JP2018147749A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery in which a dead space in the battery is suitably reduced from a long-term viewpoint.SOLUTION: A secondary battery includes: an electrode assembly including electrode constituting layers stacked therein, each electrode constituting layer including a positive electrode, a negative electrode and a separator between the positive electrode and the negative electrode; and an exterior body to package the electrode assembly. A tab 50 of the electrode assembly 100 is bent such that a projecting dimension corresponding to a length projecting from a side face (a) of the electrode assembly 100 is reduced, and a bending back prevention member 80 for preventing the bending back of the tab 50 is provided.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a secondary battery. In particular, the present invention relates to a secondary battery having an electrode assembly composed of an electrode constituent layer including a positive electrode, a negative electrode, and a separator.

  The secondary battery can be repeatedly charged and discharged because of a so-called “storage battery”, and is used for various purposes. For example, secondary batteries are used in mobile devices such as mobile phones, smartphones, and notebook computers.

  In various battery applications including mobile devices, secondary batteries are used in a casing. That is, the secondary battery is arranged so as to partially occupy the inside of the casing of the device to be used.

Special table 2015-536036

  The inventor of the present application has found that there is a problem to be overcome in the conventional secondary battery, and has found that it is necessary to take measures for that. Specifically, the present inventors have found that there are the following problems.

  The installation space of the secondary battery in the housing needs to take into account the balance with other device elements such as a circuit board and various parts. In particular, with the diversification of needs in recent years, there is a tendency that the installation space of the secondary battery is more restricted by the casing and various elements accommodated therein, and a secondary battery having a smaller size is required. .

  In order to make the secondary battery smaller, it is conceivable to reduce the dead space in the battery. For example, a smaller secondary battery can be obtained by reducing the volume between the battery outer package and the electrode assembly inside the battery outer package.

  However, the present inventors have found that such a reduction in dead space is not particularly problematic from a short-term viewpoint, but can be a problem from a long-term viewpoint. Specifically, from the viewpoint of reducing dead space, it is conceivable to bend the “tab of the electrode assembly” positioned in the exterior body, but such bending of the tab is not always desirable in the long term. Found no. For example, tabs themselves are often made of metal and are generally considered to be plastically deformed. However, because of the unique structure of the tab of the secondary battery, it may not substantially show the behavior of plastic deformation as it is, and it has been found that the force to return to the original shape easily works in the long term. . This is particularly noticeable when the tab of the secondary battery is formed by overlapping the protruding portions of a plurality of current collectors provided on each of the stacked positive and negative electrodes.

  When the tab is deformed to the original shape, the tab presses the outer body from the inside, so there is a risk that the battery will be deformed so as to swell, and there is an undesired electrical connection between the tab and the outer body. There is also a risk of contact being caused.

  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 in which the dead space in the battery is suitably reduced from a long-term viewpoint.

  The inventor of the present application tried to solve the above-mentioned problem by addressing in a new direction instead of responding on the extension of the prior art. As a result, the inventors have reached the invention of a secondary battery in which the main object is achieved.

A secondary battery according to the present invention includes a positive electrode, a negative electrode, an electrode assembly in which an electrode constituent layer including a separator between the positive electrode and the negative electrode is stacked, and an outer package that encloses the electrode assembly. A secondary battery,
The tab of the electrode assembly is bent so that the protruding dimension corresponding to the length protruding from the side surface of the electrode assembly is reduced,
A bending return preventing member is provided for preventing the tab from being bent back.

  In the secondary battery according to the present invention, the tab is bent so that the protruding dimension from the side surface of the electrode assembly is reduced, and the dead space is reduced by the reduction of the protruding dimension. Further, in the present invention, not only the tab is bent, but also the anti-bending member is provided, so that the force for the tab to return to the original shape is effectively suppressed. It has become.

  Therefore, in the secondary battery of the present invention, it is possible to prevent the battery from being deformed so as to swell and the possibility of causing undesired electrical contact between the tab and the exterior body. That is, the secondary battery of the present invention is a battery in which the dead space in the battery is suitably reduced from a long-term viewpoint.

Schematic cross-sectional view showing a non-winding planar laminate type Schematic diagram illustrating the concept of the present invention (FIG. 2A: side view, FIG. 2B: perspective view) Side view schematically showing the concepts of dead space reduction and tab bending back Schematic side view for explaining tab bending Side view and perspective view schematically showing the manner of integral bending of the tab and the lead Schematic side view showing the first aspect FIG. 6A is a schematic perspective view showing the first aspect of FIG. Schematic side view showing the second aspect Schematic side view showing the third aspect

  Hereinafter, the secondary battery according to an embodiment of the present invention will be described in more detail. Although the description will be made with reference to the drawings as necessary, the various elements in the drawings are merely schematically and exemplarily shown for the purpose of understanding the present invention, and the appearance and size ratio are different from the actual ones. obtain.

