JP2019067619A - Secondary battery - Google Patents

Abstract

To provide a secondary battery having an improved electric stability from the view point of a separator.SOLUTION: A secondary battery 1 is configured such that a collector 20 of either one of a positive electrode and a negative electrode forms both outermost layers 120 of an electrode laminate unit 100 as well as forms a battery side surface portion 160 that extends from both the outermost layers 120 and covers a unit side surface 150 corresponding to a partial side surface of the electrode laminate unit 100. A side separator 15 is provided between the unit side surface 150 and the battery side surface portion 160, the side separator 15 is a ceramic separator, and the collector forming both the outermost layers 120 and the side separator 15 are in close contact with each other at the battery side surface portion 160.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a secondary battery. In particular, the present invention relates to a secondary battery including an electrode stack unit.

  The secondary battery is a so-called storage battery and can be repeatedly charged and discharged, and is used in various applications. For example, secondary batteries are used in mobile devices such as mobile phones, smartphones and laptop computers.

  The secondary battery is at least composed of a positive electrode, a negative electrode and a separator therebetween. The positive electrode is composed of a positive electrode material layer and a positive electrode current collector, and the negative electrode is composed of a negative electrode material layer and a negative electrode current collector. In a general secondary battery electrode assembly, a plurality of such positive electrodes and negative electrodes are stacked via a separator, and the electrode assembly having such a stack configuration is housed in an outer package.

Japanese Patent Application Laid-Open No. 2002-042855 JP, 2014-167938, A

  The inventor of the present invention noticed that there is a problem to be overcome in the conventional secondary battery, and found out the necessity of taking measures therefor. Specifically, the inventor has found that the following problems exist.

  The separator used in the secondary battery secures the ion conductivity between the positive electrode and the negative electrode while separating the positive electrode and the negative electrode. Although a large number of polyolefin-based separators (particularly, polyolefin-based microporous membranes) are used as separators that have been used before, it is also conceivable to use ceramic separators as separators for secondary batteries.

  The ceramic separator is excellent in thermal stability under high temperature environment, and although a secondary battery with improved safety can be expected in that respect, the inventor of the present application has a problem as electrical stability. I found out.

  Specifically, while the ceramic separator is positioned between the positive electrode and the negative electrode, it may become a cause of occurrence of short circuit if it is exposed to a larger stress during battery preparation and / or use of the battery. I found that there is.

  The present invention has been made in view of such problems. That is, the main object of the present invention is to provide a secondary battery with further improved electrical stability from the viewpoint of a separator.

  The inventor of the present application has attempted to solve the above-mentioned problems by addressing in a new direction, instead of addressing in the extension of the prior art. As a result, the invention of the manufacturing technology of the secondary battery in which the said main objective was achieved was reached.

The present invention is a secondary battery comprising an electrode stack unit including a positive electrode, a negative electrode, and an inter-electrode separator between the positive electrode and the negative electrode,
A battery in which any one of the current collectors of the positive electrode and the negative electrode extends from both outermost layers of the electrode stack unit while covering the unit side surface corresponding to a partial side surface of the electrode stack unit It forms a side part,
A side separator is provided between the unit side and the battery side, and the side separator is a ceramic separator,
A secondary battery is provided in which the current collectors forming the outermost layers and the side separators are in close contact with each other at the battery side portions.

  In the present invention, the electrical stability is further improved in the viewpoint of the separator. Therefore, it becomes easy to obtain a desired secondary battery.

  In particular, in the present invention, even when a ceramic separator is used, the occurrence of a short failure can be suppressed. That is, the secondary battery provided with the ceramic separator according to the present invention is more preferably prevented from the occurrence of an adverse short circuit even if it receives a larger stress at the time of its production and / or use. It is a better battery in terms of stability.

A schematic sectional view showing the structure of the secondary battery of the present invention A schematic sectional view for explaining an integrated separator (integrated structure of a side separator and an inter-electrode separator) A schematic sectional view for explaining the specific thickness dimension relationship and density relationship between the side separator and the inter-electrode separator A schematic cross-sectional view for explaining an aspect in which the electrode material layer extends between the unit side surface and the battery side surface portion Typical process cross-sectional view illustrating the manufacturing process of the secondary battery of the present invention A schematic cross-sectional view to illustrate a side separator positioned only against a single battery side A schematic sectional view for explaining an electrode assembly having a planar laminated structure A schematic perspective view for explaining the first test (confirmation test on adhesion characteristics of the ceramic separator) Second test (Confirmation test of ceramic separator thickness on side of folded battery), third test (Confirmation test of density of ceramic separator on folded side of battery) and fourth test (pole material of folded battery side) Cross-sectional view for explaining the effect confirmation test of the layer)

  Hereinafter, the "secondary battery" according to an embodiment of the present invention will be described in more detail. Although the description is given with reference to the drawings as necessary, various elements in the drawings are merely schematically and exemplarily shown for the understanding of the present invention, and the appearance, size ratio, etc. may be different from that of the real thing .

  The “cross-sectional view (or cross-sectional view)” described directly or indirectly in the present specification refers to the “cross-sectional view (or cross-sectional view)” along the stacking direction of the electrode material layers constituting the secondary battery It is based on the virtual cross section which cut off the following battery.

  Furthermore, the vertical direction, the horizontal direction, and the like used directly or indirectly in this specification correspond to the vertical direction and the horizontal direction in the drawings, respectively. Unless otherwise stated, the same reference signs or symbols indicate the same components or the same semantic content.

[General / Basic Configuration of Secondary Battery]
The term "secondary battery" as used herein refers to a battery that can be repeatedly charged and discharged. Therefore, the secondary battery obtained by the manufacturing method of the present invention is not excessively restricted by the name, and for example, a storage device and the like may be included in the object.

  The general or basic matter related to the electrode stack unit included in the secondary battery of the present invention will be described. The secondary battery includes an electrode stack unit in which an electrode configuration layer including a positive electrode, a negative electrode, and a separator is stacked. FIG. 7 schematically illustrates an electrode stack unit of a general secondary battery. As illustrated, in a general secondary battery, the positive electrode and the negative electrode are stacked via a separator to form an electrode configuration layer, and at least one such electrode configuration layer is stacked to form an electrode stack unit. Is configured. In a general secondary battery, such an electrode stack unit is enclosed in an outer package together with an electrolyte (for example, a non-aqueous electrolyte).

