JP5812884B2 - Secondary battery - Google Patents

Description

  The present invention relates to a secondary battery.

  Secondary batteries are often used in portable electronic devices such as mobile phones and notebook PCs. As these devices become smaller and lighter, secondary batteries with higher energy density are required. In particular, lithium ion secondary batteries have become widespread because of their high energy density.

  Since the conventional flat-type secondary battery has a structure in which a current collector is laminated with electrodes and separators, positional deviation between the electrodes occurs during assembly of the power generation element and the battery, and the required battery capacity cannot be obtained, There was a risk that dendrite-like Li metal was deposited on the negative electrode at the misaligned portion to deteriorate the performance, and further, short-circuited and ignited. Further, when the power generation element is incorporated into the laminate film, there is a problem that liquid leakage or the like is likely to occur due to a sealing failure due to occurrence of positional deviation between the electrodes.

  In order to suppress the occurrence of such misalignment, for example, Patent Document 1 proposes a flat plate electrochemical cell in which a positive electrode and a negative electrode are fixed to an exterior body so as to be close to each other, and the exterior body is bent and sealed. ing.

JP 2005-071658 A

  However, the structure as in Patent Document 1 cannot be applied to a case where a highly accurate device is required to accurately align the positive electrode and the negative electrode through the separator, or when a plurality of positive electrodes and negative electrodes are stacked. There was a problem such as.

  An object of the present invention is to provide a secondary battery that can be accurately aligned with a positive electrode and a negative electrode without requiring a highly accurate device, and can be applied to a structure in which a plurality of positive electrodes and negative electrodes are laminated. And

Secondary battery of the present invention includes a first electrode, and the power generating element of the laminated type having a second electrode and a nonaqueous electrolyte, a first current collector, a second collector, said first the power generating element and said in a recess provided in the first current collector the second current collector is housed, an opening is provided on at least one side surface among the side surfaces along the stacking direction of the power generating element of said recess It is characterized by.

  According to the present invention, it is possible to provide a secondary battery that can be accurately aligned with a positive electrode and a negative electrode without requiring a highly accurate device, and can be applied to a structure in which a plurality of positive electrodes and negative electrodes are laminated.

1A is a perspective view schematically showing a secondary battery according to a first embodiment of the present invention, and FIG. 2B is a cross-sectional view taken along line A-A ′ in FIG. 4A is a perspective view schematically showing a secondary battery according to a second embodiment of the present invention, and FIG. 5B is a cross-sectional view taken along line B-B ′ in FIG. It is the side view which looked at the secondary battery of Fig.2 (a) from the y-axis positive direction side. It is sectional drawing perpendicular | vertical to the x-axis which showed typically the secondary battery which is 3rd Embodiment of this invention. It is the side view which looked at the secondary battery of FIG. 4 from the y-axis positive direction side.

  The secondary battery which is 1st Embodiment of this invention is demonstrated based on FIG. In the secondary battery of the present embodiment, the first current collector 5 is provided with a power generation element 4 in which a first electrode 1, a separator 3 containing an organic electrolyte, and a second electrode 2 are laminated in this order. The second current collector 7 is disposed so as to cover the recess 6 and the power generation element 4 stored therein. Connection terminals 8 and 9 are attached to the first current collector 5 and the second current collector 7 by ultrasonic welding or spot welding, respectively.

  As described above, since the power generation element 4 is housed in the recess 6 of the first current collector 1 having an opening capable of housing the first electrode 1 and the second electrode 2, a highly accurate device can be obtained. Even if it does not use, alignment of electrodes becomes easy and the possibility of position shift at the time of assembling a secondary battery can also be reduced. In addition, the separator 3 is larger than the opening part of the recessed part 6, The peripheral part is between the 1st electrical power collector 5 and the 2nd electrode 2, and the peripheral part of the recessed part 6 of the 1st electrical power collector 5 By being positioned between the second current collector 7 and the peripheral portion, the first current collector 5 is electrically insulated from the second electrode and the second current collector 7.

  In addition, when the 2nd electrode 2 has electroconductivity, the connection terminal 9 may be directly connected to the 2nd electrode 2, and the 2nd electrical power collector 7 does not need to be used in this case.

