JP2018081749A - Power storage element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage element which enables the suppression of electrocrystallization.SOLUTION: A power storage element according to an embodiment of the present invention comprises: a case including conductive wall parts; and an electrode body encased in the case and including electrode plates. The wall parts each include a thin portion having a recessed external face. The electrode plates are each welded to an inner face of the corresponding thin portion. A power storage element according to another embodiment of the invention comprises: a case including a conductive wall part; an electrode body encased in the case; and a current collecting member for connecting the electrode body with the wall part. The wall part includes a thin portion having a recessed external face. The current collecting member is welded to an inner face of the thin portion.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power storage element.

  Various power storage elements are used as power sources for various devices, in which an electrode body in which a positive electrode plate and a negative electrode plate are stacked via a separator is accommodated in a case. Among power storage devices, there is a device in which a part of a case is formed of metal and the metal portion is used as a current collecting member and an external terminal for collecting current from an electrode plate.

  In a power storage element that uses the metal part of the case as a current collecting member, it is necessary to connect the electrode plate to the metal part. As a method of connecting the electrode plate to the metal part of the case, a plurality of concave grooves are formed on the inner surface of the metal part, and the end of the electrode plate is fitted to each concave groove from the outer surface side of the metal part. There has been proposed a method of welding an end portion of an electrode plate to a concave groove by irradiating an electron beam or a laser (see JP 2006-172780 A).

JP 2006-172780 A

  In the connection method described in the above publication, since heat is conducted and diffused through the metal part when irradiating an electron beam or the like, an electron beam or the like is used to securely weld the electrode plate to the inner surface of the metal part of the case. The output needs to be relatively large. However, when the output of an electron beam or the like is increased, the case or the electrode plate is locally excessively heated, and metal scraps such as beads and oxides are easily generated. Such metal scraps can cause a short circuit between the electrode plates by generating metal ions on the positive electrode plate and electrodepositing on the negative electrode plate. In addition, heat may be transmitted to the electrode body itself, which may cause deformation or the like.

  In view of the above disadvantages, an object of the present invention is to provide a power storage element in which the influence on the inside of the power storage element due to welding of the electrode plates is suppressed.

  A power storage device according to one embodiment of the present invention includes a case including a conductive wall portion and an electrode body that is housed in the case and includes a plate, and the wall portion includes a thin-walled portion having a concave outer surface. The electrode plate is welded to the inner surface of the thin portion.

  The power storage element according to one embodiment of the present invention can provide a power storage element in which the influence on the inside of the power storage element due to welding of the electrode plates is suppressed.

It is typical sectional drawing which shows the electrical storage element of one Embodiment of this invention. It is a typical perspective view of the electrical storage element of FIG. It is typical sectional drawing which shows the electrical storage element of embodiment different from FIG. 1 of this invention.

  One aspect of the present invention includes a case including a conductive wall portion and an electrode body that is accommodated in the case and includes an electrode plate, and the wall portion includes a thin-walled portion having a concave outer surface. It is an electrical storage element with which the said electrode plate is welded to the inner surface of a thin part.

  In the electricity storage device, the wall portion of the case has a thin-walled portion whose outer surface is concave, and the electrode plate is welded to the inner surface of the thin-walled portion, so that the heat capacity of the thin-walled portion is small and heat for welding is reduced. Difficult to diffuse. For this reason, it is relatively easy to weld the electrode plate to the case without opening a hole in the case. In addition, since the storage element has a small amount of heat required for welding, it is difficult for metal scrap to be generated at the time of welding, so that it is possible to suppress electrodeposition due to generation of metal ions, thereby preventing a short circuit between electrode plates. Can do.

  The end of the electrode plate may extend substantially parallel to the wall and be in surface contact with the inner surface of the thin portion. As described above, the end portion of the electrode plate extends substantially parallel to the wall portion and is in surface contact with the inner surface of the thin portion, so that the thin portion can be welded to the end portion of the electrode plate relatively easily. .

  The electrode body may include a bundle portion in which end portions of the electrode plates are bundled, and the bundle portion may be welded to an inner surface of the thin portion. As described above, the electrode body includes a bundle portion in which the end portions of the electrode plates are bundled, and the bundle portion is welded to the inner surface of the thin portion, whereby a plurality of electrode plates are collectively collected into a thin portion. Therefore, the storage element can be manufactured relatively easily.

