

Thus, by forming the welding regions A1 and A2 around the positive electrode plate 3, the positive electrode plate 3 is accurately held at a predetermined position between the two separators 4 forming a pair. Accordingly, the positive electrode plate 3 can be relatively accurately aligned with the negative electrode plate 5 by aligning the lower end of the separator 4 with the lower end of the negative electrode plate 5 using a guide or the like.

Further, the welded areas A1 and A2 in which the two separators 4 forming a pair are welded have higher rigidity than the two separators 4 (non-welded areas) that are stacked without being welded. , A2 is brought into contact with the guide, whereby the positive electrode plate 3 can be positioned relatively easily and accurately.

In this welding area A1, A2, there may be a fragment of the heat-resistant layer 11 that has been destroyed. The fragments of the heat-resistant layer 11 present in the welding regions A1 and A2 extend in a zigzag manner in the welding regions A1 and A2, specifically, extend in the longitudinal direction while reciprocating in a direction different from the longitudinal direction of the welding regions A1 and A2. It is preferable that the existence density is small in the existing region of the vibration wave shape. Such welding regions A1 and A2 are used to weld the resin layers 10 of the two separators 4 to each other while scraping the fragments of the heat-resistant layer 11 formed while breaking the heat-resistant layer 11 with a relatively small indenter in the width direction. Can be formed.

Moreover, it is preferable that the welding regions A1 and A2 have a translucent portion. That is, the welding regions A1 and A2 are semi-transparent portions or heat-resistant layers formed by dispersing relatively small pieces of forming material of the heat-resistant layer 11 having a light shielding property in the transparent resin forming the resin layer 10. It is good to have a transparent part with a sufficiently small content of 11 pieces.

Thus, it is necessary to remove the fragments of the heat-resistant layer 11 that are destroyed when the resin layers 10 are welded together by including the fragments of the heat-resistant layer 11 inside the welded regions A1 and A2 and around the welded regions A1 and A2. Therefore, the pair of separators 4 can be welded relatively easily.

The lower limit of the ratio of the average length of the non-welded portion (average interval of the welded portion) to the average length of the welded portion in the first weld region A1 is preferably 0.2, and more preferably 0.5. On the other hand, the upper limit of the ratio of the average length of the non-welded portion to the average length of the welded portion in the first weld region A1 is preferably 3, and more preferably 2. By setting the ratio of the average length of the non-welded portion to the average length of the welded portion in the first weld region A1 to be equal to or higher than the lower limit, it is possible to avoid a decrease in the pouring property into the paired separators 4. Thus, it is possible to avoid a decrease in manufacturing efficiency of the power storage element. Moreover, mixing the metal into the electrolyte in contact with the positive electrode plate 3 is sufficiently suppressed by setting the ratio of the average length of the non-welded portion to the average length of the welded portion in the first weld region A1 to be equal to or less than the above upper limit. And a sufficient electrodeposition preventing effect can be obtained.

The lower limit of the average width of the welding regions A1 and A2 is preferably 10 μm, and more preferably 20 μm. On the other hand, the upper limit of the average width of the welding regions A1 and A2 is preferably 1000 μm, and more preferably 300 μm. By setting the average width of the welding regions A1 and A2 to be equal to or more than the lower limit, it is possible to obtain a sufficient bonding strength of the paired separators 4 and to ensure the holding of the positive electrode plate 3. Moreover, since the separator 4 does not become unnecessarily large and the positive electrode plate 3 does not become relatively small by setting the average width of the welding regions A1 and A2 to be equal to or less than the upper limit, the laminated electrode body 1 and the The energy density of the power storage element can be sufficiently increased.