  The direction of “thickness” described directly or indirectly in this specification is based on the stacking direction of the electrode materials constituting the secondary battery. For example, the “thickness in a plate shape” of a flat battery or the like is used. In the “secondary battery”, this corresponds to the thickness direction. As used herein, “plan view” is based on a sketch when the object is viewed from above or below along the thickness direction, and “cross section view” is along the thickness direction of the secondary battery. This is based on a virtual cross section of the object obtained by cutting out. Further, the “side view / side view” is based on a side view of the object as viewed from the direction in which the thickness of the object (for example, the thickness of the secondary battery or the electrode assembly) can be captured.

  Further, “vertical direction” and “horizontal direction” used directly or indirectly in the present specification correspond to the vertical direction and horizontal direction in the drawing, respectively. Unless otherwise specified, the same symbols or symbols indicate the same members / parts or the same meaning.

[Configuration of Secondary Battery of the Present Invention]
In the present invention, a secondary battery is provided. The “secondary battery” in the present specification refers to a battery that can be repeatedly charged and discharged. Therefore, the secondary battery of the present invention is not excessively bound by its name, and for example, “electric storage device” can also be included in the subject of the present invention.

  The secondary battery according to the present invention includes an electrode assembly in which electrode configuration layers including a positive electrode, a negative electrode, and a separator are stacked. FIG. 1 illustrates an electrode assembly. As shown in the figure, the positive electrode 1 and the negative electrode 2 are stacked via a separator 3 to form an electrode constituent layer 10, and at least one electrode constituent layer 10 is laminated to form an electrode assembly. Yes. In a secondary battery, such an electrode assembly is enclosed in an exterior body together with an electrolyte (for example, a nonaqueous 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 surface of the positive electrode current collector, and the positive electrode material layer contains a positive electrode active material as an electrode active material. For example, each of the plurality of positive electrodes in the electrode assembly may have a positive electrode material layer provided on both sides of the positive electrode current collector, or a positive electrode material layer provided only on one surface of the positive electrode current collector. It may be what you have. From the viewpoint of further increasing the capacity of the secondary battery, the positive electrode is preferably provided with a positive electrode material layer on both surfaces 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 surface of the negative electrode current collector, and the negative electrode material layer contains a negative electrode active material as an electrode active material. For example, the plurality of negative electrodes in the electrode assembly may each have a negative electrode material layer provided on both sides of the negative electrode current collector, or a negative electrode material layer provided only on one surface of the negative electrode current collector. It may be what you have. From the viewpoint of further increasing the capacity of the secondary battery, the negative electrode is preferably provided with a negative electrode material layer on both sides of the negative electrode current collector.

  The electrode active materials contained in the positive electrode and the negative electrode, that is, the positive electrode active material and the negative electrode active material are materials directly involved in the transfer of electrons in the secondary battery, and are the main materials of the positive and negative electrodes responsible for charge / discharge, that is, the battery reaction. is there. More specifically, ions are brought into the electrolyte due to the “positive electrode active material included in the positive electrode material layer” and the “negative electrode active material included in the negative electrode material layer”, and the ions are interposed between the positive electrode and the negative electrode. Then, the electrons are transferred and the electrons are delivered and charged and discharged. The positive electrode material layer and the negative electrode material layer are particularly preferably layers capable of occluding and releasing lithium ions. That is, the secondary battery according to the present invention is preferably a non-aqueous electrolyte secondary battery in which lithium ions move between the positive electrode and the negative electrode through the non-aqueous electrolyte so that the battery is charged and discharged. . When lithium ions are involved in charging and discharging, the secondary battery according to the present invention corresponds to a so-called “lithium ion battery”, and the positive electrode and the negative electrode have layers capable of occluding and releasing lithium ions.

  The positive electrode active material of the positive electrode material layer is made of, for example, a granular material, and a binder (also referred to as a “binder”) is included in the positive electrode material layer for sufficient contact between the particles and shape retention. preferable. Furthermore, a conductive additive may be included in the positive electrode material layer in order to facilitate the transmission of electrons that promote the battery reaction. Similarly, the negative electrode active material of the negative electrode material layer is made of, for example, a granular material, and it is preferable that a binder is included for sufficient contact and shape retention between the particles, and smooth transmission of electrons that promote the battery reaction. In order to do so, a conductive aid may be included in the negative electrode material layer. Thus, because of the form in which a plurality of components are contained, the positive electrode material layer and the negative electrode material layer can also be referred to as “positive electrode composite material layer” and “negative electrode composite material layer”, respectively.