  A plate-like member that sandwiches the electrode plate between the thin-walled portion may be further provided. Thus, by further providing a plate-like member that sandwiches the electrode plate between the thin part and the thin part, the electrode plate can be reliably brought into contact with the thin part, so that the thin part and the electrode plate are welded. It can be made more reliable.

  The average thickness of the part which overlaps with the said thin part of the said plate-shaped member is good in it being more than the average thickness of the said thin part. Thus, when the thickness of the portion of the plate-like member that overlaps the thin portion is equal to or greater than the average thickness of the thin portion, when the thin portion and the electrode plate are subjected to electric resistance welding, the thin portion Since the welding current supplied from the outer surface side of the steel plate easily flows through the plate member without bypassing the wall portion, welding between the thin wall portion and the electrode plate can be made more reliable.

  The case has a lid including the wall portion and a cylindrical main body whose opening is sealed by the lid, and the plate-like member is sandwiched between an end surface of the main body and the lid. Good. Thus, the case has a lid body including the wall portion and a cylindrical main body whose opening is sealed by the lid body, and the plate-shaped member is between the end surface of the main body and the lid body. Since the end of the electrode plate can be brought into pressure contact with the lid relatively easily by the plate member, the thin-walled portion and the electrode plate can be more reliably welded.

  Another aspect of the present invention includes a case including a conductive wall, an electrode body housed in the case, and a current collecting member that connects the electrode body and the wall, and the wall Is an electricity storage element in which the outer surface has a concave thin portion, and the current collecting member is welded to the inner surface of the thin portion.

  In the electric storage element, the wall portion of the case has a thin-walled portion whose outer surface is concave, and the current collecting member is welded to the inner surface of the thin-walled portion, so that the heat capacity of the thin-walled portion is small and heat for welding is reduced. Difficult to diffuse. For this reason, since the said electrical storage element is hard to produce | generate a metal scrap at the time of welding, it can suppress the electrodeposition by the production | generation of a metal ion, and can prevent the short circuit between electrode plates by this.

  The thin wall portion may be provided in the vicinity of the end portion in the longitudinal direction of the wall portion. As described above, since the thin portion is provided in the vicinity of the end portion in the longitudinal direction of the wall portion, the wall portion in the vicinity of the thin portion bends even if the thin portion is pressed from the outside by a welding electrode or the like during welding. Since it is difficult, welding between the thin wall portion and the electrode plate is relatively reliable.

  The wall portion may include a plurality of the thin wall portions. Thus, when the said wall part contains the said some thin part, a pair of welding electrode can be contact | abutted to two thin parts, and it can carry out electrical resistance welding at once.

  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.

[First embodiment]
The power storage element according to the first embodiment of the present invention shown in FIGS. 1 and 2 includes a case 1 and an electrode body 2 accommodated in the case 1.

  The case 1 includes a cylindrical case body 3 and a pair of lids (a positive electrode lid body 4 and a negative electrode lid body 5) that seal the openings at both ends of the case body 3. In the case 1, an electrolyte is enclosed together with the electrode body 2. The electrolyte may be a liquid or a solid.

  On the other hand, the electrode body 2 includes a plurality of electrode plates (a positive electrode plate 6 and a negative electrode plate 7) and a plurality of separators 8 interposed between the electrode plates 6 and 7.

<Case body>
The case body 3 protects the electrode body 2 accommodated in the case 1. The case body 3 may be made of any material as long as it has strength. For example, resin, metal, or the like can be used. However, when the case main body 3 is formed of a conductive material, for example, an insulating packing is disposed between the positive electrode cover body 4 and the negative electrode cover body 5. It may be necessary to insulate between the two.

  The cross-sectional shape of the case body 3 may be a square shape (preferably a rectangular shape with rounded corners) or an oblong shape.

<Cover body>
The lid bodies 4 and 5 include a substantially cylindrical body portion 9 fitted to an end portion of the case body 3 and a conductive wall portion 10 that seals an opening of the body portion 9, and at least the wall portion 10. Is used as an electric circuit or an external terminal for electrically connecting the electrode body 2 and the outside. Accordingly, the lids 4 and 5 are formed of a material in which at least the wall portion 10 has conductivity. Although the trunk | drum 9 and the wall part 10 may be integrally formed from the same material, for example, the trunk | drum 9 formed with the material which has insulation, such as resin, is made from the material which has electroconductivity, such as a metal. The lid bodies 4 and 5 can be formed by joining the plate-like wall portions 10 to be formed.