  The positive electrode is composed of at least a positive electrode material layer and a positive electrode current collector. In the positive electrode, a positive electrode material layer is provided on at least one side of a positive electrode current collector, and the positive electrode material layer contains a positive electrode active material as an electrode active material. For example, in the positive electrode in the electrode stack unit, the positive electrode material layer may be provided on both sides of the positive electrode current collector, or the positive electrode material layer may be provided on only one side of the positive electrode current collector.

  The negative electrode is composed of at least a negative electrode material layer and a negative electrode current collector. In the negative electrode, a negative electrode material layer is provided on at least one side of a negative electrode current collector, and the negative electrode material layer contains a negative electrode active material as an electrode active material. For example, the negative electrode in the electrode stack unit may have a negative electrode layer provided on both sides of the negative electrode current collector, or may have a negative electrode layer provided on only one side of the negative electrode current collector.

  The electrode active materials contained in the positive electrode and the negative electrode, ie, the positive electrode active material and the negative electrode active material, are substances directly involved in the delivery of electrons in the secondary battery, and are main substances of the positive and negative electrodes responsible for charge and discharge, ie, battery reaction. is there. More specifically, ions are provided to the electrolyte due to the “positive electrode active material contained in the positive electrode material layer” and the “negative electrode active material contained in the negative electrode material layer”, and such ions are between the positive electrode and the negative electrode. Move to deliver electrons and charge / discharge is performed. In particular, the positive electrode material layer and the negative electrode material layer are preferably layers capable of inserting and extracting lithium ions. That is, it is preferable that a non-aqueous electrolyte secondary battery is formed in which lithium ions move between the positive electrode and the negative electrode through the non-aqueous electrolyte to perform charge and discharge of the battery. When lithium ions are involved in charging and discharging, the secondary battery corresponds to a so-called lithium ion battery, and the positive electrode and the negative electrode have a layer capable of inserting and extracting lithium ions.

  The positive electrode active material of the positive electrode material layer is preferably made of, for example, a granular material, and a binder is preferably contained in the positive electrode material layer in order to sufficiently contact particles and maintain their shape. Furthermore, a conductive support agent may be contained in the positive electrode material layer in order to facilitate the transfer of electrons for promoting the cell reaction. Similarly, although the negative electrode active material of the negative electrode material layer is made of, for example, particles, it is preferable that a binder be included for sufficient contact between the particles and shape retention, facilitating the transfer of electrons for promoting battery reaction. A conductive support agent may be contained in the negative electrode material layer in order to do so. Thus, the positive electrode material layer and the negative electrode material layer can also be referred to as a positive electrode mixture layer, a negative electrode mixture layer, and the like, respectively, because of the form in which a plurality of components are contained.

  The positive electrode active material is preferably a material that contributes to the storage and release of lithium ions. In this respect, the positive electrode active material is preferably, for example, a lithium-containing composite oxide. More specifically, the positive electrode active material is preferably a lithium transition metal complex oxide containing lithium and at least one transition metal selected from the group consisting of cobalt, nickel, manganese and iron. That is, in the positive electrode material layer of the secondary battery obtained by the manufacturing method of the present invention, such a lithium transition metal composite oxide is preferably contained as a positive electrode active material. For example, the positive electrode active material may be lithium cobaltate, lithium nickelate, lithium manganate, lithium iron phosphate, or some of their transition metals replaced with another metal. Such a positive electrode active material may be contained as a single species but may be contained in combination of two or more. Although it is only an example to the last, in the secondary battery obtained by the manufacturing method of the present invention, the positive electrode active material contained in the positive electrode material layer may be lithium cobaltate.

  The binder that may be contained in the positive electrode layer is not particularly limited, but is not limited to polyfluorinated vinylidene, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, and At least one selected from the group consisting of polytetrafluoroethylene and the like can be mentioned. The conductive aid to be contained in the positive electrode layer is not particularly limited, but may be thermal black, furnace black, channel black, carbon black such as ketjen black and acetylene black, graphite, carbon nanotubes and vapor phase growth At least one selected from carbon fibers such as carbon fibers, metal powders such as copper, nickel, aluminum and silver, and polyphenylene derivatives can be mentioned. For example, the binder of the positive electrode material layer may be polyvinylidene fluoride, and the conductive aid of the positive electrode material layer may be carbon black. For the purpose of illustration only, the binder of the positive electrode material layer and the conductive aid may be a combination of polyvinylidene fluoride and carbon black.

  The negative electrode active material is preferably a material that contributes to the storage and release of lithium ions. In this respect, the negative electrode active material is preferably, for example, various carbon materials, oxides, lithium alloys, or the like.

  Examples of various carbon materials of the negative electrode active material include graphite (natural graphite and artificial graphite), hard carbon, soft carbon, diamond-like carbon and the like. In particular, graphite is preferable in that it has high electron conductivity and excellent adhesion to the negative electrode current collector. Examples of the oxide of the negative electrode active material include at least one selected from the group consisting of silicon oxide, tin oxide, indium oxide, zinc oxide, lithium oxide and the like. The lithium alloy of the negative electrode active material may be any metal that can be alloyed with lithium, for example, Al, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, It may be a binary, ternary or higher alloy of a metal such as La and lithium. Such an oxide is preferably amorphous as its structural form. This is because deterioration due to nonuniformity such as grain boundaries or defects is less likely to occur. Although it is only an example to the last, in the secondary battery obtained by the manufacturing method of the present invention, the negative electrode active material of the negative electrode material layer may be artificial graphite.

  The binder to be contained in the negative electrode layer is not particularly limited, but at least one selected from the group consisting of styrene butadiene rubber, polyacrylic acid, polyvinylidene fluoride, polyimide resin and polyamideimide resin Can be mentioned. For example, the binder contained in the negative electrode material layer may be styrene butadiene rubber. The conductive aid to be contained in the negative electrode layer is not particularly limited, but may be thermal black, furnace black, channel black, carbon black such as ketjen black and acetylene black, graphite, carbon nanotubes and vapor phase growth At least one selected from carbon fibers such as carbon fibers, metal powders such as copper, nickel, aluminum and silver, and polyphenylene derivatives can be mentioned. In addition, the component resulting from the thickener component (for example, carboxymethylcellulose) used at the time of battery manufacture may be contained in the negative electrode material layer.

  For the purpose of illustration only, the negative electrode active material and the binder in the negative electrode layer may be a combination of artificial graphite and styrene butadiene rubber.