  The positive electrode active material is preferably a material that contributes to occlusion and release of lithium ions. From this point of view, 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 composite 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 according to the present invention, such a lithium transition metal composite oxide is preferably included 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 a part of those transition metals replaced with another metal. Although such a positive electrode active material may be included as a single species, two or more types may be included in combination. Although it is only an illustration to the last, in the secondary battery which concerns on this invention, the positive electrode active material contained in a positive electrode material layer may be lithium cobaltate.

  Binders that can be included in the positive electrode material layer are not particularly limited, but include polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, and Mention may be made of at least one selected from the group consisting of polytetrafluoroethylene and the like. The conductive auxiliary agent that can be included in the positive electrode material layer is not particularly limited, but carbon black such as thermal black, furnace black, channel black, ketjen black, and acetylene black, graphite, carbon nanotube, and vapor phase growth. Examples thereof include at least one selected from carbon fibers such as carbon fibers, metal powders such as copper, nickel, aluminum and silver, and polyphenylene derivatives. For example, the binder of the positive electrode material layer may be polyvinylidene fluoride, and the conductive additive of the positive electrode material layer may be carbon black. Although it is only an illustration to the last, the binder and conductive support agent of a positive electrode material layer may be a combination of polyvinylidene fluoride and carbon black.

  The negative electrode active material is preferably a material that contributes to occlusion and release of lithium ions. From this point of view, the negative electrode active material is preferably, for example, various carbon materials, oxides, or lithium alloys.

  Examples of various carbon materials of the negative electrode active material include graphite (natural graphite, 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 in its structural form. This is because deterioration due to non-uniformity such as crystal grain boundaries or defects is less likely to be caused. Although it is only an illustration to the last, in the secondary battery which concerns on this invention, the negative electrode active material of a negative electrode material layer may be artificial graphite.

  The binder that can be included in the negative electrode material layer is not particularly limited, but is 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 auxiliary agent that can be included in the negative electrode material layer is not particularly limited, but carbon black such as thermal black, furnace black, channel black, ketjen black, and acetylene black, graphite, carbon nanotube, and vapor phase growth. Examples thereof include at least one selected from carbon fibers such as carbon fibers, metal powders such as copper, nickel, aluminum and silver, and polyphenylene derivatives. 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.

  Although it is only an illustration to the last, the negative electrode active material and binder in a negative electrode material 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 that contribute to collecting and supplying electrons generated in the active material due to the battery 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 a metal foil, a punching metal, a net or an expanded metal. 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, a copper foil.

  The separator used for the positive electrode and the negative electrode is a member provided from the viewpoints of preventing a short circuit due to contact between the positive electrode and the negative electrode and holding the electrolyte. In other words, the separator can be said to be 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 film form due to its small thickness. Although only illustrative, a polyolefin microporous film may be used as the separator. In this regard, the microporous film used as the separator may include, for example, only polyethylene (PE) or only polyethylene (PP) as the polyolefin. Furthermore, the separator may be a laminate composed of “a microporous membrane made of PE” and “a microporous membrane made of PP”. The surface of the separator may be covered with an inorganic particle coat layer, an adhesive layer, or the like. The surface of the separator may have adhesiveness. In the present invention, the separator is not particularly limited by its name, and may be a solid electrolyte, a gel electrolyte, insulating inorganic particles or the like having the same function.

  In the secondary battery of the present invention, an electrode assembly including an electrode constituent layer 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 occluding and releasing 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) exist, and therefore, the electrolyte assists the movement of the metal ions in the battery reaction.

A non-aqueous electrolyte is an electrolyte containing a solvent and a solute. As a specific non-aqueous electrolyte solvent, a solvent containing at least carbonate is preferable. Such carbonates may be cyclic carbonates and / or chain carbonates. Although not particularly limited, examples of the 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. Examples of the chain carbonates include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dipropyl carbonate (DPC). Although it is only an illustration to the last, the combination of cyclic carbonate and chain carbonate may be used as a nonaqueous electrolyte, for example, the mixture of ethylene carbonate and diethyl carbonate may be used. In addition, as a specific nonaqueous electrolyte solute, for example, a Li salt such as LiPF ₆ and / or LiBF ₄ is preferably used.

  The outer package of the secondary battery encloses the electrode assembly in which the electrode constituent layers including the positive electrode, the negative electrode, and the separator are laminated, but may be in a hard case form or a soft case form. Good. Specifically, the exterior body may be a hard case type corresponding to a so-called “metal can” or a soft case type corresponding to a “pouch” made of a so-called laminate film.