  As the metal forming the wall portion 10, for example, aluminum, iron, stainless steel, copper, or the like is used. However, a material that can easily weld the end portions of the electrode plates 6 and 7, which will be described later, may be selected. Moreover, when forming the wall part 10 with the metal which has a possibility of rust and corrosion, such as iron, you may plate with nickel etc., for example.

  The planar shape of the wall portion 10 is preferably substantially equal to the cross-sectional outer shape on a plane parallel to the wall portion 10 of the case body 3 and is typically rectangular.

  The wall portion 10 has a thin-walled portion 11 having a concave outer surface, and the end portions of the electrode plates 6 and 7 are welded to the inner surface of the thin-walled portion 11. More specifically, the end portions of the plurality of positive electrode plates 6 are welded to the inner surface of the thin wall portion 11 of the positive electrode lid body 4, and the end portions of the plurality of negative electrode plates 7 are welded to the inner surface of the thin wall portion 11 of the negative electrode lid body 5. Are welded. The thin portion 11 has a smaller dimension in the thickness direction than the periphery of the thin portion in the wall portion.

  Further, it is preferable that a plurality of the thin portions 11 are formed on each wall portion 10. By forming a plurality of thin portions 11 on each wall portion 10, the wall portion 10 and the positive electrode plate 6 or the negative electrode plate 7 can be more reliably connected. Moreover, when the wall part 10 has the some thin part 11, when carrying out the electrical resistance welding of the edge part of the electrode plates 6 and 7 to the thin part 11, it makes a pair of welding electrodes contact | abut to the different thin part 11 The end portions of the positive electrode plate 6 can be welded to the two thin portions 11 at the same time.

  As a minimum of the average thickness of the part except the thin part 11 of the wall part 10, 0.5 mm is preferable and 1.0 mm is more preferable. On the other hand, the upper limit of the average thickness of the wall portion 10 excluding the thin portion 11 is preferably 3 mm, and more preferably 2 mm. By making the average thickness of the portion of the wall portion 10 excluding the thin portion 11 equal to or more than the above lower limit, the strength of the wall portion 10 can be prevented from becoming insufficient. Conversely, the thin portion 11 of the wall portion 10 is excluded. By setting the average thickness of the portion to be equal to or less than the above upper limit, it is possible to prevent the thin portion 11 from being easily processed and prevent the storage element from being unnecessarily enlarged.

  As a minimum of average thickness of thin part 11, 0.2 mm is preferred and 0.3 mm is more preferred. On the other hand, the upper limit of the average thickness of the thin portion 11 is preferably 2/3 of the average thickness of the wall portion 10 excluding the thin portion 11 and more preferably 1/2. By setting the average thickness of the thin portion 11 to be equal to or more than the above lower limit, it is possible to prevent a hole from being formed in the thin portion 11 when the electrode plates 6 and 7 are welded and to prevent the strength of the thin portion 11 from being insufficient. On the contrary, by making the average thickness of the thin portion 11 equal to or less than the above upper limit, it is possible to prevent welding of the electrode plates 6 and 7 from being promoted.

  The planar shape of the thin portion 11 is preferably a shape having a relatively small aspect ratio (ratio of length to width) and no corners. By reducing the planar aspect of the thin portion 11, the effect of suppressing heat dissipation during welding of the thin portion 11 and the electrode plates 6 and 7 with respect to the area of the thin portion 11 becomes relatively large. Moreover, since the planar shape of the thin part 11 does not have a corner | angular shape, while the strength reduction of the wall part 10 is suppressed, formation of the thin part 11 becomes comparatively easy.

  As a minimum of a circle equivalent diameter of a plane shape of thin part 11, 2 mm is preferred and 3 mm is more preferred. On the other hand, the upper limit of the equivalent circular diameter of the planar shape of the thin portion 11 is preferably 30 mm, and more preferably 20 mm. By setting the equivalent circle diameter of the planar shape of the thin portion 11 to be equal to or greater than the above lower limit, heat is likely to escape to the outside of the thin portion 11 when welding the thin portion 11 and the electrode plates 6 and 7, so that welding is uncertain. Can be prevented. On the contrary, the strength of the wall portion 10 can be prevented from being unnecessarily reduced by setting the planar equivalent circle diameter of the thin portion 11 to be equal to or less than the above upper limit.