  The positive electrode current collector and the negative electrode current collector used for the positive electrode and the negative electrode are members contributing to collecting and supplying electrons generated in the active material due to the cell reaction. Such a current collector may be a sheet-like metal member, and may have a porous or perforated form. For example, the current collector may be metal foil, punching metal, netting, expanded metal or the like. The positive electrode current collector used for the positive electrode is preferably made of a metal foil containing at least one selected from the group consisting of aluminum, stainless steel, nickel and the like, and may be, for example, an aluminum foil. On the other hand, the negative electrode current collector used for the negative electrode is preferably made of a metal foil containing at least one selected from the group consisting of copper, stainless steel, nickel and the like, and may be, for example, copper foil.

  The separators used for the positive electrode and the negative electrode are members provided from the viewpoint of preventing a short circuit due to contact of positive and negative electrodes, and holding the electrolyte. In other words, the separator is a member that allows ions to pass while preventing electronic contact between the positive electrode and the negative electrode. Preferably, the separator is a porous or microporous insulating member and has a membrane morphology due to its small thickness. By way of example only, a microporous polyolefin membrane may be used as a separator. In this respect, the microporous membrane used as a separator may contain, for example, only polyethylene (PE) or only polypropylene (PP) as the polyolefin. Furthermore, the separator may be a laminate composed of “PE microporous membrane” and “PP microporous membrane”.

  In a general secondary battery, an electrode stack unit including a positive electrode, a negative electrode and a separator is enclosed in an outer package together with an electrolyte. When the positive electrode and the negative electrode have a layer capable of absorbing and desorbing lithium ions, the electrolyte is preferably a "non-aqueous" electrolyte such as an organic electrolyte or an organic solvent (that is, the electrolyte is a non-aqueous electrolyte) preferable). In the electrolyte, metal ions released from the electrodes (positive electrode and negative electrode) will be present, and therefore, the electrolyte will help the movement of the metal ions in the cell reaction.

The non-aqueous electrolyte is an electrolyte containing a solvent and a solute. As a specific non-aqueous electrolyte solvent, one comprising at least a carbonate is preferable. Such carbonates may be cyclic carbonates and / or linear carbonates. Although not particularly limited, cyclic carbonates include at least one selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC) and vinylene carbonate (VC). be able to. As linear carbonates, at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and dipropyl carbonate (DPC) can be mentioned. For the purpose of illustration only, a combination of cyclic carbonates and linear carbonates may be used as the non-aqueous electrolyte, for example, a mixture of ethylene carbonate and diethyl carbonate is used. Also, as a specific non-aqueous electrolyte solute, for example, Li salt such as LiPF ₆ and / or LiBF ₄ is preferably used. The electrolyte of the secondary battery may be classified as a polymer electrolyte.

  A general secondary battery casing encloses an electrode assembly in which an electrode configuration layer including a positive electrode, a negative electrode and a separator is stacked, but may be in the form of a hard case or in the form of a soft case It may be. Specifically, the outer package may be a hard case type equivalent to a so-called metal can, or may be a soft case type equivalent to a pouch made of a so-called laminate film.

[Secondary battery of the present invention]
The secondary battery of the present invention is characterized by the entire battery structure associated with the electrode current collector and the separator associated therewith. In particular, the secondary battery of the present invention is characterized in the extension form of the electrode current collector which determines the overall structure of the battery, and also in the separator related to the extension form.

  Specifically, in the secondary battery 1 of the present invention, in the electrode stack unit 100 including the positive electrode, the negative electrode and the inter-electrode separator 10 therebetween, one of the current collectors 20 of the positive electrode and the negative electrode is an electrode While forming both outermost layers 120 of the laminated unit 100, a battery side surface portion 160 which extends from the both outermost layers 120 and covers a unit side surface 150 corresponding to a partial side surface of the electrode laminated unit 100 is formed ( See Figure 1). That is, as shown in FIG. 1, the secondary battery 1 of the present invention has, as a whole, a structure in which the current collectors 20 constituting the electrode stack unit 100 are largely folded back. In other words, the current collector 20 integrally forms a top wall and a bottom wall of the electrode stack unit 100 and also forms a side wall (specifically, a part of the side wall) of the electrode stack unit 100. .

  In the present specification, the term "electrode lamination unit" refers in a broad sense to an electrode lamination portion in which a positive electrode and a negative electrode are stacked one on another via a separator, and in a narrow sense, to a positive electrode and a negative electrode via a separator. The term “electrode stack” refers to an electrode stack that is stacked so that one of the two is held by the other. Moreover, in the present specification, “both outermost layers of the electrode stack unit” refers in a broad sense to the layer positioned on the outermost side in the electrode stack portion of the positive electrode and the negative electrode via a separator. The term “2” refers to the two outermost layers (the uppermost layer and the lowermost layer opposed in the electrode stacking direction) of the electrode stack portion stacked so that one of the positive electrode and the negative electrode is sandwiched by the other via the separator. Furthermore, in the present specification, "a part of the side surface of the electrode stack unit" broadly refers to at least a part of the side surface of the electrode stack unit, and in a narrow sense, the current collection of the "both outermost layers" It refers to a part of the side surface area of the electrode stack unit captured part of the body.

  In the secondary battery of the present invention, as the entire structure, the outer current collectors 20 constituting the electrode stack unit 100 extend so as to be largely folded back. Combined with the extended form of the electrode current collector, the secondary battery of the present invention has a unique installation form of the separator. Specifically, the side separator 15 is provided between the unit side surface 150 and the battery side surface portion 160. As can be seen with reference to FIG. 1, the side separator 15 is provided between the “electrode stack unit side surface 150” and the “collector 20 having the form folded back as a whole and forming the battery side surface portion 160”. It can be said that Thus, in the secondary battery of the present invention, in addition to the separators of the components of the electrode stack unit (that is, the inter-electrode separator 10 between the positive electrode and the negative electrode), the side to be the non-electrode stack element of the electrode stack unit It has a one-way separator 15.

  The side separators 15 provided in the secondary battery are positioned at the folded portions of the current collectors 20 of the outermost layers, as can be seen from the form shown in FIG. In the secondary battery of the present invention, the side separator is a ceramic separator. That is, the side separator 15 is a separator made of a material different from the conventionally used polyolefin separator. The term "ceramic separator" as used herein means a separator in which the proportion of the ceramic component accounts for the majority of all the components constituting the separator, and the content of the ceramic component is, for example, 60 volumes based on the total volume It refers to a separator having a% or more, preferably 65% by volume or more. Also preferably, the ceramic separator in the present invention does not have the pore or fiber structure as commonly employed in polyolefin systems and is therefore a substantially solid separator.

  The ceramic component in the ceramic separator may correspond to, for example, an oxide component and / or a nitride component. Specifically, the ceramic component may be at least one component selected from the group consisting of alumina, silica, titania, magnesia, barium titanate, silicon nitride and aluminum nitride.