  At this time, the shape of the opening and bottom surface of the recess 6 provided in the first current collector 5 is similar to the shape of the first electrode 1 and the second electrode 2, and the bottom surface of the recess 6 is defined as the first electrode. The first electrode 1, the separator 3, and the second electrode 2 are made slightly larger than the main surfaces of the first electrode 2 and the second electrode 2, for example, in the range of about 20 to 100 μm, which is equivalent to the thickness of the separator 3. When housed in, the electrodes can be more accurately aligned. Further, the size of the second electrode 2 may be smaller than that of the first electrode 1, but the size of the opening of the recess 6 is slightly larger than the size of the bottom surface of the recess 6, for example, the thickness of the separator 3. By enlarging within the equivalent range of about 20 to 100 μm, the first electrode 1 and the second electrode 2 can have the same size, and the capacity of each electrode can be used efficiently.

  Only the first electrode 1 is accommodated in the recess 6 of the first current collector 5, and the separator 3 having a larger area than the opening of the recess 6 and the second so as to cover the recess 6 and the first electrode 1. The electrode 2 and the second current collector 7 may be disposed. In this case, the separator 3 is located between the first current collector 5 and the first electrode 1 and the second electrode 2, and may not be in contact with the second current collector 7. Good. In addition, it is preferable that the size of the separator 3 is equal to or larger than the size of the first current collector 5 and the second current collector 7 from the viewpoint of preventing short circuit between the current collectors. The separator 3 may protrude from the peripheral portions of the first current collector 5 and the second current collector 7.

  The first current collector 5 is provided with a recess 6 and the second current collector 7 is provided with a recess 6 ′. The recess 6 in which the first electrode 1 is stored and the recess in which the second electrode 2 is stored. The first current collector 5 and the second current collector 7 may be overlapped so that 6 'faces the separator 3 via the separator 3. Also in this case, the electrodes can be easily aligned by aligning the recesses of the current collectors.

The shape of the concave portion 6 may be appropriately designed according to the shape of the electrode for obtaining a desired battery capacity, and may be, for example, a shape of 500 × 500 mm and a depth of 10 mm.

  In the second embodiment of the present invention, as shown in FIG. 2, the second current collector 7 in which the second electrode 2 is provided on both main surfaces is provided via the separator 3 containing an organic electrolyte. A power generation element 4 including a second current collector 7 is formed by being sandwiched between two layers of one electrode 1 and 1 ′. The first current collector comprises a first current collector 5 having a recess 6 and a first current collector 5 ′ having no recess, and the recess 6 of the first current collector 5 is: An opening is provided on one of the side surfaces along the stacking direction of the power generation elements 4 housed therein. The power generation element 4 is housed in the recess 6 so that the second electrode 2 and the second current collector 7 do not contact the side surface of the recess 6 of the first current collector 5, and further the first current collector 5 'is disposed so as to cover the recess 6 and the power generation element 4 housed therein, and the peripheral edge of the recess 6 of the first current collector 5 is directly or via a conductive material. It overlaps with the peripheral edge of the body 5 '. Connection terminals 8 and 9 are attached to the first current collector 5 or 5 ′ and the second current collector 7 by ultrasonic welding, spot welding, or the like, respectively, and attached to the second current collector 7. The connection terminal 9 is drawn out from an opening provided on the side surface of the recess 6 of the first current collector 5.

  At this time, the shape of the opening and bottom surface of the recess 6 provided in the first current collector 5 is similar to that of the first electrode 1, 1 ′ and the second electrode 2, and the bottom surface of the recess 6 is the first. The first electrode 1, 1 ′, the separator 3 and the second electrode 2 are slightly larger than the main surfaces of the electrode 1 and the second electrode 2, for example, in the range of about 20 to 100 μm, which is equivalent to the thickness of the separator 3. When the second current collector 7 having the electrodes 2 provided on both main surfaces is accommodated in the recess 6, the electrodes can be more accurately aligned without using a high-accuracy device as in the first embodiment. It can be carried out. At this time, the second current collector 7 provided with the second electrode 2 on both main surfaces is covered with the separator 3 so as not to come into contact with the side surface of the recess 6, or on the bag-like separator 3. It is preferable to be accommodated in the recess 6 in the inserted state. The separator 3 may protrude from the opening provided on the side surface of the recess 6, but the first electrodes 1, 1 ′ and the second electrode 2 are provided from the opening provided on the side surface of the recess 6. It is preferable not to protrude.