[Characteristics of the secondary battery of the present invention]
The secondary battery of the present invention has structural features related to the tab. In particular, it has structural features related to the protruding length of the tab. Specifically, as shown in FIGS. 2 and 3, the tab 50 of the electrode assembly 100 ′ is bent so that the protruding dimension corresponding to the length protruding from the side surface of the electrode assembly 100 ′ is reduced. In addition, a bending return preventing member 80 for preventing the tab 50 from bending back is provided.

  In this specification, “tab” means, in a broad sense, an external terminal element of a battery used for electrical connection to the outside, and in a narrow sense, a part of a positive or negative current collector. In particular, an electrode active material (positive electrode material / negative electrode material) is not provided, and it means an external terminal element having a form protruding from the positive electrode or the negative electrode in the electrode assembly.

  In the secondary battery of the present invention, not only the tab bending for reducing the dead space in the battery is performed, but also a “bending return preventing member” corresponding to the bending is provided in the exterior body. That is, while the tab is bent to reduce the volume between the battery outer body and the electrode assembly inside thereof, the anti-bending member is provided to make the bending more effective.

  The anti-bending member is related to an event peculiar to the secondary battery tab found by the present inventors at the time of creation of the present invention. The inventors of the present application have found that the tab of the secondary battery itself is made of metal and is generally considered to be plastically deformed, but because of its unique structure, it does not show the behavior of plastic deformation in the long term. It was. Specifically, in the tab 50 in which the protruding portions of a plurality of current collectors provided on each of the positive electrode and the negative electrode of the electrode assembly 100 ′ are overlapped and integrated with each other, the dead space in the battery is reduced. It has been found that even if the tab is bent to reduce, a force to return to the original shape is likely to work in the long term (see FIG. 3). When a force is applied to return the tab to the original shape in the outer package, the battery may be deformed so as to swell or undesired electrical contact may be caused between the tab and the outer package. In particular, in the case of a soft case type in which the exterior body is made of a laminate film, such undesired bulging deformation can be more remarkable. In this regard, in the present invention, the anti-bending member is provided so that the tab does not return to its original shape, and therefore, inconvenient events are reduced from a long-term viewpoint. That is, a dead space (particularly, “a dead space inside the exterior body”) is obtained by combining a tab bent to reduce the lateral projecting dimension and a bending return preventing member provided in view of the bending return. This results in a secondary battery in which is more preferably reduced. For example, as can be understood from the embodiment shown in FIG. 2, in the present invention, the “bent tab 50” and the “main body portion 100 ″ (particularly the side surface) of the electrode assembly 100 ′” are fixed to each other. It can also be taken as.

  In the secondary battery of the present invention, even though the dead space is reduced, the electrode assembly itself is not reduced in size, and the battery capacity is not substantially impaired. Therefore, in the present invention, a more compact battery size can be realized without substantially impairing the battery capacity. In particular, the secondary battery of the present invention effectively prevents the “bending back” of the tab, so that it not only has a higher energy density per unit volume, but also has better long-term stability.

  Here, the term “bending return prevention member” in the present invention means a member for preventing the return of the bent battery tab in a broad sense, and in a narrow sense, a protruding dimension from the electrode assembly. This means a member provided to prevent the battery tab intentionally bent to reduce the length of the battery tab from returning to its original form.

  There is no particular limitation on the type of the bending back preventing member as long as it contributes to preventing the bent battery tab from returning. In other words, the shape of the anti-bending member itself is not particularly limited as long as it prevents the battery tab intentionally bent to reduce the protruding dimension from returning to the original shape. In addition, since the tab can be formed by stacking the current collectors, it can be said that the anti-bending member is a member that contributes to “preventing anti-bending” against the bending of the tab having such an overlapping structure.

  For example, the bending back preventing member may exhibit rigidity characteristics, or the bending back preventing member may exhibit flexibility. In the present invention, an appropriate anti-bending member is employed according to the specific configuration and configuration of the secondary battery, such as “bent tab”, “electrode assembly provided with a tab” and / or “lead”. It's okay.

  In the case of “rigid characteristics”, it is preferable that the anti-bending member is substantially made of a rigid body, and the structural strength of the rigid body resists the bending return force of the tab. On the other hand, in the case of “flexibility”, the anti-bending member is made of a thin film-like member (for example, the anti-bending member has a tape form), and the material strength of the film-like member / tape member is a tab. It is preferable to resist the bending return force.

  In terms of preventing inconvenient conduction or the like, the anti-bending member is preferably insulating. For example, the anti-bending member preferably includes a resin material or a plastic material. The term “insulating” as used herein does not necessarily mean complete insulation, but may be insulation that does not cause inconvenient conduction in the secondary battery.