  The ceramic separator may be provided as a particulate consisting of a particulate ceramic component. In such a case, a binder component may be included for more sufficient contact between the particles and shape retention. As the binder component, at least one selected from the group consisting of polyvinylidene fluoride (PVDF), phenoxy resin, epoxy resin, polyvinyl butyrate resin, polyvinyl alcohol resin, urethane resin, acrylic resin, ethyl cellulose, methyl cellulose and carboxymethyl cellulose It may be an organic material of

  The ceramic separator itself used in the present invention can be formed through application of a ceramic material comprising at least a mixture of a ceramic component and an organic material. More preferably, it can be obtained by drying a ceramic raw material slurry comprising a ceramic component, an organic material and an organic solvent, after application. As the organic solvent used for this raw material slurry, N-methyl pyrrolidone (NMP), methyl ethyl ketone (MEK), isopropyl alcohol (IPA), ethanol, acetone, acetonitrile, ethyl acetate, butyl acetate, toluene, tetrahydrofuran (THF), N, Mention may be made of at least one selected from the group consisting of N-dimethylformamide (DMF) and dimethylsulfoxide (DMSO). Typically, the organic solvent in the slurry can be vaporized and removed from the coating layer by subjecting the coating layer obtained by applying the ceramic raw material slurry to drying, whereby the ceramic separator can be removed. You may get

  In the secondary battery of the present invention, the side separator has a configuration in close contact with the other layers. Specifically, the current collectors 20 forming the outermost layers and the side separators 15 are in close contact with each other at the battery side portion 160. As can be seen from the embodiment shown in FIG. 1, this means that at least two layers constituting the folded portion of the secondary battery of the present invention substantially contact each other without gaps. Such an intimate contact configuration increases the structural strength of the "folded portion" and may provide higher structural strength in the secondary battery. More specifically, in the structure of the secondary battery, the folded portion is composed of a single layer of each of the separator layer and the current collector. Therefore, although it is usually considered that the structural strength of such a folded-back portion is lower than that of the electrode laminate part of the electrode laminate unit, the structure of the adhesive layer in the present invention compensates for the structural strength decrease. Yes, and thus, higher structural strength can be provided to the secondary battery.

  Such secondary batteries of the present invention, even though they include ceramic separators, are more effective in suppressing the occurrence of short circuit defects as will be understood from the examples described later. That is, in the past, although ceramic separators are excellent in thermal stability under high temperature environment, it has been considered that there is a problem in electrical stability. In the secondary battery of the present invention, a battery is realized which has a ceramic separator and also has improved characteristics in terms of electrical stability. More specifically, in the secondary battery provided with the ceramic separator according to the present invention, the occurrence of an undesirable short circuit is more preferably avoided even if it receives a larger stress during its preparation and / or use. , Has become a better battery in terms of electrical stability.

  In a preferred embodiment, the side separator 15 and the inter-electrode separator 10 are integrated with each other (see FIG. 2). That is, the separator 15 between the unit side surface 150 and the battery side surface portion 160 has a form integrated with the separator 10 included in the electrode stack portion of the electrode stack unit 100. This means that the separator of the component of the electrode stack unit and the separator of the non-electrode stack element of the electrode stack unit are in continuous form with each other. As can be seen from the illustrated embodiment, at least one separator of the secondary battery of the present invention constitutes the electrode stack portion of the electrode stack unit, but extends and folds outward while protruding from the electrode stack portion. There is. When the side separators and the inter-electrode separators are integrated with each other, the separators can be provided collectively, which contributes to a simple manufacturing process. In addition, since the side separator and the inter-electrode separator integrated with each other can exhibit the separator function as a whole, the short circuit prevention and the like can be further promoted.

  Preferably, the interelectrode separator 10 together with the side separator 15 also constitutes a ceramic separator. That is, it is preferable that both “the separator 15 between the unit side surface 150 and the battery side surface portion 160” and “the separator 10 included in the electrode stack portion of the electrode stack unit” be a ceramic separator. More preferably, the side separator 15 and the inter-electrode separator 10 integrated with each other constitute a ceramic separator. In the secondary battery of the present invention having such a feature, the separator that constitutes the electrode lamination portion of the electrode lamination unit but extends outward from the electrode lamination portion and is folded back as a whole is a ceramic separator It can be said that If the side separators and the inter-electrode separator are both ceramic separators, it is not necessary to change the raw materials among them, which can be a simple manufacturing process. In addition, when the side separators and the inter-electrode separators are made of the same ceramic material, the material anisotropy of the overall secondary battery separator will be further reduced, and battery design may be easier.

  In the secondary battery of the present invention, the side separator and the inter-electrode separator may have a specific thickness dimension relationship with each other. In a preferred embodiment, the thickness dimension of the side separator is larger than the thickness dimension of the inter-electrode separator. For example, assuming that the average thickness dimension of the side separator 15 is T1, and the one-side average thickness dimension of the inter-electrode separator 10 is T2, it is preferable that T1> T2. If this is specifically illustrated, for example, it may be 1.2 × T2 <T1 <5 × T2 (more specifically, 1.25 × T2 ≦ T1 ≦ 4 × T2). With such a thickness dimension relationship, the occurrence of a short failure can be more effectively suppressed. That is, in the secondary battery of the present invention satisfying the relationship of T1> T2, the occurrence of an undesirable short circuit is more preferably avoided even if a larger stress is temporarily given at the time of production and / or use, etc. It is better in terms of electrical stability. Here, the “average thickness dimension T1” of the side separator is within a predetermined range corresponding to the thickness width of the electrode body not attached to “folded” in the cross sectional view as shown in FIG. Substantially means the average thickness of Simply, in the cross-sectional view as shown in FIG. 3, when the uppermost surface level of the electrode body not attached to the “folded back” is virtually extended in the lateral direction, the side separator 15 and The thickness at the crossing upper point, the thickness at the lower point at which it crosses the side separator 15 when the lowermost surface level of the electrode body is virtually extended in the lateral direction, and the current collector level of the electrode body The arithmetic mean of the mid-point thickness at the point where it virtually crosses the side separator 15 when virtually extended in the lateral direction may be employed (if there are multiple current collectors 45, at each level Arithmetic mean taking into account the thickness of crossing points may be adopted). On the other hand, the "one-side average thickness dimension T2" of the inter-electrode separator substantially means the overall average thickness of a single inter-electrode separator. Simply, as the “one-sided average thickness” of the inter-electrode separator, an electrode material layer 48 in contact with the target inter-electrode separator 10 on the inner side in a cross-sectional view as shown in FIG. The arithmetic mean of the thicknesses at the two edge points of the pole material layer located relatively inward when viewed along the stacking direction of the part may be employed.