  As a minimum of the minimum curvature radius of the plane shape of thin part 11, 0.5 mm is preferred and 1.0 mm is more preferred. On the other hand, the upper limit of the minimum curvature radius of the planar shape of the thin portion 11 is preferably 10 mm, and more preferably 5 mm. By making the minimum curvature radius of the planar shape of the thin portion 11 equal to or more than the lower limit, it is possible to prevent the strength of the wall portion 10 from being unnecessarily lowered due to stress concentration. On the contrary, the planar shape of the thin part 11 becomes comparatively free by making the minimum curvature radius of the planar shape of the thin part 11 below the upper limit.

  The thin portion 11 preferably has a substantially constant thickness, but the thickness may continuously increase at the peripheral portion so as to relieve stress concentration.

  The thin portion 11 is preferably formed in the vicinity of the end portion of the wall portion 10 in the longitudinal direction, specifically within the range of 1/3 or less of the length from the end portion in the longitudinal direction. When the wall 10 is rectangular, the upper limit of the distance from the longitudinal end of the wall 10 at the center of the thin portion 11 is preferably 1 times the width of the wall 10 in the short direction, 0.5 Double is more preferred. When the distance from the longitudinal end of the wall portion 10 at the center of the thin portion 11 is less than or equal to the above upper limit, when the thin portion 11 and the electrode plates 6 and 7 are electrically resistance welded, the welding electrode is applied to the thin portion 11. Can be prevented from being incompletely welded due to instability of the contact body with the electrode plates 6 and 7.

  The thin portion 11 can be formed by, for example, cutting or pressing.

<Positive electrode plate>
The positive electrode plate 6 has a conductive foil-like or sheet-like positive electrode current collector and a positive electrode active material layer laminated on the surface of the positive electrode current collector. Specifically, the positive electrode plate 6 has a rectangular electrode part in which a positive electrode active material layer is laminated on the surface of the positive electrode current collecting base material, and extends from the electrode part into a strip shape having a width smaller than the electrode part. The connecting portion forming the end portion of the positive electrode plate 6 connected to the thin portion 11 of the positive electrode lid 4 can be used.

  Connection portions of the plurality of positive electrode plates 6 are bundled to form one bundle portion. That is, the connecting portions of the plurality of positive electrode plates 6 are overlapped with each other and integrally welded to the inner surface of the thin portion 11. Specifically, the connecting portion of the positive electrode plate 6 that forms the bundle portion is disposed so as to extend substantially parallel to the wall portion 10 of the positive electrode lid body 4 and to be in surface contact with the inner surface of the thin portion 11. For this reason, the connection part of the positive electrode plate 6 can be relatively reliably welded to the thin part 11.

  Moreover, in order to arrange the connection part of the positive electrode plate 6 in this way, the electric storage element further includes a plate-like member 12 that sandwiches the connection part of the positive electrode plate 6 between the thin part 11 as shown in the figure. It is good to be. The plate-like member 12 is preferably sandwiched between the end surface of the case body 3 and the lid body 4, and is more preferably disposed so as to contact the end surfaces of at least two side surfaces of the case body 3 having a rectangular cross section. preferable. By sandwiching the plate-like member 12 between the case main body 3 and the lid body 4 in this way, the connecting portion of the positive electrode plate 6 can be reliably pressed against the inner surface of the thin portion 11 by the plate-like member 12. The plate-like member 12 is welded to the thin portion 11 together with the connecting portion of the positive electrode plate 6, and prevents the thin portion 11 from opening a hole.

  The plate member 12 is preferably arranged so as to overlap the plurality of thin portions 11. One plate-like member 12 is arranged across a plurality of thin-walled portions 11, so that a pair of welding electrodes are brought into contact with the outer sides of the two thin-walled portions 11, thereby allowing one thin-walled portion to flow. 11 and the current passing through the connecting portion of the positive electrode plate 6 in the thickness direction pass through the plate-like member 12 and pass through the connecting portion and the thin portion of the other positive electrode plate 6 in the thickness direction. Therefore, the connection part of the positive electrode plate 6 can be welded to each of the two thin parts 11 by one energization.