The lower limit of the average distance between the welded areas A1 and A2 and the outer edge of the positive electrode plate 3 is preferably 0.1 mm, and more preferably 0.2 mm. On the other hand, the upper limit of the average distance between the welding regions A1 and A2 and the outer edge of the positive electrode plate 3 is preferably 1.0 mm, and more preferably 0.8 mm. By making the average distance between the welding regions A1 and A2 and the outer edge of the positive electrode plate 3 equal to or more than the lower limit, the paired separators 4 can be easily welded. In addition, by setting the average distance between the welding regions A1 and A2 and the outer edge of the positive electrode plate 3 to be equal to or less than the upper limit, the positive electrode plate 3 is not unnecessarily small with respect to the separator 4 and the negative electrode plate 5, and Energy density can be increased sufficiently.

The lower limit of the average distance between the outer edge of the separator 4 and the first welding region A1 is preferably 100 μm, and more preferably 200 μm. On the other hand, the upper limit of the average distance between the outer edge of the separator 4 and the first welding region A1 is preferably 1 mm, and more preferably 0.5 mm. By setting the average interval between the outer edge of the separator 4 and the first welding region A1 to be equal to or greater than the lower limit, the first welding region A1 can be easily formed. Further, by setting the average distance between the outer edge of the separator 4 and the first welding region A1 to be equal to or less than the upper limit, the rigidity of the outer edge of the separator 4 can be sufficiently increased, and the positioning of the positive electrode plate 3 is facilitated. In addition, the energy density of the power storage element can be sufficiently increased.

It is preferable that the second welding region A2 has a cut surface, that is, is formed on the outer edge of the separator 4. Since the second welding region A2 has a cut surface, a plurality of wide welding regions are formed in the width direction on the pair of long sheet-like separator base materials, and the wide welding regions are divided into two second widths. By cutting so as to be divided into two welding regions A2, a packaged positive electrode plate in which the positive electrode plate 3 is sandwiched between a pair of separators 4 can be efficiently formed.

In other words, the lower limit of the outer edge of the separator 4, the second welding region A2, and the average interval is preferably 100 μm. On the other hand, the upper limit of the average distance between the outer edge of the separator 4 and the welded areas A1, A2 is preferably 1 mm, and more preferably 0.5 mm. By setting the average distance between the outer edge of the separator 4 and the welding areas A1, A2 to be equal to or less than the upper limit, the rigidity of the outer edge of the separator 4 can be sufficiently increased, and the positive electrode plate 3 can be easily positioned, The energy density of the power storage element can be made sufficiently large.

<Negative electrode plate>
Unlike the positive electrode plate 3, the negative electrode plate 5 is laminated in the laminated electrode body without being covered with a separator 4 or the like in a bag shape.

The negative electrode plate 5 includes a conductive foil-like or sheet-like negative electrode current collector 12 and a negative electrode active material layer 13 laminated on the surface of the negative electrode current collector 12 (a surface facing the positive electrode plate 4). Have. Specifically, the negative electrode plate 5 includes an electrode portion 14 having a polygonal shape (usually rectangular shape) in plan view in which a negative electrode active material layer 13 is laminated on the surface of the negative electrode current collector 12, and the electrode portion 14 to the electrode portion. 14 and a tab 15 extending in a band shape smaller than 14 and electrically connected to the electrode terminal of the power storage element.

In the laminated electrode body 1, all the welding regions A 1 and A 2 of the separator 4 of the positive electrode plate 3 are included inside the electrode portion 14 of the negative electrode plate 5 in a plan view. Therefore, since the electrode portion 8 of the positive electrode plate 3 included inside the welding regions A1 and A2 of the two separators 4 forming a pair is disposed in the projection region of the electrode portion 14 of the negative electrode plate 5, the negative electrode plate The current is not concentrated on the outer edge portion of the five electrode portions 14.

(Negative electrode current collector)
The negative electrode current collector 12 can have the same configuration as the positive electrode current collector 6 described above, but the material is preferably copper or a copper alloy. That is, the negative electrode current collector 12 of the negative electrode plate 5 is preferably a copper foil. Examples of the copper foil include rolled copper foil and electrolytic copper foil.

(Negative electrode active material layer)
The negative electrode active material layer 13 is formed from a so-called negative electrode plate mixture containing a negative electrode active material. Moreover, the negative electrode plate mixture forming the negative electrode active material layer 13 includes optional components such as a conductive agent, a binder (binder), a thickener, and a filler as necessary. The same components as those for the positive electrode active material layer 7 can be used as optional components such as a conductive agent, a binder, a thickener, and a filler.