  The preferred thickness difference between the side separator and the inter-electrode separator as described above may be achieved by locally changing the thickness of the separator raw material layer or by at least partially pressing the separator raw material layer. It may be achieved (see FIG. 5 described later).

  In addition, about the thickness (thickness dimension) of a side separator, it is not necessarily required that it is constant as a whole as the above-mentioned is called "average thickness dimension" etc., and thickness is not necessarily required. It may be changed. For example, the thickness of the side separator 15 is relatively toward the outside from the inside along the stacking direction of the electrode stack (that is, when viewed from the cross section as shown in FIG. The thickness may be increased as the Thus, even if the lateral separator has a local difference in thickness, the "average thickness dimension" T1 as described above falls within a certain range (for example, as described above, the electrode The current collector and / or the electrode material of the electrode body which is not attached to the “folded”, by being within the range of 1.2 × T2 <T1 <5 × T2 in relation to the thickness T2 of the intermediate separator) Shorts with layers can be suppressed more effectively.

  Further, in the secondary battery of the present invention, the side separator and the inter-electrode separator may have a specific density relationship with each other. In one preferred embodiment, the density of the side separators is greater than the density of the inter-electrode separators. For example, assuming that the average density of the side separators 15 is D1 and the average density of the inter-electrode separator 10 is D2 (see FIG. 3), it is preferable that D1> D2. Specifically, for example, D1 may be about 2% to 15% more dense than D2 (ie, 1.02 × D2 ≦ D1 ≦ 1.15 × D2). More specifically, it may be about 4% to 10% more dense than D2 (ie, 1.04 × D2 ≦ D1 ≦ 1.10 × D2). With such a density relationship, the occurrence of a short failure can be more effectively suppressed. That is, the secondary battery of the present invention satisfying the relationship of D1> D2 is more preferably prevented from causing an adverse short circuit even if it receives a larger stress during preparation and / or use. Better in terms of stability. Here, the “average density D1” of the side separator is within a predetermined range corresponding to the thickness width of the electrode body which is not attached to “folded” in a cross sectional view as shown in FIG. It substantially means the average density. Simply, in the cross-sectional view as shown in FIG. 3, when the uppermost surface level of the electrode body not attached to the “folded back” is virtually extended in the lateral direction, the side separator 15 and The density at the crossing upper point, the density at the lower point at which the lowermost level of the electrode body virtually crosses the lateral separator 15, and the current collector level of the electrode body The arithmetic mean of the median point density at the point where it virtually crosses the side separator 15 when virtually extended in the lateral direction may be employed (if there are multiple current collectors 45, the intersection at each level is taken Arithmetic mean taking into account the density of points may be adopted). On the other hand, the "average density D2" of the inter-electrode separator substantially means the average density as a whole of the single inter-electrode separator in question. Simply, as the “average density” of the inter-electrode separator, in the cross-sectional view as shown in FIG. The arithmetic mean of the densities at the two edge points of the pole material layer (relatively located pole material layer) may be employed.

  Such a suitable density difference between the side separator and the inter-electrode separator can be achieved, for example, by changing the ceramic raw material slurry between the side separator and the inter-electrode separator. A suitable density difference between the side separator and the inter-electrode separator can also be achieved by at least partially pressing the separator raw material layer. Furthermore, in addition to or in place of such pressing, the density difference of the ceramic separator can also be achieved by changing the concentration (volume concentration) of the ceramic component in the ceramic raw material slurry corresponding to so-called PVC.

  In the secondary battery of the present invention according to a preferred embodiment, when the side separator and the inter-electrode separator are compared, at least one of the thickness and the density of the former is greater than that of the latter, Is also getting bigger. That is, the side separator has a larger thickness dimension than the inter-electrode separator, and / or the side separator has a higher density than the inter-electrode separator. In the secondary battery having such characteristics of the side separator and the inter-electrode separator, the occurrence of the short failure can be more effectively suppressed.

  In the secondary battery of the present invention, either one of the positive electrode and the negative electrode material layer may extend from the electrode stack unit and be provided between the unit side surface 150 and the battery side surface portion 160 (FIG. 4). reference). That is, as shown in the figure, the unit electrode material layer included in the electrode lamination portion of the electrode lamination unit, and the side electrode material layer extending outward from the electrode lamination portion and extending laterally of the electrode lamination unit Preferably, they are integrated with one another. In other words, although a part of the electrode material layer of the secondary battery of the present invention constitutes the electrode stack portion of the electrode stack unit, it extends out while protruding from the electrode stack portion and is folded as a whole It can be said that As described above, when the side electrode material layer having the form of extending laterally to the electrode stack unit is present, battery capacity may be additionally formed on the side. That is, in addition to the capacity formation in the stacking direction of the electrode stack unit, the capacity can also be formed in the lateral direction orthogonal to that, so that a further capacity improvement can be brought about as the whole secondary battery.

  The side electrode material layer preferably has a configuration in close contact with the other layers. Specifically, it is preferable that the electrode material layer be in close contact with the side separator 15 at least at the battery side surface portion. As can be seen from the form shown in FIG. 4, this means that at least two layers constituting the folded portion of the secondary battery of the present invention are substantially in contact with each other without gaps. With such a close contact configuration, the structural strength of the "folded portion" is increased, and the secondary battery provides higher structural strength. In particular, in addition to the fact that the current collectors forming both outermost layers in the battery side portion are in close contact with the side separators, the electrode material layer is in close contact with the side separators. The structural strength is particularly increased. That is, the folded portion of the secondary battery of the present invention has a configuration in which the three members of the current collector forming the outermost layers, the side separator, and the side electrode material layer are in close contact with each other. It has higher structural strength. Here, the term "at least in the battery side portion" means that the electrode material layer is not only in close contact with the side separators, but it may also be in close contact with the inter-electrode separator. There is.

  The secondary battery of the present invention can be obtained by various manufacturing processes. One manufacturing process aspect will be exemplarily described with reference to FIGS. 5 (a) to 5 (e). First, as shown to Fig.5 (a), metal layer member 20 'used as an electrode collector is prepared. The metal layer member 20 ′ is not particularly limited as long as it is used as an electrode current collector. When the current collectors of "both outermost layers" are positive electrode current collectors, the metal layer member 20 'is made of a metal foil containing at least one selected from the group consisting of aluminum, stainless steel, nickel and the like. You may On the other hand, when the current collectors of the “both outermost layers” are the negative electrode current collector, the metal layer member 20 ′ is made of metal foil containing at least one selected from the group consisting of copper, stainless steel, nickel, etc. It may be

  Next, as shown in FIG. 5B, one of the positive electrode material layer and the negative electrode material layer 30 'is formed on the metal layer member 20'. Specifically, an electrode material layer material containing at least an active material (positive electrode active material or negative electrode active material) and a binder is applied to form an electrode material layer 30 '. As shown, it is preferable to form two sub-electrode material layers 30A and 30B separated from each other.