  As a minimum of the average thickness of the part which overlaps with thin part 11 of tabular member 12, 1.0 times the average thickness of thin part 11 is preferred, and 1.5 times is more preferred. On the other hand, the upper limit of the average thickness of the portion overlapping the thin portion 11 of the plate-like member 12 is preferably three times the average thickness of the portion excluding the thin portion 11 of the wall portion 10 and more preferably twice. By making the average thickness of the portion of the plate-like member 12 that overlaps the thin portion 11 equal to or more than the above lower limit, the effect of suppressing the opening of the thin portion 11 during welding may be small, or it functions as an electric current path for welding current. Therefore, it is possible to prevent electric resistance welding from becoming difficult. Conversely, by setting the average thickness of the portion overlapping the thin portion 11 of the plate-like member 12 to the upper limit or less, the heat at the time of welding is dissipated so that the connection between the connection portion of the positive electrode plate 6 and the thin portion 11 is performed. Incompleteness can be prevented.

(Positive electrode current collector)
As a material of the positive electrode current collector base, 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 a positive electrode current collection base material, foil, a vapor deposition film, etc. are mentioned, A foil is preferable from the surface of cost. That is, an aluminum foil is preferable as the positive electrode current collecting base material. 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 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 is preferably 50 μm, more preferably 40 μm. By setting the average thickness of the positive electrode current collecting base material to the above lower limit or more, it is possible to prevent the strength of the positive electrode current collecting base material from becoming insufficient. Conversely, by setting the average thickness of the positive electrode current collector base material to be equal to or lower than the above upper limit, the thickness of the bundle of positive current collector base materials is increased, so that all the positive electrode plates 6 are welded to the thin portion 11. Can be prevented from becoming easy.

(Positive electrode active material layer)
The positive electrode active material layer 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 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 composite oxides represented by Li _x MO _y (M represents at least one transition metal) (Li _x CoO ₂ , Li _x NiO ₂ , Li _x Mn ₂ O ₄ , Li _{x 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 , etc.), 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, 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.

  As a minimum of content of the positive electrode active material in a positive electrode active material layer, 50 mass% is preferable, 70 mass% is more preferable, and 80 mass% is further more preferable. 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 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.

  As a minimum of content of a binder in a cathode active material layer, 1 mass% is preferred and 2 mass% is more preferred. 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.

<Negative electrode plate>
The negative electrode plate 7 has a conductive foil-shaped or sheet-shaped negative electrode current collector and a negative electrode active material layer laminated on the surface of the negative electrode current collector. Specifically, the negative electrode plate 7 extends in a rectangular shape in plan view in which a negative electrode active material layer is laminated on the surface of the negative electrode current collector base material, and extends from this electrode portion into a strip shape having a width smaller than the electrode portion. And a connection part that forms an end of the negative electrode plate 7 connected to the thin part 11 of the negative electrode cover 5.

  The connection of the connection portions of the plurality of negative electrode plates 7 to the thin wall portion 11 of the wall portion 10 of the negative electrode lid body 5 is connected to the thin wall portion 11 of the wall portion 10 of the positive electrode cover body 4 of the connection portion of the plurality of positive electrode plates 6. And can be similar.

(Negative electrode current collector)
The negative electrode current collecting base material can have the same configuration as the above-described positive electrode current collecting base material, but the material is preferably copper or a copper alloy. That is, the negative electrode current collector base material of the negative electrode plate 7 is preferably a copper foil. Examples of the copper foil include rolled copper foil and electrolytic copper foil.

  Since copper has a relatively high thermal conductivity and is not easily welded by laser, when the negative electrode current collector base material is formed of copper, the plate-like member 12 is arranged to connect the connection part of the negative electrode plate 7 with two thin walls. It is preferable to perform electrical resistance welding to the part 11 simultaneously.

(Negative electrode active material layer)
The negative electrode active material layer 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 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 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 6 and the negative electrode plate 7 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.

  As the negative electrode active material, those described above may be used singly 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 6 and the negative electrode plate 7 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 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, Typical metal elements such as Ga and 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 one 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 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.