As the negative electrode active material, a material capable of inserting and extracting lithium ions is preferably used. Specific examples of the negative electrode active material include metals such as lithium and lithium alloys; metal oxides; polyphosphate compounds; carbon materials such as graphite and amorphous carbon (easily graphitizable carbon or non-graphitizable carbon). Can be mentioned.

Among the negative electrode active materials, Si, Si oxide, Sn, Sn oxide, or a combination thereof is used from the viewpoint of setting the discharge capacity per unit facing area between the positive electrode plate 3 and the negative electrode plate 5 to a suitable range. It is preferable to use Si oxide. Si and Sn can have a discharge capacity about three times that of graphite when they are made into oxides.

When Si oxide is used as the negative electrode active material, the ratio of the number of atoms of O to Si contained in the Si oxide is preferably more than 0 and less than 2. That is, as the Si oxide, a compound represented by SiO _x (0 <x <2) is preferable. The ratio of the number of atoms is more preferably 0.5 or more and 1.5 or less.

In addition, the negative electrode active material may be used alone or in combination of two or more. For example, by using a mixture of Si oxide and another negative electrode active material, the discharge capacity per unit facing area between the positive electrode plate 3 and the negative electrode plate 5 and the mass of the negative electrode active material to be described later can be reduced. Both of the mass ratios can be adjusted to be suitable values. Other negative electrode active materials used in combination with Si oxide include carbon materials such as graphite, hard carbon, soft carbon, coke, acetylene black, ketjen black, vapor grown carbon fiber, fullerene, activated carbon and the like. . Only one kind of these carbon materials may be mixed with Si oxide, or two or more kinds may be mixed with Si oxide in an arbitrary combination and ratio. Among these other negative electrode active materials, graphite having a relatively low charge / discharge potential is preferable, and a secondary battery element having a high energy density can be obtained by using graphite. Examples of graphite used by mixing with Si oxide include flaky graphite, spherical graphite, artificial graphite, and natural graphite. Among these, scaly graphite that can easily maintain contact with the surface of the Si oxide particles even after repeated charge and discharge is preferable.

As a minimum of content of Si oxide in a negative electrode active material, 30 mass% is preferred, 50 mass% is more preferred, and 70 mass% is still more preferred. On the other hand, the upper limit of the content of Si oxide is usually 100% by mass, and preferably 90% by mass.

Furthermore, the negative electrode active material layer 13 includes a small amount of typical nonmetallic elements such as B, N, P, F, Cl, Br, and I, Li, Na, Mg, Al, K, Ca, Zn in addition to Si oxide. Typical metal elements such as Ga, Ge, and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ta, Hf, Nb, and W may be contained. .

As the Si oxide (substance represented by the general formula SiO _x ), it is preferable to use a material containing both phases of SiO ₂ and Si. Such Si oxide has a small volume change and excellent charge / discharge cycle characteristics because lithium is occluded and released from Si in the SiO ₂ matrix.

The average particle size of the Si oxide is preferably 1 μm or more and 15 μm or less. By setting the average particle diameter of the Si oxide to the upper limit or less, the charge / discharge cycle characteristics of the power storage element can be improved.

The Si oxide can be used from a highly crystalline one to an amorphous one. Further, as the Si oxide, one washed with an acid such as hydrogen fluoride or sulfuric acid or one reduced with hydrogen may be used.

The lower limit of the content of the negative electrode active material in the negative electrode active material layer 13 is preferably 60% by mass, more preferably 80% by mass, and even more preferably 90% by mass. On the other hand, as an upper limit of content of a negative electrode active material, 99 mass% is preferable and 98 mass% is more preferable. By setting the content of the negative electrode active material particles in the above range, the energy density of the energy storage device can be increased.