  Next, as shown in FIG. 5C, a separator layer 10 'is formed which is the source of the inter-electrode separator and the side separator. Specifically, separator layer 10 'is formed on the two sub-electrode material layers 30A and 30B spaced apart on metal layer member 20' so as to straddle both sub-electrode material layers 30A and 30B. The separator material is entirely coated and formed on the metal layer member 20 ', but the upper surface of the separator material layer after coating is non-uniform (the separator material layer 10' partially recessed as shown) For example, screen printing may be used to obtain. From the above, it is possible to obtain a precursor member 40 'for folding which is later subjected to bending of folding.

  Then, as shown in FIG. 5D, an electrode layer member 50 ', which is the other of the positive electrode layer and the negative electrode layer, is interposed to bend the precursor member 40' for folding back. More specifically, the electrode layer 30 'and the separator layer 10' of the precursor member 40 'are on the inner side, while the electrode member 50' is sandwiched by the precursor member 40 'for folding back. The precursor member 40 'is bent so as to entirely turn around. The secondary battery 1 of the present invention can be obtained through at least the above steps.

  The secondary battery of the present invention can be embodied in various manners. The details will be described below.

(Aspect of single side installation of side separator)
In the secondary battery of this aspect, the side separators are disposed only on part of the side surfaces of the electrode stack unit (see FIG. 6). In particular, due to the overall structure in which the current collector 20 constituting the electrode lamination unit is folded back as a whole, the side separators 15 have a plurality of unit side faces in the electrode lamination unit (more specifically, For example, it may be positioned only for a single side of four sides located at the same height level. In this aspect, the side separators can be provided more simply in the manufacturing process as shown in FIG. 5, which contributes to the realization of a preferable secondary battery also in terms of manufacturing efficiency.

  The insulating sealing part may be provided to the other unit side surface in which the side separator is not provided. That is, among the plurality of unit side surfaces (more specifically, for example, four side surfaces located at the same height level), the insulating sealing portion is provided on the side surfaces other than the single side surface on which the side separator 15 is provided. (See FIG. 1). As illustrated, the current collectors forming the top and bottom walls of the electrode stack unit extend so as to protrude in a cross sectional view, and fill in between the extension parts of the opposing current collectors. Preferably, the insulating sealing portion is provided. The term "insulation sealing portion" as used herein refers to a member that "insulates" the electrode constituent layer of the electrode stack unit from the outside and "seals" the electrode constituent layer from the external environment. The material of the insulating sealing part is not particularly limited as long as it is provided with "insulating property" and "sealing property". For example, the material of the insulating sealing portion may be a resin material, and it may be a resin material containing polypropylene, which is merely an example.

  When the insulating sealing portion is provided, an electrolyte may be provided on the inside. That is, the electrolyte may be enclosed inside the folded portion and the insulating sealing portion of the secondary battery. Such an embodiment leads to the realization of a more compact secondary battery because the installation of the outer package is not particularly required.

(Aspect of outermost negative electrode layer of electrode lamination unit)
In the secondary battery of this aspect, the outermost part of the electrode stack unit forms a negative electrode. That is, in the electrode stack unit, the negative electrode is the outermost electrode, and the positive electrode is provided between the negative electrodes. In this case, the negative electrode forming the outermost electrode is preferably equivalent to a so-called "single-sided electrode". That is, it is preferable that the electrode positioned on the top wall and the bottom wall of the electrode stack unit be a single-sided negative electrode.

  In this aspect, the current collectors forming the outermost layers are the negative electrode current collectors. That is, the negative electrode current collector as a whole integrally forms the top and bottom walls of the electrode stack unit and also forms the side wall of the electrode stack unit. For example, a metal foil containing at least one selected from the group consisting of copper, stainless steel, nickel and the like as a negative electrode current collector forms the top and bottom walls of the electrode stack unit and also the side wall of the electrode stack unit. It is The negative electrode current collector is greatly folded while constituting the electrode stack unit, as can be seen from the illustrated embodiment. The negative electrode current collector may be made of, for example, stainless steel and / or nickel, from the viewpoint of more preferably developing such folded structural resistance.

  When both outermost portions of the electrode stack unit form a negative electrode, the positive electrode is provided so as to be sandwiched between the outermost electrodes of the outermost layers. The positive electrode is preferably a double-sided electrode in which a positive electrode material layer is provided on both main surfaces of a positive electrode current collector. This is because the battery capacity of the electrode stack unit can be more suitable.

  Although the embodiments of the present invention have been described above, the typical examples are merely illustrated. Accordingly, those skilled in the art will readily understand that the present invention is not limited thereto, and various embodiments are conceivable.

  For example, as one of the above embodiments, although the secondary battery without the outer package is described, the present invention is not particularly limited thereto. For example, in the secondary battery of the present invention, an outer package may be additionally provided such that an electrode stack unit formed by folding back the current collectors of both outermost layers is entirely wrapped up in the outer package.

  Various tests were conducted to confirm the effects of the secondary battery of the present invention.

[First test: confirmation test on adhesion characteristics of ceramic separator]
A test was conducted to confirm the adhesion characteristics of the ceramic separator to be subjected to the bending of the folds. In particular, the adhesion characteristics between the “ceramic separator” and the “current collector forming both outermost layer portions” and the adhesion characteristics between the “ceramic separator” and the “electrode material layer” were confirmed.

The peeling test was performed using the lamination test body which imitated lamination of a secondary battery. The layers used for this lamination test are as follows.

-Current collector: Electrodeposited copper foil (manufactured by Japan Foil Co., Ltd., thickness 10 μm)

· Ceramic / separator layer: A layer formed by applying a slurry of a raw material of the ceramic separator used in the second to fourth tests described below to a current collector or an electrode material layer and drying it.