  As a minimum of content of a negative electrode active material in a negative electrode active material layer, 60 mass% is preferred, 80 mass% is more preferred, and 90 mass% is still more preferred. 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.

  As a minimum of content of a binder in a negative electrode active material layer, 1 mass% is preferred and 5 mass% is more preferred. 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.

<Separator>
The separator 8 is formed from a porous resin film.

  Examples of the main component of the separator 8 include polyolefin derivatives such as polyethylene (PE), polypropylene (PP), ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, and chlorinated polyethylene. Polyolefins such as ethylene-propylene copolymers, polyesters such as polyethylene terephthalate and copolymerized polyesters, cupra rayon, regenerated cellulose, and cellulose can be employed. Among these, as the main component of the separator 8, polyethylene and polypropylene excellent in electrolyte 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 separator 8 is preferably 0.5 μm, and more preferably 1 μm. On the other hand, the upper limit of the average thickness of the separator 8 is preferably 100 μm, and more preferably 50 μm. By making the average thickness of the separator 8 equal to or more than the above lower limit, it is possible to prevent the separator 8 from breaking during welding. Conversely, by setting the average thickness of the separator 8 to be equal to or less than the above upper limit, it is possible to prevent the capacity per unit volume of the power storage element from being reduced due to an unnecessarily increased thickness of the separator 8.

  Moreover, it is preferable that the separator 8 is laminated | stacked on the surface facing a positive electrode with the heat resistant layer which improves heat resistance. The heat-resistant layer can include a large number of inorganic particles and a binder that connects the inorganic particles.

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

  As a main component of the binder of the heat-resistant layer, for example, fluororesin such as polyvinylidene fluoride and polytetrafluoroethylene, fluororubber such as vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, styrene-butadiene copolymer 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 ester copolymer, carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC), cellulose derivatives such as ammonium salt of carboxymethylcellulose, polyetherimide, polyester Polyimides such as amide imide, polyamide and precursors thereof (polyamic acid, etc.), 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, polyethersulfone, polyphenylene sulfide, polyester, etc.

<Advantages>
The electric storage element can be welded with a relatively small amount of heat because the welded portion has a relatively small heat capacity by welding the connecting portion of the electrode plates 6 and 7 to the thin portion 11 of the wall portion 10. The risk of opening a hole in the wall 10 is small. Further, since the power storage element requires a relatively small amount of heat for welding, metal scraps are less likely to be generated during welding, and electrodeposition due to metal scraps can be prevented.

[Second Embodiment]
The power storage element according to the second embodiment of the present invention shown in FIG. 3 includes a case 1a and an electrode body 2 accommodated in the case 1a. The configuration of the electrode body 2 in the power storage element of FIG. 3 can be the same as the configuration of the electrode body 2 in the power storage element of FIG. For this reason, with respect to the power storage element of FIG. 3, the same components as those of the power storage element of FIG.

<Case>
The case 1a is formed of a conductive material and includes a bottomed cylindrical case body 3a and a negative electrode lid 5 that seals the opening of the case body 3a. In the case 1a, an electrolyte solution is sealed together with the electrode body 2. In the energy storage device of FIG. 3, the case body 3a is used as a positive electrode external terminal. The configuration of the negative electrode lid 5 in the case 1a of FIG. 3 can be the same as the configuration of the negative electrode lid 5 in the case 1 of FIG.

(Case body)
The case main body 3a has a thin-walled portion 11a having a concave outer surface in a portion near the bottom of a wall portion 10a that forms a side wall of a cylindrical portion, for example, a square-shaped cross-section. The connecting portion of the positive electrode plate 6 is welded to the inner surface of the plate.

  The configuration of the thin portion 11a can be the same as that of the thin portion 11 of the wall portion 10 of the negative electrode lid 5 (as a result, the thin portion 11 of the positive electrode lid 4 in the case 1 of FIG. 1).

  In addition, as shown in FIG. 3, the power storage element may include a plate-like member 12 a that is opposed to the thin body 11 a of the case body 3 a and the connecting portion of the positive electrode plate 6. The shape and material of the plate-like member 12a can be the same as the shape and material of the plate-like member 12 of FIG.