  The thickness of the bending return member is not particularly limited, but is preferably as small as possible. Although it is only an example to the last, when a bending back prevention member is equivalent to what is called a film-like "adhesive tape", the thickness of a bending back member can be made especially small. Although it is only an example to the last, the bending back prevention member which has the form of an adhesive tape, Preferably it is 0.01 mm or more and 1 mm or less, More preferably, it is 0.01 mm or more and 0.5 mm or less, More preferably, it is 0.01 mm or more and 0.1 mm It is as follows.

  In the secondary battery of the present invention, the tab of the electrode assembly is bent, but in particular, is bent so as to reduce the “projection dimension corresponding to the length protruding from the side surface of the electrode assembly”. For example, the tab may be bent so as to be bent, or may be bent so as to be bent without bending.

  In the present invention, the bending of the tab is preferably such that the tip of the tab is closer to the side surface of the body portion of the electrode assembly. That is, as shown in FIG. 4, the tab 50 protruding laterally from the main body 100 ″ of the electrode assembly 100 ′ is bent toward the side surface of the main body 100 ″ so as to be displaced from the lateral direction. Preferably it is. As can be seen from the illustrated embodiment, in the present invention, “bending closer to the side surface” means that the upper surface on the tip end side of the tab is relatively closer to the side surface of the body portion of the electrode assembly on which the tab is provided ( It is substantially intended to bend the tab (relatively compared to the “form before bending”).

  The tab may consist of a stack of a plurality of current collector protrusions as described above. Specifically, the tab is formed by overlapping each protruding portion of a plurality of current collectors (for example, current collector foils) provided on each of the positive electrode and the negative electrode. In particular, as shown in FIG. 3, the tip of each protrusion (a plurality of protrusions adjacent to each other in the stacking direction) of a plurality of current collectors of each electrode (positive electrode or negative electrode) stacked in the electrode assembly It is preferred that the parts overlap so as to be in close contact with each other. In such a tab, even if the tab is bent to reduce the dead space in the battery, a force to return to the original shape is generally generated in the long term. "Is provided, so that it resists such an inconvenient force. In such a tab mode (tab mode composed of a plurality of protrusions adjacent to each other along the stacking direction), the electrode assembly has a planar stacked structure in which a positive electrode, a negative electrode, and a separator are stacked in a planar shape. Can do. That is, the secondary battery of the present invention preferably has a planar laminated structure (see FIG. 1) in which the electrode constituent layers are laminated in a planar shape without being wound.

  In the present invention, the prevention of bending back is particularly effective when the thickness of the tab formed by the overlapping of the plurality of current collector protrusions is larger. That is, this is a case where the thickness of the composite tab composed of a plurality of current collector protrusions is large. When the thickness of the composite tab is increased, it is difficult to bend, and “bending return” is generally likely to occur. Therefore, the installation of the bending back preventing member is more effective in that respect. In addition, when the positive electrode current collector foil is made of aluminum and the negative electrode current collector foil is made of copper, copper is relatively hard to bend and “bend back” is likely to occur. It can be said that the installation of the anti-bending member is more effective.

  In a preferred embodiment, as shown in FIG. 5, the lead 70 is connected to the tab 50 as a terminal element of the secondary battery, and the lead 70 is bent together with the bending of the tab 50. That is, a conductive lead for electrical connection with the outside of the battery may be provided in the electrode assembly, and the lead may be bent together with the bending of the tab. Thereby, the dead space can be reduced more appropriately in view of the external terminal elements including the leads.

  Preferably, as shown in FIG. 5, the lead 70 and the tab 50 are integrated so that the lead 70 is partially sandwiched between the side surface of the main body 100 ″ of the electrode assembly 100 ′ and the tab 50. Is bent. Since the lead 70 and the tab 50 are bent integrally, the dead space inside the exterior body can be reduced more efficiently. More specifically, the end portion of the tab 50 and the end portion of the lead 70 are connected to each other (for example, the end portions are connected by ultrasonic welding), and the integrated member so connected Is bent in the middle. In particular, it is preferable that the bent portion be bent so as to be closer to the side surface of the body portion of the electrode assembly. Although only an example, the integrated member of the tab and the lead may be bent into a “Z shape” in a side view.

  In a preferred aspect, the anti-bending member is provided inside the exterior body. In this regard, it is preferable that the bending back preventing member is attached to at least the main body portion of the electrode assembly. By attaching the anti-bending member to the main body of the electrode assembly, the attachment point serves as a support point, and the force against the anti-bending is effectively provided by the tab.