・ Double-sided tape: Made by 3M Japan, (product name) Scotch Ultra-strong Double-sided Tape Premium Gold Versatile, 15 mm Width

· Auxiliary substrate: PET material, thickness 100 μm)

・ Electrode material layer: A layer formed by applying an electrode material raw material slurry of an anode material used in the following second to fourth tests on a ceramic and drying it

  As shown in FIG. 8, two types of lamination test bodies were prepared. As the lamination | stacking test body A, the laminated body on which the auxiliary substrate 240, the double-sided tape 230, the ceramic separator layer 220, and the collector 210 were laminated | stacked in order from the lower side was used. On the other hand, a laminate in which the auxiliary substrate 240, the double-sided tape 230, the ceramic separator layer 220, the electrode material layer 250, and the current collector 210 were laminated in order from the lower side was used as the lamination test body B. The peeling external force was applied to each lamination test body, and it was investigated about which location is broken or exfoliated by it. More specifically, the adhesive force per unit width was confirmed by measuring the load at the time of pulling at a tensile speed of 500 mm / sec using a testing machine (manufactured by A & D, model TENSILON RTF 1210).

The results are shown in Table 1.

  As can be seen from Table 1, it was found that the ceramic separator layer and the metal foil had high adhesion to each other. Therefore, it has been found that there is a high possibility that even if the integrated products are folded back so as to be folded, the close contact with each other is maintained.

  Next, second to fourth tests performed in connection with the secondary battery of the present invention will be described. The battery test bodies used in the second to fourth tests were created based on the method described below.

(Slurry for electrode material of positive electrode material)
88 g of lithium cobaltate, 2 g of graphite (manufactured by Timcal, KS-6), and 6 g of graphite (manufactured by Timcal, Super P Li) were weighed.

Each material weighed was placed in a 1000 mL pot, and 200 g of PSZ grinding media with a diameter of 1.0 mm and N-methylpyrrolidone (hereinafter referred to as "NMP") as a solvent were added. Subsequently, dispersion was performed by mixing for 24 hours at 150 rpm using a rolling ball mill. As a result, secondary particles of lithium cobaltate were crushed, and the average particle diameter D ₅₀ was 2.1 μm.

  40 g of a 10% by mass NMP solution of polyvinylidene fluoride (manufactured by Kureha Co., Ltd., # 7208) is added to the solution in which each material is dispersed as described above, and the mixture is further mixed for 4 hours at 150 rpm using a rolling ball mill Then, an electrode material raw material slurry of the positive electrode was obtained.

(Slurry for electrode material of negative electrode material)
Graphite (Mitsubishi Chemical Co., Ltd. product GTR7, average particle diameter D ₅₀ = 11.0 μm) 85 g, conductive auxiliary (Hitachi Chemical Co., Ltd. product SMSC 10-4V3) 15 g, NMP 100 g, polyvinylidene fluoride (Kreha Co., Ltd. 53 g of a 10% by mass NMP solution manufactured by # 7305 was weighed and stirred by a planetary mixer to obtain an electrode material slurry of a negative electrode.

(Slurry for raw material of ceramic separator)
In a 500 mL pot, 80 g of spherical alumina powder (manufactured by Denki Kagaku Kogyo Co., Ltd., average particle diameter D ₅₀ = 0.3 μm) and 75 g of NMP as a solvent were charged. Further, a PSZ grinding media having a diameter of 5 mm was added, mixed using a rolling ball mill at 150 rpm for 16 hours, and subjected to dispersion.

  Then, 155 g of a binder solution of PVDF-HFP (SOLVAY SOLEF 20216 HFP substitution amount 12 mol%) (a solution containing 10 mass% of PVDF-HFP, 67.5 mass% of NMP, 22.5 mass% of MEK) is added using a tumbling ball mill The mixture was mixed at 150 rpm for 4 hours to obtain a ceramic separator raw material slurry. In this aspect, a raw material slurry having a ceramic component concentration (corresponding to a so-called pigment volume concentration PVC) of 70% was obtained.

(Preparation of both outermost layer parts)
A "both outermost layer portion" to be attached to the fold was prepared. First, the above negative electrode material slurry of the negative electrode is coated on a negative electrode current collector foil made of electrolytic copper foil (manufactured by Japan Foil Co., Ltd., thickness 10 μm), dried and pressed to separate from each other. To form two sub-negative electrode material layers (see FIGS. 5 (a) and 5 (b)). Next, the above-mentioned raw material slurry of the ceramic separator was coated on both of the two sub-negative electrode material layers separated on the electrodeposited copper foil to form a ceramic separator layer (FIG. 5). (C)). More specifically, the above-mentioned raw material slurry of the ceramic separator is applied by a suitable coating method (screen printing method, doctor blade method, etc.) and then dried, and if necessary it is pressed (according to the test content) Thus, a ceramic separator layer was formed.

(Production of electrode stack)
An electrode laminate portion was prepared to be interposed between the folded "both outermost layer portions". In particular, an electrode laminate portion in which a positive electrode material layer was formed on both main surfaces of a positive electrode current collector foil as shown in FIG. 5D was produced. Specifically, the positive electrode slurry of the above positive electrode is coated on a positive electrode current collector foil made of aluminum foil (made by Tokai Toyo Aluminum Sales Co., Ltd., thickness 15 μm), dried and pressed, to thereby obtain a positive electrode. The electrode laminated portion of

(Production of battery test body)
A battery test body was obtained by folding back the both outermost layer portions with the above electrode laminated portion interposed (see FIG. 5 (d)). In particular, a battery test body was produced by sandwiching the electrode laminated portion inside the outermost layer portions which are folded back so as to bend and press the whole. In the battery test body obtained in this manner, the "current collector forming the outermost layer" and the "lateral ceramic separator" were in close contact with each other at the side face portion of the folded battery. Similarly, the "electrode material layer" and the "side ceramic separator" were in close contact with each other.

[Second test: Effect confirmation test of ceramic separator thickness on side of folded battery]
A test was conducted to confirm the influence of the thickness of the ceramic separator on the side of the folded battery. Specifically, the thickness of the ceramic separator was changed variously, and "cracking in the battery side portion (folded portion)" and "occurrence of short failure" were confirmed (see Table 2 below and FIG. 9A). ). The change of the thickness of the ceramic separator was performed by changing the coating thickness of the screen printing using the raw material slurry of the ceramic separator. Here, specifically, “breaks in the battery side portion (folded portion)” are obtained by bending before applying the electrolytic solution, solidifying with a resin and a curing agent, and then observing the state obtained by polishing the cross section by SEM. I confirmed that. In addition, “occurrence of short circuit failure” was specifically confirmed by the presence or absence of charge / discharge abnormality at the time of initial charge.

The results are shown in Table 2.