  In the third embodiment of the present invention, a plurality of the second current collectors 7 and the power generating elements 4 housed in the recess 6 of the first current collector 5 in the second embodiment are stacked, and the end is located at the end. The first current collector 5 does not have a recess so as to cover the opening of the recess 6 that is not covered with the other first current collector 5 and the power generation element 4 housed therein. A first current collector 5 ′ is arranged.

  At this time, the connection terminals 9 individually connect the connection terminals 9 to the second current collectors 7 or the second electrodes 2 of the power generation elements 4, and the group of connection terminals 9 is connected to the first current collector 5. What is necessary is just to draw | extract out from the opening part provided in the side surface of the recessed part 6, and bundle and to connect by ultrasonic welding or spot welding. In addition, the connection terminal 8 is connected to the first current collector 5 in which the power generation element 4 and the second current collector 7 are housed individually, and the connection terminal 8 group is bundled and superposed. The connection terminal 8 may be connected to any one of the first current collectors 5 and 5 'electrically connected to each other by sonic welding or spot welding.

  As shown in the first to third embodiments, the power generation element 4 with the current collector and the connection terminal is housed in a can or a laminate film that is an exterior body, and a nonaqueous electrolyte solution is injected as necessary. By sealing the outer package, a secondary battery is obtained.

In any of the embodiments, by applying pressure from both the first current collector 5 side and the second current collector 7 or the first current collector 5 ′ side, each current collector is provided. Between the first electrode 1 (and 1 ') and the second electrode 2 is reduced, the electrical resistance between the electrodes is reduced, and the battery performance is improved. . This is particularly effective when a sintered body containing an active material is used for one or both of the first electrode 1 (and 1 ') and the second electrode 2. In the case where a sintered body containing an active material is used as an electrode, Pt, Au, Al, etc. are formed on the contact portion of the sintered body with the current collector in order to improve the conductivity between the sintered body and the current collector. May be deposited or a conductive adhesive may be applied.

  The recess 6 may be formed by press-molding a metal foil or a conductive material serving as a current collector. In particular, it is preferable to use a metal foil in terms of conductivity and easy formation of the recess 6.

  As a material of the current collector disposed on the positive electrode side of the power generating element 4, a material including a metal having corrosion resistance that does not generate a reaction such as dissolution at the potential of the positive electrode, such as aluminum, tantalum, niobium, titanium, gold, platinum, or the like. Can be used. Among these, aluminum, gold, and platinum are preferable because they are excellent in corrosion resistance and easily available. Aluminum is particularly preferable because it is passivated by forming an oxide film on the surface and excellent in corrosion resistance even at a high potential.

  In addition, as a material of the current collector disposed on the negative electrode side, a metal that does not cause side reactions such as alloying with a metal (such as Li) that is an ionic conductor at the potential of the negative electrode, such as copper, nickel, brass, A material containing zinc, aluminum, stainless steel, tungsten, gold, platinum or the like may be used, and stainless steel, copper, gold, platinum, or the like having high strength when used as a foil is preferable. In particular, it is preferable to use copper or nickel from the viewpoint of high conductivity and relatively low cost.

  The thicknesses of the first current collector 5 (and 5 ') and the second current collector 7 are not particularly limited as long as they can be handled without damage in the battery manufacturing process, and may be in the range of, for example, 5 μm to 100 μm.

  In order to ensure electrical connection between the electrode and the current collector, when using a conductive adhesive, for example, conductivity such as gold, silver, nickel, zinc oxide, tin oxide, indium oxide, titanium oxide, and titanium kalim oxide. A mixture composed of a filler and a polymer adhesive such as an acrylic resin, an epoxy resin, a silicon resin, a polyamide resin, a phenol resin, a polyester resin, or a polyimide resin can be used. The thickness of the conductive adhesive is 10 μm or less in order to secure the thickness of the power generation element 4 that can obtain a sufficient energy density as a secondary battery and to minimize the electric resistance due to the conductive adhesive. It is desirable to do.