  The attachment position of the bending back preventing member in the main body portion of the electrode assembly may be any of the upper surface, the lower surface and the side surface of the main body portion. That is, as shown in FIG. 2B, the “upper main surface a”, “lower main surface b”, “side surface a”, “side surface b” of the main body portion 100 ″ of the electrode assembly 100 ′, At least one of “side surface c” and “side surface d” may be an attachment location of the anti-bending member. From the viewpoint of avoiding providing an excessively large and large bending-back preventing member, it is preferable that a portion other than the “side surface c” is an attachment portion. In this regard, regarding the “upper main surface a”, “lower main surface b”, “side surface b”, and “side surface d”, the anti-bending member is attached particularly to the “tab proximal region” that is proximal by the tab. It is preferable.

  The body portion of the electrode assembly is substantially composed of a stack of electrode constituent layers including a positive electrode, a negative electrode, and a separator, and the anti-bending member is attached to any of the positive electrode, the negative electrode, and the separator. Good. Although it is only an example to the last, when the anti-bending member is attached to, for example, a separator (in particular, it is attached so as to include a separator portion protruding so as to protrude from the laminated structure of the positive electrode and the negative electrode) ), “The increase in the thickness of the“ main part of the electrode assembly ”caused by the anti-bending member” can be reduced by the bending of the separator.

  The attachment of the anti-bending member to the electrode assembly is not particularly limited, but an appropriate adhesive material may be used. That is, the electrode assembly and the anti-bending member may be bonded to each other through the adhesive material. The adhesive material itself may be provided in advance on the anti-bending member (for example, when the anti-bending member has a thin film shape, the anti-bending member is a so-called “adhesive tape” or “adhesive”. It may correspond to “tape”).

  The adhesive material itself is not particularly limited as long as it contributes to the joining and adhesion of the electrode assembly and the anti-bending member. Preferably, an insulating adhesive material is preferable. Examples of the adhesive component of the pressure-sensitive adhesive material include acrylic adhesives such as acrylic ester copolymers, rubber adhesives such as natural rubber, silicone adhesives such as silicone rubber, and urethane adhesives such as urethane resins. Agent, α-olefin adhesive, ether adhesive, ethylene-vinyl acetate resin adhesive, epoxy resin adhesive, vinyl chloride resin adhesive, chloroprene rubber adhesive, cyanoacrylate adhesive, high aqueous Molecule-isocyanate adhesive, styrene-butadiene rubber adhesive, nitrile rubber adhesive, nitrocellulose adhesive, reactive hot melt adhesive, phenol resin adhesive, modified silicone adhesive, polyamide resin adhesive Adhesive, polyimide adhesive, polyurethane resin adhesive, polyolefin resin adhesive, polyvinyl acetate Resin adhesive, polystyrene resin solvent adhesive, polyvinyl alcohol adhesive, polyvinyl pyrrolidone resin adhesive, polyvinyl butyral resin adhesive, polybenzimidazole adhesive, polymethacrylate resin adhesive, melamine Examples thereof include resin adhesives, urea resin adhesives, resorcinol adhesives, and the like.

  In the present invention, the adhesive is not necessarily required if the anti-bending member is suitably attached. For example, when the anti-bending member is made of a rigid body, the anti-bending member may be “the main body portion 100 ″ of the electrode assembly 100 ′”, “the tab 50” and / or due to the shape of the anti-bending member. It may be attached to the “lead 70”. In other words, by means of non-adhesive means such as engagement, locking, abutment and / or mating, the anti-bending member can be turned into “the body portion 100 ″ of the electrode assembly 100 ′”, “tab 50” and / or It may be attached to “Lead 70”.

  In the present invention, the attachment of the anti-bending member can be embodied in various ways. This will be described in detail below.

(First aspect)
Representative examples of the first aspect are shown in FIGS. 6 (a) to 6 (d) and FIG. In such an embodiment, the anti-bending member 80 extends over both the “main body portion 100 ″ of the electrode assembly 100 ′” and the “tab 50”. That is, the anti-bending member 80 is attached to or attached to both the “main body portion 100 ″ of the electrode assembly 100 ′” and the “tab 50”.

  In such a first aspect, the attachment point / paste location of the anti-bending member in the main body portion of the electrode assembly serves as a support point, while the attachment point / paste location of the anti-bending member in the tab serves as an anti-bending action point. Become. Therefore, it is possible to more effectively prevent the tab from being bent back by the bend return preventing member.

  In FIG. 6A, the anti-bending member 80 is attached or affixed so as to surround the tab 50 from the outside and bridge the opposing side surfaces of the main body portion 100 ″ of the electrode assembly 100 ′ (see FIG. 6A). (See also perspective view of FIG. 7). More specifically, in the main body portion 100 ″ of the electrode assembly 100 ′, bending back is prevented so that “opposing side surfaces” (side surface b and side surface d) different from the side surface on which the tab 50 is provided are bridged. Member 80 may extend in close proximity to the outer surface of tab 50.