  Further, in the electricity storage element, a current collecting member 13 formed of a conductive material is welded to the inner surface of the thin portion 11 of the wall portion 10 of the negative electrode lid 5. A connecting portion of the negative electrode plate 7 is connected to the current collecting member 13. That is, in the power storage element, the plurality of negative electrode plates 7 are connected to the wall portion 10 of the negative electrode lid 5 via the current collecting member 13.

  The current collector 13 is welded to the thin portion 11 by, for example, laser irradiation from the outside of the thin portion 11, electric resistance welding in which an electrode is in contact with the outside of the thin portion 11, or the like. The connection of the connecting portion of the negative electrode plate 7 to the current collecting member 13 can be performed by, for example, ultrasonic welding, laser welding, electric resistance welding, caulking, screwing, soldering, or the like.

[Other Embodiments]
The said embodiment does not limit the structure of this invention. Therefore, in the above-described embodiment, the 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.

  In the power storage element, the configuration in which the end portion of the electrode plate is welded to the thin portion formed on the wall portion of the case may be applied to only one of the positive electrode side and the negative electrode side.

  In the power storage element, the plate member may be omitted.

  In the electric storage element, welding to the thin portion at the end of the electrode plate may be performed from the inside of the case. For example, the end portion of the electrode plate may be welded to a thin wall portion formed on the wall portion of the case body or the lid before the case body is sealed with the lid.

  The electrode body of the power storage element is not limited to a laminated type in which a plurality of positive and negative electrode plates are stacked, and may be a wound type in which a laminated body of a long electrode plate and a separator is wound up, for example.

  In the power storage device, the end of the electrode plate may be connected to the inner surface of the thin portion formed on the wall portion of the case body by disengaging the current collecting member.

  In the said embodiment, although the example which comprised the cover body as an external terminal was shown, the said electrical storage element may have an external terminal which protrudes to a case outer surface, for example. In this case, the external terminal protruding to the outside may be either one of the positive terminal and the negative terminal, or both external terminals. The external terminal is electrically connected to the electrode body through the wall portion.

  In the power storage element, at least one of the thin portion and the plate-like member may have a protrusion on the surface facing the electrode plate. Since the protrusion increases the electrical resistance by relatively reducing the contact area, the amount of heat generated is increased when resistance welding is performed, and the weldability with the electrode plate can be improved.

  The electric storage element according to the present invention can constitute an assembled battery including a plurality of the electric storage elements.

  The electric storage element according to the embodiment of the present invention can be suitably used for an electric storage element that welds a part of a case and an electrode plate.

DESCRIPTION OF SYMBOLS 1, 1a Case 2 Electrode body 3 and 3a Case main body 4 Positive electrode cover body 5 Negative electrode cover body 6 Positive electrode plate 7 Negative electrode plate 8 Separator part 9 10, 10a Wall part 11, 11a Thin part 12, 12a Plate-shaped member 13 Current collection Element

Claims (9)

A case including a conductive wall;
An electrode body housed in the case and including an electrode plate,
An electricity storage element in which the wall portion has a thin-walled portion with an outer surface recessed, and the electrode plate is welded to the inner surface of the thin-walled portion.   The power storage element according to claim 1, wherein an end portion of the electrode plate extends substantially parallel to the wall portion and is in surface contact with an inner surface of the thin portion. The electrode body includes a bundle portion in which end portions of the electrode plates are bundled,
The electric storage element according to claim 1, wherein the bundle portion is welded to an inner surface of the thin portion.   The electric storage element according to claim 1, further comprising a plate-like member that sandwiches the electrode plate between the thin portion.   The electric storage element according to claim 4, wherein an average thickness of a portion of the plate-like member overlapping the thin portion is equal to or greater than an average thickness of the thin portion. The case includes a lid including the wall portion, and a cylindrical main body whose opening is sealed by the lid,
The electric storage element according to claim 4 or 5, wherein the plate-like member is sandwiched between an end face of the main body and a lid. A case including a conductive wall;
An electrode body housed in the case;
A current collecting member for connecting the electrode body and the wall,
An electricity storage element in which the wall portion has a thin-walled portion whose outer surface is concave and the current collecting member is welded to the inner surface of the thin-walled portion.   The power storage element according to any one of claims 1 to 7, wherein the thin portion is provided near an end portion in a longitudinal direction of the wall portion.   The electricity storage device according to any one of claims 1 to 8, wherein the wall portion includes a plurality of the thin portions.

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