  Examples of the first electrode 1 (and 1 ′) and the second electrode 2 include a positive electrode active material or negative electrode active material particles hardened with a binder, and a green compact made of a positive electrode active material or a negative electrode active material. And a sintered compact can be used. In particular, it does not contain conductive additives, binders, solid electrolytes, etc. that are not directly related to power generation, and can further increase the filling ratio of the positive electrode active material and the negative electrode active material, thereby obtaining a secondary battery with higher energy density. Therefore, it is preferable to use a sintered body.

  What is necessary is just to produce in the following procedures, when using a sintered compact as an electrode. The positive electrode active material and the negative electrode active material raw material powder and a binder such as butyral are mixed in a well-known manner using a solvent such as a dispersant, water added with a plasticizer, or an organic solvent such as toluene, if necessary. Make a slurry. The slurry is coated on a base film such as a polyethylene terephthalate (PET) film by a known method and dried to produce a green sheet having a desired thickness. At this time, the slurry may be dried and granulated, and a green sheet may be produced by roll pressing, or may be press-formed into a desired shape. The obtained green sheet is punched into a desired shape, degreased as necessary, and then fired to obtain a dense sintered body. What is necessary is just to select a calcination temperature suitably according to the sinterability of the active material which is raw material powder.

The thicknesses of the first electrode 1 (and 1 ′) and the second electrode 2 are preferably 20 μm to 200 μm, respectively. Thereby, the absolute amount of the active material necessary for obtaining the battery capacity can be secured, and a secondary battery having good charge / discharge characteristics can be obtained. Moreover, also when using a sintered compact as the 1st electrode 1 (and 1 ') and the 2nd electrode 2, it becomes an electrode with good handleability and easy handling by setting it as the said thickness.

As the positive electrode active material, in the case of a lithium ion secondary battery, a transition metal composite oxide containing lithium, such as lithium cobalt composite oxide, lithium manganese composite oxide, manganese dioxide, lithium nickel composite oxide, lithium nickel cobalt composite Examples thereof include oxides and lithium vanadium composite oxides. Among these, in particular, lithium cobalt composite oxide has a high electron conductivity and can be a secondary battery excellent in output characteristics. Further, lithium nickel manganese composite oxide (LiNi _x Mn _y O ₄ (x = 0.1 to 0.5, y = 1.5 to 1.9)) has a higher potential than other materials, and an electromotive force. High secondary battery. The positive electrode is preferably used as a sintered body having a high relative density, and the relative density is preferably 85% or more, and more preferably 90% or more.

  Examples of the negative electrode active material include carbonaceous materials such as graphite, non-graphitizable carbon, and glassy carbon, silicon-containing materials such as metal silicon and alloys thereof, compounds containing silicon, oxygen, and nitrogen, titanium oxide, and oxidation. Examples include niobium and lithium titanium composite oxide. In particular, the lithium titanium composite oxide can reduce the volume change of the negative electrode during charge and discharge even when used as a sintered body having a relative density of 85% or more, more preferably 90% or more. A secondary battery can be used.

  Metal silicon and its alloys, compounds containing silicon, oxygen and nitrogen, and the like are preferable from the viewpoint of obtaining a high capacity. Such a silicon-containing material may be used as a coating film or a sintered body containing the particles and carbon. In addition, although the particle | grains containing silicon change at the time of charging / discharging, even when using as a sintered compact, the stress which generate | occur | produced by the volume change exists in a sintered compact by making a porosity into the range of 10 to 60%. Can be absorbed by pores. A sintered body containing a silicon-containing material is prepared by mixing a raw material powder of a silicon-containing material and a carbon precursor that is carbonized by heat treatment to form a carbonaceous material, and molding and drying the resulting material in a non-oxidizing atmosphere. Obtained by heat treatment. As the carbon precursor, thermosetting resins such as phenol resin, epoxy resin, polyester resin, furan resin, urea resin, melamine resin, alkyd resin, xylene resin, naphthalene, acenaphthylene, phenanthrene, anthracene, triphenylene, pyrene, perylene, Examples thereof include organic materials such as pitch mainly composed of condensed polycyclic hydrocarbon compounds such as pentaphen and pentacene, derivatives thereof, or mixtures thereof. Note that particles of a carbonaceous material such as graphite and non-graphitizable carbon described above may be added to the carbon precursor that is carbonized by heat treatment to become a carbonaceous material. In order to form pores, a resin material that disappears during heat treatment and becomes pores may be added as a pore-forming agent. The relative density and porosity of the positive electrode and the negative electrode may be calculated using techniques such as the Archimedes method, the mercury intrusion method, and image analysis of electrode cross-sectional photographs.