The lower limit of the binder content in the negative electrode active material layer 13 is preferably 1% by mass and more preferably 5% by mass. On the other hand, as an upper limit of content of a binder, 20 mass% is preferable and 15 mass% is more preferable. By setting the content of the binder in the above range, the negative electrode active material can be stably held.

[Exterior material]
The exterior material 2 accommodates the laminated electrode body 1 and an electrolyte is enclosed therein.

The material of the exterior material 2 may be any material as long as it has a sealing property capable of enclosing an electrolyte and a strength capable of protecting the laminated electrode body 1, but a metal is preferably used. In other words, it is preferable to use a metal case that can more reliably protect the laminated electrode body 1 as the exterior material 2.

〔Electrolytes〕
As the electrolyte enclosed in the outer packaging material 2, a known electrolytic solution that is usually used for a power storage element can be used. For example, cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), or diethyl A solution in which lithium hexafluorophosphate (LiPF ₆ ) or the like is dissolved in a solvent containing a chain carbonate such as carbonate (DEC), dimethyl carbonate (DMC), or ethyl methyl carbonate (EMC) can be used.

[Other Embodiments]
The said embodiment does not limit the structure of this invention. Therefore, in the above-described embodiment, components of each part of the above-described embodiment can be omitted, replaced, or added based on the description and common general knowledge of the present specification, and they are all interpreted as belonging to the scope of the present invention. Should.

For example, the separator of the laminated electrode body may omit the welding region outside the first side of the four sides of the positive electrode plate where the tab extends.

The laminated electrode body may be one in which one packaged positive electrode plate is sandwiched between a pair of negative electrode plates.

Further, in the laminated electrode body, the heat-resistant layer can be omitted. That is, the laminated electrode body includes a positive electrode plate having a tab protruding from the first side, a resin layer, at least a pair of separators covering the first surface and the second surface of the positive electrode plate, and the separator. A plurality of welded areas in which the at least one pair of separators are welded to each other on the outer peripheral side of the positive electrode plate, and the plurality of welded areas are formed on the first plate of the positive electrode plate. It is also possible to provide a laminated electrode body including a first welding region extending substantially parallel and intermittently with one side and a second welding region extending substantially perpendicularly and continuously to the first side.

The laminated electrode body and the electricity storage device according to the present invention can be particularly suitably used as a power source for equipment that requires a relatively large energy density, such as an electric vehicle and a mobile phone.

DESCRIPTION OF SYMBOLS 1 Laminated electrode body 2 Exterior material 3 Positive electrode plate 4 Separator 5 Negative electrode plate 6 Positive electrode collector 7 Positive electrode active material layer 8 Electrode part 9 Tab 10 Resin layer 11 Heat resistant layer 12 Negative electrode collector 13 Negative electrode active material layer 14 Electrode part 15 Tab A1 First welding area A2 Second welding area S First side

Claims

A positive electrode plate having a tab protruding from the first side;
A resin layer and a heat-resistant layer formed on the resin layer, and at least a pair of separators covering the first surface and the second surface of the positive electrode plate with the heat-resistant layer facing the positive electrode plate;
A negative electrode plate facing the positive electrode plate with the separator interposed therebetween,
A plurality of welding regions where the at least one pair of separators are welded to each other on the outer peripheral side of the positive electrode plate;
The laminated electrode body, wherein the plurality of welding regions include a first welding region that extends substantially parallel and intermittently to the first side of the positive electrode plate, and a second welding region that extends substantially perpendicularly and continuously to the first side. .
The laminated electrode body according to claim 1, wherein the second weld region has a cut surface.
The laminated electrode body according to claim 1 or 2, wherein the at least one pair of separators has a portion having translucency in the welding region, and an average width of the welding region is 10 µm or more and 1000 µm or less.
The laminated electrode body according to claim 1, 2 or 3, wherein the at least one pair of separators includes a fragment of the heat-resistant layer in the welding region.
The laminated electrode body according to any one of claims 1 to 4,
An electricity storage device comprising: an exterior material that houses the laminated electrode body.
The electricity storage device according to claim 5, wherein the exterior material is a metal case.