  6B is the same as that in FIG. 6A, but the tip portion 50a of the tab 50 is exposed from the anti-bending member 80. FIG. In other words, the height dimension of the anti-bending member 80 is reduced by the exposed amount. In this aspect, while reducing the material cost of the bending back preventing member, the mounting point / pasting part of the bending return preventing member in the main body of the electrode assembly is used as a support point, and the mounting part / pasting of the bending back prevention member in the tab is performed. This point is used as an action point to prevent bending back.

  In the embodiment of FIG. 6 (c), the side portion (side portion 110 ″ closest to the tab 50) of the main body portion 100 ″ of the electrode assembly 100 ′ is wrapped, and the joint between the tab 50 and the lead 70 is encased. Is attached or affixed so as to envelop the entire surface. In particular, the anti-bending member 80 is attached or affixed so as to circulate along the stacking direction of the electrode assembly in a cross-sectional view. Even in such an embodiment, the bending back prevention member in the main body portion of the electrode assembly serves as a support point for the attachment point / paste location, while the attachment / paste location of the bending back prevention member in the tab serves as a point for preventing bending back. become. In particular, in such an embodiment, the lead back prevention member extends widely to the lead. Therefore, even if an accidental or unintentional force is applied to the lead and the tab can be bent back, the lead force can be effectively absorbed by the anti-bending member. Can be prevented from bending back.

  In the embodiment of FIG. 6 (d), the anti-bending member 80 extending from the bottom side surface of the main body 100 ″ of the electrode assembly 100 ′ is brought into close contact with the outside of the tab 50. In such an embodiment, it is preferable that the anti-bending member 80 has rigidity particularly, so that it is possible to prevent the tab from bending back more directly.

  As can be seen from the modes shown in FIGS. 6A to 6D and FIG. 7, in the first mode, the bending back preventing member 80 is bent from the main body 100 ″ of the electrode assembly 100 ′ to bend the tab 50. It extends to beyond the part. Strictly speaking, if the main body portion 100 ″ of the electrode assembly 100 ′ is taken as a starting point, the bending back of the bent portion of the bent tab 50 is returned until it exceeds the inner point (inner point in a sectional view as shown). The prevention member 80 extends. In such an aspect, the anti-bending member can be caused to function so as to more effectively / directly resist the bending return force.

  In the first aspect, as particularly shown in FIGS. 6A to 6C, the anti-bending member 80 includes the “main body portion 100 ″ of the electrode assembly 100 ′”, the “tab 50”, and the “lead”. 70 ". That is, in the present invention, the bending back preventing member 80 may be attached or pasted so as to have contacts with all of the main body portion 100 ″, the tab 50 and the lead 70. In such an aspect, the anti-bending effect acts directly on the tab and indirectly on the lead, so that the tab can be more effectively prevented from returning.

(Second embodiment)
A representative example of the second aspect is shown in FIG. In such an embodiment, the anti-bending member 80 extends over the “main body portion 100 ″ of the electrode assembly 100 ′” and the “lead 70”. That is, the tab 50 is not in direct contact with the electrode body 100 ′ and the lead 70 is attached to or attached to the body portion 100 ″ of the electrode assembly 100 ′ and the lead 70. .

  In such a second aspect, the attachment point / paste location of the anti-bending member in the body part of the electrode assembly serves as a support point, while the attachment point / paste location of the anti-bend member in the lead serves as an anti-bending action point. Become. In particular, even if accidental or unintentional force is applied to the lead, the bending of the tab can be induced and the anti-bending member can effectively absorb the force of the lead. Bending back can be prevented.

  A “protective tape provided in view of welding of the tab and the lead” may be used as the bending back preventing member of the second aspect. In general, the lead may have a “rough surface” due to the welding process, and a protective tape may be used to shield the “rough surface”. In the present invention, such a protective tape may be applied more widely so as to extend from the lead to the main body of the electrode assembly. As a result, the “protective tape” and the “bend-back preventing member” can be provided as a single member, and the number of battery parts does not have to be increased.

(Third aspect)
A representative example of the third aspect is shown in FIGS. 9 (a) and 9 (b). In this embodiment, the anti-bending member 80 is positioned between the side surface of the main body 100 ″ of the electrode assembly 100 ′ and the lead 70. In particular, it is preferable that the anti-bending member 80 is provided so as to fill the gap between the side surface of the main body 100 ″ of the electrode assembly 100 ′ and the lead 70.