  In the present embodiment, both are particularly effective when at least one of the first electrode 1 (and 1 ') and the second electrode 2 is formed of a sintered body of an active material. The other electrode may be a coated electrode, that is, a coated film obtained by applying a coating liquid containing an active material and a binder onto a current collector, and drying or heat-treating it to join the current collector. .

In particular, transition metal composite oxides containing lithium are easy to sinter and can be made into a positive electrode having a high active material filling rate. Therefore, a transition metal composite oxide sintered body containing lithium is used as the positive electrode. It is preferable to use it. In the first embodiment, the second electrode 2 is used as a positive electrode, the first electrode 1 is used as a negative electrode, and a carbon precursor containing particles of a negative electrode active material or the like is applied to the recess 6 of the first current collector 5. Then, after the heat treatment is performed as necessary, the negative electrode is formed, and then the separator 3 and the positive electrode which is a sintered body of the positive electrode active material are accommodated in the recess 6 where the negative electrode is formed, and the second collector is covered so as to cover it. By disposing the electric body 7, the positional deviation of the positive electrode that is a sintered body can be suppressed.

  Similarly, in the second and third embodiments, the second electrode 2 is used as a positive electrode, and the inside of the recess 6 of the first current collector 5 on which the negative electrode is formed is covered with a separator 3. The second current collector 7 and the positive electrode are housed, the concave portion 6, the second current collector 7 and the positive electrode covered with the separator 3, and the first current collector 5 on which the negative electrode is further formed. It may be arranged so as to be covered with the surface on which the negative electrode of 'is formed, or the negative electrode may be formed and stacked on the back side of the bottom surface of the recess 6 of another first current collector 5. In this case, the negative electrode may be formed on the entire surfaces of the first current collectors 5 and 5 '.

  As the non-aqueous electrolyte, any of an organic electrolyte, a polymer solid electrolyte, an inorganic solid electrolyte, an ionic liquid, and the like can be used.

  When using an organic electrolyte, the separator 3 is disposed between the positive electrode and the negative electrode. The organic electrolyte is composed of an organic solvent and an electrolyte salt, and if necessary, additives for the purpose of suppressing formation of a solid electrolyte layer on the electrode surface, preventing overcharge, imparting flame retardancy, etc. may be added. Good.

  As the organic solvent, those having a high dielectric constant, low viscosity and low vapor pressure are preferably used. Examples of such materials include ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, sulfolane, Mix one or more selected from 1,2-dimethoxyethane, 1,3-dimethoxypropane, dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, etc. Solvent.

Examples of the electrolyte salt include lithium salts such as LiClO ₄ , LiBF ₄ , LiPF ₆ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , and LiN (C ₂ F ₅ SO ₂ ) ₂ .

  The separator 3 can be a nonwoven fabric of organic resin fibers, a nonwoven fabric of inorganic fibers, a ceramic porous material, or the like. Ceramic particles are mixed with an organic porous film mainly composed of polyolefin such as polypropylene or polyethylene. It is preferable to use a material obtained by bonding a porous film containing a ceramic filler, an inorganic fiber nonwoven fabric, a composite porous film of an organic material and an inorganic material, or a ceramic porous material. These have high heat resistance and can improve the safety against thermal runaway of the secondary battery.

  When a polymer solid electrolyte or an inorganic solid electrolyte is used, a sheet of a polymer solid electrolyte is used instead of the separator 3 in the first to third embodiments, or a solid electrolyte layer is formed on the surface of the second electrode 2 And then cover. In the first embodiment, the first current collector 5 and the second current collector 7 may be overlapped via an insulating material, and the first current collector 5 and the second current collector 5 may be overlapped using an insulating adhesive. It is also possible to bond the peripheral portions of the two current collectors 7.

  The material of the connection terminals 8 and 9 is that Ni or Cu is used on the negative electrode side, and no side reaction such as alloying with a metal (such as Li) that is an ionic conductor in the electrolyte occurs at the potential of the negative electrode. It is preferable from the viewpoint of high conductivity and relatively inexpensive, and it is preferable to use Al on the positive electrode side from the viewpoint that it is passivated by forming an oxide film on the surface and excellent in oxidation resistance even at a high potential.