  In the second test, it was found that when the thickness a2 of the separator in the battery side surface portion (folded back portion) is larger than the thickness a1 of the separator in the non-side surface portion, it is preferable from the viewpoint of suppressing the occurrence of short circuit. In the results of Table 2, such a preferable tendency is that the ceramic separator in the battery side portion (folded portion) has a thickness not less than 1.25 times and not more than 4 times the thickness of the ceramic separator in the non-side portion You can see Therefore, in the present invention, it was found that when the thickness dimension of the side separator is larger than the thickness dimension of the inter-electrode separator, a particularly preferable secondary battery is obtained.

[Third test: Effect confirmation test of ceramic separator density in the side part of folded battery]
A test was conducted to confirm the influence of ceramic separator density on the side of the folded battery. Specifically, the density of the ceramic separator was locally changed to confirm "cracking in the battery side portion (folded portion)" and "occurrence of short failure" (see Table 3 and FIG. 9A below). . The change in density of the ceramic separator was achieved by pressing the coated layer of the ceramic separator to reduce the apparent volume. The “cracks in the battery side portion (folded portion)” and the “occurrence of short circuit failure” are the same as in the second test.

The results are shown in Table 3.

  In the third test, it was found that if the density of the ceramic separator in the battery side portion (folded portion) is higher than the density of the ceramic separator in the non-side portion, it is preferable particularly in terms of suppression of short circuit occurrence. In the results of Table 3, when the density of the ceramic separator in the battery side portion (folded portion) is 4% to 10% higher than the density of the ceramic separator in the non-side portion (that is, the ceramic separator density in the non-side portion) Such a favorable tendency can be seen as being 4% to 10%). Therefore, in the present invention, it was found that when the density of the side separator is higher than the density of the inter-electrode separator, it becomes a particularly preferable secondary battery (note that, for the third test, it corresponds to so-called PVC) Similar results could be obtained even in the case of ceramic separators with a lower concentration of possible ceramic components).

In the above test, the ceramic separator density was adjusted by pressing the raw material coating layer. However, since the density can be changed even by the difference in the concentration of the raw material slurry, a supplementary confirmation test was conducted on it. Specifically, raw material slurries having different ceramic component concentrations that can correspond to PVC (pigment volume concentration) (more specifically, raw material slurries having different ceramic component concentrations in the dried coating layer) are used. The ceramic separator layer was formed. The results are shown in Tables 4 and 5. As can be seen from the table, in addition to or instead of the pressing process, it was possible to change the ceramic separator density by changing the concentration of the ceramic component.

[Fourth test: Influence confirmation test of electrode layer on side of folded battery]
A test was conducted to confirm the influence of the electrode layer on the side of the folded battery. Specifically, an electrode layer was provided on the side of the folded battery, and the thickness was changed to confirm "cracks in the battery side (folded back)" and "occurrence of short circuit failure" (see Table 6 below and See FIG. 9 (B)). In addition, the electrode material layer in the folded battery side surface part was provided by forming continuously and integrally without separating the negative electrode material layer as a sub-layer when producing both outermost layer parts. The “cracks in the battery side portion (folded portion)” and the “occurrence of short circuit failure” are the same as the above-described confirmation test.

The results are shown in Table 6.

  In the fourth test, even if the electrode material layer is provided on the battery side portion (folded portion), if the thickness is not excessive, the point of “crack in the battery side portion (folded portion)” and “occurrence of short failure” It turned out that there is no particular problem.

  The secondary battery according to the present invention can be used in various fields where storage of electricity is assumed. For the purpose of illustration only, secondary batteries are used in the fields of electricity, information and communication in which mobile devices are used (for example, mobile devices such as mobile phones, smart watches, smartphones, notebook computers and digital cameras), homes Small industrial applications (for example, in the field of electric tools, golf carts, home / care / industrial robots), large industrial applications (for example in the fields of forklifts, elevators, harbor cranes), transportation systems (for example, hybrid vehicles , Electric vehicles, buses, trains, electrically assisted bicycles, electrically operated motorcycles), power system applications (eg, various power generation, road conditioners, smart grids, general household installed storage systems, etc.), as well as space and deep sea Used in applications (for example, fields such as space probes and diving survey vessels) Rukoto can.

Reference Signs List 1 secondary battery 10 inter-electrode separator 15 side separator 20 current collector (one current collector)
45 Current collector (other current collector)
48 electrode material layer 100 electrode lamination unit 120 both outermost layers 150 unit side surface 160 battery side portion

Claims (13)

A secondary battery comprising an electrode stack unit comprising a positive electrode, a negative electrode, and an inter-electrode separator between the positive electrode and the negative electrode,
A unit in which the current collector of either the positive electrode or the negative electrode extends from both outermost layers of the electrode stack unit while forming the both outermost layers of the electrode stack unit and corresponds to a partial side surface of the electrode stack unit The side of the battery covers the side,
A side separator is provided between the unit side surface and the battery side portion, and the side separator is a ceramic separator,
The secondary battery, wherein the current collectors forming the outermost layers and the side separators are in close contact with each other at the battery side portion. The secondary battery according to claim 1, wherein the side separator and the inter-electrode separator are integrated with each other. The secondary battery according to claim 1, wherein the inter-electrode separator also constitutes a ceramic separator together with the side separator. The secondary battery according to any one of claims 1 to 3, wherein a thickness dimension of the side separator is larger than a thickness dimension of the inter-electrode separator. The secondary battery according to any one of claims 1 to 4, wherein the density of the side separator is larger than the density of the inter-electrode separator. The electrode material layer of any one of the said positive electrode and the said negative electrode is extended from the said electrode lamination | stacking unit, and is provided also between the said unit side surface and the said battery side part. The secondary battery as described in. The secondary battery according to claim 6, wherein the electrode material layer is in close contact with the side separator at least at the battery side surface portion. The secondary battery according to any one of claims 1 to 7, wherein the side separators are positioned only on a single side surface among the plurality of unit side surfaces in the electrode stack unit. The secondary battery according to claim 8, wherein an insulating sealing portion is provided on a side surface other than the single side surface among the plurality of unit side surfaces. The secondary battery according to any one of claims 1 to 9, wherein in the electrode stacking unit, the negative electrode is the outermost electrode, and the positive electrode is provided between the negative electrodes. The secondary battery according to claim 10, wherein the current collector forming the outermost layers is a negative electrode current collector. The secondary battery according to claim 10, wherein the positive electrode is a double-sided electrode in which a positive electrode material layer is provided on both main surfaces of a positive electrode current collector. The secondary battery according to any one of claims 1 to 12, wherein the positive electrode and the negative electrode are electrodes capable of inserting and extracting lithium ions.

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