  In such a case, it is preferable that both main surfaces of the anti-bending member 80 have adhesiveness, and one of the adhesive main surfaces (80a) is in contact with the side surface of the body portion 100 '' of the electrode assembly, The other (80b) is preferably in contact with the lead 70. In the third aspect, even if accidental or unintentional force is applied to the lead and the tab can be bent back, the lead back prevention member effectively absorbs the lead force. Can prevent the tab from being bent back. The third mode is a mode that contributes to the downsizing of the battery because the thickness of the electrode assembly 100 ′ does not increase due to the bending back prevention member 80 being installed.

  As a specific example of the “bending return preventing member” in which both opposing main surfaces are sticky, for example, a double-sided adhesive tape can be mentioned. In this case, the double-sided adhesive tape is attached so that the double-sided adhesive tape is positioned between the “side surface of the main body of the electrode assembly” and the “lead side surface”. The double-sided adhesive tape generally has an insulating property. However, if the adhesive tape is provided so as to protrude from the region between the main body portion of the electrode assembly and the lead, an insulating effect is exerted on the exposed portion of the electrode in the main body portion of the electrode assembly. Can affect.

  As mentioned above, although embodiment of this invention has been described, it has only illustrated the typical example to the last. Therefore, those skilled in the art will easily understand that the present invention is not limited to this, and various modes are conceivable.

  For example, when an adhesive tape is used as the anti-bending member, the adhesive tape may be used for battery structural reinforcement. Although it is only an example to the last, you may use an adhesive tape for the connection part of a tab and a lead. In addition to ultrasonic welding, resistance welding, laser welding, or caulking is used to interconnect the tab and the lead. To further complement the connection strength provided by such processing, anti-bending is prevented. An adhesive tape as a member may be used.

  The secondary battery according to the present invention can be used in various fields where power storage is assumed. For illustration purposes only, secondary batteries are used in the electrical / information / communication field where mobile devices are used (for example, mobile devices such as mobile phones, smartphones, notebook computers and digital cameras), home and small industrial applications. (For example, power tools, golf carts, home / nursing / industrial robots), large industrial applications (for example, forklifts, elevators, bay harbor cranes), transportation systems (for example, hybrid vehicles, electric vehicles) , Buses, trains, electric assist bicycles, electric motorcycles, etc.), power system applications (eg, various power generation, road conditioners, smart grids, general home storage systems), and space / deep sea applications (eg, , Space probe, submersible survey ship, etc.).

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 10 Electrode structure layer 50 Tab 70 Lead 80 Bending prevention member 90 Exterior body 100 'Electrode assembly 100''Main part of electrode assembly

Claims (16)

An electrode assembly in which an electrode constituent layer including a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode is laminated, and a secondary battery having an outer package that encloses the electrode assembly,
The tab of the electrode assembly is bent so that a protruding dimension corresponding to a length protruding from a side surface of the electrode assembly is reduced.
A secondary battery provided with a bending return preventing member for preventing the bending of the tab from returning. The secondary battery according to claim 1, wherein the anti-bending member is attached to at least a main body portion of the electrode assembly. The secondary battery according to claim 1, wherein the bending is a bending in which a tip end of the tab is closer to a side surface of a main body portion of the electrode assembly. The secondary battery according to any one of claims 1 to 3, wherein the tab is configured by superimposing protruding portions of a plurality of current collectors provided on each of the positive electrode and the negative electrode. 5. The secondary battery according to claim 1, wherein the anti-bending member extends over both the main body of the electrode assembly and the tab. The secondary battery according to claim 5, wherein the bending back prevention member extends from a main body portion of the electrode assembly to beyond a bent portion of the bending of the tab. The secondary battery according to claim 1, wherein a lead is connected to the tab as a terminal element of the secondary battery, and the lead is bent together with the bending of the tab. The secondary electrode according to claim 7, wherein the lead and the tab are integrally bent so that the lead is partially sandwiched between a side surface of the main body portion of the electrode assembly and the tab. battery. 9. The secondary battery according to claim 7, wherein the bending back preventing member extends over the main body portion of the electrode assembly and the lead. The secondary battery according to claim 7, wherein the anti-bending member extends over the main body of the electrode assembly, the tab, and the lead. The secondary battery according to claim 7 or 8, wherein the anti-bending member is positioned between a side surface of the main body portion of the electrode assembly and the lead portion. The secondary battery according to claim 1, wherein the anti-bending member has an insulating property. The secondary battery according to claim 1, wherein the anti-bending member has flexibility. The secondary battery according to claim 1, wherein the bending back preventing member is an adhesive tape. The secondary battery according to claim 1, wherein the electrode assembly has a planar laminated structure in which a positive electrode, a negative electrode, and a separator are laminated in a planar shape. The secondary battery in any one of Claims 1-15 in which the said positive electrode and the said negative electrode have a layer which can occlude-release lithium ion.

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