As an example of the present invention, first, a positive electrode was produced as follows. Using lithium cobaltate as a positive electrode active material, a forming aid, a plasticizer, a dispersant, and a solvent were added to the raw material powder and mixed to prepare a slurry. This slurry was applied on a polyethylene terephthalate (PET) film by a doctor blade method and then dried to prepare a green sheet. The produced green sheet was punched out so that the size after firing was 40 × 50 mm, and fired at 975 ° C. in the atmosphere to produce a positive electrode which was a sintered body having a relative density of 85% and a thickness of 35 μm.

As the negative electrode active material, a carbonaceous material obtained by heat treatment of a phenol resin was used.
A phenol resin solution having a concentration of 35% by mass obtained by dissolving a commercially available phenol resin in tetrahydrofuran (THF) as a solvent is applied onto one surface of a 10 μm-thick Cu foil by a doctor blade method and dried, and then a nitrogen atmosphere. A carbonaceous material was bound on the Cu foil by heat treatment at a maximum temperature of 900 ° C. for 10 minutes to form a negative electrode of 41 × 51 mm and a thickness of 56 μm.

  The Cu foil to which the negative electrode was bound was cut into a shape having a negative electrode located at the center of a 45 × 55 mm quadrilateral and a tab having a width of 5 mm and a length of 20 mm on one short side. The position of the tab was set near the center of one region obtained by dividing the short side into two equal parts.

  A non-woven fabric made of polyethylene (45 × 58 mm, thickness 16 μm) as a separator was superimposed on the surface of the Cu foil on which the negative electrode was formed, and a concave portion having a depth of 41 × 51 mm and a depth of 90 μm was formed on the Cu foil using a press. In addition, it adjusted so that the negative electrode might be located in the bottom face of a recessed part in the case of a press.

  Pt was vapor-deposited on one main surface of the produced positive electrode, and the positive electrode was housed in the concave portion of the Cu foil so that the other main surface was opposed to the separator in the concave portion. Further, a positive electrode in which a 10 μm-thick Al foil cut into a shape having a 45 × 55 mm quadrilateral and a tab having a width of 5 mm and a length of 20 mm on one short side is accommodated in a concave portion and a concave portion of a Cu foil. The Pt was deposited so as to cover the surface deposited with Pt. At this time, the Al foil was arranged so that the tab of the Cu foil and the tab of the Al foil did not overlap.

After connecting the Ni lead wire to the tab of Cu foil and spot welding using the Al lead wire as the connection terminal to the tab of Al foil, the electrode group consisting of these power generation elements and the current collector is a bag-shaped aluminum laminate Inserted into a film and dissolved in lithium hexafluorophosphate LiPF ₆ at 1 mol / L in a solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed as an organic electrolyte in a volume ratio of 3: 7 In the state where only the lead wire was pulled out from the opening of the outer package, the opening of the outer package was sealed by thermal welding to obtain a secondary battery.

  About ten produced secondary batteries, the charge / discharge test of 500 cycles was done on condition of the following.

Charging rate: 1.0C
Discharge rate: 0.2C
Charge / discharge voltage: 3.0V-4.2V
Measurement temperature: 30 ° C
As a result of the charge / discharge test, no significant capacity deterioration was confirmed in any of the produced secondary batteries. Further, as a result of disassembling and observing the secondary battery after the charge / discharge test, no electrode misalignment or precipitation of dendritic Li metal was observed.

DESCRIPTION OF SYMBOLS 1, 1 ': 1st electrode 2: 2nd electrode 3: Separator 4: Power generation element 5, 5': 1st electrical power collector 6: Recessed part 7: 2nd electrical power collector 8, 9: Connection terminal

Claims (2)

A laminated power generation element having a first electrode, a second electrode, and a non-aqueous electrolyte;
A first current collector and a second current collector;
The power generating element and the second current collector in a recess provided in the first current collector is housed, an opening on at least one side surface among the side surfaces along the stacking direction of the power generating element of the recess A secondary battery characterized by being provided . The secondary battery according to claim 1, wherein at least one of the first electrode and the second electrode is a sintered body.

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